Security seal

A security seal of the type that comprises a locking body (1) nd a thread (2) having a first end (3) attached to the body and a second free nd (4), the body (1) having an entry opening (5) for inserting the second end (4) of the thread and also, in its interior, locking means that allow the second end of the thread to pass in the insertion direction and prevent it from being withdrawn in the opposite direction, characterized in that the locking means have:

• first and second fixed and substantially flat surfaces (14) facing each other, but angularly diverging from each other in said thread-insertion direction, from a region adjacent said opening (5);
• and
• at least one movable wedge element (6) having, on one side, a substantially flat guide surface (21), adapted to slide along said first fixed surface (14), and a substantially flat thread-locking surface (22), on an opposite side of the wedge element (6), the thread-locking surface (22) being angularly divergent with respect to the guide surface (21) in the thread-insertion direction and defining one side of a passage for the thread (2) within said body (4), the movement of the thread in the insertion direction through said opening (5) causing displacement of the guide surface (21) of the wedge element (6) along the first fixed surface (14) in the insertion direction, with the consequent increase of the width of the passage for the thread, and the movement of the thread in the opposite direction towards said opening causing displacement of the guide surface (21) of the wedge element (6) also in this direction, thus narrowing the passage for the thread on the side of the thread-locking surface and locking the thread against its withdrawal from the body, said opening (5) having a cross-section substantially equal to that of said thread (2).