GB513650A - Improvements in closures for evacuated envelopes - Google Patents

Abstract

513,650. Uniting metal to vitreous material. HYGRADE SYLVANIA CORPORATION. March 25, 1938, No. 9258. Convention date, March 31, 1937. [Class 36] [Also in Group XL] In an evacuated envelope, e.g., an electric discharge tube of the sealed-off evacuated type having a metal body portion with a vitreous closure member, the vitreous member having a rigid metal frame sealed therein in a vacuum-tight manner and sealed to the metal body portion, the body portion is provided with means to support the vitreous member against atmospheric pressure substantially independently of the frame. A cathode-ray tube comprises a frustro-conical metal body 2, Fig. 1, secured by a sealing ring 3 of an alloy having substantially the same coefficient of expansion as glass to an elongated neck 1 of glass. Any known arrangement of electrodes, e.g., that of Specification 502,124, [Group XX], is mounted in the neck. A massive transparent window 7 is provided with a rim 8 sitting in a shoulder 5 of the body portion 2, and is sealed to the body by a thin rigid metal frame 9, which is sealed into the window by the method of Specification 504,934, and which has a flange 10 which is welded, brazed or otherwise sealed to a flange 6 on the body. To prevent gas being trapped between the rim and the seal the rim may be provided with channels or with spacing projections, or the shoulder 5 with spacing projections. In the case of a valve a ceramic base 18, Fig. 6 is sealed to a frame 21, and seats on a shoulder 16 on the metal casing of the valve. A flange 22 on the frame is sealed to a flange 17 on the casing. Metal contact prongs 19 pass through the base 18. The frames 9 and 21 and the sealing ring 3 may be of the alloy sold under the Registered Trade Mark " Kovar " comprising 18 per cent. cobalt, 28 per cent. nickel and 54 per cent. iron, and the flare 4 of the neck 1 is of the glass sold under the Trade name " Corning 705 AJ." The invention may be applied to discharge tubes such as iconscopes and image dissectors and the window may be of any shape and situated on any part of the tube. Specification 505,632, [Group XL], also is referred to. The Specification as open to inspection under Sect. 91 comprises also a method of uniting the conical part 4 of the neck to the ring 3 by moulding the neck about the ring, clamping the assembly in an air tight jig and sealing on the elongated portion 1, or alternatively by mouting a preformed neck in a head stock, and the ring in a chuck and rotating under heat. This subject-matter does not appear in the Specification as accepted.