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Product Development Stories

Vacuum Compartment Structural Design

As of Sep. 2019

Through repeated trial and error,
we created a reliable product that we are truly proud of.

Hideki Yoshida and Masakazu Kano – from the Products Division Refrigeration and Heating Home Appliances Unit Design Department,
Tokyo – are the engineers who invented the first "Vacuum Compartment".

When evaluating how to preserve foods and ingredients so they do not deteriorate, we conceived the idea of creating a vacuum. We were excited by the idea, but the implementation was more challenging – it took trial and error of over a year to create a structure that could withstand a vacuum.

Relentless testing to develop perfection

The first "Vacuum Compartment" we marketed was much bulkier than the current model.
We made the top plate of glass, and added an iron plate to the plastic part to reinforce the strength. This structure weighed a massive 7 kg.
When a vacuum is created in the "Vacuum Compartment", approximately 500 kg of pressure is applied to both top and bottom surfaces of the compartment – enough pressure to damage the compartment made of regular resin materials.

The first "Vacuum Compartment" we marketed in Japan, 2007.

Through repeated trial and error – replacing bulkier with lighter, more durable materials – there were incremental structural and material improvements. Now we have developed a lighter weight yet more durable structure that uses a special high-strength resin. Based on the assumption that the owner uses it for more than 10 years, we have more than adequately cleared the tests by opening and closing it tens of thousands of times to check the durability and quality.

Quality to the finest detail

In order to create a vacuum, it is important to ensure that the compartment is hermetically sealed.
The "Vacuum Compartment" pump is high-performance yet compact. This means that even if there is a slight gap – such as one very thin strand of hair caught in the gasket part of the "Vacuum Compartment" door, the pressure cannot be lowered. Therefore, we carried out repeated trial and error tests to develop the compartment gasket from the viewpoint of maintaining a vacuum.

Quality is seen in every detail, right down to the compartment V-shaped gasket, which is composed of two different thicknesses, the thinner "fin" and the thicker "base". The thinner "fin" shape fits perfectly on the main unit. If the gasket is too thin, even if the performance is good when creating a vacuum, the ability to maintain the vacuum is reduced. In contrast, the door-side of the V-shaped gasket, called the base, is thicker. When the pressure is lowered, the collective thickness of both "fin" and "base" work together to maintain the vacuum.
We can maintain a decompression power with this V-shaped gasket structure to preserve foods freshness longer in a vacuum environment.

Ease of use, and attention right down to the sound…

Also, from the viewpoint of ease of use, it is important that we do not make things difficult for users. So we added a valve to the handle to allow the vacuum to be released in a single action when opening the compartment.

We also paid particular attention to the sound of rushing air when you release the vacuum. This gives you a pleasing sense of the vacuum more than anything else. We created several sounds and tested which would not be harsh when you use it.

Innovation uncompromised

What we value most in our work is that we made a highly-regarded and reliable product without cutting corners. We think this is an inherent characteristic of Hitachi values. We are always conscious of thinking and creating products from the individual's perspective. We persistently ask ourselves what would be comfortable and convenient for us as individuals.

We strongly believe that the "Vacuum Compartment" has an excellent ability to maintain freshness. It is a great pleasure for us as engineers to see if people are satisfied with the "Vacuum Compartment" experience, enjoy its features and love fresh foods ready at their tables anytime.

*Vacuum means the space where the pressure is lower than the atmospheric pressure. The pressure in the Vacuum Compartment is approx. 0.8 atm, which is lower than the atmosphere pressure, so Hitachi calls this a vacuum.

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