| 摘要 |
In the embodiment shown, the assembly comprises a pair of apertured weights mounted on a rotatable shaft, each of the weights having abutment surfaces one or another pairs of which close upon each other, depending upon the direction of shaft rotation. One of the weights is keyed to the shaft to rotate therewith; the other weight is freely rotatable relative to the shaft. Upon rotation of the shaft in a first direction, a first pair of the abutment surfaces engage, and the eccentricities of the weights then are so disposed as to produce a given-amplitude vibratory force. Upon rotation of the shaft in a contrary direction, a second pair of the abutment surfaces engage, and the eccentricities of the weights then are so disposed as to produce a vibratory force of a differing amplitude.
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