Note: Descriptions are shown in the official language in which they were submitted.
CA 02297467 2005-07-08
FLEXIBLE CORRUGATED MULTILAYER METAL FOIL
SHIELDS AND METHOD OF MAKING
field o . Invention
This invention relates to multilayer metal foil and metal sheet structures
which
have utility as heat shields and as acoustic shields.
$,a~c_kgrQu~d of the Invention
Mtiltilayer metal foil insulation has been used for many years, as illustrated
by
U.S. Patent No. 1,934,174. Such metal foil insulation has typically been used
in high
temperature applications for reflective heat insulation. In those
applications, the layers
of metal foils are embossed to provide separation between the layers, and the
stack of
layers are protected in a container or rigid cover to prevent the stack of
metal foils
from becoming compressed at any portion, which would decrease the heat
insulation
value of the stack.
U.S. Patent No. 5,011,743, discloses that multilayer metal foil insulation can
pmvide enhanced performance as a heat shield when a portion of the multilayer
metal
foil is compressed to provide a heat sink area through which heat is collected
from the
insulating portions of the stack and dissipated from the heat shield. Such
multilayer
metal foil heat shields are fozmed from a stack of embossed metal foil layers
by
compressing portions of the stack to create the desired heat sink areas. The
layers are
attached to each other or stapled together to prevent the layers from
separating. The
heat shields and acoustic shields formed according to the disclosure of the
U.S. Patent
5,011,743 are typically compressed in the heat sink areas and cut~~to a
desired pattern.
Such multilayer metal foil heat shields do not normally have sufficient
structural
strength for stand-alone use in many applications. For many applications, the
metal
foil heat shields are typically attached to a structural support member or pan
to provide
a fuial assembly which is then placed in service as a heat shield or acoustic
shield. The
support members are typically metal pans, metal stampings or metal castings.
Typical
applications for such heat shield assemblies include automotive heat shield
applications.
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~mmmarv of the Invention
It is an object of this invention to provide a multilayer metal foil
insulation
structure which is flexible and suitable for use in heat shield and acoustical
shield
applications.
The flexible corrugated multilayer metal foil structure according to this
invention comprises a stack of metal foil layers which are formed in
corrugations
extending across a stack of the metal foil layers, wherein all of the layers
have the same
corrugated pattern and shape as a result of the stack being shaped in
corrugations or the
layers being separately shaped in corrugations then nested into a stack. A
portion of
the corrugations of the stack of metal foil layers is compressed to fold the
layers
together whereby the layers are interlocked together in overlapping
relationship. The
resulting multilayer corrugated interlocked structure is flexible by means of
the ability
of the multilayer corrugated interlocked structure to flex along the valleys
or peaks of
the corrugations where they are not compressed and folded and along the
valleys
between the corrugations where the peaks of the corrugations are compressed
and
folded to interlock the layers together. Depending on the thickness of the
layers,
number of layers and the degree of compression of the interlocked layers, the
compressed portions of the corrugations can also flex along with the
uncompressed
portions of the interlocked structure.
The flexible corrugated multilayer metal foil structures of this invention
comprise at least three metal layers at least two of which are metal foil
layers having a
thickness of 0.006 in. (O.lSmm) or less. It is generally preferred that the
flexible
corrugated multilayer structures of this invention contain at least three
layers of metal
foil and more preferably will typically contain five or more layers of metal
foil.
Preferably, the metal foil layers will be 0.005 in. (0.12mm) or less, with
0.002 in.
(O.OSmm) metal foil being a preferred thickness, especially for the interior
layers of the
flexible corrugated multilayer metal foil structure. In addition to the layers
of metal
foil, optional protective exterior layers of metal sheet on one or both sides
of the
flexible corrugated multilayer structure can be included. Such metal sheets
have a
thickness greater than 0.006 in. (0.15 mm) and up to about 0.050 in. ( 1.27mm)
. The
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thickness of the optional exterior protective metal sheet is selected such
that it can be
corrugated into the same shape and pattern as the other layers (either
separately then
nested, or simultaneously corrugated as part of the stack) and compressed into
interlocking engagement with the other layers as part of the unitary
multilayer metal
foil structure according to this invention. Preferably, the protective
exterior metal
sheet layer will be between about 0.008 in. (0.20mm) and about 0.030 in.
(0.76mm).
One preferred flexible corrugated multilayer metal foil structure according to
this
invention is made entirely of metal foils each having a thickness of 0.006 in.
or less
without the use of heavier external sheet layers.
One or more of the individual metal foil layers comprising part of the
multilayer
structure of this invention may be embossed or contain other spacers to
provide spaces
and gaps between the layers. Even though some of the embossments or gaps may
be
reduced during the formation of the corrugations of the multilayer stack and
some may
be entirely eliminated in those areas where the corrugations are compressed to
form the
folds interlocking the layers together, the residual spaced apart gaps between
the layers
in various parts of the multilayer corrugated structure is advantageous in
many
applications with respect to the heat and acoustic insulating and shielding
properties.
However, without embossments or other spacers to hold the layers apart, the
metal foil
layers will inherently have some gaps and spaces between the layers due to
wrinkles or
other deformations that inherently occur during the formation of the
corrugations of the
multilayer metal foil structure. In addition to spacers in the form of
embossments or
wrinkles in the layers themselves, separate spacers may be used to provide
gaps
between the layers, such as compressible foil pieces or mesh, or non-
compressible
materials, so long as the presence of such spacers does not interfere with the
compression and folding of the corrugations together at desired locations in
the
structure to interlock the layers and prevent separation of the layers when
the multilayer
metal foil structure is used for its intended use.
The flexible multilayer corrugated metal foil structures of this invention,
when
formed with corrugations across the stack of layers, are rigid or at least
resist bending
in one direction but are flexible in the other direction due to the ability of
the stack to
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flex along the peaks and/or valleys of the corrugations. This flexibility of
the
multilayer corrugated structure enables application thereof as heat and sound
shields to
contoured shapes, especially curved planar surfaces such as conduits. However,
the
multilayer corrugated structures of this invention can also be fitted or
formed into or
onto any shape desired by flexing the multilayer structure in one direction
along the
corrugations and by bending, creasing or buckling the corrugation ridges to
shape the
structure in the other direction across the corrugations. In addition, the
spacing of the
corrugations can be laterally stretched out or compressed together to assist
in shaping
the multilayer corrugated metal foil structure to fit desired three
dimensional shapes.
For example, a shield can be formed to a desired shape by forming the
corrugations in
the stack of metal foil layers, shaping the stack including stretching or
compressing the
corrugations laterally (along the plane of the layer) as needed for shaping,
then
compressing the corrugations vertically where desired to fold the corrugations
and
interlock the layers together.
In an optional structure, the corrugated multilayer metal foil structure of
this
invention can be made flexible in the other direction by compressing creases
across the
corrugations, whereby the creases are compressed deeply enough into the
corrugations
to provide the bending and flexing of the multilayer structure along those
creases. It
will be recognized that in the formation of such creases to provide additional
flexibility
to the corrugated multilayer metal foil structure of this invention, the
compression to
form the creases will also provide the additional function of folding the
corrugated
layers and interlocking the layers together with one another in the same
fashion as the
above described vertical compression of the corrugations to interlock and
prevent
separation of the layers. This folding and interlocking of the layers by the
creasing can
be in addition to or instead of the first compression of the corrugations
mentioned
above to fold ~.~1 interlock the layers. Such creases can be any desired
width, fr:3~n a
knife-edge sharp crease to wide flattened strip across the corrugations, and
can be any
desired direction across the corrugations depending on the flexibility and the
heat or
sound shielding properties desired in the final product.
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The present invention provides a method of forming a flexible corrugated metal
foil structure by first providing a stack of metal foils. Each metal foil
layer optionally
may be individually embossed, wrinkled, corrugated (for example, very small
corrugations in period or height compared to the main corrugations of the
multilayer
product) or contain other spacers to provide gaps between the layers. The
stack of
metal foils is then shaped as a unitary structure into corrugations, which may
be done
using conventional metal corrugating methods and equipment. After the
corrugations
are formed in the multilayer stack, a portion of the corrugations are
compressed to fold
the layers over each other whereby the layers are interlocked together. The
interlocking of the layers prevents separation of the layers while retaining
the flexibility
of the multilayer metal foil corrugated stack along the corrugations by
flexing along the
peaks and valleys or channels of the corrugations. The portion of the
corrugations
which are compressed in order to fold and interlock the layers may be any
portion or
area of the corrugations desired for a particular product, but sufficient to
prevent
separation of the layers during handling and use. For example, in many
applications it
will be preferred that the edges of the corrugated stack be compressed whereby
the
metal foil layers are folded and interlocked around the perimeter or along at
least one
edge of the multilayer corrugated metal foil stack. Other configurations may
be
desirable depending on end use of the multilayer metal foil structure. For
example, it
may be desired to compress an interior portion of the corrugations in a strip
parallel
with the edge of the multilayer strip whereby the layers are folded and
interlocked
together in an interior portion of the corrugated multilayer metal foil
structure leaving
the edges uncompressed in the corrugated configuration. Alternatively, it may
be
desired to substantially compress periodic or alternating corrugations along
all or most
of the length of each individual corrugation, whereby a certain proportion of
the
corrugations are compressed to fold and interlock the layers together while
the entire
length of other corrugations remain uncompressed.
The shape of the corrugations can be selected by one skilled in the art
depending
on the desired properties of the structure. For example, the corrugations may
be
sinusoidal, square, rectangular, semicircular or other appropriate corrugation
shape.
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The size, height, width and spacing of the corrugations can be uniform and
regular, or
can be nonuniform and irregular, so long as the corrugations are designed so
that when
the selected portion of the selected corrugations are compressed, the layers
will readily
fold and interlock together as a result of the compression of the
corrugations.
S Similarly, the shape of the folds into which the layers are deformed and
locked together
can be selected and designed depending on the interlocking properties desired
in the
final flexible corrugated multilayer metal foil product produced according to
this
invention.
The flexible multilayer metal foil structures of the present invention have a
wide
range of utilities, but are preferred for heat and acoustical shielding
applications,
particularly in automotive use. The flexible multilayer metal foil structures
of this
invention have utility as heat insulating materials, but are preferred for use
in heat
shielding applications for spreading and dissipating heat from point sources
of heat, or
hot spots. Due to the high lateral conductivity of the multiple metal layers,
heat can be
1 S efficiently conducted laterally from a hot spot to other locations within
the flexible
multilayer metal foil structure where the heat can be absorbed by or
dissipated into
surrounding environment where the temperature is lower than in the area of the
hot
spot heat source. It will be expected that in the corrugated multilayer metal
structure
according to the present invention, heat will be most readily and rapidly
conducted
along the shortest conductive path, which is along the length of the channels
of the
corrugations. Heat will be conducted more slowly in the direction transverse
to the
corrugation channels, i.e., along or across the peaks and valleys of the
corrugations.
Heat will also be conducted more rapidly along the paths resulting from the
compressed
areas and the creased areas referred to above, where the peaks and valleys of
the
corrugations have been essentially flattened. Given these properties, one can
readily
design corrugated multilayer metal foil h~wt shielding structures according to
the
present invention to shield and insulate h~_.. spot sources of heat by
conducting and
dissipating the heat laterally along the corrugations in desired and specific
directions.
Similarly, the flexible multilayer metal foil structures of this invention
have utility as
acoustical shields due to the vibration and sound absorbing properties of the
corrugated
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multilayer metal foil structure. For acoustic applications, it will be
apparent to one
skilled in the art that it may be desirable to have alternate material layers
in between
the corrugated metal layers. Materials such as plastic films, adhesives,
fibers and other
materials may be used to enhance the acoustic damping properties of the
multilayer
corrugated metal foil structure, although some of those alternate materials
may not be
suitable for use in some heat insulation or heat shielding applications.
The corrugated multilayer metal foil structure of this invention provides two
advantages for utilization of the structure in various heat and acoustic
shielding and
insulating applications. First, the flexibility provided by the corrugations
provides
convenience in positioning the flexible corrugated multilayer metal foil
structure of this
invention in desired applications. As will be recognized, the additional
flexibility by
providing the above-referenced longitudinal creases across the corrugations
provide
additional flexibility, or the preforming the corrugated stack of metal foil
layers before
interlocking the layers together, will enable one to utilize the structures of
this
IS invention where various shapes of heat or acoustic shielding are required.
The second
property provided by the corrugated multilayer metal foil structure of this
invention is
the surprisingly high vertical strength and load bearing capability of the
flexible
corrugated multilayer metal foil structure formed according to this invention.
After the
selected portions of the corrugations are compressed to form the folding and
interlocking of the layers together, the remaining uncompressed portions of
the
corrugations will support vertical loads and exhibit resistance to compression
higher
than one would expect for metal foils. Such load bearing properties make the
flexible
corrugated multilayer metal foil structures of this invention particularly
useful as heat
and acoustic shields under the carpet in passenger compartments of vehicles.
The
corrugated multilayer metal foil structures according to this invention may be
positioned between the floor pan of an automobile and the passenger
compartment
carpet to absorb and dissipate heat from hot spot sources underneath the floor
pan, such
as a catalytic converter or exhaust systems, and to absorb and dampen noise,
such as
road noise. The corrugated shape of the multilayer metal foil structures of
this
invention provides sufficient resistance to compression and crushing under the
carpet to
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enable the corrugated metal foil structure to maintain its corrugated shape
and its heat
and acoustic shielding properties under ordinary usage where vertical loads
are applied
to the corrugated multilayer metal foil structures by passengers stepping on
the carpet.
It will be recognized by one skilled in the art that the flexible corrugated
multilayer metal structures according to this invention can be formed with
metal sheets
having thicknesses greater than 0.006 in. and without the use of metal foil
layers
having a thickness of 0.006 in. or less. Such flexible corrugated multilayer
metal sheet
structures are formed in the same way as the multilayer metal foil structures
and may
1 o be desirable for additional strength and vibration resistance in certain
end use
applications.
In another aspect, the invention provides a multilayer metal foil structure
comprising at least two layers of metal sheets wherein the layers are metal
foil each
having a thickness of 0.006 in. (0.15 mm) or less, wherein the two layers of
metal sheets
15 are corrugated and nested together in a stack, and a portion of the
corrugations of the
stack is compressed to form interlocking folds of the layers.
Brief Descri~,tion of the Drawing
2o Figure 1 is a perspective view of a multilayer metal foil stack which is
formed
into corrugations.
Figure 2 is a partial perspective view of an edge portion of the stack of
corrugated metal foils illustrating the compressed corrugations whereby the
layers are
2s folded and interlocked together.
Figure 3 is a cross section view of an alternate shape of the folding and
interlocking of the layers by compression of the corrugations.
Figure 4 is an illustration of additiohal creasing of the corrugations to
provide
3o flexibility in the longitudinal direction across the corrugations, as well
as the lateral
direction along the corrugations.
Figure 5 is a perspective view illustration of a diagonally embossed
multilayer
metal foil strip utilized for conduit insulation_
35 Figure 6 is an illustration of the application on the corrugated multilayer
metal
foil structures of this invention to a vehicle.
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I)escriptivn of the Invention
This invention adapts metal sheet corrugation forming processes to provide
novel flexible, corrugated multilayer metal foil and metal sheet structures.
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Conventional metal corrugation forming processes, such as diclosed in U.S.
Patent Nos. 3,966,646 to Noakes et al. and 4,810,588 to Bullock et al. may be
adapted for use in forming the corrugations utilized in the multilayer metal
foil
structures of this invention. While Bullock et al. is directed to non-nesting
corrugated metal foil layers, it is apparent that the corrugation.processes
similar to Noakes et al. and otherwise known in the art can be adapted to form
the corrugations in the multilayer metal foil structures of the present
invention.
In the practice of the present invention, it is preferred that a stack of
metal foils and metal
sheets first be provided in the desired number of layers, wherein the layers
may contain
embossments or other spacers far providing desired gags or separation between
the
layers. The stack of metal foils is then corrugated as a unitary structure to
form
corrugations in all of the layers of the stack simultaneously. The corrugated
stack of
metal foils is then subjected to compressing selected areas or portions of the
corrugations to cause the layers in the stack to fold over each other and
interlock
together as the corrugations are compressed to an essentially flattened
condition in the
selected areas. The resulting product provided by this invention is a
multilayer metal .
foil structure wherein all of the layers are folded and interlocked.together
in those
compressed portions of the corrugations, which holds the entire structure
together, and
the multilayer metal foil structure remains flexible due. to the bendability
in the areas of
the peaks and/or valleys of the corrugations.
In an alternative method of forming the structures of the present invention,
individual metai foil layers and metal sheet layers may be corrugated
separately, then
stacked together and nested as a stack of pre-corrugated individual sheets.
The
corrugations can be regular or irregular in shape, period, etc., so long as
each of the
sheets will substantially nest with the other sheets to enable the compression
and
folding of the stack of corrugations for the interlocking of the layers
together. The
nested stacks of corrugated sheets can then be subjected to compression of
portions of
the corrugations to fold and interlock the layers together to form the
corrugated
multilayer metal foil structures of this invention. One or more of the
individual layers
may be ertibossed or otherwise dimpled, crinkled, corrugated (in a non-nesting
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direction or pattern different than the adjacent layers) or otherwise
topographically
contoured in order to provide gaps and spacing between the layers. When metal
foils
are provided with such embossments or spacers to provide gaps, it will be
recognized
that a portion of the embossments or spacers will usually be eliminated or at
least
diminished during the corrugation process to form the corrugated multilayer
metal foil
structure according to this invention. It will also be recognized that when
portions of
the corrugations in multilayer preform stacks are compressed to fold and
interlock the
layers together, the embossments or other spacers may be substantially or
entirely
eliminated in those compressed areas. However, in many applications it may be
desirable to provide such embossments or spacers to form gaps between the
layers,
because gaps between the layers in the corrugated areas, which are not
compressed and
interlocked together, generally enhance the heat and sound insulating and
shielding
properties of the flexible corrugated multilayer metal foil structures of this
invention.
This invention is further illustrated by reference to the drawings. Figure 1
illustrates a stack (10) of metal foil sheets (1) which are corrugated in the
form of a
stack of sheets to form corrugations (2) laterally across the stack of sheets.
One or
more of the sheets can have optional embossments (7) preformed therein to
provide
preferred gaps or separation between the layers of sheets (1). The
corrugations can be
designed and selected to have any shape, sinusoidal, semicircular, square,
rectangular,
etc. , which is appropriate to provide useable corrugations which can be
compressed to
fold and interlock the metal sheets together as provided by this invention.
The height
of the corrugations and the period or distance between the corrugations
likewise can be
selected by one skilled in the art depending on the properties desired in the
final
products and depending on the economics and equipment available for forming
the
corrugations in the stack. The corrugations can be formed in the stack of
metal sheets
by conventional metal corrugating methods and equipment, such as illustrated
in U.S.
Patent 3,966,646 referred to above. It will also be recognized by one skilled
in the art
that each sheet can be corrugated separately, then the corrugated sheets
stacked and
nested to form the stack of corrugated metal sheets useful in this invention.
Similarly,
one can form a stack of metal foils, such as four layers of 0.002 in. metal
foils and
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. . CA 02297467 2005-07-08
corrugate that stack of metal foils. Separately, one can corrugate a single
cover sheet
such as a 0.010 in. thick sheet then place the corrugated cover sheet on and
nest the
cover sheet with the stack of corrugated metal foils to produce the corrugated
multilayer metal foil stack useful in forming the structures according to this
invention.
It will also be recognized that it is not required or necessary in the
corrugated
multilayer metal foil and sheet structures of this invention for all layers to
be nested
throughout the structure. For interlocking of the layers by compressing stacks
of
corrugations, the layers need to be nested at those points, but it may be
desirable to
provide portions or areas of the structure where the corrugations in the
layers do not
nest. Such a configuration of the product of this invention may be desired
where
additional total height is desired for insulation values or other purposes.
Figure 2 is a partial perspective view of the edge of the corrugated stack of
metal sheets of Figure .1 showing how the compression of the corrugations (2)
folds and
interlocks the layers together. In this illustration, the corrugations are
compressed in
edge area (5) into an omega (S2) shape in areas (26) which folds the layers
together and
interlocks the layers in the stack. Other shapes of folds can be used, such as
"T", "L"
or mushroom shapes. This type of compression of the corrugations can be
performed
along the edge of the stack as illustrated or in an interior portion of the
stack, or both,
as desired to provide su~cient interlocking of the layers to prevent
separation of the
layers during use of the final product. Figure 2 illustrates the optional
embossments (7)
remaining in the corrugated areas and providing separation of the layers and
the
flattened embossments (7a) in the area (5) where the corrugations have been
compressed. Reference to Figure 2 also illustrates the properties of..the
multilayer
metal foil structure of this invention. The flexibility of the structure is
provided by the
multilayer corrugated interlocked structure being able to flex in transverse
and
longitudinal directions, such as along valleys (24) between corrugations (2)
and at the
peaks (23) of corrugations (2) due to the transition. between the peaks and
the flattened
areas (26) of the corrugations can also flex to some extent when the.
structure is bent.
Figure 3 illustrates in cmss section view another shape of folding and
interlocking of the layers together by the compression of a portion of the
corrugations.
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The corrugations of the multilayer stack are compressed to form flattened
areas (36) to
fold and interlock the layers. Valley areas (34) remain between the compressed
portions of corrugations and the uncompressed portions to provide flexibility
of the
final corrugated structure having interlocked layers. While two examples are
shown,
other shapes of folding and interlocking of the layers together to form the
flexible
integral structure according to this invention will be apparent to one skilled
in the art
following the disclosure herein.
Figure 4 also illustrates an additional embodiment of the flexible corrugated
multilayer structure of this invention wherein parallel corrugations (42)
extending
transversely across the stack of sheets are compressed at edge area (46) and
are creased
by longitudinally extending creases (44) which, together with corrugations
(42),
provide the ability of the multilayer structure to bend and flex along creases
(44) or
along the valleys between corrugations to provide additional shapability of
the
corrugated multilayer metal foil structure of this invention. Creases (44) can
extend at
any angle across the corrugations as desired for the flexibility and
shapability to be
designed into the product. Creases (44) can also be formed by passing the
corrugated
stack formed according to Figure 1 through the same (or different) corrugation
equipment a second time but at a 90° angle {or any other angle)
compared to the first
pass through the corrugation equipment. If the same corrugation equipment is
used for
the second pass and the second pass is at a 90° angle, then creases
(44) will be spaced
apart the same as valleys (34). Variations of spacing and angles of the second
pass
cross-corrugation will be apparent to one skilled in the art following the
teachings of
this invention, including third, etc., pass cross-corrugations at various
angles and/or
spacing, i.e., period of comzgation.
Figure 5 illustrates additional embodiments of this invention wherein the
corrugations {52) are formed at a right angle or at an oblique angle across
the width of
the stack of metal foils with the corrugations compressed at edge areas (56)
to ixlterlock
the layers together. The angled configurations of the corrugated multilayer
metal foil
interlocked structure of this invention can wrapped in repeating sections (the
right angle
version) or can be spiral wrapped (the oblique angle version) around a hot,
cold or
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cryogenic conduit (58) where the multilayer stack flexes at the valleys or
peaks of the
corrugations in the structure to facilitate the wrapping of the multilayer
structure of this
invention around a conduit and corrugations (52) are positioned parallel with
the axis of
the conduit.
Figure 6 is a schematic illustration of the application of a shield
illustrated in
Figure 4 to the underbody section of a vehicle (60). Shield (41) can be
applied to the
underneath surface of the passenger compartment pan or floor (61) by
mechanical
attachment or by adhesive attachment. It is also to be understood that a
shield, such as
shield (41) from Figure 4 as well as any desired shape of corrugated
multilayer metal
foil shield, can be designed and formed according to this invention to fit any
desired
portion of the underbody of a vehicle, or the fire wall or other area of the
engine
compartment, etc. of a vehicle. The shields made according to the present
invention
are advantageously attached to the portions of the vehicle by adhesive or
other
mechanical attachment in order to provide an integral body or chassis part,
because the
efficient, light-weight, recyclable shields of this invention can be designed
to provide a
desired combination of heat shielding and acoustic shielding at any desired
location on
the vehicle. It is also to be recognized that the direct attachment by
mechanical or
adhesive attachment of the multilayer metal foil shields of this invention to
the desired
areas and components of a vehicle is enabled and made possible by the
flexibility of the
corrugated multilayer metal foil shields and pans made according to the
teaching of this
invention.
The compression of the corrugations to fold and interlock the layers together
can be performed as desired by one skilled in the art. A preferred method and
apparatus for compressing the corrugations is the use of a compression tool,
such as a
resilient, e.g., rubber or plastic, member which can compress the corrugations
to fold
the corrugations in the omega, "T", "L", mushroom or other shape to interlock
the
layers. One advantage of using a rubber compression member is that the
corrugations
are sufficiently compressed to fold and interlock the layers together but the
compressed
areas to remain somewhat more flexible than would occur if the compressions
are
flattened under more extreme pressure. Alternatively, metal, plastic, wood or
other
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compression members may be used to accomplish the compression of the
corrugations
to fold and interlock the metal foil layers of the stack together. As referred
to above in
Figure 4, the longitudinal creases which can be compressed across the
corrugations to
provide flexibility of the multilayer structure can likewise be formed using
any desired
method and compression member or corrugation equipment. As will be recognized
by
one skilled in the art the compression member may be a flat member, a V-shaped
member or a knife edge type member, depending on the type of compression and,
in
the case of the longitudinal creases across the corrugations, the flexibility
desired in the
final product. The portions of the corrugations compressed to fold and
interlock the
layers together can be at any desired location or locations, such as at the
edge of the
multilayer structure or in an interior portion of the multilayer metal foil
structure. As
will be apparent to one skilled in the art, any combination or configuration
of
compressed areas to provide the appropriate folding and interlocking of the
layers for a
particular product design can be carried out following the teachings of this
invention.
The edge portion of the multilayer structure may be left open in the
corrugated
uncompressed condition when desired, and interior portions of the corrugations
compressed to interlock the layers together. Alternatively, the edge portion
in addition
to being compressed can also be folded, rolled, curled, crimped or shaped in
any
desired pattern. A folded or crimped edge in some applications will be useful
for
providing a site for mounting hardware, when attaching the multilayer
structure to, for
example, the underbody of a vehicle. Thus, it is apparent that in addition to
the
compression of the corrugations to fold and interlock the layers, the layers
may also be
attached by other methods, such as stapled, clipped or bolted to other
structural
members for end use applications.
The materials useful in the corrugated stacks of this invention will likewise
be
apparent to one skilled in the art a~~~d wil' :!ude typically alumirru.rn,
stainle teel,
copper, similar metal foils and metal sh plastic coated metal foils and
sheers,
laminates of metals, alloys of these and other metals, and metallic materials
which are
plastically deformable and are permanently deformable. In addition to metal,
other
materials may be interlayered between two or more of the metal foil layers of
the
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multilayer structure of this invention. For example, plastic films, adhesive
layers,
spray on adhesives, coatings, etc. may be included between the metal foil
layers,
particularly in acoustic applications where additional sound damping is
desired. The
thickness of the various metal and other layers employed will depend on the
end use
application. It is preferred that the multilayer structure be made primarily
of metal
foils having a thickness of 0.006 in. or less and in particular it is
preferred that in, for
example, a five layer structure, at least the three interior layers are thin
metal foils, for
example 0.002 in. thick metal foils. The exterior layers of an all-foil
structure are
frequently desired to be heavier metal foils of 0.005 in. or 0.006 in. in
thickness.
Likewise, when the exterior layers are desired to be protective layers, they
may be
metal sheets of 0.010 or even up to 0.050 in. in thickness. In this regard, it
is also
recognized that the flexible corrugated multilayer metal structures of this
invention can
be a non-foil structure made entirely of layers of metal sheets thicker than
metal foils,
i.e., metal sheets having thicknesses in excess of 0.006 in. For example,
flexible
corrugated multilayer metal structures according to this invention can be made
using
five layers of 0.010 in. thick metal sheets.
The number of layers and the thicknesses of each layer will be selected by one
skilled in the art depending on the flexibility desired, the vertical strength
required in
the final corrugated flexible product, the capacity for lateral heat transfer,
the
requirements for sound damping, etc. The thickness of various metal foil
layers will
vary from 0.0008 to 0.006 in., with the 0.002 in. and 0.005 in. metal foils
being
preferred for many applications. When heavier sheets are used and in
particular for the
top sheets or protective exterior sheets, the metal sheets can have a
thickness of greater
than 0.006 in. up to about 0.050 in. , with the preferred top sheets or
exterior sheets
having a thickness of 0.010 in. to about 0.030 in. or about 0.050 in. Some
examples
of combinations of number of layers and thicknesses of the layers used in
forming the
flexible corrugated multilayer metal foil structures of this invention are:
(in mils, 1
mil=0.001 in.) 10/2/2/2/5; S/2/2/2/5; 8/2/2/2/4; 10/2/2/10; 5/2/2;
5/0.8/0.8/5; and
10/2/0.8/0.8/215. Examples of non-foil metal sheet structures are: 1018/8/8;
30/ 10/ 10/ 10/30; 8/8/8; and 50/8/8/ 10. The materials useful in this
invention are most
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commonly aluminum and stainless steel, but other useful materials will be
apparent to
one skilled in the art, including copper, tin, galvanized sheet, brass, etc.
One skilled in
the art can readily select appropriate combinations of materials and metal
foil and metal
sheet thicknesses for specific use applications, specific forming processes
and mold
configurations and the particular metals used. The total thickness of the
shield or part
will depend not only on the number of layers, the thickness of the layers and
the gaps
between the layers, but on the shapability and formability of the preform or
beaded
preform to provide the final desired formed and engineered part. Thickness
will range
from 0.010 in. to 0.25 in. or greater.
It will also be apparent to one skilled in the art following the above
disclosure,
that shields and parts can be made according to this invention without the use
of metal
foils, i. e. , by using metal sheets greater than 0.006 in. in thickness.
Examples of such
structures would include 10/7/ 10; 20/ 10/ 10/ 10; 30/8/8/8; and the like
where the layers
are selected to provide appropriate forming and shaping using the methods
disclosed
herein for multilayer metal sheet preforms.
The total thickness of the corrugated multilayer metal foil/metal sheet
structures
of this invention can be designed and selected by one skilled in the art to
meet the
requirements for heat or sound shielding. For example, a typical under carpet
application can utilize a structure of 10/2/2/5 mil layers with corrugation
heights to
give the structure a total vertical thickness of about 3mm to about 4mm from
the base
to the top of the corrugations.
As discussed above, the flexible corrugated multilayer metal foil and metal
sheet
structures of this invention are useful for heat insulation and dissipation
and acoustic
shielding. In these applications the structures of this invention can be
manufactured in
any desired shape and configuration for any application desired. For example,
these
structures can be designed and adapted for use on hot exhaust conduits when
;yapped
as illustrated in Figure 5; they can be made in large shaped sheets which will
conform
to the shape of the underneath side of a vehicle passenger compartment floor
pan or can
be made to conform to the shape of a vehicle fire wall. In these applications,
the
structures of this invention serve both to insulate and to laterally conduct
and spread
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heat from hot spot heat sources to the cooler areas where it can be absorbed
by or
dissipated to the environment adjacent to the multilayer metal structures of
this
invention. The flexible corrugated multilayer metal foil structures of this
invention
likewise can be placed, as discussed above, under the passenger compartment
carpet of
vehicles to spread and dissipate heat from the areas where the exhaust and
catalytic
converter systems tend to heat the floor pan of the passenger compartment.
Such
applications also provide acoustic insulation as well. Attachment of the
flexible
corrugated multilayer metal structures of this invention will be apparent to
one skilled
in the art using ordinary mechanical attachments such as clips, bolts, screws
and the
like. Adhesive attachment, for example by mastic coatings, etc. , is a
preferred method
for placing the structures of this invention on various vehicle or automotive
applications, especially for underbody applications, e.g., on the bottom of
the floor pan
of the passenger compartment. The corrugated multilayer metal foil and metal
sheet
structures of this invention may also be laminated to or between other
materials such as
metal, fabric, plastic, etc., when desired in particular applications and
service
conditions. For example, the corrugated multilayer structures of this
invention can
have a smooth layer of metal foil or metal sheet or an embossed, non-
corrugated metal
foil or metal sheet on one or both sides of the structure, attached by
adhesive or by
mechanical attachment to provide desired structural strength or shielding
properties.
Other non-vehicle and non-automotive utilities for the structures of this
invention will
be apparent to one skilled in the art, such as liners for ovens, etc. In
various acoustic
end use applications, it may be desirable to form perforations in one or more
layers in
the structure to enhance the sound and vibration absorbing capacity of the
structure.
Such perforations can be formed in conjunction with embossments, for example a
perforations can be made at the points of embossments in metal foils. Or, such
perforations can be formed in rows along the top ridges of the corrugations in
some or
all the layers of the structure.
Other variations of the methods of making and the structures of the present
invention as well as end use application designs will be apparent to one
skilled in the
art following the teachings of this invention.
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