Image Number 13 for United States Patent #4518972.
A turret head for use in a graphics plotter for holding a plurality of liquid ink pens adjacent the point of writing and for selectively changing the pens to be the writing pen. Automatic pen tip capping and uncapping is included. A plurality of spaced radial arms are mounted on a turret driven by a stepping motor between main positions. A pen holder assembly is mounted for vertical movement between raised and lowered positions and carries a pen gripping arm thereon. The pen gripping arm is adapted to move vertically between the radial arms of the turret and beneath them as the turret is rotated. The arms are provided with facing releasable gripping fingers for exchanging pens between arms upon contact.