GB606147A - Improvements in or relating to electron discharge tubes - Google Patents

Abstract

606,147. Cathode ray tubes. LIEBMANN, G., and CATHODEON, Ltd. Nov. 28, 1945, No. 32128. [Class 39 (i)] The electrode gun assembly of a cathode ray tube comprises a cathode 1, Fig. 3, held in a cylindrical sleeve 2 by means of strips 4 of metal of low heat conductivity ; the sleeve is fastened by tubular rivets 9 to an insulating disc 7 on which is mounted the control electrode 11 which is secured by tubular rivets 13 to the disc 7, and the whole is held together by a metal sleeve 15 having a re-entrant apertured end bearing on the control electrode and an internal cylinder 17 bearing against the underside of the insulating disc 7, to form a unitary structure. Terminal tabs 10, 14 are provided for the cathode and control electrode leads, and the sleeve 15 has projections with a close fit in the envelope. The outer end of the cathode body may be guided in its longitudinal expansion movements by a spider welded to the inside of the sleeve 2, Fig. 6 (not shown). Instead of an indirectly heated cathode, a filamentary cathode 73, Fig. 18, may be used, and is carried by a block 76 secured by strips 75 5 either to the inner side of the sleeve 2 or to a detachable cylinder 88 secured thereto between a stop ring 87 and deformable tabs 89. In modifications, the gun assembly may comprise in addition to the cathode and control grid, first and second anodes, which are disposed alternately with insulating discs such as mica in the form of a stack. One such arrangement is shown in Fig. 8, in which the control electrode 24 with the aperture 25 is in the form of a strip surrounded by an insulating disc 28 and is spaced from the cathode 1 and first anode 35 by stacked insulating discs 19, 21, 29, 32. In this arrangement the apertures for the passage of the electron stream are preferably provided of two dimensions to minimize the formation of a conducting bridge between the electrodes by deposits from the cathode. The insulating discs are also preferably formed with holes such as 34 to reduce capacitative effects. The arrangement in Fig. 14 has the second anode in the form of a tube 61 secured in the envelope by a flanged ring 64 and provided with two stops 63, 66. The tube forms part of the sleeve 60 holding the gun assembly as a unitary structure and bears on the top insulating disc 59 of the stack, which in addition comprises the second anode 57, control electrode 24 and cathode 1 with interposed insulating discs. A further arrangement is described with reference to Fig. 15 (not shown) in which the unitary gun structure comprises the cathode, control grid and first anode; in this case the second anode is formed by an internal coating on the envelope with a tubular electrode electrically connected thereto by a spring contact piece and slidingly fitting in the envelope. Specifications 503,074 and 503,125 are referred to.