Duplex web printer with turning mechanism

A printing machine for printing on a web, comprising:

• a plurality of guide rollers for guiding the web through the printing machine, the plurality of rollers being arranged to define a simplex path and a duplex path for the web, the duplex path being arranged adjacent and parallel to the simplex path and being laterally shifted in a lateral shift direction with respect to the simplex path;
• at least one print engine positioned for printing an image on the web while the web is moved along the simplex path and the duplex path;
• and
• an apparatus for laterally shifting the web, the apparatus being arranged to transfer the web from the simplex path to the duplex path and including:
• a first roller for guiding the web, the first roller having a first axis of rotation;
• a second roller for guiding the web, the second roller having a second axis of rotation;
• a third roller for guiding the web, the third roller having a third axis of rotation;
• and
• a fourth roller for guiding the web, the fourth roller having a fourth axis of rotation;
• wherein the first, second, third, and fourth rollers are arranged to permit guiding the web around the rollers in that order, the first and second rollers are spaced a distance which permits the web to perform a 90° twist in the strand extending between these rollers, the second and third rollers are spaced apart in the lateral shift direction, the third and fourth rollers are spaced a distance which permits the web to perform a 90° twist in the strand extending between these rollers, the first and fourth axis of rotation are substantially parallel to each other, the second and third axis of rotation are substantially parallel to each other, and the first and fourth axis of rotation are substantially at right angles to the second and third axis of rotation, wherein the web is laterally shifted in the lateral shift direction by passing around the first, second, third, and fourth rollers.