GB1223590A - Method of sealing glass - Google Patents

Abstract

1,223,590. Sealing glass. RCA CORPORATION. 10 Dec., 1968 [12 Dec., 1967 (2)], No. 58594/68. Heading C1M. A tubular glass stem 14 is sealed inside the open end of a tubular glass bulb 12, by positioning stem and bulb coaxially so that their respective walls overlap, reducing the pressure in the annular space so created, and successively heating circumferential segments of the bulb wall to at or above the glass softening temperature whilst maintaining adjacent segments at below the softening point, so that segments of bulb wall collapse on to the stem in succession to form a seal 42, whilst the unsoftened segments maintain the original relative position of bulb and stem. The successive heating of circumferential portions may be achieved by the heating means 32 shown, which comprises a gas manifold 34 in the form of a ring, with a gas burner 40 attached to it. By rotating the ring, the flame from 40 can be directed in turn on segments of the bulb's circumference. The pressure reduction may be achieved by seating the bulb 12 over a passage 31 leading to vacuum pumping equipment. In one use of the method, a vidicon camera tube may be constructed, in which case there is a layer of photo-conductive material 18 on the face-plate 16 of the bulb. Such a layer must be protected from ambient gases, and this is achieved by passing an inert flushing gas (N 2 or Ar) in through tube 70, such that ambient gases are swept by the inert gas out through the vacuum pumping system.