| 摘要 |
A depression cap comprises a first end and a second end, the second end having a compartment defined therein for engaging with a nose of a bottle. An air pump is provided for drawing air out of the bottle. A pressure-activated switch is provided for controlling on/off of the air pump. The pressure-activated switch is capable of detecting an internal pressure in the bottle. The air pump is turned on when the internal pressure is higher than a predetermined first pressure value. The air pump is turned off when the internal pressure is lower than a predetermined second pressure value that is smaller than the predetermined first pressure value.
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