Wound piezoelectric polymer flexure devices

• US 4,330,730 A
• Filed: 03/27/1980
• Issued: 05/18/1982
• Est. Priority Date: 03/27/1980
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Lee, J. Kelly, Kurz, Warren W.
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US06/134,404
• Time in Patent Office: 782 Days
• Field of Search: 310/330-332, 310/800
• US Class Current: 310/331
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/506 having a cylindrical shape and having stacking in the radial direction, e.g. coaxial or spiral type rolls
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

Disclosed herein is a piezoelectric flexure device in which the piezoelectric element(s) thereof comprises a flexible piezoelectric layer (e.g. a suitably polarized polymeric film) which is tightly wound about an axis to produce a plurality of substantially concentric layers of piezoelectric material. Positioned between adjacent piezoelectric layers are conductive layers which function as electrodes for either applying an electric field across the piezoelectric layers to cause the device to flex, or for detecting the electrical potential produced in the device as a result of subjecting the piezoelectric element to a mechanical stress. Owing to the wound nature of the piezoelectric element, the device is relatively simple to manufacture and the conductive layers are less apt to crack or break during the manufacturing process. Also disclosed herein are techniques for producing such piezoelectric flexure devices.

Claims

1. In a piezoelectric flexure device comprising a piezoelectric element having means coupled thereto for causing the device to flex in response to subjecting the piezoelectric element to an electric field, the improvement wherein said piezoelectric element comprises a light-weight flexible, elongated mandrel having a generally rectangular cross section with rounded corners, a flexible piezoelectric film which is wound about said mandrel to form a plurality of generally concentric piezoelectric layers free from sharp bends or folds, and electrode means positioned between adjacent concentric layers for producing an electric field across each of said layers upon being connected to a voltage source.

2. The flexure device as defined by claim 1 wherein said mandrel comprises polyurethane foam.

3. The flexure device as defined by claim 2 wherein said flexible piezoelectric layer comprises polyvinylidene fluoride.

4. The flexure device as defined by claim 1 wherein said electrode means comprises conductive coatings, supported by opposing sides of said piezoelectric layer and said device further comprises means for electrically isolating the coatings borne by opposing sides of said piezoelectric layer.

5. The flexure device as defined by claim 1 further comprising an adhesive means supported by said electrode means for bonding said adjacent layers together.

6. The flexure device as defined by claim 1 wherein said means for causing said device to flex comprises a second piezoelectric element.

8. The flexure device as defined by claim 6 wherein said mandrel comprises polyurethane foam.

9. The flexure device as defined by claim 6 further comprising bonding means for bonding said concentric layers together.

7. A piezoelectric flexure device comprising an elongated piezoelectric element having means coupled thereto for causing the device to flex in response to subjecting the piezoelectric element to an electric field, characterized in that said piezoelectric element comprises a light-weight, flexible, elongated mandrel having a generally rectangular cross section with rounded corners, and two flexible films of piezoelectric material, each of said films being unidirectionally polarized and having flexible electrodes disposed on opposing surfaces, said films being positioned juxtaposed so that their respective poling directions are opposed, and being wound together about said mandrel which is generally parallel to the longitudinal axis of the elongated piezoelectric element to form a plurality of generally concentric piezoelectric layers free from sharp bends or folds.

10. A piezoelectric flexure device comprising (a) an elongated piezoelectric element which is adapted to experience dimensional changes when subjected to a changing electric field, and (b) means for resisting such changes to produce changes in shape of the flexure device, characterized in that said piezoelectric element comprises a first light-weight, flexible, elongated mandrel having a generally rectangular cross section with rounded corners, a flexible layers of piezoelectric material which has been polarized unidirectionally, said layer having electrically conductive layers disposed on opposing surfaces, and being folded along a line intermediate its ends over said first mandrel, and a second light-weight, flexible, elongated mandrel having a generally rectangular cross section with rounded corners, said folded layer being wound about said second mandrel generally parallel with said line to produce a plurality of generally concentric layers free from sharp bends or folds.

11. The flexure device as defined by claim 10 wherein said first and second mandrels comprise polyurethane foam.

12. The flexure device as defined by claim 10 further comprising bonding means for bonding said concentric layers together.