Patent GB-102484-A (GB)
Title: Improvements in and relating to Vapour Electric Systems for the Conversion of Direct Electric Currents into Alternating Currents.
IPC: H02M7/51
Filed: 1916-10-17
Abstract: 102,484. British Westinghouse Electric & Manufacturing Co., (Assignees of Chubb, L. W.). Nov. 29, 1915, [Convention date]. Vacuum tubes; low-pressure metallic-vapour apparatus.-In a system for converting direct current into alternating current, use is made of a vacuum apparatus provided with means for regulating the current-flow between the electrodes by electrostatic control of the negative electrons. In the arrangement shown in Fig. 1, the casing 9 supperts two anodes 10, 11 and a cathode 12, which is maintained in an active state by the battery 13. Suppressor shields surround the anodes and consist of casings 15 with diaphragms 16 supporting conducting-tubes 17, through which the discharge passes. The tubes 17 may be connected to their respective anodes through a switch arm 18 rotated by the motor 19. The anodes are connected to the ends of a transformer primary 20, the central point of the winding being connected to a direct current circuit 26. The transformer secondary is connected to the alternating-current load 23, preferably through tuning-devices 24, 25. With the switch 18 in the position shown and the circuit 26 energized, the shield of the anode 11 is connected to the anode and thereby maintained at a positive polarity. Current therefore flows from the circuit 26 through the right-hand half of the transformer primary 20 to the anode 11 and cathode 12, and from the casing 9 back to the circuit 26. When the arm 18 is rotated through 90 degrees, the anode 10 is connected to the shield, and the discharge passes across the anode 10 and cathode 12 to energize the left-hand half of the transformer primary. The flow of current through an anode may be choked out at the end of the desired wave by producing an oscillating current through the arc and causing it to die down to a zero value. This apparatus produces an electro-motive force of a square-top wave form, and in order to obtain an approximate sine wave form, two additional anodes are employed. Simultaneously with the substitution of one anode for another, the number of active turns on the transformer primary is increased or diminished to give the required electro-motive force value in the secondary. In a modification, a hot filament cathode 59, Fig. 5, is associated with four anodes 60 - - 63 connected to the transformer and provided with suppressor shields 65 - - 68 formed of closely interwoven masses of refractory wire, such as tungsten or molybdenum. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a converter as shown in Fig. 5 (cancelled). Four cathodes 48 - - 51 of the hot filament type are associated with a common anode 52 and are heated by currents from the battery 53. As the switch arm 18 rotates, the cathode 51 is connected in circuit with the left-hand half of the transformer primary, then the cathode 50 is connected with one section of the primary, and then the cathode 51 is reconnected to the half of the primary. Similar connexions are made between the cathodes 49, 48 and the other half of the primary to obtain an electro-motive force of approximate sine wave form. This subject-matter does not appear in the Specification as accepted.