Method and apparatus for crimping a sheet

Abstract

The present invention relates to a method for crimping a sheet (2) having a thickness (11), moisture, composition, and width before crimping, the method comprising: - obtaining pre-crimp sheet (2) properties from one of the following: o sheet thickness (11), o sheet moisture, o sheet composition, o sheet width; - crimping the sheet (2) to form a plurality of corrugations on the sheet (10), the crimping comprising: o providing a pair of crimping rollers (4, 5) defining a nip (6) therebetween, the nip (6) having a nip size (14); o inserting the sheet (2) into the nip (6); - evaluating the post-crimp properties of the sheet (10) after crimping; and varying the nip size (14) based on one of the resulting pre-crimp sheet (2) properties and based on the evaluated post-crimp sheet (10) properties. The present invention also relates to an apparatus (1) for crimping a sheet (2).

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for crimping a sheet. [Background technology]

[0002] For example, in the manufacture of aerosol-generating articles, such as heat-non-combustion products, rod-shaped components are often used. The components may include an aerosol-forming substrate and a filter element. One or both of the filter element and the aerosol-forming substrate may include a plurality of channels to provide airflow through the rod. The plurality of channels may be provided by crimping a sheet of material and subsequently assembling the material in the rod to form the channels. In such an embodiment, the crimped sheet is generally formed by crimping a substantially continuous sheet.

[0003] This material to be crimped, i.e., a continuous sheet, may be, in the field of aerosol-generating articles, for example, reconstituted tobacco or homogenized tobacco such as cast leaf, a sheet made of polylactic acid, or a cotton sheet.

[0004] Methods and apparatus for producing crimped sheets for use in aerosol-generating articles are known in the art. Known methods for producing crimped sheets generally involve feeding a substantially continuous sheet between a pair of interleaved rollers to apply a plurality of crimp corrugations to the continuous sheet. The crimped sheet is then assembled to form a continuous rod having a plurality of axial channels. The rod is then rolled and cut into smaller segments to form aerosol-generating substrates or filters for the aerosol-generating article.

[0005] The crimping process is important to an effective manufacturing process for aerosol-generating articles. Summary of the Invention

[0006] The present invention relates to a method for crimping a sheet having a thickness, moisture, composition and width prior to crimping, the method including obtaining a pre-crimp sheet property among one of sheet thickness, sheet moisture, sheet composition and sheet width. The method may further include crimping the sheet to form a plurality of corrugations on the sheet, the crimping including providing a pair of crimping rollers defining a nip therebetween, the nip having a nip size, and inserting the sheet into the nip. The method may further include evaluating a post-crimp property of the sheet after crimping. The method may also include varying the nip size based on one of the obtained pre-crimp sheet properties and based on the evaluated post-crimp sheet property.

[0007] The present invention also relates to an apparatus for crimping a sheet having pre-crimp properties among thickness, moisture, composition, and width before crimping. The apparatus comprises a conveying device adapted to convey the sheet along a conveying direction, and a pair of crimping rollers for crimping the sheet to form a plurality of corrugations on the sheet, the pair of crimping rollers defining a nip therebetween, the nip having a nip size. The apparatus may also comprise a sensor adapted to evaluate a post-crimp property of the sheet, the sensor being located downstream in the conveying direction of the pair of crimping rollers. The apparatus may also comprise one of the following: a sensor adapted to evaluate one of the pre-crimp properties of the sheet and to transmit a signal function of one of the evaluated pre-crimp properties, the sensor being located upstream in the conveying direction of the pair of crimping rollers, and a memory containing data for one of the pre-crimp properties of the sheet. The apparatus may further comprise a control unit adapted to receive a signal function of one of the evaluated pre-crimp properties or to acquire data for one of the pre-crimp properties. The method may also comprise a first actuator for varying a nip size and a feedback control loop system adapted to activate the first actuator based on one of the evaluated pre-crimp properties of the sheet or based on data for one of the acquired pre-crimp properties and based on the evaluated post-crimp property of the sheet.

[0008] The material sheet is crimped between two crimp rollers forming a nip between them. Due to the crimp, multiple corrugations are formed on the sheet. A first evaluation of the pre-crimp properties of the sheet is performed upstream of the crimp roller. A second evaluation of the post-crimp properties of the sheet is performed downstream of the crimp roller. The first upstream evaluation relates to one of the sheet thickness, sheet moisture, sheet composition, and sheet width. The second downstream evaluation relates to the properties of the sheet imparted by the corrugations, for example, the properties of multiple corrugations on the sheet. If necessary, the nip size can be varied based on the evaluated post-crimp properties of the sheet and the resulting pre-crimp properties of the sheet. In this way, a continuous feedback loop for optimal crimp can be performed, since the nip size depends on the properties of the sheet present both before and after crimp. The effect of the crimp on the sheet can be monitored, and the nip size can be adapted to the specific conditions of the crimped sheet.

[0009] The term "sheet" as used herein means a laminar element having a width and length substantially greater than its thickness. The width of the sheet is preferably greater than 10 millimeters, more preferably greater than about 20 millimeters or about 30 millimeters. Even more preferably, the width of the sheet is comprised between about 60 millimeters and about 300 millimeters. The thickness of the sheet may be comprised between about 50 micrometers and 300 micrometers, between about 100 micrometers and about 250 micrometers, between about 175 micrometers and about 250 micrometers, or between about 130 micrometers and about 220 micrometers.

[0010] As used herein, the term "rod" refers to a cylindrical element of substantially cylindrical, oval or elliptical cross section that comprises two or more components of an aerosol-generating article.

[0011] An "aerosol-generating article" according to the invention may be in the form of an article in which an alkaloid-containing material, such as tobacco material, is heated rather than combusted to form an aerosol. An aerosol-generating article is an article in which an alkaloid-containing aerosol is generated from an alkaloid-containing material, for example from a tobacco extract, or other nicotine source, without combustion or heating. An aerosol-generating article according to the invention may be an assembled aerosol-forming article as a whole. An aerosol-generating article according to the invention may be a component of an aerosol-generating article that is combined with one or more other components to provide an assembled article for producing an aerosol. An example is a consumable part of a heated smoking device.

[0012] An "alkaloid-containing material" is a material that contains one or more alkaloids. The alkaloids may include nicotine. Nicotine may be found, for example, in tobacco.

[0013] Alkaloids are a group of naturally occurring compounds that contain mostly basic nitrogen atoms. The group also includes some related compounds with neutral properties, and even some related compounds with weakly acidic properties. Some synthetic compounds of similar structure are also called alkaloids. In addition to carbon, hydrogen, and nitrogen, alkaloids may also contain other elements such as oxygen, sulfur, and more rarely chlorine, bromine, and phosphorus.

[0014] Alkaloids are produced by a wide variety of organisms, including plants. They can be purified from crude extracts of these organisms by acid-base extraction. Caffeine, nicotine, theobromine, atropine, and tubocurarine are examples of alkaloids.

[0015] As used herein, the term "homogenized tobacco material" refers to a material formed by agglomerating particulate tobacco that contains the alkaloid nicotine. Thus, an alkaloid-containing material can be a homogenized tobacco material.

[0016] The most commonly used forms of homogenized tobacco material are reconstituted tobacco sheets and cast leaves. The process of forming homogenized tobacco material sheets generally involves mixing tobacco powder with a binder to form a slurry. The slurry is then used to create a tobacco web. For example, the viscous slurry is cast onto a moving metal belt to produce so-called cast leaves. Alternatively, a slurry with low viscosity and high moisture content can be used in a process similar to papermaking to create reconstituted tobacco.

[0017] Other configurations for making the sheets are possible.

[0018] A sheet of homogenized tobacco material may be formed using particulate tobacco (e.g., reconstituted tobacco) or a tobacco particulate blend, a humectant, and an aqueous solvent to form a tobacco composition.

[0019] In addition to tobacco, the homogenized tobacco sheet may also include binders. The homogenized tobacco sheet may also include aerosol formers, such as guar and glycerin.

[0020] The term "crimped sheet" as used herein means a sheet having multiple corrugations. The term "crimping" means the process of forming multiple corrugations on a sheet of material. The sheet of material is preferably an essentially flat sheet of material or a sheet of material that has not been previously processed with respect to the generation of a structured surface. However, crimping of a sheet that already contains corrugations can also be envisaged. The corrugations on the sheet can be formed by a crimping roller. The crimping roller can include corrugations on its surface.

[0021] The term "corrugation" as used herein means a plurality of ridges formed from alternating peaks and troughs joined by corrugation flanks. This includes, but is not limited to, corrugations having a square wave profile, a sinusoidal wave profile, a triangular wave profile, a sawtooth wave profile, or any combination thereof. Corrugations may be defined on a roller, such as a crimping roller, or on a sheet. Corrugations on a roller refer to a plurality of ridges formed on the outer surface of the roller. Corrugations on a sheet refer to a plurality of ridges when the sheet is placed on a flat surface without stretching the sheet itself.

[0022] The term "substantially intermeshing" as used herein, when referring to a pair of rollers formed by a first crimp roller and a second crimp roller, indicates that the corrugations of the first and second crimp rollers at least partially intermesh. This includes symmetrical or asymmetrical arrangements of the corrugations of one or both rollers. The corrugations of the crimp rollers may be substantially aligned or at least partially offset. The peaks of one or more corrugations of the first or second crimp roller may be interleaved with the troughs of a single corrugation of the other of the first and second crimp rollers. It is preferred that the corrugations of the first and second crimp rollers are interleaved such that substantially all the corrugation troughs of one of the first and second crimp rollers each partially receive the peaks of a single corrugation of the other of the first and second crimp rollers.

[0023] A "crimping roller" is a roller used to crimp a sheet. The crimping roller defines an outer surface and an axis of rotation. The outer surface includes a plurality of corrugations. The corrugations preferably extend radially around the outer surface. The corrugations preferably define a circumference on the surface of the crimping roller. As used herein, the "crimping roller diameter" is considered to be the largest diameter defined by a cross section taken along a plane perpendicular to the axis of rotation of the crimping roller.

[0024] As used herein, "the distance between a first crimping roller having a first axis of rotation and a second crimping roller having a second axis of rotation" refers to the distance between their respective first and second axes of rotation.

[0025] As used herein, the term "longitudinal" refers to a direction extending along or parallel to the length of the sheet.

[0026] As used herein, the term "width" refers to a direction perpendicular to the direction of transport of the sheet being processed.

[0027] The term "pitch value" of a corrugation as used herein refers to the lateral distance either between the troughs on either side of the peak of a particular corrugation, or between two adjacent peaks of two adjacent corrugations. In the case of corrugations on a sheet, the pitch value is calculated in a configuration in which the sheet is laid on a flat surface without stretching the sheet itself.

[0028] The term "amplitude value" of a corrugation as used herein refers to the height of the corrugation from its peak to the deepest point of the deepest immediately adjacent trough. For example, in the case of corrugations in a roller, the amplitude of the corrugation may be measured along the radial direction. The radial direction is the direction along the radius connecting the axis of rotation of the roller with the peak or trough. The radius is perpendicular to the axis of rotation. The height of the trough is measured as the distance along the radial direction between the axis of rotation and the deepest point of the trough. The height of the peak is measured as the distance along the radial direction between the axis of rotation and the highest point of the peak. Thus, the "amplitude value" is the difference between the height of the peak and the height of the trough. In the case of corrugations in a sheet, the amplitude value is calculated in a configuration in which the sheet is placed on a plane without stretching the sheet itself. The amplitude of the sheet corrugation is calculated as the distance between a first plane and a second plane, the first plane being parallel to the second plane. The first plane is in contact with the peak of the corrugation and the second plane is in contact with the deepest point of the trough adjacent to the peak.

[0029] When corrugations are formed on the sheet, the ridges may be parallel to one another. The ridges may be parallel to the direction in which the sheet is transported during crimping. The ridges may form an angle of between 0 degrees and 45 degrees with the direction in which the sheet is transported during crimping.

[0030] As used herein, the term "flank angle" refers to the angle between the corrugation flanks of a particular corrugation. The flank angle may be the same for all corrugations. Additionally, one or more corrugations may be asymmetric about the radial direction.

[0031] The term "nip" as used herein refers to the gap that exists between a first crimping roller and a second crimping roller that form a pair of crimping rollers. The sheet to be crimped passes through the nip during operation. The first crimping roller and the second crimping roller define a first axis of rotation and a second axis of rotation, respectively. Furthermore, the first crimping roller defines a first outer surface, and the second crimping roller defines a second outer surface. The nip defines a nip size. The nip size is defined for each cross section of the first and second crimping rollers along a plane perpendicular to the first or second axis of rotation. At each cross section, the nip size is the minimum Euclidean distance between the first and second outer surfaces for a given relative position between the first and second crimping rollers. The nip may vary in size during the relative rotation of the first and second crimping rollers. If the surfaces of both the first and second crimping rollers are rotationally invariant with respect to rotation about the first and second axes of rotation, the nip size may be constant or may vary. Furthermore, the nip size may be constant or may vary along the width of the rollers. It is preferred that there are two nip sizes for each cross section. The nip size may also vary along the width of the rollers. Two cross sections taken at two different positions along the axis of rotation of the crimping rollers may show different nip sizes.

[0032] The nip size at each cross section is preferably constant. The nip size is preferably constant between all of the cross sections. A constant nip size allows for consistent processing of the material across the width of the sheet.

[0033] However, the present invention also contemplates that the rollers may flex slightly during use such that a constant crimp profile in the sheet material requires the nip size to be slightly larger toward the center of the rollers.

[0034] The term "tackiness" refers to the adhesive or cohesive properties of a sheet. Adhesion is the tendency of dissimilar particles or surfaces to adhere to one another, while cohesion refers to the tendency of similar or identical particles or surfaces to adhere to one another. The stickiness of a sheet can be measured using a LIDAR (Laser Imaging Detection and Ranging) adapted to measure the distance between a measuring device and the unwound portion of the sheet from the roller. The LIDAR is positioned to face the unwound portion of the sheet. The unwound portion of the sheet is immediately removed from the roller, so that the "non-sticky" sheet has the closest distance to the LIDAR. The distance between the LIDAR and the unwound portion of the sheet increases as the stickiness increases.

[0035] In the following, the terms "upstream" or "downstream" refer to the direction of sheet movement or transport.

[0036] As used herein, the terms "collected" or "collecting" in reference to a sheet refers to the sheet being rolled into a rod form or compressed or contracted substantially transverse to the conveying direction of the sheet.

[0037] As used herein, the terms "horizontal" and "vertical" have their standard meanings.

[0038] A sheet having the following properties is provided in the apparatus of the present invention: given thickness, moisture, composition, and width. The above properties are collectively referred to as the "pre-crimp properties" of the sheet. The pre-crimp properties may be substantially uniform within the sheet or may vary at different locations of the sheet. The thickness, moisture, composition, and width of the sheet may fall within the given ranges, within each property range.

[0039] The sheet defines two opposing surfaces, the opposing surfaces defining opposing sides of the sheet.

[0040] The sheet is preferably provided by unwinding from a bobbin.

[0041] At least one pre-crimp property of the sheet is obtained. One of the pre-crimp properties obtained can be the thickness of the sheet. One of the pre-crimp properties obtained can be the moisture of the sheet. One of the pre-crimp properties obtained can be the width of the sheet. One of the pre-crimp properties obtained can be the composition of the sheet.

[0042] Composition may refer to the chemical composition of the sheet, such as the components of the sheet. For example, composition may include a blend of the sheet. A blend of the sheet is applicable when the sheet is an alkaloid-containing material sheet. In this case, the sheet is made by blending alkaloid-containing materials to obtain a predetermined blend. The alkaloid-containing material may be a tobacco material. It is preferred that a plurality of tobacco types are blended together. For example, at least two different tobacco types are blended together. The term "tobacco type" means one of the different varieties of tobacco. In the context of the present invention, these different tobacco types are differentiated into three main groups: bright tobacco, dark tobacco, and aromatic tobacco. The distinction between these three groups is based on the curing process that the tobacco undergoes before it is further processed into a tobacco product.

[0043] Bright tobacco is a tobacco having generally large, light-colored leaves. Throughout this specification, the term "bright tobacco" is used for full-cured tobacco. Examples of bright tobacco include full-cured tobacco from China, full-cured Brazilian tobacco, full-cured tobacco from the United States (such as Virginia tobacco), full-cured tobacco from India, full-cured tobacco from Tanzania, or full-cured tobacco from other African countries. Bright tobacco is characterized by a high sugar-to-nitrogen ratio. From a sensory perspective, bright tobacco is a tobacco type with a spicy, lively sensation after curing. According to the present invention, bright tobacco is a tobacco having a reducing sugar content of about 2.5 percent to about 20 percent based on the dry weight of the leaf and a total ammonia content of less than about 0.12 percent based on the dry weight of the leaf. Reducing sugars include, for example, glucose or fructose. Total ammonia includes, for example, ammonia and ammonia salts.

[0044] Dark tobacco is tobacco that generally has large, dark leaves. Throughout this specification, the term "dark tobacco" is used for air-cured tobacco. Additionally, dark tobacco may be fermented. Tobaccos that are primarily used for chewing tobacco, snuff, cigar tobacco, and pipe blends are also included in this category. From a sensory perspective, dark tobacco is a tobacco type with a smoky, dark cigar-type sensation after curing. Dark tobacco is characterized by a low sugar-to-nitrogen ratio. Examples of dark tobacco are Burley Malawi or other African Burley, dark-cured Brazilian Galpao, San-cured or air-cured Indonesian Kasturi. According to the present invention, dark tobacco is tobacco that has a reducing sugar content of less than about 5 percent based on dry weight of the leaf and a total ammonia content of about 0.5 percent or less based on dry weight of the leaf.

[0045] Aromatic tobacco is tobacco that often has small, light-colored leaves. Throughout this specification, the term "aromatic tobacco" is used in contrast to other tobaccos that have a high aromatic content, such as essential oils. From a sensory perspective, aromatic tobacco is a tobacco type that, after curing, has a spicy and aromatic feel. Examples of aromatic tobacco include Greek Orient, Oriental Turkish, and Semi-Orient tobaccos, but also fire-cured, US Burley such as Perique, Rustic, US Burley, or Maryland.

[0046] Additionally, the blend may also include so-called filler tobaccos. Filler tobaccos are not a specific tobacco type, but include tobacco types that are primarily used to complement other tobacco types used in the blend and do not bring a specific characteristic aroma direction to the final product. Examples of filler tobaccos are the stems, midribs, or petioles of other tobacco types. A specific example may be the flue-cured stems of the lower petioles of flue-cured Brazilian tobacco.

[0047] Tobacco leaves are further graded within each tobacco type, for example with respect to origin, position of the leaf on the tobacco plant, color, surface texture, size, and shape. These and other characteristics of tobacco leaves are used to form tobacco blends. Tobacco blends are mixtures of tobaccos belonging to the same or different types, such that the tobacco blend has an aggregated specific characteristic. This characteristic may be, for example, a unique taste or a specific aerosol composition when heated or burned. A blend contains specific tobacco types and grades in a given ratio of one to the other.

[0048] According to the present invention, different grades within the same tobacco type may be cross-blended to reduce the variability of each blend component. According to the present invention, different tobacco grades are selected to achieve a desired blend with certain predetermined characteristics. For example, the blend may have target values ​​of reducing sugars, total ammonia, total alkaloids per dry weight basis of homogenized tobacco material. Total alkaloids include, for example, nicotine and uncommon alkaloids (including nornicotine, anatabine, anabasine, myosmine).

[0049] For example, bright tobacco may include grade A tobacco, grade B tobacco, and grade C tobacco. Grade A bright tobacco has slightly different chemical properties than grade B bright tobacco and grade C bright tobacco. Aromatic tobacco includes grade D tobacco and grade E tobacco, with grade D aromatic tobacco having slightly different chemical properties than grade E aromatic tobacco. By way of illustration, a possible target value for a tobacco blend may be, for example, a reducing sugar content of about 10 percent of the total tobacco blend on a dry weight basis. To achieve the selected target value, 70 percent of bright tobacco and 30 percent of aromatic tobacco may be selected to form the tobacco blend. The 70 percent of the bright tobacco is selected from among grade A tobacco, grade B tobacco, and grade C tobacco, and the 30 percent of the aromatic tobacco is selected from among grade D tobacco and grade E tobacco. The amount of grades A, B, C, D and E tobacco included in the blend will depend on the chemical composition of each of the grades A, B, C, D and E tobacco to meet the target values ​​for the tobacco blend.

[0050] Various tobacco types have different chemical characteristics. There may be over 300 chemical components present in tobacco leaves. Different grades of the same tobacco type may have different chemical compositions. Tobacco chemical composition may be influenced by genetics, agricultural practices, soil type and nutrients, weather conditions, plant diseases, petiole position, harvesting, and curing procedures.

[0051] One of the resulting pre-crimp properties can be measured, for example, using a suitable sensor. The sensor preferably measures the pre-crimp property in real time, i.e. the pre-crimp property of the sheet is preferably measured during processing of the sheet. Measuring the pre-crimp property of the sheet means measuring the property of the sheet at least at a given location, i.e. measuring the pre-crimp property of at least a first portion of the sheet. Any sensor for measuring one of the pre-crimp properties is preferably located upstream of the crimp roller.

[0052] The pre-crimp property of the sheet can be measured using one or more sensors to measure the same pre-crimp property. The same pre-crimp property of the sheet may be measured at one location or more locations. When measured at more than one location, each measurement generates data and the data is collected. The data collected from the different measurements may be statistically combined. An average of all pre-crimp measurements of the same property may be performed.

[0053] If thickness is to be measured, a thickness sensor may be used.

[0054] The thickness sensor may include a mechanical sensor. The thickness sensor may include an optical sensor. The thickness sensor may include a mechanical sensor and an optical sensor.

[0055] Where moisture is measured, a moisture sensor may be used, which may include a basis weight sensor.

[0056] If the width is measured, a distance sensor may be used.

[0057] The pre-crimp properties may be obtained by a database. The method of the present invention preferably includes accessing a database and obtaining data for one of the pre-crimp properties of the sheet from the database. The database may include one or more of the pre-crimp properties, i.e., thickness, moisture, composition, or width of the sheet before crimp. The data for the one or more pre-crimp properties may be stored in an accessible memory in which the database resides.

[0058] The pre-crimp properties may be obtained by user input. A panel or other input device may be provided, and a user, e.g., an operator, may input the values ​​of the pre-crimp properties of the sheet. Additionally, data relating to one of the pre-crimp properties may be obtained by scanning data, e.g., a representative code, provided on a bobbin made of the sheet.

[0059] The pre-crimp properties may be obtained by remote signal. Wireless or wired data transmission may be used to input the pre-crimp properties.

[0060] Preferably, two or more pre-crimp properties of the sheet are obtained. Preferably, the moisture of the sheet is obtained. Preferably, the thickness of the sheet is obtained. Preferably, the moisture and thickness of the sheet are obtained.

[0061] The sheet is transported along a transport direction. The transport can be performed by any suitable means, for example, by pulling through rollers. The transport is preferably performed at a sheet speed comprised between about 50 meters / min and about 400 meters / min.

[0062] The sheet is then crimped. The crimping is performed using a pair of crimping rollers, designated as a first crimping roller and a second crimping roller. The first crimping roller and the second crimping roller are positioned adjacent to one another such that a nip is formed between the first and second crimping rollers. The first crimping roller defines a first axis of rotation and a first outer surface. The second crimping roller defines a second axis of rotation and a second outer surface. The first and second axes of rotation are preferably parallel to one another. The first and second axes of rotation are preferably horizontal. The first and second crimping rollers preferably have a width equal to or greater than the width of the sheet such that the entire sheet can be crimped between the first and second crimping rollers. A cross section of the first outer surface along a plane perpendicular to the first axis of rotation is preferably circumferential. A cross section of the second outer surface along a plane perpendicular to the second axis of rotation is preferably circumferential. At least one of the first or second crimping rollers includes corrugations. The corrugations are preferably formed on the first or second outer surface. The corrugations are preferably formed on both the first and second outer surfaces. The corrugations on the first or second crimping roller, or on both, contact the sheet when the sheet is inserted into the nip between the first and second crimping rollers. Due to the action of the corrugations on the sheet, corresponding corrugations are formed on the sheet as the sheet passes through the nip. When both the first and second crimping rollers include corrugations, the first and second crimping rollers may be designed and arranged such that at least a portion of their corrugations are substantially interleaved.

[0063] Alternatively, only one of the first and second crimping rollers may include corrugations, and the other of the first and second crimping rollers may have an essentially smooth outer surface, which may be cylindrical.

[0064] Alternatively, both the first and second crimping rollers may include corrugations in non-corresponding sections. The first crimping roller may include a section with corrugations and a section without corrugations. The section with corrugations is preferably adjacent to a section without corrugations on the first outer surface. The second crimping roller may include a section with corrugations and a section without corrugations. The section with corrugations is preferably adjacent to a section without corrugations on the second outer surface. In such a configuration, when the first and second crimping rollers face each other, the section with corrugations of the first crimping roller faces the section without crimps of the second crimping roller. For each portion of the sheet of material that contacts the first and second crimping rollers, only one of the first and second crimping rollers forms a crimp corrugation on that portion of the sheet of material.

[0065] It is preferred that the corrugations on the first or second crimping roller all have the same pitch. If corrugations are present on both the first and second crimping rollers, it is more preferred that they all have the same pitch. Furthermore, it is preferred that all corrugations on the first or second crimping roller have the same amplitude.

[0066] The nip size between the first and second crimping rollers is preferably comprised between about 100 micrometers and about 300 micrometers. A nip size that is too small, i.e., less than 100 micrometers, may damage the sheet. A nip size that is too large may not crimp the sheet sufficiently for proper further processing, e.g., for collecting the sheet into a rod.

[0067] Preferably, the pitch of the ridges on either the first crimping roller or the second crimping roller, or both, is comprised between 200 micrometers and 1500 micrometers. More preferably, the pitch is comprised between 800 micrometers and 1200 micrometers.

[0068] One embodiment of the crimping roller that can be used in the present invention is described in WO 2018 / 189325 by the same applicant. It is preferred that all the corrugations in the first crimping roller or the second crimping roller have the same flank angle. It is preferred that all the corrugations in the first crimping roller or the second crimping roller have the same amplitude. It is preferred that all the corrugations in the first crimping roller or the second crimping roller have the same pitch.

[0069] The corrugations in the first crimping roller or the second crimping roller can have an amplitude comprised between about 0.1 millimeters and about 1.5 millimeters.

[0070] The nip between the first and second crimping rollers has a given nip size. The nip size preferably varies during the rotation of the first and second crimping rollers for a given cross section taken along a plane perpendicular to the first or second axis of rotation. The nip size is preferably a step function between a first value and a second value. Before and after the "jump" between the first and second values, the nip size is preferably constant.

[0071] The nip size is determined, among other things, by the distance between the first and second crimping rollers and by the diameters of the first and second crimping rollers.

[0072] During the crimping process, the sheet passes through a nip formed between the first and second crimping rollers. The first and second crimping rollers form crimp corrugations on the sheet material having a given pattern. The corrugations on the sheet have a pattern that is determined by the pattern of the corrugations on the first and second crimping rollers. The corrugations on the sheet also define a pitch and an amplitude. The amplitude and pitch of the corrugations on the sheet may be different from the amplitude and pitch of the corrugations on the first or second crimping rollers due to the flexibility and elasticity of the sheet.

[0073] The nip size can be varied, for example, by a first actuator. The first actuator can vary the nip size by varying the distance between the first crimp roller and the second crimp roller. For example, there can be a linear drive. The linear drive can vary the position of the axis of rotation of the first crimp roller, or the second crimp roller, or both. The excentric mechanism can rotate and in the rotational motion can vary the position of the axis of rotation of the first crimp roller, or the second crimp roller, or both. The variation in nip size can be within the range of the nip size ±50 micrometers. The nip size can vary from 20 percent to 50 percent of the original nip size, and even more preferably from 20 percent to 30 percent.

[0074] Downstream in the conveying direction of the first and second crimping rollers, a characteristic of the sheet is evaluated, for example the characteristic of the corrugations formed on the sheet. For this purpose, the device may comprise a sensor for detecting one of the characteristics of the corrugations formed in the sheet by the crimping rollers. The sensor may be an optical sensor, for example an infrared or laser sensor. The optical sensor may comprise an optical emitter on one side of the sheet and an optical receiver on the other side of the sheet. The optical sensor may comprise a laser profiler.

[0075] By "post-crimp properties" of a sheet is meant at least the properties of the sheet after crimping. The post-crimp properties may be properties of the corrugations formed on the sheet. It is also possible to evaluate more properties than the corrugations. By corrugation properties is meant any property of the pattern formed on the sheet by the crimping roller. The property may be, for example, the number of corrugations formed on the sheet, the pitch of the corrugations formed on the sheet, the amplitude of the corrugations formed on the sheet, the flank angle of the corrugations formed on the sheet, the stability of the corrugations formed on the sheet, and others. The corrugations on the sheet have a given geometric pattern that defines, among other things, the pitch, the amplitude, the flank angle, and other geometric parameters. By "stability of the corrugations" is meant the stability of these geometric properties over time, i.e., a property is stable if its value does not change substantially after a certain time or changes within a certain time interval. The post-crimp property may be the diameter of the rod formed by assembling the crimped sheets. The diameter of the rod depends on the properties of the sheet such as the depth of the crimp, i.e., the amplitude of the corrugations formed on the sheet. The post-crimp property may be the resistance to pulling of the formed rod obtained by assembling the crimped sheets. Among other factors, the resistance to pulling depends on the corrugations formed in the sheet that create "air channels" in the rod.

[0076] Evaluation of the post-crimp properties of a sheet is performed after the sheet has been crimped. Evaluation of the post-crimp properties of a sheet means evaluating the post-crimp properties of the sheet at least at certain locations.

[0077] The evaluation of the crimped properties of the sheet is preferably performed in real time. The crimped properties are preferably evaluated at different times. The evaluation of the crimped properties is preferably checked at a given frequency while the sheet is moving. Statistics can be calculated based on all evaluations of the same crimped property at different times.

[0078] Preferably, evaluating the post-crimp properties of the sheet includes measuring the post-crimp properties of the sheet. More preferably, evaluating the post-crimp properties of the sheet includes evaluating the properties of corrugations formed on the sheet. Preferably, evaluating the properties of corrugations formed on the sheet includes measuring the properties of the corrugations. More preferably, measuring the properties of the corrugations includes measuring the properties of the corrugations by a sensor.

[0079] A single sensor may be used to measure the post-crimp properties of the crimped sheet. Several sensors may be used to measure the post-crimp properties of the crimped sheet.

[0080] The crimped property of the sheet may be evaluated at one location on the crimped sheet. The crimped property of the sheet may be evaluated at several locations on the crimped sheet. If evaluated at multiple locations, each determination generates data and the data is collected. The collected data from different determinations may be statistically combined, for example, a statistic may be calculated based on all determinations of the same crimped property at different locations on the sheet. An average of all determinations of the same crimped property of the sheet may be performed.

[0081] The evaluation of the post-crimp property of the sheet is used to adapt the nip size. Depending on the value of the post-crimp property of the sheet, the nip size may be determined to be not optimal. The determination of whether the nip size is optimal also depends on one of the obtained pre-crimp properties of the sheet. For each value of one of the obtained pre-crimp properties, a given value of the post-crimp property of the sheet can be expected. This expected value of the post-crimp property of the sheet therefore depends on the pre-crimp property of the sheet. If the evaluation value of the post-crimp property of the sheet differs from the expected value, it is preferable to change the nip size. "Expected value" also means a range of expected values.

[0082] For example, a particular nip size is initially set for a given resulting pre-crimp sheet thickness. However, after evaluating the post-crimp properties of the sheet after crimping, it may be found that the initially set nip size is not optimal because the post-crimp property value of the sheet, e.g., the waviness property on the sheet, is outside of a desired range. Thus, according to the present invention, the nip size is adjusted based on the evaluated post-crimp properties of the sheet after being initially set based on the pre-crimp thickness.

[0083] The step of varying the nip size based on one of the resulting pre-crimp properties and based on the evaluated post-crimp properties of the sheet may include one of the following: A single variation step based on both the pre-crimp properties and the post-crimp properties may be performed. The variation step performed in two sub-steps may be performed with a first sub-step where the variation is based on the pre-crimp properties and a second sub-step where the variation is based on the post-crimp properties. The first and second sub-steps may be reversed, i.e. a first sub-step where the variation is based on the post-crimp properties and a second sub-step where the variation is based on the pre-crimp properties may be performed.

[0084] The crimped sheet is preferably used in an aerosol-generating article.The crimped sheet is preferably used to form a component of an aerosol-generating article.

[0085] The crimping process produces a variety of effects relative to the material forming the sheet that is pressed between the crimping rollers.

[0086] The first range of benefits arises during the subsequent manufacturing process, such as the fact that a crimped sheet of material can be more easily compressed into a rod than an uncrimped sheet, and more predictable results are obtained.

[0087] A second area of ​​effect relates to crimping (such as the user's smoking experience) when the crimped sheet of material is compressed into a rod and added to an aerosol-generating article. More specifically, the crimping process affects the contact between the air penetrating the aerosol-generating article and the crimped sheet of material, and the resistance to draw (RTD).

[0088] However, a non-optimal or sub-optimal crimping process can overly weaken the crimped web of material, prevent the release of substances from the crimped sheet of material into the permeating air in the rod, and adversely affect the RTD value.

[0089] The correct nip size is related to the correct crimp of the sheet. The nip size may relate, among other parameters, to whether the crimped sheet has the correct "crimp level". The correct "crimp level" is important for the subsequent processing steps of the sheet. For example, the correct amount of crimp may make the sheet "foldable" enough to be assembled into a rod form without breaking. The correct crimp level may avoid the "foldable" sheet from containing structural damage. For example, when rolling the sheet, if the latter is crimped less than the correct crimp level, the material forming the sheet may exhibit expansion forces that can resist the wrapper after being assembled into a rod and wrapped in a wrapper. This prevents the sheet from properly forming a rod. Furthermore, a low crimp level may also affect the ability of the sheet to bend. On the other hand, if the sheet is crimped more than the correct crimp level, the sheet may exhibit structural damage. Small parts of the material forming the sheet may be detached from the formed rod. Small pieces may move inside the aerosol-generating article. Small pieces may also move inside the machinery that processes the rod. This can increase downtime for machinery cleaning. The correct crimp level is therefore a balance between the folding properties of the sheet and the absence or minimization of damage.

[0090] The correct crimp level is related to the post-crimp properties of the sheet. The correct crimp level is preferably related to the properties of the sheet caused by the corrugations formed by the crimping process. The correct crimp level may be related to the properties of the corrugations on the sheet. For example, the crimp level is determined by evaluating the amplitude of the corrugations formed on the sheet by the crimping rollers. The properties of the corrugations evaluated after crimping are preferably at least the amplitude of the corrugations formed on the sheet.

[0091] Therefore, a feedback loop control system of the crimping process is preferably implemented according to the present invention, receiving data related to the properties of the sheet before and after the crimping process. For example, the feedback loop control system may include sensors located upstream and downstream of the first crimping roller and the second crimping roller. The feedback loop system is preferably connected to the first actuator to command the first actuator. The feedback loop control system has the ability to adjust the nip size so that it can be constantly optimized during the process.

[0092] For example, for each pre-crimp property obtained, a given post-crimp property is expected from empirical data. A range of values ​​for the post-crimp property can be expected. A look-up table or database can be formed such that for a given pre-crimp property, an expected value for the post-crimp property can be obtained. A range of expected values ​​for such post-crimp property can be obtained. From the expected value or range of values ​​for the post-crimp property, a nip size value is preferably associated from the empirical data. The first crimp roller and the second crimp roller are then arranged such that the associated nip size is between them. The sheet is then crimped using the associated nip size. The expected post-crimp property is then evaluated. If the evaluated post-crimp property is different from the expected one, the nip size is changed. This also applies to several pre-crimp properties as input, and a multi-dimensional table may exist so that a given post-crimp property is first obtained and then evaluated for a selected number of pre-crimp properties.

[0093] The post-crimp property may be the amplitude of the corrugations formed on the sheet. Thus, for a given thickness or moisture of the sheet before crimping, a corresponding expected value of the amplitude of the corrugations is obtained in the database. From empirical data, it is known that the expected amplitude value is obtained with an associated nip size. The associated nip size is set and the sheet is crimped. The amplitude of the corrugations formed on the sheet is then measured. If the measured amplitude value is "too large" from the expected value, i.e., if the difference between the expected and measured amplitude values ​​is above a given threshold in absolute value, the nip size is changed.

[0094] The method preferably includes varying the nip size during crimping. The evaluations performed upstream and downstream of the crimp roller may preferably be performed at a certain frequency during the manufacturing process. For example, the evaluations may be performed several times per minute. The evaluations may be performed once between 1 and 30 minutes. The evaluations are preferably performed every 1 to 15 minutes. Pre-crimp and post-crimp data are preferably collected and evaluated continuously. The nip size may be varied during crimping of the sheet without the need to stop the manufacturing process. The process may be adapted to changing ambient conditions. The process may be adapted to changes in the pre-crimp properties of the sheet.

[0095] Preferably, the sheet is an alkaloid-containing material sheet. Preferably, the sheet is a plastic sheet. The crimping method or apparatus may be used with sheets of alkaloid-containing material, such as homogenized tobacco sheets, which are "sticky" and relatively weak. The crimping method or apparatus may be used with plastic sheets, such as polylactic acid (PLA) sheets, which are elastic.

[0096] The sheet preferably has a mechanical property, a tackiness, and a temperature. The method preferably includes determining one additional pre-crimp property of the sheet. The additional pre-crimp property of the sheet may be a mechanical property of the sheet. The "mechanical property" may include one or more of tensile strength, modulus, elastic limit, maximum elongation, hardness, melting temperature, glass transition, and others. The additional pre-crimp property of the sheet may be the temperature of the sheet. The additional pre-crimp property of the sheet may be the tackiness of the sheet. The method may include varying the nip size based on one of the determined additional pre-crimp properties of the sheet. The method may include varying the nip size based on the mechanical property of the sheet. The method may include varying the nip size based on the temperature of the sheet. The method may include varying the nip size based on the tackiness of the sheet. The method may include varying the nip size based on a combination of two parameters from the additional pre-crimp properties. The method may include varying the nip size based on a combination of three parameters from the additional pre-crimp properties. "Sheet mechanical properties, tack, temperature" are collectively referred to as additional pre-crimp properties of the sheet. Additionally, other parameters of the sheet may be determined in addition to or in place of those listed. These additional parameters may be used in the method of the present invention as a basis for varying the nip size.

[0097] Of course, the sheet has additional pre-crimp properties at a given location. This means that the sheet may have different additional pre-crimp properties depending on the location of the sheet considered for the determination. For example, different parts of the sheet may have different adhesion, temperature, mechanical properties. Preferably, at least one of the additional pre-crimp properties is determined at a given location of the sheet. The determination is performed, for example, using a suitable sensor. The determination may be performed by measurement. Alternatively, one of the pre-crimp properties may be input by a user. Alternatively, one of the additional pre-crimp properties of the sheet may be retrieved from a memory. For example, the mechanical properties of the sheet may already be known from a previous process step and data for the mechanical properties may be retrieved. In this case, no measurement is necessary. The additional pre-crimp property may be read by scanning a barcode located on the bobbin formed by the sheet.

[0098] A single additional pre-crimp property may be determined. Multiple additional pre-crimp properties may be determined. The measured additional pre-crimp property or a combination of determined (e.g., input by a user or retrieved in memory) pre-crimp properties may be used as a basis for varying the nip size. The type and number of determined additional pre-crimp properties may depend on the type and number of sensors available. Furthermore, a single determination may be made for the same additional pre-crimp property. Multiple determinations may be made for the same additional pre-crimp property. The final determination may be a statistical combination of all the determinations made. The statistical combination may include an average (mean value) of the determinations of the same additional pre-crimp property. The nip size may be changed based on one or more of these additional pre-crimp property determinations. The effect that the nip size has on the sheet may be related to the additional pre-crimp properties described above. For example, the nip size may have different "crimping effects" depending on the properties of the material being crimped, such as its mechanical properties, tackiness, composition, temperature or other parameters. Thus, these additional pre-crimp properties may also be relevant to the determination of the optimal nip size. Furthermore, the additional pre-crimp properties may vary depending on the process conditions, for example, the additional pre-crimp properties may vary depending on the temperature or humidity of the environment in which the sheet is located. Since the additional pre-crimp properties may change during the crimping process, adjustment of the nip size as a function of one or more additional pre-crimp properties is preferred. As an example, the temperature or humidity of the environment may change the brittleness of the sheet, which in turn may change its behavior during crimping. Thus, changes in humidity or temperature during the process may trigger changes in the nip size to maintain optimal crimp results.

[0099] The method preferably includes measuring the ambient temperature of the environment in which the sheet is located during crimping. The method preferably includes measuring the ambient humidity of the environment in which the sheet is located during crimping. The method preferably includes measuring the apparatus temperature of a portion of the apparatus for crimping the sheet. The method preferably includes varying the nip size based on the ambient temperature, or the ambient humidity, or the apparatus temperature. In the following, "ambient temperature, ambient humidity, apparatus temperature" are collectively referred to as ambient parameters. Other parameters may be included in "ambient parameters". At least one of the ambient parameters is preferably measured by a suitable sensor. The ambient parameters, i.e. the parameters of the environment in which the sheet is located, may affect the sheet parameters and therefore the crimping effect that the nip size has on the sheet. Depending on the available sensors, one of the ambient parameters may be measured. Two or more ambient parameters may be measured. The nip size may vary depending on these ambient parameters.

[0100] Evaluating the post-crimp properties of the sheet after crimping preferably includes evaluating the properties of a plurality of corrugations formed on the sheet after crimping.

[0101] The crimping process forms corrugations on the sheet, in particular a plurality of corrugations, the corrugations having a given amplitude and pitch. The step of evaluating a property of the plurality of corrugations formed on the sheet preferably comprises evaluating the pitch or amplitude of at least one corrugation of the plurality. A preferred property of the plurality of corrugations for determining whether the correct crimp level has been reached is the pitch or amplitude of at least one corrugation of the plurality. More preferably, the pitch or amplitude of several corrugations of the plurality is determined. An average of the determined pitch or amplitude values ​​for several corrugations may be calculated. Both the pitch and amplitude of at least one corrugation of the plurality may be evaluated. "Evaluating the pitch or amplitude of a corrugation" means evaluating a value that is a function of the pitch or amplitude of the corrugation.

[0102] The estimated pitch or the estimated amplitude of the waveforms is preferably compared to an expected pitch range or expected amplitude range, respectively. If the estimated amplitude or the estimated pitch is outside the expected amplitude range or outside the expected pitch range, respectively, the nip size is varied. The average pitch of several waveforms or the average amplitude of several waveforms is preferably compared to the expected pitch range or expected amplitude range, respectively.

[0103] Preferably, evaluating the pitch or amplitude of at least one corrugation of the plurality comprises determining a profile of at least one corrugation. More preferably, evaluating the pitch or amplitude of at least one corrugation comprises determining a profile of some of the corrugations of the plurality. The corrugation profile is preferably taken perpendicular to the conveying direction of the sheet. The corrugation profile is substantially the profile defined by a cross-section of the sheet taken at a given location by a plane perpendicular to the conveying direction. The profile preferably defines alternating peaks and troughs. The amplitude of the peaks of the profile is preferably evaluated. The average amplitude is preferably calculated by calculating the average of the different amplitudes between the different corrugations. The average amplitude may be a characteristic of the corrugation.

[0104] Preferably, evaluating the characteristics of the plurality of corrugations includes collecting the pitch or amplitude of at least one of the plurality of corrugations at different locations along the sheet or at subsequent time intervals, and comparing the pitch or amplitude of at least one of the corrugations collected at different locations along the sheet or at subsequent time intervals. More preferably, the method also includes varying the nip size based on the comparison. A parameter that can vary the effect that crimping has on the sheet is the "stability" of the corrugations created on the sheet. By "stability" it is meant that the characteristics of the corrugations, such as the pitch or amplitude of the corrugations formed on the sheet, remain substantially the same from the moment of formation by the crimping roller. The first crimping roller and the second crimping roller form corrugations having an amplitude and pitch on the sheet. It is preferable to check whether the characteristics of the corrugations remain stable on the sheet, e.g., whether the amplitude or pitch is changing, or whether the amplitude and pitch are changing. The amplitude or pitch of the corrugations may change over time, i.e., at a given time, they may have a particular value, and after a time interval, the particular value may change. The amplitude or pitch of the corrugation may vary depending on the sheet location where the measurement is made, i.e., at a given location, the pitch or amplitude may have a particular value, and at another location, the pitch or amplitude may have a different value. If this difference exceeds a threshold, i.e., the amplitude or pitch value varies more than a certain percentage of its value, the nip size may be changed, e.g., to a smaller nip size, so that a more stable corrugation is formed.

[0105] The method preferably includes removing at least a portion of the sheet based on the evaluated post-crimp property of the sheet. The method preferably includes removing a portion of the sheet based on one of the evaluated post-crimp property of the sheet and the resulting pre-crimp property of the sheet. The sheet may be removed in its entirety or only a portion of the sheet may be removed, and the remaining portion of the sheet without the removed portion may be further processed. The remaining portion of the sheet that is further processed has a post-crimp property of the sheet, such as a corrugated post-crimp property, within a desired tolerance. For example, if the value of the post-crimp property of the sheet is outside a given range for a given portion of the sheet, relative to the pre-crimp sheet property, the crimped sheet is rejected and not further processed. Alternatively, only the portion of the sheet having the post-crimp property of the sheet outside the given range is cut or otherwise removed. In this way, the portion of the crimped sheet that is outside the tolerance is removed from the processing line as soon as possible.

[0106] The method preferably includes creating a database that includes obtaining one of the pre-crimp properties of the resulting sheet related to any of the following: date of manufacture of the sheet, ambient temperature of the environment in which the sheet is located during crimping, length of fibers present in the sheet, humidity of the environment in which the sheet is located during crimping, machinability of the sheet. This database can be used for traceability purposes of the crimped sheet or components of the manufactured aerosol-generating article that includes the crimped sheet. The database may be used to generate correlations between different parameters. In this way, from such a database, the value of the desired sheet parameter (i.e. pre-crimp property of the sheet) or ambient parameter can be predicted if some sensor of the pre-crimp property or ambient parameter is not present in the device.

[0107] The method preferably includes setting a first nip size based on one of the pre-crimp properties of the resulting sheet. The method may further include adjusting the first nip size to set a second nip size based on the evaluated post-crimp properties of the sheet. The adjustment of the nip size is preferably performed in two steps: the nip size is first set to a first value based on the pre-crimp properties of the sheet. Then the post-crimp properties are evaluated. If the post-crimp properties are not as expected for the resulting post-crimp properties, the first nip size is adjusted. The first nip size becomes the second nip size. The second nip size is determined based on the post-crimp properties. Generally, the nip size is set correctly, i.e. the first nip size is generally the nip size that gives the sheet the right crimp level, taking into account the pre-crimp properties. However, in those instances where the first nip size does not provide the correct crimp level, the nip size can be changed after evaluation of the post-crimp properties.

[0108] The sensor adapted to assess one of the pre-crimp properties of the sheet preferably includes a sensor adapted to measure the thickness of the sheet. More preferably, the sensor for measuring the thickness of the sheet includes a mechanical sensor including a wheel or skate in contact with the sheet. The sensor for measuring the thickness of the sheet preferably includes an optical sensor for projecting an electromagnetic beam onto the sheet. The sensor for measuring the thickness of the sheet preferably includes an interferometer. More than one sensor may be used to measure the thickness of the sheet, for example two or more sensors of the same type, for example two optical sensors, or two or more sensors of different types, for example an optical sensor and a mechanical sensor.

[0109] The mechanical sensor may include a wheel rolling on the top surface of the sheet. The mechanical sensor may include a skate that contacts the top surface of the sheet. The height of the wheel or the height of the skate and their deformations are preferably checked and compared with the expected thickness of the sheet. The comparison is made within a preset tolerance.

[0110] The interferometer may include an optical light emitter for directing a light beam, such as an infrared light beam, onto the sheet of material and onto an additional surface, such as a highly reflective metal surface, positioned below the sheet. When the light beam strikes the sheet, some of the light is reflected back by the top surface of the sheet and some of the light passes through the sheet and is reflected by the metal sheet. The reflected light may form an interference pattern that may be detected. From the interferometry, the thickness of the sheet may be calculated from the difference in the optical path between the light reflected off the top surface of the sheet and the light reflected off the metal surface below the sheet, which creates an interference or phase difference.

[0111] The optical sensor may include LED emitters and receivers located on two opposite sides of the sheet. The LEDs may emit a beam of diffuse LED light in a parallel, uniform manner on one side of the sheet, and the light is detected by a receiver located on the other side of the sheet, for example a reference roller over which the sheet runs. Since the reference roller position is known, the thickness of the material is calculated as the difference between the roll position and the optical sensor measurement.

[0112] The sensor for evaluating the post-crimp properties of the sheet preferably includes a sensor adapted to measure the properties of a plurality of corrugations. The sensor for evaluating the properties of the corrugations on the sheet preferably includes a laser profiler. The laser profiler emits a beam of laser radiation having substantially the shape of a line. The laser profiler is adapted to determine the profile of an object on which the laser line strikes. The laser profiler preferably emits a laser line substantially perpendicular to the conveying direction of the sheet. The laser line is preferably long (wide) enough to strike several corrugations. The laser profiler is adapted to determine the profile of a cross section of the sheet on a plane perpendicular to the conveying direction. The laser profiler preferably acquires the profile at a given frequency. During the crimping of the sheet, the laser profiler is adapted to form an image. The image is formed by a sequence of acquisitions by the laser profiler, an acquisition for each laser line that strikes the sheet. The laser profiler used in the present invention is, for example, a Keyence LJV7020 using a controller XG-X2800. For the profile acquired by each laser line, the laser profiler is adapted to obtain the average amplitude. The profile acquired by each laser line includes a profile of several waveforms.

[0113] Preferably, the control unit is connected to the laser profiler, the control unit being adapted to determine the amplitude or pitch of the profile obtained by the laser profiler From the profile of the sheet, the pitch and amplitude of the corrugations formed on the sheet by the first and second crimping rollers can be determined.

[0114] The apparatus preferably includes an ambient temperature sensor adapted to measure an ambient temperature of an environment in which the sheet is located and to emit a signal representative of the measured ambient temperature. The apparatus preferably includes an ambient humidity sensor adapted to measure an ambient relative humidity of an environment in which the sheet is located and to emit a signal representative of the measured ambient relative humidity. The apparatus preferably includes an adhesive sensor adapted to measure the adhesiveness of the sheet at a given location and to emit a signal representative of the measured adhesiveness. The feedback control loop may be adapted to activate the first actuator based on a signal emitted by the ambient temperature sensor. The feedback control loop may be adapted to activate the first actuator based on a signal emitted by the ambient humidity sensor. The feedback control loop may be adapted to activate the first actuator based on a signal emitted by the adhesive sensor. Advantages of having additional sensors have been outlined with reference to the method.

[0115] The apparatus preferably includes a second actuator for disposing of at least a portion of the sheet, and the feedback control loop system is preferably adapted to activate the second actuator based on the measured pre-crimp properties of the sheet, or based on data obtained for one of the pre-crimp properties, or based on the evaluated post-crimp properties. The second actuator may include a reject gate. The second actuator is preferably activated when the sheet or a portion of the sheet needs to be disposed of because the post-crimp properties of the sheet are not within a predetermined range, a given pre-crimp property.

[0116] The control unit preferably communicates with a sensor adapted to measure one of the pre-crimp properties of the sheet, the laser profiler and the first actuator. Furthermore, the control unit may be adapted to receive input from a user. The control unit may have the ability to access a memory in which the pre-crimp properties of the sheet are stored. The control unit may be a microprocessor, a microcontroller, or a computer. The control unit preferably communicates with all pre-crimp and post-crimp sensors present in the device, so that the signals from the sensors can be refined centrally. The control unit preferably includes a memory in which the measurements can be stored. The control unit may also receive input from a user, for example via a keyboard, a touch screen, a pointing device, or a button.

[0117] The feedback loop system is preferably adapted to activate the second actuator based on a signal for the ambient temperature. The feedback loop system is preferably adapted to activate the second actuator based on a signal for the ambient relative humidity. The feedback loop system is preferably adapted to activate the second actuator based on a signal for the tackiness of the sheet. The feedback loop system is preferably adapted to activate the second actuator based on a plurality of signals arriving from different sensors.

[0118] Further advantages of the present invention will become apparent from the detailed description thereof, taken with non-limiting reference to the accompanying drawings, in which: [Brief description of the drawings]

[0119] [Figure 1] FIG. 1 is a schematic side view of an apparatus for producing a crimped sheet of material. [Diagram 2] FIG. 2 is a schematic perspective view of a pair of crimping rollers that are part of the apparatus of FIG. [Diagram 3]FIG. 3 is a schematic side view of the apparatus of FIG. 1 with the sheet of material removed to show further detail. [Figure 4] FIG. 4 is a schematic enlarged front view of a cross section of a material sheet crimped using the apparatus of FIGS. [Diagram 5] FIG. 5 is a more detailed schematic side view of a portion of the apparatus of FIG. [Figure 6] FIG. 6 is a schematic top view of a crimped sheet according to the present invention. [Figure 7] FIG. 7 is a graph illustrating steps in the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0120] In FIG. 1, there is shown in schematic side view the basic layout of an apparatus 1 for producing a crimped sheet 10 of material for an aerosol-generating article (not shown in the drawing).

[0121] The sheet of material is supplied by a supply bobbin 3. The supply bobbin 3 is provided with an "endless" sheet of flat and thin layer of material 2 to be crimped using the device 1. The material 2 may be a homogenized tobacco sheet. The sheet of material 2 wound on the supply bobbin 3 is not endless in the strict sense, but the total length of the sheet of material may be several hundred meters and is therefore much longer than its width. Furthermore, a handover mechanism (not shown) between two successive supply bobbins 3 may be provided so as to allow a continuous crimping process.

[0122] The apparatus 1 comprises a first crimping roller 4 and a second crimping roller 5. Between the first and second crimping rollers a nip 6 is formed. The nip defines a nip size 14. The first crimping roller 4 defines a first axis of rotation 24. The second crimping roller 5 defines a second axis of rotation 25. The first and second axes of rotation 24 and 25 are each indicated by a cross in Figs. 1 and 3 and can be seen in their extension in Fig. 2. The first and second axes of rotation 24 and 25 are preferably parallel and horizontal. In operation, it is preferred that one of the first or second crimping rollers 4 or 5 rotates clockwise and the other of the first or second crimping rollers rotates counterclockwise.

[0123] The first crimping roller 4 and the second crimping roller 5 exhibit a structured outer surface, including a plurality of ridges or corrugations. In the drawing, the corrugations are not visible. It is also possible that a different arrangement is chosen, in particular that only one of the first crimping roller 4 or the second crimping roller 5 exhibits a structured surface.

[0124] The sheet 2 is inserted into the nip 6 between the first crimping roller 4 and the second crimping roller 5 to be crimped. Downstream of the first crimping roller 4 and the second crimping roller 5 a crimped sheet 10 is formed, the corrugations being produced by the pressure exerted by the crimping rollers 4, 5.

[0125] The sheet 2 is conveyed towards the first crimping roller 4 and the second crimping roller 5 by a conveying device 7. The conveying device 7 defines a conveying direction of the sheet 2, indicated by the arrow 8 in FIGS.

[0126] Upstream of the first crimping roller 4 and the second crimping roller 5, pre-crimp properties of the sheet 2 are measured. For example, the caliper 11 of the sheet 2 is measured. The apparatus 1 includes a caliper sensor 9 adapted to measure the caliper 11 of the sheet 2 at one or more portions of the sheet itself before crimping. Alternatively, or additionally, the apparatus 1 includes a moisture sensor 90 adapted to measure the moisture of the sheet 2 at one or more portions of the sheet itself before crimping.

[0127] Additionally, the apparatus 1 includes a control unit 100 in communication with the thickness sensor 9 and the moisture sensor 90. The thickness sensor 9 and the moisture sensor 90 are adapted to transmit one or more signals to the control unit 100 indicative of the thickness 11 and moisture, respectively, of the sheet 2 in one or more of the portions of the sheet.

[0128] Located downstream of the first crimping roller 4 and the second crimping roller 5 is a sensor for detecting characteristics of the corrugations, such as a laser profiler 12. In embodiments where the sensor 12 is adapted to detect the profile of the corrugations formed on the crimped sheet 10 at one or more of its portions, the sensor 12 is adapted to determine the characteristics of the corrugations. The laser profiler 12 is adapted to communicate with a control unit 100 and to transmit one or more signals to the control unit 100 representative of the profile of the crimped sheet 10 at one or more of its portions.

[0129] As can be better seen in FIG. 3, where the sheet of material is not shown for purposes of clarity, the nip 6 between the first crimping roller 4 and the second crimping roller 5 is adjustable. The apparatus 1 includes a first actuator, indicated by arrow 13 in FIG. 3, which is used to change the nip size 14. The first actuator 13 can vary the distance between the first rotation axis 24 and the second rotation axis 25. The first actuator 13 is actuated by a signal sent by a control unit 100.

[0130] The apparatus 1 also comprises a second actuator 15, indicated only by an arrow in Fig. 3, adapted to dispose of the crimped sheet 10 based on a signal generated by the control unit 100 after receiving a signal from the laser profiler 12. The second actuator 15 is connected to the control unit 100, which sends a signal to the second actuator 15 if the laser profiler 12 detects a corrugated profile on the crimped sheet 10 having characteristics outside of a given time interval.

[0131] The device 1 may also comprise a temperature sensor 16 for measuring the temperature of the sheet 2, the crimped sheet 10 and the environment in which the device 1 is located, a humidity sensor 17 adapted to measure the relative humidity of the environment in which the sheet 2, the crimped sheet 10 and the device 1 is located, a temperature sensor 19 adapted to measure the temperature of the sheet 2 or the crimped sheet 10 at a given location. All sensors 16, 17, 19 (visible in FIG. 3) are connected to a control unit 100. Further sensors may be present. Furthermore, the control unit 100 comprises a memory 18 in which a database is present. In the database data such as the composition of the sheets is present.

[0132] Additionally, other data is stored in memory 18, such as expected values ​​of the corrugation characteristics formed by crimping rollers 4, 5 on the sheet, expected values ​​based on the pre-crimp characteristics of the sheet. For example, as shown in Figure 7, three expected amplitudes of the corrugation are shown, each corresponding to a pre-crimp moisture of the sheet 2. Depending on the moisture measured by sensor 90, different expected values ​​of crimp amplitude are expected.

[0133] 4, an enlarged view of the crimped sheet 10 is illustrated in a front cross-sectional view. The crimped sheet 10 includes a plurality of corrugations, all indicated at 20, that form a "wavy" pattern. The corrugations 20 define a given amplitude 23 and a given pitch 26.

[0134] The device 1 operates according to the method of the present invention.

[0135] The sheet 2 is unwound from a supply bobbin 3 and enters the nip 6 between the first crimping roller 4 and the second crimping roller 5 of the apparatus 1 as a single flat layer of material 2. Processing of the sheet of material 2 takes place in the nip 6 formed between the crimping roller 4 and the crimping roller 5 by appropriate positioning of the two crimping rollers 4, 5 at a specific distance by the first actuator 13. The size 14 of the nip 6 is typically smaller than the thickness 11 of the incoming sheet 2 such that the sheet 2 is slightly compressed in the nip 6.

[0136] The nip size 14 is selected according to signals sent by the thickness sensor 9 and the moisture sensor 90 to the control unit 100, which then controls the first actuator 13. Using the memory 18 and the data stored therein, the measured thickness or moisture data, the control unit 100 obtains expected values ​​of the characteristics of the corrugations formed on the crimped sheet 10 for the measured thickness or moisture values ​​from a graph similar to the graph depicted in FIG. 7. The graph in FIG. 7 is a representation of a look-up table depicted as a graph for the purpose of clarity. For example, the control unit 100 obtains expected values ​​of the amplitude 23 of the corrugations for the measured moisture value of the sheet. Thus, by appropriately setting the nip size 14 with the actuator 13, the expected corrugation characteristics may be obtained.

[0137] Due to the design of the first and second crimping rollers 4, 5, and particularly due to the design of the outer surfaces of the crimping rollers 4, 5, the sheet of material 2 passing through the nip 6 has corrugations 20 formed thereon. A top view of the corrugations 20 on a portion of the sheet 10 is shown in FIG.

[0138] The laser profiler 12 detects the profile of the crimped sheet 10 at a given point. To detect the profile, a laser line 21 strikes and illuminates the crimped sheet 10 as shown in FIG. 6. The laser line 21 is preferably substantially perpendicular to the conveying direction 8. The illumination of the sheet 10 by the laser profiler 12 is preferably performed while the crimped sheet 10 rotates on an idle roller 70 (see FIG. 5). The laser line 21 is preferably a few millimeters long so as to illuminate more than the corrugations 20. The profile obtained by the laser profiler 12 resembles the curve shown in FIG. 4. The laser profiler 12 illuminates the sheet 10 with a given frequency while the crimped sheet 10 moves along the conveying direction 8 so as to obtain several profiles.

[0139] For each profile shown in Figure 4, the laser profiler 12 or control unit 100 calculates the waveform amplitude 23. Then, for each profile, an average amplitude is calculated. The average amplitude is a characteristic of the plurality of waveforms 20 of interest. If the average amplitude is outside a given first range for a given measured moisture, the sensor 12 sends a signal to the control unit 100 which then sends a signal to the first actuator 13 to change the nip size 14. Alternatively, the average amplitude may be calculated directly within the control unit 100.

[0140] If the average amplitude 23 is outside the second range, the sensor 12 sends a signal to the control unit 100, which then sends a signal to the second actuator 15 to dispose of the crimped sheet 10. If the average amplitude is calculated directly within the control unit 100, no signal is sent by the sensor 12.

[0141] The first actuator 13 may also be operated to vary the nip size 14 based on a signal received from any of the sensors 16, 17, 19. The second actuator 15 may also be operated to dispose of the crimped sheet 10 based on a signal received from any of the sensors 16, 17, 19.

[0142] The signals from the sensors 9, 12, 16, 17, 19, 90 are preferably transmitted to the control unit 100 at a given frequency during the entire crimping process. Thus, continuous adjustment of the nip size 14 is possible. The control unit 100 together with the sensors 9, 12, 16, 17, 19, 90 defines a feedback control loop.

[0143] If the sheet 10 is not to be disposed of, the crimped sheet 10 is fed to a production bobbin 27 onto which the crimped sheet of material 10 is wound.

Claims

1. 1. A method for crimping a sheet having a thickness, moisture, composition, and width prior to crimping, said method comprising: - To obtain the following: o the thickness of the sheet; o the moisture of the sheet; o the composition of the sheet; o obtaining a pre-crimp sheet property across the width of the sheet; - crimping the sheet to form a plurality of corrugations on the sheet, the crimping comprising: o providing a pair of crimping rollers defining a nip therebetween, said nip having a nip size; o inserting the sheet into the nip; - evaluating the post-crimp properties of said sheet after crimping; varying the nip size based on one of the pre-crimp sheet properties obtained and based on the evaluated post-crimp sheet property.

2. 2. The method of claim 1, wherein the sheet is an alkaloid-containing material sheet or a plastic sheet.

3. The sheet has mechanical properties, tack and temperature prior to crimping, and the method comprises: - determining, hereinafter: o the mechanical properties of the sheet; o the temperature of the sheet; o the tackiness of the sheet; and - varying the nip size based on one of the determined pre-crimp properties of the additional sheet.

4. The method of any one of claims 1 to 3, wherein evaluating post-crimp properties of the sheet after crimping comprises evaluating properties of a plurality of corrugations formed on the sheet after crimping.

5. The plurality of waveforms have a pitch and an amplitude, and evaluating a characteristic of the plurality of waveforms The method of claim 4, comprising evaluating the pitch or the amplitude of at least one waveform of the plurality.

6. The method of claim 5 , wherein evaluating the pitch or the amplitude of at least one waveform of the plurality includes determining a profile of at least one waveform.

7. The method of any one of claims 1 to 6, comprising removing at least a portion of the sheet based on the evaluated post-crimp properties of the sheet.

8. - setting a first nip size based on one of the obtained pre-crimp sheet properties; - adjusting the first nip size to set a second nip size based on the evaluated post-crimp sheet properties of the sheet.

9. Before crimping, Thickness, Moisture, ・Composition, An apparatus for crimping a sheet having pre-crimp characteristics within a width, comprising: The apparatus, a transport device adapted to transport said sheet along a transport direction; a pair of crimping rollers for crimping the sheet to form a plurality of corrugations on the sheet, the pair of crimping rollers defining a nip therebetween, the nip having a nip size; a sensor adapted to evaluate the post-crimp properties of the sheet, said sensor being located downstream in the conveying direction of the pair of crimping rollers; - below: o a sensor adapted to evaluate one of the pre-crimp properties of the sheet and to deliver a signal function of one of the evaluated pre-crimp properties, said sensor being located upstream of the pair of crimp rollers in the conveying direction; o a memory containing data for one of said pre-crimp properties of said sheet; a control unit adapted to receive a signal function of one of said evaluated pre-crimp properties or to obtain data for one of said pre-crimp properties; a first actuator for varying said nip size; a feedback control loop system adapted to activate the first actuator based on one of the evaluated pre-crimp properties of the sheet or based on data obtained for one of the pre-crimp properties and based on the evaluated post-crimp property of the sheet.

10. The sensor adapted to assess one of the pre-crimp properties of the sheet includes a sensor adapted to measure the thickness of the sheet, the sensor comprising: - mechanical sensors including wheels or skates in contact with the seat, an optical sensor for directing an electromagnetic beam onto said sheet; - an interferometer.

11. 11. The apparatus of claim 9 or 10, wherein the sensor adapted to assess one of the post-crimp properties of the sheet comprises a sensor adapted to assess a property of the plurality of corrugations.

12. the sensor adapted to evaluate a characteristic of the plurality of waveforms, - An apparatus according to claim 11, comprising a laser profiler.

13. 13. The apparatus of claim 12, wherein the control unit is connected to the laser profiler, the control unit being adapted to determine an amplitude or pitch of a profile obtained by the laser profiler.

14. an ambient temperature sensor adapted to measure the ambient temperature of the environment in which said seat is located and to emit a signal representative of said measured ambient temperature; an ambient humidity sensor adapted to measure the ambient relative humidity of the environment in which the sheet is located and to emit a signal representative of said measured ambient relative humidity; - a tackiness sensor adapted to measure the tackiness of said sheet at a given location and to emit a signal representative of said measured tackiness; - a transparency sensor adapted to measure the transparency of the sheet and to emit a signal representative of the measured transparency, said transparency sensor being located downstream of the pair of crimping rollers.

15. 15. The apparatus of claim 9, further comprising a second actuator for disposing of at least a portion of the sheet, and wherein the feedback control loop system is adapted to activate the second actuator based on the evaluated pre-crimp properties of the sheet, or based on data obtained for one of the pre-crimp properties, or based on the evaluated post-crimp properties.

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