GB820181A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

820,181. Cathode ray tubes. GENERAL ELECTRIC CO. Ltd. Nov. 4, 1957 [Nov. 2, 1956], No. 33569/56. Class 39(1). At the junction of the neck and flared portions of a cathode ray tube, preferably a television receiver, the envelope is formed with four indentations 6, Figs. 1, 2, in its inner surface, the indentations being located at the corners of a rectangle so that larger extreme scanning angles can be used without cutting off the corners of the rectangular picture ; since the outside surface of the neck at the junction is smoothly cylindrical (as is the remainder of the neck) no modification of the scan coils is necessary as would be required if as in a prior art proposal the inner and outer surfaces at the junction of neck and flared portion were both rectangular. The flared portion is preferably formed by pressing in a mould the four indentations 6 preferably being formed during the pressing operation. The envelope portion produced by the pressing operation has a projecting cylindrical part with a closed end, most of which is cut off to leave a small stub 4 which is sealed to neck 5. The face plate 2 which is preferably dished and preferably carries the luminescent layer (or the luminescent layer may be on a separate support) is sealed to the flared portion 1. The rectangle at the corners of which the indentations are located may have sides in the ratio of 4 : 3. The flared part of the envelope can be of circular or rectangular cross-section (in the latter case it is of circular cross-section at the junction with the necks). Other prior art cathode ray tubes are referred to such as those in which at the junction point the neck has a thinner wall or a greater diameter than the remainder of the neck.