Sewing machine with improved shuttle drive control

A sewing machine comprising:

• a sewing machine motor;
• a main shaft driven by the sewing machine motor;
• a sewing needle driven by the main shaft;
• a shuttle for capturing a thread loop in cooperation with the sewing needle, the shuttle having a hook shaft;
• a shuttle driving motor provided for driving the hook shaft of the shuttle independent of the sewing machine motor;
• drive control means for controlling the sewing machine motor and the shuttle driving motor so that the shuttle is rotated in synchronism with the main shaft;
• loss-of-synchronism detecting means for detecting an increase to a predetermined amount in displacement of a rotational position of the hook shaft with respect to a rotational position of the main shaft;
• and
• hook shaft reverse rotation control means for controlling the shuttle driving motor so that the shuttle driving motor is reverse-rotated by a predetermined amount after interruption thereof when the predetermined amount of displacement has been detected by the loss-of-synchronism detecting means.

A storage medium for storing a program for operating a sewing machine comprising a sewing machine motor, a main shaft driven by the sewing machine motor, a sewing needle driven by the main shaft, a shuttle for capturing a thread loop in cooperation with the sewing needle, the shuttle having a hook shaft, and a shuttle driving motor provided for driving the hook shaft independent of the sewing machine motor, the program accomplishing the functions of:

• drive control means for controlling the sewing machine motor and the shuttle driving motor so that the shuttle is rotated in synchronism with the main shaft;
• thread jamming detecting means for detecting a thread jamming in the shuttle;
• and
• releasing means controlling the shuttle driving motor for releasing the shuttle from the thread jamming when the thread jamming is detected by the thread jamming detecting means.