GB714118A - Improvements in or relating to electromechanical vibrators - Google Patents

Abstract

714,118. Electromechanical impedances. PHILIPS ELECTRICAL INDUSTRIES, Ltd. June 27, 1952 [July 2, 1951; July 2, 1951], No. 16243/52. Class 40 (8) An electromechanical vibrator which may be used as a tuned impedance arm or as a filter comprises a hollow magnetostrictive member made of solid, highly-permeable non-conductive material and having rotational symmetry about an axis, one member being laced in a polarizing magnetic field substantially parallel with said axis and linked with a winding which sets up a tangential oscillatory field in the member to cause it to execute torsional vibrations. An annulus 1, Fig. 1, is arranged in a polarizing field Ho produced by the permanent magnets 3 and 4 held in the ferro-magnetic support circuit 11, 12, 13. A winding 2 supplied with alternating current is arranged about a section 10 of member 1, with the result that member 1 is set in torsionl vibration. Member 1 is supported in its nodal plane by means of studs 7 and 8. In modifications, the circuit producing the permanent field Ho and the method of supporting member 1 may be altered to produce a more compact construction, as in Figs. 3, 4 and 8 (not shown). The impedance characteristic of these four forms of the device is as shown in the curve a of Fig. 2. The initial impedance Zo shown in Fig. 2 can be compensated by the use of two coils 2, 2' (Fig. 5), coupled together by a suitably proportioned transformer 15 so that the input current, for example, traverses the winding 2 and the primary of transformer 15 in opposite sense, and for example traverses the winding 2 and the secondary of transformer 15 in the same sense. A modification comprises two vibrator members 1, 1<SP>1</SP> (Fig. 6) each supported in their nodal planes by means not shown, the input winding 2 being arranged around member 1, and the output winding 2' around member 1'. Members 1 and 1<SP>1</SP> are mechanically intercoupled by the non-magnetic elements 18, 19 and 20 and the band-pass characteristic of Fig. 7 is obtained. The solid non-conductive material of which one annulus is made may be a nickel-zinc ferrite and the permanent magnets may be made of the non-conductive material referred to in Specification 708,127, [Group XXXV]. Specification 664,174 also is referred to.