Abstract: A plurality of weight hammers (7,8) are provided, and each of the plurality of weight hammers has a shape for substantially evenly applying a hammering force with respect to a surface to be hammered of an object to be hammered (11), about a center line of the object to be hammered. Rotors (9, 10) for driving the weight hammers (7,8) are provided to the same rotating shaft (22) in such a positional relation that an engagement claw (9a) of one rotor (9) engages and drives one weight hammer (7), and, when engagement of the weight hammer (7) is released, an engagement claw (10a) of another rotor (10) in driving engages another weight hammer (8). The rotors are driven by the same driving means (26).

Abstract: A plurality of weight hammers (7,8) are provided, and each of the plurality of weight hammers has a shape for substantially evenly applying a hammering force with respect to a surface to be hammered of an object to be hammered (11), about a center line of the object to be hammered. Rotors (9, 10) for driving the weight hammers (7,8) are provided to the same rotating shaft (22) in such a positional relation that an engagement claw (9a) of one rotor (9) engages and drives one weight hammer (7), and, when engagement of the weight hammer (7) is released, an engagement claw (10a) of another rotor (10) in driving engages another weight hammer (8). The rotors are driven by the same driving means (26).