According to a preferred embodiment the invention relates to such a balloon carrying active advertisement. Passive advertise ^¬ ments are comprised of images printed on the balloon's surface. Active advertisements are for example comprised of displays or projections, which enables one to display moving and changing im- ages on the balloon. Such balloons are anchored to the ground, i.e. to the earth's surface; when used at events the balloon may display advertising messages or images of the event itself.

Such a balloon is kown in the art. For example, French patent application FR 2935828 relates to an egg shaped balloon comprising a screen for displaying images. Said screen is provided at an outer side of said balloon. This known balloon is highly sensitive to wind and the like, thus yielding an instable projection.

Other solutions are known for decreasing the balloon's insta ^¬ bility. For example, European patent application EP 2220639 re- lates to a set of two cables for keeping said balloon at a fixed position .

As a matter of fact, the international patent application O2007/077269 relates to a balloon that is comprised of a poster ^¬ like advertising plane comprising a floating body above and below said advertising plane. A rotatable rudder is thought to provide some stable positioning in the air. However, an additional rotation connector is reguired for decreasing any excessive rotation of the connection cables. As a consequence, this known balloon will not have a stable positioning in the air.

Therefore, a stable balloon is not known in the art that can be anchored to the earth's surface and that can provide an active advertising . The invention now aims at providing an improved balloon of the kind mentioned in the preamble.

The invention especially aims at providing a balloon as mentioned in the preamble and that provides a stable positioning in the air.

The invention also aims at providing an improved balloon that provides an good readability of the advertising means from the earth's surface.

The invention especially aims at providing a balloon that has a readability of 360° around said balloon.

So as to obtain at least one of the advantages or aims men ^¬ tioned above, according to a first embodiment the invention pro ^¬ vides a balloon comprising the features of claim 1. This balloon has an intrinsic stability in the air.

Due to the oblique positioning of the advertising means, for example a display, an excellent visibility and readability is obtained. Such synergetic result is completely unexpected.

It is especially preferred for the balloon to have a shape of a tetrahedron, a corner of said tetrahedron being positioned at a bottom side during use.

The term "tetrahedron" as used in the present invention relates to the number of planes in the balloon. These planes do not necessarily need to have identical shapes or dimensions. For exam ^¬ ple, the top plane may be smaller or larger than the side planes. Also, the side planes do not necessarily need to have identical shapes .

A further improved stability is obtained with the balloon ac ^¬ cording to the invention comprising three edges, defining the planes and running from the bottom side towards the top side, wherein two edges are provided with aerodynamic flaps. The balloon has a substantially tetrahedral shape (taking into account the remarks regarding the term "tetrahedron") , wherein a tip of the balloon is directed downwardly (towards the earth's surface) such that the balloon has three planes that are positioned substantial- ly vertically when in use. The edges between said planes may be rounded off somewhat or may have a sharp edge. At two of these edges, flaps may be provided for yielding an improved stability. The use of flaps is known in the egg shaped balloon mentioned above, but in that case the effect is relatively small. In the balloon according to the present invention, the effect is substantial, probably due to the inherent stability the balloon according to the present invention already possesses.

The balloon according to the present invention is especially suitable for advertising due to the substantially flat shape of the side planes. Therefore, the present invention also relates to a balloon wherein at least one side plane comprises an advertising plane with a display, said display being comprised of an OLED- display or a LED-array display. This yields a sturdy advertising plane that is integrated into the balloon's design increasing its adverting 's visibility, appeal and efficiency. Since the balloon's side planes, due to the tetrahedral shape and the edge pointing towards the earth, is positioned somewhat oblique the readability of the advertising planes from the earth is excellent. An additional advantage is that reflections, for a viewer on the ground, are reduced strongly.

A good readability from all around is obtained if all side planes have their own advertising plane. Preferably, every advertising plane has at least one display. Such provides a balloon with a 360° visibility.

On its advertising plane the balloon may comprise a single large display or, preferably due to ease of transport and replace- ment in case of damage, a plurality of displays. For example, an advertising plane may be covered with a matrix of 9 * 9 displays. Such matrix, built up of 55" displays with external dimensions of about 72 * 125 cm, yields a total viewing plane of 6,5 * 11,3 m (about 73 m ² ) . The weight of a single OLED-display with such dimen- sions is only 7 kg. As a consequence, the weight per advertising plane amounts to 567 kg. A balloon according to the present invention, filled with helium, is simply capable of carrying such weight if all three planes comprise such display or matrix of displays .

So as to obtain an optimum readability and appeal it is pre ^¬ ferred that the balloon comprises a plurality of gaplessly posi ^¬ tioned displays. It has shown that a gapless configuration pro- vides a further improved stability, especially at high wind speed.

A simple control of the balloon, like determining the location and height of the balloon, is obtained when said balloon comprises a connection cable for anchoring the balloon, preferably to the earth's surface. Through said cable, signaling cables m.ay be led for controlling or feeding the displays provided on one or a plurality of said advertising planes.

A special embodiment is obtained by providing the balloon with a nacelle for carrying a passenger. Thus, passengers m.ay en- joy a enjoy a magnificent view in a simple, environmentally friendly and inexpensive way. The balloon may be raised and low ^¬ ered through said cable, ensuring a quick exchange of passengers. Optionally, compressors may be provided in the balloon for com ^¬ pressing the balloon's lifting gas in gas tanks or the like, for reducing the balloon's lifting power. Then, raising and lowering the balloon may be performed at a higher speed.

A further improved stability, especially at higher wind speeds, is obtained when the length of the top edge of two side planes being longer than the length of the top edge of a third side plane. The shortest side may be positioned at a leeward side so as to obtain an optimum stability.

An increased stability may be increased if aerodynamic flaps are provided at both sides of said third side plane.

A simple construction of the balloon is obtained when the top plane is a slightly convex plane. The side planes are preferably flat, such that displays may be connected tension free.

A further modification of the aerodynamics may be obtained by means of a balloon wherein the top plane is comprised of segments. Instead of an embodiment as mentioned above, said top plane being shaped substantially as a single construction, the balloon will be constructed from a plurality of planes, such that a segmented shape is obtained instead of a convex or flat shape, somewhat analogous to the polished surfaces of a diamond, with the proviso that the balloon has three side planes.

It is especially preferred that said top plane comprises at least two segments, being comprised of at least one connection plane, that is positioned angled with respect to a side plane, and a top plane that is connected to said at least one connection plane .

In case the top plane of the balloon is comprised of two planes further comprising a connection plane and a top plane, the side that during use is positioned at the leeward side, may for example comprise the connection plane. This yields a most effi ^¬ cient aerodynamic shape to the balloon. In case the balloon has two connection planes, for example both said windward planes may comprise said connection planes. Such yields in the case of two connection planes, a most efficient aerodynamic shape to the bal ^¬ loon .

More in particular, a balloon may be provided with a top plane comprising four segments, comprised of three connection planes that are each angled with respect to one of said side planes and a top plane that is connected to said connection planes. This proved to provide a m.ost aerodynamically efficient and stable positioning of the balloon.

According to a further aspect, the invention relates to a display system for a balloon according to the present invention, comprising a projector within said balloon for projecting images on said at least one display and a receiver connected to said pro ^¬ jector, as well as a transmitter outside said balloon for transmitting to said receiver images to be projected.

The display system according to the invention comprises ac- cording to a further embodiment a camera and a projector connected to said camera, for displaying images recorded with said camera on said at least one display. This is an advantage at events, where the public may be provided with an overview of all festivities. However, such also is advantageous in case of criminal investiga- tions, providing a good and clear overview of the surroundings of a crime scene.

The invention will now be explained by means of a drawing. The drawing shows in:

Fig. 1 a simplified view of a balloon according to the pre- sent invention,

Fig. 2 a simplified side view of a balloon according to the present invention, Fig. 3 another embodiment of a balloon according to the present invention, and

Fig. 4, 5 and 6 other embodiments of a balloon according to the present invention.

In the figures the same and analogous parts are provided with the same reference numbers. However, for ease of understanding the drawing, not all parts that are required for a practical em.bodi- ment have been shown in the drawing.

Fig. 1 shows a schematic, simplified view of a tetrahedral balloon 1 according to the present invention. The balloon 1 comprises a body to be filled with a lifting gas, defined by three side planes, two of these side planes 2, 3 being visible, and a top plane 4. The side planes are separated from each other by ver ^¬ tical edges 5, 6, 7, and by means of horizontal edges, denoted by reference numbers 8, 9, 10 as top edges.

The balloon is shown in a position during use, the balloon 1 being directed towards the earth's surface with a bottom side 11 (not shown in Fig. 1, shown in Fig. 2) and wherein a top side 12 is directed away from the earth's surface.

At its bottom side 11 the balloon 1 comprises a cable 13, being embodied for anchoring the balloon 1 to the earth's surface. The balloon's position with respect to the earth's surface may be secured by such cable.

Fig. 2 shows a schematical simplified side view of the bal- loon 1 according to the present invention. The side plane 2 as shown in Fig. 2 comprises an advertising plane 14 that is comprised of a matrix of displays 17. In the embodiment shown, the advertising plane comprises nine displays, distributed into three rows 15 and three columns 16. Each display 17 is positioned sub- stantially gapless against a neighboring display 17, such that a spectator 18 optically perceives a single large display from the earth's surface. So as to supply to every spectator around balloon 1 a visible display, each side plane of balloon 1 comprises such advertising plane.

The images displayed on the displays 17, for example adver ^¬ tisements, may be controlled from the earth's surface from a con ^¬ trol center 20. Control of said displays may be obtained by means of electrical or optical cables, guided to the balloon via cable 13 from the ground towards the balloon, but may also be obtained wirelessly through an emitter near control center 20 and a receiver within said balloon 1.

By means of cable 13, the balloon 1 is anchored to a ground anchor 23, providing a stable local positioning. As a consequence, the balloon 1 will not be taken by the wind to another location.

In Fig. 3 another embodiment of the balloon 1 according to the invention is shown. At two side edges 6, 7 aerodynamic flaps 21, 22 are provided, providing the balloon 1 a very stable posi ^¬ tion in the air, especially at high wind speeds. The wind will blow against the balloon along edge 5, such that flaps 21, 22 will yield stability.

According to a further embodiment, side plane 3 can be shaped les wide than said other side planes, such that the length of the top edge 9 is less than the length of top edges 8 and 10. Such provides a further improved stability when side edge 5 is the wind ward edge, i.e. when wind flows towards side edge 5.

Fig. 4 shows another embodiment of the balloon according to the present invention. Balloon 1 comprises three side planes (only side planes 2 and 3 are visible) and a top plane 25. In this em ^¬ bodiment, said top plane is shaped as top plane 25 and three con ^¬ nection planes (only connection planes 26 and 27 are visible) , said three connection planes being positioned between said top plane and said respective side planes. Said connection planes pro ^¬ vide for a smooth transition from said top plane and the side planes. This positively influences the aerodynamic properties of the balloon 1.

Instead of connection planes between all side planes and top plane 4, a single connection plane may be provided, like connec tion plane 27 as shown in Fig. 5. Such embodiment is particularly useful when said single connection plane is provided at the leeward side of the balloon, that is to say, at the side opposite the edge 5 where the wind flows towards the balloon.

It is evenly possible to provide two connection planes, as shown in Fig. 6 by means of connection plane 26 and the connection plane provided at the other side (not visible in Fig. 6). Such em- bodiment is useful if the connection planes are positioned at either side of the balloon's edge 5 being the edge towards the wind flows .

The invention is not limited to the embodiments as described above and as shown in the drawing. The invention is only limited by the accompanying claims.

For example, top plane 4 may have an, optionally flattened, convex shape instead of the flattened shape according to Fig. 1 - 3 or the segmented shape shown in Fig. 4 - 6. Such convex shape corresponds somewhat to the top side of regular balloons.

The invention also extends towards every combination of fea ^¬ tures that are described above independently of each other.