US2363559A

US2363559A - Grinding machine and method

Info

Publication number: US2363559A
Application number: US434923A
Authority: US
Inventors: Selnes Alf Kristian
Original assignee: Ex-Cell-O Corp
Current assignee: Ex-Cell-O Corp
Priority date: 1942-03-16
Filing date: 1942-03-16
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

Nov. 28, 1944. K s s emnnme MACHINE AND METHOD W... m L 2:1 Z

Nov. 28, 1944. A. K. SELNES I 2,363,559

GRINDING momma: AND METHOD Filed March 16, 1942 TShets-Sheet 2 v five/afar {gill P11351124 6e Z7286 0 W EFJMA M jforiz gs.

'1: Sheets-Sheet s j ww u Nov. 28.1 1944. A. K SELNES GRINDING MACHINE AND METHOD Filed March 16, 1942 Nov. 28,1944. A. K. S ELNES 2,363,559

' GRINDING MACHINE AND METHOD I I Filed March 16. 1942 M v Jamm e/7* A fzrzlsiwz 6617286 Wei wi 5 4 9 s Ii WJVI/ h 0 2 .0 5 9 v M Nov. 28, 1944. A. K. SELN ES 2,363,559

GRINDING MACHINE AND METHOD I Filed March 16, 1942 7' Sheets-Sheet I02 Dresser Feed Backlash Compensaor Wheel Feed Or/f/cq Select/v39 fzvenz or 7 Shee ts-Sheet Nov. 28, 1944. A. K. SELNES GRINDING MACHINE AND METHOD Filed March 16, 1942 P m Km ow izverzzof iszfaiz allies ffi wvzga Nov. 28, 1944. A. K. SELNE S GRINDING MACHINE AND METHOD Filed March 16, 1942 Sheets-Sheet UNITED STATES PATENT OFFICE GRINDING MACHINE AND METHOD Alf Kristian Selnes, Detroit, Mich, assignor to Ex-Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application March 16, 1942, Serial No. 434,923

20 Claims. (Cl. 51-95) The present invention relates generally to improvements in grinding machines and methods,

and has particular reference to grinding machines, such for example as thread grinders, in

In grinding certain types of work, such as screw elements, the workpiece is commonly translated axially in forward and return directions relatively across the cutting periphery of the grinding which both the grinding wheel and the workpiece wheel, and often a grinding cut is taken in both are rotated and are relatively translated in fordirections of translation so as to avoid an idle reward and return directions axially of the workturn stroke and thereby to save time. For any piece, given direction and rate of relative translation,

I have found that, in the use of grinding mathe direction and speed of rotation of the workchines of the foregoing character, the quality of piece is determined by the hand and lead of the surface finish that is obtained, and the rate at thread to be ground. Therefore, when gri which the stock can be removed without objecduring both forward and return strokes, t e work tionable results, is influenced by the direction of t o t be reversed upon each reversal of rotation of the grinding wheel in'relation to the translation 0 that the grinding Wheel i fOllOW direction of rotation of the workpiece. This re- .15 {the thread lead- This necessarily results in a lation is not always the same for different workpieces to obtain the best operating performance and quality of machining. Workpieces of certain classes can be ground most advantageously while rotating the grinding wheel and the workpiece in opposite directions. The stock is thereby removed in a climb out in which the surfaces of the wheel and the workpiece travel in the same general direction at the point of contact. Included in this category are workpieces-having relatively small diameters, or containing tungsten, or havin a high degree of hardness, such as edge cutting tools, or requiring an uninterrupted cut, as in the relief grinding of taps. However, in grinding workpieces of other classes, such for example as aircraft cylinder barrels, and in general workpieces that have a relatively low degree of hardness or are relatively large in diameter, the best results are obtained by rotating the wheel and the workpiece in the same direction to perform a conventional cut in which the surfaces travel in opposite directions at the point of contact. More particularly, I have found that in grinding large workpieces at desirable speeds and feeds, a climb out results in the exertion of a heavy pressure against the workpiece and attendant springing thereof, in the generation of excessive heat, and

in objectionable discoloration of the ground surface due to burning, whereas a conventional cut permits the removal of the stock at a comparativelyhigh rate without causing discoloration and other objectionable results.

One of the objects of the present invention, therefore, is to provide a novel grinding machine wherein the direction of rotation of the grinding wheel relative to that of the work is subject to convenient selective control at the will T of the operator so that the grinding operation will be performed in a manner best suited to the particular requirements of each workpiece.

versal of the relative rotation between the grinding wheel and the workpiece if the wheel is rotated constantly in one direction as in conven-- tional practice;

Another object of the present invention, therefore, is to provide a novel grinding machine and method of grinding in which a predetermined relative rotation between the grinding wheel and the workpiece is maintained regardless of reversal of the work rotation.

A more particular object i to provide a novel thread grinding machine and method in which the rotation of the grinding wheel is automatically reversed upon reversal of translation and rotation of the workpiece.

p A further object is to provide a new and improved grinding machine of the foregoing character in which the workpiece is caused to dwell at the end of each cutting stroke to permit deceleration in the existing direction and then acceleration to normal speed in the reverse direction of the grinding wheel before initiating the reverse cutting stroke.

Another object is to provide a novelgrinding machine and method in which the rotation of the grinding wheel is automatically reversed upon reversal of the work rotation while the wheel is out of contact with the workpiece.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings, 1 Figure 1 is a front elevational view of a grinding machine embodying features of my invention.

Fig. 2 is a plan view of the machine.

Fig. 3 is a diagrammatic representation of the electrical drive andcontrol system used in the machine.

Fig. 4 is a front elevational view of a modified form of grinding machine embodying the invention.

,Fig. is a detail view of the feed mechanism for the grinding wheel in the machine of Fig. 4. Fig. 6 is a diagrammatic representation of the hydraulic system used in the machine of Fig. 4. Fig. 7 is a diagrammatic representation of the electrical drive and control system used in the I machine of Fig. 4.

Figs. 8 and 9 are diagrammatic views illustrating the method of the invention respectively, with 1 the word and the grinding wheel rotating in the same direction, and in opposite directions.

Machine structure bodiment, comprises a base It! supporting a horizontally translatable work slide or table II. A headstock I2 is mounted on one end of the base I0, and includes a work drive shaft I3 which is rotatably anchored at its outer end through a bearing bracket I4 to the table II and which is adapted to be rotated and simultaneously translated axially in timed relation to the rotation to translate the table II. Supported in the outer end of the shaft I3 is a live center I5. A tailstock I6 is adjustably mounted on the table I I, and has a dead center I1 in axial alinement with the 'center I5. The workpiece W to be ground is rotat ably supported between the centers I5 and I1.

The drive for the work shaft I3 includes a reversible two-speed electric motor I8 mounted on one side of the base I0, and connected through a belt I9 to mechanism (not shown) within the headstock I2 for rotating the shaft and for translating the shaft axially under the control of a master lead screw (not shown). Upon rotation of the motor I8 in one direction, the shaft I3 will be driven to translate the table II to the right in an initial or forward cutting stroke, and the workpiece W will be rotated in a predetermined initial direction in timed relation to the translation as determined by the hand and lead of the screw thread to be ground. Upon rotation of the motor I8 in-the opposite direction, the drive to the shaft I3 will be reversed to trans-. late the table to the left in a return stroke and to rotate the workpiece W in the reverse direction.

A grinding wheel assembl is mounted at the rear of the work table II on a cross slide 2[ supported on the base In for movement transversely of the axis of the workpiece W. The assembly 20 includes a spindle 22 supporting a grinding wheel 23 and adapted to be driven through a belt 24 from a reversible electric motor 25. The slide 2| is adapted to be operatedby a feed mechanism (not shown) to advance the grinding wheel incrementally toward the work for successive cuts to the desired depth, and to quickly retract the wheelfrom the work, if desired, at the end of each cutting stroke. The feed mechanism includes a hand wheel 26 and a retract lever 21 for controlling the setting of the grinding wheel, and a wheel 28 for controlling the size setting.

Coolant from a tank 29 is adapted to be supplied, by a pump 30 through a duct 3| to the grinding zone. The pump is driven by an electric motor 32.

The various motors I8, 25 and 32 are connected in an electric system and are adapted to be operated in a predetermined manner to obtain an automatic machine cycle. A number of manually operable switches are included in the electrical control, and are mounted on a panel 33 adjacent the operator's station at the front of the machine.

Electrical control circuits and operation Current is supplied for the various electric mo:

,tors I8, 25 and 32 from three main supply lines L1, L2 and L3 adapted to be connected to a suitable source of three-phase alternating current.

Two low voltage supply lines L4 and L5 for the control circuits proper are connected through a transformer 40 to the lines L1 and L3.

The coolant pump motor 32 is adapted to be connected to the main supply lines L1, L2 and L: by a starter having a set of normally open contacts P1 adapted to be closed upon excitation of a relay coil P.

The wheel drive motor 25 is adapted to be connected to the main supply lines L1, L2 and L3, to rotate the spindle 22 selectively in either direction, by a starter having two parallel sets of normally open contacts GFi and GR/l adapted to be alternately closed respectively upon selective excitation'of relay coils GF and GR.- Thus, when the coil GF is excited, the motor 25 will rotate in a forward direction, and when the coil GR isv open contacts WF1 and WR]. adapted to be alternately closed upon selective excitation ofrelay coils WF and WR to translate and rotate the workpiece W alternately in forward and reverse directions. The starter also includes two additional parallel sets of normally open contacts S1 and F1 connected in series with the direction con-'- trol contacts W1 and WRl, and adapted to be closed selectively to control the speed of the motor I8. The contacts Si and F1 are controlled respectively by two relay coils S and F adapted to be connected selectively across the supply lines L and L5 under the control of two selector switches S2 and S3 and upon closing either of two contacts WF: and WR2 under the control of the coils WF and WR. When the coil WF is excited, the contacts WFz will close a circuit through the switch S2 either for the coil S or the coil F depending on the adjustment of the switch. Similarly, when the coil WR is excited, the contacts WRz will close a circuit through the switch S3 either for the coil S or the coil F depending on the adjustment of this switch. Consequently, by selective adjustment, the motor I8 can be driven at either slow or fast speed in either direction as desired. Where a grinding out is taken in both directions of work translation, both switches S2 and S3 are adjusted to close the circuit for the coil S, and the coil F is never excited, so that the motor I8 is driven at a slow speed in both directions of rotation.

The rotation of the motors I8 and 2-5 is adapted to be reversed automatically at each endof the work translation. The direction of rotation is under the control of atwo-position limit switch 151 adapted for actuation by the table II alternately into opposite stations. During the forward movement of the table II, the limit switch LS1 serves to complete a circuit across the supply lines L4 and L5 for a relay coil U. During the reverse direction, the limit switch 1S1 serves to complete a circuit for a relay coil L. The relay coils U and L form part of a latch relay LR which controls contacts LR1 and LR: in the circuits for the coils GF and GR and contacts LR: and LE4 in the circuits for the coils WI? and WR. When the coil U is excited, the contacts LRi and LR: are closed and the contacts LR: and LR4 are opened. When the coil L is excited, the contacts LRi and LR: are opened and the'contacts LR: and LR4 are closed. The contacts remain closed in each instance even though the coil in control thereof is deenergized by opening the switch LS1 until the companion coil of the relay LR is energized.

Excitation of the coils P, GF and GR is under the control of a normally open starting push button switch S and a normally closed stopping push button switch S5. Interposed in the circuits for the coils GF and GR, in series with th contacts LR1 and LR: is a manual selector switch So which is adjustable to control the rotation of the grinding wheel 23 in relation to the rotation of the workpiece W. The switch S6 is available to reverse the connections of the coils GF and GR in the circuits, so that in one station of theswitch the grinding wheel and the workpiece will rotate in the sam direction as illustrated in Fig. 8 to perform a conventional cut, and in the other station of the switch the wheel and the work will rotate in opposite directions as shown in Fig. 9 to perform a climb out. If the master lead screw in the headstock l2 should ,be changed so as to have an opposite hand lead, it would be necessary to reverse the position of the switch S6 in order to retain the desired relative rotation between the wheel and the workpiece.

Also interposed in the circuits for the coils GF and GR is a manual selector switch S? which in the station shown serves to place the coils under the selective control of the limit switch LS1, and which, if adjusted into the opposed station, would connect the coil GF across the switch S5 to effect rotation of the grinding wheel 23 constantly in one direction regardless of reversal of the table I l and reversal of rotation of the workpiece W at each end of the table travel.

Assuming that the switch S1 is adjusted to condition the system for automatic reversal of the grinding wheel upon reversal of the work rotation, and that the switch S6 isadjusted to establish the desired direction of rotation of the wheel in relation to that of the work, operation is instituted by momentarily closing the switch S4. This completes a circuit'for the coil P from the supply line L4 through th coil P, a line 4|, the switch S4, a line 42, the switch S5, and a line 43 to the supply line L5. Interposed in the line 43 is a master stop switch S8 and a plurality of overload contacts 44. Excitation of the coil P serves to close the contacts P1 to institute'operation of the coolant motor 32, and also to close contacts P2 to establish a holding circuit across the switch S4.

With the limit switch 181 in the position shown, the contacts LRi are closed and the contacts LR: are opened. Consequently, closing of the switch S4 serves also to establish a circuit for the coil GF from the supply line L; through the coil, a line 45, the switch $6, a. line 46, the contacts LRi, a line 41, and the switch S1 to the line 4|. Exci- GFi to institute rotation of the wheel drive motor in a forward direction. If the switch S6 had been adjusted into the opposed sation, the coil GR instead of the coil GF would have been energized to institute rotation of the motor 25 initially in the reverse direction, the circuit leading from the supply line L4 through the coil GR, a line 48, and the switch S6 to the line 46. If the switch S1 had been adjusted into the opposed station, the circuit for the coil GF would have been completed from the line 45 through a shunt line49 across the switch S6 to the line 4|.

Upon reversal of the-switch LS1 at the end of the table movement in the forward direction, the coil U is deenergized and the coil L is energized, thereby opening the contacts LRi' to interrupt the circuit for the 'coil GF and closing the contacts LR: to establishthe circuit for the coil GR. Excitation of the coil GR serves to close the starter contacts GR1, thereby reversing the direction of rotation of the motor 25 and consequently-the rotation of the grinding vwheel 23.

Operation of the motor 18 for translatin and rotating the workpiece W reversibly is instituted by momentarily closing a manual switch S9. This the line 50. Excitation of the coil RA serves to close contacts RA1 to complete a holding circuit for the coils TR and RA across the switch S9.

The contacts RD and RE1 are adapted to be opened respectively upon excitation of two relay coils RD and RE.

Excitation of the timing relay TR serves to close a switch TRi, thereby connecting a line 52 from the starter coils WF and WR to the line 43.

I Two normally open contacts RD2 and REz are LRa, the line 52 and the switch TR1 to the line tation of the coil GF serves to close the contacts 75 connected in series in a shunt line 53 across the switch TRl. Since the contacts LRa are closed,

the switch TRi will complete a circuit for the coil WF from the supply line L4, through the coil, normally closed interlock contacts WR: controlled by the coil WR, a line 54, the contacts 43. The coil RD, being connected in parallel with the coil WF, is also excited, and opens the contacts RDi'and closes contacts RDz and RDa. Excitation of the coil WF serves to open interlock contacts WFa in the circuit for the coil WR, and

to close the contacts WF1 and WF2. Closing of the contacts WFz serves to effect excitation of the coil S to close the contacts S1. Consequently, operation of the motor [8 is instituted to rotate the workpiece W in a forward direction, as indicated by the full line arrow in Figs. 8 and 9, and to advance the table II in a forward direction. The grinding wheel 23 is also rotated in a forward direction, as indicated by the full line arrow in Fig. 8, so that the wheel and the. work are rotated in the same direction and hence are moving oppositely at the point of contact to produce a conventional cut.

During the forward operation of the motor l8,

a plugging switch 55 is actuated to open contacts PR and to close contacts PF. This establishes a circuit for the coilRE from the supply line L4 through the coil, a line 56, normally open contacts WF4 which are closed at this time by the coil WF, and the contacts PF to 'the supply line L5. The coil RE serves to close contacts RE:

across the contacts WF4'; also, to open the contacts RE1 and to close the contacts REz. Consequently at this time, the coil TR is deenergized since the contacts RDi and REl are both open, and causes the switch TRi to open. However, the starter circuit is maintained since the contacts RD: and R132 are both closed across the switch TRi.

At the end of the forward cut, the switch LS1 is actuated by the table II to interrupt the circuit for the coil U and to complete the circuit for the coil L, 'of the latch relay LR. As a result, the contacts LRl are opened and the contacts LR2 are closed to effect reversal of the motor 25 so as to rotate the grinding wheel 23 in the direction indicated by the dotted arrow in Fig. 8. At the same time, the contacts LR; are opened to break the circuit for the starter coil WF, thereby eife'cting opening of the contacts WFi-and WFz to interrupt the forward drive motor circuit. The circuit for the coil RD also is broken so that the contacts RDi are again closed and the contacts RDz are opened. The contacts LRA also are closed to condition the circuit for the coil WR from the line L4 through the coil, the contacts WFa which are now closed, the line 56, and the contacts LR4 to the line 52, but the circuit is not completed to the line 43 since the contacts RD2 are open. However, a plugging circuit for the coil WR is completed from the line L4 through the coil, the contacts WFa, the line 56, the contacts REs, and the plugging contacts PF to the line L5. Excitation of the coil WR serves to close the contacts WRI and WRz, and the coil break the contacts PF, thereby interrupting the exciting circuit for the coils RE and WR. De-

energization of the coil RE'opens the contacts REz and recloses the contacts REi.

Since both contacts RDi and REI are again closed, the circuit through the starting relay TR is reestablished across the manual starting switch S9 since the coil RA has not been deenergized and has maintained the sealing circuit throughthe contacts RA1. Excitation of the timing relay TR again closes the switch "R1 to establish this time a circuit for the coil WR through the contacts LR4. Excitation of the coil WR serves to open the interlock contacts We in the circuit for the coil WF and to close the contacts WRi and WRz, thereby establishing the reverse drive circuit for the motor I8. The coil RE, being connected in parallel with the coil WR through the line 56, is also excited and serves to close the contacts RE2 and RE3 and to open the contacts RE]. During reverse operation, the plugging contacts PR are closed to complete a circuit for the coil RD through the contacts WR4. Excitation of the coil RD serves to close the contacts RDz and BBQ and to open the contacts RD1. Since the contacts R131 and REl are now both open, the coil TR is deenergized to open the switch TRI, but the circuit for the coils RE and WR is maintained through the contacts RD2 and RE2.

A cutting stroke is now obtained during the rei for' another cut in the forward direction, orthe turn movement of the slide H. During this re- 75 operation can be stopped by opening the switch It will be noted that at each end of the table travel, the reversal of the table drive is delayed to provide a dwell during which the grinding wheel 23 is decelerated in the prevailing direction of rotation, and then accelerated to full speed in the opposed direction of rotation. In other words, the workpiece W is not translated while reversal of the grinding wheel 23 is being effected.

In some instances, it may be desirable to leave the grinding wheel in contact with the work while efiecting reversal so as to loosen any glazed grains and to sharpen the surface of the wheel. However; in other instances, it is preferable to effect reversal of the grinding wheel 23 while out of contact with or retracted from the workpiece W. To this end, a solenoid RC is adapted to be connected across the main supply lines 1 and L3 by two contacts RB1 and RB: under the control of a relay coil RB connected across the lines L4 and 52. When the starting circuit for either of the coils W? and WR is established across the switch TR1, the coil RB will be excited to close the contacts RBi and BB2. As a result, the solenoid RC will be actuated to advance the grinding wheel 23 into operative position. Upon interrupting the circuit from the line 52 to the line 43 at each end of the table travel, the coil RB is deenergized to open the contacts RBI and RBz. Thereupon, the solenoid RC is disconnected to effect retraction of the grinding wheel 23 from the workpiece W and it is in this retracted position that the rotation of the grinding wheel is reversed.

Hydraulic machine structure work, and has a combined hydraulic and electric control. Apart from the specific control, the machine is substantially like that disclosed in United States Letters Patent No. 2,251,961. issued August 12, 1941, to Ira J. Snader, to Which reference may be had for a more detailed understanding of the mechanical structure.

Referr'ng to Figs. 4 and 5, the machine comprises a base 60, and a work table 6| reciprocable thereon. A headstock 62 is supported on one end of the table 6|, and encloses a work spindle 63 having a live center 64. Adjustably mounted on the table 6| in spaced relation to the headstock 62 is a tailstock 65 having a-dead center 66 in axial alinement with the center 64. It will be understood that the workpiece (not shown) is adapted to be operably supported by the centers 64 and 66.

The work spindle 63 is adapted to be driven by a reversible, variable speed rotary hydraulic motor 61 mounted within the headstock 62 andconnected through a belt 68 to a mechanical drive mechanism 69. The work table 6| is adapted to be translated in opposite directions and in timed relation to the rotation of the spindle 63 by a nut and screw drive (not shown) within the base and connected to the spindle drive mechanism It. Pressure fluid for operating the motor 01 is supplied by a pump I0 mounted at the rear of the base 60, and driven by an electric motor 1 I One end of the nut and screw drive for the table 6| is connected to a backlash compensator I2 having a hydraulic cylinder I3 and an actuating piston I4 anchored to a shaft extension 15 of the screw,

Mounted on the rear of the base 60 is a grinding wheel assembly I6 including a spindle structure I'I driven by a reversible electric motor 18 and supportin a grinding wheel 79. The spindle structure 11 is mounted on a cradle 80 on a cross slide (not shown) movable toward the workpiece to feed the grinding wheel 10 step by step into the work to final depth in timed relation to successive cutting strokes of the table 6|. The cross feed is actuated a predetermined distance at each reversal of the table 6|, and includes a feed screw 8| operatively connected to the cross slide and provided with a hand wheel 82.

A hydraulic feed mechanism is provided for automatically actuating the screw 8i. In the present instance, the feed mechanism (see Fig. is operated by a hydraulic actuator 83 having a cylinder 84 inwhich a double end piston 85 is 'reciprocable. The piston 85 is formed intermediate its ends with a longitudinal gear rack 86 meshing with a pinion 81 and adapted in each stroke to rotate the latter through one complete revo-' lution. A disk 08 is fixed for rotation with the pinion 81, and carries an eccentric crank pin 89 connected to one end of an adjustable rod 90. The other end of the rod 90 is formed with a gear rack 9| meshing with a pinion 92 in turn in engagement with a gear segment 93. A feed pawl 94 is revolvable'with the segment 93, and is arranged for engagement with a ratchet 95 operatively connected to the cross feed screw ill. The depth of cut during each grinding stroke is controlled by an adjustable shield 95 arranged to lift the pawl from the ratchet 95 during a portion of each pawl stroke.

Associated with the cross feed mechanism is a hydraulic actuator 91 available to locate the grinding wheel 19 in operative position during the grinding cut, and on occasion to retract the wheel from the work. The actuator 91 comprises a cylinder 98 enclosing a reciprocator piston 99.

Associated with the grinding wheel I9 is a suitable dressing mechanism having one or more tools (not shown) movable by a reversible electric motor I00 back and forth in a dressing cycle across, the cutting periphery of the grinding wheel 19, and having a hydraulic actuator 'IIlI for advancing the tools toward the wheel in a dressing feed. The actuator IOI comprises a cylinder I02 and an operating" piston I03 reciprocaole therein.

Coolant is adapted to be supplied to the grinding zone through a duct I04 from a pump not shown) driven by an electric motor I05.

. Hydraulic system The machine comprises a hydraulic control.

The pump 10 has an inlet line Illltaking fluid from a supply tank I01, and has a pressure delivery line I08 connected to a main control valve I09 for the hydraulic motor 61. The pump 10 is of the variable delivery type, such for example as disclosed in a copending application Serial No. 147,178 filed June 9, 1937, by Ira J. Snader and Max-A. Mathys, and has a volume control line IIO for varying the displacement in accordance with the requirements of the motor Bl.

The main valve I09 is of the three-position t pe, and has a plunger III normally urged by spring pressure into the intermediate position. The ends of the valve plunger III are operatively connected respectively to two operating solenoids S01 and S02. Upon excitation of the solenoid 801, the plunger III will be shifted into the left end position to connect the pressure line I08 to a line II 2 leading to one side of the hydraulic motor 61 and to connect a line I I3 from the other I side of the motor to an exhaust line II4. Upon excitation of the solenoid S02, the plunger III will be shifted into the opposite end position to reverse the connections for the lines II?! and II 3, thereby effecting reversal of the motor 61. In the neutral position, which obtains when both solenoids are deenergized, the plunger II I blocks both lines 2 and I I3 to stop the motor 61. The valve plunger III also serves when in either end position to connect the pump control line IIO to the exhaust line H4, and when in neutral position to connect the control line through a passage I I5 to the pressure line I 08;. When the exhaust pressure is relatively low, the pump I0 will deliver a correspondingly large volumeof fluid to operate the motor 61 at a rapid rate. When the exhaust pressure is relatively high, the pump 10 will deliver a correspondingly small volume of fluid to operate the motor 61 at a slow rate. When the pressure line I08 is connected to the control line IIO, the pump delivery is at a minimum and merely enough to maintain the normal working pressure.

The displacement of the pump 10, and hence the operating speed of the motor 61., therefore is under the control of the exhaust pressure. To effect desired variations in the operating speed of the hydraulic motor 61, a plurality of adjus able restricted flow orifices H6, H1 and H8, discharging through a drain line II9 to the tank I01, are arranged for selective connection with.

the exhaust line II4 under the control of an orifice selection valve I20.

The orifice selection valve I20 comprises a shiftable three-position plunger I2I operatively connected at opposite ends respectively to two actuating solenoids S03 and S04, and normally urged into neutral position by spring pressure. In the neutral position of the plunger IZI, the exhaust line H4 is connected through a passage I22 in the plunger to the orifice III. Upon excitation of the solenoid S03, the plunger I2I is shifted into the left end position to connect the exhaust line II4 to the orifice 6. Upon excitation of the solenoid S04, the plunger I2I is shifted into the right end position to connect the exhaust line I I4 to the orifice II8. By selective adjustment of the orifice restrictions, different back pressures can be obtained in the exhaust line II4 so that the work table Bl can be. translated, for example,

with a rapid approach, a slow cutting rate in one direction, and the same or a different slow cutting rate in the opposite direction.

A series of auxiliary controlvalves I23, I24,

I25 and I26 are provided for respectively controlling the actuators I2, 63, 91 and IN. Each of these valves has a pressure connection with an auxiliary pressure line I21 supplied with fluid through a pressure reducing valve I28 from the main pressure line I08. The. valve I28 is operative to maintain a substantially constant predetermined low pressure in the line IZ'L I n the event of a pressure drop in the line I21, the valve I28 will admit additional make-up fluid thereto from the line I08. In the event of a pressure rise in the line I21, the valve I28 will spill excess fluid therefrom to the drain line H9. The backlash compensator valve I23 is of the two-position type, and has a plunger I29 connected at opposite ends respectively to two actuating solenoids S and $06. In one position,

the plunger I29 will connect the pressure line I2'I through a line I30 to one end of the cylinder I3. In the other end position, the plunger I29 will connect the line I21 through a line I3I to the other end of the cylinder I3. In each posi- 9 tion of the valve I23, the line receiving fluid displaced by the piston 14 is connected to the drain line II9.

The wheel feed control valve I24 is also of the two-position type, and has a plunger I32 connected at opposite ends respectively to two actuating solenoids S01 and S09. Upon excitation of the solenoid S01, the plunger I32 will be shifted into one end position to connect the pressure line I21 through a line I33 to one end of the wheel feed cylinder 84 and to connect the other end of the cylinder through a line I34 to the drain line II9. Upon excitation of the solenoid S08, the

connections for the lines I33 and I34 will be reversed.

The retract valve I.25 is of the two-position type, and has a plunger I35 normally located ina stop position by a spring I36 to connect the pressure line I2'I through a line I31 to one end of the retract cylinder 98, and to connect the other end of the cylinder through a line I38 to the drain line H9. The plunger I35 is connected to an actuating solenoid S09 which, when energized, will shift the plunger against the action of the spring I 36 to reverse the connections for the lines I31 and I 38. When the solenoid S09 is energized, the grinding wheel I9 is advanced into cutting position, and when the solenoid is deenergized, the wheel is retracted from the work.

The dresser feed valve I26 is similar to the valve I25, and comprises a plunger I39 normally held in a stop position by a spring I40 to connect the pressure line I21 through a line I4I to one end of the dresser feed cylinder I02, and to connect the other end of the cylinder through a line I42 to the drain line H9. The plunger I39 is connected to an actuating solenoid S019 which when energized will shift the plunger to reverse the connections for the lines MI and I42.

Electrical control circuits and operation The grinding wheel motor I8 and the coolant pump motor I05 correspond to the motors 25 and 32 of Fig, 3. These motors of the two machines across the switch SwI.

over a master stop switch Sw2. Energization of the coil H serves to close holding contacts H2 The contacts H. are located in the line L5 so that if the pump motor II is not conditioned for operation, the entire system is disabled.

To institute the machine cycle, a manual switch S103 is closed momentarily to connect'a relay coil C over the normally closed stop switch S204 across the main supply lines L4 and L5. Excitation of the,

coil C closes contacts C1, C2 and C3. The contacts C2 serve to connect a relay coil D over limit switch LS5 across the supply lines L4 and L5. Excitation of the coil D closes contacts D1, D2 and D3 and opens contacts D4 and D5. Contacts C1 and D1 establish a holding circuit across the switch Sw3 for the coils C and D, and the contacts D2 establish an additional holding circuit across the contacts C2 for the coil D.

Since contacts U1 have been closed by the coil U, while contacts L1 remain open, closing of the contacts Ca and D3 serves to connect the solenoid S01 across the supply lines L4 and L5, thereby adjusting the valve I24 to impart a forward feed to the grinding wheel. If the coil L has been energized instead of the coil U, the solenoid S09 would have been energized by closing the con-' tacts L1 to efiect the approach feed.

The retract solenoid S09 is adapted to be connected in parallel with the selected one of the starting solenoids S01 and S0: for the hydraulic motor 61. A selector switch Sw5 is adjustable to effect energization of the solenoid S09 either during the forward travel or during the return travel of the work table, or during the travel of the table in both directions, with merely a temporary tool retraction at the end of each stroke. The switch Sw5 controls the connection of the solenoid S09 through two parallel contacts U2 and U9 adapted to be actuated by the coil U. The contacts U2 are normally open and the contacts U3 are normally closed. In one adjustment of the switch Sw5, both of these contacts are interposed in the circuit so that the solenoid S09 will be energized regardless of whether or not the coil U is energized or deenergized. In another adjustment of the switch 3105, only the contacts U: are interposed in the circuit, and in this event the solenoid S9 is deenergized during the forward travel and energized during the return travel of the table. In a third adjustment of the switch Sw5, only the contacts U2 are interposed in the circuit, and in thisevent the solenoid S09 is energized during the forward travel and deenergized during the return travel of the table.

At the end of the cross feed movement, a cam lobe I43 on the disk 88 (Fig. 5) serves to close a limit switch LS4, thereby completing a circuit for a relay coil E and the solenoids S01 and $06, from the line L4 through interlock contacts F1, the contacts U4 now closed by the coil U, and the switch LS4 to the line L5. Simultaneously; the

circuit is closed for the retract solenoid S09 to tion-valve I20 is adjusted to connect the orifice v I I6 in the exhaust line I I4.

At the end of the approach, the table 6| closes a limit switch LS9 to energize a relay coil G. Ex-

asoaue drive means for rotating said spindles, said drive citation of the coil G serves to close contacts (31 in the circuit for the solenoid S02, and to open the contacts G2, thereby. eifecting adjustment of the valve I20 into neutral to connect the feed orifice H1 in the exhaust line H4. The motor 61 now operates in the forward direction at a relatively low feed rate in accordance with the setting of the orifice.

.At the end of the grinding stroke in the forward direction, the limit switch LSris actuated to effect deenergization of the relay coil U and energization of the relay 0011 L. 'I'hereupon, the contacts U1, U2, U4 are opened, and the contacts U3 and L1 to L4 are closed. This closes a circuit for the coil F and the solenoids S02 and $05, from the line L; through interlock contacts E1, contacts L2 and contacts G1 to the switch. LS4.

, Excitation of the solenoid S02 serves to reverse the valve I09 to reverse the direction of rotation of the motor 61, and excitation of the solenoid S05 serves to reverse the valve l23to re verse the backlash compensator. Also, the solenoid S07 is deenergized and the solenoid SOa is energized to impart a forward feed increment to the grinding wheel. Upon initiation of the feed increment, the limit switch LS4 is opened to interrupt the reversal of the table 6| until the feed movement is completed. During the dwell occasioned by the wheel feed. the solenoid S09 is deenergized to retract the wheel and the wheel motor I8 is reversed.

The grinding wheel may be dressed at any convenient time. To start the dressing operation, the hand switch SwB is closed, thereby completing a circuit for the solenoid S010 and the relay coil K through the normally closed stopswitch Sw'l.

The solenoid SO10 actuates the valve I26 to impart a forward feed of the'dressing mechanism toward the grinding wheel. The'ccil K closes holding contacts K1 across the switch SwB.

Atthe, end of the dresser feed, a limit switch LS3 is closed to complete a circuit for a coil DF, from the main line L; through limit switch LS6, the coil DF, normally closed interlock contacts DB2, the switch LS3, and the switch Swl to the main line L5. Excitation of the coil DF serves to close starter contacts DF1 in the circuits for the dresser motor lllll, thereby energizing a brake solenoid I to release the motor brake and causing the motor to operate in a forward direction. At the end of the forward movement, the limit switch LS6 is opened. and the limit switch LS1 is means including control means for reversing the rotation of said grinding spindle, whereby said grinding wheel may be caused to rotate selectively in either the same or opposite direction relative to the rotation of the workpiece.

2. A grinding machine comprising, in combination, means including a work spindle for supporting a workpiece for rotation about afixed axis, drive means operable to rotate the workpiece selectively in either direction, means for upporting said spindle for translation in timed closed to deenergize the coil DF and energize a coil DR. The coil DR opens contacts DR: to open the circuit for the solenoid SO10 so as to impart an additional dresser feed, and closes the motor contacts DRl to reverse the rotation of the dresser motor. I00. At the end of the cycle, the switch S101 is opened to interrupt the dressing operation.

The work table continues to reciprocate back and forth to take successive grinding cut-s until the work is ground to the desired depth. Thereeral cutting engagement with the workpiece, and II relation to the spindle rotation, a grinding spindle having a rotary grinding wheel arranged for peripheral cutting engagement with the workpiece, drive means for rotating said grinding spindle, and control means for automatically reversing said lastmentioned drive means to effect reversal of the rotation of said grinding spindle upon reversal of the translation and rotation of said work spindle, said control means including selector mean-s for determining the direction of rotation of said grinding spindle relative to the direction of rotation of said work spindle.

3. A grinding machine comprising, in combination, means including a work spindle for supporting a workpiece for rotation about a predetermined axis, drive means for rotating said workpiece selectively in either direction, means for supporting said spindle for translation in timed relation to the spindle rotation, a grinding spindle having a grinding wheel mounted for peripheral cutting engagement with the workpiece, reversible drive means for rotating said grinding spindle, and control means selectively adjustable to effect rotation of said grinding wheel constantly in one direction or the other or to efiect automatic reversal of the rotation of said grinding wheel upon reversal of the translation and rotation of the workpiece.

4. A grinding machine comprising, in combination, means supporting a workpiece for'rotation,'drive means for rotating said workpiece selectively in either direction, a grinding spindle having a grinding wheel mounted for cutting en-.

gagement with the workpiece, reversible drive means for rotating said spindle, and control means selectively adjustable to effect rotation of said grinding wheel in one direction or the other relative to the rotation of the workpiece, and operable to effect automatic reversal of the rotation of said grinding, wheel upon reversal of the rotation of the workpiece. I

5. A method of grinding rotary workpieces with a rotary grinding wheel which consists in positively rotating the workpiece in a predetermined initial direction and simultaneously rotating the grinding wheel in a predetermined initial direction relative to the workpiece with said grinding wheel and workpiece in peripheral cutting engagement. translating said workpiece axially in a given direction in timed relation to the rotation of said workpiece, reversing the translation and rotation of the workpiece, and automatically reversing the rotation of the grinding wheel upon reversal of rotation of the workpiece, whereby to maintain the preselected rotary cutting relationially in a given direction in timed relation to the rotation of said workpiece, reversing the translation and rotation of'the workpiece, and automatically reversing the rotation of the grinding wheel upon reversal of rotation of the workpiece, whereby to maintain the preselected rotary cutting relationship between said wheel and the workpiece.

7. A method of grinding rotary workpieces with a rotary grinding wheel which consists in positively rotating the workpiece in a predetermined initial direction and simultaneously rotating the grinding wheel in a direction opposite to the rotation of the workpiece with said grinding wheel and workpiece in peripheral cutting engagement, translating said workpiece axially in a given direction in timed relation to the rotation of said workpiece, reversing the translation and rotation of the workpiece, and automatically reversing the rotation of the grinding wheel upon reversal of rotation of the workpiece, whereby to maintain the preselected rotary cutting relationship between said wheel and the workpiece.

8. A grinding machine comprising, in combination, a base, a spindle mounted on said base and supporting a rotary grinding wheel, a reversible electric motor for driving said spindle, a work table for supporting a rotary workpiece and mounted on said base for reciprocation axially of the workpiece through cutting engagement with the grinding wheel, means including a reversible electric motor for translating said table and for rotating the workpiece in timed relation to the translation, and electric control means operable by said table at one end of said translation to efiect reversal of both of said motors, whereby to maintain a preselected relative rotation between said grinding wheel and the workpiece during rotation of the workpiece in the initial direction and subsequent rotation of the workpiece in the reverse direction respectively for the forward and return cutting strokes of said table.

9. A grinding machine comprising, in combione direction or the other relative to the direction nation, a base, a spindle mounted on said base and supporting a rotary grinding wheel, a reversible drive means for said spindle, a work table for supporting a rotary workpiece and mounted on said base for reciprocation axially of the workpiece through cutting engagement With the grind ing wheel, reversible drive means for translating said table and for rotating the workpiecein timed relation to the translation, and control means operable by said table at one end of said translation to efiect reversal of both of said drive means, whereby to maintain a preselected relative rotation between said grinding wheel and the workpiece during rotation of the workpiece in the initial direction and subsequent rotation of the workpiece in the reverse direction respectively for the forward and return cutting strokes of said table.

10. A grinding machine comprising, in combination, means for supporting a workpiece for timed rotation and translation in forward and return directions, a spindle supporting a grinding wheel mounted for cutting engagement with said workpiece, and means automatically operable upon translation of said workpiece into a predetermined position to effect concurrent reversal in the rotation of the workpiece and said grinding wheel.

ll. A'grinding machine'comprising, in combination, means supporting a workpiece for rotation and for translation in timed relation to the rotation, drive means for said workpiece automatically operable to effect reversal of said translation of rotation of the workpiece and operable to maintain the preselected relative rotation between saidgrinding wheel and the workpiece regardless of reversal of rotation of the workpiece.

12. A grinding machine comprising, in combination, means supporting a workpiece for rotation and for translallon in timed relation to the rotation, drive means for said workpiece automatically operable at a predetermined point in said translation to effect reversal of said translation after a. dwell period and a reversal of rotation of the workpiece during said period, a grinding spindle supporting a grinding wheel for cutting engagement with the workpiece in both directions of translation of the workpiece, drive means for rotating said spindle, and control means for said last mentioned drive means automatically operable during said dwell period to effect reversal of rotation of said grinding wheel.

13. A grinding machine comprising, in combination, means supporting a workpiece for rotation and for translation in timed relation to the rotation, drive means for said workpiece automatically operable to effect reversal of said translation and timed reversal of rotation of the workpiece, a grinding spindle supporting a grinding wheel for cutting engagement with the workpiece in both directions of translation of the workpiece, drive means for rotating said spindle, and control means for said drive means automatically operable upon reversal of said work translation and rotation to separate said wheel temporarily from the workpiece and during such separation to reverse the rotation of said wheel.

14. A grinding machine comprising, in combiting engagement with the workpiece in both directions of translation of the workpiece, drive means for rotating said spindle, and control means for,

said drive means automatically operable during said dwell period to separate said wheel temporarily from the workpiece and during such separation to reverse the rotation of said wheel.

15. A method of grinding rotary workpieces comprising translating the workpiece axiall in an initial direction and positively rotating the workpiece in timed relation to the translation in an initial direction, rotating the grinding wheel in a predetermined initial direction while in peripheral cutting engagement with the workpiece during the initial cutting stroke, stopping the translation of the workpiece with a dwell at the end of said' translation in the initial direction, reversing the direction of rotation of the workpiece and of said grinding wheel during said the grinding wheel.

16. A method of grinding rotary workpieces comprising translating the workpiece axially in aseacce an initial direction and rotating the workpiece in timed relation to the translation in an initial di. rection, rotating the grinding wheel in a predetermined initial direction while in engagement with the workpiece during the initial cutting stroke, stopping the translation of the workpiece with a dwell at the end of said translation in the initial direction, retracting said grinding wheel from the workpiece during said 'dwell, reversing the direction of rotation of the workpiece and of said grinding wheel during said dwell, returning said grinding wheel into cutting position, and translating the workpiece axially in a return stroke through cutting engagement with the grinding wheel.

17. A method of grinding rotary workpieces comprising translating the workpiece axially in an initial direction and rotating the workpiece in timed relation to the translation in an initia1 direction, rotating the grinding wheel in a predetermined initial direction while in engagement with the workpiece, reversing the direction of rotation of the workpiece and of said grinding wheel at the end of said initial translation, and then translating the workpiece axially in a return direction through cutting engagement with the grinding wheel. I

18. A method of grinding rotary workpieces comprising translating the workpiece axially in an initial direction and rotating the workpiece in timed relation to the translation in an initial direction, rotating the grinding wheel in a predetermined initial direction while in engagement with the workpiece, automatically reversing the 19. A grinding machine comprising, in combin ation, means for supporting a workpiece for timed rotation-and translation in forward and return directions, a spindle for supporting a grinding wheel mounted for cutting engagement with the workpiece, and control means automatically operable upon translation of said workpiece into a predetermined position to effect reversal in the rotation of both the workpiece and the grinding wheel, said control means including manual means selectively available at will to cause said wheel to rotate either in the same direction or the opposite direction relative to the direction of rotation of the workpiece.

20. A grinding machine comprising, in combin-' ation, means for supporting a workpiece for timed rotation and translation in forward and return directions, drive means including a reversible hydraulic motor for said workpiece and being automatically operated to effect reversal of said translation and timed reversal of the rotation of said workpiece, a spindle supporting a grinding wheel mounted for cutting engagement with said workpiece, and electric control means automatically operable upon translation or said workpiece into a predetermined position to enect substantial concurrent reversal in the rotation of the workpiece and said grinding wheel. l

ALF KRISTIAN SELNES.