Abstract:
An apparatus is provided for processing (e.g., granulating) industrial materials (e.g., synthetic resin materials). The apparatus has a rotor shaft mounted in the inside of a housing. The rotor shaft has an axis running in a generally horizontal direction. Cutters extend radially from the rotor shaft with some of the cutters extending a distance less than the others. Approximately one-half of a second plurality of cutters are positioned on the rotor shaft between a first cutter and a second cutter of the first plurality of cutters, and approximately the other half of the second plurality of cutters are positioned on the rotor between the second cutter and a third cutter of the first plurality of cutters. The cutters may contain a symmetrical blade portion such that the rotor may be run in both directions, thereby extending the time between required maintenance operations, and minimizing down-time for the apparatus.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/210,907, filed on Jun. 12, 2000, the entire contents of which are incorporated herein by reference. 
     
    
     
       BACKGROUND  
         [0002]    The present invention relates in general to material processing apparatuses, including material granulators. More specifically, it relates to a material granulator having multiple cutting blades.  
           [0003]    A typical granulator apparatus (e.g., such as that used in the manufacturing of industrial plastics) is made up of: i) a hopper (for temporarily holding and feeding the industrial material to be granulated; ii) a granulator blade portion which receives the industrial material from the hopper and contains the granulator rotor and blades; and iii) a storage portion for storing the granulated material. Such granulators typically have an integral granulator motor coupled to the granulator blade portion for transferring energy to the granulator blades.  
           [0004]    One example of a known crushing apparatus is depicted in FIG. 14. The apparatus has a material hopper  12 , a crushing chamber  14  and an opening  13  through which the crushed material is allowed to drop. The crushing chamber contains two rotor shafts  17  and  18 , each of which support multiple cutting blades  19  and  20 . The top set of cutting blades  19  are larger than the lower set of cutting blades  20 . Accordingly, the top set of cutting blades  19  are used for roughly crushing the material and the lower set of cutting blades  20  are used for finely crushing the material. During operation, the material drops from the hopper portion  12  into the crushing chamber  14 , where it is roughly crushed by the large blades  19 . The roughly crushed material then drops to the smaller cutting blades  20  where it is finely crushed. The finely crushed material then drops down through the opening  13 . The FIG. 14 crushing apparatus, although somewhat effective, has been found to be unduly large and bulky due to its two-tiered blade configuration. In addition, since two rotor shafts are required, it follows that two rotor drives must be powered. Thus, the cost to operate the FIG. 14 crushing apparatus, along with its prohibitively large size, render its use less than ideal.  
           [0005]    One proposed improvement over the FIG. 14 crushing apparatus is found in the crushing apparatus depicted in FIGS.  15 - 17 . The crushing apparatus of FIGS.  15 - 17  contains a single driving shaft  37  requiring a single power source for driving the shaft  37 . In addition, it contains two differently-sized blades  41  and  42  that are commonly mounted on the single driving shaft  37 . The differently-sized blades are made up of two large saw-tooth blades  41  used for roughly crushing the material and a multitude of small saw-tooth blades  42  used for finely crushing the material. The crushing apparatus of FIGS.  15 - 17  also includes two cover members  43  used for capturing any roughly crushed material that has been crushed by the large blades  41 , but has not yet been crushed by the small blades  42 . Since the material must be finely crushed before it is permitted to drop into the dropping opening  33 , the cover members along with the large blades  41  provide a means with which the roughly crushed material is scooped up and brought back into the crushing chamber  32  where it may be finely crushed by the small blades  42 . In addition, the crushing apparatus contains two sidewalls  32  that are generally perpendicular to the axis of the drive shaft  37 . Furthermore, the small saw-tooth blades  42  are located on either side of the drive shaft  37  between respective ones of the large saw-tooth blades  41  and the sidewalls.  
           [0006]    A problem associated with the crushing apparatus of FIGS.  15 - 17  is that the multitude of blades  41  and  42  are affixed to the driving shaft  37  in a manner such that even if only a single blade (e.g., one of the large blades  41 ) requires replacement (e.g., due to damage, regular maintenance, etc.), the entire blade assembly must be dismantled in order to reach the blade that requires replacement. That is, all of the large saw-tooth blades  41  and all of the small saw-tooth blades  42  located adjacent to the damaged blade must be removed in order to replace only the one damaged blade.  
           [0007]    Furthermore, since the blades  41  and  42  are saw-toothed in shape, the drive shaft  37  may be rotated in only one direction; i.e., the direction in which the blades are effective for cutting the material. The fact that the blades are useful for cutting in only a single direction means that they have a relatively short useful life; thus, they will require frequent replacement. In addition, the fact that only one set of blades  41  is provided for roughly crushing the material means that the small blades  42  are expected to finely crush material that had been subject to only one crushing operation; thus, replacement of the small blades due to damage is likely to be more frequent. Consequently, not only is the crushing apparatus of FIGS.  15 - 17  unduly burdensome and expensive to maintain from purely a labor standpoint, but it can be rendered useless for long periods of time while the blade assembly is dismantled, the damaged blade is replaced and the blade assembly is re-assembled during frequently required routine maintenance.  
           [0008]    In addition, since the sidewalls of the FIG. 15 crushing apparatus are generally perpendicular to the drive shaft, they are not useful for steering the material into the small blades  42 . Moreover, since any material that enters the FIG. 15 crushing apparatus will be large pieces of uncrushed material, they are likely to become trapped in between the generally perpendicular sidewalls and the large cutting blades  41 , unable to be crushed by the small blades  42 . This presents a problem in that the small blades  42  will likely become worn more quickly as a result of constantly attempting to break down large pieces of material while the material is trapped between the generally perpendicular sidewalls and the large blades  41 .  
         SUMMARY  
         [0009]    The present invention provides an apparatus for processing industrial materials.  
           [0010]    The invention also relates to a three-blade granulator apparatus, a rotor shaft and blade assembly, and a method for removing and replacing damaged blades on the rotor shaft and blade assembly. In general, the apparatus may be used to granulate, cut, shred, crush, comminute or otherwise process a variety of materials, including but not limited to synthetic resin materials. The granulator apparatus has a rotor shaft mounted in the inside of a housing. The rotor shaft has an axis running in a generally horizontal direction. A first and second plurality of cutters extend radially from the rotor shaft with each of the second plurality of cutters extending a distance less than each of the first plurality of cutters. In one embodiment, approximately one-half of the second plurality of cutters are positioned on the rotor shaft between a first cutter and a second cutter of the first plurality of cutters and approximately the other half of the second plurality of cutters are positioned on the rotor between the second cutter and a third cutter of the first plurality of cutters. Each of the cutters contains a symmetrical blade portion such that the rotor may be run in both directions, thereby extending the time between required maintenance operations, and minimizing down-time for the apparatus. Furthermore, when blade replacement is required, the damaged blade may be removed and replaced without disrupting the balance of the rotor shaft and blade assembly.  
           [0011]    In one aspect, a fractional cutter portion is provided which contains at least one cutter blade portion symmetrical in shape. The fractional cutter portion is easily coupled to and decoupled from a rotor shaft of a granulator apparatus.  
           [0012]    In another aspect, a cutting tooth assembly is provided which contains a plurality of symmetrical cutting teeth and which is easily coupled to and detached from a rotor shaft of a granulator apparatus.  
           [0013]    In another aspect, a rotor shaft and blade assembly is provided which contains a plurality of fractional cutter portions and a plurality of cutting tooth assemblies.  
           [0014]    In another aspect, an improved granulator apparatus is provided containing an improved rotor shaft and blade assembly.  
           [0015]    In another aspect, an improved cutting chamber frame is provided which is easily assembled and which contains at least one slanted sidewall. The slanted sidewall assists in feeding a material to be crushed into at least one of a first plurality of cutters.  
           [0016]    In another aspect, an improved blade system is provided which contains at least three identical cutter discs assembled on a hexagonal shaft, wherein each cutter disc may further contain at least two portions that join together on the hexagonal shaft, wherein each cutter disc contains a plurality of cutting teeth, and wherein when the three cutter discs are mounted on the hexagonal shaft, the orientation of the cutting teeth for each blade with respect to the hexagonal shaft form a staggered pattern of at least three distinct cutter teeth orientations on the hexagonal shaft.  
           [0017]    The invention also relates to a method of replacing a defective cutter in a granulator apparatus.  
           [0018]    The invention also relates to a method of operating a granulator apparatus.  
           [0019]    These and other features and advantages of the invention will be more clearly understood from the following detailed description and drawings of preferred embodiments of the present inventions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a perspective view of a granulator apparatus according to a preferred embodiment of the present invention.  
         [0021]    [0021]FIG. 2 is an exploded view of a cutting chamber frame of the apparatus of FIG. 1.  
         [0022]    [0022]FIG. 3 is a bottom perspective view of the cutting chamber frame of FIG. 2.  
         [0023]    [0023]FIG. 4 is a top perspective view of the cutting chamber frame of FIG. 2.  
         [0024]    [0024]FIG. 5 is an exploded view of a rotor shaft assembly within the cutting chamber frame of FIG. 2.  
         [0025]    [0025]FIG. 6 is another exploded view, like FIG. 5, showing the rotor shaft assembly located within the cutting chamber frame.  
         [0026]    [0026]FIG. 7 is an exploded view of the rotor shaft and blade assembly of FIG. 5.  
         [0027]    [0027]FIG. 8 is a plan view of the rotor shaft and blade assembly of FIG. 5.  
         [0028]    [0028]FIG. 9 is a view taken along line IX-IX of FIG. 8.  
         [0029]    [0029]FIG. 10 is view taken along line X-X of FIG. 8.  
         [0030]    [0030]FIG. 11 is a view taken along line XI-XI of FIG. 8.  
         [0031]    [0031]FIG. 12 is a view like FIG. 9 showing a cover member. Portions of elements that are hidden from view by the cover member are shown in the figure in phantom lines.  
         [0032]    [0032]FIG. 13 is a view like FIG. 11 showing a cover member.  
         [0033]    [0033]FIG. 14 is a known crushing apparatus.  
         [0034]    FIGS.  15 - 17  are three views of a known crushing apparatus.  
         [0035]    [0035]FIG. 18 is a perspective view of an assembled granulator.  
         [0036]    [0036]FIG. 19 is a perspective view of a cutting chamber according to another preferred embodiment of the invention.  
         [0037]    [0037]FIG. 20 is a perspective view of a rotor shaft assembly of the FIG. 19 cutting chamber.  
         [0038]    [0038]FIG. 21 is an exploded view of a portion of the FIG. 20 rotor shaft assembly.  
         [0039]    [0039]FIG. 22 is a cross sectional view taken along line XXII of FIG. 19.  
         [0040]    [0040]FIG. 23 is a plan view of a small cutter blade according to another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0041]    [0041]FIG. 1 is a perspective view of a granulator apparatus  100  in accordance with a preferred embodiment of the invention. The granulator apparatus  100  contains a cutting chamber frame  300  having an interior portion  110  and an exterior portion  115 , and a rotor shaft and blade assembly  502  located in the interior portion  110  of the cutting chamber frame  300 , which will be described in greater detail below. The granulator apparatus  100  also includes a granulator motor  104  for rotating the rotor shaft and blade assembly  502  when the two are coupled together, such as, for example, using pulleys and a drive belt (e.g.,  1820 ,  1825  and  1830 , as in FIG. 18).  
         [0042]    The rotor shaft and blade assembly  502  is located in the interior portion  110  of the cutting chamber frame  300  for granulating solid material as it is fed from a hopper ( 1805  of FIG. 18) that would have its bottom-most portion positioned to feed (e.g., gravity feed) material into the interior portion  110  of the granulator apparatus  100 . A storage portion ( 1810  of FIG. 18) would normally be located below the interior portion  110  and the rotor shaft and blade assembly  502  to receive and temporarily store the granulated material. A fully assembled granulator may also contain wheels  1815  on the bottom of e.g., its storage portion  1810 , thereby providing a degree of mobility.  
         [0043]    Referring to FIG. 2, an exploded view of a cutting chamber frame  300  according to a preferred embodiment of the invention will now be described. A top chamber plate  200  is depicted along with two bearing pads  250  and  255  and six scallop clamping blocks  265  at a lowermost portion of FIG. 2. Also depicted are a front chamber plate  205  and a rear chamber plate  210 . Just above that are a right chamber plate  215  and a left chamber plate  220 . To the left of the right chamber plate  215  (as viewed in FIG. 2) is a spring block  245 . Just above the right and left chamber plates  215  and  220  are a first slanted side plate  230  and a second slanted side plate  225 . Just above the slanted side plates  230  and  225  are comb holders  235  and  240 . Above the comb holders  235  and  240  are twelve comb holder gussets  260 . Just above the comb holder gussets  260  are four filler gussets  270 .  
         [0044]    As can be seen, the right and left chamber plates  215  and  220  are equipped with slots  275  which are insertable within corresponding slots  278  of the front and rear chamber plates  205  and  210 . Bearing pads  250  and  255  are inserted into slots  279  of front and rear chamber plates  205  and  210 . Similarly, each of the six scallop clamping blocks  265  are respectively insertable within six slots  280  of front chamber plate  205 . Comb holders  235  and  240 , in addition to slanted side plates  230  and  225 , form the chamber within which a rotor shaft assembly (not shown in FIG. 2) will sit. Similarly, each of the twelve comb holder gussets  260  are respectively insertable within twelve slots  282  of comb holders  235  and  240 . Each of the four filler gussets  270  are respectively insertable within each of the four slots  284  defined within comb holders  235  and  240 .  
         [0045]    The top chamber plate  200  is preferably formed of one-half-inch thick steel. The left and right chamber plates  215  and  220  are preferably formed of five-eighths-inch thick steel. The front and rear chamber plates  205  and  210  are preferably formed of one-half-inch thick steel. Once the plates have been assembled as described above, they are welded (e.g., stitch welded, full fillet welded, etc.) together to form its box-shaped cross-sectional, modular construction.  
         [0046]    It should be noted that the modularity of the cutting chamber frame  300  easily enables the customization of a granulator apparatus  100 . For example, if a particular industrial material (to be crushed) calls for a rotor shaft longer than the rotor shaft  730  shown in FIG. 1, many of the components shown in FIG. 2 may still be used, thus, enabling mass production of those component parts (e.g., left and right chamber plates  215  and  220 ) that can be used with granulator apparatuses  100  having different rotor  730  lengths.  
         [0047]    Turning now to FIG. 3, a bottom perspective view of the cutting chamber frame of FIG. 2 is depicted. FIG. 3 is a view of the FIG. 2 cutting chamber frame  300  filly assembled. Throughout this specification, like reference numerals designate like components.  
         [0048]    [0048]FIG. 4 depicts a top perspective view of the cutting chamber frame  300 . The FIG. 4 perspective view is a 180° rotated view of the FIG. 3 perspective view. It should be noted that slanted sidewall  225  (and slanted sidewall  230 , opposite sidewall  225 , but not visible in FIG. 4) is intended to provide a guide for helping to feed uncrushed material received from e.g., hopper  105  into the medium cutter blade portions  740  (not shown in FIG. 4), as will be described in more detail below. In order for the sidewalls  225  and  230  to provide such a feeding function, the sidewalls  225  and  230  are not perpendicular to the axis A of the rotor shaft  730  (of FIG. 7). Rather, the sidewalls  225  and  230  are skewed from being perpendicular to the axis A, preferably from approximately ten degrees to approximately twenty degrees. As shown in the illustrated embodiments, the sidewalls  225  and  230  are skewed fifteen degrees from being perpendicular to the axis A.  
         [0049]    Turning now to FIG. 5, an exploded view of a rotor shaft assembly  502  within the cutting chamber frame  300  is depicted. Rotor shaft and blade assembly  502  is affixed to the cutting chamber frame  300  with, among other things, four bolts  504  that are insertable within four mounting holes  505  of the rotor shaft and blade assembly  502 . Additionally, the bolt  504  is inserted within the mounting hole  514  of the cutting chamber frame  300 . Two washers  506  and  508 , a lock washer  510  and a nut  512  are used in four places to mount the rotor shaft and blade assembly  502  to the cutting chamber frame  300 .  
         [0050]    Also depicted are three knob assemblies  500  on a front bottom portion of the cutting chamber frame  300 . Each knob assembly  500  is mountable within respective pairs of scallop clamp blocks  265  as will be described in greater detail in connection with FIG. 6. Also depicted in the FIG. 5 exploded view are a left rotor insert  520  and a right rotor insert  522 , each being mounted adjacent to the rotor shaft and blade assembly  502  and each serving as a shield to help prevent material from escaping from the interior portion  110  of the granulator apparatus  100  as it is being granulated. Left and right rotor inserts  520  and  522  are held to the cutting chamber frame  300  with four socket head cap screws (SHCSs)  525 .  
         [0051]    Turning now to FIG. 6, an exploded view of cover members within the cutting chamber assembly of FIG. 5 is depicted. The rotor shaft and blade assembly  502  is shown as being assembled within the cutting chamber frame  300 . Left and right rotor inserts  520  and  522  are held in place with SHCSs  525  in four places. Each iron knob assembly  500  (of FIG. 5) consists of an knob  600 , a bolt  602 , the bolt  602  being insertable within the knob  600 . A hex bolt  604  is insertable within the washers  606 , a bolt  602 , a lock washer  617  and held in place with a hex nut  610 . The hex bolt  604  is insertable within the aligned holes of a pair of scallop clamp blocks  265 .  
         [0052]    Above the assembled cutting chamber frame  300  and the rotor shaft and blade assembly  502  are three cover members; two medium cover members  530  (left and right) and one large cover member  535 . Each one of the cover members  530  and  530  and  535  is associated with a respective one of three cutting blades of the rotor shaft and blade assembly  502 , as will be described below in more detail.  
         [0053]    Also depicted between the right and left chamber plates  215  and  220 , is a mounting shaft  640 . Mounting shaft  640  extends most of the length of the rotor shaft and blade assembly  502 . The three cover members  530 ,  530  and  535  are affixed to the mounting shaft  640  via their three mounting hooks  630 ,  630  and  630 . The opposite sides of the three cover members  530 ,  530  and  535  are respectively coupled to each iron knob assembly  500  such that a respective bolt  604  is inserted within each slot  650  of the cover members  530 ,  530  and  535 .  
         [0054]    Referring now to FIG. 7, an exploded view of the rotor shaft and blade assembly  502  is depicted. A perspective view of a rotor shaft  730  is depicted as being rotatable about an axis A. A right side of the rotor shaft  730  is insertable within a right pillow block bearing  700  and a left side of the rotor shaft  730  is insertable within a left pillow block bearing  700 . Two large cutter half portions  706  are depicted as being insertable within the shaft portion  765 , located at a central point of the rotor shaft  730 . Large cutter half portions  706  are mountable onto rotor shaft  730  in predetermined locations which are determined by the mounted location of cutter drive keys  708 . The cutter drive keys  708  are inserted into the shaft portions  766  in two places. The two large cutter half portions  706  are respectively positioned on top of each cutter drive key  708  via a recess portion  712  such that the large cutter half portions  706  are always mounted on the rotor shaft  730  in a predetermined manner.  
         [0055]    Each large cutter half portion  706  is screwed to rotor shaft  730  with four large SHCSs  710  (for a total of eight large SHCSs  710 ). Each cutter half portion  706  contains a symmetrical large blade portion  750 . In addition, each symmetrical blade portion  750  contains four cutting ridges  755  on each side.  
         [0056]    Still referring to FIG. 7, two pair of medium cutter halves  704  are located near opposite outer edges of rotor shaft  730 . Each medium cutter half  704  contains three medium blade portions  740  for a total of six medium blade portions  740  per each medium cutter. Similarly to large cutter blade portions  750 , each medium blade portion  740  is symmetrical. In addition, each medium cutter half  704  is mountable to rotor shaft  730  at shaft portions  770  with a cutter drive key  708  at four places, thus, ensuring that medium cutter halves  704  are mounted in a predetermined manner onto rotor shaft  730 .  
         [0057]    Each medium cutter half  704  is held in place with four medium SHCSs  713 . Each medium cutter half  704  requires four medium SHCSs  713  for a total of sixteen medium SHCSs  713 .  
         [0058]    Referring now to the center portion of FIG. 7, a pair of multiple cutter assemblies in the form of small cutter rails  714  is depicted. Each small cutter rail  714  contains eleven cutting teeth  760 . Each small cutter rail  714  is insertable onto a corresponding shaft portion  780 . Cutter retaining plate  716  is insertable between each pair of small cutter rails  714  in a manner such that the flange portions  724  are inserted within cutter rail receptacles  726  at six places. A cutter retaining wedge  718  is positioned on top of the cutter retaining plate  716 . Three wedge retaining screws  720  are used to affix each pair of small cutter rails  714  to the rotor shaft  730  via three small cutter mounting holes  722 . There are a total of forty-eight such small cutter mounting holes  722  on the rotor shaft  730  enabling sixteen pair of small cutter rails  714  to be affixed to the rotor shaft  730 .  
         [0059]    A fully assembled rotor shaft and blade assembly  502  of the illustrated embodiment includes thirty-two small cutter rails  714 , each of which contain  11  cutting teeth  760 . In addition, a fully assembled rotor shaft and blade assembly  502  contains twelve medium cutter blade portions  740  and two large cutter blade portions  750 . The present invention should not be limited, however, to the details of the preferred embodiments shown and described herein. It should be noted that the illustrated rotor shaft  730 , when fully assembled, contains two shaft portions  790  and  785  adjacent to each slanted sidewall  225  and  230  and an adjacent medium cutter portion  704  such that uncrushed material is unobstructively fed from the hopper  105  and into the path of medium blade portion  740 . That is, uncrushed material entering the blade portion of the apparatus via the sidewalls  225  and  230  will enter the path of the medium cutter blades  740  rather than small cutter blades  760 ; thus, the effective lifespan of the small blades  760  is extended.  
         [0060]    An advantage of the rotor shaft and blade assembly  502  is the fact that both the large and medium blade portions  750  and  740  are symmetrical, thereby enabling the rotor shaft  530  to be run in both directions with equal cutting efficacy and as a result, extending the time between required maintenance of the blades. Furthermore, since the cutter half portions  706  and  704  are easily coupled and decoupled to/from the rotor shaft  730  with SHCSs, maintenance of the rotor shaft and blade assembly  502  is very quick and easy.  
         [0061]    For example, if one of the large blade portions  750  becomes damaged, a maintenance worker merely needs to replace one cutter half portion  706  without disrupting any other blade portions or the rotor shaft and blade assembly  502 . As another example, when a small cutter tooth  760  becomes damaged, a maintenance worker merely detaches the particular small cutter rail  714  containing the damaged small cutter tooth  760  and replaces the same without disrupting any other components of the rotor shaft and blade assembly  502 . Therefore, not only does the configuration of the rotor shaft and blade assembly  502  provide more time in between required maintenance operations (i.e., due to the capability of running the rotor in both directions), but during those times when maintenance is required, it can be performed with minimal disruption, cost and down-time.  
         [0062]    Yet another advantage of the shape of the small teeth  760  is that they are symmetrical and square in shape such that more material may flow between individual cutting teeth  760  for granulation. This is a marked improvement over a saw-toothed configuration.  
         [0063]    Turning now to FIG. 8, a plan view of a partially assembled rotor shaft and blade assembly  502 , as described in FIG. 7, is depicted. Like components are designated with like numerals and will not be discussed further in connection with FIG. 8. Three cross sections are identified; IX-IX, X-X and XI-XI. Each of these will be respectively discussed in greater detail in connection with FIGS. 9, 10 and  11 .  
         [0064]    Turning now to FIG. 9, a view taken along line IX-IX of FIG. 8 is depicted. Section IX-IX is a cross-sectional view taken through the large cutter half portions  706 . As described above, there are two large cutter half portions  706  coupled to rotor shaft  730  and each large cutter half portion  706  contains a large blade portion  750 . Also depicted are the two cutter drive keys  708  and one large SHCS  710 . The cutter drive keys  708  ensure that large cutter half portions  706  are coupled to rotor shaft  730  in a predetermined manner with respect to the medium cutter halves  704  and the small cutter rails  714 . The predetermined couplings are such that the medium cutter blades  740  in combination with the large cutter blades  750  and the small cutter teeth  760  are formed in a staggered formation for more effective cutting action.  
         [0065]    As shown in FIG. 10, the small cutter rails  714  are located between the flange portions  795  of the rotor shaft  730 . As described in connection with FIG. 7, the small cutter rails  714  are affixed to the rotor shaft  730  in pairs with a cutter retaining plate  716  and a cutter retaining wedge  718 . The assembly is then affixed to the rotor shaft  730  with wedge retaining screws  720  in three places for each pair of cutter rails  714 . As described above, the small cutting teeth  760  are positioned in a predetermined manner onto the rotor shaft  730 . Furthermore, if a particular rail  714  becomes damaged, it is easily removed and replaced without disrupting the other rails  714  and the other cutting blades  740  and  750 .  
         [0066]    As shown in FIG. 11, the medium cutter half portions  704  are assembled onto the rotor shaft  730  in a predetermined manner with two cutter drive keys  708  such that the medium blade portions  740  are located in a predetermined position with respect to both the large blade portions  750  and the small cutter teeth  760  (as described in FIG. 10). Each medium cutter half portion  704  is affixed to the rotor shaft  730  with four medium SHCSs  712 , for a total of sixteen medium SHCSs  712  on a fully assembled rotor shaft and blade assembly  502 . FIG. 11 depicts one such SHCS  712  for exemplary purposes. As noted above, the present invention should not be limited to the details of the preferred embodiments shown and described herein.  
         [0067]    Turning to FIG. 12, a view like FIG. 9 showing a large cover member  535  is depicted. During operation, the cover member  535  is mounted within the three-blade granulator apparatus  100  such that it sits just beneath the large cutter half portions  706 . That is, rotating FIG. 12 by 90° such that cover member  535  is on the bottom provides an accurate representation of the relative positions of the cover member  535  and the large cutter portions  706  during operation.  
         [0068]    During normal operation, the large blade portions  750  are rotated, e.g., in direction A. The large blade portions  750  are used primarily for breaking down larger pieces of material into smaller pieces of material. The cover member  535  ensures that any material crushed by the large blade portions  750  and that has been forced into the opening  1205  will be pushed out of the opening  1210  by the blade portion  750  running up against the interior wall  1200  of the cover member  535 .  
         [0069]    Once the material has been forced out of the opening  1210 , it will be further crushed by either one of the blade portions  750  and  740 , where the above-described process will be repeated, until the material is small enough to be crushed by the small cutter teeth  760  for fine crushing. Once the material has been finely crushed by the small cutter teeth  760 , the material drops into a material storage portion such as the one referred to in connection with FIG. 1.  
         [0070]    Turning now to FIG. 13, the operation of the medium cover member  530  with regard to medium sized pieces of material is identical to that of the large cover member  535  with regard to large pieces of material (as described above in connection with FIG. 12).  
         [0071]    [0071]FIG. 18 depicts a perspective view of an assembled granulator  1800  according to a preferred embodiment of the present invention. The granulator  1800  includes a hopper  1805  for feeding material into a rotor shaft and blade assembly  502  situated in an interior portion of the granulator  1800 . The granulator  1800  also includes a storage portion  1810  located below the rotor shaft and blade assembly  502  to receive and temporarily store the granulated material. The granulator  1800  also includes four wheels  1815  for a degree of mobility and a granulator motor  104  for rotating the rotor shaft and blade assembly  502  when the two are coupled together, such as, for example, using a pair of pulleys  1820  and  1825  and a drive belt  1830 .  
         [0072]    Turning to FIG. 19, a perspective view of a cutting chamber  1900  is illustrated. The cutting chamber  1900  contains a shaft  1905  having an axis X running in a generally horizontal direction. A central portion of the shaft  1905  is hexagonal, as will be described more fully below. Slanted sidewalls  1910  on both sides of the cutting chamber  1900  assist with directing material to be granulated into the path of the blades. In addition, front and rear slanted wall  1920 ,  1925  assist with directing material to be granulated toward the blades.  
         [0073]    The rotor shaft assembly (FIGS. 20, 21) within the cutting chamber  1900  is depicted generally, from left to right, as containing a first medium cutter  1945  having four symmetrical cutting surfaces spaced equally around the circumference of the cutter  1945 . A spacer  1960  is directly adjacent to the first medium cutter  1945  for spacing the first medium cutter  1945  from the first section of small cutters  1950 . The first section of small cutters  1950  contains seven small cutter discs. Each of the seven small cutter discs are identical, however, they are oriented on the hexagonal portion of the shaft  1905  in three distinct positions, as will be described more fully below. The cutting teeth  2080  of the first section of small cutters  1950  are symmetrical and squared in shape so as to enable more material to be granulated.  
         [0074]    Adjacent to the first section of small cutters  1950  is a second spacer  1975  spacing the first section of small cutters  1950  from two large cutters  1930 ,  1935 . The large cutters  1930 ,  1935  are identical to each other, each one containing two symmetrical cutting surfaces located at opposite ends of the cutter from one another, however; they are placed on the hexagonal portion ( 2105  of FIG. 21) of the shaft  1905  in reverse order with respect to each other, as will be described more fully below. On the far side of the large blades  1930 ,  1935  is a third spacer  1965  for spacing the large cutters  1930 ,  1935  from the second section of small cutters  1955 . Similarly to the first section of small cutters  1950 , the second section of small cutters  1955  contains seven identical cutter discs. The cutting teeth  2075  of the second section of cutters  1955  are saw-tooth shaped.  
         [0075]    Adjacent to the second section of small cutters  1955  is a fourth spacer  1970  for spacing the second section of small cutters  1955  from a second medium cutter  1940 . The general operation of the FIG. 19 cutting chamber  1900  is similar to that of the cutting chamber described in connection with FIGS.  1 - 13  and will not be repeated here.  
         [0076]    Turning to FIG. 20, a perspective view of a rotor shaft assembly of the FIG. 19 cutting chamber is depicted from a bottom side of the assembly. Like features of both FIGS. 19 and 20 are represented with like symbols and will not be repeated here. A right shaft lock  2060  and a left shaft lock  2065  are respectively depicted on left-most and right-most portions of FIG. 20.  
         [0077]    The first and second small cutter sections  1950 ,  1955  of FIG. 19 are depicted here in greater detail. Beginning with the left side of FIG. 20, the second section of small cutters  1955  is depicted as being between the second medium cutter  1940  and the two large cutters  1930 ,  1935 . In this embodiment of the invention, the second section of small cutters  1955  is made up of seven individual cutter discs adjacent to one another on the hexagonal portion  2105  (of FIG. 21) of the shaft  1905 .  
         [0078]    Each of the cutting teeth  2075  of the second section of cutters  1955  is saw-tooth shaped, however, they need not be so. That is, the cutting teeth  2075  may be any shape that enables the desired end result. As described above, each of the seven cutter discs of the second section of small cutters  1955  is identical to each other and are placed onto the hexagonal portion  2105  of the shaft  1905  in three different orientations so that the cutting teeth  2075  are staggered on the shaft  1905 . In addition, the cutting teeth  2075  are positioned on a right side of each cutter disc, thereby inherently introducing a space between cutting teeth  2075  of adjacent cutter discs.  
         [0079]    Still referring to FIG. 20, turning to the right side of the shaft  1905 , the first section of small cutters  1950  is depicted. Each of the cutting teeth  2080  of the second section of small cutters  1950  is squared in shape, however, they need not be so. Cutting teeth  2080  may be any shape that enables the desired end result. The first section of small cutters  1950  is made up of seven individual cutting discs arranged adjacent to one another on the hexagonal portion  2105  of the shaft  1905  in three different orientations so that the cutting teeth  2080  are staggered on the shaft  1905 . In addition, the cutting teeth  2080  are positioned on a right side of each cutter disc, thereby inherently introducing a space between cutting teeth  2080  of adjacent cutter discs. It should be readily apparent that the cutting teeth  2080  need not be located on the right side of each cutter disc, but may be located on the left side or in the middle of the cutter disc.  
         [0080]    The horizontally running axis A of FIG. 20 enables one to visualize the three different orientations with which the cutter discs are placed onto the hexagonal portion  2105  of the axis  1905 . Looking to the right side of FIG. 20 (the first section of small cutters  1950 ), one can see that the orientation of cutter disc  2005  is different from the orientation of cutting disc  2010 , which is different still from the orientation of cutter disc  2015 . These three cutter discs  2005 ,  2010 ,  2015  illustrate the three different orientations for the cutter discs of the first section of small cutters  1950 . Adjacent to the aforementioned third cutter disc  2015  is a repeat of the orientation of the first cutter disc  2005 , and so on, until all seven cutter discs are located onto the hexagonal portion  2105  of shaft  1905 . When all seven cutter discs are on the hexagonal portion  2105  of the shaft  1905 , three of the discs are oriented like disc  2005 , two of the discs are oriented like disc  2010  and two of the discs are oriented like disc  2015 . The orientation order from left to right is  2005 ,  2010 ,  2015 ,  2005 ,  2010 ,  2015  and  2005 , thereby creating a staggered effect of cutting teeth  2080 .  
         [0081]    The staggered effect of cutting teeth  2075  of the second section of small cutters  1955  is obtained in a manner identical to that described above for the first section of small cutters  1950 . That is, from left to right, the seven cutter discs that contain the saw-tooth shaped cutters  2075  are arranged on the hexagonal portion  2105  of the shaft  1905  in the orientation order  2030 ,  2035 ,  2040 ,  2030 ,  2035 ,  2040  and  2030 .  
         [0082]    Turning now to FIG. 21, an exploded view  2100  of a portion of the FIG. 20 rotor shaft assembly is depicted. Specifically, FIG. 21 shows only the components of the right side of FIG. 20, however, it should be readily understood that the assembly of the left side of FIG. 20 is identical to that of the right side.  
         [0083]    Beginning on the left-most side of FIG. 21, the shaft  1905  is depicted as having a hexagonal portion  2105  onto which the large cutters  1930 ,  1935 , the cutter discs, the spacers and the first medium cutters  1945  are assembled. It should be noted that the shaft  1905  may have a portion with greater than six sides (e.g., octagonal, etc.). The greater the number of sides on the shaft  1905 , the greater the flexibility for orienting the cutting teeth in a staggered formation. The two large cutters  1935 ,  1930  are shown adjacent to one another. The large cutters  1935 ,  1930  are actually identical to one another, but are coupled to the hexagonal shaft  2105  in reverse order. Each large cutter  1935 ,  1930  contains two cutting blades on opposite sides of one another and each blade is positioned on the hexagonal shaft  2105  such that the two cutting blades are in phase with one another. In a preferred embodiment, the two large cutters  1935 ,  1930  are welded to the hexagonal shaft  2105 . Each large cutter  1935 ,  1930  also contains a cutout portion  2110  at each corner of the hexagonal center. These cutouts  2110  increase the strength and durability of the large cutters  1935 ,  1930  which is desirable since the large cutters are intended to break down the largest pieces of the material to be granulated and, therefore, are subject to the most grueling conditions. The large cutters  1935 ,  1930  also contain three circular holes  2150  for passing a cylindrical stabilizer rod (e.g., rod  2130 ), as will be described more fully below.  
         [0084]    Adjacent to the large cutters  1935 ,  1930  is a spacer  1975  having a hexagonal center for fitting onto hexagonal shaft  2105 . The spacer  1975  contains three circular holes  2150  for passing a cylindrical stabilizer rod (e.g., rod  2130 ).  
         [0085]    Adjacent to the spacer  1975  is a first cutter disc  2160  depicted as being in a first orientation  2005  for mounting onto the hexagonal shaft  2105 . The next cutter disc  2165  is depicted as being in a second orientation  2010  and the third cutter disc  2170  is in a third orientation  2015  for mounting onto the hexagonal shaft  2105 . The fourth cutter disc  2175  is depicted as having the same orientation  2005  as the first cutter disc  2160 . The fifth cutter disc  2180  is depicted as having the same orientation  2010  as the second cutter disc  2165 . The sixth cutter disc  2185  is depicted as having the same orientation  2015  as the third cutter disc  2170  and the seventh cutter disc  2190  is depicted as having the same orientation  2005  as the first cutter disc  2160  and the fourth cutter disc  2175 . Each cutter disc  2160 - 2180  is depicted as having 18 cutting teeth, however, the exact number of cutting teeth is not critical and may be increased or decreased as desired. In addition, each cutter disc  2160 - 2180  contains three circular holes  2150  for passing a cylindrical stabilizer rod (e.g., rod  2130 ).  
         [0086]    Adjacent to the cutter discs  2160 - 2190  is a spacer  1960  for creating a space between the cutter discs  2160 - 2190  and the first medium cutter  1945 . The spacer contains three circular holes  2150  for passing a cylindrical stabilizer rod (e.g., rod  2130 ). Adjacent to the first medium cutter  1945  is the left shaft lock  2065  for passing a stabilizer rod (e.g., rod  2130 ). The left shaft lock  2065  also has three receptacles  2195 ,  2197 ,  2199  for passing the stabilizer rod  2130  and also for receiving three hex nuts  2140  to lock the cutters and spacers  1935 - 1945  together. Three stabilizer rods (e.g., rod  2130 ) are respectively passed through each of the cutters and spacers  1935 - 1945 , via circular holes  2150 , and a hex nut  2140  is bolted down on either end of each rod  2130  (i.e., via hex holes  2195 ,  2197  and  2199  on the left shaft lock  2065  and also via the corresponding hex holes, including hex holes  2117  and  2115 , of the left-most large cutter  1935 ) to secure the cutters and spacers  1935 - 1945  in place. Similarly, three stabilizer rods and six hex nuts are used between the right shaft lock  2060  and the right-most large cutter  1930  in order to secure the left side of the FIG. 21 assembly.  
         [0087]    Turning to FIG. 22, a cross sectional view taken along line XXII of the FIG. 19 cutting chamber is depicted. Front and rear slanted walls  1920 ,  1925  are respectively depicted on right and left sides of FIG. 22 for helping to direct material into the path of the cutters. Large cutters  1930 ,  1935  are depicted as being in phase with one another, as described above. The first medium cutter  1945  is depicted as being out of phase with the large cutters  1930 ,  1935  and the second medium cutter  1940  is depicted as being out of phase with both the large cutters  1930 ,  1935  and the first medium cutter  1945 . The out-of-phase relationship between the first medium cutter  1945 , the second medium cutter  1940  and the large cutters  1930 ,  1935  creates less of a demand for power during the granulating process since the motor (not shown) is not attempting to granulate material on multiple blades at the same time. Rather, the blades, as well as the demand for power by the granulator, are staggered, thereby enabling more efficient operation of the granulator.  
         [0088]    [0088]FIG. 22 also shows a cross sectional view  2210  of the first and second small cutter sections  1950 ,  1955 ; however, their orientations and individual phase relationships are more easily viewed from FIGS.  19 - 21 . Also depicted in FIG. 22 are the three receptacles  2195 ,  2197 ,  2199  in the left shaft lock  2065 , the three circular holes  2150  passing through each of the cutters and spacers of FIGS.  19 - 21 , and also the hex nut  2140  from FIG. 21. FIG. 22 also depicts the hexagonal shaft portion  2105  of the shaft  1905  and the six cutout portions  2110  of the large cutters  1930 ,  1935 .  
         [0089]    Turning to FIG. 23, a small cutter disc  2300  which may be used in either the first or second section, or both, of small cutters  1950 ,  1955  is depicted in accordance with another embodiment of the invention. The cutter disc  2300  has two halves  2340 ,  2330  which may be interlocked together as shown or simply joined together without being interlocked and affixed onto a shaft such as the hexagonal portion  2105  of the shaft  1905  (of FIG. 21). In addition, the cutter disc  2300  need not have two halves  2340 ,  2330 , but rather it may be a one-piece disc that slides onto the hexagonal shaft  2105 .  
         [0090]    Each of the two disc halves  2340 ,  2330  has an interlocking feature  2305 ,  2335  located within a respective recessed portion  2310 ,  2345  in the other disc half  2330 ,  2340 . The two-piece interlocking structure of the disc halves  2340 ,  2330  allows for the assembly/disassembly of a particular disc (e.g., a disc with a damaged cutter) on the hexagonal shaft  2105  without disrupting the other discs on the shaft  2105 . When the disc halves  2340 ,  2330  are joined together, they form a hexagonal center which fits onto the hexagonal shaft  2105 .  
         [0091]    Each disc half  2340 ,  2330  may also contain three circular holes  2325  located near an outer peripheral edge of each disc half  2340 ,  2330 . Each circular hole  2325  is adapted to receive a stabilizer rod (not shown) for helping to maintain the discs  2300  stationary while mounted on the shaft  2105 . Furthermore, each circular hole  2325  is located such that it is aligned with one of the six angular intersections of the hexagonal center, as depicted in FIG. 23.  
         [0092]    In addition, when the two disc halves  2340 ,  2330  are joined together, they form a total of twenty symmetrical cutting teeth  2315  in that they can cut in either direction with equal effectiveness. In addition, the spacing d between the cutting teeth  2315  and the squared shape of the cutting teeth  2315  allow for the capturing of greater amounts of material between the teeth  2315  for granulation. The cutting teeth  2315  are located around the peripheral edge of the cutter disc  2300 , and relative to the hexagonal center such that each of the six angular intersections (of the hexagonal sides) is aligned with one of three different positions relative to each tooth  2315 . The effect of this configuration is to allow for the cutting teeth  2315  to be arranged on the shaft  2105  in a staggered formation and in more positions than the hexagonal shaft  2105  alone would allow.  
         [0093]    For example, as depicted in FIG. 23, the cutter disc  2300  is divided into six adjacent 60° portions I-VI. Each 60° portion is unique (i.e., unique with respect to the number of cutting teeth  2315  included within the 60° portion and/or the position of the cutting teeth  2315  within that 60° portion with respect to the angular portions  2360  of the hexagonal shaft  2105  which define that 60° portion) with respect to the two adjacent 60° portions directly following it when the blade is rotated in either a clockwise or counter-clockwise direction. As can be seen, 60° portion I is unique with respect to 60° portions II and III. However, 60° portion I is identical to 60° portion IV. It should be apparent from FIG. 23 that 60° portion II is identical to 60° portion V and that 60° portion III is identical to 60° portion VI. This feature enables the staggered formation referred to above in FIGS.  19 - 22  when three adjacent discs  2300  are respectively placed onto the hexagonal portion  2105  of the shaft  1905  in three different orientations.  
         [0094]    An improved granulator apparatus has been disclosed for use with crushing, e.g., industrial plastic material. The apparatus has two slanted sidewalls  225  and  230  (of FIGS. 2 and 3) angled at approximately 10-20 degrees from a perpendicular of the axis A for the rotor shaft  730 . The slanted sides of the sidewalls  225 ,  230  cause the material to be fed by gravity into the path of medium cutter blade portions  740  on both sides of the rotor shaft and blade assembly  502 . In addition, the shaft portions  785  and  790  provide an unobstructed path through which the uncrushed material may travel to be crushed by the medium blade portions  740 . Furthermore, the symmetrical shape of the cutting blades  740 ,  750  and  760  and the simplified manner with which the cutter half portions  704  and  706  and small cutter rails  714  are attached to and removed from the rotor shaft  730  makes maintenance of the crushing apparatus extremely quick and efficient.  
         [0095]    In addition, the disclosed granulator apparatus has been depicted as having an alternative rotor shaft design in which there are first and second medium cutters  1945 ,  1940  on either end of a hexagonal portion  2105  of a shaft  1905  and two large cutters  1930 ,  1935  at the center of the hexagonal shaft  2105 . In between the first medium cutter  1945  and the large cutters  1930 ,  1935  is a first section of small cutters  1950  and in between the large cutters  1930 ,  1935  and the second medium cutter  1940  is a second section of small cutters  1955 . As depicted the blades of the first and second small cutter sections  1950 ,  1955  are different from each other, however, they may be the same type of blade. In addition, each of the first and second small cutter sections  1950 ,  1955  may include a mixture of different shaped cutting teeth and need not all be the same within a section  1950 ,  1955 . In addition, although seven cutter discs have been described in connection with the first and second small cutter sections  1950 ,  1955 , any number of cutter discs may be used. Furthermore, while only two medium cutters  1945 ,  1940  and two large cutters  1935 ,  1930  are described, it should be readily apparent that any number of medium cutters and large cutters may be used. In addition, a staggered formation allowing for three distinct blade orientations of the small cutters  1950 ,  1955  on the hexagonal shaft  2105  is described. Furthermore, the large cutters  1930 ,  1935  are in phase with each other but are out of phase with both the first and second medium cutters  1945 ,  1940 . Moreover, the first and second medium cutters  1945 ,  1940  are out of phase with one another.  
         [0096]    The above description and drawings are only illustrative of preferred embodiments of the present invention, and are not intended to limit the present invention thereto. For example, the embodiments shown depict two large blades  750 , and four medium cutter half portions  704 , for a total of twelve medium blades  740 , and thirty-two small cutter rails  714 , each containing eleven teeth, for a total of 352 small cutter teeth  760 . It should be readily apparent that more or less, or different combinations of cutter teeth, whether they be large, medium or small, may be used without deviating from the spirit or scope of the present invention. In addition, although large and medium cutter half portions  706  and  704  are depicted for exemplary purposes, it should be apparent that any number of fractional cutter portions may be substituted with similar efficacy. Any subject matter or modification which comes within the spirit and scope of the following claims is to be considered part of the present invention.