Method and machine for expanding tubes in a tube sheet

Apparatus for expanding tubes comprising:

• a rolling tool for acting on a tube to expand the tube in a tube wall to form an assembly therewith;
• means for measuring simultaneously a variable expanding effort applied to the tool and a linear displacement variable as caused by said tool, which variables define the magnitudes of stresses and deformations occurring in the tube during expanding;
• said measuring means being operative successively at three operationwise states with reference to the graph of FIG. 1;
• the tube rigidity represented by segment AB, the yield point represented by portion BC and the rigidity of the tube wall represented by the direction of the straight line CD;
• control means including computer means for optimizing the expanding operation in response to both the variable effort and the linear displacement variable when as determined by said computer means the variable effort reaches an optimum value to obtain maximum strength and fluid-tightness of the assembly of the tube in the tube wall, in accordance with the geometric dimensions and the mechanical properties of the respective materials of the tube and of the tube wall;
• said measuring means being operatively connected with said computer means;
• and
• drive means connected with said tool and said control means and responsive to said computer means to de-engergize said drive means and reverse thereof when the variable effor reaches said optimum value as determined by said computer means.

Apparatus for expanding tubes, comprising:

• a rolling tool having rolls for acting on a tube to expand the tube in a tube wall to form an assembly therewith;
• means for measuring simultaneously a variable effort and a linear displacement variable, as caused by said tool, which variables define the magnitudes of stresses and deformations occurring in the tube sheet and in the tube during expanding;
• said measuring means being operative successively at three working stages with reference to the graph of FIG. 1, the first working stage beginning from the moment of contact of said rolls with the inner surface of said tube and continuing until the beginning of the plastic deformation of the material of said tube and the second stage beginning at the point when the plastic deformation of said tube material begins and ending when said tube contacts said tube sheet;
• said first working stage including an elastic bending to produce an elastic deformation of said tube and said second operationwise stage including a plastic deformation of said tube;
• the tube rigidity being represented by portion AB, the yield point represented by portion BC and the rigidity of the tube wall being represented by the direction of the straight line CD;
• and
• control means including computer means having transducers responsive to the variable effort and the linear displacement variable for optimizing the expanding operation in response to both the variable effort and the linear displacement variable when, as determined by said computer means, having received a signal from one of said transducers that the variable effort or linear variable has reached a determined optimum value to obtain maximum strength and fluid-tightness of the assembly of the tube in the tube wall, in accordance with the geometric dimensions and the mechanical properties of the respective materials of the tubes and the tube wall, whereupon a reversing command is issued to retract the rolling tool from said tube wall.