Abstract: A limit sensing device for permanently indicating when a predetermined temperature limit has been reached in a fluid conduit, includes a housing mounted on the conduit in heat transmitting relation with the fluid and an indicator movable in the housing between a retracted position and an activated, non-resettable, extended position to provide a visual indication that the predetermined temperature limit has been reached. The indicator is biased outwardly towards the activated position and a retainer in the form of a separate and discrete annulus formed of fusible material normally secures the indicator in the retracted position within the housing against the force of a biasing spring until the predetermined temperature has been reached causing the retainer to melt or fuse and thereby release the indicator to move outwardly to the extended position providing a visual indication signaling that an overtemperature condition has been reached in the fluid conduit.

Abstract: A thermal switch having contacts with one contact being movably mounted on a carrier and with movement of the carrier controlled by a bimetal actuator disc. The actuating movement is transmitted through a striker pin of molded ceramic material which is fastened in fixed relation to the carrier by a layer of adhesive of controllable thickness to establish the effective length of the striker pin.The method of manufacturing the thermal switch embodies holding of the striker pin in fixed predetermined relation to components of the thermal switch. During movement of the parts to this position, a mass of adhesive carried at an end of the striker pin is pressed between the end of the striker pin and the carrier to provide lateral flow thereof until said pressing is discontinued to provide a controlled thickness layer of adhesive which is then set with the parts held in a predetermined relation.