WO2011020999A2

WO2011020999A2 - Improved hatchcover

Info

Publication number: WO2011020999A2
Application number: PCT/GB2010/001559
Authority: WO
Inventors: Stephen John Kennedy
Original assignee: Intelligent Engineering (Bahamas) Limited; Daewoo Shipbuiling & Marine Engineering Co., Ltd; Leeming, John Gerard
Priority date: 2009-08-20
Filing date: 2010-08-18
Publication date: 2011-02-24
Also published as: KR20120068874A; WO2011020999A3; GB0914596D0; WO2011020999A8; CN102596702A

Abstract

A hatchcover comprising a framework (21) and a plurality of prefabricated sandwich panels (10) welded to the framework.

Description

IMPROVED HATCHCOVER

The present invention claims priority from GB Patent Application 0914596.2 filed 20 August 2009, the entire contents of which are incorporated herein by reference.

The present invention relates to hatchcovers for ships, in particular hatchcovers for container ships on which containers may be stacked.

Structural sandwich plate members are described in US 5,778,813 and US 6,050,208, which documents are hereby incorporated by reference, and comprise outer metal, e.g. steel, plates bonded together with an intermediate elastomer core, e.g. of unfoamed polyurethane. These sandwich plate systems may be used in many forms of construction to replace stiffened steel plates, formed steel plates, reinforced concrete or composite steel -concrete structures and greatly simplify the resultant structures, improving strength and structural performance (e.g. stiffness, damping characteristics) while saving weight.

Further developments of these structural sandwich plate members are described in

WO 01/32414, also incorporated hereby by reference. As described therein, hollow or solid forms may be incorporated in the core layer to reduce weight and transverse metal shear plates may be added to improve stiffness. Hollow forms generate a greater weight reduction than solid forms and are therefore often advantageous. The forms may be made of lightweight foam material or other materials such as wood or steel boxes, plastic extruded shapes and hollow plastic spheres.

A hatchcover formed by injection of core material into cavities in an assembled structure was described in US 6,050,208 referred to above. An arcuate hatchcover formed in a similar manner was described in WO 2004/083029. Although these hatchcovers provided advantages over traditional designs of hatchcovers, further improvement would be desirable. Traditionally hatchcovers have been formed of single layers of steel plate provided with complex arrangements of stiffeners of various sizes and arrangements. Traditional hatchcovers are labour intensive to manufacture and maintain.

It is an aim of the present invention to provide an improved hatchcover, in particular that can be manufactured more reliably and with reduced labour.

According to the present invention, there is provided a hatchcover comprising a framework and a plurality of prefabricated sandwich panels welded to the framework.

By welding pre-fabricated SPS panels to a framework, the hatchcover can be manufactured quickly and reliably. In particular, the prefabricated SPS panels can be made in factory conditions so as to provide improved dimensional accuracy to ensure a proper fit to the separately manufactured framework.

In preferred embodiments of the invention, a specific order of welding is used to reduce thermal distortion that might be caused by the welding of the prefabricated SPS panels to the framework.

In a preferred embodiment of the invention it is only necessary to turn the hatchcover over once during the manufacturing process.

The materials, dimensions and general properties of the outer plates of the SPS panels used in the invention may be chosen as desired for the particular use to which the hatchcover is to be put and in general may be as described in US-5,778,813 and US- 6,050,208. Steel or stainless steel is commonly used in thicknesses of 0.5 to 20mm and aluminium may be used where light weight is desirable. Similarly, the plastics or polymer core may be any suitable material, for example an elastomer such as polyurethane, as described in US-5,778,813 and US-6,050,208 and is preferably compact, i.e. not a foam. The core is preferably a thermosetting material rather than thermoplastic.

The present invention will be described below with reference to exemplary embodiments and the accompanying drawings, in which:

Figure l is a schematic cross-section of a prefabricated SPS panel that may be used in an embodiment of the present invention;

Figure 2 is a plan view of a first hatchcover according to an embodiment of the present invention;

Figure 3 is a partial cross-sectional view of the hatchcover of Figure 2 showing how the prefabricated SPS panels are joined to the framework;

Figure 4 is a perspective view of a part of the framework of the hatchcover of Figure

2 prior to insertion of the prefabricated SPS panels;

Figure 5 is a schematic plan view of a part of the hatchcover of Figure 2 indicating the order of welding operations for fixing of a prefabricated SPS panel to the framework.

Figure 6 is a plan view of a second hatchcover according to an embodiment of the invention;

Figure 7 is a cross-sectional view along the line "C-C" of the hatchcover of Figure 6;

Figure 8 is a partial cross-sectional view of detail "E" indicated in Figure 6 and 7;

Figure 9 is a partial cross-sectional view of detail "F" indicated in Figure 7;

Figure 10 is a cross-section of a perimeter bar usable in a prefabricated SPS panel; Figures 11 to 18 depict steps in a method of manufacturing a hatchcover according to the present invention; and

Figures 19 and 20 depict steps in another method of manufacturing a hatchcover according to the present invention.

In the various drawings, like parts are indicated by like reference numerals.

Figure 1 shows a prefabricated SPS panel 10 that can be used in embodiments of the invention. The panel, preferably presents a generally flat upper surface but the lower surface need not be flat and either or both surfaces may be provided with recesses, trenches, grooves and/or fittings if required. Injection ports and vent holes may be provided for manufacture but are desirably sealed and/or ground flush after use. In plan the panel is desirably substantially rectangular but panels of other shapes maybe used if desired.

The panel 10 shown in Figure 1 is a structural sandwich plate member that comprises upper and lower outer plates (faceplates) 11, 12 which may be of steel or aluminium and have a thickness, for example, in the range of from 3 to 8mm, more preferably 3 to 5mm. Edge members 13 (also referred to as perimeter bars), described further below, are provided between the face plates 11 , 12 around their outer peripheries to form a closed cavity. In the cavity between the face plates 11, 12 is a core 14, described further below. This core may have a thickness in the range of from 15 to 200mm; in many applications 15 to 20mm is preferable. The overall dimensions of the panel in plan may be from 1 to 2m width by 2 to 14m length. Panels may be made in standard sizes or tailor-made to specific shapes and/or dimensions.

The core may take various different forms but its major structural component is a main core layer 14 of plastics or polymer material (preferably comprising or consisting essentially of a thermoset, compact elastomer such as polyurethane as discussed above) which is bonded to the face plates 11, 12 with sufficient strength and has sufficient mechanical properties to transfer shear forces expected in use. The bond strength between the layer 14 and face plates 11, 12 should be greater than 3MPa, preferably greater than 6MPa, and the modulus of elasticity of the core material should be greater than 200MPa, preferably greater than 250MPa.

The core 14 may also include a plurality of hollow box-shaped forms enclosing voids. The size and material of the forms are chosen so that the overall density of the forms is lower than the density of the material of the main core, preferably less than 50% of the density of the material of the core layer 14, or preferably less than 25% and most preferably less than 10%. The purpose of the forms is essentially to take up space within the core and thus reduce the amount of the main core material required whilst maintaining or even increasing the desired spacing between faceplates 11 and 12. This reduces cost both directly as the forms are less expensive by volume than the main core material and secondly because the weight of the panels is reduced. The forms do not need to contribute to the overall structural strength of the floor panel 10 but if the panel 10 is formed by injection of the main core layer 14, the forms must have physical properties sufficient to withstand pressures and temperatures arising during casting and curing of the main core layer 14. The size, shape and distribution of forms 15 within the core is chosen so that a sufficient number of ribs and/or columns of main core layer material extend between and bond to faceplates 11 and 12 at regular intervals across the length and width of the panel 10. The forms do not have to be hollow, e.g. if made of a suitable lightweight material such as a foam, or may be filled with lightweight material, which may be insulating and/or fire resistant. A particularly useful material for the forms is expanded polystyrene, having a density of 20-40g/l, which may be provided, e.g., either as spheres or ribs.

An edge member 13 is provided in at least one, preferably all edges of panel 10. Edge member 13 is a solid bar of metal having a generally constant cross-section throughout its length. It may therefore be described as prismatic. In an embodiment of the invention, edge member 13 projects outwardly of the faceplates 11, 12 and is shaped to facilitate welding of the panel into the framework of a hatchcover. This is described further below in relation to specific examples.

Figure 2 is a plan view of a hatchcover 20 according to an embodiment of the invention.

As can there be seen, hatchcover 20 comprises a framework 21 which defines an array of apertures into which are welded prefabricated SPS panels 10. In this example, the hatchcover includes 12 prefabricated SPS panels in four rows of three. The panels are of four different sizes to accommodate various fittings on the hatchcover such as stoppers 23, bearing pads 25 and hold down devices 24. Given that each container ship will require a large number of hatchcovers, advantages of mass production of the prefabricated SPS panels are still obtained even if multiple different panels are used in each hatchcover. Overall, the hatchcover has dimensions of about 13 meters by 7.5 meters and the dimensions of the SPS panels are from about 2.8 meters by 2 meters to about 3.4 meters by 2.1 meters. As can be seen in Figure 2, the comers of the prefabricated SPS panels are curved, with a radius of curvature of about 100mm to 500mm, to avoid stress concentrations when the panels are welded to the frame 21.

Figure 3 is a cross-section showing the connection of panel 10 to frame 21. As can there be seen, perimeter bar 13a projects slightly from the edges of faceplates 11, 12 and acts as a backing bar for a weld 26 directly between faceplates 11 , 12 and frame 21. Between perimeter bar 13a and faceplates 11, 12, a sealant strip 15 is provided to seal the cavity formed by faceplates 11 and 12 and perimeter bar 13a during the fabrication process. It will be seen that because there is a direct weld between faceplates 11, 12 and framework 21, in this embodiment perimeter bar 13a does not form a part of composite structure of the hatchcover when completed. It is also shown in Figure 3 that the faceplates 11, 12 may be seamed, that is each faceplate is formed of two or more metal plates butt welded together. Seamed faceplates may be avoided for smaller panels. Figure 3 also shows additional stiffening 27 provided on the underside of hatchcover 20 (not visible in Figure 2) in order to provide the necessary physical strength. Nevertheless, the amount of stiffening required in a hatchcover using prefabricated SPS plates is generally less than that required in an equivalent all-steel construction, hence reducing labour costs for manufacture and maintenance.

Figure 4 shows a part of the framework 21 prior to insertion of a prefabricated SPS panel. As can there be seen, the upper plate 21a of the frame defines apertures 28 in which the prefabricated SPS panels are to be inserted. Stiffeners 27 in the form of webs and flanges, surround each aperture 28.

A weld sequence for welding prefabricated SPS panels 10 into framework 21 is shown in Figure 5. The direction and order of the welds between the upper faceplates and frame 21 are indicated by the arrows numbered by roman numerals i to viii. The order of welds is firstly to weld diagonally opposite corners in one clockwise or anticlockwise direction, then weld the other corners in the other direction. The long sides are then welded in the same direction but starting with the opposite side from the end of the last corner weld. Finally the short sides are welded in the same direction. This order of welds has been found to minimise thermal distortion in the framework and SPS panels.

Another embodiment of a hatchcover according to the present invention is shown in

Figures 6 to 9. Figure 6 is a top plan view, Figure 7 is a section along the line C-C in Figure 6 whilst Figure 8 and 9 are detail cross sections of parts "E" and "F" in Figures 6 and 7. The hatchcover shown in Figure 6 is formed of 10 prefabricated SPS panels 10 each of size about 1.8 meters to 5.3 meters or 2.5 meters by 5.5 meters. The SPS panels have faceplates of thickness of about 4mm and a solid core of thickness of about 20mm. As can be seen in Figures 8 and 9, parameter bars 13b are formed with an enlarged portion having a thickness equal to the total thickness of the SPS panel 10 and a part of reduced thickness equal to the thickness of the core. The reduced thickness part fits between faceplates 11, 12, which are butt welded to the perimeter bar 13b. The perimeter bar 13b is then fillet welded as indicated at 29 to framework 21. Thus, in this embodiment the perimeter bar forms part of the composite structure formed by framework 21 and prefabricated SPS panels 10.

Perimeter bar 13b is shown in more detail in Figure 10. The reduced thickness part has a width E equal to the core thickness of the prefabricated SPS panel whereas the main body B has a thickness equal to the total thickness of the SPS panel plus a tolerance. The edges of the main body are chamfered to facilitate welding both to the outer plates of the prefabricated SPS panel and to the framework 21. The complete perimeter bar for a prefabricated panel may be made by joining straight and curved sections, e.g. by welding. Alternatively, separate straight and curved sections may be attached to the faceplates.

A method according to the invention of constructing a hatchcover is illustrated in

Figures 11 to 18. The first steps are assembly of the frame 21 (shown in Figure 11) and prefabrication of the SPS panels (shown in Figure 12). These steps may be carried out separately, in parallel or sequentially and may be carried out at different sites. Next, as shown in Figure 13, the prefabricated SPS panels 10 are inserted into the top frame 21 and sit on temporary docks to provide alignment for welding. At this stage the top frame 21 is upside down. The next step, shown in Figure 14 is to attach and weld the hatchcover main beams and girders 27. The sizing of the frame is desirably determined so as to allow for weld shrinkage during this step without affecting the prefabricated SPS panels.

After welding of the beams and girders forming reinforcements 27, the SPS panels 10 are welded 40 to the frame. This step can be performed wholly using down-hand welding which is therefore easy, fast and safe.

After completion of the welding of the SPS panels to the underside of the hatchcover top plate, the hatchcover is turned over, Figure 16, which is the only turning operation required in the assembly procedure. Figure 17 shows completion of the welding of the SPS panels to the top side of the hatchcover top plate 21. Again this can all be performed by down-hand welding. Finally, Figure 18, container fittings and other attachments are fixed to the hatchcover to complete the hatchcover.

In an alternative assembly method according to the invention, shown in Figure 19, the hatchcover does not have a top plate, but rather framework 21 is assembled from an arrangement of beams and girders 27, which provide integral stiffening for the hatchcover. As can be seen in Figure 19, the framework is assembled around the prefabricated

hatchcovers 10.

The welding sequence is shown in Figure 20. First the framework is welded together in stages: first butt welding then vertical fillet welds and horizontal fillet welds. Once this has been completed a dimension check can be carried out and the SPS panels 10 welded to the framework via the lower faceplates in the indicated order. The hatchcover can then be turned over for additional butt welds to complete the framework and final welding of the upper faceplates of the SPS panels to the frame.

A preferred method of constructing a panel to be used in the invention is preferably performed off-site and involves:

• placing the outer metal layers 11, 12, edge members 13 and any forms or spacers in a mould to define a cavity;

• injecting liquid plastics or polymer material into the cavity through an injection port; and

• causing or allowing the plastics or polymer material to cure to form the main core layer 14.

After curing, the injection ports and vent holes are filled, e.g. with threaded plugs, and ground flush with the surface of the outer metal plate. It is to be noted that even if a single continuous cavity is present prior to injection, multiple injection ports and vent holes may be provided to ensure complete filling. As an alternative to injection of the core material, a vacuum fill technique can be used.

If the panel is to be provided with recesses, grooves or other surface features, such as fixing or lifting points, these are preferably formed in or on the outer metal plates prior to injection of the core. Grooves and other indentations can be formed by known techniques such as milling, cutting, bending, rolling and stamping as appropriate to the thickness of the plate and size of feature to be formed. Details can be attached by welding. It is also possible to form such features after injection and curing of the main core layer 14 but in that case measures may need to be taken to ensure that the heat generated by activities such as welding does not deleteriously affect the core 13.

In some circumstances it may be possible to avoid the use of a mould by welding edge plates or perimeter bars to the outer metal plates so that the panel forms its own mould. Depending on the compressibility and resilience of the inner core, it may be necessary to provide restraints to prevent deformation of the outer metal plates due to the internal pressures experienced during injection and curing of main core layer 14.

It should be noted that after the core has cured, the faceplates and perimeter bars are bound together by the core 14 so that in some cases the fixing of the perimeter bars to the face plates need only be sufficient to withstand loads encountered during the injection and curing steps, and not necessarily loads encountered during use of the floor panel 10. To improve sealing of the cavity, gaskets or sealing strips can be provided between the edge plates or perimeter bars and face plates.

It will be appreciated that the above description is not intended to be limiting and that other modifications and variations fall within the scope of the present invention, which is defined by the appended claims.

Claims

1. A hatchcover comprising a framework and a plurality of prefabricated sandwich panels welded to the framework.

2. A hatchcover according to claim 1 wherein the prefabricated sandwich panels comprise first and second outer metal layers and a core layer of plastics or polymer material bonded to the outer metal layers with sufficient strength to transfer shear forces therebetween.

3. A hatchcover according to claim 2 wherein the plastics or polymer material comprises a compact thermoset elastomer such as polyurethane.

4. A hatchcover according to claim 3 wherein the core further comprises a plurality of forms having a density less than the plastics or polymer material.

5. A hatchcover according to any one of the preceding claims wherein the prefabricated sandwich panels have radiused corners.

6. A hatchcover according to any one of claims 2 to 5 wherein each prefabricated sandwich panel comprises a perimeter bar, the perimeter bar projecting outwardly of the first and second outer metal plates and wherein the perimeter bar of each sandwich panel is welded to the framework.

7. A hatchcover according to any one of claims 2 to 5 wherein the outer metal plates of the prefabricated sandwich panels are welded directly to the framework.

8. A hatchcover according to any one of claims 2 to 5 wherein the outer metal plates of the prefabricated sandwich panels have a thickness in the range of from 2mm to 5mm.

9. A hatchcover according to any one of claims 2 to 5 wherein the core layer of the prefabricated sandwich panels has a thickness in the range of from 10mm to 30mm.

10. A method of manufacturing a hatchcover comprising:

providing a framework;

inserting a plurality of prefabricated sandwich panels into the framework; and welding the prefabricated sandwich panels to the framework.

11. A method according to claim 10 wherein the prefabricated sandwich panels have curved corners and the step of welding the prefabricated sandwich panels to the framework comprises, for each panel:

welding diagonally opposite corners of the prefabricated sandwich panel to the framework in a first direction;

welding the other corners of the prefabricated sandwich panel to the framework in a second direction opposite to the first direction;

welding a first pair of opposite sides of the prefabricated sandwich panel to the framework in the second direction; and

welding the other sides of the prefabricated sandwich panels to the framework.

12. A method according to any one of claims 10 to 12 wherein the prefabricated SPS panels are arranged in a rectangular array in the framework and the step of welding the prefabricated sandwich panels to the framework comprises welding innermost prefabricated sandwich panels to the framework before outermost prefabricated sandwich panels.

13. A method according to any one of claims 10 to 13 wherein the step of welding the prefabricated sandwich panels to the framework comprises directly butt welding outer plates of the prefabricated sandwich panels to the framework.

14. A method according to any one of claims 10 to 13 wherein the prefabricated sandwich panels have a perimeter bars which project outwardly of their outer plates and the step of welding comprises welding the perimeter bars to the framework.

15. A method according to any one of claims 10 to 14 wherein framework is fully assembled before insertion of the prefabricated sandwich plate members.

16. A method according to any one of claims 10 to 14 wherein the steps of providing a framework and inserting prefabricated sandwich panels comprise assembling the framework from a plurality of beams and girders around the prefabricated sandwich panels.

17. A method according to any one of claims 10 to 16 wherein the prefabricated sandwich panels are manufactured by the steps of:

providing first and second metal plates in a spaced apart relationship so as to define a cavity;

filling said cavity with uncured plastics or polymer material; and

allowing or causing said plastics or polymer material to cure to form a core that bonds to said outer plates with sufficient strength to transfer shear forces therebetween.

18. A vessel having a plurality of hatchcovers according to any one of claims 1 to 9.

19. A vessel according to claim 18 that is a container ship.