There are numerous enzymes which have been identified as capable of catalyzing various chemical reactions. Similarly, it has been discovered that antibodies can be elicited to catalyze a variety of chemical reactions (U.S. application Ser. No. 674,253). It is well known that antibodies and enzymes share a fundamental similarity in that both are specialized proteins that bind to other molecules. However, there are important differences between antibodies and enzymes.
Antibodies typically bind to a molecule or antigen so that the antigen is marked as foreign to the organism that produced the antibody. The binding of the antibody to the antigen enables the antigen to be removed from the organism. Enzymes are biological catalysts which bind a molecule in such a way that the activation energy of a reaction involving a molecule or substrate is lowered, thereby increasing the rate of the reaction.
Linus Pauling discovered there are two types of interactions between proteins and the molecules that bind them. Antibodies bind molecules in their ground state while enzymes bind molecules in higher energy states.
Pauling attempted to explain the mechanism of enzyme catalysis based upon such binding. During the course of the chemical reaction, the reactants undergo one or more transitions through intermediate structures or transition states which are energically less favorable than either the reactant or the product. The hydrolysis reaction of a peptide linkage or an ester bond in an aqueous medium passes through a tetrahedral carbon transition state, as depicted in FIGS. 1 (peptide) and 2 (ester). In the transition state, a tetrahedral carbon atom is bonded to: a carbon atom of the acid portion of the peptide linkage or ester bond; two oxygen atoms, one corresponding to the carbonyl group and the other corresponding to a hydroxyl ion or water molecule of the medium; and either the oxygen atom of the alcohol portion of an ester or the nitrogen atom of the amine portion of the peptide linkage. The transition state can be neither isolated nor detected since it exists for only about 10−13 sec.
In molecular terms, these transition states reflect changes in bond lengths and bond angles as well as bond formations and breakages. The energy required to achieve a transition state is denoted as the activation energy which may also be considered as the difference in energy between the energy of the transition state and the energy of the reactants. According to Pauling's explanation, an enzyme preferentially binds the transition state of a reaction, thereby stabilizing it relative to the substrate and products and reducing the activation energy of the reaction, thus increasing the reaction rate. For example, aspartic proteinases are enzymes which are known to catalyze the hyrolysis of peptide linkages within a protein molecule.
By extending this explanation, Pauling also predicted that stable analogs of a transition state would bind tightly to an enzyme. In a discussion of substrate distortion as one of several possible sources of rate enhancement by enzymes, it has been suggested that the term “transition state analog” might be used to describe an inhibitor of this kind (1a).
The expression of binding energy to compensate for geometrical strain in the substrate is a popular but unlikely mechanism of catalysis. The intermolecular force field cannot overcome the intramolecular force field of the substrate (1).
Compensation of unfavorable solvation changes by the binding energy is also a possible mechanism of catalysis because of the large solvation energies of the polar groups and ions in water. Lone pairs which may act as general bases or nucleophiles will usually be solvated by hydrogen bonding from water or enzyme. Similarly, other reactive groups will usually be “neutralized” by hydrogen bonding or other mechanisms in the initial state of the enzyme. Usually these groups must be “desolvated” before reaction can occur. This process is energetically expensive and yet an essential part of the normal activation energy which may be compensated by favorable interactions between the non-reacting part of the substrate and the enzyme.
The expression of binding energy to compensate for unfavorable electrostatic interactions is another possible mechanism of catalysis. The juxtaposition of like charges could occur in the initial state but be removed in the transition state (2).
Pauling's prediction has become the basis for the now well-established approach to enzyme inhibitor design. The strategy for designing enzyme inhibitors has suggested a strategy for preparing catalytic antibodies whereby antigens are designed based upon mechanistic principles so that antibodies raised in response to such antigens will catalyze a chemical reaction by carrying out the reaction mechanism implicit in the design of the antigen. This strategy has been attempted a number of times.
For example, a transition-state analog mimicking an intramolecular 6-member ring cyclization transition state was used to elicit a monoclonal antibody which acted as a stereospecific, enzyme-like catalyst (3). Specifically, the monoclonal antibody so elicited accelerated, by about a factor of 170, the formation of a single enantiomer of a δ-lactone from the corresponding racemic δ-hydroxyester.
Similarily, monoaryl phosphonate esters, designated as analogs of the transition state in the hydrolysis of carboxylic esters, were synthesized and used as haptens to elicit specific monoclonal antibodies capable of catalyzing the hydrolysis of carboxylic esters (4). Certain of the antibodies elicited were reportedly found to be catalytic and selective for the hydrolysis of particular aryl esters.
Phosphonamidates or phosphonate analog-ligands having conformations that substantially correspond to the conformation of a hydrolytic transition state of an amide or ester ligand and which have been used to produce antibodies are described in U.S. Pat. No. 4,659,567 to Tramontano et al. (Tramontano). Antibodies so produced include a paratope that binds to and stabilizes the tetrahedral carbon atom of the amide or ester hydrolysis transition state of the ligand to hydrolyze the ligand at a predetermined site.
Analog-ligands which can be used to produce antibody catalysts for the hydrolysis of esters and amides are also described in European Patent Application 0,251,093 of Kollmorgen Corp. (Kollmorgen).
However, none of these analog ligands have been designed in accordance with a rational design approach which maximizes stabilization of the transition state and optimizes atomic relationships within the proteolytic transition state analog, thereby enabling the elicitation of antibodies capable of producing the two dramatic effects of enzyme catalysis; these are molecular recognition and rate acceleration.
In enzyme catalysis, groups on both the substrate and the enzyme which are not involved in the chemical mechanism of bond making and breaking, make an important contribution to catalysis. This is illustrated by examining a system where the mechanism is the same for both the enzyme and the non-enzyme catalyzed reaction. For example, the mechanism of action of succinyl-CoA acetoacetate transferase involves nucleophilic attack of the enzyme's glutamate carboxylate on the thioester succinyl CoA, [1] to give an anhydride intermediate (5). The second order rate constant for this reaction is 3×1013 fold greater than the analogous reaction of acetate with the same ester [2]:
Although the nucleophilicities of the carboxylates may be slightly different because of solvation effects and the enzyme may provide some other forms of catalysis these contributions will not be large. The non-reacting part of the enzyme therefore lowers the activation energy by up to 78 KJmol−1. Similarly, changing part of the substrate structure away from the atoms involved in bond making and breaking may also significantly effect catalytic efficiency. The enzyme forms anhydride intermediates from “non-specific” substrates [3]. Even though the chemical reactivities of the two substrates, [1] and [3], are similar, e.g. towards alkaline hydrolysis, the enzyme reaction proceeds up to 3×1012 fold faster with the so called specific substrate [1](5). The non-reacting part of the substrate—the CoA residue—lowers the activation energy by 72 KJmol−1 compared with [3].
Thus, the haptens disclosed in Tramontano do not provide the correct architecture to elicit antibodies that are capable of catalyzing the cleavage of a predetermined peptide sequence in a native protein. These haptens do not provide the correct side-chain groups for production of antibodies that can react with predetermined sites on a protein and cause selective proteolysis in a sequence specific manner. Furthermore, these haptens do not incorporate amino acid side-chain sub-sites on either side of the transition state analog. Without these sub-sites, the haptens cannot provide for the elicitation of catalytic antibodies capable of recognizing a specific amino acid sequence and selectively proteolyzing a peptide linkage within that sequence.
Moreover, the haptens disclosed in Tramontano do not incorporate leaving groups which facilitate and thereby promote proteolytic catalysis. FIG. 3 (6) depicts a representation of the expected free energy diagram for serine proteinase catalysis. In this mechanism, the enzyme provides a nucleophile (Ser-195). A mechanism involving only a single transition-state requires concerted general base/general acid catalysis by the imidazole (His-57) of the catalytic triad in which the hydrogen from Ser-195 is shared between the serine (Ser 195), imidazole (His-57) and a leaving group, an unlikely situation. Given that a discrete TI exists, there must be two transition states along the acylation pathway (as shown in FIGS. 3 and 4).
The stabilization of the carbonyl oxyanion by hydrogen bonds from the protein, the so called “oxyanion hole” in the serine proteinases, is clearly a critical component of the enzyme's catalytic apparatus. The key residue Asn-155 involved in this hydrogen bonding network has been modified by site-directed mutagenesis and results in a decrease of 2–3 orders of magnitude in Kcat, with little change in Km. Decreases in transition state stabilization of 2.2 to 4.7 Kcal mol−1 were observed.
The imidazole of His-57 plays two main roles in the acylation step; first, as a base to facilitate attack by the Ser hydroxyl in formation of the tetrahedral species; and second, as an acid in protonating the leaving group in formation of the acyl-enzyme. As shown in FIG. 5, the TI/imidazole system can exist in four ionization states, including the zwitterionic form [2] in which both the imidazole and the carbonyl oxygen are charged. Only the TI species [2] and [3] can directly give transition states leading to the acyl-enzyme. These transition states differ from one another in that the carbonyl oxygen atom is either protonated [3] or in the oxyanion form [2]. Factors involved in determining the actual reaction pathway include the relative pk's of the amine leaving group nitrogen, the serine oxygen and the carbonyl oxygen.
For example, an unprotonated amine nitrogen will be a much poorer leaving group than the serine in a tetrahedral transition state (compare pk's of approximately 30 for the former against 15 for the latter). Thus the zwitterionic forms of TI and TS should be less stable, but more efficient at expelling the leaving groups than the corresponding neutral forms. Consequently, the zwitterions are expected to be the catalytically relevant forms (7). Electrostatic interactions within the enzyme's active site will contribute significantly to stabilizing the zwitterionic species.
It has been estimated that the pk of the leaving group nitrogen for amide substrates is between 8 and 11 in species such as Tl2 (8). Thus, if the pk of the imidazole remains around 7 in the transition state, then the leaving group has a higher proton affinity than the imidazolium (9). Accordingly, breakdown to the acyl-enzyme would be expected prior to complete formation of the TI. Several lines of evidence, utilizing transition state analog inhibitors, suggest that the true pk of the imidazole in the tetrahedral species is much higher than 7. Although the discussion has centered on the acylation half of the reaction (which is usually the rate-limiting step for amide and peptide substrates) the principles regarding the transition state and tetrahedral intermediate are valid for the deacylation step as well.
Thus, for example, the aromatic compounds described in Tramontano do not lend themselves to provide antibodies that catalyze the hydrolysis of amide bonds in peptides or protein sequences since the pk's of these compounds are significantly more acidic (aniline pka=4.6; p-methylaniline pKa=5.0) and the transition state stabilization afforded by antibodies raised to these immunogens will not provide for hydrolysis of peptide amide bonds since the actual reaction pathways are different.
Moreover, catalysis occurs through stabilization of the transition state of a reaction. As described below, destabilization of the ground state enzyme/substrate complex relative to the transition state is also necessary for enzymatic catalysis; this prevents accumulation of the enzyme in the enzyme/substrate complex (compare antibody/antigen complex). As noted in Tramontano, it has been suggested that the induced fit mechanism can aid catalysis by providing ground state destabilization relative to the transition state. However, while the induced fit mechanism can increase the value of Km, which reflects the energy of enzyme/substrate complexes, no catalytic advantage is provided for the following reasons.
The requirement for destabilization of the enzyme/substrate ground state is illustrated by the reaction catalyzed by two hypothetical enzymes E in FIG. 6 (10,11). Referring to FIG. 6, curve A shows the energetics for the uncatalyzed reaction of substrate S in solution. Curve B shows the reaction when the enzyme stabilizes the ground state and the transition state (ES and ES↑) to the same extent. The enzymatic ground state, ES, is more stable than free S by the amount GB, and the transition state S by the same amount. For the enzymatic reaction depicted by curve B, the rate limiting step is ESEP, and the energetic barrier for this step is ΔGA. This is the same barrier as for the reaction of free S. Thus the enzyme depicted in curve B does not catalyze the reaction, even though the transition state is stablized by this enzyme.
Still referring to FIG. 6, curve C shows what the enzyme (or antibody) must do; i.e., the transition state complex (ES) must be stabilized as in curve B but the ground state complex (ES) must also be destabilized relative to that in curve B by the amount ΔGB. The energetic barrier for the reaction in curve C, ΔGC, is much less than the barrier for free S (curve A/ΔGA) or the barrier for the enzyme of curve B (also ΔGA). The destabilization of the ground state relative to the transition state that is brought about by the enzyme of curve C is necessary for catalysis. This destabilization corresponds to an increase in Km while the value of Kcat/Km remains constant.
Enzymatic catalysis will be increased by increasing the energy of the ES complex as long as the transition state energy is not also increased; again, this corresponds to an increase in Km at constant Kcat/Km(12,13). The enhanced efficiency from increasing Km can be explained as an advantage in minimizing the amount of enzyme tied up as ES and thus maximizing the amount of enzyme available for catalysis of the reaction: E+SE+P. The enhancement in the observed rate by increasing Km at constant Kcat/Km is large when the substrate concentration is near or above Km because enzyme, which is complexed with substrate when Km is low, becomes available for catalysis. When the substrate concentration is well below Km a further increase in Km at constant Kcat/Km will yield no advantage because essentially all the enzyme is free and already catalyzing the reaction with the apparent second order rate constant Kcat/Km.
The fact that the second order rated constant for reacton of free enzyme and free substrate is Kcat/Km can be derived from the Michaelis-Menten equation:   ν  =                                          K            cat                                          [            S            ]                                            [          E          ]                          tot                      [        S        ]            +              K        m
At low substrate concentration ([S]<<Km), all of the enzyme is free and the Michaelis-Menten equation reduces to ν=(Kcat/Km) [S][E]tot. At high substrate concentration ([S]>>Km), all of the enzyme is in the form ES and the Michaelis-Menten equation reduces to ν=Kcat[E]tot.
Although an increase in Km at constant Kcat/Km is useful for catalysis, the induced fit mechanism increases Km but decreases Kcat/Km, in fact lessening catalysis (13). The decrease is Kcat/Km for the induced fit enzyme relative to the non-induced fit enzyme arises because some of the energy that is used to stabilize the transition state for the non-induced fit must be used to drive the conformational change of the induced fit enzyme. An equivalent explanation is that the decrease is Kcat/Km arises from a lower concentrtion of the active enzyme conformation in the induced fit mechanism (14).
The mechanism by which antibodies both destabilize the ground state complex and express intrinsic binding energy for the transition state of the particular reaction to be catalyzed has not been completely understood. An induced fit mechanism for antibody-antigen interaction has been proposed for a monoclonal anti-fluorescein-fluorescein hapten system (15). The binding of the antibody to the hapten was found to display a two-step mechanism; formation of an encounter complex followed by a tightening of binding to the hapten in an “induced fit” mechanism allowing for suitable contact interactions between the antibody combining site and the bound fluorescein ligand. If such a mechanism operates in binding of antibodies to their respective antigenic ligands then there exists an analogy between antibody/antigen interactions and enzyme/substrate interactions.
In order for antibodies to function as catalysts, design of the immunogen is crucial for allowing expression of binding energy for the transition state of the reaction. In order for antibodies to destabilize the antibody substrate complex, some form of conformational control of the immunogen is required which will allow for the production of strain and/or distortion of the substrate towards a transition-state trajectory in energetic terms.
Therefore, the immunogens described in Tramontano and Kollmorgen do not incorporate all these necessary features to provide for antibodies having catalytic function because they have not been rationally designed from knowledge of the mechanistic features of enzyme catalysis. Accordingly, they do not provide suitable templates for generating antibody combining sites endowed with catalytic properties.


Field of the Disclosure
This application relates, in general, to wake control systems for a watercraft, and some embodiments relate to surf wake systems for modifying a wake produced by a watercraft travelling through water.
Description of the Related Art
Wake surfing has become increasingly popular in recent years because, unlike an ocean wave, a wake produced by a watercraft is on-demand not to mention continuous and endless as long as the watercraft is moving forward. As a watercraft travels through water, the watercraft displaces water and thus generates waves including bow wave and diverging stern waves on both sides of the watercraft. Due to pressure differences, these waves generally converge in the hollow formed behind the traveling watercraft and/or interfere with each other to form a wake behind the watercraft. Such a wake, however, is generally small, choppy or too close to the watercraft to be suitable and safe for water sports, and particularly not suitable for wake boarding or surfing.
To facilitate surfing, a wake can be formed away from the stern of the watercraft, for example, about ten feet away, and with a waist-height peak, for example, about three feet or higher. Those of skill in the art will understand that a wake for wake surfing can be formed at various different distances behind the watercraft, and the wake can have various different heights. Generally hundreds, and sometimes thousands, of pounds of additional weight or ballast to a rear corner of the watercraft to make the watercraft tilt to one side, displaces more water, and hence generates a larger wake on that side. Such additional weight may be in the form of removable ballast bags, installed ballast tanks or bladders, or passengers positioned to one side of the watercraft, which is primarily used to tip the watercraft to that side. Using such additional weight to produce larger wakes, however, poses several disadvantages. For example, such additional weight may take up significant space and capacity that may otherwise reduce the passenger capacity of the watercraft. Also, such additional weight may unbalance the watercraft creating difficulties in control. Moreover, the additional weight generally must be moved from one side of the water craft to the other in order to generate a wake on the other side of the water craft. Shifting such additional weight may require significant time and effort. For example, filling and emptying ballast tanks to switch from one side to the other may require 20 minutes or more.
In light of the foregoing, it would therefore be useful to provide surf wake system that overcomes the above and other disadvantages.


In well drilling, particularly for oil or gas, casing is cemented in the well to seal off the formation. For pressure control and the protection of fresh water formations, the well will have multiple strings of casing, each string of casing being smaller in diameter than the one above. In one technique, each string of casing extends completely to the surface where it is supported at a wellhead by a casing hanger. In another technique, liners are employed. A liner is a string of casing that will overlap the next upward string of casing, but will not extend completely to the surface. This avoids additional costs of several strings of concentric casing in the shallower portions of the well.
The upper end of the liner has to be remotely attached by a liner hanger to the casing, normally near the lower end of the casing. When installing a liner, normally a special section of pipe, called a mandrel, will be attached to the upper end of the liner. The mandrel will be machined to accept the liner hanger assembly. Because the mandrel must have a performance rating equal to the pipe of the liner, normally the customer will supply for machining a section of the actual liner to be used. A running tool will engage the mandrel, and the entire assembly will be lowered into the well. After the liner reaches bottom, the operator will actuate the liner hanger to secure the mandrel to the casing.
The operator will cement the liner into the well, in some cases before actuating the liner hanger, on other cases after. Usually a cement bushing will be employed with the running tool to locate inside the mandrel. This cement bushing engages the mandrel to support the running tool and drill pipe against an upward force that occurs while pumping the cement down the drill pipe. After the cement has set and the liner hanger has been set, the operator withdraws the running tool and cement bushing. The mandrel and liner hanger assembly will remain in the well.
There are many different types of liner hangers and different techniques employed for setting liner hangers. In one technique, hydraulic force is used to set the liner hanger. The hydraulic force may be supplied by pumps on the rig pumping down the drill pipe. The flow must be diverted through a fluid port in the running tool and the mandrel to apply the fluid pressure to the liner hanger on the exterior of the mandrel. The flow is diverted by dropping a ball or dart from the surface, which opens and closes various passages once seated. A considerable amount of time is required for the ball to reach the running tool, often several hours. During this time period, the operator is normally unable to circulate fluid through the liner. If the liner has not already been cemented in place, keeping the liner stationary in an open hole without the ability to circulate can be dangerous.
In another hydraulic type, hydraulic force is supplied by a hydraulic chamber exposed to wellbore fluids. The operator must raise and lower the drill pipe to provide the increased pressure. This system may prevent the operator from raising and lowering the drill pipe prior to setting for other purposes.
Other liner hangers are operated mechanically, which involves rotating and moving the drill pipe axially to actuate the liner hanger. For example, J-pins and J-slots may be employed which, when rotated, move the liner hanger to different positions. In highly deviated wells, it is difficult to rotate the drill pipe. Other mechanical running tools do not have the ability for the operator to stroke the liner up and down after the liner reaches bottom without causing setting of the hanger. As a result, the operator may be unable to reciprocate the liner during cementing, which often is a good procedure to follow.
The requirement of specially prepared mandrels is a disadvantage. The machining is done at a shop, not in the field. Consequently, delays may occur, and it is costly to ship the liner section to a shop and back to a wellsite. Moreover, in some costly corrosion-resisting casing strings, machining may damage the properties of the mandrel. Inspections are necessary to make sure that the machining operations have not harmed the metal of the pipe.
Additionally, in very long liners it may be desired to spread the load support by the liner hanger to the casing at various points along the overlapped region. Liner hangers used, however, support the liner only at the top of the liner. Other liner hanger systems and running tools may not have the ability to automatically fill the drill pipe while the liner is being run. The customer may prefer to have the drill pipe filled while being run. If so, then the customer must manually fill it from the drill rig, which takes additionally time.


This invention relates to bioadhesive compositions, particularly electrically conductive hydrogel compositions having bioadhesive properties. The invention further relates to biomedical skin electrodes incorporating such hydrogel bioadhesive compositions that are electrically conductive.
Biomedical skin electrodes are widely used in a variety of situations, whenever for example it is required to establish an electrical connection between the surface of the body of the patient and external medical equipment for transmission of electrical signals.
Modem medicine uses many medical procedures where electrical signals or currents are received from or delivered to a patient""s body. The interface between medical equipment used in these procedures and the skin of the patient is usually some sort of biomedical electrode. Such electrodes typically include a conductor which must be connected electrically to the equipment, and a conductive medium adhered to or otherwise contacting skin of the patient, and they are of varying types with a wide variety of design configurations which will generally depend on their intended use and whether for example they are to be used as transmission electrodes or sensing i.e. monitoring electrodes.
Among the therapeutic procedures using biomedical electrodes are transcutaneous electric nerve stimulation (TENS) devices used for pain management; neuromuscular stimulation (NMS) used for treating conditions such as scoliosis; defibrillation electrodes to dispense electrical energy to a chest cavity of a mammalian patient to defibrillate heart beats of the patient; and dispersive electrodes to receive electrical energy dispensed into an incision made during electrosurgery.
Among diagnostic procedures using biomedical electrodes are monitors of electrical output from body functions, such as electrocardiograms (ECG) for monitoring heart activity and for diagnosing heart abnormalities.
For each diagnostic, therapeutic, or electrosurgical procedure, at least one biomedical electrode having an ionically conductive medium containing an electrolyte is adhered to or is otherwise contacted with mammalian skin at a location of interest and is also electrically connected to electrical diagnostic, therapeutic, or electrosurgical equipment. A critical component of the biomedical electrode is the conductive medium which serves as the interface between the mammalian skin and the diagnostic, therapeutic, or electrosurgical equipment, and which is usually an ionically conductive medium.
Biomedical electrodes are used among other purposes to monitor and diagnose a patient""s cardiovascular activity. Diagnostic electrodes are used to monitor the patient immediately and are only applied to the patient for about five to ten minutes. Monitoring electrodes, however, are used on patients in intensive care for up to three days continuously. In contrast, Holter electrodes are used to monitor a patient during strenuous and daily activities.
Although all of the biomedical electrodes just referred to are used to record cardiovascular activity, each electrode requires specific features or characteristics to be successful. Thus, the diagnostic electrode does not have to remain adhered to a patient for extensive periods but it does have to adhere to hairy, oily, dry and wet skin effectively for the five to ten minutes of use. The monitoring electrode has to adhere for a longer period of time although the patient is often immobile during the monitoring period. The Holter electrodes is susceptible to disruption from adhesion due to physical motion, perspiration, water, etc., and therefore requires the best adhesion and at the same time comfort and electrical performance.
In the biomedical electrodes known in the prior art the ionically conductive medium which serves as an interface, between the skin of a mammalian patient and the electrical instrumentation, ranges from conductive gels and creams to conductive pressure sensitive adhesives. However, while the conductive media can be in the form of pressure sensitive conductive adhesives, for monitoring or Holter biomedical electrode use such conductive adhesives are not generally adequate on their own to maintain adhesion to mammalian skin and additional hypoallergenic and hydrophobic pressure sensitive adhesives may be employed around the conductive medium to provide the required mammalian skin adhesion. U.S. Pat. No. 5,012,810 (Strand et al.) and U.S. Pat. Nos. 4,527,087, 4,539,996, 4,554,924 and 4,848,353 (all Engel) are examples of documents that disclose biomedical electrodes which have a hydrophobic pressure sensitive adhesive surrounding the conductive medium.
In general, a desirable skin electrode is one which maintains good electrical contact with the skin and is free of localised current hot spots, i.e. exhibits uniform conductivity. For example, it has been found that a prior art electrode utilising karaya gum tends to creep in use and flatten out, exposing skin to possible direct contact with the current distribution member or lead wire. A desirable skin electrode should also usually have a low electrical impedance.
It is an object of this invention to provide hydrogel adhesives possessing controlled and predictable adhesive properties which may be readily varied to suit different uses and, in the case of medical electrodes or similar devices, different configurations or applications. It is also an object of the invention to provide such hydrogel adhesives which in addition may possess superior electrical characteristics as compared to those commonly associated with bioadhesive hydrogels.


The present invention relates to a write control device, and more specifically, to a technology for rapidly performing a write operation of a nonvolatile memory device configured to sense data based on resistance change.
Generally, memory devices may be classified as volatile memory devices or nonvolatile memory devices. A nonvolatile memory device includes a nonvolatile memory cell capable of preserving stored data even when a power source is off. A nonvolatile memory device may be implemented, for example, as a flash random access memory (RAM) device, a phase change RAM (PCRAM) device, or the like.
PCRAM devices include memory cells that are implemented using a phase change material, for example, germanium antimony tellurium (GST), and are configured to store data in the memory cells by applying heat to the GST so that the GST changes into a crystalline phase or an amorphous phase.
A nonvolatile memory device, such as a magnetic memory device, a phase change memory (PCM) device, or the like, has a data processing speed similar to that of a volatile RAM device. However, unlike a volatile RAM device, a nonvolatile memory device preserves data even when a power source is off.
FIGS. 1a and 1b illustrates a conventional phase change resistance device 4.
Referring to FIGS. 1a and 1b, a conventional phase change resistance device 4 includes an upper electrode 1, a lower electrode 3, and a phase change material 2 interposed between the upper electrode 1 and the lower electrode 3. When a voltage is applied to the upper electrode 1 and the lower electrode 3, a current flows into the phase change material 2, thus inducing a high temperature in the phase change material 2. As a result, the electrical conductive state of the phase change material 2 changes depending on resistance variation due to the high temperature.
FIGS. 2a and 2b illustrate a phase change principle of the conventional phase change resistance device 4.
Referring to FIG. 2a, if a low current smaller than a critical value flows into the phase change resistance device 4, the phase change material 2 is crystallized. When the phase change material 2 changes into a crystalline phase, it becomes a low resistance material. As a result, a current can flow between the upper electrode 1 and the lower electrode 3.
On the other hand, referring to FIG. 2b, if a high current greater than the critical value flows into the phase change resistance device 4, the phase change material 2 has a temperature higher than a quenching point. When the phase change material 2 changes into an amorphous phase, i.e., a non-crystalline phase, it becomes a high resistance material. As a result, a current cannot easily flow between the upper electrode 1 and the lower electrode 3.
The phase change resistance device 4 can store data corresponding to two resistance phases. That is, in one case, if a low resistance phase in the phase change resistance device corresponds to a data “1,” and a high resistance phase corresponds to a data “0,” then the phase change resistance device 4 may store two logic states of data.
This data can be stored in the phase change resistance device 4 as nonvolatile data because the status of the phase change material 2 does not change even when a power source is off.
FIG. 3 illustrates a write operation of a conventional phase change resistance cell.
Referring to FIG. 3, heat is generated if a current flows between the upper electrode 1 and the lower electrode 3 of the phase change resistance device 4 for a given time.
If a low current, smaller than the critical value, flows for a given time, the phase change material 2 changes into a crystalline phase. As a result, the phase change resistance device 4 becomes a low resistance element having a set phase.
On the other hand, if a high current, greater than the critical value, flows for a given time, the phase change material 2 changes into an amorphous phase. As a result, the phase change resistance device 4 becomes a high resistance element having a reset phase.
Accordingly, a low voltage is applied to the phase change resistance device 4 for a long period of time in order to write the set phase in the write operation.
On the other hand, a high voltage is applied to the phase change resistance device 4 for a short period of time in order to write the reset phase in the write operation.
To change the phase change resistance cell into the set phase, it is important to control a quenching slope of a set write current, which is required for crystallizing the phase change resistance cell, by gradually reducing an amount of the set write current. This way of gradually reducing the set write current is called “quenching.”
However, for example, if a reference current, which is used to generate the set write current and is received from the outside or generated inside the chip, changes by some factors or if a clock having a wrong value is generated by mismatched circuits, the set write current may be generated with an undesired quenching slope.
Moreover, without accurately checking the quenching slope, it is impossible to precisely control the phase change resistance cell in program and verify (PNV) operations and a multi-level cell MLC where multi-leveled resistance distribution of a phase change material, e.g., germanium antimony tellurium (GST), is formed.
Meanwhile, a conventional nonvolatile memory device controls a driving voltage supplied to a memory cell array in a program operation using a write driving unit.
The write driving unit is configured to stably supply a write current even though the write current has a small current value. However, it takes a much longer time to supply cells with the write current when using a small current value than when using a large current value.
That is, when the write driving unit supplies a small write current to the cells, it takes much longer to supply the current because of parasitic components on a write path.
FIG. 4 illustrates a write time that is delayed by a large parasitic component and a small write current. Here, IT represents a driving current flowing in a driving transistor of the write driving unit, and IM represents a cell current flowing in a memory cell.
Referring to FIG. 4, the driving current IT flowing in the driving transistor reaches a stabilized current level after a settling time tsettling passes. In addition, there is a time delay due to parasitic components on a write path. A time delay tDELAY occurs in a period of time where the driving current IT of the driving transistor is transmitted to the memory cell.
A small write current is generally determined by characteristics of cells and the size of a cell array. As the size of the cell array becomes larger, the delay time occurring due to the parasitic components on the write path also become greater.
In this way, the write time becomes longer by the small write current and the large size of the cell array. A conventional write driving unit has not introduced improvements to such a write time delay phenomenon.


1. Field of the Invention
This invention pertains to a resolver to digital converter and more particularly to a resolver to digital converter which uses digital signals to provide accurate control of the excitation voltages applied to the resolver windings so that the accuracy of the digital output representation is improved.
2. Description of the Prior Art
In many types of equipment it is desirable to reliably and accurately measure the position of a rotatable shaft and to convert the resulting measurement into a digital signal which is representative of the shaft position. One such type of equipment where it is desirable to digitally measure angular position is a weapons delivery system where the elevation and azimuth pointing angles must be accurately measured. Some of the prior art converters make use of the conventional resolver or synchro transmitter having a rotor winding and a plurality of stationary windings. A voltage source and a phase shifter supply multiphase AC voltages to the stator windings to induce a magnetic flux which rotates at the frequency of the applied voltage and induces an AC voltage in the rotor winding. The AC voltage in the rotor winding has a phase angle which varies with the angular position of the rotor. Thus, the angular position of the rotor can be determined by measuring the difference in phase angle between the voltage induced in the rotor winding and a fixed reference voltage. Such difference can be measured by determining the time which elapsed between the zero passage of the reference voltage and the zero passage of voltage from the rotor winding, and this time can be expressed as a digital representation of the rotor angle. A serious disadvantage of the foregoing type of equipment is that a very high degree of accuracy must be maintained between the phase of the voltages applied to the various stator windings. Aging of the components used in the circuitry may cause a change in phase between the voltages applied to the various stator windings and therefore cause inaccuracies in the measured angle between the reference voltage and the voltage produced by the rotor winding. These inaccuracies lead to an inaccurate output reading of the angular position of the rotor.
One type of prior art apparatus as shown in prior U.S. Pat. No. 3,634,838, uses a high-frequency signal source to develop signals for the stator windings of a resolver or goniometer having three stator windings and a rotor winding. The signal source develops high-frequency pulses which are reduced to low-frequency pulses by a frequency divider. The output of the frequency divider is coupled to a filter which converts the pulses into a sinusoidal voltage that is coupled to one of the stator windings. The sinusoidal voltage from the filter is applied to a first stator winding and to a 90.degree. phase shifter. The phase shifter develops a second sinusoidal voltage shifted 90.degree. from the first voltage, the second sinusoidal voltage being applied to a second stator winding. A counter which is coupled to the signal source is used to count the high-frequency periods. In addition, a phase detector is provided for comparing the phase of an output voltage from the counter with that of a reference voltage from the goniometer. The phase of the pulses from the frequency divider is controlled relative to the phase of the voltage from the counter by varying the number of pulses supplied to the frequency divider. This prior art apparatus has no provision for correcting any variation in the phase angle between the voltages applied to the first and second stator windings of the goniometer.


In a conventional electromagnetic relay described in JP-A-2008-226547, two fixed contact supports having two fixed contacts respectively are positioned, and two movable contacts are contacted by and separated from the two fixed contacts by moving one movable body, to which the two movable contacts are fixed, so that an electrical circuit is opened and closed. More specifically, the electromagnetic relay includes a movable member driven by electromagnetic force of a coil, a pressure spring for urging the movable body such that the movable contacts contact the fixed contacts, a return spring for urging the movable body via the movable member such that the movable contacts are separated from the fixed contacts, and the like. Further, a contact surface between the movable contacts and the fixed contacts is a spherical surface.
When the coil is energized, the movable member is driven toward a side away from the movable body by the electromagnetic force, and the movable body is urged by the pressure spring to be moved. As a result, the movable contacts contact the fixed contacts, and the movable member is separated from the movable body.
In a conventional electromagnetic relay described in JP-A-62-51126, two fixed contact supports having two fixed contacts respectively are positioned, and two movable contacts are contacted by and separated from the two fixed contacts by moving one movable body, to which the two movable contacts are fixed, so that an electrical circuit is opened and closed. More specifically, the movable body is integrated with a movable member that is driven by electromagnetic force of a coil such that the movable body can be relatively moved, the movable body is held at a predetermined position of the movable member by a pressure spring, and the movable member and the movable body are urged by a return spring such that the movable contacts are separated from the fixed contacts. Further, a contact surface between the movable contacts and the fixed contacts is a spherical surface.
When the coil is energized, the movable member and the movable body are driven by the electromagnetic force and the movable contacts contact the fixed contacts. At this time, the pressure spring is bent by a stroke of the movement of the movable member after the movable contacts contact the fixed contacts, thereby the movable member and the movable body are relatively moved.
However, in the electromagnetic relay described in JP-A-2008-226547, because the contact surface is a spherical surface, the movable contacts contact the fixed contacts by point contact. When the coil is energized, the movable contacts contact the fixed contacts by two-points contact, that is, at a first contact portion between one fixed contact and one movable contact, and a second contact portion between the other fixed contact and the other movable contact. In this manner, because the movable contacts contact the fixed contacts by the point contact, i.e., the two-points contact, the movable body may vibrate around a line passing through the first and second contact portions when the movable contacts collide with the fixed contacts. In particular, in the electromagnetic relay described in JP-A-2008-226547, because the movable member is separated from the movable body when the movable contacts contact the fixed contacts, the vibration suppression effect by the movable member cannot be obtained, and thereby it becomes difficult to suppress the vibration of the movable body. Thus, the vibration of the movable body may be resonated in a casing to generate abnormal noise.
In the electromagnetic relay described in JP-A-62-51126, because the movable body is integrated with the movable member, it is easy to suppress vibration of the movable body when the movable contacts collide with the fixed contacts. However, a position of a contact portion is changed in accordance with the vibration of the movable body until the vibration of the movable body is suppressed. Thus, a resistance value between the contacts is changed, and thereby it becomes easy for the contact portion to generate heat and the wear-and-tear of the contacts may occur.


The invention relates to an improved side-guiding mechanism for a folding machine. In particular, the invention relates to an improved side guiding mechanism for a folding machine which makes outserts.
An outsert is a sheet which is folded a number of times with the outermost fold being glued tight to an inner fold in order to make a tightly folded packet. FIG. 1 illustrates a typical outsert 12 wherein a last wrap-around panel 14 is adhered by a glue or adhesive spot 15 to an adjacent inner fold 16 to complete outsert 12. Outserts are often very long, for instance, 9 to 50 inches in length, and are often used by the pharmaceutical industry to provide information concerning the drug to which the outsert is attached. Such information might include instructions for use or warnings about possible side effects of the drug. Generally, they are attached to the bottle or box in which the drug is packaged.
U.S. Pat. No. 4,812,195 (incorporated herein by reference) describes an apparatus for automatically forming sheets from a web of material. The apparatus described therein includes an outsert attachment which is attached to the rest of the folding apparatus. The outsert attachment folds and glues the sheets in such a manner as to form outserts similar to the one shown in FIG. 1. FIG. 2, which is adapted from U.S. Pat. No. 4,812,195, illustrates this prior art apparatus for forming outserts of a predetermined length from a web 20 by accumulating long lengths, for example, up to 50 inches of the web 20, in an accumulator 28. A photocell 29 detects marks on the web 20 to operate a severing means 31 at a sheet station 26 to form sheets 11 each of which is the same size. A sheet conveyor 35 extends from the sheet station 26 to a folding station 33. At the folding station 33, folding plates 37 and rollers.(not shown) fold the sheets 11 into the form shown on conveyor 38. As can be seen, a sheet 11 at this point has a folded portion 39 and an unfolded wraparound panel 14, with the folded portion 39 leading the wrap-around panel 14 in the direction of travel shown by the arrow. The conveyor 38 conveys the sheet in this fashion into a wraparound and gluing station 40 of the outsert attachment.
The precision of the last fold, and the gluing of the wraparound fold 14, is accomplished by precisely positioning the folded sheet at the wraparound and gluing station 40. More specifically, the leading edge of the folded portion 39 is stopped in its forward travel by stops 41 and, in a fraction of a second of its stopping, a side jogging mechanism 42 is activated to push the folded sheet against a side stop 43 to that the sheet is positioned precisely. As soon as this occurs, an adhesive applicator 45 is actuated to apply one or more adhesive spots 15 to the folded section 39. Immediately following this, a folding means 48 which includes an overhead folding knife 49 is operated to fold the wraparound fold 14 against the adhesive spots 15 on the inner fold 16 thereby adhering the folds together and completing the formation of the outsert.
Typically, the sheet is printed with several outserts side-by-side which must then be separated. To accomplish this, the overhead folding knife 49 which engages the folded section 39 of the folded sheets pushes the folded section 39 into the nip of underlying folding rollers 50. The folding rollers 50 force the wraparound fold 14 tightly against the glue spots 15 and against the inner fold 16 to complete the outsert. The folding rollers 50 are also provided with circular knives 53 mounted on a pair of slitting rollers. 52 which slit the sheet into a multiplicity of side-by-side outserts. The outserts are then re-oriented and discharged automatically in an edge position into a container 22.
FIG. 3, which is also adapted from U.S. Pat. No. 4,812,195, illustrates in detail the side guiding mechanism used in the apparatus described therein. The illustrated side jogger 42 comprises a solenoid 150, slidably mounted on a support slide bracket 151 mounted on the inside of a stationary side frame member 156. The support bracket 151 has a slide channel 152 into which is mounted slide 153. Suitable lock fasteners 154 lock the slide 153 in position on the slide bracket 151 to position the solenoid plunger 158. Thus, the solenoid 150 can be positioned to accommodate various widths of sheets to be side jogged. The solenoid 150 includes a plunger 158 with a sheet pusher 159 mounted at its end. The sheet pusher 159 abuts against the side edge 39a of the folded sheet to push the same laterally, thereby bringing an opposite edge 39b of the folded sheet against the side stop 43 while the sheet slides along and against the forward stops 41. The solenoid 150 includes a return spring 161 extending between a head 162 on the plunger and the solenoid body 163. A stop nut 164 on the other threaded end 165 of the solenoid limits the return travel by the spring 161.
The operation of the side jogger is as follows. The plunger/pusher 158/159, when activated by electronic sensing means, pushes the mostly folded paper against the side stop 43. This aligns (i.e., side-guides) the folded sheet for positive and consistent gluing and slitting. As the width of the mostly folded paper varies between different jobs in a typical range of 7 to 9 inches, and as the width of the paper may vary by about 1/16 of an inch during the course of a single job, a simple and safe method of adjusting both the plunger/pusher 158/159 and the side stop 43 is essential for the efficient and safe operation of the outsert attachment.
In the apparatus of U.S. Pat. No. 4,812,195, the plunger 158 extends through the body of the solenoid 150, and when the solenoid is electrically activated, the pusher 159 mounted on the end of plunger 158 travels approximately 1/4 inch to 1/2 inch. The pusher/plunger is then returned to its original position by means of spring 161. The whole assembly is bolted directly onto the side frame member 156 of the outsert attachment. While the apparatus of U.S. Pat. No. 4,812,195 discloses that adjustment is possible by sliding the entire side jogging mechanism in slide bracket 151, the commercial embodiment of this apparatus is sold without this slide mechanism. In commercially available machines, the adjustment is maintained by the use of the locknut 154 and associated washers probably because the slide mechanism is unable to maintain the desired position of the pusher/plunger during the course of the run. The locknut and washers used in the commercial embodiment permit only a limited amount of adjustment for different jobs. The locknut and washers serve a dual purpose as they also regulate the amount of the plunger's return travel to the side frame member. Because the travel distance is severely limited, the operator must maintain an inventory of different size plungers and pushers to accommodate the various widths of outserts for different jobs.
When setting up the outsert attachment for actual operation, the proper combination of plungers and pushers has to be selected and then adjusted. At the same time, the position of the side stop also has to be adjusted. The stop is bolted directly onto the folding machine which is mounted inside the side frame members of the outsert attachment. To adjust the stopper, a set screw (not shown) has to be loosened and then the stopper can be slid to the desired position. The set screw is then tightened to hold it in place. As the stopper slides freely, finding a proper position can be very difficult. This is especially true since the stopper often slips out of position and requires further adjustment when the set screw is tightened. The entire process of finding the proper plunger/pusher combination and adjustment, and the proper stopper adjustment can take as long as an hour in an initial machine setup. Furthermore, during the course of a run, constant adjustment is required as the width of the mostly folded sheet may vary by as much as 1/16 of an inch. These adjustments add hours to the time needed to complete a run.
Additionally, because the above-described adjustment process is so cumbersome, it is often carried out in a dangerous manner. As it is quite difficult to make the proper adjustments while the machine is idle, many operators are tempted to make adjustments "on the fly," i.e., while the machine is running. When the adjustments are made on the fly, the operator can see very well if the outserts are being side-guided properly. However, the problem in making adjustments on the fly is that there are many moving metal parts in the immediate proximity of the pusher/plunger and side stop, including the circular slitting knives. It is exceedingly dangerous to make any adjustments at all while the slitting knives are in operation. Many accidents have occurred in this manner.
Another disadvantage of mounting the side stop directly onto the folding apparatus is that from time to time, the outsert attachment has to be removed from the rest of the machine for repair during a job. In such cases, the side stop also has to be removed and then re-installed when the outsert attachment is replaced. This entails the re-adjustment once again of the side stop with all the inconveniences associated therewith.
Accordingly, it is an object of the present invention to provide an outsert attachment which has a more efficient and a safer mechanism for adjusting the plunger/pusher and side stop combination.


Silicon is a common semiconductive material used in the fabrication of integrated circuits. Silicon can occur in crystalline and amorphous forms, and when crystalline can be monocrystalline or polycrystalline. In some instances, silicon is combined with germanium, essentially forming a silicon germanium alloy. Such materials can be doped with conductivity enhancing impurities (i.e., boron and/or phosphorus) to modify the conducting characteristics of the silicon-comprising material.
Monocrystalline silicon can be provided in bulk substrate form or otherwise grown or deposited epitaxially from an exposed monocrystalline material. Epitaxy generally involves the growth or deposition of a single or monocrystalline layer of material such that the epitaxial layer has a crystal orientation which is common to that of the material from which it is grown. One factor that determines the quality of the epitaxial silicon-comprising layer relates to the presence and quantity of crystallographic defects. Such are non-uniformities in the crystal structure of the epitaxial layer. Many of these defects are caused by defects appearing at the surface of the substrate which propagate into the layer during growth. Examples include sidewall dislocations and stacking faults. Dislocations and stacking faults can be electrically active more so than the surrounding material within the epitaxial layer due to the presence of dangling bonds. Such can lead to unnecessary recombination generation currents, lower breakdown voltages, higher current leakage and larger junction ideality factors.
One place where epitaxial silicon has been utilized is as one or more of the components in a field effect transistor. Transistor structures comprise a channel region received between a pair of source/drain regions, and a gate configured to electrically connect the source/drain regions to one another through the channel region. The transistor constructions utilized in semiconductor constructions are supported by a semiconductor substrate. The semiconductor substrate will have a primary surface which can be considered to define a horizontal direction. Transistor devices can be divided into two broad categories based upon the orientations of the channel regions relative to the primary surface of the semiconductor substrate. Specifically, transistor structures which have channel regions that are primarily parallel to the primary surface of the substrate are referred to as planar or horizontal transistor structures, and those having channel regions which are generally perpendicular to the primary surface of the substrate are referred to as vertical transistor structures. Since current flow between the source and drain regions of a transistor device occurs through the channel region, planar transistor devices can be distinguished from vertical transistor devices based upon the direction of current flow as well as on the general orientation of the channel region. Specifically, vertical transistor devices are devices in which the current flow between the source and drain regions of the devices is primarily substantially orthogonal to a primary surface of a semiconductor substrate, and planar or horizontal transistor devices are devices in which the current flow between source and drain regions is primarily parallel to the primary surface of the semiconductor substrate.
Epitaxial silicon-comprising materials have been proposed for use in channel regions of vertical transistors. Further, one or both of the source/drain areas of a vertical transistor might also comprise epitaxially grown silicon or an epitaxially grown silicon germanium alloy. Requirements for epitaxial materials within a vertically oriented channel region are typically more stringent than for the use of such material in source/drain regions of horizontally oriented field effect transistors. Further, fabrication of vertical field effect transistors typically utilizes masks of oxide, nitride or other materials for self-aligned patterning of the epitaxial silicon-comprising material during its formation. The interface of the epi with these materials can be a defect source. Further, the selective epitaxial growth of silicon for vertical transistors typically utilizes lower deposition temperatures as compared to blanket epitaxial silicon depositions. Unfortunately, the use of lower temperatures reduces surface mobility and can also result in increased defects over that of higher temperature processing. Also and regardless, thermal stress can be generated during cool-down of the substrate from the temperature at which the epitaxial silicon-comprising material was grown. This can result in crystallographic defects being generated after growth.
Further, where the epitaxial silicon-comprising material includes germanium, such has an increased tendency for defect formation on the surface during deposition due to mismatched lattice constants of silicon and germanium. These defects propagate and either terminate with other defects or at the surface. Regardless, after deposition, crystallographic defects are extremely difficult to remove or heal within the bulk epitaxially grown material or at interfaces of such material with other materials.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.


Polymeric aromatic carbamic acid esters (polyurethanes) such as diphenylmethane dicarbamates and the related higher homologs polymethylene polyphenyl carbamates have become increasingly important products particularly, for use in the preparation of the commercially valuable diphenylmethane diisocyanates and mixtures of diisocyanates and the polyisocyanates by the decomposition of such polymeric aromatic carbamic acid esters in a suitable solvent as shown in Rosenthal et al, U.S. Pat. Nos. 3,962,302, June 8, 1976 and 3,919,279, Nov. 11, 1975.
At the present time there is no known successful commercial method for the direct preparation of polymeric aromatic esters of carbamic acid. The corresponding diphenylmethane diisocyanates and polyisocyanates, available commercially, are largely produced by the phosgenation of mixtures of diamines and polyamines obtained by the condensation of aniline and formaldehyde with catalytic quantities of a mineral acid as for example, disclosed in the Pistor et al, U.S. Pat. No. 4,014,914.
A proposed prior art process for the preparation of polymeric aromatic carbamic acid esters (polyurethanes) is disclosed in Klauke et al, U.S. Pat. No. 2,946,768 and involves the condensation of aryl carbamic acid esters with carbonyl compounds in a dilute aqueous acid condensation medium. However, in such process the carbonyl compound such as formaldehyde tends to react at the nitrogen of the carbamate to produce, along with desired polyurethanes, varying amounts, i.e., generally between 15 percent and 50 percent by weight, of undesirable (alkoxycarbonyl)phenylaminomethylphenyl compounds which includes the various dimers, trimers, tetramers, etc. of such compounds (also referred to herein as "N-benzyl" compounds). Attempts to prepare mono or diisocyanates and polyisocyanates or to otherwise use the mixture containing the undesired N-benzyl compounds, which cannot be converted to an isocyanate by pyrolysis, and polyurethanes presents many problems since there is no known method for separating the polyurethanes from the N-benzyl impurities.


A multitude of security devices exists within the prior art which teach the use of supplementary devices in conjunction with a typical latching arrangement for preventing undesirable access to one's premises. Examples of such devices are supplementary chains, dead bolts and latches.
U.S. Pat. No. 4,484,463 issued on Nov. 27th, 1984 by Hennessy describes a door lock guard for protecting the cylinder of a door lock upon the key cylinder side. Such door lock is permanently mounted as best illustrated in FIG. 3 by fastening elements 46. The shape of portion 18 of plate 12 formed from the appropriate materials ensures that the cylinder 34 cannot be accessed by a tool and subsequently rotated.
U.S. Pat. No. 4,074,552 describes a kit which adapts to a lock preventing tampering of the lock thus undesirable access to one's premises. Such a combination is accessible only by a special long key which will turn the cylinder of the lock.
U.S. Pat. No. 3,556,571 by Laub issued Jan. 19, 1971 describes a device for attachment to a door knob which in essence child proofs the door knob and prevents rotation of the lock bolt of a door until such time as an adult removes the attachment. The instant invention provides a number of alternative embodiments of a latch blocking element which is installed upon the interior of a door proximate the operating means of a door latch and thus prevents the rotation of the operating means in use until such time as the blocking device is repositioned. The blocking device thus prevents the rotation of the for example a key cylinder in a household door. Should the key cylinder be tampered with on the exterior of the door by an intruder, the rotation thereof would be prevented on the interior by blocking the rotation of the operating means connected to the key cylinder. Nowhere within the prior art is such a blocking means found which may be used by for example the occupant of a home as a night latch for securing his or her home.
It is therefore an object of this invention to provide a latch blocking mechanism which blocks the operation of operating means of a latching means thus preventing the rotation of the latching means from a locked to an unlocked position.
It is a further object of this invention to provide a blocking means embodied in alternative embodiments which cooperate with those latching means most broadly utilized in household latches. It is a further object of the invention to provide a latch blocking means which is easy to install, move, remove, or reposition.
Further and other objects of the invention will become apparent to a man skilled in the art when reviewing the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.


This invention relates to methods of evaluating the condition of oilfield tubular goods. More specifically, this invention relates to methods and apparatus for determining by measurement the extent of internal wear of subsurface pipe or casing.
A variety of problems may result from internal casing wear. Drill pipe collars may rub the casing, and possibly lead to a blowout in the casing if extremely worn. In a production well, badly worn casing may permit the undesirable "thiefing" of the flow to unwanted zones and thereby reduce surface production. In an injection well, worn casing may permit the injected fluid to flow to undesired formations.
Internal wear, which is the removal of metal from the inside casing wall occurs in three principal patterns: loss of metal from only part of the inside casing wall while the rest is unworn; uniform loss of metal around the entire inside casing wall circumference; and non-uniform loss of metal around the entire inside casing wall. In addition, there are two patterns associated with unworn casing--round internally with all of the original metal in place, and elliptical with all of the metal in place.
A number of surveys are available for assessing internal wear in downhole casing. One such survey provides a depth recording which responds to the circumferential average of the well thickness of the casing metal still in place. In particular, this survey detects changes of the wall thickness and internal diameter of downhole casing. A typical inspection instrument for performing this survey is the casing inspection instrument marketed by Dresser Atlas under the name "Magnelog tool" and disclosed in the publication "Dresser Atlas Casing Evaluation Services," pages 4-5 and 61-79; said publication being herein incorporated by reference. During operation, an inspection instrument generates an alternating (AC) magnetic field of low frequency. As the tool passes through the survey interval, the field permeates the casing wall and is detected by the receiver portion of the tool. The received electromagnetic wave is both attenuated and phase shifted by the casing wall, with the degree of phase shift in relationship to the wall thickness (weight). The degree of phase shift is detected and transmitted over the wireline for surface recording.
The phase shift curve registers the phase shift between generation of the low frequency electromagnetic wave and reception of the wave by the tool's receiver portion. The degree of phase shift increases with the increasing thickness of the casing's wall. The degree of phase shift may then be used in the calculation of the average thickness of the casing wall. While such a survey adequately calculates average thickness, it cannot detect the least wall thickness of casing or the degree of "out-of-roundness". (The term "out-of-roundness" generally refers to any non-circumferential internal wear, particularly one-sided wear) Thus, it is a distinct possibility that such a survey may fail to identify dangerously worn casing.
A second survey available for assessing internal wear in downhole casing generates a depth recording of the greatest and least internal radii of the casing, thus allowing quantitative assessment of the degree to which the casing is internally worn or out-of-round. A typical instrument for performing this survey is the casing inspection instrument marketed by Dresser Atlas under the name "Multi-Finger Caliper tool" or "MFC tool" and disclosed in the publication "Dresser Atlas Casing Evaluation Services", pages 6 and 83-103; said publication having been previously incorporated by reference into this document. During operation, the MFC tool, which may include from 40 to 60 "feeler arms" which extend outwardly from the body of the tool in all directions, is centralized and all of the feeler arms extended outwardly from the tool for contact with the entire circumference of the inside casing wall at a particular depth. As the MFC tool moves through the casing, the feeler arms follow the contour of the casing's inside wall. The feeler arm with the maximum extension operates a first potentiometer (or other alternative device) which senses the greatest measured internal radius. The feeler arm with the least extension operates a second potentiometer (or other alternative device) which senses the smallest measured internal radius. The signals from the potentiometers are coupled through the electronics section and transmitted by the wireline to a recorder for presentation. While the MFC survey allows the evaluation of the degree to which the casing is internally out of round and permits estimating the greatest and least remaining wall thickness, the MFC survey cannot distinguish casing that is seriously worn on one side from unworn casing that is merely elliptical; in other words, severe one-sided wear may not be detected at all.
Thus, while both surveys are able to provide useful information regarding the internal wear of casing, both surveys fall short of being capable of providing a comprehensive evaluation of internal wear. For these reasons, a method for a combined casing evaluation survey became necessary so that an analytical technique which provided a comprehensive evaluation of internal casing wear would be possible. While separate evaluation of the results of the two separate survey followed by integrating the information derived from the surveys is possible, such a practice proved unworkable in actual use. A better method of achieving this goal of a comprehensive survey of internal casing wear is to devise a method by which selected data of the two previous surveys are combined and subject to a single analysis technique which will yield the desired more comprehensive internal casing wear evaluation.


An electroabsorption modulator (EAM) is a photonic semiconductor device that allows the intensity of a laser beam traveling through it to be controlled via an electric voltage. The principle of operation of the modulator is based on applying an electric field to cause a shift of the material absorption threshold toward longer wavelengths. A laser beam with a wavelength longer than that of the absorption threshold will either be transmitted without applied electric field or absorbed by applied electric field. A typical EAM has a waveguide structure and electrodes for applying an electric field in a direction that is perpendicular to the modulated light beam. In order to achieve a high extinction ratio, EAMs typically include a quantum well structure in the core of the waveguide. Due to the Quantum-Confined Stark Effect (QCSE), the quantum-well structure provides a strong shift of the absorption threshold at low electric fields. EAMs based on QCSE are capable of operating at relatively low voltages and at very high speeds (e.g., gigahertz (GHz)), which makes them suitable for use in optical communications systems.
A distributed feedback laser (DFB) is a laser in which the entire cavity is made up of a periodic refractive-index structure that functions as a distributed reflector at the lasing wavelength, and contains a gain medium. An EAM can be monolithically integrated with a DFB on a single chip to form an electroabsorption modulated distributed feedback laser (EML) device that is capable of operating as a data transmitter. EML devices have been proposed that operate at high data rates (e.g., 10 gigabit per second (Gb/s)) in the 1550 nanometer (nm) and 1310 nm ranges. There are many difficulties that must be overcome in order to manufacture large volumes of these devices with high yield.
FIG. 1 illustrates a cross-sectional top view of a known EML device 2 comprising a DFB 3 and an EAM 4. The DFB 3 and the EAM 4 each have metallic contact pads 5 and 6, respectively. One end facet 7 of the EML device 2 comprises a highly-reflective (HR) or anti-reflective (AR) coating. The other end facet 8 of the EML device 2 comprises an AR coating. An inter-contact isolation region 9 electrically isolates the DFB 3 and the EAM 4 from each other. The lines labeled 11 A and 11 B represent a straight reverse-mesa ridge structure 11 that extends across the DFB 3, the isolation region 9, and the EAM 4. The lines 13A and 13B delineate the channels located on either side of the ridge waveguide structure 11, which are created when the ridge waveguide structure 11 is formed.
The EML device 2 has trenches 12A and 12B formed therein to remove defect areas that exist after a surface area growth (SAG) process has been used to grow a multiple quantum well (MQW) structure, as described below in more detail with reference to FIG. 2A. The trenches 12A and 12B are generally uniform in width through the DFB 3, the EAM 4, and the isolation region 9. The trenches 12A and 12B are generally in parallel with and run alongside the reverse-mesa ridge structure 11.
FIG. 2A illustrates a cross-sectional view of the EML device 2 shown in FIG. 1 along the A-A′ cross-section shown in FIG. 1. The different semiconductor layers that make up the EML device 2 are as follows. An n-type (001) Indium Phosphide (InP) material 21 is used as the substrate for the assembly 2. The substrate 21 has an n-type InP buffer layer 22 formed thereon. A MQW active region 23 is grown on top of the buffer layer 22 by a process known as Selective Area Growth (SAG). A p-type InP spacer layer 25 is grown on top of the MQW layer 23. A p-type Indium Gallium Arsenide Phosphide (InGaAsP) etch-stop layer 26 is grown on top of the spacer layer 25. Another p-type InP spacer layer 27 is grown on top of the InGaAsP etch-stop layer 26. A p-type InGaAsP grating layer 28 is grown on top of the spacer layer 27. A grating layer 28 is selectively etched in the DFB portion 3 to form a periodically varying refractive index region 31, which provides a filter for the laser spectrum in a desired wavelength value. A p-type InP infill 29 and cladding layer 32 are re-grown on top of layer 28. A p-type InGaAs contact layer 33 is then grown on top of the cladding layer 32.
FIG. 2B illustrates a cross-sectional view of the DFB portion 3 of the EML device 2 along the E-E′ cross-section shown in FIG. 2A. After the contact layer 33 is grown, a silicon oxide (SiO2) dielectric mask 34 represented by mask portions 34A, 34B and 34C is deposited on the top of the contact layer 33 and a wet chemical etch process is performed to etch the contact layer 33 and the cladding and infill layers 32 and 29.
FIG. 3 illustrates an enlarged view of the DFB portion 3 of the EML device 2 along the E-E′ cross-section shown in FIG. 2A after the chemical etching process has been performed. When the chemical etch process is performed, the device 2 etches relatively quickly in the (001) plane, but relatively slowly in the (111) plane, causing the waveguide ridge 35 to be formed with lateral (111) facets 36 thereon, having an angle, ω, between the (001) and (111) facets that is typically about 54.7 degrees. This ridge configuration is commonly referred to as a reverse-mesa ridge configuration due to the fact that the top of the ridge is wider than the base of the ridge.
FIG. 4A illustrates a cross-sectional view of the DFB 3 shown in FIG. 2A along the E-E′ cross-section prior to the layers of the MQW active region being grown using the SAG process. Prior to performing the SAG process to grow the MQW active region, a dielectric mask pattern comprising a plurality of rectangular mask portions 54A and 54B are deposited on top of the substrate 21, leaving openings 22 in which to grow the MQW active region.
FIG. 4B illustrates a cross-sectional view of the DFB 3 along the E-E′ cross-section shown in FIG. 2A after the layers making up the MQW active region 23 have been grown. The layers 23 are grown only on the areas of the surface of the substrate 21 that are exposed through the mask pattern 54A and 54B.
FIG. 4C illustrates a cross-sectional view of the EAM 2 along the E-E′ cross-section shown in FIG. 2A after the mask pattern 54A and 54B has been removed. After the mask pattern 54 has been removed, it can be seen that the surface is essentially non-planar. This non-planar surface is difficult to work with in performing the additional processes described above with reference to FIGS. 2A and 2B, e.g., growing the p-type InP spacer layer 25 on top of the MQW layer 23, growing the p-type InGaAsP etch-stop layer 26 on top of the spacer layer 25, growing the p-type InP spacer layer 27 on top of the InGaAsP etch-stop layer 26, growing the p-type InGaAsP grating layer 28 on top of the spacer layer 27, forming the periodically varying refractive index region 31 in the grating layer 28, etc., up through and including the formation of the reverse-mesa ridge structure 35. Because of the difficulties of working with the non-planar surface that results after the SAG process has been performed, the resulting assemblies may have performance problems, which will typically result in reduced manufacturing yield and increased costs.
With reference again to FIG. 1, it is important for the isolation region 9 between the DFB 3 and the EAM 4 to have high resistance and low capacitance. One technique that is used to provide the isolation region 9 with high resistance is to perform ion implantation in order to implant ions in the isolation region 9 to increase its resistance. One disadvantage of this technique is that it increases process complexity, which increases costs. Another disadvantage of this technique is that it is not always effective at providing the isolation region 9 with a sufficiently high resistance, which can lead to performance problems, and consequently, to reduced yield and increased costs.
A technique that is sometimes used to provide the isolation region 9 with decreased capacitance involves depositing a thick dielectric material underneath the contact pads 5 and 6. One disadvantage of this technique is that it increases process complexity, which increases costs. Another disadvantage of this technique is that it sometimes results in the contact pads 5 and 6 failing to adhere to the EML device 2. In other words, the pads 5 and 6 can peel away from the assembly 2, resulting in performance problems, and consequently, in reduced yield and increased costs.
Accordingly, a need exists for a photonic semiconductor device, such as an EML device of the type described above, for example, that is capable of operating at high speeds (e.g., 10 GB/s) over a wide temperature range in the 1310 and 1550 nm windows. A need also exists for a method for manufacturing such a device in such a way that manufacturing yield is kept relatively high and costs are kept relatively low.


Electromagnetically actuated switches exist in a variety of forms and for a variety of functions. Typically, they serve the function of opening and closing electrical circuits by controlling the bridging of a pair of contacts by a movable conductor. That conductor forms part of, or is carried by, an armature, the displacement of which is controlled by the selective energization of an electrical coil. In most such instances, the coil remains energized to maintain the contacts in one of their operative states, either open or closed. However, in many other instances, it may be necessary or at least desirable to maintain the associated switching circuitry in each of its stable states without requiring continued energization of the coil.
Exemplary of one type of the latter mentioned class of electromagnetic switches are U.S. Pat. Nos. 820,119; 1,824,973; 2,528,520; 2,851,646; 2,892,059; and 3,401,892. Each of these patents depicts an electromagnetic switch in which a linearly-moving armature or plunger is caused to rotate as a result of linear reciprocation. Such rotation is operative to move a bridging conductor between successive, angularly-displaced contacts, typically for some form of sequential control.
Exemplary of another type of electromagnetic switches of the class described earlier are U.S. Pat. Nos. 1,908,567; 2,703,348; 2,874,244; and 2,922,861. These electromagnetic switches are typically concerned with simply moving the contact-bridging element between either one of two stable states, e.g. "Contacts Closed" or "Contacts Open". Apart from the brief application of an actuating potential to the coil for moving the contact-bridging structure between its two stable states, no further energization of the coil is required. Such switches have, in some instances, been characterized as bistable relays or solenoids and will be so characterized herein. Typically, these electromagnetic switches are of a solenoid configuration in which an armature or plunger is reciprocated axially of an annular coil. Moreover, some portion of the plunger is usually axially coextensive with the coil during some portion of operation. In such bistable solenoid switches, it has been relatively common to effect the requisite bistable operation by means of a pin-and-slot arrangement. A pin, carried by the plunger, is subjected to the camming action of a stationary slot during axial displacement to provide the requisite rotational control of the plunger. U.S. Pat. Nos. 1,908,567; 2,874,244; and 2,922,861 are of that type. In another configuration represented by the aforementioned U.S. Pat. No. 2,703,348, the pin may be stationary and the slot may be formed in the plunger. The pin extends radially inward from the coil and into the slot.
The provision of such pin-and-slot arrangement to obtain a bistable solenoid switch complicates the manufacturing process and thereby increases its cost. Moreover, the integrity of the resulting system may, in some respects, be compromised. Certainly the assembly of the pin-and-slot structure in the aforementioned U.S. Pat. No. 2,703,348 patent presents a significant challenge.


A communication system is formed, at a minimum, by a transmitter and a receiver interconnected by a communication channel. The transmitter forms at least a portion of a sending station, and the receiver forms at least a portion of a receiving station. Communication signals transmitted by the sending station are transmitted upon the communication channel to be received by the receiving station. Information contained in the communication signals transmitted by the sending station is recovered once received at the receiving station. In a digital communication system, information to be communicated to the receiving station is digitized. The digitized information is then used to form the communication signal.
In some conventional, digital communication systems, the communication signals are transmitted in bursts. Blocks of digital information are communicated by a sending station to a receiving station during transmission of the bursts upon the communication channel.
In a non-ideal communication system, the communication signal is distorted during its transmission upon the communication channel. Because of such distortion, when the communication signal is received at the receiving station, the received signal differs somewhat from the communication signal transmitted from the sending station. If the communication channel is of poor quality, and the amount of distortion is significant, the informational content of the communication signal cannot be properly recovered at the receiving station.
In a digital, radio communication system, for instance, multi-path and Rayleigh distortion is sometimes introduced upon the communication signal as it is transmitted on the communication channel from the sending station to the receiving station.
Various schemes have been developed to better ensure that the informational content of the communication signal transmitted upon a non-ideal channel can be recovered at a receiving station. Several of such schemes utilize a feedback arrangement in which the receiving station reports back to the sending station whether the informational content of the received signal can be adequately recovered.
Several of such schemes have been implemented in a digital communication system in which blocks of information are communicated in bursts. The receiving station determines whether a burst of the block of information received at the receiving station is of an acceptable quality level. Indications of the determinations, forming feedback information, are returned to the sending station by way of a feedback channel. The indication may also be communicated back to the sending station implicitly. That is to say, lack of transmission of feedback information from the receiving to the sending station may be indicative of successful recovery of the informational content of the block of digital information. Or, the feedback information may be provided to the sending station in a manner other than by way of a direct feedback channel extending directly to the sending station. The indication may alternately be communicated back to the sending station indirectly. For example, the sending station might measure the channel conditions and decide that the probability of the receiving station successfully decoding the block of digital information to be so low that retransmission of the block of digital information would be justifiable.
Most simply, the receiving station simply detects whether the received signal burst is of an acceptable quality level. If the signal quality level of the received signal burst is not good enough to permit recovery of the informational content thereof, the receiving station merely requests the sending station to retransmit the block of digital information in a subsequent burst. Such a scheme is sometimes referred to as an ARQ (automatic request) scheme.
Retransmission of the block of digital information can be repeated in successive bursts until the block of digital information is received at the receiving station with at least a minimum quality level. The receiving station makes the determination of the quality of the received block of digital information responsive, for example, to detection of an error detecting code, knowledge of the communication channel upon which the block of information is transmitted, or some other suitable scheme.
The block of digital information can also be transmitted using an error protecting code, such as type I hybrid ARQ (Automatic Repeat Request) scheme, a general channel decoding technique. When the receiving station receives the block of digital information, the received block is decoded by a decoder to extract the informational content from the received signal. A determination is made if the informational content of the block of digital information can be recovered with at least an acceptable quality level. Because of the error protection, the block of digital information is better able to be recovered even if transmitted upon a communication channel of lowered quality.
Furthermore, if the decoder has the ability to exploit, not only the values of the received symbols, but also reliability information on the symbols, so-called soft information, the performance will increase substantially. Decoder circuitry at the receiving station capable of utilizing soft information is referred to as a soft input decoder.
In some other schemes, such as a type II and type III, hybrid ARQ (Automatic Repeat Request) scheme, blocks of digital information determined by the receiving station to be corrupt, i.e., to be of poor quality, are not merely discarded. Instead, the corrupt blocks are combined with subsequently-transmitted blocks of digital information. Information contained in previously-transmitted blocks is accumulated and forms accumulated knowledge. Such accumulated knowledge can be used to facilitate recovery of subsequently-transmitted blocks. Thereby, "accumulated knowledge" results, the number of times in which the blocks of digital information must otherwise be retransmitted decreases. The advantages of utilization of accumulated knowledge permitted by the combining of successive retransmissions of the blocks of digital information occur with increased amounts of information contained in the blocks of digital information.
This is advantageous as the probability of correct decoding generally increases if the accumulated knowledge is used during the decoding rather than if only the latest retransmitted block is utilized. Decoder circuitry at the receiving station capable of utilizing soft information is referred to as a soft input decoder.
In another scheme, a sequence formed of other symbols created from the same block of digital information is instead transmitted. For instance, if the first sequence is formed of an original set of parity symbols (possibly including uncoded information symbols of the block of digital information) and retransmission is requested, additional numbers of parity symbols are transmitted by the sending station in the retransmitted sequence. The receiving station accumulates the received symbols of the various transmissions and the symbols accumulated during the various transmissions are utilized together during a decoding process.
A conventional block or convolutional low rate coding process can be performed to form an encoded signal. Then, the encoded signal is "punctured." That is, selected symbols of the coded block are marked so as not to be transmitted. Only the "unpunctured" symbols, i.e., symbols which have not been marked, are transmitted. While the coded signal is weakened by transmitting only some of the encoded symbols, a higher effective coding rate is possible for a given encoder structure. If the informational content of the block of digital information can not be recovered with a desired level of quality from the symbols first received at the receiving station, additional coded portions of the signal are requested by the receiving station to be transmitted thereto. Some of the previously-punctured, and not-yet sent, symbols are thereafter transmitted by the sending to the receiving station. The receiving station utilizes both the previously-transmitted symbols and the newly-transmitted symbols. If additional retransmissions are required, yet additional symbols are subsequently transmitted to the receiving station. Such a scheme is referred to as a successive redundancy transmission scheme.
A successive redundancy transmission scheme, designed to be able to cope with adverse channel conditions, however, requires a complex decoding process to be performed to recover the informational content of the block of digital information. And, if the block of digital information is coded using a convolutional coding scheme, the decoding required at a receiving station to decode the information is complex irrespective of the amount of puncturing of the code.
When using a punctured convolutional code, a set of received redundant symbols that would, by themselves, cause a decoding error to occur still cooperate in the same way to counteract any error correcting attempts supported by additional redundant bits.
When the channel conditions of the communication channel extending between the sending and receiving stations are of poor quality, conventional codes of moderate complexity do not perform well. High-complexity codes, which perform well at such conditions, however, add unnecessary complexity when the channel conditions are of good quality. That is to say, while complex coding is necessitated when the channel conditions are of poor quality levels, such channel coding is not necessary when the channel conditions are of good quality levels.
A manner by which to adaptively select the complexity of the coding of a block of digital information to be transmitted between a sending and a receiving station would therefore be advantageous. When channel conditions are of good quality, only limited portions of a coded signal would have to be transmitted to a receiving station to permit recovery of the informational content thereof. And, when channel conditions are of poor quality, additional portions of the coded signal could be transmitted, better to ensure that the informational content of the block of digital information can be recovered at the receiving station.
It is in light of this background information related to digital communication systems that the improvements of the present invention have evolved.


The ocean has great potential for generating usable energy if it can be harnessed efficiently. For example, ocean waves, high and low ocean tides, and/or temperature differences in the water are a several ways that the ocean can be used to generate useable energy. Ocean waves, in particular, can have a significant amount of kinetic energy and this energy can be used to power various systems. Although there are many systems for generating energy from the movement of ocean water, there is a continued need for improvements in transferring energy from a power generation system to another location, such as a power grid on shore. Some such devices utilize a buoyant tube to transfer such energy.


This invention relates to preforms for blow-molded articles, and more particularly, to antinesting preforms for blow-molded synthetic resinous containers.
Food and beverage containers formed of PET (polyethylene terephthalate), and particularly PET bottles for carbonated or effervescent beverages, have become ubiquitous throughout the principal industrial countries of the world.
PET bottles are commonly formed by the reheat-stretch-and--blow procedure. Though this procedure is well known, it may be described briefly as follows.
Tubular preforms, closed at one end and open at the other, are injection-molded of a suitable grade or formulation of PET. The neck finish, that is, the finish at the open end, is formed in the injection mold in a configuration to receive a suitable closure when the resulting container is filled.
The preforms are removed from the injection mold and allowed to cool to ambient temperature, and are later introduced to a blow-molding system where they are first heated to a temperature within the glass-transition range of the material, then mechanically stretched in the longitudinal direction, and finally blow-molded to final container configuration and dimensions. The mechanical stretching and blow-molding impart biaxial molecular orientation to the material of the container body, thereby enhancing the tensile strength of the body wall while reducing its thickness.
A number of machines and systems for performing this procedure are well known and commercially available.
The finished containers take a great variety of sizes and configurations. The problem of designing a PET container for a particular purpose presents a bewildering variety of considerations, among them not only capacity and aesthetic appeal, but economy of material, and importantly, whether the container is to be filled with contents under pressure, as in the case of carbonated beverages, or under vacuum, as in the case of hot-filled products.
When container configuration has been determined, an appropriate preform must be designed. Because of the need to conserve material and yet ensure that the material will be so distributed in the finished container that it will exhibit adequate resistance to deformation and rupture under all conditions of expected use, preform design has become an exact science, and an exacting one.
In the case of certain PET bottles intended to package highly carbonated beverages subject to internal pressures of three to four atmospheres, a preform configuration has evolved in which the outer diameter of the closed end is smaller than the internal diameter of the open end, whereby one preform may, by way of its open end, receive the closed end of an adjacent preform. Simply stated, such preforms are subject to nesting with one another.
Nesting is an impediment to safe and efficient handling. Heretofore, it was necessary to detect and separate nested preforms before damage could occur to them or to the equipment in which they were being processed. In many cases, detection and separation depended exclusively upon the watchfulness and dexterity of a human operator.