US2855729A

US2855729A - Grinding machine

Info

Publication number: US2855729A
Application number: US527014A
Authority: US
Inventors: Elijah F Render
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1955-08-08
Filing date: 1955-08-08
Publication date: 1958-10-14
Anticipated expiration: 1975-10-14

Description

Oct. 14, 1958 E. F. RENDER GRINDING MACHINE 3 Sheets-Sheet 1 Filed Aug. 8, 1955 INVENTOR. EL/J/ H F. FENDER. BY

ATTORNEYS.-

Oct. 14, 1958 ND 2,855,729

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ATTORNEYS.

1958 E. F. RENDER 2,855,729

GRINDING MACHINE Filed Aug. 8, 1955 '5 Sheets-Sheet s INVENTOR. EL/JAH F. FENDER.

A TTORNEY-S.

United States Patent 2,855,729 GRINDING MACHINE Elijah F. Render, Ferndale, Mich., assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio I Application August 8, 1955, Serial No. 527,014

lClaim. (11. 51-103 This invention relates to improvements in centerless grinders and has particular reference to a machine especially adapted for utilization in the grinding by throughfeed methods of a continuous progression of articles of relatively thin character compared to their diameter such as bearing races, piston rings or the like.

Prior to the present invention, difficulty has been experienced in the attempted throughfeed centerless grinding of articles of this character due to the tendency of the leading articles to advance at an increasing rate of speed through the grinding throat during the grinding operation so that adjacent articles lose contact one with the other and in the absence of adequate lateral support have the possibility of becoming tilted or otherwise displaced in the grinding throat to an extent impairing the accuracy of the finished product.

Among the difliculties thus experienced has been that races, for example, when losing contact one with the other tend to cock which, in some instances, has resulted in'the outside diameter of the races 'being ground out of square or taper.

Various expedients have been adopted in the past to overcome this condition, as for example, the utilization of some form of pusher mechanism urging the races at the front of the machine to feed faster and catch up with the acceleratingly advancing races at the rear of the machine. Structures for effecting this result are shown, for example, in' United States Letters Patent 1,659,237 and 1,952,157.

While satisfactory results have been accomplished in this manner it has resulted in complication of machinery and equipment and a slowingdown of production due to the additional time factor in connection with loading and to the fact that in the case of such pusher devices continuous feeding under a steady urge has'not been possible on account of the necessity for intermittent return of the pusher to starting position for receptionof additional workpieces.

In other instances, the races or like parts have been mounted on a mandrel and the structure'as a unit fed through the machine avoiding the' necessity of employment of a pusher, the parts then being acted upon as a solid elongated workpiece. This again requires addi-' tional time and labor in the mounting and unmounting of the parts.

In accordance with'the present invention the foregoing and like difliculties are overcome by' the herein disclosed novel construction and arrangement of centerless grinder in which the regulating wheel is disposed and trued in a new way which provides a gradually decreasing diameter from front to rear 'of the regulating wheel. The amount of such decrease of regulating wheel diameter can be controlled'by the angle of inclination of an associated truing device effecting a' combined movement of the diamond holder longitudinally and at a radially varying amount from the axis of the regulating wheel during such truing process.

Patented Oct. 14, 1958 By employment of a regulating wheel which was so trued, and operating in the normal manner, the work feed rate can be made to decrease during the movement of the work from the front to the rear of the machine in an amount adequate to provide a sufficient slowing down of the leading workpieces to cause these workpieces such as bearing races to back up against each other and thus prevent formation of gaps between them with possible cocking ordisplacement of the individual workpieces. It is, therefore, one of the objects of the present invention to provide a novel construction and arrangement of parts in a centerless grinder which will particularly adapt said machine for the continuous progressive grinding of the periphery of workpieces of thin axial dimension as respects their diameter.

A further objectof the invention is the provision of a centerless grinder which will operate automatically to slow down the progress of the leading workpieces through the grinding throat as respects the initial rate of feed imparted to said workpieces, thus maintaining a multiplicity of workpieces in closed engagement one with the other for work steadying purposes as a series of workpieces is progressed through the grinding throat.

Another object of the invention is the provision of an improved form of centerless grinder for the production of workpieces as aforesaid in which the regulating wheel may 'be tilted in two planes substantially at right angles one to the other for determination of the relative position of the regulating wheel and the grinding wheel, and in which the work supporting rest may be angularly adjusted both with and with respect to the regulating wheel properly and adequately to support a series of workpieces in correct relationship to the regulating wheel.

An additional object of the invention is the provision in connection with a machine having the adjustments as aforesaid of an improved associated truing mechanism tiltable as an entirety with the regulating wheel in one plane including transverse guiding means angularly adjustable with respect to the axis of rotation of the regulating wheel, in combination with means for adjustably varying the radial distance of the truing device with respect to said axis during traversing movement of the truing device whereby to produce on the regulating wheel a linearly effective work engaging path of substantially frusto-conical form accurately to effect a deccelerating rate of feed of individual workpieces as they progress through the centerless grinder.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claim, without departing from or exceeding the spirit of the invention.

Figure 1 is a front elevation with parts shown in section of a centerless grinder embodying the principles of the present invention.

Figure 2 is a view taken on the line 22 of Figure 1 showing the regulating wheel and truing mechanism in elevation.

Figure 3 is a diagrammatic view indicating the nature of a selected cone angle effective to produce a slowing.

down of workpiece feed.

Figure 4 is a diagrammatic view looking at the machine from the front, indicating in exaggerated form by full and dotted lines the relationship existing between the work and the essential parts of the machine forming the grindmg throat.

Figure 5 is a diagrammatic view in elevation of the regulating wheel indicating the selected horizontal angle tilt for effecting the general feeding operation, and

Figure 6 is a diagrammatic plan view illustrating the transverse tilt of the regulating wheel and the manner in which the decelerated feeding action maintains close contact between the workpieces during the grinding operation.

In the drawings the numeral 10 designates the bed of a centerless grinder having the bearing 11 in which is journaled the spindle 12 supporting a suitably driven grinding wheel 13 rotated in a clockwise direction as viewed in Figure l as is indicated by the arrow 14. Secured in and projecting upwardly from the bed is a pivot 15 interengaged with the angularly adjustable slide 16 supported on the bed, such adjustment being elfectible as by the adjusting and locking screw 17 carried by bracket 18 on the bed. Mounted for reciprocation on the ways 19 of slide 16 is a second slide 20 adjustable by hand wheel 23 carried by the adjusting screw 22 which is threaded into the slide 20 and swiveled in bracket 21 on the slide 16. At its inner end in overlying relationship to the pivot 15 slide 20 is provided with a boss or seat 24 having a projecting pivot stud 25 engaged in base 26 for the work rest support or blade 27. The blade 27 is therefore angularly adjustable relative to slide 20 about the pivot 25, being clamped in suitably adjusted position by bolts 28. A pointer or indicator 29 on the base 24 cooperates with vernier or scale 30 on the end of the work rest supporting base 26 to facilitate determination of the exact angular adjustment of the blade.

Slide 20 is provided with longitudinally extending ways 31 guiding the movement of the regulating wheel drive unit housing 32 into which is threaded the adjusting screw 33 swiveled in bracket 34 carried by the slide 20 and provided with the operating wheel 35 for effecting movement of the housing 32 along the ways 31. Pivoted to the housing 32 for angular adjustment about the pivot 36 is the wheel head 37 supporting for movement therewith the regulating wheel spindle 38 carrying regulating wheel 39. The wheel head has an upper table portion 40 formed with a central socket at 41 receiving the circular bearing hub 42 on the underside of the track member 43 having longitudinally extending dovetail ways 44 for the truing tool head 45. This truing tool head may be reciprocated along the ways 44 in any desired manner, being here conventionally shown as actuable by the feed screw 46 swiveled in bracket 47 carried by the member 43 and provided with the actuating hand wheel 48.

Slidably mounted in the central bore 49 of the head is the axially movable truing tool holder or spindle 50 keyed against rotation relative to the head during its sliding movement by the pin 51 and downwardly urged in a direction toward the regulating wheel 39 by the spring 52. At its lower end the spindle supports the slide 53 bearing in an offset relation to the spindle axis the diamond or like truing tool 54. At its upper end the spindle is provided with the disc or handle 55 which may be used to lift or move the spindle upwardly, disengaging pin 51 from slot 56 when a slight rotation of the spindle will interlock the pin with the upper end of the head 45, thus disposing the truing tool in inoperative or nonengaging relation as respects the surface of the regulating Wheel.

For additional control of movement of the truing tool the track member 43 is provided at or near its ends with the standards or supports 57 and 58 slotted as at 59 and 60 to receive the adjusting

bolts

61 and 62 determining the angular setting of the guide bar or template 63 with respect to the plane of the track 43. Secured on the spindle 50 is a collar 64 having a lateral extension or pin 65 riding on the upper surface of the bar or template 63 for effecting automatic control of the axial movement of the spindle 5t) and thus of the truing tool 54 as the truing head is progressed along the angularly selected path determined by the adjustment of the track member 43 about the hub 42 as a pivot center.

In accordance with the present invention, desired accurate control of the feed rate of workpieces 66 can be attained by dressing the regulating wheel at an angle in a novel way which provides a gradually decreasing effective Wheel diameter from the front to the rear of the regulating wheel. The amount of decrease of regulating wheel diameter can be controlled by the angle B of inclination of the guide bar 63 operating to move the diamond holder toward and away from the regulating wheel during the operation of traversing the regulating wheel for truing.

The work feed can thus be made to decrease from the front to the rear of the regulating wheel in any amount that will provide a slowing down sufiicient to cause the races to back up against each other and thus prevent the formation of gaps between them and cocking of the individual races. In carrying out the truing of the regulating wheel under this condition, the diamond is offset relative to the axis of the diamond holder 50 an amount equal to the height H above center of the engagement of the work with the regulating wheel 39. This height or line of contact between work and regulating wheel is indicated by the line Mill in Figures 2 and 5. The diamond holder swivel track 43 is swivelled to correspond to the angle of vertical tilt or inclination of the regulating wheel axis about pivot 36 to obtain the primary desired rate of work feed as determined by the tilting of the regulating wheel about said horizontal pivot 36. Also, the guide bar 63 is tilted in a vertical plane at an angle corresponding to the tilt in a horizontal plane of the regulating wheel. For clarity of understanding, these angles have been illustrated in exaggerated amount as respects the mathematical actual values as hereinafter stated.

With the guiding members thus adjusted, as the truing tool head 45 and diamond holder 50 are reciprocated on the swivelled guide 44 while the regulating wheel is rotating, the diamond follows a path which is at a varying distance from the regulating wheel axis as determined by the angle B. And since the bar 63 is tilted toward the rear, as the diamond is moved toward the rear its distance from the horizontal plane will be gradually decreasing, removing more and more material from the diameter of the regulating wheel. The shape of the regulating wheel will then approach that of a truncated cone, with the largest diameter at the front end of the machine.

The formula for calculating the desired value of work feed change at the extreme ends of the regulating wheel is the following:

Work feed equals 21rNR (1'J:K) sin A Where:

N equals revolutions per minute of regulating wheel.

R equals radius of regulating wheel at the center of swivel in inches.

K equals percentage change in feed at front and rear of regulating wheel.

: plus sign for calculation of feed at front end of wheel, and the minus sign for calculation of feed at the rear end of regulating wheel.

A equals the angle of vertical tilt of the regulating Wheel axis.

By use of the above formula the percentage change in the wheel radius at the extreme ends of the regulating wheel for any selected value of work feed slow down can be determined. Reduction in feed as the individual hearing races are progressing through the machine results in pressure of contact between adjacent races, and in the elimination of cocking and taper grinding on the O. D.

To obtain the proper shape of regulating wheel to effect this slowdown it is necessary to know the angle B to incline bar 63.

The amount or angle of such tilt as applied to the truing tool guiding bar'63, for formation of the proper regulating wheel surface, and as applied to the slide 20 for positioning the wheel itself for the grinding operation can be determined from the following formula:

Tan B= in which:

The following values of the above factors are used to illustrate a practical example of the mathematical determination of the angle B:

Revolutions per minute of regulating wheel, 34.

Required slowdown of work feed at rear of regulating wheel 1% of work feed at the front of regulating wheel.

Diameter of regulating wheel at the front, ZR equals Diameter at the rear, ZR equals 13 (1-.01) equals Height above center, H equals Half width of regulating wheel, W equals Angle of tilt of regulating wheel axis, A equals 1% degrees.

Substituting these values in the above formula:

Tan B:

When the calculations indicated are carried out, it is found:

tan B equals .0063

from trigonometric tables the value of the angle B is 22' or very nearly B equals This is the angle at which bar 63 must be set in truing the regulating wheel for a work feed variation or slow down of 1% from start to completion of the through feed which will produce a satisfactory backup of the bearing races during the grinding operation.

By proper selection of the values indicated it is therefore possible to increase the back-up pressure between races, to release it, or to eliminate it. By use of the formula, the value of the angle B needed to shape the.

regulating wheel in accordance with the desired result can be determined.

With the above assumed factors it is mathematically determinable that an angle B of degrees diagrammatically indicated in Figures 3 and 6 will effect a progressively diminished axial feed rate from 37.732" per minute at the front to 37.355", or a drop equal to 1% of the feed from the front to the rear with a wheel radius varying from 6.75" at the front to 6.6825 at the rear.

To obtain proper relation between work and regulating wheel, the work rest 27 is pivoted on its swivel 25 to align with the path trued on the regulating wheel, being swiveled to the same angle B as used to set the bar or template 63 for the truing of the regulating wheel.

In order to maintain the work in proper contact with the grinding wheel, the main swivel slide 16 carrying the work rest and the regulating wheel is then set to the same angle B, placing the work rest parallel with the surface of the grinding wheel 12 and is locked in position.

What is claimed is:

A centerless grinder comprising a bed, a grinding wheel rotatably suported by the bed, an angularly adjustable slide supported by the bed, a regulating wheel support mounted on said slide, a regulating wheel having a spindle rotatably journaled on the support for rotation about its axis, and angularly adjustable relative to the grinding wheel by angular adjustment of the slide, a work rest blade mounted on the slide for angular adjustment with the slide and regulating wheel about a predetermined axis, means supporting the blade for independent angular adjustment relative to the slide about said axis, said blade projecting between the opposed faces of the grinding and regulating wheels and having a face for support of a workpiece, a pivot connection intervening the regulating wheel support and slide having its axis disposed at an angle to said first axis whereby the regulating wheel spindle is tiltable relative to the slide and blade, and a truing mechanism for said regulating wheel mounted on the regulating wheel support for tilting therewith and for angular adjustment relative thereto, said mechanism including a truing tool, a first angularly adjustable means guiding the tool in a traversing path at an angle to the axis of the regulating wheel spindle, and a second truing tool guiding means mounted for angular adjustment with the guiding means, and means for angularly adjusting said second guiding means in a plane angularly disposed as respects said first plane and operative for varying the radial distance between the tool and the regulating wheel spindle axis during such traversing.

References Cited in the file of this patent UNITED STATES PATENTS 1,596,701 Williams Aug. 17, 1926 1,814,431 Caster July 14, 1931 2,397,131 Decker Mar. 26, 1946 2,425,897 Peterson Aug. 19, 1947 2,520,228 Thomte Aug. 29, 1950