GB2030079A

GB2030079A - Inflatable liferafts

Info

Publication number: GB2030079A
Application number: GB7931529A
Authority: GB
Original assignee: RFD Inflatables Ltd
Current assignee: RFD Inflatables Ltd
Priority date: 1978-09-14
Filing date: 1979-09-11
Publication date: 1980-04-02
Also published as: GB2030079B

Abstract

To reduce the volume of gas needed for inflation, an inflatable liferaft has only one inflatable strut for supporting a protective canopy, the strut extending from a peripheral buoyancy tube and terminating above the floor of the liferaft. Methods for assembling the liferaft are disclosed and these include the step of forming the strut from a single sheet which is connected intermediate its ends to a panel of the buoyancy tube. Subsequently the end portions of the sheet are joined to form the strut and the panel is incorporated into the buoyancy tube. <IMAGE>

Description

SPECIFICATION Liferafts Liferafts have commonly had a floor surrounded by a peripheral buoyancy tube which is covered by a canopy. Previous proposals for supporting the canopy over the liferaft have comprised a vertical inflatable strut placed in the centre of the floor or a generally inverted U-shaped inflatable arch extending over the floor between diametrically opposed portions of the buoyancy tube or an arch formed by three inflatable struts extending from angularly spaced locations around the buoyancy tube and, at their ends remote from the buoyancy tube, connected together, above the centre of the floor.

These previous proposals have the disadvantage that, in the case of a single strut in the floor, they reduce the floor area available to users of the liferaft. In respect of the remaining proposals they have the disadvantages that they require a large volume of gas for inflation, a large amount of material for their construction and, consequently, are complicated to construct.

It is an object of the invention to mitigate these disadvantages.

According to a first aspect of the invention there is provided a method of manufacturing a liferaft having a floor surrounded by a peripheral buoyancy tube and covered by a canopy supported by an inflatable strut, the buoyancy tube being formed from a plurality of panels of sheet material, the method comprising forming the strut from a single piece of sheet material of elongate shape, connecting a section of the strut piece intermediate the ends of the strut piece to a panel for incorporation into the buoyancy tube, said section forming a foot portion of the strut and there being an aperture through the buoyancy tube panel and the foot portion for inflation of the completed strut, so connecting the edges of one end section of the strut piece on one side of the foot portion to the edges of the other end section of the strut piece to the other side of the foot portion as to form an inflatable strut which extends from the panel of the buoyancy tube and which is closed at the end thereof remote from the buoyancy tube and then connecting the buoyancy tube panel to the remaining buoyancy tube panels to form a buoyancy tube and connecting the floor and the canopy to the buoyancy tube panels.

According to a second aspect of the invention, there is provided a liferaft when made by the method of the first aspect of the invention.

According to a third aspect of the invention, there is provided a liferaft comprising a floor surrounded by a peripheral buoyancy tube and covered by a canopy supported by an inflatable strut extending from the buoyancy tube and terminating above the floor of the liferaft.

The following is a more detailed description of three embodiments of the invention by way of example, reference being made to the accompanying drawings in which: Figure 1 is a view from the front of an inflatable liferaft, Figure 2 is a vertical cross-section through the liferaft of Fig. 1 with a canopy of the liferaft removed for clarity, Figure 3 is a view from above of a strut of the liferaft of Figs. 1 and 2 connected to a panel of a buoyancy tube of the liferaft by a first method, Figure 4 is a section of the connection of Fig. 3 in a plane normal to the section on the line V-V of Fig. 3 and exploded for clarity, Figure 5 is a section on the V-V of Fig. 3, Figure 6 is a view from above of a strut of the liferaft of Figs. 1 and 2 connected to a panel of a buoyancy tube of the liferaft by a second method, Figure 7 is a section on the line VIl-VIl of Fig. 6, Figure 8 is a view from above of a strut of the liferaft of Figs. 1 and 2 connected to a panel of a buoyancy tube of the liferaft by a modified form of the second method, and Figure 9 is a section of a connection between a strut of the liferaft of Figs. 1 and 2 and a panel of a buoyancy tube of the liferaft by a third method, the section being in a plane normal to the axis of the buoyancy tube.

Referring to Figs. 1 and 2, the liferaft comprises a floor 10 surrounded by an annular peripheral buoyancy tube 11. The floor 10 is covered by a canopy 1 2 which is supported by a single inflatable strut 1 3 extending upwardly and inwardly from the buoyancy tube 11 at a position opposite a closable entrance 14 in the canopy 12. As best seen in Fig. 2, the strut 1 3 tapers along its length as it extends away from the buoyancy tube 1.

Alterntively, however, the strut 1 3 may be of constant cross-section along its length.

The strut 1 3 shown in Fig. 2 is straight along its length although it may be curved along its length or may be composed of straight and curved portions. The use of a single strut allows the use of the complete floor area for accommodating survivors. In addition, it minimises the volume of the liferaft which requires inflation and minimises the amount of material required to construct the liferaft. A single strut is also easily incorporated in the liferaft during manufacture.

The liferaft includes handles and safety lines 1 5 as well as stabilising water pockets, one of which is shown at 1 6.

Three methods of manufacturing a liferaft of the kind shown in Figs. 1 and 2 will now be described with reference to Figs. 3 to 5, to Figs. 6 to 8 and to Fig. 9 respectively. The three methods have in common the assembly of the buoyancy tube 11, the attachment of the floor 10, canopy 12, fittings 1 5 and water pocket 16. The buoyancy tube 11 is formed from generally rectangular sheets 11 a of a nylon material covered on one surface with heat-weldable polyurethane. The sheets 11 a are heat welded in pairs along ones of the two longer edges of the sheets of the pair to form panels. One panel is then connected to the strut 1 3 in one of the three ways described hereinafter with reference to the drawings before all the panels are heat-welded together to form a continuous band.The two continuous edges of the band so formed are then heat-welded together to form the buoyancy tube 11 and the floor 10, canopy 12, handles and safety lines 1 5 and water pockets 1 6 are then heat-welded onto the liferaft to complete the liferaft.

In all three methods of attaching the strut 13, the strut is formed from a single elongate piece of nylon material covered on one surface with heat-weldable polyurethane. The strut piece for the liferaft shown in Figs. 1 and 2 is generally the shape of an isosceles triangle with two very acute equal angles whose associated corners form the tip of the completed strut 1 3 and a central piece which, in the completed strut, forms a foot portion 13a of the strut 13.

Referring now to Figs. 3, 4 and 5 there is shown a first method of connecting the strut 1 3 to a panel of the buoyancy tube 11 formed by two connected sheets 11 a. This first method employs a connecting piece 1 7 formed from two areas of material 1 7a and 176 stitched together along a seam line 18 and having the upper and lower surfaces of the connecting piece 1 7 so formed, heatweldable. The seam line 1 8 is arranged inwardly of the edges of the areas of material 1 7 a, 1 7 b to leave two edge portions 1 9 a, 19bextending around the areas of material between the seam line and the respective edges thereof.The connecting piece is of generally the same shape but of slightly greater area than the foot portion 1 3a of the strut piece and has a central hole 20 of greater diameter than that of two holes 21 and 22 of equal size in the foot portion 1 3a and the panel respectively. The material of the connecting piece is a nylon material coated on one surface with polyurethane to make that surface heat-weldable.

The strut piece is first laid flat on the connecting piece 1 7 with their respective holes 21 and 22 in correspondence. One edge portion 1 9a of the connecting piece is then heat-welded to the strut piece around a weld line indicated by a darkened line 23 (Figs. 4 and 5). The strut piece is then laid flat on the panel with the connecting piece 1 7 between them and with their respective holes 21 and 22 in register. The other edge portion 1 9 b of the connecting piece 1 7 is then heat welded to the panel around a weld line 24.

The edge of the hole 21 in the foot portion 1 3a is next heat-welded directly to the edge of the hole 22 in the panel to prevent leakage of air and to form an inflation aperture for the completed strut 1 3.

The edges of one end section of the strut piece 13 to one side of the foot portion 1 3a are next welded to the edges of the other end section of the strut piece 1 3 to the other side of the foot portion 13 a to close the strut 13.

Two reinforcement patches 25 are heatwelded over a portion of the strut 1 3 adjacent the foot portion 1 3a and an adjacent portion of the panel, one reinforcement patch 25 being positioned as shown in Fig. 3 and the other reinforcement patch being similarly arranged in a position diametrically opposed thereto (see Fig. 4).

The panel is then incorporated in the liferaft as described above.

Referring next to Figs. 6 and 7, there is shown a second method of connecting the strut 1 3 to a panel of the buoyancy tube 11.

The second method differs from the first method described above with reference to Figs. 3, 4 and 5 in the following respect : The connecting piece 1 7 has, in this second method, an upper area which is of a material heat-weldable on both surfaces. This upper area includes two extensions 26a, 26b (Fig.

7) which are at diametrically opposed positions on those parts of the connecting piece 1 7 which, in the completed liferaft, are to be disposed about the intersection of a plane which includes the strut axis and which is normal to the axis of the buoyancy tube at the strut 13, and the upper and lower surfaces of the strut 1 3 and panel 11 a. When the connecting piece has been heat-welded to the strut piece and the panel, the extensions 26a, 26b are pulled over and the heat-welded to the panel, as shown in Figs. 6 and 7. This allows the reinforcement patches 25 of Fig. 3, 4 and 5 to be omitted. The remainder of the construction is as described above with reference to Figs. 3, 4 and 5.

A modified form of the second method described above with reference to Figs. 6 and 7 is shown in Fig. 8. In this case, the two extensions 26a, and 26bare divided along their lengths into two separate flaps; those for the extension 26a in Fig. 6 being given the reference numerals 28a and 28b. The two flaps of each extension 26 a and 26 b are crossed over one another before being heatwelded to the panel, as seen in Fig. 8.

Referring finally to Fig. 9 there is shown a third method of connecting the strut 1 3 to a panel of the buoyancy tube 11. In this method the strut piece is laid flat on the panel with no intermediate connecting piece 1 7.

The hole 21 in the strut piece is in register with the hole 22 in the panel. The strut piece is heat-welded to the panel around a seam line 27 around the periphery of the foot portion 1 3a and around a seam line 29 adjacent the edges of the holes 21, 22. The edges of the strut piece are then heat-welded together to form the strut 1 3 before the panel is incorporated in the liferaft.

All the heat-welding steps described above with reference to the drawings are by radio frequency heat-welding at a frequency of 27.12 MHz.

It will be appreciated that in the liferaft and in any of the methods described above with reference to the drawings, material which is heat-weldable on one surface only may be replaced by material heat-weldable on both surfaces.

It will be further appreciated that the heatwelding connection may be replaced by adhesive connections.

Claims

1. A method of manufacturing a liferaft having a floor surrounded by a peripheral buoyancy tube and covered by a canopy supported by an inflatable strut, the buoyancy tube being formed from a plurality of panels of sheet material, the method comprising forming the strut from a single piece of sheet material of elongate shape, connecting a section of the strut piece intermediate the ends of the strut piece to a panel for incorporation into the buoyancy tube, said section forming a foot portion of the strut and there being an aperture through the buoyancy tube panel and the foot portion for inflation of the completed strut, so connecting the edges of one end section of the strut piece on one side of the foot portion to the edges of the other end section of the strut piece to the other side of the foot portion as to form an inflatable strut which extends from the panel of the buoyancy tube and which is closed at the end thereof remote from the buoyancy tube and then connecting the buoyancy tube panel to the remaining buoyancy tube panels to form a buoyancy tube and connecting the floor and the canopy to the buoyancy tube panels.

2. A method according to claim 1 and further comprising the use of a connecting piece formed from two areas of material arranged in overlying face-to-face contact and connected together inwardly of their edges to leave two edge portions extending around the areas of material between the connection and the respective edges thereof, the connecting piece being of similar shape but greater area than the foot portion of the strut piece, the method comprising connecting one edge portion to the strut piece adjacent the foot portion and connecting the other edge portion to the panel of the buoyancy tube to connect the strut piece to the buoyancy tube panel, the connecting piece having an aperture in correspondence with the aperture in the foot portion.

3. A method according to claim 1 or claim 2 and comprising connecting the foot portion of the strut piece directly to the buoyancy tube panel around the aperture therethrough before the edges of the strut piece are connected together, the connection being intermediate the edge of the aperture in the connecting piece, where such is provided, and the edges of the aperture in the foot portion and the buoyancy tube panel.

4. A method according to any one of claims 1 to 3 and in which the buoyancy tube is of circular cross-section when inflated and in which the strut extends upwardly from the buoyancy tube and inwardly of the liferaft in a direction lying in a plane normal to the axis of the buoyancy tube at the strut, the method comprising, after the edges of the strut piece have been connected together, connecting a reinforcement patch over a portion of the strut adjoining the foot portion and over an adjacent portion of the panel, said portions being disposed about the intersection of said plane with the upper surfaces of the panel and strut, when inflated.

5. A method according to claim 4 and comprising, after the edges of the strut piece have been connected together, connecting a second reinforcement patch over those portions of the strut piece and the panel which are disposed about the intersection of said plane and the lower surfaces of the strut piece and the panel, when inflated.

6. A method according to claim 2 and in which the buoyancy tube is of circular crosssection, when inflated, and in which the strut extends upwardly from the buoyancy tube and inwardly of the liferaft in a direction normal to the axis of the inflated buoyancy tube, the method comprising forming the area of material of the connecting piece which is for connection to the strut piece with an extension which extends beyond the edge of the other area of material of the connecting piece, and then so arranging the connecting piece during the connection thereof to the strut piece and the buoyancy tube panel that the extension is in a position which, in the completed liferaft, is disposed about the intersection of the plane of the strut with the upper surfaces of the buoyancy tube panel and the strut, the method then comprising connecting the inner surface of extension to the buoyancy tube panel.

7. A method according to claim 6 and further comprising forming the area of material of the connecting piece for connection to the strut piece with a second extension in a position on the connecting piece opposite to said first-mentioned extension, the inner surface of second extension being connected to the buoyancy tube panel and being in a position which in the completed liferaft, is disposed about the intersection of the plane of the strut with the lower surfaces of the buoyancy tube panel and the strut.

8. A method according to claim 6 or claim 7 and in which the or each extension is divided along the length thereof towards the connection between the areas of material forming and connecting piece, the method comprising connecting separately the two parts of the or each extension so formed to the buoyancy tube panel.

9. A method according to any one of claims 1 to 8 wherein the connection steps are connections by the use of an adhesive.

10. A method according to any one of claims 1 to 8 wherein the connection steps are connections by heat-welding.

11. A method according to claim 10 wherein the material of the buoyancy tube panel, the strut piece and the connecting piece is a nylon material coated on one or both surfaces, as required, with polyurethane to make the coated surface heat-weldable.

12. A method according to claim 10 or claim 11 wherein each heat-welding step is a radio-frequency heat-welding step.

1 3. A method of manufacturing a liferaft substantially as hereinbefore described with reference to Figs. 1, 2, 3, 4 and 5 or to Figs.

1,2,6 and 7 or to Figs. 1, 2, 6 and 7 as modified by Fig. 8 or to Figs. 1, 2 and 9 of the accompanying drawings.

14. A liferaft when made by the method of any one of claims 1 to 13.

1 5. A liferaft comprising a floor surrounded by a peripheral buoyancy tube and covered by a canopy supported by an inflatable strut extending from the buoyancy tube and terminating above the floor of the liferaft.

1 6. A liferaft according to claim 1 5 wherein the strut tapers along the length thereof as the strut extends away from the buoyancy tube.

1 7. A liferaft according to claim 1 5 wherein the strut is of constant cross-section along the length thereof.

1 8. A liferaft according to any one of claims 1 5 to 1 7 wherein the strut is straight along the length thereof.

1 9. A liferaft according to any one of claims 1 5 to 1 7 wherein the strut is curved along the length thereof.

20. A liferaft according to any one of claims 1 5 to 1 7 wherein the strut is composed of successive straight and curved portions along the length thereof.

21. A liferaft according to any one of claims 1 5 to 20 wherein the buoyancy tube, when inflated is of circular cross-section, and wherein the strut extends away from the buoyancy tube in a direction which lies in a plane normal to the axis of the buoyancy tube at the strut.

22. A liferaft according to any one of claims 1 5 to 21 wherein the strut is located on that part of the buoyancy tube which is opposite an entrance provided in the canopy for access to the interior of the liferaft.

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