Electric immersion heating elements and controls therefor

摘要

An element protector unit for an electrically heated water boiling vessel comprises primary and secondary bimetals responsive to the element head temperature and each arranged for actuating a respective one of primary and secondary switching contacts connected in the line and neutral sides of the element supply via respective push rods. The secondary bimetal and associated switch contacts provide back-up protection in the event of failure of the primary protection on account for example of welding of the primary switch contacts. The primary and secondary bimetals are partially overlapped in the element protector unit for correspondingly reducing the combined area they present to the element head, and the element head plate is provided with a double-dimple formation having a first portion adapted to nest with one of the two overlapped bimetals and a second portion adapted to nest with the other bimetal. By virtue of the overlapping of the bimetals and their nesting with the double-dimple formation in the element head a compact arrangement can be achieved conforming to current trend towards a compact element and element head design.