Motors: expansible chamber type – With motive fluid valve – Relatively movable inlet and exhaust valves for single...
Patent
1997-06-23
2000-10-10
Lopez, F. Daniel
Motors: expansible chamber type
With motive fluid valve
Relatively movable inlet and exhaust valves for single...
25112917, 251331, F15B 1304
Patent
active
061290025
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a valve arrangement and, more particularly, to a pneumatic control system.
2. The State of the Art
Pneumatic control systems are widely used because of their efficiency, robustness and long life. In the simplest case, a pneumatic switching element (piston, membrane) is activated by an electropneumatic transducer using pressurized air as the pressure medium. The switching element, in turn, manipulates a flow of gas or fluid. All switching elements suffer from leakage to a greater or lesser extent. For that reason, a pilot valve has to be kept in a permanently open state under a corresponding supply of energy, in order to maintain the switching element in its deflected position. In its activated state, an electromagnetic solenoid valve requires a holding power of about 1 W.
OBJECTS OF THE INVENTION
It is a task of the instant invention to provide a valve arrangement which consumes energy only for the actual switching operation from one state to another and which is capable of maintaining its selected state without power.
The invention solves the task by a valve arrangement including a micro-valve at an intake opening and a further valve at the output opening of a chamber constituting a connection to a pressure-variable setting element, the valves being structured to maintain a closed state by an applied pressure difference, the micro-valve being provided with at least one valve seat and a movable closure member having an open switching position, a closed switching position and an idle state deviating therefrom which is not maintained by the valve in either its open or its closed position and in which a gap is open between the valve seat and the closure member and is dimensioned such that any loss of pressure medium in the chamber as a result of leakage is compensated for by pressure medium flowing through the gap. Special embodiments of the valve arrangement will additionally be described hereinafter.
The valve arrangement in accordance with the invention consists of a chamber having at least two valves, viz.: an intake valve and an output valve. The input flow of a pressure fluid (e.g. a gas) to a switching element connected with the chamber is controlled by the intake valve. The switching element may, for instance, be a piston which is moved with a cylinder by the applied pressure. The output valve controls the outflow of the pressure fluid from the switching element which is thus returned to its initial state.
The valve arrangement is characterized by the fact that the intake valve is a microvalve provided with a valve seat and a closure member which aside from an open and closed switching state may also assume an idle state different from either its closed or open states. Whereas the open and closed states of the valve are switched by external means (e.g. pressure, temperature, electric voltage), the closure member (e.g. a membrane or diaphragm) will assume its idle state when no external means are active, i.e. when it is not maintained in either its open or in its closed state. In this sense, a pressure difference exceeding a certain minimum value applied to the valve is to be understood to be an external means. The two valves are structured such that they are maintained in their closed state by an applied pressure difference. In the idle state, a gap is formed between the valve seat and the movable member, the gap being dimensioned to compensate for leakage flows at the movable member or other parts of the valve arrangement for by pressure fluid entering through the gap. In a currently preferred embodiment, the width of the gap may be selected such that at a predetermined (critical) pressure difference applied to the valve, the closure member, because of the aerodynamic effect, is pressed against the valve seat by the resulting flow of pressure fluid, that is to say, it will close automatically (closed state).
The gap may very easily and reproducibly be formed (for instance by dry etching) during fabrication of the micro
REFERENCES:
patent: 3768875 (1973-10-01), Davis et al.
patent: 4516605 (1985-05-01), Taplin
patent: 4580598 (1986-04-01), Itoh
patent: 4895500 (1990-01-01), Hok et al.
patent: 5219278 (1993-06-01), Van Lintel
patent: 5323999 (1994-06-01), Bonne et al.
Kreutzer Martin
Lisec Thomas
Wagner Bernd
Fraunhofer-Gesellschaft zur Forderung der ange-wandten Forschung
Hormann Karl
Lopez F. Daniel
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