| 摘要 |
The device is incorporated in a sewing machine having an arm enclosing and rotatably mounting an arm shaft connected to the sewing mechanism, a drive wheel rotatably mounted on the arm shaft and driven in any suitable manner, and a thread winder including a wheel selectively engageable with the drive wheel. A clutch ring surrounds the arm shaft and is pivotal on a pin extending diametrically of the arm shaft, the clutch ring having a trapezoidal engaging cam engageable in trapezoidal recesses in the drive wheel. A flat spring biases the clutch ring normally to couple the drive wheel to the arm shaft. When the thread winder is moved into a position adjacent a fixed stop, a release stirrup engages the clutch ring and pivots it to a position disconnecting the drive wheel from the arm shaft. Another spring biases the release stirrup away from the clutch ring. The increasing diameter of the thread wound on a bobbin on the thread winder, in cooperation with the fixed stop, gradually moves the thread winder away from the fixed stop and, after a predetermined such movement, the thread winder is effectively uncoupled from the drive wheel and may be swung to a position wherein the stirrup member releases the clutch ring for spring biased reengagement with the drive wheel to automatically recouple the drive wheel to the arm shaft.
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