A tennis ball comprising a hollow core and a cover, the core being formed from a composition including rubber, in which the composition comprises recycled tennis ball material.

A bag for storing tennis balls has an hermetic enclosure formed of flexible material, an opening larger than a tennis ball into the enclosure, the opening having a hermetic sealing zipper by which the opening may be opened and closed, and a flexible tubing from outside the enclosure through the flexible material, the flexible tubing having an open end adapted to engage an air pump, and a one-way valve adapted to admit air into the enclosure and to prevent air from exiting the enclosure through the tubing. Tennis balls placed into the bag are placed under pressure higher than the pressure inside a tennis ball by closing the opening by closing the hermetic sealing zipper, engaging an air pump to the open end of the flexible tubing, and operating the air pump until a predetermined pressure is established in the bag.

An apparatus having a control circuit including a computer processor and a computer memory configured with computer software. The control circuit causes a first test assembly to conduct an initial test of the air pressure within an inner chamber of a first tennis ball; and if the control circuit determines that the air pressure is below a threshold, a pressurization process increases the air pressure inside the inner chamber of the first tennis ball by piercing the outer skin of the first tennis ball with a needle, until a tip of the needle is in the inner chamber, and a first opening, plugged by the needle, is formed in the outer skin of the first tennis ball. The needle tip is thereafter withdrawn from the inner chamber of the first tennis ball, leaving the first opening unplugged and sealant is applied to the first opening to close the first opening.

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.

The aqueous adhesive for a tennis ball includes rubber latex. The rubber latex is a mixture of liquid rubber latex and solid rubber latex. When a solid content in the aqueous adhesive is measured at a temperature of 140° C. by a curelastometer, a torque is not less than 0.26 N.Math.m after 10 minutes from start of heating. The tennis ball includes a seam portion formed of the aqueous adhesive for a tennis ball.

A tennis ball including a non-foamed thermoplastic core defining an internal volume. The core includes a thermoplastic material having a specific gravity of 0.86 to 1.38, a flexural modulus of 2.0 to 50.0 MPa, and a Shore D hardness of 10 to 70. A thickness of the thermoplastic material is between 3.0 and 8.0 mm. The thickness of the thermoplastic material is configured to maintain dimensional stability at internal pressures of between zero and 15 psi.

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 μm and not greater than 50 μm. 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 including a spherical core. The spherical core including an outer surface and a raised wall integrally molded as part of the outer surface.

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.

Biodegradable tennis balls are described. A biodegradable tennis ball includes a core forming a hollow interior chamber, the core made of a blend of a rubber based material, a first petroleum based material, and a first biodegradable additive. The biodegradable tennis ball also includes a felt layer overlaying a surface of the core, the felt layer made of a second blend of a second petroleum based material and a second biodegradable additive. In some cases, the biodegradable tennis ball may include an adhesive layer adhering the felt layer to the core. In some cases, the felt layer may further include wool.