US2314312A - Grinding method and apparatus - Google Patents

Description

MarchA 16, 1943. w. c. KNAPP GRINDING METHOD AND APPARATUSy 2 Sheets-Sheet l Filed April 10, 1941 March 16, 1943. w. c. KNAPP l GRINDING METHOD AND APPARATUS 2 sheets-sheet 2 Filed April 10, 1941 .Il u 0 QAM, @1pm XL1-v CATTOMYS Hi @MA1 the improved method Patented Mar. 16, 1943 2,314,312 GmNDING METHOD AND APPARATUS William C. Knapp,

East Orange, N. J., asslgnor to Mattison Machine Works, Rockford, lll.,` a corporation of Illinois Application April 10, 1941, Serial No. 387,787

(Cl. l-94) 4 Claims.

The invention relates to the art of grinding and more particularly to an improved method of an apparatus for grinding arcuate surfaces.

One object of the invention is to provide an improved method of grinding Work pieces having limited surface areas of arcuate contour which materially reduces the operating time per piece and which is particularly suitable for the mass production of duplicate parts.

Another object is to provide apparatus of novel and advantageous construction for carrying out of grinding.

More specifically stated, it is an object of the invention to provide an improved apparatus for grinding similar arcuate surfaces on a plurality of duplicate work pieces in a single operation.

Another object is to provide novel apparatus for grinding adjacent convex and concave surfaces on a work piece in a single operation.

A further object to provide an improved fixture for grinding machines which materially facilitates loading and unloading of Athe work pieces to be ground and which embodies novel means for presenting the work pieces to an abrasive wheel.

Other objects and advantages of the invention will become apparent from the following detailed description of the novel method vand a preferred embodiment of the improved apparatus illustrated in the accompanying drawings, in which Figure 1 is a perspective view of a grinding fixture for carrying out the invention.

Fig. 2 is a transverse sectional view of the fixture taken in a vertical-plane substantially -l parallel to the axis of rotation of the abrasive Wheel.

Fig. 3 is a front view of the work supporting l xture.

Fig. 4 is' a fragmentary side View of a work piece.

Fig. 5 is a perspective view of a clamping device partially loaded with work pieces.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment and method of practicing the invention. It is to be understood, however, that I do not intend tolimit the invention by such exemplary disclosurebut aim to cover all modifications and alternative constructions, methods, and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Generally stated, the improved method of grinding contemplates the generation of an arcuate surface on a work work piece in a path substantially parallel to the plane of rotation of a rotatably drivenabrasive wheel and relatively swinging lthe wheel and work piece in a direction transverse to the plane of wheelrotation to present different portions of the work to the wheel. The center of such oscillatory movement, which may be continuous or intermittent, is coincident with the center of curvature of the arcuate surface which is to be generated.

The invention has been illustrated and will be described herein as applied to the grinding ,of the external surfaces on the ends or hubs of internal combustion engine connecting rods I0 to prepare the rods for inspection for structural flaws. It

v will, of course, be obvious tothose skilled -in` the art that the invention is applicable to grinding of other types of work pieces and for other purposes. In the present instance, each hub is ground to present a convex, generally cylindrical surface il having its centercoincident with a transverse bore l2 provided in the end of the rod for the reception of a crank pin o r thelike. Concave fillets I3 merging with the convex surface I l are also ground in the same operation.

The grinding of both surfaces i'i and i3 is accomplished in the present instance by alsingle abrasive wheel I5. The wheel is shaped to present a peripheral groove i6 complemental i'n curvature to the convex surface Il to be formed on the end of the work piece. On each side of the groove I6, the periphery of the wheel I5 is formed to provide similar rim portions of convex cross section for grinding the fillets I3 in the sides l'of the work piece. v 'i In order to utilize the wheel I5 to grind the desired arcuate contour on the work piece, provision is made for relatively reciprocating the work piece and abrasive wheel in a path substantially parallel to the plane of rotation of the wheel and, preferably, though not necessarily, simultaneously eiecting a relative oscillatory movement between the work piece and the wheel in a direction transverse to the plane of wheel rotation and about the axis of the bore I2. In the present instance, the oscillatory movement is 'substantially continuous and is effected by swinging the work piece in the direction indicated by the arrow in Fig. 1. As the work is thus oscillated back land forth, the grooved portion .of the wheel I5 grinds an arcuate end surface on the work. At the extremes of the oscillatory swing 'of the work, the rim portions Il of the wheel engage the sidescf the work piece piece by reciprocating the A understood, of course,

4 brackets and intermediate and grind the respective fillets IS-thereon. It will be observed that the relative movement between the wheel and this instance by reciprocating the work piece in the direction indicated by the arrow in Fig. 1. The reciprocatory stroke is preferably of suillcient length so that a plurality of the work pieces I8 may be presented in operative engagement with the periphery of the wheel in succession, thus enabling the entire group ofwork pieces to b e finished in a single operation.

The apparatus for carrying out the improved grinding method may be constructed either as a unitary machine tool structure or, in accordance with the present disclosure, as a fixture adapted for use with a conventional grinding machine. Herein, a motor driven abrasivewheel Il of the grinding machine is supported for rotation about a horizontal axis on a wheel head 2l which overhangs a translatable table 22. 'I'he table reciprocates along the usual horizontal ways on a rigid bed 23, the path being the plane of wheel rotation. The wheel head is ordinarily supported for vertical movement toward and from the table and horizontal movement transversely oi'v the table for purposes of adjustment and may be locked in any set position by means of a locking screw 24.

The ilxture base indicated at 2l is bolted to the top of the table 22. At each end is an upright 26 having at its upper end a bearing 21 for pivotally supporting an oscillating apron 28. The bearings 21 are located so that the pivotal axis of the apron extends tangentially of but is spaced below the wheel periphery by an amount equal to the radius of curvature of the work surface il. 'I'he apron is thus adapted to oscillate transversely of the plane of rotation of the abrasive wheel il. It constitutes a support for the work to be operated upon by the abrasive wheel and in this instance the work pieces are held in place thereon by one or more clamping devices 28 of novel construction designed to facilitate loading and unloading of the work. These devices additionally serve to position the work pieces accurately with respect to the center of curvature of their convex hub portions alined on the pivotal axis of the apron.

As shown in Figs. 2 and 3, the apron 28 comprises an elongated generally rectangular plate work is likewise eilected in.

Parallel to l piece are accurately located,

3| having spaced longitudinal anges 82 on one side to provide the rigidity essential f or accurate grinding. These ilanges may be connected by one or more cross members 33. Projecting forwardly and upwardly from the opposite or front side of the plate adjacent the ends thereof are a pair of bearing brackets 84 and 85 each terminating at its upper end in a cylindrical bearing member 38 apertured to receive the pivot pins or shafts engaging in the bearings 21. I

At their inner ends, the bearing members ll are cut away onone side to .provide upwardly opening, semi-cylindrical sockets 38. These sockets, in cooperation with similar axially alined sockets 39 formed on a bracket 48 projecting from the front of the plate substantially midway between the brackets 34 and Il, serve to support and position the clamping devices 3l on the apron as -will appear presently. It will be that the bracket 48 vand intermediate sockets will Ibe omitted in the case of aprons intended for handling only one clamping device and conversely additional sockets will be provided i'or aprons intended to carry a greater understood that and the interposed connecting rods lindrical surface on the number of clamping devices than the exemplars structure. A

Referring now to Fig. 5 of the drawings, the clamping device 28 in the exemplary form shown comprises a flat generally rectangular base member 4I at each corner of which is bolted or otherwise rigidly secured a block 42 having one end projecting laterally of the member. These blocks form rigid abutments and. with elongated'spacer bars 4l, detlne a series of parallel channels or pockets for receiving the shank portions of the connecting rods i0 constituting the work pieces. The spacer bars, as herein shown, are of generally rectangular form and are dimensioned -to provide clearance between the hubs oi' adjacent connecting rods, but it will be bars 'of other shapes and dimensions may be substituted therefor when required by a particular type o f work piece.

To provide for securely clamping the work .pieces in place, the spacer bars 4I are mounted for limited lateral movement on pilot pins 44 anchored to the base member and engaging in oversize apertures in the respective bars. A thumb screw 45 threaded into an upstanding lug 46 rigid with the base member bears against the outermost spacer bar at one end of the assembly and acts to force the entire group of bars into clamping engagement with the blocks 42 at the opposite end of the b ase.

The projecting end portions of the blocks 42 are formed with apertures 41 of the same diameter as the bores I2 in the connecting rods and a bar 48 is inserted through the apertures and the bores of the alined connecting rods, thus serving to accurately locate the same with respect to the clamping member. It will be observed that similar bars are inserted at each side of the fixture so that both ends of each work thereby enabling them to be ground without requiring removal from the clamping device. The reduced ends 50 of the bars 48 project beyond the blocks 42 at each end of the clamping device and are adapted to seat inthe sockets 28 on the apron. By simply inserting these ends in these sockets, the entire group of connecting rods carried on the clamping device is accurately located with respect to the pivotal axis of the apron. 'Ihe work piece assembly thus positioned is held in place on the apron 28 by thumb screws 52 threading obliquely through brackets 5I secured to the ends of the apron and projecting across the work assembly. 'I'he latter may be removed simply by retracting the screws 52.

In order to generate the desired arcuate or cywork, means is provided for swinging the apron 28 about its pivotal axis between the limit positions shown respectively in solid and broken lines in Fig. 2. The means i'or accomplishing this is herein shown as comprising a segmental cam member 55 pivoted at its lower end as at I8 on the upright 26 adjacent the right end oi' the fixture (as viewed in Fig. l). The upper edge of the member is formed with a cam surface adapted to coact with a follower roller 51 rotatably mounted on the bracket 34 eccentrically oi' the pivotal axis of the apron.

As will be seen by reference to Fig. 2, the cam surface is formed with anintermediate portion 58 shaped to impart substantially uniform angular velocity to the apron throughout the major portion of its oscillatory stroke, that is, while the grooved portion I 6 of the grinding wheel is in engagement with the convex portion of the surface to be ground. The surface 58 merges at either end into surfaces 59 shaped to reduce the velocity of the apron gradually. In the present instance, the surfaces are slightly inclined outwardly and away from an arc 65 concentric with the cam pivot 56. By virtue of this small riseof the cam surface 59 through a large angle of travel of the cam 55, a high degree of accuracy may be attained in establishing the limits of the strokes of the work.

Any suitable means may be utilized for rocking the cam member 55 to oscillate the work as above described. As herein shown, this means includes a shaft 50 rotatedby a motor M through a speed reducer 6I of suitable and well known character, both carried by an extension of the base 25. A crank 62 on the shaft is connected to the cam 55 by a pitman 63 secured to the crank arm through the medium of a device 55 by which the throw of the crank may be adjusted. The crank is positioned on the shaft 60 so that it passes through dead center at the time the follower 51 is engaging the cam surfaces 59. As a result, the work piece dwells in its limit positions long enough for fillets I3 of the work to contact the wheel for substantially the same length of time as the intermediate work surface which is engaged during each stroke.

In operation of the machine as described above, clamp assemblies 30 loaded With work pieces I are placed in the fixture with their upper trunnions 50 seated in the sockets 35 and 39, the screws 52 then being tightened to force the assemblies against the apron 28. With the grinding wheel rotating, the motor M is started to cause oscillation of the apron 28 and work assemblies about the center of curvature of the wheel surface I6 which axis is coincident with the axis of the work surface II after grinding thereof. Finally, reciprocation of the table 22- is initiated causing the work surfaces II and I3 to move back and forth tangentially of the grinding wheel periphery and-in contact therewith. By virtue of the shape of the cam surfaces 58 and 59 and the actuation of the cam by a crank, all parts of the work surfaces II and I3 are in contact with the grinding wheel for substantially the same length of time and are thus finished uniformly. After loosening the screws 52, the work assembly may be removed quickly and refltted in the fixture upside down preparatory to grinding the other ends of the pieces. l

It will be apparent from the foregoing that the invention provides a novel method of grinding arcuate surfaces on work pieces which is particularly suitable for the mass production of duplicate parts. The curvature of the ground surface is accurately generated and a high degree of uniformity is maintained with respectto in dlvidual work pieces.

Accurate positioning of the work with respect to the abrasive wheel is insured, thus enabling the machine to be operated by relatively unskilled workmen. Moreover, due to the efcient means provided for loading and unloading of the work pieces, optimum productive capacity of the machine is achieved. v

I claim as my invention: y

1. The combination in a grinding machine having a rotatable abrasive wheel, of a work support pivotally mounted for oscillation in a direction transverse to the plane of rotation of the wheel, means i'cr oscillating said support including a cam follower on said support eccentrically located relative to the pivotal axis of the support, a cam member pivoted to rock transversely of the plane of rotation of the wheel and having a peripheral cam surface coacting with said follower, said cam surface being shaped to impart uniform angular velocity to the support throughout the major portion of its range of oscillation, argipower actuated means for rocking said cam member.

2. The combination in a grinding machine having a rotatable abrasive wheel, of a work support mounted for oscillation in a direction transverse to the plane of rotation of the wheel, a rocking member pivoted adjacent one end of 'said work support, power actuated means including a crank arm and pitman for rocking said member, and a cam surface on said member coacting with a cam follower on said work support to oscillate the support, said cam surface being formed to impart substantially uniform angular velocity to the support throughout a portion of its oscillatory stroke.

3. A grinding machine having. in combination, a rotatable grinding wheel, a work support, means supporting said work support and wheel f-or relative reciprocation parallel to the plane of rotation of the wheel, a member on said work support supporting a work piece for movement tangentially of said wheel periphery during said reciprocation andalso for oscillation about an axis parallel to the direction of reciprocationv and spaced from the wheel periphery, an arm mounted to rock about an axis parallel to said first mentioned axis, power driven means for oscillating saidarm, and cam means on the free end of said arm acting on said member to oscillate the member about said first axis.

4. A grinding machine having, in combination, a rotatable grinding wheel, a member supporting a work piece for engagement with the wheel pei ,riphery while oscillating about an axis extending generally tangentially of but spaced from the wheel'surface, and a cam oscillated transversely of said axis and acting on a follower on said member, said cam moving the member more slowly at the ends of the strokes than during the intermediate portions thereof. y

c. KNAPP.

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