WO2002103127A1

WO2002103127A1 - Insulating panel and the manufacturing method thereof

Info

Publication number: WO2002103127A1
Application number: PCT/EP2002/006190
Authority: WO
Inventors: Gianfranco Bianchi
Original assignee: Gianfranco Bianchi
Priority date: 2001-06-15
Filing date: 2002-06-05
Publication date: 2002-12-27
Also published as: ITMI20011269A0; ITMI20011269A1

Abstract

The invention relates to a thermally and acoustically insulating panel, consisting of a honeycomb layer (2) arranged between two sheets (3, 4); the latter are kept pressed against the honeycomb layer as a result of the vacuum effect created inside the cells (6) thereof. For this purpose the latter are made to communicate with each other by holes or notches (7) and the vacuum in the panel is obtained by sucking air from the cells. The invention also comprises a method for manufacturing the panel.

Description

Insulating panel and manufacturing method thereof

The invention relates to panels having acoustic and/or thermal insulating properties for civil, naval, aircraft applications and others as well, such as the manufacture of housings for containing machinery or engines, in order to reduce the noise levels thereof.

The abovementioned panels are presently made in various ways, either as regards the materials forming them and as regards their structural configuration, suitable to achieve noise reduction.

An important aspect which relates to the manufacture of these panels consists in the fact that they must have a good acoustic and thermal insulating capacity, together with appropriate mechanical properties for allowing their use in the numerous applications mentioned above.

In particular, further to strength requirements necessary for building walls (or parts thereof) of houses, boats, aircraft or the like, the panels in question should be as light as possible and simple to manufacture, so as to be convenient from a cost and management point of view for the people using them.

Reference should be made, for example, to the superfluous weight on boats or aircraft which constitutes, in fact, a ballast giving rise to greater fuel costs for propulsion thereof.

The panels currently available do not satisfy entirely these requirements, in the sense that those which have a good insulating capacity are heavy and costly because of the materials used or of their manufacturing process .

The technical problem underlying this invention is therefore that of remedying this situation; in other terms it aims at providing an insulating panel structurally strong, light and simple to manufacture.

The idea for solving this problem consists in providing a composite panel comprising at least one honeycomb layer arranged between two sheets, wherein vacuum is formed; the characterising feature of this panel are specifically stated in the claims accompanying the present description.

The invention further comprises a method for manufacturing the aforementioned panel, whose implementing steps are also set out in the claims which will follow.

The features and advantages of the invention will more clearly result from the description provided hereinbelow, in connection with two embodiments thereof illustrated in the accompanying drawings wherein:

- Figure 1 is a perspective view, with a part removed, of a first panel according to the invention;

- Figures 2 and 3 show respective manufacturing steps of the above panel ;

- Figure 4 is a cross-section along the line IV-IV of Fig . 3 ;

- Figure 5 is a perspective view, with a part removed, of a second example of a panel according to the invention;

- Figure 6 shows a cross-sectional view of the panel in Figure 4.

With reference to the drawings, numeral 1 denotes in its entirety a panel according to the invention, having a basic structure composed of three layers, in this case a central honeycomb layer 2 arranged between two outer plates 3 and 4.

The central layer 2 is made of appropriate materials and thickness for withstanding the presence of vacuum inside the cells 6 of the honeycomb, in accordance with what will be better explained below; for example the layer 2 may be made of rigid plastics (PVC, polyethylene, etc.), carbon fibre (Kevlar® and the like) , light metal alloys (with aluminium or magnesium, etc.) and other materials.

Small notches 7 are formed on the edge of the cells 6 by means of milling operation in the longitudinal direction of the central layer 2; the notches 7 have the function of ensuring communication between the cells 6 so as to allow evacuation of the air therefrom, when manufacturing the panel in accordance with the method of the present invention.

For this purpose, one of the outer sheets (indicated by 3 in the drawings) of the panel 1 is also provided with a valve 9, of the type known per se, for connection with air suction means (a pump, a vacuum tank or the like) through a flexible hose 10 equipped with a connection 11 for engagement with the valve 9. The plates 3 and 4 are made with the same criteria as the central layer 2, using the same or different materials depending on the type of panel to be made, on the external finishing (veneered, painted or coated with other layers) thereof, the acoustic insulation level to be achieved and the like.

For example, it is possible to have plates made of rigid plastics (PVC, polyethylene, etc.), wood, carbon or glass fibres, and whatever else.

The edge of the panel 1 is then sealed hermetically by a seal 12 consisting of a strip of material suitable for obtaining a hermetic seal .

For this purpose the seal 12 may be of the type used for applications under vacuum conditions, for example rubber, Teflon® or other polymers of both natural and artificial origin such as rubber, silicone, resins of various kinds (epoxy resin, polyacrylic resin, single or dual component resins, etc.); furthermore, the seal may have in an original manner the form of a strip (as schematically shown in Fig. 3) which is applied by unrolling thereof, or be a fluid of greater or lesser viscosity which is to be spread. In this latter case it could have the appearance of a covering film (such as paint) or a bead running along the edge of the panel.

The seal 12 thus obtained is applied along the edge of the panel covering partially the plates 3 and 4 (as shown in Fig. 4) , or leaving the latter uncovered, but adhering to their inner side. The seal matches the profile of the cells 6 and the plates 3, 4 as a result of the vacuum obtained inside the panel during its manufacture, which takes place in the following manner.

Firstly the various elements are arranged one upon the other, i.e. the two plates 3, 4 and the central layer 2, placing the latter between the former; thereafter the edge of the assembly so obtained is sealed, applying the seal 12 whether it be a strip to be unrolled or a resin or other similar material to be spread.

At this point the vacuum inside the panel

(typically 0.2 to 0.8 bar) is formed, connecting the valve 9 to the pump 10; the vacuum is obtained in the whole of the panel owing to the notches 7 formed on the cells 6 .

Indeed, as mentioned above they ensure communication between the cells 6 allowing air to pass from one cell to another, even when the plates 3 and 4 adhere to the central layer 2; in this connection it is obvious that if the notches were not present, the air could not flow towards the valve 9 because the adhesion of the plates against the central layer would close hermetically the cells, preventing the air contained inside them from coming out.

Once the predefined vacuum level has been reached, the' pump 10 is disconnected and the manufacture of the panel may be considered terminated.

This is possible because the valve 9, together with the seal 12, ensure that the panel be sealed sufficiently to retain inside it the vacuum which keeps its base elements (i.e. the plates 3, 4 and the central layer 2) stably assembled together, without the need for adhesives or other additional fixing systems.

For greater safety over time, the valve 9 may be sealed externally, applying onto it a layer of resin or other sealing material (for example silicone) so as to prevent possible leakages which could occur with time, owing to prolonged use of the panel.

In this connection it should be considered that the height of the central layer 2 and the thickness of the walls of its cells 6 must be chosen appropriately to withstand the stresses caused by the vacuum inside them; for this reason, the material of the central layer 2 may be selected from among the materials referred to before, in a suitable manner so as to ensure not only the maximum strength with the minimum thickness for reducing advantageously the weight of the panel, but also the acoustic "bridges" between the outer plates which are determined by the walls of the honeycomb cells.

Also the shape of the cells (with polygonal, circular or other type of cross-section) will influence this choice.

Moreover, it must be noted that the level of vacuum inside the cells 6 will vary generally from case to case and will depend on various factors, including the possibility of defining the degree of thermal and/or acoustic insulation which is to be obtained, and the mechanical strength of the panel . Indeed the latter is linked to the force which keeps together the central layer with the outer plates, that depends on the level of vacuum present in the panel .

From what has been described hitherto it is easy to understand how the panel 1 solves the technical problem underlying the invention.

Such panel is in fact an essentially empty one: this feature provides per se to the capacity of acoustic insulation, since it reduces the propagation of vibrations inside it; in addition to this effect, there is also the anechoic effect of the cells in the honeycomb layer. In short it can be said that the vibrations between the outer plates of the panel, may be transmitted only through the walls of the cell which however occupy only a minimum percentage of the internal volume of the panel, since it is mainly empty. It is also evident that a mainly empty configuration allows to obtain light panels, with obvious advantages arising therefrom; it should be noted that this result is achieved without adversely affecting the mechanical strength imparted to the panel it by the central honeycomb layer which, as is well known, is a highly strong structure with reference to its limited weight.

In this connection it should be pointed out that the use of honeycomb structures for producing panels in general, is already known in the state of the art; this use, however, occurs in combination with materials for filling the cells (for example resins, polyurethane foams and the like) , so that the corresponding panels are different as regards both structure and acoustics, from the panel according to the present invention.

It should also be emphasized that since the panel according to the invention is mainly empty, it also has excellent thermal insulation properties. To this purpose it must be pointed out that the residual air present inside the panel (there will in fact always be air inside the panel, although at a pressure lower than the atmospheric one) is unable to move for convection owing to the presence of the cells which divide up the internal volume of the panel .

The heat-insulating effect of the panel may be further amplified by constructing the honeycomb layer using an insulating material (for example among the non-metallic materials mentioned above) and if necessary, also applying suitable coatings onto the inner sides of the plates, in order to limit the heat transmission between them because of irradiation.

The definition of insulating panel for the purposes of the present invention must therefore be understood in the broadest sense .

Furthermore the panel may be manufactured according to embodiments other than what has been explained hitherto. Reference has already been made to the various materials which may be used; it should however be pointed out that for the sake of simplicity of the explanation, in the preceding embodiment a basic configuration of the panel, consisting only of the central layer and the two outer plates, has been chosen.

This configuration, however, must be regarded as a basic module which can be repeated several times so as to construct multiple-layer panels of greater thickness .

Furthermore, also the shape of the cells of the honeycomb layer may be different from the (hexagonal) one shown in the drawings; from this change also further differences regarding the number of notches in each cell necessary to ensure communication thereof, may arise.

As regards the latter point it may be stated that notches will be provided on the cells so that the latter communicate with each other in the desired manner; for example, by forming aligned notches it is possible to connect cells lying along the same row, i.e. in a matrix arrangement, or to evacuate the air following a predefined path. It must nevertheless be underlined that the aforesaid notches 7 may be replaced by holes in the walls of the cells 6; indeed it is obvious that the communication between the latter could also be achieved by holes which allow the air to flow from one cell to the other when the vacuum is formed inside the panel.

Depending on all of these alternatives or also solely with the aim of accelerating the formation of the vacuum, it is further possible to provide several valves in the same panel, to be connected with the air suction means in a similar manner to that already explained.

It should however be pointed out that the valve

(or valves) could be associated with the honeycomb layer, instead of with the outer plates, as in the example considered; for instance a valve may be positioned on the edge of the honeycomb layer.

It must also be emphasized that the panel according to the invention could be manufactured in a different way with respect to what has been described above; for example it is possible to envisage producing industrially the panels, inside rooms under vacuum conditions: in this case the valve 9 for evacuation of the air would no longer be necessary since the vacuum in the panel would be obtained in the room wherein assembling of the parts is carried out.

Also the sealing along the edge of the panel, which in the foregoing embodiment is obtained by means of a strip-like seal 12, might be achieved in a different manner or even be dispensed with: for example the surface of the plates 3 and 4 in contact with the central layer 2 could be made of rubber or another material of this kind, capable therefore of ensuring a sealing effect per se without the need of external seals .

Finally it has just to be added that the geometry of the panel may be different from the flat one shown in the drawings, since the principles underlying it are also applicable to cylindrical panels, curved or in any case not flat.

A particular embodiment of the invention which does not require the presence of incisions or holes in order to ensure communication between the cells of the honeycomb layer, is illustrated in Figures 5 and 6.

This embodiment, wherein for the sake of simplicity the same numbering has been used for the panels elements corresponding to those of the preceding example, comprises two identical honeycomb layers 2a, 2b arranged one upon another with their cells 6 staggered: owing to this simple contrivance the cells are able to communicate with each other (as indicated by the arrows in Fig. 6) , without the need to form the abovementioned notches or holes in them. As regards the remaining aspects, this second example of the invention is similar to the preceding one in the sense that, in order to form the panel the air is again evacuated therefrom by connecting the valve 9 to a vacuum pump through the flexible pipe 10; furthermore, in this case too the edge of the panel is sealed with a strip-like seal 12 which ensures a sealing effect..

As can be seen, with this second embodiment of the invention it is possible to manufacture (using the same type of honeycomb layer) insulating panels which are thicker than that of the preceding example, in a simple and rapid manner: it goes without saying that it would be possible to use also three, four or more honeycomb layers in order to obtain panels of the desired thickness, staggering them in the manner described above so that their cells communicate with each other for evacuation of the air inside them.

Last it must be pointed out as a variant to the preceding embodiments, that the outer plates and the honeycomb layer, or at least a part thereof, could be made in a single piece and be assembled as explained in the foregoing.

In other words, reference could be made to a panel like that of fig. 5 and 6, wherein each honeycomb layer is formed in one piece with the adjacent outer face (for instance by moulding) : the panel is thus assembled by arranging the honeycomb layers in a staggered condition and providing vacuum inside, after having peripherally sealed them.

The same principle applies also to the panel of fig. 1, wherein the honeycomb layer might made integrally with one of the outer faces and where the cells are provided with notches or holes.

Furthermore, the possible variants considered above in connection with the first embodiment of panel of the invention are to be regarded valid also for the second embodiment, as well for all the other variants stated herein, which are encompassed by the following claims .

Claims

1. Insulating panel comprising at least one honeycomb layer (2, 2a) arranged between two plates (3, 4) , characterized in that the plates are kept assembled with the honeycomb layer as a result of the vacuum present inside the cells (6) thereof.

2. Panel according to Claim 1, wherein the cells (6) of said at least one honeycomb layer (2) communicate with each other and wherein there is at least one valve (9) for evacuation of the air from inside the panel, arranged on said plates (3, 4) or, honeycomb layer.

3. Panel according to Claim 2, wherein the cells (6) are made to communicate with each other by holes and/or notches (7) in their walls.

4. Panel according to Claim 2, wherein at least one second honeycomb layer (2b) is present between the plates (3, 4), juxtaposed to the first layer with the respective cells (6) staggered so that the latter communicate^' with each other as a result of this staggered arrangement .

5. Panel according to any one of the preceding claims, comprising a seal (12) applied along the edge of the honeycomb layer or layers (2, 2a, 2b) and the facing plates (3, 4) .

6. Panel according to Claim 5, wherein the seal

(12) consists of a strip, a film or a bead of polymer material .

7. Method for manufacturing an insulating panel according to any one of the preceding claims, comprising the steps of:

- providing at least one honeycomb layer (2, 2a) between two plates (3, 4) ; - evacuating the air from the cells (6) of said at least one honeycomb layer so that the plates remain pressed against it, as a result of the vacuum inside the panel .

8. Method according to Claim 7, comprising the step of providing holes and/or notches (7) in the cells

(6) of said at least one honeycomb layer (2) , so as to make them communicate with each other, and wherein the step of evacuating air is carried out by connecting at least one valve (9) provided on a plate (3, 4) or on the edge of said at least one honeycomb layer, with suction means.

9. Method according to Claim 7, comprising the step of providing a second honeycomb layer (2b) between the sheets (3, 4) and juxtaposed to the first one in a staggered manner so that the respective cells (6) communicate with each other, and wherein the step of evacuating the air is carried out by connecting at least one valve (9) provided a plate (3, 4) or on the edge of one of said honeycomb layers (2a, 2b) , with suction means .

10. Method according to any one of Claims 7 to 9, comprising the step of applying a seal (12) so as to seal the edge of said at least one honeycomb layer (2, 2a, 2b) and the plates (3, 4), before evacuating the air.