| 摘要 |
Disclosed is a positive lock mechanism for use with a moving board to move an object up or down stairs by sliding such moving board over the crests of the stairs. The positive lock mechanism comprises a shaft, spade element and torsion spring. The moving board freely mounts the shaft which carries the spade element and torsion spring. The torsion spring biases the spade element to a retractable positive lock position for engagement with a stair tread whereby the moving board and its load can remain in a free standing position of rest on the stairs. The moving board may be slid up or down over the crests of several steps before the spade element is allowed to engage a stair tread in positive lock position, or the movers may take one step at a time by allowing the spade element to engage each step successively.
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