A double-tube shock absorber includes an outer cylinder having a first working chamber, an inner cylinder located inside the first working chamber and having a second working chamber, a first piston movably inserted into the first working chamber and a second piston having a coil and movably inserted...http://www.google.com/patents/US6360856?utm_source=gb-gplus-sharePatent US6360856 - Double-tube shock absorber using a hydraulic fluid and a magnetorheological fluid
