| 摘要 |
A web feed device, particularly a tractor for feeding perforated paper, is provided with the capability of automatically cutting a margin along the edge of the paper. Where this margin is defined by side perforations, the apparatus is operative to burst the perforations automatically. The tractor has a lid which is spring biased in a closed position spaced from a surface of the frame of the tractor over which the paper is driven, as by a belt having pins which are received in feed perforations along the margin between the side perforations and the edge where the belt is entrained around a sprocket which drives the belt. The mechanism has a lower cutting disk, driven with the sprocket and presenting a cutting edge along an outside surface. An upper disk is reciprocally movable in a housing against the bias of a spring, which maintains the upper disk in retracted (non-cutting) position, to cutting position where a cutting edge between an inside surface of the upper disk overlaps the outside surface of the lower disk to form a cutting scissor for cutting the margin or bursting the side perforations. The cutting action is selectively enabled by manually advancing the upper disk, thereby selectively providing a cutting mode of operation and enabling the upper disk to release from the lower disk, when in its cutting mode position, automatically-as when a paper jams occurs and the lid is forced away its closed position when the housing is mounted on the lid.
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