An adhesive for a tennis ball of the present disclosure includes base rubber and a filler. The base rubber contains, as a main component thereof, liquid rubber having a number average molecular weight of not less than 10,000. The filler has an average nitrogen specific surface area of not less than 40 m.sup.2/g. A tennis ball of the present disclosure includes a hollow core made of a rubber material. The core includes two hemispherical half cores. The two half cores are adhered to each other by using the adhesive for a tennis ball.

An adhesive for a tennis ball includes base rubber. The base rubber contains, as a main component thereof, liquid rubber having a number average molecular weight of not less than 10,000. The adhesive has a shear viscosity of not greater than 2,000 Pa.Math.s. A tennis ball includes a hollow core made of a rubber material. The core includes two hemispherical half cores. The two half cores are adhered to each other by using the adhesive for a tennis ball.

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 (μm) of the filler by an average thickness T (μm) 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 δS of the rubber composition and a gas permeability coefficient GPL and a loss tangent tan δL of a rubber composition obtained by replacing the filler with kaolin clay having a degree of flatness DL of 20 satisfy (1): GPL/GPS≥1.02 and (2): |tan δL−tan δS|≤0.03. A tennis ball 2 includes a core 4 formed using the rubber composition.

A sealed plastic container having an airtight chamber. The container includes an elongated body portion having at least one opening and at least one enclosure portion welded to the opening of the body portion, thereby hermetically sealing the chamber. The chamber may have a pressure above atmospheric pressure. The enclosure portion and the body portion may be biodegradable.

Disclosure of the present invention relates to an inverse “L” shaped tennis practice stand or device, which is installed on ground and is considerably higher than a person's height or to a wall-mountable tennis practice device, which is installed via bracket installed at a certain point at a house or building structure. In the tennis practice device according to the present invention, when a trainee hits the ball with a racket (racquet), the ball flies along a circumferential orbit/trajectory with weight or stopper, which is at an end of a horizontal pole, as the center point—that is the ball flies in the skyward direction in front (forward region) of the trainee and then returns to the same circumferential orbit/curve due to gravity, and the trainee practices tennis by repeatedly hitting the ball that falls in front of the trainee.

A DPS (dual pressure system) sport ball incorporating a special, environment friendly casing that forms an exterior surface of the ball, which is bonded to a multiple lining layers to form a laminated sheet. The laminated sheet is sized, printed, and cut out into specifically designed panels using highly optimized and automated specifically developed machines. The panel cut outs are stitched together using a special stitching machine and a specific, compatible bladder is incorporated in the ball. The partially machine stitched ball is then finally closed by manual stitching and the seams are protected with a special adhesive. Resultantly, due to unique construction materials, their unique arrangement, innovative technology, and highly automated manufacturing processes, the DPS sport ball has advantageous durability, playability, controllability and excellent flight characteristics. The DPS sport ball qualifies under the international standards of match/professional balls at a very competitive price.

A tennis ball may include a non-foamed thermoplastic core defining an internal volume, the core having an outer meltable surface. The core may include 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. The thickness of the thermoplastic material may be between 3.0 and 8.0 mm and configured to maintain dimensional stability at internal pressures of between zero and 15 psi. The tennis ball may further include a felt cover at least partially covering the core, wherein the tennis ball conforms to ITF and USTA size, weight, deformation and rebound requirements.

A device (10) including a deformable shell (12) delimiting an inner space (14), and: a resilient band (18, 30, 32) suspended in the inner space (14) and including two ends secured to the deformable shell (12), said band (18, 30, 32) including a piezoelectric material (30, 32) to generate an electric voltage under the effect of the deformation of the shell (12) and two electrodes for collecting the voltage; and an electronic circuit (34) for processing the voltage, arranged on the resilient band (18, 30, 32) and connected to the electrodes of the resilient band (18, 30, 32).

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 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.