Tennis ball
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.
1. A tennis ball comprising:
a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm, the spherical hollow core has an initial internal pressure of no greater than 5 psi; and
a textile layer covering the spherical hollow core,
wherein the tennis ball has a first tennis ball coefficient of restitution value of at least 0.53 when measured from an initial velocity of 90 feet/second at a first time when the tennis ball is unused, and
wherein the tennis ball has a second tennis ball coefficient of restitution value measured from an initial velocity of 90 feet/second after the tennis ball is exposed to atmospheric pressure for four months following the first time and is unused, and
wherein the second coefficient of restitution value is at least 95 percent of the first coefficient of restitution value.
2. The tennis ball of claim 1 , wherein the spherical core comprises a thermoplastic layer of material underlying the textile layer and comprising one or more thermoplastic ethylene copolymers, each having a specific gravity of less than or equal to 0.9.
3. The tennis ball of claim 2 , wherein the thermoplastic ethylene copolymer has a flexural modulus of less than 35 MPA and a shore D hardness of less than 30.
4. The tennis ball of claim 3 , wherein the thermoplastic ethylene copolymer has a flexural modulus of less than or equal to 25 MPA.
5. The tennis ball of claim 2 , wherein the thermoplastic ethylene copolymer is comprised of ethylene and an alkene.
6. The tennis ball of claim 2 , wherein the ethylene copolymer includes an alkene selected from the group consisting of butane, hexene, octene, pentene, heptene, nonene and decene.
7. The tennis ball of claim 1 , wherein core has a thickness of no greater than 5.1 mm.
8. The tennis ball of claim 1 , wherein the core comprises a thermoplastic layer of material underlying the textile layer and comprising:
at least one rubber selected from a group of rubbers consisting of: natural rubber, polybutadiene, isoprene, styrene-butadiene rubber and mixtures thereof; and
a thermoplastic ethylene copolymer in an amount of within the range of 10 to 100 parts per hundred with a specific gravity of less than or equal to 0.9.
9. The tennis ball of claim 1 , wherein the textile layer comprises a woven fiber material.
10. The tennis ball of claim 1 , wherein the textile layer comprises a needle-punched fiber material.
11. The tennis ball of claim 1 , wherein the tennis ball is a competitive play tennis ball having characteristics that satisfy United States Tennis Association and International Tennis Federation standardized specifications as published by the International Tennis Federation as of Jul. 1, 2018.
12. The tennis ball of claim 1 , wherein the tennis ball has a moment of inertia of less than 1.85 oz in 2 .
13. The tennis ball of claim 1 , wherein the tennis ball has a moment of inertia of less than 1.80 oz in 2 .
14. The tennis ball of claim 1 , wherein the core has a thickness of at least 4.8 mm.
15. The tennis ball of claim 1 , wherein the spherical core comprises a thermoplastic material having a specific gravity of less than or equal to 0.9.
16. The tennis ball of claim 1 , wherein the tennis ball when unused has a first tennis ball deformation, and wherein the tennis ball has a second tennis ball deformation recorded after the tennis ball is exposed to atmospheric pressure for four months and unused, and wherein the second tennis ball deformation is no greater than 0.020 inches from the first tennis ball deformation.