Patent Application
20140109970
The present invention relates to valves and, more particularly, to cone type plug valves. A seal between the cone or plug and the seat is formed as a result of a raised sealing face on the cone. The cone travels vertically with the stem while rotation of the cone is prohibited.
Plug valves are a common type of valve used in various industries. Plug valves conventionally utilize a sealing face on a seat to seal against a plug. The seat may be milled, molded or investment cast onto an insert. The insert with the cone is then forced down onto the insert and a seal is made between the face of the cone and the raised seat area on the insert.
U.S. Pat. No. 7,965,788 discloses a technique to align a seat ring in a valve. U.S. Pat. No. 5,615,708 discloses a control valve with a non-plugging valve trim. A valve having a convex sealing surface and a concave seating surface is disclosed in U.S. Pat. No. 5,226,445. Various types of plug valves are also disclosed in U.S. Pat. No. 5,044,604 and U.S. Pat. No. 4,614,330.
The technique of sealing between a plug and a raised seat on an insert becomes difficult to manufacture as the size of the orifice in the seat is reduced. Moreover, this difficulty is exasperating when trying to form a high temperature metal-to-metal seal, since the sealing forces are high and the finish on the sealing surfaces is critical. The configuration and small size of the parts results in the proper machining being be difficult, time consuming and expensive.
The disadvantages of the prior art are overcome by the present invention, an improved remotely operated shutoff valve is hereinafter disclosed.
In one embodiment, the metal cone plug valve comprises of valve body, a valve stem axially relative to the valve body, and a cone supported on the valve stem and having a generally cone shaped exterior surface. The cone is rotatably separate from the valve stem and is axially movable in response to the axially movement of the valve stem. A seat fixably positioned within the valve body is provided for sealing engagement with the metal cone. The metal cone includes a seating surface extending outward from the cone shaped exterior surface for sealing with the seat to close off flow through the through passageway in the valve body.
These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.
The present invention effectively removes the raised sealing surface on the seat fixed to the valve body of a plug valve, and provides that sealing surface on the cone, thereby obtaining the needed pounds per square inch to reliably seal between the seat and the cone. The sealing surface on the cone may be removed completely from the assembly, resulting in the reduction of parts and simplification of the machining process. The modified cone fits within an established seat configuration and no machining of the seat is necessary for reliable sealing and thus valve shut off. The desired finish of the inside of the valve pocket may be maintained to a sufficiently high standard so that the generally conical plug will reliably seal. If the sealing surface in the cone becomes damaged due to nicks or machining marks, there is the ability to lap the sealing face on the cone to form a reliable sealed surface on the cone. By moving the sealing face to the cone, the stresses needed to maintain a seal at elevated temperatures are reduced. The present design also allows a valve configuration that will seal and operate in high temperature environments and is intrinsically fire safe. An investment casting may be used followed by a simple machining operation to face off the seat.
The cone is actuated into the seat by a stem that travels vertically (axially) within the confines of the valve bonnet. The stem to cone connection may be of a dovetail design or other design that allows the stem to turn without causing rotation of the cone. The cone orientation may be maintained by the use of an alignment pin pressed into the body of the valve which allows the cone to slide vertically (axially) while maintaining perpendicularity of the seat face on the cone to the bore. The seat face or seat sealing surface is thus aligned generally perpendicular to the throughbore in the valve body in order to maintain a reliable seal.
Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.
