CONVEYORS FOR UNIT LOADS AND PACKAGE HANDLING-NAMELY, ROLLER, WHEEL, BELT, CHAIN AND TRANSFER CONVEYORS AND PARTS THEREFOR; OVERHEAD CONVEYORS; MATERIAL LIFTING DEVICES-NAMELY, SCISSOR LIFTS AND SUSPENDED SHEET LIFTERS; AND MECHANIZED EQUIPMENT FOR HANDLING AND STORING UNITIZED LOADS-NAMELY, MECHANIZED WAREHOUSING STORAGE APPARATUS