US2390978A - Grinding machine - Google Patents

Description

Dec. 11, 1945,

S. E. WOODBURY I GRINDING- MACHINE 4 S heets-Sheet 1 Filed Aug. 26, 1943 s. E. WOODBURY G-RINDING MACHINE I Filed Aug. 26, 1943 4 Sheets-Sheet 2 Dec. 11, 1945. s, WQQDBURY 2,390,978

GRINDING MACHINE Filed Aug. '26, 1943 -4 SheetS Shet' s Fil ed Aug. '26, 1945 4 Sheets-Sheet 4 m 14 m m 2 1 i-"econ? 11, 1

Stephen E.

t 18 Claims.

This invention relates to grinding machines and consists in certain improvements increasing the efllciency, precision and safety "of such machines in operation and their-convenience of control by the operator. Surface grinders a? heretofore constructed have included-a work-carrying slide or table arranged ditions are thus created which are most favorable to travel back and forth longitudinally beneath 5 PATENT OFFICE GRINDING MACHINE Woodbury; Beverly, Mass, assignor to Reid 1 Brothers Company, Inc., Beverly, Mesa, a corporation of Massachusetts Application August, 26, 1943, Serial No. 500,078

but variable interval immediately prior to the instant of actual reversal'and provide means for regulating the interval of over running by mothe grinding wheel, and cross feed mechanism for shifting the path of the table. transversely after each reversal of its longitudinal travel.

An important feature of the present invention consists in mechanism constructed and arranged to cause operation of the cross feed mechanism in anticipation of each such point of reversal of the table, so that the cross feeding step may be effected during the final portion of the table travel, after the wheel leaves the work and before the direction of table travel is reversed. The result is that the work is brought to the wheel in a straight line movement prior to each grinding stroke of the machine and there is no traverse movement of the wheel and work during the grinding stroke. The amount of metal removed by the wheel is therefore. substantially uniform from one end of the stroke to the other, and confor great accuracy of operation.

The efficiency of the machine is also improved cross feeding operation, time that would otherwise be wasted between consecutive grinding strokes. On the contrary, my invention anticipates the point of table movement reversal and initiates the cross feeding operation as soon as the.

wheel passes off the work. To this end'I employ an oscillatory sector which is swung. through a predetermined angle by the work table itself near each end of its stroke for controlling the reversing mechanism and I utilize an intermediate portion of the sector movement for throwing the.

cross feed mechanism into and out of operation.

Another important feature of my invention consists in utilizing and controlling the momentum of V the cross feed mechanism to extend the cross feeding operation into the initial portion of the reverse travel of the work table after each point of mentum so that the cross feeding operation may extend somewhat into the period of reverse travel of the table, although of course never up to the point in which the work meets the grinding wheel.

Another important feature of my invention consists in safety mechanism for terminating the cross feeding operation independently of its regular automatic control in the normal operation of the grinding machine, and restricting the cross feeding operation under all conditionsto an a'mplitude that will prevent possible damage tothe work or disorganization of the machine. To this end I provide an actuating member, shown as a rocker, which is arranged to assume a predetermined initial position at the end of every cross feeding operation and to be clutched or connected to the cross feeding mechanism at the beginnin of each operation. A safety switch is provided in position to be engaged by this actuating member to break the circuit and stop the cross feed motor in case the cross feeding operation is unduly extended by any accident or oversight.

While the invention is herein disclosed in this thereof selected for purposes of illustration and 7 shown in the accompanying drawings in which,

Fig. 1 is a view in perspective showing the general organization of theme-chine,

Fig. 2 is a view in perspective of mechanism below the table of the machine, 6 v Fig. 3 is a view in perspective of safety mocha:

nsim for limiting the extent of cross feed,

.Fig. 4 is a view in longitudinal section of another portion of the same mechanism,

Fig. 5 is a, similar view of a portion of the motor driven crossfeed shaft,

Fig. 6 is a view in elevation of portions of the machine showing mechanism for controlling and adjusting the extent of cross feed,

Fig. 7 is a fragmentary view in perspective of the same mechanism,

Fig. 8 is a view in perspective of the controlling disk as seen from beneath.

, cross feed mechanism,

Fig; 12 is a wiring diagram of the machine,

Fig. 13 is a diagrammatic view illustrating the timing of the cross feed operation, and

Figs. 14 and 15 are diagrams of the table movements.

In its general organization the illustrated machine includes a box frame I from the rear side of which rises an upright column or post II. The grinding wheel I8, together with its spindle and individual driving motor 82, are mounted for vertical adjustment in a slide carrier movably' mounted in the post II. The operative position of the grinding wheel is adjusted and controlled by V a hand wheel Ill, convenientlyprojecting from the front wall of the machine frame I0.

Splined on the shaft assume the shaft and clutched to the hub of the hand wheel 28, whereupon longitudinal feed can be effected as a manual operation.

The pinion 23, notwithstanding its shifting with the sleeve 22, always remains in mesh with a large gear 30 fast on a grooved transverse shaft H which is journalled in bearingsprovided in the front and rear walls of the machine frame It. 3| is a collar 39 formed in tegral with a sprocket wheel 33. The collar '4 is embraced between the walls of a yoke it depending from the lower surface of the crdss slide I3, as shown in Fig. 10. When the slide is given a cross feeding movement, as will be presently The connecting mechanism is not herein shown since it forms no part of the present inventio but is well known in the industry.

In the top of the machine frame III are provided spaced transverse ways I2 and I9, .both herein shown as V-shaped, but not necessarily so, and in these ways rests the cross slide It. The

slide I3 is provided with longitudinal ways iii in its upper face toward the rear and in these slides the elongated work table It carrying an adjustably mounted magnetic chuck I'I upon which the work to be ground by the wheel I8 is clamped. I

' Longitudinal feed Longitudinal feed of the worktable I8 back and forthon the cross slide I3 is effected through outer end is suitably journalled in the front wall of the machine frame Ill. The shaft carries a loose sleeve 22 formed integral at one end with a'pinion 23 and at the other with a grooved ring in which rests a shipper segment 24. The sleeve also has clutch teeth projecting from its oppos'ite ends. The segment 2| extends outwardly.

and downwardly being provided with a shank portion which is guided for transverse movement on a guide rod 25 disposed parallel to the shaft 20. This shank portion in turn has a pin and slot connection with the short inner arm 26 of a bell crank lever (see Fig. 10) pivotally mounted to rock on a short shaft 28 projecting from the left side wall of the machine frame. The

other and longer arm of the bell crank lever comprises a handle 21 located outside the wall of the frame. When the handle 21 is swung. in one direction the sleeve 22 is shifted toward the right I .as seen in Fig. '2 and is positively clutched to the shaft 20 through the collar 2i. Under these conditions rotation of the shaft 20 to effect the longitudinal feed of the work table I8 is carried out by power from the motor. A latch it maintains this power connection.- until released by the operation. On the other hand. when the handle 21 is swung in the opposite direction, the sleeve 2: is shifted toward the left, unclutched 1mm operative connection between the two is at all times maintained.

A sprocket chain 36 runs about the sprocket wheel 33,'upwardly over idler rolls 35 and 3G in the slide I3 and thence in opposite directions to points of connection with the work table Ed ad" jacent its opposite ends and in its under face. It will be apparent; therefore, that rotation of the shaft 20 either manually or by power will, through the sprocket connections above described, im art a longitudinal feeding movement to the work table It in a direction depending on the direction. in which the said shaft 20 is rotated.

In the power operation of the machine the length of work table movement and its points of reversal are determined bya pair of dogs 4| and 42 adjustably mounted in an undercut slot 0 provided in the front edge of the table I6. as shown in Fig. 1. To this end a sector 63 is mounted to rock on a horizontal axis with a sh'aft 59 projecting forwardly from the casing of a reversing switch 49 secured to one side of the cross slide I3. The shaft 59 projects forwardly and is provided with a'knurled operating head 48 at its forward end. A pin 44 projects forwardly from one corner of the sector into the path of the dog 4! and a pin 45' projects rearwardly from the other corner of the sector into the path of the dog 62. When either dog I or 42 rocks the sector it the switch 59 is thrown and current in the longitudinal feed motor is reversed and with it the direction of feeding movement of the table.

The same result may be obtained manually by I turning the operating head 48 at any time when the sector 43 is clear of the dogs ll and 42.

At either end the table I6 carries a wedge cam I08, one only being shown in Figs. 6 and 9, which cooperates with a limit switch IIIE mounted on one side of the casing of the reversing switch 09. The switch I01 is normally closed and is opened by the depression of a roll-carrying,plunger,,l09 standing in the path of the wedge cams I08. Accordingly, if for any reason the table fails to reverse, one or the other of the cams I08 will de press the plunger I05, throw the switch I01 and stop the table motor, as will be presently explained. In the normal operation of the machine, of course, the table is reversed before the cams I08 reach the position of the plunger I00.

It will be understood that the general construc tion of the machine heretofore described is no part of my invention but that the operation and controlof its elements and the mechanism therefor npwto be described is the subject matter of my invention.

Cross feed The individual cross feed motor :1 is shown an attached to the right hand wall of the machine through a pair of coupling collars 86 to a shaft 8| journaled in a bracket 80 mounted within the machine frame I0. The shaft 8| carries a worm 82 which is always in mesh with an elongated pinion 60 mounted on a transverse shaft 6| journaled in a yoke 62 within the enclosure of the frame I0.

The elongated pinion 60 is always in mesh with a pinion 52 fast on a shaft which carries the cross feed lead screw 53 threaded into an elongated nut 54. The nut 54 is rotatably held in the front wall of the machine frame and is connected to a hand Wheel 55 projecting from the wall in convenient reach of the operator. At its inner end the shaft 5| is connected through,

thrust bearings to a, second yoke 50 projecting downwardly from the lower face of tho cross slide I3 at the right hand side of the yoke I4 already mentioned. This connection is the point of application of the cross feeding mechanism to the cross slide. In cross feeding in either direction movement is derived from manual rotation of the hand wheel 56 and nut 54 or from power rotation in the nut 54 of the screw 53, through its connections with the shaft 8| and the motor 81.-

W iring diagram The grinding wheel I1, the work table I 6,and

the cross feed slide I3 are all operated by individ- I motor 32.

ual motors connected and controlled by the system of wiring shown in the diagram of Fig. 12. Three phase power is supplied on the line switch I25 from whence it is tapped direct to the spindle From the line switch three wires also lead to the table motor, two of them through a hand controlled two pole switch 19. The reversing switch 49 is included in two of three wires of the table motor and this switch is operated by the sector 43.

A pilot or relay circuit extends between the two outside terminals of the line switch. -This includes a connection I26 to the starting switch I I1. When the switch I I1 is closed current flows in the relay circuit through the normally closed stopping switch M9, the normally closed safety switch I01, the normally closed feed limiting 1 switch 18 and the solenoid H8. The olenoid I I8 automatically closes the line switch whereupon the table motor may be started by closing the hand operated switch I9. Meanwhile current in the relay circuit flows in the branch I21 and,

the starting switch H1 remains open. Under' operating conditions, therefore, the line switch may be opened automatically by throwing the stopping switch II 9, or by the opening of the safety switch I01 by action of the dog I08, or by operation of 'the feed limiting switch 18 by the safety cam 66.

Three wires, two of them led through a. relay controlled switch 16, also lead to the cross feed motor 81. In this circuit is included the hand operated reversing switch I I0 for controlling the direction of cross feeding.

The wiring includes a second relay circuit for controlling the cross feed switch 16. This second relay circuit includes the switch 90 operated by the cam 46 and the solenoid 15 which when energized closesswitch 16 to the cross feed motor.

Current flows in this circuit only during the short double pole switch 16 under the control of a. solefeed slide, as shown in Fig. 1, where it may be hold 15 in a pilot or relay circuit which includes a. normally closing switch 90. when the switch 16 is closed the motor 81 operates and the cross feeding operation occurs. Theswitch 16 is held closed only while the plunger 41 of the pilot switch is allowed to remain in its uppermost position. The plunger 41 is controlled by a cam 46 keyed to the shaft 59 and moving with the sector 43. It has a. fiat side in its periphery and is arranged symmetrically with respect tothe sector,. that is, when the sector standsvertically the flat side of the cam 46 is disposed horizontally, permitting the plunger 41 to rise to its fullest extent in the cycle, tending to close the relay circuit and close the switch 16. When the cam 46 is swung in either direction out of its mid position the pilot switch plunger 41 is depressed at a time and for an interval depending upon the vertical position of the pilot switch 90, which, as will presently be explained, is mounted for vertical adjustment under the very sensitive control of the operator. The mode of operation thus explained is illustrated diagrammatically in Fig. 13. The movement of the sector 43 to effect a complete reversal of table movement takes place through the angle A. The cam 46 permits the cross feed motor to operate during the angle B,

for an intermediate setting of the pilot switch during only that fraction of the swing of the sector 43 (represented by the angle B or C) on each side of its mid position in which the plunger 41 is allowed to remain undepressed. A very slight depression of the plunger 41 is sufiicient to break the circuit in the switch 90 and all further movement of plunger 41 is merely idlerbvertravel.

The switch 90 has a vertical guide pin 9| projecting upwardly from its casing and arranged to slide in the horizontal arms of a guide bracket 92 fast to the casing of the switch 49. The guide pin ,9I -carries a grooved collar 93 into which projects a pin carried by a substantially horizontal arm 94. The arm 94 is keyed to the forward end of a short shaft 95 which is journaled to rock in the webs of the cross feed slide I3 as shown in Fig. 7. 'At an intermediate point the shaft 95 carries a short arm 96 against which secured to the rear of the switch 90 and to the side of the casing of the switch 49 also tends to lift the switch 90. The spring I05 is best shown in Fig. 6. At its rear end the shaft-95 carries av block 91 having a rearwardly projecting pin which engages a short arm 98 fast to the rear end of a long horizontal shaft 99 also journaled in webs of the feed slide I3. The shaft 99 goes through to the front edge of the feed slide and just within the front flange thereof is provided with a limit stop I00 and an arm I0l extending in a substantially horizontal direction toward the left as seen in Figs. 6 and '7. A pin I 02 rests upon the free end of the arm IM and passes upwardly freely through an aperture in the feed slide. It is received in a. circular groove with a spiral bottom surface cut in the under face of a I graduated disk I03 which is mounted to-rotate freely in the forward right hand comer of the conveniently reached by the operator.

It will be seen that rotation of the disk I03 gives the operator quick and delicate control of.

its uppermost position as shown in full lines in Fig. 6. In this position of the switch 90 the plungerfi'l is not permitted to reach its most elevated position and no cross feed occurs. In

other words the angle B has become zero. Now,

when the disk I03 is turned to some such reading as 0.005 the switch 90 is slightly lowered. Accordingly when the cam 46 is rocked the plungerfil is elevated to its switch closing position for only an instant during the swing of the sector 43. This might be represented by the small angle B in the diagram of Fig. 13.

From this it will be seen that the pilot switch is allowed to close only just before the sector reaches its mid position and is again opened Just after the sector passes its mid position. The full ower cross feed is therefore effected just prior to and in anticipation of the reversal of the table movement. This action is indicated by the diagram of Fig. 14 where the lin I20 indicates the movement of the table I6 toward the right and the line I22 its movement toward the left after reversal. The cross feed is effected prior to the actual point of reversal, while the table movement is represented by the line I2l. As the table approaches the point of reversal in its movement toward the left the cross feed is represented as taking place in the line I23.

, Now if the operator desires to increase the amplitude of the cross feed he has only to turn the graduated disk I03 forcing downwardly the pin I02. This has theeifect of rocking the arm IOI downwardly and moving the switch 90 downwardly against the action of th springs H3 and I05 into some such position as indicated in dotted lines in Fig. 6. The effect of this adjustment is to increasethe interval of cross feed becausethe cam 46 has to rock less before it releases the plunger 41 for movement into its upper or closedswitch position and further before it depresses it to break the relay circuit. The further the disk I03 is turned the greater is the extent of the cross feed and the steeper the angle of the lines I2I and I23 in the diagram of Fig. 12. The switch 90 cannot be set so low that the corner of the fiat side of the cam in the extreme positions The friction on the disk as may be adjusted sothat the shaft will practically come to a dead stop the instant the switch 00 is opened and under such conditions the table movement is that shown in the diagram of Fig. 14. However, by relaxing the friction on the disk 85 to a limited extent the momentum of the moving parts may be permitted to carry the shaft BI a few turns ahead after power has been cut off from the motor 01. In this way'a portion of the cross feed may be carried beyond the point of actual table reversal and take place during the initial portion of its reverse longitudinal travel.

This mode of machine operation is indicated in the diagram of Fig. 15 where I 30 indicates table movement toward the right, power cross feed occurs while the table moves in the line III and momentum cross feed occurs while the table moves toward the left in the line I32 prior to its straight line feed toward the left in the line I32. It is plain that the momentum cross feed balances the power cross feed in the cycle of the machine,

' both occurring while the grinding wheel is oil cannot rest on plunger 41, therefore the cross feed cannot be set to run continuously but must feed only near the ends of the table travel.

Hitherto it has been assumed that the cross feed takes place only during the power operation of the motor 81' and it is a fact that this is a desirable and satisfactory mode of operation.

However, I increase range of usefulness of the machine by provi g in some cases for a further cross feed which is effective after the motor is cutoff by the controlled momentum of the parts it has set in operation.

The shaft 8i carries a friction disk 85 which runs between cylindrical friction members 83 and 84 yielding and adjustably held together,

and locked against rotation by an anchor screw 88 threaded into the base of the bracket 80. The purpose of this friction mechanism is to provide a' drag on the shaft BI that will reduce the tendency of the shaft to-spin when its actuating current is cut off, that is, to limit over-running in the cross feedhig operation.

the work. I

, Cross feed safety stop The shaft BI, which is driven by the worm s2 friction face corresponding to the leather friction face 64. It also carries a triangular safety cam 68 and a counterweight 01 which holds the cam 66 normally in upright position. In the hub of the friction member 65 is carried a hardened ball adapted to be engaged by an'upstanding spring ,arm 68 fast to the machine frame. The arm 00 is oscillated to apply clutching engagement to the rocking member 65 through a horizontal rod 69 which is'connected at its'left hand end, as shown in Figs. 2 and 3, to a vertical arm' 10 loosely mounted in the left hand branch of the bracket 62.

In a bearing block II carried by this bracket is Journalled a horizontal shaft having a short upstanding arm I2 carrying an adjustable contact screw which engages the arm I0. At the other end of this shaft is a long arm I3 which rests on a pin Id projecting outwardly from the plunger of a solenoid 15 which is primarily controlled by the relay switch as already described in detail, but which is also controlled indirectly by the before mentioned limiting relay switch I0. As already stated, the switch I8 controls the solenoid II8 which operates the main switch I25, with the result that the opening of the switch I8 opens the main circuit, thus de-' energizing the solenoid I5, even though the switch 90 should remain closed. The'switch I8 is located with its operating plunger 11 beneath and in operativerelation to the triangular cam 06. The triangular cam 66 is normally caused to stand in vertical position by its counterweight l1 and the relay current flowing in the solenoid I5 normally holds the arm I4 in its elevated position so that the arm 68, through the connections described, is pressed against the end of the rocker member 65 which is thus clutched to the friction 'end of the shaft Bil This member has an inner ascoms completion of each cross feeding step, the switch ll is opened as already described and the solenoid I is de-energircd. thus releasing the rocker member it from the shaft SI and permitting the cam 68 to return by gravity to its elevated position. Since the longest single cross feed step ever utilized in practice does not require more feeding movement is not properly terminated,

current continues to flow in the relay circuit and the cam 68 continues to travel till it depresses the plunger 16 and breaks the circuit at the switch 18 allowing the line switch "to open and bringing the table to an immediate stop.

The shaft 53 as shown inFig. 11 is mounted in ball thrust bearings in the yoke 50 on the under side of the cross slide. The pinion 52 is fast on this shaft having a press fit thereon. The threaded portion of the shaft turns in the long nut El. When it has been turned enough to move up and engage the inner end of the nut, then the nut begins to spin with the pinion and the shaft 53 so that no. cross feed takes place. The hand wheel 56 is fastened to the nut 54 by a set screw so that the hand wheel 56 will spin idly when no cross feed is taking place. Under these circumstances the inside races of the roller bearings in the frame In turn with the shaft. The

shaft itself is shouldered down to present a thrust collar for the ball thrust bearings. When the threaded shaft 53 has been turned in the other direction sumciently to bring the cross slide I3 to its rearward limit of movement, frictional engagement between the shaft and the nut is in- My improved grinder has also outstanding safety and convenience features. To enumerate a few, all controls are now arranged so that-the operator can adjust the machine while-itziis running without needing to touch any moving part. The adjustment for extent of cross feed can be changed as often and as much as desired i in perfect safety while the. grinder is running, whereas previously this required that the grinder must be stopped and the adjustment made on parts that are normally in motion The hand feed is retained in such a way that it is not active until needed and thencan be used without giving any thought to the automatic anticipative cross feed. Moreover the automatic cross feed automatically goes out of 'commission at each end of the limit of travel of the cross slide in either direction.

Having thus disclosed my invention and described in detail a specific embodiment thereof I movement, a cross feed electric motor, means for directing an operatingcurrent to said motor for starting it, and mechanism thereupon operated by said motor for imparting a transverse feeding step to th table'in anticipation of andbefore its reversal and for stopping said motor at the conclusion of each cross feeding step.

and a work table,'cross feed mechanism for the table, longitudinal feed mechanism for the table,

creased to such an extent that the nut turns with the shaft in the roller bearing, thus permitting continued rotation of the shaft 53 without damage.

The advantages of my invention will be more fully appreciated when'it is remembered that in surface grinders now available on the market the .table carrying the work reverses its motion at the end of the stroke in order that the crossslide may be fed over so the grinding wheel will cut a new path. Therefore, the cross feeding takes place after the work has returned under the wheel for several inches, whereas it should preferably have occurred before the work arrived at the wheel.

My improvement consists in utilizing the time after the work has left the. wheel up to when it returns to the wheel to do the cross-slide feeding. This is usually about twice three-quarters of an inch of table travel. When all the feeding is done in this space, the wheel cuts a new path over the entire length of the work. Without this improveme e wheel returns to the work along the path dy cut and so does not grind untif the work is carried overby the feed of the cross slide several inches from the beginning. Also, as the work comes out from the wheel the metal that has been left is now groundaway as an extra amount. This loads the wheel to its limit, for no reason other than that this isnever overloaded at any point.

. and a work taiblaecross, feed mechanism for the table, a cross electric motor for operating the same, longitudinal feed mechanism for the table, mechanism timed in its operation by the longitudinal movement of the table for reversing the longitudinal feed mechanism, for startlngsaid cross feed motor to initiate the action of said I cross feed mechanism and for stopping it at the conclusion of each cross feeding step, and means adjustable by the operator for regulating the extent of each cross feed operation.

4. A surface grinder having a grinding wheel and a work table, cross feed mechanism for the I table, a cross feed electric motor for operating the same, longitudinal feedmechanism for the table, a sector oscillated by the longitudinal movement of thetable for reversing the fongi- ,tudinal feed mechanism, a cam symmetrically disposed with respect to said sector and movable therewith for starting said cross feed motor to initiate the action of said cross feed mechanism in anticipationio'f and before the reversal of the table in eachstroke, and means adjustable by and arranged to start said cross feed'moton at the sector movement.

predetermined points in its travel before the end of each reciprocation, and a controlling device. .located on the cross slide in convenient reach of the operator for advancing or delaying the action of the work table on the cross feedmechamsm.

6. In a grinder, a cross feed slide, an electric motor for operating the cross'feed slide, a work table and electrically operated mechanism for moving said table longitudinally back and forth 10 on .the cross slide, spaced dogs carried by the work table, a rocker member located in the path of said dogs and movable by them for reversin said work table mechanism, a cam operated by said rocker member, electrical means under the '7. In a grinder, a cross reed slide and a work table carried thereby, electrically operated mechanism-for moving said table back and forth in said deed slide, cross feed mechanism, an electric motor connected to operate the cross feed mechanism and arranged to be thrown into periodic action by the work table prior to each reversal, a graduated disk located on the'cross feed slide within-convenient reach of the operator, and means operated thereby for controlling the length of time the cross feed motor remains in o'peration at each reversal.

8. In a grinder having a table mounted to reciprocate on a movable cross feed slide and motor operated mechanism for eifecting table reciprocation and cr f movements, a ro r during a short interval before each point of table for bodily moving the switch to vary its time of 40,

action.

9. In a grinder having a table mounted to reciprocate on a movable cross feed slide, and motor operated mechanism for efiecting table reciprocation and cross feed movements, a rocker oscillated :by the table prior to each reversal of its reciprocation, a switch operated by said rocker for timing the cross feed movement, spring means tending to move said switch and rocker toward each other, a graduated disk'located in the '50 grinder within convenient reach of the operator, and connections between the disk and switch for positively moving the said switch away from the? rocker.

10. In a grinding machine having a reciprocatory table, a cross feed slide carrying the table, and individual motors and connecting mechanism for the table and cross feed, an oscillatory sector mounted to be swung by the table and controlling the reversal thereof, and means for throwing the g0 cross reed motor and its connections into operation during a predetermined fractional part of 11. In a grinding machine having a reciprocatory table, a cross feed slide carrying the table,

and individual motors and connecting mechanisms for the table and cross feed slide, an 05-- cillatory sector mounted to be swung in opposite, directions by the table from an inclined position on one side of a perpendicular mid-position to an by the table and determining in its movements inclined position on the otherside thereof and to effect reversal of the table motor in its said movement, andcam-controlled mechanism for throwing the cross feed motor, into operation position and, throughout an angle lessthan that oi its full oscillation.

12. In a grinding machine having a reciprocatory table,'a cross feed slide carrying the table,

and individual motors and connecting mechanisms for the table and cross feed, means for supplying operating current to the cross ieed motor at a predetermined but variable interval before the point of table reversal and for cutting of! its current before actual reversal takes place, and adjustable means for timing the overrunning of said motor, whereby the cross feeding operation may extend into the initial portion of the reverse travel of the table.

13. In a grinding machine having a reciprocatory table, a cross feed slide carrying the table, and individual motors and connecting mechanisms for the table and cross feed slide, a switch for controlling the flow of operating current to the cross feed motor arranged to be closed and opened in anticipation of the table reversal atcach end of the table travel, and adjustable means acting on the connecting mechanism of the cross feed motor to limit over-running of the motor to a time of travel of the table in reverse no reater than its travelprior to reversal.

14. In a grinding machine having a reciprocatory table, a cross feed slide carrying the table, and individual motors and connecting mechanisms for the table and cross feed slide, a switch for controlling the flow of operating current to the cross feed motor, connections including a motor driven shaft for transversely moving the cross feed slide, means for closing the switch reversal for effecting cross feeding under power, a disk fast to said driven shaft, and means for applying an adjustable friction to said disk to limit over-running of the shaft to permit cross feed under momentum to take place during the initial portion of the movement of the table after each reversal.

15. In a grinding machine having a reciprocatory work table, a cross feed slide carrying the table and individual motors for operating the table and slide, an operating member movable freely to a .predetermined initial position at the beginning of each cross feeding operation, power operated means for moving said member pro-4 gressively during the operation of the cross feed motor, and a safety switch arranged to be tripped by said member to cut 01! current to the cross feed motor when the cross seeding operation has exceeded a predetermined extent. I

16. In a grinding machine having a reciprocatory work table, a .cross feed slide carrying the table and individual motors for operating the table and slide, a rocker carrying a cam and ,arranged to occupy a predetermined initial position at the beginning of each cross feeding move-' 1 ment of the feed slide, automatic mechanism for .starting the cross teed motor prior to each reversal of the table and for'initiating rotation of vthe said rocker, and a normally closed switch arranged to be tripped by saidcam after a predetermined interval of operation by said motor.

- 17. In a grinder having a' cross ieed,slide, a reciprocatory work table thereon and motor driven operating mechanism for the slide and table, a rocker on the cross reed slide oscillated the points of reversal of table movement,.a cam movable directly by the rocker, a switch in the cross feed circuit located adjacent to the cam and having a plunger engaged thereby whereby the cross feed operating mechanism is thrown into action prior to and in anticipation of each reversal of table movement, and means on the cross feed slide for adjusting the relative positions of the cam and switch whereby the extent 5 of cross feeding movement may be regulated while the machine is in operation.

18. In a grinder having a cross feed slide, a re-, ciprocatory work table thereon and motor driven operating mechanism for the cross slide including 1

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