| 摘要 |
This invention provides an improved method and apparatus for automatically controlling travel of two transversely spaced parallel plastics film strips,which are intermittently moved, to maintain transverse alignment between register marks on the two film strips in a bag-making machine or the like that can correct rapidly and effectively the relative positional gaps produced between the register marks on the two strips by means of a single retarding device for the two strips as incorporated in the apparatus. The single retarding device is arranged to constantly and relatively impart a retarding force to the two strips and to operate such that when the retarding force imparted to the preceding strip is stepwise raised to further slow either one of the two strips that goes ahead of the other strip, the retarding force imparted to the other lagging strip is stepwise lowered and released, conversely to thereby accelerate advance of the other lagging strip relative to the decelerating preceding strip, whereby said relative positional gaps can be rapidly and effectively corrected. |
