A warhead assembly having an explosive core and a surrounding annular package with several circumferential rows of different sized preformed fragments or rods. In each of one or more row, the fragments are alternately inverted keystone shapes arranged in a circle, with the adjacent sides fitting against each other in essentially pressure-confining contact. Further, the fragments which have their wider sides facing radially outward are composed of much higher density metal than the alternating fragments having their wider sides facing inward. This causes the lower density fragments to push the higher density fragments out at a high velocity when exploded.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to fragmentation munitions, and more 
particularly, to an explosive fragmenting warhead type package having 
improved target-penetrating ability. 
2. Description of the Prior Art 
Conventional fragmentation type of warheads, bombs, rockets and the like 
have an annular body with an explosive charge in the center and rows of 
fragments or rods assembled around the center and contained in a thin 
outer cylindrical casing, for example. Some designs employ a solid type 
structure surrounding the explosive core, which splits into fragments at 
specially weakened points when the charge is set off. To penetrate an 
armored target when the fragments are thrown out by the high explosive, 
such fragments are designed to have as high a ballistic coefficient as 
possible, achieved by high density material and low cross-section area in 
the direction of travel, and to have high explosive launch velocity. The 
present invention is aimed at providing a higher relative velocity of high 
density fragments for a given initial size of package including explosive 
material and fragment material. 
U.S. Pat. No. 3,464,356 shows rod type penetrators having collapsible 
flared sections on the rear ends for aerodynamic stabilization during 
flight after separation at the time of explosion. Such stabilization has 
proved ineffective at the shorter distances from the explosion point. 
U.S. Pat. No. 3,977,327 discloses a fragmentation arrangement having 
keystone shaped fragments so that when assembled in curved fashion, the 
sides of the fragments will be in total contact with each other. However, 
when the fragments are separated from each other immediately after 
detonation, the internal pressure is at once drastically reduced. 
U.S. Pat. No. 4,080,900 discloses a spinning projectile assembly comprising 
a nose and a tail section separable by means of a longitudinally operating 
piston and cylinder when a contained explosive charge is detonated. A 
bundle of rods, initially surrounding the piston and cylinder, is thus 
freed to escape, and the rods fly apart due to centrifugal action only. 
The rods are preformed, in a certain embodiment, to triangular shapes and 
fitted side-by-side in alternate pointing directions for maximum packing 
density. 
SUMMARY OF THE INVENTION 
An overall object of this invention is to provide a fragmentation weapon 
wherein high density fragments are propelled at a maximum velocity for a 
given size (diameter) of weapon casing. 
It is another object of the present invention to provide a means and method 
of retaining the explosive gas pressures in a munition more efficiently to 
attain higher launch velocities of the fragments. 
A further object is to provide means for launching higher density fragment 
metal at velocities higher than conventionally attainable with a given 
ratio of explosive charge to total fragment metal. 
Briefly, my invention comprises preforming fragment material into keystone 
shapes and assembling an annular arrangement of alternately 
opposite-aligned shapes so that one keystone piece has the wide side 
facing outward and the adjacent keystone has the wide side facing inward. 
This arrangement is continued sequentially around the body assembly. 
Another aspect of the invention includes using appreciably higher density 
material for the fragments or pieces whose wide sides face outward than 
for the alternate fragments in the ring. The lower density portion can be 
provided as the individual separate fragments or can be composed of an 
integral casing which splits apart when exploded, such casing initially 
having the higher density fragments embedded therein at assembly. 
As well as alternating the side slopes of the fragments in the 
circumferential direction around the munition, the same is preferably done 
with the ends of the fragments in the longitudinal direction along the 
munition. 
In another embodiment, preformed "keystone" fragments of the higher density 
material are embedded in a pattern of mating formed holes in an integral 
cylindrical casing forming the exploded body of the munition. In this 
case, the casing is made of the lower density fragment material and is 
built to shatter, when exploded, into pieces serving as the opposite 
keytone shapes for pushing out the embedded preformed fragments. 
This invention will be more fully understood by reference to the detailed 
description of a specific embodiment to follow, and to the accompanying 
illustrative drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, a warhead assembly 10 is shown in longitudinal 
section. The warhead has a cylindrical exterior shape designed to be 
installed as a substantially complete section of the body of a missile 
(not shown). The overall diameter of the warhead 10 is commonly restricted 
to be equal to the missile diameter. 
Warhead 10 has a thin-walled inner plastic container 11 with a central 
passage therein. This passage contains a conventional booster composition 
12 and an explosive lead 13 coming from an arming mechanism 14 shown by 
dotted lines external to the end of the assembly 10. The remainder of 
container 11 is filled with high explosive 15. 
The container 11 is surrounded by a relatively thin exterior metal casing 
16 in which a multiplicity of preformed fragments 17 of various shapes are 
arranged, as will be discussed in more detail later. A thin tube or liner 
18 may be provided between the container 11 and the fragments 17. A right 
end cover 19 fits the end shape of container 11 and may be lightly welded 
to the casing 16, as at 22. A filler cap 20 (FIG. 2) in the right end 
cover 19 allows filling the container 11 with the high explosive 15. A 
left end cover 21 is similarly provided in casing 16 against the left end 
of container 11. The casing 16 and covers 19 and 21 together form a rigid 
but frangible housing for the warhead. 
This invention resides in the arrangement, shape, and materials of the 
fragments 17, of which there are five circumferential rings or rows in the 
example of FIG. 1. As shown in FIG. 3, the first row of fragments 
comprises alternately-placed fragment types 17a and 17b. These are 
keystone or trapezoidal shaped fragments, fragments type 17a having their 
wide sides in the inner radial direction of the warhead and fragments 17b 
having their wide sides in the outer direction. The angle of slope or 
taper of the fragments 17a is obviously less than that of the fragments 
17b so that the sides of all fragments fit against each other smoothly and 
perfectly in a circle around the warhead 10. 
The purpose of this alternate keystone shaping will be evident. When the 
warhead is exploded, and the exterior casing 16 is ruptured, the internal 
gas pressures are confined by the present fragments even as they travel 
outwardly, since the oppositely tapered adjacent sides remain in sliding 
contact until the fragments 17a push out completely beyond the fragments 
17b. This is illustrated in FIG. 6. Here, the fragments 17a and 17b are 
illustrated in motion beyond a dotted arc 25 which represents a circle 
lying significantly outward from the original inner diameter of the 
fragment assembly. Therefore, all the fragments 17 are given a greater 
maximum velocity than possible when the explosive pressure starts to 
decrease rapidly by escaping between the edges of ordinary fragments. 
FIGS. 4 and 5 give a better understanding of the shapes of fragments 17a 
and 17b. 
In addition, the fragments 17b in my invention may be made of a much higher 
density material than the fragments 17a. If the lower density pieces are 
made of steel, the higher density pieces may be made of a tungsten alloy, 
for example. Or, the lighter fragments 17a may be titanium and the heavier 
fragments 17b steel, if desired. The result is that the lower density 
fragments 17a with the wide side inward tend to accelerate more rapidly 
than the higher density fragments 17b with the narrow side inward, but 
actually push the fragments 17b out much faster than their unassisted 
velocity would be, due to the forced side contact described before. Thus, 
not all of the fragments are denser metal, but a limited number of high 
density fragments are launched at a higher velocity than normal with equal 
density fragments in a warhead of the same mass ratio of total fragment 
mass to explosive charge. Therefore, penetration of a heavily armored 
target is possible where no penetration was possible prior to this 
invention. 
This structure of fragments 17a and 17b as so far described provides 
confinement of internal pressure in the circumferential direction of the 
warhead. Reference to FIG. 1 again will show that the front and rear sides 
of adjacent rows of fragments are alternately tapered also, so as to 
confine pressure between the fragments in the longitudinal direction, 
also, during the initial period following explosion. 
Moreover, it is strongly preferred to initially confine the internal 
pressure at the opposite ends of the warhead assembly 10, to avoid losing 
the advantages of this invention due to end-escaping pressure. Note that 
the end covers 19 and 21 in FIG. 1 are propelled in the direction to 
maintain sliding contact with the inner surface of the casing 16 as the 
covers accelerate outwardly in the axial direction. Internal pressure is 
held momentarily until the distance "D" is exceeded, due to the 
appreciable length of the longitudinal sliding contact. 
The fragments in each of rows 3 and 5 of this design (FIG. 1) are identical 
to the fragments 17a and 17b in row 1. The framents in rows 2 and 4 are 
substantially longer rod-type fragments, and do not necessarily have 
alternately sloping side faces in the circumferential direction, although 
they may. 
Due to the trapezoidal shape and interlocking arrangement of the fragments 
17, and inner end flanges of the exterior casing 16 which have 
acute-angled fragment-contacting walls 24, the fragments can be stacked in 
the exterior casing 16 and then the inner container 11 inserted while in a 
vertical position. If desired, the fragments 17 may be held in place 
during assembly by a bonding material. 
The fragments 17a preferably have a larger face area exposed to the 
explosive center than fragments 17b so that a greater total force is 
exerted on the fragments 17a. This is not absolutely essential, however, 
when using lower density material for fragments 17a than for 17b, but just 
so that the fragments 17a are caused to move outwardly with respect to the 
fragments 17b to maintain contact with the adjacent sides. In one 
particular example, the relative angles on fragments 17a and 17b are such 
that the outward velocity of fragments 17a is about 15% greater than that 
of fragments 17b. 
It is thus seen that the present invention prevents initial leakage of 
explosive pressure past the fragments so that a higher fragment velocity 
is imparted. The relative fragment sizes, numbers, and keystone angles can 
be varied depending on the desired terminal effects. The fragments may be 
trapezoidal shaped or form the frustum of a cone or pyramid. It is also 
seen that this invention enables launching of heavier fragments at higher 
velocities than heretofore attainable for a fixed size of munition. 
FIG. 7 shows another physical arrangement following the concepts of my 
invention. Here, an integral casing 16a contains a plurality of machined 
apertures 26, for example, and the usual core of high explosive material 
(not shown). Each aperture 26 contains a preformed fragment 17c therein, 
shaped to fit, and having substantially wider outer surface dimensions 
than its inner surface dimensions. One fragment 17c is shown removed from 
its aperture in FIG. 7 for the purpose of illustration of its shape. 
Fragments 17c take the place of fragments 17b in the FIG. 1 design and are 
made of relatively denser fragment material than the casing 16a. They may 
be held in place by an epoxy resin, for example. The casing 16a may be 
grooved as at 27 to aid it, when exploded, to break into pieces performing 
the function of fragments 17a in the design of FIG. 1. If grooved, 
however, the grooving may be preferred to be made on the inner surface of 
casing 16a. 
The same "sliding contact" effect is maintained by the expanding casing 16a 
of FIG. 7 on the higher density keystoned fragments 17c, when the munition 
is exploded. The rows of fragments 17c are preferably staggered angularly 
around casing 16a as shown in FIG. 7, to achieve a uniform scattering 
pattern. The number, relative size and proportions of the fragments 
depicted in FIG. 7 are intended for illustration purposes only, the only 
restrictions being their exaggerated keystone shape and relatively higher 
density. 
Although this invention has been illustrated particularly as a missile 
warhead, it is obvious that the same principles of construction and 
operation apply to other types of munitions and submunitions, such as 
rockets, bombs and projectiles. Further, the exterior shape of the 
assembly can be somewhat tapered from end to end, if desired, rather than 
a straight cylinder as depicted in FIG. 1. Another layer of fragments 
constructed and arranged according to the present principles may be 
provided around the outside of the first layer and inside an enlarged 
exterior casing. 
While in order to comply with the statute, the invention has been described 
in language more or less specific as to structural features, it is to be 
understood that the invention is not limited to the specific features 
shown, but that the means and construction herein disclosed comprise the 
preferred mode of putting the invention into effect, and the invention is 
therefore claimed in any of its forms or modifications within the 
legitimate and valid scope of the appended claims.