Patent ID: 7596839

Claim:
Device for drawing a film web of thermoplastic polymer comprising a driven roller ( 2 ) driven at a speed of V 1 and a second driven roller ( 3 ) driven at a speed of V 2 , V 1 <V 2 , and the rollers ( 2 )/( 3 ) being arranged in such a way that a drawing gap ( 4 ) is formed between the two rollers ( 2 )/( 3 ), and wherein between the two rollers ( 2 )/( 3 ), a width-maintaining device is arranged which mechanically grips peripheral areas of the film web in such a way that the width of the film web remains essentially unchanged during longitudinal drawing in the drawing gap ( 4 ), and wherein the width-maintaining device includes two pairs of carriages ( 5 a ) and ( 5 b ), one pair of carriages ( 5 a ) and ( 5 b ) being positioned on one film periphery and each of the four carriages having a plurality of rolls ( 6 a ) and ( 6 b ) arranged in sequence, one carriage being arranged on each film periphery above and one carriage opposite below the film web and the carriages ( 5 a ) and ( 5 b ) arranged above and below a film periphery being positioned vis-à-vis each other in such a way that the rolls ( 6 a ) and ( 6 b ) are aligned in the direction of advance ( 9 ) of the film and the pairs of rolls ( 6 a ) and ( 6 b ) lying opposite each other touching the film web lying inbetween in the peripheral area ( 10 ).