US2718101A - Automatic infeed mechanism for centerless grinders - Google Patents

Description

Sept, 2%, 1955 A. D. c. STUCZKEY ETAL magma AUTOMATIC INFEED MECHANISM FOR CENTERLESS GRINDERS Filed Oct. 18, 1954 5 Sheets-Shget l INVENTORS. 7

AL BER T D. C. STUCKEY JACOB DECKER /0 3 AT TORNE YS.

Sept 26, 1955 A. D. c. STUCKEY ET AL 2,7183% AUTOMATIC INFEED MECHANISM FOR CENTERLESS GRINDERS Filed Oct. 18, 1954 5 Sheets-Sheet 2 INVENTORS. ALBERT D. STUCKEY JACOB DECKER 147' TORNE YS.

Sept. 20, 1955 A. D. c. STUCKEY ET L 2,718,101

AUTOMATIC INFEED MECHANISM FOR CENTERLESS GRINDERS Filed Oct. 18, 1954 5 Sheets-Sheet 3 INVENTORS, ALBERT a. 0. STUC/(EY BY JACOB DECKER /72 AT TORNE Y.

p 1955 A. D. c. STUCKEY ET AL 2,718,101

AUTOMATIC INFEED MECHANISM FOR CENTERLESS GRINDERS VWVVW wrx\ INVENTORS.

ALBER T .0. c. STUCKEY JACOB DECKER Sept. 1955 A. D. c. STUCKEY ETAL 2,718,101

AUTOMATIC INFEED MECHANISM FOR CENTERLESS GR-INDERS 5 Sheets-Sheet 5 Filed Oct. 18, 1954 a u m w m U 2 6 #2? m a m all H l R m T0 4 3 0. 3 1 HQ 5 a m RM an u a V NW w: 66 0mm T ml m N0 0 c c 7 ew w v mm h 1 Mm m 8 L M 0 (I JIM v H llll Fl m w w m M w Wm H 1 i w W 2 3 m a IN V EN TORS.

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United States Patent AUTOMATIC INFEED NIECHAN ISM FOR CENTERLESS GRINDERS Albert D. C. Stuckey and Jacob Decker, Cincinnati, Ohio,

assignors to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Application October 18, 1954, Serial No. 462,806

13 Claims. (Cl. 51165) This invention relates to grinding machines and more particularly to improvements in infeeding mechanisms for centerless grinders.

One of the objects of this invention is to provide a new and improved automatic infeed mechanism for a centerless grinding machine.

Another object of this invention is to provide an improved hydraulic infeed mechanism for a centerless grinder with automatic electric control for governing the cycle of operation.

A further object of this invention is to provide an infeed mechanism of the character described for effecting feed and rapid traverse movements in which the feed screw and nut are only relatively rotated during power feeding movements and in which the nut is mounted on a fixed part of the machine, thus providing stable and accurate operation and lengthening the life of the screw and nut.

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.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure l is a view in elevation of a machine embodying the principles of this invention.

Figure 2 is a vertical section on the line 22 of Figure 1. v

Figure 3 is a vertical section on the line 3-3 of Figure 2.

Figure 4 is a horizontal section on the line 4-4 of Figure 3.

Figure 5 is a diagrammatic view of the mechanism for the rapid traverse piston.

Figure 6 is a sectional view on the line 66 of Figure 3 showing the feed operating mechanism.

Figure 6A is a detail section on the line 6A--6A of Figure 3.

Figure 7 is a diagrammatic view of the control mechanism for the feed piston.

Figure 8 is a diagrammatic view of the cycle control electric circuit. I

Figure 9 is a detail section on line 99 of Figure 4.

In Figure 1 of the drawings the reference numeral 10 16, is supported on the work rest between the grinding wheel and the regulating wheel, and by means of an 2,718,161 Patented Sept. 20, 1955 automatic infeed cycle the regulating wheel is moved toward and from the grinding wheel to efifect reduction in the size of the work. For adjustment purposes, the regulating wheel slide 15, as shown in Figure 2, is guided at 16 on a lower slide 17 which, in turn, is guided at 18 on the top of the bed 10. The work rest is usually carried by the lower slide 17 whereby the lower slide may be adjusted to position the work rest with respect to the grinding wheel, and the upper slide is adjustable rela tive to the lower slide to adjust the space between the regulating wheel and the work rest dependent on the size of the work.

By means of this invention, a new and improved automatic infeed cycle mechanism has been provided for feeding the regulating wheel toward and from the grinding wheel. This is accomplished by first clamping the slide 15 to the slide 17 by the clamping means 17 so that the blade 12 and regulating wheel 13 move as a unit. When it is desired to move the slide 15 only it is unclamped from the lower slide, and the lower slide 17 is clamped to the bed by the conventional clamping means 18.- As shown in Figure 3, the upper slide 15 has an internally threaded sleeve or nut 19 anti-frictionally supported by thrust bearings 20 and 21 and tightly held against axial movement by a thrust nut 22 which can be adjusted to take up all lost motion in the thrust bearings. An adjusting screw 23 is threaded in the nut 19 but is connected to a power feeding mechanism in a manner to hold it against rotation and impart axial movement thereto to feed the slide.

Rotation of the nut is utilized only for manual operation and adjustment, and for this purpose the nut 19 is provided on one end with a bevel gear 24 which, as shown in Figures 2 and 3, meshes with a bevel gear 25 mounted on the end of a shaft 26 journaled in a laterally extending housing 27 of the slide 15. The projecting end of the shaft is provided with a hand wheel 28 which, as shown in Figure l, is located at a convenient position on the machine for the operator when making set-up adjustments.

For automatic cyclic power operation, the screw 23 acts as a push rod and is moved axially and for this purpose it is opcratively connected to a walking beam 29, Figures 3 and 4, by pivot pins 30 and 31 which pass through the walking beam and are inserted in holes 32 and 33 formed diametrically opposite to one another in a sleeve 34 which is secured to the screw shaft 23 by a driven tapered pin 35. it is the pin 35 which holds the screw 23 against rotation. The opposite ends 36 and 37 of the beam are bifurcated and slotted, as shown in Figure 9, to embrace square blocks 38 mounted on pivoted pins 39 which project from opposite sides of a connecting block40.

As shown in Figure 4, one of the blocks 40 is mounted on the end of the piston rod 41 which constitutes the rapid traverse piston, and the other on shaft 42 which constitutes the feeding member. It will now be seen that if the shaft 42 is held against movement, that axial shifting of the member 41 will cause axial movement of the screw 23; while on the other hand, if the piston rod 41 is held against movement, axial movement of the member 42 will likewise cause axial movement of the screw 23. It will be noted that the screw 23 never rotates; in fact, it is held against rotation by the walking beam. Power movement of the slides is eifectedby moving the screw 23 axially by means of the walking beam, while manual adjustment is effected by rotating the nut 19 relative to thescrew 23.

The actual feeding movement is imparted to the walking beam by means of a screw and nut mechanism comprising a feed screw thread 43, Figure 4, formed on the enlarged end of shaft 42, and a nut 44 secured to the end of the housing by suitable screws 45'. Rotation of the screw 43 is effected by an elongated gear 46 which is splined on a key 47 fixed with the shaft 42. The shaft 42 is capable of rotation with respect to the block 40, as shown in Figure 9, and anti-friction thrust bearings 48 and 49 are mounted on opposite sides of the block 40 and tightened by the nut 50 to take out lost motion between the shaft 42 and the block 40.

As shown in Figure 6, the gear 46 meshes with a rack 51 formed on the periphery of an elongated piston 52 slidable in a cylinder 53 to impart rotation to the gear. Opposite ends of the cylinder have ports 54 and 55 which are operatively connected by channels 56 and 57 to ports 58 and 59 respectively of a reversing valve indicated generally by the reference numeral 60 in Figure 7. This valve has a pressure port 61 which is connected by channel 62 to the output of a pump 63 which has an intake 64 through which fluid is withdrawn from a reservoir 65. A relief valve 66 is connected to the channel 62 to control the pressure therein. 7

The valve 60 also has a pair of exhaust ports 67 and 68 which are connected by channels 69 to the reservoir 65, there being a low pressure relief valve 70 in the line to maintain the line full of oil and keep air out of the system. The reverse valve 60 has a piston valve plunger 71 in which is formed annular grooves 72 and 73 which serve to alternately connect the pressure port 61 to either of the motor ports 58 or 59, while connecting the other to one of the exhaust ports 67 or 68. The valve plunger 71 is normally held in the position shown by a spring 74 mounted between the left end of the plunger 71 and the nut 75 threaded in the left end of the valve housing.

The valve 60 also has ports 76 and 77 formed in opposite ends thereof which are connected to channels 78 and 79 respectively. The channel 78 is connected to reservoir 65. The channel 79 is connected to port 80 of a solenoid operated pilot valve indicated generally by the reference numeral 81 which controls shifting of the plunger 71. The pilot valve has a valve plunger 82 in which is formed an annular groove 83 for alternately connecting port 80 to a pressure port 84 or to an exhaust port 85 to effect shifting of the reversing valve plunger 71.

The pilot valve plunger 82 is operatively connected to the solenoid 86, and a spring 87 normally urges the plunger to the right. When the solenoid is energized, the plunger 82 is shifted to the left, thereby interconnecting the pressure port 84 with the port 80 whereby fluid pressure will flow in channel 79 to shift the reversing valve plunger 71 to the left. This will interconnect the pressure port 61 with port 58, and pressure fluid will flow through channel 56 to shift the piston 52 to the right causing rotation of the gear 46 and screw 43 whereby the walking beam 29 will be oscillated about the pivot 39 in the end of the piston 41 to move the regulating wheel toward the work.

The rate of feed movement is controlled by placing a throttle valve 86 in the channel 57, thus controlling the rate of fluid flow. The throttle valve 86 may be any suitable conventional throttle valve, that shown in United States Letters Patent 2,622,6l4 being found suitable for present purposes. When the piston 52 nears the end of its stroke it is decelerated by an adjustable screw 87' :which engages a small pilot valve plunger 88 slidably mounted in a bore 89 formed in the end of the piston 52. This plunger is held by a spring 90 against the end plate 91 fastened to the end of the piston by suitable screws 92.

When this plunger is shifted by engagement with the screw 87' before the piston has completed its full stroke, an annular groove 93 formed in the plunger 88 is shifted to the left, as viewed in Figure 6A, to interconnect ports 94 and 95. The port 95 communicates with a longitudinal bore 96 formed in the piston 52 and having an outlet 97 which communicates with the chamber 98 at the left end of cylinder 53, and since this chamber is under pressure, causing movement of the piston 52 to the right, the port 95 will be under pressure, whereby when the valve plunger 88 shifts to the left, port 95 will be under pressure when connected to the port 94. Fluid pressure will thus flow through port 94, groove 99 and channel 100 to a chamber 101 containing a piston 102 to actuate the switch lever 103 of a limit switch 104. Piston 105 slidable in cylinder 106, which is mounted on the opposite side of the switch lever 103, has its cylinder connected to reservoir through channel 107, longitudinal groove 108, port 109, which is connected to exhaust port by the annular groove 111 formed in a second pilot piston 112 slidably mounted in the other end of piston 52. At this time the piston 112 is positioned to the left by a spring 113 due to the fact that the piston 52 has moved to the right away from the abutment 114.

Operation of the limit switch 104 at the end of the feeding stroke will deenergize the solenoid 86 in a manner to be explained in connection with the electric circuit, whereby the valve plunger 82 will disconnect the pressure port 80 from port 84 and connect it to the exhaust port 85. The reversing valve plunger 71 will then shift to the right, connecting pressure to channel 57 whereby the fluid will bypass the rate valve 86 by way of the check valve 114 and cause movement of the piston 52 to the left at a rapid traverse rate due to the fact that the channel 56 is connected to the exhaust line 69. This will retract the grinding wheel from the work.

Before the piston 52 completes its return movement, the second deceleration piston 112 engages the abutment 114 and is thus stopped while the piston 52 continues its movement. It should be emphasized at this point, that during movement of piston 52 to the right that the chamber 98 is full of fluid under pump pressure, and this pressure eventually passes through the axial bore 112a of piston 112 and past the ball check valve 1121) into the spring chamber 113a. At this time, the piston is extended beyond the end of the piston, because it is away from abutment 114. Thus, when the piston moves in the other direction toward the left, and the piston 112 is pushed in by the abutment, it must squeeze out the fluid pressure in the chamber 113a through the high resistance passage 113b, thus causing the trapped fluid in chamber 113a to act as a decelerating means. In so doing, the annular groove 111 is relatively positioned to interconnect the port 109 with the port 115 forming the terminus of the interdrilled passage 116. It will be realized that at this time fluid pressure is entering the right end of cylinder 53 through port 55, and thus fluid pressure will continue to flow through passage 116 and interconnected ports 115 and 109 to channel 107, thereby operating the piston 105 to throw the switch lever 103. The results of the operation of the limit switch will be explained later in connection with the electrical control circuit.

Before the feeding operation is started, however, the grinding wheel is moved at a rapid traverse rate up close to the work before the actual grinding commences. This rapid traverse movement is effected by the rod 41 shown in Figure 4 and operatively connected as previously described to one end of the walking beam 29. The rapid traverse piston 117 attached to the piston rod 41 is slidable in the cylinder 118, which has a port 119 at one end connected by channel 120 to port 121 of a reversing valve, indicated generally by the reference numeral 122 in Figure 5. This valve has a second port 123 to which is connected a channel 124 which divides into two branches 125 and 126. The branch 126 has a port 127 which communicates with the upper chamber 128 of cylinder 118. The branch 125 has a one-way check valve 128 serially connected therein, and terminates in a second port 129 communicating with chamber 123.

The reversing valve 122 has a pressure port 130 which is connected by channel 62 to pump 63 as shown in Figure 7. The valve also has a pair of exhaust ports 131 and 132 which are connected to the return channel 69. The valve plunger 134 of valve 122 is normally held in a right hand position, as shown in Figure 5, by a spring 135 interposed between the end of the valve plunger and the end 136 of the valve housing. Thus, the pressure port 130 is normally connected by the annular groove 137 in valve plunger 134 to port 123 whereby chamber 128 is under pressure. When the valve plunger 134 is shifted to the left, as viewed in Figure 5, pressure is admitted to port 119, and the piston 117 moves upward at a rapid traverse rate. As it moves upward, a deceleration plunger 138, slidably mounted in the end of the piston 117, is moved outward by a spring 139 interposed between the end of the plunger 133 and the bottom 140 of the bore 141 in which the plunger 138 is slidable. Thus, the plunger 138 moves out as the piston 11'] advances until the shoulder 142 on the plunger 138 engages the abutment 143 formed on the end of the piston. This positions the parts in such relation that the port 144, formed in the piston and connected by the interdrilled passage 145 to the lower end of the piston, is interconnected to the port 146 formed in the plunger 138 and communicating with a bore 147 formed in the end of the plunger. In this bore is a spring 148 which urges a ball 149 into closing engagement with the end of an axial bore 150 formed in the end of the plunger 138. A plug 151 is threaded in the member 138 as an abutment for the spring 148, and has a small axial bore 152 which forms communication between the drilled hole 141 and the space constituting chamber 147. This allows the fluid pressure which moves the piston to enter the bore 141 for purposes of decelerating the piston 117 on its return stroke.

As the piston 117 moves upward, a beveled shoulder 153 formed on the end of piston 117 starts to restrict the outlet port 127, thereby trapping the fluid in the upper chamber 128. This acts to decelerate the piston as it reaches the end of its upward stroke. When the piston moves the other way, the fluid pressure enters port 129 through check valve 128 and the auxiliary plunger engages the adjustable screw 154 before the piston reaches the limit of its stroke and is moved in a direction to close the port 144 and trap the fiuid in the bore 141 to decelerate the piston in its other direction of movement.

At the completion of the rapid traverse stroke of piston 117, a trip dog 155 attached to the end of the walking beam 29 engages a plunger 156 which operates a limit switch 157 to automatically start the feeding movement.

The complete cycle of operation thus consists of a rapid traverse advance movement of the wheel slide, a feeding movement, a reverse, and rapid retraction to starting position. erned by an electric control circuit shown in Figure 8 of the drawings. With the grinding wheel in a retracted position to allow space for work loading, the automatic infeed cycle is started by operating the push button 158 and closing the circuit in line 159 to the control relay CR11. Line 159 is connected at one end to .the power main 160 and at the other end .to the power main 161. A normally closed stop button 162 is serially connected in the line 159 for stopping the cycle at will. Operation of the relay CR11 will close its latching contact CR11-1 connected around the push button 158 so that after operation by the push button the circuit will remain closed.

Operation of the control relay CR11 will also close a second contact CR'112 in line 163, which will close the circuit to solenoid 164 which operates a pilot valve to start the rapid traverse movement.

As shown in Figure 5, the solenoid 164 is operatively connected to the pilot valve plunger 165 of a pilot valve 166 for controlling the positioning of the rapid traverse reversing valve 122. The valve plunger 165 is normally held in the position shown by a spring 167 interposed between one end of the plunger 165 and the end 168 of the valve 166. When the solenoid is energized the valve plunger 165 is shifted to the left against the compression of spring 167 to a position such that the annular groove The sequential control of these movements is gov- 169 in the valve plunger connects the pressure port 170, connected to line 62, to port 171 which is connected by channel 172 to the right hand end of the reverse valve housing 122. This causes shifting of the valve plunger 134 to the left and effects rapid traverse movement of the piston 117 to effect rapid infeed of the wheel slide.

At the end of this movement the dog 155 operates the limit switch 157 which, as shown in Figure 8, will close a circuit in line 173, energizing control relay CR13. This relay will close its contact CR13-1 in branch line 174 of line 163 and thereby energize solenoid 86. This will cause operation of the pilot valve 81 for the reversing control valve 60 of the feed piston whereby fluid pressure will be admitted to the feed cylinder in the manner described, so that the piston 52 will move toward the right as viewed in Figure 6, causing rotation of the gear 46 splined on shaft 42, thereby effecting rotation of the feed screw 43 in the nut 44 producing a feeding movement to the wheel slide. The rate of this feeding movement is controlled by the rate valve 86 shown in Figure 7, which operates on the exhaust flow from the cylinder 53.

A positive stop means has been provided to insure that the wheel stops at exactly the same point in each cycle. This consists of threading a stop nut 23a on the end of the shaft 23. This nut is in the form of a sleeve having a shoulder 23b which engages a finished surface 230 on the housing 45.

The control mechanism is so adjusted that the positive stop will hit just before the feed piston has completed its stroke, which produces the following effect. When the positive stop hits, the shaft 23 will no longer move forward, with the result that the pivot pin 30 is held stationary, so that further movement of the feed screw 43 Will cause the walking beam 29 to pivot about the pin 30 and move the rapid traverse piston 117 backward a little bit against the hydraulic pressure holding the piston 117 against the end of the cylinder. This insures that the stop shoulder 23b is properly squeezed against the stop surface 230.

As the feed piston nears completion of its movement the pivot valve 88 in the end of piston 52 will be shifted to the left by the adjustable set screw 57 and effect interconnection of the ports 95 and 94in Figure 6A and thereby hydraulic actuation of the limit switch 104. This switch will close a circuit in line 176 and, with the selector switch 177 closed, effect energization of the timer relay TR11. This relay has a contact TR111 in line 159, and this contact is normally closed to maintain the circuit to control relay CR11. This timer relay may be set to produce a dwell at the end of the feeding movement before reversal takes effect.

When the desired time has run out, the contact TR111 will open, breaking the circuit to control relay CR11 which will open its contacts CR111 and its contacts CR11-2 in line 163 causing deenergization of both solenoids 164 and 86. The pilot valves connected to these solenoids will thus return to their normal position and cause simultaneous retraction of both the feeding piston and the rapid traverse piston. As soon as the rapid traverse piston retracts it opens limit switch 157 and breaks the circuit to control relay CR13 which thereby opens its contact CR13-1 in line 174 and thereby reconditions that circuit for the next operation.

If the switch 178 in branch line 179 is open the grinding wheel will return to its starting positionand remain there, but if it is desired to have a continuously repeating cycle with just sufficient delay at the end of the cycle for the operator to load the next workpiece, the switch 178 is closed at the beginning of the cycle whereby when the timer relay TR11 is operated by the limit switch 164 it will close a second contact thereon TR112 which will complete a circuit to control relay CR12. Operation of this relay will immediately close its latching contact CR12-2 and asecond contact CR-12-1, which is serially in circuit 181 containing timer relay TR12.

7 connected in a parallel circuit 180 connected across the contact CR111 and around the push button 158.

The limit switch 104, which is actuated at the end of the infeed, has a second normally closed contact 1041 The contact 1041 will thus open and remain open during the rapid traverse return movement of the slide, so that when the slide has completed its return movement and limit switch 104 is again actuated the contact 104-d will close and energize timer relay TR12. This relay has a contact TR121 in line 180 connected around the push button 158, and since contact CR12--1 is closed at this time, the timed closing of contact TR12-1 will complete the circuit in line 159 without operation of the push button 158. This will cause energization of the control relay CR11 and start the next infeeding cycle.

There has thus been provided an improved automatic infeed mechanism which is of unique construction and in which it will be noted that the rapid traverse movement is effected by a mechanism which is so designed that it does not require rotation of the feed screw 43 relative to the nut 44 Whereas in most of the prior devices where a screw and nut are utilized to effect traverse, the rapid traverse movement is effected by effecting a rapid rotation between the screw and nut which causes additional wear, while in other prior art devices the screw and nut are utilized as a means for pushing or pulling the slide to effect the rapid traverse movement, whereas here the nut is anchored to a fixed part of the machine and the screw is only rotated with respect to the nut when it is necessary to effect a power feeding movement.

What is claimed is:

1. In an infeed mechanism for a wheel slide of a grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to the rod, a rapid traverse piston operatively connected to one end of the beam, a feed screw pivotally connected to the other end of the beam, a fixed nut receiving said screw and holding it against axial movement, and means to admit fluid pressure to said piston to swing said beam about the pivot on said screw to move the rod and thereby the slide at rapid traverse.

2. In an infeed mechanism for a wheel slide of a grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to the rod, a rapid traverse piston operatively connected to one end of the beam, a feed screw pivotally connected to the other end of the beam, 2. fixed nut receiving said screw and holding it against axial movement, means to admit fluid pressure to said piston to swing said beam'about the pivot on said screw to move the rod and thereby the slide at rapid traverse, power operable means to rotate said screw and control means operable by said piston to energize said power operable means.

3. In an infeed mechanism for a wheel slide of a grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to the rod, a rapid traverse piston operatively connected by pivot means to one end of the beam, a feed screw pivotally connected to the other end of the beam, a fixed nut receiving said screw and holding it against axial movement, means to admit fluid pressure to said piston to swing said beam about the pivot on said screw to move the rod and thereby the slide at rapid traverse, power operable means for rotating said screw to swing the walking beam about said pivot means to effect feeding of said slide.

4. An infeed mechanism for the Wheel slide of a centerless grinding machine comprising a push rod having a threaded connection to said slide, a walking beam pivotally connected at its center to said rod, a rapid traverse piston pivotally connected to one end of said beam, a power operable feed screw pivotally connected to the other end of the beam, a first control for energizing said rapid traverse piston, a second control for energizing said power operable screw, and manually operable means operatively connected to said threaded connection for effecting manual adjustment of said slide.

5. An infeed mechanism for the regulating wheel slide of a centerless grinder comprising a push rod threaded in a nut carried by the slide, a walking beam pivotally connected at its center to said rod, 2. rapid traverse piston operatively connected to one end of said beam to effect rapid traverse advance of said slide, a power operable feed screw connected to the other end of said beam, and sequentially operative to effect a feeding movement of said slide, and a positive stop member on said rod for limiting the advance of said slide.

6. In an infeed mechanism for the regulating wheel slide of a centerless grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to said rod, power operable rapid traverse means operatively connected to one end of said beam, power operable feeding means operatively connected to the other end of said beam, an electrical control circuit including a solenoid operated starting control for the rapid traverse means, a solenoid operated starting control for the feeding means, a start button in said circuit for energizing said firstnamed solenoid control, means automatically operable by said rapid traverse means for energizing said second solenoid, and a limit switch operable by said feeding means at the end of its stroke to deenergize both of said solenoid controls.

7. In an infeed mechanism for the regulating wheel slide of a centerless grinder, the combination of a push rod operatively connected to said slide, a Walking beam pivotally connected at its center to said rod, power operable rapid traverse means operatively connected to one end of the beam, power operable feeding means operatively connected to the other end of said beam, an electrical control circuit having a starting control relay for sequentially energizing said power operable means to effect infeed movement of the slide, a limit switch in said circuit operable by said feeding means to deenergize said control relay to cause retraction of said push rod, and automatic means operable at the end of said retraction to time-energize said starting control relay.

8. In an infeed mechanism for a grinding wheel slide, the combination of separate fluid operable means operatively connected to the slide for independently effecting a rapid traverse movement and a feeding movement respectively of said slide, separate reversing valves for each fluid operable means, separate solenoid operated pilot valves for controlling the shifting of the respective reversing valves, manually operable means for energizing one of said solenoids, and trip operable means for sequentially energizing the other solenoid.

9. In an infeed mechanism for a grinding wheel slide, the combination of separate fluid operable means opera tively connected to the slide for independently effecting a rapid traverse movement and a feeding movement respectively of said slide, separate reversing valves for each fluid operable means, separate solenoid operated pilot valves for controlling the shifting of the respective reversing valves, manually operable means for energizing one of said solenoids, trip operable means for sequentially energizing the other solenoid, and a limit switch for sequentially deenergizing both of said solenoids.

10. In a feeding mechanism for a grinding wheel slide, the combination of a feed screw operatively connected to the slide, a fixed nut having a threaded connection to said screw, rack and pinion means for imparting rotation to the screw, a reversible piston connected to said rack, decelerating pistons axially mounted in each end of said rack piston, a reversing valve for controlling the admission of fluid pressure to opposite ends of said piston and a hydraulically actuated limit switch controlled by said decelerating pistons for controlling the shifting of said reversing valve.

11. In an infeeding mechanism for the wheel slide of a centerless grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to said rod, a rapid traverse piston pivotally connected to one end of said beam, a feed screw threaded in a fixed nut and operatively connected to the other end of said beam, means to admit fluid pressure to said rapid traverse piston to effect a full stroke thereof and maintain fluid pressure thereon after the completion of said stroke, positive stop means for limiting axial movement of said push rod, power operable means for actuating said feed screw and efiect swinging movement of said walking beam about the pivotal connection established by said rapid traverse means, said positive stop being adjusted to operate before the feed screw has completed its stroke which will thereby cause retraction of the rapid traverse piston against its holding pressure to insure positive engagement of said positive stop means.

12. In an infeeding mechanism for the wheel slide of a centerless grinding machine, the combination of a push rod operatively connected to said slide, a walking beam pivotally connected at its center to said push rod, a rapid traverse piston and cylinder having a piston rod pivotally connected to one end of the beam, a feed screw threaded in a fixed nut and pivotally connected to the other end of the beam, the pivotal connection on said screw forming a fixed point for swinging movement of the walking beam during actuation of said rapid traverse piston, said piston moving through a full stroke in its cylinder to establish a fixed pivot for swinging movement of said beam by said feed screw upon operation thereof to effect a feeding movement, and positive stop means for limiting movement of said push rod by said feed screw.

13. An infeed mechanism for the wheel slide of a centerless grinder comprising a nut rotatably mounted in said slide, a push rod threaded in the nut, a walking beam pivotally connected at its center to said rod and-having its opposite ends operatively connected to independent power operable means which hold the rod against rotary movement, manually operable means for rotating the nut in said slide relative to the rod to efiect adjustment of the slide relative to said power operable means, positive stop means carried by the other end of said rod, and means to independently operate said power operable means whereby the movement imparted by one is independent and unaffected by movement imparted by the other.

References Cited in the file of this patent UNITED STATES PATENTS 2,150,749 Price et a1 Mar. 14, 1939 2,211,530 Balsiger et a1. Aug. 13, 1940 2,241,634 Decker May 13, 1941

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