Stock material or miscellaneous articles – Sheet including cover or casing – Filled with gas other than air; or under vacuum
Reexamination Certificate
1999-06-29
2001-08-28
Thomas, Alexander S. (Department: 1772)
Stock material or miscellaneous articles
Sheet including cover or casing
Filled with gas other than air; or under vacuum
C428S120000, C428S137000
Reexamination Certificate
active
06280814
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a multilayered sheet insulating material for heat insulation and sound proofing including at least two separation layers made of a flexible material and spacer elements between the separation layers. The insulating material is designated for use as heat-insulating and sound-proofing material in technology (e.g. construction of cars or vehicles, aerospace engineering) and in civil engineering.
BACKGROUND OF THE INVENTION
Insulating materials are multicomponent systems whose structure is known to be composed of solid particles and gas volumes. Due to the favorable design and arrangement of these components in the cross section, the insulating effect is generated by small gas occlusions. It is known that the effective thermal conductivity of a material consists of the heat conduction of the solid matter and the effective thermal conductivity of the occluded gas. This results from the shares of the apparent thermal conductivities caused by convection and radiation within the structure and the proper thermal conductivity of the gas.
It is known that the superinsulating materials can be constructed as a layer structure. The layers are formed by thin metal plates—mostly steel—or aluminum plates or by metallized sheets. To prevent the layers from contacting one another, there are inserted spacers which are more or less insulating. These structures can be evacuated if certain demands are met.
Vacuum insulations are mostly used as panels or components, less as large-area materials, since the labor and material expenditure is very high in the course of production.
From DE-OS 39 00 311 A1 there is known a multilayered evacuated structure. Several thin steel sheets are permanently connected with each other by supports with low thermal conductivity using a suitable adhesive. By placing thin fibres or foamed plastic in the space, the radiation losses are reduced. By the position of the fibres parallel to the steel sheets, large contact surfaces are created which increase the thermal bridges and raise the heat losses. Plastic materials or steel are used as supports. Disadvantages of this structure are its stiffness, i.e. no flexibility, and its high weight.
In DE-OS 40 03 770 A1 a heat-insulating encasement for a technical plant is shown. By profiling the aluminum foils, (i.e., forming a cross-section of the aluminum foils into a non-planar shape, which is similar and comparable to corrugating or stamping), the aluminum foils form heat-insulating pockets. In the heat-insulating mat according to DE-OS 35 07 323, metal-coated sheets are directly connected with each other by short weld seams. In the spaces, there are inserted expanding elements which are required for the insulating effect. A disadvantage of these inventions is that a direct contact between the individual sheets is created. This promotes the heat conduction within the foils. These structures are hard and not flexible. Relatively stiff sheets of heavy weight are required for the profiling.
When sheets are used in the structure, the spacing is generated by the filling-in of fibres lying parallel with the sheet by means of ceramic particles or supports of glass-fibre paper. The invention according to DE-OS 35 32 663 A1 describes a soft superinsulation in which links that are incorporated according to a specific geometry provide the spacing of the metallized sheets. In CS 24 30 75 an insulating material is presented in which a non-woven fabric consisting of polyester fibres and/or polypropylene fibres is covered with a metallized sheet. These non-woven fabrics, which are coated with a non-metallized sheet, can be twice doubled and bonded at a specific pressure. This requires great energy expenditure. In all structures, the contact surfaces between the spacers and the sheets are relatively large, because the fibres contact the sheets with their length.
Therefore, heat losses due to heat conduction can be expected.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide an insulating material with an extremely high insulating effect at low weight, slight thickness and high flexibility. Attention should be paid to economical and ecological aspects.
Another object of the invention is to produce a superlight structure with a saving of material, i.e., which requires less material than conventional multilayered sheet insulating materials.
Additional objects of the invention are to provide a multilayered sheet insulating material with economies of production expenditure, reduction of waste and lowering of transportation costs, mainly in the use of means of transport.
In order to achieve these objects and others, a multilayered sheet insulating material for heat insulation and sound proofing in accord with the invention comprises at least two separation layers made of a flexible material and single and self-supporting spacer fibres arranged between the separation layers. The spacer fibres are oriented perpendicular to the separation layers and each separation layer is linked to ends of some spacer fibres at least on one side. The perpendicular orientation of the spacer fibres is retained over their whole length as well as at the connection spot. The insulating material also includes supporting fibres arranged between the separation layers and proximate the spacer fibres for supporting the spacer fibres. The supporting fibres are shorter than the spacer fibres. The supporting fibres may be arranged between and/or parallel with the spacer fibres. An adhesive agent may be provided for linking the separation layers with the ends of the spacer fibres and the supporting fibres.
The layer structure perpendicular to the heat flow results from layer-forming parallel separation layers with a spacing of 0.5 mm to 5 mm. According to the invention, perpendicularly oriented spacer fibres are used to ensure the defined distances. The number of layers is dependent on the application and, accordingly, on the required insulating efficiency.
According to the demands, thin plane membranes with a low radiation coefficient are used as layer-forming elements or separation layers. In this way, the shares of the apparent thermal conductivities due to convection and radiation are minimized. Especially preferred membranes are polyester sheets in the range of 2 to 20 &mgr;m, also perforated ones. They may be coated with aluminum on one side or two sides. There may also be used other membranes such as non-woven fabrics, thin plates or sheets of ceramic material, cellulose and others with or without a metal coating.
In principle, all fibrous materials (e.g. polyamide, polypropylene, viscose, aramid, glass, carbon fibres) 0.5 to 5 mm in length and with a minimum fineness of 0.5 tex may be used as spacer fibres.
The fibres are advantageously arranged parallel to one another in a group and oriented perpendicular to the sheet. By the defined arrangement of the fibres cut to a specific length on the membrane, a constant spacing of the separation layers is achieved. The geometrical arrangement of the spacer fibres on the membrane can be stochastic at points or defined, as a lattice structure or an annular structure. In this way, the contact surface and, thus, the heat losses caused by heat conduction can be minimized. The dimensions are to be designed to prevent contacting among the membranes after doubling. For doubling, the following variants can be distinguished:
1. The separation layers are arranged in a defined way during any doubling, so that the spacer fibres will be superimposed exactly, partially or not at all.
2. The separation layers are stochastically arranged during any doubling, so that the position of the spacer fibres cannot be described exactly.
The advantage of the multilayered sheet insulating material according to the invention is that by upright fibres, a stable supporting function of the flexible separation layers is achieved. As related to the overall weight, the fibres only have a low percentage by weight. Due to the small contact surface of the fibre ends with the separation layer
Berschev Evgueni
Freudenberg Christiane
Hoffmann Gerald
Lobova Ludmila
Offermann Peter
Jordan and Hamburg LLP
Technische Universitaet Dresden
Thomas Alexander S.
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