Method and apparatus for joining two sheets of material

Abstract

The present invention relates to a method for splicing two sheets of material, the method comprising the steps of: providing a processing line (14) with a splice head (10) and a quality sensor (12) disposed between an upstream end of the processing line (14) and a downstream end of the processing line; providing a first sheet of material (18) and a second sheet of material; processing the first sheet on the processing line along a processing direction (24) from the upstream end of the processing line to the downstream end of the processing line; detecting a value of a quality parameter at a detected portion of the first sheet with the quality sensor; conveying the first sheet along the processing line such that the detected portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head when the value of the quality parameter is within a predetermined threshold; and splicing the first sheet and the second sheet with the splice head when the detected portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head. The present invention also relates to an apparatus for splicing two sheets of material.

Description

[Technical Field]

[0001] The present disclosure relates to a method of joining two sheets of material, and further to an apparatus for joining two sheets of material. [Background technology]

[0002] In manufacturing operations where sheets of material provided on bobbins are processed, it may be desirable to unwind the sheets from the bobbins at high speeds so that the sheets can also be processed at high speeds. For example, the sheets may be sheets of paper commonly processed in the paper industry. For example, in the manufacture of aerosol-generating articles, the sheets may be sheets of homogenized tobacco material, or sheets of tipping paper, etc. Summary of the Invention [Problem to be solved by the invention]

[0003] At some point during operation, a portion of the sheet may develop a defect that exceeds the acceptable manufacturing tolerances. For example, an unexpected problem during the production or transportation of the sheet may cause a defect in a portion of the sheet. For example, the final portion of the sheet wound onto the bobbin may exhibit a defect in the form of a narrowing of the width. For example, physical stresses on the sheet may occur when the sheet is unwound from the bobbin or when the unwound portion of the sheet is further processed in a machine, causing defects such as tears or holes in the sheet.

[0004] If a bobbin is empty, the manufacturing or production process must be slowed or stopped to replace the empty bobbin with a new one. Similarly, if a sheet is defective, the manufacturing or production process must be slowed or stopped to replace the defective sheet with a new sheet. To avoid a complete stop in production, the two sheets may be wound onto two different bobbins (an "old" bobbin and a "new" bobbin). Sheets can be spliced ​​so that a new bobbin with a defect-free sheet can replace the old bobbin with a defective sheet or the old bobbin with no sheet. However, the joint where the old sheet is spliced ​​with the new sheet may be less stable and more easily susceptible to rupture due to physical stresses during further processing downstream of the splice head.

[0005] It would be desirable to provide a joining mechanism that can reduce the mean time to restart the equipment. It would be desirable to provide a joining mechanism that can avoid machine stoppages during joining. It would be desirable to provide a more robust joining mechanism. It would be desirable to provide a joining mechanism that can provide joined sheets of the correct width. It would be desirable to provide a joining mechanism that provides high mechanical stability of the joined sheets. It would be desirable to provide a joining mechanism that can reduce wastage of material sheets. [Brief explanation of the drawings]

[0006] [Figure 1] Figures 1a and 1b show a method for joining two sheets of material. [Figure 2] Figures 2a and 2b show a method for joining two sheets of material. [Figure 3] Figures 3a and 3b show an apparatus for joining two sheets of material. [Figure 4] 4a and 4b show the buffer unit. [Figure 5] FIG. 5 shows the bonding head. DETAILED DESCRIPTION OF THE INVENTION

[0007] According to one embodiment of the present invention, a method for splicing two sheets of material is provided. The method can include providing a processing line including a splice head and a quality sensor disposed between an upstream end of the processing line and a downstream end of the processing line. The method can include providing a first sheet of material and a second sheet of material. The method can include processing the first sheet on the processing line along a processing direction from the upstream end of the processing line toward the downstream end of the processing line. The method can include detecting a value of a quality parameter at a detection portion of the first sheet with the quality sensor. If the value of the quality parameter is within a predetermined threshold, the method can include conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head, and splicing the first sheet and the second sheet with the splice head when the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head.

[0008] According to one embodiment of the present invention, a method for splicing two sheets of material is provided. The method includes providing a processing line including both a splice head and a quality sensor disposed between an upstream end of the processing line and a downstream end of the processing line. The method includes providing a first sheet of material and a second sheet of material. The method includes processing the first sheet on the processing line along a processing direction from the upstream end of the processing line toward the downstream end of the processing line. The method includes detecting a value of a quality parameter at a detection portion of the first sheet with the quality sensor. If the value of the quality parameter is within a predetermined threshold, the method includes conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head, and splicing the first sheet and the second sheet with the splice head when the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head. The steps of the method may be performed sequentially in the order described above.

[0009] A joining mechanism may be provided that reduces the mean time to restart the equipment. A joining mechanism may be provided that avoids machine stoppages during joining. A more robust joining mechanism may be provided. A joining mechanism may be provided that provides joined sheets of the correct width. A joining mechanism may be provided that provides joined sheets with high mechanical stability. A joining mechanism may be provided that reduces wastage of material sheets.

[0010] As used herein, the term "the detection portion of the first sheet is located before it enters the splice head" means that the detection portion is located upstream of the splice head, in other words, the detection portion is located upstream of the upstream entrance of the splice head relative to the process direction.

[0011] The detection portion may be located immediately upstream of the splice head when the sheets are spliced. The term "immediately upstream" means that the detection portion of the first sheet is adjacent to the upstream entrance of the splice head. For example, when the detection portion is located immediately upstream of the splice head, the distance between the downstream end of the detection portion and the upstream entrance of the splice head may be less than 100 centimeters, less than 50 centimeters, less than 20 centimeters, less than 10 centimeters, or less than 5 centimeters, as measured along the process line.

[0012] The predetermined threshold value of the quality parameter may be a measure for unacceptable defects in the detected portion of the first sheet of material. According to the method of the present invention, it is possible to locate the defective portion before it enters the bonding head from the upstream end of the processing line during bonding. Thus, the defective portion is located upstream of the bonding head during bonding. Therefore, it is possible to prevent the defective portion from forming part of the bonded sheets. It is desirable to provide a bonding mechanism that reduces the risk of defects or ruptures in the bonded sheets.

[0013] The method of the present invention allows for defects in the first sheet to be located immediately upstream of the bonding head during bonding, thereby reducing wasted material sheets.

[0014] The quality sensor detects the value of the quality parameter. This can include detecting a signal and processing the detected signal to derive the value of the quality parameter. The signal processing can be performed by the quality sensor or by the controller. For example, the quality sensor can include an optical sensor that senses an intensity profile of a detected portion of the sheet of material. The intensity profile can be processed to determine the value of the quality parameter, for example, a value of the relative density of holes or tears in the sheet of material.

[0015] Once the value of the quality parameter is derived, the value of the quality parameter is then evaluated to determine whether a splicing routine should be initiated. If the value does not fall within the predetermined threshold, the quality of the detected portion of the first sheet is acceptable, meaning that normal processing of the first sheet continues and splicing is not initiated. If the value does fall within the predetermined threshold, the quality of the detected portion of the first sheet is outside of an acceptable range, meaning that a splicing routine is initiated, including transporting the first sheet along the processing line such that the detected portion of the first sheet is positioned before entering the splicing head from the upstream end of the processing line, before the actual splicing of the first sheet and the second sheet occurs.

[0016] The step of transporting the first sheet along the processing line so that the detection portion of the first sheet is positioned before entering the bonding head from the upstream end of the processing line can include transporting at least one segment of the first sheet including the detection portion in a direction along the processing line toward the upstream end until the detection portion of the first sheet is positioned before entering the bonding head from the upstream end of the processing line.

[0017] In one embodiment of the present invention, the quality sensor may be located upstream of the bond head, in other words, the quality sensor may be positioned to detect a portion of the first sheet of material before the detected portion of the first sheet of material enters the bond head from the upstream end of the processing line.

[0018] The quality sensor may be located upstream of the splice head, and the step of conveying the first sheet along the processing line may include conveying at least one segment of the first sheet including the detection portion in a direction toward the downstream end of the processing line over a distance measured along the processing line that is less than the distance between the splice head and the quality sensor, such that the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head. As used herein, "distance measured along the processing line" refers to the distance traveled by the processed sheet as it moves along the processing line.

[0019] In another embodiment of the invention, the quality sensor may be located downstream of the splice head, in other words, the quality sensor may be positioned to detect a portion of the sheet of material after the detected portion of the sheet of material exits the splice head at the downstream end of the processing line.

[0020] The quality sensor may be positioned downstream of the splice head, and the step of transporting the first sheet along the processing line so that the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head may include transporting at least one segment of the first sheet including the detection portion in a direction along the processing line toward the upstream end until the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splice head.

[0021] The quality sensor can sense the first sheet continuously. The quality sensor can sense the first sheet at a predetermined frequency.

[0022] The quality sensor senses or measures one or more physical parameters of the first sheet to derive the quality parameter. The quality sensor may comprise one or more individual sensors for sensing different physical parameters of the first sheet. The sensed data from the one or more individual sensors may be processed to derive a final value for the quality parameter.

[0023] Evaluating whether the value of the quality parameter falls within a predetermined threshold may include evaluating a difference in value between a reference value and an actual measured value, or a value derived from the actual measured value. Evaluating whether the value of the quality parameter falls within a predetermined threshold may include evaluating whether the actual measured value, or a value derived from the actual measured value, falls within a predetermined range of values.

[0024] A controller may be provided. The quality sensor may be adapted to send a signal to the controller if the quality parameter is within a predetermined threshold. Alternatively, the quality sensor may send measured data to the controller, and the quality parameter may be processed and evaluated by the controller.

[0025] The quality sensor may comprise one or more of an optical sensor, preferably a light sensor, a photo camera, or a video camera. The optical sensor may comprise a light source.

[0026] The quality sensor may be configured to detect one or more of the width of the first sheet, the moisture level of the first sheet, the thickness of the first sheet, the viscosity of the first sheet, and the presence or absence of holes or tears in the first sheet.

[0027] The quality sensor may be configured to detect a width of the first sheet, and the quality parameter may be the width of the first sheet.

[0028] The quality sensor may include a distance sensor adapted to measure a distance between the sensor and an outer surface of the bobbin holding the sheet of material, and if the distance is outside a preset range, the quality sensor may indicate that the bobbin may be nearly empty.

[0029] The method may include evaluating the moisture content of the first sheet of material. The method may include evaluating the thickness of the first sheet of material. The method may include evaluating the width of the first sheet of material. The method may include evaluating the viscosity of the first sheet of material. The method may include evaluating the presence or absence of holes or tears in the first sheet of material. The method may include evaluating at least two of the following parameters: the moisture content of the first sheet of material, or the thickness of the first sheet of material, or the width of the first sheet of material, or the viscosity of the first sheet of material, or the presence or absence of holes or tears in the first sheet of material. Values ​​of one or more of the above parameters, hereinafter referred to as "quality parameters" of the first sheet, may indicate that the first sheet of material no longer has predetermined characteristics for producing an acceptable final product within a desired tolerance range. The final product may be, for example, an aerosol-generating article. Values ​​of one or more quality parameters of the first sheet may indicate that the first sheet of material is likely to break in the near future. For example, the values ​​may indicate that the first sheet of material is likely to break before the first sheet is collected into a rod. For example, the value may indicate that the first sheet of material may break before it is wrapped in a wrapper, or that the first sheet of material may break quickly, causing the machine to stop.

[0030] Preferably, the sensor measures the quality parameter in real time, i.e., the quality parameter of the first sheet is preferably measured while the first sheet is being processed. Furthermore, due to the fact that the first sheet moves in the process direction, one or more parameters can be measured or sensed continuously. Alternatively, one or more parameters can be measured or sensed at a predetermined frequency. The given frequency can be constant. The given frequency can be variable. The given frequency is preferably synchronized with the transport speed of the first sheet. The given frequency can vary depending on the transport conditions of the first sheet. For example, if the transport speed of the first sheet is constant, the frequency of measurement is preferably also constant. Alternatively, if the first sheet accelerates, the measurement frequency is preferably higher than the frequency maintained during a constant sheet speed, since the first sheet is subjected to higher stresses during acceleration. In this way, several portions of the first sheet are inspected. Therefore, the quality parameter of the first sheet is preferably measured at predetermined subsequent time intervals. The duration of these time intervals during which measurements are taken can vary.

[0031] Measuring the quality parameter of the sheet means measuring the quality parameter of the sheet at least at a predetermined location, i.e. the quality parameter of a different detected portion of the first sheet may be measured at each time interval.

[0032] Any sensor measuring one of the quality parameters is preferably positioned so that the quality parameter is measured on a portion of the first sheet that has already been unwound from the bobbin, i.e. the portion of the first sheet on which the quality parameter is measured preferably no longer belongs to the outer surface of the first bobbin.

[0033] The same quality parameter of the first sheet can be measured using one sensor or multiple individual sensors for measuring the same quality parameter. The same quality parameter of the first sheet may be measured at one location or at more locations at each time interval. When measured at more than one location, each measurement generates data, and the data is collected. The collected data from different measurements may be statistically combined. An average of all measurements of the same quality parameter can be calculated. Thus, for each time interval, several combinations of values ​​of the same quality parameter may be collected, with different values ​​measured at different parts of the first sheet.

[0034] If there are two different sensors measuring two different quality parameters, it is preferred that the two different quality parameters are measured on the same portion of the first sheet. It is preferred that the different quality parameters are measured at the same frequency. It is preferred that the measurement of the different frequency parameters is synchronized.

[0035] Preferably, the sensor adapted to measure the quality parameter of the first sheet is fixed and the first sheet is moving.

[0036] The first sheet has a thickness. If thickness is measured as a quality parameter, a thickness sensor may be used that is adapted to measure the thickness of the first sheet of material and to emit a signal based on the thickness measurement.

[0037] 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. In the case of an optical sensor, the optical sensor may include a light source. A beam of electromagnetic radiation emitted by the light source may impinge on the first sheet. A change in the intensity of the transmitted light beam through the first sheet may indicate a change in the thickness of the first sheet.

[0038] The bonding may be performed according to a measurement of the thickness of the first sheet.

[0039] If the measured thickness exceeds or is below the thickness threshold, the thickness sensor can send a signal to the controller, notifying that the thickness is outside the preferred range of the thickness parameter value. For example, if the thickness of the first sheet is lower than a specific threshold, a signal may be sent. Alternatively, the thickness sensor may send a signal representing the thickness of the first sheet in each measurement, and the controller may perform a comparison with the thickness threshold. For example, a threshold equal to a selected percentage of the reference value of the thickness of the first sheet can be set. The selected percentage is, for example, 25%, 20%, 15%, or 10%. The reference value of the thickness is preferably a value composed between 150 micrometers and 350 micrometers, more preferably between 200 micrometers and 300 micrometers. If the thickness of the first sheet is lower than the selected percentage above the reference value of the thickness, a signal is sent to the controller. Otherwise, the reference value of the thickness is set. If the measured thickness is lower than a fixed value exceeding the reference value, a signal is sent. The fixed value can be 50 micrometers, 30 micrometers, 25 micrometers, 15 micrometers, 10 micrometers. The thickness sensor sends a signal to the controller when the change in thickness is measured to exceed the thickness change threshold. Further, a signal may also be sent if the change in the thickness of the first sheet is too fast. For example, if the measured value of the thickness changes by 15% or more in three consecutive measurements, this indicates that there may be damage to the first sheet.

[0040] When the thickness of the first sheet is measured at a plurality of positions such as the position of N (N is an integer), at each time interval, the joining may be triggered only when the thickness is below the thickness threshold at at least the position of M (M is an integer), where 1 < M < N.

[0041] A change in thickness may indicate, for example, that the first sheet has become too sticky, causing portions of the sheet to remain stuck to the bobbin. This may trigger a tear in the first sheet in the near future, such as before the first sheet is crimped, before the first sheet is collected onto the rod, or before the first sheet is buffered. Alternatively, or additionally, a first sheet that is too thin may indicate a potential tear. A first sheet that is too thick may indicate the presence of defects in the first sheet that may potentially interfere with or result in suboptimal results in further processing steps. Further processing steps may include crimping or collecting the sheet into a rod.

[0042] The first sheet may have moisture. When moisture is measured as a quality parameter, a moisture sensor adapted to measure the moisture of the first sheet of material and emit a signal based on the moisture measurement may be used. The moisture sensor may include a basis weight sensor. The moisture sensor may include a camera. The moisture sensor may include an infrared camera. The moisture sensor may include a microwave source. As an example, an infrared gauge TM710 by NDC Technologies may be used as the moisture sensor. Another example is the Perten DA7440 near-infrared sensor.

[0043] The bonding may be performed in response to a moisture measurement of the first sheet.

[0044] If the measured moisture content is above or below a moisture threshold, the moisture sensor can send a signal to the controller to indicate that the moisture content is outside a preferred range of moisture parameter values. For example, a signal may be sent if the moisture content of the first sheet is below a particular threshold. For example, a signal may be sent if the moisture content of the first sheet is above a particular threshold. Alternatively, the moisture sensor may send a signal representing the moisture content of the first sheet at each measurement, and the controller may compare the signal to the moisture threshold. For example, the threshold can be set equal to a selected percentage of the reference moisture content of the first sheet. The percentage may be, for example, 25 percent, 20 percent, 15 percent, or 10 percent. The reference moisture content is preferably between 7% and 15 percent water by weight of the first sheet. If the moisture content of the first sheet is below or above the reference moisture content by more than a selected percentage, a signal is sent to the controller. Alternatively, a reference moisture content is set. If the measured moisture content is lower than the reference moisture content by more than a fixed value, a signal is sent. If the measured moisture content is higher than the reference value by more than a fixed value, a signal is sent. The fixed value can be 2% water by total weight, 1.5% water by total weight, 1% water by total weight, or 0.5% water by total weight. The moisture sensor can send a signal to the controller if a change in moisture content is measured that exceeds a moisture change threshold. Additionally, a signal can be sent if the moisture content of the first sheet is changing too quickly. For example, if the moisture content measurement changes by more than 15% over three consecutive measurements, this may indicate the presence of an out-of-specification first sheet.

[0045] If the moisture content of the first sheet is too low, the first sheet may easily split, resulting in tears or holes in the first sheet and the possibility of bursting. Furthermore, a sheet that is too dry during crimping may crumble, making it impossible to collect the crimped sheet onto the rod. If the moisture content of the first sheet is too high, the first sheet may be too viscous, requiring excessive force to unwind the sheet, which may exceed the tensile strength of the sheet and cause breakage.

[0046] The first sheet defines a width. The width of the sheet is a dimension of the sheet in a direction substantially perpendicular to the process direction of the sheet. The width of the sheet is also substantially perpendicular to the thickness of the sheet. When measuring width as a quality parameter, a width sensor adapted to measure the width of the first sheet of material and emit a signal based on the width measurement may be used. The width sensor may be a distance sensor. The width sensor may include a light barrier sensor. The width sensor may include a camera.

[0047] The bond may be made according to a width measurement of the first sheet.

[0048] If the measured width of the first sheet is above or below a width threshold, the width sensor can send a signal to the controller indicating that the width is outside a preferred range of width parameter values. For example, a signal may be sent if the width of the first sheet is below a particular threshold. For example, a signal may be sent if the width of the first sheet is above a particular threshold. Alternatively, the width sensor may send a signal representing the width of the first sheet at each measurement, and the controller may compare the signal to the width threshold. For example, the threshold can be set equal to a selected percentage of the reference width of the first sheet. The percentage can be, for example, 25 percent, 20 percent, 15 percent, or 10 percent. The reference width is preferably a value between 120 millimeters and 130 millimeters. If the width of the first sheet is below or above the reference width by more than a selected percentage, a signal is sent to the controller. Alternatively, a reference width is set. If the measured width is below the reference width by more than a fixed value, a signal is sent. If the measured width is higher than the reference value by more than a fixed value, the fixed value may be 5 millimeters or 2 millimeters. The width sensor can send a signal to the controller if a width change exceeding a width change threshold is measured. Additionally, a signal can be sent if the width of the first sheet changes too quickly. For example, if the width measurement changes by more than 15% over three consecutive measurements, this indicates that an out-of-specification first sheet may be present.

[0049] A width that is too small may indicate that part of the first sheet is missing, which may indicate that the first sheet may be subject to rapid breakage. A high width may indicate a flaw in the first sheet casting process, resulting in a less-than-optimal final product. A wide width may indicate that part of the material in the first sheet is loose, or that a hole or slit has formed in the center of the first sheet, causing material to shift toward the sides of the sheet.

[0050] The first sheet may have viscosity. If viscosity is measured as a quality parameter, a viscosity sensor may be used adapted to measure the viscosity of the first sheet of material and to emit a signal based on the viscosity measurement.

[0051] The viscosity sensor may include a distance sensor or an angle sensor. A quantity related to the viscosity of the bobbin is the so-called "peel angle," which is the angle formed between a reference line (e.g., the reference diameter of the first bobbin) and the separation line, i.e., the line passing through the line where the first sheet separates from the first bobbin. If this angle increases, it may mean that the viscosity of the first sheet has increased. If this angle decreases, it may mean that the viscosity of the first sheet has decreased. The angle may also be measured by measuring the distance between the first sheet unwound from the bobbin and the sensor. The viscosity sensor may include a pressure distribution sensor.

[0052] The bonding may be performed in response to a measurement of the viscosity of the first sheet.

[0053] If the measured viscosity is above or below a viscosity threshold, the viscosity sensor can send a signal to the controller, indicating that the thickness is outside of a preferred range of viscosity parameter values. For example, a signal may be sent if the viscosity of the first sheet is higher than a particular threshold. Alternatively, the viscosity sensor may send a signal representing the viscosity of the first sheet at each measurement, and the controller may compare it to the viscosity threshold. For example, the threshold can be set equal to a selected percentage of a reference value for the viscosity of the first sheet. The percentage may be, for example, 25 percent, 20 percent, 15 percent, or 10 percent. If the viscosity of the first sheet is higher than the viscosity reference value by more than a selected percentage, a signal is sent to the controller. Alternatively, a viscosity reference value is set. If the measured viscosity is higher than the reference value by more than a fixed value, a signal is sent. The viscosity sensor can send a signal to the controller if a change in viscosity is measured that exceeds a viscosity change threshold. Additionally, a signal may be sent if the viscosity of the first sheet is changing too quickly. For example, if the viscosity measurements vary by more than 15% over three consecutive measurements, this indicates that an out-of-specification first sheet may be present.

[0054] If the viscosity is too low, it could mean that the slurry used to produce the first sheet of material is ill-formulated, resulting in a final product that does not meet specifications. If the viscosity of the first sheet is too high, excessive force may be required to unwind the sheet, which may exceed the tensile strength of the first sheet and cause breakage. Without being bound by theory, a first sheet that is too viscous could be a sign that the binder in the sheet is not adequately creating a "strong" structure. This could create weak bonds between the fibers in the slurry. Therefore, a more viscous sheet, with its lower tensile strength, increases the risk of bursting during bobbin unwinding.

[0055] If the presence or absence of holes or tears is to be detected, a sensor may be used to detect the presence or absence of holes or tears in the first sheet of material.

[0056] The sensor may be an optical sensor or a sound sensor. The sound sensor may include an ultrasonic sensor. The optical sensor may include a camera. The optical sensor may include a light source. A beam of electromagnetic radiation emitted by the light source may impinge on the first sheet. A change in the intensity of the transmitted light through the first sheet may indicate the presence of a hole or tear in the first sheet. The ultrasonic sensor transmits and receives sound waves in the ultrasonic range. The ultrasonic waves impinging on the surface of the first sheet generate reflected waves. If a hole or tear is present on the surface of the first sheet, the reflected waves will change, and these changes in the reflected waves can be measured.

[0057] The "presence or absence" of a tear or hole does not mean that all holes or tears, regardless of their size, can be considered in the evaluation. First, there is a first minimum dimension for a hole or tear to be detected by the sensor. This first minimum dimension depends on the resolution of the sensor. Furthermore, a relatively "small" hole or tear may not pose a threat to the quality of the sheet and may not be a sign of an impending break. Therefore, a "second minimum dimension" for a hole or tear may be set, and only holes or tears exceeding this second minimum dimension may be considered in the evaluation when determining the presence of a hole or tear. A relatively "large" hole or tear may indicate that the first sheet is weakened and may soon break. The second minimum dimension may be 5 millimeters or 10 millimeters. This means that only holes or tears with dimensions greater than 5 millimeters or greater than 10 millimeters are considered to indicate the "presence of a hole or tear." The dimension considered is the dimension across the process direction. Furthermore, instead of a linear dimension, the threshold can be area, ie, holes or tears are considered to be holes or tears only if their area exceeds a given area threshold.

[0058] If the presence of a hole or tear in the first sheet is detected, splicing can occur.

[0059] When a change in a quality parameter is measured instead of the absolute value of the quality parameter, the change is preferably measured relative to a reference value. In other words, the change is taken relative to a reference value that should be an "acceptable" value for the quality parameter. This reference parameter may be used as a threshold for the actual measured value of the quality parameter. For example, joining may occur when the measured quality value is above or below the reference value for the same quality parameter plus or minus 10%, 15%, or 25% of the reference value.

[0060] The reference value may be a variable that is updated during measurements. For example, starting with a set reference value, every N consecutive measurements, where N is an integer, the reference value is updated and its new value is equal to the value measured by the sensor N measurements ago.

[0061] Additionally, the rate of change of the measurements may also be relevant: if the rate of change is above a given threshold, then bonding occurs independently of the absolute value of the change.

[0062] The reference quality parameter may be obtained by a database. The reference quality parameter may be used to evaluate whether there is a change in that quality parameter that exceeds a predetermined threshold. Preferably, the method of the present invention includes accessing a database and obtaining data regarding one of the reference quality parameters of the first sheet from the database. The database may include values ​​of one or more reference quality parameters of the first sheet, such as thickness, moisture, width, and viscosity. Data regarding the one or more reference quality parameters may be stored in an accessible memory in which the database resides. The data may be present on a sticker or barcode attached to the bobbin from which the first sheet is unwound. These data can be scanned and uploaded to the controller in a known manner. Furthermore, the parameter threshold value may depend on the composition of the sheet or the batch of bobbins. Thus, the database may include several threshold values ​​to which the parameter is compared, multiple threshold values ​​for a single parameter, with different threshold values ​​selected for that parameter among the multiple threshold values ​​depending on the composition of the sheet.

[0063] The reference quality parameters may be obtained by user input. A panel or other input device may be provided, and a user, e.g., an operator, may input values ​​of the reference quality parameters of the first sheet. Further, data regarding one of the reference quality parameters may be obtained by scanning data provided on the first bobbin of the first sheet, such as a representative code.

[0064] The reference quality parameters may be obtained by remote signaling. Radio or cable data transmission may be used to input the reference quality parameters.

[0065] As a result of the evaluation, for example, one or more values ​​or one or more value differences are available as a result of measurements by one or more sensors of one or more quality parameters of the first sheet. These values ​​or value differences may then be elaborated by the controller. The controller preferably elaborates one or more signals arriving from the sensors measuring the quality parameters of the first sheet. The one or more signals indicate the values ​​of the one or more quality parameters.

[0066] Preferably, one or more reference quality parameters of the first sheet are measured. Preferably, the width of the first sheet is obtained. Preferably, the presence or absence of holes and rips in the first sheet is obtained. Preferably, the width and the presence or absence of holes and rips in the first sheet are obtained. Preferably, a combination of the presence or absence of holes and rips and the thickness of the first sheet is obtained. Preferably, a combination of the presence or absence of holes and rips and the moisture of the first sheet is obtained. Preferably, a combination of the presence or absence of holes and rips and the viscosity of the first sheet is obtained.

[0067] After the evaluation, a joining step is performed depending on the value of the evaluated quality parameter or parameters. The joining is performed in a joining head. For example, if the evaluation step determines that one or more quality parameters are outside a predetermined range, the first sheet and the second sheet are joined. If the evaluation determines that holes or tears are present, joining can occur.

[0068] The controller may enforce bonding depending on the value of one or more signals transmitted by sensors measuring quality parameters, i.e., depending on the value of one or more quality parameters. The controller may enforce bonding if the refined values ​​of one or more quality parameters are outside a given range. For each quality parameter, a range may be preset. For each quality parameter, several ranges may be preset. For example, a green range may be preset for each quality parameter. If all values ​​or value differences measured by the sensors or all signals detailed by the controller are within the respective green range, bonding is not triggered by the controller. Bonding may still be performed for different measurements or commands, such as depletion of the first bobbin. However, bonding is not triggered due to the refined values ​​of the quality parameters. For example, a yellow range may be preset for each quality parameter. If one of the quality parameters has a value or value difference within its yellow range, bonding is triggered only if there is at least another different quality parameter with a value or value difference within its yellow range. If one of the quality parameters has a value or value difference within its yellow range, bonding may be configured to be triggered only if there are at least two other different quality parameters that have a value or value difference within that yellow range. Furthermore, it may be configured such that only certain combinations of quality parameters within their yellow ranges may trigger bonding. For example, bonding occurs when the refined values ​​of the viscosity and width of the first sheet are both within their respective yellow ranges. However, bonding does not occur when the refined values ​​of the moisture and viscosity of the first sheet are both within their respective yellow ranges. For example, a red range may be preset for each quality parameter. If one of the quality parameters has a value or value difference within its red range, bonding occurs regardless of the values ​​or value differences of the other quality parameters.

[0069] The quality sensor may be an optical sensor, and the method may include capturing an image of the first sheet of material with the quality sensor. Preferably, the method further includes one or more of determining the width of the first sheet of material from the image and determining the presence or absence of holes or tears in the first sheet of material from the image. The sensor adapted to measure the width of the first sheet of material, the sensor adapted to detect the presence or absence of holes or tears, or both, may include a camera. The camera may be adapted to capture images of a portion of the first sheet. Preferably, the camera captures images of different portions of the first sheet at a predetermined frequency while the first sheet is transported along the process direction. The frequency at which images of different portions of the first sheet are captured is preferably synchronized with the speed at which the first sheet is unwound from the first bobbin. The width of the sheet may be determined from the image, for example, using standard tools for digital image refinement. For example, color differences between the first sheet and the background may be used. The presence or absence of tears or holes may also be evaluated from the image. For example, blob analysis may be used. The camera may be a two-dimensional camera or a line scan camera.

[0070] The quality sensor may be an optical sensor, and the method may include directing a beam of light onto the first sheet of material. The method may also include one or more of: determining a width of the first sheet of material from a characteristic of the transmitted beam of light passing through the first sheet of material; determining a thickness of the first sheet of material from a characteristic of the transmitted beam of light passing through the first sheet of material; and determining the presence or absence of a hole or tear in the first sheet of material from a characteristic of the transmitted beam of light passing through the first sheet of material. For example, a sensor adapted to measure the width or thickness of the first sheet of material or a sensor adapted to detect the presence or absence of a hole or tear in the first sheet of material may include an optical emitter and an optical receiver. The light emitter may be located on one side of the first sheet, and the light receiver may be located on the opposite side of the first sheet. The light receiver may be, for example, an optical receiver. The light emitter may emit a beam of electromagnetic radiation that impinges on a first surface of the first sheet. The light receiver may receive the light transmitted through the first sheet. The light transmitted through the first sheet exits from a second surface of the first sheet. For example, a width difference, such as the difference between the actual width and a reference width of the first sheet, may be measured, and the intensity value of the transmitted light is known. Alternatively, a width difference between the actual width and a previous width value obtained in a previous measurement acquired by the sensor, and the intensity value of the transmitted light is known. As the width decreases, additional light may pass through the first sheet, and therefore more light is collected by the photoreceptor. In the case of a sensor for detecting the presence of holes or tears, the amount of transmitted light through the first sheet may be evaluated and compared, for example, to a reference value of the intensity of the transmitted light. If the measured intensity of the transmitted light is higher than the reference value, more light may pass through the first sheet, and therefore a hole or tear may be present. A change in thickness can be similarly evaluated by measuring a change in the intensity value of the transmitted light. A thinner section of the first sheet allows more light to pass through than a thicker section of the first sheet.

[0071] Such a sensor including light emitters and light receivers may include a grid of light emitters and a grid of light receivers. The presence of the grid of light emitters and light receivers makes it possible to determine the spatial position of changes in the intensity of the transmitted light. Thus, it is possible to determine the locations on the first sheet where increases or decreases in the intensity values ​​of the transmitted light occur. The spatial precision is given by the dimensions of the "squares" formed by the grid.

[0072] The method may include measuring the distance between the first sheet of material and the first sensor. Preferably, the method further includes determining the viscosity of the first sheet of material from the measured distance. The first bobbin is formed by coiling the first sheet around a mandrel. The first sheet defines a loose portion of the sheet unwound from the first bobbin. The first bobbin also defines a bobbin outer surface. The bobbin outer surface also defines a separation line between the loose portion of the first sheet and the remaining portion of the first sheet coiled around the first bobbin. To process the first sheet, the first sheet is unwound. The unwound is pulled in a given direction, for example, toward a downstream unit such as a buffering or crimping unit. A sensor for measuring one or more quality parameters is located between the first bobbin and the downstream unit. Pulling can be performed by a suitable pulling roller. Upon drawing and unwinding, the position of the separation line moves, i.e., the separation point of the first sheet from the first bobbin moves depending on the adhesion between the last two layers of the first sheet in the bobbin. The exact position of the separation line therefore depends on several forces (e.g., drawing forces and their reactions, compression forces, etc.), the position of the pull roller, and the diameter of the first bobbin. If one of these forces, or the position of the pull roller, changes, or the diameter of the bobbin changes, the position of the separation line may also change. Furthermore, an angle is defined between the tangent to the outer surface of the bobbin at the contact line and the free portion of the first sheet. This angle depends on the viscosity of the sheet.

[0073] If the viscosity of the first sheet becomes "high," preferably higher than a reference value, one of the forces defining the position of the separation line changes. Therefore, the position of the contact line, or the width of the angle between the tangent to the outer surface at the separation line and the free portion of the first sheet, or both, may change. If a distance sensor is located in front of the surface of the first sheet, downstream of the first bobbin and preferably upstream of the bonding head, the distance between the sensor and the surface of the first sheet changes with the change in angle or the change in the position of the separation line. This change in distance may indicate a change in the viscosity of the first sheet and may induce bonding.

[0074] Due to the fact that the position of the separation line also depends on the diameter of the bobbin, a diameter sensor adapted to measure the diameter of the first bobbin is also preferably provided. The distance sensor and the diameter sensor may send signals to the controller representing the distance between the sensor and the surface of the first sheet and the diameter of the first bobbin, respectively. The controller may use these two signals to determine the viscosity of the bobbin. The diameter sensor may comprise a roller pressed onto the outer surface of the bobbin by a spring, which follows the decrease in the diameter of the bobbin.

[0075] The method includes measuring the force required to unwind the first sheet of material from the first bobbin. Preferably, the method further includes determining the viscosity of the first sheet of material from the measured force. Another indication of the viscosity of the first bobbin is provided by force feedback from the first shaft or from a drive adapted to rotate the first shaft to unwind the first bobbin. For example, an increase in the torque required to unwind the first sheet may indicate a first sheet that is too viscous. Additionally, a force exceeding a safety limit may indicate a break in the sheet.

[0076] To join the first sheet of material with the second sheet of material, the second sheet may be unwound from a second bobbin.

[0077] Any splice known in the art that connects, preferably stably connects, a first sheet and a second sheet may be used in the present invention. The joining step preferably includes pressing the first sheet and the second sheet together. Preferably, the joining step includes cutting at least the first sheet. The cutting step may occur before, after, or simultaneously with the pressing step. Preferably, both the first sheet and the second sheet are cut. For this purpose, the splice head may be equipped with a blade.

[0078] Once the first sheet is cut, an end of the first sheet is defined. This end of the first sheet and the head of the second sheet unwound from the second bobbin are preferably joined. The second sheet is then subjected to the same treatment as the first sheet, such as crimping and gathering to form a rod.

[0079] Similarly, cutting the first sheet and the second sheet results in a defined end portion of the first sheet and a defined leading portion of the second sheet, which can be combined to form a continuous, uninterrupted sheet of material.

[0080] The splicing is performed downstream of the detected portion of the first sheet where the quality parameters that triggered the splicing were evaluated. That is, the splicing is triggered because the evaluated value of one or more of the quality parameters is within a predetermined threshold. The trigger value was measured at the specific detected portion of the first sheet. This means that the specific detected portion of the first sheet may not be suitable for further processing to produce a final product according to the desired specifications, or further processing of the sheet may cause the first sheet to burst, leading to a machine stop. Therefore, preferably, the specific detected portion of the first sheet is not used in subsequent processing, and the splicing of the first sheet and the second sheet is performed downstream of that specific portion of the first sheet. The portion of the first sheet downstream of the detected portion that triggered the splicing was previously evaluated. However, the portion of the first sheet upstream of the detected portion that triggered the splicing may also exhibit unacceptable defects. Therefore, preferably, the portion of the first sheet upstream of the specific detected portion of the first sheet is not used in subsequent processing, and the splicing of the first sheet and the second sheet is performed downstream of that specific portion of the first sheet.

[0081] The cuts on the first and second sheets can be made in a sequential manner. Preferably, the cuts are made simultaneously on both the first and second sheets. For the cutting process, the first and second sheets may be arranged adjacent to each other or overlap each other. Alternatively, each of the first and second sheets is cut independently of the other. The first and second sheets are preferably aligned so that they are centered and overlap each other along the longitudinal central axes of the first and second sheets. As described above, the first and second sheets locally define a plane. Each of the first and second sheets has a width. Preferably, the width of the first sheet and the width of the second sheet are substantially the same. The cuts preferably provide first and second cut surfaces that provide a clearly defined contact area, and the first and second sheets may contact or be joined to each other. This supports a good connection between the first and second sheets. The cuts may be made at an angle.

[0082] The cut may be made at an angle to the cross-machine direction. In other words, the width of the first or second sheet defines the cross-machine direction on the surface of the first or second sheet. This cross-machine direction is perpendicular to the process direction. The angle between the cross-machine direction and the cut line may be different from 0 degrees and 90 degrees, and is preferably about 25 degrees to 60 degrees, more preferably about 30 degrees to 45 degrees.

[0083] To connect the first and second sheets, water is preferably added onto the inclined cutting surface. Adding water to at least one of the first and second sheets moistens and softens the material of the first or second sheet. The material of the first or second sheet may have a certain viscosity by itself, but this viscosity can be strengthened by adding water. Preferably, water is added only to the inclined cutting surface, preferably to only one sheet, either the first or second sheet. This allows the added water to support the combining process of the first and second sheets at the contact area of ​​the sheets without using excess water, which may adversely affect the connection.

[0084] Preferably, pressure is applied to the first sheet and the second sheet. For this purpose, the joining head may be equipped with a compression device. The force applied to the first sheet and the second sheet then provides a strong connection between the two sheets, at least in the overlap region formed by the overlapping cut surfaces. The pressure can be applied to the combined sheets while the sheets are stationary or while the combined sheets are further moving along the direction of movement. The compression device may, for example, comprise a stationary press or, for example, press rollers into which the combined sheets are inserted. The amount of force applied is adapted to provide a good connection, but preferably does not thin or substantially thin the first sheet and the second sheet in the overlap region.

[0085] The above-described bonding may provide a strong bond without additives (other than water) or additional materials that may affect taste, and may provide a bond that has no or reduced impact on subsequent processes in the tobacco sheet processing line after the bonding process, such as subsequent crimping or rod-forming processes.

[0086] Therefore, the method of the present invention minimizes interruptions to production. Bonding may occur as soon as the first sheet exhibits "one or more signs of weakness," depending on the evaluation of these signs as detailed above, thus avoiding production stoppages. Furthermore, rejects of the final product are also minimized, since bonding may be triggered as soon as the first sheet exhibits properties outside of acceptable limits, for example, too high moisture content. This may result in a faster production process.

[0087] Furthermore, normal control of the first bobbin, for example, control of its diameter and triggering of splicing when the bobbin is nearly empty, may still be maintained, and therefore changes to existing systems and programs may be minimized.

[0088] The processing line can be operated continuously at high speeds, producing a product of continuous, consistent quality, and any waste material that may be generated can be kept to a minimum.

[0089] Preferably, the method includes buffering a predetermined length of the first sheet of material before bonding. During bonding, the speed of the first sheet is preferably reduced relative to the speed at which the first sheet moves during production. The first sheet may be stopped during bonding. To avoid delays or stops in production, a predetermined length of the first sheet is preferably buffered before bonding. This buffered length can be used during bonding so that the production speed does not change. For example, a buffering system may be used, which includes multiple rollers. The amount of buffered first sheet is sufficient to allow the bonding process without stopping production. The buffering system may include some rollers that can move toward or away from other fixed rollers ("fixed rollers"), which for this reason are called "movable rollers," and the sheet passes along these two types of rollers. However, other systems are envisioned in which all rollers can move toward and away from each other. The rollers may also be divided into pairs, with the two rollers of the same pair being installed at substantially the same height. Furthermore, pairs of rollers are arranged one above the other, forming a matrix of rollers with two columns and several rows. The buffers can be formed by vertical or horizontal sections of the first sheet. Thus, the first sheet of material forms multiple parallel sections, one above the other, passing through various pairs of rollers. The longer these sections are, i.e., the greater the distance between the two rollers of the same pair, the more buffering there is. Before splicing, the distance between the two rollers of each pair is close to the maximum possible distance. During splicing, the distance between the two rollers of each pair decreases so that the buffered first sheet can accommodate the production speed, which remains constant, and the speed of the first sheet to the splicing head, which decreases until the machine speed is reached. The buffer rollers of each pair move closer to each other, reducing the path traveled by the first sheet within the buffering system and thus providing an excess of first sheet for downstream processes to compensate for the reduced speed of the first bobbin.

[0090] Preferably, the evaluation of one of more quality parameters of the first sheet is carried out before buffering of the first sheet.

[0091] The transport of the sheet of material may be carried out at a sheet speed of about 50 meters / minute to about 400 meters / minute.

[0092] The processing line may include a buffer unit downstream of the splicing head. A portion of the processing line downstream of the buffer unit may be stopped or operated at a slower speed during the step of splicing the first sheet and the second sheet at the splicing head. The method may include buffering a predetermined length of the first sheet in the buffer unit prior to the splicing step.

[0093] The upstream portion of the first sheet may be wound onto a first bobbin. The upstream portion of the second sheet may be wound onto a second bobbin. The first bobbin may be formed by a coil of a first sheet of material. The first bobbin may be inserted into a first shaft adapted to rotate about its axis of rotation. The second bobbin may be formed by a coil of a second sheet of material. The second bobbin may be inserted into a second shaft adapted to rotate about its axis of rotation. The method may include removing the first bobbin after the joining step. The method may include exchanging the position of the first bobbin with the position of the second bobbin after joining. Preferably, a new bobbin, such as a third bobbin, is inserted into the first shaft to replace the first bobbin.

[0094] A bobbin holder unit may be provided. The bobbin holder unit may include a first shaft and a second shaft. The first shaft and the second shaft on the bobbin holder unit may be movable so that the positions of the first shaft and the second shaft are interchangeable. The first shaft and the second shaft may be arranged in a movable manner on the bobbin holder unit. Alternatively, the first shaft and the second shaft may be fixedly arranged on the bobbin holder unit. In the latter case, the bobbin holder unit may be movable, for example, rotatable, so that the second bobbin can be positioned in front of the first bobbin and vice versa. The bobbin holder unit may also be provided with one or more additional shafts for one or more additional bobbins on the sheet of material in addition to the first and second bobbins. While other interchangeable shaft mechanisms are possible, it is preferred that the positions of the multiple shafts are mutually interchangeable upon rotation of the bobbin holder unit or by rotating the shafts on the bobbin holder.

[0095] Each shaft may be associated with a quality sensor for detecting the value of the quality parameter at the detection portion of the respective sheet, for example, a first sensor and a second sensor may be provided associated with a first shaft and a second shaft.

[0096] The first and second sheets of material may comprise one or more alkaloids. The first and second sheets of material may be homogenized tobacco material sheets. The homogenized tobacco material sheets may be configured for use as an aerosol-forming substrate in an aerosol-generating article. Preferably, the first and second sheets of material are identical, i.e., they have substantially the same physical and chemical characteristics.

[0097] The method may include wetting one or both of the first sheet and the second sheet with water before bonding. The method may include drying one or both of the first sheet and the second sheet before bonding. The method may include crimping the bonded sheets. The method may include forming a rod from the crimped sheets.

[0098] The present invention further relates to a method of making an aerosol-generating article, the method comprising forming one or more rods according to the methods described herein and incorporating the one or more rods into an aerosol-generating article.

[0099] The present invention further relates to an apparatus for splicing two sheets of material. The apparatus may include a processing line having an upstream end and a downstream end and configured to process a first sheet of material and a second sheet of material. The apparatus may include a splicing head disposed between the upstream end and the downstream end. The apparatus may include a quality sensor disposed between the upstream end and the downstream end and configured to detect a value of a quality parameter at a detected portion of the first sheet. The apparatus may include a controller. The controller may be configured to evaluate whether the value of the quality parameter detected by the quality sensor falls within a predetermined threshold. If the value of the quality parameter detected by the quality sensor falls within the predetermined threshold, the controller may be configured to: control the processing line to transport the first sheet along the processing line such that the detected portion of the first sheet is positioned from the upstream end of the processing line before entering the splicing head; and, if the detected portion of the first sheet is positioned from the upstream end of the processing line before entering the splicing head, control the splicing head to splice the first sheet and the second sheet at the splicing head.

[0100] The present invention also relates to an apparatus for splicing two sheets of material. The apparatus includes a processing line having an upstream end and a downstream end and configured to process a first sheet of material and a second sheet of material. The apparatus includes a splicing head disposed between the upstream end and the downstream end. The apparatus includes a quality sensor disposed between the upstream end and the downstream end and configured to detect a value of a quality parameter at a detection portion of the first sheet. The apparatus includes a controller. The controller is configured to evaluate whether the value of the quality parameter detected by the quality sensor falls within a predetermined threshold. If the value of the quality parameter detected by the quality sensor falls within the predetermined threshold, the controller is configured to: control the processing line to transport the first sheet along the processing line such that the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splicing head; and, if the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the splicing head, control the splicing head to splice the first sheet and the second sheet together.

[0101] The quality sensor may be located downstream of the bond head.

[0102] The apparatus may include a first holder for holding a first sheet of material and a second holder for holding a second sheet of material. The first holder may be a first shaft adapted to rotatably hold a first bobbin of the first sheet. The second holder may be a second shaft adapted to rotatably hold a second bobbin of the second sheet.

[0103] The apparatus may include a bobbin holder unit including a first shaft and a second shaft. The bobbin holder unit may be adapted to exchange the positions of the first shaft and the second shaft. For example, the bobbin holder unit may include a rotating disk, and the first shaft and the second shaft may extend from the same side of the disk. Rotation of the disk may allow the positions of the shafts to be exchanged.

[0104] The processing line may be configured to allow at least a portion of the first sheet to be transported in both a downstream direction and an upstream direction.

[0105] The apparatus may comprise a buffering unit adapted to buffer a variable amount of the first sheet or the second sheet, the buffering unit being located downstream of the splicing head, and preferably comprising a movable roller for varying the amount of buffered first sheet or second sheet.

[0106] The bonding head may include a blade for cutting one or both of the first sheet and the second sheet.

[0107] The splicing head may include a dryer for drying the first sheet or the second sheet. The dryer is preferably configured to dry the spliced ​​sheets. Drying is preferably provided at least in the overlapping area or in areas where water has been applied to the first sheet, the second sheet, or both. Drying may aid the splicing process by speeding up the process of removing water, if any, dispensed onto the first sheet or the second sheet prior to joining the first and second sheets. The dryer preferably includes a heater, e.g., by hot air or infrared heating.

[0108] The apparatus may include a crimper. Crimping is preferably 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 may be positioned adjacent to each other, and a nip may be formed between the first crimping roller and the second crimping roller. The first sheet or the second sheet may be inserted into the nip to be crimped. The first crimping roller may define a first axis of rotation and a first outer surface. The second crimping roller may define a second axis of rotation and a second outer surface. The first axis of rotation and the second axis of rotation are preferably parallel to each other. The first axis of rotation and the second axis of rotation are preferably horizontal. At least one of the first crimping roller or the second crimping roller may include corrugations. The corrugations are preferably formed on the first outer surface or the second outer surface. Preferably, the corrugations are formed on both the first and second outer surfaces. The corrugations on the crimping rollers may contact the first or second sheet when the first or second sheet is inserted into the nip between the first and second crimping rollers. Due to the action of the corrugations on the first or second sheet, corresponding corrugations are formed on the first or second sheet as it passes through the nip. If both the first and second crimping rollers include corrugations, the crimping rollers may be designed and arranged so that at least some of the corrugations are substantially interleaved.

[0109] The apparatus may include a rod former, and the rods so formed may preferably be used as components of aerosol-generating articles.

[0110] As used herein, the term "sheet" refers to a laminar element having a width and length substantially greater than its thickness. Preferably, the width of the sheet of material is greater than about 10 millimeters, more preferably greater than about 20 or 30 millimeters. Even more preferably, the width of the sheet of material is between about 60 millimeters and about 2500 millimeters. Preferably, the thickness of the sheet of material is between about 50 micrometers and about 300 micrometers, more preferably between about 100 micrometers and about 250 micrometers, and even more preferably between about 190 micrometers and 220 micrometers.

[0111] As used herein, the term "aerosol-generating article" refers to an article comprising an aerosol-forming substrate capable of emitting volatile compounds capable of forming an aerosol. An "aerosol-generating article" according to the present invention may be in the form of an article in which an alkaloid-containing material, such as tobacco material, is heated without being burned to form an aerosol, and an article in which an alkaloid-containing aerosol is produced from an alkaloid-containing material, for example, from a tobacco extract or other nicotine source, without being burned or heated. An aerosol-generating article according to the present invention may be a complete assembled aerosol-forming article, or 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, such as a consumable part of a heated smoking device.

[0112] 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.

[0113] Alkaloids are a group of naturally occurring compounds that contain primarily basic nitrogen atoms. This 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.

[0114] Alkaloids are produced by a wide variety of organisms, including bacteria, fungi, and 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.

[0115] The term "homogenized tobacco material" is used to include any tobacco material formed by agglomeration of particles of tobacco material. In the present invention, a homogenized tobacco sheet is formed by agglomerating particulate tobacco obtained by grinding or otherwise pulverizing one or both of the tobacco lamina and the tobacco stem. Thus, the material can be a homogenized tobacco material containing the alkaloid nicotine.

[0116] Additionally, the homogenized tobacco material may contain one or more small amounts of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during tobacco processing, handling, and shipping.

[0117] The homogenized tobacco material may comprise one or more intrinsic binders, one or more extrinsic binders, or a combination thereof to aid in the cohesion of the tobacco particles. The homogenized tobacco material may also include an aerosol former. The homogenized tobacco material may also include other additives, including, but not limited to, tobacco and non-tobacco fibers, humectants, plasticizers, flavorings, fillers, aqueous and non-aqueous solvents, and combinations thereof.

[0118] In the present invention, the homogenized tobacco material comprises tobacco lamina and tobacco stems of different tobacco types that are appropriately blended. The term "tobacco type" refers to one of the different varieties of tobacco. In the context of the present invention, these different tobacco types are distinguished 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 being further processed into tobacco products.

[0119] Bright tobacco is generally a tobacco with large, light-colored leaves. Throughout this specification, the term "bright tobacco" is used to refer to flue-cured tobacco. Examples of bright tobacco include Chinese flue-cured tobacco, Brazilian flue-cured tobacco, American flue-cured tobacco (such as Virginia tobacco), Indian flue-cured tobacco, Tanzanian flue-cured tobacco, or other African flue-cured tobacco. Bright tobacco is characterized by a high sugar-to-nitrogen ratio. From a sensory perspective, bright tobacco is a tobacco type that has a spicy, lively sensation after curing. According to the present invention, bright tobacco is tobacco having a reducing sugar content of about 2.5 percent to about 20 percent based on dry weight of the leaf and a total ammonia content of less than about 0.12 percent based on dry weight of the leaf. Reducing sugars include, for example, glucose or fructose. Total ammonia includes, for example, ammonia and ammonia salts.

[0120] Dark tobacco is generally tobacco with large, dark-colored leaves. Throughout this specification, the term "dark tobacco" is used to refer to air-cured tobacco. Additionally, dark tobacco may be fermented. Tobacco primarily used for chewing tobacco, snuff, cigars, and pipe blends also fall within this category. From a sensory perspective, dark tobacco is a tobacco type that, after curing, has a smoky, dark cigar-type sensation. Dark tobacco is characterized by a low sugar-to-nitrogen ratio. Examples of dark tobacco are 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 contains less than about 5 percent reducing sugars based on dry weight of the leaf and less than or equal to about 0.5 percent total ammonia based on dry weight of the leaf.

[0121] 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 fragrant sensation. Examples of aromatic tobacco include Greek Orient, Turkish Orient, and Semi-Orient tobacco, but also fire-cured, US Burley such as Perique, Rustica, US Burley, or Maryland.

[0122] Additionally, the blend may also contain 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 contribute a specific characteristic aroma profile to the final product. Examples of filler tobaccos are the stems, midribs, or petioles of other tobacco types. One specific example may be the flue-cured stems of flue-cured Brazilian lower petioles.

[0123] The homogenized tobacco material preferably includes a binder. The amount of binder is preferably about 1 percent to about 5 percent of the homogenized tobacco material on a dry weight basis. The addition of a binder, such as one of the gums or pectin described herein, is advantageous to ensure that the tobacco powder remains substantially dispersed throughout the homogenized tobacco sheet. For descriptive reviews of gums, see Gums and Stabilizers for the Food Industry, IRL Press (GO Phillip et al. eds. 1988); Whistler, Industrial Gums: Polysaccharides and Their Derivatives, Academic Press (2d ed. 1973); and Lawrence, Natural Gums for Edible Purposes, Noyes Data Corp. (1976).

[0124] While any binder may be employed, preferred binders are natural pectins (such as fruit pectins, citrus pectins, or tobacco pectins), guar gums (such as hydroxyethyl guar and hydroxypropyl guar), locust bean gums (such as hydroxyethyl locust bean gum and hydroxypropyl locust bean gum), alginates, starches (such as modified or derivatized starches), celluloses (such as methylcellulose, ethylcellulose, ethylhydroxymethylcellulose, carboxymethylcellulose), tamarind gum, dextran, puralon, konjac flour, xanthan gum, and the like. A particularly preferred binder for use in the present invention is guar.

[0125] Advantageously, the homogenized tobacco material includes an aerosol former, which preferably comprises an amount of about 5 percent to about 30 percent by dry weight of the aerosol former.

[0126] Suitable aerosol formers for inclusion in a slurry for a web of homogenized tobacco material are known in the art and include, but are not limited to, monohydric alcohols (such as menthol), polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate).

[0127] For example, when a homogenized tobacco material according to the present disclosure is intended for use as an aerosol-forming substrate in a heated aerosol-generating article, the sheet of homogenized tobacco material may have an aerosol former or humectant content of about 5 to about 30 percent by weight on a dry weight basis, with about 15 to about 20 percent being preferred. Homogenized tobacco material intended for use in an electrically operated aerosol-generating system having a heating element may preferably contain from 5% to more than about 30% aerosol former. For homogenized tobacco material intended for use in an electrically operated aerosol-generating system having a heating element, the aerosol former may preferably be glycerol.

[0128] The term "stickiness" 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 facing the unwound portion of the sheet. A "non-sticky" sheet has the closest distance to the LIDAR because the unwound portion of the sheet is immediately removed from the roller. The distance between the LIDAR and the unwound portion of the sheet increases as the stickiness increases.

[0129] The terms "upstream" or "downstream" herein refer to the process direction of the sheet.

[0130] As used herein, the term "gathered" or "gathering" in reference to a sheet refers to the sheet being rolled into a rod form or compressed or contracted substantially transverse to the process direction of the sheet. [Example]

[0131] Below is provided a non-exhaustive list of non-limiting examples, any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0132] Example 1: 1. A method of joining two sheets of material, comprising: providing a processing line including a splice head and a quality sensor disposed between an upstream end of the processing line and a downstream end of the processing line; providing a first sheet of material and a second sheet of material; processing a first sheet on a processing line along a processing direction from an upstream end of the processing line to a downstream end of the processing line; detecting a value of a quality parameter at a detection portion of the first sheet by a quality sensor; If the value of the quality parameter falls within a predetermined threshold, conveying a first sheet along the processing line such that a detection portion of the first sheet is positioned at an upstream end of the processing line prior to entering a splice head; and splicing the first sheet and the second sheet together at a splice head when the detection portion of the first sheet is positioned before entering the splice head from the upstream end of the processing line. Example 2: a quality sensor is located upstream of the bonding head; conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned before entering the splice head from the upstream end of the processing line; 2. The method of example 1, comprising conveying at least one segment of a first sheet including a detection portion along the processing line in a direction toward a downstream end over a distance that is less than the distance between the bonding head and the quality sensor as measured along the processing line. Example 3: conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned before entering the splice head from the upstream end of the processing line; 2. The method of example 1, comprising conveying at least one segment of a first sheet including a detection portion along the processing line in a direction toward the upstream end until the detection portion of the first sheet is positioned from the upstream end of the processing line prior to entering the bonding head. Example 4: 4. The method of example 3, wherein the quality sensor is located downstream of the bonding head. Example 5: 5. The method according to any one of the preceding embodiments, wherein the quality sensor comprises an optical sensor, preferably a photo camera or a video camera. Example 6: 6. The method of any one of Examples 1 to 5, wherein the quality sensor is configured to detect one or more of the width of the first sheet, the moisture level of the first sheet, the thickness of the first sheet, the stickiness of the first sheet, and the presence or absence of holes or tears in the first sheet. Example 7: 7. The method of example 6, wherein the quality sensor is configured to detect a width of the first sheet, and the quality parameter is the width of the first sheet. Example 8: The method according to any one of the preceding embodiments, wherein the processing line further comprises a buffer unit disposed downstream of the bonding head. Example 9: The method of example 8, wherein a portion of the processing line downstream of the buffer unit is either stopped or operated at a slower speed during the step of splicing the first sheet and the second sheet at the splicing head. Example 10: The method of example 8 or example 9, comprising buffering the length of the first sheet in a buffer unit prior to the bonding step. Example 11: The method of any one of embodiments 1 to 10, wherein an upstream portion of the first sheet is wound onto a first bobbin and an upstream portion of the second sheet is wound onto a second bobbin. Example 12: 12. The method of example 11, further comprising the step of removing the first bobbin after the bonding step. Example 13: The method of example 11 or example 12, further comprising exchanging the position of the first bobbin and the position of the second bobbin after bonding. Example 14: The method of any one of Examples 1 to 13, comprising wetting one or both of the first sheet and the second sheet with water prior to bonding. Example 15: The method of any one of Examples 1 to 14, further comprising the step of drying one or both of the first sheet and the second sheet after bonding. Example 16: 16. The method of any one of Examples 1 to 15, wherein the first sheet of material and the second sheet of material are sheets of homogenized tobacco material for use as an aerosol-forming substrate in an aerosol-generating article. Example 17: 17. The method of any one of Examples 1-16, wherein the first and second sheets of material comprise one or more alkaloids. Example 18: The method of any one of Examples 1 to 17, further comprising the step of crimping the bonded sheets. Example 19: The method of example 18, comprising forming a rod from the crimped sheet. Example 20: 1. A method of forming an aerosol-generating article, the method comprising: forming one or more rods according to the method of Example 19; incorporating one or more rods into an aerosol-generating article. Example 21: 1. An apparatus for joining two sheets of material, comprising: a processing line having an upstream end and a downstream end, the processing line being configured to process a first sheet of material and a second sheet of material; a splice head disposed between the upstream end and the downstream end; a quality sensor disposed between the upstream end and the downstream end and configured to detect a value of a quality parameter at a detection portion of the first sheet; A controller, the controller is configured to evaluate whether a value of the quality parameter detected by the quality sensor falls within a predetermined threshold; an apparatus comprising: a controller configured to: control the processing line to transport the first sheet along the processing line so that the detected portion of the first sheet is positioned before entering the splicing head from an upstream end of the processing line when the value of the quality parameter detected by the quality sensor falls within a predetermined threshold; and to control the splicing head to splice the first sheet and the second sheet together at the splicing head when the detected portion of the first sheet is positioned before entering the splicing head from an upstream end of the processing line. Example 22: 22. The apparatus of example 21, wherein the quality sensor is located downstream of the bonding head. Example 23: 23. The apparatus of example 21 or example 22, comprising a first holder for holding a first sheet of material and a second holder for holding a second sheet of material. Example 24: 24. The apparatus of Example 23, wherein the first holder is a first shaft adapted to hold a first bobbin of a first sheet in a rotatable manner, and the second holder is a second shaft adapted to hold a second bobbin of a second sheet in a rotatable manner. Example 25: 25. The apparatus of example 24, comprising a bobbin holder unit having a first shaft and a second shaft, the bobbin holder unit adapted to exchange positions of the first shaft and the second shaft. Example 26: 26. The apparatus of any one of Examples 21-25, wherein the processing line is configured to allow at least a portion of the first sheet to be transported in both a downstream direction and an upstream direction. Example 27: 27. The apparatus of any one of Examples 21 to 26, further comprising a buffering unit adapted to buffer a variable amount of the first sheet or the second sheet, the buffering unit being positioned downstream of the bonding head. Example 28: 28. The apparatus of any one of Examples 21-27, wherein the bonding head comprises a blade for cutting one or both of the first sheet and the second sheet. Example 29: 29. The apparatus of any one of Examples 21-28, wherein the bonding head comprises a dryer for drying the first sheet or the second sheet. Example 30: 30. The apparatus of any one of Examples 21 to 29, comprising a crimper. Example 31: 31. The apparatus of any one of Examples 21 to 30, comprising a rod former. Example 32: An apparatus configured to carry out the method according to any one of Examples 1 to 20. Example 33: 1. An apparatus for joining two sheets of material, comprising: a processing line having an upstream end and a downstream end, the processing line being configured to process a first sheet of material and a second sheet of material; a splice head disposed between the upstream end and the downstream end; a quality sensor disposed downstream of the bonding head and configured to detect a value of a quality parameter at a detection portion of the first sheet.

[0133] Features described with respect to one embodiment may be equally applied to other embodiments of the invention.

[0134] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which:

[0135] 1a and 1b illustrate a method for splicing two sheets of material. A processing line is shown comprising a splicing head 10 and a quality sensor 12 disposed between an upstream end 14 of the processing line and a downstream end 16 of the processing line. A first sheet of material 18, e.g., a homogenized tobacco material sheet, is processed on the processing line along a processing direction 24 from the upstream end 14 of the processing line to the downstream end 16 of the processing line. The quality sensor 12 is disposed upstream of the splicing head 10. A double-headed arrow indicates a distance 26 between the splicing head 10 and the quality sensor 20 measured along the processing line.

[0136] As shown in Figure 1a, the quality sensor 12 detects the value of a quality parameter at a detection portion 20 of the first sheet 18. If the value of the quality parameter falls within a predetermined threshold, this indicates that the detection portion 20 contains an unacceptable defect.

[0137] Thereafter, as shown in Figure 1b, the first sheet 18 is transported along the processing line such that the detection portion 20 is positioned from the upstream end 14 of the processing line before it enters the bonding head 10. The detection portion 20 is transported along the processing line in a direction toward the downstream end 16 over a distance 28 that is shorter than the distance 26 between the bonding head 10 and the quality sensor 12. Thus, the detection portion 20 in Figure 1b is positioned immediately upstream of the bonding head 10.

[0138] In the next step, as shown in FIG. 1b, the first sheet 18 is bonded to a second sheet of material (not shown) with the detection portion 20 positioned immediately upstream of the bonding head 10. Thus, when the sheets are bonded, the detection portion 20 of the first sheet 18 is adjacent to the upstream entrance of the bonding head 10. A bonding mechanism may be provided that can reduce wasted material sheets. By conveying the first sheet 18 toward the downstream end 16, a portion of the first sheet 18 having a distance length 28 is left and used for production. Also, because the defective detection portion 20 is positioned upstream of the bonding head 10 during bonding, the defective portion of the first sheet 18 does not form part of the bonded sheet. A bonded sheet without the defective portion may be more robust. A more robust bonded sheet and its bond may reduce material waste because the risk of rupture of the more robust bonded sheet is reduced.

[0139] 2a and 2b illustrate a method of splicing two sheets of material. A processing line is shown comprising a splicing head 10 and a quality sensor 12 disposed between an upstream end 14 of the processing line and a downstream end 16 of the processing line. A first sheet of material 18, e.g., a homogenized tobacco material sheet, is processed on the processing line along a processing direction 24 from the upstream end 14 of the processing line toward the downstream end 16 of the processing line. The quality sensor 12 is disposed downstream of the splicing head 10.

[0140] As shown in Figure 2a, the quality sensor 12 detects the value of a quality parameter at a detection portion 20 of the first sheet 18. If the value of the quality parameter falls within a predetermined threshold, this indicates that the detection portion 20 contains an unacceptable defect.

[0141] Thereafter, as shown in Figure 2b, the first sheet 18 is transported along the processing line such that the detection portion 20 is positioned at the upstream end 14 of the processing line before it enters the bonding head. The detection portion 20 is transported a distance 28 along the processing line in a direction toward the upstream end 14. Thus, the detection portion 20 of Figure 2b is positioned immediately upstream of the bonding head 10.

[0142] In a next step, as shown in FIG. 2 b , the first sheet 18 is bonded to a second sheet of material (not shown) with the detection portion 20 positioned immediately upstream of the bond head 10 .

[0143] According to the method of FIGS. 1 and 2, the detection portion 20 does not form part of the spliced ​​sheets. A more robust splicing mechanism may be provided. For example, the quality parameter may be the width of the first sheet 18, and the detection portion 20 may be an unacceptably narrow width. The width reduction may progress from the detection portion 20 toward the upstream end of the first sheet 18. By splicing the first and second sheets with the detection portion 20 located upstream of the splicing head 10, the upstream portion of the first sheet 18 that has narrowed in width does not form part of the spliced ​​sheet. A splicing mechanism is provided that can provide spliced ​​sheets of the correct width. A splicing mechanism that provides high mechanical stability of the spliced ​​sheets may be provided.

[0144] 3a and 3b show apparatus for joining two sheets of material. Each apparatus comprises a first shaft 30 into which a first bobbin 32 is inserted and a second shaft 34 into which a second bobbin 36 is inserted. The first shaft 30 and the second shaft 34 are rotatable about their respective axes (not shown in the drawings). The first bobbin 32 supplies the first sheet of material 18, and the second bobbin 36 supplies the second sheet of material 22. The first sheet 18 and the second sheet 22 are preferably homogenized tobacco sheets.

[0145] In Figure 3b, the apparatus comprises a rotatable bobbin holder unit 46. The rotatable bobbin holder unit 46 comprises a first shaft 30 and a second shaft 34 extending from the bobbin holder unit 46. The bobbin holder unit 46 is therefore provided with two bobbins 32, 36 carrying two sheets 18, 22.

[0146] The apparatus of Figures 3a and 3b each further comprises a bonding head 10, shown schematically as a rectangle in Figures 3a and 3b. A first sheet 18, which is the sheet in use in Figure 3a, is fed to the bonding head 10. The first sheet 18 is unwound from a first bobbin 32 and fed to the bonding head 10 via a guide pulley 38. The first sheet 18 is transported along a processing direction indicated by arrow 24 towards the bonding head 10 and further processing stages.

[0147] Downstream of the splicing head 10, the apparatus of Fig. 3b comprises an acceleration unit in the form of two acceleration rollers 48. The first sheet 18 or the second sheet 22 can be accelerated or decelerated by the acceleration unit while passing through the splicing head 10. The first sheet 18 or the second sheet 22 can be continuously accelerated as it passes between the two acceleration rollers 48 to ensure a continuous speed of the sheets. During the splicing process, the sheets are preferably slowed down or stopped by the acceleration rollers 48. After the splicing process, the spliced ​​sheets can be accelerated again to processing speed.

[0148] The apparatus of Figures 3a and 3b includes a buffer unit 40 downstream of the splicing head 10 and, if present, downstream of the acceleration rollers 48. The buffer unit 40 includes a plurality of rollers, e.g., a series of idler pulleys 42, around which the first sheet 18 or the second sheet 22 is guided to form a loop. Some of the idler pulleys 42 are arranged in a movable manner to expand or contract the loop of the sheet, so as to allow further downstream feeding of the material sheet even if the feed from the splicing head 10 or from the first bobbin 32 or the second bobbin 36 is interrupted or reduced.

[0149] Downstream of the buffer unit 40, the apparatus of Figure 3b includes a withdrawal unit 50 which withdraws the first sheet 18 or the second sheet 22 from the buffer unit 40 and passes the sheet, preferably at a constant speed, to a sheet processing unit (not shown) located further downstream.

[0150] Further elements and units may be included in the apparatus, such as a crimper and a rod former (not shown in FIGS. 3 a and 3 b ), both of which are located downstream of the buffer unit 40 .

[0151] At least a first quality sensor 12 is disposed in the apparatus between the first shaft 30 and the bonding head 10, along the path of passage of the first sheet 18 in the process direction 24. For example, the quality sensor 12 may be a thickness sensor, a width sensor, a moisture sensor, a viscosity sensor, or a detector for the presence or absence of holes or tears in the first sheet 18.

[0152] At least one further quality sensor 13 may be disposed in the apparatus between the second shaft 34 and the bonding head 10 along the path of the second sheet 22. For example, the further quality sensor 13 may be a thickness sensor, a width sensor, a moisture sensor, a viscosity sensor, or a detector for the presence or absence of holes or tears in the second sheet 22. The quality sensor 12 and the further quality sensor 13 may be the same type of sensor. The quality sensor 12 and the further quality sensor 13 may measure the same integrity parameters of the first sheet 18 and the second sheet 22, respectively.

[0153] The apparatus further comprises a controller 44. As shown by the dotted lines in Figures 3a and 3b, the controller 44 is connected to the quality sensor 12, and, if present, one or more further sensors 13, and to the bonding head 10. The controller 44 is also preferably connected to the buffer unit 40.

[0154] 4a and 4b illustrate the general function of a buffer unit 40, such as the buffer unit 40 of the apparatus of FIG. 3a or of the apparatus of FIG. 3b. FIG. 4a illustrates a configuration in which the buffer is filled with a sheet of material and the movable idler pulley 42 is configured to lengthen the sheet turn-up of the first sheet of material 18. FIG. 4b illustrates a configuration in which the buffer is empty and the movable idler pulley 42 moves to shorten the sheet turn-up. While the buffer is emptying, another sheet of material 18 can be fed in the downstream direction 24 even if the feed from the bond head 10 or from the first bobbin 32 is interrupted or reduced.

[0155] Figure 5 shows in more detail a splicing head 10 suitable for use with the apparatus of Figures 3a and 3b. The splicing head 10 of Figure 5 includes a cutting knife 52 for cutting the first sheet 18, the second sheet 22, or both. The splicing head 10 further includes a dispensing unit 54 adapted to supply water onto the first sheet 18 or the second sheet 22. The splicing head 10 also includes a compression roller 56 for compressing the spliced ​​sheets. The splicing head 10 also preferably includes a heating unit 58, e.g., a hot air source or a heat radiation source, located adjacent to and downstream of the compression roller 56.

[0156] The general functionality of the devices shown in Figures 3 to 5 may be as follows.

[0157] In Figure 3a, a first sheet 18 unwound from a first bobbin 32 is in use and passes through the splicing head 10 in a generally straight line. No processing takes place at the splicing head 10. The first sheet 18 is then buffered to a predetermined length in a buffer unit 40 and is further conveyed to a sheet processing unit (not shown) located further downstream. Such a processing unit may be, for example, a crimping unit or a rod-forming unit.

[0158] While moving towards the bond head 10, the quality sensor 12 inspects the quality of the first sheet 18 as it moves along the process direction 24, evaluating one or more quality parameters of the first sheet 18 at a predetermined frequency. Signals representative of the quality parameters are sent to the controller 44 where they are processed, for example, compared to threshold values.

[0159] In this situation, the buffer unit 40 buffers the maximum length of the first sheet 18, as shown in the configuration of the buffer unit 40 shown in Figure 4a. The idler pulleys 42 are spaced a maximum distance apart from each other. This distance may be along the horizontal direction (see Figure 4a) or the vertical direction (see Figure 3b).

[0160] The quality sensor 12 may measure a quality parameter at a detection portion 20 of the first sheet 18 at a predetermined frequency. The parameter is then compared to a threshold value by the controller 44. At a predetermined point in time, the first detection portion 20 may be free of defects such that the quality parameter is not within the predetermined threshold, and processing of the first sheet 18 may continue. The first sheet 18 is then moved so that the sensor 12 can measure the quality of the first sheet 18 at a second detection portion 20. The parameter obtained from the results of the second detection portion 20 is then compared to a predetermined threshold value by the controller 44. This second detection portion 20 may indicate an unacceptable defect such that the quality parameter is within the predetermined threshold.

[0161] As a result, in that case, the controller 44 commands the splicing head 10 to start the splicing procedure, and before the actual splicing of the sheets takes place in the splicing head 10, the controller 44 controls the transport of the first sheet 18 along the processing line so that the second detection portion 20 of the first sheet 18 is positioned before entering the splicing head 10 from the upstream end of the processing line, as described above in relation to Figures 1a and 1b.

[0162] The second sheet 22 from the second bobbin 36 is guided via a guide pulley 38 and fed to the splicing head 10. In FIG. 5, the second sheet 22 is fed underneath the first sheet 18 during use. Both sheets 18 and 22 are cut by a cutting knife 52, after which the cut sheets 18, 22 are positioned one above the other on a support surface 60 of the splicing head 10, with the cut surfaces of the sheets overlapping and aligned to define a contact area. The two sheets 18, 22 are then guided through compression rollers 56. As the sheets pass between the compression rollers 56, they are compressed, thereby firmly securing the two sheets 18, 22 to one another. To support bond formation, a heating unit 58 heats the joined sheets. The heat rapidly dries the joint so that the newly joined sheets can be subsequently fed to a processing unit located further downstream.

[0163] While the splice is taking place, the first sheet 18 buffered in the buffer unit 40 is used in another process step because it is necessary to slow down or stop the first sheet 18 to perform the splice. Therefore, during splicing, the first sheet 18 in the buffer unit 40 is used and the idler pulleys 42 move closer to each other and reach a minimum distance, as shown in Figure 4b.

[0164] In the apparatus of Fig. 3b, when splicing is initiated as instructed by the controller 44, the first bobbin 32 is rotated counterclockwise (as indicated by the arrow in Fig. 3b) by the bobbin holder unit 46 away from the splicing head 10 before splicing occurs. The same rotational action moves the second bobbin 36 closer to the splicing head 10. The second sheet 22 from the second bobbin 36 is guided into the splicing head 10 via a guide pulley 38, where splicing can be performed. After cutting at the splicing head, the cut first sheet 18 can be removed from the first shaft 30 of the bobbin holder unit 46 together with the bobbin 32. It can be replaced with a new bobbin.

[0165] This process provides a new bobbin and prepares a sheet on the new bobbin to be spliced ​​with the sheet in use while the sheet continues to be fed into the processing line.

[0166] The bobbin holder unit 46 preferably rotates so that new sheets can be fed from above, which simplifies alignment of the new sheets with the upper surfaces of the sheets in use to be bonded therewith.

[0167] An arrangement of mechanical dancer and pulley rolls 62, 64 is provided on the bobbin holder unit 46. They are arranged next to each of the bobbins 32, 36. The sheets 18, 22 are guided over the rolls 62, 64 before being fed into the splicing head 10. By providing the mechanical dancers and pulleys 62, 64, controlled guiding of the sheets and constant clamping of the sheets can be achieved. This is particularly advantageous for tobacco sheets that tend to tear or break due to large or irregular tearing or pulling forces. In particular, the rolls compensate for fluctuating drawing forces as the bobbin rotates on the bobbin holder.

[0168] The same splice as above may occur if the controller 44 receives a signal from another diameter sensor (not shown) indicating that the first bobbin 32 is about to be empty.

Claims

1. 1. A method of joining two sheets of material, comprising: providing a processing line comprising a splice head and a quality sensor disposed between an upstream end of the processing line and a downstream end of the processing line; providing a first sheet of material and a second sheet of material; processing the first sheet on the processing line along a processing direction from the upstream end of the processing line to the downstream end of the processing line; detecting a value of a quality parameter at a detection portion of the first sheet by the quality sensor; If the value of the quality parameter falls within a predetermined threshold, conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned at the upstream end of the processing line prior to entering the splice head; and bonding the first sheet and the second sheet together at the bonding head when the detection portion of the first sheet is positioned before entering the bonding head from the upstream end of the processing line.

2. the quality sensor is located upstream of the bonding head; conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned before entering the splice head from the upstream end of the processing line, 2. The method of claim 1, comprising conveying at least one segment of the first sheet including the detection portion along the processing line in a direction toward the downstream end over a distance that is less than a distance between the bonding head and the quality sensor as measured along the processing line.

3. conveying the first sheet along the processing line such that the detection portion of the first sheet is positioned before entering the splice head from the upstream end of the processing line, 2. The method of claim 1, comprising conveying at least one segment of the first sheet including the detection portion along the processing line in a direction toward the upstream end of the processing line until the detection portion of the first sheet is positioned from the upstream end of the processing line before entering the bonding head.

4. The method of claim 3 , wherein the quality sensor is located downstream of the bond head.

5. The method according to any one of claims 1 to 4, wherein the quality sensor comprises an optical sensor, preferably a photo camera or a video camera.

6. 6. The method of claim 1, wherein the quality sensor is configured to detect one or more of the width of the first sheet, the moisture level of the first sheet, the thickness of the first sheet, the viscosity of the first sheet, and the presence or absence of holes or tears in the first sheet.

7. The method of claim 6 , wherein the quality sensor is configured to detect a width of the first sheet, and the quality parameter is the width of the first sheet.

8. 8. The method according to any one of claims 1 to 7, wherein the processing line further comprises a buffer unit provided downstream of the splicing head, the method comprising the step of buffering a predetermined length of the first sheet in the buffer unit before the splicing step, and preferably wherein a part of the processing line downstream of the buffer unit is either stopped or operated at a slower speed during the step of splicing the first sheet and the second sheet with the splicing head.

9. 9. The method according to any one of claims 1 to 8, wherein an upstream portion of the first sheet is wound onto a first bobbin and an upstream portion of the second sheet is wound onto a second bobbin, preferably further comprising the step of removing the first bobbin after the joining step.

10. 10. The method of any one of claims 1 to 9, wherein the first and second sheets of material are homogenized tobacco material sheets for use as aerosol-forming substrates in an aerosol-generating article.

11. 11. The method of any one of claims 1 to 10, wherein the first and second sheets of material comprise one or more alkaloids.

12. The method of any one of claims 1 to 11, further comprising the step of crimping the bonded sheets.

13. 1. An apparatus for joining two sheets of material, comprising: a processing line having an upstream end and a downstream end, the processing line being configured to process a first sheet of material and a second sheet of material; a joining head disposed between the upstream end and the downstream end; a quality sensor disposed between the upstream end and the downstream end and configured to detect a value of a quality parameter at a detection portion of the first sheet; A controller, the controller is configured to evaluate whether the value of the quality parameter detected by the quality sensor falls within a predetermined threshold; a controller configured to: control the processing line to transport the first sheet along the processing line so that the detected portion of the first sheet is positioned before entering the splicing head from the upstream end of the processing line when the value of the quality parameter detected by the quality sensor falls within the predetermined threshold; and to control the splicing head to splice the first sheet and the second sheet together at the splicing head when the detected portion of the first sheet is positioned before entering the splicing head from the upstream end of the processing line.

14. The apparatus of claim 13 , wherein the quality sensor is located downstream of the bond head.

15. 15. The apparatus of claim 13 or claim 14, wherein the processing line is configured to allow at least a portion of the first sheet to be transported in both a downstream direction and an upstream direction.

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