GB1139748A - Colour kinescopes - Google Patents

Abstract

1,139,748. Colour television tubes. RADIO CORPORATION OF AMERICA. 28 June, 1966 [16 July, 1965], No. 29057/66. Heading H1D. The shadow mask of a colour cathode ray tube is supported from the envelope by a flexible mounting arrangement, including a leaf spring positively connected to both the envelope and the mask electrode, such that as the shadow mask expands outwardly on being heated by electron bombardment it is caused to move towards the screen sufficiently to maintain substantial alignment of the apertures in the mask electrode with the elemental phosphor areas of the screen. In one form, Figs. 3, 4, the mounting arrangement comprises an L-shaped leaf-spring 19 which has short leg 19a welded to side 12a of the shadow mask support 12 and a hole 19d in leg 19b pivotably engaging a stud 17 of the envelope 9. Portion 19a of the leafspring, at least, is formed of bi-metallic strip which when heated curls in the direction of arrow 27, (Fig. 3); this causes the hole 19d to move in the direction of arrow 29 which, because of reaction with stud 17, causes the mask electrode to move in the opposite direction towards the screen face. In a modification, Figs. 10, 11 (not shown), the leaf spring is pivotably secured to both the envelope and mask and one end of a separate bi-metallic strip is secured to the mask support and the other end secured to the edge of the leaf spring. In this modification the bi-metallic strip may be replaced by a wedge welded to the flange with an oblique face abutting the edge of the leaf spring, Figs. 12, 13 (not shown). Alternatively, Fig. 16, the leaf spring may comprise a bi-metallic strip 21 with an expansion loop 21c which bows in the direction of arrow 27 when heated, and which, as before, causes a reaction at stud 17 which moves the mask towards the screen. In a further embodiment, Fig. 8, the resilience of the leaf spring itself provides the force that moves the mask towards the screen. The leaf spring comprises two substantially parallel end portions 41a, 41b, affixed to the mask and envelope respectively, which are interconnected by an oblique portion 41d disposed at an acute angle to both parallel portions. Four mounting arrangements, one at the midpoint of each side of the screen, are generally employed, however, three mountings may be used-one at the mid point of a long side and the other two an opposite short sides three-quarters of the way towards the other long side. When only three are used the lower two mountings are of the type described with reference to Fig. 8, modified in that the whole of the leaf spring is set at an angle to the plane of the shadow mask, Fig. 15 (not shown), to compensate for unequal movements in the plane of the shadow mask. Reference has been directed by the Comptroller to Specification 811,936.