Abstract: The present invention relates to a thermally-controlled actuator device of the type comprising a body, a part held stationary relative to the body by a low-melting point connection material, e.g. brazing or equivalent means, and a mass of exothermic material suitable for acting on command to give off intense heat energy suitable for melting the connection material so as to release the part relative to the body, wherein the exothermic material is housed in a chamber that is subdivided into a plurality of compartments suitable for confining said material in close thermal contact with the wall of the chamber.