The present invention relates to a cylinder, particularly drying cylinder for a paper machine and more particularly to a drying cylinder of the type having longitudinal ridges spaced apart from each other around the inner surface of the cylinder.  It is known to employ such ridges to break up any layer of liquid which forms on the inner surface of the cylinder during operation. 
As shown in U.S. Pat.  No.  3,217,426, it is known to fasten such ridges by means of clamping rings located radially inward from the ridges and pressing directly radially outward against the ridges.  This arrangement, however, has not been successful in practice because, with the passage of time, the clamp connection loosens as a result of differential thermal expansion of the various parts.  Federal Republic of Germany Unexamined Patent Application (Offenlegungsschrift) No.  23 03 334, discloses subdividing each ridge into segments and attaching each segment to the cylinder wall by means of screws.  This method, however, not only requires extensive drilling work but also weakens the wall of the cylinder.  Finally, Federal Republic of Germany Provisional Patent (Auslegeschrift) 23 30 199 discloses holding the ridges in place by means of spring bars.  This arrangement is, however, cumbersome to assemble and does not assure uniform spacing of the ridges, which can lead to imbalances and other disadvantages in operation.