| 摘要 |
<p>A dynamic spacing mechanism configured for dynamically changing the spacing between riding modules between S1 and S2. The mechanism comprises a drive screw having a longitudinal axis and being configured for revolving thereabout and for mounting thereon the riding modules so as to allow axial displacement of each of the riding modules along an operative portion of length L of the drive screw; a dynamic guide member extending, at least in part, parallel to and along the drive screw, configured for engaging at least some of the riding modules so as to allow rotational displacement thereof with respect to the drive screw; a restricting arrangement configured for restricting rotational movement of those of the riding modules, which are not engaged with the dynamic guide member, entailing axial movement thereof along the drive screw. The dynamic guide member is configured for displacement parallel to the longitudinal axis to define various positions of the dynamic guide member with respect to the drive screw. In at lease some of the positions, the dynamic guide member has a working portion juxtaposing a part of the operative portion of the drive screw, in which the riding modules have a spacing S2. In the remainder of the operative portion of the drive screw, the riding modules have a second spacing S1 therebetween, the length of the working portion of the dynamic guide member varying with the displacement.</p> |
