Apparatus for printing characters onto both surfaces of a sheet material

Claim 3

The apparatus as claimed in claim 1 wherein: said first printer device comprises: a first platen roller which is disposed adjacent to said path, said first platen roller having an axial center directed orthogonal to the direction in which the sheet material travels, to support said second surface of the sheet material; a first printer head which is disposed above said first platen roller and which prints characters onto said first surface of the sheet material; and a first carrier which causes the first printer head to reciprocate at a constant rate in the print line direction which is substantially parallel with the axial center of the first platen roller; and said second printer device comprises: a second platen roller which is disposed adjacent to said path, said second platen roller having an axial center directed orthogonal to the direction in which the sheet material travels, to support the first surface of said sheet material; a second printer head which is disposed above said second platen roller and which prints characters on said second surface of the sheet material; and a second carrier which moves the second printer head in the print line direction substantially parallel with the axial center of said second platen roller at a constant rate.

Claim 4

The apparatus as claimed in claim 2 wherein said first and second printer heads each comprise a thermal dot printer head each of which is arranged along the direction of sheet movement, each printer head including plural micro-dots of which heat generation is controlled electrically.

Claim 5

The apparatus as claimed in claim 2 wherein said first and second printer heads each comprise: a thermal dot printer head each of which is arranged along the direction of sheet movement, each printer head including plural micro-dots of which heat generation is controlled electrically; a thermal transfer ink ribbon which has a surface layer of pigment to be transferred onto said sheet material in a pattern corresponding to heated micro-dots of the respective thermal dot printer head; and a ribbon supply mechanism which supplies the ribbon in said print line direction concurrently with the movement of the respective thermal dot printer head.

Claim 6

The apparatus as claimed in claim 1 wherein said position detector includes: a sensor device which detects a tip end of said sheet material at a predetermined position within the path between the first and the second printer devices; and a measurement device which generates a distance signal corresponding to a distance of the sheet movement caused by the feed means.

Claim 7

The apparatus as claimed in claim 5 wherein: said sensor device includes a first sensor provided at a position nearer to said first printer device; and a second sensor which is provided nearer to said second printer device; and the controller detects a position of the sheet material based on signals output from said first and second sensors and from said measurement means, and wherein said controller concurrently and independently processes at least parts of printing operations by said first and second printer devices based on the detected sheet position.