The D180 Folding Pen with automatic ink retraction system.
Dan design this pen to be compact for putting in pocket, yet open up to a larger 6" length for convenient writing. When closing the ink automatically retracts. When opening the ink automatically extends. The mechanism using a geared section with over center cam to hold pen in the open or closed position.
The design incorporates 3D printed threads and the rear cap also unscrews to complete the storage capsule.