| 摘要 |
A speed change mechanism, which includes a housing enclosing a travelling nut on a rotatable screw shaft, incorporates a device for limiting torsional impact loads on the shaft. In a preferred embodiment, the torque limiting device is comprised of two groups of annular members at each end of the shaft for frictionally absorbing impact loads created by sudden stoppage of the nut at respective ends of the shaft. Each group is comprised of at least one friction disc rotatably fixed but axially slidable with respect to the nut, and at least one torque reaction member non-rotatable within the housing against which an associated friction disc is urged via spring. Inertial loads created at ends of nut travel are thereby transferred to the housing instead of the screw shaft. In addition, the two groups of annular members cooperate with the spring to provide a pre-load shifter function for the speed change mechanism.
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