WO1997035714A1

WO1997035714A1 - Multilayer panel

Info

Publication number: WO1997035714A1
Application number: PCT/SE1997/000474
Authority: WO
Inventors: Barin Ghose
Original assignee: Ab Volvo
Priority date: 1996-03-26
Filing date: 1997-03-20
Publication date: 1997-10-02
Also published as: SE9601156D0; SE9601156L

Abstract

Multilayer panel (2), wherein the constituent layers are manufactured from paper or carton and the panel comprises a plurality of primary layers (4) with channels (6), wherein each such primary layer is separated from the respective adjacent primary layer by means of an externally planar secondary layer (8). The secondary layers form intermediate walls between the primary layers, and the planar side surfaces of the secondary layers form delimiting surfaces to the channels (6) of the primary layers. The channels in each layer provided with channels run mutually parallel within the layer, but the different layers in the panel can have mutually different channel directions.

Description

Multilayer panel

Field of the invention

The present invention relates to a multilayer panel of the type mentioned in the preamble of claim 1.

State of the art

Cellular layer constructions with a honeycomb structure are previously known.

As an example can be mentioned honeycomb panels with a layer of six-sided cells laminated between cover sheets. One way of using such honeycomb panels is as side collision-protecting and collision energy-absorbing (impact force-absorbing) construction elements in vehicle doors. Such panels can be made of paper which gives a simple and light construction which is cheap to manufacture. One problem in this connection is how to bring about a door construction which, on the one hand, can absorb a large amount of the energy which is released in a collision and, on the other hand, has a low weight and can be manufactured at a low cost. The majority of known honeycomb panels which are cheap to manufacture and have a low weight have, however, insufficient energy-absorbing capacity when they are used as impact force-absorbing protective elements in a vehicle door which is deformed in a side collision.

In the Swedish Patent Application No. 9503134-0, which at the time of filing of the present application was not available to the public, there is described a honeycomb panel which comprises at least two layers of honeycomb elements. The layers can have the same or different thicknesses and each layer comprises a center part which is made of honeycomb cells and two outer sheets which delimit the center part. By a suitable choice of the thickness of the layers and the size of the cells, the desired energy-absorbing capacity for the panel can be achieved. The honeycomb panel can be manufactured from strips of cardboard which are glued together to form the cell structure with honeycomb shape. Such a honeycomb panel with two layers of honeycomb element indeed represents a significant advance compared to traditional cellular layer constructions with honeycomb structure but nevertheless is not an optimal solution to the use in vehicle doors which are to be essential parts in a collision safety-improving security system of the SIPS type.

Disclosure of the invention

One object of the present invention is to obtain a new type of multilayer panel which is cheap to manufacture and has a low weight but still has a strong construc¬ tion and has a large energy-absorbing capacity when it is subjected to impact forces from the side. This quality in the panel is specially desirable when it is to be an integral part of the side protection means in a vehicle door.

A further object is that the multilayer panel shall be so constructed that it can be subjected to considerable deformation forces directed obliquely to the panel without the inner supporting structure of the panel collapsing completely even if a number of the layers in the panel are substantially deformed. Among the other objects of the invention it can be mentioned that the multilayer panel should be manufactured of recyclable material which does not contain any constituents which are dangerous from an environmental point of view. Another object of the invention is that the construction of the multilayer panel shall be such that it will be easy to give the panel a desired shape through simple machining, such as punching, milling, sawing, etc. The multilayer panel shall also be easy to manufacture with different desired densities. The construction of the panel shall further be such that it offers good possibilities for the mounting of fittings and other details in or on the panel.

Another object of the multilayer panel is that it should offer good sound insulation when it is, for example, part of a vehicle construction, and the panel should also be so constructed that it does not give rise to any undesirable squeaking when sub¬ jected to the effects of forces. The above mentioned objects are achieved, according to the invention, through a multilayer panel which has the features stated in the characterizing part of claim 1.

The multilayer panel according to the invention is distinguished by the layers comprised in the panel being manufactured of paper or cardboard, and by, in each layer which contains channels, the channels extending parallel to each other. In the panel there are a plurality of - preferably at least four - primary layers with channels, and each such primary layer is separated from the nearest adjacent primary layer by an externally plane secondary layer. This secondary layer forms an intermediate wall between the adjacent primary layers, and the plane side surfaces of the secon¬ dary layer form delimiting surfaces for the channels on the neighbouring primary layers which face towards the secondary layer.

The primary layers can be manufactured as corrugated paper layers and the secon- dary layers can either be manufactured as planar layers without inner channels of their own or as hollow intermediate walls with internal, mutually parallel channels in the space between the plane side surfaces of the respective secondary layer. The primary and secondary layers are suitably mutually joined by gluing. The channels in the different layers of the panel are preferably straight and the directions of the channels for the individual primary layers can either be mutually parallel or non- parallel.

In order to facilitate the mounting of the multilayer panel in or on another construc¬ tion part, it is appropriate that the outermost layer on the opposite sides of the panel be equipped with an externally finishing cover sheet, and these two cover sheets then form external delimiting surfaces on the front and rear sides of the panel. The transverse dimensions of the channels in the primary layers are preferably consider¬ ably larger than the transverse dimensions of the channels in the secondary layers. A construction element, which is intended to be an integral part of a vehicle door and which through successive deformation shall be able to absorb energy when it is subjected to external forces, can consist of one or be comprised of several multilayer panels according to the invention.

Different embodiments of the multilayer panel according to the invention are evident from the independent claims.

Brief description of the drawings The multilayer panel according to the invention will now be described and explained further below with reference to some examples of embodiment shown in the appended drawings.

In the drawings: Figure 1 shows an end view of a portion of a first embodiment of a multilayer panel according to the invention;

Figure 2 shows an end view of a cut-out portion of four layers which are com¬ prised in a second embodiment of a multilayer panel according to the invention; Figure 3 shows a perspective view of the cut-out portion according to Figure 2; and

Figure 4 shows schematically a cut-out end portion of a third embodiment of a multilayer panel according to the invention.

Description of embodiments

Figure 1 shows in perspective one end of a portion or a part of a multilayer panel 2 which in this case comprises 17 glued together layers which are manufactured of paper or cardboard. In this case the panel 2 is comprised of two different types of constituent layers, viz. on the one hand eight pieces of primary layer 4 with mutu- ally parallel channels or pipes 6, on the other hand seven pieces of plane secondary layer 8 which are interleaved between the primary layers 4 and which in this case are formed of essentially planar paper layers (plane layers) with no inner channels. The primary layers 4 in this case consist of corrugated paper layers which in the end cross section shown have a shape which resembles a sine curve. The secondary layers 8 thus form intermediate walls between the neighbouring primary layers 4, and the planar side surfaces of the secondary layers 8 form longitudinal delimiting surfaces for the channels 6 of the primary layers which are otherwise delimited by the adjacent sine shaped corrugated paper layers of the primary layers. The channels 6 in the primary layers 4 equipped with channels extend parallel to each other.

Although the primary layers in this case are formed of sine-curve-like corrugated paper layers, it is also possible to alternatively choose some other shape of corru¬ gated paper layer, for example a trapezoidal shape, as is shown in Figure 4. The paper layers constituting the panel 2 can, for example, be made of carton, i.e. stiff paper or thin cardboard, and the quality of the paper can be chosen arbitrarily according to need. In order to hold the manufacturing cost down for the multilayer panel, one can, for example, use paper or cardboard of recycle paper quality.

The primary and secondary layers 4 resp. 8 comprised in the panel 2 are mutually joined by means of glue joints at the tops and valleys of the sine wave-shaped primary layers 4. For the multilayer panel 2 shown in Figure 1, the upper and lower primary layers 4 are equipped on the upper side resp. lower side with an external finishing cover sheet 10, which can be of the same type as the secondary layers 8 but which also can be of some other completely different type of preferably compa- ratively planar covering layer of cardboard or paper. The two cover sheets 10 thus form the external delimiting surfaces on the upper and lower sides of the panel 2. Reference is now made to Figure 2 which for the sake of simplicity only shows a few (to be more precise four) layers of the total number of layers which are com¬ prised in a second embodiment of a multilayer panel according to the invention. In this alternative type of multilayer panel, the secondary layers 8' are not formed as planar layers which lack channels of their own but instead are made as hollow intermediate walls with internal, mutually parallel channels or pipes 12 in the space between the delimiting walls of the secondary layer 8' which are made as planar cover sheets or covering layers 14 resp. 16. The lowermost primary layer 4 is also in this case covered by means of a substantially planar finishing cover layer or sheet 10, which can be of the same type as in the embodiment according to Figure 1.

Figure 2 shows only a limited region of the multilayer panel, which means that above the upper primary layer 4 in Figure 2, in reality there is positioned a further secondary layer 8', above which then follows yet another primary layer 4, a further secondary layer 8', and so on.

Although Figure 2 shows that the channels 6 in the primary layers 4 and the channels 12 in the secondary layer 8' extend parallel to each other, it is also poss¬ ible that the secondary layer 8' instead is so arranged in relation to the primary layers 4 that the channels 12 in the secondary layer 8' are not directed parallel to the channels 6 in the primary layers but are at an angle in relation to the channels 6.

As is evident from Figure 2, the channels 12 in the secondary layer 8' are consider¬ ably narrower than the channels 6 in the primary layers 4. The relationship between the transverse dimensions of the channels 6 in the primary layers 4 and the channels 12 in the respective secondary layer 8' can be chosen according to desired charac¬ teristics of the respective layer, but in the embodiment shown the transverse dimen¬ sions of the channels 6 in the primary layers 4 are approximately four times greater than the transverse dimensions of the channels 12 in the secondary layer 8' . In the embodiment in Figure 1 the ^"wave length^"' for the sine wave-shaped primary layers 4 is approximately 8 mm. while the wave length for the primary layers 4 in the embodiment according to Figure 2 is approximately 10 mm.

In Figure 3, the cut-out portion of the multilayer panel according to Figure 2 is shown seen at an angle, from above, from the end of the cut-out portion opposite to the end shown in Figure 2. The end of the portion shown in Figure 2 can thus be found at the top part of Figure 3.

Figure 4 shows very schematically a portion of a trapezoid multilayer panel 18 according to the invention. The panel in this case is equipped with sheet-shaped cover layers 20, 22 and 24 on the top side of the panel, on its vertical side wall and on the front surface. These sheet-shaped cover layers (which are shown in cross section) are built up in the same way as the channel-equipped secondary layer 8' according to Fieures 2-3. This means that the cover lavers 20. 22 and 24 consist of internal corrugated paper layers 26 with a sine-wave shape, which layers on the in- and outside are provided with flat layers 28 and 30. The multilayer panel 18 com¬ prises a plurality of primary layers 32 which consist of a corrugated paper layer 34 with a kind of square-wave shape, in this case a trapezoidal shape. The separate primary layers 32 are glued on the opposite sides of the mutually separating inter¬ mediate walls 36, which appropriately are of the same construction type as the external, sheet-shaped cover layers 20, 22 and 24 of the panel 18. The square wave- shaped primary layers 32 together with the secondary layers made as hollow inter¬ mediate walls 36 delimit the mutually parallel channels 38 inside the panel 18.

Multilayer panels according to the present invention form light, but at the same time strong, structural components of paper or cardboard, which have a very good capa¬ city to absorb and resist deformation forces which they may be subjected to, for example when they are part of SIPS-components in a vehicle construction which is subjected to collision forces. Multilayer panels according to the invention are suit¬ ably provided with force-distributing sheet-like cover layers or sheets on their outer delimiting surfaces. In this way load forces can be introduced into the multilayer panel without risk of its channel-equipped primary layers collapsing in a too early stage of the deformation process.

By equipping a multilayer panel according to the invention with suitable external cover boards or sheets, it is possible to introduce the forces which are to be absorbed by the panel in any arbitrary direction in relation to the panel. The load forces can thus act on the panel either perpendicularly or at an inclined angle to the layers com¬ prised in the panel. By equipping the multilayer panel according to the invention with suitable force-distributing cover sheets at the ends of the channels, and prefer¬ ably perpendicular to them, it will also be possible to mount the multilayer panels so that load forces are introduced in the longitudinal direction or at an inclined angle to the channels.

The multilayer panel according to the invention can advantageously be used as collision force-absorbing, occupant-protective reinforced construction elements in different parts of a vehicle, for example in the doors of the vehicle. The multilayer panel according to the invention can also suitably be used as shock-absorbing, occupant damage-reducing lining elements or panels in, or on, the internal delimit¬ ing surfaces of the cabin space.

When the multilayer panel according to the invention is used in vehicle construc- tions, it could be appropriate to treat the panels made of paper with, for example, paraffin or some other substances, in order to thereby reduce the risk that the panels absorb moisture which can have a deleterious effect on the structural stability and strength of the panel and thereby its capacity to absorb shock or impact energy.

Claims

1. Multilayer panel with channels in at least one of the constituent layers in the panel, characterized in that the constituent layers in the panel (2; 18) are manu- factured from paper or carton, that in each layer which comprises channels, these channels extend parallel to each other, that the panel comprises a plurality of, pre¬ ferably at least four, primary layers (4;32) with channels (6;38), and that each such primary layer is separated from the adjacent primary layer provided with channels by means of an externally planar secondary layer (8;8'), which forms a partition wall between the primary layers and of which the planar side surfaces form delimit¬ ing surfaces to the channels (6;38) of the primary layers.

2. Multilayer panel according to Claim 1, characterized in that the primary layers (4;32) provided with channels are formed as corrugated paper layers.

3. Multilayer panel according to Claim 1 or 2, characterized in that one or several of the secondary layers are formed as planar layers (8) without internal channels of their own.

4. Multilayer panel according to any of Claims 1 - 3, characterized in that one or several of the secondary layers are formed as hollow intermediate walls (8';36) with internal, mutually parallel channels (12) in the space between the planar side surfaces of the respective secondary layer.

5. Multilayer panel according to any of the previous claims, characterized in that the primary and secondary layers comprised in the panel (2; 18) are mutually joined by means of a glue joint.

6. Multilayer panel according to any of the previous claims, characterized in that the channels (6;38) in the panel are straight and the channel directions for the individual primary layers (4;32) are parallel to each other.

7. Multilayer panel according to any of Claims 1 - 5, characterized in that the channels in the panel (2; 18) are straight and the channel directions for at least a part of the primary layers are non-parallel.

8. Multilayer panel according to any of the previous claims, characterized in that the outermost layer on the opposite sides of the panel (2) is provided with an ex¬ ternal finishing cover sheet (10), and these cover sheets form external delimiting surfaces on the front and rear sides of the panel.

9. Multilayer panel according to any of the previous claims, characterized in that the transverse dimensions of the channels (6;38) in the primary layers (4; 2) are considerably greater, at least 2 - 3 times greater, than the transverse dimensions of the channels (12) in the secondary layers (8').

10. Construction element intended to be an integral part of a vehicle door, which element absorbs energy under the effect of forces, characterized in that the element is comprised of one or is composed of several multilayer panels (2; 18) of the type stated in the previous claims.