Patent Application
20090008493
The invention relates to a device and method for transporting material webs and for fixing said webs on a counter bearing.
Devices having these functions are known in printed literature. Thus U.S. Pat. No. 4,852,820 A and DE 10202462 A1 disclose web-winding devices. In these web-winding devices, material webs or tubes are transported usually by a plurality of transport rollers to a winding core on which the material web is wound up. When the winding core has to be changed, the material web is cut through, fixed on a new winding core and wound up there. Both the aforementioned publications describe modern winding devices—in short winders—which work in a highly automated manner and in which the described process of fixing the start of the web on the new winding core takes place at least to a large extent without an adhesive. In doing so, the described devices utilize the electrostatic attractive force which occurs between the start of the material web and the winding core when the start of the material web is charged electrostatically. The charging of the start of the web is carried out by an electrode located in the vicinity of the last transport roller of the winder over which transport roller the material web moves before it reaches the winding core.
The still unpublished German patent application having the file number 103 21 599 discloses another winding device in which several material webs or material tubes lying upon each other are provided with an electrostatic charge even before they reach the last transport roller of the winder. The goal of this measure is to bring about an adhesive behavior between these material webs or between the upper side and the lower side of the film tube, which adhesive behavior prevents the material webs from being lifted off from one another by their air resistance during their transportation. This method can be used advantageously in all types of devices in which material webs or film tubes are transported. Thus, film tubes are transported over longer distances, for example, in tubular film extrusion units, wherein it is undesirable for the upper side of the tube to get lifted off from the lower side of said tube.
If the words “material webs” are also regarded as a generic term for film tubes and if the term “counter bearing” is used to sum up all types of supports for material webs, such as for example, other film tubes, other material webs and winding cores, then the machines described in the three publications can be characterized as follows:
Said machines are devices for transporting material webs and for fixing said webs on a counter bearing, wherein the device has the following characteristics:
All these devices leave a lot to be desired when it comes to the reliability of the adhesive behavior of the material web on its counter bearing.
It is therefore the object of the present invention to suggest a device using which it is possible to bring about the adhesion of the material web on its counter bearing still more reliably than hitherto possible.
This object is attained by the fact that at least one transport roller comprises means for applying an electrostatic charge to at least parts of the material web.
The scope of improvement of the adhesion behavior by using the measure according to the present invention is astonishing. Evidently, the smaller distance of the material webs from the transport rollers and the fact that the material webs have a direct contact with the transport rollers and that the material webs can also maintain this contact for a certain period of time depending on the wrap angle and the web speed, are mainly responsible for this scope of improvement. Preferred points of use of the present invention are winding devices for film material, wherein paper-rewinding stands also come into question. As mentioned earlier, the present invention can also be used in other machines in which material webs are transported.
Additional exemplary embodiments of the present invention shall become apparent on the basis of this description and the claims.
The individual figures show:
a A schematic diagram of the winding device of a surface winder
b A schematic diagram of the winding device of the same surface winder as shown in
a A schematic diagram of the winding device of a turret winder
b A schematic diagram of the winding device of the same turret winder as shown in
a A sectional view of a transport roller with an example of means for applying a charge to a material web
b An enlarged section of
a A sectional view of a transport roller with another example of means for applying a charge to a material web
b An enlarged section of
The electrodes 5, which introduce the charge to the material web, are indicated in the contact roller. On the contact roller 2a, the transport direction z of the material web 1 is identical to the direction of rotation z of the roller 2a. When the old material web roll 7 is wound completely, the blade 6 cuts through the material web 1 and the electrodes 5 transfer a charge to the material web, the ends of which are fixed on the new winding core 4 under the influence of the electrostatic forces coming from the charge q.
Due to the especially critical space conditions around the new winding core, surface winders are a preferred point of use for transport rollers 2a, which include means for applying a charge to parts of the material web.
However, the winding behavior of turret winders—as shown by way of example in DE 102 02 462, DE 102 02 687, DE 102 03 149 and DE 102 02 463—can be improved by the use of such a roller. In such a turret winder, of which the parts that are important for the winding process are sketched in
Here also it is advantageous if particularly the last transport roller 2a, which the material web 1 touches in the transport direction z, before reaching the new winding core 4, is equipped with means for applying a charge q to the material web.
a [sic; 3a and 3b] show a sectional view of a transport roller 2b with an example of means for applying a charge q to a material web. These means cover only a certain angle area of the circumferential surface of the roller 2b, as shown in
The base body 10 of the roller 2b is often made of metal. It is surrounded by a soft rubber or plastic layer 11, which is often formed in a foam-like manner and preferably consists of polyurethane. In the region, which serves for applying a charge to the film, this layer is either formed to be thinner than in the remaining circumference of the roller or said layer is omitted altogether in this region. In this region, another insulating layer 12 follows which can be made of Teflon, for example. The purpose of this layer is to insulate the current-carrying metal film 13 reliably against the base body 10. The current-carrying metal film 13 is followed by the weakly conducting layer 14 which has greater electrical resistance than metals, but lesser than insulators, like for example the Teflon layer. So-called electrically conductive plastics, which usually consist of macromolecules having a plurality of delocalizable electrons, are used for preparing such a layer. These electrons often emanate from multiple bonds between the atoms of the molecules. In addition, such plastics are made more conductive by the addition (doping) of conductive substances such as metals or graphite.
Even after all these measures, the electrical conductivity of these plastics is less, by several orders of magnitude, than that of metals such as copper, but much higher than that of the common plastics.
The needle-shaped electrodes 15 are located on this weakly conducting layer 14. These electrodes 15 are also held by the layer 14, there being no direct electrical contact between the metal film 13 and the electrodes 15. The needle-shaped electrodes 15 are bordered in their peripheral direction by the circular cylindrical tubes 17, which are open on their front sides. The tubes 17, for their part, are cast in the plastic layer. However, they can also be removed again so that tubular channels remain in the plastic layer 16. The plastic layer 16 is flush with the layer 11 and forms with the latter the circumferential surface of the roller 2b, which is interrupted only by the openings 18, kept free by the tubes 17. Due to the openings 18, the electrodes 15 have free contact with the surrounding area of the roller although their tips do not protrude beyond the periphery of the roller.
In the axial direction of the roller 2b—said axial direction not being shown in this sectional view—several electrodes follow one another so that the electrodes can apply a charge to the entire width of a film web moving over the roller. For this purpose, current is applied to the metal film 13, which serves as a common conductor for the electrodes here. This current flows through the weakly conducting layer 14 to the electrodes 15, wherein the layer 14 performs the function of a resistor between the electrodes and the conductor. Charge q is applied from the tips of the electrodes 15 to a material film even across certain air gaps.
The process of charging plastic webs has proven to be particularly effective. However, the method suggested according to the present invention, of fixing other webs, such as for example, paper webs on different counter bearings also entails advantages.
Particularly in the use of transport rollers according to the present invention for fixing the start of a web on a winding core, it has proven to be advantageous if the web end located on the transport roller is held initially on the transport roller by means of a vacuum, in order to then be lifted off by means of an air blast acting on the film like the vacuum from the interior of the roller through air holes in the peripheral surface of said roller. The details of this method can be obtained from DE 101 40 365 A1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 049 329.4 | Oct 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/10174 | 9/19/2005 | WO | 00 | 4/9/2007 |
