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Патент USA US2406047

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‘Aug. 20, 1946.
‘w. E. SWIFT, JR
Filed Feb. 18, 1943
3 Sheets-Sheet 1
'.\l/ 25‘ I
F‘ G- ‘3
Aug. 20, 1946.
Filed Feb. 18, 1943
- 3 Sheets-Sheet 2‘
FIG. l5
. ‘
F I G‘
' Aug. 20, 1946.
FIG. 25
Patented Aug. 20, 1946
Willard E. Swift, Jr., Worcester, Mass.
Application February 18, 1943, Serial No. 476,362
‘V 1 Claim.
(01. 109-78)
‘(Granted under ‘the act of
1883, as
amended April 30, 1928,; 370, O. G. 757)
otherwise impracticable, a ?oat de?ector may be
inserted in the path or at the end thereof, se
cured to one of the walls of the opening and
forming with this wall an acute angle facing the
The invention described herein may be manu
.' factured and used by or for the Government for
governmentalpurposes, without the payment to
meof any royalty thereon.
This invention relates to the prevention of
damage caused by bullet splash or spatter enter
ing crevices and openings through the walls of
armored. structures such as combat tanks and the
incident end of the opening.
The underlying theories of the invention are
illustrated schematically, and some illustrative
embodiments are. shown in the accompanying
drawings in which:
Figures 1 to 13 inclusive are schematic illustra
,Bullet splash or spatter is the phenomenon that
tions of the behavior of bullet spatter under vari
occurs when small arms ?re strikes an armored
ous conditions described below;
Figures 14 and 15 are detail sections of a tank
surface. Particles of the outer shell and inner
‘core of the bullet are thrown in all directions
laterally from the point of impact. At least some
of these particles skim along the surface and 15
. enter any opening in line with the surface. More
over, on striking another surface, the spatter is
turret having spatter protection for the sight
Figures 16 to 20 inclusive are detail cross‘sec
tions of various armored structure equipped with
spatter protection devices;
again de?ected in all directions, although with
diminished force. Consequently, the bullet spat
Figure 21 is a detail cross section of a door
ter may be de?ected into openings and will pass 20 structure showing a di?erent form of trap for
through to the interior of the structure. This
action occurs even if the opening follows an’ ir
regular path “having right angle or obtuse angle
turns, because of the de?ection of the spatter
on striking any obstructing surface.
the crack;
Figure 22 is a detail section of a door or other
structure presenting an opening, with spatter de
?eeting surfaces formed in the opening;
Figures 23 and 24 are detail sections of a gun
Within a tank, for example, the entering spat
rotor with a spatter trap beyond the clearance;
ter ‘may cause injury to personnel or may damage
some ofitheinternal installations such as tubing
housing with spatter traps in the clearance;
Figure 216 is a reproduction of Figure 23, illus
trating the path of armor piercing fragments,
and electrical cables.
If the spatter enters be
tween relatively movable parts, such as a gun
rotor and its housing, it may wedge itself between
the parts or may raise a burr on one of them, in
.either case immobilizing the movable part.
Figure 25 is a detail section of a gun rotor and
Figure 27 illustrates a similar but shorter path
and the insufficiency thereof.
Reference to these views will now be made by
‘ The invention resides in providing various
of like characters which are employed to des
means for de?ecting the spatter either at an
ignate corresponding parts throughout.
intermediate point in its path or at the end of
its path through the opening, immediately before
it enters the interior of the armored structure.
The various forms of de?ecting means can be
best selected and applied after an understanding a
of the behavior of bullet spatter, and for this rea
son the phenomenon is discussed to some extent
By way of introduction it is pointed out that
the spatter behaves in many respects like a fluid
and follows substantially a fluid path on surfaces
and in crevices, This will be observed through
out the detailed description.
Figure 1 illustrates normal incidence against
a semi-hard ?at surface I. The bullet approaches
along the arrow 2, and the spatter is distributed
and analysis of the distribution of the spatter. 45 in all directions from the point of impact along
., The invention is basedlargely on the discovery
As a result of such observations, I have found that
a number of de?ecting surfaces introduced in the
path of the spatter will progressively reduce its
momentum until it loses its damaging effect. An
other construction based on these observations
is the provision of a concave surface presented to
the path of the spatter and extending through
approximately 180 degrees, so thatrthe direction
of the‘spatter is substantially reversed. Where
the plane of the surface as indicated by the ar
rows 3. The bullet is a ball cartridge which does
not penetrate the surface.v
In Figure 2 an armor piercing projectile 4 has
struck the member 5 and produced a similar pat
tern. The projectile‘ has also formed a crater
6, the effect of which will presently be pointed
Figure 3 ,illustratesthe. impactjat anangle of
such a construction becomes too; expensive or is 55 about 45 degrees to the member ‘I... The spatter
again radiates from the point of impact but the
distribution is not uniform.
It is about 20 per
cent in the acute angle and about 80 per cent
in the obtuse angle.
A similar effect occurs at
Figures 12 and 13 show spatter from a soft con
vex surface 21 and from a soft concave surface
The direction of the spatter is not materially
in?uenced by the shape of the surface.
larger angles of incidence, such as '75 degrees to 5
Figure 14 shows the turret 30 of a‘ tank having
80 degrees from normal, as shown in Figure 4.
As the angle of incidence is increasecLthe point
is eventually reached at which the projectile
is not broken up but simply ricochets. The an
gle at which this happens is a function of the
velocity of the bullet, the type and smoothness
of the surface, and probably» the design of the
The spatter pattern on face hardened surfaces
is similar to that on semi-hard surfaces except
where the surface is chipped by armor piercing
Figuresw5" and 6 show characteristic patterns 1
a sight opening 3|. In an unfavorable design,
this opening would be approximately in the up
ward projection of the sloping front plate 32,
since the spatter would be directed towards the
opening. Figure 14 shows the plate 32 disposed
at such an angle that its projection lies consid
erably above the opening 3|.
However, where a less favorable angle cannot be
avoided, one or more angle irons 313 are secured
across the front plate, as shown in Figure 15.
These irons obviously de?ect the spatter before
it ‘reaches the sight opening. 'If any spatter
‘should travel beneath the ?rst angle iron, it will
when the plate is chipped or- ‘when the "armor ' < be stopped by the second iron.
piercing core of the bullet is broken. Where this
Figure 16 shows a door ‘40 closing against a wall
happens, the bullet spatter from the-jacket or
or plate 41, leaving an angular crack 42. Ref
shell-is somewhat similar to that produced by
erence to Figure 9' shows that a hit on the wall
ball ammunition, skimming'along' the plate 10
would spatter through the crack. A de?ecting
bead 43 near the entrance end of. the crack is
useful on hard plate, throwing the surface spat
as indicated by arrows. H.‘ However, the ‘core
fragments and particles ofv the plate, indicated
by the numeral l2, ?y off in a haphazard man
ter upward.
ner. It might be noted here'that' an armor pierc
ing core is quite likely to shatter on striking a
semi-hard surface l3 at an angleas shown in
Figure ‘6, but would not do so with a'normal hit. '1
Figure 7 shows the effect ‘of a bullet striking a
hard, convex surface l5 at normal‘ incidence.
Whether the surface is cylindrical or spherical,
The treatment of. a direct hit at the entrance
of the crack is shown in Figure 17 where a‘ door
44 similarly closes against a wall or plate 45,
leaving an angular crack 146.
A de?ector in the
nature of a ?at strip 41 is secured to one of the
walls of the crack or a prolongation thereof,
forming with this wall an acute angle facing into
the direction of travel. spatter entering such a
the surface at the point of impact, as indicated
trap loses most of its velocity because of the
by the numeral l6; This is true even-if the in
sharp angle of de?ection and is relatively harm
cidence ‘is not radial, as indicated ‘by the nu
less on leaving the trap.
meral I1. Armor piercing ammunition on a hard
' Figure 18' shows an improvement of this ar
surface; where the, core or plate is‘ shattered,
wherein the door is beveled oil" at 48
does not follow this rule.' Softer targets are dis 40
directly adjacent to the free edge of the strip
cussed below.
the spatter is distributedin-a plane tangent to
41'. The beveled edge de?ects the spatter back
Figure 8 shows the spatter distribution result
into the crack in cases where the spatter origi
ing from an impact of ball‘ ammunition on a
mated with sufficient energy to maintain velocity
after entering the trap. Tests have shown that
occasionally 1% inch stock will be blown out by
direct hits. Therefore, twelve gauge stock should
be used and should be carefully welded in place.
The sharper the turn made by the spatter, the
hard, concave cylindrical surface It. The spat
ter radiates from the point of impact as for any
other hard surface, but is de?ectedby the ad
jacent curved surface and is substantially re
versed in direction if the total ‘curvature of the
surface approaches‘ 180" degrees. Centrifugal
force causes the particles’to hug'the surface of
the plate.
The concave surface is one of the most
useful means of spatter control‘ if it can be ‘eco
nomically incorporated in the construction.
Figure 9‘ illustrates de?ection of'spatter at an
intercepting surface. ‘ The spatter radiates along "
the ?rst plate 20 in the manner? described. A
portion striking the nearby angularly disposed
vplate 2| again radiates from the‘ point of impact.
Due to this ‘behavior, some of the spatter en
tering a jagged path will emerge at the other 60
end of the path.
The velocity is of course reduced
with each impact.
On softer surfaces, such ‘as cast armor and
soft homogeneous plate where ball ammunition
produces more or lessof a crater, the spatter
pattern is influenced by that crater. The spat
ter distribution on cast armor ‘plate 25 of about
300 Brinell is shown in‘ Figure 10 and on cold
more energy it loses in the turn. This applies also
to curved de?ecting surfaces.
Figures 19 and 20 illustrate the embodiment of
‘a concave surface for de?ecting the spatter back
into the general direction of origin by bypassing
or re-direction.
In Figure 19 a door 50 closes
against'a wall or ‘plate 5!.’ A substantial space
52 is maintained between the parts, and a concave
surface 53 is formed at the bottom of the space.
Spatter from adirect hit at the entrance to the
space is reversed or re-directed by the concave
surface as shown by the arrows.
In Figure 20 two parts 54 and 55 are spaced to
form a slit 56. A concave surface 5'! formed on
one or both of the parts adjacent to the slit throws
‘the spatter across the slit._ When the material is
cast armor and produces fragments, or when
armor piercing ammunition breaks up, a hit on a
high point of the concave surface is likely to
rolled steel plate'i?. in Figure 11. The direction
throw fragment into theslit. Where this is like
cluded angle, the narrower‘ is the pattern. Thus,
there is less danger when a crater is formed, since
a greater portion of the spatter is thrown away
door is shown in Figure 21. A curved strip>58 is
welded to the hull 59 at the emission‘end of the
of spatter is approximately a prolongation of 70 ly, a different treatment‘ should be employed.
The application of the 'involute principle to a
the wall of the‘ crater, and'the smaller the in
crack 60 between the hull and the door 6|. Pare
ticles ‘entering the strip are whirled and thus def
75 prived
of considerable momentum.
Where close tolerance is not required, the con
struction shown in Figure 22 may be used. The
part 62 overlaps the part 63 and is formed with a
this path the fragments still retain su?cient ve
locity to escape with appreciable momentum, as
shown by the arrows.
rather large concavity 64. Opposite this, the part
The foregoing illustrations and descriptions
53 is formed with a smaller concavity 65. The i) show that effective spatter traps can be built for
effect of a hit at the entrance end of the space
practically all structures. Although the traps
is illustrated by the arrows.
shown for gun rotors are not altogether effective
This construction is e?ective for ball ammuni
against fragments from small arms armor pierc~
tion but passes some fragments produced by ar
ing ammuntion on direct hits, they undoubtedly
mor piercing ammunition. It should therefore
have considerable value on less direct hits.
not be used Without additional protection.
The e?ectiveness of the trapping within a rotor
A practicable treatment of a curved path is
housing depends on the dimension of the clear
shown in Figure 23, between a gun rotor ‘H3 and its
ance and the length of the curved path. The
housing ‘I l. The spatter travels around the curve
trapping is more elfective in a longer path. Small
and is held very close to it by centrifugal force.
clearances are likely to result in locking of the
A simple trap 72 is secured to the housing and
rotor, due to the wedging of particles therein and
forming an acute angle facing into the direction
burring of the surfaces, which has the same ef
of travel, serves to catch the spatter.
feet. A clearance of % inch is not su?icient to
Closely machined tolerances are often used to
prevent locking in this manner, and a wider clear
eliminate spatter. These result in slow and ex
anoe is recommended for use in connection with
pensive production and immobilization of the
a trap.
rotor from dust, dirt, rust and burring by small
Various embodiments of the invention have
arms ?re. An e?ective trap permits larger tol
been illustrated and described. It is to be noted
that the particular construction to be used should
An alternative construction is shown in Figure 25 be selected in view of the nature of the apparatus
24 where the trap is in the form of an involute 73
Where it is to be installed and in the light of prin
having an angularly disposed end T4. The spat
ciples herein discussed. Adaptation of the trap
ter entering the trap is forced into a circular or
structure, indicated by these principles, may also
whirling movement which reduces the velocity.
be necessary.
Another arrangement for a rotor is shown in
What I claim is:
Figure 25. A number of strips 15 are secured at
A door joint comprising, in combination, a
intervals to the housing, each forming an acute
hatch member having a hatch way with an ar
angle facing into the direction of ?re. This ar
cuate shaped recess on the inner side thereof, a
rangement is very eiTective in trapping all the
hatch cover having an extending marginal por
tion for overlapping the marginal portion of the
Figure 26 is a reproduction of Figure 23 to show
hatch in said hatch member when it is engaged
the effect of armor piercing bullet fragments.
therewith, the underside of said projecting over
The fragments rebound from the armor in paths
lapping portion receding into the arcuate contour
designated by the arrows at. Little or no spat
of a recess in the outer side of said hatch cover,
ter escapes. This view illustrates the fact that 40 said arcuate shaped recess having the bottom side
adequate protection may be obtained if suf?cient
theerof in substantially the same horizontal plane
curved surface is available. Otherwise some of
with the bottom portion of the recess in the inner
the particles will escape, as illustrated in Figure
marginal portion of said hatch member.
27. Here the housing Tl’ provides a shorter
curved path than in Figure 26. At the end of
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