Method for improving the cargo capacity of a container ship and container support bracket
The present invention relates to a method according to the preamble of claim 1 for improving the cargo capacity of a container ship and a support bracket according to the preamble of claim 3 suited for use in the method.
More particularly, the invention concerns the cargo space of a container ship, wherein the containers are to be stacked. In the art are known arrangements having the cargo space provided with hatch covers on top of which and below which containers are stowed separately stacked. The container stacks below the hatch covers are supported against horizontal movements by container support brackets located in the ship's cargo space. The container stacks above the hatch covers are secured by twistlock corner fittings and lashing bars. However, this kind of restraining by means of corner fittings and lashing bars is so insecure that the overall weight of the container stack must be limited substantially. Hence, the ship's cargo capacity becomes underused as to its maximum available cargo space.
In unhatched cargo spaces, it has been possible to stack only so many containers above one another as the strength of the lowermost container has permitted. The stacks have been restrained against horizontal movements by vertical container guides. However, the strength of a conventional standard container is so low that the overall weight of each container stack must again be limited substantially to prevent the lowermost container from collapsing. Once again, the ship's cargo capacity remains underused.
It is possible to load containers into container guides onto a planar frame having essentially the same dimensions as the container bottom. The frame is then moved by a lift. After being loaded, the frame is supported to the ship's hull structures. This kind of lift-elevatable frames are bulky thus limiting
the ship's maximum cargo and slowing down the stevedoring of the cargo.
It is an object of the present invention to provide a method for improving the cargo capacity of a container ship. The method according to the invention is characterized in that the container stack is divided in its vertical height in two or more substacks by mechanically operable support means mounted on the ship's hull structures in a fixed or dismountable fashion so that the weight imposed by an overlying substack of containers will not be transmitted to the underlying container stack.
A preferred embodiment of the invention is characterized in that the vertical load imposed by the container stacks is transmitted to the ship's hull structures via the lowermost container of each substack.
It is a further object of the invention to provide a container support bracket suitable for use in the present method by way of being able to receive high vertical and horizontal forces. The support bracket according to the invention is characterized in that the support bracket is formed by a stationary pocket member and a bracket member rotatably connected thereto, whereby the rotation of the rotatable bracket member in regard to the pocket member is adapted to take place between two limit positions so that in one of the limit positions the rotatable bracket member bears the load placed thereon, while in the other limit position the rotatable bracket member is rotated aside thus forming no obstacle to cargo loading or unloading.
Another preferred embodiment of the support bracket according to the invention is characterized in that the support bracket pocket member is fixedly connected to the ship's hull structure and that the support bracket pocket member and the rotatable bracket member are contoured substantially compatible with each other as to their mating surfaces in order to prevent the movements of the rotatable bracket member in the pocket member from taking place in any other direction except that occurring between the limit positions
of the rotatable bracket member.
A still another preferred embodiment of the support bracket according to the invention is characterized in that the mating surfaces of the support bracket pocket member and the rotatable bracket member have a curved contour.
A further another preferred embodiment of the support bracket according to the invention is characterized in that the support bracket is provided with a link lever mechanism and an actuator means for rotating the rotatable bracket member.
The benefit of the support method according to the invention will be appreciated in a substantial increase of a ship's cargo capacity over conventional support arrangements. The support bracket according to the invention fea- tures a cost-efficient construction inasmuch as it facilitates supporting large loads susceptible to move in regard to the support bracket assembly by virtue of using small-sized and uncomplicated components for receiving the stress of the support forces. Furthermore, the rotatable bracket member can be removed and inserted in place using manual operations only. The construc- tion of the present support bracket is extremely safe in use and does not need locking of its rotatable bracket member into its lower position. Due to its advantageous design, the rotatable bracket member does not cause damage to cargo being lifted away from the ship's cargo space even when the rotatable bracket member has inadvertently been left in its lower position.
In the following, the invention is described in more detail with the help of an exemplary embodiment by making reference to the appended drawings in which
FIG. 1 shows a cross section of a container ship loaded with containers;
FIG. 2 shows a schematic side view of a container in a container guide frame
during the loading or unloading steps;
FIG. 3 shows a schematic side view of the uppermost container of a lower container stack loaded into a container guide frame, as well as the lowermost container of a upper container stack in a loaded ship;
FIG. 4 shows the support bracket according to the invention rotated into its upper position;
FIG. 5 shows the support bracket according to the invention rotated into its lower position for bearing a load;
FIG. 6 shows an axonometric view of the support bracket pocket member; and
FIG. 7 shows an axonometric view of the rotatable bracket member of the support bracket.
Now referring to FIG. 1 , therein is shown a cross section of a container ship. The ship has containers 1 stowed above one another and side by side adjacent to each other. The container guide frames extend vertically up to the top level of the stacked containers thus supporting the containers horizontally by the container guides to the ship's hull structures. In the vertical direction, the containers rest on each other by their abutting corner fittings.
The vertical load imposed by a stack of containers is transmitted to the ship's structures via the lowermost container. If the load imposed on the lowermost container is assumed to become excessively high, the stack can be divided vertically into substacks at a desired point by supporting the substack over- lying the intermediate support point with the help of mechanically operable support means mounted in a fixed or dismountable fashion to the ship's structures so that a substack remaining below the intermediate support point
is relieved from bearing the load of the overlying substack. Hence, the cargo capacity of a container ship can be improved in accordance with the present invention by virtue of dividing a high stack of containers into two or more substacks with the help of the above-described support means in a fashion that prevents the container substack(s) overlying the support means from being transmitted onto the underlying substack.
As a mechanical support member may act a support bracket 2 according to the invention (FIGS. 2 and 3). In FIG. 2 the support brackets are shown rotat- ed into their upper position, whereby loading of containers 1 into the cargo space and unloading therefrom is possible without the need for negotiating about the support brackets. Conversely, the support brackets are shown in FIG. 3 rotated into their supporting service position.
In FIGS. 4-7 is shown in greater detail the construction of a preferred embodiment of the support bracket 2 according to the invention. Herein, the support bracket comprises two major components, namely a stationary pocket member 2' and a rotatable bracket member 2", of which the bracket member is adapted either rotatable into an upper position or dismountable in such a fashion that the bracket member will not cause obstacle to any cargo handling such as cargo loading and unloading in the ship's cargo space. Additionally, the support bracket 2 may include a link lever mechanism and an actuator for rotating the bracket member 2". The support bracket 2 may be a dismountable assembly or permanently fixed to the ship's hull struc- tures. In the support bracket assembly, the mating surfaces of the rotatable bracket member 2" and the stationary pocket member 2' are shaped substantially conforming to each other. The movement of the rotatable bracket member 2" in the stationary pocket member is constrained from taking place in any other direction except in the vertical rotation direction of the bracket member. In FIG. 4 the support bracket is shown rotated into its upper position, where the bracket member will not disturb cargo loading or unloading operations. Conversely, FIG. 5 shows the support bracket 2 in its supporting
service position, wherein it will bear a load imposed thereon.
Under a vertical load imposed on the rotatable bracket member 2" in the downward direction, the lower surface of the horizontal leg of the bracket member rests on the top surface of the pocket member 2', while the curved leg of the rotatable bracket member rests in a slot of compatible shape made in the support bracket pocket member. Respectively, when the rotatable bracket member is subjected to a horizontal force, the curved leg of the rotatable bracket member is prevented from moving in the horizontal direc- tion and twisting about its longitudinal axis.
To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiments, but rather may be varied within the inventive spirit and scope of the appended claims. For instance, the shape of the support bracket pocket member 2' and the rotatable bracket member 2" may be varied from those described above. Herein, the leg of the rotatable bracket member and the compatible contour of the support bracket pocket member may be shaped differently. The hinge shown in the diagrams is not crucial to the implementation of the invention inasmuch as the rotatable bracket member 2" may be designed to be a detachable element that is inserted into the support bracket pocket member 2'. Furthermore, the support bracket according to the invention may additionally be employed for supporting other kind of cargo or intermediate hatch covers, for instance.