GB411879A - Improvements in or relating to pressure wave transmitters and receivers incorporating magneto-strictive devices - Google Patents

Abstract

411,879. Subaqueous audible - signalling apparatus ; acoustic reflectors. MARCONI INTERNATIONAL MARINE COMMUNICATION CO., Ltd., Electra House, Victoria Embankment, and HINTON, N. P., 57, Broughton Avenue, Finchley, both in London. Dec. 15, 1932, No. 35619. [Classes 13 and 118 (ii).] A pressure wave transmitter or receiver, more particularly for use in echo sounding, subaqueous signalling systems, and for detecting the presence of underwater bodies, such as icebergs, comprises in combination a magnetostrictive vibrator whose moving face area is such that at the working frequency substantially spherical radiation occurs and parabolic reflecting means whose focus is located substantially at the centre of said moving face area. As shown, a combined magnetostrictive transmitter and receiver unit 1 constructed as described in Specification 402,123 and comprising a bar-shaped magnetostrictive body 2 adapted to vibrate longitudinally at its fundamental frequency is mounted within a reflector 3, which may be a gunmetal casting. This reflector is of a shape obtained by dividing a hollow paraboloid into two halves and separating these by a horizontal distance substantially equal to the length of the bar 2, the curved surfaces 4, 5 having their foci located at the points 6, 7 which constitute the centres of the end faces of the body 2. The reflector is formed with a spigoted flange 12 for attachment by means of studs 13 and nuts 14 to an adaptor 15 riveted to the hull plating 16, a gasket 17 ensuring a watertight joint. The adaptor enables the unit to be positioned horizontally at a part of the ship's bottom which is sloping. The unit 1 is mounted by bolts 19 from the upwardly extending portion 18 of the reflector which is filled with paraffin wax &c. 24. An air drum 25 is provided as shown in order to exclude bilge water from the rear of the reflector and the cable 23 from the unit 1 is led out through a stuffing box 21 and gland 22 and through a conduit 28 secured to the drum 25. An air pipe 29 communicates with the interior of the reflector at the highest point within the reflector to which water has access in order that the reflector may be completely filled with water when the apparatus is in use. According to a modification, the portion 18 may be prolonged to form a chamber within which the unit 1 can be withdrawn from its operative position, the prolonged portion being split horizontally and a gate valve interposed between the two sections so that the upper section can be removed for inspection of the unit after the latter has been withdrawn into the upper section and the gate valve closed. Specification 402,830 also is referred to.