GB413762A - Improvements in and relating to magnetostrictive oscillators - Google Patents

Abstract

413,762. Sound-transmitting devices. WOOD, A. B., SMITH, F. D., Research Laboratory, Teddington, Middlesex, and DRYSDALE, C. V., Research & Experiment Department, Admiralty, London. Jan. 30, 1933, No. 2836. [Class 40 (iv).] An under-water sound oscillator of the magnetostrictive type is formed from magnetostrictive material in finely divided form treated so that the particles will be insulated from one another when in juxtaposition. The material, such as nickel, nickel alloy or cobalt alloy, can be in the form of powder, dust or small fragments having an exterior film of insulating material, the particles being consolidated into a solid block. Alternatively the finely divided material may be disseminated throughout a suitable insulating mass, preferably of the thermoplastic kind, the whole being moulded under heat and any desired pressure. An outer envelope may be applied either during the moulding process or subsequently thereto. According to a further modification, the finely divided material is sprayed on to a thin sheet of insulating material, the film so produced being painted or sprayed with a thin coating of insulating material and these processes repeated with or without the addition of thin interleaved sheets of insulating material until a slab or disc of the required thickness is built up. If desired, the finely divided and insulating materials may be sprayed simultaneously. Instead of coating the finely divided magnetostrictive material with insulating material, the former may be subjected to surface oxidation, the oxidized particles being consolidated to form a core which may be provided with an outer envelope. An enhanced magnetostrictive effect may be obtained by using a ferromagnetic dust in which particles are single crystals or portions of a single crystal, a strong magnetic field being applied when the material is in its unconsolidated state and maintained throughout the process of consolidation so as to orientate the particles in a preferred direction in which they are maintained until they are fixed in position by consolidation. If desired, the current windings may be placed in position inside the core before consolidation. The finely divided material may in some cases be brought into a magnetically soft condition by heat treatment before consolidation. Specifications 313,031, [Class 37], 314,891, [Class 40 (iv)], and 375,375 are referred to.