The invention relates to foldable system which is placeable or is placed in a daylight opening, for example a window, of an inner space of a building. In embodiments, the foldable system is a foldable insulation system. In embodiments, the insulation system may achieve R-values greater than 10 Km ² /W, which is 10 times higher than the R-value of HR++ glass and 50 times higher than the R-value of a single glass pane window. The insulation system is intended for controlling an inner climate of an inner space of a building, which inner space is partially delimited by a daylight opening, for example a window.

The invention aims to provide an efficient foldable system that is an improvement over known foldable systems.

The invention provides a foldable system according to claim 1.

Embodiments of the foldable system are described in the subclaims and in the following description, e.g. with reference to the appended drawings.

The longitudinal axis of the honeycomb cells is perpendicular to the plane of the daylight opening and in this direction the honeycomb cells are open.

A feature which is important for the comfort of a user of a daylight opening is having a free view, which is provided by the invention in folded configuration of the honeycomb body. In case it is desired that the view is partially blocked the honeycomb body of the system is unfolded. Depending on the needs of the user the daylight opening may be provided with a free view, a partially free view, or a blocked view by folding or unfolding the foldable honeycomb body.

The invention enables to place the foldable system in unfolded, folded, or partially unfolded configuration in a daylight opening. This increases the functionality of the system.

It is often sufficient for a pleasant experience of the user that it is possible to have a free view or not to have a free view. This provides value to the system, because the option of having a free view is always available. The user knows that this may be provided speedily and easily by the invention. In any intermediate configuration of folding, the honeycomb cells of the invention remain substantially in open configuration. To prevent that the honeycomb body of the system expands in a direction perpendicular to the folding direction during folding thereof, use may be made of a multi-stable metamaterial, wherein the honeycomb cells are elastically closed in the folding direction during folding. Opposing cell walls are pressed together and the shape of the honeycomb becomes substantially a V-shape. The diagonal of the honeycomb cell remains substantially equal perpendicular to the folding direction and the honeycomb body does not expand perpendicular to the folding direction. The closed and open configurations are stable, which makes the cell bi-stable. Because of the many cells, the honeycomb body of the body is multi stable, so that the body may be compressed during folding until all cells are closed and the honeycomb body is folded. The honeycomb body also remains stable in every intermediate position, until the force becomes greater than the force, which is necessary to realize opening and closing the cell elastically.

Normally forces on the cell walls are small (« 1 mPA) because of the low loads.

The cell walls may be kept thin, e.g. between8 pm and100 pm, so that the force needed to close the cells is small and so that there is little force needed to fold and unfold the honeycomb body.

The diagonals of the honeycomb cells are fixed at the ends thereof to a side (called the folding side) of the honeycomb body to the frame towards which the honeycomb body is folded. The cells are fixed by connection elements, e.g. knife shaped connection elements. During folding the connection elements, e.g. knife shaped connection elements, provide a concentration of tension on the bulk of the foldable honeycomb body. The cells, which are connected to and which approach the connection elements, will close first during folding. This effect may be enhanced by making the height of the knife shaped connection elements equal to half the height of the cells in the folding direction, so that during folding the cells close around the connection elements and so that the next row of cells near the knife shaped connection elements are closed and not the cells in the bulk of the honeycomb. The cells at the opposite side of the foldable honeycomb body, called the bar side, are connected to a moveable bar by means of connection elements, e.g. knife shaped connection elements.

The cells intermediate the bar side and the folding side are not fixed diagonally, because they will not close first when low forces are applied and no expansion of the insulation body will occur. Only cells near the folding side and the bar side will deform and only in the desired bi- stable manner, wherein expansion does not occur, because fixation near the folding side and the diagonal side is always present.

In practical embodiments, tensions in the material required for closing and opening the cells are small because the cell walls of the body are thin. It is possible to increase these tensions by increasing tension concentrations with the knife shaped connection elements, so that the cells near the bar side and the folding side open and close where the diagonals are optimally fixed by the connection elements and so that no extension of the bulk occurs.

In an embodiment, the system further comprises a perforated film which is provided between the foldable honeycomb body and a window pane. As preferred, the film is translucent, e.g. of suitable plastic material. For example, the perforated film is mounted to the frame so as to be arranged between the foldable honeycomb body and a window pane when installed in the daylight opening. The foldable honeycomb body may be protected from instability, e.g. due to gas flow through the body as explained herein, by placing, at the side of the inner space, an additional perforated film, which also protects the body from dust. A downside of the body being sandwiched between perforated films is that the bar is no longer reachable by hand directly for folding and unfolding. The best protection of the foldable body is offered if an additional window pane with a ventilation device, e.g. with a filter, is placed in the frame at the side of the inner space, so that the foldable honeycomb body is sandwiched between two window panes and one or two perforated films, e.g. with at or in each window pane a ventilation device allowing for a flow of ventilation air through the structure.

If the daylight opening is reachable by hand or with a pole, then the moveable bar may be easily placed in any configuration between the folding side and the bar side. In embodiments, the body may be folded and unfolded, without the need for a mechanism, e.g. a complicated mechanism, such as a string mechanism. These features make the folding mechanism of the invention less complex and cheaper than known folding mechanisms for foldable bodies.

In embodiments, the foldable system is a foldable insulation system for insulating an inner space according to claim 2. Herein, the system further comprises a ventilator for a gas, e.g. air, e.g. ventilation air drawn or pushed by the ventilator into the inner space from the outdoor environment.

The insulation system according to this embodiment of claim 2, preferably, operates according to the principles of the insulation system disclosed in WO2019/017784. The ease with which heat moves against the flow direction of a gas through the foldable honeycomb body is measured by the Peclet number, Pe. Herein Pe = v I p C _p / l, wherein v is the flow speed perpendicular to the surface of the foldable honeycomb body, I the path length through the honeycomb body, p the density of the gas, C _p the heat capacity of the gas and l the thermal conductivity coefficient.

If the Peclet number of the gas is greater than 1 than thermal conductivity through the foldable honeycomb body is blocked by the flow of the gas, e.g. air, e.g. ventilation air for the inner space. If the gas flows from warm to cold than a warm front occurs which blocks an opposite flux of cold. If the gas flows from cold to warm than a cold front occurs which blocks an opposite flux of warmth. There is no thermal conductivity or heat transport through the foldable honeycomb body when the Peclet number is greater than 1.

If the Peclet number is greater than 1 the flow is superadiabetic. A superadiabetic effect is the effect which provides that there is no thermal conductivity against the flow direction of the gas and occurs when the Peclet number is greater than 1.

If the gas flow has a Peclet number greater than 1 if it moves through the thermally insulation separation than a warm front or a cold front is formed in the thermally insulation separation which blocks a heat flow or a cold flow. Experiments show that a Peclet number of 3 is sufficient to block the heat flow or cold flow virtually completely.

The superadiabatic effect may be disrupted if thermal or convective turbulence occurs in the insulation system. Thus it is necessary that the flow is kept laminar.

Daylight may be allowed through by the foldable system through the daylight opening and the foldable system and an outside view may be present. Additionally sunlight that shines through the daylight opening provides heat in the inner space. This may lead, with the well-insulated daylight opening by the invention, to a net gain of heat in the inner space even in colder climates. In this case it may be beneficial from an energetic and economic point of view to provide large daylight openings, which also increases comfort for the users of the inner space.

The insulation system, preferably, makes use of a permeable foldable honeycomb insulation body, wherein the flow has to be laminar (Re « 10) and which insulation body is foldable.

The insulation body comprises honeycomb cells, wherein a longitudinal axis of the cells is perpendicular to the light opening and which are open in this direction. In embodiments, the honeycomb cells on both lateral sides of the body are opened along a longitudinal direction of the honeycomb cells. In these embodiments remaining expansion of the body, which may not be completely avoided by the multi-stable nature of the invention, is compensated, because the opened cells may press against the sides of the frame. As a result the invention may be made of standard honeycomb material, without the need to fix every cell diagonally.

In embodiments, the foldable honeycomb body is made from a translucent material. This allows the user to see through the system even when the system is in its fully unfolded configuration.

In embodiments, slats are provided on the foldable honeycomb body on the side of the daylight opening of the foldable system. The slats are rotatable connected to spacers, so that in embodiments the slats may rotate about 180°. In embodiments, a side of the slats is light absorbing and another side of the slats is light reflecting. The slats may, for example, rotate around the spacers via elastic hinges, which are connected simultaneously to the body such that the slats are perpendicular to the folding direction, so that the slats may be light and thin. So that they do not put strain on the body and so that they may be folded and unfolded with the body.

These slats improve the working of the climate control in the inner space, because in cold weather the extra absorbing side of the slats may be turned towards the (sun)light direction and thus they may give extra heat to the inner space and in warm weather the reflecting side of the slats to avoid extra heat. This also gives the possibility to protect the body which is preferably made from plastic against UV light, so that the lifetime is increased.

Because the slats are oriented perpendicular to the folding direction and because the slats are connected to the cells by the spacers, the cells in the bulk of the body will not fold before the cells near the outside of the body. Additionally, no extension perpendicular to the folding direction occurs.

Controlling or switching of the slats may, for example, be done electrostatically, e.g. because there is little force required. For this, the electrical power has to be applied in the right location. This may be done by providing the spacers of slats on both sides with an electrical conducting layer, on which an electrical power is applied. The slats may also be provided with an electrical conducting layer, which is provided with an opposite electrical power relative to the spacers. Such that with enough electrical power on the spacers and the slats, the slats flip. This allows to control the relative rotational orientation of the slats electronically. This allows an arbitrary amount of light reflection and absorption by the slats.

In embodiments, the slats may be placed in the correct orientation during folding of the body by guiding strips. Ridges may be provided on the end points of the slats which are guideably by the guiding strips. For example, when the honeycomb body is folded or unfolded the ridges are allowed to move past the guiding strips which forces the slats in the correct orientation. After being guided by the guiding strips the slats may remain the right position by friction between the slats and the spacers.

For example, in a transition from a winter configuration, wherein the absorption side is turned towards the sun, to a summer configuration, wherein the reflection side is turned towards the sun. The guiding strips are moved such that, the guiding strips guide the ridges in such a way to achieve the summer configuration or the winter configuration, e.g. during folding and unfolding of the system. An advantage of this is that the mechanism is less complex and only needs to be used a few times a year.

Control of the system may be automated, it may also be automated using artificial intelligence.

The present invention also relates to a foldable system to be placed in a daylight opening of an inner space of a building. The system comprises a foldable honeycomb body wherein a longitudinal axis of each of the honeycomb cells is perpendicular to the daylight opening. The system further comprises a frame in which the foldable honeycomb body and a bar are arranged. The body is only connected to the frame at a folding side and the body is connected to a bar at an opposite side. The bar is moveable in the frame in opposed unfolding and folding directions. The frame comprises connection elements which connect the frame with the foldable honeycomb body. The bar comprises connection elements that connect the bar with the foldable honeycomb body. The honeycomb cells are adapted to close when the bar is moved in the folding direction and to open when the bar is moved in an unfolding direction. The system may have one or more features as described herein, e.g. as described in the claimset and/or in the description, e.g. with reference to the figures.

The present invention also relates to a building provided with an inner space that is separated from an outdoor environment by an external wall, e.g. a side wall or a roof, which external wall is provided with a daylight opening therein. For example, the daylight opening is formed by a window frame provided with a window pane that is arranged between the inner space of a building and the outdoor environment. At the side of the inner space of the window pane a foldable system as described herein is mounted, e.g. as an insulating system as described herein.

In an embodiment, the foldable system is a foldable insulation system configured for thermally insulating the inner space from the outdoor environment, wherein the system further comprises a ventilator for a gas, e.g. air, e.g. ventilation air. Herein - when the foldable honeycomb body is in the unfolded configuration - a cavity is formed between the foldable honeycomb body and the window pane. The ventilator is adapted for providing a pressure difference between the cavity and the inner space and so for providing a displacement of the gas, for example air, through the honeycomb cells of the foldable honeycomb body. For example, as explained herein, a gas flow characterized by a Peclet number greater than 1 is established through the foldable honeycomb body.

In an embodiment of the building a perforated film is provided between the foldable honeycomb body and the window pane, e.g. the ventilator providing a distributed flow of gas from the cavity through the perforated film and then through the honeycomb cells of the foldable honeycomb body in the unfolded configuration into the inner space. For example, a ventilation device is provided that allows for entry of air from the outdoor environment into the cavity.

The present invention also relates to a method for providing insulation of a building having an inner space and a daylight opening, wherein the building is provided with a system as described herein.

The invention will be explained with reference to the drawing. In the drawings:

Fig. 1 is a schematic view of a foldable system according to the invention;

Fig. 2 is a schematic cross section of a foldable system according to the invention;

Fig. 3 is a schematic view of a second embodiment of a foldable system according to the invention;

Fig. 4 is a schematic cross section of a second application of a foldable system according to the invention;

Fig. 5 is a schematic view of a detail of a third embodiment of a foldable system according to the invention; Fig. 6 is a schematic view of a detail of a third embodiment of a foldable system according to the invention.

Figure 1 shows a schematic view and figure 2 shows a schematic cross section of a part of an external wall of a building 1 with a daylight opening 2 therein, a window pane 3, a ventilation device 4, e.g. grille 4, a window frame 5, a perforated film 6, a frame 7, a foldable honeycomb body 8, and an inner space 9 of building 1.

Here the ventilation device 4 is arranged along an edge of the window pane 3 within the window frame 5. In alternative embodiments, the ventilation device 4 may be integrated in the window frame or be completely absent. The ventilation device, e.g. allows for entry of ventilation air from the outdoor environment into the inner space 9 of the building, e.g. in the manner as described herein.

The body 8 comprises a honeycomb structure, having the shape of a mattress, with, preferably, diamond shaped cells 19.

The body 8 may be folded by moving a bar 12, which bar, in unfolded configuration, is near the bar side 13 of the frame 7 and may be moved towards the folding side 14 of the frame. This bar 12 is connected to the bar side 15 of the body 8. The folding side 16 of the body 8 is connected with the folding side 17 of the frame 7.

In embodiments wherein the foldable system is a foldable insulation system, air is blow through the ventilation grille 4 by, for example, a central ventilator of the building for a proper functioning of the insulation body 8. The air then flows distributed through the perforated film 6 and through the honeycomb cells 19 of the insulation body 8 to the inner space 9. This blocks heat flow to the outside and the heat is recuperated by the ventilation air.

Because the body 8 is connected with the folding side 13 to the frame 7 and with the bar 12 at the bar side, the body 8 cannot extend in a direction perpendicular to the folding side 13 and the bar side 15. Because the cells 19 of the body 8 are connected at the folding side 13 with the frame 7 and at the bar side 15 with the bar 12 with the point of the knife shaped connection elements 17, the cells 19 experience tension concentrations. This allows the cells to fold elastically near the knife shaped connection elements, instead of in the bulk wherein the cells 30 are less fixed. The cells indicated with numeral 20 at the sides 31 of the body may expand in a direction perpendicular to the folding direction. To prevent problems, these cells 20 may be cut open such that the walls 21 of these cells 20 may fold elastically and do not push against the frame 7.

The first step of multi-stable folding of the body is depicted with dashed lines in figure 1. It is shown that the cells 19 are closing and are folding around the knife shaped connection elements 17. The next row of cells 30 will experience an increase in tension and be the next to fold around the knife shaped connection elements 17.

Like components in figures 3 and 4 are depicted with like numerals. Figure 3 shows a schematic view and figure 4 shows a schematic cross section of a second embodiment of the invention.

In this embodiment of the foldable system slats 22 with spacers 23 are placed between the body 8 and the perforated film 6 and connected with the body 8. The slats 22 are perpendicular to the folding direction and are rotatable around the spacers 23 by, for example, a hinge.

The spacers 23 are provided with electrically conducting layers 25 whereon an electrical current may be provided. The slats 22 are also provided with electrically conducting layers 26 on both sides of the hinge 24, whereon an electrostatically opposite power is applied. The slats 22 may be placed in two configurations, which are realized by providing a certain polarity to the power of the conducting layers 26. Wherein the configuration changes if the power on the conducting layers flips polarity.

The slats 22 are provided on one side with a light absorbing layer, wherein light is converted to heat. The other side reflects light. The configuration of the slats 22 may be such that, when heat is required, the absorbing side is turned towards the sun. If cooling is required the reflecting layer may be turned towards the sun. In both configurations the system may be such that sufficient light still enters the inner space 9.

The slats 22 may also be placed in a certain configuration using other mechanisms, such as for example string mechanisms. However, because of the lower weight a system such as described above may be advantageous.

Components in figures 5 and 6 are provided with like reference numbers as components in figures 1, 2, 3 and 4. Figure 5 shows a schematic view of a detail in folded configuration and figure 6 shows a detail in unfolded configuration of a third embodiment of the invention. The slats 22 are provided with ridges 27, which depend on the position of guiding strips 28. The number of guiding strips 28 may depend. To move the guiding strips to a desired position, they are connected with pins 29, which may be moved in holes in the frame and towards the ridges 27. In an extended position, drawn with solid lines, the pins touch the ridges 27. In a withdrawn configuration, drawn with dashed lines, the pins do not touch the ridges 27. This allows the pins to move the ridges 23. By moving the ridges 23, the slats 22 may hinge around the hinges 24 during folding or unfolding of the system. When slats 22 have moved passed the guiding strips 28, the slats 22 keep the desired orientation. By placing the ridges 27 in the desired position by the pins they slats 22 are moved in the desired position.