Abstract:
The present invention provides a golf club head at least the face portion of which is composed of composite materials characterized by aluminum or aluminum alloy either of which are combined with ceramics which are powdery. The golf club head has high strength, high hardness, high elasticity and a good wear resistance, and the face portion of the golf club head of the present invention shows little wear so that the durability of the club head is remarkably high. Moreover, by this invention it is easy to produce a large quantity of golf club heads so that the cost of production is largely diminished and so that a golf club head which is more practical is now available.

Description:
This application is a continuation of Ser. No. 07/162,712, filed 03/01/88, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to an improvement of a golf club head whose face portion is composed of composite materials of aluminum or aluminum alloy either of which are combined with ceramics. 
     2. Description of the Prior Art 
     Heretofore, several golf club head materials have been used and such golf club heads are produced by using several methods. For example, it is common that the cutting and processing of wood including persimmon is used and that synthetic resins for example ABS resin, etc., are inserted in the face portion, and that metals, for example aluminum, brass and stainless steel, are used for the sole portion of the club head. Also, golf club heads made from aluminum alloy formed by casting, stainless steel forming and as others, graphite fiber (carbon fiber) reinforced plastics (C-FRP) by compression moulding and whisker strengthened aluminum alloy (FRM) by the squeeze casting are known to the public. 
     SUMMARY OF THE INVENTION 
     However, materials of golf club heads heretofore in use have the following defects: 
     In the case of persimmon, the strength, wear resistance and hardness of the club heads are low and have inferior durability. Also the cost of materials is high and they are not of uniform quality since persimmon is a natural material. Moreover, the wood has high moisture absorption and lacks dimensional stability. 
     In the case of C-FRP, carbon fiber is considerably expensive and so the total price of the golf club is high. Moreover carbon fiber is liable to peel off from the synthetic resin which forms the matrix causing separation and the wear resistance of the golf club head is inferior, so that carbon fiber has bad durability in practical use. 
     In the case of stainless steel, the shape of the golf club head has to be made smaller since the specific gravity of stainless steel is high, and a large quantity production of golf club heads is unsuitable because the method of production of a golf club head is of the batch type. Moreover its vibration damping property is inferior and its sound when striking the golf ball is metallic and is not good. 
     In the case of aluminum alloy, the durability of the golf club head is inferior because the modulus of elasticity and repulsive force are small. Moreover strength, wear resistance and hardness of the golf club head are low. 
     In the case of FRM, the whisker material is very expensive and aluminum molten metal must be impregnated into the sponge shaped whisker at high pressure in the method of its production. The sponge shaped whisker is broken upon the impregnation with aluminum molten metal and so the whisker is unevenly distributed and badly dispersed. Moreover whisker itself has strong directional properties and in order to control this directional property, extrusion moulding or forging is necessary and so the method of production or shape of the golf club head is greatly limited. 
     The present invention cures the above-described defects of the golf club head heretofore in use. 
     It is therefore an object of the present invention to produce a golf club head which has high strength, high hardness, high elasticity and good wear resistance. 
     Another object of the present invention is to provide a golf club head which is capable of large quantity production. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of the wood type golf club head 1 of the present invention, 2 being the face portion. 
     FIGS. 2 to 5 are enlarged sectional views of the present invention which show the appearance of the edge portion 4 of the face lines after a field test. 
     FIG. 2 shows good appearance. FIG. 3 shows wear. FIG. 4 shows a break. FIG. 5 is a typical example of the deformation of the golf club head. 
     FIG. 6 is a microscopic photograph (×100) of this invention showing the structure of the composite material composed of Al or Al-alloy either of which are combined with ceramics. In the microscopic photograph, the large particles indicate Al or Al-alloy and the small powders between Al or Al-alloy are ceramics combined with Al or Al-alloy. 
     FIG. 7 is a bottom plan view showing the sole plate 3 and bottom surface 5 of an embodiment of the golf club head of the present invention. 
     FIGS. 8-11 are flow diagrams of the sequential operational steps for preparing a golf club head according to the present invention as described in Examples 1-4, respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One embodiment of the golf club head of the present invention is shown in the drawings. 
     The present invention employs the composite material the constituents of which are aluminum or aluminum alloy either of which are combined with ceramics and said ceramics are powdery. By using composite materials in the face portion 2 of the golf club head as is shown by the photograph of FIG. 6, the problems concerning the materials of golf club heads heretofore in use can be solved. 
     This is due to the fact that the composite material of the present invention is composed of high strength, high hardness ceramics added to the aluminum or aluminum alloy and is characterized by the fact that the elasticity, strength, wear resistance and hardness of the golf club head is raised greatly, while the specific gravity is similar to aluminum or aluminum alloy. 
     EXAMPLE 1 
     Aluminum Powder of mean grain diameter 50 μm (purity 99.7%): Alumina of mean diameter 20 μm and whisker of silicon carbide of mean diameter 0.5 μm and mean length 70 μm=1:1 (volume ratio) is blended uniformly at the rate shown in Table 1, and after blending a face portion only is formed at a temperature of 600° C. and a pressure of 1 ton/cm 2 . 
     The above formed face portion is inserted to the mold by using a die casting machine, and then molten aluminum alloy is die casted by insert casting to thus form a golf club head itself which face portion is made from composite materials by casting with molten aluminum alloy, and the temperature of the molten metal is 700° C. and the pressure is 400 Kg/cm 2 . 
     EXAMPLE 2 
     Aluminum Alloy, less than 250 mesh powder (A7075): mean diameter 5 μm silicon nitride and 20 mm length pitch system graphite fiber=9:1 (volume ratio) is blended uniformly at the rate shown in Table 1, and after blending there is obtained a 150 mmφ×length 200 mm green compact by moulding and its moulding pressure is 1 ton/cm 2 . Said green compact is then heated at 480° C. and a 50 mmφ×length 1,300 mm stick formed of composite materials is obtained by hot extruder. Its pressure 850 Kg/cm 2 . 
     Said stick formed composite material is cut to a size of 50 mmφ×length 100 mm and is formed into a golf club head itself by a hot forging machine. 
     EXAMPLE 3 
     Silicon carbide having a mean grain diameter of 7 μm is added to 700° C. molten aluminum alloy at the rate shown in Table 1. 
     After these are agitated throughly by an agitator made from a fireproof material, a golf club head itself and a sole plate are formed at the same time by using a die casting machine. Its compacting pressure is 800 Kg/cm 2 . 
     EXAMPLE 4 
     Silicon carbide having the mean grain diameter as is indicated in Table 1 is added to molten aluminum alloy at a temperature of 700° C. and a golf club head itself and a sole plate are formed at the same time by the same method as 
     EXAMPLE 3 
     Blank Test 
     The inventors made Blank Tests employing the following club heads: 
     1. Head made from Aluminum Alloy (ADC12) only. 
     2. Head made from persimmon using ABS resin on the face portion. 
     3. Head made from C-FRP. 
     4. Head made from stainless steel. 
     The weight of the head, loft angle, lie angle and the number of face lines and sectional form are unified with each other and the shafts are provided with the same weight and same hardness. 
     The following tests were carried out with the samples of Examples 1-4 and the Blank Tests. 
     Test No. 1 (Wear Test) 
     The wear test was made by using a 3 mm×20 mm×40 mm plate which was cut off from the face portion, the specific wear quantity was obtained and the results are shown in Table 2. 
     The wear test was made with the Ogoshi type tester. Testing conditions were as follows: 
     Turntable SKH3 (H R  C60) was used; wear distance 100 m, weight 6.3 Kg, wear speed 3.5 m/sec. 
     
                       TABLE 1______________________________________Blending Ratio (Volume Ratio (%)Test No.   Metals       Ceramics______________________________________                Al.sub.2 O.sub.3 Particle/SiCExample 1   Al Powder    Whisker = 1/1 1        99.5       0.5 2      99           1 3      70           30 4      50           50 5      45           55Example 2   Al Alloy Powder                Si.sub.3 N.sub.4 Particle/CF = 9/1 6        99.5       0.5 7      99           1 8      70           30 9      60           4010      50           50Example 3   Molten Al Alloy                SiC Particle11        99.5       0.512      99           113      70           3014      60           4015      50           50Example 4   Molten Al Alloy                SiC Particle16      80            20 mean grain diameter 0.01 μm17      80           20 mean grain diameter 0.5 μm18      80           20 mean grain diameter 5 μm19      80           20 mean grain diameter 65 μm20      80           20 mean grain diameter 500 μm21      80           20 mean grain diameter 580 μ mBlank Test    Materials101      Aluminum Alloy (ADC12)102      Persimmon (it is used with ABS as face portion)103      C-FRD104      Stainless Steel______________________________________ Note: CF is a graphite fiber 
    
     
                       TABLE 2______________________________________(Results of Wear Test)Test No.   Specific Wear (×10.sup.-7 mm.sup.2 /Kg)______________________________________ 1         18 2         9 3         5 4         2 5         0.5 6         21 7         9 8         6 9         210         0.811         1812         713         414         215         0.416         317         318         519         720         921         9Blank Test101        60102        528103        10104        32______________________________________ 
    
     Test No. 2 (Field Test) 
     Field tests were conducted by a striking of the ball 2,000 times. The distance of travel of the ball, shot sound and the surface condition of the face portion of the club after the test were investigated and the results are shown in Table 3. 
     In the present invention, it is possible that the face insert be made from composite materials composed of ceramics made separately and fixed to the golf club head itself. Moreover, not only the face portion but also the boundary line of the face portion to the sole portion is continuously formed or the face portion and the sole portion are formed with one material (no drawing) and consequently wear, break and gap of the boundary layer are prevented. 
     It is possible to use as the ceramics material B 4  C, BN, ZrO 2 , TiC, WC, SiO 2 , MgO, TiO 2 , Y 2  O 3 , Cr 2  O 3 , CrC 2 , AlN, TiN, ZrB 2 , TiB 2 , Sialon, etc. or a mixture of over two of these compounds including ceramics material used in Example 1-4. 
     Mean grain diameters of these ceramics are 0.01 μm to 500 μm and it is unsuitable to the present invention to use ceramics whose mean grain diameters are less than 0.01 μm or over 500 μm. Wear resistance, hardness and elastic property are inferior in both cases. 
     According to the present invention, in golf club heads whose face portions are at least composed of the composite materials, the wear resistance of the face portion became higher. This is because high strength and high hardness ceramics are added as a strengthening material, and therefore it is recognized that wear of the edge of the face line does not occur and the amount of back spin is always constant in the field tests. Also the undesirable metallic shot sound which is a defect of the so-called metal wood is not heard. The natural shot sound is heard due to the better damping capacity in the interface of aluminum or aluminum alloy either of which are combined with ceramics. 
     
                       TABLE 3______________________________________Results of field test  SURFACETEST   APPEARANCE                  SHOTNO.    OF FACE PORTION  DISTANCE   SOUND______________________________________ 1.    WEAR OCCURS      ⊚ 2.    GOOD             ⊚                              ⊚ 3.    GOOD             ⊚                              ⊚ 4.    GOOD             ⊚                              ⊚ 5.    EDGE PORTION                ⊚  WAS BROKEN 6.    WEAR OCCURS      ⊚ 7.    GOOD             ⊚                              ⊚ 8.    GOOD             ⊚                              ⊚ 9.    GOOD             ⊚                              ⊚10.    EDGE PORTION                ⊚  WAS BROKEN11.    WEAR OCCURS      ⊚12.    GOOD             ⊚                              ⊚13.    GOOD             ⊚                              ⊚14.    GOOD             ⊚                              ⊚15.    EDGE PORTION                ⊚  WAS BROKEN16.    GOOD             ⊚17.    GOOD             ⊚                              ⊚18.    GOOD             ⊚                              ⊚19.    GOOD             ⊚                              ⊚20.    GOOD             ⊚                              ⊚21.    CRACKS OCCUR                ⊚BLANKTEST101.   WEAR OCCURS      Δ    Δ102.   CORNERS OF EDGE             ⊚  PORTION WERE  DEFORMED103.   WEAR OCCURS104.   WEAR OCCURS      ⊚                              X______________________________________ NOTE:  ⊚ ; VERY GOOD. ; GOOD. Δ; ORDINARY. X; INFERIOR. 
    
     Moreover, although the present invention is in the application and improvement of the known art, in the manufacturing processes of a golf club head the following steps are involved, as is illustrated by Example 1 to 3: 
     (1) hot press→insert casting 
     (2) extruding→forging 
     (3) die casting and ordinary powder metallurgy, casting, plastic processing 
     The manufacturing equipment heretofore in use are used in connection with this invention. Also the present invention is suitable for large quantity production. Thus the production costs of the composite materials which heretofore has been highly expensive can be reduced greatly and it is possible to make practical use of these composite materials. 
     In the present invention, the so-called wood type club head is illustrated, but the present invention is not limited to a wood type club head but is also applicable to the iron type club head or putter type club head.