GB1350973A - Method of and apparatus for testing liquid for particular contamination - Google Patents

Abstract

1350973 Ultrasonic inspection devices; ultrasonic probes BROCKWAY GLASS CO Inc 18 May 1971 15549/71 Headings H4D and H4J A liquid (e.g. a drug) in a sealed container is inspected for particulate contamination by introducing into it ultrasonic energy, for a predetermined time interval and at a frequency and intensity such as to produce cavitation in a contaminated liquid but not in an uncontaminated liquid, and detecting any noise generated in the liquid by the cavitation. In the Fig. 5 embodiment, container 50 is held against platform 53 by a pneumatic ram 80-83. Transmitting transducer 60 has a coupling horn 61 which passes through an aperture in platform 53 and engages the base of container 50. Hydraulic fluid pressure in vessel 51 urges platform 53 and horn 61 against the container 50 base. A manually or automatically gated oscillator (Figs. 8 and 9, not shown) energizes transducer 60 to transmit pulses of duration selectable in the range 10 to 30 milliseconds and of carrier frequency selectable in the range 25 to 300 kHz, preferably 65 to 90 kHz. Any cavitation noise (in the MHz range) is detected by annular piezoelectric transducer 65 coupled to an amplifier and detector circuit. The detector circuit (Fig. 10, not shown) may operate a warning lamp or audible alarm and also a mechanism for rejecting a container of contaminated liquid from a series being inspected automatically. Details are given of apparatus calibration using prepared liquid samples with known contaminants. In alternative embodiments (Figs. 1 and 7, not shown) the ultrasonic energy is introduced in a direction transverse to the container 10 axis, the container being gripped between a coupling member of a transmitting transducer and the receiving transducer, the latter being urged towards the coupling member by a pneumatic ram. Transducer details.-The transmitting transducer of Figs. 2 and 3 comprises two quartz elements 30, 31, sandwiched between “-wavelength aluminium sections 35, one of which has a ¢-wavelength extension including a largerdiameter portion with a horn-shaped tip 36. The transducer is resiliently mounted by O-rings 41, 42 in a cylindrical shell 38 and tip 36 is provided with a coupling member 23. Several transmitting transducers may be used to cover the frequency range of the gated oscillator. The Fig. 4 receiving transducer comprises a piezoelectric disc 47 on an aluminium "drum-head" mount 45, with a tip 46 for contacting a container being inspected.