GB1369100A - Fabrication of focus grill type cathode ray tubes - Google Patents

Abstract

1369100 Cathode-ray display tubes RCA CORPORATION 10 Nov 1972 [10 Nov 1971] 52124/72 Heading H1D A method of fabricating a C.R.T., e.g. colour TV C.R.T. including a cup-shaped face plate panel having a phosphor pattern (e.g. sets of three different strips (22), Figs. 1 to 3 (not shown)) and a wire grill spaced from the panel surface, the method comprising winding a helix of wire externally about the panel, the turns extending across the open side of the panel in a preselected relationship with the phosphor pattern sealing portions of the helix turns to the side wall of the panel, and removing the helix portions extending over the outer surface of the panel. The wires may be in etched grooves 42 aligned accurately with strips (22) by indicia references such as lugs 54 which are accurately machined after the panel is moulded. Winding cradle 60 is provided with panel 12 whose side walls extend above the cradle side wall 62. The cradle has three positioning screws 63, 64, 65 and two leaf springs 66, 67, clamp 71 additionally serving to lock. Cylindrical pins 69 enable cradle rotation about its major axis. Cradle 60 is mounted in a conventional lathe winding apparatus, rotated about axis 68 and wire 32 from spool 74 attached to cradle 60 by clamp 74. Axis 68 is offset from panel major axis 24 to ensure opposing grooves are offset an amount corresponding to the advance of the spool. Wire 32 may be 2 mm. stainless steel wound at 40 turns/inch under 6 ounce tension. Grooves 42 may be circular cross-section, 3 mm. width and 2 mm. deep. Side wall 46 and funnel member (16) are mated via heated glass frit, utilizing a conveyer belt and oven system. Conductive paint around panel 12 and funnel 14 joint provides electrical contact. Thermal expansion of wire 32 during heating to seal the above members, is compensated by a cradle of Al, or a separate Al plate, of greater expansion coefficient, or a compressive expansion member (e.g. a hollow cylinder) may be used. The cradle may be replaced by mounting jaws. Funnel member 16 may include focusing and accelerating electrodes and one or more electron guns. The phosphor screen may be formed by printing methods using photosensitive binder.