| 摘要 |
A pre-stretching mechanism, for use in an orbital wrapping apparatus whereby a web (6) of plastics film is drawn from a feed roll (5) of film and applied t o an object to be wrapped by virtue of relative rotational movement of the object and the roll, comprises a braking roller (9) in contact with the feed roll, a stretching roller (7) in contact with the web and drive transmission means (10, 11, 12) connecting the rollers such that the surface speed of the stretching roller in the direction of film movement exceeds that of the braking roller in that direction, wherein the feed roll is mounted for rotation upon slideable saddles (16) and the contact pressure between the braking roller and feed due to tension in the drawn-off web is augmented by loading springs (18) to an extent such that slippage occurs between the feed roll and the braking roller before draw-off tension in the web reaches a val ue at which the web would neck down and break.
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