GB2128649A

GB2128649A - Barriers with alarm device

Info

Publication number: GB2128649A
Application number: GB08228599A
Authority: GB
Inventors: Barrymore George Giddings; Gerald Arthur Giddings
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-10-06
Filing date: 1982-10-06
Publication date: 1984-05-02

Abstract

A barrier 10 comprises top and bottom beams 12, 14 and stretcher bars 16 all formed of tubular materials and inter-communicating to provide an interior fluid-tight chamber 20 extending throughout the structure of the barrier. The chamber is sealed and pressurised with air via a gas admission valve 32. A sensor 26 is responsive to pressure changes within chamber 20 and is arranged to energise an alarm 30 when pressure falls, whereby the alarm is actuated by cutting or bending the barrier. <IMAGE>

Description

SPECIFICATION Barriers This invention relates to barriers such as window grills, security fencing, gates, security cages and other structures intended to prevent or inhibit access to a building, or a part of a building or some other structure or area, or to provide a comparable function. The invention also relates to a method of detecting interference with such a barrier, for example by an intruder who may attempt to cut, bend or otherwise damage the barrier so as pass through the barrier or to enable articles to be passed through it.

The method and apparatus of the invention may also be applicable to structures other than barriers in which detection of weakening or failure or damage may be desirable, such as the legs of radio masts, and other large steel structures.

In the case of barriers currently available, the usual material for the construction is steel and with the advent of diamond-impregnated disc cutters the problem has arisen that it is now extremely difficult to provide a barrier which cannot be cut by an intruder. Other methods of producing an access opening through a barrier include the use of jacks to spread open the bars of the barrier, and the use of flame cutters as an alternative to disc cutters.

Presently available methods of detecting intruders intent on interfering with such a barrier include the use of photo-electric devices, trip wires, laser beams and weight-detecting pressure pads. However, none of these methods has proved entirely satisfactory, in that the devices are either visible to the intruder and therefore avoidable, or are expensive to install and maintain, or are only a supplement to the provision of expensive foot patrols.

An object of the present invention is to provide a method and apparatus for detecting interference with a barrier such as the weakening or failure or damage or attempts to bend or cut such a barrier, and offering improvements in one or more respects in relation to currently available means for this purpose.

According to the invention there is provided a method of detecting interference with a barrier comprising the steps of providing a barrier having an interior fluid-tight chamber, and providing a sensor responsive to a pressure change in said chamber and connected to a warning device, and establishing a fluid pressure difference between the chamber and atmospheric pressure, and sensing by means of said warning device a pressure change caused by damage to the barrier.

Preferably, the fluid provided in the chamber is a gas, the gas preferably being air, and the pressure difference between the chamber and atmospheric pressure being established by raising the fluid pressure in the chamber above atmospheric pressure.

According to another aspect of the invention there is provided a barrier having an interior fluidtight chamber, the chamber being adapted to be connected to a sensor responsive to pressure changes in said chamber, the arrangement being such that a fluid pressure difference may be established between said chamber and atmospheric pressure, and a warning device may be actuated by a sensor connected to the chamber upon a pressure change occurring consequential on damage to the barrier.

Preferably, the pressure sensor is responsive to pneumatic pressure changes in said chamber. The sensor may be arranged to be actuated when the pressure in the chamber falls from an initial pressure above atmospheric pressure.

Alternatively, the sensor may be arranged to respond to a rise in pressure within the chamber from an initial pressure below atmospheric pressure. The sensor may be in the form of an electrical pressure switch arranged to open orto close at a predetermined pressure.

The method and apparatus of the invention is also applicable to structures other than barriers, including steel structures such as the legs of radio masts and the like where there is a requirement to detect interference with the structure by saboteurs.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which there is shown an elevation view of a barrier in combination with an associated pressure sensor and a warning device.

As shown in the drawing, a barrier 10 comprises top and bottom beams 12, 14 respecitvely and seven stretcher bars 1 6 extending between the top and bottom beams.

The top and bottom beams 12, 14 and the seven stretcher bars are all formed of tubutar materials, welded together to form a strong unified structure, with the ends 1 8 of the stretcher bars open and communicating with the interiors of the top and bottom beams, so that the entire barrier structure has an interior fluid-tight chamber 20 extending throughout the structure of the barrier.

The joints 22 between the stretcher bars and the top and bottom beams are carefully welded to provide fluid-tight joints, and the ends 24 of the top and bottom beams 12, 14 are likewise sealed in a fluid-tight manner.

At one end of top beam 12 there is provided a sensor 26 in the form of a pressure-responsive electrical switch connected by electrical conductors 28 to an electrical source (not shown) and a warning device or alarm 30.

Sensor 26 is arranged to be responsive to pressure changes within chamber 20, and to complete the electrical circuit containing alarm 30 and the electrical source, so that the alarm is energised.

A gas admission valve 32 is provided adjacent sensor 26 to allow chamber 20 to be pressurised with air or other gas. The admission valve may include a quick attach coupling whereby security personnel can periodically and quickly attach a pneumatic coupling to the valve and verify the pressure within chamber 20 and top it up as necessary.

In-use, barrier 10 is initially pressurised to a desired pressure with air and sensor 26 is arranged to close its switch and complete the electrical circuit and energise alarm 30 upon the pressure falling significantly from its initial value.

When an intruder attempts to interfere with the barrier, for example by cutting or bending the stretcher bars 1 6 or in any other way damaging the barrier so that the air or other gas can escape from chamber 20, sensor 26 immediatelv detects the drop in gas pressure within the chamber and energises the alarm.

Among the advantages provided by the embodiment of the invention described above are its simple form, relatively low cost, and the fact that the features of it which render it a warning device can be made practically invisible, so that the barrier appears to be an absolutely normal window grill or the like and provides the intruder with no warning of its security aspects.

Maintenance of the warning system is relatively simple by means of the quick attach admission valve 32, as described above. Moreover, the device provides positive warning of interference with the barrier structure itself, whereas previously available devices have served only to detect the presence of intruders and have been liable to give false alarms when actuated by prowling animals and the like.

Among modifications which could be made in the above embodiment without departing from the scope of the invention are the provision of short welded-on open-ended lengths of the material forming stretcher bars 16, these lengths being secured on the outer sides of the top and bottom beams 12, 14 in alignment with the respective stretcher bars so as to give the barrier structure the appearance of a conventional barrier structure in which the stretcher bars extend through openings in the top and bottom beams. The whole barrier structure need not be employed to provide chamber 20. Only a portion of the barrier need be employed for this purpose if desired. For example, some of the stretcher bars could be solid if desired, or only the top and bottom beams could provide the pressure chamber.The dimensions of the parts of the barrier making up the pressure chamber can, of course, be chosen freely two suit the structural needs of the particular situation. The barrier may be constructed of any suitable material such as the various steels which are currently used for the construction of barriers, bearing in mind that in many cases it is desirable for a barrier according to the invention to be indistinguishable from a conventional barrier.

Alternatively, any other suitable material may be employed which is capable of providing the necessary pressure chamber, including even plastics materials which, though they may apparently represent little in the way of a structural barrier, when used in a barrier according to the invention provide a significant degree of protection, and it is possible that the present invention by thus enabling the use of cheaper materials may significantly reduce the cost of security barriers.

Claims

1. A method of detecting interference with a barrier comprising the steps of providing a barrier having an interior fluid-tight chamber, and providing a sensor responsive to a pressure change in said chamber and connected to a warning device, and establishing a fluid pressure difference between the chamber and atmospheric pressure, and sensing by means of said warning device a pressure change cause by damage to the barrier.

2. A method according to claim 1 wherein said fluid provided in said chamber is a gas.

3. A method according to claim 2 wherein said gas is air.

4. A method according to any one of the preceding claims wherein said pressure difference between the chamber and atmospheric pressure is established by raising the fluid pressure in the chamber above atmospheric pressure.

5. A barrier having an interior fluid-tight chamber, the chamber being adapted to be connected to a sensor responsive to pressure changes in said chamber, the arrangement being such that a fluid pressure difference may be established between said chamber and atmospheric pressure, and a warning device may be actuated by a sensor connected to the chamber upon a pressure change occurring consequential on damage to the barrier.

6. A barrier according to claim 5 wherein said pressure sensor is responsive to pneumatic pressure changes in said chamber.

7. Apparatus according to claim 6 wherein said sensor is arranged to be actuated when the pressure in the chamberfallsfrom an initial pressure above atmospheric pressure.

8. A barrier according to claim 5 or claim 6 wherein said sensor is arranged to respond to a rise in pressure within the chamber from an initial pressure below atmospheric pressure.

9. A barrier according to any one of claims 5 to 8 wherein said sensor is in the form of an electrical pressure switch arranged to open or to close at a predetermined pressure.

10. A method of detecting interference with a barrier substantially as described herein with reference to the accompanying drawing.

1 A barrier substantially as described herein with reference to the accompanying drawing.

12. A method of detecting interference with a barrier comprising any novel step or combination of steps disclosed in this application.

13. A barrier or other structure having an interior fluid tight chamber comprising any novel feature or combination of features disclosed in this application.