Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1987-03-17
1988-12-13
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
340544, G08B 1300, G08B 1320
Patent
active
047914106
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an alarm system which includes at least one signal transmission line for providing an indication of damage to the line and/or an attempt to interfere with it, said line being suitable for incorporation in a net-structure, for example a barrier net-structure for denying foreign objects, such as underwater vessels, frogmen, and the like, access to underwater passageways, channels, etc.
Barrier net-structures intended for the aforesaid purpose are constructed to take-up extreme tensile forces. Nevertheless it is desirable that they are provided with some form of alarm system which will indicate the successful passage, e.g. of a submarine through the net, in spite of all precautions, or signal an alarm should the net be interfered with in some way. Among other things, the anchorage of the net-structure to the bed of the waterway should be protected with such an alarm system.
There has been proposed in the art an alarm facility in which a closed circuit current is passed through an electric conductor incorporated in the net. Although this arrangement functions satisfactorily enough in general, it is encumbered with a number of disadvantages. For example, the arrangement is highly sensitive, especially when used underwater, and is liable to give false alarms, due to its sensitiveness to all forms of disturbance. In addition, repairs to the net-structure require it to be lifted from the water. Another drawback is that when using large net-structures comprising several sections, or a plurality of small net-structures, the task of laying the conductor or conductors in the net(s) becomes relatively complicated. The requisite alarm centre also becomes relatively complicated since in the case of an alarm, it must be capable of indicating which net-section was responsible for the alarm being given. It is impossible to indicate the exact position in any event. Moreover, the costs and time involved in investigating such false alarms are quite considerable. Minor faults in the insulation of an electrical system must be repaired immediately, however. It is also possible to manipulate electrical systems with the aid of shunt couplings, e.g. at the shoreside connections.
SUMMARY OF THE INVENTION
The main object of the invention is to provide an alarm system with which at least the aforesaid drawbacks are removed and while affording a particular advantage when used in barrier net-structures for protecting water passageways can also be used effectively in other connections--even on land.
This is achieved in accordance with the invention by replacing or complementing the electrical conductor used in prior art net-structures with a flexible tube containing a coloured indicating agent in liquid, gas, or powder form, this tube being connected to a signal-emitting sensor constructed to detect changes in pressure and/or the state of flow in the tube. The indicating agent is therewith under pressure in the tube and in the event of a fracture or rupture will flow from the tube and indicate the location of said fracture.
Such a system can be extended to any extent without becoming complicated. The system is also extremely failsafe and in the event of a fault can be repaired readily, even under water, and will indicate visually the precise location of the fault in question, or the location at which the net has been perforated, in the event of such an occurrence.
In addition to the aforesaid alarm function and to the advantage of being not-readily manipulated, the powerful action of the pressurized indicating agent as it is ejected from a fractured tube in the event of an attempt to force an entry through the net has a pronounced shock effect which can give the impression of an explosion. The indicating agent used may also be one which will totally obstruct the vision of those in the vicinity thereof and therewith render further activities impossible.
When the alarm system is to be used under water, the indicating agent shall have a density lower than that of water, so that
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patent: 4305143 (1981-12-01), Simms et al.
patent: 4688024 (1987-08-01), Gadde
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Mullen Jr. Thomas J.
Safe Bridge AB
Swann III Glen R.
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