The present invention relates to a spacer for insulating glass units, especially but not only suitable for compensating climate stress in insulating glass units.

Background technology

Heating and cooling of an insulting glazing unit IGU may be caused by usual climate changes in winter and summer, the weather, the change of day and night, or air conditioning and heating. Heating and cooling or wind pressure may cause climate stress in form of significant pressure differences between the gas volume in an IGU and the outside atmosphere and corresponding bending or curvatures of the glazing panes of the IGU. This results in high stress on the edge bond of the IGU, which leads to escaping of internal gas or to penetration of water. Both significantly reduce the performance of the IGU. In case of climate loads, the secondary sealant needs to act as spring and damper. The stiffer the spacer is, the more the secondary sealant needs to compensate. Otherwise the stress on primary sealant is too high.

US 6,823,644 and US 2006/201105 Al disclose a spacer design for compensating climate stress at the spacer in an insulating glass unit (IGU), in which sections of the inner wall facing the interspace between glazing panes of the IGU, are separated and movable relative to each other. US 2007/0077376 Al also discloses such a spacer design as prior art and additionally spacer designs in which at least one lateral side wall adapted to face a glazing pane is separated from an adjacent separate side wall of a chamber for desiccant.

WO 2004/038155 Al discloses a spacer design with a curved wall design for compensating climate stress at the spacer in an insulating glass unit (IGU). WO 2014/063801 Al discloses a spacer design with a curved wall design.

WO 2004/05783 A2 discloses muntin bar designs for compensating climate stress at the muntin bars in an insulating glass unit (IGU).

EP 2 670 758 Al discloses in its Fig. 5 to 12 spacer designs for allowing relative movements of glazing panes towards and away from each other and movements parallel to each other. It is an object of the present invention to provide an improved spacer design for compensating climate stress in an insulating glass unit (IGU).

This object is achieved by a spacer for insulating glass units according to claim 1 or 3 or an

IGU according to claim 15 or a window or door or facade element according to claim 16.

Further developments are given in the dependent claims.

Further features and advantages will become apparent from the descriptions of embodiments referring to the drawings, which show:

Fig. 1 a cross-sectional view of a spacer according to according to a first embodiment perpendicular to its longitudinal direction;

Fig. 2 a cross-sectional view of a spacer according to according to a second embodiment perpendicular to its longitudinal direction;

Fig. 3 a cross-sectional view of a spacer according to according to a third embodiment perpendicular to its longitudinal direction;

Fig. 4 a cross-sectional view of the spacer according to according to the second

embodiment perpendicular to its longitudinal direction with indication of dimensions;

Fig. 5 a partial perspective cross-sectional view of an insulating glazing unit with a spacer;

Fig. 6 a side view, partially cut away, of a spacer frame bent from a spacer profile;

Fig. 7 a cross-sectional view of a conventional spacer perpendicular to its longitudinal direction;

Fig. 8 a partial cross-sectional view of an insulating glazing unit with the spacer of Fig. 7; Fig. 9 a partial cross-sectional view of an insulating glazing unit corresponding to Fig. 8 exemplifying the effect of increased gas pressure in the IGU;

Fig. 10 a partial cross-sectional view of an insulating glazing unit corresponding to Fig. 8 exemplifying the effect of reduced gas pressure in the IGU;

Fig. 11 a partial cross-sectional view of a spacer of the embodiment shown in Fig. 3

exemplifying the effect of increased gas pressure in an IGU to this spacer;

Fig. 12 a partial cross-sectional view of a spacer of the embodiment shown in Fig. 3

exemplifying the effect of reduced gas pressure in an IGU to this spacer; .

Fig. 13 a cross-sectional view of a spacer according to according to a fourth embodiment perpendicular to its longitudinal direction; and

Fig. 14 a partial cross-sectional view of an insulating glazing unit with the spacer of Fig. 13.

Fig. 5 shows a partial perspective view and Fig. 8 shows a cross-sectional view of an insulating glazing unit (IGU) 40 with a spacer 50. The IGU 40 comprises two glazing panes 51, 52 arranged parallel to each other with a predetermined distance between the same. A spacer 50 extends in a longitudinal direction z along the edges of the glazing panes 51, 52.

As shown in Fig. 6, the spacer 50 is used to form a spacer frame, e. g. by cold-bending the spacer profile into a frame shape and connecting the ends with a linear connector 54 as known in the art. Other ways to form a spacer frame like cutting linear pieces of spacer frame parts and connecting the same via comer connectors are also possible as known in the art.

The spacer (frame) 50 is mounted at the edges of the two spaced glazing panes 51, 52. As is shown in Fig. 5, 7 and 8, the spacer 50 comprises side walls formed as attachment bases to be adhered with the inner sides of the glazing panes 51, 52 using an adhesive material (primary sealing compound) 61, e.g., a butyl sealing compound based upon polyisobutylene. The intervening space 53 between the glazing panes is thus defined by the two glazing panes 51,

52 and the spacer profile 50. The inner side of the spacer profile 50 faces the intervening space 53 between the glazing panes 51, 52. On the (outer) side facing away from the intervening space 53 between the glazing panes in the height direction y, a mechanically stabilizing sealing material (secondary sealing compound) 62, for example based upon polysulfide, polyurethane or silicon, is introduced into the remaining, empty space between the inner sides of the window panes in order to fill the empty space. This sealing compound also protects a diffusion barrier layer 30 provided at least on the outer side of the spacer 50. It is also possible to use other possibilities than a gas diffusion barrier layer 30 to provide gas diffusion-proof characteristics like selecting corresponding gas diffusion-tight materials for the body of the spacer profile.

The interspace 53 between the glazing panes 51, 52 is usually filled with a gas having good heat insulating characteristics like a rare gas such as argon or xenon. Thus, a gas filled interspace 53 is present between the glazing panes 51, 52 and the spacer (frame) 50 in the mounted state.

As shown in Fig. 5, 7 and 8, the spacer 50 comprises a spacer profile body 10. The side walls 11, 12 of the spacer are formed as attachment bases for attachment to the inner sides of the glazing panes. In other words, the spacer is adhered to the respective inner sides of the glazing panes via these attachment bases and the primary sealing compound 61 (see Fig. 5, 8). In addition, the spacer 50 is adhered to the respective inner sides of the glazing panes via the secondary sealing compound 62 (see Fig. 5, 8).

A spacer 50 according to a first embodiment is shown in Fig. 1. Such a spacer 50 is designed and adapted to be mounted in an IGU 40 in the way shown in Fig. 5 or 8 instead of a spacer of the type shown in Fig. 5 or 7 or 8. The side of the spacer 50, which is the upper side in Fig. 1 and which is the non-diffusion proof side and thus designed to face the gas filled interspace 53 in the mounted state, is named the inner side of the spacer in the following.

The spacer extends with an essentially constant cross-section x-y in the longitudinal direction z with an overall height hl in the height direction y perpendicular to the longitudinal direction z. The side walls 11, 12 having a predetermined distance wl between their lateral outer sides in the width direction x in a state in which no external pressure force or external tensional force is applied to the side walls. The spacer 50 has a generally rectangular cross section perpendicular to the longitudinal direction z. As shown in Fig. 1, the spacer 50 comprises a spacer profile body 10. The spacer profile body 10 may be made by extrusion of polyamide 66 with 25 % glass fibre reinforcement (PA66 GF 25) or could also be made of polypropylene PP with or without fibre reinforcement or of any other suitable materials. The profile body 10 extends in the longitudinal direction z with the two lateral side walls 11, 12 and an inner wall 14 located on the inner side of the spacer and adapted to face the gas filled interspace 53 in the mounted state.

Seen in the cross-section x-y perpendicular to the longitudinal direction z, the two side walls 11, 12 are separated by a distance in the traverse (width) direction x and extend essentially in the height direction y towards the inner side of the spacer up to inner ends 1 le, l2e. The side walls 11, 12 are adapted to face the glazing panes 51, 52 in the width direction x

perpendicular to the longitudinal direction z and to the height direction y. The side walls 11,

12 are directly connected with and by the inner wall 14 on the inner side of the spacer.

A one-piece diffusion barrier film 30 is formed on the outer side of the spacer which faces away from the gas filled interspace 53 (from the inner side of the spacer) and on the side walls 11, 12. The diffusion barrier film 30 may be formed partly in the side walls and/or only on part of the side walls or only on the outer side of the spacer. The diffusion barrier film 30 may be made of metal like stainless steel or of another diffusion proof material like diffusion-proof multilayer foils. The diffusion barrier film 30 may optionally be designed to also serve as a reinforcement element. Fig. 1 shows wires 31 in the comer portions on the inner side as other optional reinforcement elements.

An outer wall 13 may optionally be formed on the outer side of the spacer, as shown in Fig. 1. In such a case, the diffusion barrier film 30 is formed on the outer wall 13 as shown in Fig. 1. The outer wall 13 and the side walls 11, 12 may either be directly connected with and by the outer wall 13 or by interposed slant (oblique) wall sections, which may optionally be concave or convex in addition, as shown on Fig. 1 to 4 and 7 to 14.

A chamber 20 is formed for accommodating hygroscopic (desiccating) material. The chamber 20 is defined in cross-sectional view perpendicular to the longitudinal direction z by on its respective lateral sides the side walls 11, 12 and on its side facing the interspace 53 by the inner wall 14. Openings 15 are formed in the inner wall 14 (not shown in Fig. 1 but see Fig.

5), so that the inner wall 14 is formed to be non-diffusion-proof allowing gas exchange between the gas filled interspace 53 and the chamber 20. In addition or in the alternative, to achieve a non-diffusion-proof design, it is also possible to select the material for the entire profile body and/or the inner wall, such that the material permits an equivalent diffusion without the formation of the openings 15.

The inner wall 14 comprises a recess portion l4rs having a depth dr in the height direction y and a width w2 in the width direction x allowing to change the length of the inner wall 14 in the width direction in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress.

The recess portion l4rs has, seen in the cross-section x-y perpendicular to the longitudinal direction z, a rectangular shape with three side portions l4sl, l4sh, l4sr formed by the inner wall 14 and an open side facing the gas filled interspace 53 in the mounted state.

The recess portion l4rs has a depth dr in the height direction y in a range of 1.5 mm to 2 mm, such as 1, 5 mm or 1.75 mm or 2 mm, and a width w2 in the width direction x in a range of 2.5 mm to 4 mm, such as 2.5 mm or 3 mm or 3.5 mm or 4 mm. These values are especially suitable for spacers with a width wl of 10 to 20 mm and a height hl of 6 to 8 mm. In general, the depth dr of the (rectangular cross section) recess portion l4rs can be up to 50% of overall height hl of spacer profile and the width w2 can reach up to 50% of overall width wl of spacer profile.

The recess portion l4rs is centered in the inner wall 14 in the width direction x. It is also possible that the recess portion l4rs has an off-center position, especially if the applied forces may be not symmetrical. However, the centered position is preferred.

The recess portion l4rs of the inner wall 14 has a wall thickness which is in a range 20% to 80% of the wall thickness of the other parts of the inner wall 14. The wall thickness of the inner wall is, e.g. 0.5 mm and the thickness of the recess portion is 0.3 mm, i.e., 60%.

The transitions of the side portions l4sl, l4sh, l4sr and the other portions of the inner wall 14 are preferably rounded as shown in Fig. 1. The depth dr of the recess portion l4rs in the height direction y is measured relative to a straight imaginary line connecting the ends of the connections between the inner wall 14 and the side walls 11, 12 in the height direction y. This imaginary line is not completely shown in Fig. 1 but the end of the imaginary line is shown as hatched line in Fig. 1 at the upper end of the arrow for measure dr.

The spacer is configured such that its outer side formed by either a diffusion barrier 30 or an outer wall 13 or a combination of a diffusion barrier and at least a section of an outer wall maintains its length in the width direction x in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress.

In other words, the elements forming the outer side do not allow to change the length of the outer side in the width direction x in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress. If the diffusion barrier 30 is designed to provide this characteristic of keeping the length in width direction x constant, this can be achieved by using a material like metal or a multilayer foil of sufficient thickness providing the necessary strength to the outer side of the spacer. In case of stainless steel, the minimum thickness is about 0.06 mm. Also the shape of metal films or foils can help to keep the length in width direction x constant. The metal film or foil can, for example, have corrugations or undulations in width direction x (perpendicular to longitudinal direction) to increase resistance and strength of the metal film/foil in this direction. If the outer wall 13 is designed to provide this characteristic of keeping the length in width direction x constant, this can be achieved by a corresponding thickness and/or by reinforcements like glass fibres or other fibres. Combinations of the above measures are also possible such as, e.g., metal film sections at the outer side corner portions and a corresponding multilayer foil inbetween the metal film sections on the outer side, or a foamed outer wall with glass fibre reinforcement of 30 to 40% while the inner wall is not foamed and comprises no glass fibre reinforcement combined with a multilayer foil on the outer side, etc. In Fig. 1, a combination of a metal diffusion barrier 30 with a sufficient thickness to maintain the length in the width direction x on the outer side and of an outer wall 13 is shown as an example.

A spacer 50 according to a second embodiment is shown in Fig. 2 and 4. In Fig. 4, dimensions for a specific size of a spacer for a 16 mm nominal width of the interspace between the panes of an IGU are indicated. The spacer 50 of the second embodiment differs from the spacer 50 of the first embodiment essentially in that it comprises a recess portion l4rt instead of the recess portion l4rs.

The recess portion l4rt has, seen in the cross-section x-y perpendicular to the longitudinal direction z, a triangular shape with two side portions l4tl, l4tr and an apex l4ta between the same formed by the inner wall 14 and an open side facing the gas filled interspace 53 in the mounted state. The remaining design and features are the same as in the first embodiment unless described differently in the following.

The inner wall 14 comprises the recess portion l4rt having a depth dr in the height direction y and a width w2 in the width direction x allowing to change the length of the inner wall 14 in the width direction in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress.

The recess portion l4rt has, seen in the cross-section x-y perpendicular to the longitudinal direction z, the above described triangular shape.

The recess portion l4rt has a depth dr in the height direction y in a range of 1.5 mm to 2.5 mm, such as 1, 5 mm or 1.75 mm or 2 mm or 2.25 mm or 2.5 mm, and a width w2 in the width direction x in a range of 3.5 mm to 5 mm, such as 3.5 mm or 4 mm or 4.5 mm or 5 mm. These values are especially suitable for spacers with a width wl of 10 to 20 mm and a height hl of 6 to 8 mm. In general, the depth dr of the (triangular cross section) recess portion l4rt can reach up to 50% of overall height hl of spacer profile and the width w2 can be up to 60% of overall width wl of spacer profile.

The recess portion l4rt of the inner wall 14 has a wall thickness which is in a range 20% to 80% of the wall thickness of the other parts of the inner wall 14. The wall thickness of the inner wall is, e.g. 0.5 mm and the thickness of the recess portion is 0.3 mm, i.e., 60%.

The transitions of the side portions l4tl, l4tr and an apex l4ta and the other portions of the inner wall 14 are preferably rounded as shown in Fig. 2 and 4.

The depth dr of the recess portion l4rt in the height direction y is measured relative to a straight imaginary line connecting the ends of the connections between the inner wall 14 and the side walls 11, 12 in the height direction y. This imaginary line is not completely shown in Fig. 2 but the end of the imaginary line is shown as hatched line in Fig. 2 at the upper end of the arrow for measure dr.

A spacer 50 according to a third embodiment is shown in Fig. 3. The spacer 50 of the third embodiment differs from the spacer 50 of the first embodiment essentially in that it comprises a recess portion l4rc instead of the recess portion l4rs.

The recess portion l4rc has, seen in the cross-section x-y perpendicular to the longitudinal direction z, a curved shape with curved portions l4cl, l4cr and a thin portion l4ct formed by the inner wall 14 and a convex curvature facing away from the gas filled interspace 53 in the mounted state. The curvature could also be described as concave seen from the chamber 20. The remaining design and features are the same as in the first embodiment unless described differently in the following.

The inner wall 14 comprises the recess portion l4rc having a depth dr in the height direction y and a width w2 in the width direction x allowing to change the length of the inner wall 14 in the width direction in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress.

The recess portion l4rt has, seen in the cross-section x-y perpendicular to the longitudinal direction z, the above described curved shape.

The recess portion l4rc has a depth dr in the height direction y in a range of 1.5 mm to 2.5 mm, such as 1, 5 mm or 1.75 mm or 2 mm or 2.25 mm or 2.5 mm, and a width w2 in the width direction x in a range of 4 mm to 9 mm, such as 4 mm or 5 mm or 6 mm or 7 mm or 8 mm or 9 mm. These values are especially suitable for spacers with a width wl of 10 to 20 mm and a height hl of 6 to 8 mm. In general, the depth dr of the (curved cross section) recess portion l4rc can be up to 50% of overall height hl of spacer profile and the width w2 can reach up to 80% of overall width wl of spacer profile.

The recess portion l4rc of the inner wall 14 has a minimum wall thickness dt which is in a range 20% to 80% of the wall thickness of the other parts of the inner wall 14. The wall thickness diw of the inner wall is, e.g. 0.8 mm and the thickness of the recess portion is 0.4 mm, i.e., 50%.

The depth dr of the recess portion l4rc in the height direction y is measured relative to a straight imaginary line connecting the ends of the connections between the inner wall 14 and the side walls 11, 12 in the height direction y. This imaginary line is not completely shown in Fig. 3 but the end of the imaginary line is shown as hatched line in Fig. 3 at the upper end of the arrow for measure dr.

The IGU of Fig. 5 or 8 is subject to heating and cooling due to external conditions. If the IGU is heated, the gas in the interspace 53 is heated and, because the interspace is hermetically sealed, the gas pressure in the interspace 53 increases in comparison to the (atmospheric) pressure outside the IGU. The result are pressure forces acting on the glazing panes and bending the same to convex shapes as shown in Fig. 9. If the IGU is cooled, the opposite effect occurs. The gas in the interspace 53 is cooled and, because the interspace is

hermetically sealed, the gas pressure in the interspace 53 decreases in comparison to the (atmospheric) pressure outside the IGU. The result are pressure forces acting on the glazing panes and bending the same to concave shapes as shown in Fig. 10.

As a result of heating the IGU, tensile stress forces FTS act on the primary sealing 61 in the region at the inner ends 1 le, l2e of the lateral side walls 11, 12 of the spacer 50 located at the inner side facing the interspace 53 as shown in Fig. 9. These tensile stress forces FTS may cause a separation of the primary sealing from the glazing pane and/or the spacer and thus damage the sealing effect, which is detrimental to the long term life if IGUs due to cycling behaviour. The pressure forces Fp acting on the spacer at the remote ends 1 lf, l2f of the side walls 11, 12 of the spacer remote to the interspace 53 and on the secondary sealing are not so problematic although they cause stress (compression) to primary and secondary sealing materials.

As a result of cooling the IGU, tensile stress forces FTS act on the primary sealing 61 in the region at the remote ends 1 lf, l2f of the side walls 11, 12 of the spacer remote to the interspace 53 and on the secondary sealing as shown in Fig. 10. These tensile stress forces FTS may cause a separation of the primary and/or secondary sealings from the glazing pane and/or the spacer and thus damage the sealing effect, which is detrimental to the long term life if IGUs due to cycling behaviour. The pressure forces Fp acting on the spacer in the region at the inner ends 1 le, l2e of the lateral side walls 11, 12 of the spacer 50 located at the inner side facing the interspace 53 are not so problematic although they cause stress (compression) to primary and secondary sealing materials.

The effects of heating and cooling an IGU may be caused by usual climate changes in winter and summer, the weather, the change of day and night, or air condition and heating.

Therefore, the effects occur alternating and threaten the intended lifetime of IGUs.

The recess portion l4rs of the first embodiment allows the inner ends 1 le, l2e of the side walls 11, 12 to move away from each other in reaction to tensile stress forces FTS shown in Fig. 9. The recess portion l4rs also allows the inner ends 1 le, l2e of the side walls 11, 12 to move towards each other in reaction to pressure forces Fp shown in Fig. 10. The reason is that the recess portion allows a change of the length of the inner wall 14 in the width direction in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress. The recess portion l4rs has three side portions l4sl, l4sh, l4sr, which can change their relative angles and the relative angles to the other portions of the inner wall 14 under tension or pressure. By change of the relative angles, the length of the inner wall 14 inevitably varies in the width direction x.

In other words, the recess portion l4rs allows to change the distance between the lateral outer sides of the side walls 11, 12 at the inner ends 1 le, l2e from the predetermined distance wl in a state in which an external pressure force or an external tensional force is applied to the side walls. The distance between the lateral outer sides of the side walls 11, 12 at the remote ends 1 lf, l2f is not changed from the predetermined distance wl in a state in which an external pressure force or an external tensional force is applied to the side walls. With dimensions of the recess portion l4rs of dr = 1.5 mm and w2 = 2.5 mm for a spacer with a width wl = 16 mm and a height hl = 7 mm, a change of the width at the corresponding inner ends 1 le, l2e in a range up to 0.7 mm is achievable.

Thus, an improved spacer for IGUs is provided with superior climate stress compensation characteristics. Such improved spacer is flexible enough by its design to reduce the stress on the primary and also the secondary sealing material such that gas loss is reduced and the overall lifetime of the IGU can be extended. Additionally, less amount of secondary sealing material can be used thus improving the thermal performance of the IGU.

The same applies to the recess portion l4rt of the second embodiment, which is the presently preferred embodiment. In the second embodiment, the relative angles can change in a similar way in response to an external pressure force or external tensional force applied to the side walls 11, 12 as it occurs in case of climate stress.

Essentially the same also applies to the third embodiment. Due to the curved design of the recess portion l4rc, the length change of the inner wall 14 is obtained by straightening the curvature or increasing the curvature.

The above described effects are shown for the third embodiment in Fig. 11 and 12, as described below.

Fig. 11 shows a partial cross-sectional view of the spacer of the third embodiment shown in Fig. 3 exemplifying the effect of increased gas pressure in an IGU (see Fig. 9) to this spacer, and Fig. 12 shows a partial cross-sectional view of the spacer of the embodiment shown in Fig. 3 exemplifying the effect of reduced gas pressure in an IGU (see Fig. 10) to this spacer. The reference signs and the corresponding parts and meanings are the same except if differences are explained below.

As a result of increased gas pressure in the IGU, tensile stress forces FTS act on the primary sealing 61 in the region at the inner ends 1 le, l2e of the lateral side walls 11, 12 of the spacer 50 located at the inner side facing the interspace 53 as shown in Fig. 9 and 11. Different from the conventional design shown in Fig. 9, the recess portion l4rc of the third embodiment allows the inner ends 1 le, l2e of the side walls 11, 12 to move away from each other in reaction to tensile stress forces FTS as shown in Fig. 11.

This movement is enabled/allowed by the design of the inner wall 14 with the (in this embodiment curved and concave) recess portion l4rc and the reduced wall thickness dt of the inner wall section forming the recess portion. As illustrated in Fig. 11, the inner ends 1 le, l2e of the side walls 11, 12 can move away from each other by a distance of 2Aw l (indicated as Awli on the left side and as Awl _r on the right side in Fig. 11) thus increasing the length of the inner wall 14 in the width direction x. The distances Aw l , are a result of straightening the curved recess portion l4rc under the tensile stress caused by the tensile stress forces F _TS increasing the length of the curved recess portion l4rc in the width direction x by a distance of 2Aw2 (indicated as Aw2i on the left side and as Aw2 _r on the right side in Fig. 11). The depth dr of the recess portion l4rc in height direction y is reduced by Adr.

The shape of the recess portion l4rc without the acting forces is shown as hatched lines in Fig. 11. If the forces do not act anymore, usually because the temperatures changed and the increased pressure does not act anymore, the recess portion returns to this“force-free” state.

In other words, the recess portion l4rc is configured as an elastically deformable portion enabling/allowing the change of length of the inner wall 14.

On the other hand, the remote ends 1 lf, l2f of the side walls 11, 12 do not move in reaction to the reaction to the pressure forces Fp shown in Fig. 9. In other words, due to the non-elastic configuration of the outer side of the spacer, in this case the barrier film 30 and the outer wall 13, the width wl remains unchanged on the outer side of the spacer.

As a consequence, the danger that the tensile stress forces F _TS could cause a separation of the primary sealing 61 from the glazing pane and/or the spacer at the inner ends is overcome or at least significantly reduced, different from the case shown in Fig. 9, because the movement of the inner ends due to the increased length of the inner wall 14 relieves this stress and thus prevents a damage of the sealing effect.

As a result of reduced gas pressure in the IGU, pressure forces Fp act on the spacer in the region at the inner ends 1 le, l2e of the lateral side walls 11, 12 of the spacer 50 located at the inner side facing the interspace 53 as shown in Fig. 10 and 12, while tensile stress forces F _TS act on the primary sealing 61 in the region at the remote ends 1 lf, l2f of the side walls 11, 12 of the conventional spacer remote to the interspace 53 and on the secondary sealing as shown in Fig. 10.

The recess portion l4rc of the third embodiment allows the inner ends 1 le, l2e of the side walls 11, 12 to move towards each other in reaction to pressure forces Fp as shown in Fig. 12. This is enabled/allowed by the design of the inner wall 14 with the (in this case curved and concave) recess l4rc and the reduced wall thickness dt of the inner wall section forming the the recess. As illustrated in Fig. 12, the inner ends 1 le, l2e of the side walls 11, 12 can move towards each other by a distance of 2Awl (indicated as Awli on the left side and as Aw l , on the right side in Fig. 12) thus reducing the length of the inner wall 14 in the width direction x. The distances Awli are a result of increasing the curvature of the curved recess portion under the pressure caused by the pressure forces Fp reducing the length of the curved recess portion l4rc by a distance of 2Aw2 (indicated as Aw2i on the left side and as Aw2 _r on the right side in Fig. 12). The depth dr of the recess portion l4rc in height direction y is increased by Adr.

The shape of the recess portion l4rc without the acting forces is shown as hatched lines in Fig. 12. If the forces do not act anymore, usually because the temperatures changed and the reduced pressure does not act anymore, the recess portion returns to this“force-free” state. In other words, the recess portion l4rc is configured as an elastically deformable portion enabling/allowing the change of length of the inner wall 14.

As a result, there will be no or significantly reduced (in comparison to the conventional spacer of Fig. 10) tensile stress forces FTS acting on the remote ends 1 lf, l2f of the side walls 11, 12, which cannot and do not move in reaction to the reaction to tensile forces FTS shown in Fig.

10. Due to the non-elastic configuration of the outer side of the spacer, in this case the barrier film 30 and the outer wall 13, the width wl remains unchanged on the outer side of the spacer also in this case. However, due to the elastic behaviour of the inner wall, no significant stress is exerted on the remote ends 1 lf, l2f of the side walls 11, 12.

As a result, the danger that the tensile stress forces FTS could cause a separation of the primary sealing 61 from the glazing pane and/or the spacer at the remote ends is overcome or at least significantly reduced, different from the case shown in Fig. 10, because the movement of the inner ends due to the reduced length of the inner wall 14 relieves this stress and thus prevents a damage of the sealing effect.

Essentially the same also applies to the other embodiments. Due to the design of the recess portions, an elastic deformation to increase or reduce the length of the inner wall 14 is enabled/allowed. In the spacer according to the present teachings, the recess portion l4rs, l4rt, l4rc is adapted to change the length of the inner wall 14 by elastic deformation of the recess portion l4rs, l4rt, l4rc. The primary sealing 61 can be further protected by means of a special design of the inner wall 14 and the side walls 11, 12 of the spacer 50. Said design is described and shown in WO 2014/063801 Al on pages 7, 8, and 17 as step-like transition or step with a width h3 and in Fig. 1 (corresponding to paragraphs [0035] and [0089] and Fig. 1 of EP 2 780 528 Bl), which corresponding disclosure is herein incorporated by reference. Fig. 13 and 14 show an application of this special design with a step-like transition or step or protrusion in the width direction x to the present teachings exemplified by the second embodiment. Of course, the design can be applied to all embodiments. A corresponding step is also shown in DE 20 2016 008 421 Ul.

Spacer 50 of the fourth embodiment shown in Fig. 13 and 14 differs from the spacer of the second embodiment shown in Fig. 2 in that the spacer comprises a transition between the inner wall 14 and the side walls 11, 12 at the lateral outer sides in form of projections (or extensions or shoulders) 1 lp, 12r in the width direction x which create a step-like transition. The width wp of each projection 1 lp, 12r corresponds to the width of primary sealing 61 in the assembled state of the IGU as shown in Fig. 14. The width wp is preferably in a range from 0.01 mm to 1 mm, more preferably between 0.05 mm and 0.5 mm, more preferably between 0.1 mm and 0.4 mm, e.g., 0.2 mm or 0.25 mm or 0.3 mm or 0.35mm. The width wp of one protrusion is preferably selected to correspond to the width of the primary sealing 61 on one lateral side in the width direction x. Therefore, the total width wl of the spacer 50 measured between outermost lateral side surfaces of the projections 1 lp, 12r in the assembled state of the IGU in a state in which no pressure forces Fp or tensile stress forces FTS forces due to climate conditions are present, corresponds to distance (nominal width) between the window panes 51, 52.

Such a step-like transition/protrusion 1 lp, 12r creates a cavity between the corresponding adjacent glass pane 51, 52 and the corresponding side wall 11, 12 of spacer in which the primary sealing 61 is accommodated. The projections 1 lp, 12r are intended to contact the glass panes 51, 52 and to transmit the pressure forces Fp or tensile stress forces FTS to the spacer without stressing the primary sealing or at least significantly reducing the stress.

Without such step-like transitions/projections, the primary sealing 61 is an intermediate layer between the glass panes and the side walls of spacer 50 and acts as a force transmitting layer with potentially detrimental consequences on its integrity and durability as sealing agent.

With the provision of such protrusions 1 lp, 12r, the primary sealing 61 is relieved of the duty to transmit these forces and can better fulfill its primary function, i.e. to be a sealing layer between the glass panes and the side walls of the spacer.

Additionally, the shoulders prevent the primary sealing 61 from being squeezed out and moving into the interspace 53 (both during IGU manufacturing process and also during lifetime of IGU due to the above described climate effects), which is undesired and aesthetically not pleasant.

The spacer of present teachings having a recess portion in the inner wall, should in principle be as flexible as or more flexible than the primary sealing due to the provision of the recess in the inner wall, in order not to stress the primary sealing. To enhance the effects, the above described special design of the projections (step-like transitions) relieves the primary sealing because protrusions directly take the force exerted by the glass panes that would otherwise have to be taken by the primary sealing, at least partially.

Another means to make the spacer of the present teachings as flexible as or more flexible than the primary sealing is to provide a foamed inner wall 14 in addition to the recess in the inner wall.

Alternatively, although not covered by the present claims, it is possible to provide a spacer with a foamed inner wall 14 and with a recess having a depth dr in the height direction y of less than 1.5 mm and with the remaining features described above for the different embodiments.

For all embodiments, the dimensions and shapes of the recesses have been described as especially suitable for spacers with a width wl in a range from 10 mm to 20 mm and a height hl in a range from 6 mm to 8 mm. However, the teachings are also applicable to spacers with a width wl up to 32 mm or up to 40 mm and/or with a width wl down to 8 mm and with a height hl up to 10 mm. Aspects of the teachings

Aspect 1 : Spacer for an insulating glazing unit (40), which insulating glazing unit has at least two spaced glazing panes (51, 52) connected at their edges via the spacer (50) in a mounted state in which the spacer is mounted at the edges to limit an interspace (53) filled with gas, the spacer extending with an essentially constant cross-section (x-y) in a

longitudinal direction (z), the spacer comprising

a plastic body (10) extending in the longitudinal direction (z) with two lateral side walls (11, 12) and an inner wall (14) located on an inner side of the spacer adapted to face the gas filled interspace (53) in the mounted state, in which

the side walls are adapted to face the glazing panes in a width direction (x) perpendicular to the longitudinal direction (z),

the side walls (11, 12) extend, in the cross section (x-y), in a height direction (y)

perpendicular to the longitudinal direction (z) and the width direction (x) towards the inner side up to inner ends (1 le, l2e),

the side walls have a predetermined distance (wl) between their lateral outer sides at the inner ends in a state in which no external pressure force or external tensional force is applied to the side walls,

the inner wall (14) connects the side walls on the inner side of the spacer,

the inner wall (14) comprises a recess portion (l4rs, l4rt, l4rc) having a depth (dr) in the height direction (y) of at least 1.5 mm and a width (w2) in the width direction (x) of at least 2.5 mm allowing to change the length of the inner wall in the width direction in response to an external pressure force or external tensional force applied to the side walls (11, 12) in the width direction (x).

Aspect 2: Spacer according to aspect 1, wherein

the recess portion (l4rs) has, in the cross section (x-y), a rectangular shape with three side portions (l4sl, l4sh, l4sr) formed by the inner wall (14) and an open side facing the gas filled interspace (53) in the mounted state.

Aspect 3 : Spacer according to aspect 1, wherein

the recess portion (l4rt) has, in the cross section (x-y), a triangular shape with two side portions ( 14tl, l4tr) and an apex (l4ta) between the same formed by the inner wall (14) and an open side facing the gas filled interspace (53) in the mounted state. Aspect 4: Spacer according to aspect 1, wherein

the recess portion (l4rc) has, in the cross section (x-y), a curved shape with curved portions (l4cl, l4ct) and a thin portion (l4cr) formed by the inner wall (14) and a concave curvature facing away from the gas filled interspace (53) in the mounted state.

Aspect 5 : Spacer according to any one of the preceding aspects, wherein

the recess portion (l4rs, l4rt, l4rc) of the inner wall (14) has a wall thickness (dt) which is in a range 20% to 80% of the wall thickness (diw) of the other parts of the inner wall (14).

It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.