Abstract:
An inflatable life raft has a platform or platform portion formed by two flexible panels joined together by each of a plurality of threads to limit the distance apart that the panels can be moved, the panels being sealed to each other at their edges to form a chamber. A sensor can detect when the life raft is in the water, and an inflation system is operable in response to such detection to inflate the chamber with a gas. Preferably, the threads have similar lengths so that, when the chamber is inflated, the panels are substantially parallel. Accordingly, it is possible to fabricate an inflatable life raft which does not balloon out and which can provide a substantially flat platform.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a U.S. national phase filing under 35 U.S.C. §371 of PCT/GB2009/051552, filed on Nov. 17, 2009, and entitled “Inflatable Life Raft”, and hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to inflatable life rafts. 
       BACKGROUD OF THE INVENTION 
       [0003]    Life rafts which are inflatable have the advantage that when deflated they take up little storage space. However, a problem is that, when inflated, the inflation chamber tends to balloon out. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the present invention, there is provided an inflatable life raft comprising: a platform or platform portion formed by two flexible panels joined together by each of a plurality of threads to limit the distance apart that the panels can be moved, the panels being sealed to each other at their edges to form a chamber; detecting means for detecting an indication that the life raft is in the water; and inflating means operable in response to such detection to inflate the chamber with a gas. Preferably, the threads have similar lengths so that, when the chamber is inflated, the panels are substantially parallel. Accordingly, it is possible to fabricate an inflatable life raft which does not balloon out and which can provide a substantially flat platform. 
         [0005]    Preferably, the threads have a density of at least one thread per square centimeter of each panel. The panels preferably have respective layers of fabric joined by the threads. Indeed, the fabric layers and threads may be manufactured using the drop thread method which is known in the field of velvet manufacture. Each panel preferably has an air impermeable layer so as to render the chamber airtight. 
         [0006]    To assist climbing aboard the life raft, a rope or rope portion preferably extends around the platform adjacent the periphery of the platform. In one embodiment, the rope or rope portion extends inside the periphery of the platform. In this case, a further rope or rope portion preferably extends around the platform adjacent and inside the periphery of the platform on the opposite face of the platform, so that rope is accessible whichever way up the life raft is. 
         [0007]    Further ropes or rope portions are attached to the platform. The rope portions are preferably portions of a continuous rope, the continuous rope including an electroluminescent filament, and the life raft further including means operable in response to the detecting means for activating the electroluminescent filament. This increases the visibility of the rope in the dark to somebody attempting to climb aboard the life raft and also increases the visibility in the dark to a rescuer of the life raft as a whole. The life raft is preferably devoid of a gunwale of like feature which would impede climbing aboard the life raft. The life raft, when inflated, is preferably operable as a life raft either way up. 
         [0008]    The platform may have an opening therethrough at or adjacent the center of the platform. In this case, the detecting means, the inflating means and/or a control unit for the life raft is/are disposed in the opening. A removable cover may be provided for each end of the opening. Depending on which way up the life raft has landed, one cover may be removed to gain access to the central opening, whilst the other cover may be left in place to reduce the amount of water splashing up through the opening. 
         [0009]    The life raft is preferably provided in combination with a container for containing the life raft before inflation. In an embodiment of the invention, the container is permeable to water so that the detecting means does not need to be exposed outside the container when the life raft is packed in the container. The container is preferably arranged so that, upon inflation of the life raft in the container, the life raft can burst out of the container. 
         [0010]    The life raft is preferably provided in combination with a drogue attached to the life raft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A specific embodiment of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  illustrates an isometric view of an inflatable life raft system packed away prior to inflation; 
           [0013]      FIG. 2  illustrates an isometric view of a bag of the life raft system in its open state; 
           [0014]      FIG. 3  illustrates an isometric view of a platform and drogue of the life raft system after inflation of the platform; 
           [0015]      FIG. 4  illustrates an isometric view of a cover piece for the platform; 
           [0016]      FIG. 5  illustrates a sectioned cut-away view of part of the platform, taken on the section plane  5 - 5  shown in  FIG. 4 ; and 
           [0017]      FIG. 6  is a block diagram to illustrate the operation of the system. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0018]    The present invention may be described herein in terms of various functional components and various processing steps. It should be appreciated that such functional components may be realized by any number of hardware or structural components configured to perform the specified functions. 
         [0019]    Referring to the drawings, an inflatable life raft system  10  comprises an inflatable platform  12 , a drogue  14  and a bag  16  for the life raft  10 . The platform  12 , when inflated, has the shape of a circular disc having a diameter of, for example, 3 m and a thickness of, for example, 50 mm. The center of the platform  12  is formed with a circular opening  18  having a diameter of for example, 300 mm. The platform  12  may, of course, be made in other sizes. 
         [0020]    Referring in particular to  FIG. 5 , the platform  12  is constructed of two layers of fabric  20 ,  22  which are joined together by a large number of threads  24  using the “drop thread” method which is well-known in the field of velvet manufacture. The threads  24  have a length of, for example, about 50 mm. The density of the threads  24  may be about one third of the thread density of a typical velvet, or it may be far less than that, for example one thread per square millimeter, or even one thread per square centimeter. The outer surfaces of the fabric layers  20 ,  22  are bonded to flexible layers  26 ,  28  of plastics material such as polyurethane or polyvinylchloride so as to render them airtight. The layers  20 ,  22 ,  26 ,  28  are cut to a circular shape having a diameter of, for example, 3 meter, and a circular hole is cut in the middle of them to form the central opening  18  of the platform  12 . At the inner and outer edges, the layers  26 ,  28  of plastics material are connected by edging strips  30 ,  32  of for example, polyurethane or polyvinylchloride which are folded over the edges as shown and bonded to the layers  26 ,  28 . Prior to assembly of inner edging strip  30 , it is fitted with an inflation port  34  which is sealed to the inner edging strip. 
         [0021]    When the platform  12  is deflated, which is preferably done using a vacuum pump, the threads  24  become crushed into a dense mass, and the platform takes up little volume but can be folded. When the platform  12  is inflated with air via the inflation port  34  to a suitable pressure, it opens out into a flat circular platform with parallel faces, and the threads  24  prevent the faces ballooning out. At a suitably high pressure, the platform  12  becomes substantially rigid and is sufficiently buoyant in water so as to support at least one adult out of the water. The platform  12  is surprising stable, and permits a person to sit on the platform  12  with their lower legs hanging over the edge, without the platform  12  dipping under the water to a significant extent, and without the platform  12  tipping. 
         [0022]    Referring in particular to  FIG. 3 , a cylinder  36  of compressed air is mounted in the central opening  18  and connected to the inflation port  34  via a valve in a control unit  38 . 
         [0023]    Referring in particular to  FIG. 6 , the control unit  38  includes an exposed water sensor  40  which controls a switch  42  which, when water is detected, closes to supply power from a battery  44  to the inflation valve  46 . Referring back to  FIG. 3 , a rope  48  extends from the control unit  38  in the central opening  18  and along a winding path of several circles of increasing diameter over one face of the platform  12  before passing, at portion  50 , around the outer edge of the platform  12  to the other face of the platform  12  and continuing on a winding path of several circles of decreasing diameter back to the control unit  38 . The rope  48  is attached to the faces of the platform  12  by straps  52  (see also  FIG. 5 ) of plastics material bonded to the outer layers  26 ,  28  of the platform  12  at suitable locations. A person can use the rope  48  to help themselves climb aboard the platform  12  and to cling to the platform  12  once they are aboard. Referring in particular to  FIGS. 5 and 6 , one strand of the rope  48  is provided by an electroluminescent filament  54  which extends the whole length of the rope  48  from and back to the control unit  38 . The control unit  38  includes a suitable inverter  56  for driving the electroluminescent filament  54 , and, like the inflation valve  46 , the inverter  56  is connected to the battery  44  by the switch  42  when water is detected by the water sensor  40 . The electroluminescent rope  48  with its winding path over the faces of the platform  12  therefore significantly increases the visibility of the platform  12  in bad light or after dark. In order increase the visibility of the platform  12  during daylight, the outer layers  26 ,  28  of the platform  12  are brightly colored and marked with a contrasting marking  58  such as the “X” shown in  FIG. 3 . 
         [0024]    The platform  12  is supplied with a pair of circular cover pieces  60 ,  62  (see  FIGS. 3 and 4 ) of flexible plastics material which are slightly larger in diameter than the diameter of the central opening  18  and can be releasably attached to the outer layers  26 ,  28  of the platform  12  above and below the opening  18  by Velcro® strips  64 ,  66 . The intention is that, once the platform  12  has been deployed and boarded, the uppermost cover piece  60  can be removed to gain access to the opening  18  in which other equipment such as a torch, a laser pointer, a flare, a radio, a GPS receiver, a metallic blanket and a manual inflator may be stored in a storage compartment. However, the lowermost cover piece  62  is left in place to reduce the splashing of water up through the central opening  18 . 
         [0025]    The drogue  14  is provided with a weight  68  and is attached to the portion  50  of the electroluminescent rope  48  by an elasticated tether  70 . The bag  16  is of a size into which the platform  12  and drogue  14  can be fitted when the platform  12  is deflated and folded and/or rolled up. The bag  16  may be of any suitable design. However, the bag  16  is not waterproof so that when it is dropped into the water, the water can quickly find its way to the water sensor  40  so as to activate the inflation system. Also, the bag  16  is arranged to burst open, when the platform  12  is inflated, so as to release the platform  12  and drogue  14 . For example, as shown in  FIG. 2 , the bag  16  has a top flap  72  which, prior to inflation of the platform  12 , is held closed by a few strips  74  of Velcro®. 
         [0026]    In order to deploy the life raft system  10 , it is simply thrown, bag  16  and all, into the water from a vessel, from the land, or from an aircraft. Once the water wets the water sensor  40 , the inflation valve  46  opens, and the platform  12  begins to inflate. Also, the electroluminescent rope  48  is activated. Once the platform  12  is sufficiently pressurized, it and the drogue  14  burst out of the bag  16 , and the platform  12  continues to full inflation. It matters not whether the platform  12  stabilizes one way up or the other because the two faces of the platform  12  are similar. The drogue  14  sinks and reduces any tendency for the platform  12  to be caught by gusts of wind. Once a person in the water reaches the platform  12 , they can then haul themselves aboard using the rope  48  and await rescue, using any of the equipment stored in the central opening  18  that may assist them. 
         [0027]    It will be appreciated that many modifications and developments may be made to the embodiment of the invention described above. For example, the central opening  18  may be omitted, the inflation port  34  may be provided, for example, in the outer edging strip  32 , and the air cylinder  36  and control unit  38  may be provided at the edge of the platform  12 . 
         [0028]    Instead of the platform  12  forming a single inflation chamber, it may be subdivided into two or more inflation compartments, for example semicircular or quarter-circular in shape. Each compartment may have its own air cylinder and inflation valve. Alternatively, a common air cylinder and inflation valve may be provided, but with a check valve between the inflation valve and each compartment. Therefore, if one compartment is punctured or otherwise loses pressure, the other compartment(s) will not be affected. Other means for triggering the inflation system may be employed, such as a pressure sensor. 
         [0029]    The platform  12  may be shaped other than circular. It should be noted that the embodiment of the invention has been described above purely by way of example and that many other modifications and developments may be made thereto within the scope of the present invention. Those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present invention.