| 摘要 |
A belt and tread drum having an annular shell comprising a plurality of circumferentially spaced segments, each of which is mounted on a carrier which disposed in circumscribing relationship to a generally cylindrical actuator rotatably connected with a reciprocating piston disposed within a cavity defined between the actuator and a hub fixed to a central core of the drum. Translational movement of the piston between extended and retracted positions in a direction parallel to the rotational axis of the drum is converted into selected rotational movement of the actuator relative to the hub. A plurlaity of sets of links interposed between the segments and the actuator and hub have their first ends commonly pivotally pinned to a segment. The second end of one link of each set of links is pivotally pinned to the actuator and the second end of the other link of each set of links is pivotally pinned to the hub. Rotation of the actuator relative to the hub controls the arcuate separation of these second ends such that bringing these second ends toward contiguity moves the segments radially outwardly, and conversely, moving these second ends arcuately apart serves to move the segments radially inwardly of the drum. A hand wheel establishes maximum and minimum rotational movement of the actuator and provides a visual indication of the radial positions of the several segments, i.e. the diameter of the drum.
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