GB287065A - Improvements in or relating to diaphragms more particularly for loud speakers and the like - Google Patents

Abstract

287,065. Siemens & Halske Akt.- Ges. March 12, 1927, [Convention date]. Diaphragms; loud-speakers; magnetic instruments. - A diaphragm for acoustic instruments comprises two or more rigid surfaces, each lying in the same plane hingedly connected together and to a stationary support. As shown in Fig. 2, two surfaces s<1>, s<2> stiffened by ribs or corrugations, which may be of rectangular cross-section, are connected together elastically, by a longitudinal corrugation w<2> which acts in the manner of a hinge and the surfaces are supported on a frame through the intermediary of the elastic corrugations w', w'. As applied to electromagnetic instruments, the - diaphragm is driven by armatures secured at points along the corrugation w<2>. In a modification, two flat surfaces connected together and supported by elastic material are used. Instead of stiffening the surfaces by corrugations &c., an additional layer of material may be employed. The diaphragm may be driven by a current conductor riveted or clamped to the diaphragm and' located in a magnetic field. As shown in Fig. 3, the corrugation w<2> clamps a conductor l which extends over the whole length of the diaphragm. In a modification, Fig 4, projections e<1>, e<2> on the bent portions of the surfaces s', s<2> forming the elastic joint are fitted together and bent so as to clamp the conductor l. Fig. 6 shows a further modification wherein a current carrying conductor l is placed around the central corrugation w<2> and a wire z which strengthens the diaphragm. In another arrangement, the conductor l is located inside a deep central corrugation and is held in position by cords &c. interlaced through slots in the corrugation. When the diaphragm is of metal., the conductor is insulated by paper, rubber, or a layer of oxide, and the diaphragm is provided with slots to eliminate eddy currents. Instead of a separate conductor, the central corrugation may act as the current-carrying conductor. Elastic threads &c. connected to the central corrugation and the supporting frame are provided to facilitate axial movement, which may be damped by the provision of an apertured air chamber on one side of the diaphragm. The rigidity of the partial surfaces of the diaphragm is such that the speed of wave propagation is approximately equal to the velocity of sound in air. Fig. 8 shows a loud-speaker comprising four diaphragms d<1> - - d<4> operated by electromagnets m<1> - - m<4>.