Patent GB-739053-A (GB)
Title: Improvements in or relating to the manufacture of electrical devices having sealed envelopes including a tubular glass part
IPC: H01J5/32
Filed: 1952-02-22
Abstract: 739,053. Glass-metal seals. GENERAL ELECTRIC CO., Ltd., BREADNER, R. L., and SIMMS, C. H. Feb. 23, 1953 [Feb. 22, 1952], No. 4750/52. Class 36. [Also in Group XL (a)] The manufacture of a low-pressure mercury vapour fluorescent discharge lamp comprises the steps of forming an end-closure member for at least one end of the tubular glass envelope 33 as a metal disc or cup 1 having a coating 20 of glass sealed thereto on one side and with one or more electrical supply conductors 26, 27 for an electrode 32 insulatingly sealed through glass bushes 30, 31 in holes 6, 7 in the disc or cup, and sealing the end of the envelope to the glass coating 20, the glass coating being presented to the interior of the envelope and the arrangement being such that in the completed lamp, Fig. 4, no part of the surface of the disc or cup 1 is exposed to the interior of the envelope. In the manufacture of the lamp the chrome-iron disc 1 is located on top of a refractory die block 2, carried by a spindle 3 and arranged for rotation about a vertical axis, by a chrome-iron tube 8 passing through a hole 5 in the disc 1. The glass exhaust stem 22, located by an adjustable plunger 24, is sealed to the glass tube 21 before the glass coating 20 is collapsed on the disc 1. The holes 6, 7 in the disc 1 lie over holes 11, 12 formed in the block 2 and communicating with a circumferential recess 13 covered by a stationary ring 14 connected to a pipe 15 through which air can be sucked from or blown into the holes 11, 12. Stops 18, 19 extend across, without blocking, the holes 11, 12 and locate the conductors 26, 27 carrying the glass beads 28, 29 which are inserted through holes blown in the glass coating 20. The beads 28, 29 are melted whilst air is sucked from the pipe 15 and form the bushes 30, 31. The end of the glass envelope 33, coated with fluorescent material, is then brought into abutment or near abutment with the glass coating on the upper surface of the disc 1, the end of the envelope being preformed so as to fit just over and within the rim 4 of the disc 1. The assembly is rotated and the region about the edge of the disc 1 heated to cause the end of the envelope 33 to soften and seal to the glass coating on the disc whilst the disc is advanced slightly towards the envelope 33 so that the rim 4 bites into the wall of the envelope, Fig. 4. A protective atmosphere for the electrode 32 may be provided within the envelope during this step and the axial position of the disc 1 relative to the envelope 33 may be adjusted over a small range. The other end of the glass envelope can be closed in a similar manner or, if an exhaust stem is not required at this other end, the glass parts 20, 21 and 22 can be replaced by a continuous disc of glass. The further manufacture of the lamp can be carried out in known manner, the envelope being finally closed by tipping off the exhaust stem or stems 22 within the well formed by the tube 21, as shown at 35 in Fig. 4. Specifications 340,049 and 415,166, [both in Group XL], are referred to,