| 摘要 |
At a work clamp for buttonhole sewing machines, comprising a support plate and a clamping frame arranged at a pivotable carrying lever, spaced from the clamping frame, a hold-down device with a clamping plate resiliently pressed against the work is fastened at the carrying lever. The clamping frame, when raised is pressed into a slanting position by a spring. During the descending movement of the clamping frame and hold-down device, the hold-down device precedes the clamping frame and clamps the work to the support plate. As a next step, the edge of the clamping plate of the clamping frame which is spaced from the hold-down device impinges on the work. A clamping surface of the clamping plate forms an acute angle with the support plate. As the descending movement of the clamping plate continues, the clamping frame swings out about its bearing pin on the carrying lever. At this time the edge engaging the work moves away from the hold-down device. The work is therefore pulled smooth and stretched in the buttonhole sewing area before it is clamped by the clamping plate for the following sewing operation. By this measure, rippling of the area of the work surrounding the buttonhole is prevented.
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