Method of Hydraulic bulging and shaft pressing profile element pipe to make hydraulically bulged product

Abstract

A profile element pipe for hydraulic bulging of the present invention has a peripheral length with an outer diameter gradually increasing or decreasing from one axial side toward the other thereof and has a parallel part formed on at least one end thereof. According to a bulging device and a bulging method using this profile element pipe, for example, even when a profile steel pipe having a cross sectional shape varying in the axial direction as in a tapered pipe is hydraulically bulged, a bulging in which an internal pressure loading and an shaft pressing are combined with each other can be performed to provide a larger expansion ratio than a conventional case and a joining and socket connection thereof to the other part can also be easily performed.

1 - 15 . (canceled)  
   
   
       16 . A method of hydraulic bulging a profile element pipe comprising: 
 providing a profile element pipe having a peripheral length with an outer diameter gradually increasing or decreasing from one axial side toward the other thereof and having a parallel part formed on at least one end thereof; and    subjecting the profile element pipe to hydraulic bulging using an internal pressure loading and shaft pressing using shaft pressing tools to form a hydraulically bulged pipe.    
   
   
       17 . The method of  claim 16 , wherein the profile element pipe provided has a length of said parallel part being equal to, or more than, a total length of a distance of movement of the shaft pressing tools during the shaft pressing and a distance of movement of the shaft pressing tools necessary to produce a seal during the hydraulic bulging.  
   
   
       18 . The method of  claim 17 , wherein the profile pipe element is provided with a rectangular cross section or a polygonal cross section and a radius R of curvature of a corner part in said parallel part is varied in accordance with a change in a peripheral length of the profile element pipe as measured around an outer surface of the profile element pipe, the change in peripheral length increasing or decreasing along a longitudinal length of the parallel part.  
   
   
       19 . The method of  claim 16 , further comprising providing a hydraulic bulging device for said subjecting step, the hydraulic bulging device comprising: 
 a pair of dies, and    the shaft pressing tools also serving as sealing tools, in which front end portions of the tools are inserted into both ends of said dies for holding said profile element pipe while sandwiching the profile element pipe with said dies,    wherein a filling hole for working liquid is provided at any one of said shaft pressing tools and parallel parts are provided on at least one end-portion inner surface of said dies and an outer surface of said shaft pressing tool corresponding to the at least one end-portion inner surface, respectively,    the filling hole used for the internal pressure loading and the shaft pressing tools used for the shaft pressing.    
   
   
       20 . The method of  claim 17 , further comprising providing a hydraulic bulging device for said subjecting step, the hydraulic bulging device comprising: 
 a pair of dies, and    the shaft pressing tools also serving as sealing tools, in which front end portions of the tools are inserted into both ends of said dies for holding said profile element pipe while sandwiching the profile element pipe with said dies,    wherein a filling hole for working liquid is provided at any one of said shaft pressing tools and parallel parts are provided on at least one end-portion inner surface of said dies and an outer surface of said shaft pressing tool corresponding to the at least one end-portion inner surface, respectively,    the filling hole used for the internal pressure loading and the shaft pressing tools used for the shaft pressing.    
   
   
       21 . The method of  claim 18 , further comprising providing a hydraulic bulging device for said subjecting step, the hydraulic bulging device comprising: 
 a pair of dies, and    the shaft pressing tools also serving as sealing tools, in which front end portions of the tools are inserted into both ends of said dies for holding said profile element pipe while sandwiching the profile element pipe with said dies,    wherein a filling hole for working liquid is provided at any one of said shaft pressing tools and parallel parts are provided on at least one end-portion inner surface of said dies and an outer surface of said shaft pressing tool corresponding to the at least one end-portion inner surface, respectively,    the filling hole used for the internal pressure loading and the shaft pressing tools used for the shaft pressing.