Process for installing a shadow mask in a three-colour CRT, and a CRT with a shadow mask installed in such a way

摘要

A thin perforated steel sheet (12), forming the shadow mask of a cathode ray tube, is laid on inner and outer flat thermally insulating supports (40,41) and positioned by dowels (48) engaging slots set at right angles. A framework (14) which will carry the mask in the tube is positioned around the inner support (40) and can be raised and lowered by jacks (47) beneath. A radiant heat source (41) is located in front of the active area (13) of the mask, the framework being temporarily withdrawn. When a precalculated degree of expansion has been achieved in the active area, the jacks lift and support the frame whilst it is spot-welded (60) to an inactive zone (17) of the mask. On cooling, the mask comes under tension in both axes (X,Y) and is ready for installation with its frame in the tube front section.