GB2221212A

GB2221212A - Controlling stocking and de-stacking of containers

Info

Publication number: GB2221212A
Application number: GB8817670A
Authority: GB
Inventors: Andrew Mckaig
Original assignee: DAVY MORRIS Ltd
Current assignee: DAVY MORRIS Ltd
Priority date: 1988-07-25
Filing date: 1988-07-25
Publication date: 1990-01-31
Also published as: GB8817670D0

Abstract

In a container stack yard, a wheeled stacker crane is used to arrange containers in a stack. Means are provided for producing data representing three positions in mutually normal directions. These three positions provide a unique setting for each container in the stack. The data is stored in a base computer remote from the stack and every container has a unique identification number. Thus, in the computer the identification number and the setting data enables the exact position of every container in the stack to be determined. <IMAGE>

Description

CONTAINER STACK YARD OPERATION This invention relates to a method of operating a container stack yard.

It is becoming increasingly common for goods to be transported whilst packed in ridged containers.

The containers can be moved by mounting them on lorrytrailer units and they are transported overseas on special Container Ships. At most ports, and at some inland sites, stack yards are set up where a large number of these containers are temporarily stacked whilst awaiting further transport.

Each container is given a unique eleven digit reference number and it will be appreciated that, when there are a large number of containers in a stack yard, it is sometimes difficult to locate a selected container even when its identification number is known.

In a container stack yard one or more stacker cranes arrange the containers in a long stack consisting of parallel rows of containers in end-to-end relation, in side-by-side relation and on top of each other. The containers may be arranged in end-to-end relation in three or four rows with three or four containers arranged on top of each other.

An object of the present invention is to operate a stack yard in such a manner that the position of a selected container in the stack can readily be determined.

According to the present invention, during the operation of a container stack yard where containers are arranged by a stacker crane in a stack consisting of parallel rows of containers in end-to-end relation, side-by-side relation and on top of each other, three position references are provided automatically by the stacker crane when it is located in a position for putting a container on the stack or removing a container from the stack, said position references being taken along three mutually normal axes and thus identify the position of the container in the stack, and data comprising the three position references and a unique identification number for the container is supplied to and stored into a computer memory from where data indicating the position in the stack of a selected container can readily be retrieved.

The three references provided automatically by the stacker crane comprise a long travel reference which corresponds to the displacement of the stacker crane relative to a fixed axis along the length of the stack, the second reference is the distance moved by the crab of the crane in the direction of the length of the cross beam of the crane, in other words at right angles to the direction of movement of the crane, the third reference is the distance moved by the spreader which is directly below the crab as it is raised or lowered whilst having a container secured to it. Thus, the direction of movement of the spreader is at right angles both to the direction of movement of the crane and to the direction of movement of the crab along the cross beam.

The electrical signals can be obtained firstly, by locating transponders along the path taken by the stacker crane when it moves in the direction of its length and with one or more sensors on the crane so that, as the crane is moved in the direction of its length, the sensors identify one or more transponders.

Secondly, transponders are mounted on the cross beam of the crane and a sensor on the crab identifies the transponders as the crab moves above the rows of containers. Thirdly, an ultrasonic transducer may be mounted underneath the crab and directly above the spreader to which the containers are connected and the ultrasonic transducer measures the distance between the crab and the spreader and this is a reference of the vertical position of the container in the stack.

Containers are moved around within the stock yard by individual tugs and, by giving each tug a unique identification number, data, corresponding to the tug identification number and the identification number of a container loaded on to the tug, can be stored in the computer memory. Thus, a container which is not in the stack can be identified as being carried by a particular tug. If a container is to be added to the stack, a tug carrying the container is directed to a particular "stand" adjacent to the stack. The stacker crane identifies the tug and, hence, the container. When the crane has removed the container from the tug and placed it on the stack, the exact location of the container in the stack is automatically entered in the computer memory. It is also clear that the container has been removed from the tug and the tug is now free to accept another container.The three references provided automatically by the stacker crane are supplied to the computer memory usually by a radio link. Although attempts have been made to identify the container identification number by automatic means, this has not been particuarly successful.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows diagrammatically the steps in discharging containers from a ship to a stack in a stack yard; and Figure 2 shows diagrammatically the function steps in a container terminal.

Referring to Figure 1, a plurality of containers 1 are stacked on a container ship 2 which is brought into the quay of a container port terminal.

The containers are lifted from the deck and holds of the ship by a quay crane 3 and are deposited, in turn, on a trailer of a tug 4. As the containers are lifted from the vessel a checker identifies the unique identification number of the container and enters it by way of a portable terminal into a computer memory. He also enters the unique reference number of the tug on which it is loaded. This data is transmitted by radio to a base computer. Thus, at this stalge, data corresponding to the container and to the tug is linked together in the base computer memory. The container is transported by the tug to a "stand" alongside a stack 5 of containers and it is identified as it approaches the "stand". A stacker crane 6 unloads the container from the tug and places it in a position in the stack.When the crane lowers the container to its resting position in the stack the three position references produced by the crane 6 are sent by radio link to the base computer along with the tug data. The position of the container is thus specified in the computer memory in the form of co-ordinates along the three directions of movement of the crane and its crab. The base computer relates the twice received tug number, the container identification and the container location data. The tug 4 is now free to collect another container. This process is repeated until all the containers discharged from the ship have been located in the stack and, at this stage, the location of each container in the stack is stored in the computer memory.

In a similar manner, some of the containers in the stack are to be loaded on to another ship at the quay and tugs are employed to transport each container from the stack to the quay crane 3 ready for loading on to the ship 2. The driver of the crane 6 has downloaded into his computer terminal, from the base computer, the unique code number of the container which he wishes to find and the computor indicates the position references corresponding to the position of that container in the stack. The crane 6 is moved to the appropriate position and it can collect the container and deliver it to a tug. The container number and the tug identification number are introduced into the base computor memory to indicate that the container has been removed from the stack and is now on a particular one of the tugs. From the tug the container is lifted by the quay crane 3 on to the vessel. As soon as this occurs, a signal is introduced into the base computer memory to show that the particular container is no longer in the stack yard.

Claims

Claims:

1. A wheeled crane displaceable horizontally on its wheels in a first direction and having a crab which is displaceable horizontally along a cross beam of the crane in a second direction at right angles to the first direction; a spreader suspended below the crab and which can be raised and lowered in a vertical direction; first means for producing data representative of the position of the crane relative to a datum in the first direction; second means for producing data representative of the position of the crab relative to a datum position in the second direction; and third means for producing data representative of the position of the spreader relative to a datum position in the vertical direction; whereby data from the first, second and third means together indicate the location of a container which is attached to the spreader or the location of a container as it is detached from the spreader.

2. A wheeled crane as claimed in claim 1, in which the first data producing means comprise transponders spaced apart in the first direction and at least one sensor on the crane which identifies the position of the crane relative to the transponders.

3. A wheeled crane as claimed in claim 1 or 2, in which the second data producing means comprise transponders spaced apart in the second direction on the cross beam of the crane and at least one sensor on the crab which identifies the position of the crab relative to the cross beam.

4. A wheeled crane as claimed in claim 1, 2 or 3, in which the third data producing means comprises an ultrasonic transducer mounted on the crab or spreader and arranged to indicate the vertical position of the spreader relative to the crab.

5. A wheeled crane as claimed in any preceding claim in combination with a computer physically remote therefrom, said computer having a memory and means for transmitting data from said first, second and third means to the memory.

6. The combination claimed in claim 5, wherein the data is transmitted to the memory via a radio link.

7. A method of locating a multiplicity of containers to form a stack, wherein each container, in turn, is attached to the spreader of a wheeled crane as claimed in any of the claims 1 to 4 and is placed in a location to form the stack and, when the container is located as part of the stack, the data from the three data producing means is transmitted to, and stored in, a computer memory along with a unique identification code for the container from which memory data indicating the position in the stack of a selected container can readily be retrieved.

8. A method of operating a container stack yard where containers are arranged by a wheeled stacker crane in a stack consisting of parallel rows of containers in end-to-end relation and on top of each other, three position references are provided automatically by the stacker crane when it is located in a position for putting a container on the stack or removing a container from the stack, said position references being taken along three mutually normal axes and thus identify the position of the container in the stack, and data comprising the three position references and a unique identification number for the container is supplied to and stored into a computer memory from where data indicating the position in the stack of a selected container can readily be retrieved.