| 摘要 |
PURPOSE:To joint square cylindrical tubes without using coating material, liner etc. by expanding the inner periphery of a malleable square cylindrical tube end to the length of outer periphery of a square cylindrical tube to be joined, forming it to a square tube, and inserting the end of cylindrical tube to be joined into this joining part. CONSTITUTION:A round die 3 having outer periphery equal in length to the outer periphery of the end of a square cylindrical tube 2 is inserted into a square cylindrical tube 1 made of malleable material and the end of the tube 1 is expanded. Next, a square die 4 similar in external form with that of the end of the tube 2 is inserted into the circular cylindrical expanded part 1a thus obtained, and the expanded part 1a is formed to a square cylindrical joining part 1c. Then, the tube 1 and tube 2 are joined by inserting the end of the tube 2 into the joining part 1c. Metallic material such as Al and copper, or synthetic resin such as PVC can be used as a malleable material. |
