Patent ID: 8147224

Claim:
An air pump, comprising: a one-piece cylinder having a body having a top end, an open bottom end and a chamber defined in the body and having an inner sidewall; a cap formed on the top end and having a through hole defined through the cap; a pedal formed on the bottom end; and a base formed on and closing the open bottom end; and a piston assembly mounted slidably in the chamber and having a rod extending through the through hole in the chamber; a handle mounted on the rod out of the cylinder; and a piston mounted on the rod and hermetically contacting the inner sidewall of the chamber; wherein: the rod has an outer tube mounted through the through hole of the cap, extending slidably in the chamber of the cylinder and having a top end, a bottom end and a central hole defined through the outer tube and having a diameter; and an inner tube mounted in the central hole of the outer tube, having a top end and a bottom end and further having an outer diameter being smaller than the diameter of the central hole; and an outlet channel defined through the inner tube; the handle has an inlet hose defined on the handle and communicating with the central hole of the outer tube; and an outlet hose defined on the handle and communicating with the outlet channel of the inner tube; and the piston divides the chamber into an upper sub chamber and a lower sub chamber, has a top, a bottom and an outer edge and further has an annular groove defined in the outer edge; a radial passage defined radially in the outer edge and selectively communicating with the upper or lower sub chamber; an outlet cavity defined in the piston and communicating with the radial passage and the outlet channel of the inner tube; an inlet cavity defined in the piston and communicating with the central hole of the outer tube; multiple downstroke holes defined through the bottom of the piston and communicating with the inlet cavity and the upper sub chamber; multiple upstroke holes defined through the bottom of the piston and communicating with the inlet cavity and the lower sub chamber; an O-ring mounted in the annular groove, hermetically contacting the inner sidewall of the chamber and selectively abutting the top or bottom of the piston; a downstroke valve resiliently mounted on the top of the piston and selectively opening the downstroke holes; and an upstroke valve resiliently mounted on the bottom of the piston and selectively opening the upstroke holes.