US2206732A

US2206732A - Grinding machine

Info

Publication number: US2206732A
Application number: US172582A
Authority: US
Inventors: William D Schmidt; Harold L Blood
Original assignee: Heald Machine Co
Current assignee: Heald Machine Co
Priority date: 1936-10-12
Filing date: 1937-11-03
Publication date: 1940-07-02
Anticipated expiration: 1957-07-02

Description

y 2, 1940- w. D. SCHMIDT ET AL 6,732

GRINDING MACHINE Filed Nov. 5, 1937 6 Sheets-Sheet l Zhwentot Williarmll Schmidt y 2, 1940- V w. D. SCHMIDT ET AL 2,206,732

GRINDING MACHINE Filed Nov. 3, 1937 6 SheetsSheet 2 Snventor Willcwh Dfichmidi' y 2, 1940- w. D. SCHMIDT El AL Q 2,205,732

GRINDING MACHINE Filed Nov. 3, 1937 6 Sheets-Sheet 5 V JIIIIIIIIIIIIIII/Inr Zinnentor I) 5 William Dfichmidt Ha'rold L. 100d W X July 2, 1940,

- w. D. SCHMIDT ET AL GRINDING MACHINE Filed Nov. 5, 1937 s Shets-Sheet 4 O 76 a 77 I 01 O 7 O 1 27/ 88 f ya 5 O 78 e O In 5 L37 12 102 :56 i 1:6 {as 66 142' 3nnentor .Wi LLia-m I]. Schmid #1 Harold LBIoo 4%, g

GRINDING MACHINE Filed Nov. 3, 1937' 6 Sheets-Sheet 5 I I I I I I I I I I I ,1

a go 26 2e s as s 7 27 2 3 A I L105 ZSmaentor William D. fichmi-dt torneg y 2, 1940- w. D. SCHMIDT El AL 2,206,732

GRINDING MACHINE Filed Nov. 3, 1937 6 Sheets-Sheet 6 William D. schmidt Hmold L. Blood Gum M43 Patented July 2, 1940 GRINDING MACHINE William B. Schmidt and Harold L. Blood,

Worcester, Mass,

assignors to The Heald Machine Company, Worcester, Mass., a corporation of Massachusetts Application November 3, 1937, Serial No. 172,582 In. Great Britain October 12, 1936 23 Claims.

The present invention relates to grinding machines and particularly to a machine in which the grinding wheel is a conductor of electricity and thus forms one contact in a circuit by which to control or procure changes in the machine operation. This application is a continuation-inpart of applicants copending application, Serial No. 68,291, filed March 11, 1936.

In internal grinding machines the workpiece and grinding wheel at the start of each grinding operation, are usually ofiset from each other transversely of the machine so that, as the wheel or workpiece is moved longitudinally of the machine, the grinding wheel may enter the bore of the workpiece without engagement therewith. After the wheel is within the bore a relative crossfeed movement is imparted to bring the wheel and workpiece into grinding contact and thereafter to procure successively deeper and deeper cuts in the workpiece until the latter reaches'the desired finished size.

Similarly, in external grinders, the wheel initially occupies a retracted position, in orderto avoid any interference with the insertion of an unground workpiece in the machine. The-crossfeed movement between the wheel and workpiece then brings the wheel against engagement with the workpiece surface and thereafter feeds the wheel into the workpiece for the cutting op eration. In both internal and external grinders the time intervai-between the beginning of the crossfeed' movement and the occurrence of actual contact between the wheel and work is unproductive machine time and accordingly the rate of this preliminary crossfeed should be as 7 rapid as possible.

In prior machines the rate of this preliminary unproductive crossfeed movement before the grinding wheel engages the work has generally been thesame as the rate of the initial rough grinding feed and consequently the unproductive part of each grinding operation is much longer than would be necessary if the grinding wheel could be given a very rapid relative crossfeed movement until, the instant of contact between workpiece and grinding wheel. One of the principal objects of the present invention. is accordingly to provide for a. rapid transverse or crossfeed movement between the wheel and the workpiece until the wheel and workpiece are in engagement, at which time the rate of crossfeed movement is reduced to the desired'rou ghing feed.

Grinding machines in which there are two or more different rates of crossfeed movement are that of the desired finished size.

.well known, as for example, in the Conradson Patent No. 1,534,302, dated April 21, 1925, the Taylor Patent No. 1,682,673, dated August 28, 1928, or the Bloodand Burns Patent No. 2,027,627, dated January 14, 1936, but in the machines of each of these patents the rate ofcrossfeed movement initially established is not changed or reduced until the workpiece has been ground to a predetermined size slightly smaller than None of these machines contemplates a reduction in the rate of crossfeed movement upon contact between the grinding wheel and workpiece. The present invention contemplates the reduction of the rate of crossfeed movement in each successive machine cycle immediately upon engagement between the grinding wheel and workpiece independently of variationsin the diameter of the bores of the successive unground workpieces. It will be apparent that the machines of the aforesaid patents could not be adjusted to provide this reduction in the rate of crossfeed movement at the desired time since the suc cessively ground workpieces invariably would vary in unfinished diameter.

In the machine of the Blood Patent No. 1,970,645, dated Aug. 31, 1934, the rate of crossfeed movement is diminished when the wheel engages the workpiece by the use of a light responsive element energized by the sparks resulting from contact between the grinding wheel and workpiece. Although this device is entirely satisfactory in operation, it necessitates the use of such elements as the light responsive element, a

relay actuated thereby, and mechanism actuated by the relay for reducing the rate of crossfeed movement, thereby increasing the cost of construction of the machine. Moreover, a device of this character is not broadly applicable to the grinding of all types of workpieces since certain materials, when being ground,- do not emit sparks with a sufficient light intensity to energize the light responsive element. If a liquid coolant is used, the latter may also prevent the formation of enough sparks to'energize the light responsive element. A further object of the present invention is accordingly to provide for reducing the rate of crossfeed movement immediately upon contact between the grinding wheel and workpiece by a mechanism actuated directly by such contact rather than indirectly thereby.

One feature of the invention resides in the control of the workpiece size by means of an electrical circuit which includes the grinding 1 wheel. To this end a. contact is positioned in predetermined spaced relation to the axis of rotation of the workpiece, and in a position to be engaged by the grinding wheel while the latter is in grinding engagement with the workpiece. This contact may be engaged by the wheel before the workpiece reaches finished size and thereby procure a runout of the wheel for dressing, or may be engaged by the wheel when the workpiece reaches finished size to terminate the grinding operation. In any event it is the engagement between the wheel and the contact, during the crossfeed movement between the wheel and workpiece which completes a circuit through the grinding wheel and thereby procures a change in the grinding operation.

According to the present invention the rate of feeding movement is reduced by using the grinding wheel as an electrical conductor and establishing a circuit through the grinding wheel and workpiece when these members come together with this circuit operating to procure the desired change in the grinding operation. Other and further objects and advantages of the invention will more fully appear from the following description taken in connection with the accom-' Fig. 2 is a plan view of the machine of Fig. 1.

Fig. 3 is a large scale vertical section substantially along the line 3-3 of Fig. 2.

Fig. 4 is a vertical section substantially along the line 4-4 of Fig. 3, parts being broken away to show more clearly the crossfeed mechanism.

Fig. 5 is a plan view of a part of the crossfeed mechanism.

Fig. 6 is a fluid pressure diagram.

Fig. 7 is a wiring diagram.

Fig. 8 is a fragmentary front elevation showing a portion of the table controlling mechanism.

Fig. 9 is a side elevation of the chuck with certain parts broken away and shown sectionally.

Fig. 10'is an end elevation of the chuck of Fig. 9.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. 1, the machine base supports a reciprocatory table I as usually provided in an internal grinding machine; either the grinding wheel or the work to be ground is carried on said table, the reciprocations of the latter operating in either case to produce a relative axial movement between said grinding wheel and' the workpiece. In the'construction shown the table supports and carries a workhead 2 and the wheelhead 3 is mounted on a bridge 4 which spans the guideways 5, Fig. 3, provided by the machine base 6 for the movements of the table The grinding wheel I is carried on a spindle 8 journalled in the wheelhead 3 and is suitably rotated at a high rate of speed by any well known mechanism, which in the present instance consists of a motor, not

shown, in' the base of the machine connected by a belt, also not shown, to a pulley 9. Fig. 7, on the grinding wheel spindle. The workpiece a is mounted in a suitable work-supporting structure which may be in the form of a chuck In carried on a. spindle journalled in the workheadl The chuck I is preferably driven at a relatively slow rate of speed from a motor'l2, connected to the spindle H by a belt I3. A clutch mechanism l4 of any desired or well-known structure provides for stopping the rotation of the chuck without interfering with the rotation of the motor 2. Said clutch is under the control of a handle easily accessible to the operator of the machine.

The reciprocation of the table to cause the desired relative axial traverse between the rotating grinding wheel and the work-supporting structure is imparted in any well known manner, as by the use of fluid pressure controlling and reversing mechanism, one type of which is described in the Heald and Guild Patent No. 1,582,468, dated April 27, 1926. A similar type of mechanism is disclosed in the Blood and Burns Patent No. 2,011,705, dated Aug. 20, 1935. It is suflicient to note for the purpose of the present application that reversal of the table is procured at each end of the normal working stroke by spaced reversing dogs l6 and H which are carried by blocks 8 and I9 adjustably mounted on movements of valve 2| during the time that thegrinding wheel is piece.

Referring now to Fig. 6, a pump 22 driven by a motor 23 directs fluid under pressure from the sump 24 through a pipe 25 to a casing 26 for the reversing valve 2|. The casing 26 has an inlet port 21 to which the pipe 25 is connected and also has spaced

outlet ports

28 and 29 connected within the bore of the

workby pipes

30 and 3| respectively to the left and right hand ends of a cylinder 32 mounted in the base of the machine. A piston 33 slidable in the cylinder has a piston rod 34, the end of which is connected to 2. depending lug 35 on the table I. The reversing valve 2| serves in the well known manner to direct the fluid under-pressure supply alternately through

ports

28 and 29 to opposite ends of the cylinder 32, for the reciprocation of table and to connect each of said ports alternately to an exhaust port 36 which returns the fluid to the sump 24.

The crossfeed movement between the workpiece and the grinding wheel is obtained by transverse movement of the wheelhead 3 on the bridge 4. Movement of a cross slide 3'1, Fig. 3; on which the wheelhead is mounted, is effected by rotation of the crossfeed screw- 38 suitably journaled in said bridge and held against endwise movement by the anti-friction bearings 39 applied to a reduced portion of said screw. The thread of the crossfeed screw engages an internally threaded portion 40 of the cross slide for effecting the transverse movement thereof. the outer end of the crossfeed screw 38 is mounted a gear 4| which meshes with a gear 42 secured to a shaft 43 journalled in a housing 44 for the crossfeed mechanism. Also secured to the shaft 43 in spaced relation to the gear" is a ratchet wheel 45 engageable by the spaced and oppositely directed pawls 46 and 41, Fig. 4, carried by an annular member 48 secured to a sleeve 49 journalled on. the shaft 43. The sleeve 49 has an integral pinion 50 engageable by a rack 5| horizontally slidable on a suitable support 52 in the casing 44. The rack 5| is shiftable back and forth by a fluid pressure mechanism, hereinafter described in detail, to procure, through the pawl and ratchet arrangement, the rotative movements of the shaft 43, and accordingly slight angular movements of'the crossfeed screw' for the advance and retraction of the cross slide 31. Manual rotation of the crossfeed screw is by a hand wheel 43' on the end of the shaft 43.

The pawl and ratchet arrangement is fully described in the Guild Patent No. 1,971,138, dated Aug. 21, 1934, or in the Blood and Burns Patent No. 2,011,705, above referred to. Itis sufficient to note for the purpose of the present application that this double pawl arrangement permits, during the return of the cross slide to original position in readiness for a subsequent grinding operation, a compensation for the reduction in size of the grinding wheel as a result of wear and the dressing operation performed thereon during the preceding grinding operation. With reference to Figs. 3 and 4, it will be noted that both ofthe pawls are normally held in operative engagement with the ratchet by a spring 53, so that a rotation of the annular member 48 provides a corresponding rotation of the ratchet 45 The pawl 41 is operative for the feeding movement or advance of the cross slide, and the pawl 46 is operative for the retraction of the cross slide. The pawl 46 is rendered inoperative during a part of the movement of the annular member 48 in the counterclockwise direction so that the cross slide is retracted a slightly shorter distance than it is moved forward during the crossfeed movement.

To obtain this compensatory action, the shaft 43 has journalled thereon an arm 54 having a gear segment 55 on the outer end thereof. The

gear segment engages with a pinion 56 carried on a shaft 51 journalled in the front wall of the housing 44. The outer end of the shaft 51 has a knurled knob 58 by which said shaft is turned to adjust the position of the arm 54. Integral with the arm 54 is a cam 59 in a position for engagement with a pin 69 on the pawl 46. The cam 59 is adjusted to be engaged by the pin 60 just before the termination of the crossfeed movement and accordingly, during the first part of the retraction of the cross slide, the pawl 46 is permitted to engage with the ratchet wheel 45; in

other words, despite the reverse rotation of the annular member 48, there is no corresponding movement of the ratchet wheel until the pawl has moved far enough counterclockwise to clear the cam 59.

Referring now to Figs. 4 and 6, the rack 5| is carried on the end of a piston rod 6| extending from a 'piston 62 slidable in a horizontally positioned cylinder 63 mounted on the front of the bridge 4. Fluid under pressure is directed alternately to opposite ends of the cylinder 63 .for

procuring first the crossfeed movement of the slide 31 and subsequently the retraction thereof. As shown in Fig. 6, fluid under pressure from the pipe 25 passes through a pipe 64 to the inlet port of a. reversing valve casing 86 for a reversing valve 61 associated with the crossfeed mechanism. An outlet port 68 in the casing is connected by a pipe 89 to the left. hand end of the cylinder 63, and another outlet port 10 is connected by a pipe H and through suitable valve mechanisms, hereinafter described, to the right hand end of said cylinder. An exhaust port 12 for the reversing valve casing provides for exhaust of fluid from the left hand end of the cylinder when fluid under pressure is directed to the right hand end.

The admission of'iiuid to the right hand end vertical bores 8| and 82 in the block 'I'I in which are positioned respectively, the

valves

83 and 84. The valve 83 controls the rate of crossfeed movement for rough grinding, which is established by initial engagement between the grinding wheel and workpiece and the valve 84 con-.

trols the rate of crossfeed movement for fine grinding during the latter part of the grinding 1 operation. These

valves

83 and 84 are substantially of the same construction employed for the rough grinding feed valve and finegrinding feed valve disclosed by the aforesaid Blood and Burns Patent No. 2,027,627, and are manually adjustable by their exterior knurled knobs to vary the flow of pressure fluid therethrough.

A channel 85 in the casing 14 and the block 11, and an intersecting channel 86in the cylinder 63, provide a fluid connection from the valve 13 to the right hand end of the cylinder. With the valve 13 in the position shown, fluid under pressure from the pump under the control ofthe throttle valve 15, passes around the reduced portion 81 of-the valve 13 to enter the right hand end of the cylinder, thereby procuring a rapid preliminary crossfeed movement of the grinding wheel to bring the grinding wheel and workpiece '10 vides a connection from said channel to spaced into engagement. As soon as the grinding wheel of the coarse feed valve 83 for the rough grinding operation.

The valve 13 is normally held in the position of Figs. 4 and 6 by mechanism best shown in Figs. 4 and 5. Referring to Fig. 4, the block Tl has a plunger 90 slidable therein in line with the valve I3 and at the left hand end thereof. The plunger 98 carries on its left hand end a roller 9| engageable successively, during the crossfeed movement, with

cams

92 and 93 carried by the annular member 48 which also carries the pawls 46. and 41. Movement of the plunger 98 to the left beyond the position of Fig, 4, is limited by va cap 94 positioned in the end of the bore in which the plunger is slidable. A coil spring 95, which is positioned in a recess 98 in the block 11, engages with the right hand end of the valve 13 and normally holds said valve in engagement'with the plunger 98.

For movement of the valve to the right, when the grinding wheel engages the workpiece, a coil the right. The movement of the ring 98 is lim- 75 of these pins are engaged by one end of a lever I03 pivoted on a pin I04 carried by projecting flanges I05 on the block 11. The other end of the lever I03 has an adjustable screw I06 engageable with the lower end of a lever I01 pivoted on a pin I03 also carried by the parallel flanges The opposite end of the lever I01 is secured by a pin I 09 to the armature IIO of asolenoid III, which, at the beginning of the grinding operation, is energized, to draw the armature to the left, and thereby urge the ring 98 to the position of Fig. 4.

With reference to Fig. 7, one terminal of the solenoid III is connected by a lead II2 to one side of a source of electrical power II 3 and the other terminal of the solenoid is connected by a lead II4 to a contact II5. A connector II 6 normally establishes a circuit between the contact I I5 and a contact II1 which is connected by a lead II8 to the other side of the power supply II 3. The connector H6 is carried by the armature II9 of a solenoid I20, one terminal of which is connected by a lead I2I'to a second source of electrical power I22, which in the diagrammatic showing of Fig.7, is the secondary coil of a transformer. The other terminal of the solenoid I20 is connected by a lead I23 to a ground I24, and

the same terminal is also connected by a lead I25 to the contactl25 of a switch I21 which is normally closed. The opposite contact I28 of the switch I21 is connected by a lead I29 to a contact I30, the latter being in a position to be engaged by the connector II6 when the solenoid I20 is energized. Another contact I 3I also engageable with the connector H6, is connected by a. lead I32 to that side of the source of power I22 which is opposite to the one that is connected to the lead I2I. The lead I32 is connected by a lead I33 to the wheelhead 3, which, as best shown in Fig. 3, is insulated from the cross slide 31 by suitable strips of insulatingmaterial I34.

The grinding wheel 1 is treated to be a conductor of electricity, as by .any desired or well known means, which may be, for example, by impregnating the wheel with an electrolyte, and accordingly the wheel can form a part of a circuit. The workpiece or the workholding structure carrying the workpiece is connected to a ground I35,

and accordingly, when the workpiece and grinding wheel move into engagement as a result of the crossfeed movement, a circuit is established through the grinding wheel to energize the solenoid I20, the latter moving the connector II6 into engagement with contacts I and I3I to establish a holding circuit through the solenoid I20 for the remainder of the grinding operation.

The movement of the connector II5 by the sole- I noid I20 breaks the circuit through the solenoid III, allowing'the armature thereof to move to the right to release the ring 98 ior movement of the valve 13 to the right under the action of the spring 31.. a p

The valve 13 having been shifted to the right by. the ring 96, this movement occurring upon engagement between the grinding wheel and workpiece, as will be apparent, the grinding operation continues with the grinding wheel still given a relatively rapid crossfeed movement for the coarse 'or rough grinding operation. This rate of crossfeed movement, which is under the control of the valve 83, continues until the cam 92 engages the roller 9|, Fig. 4, thereby shifting the valve 13 even further to the right to cut off the flow of fluid through the channel 89 and to direct fluid around the reduced portion I36 of the valve 13 to a channel I31 which intersects the channel 86. Fluid passing around the reduced portion I36 must also pass through the fine feed valve-84, so that the crossfeed movement is materially reduced and is very slow for the purpose of producing afine finish on the workpiece.

The grinding operation continues with a relatively slow crossfeed movement until the roller 9| is engaged by the cam 93, thereby moving the valve 13 still more to the right to cut off the fluid connection from the fine feed valve 84 to the channel I31. The full-size portion I38 of the valve 13 which cuts oil the flow of fluid to the channel I31 has a plurality of very small axial grooves I39 which permit a very small amount of fluid to enter the cylinder 63, so that during this last part of the grinding operation the crossfeed movement is throttled down to such a slow rate as to be almost negligible, for a sparking-out operation.

The grinding operation may, for example, be under the control of any suitable gage mecha nism or under thecontrol of the crossfeed movement such as the Blood and Burns Patent No. 2,011,705, dated Aug. 20, 1935. Regardless of the typeof size-control mechanism used, the grinding wheel and workpiece are adapted to be axially separated at the completion of each grinding operation by rendering the reversing dog I1 inoperative. Simultaneously, the valve 61 is shifted to the position shown in Fig. 6 by suitable meehanism not shown, in order to obtain the usual retraction of the cross slide 31. This shifting of the valve 61 allows fluid under pressure to enter the left hand end of the cylinder 63 for movement of the piston 62 to the right. At the same time fluid under pressure from the left hand end of the cylinder 63 passes through a channel 140 which connects said cylinder to the valve 13 at the left hand end of said valve and between said valve and the plug 90. As fluid under pressure enters between the valve and plug'the valve is shifted to the right to uncover a port I to allow fluid to exhaust through the channels -86, I31,

and the channel I42 connected to the port I4I.

This channel directs'the exhaust fluid back to the sump, the fluid to the channel passing around a reduced portion I 42' of the valve 13.

As the table moves to the left to rest or loading position, a cam I43 carried by the table, engases with the actuator I44, Fig. 7, of the switch I21, thereby opening the circuit through the solenoid I20 to allow the connector II6 to 'return to the position of Fig. 7 in readiness for a subsequent grinding operation.

'The operation of the machine, which will no doubt be clear from the foregoing description, will be briefly summarized. With the machine in the position of Fig. 1, and with a workpiece a located in the 'workholding structure I0, the latter 'is set in rotation by movement of the handle I 5. The table is then moved to the right to bring the workpiece and grinding wheel into operative position by movement of the lever I which is connected to the reversing valve 2I and which moves the latter from the position shown into a position to direct fluid under pressure to the left hand end of the table cylinder. As the table reaches operative grinding position the valve 61 is shifted by any suitable mechanism, but preferably in response to the table movement, to direct fluid under pressure from the pipe 64 to the pipe II for procuring the crossfeed movement between the grinding wheel and the workpiece.

At the beginning of the crossfeed movement the valve" is in the position of Figs. 4 and 6 and the rate of the crossfeed movement is accordingly under the control of the throttle valve I5 which provides for a crossfeed movement at a rapid rate to quickly bring the grinding wheel and workpiece into engagement. Thus the time involved in the inoperative part of thegrinding operation is substantially reduced by this rapid crossfeed movement. As soon as the grinding wheel .engages the workpiece a circuit is established through the grinding wheel and workpiece to energize the solenoid I20, thereby deenergizing the solenoid I II to cause the valve 13 to move to the right. The coarse feed valve 83 is thus rend ered operative for a crossfeed movement of the grinding wheel relative to the workpiece at a rate suitable for rough grinding. This rate is materially slower than the preliminary crossfeed movement prevailing before the grinding wheel becomes operative.

After this reduction in the rate of the crossfeed movement, the grinding operation continues until the valve 13 is'shifted to the right by engagement betweenthe cam 92 and roller 9|, for reducing the crossfeed movement to a fine feed rate. A still further reduction occurs when the cam 93 engages the roller 9|. After the grinding wheel has reduced the workpiece to the desired size, as determined by any suitable size-controlling device, the table is withdrawn to the left for an axial separation of the grinding wheel from the workpiece and the cross slide 31 is retracted by shifting the valve 61 to the position of Fig. 6,

this shifting movement being preferably under the control of the same mechanism which procures the axial separation of the wheel and workpiece.

As the table reaches the rest position shown, the solenoid I2Il is deenergized by actuation of the switch I21 to again energize the solenoid III in readiness for the subsequent grinding operation. It may be noted that the reduction in size of the grinding wheel is compensated for during the retraction of the cross slide by a delay in operation of the pawl 46 due to the cam 59 above described. It may be further noted that during any axial separation of the workpiece and grinding wheel either at the completion of the grinding operation, or before completion of the grinding operation, as for a dressing operation on the wheel or for any other purpose, the cross slide may be temporarily shifted transversely of the machine to avoid the objectionable bell-mouthing which occurs when the grinding wheel is maintained in engagement with the workpiece instead of being retracted during the axial separation.

This structure is best shown in Fig. 2 and involves a lever I46 actuated by a cam I41 carried by the table. "Rocking of the lever I46 by the cam I41 temporarily shifts the crossfeed screw axially to back the wheel away from the work. This structure is not a partof the present invention and positioned in predetermined relation to the axis of the workpiece and the engagement between the wheel and the contact closes a circuit by means of which the grinding operation is terminated, or such other change in the grinding operation is procured as may be desired.

With reference to Fig. 8, the grinding operation may be under the control of a mechanism similar to that of Patent No. 2,011,705, above referred to. The table movements are under the control of the reversing dogs I6 and H, which, as above described, are pivotally mounted on blocks I8 and I9 respectively, and\alternately engage and rock the reversing lever 20, the latter being suitably connected to the reversing valve 2I. When the grinding operation is completed, or when a runout of the table is desired, ,the dog I! is raised into an inoperativeposition (to pass the lever 20) by means of a lever I48 pivoted at I49 on the front of the machine. The lever I48 has an integral arm I50, the end of which engages a pin I5I on a depending arm I52 pivotally mounted on the pin I49. A latch I53'holds the arm I52 in the position shown and a spring I54 is arranged to cause counterclockwise movement of the.arm

I52 when the latch I53 is released. This counterclockwise movement of the arm I52 causes a corresponding upward movement of the lever I48,

placing the upper end thereof in a position to engage and elevate the dog I'I, thereby preventing the dog from engaging with the reversing lever so that the normal reversal of the table does not take place and the latter continues its movement to the left until the grinding wheel and workpiece have been axially spaced from each other- For actuating the latch I53, the latter has an integral depending arm I55 engageable with the end of the armature I56 of a solenoid I51 mounted on a bracket I58 on the front ofthe machine. Energization of the solenoid causes movement of the armature I56 to the left and corresponding disengagement of the latch I53.

Referring now to Fig. '7; the solenoid I5! is positioned in a circuit which includes the grinding wheel. One terminal of the solenoid is connected by a lead I59 to the lead I2I from one side of a secondary coil of the transformer I22. The

other terminal of the solenoid I51 is connected by .end of the contact I6I, a circuit through the solenoid I51 is completed, thereby terminating the grinding operation by causing elevation of the dog I I'through lever I48, thus to produce theaxial separation-of the grinding wheel and workpiece.

The contact I6 I, as best shown in Figs. 9 and 10, is positioned radially within the chuck I0 and is insulated therefrom. To this end a ring of insulation I62 is positioned in a groove I63 in the outer surface of the chuck and a collector ring I64 is positioned in a groove in the periphery of the insulating ring I62. The contact. I6I is in the form of a threaded rod which extends radially inward of the chuck from the collector ring and the inner end of the contact is in a position for engagement by the grinding wheel when the workpiece a is ground to a predetermined finished diameter. The contact is obviously spaced from the axis of the workpiece a distance exactly equal to the radius of the finished workpiece surface, as will be apparent. A brush I65 is mounted on the table I and is suitably insulated therefrom, being carried on a spring finger I66 so that the brush is held resiliently against the collector ring I64.

As the grinding operation continues after the grinding wheel and workpiece are brought into engagement, the grinding action progresses in the usual manner until the grinding wheel, during its usual axial reciprocation over the surface of the workpiece, engages the contact IGI When this occurs a circuit through the solenoid I51 is completed, thereby disabling the dog I], thus to obtain a run-out of the table.

It will be apparent that in certain instances, where the contact IGI is not positioned within the chuck, the contact may be located outside of the chuck in a position for engagement by the grinding wheel, the contact in this case being mounted on a suitable bracket, not shown, insulated from the remainder of the machine. Where the contact is fixed in this manner it is preferably in the same horizontal plane as the axis of the grinding wheel. It will be understood that the particular advantage of positioning the contact l6l within the chuck in the position shown is to facilitate the removal and insertion of workpieces in the chuck. In certain instances the innenend of the contact l6! may be in the form of a ring whose inner diameter corresponds exactly to the flnished diameter of the workpiece and with the ring concentric -to the axis of the workpiece.

From the foregoing it will be apparent that the invention providesfor a change in the machine operation by engagement between the grinding wheel, which is a. conductor of electricity, and the workpiece itself, or a contact positioned in predetermined relation to the axis of the workpiece. This change in the machine operation may be a reduction in the rate of crossfeed movement when the grinding wheel engages the workpiece, and, following this change, the grinding wheel, by engaging a contact member, procures a second change by withdrawing the wheel and work from engagement with each other. Either of the changes above noted may be procured separately and independently of the other change, as will be apparent. The changes in the grinding operation are under the control of electrical circuits, each oi which includes the grinding wheel, and it will be understood that the circuit established by engagement between the grinding wheel and a contact in a position for engagement with the wheel may procure any other changes in the machine operation instead of, or in addition to the changes above outlined.

We claim:

1. In a grinding machine, a grinding wheel, a work-supporting member adapted to support a workpiece, fluid pressure actuated means for procuring a crossfeed movement between the wheel and the workpiece in the work-supporting member, valve means controlling the admission of fluid pressure to said means, and means responsive to engagement between the wheel and workpiece for shifting said valve.

2. In a grinding machine, a grinding wheel, a work-supporting member adapted to support a workpiece, fluid pressure actuated means for procuring a crossfeed movement between the wheeland the workpiece in the work-supporting member, and means responsive to engagement between the wheel and workpiece I01 thro t g flow of fluid to said fluid pressure actuated means, to reduce the rate of crossfeed movement.

3. In a. grinding machine, a grinding wheel, a work-supporting member adapted to support and wheel and a workpiece in the work-supporting member, and means operative in response to initial engagement between the wheel and the workpiece for ,changing the rate of flow of fluid to said fluid' pressure means.

4. In a grinding machine, a grinding wheel, a work-supporting member, fluid pressure means for procuring a feeding movement of the wheel relative to a workpiece in the work-supporting member, a valve for said fluid pressure means, and means responsive to engagement between said wheel and work for shifting saidvalve, said last means including a solenoid.

5. In a grinding machine, a grinding wheel, a work-supporting member, fluid pressure means for procuring a feeding movement of the wheel relative to a workpiece in the work-supporting .member, a valve for said fluid pressure means,

and means responsive to engagement between said wheel and work for shifting said valve, said last means including a solenoid for shifting said valve, and a circuit through said solenoid, said circuit having spaced contacts, one of which is the grinding wheel, and the other of which is a workpiece in the work-supporting member, whereby the circuit is closed by contact between the wheel and workpiece.

6. In a grinding machine, a work-supporting member adapted to support a workpiece, a grinding wheel and a circuit including said wheel and workpiece and closed by engagement thererotate a workpiece, fluid pressure actuated means *for procuring a feeding movement between the between, said circuit also including means for procuring a change in the machine operation.

7. In 'a grinding machine, a work-supporting member adapted to support a workpiece, a grinding wheel and a circuit in which the grinding wheel forms one contact and the workpiece forms another, said circuit being closed by engagement between the wheel and workpiece.

8. In a grinding machine, a grinding wheel, a work-supporting member adapted to support a workpiece, means for procuring a crossfeed movement between the grinding wheel and a workpiece in the work-supporting member, a circuit including means for procuring a change in the rate. of crossfeed movement, and means directly responsive to positive engagement of the grinding wheel and workpiece for changing the normal state of the circuit.

9. In a grinding machine, a grinding wheel, a work-supporting member having a workpiece therein, means for procuring a erossfeed movement between the wheel and the workpiece in the work-supporting member, means responsive to initial engagement between the wheel and a workpiece in the work-supporting member for procuring achange in the machine operation, means subsequently operative during the crossfeed movement for reducing the rate thereof, and additional means operative prior to completion of the grinding operation for further reducing the rate of crossfeed movement,

10. In a grinding machine, a grinding wheel, a work-supporting member adapted to support a workpiece, fluid pressure actuated means for procuring a feeding movement between the wheel and a workpiece in the work-supporting member, a valve for controlling the admission of fluid to said fluid pressure actuated means. means opera- 7 tive in response to initial engagement between the wheel and workpiece for reducing the rate of feeding movement byshifting of said valve, and means subsequently operative during the grinding operation for a further shifting movebreaking said circuit, and means included in the circuit and operative on breaking of said circuit for procuring a change in the machine operation.

12. In a grinding machine, a work-supporting I member adapted to support a workpiece, a grinding wheel, an electrical circuit, said circuit including a workpiece in the work-supporting member and the grinding wheel, the latter being a conductor of electricity, said circuit being closed directly by engagement between the grinding wheel and the workpiece, and means included in said circuit and operative upon closing of said circuit for procuring a change in the machine operation.

13. In a grinding machine, a grinding wheel, a work-supporting member adapted to support a workpiece, fluid pressure means for procuring a feeding movement between the wheel and a workpiece in the work-supporting member, a valve for controlling the admission of fluid to said means, a circuit including a solenoid for holding said valve in a predetermined position, a second circuit, including the grinding wheel and workpiece, the latter being a conductor of electricity, for opening the first circuit upon engagement between the grinding wheel and workpiece.

14. In a grinding machine in combination, a grinding wheel which is a conductor of electricity, electrically actuated means for procuring a change in the machine operation, a circuit including said electrically actuated means and the grinding wheel, and a contact in said circuit and engageable by the grinding wheel for completing the circuit by which the electrically actuated means are rendered operative.

15. In a grinding machine in combination, a work-support, a grinding wheel which is a conductor of electricity, an electrical circuit, including the grinding wheel, a contact in said circuit, associated with the work-support and engageable with the wheel during the operation of the machine for completing the circuit, and electrically actuated means operated by the closing of said circuit for procuring a change in the machine operation.

16. In a grinding machine, a workholder, a grinding wheel, an integral portion of which is a conductor of electricity, means for procuring a grinding operation on a workpiece in the workholder, a contact positioned in predetermined relation to the axis of the workpiece and in a position for engagement with the grinding wheel during the grinding operation, a circuit including said contact and said wheel and closed by engagement between the wheel and contact, and means controlled by said circuit for procuring a change in the grinding operation.

1'7. In a grinding machine, a workholder, a grinding wheel, an integral portion oi. which is a conductor of electricity, means for procuring a grinding operation on a workpiece in the workholder, a contact positioned in predetermined relation to the axis of the workpiece and ma position for engagement with the grinding wheel during the grinding operation, a circuit including said contact and said wheel and closed by engagement between the wheel and contact, and means controlled by said circuit for terminating the grinding: operation.

18. In a grinding machine, a workholder, a grinding wheel, an integral portion'of which is a conductor of electricity, a contact located in predetermined relation to the axis of the workholder and in a position for engagement by the grinding wheel, a circuit including said wheel and contact, and means under the control of said circuit for separating the wheel from a workpiece in the workholder.

19. In a grinding machine, a workholder, a grinding wheel, an integral portion of which is a conductor of electricity, a contact located in predetermined relation to the axis of the workholder and in a position for engagement by the grinding wheel, a circuit including said wheel and contact, and means under the control of said circuit for terminating the grinding operation.

20. In a grinding machine, a workholder, a grinding wheel, an integral portion of which is a conductor of electricity, means for procuring a grinding operation on a workpiece in the workholder, a contact positioned in the workholder in predetermined relation to the axis thereof and in a position for engagement with the grinding wheel during the grinding operation, a circuit including said contact and said wheel and closed by engagementbetween the wheel and contact, and means controlled by said circuit for procuring a change in the grinding operation.

21. In a grinding machine, a workholder, a grinding wheel, an integral portion of which is a conductor of electricity, means for p; ocuring a grinding operation on a workpiece in the workholder, a contact within the workholder in predetermined relation to the axis of the workpiece and adjacent to the inner end of the workpiece for engagement with the grinding wheel during the grinding operation, a circuit including said 7 contact and said wheel and closed by engagement between the wheel and contact, and means controlled by said circuit for procuring a change in the grinding operation,

22. In a grinding machine, a workholder, a grinding wheel, an integral portion of which is a conductor of electricity, means for procuring a crossfeed movement between the grinding wheel and the workholder for a grinding operation on a workpiece in the workholder, a circuit including the grinding wheel and workpiece and closed by engagement between the wheel and workpiece, means under the control of said circuit for procuring a change in the machine operation, a contact positioned in predetermined relation to the axis of the workpiece in a position for engagement with the grinding wheel during the grinding operation, a circuit including said contact and said wheel, and closed by engagement between the contact and wheel, and means controlied by said last circuit for procuring another change in the tact positioned in predetermined relation to the said last circuit for procuring another change in axis of the workpiece in a position for engagethe grinding operation, said circuits being sucment with the grinding wheel during the grindcessively closed for cont olling each 01' said ing operation, a circuit including said contact and change procuring means in ependently.

said wheel, and closed by engagement between WILLIAM D. SCHMIDT. 6 the contact and wheel, and means controlled by HAROLD L. BLOOD.

Patent No. 2,206,752;

CERTIFICATE OF C ORRECTION.

I 5 July 2, 1911.0. Y WIL IAM D. SCHMIDT, ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as followsz Page 1 first column, line 27., for the word "against" read --into line 29, for "into" read --against--; end that the said Letters Patent shou-ldbe read with this, correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this 10th day of September, 'A. D. 191D.

. Leslie Frazer,

(Seal) 3 Acting Commissioner df Patents.