Patent GB-465144-A (GB)
Title: Improvements in or relating to electron discharge devices
IPC: H01J31/06
Filed: 1935-11-02
Abstract: 465,144. Cathode-ray tubes. BULL, C. S., and KEYSTON, J. E. Nov. 2, 1935, No. 30354. [Classes 39 (i) and 40 (v)] In discharge tubes .in which an electron beam is deflected as by a signal to control the current to one or more collecting electrodes receiving the beam or to vary the part of a fluorescent collecting electrode struck by the beam, the sensitivity is increased by further deflecting means acting on the beam deflected, by the signal to increase its angular deflection and to give the beam, over a part only of the range of deflection by the signal, a component of motion in a direction opposite to that of the electrons before reaching the further deflecting means. The beam from a cathode C, Fig. 1, is deflected by the signal magnetically or through plates D, D<1> and enters the rectangular space between four electrodes, two N, N<1> of which are at or near cathode potential and two P, P<1> are positive collecting electrodes. The paths of electrons for small and large deflections by the plates D, D<1> are as shown at A, B, the further deflection produced by the field between the electrodes N, N<1>, P, P<1> varying inversely in dependence on the deflection by the plates D, D<1>. For use as a relay, the output is taken from one of the electrodes P, P<1> or from both in push-pull. For use as an amplifier, a collector such as P may be divided into triangular halves with a load impedance in the circuit to one half. In a modification, Fig. 5, the cathode C is an elongated, shallow, rectangular box containing a heater and coated on its upper surface with emissive material and is associated with electrodes M, G, H each in the form of parallel plates joined by an apertured diaphragm. The diaphragm MD of the electrode M may be replaced by a wire-mesh grid. The electrodes G, H are anodes forming an electron lens. The electron beam, after deflection by plates D<1>, D<2> enters the cylindrical field between collecting electrodes P<1> .. P<5> and a central rod F at or near cathode potential ; this field increases the deflection and, for small deflections, reverses the direction of the beam as in Fig. 1. The current to the electrodes P<1> .. P<5> is controlled. by the plates D<1>, D2 and by modulating the potential of the electrode M or of the rod F. The sensitivity may be increased by coupling the rod F to the plates D, D<1>. Two signals applied one to the plates and one to the rod F produce modulation or beats as in superheterodyne or homodyne arrangements. A modulated carrier may be applied simultaneously to the plates D<1>, D<2> and to the rod F to produce a current at modulation frequency in the collecting-electrode circuit. This circuit may be coupled to the circuit of the plates Dl, D2 to generate oscillations. The collecting electrodes P<1> .. P<5> may be replaced by a conductive fluorescent screen at positive potential for use as a voltmeter or tuning indicator. The collecting electrodes may be associated with screening grids and secondary emission to such grids may be avoided as by suppressor grids. A beam of electrons of uniform velocity may be obtained from a slot in a collecting electrode. In another modification, the cathode and plates Dl, D<2> are in a cylinder projecting- into the space enclosed by the electrodes P<1> .. P<5> and maintained at or near cathode potential. The device may have a parabolic characteristic and gain controlling bias may be applied to the plates D<1>, D<2> or to the rod F'.