Valves and valve actuation – Electrically actuated valve – With means to bias valve open
Patent
1993-12-14
1995-09-26
Rivell, John
Valves and valve actuation
Electrically actuated valve
With means to bias valve open
25112901, 251331, F16K 3102
Patent
active
054528780
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a miniature actuating device with a carrier, a diaphragm, a hollow space being formed between the carrier and the diaphragm and an insulating layer being arranged between them, and with two electrode terminals for producing an electrostatic field between the diaphragm and the carrier for an activated state of the diaphragm.
A miniature actuating device of this kind is known from GB 2 155 152 A. The actuating device serves in that case to open and close a valve, preferably for pneumatic purposes. The valve consists of three layers of silicon in which the hollow space and also a valve inlet and valve outlet are etched. The valve inlet and valve outlet open into the hollow space. In the state of rest, the valve is open. When a d.c. voltage is applied to the two electrode terminals, an electrostatic field is produced which deflects the diaphragm towards the carrier in an activated state and closes the valve.
U.S. Pat. No. 4,585,209 also describes a microvalve, in which the diaphragm opens or closes a through-opening. For that purpose, the diaphragm is in the form of a spring which is attached at one end to the carrier. When the electrostatic field is produced, the diaphragm positions itself also with its other end against the carrier, and thus closes the through-opening.
MEMS 90 (Honeywell Inc.), pages 95 to 98 "Micromachined Silicon Microvalve" describes a microvalve with a diaphragm suspended resiliently at one end, which opens the through-opening of the valve in the state of rest and closes it when an electrical field is applied.
DE 38 14 150 A1 discloses a valve arrangement of microstructured components which can be activated in different ways. A carrier is provided, with a hollow space which is covered by the diaphragm and into which a valve duct opens. The diaphragm is moved by a first force towards the carrier and is firmly held there by a second force, which is applied by an electrostatic field. The first force is produced, for example, by heating the diaphragm, the internal pressure stresses of the diaphragm etched in silicon being exploited.
DE 39 19 876 A1 describes a further microvalve in which the diaphragm and the carrier enclose a hollow space and the closure member is arranged on the side of the diaphragm remote from the carrier.
The disadvantage of all the known valves and the actuating devices located therein is that the throw, that is, the path that the actuating device is able to cover, is limited if an electrostatic field is intended to be the sole means of operation. On the other hand, the use of two different drive means for moving and holding the diaphragm requires greater complexity in the control.
The invention is based on the problem of providing an electrostatically operable actuating device having a relatively large throw.
This problem is solved in a miniature actuating device of the kind mentioned in the introduction in that the hollow space is bounded by two surfaces which in a contact region, in which the surfaces touch each other, are parallel to one another, and at least in an application region adjoining the contact region, in which the two surfaces can be brought to bear on each other, are buckle-free.
By this means, in the activated state the diaphragm and the carrier lie virtually flat one on top of the other. The diaphragm then lies in the activated position in the contact region parallel to the carrier. The throw then corresponds to the maximum height of the hollow space bounded solely by the two surfaces. The content of the hollow space, which is compressed on movement of the diaphragm into the activated position, together with the internal spring forces of the diaphragm, assumes the restoring function in order to move the diaphragm into the inoperative position or the state of rest again when the electrostatic field is turned off. Close to the contact region there is always a relatively strong electrical field and thus also relatively large forces.
Advantageously, the insulating layer extends over the entire area of the diaphragm. The insulatin
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Branebjerg Jens A.
Gravesen Peter
Danfoss A/S
Rivell John
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