GB1018781A - Improvements in or relating to apparatus for checking the contents of containers - Google Patents

Abstract

1,018,781. Testing by sound waves; valve gating circuits. U.D. ENGINEERING CO. Ltd. Jan. 24, 1962 [Oct. 24, 1960; Jan. 27, 1961], Nos. 36479/60 and 3338/61. Headings H3P and H4D. In the testing of the contents of liquid-filled containers 12 (e.g. milk bottles) for contamination by foreign bodies (e.g. chips of glass), the containers are fed to a detecting station where one or more transducer devices are disposable to create waves in the contents, an oscillator 1 is in the electric circuit of that transducer device which imparts vibrations to the contents, an indicating and/or container-rejection device 9 is energized by the transducer device which receives waves after traversing the contents, and a gate device is in circuit with the indicating and/or rejection device and is operable out of phase with the impulses from the receiving transducer device whereby only impulses from waves in a contaminated container are passed to the indicating and/or rejection device. The vibrations are preferably in the frequency range 1 kc. to 10 Mc/s. In one embodiment impulses are fed by means of a trigger device 7 to transmit/receive transducer 14 and the trigger pulses are fed via a delay device 8 to gates 5 and 16, the output of the latter when present actuating rejector 9. Limiters 17, 18 are included, their limiting levels being set respectively at levels corresponding to weak and strong, e.g. from the bottom of the bottle) reflections. The operation of the embodiment, with various combinations of the normal states of gates 2 and 5, is described in detail; for one combination the trigger device 7 is connected directly to gate 5 to deliver blanking pulses thereto during movement of bottles to and from the testing station. In another embodiment (the Figure of Provisional Specification 36479/60, not shown) separate transmitting and receiving transducers are utilized and items 16 ... 19 are omitted. Valve gating circuits, Fig. 2.-The gate formed by triode valve 21 is closed by a pulse applied to terminal 29: cold-cathode trigger tube 30 conducts thereby placing a high negative bias on the grid of the triode. A pulse applied to terminal 36 causes tube 30 to extinguish and the gate opens.