Patent ID: 6371741
Filing Date: 2002-04-16
Classification: F04B

Abstract:
A manual air pump comprising:an outer cylinder comprising a first chamber and including a first end and a second end, a head provided to the second end of the outer cylinder, the head including an outlet passage communicated with the first chamber for supplying air to an object to be inflated, an inner cylinder securely mounted in the first chamber of the outer cylinder and including a first end secured in the second end of the outer cylinder and a second end, the inner cylinder defining a second chamber that is communicated with the outlet passage, a piston rod having a first end with a piston slidably received in the first chamber of the outer cylinder and a second end extended beyond the outer cylinder, the piston separating the first chamber into a first chamber section adjacent to the head and a second chamber section distal to the head, the piston rod defining a third chamber therein, a handle secured to the second end of the piston rod to move therewith, a plug securely mounted to the second end of the inner cylinder and in sliding contact with an inner periphery defining the third chamber of the piston rod, the plug separating the third chamber into a third chamber section distal to the handle and a fourth chamber section adjacent to the handle, the plug having a one-way valve mounted therein such that air is only flowable from the fourth chamber section into the second chamber, means for supplying ambient air into the first chamber section and the fourth chamber section during an outward stroke of the handle away from the head, and a release valve means for optionally communicating the fourth chamber section with outside, whereby reciprocating movement of the handle causes high volume/low pressure inflation when the release valve means is in an inoperative status such that the fourth chamber section is not communicated with outside, and reciprocating movement of the handle causes low volume/high pressure inflation when the release valve means is in an operative status such that the fourth chamber section is communicated with outside.