Patent Publication Number: US-8534330-B2

Title: Knife and knife assembly for a planer side head

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. Ser. No. 11/824,305, filed Jun. 29, 2007, now U.S. Pat. No. 7,891,388 which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a knife and knife assembly for a high speed planer head, which is used in commercial manufacturing of construction lumber and finished wood products. 
     BACKGROUND 
       FIGS. 1 and 2  show typical, prior art planer side heads for use in commercial manufacturing of construction lumber and finished wood products. Such heads can generically be referred to as “cutting heads” because they produce cuts in the workpiece. They include, typically, a plurality of knives and are connected, typically by a drive-shaft, to a motor or engine that rotates the cutting head about an axis of rotation. 
       FIG. 1  shows a planer side head  10  known as an “L” type, and  FIG. 2  shows a planer side head  20  known as an “LV” type.  FIG. 3  shows for greater clarity wedging elements  24  ( 24   a ,  24   b ) that form part of a wedging bolt assembly for clamping a knife in the head  20 . While persons of ordinary skill are, by definition, familiar with L and LV planer side heads, a brief description of some salient features of these heads is provided here for general understanding, and focus. 
     A planer side head has an essentially disc-shaped or cylindrical body  11 , and is caused to rotate about a cylindrical axis of rotation of the head “R.” Extending into the body are a plurality of axially extending pockets  25  that are uniformly and azimuthally spaced-apart along the circumference of the body as shown. These pockets are adapted to receive corresponding knives  27  ( 27   a  in  FIGS. 1 and 27   b  in  FIG. 2 ) that project cutting edges  35  outwardly from the pockets. 
     Each pocket  25  has a back surface  26  for receiving the knives  27 . As it appears in the end view of  FIG. 4  (corresponding to the L-type head of  FIG. 1 ), this back surface is congruent with a line “L 1 ” that joins the circumference of the body  11  at a point “P 1 .” This line L 1  is aligned closely, i.e., to an angle θ 1  that is within 5 degrees from another line “L 2 ” drawn through the same point P 1  and the axis of rotation R. This geometry is characteristic of an L or LV-type planer side head, and is for purposes herein considered to be a distinguishing characteristic with respect to other types of cutting apparatus. 
       FIGS. 5 and 6  show a knife  27   a  for use in the L-type planer side head of  FIG. 1 , and  FIGS. 7 and 8  show a knife  27   b  for use in the LV-type head. As can be seen, the knives  27   a  and  27   b  vary only with respect to their adaptations for being mounted in the pockets and are otherwise essentially identical. 
     Referring to  FIG. 9 , each of the knives  27  has a cutting end  40  that projects at an angle from a shank end  42  that is received in a pocket, giving the knife an approximate “L” shaped configuration. The shank end  42  has a back surface  43  that is received by the back surface  26  of the pocket in which the knife is installed. As can be seen particularly in  FIGS. 6 and 8 , the back surface  43  of the shank  42  has a series of axially disposed corrugations  41  that mate with corresponding corrugations  45  in the back surface  26  of the pocket ( FIGS. 1 and 2 ). These corrugations are provided for incrementally adjusting the radial position of the cutting edge  35  of each knife  27 , as discussed below. 
     Referring to  FIG. 10 , the cutting end  40  has a cutting edge  35  that includes a face-cutting edge portion  37  disposed between two corner-cutting edge portions  39  ( 39   a ,  39   b ). Each knife  27 , when mounted into the planer side head and rotated, produces a cut in an article of wood  8  (or other material) having the profile “PR.” 
     To produce a planer face-cut “F s ,” the face-cutting edge portion of the cutting edge  35  is linear, and to produce the two arcuate corner cuts “r,” the corner-cutting edge portions of the cutting edge  35  are preferably circular arcs, for producing radius cuts, although other curvatures could be provided in one or both of the corner-cutting edge portions to produce any desired arcuate corner cuts. 
     The cutting edge  35  is a line or edge of joinder of a planar front side surface  44  (see  FIGS. 5 and 7 ) of the cutting end  40 , facing the direction of rotation of the side head, and a back side surface  46  of the knife (see  FIGS. 6 and 8 ). Referring to  FIG. 11  (corresponding to the L-type head of  FIG. 1 ), the front side surface  44  (shown in edge view) defines a cutting angle θ C  with a line intersecting an outermost tip  46  of the knife and the axis of rotation R. This cutting angle is an important process parameter, and in both the L and LV-type planer side heads it has a standard, industry accepted value which is assumed for descriptive purposes herein to be 25+10/−20 degrees. 
     A grinder is used to grind the front side surface  44  of a knife  27  to refresh or recondition the knife, but this causes the cutting edge  35  to recede in both azimuthal and radial directions, changing primarily the cutting diameter of the planer head, but also changing secondarily the cutting angle. However, the recessions in both directions are found to be satisfactorily compensated for by moving the knife outwardly along the aforementioned line L 1  ( FIG. 4 ) in increments defined by the aforementioned corrugations. 
     The shank end  42  of the knives  27  provide the necessary adaptation for mounting the knife in the particular type of planer side head. Referring to  FIGS. 1 and 6 , the shank end  42  of the knife  27   a  for use in the L-type side planer head includes a, typically, planar front surface  37 . Toe bolts  41  are threadably received in the body  11  so that ends  14  of the bolts extend into the associated pockets  25  by adjustable amounts. The ends  14  make contact with the front surface  37  and, by tightening the bolts, the knife  27   a  is clamped firmly in place. 
     Referring to  FIGS. 2 and 8 , in the LV-type planer side head, a more dense knife spacing is provided by the use of axially extending wedge bolts  22  used to draw together wedge elements  24  ( 24   a ,  24   b ) against axially opposed, relatively inclined sides  38  of a knife  27   b . Tightening the axially extending wedge bolts wedges the knife firmly in place. 
     Aside from the differences in how the knives  27  are adapted for being clamped in the pockets, the L and LV type planer side heads are essentially identical for purposes herein. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, an L or an LV type side planer head is retro-fitted with knives having substantially less mass than the knives originally provided for these heads. Corresponding knife carriers are provided for clamping the smaller knives, and the knife carriers are installed in the pockets and clamped into the body of the side planer head in the ordinary manner. 
     According to another aspect of the invention, a knife assembly is used in a cutting apparatus providing for rotation of the knife assembly about an axis. The assembly includes a knife and a knife carrier. The knife carrier has a slot defining two cantilevered portions: A front cantilevered portion bears against a front side surface of a knife that faces the direction of rotation, and a back cantilevered portion bears against a back side surface of the knife which faces the opposite direction. One or more clamping bolts are employed for drawing the front and back cantilevered portions together so as to firmly clamp the knife therebetween. 
     According to yet another aspect of the invention, a knife is provided for use in a cutting apparatus providing for rotation of the knife about an axis. The knife has a front side surface for facing the direction of rotation and a back side surface facing the opposite direction and parallel to the front side surface. The knife has a cutting edge that has a linear, face-cutting edge portion disposed between two opposed corner-cutting edge portions. Each corner-cutting edge portion has associated therewith a first beveled, knife-edge forming surface that joins the back side surface and the respective corner-cutting edge portion. The knife-edge forming surfaces define a constant relief angle in the range of 25-40 degrees over substantially the full extent of the corner-cutting edge portions. The face-cutting edge portion has associated therewith a second beveled, knife-edge forming surface that joins the back side surface and the face-cutting edge portion. The second knife-edge forming surface is planar over substantially the full extent of the face-cutting edge portion. The cutting edge is provided at one end of the knife and the extreme opposite end of the knife has a planar knife seating surface, parallel to the face-cutting edge portion, for seating the knife in the cutting apparatus. 
     A method according to the invention is disclosed for repairing a cutting head having a damaged knife on a cutting head that is operatively connected to a drive means for rotating the cutting head and the knife about an axis of rotation. The method comprises removing and replacing the knife while the cutting head remains operatively connected to the drive means. 
     It is to be understood that this summary is provided as a means of generally determining what follows in the drawings and detailed description and is not intended to limit the scope of the invention. Objects, features and advantages of the invention will be readily understood upon consideration of the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a prior art L-type planer side head. 
         FIG. 2  is a pictorial view of a prior art LV-type planer side head. 
         FIG. 3  is a pictorial view of wedge elements that form part of a wedging bolt assembly for clamping a knife in the LV-type planer side head of  FIG. 2 . 
         FIG. 4  is a side elevation of the L-type planer side head of  FIG. 1 . 
         FIG. 5  is a front side pictorial view of a prior art knife for use in the L-type planer side head of  FIG. 1 . 
         FIG. 6  is a back side pictorial view of the knife of  FIG. 5 . 
         FIG. 7  is a front side pictorial view of a prior art knife for use in the LV-type planer side head of  FIG. 2 . 
         FIG. 8  is a back side pictorial view of the knife of  FIG. 7 . 
         FIG. 9  is a side elevation of the knife of  FIGS. 5 and 6 . 
         FIG. 10  is a top view of the knife of  FIGS. 5 and 6  cutting an article of wood. 
         FIG. 11  is a side elevation of a generalized planer side head and knife. 
         FIG. 12  is a front side, exploded pictorial view of a knife and knife carrier according to the present invention. 
         FIG. 13  is a back side, exploded pictorial view of the knife and knife carrier of  FIG. 12 . 
         FIG. 14  is a front side, pictorial view of the knife carrier and knife of  FIG. 12 , showing the knife installed. 
         FIG. 15  is a back side, pictorial view of the knife carrier and knife of  FIG. 13 , showing the knife installed. 
         FIG. 16  is a front side view of the knife of  FIGS. 12-15 . 
         FIG. 17  is a back side view of the knife of  FIGS. 12-15 . 
         FIG. 18  is side elevation of the knife of  FIGS. 12-15 , taken along a line  18 - 18  in  FIG. 17 . 
         FIG. 19  is a front side view of the knife carrier of  FIGS. 12-15 . 
         FIG. 20  is a back side view of the knife carrier of  FIGS. 12-15 . 
         FIG. 21  is a side elevation of the knife carrier of  FIGS. 12-15 , taken along a line  21 - 21  in  FIG. 20 . 
         FIG. 22  is a pictorial view of an L-type planer side head employing the knife and knife carrier of  FIGS. 12-21 . 
         FIG. 23  is a side elevation of the planer side of  FIG. 22 . 
         FIG. 24  is a pictorial view of an LV-type planer side head employing the knife and knife carrier of  FIGS. 12-21 . 
         FIG. 25  is a partially cut-away, back side view of the knife of  FIGS. 12-18 . 
         FIG. 26  is a section view of the knife of  FIG. 25 , taken along a line  26 - 26  thereof. 
         FIG. 27  is a section view of the knife of  FIG. 25 , taken along a line  27 - 27  thereof. 
         FIG. 28  is a section view of the knife of  FIG. 25 , taken along a line  28 - 28  thereof. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
       FIGS. 12-18  show a preferred knife  50 , and  FIGS. 12-15  and  19 - 21  show a preferred knife carrier  52 , which together are intended to replace one of the knives  27   a  described above in the L-type planer side head. 
       FIGS. 12 and 16  show a front side  54  of the knife  50 , corresponding to the front side surface  44  of the prior art knives (see  FIGS. 5 and 7 ). The front side  54  is preferably planar and faces in the direction of rotation of the planer side head. 
       FIGS. 13 and 17  show a back side  56  of the knife  50 , which is opposite the front side  54 , is also preferably planar, and is preferably parallel to the front side, as seen in  FIG. 18 , showing a side elevation and defining a width “w” of the knife. 
     With particular reference to  FIG. 17 , the knife  50  has a cutting edge  75  that includes a linear face cutting edge portion  77  disposed between two arcuate corner-cutting edge portions  79  ( 79   a ,  79   b ). The purpose of the face and corner-cutting portions is the same as described above for the prior art knives  27 . The knife also has approximately linear (though linearity is not essential) side relief portions  80  ( 80   a ,  80   b ) that are not actually used to make a cut but provide clearance to avoid undesirable interference with the wood (or other object or article) and thus provide an outstanding advantage over the prior art. The relief portions  80  in the preferred embodiment make an angle θ R  with a line perpendicular to the face cutting portion  77  that is preferably 20+5/−10 degrees. 
     Referring back to  FIGS. 12-15 , the knife  50  fits into a knife carrier slot  58  defined in the knife carrier  52 . The knife carrier is preferably an integral block of metal into which the knife carrier slot is cut; however, this is not essential. The knife carrier has a front side  59   a  ( FIGS. 12 and 14 ) and a back side  59   b  ( FIGS. 13 and 15 ). 
     Turning now to  FIG. 21 , the knife carrier slot  58  defines two cantilevered portions  60  of the knife carrier. A front cantilevered portion  60   a  bears, along a front internal surface  58   a  of the slot, against the front side  54  of the knife  50  (see  FIG. 14 ). Correspondingly, a back cantilevered portion  60   b  bears, along a back internal surface  58   b  of the slot, against the back side  56  of the knife (see  FIG. 15 ). The knife carrier slot is slightly wider than the width w of the knife so that the knife can be slid into the slot manually, without the exertion of any significant force. 
     The front and back cantilevered portions  60   a  and  60   b  define respective outer surfaces  61   a  and  61   b.    
     The cantilevered portions, by virtue of being cantilevered, are adapted to bend toward one another and thereby clamp the knife  50  with a frictional force exerted on both the front and back sides of the knife by the internal surfaces  58   a ,  58   b . This bending is caused by tightening one or more clamping bolts  64  as shown in  FIGS. 14 and 15 . In the preferred embodiment, the clamping bolts  64  extend through the back cantilevered portion  60   b , and through slots  66  in the knife (see  FIGS. 12 and 13 ) corresponding to the one or more clamping screws  64 , and are threaded into threaded holes in the front cantilevered portion  60   a . This orientation allows access to the bolt-heads from the outer periphery of the side head and providing the threads in the knife carrier eliminates the need for nuts on the ends of the bolts. The slots  66  in the knife  50  allow the knife to be slid into and out of the knife carrier slot  58  in the direction of the arrow “A” in  FIGS. 12 and 13 , merely by loosening the clamping screws  64 , without the need to remove the clamping bolts. However, it should be understood that numerous alternative clamping schemes and configurations of the knife and knife carrier allowing for clamping the knife  50  as a result of bending the cantilevered portions could be employed without departing from the principles of the invention. 
     The knife carrier  52  shown in  FIGS. 12-15  and  19 - 21  has a shank  68  adapted to fit an L-type planer side head. The shank has a front surface  68   a  and an opposed, back surface  68   b . The front surface  68   a  preferably has a planar distal end portion  69  for receiving the ends of the aforementioned toe bolts  40 , and preferably joins with the front cantilevered portion  60   a  with a cylindrical surface portion  70  of substantial radius such as shown. This radius is positioned where the largest bending forces are encountered, and is preferred because it provides a configuration that reduces stress concentration. 
     Taken together, the front surface  68   a  of the shank  68 , the cylindrical surface portion  70 , and the outer surface  61   a  of the front cantilevered portion define the front side  59   a  of the knife carrier  58 . It will be appreciated that this entire front side  59   a  may have numerous alternative configurations providing for (a) clamping the knife carrier in the pocket of the planar side head, and (b) cantilevered portions for clamping the knife, without departing from the principles of the invention. 
     The back surface  68   b  of the shank  68  preferably includes the same corrugations  41  (see, e.g.,  FIG. 20 ) provided in the prior art knives  27  as described above. 
     Referring to  FIGS. 14 and 21 , the knife carrier slot  58  has an internal surface  58   c  that registers to a corresponding knife seating surface  51  of the knife  50  (see  FIGS. 16 and 17 ), to seat the knife in the slot so that the cutting edge  75  of the knife extends from the planar side head a predetermined amount. This predetermined amount is also adjustable in increments where the aforementioned axially disposed corrugations are provided, which allow for moving the knife carrier relative to the axis of rotation R of the side planer head in essentially radial directions. 
     The internal surface  58   c  of the knife carrier slot is preferably a simple planar bottom surface of the slot, and the corresponding knife seating surface is preferably a simple planar side of the knife that is also, preferably, perpendicular to the front and back sides  54  and  56  of the knife, but other registration features as known in the art positioned in other locations of the knife and knife carrier slot may be employed for seating the knife in the slot without departing from the principles of the invention. 
       FIGS. 22 and 23  show the knife  50  and knife carrier  52  installed in the L-type planer side head of  FIG. 1 , where instances of the knife  50  and knife carrier  52  are used as replacements for corresponding instances of the prior art knives  27   a . From  FIG. 23 , it can be appreciated that the knife carrier slot  58  is angled and positioned so that, in addition to establishing the depth of seating of the knife in the knife carrier, the knife carrier slot establishes the aforementioned cutting angle θ C  for the knife. 
       FIG. 24  shows the knife  50  in a knife carrier  82  adapted particularly for use in the LV-type planer side head. The only difference between the knife carrier  82  and the knife carrier  52  is the adaptation of the shank, here  84 , to include axially opposed, relatively inclined sides  88 , for cooperation with the aforementioned axially extending wedge bolts  22  and wedge elements  24 . 
     In consideration of  FIGS. 25-28 ,  FIG. 16  shows the knife  50  looking toward the front side  54  and  FIG. 17  shows the knife looking toward the back side  56 . With additional reference to  FIG. 18 , the cutting edge  75  is formed by joinder of the front side  54  and a beveled or canted surface “S” that, in turn, joins the back side  56 . 
     Turning now to  FIGS. 25-28 , the surface S can be visualized as a series of line segments “LS” that define a “relief angle” γ with the front side  54 .  FIGS. 26-28  show this angle taken as various cross-sections indicated. The line segments LS lie in planes that are perpendicular to the cutting edge  36  and the front side  54 . The relief angle γ is preferably in the range of 25-40 degrees, and is also preferably constant over the entire surface S, including those portions of the surface S corresponding to the corner-cutting edge portions  79 . By comparison, the prior art knives  27  did not provide the equivalent of a relief angle adjacent the corner-cutting portions of the cutting edge, which increasing the risk of tearing the wood as it is being cut. 
     The knife carriers  52  and  82  provide for retrofitting an existing L or LV type side planer head for use with a knife  50 , which provides a number of outstanding advantages. The knife is small enough, typically about 1″×2″×0.125″, to be economical to dispose of when the cutting edge becomes dull. The small size eliminates the need to grind the knife, and therefore the need to keep, maintain and utilize a grinding machine. 
     Moreover, because knives according to the invention are relatively small, they can be held in place by commensurately small clamping screws (see, e.g.,  FIG. 13  and clamping screws  64 , noting that the figure is drawn to scale). Thus, it becomes an attractive option to remove the knives for replacement while the cutting head is in place, saving time and effort. 
     By contrast, the relatively large, heavy knives of the prior art are much more difficult to remove individually, justifying the standard practice of removing the entire cutting head when the knives need to be ground or replaced. 
     Often just one or only a few knives become damaged as a result of contact with a small rock, or a small piece of metal scrap. In this circumstance, there is an additional reason that the entire cutting head is typically removed to effectuate repair. That is that the relatively large, heavy prior art knives are susceptible to sufficient variation in mass that replacing just one of them can throw the cutting head out of balance. Thus, it is standard practice, when one or just a few knives are damaged, to replace all of the knives. At the least, corresponding knives on the opposite side of the cutting head would typically need to be replaced to maintain balance, doubling the replacement requirements and consequently tending to justify the time and effort involved in removing the entire cutting head. 
     It is therefore an outstanding advantage that a knife according to the present invention can be replaced with another knife of non-identical mass with relatively little impact on balance, simply because each knife has so little mass by comparison to that of the entire cutting head. Thus, if only one or a few knives are damaged, it is practical to replace them without concern for affecting the balance of the cutting head, tending to justify making the repair with the cutting head in place. 
     It is further recognized that clamping the knife by use of cantilevered portions, whether provided as part of a knife carrier or as part of the body of the planer head itself, is a particularly low profile means for clamping a knife and may have uses in many other applications, including other types of cutting apparatus, such as chipper discs and drum chippers, as well as other types of planer heads. 
     It is still further recognized that the knife described herein is particularly advantageous in any side planer head due to the provision of the constant relief over the surface S in conjunction with a single-sided knife that uses one side for registering the knife in a slot or pocket, independent of how the knife is clamped therein or thereby. 
     It is to be recognized that, while a particular knife and knife assembly for a side planer head has been shown and described as preferred, other configurations and methods could be utilized, in addition to those already mentioned, without departing from the principles of the invention. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions to exclude equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.