BACKGROUND OF THE INVENTION
As is known, the disposal of large amounts of garbage and refuse in metropolitan areas is a tremendous problem. In the past, it has been common to burn garbage in large incinerators; however this has polluted the air to the point where it can no longer be tolerated. Furthermore, the cost of building and operating incineration plants is tremendous. At least part of the garbage (foods and the like) can be ground and flushed into a sewer system; but this does not take care of tin cans, paper and other articles and tends to overload sewage disposal systems.
It has been proposed to compact garbage into bales of high density which can be used as land fill. However, the problems involved in translating this proposal into an efficient and economical system are enormous. One of the main problems is that the garbage is not of constant density. It may contain waste food, bottles, cans, paper and almost everything else imaginable.
The compression of refuse is, as a general idea, well known. For example, many garbage collection trucks include means for compressing the contents of the truck; and household appliance units have been developed for compacting the garbage of a single household. The unit pressures developed by such units, however, are relatively low, not more than about 100 pounds per square inch. This does not reduce the volume of the garbage materially nor does it crush certain types of containers. What is needed is apparatus for compressing the garbage to densities of about 1,500 to 2,400 pounds per cubic yard in order that it can be transported efficiently to a land fill site.
At first sight, it might appear feasible to compact garbage in a device similar to a hay baler wherein the material is forced through a reduced area opening in an operation somewhat similar to that of an extrusion press. This process, however, cannot produce a product having a density sufficient to make the process economical. Not only is the volume of the resulting product too great for efficient transportation, but it requires too large a land area for disposal.
The ideal way to obtain high densities is to force the garbage into a closed-end chamber by means of a hydraulic ram; but this presents a problem in removing the compressed material at the bottom of the chamber. Even if this problem is solved, there is the additional and perhaps more troublesome problem of devising a press which can compact the garbage with any speed. Press speeds on the order of those used in the metal-working industry, for example, are totally unsatisfactory because of the extremely long stroke needed to compress a large volume of low density refuse into a compact, high density mass.
SUMMARY OF THE INVENTION
In accordance with the invention, the aforementioned difficulties are overcome by means of a compaction press having a press chamber into which low density, high volume refuse is fed and into which a press ram can be forced. The side of the press chamber is provided with a hinged door which when opened with the press ram retracted, will receive refuse to be compacted. At the end of the press chamber opposite the ram is a slide box bounded on one side by a fixed wall and into which the low density refuse is forced by the ram to form a high density compact mass. After compaction of the refuse in the slide box, it is then caused to move laterally out of alignment with the press where the compacted mass can be removed and combined with other compacts to form a bale suitable for shipment to a land fill area.
The system is designed such that the compaction takes place in several stages, facilitating rapid cycling of the press. In the first stage following loading of the press chamber with low density refuse, the aforesaid hinged door is closed while a pair of differential cylinders cause the ram to move into the press chamber at relatively high speed and low pressure, shearing any refuse between the hinged door and the ram. This high speed, low pressure travel of the ram continues until a predetermined pressure is reached, whereupon a second pair of cylinders is added, increasing the tonnage on the refuse but slowing down the ram speed. Finally, when a second, higher predetermined pressure is reached, a third cylinder is added to increase the tonnage on the refuse while the ram speed is again slowed. At this point, the refuse, which was originally of low density and occupied the entire press chamber, is compacted into the slide box at one end of the chamber. As the slide box is moved laterally out of alignment with the press, means are provided for constraining it against expansion and for removing it from the slide box to leave it empty, while still preventing expansion of the refuse. The apparatus of the invention further comprises retaining fingers or the like, which serve to prevent expansion of the compacted refuse after it has been emptied from the slide box.
Further, in accordance with the invention, the slide box is provided with a cooperating plate which, when the slide box is moved out of alignment with the press, forms a false bottom for the press chamber in order that a second charge of low density refuse can be fed into the press chamber without waiting until the slide box is again retracted into its position in alignment with the press. This, of course, also facilitates rapid cycling of the press.
An important feature of the invention resides in the fact that each individual compact formed in the press is of relatively shallow depth. These compacts are then removed from the press, one by one, and strapped together to form a bale. If an attempt is made to form a complete bale in one press stroke, the friction between the sides of the press and the refuse creates a condition where the top of the bale is of high density but the bottom is of lower density. Consider, for example, the case where an attempt is made to force waste paper into a closed-end tube. If a small amount of paper is introduced into the tube, a relatively high degree of compaction can be achieved throughout. However, as the amount of material initially introduced into the tube increases, there is a tendency to compact the top portion first. But as this top portion is compacted, it tends to expand outwardly, increasing the friction on the sides of the tube. Finally, a condition is reached where the force available can no longer reduce the size of the compact which now has a greater density at the top than at the bottom. In the present invention, this condition is eliminated by virtue of the fact that the side walls of any one compact formed in the press are relatively short, whereby high frictional forces cannot occur.
In the embodiment of the invention shown herein, the refuse is fed into the press chamber by a pair of converging conveyors which reduce its density by a ratio of about 2 to 1. Thereafter, the refuse is compacted in the chamber itself under the force of a ram by a ratio of about 4 to 1, with an overall reduction in volume of about 8 to 1, assuming that the average density of the refuse before compaction is about 375 pounds per cubic yard. Lower density materials can be reduced as high as 10 to 1 or even higher.
The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification, and in which:
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is an overall plan view of a refuse compaction plant utilizing the principles of the present invention;
FIG. 2 is an elevational view, partly in cross section, showing the compacting press of the invention;
FIG. 3 is an end view of the pre-strapping unit of the press assembly of FIG. 2 which receives compacts of high density refuse and forms them into bales;
FIG. 4 is a schematic diagram illustrating the hydraulic control mechanism for the press of FIG. 2; and
FIGS. 5A and 5B are side and top views of a schematic illustration of an alternative embodiment of the invention.
With reference now to the drawings, and particularly to FIG. 1, the installation shown includes a building 10 having an unloading area 12 onto which garbage and refuse trucks can drive and unload their contents. The unloaded garbage and refuse can then be pushed by lightweight bulldozers 14 and 16 onto a feed conveyor 18 which, as shown in FIG. 1, travels to the right. The refuse thus deposited onto the conveyor 18 travels to a hopper 20 provided with a lower conveyor which forces the refuse downwardly as viewed in FIG. 1 and through an opening formed by the lower conveyor and an upper inclined conveyor into a press 22, hereinafter described in detail, provided with five cylinders 24, 26, 28, 30 and 32. The low density refuse, after being fed into the press, is compacted into a high density compact mass which is then transferred laterally out of the press to the position indicated by the reference numeral 34. At this position, the individual high density compacts are formed into bales which are then transferred laterally to a strapping unit 36 which straps them into bales. Thereafter, the strapped bales are transferred to a lift conveyor 38 and then onto a cross conveyor 40 to a crane 42 where they are lifted from the conveyor and loaded into railway cars 44 for transportation to a land fill area. The entire operation is controlled by an operator in a control console 46.
Adjacent the press 22 is a second press 22' which operates in exactly the same manner as press 22. In this case, however, the conveyor 18' moves from the right to left; and the baled, compacted refuse, after being strapped in strapping unit 36', is moved to the right rather than the left for eventual loading into the railway cars 44.
With reference now to FIG. 2, the hopper 20 is provided with a lower, horizontally extending flight conveyor 48 which causes refuse deposited in the hopper 20 to be conveyed to the left as viewed in FIG. 2. At the forward end of the conveyor 48 is an upper inclined conveyor 50 having flights provided with crossbars 52. The conveyor 50 is pivotally mounted to the frame for the hopper 20 as at 54 and is provided with a downwardly extending arm 56 connected to the piston rod 58 of a hydraulic cylinder 60. In this manner, when the cylinder 60 is pressurized, the conveyor 50 will rotate in a clockwise direction as viewed in FIG. 2. In passing between the ends of the conveyors 48 and 50, the density of the refuse will be increased, and its volume decreased, by a ratio of about 2 to 1. This is a pre-compaction which reduces the required stroke of the press ram, as will be explained. By varying the distance between the ends of the conveyors 48 and 50, the density of the refuse entering the press ram can be varied. This is essential to insure that the thickness of the resulting refuse compact will be essentially the same regardless of the density of the entering material. This will be explained more in detail hereinafter.
In FIG. 2, only the large diameter center cylinder 32 of press 22 and the two cylinders 26 and 28 are shown. It should be understood, however, that a second differential cylinder 24 corresponding to the cylinder 28 shown in FIG. 2 is disposed in front of cylinder 26 and that a second cylinder 30, the same as cylinder 26, is disposed in front of the cylinder 28 as shown in FIG. 2. All of the cylinders are carried on an upper crosshead 62 which, in turn, is supported by means of two upright plates 64, only one of which is shown in the cross section of FIG. 2. The cylinder 28 is provided with a piston and piston rod 66 while the remaining cylinders 32, 26 and 30 are provided with rams 68. The piston rod 66 and the rams 68 are all connected to a lower, movable crosshead 70.
Carried on the lower face of the crosshead 70 is a fabricated ram structure 72 adapted to be forced down into a press chamber 74. At the bottom of the press chamber 74 is a slide box 76, generally rectangular in configuration, forming a continuation of the press chamber 74 which terminates at a fixed wall 78. The slide box 76 thus forms a lower rectangular chamber 74' into which refuse fed into the press chamber 74 is compressed. The slide box is connected to the piston rod of a hydraulic cylinder 80 whereby, upon pressurization of the cylinder 80, the slide box 76 may be moved laterally from the full-line position shown to the left where it is positioned within the pre-strapping unit 34 shown in FIG. 1.
One side of the press chamber 74 is formed by a door 82 hinged at 84 and having an arcuate portion 86 connected to the piston rod 88 of a hydraulic cylinder 90. With this arrangement, the door 82 can be moved from the full-line position to the dotted-line position shown, and vice versa. During loading of refuse into the press chamber 74, the piston rod 88 is retracted, thereby causing the door 82 to pivot downwardly into the dotted-line position shown, whereupon refuse, indicated by the reference numeral 91, is fed into the press chamber 74 by the conveyors 48 and 50. After the press chamber is thus filled, the cylinder 90 is pressurized to rotate the door 82 in a counterclockwise direction about pivot point 84. At this point, the door is locked in position and the cylinders 24 and 28 are initially pressurized to force the ram 72 downwardly into the press chamber 74 containing the refuse. Note that there is a small space 92 between the lower end of the ram 72 and the upper edge of the door 82 at the beginning of a compaction cycle. The lower edge of the ram is provided with a replaceable shear blade 94 and, similarly, the upper edge of the door 82 is provided with a cooperating, replaceable shear blade 96, the arrangement being such that as the ram 72 descends, the refuse is sheared between the blades 94 and 96.
As will hereinafter be described in greater detail, the ram 72 descends into the press chamber 74 in three stages. In the first stage, only the differential cylinders 28 and 24 are employed, exerting a force of approximately 175 tons which is sufficient to shear the material at the blades 94 and 96. If additional force is required, the hydraulic system will shift from differential to full area of the cylinders 28 and 24 to deliver approximately 395 tons of force. Once the shearing is completed and the resistance drops below 175 tons, the compaction will proceed up to 175 tons, shift to produce up to 395 tons where the hydraulic system brings in the intermediate cylinders 26 and 30 and compresses the refuse up to approximately 1,200 tons, at which point the main cylinder 32 is brought into the circuit to compress the refuse to its maximum compaction, which is approximately 2,200 tons.
As will be understood, the ram 72, as the tonnage is increased, will necessarily slow down. However, at the beginning of the compaction process when the density of the refuse is relatively low, the ram will move down into the press chamber 74 rapidly. This, of course, materially increases the speed of the process over what it would be, for example, if the ram moved at a constant speed.
After the cylinder 32 has been brought into play and the force of the refuse is approximately 2,200 tons, the refuse will have been compacted into the chamber 74' formed within the slide box 76. Of course, the extent to which the ram extends into the slide box is dependent upon the material originally fed into the press chamber, its water content, and other factors. The press, however, is pressure-responsive. That is, it will stop only when the total force exerted by press is about 2,200 tons, with the result that the compact within the slide box 76 is essentially the same density, regardless of the characteristics of the starting material.
After the press has reached the maximum tonnage of 2,200 tons, the pumps delivering oil to the cylinders shift to neutral and the hydraulic system is decompressed. Once the decompression drops to a preset pressure, the pumps shift to deliver oil to retract the main crosshead 70 to a position where the lower surface 100 of the ram 72 is just above the slide box 76 containing the compacted refuse. Then, as the cylinder 80 is pressurized and the slide box 76 shifted to the left as viewed in FIG. 2, the lower surface 100 acts as a restraining wall to the compressed refuse if it tends to expand beyond the height of the opening through which it must pass while the slide box 76 is shifted to the left by cylinder 80.
After the slide box 76 is shifted to the left, the ram 72 is retracted to the position shown in FIG. 2, the door 82 opened, and a second charge of refuse fed into the press chamber 74. Note that the slide box 76 carries a plate 102 which forms a false bottom for the press chamber 74 when the slide box 76 is shifted to the left in FIG. 2. This permits the refuse to be fed into the press chamber, even though the slide box 76 is displaced laterally to the left with respect to the press chamber 74. When the slide box is subsequently retracted, the refuse, which was on the plate 102 forming a false bottom, will then drop into the chamber 74' formed by the slide box while the charging of refuse into chamber 74 continues. After the chamber is again filled with refuse, door 82 is closed by pressurizing cylinder 90 and the cycle is repeated.
The pre-strapping unit 34 is shown in FIGS. 2 and 3 and includes a bottom platen 104 mounted on the piston rod of a hydraulic cylinder 106. A second or upper platen 108 provided with slots 110 as shown in FIG. 3, is carried by the piston rod of a second hydraulic cylinder 112. The apparatus further includes fingers or forks 114 carried on guideways 116 and reciprocable by hydraulic cylinder means, not shown, from the extended position shown in FIG. 2 to a retracted position where they are to the left of the position shown in FIG. 2.
Assuming that the lower platen 104 is empty (i.e., contains no compactions from the slide box 76), the platen 104 is moved by the cylinder 106 to its uppermost position where its upper surface is in alignment with the lower surface of the slide box 76. However, before the platen 104 is moved to this position, the fingers 114 are retracted. At the same time, the upper platen 108 is moved to a position where its lower surface 118 is slightly above the upper surface of the slide box 76. Thus, as the slide box 76 is moved to the left as viewed in FIG. 2, the compacted refuse within the slide box is prevented from expanding by the platen 104 on one side and the surface 118 of platen 108 on the other side. When the slide box 76 is moved to the lateral position as viewed in FIG. 2, the cylinder 112 is pressurized to force the platen 108 downwardly, thereby forcing the compacted refuse out of the slide box 76. The pressure exerted by the cylinder 112 is greater than that exerted by cylinder 106 such that the platen 104 moves downwardly under the force of cylinder 112. When the platen 108 has completely forced the refuse out of the chamber 74' of slide box 76, the fingers 114 are caused to move to the right as viewed in FIG. 2, whereupon they move into the slots 110 formed in the platen 108. The platen 108 is now elevated by the cylinder 112 with the compacted refuse being held between the fingers 114 and the lower platen 104. At this point, the compacted refuse has been removed from the slide box, and the platen 108 elevated, whereupon the slide box 76 can again be shifted to the full-line position shown in FIG. 2. As succeeding compacts are added, the platen 104 is caused to move downwardly in steps until a complete bale is formed, whereupon the bale is shifted to the strapping unit 36 shown in FIG. 1 where it is strapped with steel bands and possibly wrapped in polyethylene or the like to seal in any odors. In FIG. 2, the compacts A, B and C are shown in the platen 104.
With reference now to FIG. 4, the hydraulic control system for the cylinders 24-32 is shown. The main pump 120 is of the reversible type and is connected to a motor 122 controlled by a motor control circuit 124. Motor control circuit 124, in turn, is controlled by a main electrical control circuit 126 connected to the operator's control console 128. The pump 120, when rotating in the forward direction, delivers fluid under high pressure to conduit 130; while fluid is fed into the input side of the pump via return conduit 132. The pressure within the return conduit 132 is maintained at a level sufficient to feed oil into the pump 120 by means of a super charging pump 134 connected to the conduit 132 through a check valve 136. The other side of the pump 134 is connected to a hydraulic reservoir 138 which is also connected through a release valve 141 to the return line 132 such that when the pressure within the return line exceeds the supercharge pressure, the valve 141 will open to bleed fluid into the reservoir 138.
At the beginning of a cycle, it will be assumed that all of the pistons and rams within the cylinders 24-32 are in their retracted positions. In the initial stage of operation, when the press ram begins its downward movement, the valve 140, controlled by solenoid 142, will open while valve 144 controlled by a solenoid 146 will be closed. With this arrangement, and assuming that the pump 120 is delivering fluid under pressure to conduit 130, fluid at a pressure of about 3,500 pounds per square inch will be delivered to the tops of the pistons within the cylinders 24 and 28. At the same time, by virtue of the fact that valve 140 is open and valve 144 closed, the fluid from the lower side of the pistons in the cylinders 24 and 28 will also be delivered to the tops of the pistons, thereby speeding the travel of the pistons downwardly.
During this time, dumping valves 148 and 150 will be open, permitting fluid from the reservoir 138 to flow through the valve 150, for example, and the conduit 152 into the top of the cylinder 32. Likewise, fluid will flow from the reservoir 138 through dumping valve 148 and conduit 154 into the tops of the cylinders 26 and 30. This fluid, however, is not under pressure but simply flows by gravity into the tops of the cylinders 26, 30 and 32.
As shown, each dumping valve includes an upper piston 156 carried within a chamber having its opposite ends connected to a pilot pressure hydraulic control valve assembly 158. Connected to the piston 156, by means of a piston rod 160, is a lower valve member 162 which, when in the position shown, will block the flow of fluid from the reservoir 138 to conduit 152 or 154. When, however, the pilot pressure hydraulic control valve assembly 158 causes the upper piston 156 to move downwardly, the valve 162 will become unseated, thereby connecting conduit 152 or 154 with the reservoir 138. The pilot pressure hydraulic control valve assembly 158, in turn, is controlled by the main electrical control circuit 126 connected to the operator's console 128. Valves 150 and 148, however, are not directly controlled by the operator. Rather, they will open up immediately upon descent of the press ram 72 and will close automatically when fluid under pressure is introduced into their associated cylinders.
Assuming again that valve 140 is open and valve 144 is closed, fluid under pressure is admitted to the tops of the pistons in cylinders 24 and 28 while the fluid at the bottoms of the cylinders is returned to the tops of the pistons, thereby increasing the speed of descent of the press ram. Under these conditions, approximately 175 tons of force are exerted on the press ram to shear the refuse between the shear blades 94 and 96 shown in FIG. 2. If, however, additional shearing force is required, the pressure switch 164 senses a rise in pressure above about 3,400 pounds per square inch, whereupon the electrical control circuit 126 will close valve 140 and open valve 144. Now, the entire pressure is delivered to the tops of the pistons within the differential cylinders 24 and 28 only, while the bottoms of the cylinders 24 and 28 are connected back to the input of the pump 120. Under these conditions, approximately 395 tons of force is imparted on the refuse which is clearly sufficient to complete shearing. Once shearing is completed by the higher pressure, this condition is sensed by the pressure switch 164, whereupon the valve again opens and the valve 144 again closes, reducing the force on the refuse to 175 tons while increasing the speed of the press ram.
The press ram will continue to descend at a force of 175 tons until the resistance it meets again causes the pressure switch 164 to trip. At this point, and by virtue of the fact that limit switch LS1 senses that the ram has descended beyond the shearing point, tripping of the pressure switch 164 will cause the valve 140 to remain closed and the valve 144 to remain open during the remainder of the compaction stroke whereby the full pump pressure is delivered to the tops of the pistons in cylinders 24 and 28.
The ram now continues to move downwardly, exerting a force of approximately 395 tons until the pressure sensed by pressure switch 164 rises above 3,400 pounds per square inch. At this time, and by virtue of the fact that limit switch LS1 has been tripped, indicating that the ram is beyond the shearing point, the electrical control circuit 126 energizes solenoid 166 to actuate valve 168 and admit fluid under pressure from the output port of pump 120 into the cylinders 26 and 30 via conduit 170. At the same time, the dumping valve 148 is closed. The press will now continue its downward travel, at reduced speed, under a force of approximately 1,200 tons by virtue of the fact that the full pressure of the pump is being delivered to the tops of the pistons or rams in all of the cylinders 24, 26, 30 and 28. This will continue until the pressure sensed by pressure switch 172 reaches about 3,400 pounds per square inch, whereupon the electrical control circuit will energize solenoid 174 to open valve 176. Fluid under pressure from the output port of pump 120 is now delivered to the top of cylinder 32, whereupon the system is able to deliver a total compressing force of 2,200 tons. When valve 176 is opened, dumping valve 150 closes.
When a total force of 2,200 tons is reached and the pressure again exceeds 3,400 pounds per square inch, this is sensed by pressure switch 178, causing the electrical control circuit 126 to return the pump to neutral and decompress the system via valve 180. When the system is decompressed, electrical control circuit 126 causes valve 144 to open while valve 140 is closed and valves 168 and 176 are open. The pump 120 is now reversed, thereby delivering fluid under pressure to the bottoms of the cylinders 24 and 28 to cause the press ram to retract up to a position where its bottom surface is just above the slide box 76. At this point, the ram stops until the slide box has been moved laterally to the left as shown in FIG. 2, whereupon the valve 144 is again opened and the ram continues its upward movement until a limit switch, not shown, is engaged by the ram, whereupon the cycle is completed preparatory to a succeeding compaction step.
With reference now to FIG. 5, an alternative embodiment of the invention is shown which again includes a plurality of hydraulic cylinders 200 mounted on a fixed crosshead 202 and having their piston rods or rams connected to a movable crosshead 204. In this case, the press is horizontally disposed rather than vertical; however the arrangement of the cylinders 200 is the same as that described in connection with FIG. 4. Carried on the crosshead 204 is a ram 206 which is forced into a press chamber 208 in successive stages, the first stage being at high speed and relatively low pressure, the second stage being at a higher pressure and lower speed, and so on.
Refuse to be compacted is fed into the press chamber 208 through a hinged door 210 actuated by means of a hydraulic cylinder 212 in much the same manner as the embodiment of FIG. 2. At the end of the press chamber 208 is a slideable end plate or block 216 adapted to be reciprocated upwardly on guideways 218 by means of a hydraulic cylinder 220. On the side of the chamber 208 opposite the ram 206 is a restraining platen 214 keyed to side slabs 215 and 217 also keyed to the crosshead 202. Platen 214 has an opening 219 through which a refuse compact is ejected when the block 216 is raised.
In this case, after refuse is fed into the chamber 208 and compacted, the block 216 is moved upwardly, and a platen 222, mounted on hydraulic cylinder 224 is moved inwardly to engage the end of the compact whereupon the ram 206 is advanced further into the press chamber 208 until the compact is pushed out of the chamber through opening 219, whereupon it can be removed by manipulating apparatus similar to that of FIG. 2.
Alternatively, instead of forming a single compact and removing it to subsequently form a bale from a plurality of compacts, the press cycle may be repeated with successive compacts being formed one on top of the other until a complete bale is formed within the press chamber. At this point, the block 216 is moved upwardly out of alignment with the press chamber and the entire bale removed. The difficulty with this method, however, is that in press strokes following the first compaction, an attempt is made to compact the refuse against a more or less resilient body (i.e., the previously formed compact); and difficulties may be encountered in obtaining high densities. This system, however, will be satisfactory where low densities can be tolerated.
With the arrangement shown in FIG. 2, for example, and assuming that the press chamber is 4 feet square, the maximum press force of 2,200 tons will exert a unit pressure of about 1,500 to 2,000 pounds per square inch on the refuse when fully compacted. This is necessary in order to achieve densities on the order of about 1,500 to 2,400 pounds per cubic yard.
As was mentioned above, densities of this sort cannot be readily achieved in an extrusion process. Naturally, the density of each compact will depend upon the nature of the charge of refuse. If the initial density is high, the ram cannot descend too far into the opening 74' in slide box 76; and when the slide box is moved to the left with the surface 100 of the ram 72 above it, very little expansion of the refuse can occur. On the other hand, when the initial density of the refuse is low (i.e., waste paper, feathers or the like), the ram 72 will descend further into the slide box 76 and the material can expand to a greater degree when the ram is retracted. This expansion of the compact, however, is relatively low and related to time. That is, if the compact is permitted to remain unconstrained over a period of time, it will tend to expand. This, however, is prevented by virtue of the fact that the compacts are strapped into bales. Very little expansion occurs between the time that the press ram is retracted and the formation of the compacts into bales.
As was mentioned above, the thickness of the resulting compact formed in the slide box 76 will be dependent upon the initial density of the material fed into the press chamber. This can be regulated by varying the distance between the ends of the conveyors 48 and 52. That is, by exerting a constant pressure on the piston within cylinder 60 shown in FIG. 2, the upper conveyor 52 will tend to move upwardly or downwardly, depending upon the density of the entering refuse. If the density is high, the two conveyors will tend to separate and relatively little compaction of the refuse will occur. However, when the density of the refuse is low, the end of conveyor 52 will be moved downwardly by cylinder 60, thereby compacting the refuse to a greater degree before it is fed into the press chamber. This tends to create a constant density of refuse fed into the chamber 74 regardless of the density of the refuse as it is deposited into the hopper 20.
Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.