Patent ID: 7351309

Claim:
A dryer group in a paper or board machine comprising: a first contact dryer cylinder, a second dryer cylinder and a turning cylinder positioned therebetween; a single dryer fabric and a paper or board web arranged to travel over the first contact dryer cylinder with the paper or board web between the first contact dryer cylinder and the dryer fabric, and the paper or board web arranged to wrap around the turning cylinder supported by the dryer fabric to define a wrap area, and the dryer fabric and the paper or board web arranged to travel over the second dryer cylinder with the paper or board web between the second dryer cylinder and the fabric so that the paper or board web remains between the second dryer cylinder surface and the dryer fabric; wherein the dryer group turning cylinder is a roll comprising a groove-like surface structure and a center shaft or a roll frame, wherein there is contact between the surface structure and the center shaft or roll frame so that a closed construction is formed except for a portion of the roll used for threading a tail; wherein the turning cylinder roll is arranged with the dryer fabric to produce a vacuum that keeps the paper or board web attached to the dryer fabric at an outer surface within the wrap area of the turning cylinder; wherein the groove-like surface structure has portions forming grooves 18-155 mm deep and 6-10 mm wide, and wherein lands of a defined width are formed between the grooves, and wherein the ratio of groove width to land width is 0.6 to 2.0, and the ratio of groove width to depth is 2.25 or greater.