DE19859702A1 - Sandwich panel manufacture by joining facing layers to core immediately after core production - Google Patents

Abstract

The panel comprises a lightweight core (17) and one or more thin facing layers (20), the latter being joined to the core layer immediately after core manufacture. An Independent claim is made for a sandwich panel in which the core layer (17) is produced from shredded strip material or an endless strip (13'). Preferred Features: A core forming die (10) comprises two or more spaced guide plates with a heater (16) for curing located between the inlet (12) and outlet. Shredded strip material or continuous strip is fed through the die and heat cured to form a core layer.

Description

The invention relates to the production of sandwich panels, especially of such sandwich panels that are used for sound radiation be used.

State of the art

According to the prior art, sandwich panels are formed in that a generally very light core layer on two opposite one another Surfaces with a thin top layer. Such sandwich Panels are typically used for low weight purposes and at the same time require high mechanical strength. For this The reason for this is that sandwich panels are used in aircraft technology. Since the sandwich panels manufactured for this purpose are used as a replacement for otherwise solidly constructed components are used, the sandwich panels dimensioned accordingly stable, so that for pressing the cover layers on the core layer can also be used considerable forces without the Core layer is destroyed by the acting pressure forces.

In addition to this type of use of sandwich panels, there has been one recently Known use in which the sandwich panels as membranes for Loudspeakers are used that work according to the flexible shaft principle. For this see, for example, the applications DE-A-197 57 097, DE-A-197 57 098, DE-A-197 57 099, DE-A-198 06 509, DE-A-198 21 855, DE-A-198 21 624, DE-A-198 21 860, DE-A-198 21 861, DE-A-198 21 862, DE-A-198 21 865, DE-A-198 21 866 and DE-A-198 21 879 pointed out, the more details on the structure and Functionality of such speakers reveal and expressly in this Registration will be involved. So sandwiches used for this purpose Panels have good sound reproduction properties, the material for the Cover layers have a particularly high expansion shaft speed. Suitable Cover layer materials are, for example, thin metal foils or fiber-reinforced plastic films.

There are also special requirements for the core layer. That's the way it is necessary that the usable materials have a low mass density and have low damping. In addition, the materials for the Core layer as high a shear modulus perpendicular to the surfaces  have, which are connected to the cover layers. Finally, it is necessary that the materials usable for core layers in the direction in which later the core layer formed from this material is its largest Has a very low modulus of elasticity. This in relation at first glance contradicting the last two requirements Requirements are most likely to be met by a core layer, the one Hole structure with between the two for coating with the top layers provided surface-running openings with preferably has a small cross-section. In addition to the core layers with the hole structure rigid foams can also be used as core layer materials because, despite their isotropic material properties still suitable shear and Have elastic moduli. It should not go unmentioned in this context remain that when using rigid foam as a material for the Core layer the top layers have the task of doing the required anisotropic Establish behavior of the sound panel.

In addition to these more general requirements, each one for sound radiation sandwich panel should meet certain conditions note if, for example, a sandwich panel for tweeter or Low-frequency reproduction must be optimized. It must be with everyone Sound radiation sandwich panel used to ensure that everyone Area of the cover film that corresponds to an area of the core layer in physical Contact is also connected to the core layer. Because of the sometimes Filigree formation of the core layer can be used for many to reproduce sound sandwich panels used the conventional joining techniques between core layer and cover layers cannot be used as the use of contact forces that press the cover layers against the core layer, very much easily leads to damage to the sandwich panels formed and one Reducing the contact pressure can not guarantee that everyone with the Cover layer in physical contact with the core layer the top layer is connected.

It is also found to be disadvantageous that the manufacture of the sandwich panels is very complex since a first step involves a plurality of individual steps comprehensive step the core layer is produced before then - after Execution of further work steps - the top layers with the core layer get connected. For this purpose, reference is made to DE-A-198 28 265, which the known method for producing the core layers explained in more detail.

The invention is therefore based on the object of a method for producing Specify sandwich panels, which have the disadvantages according to the state of the art Technology avoids and which the continuous production of sandwich Panels allowed.  

Presentation of the invention

This object is achieved with the features specified in claim 1. Advantageous training and further developments can be found in claims 2 to 9.

It is particularly advantageous if, according to claim 2, there closer described pulling tape chips or an endless belt is fed and the tape chips or the endless tape when passing through the pull or baked there arrangement for hot curing to a core layer become. In addition to the advantage that the core layer can be produced continuously can also be made very much by changing the passage accordingly Simple and fast core layers with different dimensions produce.

In this context, the Ribbon chips or the core layers produced because it was found that contrary to the other assumption not necessary regular and therefore also expensive cell structures, but also irregular and from the Ribbon chips or the endless belt structures as core layers for sandwich panels intended for sound radiation can be used without that differences are evident.

The manufacture of the sandwich panels is particularly simple and inexpensive then when according to claim 4 of the core layer formed the respective Cover layers fed continuously and with immediate physical Contact of the respective cover layers with the core layer connected to it become.

For the connection of the core layer with the respective cover layers, the Use of adhesives has proven to be advantageous because these are not just one complete connection between the one in physical contact allow standing areas of core layer and cover layer, but also can be applied very sparingly. The latter is especially for the sandwich Panels that are to be used for sound reproduction are essential because of a increased use of adhesive the sound reproduction ability of a sandwich Modify panels disadvantageously due to the associated weight gain can.

Means are provided according to claim 6, which the respective Top layer after it comes in physical contact with the core layer are pressing against the core layer, it ensures that a complete Connection of all areas in physical contact with one another  respective top layer and core layer is reached. The latter is just for Sound reproduction used sandwich panels essential, since unconnected Areas of the core layer and top layer (s) later when the sandwich Panels become noticeable.

Have according to claim 7, the means that the respective cover layers to the Press core layer, no physical contact with the cover layers or Core layer, damage to the sandwich panel will be sustainable locked out. Have proven to be particularly effective in this context Gas nozzles have been proven which direct a gas flow onto the cover layers. Becomes For example, so-called iron-on film is used as the cover layer, which is under the escaping gas flow can also be heated by the influence of heat his.

Are according to claim 8, the outer layers and the core layer of a electrical current-conducting material, the respective top layers can with the core layer can be connected very simply in that the respective Cover layers are electrically welded to the core layer as soon as the each area of the top layer its final algae on the core layer has taken.

If the cover layers according to claim 9 under slight tension with the Connected core layer, the sound reproduction will deteriorate "Sag" avoided.

Brief presentation of the figures

Show it:

FIG. 1 is a section through a core layer;

Fig. 2 shows a section through a further core layer;

Fig. 3 is a flow coating for a core layer; and

Fig. 4 is another illustration of FIG. 3.

Ways of Carrying Out the Invention

The invention will now be explained in more detail with reference to the figures.

In Fig. 1 a passage 10 is shown in side section, which in the present case is formed by two guide plates 11 arranged at a mutual distance A. The inlet opening 12 of the passage 10 is designed in the form of a nozzle and is fed with ribbon chips 13 . The outlet opening 14 of the passage 10 is located on the opposite side of the inlet opening 12 . An arrangement for hot curing 16 is placed between the two openings 12 , 14 . Now, the input port 12 of the passage 10 fed with appropriately prepared chips band 13, the band scavenger is located in the passage 10 to be moved over toward the exit aperture 14 13 at the hot-setting arrangement for the sixteenth The arrangement for hot curing 16 has the effect that the originally unconnected band chips 13 are baked and a core layer 17 is formed.

A sequence for producing a core layer 17 is also shown in FIG. 2. The only difference, which consists of the sequence according to FIG. 1, is that at the entrance opening 12 of the passage 10 no tape chips 13 , but an endless belt 13 'is fed, which after passing through the passage 10 and baking as a core layer 17 the exit opening 14 emerges from the passage 10 .

As can easily be seen, by simply changing the mutual distance A between the guide plates 11 , core layers 17 with different thicknesses can also be produced very easily. In addition, the density of the core layer 17 formed can be changed very easily by a different size of the tape chips 13 and thus adapted to changing conditions. In Fig. 3, the manufacturing process is shown in a larger context.

It can clearly be seen from this illustration that the passage 10 is provided with an endless belt 13 'for producing the core layer 17 . However, before the endless belt 13 'unwound from the reel 18 is made available to the entrance opening 12 of the passage 10 , the endless belt 13 ' is soaked in the arrangement 19 shown schematically and essentially consisting of an immersion bath. It is also shown in FIG. 3 that the core layer 17 is coated after it has left the exit opening of the passage 10 . For this purpose, the core layer 17 and the two cover layers 20 each unwound from a roll 18 ′ are coated with an adhesive via the rollers 24 . Then come the cover layers 20 and the core layer 17 by the advance of the core layer 17 to one another in physical contact, they are connected to each other simultaneously. The connection is improved if the cover layers 20 are pressed lightly against the core layer 17 with pressure rollers 21 . If physical contact between the pressing means and the cover layers 17 is to be avoided, the pressure rollers 21 shown in FIG. 3 can be replaced by nozzles 22 (shown in dashed lines) which act on the cover layers 20 with a gas stream. Depending on the type of cover layer material, hot gas can also be emitted from the nozzles 22 .

The latter is particularly useful when the core layer 17 is provided with cover layers 20 which shrink under the influence of heat or higher temperatures. This shrinkage of the cover layer material has the advantage that the areas of the cover layers 20 which are not connected to the core layer 17 are slightly stretched after the heat treatment of the cover layers 20 , ie they do not sag. If the use of materials which shrink under temperature is dispensed with, the sagging of the areas of the cover layers 20 which are not connected to the core layer 17 and which are harmful to the sound radiation can be avoided by slightly stretching the cover layers 20 before they are applied to the core layer 17 .

In FIG. 4, a core layer 17 is shown which is formed of metal. The core layer 17 is connected by electrical welding to the two cover foils 20, which are likewise formed from metal. For this purpose, the two pressure rollers 21 'are designed as welding electrodes, to which the required welding current is supplied via their bearing arrangement 23 .

For the sake of completeness, it should be pointed out that the connection techniques explained in more detail between the cover layers 20 and the core layer 17 are not limited to core layers 17 which are produced from banded chips 13 or an endless band 13 '. Rather, the connection techniques can also be applied to core layers that have a regular, for example honeycomb-shaped, cell structure.

Claims (9)

1. A method for producing a sandwich panel, which is formed from a light core layer 17 and at least one thin cover layer 20 , characterized in that the core layer 17 is formed in a first step and then the respective cover layer 20 in a second immediately following step is connected to the core layer 17 . 2. A method for producing a sandwich panel, characterized in that
that there is a passage 10 having at least two guide plates 11 arranged at a mutual spacing,
that an arrangement for hot curing 16 is present in the passage 10 between an inlet opening 12 and an outlet opening 14 ,
that the input opening 12 of the passage 10 tape chips 13 or an endless belt 13 'are fed and
that the tape chips 13 or the endless belt 13 'are moved through the passage 10 and are baked by the arrangement for hot curing 16 to form a core layer 17 . 3. Sandwich panel, characterized in that the core layer 17 is made of tape chips 13 or an endless belt 13 '. 4. The method according to any one of claims 1 or 2, characterized in that the respective cover layers 20 of the core layer 17 continuously fed and with direct physical contact of the respective cover layers 20 with the core layer 17 are wrinkle-free with this. 5. The method according to claim 4, characterized in that before the respective cover layers 20 come into physical contact with the core layer 17 either the supplied cover layers 20 Lind / or the core layer 17 are provided with an adhesive. 6. The method according to claim 5, characterized in that after the respective cover layers 20 have come into physical contact with the core layer 17 , means 21 , 21 ', 22 are provided which press the respective cover layers 20 against the core layer 17 . 7. The method according to claim 6, characterized in that the means 22 , which press the respective cover layers 20 against the core layer 17 , are neither in physical contact with the respective cover layers 20 nor with the core layer 17 . 8. The method according to claim 4, characterized in that
that the core layer 17 and the cover layers 20 are made of a material that conducts the electrical current, and
that the cover layers 20 are electrically welded to the core layer 17 as soon as the respective cover layers 20 have reached their end position on the core layer 17 . 9. The method according to claim 1 or one of claims 4 to 8, characterized in that the respective cover layers 20 , when they come into physical contact with the core layer 17 , are under slight tension.