Mill for Grinding Garbage

The present invention generally relates to mills for grinding material and particularly to grinding mills for garbage or like material.

A critical problem is the disposal of solid waste which is generated every day in today's society. A common method of solid waste disposal is landfills. However, the volume of landfills is limited and the accessibility to close landfills is becoming more restricted. Thus, a need has arisen to expand the amount of garbage that landfills can accept to extend the life of such landfills.

One method to extend the landfill life is to reduce the compacted volume of the garbage. This is performed by grinding the garbage to reduce the garbage volume by 4 to 1 or more and thereby extending the life of a landfill by that ratio. By composting the ground or processed material, the garbage volume may be further reduced in the order of one half and thereby further extending the life of the landfill. Further, by utilizing high oxygenation of the processed material to invite the growth of aerobic bacteria, the problem of methane gas production existing in current landfills can be reduced and practically eliminated.

Further, many systems for recovering reusable material from garbage or like material requires the garbage to be ground before the garbage is subjected to the various recovery processes.

Thus, a need exists for mills for grinding garbage or like material which is able to grind the garbage to the desired size and to do so efficiently and economically. Such mills should be economical to manufacture and should be able to withstand the forces associated with grinding garbage or encountered when grinding objects which may be found in garbage.

The present invention solves this need and other problems in grinding garbage or like material by providing, in one aspect, a mill including a plurality of planar grinding rotors which are rotatably fixed to a shaft rotatably mounted in a grinding chamber, with the grinding rotors located parallel to, complementary to, and intermediate the inlet opening of the grinding chamber and a plurality of planar shelves.

In another aspect of the present invention, the mill includes a plurality of grinding rotors rotatably fixed to a shaft rotatably mounted in a grinding chamber, with planar shelves being located in the grinding chamber complementary to the grinding rotors, and further including an impeller rotor rotatably fixed to the shaft and located intermediate the plurality of grinding rotors and the outlet opening for forcing the ground material passing around the grinding rotors out the outlet opening. In the preferred form, the grinding rotors include members for enhancing the creation of a vacuum by the impeller rotor and the movement of light weight ground material through the mill.

In a further aspect of the present invention, the spacing through which the material must pass decreases as the material passes through the grinding rotors of the mill. In a preferred form, the radial spacing of the free ends of the arms of the grinding rotors from the grinding chamber decreases from the grinding rotor adjacent the inlet opening of the grinding chamber to the outlet opening of the grinding chamber. Likewise, in the preferred form, the radial spacing between the planar discs of the grinding rotors from the centrally located apertures of the shelves of the grinding chamber decreases from the grinding rotor adjacent the inlet opening of the grinding chamber to the outlet opening of the grinding chamber.

In a still further aspect of the present invention, deflectors are provided in the grinding chamber for deflecting material located generally concentric with the grinding rotors toward the grinding rotors for preventing any tendency of material to simply circle the grinding rotors inside of the mill.

In the preferred form of the present invention, the housing of the mill is formed by four planar side plates interconnected together by their side edges to have a square cross section and by four planar corner plates interconnected by their side edges to adjacent side plates, with the grinding chamber of the mill being defined by the side plates and the corner plates.

In yet a further aspect of the present invention, a multiplicity of wear plates are abutted with the sides of the housing intermediate the intersections of the housing sides in the preferred form by elongated bars which are retained adjacent to the housing plates, with the wear plates preventing internal wear of the housing plates from the grinding operation.

It is thus an object of the present invention to provide a novel mill for grinding.

It is further an object of the present invention to provide such a novel grinding mill for garbage.

It is further an object of the present invention to provide such a novel grinding mill which may be operated efficiently and economically.

It is further an object of the present invention to provide such a novel grinding mill which is economical to manufacture.

It is further an object of the present invention to provide such a novel grinding mill having deflectors provided in the grinding chamber for deflecting material towards the grinding rotors.

It is further an object of the present invention to provide such a novel grinding mill including a novel housing formed by four planar side plates interconnected together by their side edges to have a square cross section and by four planar corner plates interconnected by their side edges to adjacent side plates.

It is further an object of the present invention to provide such a novel grinding mill which is manufactured from stock materials.

It is further an object of the present invention to provide such a novel grinding mill which avoids the use of cast components.

It is further an object of the present invention to provide such a novel grinding mill able to withstand the forces associated with grinding garbage or encountered when grinding objects which may be found in garbage.

It is further an object of the present invention to provide such a novel grinding mill formed by planar rotors formed of planar components which are arranged parallel to planar shelves of a grinding chamber.

It is further an object of the present invention to provide such a novel grinding mill including a propeller type rotor to force the ground material out the outlet opening and to draw the material through the mill.

It is further an object of the present invention to provide such a novel grinding mill including members provided on the grinding rotors for enhancing the vacuum created by the impeller rotor and the movement of the ground material through the mill.

It is further an object of the present invention to provide such a novel grinding mill having decreasing spacing through which the ground material must pass through the grinding rotors of the mill.

It is further an object of the present invention to provide such a novel grinding mill having a dust control system.

It is further an object of the present invention to provide such a novel grinding mill having a composting bacteria inoculation system.

It is further an object of the present invention to provide such a novel grinding mill having provisions for preventing internal wear of the housing from the grinding operation.

It is further an object of the present invention to provide such a novel grinding mill having internal wear preventing provisions formed from stock materials and only requiring cutting to size.

These and further objects and advantages of the present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings.

The illustrative embodiment may best be described by reference to the drawings where:

FIG. 1 shows a perspective view of a garbage grinding mill according to the preferred teachings of the present invention.

FIG. 2 shows a partial, cross-sectional view of the garbage grinding mill of FIG. 1 according to section line 2--2 of FIG. 1.

FIG. 3 shows a cross-sectional view of the garbage grinding mill of FIG. 1 according to section line 3--3 of FIG. 1.

FIG. 4 shows a partial, exploded view of the garbage grinding of FIG. 1.

FIG. 5 shows a partial, cross-sectional view of an alternate embodiment of a garbage grinding mill according to the preferred teachings of the present invention as though taken along view lines 5--5 of FIG. 2.

FIG. 6 shows a cross-sectional view of an alternate embodiment of a garbage grinding mill according to the preferred teachings of the present invention.

FIG. 7 shows a cross-sectional view of the garbage grinding mill of FIG. 6 according to section line 7--7 of FIG. 6.

All FIGS. are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the FIGS. with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood.

Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms "top", "bottom", "first", "second", "inside", "outside", "upper", "lower", "vertical", "horizontal", "rearward", "ends", "side", "edge", and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention.

A mill according to the most preferred teachings of the present invention for processing, resizing, or grinding solid waste, sorted recycled materials such as glass, tin, plastic, aluminium, or paper products, garbage, or like material is shown in the drawings and generally designated 10. In the most preferred form of mill 10 shown in FIG. 1, mill 10 is shown mounted on a trailer for portability. It can be appreciated that mill 10 according to the teachings of the present invention can be constructed for permanent installation. Mill 10 includes a housing 12 which is generally cylindrical in configuration which in the preferred form has a square cross section. In the most preferred form, housing 12 includes four flat or planar, generally rectangular side plates 14, 15, 16, and 17 which are interconnected together by their side edges to have a square cross section. Housing 12 further includes four flat or planar, generally rectangular plates 20, 21, 22, and 23 which are interconnected by their side edges to adjacent side plates 14, 15, 16, and 17 at 45.degree. angles. Plates 14-17 and 20-23 define a grinding chamber 26 having an octagonal cross section, and in the most preferred form the sides of the octagonal cross section have equal lengths and have equal angles therebetween. Housing 12 further includes a top plate 28 and bottom plate 30 attached to the upper and lower ends of plates 14-17 and 20-23.

Chamber 26 of housing 12 is divided into sections by horizontal shelves 32, 34, and 36 secured in chamber 26. Specifically, each of shelves 32, 34, and 36 have an octagonal periphery complementary to and for attachment to the octagonal sides of chamber 26. Each of shelves 32, 34, and 36 further include centrally located apertures 38. Apertures 38 of shelves 32, 34, and 36 in the most preferred form are of the same size. An inlet opening 40 to chamber 26 is formed in top plate 28. An outlet opening 42 from chamber 26 is formed in plate 14 intermediate plates 20 and 23 and below shelf 36.

It can then be appreciated that housing 12 is believed to be particularly advantageous. For example, housing 12 is of a strong design, with plates 20-23 acting as braces between plates 14-17. Further, shelves 32, 34 and 36 are of identical construction to reduce manufacturing set-up and inventory. Furthermore, housing 12 can be easily and rapidly manufactured and assembled with less tolerances than required to manufacture and assemble an octagonal housing as an example.

Mill 10 further includes a shaft 44 rotatably mounted in chamber 26 concentrically within apertures 38 of shelves 32, 34, and 36. In the most preferred form, shaft 44 is rotatably mounted by bearings 46 located in top and bottom plates 28 and 30. Shaft 44 may be driven in any suitable manner. For example, in the most preferred form, shaft 44 extends from chamber 26 beyond bottom plate 30 and includes a suitable drive connection such as a V-belt pulley which in turn can be driven by any suitable means such as an electric motor or an internal combustion engine.

Mill 10 further includes rotors 48, 49, 50, and 51 rotatably fixed to shaft 44 and located complementary to and intermediate opening 40 of chamber 26 and shelves 32, 34 and 36 and bottom plate 30 and in the most preferred form are located above shelves 32, 34, and 36 and bottom plate 30 respectively. Rotors 48-51 each include a circular, flat or planar disc 54 having a central opening 56 and a circular periphery 58. A hub 60 which is longitudinally adjustable but rotatably fixed on shaft 44 along a keyway 62 is located within and attached to opening 56 of disc 54. Discs 54 of rotors 48-50 have a size less than the size of apertures 38 of shelves 32, 34, and 36 and which increases from rotor 48 to rotor 50, with disc 54 of rotor 48 being smaller than disc 54 of rotor 49 and with disc 54 of rotor 49 being smaller than disc 54 of rotor 50.

Rotors 48-50 are in the form of grinding rotors and further include a multiplicity of arms 64 dynamically mounted on and extending radially from discs 54 and circumferentially spaced from each other. Arms 64 are elongated and flat or planar and have a generally rectangular cross section. In the most preferred form, arms 64 are of the same length in rotors 48-50 but are attached to discs 54 such that the radial extent of the free ends of arms 64 from shaft 44 increase from rotor 48 to rotor 50 with the free ends of arms 64 of rotor 48 extending from shaft 44 a radial distance less than the free ends of arms 64 of rotor 49 and with the free ends of arms 64 of rotor 49 extending from shaft 44 a radial distance less than the free ends of arms 64 of rotor 50. In the most preferred form, arms 64 are horizontal and attached to discs 54 by bolts 66 extending through arms 64 and discs 54, with the first or bottom surface 68 of arms 64 abutting directly with the top surface of discs 54.

Bracing structures 70 are further provided in rotors 48 and 49 intermediate arms 64. Specifically, structures 70 are wedge shaped having a thickness which in the preferred form is less than the thickness of arms 64. The bottom surfaces of wedge shaped bracing structures 70 abut directly with the top surfaces of discs 54 and are secured thereto such as by welding and plug welding. The side edges 72 of structures 70 abut directly with the side edges 74 of adjacent arms 64. Arms 64 are then located in a trough formed by adjacent bracing structures 70. It can then be appreciated that discs 54 and bracing structures 70 provide abutment and force transferring support for arms 64, with bolts 66 accepting force on arms 64 in a direction out of the trough formed by adjacent bracing structures 70. Thus, the amount and direction of force to which bolts 66 are subjected in operation are greatly restricted according to the teachings of the present invention. In the most preferred form, disc 54 of rotor 48 may have a greater thickness than discs 54 of rotors 49-51 for increased strength.

Rotors 48-50 are positioned upon shaft 44 above and parallel to shelves 32, 34, and 36, with the vertical or axial spacing of rotors 48-50 above shelves 32, 34, and 36 decreasing from rotor 48 to rotor 50, with the vertical spacing between rotor 48 and shelf 32 being greater than the vertical spacing between rotor 49 and shelf 34 and with the vertical spacing between rotor 49 and shelf 34 being greater than the vertical spacing between rotor 50 and shelf 36. Arms 64 of rotors 48-50 extend radially past apertures 38 and over shelves 32, 34, and 36, with the radial extent which arms 64 extend onto shelves 32, 34, and 36 increasing or in other words the radial spacing of the free ends of arms 64 from chamber 26 decreasing due to the increasing radial extend of the free ends of arms 64 from shaft 44 of rotors 48-50 respectively. Discs 54 of rotors 48-50 are located radially within apertures 38 of shelves 32, 34, and 36, with the radial spacing between discs 54 and apertures 38 decreasing from rotor 48 and shelf 32 to rotor 50 and shelf 36 due to the increasing size of discs 54 of rotors 48-50.

Rotor 51 is in the form of a propeller or an impeller located intermediate the plurality of grinding rotors 48-50 and outlet opening 42 for forcing ground material from grinding rotors 48-50 out of outlet opening 42. In the preferred form, impeller rotor 51 includes a multiplicity of arms 76 dynamically mounted and radially extending from disc 54 and circumferentially spaced from each other. In the most preferred form, arms 76 are formed from angle iron and specifically include a first side 78 and a second side 80. The first end of side 78 abuts directly with the top surface of disc 54 and attached thereto such as by bolts 82 extending through side 78 and disc 54. Side 80 upstands generally perpendicular from disc 54.

Mill 10 further includes a chute 84 extending from outlet opening 42 of chamber 26 to a chute opening 86.

Now that the basic construction of mill 10 according to the preferred teachings of the present invention has been explained, the operation, further enhancements, and subtle features of the present invention can be set forth and appreciated. Specifically, shaft 44 and rotors 48-51 rotatably fixed thereto are rotated. Garbage can then can be introduced through inlet opening 40 by any suitable means such as by a conveyor, not shown. Upon entry into chamber 26, the garbage is impinged by arms 64 of rotor 48 which then breaks or grinds the garbage. It can then be appreciated that to pass rotor 48 and shelf 32, the garbage must pass between arms 64 of rotor 48 which are rotating thus greatly restricting passage therethrough and/or must pass between the free ends of arms 64 of rotor 48 and plates 14-17 and 20-23 defining the walls of chamber 26 and between arms 64 of rotor 48 and shelf 32 and through aperture 38 of shelf 32. It can then be appreciated that the garbage must have been reduced to a physical size before passage is allowed as set forth.

When the garbage passes through aperture 38 of shelf 32, the garbage is impinged by arms 64 of rotor 49 which then further breaks or grinds the garbage. It can then be appreciated that to pass rotor 49 and shelf 34, the garbage must pass between arms 64 of rotor 49 which are rotating thus greatly restricting passage therethrough and/or must pass between the free ends of arms 64 of rotor 49 and plates 14-17 and 20-23 defining the walls of chamber 26 and between arms 64 of rotor 49 and shelf 34 and through aperture 38 of shelf 34. It can then be appreciated that the garbage must have been reduced to a physical size before passage is allowed as set forth. It should be further appreciated that due to the decreasing radial spacing between the free ends of arms 64 of rotor 49 and chamber 26, the decreasing vertical spacing between rotor 49 and shelf 34, and the decreasing radial spacing between disc 54 of rotor 49 and aperture 38 of shelf 34 than the corresponding spacings of rotor 48 and shelf 32, the physical size of the ground garbage passing through aperture 38 of shelf 34 is generally smaller than the physical size of the ground garbage passing through aperture 38 of shelf 32.

When the garbage passes through aperture 38 of shelf 34, the garbage is impinged by arms 64 of rotor 50 which then further breaks or grinds the garbage. It can then be appreciated that to pass rotor 50 and shelf 36, the garbage must pass between arms 64 of rotor 50 which are rotating thus greatly restricting passage therethrough and/or must pass between the free ends of arms 64 of rotor 50 and plates 14-17 and 20-23 defining the walls of chamber 26 and between arms 64 of rotor 50 and shelf 36 and through aperture 38 of shelf 36. It can then be appreciated that the garbage must have been reduced to a physical size before passage is allowed as set forth. It should be further appreciated that due to the decreasing radial spacing between the free ends of arms 64 of rotor 50 and chamber 26, the decreasing vertical spacing between rotor 50 and shelf 36, and the decreasing radial spacing between disc 54 of rotor 50 and aperture 38 of shelf 36 than the corresponding spacings of rotor 49 and shelf 34, the physical size of the ground garbage passing through aperture 38 of shelf 36 is generally smaller than the physical size of the ground garbage passing through aperture 38 of shelf 34.

When garbage passes through aperture 38 of shelf 36, rotor 51 acts as an impeller blowing or forcing the garbage through outlet opening 42 of chamber 26, through chute 84, and out of chute opening 86. It can further be appreciated that rotor 51 acting as an impeller creates a vacuum inside of chamber 26 which acts to suck the garbage from above rotor 51 and around and between rotors 48-50 and shelves 32, 34, and 36.

As a large percentage of garbage is paper or other light weight products such as from packaging, there may exist a tendency for particles when ground from such paper or other light weight products to float above the rotating grinding members. The vacuum created by impeller rotor 51 sucks these light weight particles around and between rotors 48-50 and shelves 32, 34, and 36 and through mill 10 out of chute 84. To enhance the creation of a vacuum and the movement of light weight particles through mill 10, mill 10 according to the preferred teachings of the present invention further includes flaps 88 secured axially intermediate arms 64 and shelves 32, 34, and 36 and radially intermediate discs 54 and aperture 38 of shelves 32, 34 and 36 and particularly in the preferred form to bottom surface 68 of arms 64 of grinding rotors 48-50. In the most preferred form, flaps 88 are formed by an angled member including first and second flat portions 90 and 92 which are interconnected together by an obtuse angle in the order of 150.degree.. Flat portion 90 of flaps 88 abuts directly with bottom surface 68 of arm 64 and is attached thereto such as by bolts 94. Flat portion 92 extends downwardly and rearwardly from portion 90 in a direction opposite to the direction of rotation of arms 64 and rotors 48-50. Thus, upon rotation of rotors 48-50, flaps 88 further create a downward movement of air through chamber 26. The number and location of flaps 88 provided in mill 10 can then be varied according to the actual vacuum created by rotor 51, the type of material which is to be ground, and like factors. It can be appreciated that too much vacuum is undesirable as the material may be pulled through mill 10 before being ground to the desired size. For example, flaps 88 may be provided only on selected arms 64 rather than on all arms 64 of a particular rotor 48-50, with flaps 88 being provided on diametrically opposite arms 64 in rotors 48-50. Likewise, flaps 88 may be omitted from rotor 48 to reduce the impingement area as rotor 48 initially impinge the incoming garbage, and the like.

As generally arms 64 must impinge the garbage for a grinding action to occur and as generally the bulk of the ground material must pass around the free ends of rotors 48-50, mill 10 further includes pusher bars 96 secured to the top surface of arms 64 of rotors 48 and 49 radially inside of discs 54. In the most preferred form, bars 96 are formed of angle iron including first and second flat portions 98 and 100 attached generally perpendicular thereto and triangular end braces 102 attached to the opposite ends for providing additional support for portion 100. Flat portion 98 of bars 96 abuts directly with the top surface of arm 64 and is attached thereto such as by bolts 66 which secure arms 64 to discs 54. Flat portion 100 extends generally perpendicular from the top surface of arm 64. Pusher bars 96 push any material which may have a tendency to collect around shaft 44 and on top of disc 54 radially outwardly to where the grinding action occurs. It should be noted that unground garbage entering chamber 26 through opening 40 may directly engage bars 96 of rotor 48 and/or relatively large sized material only partially ground may engage bars 96 of rotors 48 and 49, bars 96 should have the necessary strength to allow continued operation without fatigue or failure, with end braces 102 enhancing this strength and part longevity. The number and location of pusher bars 96 provided in mill 10 can then be varied according to the type of material which is to be ground and like factors. For example, pusher bars 96 may be provided only on selected arms 64 rather than on all arms 64 of rotors 48 and 49, with pusher bars 96 being on diametrically opposite arms 64 in rotors 48-50. Likewise, due to the generally ground nature of the material reaching rotor 50 and the proximity to impeller rotor 51 and the vacuum created thereby, pusher bars 96 have been omitted from rotor 50 in the preferred form.

Mill 10 further includes provisions for controlling dust from the ground material exiting opening 86 of chute 84 under the windage created by impeller rotor 51. In the most preferred form, first and second nozzles 104 are suspended from chute 84 below opening 86 and generally outside of the path of material exiting from opening 86. Nozzles 104 spray a flat, wide angle of water into the path of material exiting from opening 86 to wet down the material. The water can be supplied to nozzles 104 by pipe water pressure or by an electric pump. If the ground material is going to be composted, nozzles 104 may further inoculate the ground material with a composting bacteria to reduce the time necessary for composting.

In the most preferred form, disc 54 of rotor 49 and shelf 32, disc 54 of rotor 50 and shelf 34, and disc 54 of rotor 51 and shelf 36 are each cut from a single piece of flat material to maximize material useage. Further, disc 54 of rotor 48 in the preferred form is formed of thicker material than discs 54 of rotors 49-51 for increased strength to initially engage and grind the garbage entering chamber 26.

Mill 10 according to the teachings of the present invention is able to effectively and efficiently grind garbage. Particularly, mill 10 utilizes the sharp edges of ground materials such as glass, metal, and hard plastic found in containers, cans, and the like moving inside of chamber 26 and hitting each other and other material to increase the grinding action of rotors 48-50 of mill 10.

According to the preferred teachings of the present invention, mill 10 also includes provisions for preventing any tendency of material to simply circle grinding rotors 48-50 inside of mill 10 concentric to grinding rotors 48-50 and adjacent to the walls and perimeter of grinding chamber 26. In a first preferred form, deflectors 106 are provided for deflecting material from adjacent the perimeter of grinding chamber 26 towards the rotating grinding rotors 48-50 during operation of mill 10. In the preferred form, deflectors 106 are provided attached to plates 14-17 forming chamber 26. In the most preferred form, deflectors 106 are formed of angle iron of a length to fit between top plate 28 and shelves 32, 34, and 36. Deflectors 106 generally include first and second plates 108 and 110 integrally connected along their first edges at right angles and having equal widths. The free, second edges of first plates 108 of deflectors 106 are interconnected to chamber 26 such as by welding generally at the interconnection of plates 20-23 to plates 14-17. The free, second edges of second plate 108 are interconnected to chamber 26 such as by welding to plates 14- 17 at a location spaced from but parallel to the interconnection of plates 20-23 to plates 14-17. In the most preferred form, four deflectors 106 are provided circumferentially spaced equadistant around chamber 26 for each grinding rotor 48-50, specifically at the interconnection of the adjacent sides of the octagonal shaped grinding chamber 26, and particularly at the trailing edges of plates 20-23 relative to the rotation of grinding rotors 48-50 which in FIG. 3 of the drawings is clockwise. It should be noted that the number of deflectors 106 provided should not restrict the flying of material around in grinding chamber 26 and the grinding action caused by the sharp edges of ground material hitting each other.

It should be noted that plate 108 is arranged generally parallel to shaft 44 and generally perpendicular to grinding rotors 48-50 and specifically plate 108 has an axial height which is a multiple of the axial height of side edges 74 of arms 64 and of grinding rotors 48-50, with the height in the preferred form being generally equal to the spacings between top plate 28 and shelves 32, 34, and 36.

It is believed that the particular form and location of deflectors 106 according to the teachings of the present invention in use in an octagonal shaped grinding chamber 26 is advantageous. Specifically, plates 14-17 and 20-23 defining grinding chamber 26 generally are at a 45.degree. angle relative to each other due to the regular octagonal shape. Similarly, due to the equal width of plates 108 and 110 and their perpendicular interconnection to each other, plates 108 extend from plates 14-17 at a 45.degree. angle and thus extend from plates 20-23 and also the cylindrical perimeter or walls defining grinding chamber 26 at a 90.degree. or perpendicular angle. It can then be appreciated that ground material following the perimeter of chamber 26 would encounter and impinge upon plate 108 and thus would be deflected inwardly and away from plates 14-17. Further, due to the angular relationship of plates 108 with respect to plates 14-17 and the longitudinal positioning of deflectors 106 intermediate shaft 44 and the tangential extent of rotors 48-50, plate 108 does not deflect the ground material inwardly into grinding chamber 26 along a radial line but rather along a chord. Thus, the ground material which impinges upon deflectors 106 does not tend to collect thereon but tends to move inwardly into the grinding area of mill 10. The inward movement of material caused by deflectors 106 insures that the deflected material may be impinged by grinding rotors 48-50 and that the deflected material hits and is hit by other material circulating in grinding chamber 26 around and adjacent to grinding rotors 48-50 to increase the grinding action of mill 10.

In an alternate embodiment of mill 10 according to the teachings of the present invention, deflectors 112 are provided for deflecting material from adjacent top plate 28 and shelves 32 and 34 and above grinding rotors 48-50 towards the rotating grinding rotors 48-50 during operation of mill 10. In the preferred form, deflectors 112 are provided attached to the lower surfaces of top plate 28 and shelves 32 and 34 inside chamber 26 and intermediate top plate 28 and shelves 32 and 34 and grinding rotors 48-50 which in the preferred form is above grinding rotors 48-50 respectively. In the most preferred form, deflectors 112 are formed of angle iron of a length to fit between plates 14-17 and apertures 38 of shelves 32 and 34. Deflectors 112 generally include first and second plates 114 and 116 integrally connected along their first edges at right angles and having equal widths. In the most preferred form, deflectors 106 and 112 are formed from the same stock material. The free, second edges of plates 114 and 116 of deflectors 112 are interconnected to the lower surfaces of top plate 28 and shelves 32 and 34 such as by welding. In the most preferred form, four deflectors 112 are provided radially spaced equadistant around chamber 26 for each grinding rotor 48-50, specifically extending generally radially inwardly from deflectors 106, and particularly extending inwardly at an angle of 10.degree. from the radial in a direction of the rotation of grinding rotors 48-50 which in FIG. 5 of the drawings is clockwise. It should be noted that the number of deflectors 112 provided should not restrict the flying of material around in grinding chamber 26 and the grinding action caused by the sharp edges of ground material hitting each other.

It is believed that the particular form and location of deflectors 112 according to the teachings of the present invention are advantageous. Specifically, due to the equal width of plates 114 and 116 and their perpendicular interconnection to each other, plates 114 extend from top plate 28 and shelves 32 and 34 at a 45.degree. angle and thus do not deflect the ground material downwardly into grinding chamber along an axial line but rather at an angle. Further, due to the angular relationship of deflectors 112 with respect to a radial direction, deflectors 112 do not deflect the ground material inwardly into grinding chamber 26 along a radial line but rather along a chord. Thus, the ground material which impinges upon deflectors 112 does not tend to collect thereon but tends to move downwardly and inwardly into the grinding area of mill 10. The downward and inward movement of material caused by deflectors 112 insures that the deflected material may be impinged by grinding rotors 48-50 and that the deflected material hits and is hit by other material circulating in grinding chamber 26 around and adjacent to grinding rotors 48-50 to increase the grinding action of mill 10.

It should further be appreciated that deflectors 106 and 112 are formed from stock angle iron which is easily obtainable at low cost and specifically avoids the high capital cost required for special cast components. Additionally, second plates 110 and 116 act as braces for first plates 108 and 114 to prevent first plates 108 and 114 from bending or otherwise moving from forces created by the material engaging deflectors 106 and 112 in the operation of mill 10, with bracing being especially important for plates 108 arranged generally perpendicular to grinding rotors 48-50 and to the path of the material flying around inside of grinding chamber 26.

In an alternate embodiment of mill 10 according to the preferred teachings of the present invention, housing 12' includes 8 flat or planar, generally rectangular plates 14', 20, 15', 21, 16', 22, 17', and 23 which are interconnected by their respective side edges to define a grinding chamber 26 having an octagonal cross section, and in the most preferred form, the sides of the octagonal cross section have equal lengths and have equal angles therebetween. In the preferred form, housing 12' is formed by bending a sheet of steel into the octagonal shape and then welding the free edges of the sheet together to form grinding chamber 26. Housing 12' further includes an elongated, closeable vertical opening providing access to grinding chamber 26.

Mill 10' further includes 24 flat or planar, generally rectangular wear plates 120 of a height generally equal to fit between top plate 28 and shelf 32, between shelves 32 and 34, and between shelves 34 and 36 and a length generally equal to but slightly less than the length of the sides between the side edges of the octagonal cross section of housing 12'.

Apertures 122 are formed in top plate 28, and shelves 32 and 34 at the interconnections of plates 14', 20, 15', 21, 16', 22, 17', and 23. In the preferred form, each aperture 122 has an angular outside edge corresponding to the interconnection of the respective plates 14', 20, 15', 21, 16', 22, 17', and 23, spaced, parallel side edges extending at an angle from plates 14', 20, 15', 21, 16', 22, 17', and 23 on opposite sides of their interconnections, and an inside edge extending perpendicularly between the side edges.

Mill 10 further includes 8 elongated, vertical bars 124 vertically slideably received in apertures 122 of top plate 28, and shelves 32 and 34 at each of the interconnections of plates 14', 20, 15', 21, 16', 22, 17', and 23. In the most preferred form, bars 124 are of stock material and have a rectangular cross section of a size and shape complementary to and for vertical slideable receipt in apertures 122.

It should be noted that each of bars 124 extend over the adjoining vertical side edges of wear plates 120, with an elongated vertical space existing between the adjoining vertical side edges of wear plates 120 due to the lesser length of wear plates 120 as versus plates 14', 20, 15', 21, 16', 22, 17', and 23 defining the sides of grinding chamber 26. A plurality of bolts 126 extend through housing 12' and are threadably received in bars 124 for holding bars 124 in place and for sandwiching the adjoining vertical side edges of wear plates 120 between housing 12' and bars 124. A ring 128 can be provided on the upper ends of each bar 124 to allow ease of insertion or removal of bars 124 such as by the use of a crane or other lifting device.

It can be appreciated that during operation of mill 10 according to the preferred teachings of the present invention, ground material impacts the sides of grinding chamber 26 which over time results in wear. Mill 10 according to the teachings of the present invention provides replaceable wear plates 120 which are then subject to such wear caused by the grinding operation and which prevent such wear to housing 12'. Thus, with timely replacement of wear plates 120, housing 12' is not subject to wear from internal, grinding forces but only from external, environmental forces.

Specifically, after wear plates 120 have been worn to a point requiring replacement, bolts 126 are removed from mill 10. Bars 124 may then be vertically raised from apertures 122 and out of mill 10. After removal of bars 124, wear plates 120 are not retained in housing 12' but can be tipped between top plate 28 and shelf 32, between shelves 32 and 34, and between shelves 34 and 36 for passage around rotors 48, 49, and 50 through the vertical opening of grinding chamber 26. After the worn wear plates 120 have been removed, new wear plates 120 can be positioned against plates 14', 20, 15', 21, 16', 22, 17', and 23 and bars 124 inserted into apertures 122 and fixed in place by bolts 126.

It can then be appreciated that due to the flat or planar nature of wear plates 120, wear plates 120 may be cut from stock sheets of material. In addition to ease of manufacture, this is particularly advantageous as wear plates 120 can be formed of material which is extremely resistant to abrasion to provide a very high degree of wearability, more so than if the wear plates had to be bent, cast, or welded.

In addition to providing a very unique method of holding and fixing wear plates 120 inside of housing 12', bars 124 are advantageous in that they deflect material from adjacent the perimeter of grinding chamber 26 towards the rotating grinding rotors 48-50 during operation of mill 10 much in the same manner as deflectors 106. It should then be noted that initially the unworn sides of bars 124 as shown in the drawings do not extend at the same angle from grinding chamber 26 as do plates 108 of deflectors 106. However, as the inside corners of bars 124 wear away, the worn sides of bars 124 approximate the angle of plates 108. It can be appreciated that the corners are relatively easy to wear away but as wear continues, more and more surface area is required to be worn away and the rate of wear decreases.

It should be noted that bolts 126 prevent bars 124 from moving vertically upwardly. Further, when tightened, bolts 126 draw bars 124 tightly against plates 120 and thus drawing plates 120 tightly against housing 12' and sandwich plates 120 between bars 124 and housing 12'. Thus, plates 120 are held flush and tightly against housing 12' to prevent relative movement or rattling of plates 120 relative to housing 12' during operation of mill 10.

In the most preferred form, mill 10 includes a cylindrical shroud located between shelf 36 and bottom plate 30 encircling rotor 51. This shroud increases the efficiency of air movement by rotor 51 through outlet opening 42 as well as protect plates 14', 20, 15', 21, 16', 22, 17', and 23 from internal wear.

Furthermore, in the preferred form, bracing structures 70 of rotors 48 and 49 have been eliminated. Further, bolts 66 have been replaced by a first bolt 130 of relatively high shear strength and second and third shear bolts 132 of lesser shear strength than bolt 130, with first bolt 130 located at a first radial distance from shaft 44 and second and third bolts 132 located at a second radial distance from shaft 44. In the most preferred form, the first radial distance is greater than the second radial distance. The advantage of this attachment arrangement is that in the event that arms 64 of rotors 48-50 should strike a relatively solid object, second and third bolts 132 are allowed to be sheared such that arm 64 is allowed to pivot out of the way of the solid object about first bolt 130. Previously, if arms 64 engaged such a solid object, arms 64 would be subject to bending or breaking if bolts 66 held. On the other hand, if bolts 66 sheared, the sheared off arm 64 as well as the solid object would fly around in mill 10 potentially harming other arms 64 and/or housing 12. With the present invention, arms 64 are allowed to give to prevent damage thereto but are retained on respective rotors 48-50 by first bolt 130 such that it does not potentially harm the remaining components of mill 10.

It is further believed that the construction of mill 10 according to the preferred teachings of the present invention is particularly advantageous. For example, wear plates 120, bars 124, rotors 48-50, and housing 12 and 12' are formed from stock materials which are easily obtainable at low cost and specifically avoid the high capital cost required for special cast components. Additionally, the components of rotors 48-51 directly abut each other without wedge shaped members and the like located intermediate thereto. Thus, the amount of stress placed upon bolts 66, 94, 130, and 132 is reduced and can be more easily controlled.

Now that the basic teachings of the present invention have been explained, many extensions and variations may be obvious to one having ordinary skill in the art. For example, a dust separator can be provided at the output end of mill 10 in addition to or alternately to nozzles 104 of the most preferred form.

Although the preferred teachings of the present invention has been explained for grinding garbage and mill 10 is believed to be particularly advantageous therefor, mill 10 may be utilized for grinding like material. For example, mill 10 may be utilized for grinding tires and teeth may be provided on arms 64, in chamber 26, and/or on bars 126 to aid in cutting rubber.

Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.