| 摘要 |
An apparatus for annotating a workpiece with powder comprises a writing device which outputs a stream of powder and a mechanism such as an X-Y plotter for moving the device and the workpiece relative to one another to shape the annotation. One such writing device comprises a grinding wheel which grinds powder from a stick of chalk, a nozzle aimed at the workpiece, and air moving means for entraining the powder and transporting it through the nozzle. Another such writing device comprises a storage means for the powder, the storage means tapering to form a downwardly sloping guide which collects powder and leads to an outlet, and a gear adjacent the guide having teeth which move the powder along the guide towards the outlet. Both the rate of powder grinding by the first device and the rotational speed of the gear in the latter device are variable in proportion to the writing speed to adjust the output of powder and thereby provide an annotation of generally uniform intensity despite variations in writing speed.
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