Single facer for manufacturing a corrugated board with a pressing unit with a continuous flexible member

A single facer for manufacturing a single face corrugated board, the single facer comprising:

• a load-bearing frame;
• a first corrugating roller and a second corrugating roller, meshing with each other and associated with the load-bearing frame;
• a pivoting structure pivoted to the load-bearing frame about a pivoting axis;
• a first guide roller rotatably supported about a first rotation axis on the pivoting structure;
• a second guide roller rotatably supported about a second rotation axis on the pivoting structure;
• a continuous flexible member, guided about the first guide roller and the second guide roller;
• wherein the continuous flexible member comprises a first branch, facing toward the second corrugating roller, and a second branch, opposite the second corrugating roller;
• a control system adapted to displace the pivoting structure to a working position, wherein the continuous flexible member is pressed against the second corrugating roller, and to a raised position, wherein the first guide roller and the second guide roller are spaced from the second corrugating roller;
• and
• a stretching device adapted to stretch the continuous flexible member when the pivoting structure is in the raised position, comprising a stretching bar, extending approximately parallel to the first rotation axis of the first guide roller and the second rotation axis of the second guide roller and carried by the pivoting structure pivoted to the load-bearing frame;
• wherein the stretching bar is positioned between the first branch and the second branch of the continuous flexible member;
• and wherein the stretching bar is moveable with respect to the first guide roller and to the second guide roller to push the second branch of the continuous flexible member and stretch the first branch of the continuous flexible member between the first guide roller and the second guide roller when the pivoting structure is in the raised position and the continuous flexible member is spaced from the second corrugating roller.