Mandrel for bending

Abstract

A mandrel for bending of simple construction and sufficient rigidity is obtained. The mandrel comprises a plurality of plugs. Each plug is provided with a spherical outer peripheral surface A fulcrum pin is fitted through the plug. The first and second link members are rotatably attached to the fulcrum pins of the neighboring plugs so as to connect the neighboring plugs. The plug is also provided with a spherical depression which the adjoining plug can enter during the bending. The plugs are connected to the shank via the second link members.

What is claimed is:  
     
         1 . A mandrel for bending a pipe, comprising 
 a plurality of plugs, each plug being provided with a spherical outer peripheral surface,    a fulcrum pin being fitted through the plug, and    a link mechanism being rotatably attached to the fulcrum pins of the neighboring plugs so as to connect the neighboring plugs,    wherein each plug is provided with a depression which the adjoining plug can enter during the bending process.    
     
     
         2 . The mandrel for bending as set forth in  claim 1 , wherein said plugs are connected to a shank via the link mechanism.  
     
     
         3 . The mandrel for bending as set forth in  claim 1 , wherein said depression is spherical.  
     
     
         4 . The mandrel for bending as set forth in  claim 1 , wherein said link mechanism comprises 
 a plate-like first link member which connects two neighboring plugs, and    a plate-like second link member which connects one of said two neighboring plugs with another plug which adjoins said one of two neighboring plugs.    
     
     
         5 . The mandrel for bending as set forth in  claim 4 , wherein said second link members are provided in pairs and the first link member is arranged to be held therebetween.  
     
     
         6 . The mandrel for bending as set forth in  claim 4 , wherein said plug is provided with a rotation restriction mechanism which restricts the rotation of the first link member around the fulcrum pin of the plug to regulate a bending direction of the mandrel during the bending process.