US2758426A - Rapid infeed control for grinding machines - Google Patents

Description

Aug. 14, 19 G. E. COMSTOCK 3D RAPID INFEED CONTROL FOR GRINDING MACHINES 2 Sheets-Sheet 1 Filed Nov. 9, 1955 Q N & T\ N INVENTOR 560/355 5 lia/wsma/cr v BY WLAEJZW Aug. 14, 1956 s. E. COMSTOCK 30 2,758,426

RAPID INFEED CONTROL FOR GRINDING MACHINES Filed Nov. 9, 1955 2 Sheets-Sheet 2 i252. 5am $25223 BY- 44 Mum HTTO ENE I United States Patent'Ofice 2,758,426 Patented Aug. 14, 1956 RAPID INFEED CONTROL FOR GRINDING MACHINES George E. Comstock 3d, Princeton, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application November 9, 1955, Serial No. 545,914 6 Claims. (Cl. 51-95) The invention relates to grinding machines and more particularly to a grinding wheel feeding mechanism.

One object of the invention is to provide a simple and thoroughly practical grinding wheel feeding mechanism. Another object of the invention is to provide means whereby the grinding wheel may be fed at a rapid rate until the wheel moves into engagement with the work piece to be ground and to thereafter reduce the feed to a normal grinding feed. Another object of the invention is to provide a feeding mechanism for a grinding machine whereby the grinding wheel may be fed rapidly into engagement with the surface of the work piece, thereby minimizing the time lost in grinding air.

Another object of the invention is to provide a grinding wheel feeding mechanism whereby the grinding wheel is fed rapidly into operative engagement with the work and a back pressure within the feed motor actuates a mechanism to reduce the feed to a normal grinding feed. Another object of the invention is to provide a pressure switch which is actuated by back pressure in the feed motor when the wheel engages the work piece automatically to reduce the rate of feed to a normal grinding feed. A further object of the invention is to provide a normally inoperative pressure switch which is rendered operative in timed relation with the feeding mechanism in which a magnetic clutch renders the pressure switch operative so that back pressure in the feed motor caused by the grinding wheel engaging the work actuates the pressure switch to reduce the rapid feeding movement to a normal grinding feed.

Other objects will be in part obvious or in part pointed out hereinafter.

In the accompanying drawings, in which is shown one of various possible embodiments of the mechanical features of this invention,

Fig. 1 is a vertical sectional view grinding machine showing the wheel feeding mechanism; and Fig. 2 is a combined electrical and hydraulic diagram of the wheel feeding mechanism and the controls therefor.

A grinding machine has been illustrated in the draw ings of the type shown in U. S. patent to H. A. Silven and C. G. Flygare No. 2,522,485 dated September 12, 1950, to which reference may be had for details of disclosure not contained herein. This machine comprises a base 10 which serves as a support for a transversely movable wheel slide 11. The wheel slide 11 is supported on the usual V-way and flatway (not shown). The wheel slide 11 serves as a support for a rotatable wheel spindle 12 having a grinding wheel 13 mounted adjacent to one end thereof. The grinding wheel spindle 12 may be driven by any suitable source such as for example an electric motor (not shown) mounted on the wheel slide 11.

The wheel slide 11 is arranged to be fed transversely by a feeding mechanism comprising a rotatable feed screw 15 which is slidably keyed at its left hand end through a cylindrical within a rotatable sleeve 16 which is supported by antifriction bearing 17 carried by the base 10. The right hand end of the feed screw 15 is rotatably supported in a bearing (no-t shown) supported within a slidably mounted sleeve 18. The feed screw 15 meshes with or engages a rotatable feed nut 19 supported by a bracket 14 depending from the underside of the wheel slide 11.

A manually operable feed wheel 20 is mounted on the front of the machine base 10. The feed wheel 20 is operatively connected to rotate a gear 21 which meshes with a gear 22. The gear 22 is supported on the forward end of a rotatable shaft 23. The shaft 23 is supported in anti-friction bearings 24 carried by the base 10. The right hand end of the shaft 23 is slidably keyed Within the left hand end of the rotatable sleeve 16. It will be readily apparent from the foregoing disclosure that a rotary motion of the feed wheel 20 will be imparted through the mechanism above described to rotate the feed screw 15 so as to impart a transverse feeding movement to the wheel slide 11. The direction of rotation of the feed wheel 20 serves to determine the direction of movement of the wheel slide 11.

The feed wheel 20 is provided with a stop abutment 25 which is adjustable relative to the feed wheel by means of a micrometer adjusting mechanism 26. A stop pawl 27 is pivotally supported by a stud 28 on the front of the machine base- The upper end of the pawl 27 is provided with a stop surface 29 so that when the pawl 27 is in an operative position, a Wheel 26 may be continued until the stop abutment 25 engages the stop surface 29 to positively limit the infeeding movement of the grinding wheel 13 and wheel slide 11.

In order to facilitate a rapid positioning movement of the grinding wheel 13, that is, rapidly moving the grinding wheel 13 together with the wheel slide 11 to and from an operative position, a hydraulically operated mecha nism is provided. This mechanism comprises a cylinder 30 which is arranged in axial alignment with the sleeve 18 and feed screw 15. The cylinder 30 contains a slidably mounted piston 31 which is connected to the right hand end of a piston rod 32. The other end of the piston rod 32 is fixedly connected to the slidably mounted sleeve 18. The rapid movement of the wheel slide 11 caused by the piston 31 may continue until the piston 31 engages the left hand end of the cylinder 30 or until a stop surface 33 on the left hand end of the feed screw 15 engages an adjustable stop screw 34 carried by the right hand end of the shaft 23.

A feed control valve 35 is provided for controlling the admission to and exhaust of fluid from the cylinder 30. The valve 35 is preferably a piston type valve comprising a valve stem 36 having a plurality of valve pistons 37, 38 and 39 formed integrally therewith. A compression spring 40 serves normally to maintain the valve stem 36 in its right hand end position. A solenoid S1 is operatively connected to the right hand end of the valve stem 36 and is arranged so that when energized, it serves to shift the valve stem 36 toward the left into a reverse position.

A suitable fluid pressure system is provided comprising a motor driven fluid pump 42 which draws fluid through a pipe 43 from a reservoir 44 and forces fluid under pressure through a pipe 45 to the feed control valve 35. A pressure relief valve 46 is connected to the pipe 45 by means of which excess fluid under pressure may be bypassed directly through a pipe 47 into the reservoir 44 to facilitate maintaining a substantially uniform operating pressure in the hydraulic system.

In the position of the valve 35, as shown in Fig. 1, fluid under pressure passing through the pipe 45 enters a valve chamber 48 located between the valve pistons 37 rotary motion of the feed corresponding axial movement to nut 19, the wheel slide 11 so as and 38 and passes through a passage 49 into a cylinder chamber SOformed at the 30 to move the piston 31 ward or inoperative position as shown in Fig. 1. Movement of thejpis ton 31 toward the right also imparts a to move the grinding wheel to a rearward orinoperative position. During this movement of the piston 31, fluid within a cylinder chamber 51 may exhaust through a passage 52, through a valve. chamber 53 located between the valve pistons 33 I and 39 and passes. out through an exhaust pipe 54 into the reservoir 44. e

In order to slow down the. rapid rearwardmovement of thepiston 31, a dash pot mechanism 55 is provided to facilitate slowing iiown and cushioning the reaward moveofttl'xe whe slide'at the end its strbke. 7 po is su 1 Lb. th

s the mor U. S. pa-mat i. swain 2,532,610 dated January 1952, to which; reference may be had for details of disclosure not contained herein. throttle valve,56 is provided in the pipe line 57 for controllin the exhaust of fluid from the clash pot mechanism 55 so as to regulate the rate of slow down or cushioning of the movement of thepiston 31 as it moves toward the This ' right.

It is similarly desirable to provide acushioning or slowing down movement of thepiston 31 as it moves rapidly toward the left as the grinding wheel approaches a workpiece 60 tobe ground, During the initial rapid movemnt of the piston 31 toward the left, fluid may exhaust from thecylinder chamber '50 through a port 61, through thevalvechamber 48 and out through the exhaust pipe 54 at a substantially unrestricted rate. When the piston 31 closes theport 61. just before the piston 31 reaches the lefthand end of'its stroke, fluid may then exhaust through i a passage 62, through a throttle valve 63 into the passage-19 and throughthe valve chamber 48 and exhausts through thepipe 54. By manipulation of the throttle valve63, the rate of the cushioning movement of the piston 31, asit trolledrotarvmotionto the feed screw 15. The fluid motor 70 comprises a cylinder 71 which contains a slidablymounted piston 72. The upper surface of the piston 72 is provided with rack teeth 73 which mesh with a gear 74- carried by a'shaft 75. The shaft 75 is also providedwith a gear 76'which meshes with the gear 22. It

will be "readily apparentrfro m the foregoing disclosure that when the piston 72 is moved endwise within the cylinder 71, arotary motion will be imparted to the feed scr w 15' through the rack and gear mechanism above dcscribcitL 2 A; valve so "is provided 'fcr conxnder 71. The 'vzllvc 0 comprises a slidzl'bly mountcd .valve member having axplurality of spaced valve pistons 81, 82ancl "83 forming a pair of spaced valve chambers 84 and 85. Acompre'ssioh spring 86 is provided normally tohol'd the valvejSQ in a left haud end position, asshown in Fig. 2. InLorder to shift the valve'St) toward the right, the pipe 45. is connected through valve '87 and a'pipe88 with alefthandend chamber 89 in the valve 80.

When it is desiredto shift the valve 80 into a right hand.

moves toward the left hand end of its stroke maybe readily controlledas desired. A ball an exhaust of fluid from the cy1-' left hand end of the cylinder toward the. right into a rearthe feed screw 15, the

4 end position, the valve 87 may be opened to admit fluid under pressure into the end chamber 89.

In the position of the controlvalves 35 and 80 (Fig. 2) fluid under pressure entering the valve chamber 48 may pass through a pipe 90, througha throttle valve 100, through a ball check valve 101, also through a solenoid valve 102, through a throttle valve 103, and a pipe 91into the valve chamber 35 in the valve 80, through a passage 92 into a cylinder chamber 93 formed at the right hand end of the cylinder 71 to move the piston 72 toward the left into the position illustrated in Fig. '2. The left hand movement of the piston 72 serves toimpart a rotary motion to the feed screw 15 to cause a rearward movement of the nut 19, the Wheel slide 11 and the grinding wheel 13. During this movement of the piston '72, fluid Within a cylinder chamber 9-1 may exhaust through a assage 95, through the valve cloambezr 84, through a 54 into the reservoir 44. It W53.

from the foregoing disclosure that the feed control valve.

35 is arranged to control the admission to an exhaust of feed cylinder 70. a

In order to obtain the maximum efficiency of the grindingmachine it is desirable to feed the grinding wheel rapidly until it moves into operative engagement with the workpiece 60 to be, ground. As illustrated and described the above movement of the piston 31 toward the left causes a rapid approaching movement of the grinding wheel which continues at a rapid rate until the piston engages the lefthand end of the cylinder 30 or until the stop surface 33 engages the stop screw 34. During this movement of the piston 31 toward the left, fluid under pressure is) passed through the pipe 95 into the end chamber 94 of the cylinder 71 to start the piston 72 moving toward the right as governed by the throttle valve 103. This allows a reduced forward movement of the wheel slide 11. and

grinding wheel 13 which movement continues at a faster rate'than the normal grinding infeed until the grinding wheel 13 moves into operative grinding the workpiece 60.

The solenoid valve 102 is a piston type valve comprising a valve stem 104 having a pair of spaced valve pistons 105 and 106 which form a valve chamber 107. A compression spring 108 serves normally to exert a pressure tending to move the valve stem 104 toward the right. A solenoid S2 which is normally energized serves to hold the valve 102 in the position illustrated in Fig. 2 so that fluid may pass unrestricted through the valve chamber-107 in either direction.

A normally closed limit switch LS1 is provided nor mally to maintain the solenoid S2 energized. A switch actuating arm 110 is pivotally supported on a shaft111. A compression spring112 serves normally to maintain the arm 110 in engagement with an adjustable stop screw 113.

A pressure actuated mechanism is provided comprising a cylinder 114 which contains a slidably mounted piston 115. "The piston 115 is connected to the lower end of a piston rod 116. The upper end of the piston rod is provided with a. stud 117 which rides in an elongated slotf118 formed in a pivotally mounted arm 119. A compression spring serves normally to maintain The: upper end ovidcd with 1 wh ch serves 'tc'vag the donllpression 02 time The 'arms 110 and 119 are normally free to move is dependently about the shaft 111 as an axis. A magnetic clutch 125, shown diagrammatically in Fig. 2 serves when energized to connect the arm 110 with the arm 119. The magnetic clutch may be any of the standard well'known commercial units, such as, for example that manufactured by Warner Electric Brakean'd Clutch Comengagemcnt with.

greases pany of Beloit, Wisconsin. The pipe 96 is connected to pass fluid under pressure to a cylinder chamber .123 formed at the bottom of cylinder 114. When fluid under pressure is passed through the pipe 96 to start the feed piston 72 moving toward the right a slight back pressure is built up in the cylinder chamber 123 to raise piston 115 through a slight distance against the compression of the spring 120 which causes an idle movement of the arm 119 in a clockwise direction. The piston 1115 remains in this position until the grinding wheel engages the work at which time a back pressure is built up within the chamber 123. Movement of the piston 72 toward the right serves to close the limit switch LS2 to energize magnetic clutch 125. As the grinding Wheel engages the work an increased pressure in the chamber 123 causes the arms 1l9lilii to actuate the limit switch LS1.

The gear 22 is provided with a cam 126 which is arranged to engage the actuating roller of a normally closed limit switch LS2. At the start or" an infeeding movement, the cam 126 is positioned to hold the limit switch LS2 open so that the magnetic clutch 125 is deenergized. When pressure is passed through the pipe as to start a grinding feed, fluid also passes into the cylinder chamber 123 to cause a slight upward movement of the piston 115. The magnetic clutch 125 being deenergized, the arm fl? is free to swing about the axis of the shaft ill. As continued movement of the piston 72 toward the right causes the gear 22 to rotate in a clockwise direction so that the cam 126 rides off the actuating roller of the limit switch LS2 allowing the limit switch LS2 to close thereby energizing the magnetic clutch 125 so that the arm 119 is thereafter locked to move the arm lid. The grinding wheel continues its first feeding movement into engagement with the work piece 6i? to be ground. When the grinding whee 13 engages the periphery of the work piece 60, a slight back pressure builds up within the cylinder chamber 94 which also builds up a pressure within the cylinder chamber 123 to keep further upward movement of the piston 115 to rock the arms 119-110 so that the arm 11d opens the normally closed limit switch LS1. The opening of the limit switch LS1 serves to deenergize the solenoid S2 thereby allowing the compression of the spring 198 to shift the valve stem ltd- 5 toward the right to cut off the unrestricted exhaust of fluid through the valve chamber lit? so that thereafter fluid exhausting from the cylinder chamber 93 is. governed by the throttle valve lltld which determines the grinding feed of the wheel into the work during the grinding oper ation. It will be readily apparent from the foregoing disclosure that by manipulation of the throttle valve N3 the initial feeding movement of the grinding wheel 13, after the rapid approaching movement by the piston 31 is governed by the throttle valve 1% and the desired grinding feed is regulated by fluid exhausting through the throttle valve res after the solenoid S2 has been deenergized. It will be readily apparent from the foregoing disclosure that a rapid approaching movement of the wheel 13 is obtained which is slowed down somewhat after the piston 31 completes its movement. The grinding wheel thereafter continues at a faster than grinding speed until the wheel actually moves into grinding engagement with the work iece at which time a back pres sure builds up Within the system to further reduce the movement of the grinding wheel to the desired and predetermined speed for the grinding operation.

An automatic control mechanism is provided for automatically controlling the duration of the grinding cycle comprising an electric time-r which is preferably an automatic re-set type adjustable timer such as, for example the Microflex timer manufactured by the Signal Electric Corporation of Ivioline, lllinois. A pair of power lines Mil and i l-ll serve to supply electric power to the operating mechanisms of the machine. A feed cycle control lever M2 is pivotally supported by a stud 143 on the front of the machine base. The lever 14-2 is arranged to actuate a normally open start switch 144 and a non mally closed start switch 147. When it is desired to start a grinding cycle, the lever 142 is rocked in a counter-clockwise direction to close the start switch 144 which serves to start the timer 150 and at the same time to energize the solenoid S1 to shift the feed control valve 35 so as to admit fluid under pressure to the cylinder chamber 51 to cause a rapid approaching. movement of the piston 31 the wheel slide 11 and the grinding wheel 1t) 13. At the same time the feed control valve 35 passes fluid under pressure to start movement of feed piston 72 toward the right to start a rotary motion of said screw.

The grinding operation proceeds in a manner above described and continues until the timer 50 times out at 15 which time the solenoid S1 is deenergized to shift the feed control valve 35 into the position shown in Fig. 2 to cause the wheel slide 11 and grinding wheel 13 to move to a rearward or inoperative position. At any time during the grinding cycle, the feeding cycle may be stopped if necessary by shifting the lever 142 in a clockwise direction to open the stop switch 147 thereby deenergizing the timer which automatically resets and at the same time deenergizes the solenoid S1 to cause a rearward movement of the wheel slide 11 to an inoperative position.

The operation of this improved feeding mechanism will be readily apparent from the foregoing disclosure. Assuming all of the adjustments there have been previously made, a work piece 60 is positioned in the machine after which the control lever 142 is rocked in a counter clockwise direction to start a grinding cycle. The timer and the solenoid S1 are energized to shift said conu valve which simultaneously starts the piston 31 moving rapidly toward the left and the feed piston 72 moving slowly toward the right. The rapid approaching 35 movement governed by the piston 31 continues until the piston Sal engages the left hand end of the cylinder 30,

or until the stop surface 33 on the feed screw engages the adjustable stop screw 3-3. The piston 72 continues its movement toward the right at a rate governed by the throttle valve 31593 which causes a faster than grinding of the wheel until the earn 126 rides off the actuating roller of the limit switch LS2 which energizes the magnetic clutch 12:5 so that when the grinding wheel moving at a faster than grinding speed engages the work piece 69 to be ground, a back pressure is built up to open the limit switch LS in a manner above described to deenergize the solenoid S2 thereby cutting olf exhaust of fluid from cylinder chamber 93 through the throttle valve by allowing fluid to exhaust through throttle valve 1% which is set to produce the desired rate of infeed for the grinding operation. After a predetermined grinding operation, the timer 1S0 times-out, thereby deenergizing the solenoid Si so thatthe wheel slide in 311G inding wheel 13 move rearwardly to an inoperaon. it will be readily apparent from the foremay be fed at a fairly rapid rate until it engages it after which the feed is reduced to the desired at d predetermined feed thereby increasing the efficiency e machine by reducing the time in which the grinding wheel so-called grinds air.

it will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above inventi 1 and as many changes might be made in the embodirn above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying 70 drawings is to be interpreted as illustrative and not in a limiting sense.

1 claim: 1. in a grinding machine having a transversely movable wheel slide, a rotatable grinding wheel thereon, and a feeding mechanism therefor including a nut and screw H rate of'movement-of said motor toproduce a rapid rotation of said feed screw, a secondcontrolrneans to control thei' rate of said motor to produce a slow-rotation of said feed screw to impart a grinding feedto ,said slide and means including a pressure switch actuated by back-pressure from said motor caused by engagement of the grinding wheel with the Work piece to be ground to render the control means inoperative to facilitate reducing the feeding movement of the slide to a controlledlgrinding feed when the grinding wheel engages the work piece.

2. In a grinding machine having a transversely movable wheel slide, a rotatable grinding wheel thereon, a feeding mechanism therefor including a nut and screw mechanism, 'afluid motor to rotate said screw to impart a feeding movement to said-slide, a control valve operativelyconnected to control the admission to and exhaust of fluid from said motor, a throttle valve to control the rate of movement of the said motor to produce a rapid rotation. of said feed screw, a. second throttle valve to control the rate of movement of said motor to produce a slow' rotationiof said feed screw to impede grinding feed to said slide, and means including a pressure switch actuated by back pressure from said motor caused by engagement of the grinding wheel with the work piece to be. ground to render the firstthrottle valve inoperative to facilitate reducing the feeding-movement of the slide to a controlled rinding feed when the grinding wheel engages the work piece.

3, In a. grindin combination wit: th of means including a solenoid. acmated valve operativcly connected to render the first throttle valve inoperative,

and a pressure actuatedswitch including a piston and cylinder. operatively connected to said motor which is actuated byback pressure from said motor caused by engagement 'of the grinding wheelwith the workpiece to energize said solenoid valve thereby rendering the first throttle valve inoperative to facilitate rcducingthe feeding movement of the slide to a controlled grinding feed when the grinding wheel engages the work piece.

4. In a grinding machine, as claimed in claim 2, in

combination with thecparts and features therein specified of a solenoid actuated valve operatively connected in one position to render the first throttle valve inoperative, a i

normally inoperative pressure actuated switch including a piston and cylinder operativelyconnected to said fluid motor, means including a magnetic clutch actuated by and in timed relation with the rotary movement of said feed screw. to render said pressure actuated switch operative so that back pressure fromthe motor caused by engage- '8 ment of the grinding wheel with the workpiece-to be ground serves to; actuate thesolenoid valve to render the first throttle valve inoperative so as to redtice the feeding movement of the slide to a controlled grinding feed when the grinding wheel engages'the work piece.

5. In a grinding machine having a transversely movable wheel slide, and a feeding mechanism therefor including a nut and screw 'feed mechanism, a fluidmotor to move 'said 'screw axially to cause a rapid approaching movement of said slide, a fluidmotor to rotate said screw to impart a slower feed to said slide, acontrol valve operatively connected to simultaneously control the admission to and exhaust of fluid from both of said motors, a throttle valve to control the rate of movernent ofsaid second fluid motor to produce a rapid rotation of said feed screw, 21 second throttle valve to control the rate of said second motor to produce a slow rotation of said feed screw to impart a grinding feed to said slide, and means including a pressure actuated switch actuated by back pressure from said second motor caused by engagement of the grinding wheel with the work piece to be ground to render the first throttle valve inoperative to facilitate reducingthe feeding move ment of the slide to a controlled grinding feed when the grinding wheel engages the work piece.

6. In agrinding machine having a transversely movable whe'el slide, a rotatablegrinding wheel thereon, and a feedingmechanism therefor including a nut and screw mechanism operatively connected to move said slide, a piston and cylinder to move said screw axially to cause a rapid approaching movement of the wheel slide, a

second piston and cylinder operatively connected to irnm a. ratin motion to said feed screw, 2. feed control valve y simul to the: aa -us lon 1 and emust of fluid from both of me said cylinders, a throttle valve to control the initial movement of saidsecond piston to impart a controlled rotary motion to the feed screw, a second throttle valve operatively connected to the second cylinder to produce a slower rotary motion of the feed screw for a grinding 'feed, a solenoid actuated valve operatively connected to render the first throttle valve inoperative, and a pressure actuated switch actuated by back pressure in the second cylinder caused by engagement 'of the grinding wheel with the work piece to be ground to actuate said solenoid valve to reduce the rapid rotary motion of the feed screw to a grinding feed as controlled by the second solenoid valve.

Doran Sept. 6, 1938 Swainey May 26, 1953

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