Editing Fountain pen (section)

===Self-filling designs===
The Conklin crescent filler, introduced c. 1901, was one of the first mass-produced self-filling pen designs. The crescent-filling system employs an arch-shaped crescent attached to a rigid metal pressure bar, with the crescent portion protruding from the pen through a slot and the pressure bar inside the barrel. A second component, a C-shaped hard rubber lock ring, is located between the crescent and the barrel.<ref>{{cite web|title=Conklin Crescent Fillers|url=http://www.vintagepens.com/Conklin_crescent_fillers.shtml|website=Vintage Pens|access-date=26 July 2016|archive-date=12 August 2016|archive-url=https://web.archive.org/web/20160812093309/http://www.vintagepens.com/Conklin_crescent_fillers.shtml|url-status=live}}</ref> In normal use the ring blocks the crescent from being depressed. To fill the pen, the ring is turned until the gap in the ring is aligned with the crescent, allowing the crescent to be depressed, thus compressing the sac.<ref>{{cite web|title=Conklin – Crescent Filler Collection|url=http://www.conklinpens.com/crescent_filler_collection_page.html|website=Conklin Pens|access-date=26 July 2016|archive-url=https://web.archive.org/web/20160715121244/http://www.conklinpens.com/crescent_filler_collection_page.html|archive-date=15 July 2016|url-status=dead}}</ref>

Many other variations on the basic sac and pressure bar mechanism were introduced in the first decades of the 20th century, such as the coin-filler (with a slot on the barrel, allowing the pressure bar to be depressed by use of a coin), the matchstick-filler (with a round hole, for a matchstick) and the blow-filler (with a hole at the end of the barrel, through which one blew to compress the sac).<ref name="ReferenceA"/>