Air gun

Abstract

A firing mechanism for a compressed gas gun includes a heating chamber attached to a fluid source. Gas or liquified gas from the fluid source is admitted into the heating chamber through a valve, which seals the gas source from the heating chamber thereby preventing back flow of the gas from the heating chamber to the source. A heating element inside the heating chamber is then energized to heat the gas to a temperature and pressure to well above that of the gas source. When a predetermined temperature and pressure is achieved, the heating chamber is exhausted into the breech of the gas gun to expel the projectile.

What is claimed is: 
     
         1 . A firing mechanism for a gun having a gun barrel, the gun barrel having a breech end and a muzzle end, the firing mechanism comprising:
 a heating chamber having an inlet and an outlet, the outlet operatively attached to the breech end of the gun barrel;   a source of working fluid operatively attached to the inlet of the heating chamber;   a heating element disposed within the heating chamber for heating a working fluid within the chamber; and   a discharge valve operatively disposed in the outlet, the discharge valve being operable by a user to release the working fluid from the heating chamber into the breech end of the gun barrel.   
     
     
         2 . The firing mechanism of  claim 1 , further comprising:
 an inlet valve disposed in the inlet of the heating chamber, the inlet valve being operable to seal the heating chamber from the source of working fluid at a predetermined pressure, whereby pressure in the heating chamber can exceed pressure in the source without bleeding heated fluid back to the source.   
     
     
         3 . The firing mechanism of  claim 1 , further comprising:
 a sensor for determining a temperature of the heating element.   
     
     
         4 . The firing mechanism of  claim 3 , wherein:
 the sensor comprises a lux sensor optically coupled to the heating element.   
     
     
         5 . The firing mechanism of  claim 1 , wherein:
 the discharge valve comprises a main poppet valve in combination with a pilot valve, the main poppet valve having a first valve head and a first valve seat,   
     
     
         6 . The firing mechanism of  claim 5 , wherein:
 the pilot valve comprises a poppet valve having a second valve head that is smaller than the first valve head.   
     
     
         7 . The firing mechanism of  claim 5 , wherein:
 the pilot valve is coaxial with the main poppet valve.   
     
     
         8 . The firing mechanism of  claim 5 , further comprising:
 a balance piston disposed within a balance piston chamber, the balance piston having a diameter that is greater than a diameter of the first valve seat, the balance piston operably attached to the main poppet valve to open the main poppet valve when the pilot valve opens admitting pressure into the balance piston chamber.   
     
     
         9 . The firing mechanism of  claim 1 , wherein:
 the source of working fluid is a hand-operated pump.   
     
     
         10 . The firing mechanism of  claim 1 , wherein:
 the working fluid is liquid carbon dioxide.   
     
     
         11 . The firing mechanism of  claim 1 , wherein:
 the heating element comprises an electric heating element.   
     
     
         12 . The firing mechanism of  claim 1 , wherein the inlet valve has a flow area, the firing mechanism further comprising:
 an orifice operably disposed between the inlet valve and the heating chamber for controlling a rate at which fluid flows into the heating chamber, the orifice having a flow area less than that of the inlet valve.