GB354018A - Improvements in or relating to acoustic diaphragms - Google Patents

Abstract

354,018. Diaphragms. ROGERS, F. H., 181, Queen Victoria Street, London.- (Skala Research Laboratories, Inc. ; 2300, South 56th Court, Cicero, Illinois, U.S.A.) June 30, 1930, No. 19886. [Class 40 (iv).] An acoustic diaphragm comprising an organic membrane 10 of pure parchment, paper, skin, wood, &c., has a magnetic armature 11 secured thereto by cathodical impact. The diaphragm is first moistened and secured to a frame 12 by ring 14 and screws 14a. The diaphragm becomes taut when dry and the armature is then deposited thereon by the known cathode sputtering process. The parts of the diaphragm not to be covered are shielded by material, such as glass or mica, and the diaphragm is cooled during the sputtering process. The cathode is of chemically pure iron or other magnetic material. The armature when produced is immediately protected against oxidation by a coating of collodion &c. A thin and elastic film of a non-magnetic metal, such as gold or silver, is also preferably secured by cathodical impact on the opposite side of the membrane to the armature. In a modification, a plurality of armatures are deposited on a membrane, each armature co-operating with an electromagnet, the electromagnets being preferably connected in series. The ring 14 serves as a means for variably tensioning the diaphragm.