Method for binding leaves and a binding element and binding device applied thereto

Method for binding a bundle of leaves (11) in a binding element (1) in the form of a folder with a U-shaped back (2) of a pliable and thermally conductive material, with a base (3) and two upright arms (4) and two cover sheets (5) that are each connected by an edge (6) to a free edge (7) of the arms, wherein a hot-melt adhesive (8) is provided on the inside of the back (2), at least on a part of the base (3), wherein the bundle of leaves (11) is introduced with the edge to be bound (12) against the hot-melt adhesive (8) in the back (2), and then heating up the back (2) to melt the hot-melt adhesive (8), wherein an oversized binding element (1) is chosen in which the bundle (11) with the thickness (B) of the edge (12) to be bound is received with a certain sideways play (C) between the arms (4) of the back (2), and the binding element (1) with the bundle (11) therein and the hot-melt adhesive (8) in the molten state, is placed with the base (3) of the back (2) on a seat (15) that fits closely to the base (2) with the arms (4) between two parallel pressure bars (17) that are moved towards one another with a force in order to press the base (3) of the back (2) against the seat (15) and at the same time to fold the arms (4) symmetrically towards one another at an angle (D) with respect to the base (3) until the bundle (11), with a desired force from the pressure bars (17), is clamped in between the arms (4) of the back (2), after which the pressure bars (17) are again moved away from one another in order to be able to remove the finished binding element (1) with the bound bundle (11), and wherein the desired force is chosen such that by clamping in the bundle (11) a force is exerted on the bundle (11) that is directed towards the base (3) of the back (2).