GB775204A - Improvements in or relating to colour television picture display tubes - Google Patents

Abstract

775,204. Colour television tubes. COLUMBIA BROADCASTING SYSTEM, Inc. Nov. 23, 1954 [Dec. 21, 1953], No. 33957/54. Class 39(1). A colour display tube has a shadow mask or colour switching grid adjacent the phosphor screen, the screen and the mask both being curved and being provided with co-operating locating means such as springs with V feet on the mask and projections on the screen, held in engagement by resilient means preferably springs. Since the mask is curved thermal expansion and contraction of the mask does not alter substantially either the registration or the spacing of the mask and screen. In one form, Figs. 1, 4 the shadow mask 13 is located with reference to the tube and wall 12 carrying the tri-colour phosphor dots by three hemispherical glass projections 14 which may be moulded integrally with 12 or cylinders with rounded ends sealed into holes in the surface of 12. The rim 15 of mask 13 has three apertures 16 which receive three springs 17 with V-shaped feet which engage the three projections 14. The mask is also biased by three springs 19 which may or may not be similar to 17 and co-operating with metal spacer protrusions 20. The six springs 17, 19 of laminated steel strips bear against the inner edge of rim 21. The mask and tube end wall 12 are spherically shaped. The protrusions 20 can be replaced by glass pads integral with or attached to the screen 12. The screen 12 and mask 13 can be rectangular instead of circular, Figs. 2, 2A (not shown). In a further embodiment, Fig. 5, a rod 62 is sealed in projection 54 and extends through the vee 61 and carries spring 64 maintained in tension by crosspiece 66 and washers 63, 65. In further modifications, not illustrated (a) the vees may be formed by embossing the mask, (b) the phosphors may be in lines, (c) the masks can be of the shadow or colour switching type and formed as grids or sheets with rectangular apertures. The tube is sealed by welding metal flanges 21, 22 together. U.S.A. Specification 2,690,518 is referred to. A prior art colour receiver is referred to wherein in assembly a shadow mask is laid on a frame member, three slots in the mask resting on three eccentric pins on the frame, a second frame member is placed over the mask, screws are put in but not tightened, the mask is "hot blocked" and the screws tightened so that on cooling the mask is kept flat. The three eccentric fins on the frame have rounded ends which fit in grooves in the phosphor dot plate. The mask assembly is now fastened to three studs 120 degrees apart and carried on an envelope flange, and the decorative mask is snapped in place. The viewing end of the bulb having a similar flange is placed over the decorative mask and the two flanges are sealed together.