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<noinclude>{{ReferBox|Filling systems}}</noinclude>The [[lever filler]] is probably the [[filling system]] most common among vintage pens (and has also been used, as a form of revival, by some modern manufacturers). Introduced massively to the market in 1912 by [[Sheaffer]], who has always proclaimed its invention, it has been produced in countless variations and versions, many of which, often technically inferior, have been created only to circumvent the patent ({{Cite patent|US|896861}}) that covered the invention of ''Walter Sheaffer'' that originated in 1908.

<noinclude>{{ReferBox|Filling systems}}</noinclude>The [[lever filler]] is probably the [[filling system]] most common among vintage pens (and has also been used, as a form of revival, by some modern manufacturers). Introduced massively to the market in 1912 by [[Sheaffer]], who has always proclaimed its invention, it has been produced in countless variations and versions, many of which, often technically inferior, have been created only to circumvent the patent ({{Cite patent|US|896861}}) that covered the invention of ''Walter Sheaffer'' that originated in 1908.

[[Image:LeverSchema.svg|center|500px|Diagram of a pen with ''lever filler'']]

[[Image:LeverSchema.svg|center|500px|Diagram of a pen with ''lever filler'']]

In fact, the ancestry of [[Sheaffer]] is seriously under discussion; in fact, there are previous versions of this loading system, a Swedish Johansson patent from 1898 and an American Barnes patent ({{Cite patent|US|726495}}) from 1903, the presence of which has allowed other companies, such as [[Waterman]], to use variants of the same system. However, the success of the system and its enormous diffusion can be attributed to the massive investments of [[Sheaffer]].

In fact, the ancestry of [[Sheaffer]] is seriously under discussion; in fact, there are previous versions of this loading system, a Swedish Johansson patent from 1898 and an American Barnes patent ({{Cite patent|US|726495}}) from 1903, the presence of which has allowed other companies, such as [[Waterman]], to use variants of the same system. However, the success of the system and its enormous diffusion can be attributed to the massive investments of [[Sheaffer]].

In the case of the [[Sheaffer]] patent the mechanism involves the compression of the sac using a lever that press on an elastic metal bar (the so-called ''[[spring bar]]'') shaped like a "J", this one is inserted in the body of the pen with the curved part towards the bottom so as to make to adhere the straight part on the barrel of the pen, in correspondence of the lever. In many cases the pressure on the sac is not directly exerted by the ''[[spring bar]]'' that is hooked to a ''[[pressure bar]]'' which is the one that is pressed against the bag.

In the case of the [[Sheaffer]] patent the mechanism involves the compression of the sac using a lever that press on an elastic metal bar (the so-called ''[[spring bar]]'') shaped like a "J", this one is inserted in the body of the pen with the curved part towards the bottom so as to make to adhere the straight part on the barrel of the pen, in correspondence of the lever. In many cases the pressure on the sac is not directly exerted by the ''[[spring bar]]'' that is hooked to a ''[[pressure bar]]'' which is the one that is pressed against the bag.