Patent ID: 7905189

Claim:
A bobbin thread winder which is provided in an arm of a sewing machine so as to be supplied with a driving force from a timing pulley to wind a thread supplied from a thread supply onto a bobbin, the bobbin thread winder comprising: a thread winding shaft to which the bobbin is detachably set and which is rotated by the timing pulley, the thread winding shaft having an end; a thread winding shaft gear attached to the thread winding shaft and having a first gear portion rotatable relative to the thread winding shaft; a second gear portion provided integrally on the timing pulley so as to be mesh-engageable with the first gear portion of the thread winding shaft; and a torque limiter mechanism transmitting rotation of the thread winding shaft gear to the thread winding shaft when a load exerted on the thread winding shaft is below a predetermined value, the torque limiter mechanism cutting off transmission of rotation of the thread winding shaft gear so that the rotation of the thread winding shaft gear is prevented from being transmitted to the thread winding shaft when the load exerted on the thread winding shaft is not less than the predetermined value, wherein: the torque limiter mechanism includes a closely wound portion on a periphery of the thread winding shaft and a coil spring having a spring end engaged with the thread winding shaft gear; the rotation of the thread winding shaft gear is transmitted to the thread winding shaft by a frictional force of the closely wound portion when the load exerted on the thread winding shaft is below the predetermined value; and when the load exerted on the thread winding shaft is not less than the predetermined value, the closely wound portion is loosened such that the rotation transmission is cut off.