IMPROVEMENTS RELATING TO THERMALLY-RESPONSIVE ACTUATORS

摘要

A steam sensor switch for an automatic kettle employs a snap-acting bimetallic actuator to operate an overcentre arrangement by means of a push rod, the overcentre arrangement comprising a C-spring and a trip lever sprung between spaced-apart abutments. Whereas in prior arrangements of this type the trip lever has been arranged to interact with cantilevered spring contact elements which are mechanically deformed in switch operations, in the steam sensor of the invention the spring contact elements are integrally formed with the C-spring so that they pivot about a fulcrum when the overcentre arrangement switches between its two stable conditions and are not subject to mechanical deformation. This contact arrangement, which makes use of an E-shaped spring having the C-spring as the middle one of its three horizontal strokes, enables greater contact separation to be achieved in a small size switch than does the conventional cantilevered arrangement and thereby enhances electrical safety.