Pump control system

Claim 2

In a hydraulic system including a variable displacement pump as a source of fluid pressure, a sump, fluid conduits, and a fluid motor all operatively connected; a fluid actuated displacement control mechanism connected to said pump and adapted to control the displacement of said pump in response to fluid pressures applied to said displacement control mechanism; a sensor valve operatively connected to said displacement control mechanism and to said hydraulic system and being adapted for being moved by a force balance to displacement increasing and displacement decreasing positions wherein connections are made between said system and said displacement control mechanism to control the fluid pressures applied to said displacement control mechanism and to increase and to decrease the displacement of said pump; force balance means consisting of bias force means and fluid responsive means and adapted to move said sensor valve to said displacement increasing and displacement decreasing positions in response to a control signal pressure; control signal pressure supplY means interconnecting said fluid responsive means with a source of fluid pressure in said system whereby said sensor valve is moved to said displacement increasing position by said control signal pressure; over-ride valve means consisting of a power amplifier means having one port in fluid communication with said fluid responsive means and having another port in fluid communication with said sump; and fluid restrictor means interposed into said control signal pressure supply means and being adapted to reduce the fluid flow that is required through said over-ride valve means to reduce said control signal pressure applied to said fluid responsive means, to change said force balance; and to move said sensor to said displacement decreasing position; whereby actuation of any one of said over-ride valves is effective to reduce the displacement of said pump.

Claim 3

The system as claimed in claim 1 in which said over-ride valve means includes a pilot relief valve operatively connected to said fluid responsive means and to said pump and being adapted to control the force balance of said sensor valve in response to the pressure produced by said pump; the displacement of said pump being reduced when pump pressure exceeds a predetermined value.

Claim 4

The system as claimed in claim 1 in which said sensor valve includes a position in which fluid is bypassed from said pump to said sump, and said control signal pressure is effective to move said sensor valve to said position, whereby position of said sensor valve comprises a bypass valve means.

Claim 5

In a hydraulic system including a variable displacement pump as a source of fluid pressure, a sump, fluid conduits, and a fluid motor all operatively connected; a fluid actuated displacement control mechanism connected to said pump and adapted to control the displacement of said pump in response to fluid pressures applied to said displacement control mechanism; a sensor valve operatively connected to said displacement control mechanism and to said hydraulic system and being adapted for being moved by a force balance to displacement increasing and displacement decreasing positions wherein connections are made between said system and said displacement control mechanism to control the fluid pressures applied to said displacement control mechanism and to increase and to decrease the displacement of said pump; force balance means consisting of bias force means and fluid responsive means and adapted to move said sensor valve to said displacement increasing and displacement decreasing positions in response to a control signal pressure; control signal pressure supply means interconnecting said fluid responsive means with a source of fluid pressure in said system whereby said sensor valve is moved to said displacement increasing position by said control signal pressure; over-ride valve means consisting of a transducer which is pressure and displacement sensitive and comprises; a pressure-to-position transducer; a mechanical displacement reference mechanism; and a variable fluid resistance means; fluid restrictor means interposed into said control signal pressure supply means and being adapted to reduce the fluid flow that is required through said over-ride valve means to reduce said control signal pressure applied to said fluid responsive means, to change said force balance; and to move said sensor to said displacement decreasing position; whereby actuation of any one of said over-ride valves is effective to reduce the displacement of said pump.

Claim 6

In a hydraulic system including a variable displacement pump as a source of fluid pressure, a sump, fluid conduits, and a fluid motor all operatively connected; a fluid actuated displacement control mechanism connected to said pump and adapted to control the displacement of said pump in response to fluid pressures applied to said displacement control mechanism; a sensor valve operatively connected to said displacement control mechanism and to said hydraulic system and being adapted for being moved by a force balance to displacement increasing and displacement decreasing positions wherein connections are made between said system and said displacement control mechanism to control the fluid pressures applied to said displacement control mechanism and to increase and to decrease the displacement of said pump; force balance means consisting of bias force means and fluid responsive means and adapted to move said sensor valve to said displacement increasing and displacement decreasing positions in response to a control signal pressure; control signal pressure supply means interconnecting said fluid responsive means with a source of fluid pressure in said system whereby said sensor valve is moved to said displacement increasing position by said control signal pressure; over-ride valve means consisting of a transducer which is pressure and displacement sensitive and comprises; a pressure-to-position transducer; a mechanical displacement reference mechanism; and a variable fluid resistance means; fluid restrictor means interposed into said control signal pressure supply means and being adapted to reduce the fluid flow that is required through said over-ride valve means to reduce said control signal pressure applied to said fluid responsive means, to change said force balance; and to move said sensor to said displacement decreasing position; whereby actuation of any one of said over-ride valves is effective to reduce the displacement of said pump.

Claim 7

The system as claimed in claim 4 in which said displacement control mechanism includes a control piston; and said variable fluid resistance means comprises two relatively movable elements, one of said elements being connected to and coaxial with said control piston in said displacement control mechanism whereby said control piston provides said mechanical displacement reference.