GB560206A - Improvements in and relating to pressure switch mechanism - Google Patents

Abstract

560,206. Actuation of switches. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 24, 1942, No. 13445. Convention date, Sept. 26, 1941. [Class 38 (v)] In a pressure, temperature or other conditionresponsive switch, the pressure acts through a bellows 51 or other device on a lever 28 mounted in a channel frame and having a finger 30 passing out through a hole in the frame to operate-the switch. The lever 28 acts against the bias of two springs 60, 83, one spring 60 being alone effective as the switch moves into one position but both springs acting additively as the switch moves into its other position. Thus the switch may be opened when the pressure round the bellows exceeds the combined effective pressure due to the two springs and may be closed when the pressure falls below that due to the spring 60. As the pressure round the bellows increases, a pin 50 is moved up and the L-shaped lever 28 rocked about its axis 27 against the pull of the tension spring 60. After a little movement a projection 78 on the lever 28 engages the L-shaped lever 75 which has been resting against a stop, and rocks it about its axis 76 against the pull of the spring 83. The sideways projection 30 on the lever 28 eventually moves a snap action switch " off." The springs 60, 83 are adjustable by four screws at their ends, two of these screws being for factory adjustment. One of the other screws 66 determines the position of the R.H. end of the spring 60 and of a pin 62a fixed to a scale 70 which moves relatively to a fixed pointer and so indicates the pressure of the spring 60. The remaining screw 87 determines the position of the L.H. end of the spring 83 and of a pin 90 which co-operates with the - scale 70 to indicate the sum of pressure due to the two springs 60, 83.