Motors: expansible chamber type – With motive fluid valve – Plural actuators for single valve means
Reexamination Certificate
2000-06-30
2001-11-20
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Plural actuators for single valve means
C091S459000, C091S461000
Reexamination Certificate
active
06318234
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the control of an electro-hydraulic circuit and more particularly to a line vent arrangement for venting an actuator in an electro-hydraulic circuit.
BACKGROUND ART
When turning the engine off on a machine, it is desirable to ensure that no pressure is trapped in any of the actuators. This is very important when it is desirable to change the implement/work tool. Some implements have actuators or motors located thereon and fluid is provided thereto through quick disconnect hydraulic lines. In previous hydraulic systems, the operator was able to mechanically move the main control valve to each of the operative positions with the engine shut down, thus venting any fluid trapped in the associated actuator or motor. In previous electro-hydraulic systems having electro-hydraulic controls associated with the directional control valves, movements of the directional control lever does not permit operation of the directional control valve. This is true since the electrical control merely moves a hydraulic pilot valve which directs pressurized fluid from a source of pressurized fluid to move the main directional control valve. With the engine shut down, there is no power to operate the source of pressurized fluid. Consequently, there is no pressurized fluid to move the main control valve. Such an arrangement is shown in U.S. Pat. No. 5, 138, 838 which issued on Aug. 18, 1992 and assigned to Caterpillar Inc.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In an aspect of the present invention, a line vent arrangement is provided for an electro-hydraulic system in a machine having an engine. The electro-hydraulic system has a source of pressurized fluid selectively connected to an actuator through an electro-hydraulic directional control valve, a source of pressurized pilot fluid connected to the electro-hydraulic directional control valve and operative to move the electro-hydraulic directional control valve from its neutral position to its operative position, a reservoir, and an electronic controller. The line vent arrangement includes a pressure storage arrangement connected to the electro-hydraulic directional control valve in parallel with the source of pressurized pilot fluid, an electrically controlled valve disposed between the electro-hydraulic directional control valve and both the source of pressurized pilot fluid and the pressure storage arrangement. The electrically controlled valve is operative, when the engine is shut down, to selectively connect the pressure storage arrangement to the electro-hydraulic directional control valve in response to receipt of an electrical signal from the electronic controller.
In another aspect of the present invention, a method is provided for venting an actuator in an electro-hydraulic system for a machine having an engine. The electro-hydraulic system has a source of pressurized fluid selectively connected to an actuator through an electro-hydraulic directional control valve, a source of pressurized pilot fluid connected to the electro-hydraulic directional control valve and operative to move the electro-hydraulic directional control valve from its neutral position to its operative position, an electronic controller, and a reservoir. The method steps includes connecting a pressure storage arrangement to the electro-hydraulic directional control valve in parallel with the source of pressurized pilot fluid, connecting an electrically controlled valve arrangement between the electro-hydraulic directional control valve and both the source of pressurized pilot fluid and the pressure storage arrangement, moving the electrically controlled valve arrangement to a position, when the engine is shut down, connecting the pressure storage arrangement to the electro-hydraulic directional control valve in response to an electrical signal from the electronic controller to selectively move the electro-hydraulic directional control valve to its operative position, and moving the electrically controlled valve arrangement to a position blocking the pressure storage arrangement from the electro-hydraulic directional control valve in the absence of the electrical signal.
REFERENCES:
patent: 4006667 (1977-02-01), Bianchetta et al.
patent: 4362089 (1982-12-01), Melocik et al.
patent: 5138838 (1992-08-01), Crosser
patent: 5220862 (1993-06-01), Schexnayder
patent: 5355675 (1994-10-01), Mayhugh et al.
patent: 6109284 (2000-08-01), Johnson et al.
Burrows J. W.
Caterpillar Inc.
Leslie Michael
Look Edward K.
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