Stock material or miscellaneous articles – All metal or with adjacent metals – Plural layers discontinuously bonded
Reexamination Certificate
1999-02-24
2001-03-27
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Plural layers discontinuously bonded
C428S603000, C428S604000, C072S363000, C072S379200, C072S379600
Reexamination Certificate
active
06207293
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to multilayer metal foil and metal sheet structures which have utility as heat shields and as acoustic shields.
BACKGROUND OF THE INVENTION
Multilayer metal foil insulation has been used for many years, as illustrated by U.S. Pat. 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. Pat. No. 5,011,743, discloses that multilayer metal foil insulation can provide 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 formed 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. Pat. No. 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 final 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.
The disclosures of the above patents are incorporated herein by reference.
SUMMARY 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. (0.15 mm) 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. (0.12 mm) or less, with 0.002 in. (0.05 mm) 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. (1.27 mm). The 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. (0.20 mm) and about 0.030 in. (0.76 mm). 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 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 mu
Ragland Christopher V.
Ragland G. William
Ragland Raymond E.
ATD Corporation
Burns Doane Swecker & Mathis L.L.P.
Zimmerman John J.
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