Abstract: A sheet-feeding mechanism comprises feed rollers attached to a first driving shaft and spaced from each other by a predetermined distance, two of the feed rollers being end feed rollers located at both ends of the first driving shaft. A pair of end ball rollers are attached to a second driving shaft and located in correspondence to the end feed rollers. A double-structure bail roller is attached to the second driving shaft in correspondance to the feed rollers, except for the end feed rollers. The double-structure bail roller includes an inner core and an outer layer having a small friction coefficient. The iner core is elastically deformable in a direction in which the end feed rollers are pressed against the corresponding bail rollers.

Abstract: A positioning device for a printer for driving a ribbon base on which a ribbon cassette is carried by means of a stepping motor to position a ribbon to any of predetermined shift positions. The device includes a stopper for defining a home position of the ribbon cassette, and a power transmitting mechanism for transmitting a power of the stepping motor to the ribbon base. The power transmitting mechanism includes therein a torque limiter which yields a slip therein when a torque lower than a pull-out torque of the stepping motor is applied thereto. Accordingly, when the ribbon cassette is abutted with the stopper, the stepping motor is allowed to continue rotation thereof without stepping out by the torque limiter, thereby preventing an out-of-phase condition of the stepping motor at a stopped position thereof. Consequently, upon subsequent operation, the ribbon cassette can be shifted accurately, and hence color mixture in printing can be eliminated.