Apparatus for damping resonant vibration

Claim 1

In combination with a hydraulic actuator of the type having a piston slidably mounted in an actuator chamber and dividing the chamber into first and second chamber portions on opposite sides of the piston, an actuator rod connected between the piston and a load, and means for selectively conducting hydraulic fluid to the respective chamber portions, a damping apparatus comprising: a housing enclosing a damping piston chamber having an axis, the housing also enclosing first and second compression chambers intersected by said axis and disposed on opposite sides of the damping piston chamber; a damping piston slidably and sealingly seated within the damping piston chamber and dividing said chamber into first and second cavities, the housing having a first passageway communicating between the first cavity and the first compression chamber and a second passageway communicating between the second cavity and the second compression chamber; a piston rod affixed to the damping piston and having a first portion extending from the damping piston, through the first passageway, and within the first compression chamber and also having a second portion extending from the damping piston, through the second passageway, and within the second compression chamber, the piston rod having sealing and sliding association with the housing within the first and second passageways, whereby the first and second piston rod portions form pistons projecting within the first and second compression chambers, respectively; first conduit means communicating between the first chamber portion and the first cavity and second conduit means communicating between the second chamber portion and the second cavity; a hydraulic fluid filling the chamber portions, cavities, compression chambers, and conduit means; means for restricting fluid flow through at least one of the conduit meAns.