GB1304085A - - Google Patents

Abstract

1304085 Fluid actuation of switches AUTOMOTIVE PRODUCTS CO Ltd 23 July 1971 [1 Sept 1970] 41824/70 Heading H1N A fluid pressure operated electric switch comprises a plunger 35, Fig. 1, acting against resilient means 36, fixed contacts 18, 19, 20, a flexible bridging moving contact 27 (a helical compression spring) permanently in contact with fixed contact 18 and operable by plunger 35 from a position where it is out of engagement with fixed contacts 19, 20, to complete a circuit with firstly contact 19 and subsequently contact 20. The object is to indicate pressure decrease. When the pressure decreases, plunger 35 moves to the left from the switch open position followed by insulating member 28 which has a shoulder engaging spring 27, which shoulder is inclined to the longitudinal axis of the switch so that portion 33 of the shoulder is further from fixed contact 18 than portion 34. Consequently as plunger 35 moves to the left, spring 27 expands and the portion of spring 27 abutting shoulder portion 33 engages fixed contact 19 before the portion of spring 27 abutting shoulder portion 34 engages fixed contact 20. In a second embodiment, Fig. 2, the flexible moving contact 66 (not a spring) is a tapering helix, the larger end of which is permanently in contact with fixed contact 52 and the smaller end of which completes a circuit with firstly fixed contact 59 and subsequently fixed contact 53. In the normal pressure state, plunger 70 is to the right of the position shown with secondary metal plunger 62 to the right and insulating sleeve 68 under the action of compression spring 69 holding the smaller end of helix 66 to the right away from contact 53 and with the head 64 of secondary plunger 62 to the right out of contact with the smaller end of helix 66. As the pressure decreases, plunger 70 moves to the left, secondary plunger 62 moves to the left under the action of compression spring 65 and head 64 engages the smaller end of helix 66 completing a circuit between helix 66, head 64 and spring 65 to fixed contact 59. As plunger 70 moves further to the left, head 64 moves the smaller end of helix 66 against the action of spring 69 to the left to engage fixed contact 53.