Foil for packaging bakery products perforated for ventilation - immediately before making into bags thus ensuring correct positioning

摘要

A pneumatically vertically driven puncturing device is intended for producing a very large number of small holes in a plastic sheet, tube or half-tube intended for prodn. of packaging bags. The puncturing device is mounted in and on the upper part of the automatic bag-making machine directly in front of the sealing (welding)bar. The puncturing device comprises an electrically heated needle puncturing plate with a large number of needles projecting from its lower side closely packed together and staggered, the upper part is recessed to contain the heating elements and the plate contains a number of guide bores which fit onto corresp. rods of the machine frame the needle plate is raised and lowered by a piston-cylinder pneumatic unit. Pref. the needle plate is longitudinally and transversely adjustable and telescopic in construction with facility for incorporation of intermediate pieces. Used esp. for prodn. of ventilated bags for packaging of bread rolls and other bakery prods. which must be ventilated to keep their freshness. The needle plate is incorporated as a direct auxiliary unit to the automatic bag-making machine, with the result that the large number of perforations is produced in the correct position, and in partic. does not spread to the edges of the sheet where perforations can be adversely affect the correct prodn. of welds.