Calibrated clamping device

A clamping device for applying a calibrated clamping force to a pair of abutting pieces, the device comprising, in combination:

• a straight threaded rod extending in an axial direction;
• at least a first, a second and a third visible reference element located on the rod and lying in planes perpendicular to said direction and axially spaced apart from one another along the rod;
• a shoulder selectively lockable in a plurality of axial positions along the rod;
• a threaded body threadedly coupled to the rod so as to allow the axial position of the body to be adjusted along the rod;
• a fourth visible reference element located on the threaded body and lying in a plane perpendicular to the axial direction;
• an axially compressible elastic means mounted on the rod at a position axially interposed between the threaded body and the shoulder;
• the clamping device being able to take at least two different working conditions:
• a first, zero load condition, in which:
• the rod is inserted through two axially aligned holes in two abutting pieces,
• the shoulder abuts against a first surface of one of the two pieces,
• the first reference element is coplanar with a second surface of the other of the two abutting pieces, the second surface being located on a side opposite the first surface, and
• the threaded body is positioned along the rod in a first axial position in which the second and fourth reference elements are in the same plane perpendicular to the axial direction, and in this first axial position the elastic means is locked in a non-compressed state between the threaded body and the second surface of the piece;
• and
• a second condition of calibrated clamping, in which:
• the rod and the shoulder are positioned as in the first working condition;
• the threaded body is positioned along the rod in a second axial position such that the elastic means is compressed axially between the threaded body and the second surface of the piece,
• the third and fourth reference elements are in the same plane perpendicular to the axial direction, whereby the two pieces are clamped with a calibrated axial force between the shoulder and the elastic means.