Patent ID: 7513011

Claim:
A hinge comprising: a first bracket having a base; a support extending from the base and having a pivot hole defined through the support; and two holders mounted on the base and each holder having a pivot hole defined through the holder and aligning with the pivot hole in the support; a pivot pin rotatably mounted through the pivot holes in the support and the holders on the base of the first bracket and having an enlarged head abutting with the support and having two ends; a shaft protruding from one end of the enlarged head, rotatably extending through the pivot holes in the support and the holders and having a distal end, two outer threads and one outer thread formed on the shaft adjacent to the enlarged head and the other outer thread formed on the distal end of the shaft; and two nuts respectively screwed on the threads, the nut adjacent to the enlarged head located aside the support opposite to the enlarged head and the other nut on the distal end of the shaft abutting with one of the holders; a second bracket mounted to the pivot pin; and two torsion spring assemblies mounted on the pivot pin, corresponding respectively to the holders on the first bracket, with each torsion spring assembly having a disk mounted securely, to the pivot pin and having a mounting hole defined through the disk and through which the pivot pin extends and a spring hook formed on the disk; and a torsion spring mounted around the pivot pin between the disk and a corresponding holder on the first bracket, having two ends with one end mounted to the corresponding holder and the other end hooked detachably onto the spring hook on the disk; wherein the spring hooks on the disks of the torsion spring assemblies are formed in opposite directions perpendicular to the pivot pin.