GB2369111A - Flatrack with additional lifting connector - Google Patents

Abstract

A conventional flatrack has additional connectors 21 or 24 along the length of the corner posts 5 arranged such that the flatrack can be lifted by a crane hook and slings without the corner posts suffering buckling or like damage. The connectors can be rods or bars 21 recessed inside the corner posts or flanges 24 extending therefrom. Links 22 can be provided to enable a sling hook 16 to more easily be attached. The links can rest out of the way when not in use.

Description

A LIFTING CONNECTOR FOR A FLATRACK In the field of shipping containers there is a type of container commonly known as a flatrack, which is platform based and has at each end a vertical wall.

These types of containers were originally developed as one of a range of containers, which included those shaped as a large rectangular box. These containers are of a size 20ft long up to 53ft long and carry cargo weight of up to 40 tons. They are characterised by having at each of their eight corners a comer fitting comprising a hollow rectangular box with apertures formed in their three outermost faces. The apertures are used for connecting to standardised handling machines and connectors such as twistlocks and hooks. It was quickly realised that if the flatracks were to be lifted by the top of the comer posts, the lifting forces would have to be applied vertically if the posts were not to receive a massive bending moment likely to damage them. Thus handling devices were devised which comprised rigid lifting frames called spreaders comprising a rectangular frame of a size closely approximating to the plan profile of a container. At each comer of a known spreader is a lifting device typically a twistlock such that when a container is being lifted, the lifting forces are applied vertically to the container and thence to the spreader frame.

The platform comprises a rectangular steel frame, which is floored with timber or steel sheet.

The ends of the flatrack comprise two comer posts typically joined with a panel and additional framework. These posts do not have a supporting structure between it and the base other than the connection they have at the bottom of the post.

The end walls are sometimes foldable down onto the base and connect to the base via lockable hinges. Although the hinges are very strong they can only support a reasonable amount of bending and certainly not the sort of forces, which would be applied, should the corner posts be top lifted by inclined sling angles exceeding five degrees to the vertical.

In operation of containers, they are often close stacked together or stowed on ships close to the structure of the ship indeed the cell guides of a ship block off all apertures except those four on the very top of the container. Only the tops of the comer posts are available for connection to the spreader.

Flatracks however are open containers and used for cargoes, which cannot easily fit inside box containers. The cargo sometimes projects above the top of the comer posts thus making lifting with a spreader frame sometimes impossible.

In developing countries, not all ports have the wealth to invest in spreader frames and are more likely to have simple hook cranes with four lifting slings coming from it. Ideally they would like to be able to simply lift the flatrack with inclined slings connected to the top corners because the bottom corners are not accessible due to close stacking of the containers side by side. indeed such lifting often happens with disastrous results.

Whereas the facility to be able to lift a flatrack with inclined slings from the top comers would be an advantage, some compromise is needed to enable sling lifting not from the top but at least as high up the corner post as is reasonable to avoid contact with the cargo.

Such a facility however, should ideally not encroach on the cargo space nor project outside the profile of a normal container to avoid it being snagged on other adjacent containers.

The present invention seeks to address this common handling problem by providing a lifting device within the corner posts, which would allow the container to be lifted with inclined slings without the resultant forces breaking the container.

In the present invention there is provided a flatrack shipping container comprising a rectangular platform base with vertical posts located near each end, there being provided as part of the comer post structure one or more connectors to enable the lifting of the container by lifting devices.

In Figure 1 there is seen in perspective a typical flatrack shipping container (1) having a rectangular platform base (2) with timber decking (3), at each end there is seen an end wall (4) comprising two corner posts (5) each post (5) being capped by a comer fitting (6) comprising a rectangular box typically of cast steel and having in its three outer most faces a standardised handling aperture (7). When a flatrack (1) is loaded with cargo (8), it can be seen that the cargo (8) projects above the top of the comer fittings (6) in this example. The cargo (8) comprises a large packing case, which could not otherwise fit inside a standard container.

The problem is further illustrated in Figure 2, which shows a side elevation of the flatrack with cargo (8) also seen in side elevation. Above the flatrack is seen a lifting spreader (9) which is suspended from a crane hook (10) by slings (11). The spreader (9) comprises a rigid steel framework which resists the tension in the slings (11). At each comer of the spreader there is a twistlock (12) of known technology which, but for the size of the cargo (8), would have been able to engage in the top most aperture of fittings (6). The lifting position of the spreader (9) is shown in dotted line (9') in which position the spreader would have been in contact with the top fittings (6) and the twistlocks (12) engaged inside each of the fittings (6). The base (2) of the flatrack (1) has, at each comer, another comer fitting termed bottom fitting (13) of similar size and geometry to the top fitting (6). The bottom fitting (13) has handling apertures (14) in the side which, under certain circumstances, can be used as lift points for the flatrack, however, in this example it is to be assumed that access to those apertures 14 is not available because although not illustrated the flatrack is located close beside another structure or side by side another shipping container or within the cell guides of a ship thereby blocking off access to the aperture 14.

In Figure 3 there is seen the same flatrack (1) with cargo (8) loaded upon it but unfortunately as happens in practice, a crane can be seen to be attached by slings (15) and hooks (16) to the top fittings. As the crane lifts (denoted by arrow (A) ) tension is developed in slings (15), which have a high horizontal component (denoted by arrow (H) in Figure 4) tending to bend the comer posts (5) into position (5') where the slings take up a more shallow angle denoted by dotted line (15). As happens in practice under this severe loading the corner post (5) bends it somewhere along its length most likely down at the bottom where it connects to base (2). Typical damage is permanent and costly to repair. For a typical flatrack, the sling angle B to the vertical can be as little as 5 degrees to the vertical before the comer posts become strained beyond their normal strength. Yet to make a sling long enough to sustain this angle the crane would have to be perhaps 250ft tall for a 40ft container. This is illustrated in Figure 4 where sling (15) is hooked to the top fitting (6) and exerts a lifting force (F) and a horizontal component (H). The horizontal component (H), in this example we will assume to be within the strength limits of the corner posts (5). Since the comer post fails due to bending near the junction between post (5) and base (2), if the lift point was not at fitting (6) but lowered to connector (25) located half way up the post, then the horizontal component (H) could be twice as large before the post reached its limits of bending strength.

The lift force (F) required to raise the flatrack remains the same when connected at (25) and thus the resultant sling angle (B') is much larger to the vertical, resulting in a more practical crane hook position at (10).

The result is that a flatrack (2), with cargo (8), can be lifted by inclined slings (15) without exceeding the strength limits of the comer posts (5).

Of course, other connectors (25) can be arranged up and down the comer post such as (25') to accommodate different sling angles as the weight of the cargo and flatrack allow. The comer posts (5) can be reinforced particularly towards the base so that the connector (25) can be located at a higher position or a larger sling angle to the vertical be allowed.

In Figure 5, there is seen more detail of a connector (25). Figure 5 shows a part of a typical corner post (5) comprising a structure having a profile of an'I'section beam fabricated or hot rolled having outer most flange (17) web (18) and inner most flange (19). The connector 25 comprises an aperture (20) formed in the post with a horizontal bar (21) closing off part of the aperture (20). It is envisaged that the post might be formed from other profiles such as box or other suitable fabrication. in Figure 6 there is seen a side elevation in section of the preferred connector (25) through which one can see a typical handling hook (16) engaged with bar (21) being raised by sling (15). It can be seen that the whole of the attachment device comprising aperture (20) and bar (21) is contained within the limits of the comer post (5). This is convenient to do so but in an alternative arrangement seen in Figure 7 where the connector 25 includes an additional handling link (22) is fitted around bar (21) which can be stowed in position (22') within the post profile but when pulled up to project from the post (5) it can be connected to hook (16) and sling (15).

In Figure 8 a more permanent arrangement is shown with connector (23) which is fixed to the corner post (5) projecting from it permanently, it having a hole (24) through which is fitted a link similar to (22) stowing in (22') through which a hook (16) connected to sling (15) can pass. It is envisaged that a number of handling devices can be fixed to the flatrack up and down the height of the posts or indeed on the end wall in some other position. Alternatively, connectors 25 might be fixed to the base close to the base of the posts 5 where they connect to the base 2..

A scale (26) might be fixed to the connector (23,25) to enable safe working angles and lifting forces to be assessed by the operator, the variables being cargo weight and sling angle for a given connector location and thus fairly simply calculated.

Where the flatracks are collapsible flatracks of known type where the comer posts (5) are connected to the base (2) by hinges not illustrated, then as the posts are folded down onto the base, or adjacent to the base, the handling devices may be so arranged to nest within the base.

In another arrangement it is envisaged that the handling apertures (20) are shaped to receive and mate with existing standardised handling devices such as hooks, twistlocks and elephants foot fittings. To this end the aperture shape, geometry and strength can be adapted to be the equivalent of those handling apertures already known and standardised in the corner fittings (6) and (13).

Claims (10)

1. Claims 1. A flatrack shipping container comprising a rectangular platform base with two vertical posts located near each end, there being provided one or more connectors to enable the lifting of the container via the connectors.
2. 2. A flatrack shipping container as in claim 1 in which the connector is located adjacent to the base of the posts.
3. 3. A flatrack shipping container as in claim 1 in which the connector is recessed within the profile of the post.
4. 4. A flatrack shipping container as in claim 1 in which the connector projects outside the profile of the post.
5. 5. A flatrack shipping container as in claim 1 in which the connector includes a link which in use projects outside the profile of the post and when not in use stows within the profile of the post,
6. 6. A flatrack shipping container as in claim 1 in which the connector is located on the inboard face of the post.
7. 7. A flatrack shipping container as in claim 1 in which the connector is located on the side faces of the post structure.
8. 8. A flatrack shipping container as in claim 1 in which the connector comprises an aperture.
9. 9. A flatrack shipping container as in claim 8 in which the aperture is shaped to interface with known standardised handling devices.
10. 10. A flatrack shipping container as in claims 1 to 9 in which the posts are connected to the base by hinges and are collapsible.