Patent ID: 7721641

Claim:
An air compression apparatus having a frame and a tank and a motor mounted to the frame, the improvement comprising: a drive mechanism operably connected to the motor; at least one piston assembly operably connected to the drive mechanism and configured to move within a respective cylinder mounted to the frame, the piston assembly comprising: a piston body sealingly and slidably installed within the cylinder so as to form an upper chamber above the piston body and a lower chamber below the piston body, the piston body being further formed with a cavity in communication with at least the lower chamber; a piston rod having a hollow bore communicating between a drive end and a piston end, the drive end being connected to the drive mechanism such that the hollow bore is in communication with ambient air, the piston rod passing through the cylinder and the upper chamber so as to be connected at the opposite piston end to the piston body, the piston rod having at least one opening formed therein substantially at the piston end such that the hollow bore is in communication with the cavity; and a lower piston valve installed on the piston body so as to selectively seal the lower chamber from the cavity; and at least one air line connected between the cylinder and the tank for the passage of compressed air therethrough, whereby upward travel of the piston body as caused by the drive mechanism acting through the piston rod opens the lower piston valve and allows ambient air to be drawn through the hollow bore, the at least one opening, and the cavity into the lower chamber, and whereby downward travel of the piston body as caused by the drive mechanism acting through the piston rod closes the lower piston valve so as to compress the air within the lower chamber.