| 摘要 |
876,279. Piezo-electric devices. BENDIX CORPORATION. July 30, 1959 [Sept. 8, 1958], No. 26249/59. Class 40 (4). A transducer for generating sonic and ultrasonic vibrations in a tank of liquid comprises a hollow cylindrical element 25 of barium titanate in which the electrodes 29, 30 of two sets are arranged alternately. The two sets are used to generate electrical fields and mechanical vibrations in a longitudinal direction. Inner and outer cylindrical electrodes can be used. The transducer has an aluminium head 26 and a stainless-steel face plate 27. The tank bottom comprises a layer 14 of rubber between two thinner layers 15, 16 of metal. The head 26 is a press fit in an aperture in the rubber layer 14 but the face plate 27 overlies the layer 14 around the edge of the aperture and does not contact the edge of a larger aperture in the top layer 16. There is also a gap between the bottom layer 15 and the wall of the element 25. A massive ring 28 may be attached to the transducer. In a modification, Fig. 2, the head 34 is formed as an integral part of the ceramic element and the part 35 joining the head to the active section 33 is formed as a coupling with a cross-section as shown. The modification is suitable for use with a liquid at a temperature above 120‹ C. at which temperature barium titanate loses its electromechanical properties. The active section is divided into four segments by slots 37. Electrodes 38, 39 are arranged alternately as before. Each electrode may extend around its segment. Electrodes on adjacent segments are linked by connectors 40. In each of the embodiments shown, the length of the transducer is one or more half wavelengths. In Fig. 2, the overall length may be one half wavelength and the active portion 33 may be a quarter wavelength. |
