US Patent 7753815 Bicycle chain wheel assembly

A bicycle chain wheel assembly is provided with a chain wheel and a chain wheel cover. The chain wheel has a central mounting portion and an outer gear with a plurality of outer gear teeth. The chain wheel cover is disposed on an exteriorly facing side of the chain wheel. The chain wheel cover has a mounting portion coupled to the chain wheel and an outer peripheral portion with a chain drop prevention protrusion projecting outwardly from the outer peripheral portion at a location that is radially inward of the outer gear teeth.