Abstract: A bimetal operated latch subassembly (600) for an electrical device such as an overload/switch device which is a self-contained unit that can be mounted into operative position relative to the trippable member (012) of the electrical device. A bimetal assembly (660) and a pair of terminals (604,621) electrically connected thereto are mounted on a main insulating base (601). A vibration and shockproof latch assembly (610) is preassembled on a stainless steel sub-base (611) which is then secured by a single screw (605) to the main base (601) at the same time coupling the bimetal assembly (660) to the latch (610) in operative relationship. The latch (610) is rendered shockproof by providing a spring-biased linear slider (650) that latches to a transversely pivoted latch lever (613). The latch friction that must be overcome by the bimetal (608) is reduced to a minimum by providing the latch lever (613) with an adjustable bias (614,615) that almost balances the tripping force (Y) of the trippable member (012 ).

Abstract: An electrothermal responsive protective mechanism for an electrically powered load wherein the overload tripping force is provided by the cool, ambient temperature compensating bimetal (12) rather than the hot electrically heated bimetal (6) to prevent over-stress. The bimetal members (6,12) are preloaded by a link actuator (22) having a positive temperature coefficient of expansion to minimize unloading of the bimetal members due to ambient temperature change thereby to prevent tripping motion. A screw (16) adjusts the preload and a screw (24) provides a coupling gap in the tripping linkage to prevent shock or vibration propagation therethrough. An insulating base (2) and carrier (14) provide thermal and electrical isolation of the bimetal members. Identical bimetal members (6,12) are used to prevent any actuator motion under ambient temperature changes.