GB946590A - Improvements in or relating to recording systems for ultrasonic flow detectors - Google Patents

Abstract

946,590. Ultrasonic flaw detectors. ROLLSROYCE Ltd. Jan. 9, 1962 [Feb. 24, 1961], No. 6962/61. Heading H4D. [Also in Division G1] Recording apparatus for use with an ultrasonic flaw detector comprises (1) a rotatable table 2, Fig. 1, for carrying the test piece 3 and a support 4 running on rails 5 carrying a probe 7, and being driven to move slowly across table 2 by mechanical connection to the table rotating means, (2) a rotatable table 9 carrying a paper chart disc, retained by clips 11, and a stylus at one end of arm 12 to mark the chart on receipt of a signal indicative of a flaw in the test piece, (3) means for mechanically coupling tables 2 and 9 and means for mechanically coupling support 4 and arm 12, such that whenever table 2 is rotated and relative movement occurs between it and support 4 a proportional relative movement in a corresponding direction occurs between table 9 and arm 12. A water tank 1 is provided to couple probe 7 to the test piece; electro-chemical recording with a platinum stylus is employed; a pillar 13 slidable in a slot supports arm 12 and the lower end of the pillar is secured to a cable 14, Fig. 2, which passes over idler pulleys 15 at each end of the slot and is wrapped around a shaft 6 connected via reduction gearing to a vertical shaft on which table 2 is secured. A 5 mc/s. pulse-echo flaw detector is employed and probe 7 incorporates adjacent piezo-electric transducers connected to separate transmitter-receiver units which are fed with control signals simultaneously from a blocking oscillator; the receiver outputs are passed after detection to respective Schmitt trigger circuits which deliver their outputs, one output directly and the other via an inverter, to a gate circuit controlled by a multivibrator of adjustable pulsewidth duration; the gate is arranged to close just after reception of the bottom echo from the test piece, Fig. 3 (Prov.) (not shown). It is arranged, by effective subtraction of receiver outputs, that only flaw echoes are recorded. A " diode pump " integrating circuit is incorporated. A flaw depth indication may be obtained by utilizing a cathode-ray tube indicator. " Swept gain " may be incorporated in the receiving circuits. Specification 868,258 is referred to.