Abstract:
A cutter hub pin drive mechanism and a quick disconnect hub for a pelletizer and a pelletizer having a cutter hub pin drive mechanism are provided. The pelletizer has a cutter hub that includes a cutter hub holder which is engaged with the pelletizer shaft through a plurality of drive pins. The drive pins ride in drive pin channels formed by grooves cut into an inner surface of the cutter hub holder and aligned grooves formed in the outer surface of the forward end of the pelletizer shaft. By machining of grooves into the cutter hub holder and shaft to form channels that receive the drive pins, more precise engagement between the pelletizer shaft, cutter hub holder and drive pins is obtained, resulting in improved torque transmission from the shaft to the cutter hub. Also provided is a seal around the pelletizer shaft to prevent the egress of fines into the drive pin area which might otherwise interfere with the unobstructed movement of the cutter hub holder necessary to adjust blade position. Finally, a quick disconnect hub is provided by which the pelletizer shaft can be readily disconnected from the cutting assembly to facilitate the removal of agglomerated polymer in the cutting chamber.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending application Ser. No. 14/205,738 filed Mar. 12, 2014, which is based on U.S. Provisional Application Ser. No. 61/788,648 filed Mar. 15, 2013, and hereby claims the priority thereof to which it is entitled. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention is related to the field of pelletizers for production of pellets from polymer containing materials and other pelletizable formulations. 
         [0004]    Description of the Related Art 
         [0005]    Various pelletizer designs are disclosed in U.S. Pat. No. 5,059,103 (“the &#39;103 patent”), U.S. Pat. No. 7,033,152 (“the &#39;152 patent”), and U.S. Pat. No. 8,303,871 (“the &#39;871 patent”), all of which patents are co-owned by the applicant and assignee of the instant application. The disclosures of the &#39;103 patent, the &#39;152 patent and the &#39;871 patent are relevant to the subject matter of the instant application and therefore these three patents are hereby expressly incorporated herein by reference as if fully set forth in the instant application. 
         [0006]    The prior art pelletizer design shown in  FIGS. 1, 5 and 5A  utilizes a pelletizer shaft  100  that is bolted to the motor shaft  105  of motor  190  with set screws  110 . A cutter hub holder  115  is retained on the pelletizer shaft  100  with a bolt  120  and has a spring  125  for adjustment as the blades  130  wear down. This cutter hub holder  115  has multiple keys  135 , typically 2 to 4 keys are used, which are welded in place to slide in key slots that are cut in the pelletizer shaft  100 . Several problems with this design may arise. 
         [0007]    First, the keys  135  can sometimes break loose from the weld that holds them in the cutter hub holder  115 . Further, due to the nature of welding, the keys may not be precisely positioned to exactly match the key slots in the pelletizer shaft, resulting in less than the desired amount of surface contact between each of the keys and their corresponding slot. As a result, torque that is transmitted from the cutter hub to the pelletizer shaft during operation of the pelletizer may be borne by less than all of the keys, creating even higher stresses on the torque-bearing keys which can impair pelletizer performance and/or lead to breakage of the keys. 
         [0008]    Second, the keys can wear into the sides of the key slots in the pelletizer shaft  100 . Since they do not extend beyond the end of the pelletizer shaft  100 , the keys can become caught within notches formed by the wear of the keys against the sides of the key slots. The wear pattern of these notches creates a “hook” that can trap the keys and prevent the spring  125  from pushing the cutter hub holder  115  forward to compensate for blade wear, causing poor cutting performance and thus poor pellet quality. 
         [0009]    Third, fines that are generated when cutting the polymer strands with the blades can accumulate and pack within the key slots, also locking the cutter hub holder  115  in place and preventing movement thereof as the blades  130  wear down or when new blades are installed. Fines packed in the key slots can also produce cross contamination from one pelletizing run to the next. 
         [0010]    Another prior art pelletizer design is shown in  FIGS. 2, 6 and 6A  and utilizes a pelletizer shaft  200  that is bolted to the motor shaft  205  of motor  290  with set screws  210 . A cutter hub holder  215  is retained on the pelletizer shaft  200  by threaded engagement with the motion rod  220  which provides for adjustment of cutter hub position as the blades  225  wear down. 
         [0011]    Like the design shown in  FIG. 1 , the  FIG. 2  cutter hub holder  215  has multiple keys  230  welded thereto that can sometimes break loose from the weld holding them in the cutter hub holder  215 . These keys can also wear into the sides of the key slots in the pelletizer shaft  200  since they do not extend out of the end of the pelletizer shaft  200 , again creating the “hook” wear pattern that requires more effort to push the cutter hub holder  215  forward to compensate for blade  225  wear and causing poor cutting performance and thus poor pellet quality. Also, like the  FIG. 1  design, fines that are generated from trying to cut the polymer strands by the blades can accumulate and pack within the key slots, preventing movement of the cutter hub holder  215 . 
         [0012]    An additional problem with both the  FIG. 1  and  FIG. 2  designs is that the cutting area within the cutting chamber or water box can become agglomerated with molten polymer or polymer blend material, allowing the polymer to wrap around the cutter hub and blades and flow either up the slurry outlet piping  150 ,  245  or down the water or fluid inlet piping  145 ,  240 , or into both the inlet and the outlet. Simultaneously, the molten polymer can begin to quickly solidify before the operator can safely get to the pelletizer and unclamp the pelletizer from the cutting chamber or water box. The pelletizer, now being held in position by the solidifying polymer, cannot be easily removed from the cutting chamber  155 ,  250 . As used herein, “polymer” is intended to refer to both pure polymer melts as well as extrudable material that contains a mixture of one or more polymers and other non-polymer material such as biomaterials, additives, and the like. Also, the terms “water box” and “cutting chamber” are used interchangeably herein. 
         [0013]    There is no easy way with either the  FIG. 1  or the  FIG. 2  design to remove the cutter hub  140 ,  235  or the cutter hub holder  115 ,  215  from the pelletizer shaft  100 ,  200  so the operator can remove the pelletizer and get into the cutting chamber to remove the agglomerated polymer and clear the cutter blades of any obstructions so to be able to re-start the pelletizer and process line. Ideally, in the case of polymer agglomeration the operator should proceed to take certain disassembly steps such as unbolting the cutting chamber  155 ,  250  and die plate  160 ,  255  from the upstream equipment to clean out the polymer wrap. Alternatively, in the  FIG. 2  design, the operator can remove the fan cover (not shown) on the back of the motor  290 , disconnect the motion rod  220  from the motion rod adjuster (not shown) and then unscrew the motion rod  220  from the cutter hub holder  215 . If the motion rod is not disconnected from the correct point, however, then the forward travel must be readjusted when reassembling the components. If the forward travel is not adjusted correctly, the operator could, in the best case, not get full blade life out of the blades  225 , or in the worst case, the operator could run the cutter hub  235  into the face of the die  255  as the blades  225  wear down, which will damage the face of the die  255  requiring that the die be replaced or repaired. 
         [0014]    Unfortunately, rather than undertaking disassembly procedures such as those just described, many operators will try to introduce pry bars to increase leverage to get the pelletizer separated from the cutting chamber. The heavy duty pry bars can damage the precision mating surfaces of the pelletizer front-end and the connecting flange of the cutting chamber. Further, the pry bars put very high stresses on the various components on the front end and throughout the pelletizer and its motor. In some extreme cases, operators or maintenance staff have brought in a forklift truck to pull the pelletizer away from the cutting chamber. Needless to say, such forceful separation can severely damage the pelletizer and its components, creating costly failures, extensive down time awaiting replacement parts to repair the damage, and/or safety hazards. 
         [0015]    Hence, there is a need for a cutter hub drive mechanism that produces better torque transmission from the pelletizer shaft to the cutter hub while reducing the likelihood of drive mechanism breakage and drive key entrapment arising from wear patterns formed in the pelletizer shaft by the keys. In addition, there is a need for a structure to prevent the entry of fines into the drive key area, and also a process by which the removal of agglomerated polymer within the cutting chamber is shortened and simplified. 
       SUMMARY OF THE INVENTION 
       [0016]    In view of the foregoing, the present invention is directed to a cutter hub pin drive mechanism for an underfluid pelletizer having a pelletizer shaft and a cutter hub. The cutter hub includes a cutter hub holder having a plurality of longitudinally extending grooves formed on an inner surface thereof. The forward end of the pelletizer shaft fits within the cutter hub holder and has an outer surface with a corresponding plurality of longitudinally extending grooves cut therein in longitudinal alignment with the grooves in the cutter hub holder. The respectively aligned cutter hub holder grooves and pelletizer shaft grooves form a plurality of longitudinally extending drive pin channels. A plurality of drive pins are received within the drive pin channels, respectively. Torque is transmitted from the pelletizer shaft to the cutter hub holder and cutter hub by the drive pins which are captured within the drive pin channels. The drive pins are preferably held within the cutter hub holder by retaining the ends of the drive pins nearest the cutter hub in holes formed in the bottom of the cutter hub holder, preferably by a press fit. Other holding mechanisms could be used such as glue or other adhesive, brazing, and the like. 
         [0017]    The present invention also includes a quick disconnect hub for a pelletizer or a cutter hub pin drive mechanism. The quick disconnect hub is configured to secure the pelletizer shaft to the cutter hub holder with a retaining element. To separate the cutting assembly from the pelletizer with minimal effort in order to clear the cutting chamber from agglomerated polymer and the like, the quick disconnect hub is separated from the retaining element, allowing the pelletizer shaft to be pulled out of the cutter hub holder while the cutter hub remains in the cutting chamber. Once the chamber is cleared, the pelletizer shaft can be easily reconnected to the cutter hub holder by resecuring the quick disconnect hub with the original or a replacement retaining element. 
         [0018]    The present invention is also directed to an underfluid pelletizer for extruding and cutting a process melt into pellets, the pelletizer including a pelletizer shaft and a die plate with a plurality of extrusion orifices formed therein through which the process melt is carried from the die plate to a cutting face on a downstream side of the die plate. A rotary cutter blade assembly, in opposed relation to the cutting face, has a cutter hub and at least one cutter blade mounted on the hub. The cutter blade assembly, which is driven by the pelletizer shaft using a cutter hub pin drive mechanism, is capable of moving in a plane generally parallel to and closely adjacent the cutting face to cut strands of process melt extruded through the orifices into pellets. 
         [0019]    The pelletizer further includes a cutting chamber that encloses the cutting face and cutter blade assembly. The cutting chamber includes a fluid inlet for introducing cooling fluid into the cutting chamber and an outlet for discharge of fluid and pellets entrained in the fluid. In an underwater pelletizer, the fluid is typically water or a fluid mix containing water but other fluids may be used. Therefore, the term underfluid pelletizer is intended to include all pelletizers operating with a fluid in the cutting chamber. 
         [0020]    The cutter hub pin drive mechanism of the cutter blade assembly includes a cutter hub holder having a plurality of longitudinally extending grooves formed on an inner surface thereof. The forward end of the pelletizer shaft fits within the cutter hub holder and has an outer surface with a corresponding plurality of longitudinally extending grooves cut therein in longitudinal alignment with the grooves in the cutter hub holder. The respectively aligned cutter hub holder grooves and pelletizer shaft grooves form a plurality of longitudinally extending drive pin channels. A plurality of drive pins are received within the drive pin channels, respectively, with torque being transmitted from the pelletizer shaft to the cutter hub holder and cutter hub by the drive pins as captured within the drive pin channels. The drive pins are preferably held within the cutter hub holder by retaining the ends of the drive pins nearest the cutter hub in holes formed in the bottom of the cutter hub holder, preferably by a press fit although other holding mechanisms such as adhesives, brazing, and the like, could be used. A sealing member is positioned around the pelletizer shaft and under the cutter hub holder to prevent the egress of fines into the drive pin channels. 
         [0021]    The pelletizer may further include a quick disconnect hub configured to secure the pelletizer shaft to the cutter blade assembly through the cutter hub holder with a retaining element. To separate the cutter blade assembly from the pelletizer shaft with minimal effort in order to clear the cutting chamber from agglomerated polymer and the like, the quick disconnect hub with the retaining element is separated from the pelletizer shaft, allowing the pelletizer shaft to be pulled out of the cutter hub holder while the cutter hub assembly remains in the cutting chamber. Once the chamber is cleared, the pelletizer shaft can be easily reconnected to the cutter hub holder and cutter hub assembly by resecuring the quick disconnect hub with the original or a replacement retaining element. 
         [0022]    Accordingly, it is an object of the present invention to provide a underfluid pelletizer having an improved cutter hub drive mechanism. 
         [0023]    Another object of the present invention is to provide a cutter hub drive mechanism for an underfluid pelletizer that provides a better distribution of the forces of torque along the pelletizer shaft components thus reducing wear and subsequent premature failures. 
         [0024]    Still another object of the present invention is to provide a cutter hub pin drive mechanism for a pelletizer in accordance with the preceding object in which drive pins are used that extend beyond the forward end of the pelletizer shaft and reduce wear thereon to keep the surfaces that slide against one another smoother so blade adjustment will remain reliable and irregular wear patterns that impede forward adjusting movement of the cutting blades are reduced. 
         [0025]    Yet another object of the present invention is to provide a cutter hub pin drive mechanism for a pelletizer in accordance with the preceding objects in which grooves complementary to the shape of the drive pins are machined into abutting surfaces of the cutter hub holder and pelletizer shaft to form drive pin channels having improved precision to increase the effective surface contact area of the interface between these components and the drive pins fitted in the channels. 
         [0026]    A further object of the present invention to provide a cutter hub pin drive mechanism for a pelletizer in accordance with the preceding objects that has at least one sealing feature to reduce or eliminate the egress of fines or very small pellets into the drive pin area, and thus help to prolong the performance of the pelletizing cutting features and/or to help reduce any cross contamination of such entrapped materials, from one pelletizing run to the next. 
         [0027]    A still further object of the present invention to provide a pelletizer in accordance with the preceding objects which includes a quick disconnect hub that simplifies the process needed to address the problems that arise when polymer agglomerates in the cutting chamber, as can occur from time-to-time with underfluid pelletizing, requiring that the pelletizer be disengaged from the cutting chamber. 
         [0028]    Yet another object of the present invention is to provide a pelletizer with a quick disconnect hub in accordance with the preceding object in which the front area of the pelletizer within the cutting chamber is designed to be much more easily and quickly disconnected from the cutter hub holder in the event of an agglomeration of extruded materials within the cutting chamber. 
         [0029]    It is still another object of the invention to provide a pelletizer with quick disconnect hub in accordance with the preceding two objects in which the disconnect device is not complex in structure and can be manufactured at low cost but yet efficiently enables the pelletizer to be disconnected from the cutting chamber easily and quickly without the need for complicated or lengthy disassembly procedures. 
         [0030]    These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a partial section view showing the relation on a prior art assembly of the cutter hub, blades, die plate, cutting chamber and front of the pelletizer motor. 
           [0032]      FIG. 2  is a partial section view showing the relation on another prior art assembly of the cutter hub, blades, die plate, cutting chamber, and front of the pelletizer motor with motion rod. 
           [0033]      FIG. 3  is a partial section view of a first embodiment of a pelletizer in accordance with the present invention showing the relation of the cutter hub, blades, die plate, cutting chamber, front of the pelletizer motor and quick disconnect hub. 
           [0034]      FIG. 4  is a partial section view of a second embodiment of a pelletizer in accordance with the present invention showing the relation of the cutter hub, blades, die plate, cutting chamber, front of the pelletizer motor, pelletizer shaft and motion rod, and quick disconnect hub. 
           [0035]      FIG. 5  is a sectional view of the cutter hub holder and pelletizer shaft components of the first prior art embodiment shown in  FIG. 1 . 
           [0036]      FIG. 5A  is a sectional view taken along line A-A of  FIG. 5 . 
           [0037]      FIG. 6  is a sectional view of the cutter hub holder, pelletizer shaft and motion rod components of the second prior art embodiment shown in  FIG. 2 . 
           [0038]      FIG. 6A  is a sectional view taken along line B-B of  FIG. 6 . 
           [0039]      FIG. 7  is an assembled sectional view of the cutter hub holder, pelletizer shaft and quick disconnect hub components of the first embodiment of the present invention shown in  FIG. 3 . 
           [0040]      FIG. 7A  is a sectional view taken along line C-C of  FIG. 7 . 
           [0041]      FIG. 8  is an assembled sectional view of the cutter hub holder, pelletizer shaft and motion rod, and quick disconnect hub components of the second embodiment of the present invention shown in  FIG. 4 . 
           [0042]      FIG. 8A  is a sectional view taken along line D-D of  FIG. 8 . 
           [0043]      FIG. 9  is a sectional view of the cutter hub holder, pelletizer shaft and quick disconnect hub components of the first embodiment of the present invention shown in  FIGS. 3 and 7  when the components are disconnected from one another. 
           [0044]      FIG. 10  is a sectional view of the cutter hub holder, pelletizer shaft and motion rod, and quick disconnect hub components of the second embodiment of the present invention shown in  FIGS. 4 and 8  when the components are disconnected from one another. 
           [0045]      FIG. 11  is an assembled sectional view of a third embodiment of the present invention, that does not include a disconnect hub, showing the relation of the cutter hub, blades, die plate, cutting chamber, front of the pelletizer motor, and pelletizer shaft and motion rod. 
           [0046]      FIG. 12  is an assembled sectional view of the cutter hub holder and pelletizer shaft and motion rod components of the third embodiment of the present invention shown in  FIG. 11 . 
           [0047]      FIG. 12A  is a sectional view taken along line E-E of  FIG. 12 . 
           [0048]      FIG. 13  is a sectional view of the cutter hub holder and pelletizer shaft and motion rod components of the third embodiment of the present invention shown in  FIGS. 11 and 12  when the components are disconnected from one another. 
           [0049]      FIG. 14  is a cross-sectional view of a cutter hub holder having inner surface grooves according to the present invention. 
           [0050]      FIG. 15  is a cross-sectional view of a pelletizer shaft having outer surface grooves according to the present invention. 
           [0051]      FIG. 16  is a cross-sectional view of the pelletizer shaft of  FIG. 15  fitted within the cutter hub holder of  FIG. 14  to form drive pin channels for a cutter hub pin drive mechanism according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0052]    In describing preferred embodiments of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms 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. 
         [0053]    A first embodiment of the present invention is shown in  FIGS. 3, 7, 7A and 9 . The pelletizer, generally designated by reference numeral  30 , includes a pelletizer shaft  300  coupled to a motor shaft  305 , a cutter hub  350  with cutter blades  335 , a cutter hub holder  315 , a cutting chamber  355 , a die plate  359 , a cutter hub pin drive mechanism including a plurality of drive pins  345 , a sealing member  360 , a disconnect hub  320  and a retainer ring  340 . The pelletizer shaft  300  is bolted to the motor shaft  305  of motor  390  with set screws  310 . The cutter hub holder  315  is secured to the disconnect hub  320  with a bolt  325 . A spring  330  is provided for adjustment of the cutter hub holder  315  and blade position as the blades  335  wear. 
         [0054]    The cutter hub pin drive mechanism includes multiple drive pins  345 , with typically 6 to 12 being used depending upon various factors including but not limited to the model of the pelletizer, the power of the motor, space constraints and the diameter of the pelletizer shaft. The drive pins  345  ride in drive pin channels, generally designated by reference numeral  339 , that are formed by longitudinally extending grooves  317  formed in an inner surface  319  of the cutter hub holder  315  and matching longitudinally extending grooves  327  formed in the outer surface  341  of the forward end  329  of the pelletizer shaft  300  and aligned with the cutter hub holder grooves  317  as shown in  FIG. 7A  and  FIGS. 14-16 . The forward ends  323  of the drive pins  345  are inserted in holes  321  at the bottom of the cutter hub holder  315  to retain the drive pins  345 , and are preferably held with a press fit in the holes. Other holding mechanisms could also be used as would be understood by persons of ordinary skill in the art. In this way, the pins stay in engagement with the cutter hub holder when the cutter hub holder is disconnected from the pelletizer shaft. The use of the machined mating grooves  317 ,  327  and the drive pins positioned therein to drive the cutter hub holder  315  eliminates the need for a drive key weld of the type discussed in connection with the prior art  FIG. 1  and  FIG. 2  designs that sometimes failed and released the keys. As shown, the pins  345  and grooves  317 ,  327  extend parallel to the axis of the pelletizer shaft  300  and motor shaft  305  and are preferably evenly spaced around the inner surface of the cutter hub holder. 
         [0055]    The drive pins  345  extend all the way into the bottom of the cutter hub holder  315  so that the forward ends  323  extend past the forward end  329  of the pelletizer shaft  300 . This extension eliminates the wear problem in the prior art designs which resulted in the drive keys being caught within notches (not shown) formed in the outer surface  341  of the pelletizer shaft  300  and thus hindering or blocking movement of the cutter hub holder  315  to allow for adjustment of the blades  335 . 
         [0056]    The drive pins not only eliminate the need for welding as well as reducing the wear problem of the drive keys against the pelletizer shaft, but the drive pins also provide for a larger area of surface contact in the interface between the pins and the cutter hub holder grooves  317  and pelletizer shaft grooves  327 . The cutter hub holder  315  and pelletizer shaft  300  can be machined with greater precision than is possible when welding the prior art drive keys in place, improving the interface of the shaft with the drive pins  345 . As a result, torque transmission is greatly improved because all of the drive pins  345  are in contact with the pelletizer shaft  300  and therefore torque is distributed and does not fall onto only one or two of the drive elements. 
         [0057]    In the embodiments shown herein, the drive pins are cylindrical with a circular cross-section as shown in  FIGS. 7A, 8A and 12A . The grooves are therefore semi-circular so that when placed in abutment a cylindrical groove results with a circular cross-section as shown in  FIGS. 14-16 . However, pins having different cross-sectional shapes, such as square, hexagonal and the like, may be used provided the grooves are complementary in shape to the cross section of the pins. 
         [0058]    To prevent the egress of fines into the area of the drive pins, the pelletizer according to the present invention further includes a sealing member  360 , such as an o-ring, mounted on the pelletizer shaft  300  under the outer end of the cutter hub holder  315 . The o-ring seals fluid and fines out of the drive pin area ensuring that fines do not accumulate or otherwise obstruct the free sliding relationship of the cutter hub relative to the pelletizer shaft that allows for smooth and unhindered adjustment of the position of the blades  335  against the cutting face of the die plate  359 . 
         [0059]    As shown, the cutter hub holder  315  in the first embodiment is coupled to the quick disconnect hub  320  via threads  322  on the end of the bolt  325 . The disconnect hub  320  has a groove  301  formed in an outer surface  307  thereof (see  FIG. 9 ). A retaining element such as a retainer ring  340  is held within the groove  301 . The depth of the groove  301  is undersized with respect to the diameter of the retainer ring  340  so that the ring, while remaining captured in the groove  301  at all times, protrudes beyond an outer surface  307  of the disconnect hub  320  when the disconnect hub is separated from the pelletizer shaft. The shaft  300  has a bore  305  having an inner surface  303  with a groove  311  formed therein. As the disconnect hub is inserted into the bore  305  of the shaft, the retainer ring is compressed into the groove  301  through contact with the inner surface  303  of the shaft. When the disconnect hub is fully inserted, the retainer ring  340  reaches and snaps out into the pelletizer shaft groove  311  to couple the cutter hub holder  315  to the pelletizer shaft  300 . While a retainer ring  340  is shown, other configurations of the retaining element are also considered to be within the scope of the present invention, including both reusable and frangible retaining elements. 
         [0060]    The disconnect hub  320  is operative with the spring  330  that is secured to the cutter hub holder with a fastening element such as bolt  325  or the like. The rearward end  314  of the fastening element  325  is coupled to the quick disconnect hub  320 . The spring  330  is fitted onto the shaft of the bolt  325  with a rearward end  351  of the spring being in abutment with the disconnect hub  320 , and a forward end  353  of the spring being in abutment with an inwardly directed flange  357  on the cutter hub holder. The spring  330  exerts force to press the cutter hub  350  against the die plate  359  for adjustment of the cutter hub position as the blades  335  wear down. 
         [0061]    Through the use of the disconnect hub  320  and retainer ring  340 , if the cutter hub  350  gets wrapped up with polymer in the cutting chamber  355 , the operator can more gently pull the pelletizer away by hand causing the retainer ring  340  to compress into slot  301  and disengage from the pelletizer shaft  300 . Upon disengagement, the pelletizer can be pulled back from the cutting chamber  355  without damaging any components and leaving the cutting assembly including the cutter hub  350 , cutter hub holder  315 , disconnect hub  320 , retainer ring  340 , bolt  325 , spring  330  and drive pins  345  inside the cutting chamber  355 . The operator can then clean out the polymer wrap from the cutting chamber  355  and then reinsert the disconnect hub  320  of the cutting assembly into the bore  305  of the pelletizer shaft  300 , making sure the disconnect hub  320  gets locked in place by the retainer ring  340  to lock the cutting assembly back in place on the pelletizer. The pelletizer can then be rolled back into the cutting chamber  355  and restarted. 
         [0062]    A second embodiment of the present invention is shown in  FIGS. 4, 8, 8A and 10 . The pelletizer, generally designated by reference numeral  40 , includes a pelletizer shaft  400  coupled to a motor shaft  405 , a cutter hub  445  with cutter blades  435 , a cutter hub holder  415 , a cutting chamber  450 , a die plate  459 , a cutter hub pin drive mechanism including a plurality of drive pins  440 , a sealing member  455 , a quick disconnect hub  425  and a retainer ring  420 . The pelletizer shaft  400  is bolted to the motor shaft  405  of motor  490  with set screws  410 . The pelletizer shaft has a motion rod  430  that is threadedly coupled to the quick disconnect hub  425 , with the connection between the hub  425  and the motion rod  430  then being used to secure the pelletizer shaft to the cutter hub holder  415  and cutter hub assembly. 
         [0063]    As in the first embodiment, the cutter hub pin drive mechanism includes multiple drive pins  440 , with typically 6 to 12 being used depending upon various factors including but not limited to the model of the pelletizer, the power of the motor, space constraints and the diameter of the pelletizer shaft. The drive pins ride in drive pin channels, generally designated by reference numeral  439 , formed by longitudinally extending grooves  417  cut in the inner surface  419  of in the cutter hub holder  415  and corresponding longitudinally extending grooves  427  cut in the outer surface  441  of the pelletizer shaft  400  that are aligned with the cutter hub holder grooves  417  as shown in  FIG. 8A  and  FIGS. 14-16 . Capturing of the drive pins  440  in the drive pin channels  439  to transfer torque from the pelletizer shaft  400  to the cutter hub holder  415  eliminates the need for the weld that was required to secure the rectangular drive keys to the cutter hub holder in the prior art embodiments of  FIGS. 1 and 2 , previously described herein. As shown, the pins  440  and grooves  417 ,  427  extend parallel to the axis of the pelletizer shaft  400  and motor shaft  405  and are preferably equally spaced around the inner surface of the cutter hub holder. 
         [0064]    As in the first embodiment of the present invention, the forward end  423  of the drive pins  440  extend beyond the forward end  429  of the pelletizer shaft  400  and are inserted in holes  421  at the bottom of the cutter hub holder  415  to retain the drive pins  440  in the cutter hub holder  415 . The extension of the pins past the forward end of the pelletizer shaft  400  reduces the wear problem encountered with the prior art drive keys that would dig into the outer surface  441  of the pelletizer shaft and then “catch” on the notches (not shown) formed as a result of this wear pattern, preventing free movement of the cutter hub holder and cutter hub for blade position adjustment. 
         [0065]    Also as in the first embodiment, the second embodiment of the pelletizer includes sealing member  455 , such as an o-ring, placed around the pelletizer shaft  400  under the outer or rearward end of the cutter hub holder  415  to seal fluid and fines out of the drive pin area. By preventing the egress of fines and other contaminants into the drive pin area, the sealing member  455  ensures that fines do not accumulate or otherwise obstruct the free sliding relationship of the cutter hub  415  relative to the pelletizer shaft  400 , which relationship allows for smooth adjustment of the position of the blades relative to the cutting face of the die plate. 
         [0066]    The quick disconnect hub  425  is coupled, preferably by a threaded engagement, as at  422 , to the forward end  414  of the motion rod  430 . The motion rod is used to push and pull the cutter hub toward and away from the die plate  459  to adjust blade position with respect to the die plate  459  as the blades wear. 
         [0067]    The disconnect hub  425  has a groove  401  formed in an outer surface  407  thereof. A retainer ring or snap ring  420  is captured within the groove  401 . The depth of the groove  401  is undersized with respect to the diameter of the retainer ring  420  so that the ring, while remaining captured in the groove  401  at all times, protrudes beyond the outer surface  407  of the disconnect hub  425  when the disconnect hub is separated from the cutter hub holder  415 . The cutter hub holder  415  has a bore  405  having an inner surface  413  with a circular groove  411  formed therein. As the disconnect hub is inserted into the bore  405  of the cutter hub holder  415 , the ring  420  is compressed into the groove  401  through contact with the inner surface  413  of the cutter hub holder. When the disconnect hub is fully inserted, the retainer ring reaches and snaps into the cutter hub holder groove  411  to couple the cutter hub holder to the pelletizer shaft. While a snap ring  420  is shown, other configurations of the retaining element are also considered to be within the scope of the present invention, including both reusable and frangible retaining elements. 
         [0068]    As also in the first embodiment, the separable connection between the disconnect hub  425  and the cutter hub holder  415  provides a simple means of separating the pelletizer shaft from the cutter hub holder if the cutter hub  445  gets wrapped up with polymer in the cutting chamber  450 . The operator can manually pull the pelletizer away from the cutter hub holder  415 , causing the retainer ring  420  to compress into groove  401  and disengage from the cutter hub holder  415  which allows the pelletizer to be pulled back from the cutting chamber  450  without damaging any components. The cutting assembly including the cutter hub  445 , cutter hub holder  415 , and drive pins  440  remain in the polymer inside the cutting chamber  450 . The operator can then clean out the polymer wrap from the cutting chamber  450  and then reconnect the pelletizer shaft to the cutter hub holder  415  making sure the cutter hub holder  415  gets locked in place by the retainer ring  420  to the disconnect hub  425  to lock the cutting assembly back in place on the pelletizer. The pelletizer can then be rolled back into the cutting chamber  450  and restarted. 
         [0069]    A third embodiment of the present invention is shown in  FIGS. 11, 12, 12A and 13 . The pelletizer, generally designated by reference numeral  50 , includes a pelletizer shaft  500  with a motion rod  520  coupled to a motor shaft  505 , a cutter hub  540  with cutter blades  530 , a cutter hub holder  515 , a cutting chamber  545 , a die plate  559 , a cutter hub pin drive mechanism including a plurality of drive pins  535 , and a sealing member  550 . The pelletizer shaft  500  is bolted to the motor shaft  505  of motor  590  with set screws  510 . The cutter hub holder  515  is retained on the pelletizer shaft  500  through threaded engagement with the motion rod  520 . The motion rod  520  is used to adjust and fix the position of the cutter hub  540  relative to the die plate  559  as the blades  530  wear down. Once the motion rod is positioned as desired, the set screw  525  is used to secure the motion rod to the cutter hub holder. 
         [0070]    Like the first and second embodiments, the cutter hub pin drive mechanism includes multiple drive pins  535 , with typically 6 to 12 being used depending upon various factors including but not limited to the model of the pelletizer, the power of the motor, space constraints and the diameter of the pelletizer shaft. The drive pins ride in drive pin channels, generally designated by reference numeral  539 , formed by longitudinally extending grooves  517  in the inner surface  519  of the cutter hub holder  515  and corresponding longitudinally extending grooves  527  in the outer surface  541  of the pelletizer shaft as shown in  FIG. 12A  and  FIGS. 14-16 . The forward ends  523  of the drive pins  535  and are inserted in holes  521  at the bottom of the cutter hub holder  515  to retain the drive pins  535  in the cutter hub holder, again eliminating the need for any welding of the pins to the cutter hub holder. The pins extend past the forward end  529  of the pelletizer shaft  500  which reduces the prior art wear pattern in the pelletizer shaft that resulted in obstructed movement of the cutter hub holder. As shown, the pin  535  and grooves  517 ,  527  extend parallel to the axis of the pelletizer shaft  500  and motor shaft  505  and are preferably equally spaced around the inner surface of the cutter hub holder. 
         [0071]    Also like the first two embodiments, the third embodiment includes the sealing member  550 , which may be embodied as an o-ring, on the pelletizer shaft  500  under the outer or rearward end of the cutter hub holder  515  to seal fluid and fines out of the drive pin area as has already been described herein. 
         [0072]    As shown herein, the third embodiment does not include a quick disconnect hub. However, the structure shown in  FIGS. 11-13  could be modified in a manner like that shown in  FIGS. 4, 8 and 10  of the second embodiment to include a quick disconnect hub feature if desired. 
         [0073]    In the absence of a quick disconnect hub, as in the embodiment shown in  FIGS. 11-13 , if the cutter hub  540  gets wrapped up with polymer in the cutting chamber  545 , the operator must remove the motor fan cover (not shown) on the back of the motor  590  and disconnect the motion rod  520  from the motion rod holder (not shown). The operator then unscrews the motion rod  520  from the cutter hub holder  515 , leaving the cutter hub  540 , cutter hub holder  515  and drive pins  535  as a cutting assembly in the polymer inside the cutting chamber  545 . The operator can then clean out the polymer wrap from the cutting chamber  545 , reinsert the cutting assembly onto the pelletizer shaft  500 , screw the motion rod  520  back into the cutter hub holder  515 , and tighten the set screw  525 . The motion rod is then reconnected to the motion rod holder (not shown) and the fan cover (not shown) is reinstalled on the back of the motor. The pelletizer can then be rolled back into the cutting chamber  545  and restarted. 
         [0074]    The foregoing descriptions and drawings should be considered as illustrative only of the principles of the invention. The invention may be configured in a variety of shapes and sizes and is not limited by the dimensions of the preferred embodiment. Numerous applications of the present invention will readily occur to those skilled in the art. Therefore, it is not desired to limit the invention to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.