Flow compensated restrictive orifice for overrunning load protection
AssigneeClark Equipment Company
InventorsJoseph St. Aubin, Rodney Koch, Jason Asche, Jeret Hoesel, Todd Vanderlinde
Life of this patent
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Abstract
A hydraulic circuit for an actuator that has a piston and piston rod that will move a load in a first direction, and which can be externally loaded in an opposite direction, includes a flow compensated valve between the actuator and a control valve. When the piston in the actuator is moved in the second opposite direction under the external load and the rate of flow of fluid out of the actuator through the flow compensated valve exceeds a selected rate, an orifice is introduced in the flow path to restrict flow from the actuator.
Claims19
A hydraulic system for providing fluid under pressure to an actuator having an extendable and retractable piston rod and first and second ports, comprising:
- a hydraulic fluid pressure source configured to draw hydraulic fluid from a reservoir and in communication with the actuator to move the piston rod in a first direction and in a second direction that opposes the first direction, and wherein a load on the actuator acts to move the piston rod in the second opposite direction in concert with the hydraulic fluid pressure source;
- a control valve for directing hydraulic fluid under pressure from the hydraulic fluid pressure source to the actuator to move the piston rod;
- and
- a flow compensated valve carrying flow between the control valve and the first port of the actuator and having at least two flow states, a first flow state of the flow compensated valve providing flow from the hydraulic fluid pressure source to move the piston rod in the first direction and, when the hydraulic fluid pressure source and the load on the actuator are acting upon the piston rod to move it in the second direction, providing substantially unrestricted flow from the first port of the actuator below a selected flow rate, and a second flow state of the flow compensated valve for substantially restricting flow through the flow compensated valve to a selected flow rate, when the flow rate through the flow compensated valve exceeds the selected flow rate, detected as a pressure drop across the flow compensated valve.
A loader having a frame and a lift arm pivotally coupled to the frame, an actuator for rotating the lift arm with respect to the frame, said actuator having an internal piston and a piston rod, and the actuator having first and second pressure ports, a control valve connected to a pump configured to draw hydraulic fluid from a reservoir, the control valve configured to selectively direct hydraulic fluid under pressure from the pump to the first and second pressure ports to position the lift arm, a flow compensated valve connected between the control valve and the first pressure port, said flow compensated valve having a first flow state for passing a flow of fluid under pressure at a first flow rate, and a second flow state for passing a flow of fluid under pressure at a second flow rate in response to an increase in pressure between the flow compensated valve and the first pressure port when the control valve is selected to direct hydraulic fluid from the pump to the second pressure port.
A flow control for controlling maximum flows from an actuator configured to selectively receive hydraulic fluid under pressure from a pressure source at a first port to move a load in a first direction against a force tending to move the actuator in a second direction opposing the first direction and selectively receive hydraulic fluid under pressure from the pressure source at a second port to move the load in the second direction cooperatively with the force, a flow compensated valve in a line connected from the control valve to the first port, said flow compensated valve having two flow states, a first state carrying a flow of fluid through the flow compensated valve at a first rate, and said flow compensated valve being changed to a second flow state to restrict flow through the flow compensated valve to a second rate when flow of fluid from the first port to the flow compensated valve exceeds a selected amount, resulting in a pressure buildup between the first port and the flow compensated valve.
A method for providing overrunning load protection for a loader having a lift arm, a hydraulic actuator for raising and lowering the lift arm, said actuator having an internal piston and a piston rod, and the actuator having first and second pressure ports, the method comprising connecting a control valve to a pump for selectively directing hydraulic fluid under pressure from the pump to the first and second pressure ports to position the lift arm, connecting a flow compensated valve in the line between the control valve and the first pressure port, providing a first flow state in the flow compensated valve for passing a flow of fluid under pressure at a first flow rate and a second flow state for passing a flow of fluid under pressure at a second flow rate when a flow rate of fluid from the first pressure port to the flow compensated valve exceeds a selected flow rate greater than the first flow rate when the control valve directs hydraulic fluid under pressure from the pump to the second pressure port.
Dependencies are inferred from the claim text.