Ammunition arrangement

[57] ABSTRACT

A cartridge arrangement having a longitudinally plastically deformably expandable propellant-bumingcontrol cup formed of malleable material, which is initially retained in place to assist in propellant burning and is subsequently forwardly expelled as a function of its longitudinal expansion through reverse bend rolling action.

Claims, 2 Drawing Figures

<img file="US3776136A_D0001.tif" />

PATENTED DEC 41973

3.776,136

<img file="US3776136A_D0002.tif" />

<img file="US3776136A_D0003.tif" />

7/

3,776,136

AMMUNITION ARRANGEMENT

This invention relates to cartridge arrangements, and more particularly to cartridge arrangements employing high-low propellant gas chamber arrangements for initially containing propellant mix within a high pressure zone, to assist in, and control the rate of, burning of the propellant, and subsequently permitting the propellant gases to flow into an enlarged zone at a lower pressure in the course of propulsion of a projectile from the cartridge.

High-low ballistic systems have been employed previously in cartridge arrangements, for the purpose of controlling the burning rate of the propellant. One common prior art arrangement employs a unitary node in the base of the cartridge case, which has rupturable side openings therein forming initially closed gas ports which are subsequently opened by rupturing of a membrane over the gas ports. The burning of the propellant contained within the node is assisted by the initial restraint exerted by the initially substantially totally closed node, such that the gas pressure builds up, prior to rupture, to effect a desired rate and extent of burning of the propellant. The burning rate is controlled by both the initial restraint afforded by the closed gas ports, and by the size of the gas ports through which the gas may pass after rupture of the gas port seals. It will thus be apparent that the initial restraint on the propellant is governed by the strength of the material used to make the gas port seals. Thus, the production of the seal must be closely controlled in order to achieve an acceptable tolerance variation in the velocity of the projectile fired from the cartridge, as between various lots of ammunition. Also, as noted above, another factor controlling the burning characteristic of the propellant of this prior high-low ballistic system, is the size of the gas ports. Several manufacturing processes are normally required to produce a cartridge case, which manufacturing processes are substantially increased due to the requirement for formation of the gas ports. These manufacturing processes include costly machining to maintain required tolerances, particularly of the gas port area. Past experience has indicated that not only must the size of the gas ports be controlled in tolerances, but also the quality of the surface finish in the port area is of substantial importance, and such is conventionally formed by an anodic coating. This anodic coating must be closely controlled in the area of the gas ports, as slight flaws in the coating enable the venting gases to erode the case material, which may conventionally be aluminum or brass, and increases the size of the gas ports, with resulting unpredictable velocity variations for the fired projectile. In addition, due to the substantially high and to some extent unpredictable peak pressures attained in the node of this prior arrangement, several problems have been encountered in retaining a primer plug which is required as an extra part in the base of the case for holding a primer, due to presence of the anode. In order to eliminate these primer plug retention problems, very close tolerance fits must be maintained on both the primer plugs and the primer plug bore in the case, thus requiring further very precise machining operations, all of which are costly and undesirable from a production manufacturing standpoint.

It is an important object and feature of the present invention to provide a high-low ballistic arrangement which enables simplified and less expensive production of the cartridge, and particularly the cartridge case.

It is a further feature to provide a cartridge case arrangement enabling high-low ballistic propellant gas control, and which eliminates the requirement for a side ported node and concomitant plug into which the primer is inserted.

It is a further feature of the invention to provide an improved high-low ballistic cartridge arrangement which utilizes a propellant burning control cup which is longitudinally expandable, to maintain a controlled high pressure retention chamber during initial burning of the propellant, and which is subsequently ejected forwardly from its retained position as a function of its expansion, and without requiring rupture thereof, to thereby enable the propellant gases to flow into a larger chamber area at a lower pressure for propulsion of the projectile from the cartridge.

Still other objects, features and attendant advantages will become apparent to one skilled in the art from a reading of the following detailed description of a preferred embodiment constructed in accordance therewith, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a longitudinal section view of a cartridge according to the invention.

FIG. 2 is a longitudinal section view showing the cartridge of FIG. 1 in the course of firing, the propellant burning control cup being schematically illustrated in its configuration after forward expansion and release from its initially retained position in the cartridge case.

Referring now in detail to the Figures of the drawing, a high-low ballistic cartridge 11 is provided, having a case 21 and a projectile 41. Projectile 41 may be of any suitable or desired configuration and construction, such being illustratively shown as a unitary mass having an ogive shaped forward end 43, with a central annular retention groove 47 which enables retention in the cartridge case 21, as through the crimping of the forward end of the case wall 23 as indicated at 23/. The curved rear end zone 45 of the projectile may be suitably located by a shoulder 23b formed between the enlarged bore 23α of case wall 23 and a further enlarged bore section 23c. |

As noted above, the case wall 23, which is open at its forward end to receive and contain the projectile 41, has a bore 23α, and in addition the base end 25 of case 21 has a reduced diameter bore 25α in which is disposed a propellant burning control cup 31. A primer 61, which may be a conventional percussion primer, is press-fit or otherwise secured in a bore 25b in case base 25, which communicates through a flash ignition passageway 27 with the interior of cup 31. A desired propellant mix 51, which may be of conventional or other desired composition, is contained within the chamber formed by the base end of bore 25α and the cup 31.

Propellant burning control cup 31 takes the form of a plurality of longitudinally extending tube sections 33 and 35, connected through an integral annular reverse bend 34, the inner tube section being closed at its forward end by an integral web section 37. The outer tube section 33 extends forwardly of the base wall 25b and engages with the rear surface 45 of projectile 41. This engagement is advantageously effected in the illustrative embodiment by flaring the forward end of the tube section 33, as indicated at 33α.

3,776,136

The cup 31 is bottomed in bore 25α with its reverse bend 34 engaging with the bottom wall 25c at the end of bore 25α, and the inner tube section 35 may be provided with a sufficient longitudinal extent to contain a desired quantity of propellant mix 51, while the extended length of tube section 33 is sufficient to enable the tube section 35 to be rolled forwardly to an extent sufficient to enable the cup 31 to be released from engagement with the bore 25α prior to engagement of the forwardly movable closed forward end 37 with the projectile 41.

The cup 31 is preferably press-fit, as with a light press-fit, into bore 25α, to provide a full fluid seal in the prefired portion of the cup 31. However, it is feasible, though substantially less desirable, to permit a small tolerance clearance between tube section 33 and bore 25α to enable easier manufacturing, in which event a small leakage of propellant gas will occur past the cup during the high pressure burning phase operation of the cup.

The propellant burning control cup 41 may be formed of various suitable malleable materials, which have the characteristic of affording sufficient stiff columnar compressive strength to enable retention action by the projectile 41 on the tube section 33 during the initial burning of the propellant 51, while enabling plastic cold flow sequential incremental rolling of the tube section 33 through reverse bend 34 and inwardly to form an extension of tube section 35, and being of sufficient rupture strength to enable containment of the gas at the burning pressures without rupture in the course of the forward rolling expansion and subsequent essentially self-release and pressure-responsive forward expulsion of the cup 31. Examples of suitable materials are aluminum, brass, nickel, and steel, although it will be apparent that other materials may also be employed which provide the desired characteristics as noted above, in a particular illustrative embodiment. As an illustration of wall thicknesses for one suitable material, an aluminum cup 31 having a wall thickness of between 0.010 inch and 0.060 inch may be suitably employed, it being apparent that the particular wall thickness for a particular material will be a determining factor for both the column strength of the tube section 33 and the resistance to in-rolling of the tube section 33 through reverse bend 34, and therefore also affects the rate of unrolling for a given propellant burning pressure, thus exerting a control function on the propellant burning rate and peak pressure of the burning propellant 51. The particular choice of materials, thickness of tube section, and size of the chamber formed by the cup 31 may be readily determined for a given required use, as one skilled in the art may find desirable and/or necessary.

In operation, the cartridge 11 may be conventionally chambered and fired in a suitable barrel as indicated in FIG. 2 at 71, as through the medium of a percussion firing pin, not shown. Upon firing of the primer 61, the propellant mix 51 is ignited by flash ignition through passageway 27 from primer 61, and burning of the propellant 51 causes a substantial increase of pressure within the chamber formed by inner tube section 35 and wall 37 of the cup 31. This increase in pressure exerts a corresponding substantial force on the cup walls 35 and 37. However, the mass and inertia of projectile 41, together with the retentive gripping exerted by crimp 23/ and groove 47, prevent the cup 31 from being ejected from bore 25α during the initial burning of the propellant. The propellant gas pressures thus act to enlarge the chamber formed by walls 35 and 37 of the cup 31, this action taking the effect of longitudinally moving the wall 37 forwardly through sequential incremental reverse rolling of the outer tube section 33 through reverse bend 34 and inwardly into and forming an extension of tube section 35, as generally indicated in broken lines in FIG. 1. It will be noted that the primary expansion of this chamber is effected by this longitudinal rolling action, although there is some small lateral expansion effected on the inner tube wall section 35 as schematically illustrated in this Figure as well as in FIG. 2. The propellant burning chamber is thus maintained in a relatively small size, while increasing to a sufficiently small extent as to maintain adequate burning of the propellant for desirably complete propellant combustion. Also, the controlled expansion of this chamber by forward motion of the wall 37 and unrolling of the tube sections 33 and 35 through reverse bend 34, enables the peak pressure within this chamber to be lowered, while still enabling the desired burning of the propellant within a desired restricted small chamber size.

Upon the tube wall sections 33 and 35 being unrolled through reverse bend 34 to an extent that the reverse bend is at the forward end of bore 25α, a communication path is formed between bore 25α and enlarged bore 23α, thereby enabling the propellant gases to escape into this enlarged chamber 24 for direct exertion of gas propulsion pressure on the projectile 41 to effect propulsion of the projectile 41 from the case 21. This generally unrolled and expanded configuration of the cup 31 is indicated in FIG. 2, the general configuration of the sections 33,34 and 35 being indicated at 33', 34' and 35', although it will be appreciated that this illustration is schematic and only for illustrative purposes. Generally, the burning control cup 31 may be expected to be propelled forward with the projectile 41 during the movement of the projectile from the cartridge case 21, although at some point downstream the air resistance will cause the high resistance, low mass tube section 31 to drop away from the projectile 41 and fall to the ground, while the projectile 41 continues toward its target.

While the invention has been illustrated and described with respect to a single illustrative and preferred embodiment, it will be apparent that various modifications and improvements may be made without departing from the scope and spirit of the invention. For instance, while a propellant burning control cup has been illustrated with only two reverse folded generally concentric tube sections and a single interconnection reverse bend, additional reverse folds and interconnecting reverse bends may be employed for a given desired propellant burning control cup embodiment. Also, while a unitary projectile has been illustrated which is in direct contact with the cup 31, different projectiles may be employed, such as multiple projectiles, and/or a sabot may be employed for the projectile or projectiles, in which latter event the sabot may be disposed between the projectile and the propellant burning control cup to effect the desired retention resistance on the cup during initial firing of the cartridge. Accordingly, the invention is not to be limited by the particular illustrative embodiment, but only by the scope of the appended claims.

3,776,136