Abstract:
A grinding machine has a shearing chamber that includes one or more edges that provide fulcrum points against which frozen block of material, such as frozen blocks of meat, can be held against during a reduction or shearing process. The edges may be arranged to limit the advancement of reduced blocks of material to provide more control on the size of the ground material that is ultimately output by the grinding machine. The grinding machine may also include an expansion zone into which reduced blocks can be temporarily held to accommodate volume increases during the reduction process. A feed screw advances the frozen blocks through the shearing chamber and includes pressure flighting to help shear material from the frozen blocks. The feed screw may include a knife holder that provides support for a knife held therein against the lateral forces experienced by the knife as the knife shears material adjacent the orifice plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of U.S. Ser. No. 60/946,301, the disclosure of which is incorporated herein. 
     
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
       [0002]    The general structure of grinding machines is well known. Typically, a grinding machine has a hopper into which the material to be ground is placed, a grinder portion, including a grinding head, a mounting ring, a bridge, and a collection tube. A feed screw is located within the grinding head to advance material in the hopper through the head. A knife assembly is mounted at the end of, and rotates with, the feed screw and, in combination with the orifice plate, serves to grind material that is advanced toward the orifice plate by the feed screw. Typically, the orifice plate includes collection passages that lead to a collection cavity defined by a collection cone, which supplies material to a discharge passage. An orifice plate guard is located downstream from the orifice plate and maintains the collection structure in place, and a mounting ring holds a guard against the orifice plate and mounts the intervening structures to the body of the grinding head. 
         [0003]    When frozen material is to be ground in a conventional grinding machine, the feed screw rotates in an internal chamber of the hopper to shear the frozen material. The internal chamber is defined by a longitudinal wall spaced from the feed screw. The frozen material is thus translated by the feed screw against the longitudinal wall as the frozen material is moved toward the orifice plate. This can place an undesirable side load on the feed screw. In addition, because the longitudinal wall is relatively smooth, the frozen material slides along the wall as it is moved toward the orifice plate. Moreover, the spacing of the wall from the feed screw can result in chunks that are sheared from the frozen material undesirably bouncing around as the feed screw rotates. 
         [0004]    Another drawback of a conventional grinding machine is the limited number of shearing surfaces that are available. More particularly, in a conventional grinding machine, the frozen material can be sheared either by the knife at the forward end of the feed screw or by the pressure flighting on the body of the feed screw as the frozen material is pressed against the longitudinal wall of the internal chamber. However, as the block is reduced and/or the chunks of the block are bouncing around, it is difficult to hold the reduced blocks between the feed screw and the internal chamber wall. As such, reduced blocks of material may be advanced by the feed screw that are larger than desired. 
         [0005]    Another drawback of conventional hoppers is the lack of post-reduction but pre-discharge volume. More particularly, a frozen block placed into the hopper will occupy a given volume. As the frozen block is sheared and thus reduced, the collective volume for all the reduced portions of the block will be greater than the volume originally occupied by the whole block. This is a result of air pockets that form between the sheared portions. 
         [0006]    As noted above, conventional grinding machines use a knife positioned at a forward end of the feed screw. The knife is positioned in a knife holder that is coupled to the feed screw. The knife is an effective shearing tool as long as it is capable of withstanding the torsional loads placed on the knife during the shearing or grinding process. 
         [0007]    Therefore, in accordance with one aspect of the invention, the internal chamber of a grinding machine includes one or more shearing edges that provide fulcrum points against which frozen blocks of material can be held to assist with shearing of the frozen blocks by a feed screw. The shearing edges may be arranged to limit the advancement of over-sized blocks by the feed screw. 
         [0008]    In accordance with another aspect, the invention provides a grinding machine having a transition or expansion zone into which frozen material may be fed by the feed screw before ultimately being discharged by further advancement of the feed screw. The transition zone is designed to accommodate the increased volume of material that results as a frozen block is reduced. 
         [0009]    In accordance with a further aspect of the invention, a feed screw for use with a grinding machine includes fins designed to provide support for a knife as the feed screw is rotated and the knife shears frozen material against the orifice plate. 
         [0010]    It is therefore an object of the invention to provide a grinding machine that provides improved shearing efficiency. 
         [0011]    It is another object of the invention to provide a grinding machine that provides improved control of the blocks as the blocks are moved toward the discharge of the grinding machine. 
         [0012]    It is a further object of the invention to provide a knife holder that provides improved support for the torsional loads placed on a shearing knife used to shear frozen material. 
         [0013]    Various other features, objects and advantages of the present invention will be made apparent from the following detailed description taken together with the drawings, which together disclose the best mode presently contemplated of carrying out the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which: 
           [0015]      FIG. 1  is an isometric view of a grinding machine incorporating the various aspects of the present invention; 
           [0016]      FIG. 2  is a section view of the grinding machine of  FIG. 1  taken along line  2 - 2  of  FIG. 1 ; 
           [0017]      FIG. 3  is an exploded view of a grinder section of the grinding machine of  FIG. 1 ; 
           [0018]      FIG. 4  is an partial section view of a portion of the grinding machine of  FIG. 1 , taken along line  4 - 4  of  FIG. 2 ; 
           [0019]      FIG. 5  is an enlarged view of a portion of that shown in  FIG. 4  taken along line  5 - 5  of  FIG. 4 ; 
           [0020]      FIG. 6  is a longitudinal section view of the portion of the grinding machine shown in  FIG. 4 ; 
           [0021]      FIG. 7  is an enlarged view of a portion of that shown in  FIG. 6  taken along line  7 - 7  of  FIG. 6 ; 
           [0022]      FIG. 8  is cut-away isometric view of the portion of the grinding machine shown in  FIG. 5 ; 
           [0023]      FIG. 9  is an enlarged view of that shown in  FIG. 8  taken along line  9 - 9  of  FIG. 8 ; 
           [0024]      FIG. 10  is an isometric view of an end portion of a feed screw for use with the grinding machine of  FIG. 1  and having a knife holder according to one embodiment of the invention; 
           [0025]      FIG. 11  is an exploded view of that shown in  FIG. 10 ; 
           [0026]      FIG. 12  is an end view of the feed screw shown in  FIG. 10 ; and 
           [0027]      FIG. 13  is an elevation view of the feed screw shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Referring to  FIG. 1 , grinding machine  50  has a hopper section  52  and a grinder section  54  which are designed to receive and reduce material, which may be frozen blocks of an edible material such as frozen beef, pork, poultry, or fish. The frozen blocks are reduced by a feed screw assembly  56 , which includes a feed screw  58 , shown in  FIG. 2 , and which extends through the grinder section  54 . The feed screw assembly  56  includes a drive motor contained within a motor housing  60  that is designed to rotate the feed screw  58 . The grinding machine  50  also includes a bulkhead  62  into which the reduced material is fed and collected, as known in the art. It is understood that the grinding machine  50  illustrated is representative and that the present invention may be used with other types of grinding machines. 
         [0029]    Referring now to  FIG. 2 , grinder section  54  includes a main housing section  64  and a feed section  66 . A grinding head section  68  extends forwardly from feed section  66 . Feed screw  58  extends throughout the length of main housing section  64 , feed section  66  and grinding section  68 . Feed screw  58  includes pressure lighting  70  that advances the material through main housing section  64  and through feed section  66  and grinding section  68  upon rotation of feed screw  58 . An orifice plate  72  is secured to the end of grinding section  68  via a mounting ring  74 , in a manner as is known. A bridge  76  extends outwardly from mounting ring  74 . 
         [0030]    Feed section  66  is generally tubular and extends forwardly from main housing section  64 . Feed screw  58  and feed section  66  are configured such that the end of feed screw  58  extends outwardly from feed section  68  and through grinding section  68 , such that the end of feed screw  58  is located adjacent to the inner surface of orifice plate  72 . 
         [0031]    Referring now to  FIG. 3 , a knife holder  78  is mounted at the end of, and rotates with, feed screw  58 . Knife holder  78  may hold one or more knife blades or inserts  79 , in a manner as is known. Knife holder  78  is located adjacent an inner grinding surface of orifice plate  72 , which is secured in the open end of head section  66  by mounting ring  74  and bridge  76 . The knife inserts  79  bear against the inner grinding surface of orifice plate  72  to shear material as the material is advanced by operation of feed screw  58  from grinding section  68  toward and through the orifices of orifice plate  72 . The end of grinding section  68  is provided with a series of external threads  80 , and mounting ring  74  includes a series of internal threads  82  adapted to engage external threads  80  of feed section  68 . Mounting ring  74  further includes an opening  86  defined by an inner lip  88 . While a threaded connection between mounting ring  74  and feed section  68  is shown, it is understood that mounting ring  74  and feed section  68  may be secured together in any satisfactory manner. 
         [0032]    Bridge  76  includes an outer plate maintaining portion  90 , which has an outwardly extending shoulder  92  adapted to fit within lip  88  so that bridge  76  is held within ring  74 . Shoulder  92  engages the outer peripheral portion of orifice plate  72  to maintain orifice plate  72  in position within the open end of grinding section  68 . 
         [0033]    A center pin  94  has its inner end located within a central bore  96  formed in the end of feed screw  58 , and the outer end of center pin  94  extends through a central passage  98  formed in a central hub area of knife holder  78  and through the center of a bushing  100 . Bushing  100  is received within an opening  101  in orifice plate  72  and supports center pin  94 , and thereby the outer end of feed screw  58 . Center pin  94  is keyed to feed screw  58  by means of recessed keyways on center pin  94  that correspond to keys on the hub of knife holder  78 . An inner portion  102  of bridge  76  defines a pin support  103  within which the end of a center pin  94  is received. With this arrangement, center pin  94  rotates in response to rotation of feed screw  58 , driving knife assembly  78 . Bushing  100  and orifice plate  72  remain stationary, and rotatably support the end of center pin  94 . 
         [0034]    As noted above, feed section  68  provides an internal chamber in which feed screw  58  rotates to shear the frozen block material. Conventionally, the internal chamber is defined by a wall along which chunks of material, which are sheared from the frozen block of material, are moved through main section  64 . The sheared chunks of material typically rotate upon rotation of the feed screw  58  until discharged. 
         [0035]    Referring now to  FIGS. 4-9 , feed section  68  has a primary longitudinal shear edge  104 . The shear edge  104  runs along the length of the main section  64 , and is positioned generally along the backside  106  of an internal chamber  108  defined by main section  64 . As particularly illustrated in  FIG. 6 , the shear edge  104  is positioned below the inlet  105  into the chamber  108 . As the feed screw  58  rotates counter-clockwise within chamber  108 , sheared chunks of frozen material will be rotated along with the pressure flighting  70  of the feed screw  58 , similarly in a counter-clockwise direction. As the sheared chunks are rotated they will be forced against the primary shear edge  104 . The primary shear edge  104  thus effectively provides a pinch point against which the frozen blocks are forced and held. As such, the primary shear edge  104  provides a fulcrum point against which further shearing of the frozen blocks may take place, thereby reducing the side load on the feed screw  58 . Primary shear edge  104  is also effective in holding the frozen chunks in internal chamber  108 , thereby avoiding the “bouncing around” allowed by conventional hopper and grinder assemblies in which the hopper wall is tangential to the housing wall. 
         [0036]    In addition, feed section  68  includes a secondary shear edge  112  at the forward end of main section  64 , which provides an additional fulcrum point against which a frozen block of material may be sheared as the material is advanced from main section  64  toward feed section  66 . While the primary shear edge  104  extends longitudinally along the length of the main section  64 , secondary shear edge  112  extends transversely relative to the longitudinal axis of the feed section  66  and, as shown in  FIG. 7 , extends to a plane that is below that of the shear edge  104 . The secondary shear edge  112  extends transversely across the internal chamber  108 , at the forward area of internal chamber  108 , upstream of feed section  68 . As such, in addition to providing an additional point against which frozen blocks may be held for improved shearing, the secondary transverse shear edge  112  prevents frozen blocks from being prematurely translated forward by the feed screw  58 , since the blocks of material must be reduced to a size that is less than the distance between the underside of the shear edge  112  and the exterior surface of the feed screw  58 . 
         [0037]    In yet a further aspect, head section  66  includes a tertiary shear edge  114  forward of the secondary shear edge  112  (relative to the front of the feed screw  58 ) that provides an additional fulcrum point against which the frozen block material may be held. In addition, the tertiary shear edge  114  prevents frozen blocks from passing to the front of the head section  66  until they are reduced to a size that allows them to fit between the underside of the shear edge  114  and the exterior surface of the feed screw  58 . Moreover, for blocks sized to fit between the tertiary shear edge  114  and the feed screw  58 , the underside of the shear edge  114  is angled to form an axially extending pinch point  116 , as shown particularly in  FIGS. 8-9 , against which a block may be forced by the pressure flights  70  of the feed screw  58  for additional shearing. 
         [0038]    It is understood that the terms “primary”, “secondary”, and “tertiary” are not terms of relative importance, but simply terms to distinguish the shear edges from one another. Additionally, it is contemplated that the head section  66  may be constructed to have one, all, or some combination of the primary, secondary, and tertiary edges. 
         [0039]    As particularly shown in  FIG. 6 , head section  66  includes an expansion or transition zone  118  defined at the front or discharge end. The expansion zone  118  provides a volume into which reduced blocks may be translated by the feed screw  58  until subsequently discharged by continued translation of the feed screw  58 . In addition, the expansion zone  118  is believed to improve material distribution in the head  66  and around the feed screw  58 . In one embodiment, the secondary shear edge  112  and the tertiary shear edge  114  are positioned in the expansion zone  118 . 
         [0040]    Referring now to  FIGS. 10-13 , according to another aspect of the invention, feed screw  58  has a knife holder reinforcement fin  120  preferably for each arm of the knife holder  78 . Each fin  120  forms a wall that is recessed into the feed screw  58  such that a recess  122  is formed between the pair of fins. The recess is adapted and configured to receive the knife holder  78 . More particularly, each fin  120  includes a portion that is located behind a respective knife holder arm  124  to provide support for the knife holder arm  124  during the shearing process. This support helps to prevent material flow within the head  66  from forcing the knife holder  78  into orifice plate  72 , which otherwise may cause premature wear of the knife inserts. Each fin  120  also includes a portion that is located alongside and parallel to a respective knife holder arm  124 , to reinforce the knife holder arm against side loads experienced during the shearing process. Each knife holder arm  124  is slotted to receive a knife or blade  79  in a manner that allows the blades  79  to be easily replaced as needed. 
         [0041]    Referring to  FIG. 10 , each fin  120  is specially configured to relieve side loads experienced by the knife holder arms  124 . The flighting  70  of auger  58  defines a pair of ramped end areas  130 , and each fin  120  is at the end of one of the ramped end areas  130 . On the leading side of knife arm  124 , the fin  120  extends radially outwardly to the outer edge of the auger flighting  70  so as to fully protect the leading side of the knife arm  124 . The ramped end area  130  at the end of the flighting  70  leads to the leading side of the fin  120 , so that only the portion of the knife insert  179  extending from the fin  120  and the knife holder arm  124  is exposed in order to shear the material against the orifice plate  72 . 
         [0042]    Auger  58  also defines a pair of outwardly extending arm reinforcement sections  132 , each of which is spaced from one of the fins  120 . Each arm reinforcement section  132  terminates at a location spaced inwardly from the outer edge of the auger flighting  70 . Auger  58  also defines a discharge surface  134  that extends from each arm reinforcement section  132 . Each discharge surface  134  is configured to as to route material from the flighting  70  past the portion of the fin  120  located behind the knife holder arm  124 , and toward the ramped end area  130  leading to the fin  120  adjacent the opposite knife holder arm  124 . Each arm reinforcement section  132  functions to engage its respective knife holder arm  124  in order to rotate the knife holder arm  124  upon rotation of auger  58 . In addition, the arm reinforcement section  132  extends throughout a substantial portion of the length of the knife or arm  124 , to relieve lateral stresses that may be experienced by the knife holder arm  124  when the material is sheared by the knife inserts  79  against the orifice plate  72 . It can thus be appreciated that each arm reinforcement section  132  along the trailing side of the knife holder arm  124 , in combination with the portion of the fins  120  that extends the full length of the leading side of the knife holder arm  124 , function to form a pocket within which the knife holder arm  124  is received in order to reinforce and protect the knife holder arms  124 . 
         [0043]    Each knife holder arm  124  extends outwardly from a central hub section  134  which, in the illustrated embodiment, is generally circular. The end of the auger  58  is formed with a generally circular recess  136 , which has a shape corresponding to that of hub section  134 . The walls defining the recess  136 , shown at  138 , are formed so as to extend between one of the fins  120  and the opposite reinforcement section  132 . With this construction, the hub section  134  is fully encased and protected by the end of auger  58 . 
         [0044]    Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.