AU2005269191A1 - High muzzle velocity projectiles and barrels - Google Patents

Description

WO 2006/012705 PCT/AU2005/001178 1 HIGH MUZZLE VELOCITY PROJECTILES AND BARRELS FIELD OF INVENTION This invention relates to the design of projectiles and barrels, in particular 5 projectiles that are located in a cartridge case and or barrel as well as barrels in which there are located at least two projectiles that are to be sequentially fired from the barrel and wherein the exit velocity of the projectile is above Mach 4. 10 BACKGROUND The use of a single barrel weapon from which to fire two or more co-located projectiles is known from before the end of the 19th century. Since then to the present time the exit velocity of such projectiles has been less than Mach 1. This means that the temperatures and pressures experienced by the 15 rearwardly located projectiles in the barrel or just external of the breech and any associated propellant are less than would be the case if the projectiles were designed to exit at much higher velocities. In almost all arrangements of such barrels and projectiles, one of the most 20 important design goals has been to isolate the effects of the ignition of the propellant source that is located forward of additional propellant located in the barrels It is an aim of the invention/s disclosed herein to provide means to isolate the 25 effects of ignition and explosion of forwardly located propellant from rearwardly located propellant located along the length of the same barrel or at least alternative arrangements from which to choose to implement such a weapon.

WO 2006/012705 PCT/AU2005/001178 2 BREIF DESCRIPTION OF THE INVENTION In a broad aspect of the invention a projectile firing apparatus includes a barrel having a forwardly located exit aperture having an inwardly extending circumferential ledge, at least two projectiles each having a penetrator and a 5 sabot assembly having at least two sabot parts shaped so as to surround at least a portion of a respective penetrator, the sabot assembly having an outer diameter smaller than the inner diameter of the barrel; propellant located in the barrel between the projectiles and propellant located in the barrel rearward of the rearward projectile; and, a pusher-plug located rearwardly of 10 said rearward projectile and forward of said most rearward propellant, the pusher-plug located against the circumferential ledge wherein as- a result of the expansion of gases, resulting from ignition of the forwardly located propellant the forwardly located projectile to expelled the projectile from the barrel, the pusher-plug is forced against the ledge in the barrel to form a seal 15 to the rearward movement of gases past the pusher-plug. In a further broad aspect of the invention a projectile assembly for firing from a barrel, the barrel having a forwardly located exit aperture and an inwardly extending circumferential ledge, the barrel also having two sequentially 20 loaded projectiles having propellant there between and propellant rearward of the rearward projectile, said rearward projectile includes: a penetrator; a sabot assembly having at least two sabot parts shaped so as to surround at least a portion of the penetrator, the sabot assembly having an outer diameter smaller than the inner diameter of said barrel; and, a pusher-plug located 25 rearwardly of said penetrator that is also located in said barrel against the circumferential ledge wherein as a result of the ignition of the propellant between the two sequentially loaded projectiles and expansion of gases used to expel the forwardly located projectile from the barrel, the pusher-plug is forced against the ledge in the barrel to form a seal to the rearward movement WO 2006/012705 PCT/AU2005/001178 3 of gases past the pusher-plug towards the propellant rearward of the rearward projectile. In yet a further aspect of the invention a cartridge for a firing apparatus 5 including a casing having an inwardly circumferential ledge; at least two sequentially loaded projectiles having propellant there between and propellant rearward of the circumferential ledge, each projectile including a penetrator and a sabot assembly engaging with said penetrator, and a pusher plug located rearwardly of said rearward projectile and also located in said 10 casing against the circumferential ledge wherein as a result of the ignition of the propellant between the two sequentially loaded projectiles and expansion of gases used to expel the forwardly located projectile from the barrel, the pusher-plug Is forced against the ledge in the cartridge to form a seal to the rearward movement of gases past the pusher-plug towards the propellant 15 rearward of the rearward projectile; wherein the casing holds the projectiles, propellant and pusher-plug before ignition of the propellant. Further aspects of the invention will be described in the body of the specification that follows hereafter. 20 Throughout this specification and the claims that follow unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer 25 or group of integers. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge.

WO 2006/012705 PCT/AU2005/001178 4 Specific embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative, and not meant to be restrictive of the scope of the invention. Suggestions and descriptions of other embodiments may be 5 included within the scope of the invention but they may not be iltstrated in the accompanying figures or alternatively features of the invention may be shown in the figures but not described in the specification. BRIEF DESCRIPTION OF THE FIGURES 10 Fig. 1 depicts a side and partial section view of a cartridge in which there is located two projectiles; Fig. 2 depicts a projectile of the type depicted in Fig. 1; Fig. 3 depicts a projectile depicted in Figs. 1 and 2 in part break-away condition after the projectile exits the barrel of the gun that uses the cartridge 15 depicted in Fig.1; Fig. 4 depicts a side partial view of a barrel in which there is located two projectiles of the types depicted in Figs;. 2 and 3; and Fig. 5 depicts -a seal ring member adjacent a pusher-plug. 20 DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION In all the embodiments to be described that are two projectiles located in a single barrel or cartridge in which a first projectile is located most forward of the other projectile. Rearward of the first projectile there is a first quantity of propellant which when ignited creates an explosion and high temperature 25 gaseous expansion that forces the first projectile out of the open end of the barrel. The higher the pressures created when the propellant explodes (burns and combusts) the faster the projectile exits the barrel and in the arrangements WO 2006/012705 PCT/AU2005/001178 5 described herein the pressures created are in the vicinity of 500 - 65OMPa and the resultant velocity is measured in Mach speeds above Mach 4 and typically Mach 5. 5 The explosion creates an expanding mass of high temperature gases that camot be permitted to move past the second rewardly located projectile, since if it does, a second quantity of propellant located rearward of the second projectile may be inadvertently ignited. 10 The consequences of which will be that-the rearwardly located projectile will be moved from its position, most likely to collide with the forwardly located projectile and cause serious damage to the projectile and/or the barrel. Another possibility is that the rearward projectile will be ejected unexpectedly from the barrel with an uncertain trajectory because it has travelled through 15 the turbulence of the slightly earlier ejected first projectile.. To ensure these results do not happen, the backward flow of high temperature expanding gases (blow back) must be effectively isolated from rearwardly located propellant in a multiple projectile per barrel or cartridge 20 arrangement. It is typical to use a sabot to encase projectiles that are intended for high (meaning Mach 4 and above) exit (muzzle) velocity. Sabots are designed to provide an additional outer diameter to the final projectile for temporary use 25 while the projectile is in the barrel of the weapon, the sabot being discarded as soon as the projectile exits the barrel. Various barrel bore internal diameters can be used so a sabot can make up the additional diameter of a projectile, which has a substantially smaller diameter than the barrel bore. The sabot is used primarily to support the relatively small diameter projectile during its WO 2006/012705 PCT/AU2005/001178 6 movement at very high speed-through the barrel. Sabots are not always used but tend to be so when high velocity projectiles are involved and they are not primarily designed to form a seal of the required strength to prevent blow back. .5 A problem therefore is how to provide a gaseous seal that performs at the high temperatures and pressures that occur when using such arrangements. In this invention a pusher-plug is provided that forms a seal with either the barrel or the cartridge. 10 A preferred design for a whole projectile suitable for the above application is displayed in Fig.1. The combination of the sabot and projectile (sometimes referred to as a dart projectile) is called a whole projectile or sometimes just a projectile in this specification. 15 Fig. 1 is a cross-sectional view of two whole projectiles in an encasement. The encasement can be in one instance the barrel of a cannon weapon or in another instance it can be the casing of a cartridge. The projectiles (cartridge or not) axe for use in a barrel (not shown) having a breech and bore. When the 20 cartridge arrangement is used the barrel has a bore shaped to accommodate the outer size and shape of the cartridge. When a barrel is used to house the projectiles without a cartridge it requires an inwardly projecting circumferential ledge, for assisting the formation of a seal, to be described in more detail later in the specification. 25 Fig. 1 shows a sabot provided about a projectile for firing from a cartridge, the sabot being shown in more detail in Figs. 2 and 3. Also shown in Fig. 1 are two such projectiles having propellant there between and a further propellant region rearward of the most rearward projectile.

WO 2006/012705 PCT/AU2005/001178 7 Thus in one embodiment a projectile firing apparatus includes the barrel having projectiles, propellant and a pusher-plug. In another embodiment a projectile assembly includes a penetrator; a sabot assembly and pusher-plug 5 member. In yet a further embodiment a projectile assembly includes a penetrator, propellant and sabot assembly, all working with a pUsher-plug. In yet a further embodiment a cartridge for firing from a barrel includes at least two projectiles, respective sabots, propellant and a pusher-plug. 10 A common element of all these embodiments is the pusher-plug that is located so as to be rearward of both projectiles and forward of the rearward most propellant The use of a sabot on a projectile is not new, nor is the use of a pusher-plug to 15 assist in the ejection of the projectile from the barrel. However, the use of the pusher-plug to provide the required sealing function described above is new. Once the projectile leaves the bore of the barrel the sabot separates from the projectile and the pusher-plug is discarded In this embodiment the sabot and pusher-plug engages with the rearward 20 most projectile and both move along the bore of the barrel when the associated propellant located behind the pusher-plug is ignited. In storage and during the firing process the sabot maintains the relative axial position of the projectile within the barrel bore. A pusher-plug 44a is also located rearward of the forward most projectile and 25 is ejected when the first projectile 41a is fired from the cartridge 40. Referring to Fig. 1 in more detail, the embodiment therein includes a single encasement being a partial depiction of a cartridge 40 for use in a suitable WO 20061012705 PCT/AU2005/001178 8 barrel, the cartridge contains two identical projectiles 41a and 41b located serially inside the cartridge and positioned so that their longitudinal axis is coaxial with the longitudinal axis of the cartridge. Each projectile 41 (as more clearly depicted in Figs. 2 and 3) consists of a 5 penetrator 42, a pusher-plug 44 located rewardly of the penetrator 42 and a four-part sabot 46 encasing the penetrator.. The first projectile 41a is located at the fore end of the cartridge 40 and the second projectile 41b is located towards the rear of the cartridge 40. The - propellant 48a for the first projectile is located inside the cartridge in between 10 the first and the second projectiles, while the propellant 48b for the second projectile is located in the rearmost portion of the cartridge behind the second projectile. The essence of this arrangement is that the propellant for the second projectile is isolated from the exploding first propellantby the pusher-plug 44 behind 15 the second projectile. When the front propellant 48a is ignited, the pressure generated by the gases projects the first projectile 41a from the cartridge 40 and the pusher-plug 44b located at the rear end of the second projectile is pushed backwards forming a seal against an inwardly projecting circumferential ledge, which in this .20 embodiment is the inward step 50 in the cartridge shown in Fig. 1. The gaseous seal thus isolates the rear propellant load 48b located behind the second projectile, from the high pressure and temperature environment that exists during the process of firing the first projectile from the cartridge. When in turn and under external control the rearmost located propellant 48b is 25 ignited, the resultant high temperature and pressure forces the pusher-plug 441 and the second projectile 41b from the cartridge 40. The arrangement described above is shown in'the 'unfired' state in Fig. 1.

WO 2006/012705 PCT/AU2005/001178 9 The advantage of this arrangement is that the inward step 50 in the cartridge 40 provides a simple mechanical means for keeping the second projectile in position during storage and transport, restraining the second projectile during firing of the first projectile by transmitting the rearward load to the cartridge 5 walls and sealing the rear propellant load from the effects of propellant ignition occurring forward of it. The inner bore of the barrel in which the cartridge is loaded also restrains the outer wall of the cartridge from outward expansion due to the ignition of the two propellant charges. The inward step 50 could be annular in shape and the inner diameter of the annulus is sized so 10 as to allow the passage of the result of the ignition of the rearward most propellant, located towards the rear of the rearward most projectile, so as to eject that at high velocity from the barrel. The dimension of the inner diameter of the annular step could vary with the type and nature of the propellant being used, which in turn would also depend on the size and type of 15 projectile being used. The inward step 50 could also have other shapes and may not exist around the full circumference of the bore of the barrel or cartridge. The purpose of the protrusion however configured is to provide a physical barrier to the potential rearward movement of gases when the pusher-plug is acted upon 20 by the effects of the rapid expansion of gases associated with the ignition of the propellant used to expel the forward most projectile at high velocity from the barrel or cartridge. The pusher-plug and inward step provides an effective seal as the pusher plug is a one-piece plug (no parts particularly in the form of petals) and the 25 rearward load of the front propellant ignition acts to force the pusher-plug against the cartridge or barrel inward step thus improving the seal during the relatively short time the ignition and propulsion phase used to eject the forward projectile from the cartridge.

WO 2006/012705 PCT/AU2005/001178 10 There is a need for the inward step to act in concert with the plug to form a primary seal, thus the inward step is primarily a barrier to gases and thus there will be many ways of implementing the barrier. An alternative may include an inward step that is temporarily located in the barrel or cartridge, 5 which is removed after the rearward most projectile, has been expelled from the barrel or cartridge. The pusher-plug is preferably made of aluminium or steel alloy. It is not necessary to add any other material to the interface between the pusher-plug and the step 50 although that could be done. In a preferred embodiment an 10 annular copper seal is used at the interface of the inward step of the cartridge or barrel and pusher-plug to prevent rearward leakage of gases. Various engineering design aspects of the pusher-plug and cartridge step elements include the total surface area of the interface between them, the material strength of both the step, the shape of the step which is shown in Fig. 15 1 as having a sloped edge rearward of the pusher-plug and a flat annular surface for abutment with the pusher-plug. There are also further engineering considerations required of the shape and material of the pusher-plug and the use and type of obturator ring or rings about the outer circumference of the pusher-plu& all at the likely temperatures and pressures generated to effect 20 propulsion at the exit velocity desired. All of those considerations are well within the skill of those in the art of ordinance design and testing. The sabot material used about the penetrator 42 is preferably a high strength/temperature resistant advanced plastic such as Delrin since Alumnirdum 7075, which was tested, showed considerable signs of 25 deterioration. Preferably the sabot is a four part encasement designed to separate once the projectile exits the cartridge, and when the cartridge is set within a barrel, the sabot will not separate from the projectile until it exits the end of the barrel and enters the atmosphere external of the barrel.

WO 2006/012705 PCTIAU2005/001178 11 The forward portion of the sabot is convex/parachute shaped and the high velocity of the whole projectile ensures that there is sufficient air resistance on the parachute portion of the sabot to force the parts of the sabot apart as soon as the confining volume of the barrel is exited. 5 Obturator rings 52 and 54 (Figs. 2 and 3) are located on the circumiference of the pusher-plug and two are shown which is a preferable quantity. However, less or more than two obturator rings could be used. Preferably the one or more obturator rings can be made of a heat-treated metal alloy to make them less brittle. The or each obturator ring sits proud but preferably very slightly 10 proud, of the outer circumferential surface of the pusher-plug and lies adjacent the inner bore of the cartridge and are typically required to keep the projectile central in the cartridge and the barrel as it is thrust forward- It is also possible for each or an obturator ring to be a neoprene O-ring. Using a cartridge to house the multiple whole projectiles is a convenient 15 methodology used in various applications in weapons, such as for example only, artillery, cannon, howitzers, and missile launcher use, as this form of projectile casing is well known and its storage; transport and handling procedures are well known. Artillery was characteristically smoothbore and muzzle-loaded, firing solid, round shot, until the latter part of the 19th 20 century, when breech-loaded, rifled, and shell-firing artillery became standaid. It also allows for the design of cartridges that can be used in existing barrels. Details of the apparatus and procedure for remote ignition of separated propellant are known. Also the propellant can be of a variety of types known 25 to those skilled in the art, the propellant compound being created to suit the high exit velocity requirement of the relatively light penetrator projectile WO 2006/012705 PCT/AU20051001178 12 when compared to shell and missiles normally used in the same barrel of comparable cartridge holding barrel. When the whole projectiles are used in a barrel (as shown in cross-sectional view in Fig. 4) they are sequentially loaded from the front of the barrel 58 as 5 the pusher-plug needs to be placed first into the barrel and located against an inwardly projecting (from the bore.of the barrel) circumferential ledge against which it will ultimately form a gaseous seal. The rearward most projectile assembly is then loaded and then the forward most propellant and then finally the forward most projectile assembly. The rearward most propellant 10 may have been previously loaded in proximity to and behind the inwardly projecting circumferential ledge or if shaped appropriately it may have been loaded through the inner diameter of the inwardly projecting circumferential ledge and against the rearward breech of the barrel 58. The loading order could be different for different assemblies. 15 Fig. 5 depicts an annular seal element being in one example a copper seal ring 56 adjacent the rear surface of the pusher-plug 44. The seal ring is not an essential feature but can be used to unprove the gaseous seal provided at the interface of the pusher-plug 44 and the inwardly projecting circumferential ledge 50 of a barrel or a cartridge. 20 It will be appreciated by those skilled in the art that the invention is not restricted in its -use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that various modifications can be made without departing from 25 the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

Claims (33)

1. A projectile firing apparatus includes: a barrel having a forwardly located exit aperture having an inwardly 5 extending circumferential ledge; at least two projectiles each having a penetrator and a sabot assembly having at least two sabot parts shaped so as to surround at least a portion of a respective penetrator, the sabot assembly having an outer diameter smaller than the inner diameter of the barrel; 10 propellant located in the barrel between the projectiles and propellant located in the barrel rearward of the rearward projectile; and a pusher-plug located rearwardly of said rearward projectile and forward of said most rearward propellant, the pusher-plug located against the circumferential ledge wherein as a result of the expansion of gases, resulting 15 from ignition of the forwardly located propellant the forwardly located projectile is expelled from the barrel, the pusher-plug is forced against the ledge in the barrel to form a seal to the rearward movement of gases past the pusher-plug. 20

2. A projectile firing apparatus according to claim 1 further consisting an annular seal element located at the interface of the inward step of the cartridge and pusher-plug to assist prevention of rearward leakage of gases. WO 2006/012705 PCT/AU2005/001178 14

3. A projectile firing apparatus according to caim 2 wherein the annular seal element is made of copper.

4. A projectile firing apparatus according to claim,1 wherein the pusher 5 plug is made of aluminium.

5. A projectile firing apparatus according to claim 1 wherein the pusher plug is made of steel alloy 10

6. A projectile firing apparatus according to claim 1 wherein the sabot material used about the projectile is a strong/temperature resistant plastic.

7. A projectile firing apparatus according to claim I wherein the sabot has at least a two part encasement adapted to separate once the projectile exits the 15 firing apparatus.

8. A projectile firing apparatus according to claim 1 further consisting at least one obturator ring located on the circumference of the pusher plug. 20

9. A projectile firing apparatus according to claim 8 wherein each of an obturator ring sits proud of the outer circumferential surface of the pusher plug and lies adjacent the inner bore of the barrel. 25

10. A projectile firing apparatus according to claims 8 and 9 wherein each or an obturator ring is made of a heat-treated metal alloy.

11. A projectile firing apparatus according to claims 8 and 9 wherein each or an obturator ring is a neoprene O-ring. WO 2006/012705 PCT/AU2005/001178 15

12. A projectile assembly for firing from a barreL the barrel having a forwardly located exit aperture and an inwardly extending circumferential ledge, the barrel also having two sequentially loaded projectiles having 5- propellant there between and propellant rearward of the rearward projectile, said rearward projectile including: a penetrator; a sabot assembly having at least two sabot parts shaped so as to surround at least a portion of the penetrator, the sabot assembly having an 10 outer diameter smaller than the inner diameter of said barrel; and a pusher-plug located rearwardly of said penetrator that is also located in said barrel against the circumferential ledge wherein as a result of the ignition of the propellant between the two sequentially loaded projectiles and expansion of gases used to expel the forwardly located projectile from the 15 barrel, the pusher-plug is forced against the ledge in the barrel to form a seal to the rearward movement of gases past the pusher-plug towards the propellant rearward of the rearward projectile.

13. A projectile assembly according to claim 12 further consisting 20 an annular seal element located at the interface of the circumferential ledge of the barrel and pusher-plug to assist prevention of rearward leakage of gases.

14. A projectile assembly according to claim 13 wherein the annular seal 25 element is made of copper.

15. A projectile assembly according to claim 13 wherein the pusher-plug is made of aluminium. WO 2006/012705 PCT/AU2005/001178 16

16. A projectile firing apparatus according to claim 13 wherein the pusher plug is made of steel alloy 5

17. A projectile firing apparatus according to claim 12 wherein the sabot used about the projectile is a strong/temperature resistant plastic.

18. A projectile firing apparatus according to claim 12 wherein the sabot has at least a two part encasement adapted to separate once the projectile exits 10 the barrel.

19. A projectile firing apparatus according to claim 12 further consisting at least one obturator ring located on the circumference of the pusher plug. 15

20. A projectile firing apparatus according to claim 19 wherein each of an obturator ring sits proud of the outer circumferential surface of the pusher plug and lies adjacent the inner bore of the barrel. 20

21. A projectile firing apparatus according to claims 19 and 20 wherein each of an obturator ring is made of a heat-treated metal alloy.

22. A projectile firing apparatus according to claims 19 and 20 wherein each of an obturator ring is a neoprene O-ring. 25

23. A cartridge for a firing apparatus including: a casing having an inwardly circumferential ledge; at least two sequentially loaded projectiles having propellant there between and propellant rearward of the circumferential ledge, each projectile WO 2006/012705 PCT/AU2005/001178 17 including a penetrator and a sabot assembly engaging with said penetrator, and a pusher-plug located rearwardly of said rearward projectile and also located in said casing against the circumferential ledge wherein as a result of 5 the ignition of the propellant between the two sequentially loaded projectiles and expansion of gases used to expel the forwardly located projectile from the barrel, the pusher-plug is forced against the ledge in the cartridge to form a seal to the rearward movement of gases past the pusher-plug towards the propellant rearward of the rearward projectile; 10 wherein the casing holds the projectiles, propellant and pusher-plug before ignition of the propellant.

24. A cartridge according to claim 23 further consisting an annular seal element located at the interface of the circumferential 15 ledge of the cartridge and pusher-plug to assist prevention of rearward leakage of gases.

25. A cartridge according to claim 24 wherein the annular seal element is made of copper. 20

26. A cartridge according to claim 23 wherein the pusher-plug is made of aluminium.

27. A cartridge apparatus according to claim 23 wherein the pusher-plug is 25 made of steel alloy WO 20061012705 PCT/AU2005/001178 18

28. A cartridge apparatus according to claim 23 wherein the projectile consists of a penetrator and a sabot wherein the sabot is a strong/temperature resistant plastic. 5

29. A cartridge apparatus according to claim 28 wherein the sabot has at least a two part encasement adapted to separate once the projectile exits the barrel.

30. A cartridge apparatus according to claim 23 further consisting 10 at least one obturator ring located on the circumference of the pusher plug.

31. A cartridge apparatus according to claim 30 wherein each of an obturator ring sits proud of the outer circumferential surface of the pusher 15 plug and lies adjacent the inner bore of the cartridge.

32. A cartridge apparatus according to claims 30 and 31 wherein each of an obturator ring is made of a heat-treated metal alloy. 20

33. A cartridge apparatus according to claims 30 and 31 wherein each of an obturator ring is a neoprene O-ring.