GB1389477A - Snap-action switch responsive to variations in a physical parameter - Google Patents

Abstract

1389477 Snap-action switches; fluid pressure actuation DANFOSS AS 26 June 1972 [26 June 1971] 29891/72 Heading H1N A pressure or like variable condition responsive snap-action switch comprises a main actuating lever 13 Fig. 3 movable, about pivot 14, between end stops 40, 41 over a dead-centre position of a snap -action arrangement comprising a rigid tilting plate 17 engaged at opposite ends by knife edges 16, 18 respectively arranged on the lever 13 and on a double-ended lever 19 yieldingly urged to load the system by means of a tension spring 24. The lever 19 comprises two separate members 21, 22 pivoted on a fixed pin 20 and coupled at an adjustable abutment 23. The lever 13 is moved by a fluid-pressure bellows 26 acting against an adjustable "rangesetting" compression spring 29. The "differential setting" is adjusted by varying the tension in spring 24 which operates to urge the system to one side or other of the extreme off-centre position. The stops 40, 41 are adjustable in position by screw 39 whereby either the upper or lower extreme positions of lever 13 may be arranged to be near the dead-centre position. The spring adjustment screws 33, 37 are both arranged to pass through apertures in the lever 13. A contact actuator arm (50) Fig. 4 (not shown) projects from the lever 13 between leaf spring supported contacts (45), (46) to move one or other away from opposite sides of a central fixed contact (44). Projections (51) (52) Fig. 2 (not shown) on the spring end plates 35, 38 are visible through apertures (11) (12) in the casing and 32 in an actuator strap 30 to indicate the spring settings. The top of the end-stop adjustment screw 39 is also visible externally to indicate which of the upper or lower positions is nearest to dead-centre.