GB1354601A - Lamps - Google Patents

Abstract

1354601 Glass to metal seals THORN ELECTRICAL INDUSTRIES Ltd 28 April 1972 [14 April 1971 26 May 1971] 9400/71 and 17290/71 Heading C1M [Also in Division H1] In making a lamp, a filament or electrode assembly 12 having lead-in conductors 14 with molybdenum foils 16 is inserted into a vitreous tube 10 and jaws 24, 26, Fig. 5, are applied to the tube to form two pinch seals simultaneously around the lead-in conductors on respective sides of the assembly 12, the jaws being shaped, e.g. as at 32, to leave remaining through at least one of the seals a passage 22 which is relatively narrow compared with the size of the tube, the atmosphere in the tube is then adjusted through the passage and finally the passage is closed. The whole of the tube 10 may be heated during the forming of the pinch seals and a gas under pressure may be introduced into the tube to mould it to fill out a central cavity 28 in the jaws thus forming accurately dimensioned bulb shapes. The tube 10 may be flushed with clean gas as the seals are formed, and a hypodermic needle inserted into passage 22 may effect dosing with halogen in solvent, or mercury or gas flushing prior to the exhaust or filling operation. Initially the tube envelope 10 may be closed at one end which contains solid or liquid filling components, e.g. a metal halide for an iodide discharge lamp. The two pinch seals are formed with the passage 22 extending through the seal nearest the closed end which is subsequently heated to drive the filling elements into the tube. After sealing passage 22 the tube is broken off at the pinch seal. Incandescent sealed beam automobile lamps or projector lamps, and mercury or xenon compact source discharge lamps may be made by this method.