PURPOSE: When abnormality in the yarn is sensed, an arm comes into contact with the frame for reeling the silk yarn and is hit off by frame to make the reel-stopping lever operate, thus operating the reel-stopping lever having a strong spring force with a weak shock on the sensing part.

CONSTITUTION: A knot or the like or the like on the yarn 8 causes abnormal tension of the yarn and turns the yarn collector 3 to the position of the broken line and the sensing lever 15 is rotated through the connecting lever 14. The arm 17 moves toward the reel frame 2 until coming into contact with it and is hit off by the frame to rapidly revolve clockwise around the axis 24 until the connecting part 23 collide with the stopper pin 27. The rotation of the connection part 23 releases the connection between hook parts 26 and 31 to rotate the frame-stopping lever 28 on the idling position crockwise with a strong tension of the spring 32 to press the frame 2 for braking the revolution.