Abstract: The invention relates to a temperature responsive control assembly which uses the volumetric expansion of a substance having a high coefficient of expansion, to expel a piston from a cylinder, such movements of the piston relative to the cylinder being used to control relative movements between first and second load elements, such as for example a window and a window frame, with the cylinder being connected to the first load element and the piston being connected by way of a high leverage operating linkage with the second load element, and wherein the thermally expansive substance is located in the cylinder between end plugs and the piston passes through one of the end plugs there being shaft seal means carried by the end plug and sealing around the piston passing through it, the piston having its inboard end immersed in the thermally expansive substance.

Abstract: A temperature responsive device, for example for controlling a ventilator or a valve, is provided which comprises a cylinder containing a substance which expands on being heated, thermal expansion of the substance causing expulsion of a piston rod from the cylinder. The device is characterized in that the piston rod constitutes a primary piston which passes through a central bore of a secondary piston which is movable axially in the bore of the cylinder, and in that there is provided threaded onto one end of the cylinder and surrounding the piston rod a sleeve which serves to limit movement of the secondary piston in one direction, with rotation of the sleeve relative to the cylinder being used to adjust the effective volume of the cylinder.