Method of manufacturing double pipe

Abstract

A double pipe has an outer pipe and an inner pipe that is formed in a spiral or wavy configuration and is held by an inner circumferential face of the outer pipe.

1 - 4 . (canceled)  
   
   
       5 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising; 
 forming the inner pipe having a spiral shape with a diameter equal to or less than an inner diameter of the outer pipe;    inserting the spiral inner pipe into the outer pipe; and    curving the outer pipe into a predetermined shape so that the inner pipe is fixed to the outer pipe at each curve.    
   
   
       6 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising: 
 forming the inner pipe having a spiral shape with a diameter equal to or less than an inner diameter of the outer pipe;    inserting the spiral inner pipe into the outer pipe; and    locally or wholly deforming the outer pipe inwardly so that the inner pipe is fixed to the outer pipe at each deformation of the outer pipe.    
   
   
       7 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising: 
 forming the inner pipe having a spiral shape with a diameter greater than an inner diameter of the outer pipe;    inserting the inner pipe into the outer pipe while exerting force on the inner pipe to reduce the outer diameter of the spiral of the inner pipe to be less than the inner diameter of the outer pipe; and    stopping the exertion of the force so that a resilient restoring force of the inner pipe fixes the outer pipe and inner pipe to each other.    
   
   
       8 . The method of  claim 5 , further comprising: 
 spirally winding two straight pipes around each other and releasing the wound two pipes from each other so that the released two pipes may each serve as the spiral inner pipe.    
   
   
       9 . The method of  claim 6 , further comprising: 
 spirally winding two straight pipes around each other and releasing the wound two pipes from each other so that the released two pipes may each serve as the spiral inner pipe.    
   
   
       10 . The method of  claim 7 , further comprising: 
 spirally winding two straight pipes around each other and releasing the wound two pipes from each other so that the released two pipes may each serve as the spiral inner pipe.    
   
   
       11 . The method of  claim 5 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe may serve as the spiral inner pipe.    
   
   
       12 . The method of  claim 6 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe may serve as the spiral inner pipe.    
   
   
       13 . The method of  claim 7 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe may serve as the spiral inner pipe.    
   
   
       14 . The method of  claim 5 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe has a spiral shape with a diameter greater than a required spiral diameter; and    extending the released pipe in an axial direction so that the extended pipe may serve as the spiral inner pipe having the required spiral diameter.    
   
   
       15 . The method of  claim 6 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe has a spiral shape with a diameter greater than a required spiral diameter; and    extending the released pipe in an axial direction so that the extended pipe may serve as the spiral inner pipe having the required spiral diameter.    
   
   
       16 . The method of  claim 7 , further comprising: 
 spirally winding a straight pipe around a columnar core and releasing the wound pipe from the columnar core so that the released pipe may have a spiral shape with a diameter greater than a required spiral diameter; and    extending the released pipe in an axial direction so that the extended pipe may serve as the spiral inner pipe having the required spiral diameter.    
   
   
       17 - 20 . (canceled)  
   
   
       21 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising; 
 forming the inner pipe having a wavy shape with an amplitude equal to or less than an inner diameter of the outer pipe;    inserting the wavy inner pipe into the outer pipe; and    curving the outer pipe into a predetermined shape so that the inner pipe and outer pipe are fixed to each other at each curved part.    
   
   
       22 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising; 
 forming the inner pipe having a wavy shape with an amplitude equal to or less than an inner diameter of the outer pipe;    inserting the wavy inner pipe into the outer pipe; and    locally or wholly deforming the outer pipe inwardly to fix the outer pipe and inner pipe to each other at each deformation of the outer pipe.    
   
   
       23 . A method of manufacturing a double pipe having an outer pipe and an inner pipe, comprising: 
 forming the inner pipe having a wavy shape with an amplitude greater than an inner diameter of the outer pipe:    inserting the inner pipe into the outer pipe while exerting a force on the inner pipe to reduce the amplitude of the wavy shape of the inner pipe to be less than the inner diameter of the outer pipe; and    stopping the exertion of the force so that a resilient restoring force of the inner pipe fixes the outer pipe and inner pipe to each other.