Pressure compensated pump

Claim 2

In a hydraulic circuit having a variable displacement pump, a pump displacement controlling device, a plurality of hydraulic motors and a plurality of motor control valves, each hydraulic motor having an associated motor control valve for controlling the fluid flow to such hydraulic motor, the improved pump control system comprising: a plurality of series-connected flow control valves each having its own input line and first and second output lines, said input line of the upstream most flow control valve being connected to the output of the pump, said first output line of each of said flow control valves serving as an input line to an associated one of said motor control valves and being continuously connected across such flow control valve to the input line of such flow control valve, said second output line of each of said flow control valves being connected in series with the input line of the next downstream flow control valve; feedback singal means interconnecting each of said motor control valves to its associated flow control valve and operable to sense the flow rate and flow demand through such motor control valve and to position the associated flow control valve to reduce flow from the input line to the second output line of such flow control valve when the flow demanded by such 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 such motor control valve catches up with the demand, thereby establishing a fluid supply priority among said flow control valves and their associated motor control valves which favors each upstream motor control valve relative to the next downstream motor control valve; said second output line of the downstream-most of said seriesconnected flow control valves being connected to a flow demandsensing device, 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 of said downstream-most flow control valve to signal the pump displacement controlling device to control pump displacement in inverse proportion to said flow rate, which flow rate is inversely proportional to the sum of the combined unsatisfied flow demand of all of said motor control valves.

Claim 3

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 third hydraulic motor and a third motor control valve for controlling the flow of fluid thereto; first and second flow control valves; said first 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 second flow control valve; said second motor control valve including a valve element controlling the communication between said first output line of said first flow control valve and said second motor; feedback signal means interconnecting said first 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 first 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; said second flow control valve having an input line receiving all of the flow from said second output line of said first flow control valve and being supplied with fluid only to the degree that said first flow control valve directs fluid to the second output line thereof as the flow rate across said valve element of said second motor control valve catches up with the demand, and said second flow control valve further having first and second output lines, said first output line of said second flow control valve continuously supplying fluid to said third motor control valve, said second output line of said second flow control valve selectively supplying fluid to said demand signal line; said third motor control valve having a valve element controlling the communication between said first output line of said second flow control valve anD said third motor; feedback signal means interconnecting said second flow control valve and said third motor control valve and operable to sense the flow rate demanded by said third motor control valve and to sense the flow rate across said valve element thereof, and further operable to position said second flow control valve to reduce flow from said input line to said second output line when the flow demanded by said third motor control valve exceeds the flow rate therethrough, and to increase flow from said input line to said second output line as the flow through said third motor control valve catches up with the demand; whereby the flow rate in said demand signal line is inversely proportional to the sum of the combined unsatisfied flow demands of said second and third motor control valves.

Claim 4

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 third hydraulic motor and a third motor control valve for controlling the flow of fluid thereto; first and second flow control valves; said first 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 second flow control valve; said second motor control valve including a valve element controlling the communication between said first output line of said first flow control valve and said second motor; feedback signal means interconnecting said first 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 first 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; said second flow control valve having an input line receiving all of the flow from said second output line of said first flow control valve and being supplied with fluid only to the degree that said first flow control valve directs fluid to the second output line thereof as the flow rate across said valve element of said second motor control valve catches up with the demand, and said second flow control valve further having first and second output lines, said first output line of said second flow control valve continuously supplying fluid to said third motor control valve, said second output line of said second flow control valve selectively supplying fluid to said demand signal line; said third motor control valve having a valve element controlling the communication between said first output line of said second flow control valve anD said third motor; feedback signal means interconnecting said second flow control valve and said third motor control valve and operable to sense the flow rate demanded by said third motor control valve and to sense the flow rate across said valve element thereof, and further operable to position said second flow control valve to reduce flow from said input line to said second output line when the flow demanded by said third motor control valve exceeds the flow rate therethrough, and to increase flow from said input line to said second output line as the flow through said third motor control valve catches up with the demand; whereby the flow rate in said demand signal line is inversely proportional to the sum of the combined unsatisfied flow demands of said second and third motor control valves.