US2801505A

US2801505A - Cam grinding machine

Info

Publication number: US2801505A
Application number: US544887A
Authority: US
Inventors: George E Comstock
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1955-11-04
Filing date: 1955-11-04
Publication date: 1957-08-06
Anticipated expiration: 1974-08-06

Description

Ailg- 6, 1957 G. E. coms-mcg 3D 2,801,505

v CAM GRINDING MACHINE Filed Nov. 4, 1955 s Smets-sheet 1 United States Patent O CAM GRINDING MACHINE George E. Comstock 3d, Princeton, Mass., assignor to Norton Company, Worcester, Mass., `a corporation of Massachusetts `Application November 4, 1955, Serial No. 544,887

' 3 Claims. (Cl. 51-237) The invention relates to grinding machines 'and more particularlyto a cam grinding machine.

One object of the invention is to make a simple and thoroughly practical camshaft grinding machine. Another object of the invention is to provide a cam grinding machine with a work driving mechanism whereby the surface speed of the work piece is substantially uniform at Athe line of grinding contact between the wheel and `cam beingground. Another object is to provide a work driving apparatus whereby the instantaneous rotational speed of the work piece is controlled in such a way th'atvat the point of contact between thelwork and grinding wheel, the surface of the work travels at a substantially constant linear speed.

Other objects will be in part obvious or in part pointed out hereinafter.

In the accompanying drawings, in which is shown one of lvarious possible embodiments of the mechanical features of this invention,

Fig. l` is a plan view of a cam grinding machine headstock embodying the invention, having parts broken away and shown in section;

Fig. 2 is a left hand end elevation of the headstock las shown in Fig. 1, having parts broken away and shown in section; p

Fig. 3 is` a fragmentary vertical sectional view, on a enlarged scale, taken approximately on the line 3 3 of Fig. l, showing the valve for. controllingithe speed of the work drive motor and the `actuating, mechanism therefor; p i

' Fig. 4 is a vertical sectional view, on `an enlarged scale, showing a portion of the indexing mechanism for the cam follower on the speed control mechanism;

Fig. 5 is a vertical sectional view, on an enlarged scale, taken approximately on the line 54-5 of Fig. 1, of a portion of the indexing mechanism for the speed control cam follower;

Fig. '6 is a diagrammatic view showing the relationship` of the speed control cam to the cam to be ground; and

`Fig. 7 is a curve showing the relationship of the angularvelocity to the reference angle degrees of the speed control cam as shown in Fig. 6.

A camshaft driving and speed controlling mechanism has been illustrated in the drawings as applicable to an automatic cam grinding machine of the type shown in the U. S. Patent No. 2,535,130 to C. J. Green and O.` E. Hill dated December 26, 1950, to which reference may be had for details of disclosure not contained herein.` A grinding machine has been illustrated comprising a base 10 (Fig. 2) which supports a longitudinally` indexable Work table 11on a suitable V-way 12 and a flatway (not shown). The table 11 serves as a support forV a pivotally mounted rock bar 15 which is journalled in bearings (not shown) which may be arranged identical to the above mentioned` patent. The

to'ckbar` 15 serves as a support for a master cam spini 2,801,505 Patented Aug. 6, 1957 ICC dle 16 which is journalled in spaced

bearings

17 and 18. The master cam spindle 16 is provided with a plurality of spaced master cams 19, one for each cam on the camshaft to be ground. A master cam roller 20 is slidably keyed onto a rotatable shaft 21 which is journalled in

bearings

22 and 23 which are iixedly supported with a headstock casing 24. When the rock bar 15 is in an operative position, one of the master cams 19 is maintained in operative contact with the master cam roller 20 so that a rotary motion of the master cam spindle 16 will impart a controlled rocking movement to the rock bar and the cam being ground. to generate a predetermined shape on the cam being ground.

The master cam follower roller 20 is indexed longitudinally in timed relationship with the longitudinal indexing movement of the table 11 to position the master camroller 20 opposite the cam on the cam shaft to be ground in a manner substantially the same as that shown in the expired U. S. patent to C. G. Trefethen and A. G. Belden No. 1,783,755, dated December 2, 1930, to which reference may be had for details of disclosure not contained herein. A longitudinally extending dog bar 25 is supported by a bracket 26 on the base 10. The dog bar 25 is provided with a plurality of adjustable dogs 27. A rotatable shaft 28 is journalled in suitable bearings carried by the headstock frame 24. The shaft 28 is provided with a star wheel 29 which is arranged to move` in the path of dogs 27 during longitudinal indexing movement of the table 11. The inner end of the shaft 28 is provided with a gear 30 which meshes with a gear 31 carried by a shaft 32. A gear 33 is either formed integral with the gear 31 or xedly mounted relative thereto and meshes with a slidably mounted rack bar 34. The rack bar 34 supports a yoked member 35 which engages the side face of the master cam follower roller 20. It will be readily apparent that when the table 11 is indexed longitudinally, dogs 27 on the stationary dog bar 25 actuate the star wheel 29 so as to impart a longitudinal indexing movement to the master cam follower roller 20 to position it opposite to the master cam corresponding to the cam to be ground.

The master cam spindle 16 is connected by

universal joints

38 and 39 with a drive shaft 40. The universal joints or

couplings

38 and 39 are preferably a constant velocity universal joint such as the well known joint which is disclosed in the U. S. Patent No. 2,615,317 to Alfred H. Rzeppa, dated October 28, 1952, and manufactured by the Gear Grinding Machine Co. of Detroit, Michigan, to which reference may be had for details of disclosure not contained herein."

A uid operated driving mechanism is provided for the master cam spindle 16 comprising a constant displacement pistontype uid motor 45. This motor may be any of the well known iiuid motors, such as, for example that manufactured by Vickers Inc. of Detroit, Michigan, and covered by the U. S. patent to I. A. Martin No. 2,404,309, dated July 16, 1946 (assigned to Vickers Inc.), to which reference may be had for details of disclosure not contained herein. A driven shaft 46 of the iluid motor 45 is keyed within an aperture formed in the right hand end of a rotatable shaft 47. The shaft 47 is journalled in spaced antifriction bearings 48 and 49 which are xedly supported relative to the headstock frame 24. The shaft 47 is provided with a worm 50 which meshes with a worm gear 51 which is keyed onto the shaft 40. The shaft 40 is supported by a pair of spaced bearings 52 and 53 which are in turn fixedly supported on the headstock housing 24. It will be readily apparent from the foregoing disclosure that a rotary motion of the motor shaft 46 is imparted through the mechanism above described to impart a rotary motion to the master cam spindle 16.

The master cam spindle 16 is provided with a headstock center 55 for supporting one end of a cam shaft 56 to be ground. The rotary motion of the master cam spindle 16 is imparted to rotate the cam shaft 56 to be ground during which rotation the master cams 19 and follower roller 20 impart a controlled oscillating movement to the rock bar so as to generate a predetermined shape on the cam blank being ground in a manner substantially the same as that shown in the U. S. Patent No. 2,535,130. 'Y

A fluid pressure control valve 60 is provided for-controlling the exhaust of fluid fromthe fluid motor 45 to control the speed of the motor (Fig. 3). (The valve 6 0V is a piston type valve comprising a valve stem 61 having a pair of spaced

valve pistons

62 and 63 formed integral therewith. Fluid under pressure is passed through a pressure pipe 67 to the fluid motor 45. Fluid exhausting from the motor passes through a pipe 66, through a port 71 into a valve chamber 65 and passes out through a port 70 and an exhaust pipe 64 into a fluid reservoir (not shown). A compression spring 72 serves normally to urge the valve stem 61 toward the right (Fig. 3).

In order to obtain a substantially constant surface speed to the cam being ground at the line of Contact between the grinding wheel and the cam being ground, an automatically actuated mechanism is provided for controlling the movement of the valve stem 61 to vary the aperture of the port 70 so as to vary the speed of the fluid motor 45. This is preferably accomplished by providing a plurality of spaced control cams 75 which are mounted on a rotatable shaft 76 (Fig. l) journalled in spaced

bearings

77 and 78 carried by the frame 24 of the headstock. There is one control cam 75 to correspond with each of the master cams 19.

It is necessary to synchronize the rotation of the master cam shaft 16 and the control cam shaft 76. This is accomplished by providing a cog pulley 85 on the left hand end shaft 40 (Fig. l). The cog pulley 85 is connected by a timing belt 86 with a cog pulley 87 rotatably supported on the shaft 76. In order to facilitate timing the shaft 76 and control cams 75 relative to the master cam spindle 16 and master cams 19, an adjustable connection is provided between the cog pulley 87 and the shaft 76. This mechanism comprises a plate 88 which is keyed to the shaft 76. The plate 88 is provided with a pair of upwardly extending spaced lugs 89 and 90 which carry opposed adjusting screws 91 and 92 respectively. The inner ends of the screws 91 and 92 are arranged to engage opposite sides of a stud 93 which is xedly mounted on the cog pulley 87. It will be readily apparent from the foregoing disclosure that by manipulationl of the push and pull screws 91 and 92, the timing of the shaft 76 which supports the control cams 75 may be readily adjusted as required so that the phasing of the control cams 75 may be synchronized with the rotation of the master cams 90.

A follower arm 95 is slidably keyed to a rotatable shaft 96 (Fig. 4) which is journalled in spaced

anti-friction bearings

97 and 98 respectively. The follower arm 95 (Fig. 3) is provided with a cam follower member 99 which is preferably made of a hard material, such, for example tungsten carbide. This follower member 99 is arranged normally to ride upon the periphery of the control cams 75. j

A vertically arranged arm 100 is fixedly connected to the right hand end of the shaft 96 by a taper pin 101. The arm 100 is provided with an adjustable stop screw 102 which is arranged in alignment with the valve stem 61 (Fig. 3). The compression of the spring 72 serves normally to urge the valve stem 61 toward the right to maintain it in engagement with the stop screw 102 to maintainv the follower member 99 in .operative engagement with the periphery of the control cams 75.

A hydraulically operated mechanism is provided to rock the follower arm and the follower member 99 into broken line positions 95a and 99a respectively (Fig. 3) to facilitate an indexing movement thereof. This mechanism may comprise a cylinder 105 which contains a slidably mounted piston 106. The piston 106 is connected to the left hand end of a piston rod 107. The right hand slabbed-otf end portion of the piston rod 107 passes through a vertically arranged elongated clearance slot 108 formed in the upper portion of the arm 100 (Fig. 4). The piston rod 107 is provided with a pair-of spaced

pins

109 and 110 which are arranged to engage the arm 100 when the piston 106 is moved. When it is desired to index the table 11 longitudinally to position a cam to be ground in position relative to the grinding wheel, it is necessary to rock the rock bar 15 to an inoperative position by means of a hydraulically operated mechanism comprising a cylinder 110 which contains a slidably mounted piston 111 which is connected to' the left hand end of a piston rod 112 (Fig. 2). The other end of the piston rod is arranged to actuate anl arnr113'` xedly supported on the rock bar in a manner substantiallythe same as that shown in the above mentionedy U. S. Patent No. 2,535,130 to which reference may be;

had for details of disclosure not contained herein.

When fluid under pressure is admitted to the cylinder 110 to rock the rock bar 15 to an inoperative position,` fluid under pressure is simultaneously passed throughav pipe 115 into a cylinder chamber 116 at the right handy lower arm 95 and the follower member 99 into inoperative positions, as shown in broken line positions 100a, 95a and 99a respectively (Fig. `3). Movement of the arm 100 into position 10011 serves to move the valve stem 61 toward the left so that the valve piston 62 closes the port 70 thereby cutting off exhaust of fluid from the tluid motor 45 to stop the rotation of the master-cams 19, the control cams 75 and -the cam shaft 56 being ground during an indexing movement of the follower roller 20 and the follower 99.

As previously explained, the master cam roller 20 is indexed longitudinally to position the follower roller 20 opposite the master cam 19 corresponding to the cam 80 to be ground. It is necessary at the same time to automatically index the follower arm 95 together with the follower member 99 longitudinally on the shaft 96 so that the follower member 99 will be positioned opposite the control cam 75 which corresponds with themaster cam 19 which controls the contour of the cam being ground. As shown in Fig. 2, an indexing mechanism is provided which is operated in timed relation with the indexing mechanism for the master cam roller 20.

As illustrated in Figs. 2 and 5, the shaft 28 is provided with a gear whichmeshes with a gear 121 carried by a shaft 122. A gear 123 is also supported on the shaft 122 and is xedly mounted to rotate with the gear 21. The gear 1,23 meshes with a rack bar 124 formed on the underside of a slide rod 125 supported in a housing 126 which is xedly mounted on the headstock frame 24. The left hand end of the shaft 125 (Fig. l) is connected to one end ofa flexible thruster shaft 127,v and the right hand end of the. casing 12711 of the flexible shaft 127 is supported by a bracket 128 on the rear of the headstock casing 24 (Fig. 1). The other end ofthe flexible shaft casing 127a is connected by a bracket 129 xedly mounted on the left hand end of a tubular member 130 (Fig-4).' The tubular member 130 contains a slide rod 13.1. The end of the ilexible shaft 127 is.con' nected'to the left hand end ofthe slidev rod 131 (Fig. 4); The right hand end of the slide rod 131 is provided with a :stud 132 whichrides in a groove 133 formed in the follower arm 95. It will be readily apparent from the foregoing disclosure that an indexing movement of the star wheel 29 will be impartedthrough the mechanism previously described to index the master cam roller 20 longitudinally to position it opposite the master cam 19 corresponding to the cam to be ground and at the same time through Ithe flexible shaft V127 will impart a longitudinal indexing movement to the follower arm 95 and the follower member 99 automaticallyto positionthe follower member 99 into operative relationship with the control cam 75 corresponding to the master cam 19.

The master cams 19 on the master cam shaft 16 are arranged in the inverse order from the control cams 75 on the shaft 76 so that the right hand end master cam 19 corresponds with the left hand end control cam 75 (Fig. 1). When the master cam follower roller 20 is intermittently indexed toward the left to position it opposite the master cam 19 corresponding to the cam to be ground, the follower arm 95 and the follower member 99 is indexed automatically toward the right so as to position the follower member 99 opposite to the corresponding control` cam 75.

The shape of the control cams 75 is such that a controlled metered exhaust of oil from the motor 45 causes it to rotate at a correct instantaneous angular speed together with the desired value of peripheral speed to the cam being ground at the locus of contact. The calculations of the shape of the control cam are lmade from the specified shape of the cam to be ground with due allowance for the kinematics and dynamics of the machine -tool and its drive. As shown in Fig. 6, the general shape of the control carn 75 has been illustrated for controlling the speed of the motor 45 to grind a cam 80 on the cam shaft 65 so that the surface speed of the cam at the line of grinding contact remains substantially constant. The shape of the control cam 75 (Fig. 6) has been somewhat exaggerated to illustrate the shape required. As illustrated in Fig. 7 a curve has been plotted to show the relationship of the -angular velocity to the reference angle.

degrees of the speed control cam.

The operation of the improved cam grinding machine will be readily apparent from the foregoing disclosure. A cam shaft 56 is mounted on the rock bar supported by the headstock center 55 and a footstock center (not shown). The cycle of the machine is then started and the table 11 traversed longitudinally to position the cam to be ground opposite the grinding wheel. During this movement the master cam roller indexing mechanism indexes the master cam roller 20 longitudinally to position it opposite the master cam corresponding to the cam on the cam shaft to be ground. During the longitudinal indexing movement of the master cam roller 20, the speed control cam follower arm 95 and the follower member 99 are indexed longitudinally in timed relation with the indexing movement of the master cam roller 20 to position the follower 99 into operative relationship with the control cam 75 corresponding with the master cam 19 and the cam on the cam shaft 56 to be ground. The fluid motor 45 is then started to impart a rotary motion to the master cam spindle 16 to rotate the master cams 19 in operative engagement with the follower roller 20 so that a rocking motion is imparted to the rock bar to generate a predetermined contour on the cam being ground. During this grinding operation, the shaft 76 together with the speed control cams 75 are synchronously rotated with the master cam spindle 16 and the master cams 19. During the rotation of the control cam 75 a motion is imparted to the valve stem 61 in a manner above described to control the speed of the motor 45 so that at the point of contact between the cam being ground and the grinding wheel the surface of the cam travels at a substantially constant linear speed regardless of the shape being ground or generated on the cam.

In the above disclosure, the control cams are designed and shaped so as to produce` a `,substantially `constant linear `speed of the cam being ground at the line of contact between the grinding wheel and the cam being ground. In adapting this invention for the grinding of some :shapes of cams it may be desirable to vary the linear speed of the cam being ground when portions of the cam are `in operative engagement with the grinding wheel. This may be readily accomplished by the design and shape of the control cam to obtain the desired linear speed.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a cam grinding machine having a longitudinally movable table, a rock bar pivotally mounted thereon, a master cam spindle rotatably supported on said rock bar, a plurality of spaced master cams on said spindle, means to index said table longitudinally to position successive cams for grinding, a longitudinally indexable rotatable master cam follower roller on said table, means automatically to index said roller longitudinally by and in timed relation with the indexing movement of the table to position the follower roller into operative relation with the master cam corresponding to the cam being ground, means including a variable speed motor to rotate said spindle, a control means operatively connected to vary the speed of said motor, a plurality of spaced rotatable control cams, a longitudinally indexable follower therefor which is operatively connecte-d to actuate said control means to vary the speed of said motor, operative connections between said master cam follower roller indexing mechanism and said control cam follower whereby the control cam follower is automatically indexed into operative relation with the corresponding control cam, and synchronous driving connections between said master cams and said control cams whereby the speed of said mo-tor varies so as to maintain a substantially constant linear speed of the cam being ground at the line of grinding contact between the grinding wheel and the cam being ground.

2. In a cam grinding machine having a longitudinally movable table, a rock bar pivotally mounted thereon, a master cam spindle rotatably supported on said rock bar, a plurality of spaced master cams on said spindles, means to index said table longitudinally to position successive cams for grinding, a longitudinally indexable rotatable master cam follower roller on said table, means automatically to index said roller longitudinally by and in timed relation with the indexing movement of the table to position the follower roller into operative: relation with the master cam corresponding to the cam to be gro-und, means including a constant displacement piston type fluid motor to rotate said spindle, a control valve therefor, a plurality of spaced rotatable control cams, a longitudinally indexable follower therefor which is operatively connected to actuate said control valve to vary the speed of said motor, operative connections between said master cam follower roller indexing mechanism and said control cam follower whereby the control cam follower is automatically indexed into operative relation with the corresponding control cam, and synchronous driving connections between said master cams and said control cams whereby the speed of said motor is varied so as to maintain a substantially constant linear speed of the cam being ground at the line of grinding contact between the grinding wheel and the cam being ground.

3. In a cam grinding machine, as claimed in claim 2,

7 in combination with the parts and features therein specied'of means including a plurality of adjustable dogs and a starwheel to impart a longitudinal indexing movement to the master cam roller, and means including a flexible' shaft actuated in timed relationship with said indexing mechanism to impart a longitudinal indexing movement to the control cam follower to position it into operative relationship with the control cam corresponding to the master cam.

i References Cited in the Iile of this patent i VUNITED STATES PATENTS -Y onsrud v Apr. 2.6,'

Harley Nov. 10, Johnson Mar. A27, Green Dec. 26,

FOREIGN PATENTS Switzerland Dec.. 16,