Abstract: A serial printer includes a carriage reciprocating in a main scanning direction, a reading sensor mounted in carriage, a timing fence arranged in the main scanning direction, a mechanism preventing movement of carriage in the main scanning direction, and a controlling portion detecting a set condition for image formation in accordance with read data of timing fence from reading sensor for controlling image formation. Controlling portion detects the set condition for image formation only in accordance with the read data of timing fence, so that detection of the set condition for image formation is enabled without increasing the size of an apparatus and cost, or without decreasing a processing efficiency in image formation.

Abstract: The elements of a printing mechanism, including a platen, print head and drive motors, are constructed and arranged to provide a clearance permitting an envelope to remain entirely in a flat condition in a plane tangent to the platen at the location of the printing line while the envelope is being printed by the print head. The housing of the printing mechanism is constructed with specially configured slots. First and second opposite end walls of the housing, and a third wall, extending from one end wall to the other, provide at least partial coverage of the print head and platen. The third wall has a slot extending from one end wall to the other, the slot being arranged to receive an envelope and to allow the envelope to be inserted in a flat condition between the print head and the platen. The end walls have parallel slots, meeting and continuous with the slot of the third wall.