Patent ID: 6919528

Claim:
A welding machine for welding around a circumference of cylinder members in order to join a first cylinder member and a second cylinder member into which the first cylinder member is inserted by applying welding energy to the cylinder members while relatively rotating the cylinder members with respect to the machine, the welding machine comprising: an energy source for generating energy, the energy being used for melting the cylinder members at a portion to be welded and for welding the cylinder members together; and energy-applying units for applying the energy to the cylinder members, wherein: the energy-applying units are disposed outside the cylinder members at two positions, and are directed to the cylinder members to apply the energy to two target points on a circumferential welding path on the cylinder members, two of the target points being angularly apart from each other by an angle of θ degrees, where 80≦θ≦100, and the welding machine is constructed and arranged so that the energy applying units simultaneously apply the energy to respective target points while relatively rotating the cylinder members more than one revolution with respect to the energy applying units so that the circumferential welding path is traced at least twice by the energy.