1. Field of the Invention
The invention relates to a device for cutting and transferring strips (streaks) which functions with a machine for producing a continuous material web, in particular a paper or cardboard web, and further relates to a method for cutting and transferring a threading strip inside a machine for producing a continuous material web, in particular a paper or cardboard web.
2. Description of Background and Relevant Information
Devices and methods of the type claimed here are known. They are used to introduce the web into the machine when starting the machine for producing, a continuous material web. Because the material web can be up to 8 to 10 meters wide, it is practically impossible to thread it simultaneously across its entire width. Therefore, a so-called insertion or threading strip, which is also called a belt, is cut from the material web. The threading strip is significantly narrower than the entire material web, for example, it is approximately 30 cm wide. This threading strip is threaded into the machine and, in the end, draws the entire width of the material web along with it. The threading process takes place, for example, when starting the paper machine or after a web tear.
At the beginning of a threading process, the threading strip, together with the rest of the material web, runs freely, i.e., it is conveyed away from the first drying cylinder. for example, of a drying section of the machine for producing a material web into the basement of the machine and is supplied to an additional treatment. In order to be able to guide the threading strip through the machine, it must first be severed, i.e., cut. At the beginning of the threading process, since the material web or its threading strip is traveling at the full machine running speed or at least is traveling at a speed that is only reduced by an insignificant amount, a back-up occurs during the cutting process due to which a further transfer of the threading strip is frequently problematic.
Therefore, the object of the invention is to produce a device for cutting and transferring strips as well as a method for cutting and transferring a threading strip which do not have this disadvantage and assure an optimal cutting and transfer of the threading strip.
This object is attained with the aid of a device for cutting and transferring strips which has the features that will be herein described. The device is distinguished by means of at least one guide roll which is brought into engagement with the free-running threading strip and conveys it to the cutting point. It is therefore possible to prevent a paper backup when cutting the material web and to assure a trouble-free transfer of the threading strip.
A preferable exemplary embodiment of the strip cutting and transferring device is distinguished by the fact that the guide roll cooperates with a clamping device which preferably includes at least one clamping roll. This cooperation of the two rolls improves the guidance of the threading strip so that this makes a further contribution to the clean cutting and transfer of the threading strip.
Another preferable embodiment of the strip cutting and transferring device is distinguished by the fact that the rotation speed of the guide roll and/or of the clamping roll can be adjusted so that their circumferential speed is at least as high as the traveling speed of the threading strip. Since the two rolls engage each other, they basically rotate at the same speed. It is therefore sufficient to drive one of the two rolls and to choose to have the circumferential speed of one of the two rolls be adjustable. Because of the adjustable rotation speed, the tension of the threading strip can be adjusted to a desired value so that a definite cutting process and a clean transfer of the threading strip are assured.
A particularly preferable embodiment of the strip cutting and transferring device is distinguished by the fact that the knife used for the cutting process is moveable. It is therefore possible to select the knife movement so that it travels in the transfer direction of the threading strip. As a result, the flee front end of the threading strip produced by the cutting process is deflected into the direction in which the threading strip is to be transferred.
In order to attain the object, a method for cutting and transferring a threading strip inside a machine for producing a continuous material web is proposed, which has the features mentioned herein. It is distinguished by the fact that the threading strip is supplied to the cutting point before the cutting. As a result of the defined position of the threading strip during the cutting, a paper back-up as well as transfer problems can be prevented.
A preferable embodiment of the method is distinguished by the fact that the threading strip is subjected to a definite initial tension before the cutting. This leads to a further improvement of the behavior of the threading strip when cutting. A back-up can be reliably prevented so that problems in the transfer of the cut strip end are practically eliminated.
Finally, another preferable embodiment of the method is distinguished in that the threading strip is cut by a knife which, for the cutting, is moved in the same direction as the free end of the strip end being cut. The free end of the threading strip produced in the cutting process thus receives an impetus in the direction of the subsequent travel of the threading strip. The method is therefore distinguished by a very high degree of operational safety.