CPC D05B 3/02 (2013.01) [D05B 57/36 (2013.01)] | 10 Claims |
1. A sewing machine comprising:
an upper shaft that drives a needle and a balance;
a lower shaft that drives a hook and a feed dog;
an upper and lower shaft belt that connects the upper shaft and the lower shaft and synchronizes rotation of the upper shaft with rotation of the lower shaft; and
an idler unit that includes an idler that comes into contact with the upper and lower shaft belt and pushes the idler into the upper and lower shaft belt to change a tension side belt length,
wherein the idler unit comprises:
a transmission mechanism connected to the upper shaft or the lower shaft; and
a rotating body mechanism provided with the idler and having a rotating body that rotates in synchronization with the upper shaft or the lower shaft by the transmission mechanism,
wherein a pushing amount of the idler into the upper and lower shaft belt is changed according to rotation of the rotating body, and
wherein a center of gravity of the rotating body mechanism is on a rotation axis of the rotating body.
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