GB339391A - Sectional electrostatic sound producer - Google Patents

Abstract

339,391. United Reproducers Patents Corporation. Jan. 14, 1929, [Convention date]. Condenser telephones; diaphragms.-An electrostatic loud-speaker is built up of a number of units each having a flexible conductor, a rigid conductor and projections and means for connecting a projection of one unit to an adjacent projection of another unit. The units may be connected in parallel or series or both. The units may be .connected in parallel for polarizing voltages and in series for signal voltages. Each unit comprises a metal plate portion 1, preferably curved, with its outer surface formed with ridges 2 and troughs 3 which may be slotted as at 6. The margin of the plate is formed with flanges apertured for connecting rivets or bolts 15. The dielectric 17 may be a sheet of rubber, silk or rubberized silk coated with a metal film or foil such as gold, silver, copper or aluminium. Grooves 16 at the margins of the plate receive anchoring elements 19 which may be wires or rods of conducting material serving for the connection of circuit conductors. When the dielectric comprises a woven fabric the threads should be disposed on the bias. A recess 20 in the plate receives a tensioning bar 26 which may be of insulating material, and is secured by wires 27, 28 to a leaf spring 31. A suitable circuit for use with the speaker comprises an output transformer 47 the secondary circuit of which is connected to three units 75, 76, 77 in series, one end of the secondary being connected through a condenser 86 with the back plate 78 of the unit 75, the front plate 81 of which is connected through a condenser 90 to the back plate 79 of the unit 76, the front plate of which is connected through a condenser 93 to the back plate 80 of the unit 77, the front plate of which is connected to the other end of the secondary. Polarizing potential produced by a mains transformer 122 and rectifying valve 127 is maintained between back and front plates in parallel, resistances 95, 107 of the order of half a megohm being inserted between each plate and the corresponding voltage pole.