GB599224A - Improvements in or relating to adapters or connectors for use with articles adapted to be heated electrically by means of a heater element incorporated therein - Google Patents

Abstract

599,224. Thermal switches. GAUNT, E. Aug. 29, 1946, No. 24925/45. [Class 38(v)] [Also in Group XXXVI] An adapter for connecting an electrically heated kettle or other appliance with the supply has a part in thermal contact with the appliance and is provided with a thermostatically-operated switch which maintains the temperature of the appliance at a predetermined degree or cuts off the electric supply when the article has reached a predetermined temperature. Fig. 2 shows an adapter having sockets 15 for connection to a kettle &c. and an extension 2A enclosing a spring-loaded shoe 22 which makes thermal contact with the kettle. Two contacts C are carried by spring arms 16, 18 connected respectively to one of the socket terminals 15 and to a terminal screw 19. The leads from the supply are connected to the other socket 15 and the screw 19. The free end of the arm 16 is cranked as shown in Fig. 2 and carries a plunger 17 which passes freely through an opening in the arm 18 and engages in a cam groove 14 in a rotatable knob 5. The shoe 22 is connected to a heat-conducting strip 21 which is secured at 24 to a bimetallic blade 25 carrying an insulating pad 26 which when the blade bends lifts the arm 18 and separates the contacts C. The temperature at which the contacts are separated is determined by the position of the knob 5 which can be locked in any position by rotating a screwthreaded ring 7. In the " off " position of the knob the plunger 17 is at the shallow end of the groove 14 and presses the arm 16 downwards to separate the contacts. The kettle &c. is maintained at the required temperature by the intermittent opening and, closing of the contacts C. In order to interrupt the current if desired when the appliance has reached a predetermined temperature the inner side of the knob is provided with a number of projections 30, 31, 32 situated near the centre of the knob as shown in Fig. 4, and a corresponding number of lugs or stops 33, 34, 35 on the periphery. These projections and lugs co-operate with a pair of ears 36, 37 which as shown in Fig. 5'extend from the free end of the arm 18. The ear 36 projects into the path of the projections 30, 31, 32 and rides over them when the knob 5 is rotated for setting purposes. As shown in Fig. 2 the knob is anchored to one end of a spring 9 which returns the knob to the " off " position when released. Fig. 11 shows the position of the parts when the knob is in the' " off " position. To heat the appliance to a temperature corresponding to any of the three positions of the knob the latter is rotated against the spring 9 thus allowing the plunger 17 to move into a deeper part of the groove 14 under the spring pressure of the arm 16 and causing the contacts C to engage one another. During this rotation of the knob the ear 36 rides over the projections 30, 31, 32 which prevent the return of the knob when released. If.the knob is turned to its fullest extent corresponding to the highest temperature attainable the parts assume the position shown in Fig. 5 in which the projection 32 engages the ear 36. When the appliance has reached the desired temperature the arm 18 is pressed away from the arm 16 by the pad 26, Fig. 2, and the ear 36 releases the projection 32 thus allowing the knob to rotate towards its " off " position under the influence of the spring 9. The rotation of the knob is checked when the stop 35 makes contact with the ear 37. The knob remains stationary while further cooling takes place till the contacts 16, 18 again engage one another when movement of the arm 18 releases the ear 37 from the stop 35 and the knob then continues to rotate till the projection 31 engages the ear 36. This intermittent movement of the knob continues while the projections and stops alternately engage the ears 36, 37 till the knob finally reaches the " off " position.