Control arrangement for hydraulic systems

Claim 2

In a hydraulic system including a source of fluid supply pressure comprising a pump, a sump, and a first delivery passage means providing a first working circuit including a first fluidactuated device, and a first control valve connected to said first device to control said first device; second delivery passage means providing a second working circuit including a second fluid-actuated device, and a second control valve connected to said second device to control said second device; a fluid pressure actuated mode valve in said second working circuit and operative to selectively modify the control of said second control valve over said second device in response to a control signal pressure applied to said mode valve; control signal pressure supply means including conduit means, and mechanically actuated control signal occluder means, connected between said first control vAlve in said first circuit and said mode valve, and being effective to supply a working pressure from said first control valve to provide said control signal pressure, said occluder means being interposed between said conduit means and said first control valve, and operatively connected to said first control valve for actuation thereby to selectively block fluid communication from said first control valve to said conduit means and said mode valve; and attenuator means connected to said conduit means and to said sump to provide a fluid flow path from said conduit means to said sump to attenuate said control signal pressure by allowing fluid to flow from said conduit means to said sump, and being effective to attenuate said control signal pressure only when said occluder means blocks fluid communication from said first control valve to said conduit means and said mode valve, said first control valve and said working pressure being effective to selectively control said mode valve, and said mode valve being effective to modify the control of said second control valve over said second device.

Claim 3

In a hydraulic system as defined in claim 1 wherein said attenuator means is operative to reduce the pressure level of said control signal pressure when said occluder means blocks fluid communication from said first control valve to said conduit means.

Claim 4

The system as defined in claim 1 in which said attenuator means includes valve means actuated by said first control valve to selectively establish and to selectively block communication between said sump and said conduit means.

Claim 5

The system as defined in claim 1 in which said mode valve is connected in series with said second control valve and said second fluid actuated device, said mode valve being effective to restrict the flow of fluid established between said second control valve and said second fluid actuated device by said second control valve.

Claim 6

The system as defined in claim 1 in which said mode valve is connected between said second fluid actuated device and in parallel with said control valve; said mode valve being effective to modify the flow of fluid to said second fluid actuated device independent of said second control valve.

Claim 7

The system as defined in claim 1 in which said mode valve includes first and second fluid responsive areas being adapted for differential pressure actuation of said mode valve to first and second operating positions by two fluid pressures; said control signal supply means being operably connected to one of said fluid responsive areas thereby supplying said control signal pressure thereto; and a fluid conduit connecting the other of said fluid responsive areas to said system to supply a fluid pressure from said system to said second area.

Claim 8

The system as defined in claim 6 in which said second area is connected to said source.

Claim 9

The system as defined in claim 6 which includes hydraulically actuated threshold increaser means operably connected to said mode valve and adapted to increase said differential pressure required to actuate said mode valve in response to a fluid pressure applied to said threshold increaser means; and a fluid conduit connecting said threshold increaser means to said source to obtain a fluid pressure therefrom.

Claim 10

The system defined in claim 1 which includes hydraulically actuated threshold increaser means operably connected to said mode valve and adapted to increase the magnitude of control signal required to actuate said mode valve in response to a fluid pressure applied to said threshold increaser means; and a fluid conduit connecting said threshold increaser means to said source to obtain fluid pressure therefrom.

Claim 11

The system as claimed in claim 9 in which said threshold increaser includes piston and spring means.

Claim 12

In a hydraulic system as claimed in claim 1 in which said control signal supply means includes a control port in said first control valve, attenuator means, and conduit means and being adapted to connect said Control valve to said mode valve, said control port supplying working pressure of said first device to said conduit means for use as said control signal pressure when said first control valve is supplying fluid from said source to said first device and being operative to occlude said working pressure of said first device from said conduit means when said first control valve is ineffective to supply fluid from said source to said first device, said attenuator means operatively interconnecting said conduit means and said sump and being operative to reduce the pressure level of said control signal when said control port occludes said working pressure from said mode valve, said first control valve and said working pressure being effective to control said mode valve and said mode valve being effective to modify the control of said second control valve over said second device.

Claim 13

The system as defined in claim 11 in which said first fluid actuated device includes first and second work ports, and said first control valve includes an inlet port connected to said source, a pair of exhaust ports connected to said sump, first and second work ports connected to said first and second work ports of said fluid actuated device, and said control signal supply means includes first and second control ports in said first control valve and fluid actuated poppet means, and said first control port communicating with said first work port and said second control port communicating with said second work port when said first control valve communicates said inlet port with said second work port, and fluid actuated poppet means interposed between said control ports and said conduit means and being operative to selectively provide a fluid communication path from one of said control ports to said conduit means and to block fluid communication from said one control port to the other of said control ports.

Claim 14

The system as defined in claim 12 in which said fluid actuated poppet means includes a three port shuttle valve.

Claim 15

The system as defined in claim 13 in which said control valve includes a valve body having a spool bore and a valve spool slidably fitted in said spool bore; and said valve spool is movable from a neutral position to first and second operating positions to communicate said control ports to said exhaust ports when said valve spool is in said neutral position; and said three port shuttle valve having first and second input ports connected to said first and second control ports, an output port connected to said conduit means, and a poppet capable of blocking one or the other of said input ports, said control ports, said valve spool, and said shuttle valve cooperating to provide said attenuator means.

Claim 16

In a hydraulic system including a source of fluid pressure, a plurality of working circuits each including a fluid actuated device having at least one work port and each including a control valve having an inlet port and at least one work port, and a fluid sump, the improvement which comprises: a pressure actuated mode valve interposed into a first of said working circuits which includes a first control valve and a first fluid actuated device, said mode valve being operative to modify the control of said first control valve over said first fluid actuated device in response to a control signal pressure applied to said mode valve; control signal supply means including logic means and conduit means to select a working pressure from said two control valves for use as said control signal pressure; said logic means including a plurality of control ports in said two control valves, fluid actuated poppet means, and attenuator means; each of said control ports being operatively associated with one of said work ports in said two control valves and connectible to one of said work ports by said two control valves, said fluid actuated poppet means connecting said control ports and said conduit means and being effective to select the highest working pressure from said control ports For use as said control signal pressure and to provide a fluid communication path to said conduit means; said conduit means being operatively connected to said mode valve to supply said control signal pressure thereto, and said attenuator means being operatively connected to said conduit means and to said sump and being effective to prevent a control signal pressure from being applied to said mode control valve that is higher than the highest fluid pressure in any of said work ports that are connected to said inlet port, whereby said two control valves and said working pressures therein are effective to control said mode valve and said mode valve is effective to modify the control of said first control valve over said first device.

Claim 17

In a hydraulic system including a source of fluid pressure, a plurality of working circuits each including a fluid actuated device having at least one work port and each including a control valve having an inlet port and at least one work port, and a fluid sump, the improvement which comprises: a pressure actuated mode valve interposed into a first of said working circuits which includes a first control valve and a first fluid actuated device, said mode valve being operative to modify the control of said first control valve over said first fluid actuated device in response to a control signal pressure applied to said mode valve; control signal supply means including logic means and conduit means to select a working pressure from said two control valves for use as said control signal pressure; said logic means including a plurality of control ports in said two control valves, fluid actuated poppet means, and attenuator means; each of said control ports being operatively associated with one of said work ports in said two control valves and connectible to one of said work ports by said two control valves, said fluid actuated poppet means connecting said control ports and said conduit means and being effective to select the highest working pressure from said control ports For use as said control signal pressure and to provide a fluid communication path to said conduit means; said conduit means being operatively connected to said mode valve to supply said control signal pressure thereto, and said attenuator means being operatively connected to said conduit means and to said sump and being effective to prevent a control signal pressure from being applied to said mode control valve that is higher than the highest fluid pressure in any of said work ports that are connected to said inlet port, whereby said two control valves and said working pressures therein are effective to control said mode valve and said mode valve is effective to modify the control of said first control valve over said first device.

Claim 18

The system as defined in claim 15 in which said fluid actuated poppet means includes a plurality of three port shuttle valves each having two input ports and one output port, and said output port of one of said shuttle valves is connected to one of said two input ports of another of said shuttle valves.

Claim 19

The system as defined in claim 15 in which said logic means is operative to select two control signal pressures from said working circuits and said control ports, one of said two control signal pressures being selected on the basis of the relative instantaneous working pressures in at least two of said control ports, and the working pressures in at least one of said control ports being used by said logic system in the selection of both of said two control signal pressures.

Claim 20

The system as defined in claim 17 in which one of said two control signal pressures is connected to said mode valve for control thereof, and one of said two control signal pressures is operatively connected to said source and operative to control the effective output thereof.

Claim 21

The system as defined in claim 17 in which said hydraulic system includes threshold increaser means and in which said mode valve includes two fluid responsive areas for differential pressure actuation of said mode valve, one of said areas being operably connected to one of said two control signal pressures, the other of said areas being connected to said source, and said threshold increaser being operably connected to the other of said two control signal pressures.

Claim 22

The system as claimed in claim 19 in which said one control signal pressure is operatively connected to said source and is operative to control the effective output thereof.