DE29711763U1 - Multi-layer hollow body with foam - Google Patents

Description

Hans-Jürgen Müller Gerhard D. Schupfner

Fax:' I49-89-219912-20 Hans-PeterGauger

e-mail: upon request PO Box 10 11 61 Patent Attorneys

Telegram/cable: Maximilianstraße 6 European Patent Attorneys

MAXIMARK® Munich D-80085 Munich Representatives and European licenses

7 658. GM-DE HJM/MY

Odenwald Chemie GmbH Ziegelhäuser Straße 25

D-69250 Schönau

"Multi-layer hollow body containing foam"

&THgr; MAXIMARK Form 01

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- Gerhard D. Schupfner

Telephone: *49^9-2i 9912-0 Hans-Peter Gauger

ti. Fax: «-49-89-21 9912-20 Q,»o„*,m~äl* _e

'" e-ma«: upon request PO Box 101161 Patent Attorneys

TelegramnVcable: Maximilianstraüa a European Patent Attorneys

MAXIMARK® Munich D-80085 Some agents and European certificates

7658. GM-DE Odenwald GmbH HJM/MY

Multilayer hollow body containing foam

The invention relates to a multi-layer hollow body comprising foam of the type mentioned in the preamble of claim 1.

Such hollow bodies are already known (EP 0 445 592 A2) and are produced using the known blow molding process in that the two foam layers are placed in a multi-part mold after heating and, after closing the mold, the outer edges of each foam layer are welded or fused to form a common weld edge, whereupon pressurized fluid is introduced through the weld edge into the space between the parts of the layers that are not fused together and the two layers are pressed apart and onto the inner wall of the mold, whereupon the hollow body is demolded from the mold. Instead of pure foam layers, foam layers laminated with compact thermoplastic films can also be used. It is known to use cross-linked closed-cell polyethylene foam. Since the thermoplastic film is used as an inner layer to provide better resistance to the attacking fluid when the cavity is inflated, i.e. when the two layers are pressed apart, the possible uses of such previously known hollow bodies are quite limited. It has been shown that when such hollow bodies are used as air ducts in motor vehicles, the soundproofing leaves much to be desired.

In addition, it is known (DE 42 40 296 C2) to produce hollow bodies that serve as airborne sound absorbers using vacuum deformation technology by gluing closed-cell polyethylene or polypropylene soft foam to a sheet metal support at its edges using adhesive and sucking the part of the soft foam layer between the edges to a mold wall using a vacuum and molding it from it. The deformation takes place for the purpose of forming so-called "Helmholtz resonators", which usually requires the foam layer to be permeable to air. Such hollow bodies are not suitable for many applications.

According to DE 43 07 554 Gl, sanitary articles such as bathtubs are made from two pure thermoplastic sheets by heating, vacuum drawing and welding.

The invention is based on the object of improving the foam hollow body of the type mentioned at the beginning in such a way that, despite being easy to manufacture, it offers a variety of variants with regard to the structure and therefore also the functionality and application possibilities.

The invention is characterized in claim 1 and preferred embodiments are claimed in subclaims; preferred embodiments are also shown schematically in the drawings.

According to the invention, each outer layer is impermeable to air, so that no gas exchange (at least to a no longer negligible extent) occurs between the cavity between the two layers and the outside of the hollow body. At least one of the layers of each layer consists of foam with a density preferably

between 25 and 250 kg/m ³ , in particular PE foam (formerly cross-linked) with a density of 115 kg/m and a layer thickness of between 2 and 15 mm, in particular 5 mm. The hollow body according to the invention is not produced using the so-called "blow-mold technology" as in the case of the known hollow body mentioned at the beginning; rather, the outer layer and in particular both outer layers of the layer in question are molded from the mold wall in question by suction, ie using vacuum technology.

The layer can be structured as follows:

a. outer HDPE layer on a PE foam layer facing the cavity or on a PUR soft foam layer as middle layer, which is covered on the inside towards the cavity by a polyurethane (PU) skin;

b. outer PE foam layer on a PUR foam layer as middle layer, which is covered by a PU skin on the inside of the cavity

c. only a single PE foam layer of the relevant layer.

For the HDPE-PE combination, a lower layer thickness is recommended for the outer HDPE layer, especially around 1.5 mm. The outer layer is essentially impermeable to air.

This not only simplifies the manufacturing process, but also provides a greater degree of freedom for the formation of the inner layers of each hollow body layer.

The vacuum technology used to produce the hollow bodies according to the invention is a type of deep-drawing process in which the outer layers of each layer are applied to the contours of the inner wall of a mold cavity by bringing the spaces between the layers and the mold cavity walls (before the layers are deformed) to a greater or lesser vacuum by suction forces.

These suction forces cause the outer edges of the layers that are not clamped between the edges of the molded part to deform from their initially flat plane, which is promoted by heating the thermoplastic material of the layers. After cooling, the two layers retain the configuration that is determined by the molding from the inner walls of the mold cavity.

One layer, especially the outer one of each layer, should be made of closed-cell foam, especially polyethylene foam, while the inner layers facing the cavity should be made of open-cell foam, especially polyurethane foam. With this design, the sound insulation is best in the direction of the cavity, which is why such hollow body combinations, especially with a tubular design, are particularly suitable for components in which air or other gases are guided along the inside of the pipe and at the same time the airborne sound along the pipe is to be dampened.

However, the invention is not limited to the use of polyethylene or polyurethane foam. For example, polypropylene and/or polyamide foams can also be used.

For some applications, it is useful to make the outer layer of each layer from a thin layer, especially a film made of HD (high-pressure) polyethylene, and to connect each outer layer to an inner layer made of polyethylene foam. This combination of layers and the special suction molding technique produces a relatively smooth and rigid outer layer, while the inner layer provides good thermal and/or acoustic insulation properties.

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It may be expedient to construct the hollow body from three layers, two outer layers and one middle layer, for example by having the two outer layers comprise closed-cell polyethylene foam and the middle layer comprise open-cell polyurethane foam.

For other applications, it is recommended to make the middle of the three layers from a perforated layer, especially a film made of polyethylene or polyurethane, for example. The perforated film serves to modify the absorption if the outer layers are sound-permeable.

Such hollow bodies are particularly useful in applications where parts of the hollow body are severely deformed during use.

The hollow body should have good elastic properties without the use of rubber. The advantage here is that much less force is required when pressing compared to, for example, a solid rubber seal.

The invention also offers the possibility of combining hard and soft layers.

For thermal and acoustic insulation purposes, the hollow body according to the invention is also recommended for the production of "insulation packs". The gas enclosed in the cavity promotes the insulating effect.

In such applications, the cavity can also be filled with an open-cell foam filling.

Embodiments of the invention are explained in more detail below with reference to the drawings.

Figure 1 shows a tubular design of the hollow body according to the invention, namely in Figure la in longitudinal section and in Figure 1b in cross section along the section line A-A of Figure la;

Figure 2 shows a hollow body designed as a strand-shaped sealing element according to the invention, namely in Figure 2a in longitudinal section along the section line A-A from the cross-sectional image of Figure 2b;

Figure 3 shows an insulating body with three layers in each layer. Figure 3a shows a schematic longitudinal section and Figure 3b a partial cross-section along the section line A-A of Figure 3a, while Figure 3c shows the same hollow body in partial longitudinal section in a further process step, after which the hollow space is filled with a foam filling;

Figure 4 shows a cross section through a device for deforming two layers to form the hollow body according to the invention;

Figure 5 shows a partial cross-section through a three-layer sheet;

Figure 6 shows a cross section through a two-layer layer of the hollow body.

Figure 7 shows a cross-section through a three-layer structure;

Figure 8 shows a cross-section through a finished unit in which the hollow body is installed in a corresponding formation between two metal sheets, and

Figure 9 shows a cross section through a hollow body according to the invention, which is inserted between two wall parts located at a distance from one another - filling the gap between them.

The hollow body 1 according to Figure 1 is essentially tubular. The two layers 11 each consist of two layers, namely the inner layer 3 facing the cavity 2 and the

outer layer 4 facing the outside atmosphere. Both layers are welded at the edges to form the weld seam 5 so that the inner cavity 2 is completely insulated from the outside space around the hollow body 1 and no gas exchange can take place through the layers 11 between the cavity 2 and the outside space. The inner layer 3 is 5 mm thick and consists of polyurethane foam with a density (RG) between 20 and kg/m ³ . The outer layer 4 is 2 mm thick and consists of polyethylene foam with a density between 25 and 150 kg/m ³ . The layer thickness information does not refer to the weld seam 5 because the two layers 11 are welded together there, whereby the thickness and density have changed significantly compared to the non-fused parts of the two layers 3 and 4.

According to Figure 2a, the outer layers 4 of the single-layer layers consist of PE foam with a density of 100 kg/m ³ and a layer thickness of 3.3 mm.

In the design of the hollow body 1 according to Figure 3, the inner layer 3 facing the cavity 2 consists of a 50 /zm thin PU skin, the outer layer 4 of 2 mm thick PE foam (RG kg/m ), while the middle layer 6 consists of 5 mm thick PUR soft foam (RG 30 kg/m ³ ), which improves the insulation effects. In this example, the cavity 2 is filled with air, whereas in the modification of Figure 3c of the hollow body IA, the cavity 2 is filled with an open-cell polyurethane foam filling 7 with a very low density of 25 kg/m ³ .

Figure 4 shows a schematic cross-section of a manufacturing mold, namely in the state in which the outer edges of the two layers 11 consisting of two layers 3,4 are between

Receiving surfaces Sa ₁ and Sb ₁ of the two mold halves 8a, 8b are clamped. In this state, both layers 11 are in a plane parallel to each other. If vacuum V is applied in the direction of the arrow via the connecting lines 10 to the mold cavity through the suction holes 9, a negative pressure is created in the spaces between the two layers 11 and the inner walls 12 of the mold parts 8a, 8b. As a result, the sections of the layers 11 clamped in the interior are moved away from each other, which is promoted by the softening of the same when heated. The heating and suction is continued until the outer sides of the two layers 11 rest against the inner walls 12 of the molded parts 8a, 8b, whereupon the thermoplastic materials of the layers 11 solidify by cooling and retain their configuration predetermined by the mold inner walls 12, in which a vacuum has now been created in the cavity 2 formed between the two layers 11.

In the 3-layer variant according to Figure 5, there is a middle layer 6 made of 5 mm thick PUR soft foam (RG 30) between an outer layer 4 made of 2 mm thick PE foam (RG 150 kg/m ) forming the outside and a layer 3 made of a 50 μm thin PU skin facing the cavity 2.

In the embodiment of Figure 6, the layers 11 are two-layered with an outer layer 4 made of an HDPE film and an inner layer 3 made of polyethylene foam.

The inside of the hollow body can also be sealed with a polyurethane skin, provided that the adjacent layer consists of PUR foam; the PU skin has a layer or skin thickness between 3 0 and 200 μm.

In the design of Figure 7, the three-layer structure consists of outer layers 4, made of closed-cell and air-impermeable

...13

Polyethylene foam, while the middle layer, i.e. the inner layer 3 laid through the cavity 2, consists of PUR soft foam; but it can also consist of a 25 - 200 μm thick, especially perforated or at least partially perforated film made of PE or PU.

According to Figure 8, a hollow body 1 made from layers 11 in the twin-sheet process, according to the invention, is inserted into the space formed by two sheets 13 in such a way that this is filled up except for the inner cavity 2 in the hollow body 1, with the outer surfaces of the hollow body largely completely abutting against the correspondingly shaped sheet metal parts.

In the example of use in Figure 9, the hollow body 1 fills the gap with the distance A between two wall parts 14; here, sealing measures of an acoustic nature are also taken. The hollow body 1 is clamped between the facing end faces of the wall parts 14; parts of one layer 11 each enclose the edges of the relevant wall part 11 in a bead-like manner. The hollow body is then clamped in a spring-elastic manner and can cover a large tolerance range with almost the same contact pressure.

Claims (16)

Claim wording 1. A multi-layered hollow body comprising foam, of which the outer edge of one layer (11) is connected to the outer edge of another layer (11) to form a common welding edge (5) by thermal welding or fusing, and of which layer parts located between the outer edges are deformed to ^form a cavity (2) between the layers (11) and the welding edge (5), characterized in that each layer (11) forming the outside of the hollow body has at least one outer layer (4) forming the outside and made of substantially air-impermeable material, and in that this outer layer (4) of at least one layer (11) is molded from a mold wall by suction force. 2. Hollow body according to claim 1, iUr: &bgr;,&iacgr;&idiagr;&iacgr;; characterized in that &kgr;&eegr;Scbw> that each layer (11) has at least two layers (3,4,6). 3. Hollow body according to claim 1 or 2, characterized in that each layer (111) forming the outside of the hollow body has at least one layer (3, 4, 6) of foam with a density between 25 and ²⁵⁰ kg/m and a layer thickness between 2 and 15 mm. ® MAXIMARK Form 01 —2— 4. Hollow body according to claim 3, characterized in that one layer (3,4,6) consists of closed-cell polyethylene foam. 5. Hollow body according to claim 3 _, characterized in that at least one layer (3,4,6) consists of flexible polyurethane foam. 6. Hollow body according to one of the preceding claims, characterized in that one layer (3,4,6) consists of polypropylene and/or polyamide foam. 7. Hollow body according to one of the preceding claims, characterized in that open-cell foam is used for the inner layer (3) facing the cavity (2) and/or a middle layer of each layer (11). 8. Hollow body according to one of the preceding claims, characterized in that the outer layer (4) of at least one layer (11) consists of a thin HDPE rigid film. 9. Hollow body according to claim 7, characterized in that the outer layer (4) of each layer (11) consists of closed-cell polyethylene foam and the inner layer (3) of each layer (11) consists of open-cell polyurethane foam. 10. Hollow body according to one of the preceding claims, characterized in that the cavity (2) between the layers (11) is filled with an open-cell foam filling (7). 11.Hollow body according to one of the preceding claims, characterized in that each layer (11) consists of three layers (3,4,6). 12.Hollow body according to claim 11, characterized in that the middle layer (6) of each layer (11) consists of open-cell polyurethane foam. .·:.;.■. j 13.Hollow body according to claim 11, characterized in that the middle layer (6) of each layer (11) consists of a thin layer, in particular film, provided with holes (6a). 14.Hollow body according to one of the preceding claims, characterized by a tubular design serving for sound absorption (Fig. 1). 15.Hollow body according to one of the preceding claims, characterized by an asymmetrical cross-sectional shape (Fig. 2) for use as a seal. 16.Hollow body according to one of the preceding claims, characterized by a cushion-shaped design (Fig. 3c) with a heat and/or sound insulating foam filling (7) in the cavity (2) between the layers (12).