Articulated wrench

1. In an articulated wrench having:

a box end, formed with a cavity thereon for receiving a ratchet ring, having an end formed with at least one box knuckle, the box knuckle being formed on a side thereof with an indent and a through hole penetrating the box knuckle sideway; and

a handle, having an end formed with at least one handle knuckle accommodating the box knuckle of the box end, each handle knuckle being formed with a though hole penetrating the handle knuckle sideway;

the improvements comprising a fastening device, inserted through the through holes of the box end and the handle, having a head and a shank, wherein the head gradually expands outwards from the shank to form a flared angle having a tapering angle less than 45°; and

a flexed spring disc, provided in the indent of the box end and flexed along a diameter thereof to form a curvature.

2. The articulated wrench of claim 1 , wherein one of handle knuckles of the handle is formed with inner threads and wherein the fastening device is a screw, the shank of the screw being formed with outer threads at a tail thereof for engaging the inner threads.

3. The articulated wrench of claim 1 , wherein the curvature of the flexed spring disc has a curving radius in the range of about 4.0 mm˜30.0 mm.

4. The articulated wrench of claim 1 , wherein the flexed spring disc has a total height H and a net thickness T under a free state and prior to assembly, and wherein H 1.2 T˜2.5 T.

5. The articulated wrench of claim 4 , wherein the total height of the flexed spring is compressed to a compressed height h after assembly, and wherein h=0.40 H˜0.80 H.

6. The articulated wrench of claim 1 , wherein the box end includes one box knuckle and the handle includes two handle knuckles that adapt to locate at opposing ends of the box knuckle.

7. The articulated wrench of claim 6 , wherein the through holes of the handle knuckles each include an axial line that aligns with one another.