Open center control of variable pumps

Claim 2

A hydraulic system including a variable displacement pump having a fluid actuated displacement control mechanism adapted to control the displacement of said pump, a sump, a control valve having a neutral position and an operating position and being adapted to control a fluid actuated device, and a fluid actuated device all operatively connected, the improvement which comprises: a sensor valve connected to said pump, to said sump, and to said displacement control mechanism and being adapted to establish, to block, and to control fluid communication paths from said pump to said displacement control mechanism and from said displacement control mechanism to said sump as said sensor valve is actuated to first and second operating positions; sensor valve actuating means adapted to provide an operating force to actuate said sensor valve from one of said operating positions to the other of said operating positions in response to a control signal pressure applied to said sensor valve actuating means; control signal valving means and restrictor means connected in series between said pump and said sump and being adapted to receive and to control fluid pressure from said pump for use as said control signal pressure, said control signal valving means being operatively connected to and controlled by said control valve as said control valve is moved to said positions to control said fluid actuated device; and control signal conduit means connected between said control signal valving means and said restrictor means to receive said control signal pressure and operatively connected to said sensor valve actuating means to apply said control signal pressure thereto; whereby said control signal valving means and said restrictor means cooperate to provide and to control said control signal pressure, to actuate said sensor valve to said operating positions and to control the displacement of said pump in response to the movement of said control valve to said positions.

Claim 3

The hydraulic system as claimed in claim 1 in which said control valve includes first and second working sections adapted to be actuated to control first and second fluid actuated devices; said control signal valving means includes a first control signal valve operatively connected to said first working section for actuation thereby and a second control signal valve operatively connected to said second control valve for actuation thereby; said restrictor means and said control signal valves being operatively connected together and interposed between said pump and said sump; whereby the actuation of either of said working sections is effective to control said control signal pressure and to increase the displacement of said pump.

Claim 4

The hydraulic system as claimed in claim 2 in which said control signal valves are connected in series with each other and with said restrictor means; and closing of either one of said control signal valves is effective to control said control signal pressure and to increase the displacement of said pump.

Claim 5

The hydraulic system as claimed in claim 2 in which each of said control signal valves includes two ports; each of said control signal valves has one of said ports in fluid communication with said pump and has the other of said ports in fluid communication with said sump; and openiNg either one of said control signal valves is effective to control said control signal and to increase the displacement of said pump.

Claim 6

The hydraulic system as claimed in claim 1 in which said restrictor means is located between said pump and said control signal valving means.

Claim 7

The hydraulic system as claimed in claim 1 in which said restictor means is located between said control signal valving means and said sump.

Claim 8

The hydraulic system as claimed in claim 1 which includes a pilot relief valve connected to said pump and to said sensor valve actuating means and adapted to move said sensor valve to a displacement decreasing position by increasing thP fluid pressure applied to said sensor valve actuating means.

Claim 9

The hydraulic system as claimed in claim 1 in which said first operating position of said sensor valve is effective to control said paths to increase the displacement of said pump; said sensor valve is effective in said second operating position to control said communication paths to decrease said displacement of said pump; and said sensor valve includes a third operating position in which fluid communication paths are controlled to decrease said displacement and said sensor valve establishes a bypass communication path between said pump and said sump; whereby said bypass communication path cooperates with said displacement control mechanism to control the effective output of said pump.

Claim 10

The system as claimed in claim 1 in which said sensor valve actuating means includes bias force meanS and fluid actuator means.

Claim 11

The system as claimed in claim 9 in which said sensor valve includes a sensor valve body having a bore therein and a valve plunger slidably fitted in said bore; said fluid actuator means includes the projected end area of said valve plunger; and a spring comprises said bias force means.

Claim 12

A hydraulic system including a variable displacement pump having a fluid actuated displacement control mechanism adapted to control the displacement of said pump, a sump, a control valve having a neutral position and an operating position and being adapted to control a fluid actuated device, and a fluid actuated device all operatively connected, the improvement which comprises: a sensor valve connected to said pump, to said sump, and to said displacement control mechanism and being adapted to establish, to block, and to control fluid communication paths from said pump to said displacement control mechanism and from said displacement control mechanism to said sump as said sensor valve is actuated to first and second operating positions; sensor valve actuating means including first and second fluid actuators adapted to provide operating forces to actuate said sensor valve to said first and second operating positions in response to fluid pressures applied to said fluid actuators; control signal valving means and restrictor means connected in series between said pump and said sump and being adapted to receive and to control fluid pressures from said pump to provide control signal pressures, said control signal valving means being operatively connected to and controlled by said control valve as said control valve is moved to said positions to control said fluid actuated device; first control signal conduit means connected between said control signal valving means and said restrictor means to receive said control signal pressures and operatively connected to one of said fluid actuators to apply said control signal pressures thereto; and second control signal conduit means connected between said pump and the other of said fluid actuators to apply fluid pressures from said pump for use as control signal pressures for said other fluid actuator; whereby said control signal valving means and said restrictor means cooperate to provide control signal pressures applied to one of said fluid actuators, to actuate said sensor valve to said operating positions and to control the displacement of said pump iN response to the movement of said control valve to said positions.

Claim 13

A hydraulic system including a variable displacement pump having a fluid actuated displacement control mechanism adapted to control the displacement of said pump, a sump, a control valve having a neutral position and an operating position and being adapted to control a fluid actuated device, and a fluid actuated device all operatively connected, the improvement which comprises: a sensor valve connected to said pump, to said sump, and to said displacement control mechanism and being adapted to establish, to block, and to control fluid communication paths from said pump to said displacement control mechanism and from said displacement control mechanism to said sump as said sensor valve is actuated to first and second operating positions; sensor valve actuating means including first and second fluid actuators adapted to provide operating forces to actuate said sensor valve to said first and second operating positions in response to fluid pressures applied to said fluid actuators; control signal valving means and restrictor means connected in series between said pump and said sump and being adapted to receive and to control fluid pressures from said pump to provide control signal pressures, said control signal valving means being operatively connected to and controlled by said control valve as said control valve is moved to said positions to control said fluid actuated device; first control signal conduit means connected between said control signal valving means and said restrictor means to receive said control signal pressures and operatively connected to one of said fluid actuators to apply said control signal pressures thereto; and second control signal conduit means connected between said pump and the other of said fluid actuators to apply fluid pressures from said pump for use as control signal pressures for said other fluid actuator; whereby said control signal valving means and said restrictor means cooperate to provide control signal pressures applied to one of said fluid actuators, to actuate said sensor valve to said operating positions and to control the displacement of said pump iN response to the movement of said control valve to said positions.

Claim 14

The hydraulic system as claimed in claim 11 which includes a pilot relief valve connected to said one fluid actuator and to said sump and effective to limit the control signal pressures applied to said one fluid actuator; whereby pump pressures applied to said other actuator are effective to reduce the displacement of said pump by forcing said sensor valve toward a displacement decreasing position thereby forcing fluid from said one actuator to said sump whenever said pump pressures exceed a predetermined value.

Claim 15

The hydraulic system as claimed in claim 11 in which said sensor valve includes a sensor valve body having a bore therein and a valve plunger slidably fitted in said bore; said first and second fluid actuatros include the use of the projected end areas of said valve plunger for use as fluid responsive areas; and said valve plunger is movable to a third or bypass position wherein fluid connections are made to decrease the displacement of said pump and to bypass excess pump flow from said pump to said sump.

Claim 16

The hydraulic system as claimed in claim 11 which includes fluid actuators having unequal fluid responsive areas.

Claim 17

The hydraulic system as claimed in claim 11 in which said sensor valve actuating means includes a bias spring.

Claim 18

A hydraulic system including a variable displacement pump having a fluid actuated displacement control mechanism operably connected to said pump and movable to control the displacement thereof, a control valve having a valving element movable from a neutral position to an operating position and to intermediate positions therebetween, a fluid actuated device operatively connected to said control valve for actuation thereby, and a fluid sump all operatively connected, the improvement which comprises: a sensor valve having a body, a valve plunger, and a sensor valve actuating means and being connected to said pump, to said sump, and to said displacement control mechanism; said valve plunger being operable to first, neutral, and second positions and being adapted to cooperate with said body to establish, to block and to control fluid communication paths between said pump and said displacement control mechanism and between said displacement control mechanism and said sump to increase the displacement of said pump, to decrease the displacement of said pump, and to maintain the displacement of said pump at any given value as a function of the relative position of said valve plunger to said valve body; said sensor valve actuating means consisting of bias force means and fluid actuator means and being operatively connected to said valve plunger and being adapted to move said valve plunger relative to said body in response to a control signal pressure applied to said fluid actuator and in proportion to the magnitude of said control signal pressure, whereby there exists a first proportional relationship between the magnitude of said control signal pressure and the relative position of said valve plunger to said body; control signal valving means and restrictor means being connected in series between said pump and said sump to control the flow of pressure fluid between said pump and said sump, being adapted to provide a control signal pressure in the juncture between said control signal valving means and said restrictor means, and being adapted to control the magnitude of said control signal; control signal conduit means being connected to said juncture between said control signal means and said restrictor means to receive said control signal pressure and being connected to said fluid actuator means to apply said control signal pressure thereto; said control valving means being operatively connected to said valving element to receive movement therefrom and being adapted to control the magnitude of said control signal pressure proportional to the position of said valving element from said neutral position, wherebY a second porportional relationship exists between the position of said valving element, the magnitude of said control signal pressure and the relative position of said valve plunger to said body; said feedback means operatively interconnecting said sensor valve and said displacement control mechanism and being adapted to modify said second proportional relationship in proportion to the movement of said displacement control mechanism and the displacement of said pump; whereby there exists a proportional relationship between the position of said valving and the displacement of said pump.

Claim 19

A hydraulic system including a variable displacement pump having a fluid actuated displacement control mechanism operably connected to said pump and movable to control the displacement thereof, a control valve having a valving element movable from a neutral position to an operating position and to intermediate positions therebetween, a fluid actuated device operatively connected to said control valve for actuation thereby, and a fluid sump all operatively connected, the improvement which comprises: a sensor valve having a body, a valve plunger, and a sensor valve actuating means and being connected to said pump, to said sump, and to said displacement control mechanism; said valve plunger being operable to first, neutral, and second positions and being adapted to cooperate with said body to establish, to block and to control fluid communication paths between said pump and said displacement control mechanism and between said displacement control mechanism and said sump to increase the displacement of said pump, to decrease the displacement of said pump, and to maintain the displacement of said pump at any given value as a function of the relative position of said valve plunger to said valve body; said sensor valve actuating means consisting of bias force means and fluid actuator means and being operatively connected to said valve plunger and being adapted to move said valve plunger relative to said body in response to a control signal pressure applied to said fluid actuator and in proportion to the magnitude of said control signal pressure, whereby there exists a first proportional relationship between the magnitude of said control signal pressure and the relative position of said valve plunger to said body; control signal valving means and restrictor means being connected in series between said pump and said sump to control the flow of pressure fluid between said pump and said sump, being adapted to provide a control signal pressure in the juncture between said control signal valving means and said restrictor means, and being adapted to control the magnitude of said control signal; control signal conduit means being connected to said juncture between said control signal means and said restrictor means to receive said control signal pressure and being connected to said fluid actuator means to apply said control signal pressure thereto; said control valving means being operatively connected to said valving element to receive movement therefrom and being adapted to control the magnitude of said control signal pressure proportional to the position of said valving element from said neutral position, wherebY a second porportional relationship exists between the position of said valving element, the magnitude of said control signal pressure and the relative position of said valve plunger to said body; said feedback means operatively interconnecting said sensor valve and said displacement control mechanism and being adapted to modify said second proportional relationship in proportion to the movement of said displacement control mechanism and the displacement of said pump; whereby there exists a proportional relationship between the position of said valving and the displacement of said pump.

Claim 20

The hydraulic system as claimed in claim 16 in which said bias force means includes a spring; and said feedback means includes said spring as a part of said means interconnecting said displacement control mechanism and said sensor valve.

Claim 21

The hydraulic system as claimed in claim 17 in which said pump is of axial piston type and said displacement control mechanism includes a variable inclination swash plate; said fluid actuator means includes the projected area of one end of said valve plunger; and said feedback means includes said spring interposed between said valve plunger and said swash plate, one end of said spring being adapted to receive motion from said swash plate as the displacement of said pump is changed and the other end of said spring being adapted to apply force to the other end of said valve plunger.

Claim 22

The hydraulic system as claimed in claim 16 in which said valve plunger and said body comprises first and second relatively movable valving parts; one of valving parts being operable to first and second positions by said bias force and said fluid actuator means; and the other of said valving parts being operatively connected to said displacement control mechanism to receive feedback movement therefrom.

Claim 23

The hydraulic system as claimed in claim 19 in which said displacement control mechanism includes a control piston, said one valving part is coaxial with said control piston, and said other valving part is connected to said control piston to receive feedback movement therefrom.