Machine for forming a flat stack of sheets of predetermined format

A machine for forming a flat stack of sheets of predetermined format, each of said sheets being provided on one of its faces with parallel stripes of glue at a constant pitch or interval (p), the machine comprising:

• means for picking up a sheet and wrapping at least a portion of a sheet over a pick-up and applicator device constituted by first and second mutually parallel rotary cylinders disposed over a work surface defining a laying template whose median axis is referenced and which is provided with a first sheet, such that the sheet to be stacked is wound over the first cylinder making contact therewith via its face which does not include stripes of glue;
• means for counting the number of stripes of glue that pass while the sheet is being wrapped onto the device;
• means for stopping cylinder rotation when the detected middle stripe of the sheet is located approximately vertically over the median axis;
• means for measuring the error between the position of said middle stripe and the median axis of the laying template;
• means for adjusting the position of said device to cause said middle stripe to coincide vertically with the median axis;
• means for bringing the work surface and said device closer to each other;
• means for fixing the sheet to be stacked on the preceding sheet by localized melting of the middle stripe of glue;
• means for separating the two cylinders to unwrap the two halves of the sheet to be stacked and to apply them against the preceding sheet;
• means for moving the work surface and said device apart from each other;
• means for moving the cylinders towards each other;
• and
• means for picking up the next sheet under the same conditions and, additionally, ensuring that after adjusting the position of the middle stripe relative to the median axis, said stripe is offset in alternation relative to said axis through a distance equal to one half of the pitch.