US2238760A

US2238760A - Lapping apparatus

Info

Publication number: US2238760A
Application number: US222510A
Authority: US
Inventors: David A Wallace
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1936-07-22
Filing date: 1938-08-01
Publication date: 1941-04-15
Anticipated expiration: 1958-04-15

Description

April 15, 1941.

D. A. WALLACE 2,238,760

LAPPING APPARATUS Original Filed July 22, 1936 INVENTOR DAVID W/ILLH as W BY u MW ATTORNEYS Patented Apr. 15, 1941 rnrrmc APPARATUS David A. Wallace, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Original application July. 22, 1936, Serial No.

Divided and this application August 1, 1938, Serial No. 222,510 v 6 Claims. (Cl. 51am This invention relates to improved apparatus for lapping surfaces and is a division of my which has matured as Patent No. 2,195,047, dated March 26, 1940.

More particularly, the invention pertains to lapping of surfaces of apparatus and parts thereof which operate in rubbing, sliding or rotative bearing-like or frictional contact with other obtained by lapping and such smoothness is of a much different and superior kind than that repolishing operations.

One of the main objects of the invention is to r 7 application, Serial No. 91,851, filed July 22, 1936 provide improved lapping apparatus by which physically smooth and mirror-like surfaces can be directly formed by lapping operations without producing a deceitful luster such as that formed by polishing the side surfaces of ridges of presumably, but not actually, smooth surfaces.

Another object of the invention is to provide apparatus of this character by which the inscriptions" traced on the surface operated upon by 10- parts. l 10 calized hard particles in the lapping surface can Heretofore, in polishing, lapping or otherwise be brought to a desired angular cross-hatched finishing surfaces, it has been the practice to prorelationship such that-the resulting scratch lines duce relative movement, mainly in one direction are accordingly so repeatedly crosshatched as to only, between the surfaces of the work and the destroy their normal roughness producing effect. lapping means. In some instances combinations A further object of the invention is to provide of different directional movements have been apparatus of this character by which the recipemployed in an effort to avoid scoring of the rocating movement of the lapping element is surface operated, upon by repeated action of maintained at a suillciently high velocity and freisolated hard particles of the lapping element quency to produce, smooth'surfaces free from on substantially the same areas of the work. The grooves and ores wi h a l mited amount of relative movement in one direction has, however, reciprocatory movement. been of a relatively low order of velocity as com- An additional object of the invention is to propared to the relative movement in another direcvide apparatus of this character by which a tion, and consequently, the scratch lines, scores lapping element can be conveniently reciproor inscriptions traced on the work by isolated called. ur g app thereof to a rotating hard particles in the lapping surface have not piece of work, at a relatively high rate of speed been so disturbed and cross-hatched as to proof a vibratory order. vide finished surfaces of actual mirror-like A still further object of the invention is to smoothness directly by lapping operations. provide an improved lapping device which will Polishing with extremely fine abrasives, such operate a plurality of conveniently attachable as rouge, has been required after the lappingopand detachable lapping elements so as to facilieration, to produce the desired degree of smoothtate adap tion of the device to he l pp n of a ness and finish. In this connection it should be plur li y of different ypes of pieces of w rk. noted that while polishing of this character im- Another object of the invention is to provide proves the appearance of the surfaces it does not lapping apparatus of this character by which materially change its physical smoothness. That the relative movement between the lapping elethis is true can readily be seen by microscopic mentand the work in one direction is of a recipobservation of conventionally lapped and polished rocatory nature and which movement varies in surfaces by which it is found that the multiplicity velocity from zero at ODDQ te ends of the stroke of minute ridges between adjacent scratch lines 40 while maintaining a substantially high velocity or scores are not actually removed. The polishthroughout the main portion of the stroke. ing compound merely forms a luster on the sides Other objectsof the invention are to provide of such ridges which give the final surface an an improved lapping device by which either the appearance of much greater smoothness than inner or outer surfaces of a pair of annular memactually exists. bers, such as bearing rings,'can be simultaneously I have found that by producing relative movelapped by a single reciprocating member and in ments of respectively different ranges of speed accordance with the invention; and to provide and in different directions, preferably at right lapping apparatus of this character which is angles, between the surface operated upon and adapted to simultaneously lap frusto-conical surthe lapping surface, actual smoothness is directly faces of a pair of bearing members,

An illustrative embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is a fragmentary plan view, partly in section, of an apparatus embodying the invention for lapping a pair of bearing elements.

Fig. 2 is a fragmentary, side elevational view, partly in section, of the apparatus shown in Fig. 1.

Fig. 3 is a fragmentary vertical sectional view taken on the line 3-3 of Fig. 2.

The form of the invention shownin the drawing illustrates an application of my improved lapping apparatus and process whereby the internal surface of two bearing members may be simultaneously lapped in accordance with the invention, whether such surfaces are cylindrical or -frusto-conical in shape. The apparatus" includes a substantially horizontal base structure I33 on which is slidably mounted a fixture I34 comprising a casing I35 in which a tubular shaft for sliding each unit relative to the base struc- I 36 is journalled The tubular shaft I36 is pro vided with a pulley I31 which is drivingly connected by a belt I38 with a shaft I39 of a motor I40, or other suitable driving means, preferably mounted on top of the casing I35. As illustrated in Fig. 1, two fixtures I34 are slidably mounted on the base I33 and each is provided with a casing I having a tubular shaft drivingly connected with the motor I40. Inasmuch as these units are identical, the description of one would serve for the description of the other.

Mounted on the adjacent ends of the tubular shafts I35 of each unit is a work holder comprising a cylindrical cup I 4| having a recess I42 for receiving a bearing member I43 and a counter-bored recess I44 in which a work displacing member I45 is slidably mounted. The work displacing member I45 has a stem I46 extending axially through the tubular shaft I36 beyond the pulley I31. The external end of the stem I46 is provided with an enlarged head I41 for .fa-

cilitating driving of the work I43 from the recess I42 of the work holding member. Each unit is so disposed as to bring the axis of rotation of the work holders into such angular relationship as will align the surfaces I48 of the work M3 in the manner illustrated in Fig. 1. These surfaces are frusto-conical and the units are arranged in the angular relationship shown in this figure.

Disposed between the work holders I4I of the units is a lapping fixture, generally designated by the numeral I 49, which, in this form, is disposed horizontally. The lapping fixture includes a support I50 on which the body portion of the fixture I 5| is adjustably mounted. The body portion I5I may be adjustably fixed in a selected position by clamping bolts I52 whichextend through elongated apertures in the body portion I5I and which are threaded in apertures formed in the support I50. Formed in one end of the body portion I 5| is a recess I53 in which a block I 54 is slidably mounted. Pivotally attached to the block I54 by a removable pin I55 is a lapping element holder I56 having a pair of lapping elements I51 thereon, each of which is engaged with the surface I48 of one of the bearing members I43. The lapping element I51. preferably comprises an abrading stone structure, or any suitable abrading material. The block I54 is provided with a slot- I 58 in which an eccentric pin I59 is carried by a shaft I60 of a motor I6I. The motor I 6| is mounted on the body portion of the lapping fixture or otherwise suitably supported. In order to yieldably urge the lapping elements I51 against the surface of the work operated upon, the longitudinal bar of the holder I56 may comprise a strip of resilient metal which may be deflected slightly by proper adjustment of the body portion of the lapping fixture so as tained when the angularity of the lines traced ture I 33, in order to move the work away from the lapping fixture I49. In this form of the invention, the velocity of the reciprocatory movement of the lapping elements produced by the operative driving connection thereof with the motor I6I will likewise be predetermined with respect to the rotative movement of the work in order to produce the foregoing results.

The surfaces lapped by apparatus embodying the invention and in accordance with my improved lapping process may be brought to a mirror-like actual physical smoothness much superior to that produced by the combination of aconventional lapping process followed by polishing. Of course, if it is desired to further finish surfaces which have been lapped in ac-, cordance with the invention, such surfaces may. be subjected to polishing treatment with rouge or other suitable fine abrasive. Surfaces lapped in accordance with the invention are found to be free from excessive scratches, scores and 'grooves, such as have resulted in prior lapping operation from repeated action of localized hard areas of the lapping element upon substantially the same areas of the work or areas adjacent thereto. The inscriptions traced upon the work angular relationship with respect to each other.

It is preferable to cause 'the resultants of the movements produced during successive half cycles of the reciprocatory movement to intersect at substantially right angles to each other. To accomplish this, the linear velocity of the surface operated upon and the linear velocityof the lapping elements must be substantially equal. However, since the velocity of the reciprocatory movement varies, this condition is not maintained at all-times but is approached throughout the main portions of the strokes of the lapping elements. Localized hard areas of the lapping surface, therefore, trace inscriptions on the surface-of the work during successive half cycles of the reciprocatory movement which are cross-hatched at. a plurality of different angles forming an heterogeneous arrangement of cross-hatched scratch lines, none of which develop into deep grooves or scores. While it is preferable to so predetermine the linear velocity of the movement of the work and move-. ment of the lapping elements as to bring the main portions of the scratch lines to approach right angle relationship with respect to each other, it is found that excellent results are obduring successive half cycles of the reciprocatory movement is such that the minimum angle therebetween is substantially forty degrees. In other words. the resultant of the two directional movements may vary from an inclination of substantially twenty to substantially seventy degrees to the path of reciprocatory movement. For the purpose of illustration, a cylindrical surface of substantially three and one-eighth inches in diameter would be rotated at approximately sixty R. P. M. and the lapping elements would be reciprocated at a rate of substantially 900 cyclesper minute.

In the lapping of surfaces in accordance with the invention during which the lapping element is reciprocated at a relatively high speed, it is found that the abrasive action of the lapping elements is rapid while the ridges formed during turning or other machining of the surfaces are being removed. As soon as the ridges are removed to their base line, the abrasive action decreases materially and further removal of metal is substantially discontinued. By virtue of this characteristic of the improved lapping process, surfaces can be brought to a high degree of smoothness in a relatively short time and without danger of removing sufficient material to render the articles undersize. The smoothness resulting from the actual removal of the ridges without introducing-other ridges by application of the lapping elements to the surface is of a much superior order than the mere lustrous finish resulting from polishing the side surfaces of the ridges. The large number of strokes of the lapping elements across the ridges in a direction substantially normal to their lengths, resulting from reciprocation of the lapping elements at av rate of a vibratory order, assures removal of the ridges and not mere polishing or partial flattening thereof.

Although but one specific embodiment of the invention has been herein shown and described, it is understood that various changes of details of construction and operation may be made without departing from the spirit and scope of the invention.

What I claim is:

1. Apparatus for simultaneously lapping surfaces of a pair of pieces of work including a pair of work supporting and rotating members arranged With their work supporting ends disposed inwardly in spaced relationship with respect to each other, a lapping fixture located between said work supporting ends of said members including a reciprocable lapping element adapted to simultaneously engage surfaces of pieces of work mounted on each of said members respectively, and driving means on said fixture for reciprocating said lapping element.

2. Apparatus for simultaneously lapping surfaces of a pair of pieces of work including a pair of work supporting and rotating members arranged with their work supporting ends disposed inwardly in spaced relationship with respect to each other, a lapping fixture located between said work supporting ends of said members including a reciprocable support, a lapping element pivotally mounted on said support and reciprocable in unison therewith and adapted to simultaneously engage surfaces of pieces of work mounted on each of said members respecreciprocating said lapping element.

3. Apparatus for simultaneously lapping frus- I to-conical surfaces of a pair of bearings including a pair of work supporting and rotating members having axes arranged in opposed angularly extending relationship with respect to each other and having work supporting ends directed toward but spaced from each other, a lapping fixture located between said work supporting ends of said members including a reciprocable lapping element adapted to simultaneously engage the frusto-coni'cal surface of each bearing respectively, and driving means on said fixture for' reciprocating said lapping element.

4. Apparatus for simultaneously lapping surfaces of a pair of pieces of work including a pair of work supporting and rotating members arranged with their work supporting ends disposed inwardly in spaced relationship with respect to each other, a lapping fixture located between said work supporting ends of said members including a reciprocable lapping element adapted to simultaneously engage surfaces of pieces of work mounted on each of said members respectively, and means for yieldably urging said elements against said surfaces and mechanism for simultaneously drivingly rotating said work and reciprocating said lapping element at a speed of a vibratory order.

5. Apparatus for simultaneously finishing surfaces of a pair of pieces of work including a pair of work supporting members arranged with their work supporting ends disposed inwardly in spaced relationship with respect to each other,

a fixture located between said work supporting ends of said members including a reciprocable support, an abrading element carrier including 'a resilient element carried by said reciprocable support and located between the latter and portions of said Work, abrading elements on said carrier engageable with said pieces of work and adapted to be yieldably urged thereagainst by said resilient element, and mechanism for drivingly reciprocating said reciprocable support, carrier and abrading elements in unison.

6. Apparatus for finishing a frusto-conical surface of a piece of work including a slidably adjustable tool support, a tool reciprocably mounted on said support for linear movement in a predetermined course transversely of the direction of adjustable movement of said support, said tool comprising a resilient arm having a. free end portion, an abrading element on said free end portion yieldably urged by said arm against said work, mechanism for drivingly reciprocating said tool, means for positioning and rotatably supporting said work for rotation about an axis coincident with the central axis of said surface and so inclined with respect to the linear course of reciprocation of said tool as to bring a portion of said surface into parallel relationship with respect to said course of reciprocation of said tool, means for releasably holding said tool support in a selected position to maintain said abrading element in contact with said sure 21cc; and apparatus for drivingly rotating said DAVID WALLACE.