GB499869A - Improvements in or relating to electron discharge devices - Google Patents

Abstract

499,869. Cathode - ray tubes &c. LUBSZYNSKI, H. G., MILLER, H., and CAIRNS, J. E. I. June 26, 1937, No. 17820. [Class 39 (i)] In an electron discharge device employing a photo - sensitive cathode, the envelope is provided with a re-entrant neck having a window sealed therein through which an image can be projected on to the cathode which is formed on the inner face of the window, and a conducting ring electrode surrounds the surface of the reentrant end and is in contact with the cathode, and a lead to this electrode is brought to the exterior through the annular space surrounding the re-entrant part. Or the cathode, or a photosensitive mosaic is carried by a plate spaced from the window and supported by or against the rim of the re-entrant end, the light through the window causes the release of photo-electrons from the side of the cathode or screen remote from the window, and the cathode or screen is in contact with a ring electrode connected to the exterior of the envelope. The glass window 3, Fig. 1, carrying the photosensitive cathode on its inner surface is sealed into the neck 2, which is then sealed to the tube 1. An anode 5 may be formed by silvering or other coating on the tube 1, and an electrode 4 by similar means on the neck 2, and the latter extends into contact with the cathode. The lead-to the electrode 4 is taken through a seal 7. A cell for a colour filter solution (copper sulphate is mentioned) may be formed by a second sealed window 8. Alternatively, the cathode may be formed on a mica plate 10, Fig. 2, which is clamped between two metal rings 11, 12 by members 13 which are also bent out at 14 to position the assembly within the neck 2. The assembly is held down by hooks 15 and springs 16, one of which may constitute the lead to the ring 11, which itself acts as the electrode 4 and is arranged in contact with a silvered ring on the cathode. Or the mica sheet 10 may be pressed against the end of the re-entrant neck by a ring-shaped coil spring engaged under an inwardly directed annular flange on the inside of a metal ring. The ring fits round the end of the neck and is held in position by hooks and leads, and acts as the electrode 4. In a further modification, for use in a tube in which a photo-electric mosaic is scanned by a cathoderay, the mosaic is formed on one side of a mica sheet 21, Fig. 4, the other side of which, carrying a transparent signal plate, bears against the re-entrant neck 2 into which the window 3 is sealed. The plate is supported by several rods 24 which are sealed into the envelope and may be spaced by a support 25, which may carry the helices used for depositing silver on the plate 22 according to the method described in Specification 480,946. The rods 22 may carry the current to the helices. The neck may be silvered to form an electrode in contact with the signal plate and from which a lead is taken to the outside of the tube.