A portable air pump comprising:
- an external tubular body including first and second ends, the external tubular body having an upper cover at the first end, the upper cover comprising a plurality of air inlet holes, the external tubular body further having a bottom cover at the second end of the external tubular body for sealing the second end;
- a barrel comprising first and second ends and an air passage running through the first end to the second end of the barrel in an axis direction;
- a piston mechanism comprising a piston and a check valve, the piston being disposed on the second end of the barrel, a piston ring being engaged with an outer diameter of the piston, the check valve being disposed in between the second end of the barrel and the piston, the piston and the second end of the barrel being disposed inside the external tubular body with the first end of the barrel extending out of the external tubular body, the piston comprising a center hole and at least one through hole formed on a bottom surface, the center hole being in communication with said at least one through hole via a space in the external tubular body between the piston and the bottom cover, the second end of the barrel being received in an end of the center hole of the piston, the center hole of the piston further including an other having an inner diameter, the inner diameter of the other end of the center hole of the piston being smaller than an inner diameter of the end of the center hole of the piston;
- the check valve comprising:
- a check valve seat comprising a stepped tubular body and a central hole, the other end of the center hole of the piston being spaced from the second end of the barrel, the check valve seat completely received in the center hole of the piston, one end of the check valve seat being inserted into the air passage at the second end of the barrel, and an other end of the check valve seat being inserted into the end of the center hole of the piston, the central hole of the check valve seat being in communication with and between the air passage of the barrel and the other end of the center hole of the piston, the other end of the check valve seat having a face abutting an end face of the second end of the barrel, the other end of the check valve seat further having an outer periphery perpendicular to the face of the other end of the check seat and flush with an outer periphery of the second end of the barrel, the piston having an inner periphery engaged with the outer periphery of the second end of the barrel and the outer periphery of the other end of the check valve seat, with the inner periphery of the piston being not in contact with the end face of the second end of the barrel, the end of the check valve seat abutting an inner periphery of the second end of the barrel, and
- a check valve disc disposed inside the stepped tubular body of the check valve seat, the check valve disc being movable between first and second positions in the central hole of the check valve seat, the check valve disc having an outer diameter larger than the inner diameter of the other end of the center hole of the piston, the other end of the center hole of the piston and the central hole of the check valve seat being not closed by the check valve disc when in the first position, the other end of the center hole of the piston being closed by the check valve disc when in the second position, preventing air from flowing through the end of the center hole of the piston to the air passage of the barrel via the central hole of the check valve seat;
- a head comprising an air passage running through a bottom surface and a side surface of the head, the head being disposed at the first end of the barrel, the air passage of the head being connected to the air passage of the barrel;
- and
- a dispensing head disposed at the head and being connected to the air passage of the head,
- wherein as the external tubular body moves in relation to the barrel in a direction away from the head, the check valve disc is in the second position, air flows into the external tubular body through the plurality of air inlet holes of the upper cover and then flows into the space in the external tubular body between the bottom cover and the piston through said at least one through hole of the piston, and
- wherein as the external tubular body moves in relation to the barrel in a direction towards the head, the check valve disc is in the first position, air flows from the space in the external tubular body in a direction away from the bottom cover of the external tubular body into the air passage of the barrel through the center hole of the piston and the central hole of the check valve seat and then flows out from the head and the dispensing head.