Electrostatically Actuated Device

Abstract

An electrostatic device having a relatively thin and flexible electrode strip, such as a metal coated plastic film or metal foil, which is secured to and normally curls away from an electrode member and is caused to electrostatically unfurl along the member by impressing a voltage between the member and strip. The device is capable of varied uses and is described in connection with its use as a thermal control louver and a light valve or shutter.

Description

BACKGROUND OF THE INVENTION

1. Field

This invention relates generally to electrostatically actuated devices, and more particularly to an electrostatic device having a normally curled electrode strip which is caused to unfurl by electrostatic action.

2. Prior Art

A wide variety of devices have been devised which utilize electrostatic forces to move a part from one position to another. A few of the prior art patents disclosing such devices are listed below: U.S. Pat. Nos. 2,568,824; 2,885,509; 2,885,511; 2,927,255; 2,931,954; 2,942,077; 3,553,364.

Most, if not all, of these and other electrostatic devices which have been developed to date are designed for a specific use, such as a relay, light valve, etc.

SUMMARY OF THE INVENTION

The present invention provides a novel electrostatic device capable of many diverse uses. This electrostatic device has a relatively thin and flexible electrode strip which is secured to and normally curls away from an electrode member. A voltage is impressed between the electrode member and strip in such a way that the resulting electrostatic attraction force between the member and strip causes the latter to unfurl along the member.

In the particular electrostatic devices described, the electrode member is a plate and the electrode strip is a metal coated plastic film or a metal foil. This strip is preformed to normally curl into a coil. The outer end of the coiled strip is secured to one side of the electrode plate with electrical insulation between the plate and strip and with the coil curling away from the plate. When the electrode plate and strip are electrified, the strip unfurls across the surface of the plate and then returns to its coiled configuration when the voltage is removed.

This electrostatic device is capable of many diverse uses. Two different devices are described. One is a thermal central louver. The other is a light valve or shutter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section through a thermal control louver according to the invention;

FIG. 2 is a longitudinal section through a light valve according to the invention; and

FIG. 3 is an enlargement of the area encircled by the arrow 3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrostatic device or thermal control louver 10 of FIG. 1 has an electrode member 12 including a flat metal plate 13. The upper surface of this plate is coated with a dielectric film 14. Louver 10 has a second electrode 16 in the form of a relatively thin and elastically flexible strip which may comprise metal coated plastic film, such as aluminized Mylar, or a metal foil. This electrode strip is preformed to normally curl into a coil 18, as shown in full lines. The outer end 19 of the strip is adhesively bonded or otherwise secured to the upper coated surface of the electrode member 12 with the coil 18 curling away from the member.

Louver 10 may be utilized as either a controllable thermal energy radiator for regulating radiant heat transfer from a heat source below the electrode member 12 to a heat sink above the member, as shown in FIG. 1, or as a controllable thermal energy absorber for regulating radiant heat transfer from a heat source above the electrode member to a heat sink below the member. In the case of the radiator, the electrode member 12 has a high thermal emittance and the electrode strip 16 has a low thermal emittance. This low thermal emittance of the strip may be attained by making the strip from a material which has low thermal emittance or by coating the strip with a low emittance material. In the case of the thermal energy absorber, the electrode member 12 has a high thermal absorbance and the electrode strip 16 has a low thermal absorbance.

Louver 10 has an electrifying circuit 20. This circuit includes a d-c voltage source 22 having one terminal connected to the electrode plate 13 and its other terminal connected to the electrode strip 16. A switch 24 is provided for interrupting the circuit and a current-limiting resistor 26 is connected in series with the battery.

When the switch 24 is open, the electrode strip 16 remains in its solid line coiled configuration. Under these conditions, the strip uncovers the upper thermal radiating surface of the electrode member 12 and maximum radiant heat transfer occurs between the heat source and heat sink through the plate.

When the switch 24 is closed, the terminal voltage of the d-c source 22 is impressed between the electrode plate 13 and strip 16. This voltage electrifies the plate and strip with opposite electrical polarity. The resulting electrostatic attraction force between the plate and strip causes the strip to unfurl across the electrode member, as indicated in broken lines in FIG. 1. The strip then covers the electrode member to reduce heat transfer between the heat source and heat sink. Reopening the switch 24 removes the impressed voltage and hence the electrostatic attraction force. The elastic strain energy stored in the electrode strip in its unfurled condition causes the strip to recurl itself to its coiled configuration and thereby restore the radiant heat transfer to its original high value. If desired, the switch 24, when opened to interrupt the electrifying circuit 20, may complete a short circuit path 28 for short-circuiting the electrode plate and strip to rapidly dissipate the charges on the plate and strip. Also, the d-c source 22 may be adjustable to permit unfurling of the strip to and retention of the strip in any selected partially unfurled position, so as to permit finer control of the radiant heat transfer between the heat source and sink.

The electrostatic light valve or shutter 100 of FIGS. 2 and 3 is similar to the thermal control louver just described except for replacement of the metal electrode plate 13 and dielectric film 14 of the louver by an electrode plate 102, dielectric film 104, and intervening electrically conductive film 106 which are transparent to the wavelength of the light to be controlled, and use of an electrode strip 108 which is opaque to such light. The terminals of the electrifying circuit 110 are connected to the electrode strip 108 and the conductive film 106.

When the circuit switch 112 is closed, the electrode strip 108 unfurls across the electrode plate 102 to block passage of light through the plate. Opening the switch permits the strip to recurl to its coiled configuration and permit light passage through the plate. It will be understood that the strip 108 may not be totally opaque to light but only to those wavelengths to the controlled.

Claims

What is claimed as new in support of Letters Patent is:

1. An electrostatic device comprising:

an electrode member;

a relatively thin and resiliently flexible electrode strip secured at one end to said electrode member and having its opposite end portion preformed to normally curl away from said electrode member into a coil;

means electrically insulating said electrode member and strip from one another; and

means for impressing a voltage between said electrode member and strip to cause said coiled end portion of said strip to unfurl along said member.

2. An electrostatic device according to claim 1 wherein:

said electrode member comprises a plate and said electrode strip comprises a thin sheet material such as metal coated plastic film, metal foil or the like.

3. An electrostatic device according to claim 1 wherein:

said device is a thermal control louver;

said electrode member comprises a thermal energy radiator having high thermal emittance; and

said electrode strip has low thermal emittance.

4. An electrostatic device according to claim 1 wherein:

said device is a thermal control louver;

said electrode member comprises a thermal energy absorber having high thermal absorbance; and

said electrode strip has low thermal absorbance.

5. An electrostatic device according to claim 1 wherein:

said device is a light valve;

said electrode member is transparent to light; and

said electrode strip is opaque to light.