US Patent 7181973 Air pump with a manometer received therein

An air pump includes a cylindrical casing, a manometer movably received in the cylindrical casing to be selectively extended out of the cylindrical casing, an air duct securely received in the manometer to be firmly engaged with an inner face defining the reduced bottom opening of the cylindrical casing, a tube to be received inside the manometer, a rod having an annular groove to receive therein a second O ring, a recoil spring mounted outside the manometer. Therefore, when the first O ring is moved upward relative to a downward movement of the manometer to abut a top periphery of the groove, air inside a space defined by the manometer and cylindrical casing is able to flow through a gap between the manometer and the tube and into the air duct via a channel in the rod and into an object to be inflated.