| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability of operation in forming a seam by a needle and a looper in a sewing machine by monitoring the thread vibration generated by thread consumption on the looper side between a pair of thread passages inserted into a threading hole by a sensor, and stopping the machine driving when thread break in the looper is detected. SOLUTION: In the bed of a sewing machine, a thread controlling cam 11 for changing a projecting amount from a thread reeling stand 10 according to the rotation of a main shaft S is provided, and a thread guide 12 is placed on the thread reeling stand 10 on both sides of this thread controlling cam 11. A thread break detecting device 13 for detecting thread vibration is placed on a looper thread passage between this thread controlling cam 11 and a looper 3. This thread break detecting device 13 consists of a pair of thread passages 15 each having a threading hole 15a and a sensor 16 consisting of a light emitting element and a light receiving element facing each other. Driving of the machine motor is controlled to stop when no thread vibration, namely, thread break is detected from the output of this thread break detecting device 13 by a control circuit.
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