An operative hinge for use with an opening / closing body is provided which comprises a hinge case to be installed to a
toilet bowl body for operating the opening / closing body; a shaft provided rotatably within the hinge case to support the opening / closing body; a stationary
cam fixed within the hinge case and having formed therein a central through-hole through which the rotating shaft is axially penetrated; a
cam provided within the hinge case and having formed therein a central through-hole through which the rotating shaft is axially penetrated to be slidable on, and rotatable with, the rotating shaft; and a resilient means for urging the rotatable sliding
cam toward the stationary can, the hinge further comprising, to further positively control the rotation or the rotating means, a damping means consisting of a
rubber ring fitted on the rotating shaft and interposed between the outer surface of the rotating shaft and the inner wall of the hinge case; and a
viscous oil applied between the outer surface of the
rubber ring and inner wall of the hinge case; the
rubber ring having spiral recesses formed on the outer surface thereof.