Rotor housing assembly for a harvester

A harvester comprising:

• a rotor housing assembly for a harvester comprising at least one cover plate having a generally curved shape, forming part of a generally cylindrical shaped rotor housing, said at least one cover plate including at least one top cover plate, said at least one top cover plate having a central longitudinal axis, and an outer surface and an inner surface, which, when mounted, said inner surface faces the central longitudinal axis, said inner surface including:
• at least one first curved section having a first radius;
• and
• at least one second curved section in the form of at least one symmetrically curved shape, said at least one symmetrically curved shape defining a spherical surface, and said at least one symmetrically curved shape having a radius;
• and
• a vane system comprising at least one rotatable vane rotatably mounted along the at least one symmetrically curved shape of the inner surface of the at least one top cover plate at a rotation point, said at least one rotatable vane having a contact surface with the at least one symmetrically curved shape, said contact surface of said at least one rotatable vane having a second radius, said second radius is larger than said first radius of said at least one first curved section of said inner surface, such that, during rotation of the at least one rotatable vane, the contact surface of the at least one rotatable vane substantially follows the at least one symmetrically curved shape and remains in contact with the at least one symmetrically curved shape of the inner surface of the at least one top cover plate.