Patent ID: 7647771

Claim:
A thermally driven piston assembly, comprising: a housing having a hollow portion that remains rigid throughout a temperature range of interest; a viscoelastic material slidingly fitted in said hollow portion such that said viscoelastic material is limited to movement along a single dimension of said hollow portion, said viscoelastic material undergoing at least one of a stiffness change and a dimensional change along said single dimension when subjected to a temperature change in said temperature range of interest, said viscoelastic material possessing and retaining viscoelastic properties throughout said temperature range of interest; at least one a plug of a second material slidingly fitted in said hollow portion adjacent said viscoelastic material, said second material being rigid and retaining its shape and size throughout said temperature range of interest; first means for measuring an amount of movement of said plug along said single dimension when said viscoelastic material is experiencing isothermal conditions, wherein said amount of movement is measured relative to a setpoint; and second means coupled to said first means for controlling said temperature change to negate said amount of movement wherein said plug returns along said single dimension to said setpoint.