Method for manufacturing an impeller of a pump

An apparatus for manufacturing an impeller consisting of a body having a plurality of vanes and a shroud being joined with said body, said impeller for discharging water flowed into a housing of a pump, said apparatus comprising:

• a die for chucking said body;
• a horn for supporting said shroud to be in contact with said vanes of said body, said horn amplifying a vibration transmitted thereto;
• a torque motor for generating and applying a twisting vibration to said horn,
• wherein said torque motor has a stator and an armature for generating a rotational torque through magnetic force resulting from an input half-wave rectified alternating current, a rotational shaft rotating through the rotational torque generated by the stator and the armature, and a torsion bar in which one end thereof is connected with said rotational shaft and the other end thereof is fixed at a predetermined position, whereby the twisting vibration is generated by rotation and return of said rotational shaft according to the input half-wave rectified alternating current;
• a controlling means having a fixing plate assembled with said torsion bar to be movable relative to said torsion bar along a longitudinal direction of said torsion bar, and a control cylinder for moving said fixing plate along the longitudinal direction of said torsion bar and controlling a torsion constant of said torsion bar by varying a length between the fixing plate and the rotational shaft through the vertical movement of the fixing plate;
• and
• a pneumatic cylinder for forcing the torque motor toward the die so that said shroud is in contact with said body.