Patent ID: 6190142
Filing Date: 2001-02-20
Classification: F04B

Abstract:
A manual air pump comprising:an outer tube including a first end and a second end,an inner tube coaxially mounted in the outer tube and including a first end and a second end, an inner chamber being defined in the inner tube, an outer chamber being defined between the outer tube and the inner tube,a head coupled to the first end of the outer tube and the first end of the inner tube, the head including a main passage communicated with the inner chamber and the outer chamber for supplying air to an object to be inflated,a piston assembly including:an inner piston rod having a first end with an inner piston slidably received in the inner chamber and a second end, the inner piston separating the inner chamber into a first chamber section adjacent to the head and a second chamber section distal to the head,an outer piston rod having a first end with an outer piston slidably received in the outer chamber and a second end, the outer piston separating the outer chamber into a third chamber section adjacent to the head and a fourth chamber section distal to the head, anda handle secured to the second end of the inner piston rod and the second end of the outer piston rod to move therewith,means for supplying ambient air into the second chamber section and the fourth chamber section during an outward stroke of the handle away from the head,a release passage for communicating one of the first chamber section and the third chamber section with environment, andswitchable valve means mounted in the release passage, wherein the release passage is blocked when the switchable valve means is in a first status, and wherein the release passage is opened when the switchable valve means is in a second status such that air is only flowable from said one of the first chamber section and the third chamber section to environment.