A METHOD OF WINDING A LAP SHEET ONTO A TUBE OF A LAP-FORMING MACHINE AND AN APPARATUS FOR PRODUCING LAPS ON A LAP-FORMING MACHINE

摘要

The present invention concerns a method of winding a lap sheet onto a tube on a lap-forming machine, and an apparatus for producing laps. In known devices towards the end of the lap winding process the lap width (8) is reduced in such a manner that the tailing lap sheet end wound onto the complet- ed lap roller (5) presents lap sheet edges shifted inwards. As in these devices the lap sheet tearing line (AR) of the lap sheet (6) and the position of the point where the lap sheet width has been brought back to the original width (8) do not coincide, the first lap sheet layers wound onto a new empty tube in a new lap winding process are of the narrowed lap sheet width (81). The disadvantages caused by such initial layers of narrowed width are eliminated in that at a time moment before the lap winding process ends the lap sheet (6) supplied to the tube (7) is narrowed in its width (81) during a determined time interval (I-II) and subsequently is brought back to its original lap sheet width (8).