Temperature compensating insert and integral thermal compensation for a smart material actuator

Abstract

An apparatus can have a smart material actuator, a support structure and at least one temperature compensating material insert, either externally mounted to the support structure, integrally formed with the support structure, or any combination thereof. The structure of the apparatus can be formed of various materials with different Coefficient of Thermal Expansion (CTE). The apparatus can include a mechanically leveraged electrically stimulated smart material. The support structure and actuator can be susceptible to the effects of differences in thermal coefficients of expansion of the materials used in the construction. A method for dimensioning and placement of a compensating insert with respect to the support structure provides an accurate and cost effective compensating insert. Furthermore, a method of compensating for differences in the rate of thermal expansion in one or more elements of an actuator is included with the present invention.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of patent application Ser. No. 10 / 613,138 filed on Jul. 3, 2003, which claimed the benefit of provisional application Ser. No. 60 / 393,799 filed Jul. 3, 2002, and patent application Ser. No. 10 / 993,118 filed on Nov. 19, 2004, which claimed the benefit of provisional application Ser. No. 60 / 523,808 filed Nov. 20, 2003, all of which are incorporated by reference herein in their entirety.FIELD OF THE INVENTION [0002] The present invention relates to a temperature compensating apparatus and method for a mechanically leveraged smart material actuator. BACKGROUND OF THE INVENTION [0003] Various smart material actuator technologies have been developed for a wide range of applications in different industries. One component used in this type of actuator is an electrically stimulated smart material actuator. These smart material actuators when electrically stimulated change shape. This shape change can be...

AI Technical Summary

Benefits of technology

[0013] An apparatus according to the present invention includes a support structure with first and second arms spaced apart from one another. A smart material actuator, such as a piezoelectric actuator, moves the first and second arms with respect to one another in response to expansion and contraction of the actuator. Means for compensating for the effects of different thermal coefficients of expansion of the materials used in the support structure and actuator is provided to reduce or eliminate movement of the arms resulting from variations in working temperature and / or ambient temperature.

Problems solved by technology

This method suffers from several problems.

One such problem is the length of the compensating element inserted between the main body and the smart material increases the overall length of the actuator.

This is a difficult combination to achieve with inexpensive materials.

This system uses several parts, all of which are complex, and costly to machine and increases the overall size making it less desirable.

This difference in CTE between the steel mechanical structure and the CMA will result in a change in the force applied on the amplifying mechanism during a change in ambient temperature conditions.

Such a thermal effect can result in an improper operation of a device, such as the previously mentioned valve, using such an actuating mechanism.

This reduction in stroke or force could cause an associated valve to demonstrate a flow rate that is less than nominal or inadequate sealing force resulting in leaking.

However, it does so with a severe impact to multiple characteristics, for example structural reliability, production complexity and cost.

These will, in turn, limit the potential physical size and work capability.

Therefore, also limiting the applicability of such an approach.

In general, this approach adds substantial complexity and cost to the actuation system.

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