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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.

As mentioned above, there are several different versions of this mechanism. For example, [[Waterman]], in order to circumvent [[Sheaffer]]'s patent, introduced, based on Barnes's patent, a lever pivoted directly inside a metal cage that contained the entire mechanism. This in turn was fixed with fins to the pen, using as housing a special slit created in the barrel side.

As mentioned above, there are several different versions of this mechanism. For example, [[Waterman]], in order to circumvent [[Sheaffer]]'s patent, introduced, based on Barnes's patent, a lever pivoted directly inside a metal cage that contained the entire mechanism. This in turn was fixed with fins to the pen, using as housing a special slit created in the barrel side.

A more efficient system, later used by other producers including [[Sheaffer]] itself, requires the lever to be held in place by a metal ring through it. This is inserted inside the pen and maintained in position by means of a special groove, made internally on the barrel in correspondence with the lateral opening from which the lever itself is housed. This system has the considerable advantage of greater mechanical strength, since it does not require drilling holes for the pin in the material of the barrel, which in ebonite pens was often quite fragile.  

A more efficient system, later used by other producers (including [[Sheaffer]], but only after patent expiry), requires the lever to be held in place by a metal ring through it (patent {{Cite patent|US|1292736}}). This is inserted inside the pen and maintained in position by means of a special groove, made internally on the barrel in correspondence with the lateral opening from which the lever itself is housed. This system has the considerable advantage of greater mechanical strength, since it does not require drilling holes for the pin in the material of the barrel, which in ebonite pens was often quite fragile.  

Other variations of the system concern the way in which the lever exerts pressure on the sac: for example the [[Eversharp]] did not use a flexible bar but a flat bar with the sides folded like a "U", anchored on a hook on the bottom of the pen. The lever was equipped on the external end with two tips that went to fit in the rail obtained from the folding of the bar, so as to raise it to the rest position after filling, furthermore to keep the lever locked in the rest position, it was equipped with small protrusions that went to fit into special recesses created in the housing slit.

Other variations of the system concern the way in which the lever exerts pressure on the sac: for example the [[Eversharp]] did not use a flexible bar but a flat bar with the sides folded like a "U", anchored on a hook on the bottom of the pen. The lever was equipped on the external end with two tips that went to fit in the rail obtained from the folding of the bar, so as to raise it to the rest position after filling, furthermore to keep the lever locked in the rest position, it was equipped with small protrusions that went to fit into special recesses created in the housing slit.