GB562909A - Improvements in and relating to switching mechanism for electric discharge lamps - Google Patents

Abstract

562,909. Electric supply. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 17, 1943, No. 2610. Convention date, Feb. 26, 1942. [Class 38 (iv)] [Also in Group XXXVII] A switch is adapted to connect, on manual operation, a discharge lamp with a current supply, and at the same time temporarily to close a circuit through the filaments in series to heat them, and is arranged so that on release of the operating button the series connection is broken, to light the lamp. When more than one lamp is used they may be connected with their filaments in parallel, as shown in Fig. 7, or with all filaments in series, Fig. 8 (not shown). Fig. 6 shows the parts of a switch for effecting the operations. On depressing the button 43, a head 47 bears on a contact disc 36, the underside of the head being so shaped that it coacts with cam surface 37 to allow relative rotation in one direction only. The disc 36 bears arcuate contact bars 39, 40. As it descends a helically twisted strip 31 is caused to rotate as it passes through slot 35, turning a bridging contact 27 to snap over stepped contact surfaces 22 while the bars 39, 40 connect contacts 54, 55 and 56, 57 respectively. As shown in Fig. 7, the closing of these contacts will heat the filaments of the two lamps 60, 61 as long as the button is pressed. On releasing the button, springs 42, 51 cause the disc 36 and plunger 43 to rise, breaking the circuits through the filaments. Since the bridging contact 27 has arms 28 that slip over steps 18 on the base, this contact holds helical strip 31 against turning, thus causing disc 36 to turn as it rises so that bars 39, 40 are no longer opposite their respective contacts 54, 55 and 56, 57. The next depression of plunger 43 will now caupe contact 27 to turn clear of contacts 22, thus switching off the lamp. While bars 39, 40 will, on rising again, rotate into position for restarting the lamps on'a subsequent depression.