Golf club head

[0001] The present invention relates to a golf club head, more particularly to a coupling structure between a face member and main body of the golf club head.

[0002] In recent years, in order to provide golf clubs which are easy to use for average golfers, the club heads are designed to render the position of the gravity point of the club head lower and deeper and to increase the moment of inertia around a vertical axis passing the gravity point.

[0003] On the other hand, the recent trend of manufacturing such golf club heads is to form major parts of a head by casting. Even in the precision castings, however, in terms of shape and dimensions, the degree of accuracy of the casting sometimes becomes lower than acceptable levels. This is especially remarkable at the edges of the cast articles which edges are usually utilized to connect the parts with each other. Also in case of forgings which is provided with a thickness decreased part and/or a largely bent part in particular, the degree of accuracy is liable to become lower than acceptable levels. Thus, such lowering of accuracy deteriorates not only the dimensions, shape and other important parameters such as loft angle and lie angle but also the strength, durability and the like.

[0004] It is therefore, an object of the present invention to provide a golf club head, in which joint surfaces which contact with each other and form a junction between a face member and a main body are finished using a machine tool to eliminate dimensional variations to improve the accuracy of the junction.

[0005] According to the present invention, a golf club head comprises a face member forming at least a part of the club face for hitting a ball, and a main body to which the face member is attached to form a junction in which a joint surface of the face member and a joint surface of the main body come into contact with each other, and at least one of the joint surface of the face member and the joint surface of the main body is machined using a machine tool.

[0006] Here, the junction means that of various joints such as welded joint and caulking joint (press fit joint) as far as the joint surface of the face member and the joint surface of the main body come into contact with each other by a certain contact area or along a line (namely, almost zero contact area) and the contact determines the relative physical relationship between the face member and the main body.

[0007] The machined surface means to remove the substance in unwanted part of the work as fine metal shavings, powder and the like using a machine tool so that the finished surface (P) of the work becomes specific predetermined dimensions and shape.

[0008] The machine tool means lathe turning machine, milling machine and the like. Here, manual type machine tools may be used, but NC type, namely, numerical control machine tools of which cutware is numerically controlled by a NC program are especially preferably used in view of the productivity.

[0009] FIG. 1 is a front view of an iron-type club head according to the present invention.

[0010] FIG. 2 is a cross sectional view thereof taken along a line A-A in FIG. 1.

[0011] FIG. 3 is an exploded perspective view of the club head showing a face member and a main body, wherein the main body shown is that in such a state that the main body is not yet undergo press working for fixing the face member mounted thereon.

[0012] FIG. 4 is an enlarged cross sectional view corresponding to that shown in FIG. 2, wherein the face member is mounted on the main body, but the main body is not yet undergo the press working for fixing the face member.

[0013] FIG. 5 is a cross sectional view for explaining an example (milling) of the machine work.

[0014] FIG. 6 is a cross sectional view showing a modification of the face member shown in FIG. 2.

[0015] FIG. 7 is a top view of a wood-type golf club head according to the present invention.

[0016] FIG. 8 is a cross sectional view of the front part of the club head crown taken along a line B-B in FIG. 7, showing a junction of a face member and a main body.

[0017] FIG. 9 is an exploded perspective view of the wood-type golf club head.

[0018] FIG. 10 is a cross sectional view of a wood-type golf club head according to the present invention.

[0019] FIG. 11 is a cross sectional view showing the machined joint surfaces of the face member and main body thereof.

[0020] FIG. 12 is a partial cross sectional view of a wood-type golf club head according to the present invention.

[0021] FIG. 13 is a back view of the face member thereof.

[0022] FIG. 14 is a partial cross sectional view of thereof.

[0023] FIG. 15 is a front view of the main body of the wood-type golf club head shown in FIG. 12.

[0024] Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.

[0025] In the drawings, golf club head 1 according to the present invention comprises a face member 2 and a main body 3. The face member 2 is fixed to the main body 3, forming a junction.

[0026] In the following embodiments, the face member 2 forms the entirety of the club face F for hitting a ball. But, it is also possible to design the face member 2 to form a part of the club face F.

[0027] At the junction of the face member 2 and main body 3, at least one of the joint surface of the face member 2 and the joint surface of the main body 3 is a machined surface (P). In other words, the surface is finished using a machine tool. In the following embodiments, NC lathe turning machine and/or NC milling machine are used as the machine tool.

[0028] Iron-Type Club Head

[0029] FIGS. 1, 2, 3 and 4 show an iron-type club head 1 according to the present invention.

[0030] The face member 2 in this embodiment is a generally trapezoidal metal plate of which front face defines the club face F. In order to increase the sweet spot area of the club face, the face member 2 is made of a metal material having a specific gravity of less than the undermentioned metal material of the main body 3. In this example, a titanium alloy is used. The thickness (t) thereof is set in a range of from 1.5 to 4.5 mm, preferably 2.0 to 4.0 mm, more preferably 2.0 to 3.5 mm in view of the rebound performance and durability. Aside from titanium alloys, however, various materials such as pure titanium, maraging steel, aluminum alloys and amorphous alloys may be also used.

[0031] The face member 2 is a cast article having a front face (F) which is substantially flat, a back face 2b which is also substantially flat in this example, and a side face 2a extending between the front face (F) and the back face 2b.

[0032] In this example, the side face 2a is made up of

[0033] a protruding face 2a1 on the back face side which is substantially perpendicular to the front face (F),

[0034] a relatively recessed face 2a2 on the front face side which is substantially perpendicular to the front face (F), and

[0035] a linkup face 2a3 which extends between the front edge of the protruding face 2a1 and the rear edge of the recessed face 2a2 in substantially parallel to the front face (F).

[0036] Thus, the side face 2a displays a zigzag contour in a cross section as shown in FIG. 2.

[0037] The substantially flat front face (F) is provided with small parallel horizontal grooves SC to increase friction of the club face F against a ball.

[0038] Although the recessed face 2a2 and linkup face 2a3 in this example intersect perpendicularly with each other, they can be formed as a single face tapering from the front edge of the protruding face 2a1 to the front face (F).

[0039] The main body 3 in this embodiment is made of a metal material having a specific gravity larger than that of the face member 2.

[0040] The main body 3 comprises an upper part 3a forming a top blade of the club head, a lower part 3b forming a sole of the club head, a toe part 3c and heel part 3d extending therebetween, a hosel 3e extending upwards from the heel part 3d and having an opening for a club shaft.

[0041] The lower part 3b is thick and provided with a large volume backwards extension to render the gravity point of the club head 1 lower and deeper.

[0042] The main body 3 in this example is a cast article of a stainless steel formed by lost-wax precision casting. Specifically, a stainless steel SUS630 is used. But, other metal materials such as soft iron, titanium alloy, aluminum alloy and the like may be used aside from stainless steel.

[0043] The above-mentioned upper part 3a, lower part 3b, toe part 3c and heel part 3d continue annularly and forms a through hole which defines an opening (O) on the front of the main body 3 as shown in FIG. 3. FIG. 3 shows the main body 3 and face member 2 which are not yet assembled.

[0044] The opening (O) forms a face mount 4 to which the face member 2 is attached. The face mount 4 comprises a side-support circumferential wall 4A contacting and supporting the side face 2a of the face member 2, and a back-support wall 4B protruding into the opening (O) from the rear end of the wall 4A and contacting and supporting the back face 2b of the face member 2.

[0045] At first, the main body 3 is, as shown in FIG. 3 and FIG. 4, provided continuously along the front edge of the opening (O) with a thin part 6 protruding ahead of the front face of the main body 3. The above-mentioned side-support circumferential wall 4A is extended through this thin part 6 to the front end of the protruding part 6 from a certain depth from the front face of the main body 3 in a perpendicular manner to the front face of the main body 3. On the contrary, the circumferential outside face 6a of the protruding part 6 is inclined so that this part 6 tapers towards the front. As a result, the cross sectional shape of the protruding part 6 becomes trapezoidal.

[0046] Form the rear end of the side-support circumferential wall 4A at that depth, the above-mentioned back-support wall 4B protrudes to support a peripherally part of the back face 2b of the face member 2. As shown in FIG. 3, the wall height is large in the lower part 3b but small in the upper part 3a. In the toe part 3c and heel part 3d, the wall height gradually decreases from the lower part 3b to the upper part 3a.

[0047] As shown in FIG. 4, the face member 2 is pushed into the opening (O), and using a pressing machine, the protruding part 6 is squashed into the groove formed by the wall 4A and faces 2a2 and 2a3 to lock the face member 2 as shown in FIG. 2.

[0048] This locking part 4A2 squashed into the groove has a thickness t1 in a range of from 0.3 to 2.0 mm, preferably 0.5 to 1.0 mm, and a height W1 in a range of from 0.3 to 2.0 mm, preferably 0.5 to 1.0 mm. If the thickness t1 is less than 0.3 mm and/or the height w1 is less than 0.3, the locking force becomes insufficient, and there is a tendency for the face member 2 to come off during use. If the thickness t1 is more than 2.0 mm and/or the height W1 is more than 2.0, it becomes difficult to squash without causing damage to the face member 2.

[0049] In case the locking part 4A2 is relatively small, it is preferable that an adhesive agent is used at the same time.

[0050] In this embodiment, using an end mill E as shown in FIG. 5, the back-support wall 4B is finished with the end Ea of the end mill head, and the side-support circumferential wall 4A is finished with the side face Eb of the end mill head.

[0051] As to the face member 2, on the other hand, similarly the side face 2a is finished by end milling, and a peripherally part 2be of the back face 2b is finished by end milling or face milling. In this embodiment, both of the face member 2 and main body 3 are made by casting. Therefore, the joint surface of the face member 2 (namely, the side face 2a and a part of the back face 2b) and the joint surface of the main body 3 (namely, the walls 4A and 4B) which are originally casting surfaces are machine finished to improve the accuracy.

[0052] The contour of the face member 2 defined by its side face 2a and the contour defined by the side-support circumferential wall 4A are formed in the substantially same size OR in order to further increase the locking force by press fitting, the side-support circumferential wall 4A is made relatively 0.1 to 0.5 mm smaller than the face member 2.

[0053] The portion to be machine finished is formed to have a cutting stock or a margin of 0.5 to 2.0 mm, preferably 0.5 to 1.0 mm.

[0054] FIG. 6 shows a modification of the above-mentioned face member 2, wherein a central part 7 (thickness ta) is formed to be thicker than the peripheral part 9 (thickness tb) to improve the durability of the club face portion.

[0055] The thickness (tb) of the thin peripheral part 9 is set in a range of from 1.5 to 3.5 mm, preferably 1.5 to 2.5 mm to improve the rebound performance of the face portion while maintaining the durability.

[0056] As with the former example, the face member 2 is a cast article and each face 2a1, 2a2 and 2a3 of the side face 2a is a machined surface (P).

[0057] Further, the back face 2b of the face member 2 is a machined surface (P) in at least the back face 2f of the thin peripheral part 9 including the part 2be.

[0058] The area of the machined surface (P) in the back face 2b is preferably in a range of not less than 50%, more preferably not less than 70%, still more preferably 100% of the area of the front face (F) in view of the accuracy in thickness and minimizing the thickness in the thin part. For the same reason, it is also preferable that the front face (F) is finished using the NC machine tool and the area of the machined surface is preferably in a range of not less than 50%, more preferably not less than 70%, still more preferably 100% of the area of the front face (F).

[0059] Comparison Test

[0060] The face member was made of a titanium alloy Ti-6Al-4V by precision casting. The main body was made of a stainless steel SUS630 by precision casting. In order to evaluate the strength of the junction, a hitting test was conducted as follow. The club head was attached to a shaft to make an iron club, and the club was mounted on a swing robot. The club head struck two-piece golf balls 3000 times at the head speed of 45 meter/second, and thereafter the club face portion including the junction was checked for deformation and/or damage. The test results are shown in Table 1.

TABLE 1
Iron type head	Ref.	Ex.1	Ex.2	Ex.3	Ex.4	Ex.5	Ex.6	Ex.7
Face member
Making method	casting	casting	casting	casting	casting	casting	casting	casting
Finishing	sand blasting	sand blasting	machine	machine	machine	machine	machine
Machined face			2a1 & 2be	2a1 & 2be	2a1 & 2be	2a1 & 2be	2a1 & 2be	2a1 & 2be
Thickness (mm)
Central portion	2	2	2	2	3	3	2	2
Peripheral portion	2	2	2	2	2	2	2	2
Main body
Making method	casting	casting	casting	casting	casting	casting	casting	casting
Finishing	sand blasting	machine	sand blasting	machine	machine	machine	machine
Machined face		4A & 4B		4A & 4B	4A & 4B	4A & 4B	4A & 4B	4A & 4B
Locking part (4A2)
Thicknesstl (mm)	1.5	1.5	1.5	1.5	1.5	1	1	0.3
Height wi (mm)	1	1	1	1	1	0.7	0.7	0.3
Hifting test	Face	OK	Joint gap	OK	OK	OK	OK	Joint gap
	member		was caused					was caused
	came off

[0061] Wood-Type Golf Club Head

[0062] FIG. 7 shows a wood-type club head according to the present invention.

[0063] This wood-type club head 1 comprises a hollow main body 3 having an opening (O) on the front thereof, and a face member 2 welded to the main body 3 so as to close the opening (O). Thus, in this embodiment, the above-mentioned junction is a welded joint B.

[0064] As shown in FIG. 9, the face member 2 comprises a main part 10 defining the club face F, and an extension 12 extending backward from the edge FE of the club face F and having a width D of from 7 to 30 mm along the surface. The backward extension 12 is formed continuously around the main part 10 which forms the entirety of the club face F.

[0065] In this embodiment, the hollow main body 3 is made by casting a metal material such as titanium alloys. And the face member 2 is made by forging a metal material such as titanium alloys. As shown in FIG. 8 and FIG. 9, the rear edge of the backward extension 12 is machined to remove unwanted part 12u, and the edge of the opening (O) is also machined so that the machined surface 12e of the backward extension 12 and the machined surface 13e of the main body 3 form a V-shaped groove 14 which is filled with the weld metal B. And they are butt welded.

[0066] FIG. 10 shows another example of wood-type golf club head 1 according to the present invention.

[0067] In this embodiment, the face member 2 is not provided with the above-mentioned backward extension 12. Thus, the face member 2 is an almost flat or slightly curved metal plate. The face member 2 is made by forging a metal plate, and the edge thereof is machined such that the side face 2a tapers from the front face (F) to the back face 2b at an angle of a as shown in FIGS. 10 and 11. Thus, the side face 2a of the face member 2 is the machined surface (P).

[0068] The main body 3 is hollow and it has an opening (O) on the front thereof. The main body 3 is made by forging a metal plate, and the edge of the opening is machined such that the surface 13e of the edge inclines backwards at an angle of b as shown in FIGS. 10 and 11.

[0069] The side face 2a of the face member 2 and the surface 13e of the main body 3 are the machined surface (P). They are confronted to form a V-shaped groove 14 and are butt welded. The angle of the groove 14 is set in a range of from 30 to 120 degrees, preferably 30 to 100 degrees, more preferably 45 to 90 degrees. The angles a and b are preferably set in a range of from 15 to 60 degrees with respect to the respective thickness direction N.

[0070] FIGS. 12, 13, 14 and 15 show a still another example of wood-type golf club head 1.

[0071] In this embodiment, the face member 2 is an almost flat or slightly curved metal plate.

[0072] The main body 3 has an opening (O) on the front thereof as shown in FIG. 15, and a back-support wall 4B is provided along the circumferential edge of the opening (O) to protrude into the opening (O) and to support the periphery part 2be of the back face 2b of the face member 2. The back-support wall 4B can be formed continuously along the edge of the opening (O), but in this example, it is formed discontinuously so that each wall 4B has a V or U-shape when viewed from the front.

[0073] The face member 2 is made by dies cutting a rolled metal plate, such as titanium alloy plate. The main body 3 is made by casting a metal material such as titanium alloys.

[0074] As the back-support wall 4B and the periphery part 2be come into contact with each other, they are the machined surface (P).

[0075] In order to form a v-shaped groove 17 for welding metal B annularly between the circumferential wall 4A of the main body 3 and the circumferential side face 2A of the face member 2, the circumferential side face 2A is machined to taper from the back face 2b to the front face (F). Preferably, the circumferential wall 4A is also machined to taper reversely as shown in FIG. 12.

[0076] As shown in FIGS. 13 and 14, the machined periphery part 2be of the face member 2 extends continuously along the circumferential edge of the face member 2 to have a certain width KW and also to have a certain depth AW so that a central portion surrounded by the machined periphery part 2be is protrude from the periphery part 2be and thus the central portion is thicker than the periphery part. Preferably, the width KW of the machined periphery part 2be is such that a thin part 7 is left between the thick central portion 9 and the back-support wall 4B, and the thin part 7 extends continuously around the thick central portion 9 to improve the rebound performance.

[0077] Comparison Test

[0078] Wood-type club heads of the substantially same outer shape were made according to the specifications shown in Table 2, wherein the face member and main body were made of a titanium alloy Ti-6Al-4V, and they were welded. The designed targeted value for the loft angle was 10 degrees. The real loft angle of each of the club head was measured. The results are shown in Table 2.

[0079] In order to evaluate the strength of the weld joint, a hitting test was conducted as follows. The club head was attached to a shaft to make an wood club (ten samples per each), and the club was mounted on a swing robot. The club head struck two-piece golf balls 3000 times at the head speed of 50 meter/second, and thereafter the junction was checked for damage. The test results are shown in Table 2, wherein the number of the club heads which had acceptable small damage or no damage is shown. As the sample number was ten, the number ten means the best.

TABLE 2
Wood type head	Ex.1	Ref.1	Ex.2	Ref.2	Ex.3	Ref.3
Structure
Face member
Making method	casting	casting	casting	casting	dies cutting	dies cutting
					rolled plate	rolled plate
Finishing	machine	sand blasting	machine	sand blasting	machine	as it is
Machined face	12e		2a		2be
Main body
Making method	forging	forging	forging	forging	casting	casting
Finishing					machine	sand blasting
Machined face					4B
Real loft angle (deg.)
Average	10.2	10.5	10.3	10.7	10.1	10.6
Maximum	10.9	11.5	11	11.9	10.5	11.8
Minimum	9.6	9.3	9.5	9.3	9.6	9.5
Dispersion ()	0.6	1	0.7	1.2	0.5	1.1
Hitting test	10	9	10	7	10	9

[0080] From the test results, it was confirmed that the loft angle variation and durability can be improved.

[0081] The present invention can be applied to various golf club heads such as utility-type and patter-type aside from iron-type and wood-type.

[0082] Incidentally, if the joint surface is made with accuracy by, for example, hot forging using dies, it will be not necessary to finish it using a machine tool.