GB1216924A - Improvements in and relating to the measurement of registration errors - Google Patents

Abstract

1,216,924. Selective signalling. HURLETRON Inc. 26 April, 1968, No. 19883/68. Heading G4H. In a system for measuring errors in registration between a travelling web and a machine operating thereon, scanner 14 senses reference marks on the web, a presettable counter 68, 70 counts pulses from encoder 50 produced in synchronism with movement of a part of the machine and produces an output at 78 simultaneously with a scanner pulse when the registration is correct, and a counter 108 counts encoder pulses between the occurrence of the scanner pulse and output 78, regardless of which occurs first, to indicate errors in registration. Zero reference generator 52 provides a pulse at a fixed point in a cycle of machine operation to start feeding encoder pulses to counter 68, 70 and to set bi-stables 86, 88. When counter 68, 70 reaches a count of 100, it is reset to a number determined by the setting of switches 44, 46 and corresponding to the desired degree of offset between the reference marks on the web and the zero reference of the machine. The first occurring output from 78 or scanner 14 resets the corresponding bistable 86, 88 and an output is obtained from gate 96 until the second of the two pulses occurs. Bi-stable 98 assumes a condition depending on which pulse occurs first and controls the polarity of the output from a digital to analogue converter 114. The output of converter 114 is fed to a zero centred meter 48, though it could be used for automatic correction of the web registration.