Traditional insulating panes comprise at least two plane-parallel panes of glass or another transparent material. The panes are placed on each side of a spacer profile shaped to form the perimeter of a plane geomet- ric figure, so that, when assembled, a cavity defined by the two panes and the spacer profile is provided.

This cavity is normally filled by air, typically atmospheric air, but may also be filled with a gas or a gas mixture having suitable heat transfer properties.

The shape and the size of the panes and the geometric figure created by the spacer profile are normally adapted to each other, so that the spacer profile, when the insulating pane is assembled, is positioned at the edge of the plane-parallel panes.

Typically, such insulating panes and thus the geometric figure formed by the spacer profile are rectangular, but they may in principle have almost any geometric shape, and circular insulating panes are thus for instance not unusual.

The spacer profile is typically of metal and has in itself a rectangular, tubular cross-section. It is desirable that the spacer profile has so small an abutment surface as possible against the window panes to avoid to the highest extent heat conduction between the two panes through the spacer profile and to avoid that the pane itself does not limit the effective window area more than absolutely necessary.

In use such a pane is usually mounted in a sash which, on one hand, has an aperture which as to size

and extent substantially corresponds to the effective window area of the insulating pane and which, on the other hand, is provided with a rabbet along the periph- ery of the aperture, said rabbet serving as abutment surface for the insulating pane and having dimensions corresponding to the overall dimensions of the insulat- ing pane. Thus, the insulating pane, on one hand, lies in a recess corresponding to its own size, on the other hand substantially only abuts the abutment surface with the part, in which the spacer profile is present. The pane is typically secured by means of securing beads fastened on the sash.

However, this way of mounting presents some problems if it is used in connection with a window mounted in an oblique surface, as precipitation hitting the pane will run down over it and to the sash. Irre- spective of the fact that a sealing material will normally be used for sealing between sash, pane and securing bead, moisture may gather and penetrate between the sash and the insulating pane.

As such a penetration of moisture is undesirable, the rabbet at the lower edge of the insulating pane has been left out in certain windows to be mounted in oblique surfaces, as illustrated to the right in Fig.

1. Instead, the lower part of the sash is flush with the bottom of the rabbet all the way to the edge, and the insulating pane is placed in such a manner that it overlaps the sash all the way to its edge. The securing of the insulating pane is in this connection carried out by clamps. With this mounting, precipitation may run off the insulation pane, so that moisture accumula- tion and thus penetration of moist between insulating pane and sash is avoided.

Although this kind of mounting has proved effec- tive in preventing moisture penetration between sash

and window, the overlap between sash and insulating pane does, however, present some problems.

By influx of sunlight through the insulating pane a part of the influx of sunlight will pass directly through the pane and the aperture of the sash into the room behind without any energy worth mentioning being dissipated in the panes of the insulating pane and the cavity between them. A part of the sunlight passing the insulating pane will, however, not pass the aperture, but instead hit the part of the sash overlapped by the pane. This sunlight will heat the part of the sash overlapped by the insulating pane, so that this part of the sash in return heats the insulating pane. Moreover, a certain heat-conduction will take place through the sash to the air in the cavity in the insulating pane from the room behind it.

Thereby, a non-uniform heating of the air in the cavity in the insulating pane takes place, the air in the part of the cavity adjacent the overlap being heated differently from the air in the part of the cavity adjacent the aperture, the air here being heated by heat-conduction from air in the room behind.

In situations where little or no influx of sun- light takes place, e. g. during the night, the air in the part of the cavity adjacent the aperture will to a larger extent be heated by heat-conduction from the air in the room behind than will be the case for the part of the cavity overlapping the sash.

Thus, also in this situation a non-uniform heating of the two parts of the cavity between the panes will take place.

This non-uniform heating causes convection cur- rents in the cavity in the pane. These air currents also entail an increased heat transfer between the two panes and thus lead to an undesirable deterioration of

the thermal insulation properties of the insulating pane. Similar problems will occur along the entire edge of a window, if it is the wish to use a pane which does not only overlap the sash at the bottom but overlaps the sash all the way around it.

This wish exists among others on account of the condensation problems occurring due to the temperature gradient when the outside temperature is low. At low outside temperatures the conducting of heat away from the interior side of the pane through the spacer profile, which is typically of metal, will cause the temperature at the edge of the pane to become so low on the interior side that the moisture of the atmosphere condenses, which is not only undesirable for aesthetic reasons but also increases the risk of dry rot.

If in that case the heat-conducting spacer profile is moved further in on the sash, i. e. away from the aperture, the heat-conduction through the spacer profile will not occur in the immediate vicinity of the edge of the aperture of the sash, where the air with its content of moisture has access.

Hereby a lower temperature gradient at the edge of the aperture of the sash and consequently less conden- sation is obtained due to the fact that the insulating properties of the pane at this place are better than would be the case if the spacer profile was present there.

Furthermore, there is a sound insulation problem in window panes mounted in sashes which, in the manner described above, have an aperture corresponding to the effective area of the insulating pane, i. e. the area within the figure formed by the spacer profile.

On account of the tight joining of the two plane- parallel panes and the spacer profile a higher sound transmission occurs through the spacer profile than

through whatever air may be present in the cavity between the plane-parallel panes.

In order to reduce the effect of this sound transmission it is also here desirable to place the spacer profile on the sash, i. e. away from the aper- ture.

However, this overlap has the effect that convec- tion problems of the type described above occur.

It is the object of the invention to provide an insulating pane according to the opening paragraph which solves this problem.

The invention overcomes this problem through an insulating pane according to the opening paragraph which is characterized in that in the cavity between the two plane-parallel panes and at a distance from the spacer profile an elongate wall member dividing the cavity is provided.

In an advantageous embodiment of the invention a number of openings are provided in the elongate wall member, said openings being circular and having a diameter of less than 1 mm, preferably 0.2-0.4 mm.

Surprisingly, in addition to the improvement of the thermal insulation properties of the pane, also an improvement of the acoustic insulation properties of the insulating pane is thereby obtained.

The elongate wall member is preferably provided in the form of a metal strip having a thickness of ap- proximately 0.05 mm.

This thickness ensures a low heat conduction through the strip and is at the same time sufficient for the functioning of the elongate member as a cavity divider, as, in this respect, there are no substantial strength aspects to be taken into account, the cavity between the panes being filled with air, preferably

atmospheric air at normal atmospheric pressure (approx- imately 1013 hPa).

In another advantageous embodiment, the elongate wall member extends along a number of the sides of the closed spacer profile.

In a particularly preferred embodiment the closed spacer profile substantially has the form of a rect- angle, and the elongate wall member extends at a distance from and along a first side of the closed spacer profile and between two other mutually opposite sides.

In both the two abovementioned embodiments the elongate wall member extends at the same distance, preferably 40 mm, from the sides of the closed spacer profile, along which it extends.

In this way the elongate wall member may be positioned in such a manner relative to the sash that it does not affect the aesthetic appearance of the window seen from indoors, which is in particular advantageous, when the elongate wall member is opaque, which is for instance the case when said metal strip is used as the wall member.

The invention will now be described in detail with reference to the schematic drawing, in which Fig. 1 is a perspective sectional view through a window sash, on which an insulating pane according to the present invention has been mounted.

Fig. 1 shows, seen from the side and in perspec- tive, a sectional view through a rectangular window sash 1, in which an insulating pane 2 according to the present invention has been mounted. In Fig. 1 three sash sides la, lb, lc are shown, attention being called to the fact that for illustrative reasons the middle of the insulating pane 2 as well as one sash side lb have been removed.

Of the four sash sides three, i. e. on the figure sash sides la, lb, the fourth side not being shown, have the same L-shaped profile, whereas the last sash side lc has a substantially rectangular profile.

The L-shaped sash profile thus provides a rabbet 3, in which the insulating pane 2 according to the invention has been mounted. The insulating pane 2 is secured at the three sash sides lb, lb in the rabbet by means of a securing bead 4. In a manner known per se a sealing material (not shown) is provided in connection with the rabbet 3, the insulating pane 2 and the securing bead 4.

As mentioned, the last sash side lc has a substan- tially rectangular profile. The insulating pane 2 is secured at this sash side lc not by means of a securing bead, but instead by means of clamps (not shown).

Moreover, sealing material is provided between the insulating pane 1 and the sash side lc.

This way of mounting an insulating pane in a sash with a rabbet on three sides is known per se. When a window of this construction is mounted in such a manner in a frame in an inclined surface, for instance a roof, that the sash side lc is at the bottom and the sash side la at the top, rainwater, melted snow and other kinds of precipitation will not gather at the sash member lc and penetrate between the insulating pane and the sash member, but instead run off the insulating pane without doing any harm.

As will be seen from Fig. 1, the insulating pane 1 comprises a tubular spacer profile 5a, 5b, 5c having rectangular cross-section. This spacer profile 5a, 5b, 5c is shaped into a closed, rectangular, geometric figure corresponding to the shape of the two individual panes 2a, 2b of the insulating pane. The tubular spacer profile 5a, 5b, 5c will typically be made from stain-

less steel or aluminium, but other kinds of material might be applicable too, like for instance plastics or composite material. The two panes 2a, 2b are in the preferred embodiment made from glass, but may in principle be made from any transparent material having sufficient strength.

As will be seen from Fig. 1, the insulating pane overlaps the sash. This overlap corresponds on the three sides la, lb and the side not shown to the width of the tubular spacer profile 5a, 5b, 5c and to the width of the abutment surface 3a of the insulating pane against the rabbet 3. That is to say, the interior side of the rectangular geometric figure constituted of the tubular spacer profile flushes at the three sides substantially with the interior part of the sash, i. e. with the three sides of the aperture 7.

At the last side lc the overlap is bigger. Here there is not only an overlap corresponding to the width of the spacer profile 5a, 5b, 5c, but an overlap corresponding to the width of the entire sash.

This overlap has the effect that there is part of the area of the insulating pane, in which the sunlight passing the insulating pane does not just continue through the aperture 7 to the room behind, but instead hits an area 6 of the sash, thus heating the sash member 1c.

The sash member lc will moreover be heated by heat conduction from the room behind.

The heated sash member lc will through the pane 2a heat the air in the area of the cavity adjacent the sash member lc and between the two panes 2a, 2b. This heating occurs substantially by heat transmission through the pane 2a.

In the remaining area of the cavity between the two panes 2a, 2b, viz. the area 9a adjacent the aper-

ture 7, the air will be heated substantially through heat conduction from the room behind through the pane 2a.

In situations without influx of sunlight, the heating may be such that the air in the area 9a adjac- ent the aperture 7 is heated to a larger extent than the air in area 9b adjacent the sash, because the heat conduction is higher through the pane 2a than through the sash member lc.

To prevent convection due to the air in the cavity 9a, 9b between the two panes 2a, 2b not being uniformly heated in the areas corresponding to adjacent the aperture 7 and adjacent the sash member lc, respective- ly, a wall member 8 has been inserted.

The wall member 8 is in the embodiment shown in Fig. 1 positioned in such a manner that it extends along one side 5c of the tubular spacer profile and between to other sides, viz. the side 5b and opposite side (not shown). The distance between the side 5c of the tubular spacer profile and the wall member 8 will normally be adapted so that the wall member 8 substan- tially flushes with the interior side of the sash member lc. In the case shown, the wall member flushes with a chamfering but might just as well flush with the side 11 of the sash itself.

By this positioning of the wall member 8 is obtained firstly a division of the cavity 9a, 9b into two parts corresponding to the aperture 7 and the overlap between the insulation pane 2 and the sash member lc, respectively, so that convection is to the largest possible extent avoided. Secondly, a good aesthetic effect is obtained, the lower part 9b of the cavity between the two panes 2a, 2b will not be visible through the wall member 8 to a person looking at the window from the room behind. The person thus does not

get the impression that a part of the insulating pane is covered by the sash and thus is not utilized.

As the lower part 9b of the cavity thus cannot be seen from inside and is only visible from a distance outside, there is no aesthetic reason hindering the introduction of insulating material in this lower part 9b of the cavity between the two panes 2a, 2b.

From outside, the aesthetic problems will be smaller, the viewing typically taking place from below and at a far greater distance, as such panes are usual- ly used in roof constructions.

If the wall member 8 is made from the same material as the tubular spacer profile 5a, 5b, 5c, the wall member 8 may in practice be designed in such a manner that it cannot immediately be distinguished from the tubular spacer profile 5a, 5b at the remaining three sides of the sash.

Preferably, the distance will in practice be approximately 40 mm corresponding to the width of the sash member lc.

It should, however, be emphasized that the strip does not necessarily have to run smoothly in the longitudinal direction but may be bent in zig-zag shape or be provided with corrugations.

Further, attention is called to the fact that the term"elongate"is to be understood in relation to the strip itself. Thus, it may also occur that the elongate strip is formed to a closed figure, for instance a circular or rectangular figure, for instance correspon- ding to the shape of the pane, in which it is inserted.

The wall member 8 is in the embodiment according to Fig. 1 secured directly to the panes 2a and 2b by means of an adhesive and sealing mass, for instance isobutylene-isoprene rubber or silicone.

Preferably, the wall member 8 is designed as a metal strip, for instance of steel, stainless steel or aluminium, and has a thickness of 0.05 mm and a width corresponding to the distance between the two panes 2a and 2b. Alternatively, also other materials like plastics or composite materials may be used for the wall member 8. In respect of the insulating panes used for the time being, a typical value for this distance and thus the width of the strip lies between 10 mm and 18 mm, typically 14 mm.

It has turned out that the wall member 8 also meets its primary function, i. e. to prevent convection in the cavity 9a, 9b between the two panes 2a, 2b to a sufficient degree, even though there is no airtight separation between the separated parts of the cavity 9a, 9b.

Therefore, the wall member 8 is in a preferred embodiment of the invention provided with a large number of perforations. The perforations are preferably made as circular openings having a diameter of between 0.1 and 0.4 mm. Preferably, the total area of these holes amounts to less than 1% of the complete area of the strip.

Tests have shown on one hand that these perfor- ations cause an improvement of the sound-attenuating properties of the window, on the other hand that the geometry of the holes determine which frequencies are to be attenuated. Thus, other shapes than the circular holes may be taken into account if a particular sound- attenuation is desired at certain frequencies, i. e. another sound-attenuation than the one established by the circular holes.

Finally, it should be mentioned. that also the securing of the wall member 8 to the plane-parallel respective panes play a role in respect of sound-

attenuation, partly, the point of securing affect the mutual oscillations of the two plane-parallel panes, partly has the securing material, if suitably chosen, a damping effect on the oscillations of the plane- parallel panes.

In an insulating pane having a distance of 16 mm between the two panes 2a, 2b, the perforations cause according to the tests a sound-attenuation in the order of up to 1.5 dB RW and typically between 0.4-0.5 dB RW.