US2715801A

US2715801A - Bevelled knife blade grinding

Info

Publication number: US2715801A
Application number: US208729A
Authority: US
Inventors: Charles A Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-01-31
Filing date: 1951-01-31
Publication date: 1955-08-23
Anticipated expiration: 1972-08-23

Description

Aug. 23, 1955 c. A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 Sheets-Sheet 1 Filed Jan. 31, 1951 1y M1414 k m vl llll II Aug. 23, 1955 c. A. JOHNSON 2,715,801

BEVELLED KNIFE BLADE GRINDING Filed Jan. 31, 1951 6 Sheets-Sheet 2 1521213824302 Coaafl J1 Jofuwon,

Aug. 23, 1955 c. A. JOHNSON BEVELLEZD KNIFE BLADE GRINDING 6 Sheets-Sheet 3 Filed Jan. 31, 1951 l i EFF- ILL.

[T I L 3, 1955 c. A. JOHNSON 2,715,801

BEVELLED KNIFE BLADE GRINDING Filed Jan. 51, 1951 6 Sheets-Sheet 4 IIEii \\\\\'!2//// wgmfi (O W; Q] r Q 5 \L 7 a i kw \\?\lll A i'i 1320922302 3; WWAIO ow,

Aug. 23, 1955 c. A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 SheetsSheet 5 Filed Jan. 31, 1951 (F202 MIN! oiwow, V 611L61 l x l Aug. 23, 1955 c. A. JOHNSON BEVELLED KNIFE BLADE GRINDING 6 Sheets-Sheet 6 Filed Jan. 51, 1951 United States Patent BEVELLED KNIFE BLADE GRINDING Charles A. Johnson, Berlin, N. H.

Application January 31, 1951, Serial No. 208,729

9 Claims. (Cl. 51-122) This invention relates to grinding and more specifically to a machine and method for grinding a fiat-surfaced material to provide a surface which intersects the fiat surface of the material along a straight line at an angle which varies progressively along the line of intersection.

A rigid material supplied with such interrelated surfaces meeting at an acute progressively varying angle (hereinafter referred to as the angle of bevel) forms a knifesharpened along the line of surface intersection to form a cutting edgehighly useful in log chipping in the pulp industry, where the knife or several such knives are mounted on a rotating disc with the cutting edge of each projecting beyond the face of the disc and extending along a line tangent to a circle having as an axis the axis of the disc, for cutting logs fed end-on into the path of the rotating knives at an angle to the face of the disc.

Such a knife, its method of mounting and the advantages of the resulting cuts produced in logs fed to a log chipper provided with such knives are described and claimed in my co-pending application Serial No. 117,676 filed September 24, 1949, now Patent No. 2,655,319, dated October 13, 1953.

A specific object of this invention, therefore, is the production of a grinding machine useful for the initial production and subsequent maintenance of such log chipping knives.

In general, a grinding machine of this invention comprises a shaft for rotatably supporting a grinding wheel and a work holder mounted adjacent the end of the shaft, the grinding wheel and work holder having in addition to the relative movement caused by the rotation of the grinding wheel shaft, three other relative movements including (a) reciprocation towards and away from each other, (b) transverse reciprocation and (c) rotation about an axis extending in the direction of the path of transverse reciprocation (b). In the simplest form of the machine the rotation axis (0) is parallel to the path of reciprocation (b); but in a refined version of the machine, provision is made for having the relative rotation (0) about an axis which, permanently or by adjustment, is not parallel to the path of reciprocation (b), but, though extending in the same direction, is inclined relative thereto.

The relative movement (a) permits the grinding to proceed progressively into a'work piece held in the work holder. The relative movement (b) permits the grinding to take place back and forth along the length of the work piece and the rotation (c) is responsible for varying the angle of the bevel of the cutting edge along its length.

Structure for accomplishing these movements are shown in, and the results of coaction of the parts are illustrated by, the accompanying drawings wherein:

Fig. 1 is a plan view of the parallel rotation axis type machine;

Fig. 2 is a front elevation thereof;

Fig. 3 is an end elevation;

2,715,801 Patented Aug. 23, 1955 Fig. 4 is a vertical section taken along the line 44 of Fig. 1;

Fig. 5 is an enlarged detail cross-sectional view taken along the line 55 of Fig. 2;

Fig. 6 is an isometric view of a work piece ground on the apparatus;

Fig. 7 is a front elevation of a refined version of the machine;

Fig. 8 is a detail inside View of a part of the apparatus of Fig. 7;

Fig. 9 is a plan view of the detail of Fig. 8;

Fig. 10 is a schematic illustration of a knife chipper; and

Figs. 11 and 12 are graphical illustrations of certain relations between the knife, the grinder and the chipper as will be hereinafter described.

The apparatus comprises a conventional base 10 having mounted thereon a reciprocating carriage 12 which carries at each end thereof an upright 14 containing bearings 15, in which are journalled the trunnions 16 of a work holder 20 in such manner that the trunnions have a common axis extending in the direction of the path of reciprocating carriage 12 and, in the embodiment of Figs. l6, inclusive, being shown parallel thereto. At the right-hand end of the work holder an upstanding member 22 has fixed to it, as more clearly shown in Fig. 5, control arm 24 which extends towards the front of the machine and carries on its end a rotatable cam follower 26 which bears against a bar 28, forming a cam track extending in the same direction as the path of carriage reciprocation. The ends of the track 2% are supported respectively at pivotal connections 29 on uprights 3t and 32. These uprights 3i and 32 may be mounted on the base of the apparatus for independent slidable vertical adjustment relative thereto to vary the slope of the cam track 28 relative to the base and path of carriage reciprocation.

It will, therefore, be understood that the motion of the knife holder 20 about the common axis of its trunnions 16 under the influence of gravity is resisted and limited by the cam track 28 to an extent depending upon the particular longitudinal position of the cam follower 26 on the cam track 28 as results from the particular position of the carriage 12 in its reciprocation relative to the base 10.

The work holder 20 is provided with fastening means such as bolts 40, retainer plates 42 and nuts 44 for retaining against the upper surface of the holder a work piece A to be ground. In the form shown in the drawings, this work piece A is of uniform thickness having a flat upper surface a and provided with three re-entrant recesses 12 along its back edge and through which recesses one or more of the bolts may extend to hold the work piece A firmly against the upper surface of the work holder.

Moreover, the work holder 20 is so designed with respect to the thickness of the work piece A so that it may be positioned in the work holder with its upper surface a extending exactly through the common axis of the work holder trunnions 16.

A cup-shaped grinding wheel is mounted on a shaft 52 for rotation in a vertical plane which, though nearly parallel to the path of reciprocation of the carriage 12, is not exactly so but is at a slight angle thereto so that only one side of the wheel 50 actually bears against the work piece to do the grinding.

The shaft 52 is connected by suitable pulleys 53 and belting to the motor 54 and the assembly of shaft 52 and motor 54 is mounted on a slide 55 held on base 10 in guideways 56 for reciprocation towards and away from the work holder 20 by means of operation-of the hand wheel 60 extending at the front of the machine and 3 r V connected'by suitable conventional means, including a shaft 61 threaded through a block 62 depending from slide 55, 'to slide 55.

' There are also provided on the frontface of the carriage 12, two 'abutments 70 and'71, which, in th eir paths oftravelwith reciprocating carriage 12, alternately trip a trip arm 72 for automaticallychanging the'direction of the automatic movement of the carriage 12. Since 7 construction for automatically-driving carriage 12' is' Conventional it is not further described, asit forms no 7 part of the invention per se.

In operation, a blade to beground is fastened to the blade holder in such a manner that its upper flat surface a passes through the axis of the trunnions '16 and vprojects towards the path of rotation of wheel50. The carriage isthen moved to one position of itsreciprocation so that the working surface of wheel 50 is opposite one end of the workpiece A. a One of the upblade. p

The carriage is then moved to bring the other end of the blade opposite the grinding wheel working surface andthe other upright is then adjusted according to the angle of bevel desired atthe other end of the blade. As shown in Fig. 2, the outer end of track 28 is slightly lower than the inner end so that the right hand end of the work A will be given a sharper angle of bevel than .the left-hand end, as seen in Fig. 2 and as indicated by the dotted line ground edge in Fig. 5, and as shown in the completed ground knife of Fig.6. V

The carriage is then set into automatic reciprocation whereupon the grinding wheel may be moved by hand wheel '60 towards the projecting. blade to grind the edge surface.

' Inasmuch as the bearing surface of camtrack 28 is,

f a straight line, the amount of oscillation of the work 7 holder 20 is uniform per given unit of reciprocal movement of carriage 12 throughout the length of the blade 7 holder. e

rights

30 or 32 is then adjusted vertically for securing that angle of bevel which is desired at that end of the V The grinding ,is continued by advancing the grinding wheel by hand wheel 60 until the path of rotation of whee1'50 reaches'the axisof trunnions 16, i. e. until the surface being ground 0 has its upper edge lying exactly along that axis. If grinding is stopped at this point, the plane of the ground surface 0 will then intersect 'the' top surface a of the work along a straight line cutting edge d '(Fig. 6)-but the angle of intersection of the two surfaces will, because of the straight line uniform slope of track 28, vary uniformly from a wide angle e at one end to a sharper angle f at the other end with the ground surface 0 being a warped surface, thus creating that geometry A which features the novel cutting knife described in the aforesaid co-pending application. 'Fig.;6, for purposes of clarity, exaggerates the difference in the two angles e and f. V I i In the embodimentof the invention so far described and shown in Figs. 16 inclusive, the rotation of the work holder20 'is'about an axis which is parallel to the path of transverse reciprocation of the carriage 12 and intersects the axis of the shaft 52 of grinding wheel.50. With the grinding taking place at only one side of the wheel because of the biasof the shaft 52'as hereinbefore' explained, the external cylindrical plane of revolution of the wheel 50 will intersect the blade A at the same. angle no matter where the blade is in its transverse reciprocation.

disc but offset relative to the radius so that it is tangent to a circle having as a center the axis of the chipper:

4 disc, as illustrated in Fig. 10, a certain refinement is desirable by way of varying the angle of grinding alongthe length of the cutting edge. a It will be noted, as demonstrated in Fig. 11 where100 represents the chipper disc center, that, in the c ase of the offset mounting, the tangentsto the paths of chipper revolution of successive points along ,the cutting edge Z32 approachas a limit outwardly of the chipper disc a line normal to the projection of the cutting edge and as an inner limit a line coincident with the projection of the cutting edge. These tangents, which represent the.

varying angle of attack, so to speak, at different points along the cutting edge intothe wood, thus progressively vary along the length of the cutting edge, increasing outwardly thereof. In order to make the angle of grind more nearly coincide with these varyingangles of .attack, I have found that I can readily vary the grinding angle over the length of the blade, by grinding with different arcsof the grinding wheel 50 at different points along theblade. Thus, if I use at one'end ofthe blade a section of the wheel near the. top of the lower left-hand quadrant, as viewed in Fig. 2,1 may progressively decrease the angle of intersection as the blade moves to the left so that nearits right-hand end, the cutting will be taking place near the bottom portion of the left-hand lower quadrant of the grinding wheel as shown in Fig." 2. I do this by mounting the work holder 20 as shown in Fig. 7 so that its axis of rotation is not parallel to its path of reciprocation but is inclined relative thereto. Thus, instead of having the fixed uprights 14 of Figs. 1-6,

the trunnions 16a are mounted for limited universal movement'in blocks 80 and take the form of studs journalled in crosswise rocker cylinders 81, which, in

' in Fig. 7, it will be seen that the cutting at the left-hand end of the blade will be done at a higher section of the turn, are journalled in the blocks 80. Also, the blocks 80 are adjustablymounted in upright slide guides -82 for vertical motion relative to the, base 10. Adjusting screws 83 extend upwardly from the base in order tohold the slides 82 in adjusted position. The construction is identi- 1 calrat both sides of the machine. In a machine thus constructed and with the work holder axis of rotation in an inclined position asshown lower left-hand quadrant of the grinding wheel than the cutting at the right-hand end which, in fact, will be at an angle which will be in a directionmore nearly horizontal, A blade so ground should have, by adjustment of the slope of cam track 28, its largest angle of intersection of its cutting edge forming surfaces at the left-hand end and its smallest angle of intersection of its cutting edge forming surfaces at the right-hand end. When flipped end-to-end for mounting in the chipper disc of Fig. 10,

its right-hand end as seen inrFig. 7 will then be towards I the center of the disc audits left-hand end as shown in Fig. 2 towards the peripheryof the disc, and with its cutting edge 102 tangent to a circle having, as a center,

the disc axis. As so mounted, the disc is designed to rotate in a counter-clockwise direction looking atthe face. of the disc, as in Fig. .10.

In fact, the adjustment-of the relative heights of the revolution of the grinding wheel 50 at its arc point of j grinding contact should intersect the axis of rotation of the. 1 work holder at any given point along said axis of work I holder rotation at'substantially the same angle asithe angle which the tangent to the path of revolution of a.

pointalong the cuttingedge, when it is 'rotated on. a r0 tating disc, corresponding to the work holder'axis point, makes with the cuttingedge V p j For example, Fig. 11 is an enlarged graphical representation of one of the cutting blades shown in Fig. 10, the point 100 representing the center of the chipper disc.

Because of the radial oifset of the cutting edge 102, the angle of attack, so to speak, of the cutting edge 102 during counter-clockwise rotation of the disc, increases progressively outwardly of the cutting edge 102; Thus, in Fig. 11, the tangents to the respective paths of revolution of the

points

103, 104 and 105 are approximately 46, 52 and 56.

What I attempt to do is to grind the blade at point 103 therealong with a point on the grinding wheel whose tangent plane intersects the cutting edge 102 when it is in the work holder of the grinding machine as the grinding is completed (i. e. the axis of work holder rotation) at an angle as nearly as possible the same as the 46 angle of Fig. 11; whereas further outwardly of the blade, as shown in Fig. 11 and more to the left-hand of the blade, as shown in Fig. 7, I utilize a point on the grinding wheel which is higher up on the left-hand lower quadrant of the grinding wheel where the tangent plane to the grinding wheel point intersects the work holder axis of rotation at a larger angle, namely 52. This is accomplished by reason of the inclination of the work holder axis of rotation in Fig. 7.

Fig. 12 shows a graphical method for determining the approximate relative inclination of the work holder axis of rotation relative to a horizontal plane through the axis of rotation of the grinding wheel 50 for a particular disc mounting. For this purpose, one may lay out the relative geometry of the center of the chipper disc 100 and the locus of the cutting edge 102. A series of straight lines are then constructed from the center 100 to a series of points located along the cutting edge. From the cutting edge points one then lays ofi on each of the connecting lines the radius of the proposed grinding wheel which will be used and from these points one may draw the arcs 1-6 inclusive shown in Fig. 12, the tangents of which at their intersection with the cutting edge 102 will correspond respectively to the tangents of cutting edge points of attack in counterclockwise rotation of the disc. The locus of the arc centers is a curve of ever-decreasing slope shown in dotted lines in Fig. 12. A straight line 110 may thus be drawn approximately through these centers and the angle a of its intersection with the projection of the cutting edge 102 represents as an approximation the angle of inclination between the work holder axis and the horizontal plane through the axis of the grinding wheel which should be utilized in order to procure the refined type of grinding hereinbefore described.

A diiferent form of work holder clamp for the blade is shown in Fig. 7, from that shown in Fig. 2, but since this forms no part of this invention, it need not be further described. The form of Fig. 2 may as well be used in the refined version of the machine shown in Fig. 7.

Regardless, however, of whether this grinding refinement is introduced or not, the apparatus of this invention may be utilized in the production of new and improved chipper disc knives.

I claim:

1. Apparatus of the character described comprising a base, a carriage mounted on said base for reciprocation relative thereto, a work holder mounted on said carriage for rotation about one side of an axis extending in the direction of the path of reciprocation of said carriage, said work holder being adapted to hold a fiat-surfaced piece of work with its flat surface lying in a plane passing through said axis, camming mechanism for rotating said holder about said axis as said carriage reciprocates, and a grinding wheel mounted on said base for rotation in a path disposed on the opposite side of said axis from said work holder and intersecting the plane of said fiat surface and for movement towards said work holder to move the path of wheel rotation towards said axis of work holder rotation, and means for progressively moving said grinding wheel towards said work holder as said carriage reciprocates to grind the projecting edge of a piece of work so held in said work holder until the path of rotation of said wheel passes through said work holder axis, to provide a straight cutting edge for said piece of work.

2. Apparatus of the character described comprising a base, a shaft mounted on said base for rotatably supporting a grinding wheel, a work holder mounted on said base and extending generally transversely of said shaft, said work holder and shaft being mounted on said base for (a) relative reciprocation towards and away from each other, (b) transverse reciprocation relative to one another, (0) rotation relative to one another about an axis extending in the direction of the path of said relative transverse reciprocation and interposed between said shaft and said work holder, said work holder being adapted to hold a flat-surface piece of work with its flat surface projecting therefrom towards, and lying in a plane intersecting, the path of rotation of a grinding Wheel carried on the end of said shaft, camming mechanism for rotating said work holder and said shaft relative to one another about the said axis as they reciprocate transversely relative to one another and means for relatively moving said work holder and shaft towards each other as they reciprocate transversely to grind the edge of said work until the path of rotation of the grinding wheel carried on said shaft intersects the fiat surface of the work at the said axis of relative rotation, to provide a straight cutting edge for said piece of work.

3. Apparatus as claimed in claim 1, wherein the camming mechanism rotates the work holder to one extreme position of rotation as said carriage reaches one extreme position of reciprocation and to the other extreme position of rotation as said carriage reaches the other extreme position of carriage reciprocation.

4. Apparatus as claimed in claim 1, wherein said camming mechanism rotates said holder about said axis through the same angle of rotation for each unit distance of work holder reciprocation whereby the angle which the surface ground on said piece of work makes with the flat surface of the piece of work varies progressively uniformly along the length of the work piece.

5. Apparatus as claimed in claim 1, wherein said camming mechanism includes a cam track mounted on said base, a cam follower carried by said work holder resting on said cam track, said cam track being constituted of a straight bar extending in the same direction as the path of carriage reciprocation, and means for independently varying the position of both ends of said bar relative to the base to vary the slope of said bar relative to said path of carriage reciprocation and hence the amount of rotation of said Work holder in reciprocation of the cam follower therealong.

6. Apparatus as claimed in claim 1, wherein said Work holder is suspended from trunnions journalled on said carriage and wherein the camming mechanism includes a cam follower extending from said work holder and resting on a cam track whereby the weight of said Work holder maintains said cam follower against said cam track during reciprocation of said track for causing rotation of said work holder relative to said carriage.

7. Apparatus as claimed in claim 1, wherein the axis of rotation of the work holder is angularly inclined to the path of carriage reciprocation.

8. The method of grinding a knife blade having a straight cutting edge adapted to be mounted on a disc for rotation during cutting with its cutting edge extending tangentially to a circle concentric with the axis of blade rotation, comprising grinding said blade with a rotating abrasive surface and continuously and progressively varyin the angle of intersection of the path of revolution of said abrasive surface with the blade along its cutting edge length substantially in accordance with the varying angles which the tangents to the paths of revolution of each points along the cutting edge make with ,said cutting edge when 'said bladeiis rotated on said disc.

9. The method'of forming astraight knife edge having a Warped bevelled surface comprising grinding a knife blade blanlcby reciprocating said'blank backan'd forth across a transversely 'moving. abrading surface while simultaneously oscillating the blank; initinied relation with its reciprocal motion, about an axis lying along a surface of the blank inwardly offthe end ofthe blank which is being ground, progressively in one direction during reciprocal motion of the blank one Way and progressively in a return direction during return reciprocal mosecte said axis.

References Cited in the' file of this patent UNITED STATES PATENTS 8 Wolf etal. July 19, Abbott 'Feb. 10, Hamming May 26, Osterholm .Iu1y 24, Runshang Aug; 16, Jackson Nov. 19, Cornell Nov'. 15, Nicholas May 11, Monkle y l l Nov. 23,

FOREIGN PATENTS Great Britain 'July 2, Austria May 11, Great Britain July 7,