GB799201A - Improvements relating to electro-acoustic delay lines - Google Patents

Abstract

799,201. Electromechanical delay lines. FERRANTI, Ltd. June 1, 1956 [June 6, 1955], No. 16104/55. Class 40 (8). An electromechanical delay line comprises a wire for propagating torsional stress waves associated with input and output transducers each including elongated magnetostrictive members extending tangentially from the wire. As shown in Fig. 2, the magnetostrictive members are two in number and consist of nickel strips 12 whose broader faces are welded to diametrically opposite points on the stress-wave propagating wire 11. The strips are associated with series or parallelconnected coils 13 whereby simultaneous longitudinal stress wave pulses may be set up in the strips. The effect is to produce a torsional stress wave pulse in the wire 11. The output transducer is similar to the input transducer except for the addition of polarizing magnets 19. Such magnets may also be associated with the input transducer. Alternatively, polarization may be produced by a direct current in the coils. In a modification (Fig. 5, not shown) the elements 12 extend from the wire in the same direction. In this case the elements must be polarized in such a manner that the stress waves are of opposite sense in the two elements and thus act in the same peripheral direction at the wire. Three magnetostrictive elements spaced at angular intervals of 120 degrees may be used (Fig. 6, not shown). The wire may be of a hard nickel-iron-titanium alloy and may be bent into a spiral. The Specification discusses the relative dimensions of wire and elements of given compositions necessary to achieve a good acoustic match.