US Patent 7530291 Crank device for bicycle

A crank device includes a crank arm having an opening formed in one end and defined by an outer peripheral fence for attaching to a crank shaft, and an orifice formed in another end and defined by an outer peripheral wall for coupling to a foot pedal, and the crank arm includes one or more apertures formed in the other end and formed in the outer peripheral wall for weight reducing purposes. The aperture may be laterally formed in the other end of the crank arm, or formed through the outer peripheral wall of the crank arm and communicating with the orifice of the crank arm. The crank arm may further include one or more depressions for further weight reducing purposes.