Patent ID: 7314124

Claim:
A damping apparatus, for damping vibrations in a helicopter rotor system, including a piston which is reciprocally movable in a hydraulic fluid-filled damper chamber, piston movement in either direction of movement being resisted by fluid pressure in the damper chamber behind the piston, which resistance provides damping forces which act to oppose piston movement, the piston being connected to one component of the vibrating system and the damper chamber being connected to a second component of the vibrating system, wherein the fluid at at least a first side of the piston acts on a movable member which is movable in a relief chamber in response to changing fluid pressure in the damper chamber at the first side of the piston as the piston moves, the movement of the movable member providing a variable relief volume in the relief chamber for the fluid into which and from which fluid may flow from and towards the first side of the piston without passing to an opposite second side of the piston.