Folding device The present invention relates to a folding device.

In many different processes, continuous lengths of material are folded to obtain a fan-fold (i.e. accordion fold or zigzag) orientation. Fan-folded continuous lengths of material comprise a plurality of segments which are each separated by a fold. In a compressed state, these segments are stacked parallel to each other.

In the state of art, a pair of rollers is commonly used for the continuous production of a fan-folded length of material. The continuous length of material is conveyed through the pair of rollers, wherein each roller has rib-like protrusions and grooves running in the axis-parallel direction. JP2002343342 discloses a folding device having such a pair of rollers, for example.

JP5865075B2 discloses a pair of rollers having a star-shaped form looking along their axes of rotation for folding a continuous length of material into a zigzag form.

US3048389A and JP S54 138726 A each discloses a pair of rollers in a folding machine, comprising a first and second creasing roller means each comprising a section with a rubber tread and a longitudinal projection. DE 10 2012 020943 A1 discloses a device for folding a web element with the help of a feed device comprising support elements on a circulating web.

WO 2016/029924 A1 discloses a lay-flat book block apparatus comprising a pair of folding rollers, wherein the first roller comprises a protrusion and the second roller comprises a notch.

A disadvantage of folding rollers according to the state of art is that imprecise folds are obtained, in particular if a material having an irregular thickness or a thin material is used. Furthermore, the folds obtained with the folding devices according to the state of art are severely squeezed instead of being properly folded.

It is an object of the present invention therefore to provide a folding device that allows folding a continuous length of material into a precise zigzag form in a rapid manner without the disadvantages of the known prior art.

It has been found that the above-mentioned disadvantages can be dealt with when a folding device is provided comprising two folding rollers each having an elastic top layer and at least one elevated hard ridge, referred to as a 'blade', wherein the rotation axes of the two folding rollers and the at least one blade are parallel to each other, and wherein the blade(s) are heatable. The term 'at least one' as used herein refers to any number such as 'one', 'two', 'three', 'four', 'five', etc. As used herein, the term 'blade(s)' refers to any number of blades. Thus, the term 'blade(s)' encompass one blade, two blades, three blades, four blades, five blades, etc.

The two folding rollers, preferably having the form of a cylinder, are arranged that their rotation axes are parallel to each other and that the continuous length of material can be conveyed between the rollers by rotating the rollers around their rotation axes.

At least the top layer of each folding roller is made of an elastic material and blade(s) of non-elastic material are arranged on the surface of each folding roller, wherein the blade(s) run parallel to the rotation axes of the folding rollers. Preferably, the elastic top layer extends over the entire surface of the roller with the exception of the areas where the blade(s) are located. The blade(s) are arranged so that it/they extend over the entire width of a continuous length of material, which can be conveyed between the two folding rollers. The blade(s) run preferably from one end of the folding roller to the other. The blade(s) preferably have the form of a longitudinal wedge, whose tip faces out. Thus, a precise fold is obtained due to the sharp edge of the wedge. It is however also possible that any of the blade(s) do not have a sharp edge, but rather a broader structure. According to the present invention, the blade(s) are fixed on the elastic top layer or integrated in the elastic top layer. Preferably, the blade(s) are only in contact with an electrically non-conductive material. More preferably, the blade(s) are only in contact with the elastic top layer. Preferably, the blade(s) are anchored and/or glued to the elastic top layer. According to the present invention, the blade(s) can indent the elastic top layer so that the elastic top layer beneath the blade(s) is compressed. The elastic top layer preferably has a thickness greater than the shortest distance between the surface of the other roller and the outer edge of the blade(s) of the other roller (when looking along the rotation axis of the folding roller). The blade(s) are heatable. Preferably, the blade(s) can be heated to temperatures in the range of 80 °C to 220 °C, more preferably in the range of 150 °C to 200 °C.

An "electrically non-conductive material" as understood within the scope of the present invention designates a material that has an electrical conductivity of < 10 ^"8 S/m at 25 °C. An "electrically conductive material" as understood within the scope of the present invention designates a material that has an electrical conductivity of > 10 ⁶ S/m at 25 °C.

In case a folding roller comprises more than one blade, the blades are preferably arranged uniformly along the circumference of the folding roller. Thus, the circumference of the folding rollers is a multiple of the height of folds.

Preferably, the folding rollers have the same number of blades. Preferably, each folding roller comprises an uneven number of blades.

The blade(s) preferably protrude from the elastic top layer. More preferably, the blade(s), when having the shortest distance to the rotation axis of the other roller, extend at least to the elastic top layer of the other folding roller in an uncompressed state. In particular, the blade(s), when having the shortest distance to the rotation axis of the other roller, extend into the elastic top layer of the other folding roller thereby compressing the elastic top layer of the other folding roller. Thus, when a continuous length of material is conveyed through the two folding rollers, it is precisely folded without being squeezed. In one embodiment, the blade(s) protrude from the elastic top layer a distance not more than the sum of the thickness of the elastic top layer of the other roller and the distance between the elastic top layers of the two folding rollers in an uncompressed state.

The two folding rollers are arranged in a distance to each other so that the continuous length of material is transported by rotation of the folding rollers. The distance between the elastic top layers of the two folding rollers in an uncompressed state shall not exceed the thickness of the continuous length of material so that the continuous length of material can be transported due to friction between the elastic top layers and the surfaces of the continuous length of material. Thus, there is no need for additional transport rollers. Nevertheless, one or more transport rollers can be arranged upstream and/or downstream of the two folding rollers.

According to a preferred embodiment of the present invention, the two folding rollers are identical in construction.

The folding rollers of the folding device according to the present invention are preferably arranged that the continuous length of material is transported in the vertical direction through the rollers.

In a preferred embodiment, the blade(s) comprise electrically conductive material. The folding device preferably further comprises an induction heater. The induction heater is preferably arranged that the blade(s) comprising electrically conductive material can be heated, whereby a more accurate fold is obtained. It was surprisingly found that the folding was significantly improved due the heated blades. The induction heater allows the blade(s) to be heated without heating other components of the roller or a large area of the material to be folded. To achieve this, the blade(s) are preferably made of electrically conductive material. In particular, the blade(s) consist of aluminum, silver, gold, steel, stainless steel, iron or mixtures thereof. The elastic top layer of the two folding rollers can be of any material that returns into its original shape once forces are no longer applied. The elastic top layer can be of rubber, natural rubber or foam materials, for example. Preferably, the elastic top layer comprises polysiloxane, more preferably, the elastic top layer consists of polysiloxane. Therefore, the elastic top layer preferably consists of an electrically non-conductive material that prevents the current or heat form being transferred form the blades to the inside of the roller, such as to the drive shaft and other components of the folding device.

In a preferred embodiment, the two folding rollers rotate synchronously but in opposite directions.

The folding device preferably comprises a rotary encoder. Preferably the two folding rollers each comprise a rotary encoder. The rotary encoders allow to determine the rotary position of the two folding rollers in relation to each other so that the rotary position of the folding rollers can be adjusted if necessary.

During the operation of the folding device, the two folding rollers are preferably adjusted that the blade(s) of a folding roller hit the surface of the other folding roller along a line that is in the middle of the two closest blades of the other folding roller.

In a preferred embodiment, the folding device of the present invention comprises a fold sorting device downstream, with respect to the transfer direction of a continuous length of material, of the two folding rollers. Said fold sorting device preferably comprises two rollers, referred to as 'fold sorting rollers', each having the form of a n-sided prism, preferably two fold sorting rollers each having the form of a triangular prism. The rotation axes of the two fold sorting rollers of the fold sorting device are parallel to each and correspond to their longitudinal axes, which run from base to base. The folded continuous length of material is conveyed through the two fold sorting rollers of the fold sorting device after having passed two folding rollers. The two fold sorting rollers of the fold sorting device are preferably driven by gearwheels, which preferably are arranged at one of their bases. Preferably the two fold sorting rollers of the fold sorting device have concave faces. In a preferred embodiment, the two rollers of the fold sorting device are identical in construction.

The present invention further provides a method for folding a continuous length of material comprising the step of conveying a continuous length of material through two folding rollers each having an elastic top layer and blade(s), wherein the rotation axes of the two folding rollers and the blade(s) are parallel to each other.

The folding devices according to the present invention can be used for folding of continuous lengths of material, which can be a single or multilayer material such as coated or uncoated paper webs, metal films, polymer films or mixtures thereof. The folding device of the present invention can be used for the production of various folded products. Thus, the folding device of the present invention can be used for the production of fan-folded filters, for example.

Thus, the present invention is further directed to the use of a folding device according to the present invention for folding a continuous length of material.

Preferred embodiments of the present invention will be described with reference to the drawings as follows. Fig. 1 illustrates a folding device according to the present invention.

Fig. 2 illustrates a cross-section perpendicular to the rotation axis of the two folding rollers of the folding device according to present invention.

Fig. 1 illustrates a folding device 1 according to the present invention, which comprises a first folding roller 2, a second folding roller 3, a first fold sorting roller 4 and a second fold sorting roller 5. A continuous length of material 6 is conveyed through the pair of folding rollers 2,3 and the pair of fold sorting rollers 4, 5 downstream of the folding rollers 2, 3. Each folding roller comprises three blades in form of metal blades 7, 8, 9, 10, 1 1 , 12, which are integrated in the elastic top layers 13, 14 of the two folding rollers 2, 3. The rotation axes 16, 17 of the two folding rollers 2, 3 and the six blades 7, 8, 9, 10, 1 1 , 12 are parallel to each other. The folded continuous length of material 15 obtained downstream of the folding rollers 2, 3 is sorted by the fold sorting rollers 4, 5.

Fig. 2 illustrates a cross-section perpendicular to the rotation axis of the two folding rollers 2, 3 of the folding device 1 according to present invention. The two folding rollers 2, 3 comprise elastic top layers 13, 14, in which three blades 7, 8, 9, 10, 1 1 , 12 per roller are integrated. The blades 7, 8, 9, 10, 1 1 , 12 have the form of a wedge, whose tip faces out. The blades 7, 8, 9, 10, 1 1 , 12 protrude from the elastic top layers 13, 14. Blade 12 is in the position that it has the shortest distance to the rotation axis 16 of the other folding roller 2. It extends into the elastic top layer 13 of the other folding roller 2 thereby compressing the elastic top layer 13 of the other folding roller 2. The blades 7, 8, 9 protrude from the elastic top layer 13 a distance not more than the sum of the thickness of the elastic top layer 14 of the other folding roller 3 and the shortest distance between the elastic top layers 13, 14 of the two folding rollers 2, 3 in an uncompressed state. The blades 10, 1 1 , 12 protrude from the elastic top layer 14 a distance not more than the sum of the thickness of the elastic top layer 13 of the other folding roller 2 and the shortest distance between the elastic top layers 13, 14 of the two folding rollers 2, 3 in an uncompressed state.

Reference signs

Folding device

2 First folding roller

3 Second folding roller

4 First fold sorting roller 4

5 Second fold sorting roller 5

6 Continuous length of material

7 Blade

8 Blade

9 Blade

10 Blade Blade

Blade

Elastic top layer

Elastic top layer

Folded continuous length of material Rotation axis of the first folding roller Rotation axis of the second folding roller