GB2149622A

GB2149622A - Marine distress transmitter

Info

Publication number: GB2149622A
Application number: GB08329437A
Authority: GB
Inventors: Rolf Johannessen
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1983-11-03
Filing date: 1983-11-03
Publication date: 1985-06-12
Also published as: GB2149622B; GB8329437D0

Abstract

A transmitter is encased in a two-part fireproof canister (1, 4, Fig. 2) which floats free after a ship sinks. A temperature sensor (5) determines when the canister is free of burning oil on the sea surface and causes one part (4) of the canister to be jettisoned. The other part (1) contains a radio transmitter and includes a section having a metal thermal insulation cover (2) and a section having a fibre glass cover (3). Initially the metal section is uppermost but when the part (4) is ejected the part (1) inverts leaving the fibre glass section uppermost. Consequently a radio aerial is deployed for the transmission of emergency signals. <IMAGE>

Description

SPECIFICATION Marine distress transmitter This invention relates to a marine distress transmitter for automatic broadcasting of distress radio signals in the event of a marine disaster.

It is now common practice for aircraft, particularly civilian passenger aircraft, to be equipped with a so-called "black-box" flight recorder in which data concerning each flight, e.g. instrumentation readings and cockpit voice communications, are recorded. The flight recorder is also equipped with a radio beacon which is automatically energised in the event of a crash, thus aiding its recover by rescue teams. The recorded data is then available to crash investigators who need the information to determine the cause of the crash.

It is now proposed that a similar device be fitted to ships, with special adaptation for the nature and duration of sea voyages. Such a device will be required to monitor and record voyage data such as course and speed, vital instrumentation data, radio communications and even data from the ship's radar. The device must be readily recoverable after an accident at sea and it must be designed to withstand the rigours of sea voyages in all climates and weather conditions, and to survive prolonged immersion in sea water, e.g. when released from a striken vessel and subsequently left floating in the sea. Typically the device will contain the recording and emergency radio transmission equipment in a sealed container which will retain a positive buoyancy and will continue to provide adequate protection for the equipment even when floating in a burning oil slick.

A report issued by a marine classification society indicates a desire for the equipment to be protected to withstand fire on board ship at 1100 C for 6 hours, followed by floating in an oil fire on the sea surface for a further 1 hour. However, the Fire Protection Association in the United Kingdom indicate that such sea surface oil fires have lasted for as long as 36 hours. Both onboard and sea surface fires pose special technical problems for thermal insulation. The radio equipment can be contained in a buoyant canister which is, in turn, placed within a box on the ship.The box, which is required to provide thermal insulation against a fire aboard ship, can be heavily lined with layers of steel and asbestos or other thermally insulating material like mahogany which has a large thermal time constant, or kaolin insulating brick which has a low thermal conductivity. Eventually the ship sinks and with it the box, which is constructed to allow the canister to float free.

The problems faced when the canister floats in a burning oil slick are completely different from those of the on board fire. The portion of the canister floating above the sea surface will be subjected to intense heat whilst the portion floating below the sea surface will be relatively cool. To provide adequate thermal protection for the equipment whilst the canister is floating in an oil slick fire and yet to ensure eventual electromagnetic transparency can result in conflicting requirements for the canister construction.

According to the present invention there is provided a marine distress transmitter having a buoyant protective canister containing a radio transmitter, the canister comprising a first part within which the transmitter equipment is located and a second part cooperating with the first part to provide a high degree of thermal insulation for the enclosed equipment, the canister being provided with release means adapted to release the second part from the first part when the canister is floating in the sea and a predetermined condition occurs.

In one embodiment of the invention the second part of the canister is constructed with a negative buoyancy whereby the complete canister has a first stable buoyant attitude and the first part alone has a second stable buoyant attitude in which it is inverted with respect to the first stable buoyant attitude.

In another embodiment of the invention the canister is constructed to have a single stable buoyant attitude with the second part uppermost and the release means is constructed to propel the second part away from the first part whereby the first part floats with its consequently uncovered portion uppermost.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figures 1-3 illustrate a canister having a bistable buoyancy, and Figure 4 illustrates a canister having a monostable buoyancy.

In the construction shown in Figures 1-3 the canister has a first part 1 which contains the radio transmitter. This first part is constructed partly with a metal-thermal insulation outer cover 2 and partly with a fibre-glass cover 3. The weight distribution within the first part is such that, without the second part 4 the first part has a stable buoyant attitude with the fibreglass section uppermost. The second part 4 of the canister, which may be constructed with a steel cover, and which may contain ancillary equipment such as a standby battery, the function of which is to maintain the radio battery in a fully charged state, is heavy enough to cause the complete canister to float in a stable buoyant attitude with the metal section of the first part uppermost.

When initially discharged from the stricken ship the complete canister therefore floats in the stable attitude shown in Figure 1, with the second part 4 below the first part. The release mechanism built into the first part includes a temperature sensor 5.

When the sensor 5 determines that the ambient temperature above the sea surface is below a given threshold, either because the oil slick fire has died or the canister has floated away or there is no oil slick fire at all, then the release mechanism releases the second part 4 which falls away, as shown in Figure 2. This results in the first part alone becoming unstable in its original attitude and turning over to the stable attitude shown in Figure 3. The fibrelass cover is now uppermost and the radio antenna is in a position where transmission becomes effective. At the same time the inversion of this part of the canister can operate an attitude dependent switch to energise the radio transmitter.

In the alternative embodiment shown in Figure 4 the first part 41 always floats in its monostable attitude, with its upper part covered by a fireproof second part 42. When the temperature sensor 43 determines that the ambient temperature is below the threshold the release mechanism is activated and allows springs 44 to throw the upper second part 42 clear. The exposed fibreglass portion 45 of the first part houses the radio antenna and the radio transmitter is now enabled.

In either embodiment the release mechanism can instead be activated by a preset timer or by a combination temperature sensor and timing device to ensure that the ambient temperature is below the threshold for a predetermined time before the second part of the canister is released. The radio aerial in each case can be contained wholly within the fibreglass cover, it can be a coiled whip aerial which uncoiled when released by the departure of the first part of the canister, or it can even be a thin flexible wire aerial the free end of which is carried aloft by a balloon filled with a light gas, e.g. helium.

Claims

1. A marine distress transmitter having a buoyant protective canister containing a radio transmitter, the canister comprising a first part within which the transmitter equipment is located and a second part cooperating with the first part to provide a high degree of thermal insulation for the enclosed equipment, the canister being provided with release means adapted to release the second part from the first part when the canister is floating in the sea and a predetermined condition occurs.

2. A transmitter according to claim 1 wherein the second part of the canister is constructed with a negative buoyancy whereby the complete canister has a first stable buoyant attitude and the first part alone has a second stable buoyant attitude in which it is inverted with respect to the first stable buoyant attitude.

3. A transmitter according to claim 1 wherein the canister is constructed to have a single stable buoyant attitude with the second part uppermost and the release means is constructed to propel the second part away from the first part whereby the first part floats with its consequently uncovered portion uppermost.

4. A transmitter according to any preceding claim wherein the release means incorporates temperature sensing means arranged to activate the release means when the ambient temperature above the sea surface is below a predetermined threshold after the canister is not floating free in the sea.

5. A transmitter according to any one of claims 1-3 wherein the release means incorporates a timing mechanism arranged to activate the release means a predetermined time after the canister is set floating free in the sea.

6. A transmitter according to claim 4 or 5 including immersion responsive means to enable the temperature sensor and/or timing mechanism when the canister is set floating free in the sea.

7. A marine distress transmitter substantially as described with reference to Figs. 1-3 or Fig. 4 of the accompanying drawings.