GB2291843A - Buoyancy aid for vehicles - Google Patents

Abstract

A vehicle is prevented from or delayed from sinking in water by entraining atmospheric air within one or more air and water impervious mechanically expandable devices. The device may comprise an envelope supported by a central hollow post 6, and struts 4 pivotally connected to ribs 11, the struts and ribs being deployable by means of a roller 12, slidable on the post and operable to obturate air inlet apertures (24) (Fig. 4) in the post 6, once the struts and ribs have been extended. The device may be actuated automatically upon impact of the vehicle with water and is particularly applicable to helicopters. <IMAGE>

Description

BUOYANCY AID FOR VEHICLES This invention relates to buoyancy aids for vehicles.

Although the invention has been developed primarily for use as a buoyancy aid for ditched helicopters and other aircraft, the invention is not so limited but, for example, may be employed as a safety device for watercraft in difficulty or for motor vehicles which may inadvertently enter the water.

A particular problem is perceived in relation to rotary winged aircraft surviving forced landings in the sea.

Following accidents in the North Sea, the Department of Transport in the United Kingdom and the Civil Aviation Authority have set up a Review Steering Group to seek a solution to the problem of keeping ditched helicopters floating and upright longer than heretofore. The problem is not restricted to rotary winged aircraft. Fixed wing aircraft, particularly at waterside airfields with limited runway capabilities pose a problem should an aircraft inadvertently run out of landing space and have to ditch in the water. The length of time that the craft remains buoyant has a substantial effect on the numbers of passengers and crew who can survive such an accident.

Buoyancy aids may also have a significant effect on the survival rate of passengers in a watercraft in difficulties or in a motor vehicle which inadvertently enters the water.

Up to now, attention has been given primarily to the development of inflatable bags. However, these suffer from a number of disadvantages, namely the need for storage of substantial volumes of gas or of chemicals capable of generating gas. Moreover, the inflatable structures themselves present a structure which is vulnerable to damage in crash conditions.

The present invention has been developed with a view to overcoming or avoiding these problems.

In accordance with one aspect of the invention, there is provided a method of preventing or delaying a vehicle from sinking in water by entraining atmospheric air within one or more generally air and water impervious mechanically expandable structures.

Preferably there are a plurality of such structures which may be disposed about the vehicle. These may be stowed in a vertical orientation in which they take up little space and do not significantly affect visibility from the vehicle; but preferably they are pivoted to the main structure of the vehicle so as to be stowed out of the way and arranged so as to be automatically deployed if the vehicle enters water. The structures are suitably rigidified following expansion so as to resist water pressure when wholly or partially submerged. Air is entrained through a valve system which lets in air as the structure expands and thereafter prevents the ingress or egress of air or of water. The structure may preferably comprise a plurality of bracing struts pivoted at one end to an axial support and mechanically openable to form a generally inverted cone or pyramid.The inverted base of the cone is suitably covered by a second envelope portion which may also be braced. Valve means are preferably formed in said second envelope portion or in the axial support opening to atmosphere above the second envelope portion.

In a second and alternative aspect of the invention, we provide a buoyancy aid for a vehicle in water and consisting of one or more devices each comprising an envelope generally impervious to air and water and an internal bracing structure therefor, the device being adapted to be stowed with the bracing structure in a collapsed condition, means being provided for mechanically expanding said structure, thereby to entrain atmospheric air within the envelope via valve means communicating with the interior of the envelope.

Preferably the means for mechanically expanding the internal bracing structure are automatically triggered as the vehicle enters the water (or begins to sink, if a watercraft) and are adapted to cause the bracing structure to move to an over-centre configuration in which external pressure on the device acts to oppose collapse of the structure to its initial collapsed condition.

In a preferred arrangement, each of the devices comprises an axial support, an outer envelope generally impervious to air and water, a plurality of elongate bracing struts for said envelope, at least some of which are pivoted at one end to said axial support, and means for opening said envelope by separating said struts at their other ends to form a generally inverted cone or pyramid and, thereby to entrain atmospheric air within said envelope via a valve means communicating with the interior of said envelope.

The said other end of each of the bracing struts may be pivoted to a rib, the other end of which is mounted on a collar which is displaceable along the length of the axial support to expand the envelope, the collar being movable axially along the axial support to an over-centre position in which external pressure on the envelope tends to obstruct return of the collar to its position before expansion of the structure. Since the buoyancy aid is likely to be deployed in crash situations, the material of the outer envelope is preferably formed of a material which is not only both strong and resistant to water but which is also fire resistant. Suitable such materials include silicone rubber impregnated fabrics (for example, polyester, polyimide or glass fibre).Preferably, the internal space within the outer envelope is divided into a number of compartments by internal partitions, in case any part of the envelope becomes damaged either in a crash, upon deployment of the buoyancy aid, or thereafter.

The invention is hereinafter more particularly described by way of example only with reference to the accompanying drawings in which: Fig. 1 shows an embodiment of buoyancy aid in accordance with the present invention shown in a generally elevational configuration and in its deployed configuration; Fig. 2 shows a bracing strut and associated rib for supporting the outer envelope, shown in an open configuration on the lefthand side of the drawing and in a closed configuration on the righthand side of the drawing; Fig.3 is a sectional view through an axial support and sleeve showing how air is entrained (leftside) and shut off (right side); Fig. 4 shows an over-centre bracing structure suitable for incorporation in the structure of Figs. 1 to 2 to provide resistance or additional resistance against collapse; ; Fig. 5 and Fig. 6 schematically illustrate the cabin of a helicopter together with an embodiment of buoyancy aid in accordance with the present invention illustrated in its deployed configuration in Fig. 5 and in a stowed configuration in Fig.6 ; and Fig. 7 and Fig.8 schematically illustrate exemplary electrical (Fig. 7) and mechanical (Fig.8 ) control systems for deployment of buoyancy aids in accordance with this invention.

The device illustrated in Fig. 1 would normally comprise one of a plurality of similar such devices mounted about a vehicle such as a helicopter. The illustrated embodiment of device comprises an envelope 1 formed in two portions. The main portion 2 in the expanded configuration illustrated in Fig. 1 comprises a generally inverted cone or pyramid divided internally by vertical membranes 2a extending between the envelope and a central tube 2b. The main portion 2 may be formed in a single piece or as separate generally triangular panels 3 with the join between two adjacent panels corresponding to the position of a bracing strut 4 (see Fig. 2 ) rather in the manner of an inverted umbrella.The polygonal inverted "base" of the cone or pyramid, when the device is erected in its expanded configuration as shown, faces skyward and so would normally be directly above the apex of the cone. This base is covered by a further section of envelope 5 also, in the illustrated embodiment, of generally cone or pyramidal configuration but with the opposite configuration to the main portion 2 and generally much shallower in height. The envelope structure is mounted on an axial support 6 here in the form of a post which may be provided with a clevis 7 at its lower end for pivotal coupling to a beam attached to or forming part of the structure of the vehicle. The upper end of tube 2b is attached to a sleeve 12 referred to below.

The material chosen for the envelope must be both strong and impervious to air and water. Preferably, as noted above, the material should also be chosen to be fireresistant. Preferred materials comprise silicone rubber impregnated fabrics, suitably of polyester, polylmlde or glass fibre. Alternatively, the envelope may be formed as a double membrane structure comprising separate water seal and strength components. Where the envelope is made of a plurality of panels 3 as illustrated in Fig. 1, the seams between the panels must be made both adequately strong and watertight, but otherwise the precise method of fabrication of the envelope is not critical to success.

The material of the membranes forming vertical partitions 2a is not so critical. In general, those membranes will be quite well protected and so need not be so robust. Rubberised spinnaker cloth may suffice.

As is perhaps best shown in Fig. 2 which illustrates the skeleton or bracing structure for any one buoyancy device, there is a central or axial support in the form of a post 6, suitably formed as a tube. In addition to some form of attachment means to the vehicle, suitably via a beam at its lower end, the post 6 mounts a plate 8 adjacent its lower end to which are pivoted at 9, in this embodiment, each of the bracing struts 4. The other end of each of the bracing struts is pivoted at 10 to a corresponding rib 11.

The other ends of each rib 11 are pivotally coupled to a sleeve 12 which is slidable axially along the post 6 between a closed or stowed configuration shown on the righthand side of Fig. 2 and a fully open condition shown on the lefthand side of ily. 2 in which the sleeve 12 is pushed beyond dead centre so that pressure applied to the envelope and hence to the bracing struts 4 opposes return of the sleeve 12 from the configuration at the lefthand side of Flg.2 to that shown at the righthand side. Material tube 2b for the vertical partitions 2a is coupled at its lower end to plate 8 and at its upper end to sleeve 12.

The invention is not restricted to the pvlrtlcular form of skeleton illustrated in Fig.2 , namely that In which each element of the skeleton or bracing structure comprises d bracing strut and a corresponding rib. Otter arrangements are feasible in which two or more ribs may be pivoted to the strut or the strut may be articulated.

Movement of the collar axially of the post to the position shown at the lefthand side of Fig. 2 may be achieved by any suitable means. The means may be effectively loaded, awaiting only triggering to erect the device when, say, a helicopter ditches in the sea. Loaded devices capable of being triggered in this way include a gas spring or a coil spring. Another alternative would be a pyrotechnic actuator.

Since these various means will be well known to the man with skills in this art, it is deemed unnecessary to describe any of these devices in detail. The particular manner of the coupling of such device to the sleeve 12 is also not of importance to the present invention.

As sleeve 12 slides axially upwardly and the envelope 1 opens out, air is entrained within the envelope. This can be accomplished in a simple fashion by the structure illustrated in Fig. 3. A plurality of openings 24 communicate beteween atmosphere and the interior of hollow axial post 6. A plurality of openings 25 are provided adjacent the lower end of post 6, there being at least one for each compartment into which the internal space within the envelope is divided. As can be seen, at the uppermost position sleeve 12 obscures upper openings 24 thereby preventing egress of air already entrained. A simple spring latch is illustrated at 26. After the sleeve 12 passes latch 26, it is prevented from return downwardly until latch 26 is depressed into post 6 in a similar manner to the latches to be found on umbrellas.

In addition to the resistance to collapse provided by moving of the collar to a position such as tllat shown on the lefthand side of Fig.2 in which the rib 11 has been moved to an over-centre position in which movement of the collar in the reverse direction is opposed by increasing external pressure on the envelope braced by the strut and rib, and/or by a latch such as that illustrated at 2G in Fig. 3, additional further rigidizing means are desirable in order to improve resistance of the device to asymmetric loads caused, for example, by wave pressure or by non-vertical immersion of the vehicle. Such further rigidization may be achieved by incorporating centre-hinged circumferential braces between adjacent bracing struts.

Fig. 4 illustrates one such arrangement in which these circumferential braces are provided at the midpoint of each strut 4. The brace is formed in two portions, one 13 being pivoted at 14 to one brace and the other 15 being pivoted at 16 to the other brace. The two portions 13 and 15 are pivoted together at 17 with one portion 15 of the brace having an extension 18 beyond the pivot, the effect of which is to lock the brace against further movement after straightening of the angle between the two portions 13 and 15 by pulling on the pivot 17 in the direction of the arrow in Fig. 4 . The effect of the extension 18 beyond the pivot 17 is to lock the two portions preferably in a slightly over-centre position. Movement to the configuration of Fig.

3 may be achieved by spring energization.

Although Fig. 4 illustrates a circumferential brace at a midpoint of the respective struts 4, the brace or a similar such brace may also, or alternatively, be provided at the upper ends of each strut 4.

Figs. 5 and 6 show how devices such as that illustrated in Fig. 1 may be deployed in a typical application of the invention, in this case to a helicopter for which the cabin is schematically illustrated at 19.

Typically, each of the flotation devices of Fig. 1 may be approximately 2 metres in diameter. A device of this size will displace about 1 cubic meter and provide buoyancy of the order of 1 tonne. For a medium sized helicopter, four such flotation devices are envisaged. The pivot 7 for each of the devices must accordingly be located at least one metre from the side of the craft and preferably at a level as near to the base of the craft as possible. Figs.5 and 6 illustrate one way in which this may be achieved. Fig. 5 shows the device in its deployed configuration and Fig. 6 shows how it may be stowed. The device of Fig. 1 is mounted at its pivot 7 to a beam 20 suitably of U- or channel-shaped configuration. The other end of the beam 20 is pivoted at 21 to the chassis of the helicopter. An actuator 22 is coupled between the helicopter and an intermediate position on the beam 20.The actuator, typically a piston and cylinder device is effective to pivot the beam about its pivot 21 from a vertical configuration as shown in Fig. 6 to a generally horizontal configuration as shown in Fig. 5 In the stowed configuration of Fig. 6, the collapsed device is housed within the side walls of the U- or channel-shaped beam 20.

The illustrated arrangement provides the necessary "freeboard" permitting safe passenger egress. As an alternative to the pneumatic or hydraulic actuator in the form of a piston and cylinder, a spring actuator may be employed. Whichever arrangement is used, there preferably is provided a latch, typically of the over-centre form, to prevent ready return. This latch must be of adequate strength to carry the full buoyancy load of the expanded device at the beam's farthest end. The illustrated arrangement which results in the generally cone-shaped device being mounted in its collapsed position as shown in Fig. 6 with the apex of the cone uppermost and largely protected within the U- or channel-shaped beam 20 ensures that rain, condensation or water spray will not tend to accumulate within the cone.

Other stowage arrangements are contemplated. For example, rather than a pivot point at the side of the craft, a pivot may be provided at 23 under the belly of the craft, the beam being intended to be swung outwardly to a generally horizontal position.

Deployment of the device as a whole can be achieved either by deliberate action at the controls of the vehicle or automatically upon impact of a ditched craft in water by means of appropriate pressure sensors. Release of the retention latch for the beam and the over-centre locks in each device, when deployment of the device is no longer required, can be achieved either by lanyard or by a local pyrotechnic or electromagnetic actuator. The precise details of such arrangements are not of importance to the details of the present invention but may be selected on the basis of preference for a particular utility or for a particular customer.

By way of illustration, a typical electrical system is illustrated in Fig. 7 and a typical alternative mechanical system in Fig. 8 Desirably, the deployment means should be: a) independent of the vehicle's other control systems, b) directly actuated by water impact, and c) connected to each of the buoyancy aids.

Fig. 7 schematically illustrates an electrical system in which a pressure transducer 27, suitably mounted on the belly of the craft is coupled to an amplifier/switch 28, operated by a battery 29 independently of the main electrical system, and coupled to respective actuators 30 for the various buoyancy aids.

Alternatively, as shown in Fig.8 , a large surface area piston device 31 may be moved on water impact to operate Bowden cables 32 in a lanyard system. Movement of the outer sleeve and inner wire of each Bowden cable 32 as illustrated in Fig. 8 releases a pawl 33 freeing a spring-loaded piston 34 to operate and deploy the corresponding buoyancy aid.

As an alternative to the illustrated arrangement of Figs. 5 and 6, the buoyancy aid may also be stowed internally of the craft, for example being hidden behind protective panels.

Claims (21)

1. A method of preventing or delaying a vehicle from sinking in water by entraining atmospheric air within one or more generally air and water impervious mechanically expandable structures.

2. A method according to Claim 1, wherein there are a plurality of such structures disposed about the vehicle.

3. A method according to Claim 1 or Claim 2, wherein the or each said structure has a stowed condition in which it has a generally vertical orientation, being placed so as not significantly to affect visibility from the vehicle.

4. A method according to Claim 1 or Claim 2, wherein the or each mechanically expandable structure is pivoted to the main structure of the vehicle so as to be stowed out of the way and arranged so as to be automatically deployed if the vehicle enters water.

5. A method according to any preceding claim, wherein air is entrained through a valve system which lets in air as the structure expands and thereafter prevents the ingress or egress of air or of water.

6. A method according to any preceding claim, wherein the or each structure is rigidified following expansion so as to resist water pressure when wholly or partially submerged.

7. A method according to Claim 6, wherein the or each mechanically expandable structure comprises a plurality of bracing struts pivoted at one end to an axial support and mechanically openable to form a generally inverted cone or pyramid.

8. A method according to Claim 7, wherein the inverted base of the cone is covered by a second portion serving as an envelope.

9. A method according to Claim 8, wherein said second portion is also braced.

10. A method according to Claims 8 or 9, wherein valve means effective to allow atmospheric air to be entrained therethrough as the structure expands are formed in said second envelope portion or in the axial support opening to atmosphere above the second envelope portion.

11. A buoyancy aid for a vehicle in water and consisting of one or more devices each comprising an envelope generally impervious to air and water and an internal bracing structure therefor, the device being adapted to be stowed with the bracing structure in a collapsed condition, means being provided for mechanically expanding said structure, thereby to entrain atmospheric air within the envelope via valve means communicating with the interior of the envelope.

12. A buoyancy aid according to Claim 11, wherein the means for mechanically expanding the internal bracing structure are adapted to be automatically triggered as the vehicle enters the water (or begins to sink, if a water craft) and are adapted to cause the bracing structure to move to an over-centre configuration in which external pressure on the device acts to oppose collapse of the structure to its initial collapsed condition.

13. A buoyancy aid according to Claims 11 or 12, wherein the or each said device comprises an axial support, an outer envelope generally impervious to air and water, a plurality of elongate bracing struts for said envelope, at least some of which are pivoted at one end to said axial support, and means for opening said envelope by separating said struts at their other end to form a generally inverted cone or pyramid and thereby to entrain atmospheric air within said envelope via a valve means communicating with the interior of said envelope.

14. A buoyancy aid according to Claim 13, wherein the said other end of each of the bracing struts is pivoted to a rib, the other end of which rib is mounted on a collar which is displaceable along the length of the axial support to expand the envelope.

15. A buoyancy aid according to both Claims 12 and 14, wherein the collar is movable axially along the axial support to an over-centre position in which external pressure on the envelope tends to obstruct return of the collar to its position before expansion of the structure.

16. A buoyancy aid according to any preceding claim, wherein the material of the outer envelope is formed of a material which is not only both strong and resistant to water, but which is also fire-resistant.

17. A buoyancy aid according to Claim 16, wherein the material of the outer envelope is formed of silicone rubber impregnated fabric.

18. A buoyancy aid according to Claim 18, wherein said fabric is formed of polyester, polyimide or of glass fibre.

19. A buoyancy aid according to any of Claims 11 to 18, wherein the internal space within the outer envelope is divided into a number of compartments by internal partitions.

20. A buoyancy aid substantially as hereinbefore described, with reference to and as shown in the accompanying drawings.

21. A method of preventing or delaying a vehicle from sinking in water, substantially as hereinbefore described, with reference to the accompanying drawings.