Method and apparatus for adjusting the spacing between head and platen

Abstract

A printer of the kind having a printing head for printing on a sheet being held against a platen roll by a sheet presser, with both printing head and sheet presser mounted fast to a head carriage which is movable not only in a direction parallel to the axis of the platen roll but also in a direction normal thereto. For adjusting the spacing between the printing head and the platen roll to the thickness of the sheet to be printed upon, a drive motor is coupled to the head carriage via a yieldable clutch. The drive motor is energized first for driving the head carriage toward the platen roll to an extent equal to, or preferably somewhat exceeding, a predetermined stroke of head travel toward and away from the platen roll, in order to positively hold the sheet presser directly against the platen roll, then for driving the head carriage away from the platen roll over said predetermined stroke, then, after the sheet to be printed upon has been introduced between the platen roll and the sheet presser, for driving the head carriage toward the platen roll to an extent equal to or exceeding said predetermined stroke, in order to positively hold the sheet presser against the platen roll via the sheet, and then for driving the head carriage away from the platen roll a variable distance depending upon the thickness of the sheet, in order to provide a required spacing between the printing head and the platen roll.