Fluid handling – Systems – With selective motion for plural valve actuator
Patent
1997-05-09
1998-10-20
Michalsky, Gerald A.
Fluid handling
Systems
With selective motion for plural valve actuator
91426, 1375961, 251297, F15B 1302
Patent
active
058232273
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic pilot valve to be used for switching operating valves for supplying a pressurized fluid to hydraulic cylinders in a construction machine and in an industrial machine.
BACKGROUND ART
As operating valve for supplying pressurized fluid to a hydraulic cylinder of a construction machine, it has been known that a pilot actuation type operating valve, in which a spool bore is provided in a valve body, a spool is disposed within the spool bore slidably between a neutral portion and a pressurized fluid supply position. The spool is maintained at the neutral position by means of a spring, and the spool is move toward to the pressurized fluid supply position by the pressurized fluid supplied to a pressure receiving portion provided at the end portion side of the spool. In order to switch the pilot actuation type operating valve, the pressurized fluid is supplied to the pressure receiving portion from a hydraulic pilot valve.
Various valves have been employed in the prior art as the hydraulic pilot valve known. For example, as disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. Heisei 2-56985, a hydraulic pilot valve is provided with a pressure reduction valve portion, a piston for actuating the pressure reduction valve and being returned to the neutral position by means of the spring, a pushing member for pushing down the piston, and an operation lever rockable between the neutral position and the actuating position. The operation lever is pushed down by a pushing member against the spring from the neutral position to the operating position to push down the piston to place the pressure reduction valve portion into pressure supply state.
In the above-mentioned hydraulic pilot valve, a detent device, constituted of a attraction disc and a attracting coil, is provided so that the attracting coil may bias the attraction disc when the pressure reduction valve portion is placed at the pressurized fluid supply position by rocking the operation lever from the neutral position to the actuating position. Thus, even when a hand is released from the operation lever, the operation lever will not be return to the neutral position by the spring force and is thus maintained at the actuating position.
However, the hydraulic pilot valve constructed as set forth above requires a space for providing the attraction disc and the attracting coil. Thus, the overall device becomes bulky. Also, the attracting coil requires a power source for supplying power to the attracting coil which results in higher costs.
Therefore, the present invention has been developed in view of the problems set forth above. Accordingly, it is an object of the present invention to provide a hydraulic pilot valve which makes the overall valve compact and the production cost low.
DISCLOSURE OF THE INVENTION
In order to accomplish the above-mentioned object, according to one aspect of the invention, there is provided a hydraulic pilot valve, in which a plurality of pressure reduction valve portions, each having an inlet port, an outlet port and a pressure regulating valve for establishing and blocking communication between both ports by movement of the pressure regulating valve, a plurality of pistons actuating the pressure regulating valves of the pressure reduction valve portions in the direction establishing communication, an operation lever having a pushing member pushing the plurality of pistons, and springs for biasing the pistons upwardly beyond the neutral position to retain them in abutting contact on the pushing members, so that, by rocking the operation lever from the neutral position in one direction to place it at an actuating position to push one piston to place one of the pressure reduction valve portions in a pressurized fluid supply condition to establish communication between the inlet portion and the outlet portion. A switching valve portion is provided in the other piston which assumes a valve open position when the other piston is pushed up. Also, a pressure rece
REFERENCES:
patent: 4342335 (1982-08-01), Reinicker et al.
patent: 4530376 (1985-07-01), Chatterjea
patent: 4566492 (1986-01-01), Bessard
Hori Shuji
Kawabata Kei
Maruyama June
Komatsu Ltd.
Michalsky Gerald A.
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