Ammunition and explosives – Cartridges – Shot
Patent
1992-04-01
1993-11-23
Tudor, Harold J.
Ammunition and explosives
Cartridges
Shot
102532, F42B 708
Patent
active
052634175
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
I. Field of the Invention
This invention relates to shot-gun cartridges.
II. Related Art and Other Considerations.
The cartridge illustrated comprises a cylindrical plastics (polyethylene or similar) casing 1 and a brass coated steel-base 2 with retaining rim 3 crimped onto the casing. A percussion actuated primer pad 4 is positioned centrally in the base 2. A base wad 5 being a thick plug of polyethylene or similar is positioned above the primer pad 4. A charge 6 of explosive, typically SANC (small arms nitro compound) is contained in the cartridge above the base wad and a plastics piston-shaped main wad 7, containing the shot pellets 8 is contained in the upper part of the cartridge. The cartridge is completed by a recessed front end closure 9. Thus far described the cartridge is conventional and conventional variations in it may be made.
SUMMARY
The present invention provides a wad for a shot-gun cartridge, the wad having a cup to contain pellets and being molded from a polyolefin-based resin composition. The composition comprises granular starch and is rendered effectively biodegradable by the firing of the cartridge.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially sectioned side view of a shot-gun cartridge.
FIG. 2 is a partially sectioned side view of a cartridge wad.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention is concerned with the construction of the main plastics wad 7 shown in FIG. 2, hereinafter referred to as the cartridge wad.
This cartridge wad 7 in the embodiment being described comprises a cylindrical cup 10, the shot cup, which contains the pellets, a piston head or obturator disc 11 to compress the explosive and an 0 or similar shock absorbing cushioning structure 12 intermediate the shot cup 10 and the obturator 11. The cup, cushion and obturator are formed integrally from a synthetic resin (polyethylene or the like) and the cup and obturator fit the cylindrical interior of the cartridge case.
When the gun is fired the cartridge wad emerges from the barrel with the shot and is propelled some considerable distance forward. Unlike the spent cartridge case, which can be collected by the shooter, a fired wad remains in the environment as litter, undesirable and possibly hazardous.
In accordance with the present invention there is provided a piston-type wad for a shot-gun cartridge having a cup to contain pellets and moulded from a polyolefin-based resin composition, said composition comprising granular starch so as to be rendered effectively biodegradable by firing the cartridge.
Degradable plastics are known and this degradation may be initiated by photo; bio- or other mechanisms. Biodegradability as used in this Specification means that the wad is stable for at least its estimated working life. When discharged into a biologically active environment or biosphere and left biodegradation takes place within an environmentally acceptable period of time.
Starch granules are capable of being injection moulded when in admixture with plastics and starch/plastics formulations perform satisfactorily as cartridge wads. However, to achieve realistically effective biodegradation some other additive, which is initiated in the biosphere, is usually required and to act chemically tend to cause attack on the stable structures of the synthetic resin. Examples of such biodegradable compositions based on synthetic resins and starch are described in U.K. Patent Specification No. 1,485,833 and International Application WO 88/06609. A particularly suitable composition is, however, described in International Application WO 88/09354. This composition comprises a saturated polymer such as polyethylene and a less stable chemically unsaturated polymer or copolymer such as a block copolymer of styrene and butadiene. The composition also includes natural starch or an equivalent vegetable material.
Biodegradable plastics have heretofore been proposed primarily for thin packaging films. In contrast the cartridge wads in accordance with the invention are relatively thick with a w
REFERENCES:
patent: 3363561 (1968-01-01), Irons
patent: 3804019 (1974-04-01), Hurley
patent: 3827363 (1974-08-01), Curran
patent: 4239006 (1980-12-01), Kelson
patent: 5009165 (1991-04-01), Morris
The Kent Cartridge Manufacturing Company Limited
Tudor Harold J.
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