First and second mechanical hydraulic valves are disposed between a pump and the cap side chamber of an actuator and the pump and the rod chamber of the pump. The first and second valves are actuated as a result of respective pressure differentials applied across the valves. A controller controls fl
First and second mechanical hydraulic valves are disposed between a pump and the cap side chamber of an actuator and the pump and the rod chamber of the pump. The first and second valves are actuated as a result of respective pressure differentials applied across the valves. A controller controls flow from a pump in response to a commanded motion to control movement of the actuator, and cause the valves to open. The valves are disposed in their no-flow positions when the pump is not operative, and when the hydraulic system of off or locked out to hold a load.
대표청구항▼
1. A hydraulic system comprising: an actuator having a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder, the piston defining a rod chamber and a cap side chamber within the cylinder,a pump adapted to operate as a pump or as a motor, the pump be
1. A hydraulic system comprising: an actuator having a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder, the piston defining a rod chamber and a cap side chamber within the cylinder,a pump adapted to operate as a pump or as a motor, the pump being adapted to selectively provide varied flow rates, the pump being adapted to deliver pressurized hydraulic fluid to and receive pressurized hydraulic fluid from the chambers of the actuator, movement of the piston relative to the cylinder being dependent upon the selectively varied flow rates,a controller configured to control the displacement of the pump in response to a commanded motion and relative positions of the piston and cylinder,a rod side fluid connection between the pump and the rod chamber,a cap side fluid connection between the pump and the cap side chamber,a first mechanical hydraulic valve disposed in the cap side fluid connection, the first mechanical hydraulic valve having at least a first position preventing flow through the cap side fluid connection, and a second position permitting flow through the cap side fluid connection, the first mechanical hydraulic valve being adapted to be disposed in at least one of its first or second positions as a result of a first hydraulic pressure differential applied across the first mechanical hydraulic valve, anda second mechanical hydraulic valve disposed in the rod side fluid connection, the second mechanical hydraulic valve having at least a first position preventing flow through the rod side fluid connection, and a second position permitting flow through the rod side fluid connection, the second mechanical hydraulic valve being adapted to be disposed in at least one of its first or second positions as a result of a second hydraulic pressure differential applied across the second mechanical hydraulic valve,wherein the first and second mechanical hydraulic valves are maintained in the respective first positions when the pump is not operative. 2. The hydraulic system of claim 1 wherein the pump is a variable displacement pump. 3. The hydraulic system of claim 1 wherein the first mechanical hydraulic valve includes first and second actuating surfaces of the first mechanical hydraulic valve, the second mechanical hydraulic valve includes first and second actuating surfaces of the second mechanical hydraulic valve, the hydraulic system further including at least one first fluid takeoff from the cap side fluid connection to the second actuating surface of the first mechanical hydraulic valve and at least one second fluid takeoff from the rod side fluid connection to the second actuating surface of the second mechanical hydraulic valve, the first fluid takeoff being adapted to direct hydraulic fluid pressure from the cap side chamber through the cap side fluid connection to the first actuating surface of the first mechanical hydraulic valve to move or maintain the second mechanical hydraulic valve in its first position, and the second fluid takeoff being adapted to direct hydraulic fluid pressure from the rod chamber through the rod side fluid connection to the second actuating surface of the second mechanical hydraulic valve to move or maintain the second mechanical hydraulic valve in its first position. 4. The hydraulic system of claim 3 further including at least one third fluid takeoff from the cap side fluid connection to the first actuating surface of the first mechanical hydraulic valve and at least one fourth fluid takeoff from the rod side fluid connection to the first actuating surface of the second mechanical hydraulic valve, the third fluid takeoff being adapted to direct hydraulic fluid pressure from the cap side chamber through the cap side fluid connection to the first actuating surface of the first mechanical hydraulic valve to move or maintain the first mechanical hydraulic valve in its second position, and the fourth fluid takeoff being adapted to direct hydraulic fluid pressure from the rod chamber through the rod side fluid connection to the first actuating surface of the second mechanical hydraulic valve to move or maintain the second mechanical hydraulic valve in its second position. 5. The hydraulic system of claim 3 further comprising a hydraulic fluid source and a makeup hydraulic circuit disposed to provide selective flow between the cap side fluid connection and the hydraulic fluid source, and between the rod side fluid connection and the hydraulic fluid source, the make-up hydraulic circuit including a second pump and at least one makeup valve, the second pump being disposed to provide hydraulic fluid from the hydraulic fluid source to the makeup valve, the makeup valve being operable in response to a minimum pressure differential between the rod side fluid connection and the cap side fluid connection to provide said selective flow between the cap side fluid connection and the hydraulic fluid source, and between the rod side fluid connection and the hydraulic fluid source. 6. The hydraulic system of claim 3 further comprising an electro-hydraulic displacement control circuit including at least one valve and a fluid connection to at least one of said first and second actuating surfaces of said first and second mechanical hydraulic valves, operation of said at least one valve selectively providing hydraulic fluid flow through said fluid connection or preventing hydraulic fluid flow through said fluid connection. 7. The hydraulic system of claim 1 further including at least one position sensor associated with at least one of the cylinder and the rod, the position sensor being adapted to provide a signal to the controller. 8. A method of controlling a hydraulic system including an actuator having a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder, the piston defining a rod chamber and a cap side chamber within the cylinder, a pump, a rod side fluid connection between the pump and the rod chamber, and a cap side fluid connection between the pump and the cap side chamber, the pump adapted to deliver pressurized fluid to and receive pressurized fluid from the chambers of the actuator, the method comprising the steps of: disposing a first mechanical hydraulic valve in the cap side fluid connection, the first valve having at least a first position substantially preventing flow through the cap side fluid connection, and a second position permitting flow through the cap side fluid connection,disposing a second mechanical hydraulic valve in the rod side fluid connection, the second valve having at least a first position substantially preventing flow through the rod side fluid connection, and a second position permitting flow through the rod side fluid connection,moving the first mechanical hydraulic valve from its first position to its second position to allow flow through the cap side fluid connection and moving the second mechanical hydraulic valve from its first position to its second position to allow flow through the rod side fluid connection when motion of the actuator is commanded,controlling the pump to control the flow rate in response to relative positions of the piston and cylinder and a commanded motion of the actuator,moving the first mechanical hydraulic valve from its second position to its first position and moving the second mechanical hydraulic valve from its second position to its first position when at least one of movement of the piston is not commanded or the hydraulic system is turned off,at least one of the steps of moving occurring as a result of a pressure differential across the respective mechanical hydraulic valve. 9. The method of claim 8 wherein the steps of moving the first and second mechanical hydraulic valves include steps of directing hydraulic pressure to first or second mechanical hydraulic valve to move the first or second mechanical hydraulic valve from its first to its second position. 10. The method of claim 8 wherein the step of moving the first mechanical hydraulic valve from its second position to its first position includes directing hydraulic pressure from the cap side fluid connection to a second actuating surface of the first mechanical hydraulic valve to move the first mechanical hydraulic valve from the second to the first position or to maintain the first mechanical hydraulic valve in the first position to substantially prevent flow through the cap side fluid connection, and the step of moving the second mechanical hydraulic valve from its second position to its first position includes directing hydraulic pressure from the rod side fluid connection to a second actuating surface of the second mechanical hydraulic valve to move the second mechanical hydraulic valve from the second to the first position or to maintain the second mechanical hydraulic valve in the first position to substantially prevent flow through the rod side fluid connection. 11. The method of claim 8 wherein the step of moving the first mechanical hydraulic valve from its first position to its second position includes directing hydraulic fluid pressure from the cap side fluid connection to a first actuating surface of the first mechanical hydraulic valve, and the step of moving the second mechanical hydraulic valve from its first position to its second position includes directing hydraulic fluid pressure from the rod side fluid connection to a first actuating surface of the second mechanical hydraulic valve. 12. The method of claim 8 further comprising the steps of a controller receiving a signal from an operator input, the controller directing an electro-hydraulic displacement control circuit including at least one load holding control valve and at least one fluid connection to at least one a first and second actuating surface of at least one of the first and second mechanical hydraulic valves, the controller providing a signal to operate said at least one load holding control valve to selectively provide hydraulic fluid flow through said at least one fluid connection in response to a commanded motion, deactivating said fluid connection from said at least one load holding valve to said first or second actuating surface to substantially prevent flow through said fluid connection when no motion is commanded. 13. The method of claim 8 wherein the step of moving the first mechanical hydraulic valve from its second position to its first position includes directing hydraulic pressure from the cap side fluid connection to a second actuating surface of the first mechanical hydraulic valve to move the first mechanical hydraulic valve from its second to the first position or to maintain the first mechanical hydraulic valve in its first position to substantially prevent flow through the cap side fluid connection, and the step of moving the second mechanical hydraulic valve from its second position to its first position includes directing hydraulic pressure from the rod side fluid connection to a second actuating surface of the second mechanical hydraulic valve to move the second mechanical hydraulic valve from the second to the first position or maintain the second mechanical hydraulic valve in its first position to substantially prevent flow through the rod side fluid connection, the step of moving the first mechanical hydraulic valve from its first position to its second position includes directing hydraulic fluid pressure from the cap side fluid connection to a first actuating surface of the first mechanical hydraulic valve, and the step of moving the second mechanical hydraulic valve from its first position to its second position includes directing hydraulic fluid pressure from the rod side fluid connection to a first actuating surface of the second mechanical hydraulic valve. 14. A method of controlling a hydraulic system including an actuator having a piston disposed within a cylinder, and a rod extending from the piston and extending out of the cylinder, the piston defining a rod chamber and a cap side chamber within the cylinder, a pump, a rod side fluid connection between the pump and the rod chamber, and a cap side fluid connection between the pump and the cap side chamber, the pump adapted to deliver pressurized fluid to and receive pressurized fluid from the chambers of the actuator, the method comprising the steps of: disposing a first load holding valve in the cap side fluid connection, the first valve having at least a first position substantially preventing flow through the cap side fluid connection, and a second position permitting flow through the cap side fluid connection,disposing a second load holding valve in the rod side fluid connection, the second valve having at least a first position substantially preventing flow through the rod side fluid connection, and a second position permitting flow through the rod side fluid connection,controlling the pump to control the flow rate in response to relative positions of the piston and cylinder and a commanded motion of the actuator,moving the first load holding valve from its first position to its second position to allow flow through the cap side fluid connection when motion of the actuator is commanded,moving the second load holding valve from its first position to its second position to allow flow through the rod side fluid connection when motion of the actuator is commanded,determining when the piston is within a predetermined distance of an end of the cylinder,cushioning the movement of the piston as it nears the end of the cylinder by controllably moving at least one of the first or second load holding valves from its second position to its first position to reduce a flow rate of fluid to and from the rod and cap side chambers,moving the first load holding valve from its second position to its first position when the pump is not commanded, the hydraulic system is turned off, or hydraulic operation of the actuator is locked out, andmoving the second load-holding valve from its second position to its first position when at least one of the pump is not commanded, the hydraulic system is turned off, or hydraulic operation of the actuator is locked out. 15. The method of claim 14 wherein the step of moving the first load holding valve from its first position to its second position includes at least one controller energizing a first solenoid associated with the first load holding valve, the step of moving the second load holding valve from its first position to its second position includes the controller energizing a second solenoid associated with the second load holding valve, the step of moving the first load holding valve from its second position to its first position includes de-energizing the first solenoid when at least one of the pump is not commanded, the hydraulic system is turned off, or hydraulic operation of the actuator is locked out, and the step of moving the second load holding valve from its second position to its first position includes de-energizing the second solenoid when at least one of the pump is not commanded, the hydraulic system is turned off, or hydraulic operation of the actuator is locked out. 16. The method of claim 15 further including steps of reading a first hydraulic pressure proximal to the cap side chamber, providing a first signal representing the first hydraulic pressure,reading a second hydraulic pressure proximal to the rod chamber,providing a second signal representing the second hydraulic pressure,controlling at least one of the first and second load holding valves to provide desired first and second hydraulic pressures to provide a desired actuator speed. 17. The method of claim 14 wherein the determining step includes a step of providing a signal from at least one of a position sensor or a proximity sensor to a controller. 18. The method of claim 14 wherein the determining step includes a step of calculating the location of the piston with the cylinder based upon at least one of calculated piston speed and fluid flow rate. 19. The method of claim 14 wherein the controlling step includes a controller providing a signal to control the flow rate of the pump, and the cushioning step includes the controller providing a signal to at least one of the first or second load holding valves to provide a controlled movement of the at least one of the first or second load holding valves from its second position to its first position to reduce the flow rate of fluid to and from the rod and cap side chambers.
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이 특허에 인용된 특허 (8)
Dennis J. Hausman ; Andrew H. Nippert ; Mark D. Shane, Apparatus for multiplexing a plurality of hydraulic cylinders.
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