The present invention relates to blast resistant windows, for instance such windows that are installed in embassies and other high profile buildings or the like that require protection from explosive blasts. In particular, the present invention relates to a method of installing a blast resistant window.

Currently, a known blast resistant window is constructed from a window pane surrounded by an extruded aluminium profile. Such windows are manufactured from profiles having increased wall thicknesses when compared to profiles used for the construction of standard, commercial windows. A front and back aluminium extrusion are typically separated by a thermal barrier. The formed profiles are mitred and joined at corners to form generally square or rectangular window frames. The corners are formed by inserting an angled former and crimping the extrusions so that internal areas of the extrusions squeeze parts of the former to secure in place. Due to the crimping, operation, the profiles need to maintain a degree of malleability. Thus there is a limited the thickness of the material in order to continue crimping the frames. For added strength, the corners may have a resin adhesive applied, and are tapped and screwed in place. Window panes are fitted to the frame using gaskets and secured in place using a bead that interlocks with the frame and is again screwed in place for added protection against being blasted off.

It is currently known for these frames to be fixed within in a window opening (also referred to as a window casing or structural opening) using metal fixing lugs. These fixing lugs are metal straps, secured to the window frame at specified intervals so that they extend from the face of the window along the insides of the window reveals. So as to spread and dissipate the force, the straps are pitched at around 300mm centres around the whole perimeter of the window frame. I nvariably, these straps are cranked, such that when the installation is complete, the straps and the studs anchoring them into the masonry are sunk below the level of the finished plastered / decorated window reveals and are thus concealed. To install the window frame therefore, pockets must first be machined out of the window opening in order to accept the straps. The pocket locations need to be precisely machined. The window is then supported in position and each strap fixed into the masonry. Typically, the straps are fixed using resin anchors. Finally, it is necessary to back fill the pockets, over the straps, with plaster or the like in order to retain the building's aesthetic appearance.

The straps are necessary to accommodate the forces applied during the bomb blast. In such an event, the straps bend and deform, spreading, absorbing, and transferring the load to the building structure. If the windows were screwed directly through the aluminium frame into the structural opening, as is the usual simple method of fixing standard commercial windows, when subjected to the tremendous forces exerted during a blast situation, the window frame would tear locally around the fixings and be blown out of the structural opening.

The material costs of the straps can add significant costs to the price of a window installation. Moreover, the machining and backfilling of the pockets can also involve considerable manual labour and disruption.

It is an aim of the present invention to attempt to overcome at least one of the above or other disadvantages. It is a further aim to provide a blast resistant window and method of installation having a lower cost. It is a further aim to provide a blast resistant window and method requiring less disruption to the fabric of the building.

According to the present invention there is provided a blast resistant window and method of installation as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

I n an exemplary embodiment, a blast resistant window having a window pane encased by extruded profiles is provided, wherein the load absorbing and dissipating elements of the window fixing arrangement are brought within the profiles themselves. That is, rather than relying on straps to tie the window to the window casing external to the window frame, and therefore requiring extensive preparation prior to (and similarly extensive cosmetic finishing following ) the fixing of the window frame, the windows are fixed to the window casing directly through the window profiles. This is possible, whilst maintaining the blast resistant capability, the profile extrusions are moulded to include internal pockets / grooves for receiving strengthening bars, slid into them during fabrication of the window. These enable the window to be directly secured to the masonry opening without the need for fixing lugs, as they strengthen the area through which the resin anchors pass, preventing the profile from tearing away around the fixings. The fixings are hidden by the window thus reducing the need for cosmetic touch-ups. As a consequence, blast resistant windows according to the exemplary embodiments are able to be installed on site by fixing directly through the side of the frame. As the metal lugs are not needed - nor are the assembly steps of machining pockets and back filing/rendering - this is expected to lead to a cost saving of around 15% on the overall project, plus around 30% on installation time.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1 is a cross sectional view through a first embodiment;

Figure 2 is a cross sectional view showing an enlarged area of Figure 1 ; and

Figure 3 is a cross sectional view through a second embodiment of the present invention.

Referring to Figure 1 a blast resistant window assembly 10 is provided. The blast resistant window assembly 10 comprises a window casing 20 and a blast resistant window 30. The blast resistant window 30 comprises a window pane 40 that is encased within a window frame 50. The blast resistant window 30 is secured to the window casing 20 directly through the window frame 50 using fixings 60. In the event of a blast, the blast resistant window 30 is prevented from being ripped from the fixings 60, which would otherwise happen with the fixings tearing through the window frame, due to a strengthening means 70 that is inserted in to the window frame 50.

It will be appreciated that the window casing 20 refers to a structural opening, window opening, o r t h e l i ke formed in the building structure to receive a window. Consequently, it is intended that the terms structural opening, window opening, and window casing can be used interchangeably. Referring to Figure 2, an exemplary strengthening means 70 is shown. Suitably, the strengthening means is an elongate member. An aperture is formed through the strengthening means for receiving the fixing . Although the fixing may extend only through the strengthening means in the exemplary embodiments, the fixing extends through both the strengthening means and the frame 50. Here, the aperture is aligned with an aperture through the window frame to provide a passageway through the window for the fixing to reach the window casing 20. Although the strengthening means may comprise a plurality of members, it is preferable if the strengthening means includes more than one aperture. For instance, fixings may be spaced about the periphery of the window frame 50 substantially the same pitch as in existing installations. Thus the strengthening means may comprise an elongate member such as an elongate bar having a plurality of apertures formed therein . Since the strengthening means and window frame are manufactured and assembled in manufacturing conditions, the tolerances on the apertures and respective alignment is easily achieved. This is in contrast to the respective difficulty in machining precise pockets in the window casing at the installation site.

Suitably, the strengthening means may be formed of the same material as that of the window frame 50. Here the strength comes from effectively increasing the thickness of the wall of the window frame 50 through which the fixing 60 is secured. However, alternative materials may be used for the strengthening means with the added strength coming from these material properties.

It is envisaged that the window frame 50 will be formed following existing techniques. For instance, a frame is formed from a number of extruded profiles mitred together. Suitably, the profiles are extruded aluminium. However, importantly, on the inside of the profile's wall through which the fixing is secured, a retaining means 80 is supplied. Still referring to Figure 2, suitably the retaining means is shown as a pocket or slot. Here, the pocket or slot is formed by opposed protrusions 82. Each protrusion extends outward from a side wall. The side walls extend away from a wall through which the fixings are secured. The protrusions 82 may be parallel to the wall through which the fixings 60 are secured. Whilst the size of the strengthening means 70 may mean that they are retained in position without the need for protrusions, it is preferred if the strengthening means 70 is retained snugly so that the retaining means does not move or rattle during movement. I n one embodiment, the retaining means 80 is arranged to receive the strengthening means in an interference fit. Importantly, the strengthening means dissipates the force of a blast through the retaining means, preventing the frame from being ripped from the fixings.

Importantly, the strengthening means enables a blast resistant window to be formed from existing materials and thickness. Moreover, because the thickness or material strength/ductility characteristics of the extruded profiles for forming the window frame are not increased, the frame can still be assembled using established techniques including crimping. Moreover, because the strengthening means can be assembled to each profile once it has been cut to size, for instance, the strengthening means can be slid into the retaining means from one end, it is not necessary to process profiles having a large thickness. Also, a single profile can be extruded for multiple functions. For instance, in certain instances it may not be possible to directly fix the window 30 through the frame, in which case a traditional method can be used, without producing an alternative profile, with the strengthening means omitted. Also, it may be possible to use the same profile for alternative portions of complex blast resistant window assemblies and again, the strengthening means may be omitted or replaced with a more suitable insert.

The fixings are shown as a resin anchor as used currently when securing the straps. However, any other suitable fixing may be employed. Advantageously, because the holes in the window casing 10 can be machined through the apertures when the blast resistant window 30 is initially supported in position, the location of the holes for the resin anchors is exact. Consequently, the method of installing is simplified and less prone to error. It may also be possible to form the window frame 50 without preformed apertures for receiving the fixings, wherein the apertures are machined onsite.

As mentioned, the window frame 50 may be assembled substantially as in established techniques. Here, the window pane 40 is held in place with gaskets and beads. As shown in Figures 1 and 3, it may be advantageous to also include strengthening means on the inside of the wall through which the bead is secured. Here the strengthening means may be as previously described.

It will be appreciated that a method of installing the herein described blast resistant window 30 is provided. The method comprises initially supporting the window 30 in position within the window casing 20 and directly fixing the window 30 to the casing 20 by secu ri n g fixi n gs 60 th rou g h th e fra m e 50. For i n stance, in exemplary embodiments, apertures are formed through the frame or the frame is supplied with preformed apertures, wherein each aperture extends th rough the frame and strengthening means. Preferably, mu ltiple apertures are formed through the strengthening means. When using fixings such as resin anchors that require pre- drilling, the window casing can be machined whilst the window blast resistant window 30 is held in initial position.

Referring to Figure 3, in certain instances it may not be possible to directly fix through the window frame 50. For instance, it is necessary to maintain at least 0.1 5m between the fixing and inside edge of the window casing. This is in order to prevent the inside of the window casing from being busted into the building in the event of a blast. In this case, it may still be necessary to employ a strap in accordance with established installation techniques. Suitably, the strap 90 may be secured through the window frame 50 and into the strengthening means 70. Thus, again, increased strength is provided.

Because the installation method eliminates the requirement of fixing straps, the installation cost is reduced. Moreover, the cost of the installation is reduced because the need to machine pockets for the straps and the subsequent back filling operation is redundant. For the same reason , the disruption and cosmetic finish of the installation is improved. Consequently, although the exemplary embodiments have herein been described in relation to blast resistant windows, the window panes may be other panes such as opaque panes or sheets.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.