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wrote an article| seven Lords

Today, I tell you a cold but warm knowledge: if there is a sticker at the bottom of the thermos cup, it is recommended that you do not tear it off, otherwise the thermos cup will become a chicken stick.

Recently, a Japanese vacuum cup manufacturer posted on Twitter that the insulation effect may disappear if the sticker at the bottom of the vacuum cup is removed.

The thermos cup has a sticker on the bottom that actually protects it (photo credit: twitter / waheifreiz). He said the sticker is actually called a protective sheet in the industry. If you remove the protective sheet, the thermos cup will lose its insulation.

The sticker at the bottom of the thermos cup is actually a protective patch protecting the exhaust hole left by the tailless technology thermos cup (see below)(Photo source: CN112894109A). Is this sticker or vacuum seal? Is this true?

It's true, the sticker does protect the vacuum. Not only that, but I advise you not to drop the thermos cup with stickers at the bottom. If you drop it, it may leak.

All of this starts with the principle of thermos cups.

(Photo credit: thermos) Insulation is usually achieved by two metal drums separated by vacuum. Vacuum thermal conductivity is very poor, so the liquid in the liner can be kept warm.

So the question arises, how do you create a vacuum between two layers of metal?

If the two layers of metal were directly sleeved together during manufacture, there would be no way to extract the air in the middle. So vacuum must have a leak!

So after vacuumizing, how should this hole be treated to achieve sealing?

There are two schools here.

The old vacuum method is called with tail vacuum. It works by leaving a copper tail at the bottom of the shell to evacuate.

How do you seal it after the tail seal is evacuated?

In fact, it is to bend the copper tail and then seal it, which is similar to making a knot with metal. Obviously, the sealing performance of this method is not good. Thermos, the manufacturer of the thermos cup, introduced in a patent in 2015 that after long-term use of the thermos cup with tail seal, the space between the inner and outer layers of the thermos cup will gradually be filled with gas, no longer vacuum, and the insulation effect will be lost.

To protect the tail, the tail-sealed thermos has a "tail-hiding chamber" at the bottom. However, in this way, the usable volume of the tail-sealed thermos cup will become smaller. So if you buy a thermos cup with a large volume but a small capacity, it is highly probable that it is made with a tail seal, and it will not take long to keep warm.

So what is the new vacuum method?

Now the vacuum cup vacuum practice is called tailless vacuum (tailless vacuum), in short, is_make glass.

Specifically, the tailless vacuum evacuation hole is also in the outer layer, and there is a small glass bead next to the evacuation hole. Before vacuum pumping, the glass bead can move on the pumping hole without affecting the pumping, a bit like the valve core of a bicycle.

Before vacuuming, the tailless vacuum cup has a vacuum hole and glass beads at the bottom (photo credit: youtube / high caliber line). After the liner is fitted into the shell, the vacuum cup is placed in an evacuated furnace and evacuated. After the vacuum is pumped, the glass beads cannot be moved, otherwise they will leak air.

To immobilize the glass beads, the furnace heats up to 500-700 degrees Celsius, melting the glass and sealing the evacuation holes. In this way, the thermos cup will not have a metal tail, so it is called "tailless vacuum," and this technology of sealing by melting glass is also called "fusion sealing" technology.

The process of tailless vacuum cup detection is also very interesting. After being removed from the vacuum furnace, the outside of the cup is heated for 20 seconds, and then the inspector manually touches the inside. If it is hot, it means that the thermal conductivity is very good, that is to say, there is no heat preservation (insulation) effect, and such a cup is a unqualified product.

The final vacuum pumping and sealing steps of the current high-end metal vacuum cups, including stainless steel and titanium vacuum cups, are manufactured using tailless vacuum technology.

Although tailless vacuum insulation effect is better than tailless seal, and the inner container capacity is larger, but it also has many disadvantages.

First of all, the technical term for this glass bead is "glass-based solder." This glass-based solder is more expensive, so the tailless vacuum flask is more expensive than the tailed one.

Secondly, the conductivity of glass-based soldering agent is poor, so when giving the thermos cup "beauty", that is, when doing electrostatic spray technology, there is no way to color the place where the glass bead is located, and it is incompatible with the surroundings. For this reason, tailless vacuum thermos must add a butt plug above the glass beads to fill this "loophole."

Remove the protective sticker, revealing the bottom of the tailless vacuum cup evacuation hole (photo credit: twitter / waheifreiz) Finally, and most importantly, glass is easy to break, so if the tailless vacuum cup accidentally dropped or bumped, the glass bead may break, then the vacuum leaks, and the insulation effect is lost.

Manufacturers also consider these factors, so they will use steel sheets or silicone pads in this place. In order not to appear obtrusive, this protective layer is integrated into the label. This is an important reason why the label at the bottom of the thermos cup cannot be torn off.

I let go and the thermos gasped.

Source: Pickpik

References:

https://docs.qq.com/doc/DVHp4TXJsUmZVdEtn

This article comes from Weixin Official Accounts: Bring Science Home (ID: steamforkids), Author: Everything

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