Patent ID: 6938888

Claim:
A vibration damper for a helicopter rotor, the damper comprising both a driving element having a main axis and designed to be driven by a driver element, and a rigid element designed to be mounted on a structure, and including a damper assembly functionally connecting the driving element and the rigid element to damp vibration in at least one direction perpendicular to said main axis, the damper assembly having firstly at least one viscous fluid cavity and a hydraulic damper device placed in said at least one viscous fluid cavity and secondly a flexible device presenting high stiffness in a direction parallel to said main axis, and low stiffness in said direction perpendicular to the main axis, the hydraulic damper device presenting first and second sets of plane vanes, each having its plane perpendicular to the main axis, the first set being mounted on the driving element via a first mechanical link and the second set being mounted on the rigid element via a second mechanical link, the vanes of the first and second sets being disposed in interleaved manner and being closely spaced apart so as to present viscous damping zones each situated between a vane of the first set and a vane of the second set, wherein the hydraulic damper device also comprises at least one damper element which is disposed in one of said at least one viscous fluid cavities and which is secured to the driving element, said damper element presenting an outer outline that tapers going from a base situated beside one axial end of the damper to an apex situated adjacent to the sets of plane vanes to provide a viscous dampening effect that increases as amplitude increases, wherein the at least one viscous fluid cavity has an outer outline that is elongate in a first direction perpendicular to the main axis, and wherein at least the base of the damper element is elongate in a second direction perpendicular to the first direction.