CA2184228C - Method for sharpening a chipper knife - Google Patents
Method for sharpening a chipper knifeInfo
- Publication number
- CA2184228C CA2184228C CA002184228A CA2184228A CA2184228C CA 2184228 C CA2184228 C CA 2184228C CA 002184228 A CA002184228 A CA 002184228A CA 2184228 A CA2184228 A CA 2184228A CA 2184228 C CA2184228 C CA 2184228C
- Authority
- CA
- Canada
- Prior art keywords
- cutting edge
- knife
- underside
- chipper
- resharpening
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27L—REMOVING BARK OR VESTIGES OF BRANCHES; SPLITTING WOOD; MANUFACTURE OF VENEER, WOODEN STICKS, WOOD SHAVINGS, WOOD FIBRES OR WOOD POWDER
- B27L1/00—Debarking or removing vestiges of branches from trees or logs; Machines therefor
- B27L1/10—Debarking or removing vestiges of branches from trees or logs; Machines therefor using rotatable tools
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Debarking, Splitting, And Disintegration Of Timber (AREA)
Abstract
Sharpening the cutting edge of a chipper knife having a chip-breaking shoulder in its underside remote from the cutting edge apex which is integral with the chipper knife is effected by removing a layer of material of uniform thickness from the underside of the cutting edge and thereby removing the bluntness of a dulled cutting edge and forming a resharpened cutting edge having the same wedge angle as the cutting edge prior to resharpening.
Description
21~4228 METHOD FOR SHARPENING A CHIPPER KNIFE
This invention relates to a method for ~1 Idl ~t:l lil ,g knives used in wood chippers such as a rotatable disc type in which the disc carries a plurality of circ~""rer~nli~lly spaced radial knives alongside chip-discharge openings through the disc.
Wood chippers having rotatable cutters, or drums, or rotatable chipping discs fltted with double-edged knives are known.
One aspect of the geometry of chipper knives is that knives having a large o wedge angle, i.e., the angle between the two surfaces converging to the cutting edge, remain sharper longer and therefore are more popular. However, the larger wedge angles are more likely to cut a chip by shearing the chip from the incoming material rather than by cleavage. More force is required to sever chipsby shearing than by cleavage, and thus more power is required to operate a disc chipper having knives with larger wedge angles.
Another problem is the pt:n~ll dliUIl of chip particles between the knife and the knife holding means beneath the knife, typically a counter knife, that can cause excessive pressure on the knife which may bend it outwardly sufficiently to hit the anvil.
The principal object of the invention is to provide a new method of :~hdl ~ e"i"g chipper knives which is particularly valuable fo m ~ha, 1~l ,i"g various types of chipper knives so that a cutting edge can be ~,ondiliul ,ed for use oneor more times instead of being unusable after it has been dulled the first time by use.
A further object is to provide a chip deflector and chip breaker which is integral with a cutting edge of a chipper knife.
The benefits of the present invention can be achieved by a method of I ~:7hdl ,~JC~I lil l9 a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises undercutting the underside of the cutting edge by removing material and thereby removing the bluntness of the dulled cutting edge and forming a chip breaker .
~ 218~228 shoulder remote from the cutting edge apex which is integral with the chipper knife.
Also the benefits can be achieved by a method of, t,~l Idl ~ I lil l9 a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex and having a chip breaker shoulder in the underside remote from the cutting edge apex, which comprises removing material from the upper surface of the cutting edge and thereby removing the bluntness of the dulled cutting edge and removing material from the cutting edgeunderside shoulder to maintain the cutting edge underside between the cutting o edge apex and the shoulder dlJpl~AillldLely the same width as the width of thecutting edge underside prior to the cutting edge being 1 ~h dl ~I.ened.
In addition, the benefits can be achieved by a method of resharpening a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises forming an undercut having a chip-breaking shoulder remote from the cutting edge apex which is integral with the chipper knife by removing material only from the underside of the cutting edge and thereby removing the bluntness of the dulled cutting edge.
The invention provides a novel knife and knife-holding means for a chipper. The knife is double-edged, each cutting edge ~Ill,ni~ g an upper ~o surface, preferably a standing bevel, and an undersurface, which surfaces converge and intersect to form a cutting edge. Additionally the knife includes achip-deflecting surface forming the heel or part of the cutting edge undersurface remote from the cutting edge apex which constitutes a chip breaker that deflectsand breaks chip material cut by the knife cutting edge. This chip breaker deflects the chips so as to prevent the pen~l, dlion of chip particles between the knife and the knife holding means beneath the knife, such as a counter knife, and preferably so that the chips do not strike the knife holding means which ;It:..l ~ases wear on the knife holding means.
In drawings that illustrate the e"ll.odi",t:"t~ of the invention:
~ 21~228 FIG. 1 is a r, d911 lel ILdl y cross section through a portion of a disc chippershowing a double-edged chipper knife and its ~ ~,o. ~ d holding means which knife has been narrowed by, t:~l Idl ~l lil ,g.
FIG. 2 is an enlarged cross section of a double-edged chipper knife similar to that shown in FIG.1 and its ~sor.i..l.-d holding means.
FIG. 3 is a partial top plan of the counter knife used in the knife holding means of FIG. 1.
FIG. 4 is an enlarged cross section of a chipper knife cutting edge which has been 1 ~h dl ~ l ,ed.
0FIG. 5 is an enlarged cross section of a chipper knife similar to that shown in FIG. 2 but having a slightly modified shape.
FIG. 6 is a cross section of a chipper knife like that shown in FIG. 2 but which has been ~ ,I ,a, l,ened.
FIG. 7 is a cross section of a single-edged chipper knife and its ~csorj..lQd holding means.
FIG. 8 is a cross section of a prior art double-edged chipper knife and its so-; ,1, d holding means.
FIG. 9 is an enlarged rldL~IIIellLdly cross section of a portion of the chipper knife shown in FIG. 8 which has been, t:~l Idl ~-ened once; and FIG.10 is a similar cross section of a cutting edge of the chipper knife which has been, ~al Idl ~ened twice.
FIG.11 is a cross section of a double-edged chipper knife and its holding means of a different type one edge of which has been, t:~l Idl ,IJt:l ,ed once.
FIG. 12 is a cross section of a double-edged chipper knife and its . .;.~l~d holding means of still a different type one cutting edge of which has been It:sh dl ~-ened once; and FIG. 13 is an enlarged cross section of the same type of chipper knife which has been 1 ~h dl ~ l ,ed twice.
FIG. 14 is a cross section of a double-edged chipper knife and acsor~ d holding means of a still different type one cutting edge of which has been 30 It:~h a,~"ed and FIG. 15 is an enlarged cross section of the same type of chipper knife showing both cutting edges having been, ~I ,d, ~ned twice.
218~228 A chipper knife sharpened according to the present invention is illustrated as being used in a disc type wood or log chipper in FIG. 1, but such a knife could be used in a drum chipper or rotary knife chipper. The materials to be chipped, such as logs, are fed at an an31e to the rotating disc. The chips pass from the knives through radially elongated openings 106 in the disc 92 adjacent to the knives to be expelled from the chipper.
Knife a5st1ll "ies are carried by the disc 92 at circu",r~ lly spaced locations. Each knife assembly includes a knife 10 elongated radially or a radial series of knife sections placed end to end, and knife holding means including o knife seat 70, counter knife 30, and knife clamp 50. Each knife assembly is disposed in a recess 94 in disc 92 adjacent to a radially elongated opening 106 through the disc. The knife seat has an elongated body with a plafform 72 thereon for place~ l ~e~ l~ of the counter knife 30, and a support 74 for the knife clamp 50. The platform 72 has in it a blind bore threaded to receive a fastener such as a cap screw 104 for mounting the counter knife.
The knife is held in position by the knife clamp 50 as shown in FIG. 1.
The knife clamp has a knife en~age",el ,l surface 54 contacting the knife top surface 11. The knife clamp is secured to the disc 92 by a fastener such as a screw 102 as shown in FIG. 1.
~o The counter knife 30 has a bottom surface 36 in contact with the knifeseat platform 72, a top surface 34 for enydge",c:"~ by the bottom surface 13 of the knife body 10, an inner end 40 abutting a shoulder in the knife seat platform 72, a recess 42 to receive the head of the mounting screw 104, and longitudinal recesses 46 for pldcellle~ of i"L~I lochil ,~ means or keys 90 engaged between knife 10 and counter knife 30.
The double-edged knife 10 comprises a radially elongated body the opposite edges of which are cutting edges. The body of the knife has a top surface 11 and a bottom surface 13 as shown in FIG. 2. Each cutting edge has an upper surface 15 or 15', preferably a standing bevel at an obtuse angle to the 30 top surface 11, which projects beyond and preferably is inclined slightly relative to the plane of the disc. Each cutting edge addiLi~" ,..I'y has an underside or ~ ~ ~ 842Z8 s undersurface 17 or 17', which may be an under bevel. The in~ e~;~iun of the convergent upper surface and undersurface forms the cutting edge apex of the knife and the included angle between the upper surface and the undersurface def nes the wedge angle of the knife.
The knife further includes a chip breaker chip-deflecting surface 21 or 21' between the undersurface 17 or 17' and the bottom surface 13 of the knife which constitutes a heel or shoulder remote from the cutting edge of the knife. Such chip-deflecting surface 21 or 21' merges with the undersurface 17 or 17' of the knife cutting edge so as to form a dep~ ~ ,iun which may include a reentrant o angle as shown in FIG. 2 or a fillet as shown in FIG 5.
The inclination of the undersurface or underside 17 or 17' in relation to the bottom surface 13 of the knife may vary from 0 degrees (shown as the full line 17 in FIG. 2) to 20 degrees (shown as the dot-dash line 17" in FIG. 2), making the included angle between the knife bottom and the cutting edge from 180 degrees to 160 degrees. The inclination of the chip breaker shoulder or chip-deflecting surface 21 or 21' to the bottom surface 13 may vary from 20 degrees to 90 degrees, so that the included angle between the chip-deflecting surface and the bottom surface would be 160 de~rees to 90 de~rees as shown in FIG. 2, but should always be less than the included angle between the cutting 20 edge undersurface or underside 17 or 17' and the knife bottom surface 13 so that the surface 17 or 17' will be offset from the bottom surface 13 of the knife to form an undercut.
The purpose of the chip breaker and chip-deflecting surface 21 or 21 ' is to break apart chips cut by the cutting edge of the knife and to deflect the chips toward the discharge slot 106 and away from the beveled edge 32 of the knife holding means or counter knife 30 beneath the knife 10 so as to prevent chip material from wedging into the joint between the knife and the counter knife beneath the knife. The knife holding means edge 32 is set back from the chip-deflecting surface 21 or 21' so as to minimize the chip material striking the 30 knife holding means.
~ 218~2~8 Additionally, the knife cutting edge can include a small tip under bevel 19 or 19' between the cutting edge upper surface 15 and the cutting edge principal undersurface 17 or 17' to increase the wedge angle of the knife locally at the apex of the cutting edge.
While, as stated above, the wedge angle of the knife cutting edge can be selected between the line 17 and the line 17" shown in FIG. 2 or the wedge angle of the knife cutting edge can be increased at the tip as indicated by the line 19, the cutting edge formed between the upper surface 15 and the undersurface 17 may be selected as the optimum or most effective wedge angle o for a particular chipper knife. Under such circumstances it is desirable to beable to resharpen the chipper knife cutting edge without altering the original wedge angle. The type of resharpening shown in FIG. 4 does not change the blade cutting edge angle.
The degree of inclination of the chip-deflecting surface 21 or 21' could be altered during ~ l Idl l~eni"g of the cutting edge and thus affect the breaking force and chip deflection provided by contact of the chips with such surface. The setback of the heel of the chip-deflecting surface from the cutting edge could also be altered independently of the degree of narrowing of the knife effected by sharpening of the cutting edge, or could be ground to maintain the same amount ~o of setback afte m ~h dl ~ 1 ,ed by removing material from the upper surface 15 of the cutting edge as illustrated in FIG. 4.
R~:SIld~ I lil l9 of the chipper knife as shown in FIG. 4 requires shifting the blade transversely to a new position after each l ~h dl fJt~l lil l9. The grooves 46 in the top 34 of the counter knife 30 as shown in FIG. 1 are preferably of rectangular cross section and are arranged in sets. Typically each outer set closer to the ends 44 of the counter knife includes grooves 46' and each inner set farther from the ends 44 of the counter knife includes grooves 46" as shown in FIG. 3. The grooves 46' and 46" of both sets are parallel to the edge 32 of the counter knife 30 underlying the knife and parallel to the main longitudinal axis of 30 the counter knife. The grooves 46" of each inner set are staggered in relation to the grooves 46' of each outer set of grooves. The distance between adjacent ~ 2184228 grooves of each set can be very small, such as ~,uplu~ ly 1/8 of an inch on centers, and the offset distance between the centers of the grooves in one set and the centers of the grooves in the other set will be 1/16 of an inch if the grooves of one set are centered relative to the grooves of the other set as shown in FIG. 3.
The different sets of grooves 46' and 46" represent different positions for the knife 10 that is i"Lt:l locked with the counter knife 30 by keys 90 fitting in grooves 23 in the bottom 13 of thé knife as shown in FIG. 2 so as to enable the knife to be moved edgewise progressively co" ~:,,uu"di"g to small amounts of material, about 1/16 of an inch in width, i".,, t:",e, ll..lly removed from the knife cutting edge during l~l Idl ,U'3nil I~U as illustrated in FIG. 4 by grinding the upper surface 15 of the cutting edge. The original dull cutting edge is shown in dot-dash lines and the lu~ l,ut~ d cutting edge is shown in full lines.
Following I t~ha~ ~e"i, Ig of the knife, the il ~Lel locki, lg means or keys 90 would be, t l,o~iLiuned in the grooves of the counter knife 30 shown in FIGS. 1 and 3 to advance the now narrower knife by moving the knife transversely of its longitudinal axis and of its cutting edge.
Affer a knife edge has been l ~h dl ,Ut:l ,ed, the knife will be assembled with the counter knife as shown in FIG. 1 and two keys 90 will be placed in the knife20 grooves 23 and in cu"t~ ù"di"!J grooves 46' of the outer sets of counter knife grooves or in co" tl:~,UUI ,di"g grooves 46" of the inner sets of counter knife grooves in the top surface 34 of the counter knife 30, depending upon the desired degree of projection of the knife edge beyond the counter knife edge 32 as indicated in FIG. 1 and FIG. 4. Initially the keys will be placed in grooves 46' or 46" farther from the edge of the counter knife, and the keys will be moved toward the counter knife edge progressively, first in grooves 46', then in grooves 46", then back to adjacent grooves 46', until the knife edge has been -hdl ,uened as many times as there are grooves in a set 46' and in a set 46". Atthat point, the keys 90 will be located in the grooves 46' closest to the edge 32 of 30 the counter knife 30 as shown in FIG. 1.
~ 2 ~ 2 8 The dash-dot lines extending to the left of knife 10 in FIG. 1 represent the profile of a new knife prior to any use or regrinding. Subsequent regrinds make the knife narrower and narrower as both edges are, t,~l Idl ~:1 led until it is reduced to the knife 10 shown in solid lines in FIG. 1. Further shifting of the bladeedgewiseisnotpossibleafterthebladehasbeenl~:,l,d,~"~dtothefull line condition shown in FIG. 1.
Once the edges of the knife shown in solid lines in FIG. 1 are completely dulled, the knife is discarded, or the cutting edge can be, t:~l Idl ~ened further without requiring the knife to be shifted edgewise by utilizing the I ~al Idl ~eni"g technique illustrated in FIG. 6 where material is removed only from the underside of the cutting edge so that the depth of undercut formed by the undersurface 17 has been increased without changing the wedge angle between the upper surface and the undersurface 17 but such undersurface is narrower.
In such, t:~l Idl ~-e"i, Ig, the dullness of the cutting edge is removed withoutthe necessity of removing any material from the upper surface 15 of the cutting edge as in the type of l ~h dlfJ~I lil Ig illustrated in FIG. 4. In such resharpening a uniform layer of material is removed, preferably by grinding, in making or let:,ue"i"g the undercut so that the wedge angle of the cutting edge between theupper surface 15 and the new undersurface 17 is the same as the wedge angle 20 before such ~ l ,a" e"i"g. In this, t:~l Idl ~,e"i"g operation, the width of the upper surface 15 is reduced to some extent, but such width reduction does not adversely affect the effectiveness of the cutting edge and does not require edgewise advancing of the cutting edge after being l ~h dl ,J~I led in this manner.
Such l ~h dl ~ l lil l9 operation has simply reduced the extent of projection of the cutting edge of the knife beyond the body of the knife. In FIG. 6, the original undersurface of the knife cutting edge and the new undersurface after the first resharpening using this technique are shown in dot-dash lines, and the cutting edge resharpened for the second time using this technique is shown in full lines.
In FIG. 7 a single-edged chipper knife is shown. The shape of the cutting 30 edge of this chipper knife before being r t:sl Idl l~ened is similar to the shape of the cutting edges of the chipper knife shown in Salzmann, Jr. U.S. patent No.
~ 2184228 3,542,302, issued November 24, 1970. The knife of FIG. 7 has been resharpened in conventional fashion by grinding back only the upper bevel 15 and advancing the chipper knife transversely of its length to the right. A filler plug P of Babbitt metal has been inserted into the space thus produced between the inner edge of the knife and the bottom of the knife-holding socket to back the knife against inward movement resulting from the thrust produced on the cutting edge by its repeated impact with wood to be cut.
By utilizing the technique of the present invention, the knife cutting edge can be resharpened without requiring the knife to be shifted edgewise o transversely outward as discussed in uu~ euliun with FIG. 6. In such I ~shal ,ut:ni~ lg, material is removed only from the underside of the cutting edge to form a new undersurface 17 indicated by dot-dash lines in FIG. 7 with a chip-deflecting and chip breaker shoulder 21 at the end of the undercut remote from the cutting edge so that the cutting edge has a profile such as shown in FIG. 2.Moreover, in thus, t,~l Idl l,eni"g the cutting edge, the bluntness can be removed at least twice and perhaps three times by deepening the undercut successively as indicated by the dot-dash lines in FIG. 7.
FIG. 8 shows a different prior art type of double-edged chipper knife like that shown in Carpenter et al. U.S. patent No. 4,771,718, issued September 20, 1988, the Carpenter et al. U.S. patent No. 4,850,408, issued July 25, 1989 and the Carpenter et al. U.S. patent No. 4,997,018, issued March 5, 1991. It has notbeen possible heretofore to resharpen the cutting edges of this type of chipper knife because, after material was removed from the upper surface of a cutting edge in the manner shown in FIG. 4 of this I,, '; " " the type of knife holder used prevented the knife from being shifted edgewise to raise the cutting edge to its original, ~IdLion~ , to the clamp which holds the chipper knife in place.
Consequently the chipper knife could not be l~l,o~iLioned into a new effective cutting position after such, tl~l Idl 1~'3nil l~.
Each cutting edge of a chipper knife of the type shown in FIG. 8 can, however, be ~ l Idl ,U13n ed by utilizing the process of the present invention by undercutting the cutting edge to provide the recessed undersurface 17 shown in ~ 2~84228 ~o FIG. 9. To provide such an undercut, a layer of material of uniform thickness isremoved between the solid line 17 indicating the l ~h dl ~ l ,ed undersurface and the original undersurface shown in solid lines in FIG. 7 and FIG. 8 and in dot-dash lines in FIG. 9.
While such l ~h dl l,eni"g of the chipper blade by undercutting the cutting edge removes the dulled blunt tip of the cutting edge, the upper surface 15 of the cutting edge is not narrowed sufficiently to detract d,U,lJI t::CidLlly from the cutting effectiveness of the, ~sh~ ,ed cutting edge, even though the chipper knife has not been advanced edgewise. Moreover, such, ~Dh~ 1 lil l9 provides a chip o breaker shoulder 21 which improves the operation of the knife.
By using the same technique, the cutting edge of this type of chipper knife can be l ~h dl ~ 1 ,ed a second time by removing further material from the firsthdl l ~ned cutting edge shown in FIG. 9 to provide the cutting edge shown in FIG. 10 in which the second ~shd~ened undersurface 17 is shown in solid lines and the two previous undersurfaces are shown in dot-dash lines. Thus, instead of the double-edged chipper knife of FIG. 8 being discarded when both cutting edges have been dulled, each of the edges can be resharpened at least twice by utili~ing the present technique to increase greatly the useful life of the chipper knife.
Because the layer of material removed from the undersurface of the cutting edge is of uniform thickness in each instance, the wedge angle of the resharpened chipper knife cutting edge is the same as it was before even after such cutting edge has been l~:,h dl ~ ened twice.
FIG. 11 shows another double-edged chipper knife having cutting edges similar to the cutting edges of the chipper knives shown in the Carpenter patents referred to above, but this chipper knife assembly has a different type of knife-holding dl Idl Ig~,,,e, ,l. This figure shows one of the cutting edges having been resharpened by removing a layer of material from the underside of the cutting edge of uniform thickness so that the, t:~l Idl ~1~1 ,ed cutting edge has the same wedge angle as the original cutting edge, the original cutting edge undersurfacebeing indicated in dot-dash lines. Also, such undercut It:~hdl~ of the 218g228 cutting edge forms the shoulder 21 functioning as a chip-deflecting surface and chip breaker adjacent to the end 32 of the counter knife 30.
The chipper knife and its ~C$ori~l d holding means shown in FIG. 12 is of the type shown in Svensson United States patent No. 4,047,670, issued September 13, 1977 and in Holmberg et al. United States patent No. 4,694,995, issued September 22, 1987. The holding means for the offset cutting edge chipper knife of this type does not enable the knife to be shifted edgewise relative to the knife-holding means as required when a knife edge is sharpened by the technique illustrated in FIG. 4 and, consequently, such knives have not o been ~ hal l ened after both edges have become dull. The l ~h dl ,uel ,i"g method of the present invention enables each of the cutting edges of such a knife to be resharpened at least once, and perhaps twice or three times depending upon the amount of material removed from the underside of the cutting edge during each l~alldl~,ellillg.
FIG. 12 shows one of the offset cutting edges l~hd,~ened by having removed from its underside a layer of material of uniform thickness so that the wedge angle of the cutting edge is the same after it has been, ~l Idl ~ened as it was originally. Moreover, the undercutting of the cutting edge which forms the new undersurface 17 also forms the heel 21 which provides a chip-deflecting 20 surface and chip breaker as discussed in connection with the resharpened cutting edges of the chipper knives described above. While FIG. 12 shows only one cutting edge of the knife, t::,i Idl ,ue"ed, the other cutting edge of the knife could be l ~hagJ~I ,ed in a similar manner.
FIG. 13 shows both cutting edges of an offset double-edged chipper knife of the type shown in FIG. 12 I ~:,h dl ~ l led for a second time to provide the undersurface 17 shown in full lines. The locations of the original undersides ofthe cutting edges and of the undersides of the cutting edges after being resharpened for the first time are indicated in dot-dash lines. It will be noted that in none of these It:ah dl ~ 1 lil l9 ulJeldliolls is any material removed from the 30 upper side 15 of the cutting edge. By using the, t,~ , yeni"g technique of the present invention, it may be possible to resharpen a chipper knife cutting edge ~ 2~84228 twice or three times, dep~l Idi, ,9 upon how much material it is necessary to remove to remove the bluntness of the dulled cutting edge in each instance.
Also, it may be possible to increase the number of times such a chipper knife cutting edge is, ~sl1dl ,. ened by increasing the wedge angle of the cutting edge to some extent, but it is preferred to remove a layer of material of uniform thickness from the underside of the cutting edge during a I ~l Idl l~t:l lil l9 operation so as not to change the wedge angle of the cutting edge.
FIG. 14 shows a double-edged chipper knife and its ~sol,i,,lRd holding means of the type shown in Haller et al. United States patent No. 4,423,758, o issued January 3, 1984, Demopoulos United States patent No. 4,503,893, issued March 12, 1985, and Haller United States patent No. 4,351,487, issued September 28, 1982. In this type of cutting edge, the included angle between the bottom of the knife and the underside of the cutting edge is less than 180 degrees, perhaps 160 degrees or 162 degrees, for example. When such a cutting edge is re~l Idl ~J~I ,ed according to the present invention, again it is preferred that a layer of material of uniform thickness be removed from the underside of the cutting edge, as indicated in FIG. 14, but the layer removed again does not extend to the bottom of the knife. Instead the I t:5hdl ~-ened cutting edge L~l lllil Idle:s in a shoulder 21 so that the location of the cutting edge 20 heel on the bottom of the knife is not dl.lpl t:CidL)ly changed by the, t~ a~ I,e"i"9 and it is not necessary to shift the knife edgewise relative to its holding means after such I ~shdl l,e"i"g.
Again, the, t:sl ,a"~"i"g operation can be effected at least twice and perhaps three times for each cutting ed~e, as indicated by the dot-dash lines inFIG. 15 which shows a cutting edge that has been ,t,~l,d"..e,led twice without changing the wedge angle or shifting the knife edgewise. Both of the cutting edges of this double-edged knife can be l~l Idl~C~I ,ed in a similar manner to extend the life of the chipper knife
This invention relates to a method for ~1 Idl ~t:l lil ,g knives used in wood chippers such as a rotatable disc type in which the disc carries a plurality of circ~""rer~nli~lly spaced radial knives alongside chip-discharge openings through the disc.
Wood chippers having rotatable cutters, or drums, or rotatable chipping discs fltted with double-edged knives are known.
One aspect of the geometry of chipper knives is that knives having a large o wedge angle, i.e., the angle between the two surfaces converging to the cutting edge, remain sharper longer and therefore are more popular. However, the larger wedge angles are more likely to cut a chip by shearing the chip from the incoming material rather than by cleavage. More force is required to sever chipsby shearing than by cleavage, and thus more power is required to operate a disc chipper having knives with larger wedge angles.
Another problem is the pt:n~ll dliUIl of chip particles between the knife and the knife holding means beneath the knife, typically a counter knife, that can cause excessive pressure on the knife which may bend it outwardly sufficiently to hit the anvil.
The principal object of the invention is to provide a new method of :~hdl ~ e"i"g chipper knives which is particularly valuable fo m ~ha, 1~l ,i"g various types of chipper knives so that a cutting edge can be ~,ondiliul ,ed for use oneor more times instead of being unusable after it has been dulled the first time by use.
A further object is to provide a chip deflector and chip breaker which is integral with a cutting edge of a chipper knife.
The benefits of the present invention can be achieved by a method of I ~:7hdl ,~JC~I lil l9 a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises undercutting the underside of the cutting edge by removing material and thereby removing the bluntness of the dulled cutting edge and forming a chip breaker .
~ 218~228 shoulder remote from the cutting edge apex which is integral with the chipper knife.
Also the benefits can be achieved by a method of, t,~l Idl ~ I lil l9 a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex and having a chip breaker shoulder in the underside remote from the cutting edge apex, which comprises removing material from the upper surface of the cutting edge and thereby removing the bluntness of the dulled cutting edge and removing material from the cutting edgeunderside shoulder to maintain the cutting edge underside between the cutting o edge apex and the shoulder dlJpl~AillldLely the same width as the width of thecutting edge underside prior to the cutting edge being 1 ~h dl ~I.ened.
In addition, the benefits can be achieved by a method of resharpening a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises forming an undercut having a chip-breaking shoulder remote from the cutting edge apex which is integral with the chipper knife by removing material only from the underside of the cutting edge and thereby removing the bluntness of the dulled cutting edge.
The invention provides a novel knife and knife-holding means for a chipper. The knife is double-edged, each cutting edge ~Ill,ni~ g an upper ~o surface, preferably a standing bevel, and an undersurface, which surfaces converge and intersect to form a cutting edge. Additionally the knife includes achip-deflecting surface forming the heel or part of the cutting edge undersurface remote from the cutting edge apex which constitutes a chip breaker that deflectsand breaks chip material cut by the knife cutting edge. This chip breaker deflects the chips so as to prevent the pen~l, dlion of chip particles between the knife and the knife holding means beneath the knife, such as a counter knife, and preferably so that the chips do not strike the knife holding means which ;It:..l ~ases wear on the knife holding means.
In drawings that illustrate the e"ll.odi",t:"t~ of the invention:
~ 21~228 FIG. 1 is a r, d911 lel ILdl y cross section through a portion of a disc chippershowing a double-edged chipper knife and its ~ ~,o. ~ d holding means which knife has been narrowed by, t:~l Idl ~l lil ,g.
FIG. 2 is an enlarged cross section of a double-edged chipper knife similar to that shown in FIG.1 and its ~sor.i..l.-d holding means.
FIG. 3 is a partial top plan of the counter knife used in the knife holding means of FIG. 1.
FIG. 4 is an enlarged cross section of a chipper knife cutting edge which has been 1 ~h dl ~ l ,ed.
0FIG. 5 is an enlarged cross section of a chipper knife similar to that shown in FIG. 2 but having a slightly modified shape.
FIG. 6 is a cross section of a chipper knife like that shown in FIG. 2 but which has been ~ ,I ,a, l,ened.
FIG. 7 is a cross section of a single-edged chipper knife and its ~csorj..lQd holding means.
FIG. 8 is a cross section of a prior art double-edged chipper knife and its so-; ,1, d holding means.
FIG. 9 is an enlarged rldL~IIIellLdly cross section of a portion of the chipper knife shown in FIG. 8 which has been, t:~l Idl ~-ened once; and FIG.10 is a similar cross section of a cutting edge of the chipper knife which has been, ~al Idl ~ened twice.
FIG.11 is a cross section of a double-edged chipper knife and its holding means of a different type one edge of which has been, t:~l Idl ,IJt:l ,ed once.
FIG. 12 is a cross section of a double-edged chipper knife and its . .;.~l~d holding means of still a different type one cutting edge of which has been It:sh dl ~-ened once; and FIG. 13 is an enlarged cross section of the same type of chipper knife which has been 1 ~h dl ~ l ,ed twice.
FIG. 14 is a cross section of a double-edged chipper knife and acsor~ d holding means of a still different type one cutting edge of which has been 30 It:~h a,~"ed and FIG. 15 is an enlarged cross section of the same type of chipper knife showing both cutting edges having been, ~I ,d, ~ned twice.
218~228 A chipper knife sharpened according to the present invention is illustrated as being used in a disc type wood or log chipper in FIG. 1, but such a knife could be used in a drum chipper or rotary knife chipper. The materials to be chipped, such as logs, are fed at an an31e to the rotating disc. The chips pass from the knives through radially elongated openings 106 in the disc 92 adjacent to the knives to be expelled from the chipper.
Knife a5st1ll "ies are carried by the disc 92 at circu",r~ lly spaced locations. Each knife assembly includes a knife 10 elongated radially or a radial series of knife sections placed end to end, and knife holding means including o knife seat 70, counter knife 30, and knife clamp 50. Each knife assembly is disposed in a recess 94 in disc 92 adjacent to a radially elongated opening 106 through the disc. The knife seat has an elongated body with a plafform 72 thereon for place~ l ~e~ l~ of the counter knife 30, and a support 74 for the knife clamp 50. The platform 72 has in it a blind bore threaded to receive a fastener such as a cap screw 104 for mounting the counter knife.
The knife is held in position by the knife clamp 50 as shown in FIG. 1.
The knife clamp has a knife en~age",el ,l surface 54 contacting the knife top surface 11. The knife clamp is secured to the disc 92 by a fastener such as a screw 102 as shown in FIG. 1.
~o The counter knife 30 has a bottom surface 36 in contact with the knifeseat platform 72, a top surface 34 for enydge",c:"~ by the bottom surface 13 of the knife body 10, an inner end 40 abutting a shoulder in the knife seat platform 72, a recess 42 to receive the head of the mounting screw 104, and longitudinal recesses 46 for pldcellle~ of i"L~I lochil ,~ means or keys 90 engaged between knife 10 and counter knife 30.
The double-edged knife 10 comprises a radially elongated body the opposite edges of which are cutting edges. The body of the knife has a top surface 11 and a bottom surface 13 as shown in FIG. 2. Each cutting edge has an upper surface 15 or 15', preferably a standing bevel at an obtuse angle to the 30 top surface 11, which projects beyond and preferably is inclined slightly relative to the plane of the disc. Each cutting edge addiLi~" ,..I'y has an underside or ~ ~ ~ 842Z8 s undersurface 17 or 17', which may be an under bevel. The in~ e~;~iun of the convergent upper surface and undersurface forms the cutting edge apex of the knife and the included angle between the upper surface and the undersurface def nes the wedge angle of the knife.
The knife further includes a chip breaker chip-deflecting surface 21 or 21' between the undersurface 17 or 17' and the bottom surface 13 of the knife which constitutes a heel or shoulder remote from the cutting edge of the knife. Such chip-deflecting surface 21 or 21' merges with the undersurface 17 or 17' of the knife cutting edge so as to form a dep~ ~ ,iun which may include a reentrant o angle as shown in FIG. 2 or a fillet as shown in FIG 5.
The inclination of the undersurface or underside 17 or 17' in relation to the bottom surface 13 of the knife may vary from 0 degrees (shown as the full line 17 in FIG. 2) to 20 degrees (shown as the dot-dash line 17" in FIG. 2), making the included angle between the knife bottom and the cutting edge from 180 degrees to 160 degrees. The inclination of the chip breaker shoulder or chip-deflecting surface 21 or 21' to the bottom surface 13 may vary from 20 degrees to 90 degrees, so that the included angle between the chip-deflecting surface and the bottom surface would be 160 de~rees to 90 de~rees as shown in FIG. 2, but should always be less than the included angle between the cutting 20 edge undersurface or underside 17 or 17' and the knife bottom surface 13 so that the surface 17 or 17' will be offset from the bottom surface 13 of the knife to form an undercut.
The purpose of the chip breaker and chip-deflecting surface 21 or 21 ' is to break apart chips cut by the cutting edge of the knife and to deflect the chips toward the discharge slot 106 and away from the beveled edge 32 of the knife holding means or counter knife 30 beneath the knife 10 so as to prevent chip material from wedging into the joint between the knife and the counter knife beneath the knife. The knife holding means edge 32 is set back from the chip-deflecting surface 21 or 21' so as to minimize the chip material striking the 30 knife holding means.
~ 218~2~8 Additionally, the knife cutting edge can include a small tip under bevel 19 or 19' between the cutting edge upper surface 15 and the cutting edge principal undersurface 17 or 17' to increase the wedge angle of the knife locally at the apex of the cutting edge.
While, as stated above, the wedge angle of the knife cutting edge can be selected between the line 17 and the line 17" shown in FIG. 2 or the wedge angle of the knife cutting edge can be increased at the tip as indicated by the line 19, the cutting edge formed between the upper surface 15 and the undersurface 17 may be selected as the optimum or most effective wedge angle o for a particular chipper knife. Under such circumstances it is desirable to beable to resharpen the chipper knife cutting edge without altering the original wedge angle. The type of resharpening shown in FIG. 4 does not change the blade cutting edge angle.
The degree of inclination of the chip-deflecting surface 21 or 21' could be altered during ~ l Idl l~eni"g of the cutting edge and thus affect the breaking force and chip deflection provided by contact of the chips with such surface. The setback of the heel of the chip-deflecting surface from the cutting edge could also be altered independently of the degree of narrowing of the knife effected by sharpening of the cutting edge, or could be ground to maintain the same amount ~o of setback afte m ~h dl ~ 1 ,ed by removing material from the upper surface 15 of the cutting edge as illustrated in FIG. 4.
R~:SIld~ I lil l9 of the chipper knife as shown in FIG. 4 requires shifting the blade transversely to a new position after each l ~h dl fJt~l lil l9. The grooves 46 in the top 34 of the counter knife 30 as shown in FIG. 1 are preferably of rectangular cross section and are arranged in sets. Typically each outer set closer to the ends 44 of the counter knife includes grooves 46' and each inner set farther from the ends 44 of the counter knife includes grooves 46" as shown in FIG. 3. The grooves 46' and 46" of both sets are parallel to the edge 32 of the counter knife 30 underlying the knife and parallel to the main longitudinal axis of 30 the counter knife. The grooves 46" of each inner set are staggered in relation to the grooves 46' of each outer set of grooves. The distance between adjacent ~ 2184228 grooves of each set can be very small, such as ~,uplu~ ly 1/8 of an inch on centers, and the offset distance between the centers of the grooves in one set and the centers of the grooves in the other set will be 1/16 of an inch if the grooves of one set are centered relative to the grooves of the other set as shown in FIG. 3.
The different sets of grooves 46' and 46" represent different positions for the knife 10 that is i"Lt:l locked with the counter knife 30 by keys 90 fitting in grooves 23 in the bottom 13 of thé knife as shown in FIG. 2 so as to enable the knife to be moved edgewise progressively co" ~:,,uu"di"g to small amounts of material, about 1/16 of an inch in width, i".,, t:",e, ll..lly removed from the knife cutting edge during l~l Idl ,U'3nil I~U as illustrated in FIG. 4 by grinding the upper surface 15 of the cutting edge. The original dull cutting edge is shown in dot-dash lines and the lu~ l,ut~ d cutting edge is shown in full lines.
Following I t~ha~ ~e"i, Ig of the knife, the il ~Lel locki, lg means or keys 90 would be, t l,o~iLiuned in the grooves of the counter knife 30 shown in FIGS. 1 and 3 to advance the now narrower knife by moving the knife transversely of its longitudinal axis and of its cutting edge.
Affer a knife edge has been l ~h dl ,Ut:l ,ed, the knife will be assembled with the counter knife as shown in FIG. 1 and two keys 90 will be placed in the knife20 grooves 23 and in cu"t~ ù"di"!J grooves 46' of the outer sets of counter knife grooves or in co" tl:~,UUI ,di"g grooves 46" of the inner sets of counter knife grooves in the top surface 34 of the counter knife 30, depending upon the desired degree of projection of the knife edge beyond the counter knife edge 32 as indicated in FIG. 1 and FIG. 4. Initially the keys will be placed in grooves 46' or 46" farther from the edge of the counter knife, and the keys will be moved toward the counter knife edge progressively, first in grooves 46', then in grooves 46", then back to adjacent grooves 46', until the knife edge has been -hdl ,uened as many times as there are grooves in a set 46' and in a set 46". Atthat point, the keys 90 will be located in the grooves 46' closest to the edge 32 of 30 the counter knife 30 as shown in FIG. 1.
~ 2 ~ 2 8 The dash-dot lines extending to the left of knife 10 in FIG. 1 represent the profile of a new knife prior to any use or regrinding. Subsequent regrinds make the knife narrower and narrower as both edges are, t,~l Idl ~:1 led until it is reduced to the knife 10 shown in solid lines in FIG. 1. Further shifting of the bladeedgewiseisnotpossibleafterthebladehasbeenl~:,l,d,~"~dtothefull line condition shown in FIG. 1.
Once the edges of the knife shown in solid lines in FIG. 1 are completely dulled, the knife is discarded, or the cutting edge can be, t:~l Idl ~ened further without requiring the knife to be shifted edgewise by utilizing the I ~al Idl ~eni"g technique illustrated in FIG. 6 where material is removed only from the underside of the cutting edge so that the depth of undercut formed by the undersurface 17 has been increased without changing the wedge angle between the upper surface and the undersurface 17 but such undersurface is narrower.
In such, t:~l Idl ~-e"i, Ig, the dullness of the cutting edge is removed withoutthe necessity of removing any material from the upper surface 15 of the cutting edge as in the type of l ~h dlfJ~I lil Ig illustrated in FIG. 4. In such resharpening a uniform layer of material is removed, preferably by grinding, in making or let:,ue"i"g the undercut so that the wedge angle of the cutting edge between theupper surface 15 and the new undersurface 17 is the same as the wedge angle 20 before such ~ l ,a" e"i"g. In this, t:~l Idl ~,e"i"g operation, the width of the upper surface 15 is reduced to some extent, but such width reduction does not adversely affect the effectiveness of the cutting edge and does not require edgewise advancing of the cutting edge after being l ~h dl ,J~I led in this manner.
Such l ~h dl ~ l lil l9 operation has simply reduced the extent of projection of the cutting edge of the knife beyond the body of the knife. In FIG. 6, the original undersurface of the knife cutting edge and the new undersurface after the first resharpening using this technique are shown in dot-dash lines, and the cutting edge resharpened for the second time using this technique is shown in full lines.
In FIG. 7 a single-edged chipper knife is shown. The shape of the cutting 30 edge of this chipper knife before being r t:sl Idl l~ened is similar to the shape of the cutting edges of the chipper knife shown in Salzmann, Jr. U.S. patent No.
~ 2184228 3,542,302, issued November 24, 1970. The knife of FIG. 7 has been resharpened in conventional fashion by grinding back only the upper bevel 15 and advancing the chipper knife transversely of its length to the right. A filler plug P of Babbitt metal has been inserted into the space thus produced between the inner edge of the knife and the bottom of the knife-holding socket to back the knife against inward movement resulting from the thrust produced on the cutting edge by its repeated impact with wood to be cut.
By utilizing the technique of the present invention, the knife cutting edge can be resharpened without requiring the knife to be shifted edgewise o transversely outward as discussed in uu~ euliun with FIG. 6. In such I ~shal ,ut:ni~ lg, material is removed only from the underside of the cutting edge to form a new undersurface 17 indicated by dot-dash lines in FIG. 7 with a chip-deflecting and chip breaker shoulder 21 at the end of the undercut remote from the cutting edge so that the cutting edge has a profile such as shown in FIG. 2.Moreover, in thus, t,~l Idl l,eni"g the cutting edge, the bluntness can be removed at least twice and perhaps three times by deepening the undercut successively as indicated by the dot-dash lines in FIG. 7.
FIG. 8 shows a different prior art type of double-edged chipper knife like that shown in Carpenter et al. U.S. patent No. 4,771,718, issued September 20, 1988, the Carpenter et al. U.S. patent No. 4,850,408, issued July 25, 1989 and the Carpenter et al. U.S. patent No. 4,997,018, issued March 5, 1991. It has notbeen possible heretofore to resharpen the cutting edges of this type of chipper knife because, after material was removed from the upper surface of a cutting edge in the manner shown in FIG. 4 of this I,, '; " " the type of knife holder used prevented the knife from being shifted edgewise to raise the cutting edge to its original, ~IdLion~ , to the clamp which holds the chipper knife in place.
Consequently the chipper knife could not be l~l,o~iLioned into a new effective cutting position after such, tl~l Idl 1~'3nil l~.
Each cutting edge of a chipper knife of the type shown in FIG. 8 can, however, be ~ l Idl ,U13n ed by utilizing the process of the present invention by undercutting the cutting edge to provide the recessed undersurface 17 shown in ~ 2~84228 ~o FIG. 9. To provide such an undercut, a layer of material of uniform thickness isremoved between the solid line 17 indicating the l ~h dl ~ l ,ed undersurface and the original undersurface shown in solid lines in FIG. 7 and FIG. 8 and in dot-dash lines in FIG. 9.
While such l ~h dl l,eni"g of the chipper blade by undercutting the cutting edge removes the dulled blunt tip of the cutting edge, the upper surface 15 of the cutting edge is not narrowed sufficiently to detract d,U,lJI t::CidLlly from the cutting effectiveness of the, ~sh~ ,ed cutting edge, even though the chipper knife has not been advanced edgewise. Moreover, such, ~Dh~ 1 lil l9 provides a chip o breaker shoulder 21 which improves the operation of the knife.
By using the same technique, the cutting edge of this type of chipper knife can be l ~h dl ~ 1 ,ed a second time by removing further material from the firsthdl l ~ned cutting edge shown in FIG. 9 to provide the cutting edge shown in FIG. 10 in which the second ~shd~ened undersurface 17 is shown in solid lines and the two previous undersurfaces are shown in dot-dash lines. Thus, instead of the double-edged chipper knife of FIG. 8 being discarded when both cutting edges have been dulled, each of the edges can be resharpened at least twice by utili~ing the present technique to increase greatly the useful life of the chipper knife.
Because the layer of material removed from the undersurface of the cutting edge is of uniform thickness in each instance, the wedge angle of the resharpened chipper knife cutting edge is the same as it was before even after such cutting edge has been l~:,h dl ~ ened twice.
FIG. 11 shows another double-edged chipper knife having cutting edges similar to the cutting edges of the chipper knives shown in the Carpenter patents referred to above, but this chipper knife assembly has a different type of knife-holding dl Idl Ig~,,,e, ,l. This figure shows one of the cutting edges having been resharpened by removing a layer of material from the underside of the cutting edge of uniform thickness so that the, t:~l Idl ~1~1 ,ed cutting edge has the same wedge angle as the original cutting edge, the original cutting edge undersurfacebeing indicated in dot-dash lines. Also, such undercut It:~hdl~ of the 218g228 cutting edge forms the shoulder 21 functioning as a chip-deflecting surface and chip breaker adjacent to the end 32 of the counter knife 30.
The chipper knife and its ~C$ori~l d holding means shown in FIG. 12 is of the type shown in Svensson United States patent No. 4,047,670, issued September 13, 1977 and in Holmberg et al. United States patent No. 4,694,995, issued September 22, 1987. The holding means for the offset cutting edge chipper knife of this type does not enable the knife to be shifted edgewise relative to the knife-holding means as required when a knife edge is sharpened by the technique illustrated in FIG. 4 and, consequently, such knives have not o been ~ hal l ened after both edges have become dull. The l ~h dl ,uel ,i"g method of the present invention enables each of the cutting edges of such a knife to be resharpened at least once, and perhaps twice or three times depending upon the amount of material removed from the underside of the cutting edge during each l~alldl~,ellillg.
FIG. 12 shows one of the offset cutting edges l~hd,~ened by having removed from its underside a layer of material of uniform thickness so that the wedge angle of the cutting edge is the same after it has been, ~l Idl ~ened as it was originally. Moreover, the undercutting of the cutting edge which forms the new undersurface 17 also forms the heel 21 which provides a chip-deflecting 20 surface and chip breaker as discussed in connection with the resharpened cutting edges of the chipper knives described above. While FIG. 12 shows only one cutting edge of the knife, t::,i Idl ,ue"ed, the other cutting edge of the knife could be l ~hagJ~I ,ed in a similar manner.
FIG. 13 shows both cutting edges of an offset double-edged chipper knife of the type shown in FIG. 12 I ~:,h dl ~ l led for a second time to provide the undersurface 17 shown in full lines. The locations of the original undersides ofthe cutting edges and of the undersides of the cutting edges after being resharpened for the first time are indicated in dot-dash lines. It will be noted that in none of these It:ah dl ~ 1 lil l9 ulJeldliolls is any material removed from the 30 upper side 15 of the cutting edge. By using the, t,~ , yeni"g technique of the present invention, it may be possible to resharpen a chipper knife cutting edge ~ 2~84228 twice or three times, dep~l Idi, ,9 upon how much material it is necessary to remove to remove the bluntness of the dulled cutting edge in each instance.
Also, it may be possible to increase the number of times such a chipper knife cutting edge is, ~sl1dl ,. ened by increasing the wedge angle of the cutting edge to some extent, but it is preferred to remove a layer of material of uniform thickness from the underside of the cutting edge during a I ~l Idl l~t:l lil l9 operation so as not to change the wedge angle of the cutting edge.
FIG. 14 shows a double-edged chipper knife and its ~sol,i,,lRd holding means of the type shown in Haller et al. United States patent No. 4,423,758, o issued January 3, 1984, Demopoulos United States patent No. 4,503,893, issued March 12, 1985, and Haller United States patent No. 4,351,487, issued September 28, 1982. In this type of cutting edge, the included angle between the bottom of the knife and the underside of the cutting edge is less than 180 degrees, perhaps 160 degrees or 162 degrees, for example. When such a cutting edge is re~l Idl ~J~I ,ed according to the present invention, again it is preferred that a layer of material of uniform thickness be removed from the underside of the cutting edge, as indicated in FIG. 14, but the layer removed again does not extend to the bottom of the knife. Instead the I t:5hdl ~-ened cutting edge L~l lllil Idle:s in a shoulder 21 so that the location of the cutting edge 20 heel on the bottom of the knife is not dl.lpl t:CidL)ly changed by the, t~ a~ I,e"i"9 and it is not necessary to shift the knife edgewise relative to its holding means after such I ~shdl l,e"i"g.
Again, the, t:sl ,a"~"i"g operation can be effected at least twice and perhaps three times for each cutting ed~e, as indicated by the dot-dash lines inFIG. 15 which shows a cutting edge that has been ,t,~l,d"..e,led twice without changing the wedge angle or shifting the knife edgewise. Both of the cutting edges of this double-edged knife can be l~l Idl~C~I ,ed in a similar manner to extend the life of the chipper knife
Claims (7)
1. A method of resharpening a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises undercutting the underside of the cutting edge by removing material and thereby removing the bluntness of the dulled cutting edge and forming a chip breaker shoulder remote from the cutting edge apex which is integral with the chipper knife.
2. The method of resharpening defined in claim 1, including removing a layer of material from the underside of the cutting edge of substantially uniform thickness and thereby preserving in the resharpened cutting edge substantially the same wedge angle as the cutting edge had prior to being resharpened.
3. The method of resharpening defined in claim 1 or 2, including resharpening a cutting edge which has been previously sharpened to provide a shoulder remote from the cutting edge apex which comprises removing a further layer of material from the underside of the cutting edge and thereby increasing the width of the shoulder.
4. The method of resharpening a chipper knife defined in claim 1 or 2, which chipper knife is adapted to be held in a chipper by supporting means, including resharpening a cutting edge which has been sharpened previously by removing a further layer of material from the underside of the cutting edge and thereby reducing the width of the upper surface and of the underside of the cutting edge between the shoulder and the cutting edge apex, whereby it is unnecessary to reposition the chipper knife edgewise relative to its supporting means after such resharpening.
5. A method of resharpening a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex and having a chip breaker shoulder in the underside remote from the cutting edge apex, which comprises removing material from the upper surface of the cutting edge and thereby removing the bluntness of the dulled cutting edge and removing material from the cutting edge underside shoulder to maintain the cutting edge underside between the cutting edge apex and the shoulder approximately the same width as the width of the cutting edge underside prior tothe cutting edge being resharpened.
6. A method of resharpening a dulled cutting edge of a chipper knife having an upper surface and an underside converging to a cutting edge apex which comprises forming an undercut having a chip-breaking shoulder remote from the cutting edge apex which is integral with the chipper knife by removing material only from the underside of the cutting edge and thereby removing the bluntness of the dulled cutting edge.
7. The method defined in claim 6, including further resharpening the cutting edge by removing additional material from the underside of the cutting edge to deepen the undercut in the underside of the cutting edge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184228A CA2184228C (en) | 1996-08-27 | 1996-08-27 | Method for sharpening a chipper knife |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184228A CA2184228C (en) | 1996-08-27 | 1996-08-27 | Method for sharpening a chipper knife |
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| Publication Number | Publication Date |
|---|---|
| CA2184228A1 CA2184228A1 (en) | 1998-02-28 |
| CA2184228C true CA2184228C (en) | 1999-03-23 |
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| CA002184228A Expired - Fee Related CA2184228C (en) | 1996-08-27 | 1996-08-27 | Method for sharpening a chipper knife |
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| CA2686678C (en) | 2002-01-17 | 2013-05-28 | Iggesund Tools Ab | Method for the simultaneous sharpening of opposed cutting edges |
| CN111185942B (en) * | 2020-02-25 | 2023-10-27 | 深圳市誉和光学精密刀具有限公司 | Cutter and processing method thereof |
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