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.

An apparatus comprising a practice device for practice of hitting a tennis ball includes a server configured for serving the tennis ball to a user, a net disposed to intercept a flight of the tennis ball after the tennis bell has been hit by the user using a racket and to direct the captured tennis ball back towards the server to be served again to the user, an image detector configured to observe the tennis ball as the tennis ball hurtles towards the net, and a processor. The processor determines, based at least in part on image frames received from the image detector, data indicative of the tennis ball's virtual landing spot. This virtual landing spot is an estimate of where the tennis ball would have landed on an opposing court had the tennis ball not been intercepted by the net.

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 filler having a degree of flatness DL of not less than 50, the degree of flatness DL being obtained by dividing an average particle diameter D.sub.50 (m) of the filler by an average thickness T (m) of the filler. An amount of the filler per 100 parts by weight of the base rubber is not less than 1 part by weight and not greater than 150 parts by weight. A gas permeability coefficient GPS and a loss tangent tan S of the rubber composition and a gas permeability coefficient GPL and a loss tangent tan L of a rubber composition obtained by replacing the filler with kaolin clay having a degree of flatness DL of 20 satisfy (1): GPL/GPS1.02 and (2): |tan Ltan S|0.03. A tennis ball 2 includes a core 4 formed using the rubber composition.

Disclosed herein is a sporting ball with a specific image printed on the sporting ball. The image is generated, selected, or captured by a user, which triggers a process for printing the image onto the ball. Further disclosed are systems and methods for printing and delivering the sporting ball with the image. The image may be an image of the user, a favorite sports athlete, or a celebrity. Certain preferred embodiments utilize a basketball, a soccer ball, or a football. However, alternative embodiments may include any type of sporting ball. The image may be captured by numerous means recognizable by those skilled in the art, including but not limited to a computing device, a cellular phone, a tablet, a web cam, a digital cam, and other traditional non-digital cameras.

An aqueous adhesive for a tennis ball includes rubber latex and a sulfenamide-based vulcanization accelerator. When a solid content in the aqueous adhesive is measured at a temperature of 150 C. by a curelastometer, a 10% torque time t10 is preferably not shorter than 3 minutes and preferably not longer than 15 minutes, and a ratio (t10/t90) of the 10% torque time t10 to a 90% torque time t90 is preferably not less than 0.60 and preferably not greater than 0.95. A tennis ball includes a hollow core obtained by two semi-spherical half cores being adhered by using the aqueous adhesive.

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 core having an inner surface including material shift lines and a textile outer layer over and about the core.

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.