AUGER SHREDDER

Abstract: A shredder capable of grinding large objects to form material of a smaller predetermined size is described. A grinding chamber (20) is defined by a housing. Mounted within the chamber (20) is screw auger means (40, 42) using tapered flights. Motor means is provided to rotate the screw auger means. Hopper means (14) is positioned above the grinding chamber (20) to direct material therein to be shredded by the screw auger means (40, 42). Variable opening means (70, 72) are formed in the bottom of the grinding chamber below the screw auger means. An opening of a selected size allows material shredded by the screw auger means (40, 42) and reduced in size until it is sufficiently small to pass through the opening.

Description: The present invention relates to devices for grinding and shredding large, rigid objects and, more particularly, to devices utilizing large screw augers for grinding and shredding such material. Many devices are known which are capable of grinding, shredding and otherwise reducing the size of scrap material such as wooden pallets, wooden crates, fifty-five-gallon (2081.) oil drums of waste material such as concrete, railroad ties, and the like. For example, Koenig U.S. Patent No. 4,253,615 discloses a pallet auger which includes a grinding chamber within which is mounted a single screw having a tapered flight and which extends from a substantially vertical rear wall into a discharge conduit extending through the front wall of the grinding chamber. The screw flight includes teeth which project radially from the periphery of the flight and mesh with fixed breaker bars positioned on the side walls and floor of the grinding chamber, which together form a continuous, arcuate surface sloped to provide a close clearance with the tapered flight. A different design is disclosed in Wexell, et al. U.S. Patent No. 4,632,317. That device discloses a multiple screw grinding device having an open-bottomed grinding chamber and a plurality of auger screws, each having a non-tapered flight and being offset with respect to each other, as disclosed in the preamble of claim 1. A disadvantage with both types of devices is that there is no mechanism for controlling the ultimate size of the material which is ground by the auger screws. With the Koenig device, some size control can be achieved by restricting the flow of ground material through the exit conduit of the grinding chamber. This "back pressure" allows the end of the screw flight, which includes a radially-extending edge, to perform a shredding action upon a plug of material retained within the exit opening. In contrast, the Wexell et al. device is designed to be a "single pass" device in which the ultimate size of material shredded is a function of the spacing between the slighted grinding screws which are positionable relative to each other. Another disadvantage existing with the Wexell et al. device is that the non-tapered screw flights present a level and even surface to objects such as pallets and large crates so that the broad faces of those objects, when fed downwardly onto the screws, ride or bridge the screw flights. It is then necessary for an operator to manually press the material into the cutting edges of the screw flights, a labor-intensive and often dangerous procedure. Accordingly, there is a need for a device which accepts and grinds large objects such as pallets, crates, oil drums and the like which has the capability of controlling the ultimate size of the pieces of the shredded material. There is also a need for a device for grinding and shredding large objects which is especially suited to accept objects having large surfaces and which prevents a bridging or riding upon the grinding elements. In accordance with the present invention, there is provided a shredder for grinding large objects to form material of a smaller size, a shredder for grinding large objects to form material of a smaller size, comprising: a housing defining a grinding chamber; screw auger means being rotatably mounted within said chamber; motor means adapted for operatively rotating said screw auger means; hopper means positioned above said grinding chamber and adapted for operatively directing material downwardly into said grinding chamber to be shredded by said screw auger means; and an opening means formed in a bottom of said grinding chamber as disclosed in US-A-4632317), the shredder being characterised in that said screw auger means have tapered flights, the opening means are variable opening means for adjusting an opening in the bottom of said grinding chamber to a selected, predetermined size, whereby in operation of said shredder said objects fed to said grinding chamber are shredded by said screw auger means and reduced in size until said material is sufficiently small to pass through said opening. The bottom of the grinding chamber includes a pair of closure doors which are displaceable relative to each other to form an opening of a variable and predetermined size below the screw auger means. Material fed downwardly into, the grinding chamber is retained within the chamber and reduced in size by the action of the screw auger means until the resultant pieces are sufficiently small to pass through the opening. Accordingly, the shredder is capable of performing selective size reduction of large objects. In the preferred arrangement, the shredder has a pair of screw augers with parallel rotational axes within the grinding chamber and having flights which taper in reverse directions. The use of twin augers, as opposed to a single auger, provides a larger "live" grinding area for a grinding chamber of a given size. Furthermore, the reverse taper of the screws presents an uneven surface to material fed downwardly into the grinding chamber, thereby minimising the likelihood that objects with large surfaces will bridge or ride upon the screw flights. Furthermore, the tapered flights expose more of the working surface of each turn of the screw flights so that the working surfaces can engage edges or corners of large-surfaced objects and compress them towards the centre of the grinding chamber to be crushed and drawn downwardly between the screw augers. Also in the preferred arrangement, the closure panels can be completely closed to seal the bottom of the grinding chamber. Consequently, material fed downwardly into the grinding chamber is retained in the grinding chamber and the screw augers perform a blending or homogenizing function, in addition to size reduction. If different materials are fed into the grinding chamber in a single batch, they are broken up and their component pieces are homogenized or blended uniformly. Also in this mode, material which is broken up and falls between the flights of a screw is transported from the large diameter end of the screw along the screw shaft to the small diameter end where it builds up into a mass. That mass is engaged by the large diameter end of the adjacent screw and transported back to the opposite end of the grinding chamber. In doing so, the material is further reduced in size and compressed. In a preferred embodiment, the screw flights include radially-projecting teeth which mesh with stationary breaker bars attached to the side walls and bottom of the grinding chamber. The meshing of the teeth and breaker bars acts to break up particles into smaller pieces as they are ground and transported by the screw flights. The specific embodiment described in detail hereinbelow with reference to the drawings, is a dual auger shredder which is capable of reducing large objects to pieces of a predetermined size and consistency, which is capable of accepting large-surfaced objects such as wood pallets, crates and oil drums, and engaging and grinding those objects without manual assistance, which is capable of performing a blending or homogenizing function, and which is rugged and operates at a low speed to minimise projection of materials upwardly from the grinding chamber. Other objects and advantages will be apparent from the following description, and from the accompanying drawings, in which:- Fig. 1 is a somewhat schematic, side elevation of a preferred embodiment of dual auger shredder, in which the feed hopper and grinding chamber are partially broken away; Fig. 2 is a plan view of the shredder taken at line 2-2 of Fig. 1 in which the motor housing top panels are partially broken away and the closure panels are in an open position; Fig. 3 is a plan view of the shredder of Fig. 2 in which the closure panels are in a closed position; Fig. 4 is an end elevation in section of the auger shredder taken at line 4-4 of Fig. 2; Fig. 5 is an end elevation in section of the shredder taken at line 5-5 of Fig. 3; Fig. 6 is a detail side elevation in section of the shredder of Fig. 1, showing a screw auger within the grinding chamber; Fig. 7 is a detail perspective view of the side and bottom walls of the grinding chamber of the auger shredder of Fig. 1, in which the closure doors are closed; and Fig. 8 is a perspective view of the detail of Fig. 7 in which the closure doors are in an open position. As shown in Fig. 1, 2 and 3, a dual auger, generally designated 10, includes a frame 12 and hopper 14. Frame 12 is segmented into first and second motor housings 16, 18 and a grinding chamber 20. Grinding chamber 20 is defined by substantially vertical front and rear walls, 22, 24, arcuate side walls 26, 28, and bottom 30. As best shown in Figs. 2, 3, 7 and 8, the side walls 26, 28, each include angled surface 32, which is attached to the adjacent longitudinal strut 34 of frame 12 at its upper surface, a downwardly extending surface 36, and an arcuate surface 38. The arcuate surfaces 38 each include a plurality of breaker bars 39 spaced along its length. As shown in Figs. 1, 2 and 3, a pair of screw augers, 40, 42, are mounted within the grinding chamber 20. Screw auger 40 is rotatably mounted on front wall 22 and is driven by hydraulic motor 44, and screw auger 42 is rotatably mounted on rear wall 24 and is driven by hydraulic motor 46. Hydraulic motors 44, 46, are powered by a high pressure hydraulic system (not shown) of conventional design. Hydraulic motors 44, 46, are positioned within first and second motor housings 16, 18, respectively, and are thereby shielded from the corrosive environment within which the shredder 10 may be placed. Motor housings 16, 18, also house a programmable control (not shown) which actuates the screws to rotate to draw material downwardly between them, or to reverse rotation if a jam or buildup occurs, or to rotate at different speeds. An example of such a mechanism is disclosed in Koenig U.S. Patent No. 4,253,615, the disclosure of which is to be regarded as hereby incorporated by reference. As shown in Fig. 6 for screw auger 40, the screw augers 40, 42 each include a central shaft 48 which, in the preferred embodiment, tapers along its length and is mounted at its base on a disc-shaped base plate 50. Base plate 50 is bolted to a rotating ring 52, set into the front wall 22, and is supported by a bearing assembly, generally designated 54. The screw auger 40 includes a flight 56 which tapers in diameter and decreases in pitch from the base plate 50 to an outer segment 58. The flight 56 includes a hardened working edge 60 at its periphery which extends the length of the flight. Spaced along the outer periphery 62 of the flight are a plurality of teeth 64 which, as shown in Figs. 4 and 5, are wedge-shaped and extend radially from the outer peripheries 62 of the screw augers 40, 42. Teeth 64 and breaker bars 39 are spaced such that the teeth mesh with the breaker bars when the screw augers 40, 42 are rotated. The screw augers 40, 42 are positioned within the grinding chamber 20 such that the flights 56 taper oppositely to each other, as shown in Figs. 1, 2 and 3. This presents an uneven surface to an object which is dropped downwardly through hopper 14 onto the auger screws 40, 42, thereby reducing the likelihood that the object will ride upon or bridge the flights of the screws and not be engaged by the working edges 60 of the screw flights 56. Furthermore, the tapered shapes of the flights 56 expose more of the working edge 60 of the flights than would occur with a non-tapered flight. This greater exposure allows the working edge 60 to engage a corner or edge of a large-surfaced object such as a pallet or crate. The screw augers 40, 42 are cantilevered from their respective walls 22, 24, but include tips 66, extending outwardly from the ends of the screws which engage cones 68. Cones 68 are attached to walls 22, 24 opposite the wall supporting the associated screw augers 40, 42, and help direct the flow of material within the grinding chamber 20 when the auger screws are rotated. The bottom 30 of the grinding chamber includes a pair of closure doors 70, 72, which are plate-shaped and extend between front and rear walls 22, 24, as shown in Fig. 3. As shown in Figs. 4 and 5, closure doors 70, 72 slide along upper and lower pairs of rails 74, 76 respectively (shown in Figs. 4 and 5 for rear wall 24). The closure doors 70, 72 are slidably displaced along the rails 74, 76 by double acting cylinder motors 78, 80, which are attached to the doors by clevis assemblies 82 and to the side walls 84, 86 of the frame 12 by clevises 88. As shown in Figs. 7 and 8, the closure doors 70, 72 each include downwardly depending, wedges 90, 92. The wedges 90, 92 are positioned on the closure doors 70, 72 such that a complete seal is formed when the doors are closed, as shown in Fig. 7. The closure doors 70, 72 are skewed relative to each other so that they conform to the sloped contours of their associated side walls 26, 28. As a result, the side walls 26, 28 and bottom 30 of the grinding chamber 20 conform to the tapers of the flights 56 of the oppositely disposed screw augers 40, 42. Positioned below the closure doors 70, 72 is a discharge chute, generally designated 94, which is defined by walls 96, 98 and portions of front and rear walls 22, 24. Walls 96, 98 have openings (not shown) through which the clevises 82 of the double acting cylinder motors 78, 80 extend when positioning the closure doors 70, 72. The operation of the dual auger shredder 10 is as follows. The hydraulic motors 44, 46 are actuated to begin rotation of the screw augers 40, 42 at a relatively low speed, within a range of less than one revolution per minute to 30 revolutions per minute. The screws 40, 42 are counter-rotated so that the teeth 64 rotate toward the gap between the auger screws. As material is dropped through the hopper 14, it is engaged by the screw flights 56 of the screw augers 40, 42. The exposed working edges 60 of the screw flights engage the corners and edges of large-surfaced materials such as pallets, crates, fifty-five gallon (2081.) oil drums, railroad ties, and the like, compressing the object towards the centre of the grinding chamber 20. At the same time, the teeth 64, which rotate in a circular orbit perpendicular to the axis of rotation of the screw augers 40, 42, tend to hold the object they engage stationary with respect to the longitudinal axes of the screw augers. However, the working edges 60 of the screw augers 40, 42 act to move that same piece so that the piece is broken up along its length in addition to being compressed and crushed. This is because the point of engagement of the working edge 60 with the object to be shredded progresses towards the center of the grinding chamber 20 as the screw auger 40, 42 rotates, while the path of the teeth 64 remains stationary relative to its position along the longitudinal axis of the screw auger. Consequently, material is compressed toward the centre of the screw auger and broken up as it is compressed, so that it is more easily drawn downwardly between the two screw augers 40, 42. If it is desired to shred and grind material until it has reached a predetermined width, the closure doors 70, 72 are opened to form a gap of a predetermined width such as that shown in Figs. 4 and 8. Consequently, material within the grinding chamber 20 remains in the chamber and is continually ground and shredded by the interaction of the teeth 64, screw flights 56 and breaker bars until it has been reduced in size sufficiently to pass through the opening. If it is desired to operate the dual auger shredder to perform a blending or homogenizing function, the closure door 70, 72 is completely closed as shown in Figs. 5 and 7. Material fed into the grinding chamber 20 is retained in the chamber and is broken up until it is sufficiently small to fit between the turns of the flights 56 of the screw augers 40, 42. Material this size is pushed by the rotating flights 56 from the large diameter end of an auger screw to the small diameter end, where it builds up to form a plug. This plug is engaged by the large diameter end of the adjacent screw auger and is again transported along that screw auger to its small diameter end. As it progresses along the length of the grinding chamber, it is further reduced by the meshing of the teeth 64 and breaker bars 39. At the same time it is reduced in size, it is also blended and homogenized. When this action is completed, the closure doors 70, 72 are opened to allow the material to exit through the discharge chute 94.

Claims: A shredder for grinding large objects to form material of a smaller size, comprising: a housing defining a grinding chamber; screw auger means being rotatably mounted within said chamber; motor means adapted for operatively rotating said screw auger means; hopper means positioned above said grinding chamber and adapted for operatively directing material downwardly into said grinding chamber to be shredded by said screw auger means; and an opening means formed in a bottom of said grinding chamber; the shredder being characterised in that said screw auger means have tapered flights, the opening means are variable opening means for adjusting an opening in the bottom of said grinding chamber to a selected, predetermined size, whereby in operation of said shredder said objects fed to said grinding chamber are shredded by said screw auger means and reduced in size until said material is sufficiently small to pass through said opening. A shredder according to Claim 1, further characterised in that said variable opening means includes first and second closure doors slidably mounted in said bottom; and displacement means adapted for operatively displacing said closure doors toward and away from each other to vary the size of said opening. A shredder according to Claim 2, further characterised in that said displacement means comprise double-acting cylinder motor means. A shredder according to Claims 2 or 3, further characterised in that said screw auger means include first and second augers being positioned such that said flights taper oppositely relative to each other; and in that said first and second closure doors are positioned below said augers and are sloped to follow outer contours of said screw flights, whereby said first door is skewed relative to said second door. A shredder according to Claim 4, further characterised in that said first and second closure doors each include downwardly depending means extending from abutting edges thereof and adapted for completely sealing said bottom when said doors are closed. A shredder according to any of Claims 2 to 5, further characterised in that said closure doors extend the entire length of said grinding chamber. A shredder according to Claim 6, further characterised in that said grinding chamber includes front and rear walls, and in that said front and rear walls each include track means adapted for operatively receiving ends of said closure doors slidably therein.

Inventors: KOENIG, LARRY E.
Applicants: KOENIG, LARRY E.
Application year: 1990
Main classification: B02C19
IPC codes: B02C19