GB1343114A - Apparatus for the detection of irregularities in a material - Google Patents

Abstract

1343114 Photo-electric flaw detection AGFA-GEVAERT 2 June 1971 [8 June 1970] 27617/70 Heading G1A In a device for detecting irregularities in a moving sheet material 30, in which a photo-cell arrangement 38 receives radiation that has been modified by the material, the material is guided along a non-rectilinear path by a roller 24 which supports the material over part only of its width, and the photo-cell arrangement is positioned so that the radiation it receives is derived only from the part of the material passing over the roller that does not directly contact the roller. In one embodiment employing a plurality of measuring rollers (24, 26, 28) Fig. 1 (not shown) each roller consists of successive portions of smaller and larger diameter Fig. 2 (not shown). The material e.g. photographic film passing over each constricted portion is monitored by a source/ photo-cell arrangement, and the constricted portions of one roller are axially offset relative to those of another, so that the entire material width is monitored. Each source comprises a tubular incandescent lamp (42), an infra-red filter (49) and a cylindrical lens (44), while each photo-cell arrangement comprises a row of photo-transistors (16) Fig. 4 (not shown) receiving either reflected or transmitted light. The photo-cell outputs are processed by a defect-detecting circuit, such as described in Specification 1343115, and the location of any unacceptable defects is stored in a computer (36). After passing through the measuring rollers the material is cut into sheets (32) which pass to a take-up station (33-35) where defective sheets, identified by the stored computer data, are automatically rejected. In a further embodiment Figs. 6, 9 (not shown) two measuring rollers are provided, spaced along the direction of travel and each supporting a different half of the photographic film. Hence each source/photo-cell arrangement monitors a different half of the film. Any defect signal causes the winding-up spool to be stopped with the defective portion of the film opposite a non-actinic source of light (93) for visual inspection. A defect signal from the up-stream photo-cell arrangement (51) is delayed by a flip-flop circuit to ensure correct positioning of the defective portion. In another embodiment Fig. 8 (not shown) the material is supported at its margins on disc portions of a measuring roller. The device may also be used for detecting flaws in a series of previously-cut sheets which are fed through the rollers by an assembly of belts (111-113) Fig. 12 (not shown). If it is not desired to monitor the whole of the sheet material, the measuring roller, together with its source/photo-cell assembly, may be reciprocated in a direction transverse to the flow direction.