| 摘要 |
PROBLEM TO BE SOLVED: To provide a double chain stitch sewing machine which is capable of changing over a thread balancing thread tension at a low cost. SOLUTION: A thread tension device 60 of the double chain stitch sewing machine 30 is capable of vertically moving a tension releasing lever 102. When the lever is moved upward, the thread balancing thread tension in which the tension of a needle thread 77 is put into a tense state and the tension of a looper thread 79 is put into a slackened state, is attained. When the tension releasing lever 102 is moved downward, the second thread balancing thread tension, in which the needle thread 77 is put into the slackened state and the looper thread 79 is put into the tense state, is attained. When a presser foot 37 is moved upward, the tension releasing lever 102 moves upward cooperatively therewith and the thread balancing thread tension changes over to the first thread balancing thread tension. When a control lever 220 is controlled, the tension releasing lever 102 moves downward and the thread balancing thread tension is changed over to the second thread balancing thread tension.
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