Gapping system for slide-fastener manufacture

Abstract

A slide-fastener stringer is pulled through a gapping station by a motor operatively engaging the stringer without slip and at least one feed roller engaging the stringer upstream of the gapping station. A storage unit downstream of the feed roller and upstream of the gapping station loops the stringer upstream of the station in a variable-size loop and has a rotatable and movable buffer roller over which the stringer passes and a pair of rotatable but nonmoving buffer rollers flanking the movable buffer roller. The movable roller is urged away from the flanking rollers with a force sufficient to tension the stringer. The drive of the feed roller is operated in accordance with the position of the movable buffer roller for stretching the stringer between the buffer rollers by at most 1%. A gapper at the station periodically clamps and longitudinally arrests the stringer and then cuts the coupling elements therefrom at the station. A sensor roller physically engaging the stringer between the station and the loop detects and measures the displacement of the stringer after each clamping and cutting of the stringer at the station and generates an actual-value output corresponding thereto that is compared with a set point corresponding to a desired slide-fastener length after each clamping and the stringer is longitudinally advanced after each clamping and cutting of the stringer only until the actual-value output matches the set point.