ULTRASONIC CONVERTER FOR OPERATION IN GASEOUS ATMOSPHERE Russian patent published in 1998 - IPC

FIELD: nondestructive testing. SUBSTANCE: proposed ultrasonic converter on flexural vibrations for gaseous atmosphere is designed for contact-free inspection of large-sized articles and materials with high damping of ultrasonic vibrations. It may also be used for measurement of distances in air to objects and for control over them, for measurement of thickness of thin-sheet articles, for measurement of level of liquid and loose media in reservoirs and hoppers, for determination of air temperature in rooms, for determination of concentrations of gas mixtures, for environmental control, etc. Monofrequency converter has piezoelectric disc excited on diametrical vibrations, concentrator made in the form of ring and attached with its inner side surface to side surface of piezoelectric disc and with its outer side surface to thin metal plate in the form of hollow cylinder with narrow longitudinal slots starting in one of its end faces. Length of slots is chosen from condition λ_b/2 where λ_b is length of flexural ultrasonic wave in plate. Cone-shaped reflector of ultrasonic vibrations manufactured to focus vibrations emitted in axial direction is installed inside cylindrical plate. Mechanical screen is mounted at distance significantly less than wave length of ultrasonic vibrations in gaseous atmosphere on working wave of converter to enhance efficiency of converter. It is installed on side of outer surface of thin metal plate. Quarter-wavelength metal straps in the form of disc having diameter less than that of piezoelectric disc are joined to face surfaces of piezoelectric disc and placed with same purpose. Wide-band ultrasonic converter differs from monofrequency one by manufacture of piezoelectric element, concentrator, thin metal plate and acoustic screen with axially symmetric diameters changing in steps and thin metal plate is fabricated with length of narrow longitudinal slots changing correspondingly. In this case there is no quarter-wavelength metal straps on face surfaces of piezoelectric element. EFFECT: emission of ultrasonic vibrations into gaseous atmosphere with power by one order as minimum higher as compared with known analogs. 4 cl, 2 dwg