| 摘要 |
A sewing machine including a needle that is supplied with an upper thread. A drive element drives the needle to perform a reciprocating movement in order to carry the upper thread through a sewing material that is advanced between the upper thread and the lower thread, so that the upper thread forms a loop beneath the sewing material. A shuttle houses a lower bobbin for the lower thread and a shuttle arm on the shuttle which catches in the loop of the upper thread and carries the upper thread around the lower bobbin, so that a stitch is executed on the sewing material. A thread tensioning and take-up lever on each stitch draws the loop tight so that a knot is formed in the sewing material by interaction of the upper thread and the lower thread. A thread feeder feeds the upper thread to the needle and a control element on each stitch causes the thread feeder at the beginning of a stitch to advance a predetermined length of upper thread, including an excess thread, and at the end of the stitch to correct the length of the upper thread by recovering the excess upper thread, or advancing the further upper thread required.
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