Patent Application
20070298906
Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.
Wood-type golf club head according to the present invention has a hollow shell structure 1a.
The hollow shell structure 1a comprises: a face portion 3 whose front face defines a club face 2 for striking a ball; a crown portion 4 intersecting the club face 2 at the upper edge 2a thereof; a sole portion 5 intersecting the club face 2 at the lower edge 2b thereof; and a side portion 6 between the crown portion 4 and sole portion 5 which extends from a toe-side edge 2c to a heel-side edge 2d of the club face 2 through the back face BF of the club head.
At the heel side end of the crown portion 4, there is formed a hosel portion 1b be attached to an end of a club shaft (not shown) inserted into the shaft inserting circular hole 7.
In the case of a wood-type club head for number 1 wood, it is preferable that the head volume is set in a range of not less than 350 cc, more preferably not less than 360 cc still more preferably not less than 380 cc in order to increase the moment of inertia and the depth of the center of gravity. However, to prevent an excessive increase in the club head weight and deteriorations of swing balance and durability and further in view of golf rules or regulations, the head volume is preferably set in a range of not more than 470 cc, more preferably not more than 460 cc.
The mass of the club head 1 is preferably set in a range of not less than 180 grams, more preferably not less than 185 grams in view of the swing balance and rebound performance, but not more than 220 grams, more preferably not more than 215 grams in view of the shot directionality and traveling distance of the ball.
The loft angle alpha is set in a range of from not less than 7.0 degrees, preferably not less than 7.5 degrees, more preferably not less than 8.0 degrees, but not more than 20 degrees, preferably not more than 19.0 degrees, more preferably not more than 18.0 degrees.
As to the materials for the head, it is possible that the club head 1 partially includes nonmetallic materials, e.g. fiber reinforced resins, ionomer resins and the like. In this embodiment, however, the club head 1 is made of one or more metal materials. For example, stainless steels, maraging steels, pure titanium, titanium alloys, aluminum alloys and the like can be used.
According to the present invention, the ratio (W/L) of the head depth W (mm) to the head length L (mm) is set in a range of from 0.80 to 1.0.
Through experimental tests conducted by the inventor, it was found that: when the ratio (W/L) is less than 0.80, as the head length L becomes long for the head depth W, it becomes difficult to rotate the head back to the accurate address position during swing, and as a result, miss shots such as slice shot are induced. Further, the distance GL of the center G of gravity increases and the ball holding becomes insufficient, which further induce a slice shot. Thus, the directionality is deteriorated. Moreover, there is a tendency that the user feels the head as being undersized, therefore, the head can not give the user a sense of ease when addressed to the ball.
In the present invention, since the ratio (W/L) is not less than 0.80, the club head can rotate and return to the accurate address position at impact, and as a result, the directionality can be improved. From this point of view, it is desirable that, by relatively decreasing the head length L, the ratio (W/L) is set in a range of not less than 0.82, more preferably not less than 0.85.
Contrary, when the ratio (W/L) is over 1.00, as the head length L becomes short for the head depth W, there is a tendency that the head rotates beyond the accurate address position during swing, and as a result, hook shots are induced. Therefore, the ratio (W/L) is not more than 1.0, preferably not more than 0.98, more preferably not more than 0.95, still more preferably not more than 0.93.
In this embodiment, it is preferable that the distance GL is set in a range of from 36 to 41 mm.
By setting the ratio (W/L) as above, it becomes possible to proved the club head 1 with an appropriate weight distribution, which makes it easy to achieve the preferable range (36 to 41 mm) for the distance GL
If the absolute value of the head length L is too small, as the distance GL becomes decreased, a hook shot is liable to occur. Further, the head can not provide a sense of easy when addressed to the ball and it becomes difficult to meet the ball. Contrary if the head length L is too large, the ball holding is liable to be deteriorated. Therefore, the head length L is set in a range of not less than 95 mm, preferably not less than 100 mm, more preferably not less than 105 mm, but not more than 140 mm, preferably not more than 135 mm, more preferably not more than 130 mm.
If the absolute value of the head depth W is too small, as the depth of the center G of gravity (namely, the length of the straight N) becomes decreased, the directionality is liable to deteriorate. Further, the head can not provide a sense of easy when addressed. Contrary, if the absolute value of the head depth W is too large, the sweet spot height tends to be increased, and as a result, the backspin increases and the ball flight becomes a ballooning trajectory to decrease the carry distance. Therefore, the head depth W is set in a range of not less than 80 mm, preferably not less than 85 mm, more preferably not less than 90 mm, but not more than 130 mm, preferably not more than 125 mm, more preferably not more than 120 mm.
From the results of experimentally tests carried out by the inventor, it was also found that, by specifically limiting the sweet spot height H in relation to the above-mentioned ratio (W/L), a ballooning trajectory is prevented and therefore, the carry distance can be increased.
H≦76×(W/L)−31 (1)
H≦76×(W/L)−34 (2)
H≦76×(W/L)−39 (3)
It is preferable that the sweet spot height H is as low as possible in view of the prevention of the ballooning trajectory. But, if the sweet spot SS becomes distant from the average impact points of the average golfers (pints ranging from the center of the club face to 3 mm above), the rebound performance is liable to deteriorate. In this embodiment, therefore, it is preferable that the sweet spot height H is not less than 25 mm, but, not more than 45.0 mm, preferably not more than 40.0 mm, more preferably not more than 39.0 mm, still more preferably not more than 38.0 mm.
If the distance in the back-and-forth direction between the sweet spot SS and the clubshaft axis CL is too small, the distance in the back-and-forth direction between the center G of gravity and the axis CL (and the angle delta between line z and plane VP1 in
Therefore, the distance Q of the sweet spot SS measured perpendicularly to and from the above-mentioned vertical plane VP1 including the axis CL is preferably set in a range of from not less than 0.060 times, more preferably not less than 0.070 times, still more preferably not less than 0.080 times the head depth W.
However, if the distance Q is more than 0.25, the air resistance of the head increases because the position of the club shaft shifts backward as the distance Q increases and the air resistance increases as the club shaft shifts backward. Therefore, the distance Q is preferably set in a range of from not more than 0.25 times, more preferably not more than 0.22 times, still more preferably not more than 0.20 times the head depth W.
In this embodiment, the absolute value of the distance Q is preferably set in a range of from not less than 5.0 mm, more preferably not less than 7.0 mm, still more preferably not less than 9.0 mm, but, not more than 25 mm, more preferably not more than 22 mm, still more preferably not more than 20 mm.
In
In the vertical plane VP2 including the straight N, the radius Rc of curvature of the outer surface of the crown portion 4 is preferably set in a range of from not less than 150 mm, more preferably not less than 180 mm, still more preferably not less than 200 mm, but, preferably not more than 500 mm, more preferably not more than 450 mm.
Further, the maximum thickness D of the club head is preferably set in a range of from not more than 65 mm, more preferably not more than 63 mm, still more preferably not more than 60 mm, but, not less than 45 mm, more preferably not less than 50 mm.
In
In
In addition to these designs shown in
to reduce the weight of the head in the crown portion 4 and/or side portion 6 by using light weight materials having a relatively low specific gravity, e.g. metal materials such as magnesium alloys and aluminum alloys, resins such as engineering plastics and fiber reinforced resins;
to reduce the weight of the head in the crown portion 4 and/or side portion 6 by decreasing the wall thickness thereof;
to provide one or more unclosed openings in the crown portion 4;
to decrease the amount of protrusion of the hosel portion 1b; can be also employed.
In the case that the crown portion 5 and/or side portion 6 is decreased in the thickness, it is desirable to reduce the thickness to a small range of 0.3 to 0.5 mm by press molding a rolled metal sheet since it is difficult to reduce the thickness less than 0.6 or 0.7 mm by casting the meta material.
In order to weld such thin metal plates, plasma welding, especially laser welding is preferred. Further, soldering, adhesive bonding and the like can be used.
Furthermore, the following designs to lower the mass distribution of the head can be used:
to flatten the sole portion 5 by providing the outer surface with a large radius Rs of curvature (
to increase the thickness of the sole portion 5 wholly or partially; and
to provide a separate weight member 10.
The weight member 10 is made from a material having a larger specific gravity than that of the hollow shell structure 1a, especially the material of the sole portion 5. For example, stainless steels, brass, tungsten, tungsten alloys and the like can be used.
In
In this example, to mount the weight member 10, the sole portion 5 is provided with a socket protruding into the hollow shell, and the weight member 10 is put in the socket. To fix the weight member, caulking, adhesive agent and the like can be utilized.
In
Golf club heads having a head volume of 460 cc and a loft angle of 10 degrees were made based on the structure shown in
Each of the heads is composed of a hollow main body (m) having a front opening, and a face plate (f) attached to the hollow main body so as to cover the front opening.
As shown in
The face plate (f) was a casting of a titanium alloy Ti-5.5Al-1Fe (“Super Ti—X 51AF” Nippon steel corporation). The hollow main body (m) was a casting of a titanium alloy Ti-6Al-4v. The hollow main body (m) was fixed to the face plate (f) by laser welding.
In the sole portion, as shown in
The total weight of the club head was 205 grams.
The sweet spot height H was varied by changing the thicknesses of the sole portion and side portion and the position and mass of the weight member.
The specifications are shown in Table 1.
In the comparison tests, the club heads were attached to identical shafts to make wood clubs having a total length of 44.75 inches.
Using each club, ten right-handed golfers having handicap ranging from 5 to 20 hit golf balls six times per person.
The average carry distance was computed for each club from the sixty shots.
Further, the deviation (yard) of the point of fall of the struck ball from the target line of the ball was measured, providing that the value is −(minus) when the point of fall is right of the target line, and +(plus) when left of the target line. And the average deviation was computed for each club from the sixty shots. Usually, it is required that the absolute value of the average is at most 10 yards. When the absolute value is less than 5, the directionality of the head is regarded as very good.
As to easiness of swing the club, and sense of ease when addressed to the ball, each head was evaluated into five ranks (5: very good, 4: Good, 3: Average, 2: Baddish, 1: Bad) by the ten golfers. The average value was computed for each club from the evaluations by the ten golfers.
The test results are shown in Table 1.
From the test results, it was confirmed that the heads according to the present invention can be improved in the carry distance, deviation (directionality), easiness of swing, and sense of ease when addressed from a comprehensive standpoint.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-176960 | Jun 2006 | JP | national |
