Assembly of sheet materials, tube assembly, drawing method and tools for drawing

Abstract

The present invention provides an assembly of sheet materials in which a first sheet of material and a second sheet of material are disposed in an overlapping relationship, with a plurality of joint portions being formed therebetween by drawing an overlapping part of the first and second sheets of materials at a plurality of positions. The plurality of joint portions includes at least one first joint portion in which the first sheet of material is laterally extruded into the second sheet of material and at least one second joint portion in which the first sheet of material and the second sheet of material are in contact with each other in a cup-like surface configuration.

What is claimed is:  
     
         1 . An assembly of sheet materials in which a first sheet of material and a second sheet of material are disposed in an overlapping relationship, with a plurality of joint portions being formed therebetween by drawing an overlapping part of the first and second sheets of materials at a plurality of positions, 
 wherein said plurality of joint portions includes at least one first joint portion in which said first sheet of material is laterally extruded into said second sheet of material and at least one second joint portion in which said first sheet of material and said second sheet of material are in contact with each other in a cup-like surface configuration.    
     
     
         2 . A tube assembly comprising a first tubular body and a second tubular body disposed such that walls of said first and second tubular bodies overlap, a plurality of joint portions being formed between said first and second tubular bodies by drawing an overlapping part of the walls of said first and second tubular bodies at a plurality of positions, 
 wherein said plurality of joint portions includes at least one first joint portion in which the wall of said first tubular body is laterally extruded into the wall of said second tubular body and at least one second joint portion in which the walls of said first tubular body and said second tubular body are in contact with each other in a cup-like surface configuration.    
     
     
         3 . An assembly of sheet materials according to  claim 1 , wherein the laterally extruded shape of said first joint portion is formed by striking a rivet into the overlapping part of said first and second sheets of materials.  
     
     
         4 . A tube assembly according to  claim 2 , wherein the laterally extruded shape of said first joint portion is formed by striking a rivet into the overlapping part of the walls of said first and second tubular bodies.  
     
     
         5 . A tube assembly according to  claim 2 , wherein said first tubular body forms a support member and said second tubular body forms a tube for a piston-cylinder assembly.  
     
     
         6 . A tube assembly according to  claim 5 , wherein said piston-cylinder assembly forms a suspension cylinder and said support member forms one member selected from a spring seat and a knuckle bracket.  
     
     
         7 . A tube assembly comprising a dual tube including a first tubular body located on a radially outer side and a second tubular body located on a radially inner side, with a plurality of joint portions being formed therebetween by drawing an overlapping part of walls of said first and second tubular bodies at a plurality of positions in a radially inward direction, a third tubular body being provided within said dual tube, 
 wherein said plurality of joint portions includes at least one first joint portion in which the wall of said first tubular body is laterally extruded into the wall of said second tubular body and at least one second joint portion in which the walls of the first and second tubular bodies are in contact with each other in a cup-like surface configuration, and    said second joint portion is formed on a side from which said third tubular body is inserted into the dual tube.    
     
     
         8 . A tube assembly according to  claim 7 , wherein said third tubular body is tangent to said second joint portion of the dual tube.  
     
     
         9 . A tube assembly according to  claim 7 , wherein said first tubular body forms a support member and said second tubular body forms a tube for a piston-cylinder assembly.  
     
     
         10 . A tube assembly according to  claim 9 , wherein said piston-cylinder assembly forms a suspension cylinder and said support member forms one member selected from a spring seat and a knuckle bracket.  
     
     
         11 . A tube assembly according to  claim 10 , wherein: 
 said suspension cylinder forms a dual-tube type hydraulic cylinder;    said second tubular body forms an outer cylinder of said hydraulic cylinder; and    said third tubular body forms an inner cylinder of said hydraulic cylinder.    
     
     
         12 . A drawing method for forming a tube assembly of  claim 2 , comprising the steps of: 
 providing two tubular bodies, one of which is fittingly disposed in the other to thereby overlap walls of said two tubular bodies;    positioning tools for drawing an overlapping part of the walls of the two tubular bodies, said tools being arranged circumferentially along said overlapping part while being diametrically opposed to each other; and    drawing said overlapping part simultaneously at a plurality of positions by means of said tools, said positions being arranged in an equally angularly spaced relationship.    
     
     
         13 . A set of tools used in a drawing method of  claim 12 , including punches and dies, 
 said punches being provided around said overlapping part of the walls of the two tubular bodies in an equally angularly spaced relationship, while being diametrically opposed to each other,    said dies being provided inside said overlapping part, each die cooperating with a corresponding punch to thereby draw said overlapping part,    said dies being supported by a hollow mandrel for insertion into said overlapping part in a state such that the dies are capable of radially reciprocal movement,    said hollow mandrel accommodating a working rod wedged behind each die, said working rod being axially movable so as to cause radially reciprocal movement of each die.    
     
     
         14 . A set of tools according to  claim 13 , wherein at least one of said punches comprises a base portion and a distal end portion having a smaller diameter than the base portion, said base portion merging into said distal end portion through a curved surface having a predetermined radius of curvature.