Patent Publication Number: US-7712465-B2

Title: Valve for gas operated gun

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a valve for a gas operated gun, particularly although not exclusively a paintball gun. Paintball guns are used to fire balls or pellets of paint at other players of military games to mark them as “hit”. 
     In one form of paintball gun compressed gas is released to fire a paint pellet when a valve controlling the gas pathway is struck by a hammer. This rather violent action produces a substantial recoil which can spoil the user&#39;s aim and cause discomfort. It also requires the use of relatively heavy and expensive components, such as the hammer, which will be capable of standing up to the wear and tear involved. 
     A principal object of the present invention is to address this problem. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a valve assembly for a gas operated gun of the kind having a barrel, a trigger, a chamber having an inlet in communication with a source of gas under pressure, an outlet communicating with the barrel and a valve member controlling the outlet biased to the closed position but which is unseated when the trigger is pulled to allow pressurised gas to expel a pellet from the barrel, the valve assembly comprising a piston reciprocable in a bore open at one end to said chamber, the piston having a surface area exposed to the interior of the chamber not greater than the surface area of said valve member exposed to the interior of the chamber and a mechanical connection between the piston and the valve member such that pressurised gas in the chamber acting on the piston will have an unseating influence on the valve member. 
     The said bias of the valve member, which may be provided by a spring, ensures closure of the valve member after the gun has been fired and when there is no substantial gas pressure in the chamber. However with the valve member closed and the chamber pressurised the piston will reduce the force required to unseat the valve member, permitting the use of lighter and cheaper components and avoiding a violent recoil when the gun is fired. 
     Preferably the valve member and piston are at opposite ends of the chamber, the mechanical connection being a rod extending therebetween. In this case the valve member may be biased to the closed position by a spring in said bore acting on the piston. 
     The valve member may have on its face exposed from the chamber a projection which is struck by a hammer when the trigger is pulled. Preferably the hammer moves jointly with a bolt reciprocable in the barrel to select a paintball from a magazine thereof above the barrel, and gas under pressure from said outlet of the chamber may pass through the bolt to expel a selected paintball from the barrel. 
     Preferably the surface area of the piston exposed to the interior of the chamber is less than the surface area of the valve member exposed to the interior of the chamber. The ratio of said surface areas may be in the region of 2:1. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       A preferred embodiment of the present invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which: 
         FIG. 1  is a simplified sectional elevation of a paintball gun showing components in an “at rest” position prior to pulling the trigger, and 
         FIG. 2  is a similar view of the same gun showing components in the positions adopted when the trigger of the gun is pulled. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The paintball gun  10  illustrated has a barrel  11  and a grip  12 . The grip  12  incorporates a trigger (not shown) which, when pulled, opens communication between a detachable canister  13  of compressed air and the barrel  11  to expel a paint ball or pellet  14  from the latter. When the trigger is pulled a hammer  15  is caused to strike a projection  16  from a valve member  17 , unseating the latter so that compressed air can pass from the canister  13  to the barrel  11 . The hammer  15  moves jointly with a hollow bolt  18  reciprocable in the barrel  11 . A magazine  19  for paint pellets is mounted above the barrel  11  so as to release them one at a time into the barrel. As the bolt  18  moves forward it selects the lowermost paint pellet  14  and moves it forward in the barrel, at the same time closing off the opening at the bottom of the magazine  19 . An opening  26  of the bolt lines up with an opening  27  of the chamber  21  so that compressed air from the canister  13  can now blow the selected pellet  14  out of the barrel  11 . 
     As so far described the gun illustrated is conventional. In accordance with the present invention, however, the valve member  17  controls an opening  20  at one end of an elongated chamber  21 . At the other end of the chamber  21  is a tube or cylinder  22  in which a piston  23  is reciprocable. The piston  23  is rigidly connected to the valve member  17  by a rod  24 . The piston  23  (and therefore the valve member  17 ) is under the influence of a compression spring  25  located in the tube  22  which, on the side of the piston  23  remote from the chamber  21 , opens to atmosphere. 
     The surface area of the piston  23  exposed to the interior of the chamber  21  is half the surface area of the valve member  17  exposed to the interior of the chamber  21 . Thus when the projection  16  of the valve member is struck by the hammer  15  air pressure in the chamber  21  acting on the piston  23  helps to unseat the valve member  17 . On the other hand, when the valve member  17  is open there is no excess gas pressure acting on the piston  23  so that even a light compression spring  25  is sufficient to close the valve member  17  when the trigger is released. 
     Without further elaboration of the foregoing will so fully illustrate our invention that others may, by applying current or future knowledge, adapt the same for use under various conditions of service.