US3860051A

US3860051A - Chipper cutter and holders therefor

Info

Publication number: US3860051A
Application number: US251519A
Authority: US
Inventors: I Anson Anson
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-24
Filing date: 1972-05-08
Publication date: 1975-01-14
Anticipated expiration: 1992-01-14

Abstract

When installed on the cylindrical cutter surface of the chipper drum, the cutter presents a knife having an arcuate cutting edge thereon, the relatively concave face of which is described by a surface revolution, and the relatively convex face of which has a plurality of facets described by angularly successive pairs of dihedral planes passing through the concave face of the edge at acute angles thereto, so that the edge is scalloped in outline. The knife is formed on an annular blade having a plurality of such knives at angularly spaced locations thereabout; and the blade is defined by one end edge portion of an elongated tubular element which is installed in either a socket-like holder or a saddle-like holder, having means thereon whereby the element can be alternately releasably interlocked with the holder in a relative longitudinal position presenting one knife, or released and rotated to present another knife, in the same or a different such position.

Description

United States Patent [191 Anson Jan. 14, 1975 [54] CHIPPER CUTTER AND HOLDERS THEREFOR [76] Inventor: IAnson Anson, 4014 Hunts Point Rd., Bellevue, Wash. 98004 [22] Filed: May 8, 1972 [21] Appl. No.: 251,519

Related US. Application Data [62] Division of Ser. No. 75,154, Sept. 24, 1970, Pat. No.

[52] US. Cl 144/172, 144/241, 241/93 [51] Int. Cl B27l 11/02 [58] Field of Search...... 144/172, 162, 241; 83/831; 241/91, 93, 293

[56] References Cited UNITED STATES PATENTS 2,746,494 5/1956 Cox 83/831 3,327,746 6/1967 Andrus et a1. 144/241 3,661,192 5/1972 Nicholson et al 144/172 Primary Examiner-Donald R. Schran Attorney, Agent, or Firm-Christensen, OConnor, Garrison & Havelka [5 7] ABSTRACT spaced locations thereabout; and the blade is defined by one end edge portion of an elongated tubular element which is installed in either a socket-like holder or a saddle-like holder, having means thereon whereby the element can be alternately releasably interlocked with the holder in a relative longitudinal position presenting one knife, or released and rotated to present another knife, in the same or a different such position.

26 Claims, 19 Drawing Figures g ll z 6:7 -24 PATENTEU JAN 1 41915 sum 10F 4 CHIPPER CUTTER AND HOLDERS THEREFOR CROSS-REFERENCE TO RELATED APPLICATION This application is a division of a copending application entitled CHIPPER CUTTER AND HOLDERS THEREFOR, Thomas IAnson, application Ser. No. 75,154, filed Sept. 24, 1970, now US. Pat. No. 3,675,693.

FIELD OF THE INVENTION This invention relates to cutter elements and cutter assemblies for rotary chipper drums; and in particular, to elements and assemblies of this nature which are individually equipped with two or more knives that can be alternately or interchangeably presented to the woodstock.

Background of the Invention Including Certain Objects Thereof In the wood reduction industry, so-called chipper drums are employed to reduce pieces of woodstock such as peeler cores or lily pads, to a mass of elongated chips, which may or may not be subjected to further reduction thereafter. The drums are generally mounted on inclined axes, and equipped with a series of helically staggered, transversely oriented cutter elements on the outside cylindrical surfaces thereof. The cutter elements have knives thereon which project relatively outwardly from the surfaces of the drums, so as to progressively longitudinally strip the outlines of the pieces of woodstock as they are fed radially inwardly of the drums while resting on anvils in longitudinally juxtaposed positions adjacent thereto. heretofore the knives have had an angularly arcuate cutting edge which is rectilinear in outline and characterized with a plurality of facets on each face thereof, described by angularly successive pairs of dihedral planes meeting at acute angles to one another, from one face to the other, to give the knives a channel-like configuration when viewed on edge. Such a configuration has not proven to be particularly durable, however, since the cutting edges are considerably weakened by the angled form of the inside or relatively concave faces of the edges, and it has been found that the cutter elements must be frequently removed from the drum sometimes even more frequently than once a day to resharpen or replace them when they become dull or broken as a result of the punishment they receive in use. Not only is it costly and time consuming to have to resharpen or replace the elements with this frequency; but in addition, the resharpening operation itself is further complicated by the necessity for grinding and polishing the inside faces of the knives first, that is, before the outside faces are ground and polished, in order to provide a reference against which to determine the bevel given the outside faces of the knives. The resharpening operation is also complicated by the fact that the cutter elements must be set up in three different positions when grinding the knives; and then backed up with babbitting or the like when they are returned to the drum, in order to compensate for the loss of reach in the cut of the knives, due to the loss of metal in the grinding operation. The channel-shaped configuration of the knives also tends to cause the stripped wood material to undergo curling as it exits through the cutter elements into the drum; and moreover, renders the cutter elements difficult to mount in the drum, and particularly to hold or fix in position and orientation so that they will not degenerate the chip form by working themselves loose in their mountings.

With this in mind, one object of the present invention is to provide a cutter element which presents a knife having a stronger and more durable edge configuration, and one which is also less susceptible to breakage than the edge configurations of the prior art elements. Another object is to provide a cutter element of this nature which presents a knife having an edge configuration that is cheaper and easier to obtain, and also more easily and cheaply resharpened, so that the elements can be returned to the drum more quickly, and at lower cost, than were the prior art elements. A further object is to provide a cutter element of this nature which produces a better and more efficient cutting action, and which is easier to mount or install on the drum, and to hold in place during the resharpening operation; and which moreover is adapted to be more readily and securely returned to its proper position and orientation on the drum, from points outside thereof, and without the necessity for using babbitting or the like to compensate for the grinding operation. Still another object is to provide a cutter element of this nature which presents a knife having an edge configuration that lends itself to honing techniques for resharpening; and which has a reduced number of facets to be resharpened; and the inherent capacity to maintain substantially its original edge thickness when resharpened. A still further object is to provide a cutter element of this nature which lends itself to the provision of two or more knives on the same element, or in the same assembly; and moreover, to the provision of such an element or assembly which has a plurality of knives that can be alternately or interchangeably presented to the woodstock, as for example, by shifting the respective element and a holder for the same, in relation to one another, on the surface of the drum. Other objects include the provision of a cutter and holder assembly of this nature which enables the cutter element to be alternately fixed and shifted with respect to the holder, with equal ease and speed, and to be firmly secured in the relatively fixed position thereof, without causing interference to the cutting operation, nor to the steady flow of the wood strips and chips therethrough. They also include the provision of an assembly of this nature in which the holder for the cutter element may comprise one or more components which are also serviceable in the resharpening operation, as for example, in holding the cutter element in place during the same. Still further objects will become apparent from the description of the invention which follows hereafter.

SUMMARY OF THE INVENTION These objects and advantages are realized by a chipper cutter of my invention which presents or projects a knife to the woodstock, having an arcuate cutting edge thereon, the relatively concave face of which is described by a surface of revolution, as for example, a conical or cylindrical surface of revolution. Preferably, the relatively concave face of the edge extends over a continuous arcuate course bounded by the cylindrical surface plane of the drum; and is curvilinear in outline, as for example, where the relatively convex face of the edge has a plurality of facets thereon, described by angularly successive pairs of dihedral planes passing through the concave face of the edge at acute angles thereto, so that the edge is scalloped in outline.

The knives project relatively outwardly from the surface of the drum on axes of revolution coincident with progressively helically advanced chords of the drum. Those facets of the relatively convex faces of the edges which traverse the cross-sectional planes of the drum coincident with the chords, are disposed in planes which extend substantially parallel to the cylindrical surface plane of the drum; and the facets adjacent thereto are disposed in planes which extend at equal obtuse angles thereto and intersect the cylindrical surface plane of the drum.

Each knife is defined by an annular cutter blade that is seated in a recess in the surface of the drum, and equipped with a plurality of similar knives thereon, at angularly spaced locations thereabout. The blade is rotatable about the axis thereof between a plurality of angular orientations corresponding to the locations of the knives, and there are means interconnecting the blade and the drum whereby the blade can be fixed in the seated position thereof at each orientation, for alternate or interchangeable use of the knives thereon. The blade is defined by one end edge portion of an elongated tubular element which is detachably inserted in the recess and releasably interlockable with the drum at each operative orientation of the blade. The recess is defined by a stationary holder in the surface of the drum, and the element and holder have cooperable means thereon for fixing the relative angular and longitudinal positions of the element in the holder at the various operative orientations of the blade. These means include cooperating pin and groove means for fixing the position of the holder in one sense, and means threadedly interconnected with the holder to fix the position of the element in the other sense. For example, the element and recess may have cooperatively engaged threading thereon for fixing the longitudinal position of the element;'or there may be a finger-like retainer member inserted in the hollow core of the element, and means threadedly interconnected to the holder which operate to releasably clamp the element between the holder and the retainer member.

The retainer member is inserted in the knived end edge portion of the element and secured to the holder at a point between the one end edge of the element and the cylindrical surface plane of the drum. Also, the retainer member is secured to the holder at a point in which it is spaced apart from the one end edge of the element, to enable the element to be shifted relatively toward the aforesaid point, when it is unclamped. For example, the element may be fixed against relative rotation by a pin on the holder which is received in a groove in the opposite end edge portion of the element, and the space between the retainer member and the element may be such that shifting the element toward the point disengages the pin from the groove and thus frees the element for rotation.

BRIEF DESCRIPTION OF THE DRAWINGS These features will be better understood by reference to the accompanying drawings which illustrate two of the presently preferred embodiments of the invention.

In the drawings,

FIG. 1 is a part cross sectional operation view of a chipper drum employing a helically staggered array of socket-held tubular cutter elements characterized with beveled cylindrical blades; 1

FIG. 2 is a part plan view of the drumand a pair of adjacent cutter assemblies of this type therein;

FIG. 3 is a part longitudinal cross sectional view of the drum along the line 3-3 of FIG. 1, illustrating one such assembly in use;

FIG. 4 is a front elevational view of the cutter element in the assembly;

FIG. 5 is a part side elevational view of thecutter element in FIG. 4, along the line 55 thereof;

FIG. 6 is another such view of the element along the line 6-6 of FIG. 4;

FIG. 7 is a perspective view of the socket-like holder for the element;

FIG. 8 is a part cross sectional operational view of a chipper drum employing tubular cutter elements which are clamped in saddles and characterized with beveled conical blades;

FIG. 9 is a perspective view of one of the latter assemblies;

FIG. 10 isa part plan view of the saddle-like holder for the cutter element in this assembly;

FIG. 11 is a perspective view of a finger-like clamp retainer used in conjunction with the holder;

FIG. 12 is a part plan view of the assembly;

FIG. 13 is a part longitudinal cross sectional view of the assembly when it is installed on the drum with the cutter element clamped in position for use;

FIG. 14 is a similar view of the assembly on the drum with the cutter element released for rotation to a new operational setting of the blade on the same;

FIG. 15 is a part cross sectional view along the line 1515 of FIG. 13;

FIG. 16 is a front elevational view of the cutter element in the assembly of FIG. 8; l

FIG. 17 is a side elevational view of the cutter element in FIG. 16 along the line 17-17 thereof;

FIG. 18 is another such view of the element along the line 18l8 of FIG. 16; and

FIG. 19 is a longitudinal cross sectional view of the element illustrating one mode of sharpening the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, it will be seen that in each embodiment, the cutter drum 2 has a series of apertures 4' or 4" in the exterior wall'6 thereof which are spaced apart at equal intervals along a helical course about the longitudinal or rotational axis of the drum. The apertures 4 in turn have a corresponding number of cutter assemblies 8 installed therein, so as to render the drum serviceable as a chipper for a length of woodstock 10 which is passed relatively longitudinally abreast thereof and advanced relatively radially inwardly of the drum as the wood material is reduced to a mass of elongated chips 12. Each cutter assembly 8 comprises a tubular cutter element 14' or 14", and a holder 16' or 16" for the same which is slidably insertable in the aperture 4 for the assembly, from a point thereopposite within the drum; and adapted to be thereafter welded or otherwise secured to the drum 2 while projecting

flange abutments

18 or 18" on the holder (FIGS. 1 and 9) operate to fix the condition of the holder in the aperture flush with the outside cylindrical cutter surface 6' of the drum. The individual cutter elements 14 are detachably engageable, as well as detachably interlockable with their respective holders 16; and when engaged and locked in the holders, are presented to the Woodstock on equal, angularly successive chordal angles to the surface 6 of the drum, with the forward, beveled

end edge portions

19 or 19" of the same projecting in part relatively outwardly from the surface 6 of the drum to serve as thumbnail-like, part annular knives 20' or 20 for the chipper function, as shall be explained. In addition, the spacing between elements 14 of the respective assemblies is such that the knives 20 cut through the outline of the Woodstock in longitudinally successive tangential courses having a slight degree of overlap with one another, so as to remove successive parallelogrammatically crosssectioned strips 22 of the stock which in turn break into longitudinal segments or chips 12 of the same within the hollow cores 24' or 24" of the tubular cutter elements.

Referring now in particular to the embodiment of FIGS. 1-7, it will be seen that the apertures 4 in the drum are rectangular in plan configuration; and the cutter element holders 16 installed in the same are basically angularly truncated tubes 16' having threaded cylindrical sockets 25 therein, and sloped, stepped raised orthogonal crests 26 and depending heels 28 on the rearward and forward end portions thereof, respectively. The coplanar faces 30 of the steps on the respective crests and heels of the holders are formed at the inside radius of the drum; whereas the oppositely disposed, radially extending faces 32 of the steps are spaced apart by the longitudinal dimension of the apertures, to enable the holders to slidably engage in the apertures as mentioned.

The tubular cutter elements 14' employed in the embodiment of FIGS. 1-7 are complementally sized and exteriorly threaded to engage in the sockets 25 of the holders 16'; and have longitudinally extending grooves 34 in the threaded cylindrical outer surfaces 36 thereof, which are located at 90 intervals about the circumferences of the elements so that they can be detachably interlocked with the holders in four similarly spaced orientations, by means of set screws 38 threaded into radially extending bores 40 in the crests 26 of the holders. When installed, the elements 14 are threaded into the holders, and interlocked with the same, at relative longitudinal positions in which the for ward end edge portions 19' of the elements project in part relatively outwardly from the surface 6' of the drum to form arcuate or part annular knives 20' as indicated. The knives 20' are replaceable by, or interchangeable with, three other similar such knives 42 which are disposed in angular relationship thereto about the circumferences of the forward end edge portions, but normally withdrawn relatively within the sockets 25 of the holders when the knives 20 are in use. The inside or concave cutting edge faces of the resulting blades 20', 42 are coincident with the inside cylindrical surfaces 44 of the cutter elements; whereas the relatively convex cutting edge faces of the blades have

alternate facets

46 and 48 described by angularly successive pairs of dihedral planes passing through the cylindrical surfaces 44 of the elements at acute angles thereto. See FIG. 3 in particular. The bevel of the

facets

46 and 48, and the relative dihedral angles thereof, is such that the cutter elements present knives 20 or 42 of three

full facets

48, 46, 48 each, at each of the 90 intervals corresponding to the locations of the grooves 34. For example, the facets 46 with center lines at the 90 locations, may be beveled at an angle of 30; whereas the intermediate facets 48 therebetween may be beveled at an angle of 23 on center lines of 45 each, as illustrated in FIGS. 4-6. Preferably, the beveling operation is performed in opposite sequence, however, so that the respective facets are delimited by planes extending parallel to axial planes of the elements at the 90 locations. See FIG. 4.

When the knife 20' presented by an element 14' at one 90 orientation becomes blunted or otherwise worn in use, a new knife 42 can be presented to the woodstock 10 by rotating the element through a 90 interval. This operation is performed quite simply by withdrawing the setscrew 38, and then rotating the element through the interval in the direction of withdrawing it from its holder 16' in the relatively outward direction of the drum. Given a fine gauge threading between the elements and holders, the quarter turn need only have the effect of advancing the cut that is, increasing the depth of the cut by a small order of magnitude, such as one-sixteenth inch, which is well within the optimum strip thickness of three-eights inch prescribed for pulp chippers.

In the embodiment of FIGS. 8-19, the holders are also basically angularly truncated tubes 16", but the tubes have a two-part cross section, and are greatly re lieved over the truncated face 50 thereof to form slotted, shoe-like recesses or saddles 52 for the cutter elements 14". Also, the elements 14" are detachably engaged and interlocked with the holders through the use of interchangeable pin and slot connections 54 (FIG. 12) at the rear ends of the assemblies, and capscrewed, finger-like clamp retainer members 56 at the forward ends of the same.

The bottom rear end portions 58 of the holders, and the rear end portions 60 of the elements, have complemental part cylindrical and full cylindrical, inside and outside surfaces, respectively, for resting the elements in the holders; and affixed upright on the bottoms of the saddles, at center locations, are pins 62 which project inward of the holders just forward of inwardly directed flanges 64 on the rear ends thereof. The pins 62 cooperate with longitudinally relieved slots 66 in the rear ends of the elements, at 90 locations thereabout; and together with the flanges 64, enable the relative longitudinal and angular positions of the elements to be fixed in the saddles 52 of the holders, at selected 90 intervals, simply by abutting the elements against the flanges at each orientation in which the pin 62 of the respective holder engages with a slot 66. The bottom intermediate portions 68 of the holders, and the forward end portions 19" of the elements, have complemental, axially inwardly inclined, part conical and full conical cross sections, respectively, the inside and outside surfaces of which have

alternate facets

70 and 72, or 74 and 76, which are complementally described by angularly successive pairs of dihedral planes on 10V2 and 15 angles to the

rear end portions

58 and 60 thereof. The forward end portions 78 of the holders continue the part conical bottom section of the intermediate portions 68 of the same, but are reinforced by sloped heels 80 depending therefrom. The inside surfaces of the forward end portions 78 are shaped to complement the part-conical undersides 94 of the screw-down portions 82 of the retainer members 56 when the latter are inserted into and clamped over the bladed end edge portions 19" of the cutter elements. Threaded bores 84 in the forward end portions of the holders serve toreceive the cap screws 86 for this purpose.

Pairs of laterally projecting lugs 18" on the respective forward and rearward end portions of the holders serve as flange abutments for the installation procedure explained earlier.

As in the earlier embodiment, the bladed forward end portions 19" of the cutter elements are beveled at their edges to form a plurality of knives 20" which are angularly related about the circumference thereof; but in this instance, the pairs of

dihedral facets

74 and 76 on the edges of the elements are beveled back the full depth of the portions 19", whereas the relatively concave faces 88 of the edges are described by conical surfaces of revolution at acute angles to

facets

74, 76, and obtuse angles to the inside surfaces 90 of the portions 19". In this way, the edges of the elements can be sharpened from the inside, as for example, by using a complementally shaped honing wheel 92 (FIG. 19) which is inserted in the bladed end portions 19" of the elements for the purpose. Preferably, the facets 74 at the 90 intervals corresponding to the locations of the slots 66 are beveled at the previous indicated angle of and the intermediate facets 74 at 105?; while the conical inside faces 88 are honed at a reverse angle of l5 to establish a 30 edge, as in the earlier embodiment.

The upper sides 96 of the screw down portions 82 of the retainer members 56 are sharply inclined, and the members are equipped with countersunk holes 98 for the cap screws 86, so that the portions 82 are flush with the cylindrical surface 6 of the drum in the clamped condition of the assemblies 8, and the heads 100 of the cap screws are fully accommodated within the members. The hold-down portions 102 of the members have bent or crooked finger-like configurations corresponding to the obtuse angle between the surfaces 88 and 90 of the cutter elements; andare part conical, and then part cylindrical at the truncated tips thereof, so that the relatively rearward joints 104 of the portions 102 mate with the inside conical and cylindrical surfaces 90 and 108 of the cutter elements. The relatively forward.

joints 106 of the portions interconnect with the screwdown portions 82 of the members at a reverse obtuse angle, and for the most part, accommodate the holes 98 for the cap screws.

The cutter elements are fixed in the saddles 52 of the holders by screwing down the retainer members into the clamped condition of FIGS. 8 and 13. As seen, however, the screw-down portions 82 of the members are clamped to the holders at points in which they are spaced forwardly from the conical edge faces 88 of the cutter elements, to allow the elements to be partially withdrawn, that is, shifted forward in the relatively outward direction of the saddles, within the gaps 110, when the cap screws 86 are loosened. See FIG. 14. Moreover, the gaps 110 have sufficient distance to enable the cutter elements to be disengaged from the pins 62 when they are withdrawn in this manner within the saddles. Therefore, to present a new blade to the Woodstock 10 when the blade in use becomes blunted or otherwise worn, it is only necessary to loosen the respective cap screw 86, and to pull the accompanying cutter element forward, before it is rotated into the orientation of the new blade, and re-engaged with the pin 62 in its holder.

The retainer members 56 also provide a relatively smooth surfaced feeding platform for the strips 22, to prevent gouging the Woodstock, and to prevent plugging of the cutter elements with knots or the like in the stock. Moreover, when a cutter element is removed for resharpening, the corresponding retainer member in the assembly can be used to clamp it in position for the sharpening operation.

It will be noted that because of their scalloped outlines, the cutting edges of the

knives

20 or 20 effect a slicing or scything action as they cut into the woodstock. This is to say, the curved, progressively receding outlines of the edges contact the wood, first, at the pointed dihedral corners thereof, and then in progressively greater lengthwise increments of the same in the direction away from the corners, so that each knife shears across the fibers of the wood in point-to-point fashion, rather than meeting the fibers all points at once. Also, during this action, the tendency of the knives is to pull the wood into the cutter elements, so that the strips 22 are removed from the stock as fast as the edges of the knives effect severance.

Like the cutter element in the embodiment of FIGS. 8-19, the element in FIGS. 1-7 can be sharpened by inside honing. However, the former has the advantage that the facets of the same can be beveled back to a greater depth and thus provide more metal with which to work in the resharpening operation. Moreover, resharpening the element of FIGS. 8-19 does not reduce the wall thickness of the element, so that all told, the element of FIGS. 8-19 remains serviceable over a longer period of time.

What is claimed is:

l. A rotary chipper drum having a series of cutter knives on the cylindrical cutter surface thereof, each of which projects relatively outwardly from the surface of the drum, and has an arcuate cutting edge thereon, the relatively concave face of which is described by a coni- V cal surface of revolution.

2. The rotary chipper drum according to claim 1 wherein the relatively concave face of the cutting edge extends overa continuous arcuate course bounded by thecylindrical surface plane of the drum.

3. The rotary chipper drum according to claim 1 wherein the relatively convex face of the cutting edge has a plurality of facets thereon, described by angularly successive pairs of dihedral planes passing through the concave face of the edge at acute angles thereto, so that the edge is scalloped in outline.

4. The rotary chipper drum according to claim 3 wherein the knives project relatively outwardly from the surface of the drum on axesof revolution coincident with progressively helically advanced chords of the drum.

5. The rotary chipper drum according to claim 4 wherein those facets of the relatively convex faces of the edges which traverse the cross-sectional planes of the drum coincident with the chords, are disposed in planes which extend substantially parallel to the cylindrical surface plane of the drum; and the facets adjacent thereto are disposed in planes which extend at equal obtuse angles thereto and intersect the cylindrical surface plane of the drum.

6. The rotary chipper drum according to claim 3 wherein each knife is defined by an annular cutter blade that is seated in a recess in the surface of the drum, and equipped with a plurality of similar knives thereon, at angularly spaced locations thereabout.

7. The rotary chipper drum according to claim 6 wherein the blade is rotatable about the axis thereof between a plurality of angular orientations corresponding to the locations of the knives, and there are means interconnecting the blade and the drum whereby the blade can be fixed in the seated position thereof at each orientation, for alternate or interchangeable use of the knives thereon.

8. The rotary chipper drum according to claim 7 wherein the blade is defined by one end edge portion of an elongated tubular element which is detachably inserted in the recess and releasably interlockable with the drum at each operative orientation of the blade.

9. The rotary chipper drum according to claim 8 wherein the recess is defined by a stationary holder in the surface of the drum, and the element and holder have cooperable means thereon for fixing the relative angular and longitudinal positions of the element in the holder at the various operative orientations of the blade.

10. The rotary chipper drum according to claim 9 wherein the means for fixing the positions of the element include cooperating pin and groove means for fixing the position of the element in one sense, and means threadedly interconnected with the holder to fix the position of the element in the other sense.

11. A rotary chipper drum having a recess in the cylindrical cutter surface thereof, means defining an annular blade which is seated in the recess and rotatable about the axis thereof, there being a plurality of knives at angularly spaced locations about the blade, and means interconnecting the blade and drum whereby the blade can be fixed in the seated position thereof at orientations corresponding to the locations of the knives, said knives having an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.

12. The rotary chipper drum according to claim 11 wherein the axis of the blade is coincident with a chord of the drum, so that a knife projects relatively outwardly from the surface of the drum at each orientation of the blade.

13. The rotary chipper drum according to claim 12 wherein the blade is defined by one end edge portion of an elongated tubular element which is detachably inserted in the recess and releasably interlockable with the drum at each operative orientation of the blade.

14. The rotary chipper drum according to claim 13 wherein the recess is defined by a stationary holder in the surface of the drum, and the element and holder have cooperable means thereon for fixing the relative angular and longitudinal positions of the element in the holder at the various operative orientations of the blade.

15. The rotary chipper drum according to claim 14 wherein the means for fixing the positions of the element include cooperating pin and groove means for fixing the position of the element in one sense, and means threadedly interconnected with the holder to fix the position of the element in the other sense.

16. The rotary chipper drum according to claim 13 wherein the relatively convex face of the cutting edge of the knives has a plurality of facets thereon, described by angularly successive pairs of dihedral planes passing through the relatively concave face of the edge at acute angles thereto, so that the edge is scalloped in outline.

17. A rotary chipper drum having a series of cutter knives on the cylindrical cutter surface thereof, each of which projects relatively outwardly from the surface of the drum, and has a cutting edge thereon which is curvilinear in outline and extends between points coincident with spaced parallel longitudinal cross sectional planes of the drum, the relatively concave face of the cutting edge being described by a conical surface of revolution.

18. The rotary chipper drum according to claim 17 wherein each knife projects relatively outwardly from the surface of the drum on an axis coincident with a chord of the drum.

19. The rotary chipper drum according to claim 18 wherein each knife has an arcuate cutting edge, the relatively concave face of which is described by a conical surface of revolution, the axis of which is coincident with the chord of the drum.

20. A rotary chipper member having a series of cutter knives on the cutter surface thereof, arranged about the rotary axis thereof, each of which projects rela tively outwardly from the surface of the member, and has an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.

21. The rotary chipper member according to claim 20 wherein the chipper member takes the form of a drum, and the knives are arranged on chords of the drum to project relatively outwardly from the cylindrical cutter surface thereof.

22. A rotary chipper member having recesses in the cutter surface thereof, arranged about the rotary axis thereof, means defining a plurality of annular blades, each of which is seated in a recess and rotatable about the axis of the respective blade, there being a plurality of knives at angularly spaced locations about the blade, and means interconnecting the blade and member whereby the blade can be fixed in theseated position thereof at orientations corresponding to the locations of the knives, said knives having an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.

23. The rotary chipper drum according to claim 1 wherein the cutter surface of the drum has a series of recesses therein, and the recesses have cutter blades seated therein, which define the knives; and wherein the inner periphery of each of the cutter blades is described by a reversedly inclined conical surface of revolution terminating at the relatively concave face of the cutting edge.

24. The rotary chipper drum according to claim 11 wherein the inner periphery of the blade is described by a reversedly inclined conical surface of revolution terminating at the relatively concave face of the cutting edge of the knives.

25. The rotary chipper member according to claim 20 wherein the cutter surface of the member has a series of recesses therein, and the recesses have cutter blades seated therein, which define the knives; and wherein the inner periphery of each of the cutter blades is described by a reversedly inclined conical surface of revolution terminating at the relatively concave face of the cutting edge.

26. The rotary chipper member according to claim 22 wherein the inner periphery of the blade is described by a reversedly inclined conical surface of revolution terminating at the relatively concave face of the cutting edge of the knives.

Patent NO hatcd January 14, 1975 Inventor(s) Thomas I 'Anson It is certified that error appears in the above-identified patent and that: said Letters Patent; are hereby corrected as shown below:

Face sheet page, line 2 "Anson" should read --I'Anson--;

[76] Inventor's name should read "Thomas I'Anson" Signed and sealed this flat day of June 1975.

5:33,) fittest:

C. IIzaRI-SHALL DAZJE TF C. ILXSUIZ Commissioner of Patents .attesting Officer and Trademarks

Claims

1. A rotary chipper drum having a series of cutter knives on the cylindrical cutter surface thereof, each of which projects relatively outwardly from the surface of the drum, and has an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.

2. The rotary chipper drum according to claim 1 wherein the relatively concave face of the cutting edge extends over a continuous arcuate course bounded by the cylindrical surface plane of the drum.

4. The rotary chipper drum according to claim 3 wherein the knives project relatively outwardly from the surface of the drum on axes of revolution coincident with progressively helically advanced chords of the drum.

20. A rotary chipper member having a series of cutter knives on the cutter surface thereof, arranged about the rotary axis thereof, each of which projects relatively outwardly from the surface of the member, and has an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.

22. A rotary chipper member having recesses in the cutter surface thereof, arranged about the rotary axis thereof, means defining a plurality of annular blades, each of which is seated in a recess and rotatable about the axis of the respective blade, there being a plurality of knives at angularly spaced locations about the blade, and means interconnecting the blade and member whereby the blade can be fixed in the seated position thereof at orientations corresponding to the locations of the knives, said knives having an arcuate cutting edge thereon, the relatively concave face of which is described by a conical surface of revolution.