Valves and valve actuation – Pivoted valves
Patent
1982-11-19
1984-11-06
Schwadron, Martin P.
Valves and valve actuation
Pivoted valves
251306, F16K 1503, F16K 1226
Patent
active
044808151
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a sealing device for valves, comprising a valve housing which forms a through-duct with a round cross-section and wherein there is a valve seat disposed along a plane which intersects the through-duct, and a valve member which can be moved towards and away from a position in which the valve is closed and an outwardly facing sealing surface on the valve member engages an inwardly facing sealing surface on the valve seat, the valve member being pivotable around a pivot axis which is located on one side of the seat plane and preferably extends parallel thereto, and the two sealing surfaces being pressed against each other wedge-wise along an engagement line or an engagement zone when the valve is closed. The invention, which can be used in butterfly valves serving as shut-off or regulating devices as well as in non-return valves, relates more specifically to a new geometric design for one or both of the sealing surfaces comprised in the sealing device.
A number of butterfly valve designs have appeared wherein, with the aim of obtaining good sealing qualities, the two sealing surfaces have been designed so that they can be pressed against each other when the closed position is assumed. According to a line of development which has been followed for a long time by several manufacturers, the valve seat has been made so that its inwardly facing surface which co-acts with the periphery of the valve flap is in the shape of the envelope surface of a truncated cone, the axial line of the cone being disposed at an oblique angle to the plane of the seat. The sealing surface of the seat, like the engagement line or engagement zone thereon along which the two sealing surfaces are pressed against each other in the closed position, is therefore defined by an elliptical section and naturally, with such a geometrical shape for the seat, the effective sealing surface on the periphery of the valve flap must also have an elliptical shape, viewed in the plane of the seat. This gives rise to problems in the production of the sealing surfaces in a machine tool. Moreover, it can prove difficult to make the flap statically balanced. This construction is described in German Patent Specification No. 1 198 630, and elsewhere.
In order to avoid these problems other designs have been developed, comprising conical sealing surfaces in which full use is made of the functional advantages which can be gained from the tightening of the engagement in such sealing devices. Such a solution, described in Swedish Pat. No. 7404594-9 (publ. No. 400 356), entails the sealing surface of the seat being given a rotationally asymmetric cone shape which is geometrically defined by an oblique circular cone, the base of which coincides with the plane of the seat which lies closest to the pivot axis of the valve flap. The base, like every section which extends parallel to the base and intersects the sealing surface, therefore has a circular shape which enables it to be machined in a machine tool in a process where the valve housing and the cutting tool carry out a relative rotary movement during which the rotation centre of the valve housing is displaced continuously so that it is guided towards the apex of the cone. Since in this case the other sealing surface also has a circular shape the problem with the machining of the valve flap is eliminated.
The sealing device which is described in Swedish Pat. No. 7313937 (publ. No. 383 402) is closely related to this. In this device there is again a sealing surface with a rotationally asymmetric cone shape, but this is arranged on the periphery of the valve flap and faces outwards, while the valve seat is constructed with a narrow inwards-facing sealing surface bounded by a circular opening. Here again the two sealing surfaces will have an increasing pressure of abutment against each other along an engagement line or engagement zone which is substantially circular, as the valve is being closed and the valve flap periphery is pivoted into the opening in the seat.
Although the last-name
REFERENCES:
patent: 2888036 (1959-05-01), Reppert
patent: 3172424 (1965-03-01), Stillwagon
patent: 3809361 (1974-05-01), Pfundstein et al.
patent: 4036469 (1977-07-01), Robinson
patent: 4121607 (1978-10-01), Bader
Custin James R.
Nilles James E.
Saab-Scania Aktiebolag
Schwadron Martin P.
Shay James R.
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