US3039240A

US3039240A - Combination feed actuating means for grinding machines

Info

Publication number: US3039240A
Application number: US650902A
Authority: US
Inventors: Harold E Balsiger
Original assignee: Landis Tool Co
Current assignee: Landis Tool Co
Priority date: 1957-04-05
Filing date: 1957-04-05
Publication date: 1962-06-19
Anticipated expiration: 1979-06-19
Also published as: FR1204483A; NL113991C

Description

June 19, 1962 H. E. BALSIGER COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES Filed April 5, 1957 5 Sheets-Sheet 1 INVENTOR HAROLD E. BIILS/GER ZJ?M ATTORNEY June 19, 1962 H. E. BALSIGER 3,039,240

COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES Filed April 5, 1957 5 Sheets-Sheet 2 IN V EN TOR.

HAROLD E. BALE/GER ATTORNEY June 19, 1962 H. E. BALSIGER 3,039,240

COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES Filed April 5, 1957 5 Sheets-Sheet 3 IN V EN TOR.

HAROLD E. BALS/G'ER BY flly w ATTORNEY June 19, 1962 H. E. BALSIGER COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES s Shets-Sheet 4 Filed April 5, 1957 INVENTOR.

HAROLD E. BALS/GER A T TORNE Y UL? 7a June 19, 1962 H. E. BALSIGER 3,039,240

COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES Filed April 5, 1957 5 Sheets-Sheet 5 IN V EN TOR.

HAROLD [.BALS/GER BY //7 M ATTORNEY United States Patent 3,039,240 COMBINATION FEED ACTUATING MEANS FOR GRINDING MACHINES Harold E. Balsiger, Waynesboro, Pa., assignor to Landis Tool Company, Waynesboro, Pa. Filed Apr. 5, 1957, Ser. No. 650,902 20 Claims. (Cl. 51-165) This invention relates to grinding machines, particularly to wheel feed mechanisms for such machines.

In the operation of the early manually controlled and actuated machines, the operator developed certain techniques. Feed control over a long period of time settled into a general pattern whereby the operator first advanced the grinding wheel at a rapid rate by means of a handwheel feed mechanism until the grinding wheel engaged the workiece. Thereafter, he continued to advance the wheel at a slower rate but fast enough to remove a maximum amount of stock in a minimum time. This rate of feed would be continued until all but a small predetermined amount of stock had been removed. Then the operator would advance the grinding Wheel first by coarse increments and then by fine increments until finished size was indicated either by a positive stop on the feed mechanism or by some sort of an indicator in contact with the workpiece. After stopping the advance of the grinding wheel, the operator would allow the wheel and the work to remain in contact for a short period until the absence of sparks which would show no more stock being removed, or until a size indicator would read zero, or both. He then reversed the handwheel enough to reset the wheel for the next grinding operation.

Later, when power-operated rapid feed was introduced, provision was made to reduce the rapid feed movement to a speed suitable for grinding either by retarding the rapid feed mechanism itself or by providing another slower moving feed mechanism preferably operated through a portion of the rapid feed mechanism. Even with this type of feed, the slow final advance required could not be provided satisfactorily by a continuous movement and the final advance of the wheel was effected by manual operation of the hand wheel often consisting of a series of hand impulses rather than a continuous pressure until the proper size was reached. Again the handwheel was reversed to reset the manually operated portion of the feed mechanism after each operation. The wheel may be advanced beyond the range of the preliminary grinding feed to its limit of movement by a power operated ratchet mechanism or the equivalent which is notlimited in the extent to which it can advance the wheel as is a reciprocating mechanism, such as a piston and cylinder. The term ratchet mechanism as used here is intended to include other devices such as one-way clutches, etc. which, in certain applications, perform the same function as a ratchet mechanism. A ratchet mechanism may be reset a fixed amount from the point to which it has advanced and thus the operative face of a grinding wheel may be positioned so that the ratchet feed will begin with the wheel a predetermined distance from the finished size of the workpiece.

More recently, approach to final size has been by means of a sparkout operation which may be terminated by a sizing device or by a timing mechanism.

In spite of the skill developed by operators of manually controlled machines, there is one machine characteristic which has remained a problem because of the friction between the wheelbase guide surfaces, for example, and the co-acting guide surfaces on the bed of the machine. Because of the lost motion and resilience in the manually operated feed mechanism between the handwheel and the adjustable connection between the slide member and the bed, the operator had no assurance when the handwheel was moved the distance of one graduation on the dial, that 3,039,240 Patented June 19, 1962 the Wheelbase would move the amount represented by that graduation. The handwheel might even have to move the distance of one or more graduations before the slide began to move. If the friction between the guide surfaces could be reduced to zero, the resilience in the feed connection would not have to be taken up before the slide began to move. Then the movement of one graduation on the handwheel would move the slide by the amount represented by the graduation.

Where the wheel must be advanced through a variable distance to a finish size determined by a sizing device, such friction may be overcome by an impulse-type feed in which a succession of impacts, such as those applied manually by the operator as described above, moves the slide incrementally through minute distances not possible with a continuous feed. When the feed mechanism is advanced by the ratchet mechanism, there is a corresponding change in other means for actuating the feed mechanism since all feed actuating means function through the feed screw. Any advance effected by the ratchet mechanism causes a corresponding advance of the zone of movement of the wheel support by the other feed actuating means, thus maintaining a uniform relation between each of the feed elements and the finish size of the work. It is, therefore, an object of this invention to provide a feed mechanism in which the approach to final size is effected by a positive incremental advance of the wheel slide which will be continued until final size is reached rather than a mere release of strain in the machine elements.

Another object of this invention is to provide means whereby the effect of negligible friction between the sliding surfaces may be accomplished.

Another object is to reduce the grinding time by performing a rough grinding operation at a maximum rate of feed to a point where there is just enough stock left on the workpiece to correct such irregularities as out of roundness, and after a predetermined interval to resume the feeding movement by increments until it is stopped by a sizing gauge.

Another object is to provide means for resetting said incremental means by a fixed amount whereby to compensate for wheel wear.

Another object is to provide an automatically controlled power-operated feed which will function in substantially the same manner as the above described manually operated and controlled mechanism but with greater uniformity and precision.

Another object is to provide a ratchet type mechanism for advancing the grinding wheel by increments for a finish grinding operation after the wheel has been fed by other means to a point close to the finished size of the work.

Another object is to provide a ratchet type mechanism for actuating the feed mechanism in the opposite direction by a fixed number of increments in order to reset the feed mechanism for the next grinding operation.

Incremental feed may be provided by means of the pawl and ratchet mechanism described herein, or by other mechanisms designed to function in a similar manner.

FIGURE 1 is an end view partly in section of a grinding machine of which the present invention forms a part.

FIGURE 2 is a sectional end elevation of the feed hand wheel and the pawl and ratchet mechanism for actuating the feed.

FIGURE 3 is a sectional front elevation on the line 3-3 of FIGURE 2 of the feed ratchet showing the coarse feed and the fine feed mechanisms.

FIGURE 4 is a sectional front elevation on the line 4-4 of FIGURE 2 showing the reset ratchet portion of the feed mechanism.

FIGURE 5 is a hydraulic and electric diagram.

Numeral indicates the bed of the grinding machine. 11 is a grinding wheel support slidably mounted for transverse movement on said bed 10. 12 is a work carriage also slidably mounted for movement at right angles to the direction of movement of the wheel support 11. A grinding wheel 13 is rotatably mounted on said wheel support 11. Workpiece W is rotatably supported on the work carriage 12 by means of a footstock and a headstock 21. A caliper member is suitably mounted for movement into and out of engagement with the workpiece W. Said caliper 30 may be a part of any one of the well-known size control mechanisms suitably connected to retract the grinding wheel and'reset the feed mechanism at the end of a grinding operation.

The means for moving the wheel support 11 toward and from the work support 12 consists of a feed screw 40 rotatably supported in a nut 41 attached to or forming a part of the wheel support 11. Said feed screw is moved bodily endwise by means of piston 51 in cylinder 50. A cam 52 on the forward end of feed screw 4% engages a limit switch LS1 when the end of the feed screw 40 engages a positive stop 53.

The power means for rotating said feed screw 40 consists of a worm shaft 69 having a worm gear 61 thereon engaging pinion or worm wheel 62 on said feed screw 40. Said shaft 69 moves to the left for a fast preliminary feeding movement by means of piston 63 in cylinder 64. The left end of worm shaft is connected to a reset piston 71 in cylinder 70. A sliding pin 72 in the end of said cylinder engages a limit switch L838 when said fast feed mechanism reaches the end of its movement. The purpose of piston 71 is to effect a reverse or reset movement of shaft 60 and fast feed piston 63.

At the end of the fast feed movement, the remainder of the feed is taken over by a ratchet feed mechanism on shaft of hand wheel 81. Said shaft 80' has a double sprocket 82 which drives through chain 83 to sprocket 84 on shaft 35. Shaft 85 is mounted in suitable bearings in bed 10 and has a bevel gear 86 engaging another bevel gear 87 on worm shaft 60. Bevel gear 87 is also connected through bevel gear 88 and suitable reduction gearing to a motor 89.

Ratchet wheels 10% and 101 are mounted on a hub member 102 of hand wheel 81. Said hub member is keyed to shaft 80. Ratchet may be actuated by a pawl 103 on fine feed piston 104. The stroke of said piston 104 may be adjusted by a screw 186 mounted in the right end of cylinder 105.

At the other side of ratchet 100, coarse feed pawl is mounted on piston 111 in cylinder 112. The stroke of piston 111 may be adjusted by means of a screw 113 mounted in the left end of cylinder 112.

The reset ratchet 101 is actuated by a pawl on piston 121 in cylinder 122. The stroke of piston 121 may be-adjusted by means of screw 123 in the left end of cylinder 122.

Operation When the work drive motor is started, pressure limit switch lPLS is closed to energize control relay 10CR. Control relay contact 10CR4 completes a circuit to normally closed timer relay contact 9TR3 to energize control relay 21CR. Control relay contacts 2 1CR1 and 21CR2 energize valve solenoid G which serves as a pilot valve to direct fluid under pressure to, and actuate the rapid feed reversing valve 90. Valve 90 is shifted to the left against spring 91 and fluid under pressure from pump P is directed to the upper end of rapid feed cylinder 50. Rapid feed piston 51 advances to position the wheel support for the beginning of the grinding operatron.

When the rapid feed piston 51 reaches the end of its travel, cam 52 on feed screw 40 .actuates limit switch lLS to energize control relay 87CR. Normally closed control relay contact 87CR1 and normally closed control relay contact 87CR2 open to deenergize valve solenoid 4 Z which moves to the left and directs fluid under pressure to the head end of fast feed cylinder 64 shifting piston 63 to the left and rotating said feed screw 4!) for a preliminary fast grinding feed. At the end of the fast grinding feed, reset piston 71 and cylinder 70 shift a pin 72 in the head end of said cylinder 71 The head of cylinder 76 serves as a positive stop. Said pin 72 engages and closes limit switch 33LS to complete a circuit to energize control relay 71CR.

Control relay contact '71CR1 completes a circuit to energize round-out timer relay 4TR. The grinding operation continues without feed for a predetermined period after which timer relay contact 4TR2 completes a circuit to clutch relay 1CT. At this point in the grinding cycle, the distance of the grinding wheel from finished size may vary from workpiece to workpiece because of physical changes in the machine including the effect of change in temperature of lubricant and hydraulic fluid, changes in the rate of wheel wear and in the sharpness of the wheel, changes in the feed mechanism due to frictional variations, and variable forces to which the feed mechanism is subjected during a grinding cycle. The incremental feed will advance the grinding wheel from this point by a variable number of increments depending on the sum of the variables at this particular time. After the work is ground to size, the various feed actuating means are reversed to retract the grinding wheel. The incremental means will always be retracted by a predetermined amount which is equal approximately to the maximum accumulation of variables. All of these variations are compensated for by the fact that the incremental advance of the wheel is interrupted by the sizing device regardless of the number of increments required to reach final size. Clutch relay contact 1CT1 completes a circuit through normally closed timer relay contact 6TR2 to energize timer relay STR. It also completes a circuit through normally closed timer relay contact 5TR2 to energize control relay SICR and counter coil 3CT.

Control relay contacts 51CR1 and 51CR2 complete a circuit to energize valve solenoid M. The valve moves to the right and directs fluid under pressure to the right end of the pawl operating piston 111 shifting said piston to the left to rotate ratchet 100 for a coarse feed increment.

After a predetermined interval to permit this movement of piston 111, timer relay STR times out closing timer relay contact 5TR1 and opening timer relay contact STRZ. Opening timer relay contact STRZ deenergizes control relay SllCR. Control relay contacts 51CR1 and 51CR2 open to deenergize valve solenoid M. The valve is returned to the left to direct fluid under pressure to the opposite end of piston 111 to reset the piston and pawl for the next feed increment.

Timer relay contact 5TR1 completes a circuit to energize timer relay 6TR. Timer relay contact 6IR2 opens the circuit to deenergize timer relay STR resetting timer relay contact STRI and timer relay contact 5TR2. Normally closed timer relay contact STRZ completes a circuit to again energize control relay 51CR which provides another feed increment by piston 111 which is cotmted by counter coil 3C1.

After a predetermined number of such increments, 4 for example, clutch relay 1CT counts out opening clutch relay contact 1CT1 and closing clutch relay contact 1CT2.

Opening clutch relay 1CT1 deenergizes the circuit for the coarse increment feed. Clutch relay contact 1CT2 completes a circuit through normally closed timer relay contact STRZ to energize timer relay 7TR.

After a predetermined interval, timer relay contact 7TR1 closes, energizing timer relay STR and control relay 29CR. Control relay contacts 29CR1 and ZQCRZ complete a circuit to energize valve solenoid N, shifting the valve to direct fluid under pressure to the left end of fine pulse feed piston 104. Said piston 104 moves to the right to provide a line increment of feed.

Timer relay contact 8TR2 opens after an interval sufficient to permit the above described movement of fine feed piston 104. Timer relay HR is deenergized. Timer relay contact 7TR1 opens to deenergize and reset timer relay 8TR and control relay 29CR. Control relay contacts ZSiCRI and 29CR2 open to deenergize valve solenoid N which shifts to direct fluid under pressure to the right hand end of piston 104 to reset said piston for the next feed impulse. The interval provided for each increment of feed allows the wheel to advance, grind and partially spark-out before the next increment occurs so that in this final approach to finish size, the forces, such as changes in the work .and in the machine, which adversely affect the relation between the grinding wheel and the work, are kept to a minimum which determines the number of increments required to reach the desired size. When the diameter of the work reaches predetermined size, the advance of the wheel is stopped and the grinding action stops at the same time because deflection in both the work and the machine at this point is practically zero.

This cycle is repeated as often as necessary until a sizing device represented by caliper 30 is actuated indicating the predetermined size of the workpiece. The number of repetitions of the increment feed varies from workpiece to workpiece because of numerous physical changes in the workpiece and in the machine. Said caliper completes a circuit through caliper contact 31 to energize timer relay 9TR. Normally closed timer relay contact 9TR3 opens to deenergize control relay 210R. Control relay contacts 21CR1 and 21CR2 open to deenergize valve solenoid G. The valve moves to the left, connecting valve 90 with exhaust. Valve 90 is shifted to the right by spring 91 to direct fluid under pressure to the left end of fast feed reset cylinder 70 and also to the rod end of rapid feed cylinder 50 to reset the feed mechanism and retract the grinding wheel support 11 and grinding wheel 13.

When control relay 210R is deenergized, normally closed control relay contact 21CR4 completes a circuit from control relay contact 71CR2 to timer relay IOTR. It also completes a circuit to normally closed clutch relay 2CT 3 so that when timer 10TR times closed, timer relay contact 10TR1 will complete a circuit through normally closed timer relay contact 11TR2 to energize control relay 30CR and clutch relay 2CT. During the interval before timer relay 101" R closes, the retracting movement of wheel support 11 is started. Control relay contacts 30CR1 and 30CR2 then energize valve solenoid K which shifts the valve to the right and directs fluid under pressure to the right end of coarse pulse feed reset piston 120 to provide a coarse reset increment of feed shaft 80.

At the same time, a circuit is completed from counter contact 2CT3 through timer relay contact 11TR1 to energize timer relay IZTR. Normally closed timer relay contact 12TR2 opens deenergizing timer relay 11TR. Normally closed timer relay contact 11TR2 energizes control relay 30CR and counter 2CT.

Control relay contacts 30CR1 and 30CR2 complete a circuit to energize valve solenoid K which shifts the valve to the right directing fluid under pressure through the throttle valve to the left end of cylinder 122. Piston 121 and pawl 120 move to the left at a rate determined by the throttle valve 130. Pawl 120 engages ratchet 101 to turn shaft 89 in a counter-clockwise direction. Shaft 80 operates through the above described feed mechanism to cause a fixed number of reverse increments of feed screw 40 during the retracting movement of wheel support 11.

Counter ZCT counts out after a predetermined number of reset increments, in this case 4, so that the wheel support 11 and the wheel are always backed off a fixed number of increments from the point at which finished size is reached. The amount of reset of the ratchet feed may be determined as follows: Because of wheel Wear,

the wheel support need not be retracted by the same amount as it is advanced during grinding, in order to return the wheel face to the same starting position. The amount of advance of the ratchet feed is the amount of stock removal measured on the radius plus the wheel wear and other changes in the machine during stock removal. Therefore, the amount of retraction should be approximately equal to the stock removal by the incremental feeding means. For example, if this feeding means reduces the size of the workpiece /2 thousandth of an inch on the radius, the reset ratchet should be set to retract the wheel support by /2 thousandth of an inch. When the feed is reset in this manner, the preliminary grinding operation always stops with the operative surface of the grinding wheel approximately the same distance from finished size.

The above described operation represents an ideal condition in which there is either a substantial absence of variables, or the sum of the variables is nearly uniform. However, because the sum of the variables itself is subject to variation, the distance of the grinding wheel from the center of rotation of the work at the beginning and also at the end of the sparkout operation, may differ from piece to piece. The operative surface of the grinding wheel may be in a slightly different position at the end of the preliminary grinding operation in each cycle. In any event, the incremental feed which advances the grinding wheel from this point will be stopped by the sizing device when the work has been ground to the desired diameter regardless of the number of increments of feed required to reach finished size. The amount of reset is roughly the total of the maximum accumulation of variables. This total is estimated from experience. In the course of grinding a large number of workpieces, if this accumulation of variables shows a tendency to increase or decrease, the amount of reset can be adjusted accordingly.

I claim:

1. In a grinding machine, a work support, a grinding wheel support slidably mounted for movement toward and from said Work support, a grinding wheel rotatably mounted on said grinding wheel support, means for advancing and retracting said grinding wheel support, means operable between predetermined limits to continue said advancing movement at a slower rate to effect a preliminary grinding operation, a feed screw for effecting a grinding feed of said grinding wheel, a pawl and ratchet mechanism for rotating said feed screw, means for actuating said pawl and ratchet mechanism to provide a predetermined number of coarse feed increments, timing means to start said coarse feed increments a predetermined interval after the end of said preliminary operation, means operable thereafter for actuating said pawl and ratchet mechanism to provide an indefinite number of fine increments of feed, size control means operable at a predetermined size for stopping said fine increments of feed, means operable thereafter to retract said grinding wheel support, a second timer actuated simultaneously with retraction of said grinding wheel support, a second pawl and ratchet mechanism operable in a direction opposite to that of said first mentioned pawl and ratchet mechanism for resetting said feed screw, means controlled by said second timer for actuating said second pawl and ratchet mechanism a predetermined interval after the start of said retracting movement and continuing for a fixed predetermined number of coarse increments during said retracting movement to reset said feed mechanism for the next grinding operation.

2. In a grinding machine, a work support, a grinding wheel support slidably mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, means for advancing and retracting said grinding wheel support, means operable between predetermined limits to continue said advancing movement at a slower rate to effect a preliminary grinding operation, a feed screw for effecting a grinding feed of said grinding wheel, a pawl and ratchet mechanism for rotating said feed screw, for actuating said pawl and ratchet mechanism to provide a predetermined number of coarse feed increments, means operable thereafter for effecting fine increments of feed, size control means operable at a predetermined size for stopping said fine increments of feed, means operable thereafter to retract said grinding wheel support, a timer actuated simultaneously with retraction of said grinding wheel support, a second pawl and ratchet mechanism for resetting said feed screw, means controlled by said timer for actuating said second pawl and ratchet mechanism a predetermined interval after the start of said retracting movement and continuing for a fixed predetermined number of coarse increments during said retracting movement to reset said feed mechanism for the next grinding operation.

3. In a grinding machine, a work support, a grinding wheel support slidably mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, means for advancing and retracting said grinding wheel support, means operable between predetermined limits to continue said advancing movement at a slower rate to effect a preliminary grinding operation, a feed screw for effecting a grinding feed of said grinding wheel, a pawl and ratchet mechanism for rotating said feed screw, means for actuating said pawl and ratchet mechanism to provide a predetermined number of coarse feed increments, means operable thereafter for effecting fine increments of feed, size control means operable at a predetermined size for stopping said fine increments of feed, means operable thereafter to retract said grinding wheel support, a timer actuated simultaneously with retraction of said grinding wheel support, a second pa-wl and ratchet mechanism for resetting said feed screw, means controlled by said timer for actuating said second pawl and ratchet mechanism a predetermined interval after the start of said retracting movement and continuing for a fixed predetermined number .of coarse increments during said retracting movement to grinding feed of said grinding wheel, a pawl and ratchet mechanism for rotating said feed screw, means for actuating said pawl and ratchet mechanism to provide a predetermined number of coarse feed increments, timing means to start said coarse feed increments a predetermined interval after the end of said preliminary grinding operation, means operable thereafter for efiecting fine increments of feed, size control means operable at a predetermined size for stopping said fine increments of feed, and means operable thereafter to retract said grinding wheel support.

5. In a grinding machine, a work support, a grinding wheel support slidably mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism and means operable between predetermined limits to actuate said feed mechanism to effect a preliminary grinding operation, means for effecting a finish grinding feed of said grinding wheel including a feed screw, a pawl and ratchet mechanism connected for rotating said feed screw, means for actuating said pawl and ratchet mechanism to provide feed increments until the work is ground to a predetermined size, size control means operable when a workpiece has been ground to said predetermined size for stopping said incremental feed means, means operable thereafter to retract said grinding wheel support, a second pawl and ratchet mechanism for resetting said feed screw, and means operable in timed relation with the retraction of said grinding wheel support for actuating said second pawl and ratchet mechanism for resetting said feed screw by a fixed predetermined number of feed increments to reset said feed mechanism for the next grinding operation.

6. In a grinding machine, a work support, a grinding wheel support slidably mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism and means operable between predetermined limits to actuate said feed mechanism to effect a preliminary grinding operation, means for effecting a grinding feed of said grinding wheel including a feed screw, a ratchet mechanism connected for rotating said feed screw, means for actuating said ratchet mechanism to provide feed increments, size control means operable when a workpiece has been ground to a predetermined size for stopping said increments of feed, means operable thereafter to retract said preliminary grinding feed means, means for reversing said ratchet mechanism for resetting said feed screw, and means to actuate said ratchet mechanism in the opposite direction during said retracting movement.

7. In a grinding machine, a work support, a grinding wheel support mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism having means operable between fixed limits for effecting a rapid transverse feeding movement of said grinding wheel support toward and from said work support for a preliminary grinding operation, a feed screw for effecting a further feed of said grinding wheel after said first feed means reaches its forward limit, a pawl and ratchet mechanism connected for rotating said feed screw to grind a workpiece to a predetermined size, and means for actuating said pawl and ratchet mechanism to provide a fixed number of increments of adjustment in the opposite direction to reset said feed screw during said rapid transverse movement.

8. In a grinding machine, a work support, a grinding wheel support mounted for movement toward and from said work support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism having means for effecting a rapid transverse feeding movement of said grinding wheel support relative to said work support for performing a preliminary grinding operation, a feed screw for effecting a grinding feed of said grinding 'wheel, a power operated mechanism for rotating said feed screw by increments, and means for controlling said mechanism to provide a fixed number of increments of adjustment in the opposite direction to reset said feed screw.

9. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental means operable thereafter for further actuating said feed mechanism, and means responsive to said stopping means to start said incremental means.

10. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental feed means operable after said continuous moving means has stopped,

9 for further actuating said feed mechanism until it is stopped by said sizing device.

11. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, timing means, incremental feed means operable by said timing means a predetermined interval after said continuous moving means has stopped for further actuating said feed mechanism, and control means actuated by said sizing device for stopping said incremental means when a workpiece has been ground to the desired size.

12. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental feed means oper-able after said continuous moving means has stopped for further actuating said feed mechanism until it is stopped by said sizing device, retracting means actuated by said sizing device for reversing said incremental means a substantially fixed amount from the point to which it has advanced.

13. In a grinding machine, a work support, a grinding Wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental feed means operable after said continuous moving means has stopped for further actuating said feed mechanism until it is stopped by said sizing device, retracting means actuated by said sizing device for reversing said continuous moving means to the position from which it started and for reversing said incremental means a predetermined fixed amount from the point to which it has advanced.

14. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental feed means operable after said continuous moving means has stopped for further actuating said feed mechanism until it is stopped by said sizing device, and retracting means for resetting said grinding wheel after each grinding cycle to a position which is always substantially the same distance from the finished size of the workpiece, comprising control means actuated by said sizing device for reversing said continuous moving means and said incremental feed means, the continuous moving means to the position from which it started and the incremental feed means a predetermined fixed amount from the point to which it has advanced,

15. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism for moving said grinding wheel support toward and from said work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, incremental feed means operable after said continuous moving means has stopped for further actuating said feed mechanism until it is stopped by said sizing device, said incremental means being adjustable as to amplitude and frequency of the increments.

16. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, a feed mechanism :for moving said grinding wheel support toward and from said work support comprising a feed screw and a screw-engaging member in operative relation with said feed screw, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, a. sizing device, a ratchet mechanism operable after said continuous moving means has stopped for rotating said feed screw by increments until it is stopped by said sizing device, and means actuated by said sizing device for reversing said ratchet mechanism after each grinding cycle by substantially the same amount from the point at which finished size is reached.

17. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted on said grinding wheel support, :a feed mechanism for moving said grinding wheel support toward and from said work support comprising a feed screw and a screw-engaging member in operative relation with said feed screw, continuous moving means for actuating said feed mechanism to advance said grinding wheel support for a preliminary grinding operation comprising a worm wheel on said feed screw, a worm gear in operative engagement with said Worm wheel, said continuous moving means having a fixed range of movement for moving said worm gear endwise to rotate said feed screw, means to stop said endwise movement in substantially the same position for each grinding cycle before a workpiece is ground to size, incremental feed means operable when said con tinuous moving means has stopped for rotating said feed screw by increments, a sizing device for stopping said incremental feed means when the workpiece has been ground to size, and means actuated by said sizing device after each grinding cycle for reversing said continuous moving means to its starting position and for reversing said incremental feed means by substantially the same amount each time from the point to which it has advanced.

18. In a grinding machine having a work support, a grinding wheel support, a grinding wheel rotatably mounted on said wheel support, a feed mechanism for moving said wheel support toward and from said Work support, a sizing device, continuous moving means for actuating said feed mechanism to advance said wheel support for a preliminary grinding operation, means to stop said continuous moving means before a workpiece is ground to size, other feed actuating mean operable after said continuous moving means has stopped for further actuating said feed mechanism for finish grinding until it is stopped by said sizing device.

19. In a grinding machine, a work support including means for rotatably supporting a workpiece, a grinding wheel support mounted for movement toward and from said work support, a feed mechanism for effecting said movement including a feed screw and nut, one of which is attached to said wheel support, continuous moving means for actuating said feed mechanism to advance said wheel support for a rough grinding operation comprising a worm wheel on said feed screw, a worm gear in operative engagement with said worm wheel, means for moving said worm gear endwise to: rotate said feed screw at a relatively fast rate, means to stop said endwise movement of said worm gear before the workpiece is ground to size, power operated feed actuating means, and control means operable after said endwise movement of said worm gear has stopped for rotating said worm gear to rotate said feed screw at a slower rate for a finish grinding operation.

20. In a grinding machine, a work support including means for rotatably supporting a workpiece, a grinding wheel support mounted for movement toward and from said Work support, a feed mechanism for effecting said movement including a feed screw and nut, one of which 10 is attached to said wheel support, continuous moving means for actuating said feed mechanism to advance said wheel support for a rough grinding operation comprising a worm wheel on said feed screw, a worm gear in operative engagement with said worm wheel, means for moving said worm gear endwise to rotate said feed screw at a relatively fast rate, means to stop said endwise movement of said worm gear before the workpiece is ground 12 to size, incremental feed actuating means operable after said endwise movement of said worm gear has stopped for rotating said worm gear to rotate said feed screw at a finish grinding rate, a sizing device, and means operable by said sizing device when a workpiece has been ground to size for stopping said incremental feed actuating means.

References Cited in the file of this patent UNITED STATES PATENTS 1,923,762 Stevens Aug. 22, 1923 2,378,903 Baldenhofer June 26, 1945 2,582,610 Swainey Jan. 15, 1952 2,585,990 Baldenhofer Feb. 19, 1952 2,607,173 Garrison Aug. 19, 1952 2,638,719 Balsiger et al May 19, 1953 2,785,514 Koch Mar. 19, 1957 2,802,312 Gosney et a1 Aug. 13, 1957