GB190006308A - Improvements in Electric Incandescent Lamps. - Google Patents

Abstract

6308. Fessenden, R. A. April 4. Incandescent lamps.-A lamp having an incandescence rod of magnesia, kaolin, or the like, conducting only after preliminary heating, and having either a concave radiating - heater, or a means for applying to the rod a streak of graphite or other conducting-material when the lamp is about to be used, is provided with an automatic electromagnetic switch 41, 26, to connect at first wires carrying a pressure higher than normal to the heater or the incandescence rod, the pressure being lowered as the rod becomes conductive, until eventually it is connected directly to the normal supply wires 32, 36. The rod may otherwise be heated previously by a lamp. Fig. 2 is a diagram of connections for a lamp in which graphite is applied to the rod, the ends of which are connected to wires 24, 24<a>; the parts 26 of the switch, shown separately, are on the axle of a spring-controlled armature 41, movable by an electromagnet 29, the coils of which are included in the supply wire 36. The switch is shown in the starting position, alternating current being supplied from the wires 32,36 to the primary 33 of a transformer, and the secondary 37 of this connected through the switch and wires 24; 24<a> to the incandescence rod. As the current increases, the armature 41 turns into line with the magnet 29, increasing the inductance of this so as to limit the current, until the switch connects the wires 32, 24, 36, 24<a>, and cuts out the transformer. In a lamp with a heater, this is connected directly to the secondary of the transformer, and the switch is arranged to connect the primary directly between the supply wires, at starting, and afterwards disconnect it. The heater is backed with asbestos or other non-conducting material ; the incandescence rod may be supported between fixed and spring-actuated end pins, and is connected between the normal supply wires through the magnet coils.