Patent ID: 7637395

Claim:
A pump with a pressure driving head, comprising; a retaining tube having two open ends, the retaining tube having a receiving space which a liquid can flow into, a returning element being installed in the receiving space; a movable tube received in the receiving space of the retaining tube, a head extending from a top of the movable tube, the head having an outlet communicated with the movable tube; wherein when a pressure is applied to the head, the movable tube will move axially relative to the retaining tube; and an isolation device tightly slidingly engaged with an inner wall of the receiving space of the retaining tube; an air isolation chamber being formed by the isolation device and the movable tube, wherein when the movable tube is pressed, a part of the liquid in the retaining tube will remain in the air isolation chamber; wherein a negative pressure is formed in the retaining tube to suck liquid from a container when the movable tube and the isolation device are moved upwardly in the retaining tube, the sucked liquid flowing into and filling the air isolation chamber to form an isolation layer and filling a gap between the isolation device and an inner wall of the retaining tube when the movable tube and the isolation device are moved relative to the retaining tube.