Hollow rack shaft

Abstract

A workpiece for a hollow rack shaft is a substantially rectangular plate. The opposite two sides of this workpiece are respectively provided with a complementary profile composed of the continuation of a convex portion and a concave portion and when the workpiece is cylindrically formed, the profiles are mutually engaged. As the width of a part the width of which is the largest in the convex portion is larger than that of a part the width of which is the smallest in the concave portion, the two sides are prevented from being detached after engagement. Further, the opposite convex portion and concave portion are mutually caulked and hereby, mutual gap is removed.

What is claimed is:  
     
         1 . A hollow rack shaft which is formed cylindrically by bending a substantially rectangular plate so that the parallel two sides are joined and in a part of the surface of which a row of rack teeth along a direction of the axis is formed, wherein: 
 said respective sides have complementary profiles composed of the continuation of a convex portion and a concave portion so that the sides are engaged when they are joined.    
     
     
         2 . A hollow rack shaft according to  claim 1 , wherein: 
 the width of a part having the largest width of said convex portion is larger than the width of a part having the smallest width of said concave portion; and    hereby, said two sides are prevented from being detached.    
     
     
         3 . A hollow rack shaft according to  claim 1 , wherein: 
 said convex portion and said concave portion mutually opposite are caulked; and    hereby, mutual gap is removed.    
     
     
         4 . A method of manufacturing a hollow rack shaft which is formed cylindrically by bending the opposite sides of a substantially rectangular plate so that the sides are joined and in a part of the surface of which a row of rack teeth along a direction of the axis is formed, wherein: 
 a complementary profile composed of the continuation of a convex portion and a concave portion is provided to said respective sides; and    the respective sides are joined owing to this profile when they are confronted so that they are not detached.    
     
     
         5 . A method of manufacturing a hollow rack shaft according to  claim 4 , wherein: 
 further, said convex portion and/or said concave portion of said joined sides are/is caulked to deform the boundary.    
     
     
         6 . A hollow rack shaft which is formed cylindrically by bending a substantially rectangular plate so that the parallel two sides are joined and in a part of the surface of which a row of rack teeth along a direction of the axis is formed, wherein: 
 said plate is one plate acquired by welding a first plate for a rack teeth area for said row of rack teeth is to be formed and a second plate for an area except it.    
     
     
         7 . A hollow rack shaft according to  claim 6 , wherein: 
 said first plate is thicker than said second plate.    
     
     
         8 . A hollow rack shaft according to  claim 6 , wherein: 
 said first plate is made of material more satisfactory in hardenability than that of said second plate.    
     
     
         9 . A method of manufacturing a hollow rack shaft provided a row of rack teeth along a direction of the axis in a part of the surface for forming a substantially rectangular plate cylindrically by bending it so that the parallel two sides are joined, wherein: 
 said plate is one plate acquired by welding a first plate for a rack teeth area for said row of rack teeth to be formed and a second plate for an area except it.    
     
     
         10 . A method of manufacturing a hollow rack shaft according to  claim 9 , wherein: 
 said first plate is thicker than said second plate.    
     
     
         11 . A method of manufacturing a hollow rack shaft according to  claim 9 , wherein: 
 said first plate is made of material more satisfactory in hardenability than that of said second plate.    
     
     
         12 . A hollow rack shaft which is formed cylindrically by bending a plate so that the two sides of the plate are joined and in a part of the surface of which a row of rack teeth along a direction of the axis is formed, wherein: 
 said rack shaft is provided with a first area and second areas on both sides of it;    in said first area, the row of rack teeth and a semi-cylindrical part on the reverse side are formed; and    in said two second areas, a complete cylindrical part is formed and at least one of the second areas has a diameter different from the diameter of the semi-cylindrical part in said first area.    
     
     
         13 . A hollow rack shaft according to  claim 12 , wherein: 
 the diameter of at least one of said second areas is smaller than the diameter of said first area.    
     
     
         14 . A method of manufacturing a hollow rack shaft which is provide with a first area and a second area on both sides of it, in which in said first area, a row of rack teeth and a semi-cylindrical part on the reverse side are formed and in which in said two second areas, a complete cylindrical part is formed and at least one of the second areas has a diameter different from the diameter of the semi-cylindrical part in said first area, wherein: 
 a plate provided with a part with first width having width corresponding to the first area for said row of rack teeth to be formed and a part with second width corresponding to said second area and having narrower width than said part with the first width is plastically deformed cylindrically.