In roll-winding machines for the winding of paper, paperboard or cardboard webs onto respective sleeves, cradle-type roll-winding machines may be used. In the past, for a roll replacement, i.e. the removal of a fully-wound roll and its replacement by a new sleeve onto which a roll is to be built, the machine has generally been brought to standstill.
It is desirable in this industry to reduce the standstill time of the machine to a minimum and nevertheless ensure, after severing of the web to form a trailing end and a new leading end, that the new leading end can be applied effectively to the new sleeve so that the new winding cycle can commence with a minimum of difficulty.
In the automated roll-replacement system described in German patent document DE-OS 29 20 707, the roll-replacement method retains the web which is fed between the support rollers during the separation by suction on the periphery of one of these support rollers. The separation of the web is effected by means of a separating device raised through the gap between the support rollers and provided with a tearing blade which tears the web upon the ejection of the fully-wound roll from the machine. This method can only be used effectively with light papers (up to about 120 g/m.sup.2). With heavier types of paper, the separation of the web against an inactive tearing blade of this type and the retention of the web against the support roller create problems which have not been solved in this earlier system.
Cradle-type roll winding machines for heavier paper can utilize the principles of the German patent document DE-OS 31 51 256 in which swingable levers can pivot about the axis of one of the support rollers and carry a device for cutting the web and effecting adhesion thereof. The cutting device is an active blade movable across the width of the web and which severs the web upon the winding sleeve. The newly formed leading edge of the web can then be adhered to the sleeve substantially concurrently with the cutting operation.
The device for severing the web and causing adhesion of the leading edge to the sleeve is structurally complex and hence relatively expensive and its operation takes comparatively a long time.
In German patent document DE-OS 36 11 895, a roll-replacement process is described for a support roll-winding machine in which the web, before it reaches the support roll, is weakened and receives a trace of adhesive on both sides of the weakened zone. The separation of the web along the weakened zone is effected by braking the web while the latter lies against the support roll. The leading and trailing web ends formed by the separation adhere to the support roller by suction developed therein until they reach the roll to be wound and the trailing end is then bonded to this roll. The new leading end remains braked during this movement so that the support roll must rotate beneath the leading band and which is held by suction thereagainst until the fully-wound roll is discharged and the braking action is released to permit further advance of the leading end and its adhesion by a respective adhesive trace to the new sleeve.