We had a short discussion with Jim last week on Marketplace about these pens,
and someone has questioned their ink capacity. So I decided to see how much ink they hold.
Surprising it can hold about just a tiny bit less than a M600 piston filler.
Then I realized that I dont know their mechanism. What makes most of these pens are found to be in fully operational condition while the Sheaffers and other vintage plunger fillers always are found almost always in need of repair? First,I went to find the plunger filler patent of Esterbrook. US Patent 2,218,536Filing date: Jan 12, 1939 Issue date: Oct 1940, under the name Henry Clemens Klagges, a man with many Estie patents. There is also US Patent 2,500,833 Filing date: Oct 20, 1944 Issue date: Mar 14, 1950. But the actual design is much simpler.
First of all - it is friction fit... Second it has a sac!... The end of the rod has a disk (presumably with an o-ring (I still dont know how to disassemble the plunger) that slides on the sides of the barrel and created pushed the air in the barrel which compresses the sac and expels the air from inside the sac. Then you wait few seconds and presto. It does not need vacuum grease on the rod - only on the "piston". I need to get a better photo to show the plunger. Maybe next week (Engineering Week ) Till then enjoy another picture. Note the transparent collar on the late style renew point (Medium - no model number)
Filling Instructions from Penhero.com
If you reached this page, chances are that you are interested in the history of fountain pens. Patents offer an interesting insight for the history of our beloved pens. You should consider purchasing George Kovalenko's book on Fountain Pen Patents 1911-1950s. Click here for more information. This is a labor of love and is the most comprehensive collection of pen patents that exists. George works currently on the first volume, which I am waiting anxiously for.