CN1639000A - Sandwich plate ramps - Google Patents

Abstract

A moveable ramp has a load-bearing deck formed of a sandwich structure comprising upper and lower metal plates and an intermediate layer of plastic bonded to the metal plates so as to transfer shear forces between them.

Description

Sandwich ramp

The present invention relates to ramps, in particular movable ramps for use in vehicle ferries, eg allowing vehicles to be loaded and unloaded and to pass between decks.

RoRo and RoPax ferries are used throughout the world to transport motor vehicles such as cars, caravans and trucks through bodies of water. Such ferries have one or more vehicle decks on which motor vehicles are carried and are provided with movable ramps that lower a drawbridge-like body onto a quay to allow motor vehicles to drive on and off the deck . Typically movable ramps will be provided at the bow and stern of the vessel so that vehicles can be driven forward onto and off deck, thus avoiding delays when the vehicle is turning or reversing. In ships with more than one deck, movable ramps may be provided to allow vehicles to pass between decks, and in some cases such movable ramps may be arranged to be raised and held in a raised position, At the same time the vehicle is on the ramp.

Movable ramps of this type must be strong enough to carry anticipated vehicle loads, including concentrated wheel loads from forklifts, cars, trucks, tractors, trailers, etc., which in the case of multiple heavy trailers may reach 150 tons, and the movable ramp must be durable. In particular, the upper surface on which the motor vehicle runs is preferably non-slip, which upper surface is subject to significant wear and must be able to withstand such wear for a reasonably long period without loss of the structural strength of the ramp. At the same time, the weight of the ramp and the space it occupies must be minimized in order to maximize the useful cargo space and tonnage of the vessel.

So far such ramps have been made of reinforced steel structures, but these are rather complex and heavy structures which require many welds which are difficult to protect from the corrosive sea air, and Fatigue fractures often occur at or near the end of the ramp in the wear plate and on the reinforcement.

It is therefore an object of the present invention to provide an improved ramp construction, for example lighter in construction, simpler in construction and/or easier to protect against corrosion and eliminating elements prone to fatigue.

According to the present invention there is provided a movable ramp comprising a load-bearing deck mountable at one end to a rotatable hinge, wherein the load-bearing deck comprises a sandwich structure having upper and lower metal plates and plastic material An intermediate layer bonded to the metal sheet to transmit shear forces therebetween.

The sandwich structural panels used to form the load bearing deck have increased stiffness compared to steel plates of comparable thickness and avoid or reduce the need to provide stiffening elements. As a result this results in a relatively simple structure with fewer solder joints, resulting in a simplified manufacturing process and fewer components and areas prone to corrosion and fatigue. Additional elements of sandwich panel construction suitable for use in the present invention can be found in US Patent 5,778,813 and British Patent Application GB-A-2337 022. The intermediate layer may also be a composite core as described in International Patent Application No. WO 01/32414. These documents are incorporated herein by reference.

The movable ramp of the present invention preferably has the upper deck on which the vehicle travels thicker than the lower deck. The upper surface of the upper plate may be provided with a surface finish, a profiled surface or a coating in order to improve the traction of vehicles passing on the upper surface.

The preferred thickness of the upper plate is 4-20 mm, the thickness of the lower plate is 3-20 mm, and the thickness of the middle layer is 20-200 mm.

It is also preferred that the distal end of the load deck (furthest from the hinge) is tapered in thickness. Preferably, this taper is accommodated in the middle layer, the outer metal layer having a constant thickness. The lower metal layer may actually have an increased thickness in this area in order to withstand the wear and tear of the quayside.

Ramps according to the invention may also be used in non-maritime applications, such as construction and civil engineering.

The invention will be further described with reference to the following description of exemplary embodiments and the accompanying drawings, in which:

Figure 1 represents a movable ramp according to the invention in a vehicle ferry;

Fig. 2 is a plan view of the underside of the movable ramp according to the first embodiment of the present invention;

Fig. 3 is a side view of the movable ramp of Fig. 2;

Figure 4 is a vertical cross-sectional view of the movable ramp of Figure 2 along line A-A;

Figure 5 is a vertical cross-sectional view of the movable ramp of Figure 2 along line B-B;

Figure 6 is a vertical cross-sectional view of the movable ramp of Figure 2 along line C-C;

Figure 7 is an enlarged side view of the hinged end of the movable ramp of Figure 2;

Figure 8 is a horizontal sectional view of the hinged end of the movable ramp of Figure 2 along line D-D in Figure 7;

Figure 9 is a vertical cross-sectional view of the hinged end of the movable ramp of Figure 2 along line E-E in Figure 8;

10 is a plan view of the underside of the movable ramp according to the first embodiment of the present invention;

Figure 11 is a sectional view along line F-F of the movable ramp of Figure 10; and

Fig. 12 is a sectional view along line G-G of the movable ramp of Fig. 10 .

In the figures, the same components are denoted by the same reference numerals.

FIG. 1 shows a vehicle ferry 1 , which may be a RoRo or RoPax ferry, which has a movable ramp 2 at its bow to enable motor vehicles 3 to travel directly from the vehicle deck 4 to the quayside 5 . The ramp 2 is hinged at its inboard (near) end and may be provided with cables and winches or hydraulic cylinders (not shown) to raise and lower it. The ramp may be formed from several independently hinged adjacent sections in order to minimize lateral stresses and accommodate the movement of the vessel at the anchorage point if the quayside is not level. Some such structures are sometimes referred to as bow fingers. Similar ramps may be provided at the stern of the vessel for motor vehicle through loading and unloading. Vehicle entrances and exits will generally be closed by bow and stern doors (not shown) when the vessel is underway, but in the case of small open deck ferries in sheltered waters this may not be necessary. The ramp of the present invention can form a watertight door when raised.

Figure 2 is a plan view of the underside of a movable ramp 2 according to a first embodiment of the invention, which is substantially square or rectangular in plan, for example about 3-4m long and 0.5-1m wide. At the inboard (proximal) end there are side flanges 6 for mounting on hinges on the vessel and at the outboard (distal) end the ramp has a beveled portion 7 in order to reduce jumping of the end of the ramp in the quayside Leave. These details can also be seen in Figures 3 and 4, which are a side view and a vertical section on line A-A in Figure 2, respectively.

The upper plate 8 of the ramp 2 may be formed, for example, of 8 mm steel plate provided with a suitable anti-corrosion coating. The upper surface on which the vehicle will run is substantially flat and may be provided with a surface treatment to improve traction to the vehicle's tires. For example, the upper surface may be provided with a self-draining, non-slip raised pattern of evenly spaced raised posts, such as that manufactured by Corus Group plc under the trademark "Durbar".

The lower plate 9 is formed in two parts, a main part 9a of eg 4mm steel plate extending over most of the length of the ramp 2 and a distal part 9b furthest from the hinge formed of eg 8mm thicker steel plate. This part of the ramp will be in contact with the docklands as the ramp descends, and the thicker plates are used to accommodate the resulting wear. The length of the distal portion in which the ramp is also beveled may be approximately 0.3-1 m.

Side walls 12 of eg 10 mm steel plate connect the upper and lower panels 8, 9 and one or more longitudinal dividers may be provided, eg also 10 mm plates. The upper and lower panels 8,9 and the side walls 10 thus form a box-like structure, which may be filled with an intermediate layer 12, which is a plastic or elastomer bonded to the upper and lower panels 8,9 materials in order to transfer shear forces between them. In the main part of the ramp the upper and lower plates are spaced 60mm apart, tapering to about 25-30mm in the end sections. The box-like structure and the beveled portion are shown more clearly in Figures 5 and 6, which are vertical cross-sectional views along lines B-B and C-C in Figure 2, respectively. As shown in Figures 5 and 6, the side walls 10 can be inserted slightly from the edges of the upper and lower panels 8, 9, so this forms a small lip.

At the hinged ends of the ramp, the box-like structure is closed by an end plate 13, eg 12mm steel plate, which extends below the lower plate 9 and straddles between the side flanges 6 to reinforce them. At the distal end, the box-like structure is closed by an end rod 14 of solid metal, eg steel, having a diameter of eg 40 mm. This is because the end of the ramp will be subject to considerable wear as the vehicle travels on the ramp in order to board the vessel 1 .

Bosses 15 may be provided protruding from the sides of the ramps at suitable locations to engage adjacent ramps so that a set of ramps can be raised and lowered as a unit.

Details of the hinge structure and inboard end of the ramp are shown in Figures 7, 8 and 9. As can be seen in these figures, the side flanges 6 extend below the lower plate 9 and have a main part 6a which is a relatively thick plate, for example 25 mm, in which a through hole 16 is provided for mounting on the hinge pin (not shown). A bushing, for example copper, is arranged in the through hole 16 . The main part 6a extends close to the end plate 13, which may be provided with a horizontal flange on its lower edge for additional reinforcement. Extending away from the end plate 13 is an additional plate 6b, for example 10 mm thinner and of reduced depth than the main plate 6a of the side flange 6, terminating at about 0.3-1 m from the end plate 13. A further reinforcing plate 17 similar in shape to the plate 6b may be provided extending away from the end plate 13 in the middle part of the end plate.

The presently preferred method of manufacturing the ramp of the present invention is to weld the side walls 10 and dividers 11 to the inside of the upper plate 8 . The two parts 9a, 9b of the lower plate 9 are then welded to form a box-like structure which is then closed by welding the end walls 13 and end rods 16 in place. Uncured plastic is then injected through injection ports 18 (shown in FIGS. 2 and 3 ) and vent holes 19 (shown in FIGS. 2 and 3 ) to allow air to escape, thereby forming the intermediate layer 12 . The plastic can then be cured or heat cured as desired. After curing, the sprue can be ground off and sealed along with the vent hole. Optionally, the upper side flanges 6 and other fittings can be welded before or after the injection and curing of the elastomer. It is preferred that all welding be done prior to injecting the elastomer in order to minimize thermal damage to it.

A second embodiment of the invention is shown in FIGS. 10 , 11 and 12 . In this embodiment the moveable ramp is a single structure of eg approximately 16m x 16m rather than being segmented into smaller ramps as in the first embodiment.

The ramp 20 according to the second embodiment comprises a main ramp plate 21 reinforced by transverse beams 22 and longitudinal braces 23 . The main ramp plate 21 is a sandwich structure comprising an upper plate 24 , an intermediate plate or core 25 and a lower plate 26 . Hinge elements 27 are provided to connect the ramp to the vessel. The core 25 comprises a foam molding occupying eg 50% of the volume of the cavity between the upper and lower plates 24, 26 and elastic ribs occupying the remaining volume. As an example, the thickness of the upper plate may be 6 mm, the core 75 mm, and the lower plate 7 mm. Structurally, the foam provides negligible strength, but resilient ribs are attached to the upper and lower plates 24, 26 to transmit shear forces therebetween.

The ramp 20 may also form the main door of the vessel and may be provided at its distal end (left end in Figure 10) with a separate smaller ramp. These separate smaller ramps may be of similar construction to that of the first embodiment. Bases and other elements may be provided to withstand concentrated loads such as those associated with latches, locks, attachments of cables or other actuators and the like.

To construct the ramp 20 , the lower plate 26 is positioned upside down, and the transverse beams 22 and longitudinal braces are welded to the lower surface of the lower plate 26 . The partial structure is then turned over and spacer bars and side walls are welded to the upper surface of the lower plate 26 . Next, the foam formations (blocks) were placed so as to cover 50% of the area of the board. The upper plate 24 is then welded to the spacer rods and side walls to form an airtight cavity. The anti-skid bars and other components can then be welded in place. Finally, the airtight cavity is injected with an elastomer which cures to completely make the core 25 .

An equivalent all-steel structure of conventional design employs an upper plate of 13mm steel reinforced by longitudinal spherical plates. It also requires additional transverse beams. Compared to this, the ramp according to the invention has a moderate weight, at the same time does not require spherical plates, and the number of beams greatly reduces the amount of welding required and generally simplifies the construction. It also greatly reduces the area of steel that must be painted and eliminates many points on which moisture can collect.

The upper and lower metal plates and other metal parts of the ramp of the present invention are preferably structural steel, as described above, but they may also be aluminum, stainless steel in applications requiring light weight, corrosion resistance, or other special properties or other structural alloys. The metal should preferably have a minimum yield strength of 240 MPa and an elongation of at least 10%.

The interlayer should have a modulus of elasticity E of at least 250 MPa, preferably 275 MPa, at the maximum expected temperature in the environment in which the component will be used. In a shipbuilding application this temperature may be 100°C.

The ductility of the elastomer at the lowest operating temperature must be greater than that of the metal layer, which is approximately 20% ductile. A preferred value for the ductility of the elastomer at the lowest operating temperature is 50%. The thermal conductivity of the elastomer must also be close enough to that of the steel that temperature changes through the expected operating range and during welding will not cause delamination. The degree to which the thermal conductivity of the two materials may differ will depend in part on the elasticity of the elastomer, but we believe that the coefficient of thermal expansion of the elastomer may be approximately 10 times that of the metal layer. By adding fillers to elastomers, the coefficient of thermal expansion can be controlled.

The bond strength between the elastomer and the metal layer must be at least 0.5 MPa, preferably 6 MPa, over the entire operating range. This is preferably achieved through the inherent adhesion of the elastomer to the metal, but additional bonding agents may also be provided.

If the ramp is to be used in a shipbuilding application, additional requirements include that the elastomer must be hydrolytically stable to both sea and fresh water.

Thus, elastomers may essentially comprise polyols (eg polyesters or polyethers) together with isocyanates or diisocyanates, chain extenders and fillers. If desired, fillers are provided to reduce the thermal conductivity of the interlayer, reduce its cost and otherwise control the physical properties of the elastomer. Further additives and flame retardants may also be included, for example in order to modify the mechanical properties or other properties such as adhesion and water or oil resistance.

While embodiments of the invention have been described above, it should be understood that this is exemplary and not intended to limit the scope of the invention, which is defined by the appended claims. Specifically, the dimensions given are for guidance purposes and are not prescriptive.

Claims (11)

1. A movable ramp comprising a load-bearing deck mountable at one end to a rotatable hinge, wherein said load-bearing deck comprises a sandwich structure having upper and lower metal plates and an intermediate layer of plastic material, The intermediate layer is bonded to the metal sheet to transmit shear forces therebetween. 2. The movable ramp of claim 1, wherein the upper plate is thicker than the lower plate. 3. Movable ramp according to claim 1 or 2, characterized in that the upper surface of the upper plate is provided with a surface finish, a profiled surface or a coating in order to improve the safety of vehicles passing on the upper surface. traction. 4. The movable ramp according to claim 1, 2 or 3, characterized in that, the thickness of the upper plate is 4-20mm, the thickness of the lower plate is 3-20mm, and the thickness of the middle layer The thickness is 20-200mm. 5. A movable ramp as claimed in any one of the preceding claims, wherein the distal end of the load bearing deck is tapered in thickness. 6. The movable ramp of claim 5, wherein the tapered portion is housed in an intermediate layer. 7. The movable ramp of claim 6, wherein the lower plate has an increased thickness in the distal end. 8. A movable ramp according to any one of the preceding claims, wherein the intermediate layer comprises a compact elastomer. 9. Movable ramp according to any one of claims 1-7, characterized in that said intermediate layer comprises a shaped body and said plastic material between said upper and lower metal plates In the space not occupied by the shaped body. 10. A movable ramp constructed substantially as hereinbefore described with reference to the accompanying drawings. 11. A vessel having at least one movable ramp according to any one of the preceding claims.

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