Abstract: An impact dot line printer has a hammer bank equipped with a plurality of printing heads along printing lines mounted on the upper side of a belt extended between a pair of rotational drums. A counter balancer is mounted on the lower side thereof, the hammer bank and the counter balancer being reciprocated in the directions reverse to each other. Since repelling springs are provided on both left and right sides in order to reduce thrust required for deceleration at the end of shuttling operation of the hammer bank and the counter balancer, vibrations or noises caused by the collisions with the spring might occur. But by the present invention, rotors are provided with eccentric weights which act so as to offset force couple at the time of the collisions with the repelling springs, whereby the shock force caused by the collisions is sharply decreased to suppress the vibrations or noises.