Hydraulic damper

Abstract

A hydraulic damper comprises a reciprocal piston in a cylinder containing a hydraulic fluid, a piston rod including a reduced diameter valve sleeve fixedly received in a through bore of the piston, and a valve element disposed in the valve sleeve for relative movement to the valve sleeve between a plurality of positions. The relative position of the valve element to the valve sleeve is adjustable via a control rod from the outside, such as by an actuator. The valve sleeve has an inlet port communicating with a first chamber on one side of the piston and an outlet port. The valve element has a transfer groove. The valve element covers the inlet port and is moveable to uncover the inlet port to allow fluid communication between the inlet port and the transfer groove that in turn communicates with the outlet port. A first increased damping force generating valve and a second decreased damping force generating valve are mounted to the piston. The second decreased damping force generating valve means prevents fluid flow into the outlet port from a second chamber on the opposite side of the piston and restricts hydraulic fluid flow out of the outlet port into the second chamber.