Abstract:
A grinder having a grinding structure and a sizing screen is disclosed herein. A top cover covers the grinding structure. The sizing screen can be removed from the grinder by opening the cover, and lifting the sizing screen through the opening left by the cover.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. application Ser. No. 11/015,173, filed Dec. 17, 2004, now U.S. Pat. No. 6,978,955; which is a divisional application of U.S. application Ser. No. 10/299,981, filed Nov. 18, 2002, now U.S. Pat. No. 6,843,435; which applications are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention generally relates to grinding machines known as horizontal grinders, and more particularly to the apparatus and methods that enable access to the grinding drum and for changing the sizing screens. 
   The grinding of a variety of materials can have a desirable effect. For instance grinding of some types of waste results in increased rate of decomposition, which is useful in landfill operations. Ground wood waste results in mulch, which is useful in landscaping applications. Ground asphalt can be reused. Some types of ground shingles can be used in asphalt production. The benefits of and need for such recycling processes continue to grow. 
   Several types of machines are useful in the variety of grinding applications. One type is particularly adaptable to a wide variety of applications, known as a horizontal grinder. Horizontal grinders typically include a horizontal feed table onto which the materials to be ground can be placed. The feed table is capable of moving the product to a point where a feed roller begins to cooperate with the feed table, generally pressing down on top of the material and being rotationally powered. The material is then forced, by the cooperation of the feed roller and the feed table, into contact with the side of a grinding drum. The grinding drum is as wide as the feed table and rotationally powered on a generally horizontal axis perpendicular to the direction of travel of the feed table. 
   The grinding drum typically includes hammers or cutters that impact the material as it is fed from the feed roller/feed table. These hammers or cutters tend to propel the material around the axis of rotation of the drum, eventually moving the material past a stationary bar, typically known as an anvil, that is in relatively close proximity to the outer swing diameter of the hammers or cutters. The material will be reduced in size to some extent, as necessary to travel past the anvil. However, further size reduction is typically required. 
   The additional size reduction is typically accomplished by the interaction of the hammers or cutters with a sizing screen that is also in relatively close proximity to the outer swing diameter of the hammers or cutters. The sizing screen includes holes to allow the material to pass after being reduced to the desired size. It has been found that the shape and size of the holes affects the performance of the machine and the resulting size of the ground material. 
   The sizing screens are typically provided on the bottom of the grinding drum, so that as material exits the holes in the sizing screen it will fall to a conveyor. A cover is typically provided over the top of the grinding drum to hold material from being thrown out and to carry material not yet sufficiently ground back around. 
   The grinding drum, sizing screens and cover are mounted in a mill box that provides the support needed for the tremendous loads that can be generated, particularly when grinding the more difficult materials. These tremendous loads result in the sizing screens being constructed of thick metal, and are thus heavy and difficult to handle. The normal operation of the grinding machine results in substantial loading and wear of the sizing screens. Thus, they must be removed for repair or replacement. In addition, they are changed out to modify the quality of the resulting ground material when being used for varying applications. 
   In some materials there is a possibility that the material will be wrapped around the grinding drum, between the hammers or cutters, and eventually pinched between the drum and the sizing screens. In this condition there may be sufficient drag on the drum to stall it. In this situation it is necessary to gain access to the drum to remove the wrapped material. 
   SUMMARY OF THE INVENTION 
   The present disclosure includes examples of inventive aspects adapted for facilitating providing access to the sizing screen of a grinder. The present disclosure also includes examples of methods for installing and removing sizing screens. Examples of a variety of inventive aspects are set forth in the description that follows. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the broad inventive aspects disclosed herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a materials grinder having features that are examples of inventive aspects in accordance with the present disclosure; 
       FIG. 2  is a schematic, partial side elevation view of the grinder shown in  FIG. 1 ; 
       FIG. 3  is a cross section taken along line  3 - 3  as illustrated in  FIG. 1 ; 
       FIG. 4   a  is the same view as seen in  FIG. 3  with the cover in the open position and the sizing screen ¼ removed; 
       FIG. 4   b  is the same view as seen in  FIG. 3  with the cover in the open position and the sizing screen ½ removed; 
       FIG. 4   c  is the same view as seen in  FIG. 3  with the cover in the open position and the sizing screen fully removed; 
       FIG. 5   a  is a perspective view of a mill box of the horizontal grinder of  FIG. 1 , the mill box is shown in the open position with the sizing screen in a partially removed position; 
       FIG. 5   b  is a perspective view of the mill box of  FIG. 5   a  in a closed position; 
       FIG. 6  is a side view of a sizing screen of the grinder of  FIG. 1  shown in the installed orientation and in the removed orientation. 
       FIG. 7  is an isometric view showing the sizing screen in the removed position, as suspended by the lifting bar. 
   

   DETAILED DESCRIPTION 
   Referring to the drawings, and in particular to  FIG. 1 , a materials grinder  100  is illustrated that includes features that are examples of inventive aspects in accordance with the present disclosure. This materials grinder is of the type known as a horizontal grinder and includes a feed hopper  110  for supporting a wide variety of materials. The grinder  100  is capable of holding loose materials such as leaves, shingles, small branches and also capable of holding larger objects such as large branches, boards, planks. A feed table  112 , in cooperation with side panels  114 , provides this capability. 
   The materials loaded into the feed hopper  110  are propelled towards a mill box  150  by conveyor bars  116  that are attached to conveyor chain  117 . Conveyor chain is routed around conveyor sprockets  119  that are mounted onto conveyor roller shafts  118 . One of the conveyor roller shafts  118  is powered, typically by a hydraulic motor in a manner that allows the conveyor bars to be propelled in either direction. 
   As the material is propelled towards the grinding drum, it will contact feed roller  120 . Feed roller  120  is mounted on a feed roller shaft  122  that is supported on mount arms  126 . The feed roller  120  is driven by a hydraulic motor, and typically includes feed bars  124 . The feed bars engage the material to be ground tending to keep it on top of the material and providing additional feed pressure on the material, urging it towards the mill box  150  which will contact the material and grind it to a desired size. 
   Ground material will exit mill box  150  and fall onto a discharge conveyor  200  that will transport it to a position beside the materials grinder  100 . 
     FIG. 2  illustrates the mill box  150  area in more detail. The mill box  150  includes a grinding drum  160  mounted on drum shaft  162 , a sizing screen  180  and top cover  170 . The sizing screen  180  extends below the drum  160 . The top cover  170  is positioned directly above the grinding drum  160  as further illustrated in  FIG. 3 . It serves to hold material that is being ground from being thrown from the machine and provides pivotal support for the feed roller mount arms  126  at pivot points  128 . 
   The operating positioning of the components of the mill box is illustrated in  FIG. 3 . The feed hopper  110  retains the material to be ground while the conveyor bars  116  propel it towards the mill box  150 . As it nears the mill box  150  feed roller  120  will contact the top portion of the material to be ground and assist in forcing it into contact with the grinding drum  160  which is being rotated about drum shaft  162 . An example of a grinding drum can be seen in U.S. Pat. No. 6,422,495, herein incorporated by reference, including cutters  164  mounted on hammers  166 . Many different styles of grinding drums are available. The cutters  164  will contact the material and drive it down, towards an anvil  182 . The initial impact of the cutters  164  will cause the material to be partially ground. Further impact and shearing forces will be applied as the material passes between the anvil  182  and the grinding drum  160 . The clearance between the outer swing diameter of the cutters  164  and the anvil  182  will affect the size of the ground material, and the anvil is typically located close to this outer swing diameter. 
   Once the material passes the anvil it is trapped between an inner surface  182  of the sizing screen  180  and the drum  160 . There it may pass through a hole in the sizing screen  180  and be ejected from the mill box  150 . Bigger pieces may become partially engaged with a hole in the sizing screen  180  and then subsequently impacted again by a cutter  164  causing them to be reduced in size to fit through the holes and be ejected. Other larger particles may be carried around the inside surface  182  of the sizing screen  180 , the inside surface  172  of the top cover  170 , and carried back to the feed hopper  110 . 
   The inner surface  182  preferably defines a curvature of constant radius that is centered about the axis of rotation of the drum  160 . The clearance between the inner surface  182  of the sizing screen and the hammers, and the size and configuration of the holes in the sizing screen  180  will affect the performance. Changing these parameters will affect the quality of the ground material as required by the variety of applications. In addition, when grinding some products, they will tend to wrap around the drum  160  rather than being ground, and can wrap sufficiently to prevent free rotation of the grinding drum  160 . In this case it may be necessary to interrupt operation, to relieve the pressure on the wrapped material, and to remove it prior to resuming operation. 
   The mill box of the present invention provides enhanced access capabilities as illustrated in  FIGS. 4   a ,  4   b  and  4   c .  FIG. 4   a  illustrates the top cover  170  pivoted about pivot point  178  into an open position. In this position an operator is able to gain access to the grinding drum  160  to clear any obstacles. It is also possible to attach a lifting device (e.g., a crane or hoist) to a lift member such as a lift bar  186  of the sizing screen  180  in order to lift the sizing screen out of the mill box. As shown in  FIG. 7 , the lift bar  186  can include an eyelet  187  or other type of structure for receiving a hook, chain or other component of a lifting device.  FIGS. 4   b  and  4   c  illustrate the sizing screen and lift bar as they are further removed from the mill box, to the position illustrated in  FIG. 4   c , where the sizing screen is completely removed. 
   The first step of the removal process is to pivot the top cover into the open position of  FIG. 4   a . This step is enabled by cylinder  174 , as illustrated in  FIG. 5   a  with the top cover in its open position. This figure illustrates the top cover  170  in the open position where the cylinder  174  has been extended. The initial extension of cylinder  174  will rotate latch  176  around latch pivot  177  to disengage from latch pin  152  (shown in  FIG. 5   b  where the cover is closed). Additional extension of cylinder  174  will rotate top cover  170  around pivot  178  to the open position illustrated. In this position any material that had been trapped between the drum  160  and the top cover  170  will be released and an operator can gain access to the grinding drum  160  to remove wrapped material. 
   In the normal operating position of the mill box, illustrated in  FIG. 5   b , the top cover  170  will be in the closed position where cylinder  174  is retracted and has pulled latch  176  into engagement with latch pin  152 . Latch pin  152  is secured to mill box frame  154 , which is comprised of two sides  155  and cross members  158 ,  159  and anvil  182 . The mill box frame also provides support for the top cover pivot  178 , grinding drum bearings  168  and a pair of sizing screen slides  156  (i.e., guides or tracks as shown in  FIG. 5   a ). In the closed configuration, with the latch  176  engaged with the latch pin  152 , the forces of the grinding action, occurring between the cutters  164 , the sizing screens, and top cover  150 , are retained within the structural component defined by the mill box frame  154 . 
   Referring to  FIG. 7 , the sizing screen  180  includes a sizing plate  181  defining a plurality of sizing openings  183 . The plate  181  (i.e., one or more plates) has an upper end  185  and a lower end  187 . Edges  189 ,  191  of the plate  181  extend between the upper and lower ends  185 ,  187 . Curved reinforcing flanges  193  are secured to the outer side of the plate  181  and extend generally along the edges  189 ,  191 . Cross-braces  195 ,  197  extend between the flanges  193 . A top plate  184  extends outwards from the upper end  185  of the plate  181 . The top plate  184  is reinforced by enlargements  199  of the flanges  193 , as well as a pair of reinforcing plates  201  that extend between brace  197  and the top plate  184 . 
   Referring to  FIG. 5   a , the slides  156  are connected (e.g., welded or fastened) to opposite side walls  155  of the mill box. As shown schematically in  FIGS. 4   a - 4   c , the slides  156  have a curvature that curves about the axis of rotation of the drum  160 . The slides  156  are oriented such that lower regions  157  of the slides are positioned closer to the axis of rotation of the drum  160  than upper regions  159 . As shown in  FIG. 3 , the mill box also includes a stop  205  positioned adjacent the anvil  182 . The stop  205  is adapted to abut against the lower end  187  of the sizing plate  181 . 
   Referring still to  FIG. 3 , an end plate  207  projects outwardly from the lower end  187  of the sizing plate  181 . The end plate  207  underlaps the stop  205  to prevent the lower end  187  of the sizing plate  181  from flexing inwardly. 
   In this normal operating position, as illustrated in  FIG. 3 , a flange  171  of the top cover  170  opposes the top plate  184  of the sizing screen  180 , trapping and holding the top plate  184  in position. With the top cover in the open position, there are no retainers holding the sizing screen in position. It is, at that time held in position by slides  156  and cross member  158  of the mill box frame  154 . For example, the top plate  184  seats on cross-member  158 , the edges  189 ,  191  of the sizing plate  181  seat on the lower regions  157  of the slides  156 , and the lower end  187  of the sizing plate  181  abuts against the stop  205  of the mill box. 
   To remove the sizing screen  180  a lifting device, not shown, is attached to the lifting bar  186  in order to lift it out of the mill box frame  154 , as shown in  FIGS. 6 and 7 . As the sizing screen  180  is lifted it will tend to follow the slides  156 , rotating around the centerline of the grinding drum  160 , as the slides  156  are arcuate and extend generally along an exterior of the drum  160 . Lift bar  186  is pivotally attached to the sizing screen  180  at a pivot point  188  that is positioned such that when removed, the sizing screen will be moved by gravity to the orientation illustrated in the upper position of  FIG. 6 . In this manner the lift mechanism can operate to provide a nearly straight lift, and the sizing screen will be removed in a manner that makes it easy for an operator to control. 
   Likewise for installation, the sizing screen  180 , when lifted by the lift bar  186 , will be in the correct orientation to begin to engage with slides  156 . The installation process will then include first lifting the sizing screen into position so that its lower end  187  engages the slides  156 . The sizing screen is then lowered. As it is lowered it will rotate around pivot point  188  as the screen rides downwardly along the slides  156 . As the sizing screen moves downwardly along the slides  156 , the sizing screen is gradually moved into its final position in close proximity to the drum  160  by the lower regions  157  of the slides  156 . In other words, the transition from the upper regions  159  of the slides to the lower regions  157  of the slides causes the sizing screen  180  to move gradually towards the drum  160  to its final position in close concentric proximity to the drum  160 . After it has been completely lowered, the back surface of the lift bar  186  will be resting against cross member  158 , and the lift bar  186  is positioned between the reinforcing plates  201  of the sizing screen  180 . Once the screen  180  is fully lowered, the lifting device will be detached from the lift bar  186 . The top cover will then be closed, resulting in flange  171  contacting top plate  184 , trapping the sizing screen in place. Sizing screen  180  is then held in place by the lower portions  157  of slides  156 , the cross member  158  and the stop  205 . The cylinder  174  will then fully retract and latch  176  will reengage latch pin  152 . 
   In this manner the present invention provides a mill box that allows the operator to quickly and conveniently gain access to the grinding drum to release pressure of wrapped material and clean out wrapped material. It also provides for a quick and convenient method to remove, and exchange or repair the sizing screens. 
   The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. While a preferred embodiment of the present invention relates to horizontal grinders, it will be appreciated that the various inventive aspects are also applicable to other types of grinder configurations. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.