Roll Assembly for a Fiber-Web Machine and Method of Attenuating Vibration of a Fiber-Web Machine Roll

A roll assembly for a fiber-web machine comprising:

• a roll having a first end, a second end, a roll center, and a shell between the first end and the second end, the shell defining a diameter, the shell having a selected length which is at least 7 time the shell diameter;
• wherein the roll defines a lowest bending eigenfrequency of the roll;
• two bearing assemblies, each bearing assembly having a bearing housing, said bearing assemblies supporting the roll one at each of the first end and the second end;
• wherein each bearing housing has a flexibility and attenuating attachment arrangement for mounting on a frame or foundation of a fiber-web machine;
• wherein the flexibility and attenuating attachment arrangement has a selected spring constant and a selected loss factor η;
• a mass absorber arranged in conjunction with each bearing housing, such that damping of vibration of the roll assembly is produced by a cooperative interaction of the bearing housings that are attached in a flexible and attenuating manner to a frame or foundation of a fiber-web machine and the mass absorber;
• and
• wherein the selected spring constant and the selected loss factor η are selected such that the bearing housings will have an amplitude of movement of the bearing housings which is at least 10% of an amplitude of movement of the roll center when at an eigenmode corresponding to the lowest bending eigenfrequency of the roll.

A method of attenuating the vibration of a roll of a fiber-web machine, the roll having a center, a shell defining a length and a diameter, and having a ratio of shell length to diameter of at least seven, and wherein said roll has a lowest bending eigenfrequency, the method comprising the steps of:

• rotating the roll between two bearing housings, each bearing housing forming part of a bearing assembly, each bearing housing being attached at an end of the roll;
• wherein the rotation of the roll results in vibration of the roll, the vibration of the roll center defining an amplitude of movement of the roll center;
• attaching a mass absorber having a selected natural frequency to each bearing housing;
• mounting the bearing housings to a frame or a foundation of the fiber-web machine so that each bearing housing is supported on the frame or the foundation with a selected spring constant and a selected loss factor η so that the bearing housing vibrates with an amplitude of at least 10% of the amplitude of the movement of the roll center at an eigenmode corresponding to the lowest bending eigenfrequency of the roll.

A method of attenuating the vibration of a roll in a winding section of a slitter-winder, the roll having a center, a shell defining a length and a diameter, wherein the shell has a ratio of length to diameter of at least seven, said roll having an eigenmode corresponding to a lowest bending eigenfrequency of the roll, the method comprising the steps of:

• supporting the roll at a first end on a bearing housing in a first bearing assembly and supporting the roll at a second end on a bearing housing in a second bearing assembly so the shell and the roll center is between the first housing assembly and the second bearing housing;
• mounting each bearing housing with a selected spring constant in the range of 0.04 GN/m-1 GN/m and a selected loss factor η in the range 0.01<η<2 on a frame or foundation of the a slitter winder;
• mounting a mass absorber on each bearing housing, such that damping of vibration of the roll assembly is produced by a cooperative interaction of the mass absorbers and the bearing housings;
• operating the winding section of a slitter-winder so the roll rotates and vibrates at the eigenmode corresponding to the lowest bending eigenfrequency of the roll, producing an amplitude of movement of the roll center;
• and
• selecting the spring constant and the selected loss factor η so that the bearing housings will have a movement of an amplitude which is at least 10% of an amplitude of movement of the roll center.