Golf Club Head With Peripheral Weight

(a) Field of the Invention

The present invention relates to a golf club head, especially relates to so-called an iron golf club head or a putter golf club head.

(b) Description of Prior Art

It is mainly for the purpose of enlarging so-called a sweet area and lowering the center of gravity of a golf club head that the weight distribution of a golf club head including an iron golf club head or the like is adjusted in an invention related to a golf club head. It is obvious to those skilled in the art that to enlarge a sweet area, the center of gravity of a club head should be positioned comparatively backward, and/or, the weight distribution of a golf club head should be concentrated upon a peripheral portiton of a main body of a head besides the enlargement of a bulk of a golf club head itself. One of the representatives of a means for realizing such weight distribution is disclosed in U.S. Pat. No. 3,847,399, in which a head body is formed hollow, or a back surface of a club head is formed with a cavity.

On the other hand, it is mainly for the purpose of making a golf ball travel more upwardly and a longer distance to lower the center of gravity of a club head.

However, especially for an iron club head, it is difficult to make the same hollow. Further, if merely provided with a cavity in a back surface of a club head made of the same material, you cannot sufficiently concentrate the weight distribution of a club head upon a peripheral portion, thus setting limits to enlargement of a sweet area.

It is, therefore, an object of the present invention to further enlarge a sweet area in a golf club head such as an iron golf club head.

It is another object of the present invention to provide a method for manufacturing a golf club head having such a larger sweet area.

According to a major feature of the present invention, a golf club head comprising a head body having a face and a back; an embedding groove formed in a peripheral portion of the back of said head body; a balance weight formed of a material denser than that of said head body, which is press-fitted into said embedding groove along a peripheral portion of the back of said head body; a cavity which is machined in an area on the back of said head body, said cavity being either provided in the area surrounded by said balance weight or enlarged to span a part of said balance weight.

Other objects, features and advantages of the invention will be apparent to those skilled in the art from the following description of the preferred embodiments of the invention, wherein reference is made to the accompanying drawings, of which:

FIG. 1 is a section showing a first embodiment of a golf club head of the inveniton.

FIG. 2 is a perspective view showing a first embodiment of a golf club head of the invention.

FIG. 3 is an explanatory section showing a first embodiment of a golf club head of the invention, illustrating a manufacturing method of a golf club head of the invention.

FIG. 4 is a section showing a second embodiment of a golf club head of the invention.

FIG. 5 is a perspective view showing a second embodiment of a golf club head of the invention.

FIG. 6 is a perspective view showing a third embodiment of a golf club head of the invention.

FIG. 7 is a section showing a fourth embodiment of a golf club head of the invention.

FIG. 8 is a perspective view showing a fourth embodiment of a golf club head of the invention.

FIG. 9 is a section showing a fifth embodiment of a golf club head of the invention.

FIG. 10 is a perspective view showing a fifth embodiment of a golf club head of the invention.

FIG. 11 is a section showing a sixth embodiment of a golf club head of the invention.

FIG. 12 is a perspective view showing a sixth embodiment of a golfclub head of the invention.

Hereinafter are described embodiments of the present invention with reference to the drawings. All of the following embodiments relate to so called an "iron" golf club head except a sixth embodiment. As to reference numbers attached to the drawings, the same portions in each embodiment are designated by using common numbers, thus the repeated description will be suitably omitted on or after the description of a second embodiment, while alphabetical small letters are attached to each reference number, thus indicating sequently the number of the embodiment.

In FIGS. 1 to 3 showing a first embodiment of the ivention, a reference numeral 1a designates a face, 2a a back, 3a a sole, 4a a top, 5a a heel, 6a a toe and 7a a neck for conneting a shaft thereto respectively. A golf club head of the embodiment is so-called an iron-type club head, comprising a head body 11a and a balance weight 12a. The head body 11a is made of titanium alloy (the specific gravity approx. 4.5) which forms the aforedsaid face 1a, neck 7a and the like. The weight 12a is made of beryllium copper alloy (the specific gravity approx. 8.2), which forms a part of the back 2a and sole 3a.

Along a peripheral portion of the head body 11a at the back 2a side is formed an annular concave embedding groove 13a, which has an extension groove 14a extending down to the sole 3a. The embedding groove 13a is dovetail-shaped, as designated 15a, tapering in the front-to-back direction. Into the embedding groove 13a is press-fitted the annular weight 12a. Thus, the annular weight 12a is firmly secured to the head body 11a by the mortise/tennon joint. Corresponding to the above structure of the embedding groove 13a, the annular weight 12a has a weight-sole portion 16a at a lower side to be fitted into the extension groove 14a of the embedding groove 13a, thus forming the sole 3a of the head. Likewise, a distal end of the weight 12a is widened, as designated a widened portion 17a to be fitted into the dovetail-shaped portion 15a of the embedding groove 13a, thereby ensuring the firm securing of the head body 11a to the weight 12a.

In a preferred form of the invention, an area on the back 2a surrounded by the annular weight 12a is formed with a concave cavity 18a. Additionally, there is provided an extension recess 19a above said cavity 18a at the back 2a of the head body 11a, which spans across a part of said weight 12a, while there is provided a cover portion 20a contacting an inner surface of the weight 12a, said cover portion 20a being integral with the head body 11a. In addition, above the weight 12a is provided a step-formed recess 21a at the back 2a side of the head body 11a.

Now the method for manufacturing the above-structured golf club head will be described with reference to FIG. 3.

The head body 11a is basically formed by forging process, and either at the same time or after that, the embedding groove 13a is formed by machining. In the same manner, the weight 12a is formed by forging. Then, as illustrated in an arrow, the weight 12a is pressed into the embedding groove 13a of the head body 11a. During such press-in process, the distal end of the weight 12a is subjected to a plastic deformation, thus forming widened portion 17a to be fitted into the dovetail portion 15a of the embedding groove 13a. After the above press-in process, the cavity 18a, the extension recess 19a and the step-formed recess 21a are each formed by milling with the use of a machining center, as shown in a dotted line. At this stage, the amount removed by milling is approximately 20g.

According to the structure shown in a first embodiment, as the weight 12a made of beryllium copper alloy is embedded in the peripheral portion at the back 2a side of the head body 11a made of titanium alloy with the cavity 18a provided in the center of the back 2a thereof, the weight distribution of the whole head can be greately concentrated on the peripheral portion thereof and be shifted backwards relative to the face 1a, with the whole weight of the club head being kept within a regular value, thus greatly enlarging a sweet area. Furthermore, as the weight 12a forms the sole 3a, the center of gravity of the whole head can be positioned still lowerly and backwards. In addition, owing to the extension recess 19a and the step-formed recess 21a each provided at an upper part of the head body 11a, the center of gravity of the whole head can be still lowered, which allows the balls to travel more steadily and easily upward and a longer distance. As a result, a golf club head with which balls can be more easily controlled can be provided.

In addition, as the cavity 18a is formed by machining after the press-fitting of the weight 12a into the embedding groove 13a of the head body 11a, the cover portion 20a of the head body 11a contacting the inner periphery of the weight 12a can be formed thinner, thus enabling the enlarging of the cavity 18a. That is because: assuming that a cavity is pre-formed at the back side of a head body prior to the embedding of a weight, a cover portion between a cavity and an embedding groove must be thickened to a certain degree in terms of its strength.

Accordingly, a cavity cannot be sufficiently enlarged. However, in this embodiment, the cavity 18a can be provided so as to be as close to the weight 12a as you like by machining the same after the press-fitting of the weight 12a. Therefore, such enlargement of the cavity 18a makes the aforesaid weight distribution more effective. Further, the adjustment of the machining position or amount realizes the easy adjustment of the weight distribution of a club head in fabrication.

Incidentally, the same method can be applied to each embodiment described below.

In FIGS. 4 and 5 showing a second embodiment of the invention, a sole 3b is formed by a head body 11b, not by an annular weight 12b. Like a first embodiment, a cavity 18b and a step-formed recess 21b are each machined after the press-fitting of the weight 12b into the head body 11b. Though the center of gravity can be lowered further in accordance with a first embodiment, a second embodiment is advantageous in that as the weight 12b and embedding groove 13b are more simply shaped, they can be more easily machined.

In FIG. 6 showing a third embodiment, both an embedding groove 13c and a weight 12c are each formed semi-annular, which are provided along a sole 3c, heel 5c and toe 6c sides only, not including top 4c side. Thus, the center of gravity of the whole head can be relatively lowered and positioned backwards.

In FIGS. 7 to 8 showing a fourth embodiment of the invention, a weight 12d is divided into four parts at a sole 3d, a top 4d, a heel 5d and a toe 6d sides respectively. Four weights designated at the same numeral are formed tabular respectively. On the other hand, four embedding grooves 13d corresponding to the four weights 12d penetrate from a back 2d of a head body 11d through a face 1d thereof. As shown in FIG. 7, there is provided wedge-shaped portion 31d of each embedding groove 12d adjacent the face 1d side. Each of the wedge-shaped portions 31d has a vertical surface at its back, while it tapers in the back-to-front direction so that a wedge portion 32d at a distal end of the weight 12d may be fitted into the corresponding embedding groove for preventing the weight 12d from being loosened. Further, a cavity 18d provided at a back 2d side of the head body 11d has wide recesses 26d and 33d, thus providing two-step-formed recesses in this embodiment. In fabrication, each weight 12d is press-fitted from the back into each corresponding embedding groove 13d of the head body 11d. At this time, each weight 12d is struck at a support plate (not shown) provided at the face 1d side, whereby the distal end of the weight 12d is subjected to a plastic deformation to form the wedge-shaped portion 32d fitted into each wedge-shaped portion 31d of each embedding groove 13d. The cavity 18d, of course, is machined thereafter.

According to the structure shown in a fourth embodiment, as each weight 12d penetrates from the back 2d through the face 1d, the weight distribution of the club head can be still concentrated upon the peripheral portion relative to the face 1d.

In FIGS. 9 to 10 showing a fifth embodiment of the inventon, nearly a whole portion of a back 2e side of a club head including a sole 3e is constructed by an annular weight 12e. To ensure such structure, an embedding groove 13e for press-fitting of the weight 12e thereinto is step-formed at a peripheral portion of the back 2e side of the head body 11e. In addition, to firmly secure the weight 12e to the head body 11e, there is provided a dovetail groove 36e provided in a bottom surface of the embedding groove 13e, into which is press-fitted a protrusion 37e formed on a front surface of the weight 13e with the same being subjected to a plastic deformation.

Like the foregoing embodiments, a cavity 18e is formed by machining process after the press-fitting of the weight 12e into the head body 11e. However, unlike the foregoing embodiments, the cavity 18e is formed by removing the entire area of the back 2e surrounded by the annular weight 12e, so that there remains no cover portion contacting an inner peripheral surface of the weight 12e descirbed in the foregoing embodiments.

With the structure thus made, as approximately a whole poriton of the back 2e side of the club head is constructed by the annular weight 12e, the center of gravity of the head can be positioned further backward, and the weight distribution thereof can be further concentrated upon its peipheral portion.

In FIGS. 11 to 12 showing a sixth embodiment of the invention, the above-mentioned structures described in the foregoing embodiments are applied to a putter golf club head. In a back 2f adjacent a sole 3f side of a head body 11f are provided two weights 12f, one of which is provided at a heel 5f side, while the other at a toe 6f side. Thereafter, between the weights 12f is formed a cavity 18f.

Incidentally, the present invention should not be limited to the foregoing embodiments, but may be modified within a scope of the invention. For example, the material of the head body may be other metallic material such as aluminium or pure titainium other than titanium alloy. Furthermore, the material of the weights may be comparatively denser metallic material such as copper alloy or stainless steel (the specific gravity approx. 7.9) other than beryllium copper alloy. In addition, any suitable configurations of the whole head may be chosen.