Gas operated gun mechanism

Abstract

In a paintball gun mechanism compressed air is admitted through passages ( 16 ) to the interior of the barrel ( 10 ) where it will move forward a hollow bolt ( 11 ) until it can escape through the bolt ( 11 ) to fire a paintball. The bolt ( 11 ) is then moved backward by compressed air in a chamber ( 15 ) until a central formation ( 12 ) of the bolt ( 11 ) enters a guide ( 13 ) to close a firing chamber ( 14 ) behind the bolt ( 11 ). The invention provides a valve member ( 17 ) independent of the bolt ( 11 ) which is biased by a spring ( 18 ) to close off the firing chamber ( 14 ) from the passages ( 16 ) except when displaced by the formation ( 12 ) of the bolt ( 11 ) during a final part of the rearward movement of the bolt ( 11 ).

1 . A gas-operated gun mechanism comprising a bolt which is reciprocable in a barrel between positions opening and closing communication between a source of compressed gas behind the bolt and an interior of the barrel forward of the bolt, thereby in said open position being adapted to expel a paintball from the barrel, communication between the source and the rear of the bolt being through a firing chamber of the barrel behind the bolt, wherein between said source and the rear of the bolt and not connected to the bolt a valve is provided which is biased to a closed position in which it closes communication between said source and the firing chamber but which is displaced by the bolt to an open position during a final part of a movement of the bolt to a closed position of the bolt, thereby re-charging the firing chamber. 
   
   
       2 . A gas-operated gun mechanism as claimed in  claim 1 , wherein the valve is spring biased to the closed position. 
   
   
       3 . A gas-operated gun mechanism as claimed in  claim 1 , wherein the bolt is tubular with a coaxial formation which enters a guide within the barrel when the bolt is retracted, said formation leaving the guide as the bolt reaches a forward, firing position thereby allowing compressed gas from the firing chamber to flow through the bolt. 
   
   
       4 . A gas-operated gun mechanism as claimed in  claim 1 , wherein the bolt is moved forward to firing position by compressed gas from the firing chamber and is retracted from the firing position by admission of compressed gas to an annular chamber between the a periphery of the bolt and the barrel. 
   
   
       5 . A mechanism for a gas-operated gun having a barrel from which a projectile is fireable, the mechanism comprising:
 a bolt;   a sleeve fixedly locatable in the barrel;   a valve assembly; and   and a chamber located between the sleeve and the valve assembly,   wherein: (a) the bolt is reciprocable within the sleeve between a forward firing position and a retracted position, (b) the valve is actuatable to permit communication between a gas source and the chamber when the bolt is in the retracted position but closed to prevent said communication as the bolt moves to the firing position, (c) and the bolt allows secondary communication between the chamber and the barrel, via the sleeve, as the bolt moves to the forward firing position, to fire the projectile located in the barrel of the gun.   
   
   
       6 . A mechanism according to  claim 5 , wherein the valve assembly comprises a forward end which is reciprocable within the sleeve when the bolt alternates between the forward and retracted positions. 
   
   
       7 . A mechanism according to  claim 5 , wherein the valve assembly is spring biased to a closed position.