GB1182730A - Improvements in and relating to Roller Apparatus more especially for Stretching Film Webs Longitudinally - Google Patents

Abstract

1,182,730. Film web stretching apparatus. KALLE A.G. 7 May, 1968 [8 May, 1967], No. 21544/68. Heading B5B. A roller assembly, for use more especially for the longitudinal stretching of webs of plastics film, comprises freely rotatable rollers 1, 2 (Figs. 1 and 2) mounted parallel to one another on fixed axes. A third roller 3, acting as a driving roller and itself driven through a suitable flexible coupling 25 by means of a motor 26, is mounted in two vertically yieldable bearings, one of which is shown at 9, the axis of the roller 3 being located in the plane of symmetry a-b of the rollers I and 2. The bearings 9 of the driving roller 3 are adapted to allow the roller to move in a vertical plane so that its weight is supported by the rollers 1 and 2 |(or by the film web passing through the nips between the rollers 3 and 1 and 3 and 2 respectively). In a plane perpendicular to the three roller axes, lines joining them form a triangle having an apical angle of 120 degrees. A further roller 4 parallel to the other rollers is positioned over the driving roller 3, its axis being in the plane of symmetry a-b of the other three rollers, and the journals of this roller, one of which is shown at 5, are mounted to be freely rotatable in bearings at the outer ends of levers 6 mounted on pivots 7. The arrangement is such that the plane in which lie the pivots 7 and the axis of the roller 4 also contains the line on the further side of the periphery of the roller 4 where the approaching film web 8 first contacts the roller, the direction of this approach being such that there is a small clearance between the web and the periphery of the roller 1. The web 8 after passing around the freely rotatable roller 4 passes around the driving roller 3 after which the emerging web 10 continues its course from any required line on the periphery of the roller 2. When first introducing the web 8 into the roller assembly the rollers 3 and 4 are raised by known means, such as hydraulic jacks, so as to facilitate the introduction of the web. In the modification shown in Fig. 3, the freely rotatable pivotably mounted roller 4 is replaced by two rollers 12 and 13 freely rotatable in bearings at the ends of levers pivoted on pivots one of which is shown at 18. An apparatus for the longitudinal stretching of a film web may comprise a mirror-image duplication of the roller assemblies shown in Figs. 1 and 2. In this case the web is stretched between a zone between the two assemblies and the zone is provided with heating means. The positively driven roller of the draw roller assembly is driven at a higher peripheral speed than the corresponding roller of the feed roller assembly. The arrangement according to the invention enables the forces necessary to exert pressure at the roller nips to be derived from the tension in the film web.