| 摘要 |
<p>A method of detecting the condition of a rectangular sheet (8), comprising feeding the sheet, e.g. by belts (2, 4), :hrough a checking station (adjacent to II-II), the direction of ceding (6) being along the length or the width of the sheet; deflecting, e.g. by stationary guide rails (10a, 12a 10b, 12b), a portion of a side edge of the sheet at the checking station elatively to the remainder of a zone of the sheet (8) lying adjacent to a line through the checking station transverse to the direction of feeding, the direction of deflection of the deflected portion being orthogonal to the line and to the direction of feeding, so that the deflected portion is stretched along the direction of feeding; and subjecting the deflected portion to a beam of radiation directed from means (14a, 14b) towards sensing means (16a 16b) and intercepted by the deflected portion, whereby any substantial tear from the side edge into the deflected portion will be opened, and will be revealed by the sensing means (16a, 16b) receiving radiation through the opened tear.</p> |
