BACKGROUND TO THE INVENTION Water search and rescue operations are immensely expensive and not without risk to personnel involved. Accordingly, a number of devices have been developed to minimise the time, risk and expense required in locating downed aircraft, submerged vessels, and persons lost at sea.

Because personnel may fail to manually actuate such marker devices in an emergency (for example due to confusion or injury), these devices are often designed to release or actuate a marker automatically in response to an emergency situation. A problem exists in that it is possible for these markers to actuate in non-emergency situations.

Other types of marker devices are designed to be dropped from aircraft to allow a location to be identified. However, accurate placement of a locating device from an aircraft requires considerable skill, and drifting and misplacement of markers is a considerable problem.

There is a need to provide a marker device which signals the position of a distressed craft or man overboard, does not rely on human activation and is less likely to actuate in a non-emergency situation.

SUMMARY OF THE INVENTION According to the present invention, there is provided a marker device which includes a housing and a position marker enclosed within said housing, first means for facilitating controlled ingress of water into said housing where said marker device is at least partially immersed in water, wherein upon ingress of a predetermined amount of water into said housing, second means open said housing to facilitate operation of said marker device.

The entry of water into the housing is generally facilitated. by a conduit extending from the housing, the conduit providing means for controlling the entry of water to the housing containing the marker when the device is at least partially immersed in water. The length, diameter, inlet size, and shape of the conduit can be altered to provide adequate protection of the marker from water when the housing is not at least partially immersed, while providing controlled entry of water to the housing when the device is at least partially immersed in water.

In one aspect, the present invention provides a marker device including a housing for containing a marker and having a frangible housing portion for enclosing the marker in the housing; a conduit for providing controlled ingress of water to the housing when the device is at least partially immersed in water; and rupture means for rupturing the frangible portion, wherein the rupture means is responsive to the ingress of water from the conduit to apply a rupturing force to the frangible portion.

In a particularly preferred form of the invention the opening of the conduit inside the housing is positioned above or adjacent to the marker and most preferably above the marker. This arrangement has the advantage of providing greater protection for the marker from errant splashes of water by forcing incoming water to travel by an indirect path in order to access the marker. This results in a lower probability of accidental discharge of the marker.

Preferably the housing includes a vent to allow the escape of air resulting from the ingress of water from the conduit.

Preferably the conduit is a tube. More preferably the end of the tube is closed, and the inlet is radially adjacent to the end of the tube.

Most preferably the conduit is straight.

In one form of the invention the conduit may have a baffle that acts to further control the ingress of water into the housing. The baffle may be attached to the outside of the conduit or housing. Alternatively the baffle may be attached to the inside of the conduit. If the baffle is inside the conduit it may be moveable and/or buoyant. In a preferred form of the invention the moveable baffle is a ball that may be solid or perforated.

In one embodiment of the invention the rupture means may include a gas source which may be provided as a cylinder of compressed gas, with the gas being released from the cylinder by dissolution of a water soluble plug which is located to be in contact with water only upon ingress with the housing of the predetermined amount of water. For this, the plug preferably is located toward an upper end or portion of the housing, so that small amounts of water which enter the housing do not result in the plug dissolving. In another embodiment the gas source is a chemical or combination of chemicals which releases a gas upon exposure to water.

Most preferably, the gas is released into a bladder contained within the housing.

In a preferred embodiment the housing is divided into two chambers by a water permeable partition. Where the housing is divided, one chamber contains the water expandable device and the other contains the marker.

Preferably the marker is a dye. More preferably the marker is a powdered fluorescent marker dye.

The marker may also be a flotation device, which upon release from the housing floats on the surface of the water to provide a visual signal to search and rescue personnel.

In a second aspect, the present invention provides a device including a housing for containing a marker, a conduit for providing controlled ingress of water to the housing when the device is at least partially submerged in water, wherein the marker is actuated in response to the ingress of water.

In a particularly preferred form of the invention the opening of the conduit inside the housing is positioned above or adjacent to the marker. Preferably the housing includes a vent to allow the escape of air resulting from the ingress of water from the conduit.

Preferably the conduit is a tube. More preferably the end of the tube is closed, and the inlet is radially adjacent to the end of the tube.

In one form of the invention the conduit may have a baffle that acts to further control the ingress of water into the housing. The baffle may be attached to the outside of the conduit or housing. Alternatively the baffle may be attached to the inside of the conduit. If the baffle is inside the conduit it may be moveable and/or buoyant. In a preferred form of the invention the moveable baffle is a ball that may be solid or perforated.

In one arrangement, the marker is actuated by the completion of an electrical circuit by the water. The marker may be a device for emitting a radio signal (eg a water activated Emergency Position Indicating Radio Beacon), light, or sound. In this arrangement, the housing still needs to be opened for operation and/or release of the marker. If the device emits a signal, then it will have an aerial that has to be exposed. Equally, for a light or sound to be effective, the housing must be opened.

In use, the marker device will be generally retained in a vessel in an upright position, with the open end of the conduit directed generally downward.

This orientation will minimise accidental activation of the marker by splashing, for example.

When the water level rises to at least partially immerse the device, the device operates as follows. The vent and conduit inlet provide for the controlled ingress of water to the bladder chamber. The incoming water then acts to dissolve the water soluble plug which is positioned between the outlet of the compressed gas source and the inlet for the bladder. Release of the compressed gas results in inflation of the bladder, providing an expanding force to the lid to fracture the frangible retaining means. The water may then enter to rapidly disperse the marker dye as the housing sinks.

Thus, the device of the present invention acts to keep an enclosed marker substantially dry when the housing is not at least partially immersed, but allows contact of the marker with water when the device is at least partially immersed. The marker devices currently in use have no mechanism for controlling the ingress of water to actuate the marker.

The present invention will now be more fully described with reference to the accompanying figures. It should be understood, however, that the description following is illustrative only and should not be taken in any way as a restriction of the generality of the invention described.

DETAILED DESCRIPTION OF THE INVENTION The following description refers to preferred embodiments of the marker device of the present invention. The embodiments described are useful for markers which must be physically released from a housing in order to function as a marker (eg a marker dye). To facilitate an understanding of the invention, reference is made to the description of the accompanying drawings where the marker devices illustrated are preferred embodiments, and in which:

Fig. 1 is a cutaway perspective view of the housing of a marker device according to a preferred embodiment of the present invention; and Fig. 2 is a lateral view of the folded bladder (ie not expanded) which is placed in the bladder chamber of the housing of Fig. 1.

Fig. 3 is a cutaway lateral view of a marker device according to a preferred embodiment of the present invention.

Fig. 4 shows a marker device according to a preferred embodiment of the present invention detailing a perspective view of the housing and lid, and a lateral view of the assembled housing. Further detailed are perspective, lateral and longitudinal views of the trough/conduit assembly.

Fig. 5 shows a marker device according to a preferred embodiment of the present invention in a lateral cutaway view.

Referring initially to Fig 1 of the drawings, there is generally shown the housing including a housing body 10 and a lid 28. The lid is designed to form a water tight seal with the upper edge of the housing body when fitted correctly.

The housing body and lid may be manufactured from any water impermeable material such as plastic or metal. Water tightness of the housing as a whole is ensured by the presence of a seal 30 which is provided on the lower face of the lid. The seal may be made of rubber, silicone or any other material capable of forming a watertight seal.

The lid 28 is attached to the housing body 10 by frangible retaining means. In a preferred embodiment the lid is retained by aligning the screw threaded openings 26 with the openings 32 in the lid and securing the lid by means of two screws 34. The screw and screw base are designed to retain the lid sufficiently firmly so as to maintain watertightness of the housing, but not so firm that the lid will not be separated from the housing body upon inflation of a bladder housed therein.

The housing is divided into a bladder chamber 12 and a marker dye chamber 14. The two chambers of the housing are separated by a partition 16 which includes a plurality of openings 18. The function of the partition 16 is to maintain the bladder as close as possible to the lid 28 so that a greater force is applied to the lid 28 upon inflation of the bladder. The partition 16 is designed to dislodge from its position within the housing body 10 after the housing has ruptured, leading to the release of the marker dye. In case the partition does not completely dislodge, the openings 18 in the partition 16 allow the movement of water into the marker dye chamber 14 allowing for the effective dissolution of the dye, followed by diffusion of the dye into the surrounding water.

A conduit 20 is provided which has an inlet 22 opening outside the housing body 10 to allow the controlled ingress of water to the bladder chamber 12 from outside the housing. The end of the conduit outside the housing is closed with the inlet 22 adjacent to the closed end. An unrestricted opening of the conduit is provided to the bladder chamber 12 of the housing at the opposite end 24. The length, shape, diameter and opening of the conduit 20 may be varied as required according to the proposed use for the marker release device.

The size, length or shape of the conduit 20 can be used to predetermine the time taken to actuate the marker. For example, the longer the conduit 20, the more difficult it is for water to travel all the way to the end 24 inside the housing.

It would subsequently require the presence of a larger amount of water for a longer period of time around the inlet 22 of the conduit 20 to actuate the marker release or marker actuation mechanism. Conversely, a short conduit would require only a small amount of water for a short time to activate the mechanism.

Therefore, if the marker device is expected to be kept in a substantially dry environment (eg the cabin of an aircraft) the conduit could be quite short so that only a small amount of water present in the cabin would lead to the release of the marker. If the marker device were to be placed in a wet environment (eg the deck of a yacht) a longer conduit could be used so that the marker would only be released upon at least partial submersion of the vessel.

The conduit 20 need not be straight. A non-linear conduit results in a more tortuous path between the inlet 22 and outlet 24 of the conduit 20. This

results in a lower probability of water entering the housing. A straight conduit is preferable, however, since this allows for easy visual inspection for blockages which could impede functioning of the marker device and supply of conduit for manufacturing purposes is quite simple.

Upon entry of water into the conduit 20 air is expelled through the opening 24. The expelled air is allowed to escape from the housing through a vent 36 which extends into, but does not occlude, the conduit 20. The vent 36 is mounted in the lid and allows air present in the housing to escape when water enters the conduit 20, but not to allow entry of water into the housing through the vent. The vent 36 (like conduit inlet 22) can act to control the rate of ingress of water. A smaller vent results in a decreased rate of air expulsion from the housing in response to the ingress of water into the conduit 20. A lower rate of air expulsion therefore acts as a partial barrier to the entry of water. Thus the size and shape of the inlet 22, conduit 20 and vent 38 can be varied separately or together to predetermine the length of time taken for water to enter the bladder chamber 12. It would be a simple matter for the skilled person to custom design a marker device for a particular use by varying these design parameters.

Referring to Fig. 2, the bladder 38 is shown in its unexpanded state. The bladder 38 is connected to a compressed gas source 40 via a water soluble plug 42. In a preferred embodiment, the gas source is compressed carbon dioxide in a cylinder.

In a preferred embodiment, the water soluble plug 42 is the same as that commonly used on life jackets which are designed to inflate upon contact with water, and therefore well known to the skilled artisan. Other mechanisms will be apparent to the skilled person, and are included within the scope of the invention.

As an alternative to the arrangement described above, the means for fracturing the housing may be a chemical or combination of chemicals which release a gas upon exposure to water. In this case, water entering the housing

via the conduit contacts a chemical, the dissolution of which leads to the liberation of a gas and subsequent fracture of the housing due to an increase in pressure therein.

To assemble a preferred embodiment of the marker release device ready for use, a suitable marker dye is placed in the chamber 14, and the folded bladder 38, coupled to the compressed gas source 40 via the water soluble plug 42, is placed in the bladder chamber 12. The lid 28 is affixed to the housing 10 using the screws 34 which are inserted through the openings 32 to engage with the threaded openings 36. The engagement of the lid 28 with the housing body 10 must be sufficiently firm to seal the housing against the entry of water, but not so firm so that the lid 28 cannot be removed by the expansion of the bladder 38.

When the marker release device is at least partially immersed, water enters the conduit 20 via the inlet 22 and displaces air through the vent 36.

Upon entering the conduit, the water travels until it exits via the opening 24 at the opposite end. The plug 42 is then dissolved by the water leading to release of gas from the compressed gas source 40 into the folded bladder 38. The bladder 38 in turn expands leading to disruption of the screws 34 and the subsequent release of the lid 28. Further water then enters the housing leading to complete flooding of the bladder chamber 12 and marker dye chamber 14.

The soluble dye is then free to exit the marker dye chamber 14 via the openings 18, leading to colouration of the surrounding water.

In a preferred embodiment the gas source is connected to a bladder which expands thereby fracturing the frangible area of the housing. It will be obvious to the skilled person however that the invention would still function without the bladder. In this case the release of gas directly into the housing could increase the pressure within the housing sufficiently high so as to fracture the frangible portion of the housing.

The embodiment as described above is suitable for markers which must be physically released from the housing in order to act as a marker. This

arrangement is therefore useful for marker dyes, inflatable devices which float on the surface of the water, and the like.

Referring to Fig. 3 of the drawings there is shown another preferred embodiment of the present invention having a housing 2 including a base 4, a vent hole 6, and a conduit 8. The marker is placed in the void 12. In this embodiment the outer opening of the conduit 8 is sealed with a plug 10 which must be removed in order to arm the marker device. Therefore, in this embodiment, further protection from accidental actuation is provided by the removable plug.

Referring to Fig. 4 there is shown a further preferred marker device including a housing 2, having an upper chamber 4 and a lower chamber 6. The housing is sealed with a lid 8 which is secured using a light weight tie arrangement 10. In this embodiment, the housing is fitted with a trough 12 which is attached to the conduit 14. The trough has a number of openings 16.

When the device is a least partially immersed, water enters the housing 2 via the conduit 14 to the upper chamber 4 above the marker located in the lower chamber 6. Once sufficient water has entered the housing 2, the trough overflows so that water passes through the perforations 16 and into the lower chamber 6. The marker (which is stored in the lower chamber 6) is then activated.

Referring to Fig. 5 of the drawings there is shown a preferred marker device according to the present invention having a housing 2 with air vents 4, a lid 6 having an inspection port 8. The housing communicates with the outside by a conduit 10. A removable internal partition 12 composed of buoyancy foam is supported by support member 14. The partition 12 defines an upper chamber 15 and a lower chamber 16. The outside opening of the conduit 10 is covered by a baffle 18 having openings 20. The device is further equipped with a gas cylinder 22 sealed with a water soluble plug 24. When the device is at least partially immersed, water enters the conduit 10 via the openings 20. Water travels into the conduit 10 to dissolve the water soluble plug 24 leading to the escape of gas. Increasing pressure in the housing 2 leads to ejection of the lid

6. Large amounts of water may then enter the housing 2 leading to dissolution of a marker dye substance, for example, which is stored in the lower chamber 16. In this embodiment the baffle 18 acts to protect the water soluble plug 24 from accidental contact with water in a non-emergency situation.

Referring to Figure 6 of the drawings there is shown a further preferred marker device according to the invention. This preferred device has a housing 7 and a lid 4 defining a chamber 6. The housing communicates with the outside by a conduit 8. The lid includes an inspection port 1, allowing inspection of the water soluble plug 3 attached to the gas cylinder 5. The thread of the inspection port is interrupted to form a vent 2 that allows the escape of air that is displaced by incoming water. The outside opening of the conduit 8 is covered by a baffle 10 having perforations 9. This preferred device operates in a similar manner to the embodiment described in Fig 5.

Referring to Figure 7 of the drawings there is shown a further preferred form of the invention. This embodiment has a housing 7 and a lid 4 defining a chamber 6. The housing communicates with the outside by a conduit 8. The lid includes an inspection port 1, allowing inspection of the water soluble plug 3 attached to the gas cylinder 5. The thread of the inspection port is interrupted to form a vent 2 that allows the escape of air that is displaced by incoming water. Inside the conduit 8 there is perforated ball 9 acting as a moveable baffle. A ledge 10 prevents the moveable baffle being lost from the conduit 8.

In use, the ingress of water is at least partially inhibited by the moveable baffle.

In this embodiment the moveable baffle is manufactured from buoyant material and is perforated. The incoming water floats the moveable baffle towards the water soluble plug, with the perforations allowing penetration of water into the plug.

Figure 8 illustrates yet a further embodiment of the present invention.

The device shown in Figure 8 includes a housing body 40 having a bottom end 41 and a top end 42. A conduit 43 extends through the housing body 40 and includes a baffle 44 having openings 45. Disposed within a top end of the conduit 43 is a gas cylinder 46 which is connected to a water soluble plug 47.

The top end 42 of the housing body 40 includes a push-on collar 48. The collar 48 includes a bottom edge 49 which is shown immediately adjacent the edge as including a cut-out portion 50 which receives a spigat 51. This arrangement locates the collar 48.

The collar 48 includes an outer thread 52 and the device includes a screw-on cap 53 which screw onto the collar. In Figure 8, the cap 53 is shown prior to threaded connection with the collar 48. The arrangement is such that ingress of water through the conduit 43 wets the soluble plug 47 to facilitate release of gas from the cylinder 46. Expanding gas causes both the collar 48 and the cap 53 to be dislodged from the housing body 40, for activation of the marker device. The advantage of this arrangement, is that the cap 53 can easily be removed from the housing body 40 for inspection of the device arrangements within the body 40 by unscrewing the cap 53 from the collar 48.

An example of an inflatable device for which the present invention is useful is that known as a"Dan Buoy". These flotation devices are deployed into the water as soon as a man overboard situation occurs, thereby marking the position of the sailor to assist rescuers. A Dan Buoy consists of an elongate member which is weighted at one end so that the non-weighted end extends high above the water surface, thereby acting as a visible beacon. These devices can be stored in a non-inflated state on board a vessel to save room, and may be automatically inflated by contact with water, often using compressed carbon dioxide. Because such devices must be deployed rapidly by crew members in an emergency situation they are often stored on the deck of a vessel where they are easily accessible. A problem is that Dan Buoys often automatically inflate in response to water splashing onto the deck. The present invention could be used with a water activated Dan Buoy to decrease the incidence of accidental inflation.

The present invention may also be used to control the actuation of electrical devices such as a light, radio transmitter or sound source, any of which may attract the attention of search and rescue personnel. In this case there is no requirement for the housing to fracture to physically release the

marker. Instead, the housing remains intact and the device is actuated directly by the water entering the housing. For example, the housing may contain a radio beacon which is switched on due to the ingress of water which completes an electrical circuit. In this case the conduit and vent of the present invention provide a means for controlling the ingress of water into the housing, the water then actuating a beacon inside the housing.

Further uses for the present invention will occur to the skilled worker, and are included in the scope of this invention. For example, the device could be used to control the water actuated inflation of safety devices such as life jackets.

The present invention is not limited to use in search and rescue settings.

For example, marker devices as described herein could be used for marking areas in the water with dye. Such devices are often deployed with a parachute.

In these applications, the device could be used to delay release of the dye until the marker is at least partially submerged to prevent scattering of the dye as it is dropped from an aircraft.

The devices of the present invention could be also attached to shipping containers thereby aiding location if a container is lost overboard.

Finally it is to be understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.