TECHNICAL FIELD

The present invention relates to a life preserver having one or more torso portions extending over the front of a wearer' s torso and a neck portion extending behind the wearer' s neck . The present invention also relates to methods of operating a life preserver .

BACKGROUND TO THE INVENTION

Known life preserver units (LPUs ) , such as lifej ackets , include an inflatable body for providing buoyancy for the wearer so that the wearer' s head is supported above the surface of the water in order to prevent drowning .

Figure 1 shows one known form of an LPU A, which comprises a body B that is generally U-shaped and is for fitting around a wearer ' s neck .

The body B comprises first and second inflatable buoyancy sections C and D which form symmetrically disposed legs of the "U" , arranged to lie on opposite sides of the front a wearer ' s torso . First ends of the first and second buoyancy sections C, D are j oined together by a neck portion E . The first and second buoyancy sections C, D, together with the neck portion E , define an aperture F for receiving a wearer ' s head and neck .

In use , the first and second buoyancy sections C , D define a space below the wearer ' s chin . For example , the second buoyancy section D is provided with an integral chin support G which extends from a portion second buoyancy section D provided towards the neck aperture F .

Standard ISO 12402-2 requires an LPU to meet amongst other performance requirements two test standards : 1 ) That the LPU when inflated will turn an unconscious survivor from a face-down attitude in the water, as shown in Figures 2 and 3 , to a face-up orientation, as indicated by arrow H . A problem is that unconscious survivors in the water will tend to take up a face-down orientation, particularly if wearing buoyant clothing , when the face will be immersed and they will drown . It can be difficult to create a desired self-righting effect , to rotate the wearer from a face-down orientation to a face-up orientation, particularly if wearing buoyant clothing , as the buoyancy in the clothing acts against any turning moment ( indicated by arrow H ) that the LPU is creating . Further, in a conventional LPU the entire LPU is inflated at the same time , and inflation of the neck portion E can work against any turning force ( indicated by arrow H ) generated by inflation of the first and second buoyancy sections C , D .

2 ) That the LPU supports the wearer with the head and trunk at the correct angles and that the height of the airways above the water level is sufficient to prevent drowning . The first of these requirements is known as the FPA ( Face Plane Angle ) , which the buoyancy around neck and shoulders creates , and this has to be typically in the range of 15° to 25° . If the FPA is too shallow ( e . g . less than 15° ) then waves can wash over the mouth and cause choking ( dry drowning ) and if it is too steep then the subj ect cannot breathe properly . The second of these requirements is known as the HOM ( Height of Mouth ) . This is vital in achieving survival and the height of the mouth from the water surface should generally be a minimum of 120 mm to comply with current regulated standards .

With known LPU designs , improving one of these performance requirements adversely affects the other of these performance requirements . For example , providing greater buoyancy at the front of the wearer' s torso will increase the self-righting motion ( improving the first performance requirement ) but this greater buoyancy at the front of the wearer' s torso will decrease the FPA and HOM ( the second performance requirement ) . Further, providing greater buoyancy behind the wearer' s neck will increase the FPA and HOM ( improving the second performance requirement ) but this greater buoyancy behind the wearer' s neck will resist the self-righting motion ( the first performance requirement ) .

Embodiments of the present invention seek to provide an improved life preserver .

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a life preserver having one or more torso portions configured to extend over a front of a wearer' s torso in use ; a neck portion configured to extend behind the wearer' s neck in use ; a first inflatable volume ( or space ) configured to provide buoyancy primarily to the one or more torso portions when inflated; and a second inflatable volume ( or space ) configured to provide buoyancy to the neck portion when inflated; and inflation means ( or inflator device ( s ) ) configured to control inflation of the first inflatable volume and the second inflatable volume such that the second inflatable volume begins inflation after the first inflatable volume .

Advantageously, such an arrangement initially provides buoyancy primarily at the front of the wearer' s torso ( due to inflation of the first inflatable volume ) which tends to rotate the wearer if they are lying face-down in water to a safer position where they are face-up in the water ( i . e . the life preserver provides self-righting of the wearer e . g . when unconscious ) . The subsequent inflation of the second inflatable volume in the embodiment provides buoyancy behind the wearer' s neck and shoulders to provide the desired Face Plane Angle and Height of Mouth . The second inflatable volume is initially deflated and so does not counteract the self-righting effect of the first inflatable volume . The subsequent inflation of the second inflatable volume may occur after the self-righting has taken place . In this way, the conflicting aims in the prior art of providing self-righting, and the desired Face Plane Angle and Height of Mouth, can both be achieved effectively according to the embodiment of the present invention .

The life preserver may have an outer casing that forms the one or more torso portions and the neck portion, the first and second inflatable volumes being contained in a chamber defined by the outer casing .

The outer casing may have a top surface and a bottom surface that form the chamber , wherein a baffle is provided that extends between the top surface and the bottom surface , the baffle being configured to divide the chamber into a first region located on a first side of the baffle and a second region located on a second side of the baffle , and wherein the first inflatable volume is in the first region and the second inflatable volume is in the second region .

The baffle may extend obliquely between the top surface and the bottom surface such that the first region and the second region partially overlap one another .

In the embodiment to be described, the life preserver has a first inflatable bladder that provides the first inflatable volume and a second inflatable bladder that provides the second inflatable volume . However, the bladders are not essential . The inflatable volumes may be formed by using appropriate gas impermeable materials for the top and bottom surfaces and for the baffle , and by connecting these elements together in a gas-tight manner . The baffle may be configured to constrain the location of the bladders such that the first bladder in located in the first region and the second bladder is located in the second region .

The first bladder and the second bladder may be located by the baffle such that they partially overlap one another when inflated .

The inflation means may be automatically triggered by contact with water . For example , a hydrostatic inflator may be used .

The inflation means may include a first inflator configured to inflate the first inflatable volume and a second inflator configured to inflate the second inflatable volume , the second inflator being arranged such that it is automatically triggered after the first inflator is triggered .

The second inflator may be mechanically triggered by inflation of the first inflatable volume . For example , the first inflator is first triggered ( such as by contact with water ) , which starts inflation of the first inflatable volume . The movement caused as the first inflatable volume becomes fully inflated then caused the mechanical triggering of the second inflator .

The second inflator may include a trigger mechanism and cable coupled to the first inflatable volume , and that is moved by inflation of the first inflatable volume , the movement of the cable operating the trigger mechanism and triggering operation of the second inflator to inflate the second inflatable volume . For example , as the first inflatable volume becomes fully inflated, its surface to which the cable is attached becomes taught - which pulls the cable and operates the trigger mechanism .

In the embodiment , only the first inflator is automatically triggered by contact with water . For example , the first inflator may be a hydrostatic inflator . The second inflator is not automatically triggered by contact with water . Currently, conventional inflatable life j ackets have a single inflation device which inflates the whole lifej acket in one go ( for example , there is a single bladder that is inflated by a single inflator ) . The embodiment aims to enhance the performance of a lifej acket by staging the inflation to provide the turning capability first . The embodiment inflates a turning bladder in front of the torso in the first stage and then at the second stage inflates the neck support bladder for the desired mouth freeboard . This may allow for quicker turning in the water and then creating the rest of the HOM and FPA performance needed after .

In the embodiment , the first stage inflates only a front turning bladder which is of sufficient front centralised buoyancy and dynamic action to create the self-righting moment . The subsequent second stage then, after the self- righting moment , supports the survivor with the head and trunk at the correct angles and the height of the airways above the water level sufficient to prevent drowning .

According to a second aspect of the invention, there is provided a method of operating a life preserver having one or more torso portions configured to extend over a front of a wearer' s torso in use , a neck portion configured to extend behind the wearer' s neck in use , a first inflatable volume configured to provide buoyancy primarily to the one or more torso portions when inflated, and a second inflatable volume configured to provide buoyancy to the neck portion when inflated, the method including controlling inflation of the first inflatable volume and the second volume such that the second inflatable volume begins inflation after the first volume . By operating the life preserver in this way, the self- righting force provided by the inflation of the first inflatable volume is not counteracted by any volume of air in the neck portion . The inflation of the neck portion may be delayed until self-righting has occurred . According to a third aspect of the invention, there is provided a method of operating a life preserver having one or more torso portions configured to extend over a front of a wearer' s torso in use and a neck portion configured to extend behind the wearer' s neck in use , the method including inflating a first inflatable volume to provide buoyancy primarily to the one or more torso portions to rotate a wearer from a face-down position to a face-up position on water, and subsequently inflating a second inflatable volume configured to provide buoyancy to the neck portion to increase the distance of the wearer' s mouth from the water surface and/or to vary a face plane angle of the wearer .

All of the features described herein may be combined with any of the above aspects , in any combination .

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention an embodiment will now be described by way of example , with reference to the accompanying drawings , in which :

Figure 1 shows a plan view of the front of a known life preserver;

Figure 2 shows a side view of a known life preserver with the wearer in an undesirable face-down position in water;

Figure 3 shows an end view of a known life preserver with the wearer in an undesirable face-down position in water;

Figure 4 shows a plan view of a bottom layer of material used to form a life preserver according to an embodiment of the invention;

Figure 5 shows a plan view of a top layer of material used to form the life preserver according to the embodiment of the invention;

Figure 6 shows a plan view of a generally U-shaped baffle of the life preserver according to the embodiment of the invention;

Figure 7 shows a plan view of the baffle attached to the bottom layer along an upper attachment line ;

Figure 8 shows a plan view of the baffle attached to the top layer along a lower attachment line ;

Figure 9 shows a plan view of an upper bladder ( or "angles" ) bladder of the life preserver ;

Figure 10 shows a plan view of a lower ( or "turns" ) bladder of the life preserver ;

Figure 11 shows the relative locations of the upper and lower bladders when mounted in the life preserver prior to inflation;

Figure 12 shows the upper and lower bladders within the bottom layer of the life preserver ;

Figure 13 shows a front view of the life preserver with the attachment lines of the top layer shown;

Figure 14 shows a rear view of the life preserver with the attachment lines of the bottom layer shown;

Figures 15 , 16 , 18 and 19 show schematically right side views ( the opposite side corresponds ) of the life preserver in various states of operation of the inflation arrangement ;

Figures 17A and 17B show partial close-up views of an upper inflator where it is attached to the top layer of material ; Figure 20 shows a side view of the life preserver with the wearer in the desirable face-up position in water; and

Figure 21 shows an end view of the life preserver with the wearer in the desirable face-up position in water.

In the drawings like elements are generally designated with the same reference sign.

DETAILED DESCRIPTION OF EMBODIMENT OF THE INVENTION

Referring initially to Figures 4 and 5, there is shown a life preserver unit (LPU) 1, such as a lifejacket. The life preserver 1 comprises a body 2 that is generally U-shaped and is for fitting around a wearer's neck.

The body 2 comprises first and second inflatable buoyancy sections 3 and 4 which form generally symmetrically disposed legs of the U-shape, arranged to lie on opposite sides of a wearer's torso. First ends of the first and second buoyancy sections 3, 4 are joined together by a neck portion 5. The first and second buoyancy sections 3, 4 each extend from said first end to a second end, which is a free end. The first and second buoyancy sections 3, 4 each comprise a lobe 20, 22 that is formed by width of the first and second buoyancy sections 3, 4 being greatest at a position between the first end and the second, free end of the buoyancy sections 3, 4. The first and second buoyancy sections 3, 4, together with the neck portion 5, define an aperture 6 for receiving a wearer's head and neck.

The lifejacket body 2 is formed from bottom and top layers of material 8, 9 sealed together along a seam (as described below) , towards a peripheral edge.

When inflated, each buoyancy section 3, 4 is an elongate member of generally oval cross section. In use the first and second buoyancy sections 3, 4 lie on opposite sides respectively of a wearer's chest, in side-by- side relationship.

In use, the first and second buoyancy sections 3, 4 define a space below the wearer's chin. In the example shown, the second buoyancy section is provided with an integral chin support 11 which extends from a portion of the second buoyancy section 4 provided towards the neck aperture 6. A neck support 11 may additionally, or alternatively, extend from the first buoyancy section 3, or may be omitted.

When the chin support 11 is nested under the wearer's chin, it may act to prevent the first and second buoyancy sections 3, 4 from riding up over the wearer's head.

Figure 4 shows a plan view of the bottom layer of material 8 used to form the life preserver 1. Figure 5 shows a plan view of the top layer of material 9 used to form the life preserver 1. In order to form the life preserver 1, the top layer 9 is placed over the bottom, substantially identical, layer 8 and aligned with the bottom layer. In accordance with an embodiment of the invention, various elements are located between the top layer 9 and the bottom layer 8, as described below .

A generally U-shaped baffle 30, as shown in Figure 6, formed by a layer of flexible material, is provided between the top layer 9 and the bottom layer 8. The baffle 30 comprises first and second symmetrically disposed legs 33, 34 of the U-shape, arranged to lie on opposite sides of a wearer's torso. First ends of the first and second legs 33, 34 are joined together by a baffle neck portion 35. The first and second legs 33, 34 each extend from said first end to a second end, which is a free end. The first and second legs 33, 34 each comprise a baffle lobe 40, 42 that is formed by width of the first and second legs 33 , 34 being greatest at a position between the first end and the second, free end of the legs 33 , 34 . The first and second legs 33 , 34 , the baffle neck portion 35 and the baffle lobes 40 , 42 are smaller than the corresponding parts of the top layer 9 and the bottom layer 8 , so that the baffle 30 can fit within the outline of the top layer 9 and the bottom layer 8 - as shown in Figures 7 and 8 .

The baffle 30 is attached to the bottom layer 8 along an upper attachment line 50 shown in Figure 7 . This line generally follows the shape of the upper part ( shown in Figure 7 ) of the baffle 30 . The baffle 30 may be attached to the bottom layer 8 along the upper attachment line 50 by stitching along the line 50 .

The baffle 30 is also attached to the top layer 9 along a lower attachment line 52 shown in Figure 8 . This line generally follows the shape of the lower part ( shown in Figure 8 ) of the first and second legs 33 , 34 of the baffle 30 . The baffle 30 may be attached to the top layer 9 along the lower attachment line 52 by stitching along the line 52 .

According to the embodiment , two inflatable bladders are provided at different positions between the top layer 9 and the bottom layer 8 . The two inflatable bladders are different in shape from one another . Figure 9 shows an upper ( or "angles" ) bladder 60 and Figure 10 shows a lower ( or "turns" ) bladder 80 .

The upper bladder 60 is generally U-shaped and is formed by two identical layers of air-impermeable flexible material that are j oined together by peripheral upper bladder attachment line 62 . The two identical layers of air-impermeable flexible material may be welded or heat sealed together along the attachment line 62 . In order to achieve this heat sealing , a layer of heat melt adhesive may be provided between the first and second layers of material . The layers of material may be a plastic-coated fabric that is gas impermeable . It will be appreciated that any suitable material or method of heat sealing may be used .

The upper bladder 60 comprises first and second symmetrically disposed upper bladder legs 63 , 64 of the U-shape , arranged to lie on opposite sides of a wearer ' s torso . First ends of the first and second legs 63 , 64 are j oined together by an upper bladder neck portion 65 . The first and second legs 63 , 64 each extend from said first end to a second end, which is a free end . The first and second legs 63 , 64 each comprise an upper bladder lobe 70 , 72 that is formed by width of the first and second legs 63 , 64 being greatest at a position between the first end and the second, free end of the legs 63 , 64 . The first and second legs 63 , 64 , the upper bladder 60 and the upper bladder lobes 70 , 72 are smaller than the corresponding parts of the bottom layer 8 ( and the top layer 9 ) , so that the upper bladder 60 can fit within the outline of the top layer 9 and the bottom layer 8 - as shown in Figure 12 . As also shown in Figure 12 , the upper bladder 60 is shaped and sized to fit within the bottom layer 8 ( and the top layer 9 ) above the lower attachment line 52 .

The lower bladder 80 is also very generally U-shaped and is formed by two identical layers of air-impermeable flexible material that are j oined together by peripheral lower bladder attachment line 82 . The two identical layers of air- impermeable flexible material may be welded or heat sealed together along the attachment line 82 . In order to achieve this heat sealing, a layer of heat melt adhesive may be provided between the first and second layers of material . The layers of material may be a plastic-coated fabric that is gas impermeable . It will be appreciated that any suitable material or method of heat sealing may be used .

The lower bladder 80 comprises first and second symmetrically disposed lower bladder legs 83 , 84 of the U-shape , arranged to lie on opposite sides of a wearer ' s torso . First ends of the first and second legs 83 , 84 are j oined together by a lower bladder neck portion 85 . The first and second legs 83 , 84 each extend from said first end to a second end, which is a free end . The first and second legs 83 , 84 each comprise a lower bladder lobe 90 , 92 that is formed by width of the first and second legs 83 , 84 being greatest at a position between the first end and the second, free end of the legs 83 , 84 . The first and second legs 83 , 84 , the lower bladder neck portion 85 and the lower bladder lobes 90 , 92 are smaller than the corresponding parts of the bottom layer 8 ( and the top layer 9 ) , so that the lower bladder 80 can fit within the outline of the top layer 9 and the bottom layer 8 - as shown in Figure 12 . The lower bladder also includes inflatable region 86 for inflating the integral chin support 11 provided towards the neck aperture 6 . As also shown in Figure 12 , the lower bladder 80 is shaped and sized to fit within the bottom layer 8 ( and the top layer 9 ) below the upper attachment line 50 .

The lower bladder 80 is positioned between the top layer 9 and the baffle 30 . The upper attachment line 50 constrains the location of the lower bladder 80 to be below the upper attachment line 50 . The upper bladder 60 is positioned between the bottom layer 8 and the baffle 30 . The lower attachment line 52 constrains the location of the upper bladder 60 to be above the lower attachment line 52 . The relative locations of the bladders 60 , 80 are shown in Figure 11 .

After the upper bladder 60 and the lower bladder 80 are positioned as described above , the bottom layer 8 and the top layer 9 are attached together around their peripheries .

Figure 13 shows a front view of the LPU 1 with the attachment lines of the top layer 4 shown . Figure 14 shows a rear view of the LPU 1 with the attachment lines of the bottom layer 3 shown . Figures 13 and 14 show an example position of the position of a peripheral attachment line 98 between the bottom layer 8 and the top layer 9 . The bottom layer 8 and the top layer 9 may be stitched together along the attachment line 98 . Figure 13 also shows the position of the lower baffle attachment line 52 . Figure 14 also shows the position of the upper baffle attachment line 50 .

The baffle 30 , by attachment to the bottom layer 8 by the upper baffle attachment line 50 and by attachment to the lower layer 9 by the lower baffle attachment line 52 creates an upper pocket 100 that locates the upper bladder 60 and a lower pocket 102 that locates the lower bladder 80 .

Figures 15 , 16 , 18 and 19 show right side views of the LPU 1 in various states of inflation, including the position of selected internal elements . In all these Figures the outline of the LPU 1 shown is the outline when fully inflated . This outline is shown for convenience and it should be appreciated that the actual outline will be different according to the state of inflation . For example , in Figure 15 the LPU 1 would be deflated and therefore will be generally flat (with the bottom layer 8 and the top layer 9 generally resting close to each other with the intervening parts in between) .

As j ust mentioned, Figure 15 represents the LPU 1 when it is deflated, as it is submerged into water . A lower inflator 110 is positioned on the first buoyancy section 3 . The lower inflator 110 may include an inflation cartridge , containing compressed gas . Following actuation, lower inflator 110 supplies the compressed gas to inflate the second bladder 80 . An upper inflator 112 is positioned where the first buoyancy section 3 meets the neck portion 5 . The upper inflator 112 may include an inflation cartridge , containing compressed gas . Following actuation, upper inflator 112 supplies the compressed gas to inflate the first bladder 60 .

The lower inflator 110 is automatically triggered by contact of its triggering mechanism 114 with water . The upper inflator 112 is not automatically triggered by contact with water . The upper inflator 112 has a trigger cable 116 attached at one end to a triggering mechanism 117 of the upper inflator 112 and attached at the other end to the top layer of material 9 at first upper inflator attachment point 118 .

Figures 17A and 17B show partial close-up views of the upper inflator 112 where it is attached to the top layer of material 9 . The body of the inflator 112 is attached to the top layer of material 9 at second upper inflator attachment point 120 and, as mentioned above , the trigger cable 116 is attached at the first upper inflator attachment point 118 .

When the second bladder 80 is deflated the top layer of material 9 in the region around the upper inflator 112 is generally slack and can readily wrinkle or fold, as shown in Figure 17A . When the second bladder 80 is inflated, by the automatic activation of lower inflator 110 on contact with water, the top layer of material 9 in the region around the upper inflator 112 becomes taught ( comes into tension) due to pressure applied by inflation of the second bladder 80 . This pressure removes the wrinkles or folds , as shown in Figure 17B, which increases the distance between the first upper inflator attachment point 118 and the second upper inflator attachment point 120 . The position of the attachment points 118 , 120 and the length of the cable 116 are selected such that the cable is shorter than the distance between the first upper inflator attachment point 118 and the second upper inflator attachment point 120 when the second bladder 80 is fully inflated . As inflation of the second bladder 80 occurs , the cable 116 pulls the triggering mechanism 117 of the upper inflator 112 , which activates the upper inflator 112 and inflates the first bladder 60 .

The arrangement of the lower and upper inflators 110 , 112 is such that , when the LPU 1 enters water, the lower inflator 110 is automatically activated first - which later starts inflation of the second bladder 80 . As the second bladder 80 inflates this increases the distance between the attachment points 118 , 120 - which then activates the upper inflator 112 and starts inflation of the first bladder 60 . The triggering of inflation of the second bladder 80 at a first time therefore causes the triggering of inflation of the first bladder 60 to occur at a second, later time . The first time and the second time may be 3 to 4 seconds apart , for example .

Figures 16 , 18 and 19 show the inflation stages of the LPU 1 . In Figure 16 the lower inflator 110 is automatically activated first - which starts inflation of the second bladder 80 . Figure 18 shows that , as the second bladder 80 inflates , this then activates the upper inflator 112 and starts inflation of the first bladder 60 . Figure 19 shows the LPU 1 after the first and second bladders 60 , 80 are inflated . The baffle 30 is shown by the dashed lines in Figure 18 and 19 , and locates the first and second bladders 60 , 80 within the LPU .

Due to the location of the second bladder 80 , upon automatic activation of the lower inflator 110 , buoyancy is first provided at only or primarily at a region at the front of the wearer' s torso . If the wearer is face down in the water, this buoyancy at only or primarily at the region at the front of the wearer' s torso tends to cause the wearer to rotate in the water so that they lie face up in the water ( i . e . self- righting occurs ) .

The shape of the lobes 20 and 22 of the first and second buoyancy section 3 , 4 tends to cause the first and second buoyancy section 3 , 4 to rotate in opposite directions by approximately 45 degrees with respect to the neck portion 5 , when inflated by the lower inflator 110 . The lobes 20 and 22 are generally oval in transverse cross-section, the width dimension being greater than the depth dimension . As the buoyancy sections 3 , 4 rotate relative to the neck portion 5 so that the larger dimension, instead of overlying and being generally parallel to the chest of the wearer , extends generally perpendicular to or obliquely to the chest of the wearer . This enhances the self-righting motion .

The subsequent inflation of the first bladder 60 provides buoyancy at the neck portion 5 behind the wearer' s head and behind the wearer' s shoulders , as shown in Figures 20 and 21 . The LPU 1 supports the wearer with the head and trunk at the correct angles and with the height of the airways above the water level sufficient to prevent drowning . These performance requirements are shown as the FPA ( Face Plane Angle ) = (X) , created by the buoyancy around neck and shoulders . Typically the FPA ( the angle (X) measured between the face plane and the water surface ) should be in the range of 15° to 25° . The buoyancy may also provide a desired body trunk angle (Y ) , which is measured as the angle between the trunk plane and the water surface . The buoyancy may further provide the height of the airways (mouth and/or nose ) above the water surface shown as ( Z ) . These angles (X) , ( Y ) and height ( Z ) are all produced by the first bladder 60 .

The upper and lower inflators 110 , 112 may each include a 33- gram CO2 compressed gas container . The upper and lower inflators 110 , 112 may have a smaller capacity than on a conventional inflator for a single bladder LPU . The smaller capacity inflators may inflate the bladders faster than conventional large capacity inflators , thereby increasing safety .

The staged inflation of the body first and second bladders 60 , 80 may be provided by any suitable arrangement . The use of a cable 116 and attachment point 118 is j ust one example of a suitable arrangement . An alternative arrangement is an electronic timer that automatically starts a count-down process when the lower inflator 110 is triggered; when the count-down is complete ( after a pre-set time has passed ) , the upper inflator is automatically triggered electronically by the timer .

The first bladder 60 may be deflated if desired to reduce bulk, e . g . to help the wearer board a rescue craft .

Each of first and second bladders 60 , 80 may be provided with a mouth-operable inflator in the form of a tube extending from the exterior of the LPU 1 . This allows manual inflation of the first and/or second bladders 60 , 80 in the event of failure of the lower inflator 110 or the upper inflator 112 . Each tube 10 is provided with a non-return valve and a closure cap to prevent water flowing down the tube and into the body first and second bladders 60 , 80 .

Rather than first and second inflatable buoyancy sections 3 and 4 which form symmetrically disposed legs of the U-shape , arranged to lie on opposite sides of a wearer ' s torso , the LPU may have a single buoyancy section that lies over the front of the wearer' s torso .

One or more straps may be attached to the LPU 1 and may pass around the torso of the wearer to secure the LPU 1 to the wearer .

The above embodiment is described by way of example . Many variations are possible without departing from the invention .

For example , rather than provide inflatable upper bladder 60 and inflatable lower bladder 80 , instead a similarly located upper inflatable volume and a lower inflatable volume may be provided within a chamber formed by the top layer 9 and the bottom layer 8 , which chamber is divided into the upper inflatable volume and lower inflatable volume by the baffle

30 .