US2568030A

US2568030A - Control for hydraulic motors

Info

Publication number: US2568030A
Application number: US492526A
Authority: US
Inventors: Thomas F Stacy
Original assignee: French Oil Mill Machinery Co
Current assignee: French Oil Mill Machinery Co
Priority date: 1943-06-28
Filing date: 1943-06-28
Publication date: 1951-09-18
Anticipated expiration: 1968-09-18

Description

Sept. 18, 1951 CONTROL FOR HYDRAULIC MOTORS Filed June 28, 1943 T. F. STACY 4 Sheets-Sheet l INVENTOR Thb mas FStacy BY 46., m 242% ATTORNEYS Sept. 18, 1951 Filed June 28, 1945 T. F. STACY CONTROL FOR HYDRAULIC MOTORS 4 Sheets-Sheet 2 VII. '1!

INVENTOR I I FSzacy ATTORNEYS Thomas Sept. 18, 1951 T. F. STACY 2,568,030

CONTROL FOR HYDRAULIC MOTORS Filed June 28, 1943 4 Sheets-Sheet 5 s w s0-%- 94 4 W Va f 19/77 mm 9 mu I .2 L 42 A 52 .J 25 .5 29 3;; W LSL R 511 77 INVENTOR 4 Thomas F Stacy ATTORNEY S T. -.F. STACY CONTROL FOR HYDRAULIC MOTORS Sgpt. 18., 1951 4 Sheets-Sheet 4 Filed June 28, 1,943

1 ATTORNEYS w a Rt 5 vl m m m m T Patented Sept. 18, 1951 asses 2,568,030 CONTROL FoR HYDRAULIC MOTORS Thomas F. Stacy, Piqua, Ohio, assignor to The French Oil Mill Machinery Company, Piqua,

Ohio

Application June 28, 1943, Serial No. 492,526

Claims. 1

This invention relates to hydraulic motors having a working member which is advanced and retracted hydraulically, and more particularly to the control of such motors.

In prior hydraulic motors, the controls are frequently a substantial distance away from the mechanism to be controlled and operated by rods which extend vertically for substantial distance so that in operating such controls, both the weight and inertia of such rods must be overcome at each operation thereof. This has made mechanical controls somewhat sluggish and objectionable, and there has been a tendency to adopt electrical controls or pilot controlled fluid systems for remote control of the hydraulic motor.

It has been proposed, heretofore, to have the working member advance rapidly, in what is commonly known as .a fast traverse movement, in order to have the working member approach as quickly as possible to a position where it becomes effective, and then to sloW down, so that there will be no impact by the working member engaging the work while travellin at too high a speed. Various plan have been adopted for slowing down this advance, but have not been entirely satisfactory for a number of reasons.

An object of this invention is to provide an improved hydraulic motor and controls therer for; with which remote control of the valves and other controlling mechanism may be obtained by the use of relatively long rods; withwhich the inertia of the rods to be overcome at each operation will be negligible; which will require a minimum of power to operate; which will give a very sensitive and rapidly acting control; 'which will not materially increase the overall dimensions of the motor, and which will be particularly simple, compact and sensitive.

Another object of the invention is to provide an improved control for the hydraulic circuit of a hydraulic motor, with which one may obtain a rapid initial advance or closing of the working member; with which the rate of travel of the working member may be automatically slowed down when the working member is travelling through a selected working zone; with which the slowdown may be accomplished with imple controls; which will be sensitive in operation; which will not create too violent or abrupt a change in speed at the slowdown; which will provide power and speed for initial or closing movement of the ram; and which will be exceptionally simple, compact, free of trouble and inexpensive.

Another object of the invention is to provide an improved arrangement and mounting of the valve mechanisms for controlling the movements of the working member-in a hydraulic system; with which the piping required will be a, minimum, and with which any leakage will be directly into the reservoir.

Other objects and advantages will be apparent from the following description of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. l is a side elevation of a hydraulic motor which is constructed in accordance with this invention;

Fig. 2 is a front elevation of the same;

Fig. 3 is a side elevation of the same;

Fig. 4 is a sectional view through a part of the control mechanism, the section-being taken approximately along the line 4-4 of Fig. 7;

Fig. 5 is a sectional elevation through the mounting of the lower ends of two of the control rods;

Fig. 6 is a plan of part of the top of the press;

Fig. '7 is a similar plan on a larger scale, but with a portion broken away to show interior mechanism, and

Fig. 8 is a diagram of the hydraulic circuit and controls utilized with the same.

In the illustrated embodiment of the invention, the hydraulic motor is shown as a hydraulic press of the vertical type having a base I, an upright frame 2 and a top member 3. A suitable working block 4 is mounted upon the upper face of the base I between the sides of the frame 2. Mounted on the top of the member 3 is a reservoir 5 which carries the supply of operating fluid, such as oil. Extending up into the reservoir 5 from the bottom thereof, is the ram cylinder 6, see Fig. 8, in which a ram 1 reciprocates. The inner end of the ram 1 is provided with a piston head 8 and the chamber at the inner end of cylinder 6 is a main or advancing chamber 9, and the annular chamber at the opposite face of the piston head 8 is a retracting or pull back chamber [0.

The lower end of this cylinder 6 is below the bottom of the reservoir, so that the packing gasket l2 will be easily accessible for the renewal or tightening of packing l3 around ram 1. The upper end of the advancing chamber 9 is connected through a pilot-operated check valve M to the reservoir. This check valve M has a valve seat l5 and a valve element [6 urged into closed position against the seat by a spring IT. The

stem l8 of the valve element It extends into a pilot chamber l9 where it abuts against the stem 20 of a pilot piston 2| that reciprocates in the chamber IS. A spring 22 urges the pilot piston 2| into retracted position.

Operating fluid is withdrawn from the reservoir by the intake of a variable delivery pump 23, which is operated continuously by a motor adjoining the reservoir, and delivered under pressure therefrom through pipe 24 to a main or reversing valve 25 (Fig. 8). This valve 25 has a reciprocating valve element 23 with spaced lands 2! and 28 thereon. The chamber 29 of the valve 25 is provided with a port 33 into which the pipe 24 opens. Spaced along the chamber 29 from the port 30 are two annular ports 3| and 32. The port 3| is connected by a pipe or conduit 33 to the advancing chamber 9 and the port 32 is connected by a pipe 34 to the retracting chamber ID. The valve element 26 is movable between two end positions and may be stopped in an intermediate position, shown in full lines in Figs. 7 and 8. This intermediate position is the position taken when the press is idle with the working member retracted or elevated. Spaced along the chamber 29 and beyond the ports 3| and 32 are exhaust ports 35 and 36 which lead to the reservoir. When the valve element 26 is in its intermediate position, the land 28 bridges and closes the port 32 so as to close that end of the pipe 34. The land 2'! has bevelled sides so that when it is alined with the port 3|, fluid from the pump may pass from the inlet port 34 around the edges of the land 21 to the exhaust port 35 and thence to the reservoir.

When the valve element 26 is moved into one end position (upwardly in Fig. 8) the land 2? will be carried into a position between the ports 3| and 35 which will cut off this idle circulation of fluid through the reversing valve from the pump, and at the same time the land 28 will uncover the port 32 and move into a position between the ports 30 and 32. This uncovers the end of the pipe 34 and places it in communication through the valve chamber with the exhaust port 36. The fluid from the pump will then pass through the valve chamber 29 between lands 28 and 21 into the pipe 33, and then to the advancing chamber 9, where it tends to force the piston 8 downwardly. The fluid displaced from chamber H] by the downward movement of the piston 8 will escape through the pipe 34, valve chamber 29 and port 35 to the reservoir. The pilot chamber I9 is connected by a pipe 31 to the pipe 34, so that the pressure in pipe 34 will be communicated through pipe 37 to the chamber l9.

A platen or working member 38 (Figs. 1 and 2) is provided on the lower end of the ram 1, and the weight of the platen plus that of ram 1 will cause them to descend rapidly and faster than the space behind piston 8 can be filled by the delivery of the pump. This will create a suction in the advancing chamber 9 which will cause valve IE to unseat and permit operating fluid to pass directly from the reservoir through valve l4 into the advancing chamber, but when the ram and working member in their descent encounter resistance, the descent of the ram will be less rapid and, consequently, the suction in the advancing chamber will decrease. This decrease will allow the valve [6 to seat and the descent will then be only at the rate caused by the delivery of fluid from the pump through pipe 33.

When the valve element 26 is moved into its other end position, which would be down in Fig. 8,

the land 21 will move between the

ports

34 and 3| and discontinue delivery of fluid from the pump to the pipe 33, and the land 28 will move between the ports 32 and 36 so as to interrupt escape of fluid from the pipe 34 thru valve chamber 29 to the exhaust port 36-. This will connect ports 30 and 32, and the delivery of the pump Will then be from port 30 through valve chamber 29 to pipe 34 and thence to the retracting chamber ID. This causes the ram 8 to move upwardly. When the land 21 moved between the

ports

30 and 3|, this connected ports 3| and 35 so that fluid from the advancing chamber may escape from chamber 9 through the pipe 33 and valve chamber 29 to the exhaust port 35. When the pressure falls in the advancing chamber, the pressure on the check valve l6 tending to prevent it from being opened, will also fall, and since the pilot chamber I9 is connected to the pipe 34, the pressure of the fluid from the pump passing to the retracting chamber It will force the pilot piston 2| to the left and forcibly open the valve l6, which will allow the fluid to escape from the advancing chamber through the check valve I4 directly into the reservoir Without all of it passing through the reversing valve 25.

The valve element 25 has a land 38, Fig. 8, below or beyond the exhaust port 36, and in the extreme lower end of the housing of the valve 25 is a subchamber 39 of larger diameter than the portion of the chamber in which the land 33 reciprocates. In this chamber 39 is a piston 40 which has a stem 4| abutting against the adjacent end of the valve element 26. The movement of the piston 40 in the chamber 39 is limited by a shoulder 42 to that shown in full lines in Fig. 8, where piston 40 prevents movement of the valve element 26 downwardly beyond the intermediate position shown by full lines in Fig. 8. The other end of the housing of the valve 25 is provided with a latch chamber 43, and the valve element '26 has an operating shank or stem 44 extending therethrough to the exterior of the housing of valve 25. Slidingly mounted in the chamber 43 is a cup-shaped, latch release sleeve or element 45 having an aperture in the end of the cup through which the stem 44 of the valve element 26 slidingly passes. A spring 46 acts between a shoulder on the valve element 25 and the inner end of the chamber of the member 45, so as to yieldingly and resiliently urge the valve element 26 downwardly and the member 45 upwardly in Fig. 8.

The outer periphery of sleeve 45 at its lower end is bevelled as at 41 to engage and cam aside a spring latch 43 which is mounted in the housing to slide crosswise of the direction of travel of the element 23 into and out of engagement in a recess or annular groove 49 in the valve element 23. When the valve element is moved upwardl in Fig. 8, into its one end position in which it causes an advance or descent of the rarn, th recess or annular groove 49 will be brought into alinement with the nose of the spring-operated latch 48, and the latch will snap into the groove 49 and prevent movement of the valve element 26 under the action of spring 43. When sleeve 45 is moved endwise in opposition to spring 46, however, its bevelled, lower end or end edge 41 will engage a correspondingly bevelled surface 53 of the latch and cam the latch out of the groove or recess 49 and thus release the valve element 28. The spring 48 urges the valve element 26 into its other end position.

The valve 52 is provided with ports on opposite sides of the connection to the pipe 5|, measured along the length of the chamber of the valve, one of which ports is connected by a pipe 55 to the pipe 34 coming from the port 32 of the reversing valve. The other of these spaced ports is connected by a pipe 56 to a pipe 33 and also to a pressure relief valve 51, and then by a pipe 58 to the upper or closed end of the chamber 43 in which the latch-release sleeve 45 is disposed. This sleeve 45 has a reduced, tubular, closed end which reciprocates in an aperture in the end of the valve housing, and the shoulder thus provided by this tubular end by engagement with the end of the housing limits the retraction of this sleeve 45 by the spring 46.

When the pressure in the advancing chamber 9 builds up to a suflicient extent for which the pressure relief valve 51 is set, that valve will open and pass fluid from pipe 33 to pipe 58 and thence to chamber 43 behind the sleeve 45. This fluid pressure will overcome the spring 46 and move the sleeve 45 in a direction to cam aside the latch 48 and release the valve element, whereupon the valve element will move into its intermediate position shown in full lines in Fig. 8, where it is stopped by engagement with the piston 49. The valve element 53 is moved endwise by the platen, as the latter approaches the end of its retraction movement, into the position shown in full lines in Fig. 8. While in that position, the spaced lands of the valve element 53 serve to connect the pipes 5| and 55, but when the ram moves in an advancing direction, it immediately releases the valve element 53, and the spring 54 then moves it into a position in which the valve element interrupts the connection between the pipes 5| and 55 and connects pipe 5| to 56, which connection remains until the ram returns to its initial retracted position.

While the ram is advancing, the pipe 56, which is always connected to the pipe 33, is connected to the pipe 5|, and thence to chamber 39, so that the pump pressure in chamber 39 will hold the piston 40 in its upper position where it stops the valve element 26 in its intermediate position. This shuts off port 32 leading to pipe 34, and vents pipe 33 so that the pressure in the advancing chamber can fall substantially to a safe low pressure, and then spring 46, which is continually acting, forces the valve element 26 into its other end position where it connects the pump to the pipe 34 and the pipe 33 to exhaust.

A free check valve 59 is included in the pipe 24 before it reaches the port 39. This valve 59 will open to pass fluid from the pump to the reversing valve, yet it will close automatically and prevent reverse flow. Also included in the pipe 24 between the valve 59 and the pump is a safety valve 66 which opens to connect the pipe 24 to the reservoir when an unsafe pressure is built up by the pump. That feature, however, is not a part of the present invention and for that reason the valve 69, its connections, and its usefulness will not be further described.

The pump 23 has included therein as it is purchased in the open market, a compensator 230 which is merely a pressure relief valve that is similar to the valve construction shown in valve 51, and also a pilot device which pulls the pump to neutral when the compensator valve opens to pass pump fluid into the pilot device.

The ball check relief vent on the pump compensator is similar to that in the valve 51 and is connected by a pipe 23a to the vent 51a in the valve 51 and also to the corresponding vent in the valve 60. The ball check valve 51b in the valve 51 is set to open at a somewhat lower pressure than the corresponding ball checks in the vents of the valve 60 and the compensator 230 of pump 23, so that when the ball check 51b opens, which occurs when the desired but adjustable pressure on the main ram has been reached, it not only causes an opening of the valve 51 and a release of the flow controlling means or main reversing valve, but it also operates the safety valve 69 to preventthe building up of an unsafe pressure, and also it causes an operation of the compensator and a setting of the pump to neutral as a further safety feature.

Included in series in the pipe 34 is a valve 6| having a valve element 62 with spaced

lands

63 and 64. The chamber of the valve 6| has

ports

65 and 66. The port 66 opens into the section of the pipe 34 running directly to the reversing valve, and the port 65 opens into the other section of the pipe 34 which runs directly to the retracting chamber ID. A spring 61 urges the valve element 62 into the full line position shown in Fig. 8, where it places both sections of the pipe 34 in communication with each other. The platen or working member, in a selected zone of its advance movement, operates the valve element 62 upwardly in Fig. 8, into a position in which the land 63 interrupts communication between the pipe sections 34, as will be explained more fully hereinafter. A free check valve 68 having a valve element 69 is connected between the annular port 66 and the pipe section 34 between the valve 6| and the retracting chamber I. This check valve is spring operated into closed position, and it opens freely to pass fluid between the pipe sections 34 in a direction toward the retracting chamber ID from the reversing valve, but it closes automatically to prevent reverse flow around the valve 6 A pressure relief valve 19 is connected at one side by a pipe 1| to the pipe section 34 which connects the valve 6| to the retracting chamber l0, and a pipe 12 connects the other side of the valve 10 to the pipe 33 that leads to the advancing chamber. This pressure relief valve 19 opens under pressure to pass fluid from the retracting chamber I0 and the adjacent pipe section 34 to the pipe 33 and the advancing chamber whenever the pressure in pipe 34 exceeds that for which valve 10 is set to open, but normally preyents reverse flow. Any suitable pressure relief valve may be utilized for this purpose, but that illustrated is sold in the open market under the :name Vickers Hydrocone Pressure Relief Valve,

one general type of which is disclosed in U. S. Patent No. 2,043,453 issued June 9, 1936.

The valve element 26 of the main reversing valve may be operated manually through the stem 44, in a manner which will be explained more fully hereinafter, into a position in which it causes an advance of the ram, but when a regular operation of the ram or working member is desired, a pilot operation of the reversing valve is available. For this purpose a pilot valve 13 having a valve element 14 is supplied with fluid under pressure from any suitable source through the pipe 15. The valve 13 also has an exhaust pipe 16, and in between the pipes 15 and '16 this valve has an outlet through pi e 11 leading to the valve chamber 29 between the piston 40 and the land 38. The valve element I4 has lands I8 and I9 spaced apart and is operated by a helical spring 89 in a direction to place the land I8 across the port opening into the pipe 15, and connect the pipe 11, through the space between the lands, to the exhaust pipe "I6. A solenoid 8| is provided with a core 82 which is connected to the valve element 14, and when this solenoid is energized, it moves valve element I4 against the action of the spring 89 sufiiciently to place the land 19 between the openings to pipes I6 and IT and place the land I8 in a position to uncover the opening to pipe I5, and thus connect pipes I and TI. The solenoid BI is connected in series with line wires L and L having in series therein any desired number of switches 83 which, when closed, will energize the solenoid.

Referring now to Figs. 1 to 3, a vertically extending, reversing control rod 84 is disposed along one side of the press frame, so as to extend from adjacent the base I to substantially the top of the reservoir 5. This rod is rotatably mounted, adjacent its ends, by

bearings

85 and 85 and intermediate of its ends by a bearing 8'I. Fixed upon the lower end of this rod 84 is a bevel gear 98, which meshes with a bevel gear 89 on a shaft 99 that is rotatably mounted on the frame of the machine. This shaft 99 has an operating handle 9| thereon, and a lost motion connection therein, so that a limited rocking movement of the rod 84 may occur without movement of the handle 9|. The handle 9| is yieldingl urged into an intermediate position, shown in Figs. 1 and 2, so that it will not be moved by ordinary rocking movements of the rod 84. The details of this lost motion connection are not material, but one example of such a construction that may be used to provide the lost motion connection is found in U. S. Patent No. 1,711,378. Fixed upon the upper end of the rod 84 is an arm 92 which, at its free end is forked, see Fig. 6, and received between the flanges of a spool 93 that is confined on a rod 94 by a nut 95 which is adjustable along the rod 94.

The rod 94 is connected to one arm of a U- shaped element 95, the other arm of which is confined on the threaded end of the stem 44 of the reversing valve 25. A nut 91 and lock nut 98 on the threaded end of the stem 44 limit movement of the U-shaped element 98 in one direction, which would be in a direction to remove it from the stem 44. This element 96 abuts against the end of the latch release sleeve 45 so that movement of the rod 94 in one direction, which would be to the right in Fig. 6, will cam the sleeve 45 in a direction to disengage thelatch 48 from the recess 49 in the valve element, whereas movement of the rod 94 in the other direction will pull the valve element 28 in a direction to cause an advance of the ram, and if the pull is of sufiicient extent, it will bring the valve element 26 into position to be re-engaged by the latch 48.

It will be observed that merely rocking the rod 84 about its longitudinal vertical axis in one direction will cause the forked arm 92 to pull the valve element 2'6 of the reversing valve in a direction to cause an advance of the ram or when rocked in the other direction, it will cause an operation of the latch release sleeve 45 to cause a release of the valve element 26. These rocking movements of the rod 84 may be caused by operation of the handle 9| when purely manual operation is desired, the handle 9| being rocked in one direction to cause operation of the valve element 26 in a direction to start an advance of the ram and in the other direction from its central position, shown in Figs. 1 and 2, when an operation of the latch release sleeve 45 is desired to cause a release of the valve element 26.

On the other side of the press frame is a valve centering rod 99 and a slow-down control rod I99. These rods are disposed side by side and rotatably mounted at their lower ends, near the base of the press, in a bearing NH, and intermediate their ends in a bearing I92. The upper end of the rod I99 is rotatably mounted in a bearing I93, and the upper end of the rod 99 is rotatably mounted in a bearing I94. An arm I is fixed on the upper end of rod I99, and an arm I96 is fixed upon the upper end of rod 99 below bearing I94. These arms I95 and I96 extend in opposite directions past the other adjacent rotatable rod. Secured on and adjustable along the rod 99, below the bearing I92, is an arm I91 carrying on its end a roller I98 in a position to be engaged and rocked to one side to a limited extent by a cam I99 carried on the platen or working member 38.

Secured on and adjustable along the rod I99 below the bearing I92 is an arm II9 with a cam roller III in a position to be engaged and rocked to one side by a cam 2 also provided on the platen Or working member 38 of the ram. The cam I99 and the arm II]? are so disposed that the cam will engage and rock the arm I91 when the platen or working member reaches its upper desired limit of movement during retraction, as determined by the adjustment of the arm I9! along the rod 99. When the arm I9? is rocked (see Fig. 3) by the cam I99, it will rock rod 99 and the arm I98 thereon in a direction to carry the free end of arm I99 towards the reservoir 5. The free end of arm I95 is operatively connected to valve element 53 of the valve 52 so as to move the valve element 53 into the full line position shown in Fig. 8, where it connects the pipe 34 to the pipe 5|. When the platen or working members move downwardly or advance, the cam I99 immediately releases the arm I 91, and the spring 54, Fig. 8, then moves the valve element 53 in a direction to disconnect the pipes 5| and 55 and connect the pipes 5| and 56, and at the same time return the roller I98 into the return path of the cam I99.

The arm I95 fixed on the upper end of the arm I99, Fig. 3, is operatively connected to the valve element 92 of the valve 6|. When cam II2 engages roller III at a selected zone in the advance of the ram. it will rock arm III) and through it rod I99 about the longitudinal up right axis of rod I99 in a direction to move the arm I95 toward the end of the valve element 62, and thus move that valve element from the full line position shown in Fig. 8, into a position in which the land 63 interrupts communication between the two pipe sections 34. When the arm 9 is released by the cam ||2 during retraction of the ram, the spring 61 will not only return the valve element 62 to the full line position shown in Fig. 8, but it will also rock the rod I99 in a direction to return roller III into the path of cam H2. The connections between the arms I95 and I98 and the valve elements 82 and 53 respectively, are shown in Fig. 6, but it will be understood that any suitable form of connection between these arms I95 and I95 and the valve elements to which they are connected I crank lever II3, the other end of which is operatively connected to the stem of the valve element 74 of the pilot valve 13.

The bearings IIlI at the lower ends of the rods 99 and Ill!) are preferably radial and end thrust ball bearings, which provide the endwise support as well as rocking bearings for the rods 99 and I00. It will be noted that although these rods 99 and I90 are disposed upright or generally vertical, they are not moved endwise, but merely rocked through a small increment of angular rotation when operated. Consequently, there is no weight and very little inertia to overcome, such as would be necessary if the rods were moved endwise, and a very small angular rocking movement is all that is necessary to cause the necessary movement of the valves. It has been found that notwithstanding the lengths of these rods 99 and I09, they are very sensitive in operation and require but a minimum of power to operate them.

In accordance with this invention, I have also provided a novel way of simplifying the piping of the hydraulic system and eliminating objectionable leakage. The top of the tank or reservoir is covered or closed by a plate H4, which is relatively thick, and various conduits corresponding to the pipes are formed by drilling passages in the plate between the faces thereof. Also passages are drilled or turned in the plate between the faces for providing the valve chambers. The edge faces of the plates where the holes are drilled, when not used for connections, may be plugged. With such an arrangement, any leakage will be directly into the reservoir. All of the valves and parts are arranged in close proximity so that the passages will be relatively short in length and, consequently, the resistance to flow will be reduced to a minimum. This arrangement of valves and passages is shown in Figs. 6. and 7.

The operation of this device will be briefly summarized and in following the description of the operation, reference may be had mainly to Fig. 8 with occasional reference to Figs. 1 to-3 and 6. When the press is open and idle, the ram 8 will be in its elevated position, and the cam I09 will have engaged and rocked the arm ID! in a direction to operate the valve element 53 into the position shown in full lines in Fig. 8, in which it connects the pipes 5I and 55. This places the chamber 39 at the end of the reversing valve in communication with the pipe section 34. At this time, the pipe 34 is closed at the port 32 by the land 28, and the valve element 92 of valve 6| is in its full line position of Fig. 8, where it connects both sections of the pipe 34. The weight of the ram exerts a pressure in the chamber I0 because the operating fluid cannot escape through pipe 34, and this pressure is communicated through valve 52 to the chamber 39 of the main reversing valve, which holds the piston 40 in the full line position where it centers the reversing valve element 26. The pump delivers fluid to the reversing valve, but this fluid passes idly around land 21 and then back through the exhaust port 35 to the reservoir. This pressure in pipe 34 is also communicated to the pilot chamber I9, and this forces the pilot piston 2I to the left in Fig. 8, to open and hold open the check valve I6.

To start an advance or descent of the ram or working member, one may operate the handle 9I sidewise in a direction to shift the valve element the switches 83 to energize solenoid SI.

10 26 of the reversing valve endwise against the action of the spring 49, as in inching the platen, or to start a full downward movement, but ordinarily an advance movement is caused by closing This solenoid moves the pilot valve element l4 out of the full line position shown in Fig. 8 against the action of spring 80, so as to uncover the port opening into pipe 75, connect pipes I5 and ll and disconnect pipes I6 and TI. The pipe I5 receives fluid under pressure from any suitable source,

such as from an auxiliary gear pump connected to upon the latch moves into latching engagement with the valve element 26 and holds it in that elevated or operative end position. It is only necessary that the switch buttons 83 be held closed long enough to enable valve element 26 to be moved into latched position, and then the buttons may be released which deenergizes solenoid 8 I. The valve element 14 then returns to its full line position, Fig. 8, which vents chamber 39 between piston 49 and valve element 28, but the valve element 26 is held in operated position by the latch 48. I

This movement of the valve element 25 of the main reversing valve places land 21 between exhaust port 35 and port 3| of pipe 33, thereby connecting pipe 24 from the pump to pipe 33, and at the same time land 28 between ports 39 and 32 connects pipe 34 to the exhaust port 36 so as to release fluid from pipe 34. The ram then starts its descent by gravity, and the pressure in pipe 34 falls, which releases the preflll valve element I6. Suction in chamber 9 causes valve I6 to remain open, but when the piston 9 is slowed down by resistance to a speed such that suction in chamber 9 is practically nil and the pump is able to supply all of the fluid necessary to follow the advance or descent of the ram, the valve I6 will close and then all of the fluid must be delivered to the advancing chamber directly from the pump through the main valve 25. As soon as the ram began its advance or descent, the cam I09 released the arm I01. This caused a rocking of the rod 99 and, consequently, an operation of the valve element 53 which disconnected pipes 5| and 55 and connected pipes 5| and 56, thus connecting the chamber 39 of the main reversing valve to the pipe 33.

As the descent of the ram continues, the cam II2 will engage the roller II on arm H9 and rock the rod I99 about its longitudinal axis, and through it operate the valve element 92 against the action of spring 61 into a position in which the land 63 interrupts flow between the pipe sections 34. This prevents escape of fluid'from the retracting chamber It! through pipe 34 back tothe main reversing valve. The pressure in the advancing chamber then builds up and when the back pressure in pipe 34 is suflicient to open the pressure relief valve 39 this will connect the retracting chamber I9 t0 the advancing chamber of the ram. This opposes advance oi the ram, but since the pump is continuing to deliver fluid under pressure through pipe 33, the advance of the ram will continue at work stroke speed. Since the fluid from the retracting chamber I o is circulated back to the advancing chamber, the ram will operate slighty faster than before this recirculation occurred. This gives a working speed of the ram slightly faster than would be obtained with a pump of a given capacity, but without such recirculation of fluid from the retracting chamber to the advancing chamber.

When the ram reaches its required, final posi tion in the work stroke, a cam II5, Fig. 1, on the platen 38 engages and operates a roller I IS on an arm II'I fixed on the rod 84, and rocks the rod 84 in a direction to cause the forked lever 92, Fig. 6, to move the rod'94,

U-shaped member

96, 91 and latch relief sleeve 45 and cause a disengagement of latch 48 from groove 49. This releases valve element 26 of the main reversing valve 25, and spring 46 then moves the valve element 26 toward the other end position, but the pressure in pipe 33 at this time, as explained above, is communicated to chamber 39, so as to hold piston 49 in its .full line position, Fig. 8, which stops the valve element 26 of reversing value in the intermediate position, where the pipe sections 34 are both closed and the pipe 33 is vented. The high pressure from the advancing chamber is then released through valve 25, and as soon as the pressure falls to a safe, relatively low pressure, the resulting lower fluid pressure in chamber 39 of the main reversing valve will be overcome by the spring 46, and the valve element 26 will then continue its advance into its other end position, where the pump is connected to the pipe 34 and the pipe 33 is connected to exhaust.

The fluid pressure delivered to the retracting chamber Ill causes an ascent or retraction of piston 9, and hence of platen 38, and as soon as this ascent begins, cam II releases arm I I1, and the latch release sleeve 45 is returned by spring 46 to its former position, shown in full lines in Fig. 8. The pressure in pipe 3'4 is communicated to pilot cylinder I9, which causes the pilot piston to operate in a direction to open the prefill chamber valve It, so that some fluid from the advancing chamber may escape directly through valve I4 to the reservoir without passing through main reversing valve 25. This gives a rapid return of the platen. As the platen closely approaches its limit of return movement, the cam I09 on the platen will engage roller I08 and rock rod '99 "in a direction to operate valve element 53 and reconnect pipes 5I and 55, thus placing the chamber 39 under the same pressure as that in retracting chamber ID. This pressure will then force piston 49 in a direction to center valve element 26, which discontinues the delivery of fluid from the pump to pipe 34, and causes a bypassing of this fluid around land 21, thus stopping further retraction or ascent of the ram.

When the ram in its ascent or return, passed the point at which cam Il2 first engaged roller III, the roller III was released by cam H2, and thereupon rod I00 was rocked by spring 61 in a direction to return valve element 62 to its full line position shown in Fig. 8, in which communication between pipe sections 34 is re-established. It will be noted that the check valve 68 is in parallel across the valve 6|, so that at the start of the return movement of the ram and while the land 63 of valve 6| closes communication between pipe sections 34, the fluid from the pump, after passing through pipe section 34 to the. valve 6|, may pass through check valve 68 and thence into the other section 34. The ascent of the ram is thus completed and the parts restored to their initial, idle position.

If one desires to cause reversal of the travel of the ram in response to a predetermined pressure exerted by the ram, instead of at a selected position in the travel of the ram, then the arm III is moved downwardly so that it will not normally be engaged by cam I I5 until after a desired pressure has been built up. In such a case, when the pressure in the advancing chamber has reached that for which the pressure relief valve 51 is set, that valve will open and pass fluid from pipe 33 to the chamber of the main reversing valve behind the sleeve 45. This will cause a rapid advance of sleeve 45 to cam the latch 48 aside and release valve element 26. The pressure sufficient to open the pressure relief valve 51 should preferably be higher than that to overcome the pressure of spring 46, so that once valve 57 opens the operation of sleeve '45 and release of valve element 26 will be fairly rapid. The pressure relief valve 51 is, of course, preferably adjustable so that it may be set to open at dilferent desired pressures for different jobs requiring different maximum pressures.

It will be understood that various changes in the details and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim as my invention:

1. In a control for a hydraulic motor and its operating system of the type having an advancing cylinder, a retracting cylinder, a working member having portions rigidly connected thereto received in said cylinders and movable back and forth by pressure alternately applied to said cylinders, a connection from each cylinder, and means for delivering fluid under pressure alternately to each connection and releasing the pressure in the other connection, that improvement in said system which comprises a conduit directly between said cylinders and having inseries therein a pressure relief valve open-ing under pressure to pass fluid from said retracting cylinder to said advancing cylinder, another valve in the connection from said retracting cylinder, a cam device disposed for direct operation between two positions by said member with the change of positions occurrin in a zone of advance movement of said member intermediate its limits of possible movement, while said member can continue its advance, means acting between said device and said another valve for causing a closing of said another valve while said device is in the position occupied during the portion of said advance after said zone of change, and an opening of said another valve while said device is in the initial portion of said advance, and means for conveying fluid past said another valve solely towards said retraction chamber.

2. In a control for a hydraulic motor and its operating system of the type having an advancing cylinder, a retracting cylinder, a working member having portions rigidly connected thereto received in said cylinders and movable back and forth by pressure alternately applied to said cylinders, a connection from each cylinder, and means for delivering fluid under pressure alternately to each connection and releasin the pressure in the other-connection, that improvement in said system which comprises a pressure relief valve connected between said "cylinders and opening by pressure to pass fluid from the retraction cylinder to the advancing cylinder, another valve in the connection from the retracting cylinder to said means, a cam device disposed for direct operation by said member between two positions, and occupying one position during an initial zone of advance movement of said member and another position during the remaining zone of advance movement of said member, with said member free to continue its movement unrestricted by said cam device, and motion-transmitting parts between said cam device and said another valve by which said another valve is open during said initial zone of movement and closed during said remaining zone of advance movement.

3. A hydraulic device comprising an upright frame, a working member guided by said frame for vertical movements thereon, hydraulic means havin advancing and retracting chambers for said member, a pump, control means by which fluid under pressure is delivered by said pump selectively and alternately to said chambers to cause descent and ascent of said chamber, said pump, hydraulic means and control means being mounted on the upper end of said frame, a reservoir on the upper end of said frame in which said control means are disposed, and a generally flat, thick plate, closing the upper end of said reservoir and having horizontal passages formed therein, and said control means including valves in said passages in said plate, whereby leakage from any of said passages and control valves will drip into said reservoir.

4. A hydraulic device comprising an upright frame, a working member guided by said frame for vertical movements thereon, hydraulic means having advancing and retracting chambers for said member, a pump, control means by which fluid under pressure is delivered by said pump selectively and alternately to said chambers to cause descent and ascent of said member, said pump, hydraulic means and control means being mounted on the upper end of said frame, a reservoir on the upper end of said frame in which said control means are disposed, a generally flat, thick plate closing the upper end of said reservoir and having horizontal passages formed therein, and said control means including valves in said passages in said plate, whereby leakage from any of said passages and control valves will drip into said reservoir, and individual control rods extending vertically along said frame for rocking about their longitudinal, vertical axes, and connected at their upper ends to said valves, and at their lower ends havin arms operable by said working member as the latter moves in selected zones of its travel.

5. A hydraulic device comprising a hydraulic motor, a variable delivery pump having a compensator which operates under pressure differentials to set the pump to reduced delivery, a

connection from said pump to said motor, flow controlling means associated with said connection for controlling the direction of operation of said motor, means for holding said direction delivery means in one position in which it causes movement of the motor in one direction, means yieldingly urging said flow controlling means into a position to cause a reverse operation of the motor. a pressure relief valve connected at its intake side to the motor, and at its discharge side to said holding means to deliver operating fluid to the latter and cause a release of said flow controlling means, said relief valve having a pressure balanced valve element and a vent with a selected pressure relief which opens when said selected pressure is reached to unbalance the pressures on said valve element, cause an opening of the relief valve, and a release of said flow controlling means, a connection from said compensator to said vent whereby the unbalance of pressures created by the opening of said vent will unbalance pressures in said compensator and cause a reduction in volume delivery of said pump until said vent closes.

THOMAS F. STACY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 523,419 Thorpe July 24, 1894 1,552,768 Smith Sept. 8, 1925 1,619,475 Hubbard Mar. 1, 1927 1,884,060 MacMillin Oct. 25, 1932 1,978,346 Ernst et al Oct. 23, 1934 1,990,052 Sosa Feb. 5, 1935 2,000,553 Alden May 7, 1935 2,063,414 Tweddell Dec. 8, 1936 2,067,265 Ernst Jan. 12, 1937 2,072,488 Stacy Mar. 2, 1937 2,113,110 Ernst et a1 Apr. 5, 1938 2,218,818 Harrington Oct. 22, 1940 2,241,556 MacMillin et al. May 13, 1941 2,244,420 Dinzl June 3, 1941 2,284,897 Harrington June 2, 1942 2,285,069 Vickers June 2, 1942 2,335,809 Stacy Nov. 30, 1943 2,346,141 Snyder Apr. 11, 1944 2,419,235 Stacy Apr. 22, 1947