JPS54117370A - Tube expander - Google Patents

Abstract

PURPOSE: To prevent the O-ring from the break to be caused when the O-ring plunges into the clearance generated from the deformation or the movement of the backup ring, by forming a ring type projection on the outer surface of the mandrel, and by setting the backup ring between this ring type projection and the O-ring.

CONSTITUTION: The tube 2 is inserted into the hole 1a provided in the tube plate 1, and the mandrel 3 is inserted into the tube 2 so as to be expandable the specified position; the htdraulic medium like as water or oil is introduced through the hydraulic path 6 into the space formed by the O-ring 5, the tube 2 and the mandrel 3. Hereby, the tube 2 expands outside depending on the pressure being sealed by the O-ring 5, and at the same time, the backup ring 4 is compressed by the axial pressure component, and swells toward the outside diameter, and occupies the clearance formed between the backup ring 4 and the tube 2. As a result, the break of the O- ring 5, usually caused when the O-ring 5 plunges into above stated clearance, is greatly prevented. Besides, the backup ring 4 effects a supplementary expanding work against the tube 2, and makes mild the deforming gradient at the end zone of the expanded portion; hereby, the residual stress is greatly reduced.

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