GB1434552A - Manufacture of small bulbs - Google Patents

Abstract

1434552 Making electric bulbs HAMAI DENKYU KOGYO KK 20 July 1973 [31 July 1972 (2) 28 Aug 1972 (2)] 34645/73 Heading C1M Small electric light bulbs, which consist of a bead 3 mounted on a pair of lead wires 1, 2 with an envelope 7 sealed to the bead, are produced by assembling the bead 3 and envelope 7 on a carbon jig 5 so that the bead is located within the jig, placing the carbon jig 5 in a container; evacuating the container; and heating the carbon jig 5 to seal together the bead 3 and envelope 7. In one embodiment the carbon jig is heated by passing an electric current therethrough. The jig is mounted in a thermally insulated box which is in turn mounted in a vacuum chamber. The box is lined with insulating sintered plates 27 and molybdenum or stainless steel reflectors 28, the latter sensing to reflect thermal radiation back on to the jig 5. In a second embodiment the jig 38 is heated by means of infra-red heaters 43. The heaters 43 and jig 5 are mounted within a single evacuatable container 36, 37 provided with internal infra-red reflectors. In both embodiments the jig is initially heated to a temperature below the sealing temperature to induce the generation of impurity gases from the container which may then be evacuated, the temperature is then raised to a valve close to the sealing temperature and finally after elimination of impurity gases further raising the temperature to bring about sealing. After sealing the container is cooled by the introduction of nitrogen.