Internal combustion engine piston

Claim 1

An integral plunger trunk-type piston cast in one piece from spheroidal graphite cast iron for an internal combustion engine and including a closed ended head portion having a transverse top end crown wall and a side wall formed with ring-receiving grooves, a hollow open ended skirt portion depending from said head portion, and a pair of transversely spaced bushing-like wrist pin bearing bosses located inside of said skirt portion in symmetrical relation to a plane passing through the longitudinal axis of the piston and formed with journal bores aligned diametrically of said skirt portion, wherein the improvement consists in the combination comprising: a substantially annular cooling-oil splash chamber provided in said head portion in coaxial relation thereto and adjacent to said top end wall and to at least the first ring-receiving groove; a pair of spaced longitudinal arcuate webs depending from said top end wall in parallel symmetrical relation to said piston axis with their concave sides facing each other and being connected to the tops of said pin bearing bosses for supporting same so as to leave a freely projecting outer end on each boss; each boss being connected to said skirt portion by a pair of transverse webs located in substantially registering relationship on opposite sides of said boss nearer its inner end than its outer end and extending in substantially parallel relation to said plane; said skirt portion having its wall formed with a pair of diametrically opposed openings in substantial coaxial relation to said journal bores, said openings being of a diameter larger than the outside diameters of the outer ends of said bosses and the outer ends of said bosses being spaced inwards from the inside wall of said skirt portion and clear of the edges of said openings; said chamber being bounded by said top end wall whereas the upper portion of each arcuate longitudinal web forms the radially inner wall of said chamber; the radially outer wall of said chamber being substantially conical and generally inclined uniformly inwards from top to bottom while extending from above the first ring-receiving groove down to a level above the last ringreceiving grooves of said head portion; each arcuate longitudinal web being connected to the side wall of said head portion on either side of an axial plane passing through the axis of said journal bores, by a pair of ribs extending at right angles to each other adjacent to one end portion of said web, each rib being of generally triangular contour and connecting with the bottom portion of the side wall of said head portion and of said chamber; at least one oil inlet duct extending in substantially parallel relation to said piston axis and opening at its top end from below into said annular chamber while opening at its bottom end into an open circumferential lubrication groove formed in the bore of one boss in substantially tangential relationship therewith; and at least one oil outlet duct formed in the bottom of said annular chamber in at least approximately diametrically opposed relation to said inlet duct; said inlet duct extending through a radially outward projecting longitudinal formation integral with one of said arcuate webs and each duct terminating at its top end in a tubular extension projecting into said annular chamber over one portion of the height of the latter.