The tooth profiles at the tooth fac

The tooth profiles at the tooth faces of the gears are assured to contact with each other properly at sections corresponding to the values of κ associated with the values of y through which the teeth of the external gear move in the tooth grooves of the internal gear. This is based on the facts that the tooth apex P of the flexible external gear is on the point obtained by extending two times the straight line EQ beyond the point Q from the point E, and the inclinations of the tangents at the point Q of the both tooth profiles are equal, which facts are derived from the fact that the tooth profiles of the both gears contacting with each other, for example, at the point Q in the drawing are symmetrical with respect to the point Q when viewed through the rack approximation, and by the process of defining the tooth profiles at the tooth faces as mentioned above.