GB191309449A - Improvements in or relating to X-Ray Tubes and the like and the Manufacture thereof. - Google Patents

Abstract

9449. Friedrich, C. A. April 22. Vacuum tubes.-During the exhaustion of X-ray and other tubes, the electrodes are heated, electrically or otherwise, without discharge through the vacuum, so as to prevent the formation on the glass of metallic deposits which may produce shortcircuits with a high vacuum. Regulation of the vacuum during working may be effected by the same heating devices. In one arrangement, an aluminium cathode 14, Fig. 1, and a copper anode 3, forming also an anti-cathode and supported by a split steel tube 4, are surrounded by sleeves of mica, asbestos, or the like, on which are wound heating-coils 20, 8. Each coil is connected at one end to the electrode within it, the other end of the anode coil 8 being connected to an external cap 35, and that of the cathode coil 20 to a terminal near but insulated from the cathode terminal. The coils may be connected in series across an ordinary supply circuit during exhaustion. For subsequent regulation of the vacuum, current may be passed through one of the coils, preferably the anode coil 8, to cause liberation of gas from the asbestos or mica sleeve. The working current, or current from a separate source, may be used for this purpose; in the former case the negative conductor is attached to a spring-urged arm 25 pivoted at 29 to the container and operated by a cord 34 so as to engage either the cathode terminal or the cap 35 connected to the anode coil. A copper rod enclosed in a glass tube supports the cathode. In a modification, each coil is short-circuited and current is induced in it by means of an external coil temporarily fitted over the side tube containing the electrode support. In another arrangement, a hollow electrode contains a coil wound on an asbestos tube flanged at its ends, the connexions and electrode support being similar to those of Fig. 1. In a further modification, a hollow electrode 50, Fig. 4, is open to the air, being attached to a platinum ring 52 sealed to the bulbed end of a side-tube. The electrode may consist of an inner tube of thin copper and an outer one of steel with an air space between. Heating is effected by a blow-pipe jet, or by inserting white-hot rods, or a resistance coil wound on the lower end of a mica or other insulating tube 55, Fig. 5, and attached to conductors respectively inside and outside the insulating tube, which is flanged at two points 59. During working, the hollow electrode may be cooled with water by means of rubber connectors, or may be filled by a metal rod.