Patent GB-1040242-A (GB)
Title: Improvements relating to ultrasonic testing of articles
Inventor: DAVIES DAVID HARRIS
IPC: G01N29/06
Filed: 1963-01-02
Abstract: 1,040,242. Ultrasonic inspection devices. STEWARTS & LLOYDS Ltd. Dec. 23, 1963 [Jan. 2, 1963], No. 253/63. Heading H4D. Thickness of a product and location of a defect therein are recorded by scanning the surface thereof with ultrasonic pulses, reflected pulses after detection operating recording means to provide a record of the product's thickness and depth of a defect in relation to one other dimension of the product and a further record of the position of the defect in relation to that other dimension and the third dimension of the product. The embodiment relates to the inspection of a tube fed longitudinally and about which four transducers A, B, C, D at 90 degrees to one another revolve together to generate a helical scan of the tube, Fig. 2. A chart X has a width corresponding to a standard wall thickness and moves longitudinally to afford a dimension proportional to the length of the helical scan and hence the length along the tube; a chart Y has a width proportional to the circumference of the tube and moves longitudinally similarly to chart X. Each chart has 100 fixed marking devices at regular intervals across its width. The apparatus isolates the second and fifth of the multiple reflections in the wall of the tube (pulses 13, 16, Fig. 1) after the interface echo 11 and by counter means measures the time interval therebetween, a count of 100 being made the equivalent of one inch thickness. A defect may be included matter presenting absorption and dispersion but no reflecting surface; to ensure that such a defect does not escape detection electronic means detects that no thickness measurement has been made, the first two markers on chart X being energized and appropriate markers on chart Y also. A cathode-ray tube monitor of a selectable transducer-receiver output is made available. Audible and visual alarms are given when a flaw has been judged to be present; the audible note is given a characteristic dependent on the nature of the defect. Detailed arrangements, Fig. 3A ... F.-A first unit, the "co-ordinator," Fig. 3A, ensures that the transducers operate sequentially and provides timing waveforms for the remainder of the apparatus. The received pulses pass to " Logic I ", Fig. 3B, in which the interface echo (11, Fig. 1) and the second (13) and fifth (16) of the multiple reflection pulses are extracted; to inhibit the counting of spurious pulses, counting begins a predetermined time after transmission. The fifth multiple reflection pulse may be absent; to prevent counting of a further and spurious pulse an inhibiting pulse is generated a further predetermined time after transmission. Logic I also determines when the tube's thickness has decreased below a prescribed tolerance; inverted pulse 13 triggers a monostable device 50 which generates a rectangular pulse of width adjusted such that with nominal tube thickness no coincidence exists with pulse 16, for a gate 55 and a monostable device 56 which feeds a monitor cathode-ray tube 57 also fed with the output of a monostable device 42A triggered by inverted pulse 16. In the " thickness decoder," Fig. 3E, clock pulses are gated into a counter chain 91 ... 98 by a bi-stable device FF4 actuated from pulses 13, 16, the counters being re-set to zero at each transmission moment; the count is decoded by a diode matrix to actuate the appropriate marker for chart X. Calibration marks are periodically added to the chart. " Logic II ", Fig. 3C, provides for recognition that a measurement of wall thickness has not been made, i.e. pulse 13 absent for six consecutive occasions, and comprises four similar sections J, K, L and M corresponding to the four transducers. " Logic III " comprises means for dividing the circumference of the tube into 100 equal portions for association with chart Y.