US Patent 8926185 Spherical plain bearing with lubrication groove

A spherical bearing has an outer ring with a concave bearing surface and an inner ring having a convex bearing surface, which is in sliding engagement with the concave bearing surface. A lubrication groove is formed in the convex bearing surface and/or the concave bearing surface. The lubrication groove is defined by a concave central portion and by convex side portions. The concave central portion has a first radius of curvature and the convex side portions have a second radius of curvature. The second radius of curvature is at least 0.7 times the first radius of curvature.