Current drawing and writing implements such as pens and pencils are relatively static devices in relation to the characteristics of the marking that they produce. A pencil, fountain or ball type pen generally has a single marking point which deposits a single color of lead or ink. The marking point of a pen cannot be modified other than by replacement and any modification of the characteristics of markings made rely on the user changing the orientation of the implement, the direction of movement and the force applied to the substrate. Whilst some ball type pens are available with multiple separate cartridges, these merely provide the user with the ability to select a particular color. Because each color is provided by a separate cartridge, there is a limit on the number of colors which may be practically provided.
USPTO Backgrounds
USPTO Backgrounds