摘要:
A residual bobbin thread amount detection apparatus for a sewing machine which includes a hook rotating in association with a main shaft of the sewing machine and a bobbin rotatably mounted on the hook. A first detector detects the rotation speed of the main shaft and a second detector detects the rotation speed of the bobbin. A comparator responsive to the second detector generates a signal when the rotation speed of the bobbin exceeds a predetermined value, whereby a controller operates an alarm.