Abstract:
A comminuting striker assembly for mounting on a rotor of a comminuting apparatus comprising: a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining a pair of perpendicular slots; a striker retainer having a leading face for attachment to the striker, the leading face defining a pair of perpendicular keys to be received by the slots; and a single threaded fastener for joining the striker to the striker retainer.

Description:
RELATED APPLICATION 
     This is a continuation-in-part of patent application Ser. No. 09/635,320 filed Aug. 9, 2000 now U.S. Pat. No. 6,394,378. 
    
    
     FIELD OF THE INVENTION 
     The invention provides an improved striker attachment for wood comminuting rotors which facilitates a keyed attachment enabling both a single fastener to be utilized attaching the striker to the striker retainer, and rapid removal and replacement of the striker. 
     BACKGROUND OF THE INVENTION 
     Prior art comminuting apparatus for reducing large diameterwood products and stumps to a desired size, have comprised a reduction chamber, with an impact rotor positioned concentrically therein, in combination with a housing, drive motor and infeed chute. The impact rotor is formed with a plurality of horizontally elongate impact strikers at its periphery. The rotor is positioned so that the elongate wood product or stump falling under the influence of gravity through the infeed chute is directed against the strikers, and repelled ahead of the rotor&#39;s rotational direction against an anvil formed along one side of the reduction chamber. 
     Prior art wood comminuting apparatus are often capable of comminuting trees or parts thereof up to 40 inches in diameter (see e.g. U.S. Pat. No. 5,165,611). Strikers used for the comminution are bolted directly to mounting projections on the rotor which is rotated to produce the comminution. Maintenance to change strikers has required complete removal of the striker mounting bolts with the consequent potential loss of bolts and uneconomical use of maintenance time, especially in view of the substantial number of strikers on a rotor of such apparatus. Strikers of the prior art are typically fastened with two (2) hex head or similar studs, stud-bolts or bolts, relying on fastener torque to position and retain the strikers, resulting in the above noted potential loss of bolts and uneconomical use of maintenance time. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to improve maintenance time and ease of striker replacement in comminution apparatus minimizing the potential for loss of components including fasteners. 
     It is a further object of the invention to improve the fixed positioning of the strikers for initial installation of the strikers, during operation of the comminuting device, and during maintenance or replacement of strikers. 
     According to the invention there is provided a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising: a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining at least one slot; a striker retainer having a leading face for attachment to the striker, said leading face defining at least one raised key, and an opposed following face; a threaded fastener for joining said striker to said striker retainer, whereby the slot of the striker closely mates with the key of the striker retainer. 
     Also according to the invention there is provided a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising: a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining at least one raised key; a striker retainer having a leading face for attachment to the striker, said leading face defining at least one slot; a threaded fastener for joining said striker to said striker retainer, whereby the key of the striker closely mates with the slot of the striker retainer. 
     In an alternative embodiment there is provided a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining first and second slots transverse of one other, the first being parallel to the at least one cutting edge; a striker retainer having a leading face for attachment to the striker, said leading face defining first and second raised keys, to be received by said slots; wherein the second raised key closely engages the corresponding slot; and the striker retainer defines a striker support surface engaging a cooperating surface on the striker to provide primary support for the striker by virtue of a cooperating surface on the striker and a clearance between the first slot and the raised key received thereby. 
     According to the invention there is also provided a method to attach a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising the steps of: providing a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining first and second slots perpendicular to one another; providing a striker retainer having a leading face for attachment to the striker, said leading face defining first and second raised keys to closely engage the slots; providing a bore through the striker retainer for a fastener means; providing a single fastener joining means in the striker; mating the striker slots with the striker retainer raised keys; and installing a single fastening means through the bore and mating with the fastener joining means in the striker for joining said striker to said striker retainer, whereby the slots of the striker closely mate with the keys of the striker retainer. 
     Also according to the invention there is provided a method to attach a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising the steps of: providing a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining first and second raised keys perpendicular to one another; providing a striker retainer having a leading face for attachment to the striker, said leading face defining first and second slots to closely engage the keys; providing a bore through the striker retainer for a fastener means; providing a single fastener joining means in the striker; mating the striker raised keys with the striker retainer slots; and installing a single fastening means through the bore and mating with the fastener joining means in the striker for joining said striker to said striker retainer, whereby the keys of the striker closely mate with the slots of the striker retainer. 
     In another embodiment of the invention, there is provided a method to attach a comminuting striker assembly for mounting on a rotor of a comminuting apparatus, comprising the steps of providing a striker having first and second opposed faces, the first face defining at least one cutting edge, and the second face defining first and second slots perpendicular to one another, the first being parallel to the at least one cutting edge; providing a striker retainer having a leading face for attachment to the striker, said leading face defining first and second raised keys to be received in the slot; providing a support surface on the striker retainer, separate from the keys, to engage a cooperating surface provided on the striker to provide primary support for the striker; providing a bore through the striker retainer for a fastener means; providing a single fastener joining means in the striker; mating the striker slots with the striker retainer slot; and installing a single fastening means through the bore and mating with the fastener joining means in the striker for joining said striker to said striker retainer, whereby the second raised key closely mates with the corresponding slot and the cooperating surface on the striker rests on the support surface on the striker retainer to provide primary support for the striker by virtue of a clearance provided between the first slot and the first raised key. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is an orthogonal view of a rotor with a plurality of strikers and retainers mounted thereto, showing two types of strikers; 
     FIG. 2 is a sectional end view of a rotor of the present invention showing two types of strikers attached to the rotors by way of retainers and bases; 
     FIG. 3 is a perspective view of a preferred embodiment two edged striker with cruciform key slots, and a single fastener hex opening; 
     FIG. 4 is a side elevation of the striker of FIG. 2; 
     FIG. 5 is a rear view of the striker of FIG. 2 showing the cruciform key slots; 
     FIG. 6 is a perspective view of a striker retainer according to the present invention with male cruciform keys to engage the cruciform key slots; 
     FIG. 7 is a front elevation of the striker retainer of FIG. 6; 
     FIG. 8 is an alternative embodiment single tooth striker according to the invention; 
     FIG. 9 is an elevation of a further embodiment of striker and striker retainer of the present invention shown assembled and bolted together; 
     FIG. 10 is a perspective view of the striker retainer shown in FIG. 9; and 
     FIG. 11 is a perspective of the striker shown in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to FIG. 1, a prior art assembly of rotor  2  of a wood comminutor defines striker carrying faces  4  for supporting a retainer bases  6  which supports strikers  8  by way of striker retainers  10  against comminuting forces during comminution with the face  4  and cutting edge  12  of the striker  8  facing in the direction of rotor rotation  14  about rotor axis  16 . Projections  18  on the rotor  2 , one for each striker  8 , direct a work piece (not shown) into the cutting edge  12  of each striker  8  and away from striking the work piece facing side of retainer base  6 . The configuration of strikers, striker retainers, and projections shown herein are based on prior art designs, and are therefore not discussed in detail herein. 
     Referring to FIG. 2, the cruciform slot and key attachment of a striker  20  to striker retainer  22 , of the present invention, is shown. The striker  20  is captively mounted to striker retainer  22  by a single bolt  28  extending through bore  26  to a nut  24  and fixed against rotation by a hex machined opening  30  in striker  20 . Striker retainer  22  is captively mounted by a weld joint  32  to retainer base  6 , which in turn is captively mounted to rotor  2  at retainer carrying face  4  by two bolts  34  extending through two countersunk bores  35  through retainer base  6  and mating threaded bores  36  in rotor  2 . 
     Also shown in FIG. 2 is a second design of striker  38  which has a blind threaded hole for accepting bolt  40 . The arc of striker rotation  42  is shown in FIG.  2 . 
     Referring to FIGS. 3,  4  and  5 , preferred embodiment two edged striker  20  is shown. Cutting edges  12 , hex shaped machined recessed opening  30 , bolt clearance bore  44 , and slots  46  are shown. Two slots  46  are machined perpendicular to each other and each centrally aligned with a centerline of clearance bore  44 . The width X of slots  46  are machined to matingly receive the machined keys  50  of a striker retainer  22  (FIGS.  6  and  7 ), with a tight clearance fit. A tight clearance fit ensures minimal twisting motion is permitted between the striker and striker retainer. The machined depth D of slots  46  are equal to at least the height H of mating keys  50  shown in FIGS. 6 and 7 to ensure complete engagement of keys  50  within slots  46 . 
     Referring to FIGS. 6 and 7, a striker retainer  22  is shown, with the raised machined keys  50 , machined to mate in a tight clearance fit with the slots  46  of striker  20 . Striker retainers are shaped to have a relatively tall leading face to which the striker is attached, and a relatively short opposed following face, which allows clearance between the work piece in contact with the striker cutting edge and the shorter face, such that only the cutting edge directly contacts the work piece. A relatively larger diameter counterbore  52  than the diameter of bore  48  is machined in central alignment with bore  48  to a counterbore depth which is at least the height H of keys  50 . Counterbore  52  eliminates the machining difficulty of squaring the inside corners of keys  50  where the keys  50  intersect bore  48 . This ensures mating alignment between keys  50  and slots  46  for the entire height H of keys  50 . Key width W is machined on striker retainer  22  for the tight clearance fit with slots  46  discussed herein. Bore  48  is shown vertically off center of striker retainer  22  in FIG. 7, to provide a desired clearance of the bore from the retainer base  6 . 
     FIG. 8 is an alternative embodiment of a striker having a cutting edge  54  rotated 90 degrees compared to cutting edges  12  of FIG. 3, and including the cruciform slots of the present invention. 
     In use, slots  46  in striker  20  mate with the keys of striker retainer  22  such that motion between the mating faces of striker  20  and striker retainer  22  is minimized and alignment is assured. While connecting the striker  20  to striker retainer  22 , the head of a hex bolt  28  is matingly positioned in hex machined opening  30 . The bolt  28  connects with nut  24 . Bolt  24  extends through clearance bore  44  in striker  20  and through bore  26 , to threadably engage with hex nut  24 . Torquing hex nut  24  to bolt  28  mechanically fastens striker  20  and striker retainer  22 . 
     When the first of striker  20  cutting edges  12  becomes dull through use, nut  24  is removed, striker  20  is lifted away from striker retainer  22  until the slots  46  and keys  50  no longer engage, and striker  20  is rotated 180 degrees and its slots  46  re-mated to keys  50  of striker retainer  22 . Nut  24  and bolt  28  are then rethreaded and torqued to complete the reassembly. If both cutting edges  12  of striker  20  become dull from use, and resharpening or replacement of striker  20  is required, the above steps to remove and reassemble striker  20  are applied, eliminating the rotation step. 
     It is desirable to rotate a sharp cutting edge  12  into position by loosening, but not totally removing, nut  24  from bolt  28 . This prevents loss of either or both nut  24  and bolt  28 , and speeds up this maintenance evolution. 
     The preferred embodiment of the invention includes cruciform shaped, or two (2) perpendicular slots, mating with two (2) perpendicular raised keys. Other forms of slot and key attachment are feasible, including but not limited to a single slot and mating key, more than two slots and mating keys, and slot/key combinations machined transversely. It will be understood that the use of at least one slot and key combination provides a face to face horizontal locking means between the striker and striker retainer which enables use of a single fastener or fastening technique to be applied to positively join the faces of the striker and striker retainer of a comminuting device. 
     It should also be understood that the items receiving the slot and key may be reversed. In the claimed invention, the striker may therefore have a raised key or keys in place of the female slot(s), and the striker retainer may have a slot or slots in place of the male key(s). The raised keys, if more than one is employed, would then be counterbored as noted herein. Other aspects of the claimed invention would remain similar to those described herein. 
     Referring now to FIGS. 9,  10  and  11 , an alternative embodiment of striker  20  and striker retainer  22  is shown in which, when assembled together (FIG.  9 ), an upward facing surface  56  on the retainer  22  provides primary support for the striker  20  by virtue of the engagement of the surface  56  with a corresponding surface  58  machined in the striker  20 . This primary support is facilitated by the provision of a clearance  60  (e.g. 0.010 inch) between the machined key  50   a  of the striker retainer  22  and the corresponding slot  46   a  in the striker, this clearance  60  is between the upwardly facing surface of the key  50   a  and the downwardly facing surface of the slot  46   a  (as seen in the orientation of the assembly in FIG.  9 ). 
     The key  50   a  and slot  46   a  are designed to provide a secondary support for the striker when wear of he striker  20  sufficient to reduce the clearance  60  to zero has occurred. 
     To facilitate this embodiment the key  50   b  is foreshortened. 
     Preferably the striker  20  has carbide surfaces as shown by cross-hatching in FIG.  11 . 
     Other features of this embodiment are similar to the embodiment described with reference to FIGS. 2-7 except for the omission of the hex machined opening  30  and will therefore not be described again here. 
     REFERENCE NUMERALS 
       2  rotor 
       4  retainer carrying face 
       6  retainer base 
       8  striker 
       10  striker retainer 
       12  striker cutting edge 
       14  rotor rotation 
       16  rotor axis 
       18  projection 
       20  modified striker 
       22  modified striker retainer 
       24  nut 
       26  bore 
       28  bolt 
       30  hex machined opening 
       32  weld joint 
       34  bolt 
       35  countersunk bore 
       36  threaded bore 
       38  alternative striker 
       40  bolt 
       42  striker arc 
       44  clearance bore 
       46 ,  46   a  slot 
       48  bore 
       50 ,  50   a ,  50   b  raised keys 
       52  counter bore 
       54  striker cutting edge 
       56  upward facing surface 
       58  corresponding surface 
       60  clearance 
     D slot depth 
     H key height 
     X slot width 
     W key width