Abstract: In a wood club head having a hollow metal shell structure with a double face constituted by a front face and a rear face which is disposed behind the front face through an air gap of predetermined width, there is provided a characteristic that when a golf ball is made to collide with the front face at an entrance speed (head speed) V (m/s), the restitution coefficient of the face is in a range of from 0.84 to 0.88 when the entrance speed V is in a range of from 35 to 40 (m/s), and not lower than 0.80 and lower than 0.83 when the entrance speed V is in a range of from 48 to 53 (m/s).

Abstract: There is disclosed a golf ball including a layer made of a shape memory alloy. For example, fine thread of a shape memory alloy is wound around a core so as to provide a shape memory alloy layer between the core and a cover of the golf ball. In this structure, the shape memory alloy layer provides an effect of tightening the core, thus improving the golf ball's resiliency, resulting an increased travel distance. Moreover, since the shape memory alloy layer has a high specific gravity, the moment of inertia of the golf ball increases, so that the spin and roll performances of the golf ball are improved. Furthermore, the shape memory alloy layer having higher strength and hardness functions as a reinforcement layer of the cover, thereby improving cut resistance and impact durability of the cover.

Abstract: A golf ball has a multiplicity of dimples formed in its surface. It is assumed that the ball has a phantom sphere and spherical surface when the ball surface is free of dimples. A tangent angle .theta. is 5.degree..ltoreq..theta..ltoreq.20.degree. wherein .theta. is defined between a tangent at an arbitrary point on an edge of an individual dimple to the phantom spherical surface and a tangent at that point to the actual ball surface. A percent dimple volume Vr is 0.8%.ltoreq.Vr.ltoreq.1.1% wherein Vr is the sum of the volumes of the entire dimples divided by the volume of the phantom sphere. This dimple design prevents lowering of spin susceptibility by repetitive hits without detracting from the dimple effect of increasing flight distance.

Abstract: A thread-wound golf ball includes a wound core (3) consisting of a center (1) and a thread rubber layer (2) thereon, and a cover (4) having a plurality of dimples (5). The core (3) wherein the thread rubber layer (2) has a thickness of 5 to 9 mm and a larger weight than the center (1) is enclosed in the cover (4) made of an ionomer resin having a thickness of 1 to 2.5 mm and a Shore D hardness of 52 to 68. The ball has an outer diameter of 42.9 to 46 mm. The total volume of dimples is 300 to 400 mm.sup.3. The ball having a relatively large diameter and an increased amount of thread rubber provides an increased flying distance and improved feeling on impact.

Abstract: In a thread-wound golf ball comprising a solid center, a thread rubber layer and a cover, the solid center has a single structure and is continuously increased in hardness from its center to its outer surface such that the difference in hardness between the center and 2 mm inside the outer surface is at least about 4 in JIS C scale hardness. The ball is improved in hitting feel.

Abstract: An electroviscous fluid comprising:1 to 60% by weight of a dispersed phase comprising a fine powder of a silicone resin containing a hydrocarbon group substituted with an amino group or an ammonium group, the fine powder containing 0.1 to 20% by weight of water and having an average particle size of 0.05 to 100 .mu.m; and40 to 99% by weight of a liquid phase comprising an electrically insulating oil having a viscosity at 25.degree. C. of 0.65 to 500 cSt.

Abstract: The inner layer of the core has a diameter of 15-25 mm, a weight of 2-14 grams, a specific gravity of 1.2-4, and a hardness of 55-80 JIS C. The outer layer has a specific gravity lower than that of the inner layer by 0.1-3.0. The cover has a radial thickness of 1.5-2.5 mm.A three-piece solid golf ball comprising a two-piece solid core consisting of inner and outer layers and a cover enclosing the core is improved in durability and flying performance through a proper choice of physical parameters of the core inner and outer layers and the cover.

Abstract: A one-piece golf ball or a core of a multi-layered golf ball is formed from a rubber composition containing a base rubber component in the form of a modified rubber which is prepared by introducing an unsaturated carboxylate group into a polybutadiene rubber. The ball is satisfactorily durable and shows good flying performance.

Abstract: A pressure-sensitive sensor comprises an optical wave guide consisting of a core and a clad, and a light emitting means and a light receiving means each connected to the optical wave guide. The core is made from a transparent material having a refractive index somewhat larger than that of a material constituting the clad and selected from chloroprene rubber, urethane rubber, silicone rubber, fluorine rubber, acrylic rubber, ethylene-propylene rubber, ethylene-propylene-diene terpolymer rubber and epichlorohydrin rubber.

Abstract: A pressure-sensitive sensor comprises an optical wave guide consisting of a core and a clad, and a light emitting means and a light receiving means each connected to the optical wave guide. The core is made from a transparent material having a refractive index somewhat larger than that of a material constituting the clad and selected from chloroprene rubber, urethane rubber silicone rubber, fluorine rubber, acrylic rubber, ethylene-propylene rubber, ethylene-propylene-diene terpolymer rubber and epichlorohydrin rubber.

Abstract: A vulcanizable rubber composition having an excellent adhesive property when vulcanized in contact with metals is obtained by compounding(a) 100 parts by weight of a raw rubber(b) from 0.5 to 10 parts by weight of a vulcanizing agent, and(c) from 0.01 to 1 part by weight (as metal content) of at least one metal compound selected from the class consisting of organic acid salts of titanium and molybdenum and organic complex compounds of titanium, molybdenum and cobalt.The vulcanizable rubber composition thus obtained is not susceptible to the oxidative deterioration in unvulcanized state during the storage.