Abstract: In dot impact printers, a platen or a print head may be thermally expanded or contracted due to heat generated from a driver of a print head, with the result that a gap between the print head and a sheet of print paper on the platent varies. In order to maintain a proper gap therebetween regardless of the thermal deformation of the platen and/or print head, a temperature sensor is provided for sensing the temperature of the platen or the print head, and the gap therebetween is adjusted based on the sensed temperature. This adjustment is performed each time when a number of printed characters have reached a predetermined number.

Abstract: For dot impact printers having a platen which may be installed such that the geometric central axis thereof is displaced off a rotation axis about which the platen rotates, a carriage on which a print head is mounted is moved toward the platen from a predetermined position until the distal end portion of the carriage is brought in abutment with the circumference of the platen to thereby measure the surface level of the platen. This measurement is repeatedly carried out while angularly rotating the platen. The thus measured surface levels of the platen are averaged, and based on the average data an optimum position of the print head to be located apart from the sheet of print paper supported on the platen is determined.

Abstract: A paper feeding device for feeding paper to a printer wherein the paper is advanced by a paper feed motor and a print head prints on the paper while the paper is supported by a platen. The feeding device includes a paper stacker for storing a stack of paper sheets, a feed roller which is disposed for contact with a top sheet of the paper stack for feeding the top sheet when the roller is rotated, a first paper path for directing the top sheet from the paper stacker to the printer, a second paper path for directing another sheet of paper to the printer without passing the feed roller, a transmission mechanism disposed between the feed roller and the paper feed motor for transmitting a rotary motion of the paper feed motor to the feed roller, and a cut-off mechanism disposed in the transmission mechanism which is manually operated to a cut-off position in which the feed roller is operatively disconnected from the paper feed motor.