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.

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 overcap for a container for storing at least one tennis ball, the container extending along a longitudinal axis and having an open end. The overcap includes a body adapted for removably attachment to the open end of the tennis ball container. The body includes a peripheral rim for engaging an outer surface of the container at the open end, and a lip projecting from the peripheral rim toward the longitudinal axis. The peripheral lip extends over a portion of the open end of the tennis ball container. The lip defines a first opening.

An overcap for a container for storing at least one tennis ball, the container extending along a longitudinal axis and having an open end. The overcap includes a body adapted for removably attachment to the open end of the tennis ball container. The body includes a peripheral rim for engaging an outer surface of the container at the open end, and a lip projecting from the peripheral rim toward the longitudinal axis. The peripheral lip extends over a portion of the open end of the tennis ball container. The lip defines a first opening.

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.

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 improved and safer opening mechanism for a pressurized container is provided that includes a synchronous relationship between a safety cap and a sealable plate, such that the safety cap covers the sealable plate when it is removed from the container.

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 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.

The disclosure relates to a sealed pressure container, which solves the problem in the prior art that a pump is required for providing air pressure in the container. The conventional product is inconvenient for carrying and is expensive. The sealed pressure container includes a body and a winding member. The body has an open end and a flexible portion, the flexible portion is at least one part of the body at one side where the open end is formed. The flexible portion can be wound around the winding member from the open end to provide air pressure in the body by compressing the air inside the body. Thus, without using a pump, tennis balls can be prevented from releasing pressure by keeping in the low-cost sealed pressure container. The sealed pressure container is convenient for carrying and operating and has reduced manufacture cost.