Devices for firing a projectile

Abstract

A housing ( 1; 100, 104, 102 ) of a cartridge for a device for firing a projectile has separate first and second chambers ( 10, 12; 106, 114 ), each of which contains a respective charge ( 34, 36; 108, 110, 116, 120 ) of propellant material. Gas produced by the detonation of one of the charges exits the first chamber to propel the projectile, whilst gas from the detonation of the second charge exist rearwardly from the device so as to counteract recoil. A one way valve may also be provided to help to achieve a high pressure difference between the chambers, where the cartridge has a common igniter assembly.

1 . A cartridge for a device for firing a projectile, the cartridge comprising a housing having first and second chambers, respectively containing first and second charges of propellant material, and each having, when the cartridge is fired, a respective outlet, wherein, in use, the outlet of the first chamber allows the expulsion from the cartridge of gas produced by the detonation of the first propellant charge, so as to fire the projectile, whilst the outlet of the second chamber allows the expulsion from the cartridge of gas produced by the detonation of the second propellant charge, which gas exits the device rearwardly so as to counteract recoil. 
   
   
       2 . A cartridge according to  claim 1 , in which the chambers of the cartridge are situated one in front of the other in the housing, the first chamber being in the front portion of the cartridge, the second in the rear. 
   
   
       3 . A cartridge according to  claim 2 , in which the outlet of the first chamber comprises a port in the front of the cartridge, the outlet of the second chamber comprising a port in the rear of the cartridge. 
   
   
       4 . A cartridge according to  claim 3 , in which the ports are substantially circular, and are coaxial. 
   
   
       5 . A cartridge according to  claim 1  in which the chambers are cylindrical and are coaxial with each other. 
   
   
       6 . A cartridge according to  claim 1 , in which the second charge of propellant is more powerful than the first charge. 
   
   
       7 . A cartridge according to  claim 1 , in which the second chamber is of a larger volume than the first chamber. 
   
   
       8 . A cartridge according to  claim 7 , in which the second chamber has a larger cross-sectional area than the first chamber. 
   
   
       9 . A cartridge according to  claim 1 , in which the propellant material is explosive. 
   
   
       10 . A cartridge according to  claim 1 , in which the two chambers have a common igniter assembly for detonating the propellant charges. 
   
   
       11 . A cartridge according to  claim 10 , in which the igniter assembly comprises an ignition chamber having ignition ports to each of the first and second chambers and containing an initiator charge of explosive material, hot gases produced by the detonation of which pass through the ignition ports to ignite the first and second charges of propellant material. 
   
   
       12 . A cartridge according to  claim 11 , in which the ignition chamber is interposed between said first and second chambers. 
   
   
       13 . A cartridge according to  claim 1 , in which the cartridge housing includes at least one wall or bulkhead separating the two chambers. 
   
   
       14 . A cartridge according to  claim 13 , in which the bulkhead also contains the igniter assembly. 
   
   
       15 . A cartridge according to  claim 1 , in which the second chamber has a portion of reduced cross section adjacent to the outlet of that chamber, the portion acting as a choke which helps to increase the pressure of gases ejected from the second chamber. 
   
   
       16 . A device for firing a projectile, the device comprising a barrel for housing the projectile and for housing a cartridge in accordance with  claim 1 , wherein the barrel has a rear outlet through which said gas from the detonation of the second propulsive charge of such a cartridge is expelled so as to counteract recoil. 
   
   
       17 . A device according to  claim 16 , in which the barrel has a breech module, the rear portion of which is of a larger cross sectional or area than the front portion. 
   
   
       18 . A device according to  claim 16 , in which the rear outlet is connected to a constriction for accelerating the flow of gas from the rear of the device. 
   
   
       19 . A device according to  claim 18 , in which the constriction is a venturi. 
   
   
       20 . A device in accordance with  claim 16  when loaded with the cartridge. 
   
   
       21 . A cartridge according to  claim 2 , in which the cartridge includes a one way valve arranged to allow gases from the igniter assembly to reach, and ignite, the second charge, but subsequently to prevent gases flowing back from the second charge into the first chamber. 
   
   
       22 . A cartridge according to  claim 21 , in which the valve is situated between the igniter assembly and the second chamber and prevents gas reaching the first chamber by blocking the flow of gas from the second chamber to the igniter assembly. 
   
   
       23 . A cartridge accordingly to  claim 22 , in which the valve comprises a ball moveable in a gallery from a position in which it is clear of a passage to the gallery from the igniter assembly and of a passage leading from the gallery to the second chamber into a position in which the ball is urged against a seat to block the first said passage. 
   
   
       24 . A cartridge according to  claim 23 , in which the valve includes a further passage from the gallery to the second chamber, said further passage being so positioned as to convey gas from the second chamber to the ball to urge the latter against its seat. 
   
   
       25 . A cartridge according to  claim 24  in which the further passage, the ball and the passage from the gallery to the igniter assembly are aligned. 
   
   
       26 . A cartridge according to  claim 1 , in which each charge is constituted by a respective pair of charge portions: a fast burning portion and a slow burning portion interposed between the igniter assembly and the fast burning portion.