| 摘要 |
A pair of tension discs is disposed on a tension stud fixed in part of a sewing machine main body. A pneumatic cylinder has a drive rod. The drive rod moves at least one of the tension discs to other tension disc so that one tension disc is pressed to other tension disc. An air regulator is interposed between the pneumatic cylinder and an air supply source, being composed in an electropneumatic system for converting between voltage and air pressure. By controlling the applied voltage to the electropneumatic air regulator on the basis of an instruction from a microcomputer, the set pressure of the air supplied to the pneumatic cylinder is adjusted. Thereby the pressure to the thread held between the pair of tension discs, that is, the thread tension is controlled. As a result, without having to stop the operation of the sewing machine, the thread tension can be adjusted promptly and appropriately.
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