SEAL RING FOR PYROTECHNICALLY INITIATED PROJECTILE

Abstract: A pyrotechnically initiated explosive projectile (10) has coaxially arranged, a nose incendiary (18), a penetrator core (14), a high explosive (20), and an overall jacket (12). A seal (24) ring is installed between the nose incendiary (18) and the penetrator core (14) to preclude relative movement between the core and the jacket (12) during projectile (10) assembly, acceleration and spin up form prematurely igniting the incendiary charge. The seal ring (24) has a front collar portion (28) which preferably has a diameter greater than that of the inside diameter of the jacket (12) so that the collar (28) scrapes the inside wall of the jacket (12) during insertion to remove incendiary residual so that no incendiary can lodge between the jacket (12) and the penetrator core (14).

Description: SEAL RING FOR PYROTECHNICALLY INITIATED PROJECTILE This invention generally relates to projectiles having explosive charges therein and more particularly to a pyrotechnically initiatied explosive (PIE) projectile which is ignited by a pyrotechnic incendiary charge located in the nose of the projectile. More specifically, the invention relates to a barrier which prevents preignition of the pyrotechnic charge from relative frictional movement between the projectile components. The potential for premature ignition of incendiary or explosives contained in projectiles during handling and/or acceleration has long been recognized. Various attempts to alleviate this problem are exemplified by the following U.S. patents. US Patent No. 47,544 to Hotchkiss discloses an explosive ordnance shell having transverse ribs to partition the explosive charge so as to limit friction between the shell contents during spin up. US Patent No. 373,459 to Howell also discloses an explosive shell having transverse diaphrarns between and separating the explosive charge. US Patent No. 383,223 to Graydon discloses an explosive shell containing separated explosive charges. The charges are separated by transverse partitions which also may have perforations to conduct the flame between the charges. US Patent No. 3,720,169 to Johnson et al discloses a projectile having two nose incendiary charges separated from one another by a partition disk. US Patent No. 4,876,964 to Strandli et al discloses an incendiary containing projectile which has an interior coating or lining to prevent inadvertant ignition of the incendiary if the projectile is dropped. Several designs of PIE projectiles have been developed in recent years for small caliber ammunition with varying degrees of success. One such projectile is disclosed in US Patent No. 4,625,650, assigned to the assignee of the present invention. This copper jacketed explosive bullet for penetrating light armor has an inner tubular hard heavy metal penetrator body filled with a high explosive. It has a nose portion forward of the penetrator which is filled with an incendiary material. The incendiary is designed to ignite upon target impact, in turn igniting the explosive after penetrating light armor. Around the outside of the penetrator and nose portion is an outer copper jacket which forms the final aerodynamic shape of the bullet. Another PIE projectile is disclosed in US Patent No. 4,353,302. This patent discloses a projectile having a tubular steel body filled with explosive and also having a nose filled with an incendiary ignition material. Also within the tubular body is a subcaliber, solid tungsten penetrator core for the penetration of light armor. During spin-up of these types of projectiles in the weapon bore, there is some relative movement between the jacket and the tubular body. This movement may result in premature ignition of the incendiary material and the explosive in the weapon bore which is highly undesirable. The cause of the preignition is not the relative movement per se. It is due to the presence of small amounts of incendiary material between the jacket and the tubular body at the location of relative movement. The incendiary material may frictionally cling to the jacket sidewall as a result of the charging operation. Under assembly pressures, the material may also flow into undesired locations where normal part tolerances provide an opening. The friction from relative movement, occuring during spin-up, ignites this small amount of incendiary which in turn ignites the main incendiary and/or explosive charge. The present invention prevents preignition by providing a flexible seal ring partition between the tubular body and the jacket where the incendiary joins with the tubular body and the jacket, and by designing the seal ring to scrape the inner wall of the jacket during installation to remove residual incendiary material from the wall of the jacket. Thus there is no residual incendiary material on the jacket wall when the tubular body is installed in the jacket. Further, the shape of the seal ring tends to guide itself during insertion into the jacket to ensure coaxial alignment of the seal ring with the jacket. The seal ring of the present invention comprises a ring shaped plastic body generally symmetrical about a central axis. The body has an outwardly flared front collar portion and an outwardly flared rear skirt portion which are integrally joined to a central tubular portion. The central portion has an inwardly projecting curved lip protruding inward toward the central axis. The curved lip has a smooth concave surface oriented forwardly toward the projectile nose. The seal ring is designed to be installed within the jacket after the incendiary material is deposited in the nose end of the jacket and prior to the insertion of the tubular hard metal body containing the high explosive. The seal ring is sized so as to frictionally fit into the projectile jacket. The front collar portion is sufficiently large in diameter so that it is constricted during insertion within the jacket to scrape or swab along the inner wall of the jacket to remove any incendiary material which has adhered to the inner wall. Thus, all of the residual incendiary is moved to the forward, proper location during component assembly. The front collar portion is also short enough in length so that the material of the collar does not wrinkle when it conforms to the inner wall of the jacket. The rear skirt portion is sized slightly larger in diameter than the front collar portion so as to act like a shuttle cock during seal insertion. This keeps the seal in proper axial alignment. The rear portion is also segmented or provided with cutout portions to avoid wrinkling when it is constricted during insertion. The rear portion is sized to fit over the front end of the tubular body and is ultimately swaged between the tubular metal body and the jacket to seal this interface. Finally, a central bore through the seal ring permits an incendiary interface with the high explosive charge to maintain continuity of the explosive train. The size of this bore may be varied to control the detonation efficiency by providing greater confinement of the high explosive. Other objects, features and advantages of the invention will become more apparent from consideration of the following detailed description when taken in conjunction with the drawing and appended claims. Figure 1 is a longitudinal sectional view of a PIE projectile incorporating one preferred embodiment of the seal ring in accordance with the present invention. Figure 2 is an enlarged view of a portion of the projectile in Figure 1. Figure 3 is a separate rear end view of the seal ring shown prior to insertion into the projectile of Figure 1. Figure 4 is a sectional view of the seal ring taken on the line 4-4 in Figure 3. A PIE projectile 10, shown in Figure 1, preferably comprises a copper/zinc jacket 12, a hard metal tubular penetrator body 14 coaxially within the jacket 12, a base plug 16 closing the rear of the penetrator 14, a nose incendiary 18 in front of the penetrator 14, and a high explosive 20 packed within the penetrator 14. Behind the base plug 16 is a lead seal 22. The penetrator 14 is preferably a tungsten alloy tubular body having the shape of a hollow cylinder tapered front and rear. The penetrator 14 is preferably filled with . a plasticised high explosive 20 which is designed to fragment the tubular penetrator 14 upon detonation. The high explosive is preferably sufficient to fill at least 80% of the internal volume defined by the internal wall of the penetrator body. The nose incendiary 18 is located immediately forward of the high explosive 20 and can project either partly within penetrator 14 as shown in Figure 1 or reside wholly forward of penetrator 14. The nose incendiary 18 is designed to ignite when the projectile 10 impacts a target at a sufficient velocity and to thereby ignite the high explosive 20 after a sufficient amount of delay time for the penetrator 14 to pass through at least an initial layer of " target material. Accordingly, the high explosive will detonate and fragment the penetrator 14 behind the initial target layer. To preclude preignition and inbore detonations of the explosive 20, a seal means is installed which precludes incendiary material from being trapped between the penetrator 14 and the inner wall surface of the copper jacket 12. This seal means, a flexible, generally circular seal ring 24 in accordance with the present invention, is installed between the penetrator 14 and the nose incendiary 18. It comprises a generally ring shaped body 26 which is inwardly compressible, outwardly resiliantly biased and which is symmetrical about a central longitudinal axis A. The body 26 has an outwardly flared front collar portion 28 and an outwardly flared rear skirt portion 30 which are integrally joined to a central ring portion 32. The central portion 32 has an inwardly projecting curved lip 34 protruding from its inner side toward the central axis. As shown in Figure 2, the curved lip 34 is designed to form a smooth, curved forwardly concave surface against the incendiary material 18 when the seal ring 24 is installed into the jacket 12 so that no sharp breaks or corners are present against the incendiary material 18 to create a frictional pinching location during projectile assembly and during acceleration and spin up. The interior front collar portion 28 of the seal ring 24 is accordingly sized to frictionally conform to the projectile jacket 12 interior profile and still maintain a smooth contour after insertion. The ring 24 is designed to be installed within the jacket 12 after the incendiary material 18 is deposited -in the nose end of the jacket. It may be installed along with or prior to the insertion of the tubular hard metal body 14 containing the high explosive 20. The front collar portion 28 of the seal ring 24 has a maximum outer diameter greater than the inside diameter of the jacket so that it flexibly engages with the inner wall surface of the jacket 12 during seal insertion to scrape or swab any residual incendiary material from the wall to ensure that there is no incendiary present on the wall when the penetrator 14 is inserted into the jacket 12. Thus, all of the residual incendiary material is moved to the proper forward location during assembly. The front collar portion 28 is short enough in length so that the material of the collar uniformly deforms and does not wrinkle when it is compressed and constricted to conform to the inner wall surface of the jacket 12. The rear skirt portion 30 is sized slightly larger than the collar portion 28 and has a maximum outer diameter greater than the inside diameter of the jacket 12 so as to act like a shuttle cock during seal insertion. This shape maintains the seal ring 24 in proper axial alignment. The rear, portion 30 is also provided with cutout portions 36 to form segments to avoid wrinkling and/or unwanted material thickening when it is constricted during insertion. The interior of the rear portion 30 is also sized to fit around the front end of the penetrator 14. The rear skirt portion 30 is ultimately swaged between the tubular metal body of the penetrator 14 and the jacket 12 to seal this interface. The curved lip 34 extends over the front end of the penetrator 14 so that the seal ring 24 presents a smooth contoured surface 38 in contact with the rear of the nose incendiary charge 18. Finally, a central bore 40 through the seal ring 24 permits an interface between the incendiary 18 and the high explosive charge 20 to maintain continuity of the explosive train. The size of bore 40 may be varied to control the detonation efficiency by providing greater or lesser confinement of the high explosive. The base plug 16 preferably has a central blind bore 42 which contains a portion of the high explosive charge 20. This arrangement facilitates disintegration of the base plug upon explosive detonation. The base plug is preferably made of sintered zirconium so that it fragments into many burning particles upon detonation. In addition, the base plug 16 has an outwardly and forwardly flared front portion 44 which engages a tapered rear portion 46 of the tubular penetrator 14 so as to interlock the base plug 16 and penetrator 14 together. The interface between the high explosive charge 20 and the incendiary charge 18 may be a flat transverse surface or preferably is a recessed, stepped surface 48 as shown in Figure 1. Such a recessed, stepped surface 48 presents a large surface area contact between the high explosive and the incendiary for efficient detonation. Assembly of the projectile 10 starts with the formation of the jacket 12. Then, the nose incendiary 18 is deposited in the nose of the jacket 12. The seal ring 24 may be installed next. The seal ring 24 is basically a swab to clean any residual incendiary material from the jacket as the seal or swab is passed through the jacket and lodged against the incendiary charge. Then the penetrator 14, base plug 16, high explosive 20, and lead seal 22 are assembled together and then installed so that the forward end of the penetrator 14 butts against the flat rear of the curved lip 34 of the seal ring 24. The rear portion 30 is swaged between the penetrator 14 and the jacket 12. Alternatively, the seal ring 24 may be installed on the front end of the penetrator assembly first and then both inserted together into the jacket 12. If the penetrator has a recessed front surface as shown in Figure 1, the recessed surface 46 may be filled with a partial charge of incendiary material prior to installation of the penetrator 14 in the jacket 12. The rest of the incendiary material will already have been installed in the jacket as just described. In this case the seal ring 24 is preferably installed on the front end of the penetrator assembly containing the high explosive and the partial incendiary charge and then installed within the jacket 12. The collar portion wipes or scrapes the inside of the jacket clean of incendiary material as it is inserted. Finally, the jacket 12 is crimped over the rear of the lead seal 22 to complete the assembly of the projectile 10. As can readily be seen from the sectional views of Figures 1 and 2, any relative movement between the penetrator 14 and the jacket 12 during acceleration or spin up in the weapon bore will not involve contact with the incendiary to cause premature detonation of the high explosive because of the presence of the seal ring 24. This ring thus cushions the penetrator and partitions and prevents any contact between the incendiary and the front end of the penetrator. Further, the seal will desensitize the round to rough handling and dropping. The seal ring 24 preferably has a relatively large central bore 40 therethrough so that the incendiary 18 has direct contact with the high explosive 20. In some applications, however, it may be desirable to restrict the size of the bore to provide a greater initial confinement of the high explosive hence, more efficient detonation. The detonation efficiency may be controlled by an appropriate choice of seal ring bore size. The seal ring 24 is preferably made of a highly moldable material such as low density polyethylene. A highly combustible material such as a moldable nitrocellulose material may also be used which can minimize the parasitic mass in the projectile. The installed seal ring 24 also prevents particles of incendiary material from lodging between the front end of the penetrator and the jacket during storage, transport, and handling. This can substantially reduce the probability of ignitions due to mishandling and dropping the rounds. Further, the seal permits a more severe taper at the front end of the penetrator than would otherwise be permitted, as shown in Figure 2, which may be advantageous against some armor targets. While the invention has been described above with reference to specific embodiments thereof, it is apparent that many changes, modifications and variations can be made without departing from the inventive concept disclosed herein. For example, the penetrator may be solid or tubular and the projectile may or may not contain a high explosive charge. The seal ring 24 may or may not have cutouts in the collar portion to prevent wrinkling as in the rear portion, thus allowing the collar portion to be longer, extending further between the incendiary 18 and the jacket 12 forward of the penetrator body 14.

Claims: WHAT IS CLAIMED IS: 1. A seal (24) for use in a pyrotechnically initiated projectile (10) coaxially including a hollow ductile metal jacket (12) forming a generally pointed nose, an incendiary charge (18) within said nose, and a metal penetrator body (14) within said jacket (12) behind said nose; the seal (24) characterized by: a generally circular, flexible body (26) symmetrical about a central axis therethrough, said flexible body having an integral front collar portion (28), a central portion (32), and a rear skirt portion (30), said portions coacting to preclude incendiary material (18) from being positioned between said jacket (12) and said metal penetrator body (14). 2. The seal (24) according to Claim 1 characterized in that said skirt portion (30) of said seal diverges rearwardly and outwardly so as to fit around a generally circular front end of the penetrator (14) and between the front end of the penetrator and the jacket (12). 3. The seal (24) according to Claim 1 characterized in that said collar portion (28) forwardly outwardly diverges from said central portion (32) in a flare which has a maximum outer diameter greater than said jacket (12) inside diameter so that said collar (28) is compressed against said jacket (12) when said seal is inside said jacket (12). 4. The seal (24) according to Claim 1 characterized in that said central portion (32) of said seal (24) further comprises an inwardly directed annular lip (34) for engaging the front end of said penetrator body (14) . 5. The seal (24) according to Claim 4 characterized in that said lip (34) and said collar (28) form a smooth contoured surface (38) against said nose incendiary charge (18) when installed against the nose incendiary charge (18) inside the metal jacket (12). 6. The seal (24) according to Claim 1 characterized in that said central portion (32) has a central bore (40) therethrough providing an interface between said nose incendiary charge (18) and a high explosive charge (20) within said penetrator body (14). 7. The seal (24) according to Claim 2 characterized in that said skirt portion (30) has an outwardly flared shape with an outer diameter greater than that of said jacket (12) and has at least one cutout portion forming at least two spaced segments to help preclude wrinkling of the skirt portion (30) during insertion of the seal (24) inside the jacket (12) of the projectile (10) . 8. The seal (24) according to Claim 7 characterized in that said collar portion (28) outwardly diverges from said central portion (32) in a flare which has a maximum outer diameter greater than the inside diameter of said jacket (12) so that said collar (28) is compressed against said jacket (12) when said seal (24) is inside said jacket (12). 9. The seal (24) according to Claim 8 characterized in that said skirt portion (30) has a greater maximum outer diameter than said collar portion (28). 10. A pyrotechnically initiated projectile (10) characterized by in coaxial alignment a nose incendiary charge (18), a hard metal penetrator body (14) behind said charge, a metal jacket (12) over said nose incendiary charge (18) and said body (14), and a means (24) for precluding said incendiary charge from being positioned between said jacket (12) and said body- (14). 11. The projectile (10) according to Claim 10 characterized in that said means comprises a seal ring (24) between said jacket (12) and said body (14) having a central portion (32), a flared front collar portion (28), and a rear flared skirt portion (30). 12. The projectile (10) according to Claim 11 characterized in that said collar portion (28) of said seal (24) outwardly diverges from said central portion (32) in a flare which has an outer diameter greater than said jacket (12) so that said collar is compressed against said jacket (12) when said seal (24) is installed inside said jacket (12) and against said nose incendiary charge (18). 13. The projectile (10) according to Claim 11 characterized in that said central portion (32) of said seal (24) further comprises an inwardly directed circumferential lip (34) engaging the front end of said penetrator (14) . 14. The projectile (10) according to Claim 13 characterized in that said lip (34) and said collar (28) of said seal (24) form a smooth contoured forward surface (38) against said nose incendiary charge (18). 15. The projectile (10) according to Claim 11 further comprising said penetrator body (14) having a tubular shape containing a high explosive charge (20). 16. The projectile (10) according to Claim 15 further comprising said central portion (32) of said seal (24) having a central bore (40) therethrough providing an interface (48) between said nose incendiary (18) and said high explosive charge (20). 17. The projectile (10) of Claim 10 characterized in that the means comprises an inwardly compressible outwardly resiliently biased seal ring (24) for scraping the inside of the metal jacket (12). 18. The projectile (10) of Claim 17 characterized in that the seal (24) includes a rear portion (30) conforming to the front of the penetrator body (14) so that the seal ring (24) may be placed upon the metal penetrator body (14) prior to and during insertion of the penetrator body (14) into the metal jacket (12), said seal (24) ring scraping the inside of the metal jacket (12) during such insertion. 19. The projectile (10) of Claim 18 characterized in that said seal ring (24) has an outwardly . and forwardly flared collar portion (28) engaging and scraping the inside of said metal jacket (12). 20. The projectile (10) according to Claim 10 characterized in that said penetrator body (14) is a tubular penetrator having a high explosive charge (20) therein communicating with said incendiary charge (18) through said means. 21. The projectile (10) according to Claim 20 characterized in that said high explosive charge (20) in said penetrator (14) has a recessed forward surface interfacing with said incendiary charge (18). 22. The projectile (10) according to Claim 21 characterized in that said forward surface (48) interfacing with said incendiary charge (18) has a stepped shape. 23. The projectile (10) according to Claim 22 characterized in that said means comprises a seal ring (24) between said jacket (12) and said body having a central portion (32), a flared front collar portion (28), ""and a rear flared skirt portion (30). 24. The projectile (10) according to Claim 23 characterized in that said collar portion (28) of said seal (24) outwardly diverges from said central portion (32) in a flare which has an outer diameter greater than said jacket (12) so that said collar (28) is compressed against said jacket (12) when said seal (24) is installed inside said jacket (12) and against said nose incendiary charge (18). 25. The projectile (10) according to Claim 24 characterized in that said central portion (32) of said seal (24) further comprises an inwardly directed circumferential lip (34) engaging the front end of said penetrator (14) . 26. The projectile (10) according to Claim 25 characterized in that said lip (34) and said collar (28) of said seal (24) form a smooth contoured surface (38) and after positioning against said nose incendiary charge (18) . 27. The projectile (10) according to claim 10 characterized by a base plug (16) coaxially arranged behind said penetrator (14). 28. The projectile (10) according to Claim 27 characterized in that said penetrator (14) is a tubular body having its rear end (46) interlocked with said base plug (16). 29. The projectile (10) according to Claim 28 characterized in that said penetrator body (14) has a high explosive charge (20) therein. 30. The projectile (10) according to Claim 29 characterized in that said high explosive charge (20) has a recessed front end (48) interfacing with said incendiary charge (18). 31. The projectile (10) according to Claim 30 characterized in that said means comprises a seal ring (24) between said jacket (12) and said body having a central portion (32), a flared front collar portion (28), and a rear flared skirt portion (30). 32. The projectile (10) according to Claim 31 characterized in that said collar portion (28) of said seal (24) outwardly diverges from said central portion (32) in a flare which has an outer diameter greater than said jacket (12) so that said collar (28) is compressed against said jacket (12) when said seal (24) is installed inside said jacket (12) and against said nose incendiary charge (18). f 33. The projectile (10) according to Claim 32 characterized in that said central portion (32) of said seal (24) further comprises an inwardly directed circumferential lip (34) engaging the front end of said penetrator (14). 34. The projectile (10) according to Claim 33 characterized in that said lip (34) and said collar (28) of said seal (24) form a smooth contoured surface (38) and after positioning against said nose incendiary charge (18) . 35. The projectile (10) according to Claim 34 characterized in that said central portion (32) has a central bore (40) therethrough providing an interface (48) between said nose incendiary charge (18) and a high explosive charge (20) within said penetrator body (14). 36. The projectile (10) according to Claim 35 characterized in that said skirt portion (30) has an outwardly flared shape with an outer diameter greater than that of said jacket (12) and has at least one cutout portion (36) forming at least two spaced segments to help preclude wrinkling of the skirt portion (30) during insertion of the seal (24) inside the jacket (12) of the projectile (10). 37. The projectile (10) according to Claim 36 characterized in that said collar portion (28) outwardly diverges from said central portion (32) in a flare which has a maximum outer diameter greater than the inside diameter of said jacket (12) so that said collar (28) .is compressed against said jacket (12) when said seal (24) is inside said jacket (12). 38. The projectile (10) according to Claim 37 characterized in that said skirt portion (30) has a greater maximum outer diameter than said collar portion (28). 39. A pyrotechnically initiated armor penetrating projectile (10) characterized by: a metal jacket (12), a penetrator body (14) within the metal jacket (12), a pyrotechnic material (18) within a front portion of the jacket (12) and a resilient swab (24) between the body (14) and the material (18). 40. A pyrotechnically initiated armor penetrating projectile (10) characterized by: a metal jacket (12), a penetrator body (14) within the metal jacket (12), a pyrotechnic material (18) within a front portion of the jacket (12) and a resilient swab (24) between a front end of the body (14) and the jacket (12). 41. The projectile (10) of Claim 40 characterized in that the swab is behind a rear periphery of the pyrotechnic material (18), whereby to prevent the material (18) from moving to a position between the body (14) and the jacket (12). 42. A method of assembling a pyrotechnically initiated projectile (10), characterized by the steps of: a) introducing a quantity of incendiary material (18) into the nose of the projectile (10), b) attaching a flexible seal ring (24) to the front of a metal penetrator body (14); and c) inserting the seal ring (24) and penetrator body (14) into the projectile (10) against the incendiary material (18) while wiping incendiary material from the inside of the projectile (10) with the seal ring (24).

Inventors: SCHLUCKEBIER DAVID K, SCHLUCKEBIER, DAVID, K.
Applicants: OLIN CORP, OLIN CORPORATION
Application year: 1991
Main classification: F42B33
IPC codes: F42B12