Method for separating partial webs in a slitter winder

A method for separating partial webs in a slitter-winder with a spreader device having two bowed rotating spreader rolls, comprising the steps of:

• separating the partial webs by spreading in a spreading device, wherein the spreading device has at least a first bowed spreader roll which forms a first arc fitted on one side of the partial webs and a second bowed spreader roll forming a second arc fitted on an opposite side of the partial webs, wherein the first arc has a radius of curvature that is less than a radius of curvature of the second arc;
• wherein the first arc is bowed in a first direction and wherein the second arc is bowed in a second direction, and the first direction and the second direction are divergent;
• wherein the partial webs move along a web path in the slitter-winder between slitter blades and a winding roll to define a main running direction of the partial webs, wherein the main running direction defines an X-direction, and wherein a Z-direction is defined in a cross direction of the webs as the webs move in the main running direction, and a Y-direction is defined perpendicular to the X-direction and the Z-direction;
• wherein the partial webs travel under the first bowed spreader roll and over the second bowed spreader roll and then under the winding roll and then wind on to a plurality of partial web rolls;
• wherein the plurality of partial web rolls define gaps therebetween, the gaps located downstream of the first bowed spreader roll and the second bowed spreader roll, the gaps having a width;
• increasing the width of the gaps by moving the first bowed spreader roll more in the Y-direction than in the X-direction, so that a wrap angle about the first spreader roll becomes larger, and moving the second bowed spreader roll more in the X-direction than in the Y-direction away from the first spreader roll, so that the first direction and the second direction become more divergent when increasing the widths of the gaps;
• decreasing the width of the gaps by moving the first bowed spreader roll more in the Y-direction than in the X-direction so that the wrap angle about the first spreader roll becomes smaller, and moving the second bowed spreader roll more in the X-direction than in the Y-direction toward the first spreader roll so that the first direction and the second direction become less divergent when decreasing the widths of the gaps;
• wherein an XY-plane is defined as a plane containing the Y-direction and the X-direction, and a XY-direction is defined as a direction having a X-direction component and a Y-direction component in the XY-plane;
• wherein the partial webs are guided over the first spreader roll to wrap the first spreader roll the first wrap angle, and are guided over the second spreader roll to wrap the second spreader roll a second wrap angle, so that the first wrap angle and the second wrap angle are unequal;
• wherein the partial webs are guided to the first spreader roll in a lead-in direction in a first XY-direction and the partial webs are guided from the second spreader roll in a lead-out direction in a second XY-direction;
• and
• wherein the first XY-direction and the second XY-direction are such that the lead-in direction and the lead-out direction are divergent.