GB1470366A - Electric immersion heaters - Google Patents

Abstract

1470366 Thermal switches OTTER CONTROLS Ltd 13 May 1974 [13 Feb 1973 25 April 1973 28 June 1973 3 July 1973 22 Oct 1973] 21104/74 21105/74 30897/73 31630/73 and 49077/73 Divided out of 1470364 Heading H1N [Also in Division H5] A thermally controlled immersion heater comprises a heating unit H and a clamping unit C, the heating unit H having a flat or dished metal mounting head 2, and the clamping and heating units being mounted on opposite sides of a vessel wall and being clamped around an access aperture therein by a plurality of connecting means 11, 93, 92. As shown, the clamping unit is separate from a thermal switch unit but it may be integral therewith (Figs. 1-4, not shown). The Fig. 1-4 embodiment is also disclosed in copending Specification 1,470,365 which has claims directed to the mounting of the bimetallic snap action actuator on a thermally insulating portion of the switch housing. The immersion heater shown is controlled solely by the element overheating switch S. Switch S comprises a moving contact 34 on a blade 80 which co-operates with trifurcated bimetal 23 via a push rod 78, so that when the element 3 overheats bimetal 23 snaps from contact with convex boss on head 2 and moves the contact 34 away from fixed contact 35. The switch housing 73 is clamped to the head 2 by means of threaded sleeves 93 screwed in to studs 11 of the head 2. The housing 73 fits within the aperture in the vessel wall, a sealing ring 10 surrounding it being compressed by the head 2 against the wall when the clamping unit C is secured to the switch unit S by screwing the bolts 92 into the sleeves 93. The clamping unit C surrounds the switch unit and bears against the vessel walls. In Fig. 7, the switch unit C is clamped to heater H by nuts 114, 115 screwed on to studs 11 of the head 2. Sealing rings 10, 20 are interposed between the vessel wall K and the units C, H. The bimetal actuator 23 is mounted directly on the base 8 of the head 2 by a nut and bolt or by riveting. The fixed contact 35 of the switch is mounted on a cold lead 40 of the heating element 3, and co-operates with moving contact 34 on blade spring 105. A push rod 103 couples the actuator 23 and the moving blade spring 105. An earth terminal pin 111 is welded directly to head 2. A protective shroud is secured to the switch unit S by a bolt 116 engaging in the nut 115. Instead of the connecting means being in the form of studs and nuts, bolts extending through the switch unit and engaging in threaded bosses on the head plate, may be used instead, spring clips may be used instead of nuts. The thermal actuator may be replaced by a float which de-energizes the element at a low liquid level of by a weight operated switch which de-energizes the element when the weight of liquid falls to a predetermined level. The bimetal actuator may be replaced by a vapour capsule or a Curie point device. The immersion heater may have a steam sensitive switch only so that it may be utilized with the kettle described and claimed in copending Specification 1,470,364.