The invention relates to a winding device of the art accord¬ ing to the preamble of the main claim, that is, a winding de¬ vice for winding a material web, particularly a plastic webf continuously running in the conveying direction and guided over a part of the casing of a contact roller onto a winding core, comprising transversely separating means for separating the material web transversely to the conveying direction in the area of its close fit with the contact roller and com¬ prising a guided material web including an electrostatic charging device for initially winding the front end in the conveying direction of the transversely separated web ar¬ ranged on a winding shaft between the contact roller and an empty winding core which can be swung into position towards the contact roller when the winding core is almost fully wound.

Winding devices are known per se (DE-A-100 59 622 and DE-U- 201 17 258) . When the leading edge of the front end of the transversely separated web is initially wound onto the empty winding core, they solely function mechanically and with blow means, respectively, and therefore have not proven successful because of the complicated initial winding as well the expen¬ sive manner of working resulting therefrom.

Furthermore, winding devices of the art are known wherein the initial winding device, which in addition to blow means also includes an electrostatic charging device, is arranged in the conveying direction behind the point of initial winding (DE- A-IOl 16 973) . In this case the front end of the material web is electrostatically charged and, under the effect of the blow means in the shape of an air flow, at the same time is moved tangentially in the direction of the empty winding core to which it adheres due to its charge without the use of an adhesive.

It has turned out, however, that with the winding device of the art adhesive-free initial winding without the use of glue to fasten the front end of the transversely separated mate¬ rial web without complications is not possible. For example, turn-over folds or dog ears occur during high speeds. In critical materials, however, such dog ears lead to problems during further processing and therefore they are undesirable.

Therefore, it is the object of the invention to further de¬ velop a winding device of the art according to the preamble of the main claim such that dog ear-free and adhesive-free initial winding of the material web is also possible at high speeds thereof.

In a winding device of the art according to the preamble of the main claim this problem is solved according to" the inven¬ tion by its characterizing features, i.e., by the fact that the electrostatic charging device comprises first and second electrostatic charging means, that in front of the trans¬ versely separating means for the material web the first elec¬ trostatic charging means for electrostatically charging at least one of the two sides of the material web is provided with a polarity, that the surface of the contact roller is developed to be electrically semiconducting or conducting and can be connected to the second electrostatic charging means for electrostatically charging the surface with the same po- larity as the charged material web and that the winding shaft for the empty winding core is earthed or may be connected to third electrostatic charging means of the electrostatic charging device with a different polarity than the charged material web.

Thus/ contrary to the generic prior art, the inventive prin¬ ciple arranges a first electrostatic charging means already in front of the transversely separating means, with which at least one of the two sides of the material web is charged with an electrostatic charge of one polarity. Likewise, the same polarity is imparted to the outer surface of the contact roller such that due to the electrostatic repulsive, forces acting between like charges the front end of the transversely separated material web is lifted from the surface of the con¬ tact roller firstly and contrary to the generic prior art only due to the electrostatic repulsive forces. At the same time an electrostatic attractive force is superimposed on this repulsive force between the front end of the material web and the preferably earthed winding shaft of the empty winding core such that these superimposed forces reliably guide the front end of the material web towards the empty winding core. In addition to this there is another electro¬ static effect in that due to the point effect the front edge of the material web together with the electrical field, which develops the strongest there, is thus pulled along its field lines with the largest resulting force in the direction of the winding shaft and thus reaches it first so that it is not possible that the front end of the material web turns over. This means that the winding core is reached first by the leading edge of the front area of the material web such that the part touching it clings to it and only after that the subsequent area of the front area of the material web clings to the surface of the winding core, i.e., without a dog ear, bend or the like and remains in this position because of the charge so that the initial winding can be carried out easily without an adhesive.

Therefore, with the winding device according to the invention dog ear-free as well as adhesive-free initial winding is made possible even at high speeds.

In this case the form of the first electrostatic charging means for electrostatically charging at least one of the two sides of the material web with a polarity is of no importance for the principle of the invention. There may be effected a contact-free charging of the at least one side of the mate¬ rial web only by means of a corona-charging electrode from the outside (WO98/43905, Fig. 4) or by releasing the charge of the casing of a roller contacting the material web (WO98/43905, Figs. 1-3) to the at least one side of the mate¬ rial web. Also a roller which is charged via a sliding con¬ tact and developed in such a manner may be used (US-A- 3,625,146) . The contact roller which can be connected to the second electrostatic charging means may also be formed in double or triple layers (EP-A-I 285 875) or like an impres¬ sion roller (WO98/03049) and charged as disclosed therein.

Further useful developments and improvements are character¬ ized in the subclaims.

In the following, an embodiment of the invention will be ex¬ plained with reference to the drawing, wherein:

Fig. 1 shows an exemplary embodiment of the winding device according to the invention in a schematic representation, and Fig. 2 shows a detail according to Fig. 1.

The material web 9 constantly moved in the conveying direc¬ tion T is diverted via a feed shaft 6 and then fits closely over a part of the casing of a contact roller and is finally wound as a coil onto a winding core 4 rotated by a shaft 41. When the coil on the winding core 4 is almost fully wound an empty winding core 3 located on an earthed winding shaft 31 (Fig. 2) can be swung into position in the direction of the contact roller 1 in such a manner that the material web 9 runs between it and the empty winding core 3. In the area where it fits with the contact roller 1 and behind the feed shaft 6 the winding device is provided with transversely separating means 5 for separating the material web 9 trans¬ versely to the conveying direction T.

As first electrostatic charging means of each of the two sides of the material web 9 corona-charging electrodes 71, 72 aligned thereto are assigned to them and connected to one po¬ larity of the high voltage source 81 of a direct voltage of 15 JcV in the conveying direction T in front of the feed shaft 6.

In the embodiment as shown the contact roller 1 is provided in triple layers with an electrically semiconducting surface 13 forming the outer casing, an innermost electrically insu¬ lating layer 11 and a conductor layer 12 conducting well electrically and arranged between the insulating layer and the surface 13, which is connected to the shaft 15 of the contact roller 1 via an - inner - connecting line 14. The shaft 15 is connected to second charging means formed as a second high voltage source 82 via a sliding ring contact 2, namely having the same polarity as the first high voltage source 81 such that high voltage of the same polarity as that of the first high voltage source 81 is applied via the con¬ ducting layer 12 to the electrically semiconducting surface 13.

When the coil on the winding core 4 is almost fully wound the empty winding core 3 located on an earthed winding shaft 31 is swung to the material web 9 and the transversely separat¬ ing means 5 for separating the material web 9 transversely to the conveying direction T is actuated, thus the end edge 92 of the back end of the transversely separated material web having been wound is pulled onto the winding core 4 before it is removed (Fig. 2) with the material web 9 running with un- diminished speed. During this process, due to the electro¬ static repulsive forces acting between like charges the front end 91 of the material web 9 which before that was trans¬ versely separated is lifted from the surface 13 of the con¬ tact roller 1 at first and contrary to the generic prior art merely because of these electrostatic repulsive forces. At the same time an electrostatic attractive force between the front end 91 of the material web 9 and the preferably earthed winding shaft 31 for the empty winding core 3 is superimposed on this repulsive force such that these superimposed forces reliably guide the front end 91 of the material web 9 towards the empty winding core 3. In addition to this there is a fur¬ ther electrostatic effect in that due to the point effect the front edge 91 of the material web 9 together with the elec¬ trical field, which develops the strongest there, is thus pulled along its field lines by the largest resulting force in the direction of the winding shaft 31 and consequently reaches it first so that it is not possible that the front end of the material web turns over. This means that the empty winding core 3 is reached first by the leading edge 91 of the front area of the material web 9 such that the part touching it clings to it and only after that the subsequent area of the front area of the material web fits closely to the sur¬ face of the winding core, i.e., without a dog ear, bend or the like and remains in this position due to the charge so that the initial winding of the material web to the empty winding core 3 can be carried out easily also without an ad¬ hesive.