Expansible chamber devices – With force exerting means to move fluid from non-working...
Patent
1995-11-29
1997-12-30
Lopez, F. Daniel
Expansible chamber devices
With force exerting means to move fluid from non-working...
92 82, 92111, 92112, 92160, 184 24, 417431, F15B 2104
Patent
active
057017972
DESCRIPTION:
BRIEF SUMMARY
The invention relates to sealing systems for members which are reciprocably movable within a cylinder.
In many types of equipment, a piston or like member is reciprocably movable in a cylinder, its two opposed sides being exposed to different fluid pressures. This pressure differential produces a tendency for leakage between the reciprocable member and the cylinder wall of fluid from the higher pressure side to the lower. Such leakage can be disadvantageous where the lower pressure fluid would be contaminated by admixture with the other, or where the other fluid contain abrasive material which needs to be excluded from the lower pressure fluid in order to protect other parts of the equipment with which that fluid is in communication.
The invention is accordingly concerned with the provision of an improved sealing system for a member reciprocably movable within a cylinder.
There is known from EP-A-0 314 493 an effective sealing system for a member reciprocably movable within a cylinder of the kind in which overpressure fluid, that is, fluid at a pressure greater than those of the fluids on the opposed sides of the member, is supplied to the space between two seals operative between the member and the cylinder wall. The overpressure of the fluid is obtained by constructing the reciprocable member in two portions capable of relative axial movement, the portions defining an intensifier chamber between them into which fluid is drawn through non-return valve means on relative movement apart of the two portions and from which the fluid is urged into the space between the seals by movement of the portions together.
In accordance with a first aspect of the invention, there is provided, in a sealing arrangement of this kind, an accumulator or auxiliary intensifier chamber from which overpressure fluid is supplied to the space between the two seals when the pressure in the main intensifier chamber drops.
It will be evident that the pressure within the intensifier chamber varies during the cycle of movement of the two portions of the member, falling at the end of each stroke, thereby reducing the effectiveness of the sealing arrangement at critical times during the cycle. The provision of the auxiliary intensifier chamber in accordance with the invention provides a reserve overpressure which tends to regulate the effective fluid pressure in the space between the two seals.
A sealing system embodying the present invention thus conveniently includes passage means leading from the intensifier chamber to the accumulator and the space between the seals by way of a non-return valve permitting flow from the intensifier chamber only. Biassing means tending to reduce the volume of the accumulator is provided.
When the two portions of the reciprocable member are moving together during a compressive stroke, the accumulator is expanded by pressure fluid from the intensifier chamber. The pressure in this chamber then falls as the two portions of the member commence the return stroke, and the accumulator pressure is applied to the space between the seals, under the biassing means, the non-return valve isolating the space and the accumulator from the intensifier chamber.
In accordance with a second aspect of the invention, there is provided a sealing arrangement of the kind described in which the two seals between the member and the cylinder wall are constituted respectively by first and second groups or pluralities of separate seal rings.
The seal rings of the first and second groups of sealing rings, which are conveniently carried by the reciprocable member, are selected as regards material and dimensions so as to perform specific functions. Preferably, the seal ring located at the forward end of the reciprocable member is such as to prevent passage of particles in the process or working fluid to the next following seal ring or rings, so that the operating conditions for such ring or rings are improved. The forward seal ring can thus be a segmented ceramic ring or two such rings received in a common groove. The following ring or r
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patent: 4229011 (1980-10-01), Wikelski et al.
patent: 4472111 (1984-09-01), Yamatani
patent: 4691620 (1987-09-01), Kao
Framo Engineering AS
Lopez F. Daniel
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