Patent Application
20210107756
The invention relates to a method of rerolling a rolled-up material web, in particular a rolled-up material web of an elastic material, on a rerolling device. In addition, the invention relates to a rerolling device for performing the method.
Modern high-performance facilities for producing material webs nowadays operate with such high output performance and correspondingly such high production speeds that it is no longer useful to use inline rolling machines. The material webs are in particular plastic films produced with the casting or the blowing method. Nonwoven fabric webs coming from spunbonded or meltblown facilities can also be such material webs. Such webs are rolled up so as to be further processed later to form the final product. During further processing, the rolls are unrolled, stretched, if desired, by means of a stretching unit consisting of several drums, cut to width dimension (sections) by means of a cutting station, and material web portions are processed to form separate products. Due to today's high production speeds, change of rolls has a very strong impact. Changes of rolls can mean interruptions of production, the stopping and restarting of the production facilities implying great efforts. Therefore, large rolls with diameters of up to four meters are increasingly produced which are subsequently rerolled to form rolls with smaller diameters in an offline facility, a rerolling device or rerolling machine. Such a rerolling device, which meets its limitations in terms of time, is nowadays a bottleneck in this process. Therefore, frequently several rerolling devices are operated in parallel. Such rerolling devices have an uncoiler which takes up the large rolls. The material web is unrolled from the large roll, sections are cut and subsequently rerolled to form smaller rolls on the recoiler. The large rolls frequently have a mass of up to ten tons and must accordingly be accelerated and decelerated, i. e. braked, smoothly so as to prevent damage to the material web. Therefore, constant acceleration ramps are preset in conventional rerolling devices.
In the following, “acceleration” is intended to mean both positive and negative acceleration, i. e. deceleration.
Another problem is that material webs consisting of plastics or nonwoven fabric are webs with high elasticity. This elasticity is larger by orders of magnitude than that of many other materials, in particular metal or paper. What makes the process even more difficult is that material webs of plastics or nonwoven fabric can be subject to aftershrinkage for up to 48 h, in extreme cases even up to one week, after production. The reason is that most plastics used for films or nonwoven fabrics are crystalline or semi-crystalline. Crystallization is dependent on time and temperature, so that aftercrystallization processes can still take place several days after production. Aftershrinkage can amount to approximately 10% and more. If a material web consisting of such material is rolled up immediately after production, i. e. when aftercrystallization and therefore aftershrinkage are not yet completed, aftershrinkage must be taken into account. A closed material web (e. g. a CPP film) may not be rolled up with too much force; instead, depending on the processed material and its shrinkage behavior, air layers must be taken into account as buffers between the individual layers of the material web on the roll. For purposes of simplification, in the following an elastic material will be understood to be a material with a much higher elasticity than that of metals or paper, whose shrinkage is not completed directly after production of the film web or the web of nonwoven fabric, and whose shrinkage behavior must consequently be taken into account during rolling and rerolling.
It is desirable to reduce the rerolling times.
It is therefore an object of the invention to provide a method of rerolling a rolled-up material web of an elastic material on a rerolling device, by means of which the rerolling times can be reduced with respect to the state of the art.
Another object of the invention is to provide a device for performing the method.
The first object of the invention is achieved by a method according to the independent claim 1. Advantageous further developments of the method are disclosed in claims 2 through 14. The second object of the invention is achieved by a device according to the independent claim 15.
The inventive method of rerolling a rolled-up material web of an elastic material on a rerolling device having an uncoiler and a recoiler, with the material web being rerolled from a large roll with a diameter D, rolled up on the uncoiler, onto a section roll to be rolled up on the recoiler, and with the uncoiler and/or the recoiler having an actuator, is characterized in that during the rerolling process the diameter D of the large roll on the uncoiler and/or the diameter d of the section roll on the recoiler are continuously determined and the performance of an actuator is continuously adjusted by means of this determined parameter. The terms “continuously determined” and “continuously adjusted” are not only to be understood here as an actually continuous, i. e. ongoing, determining or adjusting process, but also as one that takes place in discrete time intervals, the determining taking place multiple times during the rerolling process.
In rerolling a material web from a large roll onto a second roll, the outer diameter and thus the mass of the large roll are permanently reduced. The large roll is tensioned on an uncoiler and the second roll on a recoiler. At least one of uncoiler and recoiler has an actuator, for instance in the form of a motor or of a belt or chain drive. Also, an actuator in the form of a tape drive can be attached to a roll in any position. Another embodiment may contain an actuator with self-driven bearer drums which both support a roll, either by themselves or in combination with other drums, and perform the recoiling by motor power. A lay-on drum can be a different type of actuator. Lay-on drums are normally placed on a roll and are used, for example, as additional self-driven actuators. They can act on the roll by themselves or in combination with several other drums, for instance bearer drums. The actuator can also apply a braking torque to the uncoiler or the recoiler, for instance in order to control the tension of a material web during the rerolling process, especially when starting and finishing a rerolling process. By continuously determining the diameter of at least one roll, the performance of an actuator is continuously adjusted according to the inventive method.
Additionally or alternatively, the material web can also be driven by means of a drum which is arranged between the uncoiler and the recoiler. During this process, the material web is guided over this drum, which may have an actuator able to apply a torque to the drum. The material web partially surrounds the drum. The drum can also be part of a drum assembly with several drums, for instance of a drum pair.
It is explicitly pointed out that within the framework of the present patent application, indefinite articles and numerals such as “one”, “two” etc. are normally to be understood as indicating a minimum, that is, “at least one . . . ”, “at least two . . . ” etc., unless it becomes explicitly clear from the context or is obvious to the person skilled in the art or inevitable from the technical point of view that only “exactly one . . . ”, “exactly two . . . ” etc. can be intended.
By adjusting the rerolling parameters, in particular the rolling velocities and the acceleration ramps, to the continuously changing situation of the rerolling process in the rerolling device, much time can be saved. In some situations, this even makes it possible to do without a second, parallel rerolling device. The important rolling parameters, such as, for example, acceleration forces, can thus be kept constant or nearly constant over the entire process. A change in rolling quality at the recoiler is therefore not to be expected.
In one embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are continuously measured by means of an optical sensor. Such a sensor can be, for instance, a camera with a corresponding image evaluation device. Movable light barriers, for example, are conceivable as optical sensors as well. Optical sensors operate fast and reliably.
Alternatively or in addition, in another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are continuously measured with an electromechanical sensor. Such an electromechanical sensor can be embodied, for instance, as a button. Electromechanical sensors are normally less expensive than optical sensors.
Alternatively or in addition, in another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are continuously measured with an electronic sensor.
In an advantageous embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are continuously calculated. Using the take-off speed and the thickness of the material web as well as of the air cushions between the individual layers, the diameter(s) can easily be calculated. If for calculation input parameters are used which are already present in the process, no additional sensors need to be used for controlling the performance of an actuator.
The following parameters, for example, can be used as desired input parameters:
For all desired values, ranges can be defined, where the limit values can be calculated values or empirical values.
In another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are determined using the continuously determined roll weight.
In another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are determined using the continuously measured speed of the material web at one of the rolls of the uncoiler and the recoiler, preferably at all rolls.
In another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are determined using the continuously measured speed of the material web and rotational speeds of the rolls of uncoiler and recoiler.
In another embodiment, the diameter D of the large roll rolled up on the uncoiler and/or the diameter d of the section roll to be rolled up on the recoiler are determined using the cumulated layer thicknesses of the material web layers at one of the rolls of uncoiler and recoiler, preferably at all rolls. The layer thickness of a material web layer can be measured, for instance, by means of an optical sensor.
It has proved to be advantageous for all determined parameters to be processed by a control unit.
It has also proved to be advantageous for the control unit to control an actuator, preferably all actuators.
In an alternative embodiment, an actuator is controlled manually.
In another advantageous embodiment, the rerolling device has a drum preferably arranged between the uncoiler and the recoiler and vertically displaceable, with the material web being guided over the drum. Driving of the material web can additionally or alternatively take place via the drum. During this process, the material web is guided over this drum, which may have an actuator which can apply a torque to the drum. The material web partially winds around the drum. The drum can also be part of a drum assembly having several drums, for instance of a drum pair.
Furthermore, it has proved to be advantageous if a change of the large roll on the uncoiler and/or of the section roll on the recoiler is performed without interruption of the rerolling process.
A device according to the invention is provided for performing the inventive method.
Other advantages, particularities and advantageous further developments of the invention become clear from the dependent claims and from the subsequent presentation of a preferred example of embodiment by means of the Figures, wherein
The uncoiler 200 and the recoiler 300 each have an actuator 201, 301 by means of which the rolls 200, 300 can be driven and decelerated. During rerolling, the diameter D of the large roll 210 on the uncoiler 200 and the diameter d of the section roll 301 on the recoiler 300 are continuously determined, and using these determined parameters, the performance of the actuators 201, 301 is continuously adjusted.
The embodiments shown here are only given by way of example and are therefore not to be understood as limiting. Alternative embodiments considered by the person skilled in the art are equally covered by the scope of protection of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 127 838.4 | Oct 2019 | DE | national |
