Multi-head sewing machine free of twist and vibration in main shaft

摘要

A multi-head sewing machine has the heads (3), each having at least one needle bar and one take-up lever, and shuttle holders (6) arranged in a row, the number of shuttles and heads matching. A main shaft (20a, 20b) runs through the row of heads rotates to drive the needle bars and take-up levers in the heads and a lower shaft (33), running through the row of shuttle holders, rotates to drive the shuttle (15) in each holder. There is also a drive shaft (21a, 21b) parallel to the main shaft driven to rotate by a motor (27) such that its torque is transmitted to the main shaft at more than one point. Also claimed is a variation of the machine where the driving force from a motor is transmitted to the main or the lower shaft at a mid-point and the ends of the lower shaft are connected to the ends of the main shaft via torque transmission mechanisms. Also claimed is a further variation of the machine where the driving forces of motors placed on the ends of the lower or main shaft are transmitted from the one shaft to the other via torque transmission mechanisms and the motors are designed to drive synchronously. Pref. the drive shaft dia. is greater than that of the main shaft and the motor torque is transmitted to the end sections of the drive shaft. Alternatively the torque is transmitted to the drive shafts at points which lie at a pre-determined distance from the ends of the drive shaft. The main shaft is divided into two shorter parts and the drive shaft torque is transmitted to the divided main shaft part (20a or 20b) in its middle section.