US Patent 7836815 Lubricant-cooled and wristpin lubricating piston

A piston for an internal combustion engine, the engine having a connecting rod coupled to a wristpin, the wristpin being connected to the piston for pivotal movement about an axis, the piston comprising: a top portion and a generally cylindrically-shaped wall portion extending from the top portion, the top and wall portions defining a skirt cavity, the top portion having thereon a downwardly extending projection with a downwardly facing bearing surface for the wristpin, the bearing surface extending in the direction of the axis and defining a portion of a cylinder centered on the axis, and the projection having opposite sides facing the skirt cavity; at least one lubricant passage extending through the projection from one of the opposite sides and over the bearing surface to the other of the opposite sides; and a lubricant opening communicating between the lubricant passage and the bearing surface to supply lubricant to the bearing surface and to the wristpin.