| 摘要 |
PROBLEM TO BE SOLVED: To eliminate generation of burr and improve productivity by specifying the relation of both front/rear leg lengths of a sticking part having a U-shaped cross section in a seal part which is weld and coated across the circumferential edge face and the front/rear both surfaces of the piston main body. SOLUTION: A seal part 4 is provided with an end face 7 of an outer circumferential edge 6 of a piston main body 3 and a sticking part 10 having a U-shaped cross section which is weld and coated across the front/rear both surfaces 8, 9, and when the leg length in a side opposed to a projecting seal lock part 11 of a die of the sticking part 10 and the leg length in the opposite side are set to Lp and Ls respectively, they are set to Lp <=Ls . The upper die 12 is made to approach to the lower die 13, the projecting seal lock part 11 is firmly pressurized against the top surface of the piston main body 3 to cause the operation of the external force of an arrow F, however, the same place as a joggling part 14 of the lower die 13 or a little toward the edge is pressurized by the external force F so that this constitution can prevent the edge side of the piston main body 3 from being warped upward, prevent it from floating from a flat seal lock part 15, prevent the material of the seal part 4 from flowing in, and prevent burr from being generated. |
