| 摘要 |
An apparatus for providing a variable pitch thread includes a hollow cylindrical element configured to provide a plurality of parallel, radially projecting ridges extending circumferentially around the cylindrical element and spaced apart with a given step as measured parallel to a central axis of the cylindrical element. The cylindrical element also featuring a slit extending substantially parallel to the central axis along the length of the cylinder. An actuation mechanism is configured to selectively generate controlled relative displacement between the opposing edges on opposing sides of the slit so as to vary a helical angle of the projecting ridges relative to the central axis. The actuation mechanism is preferably configured to relatively displace the opposing edges such that the plurality of projecting ridges together form alternatively a helical pattern and a pattern of substantially closed rings. |
