Crosshead piston and bearing assemblies

A piston assembly, comprising:

• a piston body having an upper head portion formed with a plurality of ring grooves, a lower stem portion extending downwardly from said head portion along a longitudinal axis of said body, a pin bore formed in said lower stem portion extending along a pin bore axis transverse to said longitudinal axis between laterally opposite outer surfaces of said lower stem portion, said lower stem portion including a pair of mounting ears having laterally inner surfaces spaced laterally from one another across a lateral gap therebetween, said mounting ears presenting respective lower concave bearing support surfaces extending between said laterally opposite outer surfaces of said stem and each associated said laterally inner surface of said mounting ears such that said lower bearing support surfaces are discontinuous across said lateral gap, said lower stem portion including an upper concave bearing support surface disposed longitudinally opposite and facing said lower concave bearing support surfaces of said mounting ears and extending continuously between said laterally opposite outer surfaces of said lower stem portion so as to span said lateral gap between said mounting ears;
• said upper concave bearing support surface including an oil supply hole formed centrally between said laterally outer surfaces of said lower stem portion and opening to an oil cooling space disposed longitudinally above said upper bearing support surface for accommodating a flow of cooling oil through said oil supply hole for cooling said upper head portion of said piston body;
• a three-piece slipper bearing set disposed in said pin bore, said three-piece bearing set including a pair of lower bearing portions supported by said lower concave bearing support surfaces and a separate upper bearing portion supported by said upper bearing support surface and extending continuously between said laterally outer surfaces of said lower stem portion, said upper bearing portion having an oil supply hole aligned with said oil supply hole of said upper bearing support surface;
• a wrist pin disposed in said pin bore and supported by said three-piece slipper bearing set, said wrist pin having an oil supply hole aligned with said oil supply holes of said upper bearing portion and said upper bearing support surface, said oil supply holes being free and unencumbered by any bearing retention structure which would operate to support said upper bearing portion against movement relative to said upper bearing support surface;
• and
• aligned retaining holes formed in said upper bearing support surface and said upper bearing portion in spaced relation to said oil supply holes, and a retention pin disposed in said aligned retaining holes supporting said upper bearing portion against movement relative to said upper bearing support surface independently of said oil supply holes.