# US 2009/0260352 A1 · Hydraulic system having load sensing capabilities > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260352 A1 - Document ID: US20090260352A1 - Status: Published application - Kind: A1 - Application number: 12/422,899 - Filed: 2009-04-13 - Published: 2009-10-22 - Earliest claimed: 2008-04-11 - Assignees: Eaton Corporation - Inventors: Duqiang Wu; G. Clark Fortune; Aaron H. Jagoda; John R. Kess; Thomas J. Stoltz; Paul Brenner; Benjamin Morris - Web page: https://patentgrep.com/patent/US20090260352A1 ## CPC - F15B 13/07: in distinct sequence - F15B 1/021: {used for damping} - F15B 11/162: {for giving priority to particular servomotors or users} - F15B 21/08: Servomotor systems incorporating electrically operated control means (F15B21/02, {F15B21/065} take precedence) - F15B 2211/20538: constant capacity - F15B 2211/405: characterised by the type of flow control means or valve - F15B 2211/411: the positions being discrete - F15B 2211/427: with signal modulation, e.g. using pulse width modulation [PWM] - F15B 2211/455: Control of flow in the feed line, i.e. meter-in control - F15B 2211/625: Accumulators - F15B 2211/63: Electronic controllers - F15B 2211/6654: Flow rate control - F15B 2211/7135: Combinations of output members of different types, e.g. single-acting cylinders with rotary motors - F15B 2211/781: one or more output members having priority - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR ## Abstract An exemplary hydraulic system includes a digital valve operable to fluidly connect a hydraulic load to a pressure supply, and an orifice disposed in a flow path between the hydraulic load and the digital valve. A digital controller is operably connected to the digital valve. The digital controller stores a target pressure drop across the orifice and is configured to determine an actual pressure drop across the orifice and formulate a control signal based on the target pressure drop and the actual pressure drop. The controller transmits the control signal to the digital valve for controlling the operation of the valve. ## Claims ### Claim 1 A method comprising: selecting a target pressure drop across an orifice disposed in a fluid path between a valve and a hydraulic load, the valve operable for selectively fluidly connecting the hydraulic load to a source of pressurized fluid; determining an actual pressure drop across the orifice; formulating a control signal based on the target pressure drop and the actual pressure drop; and transmitting the control signal to the valve. ### Claim 2 (depends on 1) The method of claim 1, further comprising: adjusting the cross-sectional flow area of the orifice to selectively vary the rate at which pressurized fluid is delivered to the hydraulic load; monitoring the pressure drop across the orifice while adjusting the cross-sectional flow area of the orifice; and selectively adjusting the control signal to maintain the pressure drop across the orifice within a selected tolerance range of the target pressure drop. ### Claim 3 (depends on 2) The method of claim 2, wherein the step of adjusting the control signal includes determining a duty cycle of the valve calculated to produce a pressure drop across the orifice that is within the selected tolerance range of the target pressure drop. ### Claim 4 (depends on 3) The method of claim 3, wherein the duty cycle defines a time period during which the valve is cycled between an open position and a closed position. ### Claim 5 (depends on 2) The method of claim 2, wherein increasing the cross-sectional flow area of the orifice increases the rate at which pressurized fluid is delivered to the hydraulic load. ### Claim 6 (depends on 2) The method of claim 2, wherein decreasing the cross-section flow area of the orifice decreases the rate at which pressurized fluid is delivered to the hydraulic load. ### Claim 7 (depends on 1) The method of claim 1, wherein the step of formulating a control signal includes determining a duty cycle of the valve calculated to produce a pressure drop across the orifice that is within a selected tolerance range of the target pressure drop. ### Claim 8 (depends on 1) The method of claim 1 further comprising: monitoring the actual pressure drop across the orifice; and adjusting the control signal to maintain the pressure drop across the orifice within a selected tolerance range of the target pressure drop. ### Claim 9 (depends on 1) The method of claim 1 further comprising: monitoring a system pressure; and adjusting the control signal if the monitored pressure falls below a selected low standby pressure. ### Claim 10 (depends on 9) The method of claim 9, wherein the step of adjusting the control signal includes determining a duty cycle of the valve for maintaining the system pressure equal to or greater than the low standby pressure. ### Claim 11 (depends on 1) The method of claim 1 further comprising: monitoring a system pressure; and adjusting the control signal if the monitored pressure exceeds a selected high standby pressure. ### Claim 12 (depends on 11) The method of claim 11, wherein the step of adjusting the control signal includes determining a duty cycle of the valve for maintaining the system pressure equal to or less than the high standby pressure. ### Claim 13 A hydraulic system comprising: a digital valve operable to fluidly connect a hydraulic load to a pressure supply; an orifice disposed in a flow path between the hydraulic load and the digital valve; and a digital controller operably connected to the digital valve, the digital controller storing a target pressure drop across the orifice, the digital controller configured to determine an actual pressure drop across the orifice and formulate a control signal based on the target pressure drop and the actual pressure drop, the controller transmitting the control signal to the digital valve for controlling the operation of the valve. ### Claim 14 (depends on 13) The hydraulic system of claim 13, wherein the orifice includes a variable cross-sectional flow area that is adjustable to selectively vary the rate at which pressurized fluid is delivered to the hydraulic load, the controller configured to monitor the pressure drop across the orifice as the cross-sectional flow area is adjusted and modify the control signal to maintain the pressure drop across the orifice within a selected tolerance range of the target pressure drop. ### Claim 15 (depends on 14) The hydraulic system of claim 14, wherein the controller is configured to determine a duty cycle of the digital valve calculated to produce a pressure drop across the orifice that is within a selected tolerance range of the target pressure drop. ### Claim 16 (depends on 15) The hydraulic system of claim 15, wherein the duty cycle defines a time period during which the digital valve is cycled between an open position and a closed position. ### Claim 17 (depends on 14) The hydraulic system of claim 14, wherein increasing the cross-sectional flow area of the orifice increases the rate at which pressurized fluid is delivered to the hydraulic load. ### Claim 18 (depends on 14) The hydraulic system of claim 14, wherein decreasing the cross-section flow area of the orifice decreases the rate at which pressurized fluid is delivered to the hydraulic load. ### Claim 19 (depends on 18) The hydraulic system of claim 18, wherein the duty cycle defines a time period during which the digital valve is cycled between an open position and a closed position. ### Claim 20 (depends on 13) The hydraulic system of claim 13, wherein the controller is configured to determine a duty cycle of the digital valve calculated to produce a pressure drop across the orifice that is within a selected tolerance range of the target pressure drop. ### Claim 21 (depends on 13) The hydraulic system of claim 13, wherein the controller is configured to monitor the actual pressure drop across the orifice and adjust the control signal to maintain the pressure drop across the orifice within a selected tolerance range of the target pressure drop. ### Claim 22 (depends on 13) The hydraulic system of claim 13, wherein the controller is configured to monitor a system pressure and adjust the control signal if the monitored pressure falls below a selected low standby pressure. ### Claim 23 (depends on 22) The hydraulic system of claim 22, wherein the controller is configured to determine a duty cycle of the digital valve for maintaining the system pressure equal to or greater than the low standby pressure. ### Claim 24 (depends on 13) The hydraulic system of claim 13, wherein the controller is configured to monitor a system pressure and adjust the control signal if the monitored pressure exceeds a selected high standby pressure. ### Claim 25 (depends on 24) The hydraulic system of claim 24, wherein the controller is configured to determine a duty cycle of the digital valve for maintaining the system pressure equal to or less than the high standby pressure.