Patent ID: 7216597

Claim:
A threading device for a sewing machine comprising: a threading shaft disposed in parallel with a needle bar having a needle provided at a lower end thereof, and supported rotatably and movably in a vertical direction with respect to a machine frame; a threading member provided at a lower end of the threading shaft, and having a threading hook capable of being inserted through a needle eye of the needle; a pin fixed to the threading shaft, and having both ends protruded outward in a radial direction with respect to the threading shaft; operation means having a guide groove formed in a spiral shape with respect to a rotating axis of the threading shaft, and capable of being operated in a vertical direction, one end of the pin being inserted through the guide groove; and a guide member having a stopper portion disposed on a vertical moving path of the other end of the pin, and a clearance groove formed seamlessly with respect to the stopper portion, and fixed to the needle bar, wherein the threading device for a sewing machine further comprises an erroneous rotation preventing member provided on the threading shaft, the erroneous rotation preventing member having a disengaging portion capable of being engaged with the stopper portion and a rotation regulating portion capable of being engaged with the pin, further wherein the other end of the pin engages with the stopper portion when the threading shaft moves downward by operating the operation means to move downward, the threading shaft rotates along the guide groove so that the threading member penetrates through the needle eye of the needle when the threading shaft further moves downward, the disengaging portion engages with the stopper portion before the other end of the pin engages with the stopper portion in the downward movement of the threading shaft, and the rotation regulating portion engages with the pin to prevent the rotation of the threading shaft until at least the threading shaft further moves downward after the disengaging portion engages with the stopper portion.