Piezo-electric actuator operable in an electrolytic fluid

Details Piezo-electric actuator operable in an electrolytic fluid Piezo-electric actuator operable in an electrolytic fluid

2000-06-28

2001-11-13

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S340000

Reexamination Certificate

active

06316864

ABSTRACT:

TECHNICAL FIELD
The present invention relates to piezo-electric actuators, and more particularly, to piezo-electric benders that are operable in electrolytic fluids such as water.
BACKGROUND ART
A common application of piezo-electric actuators is for controlling fluid flow through a valve. Piezo-electric actuators such as benders are typically made from layers of piezoceramic material (such as lead zirconate titanate, for example) stacked between conducting electrodes, typically metal, across which electric potentials are applied for creating electric fields across the piezoceramic layers.
Piezo-electric benders, when used to control fluid flow, are typically isolated from the fluid to prevent corrosion and chemical attack by the fluid on the metal and piezoceramic layers. One failure mode of piezo-electric benders immersed in water is the growth of metallic dendrites through the ceramic layers with subsequent shorting together of the conducting layers. Even if the bender is coated, water may interact corrosively with the coating and cause its breakdown.
Accordingly, it is desirable to develop a configuration permitting a piezo-electric actuator to work immersed in water or other electrolytic fluid.
SUMMARY OF THE INVENTION
The present invention, in one embodiment, is directed to a piezo-electric actuator operable in a fluid. The piezo-electric actuator has an interior electrode and one or more exterior electrodes. Each of the exterior electrodes is kept at a constant electrical potential, while electrical circuitry switches the electrical potential of the interior electrode. A seal is provided surrounding the piezo-electric element that is substantially impermeable to the fluid.
In alternate embodiments of the invention, the constant electrical potential of the exterior electrodes is electrical ground. There may be more than one group of interior electrodes, and a circuit may be provided for applying differential electrical potential between or among the groups.
In accordance with another aspect of the present invention, there is provided a method for activating a piezo-electric actuator that has an interior electrode and one or more exterior electrodes. The method includes the steps of sealing the actuator from the fluid by means of a seal substantially impermeable to the fluid, maintaining the at least one exterior electrode at a fixed electrical potential, and applying an electrical potential to the interior electrode with respect to the at least one exterior electrode. Alternatively, a plurality of exterior electrodes may be provided, with the method comprising sealing the actuator from the fluid by means of a seal substantially impermeable to the fluid, maintaining constant the electrical potential of each exterior electrode, and applying an electrical potential to the interior electrode with respect to the exterior electrodes.


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