Patent 7713156 was granted and assigned to Tsubakimoto Chain on May, 2010 by the United States Patent and Trademark Office.
In a chain transmission having a sprocket with an elastic ring sandwiched between a central hub and an annular toothed outer member, the tooth form is such that the root diameter, that is, the diameter of the tooth gap bottom circle, is greater than the root diameter in a sprocket having a standard ISO tooth form.