| 摘要 |
A device for supporting a chair at a selected height, comprising a hydraulic cylinder operative to support the chair, the cylinder being contractable to lower the chair under the weight of the chair occupant and being subject to a spring bias which extends the cylinder to raise the chair when unoccupied. The cylinder comprises two fluid-filled chambers separated by a valve. The fluid flows between the chambers via the open valve during expansion and contraction of the cylinder, and the valve when closed blocks the fluid flow whereby to hydraulically lock the cylinder. The hydraulic fluid is preferably a grease. |
