US2795088A

US2795088A - Microcentric grinder

Info

Publication number: US2795088A
Application number: US597650A
Authority: US
Inventors: Carl J Schonhoft; Bernhard Robert
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1956-07-13
Filing date: 1956-07-13
Publication date: 1957-06-11
Anticipated expiration: 1974-06-11

Description

J1me 1957 c. J. SCHONHOFT EFAL 2,795,088

MICROCENTRIC GRINDER Filed July 13, 1956 s Shets-Sheet 1 INVENTORS. 'OflRL J. SOHONH OFT B POEERT BERNHARD A TTORNE'YS.

m n N m June 1957 c. J. SCHONHOFT ETAL MICROCENTRIC GRINDER 5 Sheets-Sheet 3 Filed July 13, 1956 Q INVENTORS. CARL J. SCHONHOFT h YROBERT BERNHARD B V mrfwrzjww ATTORNEYS June 1957 c. J. SCHONHOFT ETAL 2,795,088

7 MICROCENTRIC GRINDER Filed July 13, 1956 5 Sheets-Sheet 4 STOP START 52 5/2593 WITHOUT GA.

527 559 z 28 5 4 0x 0x START 5 .s'rop P-LLk-v d} 529 590 INVENTORS.

GARLE J. SOH/gflZZ/Fg ROB RT B5 59 I 74 /8 E/ ATTORNEYS.

v 6 li-ES. WITH an. ([52/535536 AUTO. LOAD.

LOAD. FIXTURE June 11, 1957 Filed July 13, 1956 CONT/N. 0). [L8

c. J. SCHONHOFT ETAL MICROCENTRIC GRINDER 49R Y a awe: UNIT 6 9 @2165 u/w'r msrm o.

new V 5 Sheets-Shee t 5 I N VEN TORS.

CIJRL d. SOHONHOF'T ROBERT BERNHARD A T-TORNEYS.

United States Patent Oi'ice MICROCENTRIC GRINDER Carl J. Schouhoft and Robert Bernhard, Cincinnati, Ohio,

assignors to The Cincinnati Milling Machine (10., Cincinnati, Ohio, a corporation of Ohio Application July 13, 1956, Serial No. 597,650

9 Claims. (Cl. 51-103) mechanism for determination of the size of the individual work piece being ground and control of the automatic cycle of operation by such size determining mechanism.

A further object of the invention is to provision of an improvement of a structure for determination during grinding of the final size or dimension of the individual work pieces being produced.

An additional object of the invention is the provision of an automatic cycle control for the effective positioning and operation of the gauge mechanism in conjunction with the machine activation and cycle determining mechanisms controlled thereby.

Another object of the invention is the provision of an improved mechanism for coordination of the work positioning, grinding, gauging and work ejecting functions of a precision grinding machine.

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

Figure 1 is a fragmentary view partially in section of the essential operating mechanisms of a machine embodying the present invention.

Figure 2 is an enlarged view, partially in section on the line 22 of Figure I, particularly illustrating the work supporting and gauging mechanisms.

Figure 3 is a diagrammatic view of the hydraulic control mechanisms of the machine and associated electrical operating devices therefor, and

Figures 4 and 5 jointly constitute an electrical diagram illustrating the basic essential electrical circuits and controls for machine operation.

In the drawings the numeral designates the base or bed of the machine having bearings such as 11 for the trunnion 12 pivotally supporting the wheel head 13 rotatably mounting the grinding wheel 14.

Carried by the bed in opposed relation to the grinding wheel 14 is the slide support 15 for the work positioning and. rotating portion of the machine. This portion includes the upright standard or column.16 on which is mounted the work drive unit 17 terminating in the rotatable work engaging face plate 18. Additionally carried 2,795,088 Patented June 11., 1957 2 by the member 16 is the arcuate guide 19 for the adjustable

work supporting shoes

20 and 21 which during performance of the grinding operation peripherally engage and positionally locate the work piece 22.

In operation of the machine the work pieces are loaded from a hopper or otherwise into the delivery chute 23 from which they are transferred by the vertically reciprocable work feeding mechanism 24 which may be the type shown in Patent 2,478,562, previously referred to, into a position to freely rotatably rest on the

shoes

20 and 21. At the completion of a grinding operation as the work transferring mechanism 24 is moved upwardly the finished work piece will be discharged through the chute 25 and the fresh workpiece to be ground will then move from the chute 23 into position within the work feeding orv transfer mechanism 24 to be inserted into the grinding position as particularly illustrated in Figure l of the drawmgs.

With the work in the position shown in Figure l the wheel head is first given a rapid forward feeding or oscillatory movement to bring the grinding wheel into proximity with the work piece and is then fed forward the necessary amount for proper stock removal. For effecting initial rapid advance of the wheel, indicated by space 114, use is made of the hydraulically actuable piston 26 contained within the cylinder 27 and having a depending rod portion 28 engaging the abutment roller 29. This roller is carried by arm 30 of an L-shaped or bell crank lever pivoted at 31 to the bed section 10 and having a depending arm 32 whose forward position is controlled by abutment 33 on the adjusting rod 34. Rod 34 has a splined portion at 35 slidably fitting the bushing 36 carried by the bed section 10 and is further provided with a screw threaded portion at 37 on which is mounted the sleeve nut 38 having an exterior worm wheel 39 rotatable as by hydraulic motor iil. It will be evident that as the sleeve 38 is restrained against axial movement relative to the bed 10 by the bearings 41 any rotation of the worm will impart an axial, back and forth movement to the rod 34,thus varying the up or down position of abutment 29, which variant will be transmitted through rod28 to the wheel head 13.

The movement thus imparted to the wheel head is limited in amount as ordinarily but slight peripheral stock removal from the work piece is necessary in order to shape it to correct size and form, and this stock removing feeding operation of the wheel is preferably performed in two steps or increments diagrammatically illustrated by the spacings 42 and 43 of the wheel head tilt indicating lines shown in Figure l. Preferably, the movement through the space 42 is at a more rapid feed rate for quick grinding or general stock removal, while the movement through the space 43 is at a slower feed rate for accurate finishing and more ready control or discontinuance of grinding when the work piece has been reduced to the desired fin- ,ished diameter. The speed of these two feeding movements and initial retraction of the wheel at the end of the feeding operation is controlled by the rate and direction of operation of the feed motor 40.

For determination of work piece size and control of termination of the grinding operation, use is made of the gauging mechanism particularly illustrated in Figure .2. As there shown, the angularly adjustable bracket .44 is adjustably mounted on the slide section 15. Secured to this bracket is the piston rod 45 having piston 46 adjustably mounting the movable hydraulic cylinder 47. Carried by the cylinder 47 is the bracket 48 for the gauge mechanism casing 49, which is thus supported for diagonal upward and outward movement as will be evident by reference to Figures 2 and 3.

Supported within the casing 49 is the frame member Sl) of a suitable gauging mechanism such as the "Federal Air Electric Gauge manufactured by the Federal Products Corporation.

In the form here used, this gauge structure includes the pair of supporting or vibrating blade spring elements 51, 52 supporting for substantially ,vertical movement the vibrating gauge arm 53 havinga lateral extending finger 54 movable in slot 55 of the work loading mechanism 24 and provided with a hearing or contact shoe 56 for engage ment with the periphery of the work piece being ground. Carried by the bracket 50 is the L-shaped air or fluid bypass discharge nozzle 57 having a chamber 58 with a how resistance groove 59 circumscribing the adjustable flow restricting valve 60 carried by the frame 49. The nozzle 57 has a terminal edge 61, opposing edge 62 of th e floating valve block 63 secured to and movable with the gauging arm 53.

Arm 53 is urged downward, tending to move edge 62 toward edge 61 and the follower 56 into engagement with the periphery of the work piece 22 by a spring 65 having one end secured to the arm 53 and its opposite end to a pin 66 carried by the frame 49 and projecting through aperture 67 in arm 53.

By reference to these parts as shown in Figure 2 it will be evident that the adjustment of the position of the valve 60 withrespect to the circumscribing throttle passage 59 will determine normal resistance to flow through nozzle 57 for discharge through the aperture between the surfaces 61 and 62 to provide a normal stabilized condition when the member 63 is in a raised position.

It will be noted from the diagrammaticshowing in Figure 2 that the nozzle 57 is connected by conduit 68 with the air electric pressure gauge structure 69 of conventional type. Actuating pressure for this gauge is supplied as by pump 70 by way of conduit means 71 containing variable throttle 72 and actual pressure indicator 73. Pressure in conduit 71 reacts against the pressure actuable gauge device 74 having the movable pointer 75 shiftable by pressure increases in a clockwise direction as viewed in Figure 2. This pointer is provided with a contact portion 76 for successive actuation of electrical contacts 1A and 2A for changing the feed rate of motor 40 from fast to slow and for stopping said motor.

The gauge 74, as is conventional in commercial structures of this type, is responsive to the intermediate pressure between input conduit 71 and output or bypass conduit 68 whose discharge is controlled by the work size measuring gauging mechanism. In operation the gauging mechanism operates substantially on the diameter of the work piece such as the contact shoe 56 riding on the periphery of the work in opposition to the fixed two point .suspension of 20-21 of the, work and may continuously vary as the Work diameter decreases, being thus more accurate than gauging mechanisms working from a fixed point in regard to an axial position ,of the work and thus having to measure radial rather than diametrical dimensions. It will be evident that as the contact shoe 56 moves toward the shoes 20-21 on a reduction of work diameter that the surfaces 61, 62 will provide an increasing resistance to discharge of the air or other pressure medium supplied by pump 70 which will cause a pressure increase reacting against the gage structure 74 to cause clockwise movement of pointer 76.

When the work has been reduced to the desired predetermined size, the circuit controlled 'by contact 2A will stop operation of motor 40 and further in-feed of the grinding wheel, after which the gauge will be automatically diagonally withdrawn to clear both the work piece and the loading fixture, the grinding wheel will be retractedas to the amount of previous feed as well as rapid advance movement, the work feeding mechanism 24 will be operated to eject the finished work piece and by its retraction abutment 77 will engage limit switch 1LS and through the various connections shown aid in effecting initiation of a new cycle of operation of the machine.

Attention is invited to the fact that while an air-electric gauge is preferably employed for size determination that the remainder of the essential movements of the machine are hydraulically effected. For their understanding, reference is made to Figure 3 of the drawings in which the hydraulic connections for effecting the several basic machine movements above referred to have been diagrammatically shown. As there indicated, necessary activating hydraulic pressure is supplied to or created in pressure conduit 80 'by pump 81, the amount of pressure being controlled by variable relief valve 82. The return or exhaust pressure conduit system has been indicated by the reference character 83, the hydraulic pressure medium being discharged through the variable resistance 84 determining the back pressure, if any, existing in the system and to the tank or source of hydraulic medium 85 from which pump 81 derives its supply. As indicated, the pressure conduit system is connected to the valve casing 86 of the reversing valve 87 having a normal intermediate or flow blocking position. Activation of solenoid SOLIA causes movement of the valve 87 in a direction to couple the actuating medium by way of conduit containing throttle valve 88 to the upper end of cylinder 89 containing piston 90 for reciprocation of the work control fixture 24. Alternatively, activation of SOLIB will cause opposite movement of the valve and thus retraction of the work holding fixture. As shown, the work loading fixture 24 is provided with the abutment 91 for actuation of limit switch lLS in one direction when the fixture is moved into lowered position and the second abutment 77 for opposite actuation of the limit switch when the fixture is in retracted position.

When the fixture is in lowered position with the work in position on the

shoes

20 and 21 solenoid SOL2 is energized to shift valve 92 coupling pressure from conduit 80 to conduit means 93, introducing pressure into the upper end of cylinder 27, reacting through piston rod 28 resting on abutment 29 to move the cylinder upward with respect to the piston, thus rocking the wheel head 13 inwardly to bring the grinding wheel 14 into proximity with the work piece. During this movement limit switch 2LS will be brought into engagement with the fixed abutment 94, and solenoid SOL17 will be energized to effect downward movement of valve 95 for fast grinding feed rate and solenoid SOL13 energized to effect downward movement of valve 96. Downward movement of valve 96 will couple pressure conduit 80 by way of conduit 97, blocking valve 98 and conduit 99 with one side of the rotary hydraulic motor 40. At the same time conduit 100 from the opposite side of the motor will be connected by way of conduit 100, blocking valve 98, conduit 101 and fast feed rate throttle 102 in conduit 103, return conduit 104 and valve 96 to the general return conduit system 83. By this coupling the valve 102 will determine the rate of back pressure or return flow from motor 40 and thus the speed of operation of this motor.

SOL16 is energized to couple pressure line 80 with conduit 105, moving cylinder 47 diagonally inward to bring the gauge finger 56 into work contacting position as indicated in Figure 2. Grinding continues until movement of the gauge causes a build-up of pressure and shifting of contact 76 to trip electrical contact 1A, deenergizing solenoid SOL17 so that valve 95 may move to the position shown in Figure 3 where the discharge flowfrom motor 40 will be through conduit 106 and the slower feed rate throttle 107. Feed will then continue at this lower rate until trip 76 actuates electrical contact 2A to deenergize SOL14, allowing valve 98 to move to the blocking position shown in Figure 3 for discontinuance of power infeed.

Sparking out grinding continues until electronic timer 1TR times out lTR, then deenergizes solenoid SOL2 connecting 93 to 83 for release of pressure against piston 26 and deenergizes solenoid SOL13 for release of valve 96 which is then spring actuated in the position shown in fixture when SOLlB is not energized.

Figure 3, connecting pressure line 80 with 104 for free flow through check valve 108 while solenoid SOL14 is energized to open the blocl-.ing valve 98 coupling 101 with 100 for reverse actuation of the feed motor 40. SOLlA is also deenergized by 1TR; however, valve 87 remains detented in position to hold fixture forward.

By this operation the wheel head is retracted until trip 110 engages and operates limit switch 12LS to stop the feed retracting motor 40.

Simultaneously, SQL16 is deenergized by lTR, retracting gauge cylinder 47, causing trip 111 to be moved in position to actuate limit switch 13LS and solenoid SOLlB is energized, moving valve 87 to connect pressure conduit with conduit 112 extending to the lower end of cylinder 89, raising the work fixture to discharge the finished work piece through chute 25. Continued upward movement of the fixture brings trip 77 into engagement to reverse limit switch 1LS. Solenoid SOLlB is deenergized and solenoid SOLlA is energized to reverse valve 87 and initiate anew cycle of operation of the machine.

From the foregoing it will be evident that in the present improved machine there is provided a continuous automatic cycling operation into the work piece which is automatically placed in proper grinding position within the machine, the grinding wheel given a rapid approach movement and fast grinding infeed movement for initiating stock removal from the position work piece. Preferably, after initial grinding of the work piece surface has been effected, an automatic air electric gauge device is brought into contact with the surface of the work piece operating in opposition to the pair of spaced work periphery engaging work supporting shoes for measuring in cooperation with this pair of supports the existing diameter of the work piece. Associated with this work piece gauge or size measuring member is a variable orifice resistance device operated by the work gauging or measuring member for determining the effective pressure within the gauge unit 69. As the work diameter decreases and pressure builds up in the unit 79, the unit is effective to first slow down the grinding feed and subsequently to effect reversal of the cycle of operations of the machine.

One arrangement of electric control circuit for determining the sequential effective cyclic operation of the several parts of the machine when conditioned for automatic operation has been diagrammatically indicated in accordance with established electrical engineering practice in Figures 4 and 5.

In operation of the machine with the controls set for automatic cycle of operation, with automatic gauging, continuous cycle, automatic loading and automatic headstock operation, the sequence is as follows:

Cycle start push button is depressed to energize relays lCR (El-29) and ZCR (13-31). lCR contact (E-30) closes to hold in relays lCR and ZCR, ZCR contact (E /-31) closes to hold relay ZCR energized. 2CR contact E-3) closes to energize SOLlA, this advances the work ZCR contacts (-36) and (13-37) close to set up circuit for automatic infeed of wheelhead. When the work fixture is fully advanced lLS (E-37) is actuated. This energizes relay 3CR (E47). 3CR contact (E-S) energizes SOL-2 to rapid advance the wheelhead forward. 3CR contact (E-36) latches around 12LS whose contact opens as soon as feed motor 40 starts. 3CR contact (E-39) closes to allow 4CR to be energized later on. 23TR (E34),is also energized instantly, opening 23 TR timing contact (E-35).

At the end of the wheelhead rapid stroke ZLS (15-39) is actuated, closing its contact and energizing relay 4CR (E-39). 4CRcontact (E-34) opens to deenergize 23TR. 4CR contact (E-35) and 23TR contact (E-35) then 'ener'gizes 210R.

6 energize SOL-14, thus feed motor 40 is turning to move wheelhead in at a fast feed rate. At this time trip releases 12LS and 12LS contact (E-77) closes to energize relay 410R. 41CR contact closes to initiate circuit for wheelhead return later on in cycle. 23TR contact (15-35) closes after a period of time and energizing 210R relay. 210R contact (E -35) holds 21CR relay energized through 1LS contact (E-37). 21CR contact (E-16) energizes SOL-16 to advance gauge. When gauge unit is fully advanced 13LS is actuated and 13LS contact (E-SS) is closed to energize 20TR timing relay. ZOTR Contact (El-36) closes instantly to energize 8TR timing relay. 8TR contacts (E-51) function is to electrically cock the gauge. The gauge is now in full control of the sizing cycle of the entire machine. The wheelhead is grinding at a fast feed rate and continues this until the gauge signals the right amount of stock remains on the work piece to be removed at a slower feed rate. At this time gauge contact 1A(E53) closes to energize 16CR relay (13-53). 16CR contact (E-54) closes to hold R relay energized. 16CR contact (E-10) opens to deenergize SOL17, allowing the wheelhead to continue feeding at a slower feed rate.

When the work has been reduced to the desired predetermined size, gauge contact 2A (E-54) closes to energize 22CR relay (E-54).

Instantly 22CR contact (El-12) opens to de-energize SOL14, thus blocking hydraulic feed motor 40 and preventing the wheelhead from feeding any further. 22CR contact (El-21) closes to initiate tarry timer 1T R (E-23). lTR allows the work to spark out for a very short period of time. At the end of this preset time 1TR contact (E-31)opens to deenergize 2CR relay (E-31). 2CR contact (E-3) opens to deenergize SOLlA (E-3). ZCR contact (Er-4) closes to allow 1A SOL (E4) to be energized when gauge is clear of work fixture and fully retracted. 2CR contact (E-31) opens to disconnect ZCR relay from power. 20R contact (E66) opens to deenergize ZICR (Er-'35), 8TR (El-36), 3CR (Er-37), 4CR E49. 21CR contact (E46) opens to deenergize SOL16, thus retracting gauge. 3CR contact (E-S) opens to de-energize SOL2 to retract wheelhead. 4CR contact (E-9) opens to de-energize SOLIS and 4CR contact (E-12) opens forward feed circuit to SOL14, 4CR contact (E-10) closes to energize SOL14 and return hydraulic feed motor 40 to home or rear position. When this home position is reached 12LS is actuated by trip 110. 12LS contact '(E-77) opens to de-energize 416R. '41CR contact (E-10) opens to de-energize SOL14. Now if this gauge is fully retracted 13LS contact (E-56) is operated by trip 111 and closed to energize 51CR relay (E56). 51CR contact (E4) is closed to energize SOLIB to retract work fixture or loader. Retraction of work fixture closes 1LS (E37). 51CR contact (E42) closes to start next cycle by energizing ZCR relay and thus SOLlA when 1TR (E-31) is electrically reset from previous cycle. It will be noted in normal cycle operation, using the auto gauge for sizing that 3LS is not actuated. Only if for some reason such as gauge failure or otherwise would 3LS be actuated by trip dog 109. When so actuated, 3LS contact (E-40) energizes 6TR timing relay which in turn will retract the loading fixture, wheelhead and gauge unit in the same sequence as initiated when the gauge signals the work is to size. This completes the electrical automatic cycle sequence.

From the foregoing it will be noted that the machine is designed for completely automatic cyclic operation. When the startswitch is closed, the work fixture advances to deposit a work piece on the supporting

shoes

20 and 21, while the grinding wheel and wheel head are given a rapid advance by a first motor in the non-cutting zone of its movement. Bodily movement of the wheel head energizes feed motor 40 to effect continued movement of thegrinding wheel at a fast feed rate, and to advance the gage into work contacting position. The gage then takes control at a prescribed position to slow down the feed rate and subsequently to stop the feed for a sparking out cut. A gage activated tarry device then causes retraction of the gage and of the wheel head and reversal of operation ofthe feed motor. Means actuated by feed motor reversal at a predetermined point effect blocking and thus stopping of the motor, while the gage retraction controls sequential retraction of the work fixture. Dur ing retraction trip means actuated by the fixture reverse its movement to initiate, another cycle of operation.

What is claimed is:

1. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a ,work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gage supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a Work piece supported by the shoes, and means activated by movement of the loading fixture for effecting movement of the gage toward the shoes. I v

2. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece tobe ground on the shoes and for removal of a finished workpiece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, and means activatedby movement of the loading fixture for initiating advance of the grinding wheel, and an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes.

3. In a centerless grindingmachine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoesfor engagement with a work piece supported by the shoes, and means activated bymovement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, and means controlled by the gauge for determining the extent of movement of the wheel by said feed motor. I t

4. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes, and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing down the feed rate of the motor, and additional means controlled by the gauge for stopping said motor.

5. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement ina direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed 'IllOlJOI for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing down the feed rate of the motor, additional means controlled by the gauge for stopping said motor, a tarry timer coupled to the gauge for activation thereby, and delayed action gauge retracting means connected to said timer for activation thereby.

6. In a centerless grinding machine embodying a bed,

'work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement 'of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing downthe feed rate of the motor, additional means controlled by the gauge for stopping said motor, a tarry timer coupled to the gauge for activation thereby, and a first grinding wheel retracting means connected to said timer for activation thereby.

7. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a workpiece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding Wheel for grindinga work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing down the feed rate of the motor, additional means controlled by the gauge for stopping said motor, a tarry timer coupled to the gage for activation thereby, and feed motor reversing means connected to said timer for activation thereby.

8. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for eifecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing down the feed rate of the motor, additional means controlled by the gauge for stopping said motor, a delayed action gauge retracting means, a first grinding wheel retracting means, a feed motor reversing means, electrical controls for activating each of said means, a tarry timer coupled to the gauge for actuation thereby, and a control circuit for said electrical controls including circuit completing relays connected to said timer for activation thereby.

9. In a centerless grinding machine embodying a bed, work supporting shoes carried by the bed, a loading fixture movable to position a work piece to be ground on the shoes and for removal of a finished work piece from the shoes, a grinding wheel carried by the bed, and means for effecting relative advance and retraction movement of the shoes and grinding wheel for grinding a work piece supported on the shoes, sizing means for controlling said relative movement including a gauge supported by the bed for movement in a direction toward and from said work supporting shoes for engagement with a work piece supported by the shoes, means activated by movement of the loading fixture for initiating advance of the grinding wheel, an electrical control activated by advance of the grinding wheel for initiating movement of the gauge in the direction of the work supporting shoes, a feed motor for effecting advance of the grinding wheel at a feed rate, a first means controlled by the gauge for slowing down the feed rate of the motor, additional means controlled by the gauge for stopping said motor, means controlled by the gauge for effecting retraction of said grinding wheel and said loading fixture, and a trip device operable during retraction of one of said elements for initiating reversal of movement of said loading fixture.

No references cited.