| 摘要 |
969,852. Stretching films. FMC. CORPORATION. Nov. 29, 1960 [Jan. 22, 1960], No. 41020/60. Heading B5B. A film 11 consisting of organic thermoplastic polymeric material and having a web 13 of uniform thickness and beaded longitudinal edges 15 is continuously stretched in an apparatus (Figs. 1 to 3) in which a pair of rolls 17 and 19 guide the film to a pair of laterally spaced parallel metal guides or tracks 21 adapted to slidably engage with the film beaded edges 15. The film 11 is advanced relative to the tracks 21 by a metering device 23 and is advanced between a pair of diverging metal tracks 25 by a pair of take-up rolls 31 and 33 driven at a higher peripheral speed than the metering device 23 to stretch the film longitudinally. The tracks 21 are secured to elongated closed ducts 35 through which a heating medium may be circulated. Heating panels 39 are adjustably mounted above and/or below the path followed by the film between the tracks 21 for heating the film web 13 to a temperature above that of the beads independently of the means for heating the beaded edges of the film. The metering device comprises a frame 41 on which are rotatably mounted a pair of shafts 43, 45 to which are fixed bead-engaging peripherally grooved rollers 47, 49. These rollers are driven in opposite directions at equal and uniform peripheral speeds. To facilitate lacing up of the apparatus the shaft 43 is resiliently mounted by means of journal blocks 55 slidably mounted in the frame 41. Springs 59 adjustable by screws 63 urge the rollers 47 against the film beads 15 with sufficient force to grip the beads firmly. The film is both longitudinally and transversely stretched during its passage between the guides 25, which may include endless conveyers. In addition to or instead of the rolls 47, 49, a series of metering rollers may be disposed at spaced intervals along the entrance portion or the entire length of each of the stretching tracks. In this case each successive pair of rollers may be driven at a slightly higher speed than the immediately preceding pair of rollers to achieve a progressive longitudinal stretching of the film as it travels between the diverging tracks. In two other embodiments of the apparatus of the invention the shafts on which the rollers are mounted are at rightangles to the plane of the film. Specification 969,005 is referred to.
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