US2429830A - Grinding machine - Google Patents

Description

Oct. LJUNGGREN 2,429,830

GRINDING MACHINE Filed Aug. 22, 1942 8 Sheets-Sheet l T. H. LJUNGGREN GRINDING MACHINE Filed Aug; 22. 1942 8 Sheets-Sheet 5- Oct. 28, 1947. 'r. H. LJUNGGREN GRINDING MACHINE Filed Au 22, 1942 a Sheets-Sheets Oct. 28, 1947. T. H. LJUNGGREN GRINDING MACHINE Filed Aug. 22, 1942 8 Sheets-Sheet 6 Q0 5 E f i M w EN sq 5 g E 3 s S 3 \m E 0a; 28, 1947. "r. H. LJU GGREN 4 9,

I GRINDING MACHINE Filed Au 22, 1942 e she ts-sheet a Patented Oct. 28, .1947

UNITED STATES OFFICE GRINDING momma Thor H. Ljunggre'n, Charlestown, N. H.. assignor to Bryant chucking Grinder Company, spring- 1 field, Vt.,a' corporation of yermont r V Application August 22, 1942, Serial No;.455,-737 31 Claims. (or 51-50) This invention relates to metal working machines, and in its more specific aspects, to grinding machines.

One object of the invention is to provide improved controls for the cycle of operation.

A further object is to provide mechanism for moving the work and grinding wheel operated by fluid pressure, preferably hydraulic, together with electrical control of the fluid pressure mechanism.

Still another objectis to provide for an automatic cycle of operations including rough and finish grinding with truing of the grinding wheel between the rough and finish grindings and with limit stops independently adjustable to determine the limits of wheel feed for both rough and-finish grinding.

A further object is to provide for a feed and retractive motion of predetermined extent and superposed thereon an additional small feed increment to compensate for wheel wear and truing.

For a complete understanding of this inven-- tion, reference may be had to the accompanying drawings in which Figures 1 and 2 are fragmentary front and top plan views of an internal grinding machine embodying the invention. I

Figure la is a detail sectional View on line la-la of Figure 1.

Figure 3 is a detail sectionalview on line 3 3 of Figure 1, i

Figures 4 and 5 are detail sectional views on lines 4-4 and 55, respectively, of Figure 3.

Figures 6 and 7 are detail sectional views on lines E--5 and 1-1, respectively, of Figure 5.

Figure 8 is a fragmentary left end elevation of parts shown in Figures 1 and 5.

Figure 9 is a detail sectional view on line 9-9 of Figure 8.

Figure 10 is a detail sectional View on line [0-40 of Figure 9.

Figure 11 is a diagrammatic view showing the control and actuating mechanism in position for rough grinding and with the wheel traversing to the left.

Figure 11a is a fragmentary top plan showing a control member.

Figure 12 is a view similar to Figure 11, but showing the parts in dress position between rough and finish grinding.

Figure 13 is a view similar to Figures 11 and 12, but showing the parts in final grinding position traversing to the left.

Figure 14 is a diagram showing the parts in final fast traverse position.

Figure 15' is a view similar to portions of Figures 11' to 13 but with the parts shown in position for traverse of the: wheel to the right.

Y Figure 16 is an elevation of an electrically actuated switch shown diagrammatically in Figures 11 to 14, inclusive.

Referring first to Figures 1, 2 and 3, the machine as shown is an internal grinding machine. This machineis provided with a bed 1 having mounted at the left hand end thereon a work holder carriage 2. This work holder carriage carries thereon 'a.--head 3 which is angularly adjustable along curved ways 4.- It supports a rotary'work spindlecarryingat its right hand end asuitable work holding chuck 5, and at its left end pulleysfi and 1. Either selected of these pulleys may be connected as by the V-belts 8 to aicorresponding pulley 9 or 10 on the shaft of a motor indicated generally at H, this motor providing means for rotating the work'carried by the ehuck-5 and indicated generally at l2. This work holder -2 is mounted for sliding motion from front to back, thus providing for a feed motion-between the wheel and the work. The feed mechanism will be further described.

To the lighter the work holder 2 is mounted a wheel carriage I5 rotatably supporting a spindle l6 carrying a wheel shaft I! at the end of which is carried the grinding wheel l8. This wheel carriage isfixed to a tubular member 20 (see Figure 3) which is rockably and axially movable on arcuate bearing members, one of which is shown at Zi in Figure 3. The member 23 is formed with acentral partition 2| as shown best in Figure 11, and forms a pair of axially alined cylinders receiving through their outer ends a pair of. tubes 22 through which fluid may be passed into or discharged from the respective cylinders through the pipes 23 and 24, thus to produce axial. reciprocation of the member 23, and with it, a corresponding motion of the wheel carriage I5. This motion of the wheel carriage produces the desired traverse of the work by the grinding wheel during the grinding operation, as well understood 'in'the art.

Feed mechanism As before noted the feed between the work and the wheel is produced by motion of the work transverse to the traverse direction. Referring to Figure 8, the work carriage 2 has a bracket 25 secured to a depending front apron portion 26 as by screws 21. This bracket has journaled therein a feed shaft 28. TIhe rearor inner end of this feed shaft is formed. as a feedscrew 30 which is 3 threaded through a nut 3| mounted for rotation in a sleeve 32 of a bearing 33 carried by the base I of the machine. It will be evident that feed may be produced either by rotating the shaft 28 or by rotating the nut 3 I.

Rotation of the shaft 28 may be produced by rotation of a hand wheel 29 having a hub portion 290 secured to the shaft 28, as by means of a nut 29I engaging a threaded extremity of the shaft 28. Shaft 28 may also be rotated by the rotation of a gear ring 34 secured to the hub portion 290 as by screws 35. This gear ring 34 acts as aworm wheel and may have engaged therewith a worm 37 keyed to a shaft 38 to the outer end of which is keyed a suitable hand knob 39 by which it may be turned as shown in Figure 4. This shaft 38 is journaled eccentrically in a bushing 40 having a hub II to which is secured a handle 42. By turning this bushing 40 to bring its handle 42 between the full line position and the dotted line position of Figure 4, the shaft 38 is lifted bodily so as to lift the worm 31 out of contact with the gear ring 34. In this position the shaft 28 may be turned freely by rotation of the hand wheel 29. In the full line position shown in Figure 4, the engagement of the worm 31 with the gear 34 look the shaft 28 against turning by rotation of the hand wheel 29 but permits a very slow rotation to be imparted thereto by rotation of the hand knob 39. This mechanism provides an operator actuatable mechanism for determining the initial feed position as when setting up the machine.

The feed may then be effected by power in accordance with the predetermined cycle of the machine. This power feed is produced by rotation of the nut 3| for which purpose there is secured thereto, as by screws 45, a ring gear 48. This ring gear projects through an opening 41 in the top wall of the bed I and meshes with a gear 48 havinga hub portion 49 journaled on a bush n 58 carried by a stud shaft secured to a bracket 52 as shown in Figures 3 and 5. This bracket 52 is secured to a partition member 53 of the base I as by screws 54. The hub 49 is provided with an integral worm wheel portion 56, which as shown best in Figure 5, meshes with the threads on an externally threaded quill 58. This quill forms the piston rod of a power feed cylinder 80, the quill having an enlarged diameter portion 6I fittin within the cylinder 69 and a somewhat smaller diameter extension 62, which is guided through the cylinder head 63. The cylinder 85 and its head 63 are fixed to the feed bracket 52 as by screws 64. The quill 58 is mounted for both axial and rotary motion within the cylinder 80 and when moved axially its threads act as a rack in engagement with the teeth of the worm gear 56. This axial motion of the quill produces the normal feed motion of the work relative to the wheel, while rotary motion of the quill produces a slow additional feed motion, which is for the purpose of compensating for wheel wear and truing.

Rotation of the quill 58 may be produced by rotation of a splined shaft 65, the splined portion of which extends into an enlarged bore 66 of the quill; This shaft 65 is journaled in a bearing 68 and just rearwardly of this hearing it is provided with the outer or cup member (see Figures 5 and 6) of a one direction roll clutch device. The inner member II of this clutch device is carried by a shaft I2 and between these elements and seated in inclined recesses in the inner clutch element II are the clutch balls I3. Rotation of the shaft 12 in one direction, therefore, serves to rotate the splined'shaft 65 and through it the 4 quill 58, thus to produce as low rotation of the worm wheel 58 while rotation of the shaft I2 in the opposite direction is ineffective to transmit turning motion to the quill.

The shaft 65 may also be locked against rotation, except when it is desired to turn it. This may be produced by forming the outer periphery of the cup element '10 with serrations into which may be projected the edge of a locking bolt I5 (see Figures 5 and 6). This locking bolt may have a head 78 riding in a fluid pressure cylinder 71 and may be normally pressed into locking engagement with the cup element I0 as by a spring 18. A screw 79 extending through the cylinder wall and engaging in a slot 80 in the head 16 prevents the locking bolt 75 from being turned out of position to properly register with the serrations of the element 10. This locking bolt may be retracted by fluid pressure admitted above the head '18 as through a pipe 8|. Retraction of the lockin bolt 15 opens a port leading to a pipe 82 from which fluid pressure may be 1ed to a mechanism for rotating the shaft 85.

Fluid pressure mechanism for rotating the shaft 85 is shown best in Figure 7. The rear end of the shaft 12 has fixed thereto a pinion 85 with which meshes rack teeth on a cylindrical rack bar 88. This rack bar forms the plunger of a hydraulic cylinder 81 and is provided with a head 88 at its inner end which may abut against an adjusting stop screw 89 threaded through the head 90 of a hydraulic cylinder. The plunger is normally held in this position as by means of a coil spring 93 seated in a socket 9| in the outer end of the plunger engaging over a centering pin 92 carried by the fixed frame member 53. The pipe 82 permits fluid under pressure to be introduced into the pressure cylinder 81, this acting to force the plunger 85 outwardly to rotate the pinion 85 in one direction, while when the fluid under pressure is permitted to discharge through the pipe 82, the spring 98 forces the plunger back and turns the gear 85 in the opposite direction. A check valve 85 (Figures 11 to 14) prevents the fiuid under pressure from reaching the cylinder 87 from the pipe 8| so that the latch bolt has to be first released, opening the pipe 82. The direction 6i motion produced by the fluid under pressure is such as to rotate the shaft I2 in the direction to turn the splined shaft 85 and thereby rotate the quill 58.

As before noted, the axial motion of the quill 58 produces the normal feed motion of the work carriage, and this feed is produced by motion of the quill to the left from the position shown in Figure 5. Its limit of motion is determined by either of a pair of switch actuating stops I08 and It! which are mounted for sliding motion through a plunger I82. This plunger is supported adjacent to opposite ends in cylindrical guide members I83 and I84. The guide member I83 is provided with a key way I85 fOr the reception of a key I85 carried by the plunger I62 and by which this plunger I82 is prevented from turning. The plunger I82 is normally urged toward the position shown in Figures 5, 9, l2 and 13 as by a spring I01 seated in a socket I98 in one end of the plunger and reacting against a head plate I09 bridging across the cylindrical bore of the guide member I83 and fixed as by the screws H0. The bore of the guide member I 84 forms a hydraulic cylinder closed off at its outer end by a cover plate II 5 secured in position as by the screws H6, and through this cover plate extends a hydraulic pipe II 8 through which fluid under 14 the stop IDI rather than the stop I is in lallnement with the plug 420.

The stops I00 and .IllI, as shown, are identical in construction. Referring to .Ffigure 9, each stop comprises a screw I having -a head i216 which facilitates turning .it .for adjustment, .this screw having threaded engagement in .a sleeve I21 which is slidably keyed in a bore I28 of the plunger I02. At its inner end this sleeve I21 has an enlarged head I38 with an enlarged diameter flange I3I. Between this flange and .a

counterbored portion .IBZ of the bore of the plunger I23 is positioned a coil spring [33 which acts to holdthe stop projected toward the plug I 20 as far as is permitted by a collar -I 35 threaded onto a. portion of the sleeve I2] and secured in adjusted position thereon as by .a, set screw 135. By turning the screw I25 the amount by which it projects beyond the head I33) maybe adjusted,

and it may be fixed .in such adjusted position as by a lock nut M0 threaded thereon and bearing against the rear extremity of the sleeve I21. It will thus be seen that the stops are individually adjustable axially and as shown one of these, the stop MI, is adjusted further inwardly than the stop I00. This stop l.0.I limitsthe extent of feed for a rough grinding operation and this limit, of

course, should .be somewhat short of the .full

depth of cut. The stop I 00 is set for .the final work dimension as the .result of a finishing out and is therefore retracted by the amount required for the finishing cut over the position .of the stop IOI.

The axial motion permitted these stops is made use of to actuate a pair of controlling electric switches .shown at I and I46 (see Figures 8,.9 and'lO) and these are actuated simultaneous- 1y by the rocking of a lever plate 14] iournaled between two cone centers I48 and I45 carried by a. forked supporting plate I50 securedto a bracket I5I (see Figure 10) as by the screws I52. one end of the plate I4], as at I55, projects suficieinz- 'ly toward the stops so that it may be engaged by either of the collars I35 which happens to be opposite thereto, depending on the axial position of the plunger I02, so that when the stop engaged by the plug I20 of the quill is pushed outwardly thereby, the lever I4! is rocked from the position shown in Figure 10 until it contacts and depresses the two push button switches I45 and 146. This lever plate I4! is normally held away from the push button switches as by a leaf spring I and in contact with a. stop pin I51. The functions of the switches I45 and I46 will be later explained.

While the .feed is taking place there is also efiected a traverse of the wheel relative to the work. This is done automatically and during the normal grinding operation the traverse is produced through an amplitude of definite length. .As will later appear, after the rough grinding has been effected, the machine is conditioned automatically for an extended traverse of the wheel in one direction which brings it away from the work, and during this extended traverse the wheel is trued. The machine is then automatically conditioned to return to the grindin cycle to effect finish grinding within the normal grind- 6 ing traverse limits and the stop plunger is moved to present the .finish grinding .stop into operative position, The feed is resumed and when the desired finish size is ground, the grinding cycle stops with the wheel at .a further-extended traverse .limit .away from the work, whereupon the ground work maybe removed and an unground piece substituted therefor. The cycle of grinding for the new .piece may then be initiated by the operator.

' Traverse mechanism Asshown the means for producing traverse of the work carriage is hydraulic, the control being fihroughaplurality of valves, some of which are controlled by electrical circuits as will later appear. Movable with the tubular member 20, and thus with the wheel carriage, is a support 200 having a .phira'lity of longitudinal grooves therein along which may he adjustabl-y fixed stops 2!, 202 and 203. The stop MI is longer than the stops 202 and 203 and .determines the limit of stroke of the wheel carriage inwardly. The stop 202 .is the shortest of the three and determines the outer limit of traversing motion during the normal .grinding operation only, The stop 203 is intermediate in length between the stops 20! and 202 and determines the outward limit f extended traverse during which the wheel is dressed. Another limit of outward motion at which the finished work is removed and new work to be ground inserted .is determined by the maximum travel of the wheel slide which is reached when the partition 2| contacts with the end of the member 22.

The determination of which of these stops is effective at any time is efiected by the axial position of a .control member 204 which may be moved axially by hydraulic means and is also permitted a rocking motion. The rocking motion acts to reverse the direction of traverse at the desired traverse limits. Eccentric to this member 204 is a post 205 projecting therefrom which may be struck by the stops 202 or 203 as the wheel carriage traverses, depending on the axial position of'the member 204, to rock the member 204 in one direction, while contact of the stop 20I with the post 205 or on a cutaway edge of the collar portion 200 of the member 204 (see Figure 11a) acts to rock the member 204 in the opposite direction. This general arrangement per so with the three stops and a rockable and axially movable control member is not per so my invention, but the construction of the member 204 and associated parts and its hydraulic control does form a portion thereof. This member 204 is rockably carried by a yoke 208, but is connected for axial motion therewith. This may be produced by providing the yoke member 208 with a shaft extension 209 having a peripheral groove 2I0 therein, this shaft extension bein rotatable within a socket 2 in the lower end of the member 204. Any suitable means, such as a set screw 2 I2 having its inner end riding in the peripheral groove 2), may be employed to retain the yoke and member 204 in assembled relation for simultaneous axial motion but with capability of relative rotation. The yoke member 208 has a central plunger portion 2I4 which projects into a casing 2I5 within which is slidable a cup member 2I6 having a shank portion 2II. This shank portion projects through the lower end of the casing 2I5 and through it extends a port 2 I8 connecting with a pressure supply and discharge pipe 2 I 9. A similar pipe 220 passes through the wall of the easing 215 and opens up beneath the cup-shaped portion 2I5 outwardly of its shank 2H. When fluid pressure is admitted through the passage 2|8, the plunger H4 is lifted to its top position as shown in Figure 11, at which time the element 205 is in position to contact the stop 202, while either the element 205 or the cut away portion of the flange 206 remains in all of the axial positions of member 204 in position to be contacted by the stop 20L If the fluid pressure is not admitted through the pipe 2l9 and the port 2|8, the plunger 2l4 may descend to the bottom of the cup 2H5, and where this cup 216 is in its lowered position as shown in Figure 11, the member 2| 4 is then in its lowest position as shown in Figure 14. In this position the element 205 is too low to be contacted by either of the stops 202 and 203 and the grinding wheel carriage can then make its full stroke away from the stop 21 to the work loading and unloading position, When fluid pressure is introduced through the pipe 220 beneath the cup member 216, this cup member is lifted to its upper position shown in Figure 12 and with the member 204 in a, position which is intermediate to its top and bottom positions and in which it may be contacted by the stop 203, but is too low to be contacted by the stop 202. The grinding wheel may then take its extended traverse for truing.

It will be noted that when contact is made on the member 204 with any of the stops, it is turned angularly first in one and then in the other direction. This turning causes reversal of the direction of traverse of the wheel carriage. To this end a portion of the length of the member 204 on its back face is provided with gear teeth which mesh with teeth of a rack bar 225. This rack bar is a part of or forms an extension to a pilot valve 226, and rocking of the member 284 from one to the other of its Positions changes the axial position of the pilot valve 226 between the positions shown in Figures 11 and 15.

Referring first to Figure 11, a liquid suitable for a hydraulic system, such as oil, is pumped from the supply reservoir 230 by the pump 23! into a pipe 232. A pressure relief valve at 233 connected to the pipe 232 and leading back to the tank 230' limits the pressure of the liquid in the pressure pipe 232. This pipe 232 leads to a valve casing 234 having within it a reciprocable reversing valve 235. In the position shown in Figure 11, the reversing valve is at the right hand end of its cylinder, opening communication from the pressure pipe 232, around the neck 236 of the reversing valve, through the pipe 23'! to the casing 238 of the pilot valve, around the neck 239 of this pilot valve and into an axial passage 240 therein, and out around the neck 241 of this pilot valve through the pipes 242, 2420 t the left hand end of the reversing valve, thus retainin the reversing valve in the position shown. The fluid under pressure also passes around the neck portion 236 of the reversing valve through the pipe 23 and the member 22 into the right hand end of the cylinder 20, thus to move this cylinder and the wheel carriage to the left. At the same time liquid is escaping from the left hand end of the cylinder 20 through the pipe 24, around the neck 245 of the reversing valve, pipe 245, to the pilot valve, around the neck 24! of this pilot valve and through the pipe 243 to the valve casing 249 within which is axially slidable the valve 250 fixed to one arm of the yoke 208, the discharge passage around a neck 25! of this valve, through the pipes 252 and 2520, through the throttle valves 253 and 2530, and the pipe 254 to the discharge pipe 255,

through the pipes 260 and 26!, around the neck 262 of the pilot valve, through the central passage 263, around the neck 264 of the pilot valve, and. out through the discharge line 255. After the pipe 260 has been closed by the reversing valve as shown in Figure 11, discharge continues to take.

place through the pipe 26l at the end of the valve at a reduced rate of speed until the valve is in its extreme right hand position shown. This arrangement of the two end pipes 250, 26| and 242 and 2420 leading from the reversing valve, one of which is shut oif before the other one, provides for the slowing down of the travel of the reversing valve adjacent to the ends of its stroke and this with the tapered end of the valve head 2360, for a dwell in the motion of the wheel slide.

When the member 204 is turned by impingement of the member 201 thereon, the pivot Valve 226 then takes the position of Figure 15. In this position pressure from the pressure pipe 232 passin to the reversing valve casing 235 with the reversing valve in the position of Figure 11, passes around the neck 236 of this reversin valve, through the pipe 231 to the pilot valve, around the neck 239 of this pilot valve, as shown in Figure 15, through the axial passage 265 to the pipes 201 and 260, while the pipes 242 and 2420 at the left hand end of the reversing valve are connected around the neck 210 of the pilot valve through the axial passage 2', and the neck 212 of the pilot valve to the discharge pipe 255. Thus the reversin valve is pushed to its left hand position shown in Figure 15 where the pressure pipe 232 is connected around the neck 245 of this valve to the pipe 24 leading to the left hand end of the cylinder 20, while the pipe 23 is connected around the neck 23B of the reversing valve and the pipe 231, around the neck 24! of the pilot valve, and to discharge through the pipe 248, as previously described. The direction of carriage travel is thus reversed. On turning of the member 204 back to its original position so that the pilot valve 226 is in the position shown in Figure 11, and the pilot valve is in the position shown in Figure 15, the pressure connections to the pilot valve and to the reversing valve through the pilot valve are as previously described, causing the reversing valve to be moved to the position of Figure 11, and reversing the pressure and discharge passages with respect to the ends of the cylinder 20. This action of reversing takes place regardless of the axial position of the member 204, so long as there is some means for turning the member 204,

At the end of the cycle of operations where the member 204 is too low to be contacted by either of the stops 202 or 203, and the carriage proceeds to its extreme outward limit of motion, where it stops for loading and unloading, there is nothing to turn the member 204 to effect reversal, hence the machine stops at this position. When it is desired to start it again, the operator turns the member 204 by hand as by means of the handle 215, whereupon the traverse commences, the member 204 being lifted first to its uppermost position by mechanism which will later be described.

Cycle control mechanism Besides carrying the valve 250, the yoke 200 ans-sea also carries another valve 280' having a pair of necks 281 and 282 and this valve forms part of the mechanism which controls the feed motion of the work carriage which is operated from a pressure circuit independent of that which operates the wheel traverse.

The axial position of the member 204 is determined by the pressure circuit which operates the traverse, through electrically controlled valves A and B. The wheel feed and retraction is controlled by electrically actuated valves and I), while the positioning of the rough grinding and finish grindin stops is controlled. by the electrically operated valves E and F. All of these valves A, B, C, D, E, and F are of the same construction, each being provided with a singleneck between two heads, and each controlling connections between a single pipe on one side and two pipes on the other so as to connect the two pipes alternately to the single pipe, depending upon the valve position. Each of these valves is normally held in. one axial position, but is adapted to be moved to the other axial position by energization of an actuating coil A, B, C, D, E, and F, respectively, and these are controlled partly by the switches 145 and 145, three relays 3'00, 301, and 302 and two mo tor actuated switches 303 and 304. Each of the motor actuated switches 303 and 304- is of the type shown in Figure 16, in which energization of a motor 305 rotates a cam. 306. The rotation of this cam 306, acting upon a follower lever 30'1, first closes contacts at 300 and 309, as soon as this rotation has been permitted by the re lease of a latch member 3l0 from a notch 3100 in a disk 31'! rotatable with the cam 306, by energization of the solenoid 311. Such energization pulls backwardly on a hook 312 which engages the lower end of the latch 310 and also closes contacts at 313 and 314 which complete the circuit to the motor 305 through a lead 315 in parallel with the solenoid 311,, starting-rotation of the motor. The solenoid 31 1 retracts the hook 312 until it snaps out of. contact with the latch 3H1 which then rides on the surface of. the disk 311 rotatable with the cam 306 and holds the motor control contacts 313' and 314 closed until the camhas made a complete rev olution, whereupon the latch snaps back into the notch 3100', opening the contacts 313 and 314, stopping further rotation of the motor305, and permitting the hook 312 on de-energization of the solenoid 301 to be brought back by a spring into catching relation with the latch 310, the hook yielding to pass beneath the latch 3 and engage its forward face. The action of: each of the switches 303 and 304'is therefore to close a circuit for a short time and then after a predetermined interval to open it again, the opening taking place when the cam 306 permits the fol-.- lower portion 301 to break the contacts at 309.

Each of the relays 300', 301 and 302 take either of two positions, each havin a pair of spaced solenoids with an armature therebetween, the armature being attracted to one or the other of the solenoids, depending upon which one is energized at a particular time, and the position of the armature defining. the position of a plurality of pivotally mounted switch arms. As shown each of these armatures is one arm of a bell crank lever, the other arm of which is con.-

nected to a rod pivotally connectedito the various switch arms controlled thereby, spaced from their pivots. The relay 300 is provided with an armature 320 10 which is connected through the rod 321 with the switch arms" 322;, 3'23, 324 and 325-, and it has the actuating solenoids 326 and 321'. The switch 301 is provided with an armature 330 which actuates the switch rodl33l] controlling the switch arms 332, 333, as! and 335', and is provided with the actuating solenoids 33B and 331'. The relay 302 is rovided with an armature m which ati .tiiat'es' tne'switch' controlling'rodf 3t! controlling the" positions if the switch arms 34'? and 343', and it? is provided with the actuating solen'o'i'd's 381 andstfi. a In tne'positicn' of the parts shown in Figure 1'1 hiring an intermediate portion of the rough gr nding the valve coils A" and E are energized, whilethe valve coils B, C", 'D" and F" are not energized. The valve A is then in position for iiuidpres'sure'from the pressure line 232 to reach this valve through the pipe 350, to pass around the neck 351 of this valve, and through the pipe Zililintb' the cup member-1 ls ben-eani the plunger 214', thus holding the member 204 in its highest position where it is in position to bev imp'in'g'ed upon on; opposite ends of its traverse by the stops 202 and 201", tfhus't'o produce the relative" snort working traverse orthe wheel carriage; Thi energiza'tion of theyalve coil A produced from the power lines 335 mm 3stthrough the lead from the line 3B5,, tn ecci11i, lead 358, contact 359", switcnarm azt of relay b, and lead fluid under pressur from a pressure ump 3'65, 7

drawing. from the'supply'tank' 230, through a pressure-pipe-SGB inlwhich the pressure is limited by the pressure relief valve 305 discharging back into the supply tank 230, through pipes 361 and 36a to the valve E, around the neck 36!! of this valve; and through'thepipe 310' to the lower end 01? the member 102. before noted; this upper positibn'of themember 2M holds" the valve membe: 250 in its-uppermost position wherein the discharge of fluid from the traversin cylinder for both directions of traverse takes place through thctlirottle valves 233- and 2530, thereby holding the speed or traverse to the desired low value. Iii-the same position of the member'zlll' and duri'ng grinding, thevalvemember 230' is in its uppermost position in v'vliichfluid under pressure from the pressure pipe 366 reaching the valve 201 passes around the neck 282 of this valve and through the pipe 3'11 to" the right hand end of the feed cylinder 60; while the mild under pressure is discharged irom the left hand end of this cylinder through the pipe 3'12, around the neck 281 of the valve" 280; through the pipe 313', around the neck 314 of the valve C, through the pipe 3'15, around the neck 316 of the valve D, through the pipe 311 and the throttle valve 310 to' the discharge pipe 319,-whi'cli leads back to the supply tank 230'. The speed of'feed is thus governed by thesetting of'tlieth'rottl e'valve 3T8.

It is desirable in the retracted relative positions of the wheel and work, that the wheel be spaced somewhat from the work in order to fully clear it. In order tosave time it is therefore desirable to feed the wheel and work relatively from the wheel retracted position quickly to bring the wheel up close to the workand thereafter toproduce feed. at the slower normal speed proper for cutting. Means to provide this initial relatively 11 quick feed comprise the hydraulic valve C with associated parts and its controlling switch 304. In the position of the relay 300 shown in Figure 11, the switch arm 324 is closed, closing a circuit from the line 356 through lead 360, switch arm 324, lead 3040, the solenoid 3H and then the motor of the switch 304 and lead 3042 to line 355. This acts immediately to close and hold closed but for only a limited time the switch arm 304i, which closes a circuit from line 356 through leads M4, 3043, switch arm 304I, lead 3044, solenoid C and lead 3045 to line 355. This moves the valve to a position where discharge from pipe 313 passes around the neck of valve C, through the pipe 3140 to the discharge pipe 319, cutting out the restricted discharge through pipe 315 past the valve D and through the throttle valve 381. As soon as the motor of switch 304 allows the switch arm 3042 to open, the valve solenoid C becomes de-energized, and the valve C returns to its upward position as shown, the initial rapid feed having already been completed, whereupon the unrestricted discharge is cut ofi and the discharge throttled by the valve 318. Further feed during the rough grinding then proceeds slowly after the rapid initial feed which brings the work and wheel close together. The switch 304 with its motor drive is thus a timing device controlling the time of the rapid initial idle feed between the work and wheel which brings them close to each other before the slow working feed is thrown in. The slow feed is thus in action when the wheel and work contact and during the entire time of grinding. The slow grinding feed continues, the wheel traversing the work and being gradually fed into the work until the feed sleeve 58 through its plug I20 contacts the stop IOI which it pushes outwardly against the lever I41 (see Figure until it closes both of the switches I45 and I46.

The closing of the switch I45 closes a circuit from the line 355, through leads 380, 38I, switch I45, lead 382, solenoid 321 of the relay 300, lead 383, switch arm 323 of relay 300, lead 360 back to the line 356. This moves the armature 320 over to the solenoid 321, and in doing this it breaks the connection between the switch arm 323 and the lead 383, thus immediately de-energizing the solenoid 321, the relay 300 then being in the position shown in Figure 12. The closing of the switch I46 acts to close a circuit from the line 356 through the leads 385 and 386, switch I46, lead 381, switch arm 343, lead 388, solenoid 331 of the switch 30I, lead 389, switch arm 332 and lead 390, back to the line 355. This immediately throws the armature 330 over toward the solenoid 321, which immediately breaks the contact between the switch arm 332 and the lead 389, thus opening the circuit through the solenoid 331, but leaving the switch 30I in the condition shown in Figure 12. It will thus be seen that the relays 300 and 30I have been thrown to their opposite positions from the showing of Figure 11 to the showing of Figure 12, but for the present the relay 302 remains in the position of Figure 11.

With the switches 300 and 30I in the position of Figure 12, the solenoid A has been de-energized through the breaking of the contact between the switch arm 325 of relay 300 and the lead 359 so that the valve A takes its other position. This connects the pipe 2I9 around the valve neck 35I of the valve A, through the pipe 39I t0 the disc arge P pe 255, so that the plunger 2I4 descends to the bottom of the cup member 216. However, the valve coil 13 is new ener ized by closing of the switch arm 325 to the lead 421, which completes the circuit from the line 356, lead 360, switch arm 325, lead 42I, coil B, lead 420, switch arm 335, lead 390' to line 355 so that pressure from the pressure pipe 350 passes around the neck 393 of valve B through the pipe 220, be:- neath the cup member 2 I6, thus raising this cup member, together with the plunger 2| 4. The reversal of the positions of the relays 300 and 30I thus acts to lower the member 204 one step to its truing position as shown in Figure 12. This lowering of the member 204 lowers the valv 280 from the position shown in Figure 11 to that shown in Figure 12, reversing the connections from the fluid pressure line 366, so that pressure now flows through the line 312 to the left hand end of the feed cylinder 60 and connects the pipe 31I from the right hand end of the feed cylinder to around neck 282 of the valve 280 through the ipe 3130 to the discharge pipe 313. This discharge is unrestricted so that the feed quill is returned quickly to its starting position. In this position of the member 204, also, the valve 250 has moved from the position in Figure 11 to the position shown in Figure 12, so that the discharge of fluid from the pilot valve casing through the pipe 248 no longer takes place through both of the throttle valves 253 and-2530, the pipe 2520 having been blanked by the valve 250, but takes place through the single throttle valve 253 so that the speed of traverse is reduced, at which time the stop 202 is no longer effective to reverse the direction of traverse so that the wheel slide is given an extended traverse until the stop 203 is effective, and during this extended traverse the wheel is automatically trued. The pressure from this pipe 220 also flows through a pipe 394 to a cylinder 395 of a wheel truing device 396 (shown best in Figure 1a) passing to the left of a piston 391 whose piston rod is connected to one arm 392 of a bell crank lever, the other arm of which carries the truing diamond. A spring 398 engaging the back face of the piston 391 holds the bell crank lever tilted with the truing device at the inoperative position except when pressure is applied to the cylinder 395 through the pipe 220. This inoperative position is shown in full lines in Figure 1a and Figures -11, 13 and 14. This truing device is positioned as shown in Fi ures 1 and 2 beyond the end of the work, where when the truing device is in operative position, it will be engaged by the grinding wheel during its extended traverse, thus to true the wheel.

The throwing of the relay 30I from the position shown in Figure 11 to that shown in Figure 12 closed the switch arm 334 to the lead 408 which established a circuit from the line 355, lead 390, switch arm 334, lead 408 and 409, to the motor of the switch 303 and lead 4I0 to the line 356. This, as before noted, closed for a short period the switch arm 4I5 which established a circuit from the line 355 through the leads 380 and 412, solenoid F, lead 4I3, switch arm 5, lead M4 to the line 356. Energization of the solenoid F pulled the valve F downwardly for a short period of time and in this downward position, fluid from the pressure line 366 and pipes 361 and 368 passing the neck of this valve flowed into the pipe BI which acted to pull the latch 15 into unlocking position and thereafter to force the plunger 88 inwardly from the position shown in Figure '1 to impart rotation to the gear the extent of which was determined by the setting of the stop 89 shown in Figure 7, thus turning the splined shaft 15 tracted position, while the pipe 248 leading from the pilot valve casing is connected directly to discharge through the pipes 565 and 355. As there is no throttle valve in this discharge path, the final outward traverse is at a rapid rate.

The finished ground work may then be removed from the machine and new work placed in position therein. The machine may then be started by turning the member 204 by hand, as by operation of the handle 205, to start the inward traverse. As the dog 400 passes beneath the switch 40! on this inward traverse itcloses this switch, re-establishing a circuit between the leads 402 and 385. This completes the circuit from the line 356 through lead 385, switch 4M, leads 402 and 4551, switch arm 322, left hand solenoid 326 of the relay 300, lead 45!, to the line 355. It also establishes a connection from the lead 402, through the switch arm 342 of relay 362, the left hand solenoid 344 of this relay, lead 4', switch arm 333 of relay 30!, and lead 350 to line 355. This acts to return the relays 300 and 302 to the positions shown in Figure 11, thus automatically conditioning the machine for the rough grinding operation as previously described between the.

stop limits 2!)! and 262, lifting the member 254 to its grind position, giving a fast and then a slower machine feed, and lifting the stop carrying member I02 to position the rough grinding stop l! into alinement with the plug I20 and the machine repeats its cycle,

From the foregoing description of an embodiment of this invention, it should be evident to those skilled in the art that various changes and modifications might be made without departing from the spirit or scope of this invention.

I claim:

1. A carriage moving means including a rotary shaft, connections from said shaft to said carriage causing rotation of said shaft to move said carriage, a gear fixed to said shaft, an externally threaded quill engaging the teeth of said gear and mounted for axial and rotational motion, the threads of said quill acting as a rack with respect to the teeth of said gear on axial motion of said quill and as a worm on rotation of said quill, a rotary shaft splined to said quill, means for moving said quill axially to impart a relatively rapid rotation to said rotary shaft, and means for rotating said splined shaft to impart a relatively slow rotation to said first mentioned rotary shaft.

2. A carriage moving means including a rotary shaft, connections from said shaft to said carriage causing rotation of said shaft to move said carriage, a gear fixed to said shaft, an externally threaded quill engaging the teeth of said gear, said quill having a piston portion, a fluid pressure cylinder within which said piston and quill may move axially and rotate, fluid pressure means communicating with said cylinder for moving said quill axially, said quill then acting as a rack with respect to said gear, a shaft splined to said quill, and means for rotating said splined shaft, said quill acting as a worm with respect to said gear on rotation of said quill.

3. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage in a direction to feed a grinding wheel on said carriage relative to work on said holder, said moving means comprising a one direction driving clutch, an oscilout motion of said plunger, spring means for re- 16 turning said plunger on release of fluid pressure thereon, and means effective to apply and release fluid pressure on said plunger.

4. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage in a direction to feed a grinding wheel on said carriage relative to work on said holder, said moving means comprising a one direction driving clutch, an oscillatory shaft for driving said clutch, a fluid pres sure actuated plunger connected to said shaft to rock said shaft in opposite directions by in and out motion of said plunger, spring means for returning said plunger on release of fluid pressure thereon, a latch engageable with said moving means and biased to hold said moving means stationary, fluid pressure means for first retracting said latch and then acting on said plunger, and means for controlling said fluid pressure means.

5. In combination with a movable carriage havng a grinding Wheel mounted thereon, a wheel truing device, means for moving said carriage to feed the grinding wheel relative to work and to said wheel truing device, said carriage moving means comprisinga rotary shaft, connections from said shaft to said carriage causing rotation of said shaft to move said carriage, a gear fixed to said shaft, an externally threaded quill engaging the teeth of said gear, andmounted for axial and rotational motion, the threads of said quill acting as a rack with respect to the teeth of said gear on axial motion of said quill to effect normal feed of said wheel relative to the work and to said device, and acting as a worm on rotation of said quill to effect a further slight feed of said device relative to the wheel to compensate for wheel wear and truing, means for moving said quill axially, and means for rotating said quill.

6. A grinding machine having a work holder, a, grinding wheel carriage, means for relatively moving said holder and carriage in a direction to feed and retract a wheel on said carriage relative to work on said holder, a pair of means selectively actuated by said feeding means for returning said feeding means to starting position after a predetermined extent of feed, one of said pair of means being set to permit a'greater feed motion than the other pair ofmeans, and means acting automatically on return. of said feeding means to starting position by the action of the means of said pair set for the less feed for restoring said feeding means to feeding actuation.

'1. A grindin machine having a work holder,

a grinding wheel carriage, means for relatively moving said holder and carriage to effect traverse of said wheel along work carried by said holder, means for relatively moving said holder and wheel transverse to the line of traverse to produce relative feed between the work and wheel, a pair of movable stops one or the other of which may be made operative to limit the extent of feed, means for automatically moving said stops to position one of said stops into operative position to limit the feed and consequent depth of cut for a rough grinding operation and thereafter to position the other of said stops into operativeposition to limit the feed and consequent depth of cut during finish grinding, and means actuated by each stop when the feed is stopped thereby, to actuate said trans-'- verse moving means in reverse to separate the work and wheel to a predetermined feed starting position.

8. A grinding machine having a work carriage. a grinding wheel carriage, means for moving one of said carriages to produce a relative traverse efiecting reversal of traversedirections said member being movable to any of three positions to cooperate selectively with certain of said elements to thereby select the amplitude of traverse at one-end -to normal grinding, extended truing, or to and from a loading and unloading position, a truing device movable; to and from operative position to true the wheel in said extended traverse, and means controlled by the position of said member to control the speed of traverse to a slow grinding speed while said member is in grinding position, to a slower speed when said member is in truing position and to operatively position said truing device so that the wheel is trued by said device during extended traverse, and to a fast speed when said member is in loading and unloading position.

9. A grinding machine having a work carriage, a grinding wheel carriage, means for moving one of said carriages to produces. relative traverse between said 'carriagcs, elements movable with said movable carriage defining traverse limits, 2.

member with which said elements cooperate for,

effecting reversal of traverse directions, said member being movable to any of three positions to cooperate selectively with certain of said elements to thereby select the amplitude of traverse at one end to normal grinding, extended truing, or to and from a loading and unloading position, a truing device movable to and from operative position to true the wheel in said extended traverse,

means controlled by the position of said member to control the speed of traverse to a slow grinding speed while said memberis in grinding position, to a slower speed when said member is in truing position and to operatively position saidtr'ui'ng device so that the wheel is trued-by said device during extended traverse, and to a fast speed when said member is in loading and unloading position, and mechanism. automatically moving said memher in predetermined sequence from one to another of said positions to define a cycle of operations of the machine.

10. A grinding machine having a work carriage, a grinding wheel carriage, means for moving one of said carriages to. produce a relative traverse between said carria es, elements movable with said movable carriage defining traverse limits, a member with which said elements cooperate for effecting reversal of traverse directions, said member being movable to any of three positions to cooperate selectively with certain of said elements to thereby select the amplitude of traverse at one end to normal grinding, extended truing, or to and from a loading and unloading position, a truing device movable to and from operative position to true the Wheel in said extended traverse, means controlled by the position of said member to control the speed of traverse to a slow grinding speed while said member is in grinding position, to a slower speed when said member is in truing position and to operatively position said truing device so that the wheel is trued by said device during extended traverse, and to a fast speed when said member is in loading and unloading position, means for effecting relative feed and retraction between said carriages, and mechanism partly responsive to the relative feeding relation between said carriages for moving said member in predetermined sequence from one to another of said positions to define a cycle of operations of the machine.

11. A grinding machine having a work carriage, a grinding wheel carriage, means for moving one of said carriages to produce a relative traverse between said carriages, elements movable with said movable carriage defining traverse limits, a. member with which said elements cooperate for eflccting reversal of traverse directions, said member being movable to any of three positions to cooperate selectively with certain of said-elements to thereby select the amplitude of traverse at one end .to normal grinding, extended truing, or to and from a loading and unloading position, altruing device movable to and from operative position to true the wheel in said extended traverse, means controlled by the position of said member to control the speed of traverse to a slow grinding speed while said member is in grinding position, to a slower speed when said member is in truing position and to operativel position said truing device so that the wheel is trued by said device during extended traverse, and to a fast speed when said member is in loading and unloadlng position, means for effecting relative feed and retraction between said carriages, and mechanism partly responsive to the relative feeding relation between said carriages and partly responsive to the traverse relation between said carriages for moving said member in predetermined sequence from one toanother of said positlons to define a cycle of operations of the ma chine.

12. A grinding machine having a work carriage, a grinding wheel carriage, means for moving one of said carriages to produce a relative traverse between said carriages, elements movable with said movable carriage defining traverse limits, a member with which said elements cooperate for efiecting reversal of traverse directions, said member being movable to any of three positions to cooperate selectively with certain of said elements to thereby select the amplitude of traverse at one end to normal grinding, extended truing, or to and from a loading and unloading position, a truing device movable to and from operative position to true the wheel in said extended traverse, means controlled by the position of said member to'control the speed of traverse to a slow grinding speed while said member is in grinding position, to a slower speed when said member is in truing position and to operativel position said truing device so that the wheel is trued by said device during extended traverse, and to a fast speed when said member is in loading and unloading position, means for effecting relative feed and retraction between said carriages, means controlled by said feeding means when said carriages reach a predetermined relative feed position to condition said feeding and retracting means to retract said carriages relatively from said position, and mechanism actuated in part by the motion of said one carriage at a. predetermined point in its traverse path and in part by said controlling means when so actuated, for moving said member in predetermined sequence from one to another of said positions to define an automatic cycle of operations of the machine.

13. A machine of the class described, comprising a tool carriage, a work holding carriage, means for moving one of said carriages to produce a relative traverse motion between said carriages, stops carried by said one carriage and projecting by different amounts therefrom, a member rockably mounted to be turned by impingement thereon of said stops adjacent to traverse limits of said one carriage, said member being mounted for adjustment toward and from said stops, a non-rockable axially movable member secured to said rockable member for simultaneous, axial motion therewith, said non-rockable member having a plunger portion, connections from said rockable member to said carriage moving means causing the rock ing of said rockable member by impingement of said stops thereon to reverse the direction of traverse, a. fluid pressure cylinder within which said plunger portion extends, and means for controlling a supply of fluid pressure to said cylinder to thereby determine the axial position of said rockable member and thus determine the limits of traverse motion.

14. A machine of the class described, comprising a tool carriage, a work holding carriage, means for moving one of said carriages to produce a relative traverse motion between said carriages, stops carried by said one carriage and projecting by different amounts therefrom, a member rockably mounted to be turned by impingement thereon of said stops adjacent to traverse limits of said movable carriage, said member being mounted for adjustment toward and from said stops, a non-rockable axially movable member secured to said rockable member for simultaneous axial motion therewith, said non-rockable member having a plunger portion and a control portion, connections from said rockable member to said carriage moving means causing the rocking of said rockable member by impingement of said stops thereon to reverse the direction of traverse, a fluid pressure cylinder within which said plunger portion extends, means for controlling a supply of fluid pressure to said cylinder to thereby determine the axial position of said rockable member and thus determine the limits of traverse motion, and means controlled by the position of said control portion for determining the rate of motion of said one carriage.

15. A machine of the class described, comprising a tool carriage, a work holding carriage, means for moving one of said carriages to produce a relative traverse motion between said carriages, a tool carried by said tool carriage, means for moving one of said carriages transverse to the direction of traverse to feed said tool and work holding carriage relatively, stops carried by said traversing carriage and projectin different amounts therefrom, a member rockably mounted to be turned by impingement thereon of said stops adjacent to traverse limits of said traversing carriage, said member being mounted for adjustment toward and from said stops, a nonrockable axially movable member secured to said rockable member for simultaneous axial motion therewith, said non-rockable member having a plunger portion and a control portion, connections from said rockable member to said carriage moving means causing the rocking of said rockable member by impingement of said stops thereon to reverse the direction of traverse, a fluid pressure cylinder within which said plunger portion extends, means for controlling a supply of fluid pressure to said cylinder to thereby determine the axial position of said rockable member and thereby determining the limits of traverse motion, and means controlled by the position of said control portion to determine the limit of said feed motion.

16. A machine of the class described, comprising a tool carriage, a work holding carriage, means for moving one of said carriages to produce a relative traverse motion between said carriages, stops carried by one carriage and project- 20 ing by dififerent amounts therefrom, a member rockably mounted to be turned by impingement thereon of said stops adjacent to traverse limits of said movable carriage, said member being mounted for adjustment toward and from said stops, a non-rockable axially movable member secured to said rockable member for simultaneous axial motion therewith, said non-rockable member having a plunger portion and a valve portion, connections from said rockable member to said carriage moving means causing the rocking of said rockable member by impingement of said stops thereon to reverse the direction of traverse, a fluid pressure cylinder within which said plunger portion extends, fluid pressure means for controlling a supply of fluid pressure to said cylinder to thereby determine the axial position of said rockable member and thus determine the limits of traverse motion, and fluid pressure means controlled by the position of said valve portion for determining the rate of motion of said one carriage.

1'7. A machine of the class described, comprising a tool carriage, a work holding carriage, means for moving one of said carriages to pro? duce a relative traverse motion between said carriages, a tool carried by said tool carriage, work carried by said work carriage, means for moving one of said carriages transverse to the direction of traverse to feed said tool and work relatively, stops carried by said traversing carriage and projecting different amounts therefrom, a member rockably mounted to be turned by impingement thereon or said stops adjacent to traverse limits of said traversing carriage, said member being mounted for adjustment toward and from said stops, a non-rockable axially movable member secured to said rockable member for simultaneous axial motion therewith, said non-rockable member having plunger portion and a valve portion, connections from said rockable member to said carriage moving means causing the rocking of said rockable member by impingement of said stops thereon to reverse the direction of traverse, a fluid pressure cylinder within which said plunger portion extends, means for controlling a, supply of fluid pressure to said cylinder to thereby determine the axial position of said rockable member and thereby determining the limits of traverse motion, and fluid pressure means controlled by the position of said valve portion to determine the limit of said feed motion.

18. A machine of the class described, comprising a tool carriage, a work carriage, means for effecting relative traverse between said carriages, mean producing relative feed between said carriages transverse to the direction of traverse, said traversing means including elements stopping the traverse at points defining the traverse limits, a movable member selectively cooperating with certain of said elements to determine by the position of said member which of said certain ele ment shall be effective, means actuated by said feed producing means at the feed limit for moving said movable member to a, difierent position, and means controlled by said member in accordance with its position determining the speed of traverse,

19. A machine of the class described, comprising a grinding wheel carriage, a work carriage, means for traversing one of said carriages with respect to the other carriage, spaced stop elements carried by said traversing carriage and extending to different distances therefrom, the longest of said stops defining one limit of traverse motion. a shorter stop defining the other limit of an extended traverse, and a stop of intermediate length defining the other limit of a working traverse, a rockable and axially movable member extending toward the path of motion of said stops and having three definite axial positions in all of which it is in the path of motion of said longest stop to be rocked in one direction by impingement of said longest stop thereon, in the inner of which axial positions said member is in position to be impinged upon by said shortest stop to be rocked thereby into another angular position, and in the intermediate of which positions it is not contacted by said shortest stop but is contacted and rocked to said other angular position by the stop of intermediate length, and in the outermost position said member is contacted by neither said shortest stop nor said stop of intermediate length, a wheel truing device positioned to act on a wheel carried by said wheel carriage during said extended traverse, operative connections between said member and traversing means causing rocking of said member by said stops to reverse the direction of traverse, and mechanism effective to position said member in each of said axial positions in a predetermined cycle.

20. A- machine of the class described, comprising a tool carriage, a work carriage, means producing a relativ feed between said carriages from a retracted position when a tool on said tool carriage is out of contact with work on said work carriage, means normally limiting the rate of such feed, a normally open switch, a rotary cam engaging said switch and having a surface portlon positioned to close said switch, a, latch normally holding said cam stationary in angular position permitting said switch to be open, a motor for turning said cam, an electrically operated device acting when energized to momentarily trip said latch allowing said cam to be turned and to close a circuit to said motor, said cam having a surface portion engaging and holding open said latch during a predetermined extent of rotation of said cam during which said switch is closed and then allowed to open, means for energizing said device at the start of such feed from the retracted position, and means responsive to the closing of said normally open switch and operative only so long as said switch remains closed for rendering inoperative said rate limiting means to increase the rate of feed to bring the work and tool close together after which said rate limiting means is effective to slow the rate of feed.

21. A machine of the class described, comprising a grinding wheel carriage, a wheel truing mechanism, means for presenting said mechanism in wheel truing position and then retracting said mechanism, a normally open switch, a rotary cam engaging said switch and having a surface portion positioned to close said switch, a latch normally holding said cam stationary in angular position permitting said switch to be open, a motor for turning said cam, an electrically operated device acting when energized to momentarily trip said latch allowing said cam to be turned and to close a circuit to said motor, said cam having a surface portion engaging and holding open said latch during a. predetermined extent of rotation of said cam during which said switch is closed and then allowed to open, means energizing said device when said mechanism presenting 22 nismand carriage relatively to compensate for wheel wear and trains.

22. A grinding machine having a. work holder. a grinding wheel carriage. hydraulically actuated means for relatively moving said holder and carr ge in a direction to feed a wheel on said carriage relative to work on said holder, means actuated by said feeding means after a predetermined amount of feed for returning said feed means to starting position, means acting automatically thereafter to restore said feeding means to feeding actuation, and means actuated by said feeding means automatically after a predetermined amount of feed larger than the amount for said first feeding motion to return said feeding means to starting Position.

23. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage to effect traverse of said wheel along work carried by said holder, means for relatively moving said holder and wheel transverse to the line of traverse and during such traverse to produce relative feed between the work and wheel, a pair of stops one or the other of which may be made operative to limit the extent of feed, and means for automatically moving both stops to position one of said stops into operative position and the other out of operative position to limit the feed and consequent depth of cut for a rough grinding operation and thereafter to position the other of said stops into operative position and said one stop out of operative position to limit the feed and consequent depth of cut during finish grinding.

24. A machine or the class described, comprising a tool carriage, a work carriage, means for moving one of said carriages relative to the other carriage to eflect relative traverse between said carriages, means for moving one of said carriages relative to the other carriage transverse to the direction of traverse to effect a relative feed and retraction between said carriages, said traverse moving means including a reversing member movable to control the direction of traverse, elements carrled by the movable carria e for actuating said reversing member to reverse the traverse direction, said member being movable into and out of cooperative relation to certain of said traverse reversing actuating elements to selectively limit the length of traverse in ac cordance with the position of said member relative to said elements, feed limiting elements selectively positioned to control said feed moving means to limit the feed between said carriages to different amounts, and means actuated by the feed moving means through the limiting element selected at any one time to determine the position of said member and thus the limit of traverse of the next succeeding traverse motion.

25. A machine of the class described, comprising a tool carriage, a work carriage, means for moving one of said carriages relative to the other carriage to efiect relative traverse between said carriages, means for moving one of said carriages relative to the other carriage transverse to the direction of traverse to effect a relative feed and retraction between said carriages, said traverse moving means including a reversing member movable to control the direction of traverse. elements carried by the movable carriage for actuating said reversing memher to reverse the traverse direction, said member being movable into and out of cooperative relation to certain of said traverse reversing actuating elements to selectively limit the length 23 of traverse in accordance with the position of said member relative to said elements, feed limiting elements movable to position one or another in cooperative relation to said feed moving means to control said feed moving means to limit the feed between said carriages to difierent amounts depending upon which element is in cooperating position, means actuated by the feed moving means through the limiting element in cooperative relation to said feed moving means at any one time to determine the position of said member and thus the limit of traverse of the next succeeding traverse motion, and means controlled by said member in accordance with its position for determining the speed of traverse.

26. A machine of the class described having a tool carriage, a work carriage, means for moving one of said carriages relative to the other carriage to efiect relative traverse between said carriages, said means including a member operable to reverse the direction of traverse and movable from one to another of a plurality of operative positions, traverse stops carried by that carriage which is movable for traverse each stop cooperating with said member in certain of the operative positions of said member to selectively determine the length of traverse, means for moving one of said carriages to eiiect relative feed and retraction between said carriages transverse to the line of traverse, a feed stop carrier, a plurality of feed stops set for different feed limits carried by said carrier, means for moving said carrier to present any of said feed stops selectively into operative position, means for moving said member from one to another of its operative positions, and mechanism controlled partly by said carrier and partly by said carriages in accordance with their relative positions actuating said member moving means, said carrier moving means, and both of said carriage moving means in a predetermined cycle.

27. A machine of the class described having a tool carriage, a work carriage, means for moving one of said carriages relative to the other carriage to effect relative traverse between said carriages, said means including a member operable to reverse the direction of traverse and movable from. one to another of a plurality of operative positions, traverse stops carried by that carriage which is movable for traverse each stop cooperating with said member in certain of the operative positions of said member to selectively determine the length of traverse. means for moving one of said carriages to effect relative feed and retraction between said carriages transverse to the line of traverse, a feed stop carrier, a plurality of feed stops set for different feed limits carried by said carrier, fluid pressure means for moving said carrier to present any of said feed stops selectively into operative position, means for moving said member from one to another of its operative positions, and electrical mechanism controlled partly by said carrier and partly by said carriages in accordance with their relative positions actuating said member moving means, said carrier moving means, and both of said carriage moving means in a predetermined cycle.

28. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage to effect traverse of said wheel along work carried by said holder, means for relatively moving said holder and wheel transverse to the line of traverse and during such traverse to produce relative feed between the work and wheel, a movable member, a pair of stops carried by said member one or the other of which may be made operative by movement of said member to limit the extent of feed and to return said holder and wheel to starting feed relation, and means for automatically moving said movable member to position one of said stops into operative position to limit the feed and consequent depth of cut for a rough grinding operation and the other stop out of operative position and thereafter moving said movable member to position said one stop out of operative position and the other of said stops into operative position to limit thefeed and consequent depth of cut during finish grinding.

29. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage to effect traverse of said wheel along work carried by said holder, means for relatively moving said holder and wheel transverse to the line of traverse to produce relative feed between the work and wheel, a. pair of movable stops one or the other of which may be made operative to limit the extent of feed, and means for automatically moving said stops simultaneously to position one said stops into operative position to limit the feed and consequent depth of cut for a rough grinding operation and while the other stop is moved out of operative position and thereafter to position the other of said stops into operative position to limit the feed and consequent depth of cut during finish grinding and while said one stop is moved out of operative position.

30. A grinding machine having a work holder, a grinding wheel carriage, means for relatively moving said holder and carriage to effect traverse of said wheel along work carried by said holder, means for relatively moving said holder and wheel transverse to the line of traverse and during such traverse to produce relative feed between the work and wheel, a pair of stops both movable together to present one or the other operative to limit the extent of feed while the other is out of operative position, means for automatically moving said stops to position one of said stops into, operative position and the other out of operative position to limit the feed and consequent depth of cut for a rough grinding operation and thereafter to move said stops to position the other of said stops into operative position and said one stop out of operative position to limit the feed and consequent depth of cut during finish grinding, means for automatically truing the wheel between the rough and finish grindings. and supplemental means for automatically actuating said feed means an additional amount independent of said stops, to compensate for wheel wear and truing preparatoiy to truing the wheel.

31. A machine of the class described comprising a tool carriage, a work supporting carriage, means for effecting relative traverse between said carriages, means for producing a relative feed between said carriages transverse to the direction of traverse, said traversing means including elements defining different traverse limits, a movable member selectively cooperating with certain of said traverse elements to determine by the position of said member which of said certain elements shall be effective, said feed means including elements defining difl'erent feed limits, means actuated by said feed producing means at any of said feed limits for moving said movable member to a different position to

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