Patent ID: 8349020

Claim:
An artificial muscle comprising: a first chamber having a flexible wall of plastics material; a second chamber; a low-boiling-point fluid in the chambers; first valve means for permitting flow of the fluid through the first valve means between the second and first chambers in only a first direction; venting means for permitting the fluid to vent through the venting means between the first and second chambers in a second direction opposite to said first direction, wherein the venting means is a tube allowing the passage of fluid out of the expansion chamber via a controllable restrictor valve and onto a recirculation system; controllable operating means for heating and/or cooling the fluid and for controllably causing fluid to move through the first valve means between the first and second chambers so that at least some of the moved fluid changes state between liquid and gaseous and at least one of: the force of the fluid in the first chamber on the flexible wall changes, and the flexible wall moves to change the volume of the first chamber; and force and/or movement transmitting means for transmitting the force on and/or movement of the flexible wall to a load, wherein the controllable operating means comprises a control unit, wherein the control unit operably connects to (a) the heater element, (b) the controllable restrictor valve, and (c) the recirculation system.