Current interrupt apparatus for electrochemical cells

Electrically conductive end cap apparatus for use with an electromechanical cell comprising an electrically conductive header having a rigid, circumferential flange extending about the periphery thereof, a switch cavity formed in, the header,

• a stationary electrical contact mounted within the switch cavity electrically connected to the header,
• a generally annular insulative member received in the switch cavity, the annular insulative member having a disc seat,
• an electrically conductive spring member having a movable contact portion movable into and out of electrical engagement with and normally biased into engagement with the stationary contact,
• a snap acting thermostatic disc having first and second oppositely dished configurations and having a centrally disposed aperture, the disc being received on the disc seat, the stationary electrical contact aligned with the centrally disposed aperture, the stationary contact extending through the centrally disposed aperture when the disc is in one of the first and second configurations, the disc biasing the movable contact away from the stationary contact when in the other of the first and second configurations,
• an electrically conductive top cap having an outer periphery supported on the annular insulative member and electrically connected to the spring member, the header having a peripherally extending lip deformed over to fixedly grasp the outer peripheral portion of the top cap with a portion of the insulative member therebetween to electrically separate the header from the top cap, the top cap having vent holes formed therethrough,
• the header having a thin diaphragm extending across the switch cavity formed with a frangible portion aligned with the switch cavity, the frangible portion being breakable when exposed to a selected pressure, the diaphragm being snap-acting when exposed to sufficient increase in pressure up to the selected pressure;
• and
• and electrically insulative motion transfer member movably mounted in the switch chamber between the diaphragm and the spring member and having a length selected so that an increase in pressure above a given level will cause the diaphragm to snap to transfer motion to the spring member via the motion transfer member so as to move the movable contact out of engagement with the stationary contact.