Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
1999-11-12
2001-01-30
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C091S454000, C137S596160
Reexamination Certificate
active
06179000
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a solenoid-operated three-way valve for electrically controlling the application of pressurized air to a pneumatically operated tool, control valve, or other device. More specifically, this invention improves upon the pilot operated three-way valves described in U.S. Pat. No. 2,881,801, the disclosure of which is incorporated herein by reference.
Although the three-way valve of U.S. Pat. No. 2,881,801 performs its function admirably, its performance can be hampered under particular operating conditions. For example, if the input pressure should decrease rapidly while the valve is energized and open to apply pressurized air to a device, an instantaneous pressure differential can close and lock the valve in the closed state even after the valve is deenergized.
SUMMARY OF THE INVENTION
The aforementioned problems of the prior art are overcome by the instant invention which provides for a three-way valve which has a working chamber with an inlet port, an exhaust port and a work port, a pressure chamber with an inlet port adapted to be connected to a source of pressure, and an outlet port, and a main pressure valve seat circumscribing a main pressure valve opening at an interface between the work chamber inlet port and main pressure valve outlet port. A main pressure valve member is movable in response to differences in force exerted on a front side thereof by the pressures in the work chamber and pressure chamber, and on a rear side thereof by the pressure in a space behind the main pressure valve member for seating on, and unseating from, the main pressure valve seat.
The three-way valve also has an exhaust chamber with an inlet port, and an outlet port adapted to open into the ambient atmosphere, and a main exhaust valve seat circumscribing a main exhaust valve opening at an interface between the work chamber outlet port and main exhaust valve inlet port. A main exhaust valve member is movable in response to differences in force exerted on a front side thereof by the pressure in the work chamber and in the exhaust chamber, and on a rear side thereof by the pressure in a space behind the main exhaust valve member for seating on and unseating from the main exhaust valve seat.
One bleed passageway extends from the pressure chamber to the space behind the main pressure valve member. Another bleed passageway extends from the work chamber to the space behind the main exhaust valve member.
A pilot valve has a pilot pressure valve seat which circumscribes a pilot pressure valve opening at an interface between the space behind the main pressure valve member and the space behind the main exhaust valve member, and a pilot exhaust valve seat which circumscribes a pilot exhaust valve opening at an interface between the space behind the main exhaust valve member and the ambient atmosphere.
The pilot valve has an off state in which a pilot valve member seals the pilot pressure valve opening while exposing the exhaust pressure valve opening, and an on state in which a pilot valve member seals the exhaust pressure valve opening while exposing the pilot pressure valve opening.
A unidirectional flow device, e.g., a check valve, is mounted between the working chamber and the space behind the main exhaust valve member for preventing flow of fluid from the working chamber to the space behind the main exhaust valve member through the exhaust bleed passageway which would lock up the three-way valve, but permitting flow of fluid from the space behind the main exhaust valve member to the working chamber through the exhaust bleed passageway as is necessary for the three-way valve to function.
It is therefore an object of the invention to provide a three-way valve which is resistant to lock-up due upon loss of inlet pressure.
Another object of the invention is to provide a three-way valve with a unidirectional flow means between its work chamber and the space behind its exhaust valve member.
Still another object of the invention is to provide a three-way valve member with a check valve in its exhaust bleed port.
Other and further objects of the invention will be apparent from the following drawings and description of a preferred embodiment of the invention in which like reference numerals are used to indicate like parts in the various views.
REFERENCES:
patent: 2881801 (1959-04-01), McCormick
Epler Christopher E.
Zdobinski David B.
Automatic Switch Company
Levine & Mandelbaum
Michalsky Gerald A.
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