IMPROVEMENTS RELATING TO THERMALLY RESPONSIVE ELECTRIC SWITCHES

摘要

Steam sensor controls in electrical water heating appliances, such as jugs and kettles, operate to switch off the power supply to the heating element of the appliance when water boils in the appliance. The control operates in a wet environment on account of steam condensing on relatively cold parts of the control and this can lead to electrical arcing across wet surfaces of the control. The control is commonly manufactured using moulded plastics material parts (20, 21, 22) and these can be degraded by arcing and give rise to carbon tracks which progressively degrade the electrical insulation properties of the plastics mouldings and can result in failure of the control. To resolve this problem without need for expensive sealing the invention proposes to continue to utilize moulded plastics material for the major component parts (20, 21, 22) of the control, but to insulate electrical terminal parts (23, 24) of the control from each other by means of ceramics material parts (25) incorporated into the control, preferably as push-fit components which engage with appropriately formed apertures in plastics material components of the control. Ceramics materials are generally not susceptible to carbon tracking when wet.