Abstract: An electrical interruption device is disclosed in which an overcurrent protective device is provided to interrupt electric current flow on a sustained overcurrent current occurring. The overcurrent protective device is characterized by a plunger which is held in tension against the force of a spring by a low temperature solder, and further in which a sleeve of insulating material, such as silicone, is provided about the plunger. Preferably, the overcurrent protective device includes a housing, with the plunger disposed in the housing and having one end extending therefrom to provide electric communication with the remainder of the electric circuit. The sleeve of insulating material preferably being located about the end of the plunger which extends from the housing. On a predetermined condition causing the solder to melt, the plunger is released and under the force of the spring is moved to a position retracted within the sleeve, interrupting the current flow.

Abstract: An electrical interruption device is disclosed in which a space efficient spiral spring activates current interruption. The spring is characterized by coils which wind continuously about and approach a central axis, with successive coils of the spring having reduced radius to pass axially through the center of an outwardly adjacent coil. The spring may further be made to assume a flat condition with the spring coils lying flat, nesting interposed between adjacent coils. Advantageously, the spiral spring is conical in shape and is tensioned in a reverse loaded configuration wherein the coils of one end of the spring are pulled axially inward, through and past the coils of other end. Preferably the reverse loaded conical spring forms part of a thermally sensitive device which includes a housing having disposed therein a plunger which is in a biased relationship with the spring.