This invention relates to a method for the combustion of coal in a cyclone combustor, and more particularly, to a method which minimizes the emission of ash particles and other pollutants from such a combustor.
The apparatus known as a cyclone coal combustor consists of a cylindrical chamber into which pulverized coal is injected and centrifuged to the cylindrical wall of the chamber by a high velocity, swirling gas flow. Heretofore, most cyclone combustors have been designed for combustion to take place near or at the cylindrical wall, and at a temperature sufficiently high, on the order of about 3000.degree. F., to melt the coal ash. Conventionally, the melted coal ash, or slag, has been drained continuously from the combustor. Although there are two general types of cyclone combustors, the horizontal cyclone of interest in connection with the present application and the reverse flow vertical cyclone, most prior commercial experience is with the horizontal cyclone.
Commercial horizontal cyclone combustors heretofore used have removed from 70 to 85 percent of coal ash as slag. These commercial cyclone combustors, typically of 100 to 700 million BTU/per hour capacity, were used extensively in large utility and industrial boilers in the 1950's and early 1960's. Their inability however, to control the emission of NO.sub.x, led to the discontinuance of their use in the late 1960's, as environmental concerns grew. Renewed interest arose in the cyclone combustor in the mid 1970's due to the need for a low ash output combustor in conjunction with the U.S. Department of Energy's magnetohydrodynamics ("MHD") program. This work, as well as greatly expanded research and development efforts on coal combustion phenomena, led to an improved understanding of the cyclone combustor (C. S. Cook, et al., "Evaluation of Closed Cycle MHD Power", DOE Contract Report No. DE-AC01--78ET 10818, Nov., 1981) ("Ref. 1").
A one million BTU/hr. air cooled, horizontal cyclone coal combustor, which was tested as part of an MHD program activity, had a central oil gun located at the center of the closed end of the unit. The oil gun was used to preheat the combustor wall, which was ceramic lined, and to start coal combustion. Pulverized coal, in this combustor, was transported by a primary air stream in about a one-to-one air/coal mass ratio, and injected into the combustor in an annular region surrounding the oil gun. The ceramic liner was maintained at a temperature of about 2200.degree. to 2500.degree. F., a temperature high enough to keep the coal slag in a liquid free flowing state. The ceramic liner was cooled by an air stream which was also used as the secondary air stream. The cooling/secondary air stream was injected at the closed end of the combustor to produce the characteristic swirling gas motion around the axis of the combustor, and the injection velocity was high enough to obtain tangential gas velocities of several hundred feet per second at the cylindrical walls of the combustor. In the above-described apparatus, efforts were made to burn as much of the coal particles as possible in suspension near the cylindrical wall of the combustor, and the unit was operated with conventional pulverized coal, having a conventional particle size distribution. Nevertheless, the above-described prior art device achieved slag retention values in excess of 80 percent and, in some cases, when operated with a somewhat more coarse coal particle size distribution (70% through 200 mesh), slag retention above 90 percent was evident. Significant NO.sub.x emission reductions were obtained with this apparatus and method by operating it at sub-stoichiometric conditions in the range of 60-90% of the stoichiometric air/fuel ratio (Ref. 1). In addition, pulverized limestone was injected as a sorbent directly through the closed end of the combustor, and this resulted in 25 to 35 percent reductions in the SO.sub.2 emissions from the combustor. The reacted sorbent was embedded in the slag and removed with it through a slag tap located at the down stream end of the combustor.
Horizontal cyclone combustors which were in commercial use in the United States and Germany in the 1950's and '60's had the primary air (which carried the coal) and the secondary air (which produced the swirl) injected tangentially along most of the top axial length of the unit. (Babcock & Wilcox Co., STEAM, ch. 10 (1978 ed.) ("Ref. 2")). The U.S. units typically operated with coarse crushed coal (50 percent through 20 to 40 mesh), in order to conserve pulverization power and to provide a method for burning coals having low ash fusion temperatures. Due, however, to the use of such very large coal particles, it was assumed that most of the coal combustion process took place on the surface of the slag, so that excess air, scrubbing the slag layer, was necessary for complete combustion. This, of course, produced high NO.sub.x emissions, and ultimately led to discontinuance of the use of such combustors.
The German commercial horizontal cyclone coal combustors were similar in design to the above-described U.S. units. (H Seidl, "Development & Practice of Cyclone Firing in Germany", Proc. Jt. Conf. on Combustion ASME-I.Mech.Eng., MIT, Cambridge, Mass., June, 1955, p. 92) ("Ref. 3"). However, in the German case, the intended application was the combustion of very high ash (up to 40 percent) coal which had low volatile matter content (under 20 percent). Consequently, a finer, but still relatively coarse pulverized coal particle distribution (approximately 60 percent through 100 mesh, i.e., 150 micron diameter coal particles) was used. These units obtained up to 85 percent slag retention, as compared to only 70 percent in the U.S. units.
Another class of cyclone combustors is the vertical, reverse flow type, whose design principles are very similar to those of conventional cyclone dust separators. A detailed experimental study of such a device was performed by Hoy (H. R. Hoy, et al., "Some Investigations with a Small Cyclone Combustor" in Jrn. Inst. Fuel, Oct., 1958, p. 429) ("Ref. 4"). In the unit studied by Hoy, which had a relatively large 20 million BTU/per hr. coal energy throughout, 80 to 85% of the slag was retained in the combustor. It was observed, however, that the reverse flow had a tendency to re-entrain slag from the walls in some cases.
One observation of importance in relation to the present invention should be made here in connection with the above-described cyclone combustors and other cyclone combustors being developed for MHD applications. In this regard, it is of significance that in these units coal was injected very close to the hot, liquid slag-covered walls, and as a result, the coal particles impinged very rapidly on the slag-covered walls. Thus, in such units, even the smaller particles that remained in suspension in the gas stream for but brief periods were in a gas temperature environment in the 3000.degree. F. range. Under these conditions, convective heating of the particles results in rapid pyrolysis and devolatilization of the coal particles. In the cyclone combustors developed for MHD applications, discussed below, in which different coal injection techniques were used, the use of very high temperature air preheat (in the 2000.degree. to 3000.degree. F. range) produces a similar effect. By contrast, in the air-cooled cyclone combustor of the present invention, coal injection occurs in a relatively cold gas environment, and therefore, considerably longer time periods are required and employed for coal pyrolysis.
The MHD program gave rise to a need for a high slag retention combustor. Several investigators designed and tested different versions of cyclone combustors intended for the MHD application. The Pittsburgh Energy Technology Center designed and tested a vertical unit similar in concept to Hoy's device. (W. S. Lewellen, et al., "Modeling Two Phase Flow in a Swirl Combustor", Aeronautical Research Rpt., (00-4062-5 (1977)) Princenton, N.J.) ("Ref. 5"). TRW designed a horizontal unit, similar to the early United States and German units described above. (J. A. Hardgrove, "MHD Cost Fired Combustor Dev.", 9th Energy Tech. Conf. Proc., Wash., D.C. Feb., 1982) ("Ref. 6"). The TRW unit, however, differed in that it used axial coal injection, as distinguished from the tangential injection used in the commercial units.
One significant operational difference between the processes performed by the cyclone combustors intended for the MHD application and the U.S. and German commercial units is the extremely rapid devolatilization that occurs in the MHD units due to the very high temperature air preheat which is used. This condition, coupled with the general use of relatively fine coal particle size distributions in such units appears to have resulted in the MHD units not only in rapid devolatilization, but also very rapid char gasification of much of the fuel while the coal particles were in suspension in the gas stream. These conditions account for very high carbon conversion, but low slag retention (in some cases as low as 30 percent) (Ref. 6).
Another prior art technique for the control of certain emissions in the combustion of coal is the injection into combustion chambers and furnaces of limestone or similar calcium oxide compounds as sorbents or binders for sulphur compounds. In the case of the million BTU/hr. combustor described above, 25 to 35 percent reductions in SO.sub.2 emissions were observed with the injection of pulverized limestone, and the reaction products of the limestone were removed with the coal slag. No explanation for this capture process was given (Ref. 1). Generally, the physical states of the sulphur capture process using calcium oxide compounds is by now well understood. The first step in the process is calcination, wherein CaCO.sub.3 is converted to CaO by removal of CO.sub.2 from the CaCO.sub.3 particle. A porous structure is left after calcination. With excess oxygen, sulphur capture leads to the formation of CaSO.sub.4. Under equilibrium conditions, this compound moves toward dissociation above about 2000.degree. F. Sulfation takes place heterogeneously by SO.sub.x contact with CaO, and it is affected by SO.sub.x diffusion through the CaO pore structure. Eventually, however, a layer of CaSO.sub.4 encapsulates the particle and stops the reaction.
For cyclone combustor applications, the average gas temperature is 3000.degree. F., which is much too high for equilibrium sulphur capture. However, it is now hypothesized in accordance with this invention that sulphur capture takes place during the time in which the CaCO.sub.3 particle is suspended in the combustion gases, the time for sulphur capture is in the 100 milliseconds time range.
Still another mechanism by which pollutants are removed from cyclone combustors utilizes the slag layer. The slag removes the mineral matter from the coal in liquid form, and serves as well as a base upon which one can burn up the remaining particles of char in the coal which floats on the slag and to remove the calcium-sulphur compounds resulting from the limestone injection. One problem, however, with prior art techniques has been the reevolution of SO.sub.2 from the slag layer. This occurs because at the temperatures of the slag layer, approximately 2200.degree. to 2500.degree. F., calcium sulphate in the slag will melt and react with species in the slag such as iron compounds or gases above the slag layer such as 0.sub.2 or CO.sub.2. For partial pressures of oxygen of less than 0.1 atmospheres, a condition likely to exist in a cyclone combustor, the rate of SO.sub.2, evolution from slag is in the time range of 15 to 20 minutes. It is, therefore, essential to remove the slag in a time less than this to avoid reevolution of sulphur. Reevolution is retarded somewhat, it has been found, by maintaining local reducing conditions above the slag. However, as noted, compounds such as those of iron can catalyze the reaction which converts chemically bound sulphur in the slag to gaseous form.


(1) Field of the Invention
The present invention relates to ash formation during the burning of coal and more particularly to methods and compositions for treatment of coal to reduce the amount of ash deposition onto surfaces during the burning of coal.
(2) Description of the Related Art
Sub-bituminous coal of the Powder River Basin of the United States typically includes a significant amount of calcium bound within the coal structure. In fact, the typical calcium level of this type of coal burned in industrial boilers in the United States today is substantially higher than it had been in the past and that level is expected to increase in the future as industries continue to turn to lower sulfur level coal.
When the coal is burned, the calcium in the coal is converted to calcium oxide. The formation of calcium oxide results in an ash that is reflective and whiter than the fly ash produced upon combustion of bituminous coal. This reflective ash accumulates on surfaces situated in the structure in which the burning takes place. Such structures will be referred to herein as xe2x80x9cfurnaces,xe2x80x9d as such term is considered in its broad sense to refer to any enclosed structure in which heat is produced. A particular situation in which such ash formation is encountered is in furnaces employed in boiler systems, but the furnaces contemplated herein are not limited to such systems and may be incorporated into any number of uses.
Prominent among the surfaces on which reflective ash tends to accumulate are the furnace tube walls through which heat is to be transferred from the combustion taking place in the furnace. Such ash accumulation is undesirable because the layer it forms over the surfaces is an insulative barrier that reduces the heat transfer through the surfaces, thereby reducing the efficiency of heat transfer from the furnace. Such ash accumulation is also undesirable because the reflective ash layer reflects the heat back into the burner area, increasing the gas and flame temperatures beyond that for which the furnace was designed, which in turn causes the increased heat to radiate back to the fly ash, eventually creating a slagging environment. Moreover, because of the inadequate heat transfer to the water flowing through the furnace wall tubes, the furnace exit gas temperature (FEGT) rises above the design level, increasing the fouling propensity in the convective zone and, in the case of the boiler, finally increasing the boiler exit gas temperature. The increased FEGT also raises the temperature of steam in downstream heat absorption sections above design conditions, requiring use of cooling spray water to reduce the steam temperature.
The formation of this type of ash has become more pronounced in recent years. Many boiler furnaces were designed for burning high sulfur bituminous coal. However, as alluded to above, beginning in the late 1970""s and early 1980""s, environmental concerns led to conversion from burning high sulfur bituminous coal to burning low sulfur coals, such as that from the Powder River Basin in Wyoming (PRB coal), began. Even though the ash content of PRB coals is lower than that of the high sulfur coals they replace, PRB coals tend to be high in calcium. Thus, burning the lower sulfur coals in the furnaces designed for relatively high sulfur coal has resulted in increased slagging, and particularly increased white ash formation. See, for example, xe2x80x9cPRB Coal Switch Not a Complete Panacea,xe2x80x9d by Buecker, B. and Meinders, J., Power Engineering, November 2000, pp. 76-80.
Conventionally, equipment such as soot blowers and water lances have been employed to reduce slagging and lower the FEGT, but with limited success and the additional costs, efforts and interference associated with such equipment. Moreover, use of a water lance is undesirable because it introduces cold water into the furnace, inducing thermal stress to the tubes, decreasing the furnace wall tube life and increasing the maintenance and replacement costs of the boiler.
Other prior art methods have addressed the problem of ash accumulation on furnace walls with chemical techniques for darkening the ash on the walls. For example, U.S. Pat. No. 5,819,672, incorporated herein by reference, describes the addition of a darkening agent such as iron oxide and, preferably, also a fluxing agent to produce a dark ash coating or an additional dark ash coat over the existing ash on the furnace walls. Because the ash is darkened, not only is the tendency of the ash to reflect heat back into the furnace reduced, but the heat absorption by the ash is increased, thereby reportedly aiding transfer of heat from the furnace through the walls thereof. Although the additives may be applied to the coal, the preferred method contemplates applying the dark coat directly to the ash. In any event, such techniques do not eliminatexe2x80x94or even reducexe2x80x94ash accumulation and suffer from various other disadvantages as well. For example, pursuant to such techniques, ash still is allowed to build up on the surfaces at previous rates with the attendant problems, such as the need for routine cleaning or replacement.
In the above-noted article in Power Engineering, it is reported that ADA Environmental Solutions has experimented with the application of a proprietary mixture of iron oxides and stabilizing chemicals to coal prior to combustion to enhance the viscosity characteristics of the slag formed from burning PRB coal and that the preliminary results from this experimentation xe2x80x9chave been very promising.xe2x80x9d However, no further information is provided in the article as to the composition of the additive and, although the article later discusses ash control, the article nowhere discusses the additive with respect to the ash control. Indeed, the article indicates that ash accumulation and high FEGT are still significant problems, requiring the use of water lances.
Thus, the industry is still searching for an effective and efficient means for darkening the ash and reducing the FEGT, slagging and ash accumulation on surfaces in coal-burning furnaces. Techniques that accomplish such objectives, while avoiding the need for purchasing and operating equipment such as soot blowers and water lances would be particularly desirable. And, of course, it is also especially desirable that the technique avoid raising adverse environmental implications.
Briefly, therefore, the present invention is directed to a novel method for inhibiting accumulation of reflective ash on surfaces in a furnace in which high calcium-containing coal is burned. According to the method, an effective amount of an iron compound is added to the coal to produce treated coal, free of added fluxing agent, and the treated coal is then burned.
The present invention also is directed to a novel method for increasing the melting point of ash produced during the burning of calcium-containing coal. According to the method, an effective amount of an iron compound is added to the coal to produce treated coal, and the treated coal is burned, producing ash of increased melting point.
Among the several advantages found to be achieved by the present invention, therefore, may be noted the provision of a method for darkening ash formed in the combustion of coal; the provision of such method that also reduces the tendency of the ash to accumulate on surfaces in the furnace; the provision of such method that also reduces the FEGT in the furnace; the provision of such method that improves the overall boiler efficiency and reduces generation cost; the provision of such method that eliminates the need for soot blowers and water lances; the provision of such method that reduces slagging in the furnace; and the provision of such method that avoids introduction of adverse environmental consequences.
In accordance with the present invention, it has been discovered that, surprisingly, a darker ash may be produced and accumulation of reflective ash on surfaces in a furnace may be reduced simply by adding iron oxide to calcium-containing coal prior to combustion of the coal in the furnace. Thus, rather than lowering the melting point of the ash or calcium components thereof by addition of a fluxing agent to encourage adhesion to the furnace surfaces as described in U.S. Pat. No. 5,819,672, the process of the present invention involves raising the melting point to inhibit such adhesion. Moreover, it has been found that the addition of the iron oxide not only darkens the ash and inhibits the tendency of the ash to adhere to the furnace surfaces but, accordingly, also reduces the FEGT and consequently slag and fouling deposit formation. In fact, the improvements in furnace performance resulting from the method of this invention have been discovered to be even greater than those achieved with the conventional treatments by soot blowers and water lances, thus eliminating the need for such equipment. And all of this has been found to be accomplished without any detected adverse environmental consequence.
While not wishing to be bound by any particular theory of operation, applicant believes that the present invention operates by conversion of the calcium oxide formed upon combustion of the coal to calcium ferrite, thereby converting calcium oxide in the ash to relatively higher melting point and darker calcium ferrite. This conversion may be illustrated by the following idealized formula wherein ferric oxide is the additive:
CaO+Fe2O3xe2x86x92Ca(FeO2)2
In any event, according to the present invention, a composition comprising an iron compound is added to the calcium-containing coal prior to combustion of the coal, preferably prior to delivery of the coal to the furnace and most desirably prior even to grinding the coal. The iron compound in the most desirable embodiment contemplated by the invention is iron oxide, especially ferric oxide. It is also desirable that the additive composition contain no other component that interferes with the ability of the iron compound to raise the melting (or fusion) point of the resulting ash. The additive composition particularly should not contain a fluxing compound or an adhesive or other substance that increases the tendency of the ash to adhere to the furnace surfaces.
In one preferred embodiment, the additive is a composition of iron oxide (especially in the form of ferric oxide) and clay, which is primarily silica with traces of alumina and other calcium and magnesium compounds. One such preferred formulation comprises 93% by weight ferric oxide, 5% by weight silica, with the remainder made up of alumina and other calcium and magnesium compounds. Hematite ore has been found to be a particularly appropriate additive composition. However, in another preferred embodiment, the additive composition may be the iron compound, with no other ingredients other than at most minor impurities.
The preferred form of the additive composition is a powder. However, other forms, such as a suspension of that powder in a liquid such as a liquid hydrocarbon (e.g., kerosene), may be employed if so desired. Although the liquid may be water, such is not desirable for the obvious thermodynamic and other disadvantages of introducing water into the combustion process.
The additive composition is applied to the coal, such as by spraying or spreading, in an amount sufficient to provide an effective amount of the iron compound to combine with the calcium content of the coal. In the context of inhibition of ash on the furnace walls, by xe2x80x9can effective amountxe2x80x9d of the iron compound what is meant is an amount that is sufficient to result in less ash deposition on the furnace walls when the coal treated with the iron compound is burned than forms on the walls when equivalent coal without the iron compound treatment is burned under equivalent conditions. In the context of increasing the melting point of the ash produced when the coal is burned, by xe2x80x9can effective amountxe2x80x9d of the iron compound what is meant is an amount that is sufficient to increase the melting point of the ash produced when the coal is burned over the melting point of the ash produced when equivalent coal without the iron compound treatment is burned under equivalent conditions. Such ash having a melting point higher than that of the ash produced when equivalent coal without the iron compound treatment is burned under equivalent conditions is referred to herein as xe2x80x9cash of increased melting point.xe2x80x9d
The optimal amount of iron compound to be added to the coal depends on the calcium content of the coal. Generally, however, when the iron compound is ferric oxide and the coal is of sub-bituminous type from the Western United States and particularly PRB coal, the optimal amount of iron compound has been found to be from about 0.1% to about 1.0%, such as about 0.1% to about 0.75%, more preferably about 0.25% to about 1.0%, even more preferably about 0.25% to about 0.75%, especially about 0.5%, based on the weight of the coal. Based on the theorized formula set forth above, this represents, surprisingly, only about one-sixth the amount of ferric oxide required by the stoichiometry. Although greater amounts of iron compound may be used, it is believed that there is currently no economic advantage to doing so.
After application of the additive composition to the coal, the treated coal then is ground, if not already ground, and conveyed to the furnace, wherein it is exposed directly to the flame envelope of the furnace combustion process. As described above, the resulting ash is darker and has a higher melting point compared to the ash formed from coal not treated in accordance with this invention. In fact, rather than tenaciously adhering to the exposed surfaces, the darkened ash is gas-borne fly ash, most of which escapes from the furnace with the exhaust gases, reducing or even eliminating the need for cleaning out the ash from the furnace wall. And because the product comprises calcium, iron and oxygen, which pose no environmental concern. Moreover, because the FEGT is lower when the coal is treated with the iron compound according to this invention, use of the water lance may be eliminated.
The following examples describe preferred embodiments of the invention. Other embodiments with the scope of the claims herein will be apparent to one skilled in the art from consideration of the specification or practice of the invention as disclosed herein. It is intended that the specification, together with the examples, be considered exemplary only, with the scope and spirit of the invention being indicated by the claims which follow the examples.


1. Field
The present invention relates generally to a manufacturing method of an organic light emitting diode (OLED) display.
2. Description of Related Art
Display devices display images, and recently, an organic light emitting diode display has been in the spotlight.
The organic light emitting diode display has a self-emitting characteristic and does not need a separate light source such that the thickness and weight thereof are reduced in comparison to a liquid crystal display. In addition, the organic light emitting diode display has low power consumption, high luminance, high response speed, and the like.
In general, the OLED display includes a substrate, a plurality of organic light emitting diodes disposed on the substrate for displaying an image, and an encapsulation member facing the substrate while encapsulating the organic light emitting diodes therebetween.
Recently, an OLED display using a thin film encapsulation layer as an encapsulation member has been developed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.


1. Field
The present application relates to a fuel-level measuring apparatus that measures the fuel level in a fuel tank installed in a vehicle.
2. Description of the Related Art
In a vehicle that uses gasoline or light oil as fuel, it is necessary to indicate the fuel level in a fuel tank so that the driver can know when the tank needs to be refilled and how far the car can drive.
A known fuel-level measuring apparatus that measures the fuel level in a fuel tank is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2013-50410. The apparatus disclosed therein includes a float provided in a fuel tank, the float moving up and down with the surface level of the fuel, and, by making a float arm of the float slide over a resistor plate and converting the surface level into an electric potential difference, the apparatus measures the height of the surface and indicates the fuel level calculated from the height of the surface to a driver.
However, the technique disclosed in Japanese Unexamined Patent Application Publication No. 2013-50410 has the following problems: because the fuel-level measuring apparatus, such as the float, is disposed in the fuel tank, the capacity of the fuel tank decreases by an amount corresponding to the volume of the fuel-level measuring apparatus; because the fuel-level measuring apparatus needs to be disposed in the fuel tank, the shape of the fuel tank is restricted and cannot be thin or complicated; and, because the surface level of the fuel in the tank changes significantly depending on the orientation and driving conditions of the vehicle, it is impossible to measure the accurate fuel level.


Users may interact with various types of media objects comprising a wide range of information. In an example, a user may view a beach image shared by another user through an image sharing service. In another example, the user may read a videogame console article published through a videogame website. In another example, the user may watch a live video stream of a soccer game through a video streaming app. In another example, the user may listen to a podcast through an online radio station. Many content providers may spend substantial amounts of time and computing resources attempting to combine content (e.g., a message, a link, an image, an interactive game, etc.) and media objects (e.g., an image, video, and/or audio). For example, a website may play an initial video before playing a requested video (e.g., a videogame website may force users to watch a video about a brief history of the website before being able to watch a videogame review show). In another example, a news website may display an image overlaying a news article. Unfortunately, the combination of content and media objects may be arbitrary, random (e.g., subject matter of the image may have little to do with subject matter of the article, such as a weather image overlaying an article about a corrupt politician), and/or annoying (e.g., the image may obscure part of the article). Thus, manual and human intervention are required to improve the combination of content and media objects so that they better match.


This invention relates to a novel integrated-circuit RC oscillator. More specifically, this invention relates to an RC oscillator which is entirely fabricated on an integrated-circuit chip, and has an output oscillation frequency which may be externally trimmed.
Oscillators are used in microprocessors to convert energy from a DC source into a cyclic energy which is usually supplied to the microprocessor clock. Crystal oscillators are sometimes employed to produce the desired oscillation frequency. While crystal oscillators produce good quality oscillating voltage signals, they are more expensive than most oscillators. Therefore, other types of less expensive oscillators have been used. In the past, RC oscillators were made having the passive resistive and capacitive elements positioned off the integrated-circuit chip because the elements occupied a considerable amount of semiconductor area. As semiconductor technology has advanced, it has been possible to position some of the resistive or capacitive elements on the IC chip.
It is oftentimes desirable for a user to be able to change the output voltage signal frequency of an oscillator after purchasing the oscillator. In order to do so, a user would purchase a new IC chip having an oscillator which produced the desired oscillation frequency. However, this method of modulation is expensive and inefficient. RC oscillators were then developed which included some resistive and capacitive elements off-chip so that the user could adjust the oscillating frequency. These oscillators were not entirely satisfactory, however, because the off-chip elements utilized too much space.
The difficulties in the preceding are not intended to be exhaustive but rather are many which may tend to reduce the usefulness of prior art RC oscillators. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that RC oscillators appearing in the past will admit to worthwhile improvement.
It is therefore a general object of the invention to provide a novel RC oscillator which will obviate or minimize difficulties of the type previously described.
It is a specific object of the invention to provide an RC oscillator which produces an output voltage signal at an oscillating frequency which may be easily adjusted.
It is another object of the invention to provide an RC oscillator which minimizes the number of components which are external to the semiconductor chip on which the oscillator is fabricated.
It is still another object of the invention to provide an RC oscillator which is inexpensive and which provides a good quality voltage signal which consistently oscillates at a desired frequency.


A liquid crystal display apparatus has been widely used as a display apparatus such as a television or a monitor.
Particularly, an active matrix liquid crystal display apparatus in which a transistor which serves as a switching element is provided in each of pixels has been recently mainstream of liquid crystal display apparatuses, from viewpoints of high display quality and high-speed response.
In general, a liquid crystal display panel constituting the active matrix liquid crystal display apparatus is made by combining, as a pair, a color filter substrate serving as a counter substrate with an active matrix substrate.
The active matrix substrate includes pixel electrodes arranged in a grid pattern, a plurality of gate lines and a plurality of source lines, and thin-film transistors (TFT) each serving as a switching element and each provided in the vicinity of an intersection of a corresponding one of the plurality of gate lines and a corresponding one of the plurality of source lines. Each of the plurality of gate lines is provided between corresponding two adjacent ones of the pixel electrodes, and each of the plurality of source lines is provided between corresponding two adjacent ones of the pixel electrodes. The plurality of gate lines and the plurality of source lines are provided so as to orthogonally intersect with each other.
In a pixel region which is a display region of the liquid crystal display panel, in general, an insulating layer is provided between (i) a gate line and (ii) respective of a pixel electrode and a source line.
The plurality of gate lines and the plurality of source lines are provided so as to be partially exposed, for their electrical connections with other components, in a terminal region which is a peripheral region of the liquid crystal display panel.
(Patent Literature 1)
A liquid crystal display apparatus having such an arrangement is exemplified by a liquid crystal display apparatus disclosed in Patent Literature 1. Specifically, Patent Literature 1 discloses an arrangement as below. In a display region (pixel region), a gate electrode and a source electrode are formed on a first transparent substrate via a gate insulating film. Further, the gate electrode, the gate insulating film, and the source electrode are covered by a protection film.
In a terminal region on the periphery of the display region, the protection film is formed in the terminal region except a region where a line terminal section is provided.
(Patent Literature 2)
Patent Literature 2 discloses an arrangement as below. In a pixel region, an upper insulating film is provided on a signal line (source line) so that a surface of the upper insulating film is planarized. Then, a pixel electrode is formed on the upper insulating film.
(Patent Literature 3)
Patent Literature 3 discloses an arrangement as below. In a pixel section (pixel region) and a terminal section (terminal region), an underlayer is provided on a substrate, and then, lines are formed on the underlayer.


The present invention generally relates to an image forming system, and more particularly to a toner supplying device of an image forming system, which device includes a cleaner portion for removing a residual toner from a photosensitive medium and an integrally formed toner supplying portion for supplying toner to a developing unit so that a toner image is formed on a copy sheet.
In image forming systems such as facsimile machines, printers and copiers, a cleaner toner magazine (CTM) unit is used in order to remove a residual toner on a photosensitive medium and store the residual toner, and to supply new toner to a developing unit so that a toner image is formed on a copy sheet. FIG. 12 shows a CTM unit used in an image forming system. In FIG. 12, the CTM unit includes a cleaner part 3 for removing the residual toner from a photosensitive medium (not shown) and a toner supplying part 5 for supplying new toner to a developing unit (not shown); these two parts are built into the one-piece unit. The cleaner part 3 includes a cleaning blade 1 for removing the residual toner, and a compartment 2 for storing the residual toner which is received from the photosensitive medium due to the cleaning blade 1. The toner supplying part 5 includes a toner transport screw 4 for supplying new toner to the developing unit.
In an image forming system of a different type having no CTM unit, the photosensitive medium, the developing unit, a replenishment toner storage tank, and a used toner storage tank are permanently united into a one-piece unit. When the replenishment toner in the storage tank is used up, it is necessary to replace the photosensitive medium or the developing unit, which is still usable and has not reached the end of its operating life. The image forming system with the CTM unit as described above has an advantageous feature in that the CTM unit, singly, can be replaced with a new CTM unit when the toner is used up, thus allowing the running cost per copy to be lowered.
However, when the CTM unit is replaced, for the replenishment of toner, there is a problem in that the replenishment toner partially sticks to an inside wall of the toner supplying part 5. The sticking of the toner may occur due to the changes of the chemical characteristics of the toner (e.g., the flowability or the adsorption characteristics) under certain environmental conditions or due to the physical arrangement of the CTM unit within the image forming system. For this reason, the amount of usable toner in the CTM unit is unsuitably reduced. Thus, it is desirable to make effective use of the replenishment toner in the CTM unit.


The present invention relates to a highly reliable male/female fluid coupling with an improved metallic seal for sealably maintaining fluid pressure after repeated mating and unmating operations and, more particularly, relates to an improved metallic seal coupling which allows for both axial and radial deviation between the coupling halves during the mating operation.
Conventional male/female couplings have long been used to sealingly join pressurized fluid lines. The coupling halves, when joined, automatically enable the fluid and/or fluid pressure to be transmitted through the coupling without a significant pressure differential. When unmated, the value stems in the body of each coupler half automatically seal the fluid within the coupler and its respective fluid line. Such couplers preferably are able to reliably maintain high fluid pressure after repeated mating and unmating operations.
The seal between the joined coupling halves may conventionally be provided by either an elastomeric or metallic member. The low cost, chemical inert quality and noncorrosive characteristics of elastomeric sealing materials has resulted in the commonplace use of such sealing members for many applications. Such elastomeric seals typically may be manufactured from natural or synthetic rubber, Teflon, nylon, PEEK, or similar materials.
In other applications, especially those wherein high reliability is paramount or the contained fluid is highly abrasive, metallic seals are preferable. One such application involves couplers commonly used in subsea petroleum recovery operations, wherein a plurality of coupler halves are mounted on respective control module mounting bases, so that clamping and unclamping of the bases mates and unmates the couplers and thereby interconnects numerous fluid pressure transmission lines.
One type of coupler suitable for reliably interconnecting fluid lines employs a metallic face seal. Sealing engagement is provided by a metallic seal sandwiched between surfaces of the coupler halves, with each sealing surface being generally perpendicular to the axis of the coupler. The metallic seal is permanently deformed into sealing engagement with each sealing surface by an axially directed mating force, and thus must be replaced between successive mating operations. A coupling with a reusable metallic radial seal is disclosed in U.S. patent application Ser. No. 908,593, hereby incorporated by reference.
One disadvantage of prior art metallic seal couplers is the expense and inherent decreased reliability associated with maintaining close tolerance between the sealing surfaces of the coupler halves. Close axial tolerances must be maintained between the surfaces for engagement with the face seal for the first coupler described above, and similarly close alignment or radial tolerance of the cylindrical surfaces for engagement with the radial seal is necessary for the second coupling described in U.S. patent application Ser. No. 908,593. These tolerance problems, although not particularly troublesome for many coupling operations, are particularly difficult and expensive to correct for remote coupling operations, such as petroleum subsea operations.
The disadvantages of the prior art are overcome by the present invention, and an improved coupler is hereinafter described with metallic seals positioned to allow for both axial and radial deviation between the coupling halves.


1. Field of the Invention
The present invention relates to a method of manufacturing an optical waveguide device for widespread use in optical communications, optical information processing and other general optics.
2. Description of the Related Art
In general, an optical waveguide for an optical waveguide device is constructed in such a manner that cores serving as a passageway for light are formed in a predetermined pattern on a surface of an under cladding layer, and that an over cladding layer is formed so as to cover the cores. Such an optical waveguide is typically formed on a surface of a substrate such as a metal substrate and the like, and is manufactured together with the substrate to provide an optical waveguide device.
A conventional method of manufacturing such an optical waveguide device is as follows. First, as shown in FIG. 6A, an under cladding layer 20 is formed on a surface of a substrate 10. Then, as shown in FIG. 6B, a photosensitive resin for the formation of cores is applied to a surface of the under cladding layer 20 to form a photosensitive resin layer 30A. Next, irradiation light L is directed through a photomask M formed with an opening pattern corresponding to the pattern of cores 30 (with reference to FIG. 6C) toward the photosensitive resin layer 30A. The irradiation light L is caused to reach the photosensitive resin layer 30A through openings of the opening pattern, thereby exposing portions of the photosensitive resin layer 30A thereto. The irradiation light L is directed to the photosensitive resin layer 30A at right angles thereto. A photoreaction proceeds in the portions of the photosensitive resin layer 30A exposed to the irradiation light L so that the exposed portions are hardened. Then, development is performed using a developing solution to dissolve away unexposed portions of the photosensitive resin layer 30A, as shown in FIG. 6C. The remaining exposed portions become the cores 30 formed in a predetermined pattern. The cores 30 are typically rectangular in sectional configuration. Thereafter, as shown in FIG. 6D, a photosensitive resin for the formation of an over cladding layer is applied to the surface of the under cladding layer 20 so as to cover the cores 30, to thereby form a photosensitive resin layer 40A. Next, irradiation light is directed toward the photosensitive resin layer 40A to expose the photosensitive resin layer 40A thereto. This causes the photosensitive resin layer 40A to be formed into an over cladding layer 40. In this manner, an optical waveguide W0 is formed on the surface of the substrate 10, for example, as disclosed in Japanese Published Patent Application No. 2004-341454.
In such a conventional method, however, the cores 30 have side surfaces 30a formed as roughened surfaces in some cases, as shown in FIGS. 7A and 7B. Such cores 30 increase the propagation losses of light propagating inside the cores 30 because of leakage of light from the side surfaces 30a formed as the roughened surfaces or other reasons. There is apprehension that the above-mentioned optical waveguide does not function as optical interconnection. When the surface roughening of the side surfaces 30a of the cores 30 is even slight but is greater than the wavelength of the light propagating inside the cores 30, the surface roughening causes scattering losses. Also in this case, the propagation losses increase, and there is apprehension that the above-mentioned optical waveguide does not function as optical interconnection, as described above. FIG. 7B is a view drawn based on a photograph in perspective of a core 30 enclosed with the circle C of FIG. 7A which is magnified 700 times with an electron microscope. By magnifying the core 30 700 times with the electron microscope in this manner, it can be seen that the side surfaces 30a of the cores 30 are formed as the roughened surfaces.
The present inventors have made studies to diagnose the cause of the formation of the side surfaces 30a of the cores 30 as the roughened surfaces. In the course of the studies, the present inventors have found that the surface roughening of the side surfaces 30a of the cores 30 occurs either in the case (1) where a metal substrate 11 (with reference to FIG. 8) in common use which is made of stainless steel (SUS) foil and the like is used as the substrate 10 (with reference to FIGS. 6A to 6D) or in the case (2) where a substrate (PET substrate) 12 (with reference to FIG. 9) made of a material having polyethylene terephthalate (PET) as a main component is used as the substrate 10.
As a result of further studies on the case (1) where the metal substrate 11 made of stainless steel foil and the like is used, the present inventors have found that the metal substrate 11 made of stainless steel foil and the like includes a roughened surface having an arithmetic mean roughness (Ra) of not less than 0.095 μm. For this reason, in the above-mentioned step of forming the cores 30, the irradiation light L for use in the exposure which passes through the openings of the photomask M is transmitted through the photosensitive resin layer 30A for the core formation and the under cladding layer 20, and thereafter is reflected diffusely from the roughened surface of the metal substrate 11 because of the surface roughening, as indicated by arrows shown in FIG. 8. The diffusely reflected irradiation light L is transmitted through the under cladding layer 20 obliquely upwardly from below. Then, boundary surfaces (surfaces that are to become the side surfaces 30a) for the patterning of the cores 30 are exposed to the diffusely reflected irradiation light L directed obliquely from below, as indicated by the arrows, in future core regions S included in the photosensitive resin layer 30A for the core formation. This exposure to the light directed obliquely from below results from the above-mentioned diffuse reflection, and is uneven. Thus, it has been found that an unwanted photoreaction proceeds unevenly at the surfaces that are to become the side surfaces 30a of the cores 30 because of the exposure to the light directed obliquely from below to result in the increased width of the cores 30 and the formation of the side surfaces 30a of the cores 30 as the roughened surfaces. In other words, the surfaces that are to become the side surfaces 30a of the cores 30 have both portions subjected to a low degree of exposure to light and portions subjected to a high degree of exposure to light because of the diffuse reflection of the irradiation light L. In the subsequent step of development, the portions subjected to a low degree of exposure to light are dissolved away from the surfaces that are to become the side surfaces 30a of the cores 30, and the portions subjected to a high degree of exposure to light remain unremoved. Thus, the side surfaces 30a of the cores 30 are formed as the roughened surfaces.
The present inventors have made further studies on the case (2) where the PET substrate 12 is used. As a result of the further studies, it has been found that the PET substrate 12 contains an additive component such as a lubricant material 12a and the like, as shown in FIG. 9, and that the irradiation light L for use in the exposure in the above-mentioned step of forming the cores 30 impinges upon and is reflected from the additive component such as the lubricant material 12a, to thereby follow irregular paths. It has also been found that most of the irradiation light L reaches the bottom surface (the back surface) of the PET substrate 12. That is, in the above-mentioned step of forming the cores 30, the irradiation light L for use in the exposure which passes through the openings of the photomask M is transmitted through the photosensitive resin layer 30A for the core formation and the under cladding layer 20, and thereafter enters the interior of the PET substrate 12, as shown in FIG. 9. In the PET substrate 12, the irradiation light L impinges upon the lubricant material 12a and the like to follow irregular paths, and then reaches the bottom surface of the PET substrate 12 at an angle. In general, the back surface of the PET substrate 12 is in contact with a mounting surface of a mounting table and the like (not shown) for placing the PET substrate 12 thereon, the mounting surface being impervious to the irradiation light L. For this reason, the irradiation light L reaching the bottom surface of the PET substrate 12 does not exit from the back surface of the PET substrate 12 but is reflected from the bottom surface of the PET substrate 12 obliquely upwardly as indicated by arrows in FIG. 9. Thereafter, the reflected irradiation light L impinges upon the lubricant material 12a and the like in the PET substrate 12 to follow further irregular paths, and then exits from the front surface of the PET substrate 12 obliquely upwardly. The irradiation light L exiting obliquely upwardly is transmitted through the under cladding layer 20 obliquely upwardly from below. Then, the boundary surfaces (the surfaces that are to become the side surfaces 30a) for the patterning of the cores 30 are exposed to the irradiation light L directed obliquely from below in the future core regions S included in the photosensitive resin layer 30A for the core formation. This exposure to the light directed obliquely from below comes from the diffuse reflection resulting from the lubricant material 12a and the like contained in the PET substrate 12 as mentioned earlier, and is uneven. Thus, as in the case (1) where the metal substrate 11 made of stainless steel foil and the like is used, an unwanted photoreaction proceeds unevenly at the surfaces that are to become the side surfaces 30a of the cores 30 because of the exposure to the light directed obliquely from below to result in the formation of the side surfaces 30a of the cores 30 as the roughened surfaces.
The assignee of the present application has proposed a method of manufacturing an optical waveguide device which is capable of suppressing the surface roughening of core side surfaces of an optical waveguide when the optical waveguide is formed on a surface of a substrate, and has already applied for patents (Japanese Patent Applications Nos. 2008-130727, 2008-234735, 2008-239346, and 2008-269688).
Japanese Patent Application No. 2008-130727 discloses a technique for forming an under cladding layer containing an irradiation light absorbing agent on a roughened surface of a metal substrate or forming an irradiation light absorbing layer on the roughened surface of the metal substrate prior to the formation of an under cladding layer. In this technique, irradiation light for the formation of cores is absorbed or attenuated by the irradiation light absorbing agent contained in the under cladding layer or by the irradiation light absorbing layer before or after being reflected diffusely from the surface of the metal substrate. This significantly reduces the amount of irradiation light directed obliquely from below to roughen the surfaces that are to become the side surfaces of the cores by exposing the surfaces thereto. As a result, this technique suppresses the surface roughening of the side surfaces of the cores.
Japanese Patent Application No. 2008-234735 discloses a technique in which a material that absorbs irradiation light for the formation of cores is used for a substrate having a roughened surface. In this technique, the irradiation light for the formation of the cores is absorbed by the substrate when the irradiation light reaches the surface of the substrate. This significantly reduces the amount of irradiation light directed obliquely from below to roughen the surfaces that are to become the side surfaces of the cores by exposing the surfaces thereto. As a result, this technique suppresses the surface roughening of the side surfaces of the cores.
Japanese Patent Application No. 2008-239346 discloses a technique in which either a colored-layer-coated substrate having a back surface on which a colored layer of a color that absorbs irradiation light is formed or a colored substrate entirely colored in a color that absorbs the irradiation light is used as a PET substrate. In this technique, the irradiation light for the formation of cores is absorbed by the colored layer or the colored substrate. This significantly reduces the amount of irradiation light directed obliquely from below to roughen the surfaces that are to become the side surfaces of the cores by exposing the surfaces thereto. As a result, this technique suppresses the surface roughening of the side surfaces of the cores.
Japanese Patent Application No. 2008-269688 discloses a technique in which either only a front surface or both front and back surfaces of a substrate (a silicon wafer, a glass substrate and the like) have an arithmetic mean roughness (Ra) in the range of 1 to 2 nm. In this technique, the surface that reflects irradiation light for the formation of cores is so smooth that the diffuse reflection of the irradiation light from the surface is suppressed. This significantly reduces the amount of irradiation light directed obliquely from below to roughen the surfaces that are to become the side surfaces of the cores by exposing the surfaces thereto. As a result, this technique suppresses the surface roughening of the side surfaces of the cores.
In this manner, the above-mentioned techniques of the Applications already filed by the assignee of the present application can suppress the surface roughening of the side surfaces of the cores to reduce the propagation losses of light. However, even when the surface roughening of the side surfaces of the cores is suppressed, the side surfaces of the cores are formed as roughened surfaces in some cases. The present inventors have made studies to diagnose the cause of such a phenomenon. As a result, the present inventors have found that the cause of the phenomenon lies in the contamination of the photomask for use in the formation of the cores. Specifically, a material for the formation of the cores and the like might be deposited onto portions of the photomask which surround the openings of the photomask because of the use of the photomask. In that case, the deposits on the portions of the photomask which surround the openings cause the irradiation light passing through the openings to follow irregular paths. This makes the irradiation light reaching the side surfaces of the cores uneven to result in the roughened side surfaces of the cores.
In the formation of an optical waveguide on the surface of a substrate, it has hence been required to suppress the surface roughening of the side surfaces of the cores, thereby reducing the propagation losses of light, regardless of the type of substrate.


1. Field of the Invention
The present invention relates to an apparatus for connecting and locking structural panels, and more particularly to a locking structure of floor panels and a method of locking floor panels using the locking structure.
2. Background Description
Locking mechanism for floor panels are known, for example, DE 100 08 108. In such floor panels, a groove forms an upper lip and a lower lip over the entire length of at least one lateral border, and a tongue is formed on the opposite lateral border which corresponds to the groove. To lock panels that have been connected, the tongue is provided with at least one projection and the groove exhibits at least one indentation on the lip that faces the projection. The locking mechanism created by the corresponding profiling of the tongue and the groove forms a so-called “click profile”. Two panels are connected by inserting the tongue of one panel into the groove of the other panel, until the projection on the lower side of the tongue clicks into the recess formed in the lower lip of the groove.
In addition, panels are known from U.S. Pat. No. 4,426,820 or CH 562 377 A5 which are connected in the laying process by inserting the tongue of a new panel in an angular fashion into the groove of an already laid panel, and then lowering the panel to the floor. The tongue and groove of the two panels engage with each other so that panels are locked both in the transverse direction and perpendicular to the upper panel surface. These types of floor panels, as well as others, can be manufactured from diverse materials such as, for example, from a wood material, particularly MDF or HDF. The upper side is formed with a decorative layer applied to the core.
Panels that are combined to form a floor cover must be tight at the area of connection in the top surface to prevent moisture from penetrating the connection and to prevent the core material of the panels from swelling. For this reason the “clicking” mechanisms are designed in such a way that two panels inserted into each other are in a state of tension and the connected points are solidly pressed together at the surface. However, the core material of known panels is relatively sensitive, which is often not realized, particularly by those engaged in home repair. If care is not taken when laying the panels and if strong forces are exerted when a new panel is inserted or swung downwards there is the danger that the lower lip of the groove will buckle. This results in the required stress not being able to be applied to the floor panels during installation since the position of the interlocking mechanism has changed. Accordingly, it will become impossible to firmly join the panels. Also, if the lower lip buckles too much it is possible that the groove will be broken, a circumstance that cannot be identified from the outside.
It is further noted that the production of the click profiles is rather involved, since maintaining the given tolerances requires careful milling of the core material and demands continuous quality control. If, for example, tool wear results in the projection on the tongue being insufficiently high, the two panels will not lock together in solid fashion, and the danger will arise of the panels separating or of surface gaps forming at the connecting points. If the projection is too high it will not fit the lower lip of the panel provided with the groove. The danger may also arise of the lower lip buckling and being broken or the projection being damaged (ground down), making a solid connection of the panels impossible.


Abbreviations used herein shall have the following meanings:
AF Amplify-and-Forward
CRC Cyclic Redundancy Check
DCI Downlink Control Information
DF Decode-and-Forward
DFTS Decode and Forward TS
DL Downlink
FSR Frequency Selective Relay (Repeater)
FTR Frequency Translating Relay (Repeater)
OFDM Orthogonal Frequency Division Multiplex
OFR On-Frequency Relay (Repeater)
PDCCH Physical Downlink Control CHannel
CRNTI Cell Radio Network Temporary Identifier
TTI Transmission Time Interval
UL Uplink
One recent development within modern telecommunication standards is the so-called Long Term Evolution (LTE) radio interface, and a further development of the LTE, namely LTE Advanced. These are both OFDM based systems.
One of the most important improvement areas in the so-called LTE-Advanced technology is the increase of data rates available for users at the cell edge and indoor. A very promising technique to achieve high data rates in such difficult locations is the deployment of relays. Relays are usually classified into Layer 1 (L1), Layer 2 (L2), and Layer 3 (L3) relays depending on which Open System Interconnection (OSI) layer they operate on. The OSI model is a conceptual model for telecommunication consisting of 7 layers (physical, data-link, network, transport, session, presentation, and application) Note however that the different layers refer to the user plane of the relay node and a L1 relay may use e.g. L3 control plane signaling.
L1 relays are commonly denoted Amplify-and-Forward (AF) relays or sometimes equivalently repeaters. An AF repeater operates in the physical layer and its basic functionality is, as the name suggests, amplifying and then forwarding the received signal, including any received noise and interference.
L2 relays operate in the data link layer and have the ability to detect and possibly correct errors that have occurred in the physical layer. L2 relays are therefore commonly called Decode-and-Forward (DF) relays as they decode the received data prior to retransmission. DF relays will, at the expense of an increased delay, not forward noise and interference.
L3 relays operate in the network layer and are by the Third Generation Partnership Program (3GPP) regarded as being equivalent to eNodeBs (eNBs) that are wirelessly connected to a donor cell via self-backhauling. L3 relays have the same characteristics as L2 relays in the sense that they do not forward noise and interference as they perform decoding and error correction of the received signal prior to retransmission.
There are several known methods of utilizing various repeaters or relays to further improve the quality of performance in telecommunication systems. Some of the most common include:
Cooperative relaying which enables multiple relays to cooperate during transmissions to users. For example, the cooperation may be used for increased diversity or multiplexing of data.
Multi-hop relaying which enables signals to be conveyed from a source to a destination over two or more wireless hops. The multiple hops are achieved by relaying the signal via one or more relay(s)/repeater(s). It may be used to reduce the end-to-end path loss and thus extending the coverage.
On frequency relays (or repeaters) (OFR) which are relays (repeaters) that forward on the same frequency band occupied by the received signal.
Frequency translating relays (or repeaters) (FTR) which are relays (repeaters) that translate the retransmitted signal to another frequency band that is different from that occupied by the received signal.
Frequency selective relays (or repeaters) (FSR) which are relays (repeaters) that may dynamically retransmit coordinated parts of the received signal bandwidth.
The increased path gain that comes from splitting of the signal path in two hops by repeating or relaying in an intermediate node brings several benefits: Data rates can be significantly increased; transmit power can be reduced and inter-cell interference falls rapidly. A multi-hop solution based on AF repeaters has some interesting characteristics compared to other DF relaying solutions. Since a repeater can receive and transmit on the same radio resource, which is not possible for DF types of relays, it is possible to operate without any duplex coordination loss between the two hops. A decode-and-forward (DF) relay can forward the data on the same frequency resource. However, since the decoding operation will result in an unavoidable delay the forwarding must take place at a later time instance, i.e. on another radio resource. In contrast, an amplify-and-forward (AF) repeater has a delay that typically is negligible compared to the transmission time interval, hence it can forward on the same radio resource. Repeaters also introduce less delay than DF relays which is beneficial for the performance of higher layer protocols such as TCP. Furthermore, a repeater is a simple device that typically is fairly cost efficient.
In particular, the use of OFR in OFDM based systems is interesting if the delay of the repeater is limited to the length of cyclic prefix of the OFDM modulation. In the air, the repeated signal path and the direct signal path add in the same way as normal multi-path does. In case of LTE, the additional time dispersion induced by the repeater does not result in any additional receiver complexity and/or reduced performance due to increased self interference as long as the total time dispersion is limited to the length of the cyclic prefix. Note that is not the case for single-carrier systems without cyclic prefix e.g. HSPA, where additional time dispersion typically increases the receiver complexity (i.e. more rake fingers are required) as well as the self-interference (i.e. signal components with a relative delay difference are non-orthogonal).
Despite the benefits of utilizing AF repeaters, there are a few disadvantages that prevent the use from providing the full benefit of them.
One drawback with repeaters compared to DF relays is that they forward not only signals but also noise and interference. Furthermore, a major challenge for on-frequency repeaters is to sufficiently suppress the self-interference they induce.
Repeaters (and relays) are efficient for both providing coverage in areas without coverage (see upper part of FIG. 1) and also to provide increased data rates to areas with weak signal strength (lower part of FIG. 1). This distinction is important since in the data-rate extension case the users will receive both a direct signal part as well as a repeated signal path, witch in the case of DF relaying will interfere with each other and in case of AF repetition and OFDM will add like multi-path. In addition, since AF repeaters amplify noise and interference they are only beneficial in case it is possible to replace one weak radio link with two significantly better radio links. This is more likely to be possible when the original radio link is weak due to some obstacle (e.g. a wall) that hinders the radio waves rather than pure propagation distance.
In addition, in the data rate extension scenario it is possible to dynamically turn the repeater on and off without losing coverage. It is also possible to do frequency selective repetition in the data-rate extension case without destroying the communication on the uplink and downlink control channels. Furthermore, the data-rate extension case is also particularly relevant for LTE and LTE-Advanced since, in order to compete with HSPA, their main business case is to provide high data-rates, which are only achievable in case the signal strength also is high.
In the coverage extension scenario, the options when it comes to advanced repeater behavior are more limited. It is not possible to e.g. turn the repeater off even when the repeater does not serve any UEs since that would leave the area with no coverage. In that case a UE wanting to perform an initial access would not be able to read the broadcast channel (BCH) and the system information blocks (SIBs) required for random access. Furthermore, an idle UE would not detect any paging messages sent from the network. In the coverage area extension case it is also not possible to perform frequency selective repetition on the downlink since that would hinder the UE from receiving the physical downlink control channel (PDCCH) that covers the whole downlink bandwidth. Also any frequency selective operation by the repeater on the uplink band must assure that the resources used for the physical uplink control channel (PUCCH) as well as the physical random access channel (PRACH) are always repeated.
Consequently, there is a need for a more efficient use of repeaters.


1. Field of the Invention
The present invention relates to a fixing apparatus provided in an image forming apparatus, such as a copying machine, a printer, and a facsimile, and a roller used in the fixing apparatus, and in particular, a fixing apparatus of an image forming apparatus and a roller using an induction heating system.
2. Description of the Background
In a fixing apparatus that adopts an induction heating system and is used in an image forming apparatus, such as an electrophotographic copying machine or printer, there is a device that increases the fixing speed by speeding up a warming up time of the fixing apparatus. For example, JP-A-2002-295452 discloses a heating device that heats a metal sleeve, which is positioned on the outer periphery of an elastic layer of a heat roller and has a small heat capacity, using an induction coil to thereby shorten a warming-up time.
However, in the known device, handling of expansion or contraction that occurs to the elastic layer when warming up or cooling the elastic layer is not mentioned.
Therefore, in a case when a metal belt having a metal layer on the outer periphery of an elastic layer is provided, it is preferable to develop a fixing apparatus of an image forming apparatus capable of increasing the life of the metal belt and an elastic roller by preventing the metal belt or the elastic layer from being broken at an early stage regardless of expansion or contraction occurring to the elastic layer.


This invention relates to internal combustion engines, and more particularly to plastic housings for such engines.
Small internal combustion engines--such as those used with lawnmowers, snowblowers, generators and the like--typically have a number of distinct components or housings for key parts of the engine. For example, the fuel tank is typically a separate component from the air filter housing. Similarly, the blower housing--which includes the air passageway through which forced air passes to cool the engine--is typically a separate component.
Each of these distinct components must be separately manufactured and assembled, greatly increasing the cost of the completed engine. Moreover, additional parts are typically required when these housings are distinct units. For example, a fuel line is needed between the fuel tank and the carburetor. Also, a flexible hose is often used between the air filter outlet and the air intake of the carburetor or other air/fuel mixing device. The use of these additional components also increases the cost in manufacturing and assembling the completed engine.
Since internal combustion engines by their very nature generate a great deal of heat, it has often been necessary to manufacture many of the engine components, such as the fuel tank, from metal materials due to the metal's ability to withstand the high temperatures generated by the engine. Since metal is expensive and requires a number of separate forming, punching and machining steps, the use of metal materials also increases the cost in manufacturing and assembling the component parts.


The present invention is directed to a conveyor system and more particularly to a roller conveyor system and various sub-assemblies thereof.
Conveyor systems are widely used within industry to transport raw materials, components and/or finished products along an assembly line or otherwise within or between manufacturing facilities. One common conveyor system is a belt driven roller conveyor system. In belt-drive roller conveyor systems, a moving belt is raised or lowered beneath a set of elongated cylinders (i.e., rollers) to make or remove contact between the moving belt and the rollers. When the moving belt contacts the rollers, the rollers rotate in the opposite direction as the belt. As a result, a bale of goods or other article situated on top of the rollers is conveyed along the conveyor path as the rollers rotate in place. Other roller conveyor systems are known, including gravity and chain driven systems.
Unfortunately, numerous drawbacks are associated with conventional roller conveyor systems. Among those disadvantages include that the systems are often labor-intensive to install and maintain. Because they are often used continuously in a manufacturing or warehouse environment, roller conveyor systems can be subjected to long and rigorous operating conditions, resulting in wear and tear of components that require frequent maintenance. Maintenance of roller conveyor systems is often expensive, due in large part to the procurement and installation of spare parts, many of which are heavy and cumbersome.
Still other drawbacks not adequately addressed with known roller conveyor systems relate to safety. For example, individuals cannot cross a roller conveyor system without risk of falling onto the rollers, which can spin freely underfoot as one tries to walk across them. However, the alternative, walking entirely around the roller conveyor system, is not efficient, particularly since roller conveyor systems can extend for tens of yards or more.
It would be desirable in the art for a roller conveyor system without the above-mentioned drawbacks.


The present invention generally relates to full color liquid crystal displays generated by the use of birefringent filters. More particularly, the present invention relates to full color liquid crystal displays using polarization interference filters in a passive matrix addressing scheme.
Traditionally color generation in liquid crystal displays (LCD) is accomplished by the patterning of color filters onto individual pixels. However, the use of color filters results in both a loss of resolution, due to subpixeling, and lower light transmission, due to the absorptive nature of the filters. Other methods of generating color include field sequential color in which the actual color is generated by RGB light emitting diodes (LED) and the liquid crystal (LC) pixel is driven so as to either block or transmit the colored light. This typically requires the LC to be driven at a very high frame rate which in turn calls for a very fast switching LC material and mode. Such materials and modes are difficult to find.
Another method of color generation employs polarization interference filters (PIF). Such filters work by introducing a phase shift between two orthogonally polarized field components by either a static or dynamic optical element such as a uniaxial retarder or electrically driven LC cell. Color is generated by the interference of these two components with an analyzer, and color switching is accomplished by changing the phase shift between the two components by using dynamic optical elements. Since there is no more absorption than the losses associated with polarizer absorption, the PIF can generate color with a higher luminance than absorptive color filters.
The use of retarders between polarizers to function as filters has been studied for several years, starting with the original design for monochromatic imaging by French astronomer Lyot. See I. J. Hodgkinson, Q. H. Wu: Birefringent Thin Films and Polarizing Elements, (World Scientific Press, Singapore 1997) 1st ed., Chap. 4, p. 52, incorporated herein by reference. The Lyot filter design was improved upon by the Solc design, which offered similar filtering characteristics but higher overall transmission. This design is generally disclosed in Ivan Solc, Czechoslovak Journal of Physics, Vol. 10(1), 16-34 (1960), also incorporated herein by reference. The Solc design was then generalized by Harris et al., A Optical Network Synthesis Using Birefringent Crystals, 1. Synthesis of lossless Networks of Equal-Length Crystals, J. Opt Soc. America (1964) 54(10):1267-1279, incorporated herein, describing a synthesis procedure for obtaining various filter designs.
The two original Solc designs are the “fan” and “folded” type. In the fan design, the wavelengths at which the elements have an even number of half waves of retardation pass through an output polarizer oriented parallel to the input polarizer. In the folded design, the wavelengths at which the elements have an odd number of half waves of retardation pass through the output polarizer, which is crossed with respect to the input polarizer. The passband characteristics of the Solc filters are directly related to the number of elements used to create the filter, i.e., the larger the number of elements, the sharper the passband. Another crucial element in the transmission function is the size and frequency of the sidelobes. The Solc filters, as it turns out, are not optimal in design and give passband sidelobes that can be avoided using various synthesis techniques.
The use of PIFs for the generation of color in a display device was shown by Sharp et al., U.S. Pat. No. 5,929,946. Starting from a Solc filter design, the design of a device capable of switching between a single desired color and black or white, depending upon polarizer orientations, was shown. Given that a folded Solc filter will filter the desired wavelengths by rotating them by pi/2, a second active optical element was added to the filter in order to be able to switch between a filtering and non-filtering action. Particularly, a single, switchable half wave plate was placed between the filter and the second half of the filter was repositioned. Proper repositioning required inverting the second half of the filter and rotating it by pi/2, as shown in FIG. 1, and discussed below.
With reference to FIG. 1, a single color generation stage of a display device according to Sharp is designated generally by the numeral 1. Color generation stage 1 includes a first retarder stack 2 (pre filter), a second retarder stack 3 (post filter), which is inverted and rotated by 90° with respect to first retarder stack 2, and an active matrix addressed optical element 4 (liquid crystal cell), particularly, a half wave plate, placed between first and second retarder stacks 2,3. First retarder stack 2 is oriented to rotate a desired wave length of light to an angle of pi/4, with respect to the optic axis of the active matrix addressed optical element 4 (half wave plate). As is generally known, crossed or parallel polarizers (not shown), particularly an input polarizer and an output analyzer, are employed to introduce polarized light to the color generation stage 1 and to analyze the light transmitted through color generation stage 1.
If LC cell 4 is switched so that its net retardation is zero, then the first part of the filter, first retarder stack 2, is crossed with respect to the second part of the filter, second retarder stack 3, as shown in FIG. 1. In this case, the net retardation between the two polarizers is zero and so the display appears black for crossed polarizers and white for parallel polarizers. If LC cell 4 is switched so that it is a half wave plate, then its effect on the filter depends on its orientation in the stack. Given that a folded Solc design rotates the desired wavelength by pi/2, then half the filter will rotate it by pi/4. As shown in FIG. 1, light 5 entering the filter from the left will have the desired wavelength rotated by pi/4 while light entering from the right will be rotated by −pi/4 to 3pi/4. Therefore, for light 5 to pass through the complete filter, LC cell 4 must take light polarized at pi/4 and rotate it to 3pi/4 degrees. A pi/2 rotation is easily accomplished by placing LC cell 4 at pi/4 to the incoming polarization. In this position the LC cell allows the filter to be switched on or off depending on its own state. For intermediate voltages, LC cell 4 acts as a retarder between 0 and pi/2 and so rotates the incoming linearly polarized light to some elliptical state. As a result, the desired wavelength is not completely rotated by the second half of the filter and so suffers absorptive losses at the analyzer. In this manner, intermediate grey scale colors can be created.
The effect of the filter on the rest of the spectra is as follows. In the case of a pure folded Solc filter, the undesired wavelengths entering the filter linearly polarized at 0° are all left unrotated (more so for a multiple plate retarder than a two plate) and are absorbed at the analyzer, which is crossed with respect to the polarizer. For the above design, the placement of the LC cell ensures that the unwanted spectra remains unaffected. While the desired wavelength is rotated, by the first part of the filter, to pi/4, the rest of the spectra remains at 0°. Thus, the undesired wavelengths are at pi/2 to the LC cell optics axis and the LC cell has no effect on them. Passing through the second half of the filter, they remain linearly polarized at 0° and are absorbed by the analyzer.
Therefore, in summary, Sharp design requires the following:                (1) a polarizer providing linearly polarized white light at a known orientation;        (2) a prefilter to rotate desired wavelengths to an angle of pi/4 with respect to the optic axis of the LC cell (or other electro- or magneto-optic modulator) while leaving undesired wavelengths untouched;        (3) an active matrix addressed optical element such as a LC cell (or other electro- or magneto-optic modulator) that rotates linearly polarized light by pi/2, i.e., a half wave plate, and has no effect on light polarized along or orthogonal to its optic axis; and        (4) a postfilter that is a copy of the prefilter except inverted and rotated by pi/2.
Such a filter design is capable of producing a relatively narrow passband transmission function (depending on the number of retarders making up the pre and post filter) and so can produce a single color or its grey scales from input white light. Such a filter is discussed in S. Saeed, P. J. Bos, Z. Li, SID00 Digest, 830 (2000), incorporated herein by reference. In order to produce more than one color, i.e., red, green, and blue, a stacked approach is taken to provide a full color liquid crystal display, as shown in FIGS. 2 and 3. In the stacked approach, a color generation stage according to FIG. 1 is tuned for each of the three primary colors (designated as 1B, 1G, and 1R) and then stacked one on top of the other. In FIG. 2, like parts as compared to FIG. 1 have received like numerals, with distinctions made between each stage and its elements by employing the letters B, G, and R to indicate blue, green, and red. Only one polarizer 6 and analyzer 7 is used at the two ends, and, in FIGS. 2 and 3, they have transmission axes that are orthogonal to one another, although parallel configuration may alternately be practiced. The stacked design works since each stack only rotates the wavelengths associated with its color, eg., the blue stack is designed to rotate wavelengths 430 nm to 490 nm while the rest of the spectra is left linearly polarized at 0°. Since the analyzer is placed at the end of the stack, this part of the spectra is able to move through the other two stacks, as shown in FIG. 3(B).
In FIG. 3, white polarized light is shown passing through three different stacks of filters, each stack containing three filters individually tuned for red (1R), green (1G), and blue (1B) wavelengths. At (A), the filters are all in an optically inactive mode, and the entire spectrum is blocked by the crossed polarizers. At (B), the blue filter is in an optically active mode, such that the blue spectrum is rotated and the stack ultimately outputs blue light. At (C), all three of the filters, blue (1B), green (1G), and red (1R), are in an optically active mode, and, thus, all three parts of the spectrum, blue, green, and red, are rotated, and the stack ultimately outputs white light.
Since the entire white light spectra is able to move through the three layer stack with each layer only affecting selected wavelengths, the stack can produce red, green, blue and white light or any combination thereof. This however will only be true if the red, green, and blue spectra do not overlap. As mentioned before, the bandwidth of each filter depends on the number of elements making up the filter. If only four retarders are used, for example, then the filter's bandwidth will be quite broad. If this filter was to be placed in the stacked design, it would rotate parts of the undesired spectra along with the desired spectra. For example, if the red filter is broadband, then it will rotate parts of the green spectra also. As a result, if the stack is setup to be in the white state, i.e., all three layers are rotating their selected wavelengths, then the green would be over rotated, and the resulting white output would lack some green. Therefore, in a stack design, it is important to have each filter's bandpass be as narrow as possible so as to prevent the overlap that reduces efficiency.
There are a number of orientations that the retarders making up the filter can have and still provide similar if not identical transfer functions. Synthesis techniques described by Harris et al., cited above, and Buhrer, Appl. Opt. 33, 2249-2254 (1994), are useful for obtaining the best orientations of the filter elements for a required transfer function, and each reference cited is incorporated herein. These synthesis techniques rely on the fact that each element in the filter provides one cosine Fourier component of the desired transmission function. Such synthesis techniques are useful in situations where the active element in the filter operates in the 0 to pi/2 range.
A birefringent filter based LCD employing electrically controlled birefringence (ECB) type cells, which fall into the category of optically simple active elements, was disclosed in the above-referenced Saeed et al. publication. The ECB type cells, however, require a rather expensive drive method called active matrix addressing, which involves the use of a transistor at each pixel edge to provide a switching operation.
A less expensive drive method is passive matrix addressing. A passive matrix addressing design could make use of the electro-optical characteristics of the LC mode and could drive displays without the use of transistors, and, as a result, the display would be cheaper and easier to manufacture. However, the requirement of a sharp electro-optical curve means that LC modes such as the ECB cannot be used in conjunction with passive matrix addressing. Thus, there exists a need in the art for a birefringent filter-based color generation scheme for a passive matrix display device.
In the design of a single stage of a color filter, the incident light can be considered to have two spectral components: a controlled spectral component and an un-controlled spectral component.
One of the required features of the electro-optical element in the color filter of Sharp is that the polarization state of the controlled spectral component of the light is effected by the state of the electro-optical element, but the polarization state of the uncontrolled component is not.
Sharp used an untwisted liquid crystal device for which it is well known that if light is linearly polarized with a particular state (at 45° to the projection of the optic axis on the plane of the device), that the polarization state of the light will be affected by a voltage applied to the device; but if light is polarized parallel to the projection of the optic axis, then the polarization state will not be affected by a voltage applied to the device.
However, untwisted nematic devices typically do not show that appropriate voltage versus polarization state change that is required for a multiplexed passive matrix display, and it is not clear, from Sharp, that it could be possible to use a nematic material of twisted structure. In fact, it is well known that twisted devices do not have the characteristic that a state of linearly polarized light with a wide wavelength spectral band can be unaffected by the state of the device. Therefore, the problem of designing a filter of the type discussed by Sharp, but having a twisted, multiplexable, liquid crystal device, is the focus of this invention.


1. Field of the Invention
This invention relates to computer display systems and, more particularly, to methods and apparatus for providing a graphics accelerator capable of selectively providing during any clock period color values for at least two pixels blended with a single texture or color values for a single pixel blended with a plurality of textures.
2. History of the Prior Art
In three dimensional graphics, surfaces are typically rendered by assembling a plurality of polygons in a desired shape. The polygons are conventionally triangles having vertices which are defined by three dimensional coordinates in world space, by color values, and by texture coordinates.
To display a surface on a computer monitor, the three dimensional world space coordinates are transformed into screen coordinates in which horizontal and vertical values (x, y) define screen position and a depth value (z) determines how near a vertex is to the screen and thus whether that vertex is viewed with respect to other points at the same screen coordinates. The color values (r, g, b) define the brightness of each of red/green/blue colors at each vertex and thus the color (often called diffuse color) at each vertex. Texture coordinates (u, v) define texture map coordinates for each vertex on a particular texture map defined by values stored in memory.
A texture map typically describes a pattern to be applied to the surface of the triangle to vary the color in accordance with the pattern. The texture coordinates of the vertices of a triangular surface area fix the position of the vertices of the triangle on the texture map and thereby determine the texture detail applied to each portion of the surface within the triangle in accordance with the particular texture. In turn, the three dimensional coordinates of the vertices of a triangle positioned on the texture map define the plane in which the texture map and the surface lie with respect to the screen surface.
A texture which is applied to a surface in space may have a wide variety of characteristics. A texture may define a pattern such as a stone wall. It may define light reflected from positions on the surface. It may describe the degree of transparency of a surface and thus how other objects are seen through the surface. A texture may provide characteristics such a dirt and scratches which make a surface appear more realistic. A number of other variations may be provided which fall within the general description of a texture. In theory, a number of different textures may be applied to any triangular surface.
In order to apply more than one texture to a surface, prior art graphics accelerators initially were designed to progress through a series of steps [is] in which pixel coordinates and color values describing each triangle are first generated one pixel at a time in sequence, a first texture is mapped to the triangle using the texture coordinates of the vertices and texture coordinates are generated for each pixel as the pixel coordinates are generated, texture values describing the variation of each pixel in the triangle for the first texture are generated using the texture coordinates for each pixel, the texture value describing the first texture for one pixel and the diffuse color values describing that pixel of the triangle are blended to produce a textured color value for the pixel, and the resulting triangle generated from all of the textured color values is blended with any image residing in a frame buffer from which the image may be presented on an output display. Then, texture values for a second texture mapped to the same triangle are generated and blended with the same sequence of pixel color values in the same manner, and the triangle blended with the second texture is blended with the image residing in the frame buffer.
The need to transit the graphics pipeline to blend each texture to the surface of each triangle defining an output image slows the process drastically. In many cases involving rapidly changing images, it has limited significantly the number of textures which can be applied. For this reason, a more recent development provides a pair of texture stages and a pair of texture blend stages in the pipeline. The first texture stage generates texture values describing a first texture from texture coordinates provided as each pixel is generated. These first texture values are blended with the pixel color values at the first texture blend stage as each set of pixel color values is generated. The textured color value output of the first texture blend stage is then furnished to the second texture blend stage. The textured color value output of the first texture blend stage is blended with texture values generated by the second texture stage using texture coordinates provided as each pixel is generated. The output of the second texture blend stage is ultimately transferred to the frame buffer blend stage to be blended with the image data already in the frame buffer. This more advanced pipeline allows two textures to be blended with a surface in a single pass through the graphics pipeline.
Although this most recent development is useful in accelerating texture blending in a graphics pipeline, it is limited to producing a single pixel having at most two textures during any clock of the graphics pipeline and cannot be utilized for any other purposes. More complicated functions require the use of the host processor and the frame buffer blending stage and drastically slow the rendering of surfaces by the graphics accelerator.
There are no prior art systems which have been capable of providing two or more textured pixels during each clock period.
It is desirable to provide a new computer graphics pipeline capable of rapidly selectively providing a plurality of textured pixels or a single pixel blended with a plurality of textures during any clock period.
The present invention is realized by a graphics accelerator pipeline including a rasterizer stage, a texture stage, and a combiner stage capable of producing output values during each clock interval of the pipeline which map an individual texture to a plurality of pixels.