Abstract: A metal casting die, and a method for its production, are described. By the method the die has provided over at least a part of its internal cavity forming surfaces, indentations of predetermined depth, area and distribution, by employing a technique selected from the group comprising photoetching, electrochemical etching and grit blasting. The die cavity forming surfaces also have thereon, over at least those surfaces with indentations, a coating of a hard, corrosion and erosion resistant material which extends into and between each indentation as a continuous layer.

Abstract: Piston rings for internal combustion engines and compressors are described. The piston ring comprises a generally "L-shaped" cross section and may be used in place of a conventional oil control piston ring. It may fulfill an exclusively oil scraping function or may act as a combined oil scraper and compression ring.

Abstract: A combustion chamber formed in the crown of a piston for an indirect injection diessel engine is described the combustion chamber having an elongate entry channel adjacent the gas efflux of a precombustion chamber, the channel leading into four branches which generate vortices in the burning charge and which vortices are coherent and mutually self-reinforcing.

Abstract: An improvement of pistons for alternative, endothermic four-cycle engines, in which notches or grooves are cut on opposite sides of the oval surface of the piston skirt and arranged in a parallel fashion with respect to the piston pin. The grooves create concavities which are closed off frontally by the cylinder wall and laterally by the piston skirt. The purpose of the grooves is to create a series of pockets for the lubricating oil, which is under pressure during engine operation, and to improve lubrication in the areas of maximum piston stress.