PURPOSE: To prevent danger due to the tooth tip of a pitch roller, by accommodating a first and a second pitch rollers in a carbon ribbon case and a correcting ribbon case.

CONSTITUTION: A support 16 is pushed to the direction of an arrow to part pitch rollers 14, 15 from a position opposed to wind-up wheels 22, 24 of a correcting ribbon and a carbon ribbon and protruded pieces 7, 7' provided to the front side of a correcting ribbon case 2 is inlaid with recessed parts 5, 5' provided to the front side of a platform 1 while the case 2 is pressed downwardly to introduce protruded pieces 6, 6' provided to the rear side thereof into cut and erected engaging parts 4, 4' provided to the rear part of the platform in a repulsive state to mount the case 2 to the platform 1. Subsequently, a carbon ribbon case 3 is mounted by similar operation and feed levers 19, 20 are reciprocally moved to intermittently drive feed gears 17, 18 individually and the ribbons 12, 13 are fed quantitatively.