US2416722A - Valve for hydraulic circuit - Google Patents

Description

March 4, 1947.

G. A. WALDIE VALVE FOR HYDRAULIC CIRCUITS Filed April 17, 1944 '2 Sheets-Sheet l I! PA 5 PRESSURE lNVF OR GEORGE ANVALDIE,

BY I y & m--

ATTO R N EYS Marh 4, 1947. G. A. WALDIE v v 2,416,722

VAL E FOR HYDRAULIC CIRCUITS Filed A ril 17, 1944 2 Sheets-Sheet 2 INVENTOR GEORGE A. WALDIE,

- ATTORNEYS Patented Mar. 4, 1947 UNITED STATES PATENT OFFICE I VALVE FOR HYDRAULIC cmcm'r George A. Waldie, Marel'lgo, Ohio, moi to H-P-M Development Corporation, Wilmington, DeL, acorporation of Delaware Application April 11, 1944, Serial No. 531.32:

1 21 Claims. This invention relates to valves and, in particular, to hydraulic control valves for use in connection with high pressure hydraulic circuits.

In the operation of hydraulic motors such as hydraulic presses it is desired to reverse the rain at the end of a pressure stroke as rapidly as possible and without shock or vibration within the hydraulic circuit. One way of accomplishing this is by relieving the pressure within the working chamber of the motor while simultaneously bypassing the delivery of the fluid source to a reservoir. In the patents to Walter Ernst Nos. 1,956,758 and 2,268,205 there are shown valve means comprising a pair of pistons for accomplishing this result.

One of the principal objects of this invention is to provide a valve comprising a single movable valve member for relieving the pressure from the working side of a hydraulic device while simultaneously bypassing the delivery to the other side thereof. 7

It is still another object to provide a valve ac cording to the foregoing object wherein the various functions thereof are positively'synchronized through the employment of a single movable valve member and a casing including ports for making the necessary connections.

In the operation of a hydraulic system such as a press circuit having a release and bypass valve as set forth above, the release passage must be so adjusted that there is no shock within the system during the initial period of operation of the valve. Then, as the high pressure which is being released decays, the rate ofrelease thereof ever diminishes until a predetermined low pressure has been attained whereupon the pressure is completely relieved and a surge valve is opened and the retraction movement of the ram com- Another object of the present invention is to provide a release and bypass valve wherein the release passage restriction is reduced as the said hydraulic circuit employing the valve oi this invention; I

Figure 2 is a longitudinal section through the Figure 8 is a graph of the pressure conditions existing in the circuit during the period ed operation or the valve of this invention.

General arrangement According to this invention arcciprocable hydraullc motor having a working chamber and a retraction chamber has connected thereto a reversible pump for supplying pressure fluid selectively to the said chambers. Suitable-means are provided for reversing the pump so as to cause the same to deliver selectively to the working chamber for causing the hydraulic motor to perform a; work stroke or, to the retraction chamber for causing the motor to perform a retraction stroke. i

A surge valve is provided for communicating between the advancing chamber anda surge tank so that the advancing chamber may be freely discharged during the retraction stroke. The surge valve also provides a means for filling the advancing chamber during the initial portion of the working stroke of the motor.

In order to accomplish theo'bjects of this invention, a valveis provided which is connected with the advancing chamber and retraction chamber and also with the surge tank. The valve includes a yieldable means continuously urging the valve into position to interrupt fluid com- Figure 1 isa diagrammatic view of a typical munication between the advancing chamber and the surge tank and also between the retraction chamber and the surge tank.

The valve is operable, in response to a predetermined pressure on the advancing chamber, to move to establish fluid communication between the retraction chamber and the surge tank so as to bypass the pump discharge when the same is delivering to the retraction chamber. Simultaneously, the valve effects a choked or restricted communication between the advancing chamber and the surge tank so as to relieve the pressure 1 in the former at a controlled rate: According to 1 this invention, a means is provided which, when the pressure within the advancing chamber has been reduced to a predetermined value, permits the valve to move to interrupt the fluid communication between the retraction chamber and the surge tank andalso to establish an unrestricted fluid connection between the advancingchamber and the surge tank.

Detailed description of the embodiment of Figures 2 and 3 Referring to. Figure 1, there is shown a hyjdraulic motor comprising a cylinder l6 having reciprocably mounted therein a piston I to which A reversible pump at I5 is connected by a conduit |6 with the advancing chamber and, by a conduit II, with the retraction chamber.

The pump I5 is controlled so as to deliver into the conduit l6 or the conduit selectively, by a control mechanism generally indicated at l3 which may include a solenoid l9 which, when en- Mounted in the top of the cylinder III is a surge well known methods and operable to prefill the chamber l3 during the downward travel oi. the piston II and, to eflect tree exhaust from the chamber l3 during the upward travel of the said piston. A conduit 22 connects the operating cyl- 1 inder of the valve 2| with the retraction chamber l4 so that the said valve is responsive to a predetermined pressure in said chamber. check valve 23 is arranged to permit fluid to pass from the surge tank 24 into the conduit 22 for a purpose which will become more apparent hereinafter.

A valve generally indicated at 25 is mounted conduit 26 with the advancing chamber i3 and, a by the conduit 21 with the conduit 22.

The valve 25' is more particularly illustrated in ;Figures 2 and 3 and will be seen therein to comis attached a ram or plunger l2. The cylinder l6 and piston define an advancing chamber |3 and a retraction chamber l4.

' the piston 50 when the .valvemember 46 is shifted valve 2| constructed according to any of several within the surge tank 24 and is connected by a prise a casing 30 having 'a bore 3| therethrough which may be closed at the ends by the plugs 32.

An inlet port 33 is provided for the purpose of effecting fluid communication between the bore 3| and the conduit 26 and, an inlet port 34 provides for fluid communication between the said bore and the conduit 21. The valve casing 36 is provided with an outlet port of a somewhat reduced diameter, the function of which is to "plug 39 threaded into the valve casing 30. The

ably connected by a reduced diameter portion.

thus forming a rigid member. The member 46 also includes. an extension 44 about which is mounted a spring 45. The spring 45 continuously urges the member into the position which it occupies in Figure 2. The portion 4| oi the member 40 defines, in cooperation with the bore 1 3|, a chamber 46 which is continuously connected by the passage 41 with the inlet port 34. The pressure conducted from the port 34 through the passage 41 to the chamber 46 is eflective to urge the valve member 40 rightwardly against the thrust oi the spring in a manner which will become apparent in the following description of the operation of the valve.

At the right hand end or the casing 30 is a chamber 50 within which is reciprocable a piston 6|. The chamber 56 is connected by a conduit 52 with the inlet port 33. mits tree fluid flow from the said inlet port to the said chamber but not vice-versa. The check valve 53 is bypassed by an adjustable hoke valve 54 which controls the rate of .flow from the chamber, 50 toward the inlet port' 33.

The left end wall of the chamber 56 is apertured to receive the extension 44 which abuts from its Figure 2 position. After the member 40 enga es the piston 6|, continued movement of the member 40 is effective also to move the said piston.

The arrangement of the ports in' the casing 30 is such that, when the member 40 has'moved to its Figure 4 position, fluid communication is established between the inlet port 34 and the outlet port 35 and between the inlet port 33 and the outlet port 38. Further movement of the member 46, that is, to its Figure 5 position, is

efiective to interrupt the fluid communication between the inlet port 34 and the outlet port 35 while establishing fluid communication between the inlet port 33 and the outlet port 36.

The extension 44 on the member 40 and the piston 5| within the chamber 50 are arranged to engage when the member 40 is moved to its Figure 4 position. As the valve member moves from its Figure 4 position into its Figure 5 position,

the piston 5| is also moved and fluid is expelled from the chamber 50 through the conduit 52 and the choke valve. 54 into the inlet port 33.

Detailed description of the embodiment of Figures 6 and 7 A second embodiment of this invention is illustrated in Figures 6 and 7. Referring to Figure 6, the valve will be seen tocomprise a body or casing 60 having inlet ports 6| and 62 and outlet ports 63, 64, 65 and 66.

The inlet port 6| is adapted to be connected withthe retraction chamber of a hydraulic motor such as by the conduit 21a while the inlet port 62 is adapted to be connected, by the conduit 26a, with the advancing or working chamber of the said motor. A valve member 61 is reciprocable within the bore '68 ofthe casing 66 and is effective, when moved, first to establish fluid communication between the inlet port 6| and the outlet port 63 andbetween the inlet port 62 and.

the outlet port 64 and, subsequently; to interrupt plug 39 'may be adjusted so as more or less to irestrict the port 38.

Reciprocably mounted within the bore 3| is a valve member 46 which comprises the spool portions 4|, 42 and 43. The spool portions are suit- A check valve 53 permay be similar in construction to the choke valve associated with the outlet port 38 of the valve illustrated in Figures 2 and 3.

The outlet port 55, as shown in Figure 3, is similarly provided with an adjustable choke or throttle valve 13 for a purpose which will become more apparent hereinafter.

A spring II is mounted in the right hand end of the bore 88 and engages the valve member- 81, continuously urging the latter to the left. A pasage l2 continuously connects the inlet port 8| with the chamber 13 at the left end of the bore 88 and provides a means for urging the valve member 61 to the right against the thrust of the'spring II. An extension 14 on the valve member' 51 provides a stop which limits the rightward movement of the said valve member when the same "moves-under the influence of the pressure established-in the chamber 13.

Operation of the embodiment of Figures 2 and 3 Assuming that the press in Figure 1 is in its fully: retracted position, an advancing or downward stroke is instituted by energizing the sole noid IS. The energization of the solenoid I3 is effective, through the linkage l8, to shift the pump l5 into position to deliver fluid .through the conduit l5 into the advancing chamber i3 while simultaneously withdrawing fluid from the retraction chamber I4 through the conduit ll.

As thepump draws fluid from the retraction .area, the ram l2 and piston I I descend toward the work. During the initial part of the descent of the ram and piston the chamber l3 receives fluid: from the conduit I6 and also from the surge tank 24 through the surge valve 2i. When the ram l2 engages the work, the descent thereof under the force of gravity is checked and the pressure-within the retracting chamber l4 drops to substantially zero. With the pressure in the retraction chamber and the conduit 22 reduced, the surge valve 2| closes thus sealing oil the ad vancing chamber from the surge tank.

The. ram I2 is driven into the work by the piston ll due to the pressure created within the advancing chamber l3 by the pump 5. At the completion of the working stroke, the retraction or upward stroke of the'piston II and ram I2 is instituted. by deenergizing the solenoid l3 thus permitting the pump to shift to deliver into the retraction chamber l4 through the conduit l'l.

At the moment of reversal, that is, at the moment when the pump I5 is shifted to deliver into the retraction chamber, it is desirable that the high pressure established within the advancing chamber i3 during the working stroke of the plunger 12 be reduced or bled oil until the energy stored therein is reduced to such a value that no shock will occur within the hydraulic system when the same is suddenly released. It is also desirable that this be accomplished in the shortest possible time in order not to delay the oper-' ation of the press. This is accomplished by the valve 25 inthe following manner:

During the working stroke of the plunger H the pressure within theretraction chamber i4 is substantially zero, and, therefore, the pressure standing in the conduits 22 and 21 and the inlet port 34 of the valve 25 is likewise substantially zero. The low pressure existing in the inlet port 34, passage 41 and chamber 45 permits the spring 45 to urge the valve member 43into its Figure 2 At the previously mentioned moment of rethereby. It will be noted that in this position the 1 I valve member 40' permits fluid communication between the inlet port 34 and the outlet port 35 and also between the inlet port 33 and the outlet port 38. Also, that further movement to the right of the member 45 will permit the piston portion M to commence to restrict the inlet port 34 while simultaneously permitting the piston portion 43 to commence to uncover the unrestricted outlet port 38.

The inlet port 33 is connected with the advancing chamber i3 by the conduit 25 and thereby provides for the. said chamber a restricted release passage through the outlet port 38 when the valve member 43 is in its Figure 4 position. The passage of fluid from the conduits25 and 21 into their respective inlet ports-33 and 34 and out their respective outlet ports and 35 is indicated by arrows in Figure 4.

The pressure which had previously been established in the advancing chamber I3 during the working stroke of the press and which was transmitted to the inlet port 33' by the conduit '28.likewise was conducted by the conduit 52 to the chamber 50 thus urging the piston 5| into its I Figure 2 position. The fluid, under pressure, enclosedwithin the chamber 58 is forced out through the conduit 52 and the choke valve 54 when the piston 5| is moved to the right by the extension 44 of the valve memmber 48. During the movement rightwardly the valve member 40 and piston 5| from their Figure 4 position, any differences in displacement between the piston portion 43 of the member 43 and thepiston 5| is made up from the surge tank 24 through the passage 31. I

With the valve in its Figure 4 position,--'the pressure within the advancing chamber I3 is gradually and controllably reduced through the outlet port 38 while the discharge from the pump is simultaneously bypassed through the outlet 35.

The port 35, being somewhat restricted, is efiece tive to maintain a pressure at the inlet "and within the passage 47 and the chamber 45 suf.'fl-- cient to urge the valve member 48 rightwardly with a thrust in excess of that of the sprin 45. As the pressure within the advancing chamber I3 is reduced, the pressure at the inlet port 33 is likewise reduced and the aforementioned rightwardthrust on the valve member 431s effective to urge the piston 5l' to the right to displace a portion of the fluid within the chamber 53 through the choke valve 54 and into the said inlet port 33. It will be apparent that the rightward movement of the valve member 40315 dependent upon the rate at which the pressure within the, advancing chamber I3 and, therefore, the inlet port .33,

- is reduced.

position. In this position, the valve member 40 closes 01! communication between the inlet ports 34 and 33 and the outlet ports 35, 38 or 38. respectively. v

As the valve member 48 moves to the right from its Figure 4 position under the influences mentioned above, the valve piston 4l commences to restrict the inlet port 34 thereby restricting the tially no delivery position.

1- everincreasingthrust.

- Simultaneously, the piston portion 48 commences to uncover the outlet port 38 thereby providing for a less restricted fluid passage between the advancing chamber l3 and the surge tank 24, and also, substantially reducing the pressure at the inlet port 88.

It will be apparent that the increase in pressure at the inlet port 84 and the chamber 48 and the simultaneous decrease in pressure at the inlet port will be eflective to move the valve member 48 from its Figure 4 position to, its Figure 5 position where the bypass connection is completely sealed off, while 'the inlet port 33 is in substantially unrestricted fluid communication I with the surge tank 24 through the outlet port 38. With the valve in its Figure 5 position, the delivery oi. the pump i5 is directed to the retractlonchamber l4 and the plunger i2 and pis- 1 ton ll commence their retraction stroke, which continues until the arm 20 actuates the linkage I8 to move the pump I5 to a neutral or substan- With the pump maintained in substantially neutral position by the arm 20 andlinkage It, as shown in Figure 1, the weight of the piston I I and plunger I2 is eflective l to maintain suflicient pressure 'within the retraction chamber l4, the conduits 22 and 21, the inlet port 34, passage 41 and chamber 48 to maintain the valve member 40 in its Figure 5 position. Normally, the valve member 40 will remain in this I position until the plunger l2 engages the work 1 during the forward stroke of the said plunger and 1 piston II.

It will be noted that the action of the surge valve 2| will be substantially synchromzed with 1 the action of the valve 25, tending to open to permit free evacuation of the chamber i3 when the pressures within the chamber I3 and the chamber l4 are such that the valve member 40 is caused to approach its Figure 5 position. However, it will be apparent that the surge valve 2i passage therefrom into the advancing chamber could be eliminated if the 'outlet port 86 and the i3 were of sufllcient size to permit the rapid transfer of fluid between the said chamber and the 3 surge tank 24.

It will also be apparent that the adjustable I throttle member 39 and the adjustable choke valve 54 may be adjusted to control the rate at 1 Operation of the embodiment of Figures 6 and 7 The operation of the embodiment shown in Figures 6 and 7 is substantially identical with that of the embodiment of Figures 2 and 3 except 1 that the action of the piston 5| and chamber 50 j is substantially duplicated by a portion of the bore 68 in cooperation with the valve member In operation, the valve member 61 is urged to j tbe right by pressure within the chamber is into j a position similar to the Figure 4 position of the valve member 40. That is, the member 6'! moves to the right to establish a bypass connection for i the conduit 21a through the inlet port SI and the somewhat restricted outlet port 88, while simultaneously establishing a restricted fluid communication from the conduit 26a to the inlet port 82 and outlet port 84 to the surge tank. The valve member 81 stops, or is checked, in its rightward movement when the right hand piston portion.

its rightward movement, the fluid entrapped in v the right hand end of the bore 68 by the right hand piston portion 01' the member 61 must be expelled through the outlet port 66 and past the throttle member l0.- It will be apparent that the rate of movement oi the valve member 61 rightwardly after the port 88 is closed will be a function 0! the pressure existing within the chamber 18 and the setting of the throttle valve 10.

- Thus, the valve member 61 moves, in response to a predetermined pressure established within the conduit 21a into position to establish a bypass connection to the reservoir for the said conduit while simultaneously establishing. a restricted fluid connection to the reservoir for the conduit 26a and, thereafter, moves at a reduced rate in thepositi'on to interrupt the by-Dass connection from the conduit 21a to the reservoir'while simultaneously establishing'a relatively unrestricted fluid connection between the conduit 26a and the reservoir through the outlet port 85.

Inv order more clearly to understand the operation and advantages or the present invention, the pressure conditions existing within the advancing and retraction chambers immediately prior to, during, and subsequent to the operation of the valve 25 have been plotted in Figure 8. In this figure, wherein time is the abscissa and pressure the ordinate, the graph of pressure conditions which would prevail-in the circuit if a release and bypass valve constructed according to the teachings of the prior art were used, is also plotted.

In the graphthe solid line marked A represents the pressure within the advancing chamber and passes successively, as indicated by the vertical dotted lines, from a high working pressure through a first release period and subsequently through a second release period to substantially zero pressure. At the same time, the pressure within the retraction chamber, indicated by the solid line B passes from substantially zero through a period of increasing pressure, a period of substantially constant pressure during which the pump discharge is bypassed and subsequently through a period of increasing pressure during which'time the bypass connection is interrupted.

The dashed lines A and B represent, respectively, the pressure conditions within the advancing chamber and the retraction chamber during the operation of a release and bypass valve according to the prior art. It will be noted that the period of time required to reduce the pressure I within the advancing area to a point where the surge valve may be opened is substantially greater than the same period when a release and bypass valve according to the present invention is employed.

It will. also be apparent, upon reference to Figure 8, that the rate of operation of a press equipped with the valve of this invention will be increased, thereby permitting more working strokes of the press to be made during any period of time. Likewise, in certain classes of work, such as hot forging, the reduction of the dwell piece while the same is still at forging temperature, but also reduce the chilling effect which the movable die has on the said workpiece by being in contact therewith.

It will be apparent that various modifications may be made in'the construction of either of the embodiments of this valve without in any way departing from the spirit of the invention. For example, the piston ll could be urged into its left hand position by means of a spring and the conduit 52 be replaced by a throttle valve and similar results would obtain. Likewise, it will be apparent that the arrangement, relative sizes and shapes of the various inlet and outlet ports could be considerably modified without efl'ecting the mode of operation of the device in any way what- 'said casing. a single valve member movable in saldcasing into a first position simultaneously to interrupt said passages or, into a second position to establish said passages or, into a th rd position to interru t said bypass passage while mainta n ng sa d release passage, means operable automatically initially to move said valve membe into said first posit on, thereafter to move it into said second position and'flflnally gradually to move said valve member into said third po t on. I

4 2. In a release and bypass valve. a valve casing having a bypass inlet, a release inlet,'a bypass outlet, and a release outlet, a single valve member movable in said casing for controlling the communication between said inlets and their respectiv outlets, yielding means associated with said valve member for continuously urging the same into position to interrupt flu d communication between said inlets and their respective outlets, fluid operable means continuously hydraulically connected with said bypass inlet and operable in response to a predetermined pressure therein to move said valve member into position to establish fluid communication selectively be tween said inlet ports and their respective out- 1 let ports, said bypass outlet ofiering a predetermined restriction to the flow of fluid therethrough so as to maintain a predetermined pressure at said bypass inlet and, therefore, in said fluid op-' erable means.

I a predetermined pressure at said inlet to move said valve member into position to establish fluid communication between said inlets and their respective outlets; and means associated with said valve operable subsequent to the operation of said last mentioned means to permit said valve mem- 3; In a valve; a casing having a first inlet port and a second inlet port; outlet means for each of said inlet ports and a bore interconnecting said ports and said outlet means; a single valve member movable in said bore for controlling said ports; yielding .means associated with said valve member for continuously urging ,the

same into position to interrupt fluid'communi- :cation between said inlets and their respective outlets; fluid operable means hydraulically connected with one of said inlets and associated with said valve member and'op'erable in response to,

4. In a release and bypass valve, a valvecasing having a bypass inlet and a, release inlet; a restricted bypass outlet port, a restricted release outlet port and an unrestricted release-outlet port; a bore in said casing interconnecting said ports; a valve member reciprocably mounted in said bore for controlling said ports and movable into a first end position for interrupting fluid communication between said inlet ports and their respective outlet ports or, into an intermediate position for establishing fluid communication between said bypass inlet port and said bypass outlet port and between said release inlet port and said restricted release outlet port or, into a second end position for again interrupting said bypass connection while establishing fluid communication between said release inlet port and said unrestricted release outlet port; and means automatically operable for actuating said valve.

membe from said first end position into said intermediate position and then gradually into said second end position.

' 5. In a release and bypass valve: a valve casing having a bypass inlet and a release inlet; a restricted bypass outlet port, a restricted re-' lease outlet port and an unrestricted release outlet port; a bore in said casing interconnecting said ports; a valve member reciprocably mounted in said bore for controlling said ports and movable into a first end position for interrupting fluid communication between said inlet ports and their respective outlet ports or, into an intermediate position i'or establishing fluid communication between said bypass inlet port and said bypass outlet port and between said release inlet port and said restricted release outlet port or. into a second end position for again interrupting said bypass connection while establishing fluid communication between said release inlet port and said unrestricted release outlet port; and fluid pressure responsive means hydraulically connected with said bypass inlet port and operable in response to a predetermined pressure therein to move said valve member freely from said first end position into said intermediate position and thereafter at controlled speed from said intermediate position into said second end position.

6. In a valve; a casing having a first, a second and a third passage therethrough; a valve member in said casing for controlling said passages and movable into a first position for interrupting said passages and, into a second position for establishing the first and second of said, passages and, into a third position for interrupting the first of said passages while establishing the third thereof; yielding means for continuously urging said valve member toward said first position; fluid operable means for urging said valve member from said first position toward said third position; and means for interrupting the movement of said valve member at said second position as said valve member is being moved by said fluid operable means.

7. In a release and bypass valve; a casing hav-- said bypass connection while establishing fluid communication between said release inlet and said second release outlet port; yielding means continuously urging said valve member toward said first end position; fluid operable-means associated with said valve member for moving the same from said first end position into said second end position; and means automatically operable to retard the movement of said valve member from said first end position to said second end position when the same has reached said intermediate position.

8. In a release and bypass valve; a casing having a bypass inlet and a release inlet, a bypass 'outlet port, a first and a second release outlet port and a bore interconnecting said ports; a valve member in said bore for controlling said ports and movable into a first end position for interrupting fluid communication between said inlets and their respective outlet ports or, into an intermediate position for establishing fluid communication between said bypass inlet and said bypass outlet port and between said release inlet and the first of said release outlet ports or, into a second end position for again interrupting said byp ss connection while establishing fluid communication between said release inlet and said second release outlet port; yielding means continuously urging said valve member toward said first end position; fluid operable means associatedwith said valve member for moving the same from said first end position into said second end position: and fluid'operable means operable automatically to control the rate of movement oi! said valve member from said intermedi- 12 i said intermediate position into saidsecon position atacontrolled rate.

end

10. .m a release and bypass valve; a casing having a bypass inlet and a release inlet, a bypass outlet port, a first and a second release outlet port and a bore interconnecting said ports; a

valve member in said bore for controllingsaid ports and movable into afirst end position for interrupting fluid communication between said inlets and their respective outlet ports or, into an intermediate position for establishing fluid communication between said bypass inlet and said bypass outlet port and between said release inlet and the first of said release outlet ports or, into a second end position for again interrupting said bypass connection while establishing fluid communication between said release inlet and said, second release outlet port; yieldin means continuously urging said valve member toward said first end position; fluid operable means associated with said valve member for moving the same from said first end position into said second end position; a fluid operable piston adapted to engage and halt said valve member in said intermediate position; and means hydraulically connected with said release inlet and operable in response to a predetermined reduced pressure ate position to said second end position when said a valve member 'is actuated by said fluid operable means.

9. In a release and bypass valve acasing having a bypass inlet and a release inlet, a bypass said second release outlet port; yielding means continuously urging said valve member toward said first end position fluid operable means as sociated with said valve member for moving the same from said first end position into said second end position; a fluid operable piston adapted to engage said'valve member and to halt the same in said intermediate position; and means associated with said piston for permitting the same together with'said valve member in move irom ,therein to permit said fluid operable means to move said valve member from said intermediate position into said second end position.

l1. In combination in a hydraulic circuit, a

fluid operable motor having an advancing chamber and a retraction chamber, a source of fluid pressureior supplying pressure fluid selectively to said advancing chamber or to said retraction chamber, a valve hydraulically connected with said advancing chamber and said retraction chamber and operable in response to a predetermined pressure in said retraction chamber for first establishing a restricted release passage irom said advancing chamber to exhaust while simultaneously establishing a restricted bypass passage from said retraction chamber to exhaust stricted release outlet port, a relatively unre-' stricted release outlet port and a bore interconnecting said ports; a valve member reciprocably mounted in said bore for controlling said ports and movable into a first end position for interrupting communication between said inlet ports and their respective outlet ports or, into an in-' termediate position for establishing fluid communication between said bypass inlet port and said bypass outlet port and between said release inlet port and said restricted release outlet port or, into a second end position for again interrupting said bypass connection while establishing fluid communication between said release inlet port and said unrestricted release outlet port; fluid pressure responsive means hydraulically connected with said bypass inlet'port and operable in response to a predetermined pressure therein to move said valve member from said first end position toward said second end position; fluid operable means for interrupting the movement of said valve member when the same has reached said intermediate position; and adjustable means associated with said last mentioned means for regulating the rate of movement of said valve ing a bypass passage and a pair of release pas-- sages of varying restrictions therein, a valve member in said casing for controlling said passages and movable into a first end position for interrupting said passages or, into an intermediate position for establishing said bypass passage and one of said release passages or, into a third posi-- tion to again interrupt s'aid bypass passage while establishing the other of said release passages, yielding means for continuously urging said valve member into said, first end position, fluid operable means hydraulically connected with the inlet of said bypass passage and operable in response to-a predetermined pressure therein for moving said valve member toward said second end position, fluid operable means comprising a chamber closed by said valve member when the same has reached said intermediate position for interrupting the movement of said valve member at said intermediate position, and an adjustable choke valve hydraulically connected with said chamber for regulating the rate of movement of said valve member from said intermediate position into said secondend position so as gradually to interrupt said bypass passage while gradually establishing said second release passage.

14. In a hydraulic system; a press cylinder; a ram reciprocable therein and having fluid operable advancing and retracting means associated therewith; a source of pressure fluid for selectively supplying actuating fluid to said advancing or retracting means for reciprocating said ram; and a valve-connected between said advancing means and said retracting means and exhaust operable automatically-at the end of an advancing stroke of said ramand in response to a predetermined pressure in said retracting means for establishing a restricted by-pass for the delivery of said fluid source and for releasing the pressure from said advancing means at a predetermined rate, said valve also being automatically operable in response to a predetermined reduced pressure in said advancing means for gradually increasing the rate of release of pressure therefrom while simultaneously gradually restricting said bypass connection, and finally completely to release said pressure while interrupting said bypass connection.

15. In a hydraulic circuit; a fluid operable ram .having advancing and retracting means; a surge valve for establishing a free connection between said advancing means andexhaust; a first and a second release passage between said advancing means and exhaust; a restricted bypass passage between said retracting means and exhaust; and means responsive to a predetermined pressure in said retracting means for establishing said bypass passage and the first of said release passages, and for thereafter gradually closing off said bypass passage while gradually establishing the second of said release passages, and finally for completely closing ofi, said bypass passage .while opening said surge valve.

16. In a hydraulic circuit; a fluid operable ram having advancing and retracting means; a first valve means comprising a surge passage for freely connecting said advancing means with exhaust; a second valve means comprising a first and a second release passage between said advancing means and exhaust and a restricted bypass passage between said retracting means and exhaust, said second valve means also comprising a valve member for controlling said release and bypass passages; means operable during the advancing stroke of said ram for moving said valve member into position to interrupt said passages; and

means operated by pressure in said retracting means and operable at the beginning of the retraction stroke of said ram for movingsaid valve member into position to establish said bypass passage and the first of said release passages, and for thereafter gradually moving said valve member to close ofl. said-bypass passage while establishing said second release passageyand finally to move said valve member completely to close 011' said bypass passage and also to move said surge valve into open position. v

17. In a hydraulic circuit; a fluid operable ram having advancing and retracting means; a surge valve for establishing a free connection-between said advancing means and exhaust; a second valve means comprising first and second release passages of diflerent restrictions connected with said advancing means and exhaust; said second valve also comprising a restricted bypass passage connected between-said retracting means'and exhaust; a valve member in said valve movable into a first position for interrupting said passages and into a second position for establishing one of said release passages and said bypass passage and into a third position for interrupting said bypass passage while establishing the other of said release passages; means operable prior to a working stroke of said ram inthe advancingdirection for moving said valve member into said first position; means operable at the end of a working stroke of said ram for moving said valve member into said second position; and means operable at the initiation of the retraction stroke of said rain for moving said valve member into said third position and for opening said surge valve.

18. In a hydraulic circuit; a fluid operable ram having advancing and retracting means; a surge valve for establishing a tree connection between said advancing means and exhaust; a second valve means connected with said advancing means and with said retracting means and comprising a restricted bypass passage between said retracting means and exhaust, a first release passage between said advancing means and exhaust of a predetermined restriction, and a second release passage between said advancing means and exhaust of a lesser restriction; a valve member in said valve movable into a first position for interrupting said passages, or into a second position means connected with said retracting means for urging said valve member toward said second and third position; means automatically operable for retarding the movement of said valve member from said second position to said third position when said valve member is moved by said fluid operable means against the thrust oi! said yielding means; and means operable to open saidsurge valve when said valve means-is moved intosaid' third position. v p

' 19. In a hydraulic circuit; a fluid operable ram having advancing and retracting means; a surge tween said advancing means and exhaust of a predetermined restriction, and a secondrelease pas-' sage between said advancing means and exhaust of a lesser restriction;'a valve member in said valve movable into a first position for interrupting said passages, or into a second position for establishing said bypass passage and the first of said release passages, or into a third position for interrupting said bypass passage while establishing the second of said release passages; yielding means continuously urging said valve member toward said first position; fluid operable means connected with said retracting means for urging said valve member toward said second and third position; means hydraulically connected with said advancing means operable to halt said valve member in said second position when the same is said valve member into said third position.

20. In a fluid operable system a reciprocable ram having advancing and retracting means, a

fluid source adapted selectively to supply said means, and means for effecting a rapid and substantially shockless reversal of said ram comprising, a release passage from said advancing means to exhaust, a bypass passage from said retracting means to exhaust, a valve member movable from a first position where said passages are interrupted to a second position where said passages are established and into a third position where 45 2,320,759

1e said bypass passage is again interrupted, means for moving said valve member into its first position during an advancing stroke of said ram,

. means responsive to a predetermined pressure in said retracting means for moving said valve mem her into its second position and for urging said valve member toward its third position for a dwell period of said ram, and means'for retarding the movement of saidvalve member into its third position comprising means responsive to the pressure in said advancing means.

- 21. In a fiuid operable system, a ram having advancing and retracting means, a fluid source to supply said means selectively, and means for eflecting a shockless reversal of said ram comprising a. valve member controlling communication between said advancing and retracting means and exhaust and movable from a first position wherein said communication is interrupted into a second position wherein said communication is established and into a third position wherein the communication between the said retracting means and exhaust is again interrupted, fluid operable means connected with said retracting means for moving said valve member from its first through its second and into its third position, other fluid operable means connected with said advancing means for interrupting the movement of said valve member when it reaches its second position and for controlling the movement thereof into, its

- third osition, and means for returning said valve member to its first position when the pressure in said retracting means is reduced.

- GEORGE A. WALDIE.

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

UNITED STATES PATENTS Number Name Date 2,268,205 Ernst Dec. 30, 1941 1,956,958 Ernst May 1, 1934 2,042,186 Peterson May 26, 1936 Stacy June 1, 1943

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