Printer with horizontally movable print head

Claim 1

In a printer having a horizontal platen for supporting paper and having a print head which moves horizontally opposite the platen and is reciprocatingly driven toward said platen when printing a character, the improvement comprising: a shaft extending along a line parallel the platen and having a length substantially equal to the length of the platen, said shaft having a cross-section in the form of a first regular polygon with vertices; means for controllably rotating said shaft; and a bearing block spindled on said shaft, said bearing block having a through passageway with a cross-section which is delimited by the concentric superposition of a circle and another regular polygon similar to said first regular polygon, the radius of said circle being shorter than the distance from the center to the vertex of said other regular polygon so that a gap exists between the portions of said shaft intermediate said vertices and the opposing wall of the passageway, said bearing block having a channel for accepting the head.