Thermostat actuated by an expanding wax capsule and incorporating a safety device

Thermostat actuated by a wax capsule comprising a wax capsule including a casing, a piston, and wax in said casing, which said wax capsule by virtue of relative movement between said casing and said piston caused by thermal expansion of said wax is adapted in normal operation to open a main valve disposed in a fluid circuit immediately after the temperature of said wax capsule exceeds a predetermined first threshold to allow fluid flow through said thermostat, said main valve being closed against fluid flow below said threshold, said thermostat incorporating a safety means adapted not to contribute to the flow of fluid through said thermostat if the temperature is below a second threshold slightly greater than said first threshold but to allow the flow of fluid through the thermostat if the second threshold is exceeded irrespective of the opening of said main valve by said wax capsule, wherein said safety means incorporated in said thermostat includes a moving means made from a single-acting memory alloy for irreversibly moving as a result of a memory of said memory alloy from a first position to a second position at a transformation temperature of said memory alloy approximately equal to said second threshold and which movement thus allows fluid flow through said thermostat.