GB2562105A

GB2562105A - Container accessory

Info

Publication number: GB2562105A
Application number: GB1707216.6A
Authority: GB
Inventors: Marie Vincent Andersen Ingrid; Posborg Troels
Original assignee: AP Moller Maersk AS
Current assignee: AP Moller Maersk AS
Priority date: 2017-05-05
Filing date: 2017-05-05
Publication date: 2018-11-07
Also published as: GB201707216D0

Abstract

A container accessory 600 for a stack of shipping containers (108, Fig. 1) for the purposes of dampening vibrational movement. The accessory comprises a frame 602, a releasable lockable coupler (400, Fig. 4) designed to secure the frame to the stack of shipping containers and a vibration dampener 620 (or damper). The dampener comprises a moveable mass 622 and resiliently deformable connector 624 (preferably a spring) coupled between the frame and the mass. Preferably there may be two resiliently deformable connectors positioned either side of the mass. The mass may be on a guided rail 628 and/or have rollers (702, 704, Fig. 7). There may be more than one releasable lockable coupler, preferably one at each corner of the frame. The stiffness of resiliently deformable connector may be adjustable either by hand or a motor. The frame may also be elongated with the mass moving between the long sides of the frame. The moveable mass may be 1% - 2% of the total mass of the shipper container stack (about 800kg 6000kg) and have a natural frequency between 0.3Hz 1Hz.

Description

(54) Title of the Invention: Container accessory

Abstract Title: A mass dampener for a stack of freight containers (57) A container accessory 600 for a stack of shipping containers (108, Fig. 1) for the purposes of dampening vibrational movement. The accessory comprises a frame 602, a releasable lockable coupler (400, Fig. 4) designed to secure the frame to the stack of shipping containers and a vibration dampener 620 (or damper). The dampener comprises a moveable mass 622 and resiliently deformable connector 624 (preferably a spring) coupled between the frame and the mass. Preferably there may be two resiliently deformable connectors positioned either side of the mass. The mass may be on a guided rail 628 and/or have rollers (702, 704, Fig. 7). There may be more than one releasable lockable coupler, preferably one at each corner of the frame. The stiffness of resiliently deformable connector may be adjustable either by hand or a motor. The frame may also be elongated with the mass moving between the long sides of the frame. The moveable mass may be 1% - 2% of the total mass of the shipper container stack (about 800kg - 6000kg) and have a natural frequency between 0.3Hz - 1 Hz.

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Container accessory

The present invention relates to an accessory for a container. In particular the present invention relates to a vibration dampener for a stack of a plurality of shipping containers.

Container ships have increasingly become larger over the years with the desire to increase fuel efficiency and decrease the unit transportation cost of each shipping container. This means container ships have tended to become longer, wider and deeper. Indeed the biggest ships can stack up to ten or eleven tiers of shipping containers high on the ship deck when fully laden. It is likely that container ships will become even larger in the future. For example there may be more than 11 tiers on the deck.

Shipping containers are arranged along the length of a container ship in bays. Each bay can be separated by a bulkhead and I or other structural parts of the ship like lashing bridges. On the deck each bay can be separated by a lashing bridge. Within each bay the containers may be stacked in two parts; within the hull and on the deck. The containers are arranged across the breadth of the ship in each bay in a plurality of rows. The number of bays, rows and tiers may vary with the size and shape of the ship.

When a container ship sails on the ocean, the containers must be securely fastened to the ship to make sure that the containers do not move relative to the ship in rough seas. This can help protect the crew from injury and the cargo from being lost overboard.

It is known to fasten the containers to the deck of the ship. Typically the bottommost container in a stack will be securely fixed to the deck or a hatch cover. For example the bottommost container will have cube shaped corner fittings on each of its eight corners. The cube shaped corner fittings each have a plurality of coupling holes on each outwardly facing surface of the corner fitting. The underside coupling hole is arranged to receiving a locking fastener which is securely fixed to both the container and a reciprocal hole in the deck or hatch cover.

A plurality of containers are then stacked on top of the bottommost container. Similar locking fasteners and corner fitting arrangements couple a container in one tier to another to in the tier below or above.

It is also known to secure the containers to lashing bridges. The lashing bridges are an upstanding part of the structure of the ship. Typically the lashing bridges are mounted on each of the bulkheads that separate the bays. The lashing bridges typically extend upwardly for a portion of full height of the container stack. For example some known lashing bridges are the height of one to three containers above the hatch covers.

The containers at the lower portion of each stack at a height equal to or lower than the height of the lashing bridges are fastened to the lashing bridges. The containers are fastened to the lashing bridges with lashing rods which couple between the corner fittings of the containers and the lashing bridge. The tier of containers above the lashing bridge can also be secured to the lashing bridge. The lashing rods can comprise turnbuckles for tightening the lashing rods to vary the force securing the containers to the lashing bridges.

The containers are coupled to the lashing bridges at the longitudinal ends of the containers. Since the lashing bridges only extend part way the height of the container stack, the topmost containers in the stack are only secured to the ship through the container stack itself, for example via the corner fittings and the locking fastenings. One type of locking fasteners are twist locks.

It has been noted that in certain rough sea conditions, the ship can experience periodic or random impacts from waves. It is thought that such wave impacts cause vibrations in the ship hull. The periodic vibrations are transmitted through the ship structure to the container stacks. This means that the container stacks can sway breadthways with respect to the ship. Excessive prolonged swaying can cause catastrophic failure in the securing mechanism such as the lashing rods which can damage the containers or result in the cargo being lost overboard.

One known solution for reducing vibrations is disclosed in WO2015/140389 where the lashing bridge comprises a flexible element and mass element for dampening the vibrations in the lashing bridge itself. However, a problem with this arrangement is that the lashing bridge is only designed to work when there are no containers on the ship. This means that the container stack will still experience forces transmitted through the hatch cover and the container stacks can still sway uncontrollably.

Embodiments of the present invention aim to address the aforementioned problems.

According to an aspect of the present invention there is a container accessory for a stack of shipping containers comprising: a frame; at least one lockable coupler mounted on the frame and arranged to releasably secure the frame to one or more shipping containers in the stack of shipping containers; and a vibration dampener comprising: a moveable mass arranged to move between a first position and a second position when the stack of shipping containers moves; and at least one resiliently deformable connector coupled between the moveable mass and the frame. This means that the container accessory suppresses or dampens the oscillation and prevents the one or more containers in a stack from swaying or starting.

Preferably the at least one resiliently deformable connector is two resiliently deformable connectors coupled between the sides of the frame. This means that the moveable mass is securely mounted to the frame. Accordingly the moveable mass is guided to move in a predetermined direction.

Preferably the resiliently deformable connector is one or more of the following:

a spring, a rubber mount, a hydraulic piston, a pneumatic piston. The dampening of vibrations can be achieved in different ways.

Preferably the moveable mass is mounted on rollers. This means that the moveable mass can be partly supported by the frame through the rollers. This prevents the resiliently deformable connection from becoming damaged.

Preferably the at least one mount is a plurality of mounts each located at the corners of the frame. This means that the mounted are aligned with the connection points of a shipping container.

Preferably the resiliently deformable connector comprises an adjustment mechanism for adjusting the stiffness of the resiliently deformable connector. Preferably the adjustment mechanism comprises a manually adjustable actuator. Preferably the adjustment comprises a motor for automatically adjusting the stiffness of the resiliently deformable connector. By adjusting the stiffness of the resiliently deformable connector, the response characteristics of the vibration dampener can be adjusted. This means that the container accessory can be tuned to different conditions and different frequencies of vibration.

Preferably the frame is elongate and the moveable mass is moveable between the long sides of the frame. This means that when the container accessory is mounted on the shipping container, the vibrations are dampening in a port-starboard or side to side direction.

Preferably wherein the frame comprises rails for guiding the moveable mass. This means that the moveable mass is constrained to a single degree of freedom.

Preferably the moveable mass is between 1 % - 2% of the mass of the stack of containers. Preferably the vibration dampener has a natural frequency between 0.3Hz - 1Hz. In this way the moveable mass is tuned to the sea conditions which cause container stack swaying.

Preferably the at least one lockable coupler is four lockable couplers mounted in each corner of the frame. This means that the container accessory is mountable on a shipping container.

Preferably the frame is hollow and the vibration dampener is mounted inside the frame. This means that the vibration dampener mechanism is protected from the maritime environment.

Preferably the moveable mass has a mass between 800kg and 6000kg. This means that the moveable mass is tuned to the total average mass of the stack of the containers on deck.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which:

Figure 1 shows a side view of a container ship;

Figure 2 shows schematic cross section of a container ship across the axis AA;

Figure 3 shows a perspective view of a shipping container;

Figure 4 shows a perspective view of a lockable coupler for a shipping container;

Figure 5 shows another schematic cross section of a container ship;

Figure 6 shows a schematic perspective view of a container accessory; and Figure 7 shows a cross section of a container accessory along the axis D-D.

Figure 1 shows a side view of a container ship 100. The container ship 100 comprises a hull 102 that extends over the full length of the container ship 100. The hull 102 extends between a bulbous bow 104 at the front of the ship 100 and the stern 106 at the back of the ship 100.

The hull 102 typically houses one or more engine rooms, fuel tanks and other facilities (not shown) required for the operation of the container ship 100. The hull 102 defines an enclosed volume, which may also be known as the hold. A major part of enclosed volume defined by the hull 102 is used for stowing containers 110. The containers 110 stored below deck are not visible in Figure 1 but can be seen from Figure 2 which shows a cross section along axis A-A. For the purposes of clarity only one container 110 in Figure 1 has been labelled. In some embodiments, each container 110 as shown in Figure 1 has the same dimensions, each being made to the same international standard. In other embodiments the containers 110 may have plurality of predetermined standard dimensions.

The container ship 100 comprises a bridge 116 and one or two funnels 118. The bridge 116 projects above the containers 110 and provides visibility for the crew when navigating. The bridge 116 is located on top of the accommodation quarters 120. The accommodation quarters 120 comprise the sleeping, eating and leisure amenities for the crew.

Figure 1 shows that the superstructure of the bridge 116 and the accommodation 120 is separate from the superstructure of the funnel(s) 118. The funnel(s) 118 comprise the exhaust flues connected to one or more engines (not shown). Both the funnel(s) 118 and the bridge 116 superstructures separate the bays 108. No containers 110 are stowed across the breadth of the ship 100 in the vicinity of the funnels 118 and the bridge 116. The embodiment shown in Figure 1 shows a “twin island” superstructure arrangement. In other embodiments, it is understood that the container ship 100 can also be a “single island” superstructure arrangement where the bridge 116 and the funnel 118 are part of the same superstructure.

The arrangement of shipping containers 110 as shown in Figure 1 is schematic and the actual arrangement of tiers, bays and rows can vary in number. The shipping containers 110 are arranged along the length of the container ship 100 in bays 108. This arranges the containers 110 into separate sections along the length of the ship 100. For the purposes of clarity, only one bay 108 has been labelled. Each bay is separated by a bulkhead 200 below deck and I or other structural parts of the ship like lashing bridges 112 above deck. The shipping containers 110 below deck are not visible in

Figure 1, but are shown in Figure 2. Within each bay the containers 110 are vertically stacked in two parts; within the hull 102 and on the deck 114. The containers 110 are arranged across the breadth of the ship 100 in each bay 108 in a plurality of rows 220a, 220b, 220c, 220d, 220e, 220f. The containers 110 are stacked vertically in a plurality of tiers. The number of bays, rows and tiers may vary with the size and shape of the ship 100.

The stacking of the containers 110 will now be discussed in more detail with respect to Figure 2. Figure 2 shows a schematic cross sectional representation of the container 100 along axis A-A in Figure 1. The cross section shown Figure 2 is through a bay 108. As previously mentioned, a portion of the containers 110 are stowed within the cargo hold 202. The breadth of the bay 108 is separated into rows 220a, 220b, 220c, 220d, 220e, 220f for separate stacks 204 of containers 110. Figure 2 shows the hold 202 of the container ship 100 completely full. Each row 220a, 220b, 220c, 220d, 220e, 220f comprises flared guide rails for guiding containers in and out of the hold 202. The bottommost container of each row 220a, 220b, 220c, 220d, 220e, 220f below deck rests on a tank top 206. A passageway 211 is located in the hull 102 and runs for-aft along each side of the hull.

Each bay 108 is covered with a hatch cover 208 for closing the hold 202. Each bay may be covered by one or more hatch covers 208. The hatch cover 208 is arranged to close and seal the hold from the outside elements. In this way the hatch cover 208 limits or stops water ingress into the hold. This means that the hatch cover 208 limits the amount of water damage caused to the cargo. The hatch covers 208 are removed and replace by gantry cranes when the ship is in port. For example a hatch cover 208 may be lifted off the ship 100 and placed on the dockside during a loading operation. The gantry crane is the same equipment used to lift containers 110 from the container ships 100.

The hatch covers 208 can be fixed with cleat bolts (not shown) to the hull 102 with locking fasteners during a journey. Alternatively the hatch covers 208 may simply be placed in position without fastening to the hull 102. In this case the weight of the hatch cover 208 and the containers 110 loaded thereon is sufficient to keep the hatch cover 208 from moving with respect to the container ship 100. In some embodiments, the hatch covers 208 are moveably fixed to the structure of the ship 100. The hatch cover 208 can move horizontally or vertically with respect to the hull 102. In this way the hatch cover 208 may comprises a hinge for folding out of the way during a loading operation.

Figure 2 shows hatch covers 208 in place and abutting against a portion of the hull 102. In this way the hatch covers 208 resting on the hull 102 effectively form a part of the deck of the container ship 100. In some embodiments the hatch covers 208 rest on a raised coaming 210. The coaming 210 is an upstanding rim from the deck 114 coupled to the hull 102. In this way the coaming 210 and the hull structure 102 bear the weight of the hatch cover 208 when positioned in place.

Once the hatch covers 208 are located on the coaming 210 of the ship 100, the hatch covers 208 provide a surface for stacking more containers 100. Figure 2 shows one hatch cover 216 free from containers 110 and another hatch cover 208 with a plurality of containers 110 stacked thereon. The containers 110 on the hatch cover 208, 216 are stacked in deck container stacks 214. These stacks 214 of containers are similar to the stacks 204 in the hold except that the stack 214 are located on the deck. This means that the containers 110 in the deck container stacks 214 are in the open and exposed to the environmental weather conditions.

In some embodiments the hatch covers 208 are optional and containers 110 are only stacked on the deck of the ship 100. For example there are no hatch covers 208 because the hold is not designed to receive containers 110. Alternatively the ship 100 does not have a deck 114 and the ship has an open top. In this way the containers 110 are only stacked on the tank top 211 of the ship’s hull 102. In yet another embodiment a portion of the ship 100 does not have any hatch covers 208, 216 because there is no cargo hold below deck. For example the containers 110 are standing and secured on the ship structure in the aft-most bay and a mooring deck is directly below the aft-most bay.

The hatch covers 208 comprise at least one fixing point 212. In some embodiments the hatch covers 208 comprise a plurality of fixing points 212 for example there can be fixing points spaced every meter or so around the perimeter of the hatch cover 208. The fixing points 212 are suitable for releasably coupling one or more shipping containers 110 to the hatch cover 208 by the use of locking devices such as base locks.

Turning to Figure 3, a container 110 will be briefly described. Figure 3 shows a perspective view of a shipping container 110. A typical shipping container 110 is subject to ISO standards which define the required height, length and breadth. The shipping container 110 come in several standard sizes including 20ft long x 8ft wide x 8ft 6inches high (6.096m x 2.438m x 2.591m) long and 40ft long x 8ft wide x 8ft 6 inches high (12.192m x 2.438m x 2.591m) as defined in international organisation for standardization (ISO) documentation. The container 110 is enlongated along a longitudinal axis B-B and cuboid in shape. At each corner of the container 110, the container 110 comprises a corner fitting 302. The corner fitting 302 comprises holes 304 on three outwardly facing surfaces for receiving locking couplers or fasteners.

Turning back to Figure 2, the fixing points 212 are arranged to engage with the holes 304 of the bottommost container 110 of a deck container stack 214. A locking fastener is employed to releasably fix the fixing points 212 to the holes 304. In some embodiments a twistlock mechanism (which is shown in Figure 4) is used which is arranged to move between an unlocked position and a locked position. When the twistlock is in the locked position, the container 110 is secured to the hatch cover 208. In other embodiments other types of locking mechanism are used such as cleats, bolts or any other suitable releasable fastener.

The lower containers 110 in the deck container stacks 214 are also fastened to the lashing bridges 112. In Figure 2, the tiers 218a, 218b are fastened to the lashing bridge with an elongated fastening mechanism 222. In some embodiments the elongated fastening mechanism 222 is a lashing rod 222. A lashing rod is a steel rod that coupled into the holes 304 of the container 110 and couples to the lashing bridge 112. The lashing rod 222 may also comprise a turnbuckle for adjusting the securing force of the lashing rod 222 on the container 110. Different lashing patterns e.g. external lashing pattern or internal lashing patten of lashing rods 222 may be used to secure the container 110 to the ship 100, the lashing bridge 112 or another container 110. For example in the external lashing pattern the lashing rods 222 extend outwardly from the container 110 from the holes 304 and is shown in Figure 2. In the internal lashing pattern the lashing rods 222 overlap a portion of the container 110 before extending outwardly from the container 110. Tier 218a is the bottommost tier and 218b is the tier which is one tier higher than the height of the lashing bridge. Containers 110 in higher tiers above the lower tiers 218a, 218b are not secured to the lashing bridge 112 with lashing rods 222. This is due to the height of the deck container stacks 214 and the physical constraints of manually locking a lashing rod 222 to the containers 110. In other words it is not physically possible to manually move a lashing rod 222 into place above a certain length because they are too heavy and cumbersome.

Figure 4 shows an optional fastening mechanism 400 in the vicinity of a corner fitting 302. As mentioned, the corner fitting 302 comprises a plurality of holes 304. The holes 304a, 304b, 304c are located on the outer surfaces of the container 110. The fastening mechanism 400 comprises a body portion 402 and a rotatable lock portion 404 which rotates with respect to the body portion 402 about axis C-C. The upper hole 304a is elongate and receives a projecting fixed elongate lock portion 406 which is coupled to the body portion 402. The fixed lock portion 406 is inserted into the upper hole 304a and rotated about the axis C-C until the fixed lock portion engages with the internal surface of the corner fitting 302. Since both the elongate hole 304a and the fixed lock portion 406 are elongate, the relative rotation therebetween means that the body portion 402 is prevented from moving along the axis C-C. At the same time rotation of the body portion 402 causes the rotatable lock portion

404 to be aligned with the longitudinal axis of the elongate hole 304a. Another corner fitter from another container is then placed over the rotatable lock portion 404. The rotatable lock portion 404 is then rotated with respect to the fixed body portion 402. After rotation of the rotatable lock portion 404, the rotatable lock portion 404 is not aligned with the elongate hole 304a. This means that the two corner fittings 302 are secured together because the fastening mechanism cannot move out of the holes 304a along the axis C-C.

The rotatable lock portion 404 in some embodiments is actuated with a handle 408. In other embodiments the lock portion 404 is actuated automatically with a motor (not shown) or automatically actuated by the gantry crane which lifts and moves the containers 110. In other embodiments other means for securely fastening the containers together are used such as bolts, cleats or any other suitable fastener.

Figure 5 shows a schematic cross sectional representation of the container 100 along axis A-A in Figure 1. Figure 5 is the same as Figure 2 except that there is only one deck container stack 214 shown. The container stack 214 as shown in Figure 5 is illustrative of the number of tiers of containers 110 in the container stack 214. Whilst only eight containers 110 are shown in the stack 214 there can be any number of containers 110 in the stack 214 such as 10, 11, 12 or more containers 110. The deck container stack 214 is shown how it can sway from side to side with respect to the ship. The solid line representation of the container stack 214 is one extreme positon of the stack 214 and the dotted line representation of the container stack 214 is another extreme position of container stack 214. Despite robust construction and securing, each container 110 is not totally rigid. This means that locking couplers 400 between the containers 110 allow a limited amount of movement if the forces incident on the container stack 214 are great enough.

The oscillating motion of the deck container stack 214 may be experienced when the ship 100 is moving or rolling in moderate to rough sea conditions.

Alternatively the ship 100 can be hit by a wave causing whipping and springing motions in the ship hull 102. It has been noted that certain weather conditions including wave height, relative wave direction and wind direction may cause deformation and structural vibrations on the ship hull 102. The hull girder vibrations under particular conditions appear to cause resonance in some of the deck container stacks 214. The excessive swaying from side to side of the deck container stacks 214 can cause the containers 110 and container securing arrangement to become damaged. In a worst case containers 110 can be lost overboard.

The deck container stack 214 may experience increased oscillating motion if the oscillating period of the deck container stack 214 is approximately the same as the period of hull girder vibrations of the ship 100. In this way the oscillating period of the ship 100 is the same or approximate to the resonant frequency of the deck container stack 214. In this way the deck container stack 214 will sway to and fro in a more pronounced motion. In comparison Figure 2 shows the deck container stack 214 which is steady and not experiencing a periodic oscillating motion.

Figure 5 shows the deck container stack 214 having eight tiers. In other embodiments, the number of containers 110 in the deck container stack can be any number N of containers. For example the deck container stack 214 can comprise 8,9, 10, 11... N tiers in the deck container stack 214. In some embodiments the number of tiers in the deck container stack is greater than 2 and less than 20. The embodiments discussed herein are applicable to any maximum height of containers 110 in a deck container stack 214. In some further embodiments the number of tiers in the deck container stack 214 is 10 or 11.

The invention will now be described in more depth with reference to Figure 6. Figure 6 shows a schematic perspective representation of a container accessory 600 according to the invention. The container accessory 600 comprises a rigid frame 602. In one embodiment, the container accessory 600 is flat and elongate in construction. For example the container accessory 600 can be a flat rack. The flat rack 600 is mountable on the top of a shipping container 110. The flat rack 600 comprises a frame having a substantially similar area footprint to a shipping container 110. The flat rack 600 having the same footprint means that the locking couplers 400 are aligned with the holes 304 on the top of the shipping container 110. The height of the frame of the flat rack 600 is substantially less than that of a shipping container 110. In one embodiment dimensions of the flat rack 600 which couple to a 20ft or 40ft container 110 are 20ft long x 8ft wide x 1ft high (6.096m x 2.438m x 2.591m) long and 40ft long x 8ft wide x 8 high (12.192m x 2.438m x 2.591m). In other embodiments the height of the flat rack 600 is less than 1.5m, for example a height of 0.5m, 0.75m, 1 m, or 1,25m.

The frame 602 comprises a top surface 604, four peripheral side walls 606,608 (only two of which are shown in Figure 6) and a bottom surface 610. In some embodiments the walls and surfaces 604, 606, 607, 608, 610 of the frame 602 enclosed a space and the frame 602 is hollow. In other embodiments, the frame may have one or more open sides or surfaces. Additionally or alternatively the frame 602 may comprise removable panels (not shown) for revealing and providing access to the inside of the frame 602.

At least one mount 612 for receiving a lockable coupler 400 is mounted on the frame 602. In some embodiments there are 4 lockable couplers 400, each located at a corner of the container accessory 600. Optionally the lockable couplers 400 are the same as described in reference to Figure 4. Additionally or alternatively the lockable coupler can be a bolt, a clamp, a cleat or any other suitable fastener. In some embodiments the lockable coupler 400 is a twist lock. In this way the lockable coupler 400 is arranged to releasably fix and secure the frame 602 to one or more shipping containers in a stack 214 of shipping containers 110. The mounts 612 for the lockable couplers 612 are positioned at the corners of the frame 602. The orientation and positioning of the mounts 612 are arranged to align with the dimensions of a 40 foot or 20 foot shipping container. In other embodiments the positions of the mounts 612 are not at the corners and located at a position on the sides or in the middle of the rack remote from the corners.

Preferably the position of the mounts 612 are at the corners of the frames because the container accessory 600 will align with the corner fittings 304 of standard shipping containers. Advantageously by making the container accessory 600 the same footprint to a shipping containers 110, a gantry crane arranged to lift and move a shipping container 110 can also lift and move the container accessory 600. Since the flat rack container accessory 600 is the correct shape and size, existing cranes in ports can load the container accessory 600 onto the top most container 224. This makes loading the flat rack container accessory 600 easy and is not dependent on the height of the deck container stacks 214. In other words a plurality of separate container accessories 600 can be fitted to a plurality of container stacks 214 each having a different height. Furthermore the container accessories 600 are individually stackable. This means that when the container accessories 600 are not in use, the container accessories 600 can be stacked in a separate container accessory stack. Since each container accessory 600 comprises a lockable coupler 400 and reciprocal holes 304, the container accessories 600 secure together in a stack in a similar way to to containers 110. Since the height of the container accessories 600 is smaller than the height of a container 110, the height of the stowed container accessory stack is much smaller than a container stack 214. This means that the container accessories 600 can be parked out of the way when not in use.

The frame 602 comprises a vibration dampener 620. The vibration dampener 620 is mounted within the hollow frame 602 and comprises a moveable mass 622 and at least one resiliently deformable connector 624. In other embodiments the vibration dampener 620 is mounted on the top surface 604 of the frame 600. Preferably the vibration dampener 620 is mounted inside the frame 602 and this means that the side walls 606, 608 and the other surface 604, 610 can protect the vibration dampener 620 from the external marine environment.

The resiliently deformable connector 624 in some embodiments is a spring or other suitable element for converting kinetic energy into potential energy or other types of energy and removes energy from the deck container stack 214.

For example the resiliently deformable connector 624 can be a spring, a rubber mount, a hydraulic piston, a pneumatic piston. For the purposes of clarity hereinafter the resilient deformable connector 624 shall be referred to as a spring 624, but it may be any other suitable equivalent component for absorbing kinetic energy from the moveable mass 622.

In some embodiments the moveable mass 622 is mounted on a single spring 624. The spring 624 is coupled to the frame at a first end and to the moveable mass 622 at the other end. In an alternative embodiment, and as shown in Figure 6, the moveable mass 622 is coupled to the frame 602 with a first spring 624 and a second spring 626. The first and second springs 624, 626 are mounted between the long sides 606, 607. The arrangement as shown in Figure 6 shows the vibration dampener 620 which has a single degree of freedom. In this way the moveable mass 622 is constrained and only moves in one plane. For example the plane is a horizontal plane or a plane which is substantially aligned with the plane of the deck 114. That is the moveable mass 622 is arranged to move to and fro between the long sides 606 of the frame 602 along axis D-D. The moveable mass 622 is suspended in free air between the first and second springs 624, 626.

The moveable mass 622 is guided between a pair of guide rails 628. The guide rails 628 ensure that the moveable mass 622 is restricted to movement only in one direction. For example the moveable mass 622 in Figure 6 is limited by the rails 628 to move along a path between the long sides 606, 607 of the frame 602 along axis D-D.

In other embodiments (not shown) the moveable mass 622 is arranged to move in two degrees of freedom. In some embodiments the directions of movement are a for-aft direction and a port-starboard direction. In other embodiments, the movement in the axes of two degrees of freedom can be offset from the natural directionality of the ship 100. The dotted arrow in Figure 6 represents the second degree of freedom. In this way the moveable mass 622 is again constrained and only moves in a plane e.g. a plane which is substantially aligned with the plane of the deck 114. In this way there are no rails and the moveable mass 622 is further coupled with more springs (not shown) between the shorter side walls 608 of the frame 602.

Operation of the container accessory 600 will now be described. Each deck container stack 214 is fitted with a container accessory 600 which comprises a vibration dampener 620. The container accessory 600 is mounted on the topmost container 224 of each deck container stack 214. In this way the container accessory 600 is independent of the relative height of adjacent deck container stacks 214. The container accessory 600 is the same footprint as a shipping container 110 and has the same relative positions of corner fittings 302 as the shipping container 110. This means that a dockside crane in a port that can lift a shipping container 110 can also lift the container accessory 600.

When the deck container stack 214 sways from side to side in rough conditions, the moveable mass 622 will also move. Initially the moveable mass 622 will move together with the deck container stack 214. However when the deck container stack accelerates and decelerates, the moveable mass 622 will move out of phase with the deck container stack 214. As the moveable mass 622 exerts a force on the resiliently deformable connectors 624, 626, the moveable mass will exert an out-of-phase force on the frame 602 of the container accessory 600. Since the container accessory 600 is coupled to the deck container stack 214, the out-of-phase force is transmitted to the deck container stack 214. The out-of-phase force will act against the swaying action of the deck container stack 214 and suppress or dampen the oscillation. In some embodiments the container accessory 600 will prevent the container stack 214 from starting to sway. Accordingly the container accessory 600 can stabilize a swaying deck container stack 214.

The vibration dampener will now be further discussed in reference to Figure 7. Figure 7 is a schematic cross section of the container accessory 600 along the line D-D. The vibration dampener 620 is the same as described in reference to Figure 6. Optionally the moveable mass 622 may be mounted on rollers 702, 704 to promote the translational movement of the moveable mass

622 between the side walls 606, 607. The rollers 702, 704 can roll between the rails 628 or roll on the rails 628. Alternatively the rollers 702, 704 do not need the rails at all. The rollers 702, 704 support the weight of the moveable mass 622 through the bottom surface 610. This means that the springs 624, 626 are not bearing the weight of the moveable mass 622 and are less likely to be stretched over time. Alternatively the moveable mass 622 is slidable across the bottom surface 610 of the frame 602.

A further embodiment will now be described in reference to Figure 7. The arrangement of the vibration dampener as shown in Figure 6 has a fixed optimal operational frequency. The natural frequencies of the deck container stack 214 and the ship hull 102 are in a low frequency range. In some embodiments the frequency range is less than 1 Hz. The low frequency range may be between the range of 0.3Hz-1Hz. In some embodiments the natural frequency of the vibration dampener 620 is tuned to be between 0.3Hz- 1Hz. In other embodiments the vibration dampener 620 comprises a natural frequency between 0.1 Hz to 5Hz.

This means that in order to change the response frequency of the vibration dampener, either the tension of the springs is changed to modify the damping coefficient of the vibration dampener 620 or the mass of the moveable mass 622 is varied. In some embodiments the moveable mass 622 is replaceable. This means that the moveable mass 622 can be removed for a mass of different weight. This moveable mass 622 can be replaced before a journey depending on the height of the deck container stack 214.

In other embodiments the springs 624, 626 are replaceable. Similar to the moveable mass 622, the springs 624, 626 are replaced for other springs of different stiffness. The choice of spring stiffness will depending on the height of the deck container stack 214 in the journey.

Additionally or alternatively the vibration dampener 620 is adjustable. Turning to Figure 7 the resiliently deformable connector 624, 626 further comprises a first and second tension adjustment mechanism 706, 708. The first and second tension adjustment mechanisms 706, 708 are each coupled between the side walls 606, 607 and the end of the first and second springs 710, 712. The adjustment mechanisms 706, 708 each comprise a housing 714 fixed to the frame 602 and a moveable element (not shown). The moveable element is coupled to the end of the spring 710, 712 and moves the end of the spring 710, 12 relative to the housing 714 and the frame 602. The moveable element can be a worm gear and moves the end of the spring 710, 712 with respect to the frame 602. In other embodiments other arrangements for generating translational movement of the end of the springs 710, 712 can be used. For example a rack and pinion arrangement may be used. Movement of the end of the springs 710, 712 changes the tension in the springs 710, 712 and the response frequency of the vibration dampener 620. The tension of the springs 710, 712 can be adjusted with a manual tool such as a screwdriver or a wrench.

Additionally or alternatively the worm gear is coupled to a motor (not shown) and actuation of the motor will tension or loosen the spring 710, 712 depending on the direction that the motor is driven in. If the ends of the springs 710, 712 are moved away from the moveable mass 622, the springs 710, 712 will have a higher tension and if the ends of the springs 710, 712 are moved towards the moveable mass 622, then springs 710, 712 will have a lower tension.

The deck container stack 214 when full or nearly full can have a mass between 80 - 300 tonnes. It has been found that approximately a 10% dampening effect can be achieved with the moveable mass 622 having 1%2% of the mass of the deck container stack 214. In some embodiments the moveable mass 214 is between 0.8 to 6 tonnes. Preferably the moveable mass is between 1.5 to 4 tonnes. In this way 1.5-4 tonnes moveable mass 622 is close to the average weight of a container stack 214 and the container accessory 600 can be mounted for most container stacks 214. In other embodiments the moveable mass can have a mass of between 0.1 and 10% of the mass of the deck container stack 214. More preferably the moveable mass 622 has a mass of between 0.5% and 5% of the mass of the deck container stack 214. The moveable mass 622 can be replaced with different moveable masses have different sizes and masses arranged to react differently to different side motions of the ship 100.

The moveable mass 622 and the spring 624, 626 can be tuned depending on the height and weight of the deck container stack 214. This this can be done preloading, or after loading the containers 110 on to the ship 100. For example the strength of the spring 624, 626 and the allowed travel of the moveable mass 622 can be modified to alter the frequency characteristics of the vibration dampener 620. This will provide the advantage that higher deck container stacks 214 will be permitted because the resonance and catastrophic stack oscillation can be mitigated.

In another embodiment the frame 602 of the container accessory 600 can be the same size and shape as a shipping container. In this way the vibration dampener 620 is mounted inside an empty shipping container.

In another embodiment two or more embodiments are combined. Features of one embodiment can be combined with features of other embodiments.

Embodiments of the present invention have been discussed with particular reference to the examples illustrated. However it will be appreciated that variations and modifications may be made to the examples described within the scope of the invention.

Claims

1. A container accessory for a stack of shipping containers comprising: a frame;

at least one lockable coupler mounted on the frame and arranged to releasably secure the frame to one or more shipping containers in the stack of shipping containers; and a vibration dampener comprising:

a moveable mass arranged to move between a first position and a second position when the stack of shipping containers moves; and at least one resiliently deformable connector coupled between the moveable mass and the frame.

2. A container accessory according to claim 1 wherein the at least one resiliently deformable connector is two resiliently deformable connectors coupled between the sides of the frame.

3. A container accessory according to claims 1 or 2 wherein the resiliently deformable connector is one or more of the following: a spring, a rubber mount, a hydraulic piston, a pneumatic piston.

4. A container accessory according to any of the preceding claims wherein the moveable mass is mounted on rollers.

5. A container accessory according to any of the preceding claims wherein the at least one mount is a plurality of mounts each located at the corners of the frame.

6. A container accessory according to any of the preceding claims wherein the resiliently deformable connector comprises an adjustment mechanism for adjusting the stiffness of the resiliently deformable connector.

7. A container accessory according to claim 6 wherein the adjustment mechanism comprises a manually adjustable actuator.

8. A container accessory according to claims 6 or 7 wherein the adjustment comprises a motor for automatically adjusting the stiffness of the resiliently deformable connector.

9. A container accessory according to any of the preceding claims wherein the frame is elongate and the moveable mass is moveable between the long sides of the frame.

10. A container accessory according to any of the preceding claims wherein the frame comprises rails for guiding the moveable mass.

11. A container accessory according to any of the preceding claims wherein the moveable mass is between 1% - 2% of the mass of the stack of containers.

12. A container accessory according to any of the preceding claims wherein the vibration dampener has a natural frequency between 0.3Hz 1Hz.

13. A container accessory according to any of the preceding claims wherein the at least one lockable coupler is four lockable couplers mounted in each corner of the frame.

14. A container accessory according to any of the preceding claims wherein the frame is hollow and the vibration dampener is mounted inside the frame.

15. A container accessory according to any of the preceding claims wherein the moveable mass has a mass between 800kg and 6000kg.

GB1707216.6

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