Door hinge with automatic returning means

A door hinge with automatic returning means is comprising a male hinge member, a female hinge member, an inner sleeve, a transmission rod, main spring, a driving element, a buffer spring and a retainer, in which:

• a hollow annular element is provided at inner side of flat surface of male hinge member, on which is formed with a pin hole;
• a outer sleeve is also provided at the inner side of flat surface of the female hinge member and the outer diameter of which is in match with the annular element:
• inside of this outer sleeve is a channel in polygon shape and configurate to accommodate a driving element of same polygon shape in loose fit;
• an inner sleeve is inserted into outer sleeve with its lower portion and inserted into annular member with its upper portion, on which a pin hole is also formed in alignment with the pin hole of annular member;
• the transmission rod is cylinder in shape and the upper end of which is housed in inner sleeve with a pin to pierce through the holes of annular member, the inner sleeve and hole on the upper portion of this rod, all these parts--the annular member, the inner sleeve and transmission rod--shall be connected as one moving unit, an external thread is provided around the intermediate portion of this rod and a retainer groove is formed at its lower end;
• the main spring enveloped transmission rod with its upper end urge against the bottom of inner sleeve and its lower end contacted the top surface of driving element:
• the driving element is accommodated within the outer sleeve with its outer diameter in same configuration with the inner diameter of outer sleeve but little less sized, so that, it can be housed in outer sleeve in loose fit, the inner shape of driving element is a circular hollow channel, on which an internal thread is provided which shall be engaged with above mentioned external thread so as to produce a helical motion;
• the buffer spring also enveloped the transmission rod with its upper end urge against the bottom of driving element and with its lower end contacted and supported by retainer;
• and the retainer is engaged with retainer groove which is formed at the lower end of transmission rod in the portion extended further from outer sleeve.