TECHNICAL FIELD
[0001] The present invention relates to methods for increasing the internal pressures of
hollow balls such as a regulation tennis ball, a soft tennis ball, and the like, and
apparatuses therefor.
BACKGROUND ART
[0002] In order to obtain appropriate elasticity of hollow balls such as a regulation tennis
ball, a soft tennis ball, and the like, the internal pressures of the balls are kept
higher than the atmospheric pressure. For example, the internal pressure of a regulation
tennis ball is set to be about 1.6 times to 1.9 times of the atmospheric pressure.
If a ball has an internal pressure higher than this, a user feels that the ball is
too hard or flies too far. If a ball has an internal pressure lower than this, the
user feels that the ball is too soft or has insufficient resilience. A hollow ball
needs to be manufactured such that the internal pressure thereof has an appropriate
value, and the internal pressure of the manufactured ball needs to be kept in an appropriate
range.
[0003] In order to increase the internal pressure of a ball, for example, in manufacturing
a regulation tennis ball, there are a case where a method of generating gas by a chemical
reaction is used and a case where air is compressed and injected. The ball includes
a core which is a hollow sphere made of rubber; and two felt portions (also referred
to as "melton") which cover the surface of the core. The core is obtained by attaching
together two half shells. In the case where the internal pressure is increased by
a chemical reaction, prior to attaching together the two half shells, a tablet of
ammonium chloride, a tablet of sodium nitrite, and water (or aqueous solutions thereof)
are put into the core. In crosslinking the core, they are heated, so that ammonium
chloride and sodium nitrite cause a chemical reaction. Nitrogen gas is generated by
the chemical reaction. The internal pressure of the core is increased by the nitrogen
gas.
[0004] In a ball having an internal pressure higher than the atmospheric pressure, the gas
within the ball passes through an outer shell to come out of the ball due to the difference
between the internal pressure and the atmospheric pressure. That is, even when a ball
is manufactured so as to have an appropriate internal pressure, the internal pressure
decreases over time. For example, when a regulation tennis ball is left in the atmospheric
pressure for about two months, the internal pressure thereof decreases to such a degree
that a user recognizes the decrease in the internal pressure.
[0005] Results of examination of storage containers for suppressing a decrease in the internal
pressures of tennis balls are disclosed in
JP7-155406,
JP7-187252, and
JP8-89600. These storage containers are all airtight containers. After tennis balls are stored
in these containers, the air pressures within the containers are increased to a pressure
equal to or higher than the atmospheric pressure. By decreasing the difference between
the internal pressure of each tennis ball and the air pressure of each container outside
the tennis ball, a speed at which the gas within the ball passes through an outer
shell can be decreased. By eliminating the difference between the internal pressure
of each tennis ball and the air pressure of the container, the gas within the ball
does not come out. In other words, the internal pressure of the tennis ball does not
decrease. By making the air pressure of the container higher than the internal pressure
of the tennis ball, the internal pressure of each tennis ball can be increased reversely.
CITATION LIST
PATENT LITERATURE
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0007] Regarding each of the storage containers in
JP7-155406,
JP7-187252, and
JP8-89600, while balls are stored in the container, a decrease in the internal pressure of
each ball can be suppressed. However, when these balls are taken out from the container,
the balls are exposed to the atmospheric pressure, and the internal pressure of each
ball decreases. When each ball is used, the internal pressure thereof further quickly
decreases. Then, once the internal pressure of each ball decreases, it is difficult
to restore the internal pressure of the ball with these storage containers. As described
above, theoretically, if the air pressure within the container is made higher than
the internal pressure of the ball, the internal pressure of the ball is restored.
However, for example, even if a regulation tennis ball whose internal pressure has
decreased by 10% is put into a container filled with air pressurized to a pressure
which is about 2.5 times of the atmospheric pressure, it takes about one month to
two months to restore the internal pressure. By increasing the air pressure within
the container, the restoring speed can be increased. However, an expensive pressure
container is required. Eventually, a regulation tennis ball whose internal pressure
has decreased is thrown away, even when the felt portions of the ball are in a usable
condition.
[0008] A soft tennis ball includes a valve for restoring a decreased internal pressure thereof.
By supplying air through the valve with a dedicated air pump, the internal pressure
is restored. However, the valve is thicker and harder than rubber surrounding the
valve, and thus may be broken during use. The valve impairs the durability of the
ball. In addition, if the valve hits against a racket when the ball is hit with the
racket, the hit ball becomes unstable. Furthermore, it is necessary to supply air
into balls one by one, and thus it takes much time and effort to restore the internal
pressures of the balls.
[0009] An object of the present invention is to provide a method for easily increasing the
internal pressure of a hollow ball in a practical time.
SOLUTION TO THE PROBLEMS
[0010] A method for increasing an internal pressure of a hollow ball according to the present
invention includes the steps of:
- (1) putting a hollow ball including an outer shell and a space surrounded by the outer
shell, into a housing portion;
- (2) filling the housing portion with a gas which is more excellent in permeability
relative to the outer shell than oxygen gas and nitrogen gas; and
- (3) causing the gas to pass through the outer shell.
[0011] When the outer shell contains natural rubber, preferably, in the step (2), the housing
portion is filled with a gas having a permeability coefficient of 20 × 10
-17 m
4/ (N·s) at 25°C for the natural rubber.
[0012] Preferably, in the step (2), the housing portion is filled with carbon dioxide gas
or a gaseous mixture of carbon dioxide gas and air.
[0013] Preferably, the method further includes, between the steps (1) and (2), a step (4)
of discharging air within the housing portion.
[0014] Preferably, a temperature within the housing portion in the step (3) is not lower
than 35°C and not higher than 60°C.
[0015] Preferably, a difference between an internal pressure of the housing portion and
an atmospheric pressure immediately after end of the step (2) is equal to or lower
than 1.84 kgf/cm
2.
[0016] Preferably, the difference between the internal pressure of the housing portion and
the atmospheric pressure immediately after the end of the step (2) is equal to or
lower than 0.9 kgf/cm
2.
[0017] Preferably, a partial pressure of the air within the housing portion immediately
after the end of the step (2) is higher than the atmospheric pressure.
[0018] Preferably, the difference between the internal pressure of the housing portion and
the atmospheric pressure immediately after the end of the step (2) is equal to or
lower than 0.1 kgf/cm
2.
[0019] Preferably, the housing portion is a bag formed from a resin composition.
[0020] Preferably, a ratio (Vg/Vb) of a volume Vg of the gas with which the housing portion
is filled in the step (2), relative to a sum Vb of capacities of all hollow balls
put into the housing portion in the step (1), is equal to or greater than 1.0.
[0021] The housing portion may be a container formed from a metal.
[0022] An apparatus for increasing an internal pressure of a hollow ball according to the
present invention includes: a housing portion into which a hollow ball including an
outer shell and a space surrounded by the outer shell can be put; and a feed portion
configured to feed a gas to the housing portion. The gas is more excellent in permeability
relative to the outer shell than oxygen gas and nitrogen gas.
[0023] A soft tennis ball according to the present invention has an internal pressure which
is increased by a method for increasing an internal pressure, the method including
the steps of:
- (1) putting a soft tennis ball into a housing portion;
- (2) filling the housing portion with a gas which is more excellent in permeability
relative to an outer shell of the soft tennis ball than oxygen gas and nitrogen gas;
and
- (3) causing the gas to pass through the outer shell of the soft tennis ball.
The soft tennis ball does not include a valve.
[0024] A housing container for a method for increasing an internal pressure of a hollow
ball according to the present invention includes a main body and an opening/closing
tool mounted to the main body. The main body includes therein an intake port for feeding
gas into an interior thereof and an exhaust port for discharging gas from the interior
thereof. A portion of the main body is capable of being opened/closed by the opening/closing
tool. When the portion of the main body is opened, a hollow ball can be taken in and
out through an opening of the portion; and when the portion of the main body is closed,
the main body enters an airtight state.
[0025] Preferably, the main body is composed of nylon.
[0026] Preferably, the opening/closing tool is an airtight fastener.
[0027] Preferably, the intake port is located below the exhaust port.
[0028] Preferably, when a height from a lower end of the main body to a center of the exhaust
port is denoted by Ho, a ratio (Ho/H) of the height Ho relative to a height H of the
main body is equal to or greater than 90%.
[0029] Preferably, when a height from the lower end of the main body to a center of the
intake port is denoted by Hi, a ratio (Hi/H) of the height Hi relative to the height
H of the main body is equal to or less than 10%.
[0030] The housing container may further include a hose. Within the main body, the hose
is mounted to the main body such that an opening of a first end of the hose overlaps
the intake port. A second end of the hose is located below the exhaust port.
[0031] Preferably, when a height from the lower end of the main body to the second end of
the hose is denoted by Hh, a ratio (Hh/H) of the height Hh relative to the height
H of the main body is equal to or less than 10%.
[0032] Preferably, the housing tool further includes, within the main body, a frame for
reinforcing the main body.
[0033] A pressure container for a method for increasing an internal pressure of a hollow
ball according to the present invention includes: a housing portion configured to
house a hollow ball; and a heater configured to heat the housing portion. The housing
portion includes: a trunk portion having an input port through which the hollow ball
is taken in and out; a lid configured to cover the input port; and an intake port
through which a gas is fed into an interior of the housing portion.
[0034] Preferably, the heater is mounted on an outer side of the housing portion.
[0035] The heater may be mounted within the housing portion.
[0036] Preferably, each of the trunk portion and the lid is formed from a metal.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0037] In the method for increasing an internal pressure of a hollow ball according to the
present invention, the housing portion in which the hollow ball is housed is filled
with a gas having a higher permeability relative to the outer shell of the hollow
ball than those of oxygen gas and nitrogen gas. A speed at which the gas enters from
the housing portion into the interior of the ball is higher than a speed at which
air enters into the interior of the ball. Thus, the internal pressure of the hollow
ball can be increased in a short time as compared to a conventional method for filling
a container with air. According to this method, it is possible to easily reuse a ball
whose internal pressure has decreased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038]
[FIG. 1] FIG. 1 is a conceptual diagram showing an apparatus for a method for increasing
the internal pressure of a hollow ball according to an embodiment of the present invention.
[FIG. 2] FIG. 2 is a conceptual diagram showing an apparatus for a method for increasing
the internal pressure of a hollow ball according to a second embodiment of the present
invention.
[FIG. 3] FIG. 3 is a conceptual diagram showing an apparatus for a method for increasing
the internal pressure of a hollow ball according to a third embodiment of the present
invention.
[FIG. 4] FIG. 4 is a perspective view of a housing container for a method for increasing
the internal pressure of a hollow ball according to an embodiment of the present invention.
[FIG. 5] FIG. 5 is a perspective view of a housing container for a method for increasing
the internal pressure of a hollow ball according to another embodiment of the present
invention.
[FIG. 6] FIG. 6 is a conceptual diagram showing a state where the housing container
in FIG. 5 is used.
[FIG. 7] FIG. 7 is a perspective view showing a state where a housing container for
a method for increasing the internal pressure of a hollow ball according to still
another embodiment of the present invention is used.
[FIG. 8] FIG. 8 is a perspective view of a housing container for a method for increasing
the internal pressure of a hollow ball according to still another embodiment of the
present invention.
[FIG. 9] FIG. 9 is a conceptual diagram showing a state where the housing container
in FIG. 8 is used.
[FIG. 10] FIG. 10 is a front view of a pressure container for a method for increasing
the internal pressure of a hollow ball according to an embodiment of the present invention.
[FIG. 11] FIG. 11 is a right side view of the pressure container in FIG. 10.
[FIG. 12] FIG. 12 is a plan view of the pressure container in FIG. 10.
[FIG. 13] FIG. 13 is a portion of a cross-sectional view taken along a line XIII-XIII
in FIG. 12.
DESCRIPTION OF EMBODIMENTS
[0039] The following will describe in detail the present invention based on preferred embodiments
with appropriate reference to the drawings.
[0040] FIG. 1 shows an apparatus 2 for a method for increasing the internal pressure of
a hollow ball according to an embodiment of the present invention. The apparatus 2
includes a pressure container 4, a vacuum pump 6, a gas cylinder 10, an exhaust pipe
12, and an intake pipe 14.
[0041] The pressure container 4 houses hollow balls 18 each of which includes an outer shell
and a space surrounded by the outer shell. The pressure container 4 is typically made
from a metal. The pressure container 4 may be made of a resin composition. The pressure
container 4 is kept airtight.
[0042] The pressure container 4 includes a main body 20 and a lid 22. The main body 20 has,
at an upper portion thereof, an input port 24 for putting in the hollow balls 18 therethrough.
The lid 22 is provided with an intake hole 26 and an exhaust hole 28. The exhaust
hole 28 extends through the lid 22. One end of the exhaust pipe 12 is passed through
the exhaust hole 28. The other end of the exhaust pipe 12 is connected to the vacuum
pump 6. The pressure container 4 and the vacuum pump 6 are connected to each other
by the exhaust pipe 12.
[0043] The intake hole 26 of the pressure container 4 extends through the lid 22. One end
of the intake pipe 14 is passed through the intake hole 26. The other end of the intake
pipe 14 is connected to the gas cylinder 10. The pressure container 4 and the gas
cylinder 10 are connected to each other by the intake pipe 14.
[0044] The vacuum pump 6 sucks the gas within the pressure container 4 through the exhaust
pipe 12. The interior of the pressure container 4 can be substantially evacuated by
the vacuum pump 6.
[0045] The gas cylinder 10 has stored therein a gas to be fed into the pressure container
4. The gas is more excellent in permeability relative to the outer shell of each hollow
ball 18 than oxygen gas and nitrogen gas. The gas cylinder 10 feeds the stored gas
through the intake pipe 14 into the pressure container 4. The gas cylinder 10 can
cause the pressure of the gas within the pressure container 4 to be equal to or higher
than the atmospheric pressure.
[0046] A compressor may be provided between the gas cylinder 10 and the pressure container
4. The compressor is used when the pressure in the gas cylinder 10 is not sufficient
to increase the pressure in the pressure container 4. The compressor increases the
pressure of the gas from the gas cylinder 10 and feeds the gas into the pressure container
4.
[0047] In a method for increasing the internal pressures of the hollow balls 18 according
to the present invention, in an initial step, the hollow balls 18 are put into the
pressure container 4, and, in addition, the air within the pressure container 4 is
discharged. In this step, the intake pipe 14 is closed, and the pressure container
4 is kept airtight. The vacuum pump 6 is operated, and the air within the container
is discharged through the exhaust pipe 12. When the interior of the container becomes
substantially evacuated, the operation of the vacuum pump 6 is stopped.
[0048] In the next step, the pressure container 4 is filled with the gas. The gas from the
gas cylinder 10 is fed through the intake pipe 14 into the pressure container 4. The
pressure container 4 is filled with the gas. When the pressure within the pressure
container 4 reaches a predetermined air pressure, the filling with the gas is stopped.
[0049] In the final step, the filled gas is caused to pass through the outer shells of the
hollow balls 18. In this step, the hollow balls 18 are left within the pressure container
4 for a predetermined time period. Due to the difference between the pressure of the
filled gas within the hollow balls 18 and the pressure of the filled gas within the
pressure container 4, the gas passes through the outer shells of the hollow balls
18 to enter into the hollow balls 18. Thus, the internal pressures of the hollow balls
18 are increased.
[0050] In the method for increasing the internal pressures of the hollow balls 18 according
to the present invention, the pressure container 4 is filled with the gas which is
more excellent in permeability relative to the outer shell of each hollow ball 18
than oxygen gas and nitrogen gas. The speed at which the gas enters from the interior
of the pressure container 4 into the interior of each hollow ball 18 is higher than
the speed at which air enters into the interior of each hollow ball 18. Thus, the
internal pressures of the hollow balls 18 can be increased in a short time as compared
to a conventional method of filling a container with air. In addition, in this method,
by merely leaving the hollow balls 18 within the pressure container 4, the internal
pressures of many hollow balls 18 can be increased. According to this method, the
internal pressures of the hollow balls 18 can be easily and efficiently increased.
[0051] The following will specifically describe the above-described effects with, as an
example, the case where carbon dioxide is used as the gas with which the pressure
container 4 is filled, to increase the internal pressures of regulation tennis balls.
It should be noted that a description will be given on the assumption that the atmospheric
pressure is 1.0 kgf/cm
2.
[0052] When: the permeability coefficient of a gas for a film is denoted by Cp; the partial
pressure difference of the gas between the outer side and the inner side across the
film is denoted by P; and the thickness of the film is denoted by W, a speed V at
which the gas passes through the film is represented by:

[0053] The outer shell of each regulation tennis ball 18 is generally made from natural
rubber. A description will be given on the assumption that the gas within each regulation
tennis ball 18 is composed of 80% of nitrogen gas (N
2) and 20% of oxygen gas (O
2), similarly to the atmosphere. As described above, in order to increase the internal
pressure during manufacturing, there are a method of generating nitrogen gas within
the balls 18 and a method of compressing and injecting air. In the case where the
method of generating nitrogen gas is used, the proportion of nitrogen gas is predicted
to be actually higher than that in the atmosphere, but this does not have a great
impact on the effects of the present invention. Similarly to the atmosphere, carbon
dioxide gas (CO
2) is also present within each regulation tennis ball 18, but the amount thereof is
negligibly small. The permeability coefficients Cp of nitrogen gas, oxygen gas, and
carbon dioxide gas for natural rubber are shown in Table 1. In addition, a ratio Cc
of each permeability coefficient obtained when the permeability coefficient of nitrogen
gas at 25°C is defined as 1 is described in Table 1. The thickness W of the film can
be considered constant, and thus the speed V is proportional to the ratio Cc and the
partial pressure difference P. When a constant of the proportionality is denoted by
C0, the speed V can be rewritten as follows.

The following will describe the effects by using this formula.
[Table 1]
Table 1 Gas permeability coefficient for natural rubber
Temper ature |
Item |
Nitrogen |
Oxygen |
Carbon dioxide |
25°C |
Permeability coefficient Cp [10-17 m4/ (N·S) ] |
6.0 |
17.5 |
98.3 |
Ratio Cc |
1.0 |
2.9 |
16.3 |
50°C |
Permeability coefficient Cp [ 10-17 m4/ (N·S) ] |
19.1 |
46.4 |
218 |
Ratio Cc |
3.2 |
7.7 |
36.3 |
[0054] Restoring the regulation tennis balls 18 whose internal pressures have decreased
to 1.60 kgf/cm
2 due to use of the balls 18, by the method according to the present invention, will
be considered. For this, it is assumed that after the pressure container 4 is evacuated,
the pressure container 4 is filled with carbon dioxide gas until the pressure of carbon
dioxide reaches 2.84 kgf/cm
2. Within the pressure container 4, no nitrogen gas and no oxygen gas are present.
Therefore, the partial pressures of nitrogen gas, oxygen gas, and carbon dioxide gas
within the pressure container 4 are as follows.
Nitrogen gas: 0.00 kgf/cm2
Oxygen gas: 0.00 kgf/cm2
Carbon dioxide gas: 2.84 kgf/cm2
[0055] As described above, the gas within each regulation tennis ball 18 is composed of
80% of nitrogen gas and 20% of oxygen gas. The internal pressure of each regulation
tennis ball 18 is 1.60 kgf/cm
2, and carbon dioxide gas can be neglected. Thus, the partial pressures of nitrogen
gas, oxygen gas, and carbon dioxide gas within the regulation tennis ball 18 are as
follows.
Nitrogen gas: 1.60 × 0.8 = 1.28 kgf/cm2
Oxygen gas: 1.60 × 0.2 = 0.32 kgf/cm2
Carbon dioxide gas: 0.0 kgf/cm2
[0056] On the basis of the values of the partial pressures at the outer side and the inner
side of the regulation tennis ball 18 and the values of the permeability coefficient
Cc in Table 1, a speed V(N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
18, which outer shell is made from natural rubber, from the outer side toward the
inner side, a speed V(O
2) at which oxygen gas passes through the outer shell of the regulation tennis ball
18, and a speed V(CO
2) at which carbon dioxide gas passes through the outer shell of the regulation tennis
ball 18 are as follows.

[0057] Nitrogen gas and oxygen gas within the regulation tennis ball 18 come out of the
interior of the ball 18, but carbon dioxide gas enters into the interior of the ball
18 at a speed which is equal to or higher than 20 times of that of nitrogen gas and
oxygen gas. According to the present method, a speed Vpro at which the gas enters
into the regulation tennis ball 18 as a whole is as follows.

[0058] Meanwhile, a speed at which the gas enters into the regulation tennis ball 18 when
the pressure of the air within the pressure container 4 is set to 2.84 kgf/cm
2 in the conventional method of filling with air, is calculated. At this time, the
partial pressures of nitrogen gas and oxygen gas within the pressure container 4 are
as follows.
Nitrogen gas: 2.84 × 0.8 = 2.27 kgf/cm2
Oxygen gas: 2.84 × 0.2 = 0.57 kgf/cm2
[0059] The partial pressures of nitrogen gas and oxygen gas within the regulation tennis
ball 18 are as follows.
Nitrogen gas: 1.6 × 0.8 = 1.28 kgf/cm2
Oxygen gas: 1.6 × 0.2 = 0.32 kgf/cm2
[0060] Thus, a speed V(N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
18, a speed V(O
2) at which oxygen gas passes through the outer shell, and a speed Vcov at which the
gas enters into the regulation tennis ball 18 as a whole are as follows.

[0061] When the speed Vpro at which the gas enters into the ball 18 by the present method
is compared to the speed Vcov at which the air enters into the ball 18 by the conventional
method, the effect of the present invention is clear. That is,

[0062] Immediately after the pressure container 4 is filled with the gas at 2.84 kgf/cm
2, according to the present method, the gas enters into each ball 18 at a speed which
is equal to or higher than 26 times of that in the conventional method. This significantly
improves a speed of increasing the internal pressure of the ball 18. According to
the present method, it is possible to restore the internal pressure of the regulation
tennis ball 18 whose internal pressure has decreased, and use the regulation tennis
ball 18 again.
[0063] In the above, the speed at which the gas enters into the hollow ball 18 in a state
immediately after the pressure container 4 is filled with the gas, is calculated.
Actually, when the gas within the container enters into each hollow ball 18, the pressure
of the gas within the container decreases. Furthermore, the partial pressure of the
gas within the hollow ball 18 also changes. Thus, the speed at which the gas enters
into each hollow ball 18 changes over time. In the present specification, a result
of calculation of a speed that takes time elapse into account is not shown. This is
because effectiveness of the present method becomes clear through comparison of a
speed at which the gas enters into each hollow ball 18 immediately after the pressure
container 4 is filled with the gas.
[0064] As described above, when the gas within the pressure container 4 enters into each
hollow ball 18, the pressure within the container decreases. This causes a decrease
in the speed at which the gas enters into each hollow ball 18. In order to prevent
this decrease, a method of supplying again the gas from the gas cylinder 10 can be
used. For example, a method can be used in which, although not shown in the drawing,
a pressure monitor for observing the internal pressure of the pressure container 4
is installed, and the gas is supplied again from the gas cylinder 10 when the internal
pressure has decreased to a certain value or lower. Such a method of supplying again
the gas is used as appropriate depending on an intended use.
[0065] In the above-described method, in the initial step, the pressure container 4 is evacuated.
The pressure container 4 may not be evacuated. Air having a certain pressure may remain
therein. Air may not be discharged at all, and air having the same pressure as the
atmospheric pressure may remain. In this case, in the initial step, a process of discharging
air from the interior of the pressure container 4 is unnecessary. In FIG. 1, the vacuum
pump 6 is unnecessary. In addition, a gas which is a mixture of carbon dioxide and
air may be put in the gas cylinder 10 beforehand, whereby carbon dioxide may be fed
into the container, and the partial pressure of air after the container is filled
with the gas may be made equal to or higher than the atmospheric pressure. This is
effective for increasing the internal pressure of each hollow ball 18 by causing carbon
dioxide to enter into each hollow ball 18 while suppressing coming-out of the air
within each hollow ball 18.
[0066] The following will describe the effectiveness of the present method with, as an example,
the case where the air within the container is not discharged and the pressure container
4 is filled with carbon dioxide and air such that the internal pressure of the pressure
container 4 is 2.84 kgf/cm
2. In the following example, after filling with the gas, the partial pressure of the
air within the container is 1.84 kgf/cm
2 which is equal to or higher than the atmospheric pressure, and the partial pressure
of carbon dioxide is 1.00 kgf/cm
2 which is equal to the atmospheric pressure. The internal pressure of the ball 18
is set to 1.60 kgf/cm
2 which is equal to that in the above example. At this time, the speed V (N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
18, the speed V (O
2) at which oxygen gas passes through the outer shell of the regulation tennis ball
18, and the speed V(CO
2) at which carbon dioxide gas passes through the outer shell of the regulation tennis
ball 18 are as follows.

The speed Vpro at which the gas enters into the regulation tennis ball 18 as a whole
is as follows.

When the speed Vpro is compared to the speed Vcov = 1.71 × C0 at which the gas enters
into the ball 18 by the conventional method,

This means that the gas enters into the ball 18 at a speed which is 9.7 times of
that in the conventional method.
[0067] Meanwhile, nitrogen gas and oxygen gas also enter into the interior of the ball 18
at a speed of (0.19 + 0.14) × C0 = 0.33 × C0. In the case where the container is evacuated,
from the above-described results, nitrogen gas and oxygen gas come out of the ball
18 at a speed of (-1.28 - 0.93) × C0 = -2.21 × C0. In this method, as compared to
the conventional method, the internal pressure of the hollow ball 18 can be increased
at a high speed while suppressing coming-out of the air from the interior of the ball
18.
[0068] Table 1 shows the permeability coefficients of nitrogen gas, oxygen gas, and carbon
dioxide gas for natural rubber at 25°C and 50°C. The permeability coefficients of
these gases at 50°C are 2 to 3 times of the permeability coefficients thereof at 25°C.
That is, by increasing the temperature within the pressure container 4 from 25°C to
50°C, the speed at which the gas enters into each hollow ball 18 can be increased
by 2 times or more. This can be easily achieved, for example, when the pressure container
4 includes a heater. The temperature within the pressure container 4 may be increased
by using a band heater. From the standpoint that the permeability coefficient of gas
is increased to increase the speed of increasing the internal pressure of the hollow
ball 18, the temperature within the pressure container 4 is preferably equal to or
higher than 35°C. From the standpoint that the quality of natural rubber which is
used in a large amount as the material of the outer shell of the hollow ball 18 is
maintained, the temperature within the pressure container 4 is preferably equal to
or lower than 60°C.
[0069] In the present method, the difference between the internal pressure of the pressure
container 4 and the atmospheric pressure after the pressure container 4 is filled
with the gas is preferably equal to or lower than 1.84 kgf/cm
2. This corresponds to the case where the internal pressure of the pressure container
4 is equal to or lower than 2.84 kgf/cm
2 when the atmospheric pressure is 1.00 kgf/cm
2. The pressure container 4 which is used at an internal pressure whose difference
from the atmospheric pressure is equal to or lower than 1.84 kgf/cm
2 is easily handled and managed. In addition, the pressure container 4 is preferably
made from a metal. The pressure container 4 made from the metal has strength sufficient
to withstand an internal pressure whose difference from the atmospheric pressure is
1.84 kgf/cm
2. In this respect, examples of more preferable metals include stainless steel and
aluminum alloys.
[0070] The permeability coefficient Cp of the gas, with which the pressure container 4 is
filled, for natural rubber at 25°C is preferably equal to or greater than 20 x 10-
17 m
4/(N·s). When the gas whose permeability coefficient Cp at a temperature of 25°C is
equal to or greater than 20 × 10
-17 m
4/(N·s) is used in the present method, the internal pressure of the hollow ball 18
can be increased in a shorter time than in the conventional method. In this respect,
the permeability coefficient Cp is more preferably equal to or greater than 50 × 10
-17 m
4/(N·s).
[0071] FIG. 2 shows an apparatus 30 for a method for increasing the internal pressure of
a hollow ball according to a second embodiment of the present invention. The apparatus
30 includes a storage container 32, a gas cylinder 34, and an intake pipe 38.
[0072] The storage container 32 houses hollow balls 42. The storage container 32 is typically
made from a resin composition. The storage container 32 may be made from a metal.
The storage container 32 is kept airtight.
[0073] The storage container 32 includes a main body 44 and a lid 46. The main body 44 includes,
at an upper portion thereof, an input port for putting in the hollow balls 42 therethrough.
The main body 44 includes an intake hole 48 in a lower portion thereof. One end of
the intake pipe 38 is passed through the intake hole 48. The other end of the intake
pipe 38 is connected to the gas cylinder 34. The storage container 32 and the gas
cylinder 34 are connected to each other by the intake pipe 38.
[0074] The gas cylinder 34 has stored therein a gas to be fed into the storage container
32. The gas is more excellent in permeability relative to an outer shell of each hollow
ball 42 than oxygen gas and nitrogen gas. The gas cylinder 34 feeds the stored gas
through the intake pipe 38 into the storage container 32. The gas cylinder 34 can
cause the pressure of the gas within the storage container 32 to be equal to or higher
than the atmospheric pressure.
[0075] In a method for increasing the internal pressures of the hollow balls 42 according
to the present invention, in an initial step, the lid 46 is opened, and the hollow
balls 42 are put into the storage container 32.
[0076] In the next step, the storage container 32 is filled with the gas. First, while the
lid 46 is opened, the gas from the gas cylinder 34 is fed into the storage container
32. The air within the storage container 32 is pushed by the gas fed through the lower
portion of the main body 44, to be discharged through the input port at which the
lid 46 at the upper portion of the main body 44 is kept opened. Thus, most of the
air within the storage container 32 is discharged. After elapse of a certain time
period, the lid 46 is closed. The storage container 32 continued to be filled with
the gas. When the pressure within the storage container 32 reaches a predetermined
air pressure, the filling with the gas is stopped.
[0077] In the final step, the filled gas is caused to pass through the outer shells of the
hollow balls 42. In this step, the hollow balls 42 are left within the storage container
32 for a predetermined time period. Due to the difference between the pressure of
the filled gas within the hollow balls 42 and the pressure of the filled gas within
the storage container 32, the gas passes through the outer shells of the hollow balls
42 to enter into the hollow balls 42. Thus, the internal pressures of the hollow balls
42 are increased.
[0078] In the method for increasing the internal pressures of the hollow balls 42 according
to the present invention, the storage container 32 is filled with the gas which is
more excellent in permeability relative to the outer shell of each hollow ball 42
than oxygen gas and nitrogen gas. The speed at which the gas enters from the storage
container 32 into the interior of each hollow ball 42 is higher than the speed at
which air enters into the interior of each hollow ball 42. Thus, the internal pressures
of the hollow balls 42 can be increased in a short time as compared to the conventional
method of filling a container with air. In addition, in this method, by merely leaving
the hollow balls 42 within the storage container 32, the internal pressures of many
hollow balls 42 can be increased. According to this method, the internal pressures
of the hollow balls 42 can be easily and efficiently increased.
[0079] In the method for increasing the internal pressures of the hollow balls 42 according
to the present invention, the air within the storage container 32 is discharged by
the fed gas. In this method, the vacuum pump 6 is unnecessary. In this method, the
internal pressures of the hollow balls 42 can be increased by the apparatus 30 which
is low in cost.
[0080] In the apparatus 30 in FIG. 2, the intake hole 48 through which the gas is fed is
provided in the lower portion of the main body 44. The input port through which air
is discharged is located in the upper portion of the main body 44. According to the
positional relationship therebetween, when the storage container 32 is filled with
a gas heavier than air, such as carbon dioxide, the filled gas can efficiently push
air out of the container. When the storage container 32 is filled with a gas lighter
than air, preferably, the intake hole is provided in the upper portion, and the exhaust
hole is provided in the lower portion.
[0081] The following will specifically describe the above-described effects with, as an
example, the case where carbon dioxide is used as the gas with which the storage container
32 is filled, to increase the internal pressures of the regulation tennis balls 42.
[0082] Restoring the regulation tennis balls 42 whose internal pressures have decreased
to 1.60 kgf/cm
2 due to use of the balls 42, by the method according to the present invention, will
be considered. It is assumed that filling with carbon dioxide gas is performed until
the pressure of carbon dioxide reaches 1.80 kgf/cm
2. It is assumed that the air within the storage container 32 is fully discharged.
Therefore, the partial pressures of nitrogen gas, oxygen gas, and carbon dioxide gas
within the storage container 32 are as follows.
Nitrogen gas: 0.00 kgf/cm2
Oxygen gas: 0.00 kgf/cm2
Carbon dioxide gas: 1.80 kgf/cm2
[0083] The gas within each regulation tennis ball 42 is composed of 80% of nitrogen gas
and 20% of oxygen gas, substantially similarly to the atmosphere. The internal pressure
of each regulation tennis ball 42 is 1.60 kgf/cm
2, and carbon dioxide gas can be neglected. Thus, the partial pressures of nitrogen
gas, oxygen gas, and carbon dioxide gas within the regulation tennis ball 42 are as
follows.
Nitrogen gas: 1.60 × 0.8 = 1.28 kgf/cm2
Oxygen gas: 1.60 × 0.2 = 0.32 kgf/cm2
Carbon dioxide gas: 0.00 kgf/cm2
[0084] On the basis of the values of the partial pressures at the outer side and the inner
side of the regulation tennis ball 42 and the values of the permeability coefficient
Cc in Table 1, a speed V(N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
42, which outer shell is made from natural rubber, a speed V(O
2) at which oxygen gas passes through the outer shell of the regulation tennis ball
42, and a speed V(CO
2) at which carbon dioxide gas passes through the outer shell of the regulation tennis
ball 42 are as follows.

A speed Vpro at which the gas enters into the regulation tennis ball 42 as a whole
is as follows.

[0085] Meanwhile, a speed at which the gas enters into the regulation tennis ball 42 when
the pressure of the air within the storage container 32 is set to 1.80 kgf/cm
2 in the conventional method of filling with air, is calculated. At this time, the
partial pressures of nitrogen gas and oxygen gas within the storage container 32 are
as follows.
Nitrogen gas: 1.80 × 0.8 = 1.44 kgf/cm2
Oxygen gas: 1.80 × 0.2 = 0.36 kgf/cm2
The partial pressures of nitrogen gas and oxygen gas within the regulation tennis
ball 42 are as follows.
Nitrogen gas: 1.6 × 0.8 = 1.28 kgf/cm2
Oxygen gas: 1.6 × 0.2 = 0.32 kgf/cm2
Thus, a speed V(N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
42, a speed V(O
2) at which oxygen gas passes through the outer shell of the regulation tennis ball
42, and a speed Vcov at which the gas enters into the regulation tennis ball 42 as
a whole are as follows.

[0086] When the speed Vpro at which the gas enters into the regulation tennis ball 42 by
the present method is compared to the speed Vcov at which the air enters into the
regulation tennis ball 42 by the conventional method, the effects of the present invention
are clear. That is,

Immediately after the storage container 32 is filled with the gas at 1.80 kgf/cm
2, according to the present method, the gas enters into the regulation tennis ball
42 at a speed which is 97 times of that in the conventional method. This significantly
improves a speed of increasing the internal pressure of the regulation tennis ball
42. According to the present method, it is possible to restore the internal pressure
of the regulation tennis ball 42 whose internal pressure has decreased, and use the
regulation tennis ball 42 again.
[0087] The difference between the internal pressure of the storage container 32 and the
atmospheric pressure after the storage container 32 is filled with the gas is preferably
equal to or lower than 0.90 kgf/cm
2. For the storage container 32 which is set at an internal pressure whose difference
from the atmospheric pressure is equal to or lower than 0.90 kgf/cm
2, a resin composition can be used as a material of the storage container 32. The storage
container 32 is low in cost. The storage container 32 is lighter in weight than a
metallic container. The resin composition is preferably polyethylene terephthalate.
The storage container 32 made from polyethylene terephthalate has strength sufficient
to withstand an internal pressure whose difference from the atmospheric pressure is
0.90 kgf/cm
2.
[0088] The speed at which the gas enters into the hollow ball 42 can be increased by increasing
the temperature within the storage container 32. From the standpoint that the permeability
coefficient of gas is increased to increase the speed of increasing the internal pressure
of the hollow ball 42, the temperature within the storage container 32 is preferably
equal to or higher than 35°C. From the standpoint that the quality of natural rubber
which is used in a large amount as the material of the outer shell of the hollow ball
42 is maintained, the temperature within the storage container 32 is preferably equal
to or lower than 60°C.
[0089] FIG. 3 shows an apparatus 50 for a method for increasing the internal pressure of
a hollow ball according to a third embodiment of the present invention. The apparatus
50 includes a housing bag 52, a gas cylinder 54, and an intake pipe 56.
[0090] The housing bag 52 houses hollow balls 58. The housing bag 52 is typically made from
a resin composition. The housing bag 52 is flexible, and thus easily deforms due to
an external or internal pressure. The housing bag 52 includes an input port 60 for
putting in the hollow balls 58 therethrough. The input port 60 is provided with a
zipper 62. By closing the zipper 62, the housing bag 52 is kept airtight.
[0091] The gas cylinder 54 has stored therein a gas to be fed into the housing bag 52. The
gas is more excellent in permeability relative to an outer shell of each hollow ball
58 than oxygen gas and nitrogen gas.
[0092] In a method for increasing the internal pressures of the hollow balls 58 according
to the present invention, in an initial step, the zipper 62 of the housing bag 52
is opened, and the hollow balls 58 are put into the housing bag 52. At this time,
the housing bag 52 is pressed to come into close contact with the hollow balls 58,
whereby the air within the housing bag 52 is discharged to the outside. The zipper
62 may be opened to a necessary degree, a suction opening of a vacuum cleaner may
be inserted, and the vacuum cleaner may be operated, whereby the internal air may
be discharged. The internal air may be discharged by a vacuum pump. After the air
is discharged, the zipper 62 of the housing bag 52 is closed.
[0093] In the next step, the housing bag 52 is filled with the gas. The zipper 62 of the
housing bag 52 is opened to a necessary degree, and the intake pipe 56 of the gas
cylinder 54 is inserted into the housing bag 52. The gas is fed directly from the
gas cylinder 54. After the housing bag 52 is filled with the gas, the intake pipe
56 is pulled out, and the zipper 62 is closed. The pressure of the gas within the
housing bag 52 becomes substantially equal to the atmospheric pressure. By using the
pressure by which the gas is fed from the gas cylinder 54, the pressure of the gas
within the housing bag 52 may be made equal to or higher than the atmospheric pressure.
[0094] In the final step, the filled gas is caused to pass through the outer shells of the
hollow balls 58. In this step, the hollow balls 58 are left within the housing bag
52 for a predetermined time period. Due to the difference between the pressure of
the filled gas within the hollow balls 58 and the pressure of the filled gas within
the housing bag 52, the gas passes through the outer shells of the hollow balls 58
to enter into the hollow balls 58. Thus, the internal pressures of the hollow balls
58 are increased.
[0095] In the method for increasing the internal pressures of the hollow balls 58 according
to the present invention, the housing bag 52 is filled with the gas which is more
excellent in permeability relative to the outer shell of each hollow ball 58 than
oxygen gas and nitrogen gas. The speed at which the gas enters from the housing bag
52 into the interior of each hollow ball 58 is higher than the speed at which air
enters into each hollow ball 58. Thus, the internal pressures of the hollow balls
58 can be increased in a short time as compared to the conventional method of filling
a container with air. In addition, in this method, by merely leaving the hollow balls
58 within the housing bag 52, the internal pressures of many hollow balls 58 can be
increased. According to this method, the internal pressures of the hollow balls 58
can be easily and efficiently increased.
[0096] In the method for increasing the internal pressures of the hollow balls 58 according
to the present invention, the housing bag 52 is pressed to come into close contact
with the hollow balls 58, whereby the air within the housing bag 52 can be discharged
to the outside. In this method, a vacuum pump is unnecessary. In this method, the
internal pressure of the housing bag 52 is made substantially equal to the atmospheric
pressure, and thus filling with the gas is easy. In this method, the internal pressures
of the hollow balls 58 can be increased by the apparatus 50 which is further low in
cost.
[0097] The following will specifically describe the above-described effects with, as an
example, the case where carbon dioxide is used as the gas with which the housing bag
52 is filled, to increase the internal pressures of the regulation tennis balls 58.
In the following description, the air within the bag is fully discharged.
[0098] Restoring the regulation tennis balls 58 whose internal pressures have decreased
to 1.60 kgf/cm
2 due to use of the balls 58, by the method according to the present invention, will
be considered. Filling with carbon dioxide gas is performed such that the pressure
of carbon dioxide gas is 1.00 kgf/cm
2 which is equal to the atmospheric pressure. It is assumed that the air within the
housing bag is fully discharged. Therefore, the partial pressures of nitrogen gas,
oxygen gas, and carbon dioxide gas within the housing bag are as follows.
Nitrogen gas: 0.00 kgf/cm2
Oxygen gas: 0.00 kgf/cm2
Carbon dioxide gas: 1.00 kgf/cm2
[0099] The gas within each regulation tennis ball 58 is composed of 80% of nitrogen gas
and 20% of oxygen gas, substantially similarly to the atmosphere. The internal pressure
of each regulation tennis ball 58 is 1.60 kgf/cm
2, and no carbon dioxide gas is present. Thus, the partial pressures of nitrogen gas,
oxygen gas, and carbon dioxide gas within the regulation tennis ball 58 are as follows.
Nitrogen gas: 1.60 × 0.8 = 1.28 kgf/cm2
Oxygen gas: 1.60 × 0.2 = 0.32 kgf/cm2
Carbon dioxide gas: 0.00 kgf/cm2
[0100] On the basis of the values of the partial pressures at the outer side and the inner
side of the regulation tennis ball 58 and the values of the permeability coefficient
Cc in Table 1, a speed V(N
2) at which nitrogen gas passes through the outer shell of the regulation tennis ball
58, which outer shell is made from natural rubber, a speed V(O
2) at which oxygen gas passes through the outer shell of the regulation tennis ball
58, and a speed V(CO
2) at which carbon dioxide gas passes through the outer shell of the regulation tennis
ball 58 are as follows.

A speed Vpro at which the gas enters into the regulation tennis ball 58 as a whole
is as follows.

[0101] Meanwhile, in the conventional method of filling with air, the internal pressures
of the regulation tennis balls 58 cannot be restored unless the pressure of the air
within the housing bag 52 is equal to or higher than the internal pressure of each
regulation tennis ball 58. In the conventional method, with the apparatus 50 shown
in FIG. 3, it is impossible to restore the internal pressures of the regulation tennis
balls 58. In addition, as described above, in the conventional method, the speed Vcov
at which the gas enters into the regulation tennis ball 58 when the pressure container
4 is used and the pressure of the air within the pressure container 4 is set to 2.84
kgf/cm
2 is 1.71 × C0. In the present method, even when the simple apparatus 50 shown in FIG.
3 is used, the gas enters into the regulation tennis ball 58 at a speed which is equal
to or higher than 8 times of that in this method. The effect of the present invention
is clear.
[0102] In the example of FIG. 3, the gas cylinder 54 is used for filling with carbon dioxide.
For filling with carbon dioxide, dry ice may be put into the bag instead of using
the gas cylinder 54. When the dry ice melts and vaporizes, the bag is filled with
carbon dioxide. In this method, the gas cylinder 54 is unnecessary. In this case,
the apparatus 50 can be further decreased in cost.
[0103] In the case where the internal pressures of the hollow balls 58 are increased by
using a container having a fixed shape such as the pressure container 4 or the like,
when the gas within the container enters into each hollow ball 58, the pressure of
the gas within the container decreases. This causes a decrease in the speed at which
the gas enters into each hollow ball 58. In the method shown in FIG. 3, when the gas
within the housing bag 52 is absorbed by each hollow ball 58, the housing bag 52 is
pressed and deformed by the external atmospheric pressure, and the capacity of the
housing bag 52 decreases until the pressure within the bag 52 becomes equal to the
atmospheric pressure. That is, unless all of the gas with which the housing bag 52
is filled enters into the interior of the hollow balls 58, the pressure of the gas
within the bag is kept at 1 kgf/cm
2 which is equal to the atmospheric pressure. In the method shown in FIG. 3, a decrease
in the speed at which the gas enters into the hollow ball 58 can be reduced without
supplying again the gas from the outside.
[0104] The internal pressure of the hollow ball 58 that is left in the atmosphere decreases
to the atmospheric pressure when the internal pressure is the lowest. Most of currently-used
hollow balls 58 such as regulation tennis balls have an internal pressure equal to
or lower than 2 times of the atmospheric pressure, when being used. Therefore, it
is useful to provide a method for increasing the internal pressures of the hollow
balls 58 whose internal pressures have decreased to the atmospheric pressure, to a
pressure which is 2 times of the atmospheric pressure, by using the housing bag 52
filled with the gas such that the internal pressure thereof is equal to the atmospheric
pressure.
[0105] In order to double the internal pressure of each hollow ball 58, the amount (molar
quantity) of the gas within the hollow ball 58 needed to be doubled. This means that
carbon dioxide gas is put into the hollow ball 58 in an amount equal to the amount
of the gas within the hollow ball 58. Therefore, the molar quantity of the gas with
which the housing bag 52 is filled is preferably equal to or greater than the sum
of the molar quantities of the gas within all the hollow balls 58 stored in the housing
bag 52. Since the temperature of the gas within each hollow ball 58 is equal to the
temperature of the gas within the housing bag 52 and the pressures thereof are the
same and equal to the atmospheric pressure as described above, the ratio of the molar
quantity of the gas within each hollow ball 58 and the molar quantity of the gas within
the housing bag 52 is equal to the volume ratio of these gases. Therefore, the ratio
(Vg/Vb) of the volume Vg of the gas with which the housing bag 52 is filled, relative
to the sum Vb of the capacities of all the hollow balls 58 (the volumes of the spaces
within the hollow balls 58) put into the housing portion is preferably equal to or
greater than 1.0. When the housing bag 52 is filled with the gas until the ratio (Vg/Vb)
becomes equal to or greater than 1.0, the internal pressures of the hollow balls 58
whose internal pressures have decreased to the atmospheric pressure can be 2 times
of the atmospheric pressure without supplying the gas in midstream. In this method,
an operation of supplying the gas in midstream is unnecessary.
[0106] Each regulation tennis ball 58 typically has a capacity which is 0.5 times of the
volume of the ball 58. In other words, the gas whose amount is 0.5 times of the volume
of the regulation tennis ball 58 is needed to double the internal pressure of the
regulation tennis ball 58. Therefore, the above condition can be rephrased as "the
ratio (VC/Vt) of a capacity VC of the housing bag 52 after the regulation tennis balls
58 are put therein and the housing bag 52 is filled with the gas, relative to the
sum Vt of the volumes of all the regulation tennis balls 58 put in the housing portion,
is preferably equal to or greater than 1.5". By putting the regulation tennis balls
58 and the gas into the housing bag 52 such that the ratio (VC/Vt) is equal to or
greater than 1.5, a user can increase the internal pressures of the regulation tennis
balls 58 whose internal pressures have decreased to the atmospheric pressure, to a
pressure which is 2 times of the atmospheric pressure, without supplying the gas in
midstream.
[0107] In the present method, the difference between the internal pressure of the housing
bag 52 and the atmospheric pressure after the housing bag 52 is filled with the gas
is preferably equal to or lower than 0.1 kgf/cm
2. For the housing bag 52 which is set at an internal pressure whose difference from
the atmospheric pressure is equal to or lower than 0.1 kgf/cm
2, a resin composition can be used as a material of the housing bag 52. The housing
bag 52 is low in cost and lightweight. In addition, the permeability coefficient of
this bag for nitrogen gas, oxygen gas, and carbon dioxide gas is negligibly small
as compared to that of rubber. Thus, it is not necessary to take into account an effect
that gas comes out of this bag. In light of being excellent in durability, low in
cost, and lightweight, and having a sufficiently low permeability coefficient, the
principal component of the base resin of the resin composition is preferably nylon.
In this respect, the principal component of the base resin of the resin composition
may be polyethylene.
[0108] By increasing the temperature in the housing bag 52, the speed at which the gas enters
into each hollow ball 58 can be increased. From the standpoint that the permeability
coefficient of gas is increased to increase the speed of increasing the internal pressure
of the hollow ball 58, the temperature within the housing bag 52 is preferably equal
to or higher than 35°C. From the standpoint that the quality of natural rubber which
is used in a large amount as the material of the outer shell of the hollow ball 58
is maintained, the temperature within the housing bag 52 is preferably equal to or
lower than 60°C.
[0109] A soft tennis ball includes a valve. The internal pressure of the ball is restored
by supplying air through the valve with an air pump. However, the valve is harder
than rubber surrounding the valve, and thus may be broken during use. The valve impairs
the durability of the ball. In addition, if the valve hits against a racket when the
ball is hit with the racket, the hit ball becomes unstable. Furthermore, it is necessary
to supply air into balls one by one, and thus it takes much time and effort to restore
the internal pressures of the balls.
[0110] When the internal pressure is restored by using the present method, a soft tennis
ball does not need to have a valve. Thus, a soft tennis ball which does not have a
valve can be realized. The soft tennis ball which does not have a valve is excellent
in durability. When the ball is used, a racket does not hit against a valve. In addition,
if the present method is used, when a plurality of balls are put into the housing
portion, the internal pressures of these balls can be restored at one time. This method
does not need time and effort.
[0111] The effects of the method for increasing the internal pressure of a hollow ball according
to the present invention have been described above in the three types of embodiments.
Embodiments of the present invention are not limited to the three types described
here. For example, what to select as the housing portion, which to use as a method
for discharging the air within the container, whether to discharge the air, and what
pressure the internal pressure within the housing portion is set to after balls are
put therein, can be determined and combined as appropriate according to a use purpose
of the present method. For example, in the case where balls are used every half-day
at a tennis school, in the case where balls are used in a club activity at a school
only in after-school hours, or in the case where balls are used only on holidays by
ordinary family, an appropriate embodiment can be realized. According to the present
invention, in any of the embodiments, the internal pressures of hollow balls can be
easily increased in a significantly shorter period as compared to the conventional
method. Due to the above, advantages of the present invention are clear.
[0112] FIG. 4 is a perspective view of a housing container 70 for a method for increasing
the internal pressure of a hollow ball according to an embodiment of the present invention.
In FIG. 4, an arrow X indicates a rightward direction, and the opposite direction
is a leftward direction. An arrow Y indicates an upward direction, and the opposite
direction is a downward direction. The housing container 70 includes a main body 70
and an opening/closing tool 74.
[0113] The main body 70 has a box shape. The main body 70 stores hollow balls therein. The
main body 70 includes an intake port 76 for feeding gas thereinto and an exhaust port
78 for discharging gas from the interior thereof. The intake port 76 is provided at
the lower side of a side surface of the main body 70. The intake port 76 is provided
with a cap 80. The intake port 76 can be closed by the cap 80. The exhaust port 78
is provided in an upper surface of the main body 70. The exhaust port 78 is provided
with a cap 82. The exhaust port 78 can be closed by the cap 82.
[0114] The opening/closing tool 74 is located in a front surface of the main body 70. The
opening/closing tool 74 is an airtight fastener. The airtight fastener 74 extends
along a right side, a lower side, and a left side of the front surface of the main
body 70. By opening the airtight fastener 74, the front surface of the main body 70
can be opened. Through this opening, hollow balls can be taken in and out. By closing
the airtight fastener 74, the main body 70 enters an airtight state.
[0115] In order to increase the internal pressures of hollow balls by using the housing
container 70, the airtight fastener 74 is opened, and the hollow balls are put through
this opening into the main body 70. Next, the airtight fastener 74 is closed. In a
state where the cap 80 of the intake port 76 and the cap 82 of the exhaust port 78
are opened, a gas which is more excellent in permeability relative to an outer shell
of each hollow ball than oxygen gas and nitrogen gas is fed through the intake port
76 into the interior of the housing container 70. The air having been present within
the main body 70 is pushed by the gas to be discharged through the exhaust port 78.
After the housing container 70 is filled with the gas, the intake port 76 and the
exhaust port 78 are closed. The pressure within the housing container 70 is equal
to the external atmospheric pressure. The hollow balls are left in this state for
a certain time period. The gas enters into the hollow balls, so that the internal
pressures of the hollow balls are increased.
[0116] In the case where the internal pressures of hollow balls are increased by using the
housing container 70, the air within the housing container 70 is discharged by the
fed gas. When the internal pressures of the hollow balls are increased by using the
container, a process of discharging the air within the container is unnecessary. In
addition, the pressure within the housing container 70 is equal to the atmospheric
pressure. Thus, the housing container 70 can be made from a low-cost material. In
this method, the internal pressures of hollow balls can be increased with a low-cost
apparatus.
[0117] As described above, in the housing container 70 in FIG. 4, the intake port 76 is
located at the lower side of the side surface of the main body 70, and the exhaust
port 78 is located in the upper surface of the main body 70. The exhaust port 78 is
located above the intake port 76. In the case where the housing container 70 is filled
with a gas heavier than air, such as carbon dioxide, the exhaust port 78 is preferably
located above the intake port 76 as described above. Since the exhaust port 78 is
located above the intake port 76, the filled gas can efficiently push the air out
of the container.
[0118] In FIG. 4, a double-headed arrow Hi indicates a vertical height from a lower end
of the main body 70 to the center of the intake port 76. A double-headed arrow H indicates
the height of the main body 70. The ratio (Hi/H) of the height Hi relative to the
height H is preferably equal to or less than 10%. When the ratio (Hi/H) is equal to
or less than 10%, the fed gas can efficiently push out the air having been present
within the main body 70.
[0119] Although not shown, a vertical height from the lower end of the main body 70 to the
center of the exhaust port 78 is represented by a reference character Ho. In the housing
container 70 in FIG. 4, the height Ho is equal to the height H. The ratio (Ho/H) of
the height Ho relative to the height H is preferably equal to or greater than 90%.
When the ratio (Ho/H) is equal to or greater than 90%, the air having been present
within the main body 70 is efficiently discharged through the exhaust port 78.
[0120] In the housing container 70, the main body 70 is preferably made from a resin composition.
The housing container 70 which includes the main body 70 made from the resin composition
is low in cost and lightweight. The permeability coefficient of the main body 70 of
the resin composition for nitrogen gas, oxygen gas, and carbon dioxide gas is negligibly
small as compared to that of rubber. The container is kept airtight. In light of being
excellent in durability, low in cost, and lightweight, and having a sufficiently low
permeability coefficient, the principal component of the base resin of the resin composition
is preferably nylon. In this respect, the principal component of the base resin of
the resin composition may be polyethylene.
[0121] The opening/closing tool 74 is not limited to the airtight fastener 74. The opening/closing
tool may be a zipper seal. Another type of opening/closing tool may be used as long
as the tool is capable of being opened/closed and airtightness is maintained.
[0122] The housing container 70 in FIG. 4 includes the one intake port 76 and the one exhaust
port 78. The housing container 70 may include two or more intake ports 76 or two or
more exhaust ports 78. In this case, the air within the housing container 70 can be
efficiently discharged or the housing container 70 can be efficiently filled with
the gas.
[0123] The distance between the intake port 76 and the exhaust port 78 is preferably as
long as possible. Thus, the gas injected through the intake port 76 can be prevented
from leaking directly through the exhaust port 78. Accordingly, filling with the gas
can be efficiently performed.
[0124] FIG. 5 is a perspective view of a housing container 84 for a method for increasing
the internal pressure of a hollow ball according to another embodiment of the present
invention. The housing container 84 includes a main body 86, an opening/closing tool
88, a hose 90, and a frame 92.
[0125] The main body 86 has a box shape. The main body 86 stores hollow balls therein. The
main body 86 includes an intake port 94 for feeding gas thereinto and an exhaust port
96 for discharging gas from the interior thereof. The intake port 94 and the exhaust
port 96 are provided in an upper surface of the main body 86. The intake port 94 is
provided with a valve 98 and a cap 100. A feed pipe of a gas cylinder is connected
to the valve 98. In addition, the intake port 94 can be closed by covering the valve
98 with the cap 100. The exhaust port 96 is provided with a cap 102. The exhaust port
96 can be closed by the cap 102.
[0126] The opening/closing tool 88 is located in a front surface of the main body 86. The
opening/closing tool 88 is an airtight fastener. The airtight fastener 88 extends
vertically at the center of the front surface of the main body 86. By opening the
airtight fastener 88, the front surface of the main body 86 can be opened. Through
this opening, hollow balls can be taken in and out. By closing the airtight fastener
88, the main body 86 enters an airtight state.
[0127] The hose 90 is located within the main body 86. The hose 90 is mounted to the main
body 86. An opening of a first end of the hose 90 overlaps the intake port 94. A gas
fed through the intake port 94 passes through the hose 90 to fill the main body 86.
A second end 104 of the hose 90 is located below the exhaust port 96.
[0128] The frame 92 is located within the main body 86. The frame 92 supports the main body
86. In addition the frame 92 can be a rack for placing a basket containing hollow
balls. The frame 92 is typically made from plastic or metal.
[0129] In order to increase the internal pressures of hollow balls by using the housing
container 84, the airtight fastener 88 is opened, and the hollow balls are put through
this opening into the main body 86. Next, the airtight fastener 88 is closed. As shown
in FIG. 6, a gas cylinder 106 is connected to the valve 98 of the intake port 94.
In a state where the valve 98 of the intake port 94 and the cap 100 of the exhaust
port 96 are opened, a gas which is more excellent in permeability relative to an outer
shell of each hollow ball than oxygen gas and nitrogen gas is fed through the intake
port 94 into the interior of the housing container 84. The gas fed through the intake
port 94 passes through the hose 90 to fill the main body 86. The air having been present
within the main body 86 is pushed by the gas to be discharged through the exhaust
port 96. After the housing container 84 is filled with the gas, the intake port 94
and the exhaust port 96 are closed. The pressure within the housing container 84 is
equal to the external atmospheric pressure. The hollow balls are left in this state
for a certain time period. The gas enters into the hollow balls, so that the internal
pressures of the hollow balls are increased.
[0130] In the case where the internal pressures of hollow balls are increased by using the
housing container 84, the air within the housing container 84 is discharged by the
fed gas. When the internal pressures of the hollow balls are increased by using the
container, a process of discharging the air within the container is unnecessary. In
addition, the pressure within the housing container 84 is equal to the atmospheric
pressure. Thus, the housing container 84 can be made from a low-cost material. In
this method, the internal pressures of hollow balls can be increased with a low-cost
apparatus.
[0131] As described above, in the housing container 84 in FIG. 5, the second end 104 of
the hose 90 is located below the exhaust port 96. Thus, in the case where the housing
container 84 is filled with a gas heavier than air, such as carbon dioxide, the fed
gas can efficiently push the air out of the container. In the housing container 84,
the intake port 94 may be located above the exhaust port 96. The intake port 94 may
be located at any position in the main body 86. In this container, the intake port
94 can be located at a position where the user easily uses the intake port 94.
[0132] In FIG. 6, a double-headed arrow Hh indicates a vertical height from a lower end
of the main body 86 to the second end 104 of the hose 90. A double-headed arrow H
indicates the height of the main body 86. The ratio (Hh/H) of the height Hh relative
to the height H is preferably equal to or less than 10%. When the ratio (Hh/H) is
equal to or less than 10%, the taken-in gas can efficiently push out the air having
been present within the main body 86.
[0133] The housing container 84 includes the frame 92 therein. The frame 92 reinforces the
main body 86. Even in the case where the main body 86 is made from a flexible resin
composition, the housing container 84 can be stably placed. In addition, the frame
92 can be used as a rack for storing a basket containing hollow balls. This makes
it easy to take in and out the hollow balls.
[0134] FIG. 7 is a conceptual diagram showing a state where a housing container 110 for
a method for increasing the internal pressure of a hollow ball according to still
another embodiment is used. An intake port 112 of the housing container 110 is located
in an upper surface of the housing container 110. This container does not include
a hose. In this container, the inner diameter of the intake port 112 is larger than
the outer diameter of a pipe 116 of a gas cylinder 114. The pipe 116 of the cylinder
which feeds a gas is inserted through the intake port 112 into the interior of a main
body 118. A leading end of the pipe 116 is located below an exhaust port. Thus, in
the case where the housing container 110 is filled with a gas heavier than air, such
as carbon dioxide, the filled gas can efficiently push the air out of the container.
[0135] FIG. 8 is a perspective view of a housing container 130 for a method for increasing
the internal pressure of a hollow ball according to still another embodiment of the
present invention. The housing container 130 includes a main body 132 and an opening/closing
tool 134.
[0136] The main body 132 has a box shape. The main body 132 stores hollow balls therein.
The main body 132 includes therein an intake port 136 for feeding gas thereinto and
an exhaust port 138 for discharging gas from the interior thereof. The intake port
136 and the exhaust port 138 are provided in an upper surface of the main body 132.
The intake port 136 is provided with a cap 137. The intake port 136 can be closed
by the cap 137. The exhaust port 138 is provided with a cap 139. The exhaust port
138 can be closed by the cap 139.
[0137] The opening/closing tool 134 is located in a front surface, both side surfaces, and
a rear surface of the main body 132. The opening/closing tool 134 extends around the
main body 132 near upper sides of the front surface, both side surfaces, and the rear
surface. The opening/closing tool 134 is an airtight fastener 134. As shown in FIG.
9, the entire upper side of the main body 132 can be opened by opening the airtight
fastener 134. Through this opening, hollow balls can be taken in and out. By closing
the airtight fastener 134, the main body 132 enters an airtight state.
[0138] In order to increase the internal pressures of hollow balls by using the housing
container 130, the airtight fastener 134 is opened, and the hollow balls are put through
this opening into the main body 132. Next, the airtight fastener 134 is closed. In
a state where the cap 140 of the intake port 136 and the cap 139 of the exhaust port
138 are opened, a gas which is more excellent in permeability relative to an outer
shell of each hollow ball than oxygen gas and nitrogen gas is fed through the intake
port 136 into the interior of the housing container 130. The air having been present
within the main body 132 is pushed by the gas to be discharged through the exhaust
port 138. After the housing container 130 is filled with the gas, the intake port
136 and the exhaust port 138 are closed. The hollow balls are left in this state for
a certain time period. The gas enters into the hollow balls, so that the internal
pressures of the hollow balls are increased.
[0139] The housing container 130 may include a hose within the main body 132. Alternatively,
a pipe of a gas cylinder may be inserted through the intake port 136 into the interior
of the housing container 130.
[0140] As described above, in the housing container 130, the entire upper side of the main
body 132 can be opened. This makes it easy to take in and out hollow balls 136. The
user can put the entirety of a basket 138 containing the hollow balls 136, directly
into the container 160. This greatly reduces time and effort to take in and out the
hollow balls 136.
[0141] The distance between the intake port 136 and the exhaust port 138 is preferably as
long as possible. Thus, the gas injected through the intake port 136 can be prevented
from leaking directly through the exhaust port 138. Accordingly, filling with the
gas can be efficiently performed.
[0142] FIG. 10 is a front view of a pressure container 140 for a method for increasing the
internal pressure of a hollow ball according to an embodiment of the present invention.
In FIG. 10, an arrow X indicates a rightward direction, and the opposite direction
is a leftward direction. An arrow Y indicates an upward direction, and the opposite
direction is a downward direction. A direction perpendicular to the surface of the
sheet is a front-rear direction. FIG. 11 is a right side view of the pressure container
140, and FIG. 12 is a plan view of the pressure container 140. In FIG. 12, an arrow
Z indicates a frontward direction, and the opposite direction is a rearward direction.
The pressure container 140 includes: a housing portion 142 which houses hollow balls;
and a heater 144 which heats the housing portion 142. The housing portion 142 includes
a trunk portion 146, a lid 148, a clamp 150, an intake port 152, an exhaust port 154,
a temperature meter 156, and a pressure meter 158.
[0143] The trunk portion 146 has a cylindrical shape with a bottom 160. The bottom 160 of
the trunk portion 146 is rounded so as to be convex downward. Although not shown,
the trunk portion 146 includes, in an upper portion thereof, an input port for putting
in hollow balls therethrough. The inputted hollow balls are stored within the trunk
portion 146
[0144] The lid 148 is put on the trunk portion 146. An upper portion of the lid 148 is rounded
so as to be convex upward. The outer diameter of the lid 148 is equal to the outer
diameter of the trunk portion 146. When the lid 148 is put on the trunk portion 146,
the lid 148 closes the input port of the trunk portion 146.
[0145] The clamp 150 is located at the boundary between the trunk portion 146 and the lid
148. The clamp 150 extends around the trunk portion 146 and the lid 148. The clamp
150 includes a circular arc portion 162, a bolt 164, and a nut 166. As shown in FIG.
12, the circular arc portion 162 has a circular arc shape which is opened at the front
and is close to a circle. Two ends 168 of the circular arc are bent frontward.
[0146] FIG. 13 shows a portion of a cross section along a line XIII-XIII in FIG. 12. As
shown in the drawing, the circular arc portion 162 has a substantially U-shaped cross
section. An upper end of the trunk portion 146 and a lower end of the lid 148 are
bent outward and overlap each other. The circular arc portion 162 is fitted to the
overlap portion. As shown in FIG. 12, the bolt 164 is inserted through the two ends
168 of the circular arc portion 162. The bolt 164 is further inserted through the
nut 166. The circular arc portion 162 strongly tightens the trunk portion 146 and
the lid 148 by means of the bolt 164 and the nut 166. Thus, the trunk portion 146
firmly adheres to the lid 148. The trunk portion 146 and the lid 148 firmly adhere
to the circular arc portion 162. The gas within the pressure container 140 does not
leak through between the trunk portion 146 and the lid 148 to the outside. The pressure
container 140 is kept airtight.
[0147] The intake port 152 is provided to the lid 148. The intake port 152 is composed of
a valve capable of opening/closing. By connecting a gas cylinder to the valve and
opening the valve, a gas is fed into the interior of the housing portion 142.
[0148] The exhaust port 154 is provided to the lid 148. The intake port 152 is composed
of a valve capable of opening/closing. By opening the valve, the gas is released from
the housing portion 142. Also when the pressure within the pressure container 140
becomes excessively high, the gas is discharged through the exhaust port 154.
[0149] The temperature meter 156 is located on the lid 148. The temperature meter 156 monitors
the temperature within the pressure container 140.
[0150] The pressure meter 158 is located on the lid 148. The pressure meter 158 monitors
the pressure within the pressure container 140.
[0151] The heater 144 is wound around the trunk portion 146. The heater 144 is a rubber
heater. The heater 144 is mounted on the outer side of the housing portion 142. The
heater 144 heats the interior of the housing portion 142 from the outside of the housing
portion 142. Although not shown, the heater 144 includes a knob for temperature adjustment.
Thus, the temperature within the housing portion 142 is adjusted to a desired value.
[0152] In order to increase the internal pressures of hollow balls by using the pressure
container 140, first, the hollow balls are put through the input port of the trunk
portion 146 into the trunk portion 146. The lid 148 is put on the trunk portion 146.
The clamp 150 is mounted to the boundary between the trunk portion 146 and the lid
148, and the bolt 164 of the clamp 150 is tightened. Thus, the pressure container
140 enters an airtight state. The air within the pressure container 140 is discharged
through the exhaust port 154 of the pressure container 140. A gas which is more excellent
in permeability relative to an outer shell of each hollow ball than oxygen gas and
nitrogen gas is fed through the intake port 152 into the interior of the pressure
container 140. The gas is fed until the pressure within the pressure container 140
reaches a predetermined value. The heater 144 is operated. Thus, the pressure container
140 is heated to a predetermined temperature. The hollow balls are left in this state
for a certain time period. The gas enters into the hollow balls, so that the internal
pressures of the hollow balls are increased.
[0153] As described above, the permeability coefficient of each of nitrogen gas, oxygen
gas, and carbon dioxide gas at 50°C for natural rubber is 2 times to 3 times of the
permeability coefficient thereof at 25°C. The pressure container 140 includes the
heater 144. Thus, the temperature within the pressure container 140 can be easily
increased. In the case where carbon dioxide gas is used as the gas with which the
pressure container 140 is filled, by increasing the temperature within the pressure
container 140 from 25°C to 50°C, a speed at which the gas enters into each hollow
ball is increased by substantially 2.2 times. With the pressure container 140, the
internal pressures of the hollow balls can be easily increased in a shorter time.
[0154] The heater may not be a type mounted on the outer portion of the housing portion
142. The heater may be a type mounted within the housing portion 142. For example,
a pocket heater which is a heat source may be provided within the housing portion
142. In this case, a partition is preferably provided so as to prevent the heat source
from being in direct contact with the hollow balls.
[0155] Each of the trunk portion 146 and the lid 148 is preferably made from a metal. The
pressure container 140 in which each of the trunk portion 146 and the lid 148 is the
metal has favorable heat resistance. This container is not damaged even when being
heated by the heater 144. Furthermore, the pressure container 140 has favorable pressure
resistance. When this container is used, the pressure within the container can be
made higher than the pressure of the atmosphere. With this container, the internal
pressures of hollow balls can be further efficiently increased. In this respect, examples
of preferable metals include aluminum alloys. The container may be made from stainless
steel.
[0156] The pressure container 140 in FIG. 10 includes the one intake port 152 and the one
exhaust port 154. The pressure container 140 may include two or more intake ports
152 or two or more exhaust ports 154. In this case, the air within the pressure container
140 can be efficiently discharged or the pressure container 140 can be efficiently
filled with the gas.
EXAMPLES
[0157] The following will show effects of the present invention by means of examples, but
the present invention should not be construed in a limited manner based on the description
of these examples.
[Example 1]
[0158] In Example 1, the apparatus shown in FIG. 1 was prepared, and a method for increasing
the internal pressures of hollow balls was executed with specifications shown in Table
1. At the ball type in the table, "regular TB" means that regulation tennis balls
were used. Carbon dioxide was used as a gas to be filled. A ball internal pressure
was measured as a difference from the atmospheric pressure. The used regulation tennis
balls had an internal pressure decreased to the atmospheric pressure. Therefore, the
difference between the atmospheric pressure and the ball internal pressure was 0.0
kgf/cm
2. The outer shells of the tennis balls were made from natural rubber. These balls
were put into a pressure container made from stainless steel. In the table, "Vacuum"
in the cell of deaeration operation indicates that prior to filling with carbon dioxide,
the air within the pressure container was discharged by using a vacuum pump. Therefore,
the partial pressure of the air within the pressure container was -1.0 kgf/cm
2 as a difference from the atmospheric pressure. The filling with carbon dioxide was
performed until the pressure of carbon dioxide reached a pressure equal to the atmospheric
pressure. Therefore, the difference between the pressure of carbon dioxide and the
atmospheric pressure was 0.0 kgf/cm
2. The temperature within the pressure container was set at 25°C. In the table, "Container
weight" indicates the weight of the container per one input ball. In the table, "1"
at CO
2 supply times means that after initial filling with carbon dioxide, no carbon dioxide
gas is supplied again.
[Examples 2 and 3]
[0159] Examples 2 and 3 are the same as Example 1, except the pressure of filled carbon
dioxide was as shown in Table 2.
[Comparative Example 1]
[0160] Comparative Example 1 is the same as Example 3, except the gas to be filled was air.
[Example 4]
[0161] Example 4 is the same as Example 1, except the air within the pressure container
was not discharged, a gaseous mixture of carbon dioxide and air was used as the gas
to be filled, and the difference between the atmospheric pressure and the partial
pressure of the air within the pressure container after filling with the gas was as
shown in Table 3.
[Examples 5 and 6]
[0162] Examples 5 and 6 are the same as Example 1, except the temperature within the pressure
container was as shown in Table 3.
[Example 7]
[0163] Example 7 is the same as Example 1, except the ratio (Vg/Vb) was as shown in Table
3 and carbon dioxide gas was supplied in midstream once. In the table, "2" at CO
2 supply times means that after initial filling with carbon dioxide, carbon dioxide
gas was supplied in midstream once until the pressure of carbon dioxide reached a
pressure equal to the atmospheric pressure.
[Example 8]
[0164] In Table 4, "Pushing out" in the cell of deaeration operation indicates that deaeration
with the vacuum pump was not performed, and air was pushed out by putting in carbon
dioxide gas. Example 8 is the same as Example 1, except deaeration operation was the
pushing out.
[Example 9]
[0165] Example 9 is the same as Example 8, except the ratio (Vg/Vb) was as shown in Table
4 and carbon dioxide gas was supplied in midstream once until the pressure of carbon
dioxide reached a pressure equal to the atmospheric pressure.
[Example 10]
[0166] In Example 10, the apparatus shown in FIG. 2 was prepared, and a method for increasing
the internal pressures of hollow balls was executed with specifications shown in Table
4. At the container in the table, "PET" indicates that the storage container was made
from polyethylene terephthalate. The deaeration operation was executed through "Pushing
out". Filling with carbon dioxide gas was performed such that the difference between
the partial pressure of carbon dioxide within the pressure container and the atmospheric
pressure was 0.9 kgf/cm
2.
[Example 11]
[0167] In Example 11, the apparatus shown in FIG. 3 was prepared, and a method for increasing
the internal pressures of hollow balls was executed with specifications shown in Table
5. At the container in the table, "Nylon" indicates that the housing bag was made
from nylon. At the deaeration operation, "Vacuum cleaner" indicates that after the
balls were put into the housing bag, the air within the bag was discharged by a vacuum
cleaner. Filling with carbon dioxide was performed until the pressure of carbon dioxide
reached a pressure equal to the atmospheric pressure. Therefore, the difference between
the partial pressure of carbon dioxide within the pressure container and the atmospheric
pressure was 0.0 kgf/cm
2.
[Example 12]
[0168] Example 12 is the same as Example 11, except the ratio (Vg/Vb) was as shown in Table
5 and carbon dioxide gas was supplied in midstream until the volume of carbon dioxide
reached a capacity Vg.
[Example 13]
[0169] Example 13 is the same as Example 12, except the material of the housing bag was
polyethylene.
[Example 14]
[0170] Example 14 is the same as Example 12, except the internal pressures of soft tennis
balls were increased. At the ball type in the table, "Soft TB" means that soft tennis
balls were used.
[Evaluation of Internal Pressure Increasing Speed]
[0171] After the housing portion was filled with the gas by the method shown in each of
the Examples, the balls were left within the housing portion for 24 hours. In Examples
7, 9, 12, 13, and 14, carbon dioxide gas was supplied once after 12 hours. Then, the
balls were taken out from the housing portion, and the internal pressure thereof was
measured. The difference between this internal pressure and the internal pressure
before filling with the gas is shown as an internal pressure increasing speed in Tables
2 to 5.
[Table 2]
Table 2 Evaluation Results
|
Example 1 |
Example 2 |
Example 3 |
Comparative Example 1 |
Ball type |
Regular TB |
Regular TB |
Regular TB |
Regular TB |
Ball internal pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
0.0 |
Deaeration operation |
Vacuum |
Vacuum |
Vacuum |
Not performed |
CO2 partial pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.9 |
1.84 |
-1.0 |
Air partial pressure (difference from atmospheric pressure) [kgf/cm2] |
-1.0 |
-1.0 |
-1.0 |
1.84 |
Container |
Stainless |
Stainless |
Stainless |
Stainless |
Ratio (Vg/Vb) |
4.0 |
4.0 |
4.0 |
4.0 |
Storage temperature [°C] |
25 |
25 |
25 |
25 |
Container weight [g/one ball] |
300 |
300 |
300 |
300 |
CO2 supply times |
1 |
1 |
1 |
1 |
Internal pressure increasing speed [kgf/cm2 day] |
0.25 |
0.45 |
0.92 |
0.013 |
[Table 3]
Table 3 Evaluation Results
|
Example 4 |
Example 5 |
Example 6 |
Example 7 |
Ball type |
Regular TB |
Regular TB |
Regular TB |
Regular TB |
Ball internal pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
0.0 |
Deaeration operation |
Not performed |
Vacuum |
Vacuum |
Vacuum |
CO2 partial pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
0.0 |
Air partial pressure (difference from atmospheric pressure) [kgf/cm2] |
0.8 |
-1.0 |
-1.0 |
-1.0 |
Container |
Stainless |
Stainless |
Stainless |
Stainless |
Ratio (Vg/Vb) |
4.0 |
4.0 |
4.0 |
2.0 |
Storage temperature [°C] |
25 |
50 |
35 |
25 |
Container weight [g/one ball] |
300 |
300 |
300 |
300 |
CO2 supply times |
1 |
1 |
1 |
2 |
Internal pressure increasing speed [kgf/cm2 day] |
0.27 |
0.54 |
0.36 |
0.25 |
[Table 4]
Table 4 Evaluation Results
|
Example 8 |
Example 9 |
Example 10 |
Ball type |
Regular TB |
Regular TB |
Regular TB |
Ball internal pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
Deaeration operation |
Pushing out |
Pushing out |
Pushing out |
CO2 partial pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.9 |
Air partial pressure (difference from atmospheric pressure) [kgf/cm2] |
-1.0 |
-1.0 |
-1.0 |
Container |
Stainless |
Stainless |
PET |
Ratio (Vg/Vb) |
4.0 |
2.0 |
4.0 |
Storage temperature [°C] |
25 |
25 |
25 |
Container weight [g/one ball] |
300 |
300 |
1 |
CO2 supply times |
1 |
2 |
1 |
Internal pressure increasing speed [kgf/cm2day] |
0.25 |
0.25 |
0.45 |
[Table 5]
Table 5 Evaluation Results
|
Example 11 |
Example 12 |
Example 13 |
Example 14 |
Ball type |
Regular TB |
Regular TB |
Regular TB |
Soft TB |
Ball internal pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
0.0 |
Deaeration operation |
Vacuum cleaner |
Vacuum cleaner |
Vacuum cleaner |
Vacuum cleaner |
CO2 partial pressure (difference from atmospheric pressure) [kgf/cm2] |
0.0 |
0.0 |
0.0 |
0.0 |
Air partial pressure (difference from atmospheric pressure) [kgf/cm2] |
-1.0 |
-1.0 |
-1.0 |
-1.0 |
Container |
Nylon |
Nylon |
Polyethylene |
Nylon |
Ratio (Vg/Vb) |
4.0 |
2.0 |
2.0 |
2.0 |
Storage temperature [°C] |
25 |
25 |
25 |
25 |
Container weight [g/one ball] |
1 |
1 |
1 |
1 |
CO2 supply times |
1 |
2 |
2 |
2 |
Internal pressure increasing speed [kgf/cm2 day] |
0.25 |
0.25 |
0.24 |
0.25 |
[0172] As shown in Tables 2 to 5, in the method for increasing the internal pressures of
the balls in each Example, the internal pressures of the balls are restored at a significantly
higher speed as compared to the method for increasing the internal pressures of the
balls in each Comparative Example. From the evaluation results, advantages of the
present invention are clear.
INDUSTRIAL APPLICABILITY
[0173] The method described above can be used for increasing the internal pressures of various
hollow balls.
DESCRIPTION OF THE REFERENCE CHARACTERS
[0174]
2, 30, 50 · · ·apparatus for method for increasing internal pressure of hollow ball
4, 140 · · ·pressure container
6 · · · vacuum pump
10, 34, 54, 106, 114 · · ·gas cylinder
12 · · ·exhaust pipe
14, 38, 56 · · ·intake pipe
16, 40 · · ·feed pipe
18, 42, 58, 136 · · ·ball
20, 44, 72, 86, 118, 132 · · ·main body
22, 46, 148· · ·lid
24, 60 · · ·input port
26, 28, 48 · · ·hole
32 · · ·storage container
52 · · ·housing bag
62· · ·zipper
76, 94, 112, 136, 152· · ·intake port
84, 78, 96, 120, 138, 154· · ·exhaust port
70, 84, 110, 130· · ·housing container
74, 88, 134· · ·opening/closing tool (airtight fastener)
80, 82, 100, 102, 137, 139· · ·cap
90· · ·hose
92· · ·frame
98· · ·valve
104· · ·second end
116· · ·pipe
138· · ·basket
142· · ·housing portion
144· · ·heater
146· · ·trunk portion
150· · ·clamp
156· · ·temperature meter
158· · ·pressure meter
160· · ·bottom
162· · ·circular arc portion
164· · ·bolt
166· · ·nut
168· · ·end