WO2003006917A1

WO2003006917A1 - Multiple propellant initiation

Info

Publication number: WO2003006917A1
Application number: PCT/AU2002/000932
Authority: WO
Inventors: James Michael O'dwyer
Original assignee: Metal Storm Limited
Priority date: 2001-07-11
Filing date: 2002-07-10
Publication date: 2003-01-23
Also published as: TW200412416A; AUPR629901A0

Abstract

A barrel assembly (10) including a barrel (11), a plurality of projectiles (12, 13) axially disposed within the barrel (11) for operative sealing engagement with the bore of the barrel, and discrete selectively ignitable propellant charges; wherein each projectile (13) is associated with a plurality of the propellant charges (16, 18, 20) for propelling the projectiles from the barrel. Operative sealing engagement may be provided by complementary end faces (22, 23 and 25, 26) formed on end portions of cup shaped casings (17, 19) containing the propellant charges (16, 18, 20) and on the body of the projectile. Suitably the propellant charge (16) adjacent the projectile (13) is initially ignited followed by the next adjacent propellant charge (18) in sequence towards the rear of the barrel (11), whilst the projectile remains in the barrel.

Description

MULTIPLE PROPELLANT INITIATION

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to the firing of projectiles, in particular to the firing of projectiles using the detonation of multiple propellant charges.

Discussion of the Background Art In order to attain greater muzzle velocities, larger propellant charges are often employed in barrel assemblies. However, this has the disadvantage of increasing in-barrel peak pressure that must be resisted by a barrel in such an assembly, which in turn requires strengthening of barrels and attendant increases in the complexity and cost of manufacture.

SUMMARY OF THE INVENTION Object of the Invention

It is an object of this invention to provide a barrel assembly and method of firing projectiles from a barrel assembly at a greater muzzle velocity but with reduced in-barrel peak pressure than possible with conventional propellant charges.

It is a further object of this invention to provide a barrel assembly of relatively lightweight and cost-effective construction that provides enhanced muzzle velocity for projectiles.

Disclosure of the Invention

According to the present invention there is provided a barrel assembly including a barrel, a plurality of projectiles axially disposed within the barrel together with a plurality of discrete selectively ignitable propellant charges associated with each of the projectiles for propelling the projectiles from the barrel.

In a second aspect, the present invention provides a method of firing a projectile from a barrel assembly including a plurality of projectiles axially disposed with a barrel, said method including the step of sequentially igniting a plurality of selectively ignitable discrete propellant charges associated with a projectile in the barrel assembly.

The present invention advantageously relates in particular to barrel assemblies of the type described in International Patent Application Nos. PCT/AU94/00124 and PCT/AU96/00459. Such barrel assemblies include a barrel, a plurality of projectiles axially disposed within the barrel for operative sealing engagement with the bore of the barrel, and discrete propellant charges for propelling the projectiles sequentially through the muzzle of the barrel. The projectiles may be rounded, conventionally shaped and dart-like. The projectiles may also have fins that may be offset to generate a stabilising spin as the projectile is propelled from a barrel that may be a smooth-bored barrel.

Each projectile may include a head and extension means for at least partly defining a propellant space. The extension means may include a spacer assembly that extends rearwardly from the head of the projectile.

The head may define a tapered aperture at its rearward end into which is received a complementary tapered spigot disposed on the leading end of the spacer assembly, wherein relative axial movement between the head and the complementary tapered spigot causes a radially expanding force to be applied to the head of the projectile.

The barrel may be non-metallic and the bore of the barrel may include recesses that may fully or partly accommodate the ignition means. In this configuration the barrel houses electrical conductors that facilitate electrical communication between the control means and ignition means. This configuration may be utilised for disposable barrel assemblies that have a limited firing life and the ignition means and control wire or wires therefore can be integrally manufactured with the barrel.

A barrel assembly may alternatively include ignition apertures in the barrel and the ignition means are disposed outside the barrel and adjacent the apertures. A non-metallic outer barrel that may include recesses adapted to accommodate the ignition means may surround the barrel. The outer barrel may also house electrical conductors that facilitate electrical communication between the control means and ignition means. The outer barrel may be formed as a laminated plastics barrel that may include a printed circuit laminate for the ignition means.

The barrel assembly may have adjacent projectiles that are separated from one another and maintained in spaced apart relationship by locating means separate from the projectiles, and each projectile may include an expandable sealing means for forming an operative seal with the bore of the barrel. The locating means may be the propellant charge between adjacent projectiles and the sealing means suitably includes a skirt portion on each projectile that expands outwardly when subject to an in-barrel load. The in-barrel load may be applied during installation of the projectiles or after loading such as by tamping to consolidate the column of projectiles and propellant charges or may result from the firing of an outer projectile and particularly the adjacent outer projectile.

The rear end of the projectile may include a skirt about an inwardly reducing recess such as a conical recess or a part-spherical recess or the like into which the propellant charge portion extends and about which rearward movement of the projectile will result in radial expansion of the projectile skirt. This rearward movement may occur by way of compression resulting from a rearward wedging movement of the projectile along the leading portion of the propellant charge it may occur as a result of metal flow from the relatively massive leading part of the projectile to its less massive skirt portion.

Alternatively the projectile may be provided with a rearwardly divergent peripheral sealing flange or collar which is deflected outwardly into sealing engagement with the bore upon rearward movement of the projectile. Furthermore the sealing may be affected by inserting the projectiles into a heated barrel that shrinks onto respective sealing portions of the projectiles. The projectile may comprise a relatively hard mandrel portion located by the propellant charge and which cooperates with a deformable annular portion may be moulded about the mandrel to form a unitary projectile which relies on metal flow between the nose of the projectile and its tail for outward expansion about the mandrel portion into sealing engagement with the bore of the barrel.

The projectile assembly may include a rearwardly expanding anvil surface supporting a sealing collar thereabout and adapted to be radially expanded into sealing engagement with the barrel bore upon forward movement of the projectile through the barrel. In such a configuration it is preferred that the propellant charge have a cylindrical leading portion that abuts the flat end face of the projectile.

The projectiles may be adapted for seating and/or location within circumferential grooves or by annular ribs in the bore or in rifling grooves in the bore and may include a metal jacket encasing at least the outer end portion of the projectile. The projectile may be provided with contractible peripheral locating rings which extend outwardly into annular grooves in the barrel and which retract into the projectile upon firing to permit its free passage through the barrel.

The electrical ignition for sequentially igniting the propellant charges of a barrel assembly may preferably include the steps of igniting the leading propellant charge associated with a projectile by sending an ignition signal and causing ignition of the leading propellant charge. Subsequently, and whilst the projectile is in the barrel, the adjacent propellant charge disposed rearwardly from the propellant charge initially fired is detonated to increase the pressure on the projectile and consequently increase its velocity. Adjacent propellant charges may be similarly detonated. The timing of the detonation sequence may allow the muzzle velocity of the projectile to be controlled.

Ignition of the propellant may be achieved electrically or ignition may utilise conventional firing pin type methods such as by using a centre-fire primer igniting the outermost projectile and controlled consequent ignition causing sequential ignition of the propellant charge of subsequent rounds. Controlled rearward leakage of combustion gases or controlled burning of fuse columns extending to the adjacent propellant charge may achieve this.

In another form the ignition is electronically controlled with respective propellant charges being associated with primers that are triggered by distinctive ignition signals. For example the primers in the stacked propellant charges may be sequenced for increasing pulse width ignition requirements whereby electronic controls may selectively send ignition pulses of increasing pulse widths to ignite the propellant charges sequentially in a selected time order. Preferably however the propellant charges are ignited by a set pulse width signal.

Suitably in such embodiments all propellant charges inwardly from the end of a loaded barrel are disarmed by the insertion of respective insulating fuses disposed between insertion of respective insulating fuses disposed between normally closed electrical contacts, the fuses being set to burn to enable the contacts to close upon transmission of a suitable triggering signal and each insulating fuse being open to a respective leading propellant charge for ignition thereby. In certain embodiments the barrel assemblies may be of the low-pressure type, which fire grenade-like projectiles although high muzzle pressure barrel assemblies may be used.

Suitably each projectile includes a trailing collar captively mounted to the projectile body and when stored in the barrel, extends rearwardly to wedge against the nose portion of a trailing projectile body. Suitably a shallow wedge provides the wedging action whereby, in use, the trailing end of the collar is expanded into operative sealing engagement with the barrel.

The trailing collar may be mounted for limited axial movement relative to the projectile body and the leading end of the collar formed with an annular sealing face engageable with a complementary face formed on the projectile body whereby rearward movement of the projectile body resulting from the reaction of propellant gases thereon forces the its complementary face into sealing engagement with the annular sealing face at the leading end of the collar.

The complementary face and the annular sealing face may extend substantially radially and be formed with complementary sealing features thereon. However it is preferred that these faces are complementary part-conical sealing faces which wedge into tight sealing engagement with one another. The leading end part may also be expandable into operative sealing engagement with the barrel. Suitably however the wedging between the part-conical faces are relatively steep faces whereby the leading end of the collar is not expanded into operative sealing engagement with the barrel by the wedging action.

In low-pressure applications preferably, each projectile may be associated with a high-pressure propellant chamber that exhausts to respective low-pressure propulsion chambers formed between the adjacent projectiles for efficient low muzzle velocity operation. The high-pressure propellant chambers may be formed integrally with the projectile body, the trailing collar, spacers or be provided at the exterior of the barrel to communicate therewith through ports provided through the barrel wall. The configuration of the space into which the ignited propellant propagates and the propellant properties may be such that only low barrel pressures occur in use, such as in the order of 2,000psi to 5,000psi. Typically the collar is such that in its relaxed attitude it does not prevent free movement of the projectile through the barrel either for loading purposes or during firing. Whilst the present invention primarily provides a method of providing increased muzzle velocity, the aspect of controlling the timing of the detonation of the sequence of propellant charges permits the control of the muzzle velocity even in low-pressure applications.

The projectiles are each associated with a plurality of propellant charges. Each projectile is fired from the barrel by detonating in sequence the plurality of propellant charges. The propellant charge adjacent the projectile is initially detonated followed by the following propellant charges in sequence towards the rear of the barrel. A seal that prevents, or at least delays, the detonation of adjacent propellant charge preferably separates the propellant charges. The seals may be integrally formed with a spacer assembly that incorporates the plurality of propellant charges and extends through the propellant space. The spacer assembly may include a plurality of cup shaped casings associated with respective propellant charges. If required, at least two of the cup shaped casings may be integrally formed at a common wall. The spacer assembly may extend through the propellant space and abut the head of the subsequent projectile whereby compressive loads are transmitted directly through abutting adjacent spacer assemblies. In such configurations, the spacer assembly may add support to an extension means that may be a thin cylindrical rear portion of the head. Furthermore the extension means may form an operative sealing contact with the bore of the barrel to prevent burn leakage past the projectile.

The spacer assembly may include a rigid collar which extends outwardly to engage a thin cylindrical rear portion of a malleable head inoperative sealing contact with the bore of the barrel such that axial compressive loads are transmitted directly between spacer assemblies thereby avoiding deformation of the malleable head.

Complementary wedging surfaces may be disposed on the spacer assembly and projectile head respectively whereby the head is urged into engagement with the bore of the barrel in response to relative axial compression between the spacer assembly and the head. In such arrangement the head and spacer assembly may be loaded into the barrel and there after an axial displacement is caused to ensure good sealing between the projectile and barrel. Suitably the extension means is urged into engagement with the bore of the barrel. The propellant charges may be form of a solid block and cooperate to operatively space the projectiles in the barrel or the propellant charges may be contained in individual cup members of metal or other rigid material, that may include embedded primers having external contact means adapted for contacting pre-positioned electrical contacts associated with the barrel. For example the primers could be provided with sprung contacts which may be retracted to enable insertion of the cased charge into the barrel and to spring out into barrel apertures upon alignment with those apertures for operative contact with their mating barrel contacts. A number of propellant charges may be fired simultaneously, or in quick succession. In such arrangements the electrical signal may be carried externally of the barrel or it may be carried through the superimposed projectiles that may clip on to one another to continue the electrical circuit through the barrel, or abut in electrical contact with one another. The projectiles may carry the firing control circuit or they may form a circuit with the barrel.

BRIEF DETAILS OF THE DRAWINGS In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical embodiment of the invention and wherein:

FIG. 1 is a sectional schematic view of a first embodiment of a barrel assembly according to the invention;

FIG. 2 is a sectional schematic view of the barrel assembly shown in FIG. 1 after the detonation of a first propellant charge; FIG. 3 is a sectional schematic view of the barrel assembly of FIG. 1 after the detonation of a second propellant charge;

FIG. 4 is a sectional schematic view of the barrel assembly shown in FIG. 1 after the detonation of a third propellant charge; and FIG. 5 is a sectional schematic view of a projectile assembly for a barrel assembly of a second embodiment of the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIGs 1 , 2, 3 and 4 each show a barrel assembly 10 according to a preferred embodiment of the present invention. The barrel assembly 10 includes a barrel 11 , shown in fragmentary form in the drawings, within which barrel 11 is located a plurality of projectiles 12, 13 . . .n.

FIG. 1 shows the barrel assembly 10 prior to the firing of the projectile 13 and subsequent to firing a leading projectile (not shown) which has exited the muzzle of the barrel 11. The projectiles 12, 13 each include a tapered skirt or collar 14. The tapered skirt 14 is configured to engage a corresponding tapered body portion 15 of the forward projectile 13 upon detonation of a propellant charge (not shown) in front of the projectile. The tapered skirt 14, upon engagement with the projectile 13 in response to the detonation of the forward propellent charge

(not shown) causes the tapered skirt 14 to sealably engage the bore of the barrel

11. This engagement of a tapered skirt 14 with the bore of the barrel 11 effectively formed a breach against which the leading projectile (not shown) was propelled.

A first propellent charge 16 is located immediately behind the forward projectile 13. The first propellant charge 16 is contained within a cup shaped casing 17. A second propellant charge 18 is located rearwardly of the cup shaped casing 17 and contained within a further casing 19, which also contains a third propellant charge 20. The third propellant charge 20 is spaced apart from the second propellant charge 18 by an intermediate wall 21 of the further casing 19, which comprises two cup-shaped casings integrally formed at the intermediate wall 21.

In the present embodiment, a leading face 22 of the propellant cup 17 has a shallow wedge cross-sectional shape, which face 22 is arranged for engagement with a complementary wedge-shaped trailing face 23 on a tail portion 24 of the first projectile 13. Similarly shaped complementary faces 25 and 26 are provided on the trailing end of the propellant cup 17 and the leading end of the further casing 19, respectively. When the projectile 13 and spacer assembly, comprising the cup shaped casing 17 and further casing 18, are subject to an in-barrel load the outer surfaces of end portions of the spacer assembly are expanded into operative sealing engagement with the bore of the barrel 10. This sealing engagement prevents or at least slows the sympathetic ignition of propellant charges disposed rearwardly in the barrel of an intentionally ignited charge. It will be appreciated that, in other embodiments of the invention, the tapered collar 14 carried by the projectile may not be required when operative sealing engagement provided by the spacer assembly 17, 19 performs to substantially prevent sympathetic ignition of propellant charges rearward of the second projectile 12.

FIG. 2 shows the detonation of the first propellant charge 16 and the initial resultant movement of the projectile 13. The configuration of the tapered skirt 14 and tapered body portion 15 of projectile 13 as such that forward movement of the projectile causes disengagement of the skirt 14 from the bore of the barrel 11. FIG. 3 shows the initiation of the second propellant charge 18 and the further movement of the projectile 13 together with cup shaped casing 17. A trailing face 27 of the further casing 19 is provided, in contrast to the leading end portion, with a shape configured to engage a tapered head portion of the second projectile 12. FIG. 4 shows the detonation of the third propellant charge 20. The three propellant charges 16, 18 and 20 are sequentially detonated whilst the projectile 13 is within the barrel 11 , such that the propulsion of the projectile 13 is greater than would occur by the detonation of a single equivalent propellant charge.

The sequential detonation of the propellant charges permits the projectile 13 to attain a far greater muzzle velocity, without the resultant peak force that would normally be applied to the barrel 11 by a single equivalent propellant charge in order to achieve such velocity.

In the drawings, the barrel assembly 10 may include additional segments including similar projectiles 13, propellant charges 16, 18 and 20, and casings 17 and 19 to those presently identified. This is represented by the fragmentation lines through the barrel assembly 10 at projectile 12.

A further embodiment of a projectile assembly 30 of the invention is illustrated in FIG. 5. The projectile assembly includes a skirt or collar 31 that may for example be captively mounted to the projectile body, extends rearwardly of a head portion 32 the projectile body 33. A spacer assembly comprising two cup shaped casings 34, 35 cooperate with the skirt 31 to contain the propellant charges 36, 37 and 38 associated with the projectile assembly. The end portions of the cup shaped casings include cooperating faces 40, 41 that function similarly to those described in relation to the first embodiment, in delaying sympathetic ignition of rearward propellant charges, eg. charge 38. A rear end of the skirt 31 also includes a cooperating shaped face 39.

We have found that by the detonation of multiple propellant charges whilst the projectile is in the barrel, the projectile may attain a greater muzzle velocity with less in-barrel peak pressure than would generally be required to achieve the desired muzzle velocity. Advantageously this may allow the materials of construction to be selected whereby the barrels may be of lighter weight or of lower cost. Further, by staggering the detonation of the multiple propellant charges a lesser peak force is applied to the subsequent projectiles.

It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is herein set forth in the following claims.

Claims

1. A barrel assembly including a barrel, a plurality of projectiles axially disposed within the barrel for operative sealing engagement with the bore of the barrel, and discrete selectively ignitable propellant charges; wherein each projectile is associated with a plurality of the propellant charges for propelling the projectiles from the barrel.

2. The barrel assembly as claimed in claim 1 wherein each projectile is fired from the barrel by igniting in sequence the plurality of propellant charges.

3. The barrel assembly as claimed in claim 2 wherein the propellant charge adjacent the projectile is initially ignited followed by the next adjacent propellant charge in sequence towards the rear of the barrel.

4. The barrel assembly as claimed in any one of claims 1 to 3 wherein a seal for at least delaying detonation of an adjacent propellant charge separates the propellant charges.

5. The barrel assembly as claimed in claim 4 wherein each projectile includes a head and extension means for at least partly defining a propellant space.

6. The barrel assembly as claimed in either claim 4 or claim 5 wherein the seals are integrally formed with a spacer assembly that incorporates the plurality of propellant charges and extends through the propellant space rearwardly of each projectile.

7. The barrel assembly as claimed in claim 6 wherein the spacer assembly includes a plurality of cup shaped casings associated with respective propellant charges.

8. The barrel assembly as claimed in claim 7 wherein at least two of the cup shaped casings of the spacer assembly are integrally formed at a common wall.

9. The barrel assembly as claimed in any one of claims 6 to 8 wherein the spacer assembly includes at least one end face for engagement with the projectile in order to wedge an outer surface portion of the spacer assembly and provide said operative sealing engagement with the bore of the barrel when the projectile is subject to an in-barrel load.

10. A method of firing a projectile from a barrel assembly including a plurality of said projectiles axially disposed within a barrel, said method including the step of sequentially igniting a plurality of selectively ignitable discrete propellant charges associated with a projectile in the barrel assembly.

11. The method of claim 10 wherein sequentially igniting the plurality of propellant charges associated with the projectile further includes the steps of: (a) igniting a leading propellant charge associated with a projectile by sending an ignition signal and causing ignition of the leading propellant charge;

(b) subsequently, and whilst the projectile is in the barrel, an adjacent propellant charge disposed rearwardly from the leading propellant charge is ignited to increase the pressure on the projectile and consequently increase its velocity.

12. The method of claim 11 wherein further adjacent propellant charges associated with the projectile are similarly ignited in sequence.

13. The method of any one of claims 10 to 12 wherein the timing of the ignition sequence allows the muzzle velocity of the projectile to be controlled.