US Patent 7281466 Piston coolant gallery

A cast piston, for an internal combustion engine or pump has an integral coolant ring gallery, with localized extensions, to achieve a coolant interchange with the gallery upon piston reciprocation. At least a portion of an extension lies generally parallel to the longitudinal piston axis and towards an upper end of the piston adjacent the working fluid. This provides an attendant increase in surface area exposed to coolant allowing either a decrease in operational piston temperature or an increase in allowable heat flow into the piston from a working fluid.