The object of the present invention is an arrangement for determining the weight of a ship's hatch cover and of the load, such as containers, on it, which hatch cover is supported on support members, and on top of which hatch cover are fastening elements and/or twistlocks for securing the load. In addition, the object of the invention is a support member.

The invention thus relates in the first place to a hatch cover to be installed on the deck of a cargo ship and to the determination of the weight of the load that is on top of the hatch cover. In this context, containers are used as an example load, but the load on top of a hatch cover can also be some other cargo or e.g . a loading caused by waves and seaway. On a cargo ship containers are transported in a hold below hatch covers and also on deck on top of the hatch covers in a number of parallel rows and lines and also in a number of tiers one on top of the other. On deck, therefore, are detachable hatch covers, with which the hold below is closed. The containers above deck are transported on top of the hatch covers. On the deck of the ship there are typically also fixed structures, so-called lashing bridges, on which some of the containers are supported with separate lashing bars. The lowermost container of each container stack is locked onto the hatch cover with twistlocks and containers that are one on top of the other are further locked to each other with twistlocks.

A large loading is exerted on the hatch cover from the weight of the containers, the loading also varying dynamically in a seaway. Computational maximum limits are set for an acceptable load on top of hatch covers and the loading of hatch covers is conventionally determined on the basis of the notified weight of the cargo and, on the other hand, on the basis of calculation rules issued by classification societies. The actual loadings, either in the hold or on top of a hatch cover, have not previously been measured at all, either during loading or at sea. The only load determination method in use, and then only when loading a ship, is to measure the changes in the draught of the ship and to determine, on the basis of the shape of the hull, the weight of the water displaced.

Assessment of the adequacy of the strength of fittings used for securing the hatch cover and cargo are based on the notified weight of the cargo. The actual weight of the cargo can, however, be greater than what is notified, in which case safe transportation of a load is not possible. In the worst case, the devices used to secure the cargo break because of overloading and the cargo can be damaged or even fall into the sea.

The aim of the present invention is to achieve an arrangement for measuring the weight of a ship's hatch cover and of the load that is on it. The arrangement according to the invention is characterized by what is defined in the characterization part of the independent claim 1. Preferred embodiments of the arrangement according to the invention are characterized by what is defined in the dependent claims 2-6.

Additionally the aim of the invention is to achieve a support member, by means of which the weight of a load can be determined. The support member according to the invention is characterized by what is defined in the independent claim 7. Preferred embodiments of the support member according to the invention are characterized by what is defined in the dependent claims 8-10. Some of the advantages of the invention that can be mentioned is that it is possible by means of it to determine the weight of cargo units, such as containers, during the loading of a ship and also e.g . the loading exerted by the whole load, such as stacks of containers, on the hatch cover when the ship is under way.

When the weight of a hatch cover and of the cargo that is on top of it can be measured accurately, the securing of the cargo can be made in an adequate manner and at the same time safe transportation of the cargo can be ensured. Simultaneously, it can be ensured that the hatch cover and, e.g. in the case of a container ship, the lashing bridges are not overloaded .

If an excessive increase in the loading of a hatch cover due to a seaway is noticed when the ship is under way, the headway speed or route of the ship can be changed to avoid overloading.

The actual weight of the cargo can also be lower than what is notified. When this is noticed during loading, it is possible to take on extra cargo, e.g. one more tier of containers.

It is also possible to use the invention for determining the weight of the cargo being loaded into the hold. In the following, the invention will be described in more detail by the aid of some preferred embodiments with reference to the attached drawings, wherein

Fig. 1 presents a general view of the deck of a container ship.

Fig. 2 presents in more detail a hatch cover, its support members and a container disposed on top of the hatch cover. The hatch cover 1 lies on top of the hatch coaming 2 that is on the deck of a container ship. A hatch cover functions as the cover of the cargo compartment and at the same time it is possible to transport cargo, such as containers 4, on top of the hatch cover. There are typically a number of hatch covers side by side on top of one cargo compartment. A lashing bridge 5 for supporting the containers can also be installed on the coaming 2.

A hatch cover is supported on the coaming 2 with support members 3, which bear the self-weight of the hatch cover and the weight of the load on top of the hatch cover. The support members 3 also allow movement between the hatch cover 1 and the coaming 2. There are typically a number of units of support members 3 on each hatch cover.

If containers 4 are loaded onto the hatch cover, fixed or detachable fastening elements 6 for each container corner, i.e. four per container, are installed on the top plating of the hatch cover. A fixed fastening element 6 can be a support welded onto the top plating of a hatch cover, to which support the container 4 is fastened with a twistlock 7. A detachable fastening element 6 can, for its part, be a support that is slid into position or is locked into position. A detachable fastening element can also mean the twistlocks 7 disposed under the lowermost container in a stack of containers, there being four such twistlocks per container.

In the hatch cover according to the invention a support member 3, container fastening element 6 and/or twistlock 7 is provided with a measuring sensor, which directly or indirectly measures the load that is on it.

When loading a cargo onto a hatch cover, the weight of the cargo can be determined by means of a support member 3, container fastening element 6 and/or twistlock 7 provided with measuring sensors. Furthermore, the changes in the loading of the hatch cover caused by a weather load and the ship's movements, such as pitching or rolling, in a seaway can be determined with the devices in question.

In the hatch cover according to the invention at least one of the support members 3, container fastening elements 6 or twistlocks 7 is provided with a measuring sensor. The measuring sensor can be integrated directly into the structure of the support member 3 or of the fastening element 6 of a container 4, or the measuring sensor can be a separate device, which measures the load acting on the support member or fastening element.

The magnitude measured by the measuring sensor can be elongation or displacement, by means of which the loading can be determined. The measuring sensor can be based also on the measurement of some electrical property, such as resistance.

The support member 3, the structure of which is formed from both elastic and strong layers, such as a rubber-steel sandwich construction, can be made into a measuring sensor by providing at least one of the strong structural layers of the support member with at least one strain gauge.

A support member 3 provided with a measuring sensor can measure, in addition to force/weight, also the movement between the hatch cover and the hull of the ship. Likewise, it is possible that a support member 3 or container fastening element 6 provided with a measuring sensor can also measure the accelerations acting on the ship and cargo. A support member 3 provided with a measuring sensor can alternatively, or also, be disposed in the hold under the lowermost container in a stack of containers.

A measuring sensor can receive its operating energy by wireline, wirelessly, from a battery or by generating the energy itself e.g. by utilizing movements of the ship or of the hatch cover in a seaway. The measuring data of the measuring sensor can be transmitted by wireline or wirelessly e.g. to the navigation bridge of the ship.

It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, but that it can be varied within the scope of the claims presented below. Determination of the weight of the hatch cover and cargo can also be based on the stresses of the steel structure of the hatch cover, which stresses can be measured e.g. with strain gauges. Correspondingly, by measuring the dominant deformations and stresses in a lashing bridge and in the locking devices of the containers, the forces exerted on both the components in question and also indirectly on the hatch cover can be determined. It is also possible to furnish container fastening elements or twistlocks that are installed on the rigid structures of the ship with measuring sensors.

The characteristic features possibly presented in the description in conjunction with other characteristic features can also, if necessary, be used separately to each other.