| 摘要 |
A hydraulic height adjusting device includes a sealed upright cylinder body in which a piston is provided. A piston rod is connected to the piston at one end and extends through a lower end of the cylinder body. A first positioning member is fitted in the cylinder body adjacent to an upper end of the latter. A second positioning member has an axial hole formed therein and is fitted in the cylinder body between the first positioning member and the piston. A hollow tube has a radial hole formed through a wall portion thereof and extends axially in the cylinder body between the first and second positioning members. The piston and the first and second positioning members cooperatively partition the cylinder body into a first oil chamber filled with hydraulic oil, a second oil chamber filled with hydraulic oil and communicated with the first oil chamber by an oil passage formed in the piston, and a receiving chamber receiving compressible nitrogen therein and communicated with the second oil chamber by the axial hole and the radial hole. A movable shaft extends axially into the tube and has a lowermost end which extends into the second oil chamber and which is provided with a valve piece that is biased to selectively block or unblock the axial hole.
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