Cartridge Ignition System

Abstract

A rim-fire ignition system in which a ring-type primer is provided in an ular receptacle adjacent the periphery of the rearward end of the large caliber cartridge case. The primer is an annulus of extruded ignition material and preferably includes an extruded aluminum sheath surrounding a fixed core load of priming mixture that can be ignited by an offset firing mechanism. The arrangement assures good quality control of the primer charge weight from cartridge to cartridge.

Description

The invention described herein may be manufactured, used, and licensed by or for the government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to cartridges and, more particularly, to cartridge ignition systems.

Previous endeavors to employ rim-fire cartridges in larger caliber ammunition have presented several problems, notably the difficulty in controlling the weight of the priming mixture that heretofore had filled its cavity via spinning techniques.

It is an object of the invention to provide a large caliber cartridge ignition system which has good quality control of the priming mixture weight.

Another object of the invention is to provide such a system that permits location of the firing pin in any possible axially offset position in the face of the gun breech.

These and other objects, features and advantages will become apparent from the following description and accompanying drawings in which:

FIG. 1 is a longitudinal sectional view of a preferred cartridge ignition arrangement embodying the principles of the invention.

FIG. 2 is an enlarged sectional view of the primer construction in the FIG. 1 arrangement.

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a longitudinal sectional view of a modified cartridge ignition system.

In a preferred cartridge ignition system the cartridge case 10 (FIG. 1) has a closed rearward base or end wall 11, the interior surface 12 of which partially defines the propellant chamber 13 which contains an appropriate munition propellant 14 to fire a projectile (not shown) which is normally secured at the forward end of the cartridge. At a predetermined location in the rearward surface of base 11, preferably adjacent the radial periphery thereof there is provided a rearwardly opening circular groove 16 of substantially rectangular cross-sectional configuration. The base of the groove 16 has an annular rib or protuberance 17 for a purpose to be described. A longitudinal vent passage 18 through the base 11 and rib 17 places the ring-shaped groove 16 in fluid communication with propellant charge 14.

A ring-type primer housing 20 (FIGS. 1, 2), that has a substantially U-shaped cross-section terminating in circular free end portions 21 and 22 (FIGS. 2, 3), press-fittingly receives a predetermined length of extruded primer ignition material 23 which is formed of an extruded aluminum or other metal sheath surrounding a fixed core load of priming mixture 24. The length of primer material 23 is selected so as to substantially fill housing 20 with an annular shaped primer, the cross-section of which is initially substantially circular, with the primer core preferably being of circular cross-section also.

When the primer contained housing 20 is pressed or seated into the base groove 16, the primer annulus 23 is deformed and the primer core is both deformed slightly and sensitized by the annular rib 17 which the primer annulus 23 abuts and preferably surrounds upon deformation. A predeterminedly positioned firing pin mechanism (not shown) can thus penetrate and ignite the primer from an axially offset location, regardless of the rotational position of the cartridge case relative to the barrel or weapon breech. The corresponding diametric dimensions of the primer housing and base groove can be varied, so long as the firing pin is arranged to strike along an axis that contains the primer core.

In the modification of FIG. 4, the cartridge ignition system is substantially limited to a rim-fire functioning. The cartridge case 30 has a ring-shaped receptacle 32 formed at the juncture of the case thin rearward end 31 and the sidewall of the cartridge case. The formed receptacle 32 has a diameter greater than that of the case sidewall such that a predetermined length of primer material 23 can be pressed into or fitted to substantially fill the receptacle 32, prior to loading of the propellant charge 14 and securing a suitable projectile (not shown) in the forward end of the cartridge. An appropriate firing pin mechanism can be positioned to strike a predetermined peripheral wall portion of the thin-walled receptacle 32 to ignite the primer mix core 24 and propellant charge surrounding the primer annulus 23 to rim-fire the round of ammunition.

Various modifications, changes or alterations may be resorted to without departing from the scope of the invention as defined in the appended claims.

Claims

We claim:

1. In a cartridge case having a propellant chamber containing propellant for firing a projectile, said case having a closed rearward end defining a portion of said propellant chamber,

said case rearward end having an annular receptacle, and

a primer annulus of extruded ignition material located in said annular receptacle adjacent a substantially peripheral portion of said case rearward end, said primer annulus including an extruded aluminum sheath surrounding a core of priming mixture,

so constructed and arranged that an offset firing mechanism can ignite said primer annulus.

2. The structure of claim 1 wherein said case rearward end has a rearwardly opening circular groove, the base of said groove having an annular protuberance and a vent passage fluidly communicating said groove with said propellant chamber, and said annular receptacle is a ring-type primer housing containing said primer annulus and seated in said groove with said primer annulus in abutment with said protuberance.

3. The structure of claim 1 wherein said cartridge case includes a sidewall, the annular receptacle is a ring-shaped receptacle at the juncture of said case rearward end and the sidewall of said case, said ring-shaped receptacle having a diameter larger than the diameter of said case sidewall, and said primer annulus being positioned within said ring-shaped receptacle.