METHOD AND DEVICE FOR DETERMINING THE PRESENCE OF AT LEAST ONE EDGE OR THE OTHER AND THE OTHER OF TWO OVERCOMING EDGES OF A DISC OR A TAPE OF TRANSPARENT MATERIAL IN A SPECIFIED AREA

摘要

1429544 Detecting edge of transparent sheet photo-electrically GLAVERBEL-MECANIVER 28 Sept 1973 [3 Oct 1972] 45494/73 Heading G1A To detect the presence or position of a glass ribbon 10 in an annealing lehr 11 a light beam 5 is caused to scan to and fro across the ribbon and enters an edge 8 or 9 of the ribbon wherein it is internally reflected so that it produces a deflected beam 6 or 26 respectively producing respective pulses at detector 21 at time intervals indicative of the width of the ribbon, which intervals are determined by timing device 23. The beam is produced by a laser 20 and rotating mirror 18 and passage of a direct beam to the detector is prevented by screen 25, or the roof 14 and/or bottom 12 of the lehr may be opaque. In an alternative embodiment Fig. 4 (not shown) a reference detector (27) is disposed to receive a beam from the mirror without it passing through the glass ribbon, reception of which beam causes detector (27) to transmit a pulse to start the timing device 23. Angle alpha is swept by the beam in scanning from the reference detector to the edge of the ribbon 10 whereby it is deflected to reach detector 21 which pulses the timer to stop, whereby the angle alpha, and thus the position of the edge of the ribbon, may be determined. If the position of the other edge is determined then the position of the ribbon inside the lehr may be determined. Alternatively, Fig. 5 (not shown) the laser itself is pivoted to scan the glass ribbon.