Problems associated with double security door constructions are that it is relatively easy for an intruder to force the two doors apart using a lever such as a crow bar. The lever is first inserted into a gap between where the two doors meet, and then pushed through the gap sufficiently far such that the intruder can use his weight and the rigidity of each door as resistance in order to lever the doors open.

One attempt at minimising the ease with which a lever may be inserted into the gap between the two doors is by providing an overlap which extends from one of the doors over the gap. This overlap is known as an astragal.

However, problems still arise because, the leverage applied by the intruder is normally sufficient to bend the overlap over thereby allowing access to the gap.

It is one aim of embodiments of the present invention to address the above problem and to provide a door construction with improved security.

According to a first aspect of the present invention, there is provided a door construction comprising first and second doors each having first and second ends, the doors being mountable at the first ends thereof onto support means, the said second end of the first door comprising engagement means, which engagement means extends

substantially away from a plane of the first door, the said second end of the second door comprising receiving means, which receiving means extends substantially away from a plane of the second door, wherein the engagement means and the receiving means are operable to substantially engage each other, thereby preventing unauthorised opening of the door construction.

Preferably, the first and second doors comprise first and second sides, which sides correspond to the interior and exterior of a building, respectively.

Preferably, said engagement means comprises a protrusion.

The protrusion may comprise a projection or a lip preferably a recessing lip. Preferably, the engagement means extends in a direction substantially towards the first side of the first door preferably towards the interior of the building.

Preferably, said receiving means comprises a recess. The recess may comprise a notch or a cavity operable to accommodate the engagement means. Preferably, said receiving means extends in a direction substantially towards the first side of the second door preferably towards the interior of the building.

Preferably, the second ends of the first and second doors comprise profiles which are complimentary to one another.

Preferably, said second end of the first door comprises at least one region which is substantially complimentary to the second end of the second door. Preferably, the at least one complimentary region of the second end of the

first and second doors extends along substantially the length thereof.

Preferably, the second ends of the first and second doors and, preferably, the at least one complimentary region thereof are operable to substantially restrict lateral movement of the doors. Advantageously, the profile of the door construction provides improved resistance to unauthorised entry by a potential intruder.

Preferably, the at least one complimentary region of the first door comprises the engagement means. Preferably, the at least one complimentary region of the second door comprises the receiving means. Preferably, the engagement means substantially mutually engages with the receiving, means when the doors are closed.

Preferably, the second end of the first door further comprises a substantially elongate region operable to attach the engagement means to the second end of the first door. Preferably, the elongate region comprises an overlapping arm region which extends along the second side of the first door. Preferably, the width of the elongate region is less than the width of the first door between the first and second sides. Preferably, the elongate region is substantially reinforced. Preferably, the width of the elongate region is substantially wide to prevent it from distorting during unauthorised entry by an intruder.

Preferably, the second end of the first door further comprises a step region located in between the first end and the elongate region. Preferably, the width of the step region is less than the width of the first door.

The door construction may comprise a gap or space extending around the engaging profile of the first and second doors. Preferably, the gap is sufficiently narrow to provide a complimentary fit between the second ends of the first and second doors and preferably sufficiently wide such that the first and second doors may be moved from the first configuration to the second configuration without coming into contact with each other when they are opened and/or closed.

Preferably, the door construction comprises double security doors. Preferably, the first and second doors are manufactured out of a substantially impact resistant infill. Preferably, the doors are mountable by hinge means onto the support means, which support means preferably comprises a wall. The door construction may comprise an astragal, said astragal comprising an overlap extending from the second end of the first door substantially towards the second door thereby preferably substantially covering the gap.

Preferably, the first and second doors are operable to move from a closed configuration to an open configuration.

Preferably, the first door is operable to move from the open configuration to the closed configuration before the second door is moveable. Preferably, the second door is operable to move from the open configuration to the closed configuration before the first door is moveable.

Advantageously, if a lever such as a crow bar is inserted into the gap, the leverage causes the engagement means to move within the receiving means thereby causing the lip to

abut the side of the first door. Advantageously, this prevents the door construction from being opened.

All of the features described herein may be combined with any of the above aspects, in any combination.

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 shows a schematic side view of a double door construction ; Figure 2 shows a schematic plan view of the double door construction along the line A-A as shown in Figure 1 ; and Figure 3 shows a schematic plan view of the double door construction along the line B-B shown in Figure 2.

Referring to Figure 1 there is shown a double security door construction 2 consisting of two doors 4,6. The doors 4,6 are attached by hinges 8 to a wall 10. The doors 4,6 meet along a region 20.

Referring to Figure 2, there is shown the double security door construction 2 from above illustrating how the doors 4,6 are opened and closed with respect to one another.

Door 4 opens outwardly first in the direction as shown by arrow X. This allows door 6 to open second in the direction as shown by arrow Y. The double door construction 2 is closed in the opposite way, i. e. door 6 is closed first in the direction opposite to arrow Y, followed by door 4 which is then closed in the direction

opposite to arrow X. Due to the shape of the doors 4,6 along the region 20 where they meet, it is not possible to open door 6 first and door 4 second and vice versa for closing the door construction 2.

Referring to Figure 3, there is shown a detailed view of the double door construction 2, and in particular, the configuration of the region 20 where the two doors 4,6 engage one another. The doors 4,6 are attached to the hinges 8 by bolts 22, and the hinges 8 are secured to the wall 10 by screws 12. The doors 4,6 are manufactured out of an impact resistant infill material 14.

The two ends of the doors 4, 6 which engage with one another are complimentary with each other and provide a resistant barrier against unauthorised entry to the interior of the building. The end of door 4 which engages with the end of door 6 reduces from a total width of about 50mm to a width by about 12mm thereby forming a step region 30. The step region 30 extends in the direction along the longitudinal axis of the door 4 for a length of about 23mm. The width of the step region which is about 38mm then reduces to form a forwardly facing overlapping arm 16 which has a width of about 7mm. The forwardly facing overlapping arm 16 faces towards the exterior of the building and extends for a length of about 70mm at the end of which there is formed a recessing lip 18. The recessing lip 28 extends transversely to the forwardly facing overlapping arm 16 in a direction towards the interior of the building. The width of the recessing lip 18 is about 6mm and its length is about 15mm.

The end of the door 6 which engages with the end of door 4 has a shape and configuration which is complimentary to that of the end of door 4. The end of door 6 has a notch 28 which accommodates the recessing lip 18 of door 4, a block region 26 having a width of about 39mm and a length of about 54mm which is complimentary to the forwardly facing overlapping arm 16. Finally, the width of the end of door 6 reduces to about 6mm for a length of about 25mm to form a rearwardly facing overlapping arm 24 which is complimentary to the step region 30 on the end of door 4.

The rearwardly facing overlapping arm 24 faces towards the interior of the building.

A separation gap 20 having a constant width of about 3mm extends between the engaging ends of the doors 4,6 is sufficiently narrow to provide a good complimentary fit between the end of the two doors 4,6, and sufficiently wide such that the doors 4,6 may be open and closed without making contact with each other.

Advantages of the double door set construction 2 reside in its improved resistance to unauthorised entry which would normally be attempted by inserting a lever such as a crow bar or other similar device (not shown) into the gap 20 between the two doors 4,6 on the exterior of the door set 2. An intruder attempting to gain unauthorised entry would insert a lever in between the two doors 4,6 and push it sufficiently far enough through the gap so that at least part of the lever could be levered against the rearwardly facing side of either door 4,6 to force the other door 4,6 open.

However, this operation is prevented by the presence of the recessing lip 18 and notch 28 of the present application. As an intruder inserts a lever into the gap 20, further movement towards the interior of the building is prevented when the lever enters into and abuts the bottom of the notch 28. The intruder would then attempt to lever the doors 4,6 open by moving the lever from side to side. However, the recessing lip 18 has limited space for movement making leverage within the notch 28 difficult.

The recessing lip 18 would either move to the right in Figure 3 where the main section of door 6 would present a large resistance preventing further movement, or it would move to the left in Figure 3 and abut a side of the block region 26 which would also present a resistance preventing further movement.

As a result, it is very difficult for an intruder to insert the lever sufficiently far enough in between the doors 4,6 to gain the required leverage to force the doors 4,6 open. In addition, the forwardly facing overlapping arm 16 is considerably widened and reinforced. This decreases the likelihood of the intruder successfully bending or distorting the recessing lip 18 by penetrating the lever down into the gap 20, into the notch 28 and around behind the lip 18.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.