| 摘要 |
This disclosure relates to a multiple head for a remotely controllable plotting device in which a body carries a plurality of pen carriers each of which in turn carries a pen having a tip, each pen carrier including a hollow bobbin of non-magnetic material having an axial bore for movement of a pen therealong in a generally downward advancing direction and an opposite retracting direction, in electromagnetic coil surrounding the bobbin, a first magnetic element movable with the pen axially with respect to the bore, a second magnetic element carrried by the bobbin, at least one of the magnetic elements being a magnet whereby when the coil is energized, it influences the first magnetic element to cause the pen to move in one of the directions depending upon the sense in which the coil is energized, the first and second magnetic elements cooperating to hold the pen in a retracted position, the bore defining an axis and the axes being convergent in a single common point externally of the bobbin such that when any one pen is retracted from a position in which its tip is at the common center, and the other one of the pens can be advanced to a position in which its tip is at precisely the same common point without any movement of the body taking place.
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