Grain bin extension deployment apparatus for agricultural harvesting machine

A combine harvesting machine used for harvesting a crop and directing the harvested grain to a grain bin located atop the machine for receiving and holding said harvested grain, said grain bin comprising:

• upstanding walls comprising a forward wall, a rear wall opposite said forward wall, and opposed side walls extending between said forward and rear walls, wherein said upstanding walls comprise a substantially continuous, rectangular upper edge defining an upper end of grain bin and an upwardly facing rectangular opening;
• a grain bin extension about said upper edge configured to expand the capacity of said grain bin, said extension being deployable between an extended position in which said extension extends upwardly and outwardly from said upper edge of the grain bin for increasing the grain holding capacity thereof, and a retracted position, wherein said extension comprises extension panels;
• a cap overlaying the opening of the grain bin, said cap supported by a cap frame that is also deployable between an extended position such that the cap extends upwardly and outwardly from the upper edge of the grain bin, and a retracted position;
• extension deployment apparatus configured to raise and lower the extension panels between said extended and retracted positions, said extension deployment apparatus comprising two extension deployment mechanisms located at opposing corners of the grain bin such that each extension deployment mechanism controls the deployment of its two adjacent extension panels, each extension deployment mechanism comprising a first rack fixed to one of the upstanding walls and a trunnion movable on the first rack, wherein the two adjacent extension panels are pivotally connected to the trunnion, such that movement of the trunnion on the first rack drives the extension panels in a vertical direction and pivots the panels in an outward direction, and a second rack mounted to the trunnion, the cap frame being connected to the cap frame, such that movement of the second rack with respect to the trunnion drives the cap frame in a vertical direction, and an internal gear between the first and second racks to drive the raising and lowering of the extension, wherein rotation of the internal gear moves the second rack with respect to the trunnion, and also moves the trunnion with respect to the fixed first rack such that both the movement of the trunnion with respect to the first rack and movement of the second rack with respect to the trunnion contribute to vertical movement of the cap frame, wherein the internal gear is connected to an extension drive source with an input shaft.