US2889665A

US2889665A - Compensating device for grinding machines

Info

Publication number: US2889665A
Application number: US688521A
Authority: US
Inventors: Wilbur F Jessup; George L Grove
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-10-07
Filing date: 1957-10-07
Publication date: 1959-06-09
Anticipated expiration: 1976-06-09
Also published as: NL113550C; GB850049A; DE1116570B; FR1212313A

Description

June 9, 1959 w. F. JESSUP ET AL 2, 8 5

COMPENSATING DEVICE FOR GRINDING MACHINES Filed Oct. 7, 1957 4 Sheets-Sheet l IN V EN TORS.

0 W/LBUR F. JESSUP I GEORGE L.GROV Fi ,2: mw

flT'TORNEYS.

June 9, 1959 w. F. JESSUP ET AL COMPENSATING DEVI 4 Sheets-Sheet 2 Filed Oct. 7, 1957 3N L U $h h ow m. Q \h mm m? w? X m8 Q \Q 5v llrlwazzzzzfarz fi FI/IIIIL l// R fi g .3 R

m 3 3 IL m3 no Q INVENTORS.

W/LBUR I JESSUP GEORGE L. 6R0 V5 457% v7. 7. NW

ATTORNEYS- June 9, 1959 w. F. JESSUP ET AL 2,889,665

COMPENSATING DEVICE FOR GRINDING MACHINES Filed Oct. 7, 1957 4 Sheets-Sheet 3 INVENTORS.

W/LBUR F. JESSUP GEORGE L GROVE ATTORNEYS.

States This invention relates to grinding machines and, more particularly, to a device for automatically adjusting the position of the wheel head of a grinding machine to compensate for wear of the wheel.

The conventional grinding cycle of either centerless or center type grinding machines generally consists of a rapid traverse movement of the wheel head toward the work to bring the wheel into grinding position followed by a fast infeed movement of the wheel for coarse grinding of the work to approximately the finish diameter. At the end of the coarse grinding operation the infeed is reduced to a slow feed rate for finish grinding the work to final size after which the wheel head is retracted from the work. The point at which coarse grinding ends and finish grinding begins is normally determined by a gauge which signals the approach of the work to final size. When the work has reached its final diameter, the gauge provides another signal which stops the slow feed and initiates retraction of the wheel head from the work so as to permit loading of the next'piece to be ground. This grinding cycle is repeated for each successive piece of work with intermittent truing of the grinding wheel to maintain a sharp and accurate cutting surface thereon.

As the grinding operation continues, the diameter of the grinding wheel becomes progressively smaller due to attrition of the wheel caused by the grinding and truing operations. Unless some means is provided to compensate for this wear of the wheel, the fast feed rate portion 'of the infeed cycle will continually increase due to cutting of air as the face of the grinding wheel recedes further and further from the work. This is undesirable since it lengthens the time of the grinding cycle and reduces the production rate of the machine.

Means have heretofore been provided for automatically compensating for wheel wear, one such means being shown and described in the Decker and Kearns Patent No. 2,641,876, patented June 16, 1953. The mechanism shown in this patent includes mechanical, electrical, and hydraulic components which function to maintain the distance moved by the wheel during infeeding movement substantially constant despite the wear of the wheel.

It is an object of the present invention to provide a simple mechanical device which will produce a compensation similar to that produced by the more complicated mechanism of the Decker et al. patent.

Another object of the invention is to provide a wear compensation device for a grinding machine which utilizes a one-way driving connection to measure the amount of wear of the wheel and to advance the wheel toward the work by a corresponding amount.

With these and other objects in view, which will become apparent from the following description, the invention includes certain novel features of construction and combination of paits, the essential elements of which are set forth in the appended claims, and a preferred form atent or embodiment of which will hereinafter be described with reference to the drawings accompanying this application. In the drawings:

Patented June 9, 1959 2 Fig. 1 is a front view of a machine embodying the principles of the present invention.

Fig. 2 is a front elevation of a portion of the machine shown in Fig. 1 with parts broken away to show the rela tion of the novel structure with the prior art grinding machine.

Fig. 3 is a horizontal cross sectional view taken through the structure shown in Fig. 2. v

Fig. 4 is an end view taken along the line 44 in Fig. 3.

Fig. 5 is a hydraulic diagram which illustrates the operation of the infeed mechanism of the present machine.

Fig. 6 is a wiring diagram which shows the electrical circuits employed for controlling the infeed mechanism.

Fig. 7 is aschematic view illustrating one form of gauge which is adaptable for use with the present machine.

In the accompanying drawings, the invention is shown applied to a centerless grinder of the infeed type. It will be appreciated as the description proceeds, however, that the invention might equally well be applied to a center type grinder such as that shown in the Decker et al. patent.'

As shown in Fig. l, the grinder is provided with a base 10 on which is supported a grinding wheel 11 for rotation about an axis which is fixed with respect to the base 10. The work piece 12 to be ground is supported on a work rest blade 13 and is pressed against the wheel 11 by a second grinding wheel 14 which rotates at a reduced speed and serves to regulate or control the rotation of the work piece 12 as it is being ground by. the wheel 11. The wheel 14 is carried by a wheelhead 15 which is guided by ways 16 carried by a lower slide 17.

The lower slide is suitably guided for sliding movementi 'on the base 10 and carries at its forward end the work rest blade 13 as illustrated in Fig. 1. A clamp 18is provided for securing the wheelhead 15 to the lower slide 17 so that the two will move as a unit on the base 10.

A second clamp 19 is provided for securing the lower slide to the base whereupon the wheelhead may be traversed along the lower slide by releasing the clamp 18.

For setup purposes, the wheelhead is provided with a hand wheel 20 which is adapted to rotate a nut journaled in the wheelhead and meshing with a feed screw. This mechanism is fully explained and described in the Ball and Grove Patent No. 2,709,877, issued June 7, 1955. In setting up the machine, the wheel head 15 is clamped to the lower slide 17 by tightening a clamping lever'18,

and clamp 19 is loosened to permit the lower slide to move with respect to the base 10. The handwheel 20 is then turned to feed the wheelhead 15 and lower slide 17 as a unit along the bed until the work rest blade is brought into proper position. The clamp 19 is then tightened, and the clamp sired setting of the wheel 14 independently of the work rest blade 13. The clamp 21 (Fig. 1) is then tightened to clamp the nut with respect to the wheelhead 15 as explained in the Ball et feeding movement of the rotation of the feed screw.

The present machine is desirably provided with the wheelhead to be effected by these parts being similar to those bearing similar numbers in the last-mentioned patent. ever, that in the patent, the sleeve 34 is pinned to the feed screw 23, whereas in the present machine the sleeve is journaled for rotation on the feed screw by means of and a combined radial and thrust,

a thrust bearing 35 hearing 36. These bearings are interposed between the feed screw 23 and the sleeve 34 and are held in place between a nut 18 loosened to permit the de-' al. patent to thereby enable.

It is to be noted, how-- 37 threaded on the feed screW- and -a shoulder 38v suitably formed on the feed screw. As 'ex-' assaeezs 3 plained in the'Stuc'key et al. patent, the walking beam operatesto bodilymove the feed screw'in an axial direction to effect rapid traverse movement of the wheelhead and advance the grinding wheel 14 into grinding position with respectto the work.

, Inasmuch as in the present construction thefe'ed screw 23 is journaled for rotation with respect 'to the walking beamf29, it is desirable for set-up'purposes to provide a clamp screw 39 '(Fig. 2) for preventing such relative rotation ofthe parts. For this purpose, the clamp screw 39 is received ina tapped hole provided in the pivot pin 30 with the inner end of the screw adapted to bear against the feedscrew 23 and thereby secure the latter-against rotation when the clamp screw 39 is tightened. This will prevent rotation of the feed screw when the hand wheel 20 is turned to rotate the nut during the set-up of the machine. In the following description, it will be assumed that the'machine has been properly set up and that the clamp screw 39 has been loosened so as to permit rotation of the feed screw. It will also be assumed that the clamp 21 (Fig. 1) has been tightened so as to prevent rotation of the nut in the cross slide whereby rotation of the feed screw will effect feeding movement of the wheelhead.

, Secured to the right hand end of the base is a frame 45 which provides support for the walking beam 29 and other parts of the infeed mechanism for the grinding wheel 14. This frame is provided with an end cover or housing '46 which serves to enclose the compensating mechanism which forms the subject matter of the present invention. As shown in Fig. 2, the feed screw 23 is provided at its right hand end with an extension 47 on which is mounted the automatic wear compensating mechanism 48 which is more completely shown in Figs. 3 and 4. Fig. 3 also shows the principal elements of the walking beam type infeed mechanism which is fully disclosed in the Stuckey et al. patent but which will be briefly described herein in order to provide a more complete understanding of the present invention.

The walking beam 29 is provided at each end with bi-.

furcations in which are slidably received

blocks

49 and 50 which are pivotally supported by studs 51 and 52. The stud 52 is carried by a piston rod 53 which extends into a cylinder 54 formed in the frame 45. Secured to the piston rod is a piston 55 which works in the cylinder 54 and which is adapted to be moved to the position shown in Fig. 3 when hydraulic fluid under pressure is admitted to the cylinder through a port 56. Fluid is perrnittedto escape from the right hand end of the cylinder through a port 57. The piston 55 provides rapid traverse movement of the wheelhead toward the work by effecting axial movement of the feed screw 23 towardthe left as viewed in Fig. 3. When rapid traverse movement of the wheelhead is desired, fluid under pressure is admitted to the cylinder 54 through port 57 while port 56 is connected to reservior. This will cause the piston 55 to move to the left end of the cylinder and cause the walking beam 29 to be rocked about the pivot pin 51. The walking beam will thereupon translate the shaft 23 toward the left by means of pivot pins 30 and 31 (Fig. 2) which have the connection previously described withthe feed screw 23. An adjustable stop screw 58 is threaded into atapped hole provided in the right hand end cap of the cylinder 54 to establish the retracted position of. the wheelhead. Near the end of the rapid traverse movement of the wheelhead, a bracket 59 operates a lever 60 of a limit switch 2LS to initiate coarse grinding ofthe work. While, in the present disclosure the bracket 59 is shown secured to the piston rod 53, it will be appreciated that it might equally well be attached to the walking beam 29 orformed as an integral portion thereof. The

limit switch 2L8 is held in a fixed positon on the frame 45 by asuitable supporting bracket.

a screw 66 meshing with a nut 67 which is fastened to the frame 45. At its opposite end the feed shaft 65 passes through a bearing cap68 and has journaled thereon a sleeve which carries the pivot stud 51. Intermediate its ends, the feed shaft 65 is provided with a key 69 which slides in a keyway formed in a pinion gear 70 which is journaled for rotation in the frame 45 by antifriction bearings 71. Hence, when the gear 70 is rotated by means hereinafter to be described, the feed shaft 65 will be rotated and the screw 66 meshing with nut 67 will cause the shaft to be advanced toward the left as viewed in Fig. 3. The rate at which the gear 70 is rotatedwill determine the fast or slow feed rate of the wheelhead toward the work. i

The portion of the hydraulic circuit of the grinding machine which is pertinent to the infeed mechanism heretofore described is shown in Fig. 5 of the drawings. Fluid pressure for operating the system is provided by a hydraulic pump 75 which is driven by a suitable motor and delivers hydraulic fluid under pressure from a reservoir 76 to a pressure line 77. The pressure in the line 77 is maintained at a desired value by a relief valve 78 which returns excess fluid into the reservoir 76. A return line 79 empties into the reservoir 76 in a con ventional manner. Rapid traverse of the wheelhead is effected by energizing a solenoid 1SOL whereby a spool 84 of a solenoid valve 85 is moved toward the right against the force of a spring 86. Thereby hydraulic fluid connected by valve 88 withthe reservoir line 79 so as to permit fluid in the left hand end of the cylinder 54 to escape threefrom. Hence, the piston 55 will be moved rapidly to the left as viewed in Fig. 5, thereby moving the feed screw 23 to the left as viewed in Fig. 3. At the end of the rapid traverse movement, the limit switch ZLS is operated, thereby energizing a solenoid 2SOL (Fig. 5). This causes a spool 95 of a solenoid valve 96 to be moved toward the right against the urgency of a spring 97. Thereby, fluid under pressure from line 77 is delivered through a line 98 to the right hand end of a control valve 99. This valve contains a spool 100, which is thereby moved toward the left against the urgency of a spring 101 so as to connect the pressure line 77 with a line 102 connected to the left hand end of a cylinder 103 containing a rack piston 104. The rack teeth on the piston mesh with the teeth of the gear 70 (see also Fig. 3). I

i the urgency of a spring 108 when a solenoid 3SOL is energized. This connects line with a fast feed rate throttle valve 110, and thence through a check valve 111 and a line .112 back to the valve 99. In the operated position of the valve 99 the line 112 is connected to the reservoir line.79, thereby permittingfluid to flow out of the right hand end of cylinder 103 and through the throttle valve to reservoir. As the work approaches final size, a gauge hereinafter to be described provides a signal which deenergizes 3SOL, thereby blocking the flow of fluid from line 105 through the fast feed rate throttle Coarse and fine grinding movement of the wheelhead" is provided by a feed shaft 65 which has'secured thereto valve 110. The fluid flowing through line 105 is thereby constrained to pass through a slow feed rate throttle valve 113 to line 112 and thence through valve 99 to the reservoir line 79. The speed at which the piston 104 moves ,toward the right as viewed in Fig. 5 is thereby reduced so asto reduce the feed rate of the wheelhead produced by the screw 66 (Fig. 3) and the feed shaft 65.

When the work reaches final size, the gauge provides a second signal which causes solenoids 1SOL and 2SOL to be deenergized. When 1SOL is deenergized the solenoid valve 85 and control valve 88 return to the positions shown in Fig. in which the motor line 92 is connected with the pressure line 77, and the motor line 91 is connected with the reservoir line 79. The piston 55 is thereby moved to its right hand position as determined by the setting of the adjusting screw 58. When solenoid 2SOL is deenergized, the solenoid valve 96 and control valve 99 return to the positions shown in Fig. 5 wherein the motor line 102 is connected with the reservoir line 79 while the motor line 112 is connected with the pressure line 77. Thereby fluid under pressure flows through a check valve 114 connected in parallel with the throttle valve 113 and through line 105 into the right hand end of the cylinder 103. The rack piston 104 is thereby rapidly returned to the position shown in Fig. 5 which corresponds to the retracted position of the wheelhead.

The gauge which provides the signals for controlling the infeed mechanism as the work is ground to size may be of the type shown in Fig. 7 in which a feeler 120 turning on a shaft 121 is providedat its distal end with a finished surface 122 against which air from a nozzle 123 im pinges. Thus, as the work 12 is ground to size, the flow of air through orifice 123 is restricted by the approach of the surface 122, and signals are provided which control the operation of the infeed mechanism. Provision may be made for moving the feeler 120 away from the work at the conclusion of the grinding cycle so that a new piece of work may be placed in position for grinding. For this purpose, the feeler carries a gear 124 which meshes with a rack 125 which is normally held elevated in the position shown in Fig. 7 by a tension spring 126 stretched between a spring stud 127 on the rack and the shaft 121. By lowering the rack 125 at the conclusion of the grinding cycle, the feeler may be swung away fromthe work and from the nozzle 123 for the loading operation, after which it may be returned to the position shown in Fig. 7 by release of the rack 125.

'-'The gauge includes a pressure regulating valve 131 connected by a line 130 with a source of air under pressure. The valve 131 delivers air at constant pressure to a variable restriction or throttle valve 132. The delivery side of the valve 132 is connected by a line 133 and a flexible hose 134 with the orifice 123. Pressure in the line 133 is communicated to pneumatic relays 135 and 136 by

lines

137 and 138. The relays are also provided with a source of reference pressure delivered thereto through a line 140 which is connected with the delivery side of a pressure regulating valve 139 which has its input connected to the supply pressure line 130. Pneumatic relays 135 and 136 are connected by

air lines

141 and 142 with electric pressure switches 143 and 144 which signal the approach of the work to final size and also its arrival at the finish diameter.

The specific manner in which the gauge controls the operation of the infeed mechanism is shown by the wiring diagram in Fig. 6. The electrical circuit includes a pair of

conductors

150 and 151 which are connected by terminals 152 with a source of energizing current. A grinding cycle is initiated by depression of a start push button 153 (line 2) which energizes a control relay 3CR through a normally closed stop push button 154 and the normally closed contacts of a relay CR. When the relay 3CR is energized, the normally open contacts of this relay in line 3 are closed, thereby establishing a holding circuit around the start push button 153 which maintains' the relay energized. At the same time, a pair of normally open contacts of the relay 3CR in line 4 are closed, thereby energizing the solenoid 1SOL (see also Fig. 5) which operates valve 85 and initiates rapid traverse of the wheelhead toward the work. At the conclusion of the rapid traverse movement, the limit switch 2LS (line 5) closed, thereby energizing solenoid 2SOL (line 5) which operates solenoid valve 96 and initiates operation of the rack piston 104 (Fig. 5). Simultaneously, the solenoid 3SOL (line 7, Fig. 6) is energized through the normally closed contacts 155 of the electric pressure switch 143 (Fig. 7). Hence, the solenoid valve 106 is operated, thereby connecting the rapid feed rate throttle valve with the line 105 so as to cause the wheelhead to be advanced toward the work at a fast feed rate. At this time a signal light 159 (line 6) will be illuminated so as to indicate that the machine is in the coarse grinding phase of its cycle.

As the work 12 approaches its final diameter, restriction of the orifice 123 (Fig. 7) increases the pressure in line 133 to the point where the pneumatic relay 135 operates the electric pressure switch 143, thereby opening the contacts 155 (line 7) and closing a set of normally open contacts 156 (line 8). Thereupon, solenoid 3SOL will be deenergized, thus closing valve 106 and cutting 0E the flow of return fluid through the fast feed rate throttle valve 110. The fluid from the cylinder 103 will now be forced to flow through the slow .feed rate throttle valve 113, thereby reducing the infeed movement of the wheelhead to a feed rate suitable for finish grinding the workpiece. At the same time, a signal lamp 160 (line 8) will be illuminated to indicate a slow feed rate while the lamp 159 will be extinguished; When the diameter of the work has reached its finished size, the pressure in line 133 will be such as to operate pneumatic relay 136 and the electric pressure switch 144. This will cause the normally closed contacts 157 (line 9) of the switch to open and the normally open contacts 158 (line 10) of the switch to close. As shown in Fig. 6, the contacts 157 have no connection in the electrical circuit while the contacts 158, when closed, energize a control relay 10CR, thereby opening the contacts of this relay in line 2. The relay 3CR is thereby deenergized so as to open its contacts in line 4 and deenergize solenoid 1SOL.

The solenoid valve 35 (Fig. 5) thereby returns to the position shown in Fig. 5- which causes the piston 55 to move to the right in cylinder 54 and retract the wheelhead from the work. The opening of contacts 3CR in line 4 also deenergizes solenoid 2SOL thereby returning the rack piston 104 to the position shown in Fig. 5. The lamp 160 will also be extinguished while a lamp 161 (line 11, Fig. 6) will be illuminated by the closure of contacts 10CR in line 11, thereby signaling that the work piece has been reduced to its finish diameter. The Work 12 is now ready to be ejected from the machine and a new piece of work loaded therein in preparation for the next grinding operation. At this time the feeler is swung out of position by the rack (Fig. 7) so as to move the finished surface 122 away from the orifice 123. This causes the pressure in line 133 to drop, thereby deactivating the pneumatic relays and 136. This returns the electric pressure switches 143 and 144 to their normal positions whereby contacts and 157 are again closed while

contacts

156 and 158 are again opened. Control relay 10CR is thereby deenergized to extinguish lamp 161 and again close contacts 10CR in line 2 ready for the next operation. Since contacts 3CR in line 3 are now open, relay 3CR will remain deenergized until the start push button 153 is again depressed in order to initiate the next grinding cycle.

For the purpose of automatically adjusting the position of the wheel 14 (Fig. l) to compensate for wear of the grinding wheel 11, the feed shaft 65 (Fig. 3)'has secured to its right hand end a spur gear 165 which meshes with a corresponding gear 166 journaled for free rotation on the right hand end of extension 47 of feed screw 23 by ball bearings 167. A portion of the teeth of gear 166 are removed to provide a seat for a block 168 which is secured to the gear 166 and provided with a projecting tooth or driver 169 as shown in Fig. 3. This tooth is adapted to cooperate with a pair of abutment blocks 170 and 171 which are clamped by nuts 172 on tee bolts 173 7 to the periphery of an annular control member 174. A portion of the periphery of member 17 4- is provided with serrations 175 as shown in Fig. 4, which cooperate with corresponding serrations provided on the underside of

blocks

170 and 171 to prevent slipping of the abutment blocks on the member 174. v t

The member 174 is fastened by a key 178 (Fig. 3) to a cam clutch 179 having sprags 180 which provide a oneway driving connection between the shaft extension 47 and the'member 174. The member 174 and the cam clutch 179 are retained on the end of shaft 147 by a nut 181 screwed on the end of shaft47 and a washer 182 When the wheelhead is in its retracted position with the rack piston 164 (Fig. in its left hand position as shown in Fig. 5, the tooth 169 is adapted to engage with the block 170 as shown in Fig. 4. However, during infeed movement of the wheelhead, the feed shaft 65 is rotated, thereby driving gear 166 through gear 165 to move the tooth 169 in a clockwise direction as viewed in Fig. 4. The tooth thereby leaves the block 170 and moves toward the block171. Theinitial setting of the block 171 on the member 174'as indicated by the scale 185 (Fig. 4), which represents the travel of the tooth 169 in terms of thousandths of an inch of movement of the wheelhead, is such that the tooth 169 will not quite contact the block 171 at the start of the grinding operation. However, as the grinding operation continues and the wheel wears, the'infeeding movement ofthe whe elhead under the control of the gauge will increase and the tooth 169 willfcontact the block 171. When this occurs, the member 174 will be moved clockwise as viewed in Fig. 4' a slight amount, thereby causing slippage of the cam clutch on the shaft extension 47. When the wheelhead 1s retracted at the end of the infeed cycle, the tooth 169 will return to the position shown in Fig. 4, However, since the member 174 has beendisplaced slightly in a clockwisedire'ction, the tooth 169 will contact the block 170 andreturn the member 174 to the position shown in Fig. 4. Since this is in the driving direction of the cam clutch 17 9, the shaft extension 47 and feed screw 23 will be turned slightly in a'counterclockwi'se direction, thereby infeeding the wheelhead slightly toward the work. As the wheel continues to wear, this operation will be repeated, the amount of infeed movement of the wheelhead provided by the feedscrew 23 being equal to the Wheel wear. Hence, the in'feed movement of the'wheelhead provided by the feed shaft 65 will always rem'ain the'same' regardless of wheel wear and the time of the grinding cycle'will remain constant. This will be true regardless of whether the reduction in diameter of the grinding Wheel is due'to the normal wheel wear or whether it results from a truing operation of the wheel. If the wheel is trued between grinding cycles, the control member 174 will beadvanced during the next grinding cycle by an amount equal to the amount of material removed from the wheel during the truing operation, and, atthe end of the infee'd cycle when the wheel head is retracted, the tooth 169 will engage the block 170 and turn the member 174 and the feed screw' 23 by alike amount so'as .to infeed the wheel head by an amount equal to the stock removed from the wheel during the truing operation.

.While. we have described our invention in connection with one possible form or embodiment thereof and have used, therefore, certain specific terms and language herein, it is to be understood that the present disclosure is illustrative rather than restrictive and that changes and modifications may be resorted to without departing from the spirit of the invention or the scope of the claims which follow.

We claim:

1. In a precision grinding machine having a grinding" wheel carried by a wheelhead supported for movenient toward andifrom a workpiece, the combination of feeding means for inoving the wheelhead from a starting position to an advanced position and back t'othe startingposition',-'"

means to stop the"- advance of the wheelhead by said feed: ing" means when the workpiece reaches a predetermined siz e, and'rneans to-adjust the feeding means to maintain successive strokes of the wheelhead substantially constant despite any reduction in the diameter of'the grinding wheel, saidmeans including a rcciprocable driveroperatively connected-with saidgfeeding means for-movement in synchronism with the advance and return strokes of the wheelhead, a driven member, a pair of spaced abutments on said driven member disposed on opposite sides of said driver, one of said abutments beingengageableby said driver nearthe end of its advance stroke when such strokeis' greater than the previous advance stroke thereof to move the driven member in one direction, and the other of said abutments being engageable by said driver upon its return stroke 'to return the driven member to its original starting; position, and a'one-way driving connection between said driven member and said feeding means to permit free rotation of said member with respect to said feedingrneans'in one direction of movement of said member, and to'cou'ple said member to said feeding means in the'other dir'ection nf-movement of said member to adjust said feedingmeansand advance the starting position of I thewheelha'd with respeot'to the workpiece in-accordance member,- a pair of spaced abutments on said driven mem with the reduced diameter of the grinding wheel.

1 2. In a precision grinding machine having a grinding wheel carried by -a wheelhead supported for movement toward and from a workpiece," the combination of feeding means for'moving the wheelhead from a starting position to' fari advanced position and back to th'e'star'ting position,

means to stop the advance of the wheelhead bysaid feed-' ing means when theworkpiece reaches a predetermined size, and means-'to'maintain' successive strokes of the wheelhead substantially constant despite any reduction in the diameter of the grinding wheel, said means including means toadju'st the starting position of said wheel'- head, a 'reciprocable driver 'operatively connected with said feeding means for movement in synchronism with the advance and return strokes of the wheelhead, a-driven member, a pair of spaced abutments on said driven member disposedon opposite sides of said driver, onejof said abutments'being engageable by said driver near the end or its advance stroke when'such stroke is greater than thepi-eviousadvance stroke thereof to move the driven member i'n'one direction,- and the other of said abutments being eh'gageable by said driver upon its return stroke to return the drivenmember'to'its original starting position, and a one-way driving connection between said driven member and said" adjusting means to permit the free rotation of said m'emberwith respect to said adjusting means in one direction of movement of said member, and to couple said member to said adjusting means in the other direction ofmovement 'of said member to advance the starting position of the wheelhead with respect to the workpiece in accordancewith the reduceddiam'eter of the grindingwheel. 3. In a precision grinding machine having a wheelhead supporting. a grinding wheeland a feed screw having a threaded connection with saidwheelhead for adjusting the relative position of the wheelheadwith respect to thefeed screw upon rotation of the latter, the combination of feeding meansfor bodily moving said feed'screw intthe" direction of its axis from a fixed starting position to an advanced position and back to its starting position'toadvance'the wheelhead toward the work and retract it therefrom, means for stopping the advance of the feed screwi by said feeding means when the workpiece reachesa predetermined size, andmeans to maintain successive strokes of the feed screw substantiallyconstant despite any reduc-! tion in the diameter of the grinding wheel, said means'includinga'recipro cable driver operatively connected with said feedingmeans for movement in synchronism with the advance andret'urn strokes of the feed screw, a driven ber disposed on opposite sidesof said driver, one of said abutments being engageable by said driver near the end her to thereby rotate the screw and advance the starting of its advance stroke when such stroke is greater than position of the wheelhead toward the workpiece in accordthe previous advance stroke thereof to move the driven ance with the reduced diameter of the grinding wheel. member in one direction, and the other of said abutments being engageable by the driver upon its return stroke to 5 References Cited in the file of this patent return the driven member to its original starting position,

and a one-way driving connection between said driven UNITED STATES PATENTS member and said feed screw to permit free rotation of 1,993,830 Conover Mar. 12, 1935 said member with respect to said screw in said one direc 2,049,611 Harrison et a1. Aug. 4, 1936 tion of movement of said member, and to couple said 10 2,518,600 Cox Aug. 15, 1950 member to said screw on return movement of the mem- 2,718,101 Stuckey Sept. 20, 1955