METHOD AND APPARATUS FOR CHECKING THE WIDTH AND PARALLELISM OF MARGINS FOLLOWING CENTERING OF A PRINT WITH RESPECT TRESPECT TO A SUPPORT

摘要

A method and apparatus for checking the width and parallelism of margins following the centering of a print with respect to a support. The support is moved in front of two opto-electronic reading devices with the margins to be checked arranged transversely with respect to the direction of movement of the support. The reading devices are used to produce two counting periods for each margin, the widths of the periods corresponding to the widths of the margin at two points thereof. Clock pulses are produced depending on the movement of the support by means of an opto-electronic detector. Clock pulses appearing in the counting periods are counted and the resultant count compared with maximum and minimum reference values to check the width of the margins. Clock pulses appearing in one of the counting periods are counted only when the counting periods do not coincide with regard to time and the number of pulses counted is compared with a reference value representing the tolerance limit of non-parallelism.