Abstract:
An apparatus for producing selectively sized multiple portions of meat from a larger piece of meat. A plurality of product carriers having open-top recesses are mounted on a conveyor for travel along a path. At least two transverse sets of parallel slots are provided in each carrier. Each product carrier is moved through a pair of cutting stations having a number of spaced knife edges extending downwardly into a passage that receive the product carriers. The blades are removably mounted to removable knife blocks. The product carrier is rotated via engagement between a rotation gear on the carrier and a rotation bracket along the path of travel. In this manner, a plurality of laterally spaced cuts are made in two directions through the larger piece of meat to produce a multiplicity of smaller portions having a similar size, shape and weight.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
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   STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT 
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   REFERENCE TO AN APPENDIX 
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   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to food processing equipment and particularly to an improved apparatus for making a plurality of selectively sized portions from a larger piece of meat. 
   2. Description of the Related Art 
   The food industry has, for many years, relied upon making several smaller pieces or portions from a larger piece of meat. Typically, this process was performed by manual cutting of the larger portion into smaller pieces. This process was very labor intensive and lacked a level of consistency in the size, shape, and weight of the smaller portions produced. In the food service or restaurant business, selective consistently sized portions have become very popular. This is particularly true as applied to poultry breast or beef products wherein smaller chunks or cube-like pieces are prepared from a larger cut of meat and a selective number of such pieces produced are sold in single servings. In view of this practice, it is highly desirable to make each piece as consistent in size and weight as possible. This creates a better customer image and provides a higher degree of control of costs relative to the weight of product sold. 
   Many prior attempts have been made to create an automated machine to perform the cutting and sizing functions described above. Some of these attempts have been improvements over the manual cutting process. For example, U.S. Pat. No. 7,364,504 to Gasbarro discloses a portion cutting apparatus that performs particularly well. However, the means incorporated by that apparatus for rotating the piece of meat being processed is known to introduce a level of inconsistency of performance. Additionally, the cutting stations of that apparatus incorporate fastening means that must be removed in a time-consuming manner to perform routine maintenance on components of the stations. 
   It would therefore be desirable to have a portion cutting apparatus that employs an effective, reliable means for rotating a piece of meat that is being processed. It would further be desirable to have such an apparatus that incorporates cutting stations that can be easily disassembled for maintenance. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates to an automated portion control apparatus for cutting a larger piece of meat into discrete, consistently sized portions. 
   In accordance with the preferred embodiment of the present invention, multiple carrier blocks are mounted on a conveyor for travel along a selected path. Each block includes a recess having a shape selected to most efficiently receive the larger pieces of meat that are to be cut into pieces of a selected size and weight. 
   Multiple slots are provided in each carrier block that extend through the upper surface of the block to a depth at least equal to the bottom surface of the recess. The slots are arranged in a predetermined pattern wherein a first set of slots extends in a direction parallel to the intended path of travel and a second set of slots extends across the first set at a selected angle thereto. Usually, the angle is approximately ninety degrees if one chooses to create smaller sized portions having a generally rectangular or cube-like shape. 
   The carrier blocks are mounted on the conveyor for selected pivotal movement at a point along their path of travel to align one set of the slots parallel to the path of travel prior to encountering a plurality of knife blades fixed at one of a pair of cutting stations in spaced relationship along the path of travel. Specifically, it is a critical feature of the invention that a rotation gear is mounted to the bottom of each carrier block and has a plurality of gear teeth for cooperatively engaging pivot teeth that extend from a rotation bracket mounted at a fixed position between the cutting stations. The engagement between the gear teeth and the pivot teeth causes the carrier block to selectively pivot between a first rotated position and a second rotated position for moving the second set of slots in the carrier block into parallel alignment with the path of travel before passing through the second cutting station. Preferably, a second rotation bracket is provided after the second cutting station for rotating the carrier block back to its first rotated position, or at least to place the first set of slots parallel to the path of travel before passing back through the first cutting station. 
   Each cutting station includes a knife block that is removably mounted to a pair of laterally opposing side panels. Each knife block includes a knife cartridge removably mounted to a cartridge holder. The knife blades are removably mounted to the knife cartridge and are laterally spaced from one another across the path of travel of the carrier blocks and aligned to enter the set of slots which are aligned parallel thereto to engage and cut the meat product carried in the recess. The number of knife blades employed and the angular relationship between the two sets of slots and their spacing determine the size and shape of the final portions of the original larger meat product. 
   It is another feature of the invention that the knife blocks have mounting posts extending laterally therefrom for slidably fitting into vertical J-channels formed in the side panels of the cutting stations. The engagement between the mounting posts and the J-channels holds the knife blocks securely in place during operation while allowing the blocks to be removed easily from the cutting stations for convenient maintenance. 
   It is therefore an object of the present invention to provide an efficient, high volume, automated meat processing apparatus which produces selectively cut portions of meat and that employs an effective means for reliably rotating pieces of meat that are being processed. 
   It is another object of the present invention to provide an apparatus of the type described that incorporates cutting stations that can be disassembled easily for maintenance. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view illustrating the preferred embodiment of the present invention. 
       FIG. 2  is an exploded view in perspective illustrating a knife block of the preferred embodiment of the present invention shown in  FIG. 1 . 
       FIG. 3  is a top detail view illustrating a cutting station of the preferred embodiment of the present invention shown in  FIG. 1 . 
       FIG. 4  is a right side detail view illustrating the cutting station of the preferred embodiment of the present invention shown in  FIG. 3 . 
       FIG. 5  is a rear detail view illustrating the cutting station of the preferred embodiment of the present invention shown in  FIGS. 3 and 4 . 
       FIG. 6  is an exploded view in perspective illustrating a carrier block and related components of the preferred embodiment of the present invention shown in  FIG. 1 . 
       FIG. 7  is a top detail view illustrating a carrier block, rotation bracket and wearstrip of the preferred embodiment of the present invention shown in  FIG. 1 . 
       FIG. 8  is a detail view in perspective illustrating a rotation bracket of the preferred embodiment of the present invention shown in  FIG. 1 . 
       FIG. 9   a  is a top detail view illustrating a carrier block of the preferred embodiment of the present invention shown in  FIG. 1  as it is being rotated. 
       FIG. 9   b  is the same view shown in  FIG. 9   a  with the carrier block removed to illustrate the rotation gear and the rotation bracket. 
       FIG. 10   a  is a top detail view illustrating the carrier block of the preferred embodiment of the present invention shown in  FIG. 1  after it has been rotated. 
       FIG. 10   b  is the same view shown in  FIG. 10   a  with the carrier block removed to illustrate the rotation gear and the rotation bracket. 
       FIG. 11  is a detail view in perspective illustrating the rotation bracket, rotation gear and wearstrip of the preferred embodiment of the present invention shown in  FIG. 1 . 
   

   In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word “connected” or terms similar thereto are often used. They are not limited to direct connection, but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a meat cutting apparatus  10  in accordance with the present invention is illustrated. The apparatus  10  is for producing a plurality of pieces of meat of a selected size and weight from a larger piece of meat. The apparatus includes a support frame  20  having legs  22 , horizontal support members  24  and an upper support surface  26  mounted to the legs  22 . The legs  22  may include wheels  23  to permit convenient movement of the frame  20  as a whole unit. 
   The upper support surface  26  forms a deck-like structure having a longitudinally extending central opening that exposes the upper run of an endless, chain-type conveyor  28 . The conveyor  28  is mounted on a pair of sprockets in a conventional manner as will be understood by those skilled in the art. The conveyor  28  supports a plurality of product carrier blocks  30  that are mounted to the chain conveyor  28  in a longitudinally spaced relationship along the selected path of travel of the blocks  30 . 
   The support frame  22 , the upper support surface  26  and the conveyor  28  are of conventional form and may be constructed in any conventional, well-known manner to support any form of conventional conveying means deemed suitable for the purpose of the present invention by one of ordinary skill. The frame  20 , upper support surface  26  and conveyor  28  may consist of many conventional designs that are suitable to function according to the present invention. Therefore, the frame  20 , upper support surface  26  and conveyor  28  will only be briefly described herein to the extent necessary for enabling one of ordinary skill to understand, make and use the present invention. 
   The upper support surface  26  comprises opposing L-shaped beams  25  and  27  that are fixed to the legs  22 . The L-shaped beams  25  and  27  support a pair of cutting stations, indicated generally at  32  and  34 , fixed in longitudinally spaced relationship to one another along the path of travel defined by the chain conveyor  28 . A conventional electric motor and gear box assembly  36 , and a drive shaft and idler shaft (not within view), are provided to drive the chain conveyor  28  in a conventional manner. 
   A guide rail  42 , along which carrier blocks  30  move, may be fixed in any conventional manner to the upper support surface  26 . Each cutting station  32  and  34  may be removably fixed to the upper support surface  26  by a threaded pin extending into a complimentary hole (not within view) in L-shaped beams  25  and  27 . Preferably, the cutting stations  32  and  34  are constructed to be easily disassembled for cleaning or for replacement to modify the number or spacing of knife blades desired. In the preferred embodiment shown in  FIGS. 1 and 5 , each of the cutting stations  32  and  34  includes a pair of opposing side panels  46  mounted to a respective one of the beams  25  or  27 , as noted above, and a knife block indicated generally at  48  (the knife block of the cutting station  32  is shown removed in  FIG. 1 , but is substantially identical to the knife block of the cutting station  34 ). 
   Referring now to  FIG. 2 , each knife block  48  comprises a knife cartridge  50  and a knife cartridge holder  52 . The knife cartridge  50  matingly fits into a recess  53  that is formed in the bottom surface of the cartridge holder  52 , which recess is substantially equal in size and shape to the cartridge  50 . Conventional removable fasteners  54  extend through vertical mounting holes  56  and  58  formed in the cartridge holder  52  and in the knife cartridge  50  for securely and removably fastening the cartridge  50  to the cartridge holder  52 . 
   The knife cartridge  50  has a pair of parallel through-holes  60  for accepting a pair of rods  62 . The knife blades  64  are secured in the slots  66  in parallel spaced relationship across the width of cartridge  50 . The rods  62  removably pass through the holes  60  that are aligned with the holes  68  in the knife blades  64  when the knife blades  64  are aligned in the slots  66 . The knife blades  64  are fixed at a downwardly inclined angle determined by the shape of the slots  66  and the relative positions of the holes  60 . The angle can be, for example, 30 degrees from horizontal. 
   The rods  62  are held in place by friction and by inserting the upturned portions  67  of the rods  62  into the vertical grooves  70  that are formed in the side of the knife cartridge  50 . The knife blades  64  may thus be conveniently released from the knife cartridge  50  by simply withdrawing the rods  62  from the through-holes  60 . 
   Referring to  FIGS. 2-5 , the cartridge holder  52  has longitudinally-spaced mounting posts  72  extending laterally from both of its sides. Vertically oriented J-channels  74  are formed in each of the side panels  46  and have open top ends for receiving the mounting posts  72  from above. The width of each channel  74  is substantially equal to the diameter of the mounting posts  72  for providing a close-clearance fit between the exterior surfaces of the posts  72  and the surfaces of the side panels  46  that define the channels  74 . When the mounting posts  72  are lowered into the channels  74 , the contours of the channels  74  guide the posts  72  down and rearward to the closed ends of the channels  74 . Vertical movement of the mounting posts  72  is thereby restricted and the knife block is secured against rearward and upward movement. Metal straps  76  are mounted to the top surface of the cartridge holder  52  in any conventional manner, such as by removable fasteners  78 , to form hand-grippable handles. 
   In this manner, the knife block  48  is securely mounted to the side panels  46  in an easily removable fashion for convenient cleaning, repair or replacement. The side panels  46 , which are preferably screwed to the beams  25  and  27 , remain in place on the beams, even when the knife block  48  is removed. For example, in order to remove the knife block  48  from the side panels  46 , a user simply grips the metal straps  76 , shifts the knife block forward to move the mounting posts  72  away from the closed ends of the J-channels  74  and into position below the open ends of the channels  74 , and lifts the block  48  upwardly to remove the posts  72  from the channels  74 . Although it is preferred that the channels  74  be generally J-shaped with a curved contour intermediate a substantially vertical segment and a substantially horizontal segment, it is contemplated that the channels can have any other suitable shape, such as an L-shape, that would require the mounting posts  72  to be inserted vertically and shifted horizontally and that would thereafter restrict the upward and rearward movement of the mounting posts  72 . It is contemplated that other fasteners that can be rapidly removed without the need for multiple operations with tools can substitute for the preferred fasteners. 
   It is contemplated that the mounting posts  72  and J-channels  74  of each cutting station  32  and  34  can be longitudinally staggered so that each knife block  48  will only fit into particular side panels  46  with the corresponding spacing. This tends to assure that when the number and spacing of the knife blades  64  mounted in the knife cartridge  50  of each cutting station  32  and  34  are different from one another, each knife block  48  will only fit into a particular side panel  46  mounted on the frame  20  to provide the selected portion sizes of meat desired. This eliminates or tends to reduce the potential for human error in setting up the apparatus  10  to provide the desired result. When the number and spacing of slots  66  and knife blades  64  are the same in each knife block  48 , as shown in the preferred embodiment, this feature is not critical. 
   It should be pointed out that one of ordinary skill will readily understand from the foregoing description that other conventional means may be employed to provide equivalents to cutting stations  32  and  34  which function in a similar manner to accomplish the primary results of the present invention. 
   Now referring specifically to  FIG. 6 , the carrier block  30  and its related components are shown in detail. Preferably, the carrier block  30  comprises a main body portion  80  provided with an upwardly facing or open-top central recess portion  82  and a plurality of intersecting slots, such as shown at  84  and  86 . The slots  84  and  86  intersect each other at a selected angle. The typical angle would be approximately ninety degrees to provide a generally rectangular or cube-like portion size. However, the angle of intersection could be varied, if desired, to accommodate other shaped portions as will be apparent from the following description. 
   It should be noted that testing has indicated that the shape of the recess  82  need not be square or rectangular. However, for generally irregularly shaped initial meat products, such as poultry breasts, a generally square or rectangularly shaped recess works very well and is generally preferred to yield very good results relating to efficiency and consistency of the resulting control of portion size and weight. 
   As shown in the preferred embodiment herein, there are an equal number of slots  84  and  86  equally spaced from one another. However, it should be noted that the number of slots in the blocks  30  that are oriented in any direction and/or the spacing of the slots may differ from the number and/or spacing of the intersecting slots  66  in the knife block. Thus, a variety of sizes and shapes may be readily chosen for the final meat portion created. Of course, the number of knife blades  64  and their spacing in the knife cartridges  50  would also be changed to accommodate the number of slots  84  and  86  chosen. 
   Still referring to  FIG. 6 , each carrier block  30  is provided with a rotation assembly  90  for removably and rotatably mounting the carrier blocks  30  to the chain conveyor  28 . The rotation assembly  90  forms part of a turning or rotating actuating means for causing the selective rotation of the carrier block  30 . This rotation through a selected angle occurs after passing through the first knife block  32  and before entry into the second knife block  34 , and subsequently prior to passing into the first knife block  32  on a repeat run of the cutting cycle. 
   The rotation assembly  90  includes a pivot plate  92 , a rotation gear  94 , a locking disc  96  and threaded spacers  98 . The pivot plate  92  is removably mounted to the conveyor  28  by any conventional method, such as by mounting the plate to a cross member that is rigidly fastened to the conveyor  28  (not shown). The plate  92  is provided with an upwardly extending, substantially cylindrical pivot post  100 . The pivot post  100  has an annular groove  102  that separates the post into a lower shaft segment  104  and an upper head segment  106 . Two opposing semi-circular notches  108  are formed in the outer surface of the head segment  106 , and extend from the top of the upper head segment  106  to the top of the groove  102 . 
   The rotation gear  94  is a gear of a conventional variety with a plurality of gear teeth  110  and a central aperture  112 . The central aperture  112  has a diameter that is substantially equal to the diameter of the pivot post  100 . The locking disc  96  is a round, substantially planar body that has a locking aperture  114  that is substantially equal in diameter to the central aperture of the rotation gear. Two semi-circular protrusions  116  extend inwardly from the edges of the locking aperture  114  that correspond in size, shape and relative position to the semi-circular notches  108  in the pivot post  100 . The thickness of the locking disc  96  is substantially equal to the width of the annular groove  102  in the pivot post  100 , permitting the protrusions  116  to slide within and around the groove  102 . 
   Threaded fasteners, such as the screws  118 , extend upwardly through mounting holes in the rotation gear  94  and in the locking disc  96 , through the threaded spacers  98 , and into threaded bore holes in the bottom of the carrier block  30  (not within view). This is for the purpose of holding the gear  94 , disc  96 , and spacers  98  in firm engagement with one another and with the carrier block  30  and preventing relative rotation between these components during normal operation. Although threaded fasteners are preferred, all other means for securely holding the described components together are contemplated, such as welding, adhesives or various other types of fasteners. When all of the components are fastened together, the threaded spacers  98  create a gap between the lower face of the carrier block  30  and the upper face of the locking disc  96 . The spacers  98  have a length that is substantially equal to the width of the head segment  106  of the pivot post  100 , and therefore the gap created by the spacers  98  has a width that is substantially equal to the width of the head segment  106 . This is preferred so that the block  30 , gear  94  and disc  96  can freely rotate about the post  100  when the protrusions  116  are slidably mounted in the groove  102 . 
   In order to rotatably mount the carrier block  30  to the conveyor  28 , the plate  92  is fixed to the conveyor  28 , and the rotation gear  94  and the locking disc  96  are lowered onto the attached pivot post  100 . The semi-circular protrusions  116  of the disc  96  must be vertically aligned with the semi-circular notches  108  in the head segment  106  of the pivot post  100  to allow the head segment  106  to pass through the central aperture  112  and then the locking aperture  114 . When the bottom surface of the carrier block  30  is brought to rest upon the upwardly-facing surface of the head segment  106  of the pivot post  100 , the upper and lower faces of the semi-circular protrusions  116  are aligned with the upper and lower surfaces defining the annular groove  102 . Simultaneously, the upper and lower faces of the head segment  106  of the post  100  are aligned with the upper and lower edges of the gap between the carrier block  30  and the locking disc  96 . The carrier block  30  is thus able to rotate about the pivot post  100  with the semi-circular protrusions  116  of the locking disc  96  traveling within the annular groove  102 . As long as the protrusions  116  are not vertically aligned with the notches  108 , the carrier block  30  is prevented from lifting off the pivot post  100  by the surfaces defining the annular groove  102 . It is therefore desirable to orient the block  30  upon the pivot post  100  in such a manner that the protrusions  116  are kept out of alignment with the notches  108  during operation of the apparatus  10 , other than during brief moments while the block  30  is rotating. 
   The close clearance relationships between the surfaces of the carrier block  30 , the locking disc  96  and the pivot post  100  provide the carrier block  30  with a reasonable degree of upright stability without greatly inhibiting the rotation of the block  30 . It is generally desirable, however, that some significant degree of force be necessary to cause the carrier block  30  to rotate so that the block is not accidently rotated by forces such as vibration, air resistance or gravity (should the block  30  and/or the pivot post  100  not be level). Resistance to rotation can be adjustable using conventional devices, such as a friction brake. 
   Referring now to  FIG. 7 , after the carrier block  30  emerges from the first cutting station  32  (not within view), where the knives extend through at least some of the slots  84 , the carrier block  30  engages a rotation bracket  120  that is mounted to the L-shaped beam  25  in a longitudinal orientation intermediate the cutting stations  32  and  34 . Referring to  FIG. 8 , the rotation bracket is a generally L-shaped member, when viewed from the end, having a vertical segment  122  and a horizontal segment  124 . A pivot tab  126  extends from the horizontal segment  124  and terminates in a pair of pivot teeth  128  that extend into the path of the gear  94  and are similar in size and shape to the spaces between the teeth  110  of the rotation gear  94  described above. The upper face of the pivot tab  126  is substantially coplanar with the upper face of the rotation gear  94  when the carrier block  30  is mounted on the pivot post  100 . Thus, as the chain conveyor  28  moves the carrier block  30  into engagement with the rotation bracket  120 , the bottom surface of the block  30  passes over the top surface of the pivot tab  126  and the teeth  110  of the rotation gear  94  engage the space between the pivot teeth  128  as best shown in  FIGS. 9   a - 10   b . The engagement between the teeth  110  of the moveable rotation gear  94  and the stationary pivot teeth  128  causes the carrier block  30  to rotate through a selected ninety degree angle to align the intersecting slots  86  parallel with the knife blades  64  in the second cutting station  34 . 
   Referring back to  FIG. 8 , the vertical segment  122  of the rotation bracket  120  has a longitudinal gap  130  adjacent the pivot tab  126 . The vertical segment  122  is disposed adjacent the edge of the block&#39;s  30  laterally-facing edge, and thus provides the carrier block  30  with lateral stability when the block  30  is not being pivoted as shown in  FIG. 10   a . The gap  130  allows the block  30  to rotate without striking the vertical segment  122  (as illustrated in  FIG. 9   a ) when the block  30  is being rotated. 
   Referring now to  FIGS. 7 and 11 , an elongated wearstrip  132  is mounted to the L-shaped beam  27  laterally opposite the rotation bracket  120 . The upper face of the wearstrip  132  is substantially co-planar with the upper face of the pivot tab  126 . As the carrier block  30  passes along the rotation bracket  120 , the bottom surface of the block  30  passes over the top of the wearstrip  132  and the rotation gear  94  passes along the inward-facing surface of the wearstrip  132  in a close-clearance relationship. The top surface of the wearstrip  132  thus provides the carrier block  30  with additional vertical support, and the inward-facing surface of the wearstrip  132  acts as a barrier against lateral movement of the rotation gear  94 . The gear  94  is thereby provided with additional lateral support and is prevented from skipping, riding over or otherwise moving laterally away from the pivot teeth  128  of the pivot tab  126  to ensure full engagement between the gear teeth  110  and the pivot teeth  128 , and therefore full and proper rotation of the carrier block  30 . 
   By rotating the carrier block  30  at a point between the two cutting stations  32  and  34  in the manner described above, the piece of meat product disposed in the recess  82  of the carrier block  30  is sliced along two paths that are angled ninety degrees from one another to create the size and weight portions desired. This process is described in U.S. Pat. No. 7,364,504, which is incorporated herein by reference. Although the pivot teeth and the teeth of the rotation gear in the preferred embodiment of the invention are configured to rotate the carrier block  30  by an angle of 90 degrees, it is contemplated that the size, shape, and/or spacing of either or both sets of teeth  110  and  128  can be modified to rotate the block  30  more or less than 90 degrees as desired for producing meat portions of different shapes and sizes. If the angle of rotation is varied, the orientation of the intersecting slots  84  and  86  must be modified accordingly. 
   It is preferred that slots  84  and  86  extend slightly beyond the bottom or floor  83  of the recess  82  and that the extreme tips of the blades do not contact the deepest wall of the slots  84  and  86 . This assures a clean and complete cut of the meat product upon entry of the knife blades  64 , as described herein, without causing undue wear of the sharp-knife edges which otherwise would engage the floor  83  of the recess  82 . 
   In the preferred embodiment of the invention, a second rotation bracket and second wearstrip (not pictured) are mounted to the L-shaped beams  25  and  27  on the opposite side of the second cutting station  34  relative to the rotation bracket  120  and the wearstrip  132  described above. The second rotation bracket and wearstrip are mounted in an opposite orientation relative to the rotation bracket  120  and wearstrip  132  (i.e., the second rotation bracket is mounted to the L-shaped beam  27  and the second wearstrip is mounted to the L-shaped beam  25 ) and function to rotate the carrier block  30  back to its position before it engaged the first rotation bracket  120 . This ensures that the slots  84  in the carrier block are realigned with the knife blades  64  of the first cutting station  32 . For example, if the first rotation bracket were configured to rotate the carrier block  30  by an angle of 60 degrees clockwise, the second rotation bracket would be configured to rotate the block  30  by an angle of 60 degrees counterclockwise. If the first rotation bracket  120  were configured to rotate the carrier block  30  by 90 degrees as in the preferred embodiment, the incorporation of a second rotation block and a second wearstrip is not critical, but can nevertheless carried out. 
   This detailed description in connection with the drawings is intended principally as a description of the presently preferred embodiments of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the designs, functions, means, and methods of implementing the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and features may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention and that various modifications may be adopted without departing from the invention or scope of the following claims.