Position indicating apparatus for transporters on tracks

Abstract

A position indicating apparatus, particularly for overhead transport systems (1), includes a elongated code carrier (11) carrying multi-value code marks (17) along its length. A code reading device (12) secured on a transport carrier (4), such as a trolley, crane, or other traveling mechanism, reads the code marks on the code carrier. To prevent erroneous reading when the transport carrier (4) and thus the code reading device (12) is tilted or skewed with respect to the code carrier, and to ensure accuracy of position of reading of the code carrier, the code marks (17) are arranged on the code carrier (11), one next to another in a single row or track, and formed such that m of the code marks provides one code word, the code words being positioned one next to each other and appear only once, or are unique along the entire code carrier. The code reader (12) has a reading station (19), for each bit, with three sets of reading heads (58a, 58b, 58c) per station ( 19) which are equidistantly distributed by a distance corresponding at least to the number of digits of a code word to provide, upon processing of outputs from all three reading heads, an unambiguous position indication.