Multihead sewing machine with improved shuttle drive control

A multihead sewing machine comprising:

• a sewing machine motor;
• a main shaft rotated by the sewing machine motor;
• a plurality of sewing needles driven by the main shaft;
• a plurality of shuttles for capturing thread loops in cooperation with the sewing needles respectively, each shuttle having a hook shaft;
• a plurality of shuttle driving motors for rotating the hook shafts of the shuttles independent of the sewing machine motor respectively;
• sewing control means for controlling the sewing machine motor and the shuttle driving motors so that the sewing machine motor and each shuttle driving motor are rotated in synchronism with each other;
• loss-of-synchronism detecting means for detecting loss of synchronism of each shuttle relative to the corresponding sewing needle;
• and
• emergency stop control means for instructing the sewing control means to rotate, in synchronism with the main shaft, at least the shuttle driving motor or motors other than the shuttle driving motor regarding which the loss of synchronism has been detected by the loss-of-synchronism detecting means, when the main shaft is stopped and subsequently rotated manually or mechanically in an abnormal condition wherein the loss of synchronism has been detected with respect to the shuttle driving motor.

A storage medium for storing a program for operating a multihead sewing machine comprising a sewing machine motor, a main shaft rotated by the sewing machine motor, a plurality of sewing needles driven by the main shaft, a plurality of shuttles for capturing thread loops in cooperation with the sewing needles respectively, each shuttle having a hook shaft, and a plurality of shuttle driving motors for rotating the hook shafts of the shuttles independent of the sewing machine motor respectively, the program accomplishing the functions of:

• sewing control means for controlling the sewing machine motor and the shuttle driving motors so that the sewing machine motor and each shuttle driving motor are rotated in synchronism with each other;
• loss-of-synchronism detecting means for detecting loss of synchronism of each shuttle relative to the corresponding sewing needle;
• and
• emergency stop control means for instructing the sewing control means to stop rotation of the main shaft in an abnormal condition wherein the loss of synchronism has been detected with respect to at least one of the shuttles by the loss-of-synchronism detecting means, the emergency stop control means further instructing the sewing control means to rotate, in synchronism with the main shaft, at least the shuttle driving motor or motors other than the shuttle driving motor regarding which the loss of synchronism has been detected, until rotation of the main shaft stops.