GB2277182A - Sea-going vessel warning system - Google Patents

Abstract

A warning system for a fishing vessel comprises a sonar transmitter 2 mounted on the hull of the vessel; a control unit 1 for energising the transmitter; and a compass 4 for applying heading signals to the control unit. The control unit includes an automatic encoding device 5 which, when the vessel is fishing, encodes energising signals applied to the transmitter with information concerning the length and the direction of the fishing nets, the encoded sonar signals being thus available to submarines. <IMAGE>

Description

SEA-GOING VESSEL WARNING The invention relates to a sea-going vessel warning system. Fatal accidents have occurred when submarines have fouled the nets of sea-going vessels which were fishing by trawl or drift net, for example.

Other accidents may occur if a submarine should inadvertently foul or interfere with surveying, diving, or cable-laying operations being carried out by a surface vessel. Furthermore, there is a danger that a submarine may surface too close to, or in the path of, a surface vessel such as a slow-moving yacht.

A object of the present invention is to provide a system for warning submarines of the hazard presented by the presence of a surface vessel which may be engaged in under-water operations.

According to the invention there is provided a warning system for a sea-going vessel which comprises a sonar transmitter mounted on the hull of the vessel; a control unit for energising the transmitter; and a compass for applying heading signals to the control unit, the control unit including an automatic encoding device which encodes energising signals applied to the transmitter with information concerning the presence of the vessel and any under-water activities associated with the vessel, the encoded sonar signals being thus available to submarines.

It is envisaged that the sonar signals may be continuously transmitted when the vessel is operational. However, one aspect of the invention provides that the sonar transmitter is part of a transponder which receives interrogating sonar signals from a submarine and which automatically responds by transmitting the coded information. The sequenced response of the transponder may comprise three parts: a first part which is a fixed length to enable a position fix of the vessel to be obtained; a second part which is coded to designate the type of fishing being carried out; and a third part designating the length and direction of the nets. Typically the sequence may be a five-part sequence in which the first three parts are followed by a repetition of parts two and three. The first part of the signal may be used to indicate that there is a pair of vessels fishing together.

The information may be conveyed by modulating the sonar signals in any convenient way. One method is to use the Morse code.

The invention will further be described with reference to the accompanying diagrammatic drawings, Figures 1 and 2 of which illustrate equipment to be installed on a sea-going vessel to implement alternative embodiments of the invention.

Referring to Figure 1 of the drawings, the equipment for installation on a sea-going vessel such as a fishing vessel comprises a control unit 1 for mounting in the wheelhouse; a sonar transmitter/receiver 2 to be mounted in the hull of the vessel near the keel amidships; and a disk drive unit 3. The control unit has three manual switches: SWl is a on/off switch; SW2 is a test switch; and SW3 is a gear up/gear down switch. Furthermore there are four indicator lamps: ILl is an on/off lamp; IL2 is a system fail lamp; IL3 is a proximity lamp; and IL4 is a gear fouled lamp. Within the control unit housing is a fluxgate compass 4 and an encoder 5 which includes an Erasable Programmable Read Only Memory (EPROM) unit 6.

In use, the control unit is switched on when required, tested by operation of the test switch to determine whether the failure lamp illuminates, and switched to the "gear down" condition when the fishing nets have been deployed. The transmitter/receiver unit 2 is then responsive to sonar interrogation signals at a predetermined frequency. A submarine in the vicinity, typically within 6 nautical miles or so, may issue such interrogation signals when it detects a vessel on the surface which might be fishing.

The unit is programmed, by virtue of the EPROM, to issue encoded energising signals to the transmitter/receiver 2 on detection of the interrogation signal. The encoded signals take an input from the fluxgate compass 4 to give directional information but otherwise consist of pre-programmed information concerning type of fishing being carried out and the length of the nets. The information is encoded in Morse code in a five-part signal: 1. a six second string of A's to enable the vessel to be position fixed by the submarine 2. a code indicating the type of fishing in progress (e.g. trawling or drift net fishing) 3. a code indicating the length of the net and the direction of the nets from the vessel 4. a repeat of 2 5. a repeat of 3 The sequence is repeated every two minutes or so for perhaps 20 minutes. The direction of the nets with respect to the heading of the vessel depends on the type of fishing being carried out. Thus, in trawling the nets extend behind the vessel with respect to its heading and in drift net fishing the nets extend ahead of the vessel with respect to its heading. The program in the EPROM takes this into account in giving a coded heading for transmission.

In this embodiment the net direction is given as one of eight numbers corresponding to the appropriate 45" segment of the compass. The code for part l of the sequence may be changed to a string of Morse code T's to signify pair trawling and in this case only the transponder of the starboard vessel would be activated to avoid confusion and to give a precise indication to the submarine.

The proximity lamp IL3 is illuminated when an interrogation signal is received from a submarine to give the fishing vessel warning. This may be augmented by an audible signal. However, for security reasons it may be desired to suppress these proximity indicators. The facility may be omitted.

Alternatively, it is envisaged that the system may employ two types of interrogation signals, one of which activates the proximity indicators in the vessel and the other of which does not, while otherwise operating the system identically. The submarine can then determine whether the vessel receives an indication of its presence or not.

The EPROM receives an input from a navigation position system (not shown) and is programmed to detect when the vessel has become stationary for, say 2 minutes. This suggests that the nets have become fouled. Accordingly, a "net fouled" signal is given to illuminate the lamp IL4 and also to initiate a sonar transmission for 10 seconds in every 200 seconds consisting of the letter "Z". This is to distinguish the vessel as a fishing vessel which is stopped in the water. This applies also to a drift net fishing vessel.

The purpose of the disk drive unit 3 is to provide a permanent record of interrogations and responses, together with the status of the nets, and the position and heading of the vessel etc. This is useful in order to verify the cause of any accidents.

Figure 2 shows a second embodiment of the invention which does not require interrogating sonar signals from a submarine.

In this second embodiment there is shown a warning system unit 20 to which there is input heading information from a fluxgate compass 22 corresponding to the fluxgate compass 4 of the first embodiment.

There is also provided an engine load sensor 24 which inputs engine load information into the system unit 20.

The unit 20 is powered from a power supply 26 and controls a sonar transmitter 28 which is mounted in the hull of the vessel near the keel amidships.

The unit 20 is provided with a green "on" lamp 30, which, when actuated, indicates that the unit is operative. There is also provided a red "system-fail" lamp 32 which is arranged to flash if a fault in the system occurs. An array of switches 34 is provided to indicate what mode of operation the vessel is working under; e.g., net fishing or trawl fishing if it is a fishing vessel. The switch array 34 may also include on/off and test switches (if required).

In operation, the unit 20 determines from the engine load sensor 34 whether or not the vessel is moving, and, if so, its approximate speed. The unit also determines the heading of the vessel from the fluxgate compass 22. Signals representing the vessel's heading and speed, and the mode of operation the vessel is working under, are sent to the sonar transmitter 28 and transmitted under water over 360" x 1800. The signals made be modulated and encoded in the same manner as the encoded signals sent to the transmitter/receiver 2 of the first embodiment.

However, the principal difference from the first embodiment is that there is no receiver to receive signals transmitted by a submarine and hence the signals transmitted by means of the unit 20 do not depend on the presence or otherwise of a submarine.

Interrogation by a submarine of the fishing vessel is therefore not necessary because sufficient and necessary information will be transmitted at all times by the vessel to enable a submarine in the vicinity to take avoiding action.

Although the invention has been described in relation to fishing vessels it will be appreciated that it may be applied to vessels engaged in marine surveying operations, dredging, submarine cable laying, and diving operations. The invention may also be applied to other sea-going vessels such as slowmoving yachts which tend to have a low under-water noise signature.

Claims (12)

1 A warning system for a sea-going vessel which comprises a sonar transmitter mounted on the hull of the vessel; a control unit for energising the transmitter; and a compass for applying heading signals to the control unit, the control unit including an automatic encoding device which encodes energising signals applied to the transmitter with information concerning the presence of the vessel or any under-water activities associated with the vessel, the encoded sonar signals being thus available to submarines.

2 A warning system as claimed in claim 1, wherein the response of the transponder is a sequenced response comprising three parts: a first part which is a fixed length to enable a position fix of the vessel to be obtained; a second part which is coded to designate the type of under-water activity being carried out; and a third part designating the length and direction of under-water apparatus associated with the under-water activity.

3 A warning system as claimed in claim 2, wherein the sequence is a five-part sequence in which the first three parts are followed by a repetition of parts two and three.

4 A warning system as claimed in claim 2 or 3, wherein the first part of the sequence is used to indicate that there is a pair of vessels operating together.

5 A warning system as claimed in any preceding claim, wherein the information is conveyed by modulating the sonar signals.

6 A warning system as claimed in any preceding claim, wherein the encoded signals take an input from the compass to provide directional information.

7 A warning system as claimed in any preceding claim, wherein the sonar transmitter is part of a transponder which is adapted to receive interrogating sonar signals from a submarine and to respond automatically thereto by transmitting said coded information.

8 A warning system as claimed in claim 7, wherein means is provided to indicate when a said interrogation signal is received from a submarine to give the vessel warning.

9 A warning system as claimed in claim 7, wherein the system employs two types of interrogation signals, one of which is arranged to activate a proximity indicator in the vessel and the other of which is arranged not to activate said proximity indicator while otherwise operating the system identically, whereby a submarine may then determine whether the vessel receives an indication of its presence or not.

10 A warning system as claimed in any preceding claim, wherein there is provided programmable means adapted to receive an input from a navigation position system, the programmable means being programmed to detect when the vessel has become stationary for a predetermined period of time.

ii A warning system as claimed in claim 10, wherein when the programmable means has detected that the vessel has become stationary for said period of time, the system initiates a sonar transmission to distinguish the vessel as a vessel which is stopped in the water.

12 A warning system for a sea-going vessel, substantially as hereinbefore described with reference to the accompanying drawings.