| 摘要 |
The invention provides an apparatus for transversely stretching and molecularly orientating a continuously advancing flexible web, comprising an arrangement for preventing substantial inward movement of the web margins and a pair of opposed hanks of transversely spaced pressure elements between which banks the web can travel whilst its margins are engaged by the restraining means. The pressure elements of one bank are transversely staggered in relation to the elements of the other bank, and, as seen looking in the transverse direction, overlap the pressure elements of the other bank with such a degree of overlap that the pressure elements cause the web to take up an extended form from margin to margin by applying opposed forces respectively to the opposite surfaces of the web at spaced locations across the width of the web and transversely stretch the web into a pleated form without substantial inward movement of the web margins. The pressure elements of at least one of the banks are stationary pressure members having web-engaging slide surfaces arranged to provide a gradually increasing amount of overlap with the pressure elements of the other bank in the direction of advance of the web. A drive arrangement is provided for continuously advancing the web longitudinally between the banks so that the pressure elements continuously transversely stretch the web. In this manner the angle of attack of the pressure elements on the web can be reduced to allow proper feed of the web, particularly in the centre. In addition, the rate of transverse stretching can be more accurately controlled. |
