| 摘要 |
A pair of pull-down belts pulls longitudinally a tubularly formed elongated bag-making film along a filling cylinder of a bag maker-packaging machine. A pair of members supporting the pull-down belts can move towards or away from each other depending on the size of the former, and elastic springs for providing each of the pull-down belts with a force which depends on their relative positions with respect to the corresponding belt-supporting members. An adjustment motor moves the pull-down belts initially to specified reference positions separate from the tubularly formed film and therefrom towards the filling cylinder. The distance traveled by the pull-down belts from their reference positions towards the filling cylinder is monitored. The distance by which the pull-down belts must be moved for each of different kinds of former is measured and stored in a memory device. Thus, whenever a particular former is selected and installed, the pull-down belts can be automatically moved to optimum positions for pulling down the film effectively by controlling the adjustment motor.
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