Valve

Details Valve Valve

1999-05-14

2000-09-12

Shaver, Kevin

Valves and valve actuation

With means to increase head and seat contact pressure

Gate valve

251327, 251328, 251333, 251266, F16K 2500

Patent

active

061165727

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention refers to a slanted seat valve with a valve inlet, a valve outlet and a passage extending through the valve housing between the valve inlet and the valve outlet.
Valves are often used to block pipe lines against media flowing therein, which valves are, in particular, stroke valves with a conical seat surface and a blocking element fixed at a spindle and displaced vertically to the flow direction when the valve is closed. Such valves are disadvantageous because of their high drag and the resulting great flow losses occurring in the closing area due to the deflection of the flow.
Slanted seat valves represent a development of these straight seat valves; here, the valve seat is a slanted portion of a circular cone, the symmetrical axis of which extends in parallel to the spindle axis. A slanted arrangement of the valve seat and the blocking element may well effect a reduction of the drag, but in case of a spindle arranged obliquely with respect to the pipe axis, this valve is disadvantageous because of a larger stroke and an impaired operability resulting therefrom. With slanted seat valves having the spindle axis and the pipe axis arranged at right angles, larger pressure differences between the blocking element sides, due to the imbalanced distribution of surface pressure, will cause leaks at the valve seat, since the required surface pressure doses not prevail everywhere. With such slanted seat valves, an eccentric arrangement of the blocking element at the spindle requires an additional fixing against rotation using fixing elements such as pins.
From DE-A-43 42 025 und DE-A-36 09 772, slanted seat valves optimized with respect to the sealing problems are known. The balancing of the surface pressure caused by the force of the spindle over the valve seat surface is achieved by disposing the spindle axis connected with the blocking member eccentrically relative to the center of the plane formed by the valve seat surface and projected in the direction of the spindle axis. The spindle axis is shifted towards a (top) portion of the blocking element proximal to the spindle, the point of attack of the spindle force being arranged such that its effective direction intersects the perpendicular lines to the valve seat surfaces in the intersection of the center plane of the blocking element and the valve seat surface and the pressure component vertically attacking the blocking element within a triangle formed by these intersecting straight lines.
A study of the force relations at the blocking element reveals that there is a limit pressure difference .DELTA.p.sub.G in this embodiment as well, at which the limit pressure force F.sub.pG is canceled at one point of the sealing surface so that leaks can occur. Increasing the spindle force may result in a limited improvement; however, the increase of the spindle force is limited by the strength of the spindle and the valve housing.
Further possibilities to increase the limit pressure force F.sub.pG are known, using, on the one hand, valves having a very steeply inclined, almost vertical valve seat or, on the other hand, valves having a conical valve seat, the cone axis being inclined towards the spindle axis. A steeply inclined seat surface is disadvantageous in that, upon opening the valve, the valve plate may jam due to some self-locking effect and cannot be opened without damage. In the slanted embodiment of the conical seat only very shallow elliptic flow cross sections are achieved so that the drag is rather great in these valves.
From DE-A-24 30 537, a slanted seat valve with a wedge-shaped blocking element is known that is movable transversely into the passage of a valve housing. The oblique face of the blocking element seals against a valve seat formed in the passage and having a continuous bead shaped valve sealing surface. The valve housing comprises guides for the wedge shaped blocking element, thereby preventing that the blocking element cannot be deflected in the direction of the length of the passage when being press

REFERENCES:
patent: 762436 (1904-09-01), Osgood
patent: 2269404 (1942-01-01), Haven et al.
patent: 4765586 (1988-08-01), Yoshida
patent: 5143350 (1992-09-01), Osgood

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