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== Breather tube fillers ==

== Breather tube fillers ==

These filling systems have in common the use of the presence of a ''[[breather tube]]'' which allows to perform the refill by repeating several times some mechanical action (different depending on the different filling systems) which allows to create a compression of the air inside the pen tank. The variety of ways in which this compression is carried out has been extremely wide, but in most cases provides some mechanism that acts on a flexible bulb.  

These filling systems have in common the use of the presence of a ''[[breather tube]]'' which allows to perform the refill by repeating several times some mechanical action (different depending on the different filling systems) which allows to create a compression of the air inside the pen tank. The variety of ways in which this compression is carried out has been extremely wide, but in most cases provides some mechanism that acts on a flexible bulb.

The breather tube is inserted in the feeder and kept in a central position with respect to the body of the pen, which normally acts as a tank. During the compression phase, the air in the pen comes out of the blowhole, from which, due to the depression created, the ink that ends up in the tank is loaded; the presence of the blowhole means that the ink loaded is not expelled in the subsequent compression phases, until the entire tank is filled up to the level of the blowhole.

The breather tube is inserted in the feeder and kept in a central position with respect to the body of the pen, which normally acts as a tank. During the compression phase, the air in the pen comes out of the blowhole, from which, due to the depression created, the ink that ends up in the tank is loaded; the presence of the blowhole means that the ink loaded is not expelled in the subsequent compression phases, until the entire tank is filled up to the level of the blowhole.