1327364 Cathode-ray tubes RCA CORPORATION 6 Dec 1971 [7 Dec 1970] 56603/71 Heading H1D A cathode ray tube comprises an envelope with a rectangular faceplate with a phosphor screen and funnel portion of truncated pyramidal shape, and a funnel shaped internal magnetic shield 35 of truncated pyramidal geometry and made of four trapezoidal pieces of magnetic sheet metal attached along their non-parallel sides. The shield screens electron beams from stray magnetic fields such as the earth's field, and eliminates misregister of beam spots and colour phosphor elements such as in shadow mask type TV picture tubes and with high deflection angles (e.g. 110 degrees), which have shields extending at least along the forward half of the screen. The shield may be made up of four pre-annealed trapezoidal pieces of magnetic sheet metal, preferably attached by welding or riveting overlapping flanges (41) Fig. 3 (not shown) integral with the metal pieces and mounted on an electrode, e.g. a shadow mask frame 23 such as by welding flanges (45), (49) (Figs. 3 to 5, not shown) which are telescoped over the frame. Notches (49) are provided to clear mounting springs (31) or plates. Flange 29 may intercept over-scanned electrons, and four leaf springs 31 may be welded to the frame or intermediate bi-metallic plate. The plates may be cut from Al-killed steel of 4 to 8 mm. thickness and stamped to form the integral flanges and then preferably annealed. Alternatively annealing may be before stamping. The tubes may be colour tubes other than shadow mark types, and may be oscillograph tubes.
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