Note: Descriptions are shown in the official language in which they were submitted.
CA 02250634 1998-10-14
TITLE
Welded Joint for Armored Vehicles
FIELD OF THE INVENTION
This invention relates to a welded joint, and more particularly to a welded
joint
for armored vehicles.
BACKGROUND OF THE INVENTION
The armoring of vehicles usually requires that plates are held together and/or
in
place by some form of mechanical fastener or welding. Ballistic protection is
enhanced
either by overlapping the armor plates or by covering over joints with
additional plates.
In most cases the armor materials are parasitic and do not add any significant
strength to
the vehicle.
The high overpressures and shock waves produced by the explosives cause the
plates to exert a great amount of force on the mechanical fasteners and/or
welds. As a
result, pieces of armor can become dislodged and become shrapnel as well.
Often the
armor will fail at the site of a pre-formed hole or a weld. The net effect of
non-
directional explosive attack on most current armor systems is to dislodge the
armor and
significantly alter the structure of the vehicle to the point that it is no
longer continuous.
As indicated above, a particular problem associated with joined armor plates
is
that the failure tends to occur at the joint. Once a crack is initiated, it
tends to propagate,
and often results in catastrophic failure of the entire plate.
SUMMARY OF THE INVENTION
2 5 An object of the present invention to provide an improved an improved
joint for
armored plates that provides reduced susceptibility to failure of the plates.
CA 02250634 1998-10-14
A specific object of the present invention is to provide a joint configuration
whereby the propagation of any crack is directed to the outside of the plate.
Another object of the invention is to allow utilizing the armor plates to
provide a
continuous unitary mechanical structure for the vehicle.
It has been found that an improved joint for armored plates can be obtained by
providing one of the armor plates, or an interconnecting element, with a semi-
circular
rounded lobe; and welding the lobe to the plate to be joined near to an
outside edge
thereof to form a U-shaped welded region such that the ends of the welded
region are
directed to the outside edge of the plate so that a crack formed in the weld
will tend to
propagate along the weld to the outside of the plate rather than into the
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic representation of one embodiment of the invention,
showing
a single lobe welded in a lap joint.
Fig. 2 is an side view of the joint of Fig. 1.
Fig. 3 is a schematic representation of another embodiment of the invention
showing a lobed connecting element welded to form a corner joint.
Fig. 4 is an side view of the joint of Fig. 3.
Fig. 5 is a schematic representation of another embodiment showing a lap joint
2 0 with a plurality of interconnected lobes.
Fig. 6 is an side view of the joint of Fig. S.
Fig. 7 is a schematic representation of another embodiment showing a corner
joint with a plurality of interconnected lobes which are provided with
reinforcing gussets.
Fig. 8 is an side view of the joint of Fig. 7.
2 5 Fig. 9 is a perspective view showing the welded joint structure for an
armored
door.
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Fig. 10 is a sectional view showing the roof of an armored vehicle, with the
section taken at 10-10 of Fig. 11.
Fig. 11 is a bottom view showing the welded structure on the roof of an
armored
vehicle as shown in Fig. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 and 2 show the present invention in its simplest form, wherein two
plates 1
and 2 are joined by welding. One of the plates I is provided with an edge
configured
with a rounded semi-circular lobe 3. The lobe of plate 1 is welded to plate 2
to form a
U shaped welded regions 4 in such a manner that the ends 5 of the welded
regions 4 are
directed to the outside edge 6 of the plate 2.
This U-shaped configuration of the welds provides that a crack formed in the
weld will tend to propagate along the weld to the outside edge of the other
plate 2 to
which the lobes are welded This arrangement whereby any failure follows the
weld line
and runs out of the plate and not into them in turn prevents catastrophic
failure of the
joined plate.
Figs. 3 and 4 show another embodiment of the invention wherein two plates 31
and 32 are joined at right angles by means of an intermediate connecting
element 33. The
connecting element 33 is provided with semi-circular lobes 34 and 35 on
opposite sides
2 0 and bent at an angle to conform to the angle desired of the plates 31 and
32, which are
shown at right angle. As in the embodiment of Fig. l, the lobes 34 and 35 are
welded in a
U-shaped configuration 36 and 37, respectively. As in the embodiment of Fig. I
and 2,
the ends of the welded regions 36 and 37 are directed to the outside edge of
the
respective plate so that any cracks will be directed to the outside edge of
the plate, rather
2 5 than inwards.
In the embodiment of Figs. 5 and 6, one of the plates 51 to be joined has a
plurality of lobes 53 interconnected to one another by an intermediate smooth
curved
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CA 02250634 1998-10-14
edge portion 57 to form a sine-wave-like appearance. As in the previous
embodiments
the welding 54 of each lobe forms a U-shaped weld with ends that are directed
to the
outside of the plate.
In the embodiment of Figs. 7 and 8, two plates 71 and 72 are joined at right
angles by means of an intermediate connecting element 73. The connecting
element 73 is
provided with a plurality of semi-circular lobes 74 and 75 on opposite sides
and bent at
an angle to conform to the angle desired for the plates 71 and 72, shown as
right angle.
As in the previous embodiments the lobes 74 and 75 are welded in a U-shaped
configuration 76 and 77, respectively. As in the previous embodiments, the
ends of
welded regions 76 and 77 are directed to the outside edge of the plate so that
any cracks
will be directed to the outside edge of the plates.
Figs. 7 and 8 show the connecting element provided with triangular gussets 78
welded to the lobed connecting element to reinforce the corner joint. For most
applications it is preferable that the gusset does not extend to the extreme
end of the
lobe, so as to maintain some flexibility of the end of the lobe in the region
of the weld.
For maintaining the greatest flexibility of the welded lobe, the gusset would
extend only
to the base portion, or root, of the lobe.
Fig. 9 shows the use of lobed elements such as shown in Figs. 3 and 7
incorporated into a welded structure suitable for an armored door.
2 0 Referring to Fig. 9, the door structure includes a hinge plate 92, a lock
plate 93, a
top belt-line bar 94, and bottom plate 95. The hinge plate 92 and lock plate
93 are shown
connected to the door armor plate 91 by means of interconnecting elements 96
similar to
those shown in Fig. 3 and 4. The top and bottom plates 94 and 95 are shown
connected
to the door body 91 by means of interconnecting elements 97 similar to those
shown in
2 5 Fig. 7 and 8. As in the previous embodiments, the ends of welded regions
98 are directed
to the outside edge of the plates so that any cracks will be directed to the
outside of the
plate 91.
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As detailed in the examples below the door structure will preferably comprise
a
number of layers including a hard outer layer and a softer tough layer which
is connected
to the hinge plate, a lock plate, a top belt-line bar, and bottom plate with
the connecting
means of the present invention, as described above.
The hard outer armor layer is designed to redirect or alter bullets or
shrapnel
while the softer tough inner layer absorbs energy and provides a tough
mechanical
structure. An additional inner layer of a material such as SpectraTM may be
used to trap
any fragments of the first two layers of armor that may have become dislodged
or passed
the first two armor layers.
Fig. 10 and 11 show the present invention incorporated into the roof of an
armored vehicle.
Referring to Fig. 10 and 1 l, the welded joint of one of the layers I O I of
the roof
uses lobes 103 similar to that of Fig. 5. In addition, the layered structure
uses circular
elements 105, that are welded to form an annular welded region 106, to
reinforce the lap
joint of an adjacent layer 107. As in the previous embodiments, the ends of U-
shaped
welded regions 104 are directed to the outside edge of the plate so that any
cracks will be
directed to the outside of the plate 102. These U-shaped elements employ the
same
principle as the lobes in directing any cracks to the outside of the plate.
The armor plates used for the roof of a vehicle will preferably comprise a
2 0 plurality of layers of different materials having differing hardness and
modulus
properties, specifically, a relatively hard outer layer 108 and a softer but
tougher layer, or
layers (101 and 107) as shown in Fig. I0. Fig. IO also shows the use of a tab
strip 109
covering a butt joint in the outer hard layer 108.
The combination of a hard steel backed by a softer steel provides the strength
and
2 5 toughness desired to withstand the impact of explosives. The use of
overlapping plates
and staggered weld lines and the use of the semi-circular lobes of the present
invention
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CA 02250634 1998-10-14
causes the explosive energy to be redirected and reduces the likelihood of
catastrophic
failure of the welds.
It should be noted that in multiple layer configurations involving hard and
relatively soft layers, the welded connection will preferably be made onto the
softer layer
which is affected less, with regard to mechanical properties, by the welding.
The construction of the door and roof as described above, effectively provides
a
continuous unitary mechanical structure whereby impact forces are distributed
to the
entire cage of the vehicle.
The present invention can be used for plates in various configuration. As
illustrated above the present invention can be used for lap joints or corner
joints. It will
be understood that the plates can be various shapes and connected at various
angles.
Examples/Tests
Tests were conducted to determine if armor plates comprising of 3 mm of
Sanderson Keyser Bulloy 500 steel, or 3 mm of Compass B555 steel, and 3 mm of
Jessop
529 steel connected to a hinge plate, a lock plate, a top belt-line bar, and
bottom plate by
welded joints in accordance with the present invention can be used as an
armour system
in an automotive door to provide protection against a contact detonated steel
pipe bomb
filled with 454 g of smokeless powder. The arrangement was similar to that
shown in
2 0 Fig. 9.
The door structure comprised an outer door skin of 1 mm mild steel, an outer
armor layer of 3 mm Sanderson Keyser Bulloy 500 steel, or 3 mm of Compass B555
steel, a 3 mm layer of Jessop 529 steel, a layer of 4.9 kg/mz Spectrashield
T'", and an
inner 1 mm aluminum witness panel. For some tests the armor layers were bonded
with
2 5 a bonder layer of urethane or polysulphide. The outer armor layer of 3 mm
Sanderson
Keyser Bulloy 500 steel or Compass B555 steel has a high hardness designed to
redirect
or alter bullets or shrapnel while the layer of Jessop 529 steel is softer and
tougher and
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provides a tough mechanical structure and absorbs energy. The inner SpectraTM
layer
traps any fragments of the first two layers of armor that may have become
dislodged or
passes the first two armor layers.
The joints between the inner armor plate and the hinge plate, lock plate, belt-
line
bar, and bottom plate each comprised four lobes reinforced with gussets
similar to that
shown in Fig. 9.
The pipe bomb was suspended against the door skin with its axis parallel to
the
vehicle's axis and located adjacent to the center of the lower half of the
door. The door
was complete with glazing.
In one test in which the gussets extended to the edge of the lobe, one of the
lobes
close to the site of impact pushed the inner layer of armor into the other
layer so that the
outer layer had a semi-circular crack. Although this crack was not considered
a system
failure, the gussets were shortened so as not to extend to the edge of the
lobe thereby
allowing the lobe to flex and avoid such damage to the other armor layer.
Subsequent
test proved this to be effective.
Following the tests it was observed that the outer door skin was badly damaged
and pulled out at the bottom. The armor system was depressed (eg. 57 and 71 mm
depression) but remained intact. There was no penetration of the inner witness
panel.
It was concluded that an occupant would not have been harmed by such a contact
2 0 detonated steel pipe bomb filled with 454 g of smokeless powder.
A further test was conducted to determine if welded joints in the roof of an
armored vehicle could withstand the force of a pipe bomb detonated in contact
with the
roof pan. The arrangement of armor layers and joints between the roof pan (two
layers)
2 5 and roof rail (3 layers) was similar to that shown in Figs. 10 and 11.
The front and side welded joints were as follows; an outer layer of steel butt
welded together; a second layer of steel butt welded and lap welded to the
outer layer 12
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mm from the outer layer weld; a third layer of steel overlaped both butt welds
and had
semi-circular lobes lap welded to the second layer of steel. The side joints
are shown in
Figs. 10 and 11. A weld joint at the center of the roof was identical to the
front except
that the third layer was a double sided strip of semi-circular lobes designed
to support the
two butt welds above it (not shown).
The armor system remained intact although it was depressed and there were
cracks in the second layer of armor along the welds on the lobes. The second
layer of
steel cracked only at the weld sites on the front and side joints. The cracks
followed the
welds and did not extend beyond the welds. Only the side of the center joint
adjacent to
the bomb cracked. However, as this was the most highly stressed area, the
crack in the
second layer followed the weld line for three lobes. No cracks ran into the
plate.
The single sided and double sided lap joints formed with semi-circular lobes
(welded only on the lobes and not the roots) were effective in keeping the
roof armor in
place when subjected to a steel pipe bomb filled with 454 g of smokeless
powder.
Details of a composite material suitable fox use in vehicle armoring are the
subject of applicant's U. S. Patent No. 6,216,579 issued April 17, 2001.
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