5 Fascinating Pen Patents

5 Fascinating Pen Patents

February 25, 2013 - Posted by Lucy to Fun Facts

Pen Patents Article

Ever wonder what FriXion erasable ink is made of? Or why NASA preferred Fisher Space Pens to pencils?

There’s a world of technology hidden inside the deceptively simple surface of your pen. In this article, we’ll take a look at 5 innovative pens and explain how they work. Click through to the patents for even more details and diagrams!


1. Pilot Frixion Erasable Gel Ink Pen

Rubbing the thermo-sensitive FriXion ink with its eraser causes the ink to heat up and become invisible. However, the ink is still there, and extreme cold (-10 degrees Celsius or under) will cause it to reappear.

Pilot FriXion Gel Ink Pen writing sample

The Patent: Paper Mate invented the erase-by-friction ballpoint pen (and the associated special ink formula) in 1979, but Pilot has since improved on the formula in several ways. The most obvious improvements have to do with the eraser and erasing process. Pilot addresses three problems that often arise with erase-by-friction pens:

    1) The eraser rubs off and leaves grit behind
    2) The eraser is too fine and requires too much force to erase
    3) The eraser is too rough and damages paper, rendering it unsuitable for reuse.

The FriXion’s simple rubber eraser creates the perfect amount of friction against paper -- it’s enough to erase the ink easily, but won’t scuff the paper. The secret is that the friction coefficient between the rubber eraser and the paper should be between 0.4 and 0.8. (View Patent)

Gentian Osman's video illustrates what happens when the ink is exposed to heat from a tea kettle, then cold air from a freezer.

Fun Fact: Pilot also has a patent in the works for special erase-by-friction ink that does not re-appear under low temperature conditions. This ink mixture supposedly has “excellent stability” and “vivid hue intensity”, but is not yet approved. (View Patent)

2. Fisher Space Pen

The Fisher Space Pen uses a special pressurized ink cartridge to push its ink out, which allows it to work in extreme temperatures, on airplanes, or in space.

Fisher Space Pen

The Patent: The pressurized ink cartridge would make the pen leak uncontrollably if you used regular ink. The thixotropic ink, which has the consistency of very thick rubber cement, is actually what enables the Space Pen to work properly. It’s a viscous gel at rest, but when you write, the shearing motion from the rolling ball turns it into a liquid. (View Patent)

Fisher Space Pen patent drawing

Fun Fact: There is a famous claim that NASA spent millions of dollars developing a space pen, while the Russians simply used a pencil. In reality, the pencils were somewhat hazardous for several reasons: loose graphite floating in the air could be inhaled or short out electronics, and both the lead and wood of the pencil would burn easily in the oxygen-rich atmosphere of a spacecraft.

NASA never asked Fisher to make the Space Pen, nor did they ever pay him any development costs. Fisher spent over a million dollars trying to perfect the pen, before sending it to the Houston Space Center for testing. The criteria of the test were that the pen: A) Could not burn in a 100% oxygen atmosphere, and B) Must work in a vacuum, with no gravity, and in temperatures ranging from +150 degrees Celsius to -120 degrees Celsius. After it passed, it was used on the Apollo, Shuttle, and ISS missions. Now, modern astronauts have the choice of using a felt tip marker instead.

3. Lamy Dialog 3 Fountain Pen

The fountain pen is retractable; when you twist the pen body to expand, the nib slides out. When the pen body is retracted, a solid ball valve covers the nib opening, creating a protective shell over it that is extremely secure. Other retractable fountain pens have similar mechanisms that protect the nib and seal it off, but they don't feel quite as robust.

Lamy Dialog 3 Fountain Pen

The Patent: The patent for the Lamy Dialog 3 is purely ornamental, meaning that it protects only the appearance of the pen. Jewelry, furniture, computer icons, and fonts can all qualify for an ornamental (or design) patent, as long as it’s new and nonobvious. If you click through to the actual patent, you’ll see that it has a long list of citations. One of these citations is the design for a fountain pen, which relies on another twenty-two inventions for its existence. Despite its deceptively smooth and minimalist design, the Dialog 3 is the culmination of over a hundred different patents! (View Patent)

Lamy Dialog 3 Fountain Pen patent drawing

Fun Fact: The Dialog 3 was designed by award-winning Swiss designer Franco Clivio, who is also listed as the inventor on the patent above. Check out the top view of the fountain pen -- what does it remind you of? If you guessed jet engines, then you guessed right.

4. Field Notes Color Cover Memo Book - Expedition Edition

These sturdy pocket notebooks contain 48 pages of Yupo synthetic paper, which is waterproof, tear-proof, and 100% recyclable. The paper is made primarily from polypropylene film, which is very strong and has excellent ink adhesion.

Field Notes Expedition Memo Book

The Patent: Yupo patented the specific process it uses to manufacture the synthetic paper. Although polypropylene film is the main component, some inorganic fine powders and organic fillers are added to it. The film is stretched biaxially, then layered until it reaches the desired thickness (20 to 350 µm). After stretching, it undergoes a surface oxidation treatment and is coated with an aqueous solution that enhances water resistance. (View Patent)

Field Notes: Extreme Lab Series, Ballistics Test

Fun Fact: In twelve videos called the Extreme Lab Series, Field Notes subjects the Expedition to a series of pass/fail tests. Some are obvious and easy to pass, like the Waterproof Test, but others are more extreme. The notebook is set on fire in the Flame Resistance Test, then gets thrown into a tub of acid (alongside a regular Field Notes Memo Book) in the Acid Resistance Test. What other tests would you like to see? We think Field Notes should try running the Expedition through a laundry machine, or give it to the dog for a thorough chewing session.

5. Sakura Gelly Roll Gel Ink Pens

Creating the perfect formula for metallic and glitter inks is hard. Sakura comes pretty close with pigment inks that shine brightly, have good ink flow, and remain evenly mixed. The secret is a thickening, or thixotropic, agent that increases the overall viscosity of the ink. That way, the aluminum particles used for that metallic sheen won’t sink to the bottom!

Sakura Gelly Roll Gel Ink Pens - 64 Color Set

The Patent: All marker inks must contain a colorant and a solvent in order to write. Gelly Roll ink uses pigments as colorants and water-based solvents as solvents; however, this can pose a problem because pigments tend to separate in the pen body over time. Since the ink is contained in a central core, shaking the pen won’t help to evenly mix the pigments. This causes written marks to have undesirable gradation. In particular, the aluminum particles present in metallic pigments are heavy and tend to settle into a separate later. Sakura solves the problem by adding a thickening agent (such as water soluble resin) to the ink. The thickening agent adjusts the viscosity of the ink so that pigment separation is slowed.

Sakura Gelly Roll Pen writing sample

Since the feeling of “metallic-ness” is increased by the size and presence of aluminum particles, it becomes a balancing act of sorts. Bigger aluminum particles create a nice metallic effect, but can clog the tip. A diameter of 3µm to 7µm is best. Also, despite the nice glittering effect, too many aluminum particles can also inhibit ink flow. (View Patent)

Fun Fact: In the early 1980s, Sakura assembled a team of four technicians to develop a successful gel ink pen. They accumulated more than a thousand materials for creating the perfect gel ink, including grated yam, egg whites, and any jelly-like materials. However, something was missing. One team member recalls scouring newspaper headlines day after day, looking for leads. One day, he came upon an ad in a chemical trade publication for xanthan gum... and the rest was history. Sakura introduced the first ever gel ink pen in 1984, naming it the "Ballsign 280". "Ballsign" was the combination of the words "ballpoint" and "sign". The name "Gelly Roll" wasn't used until 1988, when Sakura started trying to break through to the American market.


Every object has a rich story lurking under the surface. In the past century, we've witnessed the invention of the felt tip marker, erasable ink, synthetic paper, metallic pens, and countless others. Man has gone to the moon, and pens have gone with him. With tons of potential products still marked “patent pending”, the possibilities are endless...

Do you have any ideas for a pen, pencil, or notebook related invention? Share in the comments!

Model Patent
Pilot Frixion Erasable Gel Ink Pens EP1939259A2
Fisher Space Pen Bullet Model Ballpoint Pens 3285228
Lamy Dialog 3 Fountain Pens D633560
Field Notes Color Cover Memo Book - Expedition Edition EP1104702A2
Sakura Gelly Roll Gel Ink Pens EP1411094B1

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