FIELD OF THE INVENTION

The present invention relates to the field of operable windows, generally for buildings.

STATE OF THE ART

Nowadays operable windows are designed as an assembly of three elements, a glass, a mobile frame supporting the glass, called together sash, and a fixed frame fixed to a building structure. These elements have to satisfy structural requirements, like supporting glass weight and wind loads by the mobile and fixed frames and to transfer them to the building structure. To achieve this result, depending on the magnitude of the cited loads, it is common practice to use frames with big transverse sections which need to be clearly even bigger when the window pane has large dimensions and in this manner entails higher wind loads and own weight.

On another side, there is a demand of the market to reduce dimensions of frame cross section at the minimum. In fact, to meet architectural standards and obtain a good looking product, that is to say elegant and discrete, the best solution is to make the thinnest possible frame to reduce its visual impact. Furthermore, in order to guarantee a proper thermal insulation, the windows should also be designed to reduce thermal bridges, i.e. the places where a large quantity of heat transmission occurs. In this respect the most disadvantageous part of the window structure is the frame which, especially when made of metal, has a higher conductivity index than the glass and thus, to reduce thermal transmission, the glass to frame surface ratio should be maximized as much as possible.

Another important factor contributing to the difficulty of solving this problem is the fact that glasses have no standardized measures not only as far as length and width of the glass pane are considered, as readily understandable, but also with regard to glass pane thickness, so there is a need for a window with a new frame that fits easily glass panes of different dimensions without need to proportionally increase its cross sectional dimensions, while reaching performance levels enabling to withstand wind loads beyond 2000 Pascal with a relatively low number of components and with maximum sizes of approx. 1 ,5 by 1 ,8 m, and naturally meeting all thermal and acoustic regulations of modern legislations.

SUMMARY OF THE INVENTION

It is therefore the main purpose of the invention to create a new operable window that meets high aesthetic standards, while ensuring optimal thermal insulation and low production cost. These and other aims are achieved by means of a window frame which, according to claim 1 , comprises a primary frame, adapted to be fixed to a building structure, a secondary frame fixed to the primary frame by ironmongery allowing opening and closing movements of the secondary frame in respect of the primary frame, wherein a plane of the window frame is defined when the secondary frame is closed, wherein the primary frame comprises at least four primary profiles, each of the at least four primary profiles comprising a primary first profiled bar having a primary parallel side having a first height w1 when measured parallely to the plane of the window frame and of the glass pane, and a primary orthogonal side, a primary second profiled bar fixed transversely to the primary first profiled bar on an outermost perimeter of the window frame and wherein the secondary frame comprises at least four secondary profiles, each of the at least four secondary profiles comprising a secondary first profiled bar having a secondary parallel side, having a second height w2 when measured parallely to the plane of the window frame, a secondary orthogonal side, a secondary second profiled bar solidarily fixed to the secondary first profiled bar transversely and oriented toward the secondary side and adapted to support a side of a glass pane parallely to the plane of the window frame and wherein the secondary second profile has a longitudinal slot where one or more retainers adapted to fix the glass pane are held, wherein the first w1 and second w2 height have substantially the same magnitude, so that the secondary first profiled bar has a distal edge laying at an outermost perimeter of the window frame, and wherein only the secondary parallel side of the secondary first profiled bar constitutes the front side of the window frame when mounted on a building.

According to another aspect of the present invention those aims are achieved by means of a window comprising a window frame having the above features. According to a further aspect of the present invention those aims are achieved by means of a kit comprising the window frame with the above features wherein one or more primary second profiled bars are of different dimensions and/or one or more secondary second profiles are of different dimensions and/or one or more retainers are of different dimensions.

Thanks to the features of the invention, in case of a variation in the thickness of the glass pane, for example, it is sufficient to replace the primary second ( composite) profiled bar by a longer primary second (composite ) profiled bar, the secondary second (composite) profiled bar by a longer secondary second

( composite) profiled bar, the primary first (aluminum) profiled bar by a longer primary first (aluminum) profiled bar as well as the composite clip to retain the glass by a longer composite clip, and this allows to select a different thickness of the window frame for different thicknesses of glass, at the same time keeping all other components of the window frame the same. This is achieved by means of kits comprising few different profiles and of different dimensions, as it is shown in the figures and description, making it possible to install a wide range of glasses of different thicknesses whilst the internal and external appearance of the window frame remains the same. So it’s readily apparent that the window frame according to the invention is made by few components which can be assembled easily and therefore it makes less costly to produce windows. Another advantage of the window of the invention is definitely an increased thermal insulation. In fact, according to the fact that the glass thermal conductivity index is lower than the thermal conductivity of aluminum or of other metals, the window has a superior global insulating capacity, because the frame dimensions, which are mainly of aluminum, are reduced at a minimum, which is achieved thanks to the slender frame, when observed in a front view. This feature gives also the impression to look“through” a window instead of looking“at” a window, because the glass area of the window is maximized and has no interruptions, while the frame surface is minimized and without any disturbance caused by visual joints, hairlines, groves, steps or the like and keeps the same width“w” for all window frame thicknesses. On another side, as the frame is not made only of aluminum components, but the core of the frame is made of composite material with lower heat conductivity index, which are not visible when the sash is closed, the window of the invention provides a good-looking window with a maximum of thermal insulation capacity.

All these advantages are achieved in a window frame with a visual outer frame surface dimension at both sides of the frame preferably between 60 and 62 mm and a distance from the outer frame surface to the glass surface of preferably

20mm on both sides of the window pane.

Furthermore, the window of the invention is so flexible that it can accommodate glass panes thicknesses from 24 to 62 mm. This very broad variation of the thickness of the window frame is achieved while keeping on both sides of the window the maximum dimensions of 64mm and 24mm as mentioned before.

Within these ranges of dimensions, the window of the invention is capable to withstand wind loads beyond 2000 Pascal with maximum sizes of approximately 1 ,5 by 1 ,8 m and meeting all thermal and acoustic regulations.

Not least important is that these performances are achieved by utilising a relatively low number of components.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of this invention will become apparent from the following detailed description of preferred embodiments thereof, with reference to the accompanying figures, where:

Fig. 1 shows a front view of a window according to the invention in the closed position,

Fig. 1a shows a section of the sash of the window of fig. 1 along a vertical plane,

Fig. 1 b shows a scheme of the way of opening of the sash by means of a turn and tilt system, and provisions to support the load of the glass to the sash of the window of fig. 1 ,

Fig. 2 shows a sectional view of the fixed frame on a plane A-A transversal to the plane of the window of fig. 1 ,

Fig. 3 shows a sectional view of the sash on a plane A-A transversal to the plane of the window of fig. 1 ,

Fig. 4 shows a sectional view of the window frame on a plane A-A transversal to the plane of the window of fig. 1 , with sash frame in closed position;

Figures 5, 6 and 7 show three stages of the glass disassem bling operation from the sash frame;

Figures 8a to 8c show secondary components of different dimensions of the sash frame of the window of the invention;

Figures 9a and 9b show components of different dimensions for retaining the glass in the sash frame of the window of the invention;

Figure 10 shows the assessment of the self-weight of the sash including glass and the vertical load from operating the sash;

Figures 11 a to 11 d show corner cleats of the sash of the window frame of the invention;

Figures 12a to 12c show other corner cleats of the fixed frame of the window frame of the invention;

Figures 13a to 13c show secondary components of the fixed frame of the window of the invention; Figures 14a to 14f show a sectional view of the window frame of the invention on a plane A-A of figure 1 transversal to the plane of the window frame, with the sash in position closed and in various embodiments with a glass pane of various thicknesses;

Figure 15a to 15b show primary components of the window of the invention;

Figure 16 shows the assessment of the sash due to wind loads;

Figure 17 shows the insertion of corner cleats of the window sash;

Figure 18 shows a scheme of the structural concept of accommodating the weight of the glass by the sash frame corners;

Figure 19 shows the principle of location of locking and hinge points to transfer dead, vertical and wind-loads to the structure;

Figure 20 shows the maximum sizes and associated number of locking/load transfer points taken into account for the window design;

Figures 21a and 21b show the fixing-bracket to the building structure at corner/hinge positions;

Figures 22a and 22b show the fixing/bracket to the building structure at intermediate wind-load interlock positions; Figure 23 shows the fixing/bracket to the building structure connected with the corner hinge of the ironmongery. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be better understood by reading hereafter the description of preferred embodiments of the window according to the invention.

With reference to the figures, a window frame indicated globally with reference numeral 100 comprises a fixed frame 1 , a sash frame 2 with a glass pane 3. Depending on the loads, there are also provided several brackets to fix the fixed frame 1 to the building structure and in this configuration there are shown some brackets 101 to 112. It is clear to a skilled person that any number of brackets type 102, 104, 108, 111 appropriate to the structure of the window and dependent from wind load can be inserted on the fixed frame 1. The glass pane 3, in order to meet market or legislative standards on thermal or acoustic insulation performance, can be made with a multi-layered glass with internal chamber(s) or even opaque panels. Hereafter, to ease understanding of the invention embodiments, all components which are a part of the fixed frame 1 are defined conventionally with the affix“primary”, while those which are a part of the sash frame 2 are defined specifically with the affix“secondary”. The fixed frame 1 , has basically a rectangular or square shape, although other shapes are possible, without going out of the scope of the invention, and comprises four primary profiles 21 , 22, 23, 24 which define the window’s perimeter. Like the fixed frame 1 , also the sash frame 2 is made of four secondary straight profiles 31 , 32, 33, 34, arranged in a rectangular or square shape too. Fixed frame 1 and sash frame 2 are configured to match the primary profiles with their corresponding secondary profiles, thus 21 with 31 , 22 with 32, 23 with 33, 24 with 34. The shape of the section of the sash frame 2 holds the glass pane 3 in position in the centre of the window frame 100. As all four primary profiles 21 , 22, 23, 24 have the same transversal section shape, we refer only to the section of the primary profile 21 to describe its structure. The primary profile 21 comprises a primary first profiled bar 4, made preferably of aluminum or of another metal or alloy, a primary second profiled bar 5 made of composite material, with low thermal conductivity, e.g. polyamide and primary gaskets 6, 7. The primary first profiled bar 4 has a substantially C-shaped section with a longer side parallel to the window plane and three aluminum flanges 10, 11 and 12. The flange 10, which is orthogonal to the plane of the window frame comprises the open channel 25 located at the end of the profile proximal to the center of the window frame 100 and directed transversely to the profiled bar towards the internal side I of the window frame. In this description the primary fixed profile is supposed to be on the external side E of the building in which the window is installed and therefore the sash is opening towards the internal side I of the building. It is possible to reverse the external and the internal side of the window in order to apply the window with an outward opening sash, whilst keeping all profiled bars and components the same, except using the appropriate ironmongery. Advantageously , this is achieved thanks to the selection of appropriate length d2 of the flange 10 as explained below.

Two flanges 11 , 12, are located at the distal end of the primary profile 21. These two flanges are straight and parallel and directed substantially transversely to the primary first profiled bar 4. They are provided with two ribbed surfaces 13, 14. The flange 11 is empty and defines a hollow cavity. The primary first profiled bar 4 has also a flange 9 which, with the flange 10, defines the longitudinal channel. The primary second profiled bar 5 is a profile with 2 hollow cavities with, at one side, two primary composite flanges 15, 16 which are parallel and each one has its own composite ribbed surface, respectively 17, 18. The primary second profiled bar 5 and the primary first profiled bar 4 are jointed by coupling the ribbed surfaces, surface 13 with surface 17 and surface 14 with surface 18. By mutually sliding these surfaces one onto the other, the primary first and second profiled bars 4, 5 can be interlocked, thus creating a shape in section of an L for profile 21. The primary second profiled bar 5 has two longitudinal open channels 26, 44. The fixed frame 1 has also two gaskets 6, 7 which seal the gaps between the fixed frame 1 and sash frame 2 when the sash frame 2 is closed on the fixed frame 1. The first gasket 6 has a cross section wide and thin with a rounded extrusion 19 that is empty inside to fix it into the channel 25. The second gasket 7, has a substantially square cross section and is empty inside, with the rounded extrusion 20 that is empty inside to fix it into the channel 26. The gaskets 6, 7 which function as seals between the internal space of a building and the external open space, when the sash frame 2 is closed, are subject to sufficient pressure on their contact surface to prevent the passage of too much air and water between the gaps that exist between the fixed frame 1 and the sash frame 2. The shape of the gaskets 6, 7 also allows the necessary water drainage from the internal of the window frame to the outside and gasket 7 creates a mid-seal between fixed frame 1 and sash frame 2 as is appropriate in operable window technology. As the fixed frame 1 has a square or a rectangular shape composed by the four mitered primary profiles 21 , 22, 23, 24 as sides, at each comer it is connected by three comer-cleats 51 , 52, 53, shown in Fig. 12 that fix them together and reinforce the connections. As all corners of the fixed frame 1 have the same structure, we describe here only the structural principle of the corner between the primary profiles 21 and 22. The three corner-cleats 51, 52, 53 are made of metal, preferably, and have the function of corner connectors fixing solidarily the primary profile 21 to the primary profile 22 to make the fixed frame 1 a solid structure that enables to connect the window frame 100 solidarily to the building structure. Loads imposed on the comers of the primary frame and the sash frame resulting from opening the sash, from the weight of the frames and the glass and from the wind loads are accommodated by the corner cleats and transferred to the building structure over the hinges or hinge system being part of standard ironmongery connecting the fixed frame 1 to the sash frame 2 and the corner brackets of the fixed frame. The three corner cleats 51 , 52, 53 are all L-shaped and of different dimensions and cross sections to fit in the appropriate channels and guides of the profiled bars 4 and 5. With particular reference to Fig 3 where the cross section of the secondary profile 31 is shown, the secondary profile 31 comprises a secondary first profiled bar 27 made of aluminium preferably or of another metal or alloy, a secondary second profiled bar 28 made of a composite material preferably thermally low conductive, e.g. polyamide, a retainer or clip 36 and two gaskets 29, 30. The secondary first profiled bar 27 has a substantially P-shaped transverse section with a longer side parallel to the plane of the window frame and of the glass pane. The profiled bar 27 contains an empty hollow 61 and several flanges, two of which make the guide or channel 88. The flange 41 is disposed orthogonally to the longer parallel side of the profiled bar and is shorter, with length d1. The secondary second profiled bar 28 has a longitudinal slot or channel 39 which provides a C-shaped transverse section to accommodate the extremity 37 of the clip 36. The secondary second profiled bar 28 has also an extrusion 38, that fits in the guide 88 to fix solidarily the secondary first profiled bar 27 and second profiled bar 28 in appropriate manner for thermal break connections in window profiles. The slot 39 has a width that is not constant along its depth: it is thinner at the entrance but has a wider area in the inner part. The gaskets 29, 30 are fixed by inserting them into the respective open channels 89 and 87. These gaskets, as those of the fixed frame, have both sealing functions and gasket 30 avoids dangerous contacts of the glass surface with other components of the window frame made of metal. The clip 36 keeps the glass pane 3 fixed to the sash frame 2. Its longitudinal dimension is generally of few centimeters and can be made also longer if need arise ( see figure 9 a-b). It has an L-shaped cross section and its extremity 37 has a cogged or ribbed surface to have a better grip in the slot 39 using the flexibility of the composite material that makes the secondary second profiled bar 28. Advantageously a gasket 35 is also provided to protect the contact with the glass 3.

The procedure to mount the glass on the sash frame 2 and to dismount is herein described with particular reference to Figures 5, 6 and 7. The glass pane 3 is inserted into its housing on the sash frame 2 and the extremity 37 of the clip 36 is inserted into the slot 39. The clip 36 can be easily engaged by means of a number of V-shaped spring 90 housed in the slot 39, which has its V vertex 91 directed to the opposite direction of the secondary profiled bar 27 and is elastically pressed against surface 40. During insertion of the extremity 37 each cog of the clip cogged surface pushes the V-shaped spring 90 bending it and overtaking it. Once the cog is overtaken, the V-shaped spring 90 comes back and locks the clip by fitting the edge 92 of the V- shaped spring against the entered cog. The clip position can be fitted to various thicknesses of glass panes by inserting in a different number of cogs and within a predefined range of glass pane thicknesses.

The procedure to remove the clip 36 comprises the following steps. One introduces a thin tool 93, which is not a part of the invention, and squeezes the V-shaped spring 90 to get the cogged surface 37 free. Between the glass pane 3 and the clip 36 there is located the secondary seal 35.

By using clips 36 having extremities 37 of different lengths, in accordance with the invention, it is possible also to accommodate glass panes 3 of various thicknesses even larger than the length of the extremity 37. A series of two clips 36 and 36' of different dimensions is shown in the figures 9a and 9b. In accordance with the invention, it is also possible to increase further the range of thicknesses of glass panes 3 that can be inserted in the window frame of the invention by providing secondary profiled bars 28 of various lengths. In Figures 8a, 8b and 8c there are shown three secondary profiled bars 28, 28' and 28" of different lengths, made of thermally better insulating, structurally highly resistant material, e.g. polyamide. When thicker glass panes 3 are mounted on the sash frame 2, which make necessary to use longer clips 36 and/or longer secondary second profiled bars 28, e. g bar 28", it might also be necessary to use a longer primary second profiled bar 5 on the fixed frame 1 to make the primary profile 21 sufficiently thick. Primary second profiled bars 5, 5' and 5" of different lengths are shown in fig. 13.

Also it might be necessary to use a longer primary first bar 4 of the fixed frame 1 that can contribute to the thickness of the primary profile 21 , by using primary first profiled bars 4 and 4’ of fig. 15 of various thickness/length. A range of thicknesses of the primary frame can be achieved by using different lengths of primary first profile 4 and primary second profiled bar 5.

A combination of primary first bars 4 and 4’, primary second profiled bars 5, 5’ and 5”, secondary second profiled bar 28, 28'and 28” and clips 36 and 36’ enables to accommodate in the window frame glass panes 3 of thicknesses from 24 to 62 mm without affecting the visual appearance of the window inside and outside as shown in Figures14a to 14f.

The sash frame 2 is composed of four joined and mitered secondary profiles 31 , 32, 33, 34 and is connected by four metal corner-cleats 71 , 72, 73, 74 for each corner, which are shown in figures 11a to 11d in axiomatic view. Each cleat is inserted in a corresponding guide or channel of the secondary first and second profiled bars 27 and 28. Thanks to such angular connections, the sash frame 2 is particularly robust and can withstand high loads produced by its own weight and vertical loads from operating the sash as well as high dynamic loads generated by the wind. As shown in particular in figures 4 and 14, where there is shown the cross section of the window frame 100 in the closed position of the sash frame 2 in two different embodiments of the window of the invention, the invention allows a minimal width of the primary profile 21 and secondary profile 31. In the embodiments of figures 14, the secondary first profiled bar 27 has a different width w2 as shown in figure 4 and is less than the width w1 of the primary first profiled bar 4 to take into account the use of today’s standard ironmongery and the freedom of the manner in which the window frame is fixed on the building structure. The difference between w1 and w2 can be eliminated by using a custom made ironmongery.

In the embodiment of fig. 4 the width w1 of the primary first profiled bar 4 and width w2 of the secondary first profiled bar 27 are substantially equal. Additionally, the choice of an appropriate length d1 for the flange 41, equal or very close to the length d2 of the flange 10 makes the appearance of the window frame externally symmetrical and renders substantially unrecognizable which side is the operable part and which is the external side, when looking from the outside of the building when the window frame is closed. The reason is because both primary first profiled bar 4 and secondary first profiled bar 27 form a window frame which have the same distance from the surface of the glass pane thanks to the dimensions d1 and d2, and because of the choice of w1 equal to w2 the window frame appears as a singular surface of the frame on both sides of the window without any possible longitudinal interruption due to other profiled bars. Naturally the dimensions d1 and d2 take also into account the dimensions of the gaskets 6 and 30, in those cases here they are used.

Here follows an explanation, non limitative, of the principles that allows the window to have the mentioned advantages, in particular the targeted minimal visual dimensions of the frame of approximately 60 mm width and 20mm distance from the glass surface on both internal and external sides of the window, with particular reference to the main components of the window.

1- Window Sash Frame 2.

The window sash frame 2 is composed by a secondary first (alum) profiled bar 27 and a secondary second (composite) profiled bar 28. Those profiled bars cramped together over their full length in order to achieve a composite section following an existing proven process well known in the market and achieving that profiles are working sufficiently together in terms of bending and shear. The joined profiled bars 27 and 28, jointly indicated in the frame as 31 , 32, 33, 34, are mitered at each end and form a frame by corner cleat connections 71 , 72 and 73 (see fig.3). Cleats 71 and 72 are mechanically fixed to the frame members by metal threaded pins (see yellow and red pins in fig. 3). An additional corner cleat 74 is applied and fixed with a fixing pin to the frame (see pin in fig 3). For insertion of all corner cleats see also fig. 17. The glass 3 is positioned within the frame and secured against falling out by means of clip 36 that is fixed in position with the stainless steel V spring (see fig.5, 6, 7). Polymeric glass setting blocs are inserted in the space between the glass edges and comer cleats 74 at the window corners in such a way that the glass is only in contact with the sash frame at the corners. In this manner, the dead-load of the glass is diagonally transferred to the base hinge, whilst at the top hinge, the rotation load from the glass dead load is transferred along the top frame profiled bar 34 in tension directly to the top hinge. In this manner the window fixed frame and sash frame are not loaded by the glass self-weight and vertical loads due to operating the sash along their spans resulting in no bending to the profiled bars and hence a smaller and slender window section profiles (see fig.18).

Between the sash frame 2 and the fixed frame 1 there is applied a standard market available Tilt and Turn ironmongery device (see figures 18, 19, 21 a, 21b, 22a, 22b, 23). This explanation only oversees the turn function of the sash enabled by hinges incorporated in the ironmongery at the top and bottom corner along one side of the window. The window is designed for Height x Width sizes up to 1800 x1500 mm (see fig.20). The principle of transferring the glass weight to the sash frame is shown in fig.18 resulting in a vertical load on the bottom hinge and a horizontal load on the top hinge, which loads are directly transferred to brackets to the fixed frame 1 at the same location that are fixed directly transferred to the building structure via brackets of the fixed frame 1 that are directly fixed to the building structure at the same location as the hinges.

The ironmongery is designed in such a way that when the sash is closed interlocks will be achieved at corner positions and a number of intermediate positions along the perimeter of the window frame (see fig.19).

1.1- Dead load and Vertical load (see fig. 3 and 10)

The design of the sash allows up to 130 kg of glass and a vertical live load at the non-hinged side of the glass up to 80 kg resulting from opening operations, with a 1 mm maximum vertical allowable deflection of the sash frame in the opened position. The vertical live load has been considered in combination with the dead load in order to verify mechanical strength Class 4 in accordance with EN 14351-1. The resulting loads are transferred to the fixed frame and building structure as shown in fig 21a-b and 23). Fig. 10 shows that due to the described design the stresses in the aluminum profile and the composite (polyamide) profile of the sash frame remain considerable below the limits and therefore allows for minimum dimensions. 1.2 - Wind-loads (pressure and suction).

The window is designed to perform at maximum dimensions up to a maximum 2000 Pa wind pressure or suction and frame deflections within L/300 (L= distance between fixings) that corresponds with Classification C of EN14351- 1. Therefore in addition to the brackets at comer positions, the fixed frame 1 has wind load brackets along the midspan of the width (max. span = 750 mm) and 2r across the height of the window (max. span = 600 mm). (See fig 20). The ironmongery comprises interlock devices between the sash and the fixed frame at the corner positions (including hinges, see fig 21a-b and fig. 23) and in correspondence with the above mentioned wind load bracket positions (see fig 22 a-b).

Wind pressure or suction loads imposed on the glass are transferred to the window ironmongery interlock devices and in turn directly to the window frame brackets fixed to the building structure. The glass thickness for both structural adequacy and displacement is designed not as being continuously supported along the window frame but rather point supported at each ironmongery interlock/window bracket location. As wind loads are not transferred through the window frame, the framing itself is subjected to very limited bending allowing for a much more slender profile. In this way the targeted 20mm distance of the aluminum profile of the fixed window frame when viewed from the frame to the glass surface complies with the maximum allowed deflection at 2 kPa wind-load whilst stresses in the first and secondary profiles of the sash remain considerably below allowable limits and deflections do not exceed the allowable 2mm (see fig. 10). As a result the sash frame can be designed in accordance with the targeted slenderness. 2- Fixed frame 1.

2.1. Dead loads

The primary fixed frame 1 is fixed to the building structure at the corner s, one intermediate point at each horizontal frame member and two intermediate points (maximum span 600mm) at each vertical frame member (see fig.20). As the dead- and vertical loads from the sash including glass are directly transferred to the top and bottom brackets at the corners along one side of the window the fixed frame members are only required to accommodate the relatively very low dead load of the fixed frame members (self weight) and therefore comply with the targeted slender frame dimensions.

2.2. Wind-loads.

Wind-loads from the sash including glass are transferred via the ironmongery interlock points at eorner and intermediate wind bracket locations to the fixed frame and via the brackets of the fixed frame at the same locations to the building structure. As the frame members of the sash frame do not exceed a deflection of 2 mm between interlock-points the frame members of the fixed frame are not significantly loaded due to the flexibility of the seals in between sash and fixing frame accommodating such deflections. Therefore the fixed frame can easily comply with the targeted slender frame dimensions.

2.3. Burglary loads.

In terms of burglary compliance requirements, the only substantial bending load on the fixed frame members is a maximum horizontal load to the primary first (aluminum) profiled bar 4 of 0,3kN at the position of gasket 6 and the tip of flange 10 of the primary first profiled bar (see fig. 2) which do not result in substantial stresses in the profile and enable compliance with the targeted slender frame dimensions.

In view of the description above, it is clear that the window of the invention provides the expected advantages listed above.

Like wind loads, vertical loads from operating the sash and own weight are transferred by limited local points to the building structure instead of fully loading the entire length of the primary and secondary frame, this particular way of transferring loads to the building structure enables to make extremely thin edges for the window frame. By making windows frames with small edges without surface interruptions and no variation in distance between the front frame surface and the glass surface inside and outside one can reach aesthetic levels that have never been reached before.

At the same time, the window frame is extremely light and thermally performant, reducing the surfaces where heat exchange occurs. This notwithstanding, the production cost of the window frame is low, thanks to a wide range configurations and dimensions of windows obtained by coupling a low number of standard parts that can be assembled together easily and quickly. With the invention a rather small height w1 and w2 of the window frame 100 of around 60mm can be reached, which is a dimension difficult to obtain with other window frames of the state of the art for such large windows.

This solution enables to make a large range of products with a few simple interchangeable parts, which means production cost reduction and also little quantity of pieces kept in stock.

From the above description it is apparent to the skilled person that the window according to the invention contributes to redefine market standards about appearance, performances and low cost. When compared with other standard window systems in the market and taking account of aesthetics, the window according to the invention has better performances, looks better and it is also cheaper. Other advantages of the window according to our invention is a minimized visual impact of the gaskets, no identification of the openable part, the provision of aluminum finishes on both window internal and external sides, an optimization of the thermal performances thanks to a high use of composite profiles and a limited number of components to minimize system logistics.

The invention has been described in all details like a window. It is readily apparent to the skilled person that it can also be applied to a door or to any other similar opening of a building without leaving the scope of the patent. Though the window of the invention has been described in an embodiment where the sash can be opened towards the internal of a building, it is apparent to the skilled person that it can be mounted on a building also as an external opening sash. The window of the invention can also be applied in various opening modes and in shapes other than rectangular and square. In conclusion, from the above description it is clear that the invention offers at least the non-limitative list of following advantages:

• The system is made as a kit of parts;

• A stepped connection is possible between the first and the second profiled bar of the fixed frame;

• A stepped connection is possible between the second profiled bar and the clip of the sash frame;

• The sash remains concealed at an outside view when the window is closed .

• No hairlines, steps, grooves or the like are visible on the surface of the window frame on both sides.

• The provision of an integrated hinge/fixing to the building structure at the corners of the window frame.