Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1998-10-07
1999-10-26
Hepperle, Stephen M.
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
137505, G05D 1606
Patent
active
059710136
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pneumatic pressure-reducer, of the type in which a comparison capsule, sensitive to the opposing actions of a compression spring and the pressure prevailing downstream from a control valve, controls the movements of the flap of the valve, by means of a movable pressure reduction control rod.
Such a device may be used in all technical fields requiring pneumatic control, notably when a particularly accurate and stable control is desired and when the presence of micro-particles is undesirable. Among these fields, space applications will be cited in particular, and in no way limitatively.
2. Discussion of the Background
In a pneumatic pressure-reducer, a pressurised gas is reduced to a controlled lower pressure, by means of a valve formed from a flap pressed elastically against a seat. Movements of the flap away from the seat, providing the reduction in pressure of the gas, are controlled by a movable rod, usually mounted sliding in the body of the pressure-reducer. In order to provide the movements of the rod, the latter is connected to a comparison capsule acted on by a compression spring which tends to move the rod in the direction of opening the valve. In order to provide control, the face of the comparison capsule opposite the one acted on by the compression spring is placed in a comparison chamber situated downstream from the valve and through which the gas which escapes from the pressure-reducer usually passes.
In pneumatic pressure-reducers constituted in this way, compression of the spring which acts on the comparison capsule creates unwanted transverse forces, which in their turn cause friction between the control rod for the valve and the bearings which support it. This friction creates random control inaccuracies and forms micro-particles. For this reason, pressure-reducers of this type are not suited to certain specific applications such as space applications developed currently.
Furthermore, as a result of the comparison chamber being placed directly downstream from the valve, oscillations generated by the reduction in pressure of the gases are transmitted in full to the comparison capsule. Under certain flow conditions, this creates regulation instabilities also little suited to certain specific applications.
SUMMARY OF THE INVENTION
The object of the invention is precisely a pneumatic pressure-reducer, the original design of which provides a control which is substantially more accurate and more stable than that of existing pressure-reducers, while avoiding the formation of micro-particles under the effect of friction.
In accordance with the invention, this result is obtained by means of a pneumatic pressure-reducer, characterised by the fact that it comprises:
a body;
a main passage formed in the body and connecting a gas inlet aperture with a gas outlet aperture;
a valve having a seat formed in the main passage and a flap pressed elastically against this seat;
a movable pressure reduction control rod, guided and supported in the body by two spring washers, so as to be able to control a movement of the flap away from the seat; and
a comparison capsule, movable with the rod in the direction of the said movement, under the action of an elastic means acting against a gas pressure prevailing in a comparison chamber communicating with a downstream region of the main passage, situated between the valve and the outlet aperture.
Given that, instead of being mounted sliding in the body of the pressure-reducer, the rod serving to control the valve is guided and supported by two spring washers, the friction between the rod and the body of the pressure-reducer is removed. The drawbacks entailed by this friction, that is to say notably the random control inaccuracies and the formation of microparticles, are therefore also removed.
Mounting of the control rod for the valve in the body of the pressure-reducer by means of two spring washers ensures a perfectly linear movement of the rod with respect to the flap.
As the case ma
REFERENCES:
patent: 2318721 (1943-05-01), Siver
patent: 2718237 (1955-09-01), Matasovic
Beau Jean Fran.cedilla.ois
Simon Gilles
Aerospatiale Societe National Industrielle
Hepperle Stephen M.
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