Time delay fuse

Abstract

A time delay fuse comprises an initially open end insulating housing having conductive terminals at the opposite ends thereof, a current-heatable strip connected to one of said terminals, a thermal mass in heat communication with the current-heatable strip and a coil spring and current shunt strip electrically coupled between the current-heatable strip and the other terminal to complete a circuit between the terminals. A heat meltable solder connection is located between said thermal mass and the coil spring and current shunt strip, the spring and current shunt strip being spring urged away from the thermal mass so that upon the melting of the heat meltable solder connection the coil spring and current shunt strip will be pulled away from the thermal mass to break the physical and electrical connection of the coil spring and current shunt strip with the current-heatable strip. The current-heatable strip, thermal mass, coil spring and current shunt strip form a sub-assembly insertable as an untensed unit into an initially open end of the fuse housing before the associated terminal is applied thereto. The coil spring and current shunt strip are suspended from the initially open end of the housing and the rest of the sub-assembly is pushed axially inward thereof to stretch the coil spring. The housing is then deformed permanently inward to engage a portion of the sub-assembly to hold the coil spring in its stretched condition.