GB786120A - Improvements in or relating to means for controlling the lateral positions of movingwebs of material - Google Patents

Abstract

786,120. Photo-electric web control. SIEMENS - SCHUCKERTWERKE AKT. - GES. Sept. 29, 1955 [Sept. 29, 1954], No. 27789/55. Class 40 (3). To derive a signal representative of the lateral deviation of a moving web, a mark on a rotating member is arranged to be obscured to an extent dependent on the web deviation so that a photo-electric device scanning the mark produces a signal representative of the deviation. In the arrangement of Fig. 1 a roller 6 driven by the web on a separate constant speed drive carries a sloping mark 4 and rotates in the direction of the arrow. An optical scanning device projects a spot of light on to the other and produces an electrical impulse when the sloping line enters the light beam. The instant of commencement of this impulse depends on the degree of overlap of the sloping line by the edge of the web. A reference pulse is produced by a separate mark 6 which may be on the same roller or a separate member coupled to the roller. The reference pulse may also be derived magnetically. Comparison of the two impulses produces a signal which permits adjustment of the edge of the web. In the arrangement of Fig. 2 a mark parallel to the web axis is carried on a roller whose axis is parallel to the length of the web. Again the instant of occurrence of the output pulse indicates the lateral web position. In the arrangement of Fig. 3, marks 11a, 11b, 11c are carried on roller 2, the arrangement being that the number of such marks completely covered depends on the web position. Thus the frequency of the scanner output pulses indicate the web position. In a still further arrangement the roller may carry triangular marks having their base parallel to the web travel. According to the overlap of the web on these triangles the lengths of the output pulses differ.