Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Patent
1989-10-17
1991-01-15
Michalsky, Gerald A.
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
251 35, G05D 701
Patent
active
049846035
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a flow control valve assembly provided with a safety valve, and more particularly, to a flow control valve assembly in which a safety valve is so incorporated in a flow control valve as to form in the valve assembly a valve housing which is easily machined and is neat in construction.
DESCRIPTION OF THE PRIOR ART
Heretofore, it has been known in the art to provide a flow control valve as shown in FIG. 1.
In such a conventional flow control valve, a back-pressure chamber 4 of a poppet 3, for selectively shutting off an inlet port 1 from an outlet port 2, communicates with the inlet port 1 through an orifice 5. In addition, an oil hole 6, through which the back-pressure chamber 4 communicates with the outlet port 2, is formed in the poppet 3. The oil hole 6 of the poppet 3 is opened and closed in operation by a stem 7 connected to a piston 8. Specifically, in FIG. 1 the piston 8 is rightwardly biased by a compression spring 9 to close the oil hole 6.
On the other hand, the piston 8 is subjected to the pressure of a pilot pressure oil supplied from a pilot conduit (not shown) so that the piston 8 is moved to the left as viewed in FIG. 1 against a resilient force exerted by the compression spring 9 to open the oil hole 6. When the oil hole 6 of the poppet 3 is opened, the pressure oil confined in the back-pressure chamber 4 flows out of the chamber 4 to the outlet port 2 through the oil hole 6 of the poppet 3. As a result, the pressure of the pressure oil in the opposite side areas of the orifice 5 differs from each other to produce a pressure difference which acts on a shoulder portion 3a of the poppet 3 to move the poppet 3 to the left as viewed in FIG. 1 so that the inlet port 1 communicates with the outlet port 2 through a notch portion 10 of the poppet 3. The pressure oil confined in the inlet port 1 thus flows from the inlet port 1 to the outlet port 2. At this time, the flow rate of the pressure oil is controlled by the pilot oil pressure which causes the piston 8 to move leftwardly.
In the conventional flow control valve having the above construction, when an extremely high pressure is developed in the pressure oil confined in the inlet port 1, many parts of the flow control valve are damaged. Consequently, in order to prevent such damages to the parts, a safety valve 12 is provided in a communication passage 11 through which the inlet port 1 communicates with the outlet port 2. When the pressure of the pressure oil confined in the inlet port 1 exceeds the pressure setting of the safety valve 12, a piston 13 of the safety valve 12 is moved in opposition to the loading of a spring 14 to permit the pressure oil confined in the inlet port 1 to flow from the inlet port 1 to the outlet port 2 through the communication passage 11. At the same time, the pressure oil confined in the back-pressure chamber 4 flows from the chamber 4 to the outlet port 4 so as to permit the poppet 3 to move leftwardly as viewed in FIG. 1, whereby the inlet port 1 communicates with the outlet port 2.
Since the conventional flow control valve having the above construction does not perform any safety-valve function in itself, it is necessary to separately provide the safety valve 12 as described above. In this case, a communication passage 11 and a bore 16 in which the safety valve 12 is mounted must be additionally formed in a valve housing 15 of the flow control valve through machining. However, such machining of the valve housing 15 is a very cumbersome in operation. In addition, in order to additionally mount the safety valve 12 in the valve housing 15, the valve housing 15 must be a large. These are problems inherent in the conventional flow control valve.
SUMMARY OF THE INVENTION
In view of such circumstances described above, the present invention was made. Consequently, it is an object of the present invention to provide a flow control valve assembly for additionally performing a safety valve function, in a valve housing of which assembly a safety valve is incorpo
REFERENCES:
patent: 3777773 (1973-12-01), Tolbert
patent: 3987814 (1976-10-01), Hall
patent: 4549566 (1985-10-01), Fujiwara et al.
Ishizaki Naoki
Karakama Tadao
Nunotani Sadao
Takano Toshiro
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Michalsky Gerald A.
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