Patent ID: 8167604

Claim:
A fluid spring comprising: a sleeve; a first chamber configured to accommodate a fluid and formed in the sleeve; a hollow piston rod, wherein a part of the hollow piston rod is displacably accommodated in the first chamber; a second chamber configured to accommodate the fluid and formed in the hollow piston rod; a communicating passage configured to make the first chamber and the second chamber communicate with each other and formed in an end portion of the hollow piston rod, wherein the communicating passage only permits the fluid to flow in a direction from the first chamber to the second chamber; an additional passage configured to make the first chamber and the second chamber communicate with each other; and an opening/closing portion configured to open and close the additional passage; wherein the opening/closing portion includes a displacing piston rod provided at an end portion of the hollow piston rod and configured to be displaceable with respect to the hollow piston rod, and wherein the displacing piston rod is movable between an opening position for opening the additional passage and a closing position for closing the additional passage.