Load responsive fluid control valve

Abstract

A direction and flow control valve for use in a central fluid power load responsive system having plurality of loads. The valve maintains a selected constant flow level for control of both positive and negative loads, irrespective of the change in the load magnitude or change in the fluid pressure, supplied to the valve. System is powered by a single variable volume pump equipped with a load responsive control, which automatically maintains pump discharge pressure at a level higher than the pressure required by the system's largest load. Each direction and flow control valve is equipped with a differential pressure regulating control, which is responsive to the load pressure for controlling the negative loads and preferably a second differential pressure regulating control for controlling the positive loads.

What is claimed is: 
     
       1. A valve assembly comprising a housing having a fluid inlet chamber, . .a.!. .Iadd.at least one .Iaddend.fluid load chamber, a fluid outlet chamber, and a fluid exhaust means, .Iadd.signal passage means between said load chamber and said outlet chamber, .Iaddend.first valve means for selectively interconnecting said load chamber with said inlet chamber.Iadd., said load chamber with said signal passage means, and said load chamber with said signal passage means .Iaddend.and said outlet chamber to meter fluid flow to and from said load chamber, and second valve means interconnecting said outlet chamber and said exhaust means .Iadd., said second valve means having means responsive to pressure in said signal passage means and pressure in said outlet chamber and .Iaddend.operable to maintain a constant pressure difference between said load chamber and said outlet chamber when said load .Iadd.chamber, said signal passage means .Iaddend.and .Iadd.said .Iaddend.outlet chamber. .s.!. are interconnected and said load chamber is pressurized. . .2. A valve assembly as set forth in claim 1 wherein said second valve means is operable directly responsive to fluid pressure in said load 
     
     
        chamber..!. 3. . .Valve.!. .Iadd.A valve .Iaddend.assembly as set forth in claim 1 wherein said first valve means includes a valve spool axially guided in a spool bore and movable from a neutral position to at least one actuated position, said valve spool isolating said load chamber . .from.!..Iadd., .Iaddend.said fluid inlet chamber and said fluid outlet chamber . .and.!. .Iadd.from each other and blocking said signal passage means from .Iaddend.said second valve means when in . .the.!. neutral 
     
     
        position. 4. A valve assembly as set forth in claim 3 wherein said housing includes a pressure signal passage interconnecting said spool bore and said second valve means, said valve spool when displaced from its neutral position toward an actuated position first interconnecting said load chamber with said second valve means through said pressure signal passage and then interconnecting said load chamber with said outlet chamber. 
     
     
        . .    A valve assembly as set forth in claim 1 wherein said second valve means includes a control spool guided in a bore interconnecting said outlet chamber and said exhaust means..!. . .6. A valve assembly as set forth in claim 5 wherein said control spool is biased in one direction both by pressure in said outlet chamber and by spring means and in the other direction by pressure in said load chamber..!. . .7. A valve assembly comprising a housing having a fluid inlet chamber, a fluid supply chamber, a fluid load chamber, a fluid outlet chamber and fluid exhaust means, first valve means for selectively interconnecting said fluid load chamber with said fluid supply chamber and said fluid outlet chamber to meter fluid flow to and from said load chamber, second valve means interconnecting said outlet chamber and said exhaust means operable to maintain a constant pressure difference between said fluid outlet chamber and said fluid load chambe when said load chamber is pressurized and connected to said outlet chamber, and third valve means interconnecting said fluid inlet chamber and said supply chamber and operable to maintain a constant pressure difference between said fluid load chamber and said fluid supply chamber when said chambers are interconnected by said first valve means and said supply chamber is pressurized..!. . .8. Valve assembly as set forth in claim 7 wherein said second valve means is operable responsive to fluid pressure in said load chamber when said load chamber is connected to said outlet chamber by said first valve means, and said third valve means is operable responsive to fluid pressure in said load chamber when said load chamber is connected to said supply chamber by said first valve means..!. . .9. A valve assembly as set forth in claim 7 wherein said first valve means includes a valve spool axially guided in a spool bore and movable from a neutral position to at least one actuated position, said valve spool isolating said load chamber from said fluid supply chamber and said fluid outlet chamber and said second valve means and said third valve means when in the neutral position..!. . .10. A valve assembly as set forth in claim 9 wherein said housing includes a first signal passage interconnecting said spool bore and said second valve means and a second signal passage interconnecting said spool bore and said third valve means, said first and second signal passages being positioned such that when said valve spool is displaced from the neutral position in one direction it first interconnects said load chamber with said second valve means through said first signal passage and then interconnects said load chamber with said outlet chamber and when said valve spool is displaced in other direction it first interconnects said load chamber with said third valve means through said second signal passage and then interconnects said 
     
     
        load chamber with said supply chamber..!. 11. A valve assembly comprising a housing having a fluid inlet chamber, a fluid supply chamber, first and second fluid load chambers, a fluid outlet chamber and fluid exhaust means, first valve means for selectively interconnecting said fluid load chambers with said fluid supply chamber and said fluid outlet chamber to meter fluid flow to and from said load chambers, second valve means interconnecting said outlet chamber and said exhaust means and operable to provide a passage between said outlet chamber and said exhaust means open above a preselected pressure level in the load chamber connected by said first valve means to said supply chamber and progressively reduce said passage opening upon pressure in said load chamber connected by said first valve means to said supply chamber dropping below said preselected pressure level, and third valve means interconnecting said fluid inlet chamber and said supply chamber operable to maintain a constant pressure difference between said fluid supply chamber and said fluid load chamber 
     
     
        connected thereto. 12. A fourway fluid control valve assembly comprising a housing having an outlet chamber, first and second load chambers, an inlet chamber, a valve bore in direct communication with said aforementioned chambers, said valve bore axially guiding a valve spool having lands, said valve spool having a neutral position in which said lands isolate said chambers, an exhaust chamber in said housing, valve means interconnecting said outlet chamber and said exhaust chamber and operable to maintain a constant pressure differential between either one of said load chambers which is pressurized and said outlet chamber when connected thereto, said valve means including a control spool guided in a control bore, fluid throttling means on said control spool to control fluid flow between said outlet chamber and said exhaust chamber, said control spool being biased in a direction to increase fluid flow by pressure in said outlet chamber when said control bore is connected thereto and by spring means and in the other direction by pressure in one of said load chambers when the control bore is connected thereto and said load chamber is pressurized, first pressure signal passage interconnecting one region of said valve bore between said outlet chamber and said first load chamber and said control bore, second pressure signal passage interconnecting another region of valve bore between said outlet chamber and said second load chamber and said control bore, said first and second pressure signal passages being blocked by said valve spool in its neutral position, said valve spool when displaced from its neutral position in one direction first interconnecting said first load chamber through said first pressure signal passage to said control bore and then connecting said first load chamber to said outlet chamber and said second load chamber to said inlet chamber, said valve spool when displaced from its neutral position in the opposite direction first interconnecting said second load chamber through said second pressure signal passage to said control bore and then connecting said second load chamber to said outlet chamber and said first load chamber to said inlet chamber, whereby the valve will control a load under negative 
     
     
        load conditions. 13. A fourway fluid control valve assembly comprising a housing having an outlet chamber, first and second load chambers, a supply chamber, a valve bore in direct communication with said aforementioned chambers, said valve bore axially guiding a valve spool having lands, said valve spool having a neutral position in which said lands isolate said chambers, an exhaust chamber in said housing, first valve means interconnecting said outlet chamber and said exhaust chamber and operable to maintain a constant pressure differential between either one of said load chambers which is pressurized and said outlet chamber when connected thereto, said first valve means including a first control spool guided in a first control bore, first fluid throttling means on said first control spool, said first control spool being biased in one direction by pressure in said outlet chamber when connected to said first control bore and by spring means and in the other direction by pressure in one of said load chambers when connected thereto, an inlet chamber in said housing, second valve means interconnecting said supply chamber and said inlet chamber operable to maintain a constant pressure differential between either of said load chambers when pressurized and said supply chamber when connected thereto, said second valve means including second control spool guided in a second control bore, second throttling means on said second control spool to throttle fluid flow between said inlet chamber and said supply chamber, said second control spool being biased in a direction to lessen fluid flow by pressure in said supply chamber when connected thereto and in a direction to increase fluid flow by pressure in one of said load chambers when connected thereto and spring means, first pressure signal passage interconnecting one region of the valve spool bore between said outlet chamber and said first load chamber and said first control bore, second pressure signal passage interconnecting another region of the valve spool bore between said outlet chamber and said second load chamber and said first control bore, a third pressure signal passage interconnecting another region of valve spool bore between said first . .second.!. load chamber and said supply chamber and said second control spool, .Iadd.a fourth pressure signal passage interconnecting another region of the valve spool bore between said second load chamber and said supply chamber and said second control spool, .Iaddend.said first, second, third and fourth pressure signal passages being blocked by said valve spool in its neutral position, said valve spool when displaced from its neutral position in one direction first interconnecting said first load chamber through said first pressure signal passage to said first valve means and said second load chamber through said fourth pressure signal passage to said second valve means and then interconnecting said first load chamber with said outlet chamber and said second load chamber with said supply chamber, said valve spool when displaced from its neutral position in opposite direction first interconnecting said second load chamber through said second pressure signal passage to said first valve means and said first load chamber through said third pressure signal passage to said second valve means and then interconnecting said second load chamber with said outlet chamber and said first load chamber with said supply chamber, whereby the valve will 
     
     
        control a load under both positive and negative load conditions. 14. A fourway fluid control valve assembly comprising a housing having an outlet chamber, first and second load chambers, a supply chamber, a valve bore in direct communication with said aforementioned chambers, said valve bore axially guiding a valve spool having lands, said valve spool having a position in which said lands isolate said chambers, an exhaust chamber in said housing, first valve means interconnecting said outlet chamber and said exhaust chamber and operable to maintain passage between said chambers open above preselected pressure level in said load chamber connected to said supply chamber and progressively reduce said passage upon pressure in said load chamber connected to said supply chamber dropping below said preselected pressure level, said first valve means including first control spool guided in a control bore, first fluid throttling means on said first control spool, said first control spool being biased in a direction to increase the fluid passage by pressure in said load chamber connected to said supply chamber and a direction to reduce fluid passage by spring means, an inlet chamber in said housing, second valve means interconnecting said supply chamber and said inlet chamber operable to maintain a constant pressure differential between said load chamber that is connected to the supply chamber and the supply chamber, said second valve means including a second control spool guided in a second control bore, second throttling means on said second control spool, said second control spool being biased in a direction to decrease fluid flow by pressure in said supply chamber and in a direction to increase flow by pressure in the load chamber and a spring means, first pressure signal passage interconnecting an area of valve spool bore between said first load chamber and said supply chamber and said second control spool, second pressure signal passage interconnecting an area of valve spool bore between said second load chamber and said supply chamber and said second control spool, said first and second pressure signal passages being blocked by said valve spool in its neutral position, said valve spool when displaced from its neutral position in one direction first interconnecting said first load chamber through said first pressure signal passage to said second control spool and then interconnecting said first load chamber to said supply chamber and said second load chamber to said . .second.!. outlet chamber, said valve spool when displaced in opposite direction first interconnecting said second load chamber with said supply chamber and said first load chamber to said . .first.!. outlet chamber, whereby the valve assembly controls a load under both positive and negative load conditions. .Iadd. 15. A fluid control valve assembly comprising a housing having an outlet chamber, a load chamber, an inlet chamber, a valve bore in direct communication with said aforementioned chambers, said valve bore axially guiding a valve spool having lands, said valve spool having a neutral position in which said lands isolate said chambers, an exhaust chamber in said housing, a valve means interconnecting said outlet chamber and said exhaust chamber and operable to maintain a constant pressure differential between said load chamber and said outlet chamber when said load chamber is pressurized and connected thereto, said valve means including a control spool guided in a control bore, fluid throttling means on said control spool to control fluid flow between said outlet chamber and said exhaust chamber, said control spool being biased in a direction to increase fluid flow by pressure in said outlet chamber and by spring means and in the other direction by pressure in said load chamber when the control bore is connected thereto and said load chamber is pressurized, pressure signal passage interconnecting region of said valve bore between said outlet chamber and said load chamber and said control bore, said pressure signal passage being blocked by said valve spool in its neutral position, said valve spool when displaced from its neutral position in one direction first interconnecting said load chamber through said pressure signal passage to said control bore connecting said load chamber to said outlet chamber, said valve spool when displaced from its neutral position in the opposite direction interconnecting said load chamber to said inlet chamber, whereby the valve will control a load under negative load conditions. .Iaddend.