Note: Descriptions are shown in the official language in which they were submitted.
CA 02651631 2009-01-30
BULLET RESISTANT PANEL MEMBER
FIELD OF THE INVENTION
The present inventiori relates to a panel member for protecting an object
from projectiles in the form of bullets and shrapnel and the like, and more
particularly
the present invention relates to a bullet resistant panel member which is
suited for
protecting various objects, for example for mounting onto a vehicle to protect
occupants of the vehicle from builets and/or shrapnel, for mounting onto walls
and
surfaces of a mobile or fixed buildirig or shelter and the like.
BACKGROUND
The desirability of protecting persons and objects from bullets and
shrapnel from an explosion are well-known. The following US patents disclose
various
examples of devices offering protection against bullets and the like. US
Patent
4,566,237 belonging to Turner; IJS Patent 4,716,810 belonging to DeGuvera; US
Patent 4,326,445 belonging to Berniss; US Patent 4,323,000 belonging to Dennis
et
al.; US Patent 4,529,640 belonging to Brown et al.; US Patent 5,905,225
belonging to
Joynt; US Patent 5,533,781 belonging to Williams; US Patent 4,404,889
belonging to
Miguel; US Patent 4,111,097 belonging to Lasker; US Patent 4,131,053 belonging
to
Feguson; US Patent 4,186,648 blelonging to Clausen et al.; US Patent 5,851,932
belonging to Dickson et al.; US Patent 6,389,594 belonging to Yavin; US Patent
4,079,464 belonging to Roggin; US Patent 5,179,244 belonging to Zufle; US
Patent
3,601,935 belonging to Cadwell; lJS Patent 5,531,500 belonging to Podvin; and
US
Patent 5,413,026 belonging to Medden, Jr.
None of the prior art is well suited for ease of manufacturing to produce
a member of sufficient strength within a small enough and lightweight enough
panel-
like structure as would be desired for use in vehicles and the like to protect
the
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2
occupants of'the vehicle from roadside bombs and the like without greatly
interfering
with use of the vehicle.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a bullet
resistant panel member for protecting an object from a projectile, the panel
member
comprising:
an outer skin layer comprising a rigid sheet of material arranged for
facing outwardly away from the object;
an inner skin layer comprising a rigid sheet of material arranged for
facing inwardly towards the object;
a plurality of intermediate layers between the outer skin layer and the
inner skin layer, each intermediate layer spanning generally in a direction of
the outer
skin layer and the inner skin layer, and each intermediate layer comprising a
woven
material of aramid fibres;
a plurality of fastening members spanning under tension between the
outer skin layer and the inner skin layer such that the intermediate layers
are
compressed under pressure between the outer skin layer and the inner skin
layer.
Use of low weight material such as aramid fibres which are maintained
under pressure results in a panel which occupies little space while remaining
relatively
lightweight despite considerable strength and resistance to bullets and the
like. Use of
fastening members, for example bolts and the like, permits the panel member to
be
readily constructed with low skill and at a reasonable cost. In particular
embodiments
of the present invention, the outer skin may comprise rigid metal which is
shaped to a
vehicle or other object to be protected so as to provide minimal interference
to the
object being protected. Various types of fastening members can be used to
achieve
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3
considerable compression of the woven material of aramid fibres for optimal
resistance against projectiles. The fasteners can be further provided in an
evenly
spaced array following a grid pattern to ensure that even compression is
applied to
the intermediate layers between the inner and outer skin layers across the
length and
width thereof.
Preferably each intermediate layer comprises a sheet of KevlarTM
material.
The fastening members may maintain the intermediate layers under a
pressure of at least 500 psi to 1000 psi, and preferably greater than 2500
psi.
The fastening members may be arranged to compress the intermediate
layers to a combined thickness which is near half a thickness of the
intermediate
layers between the inner and outer skin layers before compression.
The compressed intermediate layers preferably have a thickness
between the inner and outer skin layers which is generally within a range of
one to
two inches.
There may be provided near 200 or greater intermediate layers.
Preferably the inner and outer skin layers comprise a rigid metal.
The outer skin layer may be formed of a softer metal than the inner skin
layer.
The fastening members may comprise mechanical fasteners, for
example threaded fasteners which arranged in a spaced apart grid pattern
relative to
one another.
The fastening members may be arranged in pairs which extend from the
outer skin layer to the inner skin layer angularly offset in diametrically
opposed
directions from an axis extending perpendicularly between the outer and inner
skin
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4
layers. The fastening members are preferabiy received through preformed
apertures
formed in the intermediate layers.
The inner and outer skin layers may be shaped so as to be arranged to
conform to a shape of the object to be protected such that the inner and outer
skin
layers are evenly spaced apart from one another along a width and a length
thereof.
More particularly, the inner and outer skin layers may be shaped to conform to
a
portion of a body of a vehicle, for example a panel of the vehicle, a door of
the
vehicle, or an under body of the vehicle.
Preferably the inner and outer skin layers are arranged to be continuous
across a length and a width of the vehicle.
Some of the intermediate layers adjacent the inner skin layer may have
more slack in a direction the inner skin layer extends than other ones of the
intermediate layers nearer to the outer skin layer.
Furthermore, some of the intermediate layers adjacent the inner skin
layer may have greater dimension in a direction the inner skin layer extends
than
other ones of the intermediate layers nearer to the outer skin layer such that
each
intermediate layer is progressively larger in dimension in a direction that
the skin
layers span than a previous one of the intermediate layers from the outer skin
layer to
the inner skin layer.
Some embodiments of the invention will now be described in
conjunction with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a partially exploded perspective view of a first embodiment of
the panel member.
Figure 2 and Figure 3 are side elevational views of further embodiments
CA 02651631 2009-01-30
of the panel member.
Figure 4 is a side elevational view of yet a further embodiment of the
panel member.
Figure 5 is a schematic illustration of the panel member shown mounted
5 in various places on a vehicle.
Figure 6 is a side elevational view of another embodiment of the panel
member.
Figure 7 is a schematic illustration of the panel member shown mounted
on a wall of a building structure.
In the drawings like characters of reference indicate corresponding parts
in the different figures.
DETAILED DESCRIPTION
Referring to the accompanying figures there is illustrated a bullet
resistant panel member generally indicated by reference numeral 10. The panel
member 10 is particularly suited for use with a vehicle 12 for mounting
against various
panels of the vehicle including panels of the door 14 or the undercarriage of
the
vehicle. In each instance the panel member is shaped to'have a mating profile
and
contour in three-dimensions which conforms to the shape of the object being
protected. In further embodiments the panel member 10 can be shaped to protect
various other configurations of objects or persons by suitably shaping the
panel
member for mating configuration therewith.
Although various embodiments of the present invention are shown and
described in the following, the common features will first be described
herein.
In each instance the panel member comprises an outer skin layer 20
which forms an outer side of the panel member 10 which is arranged for facing
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outwardly away from the object to be protected to confront the projectile at
the leading
side of the panel relative to an oncoming projectile. The outer skin layer 20
is a rigid
metal sheet which is shaped to conform to the object being protected so as to
retain
the shape thereof.
The panel member also includes an inner skin layer 22 which spans the
inner side of the panel member to face the object being protected and to be
located at
the trailing side of the panel member relative to an oncoming projectile. The
inner skin
layer 22 is also comprised of rigid metal and is shaped similarly to the outer
skin layer
20 so that the inner and outer skin layers are generally parallel and evenly
spaced
relative to one another along the length and width thereof.
The panel member further comprises a plurality of intermediate layers
24 which are stacked between the inner and outer skin layers. Each
intermediate
layer comprises a woven fabric material formed of aramid fibres in the form of
KevlarTM or other like materials. The intermediate layers 24 are each formed
into a
sheet which spans generally in the direction of the inner and outer skin to
remain
parallel thereto along length and width thereof. Up to 200 or more
intermediate layers
24 may be provided.
A plurality of fastening members 26 are provided which span under
tension between the inner and outer skin layers so as to be arranged to
maintain all of
the intermediate layers 24 under compression between the inner and outer skin
layers. The inner and outer skin layers are joined by the fastening members in
a
manner such that the intermediate layers 24 are compressed to approximately
half of
their original uncompressed thickness between the inner and outer skin layers
so that
an overall thickness of the assembled panel member is typically between one to
two
inches in thickness when using 200 intermediate layers. The fastening members
26
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serve to maintain the intermediate layers 24 under compression which may be
greater
than 500 psi and preferably greater than 1000 psi. Pressures of up to 2500 psi
are
known to be desirable and yet greater pressures may increase the effectiveness
of
the resistance to bullets of the panel member 10. The fastening members 26
comprise a plurality of individual members at evenly spaced positions relative
to one
another in laterally and longitudinally spaced directions perpendicular to one
another
to define an evenly spaced array following a perpendicular grid pattern which
ensures
even compression of the intermediate layers along the length and width
thereof. The
fastening members 26 are received through preformed holes in the intermediate
layers 24.
Turning now more particularly to Figure 1, the fastening members 26 are
shown to comprise threaded bolts which are oriented perpendicularly to the
inner and
outer skin layers. The use of threaded fasteners permits the amount of
pressure in the
form of compression applied to the intermediate layers to be readily
controlled.
In a further embodiment, as shown in Figure 2, the fastening members
26 may comprise rigid rods which are received through cooperating apertures in
the
inner and outer skin layers and the intermediate layers 24 similarly to the
previous
embodiment, but which are deformed or bent at opposing ends thereof once the
inner
and outer skin layers are compressed towards one another by the desired amount
to
retain the intermediate layers at the desired compression rate.
As shown in Figure 3, the fastening members 26 may further comprise
rivets which are mounted relative to the inner and outer skin layers similarly
to the
previous embodiments.
Turning now to Figure 4, a further embodiment is illustrated in which the
fastening members 26 span between the inner and outer skin layers 20 in a non-
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perpendicular manner relative to the skin layers. Each fastening member 26
which
extends from the outer skin layer to the inner skin layer at an inclination in
a first
direction is balanced by a second fastening member 26 which similarly extends
between the outer skin layer towards the inner skin layer at an inclination in
an
opposing second direction so that the fastening members are arranged in pairs
offset
from vertical in diametrically opposed angular directions to balance the angle
of offset
between the inner and outer skin layers. The angled fasteners ensure that the
preformed holes in the intermediate layers 24 are not all aligned with one
another
along a perpendicular axis between the inner and outer skin layers to prevent
lines of
weakness in the panel member. Any of the various types of fastening members 26
described in the previous embodiments can be mounted in an angular orientation
according to the embodiment of Figure 4. The angled fasteners may also be
combined with some fasteners which extend perpendicularly to the skin layers.
Typically the perpendicular fasteners would be located about the perimeter of
the
panel member and the angled fasteners would be centrally located. The angled
fasteners may also be oriented to be all in the same angular direction offset
from
perpendicular so as to be parallel with one another. In this instance,
perpendicular
fasteners would be provided at the perimeter and possibly at various
intermediate
locations to maintain alignment of the inner and outer skins relative to one
another.
Turning now to Figure 6, a further embodiment of the panel member 10
is illustrated in which each intermediate layer is progressively larger in
dimension in a
direction that the skin layers span than a previous one of the intermediate
layers from
the outer skin layer to the inner skin layer. The first layer adjacent the
outer skin layer
is cut to fit the dimensions of the outer skin layer, but the sheets become
gradually
larger in length and width dimensions towards in the inner skin layer.
Accordingly
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some of the intermediate layers adjacent the inner skin layer have greater
dimension
and more slack in a direction the inner skin layer extends than other ones of
the
intermediate layers nearer to the outer skin layer. The increasing larger
dimensions
of the intermediate layers may increase protection against bomb blasts due to
the
easy-undistorted expansion of the deeper layers in the panel member. As a
projectile, or bomb force progresses into the material of the panel member,
the slack
in the following layers may help encourage minimal damage to each of the
following
layers, thus saving their resistance for the force itself, and not the
residual damage
from the previous layer.
In preferred embodiments both the inner and outer skin layers comprise
a rigid metal having a relatively high strength. In some embodiments it may be
desirable to have the outer skin layer 20 comprise a tougher and more ductile
metal
such as aluminium relative to the inner layer which may comprise a more rigid
and
harder metal, for example certain types of steel. In further embodiments both
the inner
and outer skin layers may comprise a similar steel alloy.
Turning now to Figure 7, an exemplary use of the panel member 10 is
shown in which the panel member 10 is spans across the wall 40 of a building
42.
The building 42 comprises a mobile or fixed building or shelter of the type
arranged to
provide shelter to persons 44 therein.
Evidence of the effectiveness of compression of intermediate layers of
woven aramid fibres between rigid skin layers can be found in the following
experimental results.
In a first experiment, a target was placed at 5 meters distance. A
Glenfield model 30a firearm manufactured by Marlin Firearms Co. North Haven,
Conn. was used with Winchester Super X 150gr. Power point, (soft point)
projectiles
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with a muzzle velocity of 2390 ft/sec. The purpose was to determine the
limitations of
compressed KevlarT"^ within a skin of soft steel, and in turn apply this
knowledge to
creating a bullet and bomb resistant barrier for "light duty" vehicles used by
allied
military and domestic police forces.
5 A target block comprised common hot rolled soft steel, 1/8" thick
including a square tube 4" x 4" x 2" deep and two flat end plates 3 3/4" x 3
3/4". The
intermediate layers comprise KevlarTM manufactured by Canadian body armor ltd.
rated at level 2. This material was cut to fit within the square tube to form
120 layers.
Each layer was packaged with packing tape into bundles of 10 layers. This
would later
10 assist in counting the number of layers penetrated to the nearest 10th
layer.
Assembly involved welding the front faceplate onto the rearward
surface, flush with the outside edge of the square tube. A hydraulic press
then
compacted the 120 layers of KevlarTM between both end plates to approximately
25001bs/square inch. The total depth of this material, including both steel
plates was
measured at 1.5inches. This resulted in a void inside the rear of the 4" x 4"
square
tube of 1/2 inch. This void was created to prevent any extra support or
backing for the
rear plate once it was fired upon. We need to determine the strength of this
material,
and the rear plate on its own. Under the hydraulic pressure the rear plate was
then
welded in place. The press was then retracted and the pressurized area is
maintained
between the front and rear plates.
Three projectiles were fired counter-clockwise at the target block and all
three entered near the centre approximately linch apart. Prior to the test,
minor
outward swelling was observed by the faceplates, most likely the result of the
pressure within. All projectiles were contained and disintegrated by the 40th
layer.
The estimated depth of penetration was 3/4 of an inch into the target block.
After the
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test, outward swelling of the rear plate in line with each projectile was
apparent. No
fracturing occurred on this plate, but the deformity was estimated at 3/8 of
an inch. In
this experiment the projectiles penetrated up to the 40th layer. In the next
example
KevlarTM was reduced to 50 layers to see if the same depth of penetration was
seen.
In a second experiment, a similar target was positioned at a 5 meter
distance from the same firearm as the previous example with the only
difference
being the use of 50 layers of KevlarTM compressed between the end plates
instead of
120 layers. Four projectiles were fired in a counter clockwise sequence as
follows:
Bullet #1 was at top dead centre, 1/2 inch from the edge of the target; Bullet
#2 was at
the 11:00 position within 1/2 inch of Bullet #1; Bullet #3 was at the 9:00
position within
1/8 inch from Bullet #2; and Bullet #4 was at the 4:00 position just over 1
inch away
from Bullets # 1& 3. All four projectiles were contained by the 40th layer of
KevlarT""
however, a severe impression was apparent in the 50th layer. Bullet #'s 2 and
3
struck within 1/8inch of one another, and it appears that #3 followed some of
#2's
internal path. This resulted in the most damage to this target block. Bullet
#4 landed
further from the first three and left a shock wave imbedded in the 50th layer
that
measured approximately 21/4 inches wide by 1/2 inch deep. The rubber backing
that
was installed behind the KevlarTM appeared to have no benefits. This material
was
intended to relieve the swelling of the rear faceplate caused by the
projectile, however
the internal pressure applied appeared to have limited cushion effect desired.
It was observed that 50 layers of KevlarTM appear to be enough to safely
contain these projectiles at 5 meters, even when one bullet partially followed
a pre-
damaged path. All bullets were contained by the 40th layer. The final two
layers of'/z
inch rubber seemed to have allowed a more even swelling of the rear plate.
However,
the internal pressure applied to this material seems to have limited the
cushion effect
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12
desired. The shock wave in the 50th layer caused by the 4th bullet was
possibly partly
due to the rubber matting which influenced the outward re-direction of the
impact
energy. This material seems to have only a small benefit in relation to the
space it
would occupy. A ratio shared between the KevlarTM, a layer of internal added
steel,
along with another a support layer of rubber has been considered to further
justify the
rubber as an ingredient.
In a third embodiment, the target was again placed at a 5 meter distance
with the same firearm and projectiles as the previous embodiment. The
intermediate
layers from the front end plate to the rear end plate in this instance
comprise 301ayers
of KeviarTM, followed by an interior steel plate 1/8 inch thick, followed by
a'/2 inch
rubber layer. These layers were assembled similar to the previous embodiments
under pressure of approximately 25001bs/square inch.
Four projectiles were fired in a counter clockwise sequence comprising:
Bullet #1 at a 2:00 position 1'/2 inch from the right edge of the target;
Bullet #2 at a
10:00 position 1/2 inch from left edge of the target; Bullet #3 at the 8:00
position 1/2
inch from a bottom left corner of the target; and Bullet #4 at the 6:00
position 3/4 inch
from the bottom centre of the target. All four projectiles were contained, and
each
were spaced far enough from one another that one did not affect the path of
the other.
It appears that all four bullets penetrated through all the layers except for
the rear
plate. No fractures in this plate are apparent, but a definite imprint was
visible. 30
layers of KevlarTM appears to be inadequate to contain these projectiles. The
single
layer of 1/8th metal did not supply enough backing to allow the 1/2 in rubber
to disperse
the blunt force of the projectile. The 1/2 inch rubber matting couldn't make
up for the
lack of endurance of the previous two layers of KevlarTM and 1/8th metal. From
the
information gathered from experiment #1 and #2 it appears that it would be
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13
reasonable to assume that 50 layers of KevlarTM under 25001bs/sq.in. are
adequate to
contain the 150gr 30-30 calibre bullet at 5 meters distance. Further
experiments
involve more powerful firearms.
In a fourth experiment, a similar target was placed 5 meters from a
Ruger m77 mark ii firearm using federal power-shok 175gr.(soft point)
projectiles at a
muzzle velocity of 2860 fps / energy = 3180ft-lbs. The same target
construction of
end plates was used in this instance with 70 intermediate layers of KevlarTM
under
2500 lbs/square inch of pressure. Each layer was packaged with packing tape
into
bundles of 10 layers. This would later assist in counting the number of layers
penetrated to the nearest 10th layer. A single projectile was fired which
passed
completely through the target block. The 70 layers of KevlarTM along with the
1/8tn
thick rear faceplate are believed to be not strong enough to contain a 7mm
bullet.
In the 5th experiment, the same firearm and projectiles were used as the
4th experiment at a distance of 5 meters, however the target block was varied
in that
160 intermediate layers of KevlarTM were instead compressed between both end
plates by approximately 2500lbs/square inch. Four projectiles were fired in a
counter
clockwise sequence and all four bullets landed within 1.25 inches to the
centre of the
target block. The four bullets were all successfully stopped, however the
energy
forced on the target block tore the rear plate mostly off the weld. The 160
layers of
KevlarTM appear to be strong enough to contain a 7mm bullet. The weld fracture
on
the rear plate is believed to be due to the poor quality weld. Due to swelling
at the rear
of the target, a minimum of 1.5 inches between the rear plate and the backstop
is
recommended to prevent unwanted bracing against any energy coming from the
projectiles.
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14
According to a 6th experiment, a similar projectile and firearm as the
previous two embodiments was used at a distance of 5 meters from the target.
The
target was again assembled with 160 intermediate layers of KevlarTM. Each
layer was
packaged with packing tape into bundles of 10 layers. No compression was used
in
this experiment however to compare if compressing KevlarTM has benefit.
Accordingly
the 160 layers were simply laid inside the target block in this instance. The
final depth
of KevlarTM along with the face and rear plates amounted to 2.5 inches.
Six projectiles were fired. Bullet one and two were contained with
minimal damage, however, bullet #3 landed within a'/4 inch and appears to have
followed the path of bullet #2. As a result bullet #3 penetrated the block,
however, no
evidence was found of it entering the backstop. Also bullet#3 appears to have
torn the
rear plate off the weld. Projectiles 4, 5, and 6 were then fired, all with
minimal
damage, these three rounds landed within 1/2 inch of one another. The 160
layers of
uncompressed KevlarTM appear to be strong enough to contain a 7mm bullet,
however the target was required to be considerably thicker.
In the following 7th experiment, the same firearm and projectile were
used at a distance of 5 meters from the target. The target block was assembled
to
comprise 160 intermediate layers of KevlarTM between the inner and outer end
plates,
compressed to approximately 2500lbs/square inch. Six projectiles were fired.
Bullets
1, 2, and 3 landed in a triangle shape within 1/2 of an inch of one another.
All three
were contained. Bullets 4, 5, and 6 were then fired and landed similar to a
straight iine
left to right, with bullet #6 within 1/8th of an inch from bullet #2. As a
result #6
penetrated the target block and was embedded well within the wooden backstop.
The
160 layers of compressed KevlarTM appear to be strong enough to contain a 7mm
bullet. The reason projectile #6 penetrated the block appears to have been due
to the
CA 02651631 2009-01-30
fact that it found part of the path in the KevlarTM created by bullet #2. The
other 5
projectiles landed within that same region approximately 3/8th of an inch
apart and
failed to create their own path clean thru.
The compressed KevlarTM has created not only a thinner barrier, but
5 also a stiffer barrier than that of the uncompressed version. This effect
can be seen
along the outside perimeter of the block. This area has collapsed more on the
compressed version. Both blocks had 6 projectiles impacted thereon and both
blocks
were left with a 2 inch void between the rear plate, and the wooden backstop.
It
should stand to reason that the damage in this area should be very similar.
The only
10 change between these two blocks is the pressure applied to one. Upon
initial
appearance the overall swelling of the rear plate of the compressed version
seems to
have suffered more inflammation than the non-compressed target which is
believed to
be a result of the projectiles impacting in closer proximity to one another:
Upon
observation of the experimental results, it appears that when there is any
damage
15 already present from a previous projectile impact causing lines of weakness
in the
panel member, the compression of the layers results in more resistance against
subsequent projectiles following the lines of weakness in the panel member.
The
panel member is accordingly more resistant to multiple projectile impacts when
the
layers are compressed.
In the next and 8th experiment, a target block was prepared with 200
layers of KevlarTM under pressure, but with aluminum forming the surrounding
case.
The KevlarTM was also compressed with common grade 5 bolt fasteners. By using
the
bolts instead of the hydraulic press we can more accurately control the
pressure, and
furthermore this method allows us to apply and maintain the pressure by hand.
A
torque wrench can be used to estimate the pressure applied. In addition no
welding
CA 02651631 2009-01-30
16
on the case is done, which in turn prevents the KevlarTM from being burnt and
damaged.
In the 8`h experiment, the same projectile and firearm are used as the
previous embodiment at a distance of 5 meters from the target. 1/8 inch
aluminum
plate was used to form the end plates surrounding the intermediate layers
therebetween. Four 3/8th inch diameter x 3'/2 inch long grade 5 carriage bolts
joined
the end plates with the KevlarTM under compression therebetween. The bolts
were
installed thru both of plates approximately 1" in from the each of the four
corners. The
upper and lower edges of this plate were then bent forward to form the top and
bottom
sides of this target block.
Three Projectiles Were Fired. Bullet one landed approximately 3" down
and 1" inch in from the top left corner of this block. It created a swelling
on the back
plate of approximately 1'/< inch in depth. Along with this swelling this
impact pulled
the side edge of the rear faceplate away from its original position. The
sideward
movement was due to the fact that this plate has no support on the edges other
than
the four bolts. Bullet two landed in the far right corner, striking the top
edge of the
head of the bolt there. This bolt head interfered with the impact somewhat,
and as a
result minimal damage was seen on the block in this area. This impact started
what
seemed to be a previous weak spot along the edge just above the impact point.
Bullet
three landed approximately 2 inches above bullet 2. The tear in the rear plate
from the
previous bullet has allowed bullet 3 to continue this same rip to a point
where it nearly
came thru. This rip went from approximately 1 inch to approximately 4 inches.
The
200 layers of compressed KevlarTM appear to be more than adequate to contain
the
projectiles. The aluminum was used to lighten the overall weight of the
breaker, and
due to the fact that it is rust resistant. The swelling caused by the 1 st
bullet was
CA 02651631 2009-01-30
17
considerably more than what was seen previously with the steel material. As a
result if
softer material is used an increase in its thickness to '/4 inch is
recommended. The
bolts work very well to contain the pressure, and are easy to apply.
The principle design of the present invention as described herein relates
primarily to compressing layers of bullet resistant fabric between two outer
layers of
steel. These skin layers of steel provides structure and strength to contain
the
pressure of the fabric as well as the added ability to hold various shapes and
contours
that may allow it to be moulded along with other pre-formed structures, such
as a car
door.
The assembly of this product would be completed by inserting fasteners
into a pattern of pre-punched holes through the layers of fabric and steel.
These
fasteners may include a variety of methods such as rivets, threaded rod,
straight rod
with bent ends, as well as the metal case being fused by welding. Depending on
the
use of other concerns, each method holds a valid place in the productions of
the bullet
resistant member described herein.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
