Patent ID: 7775925

Claim:
An oil-free chain, elongated along a direction of elongation, comprising: pairs of inner plates and pairs of outer plates in alternating, overlapping relationship along the length of the chain, the inner plates of each pair being directly opposed to each other in a direction perpendicular to the direction of elongation of the chain, and the outer plates of each pair also being directly opposed to each other in a direction perpendicular to the direction of elongation of the chain, each of the inner plates having an inner surface and an outer surface, and each of the outer plates having an inner surface and an outer surface, a portion of the outer surface of each inner plate being in overlapping relationship with a portion of the inner surface of an outer plate; a pair of bushings for each said pair of inner plates, the bushings having inner circumferential surfaces and end portions, and being press-fit into bushing holes in the inner plates; a pair of connecting pins for each said pair of outer plates, each pin having an outer circumferential surface and being press-fit into pin holes in the outer plates and extending through, and fitting loosely in, one of said bushings; and lubricating oil sealed between the inner circumferential surface of each bushing and the outer circumferential surface of the connecting pin extending therethrough; wherein each end portion of each bushing protrudes from the outer surface of the inner plate in which it is press-fit, and extends into a bushing-supporting bore formed in the inner surface of the overlapping outer plate; wherein each said bushing-supporting bore formed in the inner surface of an outer plate is coaxial with one of said pin holes, and said one of said pin holes extends through an outwardly bulging boss formed on the outer surface of the same outer plate opposite said bushing-supporting bore, each said outwardly bulging boss having a portion surrounding the pin hole therein; wherein the thickness of each said outer plate, including the thickness of the portion of each said outwardly bulging boss thereof surrounding the pin hole therein is substantially uniform; and wherein the depth Dj of each bushing supporting bore and the extent Db by which each bushing protrudes from the outer surface of the inner plates in which it is press-fit satisfy the relationship Dj<Db, and the depth Dj of each bushing supporting bore, the extent Db by which each bushing protrudes from the outer surface of the inner plates in which it is press-fit, the distance Do between inner surfaces of the outer plates of each pair of outer plates, and the distance Di between the outer surfaces of the inner plates of each pair of inner plates satisfy the relationship Dj+Do<Di+2Db<2Dj+Do.