Improvements in or relating to methods of applying internal coatings to envelopes for discharge devices

摘要

PICT:0788553/III/1 PICT:0788553/III/2 Coating material, e.g. a colloidal graphite suspension, is applied to the axially symmetrical walls of the envelope of an electron discharge device by supporting the envelope with its axis vertical, introducing a member carried upon a shaft which is rotated about a vertical axis and has a surface extending perpendicularly outwardly from the said axis, and applying to the surface a dispersion of the coating material, whereby it is distributed to the inner walls of the envelope. Means may be provided for producing relative axial movement between the envelope and the coating member. As shown, in Fig. 4 the envelope 18 is carried by a clamp 19 attached to a nut 21 on a lead-screw 22. A shaft 23 is mounted coaxially with the envelope 18 for rotation by an electric motor 31, which also rotates the lead-screw 22 through pulleys 33 and 35 and belt 34. The shaft 23 carries a dished member 36 to which coating material is applied through a tube 37. Alternatively, as in Fig. 5, the shaft 38 is made hollow, and the supply tube 40 passes along its axis. The coating material may be applied as a series of spaced bands, or as a continuous coating.