Tightening device

A device for tightening an item comprising a portion positionable or removable by means of a rotary motion, said device comprising:

• a first holding element having a first working surface of a material apt to produce a substantial friction on said portion;
• a second holding element, comprising a tightening element having a second working surface of a material apt to produce a substantial friction on said portion and opposite to said first working surface;
• and
• a support onto which said first and second holding elements are mounted, apt to define an ideal working plane,
• wherein:
• said tightening element is apt to rotate about an axis of rotation orthogonal to said ideal working plane and is constrained to move on said plane along a substantially C- or V-like path having a concavity giving onto said first working surface,
• the distance between said first and second holding elements is such that said portion of said item is concomitantly in contact with said first working surface and said second working surface, and
• said first working surface and said tightening element are configured such that, when an external force apt to impart a rotary motion to said portion or said device is applied, generated rolling friction results in a rotation of said tightening element about its axis and a movement of said tightening element along said path, reducing the distance between said working surfaces and causing the tightening of said portion.