Cores for tennis balls
AssigneeDunlop Limited
InventorsRobert C. Haines, John G. Schofield
Life of this patent
Estimating the term…
Abstract
A core for a tennis-ball, the tennis-ball having either an internal pressure substantially equal to atmospheric pressure (a "pressureless" ball) or an internal pressure of up to 7 p.s.i. (0.49 Kg.cm.sup.-2) above atmospheric pressure (a "low-pressure" ball), in which the core is made from a rubber composition wherein up to 60% by weight of the total polymer content comprises either a copolymer of ethylene and propylene (an EPM elastomer) or a terpolymer of ethylene, propylene and up to 12% by weight of a non-conjugated diene monomer (an EPDM elastomer). The most suitable EPM and EPDM elastomers are those containing 70 mole percent or more ethylene.
Claims4
A core for a tennis ball, said tennis ball having either an internal pressure substantially equal to atmospheric pressure (a "pressureless" ball) or an internal pressure of up to 7 psi (0.49 kg.cm.sup.-2) over atmospheric pressure (a "low pressure" ball), said core being made from a composition based upon (1) a polymer selected from the group consisting of natural rubber and synthetic rubbers and (2) an effective amount of up to 60% by weight of said polymer of either an elastomeric copolymer of ethylene and propylene (EPM elastomer) or an elastomeric terpolymer of ethylene, propylene, and up to 12% by weight of said terpolymer of a non-conjugated diene monomer (EPDM elastomer), said EPM or EPDM elastomer having, in gum form, an ethylene content of at least 70 mole percent, a Tripsometer Resilience of at least 55% (21.degree. C.), a Shore A Hardness of at least 55, and a Mooney Viscosity (ML 1+4 at 100.degree. C.) of at least 60, said EPM or EPDM elastomer being present in an amount sufficient to improve the rebound and compression properties of a tennis ball as compared to a tennis ball that does not contain an effective amount of said EPM or EPDM elastomer in its core.
A tennis ball having a core and a cover therefor, said core being made from a rubber composition based upon (1) a polymer selected from the group consisting of natural rubber and synthetic rubbers and (2) an effective amount of up to 60% by weight of said polymer of either an elastomeric copolymer of ethylene and propylene (EPM elastomer) or an elastomeric terpolymer of ethylene, propylene, and up to 12% by weight of a non-conjugated diene monomer (EPDM elastomer), said EPM or EPDM elastomer having, in gum form, an ethylene content of at least 70 mole percent, a Tripsometer Resilience of at least 55% (21.degree. C.), a Shore A Hardness of at least 55, and a Mooney Viscosity (ML 1+4 at 100.degree. C.) of at least 60, said EPM or EPDM elastomer being present in an amount sufficient to improve the rebound and compression properties of a tennis ball as compared to a tennis ball that does not contain an effective amount of said EPM or EPDM elastomer in its core.
Dependencies are inferred from the claim text.