Patent ID: 7771304

Claim:
A double-sided engagement type silent chain comprising a number of link plates, each having a pair of pin holes and a flat back surface, and at least some of said link plates being formed with a pair of teeth for engaging teeth of a sprocket, the link plates being interleaved in alternate rows the rows being articulably interconnected to form an endless loop by connecting pins received in the pin holes; wherein the link plates of the chain include a plurality of inner link plates, disposed at intermediate locations in the widthwise direction of the chain, between sides thereof, said inner link plates having teeth protruding toward the interior of the loop with a tooth gap, and a plurality of outer link plates disposed along both sides of the chain and having teeth protruding toward the exterior of the loop with a tooth gap, the outer link plates including outermost link plates on both sides of the chain, said outermost link plates being the widthwise outermost plates of the chain, and outer link plates adjacent the outermost link plates but disposed inward with respect to the outermost link plates in the widthwise direction of the chain, said pins being secured to the pin holes of the outermost link plates by an interference fit, and extending through, and fitting rotatably in, the pin holes of the other link plates; wherein the minimum height, measured from the back surface to the tooth gap bottom of the outermost link plates is greater than the corresponding minimum height of the inner link plates; and wherein said link plates are composed of a bainite and martensite-mixed plate material, the bainite mixing ratio in said outermost link plates is higher than the bainite mixing ratio in the inner link plates and the outer link plates adjacent the outermost link plates, and the martensite mixing ratio in said inner link plates and said outer link plates adjacent the outermost link plates is higher than the martensite mixing ratio in the outermost link plates.