Abstract:
A barrel assembly with a barrel is provided. The barrel comprises a plurality of external chambers containing respective propellant charges, a plurality of projectiles stacked nose to tail within the barrel and comprising respective expansion spaces for propellant gases, and a control system configured to ignite the propellant charges to create the propellant gases and propel the projectiles sequentially from the barrel. Each projectile has a corresponding external chamber and an expansion space and each chamber comprises a port that conveys propellant gas from the chamber into the expansion space for propulsion of the respective projectile.

Description:
This application is a divisional of U.S. patent application Ser. No. 09/958,465, filed Feb. 26, 2002 now U.S. Pat. No. 6,722,252, which is the National Stage of International Application No. PCT/AU00/00297, filed Apr. 7, 2000; additionally, this application claims the priority to Australian Application No. PP 9613, filed on Apr. 7, 1999, and Australian Application No. PQ 3843, filed on Nov. 3, 1999, all of which are incorporated herein by reference. 

   TECHNICAL FIELD 
   This invention relates to projectiles and firing apparatus therefore and it has particular application to methods of and apparatus for firing projectiles for military use, although this invention is also applicable to civilian uses such as described in our simultaneously filed International application PCT/AU00/00296. 
   BACKGROUND ART 
   The military applications of firing projectiles are well known, such as firing grenades, firing radar deflecting chaff and missile decoy packages. In military applications such as firing grenades, each cartridge case carries a projectile assembly containing a single grenade. Accordingly the relatively slow rate of delivery of grenades provides a significant constraint on the applications or utility of the equipment. 
   This invention has particular application to projectiles which are fired from a barrel assembly having a plurality of projectiles arranged in-line within the barrel and which are associated with discrete selectively ignitable propellant charges for propelling the projectiles sequentially through the muzzle of the barrel. Sealing engagement is provided between projectiles and barrel so as to prevent rearward travel of an ignited propellant charge to the trailing propellant charge. Such barrel assemblies will be referred to hereinafter as of the type described. Such arrangements are illustrated in our earlier International Patent Applications. 
   Barrels assemblies of the type described have the disadvantage that significant time may be required to position them for firing on a selected target. This set-up time may be unsuitable for applications where time is of the essence, such as for setting up defences. 
   OBJECTS OF THIS INVENTION 
   This invention aims to provide improved means for debilitating an enemy and/or to alleviate one or more of the shortcomings associated with presently available methods of and apparatus for firing projectiles for military and/or civilian uses. 
   DISCLOSURE OF INVENTION 
   With the foregoing in view, this invention in one aspect resides broadly in a plurality of barrel assemblies of the type described arranged in a transportable pod whereby the barrels may be transported to and directed at a selected target. 
   The pod may be formed as a unitary housing or it may have side walls which can splay outwardly to accommodate the barrel assemblies contained therein when in a splayed attitude. The pod may include aiming means for selectively orienting the barrels within the pod whereby the barrels may be directed at a selected target, alternatively, the pod may include an adjustable support such as a turret mounting. 
   Then again the transportable pod may be carried in a vehicle which may be selectively oriented about any desired axis to direct the barrels at a selected target, such as an aircraft whereby fixed orientation of the pod and barrel assemblies is appropriate. 
   Such pods will require minimal set-up time for firing many projectiles at a selected target. This will be advantageous where time is of the essence, such as for establishing defences. 
   Suitably the barrel assemblies are of the low pressure type which fire grenade-like projectiles although high muzzle pressure barrel assemblies may be utilised if desired. Respective barrel assemblies in the pod may be loaded with different projectiles and the pod may, include barrel assemblies having different size bores. 
   Suitably each projectile includes a trailing collar assembly captively mounted to the projectile body and when stored in the barrel, extend rearwardly to wedge against the nose portion of a trailing projectile body. Suitably the wedging action is provided by a shallow wedge 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 could extend substantially radially and could be formed with complementary sealing features thereon. Preferably however 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. 
   Preferably, each projectile is associated with a high pressure propellant chamber which exhausts to respective low pressure propulsion chambers formed between the adjacent projectiles for efficient low muzzle velocity operation. The high pressure propellant chambers could be formed integrally with the projectile body or the trailing collar or they could be provided at the exterior of the barrel to communicate therewith through ports provided through the barrel wall. 
   The projectiles may be electronically fired at an infinitely variable frequency up to the maximum rate of fire. For firing from a barrel assembly according to an aspect of this invention and arranged for low pressure, low muzzle velocity, the rate of firing is limited by the time taken for each projectile to leave the barrel and by the time necessary for the gas pressure in the barrel to drop sufficiently to warrant the firing of the next projectile. 
   In another aspect his invention resides broadly in a weapon having a plurality of barrel assemblies of the type described arranged in a transportable pod having:— 
   a pod housing; 
   support means for stably supporting the pod housing; 
   a plurality of barrel assemblies of the type described supported in spaced relationship within said pod housing by respective swivel mounts, and 
   direction control means for selectively varying the relative alignment between the barrel assemblies so as to selectively vary the relative delivered positions of projectiles fired from different barrels at the target 
   The direction control means may permit uniform pivoting of the barrel assemblies so that the inclination of the axes of the barrel assemblies relative to a pod axis may be selectively varied to enable a target position relative to the pod to be varied. The direction control means may permit individual pivoting of each barrel assembly so that the inclination of each barrel axis relative to a pod axis may be individually varied to enable a target position or individual target positions relative to the pod to be varied. Such individual control may be associated with individual firing control of each barrel assembly if desired. 
   Then again the direction control means may permit a controlled splaying of all barrel assemblies so that the area covered at the target zone may be selectively varied. Alternatively the direction control means may permit all or some of the above variations to be achieved individually or collectively as required. 
   The pod housing may be of any suitably configuration and may taper towards its base to enable barrel assemblies to be supported in a splayed attitude. The support means may be fold out legs which may be adjustable if desired. In one form the pod has a rectangular pod housing for economy or ease of storage and/or transport and the base thereof constitutes the support means. 
   The barrel assembly variants disclosed herein may also constitute further aspects of this invention. 
   A pod of barrel assemblies according to aspects of this invention may be fired from a marine platform into water, or from a sled towed underwater. The pod may also be fired from an aircraft, or from a number of aircraft flying in formation and if desired, with the firing coordinated between the aircraft by a suitable electronic link. 

   
     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 typical embodiments of the invention, wherein:— 
       FIGS. 1 to 4  diagrammatically illustrate typical barrel assemblies according to this invention; 
       FIG. 5  is a diagrammatic cutaway end view of a cluster of barrel assemblies; 
       FIG. 6  illustrates a pod of grenade firing barrel assemblies; 
       FIG. 7  illustrates a typical application of the present invention; 
       FIG. 8  illustrates a further application of the invention utilising an unmanned aerial vehicle; 
       FIG. 9  is an underside view of one of the pod carriers of the aerial vehicle of  FIG. 8 ; 
       FIG. 10  is a diagrammatic cross-sectional view of a pod of splayable barrel assemblies, and 
       FIG. 11  illustrates a typical application of one aspect of this invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The barrel assembly  10  illustrated in  FIG. 1  has multiple grenade carrying projectiles  11 , for grenades of substantially known forms loaded or stacked in a rifled barrel  12  to impart spin upon firing for activating an arming device. 
   However a rupturable propellant cup or high pressure chamber  13  is fixed to the projectile  11  for discharging from the barrel with the projectile to clear the barrel  12  for firing the following projectile. This chamber  13  exhausts through ports  14  into the barrel space between the stacked projectiles  11 , which space forms a low pressure chamber  15 . 
   Each projectile  11  includes a projectile body  17 , which in this embodiment is a grenade housing  18  housing a grenade  22 , and a trailing sleeve or collar assembly  19  which is retained thereon for limited axial movement relative to a head part  20  of the grenade housing  18 . The sleeve  19  has a leading end which tapers inwardly to an internal collar  21  which extends into a complementary shaped external recess  23  formed in the grenade housing  18 . The sleeve  19  tapers outwardly at its rear end  24  to engage over a corresponding tapered leading face  25  on the head part or nose  20  of the projectile  11  stacked therebehind. 
   In use, as disclosed in our earlier inventions, loading or storing of the projectiles  11  into the barrel  12  forms a wedge type seal  26  between the leading end of the sleeve  19  and the trailing tapered face  26  of the head part  20  of the grenade housing  18 , which seal prevents the ignition of the leading propellant spreading about the grenade housing to the propellant in the following round. 
   Loading also effects a further wedge type seal  28  between the rear end  24  of the trailing sleeve or collar assembly  19  and the leading face  25  of the head part  20  and expands the rear end  24  into operative sealing engagement with the barrel  12 . Thus the sleeve or collar assembly to barrel seal forms a barrier to spreading of ignition thereabout to propellant charge in the trailing round. 
   Loading also effects a further wedge type seal  28  between the rear end  24  and the leading face  25  and expands the rear end  24  into operative sealing engagement with the barrel  12 . Thus the sleeve forms a barrier to spreading of ignition thereabout to propellant charge in the trailing round. 
   Firing of the leading projectile  11  releases the leading seal while maintaining the sleeve  19  captive with the grenade housing  18  but maintains an operative seal at the rear end of the sleeve with the barrel  12 . As the pressure propelling the projectile is relative low, in the order of 3000 psi, only minimal sealing is required. 
   The barrel assembly  30  illustrated in  FIG. 2  is similar in configuration to that illustrated in  FIG. 1 , the main difference being the manner in which the sleeve or collar assembly  31  is retained on the projectile body or grenade housing  32  and the configuration in which the sleeve  31  confines a smaller low pressure chamber  33  between adjacent projectiles  35  into which the high pressure chamber  36  exhausts through ports  38 . 
   The sleeve  31  also has a shallow wedge  34  at its leading end which may be expanded into sealing engagement with the barrel during loading but which is released upon firing during the initial forward movement of the housing  32  and upon subsequent impact of the propellant chamber  36  with the back face of the return  27 . 
   The barrel assembly  40  illustrated in  FIG. 3  is also similar in configuration to that illustrated in  FIG. 1 , the main difference being the wedge sealing angles α and β between the trailing sleeve  31 ′ and the projectile housing  42 . In this embodiment which is more suited to low pressure low muzzle velocity applications, the opposed ends of the trailing sleeve  31 ′ formed by the sealing angles α and β of between 30° and 55° are sufficiently blunt as to resist outward splaying into sealing engagement with the barrel under the influence of propellant pressures. Typically these would be in the order of 3000 psi to 5,000 psi with muzzle velocities of about 70 m/sec and 250 m/sec respectively. 
   It will be seen that the bulbous nose part  43  of the projectile housing  42  is hollow for carrying explosives, or fuel as referred to in relation to  FIG. 11 . As in the embodiments illustrated in  FIGS. 1 and 3  the propellant  37  in the high pressure chamber  46  is selectively ignited to expel high pressure gases through the trailing ports  39  into the low pressure chamber  33 ′ by a detonator  16 . The detonator  16  is triggered through an electrical circuit which uses the projectile column as one part of the circuit, the barrel  41  being made of insulating material or so lined and with the circuit completed by an embedded insulated wire  29  leading from the primer  16  to a contact  29 ′ on the projectile surface which is aligned when loaded, with a complementary contact  44  supported in the barrel  41 . 
   Alignment of the contacts can be achieved in a barrel and projectile located by rifling grooves during the loading process. In a non rifled design, the use of a annular contact in the barrel wall can achieve a similar result. 
   The barrel assembly  45  illustrated in  FIG. 4  substantially corresponds in mechanical configuration to the  FIG. 3  embodiment. However the high pressure chamber  46  is disposed externally of the barrel and communicates with the low pressure chamber  47 , which acts as an expansion space, through aligned ports  48  and  49  in the wall of the barrel  50  and trailing sleeve  51 , respectively. As shown cutaway in  FIG. 5  the high pressure chamber  46  is of such configuration that it will fit snugly into the space bounded by the adjacent side walls  50  of further barrels of a cluster of barrels  45 . 
   Further in each of the above embodiments the sleeve provided a relatively broad cylindrical surface which engages closely with the bore of the barrel so as to assist in preventing passage of ignited gases between the sleeve and the barrel. Further in the embodiments illustrated in  FIGS. 2 ,  3  and  4  the inward projections on the sleeve engage within complementary recesses formed in the housing and provide a labyrinth type seal across the inner face of the sleeve. 
   In all the above embodiments the propellant in the high pressure chamber is adapted to be ignited by electronically controlled ignition means, as described in our earlier International Patent Applications. 
   As illustrated in  FIG. 6 , a typical weapon according to an embodiment of this invention includes a cluster of barrel assemblies  55  adapted to fire grenades  56  and contained in a pod  57  such that a selected number of near simultaneously exploding grenades may be fired at a time. The grenades  56  are fired selectively from the pod  57  by computer control. The weapon in the illustrated embodiment contains ninety-eight barrel assemblies each containing stacked grenades  56  and having selectively ignitable internal or external propellant charges. In this embodiment the pod  57  is carried on a turret mounting  58  whereby the barrels may be swivelled about vertical and horizontal axes for aiming purposes. 
   Suitably 40 mm grenades  56  are used as the projectiles because of their ready availability. The grenades  56  are fired selectively by computer control from the pod  57  which is envisaged will contain ninety-eight barrel assemblies each containing stacked grenades  56  and having selectively ignitable internal or external propellant charges. The grenades  56  may be selectively fired to form a controlled impact array of exploding grenades on the zone to be investigated. 
   By way of example, using such a barrel assembly in a pod of ninety-eight 40 mm barrels that would measure approximately 350 mm×700 mm in cross section, with each barrel loaded with six projectiles, and with each projectile similar in size to a conventional 40 mm military grenade, a barrel length of 900 mm would be required and the assembly would provide a projectile capacity of five hundred and eighty-eight projectiles. This configuration would be suitable for seismic applications requiring a short range such as for delivering projectiles from downwardly facing barrels. For longer range delivery fewer projectiles would be accommodated in each of such barrels or longer barrels would be used and more propellant would be utilised to achieve higher muzzle exit velocities. 
   The maximum rate of fire per barrel is expected to be as high as 20,000 projectiles per minute and the maximum rate for the combined ninety-eight barrels would be 1,960,000 projectiles per minute, assuming that all barrels are fired simultaneously at the maximum rate. 
   For a ninety-eight shot burst firing the leading round from each of the ninety-eight barrels, the rate is infinitely variable and which may be a ninety-eight shot burst fired at a rapid frequency. 
   The above ninety-eight barrel pod is one example of a range of performance specifications that could be available. Different performance specifications can be generated by altering the component parts of the pod. For example, a pod may be preloaded such that the nature and weight of the explosive and/or projectile may vary between individual barrels in the pod, or within a barrel. 
   A plurality of such pods  57  may be carried on a vehicle and arranged whereby each pod  57  may be selectively directed toward a desired target and fired at a selected rate. Alternatively the pods  57  may be fired collectively at a single target. 
   In the embodiment illustrated in  FIG. 7 , the grenades  56  are fired downwardly from a pair of such pods  57 , only one of which is shown, carried by a helicopter  58  to provide bombing coverage of a tract of land. The density of such bombing and the area of land covered by the bombing can be controlled by controlling the variables such as rate of fire, elevation and speed of the aircraft. 
   The unmanned combat aerial vehicle  60  illustrated in  FIGS. 8 and 9  carries six such pods  57  in cases  61  under the wings  62  at each side of the fuselage  63 . It is envisaged that each pod could contain six 40 mm grenade pods with one hundred barrel assemblies per pod and with six grenades in each barrel. This would provide a loaded capacity of 7,200 grenades representing a payload of about 3,600 lb. 
   In this embodiment aiming of the barrels containing the grenades  56  would be achieved by remote control of the aircraft which may carry a video camera or the like for assisting its control remote from an operator. 
   The projectile firing pod  70  is illustrated diagrammatically in  FIG. 10  and cutaway to illustrate only two barrel assemblies  71  of the type described which would be contained within a rectangular pod housing  72 . The barrel assemblies  71  are swivel mounted in spaced apart relationship in the pod housing  72 , being suspended from an upper wall  73  from respective ball type mountings  74 . 
   Each barrel assembly  71  extends downwardly through the fixed ball-like mountings  74  to direction control means  75  which in this embodiment is able to individually or collectively control the barrel assemblies  71  for movement to an inclined attitude at one side or the other of their normal vertical position illustrated or to the front or back of that normal vertical position or to a combination of those attitudes as required. 
   For this purpose, each barrel assembly is provided with a cylindrical positioning block  78  supported rotatably about its lower end for eccentric motion about the axis of each barrel assembly. An intermediate wall  80  is apertured to closely receive each cylindrical positioning block  78 . The vertical position of the intermediate wall  80  is controlled by a hydraulic ram  81  supported on the base wall  82  of the pod housing  72 . 
   Extension and/or retraction of the ram  81  will move the intermediate wall  80  in a vertical direction restraining the respective apertures for movement along respective fixed axes so that, in the illustrated barrel assemblies, as the intermediate wall  80  moves downwardly, the lower ends of the barrel assemblies  71  will be moved inwards towards one another causing the barrel assemblies to splay outwardly relative to one another due to the fixed spacing of their upper ball mountings  74 . 
   Accordingly, it will be seen that by controlling the position of the hydraulic ram  81  the barrel assemblies can be positioned with their axes vertical and parallel, inclined to the vertical and parallel, or with their axes in a splayed attitude relative to an axis of the pod. 
   Each positioning block may be selectively rotated about the lower end of the barrel assembly on which it is mounted by extension or retraction of a further hydraulic ram  84  supported on the intermediate wall  80  and extending to a track  83  in the outer side wall of the respective positioning block  78 . The configuration of the track could be such that normal vertical movement of the intermediate wall  80  will not cause rotation of the blocks  78  in the direction of the arrow  85  unless the ram  84  is extended or retracted. 
   It will be seen that the vertical ram  81  connected to the intermediate wall  80  acts collectively on all barrel assemblies so as to move them in unison while individual horizontal rams  84  are provided for each barrel assembly  71 . 
   These rams  84  may be individually controlled independent of the ram  81 . Thus, for example, whereas the positioning blocks  78  are illustrated in the drawings arranged at opposing offsets with respect to the illustrated barrel assemblies  71 , one of the positioning blocks could be rotated through 780° by its ram  84  so as to arrange both cylindrical positioning blocks  78  with their axes parallel to one another and at an identical offset to the axes of the associated barrel assemblies  71 . 
   In this configuration, operation of the vertical ram  81  would pivot both barrel assemblies identically to one side or the other from the vertical, while at intermediate positions of one positioning block  78  relative to the other, splaying of the barrel assemblies could be achieved. Of course, both sets of rams  84  and  81  could be actuated simultaneously and be controlled by a suitable controller  86  to achieve a significant variation in target direction and spread of the fall of projectiles fired therefrom. In addition, the configuration of the impact pattern may be varied within a set zone. The barrel assemblies may also be controlled to provide a limited amount of turreting to achieve long range tight grouping of projectiles. 
   It will be seen that a projectile firing pod which may have an in-built remote controller  86 , which may receiving information from orientation sensors mounted on or associated with the barrel assemblies or from the ram positions, may be readily delivered and deployed very quickly to a site even though that site may be off-level and thereafter remotely controlled to fire projectiles at a common or at varying inclinations to the vertical to achieve the desired fall of projectiles at the impact zone. Also, the proportions of the impact pattern may be varied or maintained constant with varying target spread areas. 
   The drives for rotating the blocks  78  could be independent of the intermediate wall  80 , such as rotary drives with flexible or splined drives to the base of the barrel assemblies. Further the base  82  could be inclined to the side walls or be jackable to an inclined position to provide a coarse inclination toward the target zone with final aiming control achieved remotely by the direction control means  75 . 
   A typical application of pods described above, as illustrated in  FIG. 11  could be to fire a selected array of projectiles containing fuel to be dispersal therefrom in a controlled manner and pattern to form a defined fuel/air cloud to be detonated by further projectiles fired from the same pod or pods. 
   For example the fuel containing projectiles could form a fuel/air cloud  90  in a substantially conical shape and detonation could be effected simultaneously from a plurality of locations  91  about the upper portion of the cone to form a focused explosion directed to the desired target  92 . 
   The size and height of the cloud could  90  be selected to deliver high pressure shock waves to a localised area. This could be utilised to explode a land mine field, as a lethal anti-personnel attack or, by further elevating the cloud  90  to provide a concussive non-lethal attack against ground troops. 
   It will of course be realised that the above has been given only by way of illustrative examples 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 defined by the appended claims.