Overlapped-transfer detecting apparatus for mail article

摘要

A detector for use in a mail sorter is positioned along a path over which articles (letters, postcards, etc.) travel while in an upright position. A problem with such paths is that sometimes articles are overlapped, and sometimes small articles are hidden behind large articles. The invention detects such overlaps by (1) detecting height changes of any single article which trips a detector only once, and (2) forcibly displacing one article relative to the other of two overlapped articles. The change of length resulting from the forced displacement is detected.