Patent GB-314332-A (GB)
Title: Improvements in or relating to electric discharge devices
IPC: H01J21/16
Filed: 1929-06-04
Abstract: 314,332. Telefunken Ges. fiir Drahtlose Telegraphie. June 25, 1928, [Convention date]. Vacuum tubes.-In thermionic valves for rectifying, amplifying, or producing oscillations, in which the discharge is influenced by external control electrodes, the electron discharge path is substantially at right angles to the long axis of the valve and the distance of the individual parts of the cathode from the nearest part of the valve envelope is less than the distance of the cathode, or the said individual parts thereof, from the anode. The envelope may be cylindrical but is preferably of flattened or triangular section, as shown in Fig. 2<b>, the cathode K and the anode. A being arranged at opposite ends of the section. The control electrode G may be folded around a side edge of a flat envelope having vertical electrodes, as shown in Fig. 3, and it may be slidable along the envelope for adjustment with respect to the cathode, in some cases being short enough only to overlie the central part of the cathode to avoid hum. The control electrode may be disconnected from the valve and form part of the associated apparatus. In the construction shown in Fig. 5, the cathode K is central in a flat tube E and the anode A consists of a spiral wire adjacent to the glass. In the construction shown in Fig. 7, a central cylindrical anode A is surrounded by four divisions K' - - K<4> of the cathode lying near the glass, the return lead H<2> of the cathode being taken through the anode to screen it. The device shown in Fig. 8 enables four ordinary valves to be replaced by a single tube in which four cathodes K<1> - - K<4> occupy niches in the wall outside which lie four grids G' - - G<4>. There may be a single anode A common to all the cathodes, or one for each. Generally a high positive biasing voltage is applied to the grids on account of the negative charges that form on the walls of the envelopes, this being effected by connecting the grids to the positive side of the high-tension supply through resistances R<3>, as shown in Fig. 11, or through the input inductances. Fig. 14 shows a valve having three independent electrode systems shielded from each other by a screen S, two of the systems having cathodes K<1>, K<2> and anodes A<1>, A<2> co-operating with external grids G<1>, G<2>, and the third system having an internal grid G<3> as in an ordinary valve to secure high efficiency in the last stage. A similar multiple valve is shown in Fig. 15a wherein the envelope consists of a smaller tube E' sealed into a larger tube E, the system with the internal grid G<3> being mounted in the top space, and the cathodes K<1>, K<2> and the anodes A<1>, A<2> that co-operate with external grids being mounted in the space between the tubes. The external grids are arranged outside the tube E and inside the tube E'. For the production of oscillations the external grid is preferably movable to and from the envelope to vary the degree of back coupling through an oscillating system inserted between the anode and the grid. To convert mechanical or acoustic into electrical oscillations, the control electrode St, Fig. 17, is vibratable, for instance by alternating potentials applied through a transformer from a microphone. It may be used for the modulation of high frequency applied through the transformer. Vibratable control grids may be of metal foil or of insulating material covered with a conducting layer. According to the Specification as open to inspection under Sect. 91 (3) (a) the control electrode may be folded over the top edge of the envelope if the other electrodes are horizontal. This subject-matter does not appear in the Specification as accepted.