Roll unwinder, web-fed printing press, and method for operating a roll unwinder

A roll unwinder (02) for a flying roll change, comprising at least one roll station for receiving a first material roll (03) currently to be unwound and a roll station for receiving a second material roll (03′) to be unwound after a roll change has occurred, comprising a cut-off tool (14) by which a first web (B) unwound from the first material roll (03) can be severed, and comprising a pressing element (13), by which the first web (B) currently to be unwound can be pressed against an outer surface of the second material roll (03′);

• a supporting device (16) being provided, which can be transferred from an idle state into a working state in which the supporting device (16) supports the web (B) currently to be unwound, at least at the time of the severing process, in the area of the web path at a site that is situated in the web path between the first material roll (03) to be unwound and the location at which the pressing element (13) cooperates with the web (B);
• the supporting device (16) comprising a supporting element (17), which can be moved from an idle position (R), which is assumed in the idle state of the supporting device (16), into an operative position (W), which is assumed in the working state of the supporting device (16), in which the supporting element (11) is situated in a relative position, which differs from the idle position (R), with respect to an axis of rotation of the first material roll (03) and/or is situated in a position in which the web (B) is supported in the web path section between the pressing element (13) and the material roll (03) or a diverting element (12) that is provided upstream from the pressing element (13), on the web side facing away from the cut-off tool (14), during the severing process;
• the supporting element (17), in the idle position (R), being releasably arranged at a pivotable support frame (11) carrying the first and second material rolls (03;
• 03′);
• the supporting device (16) being provided so as to support the web (B) in the working state in the web path upstream from the location at which the cut-off tool (14), when activated, strikes the web (B), and a receiving unit (19) being provided at a frame (18), which carries the cut-off tool (14) and is movably mounted in a stand of the roll unwinder (02), wherein the supporting element (17), which is releasably arranged at the support frame (11), is received by the receiving unit for an impending roll change.