| 摘要 |
An air pump for use in combination with a household aquarium, the air pump comprising an electromagnet having an inner iron core, a coil arranged around the inner iron core, and a cylindrical outer iron core arranged around the coil; and a bellows unit having a permanent magnet whose magnetic pole is extended toward the inner iron core but spaced therefrom, and a diaphragm operated by the permanent magnet.
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