PURPOSE: To restrain thermal deformation and obtain uniform surface of a sheet material, by a method wherein a string material, fusible with both first and second sheet materials, is interposed between the materials and is pressurized to weld them by fusion by ultrasonic wave.
CONSTITUTION: A sheet material 24 is put on a supporting table 22, and a string material 25 is interposed between sheet materials at a position where the sheet materials 23, 24 are to be welded by fusion, then, both of the sheet materials 23, 24 are welded by fusion while pressurizing them by a predetermined pressure for a predetermined time by employing an ultrasonic horn 21. The sheet member 23 and the like are vibrated by ultrasonic vibration and the string material 25 generates friction or hammering at the contacting surfaces thereof whereby heat is generated and the sheet material 23 and the like are fused locally and welded. Non-porous or porous sheet of thermoplastic polymer, having the thickness of 5μmW500μm may be used as the sheet material while polyvinyl chloride, polyethylene, polypropylene, polycarbonate, polystyrene, polyvinylidene chloride, nylon, polyester, polysulphon or the like may be used as the thermoplastic polymer. As the material of the string material, most preferable is the same material and same constituent as the sheet material.
YOSHIMASU SHIROU
KURODA SHINICHIRO
