Attachment of an ovoid chainring
This invention is applicable to bicycle non-circular chainrings or ovoid chainrings, attachable to a drive crank arm with a spider, forming a structure with anchorage points distributed in a star like shape; the said ovoid chainring ( 1 ) having a major diameter, whose angle with the said crank arm measured in the pedaling direction defines its orientation; whereas, said ovoid chainring has a number of anchorage points to said spider which is a multiple of the number of anchorage points of the spider, constituting multiple anchorage options to this crank arm, separated in such a distance that respective orientation values differ in 3°; and for such a small variation, the proposed constructive solution is equipping the ovoid chainring with consecutive overlapped holes and respective countersinks with different depth, forming stair steps which help supporting tangential loads to the chainring.
1. An ovoid bicycle chainring for attaching to a crank arm comprising a spider and anchorage points distributed in a star-like shape, said chainring comprising:
a major diameter, whose angle with said crank arm measured in the pedaling direction defines its orientation;
a plurality of anchorage points to said crank arm spider, which is a multiple of the number of anchorage points of the spider, different anchorage points of said chainring comprising adjoined and overlapped holes corresponding to the same anchorage point on the spider, each of said holes having a countersink; and
wherein, the depth of each overlapped adjoining hole countersink decreases in the direction of pedaling, forming stair steps.
2. The ovoid bicycle chainring according to claim 1 , wherein said overlapped adjoining holes of said chainring is separated 6° from one another in their positioning perimeter.
3. The ovoid bicycle chainring, according claim 1 , wherein said spider has an odd number of chainring anchorage points, the different anchorage points corresponding to a same anchorage point on said spider, and holes placed at alternate end points of separated diameters with the same angular increment form two groups of adjoining overlapped holes disposed perimetrally opposed in the chainring.