Chair for the sitting of a user

Chair for the sitting of a user, which comprises:

• a support structure (2), intended to be placed in abutment against the ground;
• a seat (3), mounted on said support structure (2);
• a back (4), hinged to said seat (3) around a first rotation axis (R) between a rest position (A), substantially vertical, and at least one reclined position (B);
• a blocking device (5), mounted on said seat (3) and comprises:
• a first element (51), rotatably mounted on said seat (3) and actuatable in rotation by a user around a second rotation axis (T) orthogonal to said first rotation axis (R);
• a second element (52), slidably mounted on said seat (3) and movable along a movement direction (X), orthogonal to said first rotation axis (R) and to said second rotation axis (T), between a blocking position, in which it blocks the rotation of said back (4) around said first rotation axis (R), and a release position, in which it allows the free rotation of said back (4) around said first rotation axis (R);
• said chair (1) being characterized in that said blocking device (5) comprises transmission system (53), which is fixed in a single body with said first element (51) and with said second element (52), and are configured for moving said second element (52) along said movement direction (X), between said blocking position and said release position, following the rotation of said first element (51) around said second rotation axis (T);
• said transmission system (53) comprising an elbow portion (54), elastically pliable, which is configured for being elastically bent following the rotation of said first element (51) around said second rotation axis (T), and for moving said second element (52) along said movement direction (X).