Patent GB-573209-A (GB)
Title: Improvements relating to the construction and assembly of electron discharge tubes
IPC: H01J19/46
Filed: 1940-09-23
Abstract: 573,209. Electron beam valves. HARRIES, J. H. O. Sept. 23. 1940. No. 14467. [Class 39 (i)] In constructing an electron discharge tube having an envelope wholly or partly of vitreous material, each of a number of electrodes is provided with parts which co-operate with one or more aligning members which do not form a permanent part of the tube, but are supported from a platform during the assembling operation, the electrodes being held by the aligning members and by spacing washers also co-operating with the aligning members in correct relative positions until they are secured by means of stiff leads attached to them which are sealed into the vitreous wall of the envelope, after which the aligning members and spacers are withdrawn from the tube. The tube shown in course of construction in Figs. 1 and 2 comprises a target or anode T, a subanode SA, a suppressor grid S, a positive electrode L<2>, control electrode X, grids G', G<2> and cathode C. The glass envelope E is in two parts sealed on to flanges extending from the sub-anode SA. All the electrodes, other than the cathode, above the sub-anode are provided with a pair of holes by which they are threaded on to two rods 12, 13 screwed into tapped holes in the subanode, washers 14 also threaded on to the rods spacing the electrodes. The assemblage is held together by tubes 19 passed over the rods and held by collars 20. Lead-in conductors 9, which in the finished tube form the only supports of the electrodes, are then passed through pips in the tube wall, welded to leads 17 on the electrodes by means of welding electrodes in the form of tongs inserted through the open top of the tube body, and are then sealed into the wall of the tube. The cap 21, into the end of which the supports C<1>, C<2> of the cathode assembly have previously been welded, is then placed in position, the tubes 19 being removed from the rods 12, 13 and tubular washers 14a being placed on them so that an apertured mica disc m which forms part of the cathode assembly and is threaded on the rods may rest on the washers to position the cathode accurately. The disc is held by shorter tubes 19, while the cap is sealed to the open top of the body. The tubes 19, rods 12, 13 and washers 14 are then disassembled and removed through tubes 22 forming part of the cap, after which the tubes 22 may be sealed, or one may be used for exhausting the envelope and the other may have a getter support sealed in it. Figs. 4 and 6 show a jig 25 employed for assembling a pair of deflection electrodes D', D<2> of semi-cylindrical form. These are held by screws in a recess in the jig, the leads d', d<2> to them being accommodated in grooves 28. The jig is then assembled on the rods 12 and 13, which pass through apertures 26 in it, and is held in position by spacing washers. After the leads d<1>, d2 have been sealed, the jig is unscrewed from the electrodes and removed through the open top of the tube, after which the electrodes above the deflection plates are assembled. Fig. 16 shows one stage in the assembly of a tube, the central part E<1> of the envelope of which is of copper. In this case, the electrodes are first assembled on a dummy sub-anode DSA having steps for supporting certain of them, the electrodes being positioned as before by rods 12, 13 screwed into the dummy sub-anode and by spacing washers. A pair of deflection electrodes are held on the top step by screws 29. The envelope is then positioned over the assembly, the metal tubular part E <1> fitting on a flange 30 on the dummy sub-anode. The lead-in wires 9, 10 are then sealed through pips 35 in the end of the envelope, after which the dummy sub-anode, rods 12, 13 and washers are removed. The lower part of the tube, which is the same as that shown in Figs. 1, 2 is then applied, the sub-anode being positioned by a flange similar to the flange 30 on the dummy and being soldered to the metal tube E<1>. Specifications 521,199, 573,205, 573,206, 573,207 and 573,208 are referred to.