GB974902A - Improvements in or relating to beam-type electron tubes - Google Patents

Abstract

974,902. Cathode-ray tubes. LITTON INDUSTRIES Inc. Jan. 23, 1962 [Feb. 24, 1961], No. 2358/62. Heading H1D. An electron gun is located against radial movement by at least three peripherally-spaced inward protrusions of glass from the neck portion of the tube envelope, at least one of the protrusions being formed at such a peripheral point and of such depth as to move the gun structure for correction of initial misalignment of the beam from a preferred point on the tube screen. As shown, the gun electrodes of a cathode-ray display tube are secured to side rods 66, Fig. 6, of " Pyrex " (Registered Trade Mark), and initially the gun is mounted within the tube solely by its input leads. After evacuation of the tube and application of operating potentials to the gun electrodes, a first protrusion, to engage titanium end flange 60, is formed by use of a torch having a central plunger surrounded by a ring of gas jets, the plunger being used to move the gun into correct axial alignment with polar co-ordinate markings on the tube screen. Afterwards the glass is softened at two additional points to engage flange 60. Three protrusions are similarly formed to engage end flange 62, a further alignment adjustment being made, if necessary. Additional protrusions 64, 65 may engage side rods 66 if the flanges 60, 62 and tube neck have substantially different coefficients of expansion. After formation of the protrusions internal stresses may be relieved by heating the tube neck. To avoid electric field disturbances caused by the side rods, these may be omitted, the electrodes being mounted on a jig within the tube neck and secured in position by protrusions 94, 98, 102, Fig. 8. After removal of the jig, and tube exhaustion, the gun alignment may be adjusted during formation of protrusions 106. The protrusions may be made through the use of an intermediate element of glass having a higher melting point than the adjacent tube neck.