Abstract: To prevent effective print speed from being lowered, a counter is provided for each of a plurality of print hammers. A number of times a print hammer is driven during one print phase having a predetermined period of time is counted by the counter. The counted value is compared with a reference value, and when the counted value has reached the reference value during the print phase, driving of the print hammer is halted until the end of the print phase. A reference value is changed based on the number of times the print hammer is driven during a previous print phase immediately before the present print phase. The reference value represents an allowable number the print hammer can be driven during each of successive print phases.

Abstract: A printer and ribbon cassette with gears for transmitting power from the drive motor of the printer to the ribbon cassette. Guides are provided for guiding the ribbon cassette in a direction perpendicular to the rotational axis of the gears, so that the ribbon cassette slides easily into place and the gears engage easily, but the gears are tightly engaged.

Abstract: A dot line printer has a plurality of print hammers accommodated in a hammer bank, which make dot impressions on a sheet of print paper as the hammer bank reciprocally moves in a print line direction perpendicular to the direction in which the sheet of print paper is fed. To print L dot lines at a time with each of forward and backward movements of the hammer bank, the print hammers are divided into a preselected number of groups so that each group includes N number of print hammers where L and N are integers equal to or greater than 3. The print hammers in each group are displaced one dot line distance from one another in the sheet feeding direction. The print hammers in each group are further displaced in the print line direction by respective predetermined distances from their home positions so that the respective hammers in each group do not impinge upon the sheet of print paper simultaneously.