Filling System Histories: Capillary Pens — the Perfect Filler?

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PEN WORLD MagazineThis article is a revised and expanded version of one that first appeared in the February 2015 issue of PEN WORLD magazine.

The ideal fountain pen filling system should be simple, convenient, and free of muss and fuss. That last part is the real kicker — to be entirely free of muss and fuss, the system should be completely automatic: the pen should just suck up the ink all by itself and not require cleaning afterward.

Parker: First Around the Block

In the real world, it turns out that simple outcomes can sometimes require complicated designs. To make something as simple as a completely self-filling, self-cleaning fountain pen was not at all simple. It took the engineers at the Parker Pen Company about ten years and more than a dozen tries to work out the wrinkles and wrap their results into the Parker 61, which Parker introduced in September 1956, in advance of the Christmas season.

The only filling method that can be completely free of operator action must rely on capillary action to draw the liquid ink into very small spaces or passages within the pen’s reservoir. The size of these “voids” must be carefully worked out so that they will release ink when needed while retaining it when the pen is not writing. The earliest Parker patent I have found for a capillary pen is U.S. Patent No 2,462,929, filed by Harlan H. Zodtner on July 17, 1946. Zodtner’s design called for most of the pen’s body to be filled, all the way forward to the underside of the nib, with small spherical beads.

Patent drawing

Zodtner proposed using glass beads 0.6 mm (0.024”) in diameter, shaken and packed gently, then stuck together into a sort of “cartridge” by heating them just barely enough that each bead would fuse with all the other beads it was touching. The cartridge was secured in the pen by a spring-loaded plunger pushing from the back end of the barrel.

Another attempt was Ernst W. Rickmeyer’s U.S. Patent No 2,712,299, proposing a filler cartridge made of sintered metal (metal powder that has been heated and compressed enough to make it coalesce into a porous mass but, like Zodtner’s glass beads, not heated enough to close the voids between particles of the powder).

Frederick R. Wittnebert’s U.S. Patent No 2,522,553 proposed to fill the pen body with long tubes of glass, metal, plastic, or any other suitable material.

Patent drawing

The first glimmering of the design that finally made the grade came with the September 19, 1950, granting of U.S. Patent No 2,522,554, again to Harlan Zodtner, and U.S. Patent No 2,522,555, to Floyd E. Bartell. Both designs used a thin sheet of plastic or metal rolled up with some mechanism to maintain a capillary space between the layers. In Zodtner’s version, the sheet could be slightly corrugated or embossed, perhaps in a pattern like diamond safety tread; or it could be rolled with a layer of fabric whose longitudinal fibers could be gathered at their forward end to serve as the pen’s feed. In Bartell’s version, the sheet was pierced by holes that allowed ink to flow between the layers, while the holes were made by piercing with a sharp, pointed object (not a punch) so that there were rough edges around the holes to maintain the space between layers.

Parker built and tested prototypes of this basic design. With a decorative perforated “grille” under the nib and a similar perforated cover at the back of the pen, air could flow freely. As ink entered the pen, air could leave. As ink was used up, air could replace it. Shown here is one of these prototypes, referred to as the Mark II design. There was no visible joint anywhere along the pen’s body; for filling, the user just dunked the nib end into an ink bottle.

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It became apparent at some point about this time that the capillary material must be scrupulously clean. Any oily residue, even the minute traces of oil from a fingerprint, would make the oily area water repellent and therefore incapable of holding ink.

All the work described so far, along with other experiments that had produced many similar patents, had dealt with the filler only, not with the “no cleaning afterward” problem. (The Mark II prototype still needed to be wiped clean after filling.) For the solution to that problem, we must turn the clock back to April 6, 1938, and shift location to a DuPont laboratory in New Jersey.

Dr. Roy J. Plunkett and his team were working with gases related to fluorocarbon refrigerants when one of their samples polymerized spontaneously into a white, waxy solid to form the material we now know as Teflon. DuPont developed its new material into a real product and started licensing its use in 1946, early in the development of Parker’s capillary pen.

Parker engineers realized that Teflon, which is still recognized as the slipperiest solid on earth, should shed ink the way a duck’s back sheds water. They could not coat the exterior of the pen with Teflon, so they redesigned it slightly to create a joint in the middle so that the back half of the body (the barrel) could be screwed off. They coated the outside surface of their pen’s filler cartridge (which they called the capillary cell) with Teflon, and after some testing they concluded that they had achieved their goal.

The user could unscrew the barrel, stand the pen body in a bottle of ink, and allow the pen to fill itself. The user could give the cell cover a little tap against the rim of the ink bottle, and the excess ink would drop back into the bottle. Screwing the barrel back on completed the process; if a drop or two of ink remained on the Teflon, it was concealed inside the barrel.

On October 24, 1955, all the development and testing came together in a filing by Frederick R. Wittnebert, Raymond L. Spaulding, and Ray A. Lawton. This design, illustrated here by one of the drawings from the patent papers, used the plastic sheet, embossed for layer separation and pierced with neat punched holes to allow ink to travel between layers. The rolled-up sheet was wrapped around a full-length central feed that passed through the center of a Parker 51–style collector to deliver ink to the nib. To keep ink from evaporating too rapidly, the whole was wrapped within a hood, like that of the 51.

To maintain the streamlined appearance of the prototypes, there was a very narrow trim ring between the barrel and the hood; this ring proved disappointingly flimsy, and in 1962 a Mark II version of the 61 appeared with a broader ring that was distinctly decorative.

Patent drawing

One limitation the engineers discovered from their prototypes was that in order to make the pen fill reliably, they had to make the spaces in the capillary material so large that ink could drip from the nib if air was free to enter from the back of the pen. They solved that problem by building a spring-loaded “valve” into the barrel as shown in the drawing above, so that when the pen was assembled, the back end of the capillary cell was sealed.

The wheels of government ground slowly, but on May 3, 1960, U.S. Patent No 2,935,044 finally dropped through the slot. The Parker 61 was official! First Edition pens bore a small medallion below the clip; shown below are a First Edition Mark I pen in Surf Green, a Mark II pen in Vista Blue, and a Mark II Jet Flighter.

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More information about the Parker 61 is contained in Profile: The Parker 61.

Waterman’s Play for the Capillary Market

In the mid-1950s, the L. E. Waterman Company was in its death throes. It stopped producing pens in the United States in 1954, relying on pens made by its French subsidiary, JiF Waterman. The advent of the Parker 61 signaled a “do or die” moment for Waterman, and in little more than the blink of an eye, figuratively speaking, the company had an answer (courtesy of Jif Waterman) in the form of the elegantly metal-capped X-Pen.

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JiF Waterman’s engineers had taken the “quick and dirty” road to a working capillary pen; they had not concerned themselves with the “no cleaning afterward” aspect of Parker’s design, and they had produced a capillary cell by packing the barrel with nothing more exotic than a roll of gauze. The feed design harked back to Harlan Zodtner’s first design for Parker; the gauze material extended all the way forward to the nib. A small piece of a felt-like material completed the path, carrying the ink along the top surface of the hooded nib to the nib slit. This design is clearly shown by the X-Pen demonstrator illustrated below.

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The overall design of the X-Pen is described in French Patent No 1,040,173, issued on May 20, 1953, to Guy-Frédéric Rigondaud.

Patent drawing

Interestingly, although Rigondaud’s patent covers the entire pen, the technology used therein appears also to be covered in the two Zodtner patents described earlier, U.S. Patents Nos 2,462,929 and 2,522,554. The Parker patents were never registered in France, however, and it is possible that Rigondaud read them and derived his design from them.

Like the 61 prototypes, the X-Pen had no visible joint in the barrel, but it did include a clutch ring for Waterman’s Lock-Slip cap clutch system.

The X-Pen worked well, but it was not enough to save L. E. Waterman, and in 1957 the company closed its doors. For several years thereafter, JiF Waterman continued offering the X-Pen in Europe. During the pen’s product life, the company designed several versions, including the metal-capped X-Pen Junior, a plastic-capped economy version, and the stylistically updated Wat and X-Pen Super.

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More information about the X-Pen is contained in Profile: Waterman’s X-Pen.

Enter the British

In the United Kingdom, the Mentmore Manufacturing Company, Ltd, either licensed or stole the technology of the X-Pen. Platignum was a Mentmore sub-brand, and the Platignum 100 (U.S. Patent No 3,116,719, issued on January 9, 1964, to Derrick John Silver) is a virtually exact X-Pen copy. Mentmore, however, provided an improved method of securing the nib by creating a plug, shaped like a short feed, molded with tabs into which the slots on the sides of the nib would fit before being slid into the shell from the front. (In the X-Pen, the nib was merely forced into a slot in the front of the shell, a process that actually damaged the shell slightly. This was a shortcut taken ty Jif Waterman’s engineers; the Rigondaud patent includes such a plug.)

Patent drawing

Shown here is a Platignum 100; this pen’s overall quality is somewhat higher than that of the X-Pen.

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Before developing the Platignum 100, Mentmore had been working on improvements of the basic capillary design as patented by Rigondaud; it appeared that an actual feed, suitably designed (Derrick John Silver’s U.S. Patent No 2,983,254, issued on May 9, 1961), could provide better flow control than the small piece of feltlike material that Rigondaud had specified.

Patent drawing

Perhaps further testing showed that Silver’s feed design was not all it had been thought to be. It does not appear to have made it into any production pen, not even his own design that became the Platignum 100.

The End of the Line

In 1969, Parker introduced the 61 Mark III, identical externally to the Mark II but redesigned internally to use cartridge/converter filling. The capillary experiment was dead; the capillary filler, easy to fill and muss-free though it was, had turned out to require more periodic maintenance than John Q. Public was willing to give it. But it was good while it lasted.


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