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Technical Description

Technical Description: Pilot G-2 Retractable Gel Pen

Benjamin Lau

Writing for Engineering

Professor Thomas Collins

The City College of New York

Table of Contents

  • Introduction ———————————————————————- 2
  • Structure ————————————————————————– 2
  • Function ————————————————————————— 6
  • Conclusion ———————————————————————– 10
  • Glossary ————————————————————————– 10
  • References ———————————————————————– 11




From the cuneiforms (Edsitement; “CUNEIFORM Writing”) carved by wedge-shaped styluses to the first feathered quill and ink, writing has always been the best form of communication and recording. With a way to document historic events, people today are able to uncover hidden parts of history to solve mysteries of the past and learn about the cultures of ancient civilizations.  Today, the writing utensils that are most frequently used are pencils and pens, with pens being the more popular. One of the most well known pens is the Pilot G-2, a retractable gel pen with a rubber grip. The invention of the Pilot G-2 dates back into the early 1900s when Ryosuke Namiki founded the Pilot Pen Corporation in 1918 under the name of Namiki Manufacturing Company (Pilot Pen). The company is known for manufacturing and selling maki-e decorated pens and pencils (Britannica). It was not until 1964 when the company completely revolutionizes the fountain pen by creating a pen that allows the ink cartridge to retract into the barrel of the pen. This was a life-changing moment when pens no longer needed a cap, allowing for easy accessibility. Its rubber grip enables better handling, and the gel ink created smoother writing. With such great convenience and ergonomic grip, the Pilot G-2 is definitely an innovation for society. In just several years, the Pilot G-2 pens were put on the market, earning its title as the “#1 Selling Gel Pen” in America during 1997. With a rich and compelling history behind such a revolutionizing device, the pen is definitely a tool worth understanding. Thus, this paper will explore the design and mechanism of the Pilot G2 pen to comprehend its parts and functions.



The Pilot G2 Pen is composed of many parts: a pen nib (the metallic tip), a rubber grip, a pen barrel, a ink cartridge or chamber, a clicking or retractable mechanism, a clip, and a thin, coiled spring.

Figure 1. A labelled diagram of the Pilot G-2 pen showing the ink cartridge, the tip of the pen or nib, the rubber grip, the barrel, the spring, and the fully constructed pen. (This picture is taken from “Roller vs. Ballpoint: What’s the Difference?”)


Parts of the Pen:


  • Pen Nib


    • The pen nib is the metal end of the ink cartridge. It has an opening to allow the ink to exit the cartridge and produce writing on a given surface. Inside the nib is the “ink-feed.” This feed controls ink flow with its combs through capillary action (Richards Pens Website). The combs in Figure 2 draws the ink into small spaces and to allow the ink flow through the nib and onto a surface.

Figure 2. A diagram of the ink feed inside the pen nib. (This picture is taken from “Roller vs. Ballpoint: What’s the Difference?”)


  • Rubber Grip


      • The grip is designed to give the pen’s user a comfortable grip of the pen to allow for easier handling.


  • Pen Barrel


      • The pen barrel consists of two parts: the upper barrel and the lower barrel.
        • The Lower Barrel is a cone-shaped end on the bottom of the pen. On the top of the lower barrel has wedges on the inside, allowing it to be screwed into the pen’s upper barrel to keep the pen’s components inside. It is also there to hold the spring in place when the spring is compressed when the top of the pen is clicked.
        • The Upper Barrel holds the ink cartridge and the retractable mechanism. This barrel has two openings: one on the top for the retractable mechanism, and one on the bottom for the pen nib to eject out of for writing. The top opening has stop members that surround the barrel on the inside. The bottom has wedges for the lower barrel to be screwed into.


  • Ink Cartridge


      • The ink cartridge is a plastic, translucent tube filled with ink. The bottom of the cartridge is the sharp pen nib, and the top is a black cap to close enclose the ink inside the cartridge. The ink can be seen inside the cartridge along with the yellow gel on top. Because it is a gel pen, the Pilot G-2 has the ability to write smoothly like a fountain pen, and has the ability to dry faster like a ballpoint pen (“Roller vs. Ballpoint: What’s the Difference?”). This creates effortless writing or drawing, and less smudges.


  • Retractable Mechanism


      • The retractable mechanism has three parts: a tubular plunger, a cam body, and stop members.


  • The Tubular Plunger is a hollow, plastic tube with a round closing on the top side, and sharp edges along the opening on the bottom. This is the part of the pen that gets pressed in order to push the ink cartridge out of the barrel, and retract the cartridge. The plunger goes on top of the cam body with the sharp teeth connected to the teeth of the cam body, and operates when the round part of the plunger is pressed.
  • The Cam Body is a round, hollow piece of plastic. It has angled teeth surrounding it, and flat openings on both ends. The cam body is used to push the ink cartridge down the barrel and hold it in place when the plunger is pressed, and retracts the cartridge when the plunger is pressed again.
  • The Stop Members are pieces of plastic that are attached around the inside of the pen’s upper barrel. They have angled teeth so that they can keep the cam body in place when pressed, and release the cam body when pressed a second time. The stop members do not move.
  • Clip


      • The plastic clip on the outside of the pen’s upper barrel exists to hold the pen in place inside a person’s pocket. It can also be used to clip onto other flat objects or surfaces when the pen is not in use. The clip is labelled “Pilot G-2 07” with “G-2” meaning its model number, and 07 representing the 0.7mm size pen tip.


  • Coiled Spring


    • The coiled spring is a thin, metal wire that is wrapped around to form a spring. It is there to push the pen’s back into the barrel, allowing it to retract when the pen is clicked.


Because the pen can be disassembled and the ink cartridge can be removed, the Pilot G-2 Pen is refillable by simply buying a new ink cartridge and replacing the old one.

Figure 3. A diagram of the Pilot G-2 fully disassembled and its parts labelled. (This picture is taken from Instructables.com by Chikpeas Brother)


How the Pen Works:

From an outside perspective, using the pen is fairly simple. Simply press the plunger on the top of the pen to push the ink cartridge out of the barrel for writing. This process produces two clicks. To retract the ink cartridge, push the plunger again to retrieve the cartridge when the pen is not in use. These two steps make it easy for the Pilot G-2 to use, and convenient for writing because it is capless. Though the pen is easy to use, the mechanism behind the retractable pen is a little more complicated.


How the Retractable Mechanism Works:


The mechanism can be described in just a few steps (Limer). First, the round end of the plunger is pressed on the top of the pen. This forces the ink cartridge to exit the upper pen barrel and through the opening of the lower pen barrel. This means that the plunger has pushed the cam body past the stop members (Figure 5). At this point, the plunger slides down the angled teeth of the cam body, rotates the cam body, and strikes it to produce a click (Figure 6). At the same time, the spring from the lower barrel of the pen is being compressed, meaning that when the plunger is released, the spring will extend and push the cartridge up. This will therefore push the plunger past the angled tooth of the cam body (Figures 7a and 7b) and allow the cam body to rotate again. When this happens, the cam body strikes the stopper and creates the second click. Now, the cam body is locked in place because of its contact with the stop member, and the ink cartridge is extended for writing.

Next, to retract the cartridge, another press on the top of the plunger is required. With enough force, the push from the plunger will push the cam body past the stop members and release the cam body from its locked position (Figure 8b). By doing so, the cam body will rotate and strike the plunger, producing another click (Figure 8c). Now, the plunger is locked with the cam body. When the plunger is released, the spring, again, pushes the cartridge up, hence pushing up the cam body and the plunger. This will release the plunger and allow it to slide down the angle of the cam body again (Figure 9a). Finally, moving the plunger up enables the cam body to rotate one more time and strike the stop members (Figure 9b). Now, the spring is fully released from its contraction and pushes the cartridge along with the cam body up so that it can be retracted (9c).

Figure 4. This illustration shows two positions that the retractable pen can be in: the retracted position where the cartridge is retracted, and extended position where cartridge is pushed out for writing. The plunger is represented in white, the stop member in blue, the cam body in orange, and the ink cartridge in gray.

Figure 5. The cam body is pushed past the stop member in the pen.

Figure 6. The cam body is being rotated because of the plunger slides down the angled teeth. The area marked A of the cam body hits the plunger on the first press.

Figures 7a and 7b. 7a shows the plunger moving past the cam body and sliding down the angled teeth. 7b shows the plunger almost completely sliding down the cam body, and cam body before striking the stop member.

Figures 8a, 8b, and 8c. 8a shows the pen when the cam body is locked in place and before the plunger is pushed. 8b shows the plunger pushing the cam body past the stop member and releasing the cam body from its locked position. 8c shows the plunger sliding down the angled tooth. Striking the cam body at region B will create a click.

Figures 9a, 9b, and 9c. 9a is when the plunger is released from the cam body. 9b shows the cam body rotating one last time right before it strikes the stop member. 9c shows the ink cartridge fully retracted and the cam body sliding back into its original place.


Writing utensils have come a long way since the first recorded piece of writing was made. Retractable pens today are now ubiquitous, serving the purpose of easy writing and convenient accessibility. The Pilot G-2 in particular has been one of the most popular pens in society. Though it has a simple design and comes with great convenience, the Pilot G-2 retractable gel pen hides a clever engineering design inside it. The pen can retract at a push of a button with the right pieces for the retractable mechanism, allowing for a capless pen, a revolution for the writing world. In addition to its comfortable rubber grip and gel ink, the G-2 is undoubtedly a phenomenal pen that offers easy access, effortless writing, and smooth handwriting. Its cheap pricing from various stores makes the pen the perfect tool at home, the office, or at school. It definitely deserves the name “#1 Selling Gel Pen” of America.


  • Capillary: of or relating to the apparent attraction or repulsion between a liquid and a solid (Dictionary.com)
  • Cartridge: a container that holds certain objects or devices (Merriam-Webster)
  • Cuneiforms: a form of writing that is made of wedge-shaped characters on clay tablets used in writing systems from Mesopotamia, Persia, and Ugarit (Dictionary.com)
  • Maki-e: a technique that uses sprinkled gold or silver powder to coat objects with a brush for decoration (Britannica)
  • Translucent: allowing light to pass through, but objects on the opposite side are not clearly visible (Dictionary.com)


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