Automated handling in the finishing area

摘要

The finishing area has always seen the greatest requirement for labour in the tannery—traditionally, each individual piece of leather had to be presented to, and removed from, each process machine by that most versatile of tools, a pair of human hands. The rising cost of labour in developed countries, and the increasing difficulty of finding workers prepared to do monotonous, repetitive manual work, have been the impetus for many years to seek automated handling solutions. Mechanical stackers first appeared in primitive forms over twenty years ago, their purpose being to replace the operators at the end of spray lines, for example, whose function was solely to lift the leather from the conveyor and lay it onto a transfer table or drape it over a "horse". Many early stackers achieved this with a conveyor fixed in the horizontal plane, with a reciprocating carriage that moved a table or horse beneath the conveyor (Figure 2). As the leather came off the end of the conveyor, it transferred smoothly onto the table or horse moving beneath. As the stack of leather increased in height, the conveyor was elevated incrementally, either by a screwjack arrangement or by lifting chains. Reciprocation of the carriage was initiated by photocell or proximity switch mounted on the conveyor system, which detected the leading edge of the leather and intiated the sequence through an adjustable delay timer.