Method for the production of sheet-like tobacco material

Abstract

The invention relates to an apparatus and a method of manufacturing a crimped sheet (70) of material for an aerosol-generating article. The method comprises the step of feeding a substantially continuous sheet of material to a set of crimping rollers (11, 21) in a transport direction (1), the set of crimping rollers comprising a first roller (11) having a first surface (12) and having a first plurality of ridges (17) across at least a portion of its width and a second roller having a second surface, the second surface (22) being formed at least for a portion thereof in a material having an hardness lower than the hardness of a material forming the first surface. Further, the method comprises crimping the substantially continuous sheet of material to form the crimped sheet by feeding the substantially continuous sheet between the first and second rollers in the transport direction of the sheet such that the corrugations of the first roller apply a plurality crimp corrugations to the substantially continuous sheet.

Claims

1. A method of manufacturing a crimped sheet of material for an aerosol-generating article, the method comprising the steps of: feeding a substantially continuous sheet of material to a set of crimping rollers in a transport direction, the set of crimping rollers comprising a first roller having a first surface and having a first plurality of ridges across at least a portion of its width and a second roller having a second surface, the second surface being formed at least for a portion thereof in a material having a hardness lower than the hardness of a material forming the first surface; creating a plurality of substantially parallel ridges formed from alternating peaks and troughs joined by corrugation flanks in the substantially continuous sheet by crimping the substantially continuous sheet of material to form a crimped sheet by feeding the substantially continuous sheet between the first and second rollers in the transport direction of the sheet such that the first plurality of ridges of the first roller applies a plurality of crimp corrugations to the substantially continuous sheet; gathering the crimped sheet; forming a rod using the gathered crimped sheet; wrapping the rod; and cutting the continuous rod into a plurality of rod-shaped components, each rod-shaped component having a gathered crimped sheet formed from a cut portion of the crimped sheet, the crimp corrugations of the crimped sheet defining a plurality of channels in the rod-shaped component.

2. The method according to claim 1, wherein the portion of the first surface of the first roller is realized in metal.

3. The method according to claim 1, wherein the portion of the second surface of the second roller is realized in rubber.

4. The method according to claim 3, wherein the second surface of the second roller includes a portion realized in metal and a portion realized in rubber.

5. The method according to claim 1, including the step of coating the second surface of the second roller with a first layer of a material having a first hardness and coating the first layer with a second layer of material having a second hardness.

6. The method according to claim 1, wherein the second roller has a smooth second surface.

7. The method according to claim 1, wherein the second roller includes a plurality of helical ridges.

8. The method according to claim 1, wherein the sheet of material is one of: a homogenized tobacco sheet, a plastic sheet or a sheet including cellulose.

9. The method according to claim 1, wherein the hardness of a portion of the first surface of the first roller is comprised between about 48 HRC and about 58 HRC.

10. The method according to claim 1, wherein the hardness of a portion of the second surface of the second roller is comprised between about 70 and about 94 SHORE A at 25 degree Celsius.

11. Method according to claim 1, including selecting a distance between the first and the second roller depending on the material of the sheet.

12. The method according to claim 1, wherein a second plurality of ridges is realized on the second surface.

13. A method of manufacturing a crimped sheet of material for an aerosol-generating article, the method comprising the steps of: feeding a substantially continuous sheet of material to a set of crimping rollers in a transport direction, the set of crimping rollers comprising a first roller having a first surface and having a first plurality of ridges across at least a portion of its width and a second roller having a second surface, the second surface being formed at least for a portion thereof in a material having a hardness lower than the hardness of a material forming the first surface; creating a plurality of substantially parallel ridges formed from alternating peaks and trough joined by corrugation flanks in the substantially continuous sheet by crimping the substantially continuous sheet of material to form the crimped sheet by feeding the substantially continuous sheet between the first and second rollers in the transport direction of the sheet such that the first plurality of ridges of the first roller applies a plurality of crimp corrugations to the substantially continuous sheet; and coating the second surface of the second roller with a first layer of a material having a first hardness and coating the first layer with a second layer of material having a second hardness.

14. A method of manufacturing a crimped sheet of material for an aerosol-generating article, the method comprising the steps of: feeding a substantially continuous sheet of material to a set of crimping rollers in a transport direction, the set of crimping rollers comprising a first roller having a first surface and having a first plurality of ridges across at least a portion of its width and a second roller having a second surface, the second surface being formed at least for a portion thereof in a material having an hardness lower than the hardness of a material forming the first surface, a second plurality of ridges being realized on the second surface; crimping the substantially continuous sheet of material to form the crimped sheet by feeding the substantially continuous sheet between the first and second rollers in the transport direction of the sheet such that the first plurality of ridges of the first roller applies a plurality of crimp corrugations to the substantially continuous sheet.

15. The method according to claim 14, wherein the portion of the first surface of the first roller is realized in metal.

16. The method according to claim 14, wherein the portion of the second surface of the second roller is realized in rubber.

17. The method according to claim 14, wherein the second plurality of ridges includes a plurality of helical ridges.

18. The method according to claim 14, wherein the sheet of material is a homogenized tobacco sheet.

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows an isometric view of an apparatus having two main rollers and a pre-crimping roller between which a sheet of material is treated according to the invention;

(3) FIG. 2 shows a two-dimensional representation of a surface of a roller having a ridge-and-trough pattern used in the inventive method;

(4) FIG. 3 shows a schematic top view of a crimped sheet according to the invention where gathering and forming a rod and sticks is indicated;

(5) FIG. 4 shows a two conventional crimping rollers;

(6) FIG. 5 shows a crimped sheet of material treated by conventional crimping rollers of FIG. 4, comprising overextended areas prone to shredding;

(7) FIG. 6 shows a corrugated crimper roller and a counter roller comprising a smooth and soft surface according to an embodiment of the invention;

(8) FIG. 7 shows a detail of a sheet of material crimped with a combination of corrugated and smooth rollers according to the invention;

(9) FIG. 8 shows a corrugated crimper roller and a counter roller comprising a smooth and soft surface consisting two soft surface layers according to an embodiment of the invention;

(10) FIG. 9 shows a detail of a corrugated crimper roller and a counter roller comprising a smooth and soft surface having a soft surface according to an embodiment of the invention;

(11) FIG. 10 shows a counter roller comprising a smooth surface with helical soft and hard bands; and

(12) FIG. 11 shows a flow chart of a method for crimping a sheet of material according to the invention.

(13) For comparative purposes, in FIGS. 4 and 5 an apparatus 200 realized according to the prior art to crimp a sheet of material 70 and the crimped sheet of material are shown.

(14) FIG. 4 shows a partial view of two mutually facing crimping rollers 211, 212 including interleaving corrugations 217, 227 (depicted in an exaggerated manner for clarity) in a side view. Each roller 211, 212 rotates around a respective axis 218, 219. Both rollers 211, 221 have the same diameter 220 and width 221. Each roller 211, 212 includes a conventional ridge-and-trough pattern as corrugation 217, 227. The corrugation or ridge-and-trough pattern 217, 227 is comprised of circumferential ridges, each ridge defining a ridge amplitude. The ridges of the first and second roller have identical amplitude and pitch. Further, each ridge of the corrugations 217, 227 includes a top portion or tip 214 and a concave through 215 is positioned between two adjacent ridges.

(15) FIG. 5 shows a crimped sheet 700 of material treated by the conventional crimping rollers 211, 212 of the apparatus 200 realized according to the prior art as shown in FIG. 4. The crimped sheet 700, comprising overextended areas 730, 740 prone to shredding. As visible in the drawings, the overextended areas 730, 740 are extremely thin compared with the other areas of the sheet 700.

(16) According to the nature of the material of the sheet 700, such overextended areas 730, 740 could be quite localized or not, and are formed usually in corresponding areas to those where the top 214 of the ridges are positioned.

(17) These extra-thin/over-extended areas 730, 740 may create bending lines in the sheet 700 at top and bottom surfaces of the crimped sheet, as illustrated in FIG. 5. These extra-thin bending lines, thin compared to the overall thickness of the sheet 700, are weak parts that can get torn during further processing in case of tension in the material, leading to shredding of parts of the sheet 700, and so to moving particles in the rod material (“fly-out” effect), creating negative user experience when using a final product, such as an aerosol generating article (not shown in the drawings) formed using the crimped sheet 700.

(18) With now reference to FIG. 1, an isometric view of a first embodiment of an apparatus 10 to crimping a sheet of material 70 according to the invention is depicted. The apparatus 10 comprises a first and second facing crimping rollers 11, 21 between which the sheet 70 of material having the width 76 is treated according to the invention. The transport direction 1 of the sheet 70 is indicated with an arrow 1 in the FIG. 1.

(19) The first and second facing roller 11, 21 define a first and second rotation axis 18, 28, respectively. The surface 12 of the first roller 11 is provided with corrugations 17 (not clearly visible in FIG. 1), forming a ridge- and trough pattern, which include typically circumferential ridges on the surface 12 of the first roller 11. The circumferential ridges may be perpendicular with respect to the rotation axes 18, 28 or may be slightly inclined.

(20) Both rollers 11, 21 have the same diameter 16 and width 9 (visible in FIG. 6).

(21) The second roller 21 has a smooth surface 22, which is softer than the surface 12 of the first roller 11, that is, the hardness of the material forming the second surface 22 is lower than the hardness of the material forming the first surface 12 of the first roller. Typically, the counter roller 21 comprises at least a portion of the second surface 22 made of rubber.

(22) The corrugations 17 of the first roller 11 are symmetrical or asymmetrical.

(23) The two rollers 11, 21 are used for crimping a sheet of material 70, such as a homogenized tobacco sheet, so as to prevent overcrimping of the sheet 70.

(24) As can be seen in FIG. 2, where the first roller 11 is depicted as a two dimensional area for clarity, the first surface 12 of the roller 11 has a conventional ridge-and-trough pattern as corrugation 17. The ridge-and-trough pattern 17 is comprised of circumferential ridges, each ridge defining a ridge amplitude. The ridges can be oriented perpendicular to the rotation axis 18 or can be slightly inclined, e.g. by not more than 10°.

(25) The crimping on the sheet 70 is characterized among others by the number of lines of the corrugation pattern of the main crimping roller 11 and the depth of the troughs and the amplitude of the ridges of the corrugations 17.

(26) FIG. 6 shows another—more detailed—view of the apparatus 10 to crimp the sheet of material 70 including the first and the second rollers 11, 21 of FIG. 1. Preferably the first roller 11 is realized in steel, while the second roller has also a steel core the surface of which is covered by a layer a soft material, for instance rubber.

(27) As an example, the second roller 21 may be made of at least one layer 29 of rubber or a soft material around a hard core, for instance steel (the layer 29 is circonferential, however for clarity only one part of it is indicated). Such at least one soft surface helps the sheet 70 to dissipate part of the mechanical pressure of the ridges of the first crimping roller 11 pressing on it, and so helps even more the sheet 70 of not being damaged by the crimping.

(28) For instance, the soft layer 29 may have one layer of rubber, preferably polyurethane with shore A hardness of about 82±2.

(29) FIG. 8 illustrates a variant of the apparatus for crimping rollers, indicated with 40. Elements having an analog function as those described with reference to apparatus 10 are indicated with the same reference numerals. The apparatus 40 includes a first and a second roller 11, 31. The first roller 11 is substantially identical to the first roller described with reference to apparatus 10. The second roller 31 comprises a smooth and soft second surface 32 according to the invention. The smooth and soft surface 32 of the second roller 31 is composed of two soft surface layers 37, 39 arranged on top of each other.

(30) The smooth surface 32 of the counter roller 31 may be made of more than two layers of soft material such as rubber, each having a specific hardness, so as to create different compression shapes on the material being pressed.

(31) Of course, rubber as soft material on the second surface 32 second roller 31 can generally be replaced by another adequate soft material. The surface of the first roller 11 with corrugations 17 composed of ridges and troughs is made of a material harder or as hard as the surface 32 of the second roller 31.

(32) A third embodiment of an apparatus 50 to crimp sheet 70 is depicted in FIG. 9. In FIG. 9, only a portion of the apparatus is shown. The apparatus 50 includes first and second rollers 51, 21 to crimp the sheet 70. The second roller 21 is identical to the second roller of the first embodiment of apparatus 10. However, it may also be identical to the second roller 31 of the second embodiment of apparatus 40. The second roller 21 includes a flat smooth surface 22, “soft” compared to a surface of the first roller.

(33) The first roller 51 comprises a plurality of ridges 57. A first and a second adjacent ridge of the plurality are indicated with 53 and 54. A through 55 is positioned between the two adjacent ridges 53, 54. The though 55 includes a flat surface portion 58. The amplitude 19 of the ridges 53, 54 is so selected to be lower than a minimal thickness of the sheet 70 under which the sheet becomes fragile. Therefore, during crimping, the sheet 70 abuts on, or contacts, the flat portions 58 in the trough 55 of the first crimping roller 51, so that the risk of cutting the sheet 70 or reaching below a minimum thickness of the sheet 70 is avoided. For instance, a maximum amplitude 19 of the ridges 53, 54 could be of about 0.1 millimeters when the sheet 70 is made of homogenized tobacco material with a typical thickness of about 0.2 millimeters. Of course, the dimensions can vary.

(34) In FIG. 10, a different embodiment of a second roller 61 or a crimping pair of roller is depicted. This second roller can be used in any of the apparatuses 10, 40, 50 above described. The second roller 61 has a surface 62 which includes two helical bands 63, 64 comprising different materials. A first material with great hardness, e.g. a metal such as steel, and a second material with a lower hardness than the hardness of the first material, such as rubber, are provided in the helical bands around the counter roller 21, so as to create angled bands of less crimped or even uncrimped material in a crimped sheet. The helical bands 63 of harder material act as helical ridges between the helical bands 64 of softer material.

(35) Such a structure can reinforce the sheet of material for the further manufacturing processes as the less crimped or uncrimped bands in the sheet will maintain their tensile strength of the sheet before crimping. Such less textured bands can provide an attachment function for shreds if the sheet of material is overcrimped during the crimping process.

(36) The helical bands may be arranged so that the spacing of the bands 63, 64 is not more than the final stick length 84 (FIG. 3). The helical bands in the sheet can limit the detachment of shreds or particles of the material in the aerosol-generating articles. In fact, since the spacing is preferably lower than the stick length 84, there will be mandatorily a band of less crimped or uncrimped sheet of material in the stick, acting as an anchoring portion for any shred, holding together the material in the stick.

(37) Such combination creates bending lines while crimping on the sheet 70 that help compress the material from a sheet format to a rod format, while preventing overextending and damaging the material in the sheet 70 being crimped.

(38) The diameter of the first or second crimping roller according to any of the above embodiments is comprised between about 25 centimeters and about 40 centimeters, and the speed of the sheet 70 as it reaches the rollers is between about 100 meters per minute and about 300 meters per minute so that an angular speed of the rollers is typically between about 80 revolutions per minute (rpm) and about 380 rpm.

(39) Advantageously it is possible to fix a minimum distance between the tip of the ridges 17, 57 of the first roller 11, 51 with ridges and troughs and the smooth surface of the second roller 21, 31, 61 and so to fix a minimum thickness of the sheet 70 after crimping. Due to the fact that there is no over-extension of the material of the sheet 70, it is possible to ensure that the sheet 70 cannot be shredded by fixing this minimum thickness above a specific threshold value under which the material would become fragile otherwise.

(40) The sheet 70 is crimped by any of apparatuses 10, 40, 50 in the following way. The sheet 70 runs on the first main roller 11,51 and is then transported between the two main rollers 11 or 51, 21, 31 or 61 for being crimped.

(41) Usually the sheet 70 of material is about between about 0.1 millimeters and about 0.3 millimeters thick, and the average goal of crimping is to create bending lines having roughly half or less of the usual foil thickness. On a classic crimping roller such as the first roller 11, the ridges of the corrugations 17 have a bell shape, each with a total ridge height between about 0.4 millimeters and about 1.5 millimeters, a total width between about 0.4 millimeters and about 0.6 millimeters, and ridges are spaced about every about 0.5 millimeters and about 1 millimeter (pitch of the ridges).

(42) Preferably, the sheet of material 70 is a homogenized tobacco sheet (cast leaf) or a PLA sheet.

(43) The method of manufacturing a crimped sheet 70 of material for an aerosol-generating article, comprises the steps of feeding the substantially continuous sheet 70 of material to a set of first and second crimping rollers.

(44) The surface of the sheet 70 shows corrugations which reproduce the corrugations on the surface of roller 11 in FIG. 2, or 51 of FIG. 9, as well as the combination of corrugations of rollers 11 or 51 and roller 61 of FIG. 10, for instance. The crimped sheet 70 of material is gathered and formed into a rod 80 by bending the crimped sheet 70 about the bending lines created by the crimping process. The crimp corrugations of the crimped sheet 70 define a plurality of channels in the rod 80. The rod 80 is then wrapped and cut into sticks 82 having a stick length 84.

(45) FIG. 3 shows a schematic top view of the sheet 70 having a crimped surface 72 according to the invention where gathering and forming a rod 80 and cutting the rod 80 into sticks 82 is indicated.

(46) When the sheet 70 of material is pressed on the counter second roller 21, 61 by the first crimping roller 11, 51 having corrugations 17, 57 with a ridge-and-trough pattern, the ridges press on the sheet 70 and create bending lines that are lines of compressed areas of the material, and not lines of overextended areas of material. Compressed areas are less likely to shredding. By preventing shredding, the crimping according to the invention is much prone to product consistency and positive experiences than usual crimping process.

(47) In FIG. 7 a detail of a crimped sheet 70 of material is depicted which has been crimped with a combination of corrugated 11, 51 and smooth rollers 21, 31, or helical roller 61 according to the invention.

(48) The crimping process of the sheet 70 between the ridges and troughs of the first roller 11, 51 on top of the sheet 70 and the smooth and soft surface of the second roller 21, 31, 61 on the bottom of the sheet 70 create bending lines 77 in the surface 72, where only one is depicted in the figure, that are made of compressed material 71 of the sheet 70 and which are thinner than the overall thickness of the sheet 70.

(49) Slight bumps 79 at the backside of the thin bending lines 77 are created by the deformation of the soft surface of the second roller 21, 31, 61 under the pressure exerted by the ridges on the sheet 70 transmitted by the compressed material 71 on the soft surface of the second roller 21, 31, 61. On each side of the compressed material 71, other slight bumps 75 of material can be generated by the pressure, depending of the nature of the material, in particular depending on how compression spreads sideways into it and its plastic deformation ability.

(50) Due to their compressed nature, the thin bending lines 77 are more resilient versus tearing than over-extend bending lines created by conventional crimping rollers in a conventional crimping process.

(51) In case of the embodiment of FIG. 8, if the top soft layer is harder than the rubber layer under it, then the bump 79 will be less localized under the pressing ridge of the first roller 11.

(52) FIG. 11 shows a flow chart of a method for crimping a sheet of material according to the invention.

(53) In a first step 100 a substantially continuous sheet of material 70 is fed to a set of crimping rollers in a transport direction 1. The set of rollers comprises a first roller 11, 51 and a second roller 21, 31, 61. The first roller is corrugated across at least a portion of its width.

(54) The surface of the second roller is formed at least for a portion thereof in a material having an hardness lower than the hardness of a surface of the first roller.

(55) In step 102 the substantially continuous sheet of material 70 is crimped to form the crimped sheet by feeding the substantially continuous sheet between the first and second rollers in the transport direction of the sheet such that the corrugations of the first roller apply a plurality crimp corrugations to the substantially continuous sheet.

(56) In step 104, the crimped sheet of material is gathered, and a continuous rod 80 is formed using the crimped sheet of material in step 106. In step 108, the continuous rod is wrapped, e.g. in cigarette paper.

(57) In step 110, the continuous wrapped rod is cut the continuous rod 80 into a plurality of rod-shaped components (sticks) 84, each rod-shaped component having a gathered crimped sheet formed from a cut portion of the crimped sheet, the crimp corrugations of the crimped sheet defining a plurality of channels in the rod-shaped component.