GB831616A - Improvements in or relating to the manufacture of electric incandescent lamps - Google Patents

Abstract

831,616. Making incandescent electric lamps. GENERAL ELECTRIC CO. Ltd. Aug. 25, 1958 [Aug. 23, 1957], No. 26740/57. Class 39(2) In the manufacture of incandescent electric lamps, a gas flushing is carried out during the process of sealing-in of the filament assembly, the filling of flushing gas being maintained up to the evacuation and filling stage so that re-entry of the external atmosphere is prevented. Further flushing may be effected after the sealing-in of the filament assembly. In an indexing machine for carrying out the process, each head is provided with a rubber gland 43 to receive the stem 44 of the filament assembly 46 below which is a hollow chamber 49 connected by a pipe 53. to a valve consisting of a plate 50 having spaced ports 52 and rotating with the machine, abutting a fixed plate 51 having ports 54 at appropriate positions for connecting the pipe 53 to a supply of flushing gas e.g. clean dry nitrogen, a vacuum pump and a supply of argon. At successive indexing positions the heads are warmed, a filament assembly 46 is loaded, a bulbous envelope is placed over this and the envelope is sealed to the filament assembly by heating, a stream of flushing gas being passed through the stem 44 up to the stage when the sealing-in is nearly complete, the gas escaping through the narrow gap 57 between the assembly and the envelope. Thereafter the sealed envelope is further heated, additionally flushed if desired, evacuated, filled with argon and tipped off, being finally unloaded at the end of its travel. In a modification, the sealing-in is effected on one machine and the envelope then transferred to a second machine for the further stages, being heated during transfer to maintain the pressure of the flushing gas. It is stated that dry air may be used for the primary flushing.