GB1122386A - Improvements in or relating to electromechanical transducers - Google Patents

Abstract

1,122,386. Transducers. STANDARD TELEPHONES & CABLES Ltd. 9 Dec., 1965 [16 Dec., 1964], No. 51168/64. Heading H4J. In a pressure sensitive transducer, more particularly a semi-conductor microphone, an overload responsive device is included in the coupling between the diaphragm and transducer element. The latter may be a diode or a transistor having an exposed or a buried junction and may be of the type described in Specification 1,027,102. As shown, the overload device may be a slipping clutch 6 having a thixotropic filler in a silicone fluid 7 as the slipping medium (Figs. 4-6, not shown). Alternatively, it may comprise an artificial fibre (or fibres) which is biased by two leaf springs so as to be non-compressible under an overload pressure (Figs. 13 and 14, not shown). Yet again it may consist of a pivoted lever having magnets, e.g. magnetic dust in a soft rubber casing, at each end which co-operate respectively with metal plates on the diaphragm and transducer element (Figs. 15, 16, not shown). Alternatively, a plastics sheet may be used to cover the element, the sheet being shrunk under heat so as to prestress the element whereafter a fibre which collapses under overload is used to transmit pressure from the diaphragm to the element (Fig. 17, not shown). In another embodiment the diaphragm itself is made of a plastics material which deforms and collapses under overload (Figs. 20-24, not shown). In yet another arrangement, a rod, restrained against non-axial movement at its ends, is connected at its centre to a diaphragm whereby small transverse movements are effectively converted into longitudinal movements of the rod and hence pressures on the element but overload causes flexure of the rod and consequent loss of contact between the end of the rod and the element (Fig. 25, not shown). A transducer of the fibre type mentioned above (Fig. 17) may be used for demodulating an A.C. signal superimposed on an ultrasonic carrier (Figs. 18, 19, not shown). The transducer may comprise two diaphragms, one carrying the coupling and the other the element and such a transducer may be used in the pressure or the pressure gradient node (Figs. 4 to 8, not shown). The transducer may act as a microphone, an accelerometer or a pressure-sensitive switch. Reference has been directed by the Comptroller to Specification 1,077,205.