Here’s the patent for the usus.pi: WRITING IMPLEMENT FOR AN EXCHANGEABLE WRITING INSERT
Addendum: I’m not sure if this is really the patent for the usus.pi or – in other words – if the exact mechanism of that pen is covered by a patent. – Here’s another patent by Hilmar Nicolay: Writing instrument for writing or drawing has upper and lower parts of shell fixed in position relative to each other by magnetic force (I think this relates to the usus.i).
Do you have this pen? What does the action look like?
No, but it’s cheap on ebay. Assuming it follows the patent closely, it seems to be a hollow hemisphere (“toggle member”) connected to the lever. The refill has a cap with an inclined surface, onto which the hemisphere rolls and by that moves it downwards. The lever is moved past the dead center and thus remains in position.
Others that work similarly:
(Feel free to share more)
That is very cool, I might grab one
Wearever Flipit demonstration
(someone should make one from all metal)
There is one Usus Pi currently on Mercari.
