WO2023274826A1

WO2023274826A1 - Foldable sheet material

Info

Publication number: WO2023274826A1
Application number: PCT/EP2022/067130
Authority: WO
Inventors: Ivaylo Milenkov
Original assignee: Ivaylo Milenkov
Priority date: 2021-06-30
Filing date: 2022-06-23
Publication date: 2023-01-05
Also published as: DE102021116900A1; DE112022003332T5

Abstract

A foldable sheet material (10) having a plurality of stiff sections (12) which are foldable or rotatably connected along straight edges (14), wherein a straight primary edge (16) extends from a first point (18) on the margin of the sheet material (10) to a distant second point (20) on the margin of the sheet material (10), is characterized in that a secondary edge (22) extends from a third point (24) on the margin of the sheet material to a center point (26) distant to the primary edge; a tertiary edge (32) extends from the first point (18) to the center point (26); and a quaternary edge (34) extends from the second point (20) to the center point (26); wherein the secondary, the tertiary and the quaternary edge (22, 32, 34) move in the same direction from the plane of the sheet material when folded.

Description

Patent Application

Ivaylo Milenkov. Steegerstr. 70. 13359 Berlin

Foldable Sheet Material

Technical field

The invention relates to foldable sheet material having a plurality of stiff sections which are foldable or rotatably connected along straight edges, wherein a straight primary edge extends from a first point on the margin of the sheet material to a distant second point on the margin of the sheet material.

The term „origami“ designates the art to produce a variety of forms by folding paper, for example. However, not only sheet material in the form of paper but also other sheet materials are folded, such as flat articles for transport and storage.

Prior Art

US 5,842,630 discloses a square sheet material, which is folded to form a pyramid. WO 2005/044414 A2 discloses an origami-folding pattern. JP 07068059A discloses a computer program for illustrating folding edges and folding series with origami.

Folding flat material may also serve technical purposes. DE 20 2019 005 447 Ul, for example, discloses a shading material for vehicles, which consists of a material sheet which is folded between two longitudinal margins. WO 2020/201374 A1 discloses a flexible structure with an adjusting mechanism which is made of a plurality of folding elements. Such a structure may be used for vehicle seats. Disclosure of the invention

It is an object of the present invention to provide sheet material of the above-mentioned kind which can be easily and quickly folded without burdening the material.

According to the invention this object is achieved in that

(a) a secondary edge extends from a third point on the margin of the sheet material to a center point distant to the primary edge;

(b) a tertiary edge extends from the first point to the center point; and

(c) a quaternary edge extends from the second point to the center point;

(d) wherein the secondary, the tertiary and the quaternary edge move in the same direction from the plane of the sheet material when folded.

According to the invention, the sheet material can be folded in such a way that the sheet material lies on top of each other thereby forming a two-dimensional folded product with a thickness defined by the thicknesses of the folded sheets. An edge forms the margins of a section and can be either a margin of the sheet material or a folding edge which is hinged or connected to an adjacent section. The solution of the present invention enables the folding of a sheet element without stretching, bending, or otherwise stressing the sections. This enables the use of sensible or stiff materials. The edges may form a triangular lattice, for example. The primary edge extends along the entire surface between two points on the margin of the sheet. The primary edge can extend along a straight margin. It may also form a folding edge, for example, along a diagonal of a rectangular sheet. It is understood, that the sheet may assume any other form, such as with a curved margin. If the sheet material is square, for example, the secondary edge may extend perpendicular to the primary edge. It is provided, that the secondary edge does not extend up to the primary edge but only up to a center point which is the starting point of the tertiary and the quaternary edge also. Upon folding the sheet material, the center point is moved out of the plane and the surfaces of the triangles formed by the edges are moved together until they abut one another.

When fully folded, the material has the surface only of the section formed by the primary, tertiary and the quaternary edges. When adding more sections in the below described fashion, the folded shape still stays the same. Only the thickness will increase. This leads in some embodiments to a high folding ratio, defined as the ratio of unfolded to folded surface. A high folding ratio is a desired characteristic for many applications. Contrary to many known folding patterns the purpose of the present invention is the reduction of the surface size, i.e. the area covered by the folded product.

In a further modification of the invention it is provided that

(a) the first point, the second point and the third point form the edges of a triangle with corresponding internal angles;

(b) the secondary, tertiary and quaternary edge are bisectors of said internal angles; and

(c) said bisectors cross in the center point thereby defining an incenter of said triangle. When the assembly is folded each of the sections will, therefore, assume the same height and not project.

The sheet material may be provided between the second and the third point with an uneven margin which does not run straight but has a triangular cut. However, a straight margin may also be provided. In this case a further edge is provided, and wherein the further edge is foldable in the opposite direction of the secondary, the tertiary and the quaternary edge. The further edge extends from a point, which is positioned between the second and the third point on the margin of the sheet material, to the center point.

In one modification of the invention, the sheet material consists of squares where each primary edge forms a diagonal of the square and each secondary edge ends at a free corner outside of such diagonal.

Such an assembly of edges enables, in particular, the use of sheet materials, consisting of one or more squares where each respective primary edge forms a diagonal and each secondary edge ends at a corner of the respective square outside the diagonal. A corner, where the secondary edge ends, is formed by a corner where no primary edge, i.e. no diagonal ends. In particular, sheet materials may be used where two squares are used, such squares having orthogonal primary edges.

Preferably, strengthening strips are provided along at least a portion of the margins. Such strengthening strips may be fixed along the entire length of the margin. There are also embodiments, where a strengthening strip is only fixed to one or more points of the margin, while another strengthening strip may be fixed along a length of the margin.

In a particularly preferred embodiment of the invention it is provided that the first point of the sheet material is fixed to a carrier by means of a fixing element. The carrier may be advantageously formed of an elongated, stiff material. In a further modification of the invention, the second point of the sheet material is fixed to a lower strengthening strip which is connected to the carrier by means of a second fixing element. An actuator may be provided for moving at least one of the fixing elements or the carrier. By changing the distances between the fixing elements and/or rotation of at least one fixing element or the carrier, the sheet material may be folded and unfolded.

The distance may be changed by, for example, a carrier which can be pushed together telescopically, or which can be bent. In a particularly simple embodiment of the invention it is provided that the carrier is formed of an elongated, stiff material and at least one of the fixing elements is shiftable at the carrier. The actuator can be controlled by a control. In such a way it is enabled that the sheet material can be quasi automatically folded and unfolded. No manual action is necessary. The control can receive the signals of sensors or the actuator can be operated when certain conditions are met. A manual control of the actuator by means of a suitable interface may also be provided.

A particularly high stability can be achieved with the strengthening strips both in a fully and partially unfolded state of the sheet material. In particular, the use of such strengthening strips enables the folding and unfolding of the sheet material by simple rotation of the strips about a rotational axis at the corresponding fixing element, and movement of at least one of the fixing elements along the carrier.

In a further modification of the invention further edges are provided, each of them corresponding to one of the edges which is mirrored at the primary edge and wherein the primary edge is foldable in the opposite direction to the secondary, tertiary and quaternary edges. Consequently, there are two center points, two secondary edges and two tertiary edges. They are mirrored with respect to the primary edge. The primary edge is then not formed by a margin but by a folding edge. If, for example, the primary edge is formed by the diagonal of a square sheet the two secondary edges will form portions of the perpendicular diagonal in such rectangle. The tertiary edges in turn will extend from the center point to the end point of the primary edge. Further extensions can be added in a similar way as shown below in the embodiments.

In particular, such a larger sheet material may have an upper strengthening strip which is provided along an upper margin between the first point and the point defined by mirroring the third point at the primary edge and in that the actuator is configured to rotate the upper strengthening strip around the first point whereby folding of the mirrored portion of the sheet material is achieved.

With the sheet material according to the present invention the surface or a material contained therein can be exposed to radiation, chemical solutions or a fluid in a controlled manner in any desired way. Examples for uses are:

• fluid kinetic based propulsion systems for sailboats, wind mills, water mills and generators;

• airplanes with foldable wings;

• MEMS-devices for control of sensor exposure along the vertical axis;

• foldable solar panels;

• shades, umbrellas, billboards;

• foldable furniture, tents;

• transforming shapes.

The automatizing of the folding and unfolding is reversable and can be repeated as many times as desired.

Further modifications of the inventions are subject matter of the subclaims. An embodiment is described below in greater detail with reference to the accompanying drawings.

Definitions In this description and in the accompanying claims all terms have the meaning well known to the person skilled in the art which is defined in technical literature, norms and the relevant internet sites and publications, in particular of the lexical kind, such as www.wikipedia.de, www.wissen.de or www.techniklexikon.net, of competitors, research institutes, universities and associations, such as, for example, Verein Deutscher Ingenieure. In particular, the terms used here have not the opposite meaning of what the person skilled in the art will derive from the above publications.

Brief description of the invention

Fig.lA is a schematic front view of a foldable, square sheet material according to a first embodiment of the invention.

Fig. IB is a side view of the material illustrated in Figure 1 A.

Fig.2A shows the sheet material of Figure 1A in a partly folded state from a first point of view.

Fig.2B shows the sheet material of Figure 1A in a partly folded state from a second point of view.

Fig.3A shows the sheet material of the first embodiment of Figure 1 in a completely folded state.

Fig.3B is a side view of a second embodiment in a folded state with 1 carrier.

Fig.3C is a side view of a third embodiment in a folded state having 2 parallel carriers.

Fig.4 A illustrates section 13 in greater detail, showing the loose connection between the section and strengthening strip. Fig.4B illustrates a side view of the section from Fig 4A, showing a loose connection implemented by restricting band.

Fig.4C illustrates a side view of the section from Fig 4A, showing a loose connection implemented by restricting leash.

Fig.5 A is a is a schematic front view of a foldable, triangular sheet material according to a fourth embodiment of the invention. Fig.5B is a is a schematic front view of a foldable sheet material according to a fifth embodiment of the invention.

Fig.5C is a schematic front view of a foldable, square sheet material according to a sixth embodiment of the invention.

Fig.5D is a schematic front view of a foldable, square sheet material according to an seventh embodiment of the invention.

Fig.6 illustrates a means to move a sliding element with a thread for folding a foldable sheet material according to a eighth embodiment of the invention.

Fig-7 illustrates a means to move a sliding element with pull strings according to a ninth embodiment of the invention. Fig.8A is a schematic front view of a foldable, rectangular sheet material according to a tenth embodiment of the invention.

Fig.8B illustrates the foldable sheet material of Figure 8 A in a partly folded state. Fig.8C illustrates the foldable sheet material of Figure 8 A in completely folded state from a first point of view. Fig.8D illustrates the foldable sheet material of Figure 8A in a completely folded state from a second point of view.

Description of the embodiment

Figures 1A, IB, 2A, 2B and 3A show a foldable sheet material generally designated by numeral 10. The sheet material of the first embodiment is square. It is understood, however, that the material may also have different, for example curved or unsymmetrical shape. The sheet material 10 consists of sections 12 which are connected at edges 14.

The sections 12 rotate about a rotational axis extending along the corresponding edge. The connections between the sections 12 can be effected by the sheet material itself. In this case the sheet material 10 is folded along the folding edges. It is, however, also possible to join the sections 12, such as with hinges or the like. Any kind of rotatable connection can be used which is suitable for the kind and weight of the sheet material.

In the present embodiment a primary folding edge 16 is provided which continuously extends diagonally from one comer 18 to the opposite comer 20. In the present embodiment it is a folding edge 16 which is connected on both sides with sections 12. It is, however, also possible that the edge 16 forms a margin and limits only one section 12 as shown in the fifth embodiment of Figure 5 A. The comer 18 forms a first point on the margin of the sheet material 10. The corner 20 forms a second point on the margin of the sheet material 10.

A secondary folding edge 22 each extends from the two free corners 24 to a center point 26, which in the present embodiment is the incenter of the triangle formed by points 18, 20 and 24. In the present embodiment, the incenter is the intersection of the angle bisectors of this triangle. In the present embodiment, center point 26 is selected to be the incenter of the triangle defined by first, second and third point of the margins. Since the sheet material of the present embodiment is square, the extension 28 of the secondary folding edge 22 crosses the primary folding edge 16 at a right angle. Each tertiary edge 32 extends from the first point, i.e. from the corner 18 to the corresponding center point 26. A quaternary edge 34, each, extends from each of the second points, i.e. from the corner 20 to the center point 26. The section 36 limited by the points 20, 24 and 26 can be cut out. If the section 36 is present, a further edge 38 is required.

The triangle formed by the points 18, 20 and 24 is mirrored at the primary edge 16 whereby the entire sheet material 10 forms a square area. A corresponding mirrored edge corresponds to each of the edges 22, 32, 34 and 38 on the other side of the primary edge 16. A corresponding mirrored point corresponds to each of the points 24 and 26 on the other side of the primary edge 16.

The sheet material 10 can be folded. The secondary edge 22, the tertiary edge 32 and the quaternary edge 34 move upon folding in the same direction from the plane of the sheet material 10. The center point 26 is, therefore, risen from the plane. The primary edge 16 and, if present, the further edge 38 are folded in the other direction. For example, the secondary edge 22, the tertiary edge 32 and the quaternary edge 34 form a mountain whereas the edges 16 and 38 will form valleys. It is understood, however, that the folding may be carried out in the other direction where the edges 16 and 38 form mountains and the edges 22, 32 and 34 form valleys crossing at the center point. The mirrored edges are simultaneously folded in the corresponding direction.

The folding can be manually effected by taking the sections and pushing them together. The folding may, however, be carried out automatically. For this purpose, fixing elements 40 and 42 are provided at the points 18 and 24. The fixing elements 40 and 42 are fixed to a carrier 44. In the present embodiment, the carrier 44 is an elongated bar with a circular cross section. It is understood, that other shapes are also possible. The fixing element 42 is shiftably guided at the carrier.

In an alternative embodiment shown in Figure 3C, a fixing element 41 is shiftably guided at a first carrier 43 and a second fixing element 47 is shiftably guided at a second carrier 45 which is parallel to carrier 43. As long as the relative distance between fixing element 40 and 42 or 41 and 47, respectively, is changed, it can fold and unfold the part of the sheet material 10 below the primary edge. A motor 60 or 61, respectively, can be used for moving the fixing elements.

Two strengthening elements, such as strengthening strips 46 and 48 are provided at opposite margins of the sheet material 10. In the first embodiment (Figure 2A) the strengthening strip 46 is fixed to the upper margin along its entire length and the strengthening strip 48 is fixed to the lower margin of the sheet material 10 at least at point 20

The strengthening strip 48 is not connected to the sheet material 10 along the entire length of the sheet material 10 as can be seen in Figure 2A. It is connected at least at point 20, and in other embodiments it could also be loosely connected from point 20 to the crossing point 50 of the edge 38 with the margin. The range 52 between the crossing point 50 of the edge 38 with the margin is not connected to the sheet material 10.

The strengthening strip 46 is hinged to the fixing element 40 at the point 18 rotating about an axis perpendicular to the illustration plane. The strengthening strip 48 is hinged to the fixing element 42 at a point 25 rotating also about an axis perpendicular to the illustration plane. By rotating the strengthening strips 46 and 48 about such an axis, and slightly decreasing the distance between their corresponding fixing elements 40 and 42 the sheet material 10 is folded. This is illustrated in Figure 2A and Figure 2B. In the present symmetrical example, the strengthening strips 46 and 48 remain parallel when rotating during the folding of the material. In some cases, however, when rotating they might not be strictly parallel during the transition, as one of the strips might start the rotation earlier than the other.

The strengthening strip 48 is released from the sheet material 10 in the range 52. This can be well recognized in Figure 2A. The fixing element 42 moves in the direction of the fixing element 40 whereby the distance between the fixing elements 40 and 42 is reduced. Figure 3 A and Figure 3B show the fully folded state of the assembly. Figure 3 C shows a different embodiment with two carriers 43 and 45, each for one shifting element 41 and 47. For folding a simple actuator, such as an electric motor 60 (Fig.3A and Fig.3B) or motor 61 (Fig.3C), can be used, the motor 60 or 61 rotating a shaft about point 18. The strengthening strip 46 can be connected to the shaft whereby it is rotated downwards as shown in the figures. It is understood, that a hydraulic or pneumatic mechanism can also be provided. In addition or alternatively to this rotation a linear movement of the moveable fixing element 42 can also be used for folding the part of the sheet material 10 below the first edge 16.

Figure 6 illustrates a eighth embodiment where the carrier 44 is provided with an angular thread 70. The shifting element 42 is screwed onto the thread 70. Moving the shifting element 42 downwards in the direction of arrow 75 is achieved by rotating the carrier 44 in clockwise direction, indicated by an arrow 73. Moving the shifting element 42 upwards in the direction of arrow 74 is achieved by rotating the carrier 44 in a counterclockwise direction indicated by an arrow 72.

Figure 7 illustrates a ninth embodiment where strings 76 and 77 are connected to shifting element 42, and can move it upwards in the direction of arrow 74 or downwards in the direction of arrow 75.

The sheet material 10 can be used for many different functions. The uses may comprise, for example:

• airplanes with foldable wings;

• MEMS-devices for control of sensor exposure along the vertical axis;

• foldable solar panels;

• shades, umbrellas, billboards;

• foldable furniture, tents;

• transforming shapes.

Fig.4A illustrates a section 13 in greater detail. Section 13 is connected to strengthening strip 48 at least at point 20. Alternatively, section 13 can be stiffly or loosely connected to strengthening strip 48. It is connected along its entire margin 39, and not just at point 20. Such an additional connection ensures that the edge 39 is guided through the transitions and enables smooth folding of the edge 38, while avoid stucking of the material during the transitions.

Fig.4B and Fig. 4C are illustrating two possible implementations of a loose connection of a section 13 to the strengthening strip 48. Implementation in Fig. 4B utilizes a restricting band 62, while implementation in Fig. 4C utilizes a restricting leash 64. Such a loose connection ensures that side 39 will stay in the vicinity of strengthening strip 48 during the whole transition. This boundary is defined by the restricting band 62 in the embodiment in Fig4B, and alternatively, by a boundary 68 in the embodiment in Fig 4C. This type of loose connection gives a degree of freedom of the strengthening strip 48 from margin 39. This helps to overcome a transitional misalignment of about 5-10 degrees. It also forces the margin 39 to move with the strengthening strip 48 when its limits are passed, thus pushing the material to fold or unfold.

A stiff connection of the strengthening strip 48 to the section 13 along its margin 39 is also possible. In this case the transitional misalignment could be absorbed by the elasticity of the material. In this embodiment the material needs to be elastic enough in order to absorb the transitional misalignment.

The horizontal plane is where the surface of the material 10 lies in the completely unfolded state. The transitional misalignment of the margin 39 from this horizontal plane is happening when the margin 39 starts to move during the transition as illustrated in Figure 2A and Figure 2B. It “leaves” this horizontal plane, where point 50 of this margin deviates the most from this horizontal plane. Such horizontal plane is outlined by edge 31 as seen in Fig 2B . It then returns back to its surface at the end of the transition. During the transition the angle of the margin 39 with the horizontal plane can reach about 5-10 degrees, called transitional misalignment above.

In the drawings, numeral 39 designates part of the margin, i.e. edge of section 13. Numeral 62 designates a restricting band to confine the strengthening strip 48 and its range 52. Such restricting band 62 may be a fabric or other such material. Numeral 64 designates a restricting leash which could also be fabric. Numeral 66 designates a point on the surface of section 13, where the restricting leash 64 is tied or fixed. Numeral 68 designates a restriction area where strengthening strip 48 and its range 52 can be. Numeral 69 designates the point where the restricting band 62 is fixed to section 13, the other end of the band is fixed to the edge 39. Numeral 166 designates the line on section 13, where other points similar to point 66 can be placed. Numeral 169 designates a line on section 13, where other points similar to point 69 can be placed.

The above invention can be varied in many ways:

Fig.5A, Fig.5B, Fig.5C and Fig.5D show further embodiments, depending on a different combination of strengthening strips and corresponding sections and primary edges. By increasing the sections and the number of strengthening strips the folding ratio can be increased. As for example, the folding ratio of Figure 5A is 2.4, the folding ratio of Figure 5B is 4.8, the folding ratio of Figure 5C is 7.2 and the folding ratio of Figure 5D is about 9.6

Fig.8A, Fig.8B and Fig.8C are front views. Fig 8D is a side view of a rectangular sheet material 210 according to the tenth embodiment of the invention. This embodiment utilizes a well known linkage system used in some umbrella mechanisms. It rotates the strengthening strips about an axis perpendicular to the plane of the representation, which in turn folds and unfolds the material. The rotation of the strengthening strips is effected through the linkage system by shifting another fixing element along the carrier. This linkage system is defined by the linkage elements which are connected to strengthening strips, to the fixing elements and to each other at linkage points. The linkage elements can rotate around those points of connection. Linkage elements 230 and 247 are connected between themselves at point 222. Linkage element 230 is also connected to the front strengthening strip 147 at point 221 and connected to the fixing element 240 at point 219. Linkage element 247 is connected to the front strengthening strip 146 through its extension 246 at point 218. The strengthening strip 147 is connected to strengthening strip 146 at point 118, and to fixing element 140 at point 119.

The described linkage system acts in such a way that changing the distance between fixing elements 240 and 140, by for example actuator who moves them along the carrier 144, will rotate the strengthening strips 146 and 147 around point 118 simultaneously. The same approach is used for rotating the rear strengthening strips 148 and 149 simultaneously around point 124. In this case further fixing elements 142 and 242 are used which can shift along another carrier 145. Carrier 145 extends parallel to carrier 144.

With the described linkage systems for the front and rear strengthening strips, the process of folding and unfolding of the material can be performed by just shifting the fixing elements along the carriers 144 and 145. This is very simple implementation of the invented mechanism as it reduces the required movements for fold and unfold to simply shifting of fixing elements along carrier(s).

The embodiments described above serve to illustrate the invention claimed in the claims. Features which are disclosed together with further features may normally be also used alone or in combination with other features which are explicitly or implicitly disclosed in the text or in the drawings with respect to the embodiments. Sizes and diameters are indicated by way of example only. The person skilled in the art will derive suitable ranges from his/her own specific knowledge and must, therefore, not be discussed here in greater detail. The disclosure of a precise embodiment of a feature does not mean that the invention shall be limited to such a precise embodiment. Moreover, the feature may be realized by many others which are well known to the person skilled in the art. The invention may, therefore, not be only realized in the form of the described embodiments but by all embodiments which are covered by the protective scope of the accompanying claims.

The terms "up", "down", "left" and "right" only relate to the accompanying drawings. It is understood, that the claimed devices may also assume a different orientation. The term "comprising" and the term "including" mean that further not-mentioned components may be provided. The term "essentially", "mainly" or "mostly" means all features which have a property or a content more than others, i.e. more than all other components or features of the kind, i.e. with two components more than 50%.

Claims

1. Foldable sheet material (10) having a plurality of stiff sections (12) which are foldable or rotatably connected along straight edges (14), wherein a straight primary edge (16) extends from a first point (18) on the margin of the sheet material (10) to a distant second point (20) on the margin of the sheet material (10), characterized in that

(a) a secondary edge (22) extends from a third point (24) on the margin of the sheet material to a center point (26) distant to the primary edge;

(b) a tertiary edge (32) extends from the first point (18) to the center point (26); and

(c) a quaternary edge (34) extends from the second point (20) to the center point (26);

(d) wherein the secondary, the tertiary and the quaternary edge (22, 32, 34) move in the same direction from the plane of the sheet material when folded.

2. Foldable sheet material according to claim 1, characterized in that

(c) said bisectors cross in the center point thereby defining an incenter of said triangle.

3. Foldable sheet material according to any of the preceding claims, characterized by a further edge (38), and wherein the further edge (38) is foldable in the opposite direction of the secondary, the tertiary and the quaternary edge (22, 32, 34).

4. Foldable sheet material according to any of the preceding claims, characterized in that it consists of squares where each primary edge (16) forms a diagonal of the square and each secondary edge (22) ends at a corner (24) of the respective square outside of such diagonal.

5. Foldable sheet material according to any of the preceding claims, characterized in that strengthening strips (46, 48) are provided along at least a portion of the margins.

6. Foldable sheet material according to any of the preceding claims, characterized in that the first point (18) of the sheet material is fixed to a carrier (44) by means of a fixing element (40).

7. Foldable sheet material according to claim 6, characterized in that the carrier (44) is formed of an elongated, stiff material (44).

8. Foldable sheet material according to claim 7, characterized in that the second point (20) of the sheet material is fixed to a lower strengthening strip (48) which is connected to the carrier (44) by means of a second fixing element (42).

9. Foldable sheet material according to any of claims 6 to 8, characterized by an actuator for moving at least one of the fixing elements (42).

10. Foldable sheet material (10) according to any of the preceding claims, characterized by further edges, each of them corresponding to one of the edges which is mirrored at the primary edge (16) and wherein the primary edge (16) is foldable in the opposite direction to the secondary, tertiary and quaternary edges (22, 32, 34).

11. Foldable sheet material according to claim 10, characterized in that an upper strengthening strip is provided along an upper margin (46) between the first point (18) and the point defined by mirroring the third point (24) at the primary edge (16) and in that the actuator is configured to rotate the upper strengthening strip (46) around the first point (18) whereby folding of the mirrored portion of the sheet material (10) is achieved.

12. Use of the foldable sheet material according to any of the preceding claims for

• airplanes with foldable wings; • MEMS-devices for control of sensor exposure along the vertical axis;

• foldable solar panels;

• shades, umbrellas, billboards;

• foldable furniture, tents; or · transforming shapes.