| 摘要 |
<p>A drawing board includes at least one arm having a longitudinal channel-like track defined between a pair of spaced apart parallel rails and a third rail parallel to and facing said pair of rails, the rails being disposed in the configuration of an acute angled triangle. A carriage, carrying either a second arm, or carrying a drawing head, adapted to roll along said track includes two pairs of first rollers spaced along the carriage, the rollers of each pair being eccentric and adjustable by rotation to come into operative rolling contact with one of said pair of rails and said third rail respectively. At least one third roller which may also be adjustable by means of an eccentric mounting is mounted on the carriage, preferably between the two pairs of first rollers, so as to roll on the other of said pair of rails, whereby loads on the carriages are distributed on the three rails by the triangular configuration.</p> |
