Why Piston Fillers?!

Pelikan 101, brown/tortoiseshell, from about 1936

Among the various types of fountain pens available in the market, it is the piston filler that has established itself - at least in Europe - as the measure of all things. This fact naturally gives rise to the question as to which advantages have enabled the piston filler to virtually banish the other systems, above all the sac-type fountain pen, to the sidelines. As was the case with safety and eye-dropper fountain pens, the sac-type fountain pen had specific deficiencies. A new generation of fountain pens was to be developed to iron these out. These pens were to

have an ink capacity similar to that of the safety fountain pen,
have no need of a pipette for filling,
be leakproof even in the case of faulty sealing material, and
be designed so that the nib could not be damaged by the cap under any circumstances.

The principle of the piston filler was known as long ago as the first half of the 19th century. However, all attempts to actually produce one at the time failed due to the excessively basic nature of the mechanics and the low level of machining quality. It was not until 1929 that Firma Günther Wagner (later to become Pelikan) introduced a fountain pen into the market which eliminated precisely these problems by means of a simple but very effective design.

Differential piston mechanism of a Pelikan 100

The heart of the new pen was the mechanism incorporating a "differential piston". Two threads with greatly varying pitches ensure that the mechanism's button only moves very slightly backwards in turning while the piston rod travels far forward. A cork ring ensured the piston's tightness. Since even this seal no longer functioned properly after a certain period of time, the pen was given additional protection against ink leakage. When screwed in, the seat of the piston seal pressed tightly against the mechanism's retainer ("cone"). Equally tightly, the mechanism's button sealed in the retainer from above. As a result, it was not possible for any ink to leak out in the course of normal use. It was only when filling a pen which had become leaky that ink might possibly be squeezed out in the area of the mechanism. The interior of the ink compartment was given a slightly conical structure in order to enable as long a service life as possible for the cork seal. This meant that the piston was given a chance to recover when in screwed-in state. A further step towards improving long-term, leakproof operation was taken by replacing the cork with a black synthetic mass to act as piston head. However, since this material shrank slightly with time, it did not produce any advantages over a cork seal. It was not until 1954 that Pelikan introduced a new, colourless seal made from material which is in many cases capable of staying in perfect working condition for up to 50 years.

The interior of the cap was designed to guide in the shaft in such a way that the nib could not possibly be damaged when the cap was being put on.

Section view of a cap with the front part of a Pelikan 100
fountain pen dating from mid 1933

All these improvements called for a level of precision which was hardly customary in the fountain pen industry of the time. Pelikan employed a production tolerance of max. 1/100mm; this meant that all parts were easily interchangeable and faulty pens could as a rule therefore be repaired at the shop in which they were purchased, thus saving the expense of sending them back to the factory.

Martin Lehmann