US2101795A - Grinding wheel truing apparatus - Google Patents

Description

1937- c. G. FLYGARE ET AL 2,101,795

GRINDING WHEEL TRUING APPARATUS Filed Oct. 8, 1955 3 Sheets-Sheet 1 Ham 7 CARL G. FLYG'ARE HERBERT AL SILI/VEN W/ TNESS GRINDING WHEEL TRUING APPARATUS Filed Oct. 8,1955 5 Sheets-Sheet 2 POWER I LINE awe/M CARL G. FLYGAkE VV/TNEJS 4 HER ERTASILVEN imed D... 1, 1931 2,101,195

UNITED STATES PATENT OFFICE GRINDING WHEEL 'rlwnic APPARATUS Carl G. Flygare and Herbert A. Silven, Worcester,

Mass., assignors to Norton Company, 'Worcester, Mass., a corporation of Massachusetts Application October 8, 1935, Serial No. 44,069

15 Claims. (01 125-11) This invention relates to grinding machines, the hydraulic control and electrical control apand more particularly to a grinding wheel truing paratus; apparatus which is adapted to true a plurality of Fig. 3 is a cross-sectional view, on an enlarged grinding wheels to a predetermined irregular scale, through the truing apparatus, taken apcontour. proximately on the line 3-3 of Fig. 1; 5

One object of this 'invention is to provide a Fig. 4 is a fragmentary horizontal section, on simple, thoroughly practicable grindingwheel -a reduced scale, taken approximately on the truing apparatus'for truing the periphery of a line [-4 of Fig. 3;

grinding wheel to an exact contour for grinding Fig. 5 is a fragmentary rear view, partly in work of non-cylindrical shape. section, of the truing tool cross feeding mecha- 10 Another object of this invention is to provide nism; a grinding wheel truing apparatus for simultane- Fig. 6 is an end elevation, on an enlarged scale,

ously truing the peripheries of a plurality of of the vane motor for moving the truing tools to grinding wheels to predetermined irregular coninoperative positions, showing the control valve tours. I for the motor in section; 15

Another object of this invention is to provide Fig. 7 is a fragmentary detail view, on an ena grinding wheel truing apparatus for truing the larged scale, of the mountings of the valve conperiphery of a large grinding wheel to an irregtrol levers, taken approximately on the line 1-1 ular contour, in which the rotative speed of the of Fig. 1; 1 grinding wheel is automatically slowed down to Fig. 8 is a fragmentary view, on an enlarged a proper speed for truing. scale, of the timing adjustment between the drive Another object of this invention is to provide shaft and the camshaft for controlling the movea hydraulically operated cam control truing apment of the truing tool; paratus for truing the peripheries of a plurality Fig. 9 is a left end elevation, on an enlarged of wheels to predetermined irregular contours. scale, of the timing connection shown in Fig. 8;

Another object of this invention is to provide and a grinding wheel truing apparatus fortruing a Fig. 10 is a cross sectional view of the fluid plurality of wheels, in which a captrol-mechapressure control and actuating mechanism for nism is provided to automatically move and hold the truing apparatus, taken approximately on the :0 a plurality of truing tools in' an inoperative poline Ill-40 of Fig. 1.

sition during the grinding period. The embodiment of the invention selected for A further object of this invention is .to provide illustration comprises a grinding machine havan electrically controlled, hydraulically operated ing. a base It! which supports a rotatable grindfeeding mechanism for feeding a truing apparaing, wheel spindle II in bearings [2. The grind- .13 tus to move the diamond or truing tool toward ing wheel spindle ll carries a wheel mounting the peripheries of t dingwheel or wheels 13 which in turn supports a plurality of grinding by a small adjustable increment. wheels l4, l5, l6 and 11. The base In also sup- Other objects will be in part obvious'or in part ports a rotatable work support comprising a pointed out hereinafter. headstock 20 and a footstock (not shown) which -10 The invention accordingly consists in the feaare arranged to rotatably support a work piece, tures of construction, combinations of elements, such as a camshaft 2!, having a plurality of a arrangements f parts as will be exemplified cams 22, 23, 24 and 25 which are arranged to be in the structure to be hereinafter described, and simultaneously ground by the grinding wheels the scope of the application of which will be in- I4, [5, l6 and I1.' The work support including dicated in the following claims. the headstock 20 and the footstock is preferably 45 In the accompanying drawings in which is supported on a transversely movable carriage shown one of various possible embodiments of 26 which is supported on slideways l8 and I9 the mechanical features of this invention. and is arranged to be moved transversely toward \Fig. 1 is a fragmentary plan view of a grindand from the grinding wheel peripheries by a mg machine having parts broken away and suitable feeding mechanism (not shown) to grind 50 shown in section to more clearly show the conthe work pieces to a predetermined size and construction of the wheel truing apparatus; tour. The mounting for the work supports and Fig. 2 is a fragmentary plan view of the wheels the feeding mechanism therefor have not been and the truing apparatus combined with a piping illustrated in the present application since they 05 and electrical diagram to show the operation of' are not considered part of the present invention.

The feeding mechanism for the work support is fully disclosed and described in the prior patent to Wood No. 1,969,997 dated August 14, 1934, to which reference may be had for a detailed disclosure of this mechanism.

The wheel spindle II is rotated by means of an electric motor 28 having a driving pulley 29 and transmitting power to a belt 38 to a pulley 3| on theend of the wheel spindle II.

The grinding wheels are trued to an irregular non-circular contour which is the conjugate of the desired work contour, such as a cam. The grinding wheels and the work piece 2| are rotated in synchronism so that the irregular shape of the peripheries of the grinding wheels will serve to generate a conjugate shape on the earns 22, 23, 24 and 25. A bevel gear 34 is mounted on the end of the wheel spindle II and meshes with a bevel 1 headstock spindle and thereby rotate the work.

piece, such as the camshaft 2|, in synchronism with the rotation of the grinding wheels.

In order that the grinding wheels may-be properly trued to a predetermined non-circular contour which is the conjugate of the shape desired to be produced on the finished work piece, it is desirable to provide a truing apparatus for generating the predetermined shape on the peripheries of the wheels. This is preferably accomplished by providing a truing apparatus 45 with a plurality of truing tool slides 46, 41, 48 and 49-, each of which carries a diamond or truing tool 58, 5| 52 and 53 respectively which are arranged to simultaneously true the peripheries of the wheels I4, I5, I6 and I1. The slides are each supported on a pair of opposed slideways 54 and 55 (Fig. 3), only one set of ways 54 and 55 being shown in detail. The truing tool slides 46, 41, 48 and 49 arearranged to move in a path normal to the axis of the grinding wheel and are arranged for a transverse movement toward and from the wheel axis to generate a predetermined shape on the periphery of the wheels, which shapes are the conjugate of the shape to be produced on the cams 22, 23, 24 and 25.

In order that the truing tool slides 46, 41, 48 and 49 may be moved transversely to true the wheel to-a, predetermined contour, a rotatable I master camshaft 68 is supported in bearings 6|,

62 and 63 in the truing apparatus frame 45. The camshaft 68 carries a plurality of master cams 64,

65, 66 and 61 which are arranged to move the truing tool slides 46, 41, 48 and 49 respectively. Each of the truing tool slides 46, 41, 48 and 49 are provided with an adjustable follower 68, only one of which has been illustrated in detail in Figs. 3 and 4. The truing tool slides are held in an operating position with the follower 68 in engagement with the cams 64, 65, 66 and 61 by means of a pair of springs 69 and 18 which are interposed between the slides and the ends of the truing apparatus casing 45.

In order that the master camshaft 68 andthe cams mounted thereon may be rotated in synchronism with the rotation of the grinding wheel, the shaft 68 is connected to a shaft 1| carrying a bevel gear 12 which meshes with a bevel gear 13 mounted on a transverse sleeve 14 which is connected by a shaft 15 with the sleeve 36 so that the rotative power of the wheel spindle is directly .an adjusting screw 11 which is screw threaded into the slide and has its end abutting against the end of the cam follower 68. Alock nut 18 isthreaded onto each of the screws 11 and has a tubular extension 19 which passes through an aperture 88 in the truing apparatus casing and has its end bearing against the .end of the truing toolslide. By manipulation of the screw 11 and the lock nut 18, the position of the follower may be adjusted so as to vary the operative position of the truing tool relative to the camshaft 68.

In order that the entire truing apparatus assembly 45 may be adjusted bodily toward and from the grinding wheel assembly, a transversely movable slide 82 is mounted on slideways 83 and 84 and is arranged to be moved transversely thereon by means of a cross feed screw 85 which is rotatably supported in a bracket 86 on the base I8 and meshes with a nut 81 carried by the slide 82. The slide 82 carries the truing apparatus 45 and also the gear box 88. The driving shaft 15 telescopes within the sleeve 14 so as to permit the gear box 88 to move transversely when the diamond truing tools are fed toward and from the wheel periphery.

The feed screw 85 may be rotated manually by means of a graduated hand wheel 98 to manually position the truing tools relative to the grinding wheel. In the preferred construction, however, an electrically controlled,'hydraulically operated mechanism is provided so that the screw 85may be turned by very small increments by means of an electrical push button 9| mounted on the front of the machine base. When the push button 9| is closed, power from asource of power labeled Power line serves to energize a solenoid 92 to shift a valve piston 93 in thevalve 94 into the position illustrated in Fig. 5. Fluid under pressure is pumped from a reservoir 95 in the base of the machine through a pipe 96 by means of a gear pump 91 and forced through a pipe 98 and a pipe 99 into a valve chamber I88. The fluid under pressure passes out of chamber I 88 through a V-port I8I into a cylinder chamber I82 to cause a piston I83 to move upwardly within the cylinder I 84 against the tension of a spring I85. A piston rod I86 connected to the piston I83 is connected by a stud I81 at the end of a long arm I88 of a bell crank lever I89. The short arm of the bell crank lever I89 is formed as a gear segment II8 which meshes with gear teeth III which are on a portion of a plate I I2 which is rotatably supported on the outer end of the feed screw 85. The plate I I2 carries a pair of pivotally mounted pawls I I3 which are arranged to engage the teeth of a ratchet wheel I I4 which is fixedly connected to rotate the feed screw'85. A spring II5 connected between a stud IIS on the bracket 86 and a stud |I' I on-the plate 2 tends to normally turn the ratchet pawls H3 in a clockwise direction. The clockwise movement of the pawls H3 is limited by an adjustable stop screw I I8 mounted in a boss I I9 which projects from the bracket 86. Asimilar adjustable stop screw I28 carried by a projecting boss |2I serves to limit the counterclockwise movement of the pawl carrying plate II2. When the push button 9| closes the circuit and shifts the valve piston 93 into the position illustrated in Fig. 5, fluid under pressure passing into the chamber I82 moves the piston I83 upwardly into the position illustrated in Fig. 5, causing the bell crank lever I09 to rock in a clockwise direction. This movement in turn rocks the plate II2 through gear segment H0 and a gear segment III in a counterclockwise direction so that the pawls II3 engaging the ratchet wheel II4 cause a partial rotation of the feed screw 85 to feed the truing apparatus 45 toward the periphcries of the grinding wheels. By adjusting the position of the screws H8 and I20, the mecha nism may be adjusted to pick up one or more teeth of the ratchet wheel at each actuation of the mechanism.

When the push button 9I is released, the solenoid 92 is deenergized and the released tension of a spring I22 moves the piston 93 toward the right, as viewed in Figs. 2 and 5, into the position illustrated in Fig. 2. In this position of the piston 93, fluid within the chamber I02 may exhaust through a V-port I23 through the valve chamber I 00 and exhaust through a pipe I24 into the reservoir 95.

In order that the truing tools 50, 5|, 52 and 53 may be traversed across the face of the grinding wheel to true the same, the transverse slide 82 is provided with a longitudinally extending slideway I25 which mates with a corresponding way I26 on the under side of the truing apparatus 45 and serves to guide the entire truing apparatus longitudinally of the slide 82 to carry the diamonds across the face of the grinding wheel. The truing apparatus 45 is traversed longitudinally on the slideway I25. by means of a hydraulically actuated mechanism including a cylinder I21 which slidably supports a piston I 28 which is connected by a piston rod I29 and a stud I30 with a link I3I. The link I3I is connected by means of a stud I32 with a rock arm I33 pivotally mounted on a stud I34 on the under side of the truing apparatus 45. The rock arm I33 is provided at its front end with a yoked projection I35 which slidably supports a bushing I36. The bushing I36 is provided with a central aperture I31 and is connected by a stud I38 depending from the truing apparatus 45.- When the piston I 28 is moved in either direction, the linear motion of the piston will be transmitted through link I3I to rock the arm I33 and through the stud I38 cause a longitudinal traversing movement of the truing tools relative to the grinding wheels. The length of the traversing stroke of the truing tools may be adjusted by means of a pair of adjustable stop screws I40 and MI which are mounted in collars I42 and I43 on opposite ends of the piston rod I29. The adjustable screws I40 and MI are arranged to engage the ends of the cylinder head and to limit the extent of movement of the piston I28. I40 and MI, the movement of the piston I28 in either direction may be adjusted so that the truing tools move across the face of the grinding I45. The reversing valve I45 is of the sliding piston type valve including a valve stem I46 and a plurality of valve pistons I41, I48, I49 and I50. In the position of the parts as illustrated in Fig. 2, fluid under pressure enters a valve chamber between pistons I48 and I49 and then passes through a passage I5I into a cylinder chamber I52 to cause the piston I28 to move to its extreme left-hand position, as illustrated in Fig. 2.

During the movement of the piston I28 toward the left, as above described, fluid is exhausted By manipulating the screws lines in Fig. 3.

from a cylinder chamber I53 through a passage I54 and a valve chamber between valve pistons I41 and I48 and out through a pipe I55 and exhausts through a speed control valve I56 and then through a pipe I51 to exhaust into the reservoir 95. The valve I56 is preferably a needle valve which permits a fine adjustment of the oil exhausting from the system so that by controlling the opening of.the needle valve, the speed of movement of the piston I28 and also the truing apparatus is readily controlled to pass the diamond at a predetermined slow rate across the peripheries of the grinding wheels. When the reversing valve I45 is moved into its reverse position from that shown in Fig. 2, fluid under pressure passing through the pipe passes through the valve chamber between pistons I48 and I49 through a passage I54 into a cylinder chamber I53 to cause the piston I28 to move toward the right, which serves through the link I3I to rock the arm I33 in a clockwise direction which serves to move the truing apparatus 45 toward the left, as viewed in Fig, 2, so as to traverse the diamonds from their full line position into their dotted line position across the peripheries of the grinding wheels. During this traversing movement, the master camshaft 60 is continuously rotated so that the diamonds are moved transversely during the traversing movement in synchronized relation with the rotationof the grinding wheel to generate a predetermined contour on the periphery of the wheel which is the conjugate of the shape desired to be produced on the periphery of the work piece.

A control knob I60 is mounted on the end of a rod I6I slidably and rotatably supported in brackets I62 and I63.. An arm I64 is rotatably supported on the rod I6I between collars I65 and I66. I The other end of the arm I64 is connected by a stud I61 with a groove I68 in the enlarged end of the valve stem I46. When the control knob I60 is moved toward the left. as viewed in Fig. 2, into the dotted line position I60, this movement serves through the arm I64 to cause a corresponding movement to the valve stem I46 to reverse the flow of fiuidto the cylinder I21.

It is desirable to provide a mechanism for automatically and simultaneously moving all of the truing tool slides to an inoperative rearward. position after the truing operation is completed so that the followers 68 are out of engagement with the cams 64, 65, 66 and. 61 and the diamonds 50, 5I, 52 and 53 are out of operative contact with the peripheries of the grinding wheels. This is preferably accomplished by providing a transverse eccentric shaft I10 which is journaled in bearings I1I, I12 and I13. The shaft I10 is rotated about the axis of the bearings I1I, I12 and I13. When the eccentric shaft I10 is rotated into the position illustrated in Fig. 3, the shaft I10 is out of engagement with all of the truing tool slides 46, 41, 48 and 49. In this position of the parts, as illustrated in Fig. 3, the truing tool slides are moved'forward into an operating position by the tension of the springs 69 and 10 so that the cam followers 68 are in operative engagement with the earns 64, 65, 66 and 61.

When it is desired to move the truing tools to an inoperative position after the grinding wheels have been trued, the shaft I10 is rotated through a .half turn into position "M, as shown in dotted As the shaft I10 moves into this position, it engages a surface I15 on each of the truing tool slides and moves each of ,the slides rearwardly so that the surface I15 moves into broken line position I 15a, as indicated in Fig. 3. By utilizing this mechanism, it is not necessary to readjust or turn the feed wheel 90 after truing. It is merely necessary to rotate the eccentric shaft I10 and move all of the truing tools 50, 5|, 52 and 53 to a rearward or inoperative position. The grinding operation may then be resumed. After the grinding wheels become worn away due to grinding and need to be retrue'd. the shaft I10 may then be rocked from position I10a (Fig. 3) into I10 so as to again bring the truing tools into their operating position to dress or true the peripheries of the grinding wheels.

The partial rotation of the eccentric shaft I10 is hydraulically controlled by a rotary motor I11 of the single vane type having a movable vane I18 which is supported on a shaft I19 and is arranged to be moved through a half turn to shift the vane from position I18a into position I18b. A reversing valve I serves to control the admission of fluid to the motor I11. Fluid under pressure is admitted from the pipe 98 through a pipe I8I into the valve I80. The valve I80 is of a sliding piston type having a valve stem I82 and valve pistons I83, I84, I85 and I88. In the position of the parts illustrated in Fig. 6, fluid under pressure is admitted from the pipe I8I through a valve port I81 into a valve chamber I88 between the valve pistons I84 and I85. Fluid under pressure from the chamber I88 passes out through a port I89 into a chamber I90 within the vane motor I11 and passes through a port I9I into a chamber I92 to cause the vane I18 to rotate from position I18u. into position I18b. During this movement of the vane' I18, fluid is exhausted from the motor chamber I92 through a passage I93 in the vane I91 into an arcuate groove I94 in the hub of the motor casing. Fluid from the arcuate slot I94 passes through a needle valve I95 and a passage I96 into a chamber I91 formed in the hub of the motor casing and out through a passage I98 into a valve chamber I99 between the valve pistons I85 and I86 into an exhaust pipe 200 which returns the fluid to the reservoir 95. By utilizing the needle valve I95, a regulated movement of the vane I18 may be obtained so that the truing tool slides 45, 41, 48 and 49 may be moved forward into an operating position by rotation of the eccentric shaft I10 with a. controlled movement so that shocks and vibrations will be eliminated when the cam followers 68 are moved into successive engagement with the cams 64, 65, 66 and 61.

When it is desired to move the truing tools to an inoperative position after truing, the valve stem I82 is moved toward the right, as viewed in Fig. 6, to position the valve pistons in positions I83a, I84a, I85a and I86a. In this position of the parts, fluid is admitted through pipe I8I into the valve chamber I88 between pistons I84a and I850. and through a passage 20I into motor chamber 282 and through a ball check valve 203 into a motor chamber I92 to cause the vane I18 to move from position I18b'lnto position I18a.

In order to control the movement of the valve I80, the valve stem I82 is provided with a grooved spool 205 which is connected by means of pins 206 with a rock arm 201 which is mounted on the rod I8I so that the valve I80 may also be controlled by the knob I60. The rock arm 201 is slidably keyed to the rod 'I6I by means of a pivot point set screw 208 and check nut. The pivot point slides in a keyway 209 in the shaft I6 I.

When the knob I60 is rotated to turn the shaft IN, the rotary motion is transmitted through the set screw 208, keyway 209 to rock the arm 201 which serves through the pins 208 and spool 205 to move the valve stem I82 endwise to shiftthe position of the reversing valve I80. The rod I6I is free to move endwise due to the keyway 209 so as to permit the arm I64 to operate the reversing valve I45 to control the traversing movement of the truing apparatus relative to the grinding wheels. By manipulation of the single control knob I60, the vane motor I11 may be operated to move the diamonds into an operating position and then the knob I60 moved in an axial d ection to shift the reversing valve I45 so as to cause the diamond truing tools to traverse across the peripheries of the grinding wheels.

In order that the camshaft 60 may be timed to rotate in the proper relation with the rotation of the wheel spindle II, a timing mechanism is interposed between the driving shaft 1I and the camshaft 60. This mechanism comprises a flanged plate 2 I0 which is keyed to the camshaft 60 by a key 2. The flange 2I0 is provided with arcuate slots 2I2 and 2I3. Bolts 2I4 and 2I5 pass through the arcuate slots 2I2 and 2I3 and are held in a plate 2I6 placed on a shoulder on flange 2I0. The end of the camshaft H is provided with a flange 2I1'keyed to shaft 1I similar to flange 2I0 which is connected by a pin 2I8 with the plate 2I6. By adjusting the flange 2I0 relative to the plate 2I6, so that the bolts 2 and 2I5 move within the arcuate slots 2I2 and 2I3, the timing of the camshaft 60 may be regulated as desired relative to the driving shaft H. In order to facilitate the timing adjustment of the camshaft 60, a graduated scale 2I9 is provided on the periphery of the flange 2I0 and a zero index 220 is provided on the plate 2I6, so that the timing of the shaft 60 may be readily adjusted by turning the plate 2I0 the desired number of degrees on the graduated scale relative to the driving shaft 1|.

Due to the fact that the diamonds or truing tools have a combined traversing as well as an in-and-out motion to generate a formed surface on the periphery of the wheel, it is desirable to slow down the rotation of the grinding wheel for the truing operation. The slowing down of the grinding wheel is preferably accomplished automatically in timed relation with the movements of the truing tools so that when the truing tools are moved into an operative position for truing, the grinding wheel will be automatically slowed down to a desired and predetermined truing speed. This is preferably accomplished by means of a limit switch 225 which is connected by means of a link chain 226 with a pulley 221 mounted on the small diameter extension of the I, bearing I18 of the eccentric shaft I10. When the eccentric shaft I10 is rotated to move the diamond truing tools into an operating position, the rotation of the pulley 221 releases the tension on the chain 226 and closes the limit switch 225 which serves to energize the electromagnet 228 of a relay 229. The energizing of electromagnet 228 serves to move the relay arm 230 into the full line position indicated in Fig. 2. This movement serves to close a circuit to cut in a variable resistance 23I which is connected with th'e'motor 28 to slow down the rotation of the motor and thereby slow down the rotation of the grinding wheels I4, I5, I 8 and I1 to a desired peripheral speed. By adjustment of the variable resistance unit 28I, the truing speed of the wheels may be varied as desired.

After the grinding wheels have been trued and the shaft is rocked to move the truing tools to their inoperative positions, the rotation of the pulley 22! serves to pull the chain 226 and thereby open the limit switch which deenergizes the electromagnet 228 of the relay- 229, releasing the relay arm 230 so that it returns to its normal position 230a so that the full power from the power lines is connected to rotate the motor 28 and the grinding wheels at the normal grinding speed.

In the operation of this mechanism to true the grinding wheels I4, I5, I6 and H to the proper contour which is the conjugate of the finished work piece, the knob I60 is first rotated to shift the position of the valve I80 to admit fluid to the vane motor 111 so as to rock the eccentric shaft I'I0 to release the tension of the springs 69 and 10 to move all of the truing tool slides and followers 68 into operative contact with the cams 64, 65, 66 and 61 to position the diamonds 50, I, 52, 53 and 54 in operative truing position relative to the peripheries of the grinding wheels.- The knob IE0 is then moved endwise to shift the valve I45 to admit fluid to cylinder chamber I53 and thereby through link I3I and rock arm I33 traverse the truing apparatus 45 to pass the truing tools across the peripheries of the grinding wheels. When the knob I60 is turned to cause the eccentric shaft I to rotate and allow the truing tools to move into an operating position, this motion serves to operate the limit switch .225 which through relay 229 cuts in the variable resistance 23I to slow down the speed of the motor 28 and the grinding wheel spindle I I to a proper predetermined truing speed. The push button 9| may then be operated to cause the pawl and ratchet to feed the truing tools toward the peripheries of the grinding wheels by any desired number of increments. The truing tools may be passed across the peripheries of the wheels the desired number of times by manually shifting the control knob I 60 between the position I60 and I60a, as indicated in Fig. 2. After the wheels have been trued to the desired extent, the knob I60 is rotated to shift the valve I00 into'its reverse position so as to rock the eccentric shaft I'I0 to withdraw all of the truing tools to an inoperative position. This rocking of the eccentric shaft serves to operate the limit switch 225 to break the circuit, deenergizing the electromagnet 228 of relay 229, thereby releasing the relay arm 230 which returns into position 230a so that the full power from the power lines is conveyed to the motor 28 to rotate the motor and the wheel spindle II at the normal grinding 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 the matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means to rotate said wheel, a truing tool arranged to true the operative face of said wheel, means to traverse the truing tool and grinding wheel longitudinally relative to each other to true the operative face thereof, positioning means to move the truing tool to and from an operative position, means to feed the truing tool toward the operative face of the wheel to true the same to the desired extent, and a speed control mechanism which is operated by'said positioning movement of the truing tool to change the speed of the grinding wheel from a grinding speed to a predetermined truing speed at the start of the truing operation.

2. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means in-' cluding an electric motor to rotate said wheel, a truing tool arranged to true the operative face of said grinding wheel, means to traverse the truing tool longitudinally relative to the grinding wheel to true the operative face thereof, means to move said truing tool to and from an operating position, and a control mechanism operated in timed relation with said latter'means to change the speed of said motor so as to rotate the grinding wheel at a predetermined truing speed.

3. A truing apparatus for a grinding machine comprising a rotatable grindingwheel, means including a multi-speed motor to rotate the wheel, a truing tool arranged to true the operative face of the grinding wheel, means to traverse'the truing tool longitudinally relative to the grinding wheel to true the operative face thereof, means to-vary the traversing speed of said truing tool, means to move said truing tool to and from an operating position, means to feed the truing tool toward the operative face of the grinding wheel to true the same to the desired extent, and means including a speed control mechanism operated in timed relation with the truing tool positioning movement to automatically slow down the speed of said motor so as to rotate the grinding wheel at a predetermined truing speed.

4. A truing apparatus for grinding machines comprising a rotatable grinding wheel, means to rotate said wheel, a truing tool which is arranged to be moved longitudinally and transversely relative to the operative faceof the'grinding wheel to true the same, means to traverse the truing tool longitudinally relative to the grinding wheel, means to move said truing tool tranversely toward or from the operative face of said wheel to position the truing tool relative to the grinding wheel, and a control mechanism operated automatically by said transverse positioning movement to automatically change the speed of said wheel to a predetermined truing speed.

5. A truing apparatus for grinding machines comprising a rotatable grinding wheel, a multispeed means to "rotate said grinding wheel, a truing tool which is arranged to be moved longitudinally and transversely relative to the operative face of said grinding wheel to true said face, means to traverse said tool longitudinally relative to the operative face of the wheel to traverse the truing tool across said face, positioning means to move said truing tool into and out of an operative position relative to said wheel, means to feed the truing tool transversely toward the operative face of the grinding wheel, and a control device operated by said truing tool positioning movement to change the rotative speed of the grinding wheel to a predetermined truing speed.

6. A truing apparatus for grinding machines comprising a rotatable grinding Wheel, means including'a multi-speed motor to rotate said wheel at either a predetermined grinding or a predetermined truing speed, a truing tool which is arranged to true the operative face of said grinding wheel, means to traverse said truing tool longi- Elf) tudinally relative to the grinding wheel to pass the truing tool across the operative face of the grinding wheel, means to feed the tool transversely to true the-operative face of-the wheel to the desired extent, means including a rotatable cam to cause the truing tool to move transversely toward and from the periphery of the grinding wheel, means tosynchronize the rotation of said cam with the rotation of said grinding wheel so as to generate a predetermined shape on the periphery of said wheel, and means including a control mechanism which serves to change the speed of said motor so as to change the speed of the grinding wheel from a grinding to a predetermined truing speed.

'7. A truing apparatus for grinding machines comprising a rotatable grinding wheel, means including a multi-speed motor to rotate said wheel at either a predetermined grinding or truing speed, a truing tool which is arranged to true the operative face of the grinding wheel, means to traverse said truing tool longitudinally relative to the grinding wheel to pass the truing tool across the operative face of the grinding wheel, means to feed the tooltransvers'ely to true the operative face of the wheel to the desired extent, means including a rotatable cam to cause the truing tool to move transversely toward and from the periphery of the grinding wheel to true the grinding wheel to a predetermined contour, and means including a control mechanism which serves to change the speed of said motor so as to change the speed of the grinding wheel from a grinding to a predetermined truing speed.

8. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means including a multi-speed motor to rotate said wheel at either a predetermined grinding or truing speed, a truing tool which is arranged to true the operative face of said grinding wheel, means to traverse said truing tool longitudinally to the grinding wheel to pass the truing tool across the operative face of the grinding wheel, means to feed the truing tool transversely to true the operative face of the wheel to the desired extent, means including a rotatable cam to cause the truing tool to movetransversely toward and from the periphery of the grinding wheel, means to rotate said cam in synchronism with the rotation of said grinding wheel so as to generate a predetermined shape on the operative face of the wheel, and a control mechanism operated in timed relation with the truing tool positioning movement toward the operative face of the wheel to automatically change the speed of said motor from a grinding speed to a predetermined truing speed.

' 9. A truing apparatus for grinding machinescomprising a rotatable grinding wheel, means including a multi-speed motor to rotate the wheel at either a predetermined grinding or truing speed, a truing tool-which is arranged to true the operative face of said wheel, means to traverse said truing tool longitudinally relative to the grinding wheel to pass the truing tool across the operative face of the wheel, means to move the truing tool toward and from an operating position, means to feed the tool transversely to true the operative face of the wheel to the desired extent, means including a rotatable cam to cause the truing tool to move transversely toward and from the periphery of the grinding wheel, means to rotate said cam in synchronism with the grinding wheel so as to generate a predetermined shape on the periphery of said wheel, and means including a speed control mechanism operated in timed relation with the truing tool positioning movement to automatically change the speed of said motor from a grinding speed to a predetermined truing speed.

10. A truing apparatus for grinding machines comprising a rotatable grinding wheel, means including an electric motor to rotate saidwheel, a truing tool arranged to true the operative face of the grinding wheel,. means to traverse the truing tool longitudinally relative to the grinding wheel to true the operative face thereof, means to move the truing tools to and from an operating position, and means including a variable resistance unit to vary the speed of said motor, and means operated in timed relation with the positioning movement of said truing tool to cut-in said resistance and change the speed of the motor so as to rotate the grinding wheel at a predetermined truing speed.

11. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means including a multi-speed electric motor to rotate said wheel, a truing tool arranged to true the operative face of said grinding wheel, means to traverse the truing tool longitudinally relative to the grinding wheel to true the operative face thereof, means to move the truing tools to and from an operating position, a variable resistance unit connected with said motor, a limit switch actuated by said positioning movement and arranged to cut-in said resistance to change the speed of said motor to change the speed of the grinding wheel from a grinding speed to a predetermined truing speed.

12. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means including a multi-speed electric motor to rotate said wheel, a variable resistance unit in series with said motor to vary the speed thereof, a truing tool arranged to true the operative face of the grinding wheel, means to traverse the truing tool longitudinally relative tothe operative face of the wheel, means to move the. truing tool into and out of an operative position, a relay operatively connected to cut-in said resistance, and means including a limit switch actuated by and in timed relation with the truing tool positioning movement to actuate said relay and cut-in the resistance unit to change the motor speed from a grinding to a predetermined truing speed.

13. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means to rotate said grinding wheel, a truing tool which is arranged to true the operative face of the grinding wheel, means including a fluid pressure operated piston and cylinder to traverse said tool longitudinally relative to the operative face of said grinding wheel to true the same, a reversing valve to change the direction of movement of said piston, a valve to regulate the speed of movement of said piston, a positioning mechanism to-move said truing tool transversely either to or from an operating position, means to feed the truing tool transversely relative to the grinding wheel to true the same to the desired extent, a rotatable cam which is arranged to move the truing toolrelatively toward and from the operative face of the grinding wheel during the truing operation, means to synchronize the rotation of said cams and grinding wheel so as to generate a predetermined shape on the periphery of the grinding wheel and .a single control member which is arranged to control said reversing valve when moved in one direction and to control said positioning mechanism when moved in another direction.

14. A truing apparatus for a grinding machine comprising a rotatable grinding wheel, means to rotate said wheel, a truing tool, means including a fluid pressure piston and cylinder which are operatively connected to traverse said truing tool to pass the same across the operative face of the grinding wheel, a reversing valve to change the direction of movement of said tool, means including a nut and screw mechanism to feed said tool transversely relative to the operative face of the grinding wheel to true the same to the desired extent, means including a fluid motor to move the truing tool toward and from an operative posi tion, a valve to control the admission of fluid to said motor, and a single control for said hydraulic mechanism which is arranged so that when moved in one direction is serves to actuate said valve to control the admission of fluid to said cylinder to traverse the truing tool in either direction and when moved in a second direction serves to actuate said valve to control the admission of fluid to said motor to move the truing tool either into or away from an operating position.

15. A truing apparatus for a grinding machine having a rotatable grinding wheel spindle, a pluerse said truing tools across the operative faces of said grinding wheels, a valve to regulate the speed of said traversing movement, a reversing valve to change the direction of movement of said tools,

- means to simultaneously feed said tools transversely towards the operative faces of said grinding wheels to true the same to the desired extent, means including anreccentrically mounted shaft which is arranged to simultaneously move the truing tools either to or from an operating position, a fluid pressure motor to rotate said camshaft, a second reversing valve arranged to control the admission of fluid to ,said motor, and a single control for said reversing valve which serves when rotated to actuate said second reversing valve to control the admission of fluid to said motor to control the positioning movement of the truing tools and when moved endwise to actuate said first reversing valve to control the longitudinal movement of said truing tools.

CARL G. FLYGARE. HERBERT A. SILVEN.

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