| 摘要 |
A perforation blade member (1) is arranged in and protrudes beyond the surface of a roller (2). In the surface of the roller (3) there are provided two recesses or indentations (19 and 20), the recess (19) extending along half the length of the roller (3) and the recess (20) extending along the entire length of the roller (3), the recess (20) having a wider portion (21) extending along the other half of the length of the roller (3). In operation the rollers (2 and 3) rotate with a peripheral speed substantially equal to the speed of a web being moved lengthwise between the rollers and the blade member (1) may carry out four perforation operations in accordance with the position of the roller (3) and thereby the recesses (19, 20 and 21) relative to the blade member (1) in the active position of said blade member in contact with the web. In case the roller (3) is in a position to be contacted by the blade member (1) along dotted line (22), a first perforation will be carried out in the web as the blade member (1) will only perforate the web along the line (22) and not along the recess (19) where the web only will be deflected by the blade member (1). Correspondingly, a second perforation will be performed in case the blade member (1) contacts the roller (3) along the dotted line (23), and a third perforation will be performed in case the blade member (1) contacts the roller (3) along the dotted line (24) and finally, no perforation will be performed in case the blade member (1) is opposite the recess (20). |
