Patent GB-102221-A (GB)
Title: Improvements in Electric Arc Lamps.
IPC: H01J61/70
Filed: 1916-06-13
Abstract: 102,221. British Westinghouse Electric & Manufacturing Co., (Westing- house Electric & Manufacturing Co.). June 13, 1916. Arc lamps. - Solid electrodes, one of which may move for striking the arc, are enclosed in an hermetically-sealed envelope containing titanium tetrachloride, tungsten tetrachloride, or boron trichloride Vapours of these subs t a n c e s increase luminesity and a r e capable of passing repeatedly through the arc without substantial alteration Halogens may be added to promote stability of the are and to prevent deposits. A suitable atmosphere consists of equal parts of titanium tetrachloride and bromine vapours ; a little chlorine is beneficial. In such a mixture, at a working pressure of 10 cm. of mercury, an arc 4 inches long may be maintained with a pressure of 220 volts and a direct current of 4-15 amperes. Air, water vapour, and other foreign gases should be excluded. The light-increasing compound may be introduced, during exhaustion of the lamp envelope, from a receptacle 18, Fig. 1, provided with a valve operated by a rod 20, the compound flowing into a small bulb 22, whence it volatilizes into the envelope. The envelope is sealed off from the pump and from the receptacle; or the bulb 22 mav be retained with the envelope, to carry a supply of the compound. For the same purpose, charcoal or other porous material capable of absorbing and releasing the compound may be included in the envelope. Two separate receptacles 18 and bulbs 22 may be provided when it is desired to introduce substances which do not mix in a liquid state. Colour-modifying substances may be added in this way. The electrodes may be of hard coke or of tungsten. They may be placed partly within flared silica or the like sleeves to prevent the arc from creeping along their sides. A spring may support the lower electrode within its sleeve to prevent shocks when the upper electrode drops. The upper electrode mav have an axial passage 28, Fig. 3, leading to branch passages 28<a>; a current of vapour is thus produced and steadies the arc. A hood 30 and a sleeve 29 are in this case fitted around the electrode. The upper electrode may be carried bv a rod 7, Fig. 1, connected bv an iron core 8, rod 31, and coiled conductor 12 to a leading-in wire 10. The core 8 is enclosed in a tube of refractory or inert material, sliding within a tubular part of the envelope. Guides 13, 14 surround the rods 7, 31. An external solenoid 9 lifts the core and electrode to strike the arc. A condensing-chamber 32, Fig. 6, may be provided just above the arc-enclosing bulb 2 to maintain this bulb free from deposit. Circulation may be ensured by attaching to the carrier 7 of the upper electrode a flared draught tube 33 surrounding the electrode and opening into the condensing-chamber. In another arrangement, the draught tube is bell-shaped at its lower end and is stationary, its upper end communicating with the uppermost of three condensing- bulbs. Here an outer globe, with an annular cover screening the condensing-bulbs, is provided. A ventilated metal casing surrounds the upper part of the envelope and carries binding-posts connected to clip terminals on the envelope. In another lamp, the upper electrode is attached to a tube enclosing the core at its upper end, and guided by spiders above and below a condensing- bulb, a coiled conductor surrounding the tube is attached to a leading-in wire below the solenoid. Inclined electrodes 55, 56, Fig. 13, may be employed, one carrier being hinged at 57 and supported by a spring 59. The are is then struck by tilting a frame in which the lamp is mounted, or by means of a core 66 and external solenoid 67. An arc deflecting magnet 65 is provided.