US2582610A - Grinding wheel feeding mechanism - Google Patents

Description

Jan. 15, 1952 H. L. SWAINEY 2,582,610

GRINDING WHEEL FEEDING MECHANISM Filed Dec. 9, 1950 2 SHEETSSHEET l IS I 1 v Ewe tor HOMER L.$WAIN'EY Jan. 15, 1952 H. 1... SWAINEY GRINDING WHEEL FEEDING MECHANISM Filed Dec.' 9, 1950 2 SHEETS-SHEET 2 31: 5+ /r .L OZ 5. SK 5. @Q Q. E. m .w Q

#2 Y Pi Jwem r HOMER L. SWA NEY In the position of the valve 35, as shown in Fig.1. Y

1, fluid under pressure passing through the pipe 45 enters a valve chamber 48 located between the valve pistons 31 and 38 and passes through a passage 49 into a cylinderchamber 50 to cause the piston 32 to move toward the right into the position illustrated in Fig. 1. Movement of the piston 32 toward the right also imparts a corresponding movement to the feed screw 5, the half-nut la, the wheel slide so as to move the grinding wheel l3 to a rearward or inoperative v position. 7 During this movement ;-nuid within a cylinder chamber of the piston 32 may exhaust through a'passage 52, through a valve chamber 53' located between the valve pistons 38 and 39 and pass out .through an exhaust pipe 54 into the reservoir 44.

In order to slow down the rapid rearward r'novement of the piston 32, a dash pot mechanism is provided. The piston rod 3| is provided with a rearwardly extending stud 60 which is arranged when 'moved toward the right to engage a dash pot piston 6|. The dash pot piston 6| is sliuably mounted within a dash pot cylinder 62. When the dash pot 6| moves rearwardly, fluid is exhausted from the dash pot cylinder 62 through pipe 63 and through a throttle valve 64 and a into the passage 52. A ball check valve 65 is provided so that fluid exhausting from the dash pot cylinder 62 must pass through the throttle valve 1.14. It will be readily apparent from the foregoing disclosure that until the stud 60 engages the dash pot piston 6|, the piston 32 will move at a rapid rate. After the stud 60 engages the dash pot piston 6| the speed of movement of vthe piston is reduced to a predetermined slower rate as'governed by fluid exhausting from the dash pot cylinder 62 through the pipe 63 and the throttle valve 64. It will be readily apparent from the foregoing disclosure that by adjustment .of the throttle valve 64, the rapid rearward .movement of the piston 32 may be reduced to a slower speed before the piston 32 engages the rear of the cylinder 33.

.' It issimilarly desirable to provide a cushioning orslowing down movement of the piston 32 as it moves rapidly toward the left as the grinding wheel I3 approaches the workpiece to be ground. When the solenoid 4| is energized to shift the valve stem 33'toward the left fluid under pressure from the pipe 45 is passed through the valve chamber 53 and through the passage 52 into the "cylinderrchamber 5| to cause the piston 32 to move rapidly toward the left (Fig. 1). Fluid under pressure passing through the passage 52 may also pass through the throttle'valve 54 and the ball check valve 65, through the pipe 63 into the dash pot cylinder 62 to return the dash pot piston 6| to its initial position. The initial rapid movement of the piston 32 causes fluid within the cylinder chamber '50 to exhaust through a port 66, through the passage 49, through the valve chamber 48 and out through the exhaust pipe 54. .When the valve piston 32 closes the port 66 just before the piston reaches the end of its stroke toward the left, that is when the stop abutment 25 engages the stop screw 26, fluid may then be exhausted through a passage 16, and through a throttle valve 1| into the passage 49 thereby facilitating a reduction in speed of the forward movement of the piston 32 before the forward approaching movement ceases. A ball check valve 68 is connected between the port 69 and the passage 61 which serves to facilitate a substantially unrestricted flow of fluidfrom the passage 49, through the port 69 into the cylinder chamber 50 so as to start the rapid rearward movement of the piston 32 when the solenoid 4| is deenergized.

A suitable cam operated feeding mechanism is provided for producing a slow precise feeding movement of the grinding wheel during the grinding operation. In the preferred form, a hyshown in Fig. 1.

unhe ted in Fig. 1.

'draulically operated mechanism is provided in which a fluid motor serves to produce a controlled rotary movement of the feed screw i5. As illustrated in the drawings a fluid pressure cylinder 15'is provided having a slidably mounted piston 16. The upper central portion of the piston 16 is'provided with rack teeth 11 meshing with a gear 18 which is keyed'on a rotatable shaft 19. The shaft 19 isalso provided with a gear 14 which meshes with the gear 2|. It will be readily apparent from the foregoing disclosure that when the piston 16 is moved endwise within the cylinder 15, a rotary motion will be imparted to the feed screw l5 through the rack and gear mechanism above described. A shuttle-type control valve is provided for controlling the admission to and exhaust of fluid fromthe cylinder E5. The valve 80 comprises a rality. of spaced valve pistons BI, 82 and 83 forming a pair of valve chambers 84 and 85. A compression spring 86 is provided normally to hold the valve in a left-hand end position such as Inorder to shift the valve 86 into a right-hand end position, the pipe 45 is connected by a valve 81 with a pipe 88 which is turn connected to a left-hand end chamber 89 within the valve 80. When it is desired to shift the valve 80 into a right-hand end position, the valve 61 may be opened to admit fluid under pressure from the pump 42 through the pipe 88 into the valve chamber 89.

"In the position of valves 35 and an (Fig. 1) fluid under pressure entering the valve chamber '48 may pass through the pipe 96, through the valve chamber in the valve 83, through a passage 9| into acylinder chamber 92 to move therpiston :16 toward the left into the position The left-hand movement of the piston 16 serves-to impart a rotary motion to thefeed screw l5 to cause a rearward movementof the nut [8, the wheel slide H and the grinding wheel l3. During this movement of the pistcn- 16 fluid within a cylinder chamber 93 may exhaust through ,a passage 94, through the valve chamber 84, through a pipe 95 into the valve chamber 53 in the valve 35 and exhaust through the;:pipe 54 into the reservoir 44. It will be readily apparent from the foregoing disclosure that the feed control valve 35 is arranged to controlthe admission to and exhaust of fluid from the'rapid feed cylinder 33 and the grind-.' ing feedv cylinder 15. 7

It is desirable to control the grinding feed of .the wheel so that a grinding feed may be ob. tained during the initial grinding after which thefeed may be slowed down to a finishing feed before-the infeeding movement of the grinding ilwhe'el I I 3 is .positively stopped. :Thistismreferably accomplis'hed, by'imeans 1 of ai finish .tteed control valve-' 9-1 and a grinding feed control-valve 98 --which are :arranged to control the' -exhaustof fiuid' fromithe-oylinderchambenSZ. A ball check I valve 98 is providedin-thepipe ell so as to allow pressure to flow substantially unrestrioted from the valve-35=throrigh the pipe 90 te -the cylinder 15. Whenfluidis exhausted from the cylinder-chamber-SZ when the' piston '16 starts its movement to the rightto cause a feeding -movement-of'the g-rindingwheel I 3, the ball check valve 95 is arrangedto-prevent exhaust fluid passing therethrough*sothatthe entire e'xh-aus't' fluid from the cylinder chamber "92 mustpassthrough either the grindingfeed"va1ve"98-orthe finishing 'feed valve-91hr throughpoth-of the"-feed valves. "During the initial infee'ding -'movement --or "the grinding wheels ascausedby the piston 16 fluid exhausted from thet-cyiinderphamber' 592 may 'pass throughboth cfthe valves98 and 91. This exhaust of fluid serves-to control the'rate of the 'grindingfeed.

"In order to change the infeed from agrinding feed to a finishing feed, a solenoid valve 'Iflilis provided 'comprisinga valve "stem'llil having valve 'pistons "IIlZ'and I93 formed integrally therewith, the'valve pistons 102 and N13 --being arranged to form a valve chamber "I'M. "A compression spring I95 serves normally to holdthe valve stem I'OI in a 'ri'ghthand end position '(Fig. 1) so that "fluid "may exhaust through 'both of the valves '88 and Si. A solenoid I95 is provided which when energized serves to shift the valve stem H3! toward the left against the compression of the spring I05 so as to render the grinding'fee'd control valve 98 inoperative. After the valve Inc has been shifted into a left-hand end position all'flu d exhausting from the cylinder chamberdi 'must "exhaustthrough the finish feed control valve "8? 'which'is adjusted to produce a slow finishing feed of the grindingwheehbefore theiinfeeding movement is 'linally stopped.

A stop abutmentmeohanism is provided for positively stopping the rotary *motion of the feed screw I5 thereby limiting the infeeding' movementofthe'grinding wheel t3. 'This'mechanism may comprise a micrometer adjustingimechanism I Ii] carried 'by'the 'feed'wheel I9 which is' arranged to adjustably support astop abutment III. 'A 'stoppawl H2 is pivotally supportedby a stud II3 'fixedlymounted on the frontof the machine base. It will be'readily apparent'that when the stop abutment-rotates in a'counterclockwisedirection with the feedwheel" I9, the

rotarymotionof the feed-screw'15 will continue abutment I. "The detent I I6 is preferably ad- 7 dusted so that the cam -I 1 5 will engage-the detent l ft-and rock the stop pawl- H2 in a co nterclockwise direction before the stop surface H4 is engage'd by-the -stop abutment'i II. Therockiing' movement of the stop pawl I I-Z- serves to "'imill part a corresponding :motionrito.zthezaarm Iii-1; The arm II! supports an adjustablerdetent 118 -which sis arranged Ito engage :an: actuated'zroller Ililof a'limit switch 12!). .Theilimit switch :IrZO is preferably: a normally open limit switc'h .-whi'ch -is connectedso that when' itis closed,i.the solenoid I'OE is energized=toishiftithe1valve. stem 1J0 Lptoward' the-right thereby rendering vthe zgrin'ding -feedcontrol valve .98 inoperative: duringathe iinish grinding operation. I It will-be readflyapparent from the foregoing disclosure that when the feedwheel L9 is-rotated eithermanually or: by --movement "of the piston 16, the-rotarym'otion of the feed screw-i5 andfeedwheel l9 will move at a'grinding feed ratenn'til the cam' i le e'ngages the d'etentI'Isand'mocks the-stop 'pawl I t2, the arm --I l lythedetent -IIB-in a oeunterclockwise direction to actuate and close the limit "switch r29 thereby energizing the solenoid I136, close the valve ill!) thus rendering thegrin di'ng feed control valve inoperative so that thereafter fluid exhausting -from the cylinder chamber dz must pass through the finishing'feed control= val-ve '91. The slow finish feed continues until' 'the stopabutment I II engages thestopsurface I I-I on the stop pawl H2. 'In the preferred-operation the grinding wheel remains in grinding-contact with the'work after theinfeeding-movement is stopped to permit the [grinding wheel .l3- t'o spark-out or finish grind the 'work piece.

An automatic control mechanism isprovide'd for automatically controlling the "duration fof the grinding cycle comprising aworkgaging .head l25'having"a movable'work contact member. The gage head "I25 is provided with a 'slidably movable work contact member'lilflwhich .is arranged to engage the periphery of,,the' work piece I 24 being ground. The gaging head l25 is provided with a C-shaped caliper head'ifi'i' havinga pair of adjustablymounted work engaging screws I28 and I29 to facilitate maintaining the gage head [25 in a predetermined relationship with the Work piece I24 during a grinding operation. The gaging head I25'is p referably'supported by a bracket (not shown) on the wheel slide II. This type of mountingis old andw'ell known in the. art and therefor has not been illustrated in the present application.

The upper endof the work contact member I30 engages a rock arm I3l which is pivotally supported by a stud I32. A compression spring I33 is arranged to exert a downward pressure on rock arm I3I to maintain the contact member I30 in operative engagement with the-periphery of workpiece I24 during a grinding -.op-

eration. The rock arm I3I is provided with" an electrical contact member l-3 l which is arranged to move into engagement with a contact member I35 mounted within the gage head I25. An;ad- :justment screw I36 is provided for adjusting the .contact element I35 to facilitate setting up gage head for sizing to grind a work piece-to a predetermined size.

. 'Apair of power lines I40 serve to supply-electrical power to operate mechanism of the machine. A manually operable control .lever 14'! is pivotally supported by a stud I42 whichlsis in turn supported on the front of machine base. ill-he. controllever I Iiis-arranged to close a normally open start switch I 43 when the-lever l d! is rocked in a counter-clockwise direction and to open a normally closedstop switch I44 when rocked in a clockwise direction. -A relay switch I45 and a relay switch I46-together with-a selector switch I 41 are provided "for controlling the feeding mechanism in a manner to be hereinafter described.

When it is desired to start a grinding cycle, the lever MI is rocked in a counter-clockwise direction to close the start switch I43 which serves to energize the relay switch I45 to close a circuit and thereby to energize the solenoid 4| so as to shift the feed control valve 35 to start a forward approaching and feeding movement of the wheel slide I I and grinding wheel I3. The relay switch I45 is provided with a holding circuit so that only a momentary closing of the start switch I43 is required to start the grinding cycle. The piston 32 causes rapid approaching movement of the wheel slide I I and the grinding wheel I3. The rapid approaching movement continues until the piston 32 engages the lefthand end of the cylinder 33 after which the approaching movement of the slide II is reduced to a grinding feed as governed by the throttle valve 91 and 98. The grinding feed continues until the cam II5 engages the detent H6 and rocks the feed pawl H2 and the arm II? in a counter-clockwise direction to close the normally open limit switch I20. Closing the limit switch I20 serves to energize the solenoid I06 to close the valve I so as to render the throttle valve 98 inoperative thereby reducing the grinding feed to finishing feed as governed by the throttle valve 91. The finishing feed continues until the stop surface III on the feed wheel I9 engages the stop surface II4 on the feed pawl II2 thereby positively limiting the infeed movement of the wheel slide II .and the grinding wheel I3. The grinding wheel is remains in engagement with the work piece I24 for a sparking-out or dwell. Until the work contact member I30 moves downward a sufficient distance to close the contacts I34I35 thereby closing a circuit to open the normally closed relay switch I46. The opening of the relay switch I46 serves to break the holding circuit on relay switch I45 thereby deenergizing the solenoid 4! so that the feed control valve 35 returns to the position illustrated in Figure 1. The shifting of the feed control valve 35 into this position causes a rearward movement of the wheel slide I3, that is, a movement of the piston 32 toward the right, and a simultaneous movement ofthe piston I6 toward the left to re-set both of the pistons for the next grinding cycle.

The selector switch It? is provided to facilitate rendering gaging head I25 inoperative when desired to facilitate manually controlling grinding cycle.

It is desirable to provide a suitable clutch mechanism whereby the feed wheel may, if desired, be operated independent of the cylinder I for setting up the machine, or for manual operation thereof when desired. The gear I8 is supported by'anti-fraction bearings I55 and I56 (Fig. 3). The shaft I9 is provided with an internal gear I5! which is arranged to mesh with an external gear I58 which is fixedly mounted to rotate with the gear I8. As shown in Fig. 3, the gears I51 and I58 are in mesh so that rotation of the gear I8 caused by the piston I6 will impart a rotary motion to the feed screw I 5. When it is desired to declutch the power mechanism from the manual control, the shaft I9 is moved axially toward the right (Fig. 3)

to slide the internal gear I5! out of mesh with the external gear I58, after which the feed wheel I9 may be rotated manually independent of the fluid pressure piston I6.

To facilitate operation of the clutch fnech- 'anism above described, a manually operable clutch lever I60 having a hub portion I6I is arranged to rotate concentric with the axis of the feed wheel I9. The clutch lever I60 is provided with a downwardly extending arm I62 having a stud I63 projecting downwardly from its lower end. The stud I63 is arranged between a pair of adjustably mounted opposed actuating screws I64 and I65 which are adjustably mounted on a yoked member I66. The yoked member I66 is pivotally mounted on a stud I67 carried by a bracket I68 which is fixedly mounted on the front of the machine base. The yoked member I66 is provided with a downwardly extending yoked portion I69 which is provided with opposed studs IIil which ride within a groove III formed in an enlarged end portion of the shaft I9. It will be readily apparent from the foregoing disclosure that when the clutch lever i6!) is rocked in a clockwise direction (Fig. 1), the yoked member I66I69 will be rocked in a counter-clockwise direction (Fig. 3) to slide the shaft I9 toward the right thereby moving the internal gear I5! toward the right out of mesh with the external gear I58.

A suitable detent mechanism is provided for holding the clutch parts either engaged or disengaged. This mechanism may comprise an arrow-pointed surface I12 formed on the lower end of the stud I63 (Fig. 4). The arrow-pointed surface II2 is arranged to engage a spring pressed arrow-pointed plunger II3 which serves to hold the stud I63 either in a clutched or declutched position.

The operation ofthe improved wheel feeding mechanism will be readily apparent from the foregoing disclosure. Assuming all of the valves to have been previously adjusted a workpiece mounted and in position for a grinding operation the gaging head I25 moved into operative engagement with the work piece. The cycle control lever I II is rocked in a counter-clockwise direction to close the start switch I43. The closing of the start switch I43 serves to energize the solenoid 4| to shift the feed control valve 35 toward'the left to energize an infeeding cycle. Fluid under pressure is passed from the valve 35 to the cylinder chamber 5I' to cause a rapid approaching movement of the wheel slide II and grinding wheel I3 which continues until the port 66 is closed after which the rapid approaching movement is slowed down as controlled by the throttle valve II just before the stop member 25 engages the stop screw 26. At the same time fluid is admitted to the cylinder chamber 5| of the cylinder 33, fluid under pressure is also passed into the cylinder chamber 93 to move the piston I6 toward the right thereby starting a controlled rotary motion of the feed screw I5 as governed by the grinding feed control valve 98 and the finish feed control valve 91. The wheel slide continues to move at a grinding feed until the cam IE5 engages the detent H6 and rocks the stop pawl II2 so as to close the limit switch I20, as above described. The closing of the limit switch I20 energizes the solenoid I06 to close the valve I00 thereby rendering the grinding feed control valve 98 inoperative so that thereafter fluid exhausting from the cylinder chamber 92 must exhaust through the finish feed control valve 91 which reduces the grinding feed to a slower finishing feed shortly before the stop abutment III engages the stop surface II4 on the pawl Hz to positively limit the infeeding movement of the grinding wheel. The grinding wheel I3 I25. WhenJth'e contacts 'l34-l35.inthesizing head :close .as the work. piece 124 is .ground to alpredetermined.diameter, the solenoid M is deenergized toadmit fluid to the cylinder chamber 5.0 to :cause a rapid rearward movement of the piston:32 together with the slide lzl andgrinding wheelel3 to:move the wheel l3 to an inoperative position. At the same'timexfluid under pressure is admitted through the check'valve 93 into the cylinder chamber 92 to cause the piston 1610 move toward the left .therebysrotating 'the'rfeed screw in the reverse direction to re-set the feed mechanism 'for'thernext cycle of operation. ,As soon .asrthe feed wheel l9 starts rotation in a clockwise direction, during the re-setting' motion,:the cam ll5 moves out 'of engagement .with the detent 'I [6' thereby allowing the limit switch I20 toropenxto deenergizethe solenoid I05 thereby open'ing the valve l00'for the next grinding cycle. 'This cycle of operation may then'be successively repeated by merely actuating the cycle controlilever l4l'.

If desired, the feeding mechanism may be operated without .the use of the stop abutment I I l The'parts'are adjusted so that the cam I l brooks the pawl H2 so that the detent! l8 actuates the limit switch I20 :to..ch'a'nge.from.a grinding feed to a finishing'feed as above described. When the workpiecereaches a predetermined size,"the con-- ward movement of the grinding wheel is and wheel slide .l'l to 'an inoperative position.

It will thus be seen that there has been provided by this invention 1 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 invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine having a transversely movable wheel slide, rotatable grinding wheel thereon, a feeding mechanism to feed said slide, a rotatable feed wheel therefor, an adjustable stop abutment on said feed wheel, a movably mounted stop pawl positively to limit rotation of the feed wheel, power operated means to actuate said feeding mechanism, means to control said power means to produce a grinding feed, means to control said power means to produce a finishing feed, means including a limit switch actuated by said stop pawl before the stop abutment engages said pawl to render said grinding feed control means inoperative so as to reduce the infeed to a predetermined finishing feed, and means including a sizing head having a movable contact member in engagement with the workpiece being ground to move the grinding wheel to an inoperative position when the workpiece has been ground to a predetermined size.

2. In a grinding machine having a transversely movable wheel slide, a rotatable grinding wheel thereon, a feed mechanism to feed said slide, a feed wheel therefor, an adjustable stop abutment on said feed wheel, a pivotally mounted stop pawl positively to limit rotation of the feed wheel, means including a fluid motor to actuate said feed'imechanism, 1 an adjustable throttle valve to control thet'exhaust ofrfluidfromthe fluid motor so as to'produce a grinding feed,.a second adjustable throttle valve tolcontrol .thezexhaustof fluid from the mo.tor:so.as to produce:aafinishing feed, means including a limit switchactuated :by said pawl before the stop-abutment engages said :pawl to render said ffirst throttle valve. inoperative so as to reduce the-feed :to a predetermined; finishe ing feed, and: means including a rsizing .headin-. cludingawork engaging contactmember to move the grindingiwheel to an inoperative position when a workpiece. has been :groundto apredetermined size.

3 In grindingmachinehaving a" transversely movable wheel-slide, :a rotatable grinding 'wheel thereon, :means including a fluid motor to-"move said 'slide' rapidly to and'ifrom an operative 130519. tion,-:-a =solenoid'-actuated control valve therefor", means including a cycle. startisswitchto energize said solenoid-actuated control valve "to initiate a feeding cycle a nut and screw mechanism to feed said slide, a manually operable feed-wheeltherefor,- an adjustable :stop abutment on 1 said feed wheel, a pivotally mountedistop-paWl to limit the rotation of the feed wheelandiifeed screw, means including a fluid motor tostrotate' said feed screw, an adjustable throttle valve to control the exhaust or fluid from the. second motor so as to produce a-grinding feed, a second throttle valve to control the exhaust of fluid from the second-motor so as'to producea finish ing "feed, a solenoid-actuated valve to "render :the first throttle valve inoperative, a limit switch actuated b'y said pawl before the "stop-abutment engages said pawlto actuate the second solenoid-'- actuated valve to reduce the feed to a predetermined finishingfeed, and a sizing'head includinga movable work contacting element to deenergize the first solenoid-actuated control valve when a workpiece is ground to a predetermined size to cause a rearward movement of the grinding wheel to an inoperative position.

4. In a grinding machine having a transversely movable wheel slide, a, rotatable grinding wheel thereon, means including a fluid motor to move said slide to and from an operative position, a solenoid-actuated control valve therefor, means including a cycle start switch to energize said solenoid-actuated control valve to initiate a feeding cycle, a nut and screw mechanism to feed said slide, a rotatable feed wheel therefor, an adjustable stop abutment on said feed wheel, a pivotally mounted stop pawl positively to limit rotation of the feed wheel and said feed screw, means including a fluid motor to rotate said screw, said solenoid-actuated control valve to control the admission to and exhaust of fluid from both of said motors, an adjustable throttle valve to control the exhaust of fluid from the second motor so as to produce a grinding feed, a second adjustable throttle valve to control the exhaust of fluid from the second motor so as to produce a finishing feed, a second solenoid-actuated valve to render said first throttle valve inoperative, means actuated by said pawl before the stop abutment engages said pawl so as to actuate the latter solenoid-actuated valve to reduce the feed to a predetermined finishing feed, and a sizing head including a movable work engaging contact member which serves when a workpiece has been ground to a predetermined size to deenergize said first solenoid-actuated control valve to cause both of the fluid motors to return to' initial positions thereby moving'the grinding wheel to an inoperative position.

'In a grinding machine having a transversely movable wheel slide, a rotatable grinding wheel thereon,'means including a piston and cylinder to'move said slide to and from an operative po- -sition,fa solenoid-actuated .control valve therefor,'means including a cycle start switch to energize" said solenoid-actuated control valve to initiate a feeding cycle, a nut and screw mechanism to feed said slide, a rotatable feed wheel therefor, an adjustable stop abutment on said feed wheel,a pivotally mounted stop pawl positively to limit rotation of the feed wheel and feed screw, means including a piston and cylinder to'rotate said feed screw, said solenoid-actuated control valve serving to control the admission-to and exhaust of fluid from both of said cylinders, an adjustable throttle valve to control'the exhaust of fluid from the second cylinder so as to produce a grinding feed, a second adjustable valve to control the exhaust of fluid from the second cylinder so as to produce a finishing feed, a sec-' ond solenoid-actuated valve to render said first throttle valve inoperative, a limit switch actuated by said pawl before the 'stop abutment engages said pawl so as to actuate the second solenoidactuated valve to reduce the feed to a predetermined finishing feed, and a sizing head'which serves when a workpiece has been ground to a predetermined size to deenergize the first solenoid-actuated control valve to cause both of the pistons to return to initial positions thereby moving the grinding wheel to an inoperative position. 1 6. In a'grinding machine having a transversely movable wheel slide, a rotatable grinding Wheel spindle thereon, a feeding mechanism to feed said slide, a rotatable feed wheel therefor, an

adjustable cam on said feed wheel, a' movable pawl arranged to be actuated thereby, power operated means to actuate said feeding mechanism, means to control said power means to produce a grinding feed, means to control said power means to produce a finishing feed, means including a limit switch actuated by said pawl to render the grinding feed control means inoperative so as to reduce the infeed to a predetermined finishing feed and means including a sizing head having a movable contact member in engagement with the workpiece being ground to move the grinding wheel slide to an inoperative position when the workpiece has been ground to a predetermined size.

7. In a grinding machine having a transversely movable wheel slide, a rotatable grinding wheel spindle thereon, a feeding mechanism to feed said slide, a feed wheel therefor, an adjustable cam on said feed wheel, a pivotally mounted pawl arranged to be actuated thereby, means including a fluid motor to actuate said feeding mechanism, an adjustable throttle valve to control the exhaust of fluid from the fluid motor so as to produce a grinding feed, a second throttle valve to control the exhaust of fluid from the motor so as to produce a finishing feed, means including a limit switch actuated by said pawl to render the grinding feed throttle valve inoperative so as to reduce the infeed to a predetermined finishing feed' and means including a sizing head including a work engaging contact member to move the grinding wheel slide to an inoperative position when a workpiece has been ground to apredetermined size.

HOMER L. SWAINEY.

No references cited.

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