US2408334A - Lapping method and machine - Google Patents

Description

Sept. 24,1946. I D. s. OLIVER 2 8 4.

LAPPING METHOD AND MACHINE v Filed July 31, 1944 2 Sheets-Sheet 1 2119'. j a] E Zea/Z672! liver D. S. OLIVER LAPPING METHOD AND MACHINE Sept. 24, 1946.

Filed July 31, 1944 2 Sheets-Shee't 2 f'lverzf or eZZer'Z 5 Oliver Patented Sept. 24, 1946 LAPPING METHOD AND MACHINE Delbert S. Oliver, Euclid, Ohio, 'assignor to Pesco Products 00;, Cleveland, Ohio, a corporation of Ohio This invention relates to arrangements for highly and accurately finishing rotative bearing and sealing surfaces particularly those having an annularorringshape.

Prior to this invention it has been found extremely difficult to properly finish a'rad-ially extending bearing and seal surface on 'adrive shaft. Equal difiiculty has been encountered'in an effort to accuratelyfinish the bearing and seal surface on the ring portion of adiaphragm seal assembly.

I have found that one of the principal reasons for the 'dificulty encountered results from the .diflerences in the relative linear velocity between the particles of the abrasive and the surface being finished. In order to produce a substantially perfectbearin and seal surface this condition had to be corrected and some; arrangement worked out whereby substantially uniform abrading action could be accomplished throughoutthe bearing and seal surface notwithstanding; the fact that this surface was-annular or circular in shape. p g 7 It is a principal object ofthis invention to provide. a finishing arrangement, for annular or ring-shaped bearing surfaces wherein the abrading means is given a linear relative velocity relative to the bearing surface throughout the radial extent thereof that is substantially uniform. 1 I 1 It isa further object to provide in a finishing arrangement of the present type an improved holding means for the abrading material and holding means for the workpiece having abearingsurface thereon to be finished, the work hold ing means being effective to presentthebearingsurface with reference to'the abrading material Application July'31, 1944,. Serial No. 547,389.

' (i c aim o1i5'1 13i) drawings forming a part thereof and wherein:

Fig. l is a view in elevation indicating schematically an arrangement incorporating a preferred embodiment of my invention; v Fig. 2 is a broken away sectional view substantially on the line '2--2 of Fig.1;

Fig. 3 is a broken away sectional substantially on the line 3+3 of Fig. 1.; ,Fig. 4 is a broken away sectional view of an alternative, modified embodiment of my invenftionyand I g' w Fig. 5 is a broken away sectional view taken taken view taken I substantially on the line 5 5 of Fig. l.

Referring now in greater detail to the figures of the drawings and first to the preferred embodiment shown in Figs. 1 to the arrangement in corporating my invention is composed generally of an abrading or lapping tool assembly A, a-work piece holding assembly 13 adapted to hold a work piece C in proper relation to the lapping tool, a turning power transmission assembly indicated generally at D and a source of power E. g

V The present invention is directed particularly to the construction and mode of coaction-of abrading or lapping tool assembly A and work holding assembly B whereby to provide a more perfect annular or circular sealand bearing surface on work piece C. I v W Abrading or lapping tool assembly A comprises a base l6 rotatably supporting the finishing tool assembly for turning about a vertical axis. A

pair of concentric coaxially v extending radially and support therefor in such a manner that ro tation of-thework holder and of the abrading material .holderin the same direction at selected relative speedslproduces relativeli-near yelocity of substantially the same order between all of the particles'of the abrasive and the-porticnsof the bearing surfaces-contacted thereby. v

.A further and more detailed object is the pro-,

vision in an arrangement of the present type of a novel and particularly effective-holding and tensioning arrangement for abrasive sheet material-suchas emery cloth or sandpaper and functioning to give the requisite backing-support to the sheet when engaged by the bearing surface to be finished thereby.

Other: and; more detailed obiects, advantages" and uses-of invention will become apparent from a reading of the following specification. taken in connection with the accom'panyingv spaced walls or lands II and I2 terminate inra corresponding pair of finishing material supports ingsurfaces I la and Ma, each of these terminal surfaces-being disposed in a plane perpendicular to theaxis of rotation of the finishing tool assembly A. 3 I

The interveningspace between walls l l and I2 is preferably, enlarged to provide a chamber 13 for the reception of anyenlargement that may be present on the work piece C being finished as will appear. The space [4 between the finishing material or. abrasive supporting material-surfaces I la and Ilia forms a very important part in the mode of coaction necessary. to .th e'accom plishment of the substantially perfectbearing and seal surface on the work piece as will appear. To facilitate the introduction of any enlargement that may be present on the work piece C there is providedan enlarged. opening Hi. It will be furtherincted thatwall terminalsurfaces Ho and l2a each have a radial dimension that is only a fraction of the total radial dimension of l the Work piece and thatthe bearing seal surface complished by positioning a suitable bonded.

abrasive sheet such as emery cloth or sandpaper in supporting contact with surfaces I Ia and I2a.

The work holding assembly B preferably comprises a rotatable holding member proper I'l formed with a coaxial bore I3 having splines I9 protruding radially inwardly from the wall thereof for cooperation with complementarily formed splines 21 on the work piece C for effecting the.

driving thereof. The terminal of bore I8 is provided with a resilient cushioning ring 2 I functioning to allow' for the necessary angular adjustments between the holder and the work piece 0 and for holding the same'firmly but resiliently against the abrading or lapping tool A.

The work piece C may take a number of different forms the essential structure of each of which includes an annular or ring shaped bearing and seal surface 26 extending in a radial plane perpendicular to the normal axis of rotation of the work piece C. The work piece C must be arranged in driving relation to the holder B and in the present instance this is accomplished by the splines 21 on the work piece cooperating with the complementary splines IS on the holder. The particular work piece C shown in Fig. 3 further includes a reduced cross section coaxial stem 28 terminating in a second enlargement 29 which may also have splines thereon. The present abrading tool assembly A is particularly effective for cooperation with this type of work piece since the reduced cross section stem 28 readily passes between spaced walls II and I2 and-the enlarged chamber I3 provides for enlargement 29 carried on the terminal portion of the work piece.

Turning power transmission assembly D may take various forms the essential characteristic required thereof being that abrading or lapping tool assembly A must be rotated in the same direction as work holding assembly and work piece C. Furthermore the respective turning rate must be properly correlated with reference to one another in order to approximate as near as practicable the ideal abrading conditions. It is desired that the relative linear velocity between any radial point on the ring or annular shaped bearing and seal surface 26 and the abrading particles contacting the same be substantially the same throughout both for the inner abrading material supporting surface Na and *the outer surface I2a. It is believed that the present arrangement more nearly approximates this ideal condition than any other heretofore available. By the optimum choice of the relative dimensions of surfaces I I a of the tool assembly and the bearing seal surface 26 of the work piece and by choosing the optimum relative rate of rotation of the tool assembly and the work piece the above ideal mode of coaction is approximately realized.

I have found that particularly effective results are obtained by having the radii of walls I I and I2 several times as large as the radius of the annular surface to be finished. In addition it is important that the radial width of the respective abrasive material supporting surfaces l I! and I2 1 be no greater than the radial width of the surface 26 to be finished and preferably slightly smaller. It is of still further importance that the annular surfaces 25 overlap wall terminal surface Ila radially inwardly as indicated at 25a and likewise overlap outer terminal wall surface I2a radially outwardly as indicated at 2612. I have found that particularly elfective results are obtained if the mean radius rI2 of outer termina; wall surfaces In is made to be of the order of about six times the value of the mean radius 126 of surface 26 to be finished. By having the mean radius rI I of inner wall surface i Ia and the mean radius N2 of outer wall surface I2a arranged as described, employing a width of surfaces Ila and I211 not greater than the width of annular sur face 26 there results an overlapping between the several surfaces both radially inwardly and radially outwardly. It will now appear that when the work piece C is rotated'in the same direction as the tool assembly A the relative velocity between the outer lapping face I'Za. and annular surface 26 will be the difference between the linear velocity of the surface I2a and the linear velocity of the surface 26. The relative velocity between the inner lapping surface Ila and the annular surface 26 will be the sum of the velocity of the inner lapping surface Na and the velocity of the surface 26. While it will be apparent that, strictly speaking, this is only true as regards an average taken with reference to the median radii TI I, M2, and T26, it'is important to note that for all practical purposes this arrangement and mode of coaction produces a substantially perfectly flat surface. In other words, by means'of this arrangement it is possible for all practical purposes, to compensate for the fact that the outer lapping surface .I2a is moving faster than the inner surface Na and to thus obtain the same relative velocity between the abrading particles and the work surface 26 on both sides of the work piece C. It is found that the lapping-surfaces Ila and I2 a remain true for a long period of continuous operation and require resurfacing only after several hundred pieces have been finished.

For the purpose of applying rotative power to abrading tool assembly A and work piece holder assembly B, transmission assembly D'is provided which may comprise a pulley 3| receiving power from any suitable source indicated generally at E as being in the form of a drive belt. Pulley 3| may drive work holder assembly B directly and through means of a second pulley 32 and belt 33 drives a thirdpulley'34. Through a connecting drive shaft 36 pulley 34 drives a fourth pulley 3'1 in turnconnected by a belt38 to a pulley 39 directly associated with abrading tool assembly A. By the proper choice of the respective sizes of the several pulleys the desired optimum relative speed of rotation can be readily effected between abrading tool assembly A and work piece C. I prefer to turn abrading tool assembly A three revolutions while turning work piece C two revolutions. This has been found to give very satisfactory results. i v Turning now to the alternative modification of my invention shown in Figs. land 5, it will be apparent that the same fundamental features are involved, this arrangement being particularly adapted for finishing a radially extending bearing and seal surface of the annular type on a work piece having no protuberance extending axially in the direction of the abrading surface thus making it practicable to employ a bonded .abrasi-ve such aszemery clothrorsandpaper. The .abrading tool assembly 2A; andi-theg-work holder assembly; 23 are arranged to bezdri-ven in-ga similar manner totha-t described inv the flrstgmodiflcation, the latter functioning to,:hold and .present the workpiece "2C for finishing engagement-with the .abrading sheet forming part of theabrading :00 ass mb y. 1 A j c.

The abradingtool assembly 2-A5-compriSeS -concentric coaxiallyextending walls-fl ll and-H2 corresponding to walls H and 1250f the first modification and terminating :in abrasive sheet material I supporting spaced-apart surfaces 1 Ma and 2e. These surfaces I'I la and, l 12a arelikewise dis:

posed int-a plane perpendicular to the axis f rotation of tool assembly 2A. -'Iheradius,tuddth,

.zsupported-sealgzfand bearing :ring.

. The arrange- ;mentshownco'mprises :a seal and bearing ring proper l.28.fastened about anopening through the radial inner portionzof a flexible diaphragm support czlzaawlcy means of a fastening: ring l28b the lowetp ortion of which; cooperates with; flexrelationship.

and other relationships of terminal-wall surfaces illa and 2a with reference to thQfWOl'kaIfiBCG to be finished are determined in accordance with the same fundamentals described in connece tion with the firstmodiflcation; .Ilfhe periphery of outer wall surface :I l=2a merges with :a beveled surface portion H2b for cooperation with radial terminal portions of. a, sheet of abrasive cloth such as emery cloth or sandpaper in asmanner as will appear. An embracing ring M20 is received aboutthe outer periphery; of. wall H2 and is formed with a radially inwardly/extendingp'rotuberance 1 12d complementarily formedxon the inner side thereoffor,,cooperation with beveled surface llZbandeffectiveto firmly engage and apply the requisite-tension to the abrasive cloth I5l by contact with-the peripheral :portion' I52 thereof This; results in "snug. engagement between the abrasive cloth, -l5l and. terminalrsurfaces I I la and -l l2a,-these Qlatter surfaces func-. tioning as a backing support for the abrasive cloth and rendering the same effective in the desired critical areas sin-contact with the bearing and seal surface I26 of the work piece 20 being finished.

I Clamping ring formed in ring H20. I

Work holding assembly 2B comprises upstanding rotatable supporting shaft .l H formed with an internal bore l Ila receiving a coilcompression spring in engagement with the inner terminal thereof, the outer terminal of this spring engag .ible ring I21 1 for effectingthe flexible driving As in :the case :of. the modification of'Figu 1, it will be seen that the features: of criti'calimportance include the provision of radially spaced hacking surfaces J .I la and Him In :the more specific aspects of this modification it is. also important that wal l surfaces 1 il la 'and 1112a be 1 overlapped-both radially outwardly and radially inwardly by'theibearing and ring surface 126.

'.:.'I'his..;second modification is=of special value in'connec'tion with finishing bearing and seal surfaces .on bronze bearing rings, itbeing-quite important thatthe bearing surface bemade sub stantially perfectly flat. It-has been found necessary tohold'th'ese surfaces to a'per-l'ectionwithin the limits of two light bands. .'Bronze' or any soft material has a tendency to charge when being lapped by a loose abrasive. fore desirable that a bonded'abrasive such as emerycloth be used and this modification lends itself especially to the use of emerycloth. The novel features of the holding assemblyare-of particular advantage in maintaining the requisite tens'ionof the'emery cloth in firm-engagement with the backing surfaces thus insuring greater perfection in the finish ofthe bearing and seal surface.

While my invention has been disclosed in echnection with certain specific embodiments there- 7 H20 is fastened in abrasive cloth engaging position by means of a'radially extending locking pin |I2e carried by the wall H2 and cooperating with a bayonet slot H2 opposing said holder comprising a base rotatable ing the closed end of a work supporting member or bonnet proper I Ilc. Shaft H1 is provided with coaxial splines cooperating with complementarily formed splines l 11d formed on the inner periphery of Work supporting bonnet l I'Ic for effecting driving relation therebetween. Work supporting bonnet 1c is formed on the outer portion thereof with a recessed shoulder for the reception of a flexible ring l2! effective to resiliently and drivingly support the work piece 2C. The spring 1b is effective to supply the necessary axial pressure through the intervening flexible ring |2| to cause the desired abrading action on annular bearing and sealed ring surface I25, while at the same time this flexible ring insures the precise alignment required between bearing and seal surface I26 andthe underlying surfaces Illa and HM carry the abrading sheet in supported relation thereon.

The particular work piece 2C is characterized by the absence of any axially extending protuberance that would interfere with the proper functioning of the abrasive cloth and it may include, by way of example, a flexible diaphragm' on an axis parallel with and spaced from the holder axis; two coaxial parallel walls of substantial height having confronting abrasive supporting flanges at their ends and defining a relatively deep chamber the entrance to which is restricted by said flanges, the stem and head of the work piece being received in said chamber and entrance thereto; and radially alined recesses in said flanges effecting the insertion of the work piece head into said chamber thereby to engage the seal flange with the abrasive supporting flanges of the lapping assembly.

- '2. An apparatus for lapping a work piece as defined in claim 1 wherein yieldable cushioning means are interposed between the holder and the seal flange to accommodate angular adjustment between the holder and work piece. I

3. An apparatus for lapping a work piece having a headed stem and a flat radial seal flange;

It is thereto which is restricted by said flang'es,said flanges being spaced from each other a distance less than theldiameter of the work piece head, the stem andhead of the work piece being received in said chamber and entrance thereto, at least one of said flanges having an asymmetric region adapted to efiect the insertion'of the work piece head into said chamber thus to engage the seal flange with the abrasive supporting flanges of the lapping assembly. l

4. An apparatus for lapping a work piece which has a headed stem and an annular seal flange, comprising a rotatable work supporting holder; and a lapping assembly opposing said holder comprising a base rotatable on an axis radially oilset from the axis of said holder; spaced 00110811? tric walls of substantial height upstanding from said base; flanges on said walls projecting towards each other into the space between. said walls and having abrasive supporting surfaces that oppose opposite regions of said seal flange, said walls defining an annular chamber the entrance to which is restricted by said wall flanges,

the head and stem of said work piece being reporting the work piece; and a lapping assembly opposing said holder comprising a base rotatable on an axis parallel with and spaced from the holder axis; and two annular parallel walls of substantial height having concentric confronting flanges which provide abrasive supporting surfaces, said walls-and flanges defining a relatively deep "chamber'the entrance to which is restricted by said flanges, the distance between the confronting portions of said flanges being less than the diameter of the work piece head, the head and stem of the workpiece being received respectively in said chamber and the entrance thereto, said restricted entrance having an enlarged region for permitting the introduction of the work piece headinto said chamber past said flanges, thus providing for engagement of said seal flange with said abrasive receiving surfaces. 6. An apparatus for lappinga work piece having a headed stem and a flatradial'seal flange spaced from the head, the seal surface having an annular contour arranged in a plane perpendicular to and concentric With the stem axis; said apparatus comprising a rotatable holder supporting the work piece; and a, lapping assembly opposing said holder comprising abase rotatable on an axis parallel with andspaced from the holder'axis; means on said base defining a relatively deep annular chamber having radially spaced overhanging concentrically arranged flange portions the outer surfaces of which are adapted to receive'abrasivematerial, said flanges extending towards each other in overhanging relation'to the outer portion of said chamber thereby providing a restricted entrance of less width than the-diameter of the work piece head, the head and stem of the-work piece being received respectively in said chamber and the entrance thereto; said restricted entrance having an enlarged' region for permitting the introduction of the work piece head into said chamber past said flanges, thus providing for engagement of said seal flange with said abrasive supporting surfaces.

- DELBERT S. OLIVER.

Images