This invention relates to a door or window assembly, a security method and a method of making a door or window assembly.

It is known to provide a sensor on a door or window to detect when the door or window is closed. Such a sensor can be part of an alarm system in which the alarm will be set off if the door or window is opened. Such a sensor may comprise a magnetic strip attached to the door or window and a magnetic sensor fitted to the frame. The sensor is arranged to detect when the magnetic strip and sensor are in close proximity, thus determining that the door or window is closed. Such a sensor is however only capable of detecting if the door or window is closed - i.e. it is not able to detect that the door or window has been secured in the frame by the activation of a fastening mechanism.

In a first aspect, the present invention provides a door or window assembly comprising: a door or window; a frame arranged to receive the door or window; and a fastening mechanism, the fastening mechanism comprising: a first fastening member on the door or window moveable between an unfastened position and a fastened position in which the first fastening member is arranged to engage with a first frame member on the frame to fasten the door or window in the frame, wherein the door or window assembly comprises a sensor arranged to detect when the first fastening member is in the fastened position and engaged with the first frame member.

This invention advantageously detects when a door or window is fastened in its frame by detecting when the first fastening member is in the fastened position and engaged with the first frame member. This provides an advantage over the prior art which only detects when the door or window is closed (e.g. it has been pushed into the frame) but cannot determine whether the door or window is fastened into the frame (e.g. it is effectively locked). This is an important security consideration - the sensor of this invention is able to determine when the door or window is fastened in the frame and therefore held securely in place to prevent it being opened from the outside. This is not achieved by known sensors, which detect only that the door or window is pushed into the frame, but which may still not be fastened into the frame, so can still be opened from the outside. The sensor of this invention is suited to doors and windows which have a fastening mechanism which must be moved from an unfastened position to a fastened position by an actuator, such as a handle lever or button, operated by the user. The user may therefore push the door or window into the frame but forget to move the actuator to fasten the door or window into the frame so that it is secure. In such a position, a typical, known sensor would still sense that the door or window is closed, whereas the sensor of this invention would sense that the door or window is not fastened into the frame and conclude that the assembly is not secure. The fastening mechanism may further comprise: a second fastening member on the door or window, moveable between an unfastened position and a fastened position, in which the second fastening member is arranged to engage with a second frame member on the frame to fasten the door or window in the frame, wherein the first and second fastening members are electrically connected; and the first and second frame members are electrically connected via the first fastening member and the second fastening member when both the first and second fastening members are in the fastened position and engaged with the respective one of the first and second frame members; otherwise the first and second frame members are electrically isolated, and wherein the sensor is arranged to detect whether there is an electrical connection between the first frame member and the second frame member via the first fastening member and the second fastening member.

This invention requires detecting an electrical connection between the frame members via the fastening members. Such a connection can be used to indicate that the fastening members and frame members are fastened and engaged. This is advantageous because the fastening members positioned on the door or window must be allowed to move with respect to the frame when the door or window is closed. The inventor has realised that a typical door or window has two fastening members that are electrically connected via a mechanism that moves when an actuator (e.g. a handle) is moved by the user. Typically, the fastening members may be both connected to a single actuator so that they are moved in tandem to engage with the frame members to fasten the door or window in the frame. By making use of this existing electrical connection, the sensor of this invention requires only electrical connections to be made to components already attached to the frame. Optionally, such a system can be conveniently retro-fitted to an existing design of door or window frame and may be hidden within the body of the frame so that it is not visible during use.

In a second aspect, the present invention provides a door or window assembly comprising: a first door or window and a second door or window; and a frame arranged to receive the first door or window and the second door or window, and wherein the first and the second door or window each comprises a fastening mechanism as defined above, and wherein the first frame members of the fastening mechanisms are electrically connected, and wherein the sensor is arranged to detect whether there is an electrical connection between the second frame members of the fastening mechanisms.

This advantageously allows the sensor of this invention to detect when both windows and doors of an assembly are secured in the frame.

In a third aspect, the present invention provides a security method for detecting whether in the door or window assembly of this invention, a door or window is secured in its frame. The method comprises detecting whether the first fastening member is in the fastened position and engaged with the first frame member.

This advantageously provides a security method in which it is determined whether a door or window is actually secured in its frame, rather than only received by the frame. In a fourth aspect, the present invention provides a method of making a door or window assembly, the method comprising fitting a sensor to an existing door or window assembly to provide the door or window of the present invention.

This advantageously allows a door or window assembly of this invention to be provided by retro-fitting a sensor to an existing door or window assembly.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure la shows a window assembly according to an embodiment; Figure lb shows a detailed side view of the window of the window assembly shown in Figure l a; Figures 2a to 2j show a close-up view of part of a fastening mechanism of the window assembly of Figure l a during closing and fastening of the window.

Figure 3 shows a window assembly according to another embodiment; Figures 4a to 4j show a close-up view of part of the fastening mechanism of window assembly of Figure 3 during closing and fastening of the window.

Figure 5 shows a window or door assembly according to another embodiment; and Figure 6 shows a window or door assembly according to another embodiment.

A window assembly 100 according to a first embodiment of the invention is shown in Figure 1. This invention applies to a door or window or another similar closure means such as a hatch, trap door or the like. Any features described in the following description in relation to one closure means such as a window, can be equally applied to a door or any other closure means.

The window assembly 100 comprises a window 102 which is arranged to be received by a frame 104. Such a window can be installed in a building as is well known in the art. In the embodiment shown in Figure 1 , the window 102 is hinged along one side such that it can move between a closed position in which it is received by the frame and an open position where it is not received by the frame. In this example, in the open position, the window 102 is angled with respect to the frame. In other embodiments the window 102 may be hinged on a different side to that shown in Figure 1. In yet other embodiments, the window may be pivotally connected on more than one of its sides, such that it can move in the same plane as the frame 104 into the open position.

The window assembly 100 further comprises a first fastening mechanism arranged to fasten the window in the frame 102. The window 102 is arranged such that it may be moved into a closed position where it is received by the frame, but in this closed position it is not fastened to the frame to prevent it being opened from the outside. The window 102 may therefore be 'pushed closed' , but not fastened into the frame. Once in the closed position, the fastening mechanism can be operated by the user to fasten or secure the window 102 into the frame 104. Advantageously, this invention provides improved security by identifying when the window is both in the closed position and fastened into the frame to prevent it from being easily opened from the outside. This is particularly important where the fastening mechanism is not activated automatically by the action of the window being closed. Typically, fastening mechanisms require the user to operate them (by operation of a lever, handle or button, for example) once the window has been closed in order to fasten the window into its frame. As the user may forget to do this, the window may inadvertently be left unsecured. This invention provides a sensor that not only determines whether the window is closed, but also that it has been fastened to the frame. The sensor is thus able to provide an alert the user if the window is not secure by providing a visual or audible indicator or alarm, for example, or may provide an alert to a computer in communication with the sensor.

The first fastening mechanism comprises a first fastening member 106 mounted on the window 102 and a first frame member 108 located on the frame 104. The first fastening member 106 is moveable between an unfastened position and a fastened position in which it is arranged to engage with the first frame member 108. The first fastening member 106 and first frame member 108 form a two part fastening mechanism.

When the first fastening member 106 is in the fastened position and engaged with the first frame member 108, the window is fastened into the frame 104 and cannot easily be opened from the outside by an intruder. The first fastening member may also be moved between the unfastened and the fastened position when the window is not received in the frame, i.e. the window 102 is not in the closed position (e.g. the window is open such that the fastening member and frame member are not aligned with each other and therefore do not engage when in the fastened position). The window assembly 100 further comprises a sensor 1 10 arranged to detect when the first fastening member is in the fastened position and engaged with the first frame member. When the first fastening member 106 and the first frame member 108 are engaged they are coupled to each other and are able to resist being pulled apart. The sensor 1 10 is thus arranged to detect that the window is fastened into the frame and cannot easily be opened from the outside, rather than only pushed closed such that it can still be easily opened from the outside. This offers an advantage over known sensors, which are only able to detect that a window has been closed and are unable to detect whether the window has been securely fastened into the frame.

In the embodiment shown in Figure 1 , the first fastening mechanism comprises a second fastening member 107 and a second frame member 109. In this embodiment the first fastening mechanism therefore comprises two frame member and fastening member pairs. This embodiment makes use of these pairs to determine whether the window is secured into the frame. Such components are common in window and door fastening mechanisms, thus allowing the sensor of the present invention to be fitted to existing windows and doors with few additional components or modifications. This optionally allows the sensor of this invention to be retro-fitted to existing window assemblies. Similarly to the first fastening member 106, the second fastening member 107 is located on the window 102 and is moveable between an unfastened position and a fastened position in which it is arranged to engage with the second frame member 109 on the frame 104.

As shown in Figure 1 , the first and second frame members 108, 109 are spaced apart along the length of one side of the frame. The first and second fastening members 106, 107 are spaced apart by a corresponding distance along a corresponding side of the window 102. In other embodiments, the first and second fastening members 106, 107 may be on different sides of the window 104, and in some embodiments may be located on opposite sides of the window to each other. In some embodiments, the first fastening mechanism may comprise two frame and fastening member pairs. In other embodiments, as shown in Figure 1 , the first fastening mechanism may further comprise a third fastening member and frame member pair to further secure the window 102 into the frame 104. In other embodiments, the first fastening mechanism may comprise any number of frame member and fastening member pairs. The first and second fastening members 106, 107 are moved from the unfastened to the fastened position by the operation of an actuator 105. In the described embodiment, the actuator 105 is in the form of a handle, which can be rotated by a user. Such a handle is rotatable between a first position, in which the first and second fastening members 106, 107 are in the unfastened position and a second position, in which the first and second fastening members 106, 107 are in the fastened position. In other embodiments, the actuator may be a lever or button or the like, which can similarly be operated by the user to move the first and second fastening members 106, 107 between the fastened and unfastened positions. In the described embodiment, there is a single actuator 105 that is arranged to move both the first and second fastening members 106, 107 conjointly.

The first and second fastening members 106, 107 are connected together by a first electrically conducting element. In the described embodiment, the first electrically conducting element comprises a linkage 1 1 1. The linkage 1 1 1 is arranged to operatively couple the actuator 105 to both frame members 106, 107 so that they move together when the actuator 105 is operated by the user. The linkage 1 1 1 may comprise a rigid link, such as a plate or bar, connecting frame members 106, 107 with the actuator 105. In this embodiment, the first and second fastening members 106, 107 therefore move so that they engage with their respective frame member 108, 109 at substantially the same time. In embodiments where there are three or more frame and fastening member pairs, the linkage 1 1 1 may be connected to all of the pairs so that they move together and engage with each other at substantially the same time. In other embodiments, a separate actuator is provided for each of the first fastening member and the second fastening member such that they can be moved independently of each other. In such an embodiment, there is an actuator for each pair of frame and fastening member (e.g. a first actuator for the first fastening member 106 and the first frame member 108, and a second actuator for the second fastening member 107 and the second frame member 109) arranged to move the respective fastening member between the engaged and unfastened positions. In such an embodiment there may be no movable connection between the first 106 and the second 107 fastening members and they are instead moved by their respective individual actuators. In this embodiment therefore, the first and second fastening members (and any further fastening members that are present in some embodiments) may not be moved into engagement at the same time, but instead may be moved one at a time, or two at a time, for example.

In order to detect whether the first fastening member 106 is in the fastened position and engaged with the first frame member 108 the sensor of this invention makes use of the electrical connection that is created between the fastening members 106, 107 and the frame members 108, 109 when the fastening members are moved to the fastened position. Each of the frame members 108, 109 and fastening members 106, 107 comprise an electrically conducting material so that an electrical connection is created between them when they are moved to the fastened position. In the described embodiment, the first and second fastening members 106, 107 are electrically connected by the linkage 1 1 1. As in this embodiment, the linkage 1 1 1 comprises an electrically conducting material there is a permanent electrical connection between the first and second fastening members 106, 107. The inventor has realised that this connection can be exploited to provide a convenient sensor to detect when the first and second fastening members 106, 107 are in the fastened position and engaged with the respective frame member. The present invention therefore requires few components and can optionally be retro-fitted to an existing window assembly. In embodiments where there is no pre-existing electrical connection between the first and second fastening members 106, 107 (because for example, the linkage 1 1 1 is made from electrically insulating components, or the window is provided with separate actuators that move the first and second fastening members 106, 107 independently and they are therefore not connected), the first electrically conducting element comprises a wire connected between the fastening members 106, 107. Such an electrically conducting wire can be hidden within the body of the frame and so is not accessible or visible to the user once installed.

The first and second frame members 108, 109 are electrically connected via the first fastening member 106 and the second fastening member 107 when both the first and second fastening members 106, 107 are in the fastened position and engaged with the respective one of the first and second frame members. Otherwise, the first and second frame members are electrically isolated. The first and second frame members are electrically isolated when either the first, the second, or both of the fastening members 106, 107 are in the unfastened position (or are in the fastened position, but not engaged with their respective first or second frame member 108, 109 because the window is not closed). When the first fastening member 106 is in the unfastened position, there is no electrical connection between the first frame member 108 and the first fastening member 106 because there is no physical contact between them. This means that there is no completed electrical circuit between the first frame member 108 and the second frame member 109 via the electrical connection between the first fastening member 106 and the second fastening member 107. The circuit is broken at the point between the first frame member 108 and the first fastening member 106 because they are not engaged. Similarly, when the second fastening member 107 is in the unfastened position, there is no complete electrical circuit between the first frame member 108 and the second frame member 109 via the electrical connection between the first fastening member 106 and the second fastening member 107. In this case the circuit is broken between the second frame member 109 and second fastening member 107. When both of the first and the second fastening members 106, 107 are in the unfastened position, the electrical circuit is broken at both of these points and again there is no completed circuit between the first frame member 108 and the second frame member 109 via the electrical connection between the first fastening member 106 and the second fastening member 107. Only when both of the fastening members 106, 107 are in contact (e.g. are in the fastened position and are engaged) with the frame members 108, 109 is an electrical circuit between the first frame member 108 and the second frame member 109 completed. The sensor 1 10 is arranged to detect the completion of this electrical circuit (e.g. to detect an electrical connection between the first frame member 108 and the second frame member 109, via the first fastening member 106, the linkage 1 1 1 and the second engagement member 107). This advantageously provides a sensor to detect when the window is fastened in the frame, rather than simply when the window is closed, but the fastening mechanism has not been engaged. In the described embodiment, the frame 104 comprises an electrically insulating material (e.g. PTFE etc) and so there is no electrical connection between the frame members 108, 109 when they are not in contact with the fastening members. In other embodiments, the frame may comprise an electrically conducting material (e.g. a metal, or partly metal, frame). In such an embodiment, at least one of the first and second frame members 108, 109 or both, are provided with an insulating member to electrically insulate them from the frame. In some embodiments the insulating member may comprise a pad or other such insulating layer disposed between the frame and the frame member 108, 109. A second electrically conducting element may be arranged to electrically connect the first frame member 108 to the sensor 1 10 and a second electrically conducting element may be arranged to connect the second frame member 109 to the sensor 1 10 (as indicated by the broken lines in Figure l a). In some embodiments, each of the second and third electrically conducting elements may comprise wires which may be arranged within a body of the frame so that they are not accessible, exposed or visible to the user once the sensor 1 10 has been installed. As the frame of a window is typically hollow or contains internal channels, the electrically conducting wires can be hidden inside the frame by drilling holes into the frame and inserting the wires from the outside. In other embodiments, the electrically conducting wires may be fixed to the surface of the frame 102 and hidden by a sealant material applied to the frame.

Close up views of the fastening mechanism during the process of closing and fastening the window 102 into the frame 104 are shown in Figures 2a-2j . Figures 2a, 2c, 2e, 2g and 2i show a side view of the fastening mechanism and Figures 2b, 2d, 2f, 2h and 2j show a top view of the fastening mechanism. Although only the first frame member 108 and the first fastening member 106 are shown, it is to be understood that the second frame member 109 and second fastening member 107 (or any additional pairs of fastening members and frame members provided on the window) may be the same.

As can be seen in the side view of Figure 2a, the first frame member 108 comprises a plate 1 12 which is fixed to the frame 104 using a suitable fixing means such as screw or bolts. The plate 1 12 comprises an electrically conducting material. The plate 1 12 comprises a slot 1 14 which extends from one edge of the plate 1 12 into the body of the plate 1 12. The slot 1 14 has an open end 1 14a and a closed end 1 14b and comprises an open end portion (labelled A in Figure 2) extending from the open end 1 14a, and a closed end portion (labelled B) at or near the closed end 1 14b. In some embodiments, there may be two or more slots in the plate 1 12 arranged to each receive a separate part of the fastening member (e.g. a separate projection 1 18 as described later). In other embodiments, the plate may be split into two or more separate plates, each comprising a slot arranged to receive a respective projection.

As can be seen in the top view shown in Figure 2b, the first frame member 108 comprises a lip 1 16 that runs around the periphery of the slot 1 14. The first fastening member 106 comprises a projection 1 18 which extends from the body of the window 104 as shown in Figure 2b. In this embodiment, the projection has a generally cylindrical shape, but in other embodiments may be any other suitable shape, such as a cuboid. The projection 118 comprises an upstanding wall that extends away from the window 102. The projection 1 18 comprises an engagement portion 120 which extends outwards around an end of the projection 1 18 opposite the point where it is attached to the window 102. The engagement portion 120 forms a shoulder around the upstanding wall of the projection 1 18. The engagement portion 120 is arranged to engage with the lip 1 16 to fasten the window in the frame, e.g. the lip 1 16 forms a rail around the periphery of the slot which engages with the engagement portion 120. The projection 1 18 and slot 1 14 therefore form interlocking male and female parts which when engaged resist being separated to prevent the window 102 being opened. In other embodiments, the slot 1 14 and the projection 118 may have a different shape to that described, but will still provide the same function so long as the projection 1 18 is shaped in such a way as to engage with the slot 1 14. For example, in some embodiments, the engagement portion may comprise a recessed portion of the projection 1 18 arranged to engage with the lip 1 16.

In some embodiments, the frame member 106 may instead comprise a projection and the fastening member may comprise a slot arranged to receive and engage with the projection.

The open position of the window is shown in Figures 2a and 2b. When the window 102 is in the open position (i.e. not received by, or fastened to, the frame 104) the first frame member 108 and the first fastening member 106 are spaced apart in a direction indicated by the arrow marked X and also in the direction marked Y in the figures. As the window is closed (i.e. pushed or hinged towards the frame 104) the first fastening member 106 is moved towards the first frame member 108 in the X direction. The closed position of the window is shown in Figures 2c-2f. In this position the window has been pushed shut so that it is received in the frame, but is not yet fastened to the frame. The first fastening member 106 is moved so that it is aligned with the first frame member 108 (i.e. the engagement portion 120 is aligned with the lip 1 16 in the X direction). A known, prior art, sensor would detect that in this position the window is closed, but would not be concerned with determining that the window is not yet fastened into the frame. In this invention however, advantageously it is determined whether there is an engagement between the first fastening member 106 and the first frame member 108, thereby determining when the window is actually secured in the frame. The process of fastening the window 102 into the frame 104 is shown in Figures 2e-2j . As can be seen in Figure 2e and 2f the first fastening member 106 is moved towards the first frame member 108 in the direction of the arrow marked Y in the Figures. This motion is caused by the operation of the actuator to fasten the window 102 into the frame 104. Figures 2e and 2f show the first fastening member 106 moved partly towards the first frame member, but in a position where there is yet any engagement and so this pair is still in the unfastened position.

Figures 2g and 2h show the first frame member 108 and the first fastening members in the fastened position. In this position the projection 1 18 has entered the open end portion 1 14a of the slot 1 14 and the engagement portion 120 is engaged with the lip 1 16. In some embodiments, this corresponds to an actuator in the form of a handle having been rotated through only part of its range of motion. In this position, the first fastening member 106 and the first frame member 108 resist movement apart in the X direction and so the window 102 cannot be separated from the frame 104.

As the user continues to operate the actuator 105, the first fastening member 106 continues to move in the Y direction such that the projection 1 18 continues to move further into the slot 1 14. This movement continues until the projection is fully received into the slot and reaches the end portion 1 14b of the slot 1 14 as shown in Figure 2i and 2j . In this position the first fastening member 106 and the first frame member 108 are fully engaged. In some embodiments this corresponds to an actuator in the form of a handle having been rotated through substantially all of its range of movement, which in some embodiments may be approximately 90 degrees from its starting position. In this position, the window 102 is even more securely fastened into the frame 104 because the projection has moved all of the way down the slot. In the described embodiment, the lip 1 16 comprises an insulating member 122 arranged to electrically insulate the first frame member 108 from the first fastening member 106 until the first fastening member 106 has moved so that it is fully received by the slot. The insulating member 1 12 comprises an electrically insulating material covering the lip 1 16 at the open end portion of the slot 1 14 and extending along the lip 1 16 towards the closed end portion of the slot 1 14. The insulating material is arranged to create an electrical contact between the first frame member 108 and the first fastening member 106 only when the projection 1 18 is fully received in the slot 1 14 (e.g. when the projection 1 18 reaches, and contacts, the end portion B) as shown in Figure 2i and 2j . This is advantageous because the sensor 1 10 is able to determine when there is a very firm engagement between the slot 1 14 and the projection 1 18 and so the sensor can determine that the window 102 is securely fastened into the frame 104. In other embodiments, there may be no insulating material. In this case the sensor 110 is arranged to detect when the first fastening member 106 first makes contact with the first frame member 108. In this case, there is still engagement between the slot 1 14 and the projection 1 18 to fasten the window 102 into the frame 104.

In order to unfasten and open the window 102 the reverse of the process described above and shown in Figure 2 is carried out by the user. When the fastening mechanism is unfastened by operation of the actuator, the projection 1 18 moves back out of the slot, in the opposite direction to that indicated by the arrow Y, until it is disengages from the slot. Once the projection is no longer in electrical contact with the slot (i.e. it is in contact only with the insulating material 122), the sensor determines that the fastening member is no longer in the fully engaged position. The projection is then moved in the opposite direction to the arrow X to open the window.

An alternative embodiment of the invention is shown in Figures 3 and 4. Figure 3 shows a window assembly 200 having a window 203 received by a frame 204 as in the embodiment described above. The window assembly 200 similarly comprises a fastening mechanism having a first fastening member 206 that is provided on the window 202, and a first frame member 208 that is provided on the frame 204. The first fastening member 206 is moveable between an unfastened position and a fastened position in which it is arranged to engage with the first frame member 208. When the first fastening member 206 is in the fastened position, the window 202 is fastened into the frame.

The window assembly 200 of this embodiment comprises a sensor 210 arranged to detect when the first fastening member 206 is in the fastened position and engaged with the first frame member 208. In this alternative embodiment, the sensor 210 does not rely on an electrical connection between the first fastening member 206 and the first frame member 208 as in the embodiment described above. The sensor instead relies on a switch (e.g. a mechanical switch) located within the first frame member 208 as described below.

The fastening mechanism of the alternative embodiment is shown in detail in Figures 4a-4j . The first frame member 206 and first fastening member 208 have corresponding features to those of the first frame member 106 and first fastening member 108 as described above. Features that are common to both embodiments have been labelled accordingly in Figure 4. The first frame member 208 does not include the insulating member 122 because the control of an electrical contact is not required in this embodiment. The embodiment of Figures 3 and 4 differs from that of Figures 1 and 2 by the inclusion of a switch 230 in the first frame member 208. In the described embodiment, the switch 230 comprises an actuator 232 in the form of a plunger. In other embodiments the switch may be in the form of a rocker switch or the like. The switch is arranged to detect when the first fastening member 206 is in the fastened position and engaged with the first frame member 208. As shown in Figures 4g-4j , the switch is moved from an open position to a closed position by the action of the projection 1 18 moving in the slot 114. In Figure 4g and 4h the projection 1 18 has entered the slot 1 14, but has not yet made contact with the switch actuator 232. As the projection moves down the slot during the process of fastening the window into the frame as described above, the projection 1 18 makes contact with the actuator 232 and moves the switch 230 from the open to the closed position. As the switch is located in the end portion 1 14b of the slot 1 14, the actuator 232 is only actuated when the projection has reached the end portion 1 14b of the slot 1 14. This therefore provides an indication that the projection has reached the end portion of the slot 1 14 and therefore indicates that the first fastening member 208 is fully received in the slot 1 14. The location of the switch actuator in this way therefore serves the same function as the insulating material 122 of the embodiment described in Figure 2 - it enables the sensor 210 to determine when the first fastening member 208 is fully received in the slot 1 14 and the window 204 is firmly fastened into the frame 202.

In other embodiments, the switch 230 may be positioned in a different location in the slot 1 14 to provide an earlier indication of when the first fastening member 208 is engaged with the first frame member 206. The actuator may for example be located approximately half way along the slot 1 14 or at the open portion of the slot 1 14a. In some embodiments, the switch may move along a different axis to that shown in Figure 4, e.g. the switch may move along an axis in the X direction. In this embodiment, the switch may comprise a sloped actuator extending into the slot 1 14 which is activated when the projection 1 18 moves into the slot. In the embodiment shown in Figure 4, the switch 230 is in the form of a micro-switch that is disposed within the body of the first frame member 208. In this embodiment, the body of the first frame member 208 is provided with a hollowed-out portion (shown by the broken lines in Figure 4) to provide an aperture in which to house the micro-switch. The sensor 210 may be connected to the switch 230 by one or more electrically conducting elements, such as a wire. As with the embodiment described in Figure 1 and 2, the wire may be hidden in the body of the frame 102 so that they are not accessible or visible to the user.

A window assembly 300 according to a second aspect of the present invention is shown in Figure 5. The window assembly 300 has similar components to that of the window assembly 100 in Figure 1. The window assembly 300 differs from that of Figure 1 by having both a first window 302a and a second window 302b which are both received by the frame 304. In this embodiment, a third window 302c is included in the frame. This window is not arranged to be openable and so does not include a fastening mechanism in order to fasten it into the frame, but is instead permanently fixed to the frame 302. In other embodiments there may be more than two openable windows received in the frame 302 and any number of non-openable windows.

The first window 302a comprises a first fastening mechanism and the second window comprises a second fastening mechanism which operates independently of the first. Each of the first and second fastening mechanisms comprises the same components as mentioned in relation to the embodiment described in Figure 1. In particular, the first fastening mechanism comprises a first fastening member 306a on the first window 302a moveable between an unfastened position and a fastened position. In the fastened position, the first fastening member 306a of the first fastening mechanism is arranged to engage with a respective first frame member 308a on the frame 304 to fasten the first window 302a in the frame 304. The first fastening mechanism further comprises a second fastening member 307a on the first window 102a moveable between an unfastened position and a fastened position. In the fastened position, the second fastening member 307a of the first fastening mechanism is arranged to engage with a respective second frame member 309a on the frame 304 to fasten the first window 302a in the frame 304. The first fastening mechanism is operated by a first actuator 305a. The second fastening mechanism comprises a first fastening member 306b on the second window 302b moveable between an unfastened position and a fastened position. In the fastened position, the first fastening member 306b of the second fastening mechanism is arranged to engage with a respective first frame member 308b on the frame 304 to fasten the second window 302b in the frame 304. The second fastening mechanism further comprises a second fastening member 307b on the second window 102a moveable between an unfastened position and a fastened position. In the fastened position, the second fastening member 307b of the second fastening mechanism is arranged to engage with a respective second frame member 309b on the frame 304 to fasten the second window 302a in the frame 304. The second fastening mechanism is operated by a second actuator 305b.

In this embodiment, the first and second fastening mechanisms are arranged to operate independently of each other, but in other embodiments they may be operated by a single actuator. The window assembly 300 comprises a sensor arranged to detect when both of the first fastening members 306a, 306b and second fastening members 307a, 307b are in the fastened position and engaged with each of the respective first frame members 308a, 308b, 309a, 309b.

As shown by the broken lines in Figure 5, in each of the first and second fastening mechanisms, the first fastening member 306a, 306b is electrically connected to the second fastening member 307a, 307b. As with the window assembly 100 described above, this connection is provided by a linkage arranged to move the fastening members 306a, 306b, 307a, 307b of each fastening mechanism conjointly, or is provided by an electrically conducting element, such as a wire, connecting the first fastening members 306a, 306b to the second fastening members 307a, 307b. A further electrical connection is provided between the first frame member 308a of the first fastening mechanism and the first frame member 308b of the second fastening mechanism as again shown by the broken line connecting them in Figure 5. This electrical connection can again be provided by an electrically conducting element such as a wire. As with previously described embodiments, any such wire may be hidden in the body, or on the surface, of the frame 304.

As in the window assembly 100 shown in Figure 1 , the first and second frame members 306a, 307a of the first fastening mechanism are electrically isolated when the first, the second, or both of the first and second fastening members 306a, 307b of the first fastening mechanism are in the unfastened position. Similarly, the first and second frame members 306b, 307b of the second fastening mechanism are electrically isolated when the first, the second, or both of the first and second fastening members 306b, 307b of the second fastening mechanism are in the unfastened position.

A sensor 310 is arranged to detect whether there is an electrical connection between the second frame member 309a of the first fastening mechanism and the second frame member 309b of the second fastening mechanism. The sensor 310 is therefore arranged to determine that both of the fastening members of both the first and second fastening mechanisms are engaged and both of the first and second windows 302a, 302b are fastened in the frame 304. A single sensor is therefore able to determine the state of both windows and an indication is only provided when all of the fastening members have been engaged. The sensor 310 may comprise an electrically conducting element connecting the sensor 310 to the second frame member 309a of the first fastening mechanism and electrically conducting element connecting the sensor 310 to the second frame member 309b of the second fastening mechanism. The electrically conducting elements may be wires. Each of these wires may be arranged within a body of the frame 302 so that they are not accessible or visible during use. The sensor 310 may also be arranged within the body of the frame so that it is not visible or accessible to the user. Another embodiment of a window assembly 400 is shown in Figure 6. In this embodiment the frame 404 comprises a first window 402a and a second window 403b each having a separate fastening mechanism. In this embodiment the first fastening mechanism comprises a first fastening member 406a and a first frame member 408a. The second fastening mechanism comprises a first fastening member 406b and a first frame member 408b. In this embodiment a first switch is provided at the first frame member 408a of the first fastening mechanism. The switch has a closed position when the first frame member 408a and the first fastening member 406a of the first fastening mechanism are engaged. The switch has an open position when the first frame member 408a and the first fastening member 406a of the first fastening mechanism are not engaged. A similar switch is provided at the first frame member 408b of the second fastening mechanism. This second switch similarly has a closed position when the first frame member 408b and the first fastening member 408b of the second fastening mechanism are engaged. It also has an open position when the first frame member 408b and the first fastening member 406b of the second fastening mechanism are not engaged. The first and second switches provided at the first and second fastening mechanisms operate in the same manner as that described in the embodiment of Figure 3 and 4. All of the features and modifications relating to that embodiment apply equally to the embodiment of Figure 6. A sensor 410 is arranged to determine when both switches are in the closed position, thus determining that both the first and second window 402a, 402b are secured in the frame 404. This allows the sensor to provide an alert when either of the windows 402a, 402b are not secured in the frame 404 and they window assemble 400 is not secured.

In all of the previously described embodiments, the sensor is further arranged to communicate the determination of whether either the window of Figure 1 or 3, or the first and second windows of Figure 5 or 6, are secured in the frame, to a processing unit. The processing unit is arranged to provide an indication that the windows or doors are, or are not, secured in their respective frame. The communication may be provided by a wireless transceiver provided at the sensor. In such an embodiment, the processing unit may be part of a security system or heating control system that is arranged to manage the security system or heating system in the building in which the window assembly is installed. A sensor according to this invention may be provided at each window or door assembly of a building, with each sensor arranged to communicate the state of the window or door to the processing unit. The processing unit is therefore able to centrally determine whether all of the windows or doors in the building are not only closed, but are also secured to their respective frame. The processing unit may provide an indication such as a visual or audible signal or alarm to indicate that one or more of the windows is not secured in the frame. This advantageously allows the user to determine the state of all of the window or doors in a building from one indicator. The user may for example be alerted by the visual or audible signal that one of the doors or windows has not been secured, rather than having to check all of the windows and doors individually.