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.

1 . A temperature compensating apparatus comprising: 
 a support structure having at least one coefficient of thermal expansion;    an actuator having a coefficient of thermal expansion different than the coefficient of thermal expansion of the support structure, the actuator operably associated with the support structure; and    means, interacting with the support structure, for compensating for different coefficients of thermal expansion of materials used in the support structure and the actuator in response to variations in temperature over a predetermined operating temperature range.    
   
   
       2 . The apparatus of  claim 1 , wherein the temperature compensating means comprises: 
 at least one compensation member operably associated with the support structure, the compensation member made from a material having a different coefficient of thermal expansion relative to the support structure such that the compensation member exerts a force on the support structure in an opposite direction from any deflection force inherent in the support structure caused by a change in ambient temperature.    
   
   
       3 . The apparatus of  claim 1 , wherein the temperature compensating means further comprises: 
 bimaterial layers forming at least a portion of the support structure and spaced from the actuator, a first material layer made from a material having a different coefficient of thermal expansion relative to a second material layer such that the bimaterial layers exert a force with respect to the support structure to deflect the support structure in an opposite direction from any deflection caused by a change in ambient temperature.    
   
   
       4 . The apparatus of  claim 1 , wherein the temperature compensating means further comprises: 
 the support structure formed of a first material having a different coefficient of thermal expansion relative to a temperature compensating member formed of a second material such that the two different materials exert opposing forces on one another in response to changes in ambient temperature.    
   
   
       5 . The apparatus of  claim 4 , wherein the opposing forces are sufficient to limit temperature-induced movement of the support structure caused by differences in the coefficients of thermal expansion of the actuator material and the support structure material to no greater than ± seven percent of total movement of the support structure.  
   
   
       6 . The apparatus of  claim 1 , wherein the support structure further comprises: 
 at least one arm portion pivotally extending from a side portion through an integrally formed hinge portion located between the side and arm portions.    
   
   
       7 . The apparatus of  claim 6 , wherein the at least one arm portion folds back over the respective side portion.  
   
   
       8 . The apparatus of  claim 6 , wherein the temperature compensating means further comprises: 
 the at least one arm of the support structure formed of a first material having a different coefficient of thermal expansion relative to a temperature compensating insert associated with the at least one arm and formed of a second material such that the two different materials exert opposing forces on one another in response to changes in ambient temperature.    
   
   
       9 . The apparatus of  claim 8 , wherein the opposing forces are sufficient to limit temperature-induced movement of the at least one arm of the support structure caused by differences in the coefficient of thermal expansion of the actuator material and the support structure material to no greater than ± seven percent of total movement of the at least one arm of the support structure.  
   
   
       10 . The apparatus of  claim 1 , wherein the support structure further comprises: 
 at least one arm portion having first and second outwardly extending ends with respect to an integrally formed hinge portion; and    at least one temperature compensating member located along each outwardly extending end of the at least one arm.    
   
   
       11 . The apparatus of  claim 1  further comprising: 
 means for preloading the actuator with a compressive force.    
   
   
       12 . The apparatus of  claim 11 , wherein the preloading means further comprises: 
 a screw threadably engagable with a threaded aperture formed in a rigid, non-flexing web portion of the support structure, the screw adjustably transmitting a preload force to the actuator.    
   
   
       13 . The apparatus of  claim 11  further comprising: 
 an adjustment seat having a fourth coefficient of thermal expansion different from the first, second and third coefficients of thermal expansion, the seat for focusing a preload force on the actuator, the adjustment seat having a curved surface for distributing the preload force to the actuator as only a compressive force while simultaneously compensating for differences in coefficients of thermal expansion values between the actuator and the support structure.    
   
   
       14 . The apparatus of  claim 1  wherein the support structure further comprises: 
 a first rigid portion engagable with an opposite end of the actuator from a second rigid portion; and    complementary opposing surfaces formed on the first and second rigid portions for engagement with one another during assembly of the support.    
   
   
       15 . The apparatus of  claim 14  further comprising: 
 the complementary opposing surfaces allowing assembly of the structure with sliding engagement in a direction nonparallel with respect to a longitudinal axis of the actuator.    
   
   
       16 . The apparatus of  claim 14  further comprising: 
 the complementary opposing surfaces allowing assembly of the structure with sliding engagement in a direction perpendicular to the longitudinal axis of the actuator.    
   
   
       17 . The apparatus of  claim 1  further comprising: 
 an adjustable seat for one longitudinal end of the actuator supported by one of the rigid portions, such that preload force applied to the actuator maintains the first and second rigid portions in an assembled position with respect to one another.    
   
   
       18 . The apparatus of  claim 1  further comprising: 
 at least one pair of complementary opposing surfaces located on at least one interface between a first and a second rigid portion of the support structure, the pair of opposing surfaces interlockable with one another to form a rigid non-flexing receptacle for operably supporting the actuator therein.    
   
   
       19 . The apparatus of  claim 1  further comprising: 
 at least one pair of complementary opposing surfaces located on at least one interface between a first and a second rigid portion of the support structure, the pair of opposing surfaces defining an aperture for receiving at least one fastener for operably connecting the first and second rigid portions with respect to one another to define a rigid non-flexing receptacle for receiving the actuator therein.    
   
   
       20 . The apparatus of  claim 19  further comprising: 
 the first and second rigid non-flexing portions of the support formed of a nonhomogeneous material in a single unitary monolithic member.    
   
   
       21 . A temperature compensating apparatus comprising: 
 a support structure having at least one coefficient of thermal expansion and at least one arm;    an actuator having a coefficient of thermal expansion different than the coefficient of thermal expansion of the support structure, the actuator operably associated with the support structure;    at least one temperature compensating insert associated with the at least one arm and formed of a second material having a different coefficient of thermal expansion than the support structure, such that the coefficients of expansion exert opposing forces on one another in response to changes in ambient temperature; and    means, interacting between the actuator and the support structure, for compensating for different coefficients of thermal expansion of materials used in the support structure and the actuator in response to variations in temperature over a predetermined operating temperature range.