| 摘要 |
Positioning means include at least two axially elongatable elements (90, 112, 124, 132, 134, 136, 188, 190, 192), pivotably mounted to a support and at least in part pivotably mounted to the element to be positioned. Such elongatable elements may be positioned in one plane to give an X Y-positioning, or in different planes, in which latter case there is preferably a base (180) with a first element (182) pivotable thereon, a second element (186) pivotably mounted to the first element about a pivot axis (at 187) perpendicular to the pivot axis of the first element, and axially elongatable means on the base to move the first and second elements in at least two mutually perpendicular directions. The axially elongatable elements are preferably electrically actuable by having a cylinder with internal screw threading and a piston with external screw threading, and an electric motor to rotate one of these parts so as to vary the length of the element. |
