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Filling System Histories: Piston Pens

(This page revised June 29, 2021)

Reference Info Index | Glossopedia  ]

This article is an expanded version of a two-part series that originally appeared in the June and August 2017 issues of PEN WORLD Magazine.

From the very beginning of modern writing instrument manufacture until the early years of the twentieth century, almost all fountain pens were eyedropper fillers, even though today’s most popular filling system had been staring inventors in the face for nearly 2,000 years.

That would be the piston filler. But before you go plundering archaeological sites, let me explain: a piston-filling fountain pen is a specialized kind of syringe, a reciprocating pump. The earliest known description of syringes was penned by the first-century Roman encyclopedist Aulus Cornelius Celsus in his medical treatise De Medicina (c. 30 CE).

Piston-filling pens, in which the writer moves the piston forward to eject air and moves it backward to suck in ink, appear to date to the 1850s. The earliest patent I have found for a piston-filling fountain pen is U.S. Patent No 12,301, issued to Newell A. Prince on January 23, 1855.

Patent drawing
Patent drawing

Prince’s Protean Fountain Pen and many of its successors comprised what we today call plunger fillers or syringe fillers, but that’s just a matter of nomenclature; the operating element was a piston moved by hand. Perhaps the best known of these is the version shown here, patented in 1893 (U.S. Patent No 510,145) by the Rev. Woodruff Post, whose surname has become synonymous with the type.

Fountain pen Magnifying glass
Fountain pen Magnifying glass
Fountain pen Magnifying glass

Prince’s pen quickly became popular, but — as often happens — the public’s experience revealed a serious deficiency. When the pen was filled, the piston rod protruded for its full length past the back end of the barrel, making the writing instrument unwieldy (and potentially messy or breakable, or both), and many people would not consider the pen truly portable. On December 25, 1855, Prince received U.S. Patent No 13,995, for a pen whose piston rod could be unscrewed from the piston and carried separately.

Prince’s detachable rod was workable but inconvenient and likely to get lost. Other inventors soon arrived on the scene with improved versions. One of the earliest, the brainchild of Almon F. and C. M. H. Warren, was patented on March 11, 1856 (U.S. Patent No 14,425). As illustrated in the Warrens’ drawing, the rod passed through the piston and was attached by two hooks so that after filling the pen, the user could rotate the rod to detach it from the piston and then push it back down into the barrel without ejecting the ink.

Patent drawing

Dozens of similar designs followed, many apparently intended to do away with the potential for leakage where the rod slid through the center of the piston. For example, Paul E. Wirt’s design (U.S. Patent No 764,652) had a rod that collapsed like a folding carpenter’s rule, and Henry B. Levy’s clever model (U.S. Patent No 819,294) used the pen’s elongated cap for the rod. Most of these designs probably never progressed past the patent stage.

All of the designs with a manually operated rod probably worked more or less, but true convenience took a little longer to get off the ground. In 1888, a German-born Swiss doctor, Adolf Hommel, patented a “reservoir pen” (U.S. Patent No 394,183) that used a screw-driven non-rotating piston. Shown here are the single figure from that patent and one of Hommel’s later pens:


Because it did not provide a continuous flow of ink, Hommel’s pen was not a true fountain pen. It featured a small tube projecting from the forward end of the reservoir and curved upward to touch the underside of the nib. To write, the user turned the piston knob counterclockwise to force a drop of ink down through the tube and onto the nib. Well into the 1920s, cheap Austrian-made pens of this design flooded into the United States; they were made of thin celluloid and marketed under several brand names, including Kosmos, Manos, Standard, Victoria, Yankee, and others. Pictured below is a $1.00 “Victoria Self-Filling Fountain Pen”; this model was of the same general construction as pens offered in the backs of magazines like Popular Mechanics for 25¢, but it was of better quality.

Fountain pen Magnifying glass

A more elegant piston-filling fountain pen had to wait until the new century. On October 30, 1906, Frank O. Ellis patented a design for a piston filler whose rod was a screw (U.S. Patent No 834,373). Ellis’ design still used the rod as part of a push-pull mechanism, but by threading the rod he made it both easy to use and impossible to lose.

Patent drawing

With Ellis’ threaded rod came another possibility, one that was quickly realized: It wasn’t necessary to push or pull the piston; you could simply turn the knob and let the piston screw itself in and out. James P. Morris received notice from the U.S. Patent Office on December 17, 1906, that he had been granted U.S. Patent No 873,769 for his fountain pen design with a piston whose threaded rod was “substantially rectangular in cross-section.” The rod, or piston-screw, passed through a bushing with a rectangular hole that prevented the piston-screw from rotating. At the back end of the pen was a hollow threaded knob. Turning the knob caused the piston-screw to advance or retreat, emptying or filling the barrel accordingly.

Patent drawing

Some of Morris’ competitors did not see the need to add more cost by including a way to keep the piston from rotating; friction between the piston head seal and the barrel ought to do that job, and soon pens appeared without that feature of his patent. Shown here is one of these, a high-quality hard rubber Richter-Leblang pen sold as a souvenir at the San Francisco Panama-Pacific International Exposition in 1915. Richter-Leblang was not a pen manufacturer; it was a corporation founded in 1914 by Henry Kohn, David Richter, and Joseph Leblang to handle pens, novelties, and general merchandise. The company jobbed its products; as shown here, the pens it sold at the exposition (all of them fitted with the same filling system) came from at least two manufacturers.

Fountain pen Magnifying glass
Fountain pen Magnifying glass
Fountain pen Magnifying glass
Fountain pen Magnifying glass

Using a screw to move the piston worked well; but many turns of the knob were required to move the piston far enough to fill the barrel with ink. The solution to this deficiency appeared in the form of a piston-screw with a very long pitch, like the helical cams used in retracting safety pens. U.S. Patent No 894,667, issued on July 28, 1908, to Charles W. Knapp, illustrates the improved design.

Patent drawing

Only one more improvement remained to yield a nearly perfect piston filler. Knapp’s operating knob was attached directly to the piston-screw, and as the piston traveled the length of the barrel, so did the knob, which rode up and down along the outside of the barrel and was therefore essentially a cap on the end opposite the real cap. When the pen was full, the operating knob was fully extended. With the actual cap posted, the pen was insupportably long. The solution took a little while to shake out, but when it did, it was brilliant.

In 1923, Theodor Kovàcs, a Hungarian engineer, invented a piston filler (U.S. Patent No 1,706,616) that was similar to Ellis’ design of a couple decades earlier. It featured a long-pitch piston-screw driving a long-bodied piston like the one Ellis had used, but Kovàcs went a step further. He threaded the outside of the back end of the barrel with an ordinary short-pitch thread and threaded the operating knob internally to match it. Turning the knob turned the piston-screw, driving the piston down, and at the same time screwed the knob a little distance away from the end of the barrel.

Patent drawing

In any fountain pen whose filling mechanism penetrates the barrel, there is a risk of leakage through the aperture required by the filler. Kovàcs’ patent states that one object of his design is to close that aperture when the knob is screwed down; even if the seal does leak, the knob will serve as a blind cap to prevent leakage onto the user’s hands or clothing. Pelikan bought the rights to Kovàcs’ patent in 1925 and two years later hired Kovàcs and another man, Carola Bako, to perfect the design. In 1929 the company introduced its first fountain pen, the Pelikan 100.

Fountain pen Magnifying glass

Although the basic Kovàcs design would proliferate in Europe, it did not initially attain great popularity in the United States. Perhaps because of the post-World War I isolationist mood in America, many German products simply didn’t catch on in the U.S. The concept of the piston filler was too attractive to ignore, however, and on March 28, 1933, Conklin Pen Company engineer Andreas Bienenstein received U.S. Patent No 1,902,811, covering the features of the Nozac piston-filling pen that Conklin had introduced in 1931, illustrated here by a red/silver model featuring Conklin’s elegant Herringbone pattern.

Fountain pen Magnifying glass

Two other patents were issued to Bienenstein on the same day, covering variations that were never produced; these patents served to forestall the development of virtually any piston pen using a similar mechanism. For this or other reasons, the Nozac was the only successful U.S.-made piston pen for more than 70 years. Shown here is a cross-sectional diagram of a Nozac, illustrating the construction of the piston mechanism.

Nozac anatomy

In the Nozac, the operating knob does not move up and down; it is attached directly to the piston-screw and held from longitudinal motion by bronze thrust bearings. Although this design did not include the leakage protection that was a feature of Kovàcs’s design, it was robust and reliable, and the Nozac was the star of Conklin’s line for many years.

(Interestingly, when Aurora of Italy introduced its piston-filling Model 88 in 1948, the new pen had a hexagonal piston rod that was fitted into the pen in the same manner as the hexagonal piston rod in one of Bienenstein’s other patents.)

There have been improvements in piston-filler design since the 1930s; for example, Pelikan’s implementation of the Kovàcs filler evolved to incorporate the rectangular piston-screw that Morris had used, simplifying the design and making it less prone to damage that would allow the piston to rotate.

Several German companies, including Hebborn, Montblanc, Osmia, and Soennecken, patented telescoping piston designs that used three or even four nested tubular piston-screws to allow a longer piston movement (and therefore greater ink capacity) than was possible with the single-screw design. Although this improvement was merely incremental in nature, it is still a fascinating concept.

The first to apply for a patent on a telescoping piston were Heinrich Hebborn and Heinrich Schlicksupp, principals of H. Hebborn & Company, who filed in Germany on June 29, 1935, but did not receive German Patent No 717,288 until January 22, 1942, five and a half years after they received British Patent No 451,168 (July 30, 1936). The Hebborn design is unique in that along with the multipart piston-screw system it also incorporated a mechanism to seal the back end of the barrel when the pen was full, preventing leakage around the piston head from escaping. When the piston is fully retracted, a packing washer (callout c in the drawing) seals against the guide sleeve (callout d), preventing ink from creeping up the outside of the large piston-screw.

Patent drawing

The Hebborn drawing illustrates a three-part piston-screw, and the text of the patent indicates that greater ink capacity can be achieved by using four or even five parts.

Montblanc’s German Patent No 680,292, issued on August 25, 1939, makes a distinction between the most common German design of piston pens, which covered the piston knob with a removable (and losable) blind cap, and the design by Ernst Rösler, Heinrich Schwarting, and Konrad Kressel. The design by Rösler et al. specifies that the piston knob is fully exposed and is decoupled from the operating mechanism, ideally by a friction clutch, when the piston is fully retracted. This simple but clever concept prevents inadvertent squirting of ink should the writer accidentally turn the knob when handling the pen.

Patent drawing

Osmia’s patent had to do with the way the telescoping piston-screws were secured together, and Soennecken’s design used a spring to ensure that the piston would come to rest in the proper position. All of these were merely variants of existing technology; Soennecken’s patent even cited patents from which it had drawn the ideas that it combined in a new way.

There were, however, some attempts at radically new ideas. One that looked interesting at first glance came from Hungarian engineer Gabor Károly Bodó, who produced a design intended to extend the piston’s motion to virtually the entire length of the barrel, thereby dramatically increasing the pen’s ink capacity. Bodó received U.S. Patent No 2,198,756 on April 30, 1940, for his design using a helically wound length of stiff wire as the actuator. The wire passed through a piston made of some unspecified elastomer, which slid along the coils as the knob was turned.

Patent drawing

Bodó also proposed to make the pen barrel out of thin metal instead of thicker resin to increase the ink capacity even further. There were a few obvious problems with his design, however. It required a special nib with a tube (callout 12) sticking up from the breather hole, to aid in the manual expulsion of air as the ink was used up; and the necessarily thin-gauge wire of the helical actuator was likely to be insufficiently strong to avoid kinking. This one never saw the light of day.

Proof that there is someone to overcomplicate anything came in the form of U.S. Patent No 1,865,325. In this design, patented on June 28, 1932, inventor Malcolm MacLeod returned to the hand-operated push-pull technology — but with a twist. He added a rack-and-pinion system of gears so that pulling the operating knob outward would extend the piston to eject air while pushing the knob back to its rest position would retract the piston to fill the pen. (The knob was threaded to provide a secure attachment for the pen’s cap, which could be posted to provide a larger knob for the writer to grasp.) Thus, he kept the overall length of the pen reasonably short during use. There is no evidence that his design was ever produced, either.

Ptent drawing

The most innovative piston designs of recent years have come from the Bexley Pen Company and Montblanc.

In 2011, Bexley began producing the Corona, a pen with a uniquely simple piston filler as shown here. The square piston-screw (callout 1 in the drawing) rides in the square aperture in a collar (callout 2) whose other end is a socket for the operating knob (callout 3), which is internally threaded to match the piston-screw. By making the collar and operating knob of an acetal resin, Bexley eliminated the need for any lubrication.

Bexley patent drawing
Fountain pen Magnifying glass

Also in 2011, Montblanc filed for patent protection for its Heritage 1912 model, illustrated below, which combined a piston filler with the retractable nature of early “safety” pens made by Montblanc and numerous other companies. In this complex mechanism, invented by Stefan Niemeyer and Hendryk Sassenberg, turning the operating knob normally retracts or extends the nib. If the knob is pulled out from the barrel a few millimeters, it disengages from the retracting mechanism and engages with the piston mechanism, which thereupon operates normally as the knob is turned. Pushing the knob back into its rest position restores the retracting function. Shown here is one of the drawings from the American patent for this design, U.S. Patent No 2014/0241783, issued on August 28, 2014.

Patent drawing
Fountain pen Magnifying glass

I made a bold statement at the beginning of this article, saying that the piston is today’s most popular filling system. It’s true. In addition to all the piston-filling pens made by Montblanc, Pelikan, Aurora, Stipula, Bexley, Pilot, and a few others, virtually every cartridge/converter pen comes equipped with a piston converter. U.S. Patent No 3,134,362, issued on May 26, 1964, to Homer T. Green for the Parker 45 pen, includes the piston converter shown here, which is the basis for all modern piston converters.

Patent drawing

Add these all up, and the piston filler is all but ubiquitous. And it only took the better part of a thousand years to get there. For more about the early history of the fountain pen, check out “Who Really Invented the Fountain Pen?”

  1. Celsus, Aulus Cornelius. De Medicina. Ed. W. G. Spencer. Cambridge, MA: Harvard UP, 1938. Many sources cite Heron of Alexandria’s Pneumatica as the earliest source; but the available evidence suggests that Heron (sometimes called “Hero”) lived and wrote a few years later than Celsus.  Return

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