GB1431275A - Lamp cap connections - Google Patents

Abstract

1431275 Manufacturing electric incandescent and discharge lamps THORN ELECTRICAL INDUSTRIES Ltd 5 June 1973 [6 June 1972] 26398/72 Headings H1F and H1D [Also in Division C7] In a method of making an electric lamp in which a lead-in conductor is sealed through the lamp envelope and terminates outside it, an electrical terminal is provided by disposing the outer end of the conductor in a well having a wall which surrounds the conductor and filling the well with an alloy exhibiting superplasticity; the alloy is then heated to the temperature below its melting temperature at which it behaves superplastically to cause it to flow into a compact mass in intimate contact with the conductor to form at least part of the terminal. As shown in the incandescent filament lamp in Fig. 1 the terminals may be of the Edison screw type with the conductor 13 embedded in a mass of superplastic alloy 19 filling a brass or aluminium ferrule 18 centred in the heat resistant insulating material 20 filling the brass or aluminium cap shell 16. The other lead-in conductor 13a may similarly be affixed to the shell 16 using a mass of superplastic alloy, alternatively it may simply be trapped between the shell 16 and the cement 17 bending the envelope 12 and shell 16. Alternatively the terminals may be of the bayonet type with both terminals formed as for conductor 13 in Fig. 1. In these embodiments the metal ferrule 18 may be dispensed with and the alloy mass 19 formed directly in a hollow well in the insulating material 20. The ferrule 18 of the well in the insulator 20 preferably have re-entrant portions to key the alloy mass firmly in place. Alternatively, Fig. 4, the terminal may be in the form of a pin or post in the form of a metal sleeve 45 filled with superplastic alloy 46 and the embedded conductor 44 has an irregularity 49 at the end thereof to strengthen the joint. The lamp can also be a metal vapour arc discharge lamp, a fluorescent lamp, automobile or projector lamp for example. Preferably the superplastic alloy has the composition 22% by weight aluminium and 78 % by weight zinc and is heated within the range 250-300‹C. to render it superplastic. Other suitable alloys are also listed. The alloy may be heated by focused infra-red radiation and some alloys may require a subsequent heat treatment to prevent its superplastic properties reappearing on heating during service.