GB990575A - Electric switch - Google Patents

Abstract

990,575. Thermal switches; actuation of switches. M. CLAUSEN, [trading as DANFOSS VED. ING. M. CLAUSEN]. May 11, 1961 [May 11, 1960], No. 17271/61. Heading H2B. A snap-action switch having an over-centre tension spring 3 connecting an operating lever 1, pivoted at 2, to a contact-actuating arm 6, pivoted at 7, has an adjustable stop carried on the lever 1 to provide positive actuation of the arm 6 and to act as a back stop limiting the contact gap. The moving contact 9 is carried on a blade spring 8 biased to the closed position wherein contact 9 engages a fixed contact 11. Spring 3 is capable of overcoming spring 8, however, such that the positions shown in Figs. 1 and 4 are stable. Arm 6 engages blade 8 with lost motion by virtue of the turned-over end 13. A tongue 12 on arm 6 is positioned to reduce contact bounce and oscillation of blade 8. In a first embodiment (Fig. 1) the adjustable stop comprises a screw 18 while in the second embodiment (Fig. 4) a lever 15 is pivoted at 14 on lever 1 such that a nose 16 engages the arm 6 in the contacts-open condition while the other end of lever 15 engages an adjusting screw 17 mounted in the switch housing. The switch is operated by a force P which may be provided by an evaporator thermostat, for example. Since in the contacts-closed condition (Figs. 2 and 5, not shown) the spring 3 does not pass below pivot 2, the mechanism tends to restore to the conditions shown. The arrangement is such that if the force P is completely removed a much larger contact gap than normal results.