Method and device for further processing of sheets to produce multi-page printed products

1. A device for further processing of sheets to produce multi-page printed products comprising:

a folding unit for folding initial sheets into a folded sheet around a grooved line;

grooving means provided upstream of said folding unit in a sheet running direction, said grooving means comprising a grooving wheel having a convex curvature at its outer circumference and forming a grooved line in each of said initial sheets passing through in a running plane before folding; and

collating means in which said folded sheets are collated one on top of the other such that a fold area lies at the top and said folded sheets open downwardly, wherein adjusting means controlled by control means is provided, which adjusting means advances said grooving wheel gradually each time after the forming of a grooved line in an initial sheet towards the direction of the running plane.

2. A method for processing a plurality of sheets to produce a multi-page printed product comprising:

providing a plurality of sheets;

sequentially feeding the plurality of sheets and forming a grooved line having a concave bottom on each of the sequentially fed sheets, the grooved line having a depth and a width which increases in size on each sequentially fed sheet;

folding the plurality of sequentially fed sheets on the grooved line to produce a plurality of folded sheets; and

collating the plurality of folded sheets one on top of the other wherein each of the folded sheets opens downwardly to provide a tent structure of folded sheets comprising an inverted V, wherein the grooved line width and depth increases from bottom to top of the collated folded sheets.