Grain tank cover for an agricultural harvester

1. A grain tank of an agricultural harvester, comprising:

a top formed with an opening;

a cover overlying the opening;

a lifting mechanism for raising the cover to an elevated position;

a plurality of side panels that extend between the cover and the top of the grain tank when the cover is in the elevated position to provide an enclosed extension volume that increases the storage capacity of the grain tank, wherein at least two of the side panels are rigidly and permanently connected to the cover, wherein,

one of the at least two side panels overlies an obstruction within the grain tank, wherein the one of the at least two side panels is formed with a cut-out within which the obstruction is accommodated in the lowered position of the cover.

2. A grain tank as claimed in claim 1 , wherein the cut-out is covered by a flap of flexible material when the cover is in the elevated position.

3. A grain tank as claimed in claim 2 , having a side panel that is pivotally mounted on the cover or on the grain tank to move between a horizontal position and a vertical position in synchronism with the lifting of the cover by the lifting mechanism.

4. A grain tank as claimed in claim 1 , wherein a hinged rigid flap serves to cover the cut-out when the cover is in the elevated position.

5. A grain tank as claimed in claim 4 , wherein the rigid flap is mounted on the grain tank and is pivoted into a position to cover and close off the cut-out in the side panel by the lifting of the cover.

6. A grain tank as claimed in claim 5 , having a side panel that is pivotally mounted on the cover or on the grain tank to move between a horizontal position and a vertical position in synchronism with the lifting of the cover by the lifting mechanism.

7. A grain tank as claimed in claim 6 , wherein the lifting mechanism is operative to maintain the cover parallel to the plane of the opening in the grain tank as it is raised to the elevated position.

8. A grain tanks as claimed in claim 7 , wherein the cover is formed with depending legs which are each pivotally connected to a respective arm that is rotatably mounted in the grain tank, the arms being connected to rotate in unison.

9. A grain tank as claimed in claim 8 , wherein the cover has four depending legs connected to two pairs of arms, each pair of arms projecting radially from a respective one of two torsion tubes that are linked to rotate in unison relative to the grain tank.

10. A grain tank as claimed in claim 9 , wherein an operating lever is provided for manually turning the torsion tubes.

11. A grain tank as claimed in claim 10 , wherein the operating lever is connected to a toggle mechanism which passes through an unstable over-centre position as the cover is lifted from its lowered position to its elevated position.

12. A grain tank as claimed in claim 4 , having a side panel that is pivotally mounted on the cover or on the grain tank to move between a horizontal position and a vertical position in synchronism with the lifting of the cover by the lifting mechanism.

13. A grain tank as claimed in claim 1 , having a side panel that is pivotally mounted on the cover or on the grain tank to move between a horizontal position and a vertical position in synchronism with the lifting of the cover by the lifting mechanism.

14. A grain tank as claimed in claim 1 , having a side panel that is pivotally mounted on the cover or on the grain tank to move between a horizontal position and a vertical position in synchronism with the lifting of the cover by the lifting mechanism.

15. A grain tank as claimed in claim 1 , wherein the lifting mechanism is operative to maintain the cover parallel to the plane of the opening in the grain tank as it is raised to the elevated position.

16. A grain tank of an agricultural harvester having a top formed with an opening, a cover overlying the opening, a lifting mechanism for raising the cover to an elevated position and a plurality of side panels that extend between the cover and the top of the grain tank when the cover is in the elevated position to provide an enclosed extension volume that increases the storage capacity of the grain tank, wherein the lifting mechanism comprises legs which depend from the cover each leg being pivotally connected to a respective arm that is rotatably mounted in the grain tank, the arms being connected to rotate in unison, wherein at least one of the side panels overlies an obstruction within the grain tank, and wherein the at least one side panel is formed with a cut-out within which the obstruction is accommodated in the lowered position of the cover.