US2419457A

US2419457A - Method of grinding contours

Info

Publication number: US2419457A
Application number: US555262A
Authority: US
Inventors: Raymond A Mahlmeister
Original assignee: Sheffield Corp
Current assignee: Sheffield Corp
Priority date: 1944-09-22
Filing date: 1944-09-22
Publication date: 1947-04-22
Anticipated expiration: 1964-04-22

Description

p i 1947- R. A. MAHLMEISTER 2,419,457

METHOD OF GRINDING CQNTOURS Filed Spt. 22, 1944 I! ATTORNEY INVENTOR 44 Patented Apr. 22,1947

UNITED STATES METHOD OF GRINDING CONTOURS Raymond A. Mahlmeister, Dayton, Ohio, assignor to The Shefield Corporation, Dayton, (ihio, a

corporation of Ohio Application September 22, 1944, Serial No. 555,262

6 Claims.

This invention relates to the grinding of contours and the method of crush forming the grinding wheel employed in the grinding operation to provide an unusuall long crushing roll life.

One object resides in the method of truing a grinding wheel to impart a desired irregular form including ridges and valleys, by a crushing operation applied by a rotatable crushing roll so as to form the grinding wheel with no portion of the operative surface of the wheel at an angle closer than several degrees to a radial line, but with the diameters at opposite ends of the Wheel equalized to a large extent.

Another object resides in the method of shaping an end portion of an elongated workpiece having an area to be ground that is generally at 2 and in which the method of this invention'ma be carried out.

Referring more particularly to the drawing, and first with respect to the form of construction illustrated in Figs. 1, 2 and 5, Mi designates the grinding wheelof a grinding machine. As shown in Fig. l, the grinding wheel may be supported on a rotatable carrying shaft l l by suitable holding plates l2 and I3 fixed against rotation on the shaft and clamping opposite sides of the grinding wheel between them. The shaft I l may 7 be carried in a bearing housing l4 forming a part a large angle to the axis of the piece, the relative positioning of the axes of the piece and the grinding wheel being so coordinated with the ridges and valleys formed in the grinding wheel that the operative face of the grinding wheel is generally at only a small angle to the axis so that the crushing roll with which the grinding wheel is formed will have a very long life.

Another object resides in the method of shaping the peripheral portion of a grinding wheel to provide a desired form including ridges and valleys, in which the grinding wheel is operated in peripheral engagement with a rotatable crushing roll and in which the grinding wheel, before the crushing operation takes place, is first soaked in a lubricant While the wheel stationary so that the lubricant will be absorbed into the pores and applied through the grinding wheel to the area-engaged by the crushing roll.

Other objects and advantages of the invention will be apparent from the following description, the appended claims, and the accompanying drawing, in which Fig. 1 is an elevational view illustrating the method and. the crushing roll embodying the present invention, the grinding wheel being illustrated in central section;

Fig. 2 is a sectional view illustrating how the workpiece is held with respect to' the grinding wheel, showinga portion of the'grinding'wheel in central section; V

Fig. 3 shows a radial section through the grind ing wheel operatingin conjunction with a crushembodying'a crushing roll anda grinding wheel,

of the grinding machine structure It Which includes a horizontally movable table l6 providing a support for a work holder ll of any suitable character. Reference IB illustrates a Workpiece arranged in the holder'so that the area to be ground is in line with the plane of rotation of the grinding wheel ill. Suitable means are 'provi'ded'for reciprocating the table back and forth below the grinding Wheel, and for raising and lowering the, grinding wheel; as desired and as is customary in surface grinding machines."

This invention is particularly concerned with y ,the forming or truing of a grinding wheel to impart suitable ridges and valleys to the peripheral or operative surface of the Wheel so thatja desired irregular form is imparted to the workpiece by moving the workpiece in contact and with re spect to the rotatable grinding wheel and thus forming the workpiece to the desired surface formation. Fig. 2 shows one form of workpiece I8, which may be of substantial length in the direction of its exist! and having an area extend- ,ingbetween the points 22 and 23 that is to be area in a direction at right angles to the plane of the section of Fig. 2

as desired.

The grinding wheel at its opposite ends is of approximately the same diameter, the mean or average diameter at one end of the grinding wheel thus approximating the mean diameter'at the other end of the wheel, throughout its operative grinding area, the ridges and valleys imparted may be as long or as short to the grinding wheel being so formed in its peripheral surface that the grinding wheel is intended to operate on the workpiece with the workpiece axisinelined so that t-h'eground area onthe workpiece generally lies. in a plane that approximates parallelism to the grinding .wh eel a axis. The degree to which the axis of the workpiece should be tilted depends upon two main factors in order to obtain long life of the metallic crushing roll with which the surface of the grinding wheel is formed, and long grinding Wheel life, as will be presently described.

The grinding wheel is formed, to give it the desired shape, by operating it in peripheral pressure engagement with a rotatable crushing roll 25, see Fig. 1. This crusher roll may be mounted for free rotation about its own axis and may be carried by a suitable shaft 26 held in a supporting bracket 2'? on the table [6 of the surface grinder, or it may be suitably held in that portion of the surface grinder that carries the grinding wheel and be arranged for movement towards and from the grinding wheel under suitable control so that it may be brought into and out of crushing operation as occasion requires. The crushing roll, as shown, is rotatable about an axis that is parallel to the grinding wheel axis, and is preferably an annularly continuous steel body having a smooth peripheral surface ground or otherwise suitably formed to provide ridges and valleys which are the same in sectional shape as the ridges and valleys to be formed on the ground portion of the workpiece. Thus the crushing roll has an irregular form in which different portions of the roll are at difierent angles to lines radial of the roll, providing ridges Z2- and 29 between which is a valley 3%, while another valley 3! is provided on the other side of the rid e 2-9. It will be noted that the diametrical measurements at one end of the effective surface of the crushin roll have a mean or average measurement that is about the same as at the other end of the efiective surface of the roll, although this gives a grinding wheel shape that requires the workpiece axis to be held at a large angle to the grinding wheel axis so as to place the area that is actually ground on the workpiece into a more nearly horizontal position, that is, into a position that more closely approximates or attains a position in parallelism to the grinding wheel axis.

It is particularly pointed out that if the work axis 2i, see Fig. 2, were arranged horizontally or parallel to the grinding wheel axis the opposite sides of the grinding wheel would be relatively as shown in the dotted lines 32 and 33,

and the grinding wheel axis would be as indicated by the line .34. In such case, however, the side 32 of the grinding wheel would have a considerably greater diameter than the side 33, and the grinding wheel life will be determined by the radial length of the line 3%. As grinding wheels are ordinarily obtainable in a cylindrical form and must then be shaped to give the desired form, a comparatively large portion would have to be removed from the shorter diameter side in a case of this sort. Furthermore, if one side of the grinding wheel were much larger in diameter than the other, and the grinding wheel were formed by a rotatable crushing roll whose axis is parallel to the grinding wheel, one end of the crushing roll would have to be very much smaller in diameter than the other end of the roll. Where there is a large difference in diameter'at opposite ends of the crushing roll, that is, with a crushing roll that is generally of an accentuated cone form, the wear is very great on-the crushing roll because of the relative rubbing be-' tween the grinding wheel and the crushing sur face at both the large and the small endsof the crusher.

In accordance with the present invention, however, the amount of relative rubbing and wear that takes place on the crusher is minimized and the life of the crusher is greatly increased by generally equalizing the diameter at opposite ends of the crusher. This tends to equalize the diameter of both the crusher and the grinding wheel throughout their axial extent, and this equalization should take place to an extent limited by those surface portions of the crusher or the grinding wheel that are closest to a radial line. The axis 2i of the workpiece shown in Fig. 2 should thus be inclined only to the extent that brings that part or parts of the crusher that are at the greatest angle to the axis of rotation no closer than several degrees from a line radial to that axis. With a truly radial surface on the grinding wheel or on the crusher the grinding wheel would be so formed that any wear on that surface would require a considerable amount of reforming or crushing to attain the proper shape each time the wheel wears. However, if all portions of the effective grinding wheel surface are no closer several degrees irom a line radial to the grinding wheel axis, the wheel wear of iose parts that operate at the greatest linear speed and perform the most or" the actual grinding will control the amount that has to be taken off of the crusher in any crushing action to restore the desired form. If the surfaces of the grinding wheel that are close to a radial line are quite short in radial extent, they may be as close as from three to five degrees, although if they are of considerable radial extent, they should be from five to seven degrees away from a truly radial line so as not to cause excessive grinding wheel wear, excessive loading of the spaces between the grinding grains of the wheel, or an excessive removal of the grinding wheel surface in a crushing operation.

By tilting the axis of the workpiece so as to arrange the area to be ground at least roughly parallel to the grinding wheel as indicated for example in Fig. 2 andby crushing the grinding wheel with an annular crushing. rollas illustrated in Fig. l, the mean diameter of one effec tive portion of the crushing roll approximates the mean diameter of the other end of the roll to an extent that brings that portion or portions of the roll that are at the greatest angle to the axis of rotation of the roll no closer than several degrees from a line radial tosaid axis, and with this arrangement the bisector of adjacent diverging surfaces of the crushing roll are arranged at an angle to a line radial to the crushing roll axis, as indicated by the dotted line 35 in Fig. 1 although this is contradictory to past practice wherein the bisector of diverging surfaces to be ground have been arranged as far as possible in the direction of the grinding wheel radius. a

After grinding on area on the upper side of the workpiece it, the work may be retracted from the grinding wheel, invert-ed in its holding fixture, and another ground on the side then uppermost, opposite the first ground area to give a symmetrical shape to the ground end of the workpiece. In the form of construction illustrated inffigs. 2 and i, the ground end or the workpiece is cylindrical, partly ground in one grindilig operation andfinished in the second after the piece is inverted. With the workpiece axis inclined to a considerable angle with respect'to the grinding wheel axis, the portion of the grinding wheel that is efiective on the cylindrical end portion will come down a littl past the axis of symmetry of the workpiece to insure a complete smooth form at the very end of the workpiece, and this is accomplished without having the sur-: face on the grinding wheel that is effective on the end of the workpiece any closer to a radial line than the several degrees previously mentioned.

Before the grinding wheel is first crushed it is first soaked in lubricant while the grinding wheel is not in rotation. This is done to minimize the possibility of the wheel breaking while being crushed and also tominimize the wear on the crushing roll and to providea better crushin action on the grinding wheel. This is preferably accomplished by submerging the grinding wheel flat in a container of suitable lubricating oil in which the grinding wheel is held lon enough to permit absorption of the oil into the pores of the wheel throughout the body of the wheel. The wheel is placed in position on the shaft ii, the crusher is properly positioned against the grinding wheel and the two wheels are then started by driving one or the other or both so they will operate at substantially the same peripheral speed, pressure being maintained between the two rolls by feeding one towards the other during the crushing operation. The grinding wheel will thus be crushed away by the pressure action. at the nip of the rolls until the grinding wheel surface attains a shape which is com- Elementary to the shape of the-crusher roll. During this crushing action, it has been found that the oil that was absorbed by the grinding wheel is as a kind of bonding agent to hold the abrasive particles together and prevent wheel breakage, During. the crushing actionthe oil will be thrown out gradually to the surface of the grinding wheel where its bonding action is most needed. It is also applied to the effective surface of the crushing roll to reduce wear. .This outward travel of the oil during the crushing operation will be produced by centrifugal force which, however, is not excessive enoughto-immediately dissipate all of the oil, since the grinding wheel is rotated at a comparatively slow speed as compared to that used during the a'ctual'grinding operation. In crushing; the speed of rotation of either the crushing roll or the grinding wheel may be of the order of three hundred feet per minute.

In the embodiment of .the invention illustrated in Figs. 3 and i, the grinding wheel 36, which operates about an axis 31, is provided with an irregular surface forming ridges and vall ys, the

grinding wheel bein formed or shaped by crushing roll 38 operable about an axis as the twomembers are rotated in peripheral pressure engagement with one anotherin the same manner that has been previously described. The crushing roll is provided with ridges 59, 4t, 52 and .43, and valleys M, 65 and 56, the bisectors of diverging surfaces of the crushing roll being inclined to lines radial of the crushing roll to whatever extent may be required in so arranging the sectional form of the grinding wheel at a small angle to the grinding wheel axis. The form given to th crusher is such that the left hand end of the crushing roll, as viewed in Fig. 3 does not exceed the mean diameter at the other end of the roll to any substantially greater extent than is required by the angularity of the most steeply inclined surface portions on the crushing roll. The mean diameter of the smaller end of the roll approximates the mean diameter at the other end of the roll to an extent that brings those portions that are at the greatest angle no closer than several degrees from a line radial to the roll axis. Such a limiting angle surface is illustrated by the portions of the crushing roll contained in the dotted lines 28 and 4e. Line 49 contains only a short portion in radial depth, and consequently, the lined may be at an angle of from three to five degrees to the radial. The line at, however, contains a crushing wheel surface that is of considerably greater radial extent, and this line should be at an angle no closer to the radial line than five to seven degrees to give satisfactorily long life to both grinding wheel and the crushing roll. If the sectional form of the peripheral surface of the grinding wheel were tilted counterclockwise several degrees with respect to the axis of the grinding wheel that would provide a greater equalization in the mean diameter at different portions along the length of the crushing roll and in the mean diameter at diiferent points along the axial length of the grinding wheel and thus give better crushing roll life, but if this were done, that would make the line as substantially coincide with a radial line, preventing satisfactory operation of the grinding wheel over any extended period of time. Consequently, the mean diameter of the smaller end of th crushing roll only approximates the mean diameter at the left hand end of the roll as illustrated in Fig. 3 to such extent as to bring the most steeply inclined portion to from three to seven degrees from a radial line depending upon the radial length of the most steeply inclined portion.

Fig. 4 illustrate the grinding operation performed by the grinding wheel on a workpiece whose longitudinal axis 5! is arranged at a large angle to the axis of rotation of the grinding wheel. Here the general plane of this zone to be ground on the work is indicated by the line 53, and this is inclined only about twelve degrees with respect to the grinding wheel axis although the angularity between the ground area as represented by'the mean line d3 is about forty degrees to the longitudinal axis of the workpiece. Here it will be noted that the inclined angle between the ground area on the upper side of the work and the general mean line M of the ground surface which may be imparted to the other side of the workpiece after turning the workpiece upside down on the holding fixture is nearly a right angle, although the relative slope between the upper and lower sides of the crusher roll 38 that has formed the grinding wheel is only about twenty-four degrees. If the grinding wheel were so arranged as to grind thesame surface form on the workpiece 50 with the workpiece arranged so that its longitudinal axis 5% is parallel to the grinding wheel axis, obviously one side of the grinding wheel would be very much smaller in diameter than the other side and the effective surface of the crusher wheel used to form such a surface would have a corresponding large inclination with respect to its own axis and this would produce excessive wear on the crushing roll in the crushing operation. In accordance with the method and by use of the crusher of this invention, however, the crusher roll life is greatly increased. The grinding wheel life is also increased because of the increase in the radial length of the side of shorter diameter.

The forms of construction herein illustrated and described have been chosen as two examples of many insofar as concerns the actual shape or a formation of the crushing roll and the grinding wheel, and it is to be understood that various modifications and adaptations of the invention may be made within the spirit and scope of the appended claims.

What is claimed is:

1. The method of shaping the end portion of an elongated workpiece to provide a ground surface of a desired irregular form including ridges and valleys, and in which the area thus ground is generally at a large angle to the axis of said piece, which comprises locating said piece with respect to a grinding wheel so that the axis or" the piece is at a large angle to the axis of the grinding wheel, forming the peripheral surface of the grinding wheel by a crushing roll having ridges and valleys corresponding in shape to the idges and valleys to be imparted to the piece but with the ridges and valleys of the roll forman area at a small angle to the axis of the r il as compared to the large angle between the axis of the workpiece and the area ground on the workpiece, the mean diameter of one end of the effective portion of the roll approximating the mean diameter at the other end of the roll to an extent that brings that portion or portions of the roll that are at the greatest angle to the roll axi no closer than several degrees from a line radial to the roll axis, and grinding the workpiece with the grinding wheel while the workpiece is so located.

2. The method of shaping the end portion or an elongated workpiece to provide a ground surface of a desired irregular form including ridges and valleys, and which the area thus ground is generally at a large angle to the of said piece, which comprises locating said piece with respect to a grinding wheel so that the axis of the piece is at a large angle to the axis Of the grinding wheel, crushing the peripheral surface of the grinding wheel to form ridges and valleys that portion of the wheel that is at the greatest angle to the wheel axis several degrees from a line radial of the Wheel, and grinding the workpiece with the grinding Wheel.

3. The method of shaping the peripheral portion of a grinding wheel to provide a desired irregular form including ridges and valleys which comprises soaking the wheel while stationary in a lubricant and then running the Wheel in peripheral contact and pressure engagement with 8 a crushing roll to form the ridges and valleys in the grinding wheel, forming the mean diameter at one end of the grinding wheel approximately to the mean diameter at the other end of the grinding wheel to an extent that brings that portion or portions of the wheel at the greatest angle to a line several degrees from a line radial to the wheel axis.

i. The method of shaping the peripheral portion of a grinding wheel to provide a desired irregular form including ridges and valleys which comprises soaking the wheel in a lubricant until the lubricant is absorbed into the body of the wheel, then operating the wheel in peripheral pressure engagement with a crusher roll operating'at substantially the same peripheral speed.

5. The method of shaping the peripheral portion of a grinding wheel to provide a desired irregular form including ridges and valleys which comprises soaking the wheel in a lubricant untilthe lubricant is absorbed into th body of the wheel, bringing the periphery of the wheel intoengagement with a crusher roll while the wheel and roll are at rest, then operating the wheel "in peripheral pressure engagement with the crusher roll operating at substantially the same peripheral speed, and with the surface speed of the wheel reduced below normal grinding speed, and maintaining the pressure until the grinding wheel is formed complementary to the cross sectional form of the crusher roll.

6. The method of shaping the peripheral portion ofa grinding wheel to provide a desired irregular form including ridges and valleys which comprises soaking the Wheel in a lubricant until the lubricant is absorbed into the body of the wheel, then operating the wheel in peripheral pressure engagement with a crusher roll operating at substantially the same peripheral speed, with the roll axis parallel to the grinding wheel axis, the roll having its mean diameter at one end approximating the mean diameter at its other end to suchextent that the portion or portions of the grinding wheel formed by the crusher roll at the greatest angle to the grinding wheel axis are no closer than several degrees from a line radial to the grinding wheel axis.

' RAYMOND A. MAHLDEEIISTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,513,758 Hanson Nov. 4, 1924 FOREIGN PATENTS Number Country Date 526,075 British Sept. 10, 1940 7 183,614 British Aug. 3, 1922