US2369505A

US2369505A - Remote-control valve

Info

Publication number: US2369505A
Application number: US322657A
Authority: US
Inventors: Loyd A Ward
Original assignee: TOMKINS JOHNSON CO
Current assignee: TOMKINS JOHNSON CO
Priority date: 1940-03-07
Filing date: 1940-03-07
Publication date: 1945-02-13
Anticipated expiration: 1962-02-13

Description

Feb. 13, 1945. |4 A WARD 2,369,505

REMOTE CONTROL VALVE Filed March '7, 1940 2` Sheets-Sheet 1 22mm 7 M L c7 Y1: A. WARD l.. A. WARD REMOTE CONTROL VALVE Feb. 13, 1945.

2 Sheets-Sheet 2 Filed March 7, 1940 Patented Feb. i3, 194s escasos REMOTE-connor. vALvE Loyd A. Ward, Jackson, Mich., assignor to Tomkins-Johnson Company, Jackson, 'Mich., a

corporation of Michigan Application March 7, 194e, serial No. 322,657

16 Claims.

The present invention relates to remote control valves and more particularly to a remote control valve of the character wherein a distributing piston is reciprocated under manual control by fluid pressure within a cylinder to direct a fluid under pressure to a controlled cylinder to move a controlled piston therein from one end to the other.

In known remote control valves oi' the character described, an example of which is disclosed in Patent No. 1,791,613 lto Clay, there is a disadvantage in that it is notpossible to stop a controlled piston midway between the ends of its stroke. The reason for this is that since the distributing piston is fluid actuated, when once it is moved, it; continues to move to the end of its travel and remains in that position continuously delivering pressure fluid to one end of the controlled cylinder. According to the present invention, this disadvantage is eliminated by providing centering mechanism for automatically centering the distributing piston, at controlled times, to a position where it does not deliver pressure iluid Lto either end of the'controlled cylinder. With such a remote control valve, the controlled piston may be moved to any position along its stroke and maintained in that position with the controlled cylinder under pressure. y

An object of th'e invention is to provide a remote control valve having a distributing piston which may be automatically centered at the will of the operator.'

Another objectof the invention is to provide a remote control valve having a distributing piston which is actuated by the release of pressure fluid and which returns to a neutral, inactive position upon closing the uid pressure releasing means. A further object of the invention is to provide a remote control distributing valve actuated by the release of pressure fluid, which is automatically centered by auxiliary pistons working in auxiliary cylinders which carry the released pressure uid.

A still further object of the invention is to provide a remote control distributing valve automatically centered by auxiliary pistons working in auxiliary cylinders, the valve being moved by full line pressure overcoming the action of a predetermined one of said auxiliary pistons.

A still further object of the invention is to provide-a remote control valve which is quick in operation and which can be manipulated to stop a controlled piston at an intermediate portion of its stroke.

, A still further object of the invention is to provide a remote control distributing valve havingareciprocating piston provided with exhaust ports in the surface thereof wherein the reciprocating piston is balanced against side thrust by *showing in diagrammatic form a cylinderl and exhaust uid in the exhaust ports that are in its surface.

` These and other objects will be apparent from the following speciication when taken with the accompanying drawings in which:

Fig. 1 is a vertical section through a remote control valve according to the present invention,

piston controlled by the remote control valve and in elevation pressure releasing control valves,

Fig.l 2 is a section on the line lI-II of Fig. l., Fig. 3 is a section on the line III-III of Fig. 1, Fig. 4 is a vertical section through one of the pressure releasing valves showing details thereof, Fig. 5 is a partial vertical section of another form of the invention wherein the control valve is shifted by means of uid pressure rather than by exhausting fluid pressure,

Fig. 6 is a section on the line VI-VI of Fig. 5, and

Fig. '7 is a section of an alternativenform of valve that may be used for controlling the main line pressure for actuating the controlling valve.

Referring particularly to the drawings, the reference character I indicates the remote control valve body having an outside portion 2, preferably of cast iron, and a linerl 3, preferably of bearing bronze surrounding a chamber 4. VIn the body I is an inlet port 5, outlet ports Gand .1, and exhaust ports 8 and '9. Reciprocably slidable in the chamber 4 isa distributing piston IU provided with a distributing chamber I I open on one side to the interior wall of the body I opposite the inlet 5, as shown particularly in Figs. 1 and 3. Also in the piston IIl is a distributing port I2 providing a communication from the distributing chamber II to the opposite side of the piston I0 and moving into and out of' communication with the outlet ports S and l as the lpitson reciprocates in the chamber 4. It will be appreciated that the distributing chamber II is a. part of the distributing port I2. Providing communication between the opposite ends of the chamber 4 and the distributing chamber II are leakage ports I5 and I6 of restricted diameter for equalizing the pressure at the ends of the chamber 4 with the pressure of the distributing chamber II which is the inlet pressure.

' Caps I 1 and I8 atw opposite ends of the body I are secured thereto by the cap screws I9 or their equivalents. The caps I'I and I8 provide closures for the ends of the chamber 4 and are. provided with

auxiliary cylinders

20 and 2|. Within the auxiliary cylinders 20 andA 2I are auxiliary pistons 22 and 23 respectively. The pistons 22 and 23 are provided with stems or rods 24 and 25 respectively which project into opposite ends of the chamber 4 through bushings 26 and 21 and packings 28 and 29. Extending axially through the rods 24 and 25 are ports 35 and 36 of somewhat larger di,

ameter than the leakage ports I5 and I6. order to provide a communication with the chamber 4 through the rods 24 and 25 at such times as the ends of the ports 35 and 36 may be closed by the distributing piston I0, there are provided in the rods 24 and 25 additional ports 31 and 38 in the portion of the rods 24 and 25 within the chamber 4, communicating with the ports 35 and 36 and normal thereto. As the ports 31 and 38 extend through the rods 24 and 25 and the ports 35 and 36, their areas need be only one-half of those of the ports 35 and 36. l

The outer ends of the cylinders 20 and 2i are provided with exhaust ports 39 and 40 respectively and are connected by means of conduits 45 and 46 respectively to exhaust valves 41 and 48, the construction of the exhaust valves being shown particularly in Fig. 4 wherein the exhaust valve 41 is shown in cross-section.

The exhaust valves each comprise a, body having an inlet 49 and an outlet 50. Within the body is a removable seat member 5i bearing against a, packing 52 which in turn is seated on a shoulder 53. Bearing against the seat 5I' of the seat member 5I is a valve member 54 having a stem 55 and a manually actuable push button 56. A helical spring 51 maintains the valve member 54 against its seat 5I' and the gland packing 58 under compression to prevent the leakage of pressure iluid past the stem 55. As appears particularly from Fig. 4, communication from the inlet 49 to the outlet 50 is under the control of the valve member 54. In normal position the spring 51 prevents communication between the inlet 49 and the outlet 56, but upon pressure being applied to the push button 56, the spring 51 is compressed, the valve member 54 is moved away from the seat 5I and communication between the inlet 49 and the outlet 5|! is established. The outlet 50 opens to the atmosphere either directly or through a suitable conduit.

In order to move the distributing piston I from one end of the chamber 4 to the other, pressure uid in the end of the chamber 4 to which it is desired to move the distributing piston III is exhausted by exerting pressure on the appropriate push button 56. As shown in the drawings, the distributing piston i0 is at the right end of the chamber 4 and the push button 56 of the exhaust valve 48 is depressed. The depressing of the push button 56 opens the exhaust valve 48 to exhaust pressure uid from the right end of the chamber 4 through the ports 36 and 38 in the rod 25, the cylinder 2|, the exhaust port 46 and the conduit 46. Since the pressure at the right end of the chamber 4 is reduced, the pressure uid at the left end of the chamber 4 expands to drive the distributing piston I0 to the right. The distributing piston I0 will remain at the right end of the chamber 4 so long as the exhaust valve 48 remains open. It will be observed that when the distributing piston I8 is at the right end of the chamber 4, the rod 25 and its piston 23 are at the right end of the auxiliary cylinder 2 I, having been moved to that position under the action of the distributing piston I6. However, should the exhaust valve 48.be closed, then pressure uid from the inlet 5 and the distributing chamber Il will flow through the leakage port I6, the ports 38 and I6 in the rod 25 and into the auxiliary cylinder 2I. Then, since the pressure at both ends of the distributing piston I6 is equalized by the flow of the pressure iluid from the distributing chamber I l through the leakage ports I5 and I6, and since the eil'ective area of the auxiliary piston 23 in the auxiliary cylinder 2i is greater than the effective area of the rod 25 in the chamber 4, the unbalance of pressure will cause the auxiliary piston 23 to move to the left until it abuts against the shoulder 68 in the cap I8. In order to permit free movement of the auxiliary pistons 22 and 23 in the auxiliary cylinders 2li and 2i, there are provided at the inner ends of the auxiliary cylinders 20 and 2l, vents 6I and 62. As will be observed from Fig. l, the length oi the rods 24 and 25 are such that when they are projected to their full length in the chamber 4, the distributing piston I0 is at its central position so that the distributing port i2 is midway between tile outlet ports 6 and 1 and does not communicate with either of them. The central position of the distributing piston III is shown in dotted outline in Fig. l.

Asshown particularly in Fig. 3, when the distributing piston l0 is at the right end of the chamber 4, the pressure fluid from the inlet port 5 passes through the distributing chamber Il, the distributing port I2 and the outlet port 1 to the conduit 65 communicating with one end of a controlled cylinder 66. Pressure fluid from the inlet 5 then forces the controlled piston 61 in the controlled cylinder 66 to the right. It will be understood that the piston rod 68 operated by the piston 61 is suitably connected to and operates a machine not shown.

As the piston 61 is being moved to the right, exhaust pressure iiuid in the' right end of the cylinder 66 is forced through the conduit 69, to the outlet port 6 which as shown in Figs. l and 2 is connected to the exhaust port 8 by means of an exhaust groove 10 in the surface of the distributing piston I0. When the distributing piston I0 is moved to the left of the chamber 4 by opening the exhaust valve 41 to exhaust pressure uid from the left end of the chamber II through the ports 31 and 35 in the rod 24, the

cylinder 28, the exhaust port 39 and the conduit 45, the distributing port I2 in the distributing piston I0 moves into register with the outlet port y 6, and at the same time, an exhaust groove 1I in the distributing piston I0 moves to provide a communication between the outlet port I and the ,exhaust port 9. Thus in left position, the distributing piston I0 distributes pressure duid from the inlet port 5 through distributing chamber II and distributingport I2 to the outlet port 6, from which pressure iiuid is conducted by the conduit 69 to the right end of the cylinder 66 to drive the piston 61 to the left. As the piston 61 is moving to the left, the exhaust pressure iluid at the left-of the cylinder 66 will be forced through the conduit t'o the outlet port 1 from which it is conducted by the exhaust groove 1I to the exhaust port 9. As soon as pressure on the push buttons 56 of the exhaust valve 49 is released, thedistributing piston I0 centers under the action of the auxiliary piston 22 and the rod 24, operating in -the same manner as the auxiliary piston 23 and rod 25. In using the remote controll valve of the present invention it will be understood that valves may be used to control the exhausting fluid from theexhaust ports 8 and 9 to control the speed of movement of the piston 61 as is well known in the art.

Should it be desired to position the operated piston 61 'in some particular intermediate portion of the operated cylinder 66, the appropriate piston I so that the distributing port |2\is out of register 'with the outlet ports 9 and 1 and the exhaust grooves 'and 1|v are out of register,A

with the exhaust .portssV and 9 respectively. At

the same time the pressure iiuid in'both ends of the cylinder 55 is sealed against exhausting by the surface of thedistributing piston I0 closing the inner' ends of the outlet ports 9 and 1, asv

' shown particularly in Fig. 1. Y

m order te maintain the distributing piston' I0 against rotation with respect to the body I,

there is providedv in one side of the'distributing piston I0 a groove 19into which is projected a pin 14 disposed in a bore 15 in lthe body Thus the distributing piston I0 may reciprocate in the chamber 4 without rotation.l In order to' prevent any lateral thrust by'exhaust iiuid that may be under pressure in the exhaust grooves 10 and 1I, the distributing piston I0 is provided with circumferential grooves 18 and 19 which includeA the exhaust grooves 10 and 1I.' In this manner the exhaust uid entering the exhaust grooves 10 and '|.I is permitted to pass entirely about the distributing piston I0 to completely balance any pressure in the exhaust grooves 10 and 1| that'might cause a lateral thrust againstthe piston I0 and prevent easy reciprocation thereof.

,In order to facilitate the mounting of the body i on some suitable bracket or support, there are provided bores 80.

While the push buttons 56 in the exhaust valves 41 and 48 have been described as manually actuable, it will be understood by those skilled in vthe art that either one or both of these push buttons may be automatically actuated, as, for instance, by an arm projecting from-some moving part of a machine` to provide an automatic sequence of operation. It will be further understood that an advantage of the present construction resides in quicker operation. WhenY the valve is being operated as prior art valves, in that the distributing piston I0 is moved completely to one end or the other of the chamber 4, upon release of the push button 56, which caused the movement of the distributing valve I0, the distributing valve i0 will automatically move to its central position as in the mannerabove described. Then when it is desired to move the distributing valve to move the controlled piston 51 in the opposite direction, the distributing valve I0 will have to move only from its central position to the opposite end of -the chamber 4 rather than from one end of the chamber 4 to 'the other end thereof.

v chambers.

. the piston I0, andthe ports 35, 99,31 and Il in the'auxiliary piston rods 24 and 25.

'Ihe auxiliary .pistons 22 and 23 are .urged to their inner positions by line pressure from the inlet port 5. The'li'ne pressure to the auxiliary cylinder 20 is conducted by ports in the" body v.from the inlet port 5, comprising a port 85 ex. tending laterally from the in let port 5, a port 99 extending vertically, aport 91 extending longi-v tudinally the full length of the body l, and a port extendinglat'erally from the Dort 91 tov the auxiliary cylinder 20. The line pressure is conducted to the auxiliary cylinder 2| by ports 95, 96, I1 and a port 89 extending laterlly from the port 81 tothe auxiliary cylinder 2|. Thus there 'i's continuous line pressure exerted against the outer ends o! the auxiliary pistons 22 and 23 to yieldingly urge 'their respective auxiliaryl piston rods 24 and 25 inwardly against the ends of the distributing piston I0 to center4 it in the I n order'to 'provide metal through which the port 81 may extend 1beyond the ends of the body I', the caps I1 and I8 are provided with ridges 90, as shown particularly in Fig. 6.

Communicating with the chamber 4 at one end is a port 9|, and at the other end a port 92. By directing pressure iluid from the inlet conduit 93,

`which communicates with the inlet port 5, through the port 9| or the port 92, the distributv and may be identical in construction with the valve 4'I, disclosed in Fig. 4. Vents |05 and |06 are provided at the ends of the distributing chamber 4 for permitting free movement of the distributing piston I0 therein.

shifting the distributing piston |0. An adaptation of the form of the invention disclosed in Figs. 1 through 4, for shifting the piston I0 by line pressure, is disclosed vln Figs. 5 and 6 wherein theconstruction is substantially the same with the exceptionthat from the structure of Figs. 1 through 4, there have been omitted the exhaust ports 3s and 4u, the leakage ports It and le nl In order to operate the form of the invention disclosed in Figs. 5 and 6, one or the other of the.

valves and 91 is opened by pressing on the push buttons 98 or 99 respectively. Should it be desired to move the distributing piston I0 to the right, as shown in Fig. 5, the push button 98 is depressed to open the valve 95 to permit the passage of pressure fluid from the main conduit 93 through the conduit 94 to the port 9| and from it into the left end of the chamber 4. Since the cross-sectional area of the distributing piston I0 in the chamber 4- is greater than that of the auxiliary piston 23 at the opposite end of the body I, the distributingv piston l0 will move to the right, the pressure fluid in the right end of the chamberl escaping through .the vent |06. will be understood that since the area of the port 9| is greater than that of the vent |05 co-mmunicating with the left end of the chamber I, the escape of pressure iiuid through the vent |05 will have no'effect on the action of the pressure Vfluid in moving the distributing piston I0 to the right.

As s oon as pressure on the push button 98 is released,v pressure iiuid to the port 9| is cut off and the pressure in the left end of the chamber 4 escapes through the vent |05. Also, since the auxiliary cylinder 2| isunder full line pressure through the ports es, a6. s1 and a9, the aux-` iliary piston 23 will move the auxiliary piston rod 25 to the left to center the distributing piston l0 as shown in dotted outline in Fig. 5.

Should it be desired to move the distributing piston I0 to the left, as viewed in Fig. 5, pressure on the push button 99 will open the valve 91 to permit the flow of pressure fluid from the main pressure fluid inlet conduit 99 through. the conduit 96 and valve 91 to the port 92 at the right end of the chamber 4. In this case the movement of the distributing piston to the left and its return to center position corresponds to the movement in the opposite direction as previously explained. It will be understood that when the distributing piston |0 moves to the right or to the left, it is for the purpose of directing pressure fluid from the inlet port through the distributing chamber and oneor the other of the outlet ports 6 and 1, as described in the explanation of the operation of the form of the invention disclosed in Figs. 1 through 4.

As explained above, when pressure fluid is being directed into the chamber 4 through the port 9| or 92, there is a leakage through the vents |05 or |06 respectively. This leakage is not oblectionable when it is unnecessary to hold the distributing piston l0 at one end or the other of the stroke for substantial periods of time. However, when such a substantial holding is required the vents |05 and |06 may be dispensed with and the valves 95 and 91 each replaced by a valve of the character disclosed in Fig. '1, which includes a vent.

As shown, the valve in Fig. 7 is connected in the conduit 94, thus replacing the valve 95. The valve is provided with a body |01 and a valve member |09 seating against a seat |09. The valve member |08 is movable by a stem ||0 to which is connected a push button and is urged against its seat |09 by a spring H2, disposed between the push button and the gland nut ||3. In normal operation, pressure fluid enters the valve through the port ||4 and leaves it through the port ||5. The valve stem is also provided with a valve member for seating against a seat |2|. The valve member |20 and its seat |2| control the flow of the exhaust fluid through the vent |22.

In the operation of the valve disclosed in Fig. '1, pressure fluid is conducted to the inlet port ||4 by the conduit 94 from the .main pressure fluid supply 93. When the push button is depressed, the valve member |09 moves away from its seat |09 to permit the passage of pressure fluid from the inlet port ||4 through the outlet port ||5 from which it is conducted by the conduit 94 to the port 9| communicating with the chamber 4. At the same time the valve member 20 is urged against the seat |2| to preventl the escape of pressure fluid through the vent 22'. When pressure is removed from the push button AI the spring I |2 moves the valvemember |08 1upwardly against its seat |09, and at the same pressure fluid from the left end of the chamber 4 as viewed in Fig. 5. It will be understood that when both the vents |05 and |09 are dispensed with, both valves 95 and 91 are replaced by valves of the character disclosed in Fig. 7, for removing pressure fluid from the respective ends of the chamber 4 upon the cutting off of pressure uid thereto.

While the distributing valve, according to the present invention, is employed lparticularly for distributing compressed air, it will be understood that Ait may be employed for distributing other types lof pressure fluid, as for instance, hydraulic fluid commonly employed in hydraulic actuating mechanism.

Having thus described my invention, what I desire to-secure by Letters Patent and claim:

1. A control valve for distributing fluid under pressure comprising a body having a chamber therein, a fluid distributing piston slidably disposed in said chamber, a conducting chamber in said piston, an inlet port. in said body communicating with said conducting chamber, a conducting port in said piston communicating at one end with said conducting chamber and at the other end terminating at a sliding surface of said piston, a pair of spaced outlet ports in said body communicating with said first chamber in the path of movement of said conducting port, dif.- ferential fluid pressure means to move said distributing piston to bring said conducting port into communicatingrelation with the desired one of said outlet ports, fluid actuated means to automatically center said distributing piston in a position in which it communicates with neither of said outlet ports and continuous fluid connec- V tions between the fluid to be distributed and said fluid actuating means for providing pressure uid for actuating the same, said fluid connections ing restricted so as not to interfere with the to move said distributing piston to bring said distributing port into communicating relation with the desired one of said outlet ports, mechanism actuated by thefluid controlled to automatically center said distributing piston in a position in which it communicates with neither of said outlet ports, and a continuous fluid pressure connection between the fluid controlled and said mechanism for providing pressure fluid for actuating said mechanism, said fluid connections beingrestricted so as not to interfere with the operation of said differential fluid pressure means in moving said distributing piston.

3. A uid control valve comprising a body having a chamber therein, a fluid distributing piston slidably disposed in said chamber, an inlet port in said body, a distributing port in said piston, one end thereof communicating at all times with said inlet port and at the other end terminating at a sliding surface of said piston, a pair of spaced outlet portsin said body communicating with said chamber in the path of movement of said distributing port, said piston being movable to bring said distributing port successively into communication with said outlet ports, said piston havng a central position in which said dstributing port is between said outlet ports and in communication with neither oi' them, restricted ports for providing communication between said distributing Dort and each end of said chamber,

pressure releasing meansfo'r each end of said chamber and communicating therewith for causing said piston to move to direct fluid from said inlet through said distributing port to one of said outlet ports or to the other depending on the pressure releasing means actuated, and fluid pressure actuated centering means at each end of restricted as not to interfere with -the operation of said pressure releasing means.

4. A fluid control valve comprising a body having a. chamber therein, a fluid distributing piston slidably disposed in said chamber, an inlet port in said body, a distributing port in said piston,

one end thereof communicating at all times with said inlet port and at the other end terminating at a sliding surface of said piston, a pair of spaced outlet ports insaid body .communicating with said chamber in the path of movement of said distributing port, said piston being movable to bring said distributing port successively into communication with said outlet'ports, said piston having a central position in which said dis' p tributing port is between said outlet ports and in communication with neither of them, restrictedA ports for providing communication between said distributing port and each end of said chamber.

pressure releasing means for each en d of said chamber and communicating therewith for causing said piston to move to direct iiuid from said inlet through said distributing port to one of said outlet ports or to the other depending on the pressure releasing means actuated, and a fluid actuated centering rod at each end of said body arranged to automatically center said piston upon closing of said pressure releasing means, said fluid actuated centering rods having actuating vmeans having associated therewith restricted ports for conductingoperative fluid, said ports having communication with each end 'of said chamber respectively, said ports being sufliciently restricted as not to interfere with the operation of said pressure releasing means.

5. A uid control valve comprising a body having a chamber therein, a fluid distributing piston slidably disposed in saidl chamber, an inlet port in said body, a distributing port in said piston, one end thereof communicating at all times with said inlet port and at the other end terminating at a sliding surface of said piston, a pair of spaced outlet ports in said body communicating with said chamber in the path of movement of said distributing port, said piston being movable to bring said distributing port successively into communication with said outlet ports, said piston having a central position in which said distributing port is between said outlet ports and in communication with neither of them, restricted ports for providing communication between said distributing port and each end of said chamber, an auxiliary cylinder at each end of said body, an auxiliary piston in each auxiliary cylinder, means providing a communication between each end of said chamber and said auxiliary cylinders respectively, pressure releasing means for each end of said chamber and communicating therewith through said auxiliary cylinders respectively for causing said distributing piston to move to direct fluid from said inlet through said distributing port to one of said outlet ports or the other depending on the pressure reeaslng means actuated, and centering means actuated by said auxiliary pistons under' the action of the controlled fluid, upon closing of 'the pressure releasing means, operative to center said distributing piston.

6. A control valve comprising a body having a l chamber therein, a duid distributing piston slidably disposed in said chamber, an inlet port'in said body,a distributing port in said piston, at

vone end thereof communicating at all times with -said inletv port and at the other end terminating at a sliding surface of said piston, a pair of spaced outlet ports in said body communicating with said chamber in the path of movement of said distributing port, said piston being movable to bring said distributing port successively into communiy cation with said outlet ports, said piston having a central positionV in which said distributing port is between said outlet ports and in communication with neither of them, restricted ports for providing communication between said distributing port and each end of said chamber, an auxiliary cylinder at each end of said body, an auxiliary piston in each auxiliary cylinder, means inders respectively for causing said distributing.

piston to move to direct fluid from said inlet providing a communication between each endof said chamber and said auxiliary cylinders respectively, a piston rod connected to each of said auxiliary pistons projecting into said chamber, the

effective area of each auxiliary piston being greater than that of its rod, pressure releasing means for each end of said chamber and communicating therewith through said auxiliary cylthrough said distributing port to one of said outlet ports or the other, and depending on the pressure releasing means actuated, said auxiliary pistons, upon closing 'of the pressure releasing means, being operative under the action of the pressure 40 fluid conducted from said chamber to said auxiliary cylinders to move said rods inwardly of said chamber to engage the ends of said distributing piston to center the same.

7. The invention as defined in claim 6 wherein the pressure releasing means for each end of the first chamber comprises a port in each piston rod for conducting pressure iiuid from the respectiveA ends of the chamber to the respective auxiliary cylinders, and pressure releasing valves having communication with the auxiliary cylinders respectively.

I 8. The invention as defined in claim 5 wherein there is provided a vent at the inner end of each auxiliary cylinder for permitting free movement of the auxiliary pistons under` the action of pressure fiuid from the ends of the chamber.

9. A control valve comprising a body having a chamber therein, a fluid distributing piston slidably disposed in said chamber, lan inlet port in said body, a. distributing port in said piston, at one end thereof communicating at all times with said inlet port and at vthe other end terminating at a sliding surface of said piston, a pair of sp-aced outlet ports in said body communicating with said chamber in the pat-h of movement of said di'stributing port, said piston being movable to bring said distributing port successively into communication with said outlet ports, said piston having a central position in which said distributing port is between said outlet ports and in communication with neither of them, an auxiliary cylinder vat each end of said body, an auxiliary piston in each auxiliary cylinder, the cross-sectional area of each auxiliary piston being less than that of said distributing piston, a piston rod connected to each wardly, the respective-piston rods connected to said pistons, when in their inner positions, en-

gaging the ends of said distributing piston to hold the same in its said central position, uid conducting means operatively connected with the ends of said chamber, respectively, on opposite sides of said distributing piston for conducting Lfluid with respect to the lends of said chamber, and valve means in said fluid conducting means for controlling the flow of fluid therethrough so as to cause the overcoming of the centering action of said auxiliary pistons to move said distributing piston to move to direct fluid from said inlet through said distributing port to-one of said outlet ports or the other as desired.

10. A fluid control valve comprising a body having'a chamber therein, a fluid distributing piston slidably disposed in said chamber, a pair oi' outlet ports in said body communicating with said chamber, an inlet port in said body lcommunicating with said chamber, a distributing port in said piston for directing fluid from said inlet to one of said outlet ports in one-position of said piston and to the other of said outlet ports in another position of said piston, there being an intermediate position of said piston at which inlet 'iluid is directed to neither of said outlet ports, diierential fluid pressure means arranged to be rendered active to actuate said piston to direct fluid to said outlet ports as desired and arranged to be rendered inactive following being rendered active, and fluid actuated means operable upon said diiferential pressure fluid means being rendered inactive to dispose and maintain said distributing piston in its intermediate position, said fluid actuated means being arranged to be operative against the ends of said distributing piston to move the same to said intermediate position.

11. A fluid control valve comprising a. body having a chamber therein, a fluid distributing piston slidably disposed in said chamber, a pair of outlet ports in said body communicating with said chamber, an inlet port in said body communicating with said chamber, a distributing port in said piston for directing iiuid from said inlet to I one of said outlet ports in one position of said piston and to the other of said outlet ports in another position of said piston, there being an intermediate position of said piston at which inlet fluid is directed to neither of said outlet ports, a pair of auxiliary cylinders, means to conduct pressure fluid to said auxiliary cylinders, a piston in each ofsaid auxiliary cylinders, means connected to said auxiliary pistons for positioning said distributing piston at said intermediate position, and controlled means to conduct pressure uid to opposite ends of said chamber to act against the ends of said distributing piston to move the same to the desired one of said fluid directing positions.

v12. The invention as deiined in claim 11 wherein the pressure fluid for acting on said distributing piston and said auxiliary pistons is the fluid controlled and the cross sectional area of each auxiliary piston is less than that of said distributing piston.

distributing piston slidably disposed in said chamber, an inlet port in said body, a distributing port in said piston, one end thereof communicating at all times'with said inlet port and at the other end .f terminating at a sliding surface of said piston, a

pair of spaced outlet ports in said body communicating with said chamber in the path of movement of said distributing port, said piston being movable to bring said distributing port successively into communication with said outlet ports, said piston having a central position in which said distributing port is between said outlet ports and in communication with neither of them, restricted ports for providing communication between said distributing port and each end of said chamber, an auxiliary cylinder at each end of said body, a pressure fluid connection between the fluid controlled and each auxiliary cylinder, an auxiliary piston in each auxiliary cylinder, means for applying a diierential fluid pressure to opposite ends of said distributing piston for causing said distributing piston to move to direct uid from said inlet through said distributing port to one of said outlet ports or the other depending on the one of said means actuated, and centering means actuated by said auxiliary pistons under the action of the controlled fluid through said pressure fluid connection, upon the rendering inoperative of said means for applying a differential fluid pressure operative to center said distributing piston, said centering means comprising piston rods connected to said auxiliary pistons and extending into the ends of said chamber respectively for operative centering contact with said distributing piston.

14. The invention as defined in claim 5 wherein the pressure releasing means for each end of the rst chamber comprises a port in each piston rod for conducting pressure fluid from the respective ends of the chamber to the respective auxiliary cylinders, and pressure releasing valves having communication with the auxiliary cylinders respectively.

15. The invention as defined in claim 6 wherein there is provided a vent at the inner end of each auxiliary cylinder for permitting free movement of the auxiliary pistons under the action of pressure fluid from the ends of the chamber.

16. A control valve for distributing uid under pressure comprising a body having a chamber therein, a fluid distributing piston slidably disposed in said chamber, a pair of outlet ports in said body communicating with said chamber, an inlet port in said body communicating with said chamber, a distributing port in said piston for directing fluid from said inlet to one of said outlet ports in one position of said piston and to the other of said outlet ports in another position of said'piston, there being an intermediate position of said piston at which inlet uid is directed to neither of said outlet ports, diierential fluid pressure means arranged to be rendered active to actuate said piston to direct uid to said outlet ports as desired and arranged to be rendered inactive following being rendered active, and uid actuated means, -projectable into opposite ends oi' said chamber and engageable with said piston. operable upon said differential pressure uid means being rendered inactive to dispose and maintain said distributing piston in its intermediate position.

` LQYD A. WARD.