<p>basal end portion of a force transmitter 81 is rotatably disposed in a second support shaft 74 rotatably connecting an internal link 72 to a body 3. A distal end portion of the force transmitter 81 is projected out of a guide hole 3g formed in a top plate 3b of the body 3. A pressing portion 81b is disposed in the projected distal end portion of the force transmitter 81. A receiver 83 is disposed in an end portion that is spaced from an instantaneous rotation center of a mounting member 4 when the mounting member 4 is positioned near a closed position. The pressing portion 81b is pressed against the receiver 83 by the torsion coil spring 82, thereby causing the mounting member 4 to be rotated toward the closed position.</p>
