| 摘要 |
The pieces to be reciprocally connected are mechanically manufactured with tolerances such that the external diameter of the ends of the pipes (6,6') is suitably greater at the internal diameter of the seat ends of the star cross pieces (1). The star cross pieces are heated to a temperature which does not provoke a permanent deformity in the pieces and which is such as to slightly increase the diameter of the their seats. The pipes are inserted instead into the ends to be connected, in a liquid nitrogen bath that properly contracts the external diameter of said ends and brings them substantially to a condition of equality or inferiority with respect to the diameter of the dilated seats and the ends of the star cross pieces. The cooled ends of the pipes are then inserted into the heated end of the seats of the cross pieces and when the pieces return to room temperature, they are connected with the foreseen tightness. The finding also foresees an apparatus for the automatic execution of said manufacturing procedure.
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