Drafting machine with vertical bar to carry straight edges - has endless cable to ensure correct motion, connected to both ends of bar and passing over pulleys

摘要

A drafting machine has a rigid bar (3) to carry the straight edges (2). This rigid bar extends over the height of the drawing board (12) and is mounted on rollers which run on rails fixed to the upper and lower edges of the board. In order to ensure that the bar (3) is always aligned parallel to the side edges of the board (12) the ends of the bar are attached to an endless cable (1). This cable (1) passes around pulleys (2) in such a way that the motion of the lower end of the bar (3) is always the same as that of the upper end.