| 摘要 |
Apparatus including a frame, preferably circular in geometry and having a cental axis. At spaced apart locations about the circumference of the frame there are provided a plurality of links, each of which is pivotally mounted on a the frame and each of which carries a shoe having an arcuate surface. Each link includes at least one leg portion having an outboard end, The outboard ends of the leg portions of the plurality of links are interconnected with one another and with a drive mechansim whose operation serves to rotate the interconnected links in unison about their respective rotational mountings to the frame. As the links are rotated, their respective shoes are caused to move along an arcuate path which repositions the shoes generally radially inwardly or outwardly with respect to the central axis of the apparatus. To retain the circularity of the arcuate surfaces of the shoes as they are moved radially inwardly and outwardly, the shoes are interconnected by respective rigid rods. One end of each rod is fixedly anchored in a slot opening outwardly of one side margin of a first shoe and projects therefrom to have its opposite end slidably received in a second slot in a circumferentially adjacent shoe. The slots and rod share a common longitudinal axis, which axis is oriented normal to a radius of the frame.
|
