Fluid handling – Systems – Supply and exhaust
Patent
1995-06-01
1997-03-25
Nguyen, Hoang
Fluid handling
Systems
Supply and exhaust
13759614, 91447, 91461, F17D 100, F15B 1108
Patent
active
056135190
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an operating valve assembly with a pressure compensation valve.
BACKGROUND ART
An operating valve is known in which a spool is disposed in a spool bore of a valve body for selectively establishing and blocking communication between a pump port, an actuator port and a tank port. In such operating valve, fluid leakage from the actuator port to the tank port is blocked by the fitted portion between the spool bore and the spool so that a holding pressurized fluid in the actuator may not flow to a tank. In this case, by reducing a gap in the fitted portion between the spool bore and the spool, leakage of the holding pressurized fluid in the actuator port may be prevented to a certain extent. However, since a smaller gap may cause greater sliding resistance of the spool, a greater operation force becomes necessary.
Therefore, in the prior art, a lock valve is provided in a line connected to the actuator or at another appropriate position. However, such arrangement inherently causes high cost.
On the other hand, in Japanese Unexamined Patent Publication (Kokai) No. Showa 62-147101, there is proposed an operating valve which is provided with a pressure compensation valve capable of preventing fluid leakage from the actuator port to the tank port.
However, in the operating valve having the pressure compensation valve, a cut-out in the spool is large to make it impossible to assuredly avoid leakage of the holding pressurized fluid in the actuator port to the tank.
Therefore, it is an object of the present invention to provide an operating valve assembly with a pressure compensation valve which can make a required operation force for a spool small and can assuredly prevent leakage of a holding pressurized fluid acting on an actuator port to a tank.
DISCLOSURE OF THE INVENTION
The present invention has been developed in view of the points set forth above. In order to accomplish the above-mentioned and other objects, according to one aspect of the invention, an operating valve assembly with a pressure compensation valve, comprises:
a spool for selectively establishing and blocking communication between a pump port, an output port and a main tank port, being disposed within a spool bore of a valve body, and a pressure compensation valve being provided between the output port and an actuator port,
the pressure compensation valve having a piston pressed in the closing side by a load pressure acting on a compensation pressure acting portion, and a valve provided integrally with the piston for selectively establishing and blocking communication between the output port and the actuator port, and actuated for opening by the output port pressure acting on an area of a portion to be compensated, an area of the compensation acting area pressure acting portion being equal to the area to be compensated, and
a pilot valve for selectively establishing and blocking communication of a pressure receiving portion of the piston of the pressure compensation valve with a tank, and a shuttle valve supplying the pressure of a higher pressure side among the load pressure and the actuator port pressure to the compensation pressure acting portion of the pressure compensation valve.
With the construction set forth above, in the state where the pump port, output port and the main tank port are blocked, namely at the neutral position of the spool, the pressure of the actuator port acts on the compensation pressure acting portion of the pressure compensation valve. Then, the piston is pressed toward the position to lock communication between the actuator port and the output port by the valve. Thus, the pressurized fluid in the actuator port will not flow to the output port. Therefore, the pressurized fluid in the actuator port will not leak through the gap between the spool bore and the spool.
Accordingly, the gap between-the spool bore and spool can be made greater to make the operating force for the spool smaller. Also, leakage of the holding pressurized fluid acting on the actuator p
REFERENCES:
patent: 3596566 (1971-08-01), Krehbiel
patent: 3884123 (1975-05-01), DeVita et al.
patent: 4154262 (1979-05-01), Blume et al.
patent: 5146747 (1992-09-01), Sugiyama et al.
patent: 5273069 (1993-12-01), Akiyama et al.
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Nguyen Hoang
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