Piston assembly for internal combustion engine

A piston assembly for an internal combustion engine, comprising:

• a piston having an upper combustion surface and a lower wall surface beneath said upper combustion surface, with a pair of pin bosses formed with pin bores having concave bearing surfaces aligned axially and radially along a common pin bore axis and including an intermediate wall extending between said pin bosses, said intermediate wall having a concave bearing surface extending in axial and radial alignment with respective concave upper portions of said concave bearing surfaces of said pin bores so as to provide a load bearing extension of said concave upper portions for operatively supporting a wrist pin when installed in said pin bosses;
• a skirt constructed as a separate piece of material from said piston, said skirt being fixed to said piston against relative movement and having a cylindrical wall with inner and outer cylindrical surfaces;
• and
• wherein said piston further includes at least one rib extending upwardly from said intermediate wall on opposite sides of said pin bore axis to said lower wall surface to provide structural support to said intermediate wall against unwanted deflection.