Abstract:
An apparatus for fine grinding material, such as waste automotive tires. The apparatus includes first and second plates mounted within a housing. The first and second plates include respective, opposed inclined surfaces and respective pluralities of generally radially extending cutting elements. Each of the generally radially extending cutting elements define a serrated edge extending above the corresponding inclined surface. The serrated edges on the first and second plates intermesh with one another while the opposed inclined surfaces define a grinding space therebetween that gradually becomes more narrow in a radially outward direction. One of the plates is mounted for rotation and a drive is operatively coupled with the one plate for rotating that plate during a grinding operation.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to apparatus for size reduction of material pieces and, more specifically, to an apparatus for fine grinding operations used to reduce material, such as rubber, wood, plastic or other materials, into a fine powdered form. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to improvements on the apparatus disclosed and claimed in U.S. Pat. No. 5,509,610 (the &#39;610 patent), the disclosure of which is hereby fully incorporated by reference herein. The apparatus disclosed in the &#39;610 patent may be converted from a centrifugal chopping apparatus to a centrifugal grinding apparatus to reduce particulate material in stages to smaller and smaller particulates. Often, different machines and operations are necessary in order to reduce large objects, such as waste automotive tires, into useful recyclable powered form. Two other examples of apparatus for shredding waste automotive tires are disclosed in U.S. Pat. Nos. 4,684,071 and 4,927,088. 
     Such apparatus as disclosed in U.S. Pat. Nos. 4,684,071 and 4,927,088, and other similar devices, are incapable or at least very inefficient at reducing tires into the fine, powered form necessary for recycling or other constructive uses of the rubber material. For example, finely powered rubber may be added to asphalt for paving roads and highways or may be recycled and formed into various rubber containing products. Therefore, it is very important from an environmental standpoint to further increase the efficiency of reducing waste automotive tires to the most useful form, i.e., a powered form, in order to take these waste tires completely out of landfills and recommit their materials of construction to many useful purposes. 
     Reducing waste automotive tires, and other materials, down to a size of about ¼ inch to ⅜ inch pieces has not been a significant problem in the past. However, the costs associated with the manufacture, operation and maintenance of past grinding machines or size reduction machines capable of grinding or milling these pieces down to, for example, −40 mesh to about 100 mesh is quite high. For example, the costs associated with manufacturing minute openings in the screens used in typical hammer mills and granulators are especially high when considering that the screens must be constantly replaced. The present invention provides even further improvements to the fine grinding abilities of the apparatus disclosed in the &#39;610 patent. 
     It would also be desirable to address other problems with past methods and apparatus for producing minute particle sizes, including improvements related to more efficient and inexpensive manners of setting up and maintaining the apparatus in an optimum grinding configuration. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a centrifugal grinding apparatus especially useful for fine grinding or milling operations. The apparatus generally includes a housing having an inlet and an outlet. A first disc or plate is secured within the housing and includes a first inclined surface and a plurality of generally radially extending cutting elements. Each of the first plurality of generally radially extending cutting elements define a first serrated edge extending above the first inclined surface. A second disc or plate is mounted within the housing and includes a second inclined surface and a second plurality of generally radially extending cutting elements. Each of the second plurality of generally radially extending cutting elements defines a second serrated edge extending above the second inclined surface and intermeshing with the first serrated edge. The first and second inclined surfaces oppose one another and define a grinding space therebetween that gradually becomes more narrow in a radially outward direction relative to the centers of each plate. At least one of the first and second plates is mounted for rotation within the housing and a drive is operatively coupled to the one plate for rotating same during a grinding operation. 
     Each of the radially extending cutting elements of the first and second pluralities of generally radially extending cutting elements further includes a plurality of multi-sided blade elements retained on an elongate support member. The multi-sided blade elements each have at least three sides with each side defining a cutting edge and each blade element is retained on the elongate support member in a manner allowing rotation thereof to select different cutting edges thereon to define a corresponding one of the serrated edges. At least some of the multi-sided blade elements have four sides with each side defining one of the cutting edges. A shearing space is defined between the first and second serrated edges and the shearing space also becomes gradually more narrow in a radially outward direction. The inlet is defined at a radially inward location, and preferably a central location of a stationary one of the plates and the outlet is disposed at a radially outward position, preferably at the periphery of the plates such that grinding takes place as the particulate material moves from the radially inward inlet toward the radially outward outlet through the gradually narrowing spaces between the two plates and serrated edges of the cutting elements. 
     As another feature, at least three adjustment pads are positioned adjacent one of the first and second plates and engage another set of pads adjacent the other plate during the grinding operation. The engagement of these two sets of pads defines the size of the shearing space between the first and second serrated edges. The three adjustment pads are movable, such as through a threaded rotating action, toward and away from the three pads adjacent the other one of the first and second plates. Once the three movable adjustment pads are moved to the desired position they may be locked in place relative to the other three pads to define the size of the shearing space. 
     Various additional features, objectives and advantages of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiment, taken in conjunction with the the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic perspective view of a fine grinding apparatus constructed according to the present invention. 
     FIG. 2 is a perspective view of the stationary disc or plate of the apparatus showing one of the generally radially extending cutting elements being inserted into a recess thereof. 
     FIG. 3 is an enlarged perspective view of the stationary disc and cutting elements shown in FIG.  2 . 
     FIG. 4 is a perspective view of a cutting element associated with the stationary disc and showing one of the multi-sided blade elements removed. 
     FIG. 5 is a perspective view, partially exploded, showing one of the elongate cutting elements of the rotating disc or plate with one of the multi-sided blade elements removed. 
     FIG. 6 is a diagrammatic top view of the grinding portion of the apparatus shown in FIG. 1 schematically illustrating the door and attached stationary disc being moved to the closed position adjacent the rotating disc or plate. 
     FIG. 7 is a cross sectional view taken generally radially through the stationary and rotating discs or plates in a position suitable for grinding. 
     FIG. 8 is an enlarged view similar to FIG. 7, but better illustrating the engagement of the serrated cutting element edges and the adjacent inclined or ramped surfaces of each disc or plate. 
     FIG. 9 is a diagrammatic front elevational view of the apparatus. 
     FIG. 10 is an enlarged, fragmented front elevational view similar to FIG. 9, but illustrating the parallel interaction between the cutting elements on the respective discs or plates. 
     FIG. 11 is a cross sectional view of one adjustment mechanism of the apparatus taken along line  11 — 11  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring generally to FIG. 1, the preferred apparatus  10  of the invention comprises a housing  12  including first and second spaced apart plates  12   a,    12   b  affixed to one another in spaced relation by a plurality of generally radially extending ribs  14 . In addition, plates  12   c  (FIG. 7) are welded between plates  12   a  and 12 b  to form a grinding chamber within housing  12  as will be understood from the description below. Housing  12  generally includes a material inlet  16  and a ground material outlet  18 . A base  20  having a plurality of feet  22  supports apparatus  10 . Feet  22  preferably have a leveling capability. A drive  30  generally comprising a belt  32  and a wheel  34  which may be driven by a suitable electric motor (not shown), such as discussed in the &#39;610 patent, having sufficient power for the particular application. Drive  30  couples to a rotatable shaft  36  extending into a grinding chamber  40 . A material distribution wheel  42  is coupled with rotatable shaft  36  and includes a plurality of generally radially extending blades  44  adapted to distribute material falling into grinding chamber  40  through inlet  16  in a radially outward direction upon rotation by drive  30 . A rotating grinding plate  50 , shown for clarity as a dash-dot line in FIG. 1, is also coupled with rotatable shaft  36 . A pivoting and linearly movable door  52  carries a stationary grinding disc or plate  60  also shown for clarity as a dash-dot line in FIG.  1 . Door  52  is closed as discussed in more detail below against a plurality of size adjustment mechanisms  70  mounted on plate  12   b.  Mechanisms  70  set the distance between the respective rotating and stationary grinding plates  50 ,  60  and thereby set the size reduction capability of apparatus  10 . 
     FIGS. 2-4 better illustrate the construction of each generally radially extending cutting element  80  and generally of stationary disc or plate  60 . Each cutting element  80  generally defines a serrated cutting edge  82  formed along the length of a plurality of multi-sided blade elements  84   a,    84   b,    84   c,    84   d.  As shown in FIG. 2, each cutting element  80  is retained with a corresponding generally radially extending recess  86  within an annular support ring  88  rigidly affixed to an outer mounting plate  90 . The inner surface  92  of the annular support ring  88  comprises a ramped or inclined surface, the purpose of which will be described in greater detail below. The serrated edge  82  of each cutting elements  80 , as best shown in FIG. 3, extend above the inclined surface  92  of the annular support ring  88 . It will be further appreciated that the inclined surface  92  is an undulating surface in which the undulations  92   a,    92   b,    92   c  generally correspond to the serrated edge  82  and gradually get closer to the serrated edge  82  in a radially outward direction as also indicated by FIG.  3 . Blade elements  84   a-d  are secured to an elongate support member  94  using threaded fasteners  96  retained in threaded holes  98 . 
     FIG. 5 illustrates a cutting element  100  associated with the rotatable disc or plate  50  also forming a serrated edge  102  with a plurality of multi-sided blade elements  104   a,    104   b,    104   c,    104   d  affixed to an elongate support member. Blade elements  104   a-d  are secured to an elongate support member  105  using threaded fasteners  1 - 6  retained in threaded holes  108 . It will therefore be appreciated that each of the multi-sided blade elements  84   a,    84   b,    84   c,    84   d  and  104   a,    104   b,    104   c,    104   d  shown in FIGS. 4 and 5 may be removed and replaced with new sharpened blade elements or may be removed and rotated such that dull edges of the multi-sided blade elements  84   a-d,    104   a-d  are replaced by sharp edges of the same element to form the corresponding serrated edge  82 ,  102 . 
     FIGS. 2,  6  and  9  illustrate the general construction and operation of the stationary disc  60 , which also serves as a door to grinding chamber  40 . The door  60  includes a pair of upper and lower hinges  110 ,  112  coupled together by a connecting rod  113  for allowing the pivoting motion shown schematically in dash-dot lines of FIG.  6  and further includes a pair of upper and lower bushings  114 ,  116  and linear rods  118  (FIG. 6, only one shown) for allowing linear motion of the door  60  upon movement to the initial closed position shown in FIG. 6 in solid lines. Upon movement to this position, a pin  120  is dropped into a hole  122  (FIG. 9) in the upper hinge structure  110  to prevent further pivoting motion and the door  60  then may be pushed linearly using bushings  114 ,  116  in the direction indicated by the arrows  124  from the spaced apart position shown in FIG. 6 to the position suitable for grinding, as will be discussed below in connection with FIGS. 7 and 8. As further shown in FIG. 9, holes  130  are provided in the door  60 , as well as in the three mounting flanges  132 ,  134 ,  136  to allow access to fasteners used to fix the cutting elements  80  in place in the annular support ring  88  as will be discussed below. Two mounting flanges  132 ,  134  form parts of hinges  110 ,  112 , while the third flange  136  mounts a handle  140  of door  60 . Once the door  60  is in the fully closed position, three threaded rods  146 ,  148 ,  150  are tightened to secure three pads  152 ,  154 ,  156  of the door  60  against three pads (to be described below) associated with the respective adjustment mechanisms  70 . 
     As shown in FIGS. 7 and 8, an annulus support ring  158  is mounted for rotation within housing  12  and carries the plurality of generally radially extending cutting elements  100 . Cutting elements  100  are received and retained in recesses  160  of support ring  158  using fasteners  162 . Similar fasteners  164  are used to retain cutting elements  80  in respective recesses  86  of annular support ring  88 . Fasteners  166  retain material distribution wheel  42  on annular support ring  158 . The remaining connections and fastening structure, bearings, etc., necessary to rotate annular support ring  158  and cutting elements  100  with respect to annular support ring  88  and cutting elements  80  may be the same as described in the above incorporated &#39;610 patent. Once the door  60  is closed and fixed in the grinding position, a grinding space  170  is created between two generally inclined and undulating surfaces  92 ,  163  of the annular support rings  88 ,  158  that respectively mount the generally radially extending cutting elements  80 ,  100 . As best illustrated in FIG. 8, this grinding space  170  generally narrows in a radially outward direction to help ensure size reduction of the particulate material as it is centrifugally thrown in a radially outward direction into the space by the distribution wheel  42 . In addition, a gradually narrowing shearing space  172  (FIG. 8) is formed between the respective serrated edges  82 ,  102  to ensure size reduction between a radially inward location  176  and a radially outermost position  178 . Once the particulate material exits at the radially outermost position  178 , the material falls downward in housing  12  (FIG. 1) and out from outlet  18 . A seal  180  prevents any of the particulate material from exiting the housing at the juncture with the door  60 . 
     FIGS. 9 and 10 further illustrate the parallel relationship between the respective elongate cutting elements  80 ,  100 . These cutting elements  80 ,  100  preferably do not extend exactly along a radially directed line through the center or axis of rotation of each plate  50 ,  60 , but rather extend parallel to one another so that upon closing the door  60  into the grinding position shown in FIGS. 7 and 8, each of the cutting elements and, more specifically, the serrated edges  82 ,  102  (FIG. 8) intermesh in a precise manner. 
     FIG. 11 illustrates a cross section of one of the adjustment mechanisms  70  with the understanding that the remaining adjustment mechanisms  70  are constructed in an identical manner. A block  200  retains an inner sleeve  202  by way of a roll pin  204 . The inner sleeve  202  includes threads  206  on its outer surface which engage threads  208  in the bore  210   a  of a pad  210 . The pad  210  is retained within a recess  212  of the block  200  and a spacer  214 , retained by a fastener  216 , is used to set the minimum outward extension of a gauge surface  210   b  the pad  210  from the block  200 . The pad  210  may be rotated, when a set screw  218  is loosened, to set the distance that its outer gauge surface  210   b  extends toward the door  60 , or generally away from plate  12   b  the housing  12 . The spacer  214  defines the minimum distance that the door may be closed with respect to plate  12   b.  This sets the minimum gap between the respective cutting elements  80 ,  100  and serrated edges  82 ,  102  thereof to ensure that these cutting elements  80 ,  100  and serrated edges  82 ,  102  cannot come into contact with one another. Conventional measurement indicators, such as a dial indicator, may be used to set each of the pads  210  associated with the three adjustment mechanisms  70  at the proper position. Adjustment mechanisms  70  are spaced apart by 60° on the housing  12  to achieve a proper and consistent gap at all grinding surfaces between the grinding plates  50 ,  60 . When the door or plate  60  is closed, the plurality of threaded rods  146 ,  148 ,  150  are received within the respective inner sleeves  202  and threaded into the housing plate  12   b  as shown in FIG.  6 . The threaded rods  146 ,  148 ,  150  are tightened until pads  152 ,  154 ,  156  on the door are tightened against the pad gauge surfaces  210   b  associated with each corresponding adjustment mechanism  70 . 
     In operation, material (not shown) such as waste automobile tire pieces is fed into the inlet  16  and into the grinding chamber  40 . The drive  30  rotates the material distribution wheel  42  and the attached rotating disc or plate  50  with respect to the stationary disc or plate  60 , for example, at a speed of approximately 325 rpm. The centrifugal force created by this rotating action forces material pieces in a radially outward direction within grinding space  170  and shearing space  172  such that these pieces, which may be on the order of ¼ inch to ⅜ inch in size are ground into smaller and smaller particulate pieces until they reach the radially outermost position  178  of each plate where upon they reach a size sufficiently small to exit the grinding chamber  40 . When the distance between the respective serrated edges  82 ,  102  at the radially outermost position  178  is approximately 0.006 inch, particulates exiting this gap may be on the order of −20 to −40 mesh. In this example, the gap at radially inner position  176  between serrated edges  82 ,  102  may be approximately 0.012 inch. The output particles are directed into material outlet  18  located at the bottom of the housing either by gravity or by an air assist or vacuum pressure which may be operatively connected to the outlet  18 . 
     While the present invention has been illustrated by a description of a preferred embodiment and while this embodiment has been described in some detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features and concepts of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims, wherein