GB2287564A

GB2287564A - Overboard alarm and detector

Info

Publication number: GB2287564A
Application number: GB9404558A
Authority: GB
Inventors: John Adam French
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-09
Filing date: 1994-03-09
Publication date: 1995-09-20
Also published as: GB9404558D0

Abstract

The overboard alarm comprises an immersion detector (2) which activates the overboard alarm when it is immersed in water. The overboard alarm generates an ultrasonic distress signal which can be transmitted through the water, The detector Fig. 3, not shown, receives the distress signal and activates an alarm. The overboard alarm may be manually triggered. <IMAGE>

Description

DESCRIPTION OVERBOARD ALARM AND DETECTOR The present invention relates to overboard alarms, and in particular, but not exclusively, to alarms which activate when immersed in water.

If a person, on board a yacht, boat, ship, oil rig etc., falls into the water, their absence may not be detected until its too late, with the result that the person drowns or dies of hyperthermia.

Furthermore, rescue attempts can be difficult if the person in the water has drifted from the course of the vessel, or is underwater making them difficult to locate, especially in foul weather or darkness.

It is an object of the present invention to overcome or alleviate the above described problems.

In accordance with one aspect of the present invention there is provided an overboard alarm having a transmitter which generates an ultrasonic distress signal when the alarm is substantially immersed in water and/or is manually activated.

This has the advantage that a yachtsman, sailor, oil rig worker, or even an object, such as a piece of machinery which may fall overboard can carry the overboard alarm and in the event that the person or object falls into the water, a distress signal is emitted, which upon detection will allow rapid recovery of the person or object.

Preferably, the ultrasonic distress signal is digitally encoded. This allows the signal to be rapidly distinguished from other signals of ultrasonic frequency such as those of depth sounders.

In accordance with a second aspect of the present invention, there is provided an overboard alarm detector having a receiver for monitoring for and detecting the ultrasonic distress signal of an overboard alarm which transmits an ultrasonic distress signal when substantially immersed in water and/or is manually activated, which receiver activates a distress alarm.

This has the advantage that the detector can be carried on a vessel or oil rig etc. and if a person or object falls into the water carrying an overboard alarm, the distress signal emitted by the overboard alarm is rapidly detected and a distress alarm activated to alert other people on the vessel or oil rig that a person or object is in the water.

Preferably, the overboard alarm detector has a position finder for locating the position of the overboard alarm relative to the detector. This has the advantage of allowing the position of the person or object carrying the overboard alarm to be located.

In a preferred embodiment, the overboard alarm and/or overboard alarm detector comprises means for producing or activating an audio distress signal, and/or satellite automatic tracking systems, and/or visual distress signal in the form of a light, and/or automatic banbuoy release, and/or smoke release, and/or dye release.

By way of example only, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram illustrating an overboard alarm constructed in accordance with one embodiment of the present invention; Fig. 2 is a circuit diagram of the transmitter of the overboard alarm of Fig. 1; Fig. 3 is a block diagram illustrating a unit for detecting the alarm signal from the overboard alarm of Fig. 1; and Fig. 4 is a circuit diagram of the emergency signal detector and alarm trigger circuit of the detector of Fig. 3.

As best illustrated in Fig. 1, the overboard alarm has an immersion detector 2, an ultrasonic oscillator 4, a digital coding circuit 6, an amplifier 8 and an ultrasonic transmitter 10.

The immersion detector 2 comprises a resistance switch (not illustrated) having two probes for detecting the presence of water. The probes are protected by a plastics shield which substantially prevents water splashing against the resistance switch from activating the immersion detector 2, but allows water to ingress behind the shield to activate the detector once the immersion detector 2 is immersed in water. Alternatively, the immersion detector 2 could be such that it is activated by a change in pressure, or by a mixture of pressure and moisture, such that immersion in water is detected and the overboard alarm is activated. Also, the detector could be manually operable.

When immersion is detected, the overboard alarm is activated as follows. The ultrasonic oscillator 4 produces a source of current of ultrasonic frequency.

The digital coding circuit 6 encodes the waveform with series of pulse elements 12 of substantially rectangular waveform. The amplifier 8 boosts the now encoded signal from the oscillator 4, whilst the transducer 14 of the ultrasonic transmitter 10 converts the signal to an ultrasonic waveform suitable for transmission through the antenna of the transmitter (not illustrated). In Fig. 2, the circuit of the transmitter is illustrated in which a 150 kHz signal is generated pulsed at a frequency of 500 Hz.

The ultrasonic wave is transmitted through the water.

As best illustrated in Fig. 3, the unit for detecting the alarm signal, i.e. ultrasonic wave emanating from the overboard alarm, comprises an ultrasonic receiver 16, an amplifier 18, a unit for filter and signal conditioning 20, a digital decoder circuit 22 and an overboard alarm activator 24.

In use the ultrasonic receiver 16 constantly monitors for the alarm signal and for this purpose has an antenna (not illustrated) for receiving the alarm signal, this is either suspended in the water or strapped to the hull of the vessel such that is can receive the signal through the hull. The receiver 16 converts the signal back to electrical current which is amplified by the amplifier 18, filtered by the filter unit 20 and decoded by the digital decoder 22, before an audio and/or visual alarm is activated on board the vessel by the overboard alarm activator 24.

In Fig. 4, the layout of the emergency signal detector and alarm trigger circuit is illustrated in greater detail.

The overboard alarm and/or detector can be modified to activate a number of man overboard protection and recovery systems such as automatic banbuoy release, smoke and dye release, position logging, satellite automatic tracking systems etc.

The detector can be modified to incorporate an ultrasonic depth finder unit, for determining the depth of the overboard alarm under the water, or a position finder for more accurately locating the position of the overboard alarm.

The distance and/or depth from the receiver to which the overboard alarm can be detected depends on the power and the frequency of the waves employed as the signal. In the described embodiment, a signal of 150 kHz was described, but any frequency in the ultrasonic range can be used, i.e. substantially within the range 20 kHz to 450kHz, for example 50 kHz or 192 kHz, the frequency often used for echo sounders.

In use, the overboard alarm is strapped, for example, to the belt or life jacket of the user, ie sailor, worker on an oil rig, or object which may fall overboard. The overboard alarm can be battery powered, with indicator to show when the batteries are low. A recharging unit can be provided for recharging the batteries.

The detector could be a complete unit, or an addon unit for converting signals detected by a conventional echo sounder.

Claims

1. An overboard alarm having a transmitter which generates an ultrasonic distress signal when the alarm is substantially immersed in water and/or is manually activated.

2. An overboard alarm as claimed in claim 1, comprising an immersion detector for detecting the presence of water and activating the overboard alarm.

3. An overboard alarm as claimed in claim 1 or claim 2, wherein the ultrasonic distress signal is digitally encoded.

4. An overboard alarm as claimed in any one of the preceding claims, comprising means for activating an automatic banbuoy release and/or smoke release, and/or dye release, and/or audio signal, and/or light signal, and/or satellite tracking system.

5. An overboard alarm as claimed in any preceding claim, wherein the overboard alarm is battery powered and has a battery recharging unit.

6. An overboard alarm detector having a receiver for monitoring for and detecting the ultrasonic distress signal of an overboard alarm which transmits an ultrasonic distress signal when substantially immersed in water and/or manually activated, which receiver activates a distress alarm.

7. An overboard alarm detector, as claimed in claim 6, having a decoder for decoding digitally encoded distress signals.

8. An overboard alarm detector as claimed in any one of claims 6 or 7, having a position finder for locating the position of the overboard alarm relative to the detector.

9. An overboard alarm detector as claimed in any one of claims 6,7, or 8 wherein the distress alarm is an audio signal and/or visual signal in the form of a light and/or automatic banbuoy release and/or smoke release and/or dye release, and/or the detector activates a satellite automatic tracking system.

10. An overboard alarm detector as claimed in any one of the preceding claims, in which the detector is an add on unit for converting signals detected by a conventional echo sounder.

11. An overboard alarm constructed and adapted to operate substantially as hereinbefore described, with reference to and as illustrated in, Fig. 1 and/or Fig. 2.

12. An overboard alarm detector constructed and adapted to operate, substantially as hereinbefore described, with reference to, and as illustrated in, Fig. 3 and/or Fig. 4.