Patent GB-429671-A (GB)
Title: Improvements in and relating to potential changers
IPC: H02M7/62
Filed: 1933-09-26
Abstract: 429,671. Converting. MALLORY & CO., Inc., P. R., 3029, East Washington Street, Indianapolis, Indiana, U.S.A. Sept. 26, 1933, No. 26464. Convention date, Sept. 27, 1932. [Class 38 (ii)] [See also Group XXXVII] A device for supplying hightension current to a radio receiver comprises a transformer having its primary winding 17, Fig. 1, connected to a low tension source such as an automobile battery 16 through a mechanical interrupter 18, preferably of the magnetic type, and an electro-magnetic switch 24. The transformer secondary 63 is connected through a rectifier 64 having its heating filament 67a energized from the battery 16 through a circuit independent of the high tension circuit, and through a filter circuit 65 to a potential divider 77 to the terminals of which the radio receiver is connected. A bridge piece 85 on the rectifier forms part of the primary circuit so that when the rectifier is removed from the device the primary circuit is broken. The rectifier may be of the full wave type and the magnetic interrupter 18 may have its coil 55 connected so that only a part of the current in the primary circuit flows therethrough. The condenser 70 connected across the rectifier 64 is stated to be of such a magntude as to prevent the passage through it of low frequency currents and to permit the passage of high or radio frequency disturbances generated in the rectifier. The Specification as open to inspection under Sect. 91 describes a method of heating the rectifier cathode by means of a small third winding on the transformer and also describes a modified form of the device, Fig. 9 (Cancelled), provided with a system of shielding to reduce high frequency interference effects in the apparatus. In this system the various parts of the apparatus are enclosed in the grounded metallic casings shown in broken lines in the drawing the magnetic interrupter 18 being provided with a base having four prongs to which the various leads are connected. In a modified arrangement of the interrupter 18 in which the condensers 60 and 62 and the resister 61 are enclosed in the grounded interrupter casing 92 only two prongs are provided in the interrupter base. The primary and secondary of the transformer are separated by a grounded static shield 89 which may comprise a sheet of copper or a layer of insulated wire. A constructional form of the electromagnetic switch 24 is also described and comprises a core 31, Fig. 6 (Cancelled), carrying a coil 32 and mounted on a base 30 An L-shaped member 34 is mounted between the insulation 33 on the base of the coil 32 and carries a movable arm 28 by means of a resilient strap 35. The arm 28 co-operates with a back stop 39 and is attracted by the core head 311 when the coil 32 is energized to close the contacts 26, 27 against the action of the spring blade 29. The cables connected to the device are covered by suitable shielding such as flexible woven copper. The electromagnetic interrupter which forms the subject of Specification 431,137, is also described. This subject-matter does not appear in the Specification as accepted.