Ball joint

A ball joint for a duct assembly of a gas turbine engine, the ball joint comprising:

• a housing configured to connect a first and second tubular portions of the duct assembly, the first and second tubular portions having respective longitudinal axis;
• a bellow arranged inside the housing and connected to the housing, the bellow being configured with limited flexure capability to accommodate variations in the angle between the longitudinal axes of the first and second tubular portions respectively;
• the housing being further configured to hold the tubular portions against axial forces while allows the flexure of the bellow within predetermined angle limits, the housing comprising:
• an inner shroud extending from a first end to a second end, the first end being configured to be in contact with the first tubular portion of the duct assembly and the second end being located over the bellow;
• and
• an outer shroud extending from a first end to a second end, the first end being configured to be in contact with the second tubular portion of the duct assembly and the second end being arranged above the inner shroud, so that the outer shroud partially overlaps above the inner shroud, forming an overlapping interface between the inner shroud and the outer shroud;
• wherein
• the inner shroud comprises a first thickening at a region located between the first end and the second end and a spherical portion extending between the second end and the first thickening, further wherein the first thickening is configured as a projection in an inner surface of the inner shroud so that the projection protrudes towards the bellow;
• the outer shroud comprises a spherical portion arising from the second end and a second thickening at the second end;
• further wherein the second thickening is configured as a projection in an outer surface of the outer shroud so that the projection protrudes towards outside the ball joint;
• in a rest position where the ball joint is not subjected to flexure stresses, the overlapping interface between the inner shroud and the outer shroud is annularly constant along the ball joint;
• and
• in at least one operating position where the ball joint is subjected to flexure stresses, the overlapping interface between the inner shroud and the outer shroud varies annularly along the ball joint while the outer shroud still overlaps over the inner shroud;
• where in the first and second thickenings are arranged such that, in the rest position of the ball joint, the first and second thickenings are axially aligned.