Device for making a thrice parallel folded sheet in which the open bent covers are directed towards the middle

Claim 1

In a device for folding a twice prefolded sheet having two open inwardly directed sheet flaps on one side of said sheet and two folded end edges, said two end edges being formed by two folds connecting said flaps to said sheet, the improvement comprising means for making a gate fold in said sheet as a third fold parallel to and midway between said end edges on said one side of said sheet so that said sheet flaps abut against each other: a folding table having a table plate forming an upper table surface, said table plate having a slot which divides said table surface into a front part and a back part, said twice prefolded sheet being adapted to be movingly fed onto said upper table surface; a folding stop arranged on said back part of said table surface for engaging one of said end edges of said prefolded sheet, the distance between said table slot and said folding stop corresponding substantially to the distance between said gate fold and one of said end edges; a pair of parallel fold rollers being rotatably mounted underneath said table surface and forming a folding gap therebetween which extends underneath and parallel to said slot; a folding sword operatively mounted in said device above said table slot and being disposed above and parallel to said slot, said folding sword being movable between a first position which is located above said table surface and a second position in which said folding sword extends through said table slot and into said folding gap and thereby introduces such twice prefolded sheet therein; first upper sheet engaging guiding means arranged at both sides of said folding sword above said table surface and cooperable with said folding sword to define concavely curved upper guiding surfaces when said folding sword is at least in the second position; said first upper guiding means are made of elastic material; second lower sheet engaging guiding means integral with said table surface at opposite side of said table slot and cooperable with said first upper guiding means to define convexly curved lower guiding surfaces, said convexly curved lower guiding surfaces respectively cooperating with said concavely curved upper guiding surfaces of said first upper guiding means to form a curved guiding slot leading from said table surface into said folding gap to hold said sheet flaps near such sheet when such sheet is introduced into said folding gap and to introduce said sheet flaps into said folding gap.