GB648202A - Improvements in or relating to electric switch actuating mechanisms - Google Patents

Abstract

648,202. Actuation of switches; thermal switches. BRITISH THERMOSTAT CO., Ltd. Dec. 15, 1948, No. 32478. [Class 38(v)] A switch-actuating mechanism comprises spring blade 12 held in a bowed, tensioned condition and engaged by an operating member acting along the chord of the arc defined by the blade, such that movements of said member modify the degree of curvature of the blade, and means acting radially of the blade for transmitting movements thereof to a snap-action switch. The mechanism is shown applied to a thermostatically-operated switch. The operating member comprises a thermal element of the rod-and-sleeve, differentialexpansion type, the movable rod 7 of which extends through the wall of a casing 1 in which is mounted the snap-action switch 9 and arms 14 carrying the blade 12 at their ends. One end of the blade engages an abutment 16 and the other the rod 7. Amplified movement of the rod 7 is transmitted from the centre of the blade to the switch arm 9a by a. dolly 17. The differential of the switch may be varied by adjusting the abutment 16 so as to vary the curvature of the blade. Consequent alteration of the location of the switch may be effected by adjustably mounting it in the casing. The blade-tension adjusting means may be coupled to the switch so that the latter follows adjustments of the blade. Alternatively, the switch may be fixed and the dolly adjustable in length, e.g. telescopic, or a series of different size dollys may be used to cover a range of adjustments. Bellows may replace the thermal element shown, or the switch may be operater by a pressure-responsive element. A number of switches may be operated by a common operating member through a crosshead carrying separately-adjustable abutment means.