METHOD AND APPARATUS TO CRIMP A SHEET

Abstract

A method is provided to crimp a sheet having, before crimping, a thickness, a moisture, a composition, and a width, the method including: obtaining one pre-crimping sheet characteristic among the thickness of the sheet, the moisture of the sheet, the composition of the sheet, and the width of the sheet; 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 in the nip; evaluating a post-crimping characteristic of the sheet after crimping; and varying the nip size on the basis of the obtained one of the pre-crimping sheet characteristic, and on the basis of the evaluated post-crimping sheet characteristic. An apparatus to crimp a sheet is also provided.

Claims

1.-15. (canceled)

16. A method to crimp a sheet having, before crimping, a thickness, a moisture, a composition, and a width, the method comprising: obtaining one pre-crimping sheet characteristic among the thickness of the sheet, the moisture of the sheet, the composition of the sheet, and the width of the sheet; 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 in the nip; evaluating a post-crimping characteristic of the sheet after crimping; and varying the nip size on the basis of the obtained one of the pre-crimping sheet characteristic, and on the basis of the evaluated post-crimping sheet characteristic.

17. The method according to claim 16, wherein the sheet is a sheet of a material containing alkaloids or a plastic sheet.

18. The method according to claim 16, wherein the sheet has, before crimping, a mechanical characteristic, a stickiness, and a temperature, and the method further includes: determining one additional pre-crimping sheet characteristic among the mechanical characteristic of the sheet, the stickiness of the sheet, and the temperature of the sheet, and varying the nip size on the basis of the determined one of the additional sheet pre-crimping characteristics.

19. The method according to claim 16, wherein the evaluating a post-crimping characteristic of the sheet after crimping includes evaluating a characteristic of the plurality of corrugations formed on the sheet after crimping.

20. The method according to claim 19, wherein the plurality of corrugations have a pitch and an amplitude, and wherein evaluating a characteristic of the plurality of corrugations includes evaluating the pitch or the amplitude of at least one corrugation of the plurality.

21. The method according to claim 20, wherein the evaluating the pitch or the amplitude of at least one corrugation of the plurality further includes determining a profile of at least one corrugation.

22. The method according to claim 16, further comprising removing at least a portion of the sheet on the basis of the evaluated post-crimping characteristic of the sheet.

23. The method according to claim 16, further comprising: setting a first nip size on the basis of the obtained one of the pre-crimping sheet characteristics; and adjusting the first nip size to set a second nip size on the basis of the evaluated post-crimping sheet characteristic of the sheet.

24. An apparatus to crimp a sheet having, before crimping, a pre-crimping characteristic among: a thickness, a moisture, a composition, and a width, the apparatus comprising: a transport device configured to transport the sheet along a transport direction; a pair of crimping rollers to crimp the sheet forming a plurality of corrugations on the sheet, the pair of crimping rollers defining a nip therebetween, said nip having a nip size; a sensor configured to evaluate a post-crimping characteristic of the sheet, the sensor being located downstream of the pair of crimping rollers in the transport direction; one of the following: a sensor configured to evaluate one of the pre-crimping characteristics of the sheet, and to send a signal function of the evaluated one of the pre-crimping characteristic, the sensor being located upstream the pair of crimping rollers in the transport direction, and a memory containing data relative to one of the pre-crimping characteristics of the sheet; a controller configured to receive the signal function of the evaluated one of the pre-crimping characteristics or to retrieve the data relative to one of pre-crimping characteristics; a first actuator configured to vary the nip size; and a feedback control loop system configured to activate the first actuator on the basis of the evaluated one of the pre-crimping characteristic of the sheet or on the basis of the data retrieved relative to one of the pre-crimping characteristics, and on the basis of the evaluated post-crimping characteristic of the sheet.

25. The apparatus according to claim 24, wherein the sensor configured to evaluate one of the pre-crimping characteristics of the sheet includes a sensor configured to measure the thickness of the sheet, the sensor configured to measure the thickness of the sheet including one of: a mechanical sensor including a wheel or a skate in contact to the sheet, an optical sensor to impinge an electromagnetic beam onto the sheet, and an interferometer.

26. The apparatus according to claim 24, wherein the sensor configured to evaluate one of the post-crimping characteristics of the sheet includes a sensor configured to evaluate a characteristic of the plurality of corrugations.

27. The apparatus according to claim 26, wherein the sensor configured to evaluate a characteristic of the plurality of corrugations includes a laser profiler.

28. The apparatus according to claim 27, wherein the controller is connected to the laser profiler, the controller being further configured to determine an amplitude or a pitch of the profiles obtained by the laser profiler.

29. The apparatus according to claim 24, further including one of: an ambient temperature sensor configured to measure an ambient temperature of an environment where the sheet is located and to emit a signal representative of the measured ambient temperature; an ambient humidity sensor configured to measure an ambient relative humidity of the environment where the sheet is located and to emit a signal representative of the measured ambient relative humidity; a stickiness sensor configured to measure a stickiness of the sheet at a given location and to emit a signal representative of the measured stickiness; and a transparency sensor configured to measure a transparency of the sheet and to emit a signal representative of the measured transparency, the transparency sensor being located downstream of the pair of crimping rollers.

30. The apparatus according to claim 24, further including a second actuator configured to discard at least a portion of the sheet, the feedback control loop system being further configured to activate the second actuator on the basis of the evaluated pre-crimping characteristic of the sheet or on the basis of the data retrieved relative to one of the pre-crimping characteristics or on the basis of the evaluated post-crimping characteristic.

Description

[0121] FIG. 1 is in a schematic lateral view of an apparatus for the manufacturing of a crimped sheet of material;

[0122] FIG. 2 is a schematic perspective view of the crimping pair of rollers, part of the apparatus of FIG. 1;

[0123] FIG. 3 is a schematic lateral view of the apparatus of FIG. 1 where the sheet of material has been removed and further details are shown;

[0124] FIG. 4 is a schematic enlarged front view in section of a sheet of material crimped using the apparatus of FIGS. 1-3;

[0125] FIG. 5 is a schematic lateral view of a portion of the apparatus of FIG. 1 with more details;

[0126] FIG. 6 is a schematic top view of a crimped sheet according to the invention; and

[0127] FIG. 7 is a graph representing a phase of the method of the invention.

[0128] In FIG. 1, the basic layout for an apparatus 1 for manufacturing a crimped sheet of material 10 for an aerosol-generating article (not shown in the drawings) is shown in a schematic lateral view.

[0129] The sheet of material is supplied by means of a supply bobbin 3. On the supply bobbin 3, an “endless” sheet of a flat and thin layer of material 2 to be crimped using the apparatus 1 is provided. The material 2 can be a homogenised tobacco sheet. It is to be understood that the sheet of material 2 that is wound up on supply bobbin 3 is strictly speaking not endless, however, the overall length of the sheet of material can be several hundred metres and is therefore much longer than its width. Furthermore, a handover mechanism between two consecutive supply bobbins 3 (not shown) may be provided so that a continuous crimping process is possible.

[0130] Apparatus 1 comprises a first crimping roller 4 and a second crimping roller 5. Between the first crimping roller and the second crimping roller, a nip 6 is formed. The nip defines a nip size 14. First crimping roller 4 defines a first rotational axis 24. Second crimping roller 5 defines a second rotational axis 25. The first rotational axis 24 and the second rotational axis 25 are each indicated by a cross in FIGS. 1 and 3 and visible in their extension in FIG. 2. First rotational axis 24 and second rotational axis 25 are preferably parallel and horizontal. Preferably, one of the first crimping roller 4 or second crimping roller 5 rotates clockwise while the other of the first crimping roller or second crimping roller rotates counter-clockwise during operation.

[0131] The first crimping roller 4 and second crimping roller 5 show a structured outer surface, including a plurality of ridges or corrugations. The corrugations are not visible in the drawings. It is also possible that a different arrangement is chosen, in particular that only one of the first crimping roller 4 or second crimping roller 5 shows a structured surface.

[0132] The sheet 2 is inserted between first crimping roller 4 and second crimping roller 5, in the nip 6, in order to be crimped. Downstream the first crimping roller 4 and second crimping roller 5, a crimped sheet 10 is formed, in which corrugations are created by the pressure applied by the crimping rollers 4, 5.

[0133] The sheet 2 is transported towards the first crimping roller 4 and second crimping roller 5 by means of a transport device 7. The transport device 7 defines a transport direction for the sheet 2 which is indicated by arrow 8 in FIGS. 1, 2, 5 and 6.

[0134] Upstream of the first crimping roller 4 and second crimping roller 5, a pre-crimping characteristic of the sheet 2 is measured. For example the thickness 11 of the sheet 2 is measured. Apparatus 1 includes a thickness sensor 9 adapted to measure the thickness 11 of sheet 2 in one or more portions of the sheet itself before crimping. Alternatively or in addition, apparatus 1 includes a moisture sensor 90 adapted to measure the moisture of sheet 2 in one or more portions of the sheet itself before crimping.

[0135] Further, apparatus 1 includes control unit 100 in communication with thickness sensor 9 and moisture sensor 90. Thickness sensor 9 and moisture sensor 90 are adapted to send one or more signals representative of the thickness 11 and of the moisture, respectively, of the sheet 2 in one or more of sheet's portions to control unit 100.

[0136] Downstream of the first crimping roller 4 and the second crimping roller 5, a sensor to detect a characteristic of the corrugations, such as a laser profiler 12, is located. The sensor 12 is adapted to determine a characteristic of the corrugations, in the example it is adapted to detect the profile of the corrugations formed on the crimped sheet 10 in one or more of its portions. The laser profiler 12 is in communication with control unit 100 and is adapted to send one or more signals representative of the profile of the crimped sheet 10 in one or more of its portions to control unit 100.

[0137] As better visible in FIG. 3, where the sheet of material is not depicted for clarity purposes, the nip 6 between first crimping roller 4 and the second crimping roller 5 is adjustable. Apparatus 1 includes a first actuator, indicated by an arrow 13 in FIG. 3, which is used to change the nip size 14. The first actuator 13 might change the distance between the first and second rotational axis 24, 25. First actuator 13 is actuated by signals sent by control unit 100.

[0138] Apparatus 1 also comprises a second actuator 15, indicated by an arrow in FIG. 3 only, which is adapted to discard the crimped sheet 10 on the basis of signals produced by the control unit 100 after having received signals from the laser profiler 12. The second actuator 15 is connected to control unit 100, which sends to the second actuator 15 a signal in case the laser profiler 12 detects a profile of the corrugations on the crimped sheet 10 having characteristics outside a given interval.

[0139] Apparatus 1 may also comprise a temperature sensor 16 to measure the temperature of the environment where the sheet 2, crimped sheet 10 and apparatus 1 are located; a humidity sensor 17 adapted to measure the relative humidity of the environment where the sheet 2, crimped sheet 10 and apparatus 1 are located; a temperature sensor 19 adapted to measure a temperature of the sheet 2 or of the crimped sheet 10 at a given location. All sensors 16, 17, 19 (visible in FIG. 3) are connected to control unit 100. Further sensors might be present as well. Further, control unit 100 includes a memory 18 where a database is present. In the database, data such as the composition of the sheet are present.

[0140] Further, in the memory 18 other data, such as expected values of characteristics of the corrugations formed by the crimping rollers 4, 5 on the sheet, expected values based on pre-crimping characteristics of the sheet, are stored. For example, as shown in FIG. 7, three expected amplitudes of the corrugations are shown, each expected amplitude of the corrugations corresponding to a pre-crimping moisture value of the sheet 2. Depending on the measured value of the moisture by sensor 90, a different expected value of the crimping amplitude is expected.

[0141] In FIG. 4, an enlarged view of the crimped sheet 10 is depicted in a front sectional view. The crimped sheet 10 includes a plurality of corrugations, all indicated with 20, which form a “wavy” pattern. The corrugations 20 define a given amplitude 23 and a given pitch 26.

[0142] The apparatus 1 works according to the method of the invention.

[0143] The sheet 2 unwinds from the supply bobbin 3 and enters the nip 6 between the first crimping roller 4 and second crimping roller 5 of the apparatus 1 as a single, flat layer of material 2. The processing of the sheet of material 2 is done in the nip 6 which is formed between the crimping rollers 4, 5 by an appropriate placement of the two crimping rollers 4, 5 at a certain distance by means of the first actuator 13. The size 14 of the nip 6 is typically smaller than the thickness 11 of the entering sheet 2, so that the sheet 2 is slightly compressed in the nip 6.

[0144] The nip size 14 is selected according to signals sent by thickness sensor 9 and moisture sensor 90 to control unit 100 which in turn controls the first actuator 13. Using the memory 18 and the data stored therein, and the measured data of thickness or moisture, the control unit 100 retrieves from graphs analogous to the one represented in FIG. 7 the expected value of the characteristic of the corrugations which are to be formed on the crimped sheet 10 for the measured value of thickness or moisture. The graph of FIG. 7 is a representation of a look-up table, represented as a graph for clarity purposes. For example, the control unit 100 retrieves the expected value of the amplitude 23 of the corrugations for the measured value of moisture of the sheet. The nip size 14 is thus set accordingly moving actuator 13 so that the expected characteristic of the corrugations is possibly obtained.

[0145] Due to the design of the first crimping roller 4 and the second crimping rollers 5, in particular due to the design of the outer surfaces of the crimping rollers 4, 5, the sheet of material 2 that passes through the nip 6 has corrugations formed on it 20. A top view of the corrugations 20 on a portion of the sheet 10 is depicted in FIG. 6.

[0146] The laser profiler 12 detects the profile of the crimped sheet 10 at a given point. In order to detect the profile, a laser line 21 impinges and illuminate the crimped sheet 10 as shown in FIG. 6. Preferably, the laser line 21 is substantially perpendicular to the transport direction 8. The illumination of the sheet 10 by the laser profiler 12 preferably takes place while the crimped sheet 10 rotates on an idle roller 70 (see FIG. 5). The laser line 21 is preferably several millimetres long to illuminate more than a corrugation 20. The profile obtained by the laser profiler 12 is similar to the curve depicted in FIG. 4. The laser profiler 12 illuminates the sheet 10 at a given frequency so as to retrieve several profiles while the crimped sheet 10 moves along the transport direction 8.

[0147] For each profile as shown in FIG. 4, the laser profiler 12 or the control unit 100 calculates the amplitude 23 of the corrugations. Then for each profile, a mean amplitude is calculated. The mean amplitude is the characteristic of the plurality of corrugations 20 of interest. If the mean amplitude is outside a given first range for the given measured moisture, the sensor 12 sends a signal to control unit 100 which in turn sends a signal to the first actuator 13 to change the nip size 14. The mean amplitude may be alternatively calculated directly in the control unit 100.

[0148] In case the mean amplitude 23 is outside a second range, the sensor 12 sends a signal to control unit 100 which in turn sends a signal to the second actuator 15 to discard the crimped sheet 10. In case the mean amplitude is calculated directly in the control unit 100, no signal is sent by the sensor 12.

[0149] The first actuator 13 may also be operated in order to vary the nip size 14 also on the basis of signals coming from any of sensors 16, 17, 19. The second actuator 15 may also be operated in order to discard the crimped sheet 10 also on the basis of signals coming from any of sensors 16, 17, 19.

[0150] The signals from sensors 9, 12, 16, 17, 19, 90 are preferably sent to the control unit 100 at a given frequency and during the whole crimping process. Continuous adjustments of the nip size 14 are therefore possible. The control unit 100 defines, together with the sensors 9, 12, 16, 17, 19, 90 a feedback control loop.

[0151] If the sheet 10 is not discarded, the crimped sheet 10 is fed to a product bobbin 27, on which the crimped sheet 10 of material is wound up.