| 摘要 |
An incrementally variable transmission (16) for transmitting torque between input and output rollers (4,6) in a prestretching device (2) of a stretch-film wrapping machine achieves a selectable prestretching of a plastic film with a predetermined yield point, running in contact with the rollers. The input roller (4) is caused to rotate at lower rpm than the output roller (6), and the transmission (16) comprises a multiratio gear train (22) between an input shaft (28) and an output shaft (26), said gear train (22) being arranged in a housing (18), and a device (24) engaging and disengaging the input shaft (28) to or from the gear train. The input and output shafts (28,26) of the gear train are coaxial. The coupling device is a free-wheel clutch (20) which is in its engaged position when the input roller (4) is imparted, due to tension in the film between the rollers, a torque from the output roller (6), and the clutch (20) assumes its released position when said torque is absent. <IMAGE> |
