Piezo-electric actuator operable in an electrolytic fluid

• US 6,118,207 A
• Filed: 11/10/1998
• Issued: 09/12/2000
• Est. Priority Date: 11/12/1997
• Status: Expired due to Term

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Deka Products Limited Partnership
• Inventors: Tipton, Robert R., Ormerod, William
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): MEDLEY, PETER M
• Application Number:
  US09/188,942
• Time in Patent Office: 672 Days
• Field of Search: 310/340, 310/330, 310/331, 310/332, 310/328
• US Class Current: 310/328
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/883 Further insulation means against electrical, physical or chemical damage, e.g. protective coatings

Abstract

A piezo-electric actuator operable in a fluid. The actuator has a piezo-electric element having one or more layers of piezo-electric material and electrodes adjacent to the piezo-electric material, the electrodes being coupled to electrical leads. A conductive layer surrounds the piezo-electric element, serving as a Faraday cage for shielding the fluid from effects due to electric fields within the conductive layer. A seal substantially impermeable to the fluid surrounds the piezo-electric element.

Claims

1. A piezo-electric actuator operable in a fluid, the actuator comprising:

a piezoelectric element having first and second electrical leads;

an electrically grounded conductive layer surrounding the piezo-electric element; and

a seal surrounding the piezo-electric element, the seal being substantially impermeable to the fluid.

2. A piezo-electric actuator according to claim 1, wherein the conductive layer is electrically coupled to one of the first and second electrical leads.

3. A piezo-electric actuator according to claim 1, wherein the conductive layer and the substantially impermeable seal are provided by a single material.

4. A piezo-electric actuator according to claim 1, wherein the conductive layer is enclosed by the substantially impermeable seal.

5. A piezo-electric actuator operable in a fluid, the actuator comprising:

a piezo-electric element;

an electrically grounded shield means for providing electrical shielding around the piezo-electric element; and

sealant means for sealing the piezo-electric element from fluid surrounding the piezo-electric element.

6. A piezo-electric actuator according to claim 5, wherein a single material provides the shield means and sealant means.

7. The piezo-electric actuator according to claim 6, wherein the sealant means seals the shield means from fluid surrounding the shield means.

8. A piezo-electric actuator operable in a fluid, the actuator comprising:

a piezo-electric element having exterior and interior electrodes, the exterior electrodes being electrically grounded; and

a seal surrounding the piezo-electric element, the seal being substantially impermeable to the fluid.

9. A method for activating a piezo-electric actuator for operation in a fluid, the piezo-electric actuator having first and second electrodes, the method comprising:

(a) providing an electrically grounded conductive coating at the exterior of the piezo-electric actuator;

(b) sealing the electrically conductive coating from the fluid by means of a seal substantially impermeable to the fluid; and

(c) applying an electrical potential across the first and second electrodes.

10. A piezo-electric actuator operable in a fluid, the actuator comprising:

a. a top piezo-electric layer having an outward-facing conducting side;

b. a bottom piezo-electric layer having an outward-facing conducting side;

c. a plurality of intermediate piezo-electric layers disposed between the top piezoelectric layer and the bottom piezo-electric layer, each intermediate piezo-electric layer having a piezo-electric side and a conductor side, the top, bottom, and intermediate piezo-electric layers comprising a piezo-electric stack; and

d. a seal surrounding the piezo-electric stack, the seal being substantially impermeable to the fluid,

wherein the outward-facing conducting side of the top piezo-electric layer is maintained at a first constant voltage during operation of the actuator and the outward-facing conducting side of the bottom piezo-electric layer is maintained at a second constant voltage during operation of the actuator.

11. A piezo-electric actuator according to claim 10, wherein the first and second constant voltages are equal.

12. A piezo-electric actuator according to claim 10, wherein one of the first and second constant voltages is ground potential.