US2071677A - Hydraulically operated grinding machine - Google Patents

Description

Feb. 23, 1937. w. H. WOOD HYDRAULICALLY OPERATED GRINDING MACHINE Filed Aug. 25, 1934 3 Sheets-Sheet 1 WALLACE H. W000 3W 6&

WITNESSES F eb. 23, 1937.

w. H. woop HYDRAULICALLY OPERATED GRINDING MACHINE Filed Aug. 23, 1934 3 Sheets-Sheet 2 WALLACE H. W000 Feb. 23, 1937. w, H, w 2,071,677

HYDRAULICALLY OPERATED GRINDING MACHINE- Filed Aug. 25, 1934 3 Sheets-Sheet 3 G M a so a -WITNES-SE8 I WALLACE H. W000 Patented Feb. 23 1937' UNITED STATES- 2,071,677 HYDRAULICALLY OPERATED GRINDING I MACHINE Wallace H. Wood, Worcester, Mass, asslgnor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application August 23, 1934, Serial No. 741,119

12 Claims. (01. 51-95) This invention .relates to grinding machines, and more particularly to a hydraulic table reciprocating mechanism and wheel feeding mechanism for precision grinding machines.

Heretofore, various mechanisms have been devised for reciprocating either the work support or the wheel support relative to the other member by a fluid pressure mechanism including a reversing valve to change the direction of movement of the movable member. Many of these mechanisms have been unsatisfactory for use in a grinding machine, due to the fact that when the table is run at a fast speed, there is considerableshock and vibration transmitted to the machine parts when the reversing valve is suddenly shifted to a reverse position, rapidly cutting off the fluid under pressure on one side of the system and transferring it to the other side. Also, it has been found that with previous mechanisms, when the table is run at a very slow speed, the movement of the reversing lever by the slowly moving table carriage has been insufllcient to carry the reversing lever past the central or neutral position so that it may be shifted into a reverse position.

Further hydraulic table reciprocating mechanisms have been developed, in which some of the difficulties experienced in the previously described mechanisms have been somewhat overcome. has been common practice for some time in such hydraulic systems to provide a pilot valve which is controlled by movement of the moving member to admit fluid under pressure so as to cause the reversing valve to shift under the influence of 35 fiuid pressure. Such mechanisms have proven to be fairly satisfactory, but have resulted in more or less complicated fluid pressure systems which required the use of a plurality of valves and also numerous pipe connections to operatively connect 40 the various elements of the system, thereby giving opportunity for air and oil leaks in the system which detrimentally affect the operation of the mechanism.

A further difficulty experienced in hydraulically driven cylindrical grinding machines, particularly machines adapted for traverse grinding, re-

sides in the lack of an adequately controlledthe oil prevents the system from running smoothly, since when fluid under pressure is suddenly changed in direction of flow to reverse the movement of parts, the compression of the air in the oil serves as a variable to prevent smooth operation .or valves, or if the oil in the reservoir becomes at all foamy, then air is pumped into the system with the oil.

It is the primary object of this invention to eliminate the difliculties experienced with the previous mechanisms and to provide a fluid pressure operated mechanism in which a single valve serves to combine the functions of a reversing valve and a pilot valve within a single valve casing.

It is another object of thisinvention to provide a fluid pressure system with a combined pilotreversing valve and a speed control valve within the same valve casing.

It is a further object of this invention to provide a fluid pressure operated dwell control device which serves to cause a sufllcient dwell in the table movement to allow the work to rotate through one complete turn before the table starts traversing in the reverse direction.

It is another object of this invention to provide a shuttle valve shunted around the main control valve to produce a predetermined dwell of the table at reversal.

It is a still further object of this invention to provide a fluid pressure system with a combined fluid pressure pilot-reversing valve and a speed control valve which are arranged so that when the fluid pressure in the system is cut off to stop the table movement, a by-pass is opened, permitting fluid to passreadily from one end of the fluid pressure cylinder to the other so as to enable the carriage to be traversed manually without the necessity of overcoming the pressure in the system.

It is an object of this invention to provide a hydraulically actuated wheel feed mechanism in which both the extent of infeed as well as the time of infeed relative to the table traverse and reversal may be accurately controlled.

It is. also an object of the present invention to provide a readily accessible bleeding device associated with the cylinder to draw off fluid :rom the upper portion of the main cylinder, so that any air entrapped within this portion of the system may be readily removed.

Other objects will be apparent from the foregoing disclosure. One embodiment of this invention has been illustrated in the drawings, in which like reference numerals indicate like parts:

Fig. 1 is a front elevation of a grinding machine embodying this invention;

Fig. 2 is a combined fragmentary. sectional and diagrammatic view, on an enlarged scale, showing the valves and piping arrangement for the fluid pressure system;

Fig. 3 is a fragmentary view, on an. enlarged scale, partly in elevation and partly in section, showing the reversing valve and the wheel feed actuating mechanism;

Fig. 4 is a fragmentary sectional view, on an enlarged scale, taken approximately on the line 4-4 of Fig. 3; I

Fig. 5 is a longitudinal sectional view, on an enlarged scale, through the reversing and the speed control valves, showing a fragment of the operating lever;

Fig. 6 is a fragmentary end view, on an enlarged scale, partly in section, of the feed pawl and actuating mechanism shown in Fig. 3; V

Fig. '7 is a detail view of the adjustment for the speedcontrol valve;

Fig. 8 is a fragmentary. cross-sectional view, taken approximately on the line 88 of Fig. 5, showing the spring connection between the parts of the reverse lever; and

Fig. 9 is a fragmentary view of a modified construction, partly in section, showing a fluid pressure operated dwell control apparatus.

One embodiment of the invention has been illustrated in the drawings, in which a cylindrical type grinding machine is provided with a hydraulically operated table traversing mechanism. The table may be traversed or reciprocated at a desired traversing speed, then reversed and allowed to dwell a sufllcient extent to allow the work to rotate once before the table starts'its motion in the reverse direction. A grinding wheel feeding mechanism is provided which is hydraulically actuated and is, preferably operated by means of the table reversing lever which in turn actuates a micrometer feeding mechanism to cause a rotation of a feed screw and thereby produce an infeeding of the grinding wheel while the table is at the end of its reciprocatory stroke.

This invention further includes a combined pilot and reversing valve formed as a single valve unit, in which the end chambers of the reversing valve serve and function as apilot valve to cause .a reversal of the reversing valve by means of fluid under pressure. The combined pilot-reversing valve is supplemented by an auxiliary shuttle valve, which is preferably shunted around the reversing valve and arranged to cause the table to dwell when the reversing valve is shifted from one position to the other a suflicient length of time to allow the work piece to rotate one complete turn before the table starts its movement in the-reverse direction, so as to allow the grinding wheel to grind the entire surface of the work on each relative traverse of grinding wheel and work support.

' As illustrated in the drawings, the machine'embodying this invention comprises a base III which supports a work table I I on the usual V-way and flat-way (not'shown) for a longitudinal, reciprocating movement relative to the base. A headstock l2 andfootstock l3 are mounted on the ciprocate the work table II.

table II and are arranged to rotatably support a work piece i4 in operative relation with a rotatable grinding wheel ii. The grinding wheel I! is rotatably supported on a wheel slide it of the usual type, such as shown in the expired patent to Norton No. 762,838 dated June 14, 1904. In the preferred form, an electric motor 20 is mounted on the wheel slide I4 and is provided with a pulley II which is connected by a driving belt 22 with a pulley 23 on the end of a wheel spindle 24.

A fluid pressure mechanism is provided to re- In the form illustrated, a cylinder Ill is fixedly mounted to the under side of the table II. The cylindercontains a pair of spaced pistons SI and 32 which are connected by a pair of hollow piston rods 33 and 34 respectively with a pair of hollow brackets 35 and 16 respectively which are flxedly mounted on opposite ends. of the base l0.

In the preferred construction, the base In is formed as a hollow, box-like construction in which the lower portion serves as a reservoir for the fluid pressure system. Fluid is drawn from the reservoir 40 through a pipe 4| by a pump 42 and is forced through a pipe 43 and a pipe 44 to a table control valve 45. A fluid pressure relief valve 48 is provided in the pipe 44 and isarranged to allow fluid under pressure to by-pass through a pipe 4'! and return to the reservoir 40 in case the pressure within the system increased above a desired pressure.

To attain the primary object of this invention, the control valve is provided which combines the functions of 'a reversing valve and a pilot valve, so that a lever actuated by the table movement serves to-move the valve only to a center position and then fluid under pressure serves to move the reverse valve into a reverse direction, producing a smooth reversal of the table movement without the'necessity of providing a complicated series of valve mechanisms and pipe connections. In the form illustrated, a piston type valve is provided including a movable valve member 49 having a pluralityof valve pistons 50, ii, 52, 53 and 54 integrally formed thereon. Fluid under pressure from the pump 42 is forced through the pipe 44 into a chamber 58 within the valve casing 45. Assuming the valve to be in a central or neutral position, fluid under pressure is conveyed from the chamber 58 through ports. and 80 into valve chambers 6| and 62 respectively. The valve chambers GI and B2 are formed between the valve pistons 5i and 52, 52 and 53 respectively. I

In the position of the valve illustrated in Fig. 5,

fluid under pressure passes from the valve chambers BI and 62 through ports 64 and 65 respectively into chambers 66 and 61, then through pipes 68 and 69 respectively, through brackets 35 and 36, hollow piston rods 33 and 34 respectively, into cylinder chambers I0 and H respectively and thereby to balance the pressures against opposite ends of the cylinder so as to hold the work supporting table in a stationary position. In actual operation, however, the parts are only in position shown in Fig. 5 for an instant during reversal of the table.

As illustrated in Fig. 5, fluid under pressure may pass from valve chambers ii and 62 through the ports 15 and 16, through ports 11 and 18 into valve chambers 19 and 80. The valve chambers 19 and 80 are formed between valve pistons 50., 5i and 53, 54 respectively. Fluid under pressure around the valve pistons 58 and 84.

The effective areas of valve pistons 58 and 84 is considerably less than the effective areas of valve pistons 8| and 53- respectively. By providing the differential in the pressure areas between these pistons, the chambers I9 and 88 serve to function as a pilot valve and cause a reversal of the reversing valve under the influence of fluid pressure whenever the valve is moved to a position slightly by the center position, as shown in Fig. 5; that is, so-that either the port 11 or the port I8 is cut off to a greater extent from the other, allowing fluid under pressure to flow into either chamber I9 or 88. Due to the differential piston areas, the fluid under pressure entering chambers I9 or 88 serves to move the valve piston 49 either toward the right or toward the left, as viewed in Fig. 5.

Speed control valve A speed control or throttle valve 98, as illustrated in Fig. 5, is formed integrally with the valve member 45. As illustrated in the diagrammatic showing in Fig. 2, the valve 98 is shown as a separate valve unit. The valve 98 is preferably located in'the exhaust side of the system so as to maintain a uniform fluid pressure on the operative side of the main cylinder. This valve comprises a valve stem 9| which is provided with valve pistons 92 and 93. The casing for the valve 98is provided with a V-shaped port 94 which is located at one end of a pipe or passage 95, conveying fluid from either of the valve chambers 6| or 62. A passage or outlet pipe 98 serves to exhaust fluid from a throttle valve chamber 91 into the reservoir 48 within the base of the machine.

The throttle valve is arranged so that it may be'moved longitudinallyfrom a full line position (Fig. 2) to a dotted line position. The valve is provided with an actuating knob 99 on the front end of the valve stem 8 I, which permits the valve to be rotated. In the preferred construction, the end of the valve piston 93, instead of being a plane surface at right angles to the axis of the throttle valve, is arranged at an angle thereto. By providing an angularly positioned end surface to the valve and rotating the valve member, it is possible to obtain a, fine adjustment by cutting off more or less of the V-port 94 to precisely regulate the exhaust of fluid from the system and thereby permit a fine regulation of the table speed.

In order that the valve piston 93 may be maintained in the desired adjusted position so as to enable the table to be stopped and started as desired without changing the speed adjustment, a. serrated or notched portion I88 is provided and a spring-pressed pawl I8I is carried by the valve casing 98, so that when the knob 99 is turned to adjust the valve piston 93 to give the desired table speed, the pawl I8I engaging notches in the portion I88 serves to hold the piston in its adjusted position, so as to permit moving the valve stem 9I by means of the control lever I83 to start and stop the table movement without upsetting the adjustment of the valve.

To permit the valve piston 93 to be quickly and accurately located in a predetermined position to produce a predetermined table speed, an adlusting screw I82 is provided in the sleeve I88 and is arranged to engage a fixed stop surface I82a on the knob 99. By adjusting the screw I82 relative to the sleeve, the angular position of the valve-piston 93 may be varied, so that the valve, when adjusted, may be turned to a second speed, for example, a fast speed, and then readilyturned back to a predetermined adjusted table feed by merely turning the knob 89 until the stop screw I82 engages the stopping surface I82a.

A lever I83 is pivotally mounted on a stud I84 on the base of the machine l8 to permit rapid movement of the valve stem 9| to start and stop the table movement. The lever I83 is provided with an aperture I88 fltting loosely around a sleeve I88 which is mounted on the valve stem 9|. Trunnion pins I88 are provided at opposite sides of the aperture I88 on thelever I83 and are. arranged to engage vertical slots I89 in the sleeve- I88. It will be readily apparent from the foregoing disclosure that when the throttle valve control lever I83 is in the position as indicated in full lines in Fig. 2, the valve stem 9| is positioned so that valve piston 93 uncovers a portion of the V-port 84, allowing the table to move at- Fluid by-pass When the throttle valve is in a closed position, stopping the table movement, it is desirable to provide a suitable fluid by-pass whereby fluid may readily pass from one end of the cylinder chamber to the other. In the preferred construction, a passage or pipe H8 is provided to connect the pipe 89 and valve chamber 82 with a passage III provided as an extension of the pipe 68, so that when the throttle valve 98 is in a closed position, as indicated by the broken lines in Fig. 2, fluid may readily pass from cylinder chamber I8 through pipe 68, pipe III, through a valve chamber II2 between pistons 82 and 93, out through pipe II8, through pipe 68, and into the cylinder chamber II. This by-pass in the throttle valve interconnects the cylinder chamber I8 and II so that when the fluid pressure system is shut off by closing the throttle and control valves 8I the table I I may then be moved manually, if desired.

Manual traverse In order to move the table II to traverse the table manually, a suitable hand wheel I28 is mounted on the front of the machine base. This wheel rotates a gear I2I meshing with a gear I22 on the shaft I23. The shaft I23 in turn carries a gear I28 meshing with a rack I25 depending from the table II. It will be readily appreciated from the foregoing disclosure that when the lever I83 is moved into a position to close the control valve, the table II may then be traversed longitudinally by manual rotation of the wheel I28. As the table is moved under manual control, fluid within the chambers I8 and II will readily bypass through the pipes, as above described, so as not to retard the movement of the table.

Wheel feed mechanism The grinding wheel I5 and its supporting slide I8 may be fed toward and from the work support by a pawl and ratchet wheel feeding mechanism, such as shown, for example, in the expired U. B. patent to Norton No. 782,838 dated June 14, 1904. As illustrated in the drawings, this mechanism may comprise a feed wheel I28 which carries a pinion I21 meshing with a gear I28 on a'feed screw shaft I28. The feed screw I28 (not shown) meshes with a half nut (not shown) depending from the wheel slide I8. .This

feed screw and the half nut have not been illustrated in detail, since they do not constitute any A suitable reversing mechanism is provided to change the direction of the table movement, as desired. In the preferred construction, adjustable dogs I38 and I 3| are adjustably mounted in a T-slot I32 on the table II. The dogs I88 and I3I are arranged toengage the upper end of a reverse control lever I33 which is pivotally mounted on'a stud I84 on the base of the machine. The lever I33 is operably connected to a projection of the valve stem 48.

In order that the table may be reversed with a minimum amount of'vibration, it is desirable to provide a lost motion connection between the reversing lever and the reversing valve, so that during the initial movement of the reversing lever.

under the influence of the table dogs, the valve is not moved. This mechanism preferably comprises a short lever I38 flxedly keyed to the inner end of stud I34. A similar short lever I38 is rotatably mounted on the stud I34 and is supported thereon by means of a bushing, so that the lever I38 is free to oscillate. relative to the stud I34. The lever I38 carries a pin I48 engaging agroove I in an extended portion of the valve stem 48. The lever I38 is provided with an aperture I44, within which is located a pin I45 which is fixedly mounted to the lever I38. The lower ends of the levers I38 and I38 are provided with enlarged portions I58 and I5I respectively, each of which is provided with a semi-cylindrical aperture I52 and I53. A spring I55 is provided within the semi-cylindrical apertures I52 and I53 and serves to hold the levers normally in a definite relation to each other and also aids in actuating the reversing valve through a portion of its movement.

Assuming the parts of the reversing mechanism to be in the positions illustrated in Fig. 3, the table is moving in a direction toward the left, as viewed in Fig. 1. This movement continues until the reversing lever I33 is moved from broken line position I33-(Fig. 3) into full line position I33a (Fig. 3) which serves to actuate the lever I38 through its lost motion movement until the aperture I44 engages the pin I45. This movement of the lever I38 serves to put the spring I55 under tension, and when the aperture I44 engages the pin I45, continued movement of the table serves to throw the reversing valve stem 48 into a neutral or central position indicated in Fig. 5 where the pressures are balanced to opposite sides of the main cylinder 38. The tension of spring I55 then moves the valve stem 48 a further distance toward the right, partially closing the port 18. This same movement causes the valve piston 5I to uncover the port 11, decreasing the fluid pressure passing into chamber 88 and increasing fluid pressure passing into valve chamber 18. It should be noted that the valve pistons 58 and II are provided of a different cross-sectional area, and fluid under pressure entering the chamber 18 serves through the differential pressure area on the pistons 58 and 8| to move the valve stem 48 towards the right, as viewed in Fig. 5, to throw the valve into its extreme reverse position and thereby cause a reversal in direction of movement of the fluid under pressure to pass the same to the opposite end of the main driving cylinder 38 and therebyycause, the table II to move in the opposite direction.

Due to the diiferential in the pressure areas betweenthe valve pistons 58 and 84 and II and 53 respectively, the chambers 18 and 88 function as a pilot valve to cause a reversal of the reversing valve under the influence oi fluid pressure. The reversing lever I38 serves only to cause the reversing valve to move to its central or neutral position, as is illustrated in Fig. 5. and the spring I55 then being under tension serves to throw the reversing valve slightly of! center to change the respective openings of the ports 11 and 18 and cause the fluid under pressure to operate through the chambers 18 and 88 to cause a fluid pressure reversal of the reversing valve, thereby combiningthe functions of a reversing valve and a pilot 'valve in a single valve unit, eliminating the piping connections and losses due to passages between the various valves, as experienced heretofore.

Wheel feed actuating mechanism It is desirable to provide a suitable mechanism for actuating the wheel feeding mechanism in timed relationship with the movement of the work supporting table. In the preferred construction, a fluid pressure mechanism is provided which is operated by and in timed relationship with the movement of the reverse control lever. As illustrated in the drawings, this mechanism comprises a cylinder I88 having a piston I8I connected by a piston rod I82 with a link I83 which is pivotally connected to a pawl actuating slide I84 by a stud I85. This slide I84 also carries apivotally mounted feed pawl I88 which is of a construction substantially the same as that shown in the above mentioned prior patent.-

In order to obtain actuation of the pawl I88 in timed relationship with the reversing lever I 33, a valve I18 is provided with a movable valve piston "I, the upper surface of which is formed as an inverted V-shaped surface I12 adapted to be engaged by and moved by an arrow point I13 which is mounted on the lower end of the reverse lever I33. A spring I14 within a hollow central aperture in the piston I1I serves normally to hold the arrow point in an uppermost position. An adjustable stop screw I15 mounted on the base of the machine serves to limit the upward movement of the valve member I1I. A pipe I11 is connected with the fluid pressure pump 42 to convey fluid under pressure to a valve chamber I18 which in the upper position of the valve, as illustrated in Fig. 2, passes fluid under pressure through a passage I18 into a cylinder chamber I88 to move the piston I8I and hold it in its lower position with the pawl withdrawn also to its lower position. In the position of the parts as illustrated in Fig. 2, fluid under pressure is exhausted from a cylinder chamber I84 through a passage I85, a valve chamber I88, and through an exhaust pipe I81 into the reservoir 48 in the 'movement of table II.

'base of the machine. When the table II reaches the end of its stroke, one of the adjustable dogs I30 or I3I moves the reversing lever I33 to actuate the reversing valve to change the direction of During the initial part of this rocking movement of the reverse lever I33, the arrow point I13 rides on the V-surface I12 causing a downward movement of the valve member .I1 I. This movement serves to partially close the passage I19 and open the passage I85, admitting fluid under pressure to the cylinder chamber I84 to cause an upward movement of the piston I6I and also of the feed pawl I66 to start a feeding movement. This downward movement of the valve I'll continues until the reversing lever passes the high point on the arrow and inverted V; and as the lever swings by the central position, the released tension of the spring I14 serves to return the valve member IN to its uppermost position, cutting off fluid under pressure from the passage I85 and admitting all of the fluid under pressure to the passage I19 to cause a downward movement of the piston and also a corresponding downward feeding movement of the feed pawl I66 in contact with the ratchet or feed wheel I26. It will be readily appreciated from the foregoing disclosure that at each actuation of the reversing lever I33, the feed pawl will be moved through a predetermined extent to cause the desired infeeding movement of the grinding wheel at each end of the table stroke.

Feed adjustment The extent of the feeding movement may be adjusted by means of an adjustable stop I90, which is slidably adjustable relative to an elongated slot I9I in the link I63. The stop I90 is arranged to engage a stopping surface I92 at the lower edge of the support for the slideIM. By adjusting the position of the stop I90 relative to the link I63, the extent of upward movement of the index pawl may be adjusted to produce the desired infeeding movement at each end of the table stroke.

A further adjustment is also provided on the reversing lever I33. In the preferred construction, the arrow point I13 is adjustably positioned on the lever I33 by means of an adjusting screw 200 and a stop screw 20I. This adjustment of the arrow point relative to the pivot I34 serves to vary the extent of movement of the valve in nber I1I so as to permit varying the speed of .novement of the index pawl. It will be readily seen from this construction that by permitting fluid under pressure to enter both the passage I85 and I19, and by varying the respective openings to these passages, a differential pressure is established between the cylinder chamber I80 and I84, which serves to regulate the speed of movement of the piston during the feeding movement of the pawl I66.

Dwell control The fluid pressure system is so arranged that the table reversal takes place very rapidly and in some cases reverses so rapidly that the cylindrical piece of work being ground does not have an opportunity to rotate through one complete turn to allow the wheel to grind out before the table starts its movement in the reverse direction. In order to provide a slight but predetermined dwell sufiicient to allow the work to rotate through one complete turn at the end of its stroke, a shuttle valve is provided which is preferably so the machine.

constructed and so connected in the system that upon reversal of the reversing valve the initial change in direction of fluid in the system moves through the easiest course and instead of being transmitted immediately to the opposite end of the cylinder serves to move a shuttle valve piston 205 which is slidably mounted within a cylinder 206. The opposite ends of the shuttle valve are connected by pipes 201 and 208 to the pipe lines 68 and 69 respectively. Each of these pipes 201 and 208 is provided with a shut-off valve 209 and 2I0 which permits the shuttle valve to be rendered operative or inoperative when desired.

The ends of the shuttle valve piston 205 are formed as frusto-conically shaped projections 2| I and 2I2 which are arranged to enter a pair of chambers 2I3 and 2M inopposite ends of the shuttle valve cylinder 206. The chambers 2I3 and 2 I I with the cooperating projections 2I I and 2I2 serve as dash pots to slow down the movement of the shuttle valve piston 205 as it approaches the end of its stroke within its cylinder. It should be noted in Fig. 9 that when the shuttle valve reaches the extreme end of its stroke, the projection on the right-hand end of the piston provides only a slight clearance between it and its mating chamber within the shuttle valve cylinder. By utilizing this construction, when the main reversing valve is shifted to its reverse position with the parts as indicated in Fig. 2, the instant the fluid under pressure is reversed in direction serves to cause the fluid to enter through the pipe 201 and into the chamber 2I3 to cause the throttle valve piston 205 to move toward the right as viewed in Fig. 9. This valve moves at first rapidly until the projection 2I2 starts to enter the chamber 2I4 at the righthand end of the shuttle valve cylinder. As soon as the projection starts to enter the chamber, the opening permitting exhaust from the shuttle valve cylinder is gradually reduced, and the shuttle valve piston gradually slows down until it reengages the end of its cylinder. The time interval between the shifting of the reverse valve into its reverse position to stop and reverse the table and the actuation of the shuttle valve cylinder to the opposite end of the cylinder is just suflicient to allow the work to rotate through one complete turn while the table is at the end of its stroke. When the shuttle valve piston engages the end of its cylinder, the fluid under pressure is then applied in the reverse direction to the table traversing cylinder to start the table moving in the reverse direction. All of this movement is substantially instantaneous, but there is sufficient dwell provided by varying the size of the shuttle valve piston and its projection so as to enable the work to rotate through one complete turn before the table reverses in direction, so as to allow the grinding wheel to grind out at each longitudinal reciprocation thereof.

Bleeder system In order to permit ready removal of air entrapped in the fluid pressure system, a bleeder system is provided including a port 220 and 22I located respectively at each end of the cylinder 30 at the upper edge of the cylinder. Any air leaking into the cylinder rises to the upper por-- tion of the cylinder and may be readily withdrawn by opening a valve 222 and 223 to allow the air and adjacent oil to escape through a pipe 224 and return to the reservoir 40 in the base of By utilizing such an arrangement, it is possible to bleed the system of any air which 6 may initially be 'found in the system, or which may leak into the system, thereby eliminating the undesirable eflect of air pockets within the fluid pressuresystem. v g The operation of this mechanism is readily apparent from the foregoing disclosure. Aftenadiustingthe table dogs I and ill to give the desired length of tablemovement to traverse the wheel over the desired portion of the work and adjusting the feed pawl actuating mechanism to give the desired extent and speed of movement ofthe pawl to feed the wheel into the work at'the desired rate, the operator then moves the speed control lever Ill from the broken line position I Illa (Fig. 2) into the full line position to open the v-ports so as to allow exhaust of fluid from cylinder chamber ll, thereby permitting fluid under pressure entering the cylinder chamber to cause the cylinder Ill and table II to move in the direction of the arrows, as indicated in Figs. 1 and 2. The traversing movement of the table in this direction continues until table dog III engages reversing lever I" and rocks the lever in a counterclockwise direction. This movement of the lever serves to move the valve piston 49 into a central or neutral position, thereby admitting fluid under pressure equally to opposite ends of the cylinder 30. The released tension of the spring ll! then serves to move the lever I39 relative to the lever I38, and thereby causes the valve stem 49 to be moved in a further direction toward the right sufllcient to move the valve pistons BI and I3 from their central position,

admitting fluid under pressure through port "into the chamber 19, which, due to a differential area between the piston 50 and piston 5|, serves to move the valve piston towards the right and causes a completion of the movement of the reverse valve under fluid pressure to pass fluid under 4,0 pressure into the cylinder chamber 'II. This movement allows fluid under pressure within the cylinder chamber." to exhaust through the throttle valve V-port 04 to move the table I I in the opposite direction.

At each end of the table stroke, the arrow point I'll, as previously described, causes an actuation of the valve member ill to cause a predetelrl'milned infeeding movement of the grinding w ee Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: v

1. A hydraulically operated grinding machine having a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connected to cause said relative movement, means including a piston type reversing valve to convey fluid under pressure to either end of said cylinder, means including a reversing lever and adjustable dogs. arranged on the relatively movable members to shift said valve to a neutral or central position, and a resilient con- 55 nection between said lever and valve to shift the reverse valve slightly beyond a neutral or central position to admit fluid under pressure into fluid pressure chambers in the ends of said reversing valve which serveto shift the valve by fluid under pressure into a reverse position.

2. A hydraulically operated grinding machine having a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a fluid pres- 7 sure system including a piston and cylinder opa,cv1,evv

eratively connected to cause said .relativelongitudinal movement, means including a piston type reversing valve to convey fluid under prusure to either endof said cylinder, a. reversing lever actuated by said' table, and lost motion connections between said lever and valve including a spring,saidpartsbeingsoarrsngedthat the table movement serves toshiit the lever to compress the. spring and positively move'the valve to a neutral or central position, the tension of said spring being sumcient to move the valve slightly by the central position to open a port at one end oi said valve and admit fluid under pressure directly from the pump to fluid pressure chambers in the ends of said valve which serve to shift the valve .by fluid under pressure into a reverse position."

\i- A hydraulically op rated cylindrical mming machine having a rotatable grinding wheel and a .work support which are movable longitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connected to reciprocate said table, means including a reversingvalve arranged to convey fluid under pressure to either end of said cylinder, means actuated by one of said movable elements to actuate said valve and cause a reversal in direction of movement of said member, and a shuttle valve which is operatively connected between opposite ends of said cylinder to cause a predetermined dwell suiflclent to allow the work to rotate one complete turn to grind out at the end of each table stroke.

4. A hydraulically operated cylindrical grinding machine having a rotatable grinding wheel and a rotatable work support-which are movable longitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connected -to reciprocate said work support, means including a piston type reversing valve to convey fluid under pressure to either end of said cylinder, means inveluding a reversing lever actuated by said table movement to reverse said valve after thetable has moved through a predetermined distance,

and a' dwell control mechanism including a shut tle valve shunted between the opposite ends of said cylinder to cause a predetermined dwell of the table at each end of its stroke.

5. A hydraulically operated cylindrical grinding machitne having a rotatable grinding wheel.

and a wo k support which are movable longitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connectedto reciprocate said table, means including a reversing valve which -is arranged to convey fluid under pressure to either end of said cylinder, means including a reversing lever for said valve, adjustable dogs on said table for actuating said lever and valve to reverse the direction of movement of the table after it has traversed to a predetermined extent, a dwell control device including a shuttle valve which is arranged to cause a predetermined dwell at each reversal sufllcient to allow the work to rotate one complete turn before the table starts its movement in the opposite direction, and means to render said dwell control means inoperative when desired.

6. A hydraulically operated grinding machine having a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a reversible mechanism including a reversing lever to cause said longitudinal movement, a feeding mechanism including a pawl and ratchet to cause said transverse movement, a self-contained fluid pressure mechanism including a piston and cylinder operatively connected to actuate said pawl and ratchet, a control valve associated with said piston and cylinder which is actuated by said lever to operate the feeding mechanism to cause a transverse feeding movement when the reversing lever is shifted to change the direction of said longitudinal movement and means to adjust the extent of movement of said self-contained fluid pressure mechanism and also the extent of movement of said pawl so as to obtain a desired and predetermined transverse feeding movement at each reversal of the longitudinal movement.

7. A grinding machine comprising a rotatable grinding wheel and a work support which are movablelongitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connected to reciprocate the work support, a reversing mechanism including a reversing valve which is actuated by movement of said support to cause a reversal in direction of movement of the same, a single control valve which is arranged so that in one position it allows free by-pass of fluid from one end of the cylinder to the other so that the table may be readily traversed manually and in the other position to throttle the exhaust of fluid from said cylinder and means to adjust said control valve so as to regulate the speed of said work support.

8. A grinding machine comprising a rotatable grinding wheel and a rotatable work support which are movable longitudinally and transverse- 1y relative to each other, a fluid pressure system including a piston and cylinder operatively connected to reciprocate the work support, a reversing mechanism including a reverse valve which is actuated by movement of said support to cause a reversal in direction of movement of the same, a control valve which is arranged so that in one position it allows free by-pass of fluid from one end or the cylinder to the other so that the table may be readily traversed man" ually and in the other position to throttle the exhaust oi. fluid from said cylinder, and means to rotate said control valve to regulate the speed of said work support. I

9. A grinding machine comprising a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a fluid pressure system including a piston and cylinder operatively connected to reciprocatethe work support, a reversing valve arranged to convey fluid under pressure to either end of said cylinder to reciprocate the work support, a reversing mechanism including a reversing lever arranged to reverse said valve to cause a predetermined reciprocation of the work support, a control valve which is arranged for both a rotary and an endwise movement which is arranged when in one position to allow free by-pass oi fluid from one end of the cylinder to the other to enable traversing the work table without the necessity of overcoming the fluid within the system and in nism comprising a reciprocable work table, a

piston and cylinder operatively connected to move said table, a reversing valve arranged to reverse the direction of fluid under pressure to either end of said cylinder to cause a reciprocation of the table, a control valve in said system which is arranged in one position to permit Icy-passage of fluid from one end of the cylinder to the other and in a second position serves to throttle the exhaust of fluid from said cylinder, a manually operable lever which is arranged to move said valve from a, by-pass to a speed control position, a V-port in said valve to permit a fine adjustment of the fluid exhaust line to enable the obtaining of the desired table speed, and a rotary adjustment for said valve to regulate the speed of movement of the table.

11. A hydraulically operated grinding machine having a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a reversing mechanism including a reversing lever to cause a longitudinal reciprocatory motion between the wheel and work support, a feeding mechanism including a pawl and ratchet to cause said transverse movement, a self-contained fluid pressure mechanism including a piston and cylinder operatively connected to actuate said pawl and ratchet, a control valve'associated with said piston and cylinder, and an adjustably mounted detent on said reversing lever to actuate said valve to cause a transverse feeding movement when the reverse lever is shifted to change the direction of said longitudinal movement.

12. A hydraulically operated grinding machine having a rotatable grinding wheel and a work support which are movable longitudinally and transversely relative to each other, a reversing mechanism including a reversing lever to cause a longitudinal reciprocatory motion between the wheel and work support, a pawl and ratchet actuated feed mechanism to cause said transverse movement, a self-contained fluid pressure mechanism including a piston and cylinder operatively connected to actuate said pawl and ratchet, a control valve associated with said piston and cylinder, an adjustable detent carried by-

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