Abstract:
A flechette cartridge is provided, containing a plurality of flechettes, capable of firing the flechettes in a concentrated and accurate spread pattern upon firing. In particular, both low and high velocity flechette cartridges are provided, which accurately disperse flechettes in a concentrated spread pattern. The flechette cartridge minimizes the parasitic launch mass to maximize flechette payload, flechette velocity and kinetic energy, and to maximize target effects. The flechette cartridge provides a robust means for reliably stripping the flechette payload cup.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention provides a flechette cartridge having flechettes contained therein which, when fired, are accelerated without spin being imparted thereto. In particular, a flechette cartridge is provided containing flechettes which are accelerated within the cartridge case without spin imparted thereto, and which do not engage the barrel rifling, thus allowing flechettes to stabilize quickly and avoiding an excessive spread pattern during a firing event. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional flechette rounds, such as the M1001, contain approximately 113 flechettes, each flechette weighing 18 grains. The flechettes contained within such conventional rounds reach average velocities of approximately 790 ft/sec. Such velocities are satisfactory. The M1001 uses a heavy projectile body to carry the flechette payload down the barrel. The projectile body uses a slip band obturator to minimize spinning the projectile body and flechette payload in the barrel rifling. 
         [0003]    Conventional payload carriers are stripped from the flechette payload by propellant gases and a spring, which are deficient in stripping the payload carriers from the flechette payloads. Further, the payload carrier is formed of a heavy metal body, which undesirably functions as a parasitic mass. This means of stripping the flechette payload carriers results in undesired dispersion characteristics. The relatively heavy metal body results in reduced muzzle velocities and reduced kinetic energy, reducing the effectiveness of the flechettes. 
         [0004]    It is an object of the present invention to provide a flechette cartridge which maximizes the muzzle velocity of the flechettes by minimizing the parasitic mass associated with the flechette carrier. It is a further object of the present invention to provide a robust means for reliably stripping the flechette carrier. 
       SUMMARY OF THE INVENTION 
       [0005]    In order to achieve the object of the present invention as described above, the present inventor earnestly endeavored to develop a flechette cartridge capable of launching flechettes in a concentrated, predictable spread pattern at a relatively high muzzle velocity. Accordingly, in a first embodiment of the present invention, a flechette cartridge is provided comprising: 
         [0006]    (a) a cartridge case having:
       (i) a base having a primer cavity disposed therethrough;   (ii) a cartridge case body having an outer circumference adjacent the base, and an inner circumference opposite the outer circumference, said inner circumference defining a smooth-bored cartridge barrel, the smooth-bored barrel having a open mouth at one end thereof;   (iv) a high pressure chamber disposed adjacent the primer cavity; and   (v) a low pressure chamber disposed adjacent the high pressure chamber;       
 
         [0011]    (b) a primer disposed within the primer cavity; 
         [0012]    (c) a propellant charge disposed within the high pressure chamber; 
         [0013]    (d) a sub caliber payload cup slidably disposed within the smooth-bored cartridge barrel, adjacent the low pressure chamber, the sub caliber payload cup having:
       (i) a payload cup body having an outer base, an outer circumference adjacent the outer base, an inner circumference opposite the outer circumference, and an inner base opposite the outer base; and   (ii) flechette retaining means for retaining flechettes, disposed within the inner circumference; and   (iii) a plurality of flechettes retained within the flechette retaining means.       
 
         [0017]    In a second embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, wherein the payload cup body further comprises a metal disk disposed therein, within the inner circumference of the payload cup body, adjacent the inner base. This metal disk prevents the flechettes from digging into the payload cup body upon firing. 
         [0018]    In a third embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, wherein the payload cup further comprises a payload cup stripping means in communication with the cartridge case at a first end, and with the payload cup at an end opposite the first end, 
         [0019]    wherein, when the flechette cartridge is fired, the payload cup is propelled from the smooth bored cartridge barrel and, at a predetermined distance from the smooth bored cartridge barrel, the payload cup stripping means acts upon the payload cup to strip the payload cup from the flechettes. The flechette retaining means generally disintegrates upon being exposed to the high velocity airstream, allowing the flechettes to fly unimpeded to the target. 
         [0020]    In a fourth embodiment of the present invention, the flechette cartridge of the third embodiment is provided, wherein the payload cup stripping means is comprised of a line or string. 
         [0021]    In a fifth embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, wherein a barrel ridge is formed on the smooth-bored cartridge barrel, and a payload cup ridge is formed on the payload cup, adjacent the outer base thereof. Upon firing, the payload cup ridge and barrel ridge are caused to impact one another, thereby decelerating the payload cup. 
         [0022]    In a sixth embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, comprising a plurality of sub caliber payload cups disposed within the smooth-bored barrel, with separator disks disposed therebetween. 
         [0023]    In a seventh embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, further comprising an ogive cap removably disposed on the cartridge case adjacent the open mouth of the smooth bored barrel. 
         [0024]    In an eighth embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, further comprising a metal disk disposed within the cartridge barrel between the low pressure chamber and the payload. 
         [0025]    In a ninth embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, wherein an empty volume is present within the cartridge barrel between the payload cup and the open mouth of the smooth-bored barrel. Longer cartridge barrel lengths allow for gentler payload accelerations, with lower required peak propellant pressures. 
         [0026]    In a tenth embodiment of the present invention, the flechette cartridge of the first embodiment above is provided, further comprising a closure disk disposed within the cartridge barrel, adjacent the flechettes and flechette retaining means of the sub caliber payload cup. 
         [0027]    In an eleventh embodiment of the present invention, the flechette cartridge of the first embodiment is provided, comprising a plurality of sub caliber payload cups. 
         [0028]    In a twelfth embodiment of the present invention, a flechette cartridge is provided comprising: 
         [0029]    (a) a cartridge case having:
       (i) a base having a primer cavity disposed therethrough;   (ii) a cartridge case body having an outer circumference adjacent the base, and an inner circumference opposite the outer circumference, said inner circumference defining a smooth-bored cartridge barrel, the smooth-bored barrel having a open mouth at one end thereof;       
 
         [0032]    (b) a primer disposed within the primer cavity; 
         [0033]    (c) a propellant charge disposed within the cartridge case body; 
         [0034]    (d) a sub caliber payload cup slidably disposed within the smooth-bored cartridge barrel, the sub caliber payload cup having:
       (i) a payload cup body having an outer base, an outer circumference adjacent the outer base, an inner circumference opposite the outer circumference, and an inner base opposite the outer base; and   (ii) flechette retaining means for retaining flechettes, disposed within the inner circumference; and   (iii) a plurality of flechettes retained within the flechette retaining means.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0038]      FIG. 1  is a cross sectional view of the flechette cartridge of the present invention. 
           [0039]      FIG. 2  is a cross-sectional view of the flechette cartridge of the present invention, as shown in  FIG. 1 , further illustrating the payload cup stripping means  33 . 
           [0040]      FIG. 3  is a partially cut away perspective view of the flechette cartridge of the present invention, having a plurality of sub caliber payload cups disposed therein. 
           [0041]      FIG. 4  is a cross sectional view of the flechette cartridge, illustrating the frictional payload cup stripping means. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    As illustrated in  FIGS. 1 and 2 , the present invention provides a flechette cartridge  1  comprising a cartridge case  3  having a base  5  and cartridge case body  7 . A primer cavity  9  is disposed through said base  5 . The cartridge case  3  is comprised of a cartridge case body  9  having an outer circumference  11  adjacent the base  5 , and an inner circumference  13  opposite the outer circumference  11 . The inner circumference  13  defines a smooth-bored cartridge barrel  15 , the smooth-bored barrel  15  having an open mouth  17  disposed at one end thereof. 
         [0043]    A primer  19  is disposed with the primer cavity  9 , and high pressure chamber  21  is disposed adjacent the primer cavity  9 . A low pressure chamber  23  is disposed adjacent the high pressure chamber  21 . A propellant charge  25  is disposed within the high pressure chamber  21 . When fired, the weapon firing pin strikes the primer  19 , and the primer  19  ignites, subsequently igniting the propellant charge  25 . 
         [0044]    A sub caliber payload cup  27  is disposed within the smooth-bored cartridge barrel  15 , adjacent the low pressure chamber  23 . Alternatively, a single propellant chamber can be used, wherein the propellant is ignited and propels the payload cup down the barrel, venting at the muzzle. The sub caliber payload cup  27  is comprised of a flechette retaining means  29  for retaining flechettes, and for sealing propellant case within the cartridge barrel, and a plurality of flechettes  31  retained therein. The flechette retaining means  29  is, generally, formed of a plastic or composite material, but may be formed of a metallic material, and has a structure containing numerous protrusions therein for frictionally retaining the flechettes  31 . 
         [0045]    As called for in the eighth embodiment of the present invention herein, and as illustrated in  FIG. 1 , the low velocity flechette cartridge  1  may further comprise a metal disk  43  disposed within the smooth-bored cartridge barrel  15  between the low pressure chamber  23  and the sub caliber payload cup  27 . This metal disk  43  acts to separate and evenly disperse the pressure produced by the propellant gases, so as to prevent damage to the flechettes and the flechette retaining means during firing. 
         [0046]    Preferably, the sub caliber payload cup  21  further comprises a payload cup stripping means  33 , as illustrated in  FIG. 2 . The payload cup stripping means  33 , generally comprised of a string or line, as called for the in the fourth embodiment above, to attach the sub caliber payload cup  27  to the cartridge case  3 , is in communication with the cartridge case  3  at a first end  35 , and with the payload cup  21  at an end  37  (i.e., a second end) opposite the first end  35 . When the flechette cartridge  1  is fired, the payload cup  33  is propelled from the smooth bored cartridge barrel  15  and, at a predetermined distance from the smooth bored cartridge barrel  15  (which is dependent upon the length of the payload cup stripping means  33 ), the payload cup stripping means acts  33  upon the sub caliber payload cup  27  (by restraining same) to strip the flechette retaining means  29  from the flechettes  31 , allowing only the flechettes  31  to continue direct forward travel. Thus, the sub caliber payload cup  27  is prevented from traveling with the flechettes  31  to the target. 
         [0047]    The line or string is preferably designed to break near the attachment point inside the cartridge case  3  (i.e., at or adjacent to the first end  35 ), to eliminate having the string remaining in the barrel after firing. This is accomplished by creating a weak point, such as a knot, near attachment point of the line or string to the cartridge case  3 . The process of breaking the string or line extracts sufficient kinetic energy from the flechette payload cup  33  to reliably strip the payload cup  33  from the flechettes  31 . 
         [0048]    As called for in the fourth embodiment of the present invention, the flechette cartridge  1 , as illustrated in  FIG. 3 , may comprise a plurality of sub caliber payload cups  27  and  28 , disposed within the smooth-bored cartridge barrel  15 , with separator disk  39  disposed therebetween. This separator disk  39  prevents the flechettes within the rearwardly disposed sub caliber payload cup  27  from digging into the base of the forwardly disposed sub caliber payload cup  28  during a firing event. 
         [0049]    As illustrated in  FIG. 3 , the flechette cartridge  1  may further comprise an ogive cap  41 , removably disposed on the cartridge case  3  adjacent the open mouth  17  of the smooth-bored cartridge barrel  15 . This ogive cap  41  merely prevents intrusion of foreign objects and/or moisture from entering the barrel  15  prior to firing. The ogive cap  41  is forcibly ejected from the cartridge case  3  during firing, and expelled from the weapon barrel. 
         [0050]    As illustrated in  FIG. 1  and  FIG. 2 , when the flechette cartridge  1  does not include an ogive cap  41 , means for protecting the sub caliber payload are needed. Accordingly, the flechette cartridge  1  may further comprise a closure disk  51 , as illustrated in  FIG. 1 , disposed within the smooth-bored cartridge barrel  15 , adjacent the flechettes  31  and the flechette retaining means  29  of the sub caliber payload cup  27 . This closure disk  51  performs essentially the same task as the ogive cap  41 , i.e., prevents intrusion of foreign objects and/or moisture from damaging the payload. 
         [0051]    As illustrated in  FIG. 1 , in a preferable embodiment, the flechette cartridge  1  preferably comprises an empty volume equaling or exceeding the volume of the payload cup is present within the smooth-bored cartridge barrel  15  between the sub caliber payload cup  21  and the open mouth  17  of the smooth-bored cartridge barrel  15 . This empty volume within the smooth-bored cartridge barrel  15  acts as an internal cartridge barrel, to launch the payload, rather than utilizing the weapon barrel (which can be damaged by the flechette payload and/or cause a decrease in accuracy thereof). Longer cartridge barrel lengths allow for gentler payload accelerations, with lower required peak propellant pressures. 
         [0052]    In a preferred embodiment, as illustrated in  FIG. 4 , in order to decelerate the payload cup upon firing, a barrel ridge  45  is formed on the smooth-bored cartridge barrel  15 . In addition, a payload cup ridge  47  is formed on the sub caliber payload cup  27  adjacent the base thereof. When the sub caliber payload cup  27  is fired, the payload cup  27  travels down the cartridge barrel  15 . At a certain point, the payload cup ridge  47  impacts the barrel ridge  45 . This impact produces a negative effect on the acceleration of the payload cup  27 , causing deceleration thereof. 
         [0053]    Although specific embodiments of the present invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiments. Furthermore, it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.