Abstract:
A projectile includes a head, a tail, and an interface that interconnects the head and tail. Multiple sections of the interface are deformed by being compressed radially inwardly into respective annular recesses formed between the interface and the head and tail during manufacturing or by rifling when the projectile is fired. The amount of deformation is controlled by the depth of each of the annular recesses. In all embodiments, annular ridges formed in the head, the tail, or both, define the longitudinal extent of the annular recesses. The interface includes an annular obturation region and has a beveled open leading end to facilitate insertion of the head and tail into the interface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to ammunition. More specifically, it relates to a projectile that is advantageously deformed by rifling. 
     2. Brief Description of the Related Art 
     Projectiles that include a head and a tail held together by an interface have enhanced performance characteristics relative to conventional projectiles. 
     However, the rifling in a gun barrel causes compression of the interface and the number of such compressions, as well as the location, depth and longitudinal extent of the compression is essentially uncontrollable, thereby reducing the effectiveness of the projectile. Accordingly, multiple projectiles fired in sequence will follow differing paths of travel due to the random quantity, location, depth and extent of the compressions formed in the interface. 
     The conventional wisdom is that such compression is a natural consequence of rifling and that nothing can be done about it. 
     In view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention that the effects of excessive random rifling compressions could be reduced or eliminated. Thus it was not obvious how such effects could be reduced or eliminated. 
     BRIEF SUMMARY OF THE INVENTION 
     The long-standing but heretofore unfulfilled need for a projectile that is not subject to the limitations of prior art projectiles is now met by a new, useful, and nonobvious invention. 
     In all embodiments, the novel structure includes a head, a tail, and an interface that interconnects the head and tail. 
     In a first embodiment, the head includes a frusto-conical section that extends from a leading end of the head to a point about mid-length of the head. A diameter-reducing annular step is formed about mid-length of the head. 
     The depth of the diameter-reducing annular step is equal to the thickness of the leading edge of the interface so that the leading edge of the interface abuts the diameter-reducing annular step and an exterior surface of the interface is flush with an exterior surface of the head when the projectile is in its assembled configuration, i.e., the flush relationship is formed by annular compression of the interface to the diameter-reducing step. 
     A first annular ridge is formed in the head in trailing, longitudinally spaced apart relation to the diameter-reducing annular step. Accordingly, a first annular recess extends longitudinally from the diameter-reducing annular step to the first annular ridge. 
     A second annular ridge is formed in the head in trailing and longitudinally spaced apart relation to the first annular ridge, forming a second annular recess between the interface and the head that extends from the first annular ridge to the second annular ridge. 
     A third annular recess extends from the second annular ridge to the trailing edge of the head. 
     A third annular ridge is formed in a leading end of the tail. 
     The interface has an open leading end, a closed trailing end, an exterior surface, and a cavity defined by an interior surface. The closed trailing end has an exterior bottom wall and an interior bottom wall. An annular diameter-increasing step is formed in the interior surface of the interface about mid-length of a tail-receiving section of the interface. 
     Accordingly, a fourth annular recess is formed between the interface and the tail, extending from the third annular ridge to the annular diameter-increasing step formed in the interior surface of the interface. 
     The interface has first, second, third and fourth annular sections that are compressed radially inwardly during manufacturing or by rifling when the projectile is fired so that said annular sections are respectively disposed in the first, second, third and fourth annular recesses so that each of the annular sections of the interface are deformed to conform to the contour of said head and tail. 
     All of the deformations are positioned on the leading side of the annular obturation region. The deformations are advantageous because the amount of deformation is controlled by the depth of each of the annular recesses and the longitudinal extent of each of the annular recesses. Moreover, the quantity and location of each deformation is also under the control of the projectile manufacturer. This is in sharp contrast with the deformations of the prior art that are random in number, location, depth and extent and which therefore produce random flight paths for projectiles fired in sequence. 
     In a second embodiment, only one annular recess and one annular ridge is formed in the head. The annular ridge is formed in the trailing end of the head and the annular recess is formed in the head in leading relation to the annular ridge and in longitudinally spaced apart relation to the annular diameter-reducing step formed in the head. In this embodiment, the annular diameter-reducing step is formed in the head about one-third the distance from its leading end to its trailing end. 
     In the second embodiment, as in the first embodiment, an annular recess extends from the annular diameter-increasing step formed in the interior surface of the interface to the leading end of the tail. This annular recess extends about half the length of the tail. 
     A third embodiment is similar to the second because it includes one annular recess and one annular ridge formed in the head. The annular ridge is formed in the trailing end of the head as in the second embodiment but the annular recess formed in the head in leading relation to the annular ridge extends to the annular diameter-reducing step formed in the head, reducing gradually in depth as it approaches said annular diameter-reducing step. As in the second embodiment, the annular diameter-reducing step is formed in the head about one-third the distance from the leading end of the head to its trailing end. 
     In the third embodiment, as in the second embodiment, a second annular recess extends from the annular diameter-increasing step formed in the interior surface of the interface to the trailing wall of the head, i.e., to the annular ridge formed in the trailing end of the head. 
     In all embodiments, the exterior surface of the interface has a trailing end, a uniform diameter mid-section, and an open leading end that reduces slightly in diameter relative to the mid-section. The diameter of the mid-section is also slightly greater than the diameter of the trailing end. This difference in diameter creates an interface transition region between the trailing end of the interface and the uniform diameter mid-section. 
     An annular inflection or obturation region is formed in the interface transition region. 
     The open leading end of the interface has a beveled edge that guides the tail into the cavity of the interface when the tail is dropped into the cavity. Therefore there is no need for a time-consuming precise alignment between the open end of the interface and the tail. The trailing end of the tail is in spaced apart relation to the flat bottom wall of interface cavity when the tail is dropped into the interface cavity. 
     A ram has a frusto-conical cavity that matches the slope of the frusto-conical section of the head. The head and tail are pushed into the interface by the ram until the flat trailing wall of the tail abuts the flat interior bottom wall of the interface. 
     A radially inward crimp is formed in the open leading end of the interface after the tail and head have been inserted into the cavity of the interface. The crimp abuts the diameter-reducing step formed in the head. 
     In all embodiments, the interface is compressed into the annular recesses either prior to projectile firing or during such firing, there being four such annular recesses in the first embodiment and two such annular recesses in the second and third embodiments. However, since the quantity, location, depth, longitudinal extent of each annular recess is determined by the projectile manufacturer, the depressions formed in the interface are under the control of said manufacturer. 
     All embodiments eliminate the random number, random depth, random length, and random location of rifle-created depressions that are formed in prior art projectiles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
         FIG. 1A  is a longitudinal sectional view of a first embodiment of the novel projectile assembly; 
         FIG. 1B  is a longitudinal sectional view of the projectile head of the first embodiment; 
         FIG. 1C  is a longitudinal sectional view of the projectile tail of the first embodiment; 
         FIG. 1D  is a longitudinal sectional view of the interface prior to assembly; 
         FIG. 1E  is a longitudinal sectional view of the interface after assembly; 
         FIG. 2A  is a longitudinal sectional view of a second embodiment of the novel projectile assembly; 
         FIG. 2B  is a longitudinal sectional view of the projectile head of the second embodiment; 
         FIG. 2C  is a longitudinal sectional view of the projectile tail of the second embodiment; 
         FIG. 3A  is a longitudinal sectional view of a third embodiment of the novel projectile assembly; 
         FIG. 3B  is a longitudinal sectional view of the projectile head of the second third embodiment; and 
         FIG. 3C  is a longitudinal sectional view of the projectile tail of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment of the novel structure is denoted as a whole in  FIG. 1A  by the reference numeral  10   a.    
     Structure  10   a  includes head  12 , tail  32 , and interface  48 . Head  12  is depicted individually in  FIG. 1B , tail  32  is depicted individually in  FIG. 1C , and interface  48  is depicted individually in  FIGS. 1D and 1E . 
     Leading end  14  of head  12  can be flat as depicted, rounded, or pointed. Frusto-conical section  16  extends from leading end  14  to a point about mid-length the length of said head. Diameter-reducing annular step  18  is formed at said location and the diameter of head  12  is reduced from said step  18  to the trailing end of said head. The reduced diameter increases slightly but linearly as at  20  from said annular step  18  to first transversely disposed annular ridge  22 . The diameter of head  12  is uniform from first ridge  22  to second transversely disposed annular ridge  24  and is again uniform until it reaches flat trailing wall  30 . 
     The leading end of interface  48  abuts diameter-reducing annular step  18  and an interior surface of said interface is spaced apart from head  12  by the first and second transversely disposed annular ridges  22  and  24 , thereby creating first, second and third annular recesses  20 ,  26  and  28 . 
     Three annular recesses are thus created between interface  48  and head  12 , said three spaces being denoted  20 ,  26 , and  28 . 
     Tail  32 , depicted in side elevation in  FIGS. 1A and 1C , is preferably, for manufacturing purposes, a wire that is cold formed by being punched into a die cavity. The exterior surface of tail  32  therefore conforms to the shape of the die cavity. Tail  32  includes flat trailing wall  34 , transition region  36  where its diameter increases slightly, uniform diameter section  38 , and leading wall  40 . The tail diameter increases at annular ridge  42  at the leading end of said tail. 
     Central concavity  44  formed in flat leading wall  40  is formed by a mirror image protuberance at the leading end of a ram that drives tail  32  into its die. Projection  44   a  formed in the trailing end of head  12  fits into said concavity  44 . 
       FIG. 1B  depicts head  12  of the first embodiment. It is preferably machined on a lathe although any other suitable manufacturing means is within the scope of this invention. 
       FIG. 1D  depicts interface  48  prior to assembly and  FIG. 1E  depicts interface  48  after assembly, i.e., as it appears in  FIG. 1A . 
     Interface  48  is cold formed by positioning a flat coin over a die having a cavity formed therein and by punching the coin into said cavity with a ram. The contour of the cavity determines the exterior shape of interface  48  and the contour of the ram determines the interior shape of interface  48 . 
     The bottom wall of the cavity is flat, thereby forming flat exterior trailing end  50  and the leading end of the ram is flat, thereby forming interior flat bottom wall  58 . The diameter of the cavity has its most narrow dimension at said bottom wall. A cavity diameter transition region is provided where the interior and exterior diameter of the cavity increases slightly as it extends away from said bottom wall, thereby forming interface transition region  52  in the exterior surface of interface  48 . The diameter of the cavity is uniform from the opening of the cavity to said cavity diameter transition region, thereby forming uniform diameter region  54  of said interface. 
     The annular inflection point that marks the transition from increasing diameter section  52  to uniform diameter section  54  is indicated by confronting arrows  56  in  FIGS. 1D and 1E . This annular region is known in the industry as the obturation point, band, or region. 
     The leading end of the ram is flat so that it forms flat interior surface  58  as aforesaid. The contour of the leading end of the ram produces curved interior surface  60  and an increase in diameter at a location away from its flat leading end produces annular diameter-increasing step  62  in the interior surface of interface  48 . 
     An annular recess is thus created between interface  48  and tail  32 , said annular recess being denoted  38  in  FIG. 1A . This is the fourth annular recess in the first embodiment of the novel assembly and it extends from annular ridge  42  formed in tail  32  to said annular diameter-increasing step  62 . 
     Thus, in the embodiment of  FIG. 1A , there are four annular recesses formed between interface  48 , head  12  and tail  32  with three of the four being between the interface and head  12 . 
     As best understood in connection with  FIG. 1D , the undepicted ram has a uniform diameter towards its leading end relative to annular step  62  to produce uniform diameter section  54  in interface  48 . The ram then increases in diameter linearly to produce linearly diverging section  66  at the leading, open end of interface  48 . 
     The open leading end of interface  48  is beveled as at  68  ( FIGS. 1D and 1E ). The bevel helps guide tail  32  into the hollow interior or cavity of interface  48  when said tail is dropped thereinto. More particularly, after interface  48  has been cold-formed from a flat coin at a first station by the punch and die, it is displaced by a conveyor or other suitable means to a second station where tail  32  is dropped thereinto from an overhead bowl or other device. Thus there is no need for a time-consuming precise alignment between the open end of interface  48  and tail  32 . 
     Trailing end  34  of tail  32  will not abut flat bottom wall  58  of interface  48  when said tail  32  is dropped into said interface. Head  12  is dropped into the interface after tail  32  and flat trailing wall  30  of head  12  abuts leading wall  40  of tail  32  as depicted. As depicted in  FIG. 1A , protuberance  44   a  formed in the trailing wall  30  of head  12  fits into concavity  44 . This eliminates the need to remove said protuberance. 
     The undepicted ram having a frusto-conical cavity that matches the slope of frusto-conical section  16  of head  12  pushes head  12  and tail  32  into interface  48  until flat trailing wall  34  of tail  32  abuts flat bottom wall  58  of interface  48 . Interface  48  is then crimped at its open leading end so that it assumes its  FIG. 1A  and  FIG. 1E  configuration. 
     As depicted in  FIG. 1A , the above-disclosed contours create transversely disposed annular recesses  20 ,  26 ,  28 , and  38  when head  12  and tail  32  are fully received within interface  48 . Interface  48  is compressed radially inwardly by rifling when the projectile is fired so that it occupies each of said annular recesses. The radially inward compression may also be made during the manufacturing process. All compressions/deformations of interstitial space within interface  48  are on the leading side of obturation region  56 . This compression is advantageous because it is a controlled deformation, as distinguished from a prior art random, uncontrolled deformation. The result is a projectile that more consistently hits its aiming point. 
     Referring now to the second embodiment, depicted in  FIGS. 2A-C , instead of three (3) annular recesses between head  12  and interface  48  as in the first embodiment, there is but one (1) annular recess, denoted  70 , formed in head  12 . Annular recess  70  is formed in head  12  in leading relation to drive chamfer  74  which is provided in the form of an annular raised ridge formed in the trailing end of head  12 , in trailing relation to annular recess  70 . Drive chamfer  74  imparts spin to head  12 . 
     Annular recess  70  is truncate in extent, having an extent similar to that of annular ridge  74 . An elongate annular recess of less depth extends from the leading edge of recess  70  to diameter-reducing annular step  18 . Prior to interface  48  deformation, the truncate and elongate parts of the recess are in open communication with one another. Accordingly, in the claims appended hereto, truncate recess  70  is referred to as the second part of the annular recess formed in head  12  and the elongate part of the recess is referred to as the second part of the annular recess formed in said head. The elongate second part reduces in depth as it approaches annular step  18  as depicted. 
     As depicted in  FIG. 2A , notch  32   a  formed in the leading end of tail  32  receives protuberance  12   a  formed in the trailing end of head  12 . 
     In this second embodiment, interface  48  is pre-compressed radially inwardly into annular recess  70  during assembly as indicated by directional arrows  72 . The compression is produced by a cannelure die that also produces a bullet knurl with symmetrically arranged pronged teeth. A wheel die would deform the bullet shape. 
     In this second embodiment, annular diameter-reducing step  18  is formed in head  12  about one-third of the way from its flat leading end  14  to its flat trailing end  30 . As in the first embodiment, the leading end of interface  48  has a thickness equal to the depth of step  18  so that an exterior surface of head  12  is flush with an exterior surface of interface  48 . 
     The internal diameter of interface  48  in this second embodiment increases at diameter increasing step  62  so that annular recess  76  is created between said interface and tail  32 . Annular recess  76  facilitates projectile assembly by reducing misalignment during such assembly. After assembly, radially inwardly directed arrows  78  indicate that interface  48  is compressed into annular recess  76 . The compression may be accomplished during the assembly step after tail  32  is inserted into the cavity of interface  48 , or the compression may take place during firing of the round. 
     Obturation band  54  is denoted with a bracket to indicate its length. As in the first embodiment, the function of obturation band  54  is to seal against gas pressure leakage. 
     Structural features associated with one or more preferred embodiments of the projectile include the nose and tail portions and respectively, formed of high density metal matrix composites, metals, alloys, or ceramics. More specifically, the nose and tail portions can each be formed from a material which contains one or more of the following: aluminum, antimony, beryllium, bismuth, boron carbide, brass, bronze, chromium, cobalt, copper, gold, iridium, iron, lead, magnesium, mercury, molybdenum, nickel, palladium, platinum, rhodium, silicon carbide, silver, steel, tantalum, tellurium, tin, titanium, tungsten, tungsten carbide, depleted uranium, zinc and zirconium. 
     Interface  18  may be made from a copper alloy similar to gilding metal. However, material from which interface  18  is formed may vary to include other appropriate alloys, polymers, etc., including materials which contain one or more of the following: aluminum, bronze, brass, chromium, copper, epoxy, fiberglass, Kevlar®, gold, graphite, iron, lead, magnesium, mercury, molybdenum, nickel, nylon, palladium, polycarbonate, polyester, polyethylene, polystyrene, polyamide, poly vinyl chloride, polyurethane, phenolic, thermoplastic polymer, thermoset polymer, rhodium, rubber, silicon, silver, steel, tantalum, tellurium, tin, titanium, Teflon, Torlon, Ultem, zinc, and zirconium. 
     Head  12  of this second embodiment is individually depicted in  FIG. 2B  and tail  32  is individually depicted in  FIG. 2C . 
     The third embodiment is depicted in  FIGS. 3A ,  3 B, and  3 C. It includes one annular recess  80  and one annular ridge  82  formed in head  12 , said annular ridge  82  serving as a driving chamfer. The driving chamfer serves to impart synchronous spin between the two components thereby maintaining gyroscopic stability in flight. Annular ridge  82  is formed in the trailing end of head  12  as in the second embodiment but annular recess  80  formed in head  12  in leading relation to annular ridge  82  extends to or almost to annular diameter-reducing step  18  formed in head  12 . As in the second embodiment, annular diameter-reducing step  18  is formed in head  12  about one-third the distance from the leading end of the head to its trailing end. The depth of annular recess  80  gradually reduces as it approaches annular diameter-reducing step  18 . 
     Second annular recess  84  extends from annular diameter-increasing step  62  formed in the interior surface of interface  48  to annular ridge  82  formed in the trailing end of head  12 . 
     Head  12  of this third embodiment is individually depicted in  FIG. 3B  and tail  32  is individually depicted in  FIG. 3C . 
     It will be seen that the advantages set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.