Valves and valve actuation – Fluid actuated or retarded – Piston type expansible chamber reciprocating valve actuator
Reexamination Certificate
2000-07-14
2001-06-12
Lee, Kevin (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Piston type expansible chamber reciprocating valve actuator
C251S331000, C092S151000
Reexamination Certificate
active
06244563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic two-stage switching valve in which a large flow rate and a small flow rate can be selectively obtained wherein a smooth transfer from the small flow rate to the large flow rate occurs.
2. Description of the Related Art
In general, in a known fluid system in which the flow rate is switched between a small flow rate (e.g., several cc/min.) and a large flow rate (several L/min.), a valve for the small flow rate and a valve for the large flow rate are provided in parallel, so that the valves are selectively opened. However, in the conventional fluid system, the two valves for the large flow rate and the small flow rate, parallel pipes thereof, and a three-way connector (T-connect or) are indispensable, and hence, the manufacturing cost and the number of the elements are increased, and the cost and space for the piping are also increased. Moreover, upon switching from the small flow rate to the large flow rate, it is necessary to provide a separate flow control valve in order to carry out a smooth change of the flow rate.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the above-mentioned drawbacks of the prior art by providing an automatic two-stage switching valve in which a large flow rate and a small flow rate can be switched by a single valve, wherein during the transfer from the small flow rate to the large flow rate, a change in flow rate occurs smoothly.
To achieve the object mentioned above, according to the present invention, an automatic two-stage switching valve is provided, including a valve stem which normally closes a fluid passage by a spring force; a cylinder adopted to accommodate the valve stem; a large flow rate piston and a small flow rate piston that are provided on the valve stem and are slidably fitted in the cylinder; a large flow rate pilot pressure chamber formed in the cylinder to exert a pilot pressure on the large flow rate piston against the biasing force of the spring force; a small flow rate pilot pressure chamber formed in the cylinder to exert a pilot pressure on the small flow rate piston against the biasing force of the spring force; a stopper adopted to restrict the movement of the small flow rate piston due to the pilot pressure by a predetermined amount; a pilot pressure source adopted to apply the pilot pressure simultaneously to both the large flow rate pilot pressure chamber and the small flow rate pilot pressure chamber; and a restrictor provided in a connection passage that connects the pilot pressure source to the large flow rate pilot pressure chamber.
In an embodiment, the cylinder is provided with an open end, and wherein the stopper is a cap that is screw engaged at the open end of the cylinder.
Preferably, the restrictor restricts the pilot pressure applied to the large flow rate pilot pressure chamber so that the valve stem opens the fluid passage at a small flow rate and then gradually to a large flow rate.
According to another aspect of the present invention, an automatic two-stage switching valve is provided, including a valve stem which opens or closes a fluid passage; a biasing spring for biasing the valve stem in a direction to close the fluid passage; pistons for a large flow rate and a small flow rate, provided on the valve stem at different axial positions; a cylinder in which the pistons for the large flow rate and the small flow rate are slidably fitted; a pilot pressure chamber for the large flow rate, formed in the cylinder to exert a pilot pressure on the piston for the large flow rate in a direction opposite to the biasing direction of the biasing spring; a pilot pressure chamber for the small flow rate, formed in the cylinder to exert a pilot pressure on the piston for the small flow rate in a direction opposite to the biasing direction of the biasing spring; a small flow rate connection passage, for connecting the pilot pressure chamber for the small flow rate to a pilot pressure source; a large flow rate connection passage, for connecting the pilot pressure chamber for the large flow rate to the pilot pressure source; and a restrictor provided in the large flow rate connection passage.
Preferably, a stopping device is further provided for restricting the movement of the piston for the small flow rate when the pilot pressure is introduced in the pilot pressure chamber for the small flow rate, wherein the valve stem is movable relative to the piston for the small flow rate in a valve opening direction when the movement of the piston for the small flow rate is restricted by the stopping device.
The present disclosure relates to subject matter contained in Japanese Patent Application No.11-202741 (filed on Jul. 16, 1999) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 4903939 (1990-02-01), Ariizumi et al.
patent: 4934652 (1990-06-01), Golden
patent: 5007328 (1991-04-01), Otteman
patent: 5673897 (1997-10-01), Crochet et al.
Fujikura Rubber Ltd.
Lee Kevin
McCormick Paulding & Huber LLP
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