| 摘要 |
The structure for extending and contracting 3 stage boom sequentially, comprises: double-actuated type first and second cylindrs (100)(200) fixed at second stage boom; tension or compression ports (130), (150) mounted at piston rod (110) of the first hydraulic cylinder (100), hydraulic pressure distributing chamber (120) at the end of the rod (110), for acting the pressrue regularly on the cylinder buffle in tension; tension or compression connecting tubes (240),(250) for pushing the buffle at the chamber (120) by the tension pressure entered through the tension port and a through pipe, or transmitting the compression pressure entered through a hole at the piston rod of first cylinder, to the left or right side of second cylinder.
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