Patent ID: 7967236

Claim:
An apparatus for attenuating vibration in a roll assembly of a fiber web machine, comprising; a roll in the roll assembly, the roll having a first end, a second end, and a lowest bending eigenfrequency; a first bearing housing supported on a machine frame or foundation via at least one first viscoelastic intermediate piece, wherein the roll is rotatably suspended at the first end on a first bearing in the first bearing housing, and the first bearing housing being supported on the machine frame or foundation; a second bearing housing supported on a machine frame or foundation via at least one second viscoelastic intermediate piece, wherein the roll is rotatably suspended at the second end on a second bearing in the second bearing housing, and the second bearing housing is supported on a machine frame or foundation; wherein the at least one first viscoelastic intermediate piece, and the at least one second viscoelastic intermediate piece have loss factors of greater than 0.1 at a frequency range which is ±10% of the lowest bending eigenfrequency of the roll in normal operation; wherein the at least one first viscoelastic intermediate piece has a spring constant in a range of 0.04 GN/m-1 GN/m; wherein the at least one second viscoelastic intermediate piece have a spring constant in a range of 0.04 GN/m-1 GN/m; wherein the roll has a spring constant k roll ; wherein the first end of the roll defines a first shaft journal which contacts the first bearing to define a spring constant k b between the first shaft journal and the first bearing housing; wherein the machine frame or foundation which supports the first bearing housing has a spring constant k g ; and wherein the spring constant of the at least one first viscoelastic intermediate piece k f is in the range: ⁢ from ⁢ ⁢ 0.5 · 1 2 k roll - 1 k b - 1 k g ⁢ ⁢ to ⁢ ⁢ 5 · 1 2 k roll - 1 k b - 1 k g , wherein the second end of the roll defines a second shaft journal which contacts the second bearing to define a spring constant k b between the second shaft journal and the second bearing housing; wherein the machine frame or foundation which supports the second bearing housing has a spring constant k g ; and wherein the spring constant of the at least one second viscoelastic intermediate piece k f is in the range: ⁢ from ⁢ ⁢ 0.5 · 1 2 k roll - 1 k b - 1 k g ⁢ ⁢ to ⁢ ⁢ 5 · 1 2 k roll - 1 k b - 1 k g , where k roll is the spring constant of the roll, k b is the spring constant of the contact between the shaft journal and the bearing housing; and k g is the spring constant of the frame or foundation.