Draughting instrument mounted on drawing board - has cursor with runners on rollers at each end of guide bar

摘要

The draughting instrument for use on a drawing-board has a cursor with two runners mounted on opposite ends of a guide bar. The latter carries a slide with the instrument proper, typically a head equipped with rules etc. Each runner has a face sliding over the board surface near the edge, and a second one at right angles to it, spring-loaded against the edge. Each runner (12, 13) has one roller, and preferably two (6-9), acting as guide faces. Where there are two rollers, these can each be on opposite sides of the guide bar mountings (22, 23).