| 摘要 |
To cut the upper and lower threads, in a double lock-stitch sewing machine, the thread catch (21) is moved from its rest position, and the blade (44) and thread clamp (47) are moved from the rest position into a working position near the opening (4) of the needle plate. The thread catch (21) is moved into an intermediate setting to grasp the lower thread and the part of the thread loop at the fabric side and extend it, and then it returns to the rest position, which draws out lower thread from its bobbin into the thread clamp (47), for the blade (44) to cut the upper and lower threads near the opening (4) of the needle plate. When the threads have been severed, the blade (44) and thread clamp (47) return to the rest position, and the clamp (47) withdraws a further length of lower thread from the bobbin. Also claimed is a thread cutting mechanism with a thread catch (21) on a mounting bolt (20), offset from the axis of the looper and parallel to it. It has a catch for the lower thread, a catch for the upper thread loop, and a cutting edge. A blade (44) and thread clamp (47) swing on the mounting bolt (20) for the thread catch (21). A drive system (29,50) moves the thread catch (21), blade (44) and clamp (47) to shift the catch (21) between a rest position and a movement change position and an intermediate position, and the blade (44) and clamp (47) between a rest and a cutting/holding position.
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