Patent ID: 8657588

Claim:
A compression apparatus for compressing a fluid, the apparatus having a frame and a motor mounted to the frame, the improvement comprising: a drive mechanism installed on the frame so as to be driven by the motor, wherein the drive mechanism comprises: first and second timing pulleys rotatably mounted in spaced apart relationship on a common side of the frame; a drive pulley installed on a drive shaft of the motor so as to be positioned substantially co-planar with the first and second timing pulleys; and a timing belt configured to engage the drive pulley and the first and second timing pulleys; and at least one piston-cylinder unit operably connected to the drive mechanism, the piston-cylinder unit having: a cylinder; a piston slidably installed within the cylinder, wherein the piston comprises a piston body having at least one through-hole formed therein for communication between a first space below the piston within the cylinder and a second space above the piston within the cylinder; a displacement rod interconnecting the piston and the drive mechanism so as to shift the piston up and down within the cylinder, the displacement rod having: a hollow configuration adapted to receive the fluid into an inner volume of the displacement rod; and an outside diameter relative to the inside diameter of the cylinder such that the ratio of the nominal surface area below the piston to the nominal surface area above the piston is in the range of 1.1 to 20, whereby the displacement rod serves to displace volume within the second space and thereby participate in the compression of the fluid within the at least one piston-cylinder unit; a bottom cap installed on the displacement rod adjacent to the piston and having at least one bottom channel formed therein for >communicating the fluid between the displacement rod and the first space below the piston; a first piston valve installed on the piston for selectively controlling the passage of the fluid between the displacement rod and the first space; and a second piston valve installed on the piston for selectively controlling the passage of the fluid through the at least one through-hole.