| 摘要 |
A lead screw is threaded into a lead nut to move the lead nut one way or the other depending on the direction of rotation of the lead screw. The lead screw is held in an operative position by springs which prevent it from moving from its operative position until an excessive overload occurs. Braking disks are positioned on opposite sides of a sheave mounted on the lead screw. Abutments hold the braking disks spaced from the sheave to provide a small clearance when the shaft is in its operative position. When the shaft encounters an excessive overload, it will move axially from its operative position and its rotation will be stopped by one or the other of the braking disks. A yieldable support is provided for the braking disks. In one embodiment the yieldable support is a piston-cylinder assembly. In another embodiment it consists of a set of springs.
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