US2387138A - Grinding method and apparatus - Google Patents

Description

-k 16, 1945. H. F. FRUTH GRINDING METHOD AND APPARATUS 2 Sheets-Shet 1 Filed. July 14, 1945 INVENTOR. Hal F Oct. 16, 1945. i-l. F. FRUTH GRINDING METHOD AND APPARATUS Filed July 14, 1943 2 Sheets-Sheet 2 v INVENTOR. HMIfiuZ/v, BY'

Patented on. 16, 1945 GRINDING METHOD AND APPARATUS Hal F. Fruth, Chicago, Ill., assignor to Galvin Manufacturing Corporation, Chicago, Ill'., a corporation of Illinois Application July 14, 1943, Serial No. 494,681

11 Claims.

The present invention relates to improved grinding methods and apparatus and has for one of its objects the provision of improved methods and apparatus for grinding the rounded outer surfaces of an object.

It is another object of the invention to provide improved methods and apparatus for grindingthe outer surfaces of small tubular objects or rings, such, for example, as piston rings, without abrading the edge or inner surfaces thereof.'

According to another object of the invention, I

the abrading action is produced in an .entirely tube which may be utilized in conjunction with I the apparatus shown in Fig. 1;

Fig. 6 is a side view of a modified object holding assembly;

. Fig. 7 is an end view of theholding assembly shown in Fig. 6; i

Fig. B'isan end sectional view of the holding assembly shown in Fig. 6 illustrating the manner in which the objects are supported thereon; and Fig.9 is a detail view of one of the element embodied in the assembly shown in Fig. 6.

random manner and the weight of each object alone determines the contact pressure between the abrasive surface and the abraded.

surface being In accordance with a further object of the invention, the random grinding of the surfaces to'be Y abraded is enhanced by only intermittently moving the surfaces into engagement with the abrasive surface and by utilizing the relative movement between the abrading and abraded surfaces to change the segments of the abraded surfaces which are intermittently moved into engagement with the abrasive surface. g

It is still another-object of the invention to provide improved and exceedingly simple methods and apparatus for rapidly abrading the outer surfacts of relatively small tubular objects several at a, time and with a minimum expenditur of manuallabonp I It is astill further object of the invention to provide an improved grinding tube which is well adapted for use in the surface grinding of small objects.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the followingspeciflcation taken in connection with the accompanying draw ings, in which:

Fig. 1 is a side view partially in section of improved apparatus for grinding the rounded outer surfaces of small tubular objects, which is characterized by the features of the present invention;. Fig. 2 is a side view partially in section i1lustrating the details ofthe object holding assembly forming a part of the apparatus shown in Fig. i;

Fig. 3 is an end sectional view of the assembly shown in Fig. 2;

Fig. 4 is an end sectional view illustrating the manner in whichv the objects are supported upon the holding assembly within the grinding tube forming a part of the apparatus;

Fig. 5 is a side view of an improved grinding Referring now to the drawings and more par-,

'ticularly to Figs. 1, 2, 3 and 4 thereof, the inn proved grinding apparatus there illustrated com prises a base l0 which rotatably supports an elongated grindingtube holder l l, slidably supports an-object holder-assembly indicated generally at l2, and rigidly supports an electric motor l3having the function of rotating the grinding tube holder ll. More specifically, thetube holder ll is provided with a shaft .llb and comprises an elongated portion Ila having a. tubular recess therein which is adapted to receive a grinding tube l4. Theshaft ll b is suitably journaled in bearings carried by upstanding bearing pedestals l5 and I6 which are rigidly supported upon the base "I. Sleeves I1 and 18, set screw mountedupon the shaft III) of either side of the pedestal l5, may be employed for restraining th shaft l lb against. axial movement relativeto the two bearing pedestals l5 and I6. At its left end, the

shaft l lb rigidly mounts a pulley l3 which is connected by means of a belt 20 to a driving pulley 2| carried by the rotor shaft of, the motor l3.

As best shown-in Figs. 2 and 3 of thedrawings, the object holder l2 comprises an upstanding" bracket 22 having an'elongated base portion 22a which is. provided with flared and ground edge This slot is provided with downwardlyand outwardly flared bearing surfaces 23a and 23b which guidably engage the flared edge portions of thebracket base 22a. In the upstanding portion thereof,'t bracket 22 is provided with an elongated vertically extending slot 24 fo'rslidably receiving the extended bearing portion 25a of a motor and shaft supporting bracket 25. This bracket is provided with a horizontally extending base portion 25b upon which a small electric mo t0! .6. is suitably mounted. Through the bearing portion 250 thereof, the bracket piece 25 is bored to receive a shaft 21 which rigidly mounts an eccentrically arranged tube or ring-supporting roller 28 at its leftend. A'sleeve 28 set screw'mounted upon the right end portion of the shaft 21 .may

be utilized to restrain the shaft assemb y a ainst,

axial movement relative to the bracket piece '25. At its extreme right end, the shaft 21 mounts a pulley 30 which is connected in driven relationship with the motor driving puileyflil by means of a. belt 32. In order to maintain the bracket piece 25 and associated elements rigidly supported upon the bracket 22, assembly screws 33 and 34 and associated slots spanning bars 35 and 88 are provided. More specifically, the screws 23 and 34 are threaded into tapped holes drilled into the bracket piece 25 so that the heads thereof may be drawn into tight engagement with the adjacent surfaces of the spanning bars 35 and 88 when the two bars are positioned to span the slot 24 and to engage the face surfaces of the bracket-22. In order to facilitate the explanation pertaining to the operation of the apparatus, the eccentrically mounted roller- 28 is illustrated as supp rting a plurality of piston rings 31. The rings or another-tubular obiect'telescoped over the roller "are prevented from slipping off the end of the-roller by a, retaining .plate 38, which is of: greater" diameter than the'roller 28 and is concentrically mounted upon the end of the roller by means of assemblyscrews 38. e

From the above descriptiomlit-will be understood-that the ringor "tube holdingassembly is readily-adiustable longitudinally ofthe base. [8

forthe purposeofinserting. the-roller within.

the-grinding tube 14 andwithdrawing the roller fromthis tube.v Thus the loading and unloading of the-roller with a desired number of piston rings, for example, iseas'ily accomplished. The holding assembly I2 is also such that the roller 28 may be readily adjusted in .avertical direction relative to the axis of rotation of the grinding tube [4, whereby the apparatus may be readily adapted for the grinding of tubes or rings having different outside diameters.

The grinding tubes which are used in the apparatus may be of the improved form illustratedin Figs. ;1 and 5 of the drawings. As there shown,

the illustrated grinding tube l4 comprises aflexible backing material, formed of cloth or paper, for example, which is coated at its inner surface with particles of a suitable grinding, material...

More specifically, the tube ll may be formed by spirallysedge: winding an elongated strip of ab.- rasively coated cloth and "by suitably cementing the abutting edges of the strip. In order to mini-: mizevariations in the thickness of the tube, occasioned by providing a connecting means for joining the abutting edges of the strip, the edges are preferably spliced by wrapping the tube as formed from the spirally wound strip with wire gard'that once the position of thebracket piece 25 and the elements carried thereby is established, no further adjustment is necessary so long as cloth of small mesh and thin strands, andthen pressing the strands of the wire cloth into the a cloth backing" material of the strip. When this splicing technique is employed, a tube of uniform thickness and of rugged character is obtained.

The character of the abrasive material with which the backing strip is, coated depends, of course, upon the particular grinding operation which is to be performed. If relativelywfastgrinding is 'desired, a. tube'coated with an abrasive material consisting of No. 220 screen. mesh silicon carbide may be employed. On the other: hand, if relative-.- ly slow-grinding accompanied by a high polish of the ground surfaces are desirecba tube coate with No. 320 screen mesh silicon carbide may be used. In this regard it will be understood that the particles of abrasive material may be afllxed to the surface of the strip by means of asuitable cement or adhesive substance and by employing any of the coating methods conventionally practiced in the art. The grinding tube may also be formed by impregnating a length of copper tubing with grinding powder on the inner surface thereof. Alternatively, a grinding powder impregnated copper strip may be edge wound to form the tube. As a further alternative the tube may be formed of a moldable material having the surface of the-holding cup Ha. Assuming, for

example, that the outer rounded bearing surfaces of a plurality of piston rings 31 are to -be ground and polished, the 'holding'assembly i2'is slid to the position illustrated inFig. 1 of the drawings, following which the rings are telescoped over the retaining plate 38 and are left hanging suspended upon'the roller '28, preferably'with their adjacent edges'in engagement. The assembly I2 is next slid longitudinally of the base Hi to pro ject 'the roller '28 within the tube andthus bring the-lower surface of the rings 38 into apo'-- sition for engaging the abrasively coated inner surface of'the tube. The next operation is that of adjusting the vertical position of the bracket piece 25 and its associated elements relative to the bracket piecei'22 so that when the section of the eccentri'cally mounted roller 28 of shortest radius overlies the shaft 21, the inner surfaces of the rings 31are just out of engagement with the ad,- jace'nt'u'pper surface of the roller and the lower outer surface segments of the rings engage the abrasively coated inner surface of the tube I4. This may be accomplished by loosening the screws 33 and 34, adjusting the bracket piece 25 and its associated elements to the desired vertical position, and then 'retightening the named assembly screws to retain the bracket piece 25 in its ad-' justed position. It will be understood in this rerings or tubes of the same external diameter are to be ground. After the above-described adjust ments have been made, operation of the motor l3 to rotate thegrinding tube holder II and operation of the motor 26 to rotate the roller 28 may be initiated. In this regard it is noted that the motor I3 is arranged to drive the grinding tube-holder H at a relatively high rateof speed,

whereas the motor 26 is essentially a slow speed device and is arranged to drive the shaft 21 and roller'28 at'a relatively'slow rate of speed.

As bestish'own in Fig.4 of the drawings, dur-' ing that portion of each revolution of the roller 28 when the section of theroller of shortest radius is moving to.overli ethe shaft 21, the lowermostouter peripheral se'gments of the rings 31 are droppedinto engagement with the abrasively coated inner surfaceof the grinding tube l4.

aes'mes With the roller 28 in this position, the upper surface thereof is disengaged from the upper inner peripheral surfaces of the rings, so that the rings are wholly and completely supported upon the abrasively coated inner surface of the grinding tube. As the shaft 21 continues to rotate under the influence of the driving motor 26, the radius of the roller section which underlies the inner top surface segments of the rings steadily increases until the roller surface engages the inner ring surfaces, at which time the ringsare again supported upon the roller 28. This support of i the ringsby the'roller is maintained until such time as the decreasein radius of the roller sup-f porting section again permits the surfaces of the rings to be brought into enga ement with the inner surface of the grinding tube. It will thus be apparent that during the continuouter peripheral ous rotation of the eccentrically mounted'roller 28, the rings 31 are intermittently dropped into engagement and moved out of engagement with the abrasively coated inner surface of the grind ing tube I 4.

During at least a portion of each period when the outer peripheral surfaces 'of the rings engage; the abrasive surface of the grinding tube, the

rings are wholly and freely supported upon the grinding surface. Since this surface is traveling at a relatively high rate of linear speed,relative movement occurs betweenthe abrading surface and the engaged peripheral surface segments of f the ring, with the result thatthe surface segments of the rings areabraded and polished. Because of, the frictionalengagement betwejen th'e rings and theabrasive surface of the grinding tube .14

during those short intervals when the rings are wholly supported upon this surface, the rings are spun at random about the roller 28. The extent of rotation of each-ring is of course indeter minate and may vary widely as between different grinding intervals. Accordingly, during different and succeeding grinding periods differ'ent periph- I eral surface segments of each ring are moved into engagement with the abrasive surface of the grinding tube I4. This insures that the peripheral surfaces of' the rings will be ground entirely at random. On an average basis, however, and when the grinding action isallowed to proceed for a given time interval of reasonable length, all surface segments of each ring are abraded to substantially a uniform depth. d

The random grinding of the ring surfaces'is contributed to by the rotation of theeccentrically mounted roller 28; Thus, during each'period' when the rings are supported upon the roller out of engagement with the abrasive surface, of the grinding tube I4, they are rotated through a; given and fixed angle, thus insuring that during the next succeeding grinding intervaldifferent segments of the outer peripheral surfaces of the ringswill be brought into engagement with the abrasive surface of the'tube l4. After the rings have been ground: to the desired thickness as determined by conventional methods of micrometer measurement or have been polished to the desireddegree by utilizing a tube coated with an exceedingly fine abrading material, they may be removed from the holding assembly 12 in a manner which'will -be clearly apparent from the above explanation.

In grinding to a given thickness a batch of rings which have been selected at random, the

rings may be measured as to thickness, and ground for a given time interval such that certain of the rings of the batch arebroug ht substantially to the desired thickness. The remaining rings, i. e. those initially having the greatest thickness, may be classified and subjected to further grinding for time intervals which may be calculated by correlating the grinding speed with the difference between the desired thickness and the actual thickness after the initial grinding operation is completed. In other words, following the initialgrinding operation, the rings may be grouped according to the thickness thereof and thoserings of each group may be subjected to a.

further grinding operation for an interval which. is calculated from the difference between the actual and desired thicknesses as correlated with the speed at the grinding action proceeds. In the secondary grinding operation, it may be desirable to use a grinding tube coated with abrasive particles having a substantially-greater fineness than th particles eration may proceed-at a less rapid rate and thus may 'be more accurat y'performed on a time basis.

Thedesired intermittent and random grinding, of 1 the rounded outer surfaces of tubular objects may also be obtained by utilizing the arrangeh and Q of the c'iraw theringsor tubes In 'it i' st an r. ment, which is 'of cage-like form; aC-retaining plate '40 is rigidly mountedupon an ,ass,embly, plate '4] by means of three ment illustrated in Figs; 6, .7, 8 ings for resiliently supporting within the grinding tube I4.

rods 42, 43. and 44 which extend parallel-[toeach other and are rigidlysecured to the, two plates 40 and!" at opposite ends;thereof. The plate 4| is adapted to be rigidly and adjnstably. mounted uponthepedestal bracket '22 by means of ast '45 and 46 which extend through sembly screws theguide slot '24 of the bracketZZ and are threaded'into the assembly plate 4 l tubular parts 'upon the holder assembly, a flexible element 41 in the form ofan elastic band or acoil spring of'small diameter-is stretched be.- tween the two plates 40 and 4| and suitably anchored to these plates the element to provide engages the inner or tubes.

a bearing surface which In the operation of the modifiedlholdertassembly to produce the desired random grinding .1 s of the ring or tube surfaces, the positionoi the assembly is vertically adjusted along the bracket 22 until the inner surfacesof the rings 31,, for

example, are partially supported by the tube 48- and resilient element 4'! when the lower. periph-' eral surface segments of 'therings engage the abrasive "surface ,of the grinding tube; l4. In other words, the weight of the rings 31 is partially'utilized to stretch the resilient element 41 to a deformed position which it would not occupy if the rings were not partially supported thereupon. With the ring holding assembly adjusted to the vertical position just described and during 7 rotation of the grinding tube l4 u'nderfthe influence of the'driving motor era] surfaces of the rings d 31 are continuously moved intermittently and at random into engagement with the'abrasive surface of the grinding tube; In this ca'se,the inherent irregularities, namely, the hills'and valleys, in the abrasive surface of the grinding tube employed, are utilized I of the tim mt au I used; in order that the secondary .grinding opangularly spaced apart i;

Forthepurpose of resiliently and directly 'supportingrings or short at the opposite ends there. of. In order to'prevent excessive wear and sagging of the elastic element 41,1, tube,48.formed of metal, fiber or the like may be telescoped over 50 peripheral surfaces of the rings l3, the outer periph- I abrasively coated inner surface of the grinding tube. The desired up and down movementof the rings into and out of engagement with the abrasive surface of the grinding tube is of course maintained so long as the grinding tube continues to rotate under the driving force of the motor l3.

From the above explanation, it will be understood that in accordance with the present invenj tion improved methods and apparatus have been provided for obtaining complete random grinding or the rounded outer surfaces of rings or tubular articles. The material from which such articles are constructed is of no importance since abrad-' ing materials are available in granular form and suitable for coatingthe inner surfaces of the grinding ring, which will cut the surfaces ofparts or articles formed of metal, glass, stone, quartz or practically any other material in commercial use. It will also be apparent that the grinding operations are fully automatic in character when once started and, accordingly, that a minimum intermittently moved into engagement withsaid of labor isinvolved in grinding and polishing the surfaces of a given number of articles. Further, the methods and apparatus are particularly well adapted for use in the grinding of relatively narrow or short tubular objects such as piston rings,

surface which contact said abrasive surface as said rounded surface and said abrasive surface are intermittently moved into engagement.

3. The method of grinding the surface of a round object, which comprises continuously raising and lowering said object so that the lower surface segment thereof is intermittently brought to bear against an abrasive surface, producing relative movement between said abrasive surface and the engaging segment of said rounded surface, and utilizing the frictional engagement between said abrasive surface and the engaging surface of said object continuously to change at random the segments of said rounded surface which are intermittently moved into engagement with said abrasive surface.

, 4. The method of grinding the rounded surface of an object, which comprises continuously bouncing said object upon a continuously moving abrasive surface with said rounded surface engaging said abrasive surface during each bounce cycle, and utilizing the frictional engagement between said abrasive surface and the engaging surface ofsaid object continuously to change at random the segments ofsaid rounded surface which are abrasive surface.

5. The method of. grinding the rounded outer surface of. an object, which comprises intermittently bringing said rounded surface and a continuously moving abrasive surface into engagement, and utilizing the frictional engagement between said abrasive and roundedsurfaces continuously to change at random the segments of which,-when stood on edge, have a tendency to topple over and hence are not adapted to centerless grinding methods. In this regard, it will be observed from the above explanation that the random grinding action is produced solely at the outer peripheral surfaces of the rings with absolutely no edge grinding thereof. This featureof the invention is of extreme importance in the grinding of" piston rings, wherein the edges are precisely machined to exact dimensions and-are provided'with polished surfaces which must not be scratched or otherwise marred during the peripheral surface grinding operations.

While different embodiments of the invention have been disclosed, it will be understood that various modifications may be made therein, which are within the true spirit and scope of the invention.

I claim: I 1

1. The method of grinding the rounded outer surface of an object, which comprises continuously moving said object so that the rounded surface thereof intermittently engages an abrasive surface, producing relative movement between said abrasive surface and said rounded surface,

and utilizing the frictional engagement between engagement, producing relative movement be tween said abrasive surface and said rounded surface, and utilizing the frictional engagement between said object and said abrasive surface to change at random thesegments of said rounded said rounded surface which are intermittently Y engaged by said abrasive'surface.

6. The method of grindingthe rounded outer surface .of an object, which comprises intermittently bringing said rounded surface and an abrasive surface into engagement, producing relativemovement between the engaging abrasive and rounded surfaces, and. utilizing the frictional engagement between said abrasive and rounded surfaces continuously to change at random the segments of said rounded surface which are intermittently engaged by said abrasive surface.

"I. The method of grinding the outer rounded I surface of a resiliently supported object, which comprises positioning said'object so that a surface segment thereof engages an abrasive surface, continuously moving said abrasive surface.

relative to laid object, and utilizing the irregularities of said abrasive surface to produce oscillation of the resilient structure supporting said moving said object so that the outer surface thereof is intermittently moved into engagement with said abrasive surface and means supporting said object so thatthe frictional engagement between said abrasive and outer surfaces causes the segments of said outer surface which intermittently engage said abrasive surface to be changed at random.

9. Apparatus for grinding the outer surface of a round object, comprising, in combinaand means for continuously moving said object so that the outer surface thereof is intermittently moved into engagement with the abrasively coated inner surface of said tubular member.

10. Apparatus for grinding the outer surface of a round object comprising, in combination, a tubular member provided with an abrasively coated inner surface, means for rotating said member about its axial center, and resilient means loosely supporting said object within said tubular member so that segments of the outer surface of said object may be continuously bounced into and out of engagement with the abrasively coated inner surface of said tubular member durin rotation of said tubular member.

11. Apparatus for grinding the rounded surface of an object comprising, in combination, an aurasive surface, means for alternately moving said rounded surface and abrasive surface into and out of engagement, means for producing relative movement between said surfaces when engaged, and resilient means supporting said object for bouncing engagement with said abrasive surface so that the intermittent frictional engagement between said surfaces causes the segments of said rounded surface which intermittently contact said abrasive surface to be changed at. random.

HAL F. FRUTH.

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