The present invention relates to a folding device to make two parallel folds in a leaf of paper or the like, particularly two parallel folds at a short distance from each other of, for example, two millimetres.

Such double folded leaves are used, for example, for the composition of a book, whereby the double fold of such leaves . delimits a foldable strip with which the leaves can be bound in a binding element or in the spine of a book or the like.

An advantage of such leaves is that the leaves of the book can be folded open flat and the print continues seamlessly over the folded open leaves as specified in BE 1.023.784.

Different methods and devices are known to provide leaves of paper with a fold.

BE 1.021.551 discloses a folding device with which the paper is folded upward once and folded downward once and whereby this process is possibly repeated several times, for example three times.

A disadvantage of this folding device is that the folding process is slow as the operation needs to be repeated, for example, three times, to obtain a good result. The result itself is good, but the device is not suitable for mass industrial production due to its slowness. BE 1.024.330 discloses another folding machine with which leaves of paper can be folded by means of steel bands with a much higher theoretical production rhythm, but whereby in practice the production yield is not that high for different reasons, more specifically due to:

difficult positioning of the paper on the steel bands because of the weak grip of the steel on the paper; difficulty to perfectly guide the steel bands, causing great wear and tear on the steel bands; and,

the fact that to make a second fold at a distance from the first fold, the paper must be guided through the folding machine either a second time or a second folding machine must be placed behind the first one, making the machine unpractically long.

BE 1.024.709 describes an improved version of the previous folding machine in which the steel bands are replaced by several synthetic pull-through belts, which have a strong adhesion to the paper, such that the paper stays in place much better during the transport with these pull-through belts . In this folding machine, the paper is subjected to three successive operations for each folding side: grabbing, folding and pressing and this up to four times .

However, this improved folding machine has three weaknesses, more specifically: the first fold, with right and left fold, requires belts of approximately two metres in length and for the second fold the paper must be rotated back 180°, which is a weakness as the paper must not move in the slightest to make a perfectly parallel second fold and this rotating back is always delicate, particularly when changing sizes or types of paper or thicknesses of paper;

the synthetic pull-through belts are suitable to handle paper on A4 format, but for larger paper formats the grip on the paper by the pull-through belts turns out to be insufficient, such that the paper can turn slightly, which is very bad for the rotating back and the positioning of the second fold which is no longer parallel then, which is a problem knowing that the market is always demanding larger paper formats, even up to B2 (500 x 707 mm) , which requires a folding machine in excess of a metre high, which is very problematic for the length of the conveyor belts and for the height of the machine; and,

the synthetic pull-through belts are perfectly suitable to handle paper with a density of 250 gr/m ² , but for heavier types of paper the grip on the paper by the conveyor belts turns out to be too weak because the rigidity of the paper against folding causes the paper to turn slightly which causes problems for the positioning of the second fold, which is then no longer parallel.

The purpose of the present invention is to provide a solution to one or more of the aforementioned and other disadvantages.

To this end, the invention relates to a folding device to make two parallel folds at a distance from each other in a leaf of paper or the like, characterised in that the device contains two clamps which end in a sharp, pointed folding edge, each formed by two clamping bars with pointed jaws which can be moved relative to each other between an open position with an opening between the clamping bars to feed the leaf to be folded and a closed position for clamping the leaf to be folded during the folding, whereby the clamps to feed the leaf are arranged opposite each other with their folding edges parallel and facing each other at a distance from each other equal to the desired distance between the folds to be made and whereby the device also contains means to move the clamps relative to each other in their closed position in such a way that one of the clamps with its folding edge makes a circular movement around the folding edge of the other clamp to form both parallel folds at the level of the folding edges of both clamps.

With this folding device the leaves to be folded can be guided one by one from a feeder between the clamping bars through the device in a flat linear track without having to rotate back the leaf and after folding the leaves can be guided further and stacked.

By the relative rotational movement of the one clamp relative to the other clamp, both parallel folds in the leaf are simultaneously realised at the level of the sharp folding edges of the clamps that are at the desired distance from each other and remain at this distance during the entire rotational folding movement.

For the whole duration of this relative rotational movement for folding, the leaf of paper remains firmly clamped between the clamping bars, such that the leaf cannot move and the realised folds are always perfectly parallel.

The folding device according to the invention is also suitable for larger formats of leaves, as they can be processed without any problem because the leaves can be guided in flat without rotating or folding.

Heavier types of paper can also be processed without any problem as the paper is clamped securely and there are no forces to twist or rotate the paper.

An added advantage is that the 2 folds can be made in any random location of the leaf.

On one leaf several double folding lines can be created at different positions, which, in addition to the application as described in 3E 1.023.784 for folding open leaves of a book in a flat way, can also be useful to fold greeting cards or book covers for example

According to a practical embodiment, one of both clamps is fixed in the guide direction of the leaves, whereas the other clamp is movable relative to the fixed clamp, such that only one of both clamps must be moved and a simple drive is sufficient for this.

Preferably, at least one stop is provided for the folding edge of a clamp at the end of the rotational movement of this clamp, such that an even sharper fold can be realised.

Preferably, such stop for the folding edge is made from an elastic compressible material such as rubber.

Preferably, the clamps are rotatable relative to each other over an angle of at least 180°, preferably over an angle whereby one clamp is rotated against or almost against the other clamp, in both directions of rotation.

This allows the leaf to be folded over to both sides of the leaf, resulting in a sharp fold.

The opening angle of the pointed folding edge is 25°, for example, such that the leaf can be folded over a big angle around the folding edges of the clamps. With the intention of better showing the characteristics of the invention, a few preferred embodiments of a device according to the invention to make two parallel folds in a leaf of paper are described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein: figure 1 schematically shows a folding device according to the invention in idle position;

figures 2 to 4 show the folding device of figure 1 in different positions of use;

figures 5 to 7 show a movement mechanism of the folding device of figure 1;

figure 8 shows another variant of a folding device according to the invention;

figure 9 shows the part indicated in figure 8 with frame F9 on a larger scale; figure 10 shows another variant of a folding device according to the invention in idle position;

figures 11 to 13 show the folding device of figure 10 in different positions of use.

The folding device 1 of figure 1 contains a chassis 2 with an feed opening 3 for the flat feeding of a leaf of paper to be folded 4 or the like according to a feed direction I as shown with arrow I in figure 1.

The device contains two clamps 5 to clamp the leaf 4.

The clamps 5 are made of two clamping bars 6 with pointed j aws 7.

The clamping bars 6 are movable relative to each other according to a direction X-X' perpendicular to the feed direction I between an open position, as shown in figure 1, with an opening 8 between the clamping bars 6 to feed the leaf 4 to be folded and a closed position as shown in figure 2 to clamp the leaf 4 to be folded during the folding.

In the open feed position of figure 1 the openings 8 are located between the clamping bars 6 in the extension of the feed direction I, such that the openings 8 delimit a guide channel where the leaf 4 to be folded can be fed in a linear way without rotating or folding.

In the closed position of figure 2 the pointed jaws 7 of each clamp form a sharp folding edge 9 of the clamp 5 in question with an opening angle A of the pointed folding edge amounting to approximately 25°.

In this position the clamps 5 are directly opposite each other with their sharp folding edges parallel to each other and facing each other at a distance B from each other which is equal to the desired distance between the folds to be made.

The clamp 5b is a fixed clamp, which means that this clamp 5b has a fixed position relative to the feed direction I, although the jaws 7 have been mounted movably in the direction X-X' , for example in linear guides of the chassis

2.

The clamping bars 6 of the clamp 5a have been mounted together on a carrier 1.0 which is movably mounted in the chassis 2 and on which the clamping bars 6 are slidably mounted in linear guides which extend according to the direction X-X' .

The folding device 1 is further provided with means 11 to rotate the carrier 10 together with the clamp 5a in such a way that the folding edge 9 of the clamp 5a makes a circular movement around the folding edge 9 of the fixed clamp 5b, as shown by the dashed circle in figure 2 with a radius equal to the aforementioned distance B and centre point on the level of the folding edge 9 of the fixed clamp 5b.

The means 11 are formed by a mechanism, for example, which will be further explained by means of the figures 5 to 7, which makes the carrier 10 together with the closed clamping bars 6 orbit, in other words makes it as a whole, rotate around the folding line 9 of the fixed clamp 5b, while the carrier 10, and its clamping bars always remain parallel to themselves .

Preferably, the folding device 1 is a throughput device which is provided with supply means 12 to feed the leaves 4 to be folded from a feeder (not shown) between the clamping bars 6 of the opened clamps 5. These means are formed, for example, by supply rollers that are controlled by a programmed control .

The folding device 1 is further provided with positioning means, not shown, to position the leaf 4 to be folded in the feed direction I between the clamping bars 6 in a position whereby the location where the folds need to be made in the leaf 4 are located under the folding edges 9 of the clamps

5.

These positioning means can, for example, contain a detector to detect the end of the leaf when guiding it, said detector being connected to the aforementioned control of the supply means 12.

The operation of the folding device is simple and as follows .

When the leaf 4 is positioned in the right position between the clamping bars 6, the clamps 5 are closed and the leaf 4 is clamped as shown in figure 2.

The carrier 10 with the clamp 5a is then driven to orbit around the folding edge 9 of the fixed clamp 5b.

First, the clamp 5a is turned upward against or almost against the fixed clamp 5b as shown in figure 3.

Consequently, the leaf 4 is folded around the folding edges 9 of both clamps 5 and two parallel folding lines are formed in the leaf 4 at the desired distance B from each other. It is clear that the folding edge 9 of the fixed clamp 5b also makes a relative circular movement around the folding edge 9 of the movable clamp 5a.

Subsequently, the carrier 10 with the clamp 5a is turned downward in the opposite direction around the folding edge 9 of the fixed clamp 5b into a position as shown in figure 4, whereby the leaf 4 is now folded to its other side, such that the folds are made even sharper.

Due to their narrow opening angle A the clamps 5 can be rotated over a big angle relative to each other without hitting each other, whereby preferably this angle is greater than 180°.

In this way the leaf 4 can, if necessary, be folded several times to the one, and the other, side of the leaf 4.

Afterwards, the carrier 10 can be returned to its start position of figure 2, after which the clamps 5 can be opened and the leaf 4 with the double fold in it can now be guided in the direction I towards a stack (not shown) . An example of how the means 11 can be realised is shown in figures 5 to 7. It concerns a mechanism 13 with two disks 14 that are rotatably mounted on bearings in the chassis 2 and which are provided with a radially extending slot 15, said disks 14 being rotatable in a reciprocating manner by means of a larger dial 16 that can be rotated in a reciprocating manner around a central position, as shown in figure 5, by means of a drive 17. The carrier 10 is provided with two fixed pawls 18 which are enclosed moveably in a reciprocating manner in the aforementioned slots 15 of the disks 14.

In the central position of figure 5 the clamps 5 are located in the start position of figure 2 with the clamps 5 in each other's extension.

From this central position the dial is first rotated in one direction as shown in figure 6 and then in the other direction as shown in figure 7, such that the carrier 10 with the clamp 5a is given an orbiting movement around the folding edge 9 of the fixed clamp 5b, as illustrated in the figures 6 and 7. Optionally one or both clamps 5 can be provided with a stop 19 as shown in the figures 8 and 9 which forms a stop for the folding edge 9 of a clamp 5 at the end of the rotational movement of this clamp 5, whereby the stop 19 is preferably made from an elastic compressible material such as rubber. Thanks to this stop 19 the double fold can be extra accentuated. The stop 19, for example, is formed by a notch 20 that forms a seat for the sharp folding edge 9 of a clamp 9. Figure 10 shows an alternative embodiment of a folding device 1 according to the invention whereby in this case the clamping bars 6, seen in cross-section, are provided with a square edge 21 that is perpendicular to the feed direction I and from which the aforementioned jaws 7 protrude in the direction of the opposite clamp 5.

The notches 20 for the folding edge 9 of the clamps are provided as a recess in the square edge 21 and are positioned in such a way that at the end of the rotational movement of the clamp 5 the folding edges 9 fall into these notches 20 as shown in the figures 12 and 13.

For the rest the operation of this folding device 1 is analogue to the operation as already described.

It is clear that the consecutive movements as described above can be controlled from a programmed control that controls all movements or at least part of them.

It is also clear that opening and closing the clamps 5 can also be realised in another way, for example by rotating the clamping bars toward each other to close and away from each other to open. It is also clear that both clamps 5 can be movable to impose a relative rotational movement of the one clamp relative to the other. It is also clear that with a folding device 1 according to the invention, alternative materials other than paper or cardboard can be folded, for example leaves made from a synthetic material. The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a device according to the invention to make two parallel folds in a leaf of paper or the like that can be realised in all kinds of forms and dimensions, without departing from the scope of the invention.