US3660942A

US3660942A - Ball lapping device

Info

Publication number: US3660942A
Application number: US84259A
Authority: US
Inventors: Sebastian Messerschmidt
Original assignee: Individual
Current assignee: Sebastian Messerschmidt Spezialmaschinenfabrik Firma
Priority date: 1970-10-27
Filing date: 1970-10-27
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09

Abstract

A ball lapping device comprises two superimposed lapping discs spaced by a working gap, one of the discs being stationary while the other disc is rotatable and includes concentric lapping grooves in its side facing the other disc. The discs are encompassed by a rotary magazine including a circular guide path for balls to be lapped. A radial recess in the stationary disc connects the working gap with the guide path. In one mode of operation balls on the guide path are deflected by a guide from the guide path into the working gap and after being lapped for one revolution are returned by the guide to the guide path. In a second mode of operation the connection between the guide path and the working gap is closed whereby balls in the grooves are continued to be lapped until they have attained the desired surface finish.

Description

United States Patent on 3,660,942 Messerschmidt 51 9, 1972 [s41 BALL LAPPING DEVICE 3,348,338 10/1967 Messerschmidt ..s|/3 [72] Inventor: Sebastian Messerschmldt, Schonun- I gen/Bavaria, Germany Primary Examiner-William R. Armstrong Attorney-Bane, Baxley 8L Spiecens 57] ABSTRACT A ball lapping device comprises two superimposed lapping discs spaced by a working gap, one of the discs being stationary while the other disc is rotatable and includes concentric lapping grooves in its side facing the other disc. The discs are encompassed by a rotary magazine including a circular guide path for balls to be lapped. A radial recess in the stationary disc connects the working gap with the guide path. In one mode of operation balls on the guide path are deflected by a guide from the guide path into the working gap and after being lapped for one revolution are returned by the guide to the guide path. In a second mode of operation the connection between the guide path and the working gap is closed whereby balls in the grooves are continued to be lapped until they have attained the desired surface finish.

9 Claims, 4 Drawing Figures BALL LAPPING DEVICE The present application is .a continuation-in-part application based upon my copending application Ser. No. 789,614 filed Jan. 7, 1969, now abandoned.

The invention relates to a device .for lapping balls between two concentric spaced apart discs including grooves in which the balls run, one of said discs being rotary while the other disc is stationary, the balls being alternately guided between and away from the discs.

The balls disposed between the discs are set in motion by the rotation of one disc. As the balls roll along the surfaces of the grooves and discs, a sliding movement of varying magnitude is set up which constitutes the lapping force. This lapping force, in combination with suitable lapping agents, such as corundum or the like, causes gradual altering of a nonround shape of the balls to a substantially geometrically perfect spherical shape. However, the cross section of the grooves tends to change buy its coaction with the surface of the balls, and it is this cross section of the grooves in the lapping disc which has a decisive influence upon the shaping of the balls.

DESCRIPTION OF THE PRIOR ART To improve the lapping accuracy, it has become increasingly customary to associate with the lapping devices a magazine, for instance, a ring shaped plate magazine encompassing the lapping discs, in order to increase the number of balls and to improve the running-in grooves in the lapping discs. To obtain a substantially uniform ball size, the balls after each rotation between the lapping discs are guided through the magazine from which they are returned, between the lapping discs. The result is a constant alternation as between the individual balls and the various grooves in the lapping discs. Irrespective of whether with this mode of operation the balls move at random when in the magazine or are guided in a continuous series through the magazine so that they do not change their sequence, all the balls in the machine are nevertheless uniformly processed and all thegrooves in the lapping discs have a substantially uniform and cross sectional shape.

While with this mode of operation, balls which are geometrically round with only small tolerances in diameter and very accurately shaped surfaces can be produced, it has been found that the constant removal of the balls from the lapping discs, followed by their reintroduction, causes damage to the surfaces of the balls, even if such damage may amount to only fractions of one-thousandth of a millimeter.

THE INVENTION According to the invention there is provided a lapping device in which the balls are lapped between two concentric superimposed discs including grooves in which the balls to be lapped run. One of the discs rotates while the other disc is held stationary and includes a sector-shaped radial recess. The balls are fed to the recess, received from the recess and guided, after each rotation between the discs, through the magazine. When the balls have become substantially identical in size and shape, the connection between the sector-shaped recess and the magazine is interrupted and the balls are caused to rotate continuously between the lapping discs until they have the required maximum surface finish.

Interruption of the connection between the sector-shaped recess and the magazine thereby causing the balls to rotate continuously, prevents the balls from knocking against one another outside the lapping discs and thus possibly damaging their surfaces, even if only very slightly.

A further important advantage of the invention as shown by a large number of tests is that the surface finish of the balls is decisively determined by the correlation between the groove cross section and the ball cross section. This, again presumes the use of balls of substantially uniform diameter or within a very narrow tolerance, since this is the only condition by which the necessary correlation between the cross sections of the grooves and the balls is provided. However, once this correlation has been achieved, all that is required is a brief continuous rotation of the balls between the lapping discs, while the discs are closed off for the balls now stored in the magazine. Conveniently, the feed of balls to the magazine is temporarily interrupted during this stage of the operation. The lapping discs are again connected to the magazine for feeding a further supply of balls to the discs when the balls which now have. a perfect surface polish have been removed from the discs. This operation is repeated until the last ball, first processed to the required substantially identical size and shape, has also been given the required maximum surface finish. Thus, the invention prevents damage to the surfaces of the very sensitive balls precisely during the finishing operation.

Another important feature of the invention is that the finishing operation is performed in the same lapping device in which the balls have been preliminarily processed. This ensures an accurate correlation between the cross section of the grooves in the lapping discs and the ball cross section, thus again providing the best conditions for an optimal surface polishing operation.

While the invention is particularly suitable for lapping devices including lapping discs rotating around a vertical axis and a substantially horizontal rotating magazine, it can also be successfully applied to lapping devices including different kinds of magazines and different arrangements of the lapping discs.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a plan view upon the lapping device set for alternate travel of the balls between the lapping discs and along the guide path of the magazine;

FIG. 2 is a diagrammatic section along line [1-1] of FIG. 1; FIG. 3 is a plan view of the lapping device but set for continuous lapping of the balls between the lapping discs; and

FIG. 4 is a diagrammatic section taken on line IV-IV of FIG. 3.

Referring now to the figures more in detail the exemplified lapping device comprises two coaxially superimposed lapping discs 1 and 5 which are rotatable relative to each other. As shown, the upper disc 5 is stationary and the lower disc I is rotatable and mounted for this purpose in a carrier 2 which should be visualized as being driven by a suitable power drive means (not shown). The two discs are spaced apart to define a working gap 23 therebetween. The upper disc 5 is mounted on a carrier 6 which should be visualized as being detachable from the device by lifting it. The lower disc has in its side facing the upper disc three concentric lapping grooves 3 for lapping balls 4 in the grooves by the relative rotations of the two discs. While three grooves are shown, it should be understood that more or less than three grooves can be used. The cross sectional shape of the grooves is, of course, selected in accordance with the desired dimensions of the balls to be lapped. The upper disc includes a radially disposed sectorshaped cut-out 7 the outer circumferential width of which may represent an angle of about 40.

The two lapping discs 1 and 5 are eccentrically disposed within an annular magazine 8 preferably of the plate type. The rotational axis of the magazine is spaced fromthe center axis 9 of the discs by a distance x on the diameter 10 of the magazine as it is shown in FIG. 3. Thus diameter 10 constitutes an angle bisector for cut-out 7 of disc 5.

The disc 1 is presumed to rotate in counter-clockwise direction as it is indicated by an arrow 12 while the magazine 8 rotates in clockwise direction as indicated by an arrow 13. Of course, the rotational directions of disc 1 and the magazine can be reversed. In some instances disc 1 and the magazine may be rotated in the same direction, provided that a substantial speed differential is maintained.

Magazine 8 has a rotary peripheral outer wall to which is fixedly secured for joint rotation a ring member 14 which constitutes a circular guide path. The radially inner rim of ring 14 is bordered by a stationarily mounted annular wall 16. This wall has in radial alignment with the cut-out 7 in the upper stationary disc 5 a circumferentially elongate opening 17 as it is clearly shown in FIGS. 1 and 2.

A guide strip 18 is detachably secured to upper stationary disc 5. The radially inner end 19 of the strip is bent off toward wall 20 of cut-out 17, that is, in opposition to the rotational direction of disc 1 and the radially outer end 21 is bent toward magazine wall 15 in the direction opposite to the curvature of bent-off portion 19. A closure member 24 is displaceably held by means of suitable retaining means such as guides on the upper disc 5 to permit selective opening and closing of the outer end of cut-out 7 and thus also of opening 17. Of course, closure strip 25 can also be adjustably mounted on inner magazine wall 16.

The lapping magazine as hereinbefore described can be selectively operated in two modes of operation.

According to FIG. 1 the device is set for a mode of operation in which balls 4 travelling on guide path 14 are deflected at 22 by engagement with one side of guide strip 18 into the working gap 23 and thus into coaction with lapping grooves 3. As previously explained, they are lapped while disc 1 rotates in counter-clockwise direction. After having travelled through substantially one revolution the balls enter cut-out 7 and are now deflected by engagement with guide strip 18 on the opposite side thereof into guide path 14. After travelling in this guide path through about one revolution they are returned at 22 to the working gap. This cycle is repeated as long as the guide strip 18 is inserted into the device and opening 17 is left open.

For the second mode of operation, guide strip 18 is removed and opening 17 is closed by inserting closure strip 24 as it is shown in FIG. 3. As a result, balls 4 in the grooves in lapping disc 1 remain in these grooves for an indefinite number of revolutions of the'disc while balls on guide path 14 travel around in the magazine without being subjected to lapping action.

Such continuous lapping of the balls is continued until the same has reached the desired configuration and surface finish.

As it is evident, the balls in the grooves are not likely to hit one another with any force whereas balls on guide path 14 may collide thereby causing surface damage however slight. When the lapping of the balls in the mode of FIGS. 3 and 4 is completed the operator may revert to the mode of FIGS. 1 and 2 either for a prolonged period of time or for only a period of time sufficient to feed a new supply of balls into the working gap 23 after removing the finished balls by lifting carrier 6 and thus also disc 5.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

l. A device for lapping balls of rigid material, said device comprising in combination:

a pair of lapping discs disposed in mutually parallel and spaced apart relationship, one of the discs having in its side facing the other disc a circular groove concentric with the discs, the spacing between the discs constituting a working gap, the grooved disc being rotary;

an annular magazine encompassing both said discs, said magazine defining a circular guide path for balls to be lapped substantially coplanar with the grooved side of the rotary disc,

said other disc including in its side facing the grooved disc a radially disposed cut-out communicating with said circular uide path to provide access for balls from the guide pa of the magazine to the working gap and vice versa;

and

a closure means for selectively opening and closing the connection between the guide path and the working gap.

2. The lapping device according to claim 1 wherein said closure means comprises an opening in a wall portion of the magazine facing the cut-out in said other lapping disc, and a closure member for selectively covering and uncovering said opening.

3. The lapping device according to claim 2 wherein said other lapping disc is stationarily mounted, and said closure member is releasably attached to said stationary disc.

4. The lapping device according to claim 1 and comprising a guide member detachably insertable into said cut-out, said guide member substantially extending across the radial width of the guide path and across the grooved side of the rotary disc, substantially bisecting the radial width of said cut-out.

5. The lapping device according to claim 4 wherein said magazine and said rotary disc are rotatable in opposite directions, balls on said guide path impacting against one side of said guide member being deflected into the working gap and balls in the working gap impacting against the other side of the guide member being deflected upon the guide path.

6. The lapping device according to claim 5 wherein said guide member is a guide strip terminating at its end within the guide path in a portion bent in opposition to the rotational direction of the magazine and at its end within the working gap in a portion bent in opposition to the rotational direction of the grooved lapping disc.

7. The lapping device according to claim 1 wherein said magazine comprises two concentric radially spaced walls, the outer one of said walls being rotatable and having secured thereto a ring member defining said guide path and the inner wall being stationary and including an opening constituting said connection between the guide path and the working gap.

8. The lapping device according to claim 7 wherein the center axes of the discs and the rotational axis of the outer magazine wall are eccentrically disposed, the outer peripheral wall of the rotary lapping disc and the stationary inner wall of the magazine including wall portions disposed in tangential relationship, said tangentially disposed wall portions including the cut-out in the rotary disc and the opening in the inner magazine wall in radial alignment with each other.

9. The lapping device according to claim 1 wherein the disc facing the groove is operationally stationary and mounted for lifting out of coaction with the grooved disc.

Claims

1. A device for lapping balls of rigid material, said device comprising in combination: a pair of lapping discs disposed in mutually parallel and spaced apart relationship, one of the discs having in its side facing the other disc a circular groove concentric with the discs, the spacing between the discs constituting a working gap, the grooved disc being rotary; an annular magazine encompassing both said discs, said magazine defining a circular guide path for balls to be lapped substantially coplanar with the grooved side of the rotary disc, said other disc including in its side facing the grooved disc a radially disposed cut-out communicating with said circular guide path to provide access for balls from the guide path of the magazine to the working gap and vice versa; and a closure means for selectively opening and closing the connection between the guide path and the working gap.