Importance

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Abstract

A variable resistance device comprises an inner elongate, flexible electrode having a longitudinal central axis, at least one outer electrode spaced from the inner electrode and at least partially or completely surrounding the inner elongate electrode to form a gap therebetween. The outer electrode has a longitudinal axis that is at least substantially coaxial with the central axis of the inner elongate electrode. An electroviscous fluid is positioned in the gap between the inner and outer electrodes. An electric field applied to the electroviscous fluid between the inner and outer electrodes causes an increase in the stiffness of the device. In one embodiment of the invention, the outer electrode is also flexible to form a flexible resistance device, the stiffness of which can be controlled by the application of the electric field. In a further embodiment, an enclosed chamber is filled with an electroactive fluid and a piston assembly is mounted for reciprocal movement in the chamber. The piston assembly includes a piston head that divides the chamber into separate chamber portions. At least one bore extends through the piston and is in fluid communication with the chamber portions. An inner surface of the bore forms the outer electrode, while the inner electrode, which may be flexible or stiff, extends coaxially through the bore. When an electric field is applied to the electrodes, electroactive fluid in the bore increases in apparent viscosity and resists movement of the piston in the fluid. A plurality of bores of different diameters may be provided to control the desired amount of damping. The inner electrodes need not be present in all of the bores.

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First Claim