Air pump

Abstract

An air pump comprises a main cylinder, a main piston, a piston rod, a linkage, and a pre-charger. The main piston is reciprocably movable within the main cylinder and defines a compression volume between the main piston and a first end of the main cylinder. The piston rod is connected to the main piston and extends along the main cylinder towards a second end. The linkage is configured to move the main piston and to generate pressure in the compression volume during a compression stroke, the linkage having ends pivotably connected to the main cylinder and to the piston rod. The pre-charger has a pre-charger piston movable within a pre-charger cylinder and is connected to the linkage to move within the pre-charger cylinder when the main piston moves within the main cylinder, the pre-charger generating pressure to augment operation of the main piston and main cylinder.

1 . An air pump, comprising:
 a main cylinder having a first end and a second end;   a main piston reciprocably movable within the main cylinder and defining a compression volume within the main cylinder between the main piston and the first end of the main cylinder;   a piston rod connected to the main piston and extending along the main cylinder towards the second end of the main cylinder;   a linkage configured to move the main piston within the main cylinder and to generate pressure in the compression volume during a compression stroke, the linkage having ends pivotably connected to the main cylinder and to the piston rod; and   a pre-charger having a pre-charger piston movable within a pre-charger cylinder, the pre-charger piston being connected to the linkage to move within the pre-charger cylinder when the main piston moves within the main cylinder, the pre-charger generating pressure to augment operation of the main piston and main cylinder.   
     
     
         2 . The air pump of  claim 1 , wherein the pre-charger cylinder is laterally offset from the main cylinder. 
     
     
         3 . The air pump of  claim 1 , wherein the pre-charger piston is configured to have a stroke length less than a stroke length of the main piston. 
     
     
         4 . The air pump of  claim 1 , wherein the pre-charger cylinder is connected to the main cylinder by a valved connection operable to increase pressure in a main cylinder during an upstroke of the main piston. 
     
     
         5 . The air pump of  claim 4 , wherein the valved connection comprises a check valve connected to the first end of the main cylinder. 
     
     
         6 . The air pump of  claim 4 , wherein the valved connection comprises a port in the pre-charger cylinder, a tube connected to the port and extending towards the first end of the main cylinder and check valve connected to the tube and to the main cylinder. 
     
     
         7 . The air pump of  claim 1 , further comprising a pressure relief valve configured to regulate pressure in the pre-charger cylinder. 
     
     
         8 . The air pump of  claim 7 , wherein the pressure relief valve is set to vent excess pressure in the pre-charger cylinder above about two times atmospheric pressure. 
     
     
         9 . The air pump of  claim 7 , wherein the pressure relief valve is set to vent excess pressure in the pre-charger cylinder above about 30 psia. 
     
     
         10 . The air pump of  claim 1 , wherein the pre-charger cylinder comprises a hole through which air is expelled during a downward stroke of the pre-charger piston. 
     
     
         11 . The air pump of  claim 1 , further comprising a check valve configured to transfer atmospheric pressure across the pre-charger piston to replenish the air supply in an upper portion of the pre-charger cylinder. 
     
     
         12 . The air pump of  claim 11 , wherein the check valve comprises an o-ring seal on the pre-charger piston that is movable to open a bypass channel through the pre-charger piston. 
     
     
         13 . The air pump of  claim 12 , wherein pre-charger piston comprises an o-ring groove dimensioned wider than the o-ring, and wherein the o-ring is slidable within the o-ring groove to open the bypass channel on a downward stroke and to close the bypass channel on an upward stroke. 
     
     
         14 . The air pump of  claim 1 , wherein the linkage comprises a handle and the pre-charger comprises a piston rod connected to the pre-charger piston and to the handle. 
     
     
         15 . The air pump of  claim 1 , wherein the pressure in the main cylinder generated by the pre-charger is maintained substantially constant. 
     
     
         16 . The air pump of  claim 1 , wherein the linkage comprises first, second, third and fourth members. 
     
     
         17 . The air pump of  claim 1 , wherein the diameter of the pre-charger cylinder is greater than a diameter of the main cylinder 
     
     
         18 . The air pump of  claim 1 , wherein the air pump is configured as a hand pump.