Method and device for folding a stack of sheets

Abstract

Provided herein is a device for folding a stack of sheets. The device includes a frame, means for pre-folding a stack of sheets along a crease line into a main plane such that a booklet with a straight back is obtained, means for keeping the pre-folded booklet relative to the frame, a carriage movably arranged to the frame and moveable parallel to the back of the booklet, and a nip arranged to the carriage for receiving the back of the pre-folded booklet. The nip direction forms an angle greater than zero with respect to a direction of movement of the carriage.

Claims

1. A device for folding a stack of sheets, the device comprising: a frame; means for pre-folding a stack of sheets along a crease line into a main plane such that a booklet with a straight back is obtained; means for keeping the pre-folded booklet relative to the frame; a carriage movably arranged to the frame, wherein the carriage is movable parallel to the back of the booklet; and a nip arranged with a tiltable arm connected to the carriage for receiving the back of the pre-folded booklet, wherein a direction of the nip forms an angle greater than zero with respect to a direction of movement of the carriage and wherein the nip direction is mirrored, with respect to an axis that passes through the nip and is perpendicular to the direction of movement of the carriage within a plane through which the tiltable arm and the carriage are movable, upon reversal of the direction of movement of the carriage.

2. The device according to claim 1, wherein the nip comprises at least two spring mounted nip rollers.

3. The device according to claim 1, wherein the means for pre-folding a stack of sheets comprise two parallel primary rollers and a knife plate movable into the nip of the parallel primary rollers.

4. The device according to claim 3, further comprising secondary parallel rollers arranged, relative to the carriage, opposite of the primary parallel rollers, wherein the secondary rollers are for further transporting the folded booklet.

5. The device according to claim 4, wherein the secondary rollers are driven through a unidirectional bearing.

Description

(1) These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

(2) FIG. 1 shows a schematic view of device according to the invention performing a first step of the method according to the invention.

(3) FIGS. 2-5 show schematic views of further steps of the device according to FIG. 1.

(4) FIG. 6 shows a schematic view of a second embodiment of the device according to the invention.

(5) FIG. 1 shows a schematic view of a device 1 according to the invention. This device 1 has pre-folding means having primary rollers 2, 3 and a knife blade 4. According to the method of the invention, a stack of sheets 5 is moved between the rollers 2, 3 and the knife blade 4. The knife blade 4 is moved up, while the rollers 2, 3 are driven. The knife blade 4 will push the center of the stack of sheets 5 between the rollers 2, 3.

(6) As shown in FIG. 2, the stack of sheets 5 is pre-folded between the rollers 2,3 such that a booklet with a back 6 is obtained. The rollers 2,3 keep the pre-folded booklet relative to the frame. The back 6 of the booklet is positioned by the rollers 2, 3 in front of a nip 7 formed by two nip rollers 8,9. The nip rollers 8,9 are arranged to a tiltable arm 10, which is in turn attached to a carriage 11.

(7) The nip rollers 8, 9 are spring mounted such that they are urged to each other by springs, but can also move apart to provide space for the back 6 of a booklet.

(8) As shown in FIG. 3, the carriage 11 is guided along a frame 16 comprising two rods 12, 13. When the back 6 is positioned in front of the nip 7, the carriage 11 will start to move along the length of the back 6. By the movement of the carriage 11, the back will be inserted into the nip 7 between the nip rollers 8, 9. As a result of the friction, the tiltable arm 10 will tilt relative to the direction of movement C of the carriage 11. This will cause the nip direction N to form an angle greater than zero with respect to an axis that passes through the nip 7 and is perpendicular to the direction of movement C of the carriage 11 within a plane through which the tiltable arm 10 and the carriage 11 are movable. As a result a meandering pattern will be imposed over the length x onto the respective part of the back 6.

(9) When the carriage 11 has past the full length of the back 6 of the booklet, it will reverse direction and impose again a meandering pattern on the back 6 (see FIG. 4). This will improve the crease at the back 6 of the booklet.

(10) When the carriage 11 has returned to its initial position, the folding process is completed. The booklet 5 (see FIG. 5) will be transported further by driving the primary rollers 2, 3. The back 6 will be brought in to contact with the secondary rollers 14, 15, which will transport the booklet 5 further.

(11) FIG. 6 shows a second embodiment for the nip 20 of the device according to the invention. This nip 20 can be arranged directly to a carriage and does not need a tiltable arm.

(12) The nip 20 is formed by three rollers 21, 22, 23. The rollers 21, 22, 23 are arranged on a carriage 24. Two rollers 21, 22 are positioned on one side of the booklet 25, while the third roller 23 is positioned on the opposite side of the booklet 25 and in between the rollers 21, 22. With this arrangement a meandering pattern is imposed over the length x to the back of the booklet 25.