GB843466A - Improvements in automatic tea-making appliances - Google Patents

Abstract

843,466. Thermal switches; cam-operated switches. RUSSELL, W. M. Nov. 15, 1956 [Nov. 22, 1955], No. 33468/55. Class 38 (5). [Also in Groups VI, XI, XVIII and XXV] A kettle forming part of a teamaking appliance has a removably secured lid part 22 comprising a hollow metal casing containing a ceramic base-plate 35 to support a switch. An immersion heater 29 is connected at one end by metal conductor 48 to socket pin 32 of a twopin plug 31, 32. Socket pin 31 is connected to a metal support 41 secured to plate 35, which carries a resilient contact arm 43 with a contact 44 which co-operates with a fixed contact 45 carried by a support 46 connected by a strip metal conductor 47 to the other end of immersion heater 29. The upper part of a sheath 49, enclosing the immersion heater element, supports one end of a bimetallic strip 51 whose other end carries a small permanent magnet. Magnet 52 co-operates with a mild steel blade 55 carried on one arm of a two-arm lever 54 pivoted on pin 53 whose other arm is insulating and has a toe portion 56 and abutment part 57 which co-operate respectively with arm 43 and an adjustable stop screw 58. Lever 54 is biased clockwise by spring 61 (see Figs. 3 and 4), and has a hub portion which is engaged by the tubular spindle of lever 63. In operation, lever 63 is turned to an " on " position which turns lever 54 until it is held by magnet 52 and lets contact 44 engage contact 45. After the tea has been infused, the temperature in lid 22 rises and the strip 51 straightens out moving lever 54 round until its abutment part 57 engages stop screw 58 when magnet 52 and blade 55 on lever 54 remain in contact until the stress in strip 51 is sufficient to overcome the attraction of magnet 52 when strip 51 and lever 52 move into the position shown in Fig. 4 and the portion 56 operates contact arm 43 to separate contacts 44, 45.