Pressure compensated pump

Claim 2

In a hydraulic circuit having a variable displacement pump, a pump displacement controlling device, a hydraulic motor and a motor control valve for controlling the fluid flow to the motor, the improved pump control system comprising: a flow control valve having an input line and first and second output lines, said input line being connected to the output of the pump, said first output line leading to said motor control valve and being continuously connected across said flow control valve to said input line, said second output line being connected to a flow demand-sensing device; feedback signal means connected to said motor control valve and to said flow control valve and operable to sense the flow rate and flow demand through said motor control valve and to position said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said motor control valve exceeds the flow rate therethrough, and to increase the flow from said input line to said second output line as the flow rate through the motor control valve catches up with the demand; said flow demand sensing device being connected to the pump displacement Controlling device and being responsive to the flow rate in said second output line to signal the pump displacement controlling device to control pump displacement in inverse proportion to the flow rate in said second output line.

Claim 3

The pump control system of claim 1 wherein the motor control valve includes a valve element controlling the communication between said first output line of said flow control valve and a fluid supply line leading to the hydraulic motor, said feedback signal means including first and second feedback lines, said first feedback line interconnecting the upstream side of said motor control valve element with a first portion of said flow control valve to bias said flow control valve in a direction to increase the portion of input line flow to said second output line and to decrease the portion to said first output line as the fluid pressure in said first feedback line increases, and said second feedback line interconnecting the downstream side of said motor control valve element with a second portion of said flow control valve to oppose the biasing tendency of said first feedback line as the fluid pressure in said second feedback line increases.

Claim 4

The pump control system of claim 1 wherein the pump displacement controlling device comprises a pump controlling hydraulic motor and a pump control valve having an input line supplied with fluid from the output of the pump and an output line connected to said pump controlling motor to control the action thereof; said pump control valve being normally biased to a minimum pump displacement producing position when there is no demand for fluid from said first motor control valve, and said pump control valve being responsive to the output signal of said flow demand sensing device to shift said pump controlling motor toward an increased pump displacement producing position in proportion to decreasing flow rate in said second output line.

Claim 5

An improved hydraulic control system for controlling the output of a variable displacement pump comprising: a pump controlling hydraulic motor for varying the displacement of the pump, a pump control valve having an input line supplied with fluid from the pump and an outlet line leading to said pump controlling motor to activate said motor to control the pump displacement according to the position of said pump control valve, said pump control valve being normally biased to a minimum pump displacement producing position; a flow demand sensing device connected to said pump control valve and responsive to the fluid flow rate in a demand signal line flowing through said sensing device to cause said pump control valve to increase the pump displacement in response to decreasing flow rate in said demand signal line, whereby pump displacement is inversely proportional to the flow rate in said demand signal line; a second hydraulic motor and a second motor control valve for controlling the flow of fluid thereto; a flow control valve having an input line and first and second output lines, said input line being connected to the output line of the pump, said first output line continuously supplying fluid to said second motor control valve, and said second output line selectively supplying fluid to said demand signal line; said second motor control valve including a valve element controlling the communication between said first output line of said flow control valve and said second motor; feedback signal means interconnecting said flow control valve and said second motor control valve and operable to sense the flow rate demanded by said second motor control valve and to sense the flow rate across said valve element, and further operable to position said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said second motor control valve exceeds the flow rate therethrough, and to increase flow from said input line to said second output line as the flow rate through said second motor control valVe catches up with the demand.

Claim 6

An improved hydraulic control system for controlling the output of a variable displacement pump comprising: a pump controlling hydraulic motor for varying the displacement of the pump, a pump control valve having an input line supplied with fluid from the pump and an outlet line leading to said pump controlling motor to activate said motor to control the pump displacement according to the position of said pump control valve, said pump control valve being normally biased to a minimum pump displacement producing position; a flow demand sensing device connected to said pump control valve and responsive to the fluid flow rate in a demand signal line flowing through said sensing device to cause said pump control valve to increase the pump displacement in response to decreasing flow rate in said demand signal line, whereby pump displacement is inversely proportional to the flow rate in said demand signal line; a second hydraulic motor and a second motor control valve for controlling the flow of fluid thereto; a flow control valve having an input line and first and second output lines, said input line being connected to the output line of the pump, said first output line continuously supplying fluid to said second motor control valve, and said second output line selectively supplying fluid to said demand signal line; said second motor control valve including a valve element controlling the communication between said first output line of said flow control valve and said second motor; feedback signal means interconnecting said flow control valve and said second motor control valve and operable to sense the flow rate demanded by said second motor control valve and to sense the flow rate across said valve element, and further operable to position said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said second motor control valve exceeds the flow rate therethrough, and to increase flow from said input line to said second output line as the flow rate through said second motor control valVe catches up with the demand.

Claim 7

In a hydraulic circuit having a variable displacement pump, a pump displacement controlling device for regulating the output of the pump, a hydraulic motor driven by said pump, a four-way motor control valve for controlling the fluid flow to the motor, and a flow control valve having an input line and first and second output lines, said input line being connected to an output of the pump, said first output line leading to said motor control valve, and said second output line being connected to a flow demand-sensing device, the improvement of: feedback signal means connected to said motor control valve and to said flow control valve and operable (a) to sense the flow rate and flow demand through said motor control valve, (b) to position said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said hydraulic motor exceeds the flow rate thereto, and (c) to increase the flow from said input line to said second output line as the flow rate through the motor control valve to the hydraulic motor catches up with the demand; said flow demand sensing device being connected to the pump displacement controlling device and being responsive to the flow rate in said second output line to signal the pump displacement controlling device to control pump displacement in inverse proportion to the flow rate in said second output line.

Claim 8

In a hydraulic circuit having a variable displacement pump, a pump displacement controlling device for regulating the output of the pump, a hydraulic motor driven by said pump, a four-way motor control valve for controlling the fluid flow to the motor, and a flow control valve having an input line and first and second output lines, said input line being connected to an output of the pump, said first output line leading to said motor control valve, and said second output line being connected to a flow demand-sensing device, the improvement of: feedback signal means connected to said motor control valve and to said flow control valve and operable (a) to sense the flow rate and flow demand through said motor control valve, (b) to position said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said hydraulic motor exceeds the flow rate thereto, and (c) to increase the flow from said input line to said second output line as the flow rate through the motor control valve to the hydraulic motor catches up with the demand; said flow demand sensing device being connected to the pump displacement controlling device and being responsive to the flow rate in said second output line to signal the pump displacement controlling device to control pump displacement in inverse proportion to the flow rate in said second output line.

Claim 9

An improved hydraulic control system for controlling the output of a variable displacement pump, comprising a pump controlling hydraulic motor including a piston reciprocable within a cylinder for varying the output of the pump, a pump control valve having an input line supplied with fluid from the pump and an outlet line leading to said pump controlling motor to reciprocate said motor piston to control the pump output according to the position of said pump control valve, a flow demand sensing device connected to said pump control valve and responsive to the fluid flow rate in a demand signal line flowing through said sensing device to cause said pump control valve to be activated for motor piston reciprocation to increase the pump displacement in response to decreasing flow rate in said demand signal line, whereby pump displacement is inversely proportional to the flow rate in said demand signal line, a second hydraulic motor and a second motor control valve for controlling the flow of fluid thereto, a flow control valve having an input line and first and second output lines, said input line being connected to the output line of the pump, the improvement of: said second output line selectively supplying fluid to said demand signal line, said second motor control valve including a valve element controlling the communication between said first output line of said flow control valve and said second motor; and feedback signal means interconnecting said flow control valve and said second motor control valve (a) for sensing the flow rate demanded by said second hydraulic motor, (b) for sensing the flow rate across said motor control valve, (c) for positioning said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said second hydraulic motor exceeds the flow rate thereto, and (d) for increasing flow from said input line to said second output line as the flow rate thruogh said second motor control valve catches up with the demand.

Claim 10

An improved hydraulic control system for controlling the output of a variable displacement pump, comprising a pump controlling hydraulic motor including a piston reciprocable within a cylinder for varying the output of the pump, a pump control valve having an input line supplied with fluid from the pump and an outlet line leading to said pump controlling motor to reciprocate said motor piston to control the pump output according to the position of said pump control valve, a flow demand sensing device connected to said pump control valve and responsive to the fluid flow rate in a demand signal line flowing through said sensing device to cause said pump control valve to be activated for motor piston reciprocation to increase the pump displacement in response to decreasing flow rate in said demand signal line, whereby pump displacement is inversely proportional to the flow rate in said demand signal line, a second hydraulic motor and a second motor control valve for controlling the flow of fluid thereto, a flow control valve having an input line and first and second output lines, said input line being connected to the output line of the pump, the improvement of: said second output line selectively supplying fluid to said demand signal line, said second motor control valve including a valve element controlling the communication between said first output line of said flow control valve and said second motor; and feedback signal means interconnecting said flow control valve and said second motor control valve (a) for sensing the flow rate demanded by said second hydraulic motor, (b) for sensing the flow rate across said motor control valve, (c) for positioning said flow control valve to reduce flow from said input line to said second output line when the flow demanded by said second hydraulic motor exceeds the flow rate thereto, and (d) for increasing flow from said input line to said second output line as the flow rate thruogh said second motor control valve catches up with the demand.