Axle beam for industrial vehicle, method of manufacturing the same and rear steering apparatus

Abstract

An axle beam for an industrial vehicle has a beam and a boss. The beam is supported on a vehicle body. The boss is provided at opposite ends of the beam for supporting a kingpin. The beam includes at a longitudinally middle thereof a portion having a closed cross-section perpendicular to a longitudinal direction of the beam and is shaped at the portion to form a space which is surrounded by a front and rear and a top and bottom of the beam. The portion is formed by welding two members or by one tube member.

What is claimed is:  
     
         1 . An axle beam for an industrial vehicle comprising: 
 a beam supported on a vehicle body; and    a boss provided at opposite ends of the beam for supporting a kingpin, wherein the beam includes at a longitudinally middle thereof a portion having a closed cross-section perpendicular to a longitudinal direction of the beam and is shaped at the portion to form a space which is surrounded by a front and rear and a top and bottom of the beam, the portion being formed by welding two members or by one tube member.    
     
     
         2 . The axle beam according to  claim 1 , wherein the number of welded portions that appear in the cross-section ranging from 0 to 2.  
     
     
         3 . The axle beam according to  claim 2 , wherein the number of welded portions is 0.  
     
     
         4 . The axle beam according to  claim 1 , wherein the beam is tapered at the opposite ends.  
     
     
         5 . The axle beam according to  claim 1 , wherein the beam is formed by fusing a tube material.  
     
     
         6 . The axle beam according to  claim 5 , wherein the tube material is seamless.  
     
     
         7 . The axle beam according to  claim 1 , wherein the beam is at least formed by two members welded to each other, whereby the space being surrounded by the front and rear and the top and bottom of the beam.  
     
     
         8 . The axle beam according to  claim 7 , wherein one of the two members has a U-shaped cross-section perpendicular to the longitudinal direction of the beam.  
     
     
         9 . The axle beam according to  claim 7 , wherein the two members each have an L-shaped cross-section perpendicular to the longitudinal direction of the beam.  
     
     
         10 . A rear steering device for an industrial vehicle comprising the axle beam as set forth in  claim 1 , further comprising: 
 a cylinder located in the space for power steering.    
     
     
         11 . A method of manufacturing an axle beam for an industrial vehicle having a beam and a boss, the beam including a tube portion while being supported on a vehicle body, the boss being connected to opposite ends of the beam in a longitudinal direction of the beam for supporting a kingpin, comprising the steps of: 
 fusing a tube material to form the beam in a first manufacturing process; and    connecting the boss to the beam in a second manufacturing process.    
     
     
         12 . The method of manufacturing the axle beam according to  claim 11 , wherein the first manufacturing process includes: 
 forming the beam having the tube portion at a middle portion thereof in the longitudinal direction; and    shaping the opposite ends of the beam thinner than the tube portion.    
     
     
         13 . The method of manufacturing the axle beam according to  claim 12 , wherein the first manufacturing process includes: 
 producing a plurality of identical beams from one tube material; and    determining a cutting line in staggered arrangement of the identical beams for fusing the tube material.    
     
     
         14 . The method of manufacturing the axle beam according to  claim 11 , wherein the first manufacturing process includes fusing the tube material by using a three dimensional plasma fusing apparatus or a three dimensional laser fusing apparatus.  
     
     
         15 . The method of manufacturing the axle beam according to  claim 11 , wherein the first manufacturing step includes utilizing the tube material of a seamless type.