| 摘要 |
A cover replicating the appearance, texture, and surface features of a regulation baseball enclosing a flexible, hollow, spherical core. The core is fabricated from a pair of substantially similar semispherical shells made of a homogeneous, waterproof composition and bonded one to another at the circumferential edges. The composition from which the core is formed includes by weight 30-40 percent styrene butadiene rubber, 16-20 percent natural rubber, 33-37 percent calcium carbonate, and 5-9 percent silica powder, as well as diphenyl guaniden, rubber cure accelerator, and traces of zinc oxide and sulfur. The outer diameter of the core is approximately 2.6-3.0 inches with a wall thicknesses in the range of approximately 0.08-0.16 inches. The core with the cover assembled thereon has a weight of approximately 2.5-3.5 ounces, less than that of a regulation baseball, and an outer diameter substantially equivalent thereto. The cover includes two pieces of synthetic leather secured at the edges with raised herringbone stitching in the pattern of a regulation baseball. Optionally, a layer of twine may be tightly wound in random fashion about the core and the outer cover may be adhered to the structure beneath it using an adhesive. Due to its flexibility and lighter weight in relation to a regulation baseball, the disclosed substitute baseball affords an enhanced margin or safety to young and inexperienced players.
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