| 摘要 |
A balancer is fixedly attached to a rotary input shaft of a crank mechanism that converts rotary drive of a needle bar drive source to up-and-down motion of a needle bar. The balancer is caused to rotate at substantially an opposite phase with respect to up-and-down motion of the needle bar with the rotary drive of the needle bar drive source. When the balancer is driven at substantially the opposite phase with respect to the up-and-down motion of the needle bar, inertia force in an up-and-down direction of the needle bar, generated due to the up-and-down motion of the needle bar is negated, whereby it is possible to reduce vibration generated in the up-and-down direction. Sewing heads paired with each other by being arbitrarily combined are controlled so as to be rotationally driven to cause rotational directions of the needle bar drive sources to become opposite directions to each other. |
