GB829815A - An electric switching device - Google Patents

Abstract

829,815. Thermal switches. GENERAL CONTROLS CO. June 28, 1957, No. 20472/57. Class 38 (5). A temperature or other condition responsive means 23 comprises a shell 24 with a flexible wall 26 movable in response to fluid pressure in a temperature-sensing tube 27 and carrying a stud 29 having a shoulder 31 engaging a pivoted lever 32. The lever 32 has ears 38, 39 engaging in a transverse indentation 41, of a further lever 40, against the back of which indentation another lever 67 is urged by a spring 68, so that movement of the lever 32 applies force to both levers 40, 67 on a line between the ears 38, 39. The lever 40 abuts the end 65 of an adjustable temperature setting screw 62 and carries an extension lever 46 pivotable about it at 47 and urged against it by a spring 48 on a pin 51. When the lever 40 is moved in a clockwise direction (Fig. 3) about its pivot abutment 65, under the action of the means 23 acting through the lever 32, the end 55 of the extension 46 operates the pin 56 of a microswitch 57 at a predetermined temperature. Continued movement does not damage the switch since the extension lever can pivot about 47 against the action of the spring 48. The lever 67 moves at the same time as the lever 40 but pivots about its abutment with an adjustable screw 71 to subsequently operate a second micro-switch 74 at a higher temperature. In order that the device may fail to safety if the temperature-sensing element fails and the stud 29 moves to the left (Fig. 2), a strip 76, adjustable by a screw 78, engages the lever 67 which then pivots anticlockwise about the end 77 of the strip to open the switch 74.