Patent GB-672766-A (GB)
Title: Magnetrons
IPC: H01J23/213
Filed: 1947-06-24
Abstract: 672,766. Magnetrons. STANDARD TELEPHONES & CABLES, Ltd. June 24, 1947 [Nov. 1, 1945], No. 16619/47. Class 39 (i). [Also in Group XL (b)] In a magnetron in which the anode structure defines a plurality of cavity resonators, the inductance of the resonators is varied by a first tuning means and the capacitance of the resonators is varied by a second tuning means; the tuning means comprise conducting rings carrying wedge-shaped elements which extend into the resonators. in the regions of maximum magnetic flux and electric field concentration. respectively and the rings are mounted on opposite sides of the resonators and are rigidly joined together by rods 60, 61 passing through the resonators and are actuated by an external tuning control so that as one group of tuning elements enter the resonators on one side the other group emerge from the other side. The rods 60 are journalled in guide rings 51, 56 and the rods 61 are journalled in guide ring 56 at one end and at the other end are attached to further rods 62 secured to a platform 5, rods 60 and 61 being disposed alternately. Platform 5 is movable by adjusting tuning knob 19 which actuates a flexible bellows arrangement 4. The arrangement is cooled by liquid flowing through pipes 78, 79 and includes ball races 15, 17 and balls 16, and a moving scale 20 on knob 19 co-operates with fixed scale 21 to give a measure of the longitudinal tuning motion. The cathode 31 comprises a bifilar filament in which current flows in opposite directions in adjacent turns supported at the free ends by semi-cylinders 32, 34 and conical members 33, 35, and at the other end by a rod construction 37, 38, from cup-shaped metal members 26, 27, 28 insulated from one another by glass members 29, 30. The filament is of thoriated tungsten. Terminals 39, 40, 41 are screwed on to threaded rings 42, 43, 44 brazed to members 26, 27, 28. Rod 37 is supported at its free end by insulating ring 45. Pole-pieces 46, 53, are divided into two parts 48, 49; 54, 55, with the guide rings 51, 56 supported between the pole-piece parts, and are energized by coils 75, 76. Envelope parts 2, 3 are crimped, e.g. at 52, to hold the polepieces 46, 53 in place. The output is taken to a wave-guide 69 via an impedance transformer comprising two diverging ramps 70 inside a horn-shaped member 71, the vacuum being maintained by an elliptical insulating window 72. The field set up between magnetic shoes 73, 74 deflects any free electrons escaping from the discharge space away from the window 72 so that they impinge on the inner walls of the member 71. Alternate and intermediate anode segments are strapped together by ring straps, Fig. 2 (not shown), and to further reduce the tendency for spurious modes to appear the inductance varying tuning ring is grounded to the main body of the magnetron by coiled springs compressed sidewise in echelon fashion, Fig. 4 (not shown), and platform 5 is effectively shorted to ground by the capacity between members 66, 2. The main body of the magnetron is cooled by liquid passing through tubing 77. The parts of the magnetron carrying the oscillatory currents may be of copper or tungsten.