Alignment measuring system and method

Abstract

An apparatus for measuring the alignment of two or more adjacent targets while the targets are in motion is provided. The alignment measuring apparatus includes a plurality of alignment scanners, each adapted to detecting the arrival of an associated target. A speed scanner is spaced apart from the alignment scanner for detecting said first one of the targets. First timing means are provided for measuring a first time differential indicative of the time delay between detection of the leading and trailing targets by the alignment scanners to provide a measurement proportional to the misalignment between the targets. Second timing means measure a second time differential indicative of the time delay between detection of the first target by the speed scanner and its associated alignment scanner to provide a measurement that is proportional to the speed at which the lugs are traveling and determining whether adjacent lugs are within a selected alignment tolerance based in part upon the time differential measurements. An oscillatory timing clock operates at a selected frequency and the first timing means determines the number of clock pulses that occur during said first time differential measurement. Similarly, the second timing means determines the number of clock pulses that occur during the second time differential measurement. A frequency divider proportionally dividing the number of clock pulses in said second time differential measurement by a selectable number to provide an calibration output indicative of the maximum number of clock pulses that may occur within the first time differential measurement for the targets to be within a selected tolerance. The magnitude of the calibration output is then compared to the number of pulses within said first time differential measurement to determine whether the targets are within the selected tolerance.