Liquid-cooled composite piston for internal combustion engines

In a liquid-cooled composite piston for an internal combustion engine, particularly diesel engines, which piston comprises a lower part forced against an upper part having an external cooling passage, and annular flange having a tongue which protrudes into said external cooling passage, which annular flange is clamped between an annular rib, which annular rib disposed between the inside of the upper portion and a surface which if formed on said lower portion and faces said rib, said annular rib constituting the radially inner boundary of said external passage, said external cooling passage being formed in the upper portion behind the top land and at least part of the ring-carrying portion of said piston and being open toward the interfacial plane between said upper part and said lower part of said piston, said annular rib surrounding a centrally disposed internal cooling chamber, which cooling chamber communicates with said external cooling passage through at least one radially extending coolant bores, said external cooling passage and said cooling chamber communicating with a source of coolant, the improvement wherein said tongue is curved outwardly and its inner side face and the surface of said external cooling passage which is near the combustion define between them a narrow annular gap.