Valves and valve actuation – Valve – Seats
Reexamination Certificate
1998-10-21
2001-02-20
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Valve
Seats
C137S327000
Reexamination Certificate
active
06189862
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates, in general, to a fluid controlling valve and, more particularly, this invention relates to a valve seat that can be removed and replaced for repair of such fluid controlling valve.
BACKGROUND OF THE INVENTION
As is well known in the art, valves are used throughout industry, including the railroad industry, for controlling fluid flow and fluid pressures provided by a source of such fluid flow and fluid pressures such as pumps and compressors. Fluid flow and fluid pressures are conducted through such control valves and through conduits (piping, tubing and hoses) connected to these control valves.
Valve construction varies, as is equally well known, but all fluid control valves have housings and require seats against which valve members abut to block fluid flow and cut-off fluid pressure, and which disengage the seats to allow and control fluid flow and fluid pressure directed through the valves.
Current practice involves the machining of a seat in the valve body. Such machining process is costly and can give rise to valve failures due to porosity which may be present in the cast material of the valve body and nicks in the seat area caused by machining tools.
Another costly process involves press fitting a bushing seat into place in the hollow of the valve body. This practice provides a more robust seat structure but it can lead to detrimental interior fluid leakage between the pressed fitting and the valve body. The press fitting used in this process is typically machined from bar stock.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
What is, therefore, needed in the valve manufacturing industry is a relatively inexpensive, removable, replaceable and leak-proof valve seat component. The present invention provides such a component in the form of molded valve seat made of a durable plastic material placed in the interior of the valve body and sealed therein by a sealing means located between the molded plastic valve seat and the interior surface of the valve body. The sealing means can be, for example, a simple inexpensive O-ring and the molded valve seat can be made from either a durable thermoplastic or thermoset plastic material depending upon the fluids being controlled. Such materials are appropriately moldable and curable.
Injection molding is an inexpensive way to make the plastic valve seat of the invention and the assembly process of placing the valve seat and sealing means in the valve body does not involve a press fitting operation. Rather, the plastic valve seat and sealing means can be dimensioned relative to the interior dimension of the valve body to allow a simple manual, or otherwise, insertion of the valve seat and sealing means into the valve body after the sealing means is placed on an outside surface of the valve seat. For example, the interior bore of the valve body and the external circumference (shank) of the valve seat can be threaded for easy assembly and insertion of the valve seat into the valve bore. A hexagonal recess or other non-cylindrical recess profile which will allow transfer of torsional force, such as a spline or square drive, can be provided in the seat for receiving one end of an Allen or similar type wrench for effecting rotation of the valve seat. Removal of the valve seat is thereby also easily effected when valve repair is needed.
The sealing means, such as the above-described O-ring, can also first be placed in the interior of the valve body. However, this would require that the interior of the valve body be provided with a groove for receiving and seating the sealing means, whereas it is simpler and substantially less costly to mold a peripheral groove in the exterior surface of the valve seat sized to accommodate a suitable sealing means.
REFERENCES:
patent: 1708241 (1929-04-01), Schultheiss
patent: 2602463 (1952-07-01), Stroop
patent: 5871156 (1999-02-01), Lawson
Bonderer D A
James Ray & Associates
Shaver Kevin
Westinghouse Air Brake Company
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