Electrical generator or motor structure – Non-dynamoelectric – Charge accumulating
Reexamination Certificate
2001-11-15
2003-06-24
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Charge accumulating
C310S363000, C310S800000
Reexamination Certificate
active
06583533
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/144,556 filed Jul. 20, 1999, naming R. E. Pelrine et al. as inventors, and titled “High-speed Electrically Actuated Polymers and Method of Use”, which is incorporated by reference herein for all purposes; it also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/153,329 filed Sep. 10, 1999, naming R. E. Pelrine et al. as inventors, and titled “Electrostrictive Polymers As Microactuators”, which is incorporated by reference herein for all purposes; it also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/161,325 filed Oct. 25, 1999, naming R. E. Pelrine et al. as inventors, and titled “Artificial Muscle Microactuators”, which is incorporated by reference herein for all purposes; it also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/181,404 filed Feb. 9, 2000, naming R. D. Kornbluh et al. as inventors, and titled “Field Actuated Elastomeric Polymers”, which is incorporated by reference herein for all purposes; it also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/187,809 filed Mar. 8, 2000, naming R. E. Pelrine et al. as inventors, and titled “Polymer Actuators and Materials”, which is incorporated by reference herein for all purposes; and it also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/192,237 filed Mar. 27, 2000, naming R. D. Kornbluh et al. as inventors, and titled “Polymer Actuators and Materials II”, which is incorporated by reference herein for all purposes; this application is also a continuation in part of co-pending U.S. Patent Application entitled “Elastomeric Dielectric Polymer Film Sonic Actuator” naming R. E. Pelrine et al. as inventors, filed on Jul. 19, 1999 (U.S. Application Ser. No. 09/356,801), which is a continuation and claims priority from PCT/US98/02311 filed Feb. 2, 1998, which claims priority from U.S. Provisional Application Number 60/037,400 filed Feb. 7, 1997, all of which are incorporated by reference herein.
This invention is related to U.S. patent application Ser. No. 09/620,025, filed on the same day as this patent application, naming R. Pelrine et al. as inventors. That application is incorporated herein by reference in its entirety and for all purposes.
This invention is also related to U.S. patent application Ser. No. 09/619,846, filed on the same day as this patent application, naming R. Pelrine et al. as inventors. That application is incorporated herein by reference in its entirety and for all purposes.
This invention is also related to U.S. patent application Ser. No. 09/619,848, filed on the same day as this patent application, naming R. Pelrine et al. as inventors. That application is incorporated herein by reference in its entirety and for all purposes.
This invention is also related to U.S. patent application Ser. No. 09/619,845, filed on the same day as this patent application, naming R. Pelrine et al. as inventors. That application is incorporated herein by reference in its entirety and for all purposes.
This invention is also related to U.S. patent application Ser. No. 09/619,847, filed on the same day as this patent application, naming Q. Pei et al. as inventors. That application is incorporated herein by reference in its entirety and for all purposes.
BACKGROUND OF THE INVENTION
The present invention relates generally to electroactive polymers that convert from electrical energy to mechanical energy. More particularly, the present invention relates to pre-strained polymers and their use in actuators and various applications. The present invention also relates to compliant electrodes used to electrically communicate with electroactive polymers and methods of fabricating pre-strained polymers.
In many applications, it is desirable to convert from electrical energy to mechanical energy. Exemplary applications requiring translation from electrical to mechanical energy include robotics, pumps, speakers, general automation, disk drives and prosthetic devices. These applications include one or more actuators that convert electrical energy into mechanical work—on a macroscopic or microscopic level. Common electric actuator technologies, such as electromagnetic motors and solenoids, are not suitable for many of these applications, e.g., when the required device size is small (e.g., micro or mesoscale machines). These technologies are also not ideal when a large number of devices must be integrated into a single structure or under various performance conditions such as when high power density output is required at relatively low frequencies.
Several ‘smart materials’ have been used to convert between electrical and mechanical energy with limited success. These smart materials include piezoelectric ceramics, shape memory alloys and magnetostrictive materials. However, each smart material has a number of limitations that prevent its broad usage. Certain piezoelectric ceramics, such as lead zirconium titanate (PZT), have been used to convert electrical to mechanical energy. While having suitable efficiency for a few applications, these piezoelectric ceramics are typically limited to a strain below about 1.6 percent and are often not suitable for applications requiring greater strains than this. In addition, the high density of these materials often eliminates them from applications requiring low weight. Irradiated polyvinylidene difluoride (PVDF) is an electroactive polymer reported to have a strain of up to 4 percent when converting from electrical to mechanical energy. Similar to the piezoelectric ceramics, the PVDF is often not suitable for applications requiring strains greater than 4 percent. Shape memory alloys, such as nitinol, are capable of large strains and force outputs. These shape memory alloys have been limited from broad use by unacceptable energy efficiency, poor response time and prohibitive cost.
In addition to the performance limitations of piezoelectric ceramics and irradiated PVDF, their fabrication often presents a barrier to acceptability. Single crystal piezoelectric ceramics must be grown at high temperatures coupled with a very slow cooling down process. Irradiated PVDF must be exposed to an electron beam for processing. Both these processes are expensive and complex and may limit acceptability of these materials.
In view of the foregoing, alternative devices that convert from electrical to mechanical energy would be desirable.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to polymers that are pre-strained to improve conversion between electrical and mechanical energy. When a voltage is applied to electrodes contacting a pre-strained polymer, the polymer deflects. This deflection may be used to do mechanical work. The pre-strain improves the mechanical response of an electroactive polymer relative to a non-strained polymer. The pre-strain may vary in different directions of a polymer to vary response of the polymer to the applied voltage.
In another aspect, the present invention relates to actuators comprising an electroactive polymer and mechanical coupling to convert deflection of the polymer into mechanical output. Several actuators include mechanical coupling that improves the performance of an electroactive polymer.
In yet another aspect, the present invention relates to compliant electrodes that conform to the changing shape of a polymer. Many of the electrodes are capable of maintaining electrical communication at the high deflections encountered with pre-strained polymers of the present invention. In some embodiments, electrode compliance may vary with direction.
In another aspect, the present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers. Pre-strain may be achieved by a number of techniques such as mechanical
Joseph Jose P.
Kornbluh Roy D.
Pei Qibing
Pelrine Ronald E.
Beyer Weaver & Thomas LLP
Dougherty Thomas M.
SRI - International
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