Pressure retaining valve

Details Pressure retaining valve Pressure retaining valve

1996-05-08

1998-03-10

Chambers, A. Michael

Fluid handling

Line condition change responsive valves

Direct response valves

13754313, 251 50, 2513352, F16K 1506

Patent

active

057250197

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a pressure retaining valve including which can be connected to the housing inlet passage, biased by a spring in the direction towards the valve seat and, in the closed position, seals the connection between the housing inlet passage and the housing outlet passage, and an isolating membrane which is clamped in the housing and separates the spring and the valve piston.
With pressure retaining valves of the type referred to above one refers to a flow beneath the valve seat which opens the valve piston. In another known type of construction, the housing inlet passage leads into the interior of the housing between the isolating membrane and the upper surface of the valve seat directed towards it, whereby the outlet passage commences at the underside of the valve seat; with this type of construction one refers to a flow beneath the membrane which opens the valve piston. In the case of flow beneath the membrane, so-called control oscillations do not occur as in the pressure retaining valves of the type referred to above but the flow beneath the membrane has the major disadvantage that the entire membrane surface is necessarily acted upon by the entire prevailing system pressure so that enormous spring forces must be applied by the valve spring closing the pressure retaining valve and enormous forces act on the valve seat or the valve seat seal in the event of a pressure reduction in the system down to zero and the isolating membrane constitutes a safety risk and must thus be manufactured with a high manufacturing expense and strong textile reinforcements.
In the pressure retaining valves of the type referred to above, in which flow occurs beneath the valve seat, the high forces do not occur; the isolating membrane needs only to protect the spring dome with its individual components from aggressive media. However, the occurrence of control oscillations in the pressure retaining valves of the type referred to above is disadvantageous. In order to maintain the valve sealed, the spring force is adjusted so that it just overcomes the force which is exerted by the medium on the closed valve piston and which is produced by the product of the pressure of the medium and the exposed area of the housing valve seat. In the event of a pressure rise beneath the valve piston which forces the valve to open, a pressure will be produced due to the internal resistance of the pressure retaining valve to the outlet side of the valve which can be small but which, when the valve piston opens, acts beneath the membrane surface through an internal space in the housing which, due to constructional and manufacturing reasons, extends up from the housing outlet passage to the isolating membrane. The valve piston thus lifts up accordingly. However, since the spring force is sized or adjusted for the relatively small exposed surface of the housing valve seat, a balance between the set spring force and the generated membrane force is not produced so that the valve piston is pressed again in the direction towards the housing valve seat. This up and down movement of the valve piston occurs at rapid intervals; the pressure retaining valve rattles and causes undesired control oscillations.
Pressure retaining valves in which flow occurs beneath the valve seat are known in which complicated special valve piston constructions and valve piston guides with automatically closing and opening bypass passages are used in order to alleviate the problem of the control oscillations. The constructional and functional effort therefor is, however, high and expensive.
The invention therefore has the object of constructing a pressure retaining valve of the type referred to above with simple and economical means so that no control oscillations occur.
The invention solves this object principally by the fact that isolating membrane and the valve seat, and annular gap acting as a throttling point.
There is a connection between the upper side of the housing valve seat and the underside of the isolating membrane via the constructionally determine

REFERENCES:
patent: 379880 (1888-03-01), Taylor
patent: 966999 (1910-08-01), Carssow
patent: 2859031 (1958-11-01), Hansen et al.
patent: 3393702 (1968-07-01), Ferrill
patent: 4245667 (1981-01-01), Braukmann

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