Safety filler

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The filling system called safety filler was born as an evolution of the dropper loading system. To simplify the filling operations without having to disassemble and store the section with the nib unit, and to avoid ink leakage as a result of differences in pressure and temperature, in this case the nib is mounted on a mechanism that allows you to retract it inside the body of the pen. From this feature comes also the name of reentrant with which we often identify the pens that use this filling system.

Diagram of a Safety pen

The system involves that, after inserting the nib into the body of the pen, the latter becomes accessible for filling, to be done with the usual eyedropper, and with the same problems (except that of storing the nib group in a safe place) as previously seen. In this case there is less volume available for the ink, as the inside of the barrel is also occupied by the mechanism, but always more than enough. To use the pen, simply reuse the mechanism in reverse to return the nib to the working position, making it come out of the body of the pen.

Once the nib has returned to the inside of the barrel, the pen can be hermetically sealed using a flat-bottomed cap equipped with suitable gaskets that allow it to be totally guaranteed against the leakage of ink, a characteristic to which the name safety is due, with which the pens equipped with this filling system are called. In this case, in fact, there is no possibility that the ink, due to pressure imbalances, can escape from the nib and deposit in the cap, since the latter simply serves as a cap for the barrel; all pressure imbalances are then immediately eliminated when the cap is opened.

This safety feature was a big step forward at a time when ink leaks were very common, and the holding of the caps, often simply locked by pressure on the pen barrel, was very problematic. From this point of view, pens safety remain superior to any modern pen. Moreover, the hermetic closure of the cap, which also includes the nib assembly, allows to reduce to practically zero the possibility of evaporation of the ink, which is very difficult to dry inside the pen, thus allowing the use of inks much thicker than the ordinary ones. For these peculiar characteristics Waterman has continued to produce a line of these pens, aimed at artists and musicians and aviators, until the early '40s.

The charm of this filling system lies in the mechanical complexity of its realization, which often shows the pinnacle of the technologies of the time: in fact, the nib group is generally moved thanks to a helical screw driven by the rotation of the bottom of the pen. In working position it will hermetically close the barrel by means of a gasket, while in rest position it will leave complete access to the inside of the pen.

With these pens it is essential to remember to open the cap always in a vertical position, and never to close it without having first retracted the nib inside the barrel, to avoid damaging the tip. Since this was a common drawback, some models (the first introduction of this innovation is attributed to Montblanc) require the presence of a special safety mechanism (usually a pin mounted in the center of the cap that beats on the nib assembly), which thus prevents it from closing if it has not been completely withdrawn inside the body of the pen.

Il safety filler nasce negli Stati Uniti nell'ultimo decennio del 1800, benché non sia possibile definirne in maniera precisa un inventore, se ne attribuisce se non l'invenzione almeno l'introduzione massiccia sul mercato alla Waterman, che è stato il principale produttore statunitense ad adottarlo su larga scala.[1] Esso però ha avuto un successo molto più grande in Europa, dove all'inizio del secolo praticamente tutti i produttori (ed in particolare quelli tedeschi, fra cui spicca la Kaweco, che ne realizzò anche alcuni sviluppi) facevano uso di questo sistema, e dove è rimasto in produzione molto più a lungo.

Benché lo sia classificato, forse ingiustamente, fra i sistemi di caricamento primitivi, in realtà il safety filler ha resistito sul mercato molto più a lungo di altri sistemi di riempimento creati in periodi successivi. In particolare in Europa si trovano in produzione modelli di serie che lo utilizzano fino a tutti gli anni '20. A causa del suo valore storico, che lo vede essere sostanzialmente il primo sistema meccanico dedicato al riempimento della penna, esso continua a riscuotere un innegabile interesse da parte dei collezionisti, molti dei quali hanno una particolare predilezione per le penne rientranti.

Brevetti correlati

Note

  1. ↑ l'azienda però lo ha fatto utilizzando molti brevetti di Francis C. Brown, della Caw's.
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