GB2174338A - Liferaft - Google Patents

Description

1

GB 2 174 338A 1

SPECIFICATION Liferaft

5 This invention relates to an inflatable life-raft.

Known inflatable liferafts for use by persons to escape from aircraft (fixed wing and helicopters) have comprised an annular bouyancy body surrounding and supporting a floor. The 10 body has been rendered more able to function after damage by being made in the form of a pair of superposed bouyant annuli. If one is punctured, the other can support the occupants. Such a construction meets regulations 15 laid down by various authorities for aircraft liferafts. However, the use of liferafts on helicopters has added dangers. Because helicopters have their rotors, gear boxes and engines mounted at the top of their structure they are 20 very likely to fall onto their side or capsize completely after landing in water. When a life-raft is inflated and held at the side of a passenger compartment in these circumstances there is much greater danger of damage to 25 the buoyancy due to contact with parts of the helicopter (which may be damaged). It is an object of the present invention to provide a liferaft which is more resistant to and/or more able to bear damage.

30 The present invention provides an inflatable liferaft having a surrounding buoyant body consisting of a plurality of separately inflatable annuli, each annulus being divided into a plurality of separately inflatable chambers, the 35 chambers in each annulus being circumferenti-ally offset relative to the chambers in the or each adjacent annulus.

Thus, if one chamber is punctured in each of two adjacent annuli, the loss of buoyancy 40 is not concentrated in one section of the raft periphery, but is spread over a longer length of the periphery, most of which retains appreciable buoyancy.

The raft can have two annuli, one above the 45 other and each can be divided into two generally semi-circular chambers by a pair of diametrically disposed bulkheads or walls. The bulkheads of one annulus can lie on a diameter lying at 90° to the bulkheads of the 50 other annulus.

All four chambers can be inflatable by means of a single gas cylinder having two outlet hoses each leading to one bulkhead on each annulus and there splitting to provide 55 inflation gas to each chamber of each annulus via a non-return valve.

Each annulus can be divided into three or more chambers by appropriate numbers of spaced bulkheads There can be three or more 60 annuli, some or all being divided as aforesaid.

Each annulus can be made from a strong, tear resistant envelope enclosing a plurality of individual inflatable bodies each constituting one said chamber.

65 The buoyant body can have an external buffer for bearing shocks and reducing the possibility of damage to the said annuli. The buffer can be in the form of an outer surrounding annulus inflatable from one or more of said chambers via a one-way pressure release valve. Preferably the buffer annulus is itself divided circumferentially into a plurality of separate chambers, each individually inflatable from a different one of said main chambers.

The raft can be a reversible raft having its floor within the surrounding buoyant body at or about a mid point thereof to enable the raft to be reversible. A canopy structure including one or more inflatable members can be accommodated in a pouch in the floor, the pouch being accessible from each face of the floor.

The invention also provides an inflatable liferaft having a buoyant body surrounding a floor, the buoyant body comprising a plurality of main buoyancy annuli and an additional outer inflatable buffer annulus.

The buffer annulus can be smaller than the main annuli and can be inflatable from one or more of the main annuli via pressure release valves. The buffer annulus can be divided into a plurality of circumferentially arranged compartments, each being individually inflatable. If the main annuli are themselves divided into a plurality of chambers, the individual chambers of the buffer annulus are preferably each inflatable from a different chamber of the main annuli.

The pressure relief valve supplying the or each chamber of the buffer annulus is preferably constructed so that if the or one chamber of the buffer annulus is damaged and deflates, the pressure in the associated main annulus chamber does not fall to zero. The pressure release valve can have an operating differential which is a substantial fraction, say one half, of the operational pressure of the main annuli for this purpose.

The invention will be described further, by way of example, with reference to the accompanying drawings, which illustrate a preferred embodiment thereof, it being understood that the following description is illustrative of and not limitative of the scope of the invention. In the drawings:

Fig. 1 is a plan view of a preferred liferaft of the invention;

Fig. 2 is a cross-section on line A-B of Fig.

1; and

Fig. 3 is an enlarged cross-section on line A-A of Fig. 1.

A preferred liferaft 10 of the invention comprises an octagonal annular bouyant body 11 surrounding a generally circular fabric floor 12 of proofed fabric. The body 11 has an upper main annulus 13 and a lower main annulus 14, both about 250 mm in diameter. The main annuli 13 and 14 are superposed and united to floor 12. The raft 10 is reversible in

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that it is usable with convenience whichever annulus 13, 14 is uppermost after inflation on the surface. To afford shelter to the occupants of the raft, a canopy structure is pro-5 vided and stored in a collapsed condition in a pouch 16 in the floor 12. The pouch 16 has an operable flap on each face of floor 15 accessible via a sliding clasp fastener 17. The canopy structure (not illustrated) can comprise 10 one or more inflatable supports and roof/wall forming sheeting attachable to the upper of annuli 13, 14. Such structure can be deployed if needed after occupation of the raft.

The "top" main annulus 13 is disposed by 15 diametrically disposed bulkheads 15 into two semi-circular chambers 18, 19 and the "botr torn" main annulus 14 is divided by bulkheads 20 into two semi-circular chambers 21, 22. The annuli 13, 14 can be made from strong, 20 tear resistant, non-proofed fabric such as terylene sailcloth and an individual inflatable bag made from sheet polyurethane can be incorporated into each half to form the individual chambers. Unproofed fabric has greater 25 resistance to damage than proofed fabric and such a structure is better although more expensive than a single skin of proofed fabric.

The two main annuli 13, 14 are inflatable from a cylinder 23 of compressed gas having 30 two outlet hoses 24, 25 each leading to one bulkhead of each annulus. At that bulkhead the hose 24, 25 splits to supply gas to each chamber of the respective annulus 13, 14 via non-return valves 26.

35 This structure has the advantage that if one chamber (or two chambers of one annulus) of 18, 19, 21, 22 is punctured and deflates, the other annulus is complete and there is buoyancy entirely surrounding the floor 12. If one 40 chamber in each annulus is punctured and deflates, buoyancy still surrounds 75% of the circumference of the floor. Thus after relatively severedamage the raft retains ample buoyancy for support and still has its buoyancy well 45 distributed about the raft periphery.

Level with the floor 12, the annular supporting body 11 is provided with a surrounding buffer annulus 27 attached to each main annulus 13, 14 and itself about 200 mm in dia-50 meter. The buffer annulus 27 is divided by four bulkheads 28 into four quadrant chambers 29. The annulus 27 can have the same structure of fabric plus bladders as the main annuli but preferably is made of conventional 55 proofed fabric. Each chamber 29 of the buffer annulus 27 is inflatable from a respective one of the four chambers of the main annuli 13, 14. The chambers 18, 19 supply gas to chambers 29 by means of pressure relief 60 valves 30 and chamber 21, 22 supply gas by pressure relief valves 31.

Each of valves 30, 31 is constructed to operate at a pressure differential which is a substantial fraction (say from one quarter to three 65 quarters) of the operating pressure of the main annuli. For example, of the operating pressure of the main annuli is 3 p.s.i. (s=s20KNm-z) the pressure differential of the valves 30, 31 can be 1.5 p.s.i. (^slOKNm 2). Thus, as the cylinder operates to inflate the main chambers to a pressure of 3 p.s.i., the valves 30, 31 open to inflate the chambers 29 to a pressure of 1.5 p.s.i. If any chamber 29 is punctured and deflates, its associated main annulus chamber deflates down to 1.5 p.s.i. and remains at this value. Thus, there is only a partial loss of function in that chamber.

The buffer annulus provides protection to the main annuli against damage by sharp edges of parts of a ditched aircraft and enhances the ability of the raft to function after damage.

Variations can be made to the above. For example the number of main annuli can be greater than two and the number of diameters in each can be greater than two. For example division of the main annuli into three chambers by bulkheads circumferentially spaced at 120° intervals would give a greater degree of resistance to loss of function after damage, but would require further expenditure on the inflation system.

The raft 10 of the invention can be provided with one or more inflatable boarding ramps and/or ladders and with a survival equipment store in conventional manner.

Claims (19)

1. An inflatable liferaft having a surrounding buoyant body consisting of a plurality of separately inflatable annuli, each annulus being divided into a plurality of separately inflatable chambers, the chambers in each annulus being circumferentially offset relative to the chambers in the or each adjacent annulus.

2. A liferaft as claimed in Claim 1, and having its floor extending at an intermediate position in the height of the buoyant body to be reversible.

3. A liferaft as claimed in Claim 1 or 2, wherein the annuli are superposed.

4. A liferaft as claimed in Claim 1, 2 or 3 wherein each annulus is divided into two chambers.

5. A liferaft as claimed in claim 4 wherein the chambers are of equal size, being delimited by a pair of diametrically disposed bulkheads or walls.

6. A liferaft as claimed in claim 4 or 5, wherein the degree of offsetting is 90°.

7. A liferaft as claimed in any preceding claim wherein the chambers are individually inflatable from a single container of compressed gas.

8. A liferaft as claimed in any preceding claim wherein each annulas is made from an envelope of of gas-permeable fabric and each chamber is constituted by an inflatable liner or bladder of gas impermeable material within the envelope.

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9. A liferaft as claimed in any preceding claim wherein the buoyant body has an outer surrounding buffer annulus divided into a plurality of individually inflated chambers.

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10. A liferaft as claimed in Claim 9, wherein the chambers in the buffer annulus are inflatable, via pressure relief valves, from the chambers of the main annuli.

11. A liferaft as claimed in Claim 10,

10 wherein the number of chambers in the buffer annulus is equal to the number of chambers in the main annuli.

12. A liferaft as claimed in Claim 9, 10 or

11 wherein there are two main annuli one on

15 top of the other, the buffer annulus surrounding the two at the level of their join.

13. A liferaft as defined in Claim 12,

wherein the main annuli are of equal cross-sectional diameter and the buffer annulus is of

20 smaller cross-sectional diameter.

14. An inflatable liferaft having a buoyant body surrounding a floor, the buoyant body comprising a plurality of main buoyancy annuli and an additional outer inflatable buffer annu-

25 lus.

15. A liferaft as claimed in Claim 14 wherein the buffer annulus is circumferentially divided into a plurality of individually inflatable chambers.

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16. A liferaft as claimed in Claim 15, wherein the chambers of the buffer annulus are each inflatable via a pressure relief valve.

17. A liferaft as claimed in Claim 16 wherein each pressure relief valve has an op-

35 erating differential pressure which is a substantial fraction of the working pressure of that main annulus with which it connects.

18. A liferaft as claimed in claim 17,

wherein the fraction is one half.

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19. A liferaft substantially as hereinbefore described with reference to the accompanying drawings.

Printed in the United Kingdom for

Her Majesty's Stationery Office, Dd 8818935, 1986, 4235.

Published at The Patent Office, 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.