US2243410A

US2243410A - Cam grinder

Info

Publication number: US2243410A
Application number: US220777A
Authority: US
Inventors: Harold E Balsiger; Ralph E Price
Original assignee: Landis Tool Co
Current assignee: Landis Tool Co
Priority date: 1938-07-22
Filing date: 1938-07-22
Publication date: 1941-05-27
Anticipated expiration: 1958-05-27

Description

y 1941- H. E. BALSIGER ETAL 2,243,410

CAM GRINDER Filed July 22, 1938 e Sheets-Sheet 1 lNVENTORS HmeoLp cams/ E2 May 27, 1941.

H. E. BALSIGER ETAL CAM GRINDER Filed July 22, 1958 6 Sheets-Sheet 2 iNVENTORS HA RdLD 5.541.5/45)? BY RALPH E. PRICE TORNEY \v ZZZ/Z vm v a 71% QESQQQ$ May 27, 1941.

6 Sheefs-Sheet s lnnentord HA RoLD .BALS/GER, RALPH '5. PRICE Gttomeg May 27, 1941- H. E. BALSIGER ETAL 2,243,410

CAM GRINDER Filed July' 22, 1938 6 Sheets-Sheet 4 INVENTORS HAROLD EBALSIGER BY RALPH E PR! 5 4/ A TORNEY y 1941- H. E. BALSIGER ETIAL 2,243,410

CAM GRINDER Filed July 22, 1938 6 Sheets-Sheet 5 Imnentor HAROLD E-BALSIG'ER RALPH 5. PRICE Gttorneg May 27, 1941.

H. E. BALSIGER ETAL CAM GRINDER 6 Sheets-Sheet 6 Filed July 22, 1938 311ventor HAROLD E-BALSIGER RALPH E.PRICE Gttomeg Patented May 27, 1941 CAM GRINDER Harold E. Balsiger and Ralph E. Price, Waynesboro, Pa., assignors to Landis Tool Company,

Waynesboro, Pa.

Application July 22, 1938, Serial No. 220,777

27 Claims.

Our invention relates to grinding machines, particularly machines for grinding automotive cam shafts, and it is an object to provide a machine in which the various functions are performed automatically in a rigid sequence, that is, each successive function is controlled or initiated by one or more preceding-functions.

A further object is to provide a standard timing mechanism for controlling the cycle of operations of the machine.

A further object is to provide means operable by movement of the cradle to inoperative position to stop the timing mechanism and permit same to be re-set for the next operation.

A further object is to provide means for automatically dressing the grinding wheel at each end of the carriage movement.

In the drawings:

Figure 1 is a front elevation of a cam grinding machine.

Figure 2 is a right hand end view of the headstock in section along line 2-2 of Figure 1.

Figure 3 is an end elevation of the wheel reciprocating mechanism.

Figure 4 is a combined wiring and piping diagram.

Figure 5 is a plan view of the headstock with the top cut away.

Figure 6 is a front elevation of the wheel spindie reciprocating mechanism.

In the drawings, Figure 1, numeral indicates the bed of a cam grinding machine having a work carriage II slidably mounted thereon; a cam shaft I3 is rotatably supported on said work carriage between the headstock I2 and the tailstock I4. A motor 49 is mounted on said headstock and drives same thru a suitable arrangement of belts and gears. Numeral indicates a wheel base slidably mounted on bed I0 for movement toward and from cam shaft 13. Grinding wheel I6 is rotatably mounted on bearings on said wheel base. Motor I8 for driving grinding wheel 16 is mounted on the wheel base 15. A hand wheel II together with suitable gearing (not shown) provides means for adjusting the wheel base toward and from the work. The structure and cycle of operation of our invention resembles in a general way that of the machine disclosed in Steiner Patent 2,017,927 granted October 22, 1935. The dressing device I9 having a handwheel 80 for adjusting same is shown in detail in Greiner et al. application 119,704 filed January 8, 1937.

In Figure 2 is shown a right hand elevation of the headstock in section. A work cradle 84 pivotally mounted on said carriage at rotatably supports a master cam 86 in axial alignment with work piece cam shaft I3. Said master cam is urged into engagement with a,rol1er 81 on shaft 88 by a spring 43, acting thru arm 89 to rock said cradle and the members carried thereby in a clockwise direction. Said roller is mounted for axial movement on shaft 88 in timed relation with the movement of carriage II by a mechanism disclosed in detail in Ott Patent 1,993,854 granted March 12, 1935. Said spring is mounted in a cylindrical member 90 and is supported on disks 9I and on a rod 92. One end of said rod is inserted in a cylindrical guide member 93 in the end of cylinder 90; the other end has a rounded head which abuts against the surface of a notch in arm 89. An adjustable stop member 94 on said rod determines the limit of movement of said rod to the left in Figure 2.

Piston rod 96 of piston 42 abuts against the opposite side of arm 89 and when under influence of pressure at the head end, causes said arm to move in a counter-clockwise direction to separate said master cam and said roller. Another cam 91 is mounted to rotate with said master cam. Mounted in headstock I2 opposite said cam is a normally closed switch 48. In the position shown said cam does not touch said switch. However, when piston 42 rotates arm 89 and cradle 84 in a counter-clockwise direction, the nose of said cam rotates thru the position shown in dotand dash lines and opens said switch. The fluid entering the head end of cylinder 4| is directed thereto by a valve I62 and passes unrestricted thru a check valve I40. Exhaust fluid from said head end of said cylinder must pass thru a throttle valve MI. The same line which conducts fluid to the head end of cylinder 4| also directs fiuid to a normally closed pressure switch 221. Said pressure switch is held open by either pump pressure or exhaust pressure. After the fluid is exhausted from said head end of said cylinder the switch is permitted to close. The function of this switch is to start and stop the timing cycle as will be described later.

Wheel spindle reciprocating mechanism The wheel spindle reciprocating mechanism is the same as that shown in OttPatent 1,844,791 granted February 9, 1932, except that it is ac- 'tuated hydraulically instead of manually as in engages a worm wheel I05. Said worm wheel rotates freely on shaft I06. Attached to said worm wheel is one-half of a clutch element I81. The other half I08 forms one end of a spool I88, the other end having a toothed portion II8 engaging a plate III having similar teeth and secured to wheel support 15. Said spool is slidably keyed to shaft I66. At one end of said shaft is an adjustable eccentric II2 positively connected thru a bracket II3 to spindle IOI so that rotation of said eccentric effects an axial reciprocation of said spindle. A'yoke Il4 fits between the ends of said spool and is attached to a piston rod 5 of piston H6 by means of a connecting member I I4. Said piston is slidably mounted in a. cylinder II1. Fluid under pressure is directed into said cylinder by a valve 210 to move said piston in one direction and a spring II8 moves it in the opposite direction.

Feed mechanism The mechanism for feeding the grinding wheel toward the work is shown in Figure 4 and is similar to that shown in Patent 2,150,749 granted March 14, 1939. Said mechanism consists of a rapid feed or positioning piston I20 in a cylinder I 2| and a piston I22 in cylinder I23. Movement of said pistons to an inoperative position is limited by an adjustable stop I24. Said pistons are connected to wheel support 15 thru a feed screw which is integral with said pistons, and a nut (not shown). Integral with said pistons and located between them is a pinion I25. Said pinion engages a rack I26 having a power piston I21 at one end in cylinder I28, and a dash pot piston I28 in cylinder I30 at the other end. An adjustable stop I3I limits the movement of piston I21 toward inoperative position. Said piston I21 acting thru said rack and said pinion rotates a feed screw (not shown) which provides a controlled feed movement of grinding wheel 16 toward work piece 13. The supply of fluid under pressure to the rapid feed cylinder I2I is directed to one side or the other of said cylinder by a reversing valve I80 thru lines I88 and I88. Said valve is shifted in one direction by a solenoid 240, and in the opposite diretion by a spring I8I. An extended portion I82 of valve I 80 serves as a dash pot piston. A portion of the reversing valve body is bored to provide a cylinder for said piston. Additional bores provide the necessary passages in which are inserted a check valve I83 and a throttle valve I84. This dash pot functions only when valve I80 is shifted in a direction to cause a separation of the wheel 16 and work 13. The purpose is to retard the movement of the valve and thereby prevent too abrupt a withdrawal of the grinding wheel.

Fluid under pressure is supplied to cylinder I28 from a valve I62 thru either of

lines

232 or 235. A dash pot mechanism for controlling the movement of piston I21 consists of the dash pot piston I28 and a cylinder I30 described above. Operating fluid for said dash pot is contained in a reservoir I32. Said reservoir and said cylinder are connected by a passage in which is mounted a throttle valve I33. A bypass passage around said throttle valve is controlled by a valve I34. The bypass valve I34 is shifted to bypass position by a. spring I35. Said valve is shifted in the opposite direction by fluid under pressure from line 233. Said line is a branch of line 232 thru which fluid under pressure is directed to the head end of cylinder I28 to start the grinding feed movement.

Work carriage traverse mechanism 6 Movement of the work carriage H is effected by a motor consisting of a cylinder I68 and a piston I68 slidably mounted therein. A piston rod I18 is secured to said carriage in any suitable manner (not shown). Fluid under pressure is directed to one end or the other of said cylinder by a reversing valve I65 thru lines I16 and I11. Said valve may be positioned by means of a lever I66 the movement of which" is guided by a T shaped opening in a guide plate 2. Passage I18 havingga connection to each end of cylinder I66 has a comparatively small opening, and serves to bleed air out of the cylinder while preventing escape of any appreciable volume of fluid under pressure. The traverse speed is controlled by throttle valve 226 in exhaust line 238 providing valve 223 is closed so as to prevent unrestricted passage of exhaust fluid therethru from reversing valve I65. Line I16 leading to the head end of cylinder I68 has two short branch lines, one of which leads thru a throttle valve I" to the reservoir, the other of which leads to a cylinder I13. A piston I12 is slidably mounted in said cylinder and a spring I14 urges said piston to the right. An adjustable stop I15 limits the movement of said piston toward the left. The function of valve I is to compensate for the area. of piston rod I10 during the slow down period just before the plunger I64 enters one of the notches 82 in spacing bar 8| on carriage 1I. Said valve I1I is effective only on exhaust pressure, i. e., when the carriage H is moving from right to left. The function of piston I12 is to compensate for the area of the piston rod I10 during the exhaust of fluid thru line I16 so as to delay the release of plunger I64 after withdrawal thereof from one of the notches 82. If it was not for this compensation, the plunger would be released more quickly during the movement of the carriage from right to left than from left to right, because of the difference in volume of the exhaust fluid from the two sides, and might return to the notch from which it had just been withdrawn. Valve I56 is shifted in one direction by pressure, to direct fluid to withdraw plunger I 64. As soon as the carriage piston I69 begins to move, exhaust fluid passes thru reversing valve I65 and acts against the lower end of displacement'piston I58. Said piston rises and picks up valve I56 shifting same to a position to connect passage 300 with an exhaust line and thus permit plunger I64 to be returned to contact with spacing bar 8I by the action of spring 306. The rate at which displacement piston I58 is shifted depends upon the volume of the exhaust fluid. This volume is greater from the head end of the cylinder I68 than from the rod end. The difference in volume is used in shifting piston I12 thus leaving the volume for actuating piston I58 the same for both ends of cylinder I68. This equality of volume exists only while the carriage travels far enough to prevent plunger I64 from returning to the same notch from which it has just been withdrawn.

Index mechanism The means for effecting intermittent movement of carriage H to place aseries of cams in position to be ground consists of a standard timing mechanism having a motor I85. Said for rough and flnish grinding.

motor thru a clutch controlled by a solenoid 2:8 drives a series of axially aligned relay operating cams for actuating contacts I88, I81 and I88.

Contact I88 controls the traverse speed by closing a valve 223 which prevents a free escape of exhaust fluid and causes said fluid to be exhausted at. a much slower rate thru throttle valve 228. The rate of traverse movement may be controlled also thru a switch 22I as will be described later. The traverse speed may be varied by adjusting valve 225. Said contact also controls the timer motor I85. Contact I81 energizes alternately the coils of relays 220 and 23I to control the speed of headstock motor 49 7 Contact I88 controls the movement of the grinding wheel away from the work thru solenoid 240 and valve I80.

A spacing bar 8| adjustably mounted on carriage 1i has formed therein a succession of notches each of which corresponds to a cam on a cam shaft to be ground. Said notches do not extend the full width of the bar. The purpose of this construction is to prevent breaking the portion between notches, particularly where said notches are close together. The structure is further strengthened by making the bottom of the notch curved so as to eliminate corners. Said spacing bar may be adjusted longitudinally by means of adjusting screws held in blocks 88 on said carriage and abutting the ends of said bar. The means for locating the spacing bar BI and carriage 1! includes a plunger I64 in the to of which is formed a slight projection I64. The purpose of this projection is to permit plunger 84 to first enter the notch to the extent of said projection. This movement is just enough. to cause arm 245. to actuate switch 22I to close a circuit across the lower contacts thereof thus energizing solenoid 222 to shift valve 223 to a position to prevent the passage of exhaust fluid therethru. In this position said valve 223 prevents the flow of exhaust fluid from the traverse motor thru valve 225 and causes it to flow thru valve 228 which has a smaller capacity and therefore reduces the traverse speed. Said plunger is an elongated valve stem on a valve I82. A lever 45 pivoted at M5 hasan arm extending horizontally therefrom to'engage said plunger. Another arm 245 extends in the opposite direction from said first mentioned arm to a position to actuate a two pole switch 22I and a limit switch 241. At each end of spacing bar BI is a stop member 2 38 inserted therein and protruding beyond the lower edge of said bar. Said stop serves to engage the plunger E88 and determines the limit of movement of the carriage in each direction. A pair of cam members 55 are mounted on said carriage and spaced so as to actuate a switch 20! during the period when the carriage moves from the last notch to the stop 288. The function of said switch is to control the work drive motor 48 and the dressing mechanism in either direction.

Control valve mechanism Fluid under pressure is supplied to the grinding feed mechanism, the traverse mechanism, and the cradle withdrawal mechanism from pump I5 2 thru a valve I82. An extended portion of said valve forms the plunger I88 which engages the notches 82 in spacing bar SI for locating the work carriage ll in successive grinding positions. Pressure to operate said plunger and valve is supplied from a pump I54 thru passages I55 and I8I to valve I58 and then thru another passage 300 to the top of valve I82. Said fluid also is directed .sage 3! to valve I5I.

withdraw plunger I84 from notch 82, the piston I88 begins to move carriage 1|. The plunger must be held retracted until after this movement has started otherwise it will return to the same notch. Part of the exhaust fluid passing thru valve I85 is directed against piston I58 and shifts same into valve I58. The valve does not move until said piston has completed its travel therein. When said valve is shifted it connects the top of valve I82 with an exhaust passage 305 and spring 308 returns said valve I82 and plunger I84 until said plunger engages spacing bar 8| in readinessto drop into the next notch. The delay in shifting valve I58 permits suflicient movement of carriage II to prevent the return of plunger I84 to the notch from which it was flrst withdrawn. When the exhaust is from the head end of cylinder I88 an additional delay device is provided in the piston I12 in cylinder I13 described in connection with the traverse mechanism. Valve I58 is first actuated by fluid under pressure directed thereto from valve I5I thru passage I51. However, when valve I5I returns to its initial position this passage is open to exhaust. Valve I58 is then held by fluid which is directed from itself thru passage 300. Valve I 5I is shifted in one direction by a piston I52 in cylinder I53. When fluid'under pressure is directed by valve 880 thru line I89 to cylinder I23 to cause a reverse movement of the grinding wheel support, it also passes on thru passage I to cylinder I53 to shift piston I52 and valve I5I to the right'against a spring. In this position of valve I5I, fluid from supply passage I55 is directed thru passage I51 to actuate valve I58 as described above. Valve I82 receives fluid under pressure from passage I8I and after being depressed said valve distributes said fluid thru pas- Valve I5I in its left hand position directs this fluid thru a passage 302 to valve I85 which in turn directs it thru passages I18 or I11 to one side or the other of piston I88 in cylinder I88. Valve I85 may be shifted manually by lever l88 thru arm I81. Fluid from the same port in valve I82 is directed thru passage 235 and valve I40 in passage 238 to the head end of cylinder 0! to act on piston 82 therein and rock the work cradle 08 to place the work in an inoperative position. Said fluid passes 'on thru passage 23'l to actuate pressure switch 221. Passage 235 leads to the rod end of slow feed cylinder E28. When valve I82 is in the position in which plunger I68 rests in one of the notches 82 in spacing bar iii, the head end of cylinder I28 is supplied from said valve thru passage 232.

Dressing devices The details of the dressing device are described I fully in Greiner et al. application 119,704 filed January 8, 1937. However, the principal elements of said device will be described briefly.

The dressing device 19 is mounted for adjust ment toward and from wheel 18 by means of a hand wheel 80 and associated elements. A

ratchet (not shown) on said hand wheel is actuated alternately by pawls on

pistons

258 and 258.

The length of travel of these pistons, and hence the magnitude of the feed impulse, is adjustable by means of

screws

266 and 261. In this case the first feed impulse, that effected by piston 258, is greater than that effected by piston 259. The

reason for this is to give a better surface to the grinding wheel. The dressing device 13 is mounted on a slide (not shown) and traversed across the grinding wheel by means of a piston 28L A dog 264 movable with said slide actuates a switch 268 to reverse the dressing traverse. The wheel feed hand wheel 11 is actuated during thedressing operation by means of atpawl in a piston 260. The travel of said piston may be adjusted by screw 213. The traverse speed of the dresser is controlled by throttling the exhaust from each end of cylinder 350. Throttle valve 263 is set to permit a comparatively rapid movement of the diamond in its roughing cut from right to left. Fluid is supplied to the head end during this stroke thru check valve 262 which permits a free flow. During traverse in the opposite direction the exhaust from the head end cannot pass thru the check valve. Throttle valve 268 is set to permit a comparatively slow movement for a finishing cut of the diamond on the wheel.

Operation Current is supplied to the entire machine when switch I90 is closed. With the carriage H in one of the end positions, cam 55 depresses the plunger 200 of switch I to complete a circuit from supply line 3 thru line 202 to said switch MI, and then thru the coil of relay 203 to energize same and return thru the: normally closed contact of relay 204 to line I. With relay 203 energized the circuit to relay 205 is complete except for push button switch 206. Closing said switch permits current to flow from line 3 thru switch 206, relay 203, line 201, the coil of relay 205 and return to line I. Contact 208 of relay 205 provides the holding circuit for said relay. Closing said relay starts the wheel drive motor 18 and the motor for pump I54 (not shown). Contact 208 of relay 205 completes a circuit to the coil of relay 209 except for push button switch 2I0. Said switch may be closed by the operator to complete a circuit thru relay 209 to the dressing mechanism. Once this switch is closed the holding circuit keeps the relay closed so long as the main switch I90 remains in closed position. The dressing operation will then be initiated by switch 20I, as will be described later.

The main control lever I66 moves in a T shaped guide plate 2. Movement to left or right shifts valve I65 to direct fluid under pressure to one side or the other of traverse cylinder I 68. Movement of said lever at right angles to said first movement actuates a two position switch 2I2. In the normally closed position of switch 2I2, as shown in Figure 4, the control relay C2 for work drive motor 49 is energized thru line -3I0, and the normally closed contact of C3, to the relay C2, and then to line I, and thru line 3 and the normally closed contacts of switch 20I, line 202 to line 3. Line 3I0 is common to both sides of switch 2I2. The other side of said normally open contact is connected thru line 3I2, contact 208 of relay 205, and the stop side of switch 206 to line 3. I

As carriage 1| begins to move away from the end position, cam 55 permits switch 20I to return to normal position in which a circuit from line 3 passes thru line 202 to said switch, and then thru the normally closed side of switch 2I2 and line 3Il| to the control panel oi motor 48. Said motor is arranged to travel at either a fast or slow speed, depending upon the condition of the timing relay I81-and the timer

clutch relays

228 and 238. While the timing mechanism is inoperative all the relays operated thereby are in position for starting a cycle. This condition exists when the carriage'moves from its end position, and the circuit from line 3 thru switch 208, contact 208 to relays I81 and 230 and line 3I5, is such that the coil of motor control relay 220 is energized and the motor started at a slow speed. The purpose of the slow speed at this time is to lessen the impact between the master cam and roller follower as the cradle 84 advances the workto grinding position. As the traverse proceeds, the tip I64 on plunger I64 drops into the flrst of the notches 82 in spacing bar 8I. Lever 45 swings in a counter-clockwise direction to close the lower contacts of switch 22I. Closing said contacts completes a circuit from line 3 thru switch 20I, line 3I6, timing motor I85, contact I88, and line I, to energize solenoid 222 and shift valve 223 against spring 224. Said valve closes on the less restricted exhaust of fluid from traverse cylinder I68 thru speed control valve 225, leaving as the only outlet, the valve 226 which is adjusted to permit only a small volume of fluid to pass thru and thus reduce the speed of the carriage just before the rest of the plunger enters the notch. Switch'22l is operable thru the same circuit to start timing motor I85, although the clutch which starts the actual timing cycle is not closed until later. When plunger I64 enters notch 82, valve I62 is shifted by a spring .to its upper position and releases fluid from cradle cylinder 4I thru throttle valve I4I, thru line 236, valve I62, and exhaust line 248. Spring 43 thru arm 89 moves the cradle and work to operative position at a rate determined by the setting of valve I. The action of said spring is supplemented by fluid under pressure from valve I62, thru

lines

232 and 234 to the rod end of cylinder 4|. The exhaust pressure of this fluid is sufllcient to hold pressure switch 221 in open position. When the discharge of fluid from the cylinder is completed, that is when the master cam engages its follower, said pressure switchwill be closed to complete a circuit from" line 3 to line 25I and switch 252 to energize the clutch operating solenoid 228 of the timer, and thus start the. timing cycle. The contact arrangement of the timing relay is such that when the clutch magnet is energized, the normally open and normally closed contacts of relay230 reverse. their positions. The normally closed contact opens and deenergizes the coil of slow speed relay 220 and the normally open contact closes and energizes the coil of high speed relay 23I. Said coil also actuates

relays

229 and 238. The circuit thru the normally closed contact of relay 230 to the coil-of slow speed motor relay 220 is broken and a circuit is completed from line 3 thru the normally; open contact of relay I81, the normally open butnow closed contact of relay 230 and the normally closed contact of time relay I81 to the coil of the fast speed motor relay 23I. At the same time, the circuit to slow speed relay 220 of motor 49 is broken by the opening of the normally closed circuit thru relay 230.

When plunger I64 drops in one of the notches 82, valve I62 connects pressure supply line "I thru chamber A of said valve with a line 232 leading to the head end of cylinder I28, thus starting the grinding feed. A branch line 233 directs fluid under pressure to shift valve I34 so as to stop the unobstructed passage of fluid from cylinder I36 to reservoir I32 and to cause said fluid to pass at a controlled rate thru needle valve I33. The rate of the grinding feed may be varied by use of valve I33.

The upward movement of valve I62 stops the flow of fluid under pressure from chamber B thereof, thru valve II to the traverse cylinder I68, and also to valve I56. Thus, when the plunger I64 enters a notch, valve I62 is positioned to direct fluid under pressure to advance the work cradle 84, to start the grinding feed, and to cut off the supply of fluid under pressure to the traverse motor.

As described above, the timing relay clutch is energized by closing of pressure switch 221 after the cradle has advanced to grinding position with the work rotating at slow speed.

At the end of the rough grinding operation the relative positions of relays I81 and 236 are again reversed, this time due to the action of the timing mechanism on relay I81. Current then passes thru the normally open contacts of relay I81, and thru line 3I5 to the coil of slow speed motor relay 226. At the same time the coil to high speed relay 23I is deenergized by the opening of the circuit thru the normally closed contact of relay I81 and line 3I1. Thus the work is caused to rotate at slow speed for finish grinding.

At the end of the finish grinding period timing contact I88 is opened to deenergize thru line 3I6 the feed'valve solenoid 246 and permit valve I86 to be shifted to reverse position by spring I8I. This movement of the valve is controlled by a dash pot piston I82 on one end of said valve so that while fluid under pressure is directed thru line I89 to cylinder I23 to act on piston I22 to back off the grinding wheel as quickly as possible, the controlled valve movement prevents the wheel from being started with a jerk which would be likely to leave an objectionable mark on the work. The movement of the wheel support is very slight, not more than g inch, since the purpose of the movement is merely to effect a break of contact between wheel and work. This movement is limitedby adjustable stop I24. Valve I86 also supplies fluid under pressure thru lines I89 and I95 to cylinder I53 where it acts on piston I52 to shift valve I5I against a spring. This movement of valve I5I directs fluid from supply line I55 thru line I51 to the top of valve I56. This supply of fluid under pressure first resets the displacement piston I59 inside valve I56 against adjustable stop I66 and then shifts the valve I56 to admit fluid thru passage 366 to the top of valve I62 to withdraw plunger I64 from the spacing bar BI. Fluid from the same passage is directed to the upper disk of valve I56 and serves as a hydraulic holding circuit after valve I5I returns to its original position. Upon withdrawal of plunger I64, arm 245 on lever 45 opens the lower contacts of switch 22I and closes the top contacts. Opening the lower contacts of said switch opens a circuit from line 3 thru line 3I6 and deenergizes the timer mot-or I85 and also solenoid 222. The circuit thru said top contacts energizes solenoid 222 thru switch 241 and line 3I6 and holds valve 223 in position to; block the exhaust thru line I11 and valve I65 from cylinder I68 so as to provide sufficient pressure to shift valve I56. Valve I56 then relieves the pressure on valve I62 by connecting passage 366 with exhaust passage 365 to permit plunger I64 to move against spacing bar 8|. With this movement of the plunger, switch 22I moves to neutral position, solenoid 5 222 is therefore deenergized, spring 224 shifts valve 223 to position to permit exhaust fluid from traverse cylinder I68 to escape thru passage 3I9, valve 225, valve 223, and exhaust passage 212 and the traverse movement proceeds at high speed.

Shifting valve I62 also reverses the cradle operating piston 42 by directing fluid under pressure from chamber B of said valve thru

passages

235 and 236, and check valve I46 to the head end of cylinder 4|, and opening the other end thru

passages

232 and 234 and chamber A of said valve to exhaust line 246. This causes the cradle and work to be moved away from grinding position to permit indexing to the next cam. Fluid under pressure from said chamber B of valve I62 is also conducted thru passage 235 to the rod end of cylinder I28 to reset the grinding feed, and at the same time valve I34 is reset by spring I35 which forces fluid back thru

passages

233, 232, and chamber A of valve I62 to exhaust passage 246 to permit a free flow of fluid back to cylinder I36 from reservoir I32.

The fluid under pressure which withdraws the cradle also opens pressure switch 221 thus deenergizing timer clutch solenoid 228 to disengage the clutch and permit the timer to be reset.. At the same time relays 229 and 236 return to normal position in which position, as previously described, the slow speed relay 226 of motor 49 remains energized. Resetting the timer permits closing of relay I88 which energizes solenoid 246 to shift valve I86 to direct fluid under pressure thru passage I69 to the head end of cylinder I 2I, where it acts on piston I26 to return the wheel support 15 and grinding wheel 16 to grinding position. Thus, the wheel is returned to working position before the index movement takes place, and-is ready to start grinding as soon as the cradle brings the next cam into position. When valve I86 is shifted by solenoid 246, fluid is exhausted therethru from cylinder I53 thru passages I 95 and I89 to exhaust passage 212, and valve I5I is returned toits original position by its spring. The passage 36I from valve I62 to valve I65 is opened thru valve I5I and passage 362 to one side or the other of traverse cylinder I 68 depending upon the position of valve I65. Fluid is exhausted from the top of valve I56 thru \passage I51, valve I5I, and exhaust passage 365, but as described above, the same fluid which 55 withdraws the plunger I64 acts on the upper disk of said valve I56 to hold same in the downward position.

As soon as the traverse movement begins, assuming that it is from right to left, the exhaust 60 fluid from cylinder I 68 after passing thru passage I16 to valve I acts first to shift the displacement piston I59 in valve I56 to the limit of its movement inside said valve. The exhaust fluid then shifts displacement piston I12. After this, valve I56 is shifted against the holding pressure which is permitted to escape thru check valve 326, chamber B of valve I62, and passage 235, which at this time is open to exhaust thru valve I65, and the pressure on the top of valve I62 is connected thru valve I56 with an exhaust line 365. The plunger I 64 is thus released against the spacing bar. If the traverse movement should be from left to right, valve I56 would be moved as soon as the displacement piston I59 7 therein had reached its limit of movement because displacement piston I12 is not effective under line pressure, the supply of fluid under these conditions not being limited to the volume of the cylinder and connecting parts.

Piston I12 is provided to compensate for the area of the piston rod "6, and any compensation aflorded thereby is eifective only insofar as the shifting of displacement piston I56 is concerned. For this reason valve III is also needed when traversing from right to left to make the traverse slow down equal in both directions of traverse. This slow down is caused by shifting valve 226 to block the exhaust of fluid thru throttle valve 225 and passage 3|! and causing said fluid to discharge thru the smaller opening of valve 226. The speed of the slow movement,'of course, is determined by the setting of valve 226.

When plunger I64 is released against the spacing bar, the traverse movement continues at full speed until the tip I64 enters the next notch. This slight movement of the plunger is effective thru arm 245 to close the lower contacts of switch 22I. Said contacts complete a circuit from lines 3, 3I6 and I to energize solenoid 222 which shifts valve 223 to perform the function described above. Said switch alsostarts timing motor I65. Shortly thereafter the plunger enters the notch completely, and valve I62 connects the head end of cylinder H with the exhaust line 246 thru throttle valve HI and passage 236 to permit the cradle to return to working position. This movement is controlled by valve I4I. Fluid under pressure from line I55 is also directed by valve I62 in this position thru passage 262 to the head end of cylinder I28 to start the grinding feed. As soon as the cradle 84 has been returned to operative position, the reduction in exhaust pressure at the head end of cylinder 4I permits the closing of pressure switch 221 completing a circuit from line 3, thru line 25I, and snap switch 252, to energize timer clutch solenoid 226 and start a new cycle.

When it is desired to control the traverse movement manually, the operator may depress lever 45 to withdraw plunger I64 from the spacing bar, and at the same time thru arm 245 close the upper contacts of switch 22 I. Said lever may be held in depressed position by a latch (not shown). Withdrawal of the plunger, and consequent shifting of valve I62, will have the same effect as though operated automatically, except that to cause the rapid traverse, lever 45 must be depressed far enough so that arm 245 will open limit switch 241 and thus neutralize the action of switch 22I. When the slow down is desired the operator releases the lever enough to permit switch 241 to close again, but not enough to open the upper contacts of switch 22I.

After the last cam has been ground, withdrawal of plunger I64 permits a slight traverse movement which brings a stop 246 on spacing bar 6| into contact with plunger I64 to stop said traverse movement. At the same time cam 55 opens the normally closed circuit and closes the normally open circuit of switch 26I. Rotation of motor 46 is maintained thru tappet switch 246 until cam 91 opens same. Said cam is effective to open said switch only when the cradle 64 is in back position. Opening said switch breaks a circuit from line 3 thru a normally open contact 325 of relay C2, thru line 3, normally closed contact of switch 2I2, and line 3), the normally closed contact of relay C3 to deenergize relay C2, thus opening the circuit to motor 43. However, relay 02 has a normally closed contact 621 which closes a ciruit from line I to the coil of reverse relay C3; and from there thru line 626 and zero speed switch 250 to line 3. A reverse current is sent thru motor 43, and just at the reversal point said zero speed switch 256, which has been held closed by forward rotation of the motor, opens the reverse circuit to stop said motor and the headstock spindle in a predetermined position.

Closin the normally open contacts of switch 26I directs current thru line 25I to energize solenoid 226 of the timing mechanism to close relay contact 223. This connects line 3 with line 6I6 thru switch 22I, the timing motor I65, and thru contact I66 of the timer to line I. At the same time solenoid 222 is energized and valve 226 shifted to prevent passage of exhaust fluid therethru, thus to eifect the traverse slow down so as to cushion the movement of stop 246 against plunger I64. At the end of the predetermined period the timer will open relay I66, breaking the circuit from line 6 to line 3", and stopping the motor I65, and shifting valve 223 to again release exhaust fluid from cylinder I66 to permit the next movement of the carriage to occur at a rapid rate. The timing mechanism may be disconnected thru a two pole snap switch 252. The other pole of said snap switch is connected to the dressing mechanism.

Closing the normally open contacts of switch 26I is efiective to connect lines 3 and 326 thru relay 266 and lines 636, 33I and relay 264 to line I to energize solenoid 255 and shift valve 256 so that fluid under pressure from line 251 is directed thru passage 340 to the

diamond feed pistons

256 and 259 to feed one and reset the other; thru passage 64I to wheel feed piston 266 to feed the wheel a distance equal to the wear, plus the amount to be removed by dressing; and thru passage 642 and check valve 262 to the head end of the dresser traverse piston 26I. The dresser makes the first pass across the wheel at a speed determined by the setting of valve 263 which controls the exhaust of fluid from the rod end of piston 26I. At the end of the flrst pass a dog 264 movable with piston 26I releases normally closed switch 265 which completes a circuit from line 3 thru snap switch 252 to energize and hold energized the coil of relay 264. Opening the normally closed contacts of said relay breaks the circuit from line I thru-line 33I to solenoid 255 deenergizing same and permitting valve 256 to be shifted by spring 345 to its initial position. Fliud under pressure will then be directed thru passages 3 and 344 to the opposite end of each of the

pistons

256 and 259 to cause the flrst to reset and the second to effect a feed movement smaller than that of 256. The amount of feed in each case may be adjusted by means of stop screws 266 and 261. The shorter feed movement is accomplished by adjusting the screw 261 to shorten the stroke of piston 253. Fluid under pressure is directed thru passage 3 and valve 263 to the rod end of traverse-piston 26I. The speed of said piston on the reverse movement is less than on the first pass and is determined by the setting of valve 266 which controls the flow of exhaust fluid on said reverse movement. Movement of piston 26I to the right is limited by stop screw 266. Fluid is also directed at this time thru passage 3 to the right hand end of piston 266 to reset same. Movement of said piston to the right is limited by stop screw 213.

At the beginning of the dressing operation when solenoid 255 is energized, fluid under pres sure from valve 256 is directed thru passage 342 to one end of a pressure operated valve 210. Said valve in turn connects cylinder Hl with exhaust line 212. Piston H6 is shifted by spring 8 to separate clutch members I01 and M8 to stop reciprocation of the wheel spindle NH and grind-v ing wheel 16 during the dressing operation. Said reciprocation remains stopped until the next grinding operation is started. When valve I62 directs fluid to the head end of cylinder I28 to start the grinding feed it is also directed thru line 21! to the opposite endof valve 210. This connects cylinder H! with pressure line 251 and piston H6 is shifted against spring H8 to engage the clutch members and start the reciprocating movement again.

We claim:

1. In a grinding machine, a work support, a wheel support, means for rotating a work piece on said work support, means for effecting a relative transverse movement between said supports, means responsive to said transverse movement for changing the speed of said work rotating means at the beginning of a grinding operation, and a control mechanism operable before the end of the grinding operation for changing said work speed back to the initial rate.

2. In a. grinding machine. a wheel support. a work support, means on said work support for rotatably supporting a work piece, means for rotating said work piece, means for effecting a relative transverse movement between said supports, means for effecting an intermittive longitudinal movement of said work support for successively placing a series of portions on said work piece in position to be ground including a timing mechanism, means actuated by said timing mechanism for changing the speed of work rotation, means actuated also by said timing mechanism for initiating said transverse movement for separating said work support and said wheel support, means for stopping said timing mechanism with the work rotating at slow speed, means for returning said work support and wheel support to grinding position, means responsive to said movement for starting said timing mechanism again and means actuated by said timing mechanism for increasing the work speed.

3. In a grinding machine, a work support, a wheel support, means for effecting a relative transverse movement between said supports,

mechanisms for effecting said movements intermittently to grind successive portions of a work piece, means for rotating the work at a predetermined speed, means for automatically reducing said speed during the grinding operation on each of said portions, means for initiating said transverse movement for separating the work and wheel and means responsive to said transverse movement in returning said wheel and work to operative position for restoring said predetermined speed to said work rotating mechanism.

4. In a grinding machine, a feed mechanism comprising a piston. a cylinder, a supply of fluid under pressure for effecting a relative movement between said parts, a dash pot for controlling said movement, a throttle valve in said dash pot, a valve normally positioned for bypassing fluid around said throttle valve and means for directing said fluid under pressure simultaneously to actuate said valve to cut off said bypass and to said cylinder to initiate a feeding movement.

5. In a grinding machine, a work support, a wheel support, means for effecting relative transverse and longitudinal movements between said supports including a hydraulic motor for each movement, a valve for controlling each of said motors, means for actuating each of said valves in a predetermined sequence including a timing mechanism, a switch actuated by said timing mechanism for shifting the valve for causing said transverse movement, a second valve actuated by first valve in one direction to direct fluid for shifting a third valve, a plunger for locating said work support in'predetermined positions during said longitudinal movement, means responsive to fluid under pressure from said third valve for withdrawing said plunger, a valve operable with said plunger for directing fluid under pressure to said second valve, means whereby resetting said timer releases said second valve and means whereby release of said timer operated valve is effective to direct fluid to one side or the other of said work support motor.

6. In a grinding machine, a wheel support, a work support, means for feeding said Wheel support toward and away from said work support including a motor, a reversing valve for controlling same, power means independent of cross feed movement for actuating said reversing valve in one direction after a predetermined grinding operation, and a dash pot for cushioning the movement of said valve whereby to prevent an abrupt start in moving said support.

'7. In a grinding machine, a movable carriage, a hydraulic motor for causing a traversing movement of said carriage, said motor including a cylinder, a piston slidably mounted therein, a piston rod extending thru one end of said cylinder, fluid supply lines to each end of said cylinder, means for effecting said traversing movement intermittently to locate successive portions of a work piece in position for grinding including a spacing bar and plunger, a valve for effecting withdrawal of said plunger which prevents release thereof before the beginning of said traverse movement, means for equalizing the action of said valve regardless of the direction of movement including means for compensating for the difference in effective area of the two sides of said piston including an escape valve in the line leading to the head end of the cylinder whereby to permit sufficient fluid to escape during exhaust therethru to compensate during cushioning for the displacement of the piston rod.

8. In a grinding machine, a movable carriage and hydraulic means for moving same including a piston and cylinder, a piston rod on said piston, pipe lines leading to opposite ends of said cylin-v der for directing fluid under pressure alternately thereto, means for effecting said carriage movement intermittently in either direction to locate a series of portions on a work piece in position for grinding including a spacing bar and plunger for engaging spaced portions thereon, means for slowing down the movement of the carriage just before said plunger engages one of said portions, means for equalizing the length of said slow movement in each direction including means to compensate for the difference of effective area between the two ends of said piston including a spring pressed piston, a cylinder connected to the fluid line leading to the head end of said cylinder, said compensating means having a displacement equal to the difference in displacement between opposite sides of said carriage piston as said piston moves thru the same distance in each direction.

9. In a machine of the kind described, a work support, means for enecting a longitudinal movement of said work support including a motor, means for causing intermittent operation of said motor including a .timing mechanism, means for reducing the speed of said motor as said support approaches the end of its movement in one direction and means actuated by said timing mechanism ior rendering said speed reducing means inoperative before said support begins to move in the pposite direction.

10. In a machine of the kind described, a work support, a grinding wheel support, a grinding wheel mounted thereon, means for effecting an axial reciprocating movement of said wheel, a wheel dressing device on said wheel support, mechanisms for eflecting relative transverse and longitudinal movement between said supports including a motor, means for eflfecting said movement intermittently to position said grinding wheel and successive portions of said work piece in operative relation, means for shifting said work support to an inoperative: position after a predetermined number of grinding operations, means responsive to said last movement to initiate operation of said dressing device and to stop said reciprocatingmovement including a switch, a valve actuated by said switch for directing fluid under pressure for initiating said dressing operation, a second valve actuated by fluid under pressure from said first mentioned valve for controlling operation of said wheel reciprocating mechanism.

11. In a machine of the kind described, a work support, a wheel support, a grinding wheel rotatably mounted thereon, mechanisms for effecting relative transverse and longitudinal movement of said supports, means for effecting said longitudinal movement intermittently to place the tool support and the work support in successive positions to grind a series of portions on a work piece including a motor, a spacing bar having notches spaced to correspond with the spacing of the portions of said work piece to be ground, a plunger and resilient means for holding. same in contact with said spacing bar, meansv for withdrawing said plunger and starting said motor and means operable in response to movement of said motor for releasing said plunger.

12. A machine of the kind described having a work support, means for effecting an intermittent longitudinal movement of said work support including a hydraulic motor having inlet and exhaust lines attached thereto, said exhaust line having two branches, avalve in one of said branches for permitting the discharge of a comparatively small volume of fluid, a valve in the other branch of said exhaust line which is adjustable for controlling the speed of the motor, a second valve" in the same branch with said adjustable valve, means including a time delay mechanism and a solenoid actuated thereby for shutting off said second valve whereby to leave only said first mentioned valve for releasing the exhaust fluid and thus substantially reduce the speed of said motor.

13. A cam grinder having a work support, means for efiecting an intermittent longitudinal movement of said work support including a hydraulic motor having inlet and exhaust lines attached thereto, end stops for determining the limit of said longitudinal movement in each direction, an exhaust line having two branches, a

valve in one of said branches for: permitting the discharge of a comparatively small volume of fluid, a valve in the other branchof said exhaust line which is adjustable for controlling the speed of the motor, a second valve in the same branch with said adjustable valve, and a switch actuated by movement of said work support Just before an endstop is reached for shutting oi! said second valve whereby to leave only said first mentioned valve for releasing the exhaust fluid and thin substantially reducing the speed of said motor.

14. A cam grinding machine having a work support, a wheel support, means for enacting relative longitudinal movement between said supports including a motor, means for eifecting said movement intermittently including a specing bar, a plunger for successively selected portions of said bar. and a switch operable by movement of said plunger just prior to engaging one of said portions for controlling said motor to reduce the speed thereof and thus reduce the rate of said longitudinal movement just before stopping said movement completely.

15. In a grinding machine, a grinding wheel support, a work support, mechanism including a main control valve for effecting relative transverse and longitudinal movement between said supports, mechanism independent of said work sup rt for dressing said grinding wheel including a valve, mechanism for eii'ecting a reciprocating movement of said grinding wheel, a pressure operated valve for controlling said reciprocating mechanism, said pressure operated valve being shifted in one direction by fluid under pressure from said dresser control valve and in the opposite direction main control valve.

16. In a machine of the kind described, a work support, a grinding wheel support, a grinding wheel mounted thereon, means for effecting an axial reciprocating movement of said wheel, a wheel dressing device on said wheel support, mechanisms for effecting relative transverse and longitudinal movement between said supports including a motor, means for eiiecting said movement intermittently to position said grinding wheel and successive portions of said work piece in operative relation, means for shifting said work support to an inoperative position after a predetermined number of grinding operations, means responsive to said last movement to initiate operation of said dressing device and to stop said reciprocating movement'including a switch, a valve actuated by said switch for directing fluid under pressure for initiating said dressing operation, a second valve shifted in one direction by fluid under pressure from said first mentioned valve for stopping said wheel reciprocating mechanism.

17. In a machine of the kind described, a work support, a grinding wheel support, a grinding wheel mounted thereon, means for eiiecting an axial reciprocating movement of said wheel, a wheel dressing device on said wheel support, mechanisms for effecting relative transverse and longitudinal movement between said supports including a motor, means for efifecting said movement intermittently to position said grinding .wheel and successive portions of said work piece in operative relation, means for shifting said work support to an inoperative position after a predetermined number of grinding operations, means responsive to said last movement to initiate operation of said dressing device and to stop said reciprocating movement including a switch, a valve actuated by said switch for directing fluid under pressure for initiating said dressing operation, a second valve shifted in one by 'fiuid under pressure from said 7 direction by fluid under pressure from said first mentioned valve for stopping said wheel reciprocating mechanism, and a main valve for controlling said relative transverse and longitudinal movements which is effective also after one of said portions has been positioned to direct fluid under pressure to shift said second valve in the opposite direction for starting said reciprocating movement. r

18. In a grinding machine, a work support, a cradle oscillatably mounted on said support, mechanism for rotating a work piece including a motor, a pair of switches in parallel for controlling rotation of said motor, one of said switches being operable by movement of said work support, a cam rotatable with the work for actuating said second switch for stopping said work in a predetermined angular position, said cam operated switch being operable only when said cradle is in a predetermined position.

19. In a grinding machine, a work support, a-

grinding wheel support, mechanism for effecting relative transverse and longitudinal movements of said supp rts including a motor for each, means operable when a work piece has been ground to size for initiating said transverse movement to separate said wheel and work including a valve which is shifted for a short period and then returned to its original position whereby to effect a quick withdrawal and rapid return of said transverse movement, a valve shifted by the same fluid under pressure which actuates said rapid feed, for directing another supply of fluid under pressure to actuate a pilot valve which controls withdrawal of the plunger and directs fluid under pressure to actuate said traverse mechanism.

20. A grinding machine having a work support and a grinding wheel support, mechanisms for efiecting intermittent relative transverse and longitudinal movements of said supports for successively positioning a series of portions to be ground on a work piece including a spacing bar and a plunger for engaging selected portions thereon, size control mechanism and means operable thereby for initiating said transverse movement including a valve for directing fluid under pressure to said transverse moving mechanism, and means actuated by fluid under pressure from said valve for withdrawing said plunger from said spacing bar and initiating said longitudinal movement, including a valve actuated by movement of said plunger.

21. In a cam grinding machine, a wheel support, a grinding wheel'mounted thereon, a work support, a cradle rockably mounted on said work support for movement toward and away from said wheel, mechanisms for efiecting relative transverse and longitudinal movements between said supports, means for efiecting said movement intermittently to place a series of portions of a work piece in position to be ground including a spacing bar and plunger, a timing device for determining the duration of the grinding on each of said portions, a valve actuated by said timing device for withdrawing said wheel support, a second valve actuated by fluid under pressure from said first mentioned valve, a valve actuated by fluid under pressure from said second valve for directing fluid to withdraw said plunger, a valve movable with said plunger for directing fluid to move said cradle to inoperative position, a pressure switch actuated by said cradle operating fluid for stopping and resetting said timing mechanism, means responsive to resetting said timing mechanism for returning said first two valves to original position, and means operable upon return of said second valve to original position for initiating said longitudinal movement.

22. In a cam grinding machine, a bed, a wheel support slidably mounted thereon, a grinding wheel rotatably mounted on said support. means for effecting a transverse movement of said support including a valve, a work support, means for eifecting a longitudinal movement of said work support, a work cradle oscillatably mounted on said work support for movement toward and from said wheel support, a valve for controlling said work support and said cradle, means for effecting movement of said work supports, wheel support and cradle at intervals to position selected portions of a work piece for grinding including a spacing bar and plunger for locating said parts and a timing device for determining the duration of the grinding operation, a valve for eflecting withdrawal of said plunger from said spacing bar, a main control valve for controlling said work support and cradle valve and said plunger control valve, means actuated by said timing device to shift said wheel support control valve to break contact between the wheel and work, and also to direct fluid under pressure to shift said main valve, said plunger control valve being operable in response to said main valve when so shifted to direct fluid for withdrawing said plunger, said work support and cradle valve being shifted simultaneously with withdrawal of said plunger, means operable in response to fluid under pressure for operating said cradle for stopping said timing mechanism-means operable upon stopping said timing mechanism for returning said wheel support control valve to original position whereby to return said wheel support to grinding position and said main valve to its original position, said main valve upon return to said original position being effective to direct fluid under pressure from said work support control valve to move said work support.

23. In a grinding machine, a work support, a wheel support, mechanisms for effecting relative transverse and longitudinal movements between said supports, means for efiecting first a transverse movement of the wheel support thru a distance just suflicient to break contact between the work and wheel, means for effecting a transverse movement of the 'worksupport for vcausing a further separation of work and wheel, and means operable in timed relation with said transverse movement of the work support for returning the grinding wheel to operative position substantially immediately after said transverse movement of the work support.

24. In a grinding machine, a work support, mechanism for efiecting a longitudinal movement thereof, mechanism for eiiecting said movement intermittently for grinding successive portions on a work piece and then shifting said work support to an inoperative position, a cradle oscillatably mounted on said support for moving said work transversely to inoperative position during said longitudinal movement, mechanism for rotating a work piece including a motor, a pair of switches in parallel for controlling rotation of said motor, one of said switches being operable switch for stopping said work in a predetermined angular position but only at the end of said longitudinal movement in either direction.

25. In a grinding machine, a wheel support, a work support, a cradle oscillatably mounted on said support, fluid pressure mechanism for moving said cradle toward and from operative position, a grinding wheel support, mechanism for efiecting intermittent relative transverse and iongitudinal movement between said supports including a timing mechanism mounted independent of other mechanisms on the machine, and a pressure switch operable in response to the fluid under pressure for actuating said cradle for starting and stopping said timing mechanism.

26. In a grinding machine, a work support, a grinding wheel support, a grinding wheel rotatably mounted thereon, mechanisms for eflecting intermittent relative transverse and longitudinal movements of said supports for successively grinding a series of portions of a work-piece, a dressing tool mounted independently of said work support, mechanism for eflfecting a relative traversing movement between said dressing device and said grinding wheel, a reversing mechanism for controlling operation of said dressing device, a switch for automatically shifting said reversing mechanism in one direction at the end of said longitudinal movement whereby to initiate the dressing operation, and means responsive to said dresser traverse movement for shifting said reversing echanism in the opposite direction whereby I cause said dressing tool to again pass across the grinding wheel and return to starting position.

27. In a grinding machine, a grinding wheel support, a grinding wheel rotatably mounted thereon, a work support, mechanisms for eflecting intermittent relative transverse and longitudinal movements of said supports for successively grinding a series of portions of a work piece, mechanism including a reversing control for effecting said longitudinal movement in both directions, a dressing tool mounted independently of said work support, mechanism for eflecting relative movement between said dressing device and said grinding wheel, a control device for initiating operation of said dressing mechanism, a member operable in response to said longitudinal movement in one direction for actuating said control device at a predetermined point in said movement, and another member operable in response to said longitudinal movement in the opposite direction for actuating said control device at another predetermined point in said longitudinal movement.

HAROLD E. BAISIGER. RALPH E. PRICE.