Liftable keyboard

A liftable keyboard for a portable electronic device having a top cover and a base with a sensing element, the liftable keyboard comprising:

• a plurality of key units, each of which comprises a keycap and an elastomer aligned with the keycap;
• a membrane switch circuit layer comprising a plurality of gas-inputting ports and a plurality of gas-outputting ports, wherein each of the gas-inputting ports is aligned with the elastomer of the corresponding key unit;
• a plurality of vent valves, each of which is located under the membrane switch circuit layer and aligned with the corresponding key unit, wherein each of the vent valves comprises an inlet, an outlet and a gas exhaust chamber, wherein the inlet is in communication with the corresponding gas-inputting port of the membrane switch circuit layer, and the outlet is in communication with the corresponding gas-outputting port of the membrane switch circuit layer, and wherein each of the gas exhaust chambers of the vent valves is in communication with the gas exhaust chamber of the at least one adjacent vent valve;
• and
• a pump in communication with the gas exhaust chambers of the vent valves,
• wherein when the sensing element within the base of the portable electronic device senses that the top cover is close to the base, the pump is enabled to apply suction to the gas exhaust chambers of the vent valves such that a gas in the elastomer of each key unit is extracted to the gas exhaust chamber of the corresponding vent valve, sequentially passing through the corresponding gas-inputting port of the membrane switch circuit layer and the inlet of the corresponding vent valve, after which the gas is outputted from the outlet of the corresponding vent valve and discharged from the corresponding gas-outputting port of the membrane switch circuit layer, so that the elastomer of each key unit is subjected to compressed deformation and the keycap of each key unit is moved downwardly in response to the compressed deformation of the elastomer, so as to reduce an altitude of each key unit.