| 摘要 |
A plurality of rolling elements are mounted in a support longitudinally spaced and turnable about axes extending transversely to the elongation. A continuously operable drive turns one member of a clutch which is normally engaged. A sensing device normally projects beyond the general plane defined by the rolling elements and on which a load travels, and can be downwardly deflected when a load contacts it. A worm constitutes the other part of the clutch and drives a gear fast with one of the rolling elements. The worm can be disengaged, thereby disengaging the clutch, when the mechanical sensing arrangement is depressed by a load and thereby engages with the thread or screw on the worm, whereby the latter is caused to carry out axial displacement in a sense disengaging the clutch, by the force of the drive which normally drives the clutch.
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