| 摘要 |
<p>A pair of draughtsman's compasses has two arms, one with a drawing point, and one with a spiked point, joined by a hinge at the top. An adjusting bar (3) passes through both arms. One end of the bar has a fine adjusting screw, and the other end is controlled by a quick release device for coarse adjustment. The bar passes through a trunnion (5), and a locking pin (6) passes through it, lower down and at right angles to the bar. This pin has a tapered surface to lock against the bar. It is pushed back by a spring loaded lever (10) down the arm (1) to release it. This action is assisted by an eccentric pin (12) which acts as its hinge.</p> |
