WO2009141334A1

WO2009141334A1 - Personal flotation devices

Info

Publication number: WO2009141334A1
Application number: PCT/EP2009/056052
Authority: WO
Inventors: William Joseph Mullen
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-05-23
Filing date: 2009-05-19
Publication date: 2009-11-26
Anticipated expiration: 2010-11-23
Also published as: GB2460273A; GB0809411D0; GB2460273B

Abstract

A personal flotation device (10) comprises an inflatable raft (30) having a base portion (50) and an inflatable wall portion (48) disposed around the periphery of the base portion to form a receptacle adapted to receive a user in a seated or lying position. A source of compressed gas (56) is provided for inflation of the wall portion, via a pair of gas feed pipes (64) communicating with a pair of gas inlets (66) situated in the wall portion, towards the foot end of the raft, at points generally symmetrically disposed about the longitudinal axis of the raft. A valve (78) is actuatable by a user, to cause gas to be supplied from the source (56), via the feed pipes (64), to both of the gas inlets (66) simultaneously, thereby inflating the wall portion in such a manner that opposite sides of the wall portion about the longitudinal axis of the raft inflate at substantially equal rates. The device further comprises an outer cover (32) adapted to be worn on the user's back and to enclose and retain the raft (30) when uninflated. The cover is closed around the uninflated raft by releasable closure means (34 to 46) adapted to open upon inflation of the raft. The uninflated raft (30) is packed within the outer cover (32) so that the head end is uppermost, the foot end lowermost and the longitudinal axis generally aligned with the user's spine, when worn by the user, so that, upon actuation of the valve (78) by the user when in water, the raft inflates beneath the user in a symmetrical fashion about the longitudinal axis, thereby tending to place the user within the raft upon full inflation, with the minimum of effort on his or her part.

Description

PERSONAL FLOTATION DEVICES

This invention relates to equipment for keeping personnel afloat in water. In particular, though not exclusively, it relates to survival rafts for use by aircrew of ditched aircraft (especially helicopters). The invention will also be of benefit to others at risk of finding themselves in the sea in an emergency situation, for example workers on large ships and on onshore and offshore oil and gas installations.

In the event of a crash landing at sea in a helicopter or other aircraft, the first priority for all personnel is to exit as quickly as possible, before the craft sinks. Anything likely to hinder escape greatly increases the risk of immediate drowning. Once outside the craft, flotation is crucial. In particular, it is important to minimise the time spent immersed in sea water, since prolonged immersion in cold water can readily cause hypothermia. In some circumstances there may also be a danger from marine predators such as sharks. The provision of a life raft is ideal.

Large commercial aircraft are commonly supplied with sizeable communal rafts. These are not appropriate for aircraft such as military helicopters, which have relatively small crews in limited space and cramped conditions, which are at particular risk of severe damage, for example through enemy action, and which tend to sink very rapidly. In high-risk situations such as this, it is usual for at least the pilot and co-pilot to be supplied with a personal life raft.

The standard design of personal life raft for pilots of military helicopters involves a "seat pan" system. In such a system, an inflatable lift raft is stored in a rigid container which fits into a corresponding cavity in the aircraft seat. The pilot (or other member of the aircrew) sits on top of the seat pan and straps himself to it, but normally only when flying over water. In the event of an emergency evacuation in water, he releases the seat pan from the infrastructure of the seat and must then escape from the crashed craft with the seat pan attached to his buttocks and upper legs. The bulk and rigidity of the seat pan hampers manoeuvrability and also provides a potentially fatal risk of snagging on damaged aircraft parts. Once free of the craft, the user then needs to deploy the raft and haul it towards himself using the attached lanyard, before climbing aboard. These steps can cause difficulties, particularly if the user is injured.

The unwieldy nature of the seat pan device dictates that members of the aircrew other than the pilot and co-pilot are not always supplied with them. Even when they are supplied, rear crew members tend not to wear them since they very often need to move around the aircraft to perform their duties and the seat pan provides a severe hindrance.

Aircrew who fly in larger aircraft, and rear aircrew in some smaller aircraft, have to rely on one nominated member of the rear crew to deploy a large shared raft after ditching in water. There is obviously a risk that the nominated person does not survive the crash and even if he does survive, the rafts tend to be heavy and difficult to deploy. Furthermore, in operations where weight is critical, they are often left behind.

There is therefore a need for an improved personal flotation device, which enables the user to exit a ditched aircraft with the least possible hindrance and to place himself within the inflated raft as quickly and easily as possible. The inventor has found that an improved personal flotation device may be carried on the user's back and, in preferred embodiments, remain attached during inflation. Moreover, such a raft may be constructed so that, upon deployment in water, the raft inflates in a symmetrical fashion beneath the user, tending to deposit the user within the raft automatically or, at least, with the minimum amount of effort on the user's part. The mobility impairment and snagging hazards implicit in the seat pan system are thereby mitigated to a great extent. Furthermore, the automatic "scooping" action of the inflating life raft permits even a severely injured user to board the inflated raft without the need to haul on a lanyard or clamber aboard.

The present invention therefore provides, in one aspect, a personal flotation device comprising: a raft having a head end and a foot end and a longitudinal axis of symmetry extending between said head end and said foot end, the raft comprising a base portion and an inflatable wall portion disposed around the periphery of the base portion to form a receptacle adapted to receive a user in a seated or lying position; a source of compressed gas for inflation of the wall portion; a pair of gas inlets situated in the wall portion, towards the foot end of the raft, at points generally symmetrically disposed about said longitudinal axis; a pair of gas feed pipes, each said gas feed pipe communicating between the source of compressed gas and a respective one of said gas inlets; a valve actuatable by a user of the flotation device to cause gas to be supplied from said source, via said feed pipes, to both of said gas inlets simultaneously, thereby to inflate the wall portion in such a manner that opposite sides of said wall portion about said longitudinal axis inflate at substantially equal rates; an outer cover adapted to be worn on the back of a user of the device and to enclose and retain the raft when uninflated, the cover being closable around the uninflated raft by releasable closure means adapted to open upon inflation of the raft; the uninflated raft being packed within the outer cover so that the head end is uppermost, the foot end lowermost and the longitudinal axis generally aligned with the user's spine, when worn by the user, so that, upon actuation of the valve by the user when in water, the raft inflates beneath the user in a symmetrical fashion about the longitudinal axis, thereby tending to place the user within the raft upon full inflation, with the minimum of effort on the user's part.

In preferred embodiments of personal flotation device according to the invention, the outer cover is integral with a jacket adapted to be worn the user. The jacket may conveniently be similar to a conventional life jacket, with an inflatable yoke. The back portion of the jacket preferably forms a base panel of the outer cover, and the outer cover preferably further comprises two side flaps, each side flap being attached along a lateral edge thereof to a respective side of the base panel. The side flaps may be provided, along their respective edges opposite to the edges along which they are attached to the base panel, with releasable engagement means enabling them to be releasably closed together in order to retain the uninflated raft. Such releasable engagement means may constitute the releasable closure means which is adapted to open upon inflation of the raft; alternatively, it may form a part of the releasable closure means, acting in concert with the further engagement means described below.

Preferably, the outer cover further comprises a cover panel provided with releasable engagement means along opposite sides thereof and corresponding releasable engagement means are provided along outwardly facing edge portions of the base panel or the side flaps. Attachment of the cover panel by such means serves to enclose (or assists in enclosing) the raft within the outer cover, thus constituting or forming part (or a further part) of said releasable closure means adapted to open upon inflation of the raft.

In further preferred embodiments, a top flap is attached along the top edge of the base panel and a bottom flap is attached along the bottom edge of the base panel. The top and bottom flaps are provided with releasable engagement means and the cover panel is provided with corresponding releasable engagement means along its top and bottom edges. Attachment of the cover panel to the top and bottom flaps assists in enclosing the raft within the outer cover, thus constituting or forming part (or a further part) of said releasable closure means adapted to open upon inflation of the raft.

To assist in positioning the raft during inflation, the cover base panel of a preferred embodiment of personal flotation device according to the invention is provided with releasable engagement means, with corresponding releasable engagement means being provided on a central portion of the upper surface of the base portion of the raft. In such embodiments, the raft remains attached to the base panel during inflation but may be released therefrom by the user after inflation.

Where reference is made in this specification to "releasable engagement means", any suitable means - as would suggest themselves readily to those skilled in the art - are intended to be encompassed within that term. In preferred embodiments, such means may comprise complementary strips of hook and loop attachment materials (for example, as sold under the trade mark Velcro®) and/ or press studs.

It has found to be preferable in operation of personal flotation devices according to the invention that the user's legs be brought upwards at an early stage during the inflation of the raft. When in water - and particularly when the yoke of the life jacket is inflated - the user's legs will tend to hang downwards. The legs need to be brought into a generally horizontal position in order to place the user inside the inflated raft, and it has been found that the stability of the device during operation is enhanced if this stage of the process is effected (or at least begun) before the side portions and head portion of the raft inflate. This is accomplished by the fact that the gas inlets in the wall portion of the raft are situated towards the foot end of the raft, with the result that the foot end of the raft tends to inflate first. Preferably, the gas inlets are situated at points located between 60% and 90% of the axial distance between the head and the foot end of the raft. More preferably, they are situated at points located between 70% and 85% of the axial distance between the head and the foot end of the raft.

The early inflation of the foot end is facilitated by packing the uninflated raft within the cover, so that the gas inlets are placed at the left and right bottom corners of the cover. Influx of air at these points rapidly expands the raft at the lower end of the cover and bursts the releasable engagement means between the bottom flap and the cover panel (if present), while the engagement between the side flaps and/ or between the side flaps and the cover panel remain intact for a short period. This permits substantial inflation of the foot portion (and therefore raising of the user's legs) before continued inflation puts sufficient pressure on the engagement means between the side panels, between the side panels and the cover panel and between the top panel and the cover panel to burst these also and allow the side portions and head portion of the raft to inflate. Preferably, the opposite sides of the inflatable wall are folded symmetrically within the cover, to optimise the symmetrical inflation of the side portion and minimise the risk of tipping the user out of the semi-inflated raft and into the water during inflation.

The source of compressed gas for inflation of the raft (and, if present, the inflatable yoke) conveniently comprises an elongate canister, which may be of conventional type. Typically, suitable canisters will be of generally cylindrical shape and for convenience they will be referred to hereinafter as "cylinders". While a cylindrical profile is preferred, however, it is not absolutely essential. In preferred embodiments of device according to the invention, a sleeve for retaining the cylinder is provided, attached to the underside of the base portion of the raft. The construction is preferably such that, upon release of the raft from the outer cover during inflation, the cylinder tends to hang downwardly beneath the longitudinal axis of the raft, with the cylinder generally orientated parallel with said axis. This may readily be accomplished, for example, by providing identical left and right support straps joining the sleeve to points equidistant on opposite sides of the principal longitudinal axis of the base of the raft. The sleeve and straps thereby form a cradle to support the cylinder in a central position and axially oriented beneath the raft.

This axial alignment of the compressed gas cylinder assists in ensuring that gas is supplied at a substantially equal rate to the two sides of the inflatable wall portion of the raft, thereby minimising the risk of tipping during inflation. This operation is further assisted, in preferred embodiments, by the provision of a symmetrical bifurcated junction between the gas cylinder and the gas feed lines, which ensures that substantially equal gas flows enter the two lines. The junction may, for example, comprise a "T" piece or a "Y" piece.

It is important that the gas feed lines should not be obstructed during inflation of the raft. The gas feed lines themselves are therefore preferably manufactured from tubing of the type used in self-contained underwater breathing apparatus (for example, resilient latex tubing), which resists the formation of folds or kinks when the raft is packed within the outer cover. The junction between each of the gas feed lines and the gas inlets of the inflatable wall should also be constructed so as to avoid obstruction. Preferably, each of the gas inlets comprises a joint having an upstanding section extending outwardly from the wall of the raft and an angled section connected in sealing relationship to the upstanding section. The angle may, for example, be approximately 90 degrees. Preferably, the angled section is capable of rotation about the axis of the upstanding section, so as to facilitate movement of the gas feed lines during the inflation of the raft, without causing obstruction to the gas flow. The gas inlets preferably include non-return valves, to prevent deflation of the raft after initial inflation.

While the main purpose of the present invention is to provide a life raft to provide flotation for a user, an ancillary purpose is to permit the user to escape safely from a crashed aircraft, which may be underwater. In preferred embodiments of personal flotation device according to the invention, therefore, a source of compressed oxygen-containing breathable gas (e.g. compressed air) is supplied, connected to a breathing hose terminating in a mouthpiece. This is to ensure the user can continue breathing for a limited period while underwater, before reaching the surface and deploying the life raft. The breathable gas is conveniently contained in a cylinder, retained in a side pocket of the life jacket. Preferably, the cylinder is provided with a gauge indicating the amount of gas remaining therein; preferably, also, the pocket of the jacket for retaining the cylinder comprises at least a portion composed of a transparent material to permit the user readily to read the gauge without removing the cylinder. This feature is of particular utility in enabling safety checks to be carried out prior to use.

Conveniently, the mouthpiece of the emergency breathing system engages in a mouthpiece protector attached to a front portion of the jacket. This ensures not only that the mouthpiece is retained in a convenient position readily accessible by the user in an emergency but also prevents foreign objects from entering the mouthpiece and potentially clogging the breathing line.

Apart from the outer cover and inflatable raft contained therein, the jacket may be of substantially conventional design. The right and left side portions of the jacket may, for example, be fastened by an adjustable waist strap, both for comfort and security. Additionally, the right and left portions of the yoke may be fastened by one or more adjustable chest straps, to ensure snug fitting.

In order to prevent the base portion of the outer cover moving away from the user, either during escape from a crashed aircraft or during inflation of the raft, preferred embodiments comprise a crotch strap attached at one end to the rear portion of the jacket (e.g. a rear portion of the outer cover) and at the other end to the front of the jacket, the strap being adapted to pass between the legs of a user. The outer cover containing the inflatable raft is therefore kept securely in the correct position on the user's back until the life raft has been deployed.

In order to give maximum protection to the user, after deployment of the raft, preferred embodiments of device according to the invention further comprise a weather shield adapted to cover substantially the whole of the user's body when sitting in the raft, in order to provide protection against wind and precipitation. The weather shield preferably comprises a sheet of waterproof material, attached at its lower end around a peripheral portion of the raft. Conveniently, the sheet extends upwardly and inwardly from its bottom edge and terminates at an upward peripheral edge to form a neck hole for the user. In most preferred embodiments, a hood is also provided, attached around the neck hole. The weather shield is preferably provided with a closable opening (provided, for example, by a zip fastener) permitting the user to place himself within the weather shield and to close the sheet so that it is supported by his shoulders, with only his head protruding.

Although the life raft is intended to inflate automatically beneath the user and effectively to "scoop" the user up into the inflated raft with the minimum of effort, it is conceivable that the user may part company with the raft, either during or after inflation, for example in choppy seas. In preferred embodiments, therefore, a lanyard is provided, joining the life raft to the jacket, so that the user can, if necessary, retrieve the life raft. To permit ease of rescue of the user, for example by helicopter, the lanyard preferably is secured by a releasable clip (e.g. a Martin Baker® clip) to permit quick release, when desired.

The life raft and jacket may be manufactured of conventional materials and, apart from the particular features described herein, they may be of substantially conventional design. It is preferred that all of the materials be fireproof.

One of the principal advantages of the present invention is that the personal flotation device may easily be carried by the user on his back. In embodiments specifically designed for use by pilots and other air crew members, the device may preferably be configured so that, when seated, a substantial portion of the weight is carried by the seat rather than by the back of the user. This may be achieved by judicious selection of the axial length of the outer cover in relation to the typical height of the upper body of a user.

The invention thus makes possible an integrated personal flotation device, wherein the jacket portion remains on the user throughout the deployment of the raft. Nothing needs to be attached or detached by the user and the cover portion opens automatically (preferably with the back cover being blown off) after activation, by the pressure of the life raft inflating.

The invention is hereinafter described in more detail by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is the front view of a personal flotation device according to the invention;

Fig. 2 shows the device of Fig. 1 being worn by a user;

Fig. 3 is a left side view of the Fig. 1 device, indicating (in ghosted lines) the connection between the source of compressed gas and the actuation means;

Fig. 4 is a right side view of the Fig. 1 device;

Fig. 5 is a rear view of the Fig. 1 device, with the raft fully uninflated and the cover panel fully attached;

Fig. 6 corresponds to Fig. 5 but shows the cover panel detached at its bottom end;

Fig. 7 is a rear perspective view of the Fig. 1 device, illustrating the raft in the first stage of inflation;

Fig. 8 corresponds to Fig. 7 and illustrates the raft in a more advanced state of inflation;

Fig. 9 illustrates the raft in a yet more advanced state of inflation;

Fig. 10 is an underside view of the raft illustrated in Fig. 9;

Fig. 11 is a close-up of the gas inlet of Fig. 10;

Fig. 12 is a perspective view of the fully inflated raft, with user in situ; Fig. 13 corresponds to Fig. 12 and illustrates the position of the weather shield when in use; and

Fig. 14 is a close-up corresponding to Fig. 12, illustrating the attachment lanyard.

The personal flotation device (10) illustrated in Fig. 1 comprises an inflatable yoke (12) of conventional design, attached to back panel (14) and side panels (16). In the illustrated embodiment, back panel (14) and side panels (16) are manufactured of lightweight webbing, for comfort and ease of carrying.

The lower portions of the opposite side panels (16) are joined by waist strap (18), via buckle (20). Buckle (20) is adjustable, to permit waist strap (18) to alter in length to fit the user snugly. Lower portions of the opposite ends of yoke (12) are also joined via chest strap (22), via adjustable buckle (24). To ensure correct positioning of the life raft during inflation, a lower portion of the life raft cover (see Fig. 5) is joined by crotch strap (26) to chest strap (22), via adjustable buckle (28).

Inflatable life raft (30) is contained within outer cover (32) (see Figs. 6 to 8).

Outer cover (32) comprises side flaps (34), bottom flap (36) and a corresponding top flap (not shown in the drawings). Side flaps (34) are secured around uninflated raft (30) via strips of hook and loop attachment material (37) (e.g. Velcro® strips), which serve to retain the uninflated raft securely during normal use of the device but which form a line of weakness in the outer cover, permitting opening of the cover during inflation of life raft (30).

Further strips of hook and loop material (38) are supplied on the outer surface of side flaps (34), with complementary engagement strips (40) being supplied on the inner surface of cover panel (42). Similarly, a yet further strip of hook and loop material (44) is supplied along the outwardly facing surface of bottom flap (36), for engagement with a corresponding strip (46) along the bottom inner edge of cover panel 42. Corresponding complementary strips are also provided along the outer surface of the top flap and the upper inner edge of cover sheet (42). The provision of cover sheet (42) and of the additional engagement means provides greater robustness for the outer cover and minimises the chance of inadvertent opening of the cover during normal use. The use of hook and loop strips (or other suitable releasable engagement means, such as press studs), however, ensures that the life raft may expand and escape from the outer cover during inflation.

Moreover, the arrangement of the engagement strips may be engineered to assist in ensuring that the various portions of the life raft inflate in the desired sequence. Thus, for example, it will be noted that there is only one set of releasable engagement strips (44/46) retaining the lower end of the life raft, whereas there are three such strips (37 and 38/40), which need to become disengaged before the side portions of the raft can inflate.

The features of life raft (30) itself can best be seen from Figs. 9 and 10. Inflatable wall (48) surrounds base portion (50), which preferably is also inflatable. One or more engagement strips (52) are provided on the upper surface of base portion (50) and are oriented generally along the principal axis of the raft between its head end (54) and foot end (56). These engage with corresponding strips on the outer surface of the back panel (14) of the life jacket (not shown) and serve to retain the raft in position on the user's back during the inflation. However, their releasable nature allows the user to disengage from them and sit up in the raft after inflation is complete.

The underside of the raft is shown in Fig. 10. Cylinder (56) holds compressed gas (e.g. CO2) for inflation of the life raft and is retained in sleeve (58), joined to opposite side portions of the base of the raft via straps (60). Together, sleeve (58) and straps (60) form a cradle, which serves to hold cylinder (56) in a generally central position and generally axially aligned with the raft during inflation.

Cylinder (56) is attached via "T" piece (62) to a pair of gas feed lines (64), which supply opposite sides of inflatable wall (48) with gas, during inflation. Gas feed lines (64) consists of resilient polymeric tubing of the type commonly used in underwater breathing apparatus, which is resistant to the formation of folds or kinks. The use of such material helps to ensure that the gas feed lines both remain open during inflation of the life raft. During deployment, the gas feed lines (64) supply gas at a substantially equal rate to each of gas inlets (66) , situated towards the foot end (56) of the raft. Each gas inlet comprises a joint comprising an upstanding section (68), extending outwardly from the wall of the raft, which fits with an angled section (70) (for example, forming an angle of 90 degrees), which is attached to the gas feed pipe (64). In the illustrated embodiment, the angled section (70) is capable of rotation about the axis of upstanding section (68). This freedom of movement helps to minimise tension in gas feed pipes (64) during unfolding and inflation of raft (30) and therefore helps to ensure that gas feed pipes (64) do not become bent during this process to such an extent that gas flow is hindered.

Inflation of the life raft is illustrated in Figs. 7 to 9. During the first stage of inflation, air is supplied to gas inlets (64), which are packed towards the bottom end of outer cover (32). Consequently, life raft (30) starts to inflate towards the foot end (56) and pressure is applied to engagement strips (44 and 46) along the bottom edge of the outer cover. Further inflation causes these strips to detach, permitting release of the foot end (56) of the life raft (30) from outer cover (32) (see Fig. 7). This inflation of the foot end of the life raft tends to urge the user's legs upwards in the water, bringing the user nearer to a horizontal position.

Further inflation results in expansion of the side portions of inflatable wall (48), which puts pressure on axial engagement strips (37 and 38/40). The seals formed by these strips eventually break (as illustrated in Fig. 8), permitting the side portions of the inflatable wall to inflate fully. Due to the symmetrical arrangement of the gas feed pipes (64) and gas inlets (66), gas is supplied at a substantially equal rate to the two opposite sides of the inflatable wall, which accordingly expand outwards at substantially equal rates. Thus, when correctly deployed, there is no tendency for the user to be tipped off the inflating life raft into the water; on the contrary, the controlled inflation of the life raft tends to scoop the user inside, upon full inflation.

During the inflation of the side portions of the life raft, the head portion (54) also begins to inflate, breaking the seal provided by the engagement strip between the top flap and the top edge of the cover panel. Actuation of the gas cylinder to cause inflation of the life raft is controlled by the user by means of activation handle (72) (see Fig. 3). In preferred embodiments, such as that illustrated, this is provided with means to provide ease of gripping by the user, for example the beading illustrated. Activation handle (72) is attached via activation cord (74) to a release pin (76) retained in valve (78) of gas cylinder (58). In the illustrated embodiment, activation cord (74) is housed within a sleeve provided in the life jacket, so as to minimise the risk of snagging and inadvertent inflation of the life raft.

In preferred embodiments, the activation cord is also attached to a further source of compressed gas for inflating the inflatable yoke. A first pull on the activation handle then inflates the yoke and a second pull on the same handle initiates inflation of the life raft.

As will be seen from Figures 12 and 13, the life raft is further provided with weather shield (80), which has a longitudinal opening (22) to permit the user to place himself within the weather shield. Opening (82) can be closed by releasable closure means (84). In the illustrated embodiment, this consists of complementary strips of hook and loop material (e.g. Velcro®) but it could equally well be provided by a row of press studs or a zip, for example. The weather shield is also provided with a hood (86), to provide maximum protection for the user against inclement weather.

The illustrated embodiment is provided with a personal breathing system, permitting the user to breathe underwater for a limited period of time, if necessary. The personal breathing system comprises a cylinder (88) of compressed breathable gas (e.g. air or oxygen) housed within a sleeve provided on one side of the outer cover. For comfort and ease of use, cylinder (88) may be of similar size and weight to cylinder (58) and the latter may be packed on the opposite side to cylinder (88), so as to provide balance. Sleeve (90) is provided with transparent top portion (92), through which gauge (94) may be viewed, indicating the level of breathable gas within cylinder (88).

Cylinder (88) is attached to breathing line (96), which terminates in mouthpiece (98). Mouthpiece (98) is retained by guard (100), attached to yoke (12) in a position allowing easy access by the user in case of need. The personal breathing system is actuated by a demand valve (not shown), allowing the user to breathe at will through mouthpiece (98), when needed.

In case the user should part company with the raft, either during or after inflation, the jacket is attached to the raft by lanyard (102), via releasable clip (104) (e.g. a Martin Baker® clip). This permits detachment of the user from the raft, at will, for example upon rescue by helicopter.

As will be appreciated, personal flotation devices constructed according to the invention have several advantages compared to those of the prior art. In particular, they may be constructed so as to more lightweight and comfortable than existing seat pan systems and may be constructed to be integral with a life jacket. They may also be constructed to have a much more slender profile than prior art devices and thus to present less of a snagging hazard and consequently to facilitate escape from ditched aircraft. Moreover, the "scooping" action of the symmetrically- inflating raft greatly facilitates the user in placing him or herself with the inflated raft. Modifications of the specific features described herein will suggest themselves to those skilled in the art and are intended to be within the scope of the appended claims.

Claims

1. A personal flotation device comprising: a raft having a head end and a foot end and a longitudinal axis of symmetry extending between said head end and said foot end, the raft comprising a base portion and an inflatable wall portion disposed around the periphery of the base portion to form a receptacle adapted to receive a user in a seated or lying position; a source of compressed gas for inflation of the wall portion; a pair of gas inlets situated in the wall portion, towards the foot end of the raft, at points generally symmetrically disposed about said longitudinal axis; a pair of gas feed pipes, each said gas feed pipe communicating between the source of compressed gas and a respective one of said gas inlets; a valve actuatable by a user of the flotation device to cause gas to be supplied from said source, via said feed pipes, to both of said gas inlets simultaneously, thereby to inflate the wall portion in such a manner that opposite sides of said wall portion about said longitudinal axis inflate at substantially equal rates; an outer cover adapted to be worn on the back of a user of the device and to enclose and retain the raft when uninflated, the cover being closable around the uninflated raft by releasable closure means adapted to open upon inflation of the raft; the uninflated raft being packed within the outer cover so that the head end is uppermost, the foot end lowermost and the longitudinal axis generally aligned with the user's spine, when worn by the user, so that, upon actuation of the valve by the user when in water, the raft inflates beneath the user in a symmetrical fashion about the longitudinal axis, thereby tending to place the user within the raft upon full inflation, with the minimum of effort on the user's part.

2. A personal flotation device according to claim 1, wherein the outer cover is integral with a jacket adapted to be worn the user.

3. A personal flotation device according to claim 2, wherein a back portion of the jacket forms a base panel of the outer cover.

4. A personal flotation device according to claim 3, wherein the outer cover further comprises two side flaps, each side flap being attached along a lateral edge thereof to a respective side of said base panel.

5. A personal flotation device according to claim 4, wherein said side flaps are provided, along their respective edges opposite to the edges along which they are attached to the base panel, with releasable engagement means enabling said side flaps to be releasably closed together in order to retain the uninflated raft, said releasable engagement means constituting or forming part of said releasable closure means adapted to open upon inflation of the raft.

6. A personal flotation device according to any of claims 3 to 5, wherein said outer cover further comprises a cover panel provided with releasable engagement means along opposite sides thereof, and wherein corresponding releasable engagement means are provided along outwardly facing edge portions of said base panel or said side flaps, whereby attachment of said cover panel serves to enclose or assists in enclosing said raft within said outer cover, said releasable engagement means constituting or forming part of said releasable closure means adapted to open upon inflation of the raft.

7. A personal flotation device according to claim 6, further comprising a top flap attached along the top edge of said base panel and a bottom flap attached along the bottom edge of said base panel, said top and bottom flaps being provided with releasable engagement means, and wherein said cover panel is provided with corresponding releasable engagement means along the top and bottom edges thereof, whereby attachment of said cover panel to said top and bottom flaps assists in enclosing said raft within said outer cover, said releasable engagement means between said cover panel and said top and bottom flaps forming part of said releasable closure means adapted to open upon inflation of the raft.

8. A personal flotation device according to any of claims 3 to 7, wherein the base panel of the cover and a central portion of the upper surface of the base portion of the raft are provided with releasable engagement means, whereby said raft may remain attached to said base panel during inflation and may be released therefrom by the user after inflation.

9. A personal flotation device according to any of claims 5 to 8, wherein said releasable engagement means comprise complementary strips of hook and loop attachment materials and/ or press studs.

10. A personal flotation device according to any preceding claim, wherein the gas inlets are situated at points located between 60% and 90% of the axial distance between the head and the foot end of the raft.

11. A personal flotation device according to claim 10, wherein the gas inlets are situated at points located between 70% and 85% of the axial distance between the head and the foot end of the raft.

12. A personal flotation device according to claim 2, or to any claim appendant to claim 2, wherein the jacket further comprises an inflatable yoke.

13. A personal flotation device according to claim 12, wherein inflation of said collar is triggered by manual pulling of an activation cord by the user.

14. A personal flotation device according to claim 13, wherein inflation of the raft is triggered by a second manual pulling of the activation cord by the user.

15. A personal flotation device wherein said source of compressed gas comprises an elongate cylinder, the personal flotation device further comprising a sleeve adapted to retain the cylinder and attachment means between said sleeve and the underside of the base portion of the raft, whereby, upon release of the raft from the outer cover during inflation, the cylinder tends to hang downwardly beneath said longitudinal axis of the raft, with the cylinder generally orientated parallel with said axis.

16. A personal flotation device according to any preceding claim, wherein the communication between the source of compressed gas and the gas feed pipes is via a symmetrical bifurcated junction adapted to provide substantially equal flows of gas to the two gas feed pipes.

17. A personal flotation device according to claim 16, wherein the bifurcated junction comprises a "T" piece or a "Y" piece.

18. A personal flotation device according to any preceding claim, wherein each of the gas inlets comprises a joint comprising an upstanding section extending outwardly from the wall of the raft and an angled section connected to the upstanding section and rotatable about the axis thereof.

19. A personal flotation device according to any preceding claim, wherein each of the gas inlets includes a non-return valve.

20. A personal flotation device according to any preceding claim, further comprising a source of compressed, oxygen-containing, breathable gas, connected to a breathing hose terminating in a mouthpiece.

21. A personal flotation device according to claim 20, as appendant to claim 2, wherein the compressed, oxygen-containing, breathable gas is contained within a cylinder and wherein the jacket further is provided on one side thereof with a pocket adapted to receive said cylinder.

22. A personal flotation device according to claim 21, wherein the cylinder containing said compressed, oxygen-containing, breathable gas is provided with a gauge indicating the amount of gas therein, and wherein the pocket receiving the cylinder comprises at least a portion composed of a transparent material to permit a user readily to read the gauge without removing the cylinder.

23. A personal flotation device according to any of claims 20 to 22, further comprising a mouthpiece protector adapted to engage the mouthpiece and prevent foreign objects from entering, the mouthpiece protector being attached to a front portion of the jacket, so as to retain the mouthpiece in a position readily accessible by the user in case of need.

24. A personal flotation device according to any of claims 2 to 23, wherein left and right side portion of the jacket are fastenable via an adjustable waist strap.

25. A personal flotation device according to any of claims 12 to 24, wherein left and right portions of said yoke are fastenable via one or more adjustable chest straps.

26. A personal flotation device according to any of claims 2 to 25, further comprising a crotch strap adapted to pass between the legs of a user, the crotch strap being attached at opposite ends to front and rear portions of the jacket.

27. A personal flotation device according to any of claims 2 to 26, further comprising a lanyard connecting the jacket to the raft via a releasable clip.

28. A personal flotation device according to any preceding claim, manufactured of fire-proof materials.

29. A personal flotation device according to any preceding claim, wherein the axial length of the outer cover is chosen in relation to the height of the upper body of a user, so that when wearing the jacket in a seated position, a substantial portion of the weight of the device is borne by the seat.

30. A personal flotation device according to any preceding claim, wherein the uninflated raft is packed into the outer cover so that the gas inlets are placed at the left and right bottom corners of the cover and the opposite sides of the inflatable wall are folded symmetrically.

31. A personal flotation device according to any preceding claim, further comprising a weather shield composed of a sheet of waterproof material attached at its lower edge around a peripheral portion of the raft, the sheet extending upwardly and inwardly therefrom and terminating at an upward peripheral edge to form a neck hole, the sheet having a closable opening permitting the user to place himself within the weather shield and to close the sheet so that it is supported by his shoulders with only his head protruding.

32. A personal flotation device according to claim 31, wherein the weather shield further comprises a hood to protect the user's head.