Unterdruckfüllung

Unterdruckfüllung, also known as vacuum filling, is a method used to fill reservoirs with liquid by creating a partial vacuum. This technique is commonly employed in fountain pens, but it also finds applications in other areas requiring controlled liquid transfer. The principle relies on atmospheric pressure pushing the liquid into a chamber when the internal pressure is reduced.

In the context of fountain pens, a vacuum filler operates by extending a piston or plunger within the pen's barrel. This action increases the volume of the ink chamber, thereby lowering the internal pressure. When the nib is submerged in ink and the piston is released or retracted, the higher external atmospheric pressure forces the ink to fill the evacuated space. This method allows for a relatively large ink capacity and a clean filling process compared to some other filling systems.

The mechanism can vary. Some vacuum fillers use a simple rod that is pulled out and then pushed back in to expel air, creating the vacuum. Others may feature a more complex mechanism with a spring-loaded plunger. Regardless of the specific design, the core principle remains the same: the differential in pressure between the atmosphere and the reduced pressure within the pen's ink reservoir drives the ink into the pen. This filling method is appreciated for its efficiency and ease of use, making it a popular choice for fountain pen enthusiasts.