WO2000004748A1 - Window security device - Google Patents

Abstract

A window security device is in the form of a glass pane assembly comprising a first layer of glass (11), a second layer of glass (19) and two or more arrays of electrical conductors (A, N) sandwiched between the first (11) and second (19) layers of glass. An electrical potential difference is provided between the conductors of one of the arrays (A) and the conductors of another of the arrays (N).

Description

WINDOW SECURITY DEVICE

Field of the Invention

The following invention relates to a window security device. More particularly, though not exclusively, the invention relates to a laminated window pane having electrically energised conductors therein, which conductors are housed within the glass structure, though would be exposed upon fracture of the window pane, thus presenting a shock-hazard to a potential burglar. In the context of the present invention, the term "window" is intended to include within its scope a window type glass panel of a door.

Disclosure of the Invention

There is disclosed herein a glass pane assembly comprising: a first layer of glass, a second layer of glass, two or more arrays of electrical conductors sandwiched between the first and second layers of glass, and means to provide an electrical potential difference between the conductors of one of said arrays and the conductors of another of said arrays.

One of the arrays of conductors typically includes a plurality of conductors, in between individual ones of which, individual ones of the conductors in another array are situated.

The assembly may be fitted to a frame.

Preferably, the means to provide said electrical potential difference includes a connection strap associated with one of the arrays and another connection strap associated with another of said arrays, the respective connection straps being connectable to a source of electrical potential difference. The source of electrical potential difference will typically be a remotely located energiser.

The connection straps may be housed in said frame.. The frame may be formed of electrically conductive material and be electrically connected to one of said arrays.

The assembly may further comprise means enabling it to be wired to a security alarm. Preferably, the second layer of glass is toughened glass otherwise known as

"safety glass".

In one embodiment, a plastics lamina is sandwiched between said first and second glass layers, said two or more arrays of conductors being embedded in or otherwise associated with said plastics lamina. In another embodiment air is entrapped between the first and second layers with the electrical conductors. Any such air may be evacuated from a space defined between the first and second layers of glass.

The first and second layers of glass each include a periphery, which peripheries may be exploited to maintain a close association between the first and second layers of glass. The association may be achieved by way of double-sided adhesive tape at the periphery of the first and second layers.

Typically, the double-side adhesive tape is high bonding strength adhesive tape made by the Minnesota Mining and Manufacturing Company and marketed under the trademark VBH (very high bond) tape. The first layer of glass may be one of the layers in a laminated glass pane.

Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic cross-sectional view of a window security device,

Fig. 2 is a schematic elevational view of the window security device of Fig. 1 showing the layout of electrical conductors therein, and

Fig . 3 is a schematic cross-sectional view of another window security device. Fig. 4 is a schematic elevational view of yet another window security device. Fig. 5 is a schematic cross-sectional view of the window security device of Fig. 4.

Detailed Description of the Preferred Embodiments In Figs. 1 and 2 of the accompanying drawings there is schematically depicted a laminated glass window pane 10. Pane 10 includes a first glass lamina 11 and a second glass lamina 12 between which a plastics lamina 13 is sandwiched. Embedded within the plastics lamina 13 are two arrays of conductors A and N. Conductors A are active conductors whereas conductors N are neutral. The active conductors are electrically connected at their respective opposed ends to a pair of connection straps 14 and 16. Connection straps 14 and 16 are connected by a common electric wire to an active input terminal 18A.

The neutral conductors are connected at their respective opposed ends to one of two connector straps 15 and 17. Connection straps 15 and 17 are connected by a common wire to a neutral terminal 18N, which is in turn earthed to ground. The connection straps 14, 15, 16 and 17 are typically located within a window frame (not shown). The common wires leading to the terminals 18A and 18N might also be housed within the window frame. An energiser of the type used to energise an electric fence can be connected to terminal 18. One such known type of energiser is provided by Brent- Alkay securing fence systems and provides a potential difference of 7,500 Volts.

Once the security window pane is installed into a factory, office, building or other premises, the glass layers 11 and 12 isolate the energised conductors A and N and accordingly, one can touch either of the outer glass surfaces without suffering an electric shock. However, once the window pane 10 is shattered or cracked, the conductors A and N might become exposed to a potential burglar, thus presenting him with an electric impulse or shock hazard. The conductors carry a high voltage, low amperage impulse current which ensures maximum discomfort for the burglar without the danger of injury. This complies with the Australian Standard governing electric security fences, Australian Standard No. AS3016.

The method of producing the laminated structure of pane 10 might include firstly providing a glass layer 12, then laying the arrays of conductors A and N upon the glass surface. The plastics lamina 13 might be either applied in sheet form over the metal conductor straps or poured thereover in a molten state. The molten plastics material might either be heated into its molten state or might be molten at room temperature and capable of setting as a result of a catalytic reaction with a chemical catalyst. The second glass layer 11 is then placed upon the conductors A and N and the lamina 13. Heat or other known processes can then be adopted to secure the laminated layers to form the laminated glass pane 10.

Also associated with the glass pane 10 might be other conductors associated with a security alarm system. For example, a fine, readily fractured electrical conductor might accompanying the high voltage conductors A and N. Such a readily fractured conductor would undergo a rapid change of resistance should it fracture, thus sending an appropriate trigger signal to a security system.

Alternatively or additionally a vibratory switch might be mounted on the glass pane 10 and associated with a security alarm system, such that vibration of the switch caused by breakage or attempted breakage of the glass pane sends a trigger signal to the security system.

The energiser can be associated with the security system such that it is only energised when the security system has been armed. For a security system utilising a vibratory switch mounted on the glass pane, the trigger signal sent by the vibratory switch when the glass is broken or attempted to be broken may be used to energise the energiser. In such an arrangement, the energiser will only become energised when the glass pane is under attack, presumably by a potential burglar. This arrangement further enhances the safety of the system and reduces power usage.

In Fig. 3 of the accompanying drawings there is schematically depicted another window security device. In the embodiment shown in Fig. 3, a laminated glass pane 20 includes an outward facing glass layer 11, a plastics lamina 13 and an inner glass layer 12. Situated upon the outer glass layer 11 are arrays A and N of electrical conductors with conductors A being active and conductors N being neutral. A layer of toughened glass 19 also known as "safety glass" is positioned upon the conductors A and N providing an air space 20 between the toughened glass 19 and the outer layer 11 of the laminate 20. The air space 20 might be evacuated so as to provide a vacuum between toughened glass 19 and the outer layer 11.

A double-sided adhesive tape 21 extends around the periphery of the window security device between the safety glass 19 and the outer layer 11. This double sided adhesive tape might be of the type manufactured by 3M and marketed under the trademark VHB (very high bond) tape.

The window security device of Fig. 3 should be installed such that the toughened or safety glass 19 faces outwardly of the building. That is, any attempt by a burglar to break the glass must be via toughened layer 19. It is envisaged that any breakage of toughened glass 19 will result in a complete shattering of that layer into small fragments thus exposing the electrically energised conductors A and N, thus presenting the burglar with an electric impulse or shock hazard.

The plastics lamina 13 of the laminated pane 20 may advantageously be formed of four layers of plastic instead of the usual single layer of most laminated panes. A suitable laminated pane 20 can be manufactured of A Grade Bandit Resistant Laminated Glass. Such a laminated pane 20 will be extremely difficult to penetrate. The use of A Grade Toughened Glass for the outwardly facing glass layer 19 and A Grade Bandit Resistant Laminated Glass on the inwardly facing laminated pane 20 allows shattering of the outwardly facing layer 19 to expose the conductors A and N, whilst inhibiting fracture of the inwardly facing pane 20 so as to still maintain the integrity of the window.

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, the security alarm system might be associated with the conductors A and N, rather than being associated with a separate conductor or conductors.

As a further modification of the disclosed invention, the outer layer 19, instead of being formed from toughened glass, might be ordinary window glass which might splinter away from the laminated pane 20, thus exposing the conductors A and N.

An electric shock will only be inflicted on a potential burglar if the exposed conductors A and N are bridged, or if the active conductor A and another surface connected to ground (which the neutral conductors N are earthed to) are bridged. A more intensive shock will be delivered if the conductors A and N are bridged directly rather than via ground. To increase the chance of bridging the conductors A and N, a frame in which the pane 10 of Figure 1 or the glass pane 20 and glass layer 19 is mounted may be electrically connected to the array of neutral conductors N, thus forming part of the neutral array. The frame will necessarily be formed of electrically conductive material, typically aluminium. Such a modified version of the invention is depicted in Figures 4 and 5.

The modification of Figures 4 and 5 depicts the glass assembly 40 of the embodiment of Figure 3 encased in an aluminium frame 50, and typically separated therefrom by a layer of insulation 51. As is best seen in Figure 4, the frame 50 is connected to the neutral conductors N and to the energiser neutral terminal 18N (to ground). The frame 50 is insulated from the active conductors A which are connected to the energiser active terminal 18A. When the glass assembly 40 is intact, touching of the frame 50, which is connected to the neutral array of conductors N does not present a shock hazard, as the active conductors A remain isolated. Upon shattering of the glass layer 19, however, and exposure of the active conductors A, a burglar grasping or otherwise touching the frame 50 and an active conductor A will be inflicted with a shock.

Claims

1. A glass pane assembly comprising: a first layer of glass, a second layer of glass, two or more arrays of electrical conductors sandwiched between the first and second layers of glass, and means to provide an electrical potential difference between the conductors of one of said arrays and the conductors of another of said arrays.

2. The assembly of claim 1, wherein a said array of conductors includes a plurality of conductors, in between individual ones of which, individual ones of the conductors in another array are situated.

3. The assembly of either of claims 1 and 2, fitted to a frame.

4. The assembly of any one of claims 1 to 3, wherein said means to provide said electrical potential difference includes a connection strap associated with one of the arrays and another connection strap associated with another of said arrays, the respective connection straps being connectable to a source of electrical potential difference.

5. The assembly of claim 4, wherein the source of electrical potential difference is a remotely located energiser.

6. The assembly of claim 4, when appended to claim 3, wherein said connection straps are housed in said frame.

7. The assembly of claim 3 , wherein said frame is formed of electrically conductive material and is electrically connected to one of said arrays.

8. The assembly of any one of claims 1 to 7, further comprising means enabling it to be wired to a security alarm.

9. The assembly of any one of claims 1 to 8, wherein the second layer of glass is toughened glass otherwise known as "safety glass" .

10. The assembly of any one of claims 1 to 9, wherein a plastics lamina is sandwiched between said first and second glass layers, said two or more arrays of conductors being embedded in or otherwise associated with said plastics lamina.

11. The assembly of any one of claims 1 to 9, wherein air is entrapped between the first and second layers with the electrical conductors.

12. The assembly of any one of claims 1 to 9, wherein air is evacuated from a space defined between the first and second layers of glass.

13. The assembly of either of claims 11 and 12, wherein the first and second layers of glass each include a periphery, which peripheries are exploited to maintain a close association between the first and second layers of glass.

14. The assembly of claim 13, wherein said association is achieved by way of double-sided adhesive tape at the periphery of the first and second layers.

15. The assembly of any one of claims 11 to 14, wherein the first layer of glass is one of the layers in a laminated glass pane.