An apparatus includes a supporting body, a rotating body assembled with the supporting body and rotating at least between a standard position and a deployed position through an intermediate position, and a biasing device for applying a biasing force to the rotating device in a direction of returning the rotating body to the standard position. A speed switching device changes a rotational speed of the rotating body from the deployed position to the intermediate position different from that from the intermediate position to the standard position in a return rotational movement of the rotating body. The speed switching device includes at least two damping devices; at least two first gears attached to the damping devices for applying damping forces of the damping devices to the rotating body; and at least two second gears formed integrally on the rotating body.