Among the roller chains, in particular those being used as conveyor chains, most frequently used ones are such that allow the rollers to rotate while slidingly contacting with sorts of guides or the like.
In the roller chain having such a construction, the resistance in the running direction can be indeed reduced on account of the roller rotating over the outer circumferential face of the bush, but mitigation of the resistance attributable to the transverse load can not be expected because the transverse load acting on the roller is designed to be born by the sliding contact of the end faces of the roller with the inner faces of the link plate.
Under these circumstances, the applicant has proposed, for the purpose of diminishing the resistance attributable to the transverse load, a roller chain where a thrust ring using a bearing material is made to lie between the link plate and the end faces of the roller, in the Japanese patent application No. 140889 of 1985 and its corresponding U.S. patent application Ser. No. 878,699 filed June 26, 1986.
In a roller chain of this type, however, the thrust washer (c) lying between the inside face of the inside link plate (a) and the end face of the roller (b) is made in a flat form, as shown in FIG. 6. When the transverse load is applied to the roller chain, and this roller (b) leans to one side, as shown in FIG. 7, a big gap (d) is produced on the other side of the roller (b). Therefore there arises a problem that the lubricant being stored in the interior of the roller flows out, the foreign matter intrudes from above gap (d) into the interior of the roller to wear away both the roller and the bush, thereby shortening the life of the chain. Such a problem brings upon itself, notably in the case of the chain in which the roller houses the rolls (e) in the inside of itself, as shown in FIG. 6, a sort of a catastrophe where it becomes impossible in a short time for the roller chain to be used on the basis of the rotating face of the roll being damaged owing to the efflux of the above-mentioned lubricant or the intrusion of the foreign matter.
On the other hand, it is also thinkable to lessen the gaps between the end faces of the rollers and the thrust washers in order to avoid the occurrence of the inconveniences as mentioned above, however, there are many cases where the above mentioned gaps cannot be made small enough to prevent the efflux of the lubricant or the intrusion of foreign matter in the conveyor chain for the reasons of the torsion or warp being often produced in the chain, especially with a long chain, straightness of the rail guiding the rolls is required and more than that the chain is made by interconnecting a large number of links.