Abstract:
A stump grinding apparatus having a split cutting wheel includes several replaceable cutter blocks secured to the periphery of the wheel. One or more replacement teeth are removably anchored in holes in each block and may also be mounted on holes in the side of the split wheel as well. The teeth are typically provided with a hardened cutting face, and are reinforced with an extension projecting back from the face. Each tooth includes a shank which fits into one of the holes. The shank contains a groove which receives a spring clip or a spring pin for securing the tooth in the hole. The wheel periphery contains individual recesses that are shaped to receive the cutter blocks. Each block includes means for insuring alignment of the block in the corresponding recess. The block is wedged tightly into its recess to reduce the likelihood of accidental removal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a division of patent application Ser. No. 10/035,991, filed Dec. 31, 2001, now U.S. Pat. No. 6,698,477. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of cutting wheels useful for grinding tree stumps. More specifically, it relates to a stump cutter assembly and the component parts thereof. 
   2. Description of the Related Art 
   It is known to provide a stump grinding apparatus to cut and dispose of tree stumps. The device finds use for agricultural applications, for proper lawn maintenance and care, and for site development. It is often required to lower a protruding stump to a level that is below grade so that it will not interfere with plowing, disking and other farm tasks. For pleasing appearance of residential lawns, stumps of dead and fallen trees must likewise be cut away to a point that is below grade to allow for soil to be placed thereover for seeding or planting. When used for site development, the apparatus permits soil to be moved as needed. 
   Typically, such a device includes a rotatable grinding wheel having a plurality of cutting teeth disposed circumferentially about the wheel. The wheel can be powered by a chain drive, or by gear or belt, or may be at the end of a movable boom driven by a diesel or gasoline engine. The cutting teeth of the stump grinders commonly encounter more than just wood when performing their tasks. They are brought into contact with rocks and all manner of buried debris, such as re-bar, wire, cinder block and other materials of construction. Because of these hidden obstacles, the teeth are subject to considerable wear and breakage, and the peripheral surface of the cutting wheel experiences considerable wear as well. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The present invention relates to a stump cutting wheel assembly. The assembly comprises a wheel having a plurality of recesses spaced around the circumference thereof. A replaceable cutter block is inserted into each recess and is secured to the wheel. The block has a leading surface and a trailing surface, two sides colinear with the sides of the wheel, a top with a radius of curvature corresponding to that of the cutting wheel, and a bottom surface corresponding to the surfaces of the recess. A plurality of cutting teeth, each having a shank, is removably inserted into holes in the cutter block and/or the sides of the wheel. Each shank has a free end and an abutment end, the abutment end terminating in a rearwardly extending shoulder that co-operates with the block to serve as a stop to limit linear and rotational movement of the shank in the block or the wheel. An extension on the tooth projects rearwardly of the tooth face to rest against the adjacent surface of a block or the wheel to provide additional support for the tooth to resist shock and bending moments. 
   The cutting wheel is a split wheel having a first half and a second half joined to one other along the diametric surface thereof, each half having a semicircular cut-out in the diametric surface to permit the wheel to be mounted around a hub keyed on a drive shaft. The two halves of the wheel are joined together using clamping means comprising a pair of butterfly clamps. Each butterfly clamp fits in corresponding slots in both halves of the wheel. The clamp engages a bolt extending from the semicircular periphery along mating kerfs in the diametric surfaces. Preferably, the end of the kerfs immediately radially inward of the periphery is enlarged to form a shoulder which receives a sleeve through which the bolt passes. 
   Each cutter block includes means cooperating with a corresponding recess in the peripheral surface of the wheel to align the blocks with the rotational direction of the wheel. The cooperating means includes a slot in the bottom of the recess, a corresponding slot in the bottom surface of the block and a key aligning the two slots. The back surface of each recess forms an undercut angle, and the trailing surface of the block is co-planar therewith. A hole extends through each block from the top surface of the block to the bottom surface, and a threaded fastener such, as a bolt, passes through the hole for fastening the block into the recess of the cutting wheel. The bolt is threaded into a nut plate disposed in a slot in the wheel radially beneath the block. A generally V-shaped groove is formed between the front wall of the recess and the leading edge of the block, and a wedge is located between the two walls of the groove, and is secured to said nut plate with a second threaded fastener. The shank on each tooth includes a circumferential groove, and a spring clip or a spring pin engages the groove to anchor the tooth in a corresponding hole in the block or in the wheel. 
   The invention further relates to a split wheel for a stump grinder. The split wheel comprises a first half and a second half joined to one another along the diametric surfaces thereof. Each half has an axially positioned semicircular cut-out that allows the two halves to be assembled together. The two halves are assembled on a conventional hub using a pair of clamps, such as butterfly clamps. A slot is located inboard of the semicircular periphery of each half and extends in from each mating plane to receive one clamp. A groove along the mating surface joins each slot to the semicircular periphery to receive a bolt extending in from the periphery and threaded into one of the clamps to hold the two halves together. The groove includes a shoulder recessed beneath the peripheral surface to receive a sleeve which, in turn, receives the head of the bolt. 
   The split wheel further includes a plurality of recesses in the periphery thereof, each recess shaped to receive a removable cutter block. Each recess has a front edge, a bottom edge and a rear edge. A threaded block fastener is located near the front edge. The rear edge is undercut to conform to the trailing surface of the block. A circumferentially extending slot in the bottom of the recess is adapted to receive an alignment key engageable with a corresponding slot in the bottom of each block. The threaded block fastener comprises a slot radially inwardly of each recess, and a nut plate in the slot having a threaded hole to receive the block fastener. The nut plate includes a second threaded hole to receive a threaded fastener extending through a block wedge. Each half of the wheel includes a semicircular cut-out along the diametric surface on either side of the axially positioned cut-out, forming a non-axially located circular hole with the corresponding cut-out in the other half. A conventional mounting hub comprises two flanges bolted on either side of the wheel. A pair of holes extends through the two flanges aligned with the two non-axial holes in the wheel, and drive pins extends through these holes in the mounting hub. The mounting hub includes a keyway for mounting the wheel on the drive shaft. 
   The invention also relates to a replaceable cutter block adapted to be inserted into a recess in the periphery of the cutting wheel for a stump grinder. The cutter block has a top surface with a radius of curvature corresponding to the outer periphery of the cutting wheel. The block also includes a bottom surface that is co-planar with the bottom of the recess, two parallel side surfaces, a leading surface and a trailing surface. The trailing surface corresponds to the rear surface of the recess. At least one hole in the block receives a removable cutting tooth, the hole extending from the top surface or a side surface at an angle of inclination from the said surface toward the back surface of a block. The hole extends into the block toward the trailing surface at an angle of between about 30° and about 60°. The block includes means, such as a slotted key way adapted to receive a key extending longitudinally along the bottom thereof, to engage a corresponding alignment means in the bottom of the recess. A threaded fastener secures the block into the recess of the cutting wheel. This fastener comprises a bolt adapted to be threaded into a nut plate positioned in a slot within the cutting wheel radially beneath the block. The trailing surface of the block conforms to the rear wall of the recess and has an angle of less than 90° but greater than about 60° with respect to the bottom of the block. 
   The invention further comprises a cutting tooth to be removably engaged with a stump cutting wheel or a block on the circumference of such a wheel. The tooth comprises a planar cutting surface adapted to form an angle generally orthogonal to a side or a top of said block when the tooth is engaged therewith. It also includes a shank to be inserted into a corresponding hole in the block, said shank having a free end and an abutment end. The abutment end terminates in a shoulder formed at right angles to the shank and adapted to cooperate with the block to serve as a stop to limit the linear and rotational movement of the shank into the block. An extension projects rearwardly of the tooth face and is adapted to rest against the planar side or top surface of a block when the tooth is inserted into the block, said extension serving to provide a support for the tooth when in use. The shank typically includes a circumferentially extending groove and a spring clip engaging the groove for the purpose of providing a compressive fit of the tooth in the corresponding hole in a block. The shank forms an interior angle of between about 30° and about 60°, preferably about 45°, with respect to the cutting face of the tooth. The angle corresponds to the diagonal angle in the block or cutting wheel so as to provide the proper cutting angle for the face when the tooth is properly mounted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of the overall assembly of the present invention; 
       FIG. 2  is an enlarged, exploded view of the cutting wheel clamp arrangement; 
       FIG. 3  is an assembled view of the arrangement of  FIG. 2 ; 
       FIG. 4  is a partial exploded view of the wheel and cutter block; 
       FIG. 5  is an assembled view of the cutter block assembly of  FIG. 4 ; 
       FIG. 6  is a view of the teeth of the present invention and their relationship to the cutting wheel; and 
       FIG. 7  is an exploded perspective view of the cutter block and teeth. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The grinding wheel of the present invention is fabricated in two halves that are adapted to be held together by a butterfly type clamp. The halves are aligned in place by a wheel key which is held tight by a bolt going through the middle of the wheel key and the wheel, to the butterfly wheel clamp. 
   The grinding wheel also has removable wheel sections called blocks. These blocks are held in place in four ways. One, the wheel is machined with a cut-out specifically designed for the blocks to set into them. The wheel receives the block with the back and bottom face of the block fitting into it. The space between the front face of the block and the wheel is designed for a wedge to set into it. Two, a safety bolt goes through the block to a common nut plate or a nut in the wheel. Three, a wedge is set in between the wheel and front face of the block which is held in place by a bolt that goes through the wedge and into the common nut plate or nut in the wheel. Fourth, a key and keyway slips into the block and wheel. This is called a block key. 
   The wheel and the block have holes machined into them. Some are for the teeth and some for the bolts. Each hole is machined into the wheel in such a direction that, when the cutting tooth is inserted into it, the tooth will be at the appropriate angle for stump grinding. These holes are also machined to fit the design of the tooth in such a way that they are prevented from rotating or moving in the hole when the wheel is in motion. 
   The tooth has an extension on its top backside, which rests against the wheel or block. This gives support to the tooth and also keeps a tooth from turning when in motion. The tooth has a shank that goes into the wheel hole or block hole. The shank has a spring clip on it, which holds the tooth in tight. 
   All the teeth can be easily removed from a backside of the wheel or block. Teeth are removed with a punch and hammer. A block can be changed as needed by removing the wedge bolt and the block bolt. 
   Turning now to the drawings,  FIG. 1  shows an exploded view of the stump grinder assembly  10  comprising a wheel  12 , a plurality of cutter blocks  14 , and a plurality of cutting teeth  16  inserted in holes in the top and sides of the cutter block and the sides of the grinding wheel. The wheel  12  is composed of two identical halves  12   a ,  12   b  joined to one another in the manner to be hereinafter described in greater detail in connection with  FIGS. 2 and 3 . 
   Each half of the wheel has a mating surface  20  along the diameter thereof and a peripheral surface  22 . The two mating surfaces include an axially positioned semicircular cut-out  24  adapted to be mounted on a hub (not shown). A pair of smaller semicircular cut-outs  26   a ,  26   b  are located near the axial cut-out along the mating surfaces and are adapted to receive a pair of conventional drive pins (not shown) extending through flanges in the hub. Radially outwardly thereof are slots  28   a ,  28   b  for receiving butterfly clamps  30   a ,  30   b . A pair of bolts  32   a ,  32   b  passes through annular wheel keys  34   a ,  34   b  to be threaded into the clamp, Grooves or kerfs  36   a ,  36   b  extend radially outwardly from the slots  28   a ,  28   b  to an enlarged opening  38   a ,  38   b  forming an abutment shoulder  40   a ,  40   b . The bolt  32  passes through the annular key  34  into the clamp  30  and is tightened against the key, which abuts against the shoulder  40 . 
   Turning now to  FIGS. 4 and 5 , the details of a removable cutter block  14  and the manner in which it is fastened to the wheel is shown. The block  14  includes a pair of parallel sides (one side  52  being shown), a leading surface  54 , a trailing surface  56 , a top surface  58  and a bottom surface  60 . The top surface  58  has a radius of curvature that matches that of the periphery of the wheel  12 . A recess  62  is machined, etched or molded into the periphery of the wheel, forming a front  64  and a rear  66  separated by a base  68 . The trailing edge  56  of the block  14  and the rear  66  of the recess in the wheel  12  preferably form an identical angle with respect to the bottom  60  of the block and the base  68  of the recess that is less than 90°, preferably on the order of about 70°-85°. The leading edge  54  of the block  14  and the front edge  64  of the recess diverge, forming a V into which a wedge  70  is inserted and is secured in place with a wedge bolt  72 . The wedge bolt is threaded into a bolt plate  74  or a nut (not shown) inserted into a slot  78  machined or otherwise formed in the wheel  12  radially beneath the recess  62  and the block  14 . A second bolt  80  holds the block in place, while the wedge forces the block into tight engagement with the back edge of the recess. Circumferential alignment is maintained between the block  14  and the recess  62  by suitable means, such as an elongated slot  82  in the bottom of the block, a corresponding slot  84  in the base of the recess, and a slot key  86  engaging both slots. 
   One or more holes  88  are machined at an angle into the block  14  to receive the cutting teeth  16 . The holes include a circular portion  90  that receives the shank of the tooth, and a generally square seat  92  against which the shoulder of the tooth abuts. The circular portion of the mounting hole typically extends through to the opposite side of the block  14  or the wheel  12  where it appears as an oval  18 . 
     FIG. 6  shows two teeth  16  and a partial end view of the cutting wheel  12 . The wheel is intended to rotate in the direction shown by the arrow. Each tooth  16  includes a planar cutting face  100 , a tooth body  102 , a cylindrical shank  104  having a free end  106  and an abutment end  108  which forms a generally rectangular shoulder  110  where it intersects the body  102  of the tooth. The shank  104  typically forms an angle between about 30° and 60°, preferably about 45°, with respect to the cutting face  100  of the tooth. The shank typically includes a groove  112 , which is engageable by a spring clip  114  or a spring pin  116  (shown in FIG.  7 ). The tooth  16  includes an extension  118  projecting rearwardly from the tooth face  100 . This extension includes a planar surface  120  that rests against the side of the wheel  12  when the tooth shank  104  is inserted into a tooth hole  88 . 
     FIG. 7  shows the cutter block  14  in a perspective view with two cutting teeth  16  adapted to be inserted thereinto. Shown are the side  52 , the leading edge  54 , and the curved top  58  of the block. One hole  88  is shown in the top  58  and two holes are shown in the side  52  to receive the teeth  16 . Each of these holes includes a shoulder  92  and a round portion  90  to receive the shank  104  of a tooth  16 . A hole  94  extends vertically through the block  14  to receive a block bolt (not shown) and includes a shoulder  96  against which the head of the block bolt abuts. The tooth can be easily removed from a hole on the side of the block  14  or the wheel  12  by tapping the free end  106  of the tooth shank  104  with a hammer and a punch. The teeth on the top of the block are held by a spring pin  116  pressed into and extending through a hole  50  in the side of the block. These teeth can be easily disengaged from the block by driving out the spring pin and then tapping the free end of the tooth shank if it is accessible, or by prying it loose. The free end can be accessed by machining a hole through the sides of the block tangentially to the free end of the shank so that the shank can be tapped out. 
   The tooth is typically fabricated by suitable means, such as forging or casting. The face of the tooth preferably is made from a hard, impact resistant material, such as carbide steel brazed onto the body of the tooth. 
   As mentioned, the two halves of the wheel are assembled together around a hub with the two mating surfaces joined together. The butterfly clamp  30  is inserted into each of the slots  28 , after which the bolt  32  is inserted through the key  34 , and the groove  36  and is threaded into the clamp. When the two halves of the wheel are clamped together, a plurality of bolts is inserted into the holes  18  in the wheel and corresponding holes on the two flanges of the hub. The two holes formed by the cut-outs  26   a  and  26   b  are aligned with corresponding holes in the flanges. Drive pins are then inserted through the aligned holes so that the wheel is driven by the rotation of the hub on the shaft of a suitable power source. Instead of using drive pins, other drive means may be used, such as slotted wheel halves mounted on a splined drive shaft. 
   Typically, the number and placement of teeth in the cutter block and in the grinder wheel, as well as the angles and height of the cutting teeth with respect to the rotational direction of the cutting wheel, can be altered in accordance with established practices. Furthermore, other means, such as cotter pins, can be used for anchoring the teeth in the holes in the blocks and the wheel. Likewise, the number of removable cutter blocks and corresponding recesses in the cutter wheel can be increased or decreased depending on the overall size of the wheel and the blocks. The recesses normally should be evenly spaced around the periphery of the wheel for balance of the centrifugal forces during operation. 
   While the invention has been described in combination with embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims. For example, the recesses and the cutter blocks can be shaped so that the each block is secured to the wheel using a pair of block bolts front and back instead of using a block wedge. Furthermore, the alignment of the blocks with the wheel can be achieved by using a plurality of alignment pins instead of a key and slotted keyway. 
   The teeth of the present invention can be used with other types of cutter wheels such as solid wheels with improved results. Likewise, the blocks of the present invention can be mounted on unitary cutting wheels, thereby enjoying the benefit and ease of replacing the blocks when worn or broken.