| 摘要 |
A reel of ribbon-like material disposed on a turntable is unwound by pulling the ribbon in a direction perpendicular to the plane of the turntable. The unwound ribbon passes through a sensor which prevents the ribbon from twisting as it is being unwound. The sensor includes a rotatable disc spaced above the turntable and having an opening through which the ribbon is pulled in response to a demand from an external system, such as a machine for applying tie-strips to packages or the like. The disc rotates between two fixed positions to close and open a switch for actuating and de-actuating an electrical circuit coupled to a motor which drives the turntable. When the ribbon is being pulled, it rotates the disc to a position which closes the switch to continuously drive the turntable at the rate at which the ribbon is being unwound to continuously reduce the twist in the unwound ribbon. When the ribbon demand stop, a biasing spring rotates the disc through a short distance to reduce the twist present in the unwound ribbon at the instant the demand stopped. The disc stops in a position which opens the switch to stop the turntable rotation.
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