Such a pane structure is known by the name climate gable. A pane, preferably double glass, is herein arranged in the gable of a building. Slats are placed on the inside behind the pane. A second pane is then placed behind these slats. By closing the slats a part of the radiation is reflected and a part is converted into heat. The heated air between the two panes is drawn off by suction means.

The so-called ZTA value is used to express the effectiveness of sun-screenings. This value is a factor which indicates the ratio of the radiation incident from outside and the radiation penetrating into the space.

The lower the ZTA value, the more effective the sun- screening. A standard outside sun-screening has a ZTA value of between 0.12 and 0.20. The above stated climate gable has a ZTA value of between 0.14 and 0.15.

In for instance large office buildings the air is kept at a constant temperature by cooling installations.

The air for cooling is heated by a number of heat sources. These heat sources are on the one hand people, artificial light and equipment in the space and on the other hand the heat radiation penetrating from outside.

The internal heat sources generate a constant heat which on average is about two-thirds of the total heat. The

radiation coming from outside fluctuates with the sunshine and on average supplies roughly one-third of the heat.

A cooling installation must be dimensioned such that it can also compensate the fluctuations in heat.

The greater the fluctuations, the more costly the cooling installation.

It is therefore an object of the invention to keep the fluctuating, penetrating radiant heat as low as possible.

This objective is achieved according to the invention with a pane structure in which the flat element comprises pores, and suction means connect to the cavity such that the suction means draw in air via the pores and the cavity.

An advantage of a pane structure according to the invention is that construction is simpler than with conventional devices. The ZTA value moreover lies between 0.08 and 0.09. This is significantly lower than that of known sun-screenings.

According to a specific embodiment the suction means are provided with a heat exchanger. It is hereby possible in winter to use heat collected in the cavity to heat fresh air which is subsequently blown into the space. Heating costs are hereby reduced.

It is also possible in the summer to cool warm outside air with cooler inside air.

According to a further embodiment of the invention the flat element is at least partly transparent and the side of the flat element directed toward the pane is heat-reflecting. It is hereby possible to look outside from the space, and as much heat as possible is held in the cavity.

It is known to cover a pane with curtains which can be opened or closed as desired. When direct looking-in is not desired, a second cloth can be used to cover the pane, this cloth normally being designated a net

curtain. Due to the open structure of the net curtain it is herein possible to look outside without it being easily possible to look in from outside. A drawback is that two different cloths are arranged over the pane.

It is also known to use slats as window covering.

The slats can herein have a variable adjustment, whereby the extent to which the slats are open can be varied. A drawback of such slats is that the slats obstruct part of the view. It is also possible to look directly inside from the outside.

It is an object of the present invention to obviate the above stated drawbacks.

This objective is achieved according to the invention in that the cloth consists of a fabric comprising warp threads extending mutually parallel and weft threads directed perpendicularly thereof, wherein the weft threads run alternately below and above the warp threads, wherein the mutual distance between the threads varies such that the fabric has zones with differing densities.

A pane structure is hereby provided which for instance comprises both an opaque part and a part through which it is possible to look outside but, in the case of light incident from outside, it is not possible to look inside from the outside. By arranging the cloth so that it can for instance be rolled up such that the cloth can be displaced relative to the pane, the pane structure can be placed in an open or closed position.

Attention is drawn to the fact that a cloth according to the invention, wherein the density changes in stepwise manner, which cloth therefore has discrete zones with differing densities, can be manufactured by varying the centre distance of like threads as well as by embodying the cloth such that threads in the different zones have different dimensions in the main plane of the cloth, for instance while retaining their mutual centre-to-centre distance.

It should further be understood that the threads can have different cross-sections, for instance a round shape, but also an elongate, more or less rectangular shape. In this latter case the threads are more or less ribbon-shaped.

In the case for instance the centre distance is maintained and different threads are used for the different zones, there is a change of yarn type during the weaving process.

All known types of yarn can in principle be considered suitable, for instance spun yarns, filament yarns, monofilament yarns, elastic yarns, metal yarns, ribbon yarns and the like. The threads according to the invention can even be defined as strips, tubes and rods.

In a specific embodiment the cloth according to the invention is metallized. Specific light effects can be realized herewith and the cloth is not subject to static charging.

According to another aspect of the invention the cloth according to the invention has the feature that the second threads extending perpendicularly of said first threads at varying mutual distances are elastic such that their said mutual distances can be adjusted by adjusting the tensile force in the second threads.

An alternative has the special feature that the second threads extending perpendicularly of said first threads at varying mutual distances are electrostrictive such that their said mutual distances can be adjusted by adjusting the voltage over the second threads.

The invention can likewise be used in a climate control, wherein the transparency of the cloth, or the sun-screening, can be adjusted depending on the solar radiation. The cloth herein has a density which changes evenly or continuously.

The regulation of the climate control can herein adjust the cloth subject to the required cooling such

that the air is drawn in via a zone with the desired density.

In another embodiment the weft and warp threads are of plastic. The threads can hereby be fixed relative to each other in simple manner, for instance by heating, whereby the structure of the cloth is better preserved.

It is also possible to fix the threads relative to each other by means of a coating.

According to another embodiment of the invention the pane structure comprises a rotatably drivable upper tube on which the flat element can be rolled up, which upper tube is arranged for rotation on its axis on one side of the frame, and wherein a first side of the flat element is connected to the peripheral surface of the upper tube; a lower tube on which the flat element can be rolled up, which lower tube is arranged for rotation on its axis in a sub-frame and is loaded by spring means to hold the flat element under tension, which spring means are arranged between the sub-frame and the lower tube, wherein a second side lying at least more or less opposite the first side of the flat element is connected to the peripheral surface of the lower tube.

This embodiment has the advantage that when a flat element with progressive transparency is used the transparency of the pane structure can be varied by rotating the upper tube. For this purpose the cloth is fixed to the upper tube on the side with the least transparency, while the side which is most transparent is fixed to the lower tube. By driving the upper tube the transparency of the pane structure will now increase until there is no longer any cloth rolled round the lower tube. By now rotating the upper tube further the lower tube will be lifted, whereby the cloth over the pane is removed and an unobstructed view is obtained.

In yet another embodiment of the invention the pane structure comprises a guide for guiding the sub-frame, whereby the reactive force of the spring means is

compensated. This prevents the sub-frame coming to lie against the flat element and this latter being damaged thereby.

In yet another embodiment the pane structure comprises a counter-roller which is arranged rotatably and parallel to the lower tube on the sub-frame of the lower tube, wherein the counter-roller lies against the flat element such that the reactive force of the spring means is compensated. A guide hereby becomes unnecessary but the cloth is not damaged because a counter-roller supports rotatably against the cloth.

These and other features of the invention will be further elucidated with reference to the annexed drawings.

Figure 1 shows a first embodiment of the invention.

Figure 2 shows a second embodiment of the invention.

Figure 3 shows a first embodiment of the means for displacing the cloth relative to the pane.

Figure 4 shows a second embodiment of the means for displacing the cloth relative to the pane.

Figure 5 shows a third embodiment of the means for displacing the cloth relative to the pane.

Figure 6 shows schematically a cloth with varying permeability to light and air.

Figure 7 shows an enlarged part of a first zone of the cloth.

Figure 8 shows an enlarged part of a first embodiment of a second zone of the cloth.

Figure 9 shows an enlarged part of a second embodiment of a second zone of the cloth.

Figure 10 shows schematically an enlarged part of another cloth according to the invention.

Figure 1 shows a space R in a building. Arranged in gable 2 is a pane 1 which is preferably of double glass.

A porous cloth is suspended behind this pane and parallel thereto. Pane 1 and cloth 4 bound a cavity 3.

The cloth is provided at top and bottom with rollers 5, whereby the cloth can be rolled up and displaced relative to pane 1.

The cavity is in communication with cooling means 6 via a feed pipe 7. The cooled air flows back to space R via a discharge pipe 8. It is also possible to provide ventilation means instead of cooling means 6, wherein the air supplied via pipe 7 is blown to the outside and fresh air flows from outside into space R.

The pane structure according to the invention operates as follows. The sun emits radiant heat W which falls through pane 1 and onto cloth 4. A part of this heat is reflected and will heat the air in cavity 3. The temperature of the cloth will moreover increase. Cooling means 6 draw air from cavity 3 and cool it, whereafter, at least in this embodiment, the air is blown back into the space via discharge pipe 8. The air then flows back again to the porous cloth and, via the gap under the cloth and through the cloth, back into the cavity.

Because the air flows through porous cloth 4, the cloth is cooled and, because air flows along the cloth, this heated air is carried along to the cooling means. Hereby the radiant heat is immediately discharged to the cooling means and the radiant heat cannot therefore heat space R directly.

The cooling means can form part of the climate control of a large office building.

In a preferred embodiment the porous cloth 4 is transparent, whereby the view to the outside from space R is not obstructed. It is further possible to provide the cloth with zones of differing density. This makes it possible, by displacing the cloth relative to the pane, to screen the pane or, conversely, make it transparent.

It is further also possible to provide the cloth with a continuously progressive density. Means can herein be present for displacing the cloth relative to the pane. By coupling these means to for instance a

computer it is possible to provide a control such that the fluctuations in the load of the cooling means are as low as possible and the temperature remains constant.

It is further possible to embody the porous cloth so that is can be rolled up. The pane is hereby accessible for cleaning thereof or when the sun is obscured by clouds.

Figure 2 shows a second embodiment according to the invention which corresponds by and large with the first embodiment according to the invention. The difference is that cooling means 6 are replaced by a heat exchanger 9.

This is a particularly advantageous embodiment of the invention in winter. When the sun shines it heats the air in the cavity which is subsequently extracted via feed pipe 7 of heat exchanger 9. In this heat exchanger 9 the heat of the extracted air is relinquished to fresh air, whereafter this fresh air flows back into space R.

So as to make optimum use of the incoming radiant heat the porous cloth is preferably embodied in black. All radiation is hereby converted into heat which is then discharged through the air.

The ventilation means or cooling means are preferably embodied such that a laminar flow is created in the cavity. The heat transfer between the porous cloth and the air is hereby optimal. In addition, the cavity is preferably 7 cm wide and the gap is arranged at the bottom of the porous cloth.

Figure 3 shows a perspective view of a first embodiment of the means for displacing cloth 4 relative to pane 1. The means comprise two rollers, of which the upper roller 10 is suspended rotatably in a frame 11 which is mounted for instance on the ceiling 12. Upper tube 10 is drivable by a motor (not shown). Lower tube 13 is arranged rotatably in a sub-frame 14. In lower tube 13 is arranged a spring 15 which is mounted between sub-frame 14 and lower tube 13.

In figure 3 the cloth is rolled mainly round lower tube 13. Sub-frame 14 herein lies on a surface such as a window sill 16. Spring 15 has a spring force such that cloth 4 remains tautly stretched and sub-frame 14 remains on window sill 16 as long as there is still cloth wound on lower tube 13.

When cloth 4 has progressive transparency, it is possible by controlling the motor which drives upper tube 10 to vary the transparency of the visible part of the cloth. By winding the cloth fully onto the upper tube the lower tube 13 is lifted, whereby a wholly unobstructed view to the outside is obtained. Sub-frame 14 has a mass such that the reactive force of spring 15 is compensated.

Shown in figure 4 is a second embodiment of the means for displacing the cloth relative to pane 1.

Components corresponding with figure 3 are provided herein with the same reference numerals. In this embodiment sub-frame 14 is guided in two lateral guides 17. Sub-frame 14 can hereby not tilt as a consequence of the reactive force of spring 15. The advantage hereof is that sub-frame 14 can have a smaller mass.

Figure 5 shows a third embodiment of the means for displacing cloth 4 relative to pane 1. Components corresponding with figures 3 and 4 are likewise provided herein with the same reference numerals.

In this embodiment a counter-roller 18 parallel to lower tube 13 is arranged rotatably in sub-frame 14.

This counter-roller 18 lies against cloth 4 and thus forms a lever arm with the length X for compensating the reactive force of spring 15. The advantage hereof is that, as in the previous embodiment, the mass of the sub-frame can be smaller.

It is further possible according to the invention to apply the device in a heat-transmitting plate of for instance an oven. A good cooling can hereby be obtained in simple manner.

Figure 6 shows a cloth 101 comprising a first zone VII and a second zone VIII.

Figure 7 shows an enlargement of first zone VII of cloth 101. It can be seen here that the cloth consists of warp threads 102 extending parallel and weft threads 103 directed perpendicularly thereof. The distance A between two adjacent warp threads is roughly equal to the distance B between two adjacent weft threads. The thickness of the threads and the distances A and B determine the density of first zone VII.

Figure 8 shows a first embodiment of second zone VIII of cloth 101. Warp threads 102 and weft threads 103 can likewise be seen herein. In this first embodiment the distance A'between two adjacent warp threads is smaller than the distance B'between two adjacent weft threads. Particularly assuming that the distance A' equals the distance A of figure 7, a density of the cloth is hereby obtained differing from the density of the cloth in first zone VII.

Figure 9 shows a second embodiment of second zone VIII of cloth 101. This second embodiment corresponds for the most part with the first embodiment of figure 8.

The distance A"between two adjacent warp threads is however greater here than the distance B"between two adjacent weft threads. Another density of the cloth is likewise hereby obtained.

It is thus possible to vary the density of the cloth either by varying the distance between the warp threads or by varying the distance between the weft threads, or by varying both distances.

Cloth 101 can for instance be woven on a loom. In order to retain the structure of the fabric, the threads can be fixed relative to each other by a coating. It is also possible to embody the threads in plastic and to fix them relative to each other by heating, for instance by means of calendering.

A cloth according to the invention can be embodied with a stepwise varying density or an evenly/ continuously progressing density. Such a cloth can herein be arranged on rollers in front of a pane, whereby the cloth is displaceable relative to the pane and the sun-screening or the option of looking through the pane can be varied.

Figure 10 shows very schematically an enlarged portion of a cloth 111 according to the invention.

Other than cloth 101 as according to figure 6, cloth 111 of figure 10 has no discrete zones with different densities but cloth 111 has a density changing in vertical direction, as expressed in the number of threads 112 per vertical unit of length. The mutual distance between the threads 113 extending in vertical direction is the same over the whole cloth 111.

Owing to the structure of cloth 111 the mutual distance between threads 112 depends on the position (in vertical direction in figure 10). At the top the permeability of the cloth to light, liquid, gas is thus smaller than at the bottom of cloth 111.

In this embodiment the threads 112 are everywhere the same. The described variation in density is realized by continuously adjusting the mutual distance between threads 112 during the weaving process.

The embodiment according to figure 6 is based on this same principle, be it in discontinuous or discrete form. All threads extending in horizontal direction are the same. In zone VII however, the thread density in this random embodiment is roughly twice as great as in zone VIII.

This same effect could alternatively be achieved by maintaining the same mutual centre-to-centre distance between the threads but choosing threads for zone VII of a type differing from those in zone VIII. It will be apparent that the decisive quantity here is the relevant transverse dimensioning of the threads in question. The

width of these yarns can be easily chosen, particularly in the case of ribbon-shaped yarns. During the weaving process a different type of yarn must be chosen at the transition between zones VII and VIII.