US2500634A - Work holding fixture for grinding machines - Google Patents

Description

March 14, 1950 E. M. EIGENBRODE WORK HOLDING FIXTURE FOR GRINDING MACHINES Filed Dec. 3, 1946 5 W E D o W M R 3 m 86 2 m m m B E 4T 4 M O m 4 m E W I D m E uumu [III lm. 5: E:

Patented Mar. 14, 1950 WORK HOLDING FIXTURE FOR GRINDING MACHINES Edwin M. Eigenbrode, Waynesboro, Pa., assignor to Landis Machine Company, Waynesboro, Pa.,

a corporation of Pennsylvania Application December 3, 1946, Serial No. 713,759

6 Claims. (Cl. 51103) This invention relates to improvements in grinding machines and the like and in particular to mechanism for supporting work-pleces'ln such a machine. I

An embodiment of my invention is herein shown' in association with a centerless grinding machine of the type shown and described in the patents of C. W. Hopkins and E. M. Eigen- Such members as cap screws, for example, are

threaded for only a portion of their length and therefore the thread grinding wheel can engage only such portion, leaving a considerable length of the screw unsupported. This disadvantage I propose to obviate by providing a control wheel which will engage the threaded and unthreaded between the axes of grinding wheel and workpiece.

An additional object resides in the provision of a novel mounting unit for a supplemental work supporting roller on one end of an adjustable cradle for the work rest blade and which embodies means for yieldingly urging the roller into pressure contact with the work as well as means for vertically positioning the roller for most effective contact with work-pieces of different forms and sizes and means for adjusting the axial position of the roller relative to the workpiece.

Other objects and advantages will be apparent from a study of the following description and the accompanying drawings illustrative of one embodiment of the invention.

In" the drawings:

Figure 1 is apartial front elevation of a centerless grinding machine showing one embodiment of my novel work supporting device;

Figure 2 is a fragmentary plan view of the work supporting device and associated parts of the grinding machine;

Figure 3 is a fragmentary side elevation, partially in section on line 3-3 of Figure 4 with the portions of the screw shank, and by supplement- A ing the opposing pressure of the grinding wheel upon the work by means of an adjustable roller mechanism. Similar mechanisms heretofore constructed cannot be used in such a centerless thread grinding machine since they lack adjustments which would permit the work engaging roller to be maintained in axially parallel relationship with the grinding wheel asthe work is tilted longitudinally for the production of threads of various helix angles. 4 I

It is an object of my invention to provide a means for supporting work-pieces, to be ground by the infeed method, over substantially their entire length and thereby to improve the accuracy and finish of such ground work-pieces.

It is also an dbject of the invention to provide a work support to supplement the grinding wheel in cases where the grinding wheel does not engage the entire length of the work-piece, whereby continuous contact between work-piece and control wheel is insured along substantially the full length of said work-piece, thereby minimizing liability of slippage between the work and control wheel. v a It is another object to provide a work support with means for adjustingthe same to a position of axial parallelism with the grinding-wheel regardless of the degree 01' relative inclination work-piece inclined relative to the grinding wheel axis;

Figure 4 is a front elevation, partially in section along line" 4-4 of Figure 6, 01 the parts shown in Fig. 3;

Figure 5 is a vertical sectional view taken on line 55 of Figure 4, and

Figure 6 is anelevation of the parts shown in Figure 5 but seen from the opposite direction to that of Figure 5.

Figure 1 of the drawings illustrates the principal operating parts of a centerless grinding machine for the grinding of work pieces by the infeed method. Upon a base or bed, not shown, which usually contains the motor,- gears, and other mechanism for driving the rotating parts, a grinding wheel 20 is mounted in the conventional manner. A main slide 22 is also mounted on the bed for lateral reciprocation toward and from the peripheral face of grinding wheel 20. A second slide 24 is mounted on main slide 22, for reciprocation relative thereto also toward and from- I control wheel 28.

the work is supported. The connection between hous ng 28 and slide 24 is usually such as to permit the rocking of the axis of control wheel 28 in 1 a vertical 'plane so that said control wheel axis may be inclined relative to the axis of grinding I wheel 28.

A second housing 88 is secured by screws 82 and hinge 34 to the housing 20. In housing an a con trol wheel operating shaft 38 is mounted in ali nment with the center of control wheel 28 and.

as explained in detail in the above-mentioned clutch mechanism, to rotate said control wheel 28. Such rotation is accomplished manually. in the present instance, by a lever 88,'secured to the forward end of operating shaft 38 by screws 48.

patent applications, is engageable by means of a I The control wheel 28 is provided with a series 1 of pockets in its peripheral face. two of which.

designated by the reference numerals 42 and 44. are necessary for the grinding of a particular size of work-piece. The work-piece W is first 3 placed in pocket 42 when the control wheel 28 is I rotated so that pocket 42 is disposed below the grinding position. In this position lever 38 will engage the stop 48, which limits movement of lever 88 in the counter-clockwise direction. Lever 38 is then rotated in the clockwise direction and work-pieceW is fed into the grinding throat and urged against the peripheral face of grinding wheel- 28 by the section 48 of the periphery of Grinding takes place as sur- 1 face 48 is thus rotated past the grinding throat ;and work-piece W is subsequently discharged 3 into the following pocket 44. v At this point. lever 88 will be prevented from moving further in the clockwise direction by the stop 58.

Counterclockwise rotation of lever 88 then restores pocket 42 to its starting position and the finished work-piece W may be removed from pocket 44.

The work rest mechanism shown in the drawings is similar to that disclosed in the patent of Cecil W. Hopkins, No. 2,417,4'13, issued March 18, 194W. The base portion 52 of this mechanism-is secured upon main slide 22 by screws 54. As described in said patent the arcuate slide or cradle 58 is mounted for rocking movement upon base 52 while the center of such rocking movement lies in the same horizontal plane as the center of rocking movement of the axis of control wheel 28. A work rest blade 58 is secured in the usual fashion in cradle 58 and extends transversely between grinding wheel 28 and control wheel 28 to support the work-piece W in the grinding throat.

The upper or work supporting surface" of blade 88 is inclined downwardly away from grinding wheel 28, according to well-known principles of centerless grinding, while the other details thereof must conform to the particular work-piece being ground. The blade 58 is shown (Figure 3) cut away as at 82 to provide clearance-space for the head of the work-piece W. I

According to recognized principles of centerless thread grinding, the axis of the work W must be inclined relative to the axis of grinding wheel 28 an amount substantially. equal to the helix angle of the thread to be ground, while the axis of control wheel 28 must be inclined relative to the axis of grinding wheel 28 slightly less than twice this amount. These inclinations have not been indicated in Figures land 2 of the drawings -but the axes of work, grinding .wheel and control wheel are all shown parallel in the interests of simplificationand clarity of details with which this invention is more directly concerned.

In Figure 3. work rest cradle 88 together with work rest blade 58 is shown in rotated position to incline work-piece W at the proper angle relative to the axis of grinding wheel 28. The workpiece W. shown merely as an' example, comprises three distinct portions: a threaded portion 84, a cylindrical unthreaded portion 88 and a head 88. The threads on portion 84 are formed during the grinding operation by the annular ridges and grooves I8 formed on the periphery of grinding wheel 28. Thus, since portion 88 is not ground, only threaded portion 84 is supported between the grinding'wheel 28 and control wheel 28. If this condition were-allowed to remain. the resultant free movement of work portions 88 and 88, especially in the case of very long work-pieces. would destroy the finish and accuracy of the threads being ground. A description of the means whereby this difliculty can be obviated follows.

' A work supporting unit embodying a substantially rectangular plate I2 is attached to the forward end of work rest cradle 58 by screws 14. The forward surface of plate I2 is formed with the vertically extending, integral key 18 (Figure 2). A corresponding keyway I8, formed in the rearward face of the bracket member 88, engages key 18 .to prevent relative lateral movement between bracket 88 and plate I2, to which said bracket 88 is removably secured by screws 82 and washers 84. Bracket 88 is rendered vertically adjustable by providing a slot 88 in said bracket through which screws 82 pass to engage threaded openings in the plate I2. This adjustment may be effected by rotating a set screw 88 vertically threaded in the top of, bracket 88 and having abutting contact with a pin 88, which extends forwardly from plate I2 into a second slot 82 in bracket 88, (seeFigure 4). The purpose of such adjustment will appear later.

Bracket 88 is formed with an integral portion 84 (Figure 2) extending rearwardly along one side of work rest cradle 58 and parallel with work rest blade 58. Portion 84 is provided with a cylindrical opening 88 in which one end of a bolt 88 is suitably fixed with its axis perpendicular to the plane of bracket part 84. A second bracket I88 is journalled for rocking movement upon the bolt 88 (Figures 2 and 6) and is retained thereon I by nut 88 and washer I8I. The bracket I 88 has the shaft I82 journalled therethrough with its axis substantially normal to the bolt 88. On the rearward end of shaft I82 and immediately adjacent bracket I88 a lever arm I84 is affixed for rotation with shaft I82 by the pin I88.

Lever arm I84 extends upwardly and has, at its upper end the cylindrical opening I88 in which is seated the rearwardly extending spacerv member I I8 (Figure 5). Spacer I I8 is retained in position by a screw I I 2 and washer I I 4, said screw extending rearwardly into opening I88 and threadedly engaging the forward end of spacer II8.

A pin 8 is frictionally fitted into the rearward end of spacer I I8 and between said spacer and the rearwardly spaced head of said pin II8 a roller H8 is rotatably mounted. As shown in Figures 2 and 3, roller II 8 is thus located in close proximity to the forward side of grinding wheel 28 to engage the unthreaded portion 88 of the worklever arm I22 have mutually opposed lower end surfaces provided with openings I26 and I20 respectively, for the reception of a compression spring I00. A tension adjusting screw I32 is threadedly engaged in lever arm I 22 to abut one end of spring I32 and thus adiustably control the pressure of said spring. Screw I32 is locked in adjusted position by the lock nut I34. Thus, as seen. in Figure 4, lever arm I22, shaft I02, lever arm I04 and roller IIO are all resiliently urged to rotate in a clockwise direction by spring I which consequently provides the pressure which roller I I6 exerts against the work-piece W. Rotation of lever arm I22 in clockwise direction is adjustably limited by a stop screw I36, threaded through the upper portion of lever arm I22 to abut a portion of bracket 80; Screw I36 is locked in adjusted position by a lock nut I30. Therefore, the position of screw I36 determines the initial lateral position of roller ,0 with respect to the work rest 56 and this adjustment is consequently used to locate roller IIO properly for various diameters of work.

From Figure it will be seen that the extension 04 of bracket 60 is provided with the opening I40 and the cutout portion I42. These openings are disposed on opposite sides of the pivot 98 and pins I44 and I46, which are frictionally secured in the side of bracket I00, project into the respective openings. Thus the rocking movement of bracket I00 relative to bracket 80 is limited by the relative size of pins I44 and I46 and openings I40 and I42. Bracket I00 may be locked in the desired rotated position relative to bracket 60 by means of the locking screws I 48 and I50 which are threaded through bracket portion 94 transversely of openings I40 and I42 and engage, respectively, pins I44 and I46 to prevent relative rotation of brackets 60 and I00.

It has been found necessary to maintain roller II8 exactly parallel with grinding wheel 20. If the axis of roller I II! were inclined with work rest blade 58 and slide 56 relative to the wheel axis, said roller would exert an axial force on workpiece W in opposition to the force set up by the inclination of control wheel 28 and the lead of the resulting thread could :not be controlled. Hence the necessity of the relative angular adiustment between bracket I00 which carries roller H6 and bracket 60 both of which are rocked with work rest cradle 56.

As is well understood in the art, the vertical position of work rest blade 50 and hence of the work W, is variable. The above-described adjustment of bracket 80 and the parts supported thereby, relative to plate I2, by means of slot 86 and screws 02 is provided to compensate for vertical adjustment of work rest blade 58 as well as to maintain roller H8 in proper work contacting position by eliminating the vertical displacement component caused by the tilting of cradle 56.

It will be seen that the above described device is universal in its application and that it may be employed on work having a wide range of characteristics to maintain contact between the unground portions of the work and the control wheel continuously during the grinding operation and thusprevent grinding inaccuracies and insure perfect finish of the completed work.

It will be noted that the primary elements 12, 60, I00 and I04 for adjustably mounting the work holding roller I I8 are combined in a very compact unit which can be readily applied to or removed from the end of the work rest cradle 56. As will be evident from Figures 1 and 4, this unit occupies comparatively little space at the front side of the grinding wheel to afford clear and unobstructed vision of the work piece in the grinding operation and will not be seriously impaired in its functional operation by accumulations of grinding dust. The several cooperating parts are also of simple and durable structural form and provide a work holding accessory for centerless grinders of reasonably low production cost.

The invention may be embodied in other speciflc forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a centerless grinding machine, a grinding wheel and a control wheel mounted to rotate about axes disposed in parallel vertical planes and in peripherally opposed relation, with said wheels axially inclined relative to each other, a work support, means mounting said support for angular adjustment in a plane parallel to the wheel axes to support a workpiece between the wheels at an axial inclination relative to the axes of said wheels for in-feeding movement of the workpiece by the control wheel, and means rotatably mounted on. said work support at the work entrance side of the grinding wheel, with its axis inclined to the axis of the workpiece in a vertical plane, to maintain continuous pressure contact of an unground section of the workpiece with the peripheral face of the control wheel. I

2. A centerless grinding machine as defined in claim 1, wherein said last named means comprises a roller, and means mounting said roller to laterally urge the work piece toward the control wheel, including means for adjusting said roller about a fixed axis to establish a predetermined axial relationship between the roller and work-piece and obviate substantial restraint by said roller to the in-feeding movement of the work-piece.

3. A centerless grinding machine as defined in claim 1, wherein said last named means comprises a pressure roller to laterally urge the work-piece toward the control wheel, together with means for adjusting said roller relative to the work supporting means to a pos tion of substantial axial parallelism with sa d grinding wneel.

4. An accessory work ho ding unit for grinding machines and the like having a work supporting member, said unit comprising a bracket for attachment to said member, a bearing member pivoted for rocking movement on said bracket, a shaft journalled in said bearing member with its axis substantially normal to the pivot thereof, an arm fixed to each end of said shaft, a work holding roller carried by one of said arms, a spring interposed between said bracket and the other arm to yieldingly urge the roller into holding contact with a work-piece, and means carried by the bracket coacting with means on said bearing member to adjustably rock the same and position the axis of said roller in predetermined angular relation to the axis of the work-piece.

5. An accessory work holding unit as defined in I claim 4', together with an adjustable stop member carried by one of said arms to engage said bracket and l mit movement of said roller in work-engag- REFERENCES CITED 8 UNITED STATES PATENTS Number 10 Number The following references are of record in the I flle of this patent:

Name Date Hoeg May 24, 1932 Cramer May 29,1934 Hutchinson Apr. 28, 1936 Scrivener Aug. 31, 1937 Scrivener June 18 1946 FOREIGN PATENTS Country Date Great Britain May 23, 1929

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