GB430497A - Compressional wave transmitter and receiver, more particularly for subaqueous signalling - Google Patents

Abstract

430,497. Sound transmitting and receiving devices. ATLAS-WERKE AKT.- GES., Bremen, Germany. Dec. 20, 1933, No. 35857. Convention date, Jan. 7. [Class 40 (iv)] Apparatus for producing and receiving high frequency compressional waves, more particularly for subaqueous use, consists of a vibratory structure comprising a plate having a radiating surface of dimensions large compared to the wave length of the signalling frequency, a multiplicity of elongated magnetostrictive elements rigidly fixed by one end in non-contiguous relation to each other to the opposite surface of the plate and covering substantially all of the surface thereby forming a single unitary longitudinally-vibratory body and electromagnetic means operatively associated with the elements. In a preferred construction two plates are rigidly fixed one at each end of the elements and one or both of the plates are adapted to act as radiating surfaces. Fig. 1 shows a construction employing a plurality of magnetostrictive elements in the form of wires, rods or tubes 1 arranged out of metallic contact with each other and preferably held apart in insulating discs 2. The ends of the elements are secured by soldering, brazing or welding in metallic masses 3, 4. These masses may, however, be of insulating material, in which case, the elements may be pressed therein under pressure or secured thereto by adhesive or by means of insulating material applied in a liquid state. A coil 7 surrounding the elements as shown is supplied with alternating current and, if desired, with a direct current for producing an initial magnetization. An alternative construction is described in which elements in the form of radial strips are employed. Fig. 4 shows a construction in which one of the masses 9 is threaded into a metal plate 10 of relatively very large mass which closes one end of a casing 13, the other end of which is closed by a membrane 16 secured to the radiating mass 11. If desired, the membrane may be omitted and the space between the casing 13 and mass 11 filled with a material such as rubber which is impervious to water. Fig. 5 shows a further construction in which both the masses 20, 21 radiate sound, the elements 19 being supported at a node by a plate 24 of insulating material clamped between the parts 22, 23 of the surrounding casing. The coils 25, 26 may be connected in series and supplied with alternating and direct current or one coil may be used for the direct polarization current and the other for the alternating current. In this construction, the magnetic circuit is completed by a laminated yoke 27, 28 completely surrounding the coils. The radiating surface or surfaces may be mounted at the focus of a parabolic reflector.