US3250185A

US3250185A - Circuit control valve instrumentality

Info

Publication number: US3250185A
Authority: US
Inventors: Francis H Tennis; William N Tolbert
Original assignee: Hydraulic Unit Specialties Co
Current assignee: Koehring Co; Hydraulic Unit Specialties Co
Priority date: 1964-03-23
Filing date: 1964-03-23
Publication date: 1966-05-10
Anticipated expiration: 1983-05-10
Also published as: ES304178A1; DE1242961B; BE654189A; GB1050181A; NL6503624A

Description

y 1966 F. H. TENNIS ETAL 3,250,185

CIRCUIT CONTROL VALVE INSTRUMENTALITY Filed March 23, 1964 3 Sheets-Sheet l 'QMMM Frizwzi 1? 72 2mm LEI/2:742: AZ him? RESERVOl R May 10, 1966 F. H. TENNIS ETAL 3,250,185

CIRCUIT CONTROL VALVE INSTRUMENTALITY Filed March 23, 1964 3 Sheets-Sheet 2 May 10, 1966 F. H. TENNIS ETAL 5 CIRCUIT CONTROL VALVE INSTRUMENTALITY Filed March 23, 1964 3 Sheets-Sheet 5 72 4222525 2272 222225 Q LVN/222222 AME/M22 IJnited States Patent 3,250,185 CIRQUIT CONTROL VALVE INSTRUMENTALITY Francis H. Tennis, Hartland, and William N. Tolbert, Waukesha, Wis., assignors to Hydraulic Unit Specialties Company, Pewaukee, Wis., a corporation of Wisconsin Filed Mar. 23, 1964, Ser. No. 353,710 15 Claims. (Cl. 9l420) This invention relates generally to fluid pressure operated systems of the type wherein a double acting hydraulic cylinder or other reversible fluid motor is driven in one direction or the other in consequence of actuation of a control valve therefor, and it has more particular reference to improvements in circuit control valve instrumentalities that are frequently used adjunctively with the control valves of such systems to provide more positive control over the fluid motors governed thereby.

As is well known, the conventional control valve for a double acting hydraulic cylinder or other reversible fluid motor contains a valve element or spool which is shiftable to each of a pair of operating positions to selectively direct pressure fluid from a pump to either side of the cylinder and to direct fluid exhausting'from the opposite side of the cylinder to a reservoir. In most cases, the control valve spool, when in a neutral or hold position, provides the only means of closing off the cylinder ports from both the pump and the reservoir, and the timing" of the spool is usually such that when it is shifted to one or the other of its operating positions, it connects one of the cylinder ports with the reservoir slightly before it connects the other motor port with the pump.

Due to these operating characteristics, conventional control valves that are used in the hydraulic systems of certain types of apparatus are frequently unsatisfactory in several respects. This is especially true of control valves for hydraulic actuators such as are employed to swing a heavy mechanism or load about either a hori- Zontal or a vertical axis, or both. Bulldozers, front end loaders, and power shovels especially, are examples of apparatus having loads of the type referred to. All of these are characterized by a heavy boom structure to which the work performing element of a double acting hydraulic cylinder is connected to move'the same up and down about a horizontal axis. In power shovels, the boom structure is also mounted for swinging motion in opposite directions about a vertical axis, and such swinging motion is imparted thereto by a reversible fluid motor that may comprise a double acting hydraulic cylinder or a pair of single acting cylinders.

When the spool of a conventional control valve for the raise and lower boom cylinder of such equipment is alone relied upon to close ofl' the cylinder ports from both the pump and the reservoir in'its neutral or hold position, for example to hold the boom in an elevated position, the close fit between the lands on the spool and the wall of the bore in which it operates constitutes the sole means of preventing load pressurized fluid in the raise end of the cylinder from leaking past the spool to the exhaust passage in the valve. Hence, there is no positive lockout of the cylinder or assurance against gradual lowering of the boom under the force of gravity when such leakage occurs.-

Nor can the control valve exercise positive control over the boom cylinder when its spool is shifted to effect lowering of the boom. At such times, the pressures at the opposite sides of the cylinder are unbalanced, and the timing of the spool is such that it first connects the raise port ofthe boom cylinder with the reservoir, with the result that the boom or load tends to drop in more or less uncontrolled fashion under the force of gravity. This also leads to cavitation in the lower side of the 3,250,185 Patented May 10, 1966 boom cylinder, due to expulsion of fluid from its raise port before fluid is allowed to flow into its lower port, and because the load continues to drive fluid out of the raise portfaster than the pump can supply fluid to its lower port even after the spool is fully shifted to its load lowering position.

In the case of power shovels wherein the boom also swings about a vertical axis, this same problem can be even more troublesome, especially when the power shovel is operating on a surface that is inclined to horizontal. In that event, the boom can be gravitationally biased laterally in either direction, with the result that voids can be formed in either side of it's cylinder.

Finally, the control of such boom cylinders by conventional spool type control valves alone frequently results in severe shock pressures that can be damaging to the equipment. These shock pressures result when an operator of the equipment accidentally or of necessity suddenly returns the control spool of the valve to its neutral or hold position to either stop descent of the boom or to arrest its sidewise swinging motion. At such times, the control spool closes off the cylinder ports and the inertia of the boom tends to continue driving the work performing element of the cylinder in the same direction it had been moving. Consequently, extremely high back pressure is substantially instantaneously produced at one side of the cylinder, and in the line connecting the same with the control valve.

Circuit control devices have been proposed in the past, as an adjunct to the conventional spool type cylinder control valves, in an effort to overcome the problems discussed above. Thus, such devices have incorporated valve mechanisms that are intended to positively lock hydraulic fluid in a cylinder without reliance upon the fit of the control spool of the cylinder control valve in its bore; to counterbalance or correlate the flow of hydraulic fluid to and from the opposite sides of the cylinder so as .to minimize the possibility of the load driving the cylinder and resulting void formation therein; and to effect cushioning of the shocks that inertia forces tend to produce when the control spool is suddenly returned to its neutral position to stop lowering or sidewise swingingmotion of a heavy load. One such circuit control device is disclosed in Patent No. 2,926,634, issued March 1, 1960 to E. L. Falendysz et al. That patent teaches the use of cross line relief valve mechanism to achieve cushioning of shocks, 'in addition to a pair of dual pur pose valve mechanisms which are sometimes referred to I as lockout and counterbalancing valves because of the load holding and flow correlating functions they are intended to perform.

Ingeneral, it is the object of this invention to provide a fluid flow or circuit control device for the purposes referred to, which features improved lockout and counterbalance valve mechanisms that enable more precise control over a fluid motor than was possible with past devices of this type.

Hence, one of the objects of the invention resides in the provision of a circuit control device of the character described featuring a pair of pressure responsive main valves, one for each port of a reversible fluid motor, wherein said main valves govern all fluid flow to and from themotor, and either can serve as a supply valve that opens solely in response to the force imposed thereon by supply fluid under pressure while the other valve serves as an exhaust valve.

' one side of the motor to thus effect metering of the exhaust flow from the other side of the motor except at times when the pressure of supply fluid attains a prede termined high value.

It is a further purpose of this invention to provide a circuit control device wherein each of the main valves has a piston like part thereon which operates in a pressure chamber or cylinder that is communicated with its motor port, so that pressure fluid from the opposite sides of the motor can flow into the pressure chambers to act upon the main valves and hold them tightly closed and thus very effectively provide the lookout feature of the circuit control device.

Still another purpose of this invention is to provide a circuit control device of the character described wherein tflllld can be exhausted from the pressure chamber or cylinder of each main valve through a normally closed pilot valve to permit each main valve to be opened in response to force imposed thereon by pressure fluid from its motor port, and wherein a pressure responsive pilot actuator effects unseating of the pilot valve for either main valve in response to the force imposed on the actuator by supply fluid flowing through the other main valve.

Another purpose of this invention resides in the provision of a circuit control device of the character described featuring pilot valves that are biased toward positions closing exhaust passage means for the pressure chambers of their respective main valves by a spring force which is readily adjustable to enable compensation for line pressure losses in a system incorporating the device.

A further purpose of the invention resides in the provision of a circuit control device such as described, featuring a compact body in which the lockout and counterbalancinlg valve mechanisms are incorporated, and in which crossline relief mechanism may be readily incorporlated to relieve pressure shocks in a system embodying the device, without entailing objectionable enlargement of its body.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a sectional view of a circuit control device embodying this invention, illustrating the same in its lockout position and diagrammatically showing how it is connected in a fluid pressure operated system including a pump, a reservoir, and a conventional motor control valve;

FIGURE 2 is a sectional view of a portion of the circuit control device seen in FIGURE 1, but at an enlarged scale, and illustrating the valve mechanisms thereof in fully open positions; and

'FIGURE 3 is a view similar to FIGURE 2 but illusrtrating one of the valve mechanisms in a partly open exhaust metering position.

Referring now to the accompanying drawings, the numeral 5 generally designates the circuit control device of this invention. Itis adapted to form part of a fluid pressure operated system comprising a pump. 6 having its inlet connected by a duct 7 with a fluid reservoir 8 and having its outlet connected by a duct 9 with the inlet 10 of a conventional motor control valve 11. The control valve 11 has a return port 12 connected by a duct 13 with the reservoir, and it has a pair of

service ports

14 and 15 in which are connected supply lines 16 and 17, respectively. These supply lines are communicable with the motor ports at the opposite sides of a reversible fluid motor, not shown.

As is customary, a control spool 18 in the valve 11 can be shifted out of a neutral or hold position at which it closes off the supply lines 16-17 fromboth the inlet and

return ports

10 and 12 of the valve, to each of two operating positions to selectively connect either of the supply lines with the pump and the other supply line with the reservoir and thus establish operating circuits for the motor by which its work performing element can be driven in either direction.

The circuit control device 5 of this invention comprises a body 18 having a pair of

service passages

19 and 20 therein which are respectively adapted to form continuations of the supply lines 16 and 17, and a pair of valve mechanisms 21 in the body, one for each service passage, governs fluid flow therethrough.

The service passages open to

inlet ports

22 and 23 at the supply side of the body, in which ports the supply lines 16 and 17, respectively, can be connected to enable the motor control valve 11 to communicate either service passage with the pump while communicating the other service passage with the return line 13. At the motor side of the body 18, the

service passages

19 and 20 open to

motor ports

24 and 25, respectively, which are connectible with the ports at the opposite sides of a reversible fluid motor. Hence in use, the circuit control device of this invention is interposed between the fluid motor and its control valve 11.

Each of the

service passages

19 and 20 in the body is comprised of an inlet branch 26 and an outlet branch 27. The inlet branches 26 are substantiallyL-shaped, having coplanar leg portions 28 extending inwardly from their junctions with the body inlets 22-23, and having parallel upright stem portions 29 which lie at opposite sides of a partition wall 30 in the body located substantially centrally between the ends of the body. A hole 31 through the partition wall serves to slidably mount a fluid pressure responsive plunger 32, for a purpose to be later described.

The outlet branches 27 are also L-shaped, having coplanar leg portions 33 extending inwardly from their junctions with the motor ports 2425, and parallel downwardly extending stem portions 34 spaced outwardly from the upstanding stem portions 29 of the inlet branches and communicating therewith through short bores 35 coaxial with the hole 31 in the partition wall 30. These bores open to the inner end portions or bottoms of coaxial counterbores 36, which in turn open to the stern portions of the outlet branches 27 and to the opposite ends of the body through enlarged holes that are threaded to receive plugs 37. The plugs 37 thus close the outer ends of the counterbores.

The valve mechanisms 21 are mounted in the counterbores 36, and they are identical. Each comprises a normally closed main valve 39, a normally closed pilot valve 40, and a substantially cylindrical core member 41 which slidably supports the main valve and contains the pilot valve. At the bottom of each counterbore, the body is machined to provide a tapered annular valve seat 42., which surrounds the adjacent bore 35 and faces axially outwardly toward the counterbore and the adjacent stem 34 of the outlet branch of its service passage.

The main valve 39 of each valve mechanism is of tubular construction and stepped to have opposite sleevelike end portions of different diameters, which provide both internal and external circumferential shoulders 43 and 44, respectively, on the valve. Its larger diameter end portion 45 is axially outermost and slidingly received in the closed end portion of its counterbore to serve as a piston, as will be discussed later. Its smaller diameter end portion 46 projects axially inwardly from the external shoulder 44 on the valve, across the stemportion 34 of its outlet branch passage, and its inner extremity is cooperable with the valve seat 42. While there may be sufficient clearance between the exterior of the piston portion 45 and the Wall of the counterbore to enable fluid in the outlet branch 27 of the service passage to flow past the piston portion and into the closed outer end portion of the counterbore, the main valve is shown provided with a series of small diameter holes 47 in its Wall, leading'through the shoulder 44 thereon to the interior of the piston portion 45 to communicate the closed outer end portion of the counterbore with the outlet branch of its service passage.

In addition, it will be noted thatjthe inner end portion 46 of the main valve is normally received within a reduced bottom portion 38 of its counterbore, which may have a diameter only slightly larger than that of the inner end portion of the valve to provide a small clearance space encircling the same. These bottom portions 38 of the counterbores can be considered ascomprising widened mouths for the bores 35, located axially outwardly of the main valve seats 42.

The core member 41 of each valve mechanism is tubular and it is fixed in the body coaxially of its counterbore by the adjacent plug 37. For this purpose, each core member is provided with a circumferential flange 48 on its outer axial end, which flange is held against the mouth of the counterbore, at the bottom of the threaded hole to which it opens, by the plug 37 in the latter. Each core member extends inwardly. a distance into its counterbore, in spaced relation to the wall thereof, to a point just short of the reduced portion 38 at the bottom of the counterbore.

The flange 48 provides a stop with which the piston portion 45 of the' mainvalve engages to define the outermost or fully open position of the main valve in its counterbore, and it also serves as a spring seat against which one end of a coiled expansion spring 49 abuts. The spring encircles the core member 41, extends into the interior of the annular piston portion 45 on the main valve, and engages its internal shoulder 43 so as to yieldingly hold the main valve seated.

The axially inner end portion of each core member provides a support upon which the smaller diameter end portion of its main valve is slidingly mounted, and the joint therebetween is sealed by an O-ring 50 confined in a circumferential groove in the exterior of the core member. It also has a coaxial bore 51 through its inner end portion, that opens axially outwardly to a counterbore 52 in the core member through an annular pilot valve seat 53 at the bottom of the counterbore 52, and affords communication between the hollow interior of the core member and the inlet branch 26 of its service passage through the bore 35 thereof andthe open inner end of its main valve.

Each of the valve mechanisms 21 also comprises a pilot guide member 55 of tubular construction, having at its outer axial end a radially enlarged head 56 which is received in a well 57 in the adjacent plug. This head is confined axially between the bottom of the well and the flange 48 on its core member so that the guide member is held in fixed relation to the body 18. The guide member also has a reduced inner end portion 58 which projects into the mouth of the counterbore 52 in the adjacent core member and which provides a bearing in which a stem 59 on the pilot valve 40 is slidably re- Each pilot valve comprises a cylindrical 40' located in the counterbore of its core member, axially inwardly, of its stem and the inner end of its guide member. The body is slightly larger in diameter than the stem, and

has a tapered nose 61 formed on its inner end portion to engage the seat 53 on its core member, toward which it is yieldingly biased by a coiled compression spring 62 in the interior of its guide member. This spring is confined between the outer extremity of the pilot stem 59 and a screw 63 that is threaded into the adjacent plug 37 to enable the biasing force on the pilot valve to be adjusted.

The nose 61 on each of the pilot valves normally projects axially inwardly through its seat, and has a pad 64 formed on its extremity, the exterior. of which clears the wall of the bore 51 in the adjacent core member. These pads are adapted to be engaged by the ends of stems 65 on the plunger 32, which project coaxially from its opposite ends into the bores 51 of the core members to have their extremities closely adjacent to the pads 64 on the pilot valves. Hence, axial sliding movement of the plunger 32 in opposite directions effects opening of one or the other of the pilot valves 40. The pilot valves, however, are permitted only a small amount of opening motion off of their seats, being limited in this respect by the engagement of their slightly enlarged bodies with I the inner axial ends of the guide members therefor.

. nose are equal, the forces which fluid pressure exert on the opposite ends of the pilot valve balance one another. Consequently, the pilot valves are biased only by their springs 62, which yieldingly hold them in closed positions engaging their seats 53.

With the construction of the valve mechanisms described thus far, it will be apparent that each core member cooperates with the wall of the counterbore in which it is located to define an annular pressure chamber or cylinder in which the piston portion 45 on each main valve operates. Pressure fluid can flow into these cylinders from the outlet branches of their respective service passages and exert force on the ends and internal shoulders 43 of the main valves to hold them in their closed posit-ions. Pressure fluid in the outlet branches of the service passages can also act upon the external shoulders 44 on the main valves, tending to open them. However, since pressure fluid in the cylinders acts upon surfaces of the main valves having a combined area larger than that of the surfaces of the external shoulders 44, the force which pressure fluid in the return branches 27 exerts upon the external shoulders cannot effect opening of the main valves until pressure fluid can exhaust from the cylinders. i

For this purpose, each of the valve mechanisms incorporates a cylinder exhaust passage the outlet of which comprises the bore 51in its core member 41, and includes the hollow interior of the core member in which the body 40' of the pilot valve operates, and radial holes 68 in the wall of the core member surrounding the pilot valve body.' These radial holes open into the cylinder space at areas surrounded by the piston portion of each main valve, and thus provide communication between their cylinders and the inlet branches of their respective service passages at times when the pilot valves are moved outwardly away from engagement with their seats.

Assuming that the ports 24-25 of the circuit control device of this invention are connected with the opposite sides of a double acting hydraulic cylinder or other reversible fluid motor such as is provided to drive a heavy load in opposite directions at the dictation of the control valve 11, the engagement of the main valves' 39 with their seats very eflectively and positively locks pressure fluid in the cylinder as long as the control spool 18 of the control valve 11 is in 'its neutral or non-operating position. At such times, the inlet branches 26 of the service passages are closed off from the pump 6, and the springs 49 act to hold the main valves 39 on their seats to prevent load pressurized fluid at one side or the other of the cylinder from flowing to the inlet branch of its service passage. Such load pressurized fluid in the return branch 27 of either service passage is also present in the pressure chamber or cylinder of the main valve for that service passage, where it exerts additional bias on the piston portion of the main valve in said chamber to hold the main valve more firmly on its seat.

Hence, the circuit control device of this invention provides lockout valves which preclude escape of pressure fluid from either side of a double acting hydraulic cylinder or other fluid motor, making it especially valuable for use with front end loaders and particularly power shovels 'which have a heavy boom structure mounted for up and down motion about a horizontal axis and also for side to side swinging movement about an upright axis. The boom of such apparatus constitutes a heavy load that acts to pressurize the fluid in the load raising end of the boom lift cylinder, and the boom structure also constitutes a heavy load that acts to pressurize the fluid in either side of the boom swing cylinder depending upon the inclination of the surface on which the power shovel stands.

It is important to observe that the lookout feature described above is achieved entirely without assistance from the control spool 18 of the control valve 11, as long as the spool is in a non-operating position at which it prevents pump fluid from flowing into the inlet branch 26 of either service passage 19-20. Thus, the circuit con trol device of this invention can be used with control valves having spools of either the hold-in-neutral type, or with those which are sometimes referred to as motor spools, which in their neutral position leave both supply lines 16 and 17 in communication with the return line 13.

When the spool 18 of the control valve 11 is shifted out of its neutral position to one of its operating positions, for example, to direct pump fluid into the inlet branch of the service passage 19 and to connect the inlet branch of the other service passage 20 with the return line, pressure fluid flows into the service passage 19 and acts upon the inner end of the left hand main valve 39 to open the same, thus allowing supply fluid to flow past the valve and into the outlet branch of this service passage. When the left hand valve opens at this time, it expels pressure fluid from its cylinder or pressure chamber into the outlet branch of its service passage through the holes 47 in the valve. The pilot valve 40 for the left hand valve mechanism remains in closed position, however, since it is hydraulically balanced with respect to the pressure of fluid in the inlet branch of its service passage 19.

Assuming that the outlet branch port 24 is connected to the load lowering port of a. boom lift cylinder while the other port 25 is connected to the load lifting port of the boom lift cylinder, and that the boom was in an elevated position at the time the control spool 18 was shifted as described to thus effect descent of the boom, the right hand main valve 39 governing the service passage 2 0 will temporarily remain closed due to the action thereon of load pressurized fluid in its pressure chamber or cylinder, to prevent the escape of fluid from the load raising port of the boom lift cylinder. The right hand main valve 39v is not allowed to open until the pressure of fluid builds up in the service passage 19 to a value such that the force it exerts on the left hand end of the plunger 32 tending to move it to the right is great enough to overcome the force of the spring 62 acting upon the pilot valve 40 of the right hand valve mechanism. When such force upon the plunger exceeds the biasing force of the spring 62, the plunger moves to the right and pushes the pilot valve off of its seat. This opens the exhaust passage for the pressure chamber of the main valve governing the service passage 20, allowing escape of fluid therein to its inlet branch 26, which is now in communication with the return line 13. The main valve 39 for passage 20 then opens fully in consequence of the force which fluid under pressure in its outlet branch 27 exerts upon its external shoulder 44. Fluid in the load raising end of the boom cylinder may then exhaust to the return line. Both main valves 39 are then in their fully open positions seen in FIGURE 2, and the boom accordingly begins to descend.

In the event the load on the boom lift cylinder thereafter causes exhaust fluid to be expelled therefrom through the service passage 20 at a rate faster than the pump can supply fluid to the load lowering side of the cylinder through the service passage 19, the pressure of supply fluid in passage 19 drops accordingly and results in a corresponding reduction in the opening force applied to the pilot valve of the right hand valve mechanism by the pilot actuating plunger 32. The pilot spring 62 then moves the pilot valve toward its closed position. As a result,'exhaust fluid flowing into the pressure chamber of the right hand main valve from the outlet branch of the service passage 20 can no longer freely escape past its pilot valve, and pressure builds up in said pressure chamber to cause the right hand main valve to move toward its closed position and limit exhaust flow through the service passage 20. This prevents the load represented by the boom from expelling fluid from its cylinder at a rate faster than supply fluid can flow to the cylinder through the service passage 19.

FIGURE 3 shows the right hand main valve 39 in an exhaust metering position which it can occupy during the entire descent of the boom to assure flow of pressure fluid to and from the boom lift cylinder at equal rates and thus not only control the rate of descent of the boom but to assure against drawing a void in the boom lowering side of its cylinder. As seen in FIGURE 3, the right hand main valve, 39 is in a partially closed or metering position with its small diameter end portion located within the reduced bottom portion 38 of its counterbore but off of its seat 42. It will stay in a metering position such as shown as long as the load on the boom lift cylinder tends to increase the pressure in the load raising side of the cylinder and to correspondingly decrease the pressure in the load lowering side of the cylinder. This results from the fact that relatively slight decreases in the pressure of supply fluid flowing to the load lowering side of the boom lift cylinder through the service passage 15? are more or less detected by the pilot valve mechanism for the right hand main valve. Whenever the pressure of supply fluid in the service passage 19 drops slightly for the reason described, the force it exerts on the pilot actuating plunger diminishes accordingly and the plunger is unable to fully overcome the. opposing force of the spring 62 acting on the pilot valve for the right hand main valve. The spring 62 then moves the pilot valve slightly toward its seat to a partially closed metering position restricting the outlet of the exhaust passage governed thereby, but it stops just short of its seat as soon as the opposing forces acting thereon are in balance.

The position of the right hand main valve is determined by the position of its pilot valve. It is caused to move toward and from its seat more or less in correspondence with motion of its pilot valve toward and from its seat, and the main valve will assume a partially closed or metering position such as shown in FIGURE 3 whenever its pilot valve occupies a similar partially closed position.

Thus, exhaust fluid in the outlet branch of the .service passage 20 cannot flow freely through the pressure cham-. ber of the right hand main valve 39 when its pilot valve is in its partially closed position obstructing the outlet its internal and external surfaces.

Hence, the pressure of supply fluid flowing to the cylinder through the service passage 19 constitutes an accurate measure of the rate at which fluid is expelled from the cylinder and is relied upon by the flow controlling device of this invention to determine the position of the right hand main valve 39 through the action of the pressure responsive plunger 32 on its pilot valve.

The circuit control device of this invention thus achieves a highly desirable counterbalancing function in that it serves to correlate the flow of fluid to and from a double acting hydraulic cylinder or other fluid motor despite the fact that the load operated by the cylinder at times tends to drive the cylinder and cause expulsion of fluid from one side thereof faster than the pump can supply fluid to the other side of the cylinder.

It will also be appreciated that because of the flow correlation achieved by the valve mechanism of this invention, the possibility of void formation in the cylinder ,is minimized at times when the load operated'thereby tends to cause fluid to be expelled from one side of the cylinder at a rate faster than fluid can be supplied to its other side.

As soon as the spool 18 of the control valve 11 is returned to its neutral position to again close off the service passages 19-20 from the pump, there is insufficient pressure in the inlet branch of the service passage 19 to hold the plunger 32 shifted to the right, and the spring 62 for the right hand pilot valve recloses the valve and pushes the plunger the short distance necessary to substantially center it with respect to both pilot valves. In this respect, the pilot valve springs serve as centering springs for the plunger.

Inasmuch as the bore 31 in which the plunger 32 operates provides a degree of clearance around the exterior of the plunger by which fluid displaced thereby is more or less free, to flow from one inlet branch to'the other during return movement of the plunger to its neutral position, there is nothing to interfere with prompt closure 'of the unseated pilot valve following return of the control spool 11 to its neutral position even though the spool may be of the hold-in-neutral type.

. Each main valve, of course, recloses promptly at this time due to the bias of its spring 49, and under the additional bias of load pressurized fluid that may be present in the outlet branch of its service passage. For example, reclosure of the right hand pilot valve 40 closes off the exhaust passage for the pressure chamber of its main valve, so that load pressurized fluid in the outlet branch of its service passage can flow to and be trapped in said pressure chamber and thus aid the spring 49 in reclosing the right hand main valve.

The same type of operation is achieved when the flow of pressure fluid to and from the cylinder is reversed by the control valve 11, if conditions in the'system are such that load pressurized fluid is present in the outlet branch 1O for must not close their passages 66. For this reason, the end portions of the stems on the actuating plunger have angled holes 70 therein that register with and form continuations of the balancing passages 66 in the pilot valves when the stems are in engagement with their adjacent pilot valves. I

The circuit control device of this invention also incorporates cross line relief valve mechanism generally designated 72 in FIGURE 1, which serves to cushion the system against sudden shock pressures that ordinarily result with a hold-in-neutral type spool 18 in the control valve 11 when the spool is snapped back to its neutral position to arrest motion of a heavy load connected to 27 of the service passage 19. This might be the case if the work performing element of the cylinder governed thereby. At such times, the cylinder ports are closed off from both the pump and the return line 13, and extremely high and sometimes damaging shock pressures can be generated in the system due to the inertia of the load.

The crossline relief valve mechanism 72 can be of a conventional type, but have here been shown as comprising a pair of identical bi-directional fluid pressure responsive valve devices 73 such as are disclosed in the copending application of Francis H. Tennis, Serial No. 229,601, filed October 10, 1962, now Patent No. 3,194,261 and entitled Cross Line Relief Mechanism for Reversible Hydraulic Motor. They are mounted on the outlet or motor side of the body 18 to control fluid flow through a transfer passage 74 the opposite ends of which connect with the outlet branches 27 of the service passages through short bores 75. Since the aforesaid copending applicatron contains a complete disclosure of the construction and operation of the valve devices 73, it is here sufficient to note that both are caused to open in response to rise n the pressure of fluid in the outlet branch of either service passage to an abnormally high value to connect said outlet branch with the other outlet branch. This allows fluid at abnormally high pressure in one end of a cylinder to flow to the other end of the cylinder to relieve the abnormally high pressure condition, after which the valve devices close automatically. I

From the foregoing description, together with the accompanymg drawings, it will be readily apparent to those sl qlled in the art that this invention provides a hydraulic circuit control device that has many unique features, amongst which are a pair of pilot controlled main valves WhlCh govern all fluid flow through the service passages of the device and effect metering of exhaust flowthrough either service passage in accordance with the pressure of supplying fluid in the other service passage; provision for ad ustment of the pilot valve springs to enable compensation for line pressure losses; and utility of the device with control valves having valve spools of either the hold-in-neutral or motor types.

What is claimed as our invention is:

1. Curcuit control means for a reversible fluid motor comprrsmg:

A. a body; B. a pair of service passages in the body either of which provides for flow of supply fluid at a normally high pressure value to one side of a reversible fillld motor while the other passage provides for re- :urn flow of fluid from the opposite side of the mo- C. a pair of normally closed pressure responsive valves, one for each service passage to govern all fluid flow therethrough, each of said valves being movable to an open position in response to flow of supply fluid under pressure into its service passage;

D. means associated with each valve for translating the pressure of fluid returning to its service passage into force on the valve tending to open the same;

E. other means asociated with each valve for translating the pressure of fluid returning to its service passage into force on the valve by which it can be held closed against said opening force thereon;

11 v and force controlling means associated with but mechanically independent of each valve, and sensitive to the pressure of supply fluid in the service passage for the other valve, for effecting reduction of eating each pressure chamber with the outlet branch of its associated service passage so that fluid in said outlet branch at a pressure exceeding that of fluid in its inlet branch can flow into said fluid pressure closing force on its valve to a the pressure chamber and act on the large diamvalue below that of said fiuid pressure opening force eter end .portion of the-main valve therein to thereon in response to the presence of supply fluid hold the valve closed,

at-.said normally high pressure value in the service (4) means providing a venting passage for each passage for said other valve, and for effecting inpressure chamber leading to the inlet branch crease in the fluid pressure closing force on its valve of its service passage through said hole in its in accordance with a decrease in the pressure of valve supporting member and the hollow interior supply fluid in the service passage for said other of the latter,

valve. (5) and a pilot valve in each valve supporting 2. The circuit control means of claim 1, wherein the member normally closing said hole therein to force controlling means for each valve comprises: 15 block the venting passage for its pressure cham- A. a member that is movable in one direction from a ber;

first position to a second position under the in F. pilot valve actuating means in the body responsive fluence of supply fluid at said normally high prest0 the pressure Of supply fluid in the inlet branch of sure value in the service passage for the other valve er service passage to efiect opening of the pilot to effect reduction of said closing force on its valve; ve assoc ated with the other service passage;

B. and a spring to yieldingly resist such movement of G. and a circumferential shoulder on the exterior of said member in said direction and to efiect return each main Valve, facing toward the Ollflfit bI'aHChhOf motion thereof toward said first position in cons Service Passage, 1111011 Which fluid in Said Outlet sequence of decrease in the pressure of supply fl id branch can act to open the main valve whenever its in the service passage for said other valve, whereby vP110t Valve is p 4. Circuit control means for use with a reversible fluid motor, and of the type comprising a body having a pair of h other valve at a pressure li h l b 1 id service passages either of which provides for flow of supno 'mal high pressure value limits spring biased ply fluid to one side Of the motor while the other provides turn of said member to said first position thereof, return how of fluid from the pp Side of The and whereby the valve asociated with said member motor: further Characterized y following! said member can occupy an intermediate position at times when supply fluid in the service passage for A. that each of said service pasages comprises can occupy a position intermediate its open and closed positions in correspondence with the intermediate position of said member, to meter the re- (1) an inlet branch, (2) an outlet branch having a portion laterally turn flow of fluid through its service passage. adjacent to a Portion of the inlet branch,

3, Ci it t l means, i i (3) and a bore communicating said laterally adja- A a b d cent portions of the inlet and outlet branches;

B. a pair of service passages in the body either of an annular math Valve seat on the body for each hi h provides f fl f Supply fl id to one Side servlce passage, surrounding the bore thereof and of a reversible fluid motor while the other provides facmg toward its outlet branch; for return flow of fluid from the opposite side of the the body having a cylindrical recess coaxiahy P- motor each f said Service passages comprising posite each valve seat, opening to the outlet branch (1) an i l branch, and to the bore of the associated service passage;

(2) an outlet branch having a portion laterally Valve mechanism in each recess, comprising adjacent to a portion of the inlet branch, a Valve supporting member fixed With respect (3) and a bore communicating said laterally adto the body and having its exterior spaced from jacent portions of the inlet and outlet branches; the Wall of the recess:

C. annular main valve seats in the body, one for each (2) a math Valve mounted on and encircling Said service passage, surrounding the bore thereof and member and constrained thereby to motion f i toward outlet branch; axially of the recess between open and closed D. counterbores in the body, one for each service Positions said math Valve having a large diam passage coaxial with and opening t0 its bore, and eter annular portion at one end slidably fitting to the Outlet branch th f; said recess and having a smaller diameter por- E. valve mechanism in each counterbore comprising, at its other end normally engaging the 1 a hollow Cylindrical Valve supporting main valve seat, said valve permitting transfer fi d with respect to the body, caaxial with of fluid between the inlet and outlet branches the counterbore and cooperating therewith to P its Service Passage only When the main Valve define an annular pressure chamber, each of said 13 Open but being adapted to open in response to members having a hole in one end opening to flow of supply fluid into the inlet branch of its h bore of its service passage to communicate Service Passage, its hollow interior with the inlet branch of its means defining a transfer Passage Communicatr i e a ing said recess with the outlet branch of its serv- (2) a tubular main valve encircling said valve supice Passage so that fluid in Said ou'dht branch porting member and mounted thereon axial at a pres-sure exceeding that of fluid in its inlet movement between open d l d position, branch can flow into the recess and act upon the said main valve having a large diameter porlarge diameter end portion of the main valve to tion at one end slidably received in said pressure hold it closed, chamber and a smaller diameter portion at its (4) means providing a venting passage for said other endnormally engaging the main valve seat, recess leading to the inlet branch of its service said main valves controlling all fluid flow through the service passages and being adapted to open in response to flow of supply fluid into the inlet branches of their respective service passages, (3) means defining a transfer passage communipassage,

(5) and a pilot valve for said venting passage, normally blocking the same said pilot valve being mechanically independent of its associated main valve;

E. pilot valve actuating means in the body, responsive to the pressure of supply fluid in the inlet branch of either service passage to effect opening of the pilot valve associated with the other service passage;

F. and means for efliecting opening of each main valve in consequence of opening of its pilot valve, comprising a circumferential shoulder on the exterior of the main valve, at the junction between said large and small diameter ends thereof, upon which fluid in the outlet bran-ch of its service passages acts to open the main valve at times when the venting passage for its recess is open.

5. Circuit control means for use with a reversible fluid motor,'and of the type comprising a body having a pair of service passages either of which provides for flow of supply fluid from a pump to one side of the motor while the other provides for return flow of fluid from the opposite side of the motor to a reservoir, further characterized by the following:

- A. that each service passage comprises (1) an inlet branch through which supply fluid enters the body and through Which return fluid leaves the body,

(2) an outlet branch connectible with one side of a reversible fluid motor,

(3) and a bore in the body one end of which connects with the inlet branch and the other end portion of which connects With the outlet branch, and through which all fluid traversing the service passage must pass;

B. an annular valve seat in the body surrounding said other end portion of each bore and facing toward its associated outlet branch;

C. a pair of main valves in the body, one for'each service passage normally engaging the seat thereof, and which must be open to permit fluid to flow in either direction through its service passage, said main valves being adapted to open in response to flow of supply fluid into the inlet branches of their respective service passages to permit fluid to flow to the associated outlet branch;

D. means in the body defining 'a pressure chamber for each main valve, said pressure chambers having communication with the outlet branches of their respective service passages;

E. means on each main valve defining a piston which operates in its pressure chamber and upon which fluid in the chamber supplied thereto from the outlet branch of its associated service passage can act to hold the main valve engaged with its seat as long as the pressure of fluid in said outlet branch exceeds that of its associated inlet branch; F. means in the body defining an exhaust passage for each pressure chamber to communicate the same with the inlet branch of its associated service passage; G. means on each main valve providing an external surface facing'toward the associated bore and upon which fluid in the outlet branch of its service passage at a pressure exceeding that of fluid in its inlet branch can act to open the main valve at times when its pressure chamber is vented to its inlet branch through the exhaust passage for 'said pressure chamber;

" H. a pilot valve for each main valve, normally closing the exhaust passagefor its pressure chamber and mechanically independent of its associated main valve; I t I.' and fluid pressure responsive actuating means for each pilot valve, operable in response to the pressure of supply fluid flowing into the inlet branch of either service passage to effect opening of the pilot valve associated with the other service passage, so that the main valve for said other service passage can be opened in consequence of the force exerted upon said surfacethereof by 'r'eturn'fluid' in its associated outlet branch to allow fluidto flow therefrom to the associated inlet branch.

6. The circuit control means of claim 5, further characterized by:

A. a hollow core member in each pressure chamber,

fixed with respect to the body, said core member providing an internal support for the adjacent main valve and having a hole therein opening from its hollow interior to the associated service passage bore and cooperating with the hollow interior of the core member to define the outlet portions of the exhaust passage for the associated pressure chamber;

B. and means mounting said pilot valves in the hollow interiors of the core members for movement toward and from normally closed positions blocking said holes in their respective core members.

7. Fluid control means, comprising: i A. a body having a service passage that is connectible B. an annular 'valve seat in the body surrounding the bore and facing the outlet branch of the service passage;

C. the body having a cylindrical recess therein at said side of the inlet branch, said recess opening to the outlet branch and to the bore and being coaxial with the latter;

D. valve mechanism in the recess to control fluid flow in either-direction from one branch to the other of the service passage, comprising (1) a main valve having a portion at one end providing a piston slidably fitting the recess, and having a coaxial smaller diameter portion at its other end normally engaging the valve seat, said valve being adapted to open in response to the pressure of supply fluid flowing into the inlet branch of the service passage,

(2) passage means at all times communicating said recess with the outlet branch so that fluid therefrom can flow into the recess and act upon the piston of the main valve to hold the same closed as long as the pressure of fluid in the outlet branch exceeds that of fluid in the inlet branch, (3) means defining an exhaust passage for said recess leading to the inlet branch of the service passage, and through which the recess can be vented (4) a pilot valve normally closing said exhaust passage and mechanically independent of the main valve to allow opening and closing motion E. and actuating means in the body engageable with the pilot valve, for moving the same to open position.

8. Fluid flow control means, comprising: A. a body having a service passage that is connectible with a fluid motor to provide for the flow of fluid to and from the motor, said service passage having 1) an inlet branch,

s (2) an outlet branch one portion of which is spaced "tooneside of a portion of the inlet branch,

(3) and a bore communicating said laterally adjacent portions of the inlet and outlet branches;

B. an annular valve seat in the body surrounding the bore and facing the outlet branch of the service passage;

D. valve mechanism in the recess to control fluid flow in either direction from one branch to the other of the service passage, comprising (1) a main valve having a tubular skirt portion at one end providing a piston slidably fitting the recess, and having a coaxial smaller diameter portion at its other end normally engaging the valve seat, said valve being adapted to open in response to the pressure of supply fluid flowing into the inlet branch of the service passage,

(2) a core member in the recess, fixed with respect to the body, and having a cylindrical portion encircled by the main valve and along which it slides, said core member cooperating with the wall of the recess to define a cylinder-like pressure chamber in which said piston on the main valve operates,

(3) passage means at all times communicating said pressure chamber with the outlet branch so that fluid therefrom can flow into the chamber and act upon the piston of the main valve to hold the same closed as long as the pressure of fluid in the outlet branch exceeds that of fluid in the inlet branch,

(4) means defining an exhaust passage for said pressure chamber leading to the inlet branch of the service passage, and through which the chamber can be vented,

(5) a pilot valve normally closing said exhaust passage,

(6) and a circumferential'shoulder on the exterior of the main valve, defined by the junction between said end portions thereof, said shoulder facing toward the bore and being accessible to fluid in the otulet branch so that fluid therein can act upon the shoulder to effect opening of the main valve when the pressure of fluid in the outlet branch exceeds that of fluid in the inlet branch and the pilot valve is open;

E. and actuating means in the body engageable with the pilot valve, for moving the same to open position.

9. The fluid flow control means of claim 8, wherein:

said core member is hollow; said exhaust passage comprises the hollow interior of the core member and a hole therethrough opening to said bore; the pilot valve is mounted in the interior of the core member; and said actuating means extends through the bore and said hole in the core member for engagement with the pilot valve.

10. For use in fluid pressure operated systems wherein a pair of supply lines leading to opposite sides of a reversible fluid motor provides for actuation of the motor in one direction or the other at -the dictation of a flow reversing valve that is operable to connect either supply line with a pump and the other supply line with a reservoir, a circuit control device adapted for connection in the supply lines between the reversing valve and the motor to govern operation of the latter, comprising:

A. a body having (1) a partition wall with an aperture therethrough,

(2) a pair of service passages that are adapted to provide parts of the supply lines employed to connect the opposite sides of a reversible fluid motor with a reversing valve therefor, said service passages respectively comprising (a) inlet branches having portions adjacent to one another and arranged at opposite 1% sides of the apertured portion of the partition wall,

(b) outlet branches that are connectable with the opposite sides of a reversible fluid motor and which have portions adjacent to their respective inlet branches at the sides thereof remote from the partition wall,

(c) and bores in the body, coaxial with said aperture, communicating the adjacent portions of the respective inlet and outlet branches of the service passages,

(3) an annular main valve seat in each service passage, surrounding the end of the bore thereof remote from its inlet branch,

(4) and a counterbore for each service passage,

coaxial with the bore thereof, providing a cylinder which opens toward the bore and to the outlet branch of its service passage;

B. a valve unit in each cylinder, comprising (1) a tubular pressure responsive outer valve having a small diameter end portion which normally engages the main valve seat to block transfer of pressure fluid between the inlet and outlet branches of its service passage, said outer valve being movable off of its seat in response to flow of supply fluid into the inlet branch of its service passage, each of said outer valves having (a) a large diameter end portion providing an annular piston slidably received in its cylinder,

(b) a hole in the wall of the piston providing for the transfer of pressure fluid between its cylinder and the outlet branch of its service passage,

(c) and a circumferential shoulder on its exterior, at the junction between said end portions thereof, facing toward its seat and upon which exhaust fluid returning to the outlet branch of its service passage can act to unseat the main valve,

(2) a hollow core member inside the outer valve, coaxial therewith and fixed with respect to the body, upon which the outer valve is axially slidably supported, said core member having (a) an aperture in its wall communicating its hollow interior with the cylinder,

(b) a coaxial hole opening to its interior and to the bore of its service passage, and cooperable with the aperture in its wall to define a venting passage through which the cylinder can be vented to the inlet branch of its service passage to allow the outer valve to be unseated in consequence of the force which return fluid in its outlet branch exerts upon the circumferential shoulder thereof,

(c) and an inner annular valve seat on the core member facing its interior and surrounding its coaxial hole,

(3) an inner valve axially movably mounted in the interior of the core member and normally engaging said inner valve seat to close the cylinder venting passage and thus enable the outer valve to be held in its seated position whenever fluid is present in the cylinder at a pressure exceeding that of fluid in the inlet branch of its service passage;

C. and an actuating piston for said inner valves,

slidable axially back and forth in the aperture of said partition wall, and having reduced stems projecting from both axial ends thereof into the bores of the service passages and toward said inner valves, said piston being movable in response to the force which supply fluid flowing through either service passage to one side of a reversible fluid motor exerts on the adjacent end of the actuating piston to carry the stem on its other end into unseating engagement with the inner valve for the other service passage, to effect venting of the cylinder for said other service passage to the inlet branch thereof and thus enable unseating of the outer valve in response to the force which motor exhaust fluid in its outlet branch exerts upon the circumferential shoulder on the outer valve for said other service passage.

11. Circuit control means for use with a reversible fluid motor, and of the type comprising a body having a pair of service passages either of which provides for flow of supply fluid from a pump to one side of the motor while the other provides for return flow of fluid from the op posite side of the motor to a reservoir, further characterized by the following:

A. that each service passage comprises (1) an inlet branch through which supply fluid enters the body and through which return fluid leaves the body,

(2) an outlet branch connectible with oneside of a reversible fluid motor,

B. an annular valve seat'in the body surrounding said other end portion of each bore and facing towardv its associated outlet branch;

C. a pair of main valves in the body, one for each service passage normally engaging the seat thereof, and which must be open to permit fluid to flow in either direction through its service passage, said main valves being adapted to open in response to flow of supply fluid into the inlet branches of their respective service passages to permit fluid to flow to the associated outlet branch;

D. means in the body defining a pressure chamber for each main valve, said pressure chambers having communication with the outlet'branches of their respective service passages;

E. means on each main valve defining a piston which operates in its pressure chamber and upon which fluid in the chamber supplied thereto from the outlet branch of its associated service passage can act to hold the main valve engaged with its seat as long as the pressure of fluid in said outlet branch exceeds that of fluid in its associated inlet branch;

F. means in the body defining an exhaust passage for each pressure chamber to communicate the same with the inlet branch of its associated service passage;

G. means on each main valve providing an external surface facing toward the associated bore and upon which fluid in the outlet branch of its service passage at a pressure exceeding that of fluid in its inlet branch can act to open the main valve at times when its pressure chamber is vented to its inlet branch through the exhaust passage for said pressure chamber;

H. a pilot valve for each main valve, normally closing the exhaust passage for its Pressure chamber;

1, fluid pressure responsive actuating means for each pilot valve, operable in response to the pressure of supply fluid flowing into the inlet branch of either service passage to effect opening of the pilot valve associated with the other service passage, so that the .main valve for said "other service passage can be opened in consequence of the force exerted upon said surface thereof by return fluid in its associated outlet branch to allow fluid to flow therefrom to the associated inlet branch;

I. and means hydraulically balancing each of said pilot valves with respect to the pressure of fluid obtaining in the inlet branch of its associated service passage.

12. Circuit control means for use with a reversible 18 fluid motor, and of the type comprising a body having a pair of service passages either of which provides for flow of supply fluid from a pump to one side of the motor while the other provides for return flow of fluid from the opposite side of the motor to areservoir, further characterized by the following:

(2) an outlet branch connectible with one side of a reversible fluid motor,

C. a pair of main valves in the body, one for each service passage normally engaging the seat thereof,

, and which must be open to permit fluid to flow in either direction through its service passage, said main valves being adapted to open in response to flow of supply fluid into the inlet branches of their respective service passages to permit fluid to flow to the associated outlet branch;

D. means in the body defining a pressure chamber for each. main valve, said pressure chambers having communication with the outlet branches of their respective service passages;

El means on each main valve defining a piston which operates in its pressure chamber and upon which fluid in the chamber supplied thereto from the outlet branch of its associated service passage can act to hold the main valve engaged with its seat as long as the pressure of fluid in said outlet branch exceeds that of fluid in its associated inlet branch;

-F. means in the body defining an exhaust passage for each pressure chamber to communicate the same with the inlet branch of its associated service passage;

H. a pilot valve for each main valve, normally closing the exhaust passage for its pressure chamber,.and mechanically independent of its associated main valve; .7

I. fluid pressure responsive actuating means for each pilot valve, operable in response to the pressure of supply fluid flowing into the inlet branch of either service passage to eflect opening of the pilot valve associated with the other service passage, so that the main valve for said other service passage can be opened in consequence of the force exerted upon said surface thereof by return fluid in its associated outlet branch to allow fluid to flow therefrom to the associated inlet branch;

J. and means on the pilot valves, including a passageway extending through each and communicating with the inlet branch of its associated service passage through said hole in its core member and the bore of its service passage, for hydraulically balancing the pilot valves with respect to the pressure of supply fluid in the inlet branches of their respective service passages.

13. Circuit control means for use with a reversible fluid motor, and of the type comprising a body having a pair of service passages either of which provides for flow of supply fluid from a pump to one side of the motor while the other provides for return flow of fluid from the opposite side of the motor to a reservoir, further characterized by the following:

(2) an outlet branch connectible with one side of a reversible fluid motor,

D. means in the body defining a pressure chamber for each main valve, said pressure chambers having communication with the outlet branches of their respective service passages;

E. means on each main valve defining a piston which operates in its pressure chamber and upon which fluid in the chamber supplied thereto from the outlet branch of its associated servicepassage can act to.

hold the main valve engaged With its seat as long as the pressure of fluid in said outlet branch exceeds that of fluid in its associated inlet branch;

' G. means on each main valve providing an external surface facing toward the associated bore and upon which fluid in the outlet branch of its service passage at a pressure exceeding that of fluid in its inlet branch can act to open the main valve at times when its pressure chamber is vented to its inlet branch through the exhaust passage for saidpressure chamber;

I. fluid pressure responsive actuating means for each pilot valve, operable in response to the pressure of supply fluid flowing into the inlet branch of either I service passage to effect opening of the pilot valve associated with the other service passage, so that the main valve for said other service passage can be opened in consequence of the force exerted upon said surface thereof by return fluid in its associated outlet branch to allow fluid to flow therefrom to the associated inlet branch;

J. a spring in each pressure chamber, yieldingly biasing the main valve thereof toward engagement with its seat;

K. a separate spring for each pilot valve, to yieldingly bias the same toward its exhaust passage closing position;

L. and means on the body providing for adjustment of the bias which said separate springs exert upon their respective pilot valves from the exterior of the body.

14. A valve assembly for use in a lockout valve, and of the type wherein a normally closed main valve controls transfer of fluid between an inlet and an outlet, said valve assembly being characterized by the following:

A. a body having said inlet and outlet therein and having a pressure chamber and first and second passages to respectively communicate the chamber with the inlet and the outlet;

B. a tubularv main valve slidable axially in the chamber out of a seated position in response to force exerted thereon by fluid in the inlet whenever the pressure of inlet fluid exceeds that of fluid in the outlet, to allow fluid to flow from the inlet to the outlet, said main valve also being movable out of its seated position under force exerted thereon by pressure fluid in the outlet at a value greater than that of pressure fluid in the inlet provided said first passage is open to communicate the pressure chamber with the inlet;

C. a hollow cylindrical valve supporting member fixed within said chamber and having the main valve slidably mounted on its exterior, said member having an annular valveseat in its interior through which said first passage extends;

D. and a pilotvalve inside the supporting member, yieldingly biased toward engagement with said seat to normally close said first passage, and which must be unseated to enable the main valve to open and provide for fluid flow from the outlet to the inlet.

15. The valve assembly of claim 13, further charac- 45 terized by means hydraulically balancing said pilot valve Wtih respect to the pressure of fluid obtaining in said inlet.

SAMUEL LEVINE, Primary Examiner.

P. T. COBRIN, Assistant Examiner.

Claims

1. CIRCUIT CONTROL MEANS FOR A REVERSIBLE FLUID MOTOR, COMPRISING: A. A BODY; B. A PAIR OF SERVICE PASSAGES IN THE BODY EITHER OF WHICH PROVIDES FOR FLOW OF SUPPLY FLUID AT A NORMALLY HIGH PRESSURE VALUE TO ONE SIDE OF A REVERSIBLE FLUID MOTOR WHILE THE OTHER PASSAGE PROVIDES FOR RETURN FLOW OF FLUID FROM THE OPPOSITE SIDE OF THE MOTOR; C. A PAIR OF NORMALLY CLOSED PRESSURE RESPONSIVE VALVES, ONE FOR EACH SERVICE PASSAGE TO GOVERN ALL FLUID FLOW THERETHROUGH, EACH OF SAID VALVES BEING MOVABLE TO AN OPEN POSITION IN RESPONSE TO FLOW OF SUPPLY FLUID UNDER PRESSURE INTO ITS SERVICE PASSAGE; D. MEANS ASSOCIATED WITH EACH VALVE FOR TRANSLATING THE PRESSURE OF FLUID RETURNING TO ITS SERVICE PASSAE INTO FORCE ON THE VALVE TENDING TO OPEN THE SAME; E. OTHER MEANS ASSOCIATED WITH EACH VALVE FOR TRANSLATING THE PRESSURE OF FLUID RETURNING TO ITS SERVICE PASSAGE INTO FORCE ON THE VALVE BY WHICH IT CAN BE HELD CLOSED AGAINST AND OPENING FORCE THEREON; F. AND FORCE CONTROLLING MEANS ASSOCIATED WITH BUT MECHANICALLY INDEPENDENT OF EACH VALVE, AND SENSITIVE TO THE PRESSURE OF SUPPLY FLUID IN THE SERVICE PASSAGE FOR THE OTHER VALVE, FOR EFFECTING REDUCTION OF SAID FLUID PRESSURE CLOSING FORCE ON ITS VALVE TO A VALUE BELOW THAT OF SAID FLUID PRESSURE OPENING FORCE THEREON IN RESPONSE TO THE PRESENCE OF SUPPLY FLUID AT SAID NORMALLY HIGH PRESSURE VALUE IN THE SERVICE PASSAGE FOR SAID OTHER VALVE, AND FOR EFFECTING INCREASE IN THE FLUID PRESSURE CLOSING FORCE ON ITS VALVE IN ACCORDANCE WITH A DECREASE IN THE PRESSURE OF SUPPLY FLUID IN THE SERVICE PASSAGE FOR SAID OTHER VALVE.