Yankee dryer cylinder with improved internal geometry

A Yankee dryer cylinder comprising:

• a cylindrical shell comprising a central portion, a first and a second end portion and having a longitudinal axis, said cylindrical shell, at an internal surface, being provided with a plurality of circumferential grooves;
• a first head, or end wall, fixed to said first end portion of said cylindrical shell;
• a second head, or end wall, positioned at the opposite side of said first head with respect to said cylindrical shell, said second head being fixed to said second end portion of said shell;
• a first bearing journal fixed to said first head;
• a second bearing journal fixed to said second head;
• a hollow shaft mounted inside said cylindrical shell and connected to said first and said second head;
• said circumferential grooves comprising:
• a first and a second group of circumferential end grooves positioned at said first and of said second end portion, respectively, each group of circumferential end grooves comprising at least a first and a second circumferential groove with said first circumferential groove positioned at a distance from said central portion that is higher with respect to the distance of said second circumferential groove of the same group;
• a third group of circumferential grooves positioned at said central portion;
• wherein said circumferential grooves of said first and of said second group have a width that is wider than the width of the circumferential grooves positioned at said central portion, in such a way to uniformly distribute the loads in operating conditions.