WO1995025257A1

WO1995025257A1 - Cartridge with a plurality of primer charges dispensed around the longitudinal axis of the cartridge

Info

Publication number: WO1995025257A1
Application number: PCT/GB1995/000538
Authority: WO
Inventors: James Edward Baxter; Peter Simon Henning
Original assignee: Royal Ordnance Plc; The Secretary Of State For Defence
Priority date: 1994-03-15
Filing date: 1995-03-13
Publication date: 1995-09-21
Also published as: GB9404986D0

Abstract

A round of ammunition (10) having a longitudinal symmetry axis (X), propellant material (14) which operatively causes propulsion of a projectile (12), and primer material positioned proximal one end of the round for igniting the propellant material, said end comprising a percussion cap (30) containing at least some of said primer and being adapted to provide that upon detonation of the percussion cap the resulting ignition is first communicated to propellant which is outwardly positioned relative the longitudinal axis, and from such outward locations (42) flash is directed forwardly and directly into the most forward annular region containing propellant, between the casing (18) of the round and the projectile (12).

Description

TITLE- CARTRIDGE WITH A PLURALITY OF PRIMER CHARGES DISPENSED AROUND THE LONGITUDINAL AXIS OF THE CARTRIDGE

The invention relates to ammunition primers for rounds of ammunition, for example, ammunition suitable for medium calibre weapon systems. More particularly, the invention relates to cased telescoped ammunition rounds.

Rounds of ammunition generally comprises a cartridge case containing propellant, and a projectile. Traditionally, the projectile protrudes from the end of the cartridge case but more recently there have been attempts to develop cased telescoped ammunition wherein the projectile is also housed substantially within the cartridge case. At one end of the round of ammunition there is provided a centrally located percussion cap containing an initiator material. The initiator material is arranged to ignite a primer material which in turn then communicates an ignition medium (for example hot ignition gases, hot particles, flash and/or flame) - hereinafter generally called "flash" - to the propellant thereby to cause ignition thereof which generates high pressure gases thus propelling the projectile away from the cartridge case. In the case of cased telescoped ammunition (CTA) there is a forward annulus of propellant surrounding the projectile which annulus is positioned relatively distant to a centrally and rearwardly located primer. In the particular case of the CTA round there can be difficulties in achieving satisfactory ignition of the propellant due to this arrangement.

The invention seeks to avoid or at least mitigate these and other problems of the prior art.

According to one aspect of the invention there is provided a round of ammunition having a longitudinal axis, a front end and a rear end and comprising: a projectile;

a cartridge case containing propellant material for causing forward propulsion of the projectile;

a priming charge comprising a quantity of primer material for generating an ignition flash capable of igniting the propellant material; and

initiating means for igniting the priming charge; wherein

the projectile is enclosed at least partially within the cartridge case and at least some of the propellant material is contained in a forward annular space located at the front end of the round, between the cartridge case and the projectile;

one or more distinct parts of the priming charge are provided at one or more locations radially outwards of the longitudinal axis; and

means are provided for directing the ignition flash from the priming charge directly at said one or more radially outward locations, forwardly into the propellant material contained in said annular space.

Preferably the round of ammunition includes means for directing the ignition flash substantially parallel to the longitudinal axis from one or more radially outward locations.

Also, the priming charge can comprise a plurality of individual priming charge portions disposed around the longitudinal axis. The priming charge portions can form an annular array. Alternatively, the priming charge can be in the form of an annulus disposed around the longitudinal axis.

The ignition means can comprise a percussion cap which is substantially centrally located at the rear of the round. The round can comprise means such as passageways for communicating an ignition flash from the percussion cap to the radially outwardly located priming charge. The communication means can comprise an axial bore and a plurality of passageways extending radially from the axial bore.

Preferably the portions of priming charge are contained within chambers within the rear end of the round. Each chamber can have an exit hole for communicating ignition of the priming charge in a respective chamber to propellant material. The exit hole can be sealed by a rupturable membrane. The cross-sectional area of the exit hole can be smaller than that of the associated chamber.

Each chamber can have an entry aperture which allows communication of an ignition flash from the initiating means to the priming charge in the chamber. Preferably a communication passageway from the entry aperture to a chamber can be interrupted by means for retaining the priming charge in the chamber but which means allows an ignition flash to pass through the passageway into the chamber. The interruption means can be a lip between the entry aperture and chamber.

Preferably, the rear end of the round comprises a first and second member having cooperating locking means, wherein the second member is detachable from the first and comprises means for retaining the priming charge. A third member housing the initiating means can also be provided, the third and second members comprising cooperating locking means to hold both members in place relative to the first member.

Preferably, the rear end of the round is detachable from the remainder of the round.

Preferably, the round according to any aspect of the invention is a cased telescoped ammunition round. Δ.

Other aspects and features of the invention will be appreciated from the following description and the attached claims.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

FIGURE 1 is a schematic representation in partial section of a CTA round according to the invention;

FIGURE 2 is an enlarged view of the sectional view of the end of the round shown in Figure 1;

FIGURE 3 is perspective view of an unassembled end fitting for a round according to the invention; and

FIGURE 4 is a perspective of the fitting shown in Figure 3 when assembled.

Turning the Figure 1, there is shown a cased telescoped ammunition (CTA) round 10 comprising a projectile 12, such as an armour piercing fin stabilized discard sabot (APFSDS) projectile assembly, and propellant 14. The propellant could be in many forms such as loose powder, granular, or consolidated to a greater or lesser extent or any combination thereof for example. The propellant should not however be fully consolidated i.e. interstices should be present within the propellant, so as to permit flash from the primer to pass forwardly through the propellant, in order to reach the propellant material which is located at the forward end of the round. The projectile 12 comprises a fin section 20, a sabot 22 and an obturator band 24 which holds the sabot 22 together and acts as a gas seal whilst the projectile 12 is being propelled through the bore of a gun or cannon barrel. In this particular example, the CTA round comprises a guide tube 16 which helps align the projectile with the cannon barrel. Round 10 comprising cartridge casing 18 is packed with propellant 14 including the annular volume surrounding the guide tube 16. The rear end of the rube 16 is located against transverse movement within the case by a number of radially directed lugs 17 (eg three in number) and the flash can easily pass longitudinally between the lugs. The tube 16 also preferably has numerous apertures through its tubular wall to facilitate complete and rapid ignition of the propellant material.

In order to fire a round it is necessary for it to comprise an initiating means such as a percussion cap, for example, which is struck thereby to cause a flash (of ignition gases or flame) from a charge within the percussion cap to pass through to a priming charge which itself ignites and causes a flash to pass into the propellant 14. The initiating means could be in many forms such as an electrical initiator or laser initiator for example. Additionally, the initiator need not be centrally located in the end of a round and could for example be an annular percussion device actuated by a hammer which strikes the end of the round at an off-centre position. In this particular example of the invention, a plug 28 is provided with a percussion cap 30 having a first primer chamber containing initiating material or first primer material 34, as shown in Figure 2. The plug 28 forms part of an end fitting or assembly 50, which also includes base member 52 and a disc 40 as described hereinafter.

Once struck, the primer material 34 in the percussion cap 30 causes ignition gases to pass along axial channel 36 and then into radial passageways 38 which communicate with annular recess 44 (which could alternatively be a series of individual apertures for example) in the disc 40 which disc defines a plurality of secondary primer chambers 42 ( see also Figures 3 and 4). Each chamber 42 has an exit hole 48 which enable the ignition gases from primer material contained within the chambers 42 to come into contact with propellant 14. In this way, ignition gases (or flash, as it might also be called) from primer material in the chambers 42 pass directly to propellant 14 at a variety of locations adjacent the end assembly 50.

Of particular relevance is that fact that the primer ignites propellant at a variety of locations and not just centrally substantially near the longitudinal symmetry axis X shown in Figure 2. In this way, it is intended that the propellant burns more evenly and the flash can propagate throughout the propellant 14 to enable more efficient ignition and combustion of propellant packed around the guide tube 16 at the opposite end of the round. It is also important that the flash is directed forwardly and directly into the annular region located at the front end of the round, between the cartridge case 18 and the projectile 12.

Referring again to Figure 2, there is shown an end assembly 50 which comprises a base member 52 having a cannelure 26 which can be used to indicate the initiator end of the round for ammunition handling purposes. The base member 52 can lock with cartridge casing 18 using a friction fit, a screw fit or some other similar attachment mechanism for example, or it could be an integral part of the casing. Chamber disc 40 is screwed into base member 52 in this example using cooperating screw-threading. Primer plug 28 is then also attached to form the complete end fitting 50 since plug 28 screws into disc 40 also by means of cooperating screw-threading. Plug 28 and disc 40 comprise blind holes 32 and 33 respectively which facilitate the assembly of end portion 50 when screwing the respective portions together. Radial passageways 38 in the plug 28 communicate with the chambers 42 through an annular recess 44 to enable the flame from first primer material 34 to ignite the secondary primer material in the chambers 42.

It is found that various features shown in Figure 2 can be varied to optimise the performance characteristics of a round of ammunition. For example, a restrictive lip 46 is preferably placed between the annular recess 44 and chamber 42 thereby to retain primer within chamber 42. However, a narrow passage 54 remains between recess or entry aperture 44 and chamber 42 in order to enable a flame to pass into primer contained within the chamber. The gap could, for example, be of the order of 0.1 to 0.2mm in height (as viewed in orientation of Figure 2), depending on the nature of the primer material.

Each chamber 42 is provided with an aperture 48 for the exit of primer flash in a generally forward axial direction. It is important that the apertures 48 direct the primer flash directly (ie without reflection or deflection resulting from interaction with any component other than the propellant itself), into the forward annular region which contains propellant material and is located at the front end of the round, between the casing 18 and the projectile 12. It has been found by the Applicant to be most important to avoid such refleciton or deflection, since it can lead to undesirable propellant burning charateristics. For good performance, the entire body of propellant should be ignited symmetrically and at substantially the same instant so far as possible, and this is thought to be the reason why it is important that the flash reaches the aforesaid forward annular region directly. Any reflection may lead to undersirable interference between the direct and reflected flash or pressure waves generated thereby.

For a medium calibre round of say 45mm, an optimum size for each exit aperture 48 is found to be in the order of 3 to 4mm when using a total of, say, 9 chambers in an annular array. Each chamber might be 10mm in diameter and contain an approximately equal proportion of a total of say, approximately 4 grams of primer material, such gun powder or other known materials for example, shared between all chambers. These values would be optimal for a 45mm CTA when using a 9 chamber array, however, the exit bore could be in the range of say 1 to 10mm and the total amount of primer could be between 2 and 10 grams, for example for medium calibre rounds (or between 1 to 20 grams , for different calibres). The round could be modified to suit the smallest calibre pistols to the largest guns, such as 120mm calibre guns for example, with appropriate modification of the design of the round. It will be appreciated that any number of secondary primer chambers could be used. Also, the diameter, or size of exit bore could range from about 1mm upwards, including the size of the secondary primer chamber, depending on materials being used and the calibre of the round of example.

Preferably, the exit bores 48 are each sealed with a rupturable membrane 56 which upon detonation of primer contained within a chamber 42, bursts thereby enabling a flame to pass into propellant 14.

It is also envisaged that the axial channel 36, or radial passageways 38 or entry apertures 44 might themselves contain some primer compound to enable the flame to pass from the percussion primer to the secondary primer which in turn causes ignition of the propellant. At least some of the exit apertures 48 from the chambers 42 should direct a flame axially along the longitudinal direction of the round thereby to assist in igniting the forwardmost propellant in the round. It is envisaged however that more than one aperture 48 might be provided per chamber and that one or more of the exit apertures might not be axially aligned, i.e. such that they instead direct gases from the primer chamber at an angle to the longitudinal axis of the round. The arrangement should, however, preferably be symmetrical so as to avoid asymmetric ignition of the propellant material.

In alternative arrangements, the annular array of chambers 42 may comprise either more or less than nine of the chambers 42. In another alternative arrangement, the array of chambers 42 may be replaced by a single annular chamber. In this case the annular chamber might communicate with the propellant 14 through a plurality of forwardly directed apertures, comparable to the apertures 48, preferably dispersed evenly around the annular chamber.

It is possible to use ignition pellets rather than loose powder for the primer substance. Indeed, the primer could be formed of a continuous solid medium. Such a medium would be particularly advantageous where a continuous annulus of primary of secondary primer is provided since solid primer material would prevent uneven distribution of the primer within the annulus which might be caused during storage and transportation of a round.

In an alternative form, it is possible to construct an end portion wherein an annulus of primer forms a percussion cap primer and wherein the hammer or percussion tool of a gun or cannon effected ignition of a round by hitting part or all of the annulus. Thus, it is possible to use a cannon wherein the percussion hammer is not required to hit a centrally located percussion cap on a round.

Referring to Figures 3 and 4, there are shown various views of the components providing the end fitting 50. Figure 3 shows the principal three component parts, namely, primer plug 28, chamber disc 40 and base member 52 in an unassembled form. The chambers 42 are clearly visible in Figure 3 which shows the relatively small entry apertures for communicating a flash from the percussion primer. Figure 4 shows assembled the three components shown in Figure 3. These perspective views show in particular that the exit apertures 48 shown in Figure 4 are preferably of smaller diameter than the diameter of the individual chambers 42 which are shown from below in the view of the disc 40 shown in Figure 3.

Whilst threading is show in Figure 3 as the means for interlocking the three components, it would of course be possible to use other types of locking means such as circlips, nut and bolt arrangements or interference fits. Similarly the base memner 52 could be attached to round casing 18 by interference fit, cooperating threading, welding or it might be an integral part of the casing for example.

Naturally, various materials could be used for the different components of the round. The outermost components which together form the cartridge casing can be made of metal such as aluminium, or plastics which can be injection moulded and comprise snap-fit fittings to ease assembly of a round for example.

Claims

1. A round of ammunition having a longitudinal axis, a front end and a rear end and comprising:

a projectile;

initiating means for igniting the priming charge;

wherein

means are provided for directing the igniton flash from the priming charge directly at said one or more radially outward locations, forwardly into the propellant material contained in said annular space.

2. A round of ammunition according to claim 1 including means for directing the ignition flash substantially parallel to the said longitudinal axis from said one or more radially outward locations.

3. A round of ammunition according to claim 1 or claim 2 wherein the priming charge comprises a plurality of individual priming charge portions disposed around the longitudinal axis.

4. A round according to claim 3 wherein the priming charge portions form an annular array.

5. A round of ammunition according to claim 1 or claim 2 wherein the priming charge is in the form of an annulus disposed around the longitudinal axis.

6. A round of ammunition according to any preceding claim wherein the initiation means comprises a percussion cap which is substantially centrally located at the rear end of the round, means being provided for communicating an ignition flash from the percussion cap to the radially outwardly located priming charge.

7. A round according to claim 5 wherein the communication means comprises an axial bore and a plurality of passageways extending radially from the axial bore.

8. A round according to claim 7 wherein the portions of priming charge are contained within chambers within the rear end of the round.

9. A round according to claim 8 wherein each chamber has an exit for communicating ignition of the priming charge in a respective chamber to propellant material.

10. A round according to claim 9 wherein each exit hole is sealed by a rupturable membrane.

11. A round according to claims 9 or 10 wherein the cross-sectional area of each exit hole is smaller than that of each associated chamber.

12. A round according to any one of claims 9 to 1 1 wherein each chamber has an entry aperture which allows communication of an ignition flash from the percussion cap to the priming charge in the chamber.

13. A round according to claim 1 1 wherein a communication passageway from the entry aperture to a chamber is interrupted by means for retaining priming charge in the chamber but which means allows an ignition flash to pass through the passageway into the chamber.

14. A round according to claim 13 wherein the interruption means is a lip between the entry aperture and chamber.

15. A round according to any preceding claim wherein the rear end of the round comprises a first and second member having cooperating locking means, wherein the second member is detachable from the first member and comprises means for retaining the priming charge.

16. A round according to claim 15 further comprising a third member for housing the initiating means, the third and second members comprising cooperating locking means to hold both members in place relative to the first member.

17. A round according to any preceding claim wherein the rear end of the round is detachable from the remainder of the round.

18. A round according to any preceding claim which is a cased telescoped ammunition round.

19. A round of ammunition substantially as described herein with reference to Figures 1 and 2.