TECHNICAL FIELD The present invention relates to a distress or signalling flare comprising an outer shell with a front end and a back end, a propulsion unit arranged at said back end for propulsing said signalling device through a medium, a signalling substance placed in said outer shell and an ignition arrangement for igniting said signalling substance.

BACKGROUND ART

The presence of a device for signalling distress is crucial to an underwater vessel such as a submarine, in order to be able to communicate with the surrounding world in the event of an accident or the like. A dangerous situation onboard might require immediate assistance such as a rescue operation, since the lives of the crew might otherwise be in serious danger. Devices such as distress rockets are therefore always brought onboard and can be emitted by use of a rocket launcher, for instance, in order to signalise a distress situation.

In order for the signal to be spotted, it should be detectable by radar as well as by eyesight. This way, the radar of passing ships or aircraft, as well as the sighting by a human onboard such a vessel, cooperates in detecting the distress situation and locating the submarine itself.

A device for emitting distress signals is shown by GB2241310 (Wallace) and uses a radar reflecting material for leaving an imprint that is detectable by radar, in order to create a distress signal with lasting detectability over a larger area. This signal, however, cannot be detected with the naked eye since no light or smoke signals are produced and is therefore efficient only in the vicinity of larger, radar equipped vessels.

US5834682 (Warren) shows a radar signal cartridge suitable for use at sea for signalling distress. This device uses a material such as aluminium in order to create a signal that is detectable by radar and reflections in a specific frequency band can be chosen for differentiating the signals. However, the signal created is not visible to the naked eye, and even if the device is suitable for use at sea, it cannot be seen as being designed for use with a submarine. The American patent US4805533 (Stanley) shows a signalling device meant to be used by a swimmer for signalling distress at sea. This device can be used under water as well as at the surface and emits a signal that is clearly visible to anyone looking in the direction of the signal, but the signal fails to show up on radar. Thereby, the visibility is limited to the area closest to the distress site, and can only be seen during the limited time when the signal is burning brightly and hanging in the air. Since the burning and generation of smoke is a vital part in showing the distress situation, the signalling device would also be unsuitable and even dangerous onboard a submarine, since an accidental lighting of the signalling device while still inside the submarine could result in a very dangerous situation for the crew.

The problem described above regarding the risks connected with the undesired creation of smoke if a device for emitting distress signals is activated too early, e.g. in a space where people are present, also applies to the use of illuminating flares. Smoke development inside a closed space can be a danger even if the space in question is not a submarine or other underwater application, but at the same time a material that develops a bright light when lit is necessary for the flare to work properly. Often, magnesium is used in illuminating flares, but this is generally undesirable due to the smoke development described above. In a submarine, the presence of magnesium would for this reason create a danger to those present since a premature lighting of the material in a distress flare, for instance, would not only create dangerous amounts of smoke but at the same time use a substantial amount of the oxygen present in the air, thereby causing a suffocation hazard to the crew.

There is therefore clearly a need for an improvement in the construction of distress or illuminating flares.

DISCLOSURE OF THE INVENTION

The object of the present invention is to eliminate or at least to minimize the problems described above. This is achieved through a signalling device according to claim 1.

Thereby, the signalling substance can be ignited at a conveniently low temperature and achieve a distinct light and radar chaff that will serve to maximize the visibility and detectability of the device, while at the same time minimizing the risk for the rise of a dangerous situation onboard a vessel, since the risk for smoke development or undesired ignition can be kept low. According to another aspect of the invention, said signalling substance is in the shape of a disk. Thereby, the signalling substance can be loaded into the device in a convenient manner, while at the same time comprising a large number of different objects/disks that can be spread thinly over a large area and provide a high air resistance, thereby falling more slowly after ignition and creating a signal that is visible for a longer time.

According to a further aspect of the invention, said disk is slitted. Thereby, the ignition of each disk can be substantially facilitated, since the surface that can be ignited is enlarged. Also, the time that the substance is spread in the air and giving off a signal as they fall down can be further prolonged, thus further increasing the time of detectability of the signal.

According to yet another aspect of the invention, said ignition arrangement comprises a thermal battery for creating an ignition signal, and said battery has an active period of at least 100, preferably at least 150, more preferably at least 200 s. Thereby, the energy necessary for igniting the device can be generated from the battery, thus creating a reliable and convenient ignition process even when firing from a vessel at great depth, such as 400 meters below the surface or more, since the battery is active even after the rise through the water.

According to another aspect of the invention, said ignition arrangement comprises a capacitor for creating an ignition signal. Thereby, the ignition can be performed in a simple and convenient manner through loading energy onto a capacitor sometime before ejecting the device from a vessel and using this energy as needed.

According to a further aspect of the invention, said ignition arrangement comprises a processor unit for controlling the ignition of an ignition device. Thereby, the ignition can be adapted and controlled to achieve the desired result depending on the time and intensity required for an optimal performance by the signalling device.

According to another aspect of the invention, said ignition arrangement comprises an hydrostatic device that is set to react at a pressure of less than 1 bar, preferably less than 0,5 bar. Thereby, the ignition can be postponed until the device has reached a desired water depth.

According to a further aspect of the invention, an illuminating flare comprising an outer shell, a flare body placed in said outer shell, an air resistance means for controlling a movement of said flare body, a propulsion unit for propulsing said flare through a medium and an ignition device for igniting said flare body is provided, wherein said flare body comprises an active aluminium. Thereby, the advantages of a low ignition temperature as well as the stability and reliability of aluminium can be achieved, thus providing a reliable and convenient flare for increased visibility at a desired location.

According to yet another aspect of the invention, said illuminating flare is arranged to be ejected from an ejection device that is mounted on a mobile unit. Thereby, the flare can be used at a desired location without the need for cumbersome stationary ejection devices.

According to a further aspect of the invention, said mobile unit is a weapon. Thereby, a person requiring greater visibility in a certain area can fire the flare and at the same time being prepared to use the weapon, thus lowering the risks for the person being caught defenceless while using a flare.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the appended drawings, wherein:

Fig. 1 shows a perspective view of a distress or illuminating flare according to a preferred embodiment of the invention, Fig. 2 shows a transversal view of the flare of Fig. 1, Fig. 3 shows a longitudinal cross-sectional view of the flare of Fig. 1, and Fig. 4 shows a view from above of a signalling substance used with the flare of Fig. 1- 3.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a distress or signalling flare 1 according to a preferred embodiment of the invention, with an outer shell in the form of a hull 3 comprising a flare hull 11 and a propulsion hull 21 that are connected by a spacer 31. A cover 32 covers a first end of the flare 1, while a washer 4 comprising a plurality of through holes 41 covers a second end at the propulsion hull 21. One of the through holes 41 houses a safety catch 91 that can be threaded into the flare 1 for preventing an undesired use of the flare 1 itself.

Fig. 2 shows a transversal view from the second end of the flare 1, showing the washer 4 with the through holes 41 and the safety catch 91 that has been inserted through one of these through holes 41 and secured there, in order to prevent an undesired operation of the flare 1.

In Fig. 3, a longitudinal cross-sectional view of the flare 1 is shown. The flare hull 11 comprises an ignition channel 12, connecting a propulsion unit 2 with a number of compartments 13a, 13b, 13c and ending at a dispersion charge 33 inside the cover 32. Said compartments 13a- 13c contain a signalling material in the form of a plurality of disks 8 (shown in Fig. 4) comprising a centrally placed hole through which the ignition channel 12 propagates. Threads 14 are arranged between the compartments 13a-13c.

The spacer 31 forms the boundary between the compartment 13c and the propulsion unit 2, which in its turn comprises a pressure chamber 22 that is fixated inside the propulsion hull 21 by an O-ring 23, and an electric igniter 24. The propulsion unit also comprises a hydrostatic device 25, a processor unit 26, a thermal battery 27 and a breaking pin 28, apart from the aforementioned safety catch 91 that can be inserted through one of the through holes 41 in the washer 4.

Fig. 4 shows one of the disks 8 that form part of the signalling material, with a through hole 81 and a slit 82 protruding from the edge of the disk 8 into the hole 81. The disk 8 is made from a material that can serve as radar chaff, such as aluminium, and has preferably been subjected to a process for lowering the flashpoint, such as the method described by EP 1 569 879 (Hahma).

According to this method, an aluminium material is treated with an aqueous solution such as a hydrofluoric acid and a fluoride salt of an alkali metal, which reacts with the oxide layer that can normally be found on the surface of aluminium and creates a new surface layer of a fluoride complex. The material thus created can be called active aluminium and has a substantially lower flashpoint, around 700 ⁰ C, than ordinary aluminium which is usually found with an oxide layer and has a flashpoint of around 1300 ⁰ C.

When the active aluminium is ignited, the fluoride complex melts and dissolves any remaining oxide layer and then evaporates at a relatively low temperature so that pure aluminium is exposed. The aluminium itself is ignited in order to create a bright glow, suitable for a distress flare or other signalling device.

The use of the flare 1 will now be described in more detail. Before use, the flare 1 can be kept disassembled, with the propulsion unit 2 separate from the rest of the flare 1. In order to prepare the flare 1 for operation, these parts are joined, preferably by screwing into the spacer 31, and the safety catch 91 is applied into one of the holes 41 if it has not already been inserted into the propulsion unit 2. The purpose of the safety catch 91 is to keep the propulsion unit 2 from being activated by mistake, for instance during transport or handling.

When a distress situation has occurred, the safety catch 91 is removed and the flare 1 inserted into a rocket launcher (not shown) onboard a submarine. The washer 4 is fixed in the rocket launcher, and a firing mechanism in the rocket launcher ejects the flare 1 into the water. During the firing process, the washer 4 remains fixed to the rocket launcher, and a section of the propulsion unit 2, fastened to the washer 4 by the breaking pin 28, is held back in order to create a pulling motion inside the propulsion unit 2. When the forces on the breaking pin 28 are large enough, the pin breaks and releases the flare 1 from the washer 4 and the rocket launcher, and the flare 1 is shot out from the rocket launcher.

Thanks to the pulling motion created inside the propulsion unit 2, the thermal battery 27 is activated and serves as the power supply for the electric igniter 24. The battery 27 has a life span of at 100s, preferably 150 s and more preferably least 200 s. During the rising of the flare 1 from the water, powered by the force delivered by the rocket launcher, a timer device can be used in order to delay an ignition pulse from the thermal battery 27 to the igniter 24. It would be possible, in order to further secure an ignition at a predetermined water depth, for the hydrostatic device 25 to be set set to prevent an ignition pulse from travelling from the thermal battery 27 to the igniter 24 if the pressure from the surrounding water is higher than a predetermined level. A suitable level can be 1 bar, preferably 0,5 bar, which would correspond to a depth of 5-10 meters below the surface. A higher pressure would mean that the flare 1 is still too far underneath the surface for the signalling device to function in a desired way, and thus an accidental ignition at such a depth can be prevented.

As the flare 1 reaches the surface of the water, the timer device sends a signal to the processor unit 26 to open a connection from the thermal battery 27 to the electric igniter 24, allowing a capacitor connected between them to initiate the igniter. The ignition pulse is transferred to an ignition charge, placed inside the ignition channel 12, and as the ignition charge burns, the disks 8 placed inside the compartments 13c, 13b, 13a are ignited in turn. The burning of the disks 8 in each new compartment is delayed by the burning process as the ignition travels along the ignition charge, and also by delay charges placed inside the threads 14, so that one compartment at a time is set on fire. When the flare 1 reaches a predetermined height above the surface of the water, for instance 70 m, the dispersion charge 33 is ignited, scattering the burning disks 8 in all directions. The air and wind will serve to scatter the disks 8 even more.

Thanks to the active aluminium of the disks 8, the ignition during the ascent of the flare 1 causes the material itself to burn, emitting a bright light that can easily be detected by eyesight from the surrounding area, and since the aluminium will also be detectable by radar, a maximal visibility can be achieved. Thanks to the shape of the disks 8, with a slit 82 from the central hole 81, the ignitable surface of the disks 8 is enlarged, thus facilitating the ignition and increasing the air resistance in order to prolong the time that the disks will require for falling back down to sea level.

The burning cloud will stay in the air until the disks 8 have fallen back all the way into the water and until the material can no longer burn. Thanks to the thinness of the disks 8, the air resistance can be increased while keeping the weight low, in order to slow the fall as much as possible.

If desired, the construction of the flare 1 can be modified, in order to create an illuminating flare such as an illumination shell or star shell, for creating light over a specific area. The construction of the flare 1 can in this application be made simpler, by omitting the hydrostatic device and using a timer only for determining the moment of igniting the ignition charge. The signalling substance can be located in the compartments 13a or 13b and be in the form of a flare body 6 (not shown) of active aluminium that will burn brightly and where the burn rate can be controlled through the design of the flare body itself. It might for instance be beneficial to use a series of flare bodies that are connected and equipped with an ignition device that can ignite the different flare bodies simultaneously or sequentially in order to create a brighter or a longer lighting. The compartment 13c can in this embodiment also be provided with air resistance means 81 (not shown) that will act as a parachute of sorts for controlling the speed with which the flare falls to the ground, and the flare itself can be shot out of an ejection device located above ground rather than under water.

After ignition and dispersion, the flare body, detectable by radar and clearly visible, can be created and detected from a long way off thanks to the bright light of the burning aluminium and the radar chaffing properties. Thanks to the beneficial properties of the active aluminium, the general disadvantages connected with traditional materials such as magnesium can be avoided. These disadvantages include the development of a dense smoke, which in the event of an undesired ignition before the correct time can cause serious problems for the user, especially if the ignition takes place inside a building. The active aluminium, on the other hand, will burn brightly but without an excess of smoke, which is very beneficial for the handling, transporting and using of the flares.

The lifetime of the flare can also be substantially prolonged by the use of active aluminium, since the risk of damage to the signalling substance or flare body due to the contact with air or moisture can be substantially lowered as compared with other materials such as magnesium.

The invention is not to be seen as limited by the embodiments described above, but can be varied within the scope of the appended claims, as will become readily apparent to the man skilled in the art. For instance, the construction of the flare can be modified in order to enhance or alter certain aspects of its performance, and the time of igniting the disks or dispersion them in the air can be changed in order to achieve a better function of the flare. The active aluminium can be provided in a number of different shapes, such as objects of another form than round or flat, or in the form of a powder.