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(11) | EP 4 273 079 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | WEB TENSION CONTROL |
| (57) A method for controlling a tension of a continuous web (W) comprises: moving said
web along a web path; controlling a first actuator of a first dancer mechanism (100)
to generate a first force to move first rollers (110) of said first dancer mechanism
(100) along a respective first path on a respective first surface, said first rollers
contacting said web at a first portion of said web path; and controlling a second
actuator of a second dancer mechanism (200) to generate a second force to move second
rollers of said second dancer mechanism along a respective second path on a respective
second surface, said second rollers (120) contacting said web at a second portion
of said web path, said second portion being separate from said first portion. Said
first force and second force are determined so that the tension of said web is substantially
equal near said first portion and near said second portion.
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Technical field
[0001] Example aspects herein relate to controlling tension of a web, and in particular to a method for controlling a tension of a continuous web, a computer program, a control unit, and an apparatus.
Background
[0002] A known method involves moving a web of a continuous material, such as plastic, paper, textile, metallic material, along a defined path so that devices placed along this path can perform processes on the web to convert the web and obtain a desired product. For example, processes may include the application of a product on the web (e.g. printing, coating, adhering a sheet etc.), a mechanical modification of the web (e.g. forming protrusions, hole-punching, cutting, etc.), etc.
[0003] As the web is moved along the path, guided by elements such as rollers, the tension of the web must be controlled to ensure each process is accurately performed, as a change in the tension, or a deviation from a predetermined tension, may result in differences from the expected product, leading to waste or even faults in devices contacting the web.
Summary
[0004] Variations in the tension may be caused as the web is moved, for example due to elements contacting the web such as rollers advancing the web along the path, which may result in the aforementioned manipulation issues.
[0005] This is particularly problematic for manipulations requiring the tension of the web to be substantially constant over a portion of the web path. This is even more relevant for head printing devices, in particular head inkjet printing devices, where the tension of the web over the portion under printing must be exactly controlled in order to have a final printed web that meets specific requirements.
[0006] There is therefore a need to control the tension of a web as the web is moved along a web path, and in particular, to ensure that the tension is maintained substantially constant over a portion of the web path (i.e. covering an area of the web) where a manipulation is to be performed on the web.
[0007] According to a first example aspect disclosed herein, there is provided a method for controlling a tension of a continuous web.
[0009] Preferably, the method comprises controlling a first actuator of a first dancer mechanism to generate a first force, in particular to move each of one or more first rollers of said first dancer mechanism along a respective first pat. Preferably each first path is on a respective first surface intersecting with said web path. Preferably said one or more first rollers contact said web at a first portion of said web path.
[0010] Preferably, the method comprises controlling a second actuator of a second dancer mechanism to generate a second force to move each of one or more second rollers of said second dancer mechanism along a respective second path. Preferably each of said second path is on a respective second surface intersecting with said web path. Preferably said one or more second rollers contact said web at a second portion of said web path. Preferably said second portion being separate from said first portion.
[0011] Preferably, said first force and said second force are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion.
[0012] Preferably, the tension of said web being substantially equal at said first location and at said second location leads to the tension of said web being controlled over a portion of said web path between said first portion and said second portion, and may in particular lead to the tension of said web being controlled to be constant over a portion of said web path between said first portion and said second portion.
[0013] In some implementations, a unit for forming an image on said web may be received along the web path between the first portion and the second portion.
[0014] Accordingly, the tension of the web can be made substantially constant throughout the area on which the image if formed on the web.
[0015] In some implementations, the method comprises the step of forming an image on said web along said web path between said first portion and said second portion, in particular by means of a unit for forming an image.
[0016] In some implementations where a dancer mechanism includes more than one rollers, each roller of the dancer mechanism may surface contact the web at a different part of the portion of the web path where the rollers of that dancer mechanism are said to contact the web. The different parts where each roller contacts the web may be partially overlapping, adjacent, or apart from each other. In other words, the first rollers need not continuously contact the web along the entire first portion, and the second rollers need not continuously contact the web along the entire second portion.
[0017] The first force may be applied to the first roller(s) directly (e.g. as a force having a direction along the first path), or it may be applied to an intermediate element mechanically coupled to the first roller(s), to move along its respective first path. Each first path may be defined as the collection of positions that may be taken by a given point of the first roller as it is moved by the first actuator. For example, as rollers have a generally circular cross section, the given point may be the centre of the circular cross section, a point on the surface of the first roller or any point between the centre and the surface of the first roller. For each first path, which can be defined as a finite open curve or a closed curve, a respective first surface may be defined by extending the first path, such that the first surface intersects the web path. In the present disclosure, a surface intersecting the web path would be understood to mean that the surface includes a line on both of the surfaces of the web, the lines being perpendicular to a direction of movement of the web along the web path at the intersection between the surface and the web path.
[0018] As each first surface intersects with the web path, a movement of a first roller along a first path causes a change in the length of the web path (either extending or shortening the web path), therefore causing a change in the tension of the web around the first roller. The first rollers may move independently from each other, in which case the first force may be applied to each first roller. Or, the first rollers may have a fixed position relative to each other, for example if they are located in a same dancer carriage, in which case the first paths are on surfaces that are parallel to each other. In cases where there is more than one first roller (and thus more than one first surface), each first surface intersects the web path at a different location in the first portion.
[0019] Similarly, the second force may be applied to the second roller(s) directly (e.g. as a force having a direction along the second path), or it may be applied to an intermediate element mechanically coupled to the second roller(s), to move along its respective second path. Each second path may be defined as the collection of positions that may be taken by a given point of the second roller as it is moved by the second actuator. For example, as rollers have a generally circular cross section, the given point may be the centre of the circular cross section, a point on the surface of the second roller or any point between the centre and the surface of the second roller. For each second path, which can be defined as a finite open curve or a closed curve, a respective second surface may be defined by extending the second path, such that the second surface intersects the web path (i.e. the second surface includes a point along the web path, and the web path extend away from the surface at that point). As each second surface intersects with the web path, a movement of a second roller along a second path causes a change in the length of the web path (either extending or shortening the web path), therefore causing a change in the tension of the web around the second roller. The second rollers may move independently from each other, in which case the second force may be applied to each second roller. Or, the second rollers may have a fixed position relative to each other, for example if they are located in a same dancer carriage, in which case the second paths are on surfaces that are parallel to each other. In cases where there is more than one second roller (and thus more than one second surface), each second surface intersects the web path at a different location in the second portion.
[0020] By controlling the first force generated by the first actuator and the second force generated by the second actuator, the tension of the web at the locations in or near the portions where roller(s) of the two dancer mechanisms contact the web path can be controlled to be substantially equal, and thus ensuring the tension to be substantially constant over a portion of the web path between the two dancer mechanisms. As a result of controlling the first force generated by the first actuator and the second force generated by the second actuator, the web will move at a substantially constant speed over the portion of the web path between the two dancer mechanisms (where an unit for forming an image on the web may be placed). As a consequence, blurriness or other issues in the quality of the image formed on the web may be avoided.
[0021] Although the first example aspect has been described to be controlling actuators of dancer mechanisms, in alternative implementations, the dancer mechanisms may be replaced by any other controllable means for tensioning the web, i.e. any means that can receive an indication of a desired tension and control the tension of the web based on this indication may be used instead of the first dancer mechanism, the second dancer mechanism, or both.
[0022] In alternative implementations, rollers may be replaced by (or supplemented with) other means for surface contacting the web and biasing the web in a direction which is different than the direction in which the web is being moved, to cause a change in the length of the web path.
[0023] In alternative implementations, actuators may be replaced by (or supplemented with) other means for controllably generating a force to act upon rollers (or the aforementioned other means for surface contacting the web and biasing the web), so as to counter the effect of web tension.
[0024] Although any known method of forming the image on the web may be used (e.g. printing, adhering a sheet, etc.) the unit may, preferably, be a fixed head printing device, and more preferably, a fixed head inkjet printing device.
[0025] As fixed head printing devices typically uses multiple heads to obtain multicolored images, having a substantially constant web tension along a portion of the web path where the printing device is received allows for each of the heads to apply ink at the desired location accurately.
[0026] In some implementations, one or more third rollers may be contacting said web at a third portion of said web path and move said web along said web path, said third portion being between said first portion and said second portion. Said first actuator and said second actuator may be controlled so that the tension of said web between said first portion and said third portion, and the tension of said web between said second portion and said third portion, are substantially equal to each other.
[0027] Accordingly, controlling the forces applied by the first actuator and the second actuator allows for the variations in the web tension caused by the third roller(s) moving the web, to be avoided or reduced.
[0028] In some implementations, one or more elements may be contacting the web at a portion of the web path between the first portion and the second portion. These one or more elements may be causing a tensile force (including a friction force) to act on the web in a direction along the web path, thus causing a change in the tension of the web. For example, the process performed on the web (e.g. image forming) may require a contact with the web, which creates friction. Thus, controlling the forces applied by the first actuator and the second actuator allows for the variations in the web tension caused by the one or more elements to be avoided or reduced.
[0029] In some implementations, the method may comprise sensing, at said first portion, a measure of a third force acting on said one or more first rollers as said web moves along said web path.
[0030] As the third force can be used as an indicator of the tension of the web at the first portion, the measure of the third force allows for the tension of the web at the first portion of the web path to be inferred, providing a measurement of the tension of the web at the contact of the first roller(s) and the web.
[0031] Optionally, the method may comprise controlling said first actuator based on said measure of said third force. Accordingly, the control of the first actuator can be based on the tension of the web at the first portion, thus providing a local control loop.
[0032] In some implementations, the method may comprise sensing, at said second portion, a measure of a fourth force acting on said one or more second rollers as said web moves along said web path.
[0033] As the fourth force can be used as an indicator of the tension of the web at the second portion, the measure of the fourth force allows for the tension of the web at the second portion of the web path to be inferred, providing a measurement of the tension of the web at the contact of the second roller(s) and the web.
[0034] Optionally, the method may comprise controlling said second actuator based on said measure of said fourth force. Accordingly, the control of the second actuator is based on the tension of the web at the second portion, thus providing a local control loop.
[0035] In some implementations, at least one of said first force and said second force may be a torque.
[0036] In some implementations, at least one of said first actuator and said second actuator may be an electric actuator. Preferably, the first actuator and/or the second actuator may be an electric motor.
[0037] In some implementations, said one or more first rollers may differ in number from said one or more second rollers.
[0038] In some implementations, said first force may be determined based on a number of said one or more first rollers.
[0039] In some implementations, said second force may be determined based on a number of said one or more second rollers.
[0040] In some implementations, at least one of said first actuator and said second actuator may be controlled to generate a substantially constant force.
[0041] In some implementations, said first dancer mechanism may further comprise one or more fourth rollers contacting said web at said first portion. Preferably, each of said one or more first rollers may move along said respective one or more first paths relative to said one or more fourth rollers. For example, the one or more fourth rollers may have a fixed position, or they may each move (along a respective one of the first path(s) or a different path on a surface intersecting with the web path).
[0042] In some implementations, said second dancer mechanism may further comprise one or more fifth rollers contacting said web at said second portion. Each of said one or more second rollers may move along said respective one or more second paths relative to said one or more fifth rollers. As with the fourth rollers, the one or more fifth rollers may have a fixed position, or they may move (along a respective one of the second path(s) or a different path on a surface intersecting with the web path).
[0043] According to a second example aspect disclosed herein, there is provided a computer program comprising instructions which, when executed by one or more processors, cause the one or more processors to execute the method according to the first example aspect above.
[0044] According to a third example aspect disclosed herein, there is provided a control unit for an apparatus for controlling a tension of a continuous web to be moved along a web path, the control unit comprising means for performing the method according to the first example aspect above.
[0045] According to a fourth example aspect disclosed herein, there is provided a control unit for an apparatus for controlling a tension of a continuous web to be moved along a web path.
[0046] Preferably, the control unit is arranged to control a first actuator of a first dancer mechanism to generate a first force to move one or more first rollers of said first dancer mechanism along a respective first path. Preferably each first path is on a respective first surface intersecting with the web path. Preferably said one or more first rollers are arranged to contact said web at a first portion of said web path.
[0047] Preferably, the control unit is arranged to control a second actuator of a second dancer mechanism to generate a second force to move each of one or more second rollers of said second dancer mechanism along a respective second path. Preferably each second path is on a respective second surface intersecting with said web path. Preferably said one or more second rollers are arranged to contact said web at a second portion of said web path Preferably said second portion is separate from said first portion.
[0048] Preferably, said first force and said second force are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion.
[0049] Preferably, the tension of said web being substantially equal at said first location and at said second location leads to the tension of said web being controlled over a portion of said web path between said first portion and said second portion, and may in particular lead to the tension of said web being controlled to be constant over a portion of said web path between said first portion and said second portion.
[0050] According to a fifth example aspect disclosed herein, there is provided an apparatus comprising the control unit of claim 14, said first dancer mechanism, and said second dancer mechanism.
[0051] According to a sixth example aspect disclosed herein, there is provided an apparatus for controlling a tension of a continuous web to be moved along a web path.
[0052] Preferably, the apparatus comprises a control unit, a first dancer mechanism, and a second dancer mechanism.
[0053] Preferably, said first dancer mechanism comprises a first actuator and one or more first rollers. Preferably said first actuator is arranged to generate a first force to move said one or more first rollers along a respective first path. Preferably each first path is on a respective first surface intersecting with the web path. Preferably said one or more first rollers are arranged to contact said web at a first portion of said web path.
[0054] Preferably, said second dancer mechanism comprises a second actuator and one or more second rollers. Preferably said second actuator is arranged to generate a second force to move said one or more second rollers along a respective second path. Preferably each second path is on a respective second surface intersecting with the web path. Preferably said one or more second rollers are arranged to contact said web at a second portion of said web path. Preferably said second portion is separate from said first portion.
[0055] Preferably, said control unit is arranged to control said first actuator to generate said first force and to control said second actuator to generate said second force. Preferably said first force and said second force are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion.
[0056] As used herein, the term "path" (for example when referring to the web path, a first path of the first roller(s) or a second path of the second roller(s)), defines a finite line, or curve, in a plane.
Brief description of the drawings
[0057] Embodiments of the present invention, which are presented for better understanding the inventive concepts, but which are not to be seen as limiting the invention, will now be described with reference to the figures in which:
Figure 1 shows a schematic diagram illustrating an apparatus for controlling a tension of a continuous web;
Figure 2 shows a perspective view of a dancer mechanism;
Figure 3 shows a schematic diagram illustrating elements of an apparatus for controlling a tension of a continuous web;
Figures 4A to 4C show schematic diagrams illustrating arrangements of rollers in a dancer mechanism and a web;
Figure 5 shows a method for controlling a tension of a continuous web.
Detailed description
[0058] Although example embodiments will be described below, it will be evident that various modifications may be made to these example embodiments without departing from the broader spirit and scope of the invention. Accordingly, the following description and the accompanying drawings are to be regarded as illustrative rather than restrictive.
[0059] In the following description and in the accompanying figures, numerous details are set forth in order to provide an understanding of various example embodiments. However, it will be evident to those skilled in the art that embodiments may be practiced without these details.
[0060] Figure 1 is a schematic diagram of an apparatus 10 for controlling a tension of a continuous web W according to an example embodiment, in a system for moving the web W along a web path indicated by the arrows (as Figure 1 is a two-dimensional view, the web path coincides with the web W on Figure 1). Figure 1 shows a portion of the web path, which may be initiate with a roll of web. In the example of Figure 1, the web is separated into pieces (e.g. sheets of a given size) at location on the web path after the apparatus 10.
[0061] In the example shown on Figure 1, the apparatus 10 comprises a first dancer mechanism 100 and a second dancer mechanism 200.
[0062] The first dancer mechanism 100 comprises one or more first rollers 110, and one or more fourth rollers 120.
[0063] As shown on Figure 1 the web W contacts with each of the first rollers 110 and each of the fourth rollers 120 at a first portion of the web path. Specifically, each first roller 110 and each fourth roller 120 surface contact the web W, across the width of the web W.
[0064] The first portion may be defined to be covering the length of the web path that includes all contacts between the web W and the first rollers 110 and all contacts between the web W and the fourth rollers 120.
[0065] As will be explained in more detail below, each of the first rollers 110 is arranged to move along a respective first path (i.e. there is a corresponding first path for each first roller). Each first path is on a respective first surface intersecting with the web path (i.e. there is a corresponding first surface for each first path).
[0066] Although not shown on Figure 1, the first dancer mechanism 100 comprises a first actuator arranged to generate a first force to move each first roller 110 along its respective first path. As a result, the movement of each first roller 110 along its respective firth path lengthens or shortens the web path depending on the direction of movement, causing an increase or a decrease, respectively, of the tension in the web W, around the first portion.
[0067] As the first dancer mechanism 100 and the second dancer mechanism 200 are interchangeable, the description above made using the first dancer mechanism 100 and its elements as an example will only be briefly summarized for the second dancer mechanism 200. It should however be understood that all description of the first dancer mechanism 100 or its elements also applies to the second dancer mechanism 200 or the corresponding element. Briefly, the second dancer mechanism 200 comprises one or more second rollers 210, and one or more fifth rollers 220, each contacting the web W at a second portion of the web path separate from the first portion. Each of the second rollers 210 is arranged to move along a respective second path, each second path being on a respective second surface intersecting with the web path. The second dancer mechanism 200 comprises a second actuator arranged to generate a second force to move each second roller 210 along its respective second path.
[0068] In the example shown on Figure 1, the web moves along the web path, passing first through the first portion before passing through the second portion (in which case the first dancer mechanism may be defined as an "upstream" or "infeed" dancer and the second dancer mechanism may be defined as a "downstream" or an "outfeed" dancer), or vice-versa.
[0069] As shown on Figure 1, the system also comprises a printing unit 300 and one or more third rollers 400, which are placed along a portion of the web path between the first portion and the second portion. In other words, the first roller mechanism 100 and the second roller mechanism 200 can receive the printing unit 300 (or other suitable means for forming an image on the web) and the one or more third rollers 400 along that portion of the web path between the first portion and the second portion.
[0070] The printing unit 300 is an example of unit for forming an image on the web. In the example of Figure 1, this is a fixed head inkjet printing device. The printing device 300 includes a number of heads arranged in sequence along a portion of the web path. Therefore, a given section on the web will sequentially pass under each head of the printing device, whilst the heads deposit ink on the surface of the web W facing the printing device 300, at desired locations along the width of the web. Known details of the fixed head inkjet printing device 300 will not be repeated here for brevity. However, as the desired image may require the combination of ink deposited by different heads, it is important to ensure that the tension of the web does not vary, to avoid that the locations where the ink is deposited by each head coincide accurately. Otherwise, the image obtained by superimposing on the web ink deposited by different heads may be blurry or have other quality issues. The apparatus 10 may therefore control the tension of the web along the portion of the web path where the image will be formed on the web W (whether this is using a printing device or a device forming the image using any other known method).
[0071] The third roller 400 is arranged to contact the web at a third portion of the web path, and to move the web W along the web path (i.e. advance the web). As this requires the third roller 400 to generate a tensile force acting on the web W, this causes a change in the tension of the web W.
[0072] Specifically, in the example shown on Figure 1, the web W moves along the web path, contacting the first dancer mechanism 100, the third roller 400 and the second dancer mechanism 200 in that order. Accordingly, the third roller 400 generates a tensile force which increases the tension of the web W between the first portion (where the roller(s) of the first dancer mechanism 100 contact the web W) and the third portion (where the third roller 400 contacts the web W), and which decreases the tension of the web W between the third portion and the second portion (where the roller(s) of the second dancer mechanism 200 contact the web W).
[0073] The apparatus 10 can therefore control the first actuator and the second actuator so that the tension of the web between the first portion and the third portion is substantially equal to the tension of the web between the second portion and the third portion.
[0075] As shown on Figure 2, the first dancer mechanism 100 comprises a first actuator 102, which is an electric motor, a gear 104 coupled to a shaft of the first actuator 102. The first actuator is arranged to generate a torque (as the first force), transmitted to the gear 104, to rotate a timing belt 106. A first dancer carriage 118 is fixedly coupled to a location on the timing belt 106, and is sliding along rails 108. The first rollers 110 (individually indicated as roller 112, 112' and 112") are fixedly coupled on a first dancer carriage 118.
[0076] The dancer mechanism 100 also includes fourth rollers 120 (individually indicated as roller 122, 122' and 122"), which are fixed.
[0077] Accordingly, the torque generated by the first actuator rotates the timing belt 106, thus causing the first dancer carriage 118 to move up and down the rails, resulting in the first rollers 110 also moving up and down. The movement of the first rollers 110 in the example shown on Figure 2 can be defined to be relative to the fourth rollers 120.
[0078] Figure 2 shows, merely as an example, the first dancer mechanism 100 and its elements. However, it should be understood that the description above applies to the second dancer mechanism 200 and its elements. Specifically, in an exemplary embodiment, the second dancer mechanism 200 comprises a second actuator 202, a gear 204, a timing belt 206, a dancer carriage 218, rails 208, second rollers 210 and fifth rollers 220, each corresponding to a respective element described above for the first dancer mechanism 100.
[0079] Referring now to Figure 3, elements of the apparatus 10 for controlling a tension of a continuous web will be described.
[0080] The apparatus 10 comprises a control unit 50, a first dancer mechanism 100, a second dancer mechanism 200. The first dancer mechanism 100 comprises a first actuator 102, one or more first rollers 110, and a first sensor 130. The dancer mechanism comprises a second actuator 202, one or more second rollers 210, and a second sensor 230. Some of the elements of the apparatus 10 (such as the actuators and the rollers), have already been described with reference to Figures 1 and 2 above, their description will be omitted here for brevity.
[0081] The control unit 50 is communicatively coupled to the first actuator 102 and the second actuator 202. As explained in more detail below, the control unit 50 determines a first force F1 to be generated by the first actuator 102, to move the first roller(s) 110, and a second force F2 to be generated by the second actuator 202, to move the second roller(s) 210. The control unit 50 transmits a first force control signal FS1 to the first actuator 102, indicating the magnitude of the first force F1 to be generated. The control unit 50 also transmits a second force control signal FS2 to the second actuator 202, indicating the magnitude of the first force F2 to be generated. The force control signals FS1 and FS2 may be transmitted as voltage signals, with the magnitude of the force being indicated by an amplitude of the signal, a digital signal encoding a value indicative of the magnitude as bits, or any other known type of control signal that may be transmitted to an actuator. The control unit 50 may be arranged to transmit the signals repetitively, at periodic timings, or when a predetermined event is detected (for example as explained below), triggering the transmission of the signal.
[0082] The first actuator 102, upon receipt of the first force control signal FS1, generates the first force F1 with the magnitude indicated in the received first force control signal FS1. The first force F1 is generated to move the first roller(s) 110 along the respective first path.
[0083] The second actuator 202, upon receipt of the second force control signal FS2, generates the second force F2 with the magnitude indicated in the received second force control signal FS2. The second force F1 is generated to move the second roller(s) 210 along the respective second path.
[0084] However, it would be understood that, although the first force F1 and the second force F2 may move the first roller(s) 110 and the second roller(s) 210, respectively, in a given direction along their respective path, other forces, including the tension of the web W, may prevent or hinder the movement that would be caused by the first force or the second force. During operation, i.e. whilst the web is being moved along the web path with the desired tension, the first force F1 may actually cause no movement of the first roller(s) 110, and the second force F2 may not cause any movement of the second roller(s) 210. The first force F1 and the second force F2 may instead counteracts other forces to maintain the tension of the web at the desired value.
[0085] Accordingly, in some cases, the first actuator 102 and the second actuator 202 may be controlled to generate constant forces.
[0086] Each of the first sensor 130 and the second sensor 230 may be a torque sensor, a load cell, or any known type of sensor that can be used to obtain a measure of a force.
[0087] The first sensor 130 obtains a measure of a third force acting on the first rollers 110 as the web W moves along the web path, from the first roller(s) 110, the first actuator 102, or other elements of the first dancer mechanism transmitting the first force to the first rollers (e.g. the gear 104 or the timing belt 106 shown on Figure 6). This measure of the third force can be used as an indicator of the tension of the web W at the first portion. Accordingly, the first force generated by the first actuator can be determined based on the measure of the third force, as a form of feedback.
[0088] Similarly, the second sensor 230 obtains a measure of a fourth force acting on the second rollers 210 as the web W moves along the web path, from an element of the second dancer mechanism (e.g. the second roller(s) 210, the second actuator 202 or any other element coupling the actuator 202 to the second rollers 210). Correspondingly to the measure of the third force, the measure of the fourth force can be used as an indicator of the tension of the web W at the second portion. Accordingly, the second force generated by the second actuator can be determined based on the measure of the fourth force, as a form of feedback.
[0089] In the example provided in Figure 3, the first sensor 130 and the second sensor 230 provide the sensed measure of the third/fourth force to the control unit 50.
[0090] Referring now to Figures 4A to 4C, arrangements of rollers in a dancer mechanism will now be described. As with Figure 2, Figures 4A to 4C show arrangements with reference to the one or more first rollers 110, Although it would be understood that the described arrangements may be used for the one or more second rollers 210 of the second dancer mechanism 200 instead.
[0091] Figure 4A shows an arrangement corresponding to that shown on Figures 1 and 2, where two rollers, 112' and 112" contact the web W,
[0092] Roller 112' is arranged to move along a path 114' (shown with a thick black line), between two positions indicated by arrows. By extending the path 114', as shown with the dashed lines, a first surface 116' can be defined which intersects the web path at the location indicated as "A". Similarly, roller 112" is arranged to move along a path 114", between two positions, and extending the path 114" leads to the surface 116" also intersecting the web path, at a different location on the web path.
[0093] Figure 4B shows an alternative arrangement, where a first roller 112' and a second roller 122' are shown.
[0094] Specifically, roller 112' is arranged to move along a curved path 114' (e.g. a rotation around a point), whereas roller 122' is arranged to move on a linear path 124', similar to that shown on Figure 4A. The surface 116' obtained by extending the path 114', and the surface 126' obtained by extending the path 124' both intersect the web path at respective locations.
[0095] Figure 4C shows an alternative arrangement of a single roller 112' that can contact the web W as it moves along a circular path 114'. By rotating the roller 112' along the path 114', the roller 112' can be brought into contact with the web and the roller 112' can be used to extend the length of the web path when the tension of the web W is to be increased.
[0096] In the example shown on Figure 4C, as the path 114' is a closed curve, it is extended to obtain a cylindrical surface 116' (which, on the two-dimensional view of Figure 4C, coincides with the path 114') intersecting with the web path W at two locations.
[0097] Referring now to Figure 5, a method for controlling a tension of a continuous web will be described.
[0098] This method may be used, for example, in a system as described above with reference to Figure 1, including dancer mechanisms as described above with reference to Figure 2, by an apparatus as described above with reference to Figure 3, or with other arrangements of rollers such as those described above with reference to on Figures 4A to 4C.
[0099] At step S502, the web is moved along a web path. The movement of the web may be controlled, for example, by one or more third rollers 400, or by other elements arranged to pull the web. The web, which may also be defined as a substrate is a continuous sheet formed of any material, such as plastic, paper, cardboard, plastic, metal, or any combination thereof, pulled lengthwise along the web path.
[0100] At step S504, a first actuator of a first dancer mechanism is controlled to generate a first force to move each of one or more first rollers of said first dancer mechanism along a respective first path, each first path being on a respective first surface intersecting with said web path, said one or more first rollers contacting said web at a first portion of said web path.
[0101] At step S506, a second actuator of a second dancer mechanism is controlled to generate a second force to move each of one or more second rollers of said second dancer mechanism along a respective second path, each of said second path being on a respective second surface intersecting with said web path, said one or more second rollers contacting said web at a second portion of said web path, said second portion being separate from said first portion.
[0102] The first force which the first actuator is controlled to be generated at step S504 and the second force which the second actuator is controlled to be generated at step S506 are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion.
[0103] The first location may be, for example, a point where a roller of the first dancer mechanism contacts the web, such as the first or last point of contact along the web path between a roller of the first dancer mechanism and the web (which coincides with an end of the first portion), or any other point in the first portion. Similarly, the second location may be, for example, a point where a roller of the second dancer mechanism contacts the web, such as the first or last point of contact along the web path between a roller of the second dancer mechanism and the web (which coincides with an end of the second portion), or any other point in the second portion.
[0104] Preferably, the first location is near the end of the first portion that is nearer the second dancer mechanism along the web path (the location indicated as L1 on Figure 1), and the second location is near the end of the second portion that is nearer the first dancer mechanism along the web path (the location indicated as L2 on Figure 1). In other words, if the first dancer mechanism is an "infeed"/"upstream" dancer, the preferred first location is near the last point of contact between a roller of the first dancer mechanism and the web, and the preferred second location is near the first point of contact between a roller of the second dancer mechanism and the web, or vice-versa.
[0105] The following provides, by way of non-limiting example, a detailed explanation of determining the first force and the second force to be generated, using the exemplary apparatus described with reference to Figure 1 above. However, it would be understood that the first force and/or the second force may be determined differently, depending on the arrangements of rollers in the dancer mechanisms.
[0107] The desired tension (which may be a range of values) may be defined, for example depending on the material of the web. Defining the tension of the web at the first location as Fz1, and the number of first rollers 110 as n1, the first force F1 that should be applied to the first rollers 110 (for example to a dancer carriage in which the first rollers are located) can be calculated as:
[0108] Therefore, the force to be generated by the first actuator can be determined based on a predetermined desired tension value and the number of first rollers. In the above case, the first force may be the force directly output by the first actuator, if the first actuator is coupled directly to the first rollers, or a transformation of force may be predetermined for the one or more elements connecting the first actuator to the first rollers, such as the gear 104, the timing belt 106, and the mass of the dancer carriage 1108 shown on Figure 2.
[0109] Similarly, defining the tension of the web at the first location as Fz2, and the number of second rollers 210 as n2, the second force F2 that should be applied to the second rollers 210 can be calculated as
[0110] Accordingly, the method allows for a control the tension of the web along the portion of the web path between the first portion and the second portion.
[0111] In a particular implementation, the first actuator and the second actuator may be controlled to generate a constant force.
Modifications and variations
[0113] Although examples have been described with a single pair of dancer mechanisms, the present invention is not limited to such examples, as a larger number of dancer mechanisms may be provided along the web path, each having an actuator controlled so that the tension at respective locations on the web path near consecutive dancer mechanisms are pairwise equal.
[0114] Although in exemplary embodiments provided above, the web is described to be separated into parts, the web may alternatively be formed into another roll (i.e. a "roll-toroll" type of system).
[0115] Although the example shown on Figure 1 shows three first rollers 110, three fourth rollers 120, five second rollers 210 and four fifth rollers 220, the present invention is not limited to such examples, as the number of first rollers 110, second rollers 210, fourth rollers 120, and fifth rollers 220 may each be any number, and each may different from one another.
[0116] More generally, the examples of first dancer mechanism described above includes one or more fourth dancers, the present invention is not limited to such examples, as the first dancer mechanism may include the one (i.e. a single) first roller only, or include the more than one first rollers only, for example using the arrangements shown on Figures 4B and 4C. For the same reasons, the present invention is not limited to examples where the second dancer mechanism comprises the one or more fifth rollers.
[0117] In addition, in Figure 1, the first rollers 110 and the fourth rollers 120 do not contact with the web W along the entire first portion, but only parts of the first portion. Similarly, the second rollers 210 and the fifth rollers 220 only contact the web W along parts of the second portion. However, the present invention is not limited to such examples as the web W may instead, in different arrangements, contact with at least one of the first rollers(s) 110 and fourth roller(s) 120 along all (or substantially all) the length of the first portion along the web path, and/or the web W may contact with at least one of the second rollers(s) 210 and fifth roller(s) 220 along all (or substantially all) the length of the second portion along the web path.
[0118] Although examples have been described where one or more third rollers 400 are located between the first portion and the second portion of the web path, the present invention is not limited to such examples. In other examples, one or more elements other than rollers may be contacting the web at the third portion of the web path, and causing a tensile force (including a friction force) to act on the web in a direction along the web path, thus causing a change in the tension of the web. For example, a process performed on the web (e.g. image forming) may require a contact with the web, creating friction. Thus, controlling the forces applied by the first actuator and the second actuator allow for the variations in the web tension caused by the one or more elements to be avoided or reduced, whether or not these elements are rollers for advancing the web.
[0119] Although Figure 2 shows a single actuator being coupled to the rollers, the dancer mechanisms may include two or more actuators, for example one for each roller to be moved, each generating a separate force to move a subset of the rollers. Accordingly, each actuator can be controlled to generate a respective force have a lower magnitude.
[0120] In the example described with reference to Figure 3, the first sensor 130 is used to obtain the measure of the third force. However, in other cases, the first sensor 130 may be omitted, for example if the actuator 102 is an electric actuator, and in particular an electric motor. This is because a value of the force (e.g. the torque for an electrical rotary motor) output by the first actuator 102 can be determined based on the predetermined characteristics of the actuator 102 and based on the electric power values (and specifically the voltage and current values) used by the actuator 102. As the torque is transformed into a force that is applied onto the first rollers 110, the sensed electric values can be defined as a measure of a third force acting on the first rollers 110 as the web W moves along the web path. In other cases, the first sensor 130 may be part of the first actuator 202, as part of an existing circuit in the first actuator 202 controlling the output, and therefore no separate sensor is required. In these cases, the first sensor 130 may not transmit the sensed measure of the third force to the control unit 50.
[0121] Similarly, the second sensor 230, or the feedback from the second sensor 230 to the control unit 50, may be omitted in some cases.
[0122] Other means of transmitting the force generated by the first actuator to the first rollers can be used instead of the gear 104 and/or the timing belt 106. For example, although Figure 2 shows the first actuator 102 to be an electric (rotary) motor, the first actuator 102 could instead be a linear electric actuator (e.g. a linear electric motor) generating a first force (instead of a torque) onto the first dancer carriage 118 directly to slide the first dancer carriage 118 along the rails 108. In other cases, the timing belt could be replaced by one or more transmission gears.
[0123] Additionally, the dancer carriage 118 may in some cases be omitted, for example if there is only one first roller, or if each first roller can move independently from one another.
[0124] In other cases, as shown for example in Figure 4C, the first roller 110 and/or the second roller 210 may be rotated about an axis, in which case no supporting elements such as the rails 108 would be required.
[0125] Although the first actuator 102 and the second actuator 202 have been generally described as electric actuator, and particularly electric motors, they may be of any other known type of actuator than those described above, such as hydraulic or pneumatic actuators, but preferably of types of fast-reacting actuators to ensure variations in tension are quickly reduced.
[0126] Although steps S504 and S506 have been described sequentially, it would be understood that the order of these steps is chosen purely for ease of explanation, as they will generally (but not necessarily) be performed in parallel, contemporaneously.
[0128] By way of non-limiting example, the control unit may comprise one or more processor and a memory storing a computer program. The computer program may, when executed by the one or more processors, cause the one or more processor to execute steps S504 and S505.
[0129] More generally, software embodiments of the examples presented herein may be provided as, a computer program, or software, such as one or more programs having instructions or sequences of instructions, included or stored in an article of manufacture such as a machine-accessible or machine-readable medium, an instruction store, or computer-readable storage device, each of which can be non-transitory, in one example embodiment. The program or instructions on the non-transitory machine-accessible medium, machine-readable medium, instruction store, or computer-readable storage device, may be used to program a computer system or other electronic device. The techniques described herein are not limited to any software configuration. They may find applicability in any computing or processing environment. The terms "computer-readable", "machine-accessible medium", "machine-readable medium", "instruction store", and "computer-readable storage device" used herein shall include any medium that is capable of storing, encoding, or transmitting instructions or a sequence of instructions for execution by the machine, computer, or computer processor and that causes the machine/computer/computer processor to perform any one of the methods described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, unit, logic, and so on), as taking an action or causing a result. Such expressions are merely a shorthand way of stating that the execution of the software by a processing system causes the processor to perform an action to produce a result.
[0130] Some embodiments may also be implemented by the preparation of applicationspecific integrated circuits, field-programmable gate arrays, or by interconnecting an appropriate network of conventional component circuits.
[0131] Some embodiments include a computer program product. The computer program product may be a storage medium or media, instruction store(s), or storage device(s), having instructions stored thereon or therein which can be used to control, or cause, a computer or computer processor to perform any of the procedures of the example embodiments described herein. The storage medium/instruction store/storage device may include, by example and without limitation, an optical disc, a ROM, a RAM, an EPROM, an EEPROM, a DRAM, a VRAM, a flash memory, a flash card, a magnetic card, an optical card, nano systems, a molecular memory integrated circuit, a RAID, remote data storage/archive/warehousing, and/or any other type of device suitable for storing instructions and/or data.
[0132] Stored on any one of the computer-readable medium or media, instruction store(s), or storage device(s), some implementations include software for controlling both the hardware of the aerosol generation device and for enabling the aerosol generation device or microprocessor to operate in accordance with the example embodiments described herein. Such software may include without limitation device drivers, operating systems, and user applications. Ultimately, such computer-readable media or storage device(s) further include software for performing example aspects of the invention, as described above.
[0133] Included in the programming and/or software of the aerosol generation device are software modules for implementing the procedures described herein. In some example embodiments herein, a module includes software, although in other example embodiments herein, a module includes hardware, or a combination of hardware and software.
[0134] While various example embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein. Thus, the present invention should not be limited by any of the above described example embodiments, but should be defined only in accordance with the following claims and their equivalents.
[0135] Further, the purpose of the Abstract is to enable the Patent Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is not intended to be limiting as to the scope of the example embodiments presented herein in any way. It is also to be understood that any procedures recited in the claims need not be performed in the order presented.
[0136] While this specification contains many specific embodiment details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular embodiments described herein. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
[0137] In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various components in the embodiments described above should not be understood as requiring such separation in all embodiments.
[0138] Having now described some illustrative embodiments, it is apparent that the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of apparatus or software elements, those elements may be combined in other ways to accomplish the same objectives. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments.
[0139] The apparatuses described herein may be embodied in other specific forms without departing from the characteristics thereof. Scope of the apparatuses described herein is thus indicated by the appended claims, rather than the foregoing description, and changes that come within the meaning and range of equivalence of the claims are embraced therein.
1. A method for controlling a tension of a continuous web, the method comprising:
moving said web along a web path;
controlling a first actuator of a first dancer mechanism to generate a first force to move each of one or more first rollers of said first dancer mechanism along a respective first path, each first path being on a respective first surface intersecting with said web path, said one or more first rollers contacting said web at a first portion of said web path; and
controlling a second actuator of a second dancer mechanism to generate a second force to move each of one or more second rollers of said second dancer mechanism along a respective second path, each of said second path being on a respective second surface intersecting with said web path, said one or more second rollers contacting said web at a second portion of said web path, said second portion being separate from said first portion,
wherein said first force and said second force are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion, so that the tension of said web is controlled over a portion of said web path between said first portion and said second portion.
2. The method of claim 1, further comprising forming an image on said web on a portion
of said web path between said first portion and said second portion.
3. The method of claim 1 or 2, wherein one or more third rollers are contacting said
web at a third portion of said web path and move said web along said web path, said
third portion being between said first portion and said second portion;
wherein said first actuator and said second actuator are controlled so that the tension of said web between said first portion and said third portion, and the tension of said web between said second portion and said third portion, are substantially equal to each other.
wherein said first actuator and said second actuator are controlled so that the tension of said web between said first portion and said third portion, and the tension of said web between said second portion and said third portion, are substantially equal to each other.
4. The method of any of claim 1 to 3, further comprising
sensing, at said first portion, a measure of a third force acting on said one or more first rollers as said web moves along said web path;
optionally, controlling said first actuator based on said measure of said third force.
5. The method of any of claims 1 to 4, further comprising
sensing, at said second portion, a measure of a fourth force acting on said one or more second rollers as said web moves along said web path;
optionally, controlling said second actuator based on said measure of said fourth force.
6. The method of any of claims 1 to 5, wherein at least one of said first force and said
second force is a torque.
7. The method of any of claims 1 to 7, wherein at least one of said first actuator and
said second actuator is an electric actuator, preferably an electric motor.
8. The method of any of claims 1 to 7, wherein said one or more first rollers differ
in number from said one or more second rollers.
9. The method of claim 8, wherein
said first force is determined based on a number of said one or more first rollers, and/or
said second force is determined based on a number of said one or more second rollers.
10. The method of any of claims 1 to 9, wherein at least one of said first actuator and
said second actuator is controlled to generate a substantially constant force.
11. The method of any of claims 1 to 10, wherein said first dancer mechanism further comprises
one or more fourth rollers contacting said web at said first portion, wherein each
of said one or more first rollers moves along said respective one or more first paths
relative to said one or more fourth rollers.
12. The methods of any of claims 1 to 11, wherein said second dancer mechanism further
comprises one or more fifth rollers contacting said web at said second portion, wherein
each of said one or more second rollers moves along said respective one or more second
paths relative to said one or more fifth rollers.
13. A computer program comprising instructions which, when executed by one or more processor,
causes the one or more processors to execute the method of any of claim 1 to 12.
14. A control unit for an apparatus for controlling a tension of a continuous web to be
moved along a web path, said control unit being arranged to:
control a first actuator of a first dancer mechanism to generate a first force to move one or more first rollers of said first dancer mechanism along a respective first path, each first path being on a respective first surface intersecting with the web path, said one or more first rollers being arranged to contact said web at a first portion of said web path; and
control a second actuator of a second dancer mechanism to generate a second force to move each of one or more second rollers of said second dancer mechanism along a respective second path, each second path being on a respective second surface intersecting with said web path, said one or more second rollers being arranged to contact said web at a second portion of said web path, said second portion being separate from said first portion,
wherein said first force and said second force are determined so that the tension of said web is substantially equal at a first location in or near said first portion and at a second location in or near said second portion, so that the tension of said web is controlled over a portion of said web path between said first portion and said second portion.
15. An apparatus comprising:
the control unit of claim 14,
said first dancer mechanism, and said second dancer mechanism.