Self-locking sealing device

A sealing device comprising a plug intended to be placed in a threaded hole in a case, or removed therefrom, respectively by screwing and unscrewing, the sealing device comprising:

• a central body of the plug, provided with a screw thread,
• a skirt rigidly connected to the central body and having an annular end-face capable of transmitting tightening thrust to the case,
• locking and unlocking means opposing spontaneous unscrewing of the plug, automatically activated by the rotation of the plug and its corresponding movement in the direction of screwing along a longitudinal axis, said locking and unlocking means comprising:
• a first releasable coupling component coupled for common rotation with the central body via guide means configured on the periphery of the first component and extending radially with respect to said longitudinal axis, said guide means entering respectively corresponding grooves configured inside the skirt, which extend parallel to the longitudinal axis so as to allow axial displacement of the first coupling component inside the skirt;
• and
• a second releasable coupling component in a position facing the first releasable coupling component at least during screwing and unscrewing, wherein at least in the tightened condition of the plug the second coupling component is secured against rotation with respect to the case by rotation restricting means located inside the threaded hole,
• wherein in the screwed condition the annular end face of the skirt bears against a bearing face of the second releasable coupling component to transmit tightening thrust to the case.