| 摘要 |
<p>A fast open compass comprises one handle (1), a joint part (8) and two legs (21, 22) connected to the joint part. There is a screw thread between the legs. The screw has left spin screw thread and right spin screw thread. There are nuts (41, 42) on the legs that can be connected to the left spin screw thread and the right spin screw thread, respectively. Thread of the screw (3) is selected in such manner that the coupling between screw and nuts is reversible. The angle of the left spin screw thread and the right spin screw thread of the screw is advantageously 20ˆ¼35°. When legs are been unfold or fold directly, the left spin screw thread (31) and the right spin screw thread of the screw can be unlocked and moved against each respective nuts. This invention uses an adjustable screw between legs with a relatively large rise angle. This make it possible to apply relatively small force to overcome the resistance to pull the screw out of or push it into the nuts straight way. Therefore, a precise and fast positioning is possible.</p> |
