JPH0225630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to tennis balls, and more particularly to tennis balls with improved valves and methods of manufacturing the same. Whether or not the characteristics of the ball are constant is a matter of great interest to anyone who plays tennis, unless they are beginners. A tennis ball is usually made of an elastomer material such as natural rubber or synthetic rubber and is molded into a hollow spherical shell. This shell is pre-filled with pressurized air at the factory, adhesive is applied, and then two pieces of figure-eight fabric are applied to it to cover the surface of the shell, connecting the edges that abut each other. This completes the unique structure of the tennis ball. Tennis balls are typically shipped in metal cans filled with pressurized air. When the can is opened, the tennis ball is exposed to atmospheric pressure. Sometimes the balls are already dead right out of the can. That is, the repulsive force of the ball may be insufficient and the ball may not be suitable for use as a tennis ball. Further, due to various changes in atmospheric pressure and temperature, the air pressure inside the tennis ball changes, which may cause large variations in the repulsive force of the ball. It has been conventional practice to provide valves in the walls of air-filled bowls. For footballs, basketballs, etc., which have a large air volume and are subject to relatively small impact forces infrequently, they are filled with air through a valve prior to the competition, and the required internal pressure is maintained during the competition. You can try to maintain it. Moreover, for such a ball, the internal pressure of the ball and minute changes in it do not pose much of a problem when the ball is used. In contrast, tennis balls have a small air volume and are frequently subjected to high impact forces. Therefore,
Even a small leak of air from the valve can cause enough change during play to cause a change in the usage characteristics of the ball. Therefore, for example, if the valve mounting part is exposed on the outside of the ball, when the ball violently collides with the floor during a game, dirt on the floor may enter the opening of the valve, and this dirt may enter the valve opening. This may cause air to leak from the valve. Even if a slight air leak occurs due to the intrusion of dust, there is a problem in that, as described above, the air volume of the tennis ball is small, resulting in large variations in the repulsive force of the ball. In view of these points, the main object of the present invention is to provide a tennis ball in which air is not leaked from the valve by integrally providing the valve and covering the entire outer surface of the shell, including the outer outlet of the valve, with cloth. Our goal is to provide the following. Specifically, it consists of a hollow spherical shell made of rubber that is equipped with a check valve type valve in the side wall of the shell so that gas can flow into the ball, and two roughly figure-eight shaped shells that cover the shell. A tennis ball mainly made of cloth, wherein the cloth is adhered to the entire outer surface of a hollow spherical shell with an adhesive, and the entire outer surface of the shell, including the outer outlet of the hole where the valve is attached, is covered with the cloth. Cover,
The present invention also provides a tennis ball characterized in that the cloth is made of a breathable cloth such as felt cloth. Furthermore, the main object of the present invention is to maintain a constant internal pressure without air leakage by covering the valve with cloth as described above even when the valve is used vigorously on an unclean floor of a tennis court. The object of the present invention is to provide a method for manufacturing such a tennis ball and filling it with air. Another object of the present invention is to provide a tennis ball integrally provided with a valve, by covering the entire outer surface of the shell including the outer outlet of the valve with a breathable cloth, so that the cloth covering the valve part can be peeled off. A tennis ball and manufacturing method that can be filled with air to maintain a constant internal pressure regardless of the altitude or temperature of the playing area without damaging the outer surface of the ball. It is about providing. A third object of the present invention is to provide a method for manufacturing a tennis ball equipped with such a valve. Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
This relates to known technology. Various attempts have been made to provide valves to tennis balls, but none of them have yielded satisfactory results. Examples of such tennis balls are shown in FIGS. 1-4. The tennis ball, generally indicated by the reference numeral 10, consists of a molded rubber shell 12 having two fabric skins 14 attached to each other at their edges 16 as described above. This shell 12 is provided with a through hole, into which a valve, generally indicated by the reference numeral 18, is fitted and secured with a suitable adhesive. The valve 18 is also usually made of rubber. The valve 18 has a cylindrical outer portion 20 for receiving an injection needle 22 of a syringe-like air pump as shown in FIG. Furthermore, the inner portion 26 of the valve 18 has a structure that allows air to flow in only one direction. Usually, this inner part 26 is a so-called "duckbill".
It has a structure called. Various beak embodiments are shown in FIGS. 2 through 7. The valve 18 is not only fitted into a through hole formed in a rubber shell, but also the valve may be integrally molded when the shell 12 is molded. Such a type of valve is shown in FIGS. 5, 6 and 8. The operating principle of this beak structure is the same for any tennis ball. That is, the ends of the inner portion define a pair of opposing surfaces 28 that define a slit 30. When air is injected into the inner portion by the pump 24, the opposing surfaces are moved apart and the slit 30 opens, allowing air to be pumped through the slit into the interior of the ball. When the injection of air from the outside into the inner portion 20 is stopped, the restoring force due to the stretched state of the elastomeric material constituting the beak structure,
Ball 1 trying to press both opposing surfaces 28 against each other
Due to the action of the zero internal pressure, both opposing surfaces 28 return to their original states. As mentioned above, none of the balls invented before the ball according to the present invention were satisfactory, and the reason for this will be explained with reference to FIGS. 10 to 12. In FIG. 10, the normal inner portion 26 of the beak structure is shown in a relaxed state. When this is subjected to internal pressure, it is compressed into the shape shown in FIG. However, the first
As shown in Figure 2, which is greatly enlarged, the beak-shaped valve formed by the usual method,
Small passages 32 are formed at both ends of the slit so that the space between the opposing surfaces 28 is not completely closed. The amount of air that passes through these passages is minute, but considering that the amount of air originally filled in the ball 10 is small and that the ball is frequently hit during the game, it will happen sooner or later. Sooner or later it will become impossible to ignore. Moreover, each time the shell 12 is distorted due to the high impact force that the tennis ball 10 receives from the ground or the racket, the facing surfaces 28 cannot necessarily maintain alignment and repeatedly move out of alignment with each other. , microscopic air leakage occurs over the entire area of the facing surface 28. Prior to this discovery by the inventors, the reason for air leaking from the ball was unknown, and as a result, all attempts to solve this problem had not yielded satisfactory results. In the basic beak valve shown in FIGS. 2, 3, and 5, the facing surface 28 narrows inwardly from the outer portion to form a narrow slit 3.
They are merging to form 0. Since the total contact area of the opposing surfaces in contact with each other in this region is negligible, a correspondingly large amount of air can leak. In the variant shown in FIGS. 8 and 9, both opposing surfaces 28 are formed by a pair of mutually parallel thin projections 3 having very narrow slits 30 at their free ends.
4. Further variations are shown in FIGS. 6 and 7, in which a small hole 36 is drilled in the distal end instead of the slit 30, and the distal end is sealed. A pair of mutually parallel protrusions 34 are provided. If the hole 36 is drilled so that the flow rate of air that can be injected from the valve 18 is at a common level, the amount of air leakage from the valve shown in FIGS. There is not much difference in the valves shown in FIG. 9 and FIG. However, both types of beak valves are superior to the basic type of beak valve shown in FIG. No. 4,240,630, issued to the inventor on December 23, 1980, discloses a valve suitable for use with a game ball. The valve described in the same specification functions without problems as long as it is used in a clean environment such as a racquetball court, but it cannot be used buried in the side wall of a tennis ball or in a small If air is filled with a manual pump, air may leak from the valve after the ball is used on an unclean floor of a tennis court. According to the tennis ball based on the present invention, the above-described drawbacks can be overcome. The tennis ball according to the present invention consists of a hollow spherical shell made of rubber covered by two pieces of cloth roughly in the shape of a figure eight, and the cloth has breathability, so that the air to be injected into the ball can pass through the cloth. A valve, which is a check valve as disclosed in the above-mentioned US patent, is embedded in the side wall of the ball, which is reached after passing through the ball. In a preferred embodiment of the present invention, the entire outer surface of the shell, including the outer outlet of the valve, is covered with a breathable cloth such as felt, and a gauze cloth is provided between the cloth and the outer outlet of the valve. It is placed under the skin and on the front side of the valve, and is designed to prevent the passage of particles that would impair the sealing ability of the valve if they entered the valve. To fill a ball with air to give it a reproducible repulsion ability, the ball is placed in a fixed volume can, such as on a tennis court, and the can is sealed to give the ball the desired repulsion ability. The can can be compressed to obtain an internal pressure of To manufacture the ball, two hemispherical shells, one of which is provided with a valve, are joined together. Before joining, apply silicone grease to the valve to prevent valve failure. Specifically, the valve used in the tennis ball of the present invention utilizes a wedge action and an improved sealing surface. In a preferred embodiment of the tennis ball according to the invention, reference numeral 4 from FIGS. 13 to 15
A valve sleeve with a small diameter as shown in simplified form with 2 is fitted,
And its outer surface is covered with cloth. It goes without saying that instead of welding this valve, it is also possible to form it integrally from the beginning. As shown, the valve 42 is fitted into a hole 40 drilled in the relatively rigid side wall 38 of the shell. Valve 42 is installed to allow air to flow in the direction of arrow 44 and to block air to flow in the direction of arrow 46. Valve 42
It has an integral structure and is molded from a flexible elastomer material. Soft natural rubber is preferred as the material, but other materials may be used as long as they have similar deformation and sealing properties. The valve 42 is annular and has a thickness adjacent to the hole 40 such that it receives sufficient support from the side wall of the hole 40 to prevent deformation movement along the side wall of the hole 40. However, the valve 42 extends radially inwardly, i.e. along the axis in the direction of the arrow 44 to allow air flow.
It gradually becomes thinner as it moves away from the side wall of 0. The valve 42 becomes thinner toward the end and has an elliptical cross-sectional shape, and is sealed at a position farthest from the side wall of the hole 40. Since the valve 42 is made of an easily deformable elastomer material such as soft rubber and tapers gradually toward the free end, the valve 42 is easier to deform as it approaches the center of the hole 42. As can be seen in FIG. 13, when no pressure is applied, the valve 42 is sealed at its innermost end, indicated by 48. That is, the inner end 48 is
It is a normally closed type of valve that prevents air flow in the direction of arrow 44 but allows air to enter in the direction of arrow 44. Thus, the normally closed inner end 48 has a normally open portion 50 below it in the drawing.
There is. That is, the opposing inner surface 5 of the valve 42
2 are spaced apart from each other and define passageway portions 50. Further, the shape of the valve 42 is maintained by a valve body 54 having an annular shape. Next, FIG. 14 shows how the valve operates when fluid flows in the direction of arrow 46. Fluid flow in the direction of arrow 56 is directed through valve 42 by action of normally closed inner end 48.
cannot flow through. Therefore, the fluid 56 is
The upper surface of the valve 42 will be pressed. As a result, the entire valve 42 is deformed to sink into the hole 42 due to the pressure of the fluid 56. As described above, the valve 42 is easily deformable near the center, and gradually becomes less deformable toward the periphery of the main body 54 and the like. As a result, the opposing inner surfaces of the normally open portion 50 are first closed together, resulting in the closed condition shown in FIG. 14. In the valve 42, from the wall of the hole 40 to the surface 5
2 (dashed arrow 60) is the radial distance of the hole 40 at that point (dashed arrow 6).
Since it is always longer than 2), the internal pressure of the ball is
As it increases in the direction of arrow 56' in Figure 5,
Depending on the magnitude of the pressure, the valve 42 is inserted into the hole 40 and closed more tightly. Valve 42 is comprised of a readily deformable elastomeric material, such as rubber, so that an internal compressive force in the direction shown by arrow 64 can be applied to the normally closed inner end 48 and the normally open (currently open) end. The inner surfaces of the (closed) portions 50 are pressed against each other, allowing the valve 42 to remain tightly closed even when an impact or other external force is applied. Next, referring to FIGS. 16 to 19, we will examine whether the above-described structure can be integrally molded into the rubber shell 12' of the tennis ball according to the present invention.
A preferred embodiment will be described. In this embodiment, the valve 66 is in the form of an inwardly projecting flattened tube with rounded edges (FIGS. 21 and 22) and flat sides 72 separated from each other by a lumen 74. A nipple 68 is provided. The cavity 74 has a ridge shape that gradually widens toward the outer surface of the rubber shell 12 of the ball. That is, the cavity 74 is perpendicular to the plane of the shell 12 at its inner end, but gradually curves tangentially toward its outer end. The nipple 68 is once integrally molded at its inner end, and then cut away with a sharp knife to cut a slit 76 therein. The slits 76 are normally closed due to the elasticity of the rubber, but when the pressure inside the cavity becomes higher than the pressure inside the ball, they open outward from each other. Since the tennis ball according to the present invention has the cavities 74 having such a wedge effect, it can almost completely prevent air leakage even if it receives many strong impacts during a game. The cavity 74 is molded using a male die having a knife edge and a smooth surface at least in a portion corresponding to the cavity 74. The cavity 74 formed in this way has a thin slit having smooth opposing surfaces 78 and 80 at least half its length toward the inner end. There is. This slit narrows sharply as shown in FIG. By using a smooth surface and a knife edge-like slit, there is no flow path that can cause air leakage, as seen in conventional ball check valves as described above. be able to. Therefore, when the nipple 68 is crushed by the internal pressure of the ball, a portion of the cavity 74 is hermetically closed. In such a situation,
The valve 66 is airtightly sealed due to its wedge action, and even under the most severe conditions of use in competitions, the valve 66 will remain airtight unless dirt or the like enters the cavity 74 from the outside and forcibly opens the cavity 74. , no air leaks from inside the ball. The wedge action in the valve 66 will be explained with reference to FIGS. 13 to 15. In particular, FIG. 17 shows the valve 66 in its normal state and in its pressurized state. The pressurized state is indicated by a solid line.
Each normal state is shown by an imaginary line. The portion of the nipple 68 in which the slit 76 is cut includes a normally closed portion. The portion of the rubber shell defined by dashed line 82 is labeled 40' in relation to the corresponding portion shown in FIGS. 13-15. This corresponds to the valve 42 shown in phantom in FIG. Therefore, during the process of expanding the ball from a state where it has an extremely low internal pressure, the slit 76
serves as an initial seal to collapse the sidewall of nipple 68 and prevent air from escaping before sufficient pressure is built up within the ball. As the internal pressure increases, the nipple 68 collapses under lateral pressure, and the smooth surfaces 78 and 80 are pressed against each other, creating a relatively high impact force such as that generated when a fully expanded ball is hit by a racket. The second airtight seal is adapted to withstand As the internal pressure increases further, as indicated by arrow 84, valve 66 deforms further into wedge-shaped engagement within imaginary hole 40'. Since the distance from boundary line 82 for any point on nipple 68 is greater than the radial length of hole 40' for that point, the compression indicated by arrow 56', as described above with respect to FIG. Seal force is generated internally. If the valve 66 is made of substantially the same material as the ball, the volume occupied by the nipple 68 will be the same as that of the cavity 7.
approximately equal to the volume of 4. Also, as shown in FIG. 20, the valve 66 will have a slightly greater weight, as shown by the arrow 86, distributed at a point of radius d ₂ about the center of the ball, but the opposite portion of the ball will be , is slightly smaller than the radius d ₁ of the point where the effective center of weight is located during the rotation of the ball, so the rotational inertia of both parts is approximately equal, and the balance of the tennis ball is not impaired. As a result, valve 66 has a negligible effect on the balance of the tennis ball. Figures 18 and 19 show the dimensions of an actual tennis ball with such a valve (see Table 1). In manufacturing this tennis ball, first two hemispherical shells are molded, one of which is integrally provided with a valve, and the other without a valve. The two hemispherical shells are then joined together by applying heat and pressure. Naturally, one valve will be formed inside it. Thereafter, the entire outer surface of the ball is covered with a breathable cloth, and the cloth is adhered to the entire outer surface of the shell with an adhesive to complete the tennis ball. It has been found that the use of materials that can handle pressure and completely seal the valve creates unforeseen problems. That is, the tennis ball valve according to the present invention is made of flexible natural rubber or other material with similar properties to achieve the desired air-tight properties, and when internal pressure is present, the opposite side of the valve The surfaces are tightly wedged together and exhibit a strong sealing force, but if the tennis ball based on the present invention was manufactured using conventional manufacturing technology, the molding process and bonding process were particularly difficult to perform at the initial stage. It was found that this was not suitable for maintaining effective sealing force. According to the conventional manufacturing method, when joining two hemispherical shells, the surfaces made of flexible natural rubber are firmly pressed against each other, creating an internal pressure that is almost diffusion bonded to them. . Therefore,
When the ball was subsequently placed in a pressurized container, it was not possible to overcome the pressure difference between the inside and outside of the ball and release the diffusion bonded portion. The ball simply deformed, and the internal pressure could not be adjusted to an appropriate level. Therefore, in order to solve this problem, the inventors of the present invention believe that before joining the two hemispherical shells together,
We have discovered that it is effective to lightly apply silicone grease to the opposing surfaces inside the valve. In this way, even if a certain amount of internal pressure is applied to the ball during manufacturing, the ball valve will not undergo diffusion bonding and will not lose its sealing function as a check valve. What is important in this case is to use a silicone-based grease that does not attack the flexible natural rubber like ordinary petroleum-based grease. Therefore,
Grease, as used herein, is understood to be a generic term for any material that provides the desired coating effect on the surface of the ball without attacking it. Now, as shown in FIGS. 20, 23 and 24, a cloth 90 is integrally disposed over the entire outer surface of the tennis ball shell 12' provided with the valve 66. As shown in FIG. 24, the cloth 90 consists of two pieces of eight-shaped felt cloth, and the edges of these felt cloths are connected to each other to cover the entire outer surface of the shell as described above. In addition, the gap between the edges of the felt cloth is filled with adhesive, so that
Adhesive is placed on the outer surface of the shell corresponding to the gap. The cloth 90 covering the tennis ball according to the present invention is air permeable, and as shown in FIGS. 20 and 23, the hole in the valve 66 is similar to other parts. It's hidden. The fabric 80 is conventionally applied to the rubber shell 12' with a suitable adhesive, but care must be taken to prevent the adhesive from penetrating the holes in the valve 66. Further, to prevent dirt and the like from entering the valve 66, it is preferable to cover the valve hole 66 with a patch 91 made of gauze cloth or the like before applying the cloth 90. According to experiments, it was possible to prevent the intrusion of dirt under normal usage conditions even without using gauze cloth patches, but over a long period of time,
Air sometimes leaked. When I looked into it, I found that
It has been found that even a single fiber shed from the surface of the felt cloth and entering the valve 66 is sufficient to destroy its sealing ability. The gauze cloth patch 91, which does not easily shed fibers, acts as a filter for the hole in the valve 66 and protects its sealing ability. Patch 91,
Although it may be made of other materials, gauze cloth is suitable because it is extremely thin and lightweight, and does not impair the balance of the ball. The tennis ball 92 can be pressurized in any of a variety of containers for transporting or storing balls under pressure. In this regard, fabric 90 has two functions. One is that the breathability allows air to freely flow from the valve 66 into the interior of the ball. The second function is that the sealing ability of the valve depends on the ability to maintain pressure due to the close contact between the smoothed opposing surfaces, and the cloth 90
It has the function of preventing the intrusion of dirt that would impair such pressure holding ability. Therefore, one of the important features of the present invention is that instead of preloading the tennis ball as in the past, it can be pressurized at the point of use and based on a specific gauge pressure. Rather, it is possible to pressurize based on changes in the volume of the container. The ball according to the invention is therefore capable of pressurization that fully compensates for changes in altitude and temperature. Therefore, the ball can have the same bounce characteristics regardless of the altitude or temperature where it is used. If a tennis ball 10 with a valve 66 according to the invention is desired to reduce its degree of expansion, simply insert a toothpick, paper clip, etc. into the hole in the valve and separate the sealing lips. It is only necessary to break the sealing action. Experiments have shown that by doing this, it is possible to adjust the pressure with an accuracy of a fraction of a millimeter of mercury. It has also been found that in order to maintain the desired degree of bounce, it is necessary to release the excess pressure in the ball or to re-pressurize it, depending on changes in altitude and temperature at the location of use. Therefore, as shown in FIG.
If a mark 94 is attached to the upper side of the valve 66, when releasing the excess internal pressure of the ball, the valve position can be recognized by the mark 94, and a clip or the like can be inserted through the cloth 90 into the valve 66. Therefore, the internal pressure of the ball can be reduced very easily. The mark 94 may be printed as a dot or a circle using ink at an appropriate location on the cloth 90. Finally, since the dimensions shown in FIGS. 18 and 19 are in inches, they can be converted to mm in Table 1 below. 【table】

[Brief explanation of drawings]

FIG. 1 is a front view of a known type of tennis ball with a valve mounted in the sidewall. FIG. 2 is an enlarged longitudinal sectional view taken along the line - in FIG. 1. FIG. 3 is an end view taken along the line - - in FIG. 2. FIG. 4 is a partial vertical sectional view showing how the ball of FIG. 2 is filled with air using a syringe-like pump. FIG. 5 is a longitudinal cross-sectional view of a standard beak-shaped bulb integrally molded into the side wall. FIG. 6 is a longitudinal sectional view showing another embodiment of the beak-shaped bulb. Figure 7 shows the 6th
FIG. 3 is a plan view of a portion of the valve shown in the figure. FIG. 8 is a plan view showing yet another embodiment of the beak-shaped bulb. FIG. 9 is a plan view of a portion of the valve of FIG. 8. FIG. 10 is a cross-sectional view of the beak-shaped valve in a non-pressurized state. 11th
The figure is a cross-sectional view of a beak-shaped valve in a pressurized state. FIG. 12 is an enlarged cross-sectional view showing portion XII of FIG. 11. FIG. 13 is a simplified vertical cross-sectional view showing the valve in its non-pressurized state in order to explain the operating principle of the valve according to the invention. 14th
13 is a simplified longitudinal sectional view of the valve of FIG. 13 in a semi-pressurized state where a wedge action is about to be exerted. Figure 15 shows the valve in the fully wedged and sealed condition.
FIG. 14 is a diagram similar to FIG. Figure 16 shows
1 is a longitudinal cross-sectional view of a tennis ball according to the invention having an integrally molded valve; FIG. Figure 17 shows
FIG. 17 is an enlarged vertical cross-sectional view of the portion shown in FIG. 16; FIG. 18 is a longitudinal sectional view taken along a plane perpendicular to FIG. 17, and the dimensions of each part are shown in inches. FIG. 19 is a view similar to FIG. 18 regarding a plane perpendicular to the plane of FIG. 18. FIG. 20 is a longitudinal sectional view showing a part of the ball to explain that the weight of the valve does not impair the balance of the ball. FIG. 21 is a cross-sectional view of the valve according to the present invention in a non-pressurized state. FIG. 22 is a cross-sectional view showing the pressurized state of the ball valve according to the present invention. FIG. 23 is a longitudinal sectional view of the entire ball according to the present invention. FIG. 24 is a front view of a ball according to the invention. 10... tennis ball, 12, 12'... shell, 14... cloth, 16... edge, 18... valve, 20... outer end, 22... needle, 24... pump, 26... Inner end, 28... Opposing surface, 30...
Slit, 32... Passage, 34... Projection, 36
...hole, 38 ... side wall, 40, 40' ... hole, 4
2... Valve, 44, 46... Arrow, 48, 50
... Part, 52 ... Surface, 54 ... Annular body, 56,
56'...arrow, 58...plane, 60, 62, 64
...Arrow, 66...Valve, 68...Nipple,
70, 72... Surface, 74... Hollow, 76... Slit, 78, 80... Surface, 82... Line, 84, 8
6, 88...Arrow, 90...Cloth, 91...Patch, 92...Tennis ball.

Claims (1)

[Claims] 1. A hollow spherical rubber shell 12 provided with a check valve type valve 66 in the side wall of the shell so that gas can flow into the ball, and a generally figure-eight shaped shell 12 covering the shell. The tennis ball is mainly composed of two pieces of cloth 90, in which the cloth 90 is applied to the entire outer surface of the hollow spherical shell 12, and the entire outer surface of the shell including the outer outlet of the valve 66 is covered with the cloth 90. A tennis ball characterized in that the cover and the cloth 90 are made of breathable cloth such as felt cloth. 2 a. A hollow spherical shell 12 made of rubber with a through hole 40 bored in the side wall; b. The hole 40 allows gas to flow in one direction along its axial direction, but does not allow gas to flow in the other direction. a valve 66 mounted in said hole 40 to prevent c. c. having a generally figure-eight shape and connecting its edges to cover the entire outer surface of said shell, including the outer outlet of said hole 40; and two sheets of cloth 90 that are breathable to pressurized gas, and the valve 66 is held concentrically within the hole 40, and thereby is generally deformed in the axial direction. The annular body 54 has sufficient axial thickness such that it does not
and b2 protrudes radially inward from the annular body, becomes gradually thinner and thinner toward the inner end, and at the same time becomes more deformable, so that the inner end has surfaces that abut each other for sealing. Become,
It is equipped with a sealing nipple 68 that allows gas to flow only inwardly, and when gas pressure is applied outwardly, the nipple 68 acts as a wedge and closes the annular body 54.
The shape of the nipple is perpendicular to the axis of the hole 40 from the outer end toward the inner end, and gradually changes to the axis. The hole 40 is formed along a smooth curve parallel to the hole 40.
The pressure of the gas that tends to flow outward due to the internal atmospheric pressure is applied to the nipple 68 along the direction perpendicular to the axis, so that the opposing surfaces of the inner ends are first brought into pressure contact with each other, and then the By immersing the entire nipple 68 into the hole 40 with a wedge action, gas flow is prevented, and the nipple 68 is made of natural rubber or a material having deformation characteristics and sealing characteristics equivalent to natural rubber, A tennis ball characterized in that the nipple 68 is molded so that the inner surface of the nipple 68, which is pressed together with a wedge action, forms a smooth surface. 3. Because the nipple 68 has a large axial length relative to its ease of deformation, even when the member defining the hole 40 expands and the annular body 54 deforms radially outward, the nipple 68 3. The tennis ball of claim 2, wherein the inner end of 68 is closed and the nipple 68 remains recessed into the annular body 54. 4 smooth surfaces 78 that abut each other with a sealing action;
3. The tennis ball of claim 2, wherein 80 defines a slit having a sharp end. 5 Outer outlet of valve 66 and cloth 9 covering the outlet
A filter 91 is provided between the valve 6 and the valve 6.
According to claim 2, foreign matter such as fibers that have fallen off from the cloth 90 and would impair the sealing action of the valve 66 is prevented from entering the valve 66. tennis ball. 6. The tennis ball according to claim 5, wherein the filter is made of gauze cloth 91. 7 a. A hollow spherical shell 12 made of molded rubber, in which a check valve type valve 66 made of an elastomeric material is integrally molded in the side wall; Mainly made of a cloth 90 which is coated on the same surface to cover the entire outer surface of the shell including the outer outlet of the valve 66 and is breathable to pressurized gas, and the valve 66 is axially a generally flat tubular nipple 68 having a rounded profile and generally flat sides defining an elongated cavity 74, the cavity 74 extending from an inlet end of the nipple 68 to an inner end thereof; , defined by a smooth wall surface perpendicular to the axis of the valve 66, gradually becoming parallel to the axis, and finally reaching the inner end of the nipple 68;
An opposing smooth surface 7 is provided at the inner end of the nipple 68.
A narrow slit 76 is cut, defined by 8, 80 and communicating with said cavity 74, said slit 76 being closed, usually by the elasticity of the elastomer material, so that at least the inner half of said cavity 74 is internal. It has a slit shape that gradually narrows toward the end into a knife-like shape and is defined by smooth surfaces 78 and 80, and communicates with the slit 76 at the inner end. tennis ball. 8 Outer outlet of valve 66 and cloth 9 covering the outlet
A filter 91 is provided between the valve 6 and the valve 6.
Claim 7 is characterized in that foreign matter such as fibers dropped from the cloth 90 is prevented from entering the valve 66, which would impair the sealing action of the valve 66. Tennis ball listed. 9. The tennis ball according to claim 8, wherein the filter is a gauze cloth 91. 10. A method for manufacturing a tennis ball having reproducible and predetermined repulsion characteristics regardless of different altitudes or temperatures, comprising: a) applying a pressurized gas in one direction along an axial direction; A hollow spherical shell of rubber is manufactured having a hole drilled in the side wall for holding a valve of the non-return type allowing flow but prohibiting flow in the other direction, said valve being a1 said having a sufficiently large axial thickness toward a portion adjacent the outer outlet of the hole such that it is not substantially deformed axially by being supported on the member defining the hole; and an annular body held concentrically in the hole; and a nipple protruding inward from the annular body having a sealably abutting surface on the part, gas pressure is applied to the valve in a direction opposite to the direction in which the gas can flow. Then, the nipple sinks into the annular body, and the sealing action of the valve is strengthened in accordance with the pressure, and the nipple extends from the outer end to the inner end, initially in a direction perpendicular to the axis, and gradually When pressure is applied to the valve along a smooth curve parallel to the axis and opposite to the direction in which gas can flow, the pressure is first applied to the inner end of the nipple relative to the axis. A sealing action is created by application in the orthogonal direction, and then said pressure is applied to the remainder of said nipple and plunges into said annulus with said wedging action, and said nipple has the flexibility and sealing effect of natural rubber. (b) forming the shell with two pieces of cloth roughly in the shape of a figure 8; The fabric is applied to cover the entire outer surface and its edges are connected to each other, the fabric being permeable to pressurized gas, and also covering the outlet of the valve. A method for manufacturing a tennis ball, the method comprising: 11 Prior to using a tennis ball, a tennis ball originally having a volume of V1 is changed to a volume of V2.
put it in an assembled container having a volume, seal the container, and change the volume to V3,
Said volume V is such that the change in volume V3-V2 is suitable to impart the desired repulsion properties to said tennis ball, regardless of the temperature and altitude of its place of use.
11. The method according to claim 10, further comprising the step of selecting V3. 12 When manufacturing a hollow spherical shell made of rubber, the following steps are required: a) forming a first hollow spherical shell having integrally within its wall a valve having sealably abutting surfaces; b a second hollow hemisphere; c. When joining the two hemispherical shells, a material that does not corrode the surfaces is applied to the surfaces to prevent the adjoining surfaces from adhering to each other. 11. The method of claim 10, comprising the steps of: d) joining the hemispherical shells together to form a single spherical shell. 13. A method according to claim 12, characterized in that the step of applying the material to the adjoining surfaces comprises the step of forming a coating. 14. The method according to claim 13, wherein the material forming the coating film is grease. 15. The method according to claim 14, characterized in that the grease is silicone grease.