Two tray-supporting racks are located on opposite sides of an elevator carriage which carries a mechanized retrieving system for withdrawing trays from either rack and delivering them to a work area. The elevator carriage is vertically driven by a motor, sprockets, and chains. A transport chain travels...http://www.google.com.tw/patents/US5213463?utm_source=gb-gplus-share專利 US5213463 - Mechanized storage system
