GB1113748A - Improvements in or relating to electron sources for an electron gun - Google Patents

Abstract

1,113,748. Electron guns. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 19 Oct., 1966 [22 Oct., 1965], No. 46755/66. Heading H1D. An electron source for an electron gun as in a cathode-ray tube for example comprises a perforated, cup-shaped control electrode 2, a cylindrical cathode support 1 with emissive end surface secured to supporting cylinder 4 by a plurality of supporting members 3, annular insulating body 5 surrounding and fixed to the supporting cylinder and having its outer surface secured by fusion or pressure welding for instance, to annular metallic body 6, in turn secured to a plurality of tongues 7 formed in the wall of the control electrode. In this construction the cylindrical faces only of insulator 5 need be metallized for soldering, and also, by suitable choice of angle α, preferably 35 to 60 degrees, in connection with the thermal expansion coefficients of components 1, 2, 3 and 4, the cathode to control electrode distance is near constant over large temperature variations and also the influence of mechanical tolerances in manufacture is minimized; strips 3 may have impressed grooves between bending points, or may be thin wires with depressions at the bending points to reduce the rigidity thereat. Cylinder 8 which may have two, preferably three tongues secured at 20, may be less than 25 Á thick to yield a short heating-up period, its radiation losses preventing excessive heating of the cathode, further reduction being obtained by reducing the cylinder length and blackening the outer surface of cylinder 8, support 1 and inner face of cylinder 4; cylinder 8 also serves as a metal vapour shield. Strips 3 may be of nickel-iron or nickel-iron-molybdenum, cylinder 4 of fernico, insulator 5 of pre-pressed glass, crystallized glass, or fusible ceramic material of 50% by weight of Al 2 O 3 and 50% by weight of an equal parts mixture of CaO and B 2 O 3 .