| 摘要 |
A system is used with a boom pivoted on a frame about a horizontal pivot axis between raised and lowered positions by a first fluid ram joining the frame and the boom. A releasable locking mechanism locks the boom relative to the frame to prevent pivotal movement of the boom about its horizontal pivot axis. A second fluid ram is disposed between the frame and the boom, the second fluid ram compressed between the frame and the boom when the boom is adjacent the raised position, but prior to the boom achieving a latched position substantially coinciding with the raised position. A fluid circuit of the second fluid ram has two selectable pressure levels. The first level substantially prevents the boom from achieving the latched position, the second level permits the boom to achieve the latched position while providing fluid cushioning to dissipate impact forces between the boom and frame.
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