Hinge device with a returning member for automatically closing an open door

A hinge device comprising:

• a stationary hinge member including an elongated stationary leaf, and a hollow tubular member fixed to said stationary leaf;
• a rotatable hinge member pivoted to said stationary hinge member so as to be pivotable relative to said stationary hinge member about a vertical axis between a first angular position and a second angular position angularly displaced from said first angular position;
• a cam mechanism including a rotatable cam element that is disposed within said tubular member, that is coupled to said rotatable hinge member so as to be pivotable relative to said stationary hinge member about said vertical axis together with said rotatable hinge member, and that is formed with a first cam face, and a slidable cam element that is disposed within said tubular member above said rotatable cam element, that is formed with a second cam face associated with said first cam face, and that is movable in an axial direction along said vertical axis, said rotatable cam element engaging said slidable cam element in such a manner that said second cam face moves away from said first cam face when said slidable cam element is cammed by said rotatable can element upon rotation of said rotatable hinge member from said first angular position to said second angular position by an external force applied on said rotatable hinge member, said rotatable cam element including a cylindrical portion extending in said axial direction, and having a top end that defines a top abutment face extending in a transverse direction relative to said vertical axis, said cylindrical portion being formed with two opposing V-shaped notches that extend inclinedly from said top abutment face and that cooperatively define said first cam face, said slidable cam element including a cylindrical portion that extends in said axial direction, that is disposed above said cylindrical portion of said rotatable cam element, and that has a bottom abutment face extending in said transverse direction, said cylindrical portion of said slidable cam element being formed with two opposing V-shaped notches that extend inclinedly from said bottom abutment face and that cooperatively define said second cam face;
• and
• a biasing member connected to said cylindrical portion of said slidable cam element so as to accumulate a returning force when said second cam face moves away from said first cam face and so as to urge said second cam face to move toward said first cam face when the external force ceases to be applied on said rotatable hinge member, thereby returning said rotatable hinge member from said second angular position to said first angular position, said top and bottom abutment faces abutting and pushing against each other by the returning force of said biasing member upon further rotation of said rotatable hinge member relative to said stationary hinge member from said second angular position to a third angular position, thereby permitting resting of said rotatable hinge member relative to said stationary hinge member at said third angular position.