Golf club head with deformation portion

A hollow golf club head comprising:

• a face portion having a face for striking a ball;
• and
• a main body portion including a crown wall, a side wall and a sole wall which extend from the face portion toward the rear of the head,
• wherein
• at least one wall of the crown wall, the side wall and the sole wall is provided with a folded portion for facilitating a partial elastic deformation of the main body portion when the face portion hits a ball,
• the folded portion includes a first folded portion and a second folded portion, and
• the first folded portion and the second folded portion extend along a peripheral edge of the face portion, and are connected with each other at a junction,
• each of the first folded portion and the second folded portion extends in a front-back direction of the head to have a mountain protruding toward the outer side of the head and a valley recessed toward the inside of the head,
• the first folded portion is made up of the mountain and the two valleys located on both sides of the mountain in the front-back direction of the head, and
• two side faces between the mountain and the two valleys are respectively formed by two first triangular elements whose length in a first direction which is the direction along the peripheral edge of the face is gradually increased from the mountain toward the respective valleys,
• the second folded portion is made up of the valley and the two mountains located on both sides of the valley in the front-back direction of the head, and
• two side faces between the valley and the two mountains are respectively formed by two second triangular elements whose length in the above-said first direction is gradually decreased from the valley toward the respective mountains, and
• at the junction between the first folded portion and the second folded portion, the two first triangular elements of the first folded portion are respectively connected with the two second triangular elements of the second folded portion by sharing one of three sides of triangle.

A hollow golf club head comprising:

• a face portion having a face for hitting a ball, and
• a main body portion including a crown wall, a side wall and a sole wall which walls extend from the face portion toward the rear of the head,
• wherein
• at least one of the crown wall, the side wall and the sole wall is provided with a folded portion for facilitating a partial deformation of the main body portion when the face portion hits a ball,
• the folded portion includes a first folded portion and a second folded portion,
• in the first folded portion, the wall constituting the first folded portion has alternating valleys and mountains extending in a front-back direction of the head such that the valleys are recessed toward the inside of the head and the mountains project toward the outside of the head, and
• in the second folded portion, the wall constituting the second folded portion has alternating valleys and mountains extending in the front-back direction of the head such that the valleys are recessed toward the inside of the head and the mountains project toward the outside of the head,
• in the first folded portion, side faces between the mountains and the valleys are each formed by a first triangular element whose length in a first direction which is the direction along a peripheral edge of the face is gradually increased from the mountain toward the valley, and
• in the second folded portion, side faces between the valleys and the mountains are each formed by a second triangular element whose length in the above-said first direction is gradually decreased from the valley toward the mountain,
• the first folded portion and the second folded portion are repeatedly and alternately arranged along a peripheral edge of the face portion, and are connected with each other at a junction, and
• at the junction, the first triangular elements of the first folded portion are respectively connected with the second triangular elements of the second folded portion by sharing one of three sides of triangle, whereby the folded portion has an outer surface formed by a diamond-cut face made up of triangular surfaces.