Click~Da~Why does a ballpoint pen make two sounds when you press the button?

Audit expert: Cheng Jie

Intermediate Mechanical Engineer, Huaqin Energy Storage Technology Co., Ltd.

You can write right away without having to worry about leakage or the nib drying out. There is no need to grind ink temporarily or use a knife to sharpen the nib. You can even write on the surface of most materials... It has to be said that the emergence of ballpoint pens has brought great convenience to human writing.

After two "clicks" after one press, you can write and draw as you like. But have you ever noticed that a ballpoint pen "beeps" twice when you press it? When you suddenly hear this question, have you already started thinking about it in your brain? Before finally revealing the answer, let's first understand the ballpoint pen, which seems inconspicuous but has a lot of "background".

1

The ballpoint pen was invented by journalists

Before the advent of ballpoint pens, people mainly relied on pens and pencils for writing. However, traditional writing tools also had certain flaws: pens at the time had limited capacity, it took time for the ink to dry, and a lot of ink would leak out during use, making it difficult to clean. Pencils were not only easy to become blunt and break, but the writing was also easy to erase.

"The world has been suffering from the lack of pens for a long time", especially for journalists who need to take shorthand anytime and anywhere. When people wanted to develop a new type of writing tool, the ballpoint pen came into being.

The prototype of the ballpoint pen was developed by American John Lauder in 1888. At that time, in order to make a pen that could write on rough surfaces such as leather, he added a rotating ball to the nib. However, due to the immaturity of the technology, the ball could not rotate flexibly in the nib, making it difficult to write smoothly. Although it could write on leather, it became difficult to write on ordinary paper, and it would leak, so it could not be used on a large scale.

When was the first practical ballpoint pen invented? This is where Biro Laszlo, a Hungarian journalist and inventor of the world's first real ballpoint pen, comes in.

At that time, journalists relied on pen and paper to record news, and it was very difficult to record news with a fountain pen that did not write well and had limited ink. One day, he found that the ink in the printing factory dried quickly, so he had the idea of ​​putting the ink into the pen to write. Thus, Laszlo invented the first ballpoint pen called "oil-soluble pen".

Advertisement for Biro Laszlo and his ballpoint pen

Source: Wikipedia

During World War II, ballpoint pen technology was further improved. The improved ballpoint pen adopted the principle of oil penetration, using oil-soluble pigments as ink. Under the combined effect of atmospheric pressure and ink gravity, the ink in the pen core would flow through the oil pipe to the small steel ball seat at the pen tip, and as the steel ball rolled, it would adhere to the paper.

Close-up of ballpoint pen writing

Source: Wikipedia

Afterwards, he continued to improve the ballpoint pen technology, formed a relatively complete ballpoint pen design, and provided his invention to the British government. The first batch of commercial ballpoint pens thus appeared.

Later, the French stationery company Bic bought the patent for the ballpoint pen and made it more affordable, greatly reducing the cost. The ballpoint pen soon became the mainstream writing tool.

‍2

A small ballpoint pen is actually a big project?

Through the above introduction, everyone should be able to feel that it is not easy for a ballpoint pen to go from "birth" to "growth", right?

Next, let’s take a look at how much technology is contained in this seemingly simple ballpoint pen.

First, let's look at the material composition of the pen tip. With the continuous updating and iteration of technology, the current ballpoint pens are divided into oil-based ballpoint pens and water-based ballpoint pens. The ball of the oil-based ballpoint pen tip is usually made of brass, steel or tungsten carbide; the ball of the water-based ballpoint pen tip is usually made of stainless steel, carbide or aluminum oxide.

Then there is the writing principle of the ballpoint pen: it uses the weight of the ink, and through the movement of the ball in the nib, the ink will flow out of the groove of the ball and then transfer to the surface of the writing medium. This process requires the ball to be stuck in the ball seat, and it will not fall out or sink in, and the ink will not flow freely. At the same time, the durability of the nib must be guaranteed, which is not easy.

Another thing is the manufacturing process of the ballpoint pen. As we all know, the most critical part of a ballpoint pen is the pen tip. After the small pen tip is magnified 15,000 times, you can clearly see that it has a circular step-shaped structure, 5 smooth ink guide grooves distributed at the narrowest part of the top, and a small ball. It is precisely because it can rotate at will that the ballpoint pen can write so smoothly.

Is it really difficult to make a pen tip? Such a small pen tip not only requires more than 20 steps to complete, but the production process is also very complicated.

The pen tip needs a bowl-shaped structure to hold the ball, and the thinnest part of the wall of this bowl-shaped structure is only 0.03 mm, which is equivalent to one-third of an A4 paper, and the precision must reach 0.001 mm; the width of the smooth ink guide groove is only 0.08 mm, and the precision must also reach 0.001 mm. Seeing the terrifying level of precision in the production numbers, you should know how difficult it is to make a pen tip.

Finally, and this is what everyone is most concerned about, why does the pen tip always make two sounds when you press it? This involves another core technology of the ballpoint pen.

When we write with a ballpoint pen, we first press the button. At this time, the push rod and cam are pushed down into the pen barrel, and the top of the cam drops below the fixed stop and maintains contact with the push rod.

Since the upper surface of the cam and the lower surface of the push rod are both inclined surfaces, and the cam is not restricted in the radial direction and can rotate, while the push rod is restricted in rotation by the stopper and can only slide in the axial direction.

Under the action of the axial spring force, the upper surface of the cam slides obliquely upward along the lower surface of the push rod. At the same time, the cam starts to rotate until it hits the surface of the push rod. At this time, the cam rotates 45°, which is a very fast twisting action.

When you release the button again, the spring between the push rod and the plastic pen tube will push the button to the top of the pen, and the lower end of the push rod will leave the cam. The cam will rotate 45 degrees again until it hits the stopper and stops. This is the second press of the pen. Finally, release the button completely, the cam is still locked and cannot move up and down, and you can write.

There is also a "little secret" that you don't know! Press the assembly once and the pen core will rotate 45°, so that the pen tip will not become crooked due to the fixed writing angle.

I heard that we haven't mastered the production technology of pen tips yet? In the past, we knew that the processing precision of pen tip steel is very high, and there are extremely high performance requirements for stainless steel raw materials. It is very difficult to keep the strength of steel in a reasonable range.

It is true, but that is all in the past. Our domestically produced pen tips have already been successfully developed and put into commercial use. From the steel for making the ball to the machine for making ballpoint pens, my country has started from the most basic step by step. After unremitting efforts, the core technology has long been conquered. It is no exaggeration to say that my country not only has the ability to produce qualified pen tips, but also has a world-leading technical level.

Close-up of the pen tip Source: Wikipedia

The small pen tip also has "great wisdom". Do you feel that you have a deeper understanding of ballpoint pens? Hurry up and use the convenient ballpoint pen~

Source: Digital Beijing Science Center