Fluid handling – With heating or cooling of the system – Circulating fluid in heat exchange relationship
Reexamination Certificate
1999-03-16
2001-02-06
Rivell, John (Department: 3753)
Fluid handling
With heating or cooling of the system
Circulating fluid in heat exchange relationship
C251S129070, C251S282000, C123S568260
Reexamination Certificate
active
06182684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a valving device for fluid control applications and, more particularly, to such a valving device having a pressure balanced bellows or bellows assembly.
The use of a bellows assembly within a valve is known. In valving applications, high cycle life may be difficult to achieve when the valve is subjected to high end or cyclical operating pressures. Accordingly, the bellows is preferably designed to be thin and flexible. However, the bellows may also function as a fluid barrier, and thus, the wall of the bellows may be subjected to a pressure differential. In this regard, the wall of the bellows may be designed to be thicker and less flexible, thus decreasing cycle life. To overcome this problem, various approaches have been developed to balance the pressure acting on the walls of the bellows.
In an automobile exhaust gas cleaning system, an exhaust gas recirculation valve (EGR valve) is used. The function of the EGR valve is to recirculate a part of the exhaust gas from the exhaust system to the intake system in accordance with negative pressure in the carburetor. Conventional diaphragm balanced valves, of which many are known in the art, are popular choices for EGR valves. Bellows type valves have been used, but the extreme temperature environments and pressure fluctuations present in the exhaust gas environment typically limits the effectiveness of the conventional bellows type valves.
SUMMARY OF THE INVENTION
It is, therefore, a general object of the invention to provide an improved pressure balanced bellows type valve. It is also one of several objects of the invention to provide such a pressure balanced bellows valves particularly adapted to high temperature applications and, alternatively, to applications wherein the valve is subjected to pressure fluctuations.
A bellows valve assembly according to the invention may be installed in a fluid (e.g., gas or liquid) pathway such as in an exhaust gas recirculation line in automobile installations. The valve assembly includes a valve body, a bellows housing positioned adjacent the valve body, and a valve actuator. The valve body is equipped with an inlet, an outlet, a valve bore positioned between the inlet and the outlet, and a valve seat disposed between the inlet and the outlet. A valve closure element having a sealing surface is positioned in the valve bore and is engageable with the valve seat to restrict fluid flow through the valve bore. The valve closure element also has a valve stem that extends from the sealing surface and the valve bore through the bellows housing. Preferably, the valve stem has a lower portion characterized by a first average diameter and an upper portion characterized by a second average diameter that is at least 25% smaller than the first average diameter. More preferably, the average diameter of the upper portion is about 40% to 60% the average diameter of the lower portion. Further, the actuator preferably includes a linearly-movable plunger that is engageable with the upper portion of the valve stem to move the sealing surface relative to the valve seat.
In one aspect of the invention, the valve assembly includes a pressure-balanced bellows assembly positioned in the bellows housing. The bellows assembly has at least one section secured to the valve stem such that the bellows assembly surrounds a portion of said valve stem (preferably a portion of the lower portion of the valve stem). The bellows assembly divides a pressure balancing chamber of the bellows housing into a first chamber defined inside of the bellows assembly and a second chamber defined outside of the bellows assembly. Preferably, a stem sealing assembly (e.g, including a packing material) is provided to seal or substantially seal an interface between the valve stem and the balancing chamber such that the upper portion of the valve stem is located on a side of the stem sealing assembly opposite of the lower portion and the bellows assembly. Further, a first passageway is provided to extend between the first chamber and a location in the fluid pathway downstream of the valve seat so as to communicate the fluid pressure downstream of the valve seat to the first chamber. A second fluid passageway is also provided to extend between the second chamber and a location in the fluid pathway upstream of the valve seat so as to communicate the fluid pressure upstream of the valve seat to the second chamber.
In another aspect of the invention, the bellows housing of the valve assembly includes a plurality of walls and a coolant passage in at least one of the walls. Coolant flow (e.g., water) through the coolant passage functions to effect heat transfer away from the bellows housing and components therein, and to reduce the temperature rise in other components of the valve assembly (e.g., the actuator).
In one embodiment of the present invention, an exhaust gas recirculation valve assembly is provided having a valve body, a bellows housing, a valve closure element, and a pressure-balanced bellows assembly, as described above. The valve assembly is also equipped with a first passageway communicating a first chamber of a bellows balancing chamber with fluid pressure downstream of a valve seat of the valve body, and a second passageway communicating a second chamber of the bellows balancing chamber with fluid pressure upstream of the valve seat. The valve assembly preferably includes a solenoid operated actuator having a linearly movable plunger for engaging a valve stem of the valve closure element.
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Martin Terrence
Morris Jules J.
Rivell John
Robertshaw Controls Company
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