Patent ID: 7762909

Claim:
A hollow metal golf club head having a shell structure comprising: a face portion having a club face for striking a ball; a crown portion; and a sole portion, wherein the crown portion has a thickness gradually decreasing from a front edge of the crown portion toward a rear end of the head, and the shell structure being made up of: a main shell provided with a front opening and a top opening and having a lateral frame between the top opening and the front opening, a face plate provided with a turnback which is welded to the main shell and covering the front opening, and a crown plate welded to the main shell and covering the crown opening, wherein when measured on a vertical plane including a center of gravity of the head and a sweet spot under a standard state of the head, a front zone of the crown portion formed by said turnback has a thickness in a range of 0.8 mm to 2.0 mm and a length in a range of from 0.05 to 0.3 times a length of the crown portion, a back zone of the crown portion formed by said crown plate has a thickness in a range of 0.2 mm to 1.0 mm and a length in a range from 0.05 to 0.7 times the length of the crown portion, and a middle zone therebetween formed by said lateral frame has a length in a range of from 0.5 to 2 times the front zone length and a thickness in a range between the thicknesses of the front zone of the crown portion and the back zone of the crown portion, a butt-weld junction located between a rear edge of the turnback of the face plate and a front edge of the lateral frame of the main shell, wherein the thickness of the turnback at the rear edge is substantially the same as the thickness of the lateral frame at the front edge, a butt-weld junction located between a front edge of the crown plate and a rear edge of the lateral frame of the main shell, wherein the thickness of the crown plate at the front edge is substantially the same as the thickness of the lateral frame at the rear edge, and said thickness of the middle zone gradually decreases from the front edge thereof which has a maximum thickness to the rear edge thereof which has a minimum thickness, and the difference of the maximum thickness at the front edge of the middle zone from the minimum thickness at the rear edge of the middle zone is not less than 0.02 but not more than 0.1 times the length of the middle zone, wherein said standard state is such that the head is set on a horizontal plane so that a center line of a shaft insertion hole of the head is inclined at a lie angle of the head while keeping the center line on a vertical plane, and the club face forms its loft angle with respect to the horizontal plane.