Importance

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Abstract

A system for locating the edges of a moving strip of material having two edges. In one embodiment, a pair of ultrasonic transducers are positioned above the path of the moving strip and oriented at acute angles relative to the surface of the strip. A circuit for causing each of the transducers to emit ultrasonic pulses in the direction of the two edges, respectively, a detector circuit connected to the ultrasonic transducers detects acoustic diffractions caused by the edges, respectively, and compares the times of detection of the acoustic diffractions to locate the positions of the edges relative to the pair of transducers. A microprocessor controls operation of the transducer and receiving signals therefrom and computes one or more of the following quantities: 1) the distance D.sub.1 from the transducer to the near one of said two edges, 2) the distance D.sub.2 from the transducer to the other of the two edges, 3) the distance to the center of the strip from the transducer D.sub.c =1/2(D.sub.1 +D.sub.2), and 4) the width of the strip W=D.sub.2 -D.sub.1.

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First Claim