Improvement relating to projectile cartridge obturators and wads and cartridges employing such

Abstract

An obturator for a projectile cartridge, such as a shotgun cartridge includes multiple seals that serve to prevent gas leakage past the obturator when the cartridge is fired, which in turn ensures more constant firing characteristics from one cartridge to the next. The obturator can be used in place of a powder card in a fibre wad based cartridge or it can be used a component part of a plastic wad in a plastic wad based cartridge, with both applications demonstrating improved gas sealing qualities. An associate method of manufacturing projectile cartridges with more constant ballistic characteristics is also provided.

1 . A projectile cartridge obturator comprising:
 a main body having a first face with a first centrally located projection spaced apart from a first annular skirt portion located on a periphery of the body and a second face with a second centrally located projection spaced apart from a second annular skirt portion located on the periphery of the body;   wherein a free end of each of the first and second annular skirt portions is configured to form a seal with an interior wall of a projectile cartridge case when the obturator is inserted into the case;   wherein the first annular skirt portion is further provided with a secondary seal spaced away from the free end of the first skirt portion and   wherein said secondary seal also is configured to form a seal with the interior wall of the case.   
     
     
         2 . The obturator of  claim 1 , wherein the second annular skirt portion is also provided with a secondary seal spaced away from the free end of second skirt portion, wherein said secondary seal also is configured to form a seal with the interior wall of the case. 
     
     
         3 . The obturator of  claim 1 , further comprising a vent in one or more of the seals formed by the first and second annular skirt portions and the secondary seals. 
     
     
         4 . The obturator of  claim 3 , wherein the vents are provided in adjacent seals and are offset from one another around the periphery of the body of the obturator. 
     
     
         5 . The obturator of  claim 1 , wherein the first centrally located projection comprises cut out regions that define one or more structural ribs. 
     
     
         6 . The obturator of  claim 5 , wherein the second centrally located projection comprises cut out regions that define one or more structural ribs. 
     
     
         7 . The obturator of  claim 1 , wherein the obturator is formed from a biodegradable material. 
     
     
         8 . A projectile cartridge wad comprising the projectile cartridge obturator of  claim 1 . 
     
     
         9 . The wad of  claim 8 , further comprising a fibre plug. 
     
     
         10 . The wad of  claim 8 , further comprising a cushioning structure and a shot cup. 
     
     
         11 . The wad of  claim 10 , wherein the cushioning structure is connected to the second centrally located projection of the obturator. 
     
     
         12 . The projectile cartridge wad of  claim 11 , wherein the obturator, cushioning structure and the shot cup are formed as a single piece. 
     
     
         13 . A projectile cartridge comprising the projectile cartridge obturator of  claim 1  or the wad of  claim 8  received within a case. 
     
     
         14 . A method of manufacturing a projectile cartridge, said method comprising:
 moulding an obturator from a polymer material, said obturator comprising a main body having a first face, with a first centrally located projection spaced apart from a first annular skirt portion located on a periphery of the body, and a second face, with a second centrally located projection spaced apart from a second annular skirt portion located on the periphery of the body, wherein at least the first annular skirt portion is provided with a secondary seal spaced away from a free end of the first annular skirt;   inserting the obturator into a projectile cartridge case between a charge of gunpowder and one or more cartridge projectiles such that the annular skirts and said secondary seal forms a seal with an interior wall of the cartridge case; and   closing the case to encapsulate its contents.   
     
     
         15 . The method of  claim 14 , wherein the second annular skirt portion is also provided with a secondary seal spaced away from a free end of second skirt portion, said secondary seal also configured to form a seal with the interior wall of the case. 
     
     
         16 . The method of  claim 14 , further comprising providing each of the annular skirts and said secondary seal with a vent. 
     
     
         17 . The method of  claim 16 , wherein the vents are provided in adjacent seals and are offset from one another around the periphery of the body. 
     
     
         18 . The method of  claim 14 , wherein the first centrally located projection, and the second centrally located projection, are moulded with cut outs that define one or more structural ribs. 
     
     
         19 . The method of  claim 14 , further comprising providing a fibre plug between the obturator and the cartridge projectile. 
     
     
         20 . The method of  claim 14 , further comprising moulding the obturator as part of a combined wad component that also comprises a cushioning structure and a shot cup, in which the cartridge projectile is received. 
     
     
         21 . The method of  claim 14 , wherein the obturator is moulded from a biodegradable polymer material.