A tennis ball including a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm, and a textile layer covering the spherical elastomeric hollow core. The spherical hollow core has an initial internal pressure of no greater than 5 psi. The tennis ball has a first tennis ball rebound height when measured at a first time when the tennis ball is unused and a second tennis ball rebound height measured after the tennis ball is exposed to atmospheric pressure for four months following the first time and is unused. The second tennis ball rebound height being at least 96% of the first tennis ball rebound height.

A rubber composition for a hollow ball includes a base rubber, an inorganic filler composed of a large number of flat particles, and a carbon-based filler. As to the carbon-based filler, a degree of flatness DLc obtained by dividing an average particle diameter D.sub.50.sup.c (m) by an average thickness Tc (m) is not less than 50. A weight ratio Mc/Mi is not less than 0.01 and not greater than 1.00. The rubber composition is obtained by a production method including: a first step of mixing the base rubber and the carbon-based filler to obtain a master batch; and a second step of adding the large number of flat particles that form the inorganic filler, to the master batch to orient the large number of flat particles. The hollow ball 2 includes a core 4 formed from the rubber composition.

A rubber composition for a hollow ball includes a base rubber, an inorganic filler composed of a large number of flat particles, and a carbon-based filler. As to the carbon-based filler, a degree of flatness DLc obtained by dividing an average particle diameter D.sub.50.sup.c (m) by an average thickness Tc (m) is not less than 50. A weight ratio Mc/Mi is not less than 0.01 and not greater than 1.00. The rubber composition is obtained by a production method including: a first step of mixing the base rubber and the carbon-based filler to obtain a master batch; and a second step of adding the large number of flat particles that form the inorganic filler, to the master batch to orient the large number of flat particles. The hollow ball 2 includes a core 4 formed from the rubber composition.

A tennis ball may include a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm and a textile layer covering the spherical hollow core.

A tennis ball may include a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm and a textile layer covering the spherical hollow core.

Described are balls, in particular a football, and a method for its manufacture. The ball comprises particles of an expanded material. As examples, the particles are connected, at least partially, to each other by radio frequency welding and/or infrared welding. As examples, the ball has a first layer of the particles of the expanded material, wherein the first layer is provided as an outer shell.

An improved and safer opening mechanism for a pressurized container is provided that includes a synchronous relationship between a safety cap and a sealable plate, such that the safety cap covers the sealable plate when it is removed from the container.

A rubber composition for a tennis ball includes a base rubber and a high-flatness filler. The high-flatness filler has an average particle diameter D.sub.50 of not less than 1 m and not greater than 50 m. A degree of flatness DL is not less than 40 and not greater than 200. An amount of the high-flatness filler per 100 parts by weight of the base rubber is not less than 5 parts by weight and not greater than 100 parts by weight. A ratio (E2/E1) of a tensile elastic modulus E2 in a tensile strain range from 70% to 100% to a tensile elastic modulus E1 in a tensile strain range from 10% to 30%, of a vulcanized rubber obtained by vulcanizing the rubber composition, is not less than 0.60 and less than 1.00. The tennis ball includes a hollow core formed from the rubber composition.

A rubber composition for a tennis ball includes a base rubber and a high-flatness filler. The high-flatness filler has an average particle diameter D.sub.50 of not less than 1 m and not greater than 50 m. A degree of flatness DL is not less than 40 and not greater than 200. An amount of the high-flatness filler per 100 parts by weight of the base rubber is not less than 5 parts by weight and not greater than 100 parts by weight. A ratio (E2/E1) of a tensile elastic modulus E2 in a tensile strain range from 70% to 100% to a tensile elastic modulus E1 in a tensile strain range from 10% to 30%, of a vulcanized rubber obtained by vulcanizing the rubber composition, is not less than 0.60 and less than 1.00. The tennis ball includes a hollow core formed from the rubber composition.

A tennis ball may include a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm and a textile layer covering the spherical hollow core