Aus einen Rolex Patent Nr. 11/248904:



This clasp comprises at least two branches (1, 2) articulated on one another via one of their respective ends. One of the free ends of these branches (1, 2) comprises a lever (12, 22, 33) articulated about a shaft (10, 20, 32) parallel to the articulation shaft (3) of said branches (1, 2) and fixedly attached to a hook (17, 27, 33c), the other of the free ends of these branches comprising a coupling element (4, 34) shaped to allow the hook (17, 27, 33c) to engage therewith, to keep the branches (1, 2) in the folded position. The lever (12, 22, 33) comprises elastic means (15, 25, 37) to exert a torque thereon and abutment means (13, 23) to limit its pivoting, under the effect of the torque, about said shaft (10, 20, 32) in a position corresponding at least to the engagement of said latching hook (17, 27, 33c) with the coupling element (4, 34), in which the elastic means (15, 25, 37) are under tension, such that the lever (12, 22, 33) must pivot against the elastic means (15, 25, 37) to engage and to disengage the latching hook (17, 27, 33c) of the coupling element (4, 34).