GB528113A - Improvements in or relating to thermostats for operating electric switches - Google Patents

Abstract

528,113. Thermal switches. BRITISH THERMOSTAT CO., Ltd., and SHERLOCK, J. E. April 3, 1939, No. 10358. [Class 38 (v)] [Also in Group XIII] The bulb 4, adapted to be placed in an oven, contains an inert or incondensible gas, such as nitrogen or air, and leads by capillary tube 3 to the back of a diaphragm 5 engaging a pressure pad 6, which bears on a boss 8 controlled by a 'spring 12. The remote end of the latter is removable by a nut 10 which is held against rotation and adjusted by a spindle 11 operated by a knob 14. When the latter is moved from the " off " position, a cam 16 thereon, which co-operates with a fixed stop 17 to limit its rotation, frees the end 33 of a bell-crank lever arm 23, the other arm 21 of which takes in a slot 20 in pad 6, and when the temperature to which the knob is set is attained, movable contact-arms 26 of a creeper-type switch, one on either side of the lever 23 and connected by stirrups 25 to the ends of a transverse rod 24 in the arm, are moved to open the heating circuit, the arrangement being that the contactarms 26 may, if -desired, be separated in turn so as to remove the heating current in stages. The casing 1 is secured by a boss 34 within which is an insulating sleeve 41 apertured longitudinally to pass a pair of leads 40 to contacts 42 engaging, respectively, the base contact and securing clip 44 of an indicating lamp 38 in the knob. This lamp is shunted by a coil and is in series with one or both contact-members 26 so as to be extinguished when the heating circuit is broken.