US2078749A

US2078749A - Hydraulically operated grinding machine

Info

Publication number: US2078749A
Application number: US72115A
Authority: US
Inventors: Wallace H Wood
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1936-04-01
Filing date: 1936-04-01
Publication date: 1937-04-27
Anticipated expiration: 1954-04-27

Description

W. H. WOOD HYDRAULICALLY OPERATED GRINDING MACHINE pril 27, 1937.

Filed April l, 1936 2 Sheets-Sheet 1 W. H. WOOD HYDRAULICALLY OPERATED GRINDING MACHINE Filed April l, 1936 2 Sheets-Sheet 2 www www WN Nu m x WHLLHDE H. VVDUB Mw. www,

Patented Apr. 27, 1.937

UNITED STATES PATENT OFFICE Wallace H. Wood, Worcester,

Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application April 1, 1936, Serial N0. 72,115

7 Claims.

'Ihis invention relates to grinding machines, and more particularly to a hydraulically operated cylindrical grinding machine.

' One object of this invention is to provide a 5 simple and thoroughly practical hydraulically driven cylindrical grinding machine. A further object of this invention is to provide an improved hydraulically operated table reciprocating mechanism for the reciprocable table of a cylindrical grinding machine.

A further object of this invention is to provide a simplified valve control unit which serves not only to control the table movement but also vthe wheel feeding movement. A further object is to provide a readily controllable dwell control mechanism for controlling the extent of dwell at each end of the table reciprocation. Other objects will be in part obvious or in part pointed out hereinafter.

'This invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exempliedv inthe structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is shown one of various possible embodiments of the mechanical features of this invention,

Fig. 1 is a front elevation of the improved 30 grinding machine, having parts broken away and shown in section to more clearly show the construction;

Fig. 2 is a diagrammatic view, showing the valve and piping diagram of the hydraulic table reciprocating and wheel feeding mechanism;

Fig. 3 is a fragmentary vertical cross sectional View, on an enlarged scale, taken approximately on the line 3 3 of Fig. 1;

Fig. 4 is a fragmentary vertical section, taken approximately on the line 4 4 of Fig. 3;

Fig. 5 is a fragmentary detail view of the control for the reverse and traverse valves, on an enlarged scale, taken approximately on the line 5 5 of Fig. 3; and

Fig. 6 is a fragmentary vertical section,l on an enlarged scale, taken approximately on the line 6 6 of Fig. 3, showing the connection between thereversing and wheel feed control valve.

A grinding machine has been illustrated in the drawings comprising a base :I which supports a transversely movable wheel slide II thereon. The wheel slide II is mounted for a transverse movement'on a V-way (not shown) and flat way in a mannerv similar to that shown 3 in the expired patent to`Norton No. '762,838 dated June 14, 1904. The wheel slide II supports a rotatable grinding Wheel I2 on a rotatable wheel spindle I3. The wheel spindle I3 may be rotated by means of an electric motor I4 mounted on the upper surface of the wheel slide. The motor is provided with a rotor shaft I which is provided with a pulley I 6 connected by a belt I1 with a pulleyv I8 mounted on the wheel spindle I3.

The base I0 also supports a longitudinally reciprocable work table on V-way and flat way I9, as indicated in the above-mentioned expired prior patent to Norton. The table 25 serves to rotatably support a cylindrical work piece 26 on a headstock 21 and a footstock 28. The headstock 21 is provided with a, headstock center 29 and the footstock 28 is provided with a footstock center 30 which are arranged to engage center holes in the opposite ends of a work piece to rotatably support the same during a grinding operation. The headstock 21 is provided with a rotatable face plate 3I which may be driven .from any suitable source of power, such as a motor on the headstock or an overhead belt drive. 'I'he plate 3I carries a driving pin 32 which engages a dog 33 mounted on the end of the work piece 26 25 to rotate the work piece for a grinding operation.

Wheel feed The wheel slide II may be fed transversely relative to the base I0 by' means of a half nut (not shown) and a rotatable feed screw 35 which is rotatably supported in bearings (not shown) in the base I0. These parts have not been shown in detail. since they are not considered part of the present invention. For further details of 3 construction ofthis nut and screw mechanism, reference may be had to the above-mentioned prior patent to Norton No. 762,838. The outer end of the feed screw 35 carries a gear 36 meshing with a small gear 31 rotatably mounted on a shaft 38. A feed wheel 39 is also rotatably supported on the shaft 38 and is either formed integral with the gear 31 or rigidly fastened thereto so that when the hand wheel 39 is rotated, a rotary motion will be transmitted through the gear 31, the gear 36, to rotate the feed screw 35 so as to cause a transverse -feeding movement of the slide II and grinding wheel I2 either toward or from the work piece 26, depending on the direction of rotation of the feed wheel 39. 50 The feed wheel 39 may be rotated manually, if desired. A micrometer adjusting mechanism 40 is provided on the hand wheel 39 and carries an abutment 4I which isvarranged in the path of a feed pawl 42 which is pivotally mounted on 55 a stud 83. The micrometer` adjusting device 38 facilitates the resetting of the stop abutment 8| relative to the feed wheel 88 to make compensation for wheel wear to accurately size the work 5 piece. The feed pawl 82 is preferably arranged for a reciprocatory motion to engage the teeth of thefeeol wheel t8 so as to cause an automatic infeeding movement of the grinding wheel when desired. The movement of the feed pawl i2 is preferably accomplished by means of a fluid pressure mechanism including a cylinder '88 which contains a slidably mounted piston 35. A piston rod 86 is formed integral with the piston l5 and carries at its upper end a bracket l1 which serves as a support for the stud 53. It is desirable to provide a suitable means for adjusting` the extent of movement of the feed` pawl 82. This may comprise an adjustable stop screw i8 which is carried by a projecting lug 99 on the base |8. The stop screw i8 is arranged in the path of a projecting portion of the bracket l1 carried bythe piston i6 so that the upward movement of the piston |55 together with the upward movement of the pawl i2 may be varied wheel 89 may be picked up at each reciprocation of the feed pawl 82.

Table reciprocatz'on.

The longitudinally movable work table 25 is slidably mounted on V and flat ways (not shown) and is arranged to be automatically reciprocated longitudinally relative to the base |8 so as to reciprocate the work piece 28 'in operative relation with the grinding wheel i2. The reciprocating mechanism preferably `comprises a hydraulic system including a cylinder 55 which is flxed to the under side'of the table 525. The cylinder 55 contains a pair of spaced pistons 56 and 51 which are connected by

hollow piston rods

58 and 59 respectively,l with supporting brackets 68 and lrespectively which are rigidly mounted on opposite ends of the base i8. A fluid pressure reversing valve 65 is provided to control the admission of iluid under pressure to

cylinder chambers

62 and 63 respectively, at opposite ends of the cylinder 55. The reversing valve 65 is preferably of a piston type in which a. plurality of

valve pistons

66, 61, 68 and 69 are formed integral with the valve stem 65. v

Fluid under pressure is supplied by means of 'f a pump 15 which is preferably located within the base I8. The pump 15 draws iiuid through a pipe 16 from a reservoir or sump 11 which is also located within the base |8v vand forces fiuid through a pipel 18, a passage 19\within a valve casing 18, and through a passage 88 into avalve chamber 8| located between the valve pistons '66 and 61 and through a. passage 82 into a valve ochamber 83 located between the

valve pistons

68 and 69. -In the position of the parts, as illustrated in Fig. 2, Afluid under pressure enteringl the valve 'chamber 8| passes out through a passage 84, through a ypipe 85, and through a central aperture 86 within the piston rod 58 and into the cylinder chamber 62 to cause the cyl- ,inder 55 and the table 25 to move toward the left, as viewed in Fig. 2.y Duringthe admission of fluid under pressure to the cylinder chamber 62, fluid is exhausted from the cylinder chamber 63 through a central aperture 88 within the piston rod 59, through a pipe 89, a passage 98 within. the valve casing 8, into a valve chamber 9|, and exhausts therefr m through a passage 92. In order to automatilcally control the moveas desired so that one or more teeth of the feed aoravae ment of the reversing valve 65, a pilot valve 98 is provided which is automatically actuated in timed relationship with the table movement to cause a reversal in the direction of movement of iiuid under pressure. As illustrated in Fig. 2, the pilot valve is preferably of a piston type comprising a valve stem |88 having formed integral therewith valve pistons |8l, |82, |83 and |88. The fluid under pressure from the pump l5 and pipe 18 passes through a passage |85 into a valve chamber |88 formed between the valve pistons |82 and |83. When the pilot valve is shifted toward the right (Fig. 2), fluid under pressure entering the valve chamber |86 passes outwardly through a passage |81 into a valve .4

chamber |88 in the reversing valve 65 formed between the valve piston 69 and the end of the valve casing. Fluid under pressure entering the chamberl |88 serves to move the reversing valve toward the left (Fig. 2). This movement of the reverse valve 65 toward the left causes valve piston 61 to close the passage 8d and after a further movement of the valve, shifts the valve ypiston 68 so that iiuid under pressure from the passage 82 into valve chamber 83 passes through passage 98 and pipe 89 into the cylinder chamber 63 to cause the cylinder 55 and table 25 to start moving toward the right, as viewed in Fig. 2. y

In grinding a cylindrical work piece, itis desirable to provide a dwell at the en`d of the reciprocatory stroke in order that the work piece may make at least one complete rotation while the grinding wheel is at theend of its reciprocatory stroke in order that the grinding wheel may grind completely around the work piece to grind the same to a true cylinder before the work piecesta'rts moving in the reverse direction. The extent of dwell is preferably regulated by a needle valve ||8 in the passage |81 which serves to regulate the fluid passing through the passage |81 and thereby regulates the speed of shifting of the reverse valve 65.r

Similarly, when the pilot valve stem |88 is moved toward the left, as viewed in Fig. 2, fluid under pressure entering the chamber |86 passes outwardly through a passage ||2 into a valve chamber ||3 which is formed between the valve piston 66 and the en'd of the valve casing. Admission of fluid under pressure to the chamber I3 serves to move the reversing valve 65 toward the right, into the position illustrated in Fig. 2, so as to reverse the direction of flow of fluid within the system. A needle valve ||4 is provided in the passage I2 and serves to regulate the passage of, uid under pressure through the passage ||2 and consequently regulates the speed of movement of the reverse valve 65 toward the right so as to control the extent of dwell when the table is at the end of is reciprocatory stroke. By adjusting the needle valves ||8 and I4, the extent of dwell at each end of thetable stroke may be varied, as desired.

When the pilot valve 99 is in the position as illustrated in Fig. 2, fluid within the valvephamber |88 may exhaust through passage |81, passage ||6, intovalve chamber ||1, and through a passage ||8, intda valve chamber ||9, and out` through a passage\|28 and an exhaust pipe |2| into the reservoir 11.

"Similarly, fluid within the valve chamber ||3 may exhaust through the passage ||2, a. passage |23, into a valve chamber |24, through a passage |25, into a valve chamber |26, and out through |34 with a groove |35 in an end a passage |21 voir 11.

The pilot valve 99 is normally maintained'in a central position, as indicated in Fig. 2. A yieldable device including a pair of opposed springs is utilzed to maintain the pilot valve in its neutral or central position. A bell crank lever |30 is rotatably mounted on a stud |3| which is fixedly mounted relative to the base |0. The bell crank |30 has an upwardly extending arm |32 which is connected by means of a stud |33 and a roller block 36 which is flxedly mounted on the end of the valve stem |00. In the preferred construction, the stud |3| together with the valve actuating mechanism is supported in an apron 31 which is xedly mounted on the base I0. The forward end of the bell crank member |30 is provided with outwardly extending arms |38 and |39 which extend at substantially right angles to the arm |32. The arms |38 and |39 carry adjustable stop screws |40 and |4| respectively which bear against the lower ends of a pair of vertically arranged slidable rods |42 and |43. The rods |42 and |43 are slidably supported in the apron 31. The bell crank |30 v and the valve 99 are held in a central position, as indicated in the drawings, by means of a pair of springs |45 and |46 which surround reduced end portions |41 and |48 of the rods |42 and |43 respectively. Collars |49 and |50 are xedly mounted on the lower ends of the portions |41 and |48 of the rods 42 and |43, and the springs |45 and |46 are interposed between the fixed collars |49 and |50 and a pair of slidably mounted collars |5| and |52 which are located on the portionsv |41 and |48 of the rods |42 and |43 respectively. By adjusting the screws |40 and |4|, the tension of the springs |45 and |46 may be adjusted or balanced to normally hold the bell crank |30 and the valve 99 in the central or neutral position as indicated in Fig. 2.

The rollers |58 and |59 are rotatably supported on the upper ends of vertically extending plungers |60 and |6| respectively. Ihese plungers |60 and |6| are slidably mounted within sleeves |62 and |63 respectively. The sleeves |62 and |63 are preferably removably mounted within the apron |31 so as to facilitate adjustment of the mechanism. In order to prevent the plungers |60 and |6| from turning within their respective sleeves |62 and |63 and the apron |31, and in order to maintain the rollers |58 and |59 always in operating position with respect to the dogs |55 and |56, each of the plungers |'60 and |6| is provided with a keyway |64 and |65 respectively. A screw |61 is mounted in the apron |31 and has a projecting end portion which passes through a hole in the sleeves |62 and |63 and engages the keyways |64 and |65 in the plungers |60 and IBI and the pipe 12| into the reserrespectively. Only one of the screws |61 has been illustrated in Fig. v3 as passing through the sleeve |63 and engaging the keyway |65. A similar screw passes through the apron 31 andrthrough sleeve |62 and engages the keyway |64 to hold the plunger |60 against rotation. The plungers |60 and 6| are provided at their lower ends with adjustable stop screws |68 and |69 respectively `which are screw threaded into the ends of the plungers and are held in adjusted position relative thereto by means of lock nuts |10 and |1| The heads of the screws |68 and |69 bear against the upper end surfaces of the rods |42 and |43 respectively. The plungers |60 and |'6| may be readily removed from the apron |31 by removing the screws |61 and withdrawing the plunger |60 and |6| together with its supportingl sleeve I 62 and |63 vertically from the apron. The adjusting screws 68 and |69 may then be readily adjusted so that when the plungers |60 and |6| are assembled in the machine, the rollers |58 and |59 will project vertically to the desired extent with relation to the dogs |55 and |56 respectively.

Whenl the table 25 is moved longitudinally, as shown in the drawings, the longitudinal movement continues until the dog 55 or |56 engages the roller |58 or |59 respectively and the dog serves to move the roller and plunger downwardly so as to rock the bell crank |30 against the tension of the spring |45 or |46 to move the pilot valve stem |00 from a central position and to admit fluid under pressure to either the end chamber |08 or the end chamber I3 in the reversing valve 65 so that the valve is thereafter shifted into a reverse position by fluid under pressure.

It is desirable that the reversing valve 65 be moved quickly when the table reaches the end of its stroke so as to stop the table movement. This is preferably accomplished by providing an interconnection between the pilot valve 99 and the reversing valve 65 so that during the initial movement of the pilot valve by means of the dogs |55 and 56 and rollers |58 and 59, the reversing valve will be positively shifted to cut off the exhaust of fluid from the system so as to stop the table movement. This is preferably accomplished by means of a rock arm |15 which is pivotally mounted on a stud |16. One end of the rock arm |15 is connected by a stud |11 with a groove |18 in the head valve stem |00. The other end of the rock arm |15 is provided with a stud |19 which is arranged to engage either the collar or a collar 8| which are mounted on the end of the reverse valve stem 65. As indicated the stud |19 is in engagement with the collar |80. When the table reaches theend of its stroke, that is so that the dog |56 moves the roller 59 downwardly-to rock the bell crank 30 in a clockwise direction (Fig. 4) it serves to shift the pilot valve stem 00 toward the right (Fig. 2). This movement also serves through the rock arm |15 to move the stud |19 in a counterclockwise direction (Fig. 2) toward the left so as to shift the valve '65 toward the left (Fig. 2) and thereby cause the valve piston 68 to cover the passage 90 to stop the table movement. This movement of the reverse valve is caused directly by the adjustable dog |56 on the table and roller |59 through the bell crank |30 and rock arm |15. The movement of the valve stem |00 toward the right (Fig. 2) serves to move the valve piston |03 so as to uncover the passage |01 and admit uid under pressure into the valve chamber |08 to complete the movement of the reversing valve by the controlled influence |36 xedly mounted on the end of the in Figs. 2, 5 and 6,

Cal

of fluid under pressure. By regulating the admission of fluid under pressure into the chamber |99, the extent of `dwell of the table at the end of its stroke may be varied, as desired.

Similarly, when the reverse valve 65 .is at the other end ofthe table stroke, the stud |19 engages the collar |8| mounted on the end of the valve stem 65, so that when the dog `|55 engages the the roller |58 and rocks the bell crank 199 in a counterclockwise direction to shift the pilot valve toward the left (Fig. 2), this movement serves through rock arm |15 and stud H19 to move the collar |B| toward the right (Fig. 2) to again shift the reverse valve 65 to cut off the exhaust of fluid fromv the system and admit fluid under pressure from the valve chamber |96, through the passage H2, the needle valve Hit, into the reverse valve chamber H3, to again shift the reversing valve into the position illustrated in Fig. 2.

The reversal of the table movement may be readily controlled by varying the shapeof the cam surface formed on the lower operative faces of the adjustable table dogs v|55 and B56. By varying the shape of the dog faces, the pilot valve and the reversing valve may be moved at a controlled rate to cut oif the supply of iluid and stop the table movement in one direction before the valve is shifted into a reverse direction, as controlled by the pilot valve. Thus, either an abrupt stopping of the table movement or a gradual slowing down may be obtained, as desired. v

It is desirable to provide a manual control for the reversing mechanism so that the table 25 may be manually reversed in its direction of movement when desired. In the preferred construction, a manually operable control Vis provided to shift the reversing Valve 65. A manually operable control lever is mounted on the outer end of a rock shaft |86, which is rotatably supported in a portion of the apron |31. The inner end of the rock shaft |86 is provided with a downwardly extending arm |81 having a stud |88 engaging a groove |89 in a connecting member |99 which is xedly mounted on the valve stem 65 between the collars |89 and IBI. By shifting the lever |85 either toward the right or toward the left, the reversing valve 65 may be readily shifted to change the directio-n of movement of the table 25 under the influence of fluid pressure.

Asuitable speed controlling mechanism is provided for -the table movement so that the speed of reciprocation of the table may be readily adjusted to a desired speed for grinding. This is preferably accomplished by means of a control valve |99. This val ve is preferably of a piston type and is preferably arranged to control the exhaust of fluid from! the system. As illustrated in Fig. 2 of the drawings, fluid under pressure exhausting froml the cylinder chamber 63 through the passage 86 in the connecting rod 59, through the pipe 89, the passage 99, and valve chamber 9 I, passes outwardly through a passage 92 and a port |9| into a valve chamber |92 and through a pipe |93 which exhausts into the reservoir 11.

The control valve |99 preferably comprises a pair of spaced pistons |94 and |95 which are preferably formed integral with a valve stem |91. The end |96 of the piston |95 is slabbed off at an angle relative to the axis of rotation of the piston and is arranged to throttle the fluid passing through the port |9| when the valve |99 is moved toward the left (Fig. 2). By rotating the valve piston |95, the aperture of the port |9I may be varied so that the speed of the table may be varied from, a maximum to a mnimumi speed.

v acreage The valve stem '|91 carries at its outer end an adjusting knob |98 which is provided with a dial 899 cooperating with an index linger 299 to locate the valve in the desired rotary position for producing the required table speed. The index ilnger 299 is carried by a sleeve 29| which fits on the valve stem |91 and is held against rotation by means of a manually operable control lever 292. The control lever 292 is pivotally mounted on a'stud 293 carried by a bracket 299 fixed to the base of the machine. In the full line position of the valve |99 and the control lever 292, as shown in Fig. 2, the table 25 is reciprocating at a maximum; speed. By rotating the valve control knob E98, the slabbed-oif portion may be turned to close a portion of the port |9| to slow down the table movement. When it is desired to stop the table movement, the valve control lever 292 is movedfrom the full line position into the dotted line position 292a (Fig. 2) so that the valve piston closes the port |9|,

thereby stopping the exhaust offluid from the chamber 63 and stopping the movement of the table 25. At the same time, a valve chamber 295 located between the valve pistons |99 and |95 is moved into the dotted line position (Fig. 2) which serves to connect a passage 296 with a pipe 291 so that fluid may by-pass inder chamber 62 into the cylinder chamber 63 when the table is traversed manually by mecha- Y nism to be hereinafter described. The fluid may by-pass from the cylinder chamber 62 through the passage 86 in the piston rod 58,.-through a pipe 95, through the passage 296, valve chamber 295, and pipe 291, into pipe 89, through the passage 99 within the piston rod 59 and into the cylinder chamber 63, thus forming a free passage of fluid between the opposite ends of the cylinder.

In the dotted line position 292a of the control lever 292, the table 25 may be traversed longitudinally by a manually operable traverse mechanism without the necessity of overcoming the fluid pressure within the system due to the bypass of fluid above described. A manually operable traverse mechanism has been illustrated comprising a rack bar 2| 9 depending from the under surface of the table 25. A gear 2|| which is rotatably mounted on a shaft 2|2 meshes with the rack bar 2| 0. The shaft 2| 2 also carries a large gear 2| 3 which xed to the gear 2| The gear 2| 3 meshes with a small gear 2|4 rotatably supported on a shaft 2|5 and fixed to a hand wheel 2|6. By rotating the hand wheel 2|6 in either direction, a rotary motion is transmitted through the gear 2|4, 2|3 and 2|| to move the rack bar 2|9 endwise and to impart a corresponding traversing movement to the table 25.

The wheel feeding mechanism above described is preferably interconnected with the iiuid pressure table reciprocating mechanism so that the infeeding movement of the grinding wheel takes place at the end of a reciprocatory stroke of the table. As illustrated in Fig. 2, fluid under pressure from the pipe 16'passes th'rough a pipe 2|1 into a cylinder chamber 2|8 above the piston 45. The cross sectional area of the piston rod 46 is relatively large compared with the cross sectional area of the piston 45, thereby producing a differential effective area on the upper and lower surfaces of the piston 45. The effective area of the lower surface of the piston45 is greater than'l the effective area of the upper surface thereof and serves to cause an upward movement of the piston 45 when fluid under pressure 'from is either integral with or from the cylthe samie source is admitted to a lower cylinder chamber 2|9. The piston 45 is normally held in a down position by the continuous supply of uid pressure entering the cylinder chamber 2| 8.

In order to produce a controlled infeeding movement, a feed control valve is provided forl controlling the admission of uid to the cylinder chamber 2|9. A wheel feed control valve 220 of the balanced piston type is provided comprising a valve stem 22| having formed integrally therewith

valve pistons

222, 223, 224 and 225. In order that the infeed of the grindingwheel I 2 may take place during the period of reversal, it is desirable that the control valve 220 be operated in timed relation with the reversing valve 65. As illustrated in the drawings, this is preferably accomplished by connecting the valve stem 22| with the valve stem 65, preferably by means of a link 226 which is rigidly xed to the stems of each of said valves so that when the reversing valve 65 is shifted to reverse the direction of movement of the table 25, fluid under pressurefrom' the vpassage |05 passes downwardly through a passage 221 which, as shown in Fig. 2, is blocked by the.

valve piston 223. When the reverse valve 65 starts moving toward the left (Fig. 2), the valve stem 22| is also moved toward the left by means of the link 226. After the valve vstem moves toward the left a sufiicient distance to Vuncover the passage 221, fluid under pressure may pass for an instant through a valve chamber 228 and out through a Apipe 229 into 'the valve chamber l2| 9, thereby causing a differential pressure which is greater on the under surface of the piston and serves to move the piston upwardly, carrying the feed pawl 42 to move it idly over the feed wheel 39. 'I'he passage of uid to the chamber 2|9 is permitted only for an instant, after which the valve piston 224 closes the port admitting fluid to the pipe 229, and fluid under pressure within the pipe 229 and cylinder chamber 2|9 may then exhaust through a valve chamber ||9 and out through a passage |20 and pipe |2| into the reservoir 11. y

On the reverse movement of the valve stem 22|, fluid under pressure is admitted instantaneously through the pipe 229 to cause an infeeding movement of the wheel at the other end of the table stroke. When the valve piston 224 cuts loff the ow of fluid through the pipe 229 and allows the uid within the cylinder chamber 2|9 and pipe 229 to exhaust through the valve chamber |26 and passage |21 into the reservoir 11, the continuous fluid under pressure applied through the pipe 2|1 causes the piston 45 to again move downwardly, causing the feed wheel 39 to rotate in a counterclockwise direction to cause an infeeding movement of the grinding wheel I2.

'I'he operation of the machine is readily apparent from the foregoing disclosure. A work piece 26 is mounted on

centers

29 and 30 and the work and wheel are started in rotation. The table dogs |55 and |56 are then located along the front edge of the table' 25 within the T.slot |51 so that the table may be reciprocated to pass the desired por'- tion of the work piece 25 across the operative face of the grinding wheel |2. The knob |90 is then rotated to the desired table speed and the ycontrol lever 202 is moved from the dotted line position 202a (Fig. 2) into the full line position to start the table reciprocation. 'I'he adjustable stop screw 48 may then be adjusted so that the desired movement of the feed pawl 42 may be obtained to cause either one or more teeth on the feed wheel to be picked up at each reciprocation of the feed pawl. 'I'he speed of movement of the lfeed pawl in an upward direction may be readily adjusted by means of an adjustable valve 23| which is located between the pipe 229 and the cylinder chamber 2|9. Similarly, the admission of continuous uid under pressure to the cylin- .der chamber 2|8 may be controlled by a valve 232 so that the speed of movement of the feed pawl 42 in either direction may be independently adjusted, as desired. 'Ihe needle valve ||0 and ||4 may then be adjusted to vary the extent of dwell at each end of the table reciprocation in order that the work piece may rotate at least one complete turn at the end of the table stroke before the table starts its movement in the reverse direction.

It will thus be seen that there has been provided by this invcntion apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the aboveinvention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A grinding machine comprising a transversely movable rotatable grinding wheel, means including a piston and cylinder to feed said wheel transversely, a longitudinally movable work supporting table, means including a piston and cylinder to reciprocate said table, a fluid pressure system including a pump, a reversing valve to change the direction of fluid pressure to said cylinder, a pilot valve to control the movement of said reverse valve, a bell crank lever operatively connected to said pilot valve, a pair of balanced springs to hold said lever and valve in a neutral or central position. a pair of movable plungers carried by said base which are operatively connected to actuate said lever and valve, adjustable staggered dogs on said table, and a roller on each of said plungers, each of which is arranged in the path of one of said dogs.

2. A grinding machine comprising a transversely movable rotatable grinding wheel, means including a piston and cylinder to feed said wheel transversely, a longitudinally movable work supporting table, a fluid pressure system which is arranged to reciprocate said table including a pair of adjustable staggered dogs on said table, a pair of plungers carried by said base each of which is arranged in the path of one of said dogs, a pilot valve which is normally held in a central or neutral position and which is actuated in either direction by one of said plungers, a reversing valve which is operatively connected to reverse the direction of fluid in said table cylinder, and connections between said pilot valve and reverse valve whereby movement of either of said plungers serves to move the re- 'verse valve to stop the table movement and fluid from the pilot valve serves to complete the movement of the reverse valve to start the table moving in the reverse direction.

3. A grinding machine table reciprocating mechanism comprising a longitudinally movable table, a piston and cylinder operatively connected to reciprocate said table, a reversing valve arranged to control the admission of fluid to said cylinder to reverse the direction of movement of said table, a control valve which serves to throttle the exhaust of iiuid from said cylinder,

a pair of adjustable oiiset dogs carried by said table, a vertically movable plunger associated with each of said dogs, a pilot valve actuated by said plunger, lost motion connections between the pilot valve and the reverse valve whereby the initial movement of the pilot valve serves to positively shift the reverse Valve through a sufcient distance to cut E the exhaust of iiuid from said cylinder, and controlled means nterposed between the-pilot valve to convey controlled iiuid under pressure to complete the shifting of the reverse valve.

4. A grinding machine comprising a rotatable grinding wheel, a transversely movable slide to support said wheel, a pawl and ratchet feed mechanism therefor, means includingl a piston and cylinder to actuate said pawl and ratchet,

a control valve therefor, a longitudinally reciprocable table, means including a piston and cylinder to reciprocate said table, a pair of adjustable offset dogs on said table, a pair of vertically arranged plungers each of which is aligned with one of said dogs, and means including a control valve mechanism actuated by said plungers to control the reciprocation of said table and the infeed of the grinding wheel.

5. A grinding machine comprising a rotatable grinding wheel, a transversely movable slide to support said wheel, a pawl and ratchet feed mechanism therefor, means including a piston and cylinder to actuate said pawl and ratchet, a control valve therefor, a. longitudinally reciprocable table, means including a piston and cylinder to reciprocate said table, a pair of adjustable oifset dogs on said table, a pair of vertically arranged plungers each of which is aligned with one of said dogs, means including a control valve mechanism actuated by said plungers to control the reciprocation of said table and the infeed of the grinding wheel, and connections between said table control valve and said feed control valve whereby the feed control valve is operated by and in timed relation with the table control valve to cause an nieeding movement of the grinding wheel duringthe period of reversal. t

6. 1n a grinding Amachine, a longitudinally movable table,v a piston and cylinder operatively connected to reciprocate said table, a kpair of adjustable offset dogs carried by said table, a pair of plungers, a roller on the upper end of each of said plungers which is aligned with one of said dogs, a reversing valve to control the admission and exhaust of fluid from said cylinder, means including a pilot valve which is actuated by said dogs and plungers to shift the reversing valve, and independent adjustable connections between each of said plungers and said pilot valve whereby movement of one of said plungers serves to actuate the pilot valve in one direction to reverse the movement of the table and depression of the second plunger serves to move the pilot valve in the opposite direction to again shift the direction of movement of the table.

7. In a grinding machine, a longitudinally Y movable table, a piston and cylinder operatively connected to reciprocate said table, a pair of adjustable oifset dogs carried by said table, a pair of slidably mounted plungers, a roller on the upper end of each plunger which is arranged in the path of one of said dogs, a reversing valve to control the admission and exhaust of fluid from said cylinder, means including a pilot valve to shift said reverse valve, means including a bell crank lever to actuate said pilot valve, and adjustable connections between each of said plungers and said lever whereby engagement of one of said dogs with its respective' roller serves t depress the plunger and actuate the pilot valve in one direction and engagement of the second dog with the second roller serves to depress the second plunger to actuate the pilot valve in the reverse direction to control the reversal of the table movement.

WALLACE H. WOOD.