System for distributing heavy bins in a storage grid

1. A method for storing product items in storage bins in a storage system comprising a bin storing grid in which storage bins are stored above each other in columns, wherein the method comprises:

inserting product items to or retrieving product items from the storage bins at a port;

overloading a first storage bin with product items;

underloading a second storage bin with product items;

determining a weight for each storage bin after one or more product items have been inserted to or retrieved from each storage bin;

determining a storage position for each storage bin in the bin storing grid based on the determined weight;

calculating a total weight for storage bins presently being stored above a storage bin at a lowermost level of each column;

selecting the storage position for each storage bin as a position in one of the columns in which a sum of the total weight and the weight of the storage bin at the lowermost level is below a maximum load tolerated by the storage bin at the lowermost level of the bin storing grid; and

transporting storage bins from the port to the determined storage position by means of a vehicle and a bin lift device provided on each vehicle;

wherein the storage positions for the first and the second storage bins are in a same column.

2. The method according to claim 1 , wherein determining the weight for each storage bin comprises weighing the storage bin by means of a weight sensor.

3. The method according to claim 1 , further comprising:

increasing a height of the bin storing grid for at least some columns.

4. The method according to claim 1 , further comprising:

storing the total weight for all columns in the grid based on the weight and position of the storage bins; and

updating the weight of each column each time a storage bin is removed from or added to the respective columns.

5. A storage system for storing product items in storage bins, wherein the storage system comprises:

a bin storing grid in which storage bins are stored above each other in columns;

a port where product items are inserted into or retrieved from the storage bins;

a first storage bin overloaded with product items;

a second storage bin underloaded with product items;

a vehicle configured to move horizontally along rails provided on top of the bin storing grid, wherein the vehicle comprises a bin lifting device for transporting the storage bins horizontally and vertically between the bin storing grid and the port;

a weight estimation device for estimating the weight of each storage bin after one or more product items have been inserted to or retrieved from the storage bin; and

a storage control system provided in communication with the vehicle and the weight estimation device, wherein the storage control system is configured to determine a storage position for each storage bin based on the weight of the storage bin, calculate a total weight for storage bins presently being stored above a storage bin at a lowermost level of each column, and for storage position bin as a position in one of the columns in which a sum of the total weight and the weight of each storage bin is below a maximum load tolerated by a lowermost storage bin being stored at the lowermost level of the bin storing grid;

wherein the storage positions for the first and the second storage bins are in a same column.

6. The storage system according to claim 5 , wherein the weight estimation device is a weight sensor.

7. The storage system according to claim 6 , wherein the weight sensor is located in the port.

8. The storage system according to claim 5 , wherein storage control system is configured to store the total weight for all columns in the grid based on the weight and position of the storage bins, and to update the total weight of each column each time a storage bin is removed from or added to the respective columns.