GB443864A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

443,864. Cathode-ray tubes. NICOLL, F. H., 17, The Drive, Ickenham, Middlesex. Jan. 25, 1935, No. 2556. [Class 39 (i)] A cathode-ray tube comprises in the following order a cathode 3, an accelerating electrode 9, a decelerating electrode 13, and first and second anodes 15, 21, and the accelerating electrode and first anode are connected to the same point in a continuous-current circuit so that they may have the same positive potential with respect to the cathode. The beam is focused on to the screen by the first and second anodes. An indirectly-heated cathode 3 and the surrounding shield 4, provided with the apertured diaphragm 6, are earthed. The accelerating and retarding electrodes are provided with apertured diaphragms. The first anode comprises the tubular portions 16, 17 and apertured diaphragms 19, 20. The aperture in the diaphragm 20 is larger than that in the diaphragm 19. Alternating- current is supplied through a transformer 22 to a rectifying and smoothing apparatus 23, the negative terminal of which is earthed. The anode 21 is connected to the tapping 24 and the electrodes 9, 15 are connected to the tapping 27 on the potentiometer 25. A condenser 28 connects the tapping 27 to earth. The decelerator 13 is used for modulating and the sources of modulating potential and bias are connected in series to the terminals 29. The fields on both sides of the decelerating electrode 13 may be made the same if the electrode 13 and the adjacent ends of the electrodes 9, 15 are arranged symmetrically about the diaphragm in the electrode 13, or if one side of the diaphragm is provided with a tubular portion which has a diameter and length less than those of the tubular portion on the other side. The potential, e.g. 200 volts, for the electrodes 9, 15 may be obtained from public continuous-current mains or through an independent rectifying and smoothing circuit. In another form, a second accelerating electrode and a second decelerating electrode are arranged between the decelerating electrode 13 and the first anode 15 ; the first and second decelerating electrodes and the first anode are then connected to the same point in the continuous-current circuit. Dimensions and potentials of the electrodes are given in the Specification.