| 摘要 |
A height adjustable mechanism for supporting a work support for vertical movement relative to a base includes a counterbalance mechanism for providing a force opposing a downward force tending to lower the work support; a lock mechanism for releasably retaining the work; support in a desired vertical position; ant a manual operator for selectively releasing the lock mechanism to permit vertical movement of the work surface, while preventing operation of the lock mechanism if the counterbalance force and the downward force are out of balance by some given extent. In the preferred construction, the lock mechanism is pivotally supported by a pin normally supported for axial sliding movement under the control of they manual operator, and the lock mechanism applies loading to the pin, when the counterbalance force substantially differs from the downward force, sufficient to constrain the pin against sliding movement, and thereby prevent release of the lock mechanism by the manual operator.
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