Abstract: A piston for an internal combustion engine is described, the piston having a lower crown portion and an upper crown portion, the upper crown portion including a combustion bowl and a piston ring-groove belt of generally annular form depending from the outer periphery of the crown surface, the lower crown portion comprising a generally circular plate member having an upstanding ring on the upper surface thereof, the upper crown portion and the lower crown portion being joined together by retention means between the combustion bowl and the upstanding ring, and between co-operating spigot and socket means formed on the base of the combustion bowl and on the plate member, to prevent withdrawal by axial forces, and there being an oil cooling gallery defined between the upper crown portion and the lower crown portion.

Abstract: An oil control piston ring is described comprising a pair of axially spaced apart side rails, the side rails each having a radially outer periphery forming a rubbing face with a co-operating cylinder wall, an expander having portions which lie between the inner radially extending faces of the side rails and maintain the outer peripheral rubbing faces thereof in a spaced apart relationship characterized in that the radially inner peripheral edge of each side rail is connected by bridging members extending intermittently over at least a part of the inner circumferential length. The side rails and bridge members may be formed from a substantially flat bottomed "U-shaped" channel section.

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.

Abstract: Pistons are described having oval polar profiles or both oval polar profiles and axial profiles machined to asymmetric curvatures about the plane which includes both the piston axis and the minor axis over at least a part of the skirt length, the asymmetry of the polar profile comprising a greater convexity about the major axis on the thrust face over at least part of the axial length of the skirt region.

Abstract: A piston for an internal combustion engine has the conventional skirt replaced by top and bottom bearing surfaces spaced apart by a substantial gap of constant width. The top bearing surfaces are connected to the piston crown through the ring band whereas the bottom surfaces are attached to piston bosses by struts. The gap allows the passage of lubricant to the cylinder to ensure adequate lubrication of the bearing surfaces.

Abstract: A method of shaping the gudgeon pin bores formed in gudgeon pin bosses of pistons comprises introducing into the bores portions of a pin-shaped tool before the insertion of the gudgeon pin. A load is applied to the pin-shaped tool and the direction of the load and the shape of the pin-shaped tool are chosen so that areas of bore-defining walls of the bosses subjected to high stresses by the gudgeon pin in use, and therefore liable to crack, are radially outwardly deformed to reduce the incidence of cracks.

Abstract: A piston ring for use in a reciprocating internal combustion engine or in a compressor. The ring has an outer peripheral surface provided with a rotary finish machined curved center portion, rotary finished machined chamfer edges and a final finish plated wear-resistant coating evenly over the complete outer peripheral surface.

Abstract: A Diesel engine piston conventionally has an annular conduit, at the level of the uppermost piston ring, through which lubricating oil circulates. The oil enters and leaves the annular conduit through two longitudinal holes in the piston. According to this invention, a branch conduit extends radially inwardly from the annular conduit to bring oil flow beneath the central part of the piston crown, thereby cooling the latter. The branch conduit is especially useful with a piston having a combustion chamber in its head. The usual discharge hole from the annular conduit is blocked, and a substitute discharge hole, at the end of the branch conduit, opens into the interior of the piston.

Abstract: A piston mainly composed of an aluminium alloy for use in a cylinder of aluminium alloy. The piston is provided with one or more inserts of ferritic steel. The insert or inserts extend across opposed thrust faces of the piston and form part of the running surface of the piston skirt.

Abstract: In a piston and cylinder assembly in which the piston is made of an aluminium alloy, the wall of the cylinder contacted by the piston is formed of a hyper-eutectic silicon aluminium alloy having the composition by weight percentages of silicon (Si) 12-20%; copper (Cu) 0.5-5%; iron (Fe) 1.0-6%; magnesium (Mg) 0.2-2%; nickel (Ni) 0.5-4%; and optionally manganese (Mn) 0-5%; cobalt (Co) 0-3%; chromium (Cr) 0-3%; tin (Sn) 0-8%; titanium (Ti) 0-0.3%; lead (Pb) 0-5%; and molybdenum (Mo) 0-5%, the remainder being aluminium.

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.