WO2024175577A1

WO2024175577A1 - Forming corrugations in sheet material

Info

Publication number: WO2024175577A1
Application number: PCT/EP2024/054254
Authority: WO
Inventors: Frederic Philippe Christophe NICOLAS; Antonio MARTINIELLO
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-02-24
Filing date: 2024-02-20
Publication date: 2024-08-29
Anticipated expiration: 2025-08-24
Also published as: CN120548116A; KR20250151496A; EP4669133A1

Abstract

Apparatus for crimping a sheet of material (1), the apparatus comprising a corrugated surface (12), a transport mechanism to pass the sheet of material across the corrugated surface, and a pressurised air outlet (20) configured to apply pressurised air (21) towards the sheet of material so as to press the sheet of material against the corrugated surface and thereby to crimp the sheet of material, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

Description

FORMING CORRUGATIONS IN SHEET MATERIAL

The present disclosure relates methods and apparatuses for forming corrugations in sheet material by pressing the sheet material against a corrugated surface with pressurised air.

It is known to use rollers for processing sheet material in a wide variety of industries. For example, rollers are used in a crimping process in the tobacco industry. In such a process, an uncrimped sheet of material 1 (for example in the form of a tobacco cast leaf band or a sheet of polylactic acid (PLA)) is passed between first and second crimper rollers 3, 4 of a crimping apparatus (as shown in Figure 1) to form a crimped sheet of material 2. The crimper rollers 3, 4 each have a first end 3a, 4a and a second end 3b, 4b, with a longitudinal axis A, B extending therebetween. The rollers 3, 4 are each driven to contra-rotate, that is the first roller 3 rotates in a first direction and the second roller 4 in a second, opposite direction (as indicated by the arrows in Figure 1).

Typically, each of the crimper rollers 3, 4 has a pattern formed on its circumferential working surface. The patterns are configured to cooperate with one another in use. For example, a pattern of circumferential grooves on the circumferential working surface of the first crimper roller 3 may be configured to cooperate with a pattern of ridges on the circumferential working surface of the second crimper roller 4. In use, the first and second crimper rollers 3, 4 are arranged such that the pattern on one cooperates or meshes with the pattern on the other, to thereby crimp the uncrimped sheet of material 1 passed therebetween so as to form the crimped sheet of material 2.

Figures 2 and 3 show exemplary patterns of meshed circumferential grooves 5, 6 on crimper rollers 3, 4. In Figure 2, the circumferential grooves 5, 6 have a generally square wave profile, while in Figure 3, the circumferential grooves 5, 6 have a generally sinusoidal wave profile. In each case, the circumferential grooves 5, 6 have height 7, 8 and a width 9, 10. It will be noted that the circumferential working surfaces of the crimper rollers 3, 4 must not actually touch each other, otherwise they will not be able to accommodate the sheet of material 1 , 2 between the crimper rollers 3, 4.

If the patterns on the circumferential working surfaces of the crimper rollers 3, 4 are misaligned with respect to one another, the generated pattern on a sheet of material 1 , 2 passed between the rollers 3, 4 for processing may be sub-optimally formed or may not be formed at all. On crimper rollers 3, 4 for use in the tobacco industry, the patterns, e.g. the plural grooves and ridges, on the respective circumferential working surfaces are typically formed by features on a millimetre or even a micrometre scale. Meanwhile, the sheet of material 1 , 2 may be relatively thin. Accordingly, relative alignment of the first and second crimper rollers 3, 4, and hence of the patterns on their circumferential working surfaces, must be very precise in order to satisfactorily process a sheet of material 1 , 2 therebetween. It may be necessary to move one or both of the crimper rollers 3, 4 prior to passing a sheet of material 1 , 2 through the crimping apparatus for processing. For example, the thickness of the sheet of material 1 , 2 may be different from the thickness of a previously processed sheet of material 1 , 2, thereby necessitating a different spacing between the circumferential working surfaces of the first and second crimper rollers 3, 4. Furthermore, one or both of the crimper rollers 3, 4 may need to be repaired or replaced, for example due to wear of the pattern on one or both of the crimper rollers 3, 4 through use, over time. Where the features of the patterns on the circumferential working surfaces are of a very small scale (e.g. less than 200pm), such as with crimper rollers 3, 4 for use in the tobacco industry, the effect of wear on the patterns results in relatively more rapid failure of the rollers 3, 4 to adequately process a sheet of material 1 , 2 passed therebetween. Accordingly, it may be necessary to relatively reposition the first and second crimper rollers 3, 4 relatively frequently.

Positioning or repositioning the first and second crimper rollers 3, 4 may entail moving one or both rollers 3, 4, measuring distances between the rollers 3, 4 to determine their alignment, and then moving one or both rollers 3, 4 again to further alter their relative positioning based upon the measured distances. This process of measurement and movement must typically be repeated multiple times in order to arrive at an acceptable degree of alignment between the first and second crimper rollers 3, 4. Typically, adjustment of the rollers 3, 4 takes place on a micrometre scale, making adjustment difficult and time-consuming. Accordingly, ensuring acceptable accuracy of alignment between the first and second crimper rollers 3, 4, when relatively positioning or repositioning them, is time consuming and may well prove difficult to achieve in practice. During this positioning or repositioning the crimping apparatus is off-line and, consequently, unable to process sheets of material 1 , 2. Hence, operation of the crimping apparatus is made relatively more expensive due to the downtime required for such positioning or repositioning of the first and second crimper rollers 3, 4.

Incorrect positioning or alignment of one or other or both of the first and second crimper rollers 3, 4 can cause various problems and can jeopardise the quality and consistency of the crimped sheet of material 2. For example, if a sheet of material 2 is not sufficiently crimped (due to the first and second crimper rollers 3, 4 being spaced too far apart), then the insufficiently crimped sheet of material 2 may have a tendency to expand with too much force when gathered and wrapped in a wrapper to form a rod-shaped article. This can cause the wrapper to split or become unstuck along a glue line. Conversely, if a sheet of material 2 is excessively crimped (due to the first and second crimper rollers 3, 4 being spaced too close together), this can result in unwanted cuts being formed through the sheet of material 2. These cuts can give rise to larger tears in the sheet of material 2 and also to the formation of loose debris from the sheet of material 2. When the crimped sheet of material 2 is gathered and wrapped in a wrapper to form a rodshaped article, the presence of cuts or tears can result in an unwanted reduction of resistance to draw (RTD) in finished consumables. The presence of loose material in the rod-shaped article may reduce user enjoyment of the consumables. If the first and second crimper rollers 3, 4 are imperfectly aligned, it is possible that the sheet of material 2 will be excessively crimped towards one longitudinal edge and insufficiently crimped towards an opposite longitudinal edge, thus giving rise to both of the problems outlined above.

It would be desirable to provide a method and apparatus for crimping a sheet of material that can address the problems of roller spacing and misalignment. It would be desirable to provide a method and apparatus for crimping a sheet of material that can provide easy and reactive adjustment of the crimping process.

According to an aspect of the present invention, there is provided an apparatus for crimping a sheet of material, the apparatus comprising a corrugated surface, a transport mechanism to pass the sheet of material across the corrugated surface, and a pressurised air outlet configured to apply pressurised air towards the sheet of material so as to press the sheet of material against the corrugated surface and thereby to crimp the sheet of material, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

According to another aspect of the present invention, there is provided a method of crimping a sheet of material, the method comprising passing a sheet of material across a corrugated surface, and pressing the sheet of material against the corrugated surface with pressurised air so as to crimp the sheet of material, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

In contrast to existing systems where a sheet of material is crimped between a pair of corrugated rollers, embodiments of the present disclosure allow a sheet of material to be crimped by pressing the sheet of material against a single corrugated surface using pressurised air. The use of pressurised air to impart a pressing force onto the sheet of material against the corrugated surface allows a much greater and more responsive degree of control over the crimping process, since the magnitude of the pressing force can easily be adjusted by changing the flow of pressurised air from the pressurised air outlet.

In existing systems, it can be very difficult to adjust a spacing or relative alignment of a pair of crimping rollers, especially during operation. Incorrect spacing or relative alignment of a pair of crimping rollers can result in insufficiently crimped sheets of material, or crimped sheets of material with unwanted cuts or tears. When the sheet of material is a band of material unwound from a bobbin, it may take some time before a technician notices that there is a problem with the pair of crimping rollers. When a problem is noticed, it is often necessary to stop the manufacturing process in order to adjust the crimping rollers, and this results in expensive down time. Moreover, by the time a problem is noticed, a large amount of defective product may have been manufactured, and this will need to be separated from the stream of satisfactory product and discarded, resulting in unwanted wastage. Embodiments of the present disclosure enable a dynamic and responsive adjustment to be made to the pressing force on the sheet of material so as to correct possible over- or undercrimping defects without stopping the manufacturing process. This in turn can result in less wastage.

The corrugated surface may be formed on a substantially flat substrate. For example, the corrugated surface may be formed on a surface of a substantially planar plate, and the sheet of material can be pressed against the corrugated surface of the plate by the pressurised air.

The corrugated surface may be formed on a curved substrate. For example, the corrugated surface may be formed on a surface of a curved plate. The surface of the curved plate may have a curvature defined by a conic section. For example, the surface of the curved plate may extend through an arc of one of a circle, an ellipse, a parabola and a hyperbola. The surface of the curved plate may extend through other curvatures.

The corrugated surface may be formed on a circumferential surface of a substantially cylindrical substrate. The substrate may be formed as a substantially cylindrical drum. The corrugated surface may extend over the entire circumferential surface. The corrugated surface may extend over only part of the circumferential surface.

The corrugated surface may be formed on an outer surface of an endless belt. The endless belt may pass over a pair of cylindrical rollers so as to allow a surface of the endless belt to move together with the sheet of material in embodiments where the sheet of material moves through the apparatus. This may help to reduce unwanted wear or heating due to friction between the sheet of material and the corrugated surface.

The corrugated surface may be configured to remain stationary relative to the sheet of material. This may simplify construction and operation of the apparatus.

The corrugated surface may be configured to move with the sheet of material along a direction of travel of the sheet of material. This may help to reduce unwanted wear or heating due to friction between the sheet of material and the corrugated surface.

The corrugated surface may be configured to move at substantially the same speed as the sheet of material at a location where the sheet of material is pressed against the corrugated surface. This may help to reduce unwanted wear or heating due to friction between the sheet of material and the corrugated surface.

The corrugated surface may be configured to move at a lower speed than the sheet of material at a location where the sheet of material is pressed against the corrugated surface. This may help to reduce excessive wear or heating due to friction between the sheet of material and the corrugated surface while still promoting the formation of crimping corrugations in the sheet of material due to the relative movement between the sheet of material and the corrugated surface. The corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material. This may allow the sheet of material to travel continuously across the corrugated surface while being crimped.

The sheet of material may comprise a band of material that is unwound from a bobbin before being passed across the corrugated surface. This allows a substantially continuous crimping process to be carried out, at least until all of the band of material has been unwound and a new bobbin needs to be fitted.

The pressurised air outlet may be configured to apply pressurised air directly on the sheet of material so as to press the sheet of material against the corrugated surface. In order to avoid unwanted local concentrations of pressure and to obtain an even crimp across the sheet of material, the pressurised air outlet may comprise a plurality of jets configured to apply a substantially even air pressure across a width of the sheet of material. The plurality of jets may be configured to generate overlapping cones of pressurised air. The pressurised air outlet may comprise at least one flat air jet configured to generate a substantially linear fan of pressurised air across a width of the sheet material.

The pressurised air outlet may be configured to apply pressurised air to an intervening surface that in turn presses the sheet of material against the corrugated surface. In this way, it may be possible to press the sheet of material against the corrugated surface more evenly. In this way, it may be possible to reduce the risk of perforating the sheet of material with locally- concentrated jets of pressurised air.

The intervening surface may be a flexible sheet. A flexible sheet may allow the intervening surface and the underlying sheet of material to conform more closely to the corrugated surface when pressurised air is applied.

The flexible sheet may be configured as an endless belt. The endless belt may pass over at least one drive roller. The endless belt may pass over at least two drive rollers. The pressurised air outlet may be disposed within a perimeter of the endless belt so as to enable pressurised air to be directed at a portion of the endless belt in order to press the portion of the endless belt and the sheet of material against the corrugated surface. In this way, the flexible sheet may be configured to move with the sheet of material as the sheet of material passes through the apparatus, thereby reducing unwanted wear or heating due to friction between the flexible surface and the sheet of material.

The pressurised air outlet may comprise at least one air jet.

The air jet may be a flat air jet configured to generate a substantially linear fan of pressurised air. The substantially linear fan of pressurised air may be oriented transverse to a direction of travel of the sheet material. The substantially linear fan of pressurised air may be oriented substantially orthogonal to a direction of travel of the sheet material. Generating a substantially linear fan of pressurised air may help to avoid unwanted local concentrations of very high air pressure that might perforate the sheet of material. The substantially linear fan of pressurised air may promote substantially even crimping across the width of the sheet of material.

The air jet may be a round air jet configured to generate a substantially conical flow of compressed air. Preferably, a plurality of air jets is provided. The plurality of air jets may be arranged in a line across a direction of travel of the sheet of material. The plurality of air jets may be arranged in more than one line across a direction of travel of the sheet of material. The plurality of air jets may be arranged in an array. The array may be a one-dimensional array. The array may be a two-dimensional array. A plurality of round air jets arranged in this manner may help to avoid unwanted local concentrations of very high air pressure that might perforate the sheet of material. A plurality of round air jets arranged in this manner may promote substantially even crimping across the width of the sheet of material. The plurality of round air jets may be configured to generate overlapping cones of pressurised air.

The air jets may be controllable to apply different air pressures to different areas of the sheet of material on the corrugated surface. This may provide better control of the crimping of the sheet of material. The air jets may be controllable to apply a lower air pressure at a rearward part of a direction of travel of the sheet of material across the corrugated surface and a greater air pressure at a forward part of a direction of travel of the sheet of material across the corrugated surface. The air jets may be controllable to apply a progressively increasing air pressure from a rearward part of a direction of travel of the sheet of material across the corrugated surface to a forward part of a direction of travel of the sheet of material across the corrugated surface. In this way, lower air pressures are used to initiate the crimping process at the rearward part of the direction of travel, with greater pressures used at the forward end of the direction of travel once the sheet of material has already been at least partially conformed to the corrugated surface. This can help to reduce unwanted tearing or perforation of the sheet of material due to sudden changes of applied air pressure.

The air jets may be configured to apply a substantially even air pressure across the sheet of material on the corrugated surface. This may help to promote even crimping of the sheet of material.

The pressurised air outlet, for example the air jet or the air jets, may be disposed a distance of 1cm to 30cm, preferably a distance of 5cm to 15cm, from the sheet of material on the corrugated substrate.

The corrugated surface may have corrugations of substantially regular periodicity. This may be advantageous where a sheet of material with a crimp pattern of regular periodicity is required. The corrugated surface may have corrugations not all having the same periodicity. This may be preferred where a sheet of material with a crimp profile of irregular or varying periodicity is required. The corrugated surface may have corrugations of constant depth, or may have corrugations of different depths, depending on a desired crimp profile. The corrugated surface may have corrugations that are shallower at a rearward part of a direction of travel of the sheet of material across the corrugated surface and deeper at a forward part of a direction of travel of the sheet of material across the corrugated surface. This can help to reduce unwanted tearing or perforation of the sheet of material due to large and sudden deformations of the sheet of material against the corrugated surface.

In general, since the sheet of material will be in contact with the corrugated surface for a longer duration than is customary in prior art systems where a sheet of material passes through a tangential nip point between two adjacent intermeshing crimping rollers, it is possible to modify some parameters of the sheet of material during the crimping process. For example, the sheet of material may be heated or cooled. For example, the sheet of material may be humidified or dehumidified.

The corrugated surface may comprise a heater to heat the sheet of material when pressed on the corrugated surface. The application of heat to the sheet of material may help to make the sheet of material more flexible or more plastically deformable, thereby to facilitate application of the crimp pattern to the sheet of material.

The corrugated surface may alternatively or in addition comprise a cooler to cool the sheet of material when pressed on the corrugated surface. This may also help to set the applied crimp pattern in the sheet of material so that the applied crimp pattern is better maintained after the sheet of material has left the corrugated surface.

It will be appreciated that the application of heat, the application of cooling, or the application of both heat and cooling, to set the applied crimp pattern may depend on the type of sheet material that is being crimped.

There may be provided an air heater to heat the air before the air is ejected from the pressurised air outlet. The air heater may be an electrical resistance heater. There may be provided an air cooler to cool the air before the air is ejected from the pressurised air outlet. The air cooler may be a thermo-electric cooler. Heating or cooling the air can help to heat or cool the sheet of material as it is pressed against the corrugated surface, and this may help to set the applied crimp pattern into the sheet of material.

There may be provided an air humidifier to humidify the air before the air is ejected from the pressurised air outlet. There may be provided an air dehumidifier to dehumidify the air before the air is ejected from the pressurised air outlet. Humidifying or dehumidifying the pressurised air, depending on the composition of the sheet of material, may help to set the applied crimp pattern in the sheet of material so that the applied crimp pattern is maintained after the sheet of material has left the corrugated surface.

There may be provided a supply of additive to be added to the pressurised air, either before or after the pressurised air is ejected from the pressurised air outlet. In this way, the additive may be applied to the sheet of material by way of the pressurised air. The additive may comprise a flavouring additive to impart a desired flavour to the sheet of material. The additive may comprise an aroma additive to impart a desired aroma to the sheet of material. The additive, when applied to the sheet of material, may be configured to be released when the crimped sheet of material is incorporated in an aerosol-generating device and exposed to heat. In this way, it may be possible to use the pressurised air to crimp the sheet of material and to apply a flavouring or aroma additive in a single step.

The air may be pressurised to be applied towards the sheet of material at a pressure of at least 500kPa. For example, the air may be pressurised to be applied towards the sheet of material at a pressure of at least 500kPa and not more than 10MPa, or at a pressure of at least 700kPa and not more than 7MPa. The pressure may be determined at a point just outside the or each pressurised air outlet.

The sheet material may be a sheet of tobacco cast leaf material. The sheet material may be a sheet of polylactic acid material. The sheet material may be a sheet of paper material. The sheet material may be a sheet of cellulose acetate material. The sheet material may be a sheet of fibrous material. The sheet material may be made of other materials as required.

There may be provided a controller configured to control a pressure of the pressurised air applied by the pressurised air outlet.

There may be provided at least one sensor configured to sense a parameter of the sheet of material after the sheet of material has been crimped.

The at least one sensor may be configured to send signals to the controller so as to enable the controller to adjust the pressure of the pressurised air applied by the pressurised air outlet in response to the sensed parameter of the sheet of material.

This may provide a feedback control system that allows the pressure of the pressurised air applied to the sheet of material to be dynamically adjusted in response to detected changes to the sensed parameter.

For example, the at least one sensor may be configured to sense unwanted holes or tears in the sheet of material, and the controller may be configured to reduce the pressure of the pressurised air applied by the pressurised air outlet in the event that holes or tears in the sheet of material are sensed by the at least one sensor.

Alternatively or in addition, the at least one sensor may be configured to sense a crimping depth in the sheet of material, and the controller may be configured to increase the pressure of the pressurised air applied by the pressurised air outlet in the event that the sensed crimping depth in the sheet of material is below a predetermined value.

As used herein, the term “corrugated” is used to describe a surface shaped to have a series of generally parallel ridges and grooves.

As used herein, the term “crimping” is used to describe processing a sheet of material in order to form a crimped sheet of material comprising plural corrugations or ridges and grooves. As used herein, the term “pressurised air” refers to air (or other appropriate non-toxic gas) that has been pressurised to a predetermined pressure substantially greater than standard atmospheric pressure. For example, pressurised air may refer to air that is at a pressure of at least 500kPa.

As used herein, the term “pressurised air outlet” refers to an outlet such as a nozzle or jet that is engineered to deliver pressurised air to a surface in a controlled manner and in a defined direction with predictable pressure characteristics.

As used herein, the term “sheet of material” refers to a laminar element having a width and a length substantially greater than the thickness thereof. Preferably, the sheet of material has a width of 5cm to 30cm, optionally of 10cm to 20cm, and in some examples around 12.5cm. Preferably, the sheet of material has a thickness of 50pm to 500pm, optionally of 100pm to 400pm, optionally of 150pm to 350pm, optionally of 175pm to 275pm, optionally of 200pm to 250pm, optionally around 215pm. The length of the sheet of material is not of particular importance in the context of the present disclosure. Generally, the sheet of material is unwound from a bobbin, and may have a length of 10s or even 100s of metres.

As used herein, the terms “upstream” and “downstream” are used to describe the relative positions of components of the apparatus or steps of the method with reference to a direction of travel of the sheet of material.

The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example Ex1 : Apparatus for crimping a sheet of material, the apparatus comprising a corrugated surface, a transport mechanism to pass the sheet of material across the corrugated surface, and a pressurised air outlet configured to apply pressurised air towards the sheet of material so as to press the sheet of material against the corrugated surface and thereby to crimp the sheet of material.

Example Ex2: The apparatus according to Example Ex1 , wherein the pressurised air outlet is disposed a distance of 1cm to 30cm, preferably 5cm to 15cm, from the sheet of material on the corrugated surface.

Example Ex3: The apparatus according to Example Ex1 or Ex2, wherein the corrugated surface is formed on a substantially flat substrate.

Example Ex4: The apparatus according to Example Ex1 or Ex2, wherein the corrugated surface is formed on a curved substrate.

Example Ex5: The apparatus according to Example Ex1 or Ex2, wherein the corrugated surface is formed on a circumferential surface of a substantially cylindrical substrate.

Example Ex6: The apparatus according to Example Ex1 or Ex2, wherein the corrugated surface is formed on an outer surface of an endless belt. Example Ex7: The apparatus according to any one of Examples Ex1 to Ex5, wherein the corrugated surface is configured to remain stationary relative to the sheet of material.

Example Ex8: The apparatus according to any one of Examples Ex1 to Ex6, wherein the corrugated surface is configured to move with the sheet of material along a direction of travel of the sheet of material.

Example Ex9: The apparatus according to Example Ex8, wherein the corrugated surface is configured to move at substantially the same speed as the sheet of material at a location where the sheet of material is pressed against the corrugated surface.

Example Ex10: The apparatus according to Example Ex8, wherein the corrugated surface is configured to move at a lower speed than the sheet of material at a location where the sheet of material is pressed against the corrugated surface.

Example Ex11 : The apparatus according to any preceding Example, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

Example Ex12: The apparatus according to any preceding Example, wherein the sheet of material comprises a band of material that is unwound from a bobbin before being passed across the corrugated surface.

Example Ex13: The apparatus according to any preceding Example, wherein the pressurised air outlet is configured to apply pressurised air directly on the sheet of material so as to press the sheet of material against the corrugated surface.

Example Ex14: The apparatus according to any one of Examples Ex1 to Ex13, further comprising a supply of additive and configured to add the additive to the pressurised air so as to apply the additive to the sheet of material.

Example Ex15: The apparatus according to Example Ex14, wherein the additive is a flavouring additive or an aroma additive.

Example Ex16: The apparatus according to any one of Examples Ex1 to Ex12, wherein the pressurised air outlet is configured to apply pressurised air to an intervening surface that in turn presses the sheet of material against the corrugated surface.

Example Ex17: The apparatus according to Example Ex16, wherein the intervening surface is a flexible sheet.

Example Ex18: The apparatus according to Example Ex17, wherein the flexible sheet is configured as an endless belt.

Example Ex19: The apparatus according to Example Ex18, wherein the endless belt passes over at least one drive roller.

Example Ex20: The apparatus according to Example Ex19, wherein the endless belt passes over at least two drive rollers. Example Ex21 : The apparatus according to any one of Examples Ex18 to Ex20, wherein the pressurised air outlet is disposed within a perimeter of the endless belt so as to enable pressurised air to be directed at a portion of the endless belt in order to press the portion of the endless belt and the sheet of material against the corrugated surface.

Example Ex22: The apparatus according to any preceding Example, wherein the pressurised air outlet comprises at least one air jet.

Example Ex23: The apparatus according to Example Ex22, wherein the air jet is a flat air jet configured to generate a substantially linear fan of pressurised air.

Example Ex24: The apparatus according to Example Ex23, wherein the substantially linear fan of pressurised air is oriented transverse to a direction of travel of the sheet material.

Example Ex25: The apparatus according to Example Ex23 or Ex24, wherein the substantially linear fan of pressurised air is oriented substantially orthogonal to a direction of travel of the sheet material.

Example Ex26: The apparatus according to Example Ex22, wherein the air jet is a round air jet configured to generate a substantially conical flow of compressed air.

Example Ex27: The apparatus according to any one of Examples Ex22 to Ex26, comprising a plurality of air jets.

Example Ex28: The apparatus according to Example Ex27, wherein the plurality of air jets are arranged in a line across a direction of travel of the sheet of material.

Example Ex29: The apparatus according to Example Ex27, wherein the plurality of air jets are arranged in more than one line across a direction of travel of the sheet of material.

Example Ex30: The apparatus according to Example Ex27, wherein the plurality of air jets are arranged in an array.

Example Ex31 : The apparatus according to Example Ex30, wherein the array is a onedimensional array.

Example Ex32: The apparatus according to Example Ex30, wherein the array is a two- dimensional array.

Example Ex33: The apparatus according to any one of Examples Ex27 to Ex32, wherein the air jets are controllable to apply different air pressures to different areas of the sheet of material on the corrugated surface.

Example Ex34: The apparatus according to Example Ex33, wherein the air jets are controllable to apply a lower air pressure at a rearward part of a direction of travel of the sheet of material across the corrugated surface and a greater air pressure at a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex35: The apparatus according to Example Ex33, wherein the air jets are controllable to apply a progressively increasing air pressure from a rearward part of a direction of travel of the sheet of material across the corrugated surface to a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex36: The apparatus according to any one of Examples Ex27 to Ex32, wherein the air jets are configured to apply a substantially even air pressure across the sheet of material on the corrugated surface.

Example Ex37: The apparatus according to any preceding Example, wherein the corrugated surface has corrugations of substantially regular periodicity.

Example Ex38: The apparatus according to any one of Examples Ex1 to Ex36, wherein the corrugated surface has corrugations not all having the same periodicity.

Example Ex39: The apparatus according to any preceding Example, wherein the corrugated surface has corrugations of constant depth.

Example Ex40: The apparatus according to any one of Examples Ex1 to Ex38, wherein the corrugated surface has corrugations of different depths.

Example Ex41 : The apparatus according to any one of Examples Ex1 to Ex38, wherein the corrugated surface has corrugations that are shallower at a rearward part of a direction of travel of the sheet of material across the corrugated surface and deeper at a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex42: The apparatus according to any preceding Example, wherein the corrugated surface comprises a heater to heat the sheet of material when pressed on the corrugated surface.

Example Ex43: The apparatus according to any preceding Example, wherein the corrugated surface comprises a cooler to cool the sheet of material when pressed on the corrugated surface.

Example Ex44: The apparatus according to any preceding Example, further comprising an air heater to heat the air before the air is ejected from the pressurised air outlet.

Example Ex45: The apparatus according to any preceding Example, further comprising an air cooler to cool the air before the air is ejected from the pressurised air outlet.

Example Ex46: The apparatus according to any preceding Example, further comprising an air humidifier to humidify the air before the air is ejected from the pressurised air outlet.

Example Ex47: The apparatus according to any preceding Example, further comprising an air dehumidifier to dehumidify the air before the air is ejected from the pressurised air outlet.

Example Ex48: The apparatus according to any preceding Example, configured to pressurise the air to be applied towards the sheet of material at a pressure of at least 500kPa.

Example Ex49: The apparatus according to any one of Examples Ex1 to Ex47, configured to pressurise the air to be applied towards the sheet of material at a pressure of at least 500kPa and not more than 10MPa. Example Ex50: The apparatus according to Example Ex49, configured to pressurise the air to be applied towards the sheet of material at a pressure of at least 700kPa and not more than 7MPa.

Example Ex51 : The apparatus according to any preceding Example, wherein the sheet material is a sheet selected from the group consisting of: tobacco cast leaf material, polylactic acid material, paper material, cellulose acetate material, and fibrous material.

Example Ex52: The apparatus according to any preceding Example, further comprising a controller configured to control a pressure of the pressurised air applied by the pressurised air outlet, and at least one sensor configured to sense a parameter of the sheet of material after the sheet of material has been crimped, wherein the at least one sensor is configured to send signals to the controller so as to enable the controller to adjust the pressure of the pressurised air applied by the pressurised air outlet in response to the sensed parameter of the sheet of material.

Example Ex53: The apparatus according to Example Ex52, wherein the at least one sensor is configured to sense unwanted holes or tears in the sheet of material, and wherein the controller is configured to reduce the pressure of the pressurised air applied by the pressurised air outlet in the event that holes or tears in the sheet of material are sensed by the at least one sensor.

Example Ex54: The apparatus according to Example Ex52 or Ex53, wherein the at least one sensor is configured to sense a crimping depth in the sheet of material, and wherein the controller is configured to increase the pressure of the pressurised air applied by the pressurised air outlet in the event that the sensed crimping depth in the sheet of material is below a predetermined value.

Example Ex55: A method of crimping a sheet of material, the method comprising passing a sheet of material across a corrugated surface, and pressing the sheet of material against the corrugated surface with pressurised air so as to crimp the sheet of material.

Example Ex56: The method according to Example Ex55, wherein the pressurised air is output from an outlet disposed a distance of 1cm to 30cm, preferably 5cm to 15cm, from the sheet of material on the corrugated surface.

Example Ex57: The method according to Example Ex55 or Ex56, wherein the corrugated surface is formed on a substantially flat substrate.

Example Ex58: The method according to Example Ex55 or Ex56, wherein the corrugated surface is formed on a curved substrate.

Example Ex59: The method according to Example Ex55 or Ex56, wherein the corrugated surface is formed on a circumferential surface of a substantially cylindrical substrate.

Example Ex59: The apparatus method to Example Ex55 or Ex56, wherein the corrugated surface is formed on an outer surface of an endless belt.

Example Ex60: The method according to any one of Examples Ex55 to Ex59, wherein the corrugated surface remains stationary relative to the sheet of material. Example Ex61 : The method according to any one of Examples Ex55 to Ex59, wherein the corrugated surface is moves with the sheet of material along a direction of travel of the sheet of material.

Example Ex62: The method according to Example Ex61 , wherein the corrugated surface moves at substantially the same speed as the sheet of material at a location where the sheet of material is pressed against the corrugated surface.

Example Ex63: The method according to Example Ex61 , wherein the corrugated surface moves at a lower speed than the sheet of material at a location where the sheet of material is pressed against the corrugated surface.

Example Ex64: The method according to any one of Examples Ex55 to Ex63, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

Example Ex65: The method according to any one of Examples Ex55 to Ex64, wherein the sheet of material comprises a band of material, and wherein the band of material is unwound from a bobbin before being passed across the corrugated surface.

Example Ex66: The method according to any one of Examples Ex55 to Ex65, wherein the pressurised air outlet applies pressurised air directly onto the sheet of material so as to press the sheet of material against the corrugated surface.

Example Ex67: The method according to any one of Examples Ex55 to Ex66, wherein an additive is added to the pressurised air and applied by the pressurised air to the sheet of material.

Example Ex68: The method according to Example Ex67, wherein the additive is a flavouring additive or an aroma additive.

Example Ex69: The method according to any one of Examples Ex55 to Ex66, wherein the pressurised air outlet applies pressurised air to an intervening surface that in turn presses the sheet of material against the corrugated surface.

Example Ex70: The method according to Example Ex69, wherein the intervening surface is a flexible sheet.

Example Ex71 : The method according to Example Ex69, wherein the flexible sheet is an endless belt.

Example Ex72: The method according to Example Ex71 , wherein the endless belt passes over at least one drive roller.

Example Ex73: The method according to Example Ex72, wherein the endless belt passes over at least two drive rollers.

Example Ex74: The method according to any one of Examples Ex71 to Ex73, wherein the pressurised air outlet is disposed within a perimeter of the endless belt such that pressurised air is directed at a portion of the endless belt in order to press the portion of the endless belt and the sheet of material against the corrugated surface. Example Ex75: The method according to any one of Examples Ex55 to Ex74, wherein the pressurised air outlet comprises at least one air jet.

Example Ex76: The method according to Example Ex75, wherein the air jet is a flat air jet that generates a substantially linear fan of pressurised air.

Example Ex77: The method according to Example Ex76, wherein the substantially linear fan of pressurised air is oriented transverse to a direction of travel of the sheet material.

Example Ex78: The method according to Example Ex76 or Ex77, wherein the substantially linear fan of pressurised air is oriented substantially orthogonal to a direction of travel of the sheet material.

Example Ex79: The method according to Example Ex75, wherein the air jet is a round air jet that generates a substantially conical flow of compressed air.

Example Ex80: The method according to any one of Examples Ex75 to Ex79, wherein the pressurised air outlet comprises a plurality of air jets.

Example Ex81 : The method according to Example Ex80, wherein the plurality of air jets are arranged in a line across a direction of travel of the sheet of material.

Example Ex82: The method according to Example Ex80, wherein the plurality of air jets are arranged in more than one line across a direction of travel of the sheet of material.

Example Ex83: The method according to Example Ex80, wherein the plurality of air jets are arranged in an array.

Example Ex84: The method according to Example Ex83, wherein the array is a onedimensional array.

Example Ex85: The method according to Example Ex83, wherein the array is a two- dimensional array.

Example Ex86: The method according to any one of Examples Ex80 to Ex85, wherein the air jets are controlled to apply different air pressures to different areas of the sheet of material on the corrugated surface.

Example Ex87: The method according to Example Ex86, wherein the air jets are controlled to apply a lower air pressure at a rearward part of a direction of travel of the sheet of material across the corrugated surface and a greater air pressure at a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex88: The method according to Example Ex86, wherein the air jets are controlled to apply a progressively increasing air pressure from a rearward part of a direction of travel of the sheet of material across the corrugated surface to a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex89: The method according to any one of Examples Ex80 to Ex85, wherein the air jets are controlled to apply a substantially even air pressure across the sheet of material on the corrugated surface. Example Ex90: The method according to any one of Examples Ex55 to Ex89, wherein the corrugated surface has corrugations of substantially regular periodicity.

Example Ex91 : The method according to any one of Examples Ex55 to Ex89, wherein the corrugated surface has corrugations not all having the same periodicity.

Example Ex92: The method according to any one of Examples Ex55 to Ex91 , wherein the corrugated surface has corrugations of constant depth.

Example Ex93: The method according to any one of Examples Ex55 to Ex91 , wherein the corrugated surface has corrugations of different depths.

Example Ex94: The method according to any one of Examples Ex55 to Ex91 , wherein the corrugated surface has corrugations that are shallower at a rearward part of a direction of travel of the sheet of material across the corrugated surface and deeper at a forward part of a direction of travel of the sheet of material across the corrugated surface.

Example Ex95: The method according to any one of Examples Ex55 to Ex94, wherein the corrugated surface comprises a heater to heat the sheet of material when pressed on the corrugated surface.

Example Ex96: The method according to any one of Examples Ex55 to Ex95, wherein the corrugated surface comprises a cooler to cool the sheet of material when pressed on the corrugated surface.

Example Ex97: The method according to any one of Examples Ex55 to Ex96, wherein the pressurised air is heated before pressing the sheet of material against the corrugated surface.

Example Ex98: The method according to any one of Examples Ex55 to Ex96, wherein the pressurised air is cooled before pressing the sheet of material against the corrugated surface.

Example Ex99: The method according to any one of Examples Ex55 to Ex98, wherein the pressurised air is humidified before pressing the sheet of material against the corrugated surface.

Example Ex100: The method according to any one of Examples Ex55 to Ex98, wherein the pressurised air is dehumidified before pressing the sheet of material against the corrugated surface.

Example Ex101 : The method according to any one of Examples Ex55 to Ex100, wherein the pressurised air is applied towards the sheet of material at a pressure of at least 500kPa.

Example Ex102: The method according to any one of Examples Ex55 to Ex100, wherein the pressurised air is applied towards the sheet of material at a pressure of at least 500kPa and not more than 10MPa.

Example Ex103: The method according to Example Ex102, wherein the pressurised air is applied towards the sheet of material at a pressure of at least 700kPa and not more than 7MPa. Example Ex104: The method according to any one of Examples Ex55 to Ex103, wherein the sheet material is a sheet selected from the group consisting of: tobacco cast leaf material, polylactic acid material, paper material, cellulose acetate material, and fibrous material.

Example Ex105: The method according to any one of Examples Ex55 to Ex104, further comprising controlling a pressure of the pressurised air applied by a pressurised air outlet, and sensing a parameter of the sheet of material after the sheet of material has been crimped, wherein a controller adjusts the pressure of the pressurised air applied by the pressurised air outlet in response to the sensed parameter of the sheet of material.

Example Ex106: The method according to Example Ex105, wherein the sensed parameter is the presence of unwanted holes or tears in the sheet of material, and wherein the controller reduces the pressure of the pressurised air applied by the pressurised air outlet in the event that holes or tears in the sheet of material are sensed.

Example Ex107: The method according to Example Ex105 or Ex106, wherein the sensed parameter is a crimping depth in the sheet of material, and wherein the controller increases the pressure of the pressurised air applied by the pressurised air outlet in the event that the sensed crimping depth in the sheet of material is below a predetermined value.

Examples will now be further described with reference to the figures in which:

Figure 1 shows a prior art crimping roller arrangement;

Figure 2 shows a first pattern of circumferential grooves on a pair of meshed prior art crimping rollers;

Figure 3 shows a second pattern of circumferential grooves on a pair of meshed prior art crimping rollers;

Figure 4 shows a first embodiment with a sheet of material being pressed against a corrugated surface of a substantially flat substrate by pressurised air applied by a pressurised air outlet;

Figure 5 shows a second embodiment with a sheet of material being pressed against a corrugated surface of a curved substrate by pressurised air applied by a pressurised air outlet;

Figure 6 shows a third embodiment with a sheet of material being pressed against a corrugated surface formed on outer surface of an endless belt by pressurised air applied by a pressurised air outlet;

Figure 7 shows a fourth embodiment with a sheet of material being pressed against a corrugated surface by pressurised air applied by a plurality of pressurised air outlets arranged in a line transverse to a direction of travel of the sheet of material;

Figure 8 shows a detail of the fourth embodiment of Figure 7;

Figure 9 shows a fifth embodiment with a sheet of material being pressed against a corrugated surface by pressurised air applied by a plurality of pressurised air outlets arranged in two generally parallel lines transverse to a direction of travel of the sheet of material; Figure 10 shows a sixth embodiment with an intervening surface in the form of an endless belt that runs between the pressurised air outlet and the sheet of material on the corrugated surface;

Figure 11 shows an example of a corrugated surface in detail;

Figure 12 is a flowchart illustrating a control process for embodiments of the disclosure; and Figure 13 shows a detail of two pressurised air outlets in an array of pressurised air outlets, and illustrates a combined effect of the two pressurised air outlets.

Figure 4 shows a first embodiment with a sheet of material 1 , 2 being pressed against a corrugated surface 12 of a substantially flat substrate 14 by pressurised air 21 applied by a pressurised air outlet 20. The reference numeral 1 is used for the sheet of material in its uncrimped state, while the reference numeral 2 is used for the sheet of material when it has been crimped. The sheet of material 1 , 2 travels across the corrugated surface 12 in a direction of travel indicated by the arrows. The sheet of material 1 can be a long band of material that is unwound from a bobbin (not shown). The sheet of material 1 may be a sheet of polymer material, for example poly lactic acid (PLA) material. The sheet of material 1 may be a sheet of homogenised tobacco or tobacco cast leaf material. The sheet of material 1 may be a sheet of paper material. The sheet of material may be made of other materials as appropriate.

The pressurised air outlet 20 is disposed so as to apply a jet of pressurised air 21 towards the sheet of material 1 and to conform the sheet of material 1 to the corrugated surface 12, thereby transforming the uncrimped sheet of material 1 into a crimped sheet of material 2. By varying the pressure of the pressurised air 21 , it is possible to influence a crimping depth or crimping profile in the sheet of material 2. For example, a higher pressure will tend to conform the sheet of material 1 more closely to the corrugated surface 12, giving rise to a crimping profile that closely matches a profile of the corrugated surface 12. A lower pressure will tend to conform the sheet of material 1 less closely to the corrugated surface 12, giving rise to a crimping profile that is shallower than a profile of the corrugated surface 12. The pressure of the pressurised air 21 may be dynamically adjusted so as to provide continuous control or adjustment of the crimping profile. The pressure of the pressurised air 21 may be adjusted in response to feedback from one or more sensors (not shown) downstream of the corrugated surface 12. The sensors may detect holes or tears in the crimped sheet of material 2 arising from excessive pressures of pressurised air 21 , and can feed back to a controller (not shown) to reduce the pressure of the pressurised air 21 applied by the pressurised air outlet 20. Conversely, one or more sensors downstream of the corrugated surface 12 may determine that the crimped sheet of material 2 is insufficiently crimped (for example, by checking a crimping depth of the crimped sheet of material 2), and can feed back to a controller (not shown) to increase the pressure of the pressurised air 21 applied by the pressurised air outlet 20. The corrugated surface 12 may be formed of or coated with a low friction material, for example polytetrafluoroethylene (PTFE), so as to reduce friction between the sheet of material 1 , 2 and the corrugated surface 12 as the sheet of material 1 , 2 travels across the corrugated surface 12.

The substrate 14 may be provided with heating or cooling means so as to provide an additional level of control over the crimping process. For example, the substrate 14 may incorporate an electric heater (not shown) or cooling coils (not shown).

Figure 5 shows a second embodiment with a sheet of material 1 , 2 being pressed against a corrugated surface 12 of a curved substrate by pressurised air 21 applied by a pressurised air outlet 20. In the illustrated embodiment, the curved substrate is configured as a single cylindrical crimping roller 10 that can rotate about a longitudinal axis C. The principles of operation are similar to those outlined above in relation to the first embodiment, and the features of the first embodiment may equally be implemented in the second embodiment.

In the embodiment shown in Figure 5, the crimping roller 10 can rotate as the sheet of material 1 , 2 moves in the directions of travel indicated by the arrows. The crimping roller 10 may be driven by a motor (not shown), or may rotate freely. In either case, there is no or very little relative sliding movement between the sheet of material 1 , 2 and the corrugated surface 12, and this may help to reduce unwanted friction damage to the sheet of material 1 , 2. When the crimping roller 10 is driven by a motor, rotation of the crimping roller 10 can help to unwind the sheet of material 1 , 2 from a bobbin (not shown), or more generally to help pull the sheet of material 1 , 2 through a processing station.

Figure 6 shows a third embodiment with a sheet of material 1 , 2 being pressed against a corrugated surface 12 formed on outer surface of an endless belt 11 by pressurised air 21 applied by a pressurised air outlet 20. The endless belt 11 passes over a pair of rollers 30, 31 . In this way, the sheet of material 1 , 2 and the corrugated surface 12 can move together as the sheet of material 1 , 2 moves in the direction of travel indicated by the arrows. The rollers 30, 31 may both rotate freely. Alternatively, one or both of the rollers 30, 31 can be driven so that the endless belt 11 helps to move the sheet of material 1 , 2 in the direction of travel. In either case, there is no or very little relative sliding movement between the sheet of material 1 , 2 and the corrugated surface 12, and this may help to reduce unwanted friction damage to the sheet of material 1 , 2.

The endless belt 11 is preferably kept under sufficient tension between the rollers 30, 31 so as to present a substantially flat surface that does not deform significantly when pressurised air 21 is applied. In this way, the application of pressurised air 21 from the pressurised air outlet 20 can reliably conform the sheet of material 1 to the corrugated surface 12, thereby transforming the uncrimped sheet of material 1 into a crimped sheet of material 2. The principles of operation are similar to those outlined above in relation to the first embodiment, and the features of the first embodiment may equally be implemented in the third embodiment. Figure 7 shows a fourth embodiment with a sheet of material 1 , 2 being pressed against a corrugated surface 12 by pressurised air 21 applied by a plurality of pressurised air outlets 20 arranged in a line transverse to a direction of travel of the sheet of material 1 , 2. The plurality of pressurised air outlets 20 are disposed along a manifold bar 22 which is supplied with pressurised air along a supply line 24 from a source of pressurised air 23.

In some embodiments, the transverse width of the sheet of material 1 , 2 may be between 10cm and 20cm, for example around 12.5cm. In these embodiments, since the width of the sheet of material 1 , 2 is not particularly great, the manifold bar 22 does not have to be very long to cover the width of the sheet of material 1 , 2. Accordingly, only a small number of pressurised air outlets 20 may be needed, for example between two and ten pressurised air outlets 20, or between three and eight air outlets 20. As a result, it is not necessary to manage complex air flows through the manifold bar 22 to a large number of pressurised air outlets 20.

Although Figure 7 shows the plurality of pressurised air outlets 20 arranged over a flat corrugated surface 12, it will be understood that the illustrated plurality of pressurised air outlets 20 could equally be arranged over the corrugated surfaces 12 of the embodiments of Figures 5 and 6, as well as the corrugated surface of Figure 4.

By providing a plurality of pressurised air outlets 20 in a line generally transverse to the direction of travel of the sheet of material 1 , 2, it is possible to apply a more even pressure across the entire width of the sheet of material 1 , 2, or to apply different pressures at different regions across the width of the sheet of material 1 , 2, thereby providing greater control of the crimping process.

Figure 8 shows the plurality of pressurised air outlets 20 of Figure 7 in more detail, viewed along the line of the direction of travel. The pressurised air outlets 20 are configured as jet nozzles that each apply pressurised air with a greatest pressure along a central direction 25, and with a lesser pressure along angled directions 26. Areas of the sheet of material 1 , 2 directly under each pressurised air outlet 20 are indicated as “Zone A”, and will be subjected to pressurised air with the greatest pressure along the central direction 25. Areas of the sheet material 1 , 2 located between the pressurised air outlets 20 are indicated as “Zone B”, and will be subjected to pressurised air with a lesser pressure along the angled directions 26. However, the areas of the sheet material 1 , 2 in Zone B will be subjected to pressurized air from two adjacent pressurised air outlets 20, and the sum of the pressurised air components along the angled directions 26 of two adjacent pressurised air outlets 20 may be substantially equal to the pressure of the pressurised air in Zone A. In this way, a plurality of pressurised air outlets 20 arranged across the width of the sheet of material 1 , 2 can apply a substantially even pressure across the entire width of the sheet of material 1 , 2. Alternatively, the pressurised air pressure applied by each of the pressurised air outlets 20 can be controlled so as to apply a varying pressure profile across the width of the sheet of material 1 , 2. For example, a greater pressure may be applied in a central region and a lesser pressure at edge regions, or vice versa.

Figure 9 shows a fifth embodiment with a sheet of material 1 , 2, 43 being pressed against a corrugated surface 12 by pressurised air applied by a plurality of pressurised air outlets 20 arranged in two generally parallel lines transverse to a direction of travel of the sheet of material 1 , 2, 43. Additional lines of pressurised air outlets 20 may be provided as required. This arrangement is similar in principle to that of Figures 7 and 8, but provides an even greater degree of control over the crimping process.

For example, the left hand line of pressurised air outlets 20 can apply pressurised air at a first, lower pressure to the sheet of material 1 so as to impart a partial depth crimp pattern in the sheet of material 43. The right hand line of pressurised air outlets 20 can apply pressurised air at a second, higher pressure to the sheet of material 43 so as to impart a full depth crimp pattern in the sheet of material 2. In this way, the crimp pattern can be applied progressively along the direction of travel of the sheet of material 1 , 2, 43, and this may help to reduce the unwanted formation of holes or tears in the sheet of material 43 due to very sudden conformation of the uncrimped sheet of material 1 to the corrugated surface 12. With a greater number of lines of pressurised air outlets 20, it is possible to apply the crimp pattern to the sheet of material 1 , 2, 43 with an even greater degree of progressive control.

In another example, the corrugations on the corrugated surface 12 may be shallower under the left hand line of pressurised air outlets 20 and become progressively deeper towards a position under the right hand line of pressurised air outlets 20. This may enable the crimp pattern to be progressively applied to the sheet of material 1 , 2, 43 in order to reduce the likelihood of forming unwanted holes or tears. In some embodiments, a progressive deepening of the corrugations on the corrugated surface 12 in the direction of travel of the sheet of material 1 , 2, 43 may be combined with a progressive increase in the pressure of the pressurised air applied by the successive lines of pressurised air outlets 20.

Figure 10 shows a sixth embodiment with an intervening surface in the form of an endless belt 40 that runs between the pressurised air outlet 20 (or a plurality of pressurised air outlets 20) and the sheet of material 1 , 2 on the corrugated surface 12. Although Figure 10 shows the pressurised air outlet 20 arranged over a flat corrugated surface 12, it will be understood that the illustrated pressurised air outlet 20 (or plurality of pressurised air outlets 20) could equally be arranged over the corrugated surfaces 12 of the embodiments of Figures 5 and 6, as well as the corrugated surface of Figure 4.

The endless belt 40 may pass over a pair of rollers 32, 33 so as to be able to move with the sheet of material 1 , 2 as the sheet of material 1 , 2 passes over the corrugated surface 12. This can help to reduce or avoid unwanted rubbing between the outer surface of the endless belt 40 and the sheet of material 1 , 2. In some embodiments, one or other or both of the rollers 32, 33 may be driven by a motor.

When pressurised air 21 is applied to the inner surface of a lower part of the endless belt 40 in a direction towards the sheet of material 1 , 2 and the corrugated surface 12, the lower part of the endless belt 40 will press the sheet of material 1 , 2 against the corrugated surface 12 in order to apply the crimp pattern to the sheet of material 1 , 2. Preferably, the endless belt 40 is sufficiently deformable so as to be able to conform generally to the corrugated surface 12 upon application of pressurised air 21 , sandwiching the sheet of material 1 , 2 between the lower part of the endless belt 40 and the corrugated surface. For example, the intervening layer formed by the endless belt 40 may have a thickness from about 50pm to 200pm. In this way, the sheet of material 1 , 2, which may be more delicate than the endless belt 40, is protected to some extent from excess or concentrated jets of pressurised air 21 that might otherwise form unwanted holes or tears in the sheet of material 1 , 2.

In the illustrated embodiment, the endless belt 40 is shown with a relatively large amount of slack, which allows a central part of the lower part of the endless belt 40 to hang down towards the sheet of material 1 , 2 under the pressurised air outlet or outlets 20. However, it will be understood that the endless belt 40 can be passed around the rollers 32, 33 with less or substantially no slack, provided that the lower part of the endless belt 40 can still be displaced sufficiently by pressurised air 21 applied by the pressurised air outlet or outlets 20 so as to conform the sheet of material 1 , 2 to the corrugated surface 12.

Instead of an endless belt 40, the intervening surface may be configured as a flexible foil that does not move in the direction of travel of the sheet of material 1 , 2. The flexible foil may be made of or coated with a low friction material, for example PTFE, so as to reduce friction between the sheet of material 1 , 2 and the flexible foil.

Figure 11 shows an example of a corrugated surface 12 on a substrate 14. The corrugations have a height H, which may in some embodiments be from 0.5mm to 2mm. The corrugations have a width or period L, which may in some embodiments be from 0.5mm to 2mm. The angle A between adjacent corrugations may in some embodiments be from 0 degrees (where the corrugations have vertical walls) and 30 degrees. The radii R1 of the teeth of the corrugations may in some embodiments be from 0.1 mm to 0.4mm. The radii R2 of the bottoms of the corrugations may in some embodiments be from 0.1mm to 0.4mm. R1 and R2 may be the same or different. The values given in this example are for illustration only.

Figure 12 is a flowchart illustrating a feedback-based control process for embodiments of the disclosure. Control circuitry is provided, for example in the form of a microcontroller or microprocessor, to control the pressure of pressurised air 21 applied by the pressurised air outlet or outlets 20. The system may be configured to start with an initial predetermined default pressure considered to be appropriate for crimping the sheet of material 1 , 2 against the corrugated surface 12. After the crimped sheet of material 2 has left the corrugated surface, an integrity of the crimped sheet of material 2 is checked by a first sensor or sensors. For example, the first sensor may comprise a light source and a photodetector to check for holes or tears in the crimped sheet of material 2. If the integrity of the crimped sheet of material 2 is confirmed, a crimping depth of the crimped sheet of material 2 is checked by a second sensor or sensors. If both the first and second sensors indicate that the crimped sheet of material 2 is substantially free of holes or tears and has been crimped to a sufficient crimping depth, then the default air pressure is satisfactory. However, if the first sensor or sensors indicates a lack of integrity of the crimped sheet of material 2, a feedback signal is sent to the control circuitry to lower the applied air pressure. Conversely, if the second sensor or sensors indicates an insufficient crimping depth of the crimped sheet of material 2, a feedback signal is sent to the control circuitry to increase the applied air pressure.

Figure 13 shows a detail of two pressurised air outlets 20a, 20b in an array of pressurised air outlets, and illustrates a combined effect of the two pressurised air outlets 20a, 20b. Each pressurised air outlet 20a, 20b, for example an air jet or air nozzle, applies pressurised air with a maximum pressure in a downward direction substantially perpendicular to the sheet of material 1 , 2. The pressure of the applied pressurised air at the sheet of material 1 , 2 may decrease in a generally linear manner along the horizontal (X) axis in either direction from the point vertically under each outlet 20a, 20b, and may be substantially zero at a distance D from the point directly under the respective pressurised air outlet 20a, 20b. The pressurised air outlets 20a, 20b may be spaced from each other by the distance D, such that the substantially zero pressure point of one outlet 20a coincides with a maximum pressure point of the adjacent outlet 20b. The pressure of the pressurised air at the sheet of material 1 , 2 is indicated on the vertical axis (P).

P(x) is the distribution of the air pressure P received by the material from the outlet 20a as a function of the distance from the vertical of the centre of the outlet 20a which, in Figure 13, is at x = 0. At the vertical of the centre of the outlet 20a, the air pressure received from the outlet 20a is at a maximum, and has a value P0.

Regarding the function P(x), assuming the function is linear as shown by the bold continuous line, it can be seen that P(x) is at a maximum at the vertical under the outlet 20a, when x = 0, so P(0) = P0. At a distance xO from the vertical under the outlet 20a, the air pressure coming from the outlet 20a is null, so P(x0) = 0.

Accordingly, the linear air pressure coming from the outlet 20a, as a function of the distance x, is given by:

P(x) = - P0/x0*x + P0.

If an adjacent outlet 20b, similar to the outlet 20a, is arranged so that the vertical of its centre is at xO, then the pressure P’(x) (bold dotted line) from the outlet 20b, as a function of the distance x, is given by:

P’(x) = P0/x0*x. Accordingly, the total air pressure received by the sheet of material 1 , 2 between the two outlets 20a, 20b at any distance x, is given by:

Ptotal(x) = P(x) + P’(x) = -P0/x0*x + P0 + P0/x0*x = P0.

This pressure is constant, whatever the value of x between two adjacent successive pressurised air outlets 20a, 20b (i.e. 0 < x < xO).

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 5% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

1 . Apparatus for crimping a sheet of material, the apparatus comprising a corrugated surface, a transport mechanism to pass the sheet of material across the corrugated surface, and a pressurised air outlet configured to apply pressurised air towards the sheet of material so as to press the sheet of material against the corrugated surface and thereby to crimp the sheet of material, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

2. The apparatus according to claim 1 , wherein the corrugated surface is formed on a substantially flat substrate.

3. The apparatus according to claim 1 , wherein the corrugated surface is formed on a circumferential surface of a substantially cylindrical substrate.

4. The apparatus according to claim 1 , wherein the corrugated surface is formed on an outer surface of an endless belt.

5. The apparatus according to any one of claims 1 to 4, wherein the corrugated surface is configured to move with the sheet of material along a direction of travel of the sheet of material.

6. The apparatus according to any one of claims 1 to 5, further comprising a supply of additive and configured to add the additive to the pressurised air so as to apply the additive to the sheet of material.

7. The apparatus according to any one of claims 1 to 5, wherein the pressurised air outlet is configured to apply pressurised air to an intervening surface that in turn presses the sheet of material against the corrugated surface.

8. The apparatus according to any preceding claim, wherein the pressurised air outlet comprises a plurality of air jets.

9. The apparatus according to claim 8, wherein the plurality of air jets are arranged in at least one line across a direction of travel of the sheet of material.

10. The apparatus according to claim 8 or 9, wherein the air jets are controllable to apply different air pressures to different areas of the sheet of material on the corrugated surface.

11. The apparatus according to any preceding claim, wherein the corrugated surface has corrugations that are shallower at a rearward part of a direction of travel of the sheet of material across the corrugated surface and deeper at a forward part of a direction of travel of the sheet of material across the corrugated surface.

12. The apparatus according to any preceding claim, further comprising a controller configured to control a pressure of the pressurised air applied by the pressurised air outlet, and at least one sensor configured to sense a parameter of the sheet of material after the sheet of material has been crimped, wherein the at least one sensor is configured to send signals to the controller so as to enable the controller to adjust the pressure of the pressurised air applied by the pressurised air outlet in response to the sensed parameter of the sheet of material.

13. A method of crimping a sheet of material, the method comprising passing a sheet of material across a corrugated surface, and pressing the sheet of material against the corrugated surface with pressurised air so as to crimp the sheet of material, wherein the corrugated surface has corrugations substantially aligned with a direction of travel of the sheet of material.

14. The method according to claim 12 or 13, wherein an additive is added to the pressurised air and applied by the pressurised air to the sheet of material.

15. The method according to any one of claims 12 to 14, further comprising controlling a pressure of the pressurised air applied by a pressurised air outlet, and sensing a parameter of the sheet of material after the sheet of material has been crimped, wherein a controller adjusts the pressure of the pressurised air applied by the pressurised air outlet in response to the sensed parameter of the sheet of material.