CA1196353A - Tennis ball - Google Patents

Abstract

TENNIS BALL

ABSTRACT
An improve tennis ball having an integrally molded valve in the sidewalls thereof for assuring constant pressure within the ball and, therefore, constant playing characteristics. The valve is characterized by being of unitary construction and having a normally open and a normally closed portion. The valve is constructed of a tapered deformable elastomeric material such that the normally closed portion seals the ball against low initial internal pressures sufficiently to allow the internal pressure within the ball to deform the normally opened portion into wedged engagement with the passageaway through the wall of the ball containing the valve. As thus configured, increased internal pressure wedges the normally opened portion increasingly tightly into the passageway to provide a tight seal which is resistant to opening upon impact of the ball. The normally opened portion is provide with knife edges and a polished surface on the interior to provide leak-free sealing. The fabric covering of the tennis ball is made of a gas-permeable material disposed over the valve opening which is further protected by a gauze filter between the opening and the covering fabric. The ball can be pressurized to predictable bounce characteristics regardless of altitude and temperature by placing the ball within a sealed container at the play site and then reducing the volume of the container a fixed amount.
Also, a method of making the valved tennis ball so as to preserve the automatic pressurization characteristics thereof. Two core halves are first prepared -- one having the valve molded therein. The interior sealing lips of the valve are then bonded together and the balance of the ball completed.

Description

~1963~i~

TENNIS BALL

~ cept at the novice level, tennis players are very concerne~ -~ith the consistency of tbe ~layin~
characteristics of the ball. The typical tennis ball is made oE a ~nol~e~ spherical shell of elastomeric material, such as natural or ar~ificial rubber. The shell is prepresaurized at the tactory, coate~ with an adhesive, and 13 cov~r~ with two int~rlocking, figùre-eight-shape~ pieces of fabric ~ispose~ over the surface of the tennis ball with a seam between the abutting e~ges to provi~e the charact-ristic tennis ball coniguration. Typically, such balls are shippe~ in metal cans un~er pressure. When the can is being op~ne~, the ball is subjected to at~ospheric pressure. Sometimes, a brand new ball taken from the can will be "~ea~". That is, it will have insufficient bounce to be useful for play. Also, as a result of varying atmospheric conditions an~ tem~erature changes, the internal pressure within a tennis ball can vary an amount such as to cause lar~e differences in the bounce of one tennis ball versus another.
Valves have been put into the sidewalls o inflatable bla~der type playing balls for years. 8alls su,ch as footballs and basketballs containing large volu~es of air an~ subjected to infrequent and/or low level i.mpacts can be inflate~ prior to a game to a desir2d pressure through tne valve and will ~aintain an acceptablP level of inflation throughout the game. Moreover, the pressure within the ball and minor variations thereof are not critical to the playability OL the ball.
By _ontrast, tennis balls have smaller volu~es o~
contained ~ir and are struck repeatedly with hi~h impact forces. As a ~onsequence, even l~inor leaka~e through a v~Llve can cause changes in the internal pressure of the ball ~urin~ play which is sufEicient to cause a change in '~:

~9~i353 the playing characterlstics of the ball.
The invention provides in a tennis ball having a spherical, hollow, rubber shell covered with a pair of generally figure-8-shaped pieces of Eabric, the improvement characterized by the fabric being permeable to the passage of air therethrough and by a one-way check valve disposed in the sidewall oE the shell beneath the fabric for allowing air to pass therethrough into the ball.
The invention also provides the method of producing a tennis ball having predictable and repeatable bounce character-istics at different altitudes and temperatures comprising the steps of: (a) producing a spherical, hollow, rubber shell having a bore through the sidewall thereof which bore contains a unitary check valve for sealing the bore to allow pressurized fluid to flow axially through the bore in one direction and prevent pressuri~ed fluid from flowing axially through the bore in the opposite direc-tion, said valve comprising, (al) an annular body portion carried coaxially within the bore, said body portion being thick enough in the axial direction adjacent the outer edges of the bore that in combination with the support provided by the material defining the bore said portion is substantially non-deformable in the axial direction, and, (a2) a sealing nipple portion carried within said body portion tapering radially inward and axially in the direction of desired fluid flow from said body portion on one end to meet in sealed contact adjacent the opposite end, the thickness of said sealing nipple portion in the axial direction becoming increasingly thinner and correspondingly increasingly deformable in the axial direction radially inward from said one end whereby the application .i ~ ~-2-:~3 9~

of fluid under pressure to said valve in the direction opposita desired fluid flo~ causes said nipple portion to be deformed axially into said body portion in a wedging action increasingly sealing the passageway as increased fluid pressure is applied, said taper being a smooth curve extending from a point on a line sub-stantially normal to the axis of the bore on said one end to a point on a line substantially parallel to the axis of the bore on said other end whereby fluid pressure within the bore tending to move fluid through the bore in a non-desired direction acts normal to the axis on said nipple portion adjacent said other end to initially prevent fluid passage therethrough as it also acts axially on the rest of said nipple portion to deform said nipple portion in said wedging action into said body portion, said nipple portion being of a material having the deformation and sealing ~ualities of soft natural rubber, the surfaces of said nipple por-tion that meet during said wedging deformation into said body por-tion having a finish produced by a mirror-smooth mold; ~b) bonding a pair of generally figure-8-shaped pieces of fabric to the outer surface of said shell with narrow seams between the abutting edges thereof, said fabric being permeable to the pressurizing fluid and covering the outer opening to said valve; and, (c) at the altitude and temperature whereat the tennis ball is to be used for play, placing the tennis ball being of a given volume V1 into a collaps-ible container having a given internal volume V2, sealing the con-tainer and compressing the container to a second given internal volume V3 wherein the change in volume (V3-V2) is sufficient to place the tennis ball under a pressure which will impart the desired bounce characteristics to it.

-2a-3~

~ t is yet another object oE the present invention to provide a method of making a valved tennis ball.
Figures 1-12 are drawings related to the prior art.
Figure 1 depicts a tennis ball having a valve disposed through the sidewall thereof.
Figure 2 is a cut-away enlarged view through the valve of the ball of Figure 1 in the plane II-II.
Figure 3 is an end view of the valve of Figure 2 in -the plane III-III.
Figure ~ is a partially cu-t-away drawing showing a syringe-type pump being used to inflate the tennis ball of Figures 1-3 through the valve thereof.
Figure 5 is a cut-away view through a standard duckbill type valve as integrally molded into the sidewall of a gameball.
Figure 6 is a cut-away view through an integrally molded duckbill type valve according to an alternate embodiment.
Figure 7 is a plan view of a portion of the valve of Figure 6.
Figure 8 is a cut-away view through ye-t another embodiment of a duckbill type valve.
Figure 9 is a plan view of the valve of Figure 8.
Figure 10 is a cut-away view through a duckbill type `: :
-2b-valve in an unpressurize~ con~ition.
Figure 11 is a cut-away vi~w of a ~uc~bill type valve in a pressurize~ con~ition.
Fi3ure 12 is an enlar~ed view of the valve of Figure 11 in the area XII.
Figure 13 is a ~rawing depictin~ the principle of operation of the valve e~ploy2d in the present invention in its unprossuriz2d stato.
Fi~uro 14 is a cut-away view and a si~plifie~ drawing o~ the v~lve of Fi~ure 13 in a semi-pressurized state showing the beginnirlg of the we~3ging e~Eest e,nploye~
therein.
Fi3ure 15 s'nows the valve of Figures 13 and 14 in its fully we~ge~3 an~ seale~ state.
Figure 16 is ~ cut-away view through the ~ol3e3 rubber shell of a tennis ball according to the present invention.
Fi~ure 17 is an enlarge~ view of the valve ~mploye~
in the presen-t invention as containe~ within Figure 16 in the area XVTI.
Fi~ure 13 is a cut-away view normal to the lon~i~
tu~inal ~i,nension of the valve o~ Figure 17 showing nominal ~imensions thereof in a tested e~bo3iment.
Figure 19 is a cut-away view longitudinally through the valve of Figure 17 showing the :3imensions of the test2 ~ embo~iment th~reof.
Figure 20 is a partially cut-away ~rawing through a portion of a tennis ball depicting the i3eal balance characteristics of the valve Oc the present invention when incorporate3 in a tennis ball.
Figure 21 is a cut-away view throuyh the inner portion of the valve eA~ploye~ in the presen-t invention in its unpressurized state.
Fi~ure 22 is a cut-away ~iew throuyh the inner por'ion of the valve employ~d in the present invention in its pr-ssuri~ed state.

Figure 23 i3 ~ cut-away ~iew throu~h a complete~
tennis ball accor~in~ to the present invention.
Figure 24 is a view of the outsi~e of a tennis ball accor~ing to the present invention in its pre~erre~
embo~iinent.
The insertion of a valve into a tennis ball has been attempte~ previously by others with only limite~ success.
~uch a typical ball is shown -~ith reference to Figures 1-4.
The tennis ball, generally indicated as 10, has a mol~e~
rubber shell 12 with a fabric covering 1~ a~hesively attache~ as describe~ above an~ with seams 15 between the e~ges of the covering 1~. A hole is ~rille~ through the shell 12 an~ a valve, ~enerally in~icated as 18, is inserte~ in the hole and hel~ in place by an appropriate adllesive. Typically, valve 18 is also ma-~e of rubber. The valve 18 co-nprises an outer portion 20 being cylindrical an~ a~apted for the insertion of the cylin~rical filling nib 22 of a small syringe--type pump 24 as shown in Figure 4. Valve 13 has an inn~r portion 26 which allows the one-way passage of air therethrough. Typically, inner portion 25 has been of the so-calle~ "duckbill" type construction. Various orms of such ~u_kbill valve construction are shown in Figures 2-7. In a~ition to the valve 18 being inserted through a hole made in the wall of rubber shell 12, it has also been integrally molde~ as part of the initial mol~in3 process of shell 12 as shown in the ex~ples of Figures 5, 6, an~ 8.
The orinciple of operation of a ~uckbill type valve is similar regar~less o~ the specific construction. That ia, the inner portion 2~ terminates in a pair of oppose~
surfaces 28 having a slit 30 throu~h them. Internal air pressure in outer portion 20 from l~ump 24 forces the oppose~ surfaces 28 apart opening slit 30 to allow the passage of air through it into the interior of the ball.
Upon rele~se of pressure within outer portion 20, the opposed surfaces 28 re~ume their original position ~ue to ~ 963~;3 the rest3r~tive force oE the str~tche~ elastomeric In~teriat From which they are constructe~ an~ then thQ internal pressure o~ the ball 10 ten~s to hol~ the oppose~ surEaces 28 ti3ht to~ether. Until ny valve all such valves have prove~ ultimately unsu_se3sful for use in tennis balls.
~he reason can be un~erstoo~ with reEerence to the drawings of Figures 10-12.
In Fi~ure l~, a typical inner portion 25 of a ~uckbill type valve is shown in its relaxe~ state. Un~er l~ internal preSSUr~ it is co.npresse~ to the sha?e shown in Fi~ur- ll. As shown ln the gr2atly expanded view of Fi~ure 12, however, the normal metho~ of making such ~uclcbill valves causes an incomplet2 closure across the entire surface of oppose~ surfac2s 28 creating a small passagew~y 32 at each si~e. ~hile the amount of air that can leak through the pair of passageways 32 is small, when the small initial quantity of air filling ball 10 and the number of times the ball is struck ~uring play are consi~ere~, the air loss soon becomes large on a relative basis. Also, oppose~ surfaces 23 are such that ~urin~ the ~formation of shell 12 cause~ by the hi~h impact of tennis ball lO
a3ainst th~ ground an~ the tennis racquet, oppose~ sur~aces 28 are not naint ine3 in constant alignment but are "worke~" back an~ forth relative to one another _reatin~
microscopic losses along the entire area of oppose~
surfaces 28.
Until my ~is_overy, t'ne exact nature of an-~ reason for this air loss h~s not been understoo~ an~, therefore, various attempts have been made to solve the problem with 3~ inconplete success. In the basic ~uckbill valve as shown in Figures 2, 3, an~ 5, the opposed surfaces 28 taper inwar~ly from outer portion 20 to ,neet in a small area a~j3cent slit 30. Since t~e total area of oppose~ surfaces 28 in contact is minimal in this ~esign, the air loss througn th~ valve is maxiinum. In the variation of Figures 8 3n~ 9, OppO~2~ surfaces 28 are containe~ wlthin a thln 3~

parallel proje_tion 34 having slit 30 at the extre,ne inner en~ th~reof. A further variation of this ~-neral approach is shown in Fi~ures ~ an~ 7 where the paral.lel projection 34 has the inner en~ seale~ an3 small holes 36 provi~e~
throu~h the si~ewalls of parallel proje_tion 34 to replace tne slit 30. If su~ icient holes 36 are provi~e~ to allow a rea30nable Eillin~ rate through valve 18, the lea~a3e of the variation of Figures 5 and 7 an~ that of Fi~ures ~ an~
3 is al.most i~entical. Both, however, are better than the basic 3uckbill valve of Figure 5.
In my Unite~ States L2ttees Patent ~o. 4,240,630, issued Decelnber 23, 1980, I ~isclose~ a ~lve well suited for use in a ~ame b~ll. ~nile the valve as shown in that patent wor~s well in a clean environment such as racquetball court, when place~ in the si~ewall of a tennis ball an~ inflate~ with a small handpump as taught therein, the valve~ tennis ball often be~an to leak after ~layin~
with in on the unclean surface of a tennis court.
~ y obje~tives have been met by my tennis ball which co~prises a spherical, hollow, rubber sh-ll covere~ with a pair of ~enerally fi3ure-3-sha~e~ pieces of fabric wherein the fabric is perlmeable to the passage of air an~ the one-way check valve of ,ny United States patent is positione~ dispose~ in the sidewall of the shell beneith tne fabric to allow the air to pass aforementione~ through it into the ball.
In the preferre~ embo~iment, a piece oE gauze material is positione~ beneath the fabric an~ over the openill~ to the valve to filter particles from t'ne fabric 3d which coul~ otherwise enter the valve an~ ~estroy its sealing ~ualities.
To fill the ball to achieve the repeatable bounce ~ualities ~esire~, the ball is place~ in a cani~ter o~ a fixed volu~e at the play site an~ th canister then seal~
an~ co.npa_te~ to a lesser volume such that the chan~e in ~olume subjects the b~ll to a pressure which will i~part i~6~;3 the ~esir~ bounce.
In makin~ the ball, two hemispheres comprisin~ the shell have the valve in ona and are bon~e~ together~ Prior to bon~in~ them together, the valve is ~r~ase~ with a sili_one grease to prevent valve malfunction.
SpeciEically, the valve employe~ my tennis ball works on a combin~tion of we~ging action and improved sealing surfaces. The ~referred embodiment of ~y tennis ball employs a minimu~ ~iamet~r, heat bonded valve insert, similar to the one in~icated as 42 in the simpli ie~
~rawing of Figures 13-15, but with the outer surface below the fabric coverin~. The valve coul~ also be integrally .~ol~
Valve 42 is shown positioned within a hole 40 provide3 in th2 rigi~ sidewall 38 of a container. Valve 42 is posi.ione~ to allow fluid flow in the direction of arrow 44 an~ to prevent fluid flow in the direction of arrow 45.
Valve 42 is of unitary construction an~ is mol~ed of a soft pliable 21astomeric material. Soft natural rubber is preferred. However, any material having the ~eformation and sealing qualities of soft, natural rubber can be employe~. Valve 42 is annular in shape and of such a thickness a~jacent the si~es of hole 40 that, in co,~bination -~ith -the support provi~ed by th~ si~ewalls of hole 40, it resists ~eformation in the axial direction close adjacent the sidewalls of hole 40. Valve 42, however, tapers ra~ially inward and axially in the direction of desired flui~ flow (i.e. in the ~irection of arrow 44) becoming thinner the further it gets from the si~ewa~ls of llole 40. Valve 42 tapers together becoming oval in cross section an~ ultimately coming into sealed mating relationshi~ at the opposi~e en~ from the end in contact with the sidewalls of hole 40. Bein~ o~ a deformable elastomeric material, such as soft rubber, an~
tapering towar~s increased thinness, valve 42 becomes more readily ~eformable tow~rds the center of hole 42. As can be seen in Figure 13, with no pressure applied, valve 42 is positioned with the portion at the extreme inner ends labeled 48, in sealed mating contact. Portion 48, therefore, forms a normally closed valve which resists fluid flow in the direction of arrow 46 but which will open to allow the passage of fluid in the direction of arrow 44.
Below normally closed portion 48 is a normally open portion 50. That is, the facing inner surfaces 52 of valve 42 in the area 50 are separated to provide a passagewya. The balance of valve 42 can be considered as an annular body portion, which has been labeled as 54.
Referring now to Figure 14, the action of valve 42 upon the introduction of fluid pressure in the direction of arrow 46 is shown. Fluid (as represented by the arrows 56) is initially prevented from passing through valve 42 by the action of normally closed portion 48. Accordingly, fluid 56 presses on the upper surfaces 58 of valve 42. Valve 42, therefore, begins to deform into hole 42 from the pressure of fluid 56. As previously mentioned, valve 42 is more readily deformable adjacent the center thereof and becomes incraasingly less deformable adjacent the sidewalls of hole 40 (i.e. in the area of annular body portion 54). as a result, facing internal surfaces 52 of normally opened portion 50 are first brought into sealed contact as valve 42 assumes the position of Figure 14.
Valve 42 is contructed such that the length at any point about its periphery from the sidewall of hole 40 to the facing internal surfaces 52 ( as indicated by the dashed arrow 60) is longer than the radius of the hole 40 at the same point (as indicated by the dashed arrow 62).
This being true, as greater internal fluid pressure is created, as indicated by the heavier arrows 56' in Figure 15, valve 42 is tightly wedged into hole 40 as the pressure of fluid 56 is increased. Since valve 42 is of a deformable elastomeric material, such as rubber, internal compression forces as indicated by arrows 64 are created ~196353 g within valve 42 between the si~ewalls of hole 40 actin~ on the facin~ internal surfaces 52 of both normally clo~e~
~ortion 48 an~ normally op~n (now close~) portion 53 ten~in~ to hol~ valve 42 tightly clos~d in the presence of 5 shocks an3 Eor_es.
Referring now to Fi~ures 1~ through 19, the foregoing ooeration can be seen as it is applied to the preferred embodi,nent of a valve to be employed in ny tennis ball, being molded as an integral valve in the rubber shell 12' of the tennis ball. In this embo~iment, the valve, generally in~icated as 66, is in the form of an inwardly projecting, flattene~ tubul~r nipple 58, having rounde~
edges (as shown in Figures 21 and 22) and flat si~es 70 an~
72 which are separate~ by an internal cavity 74. The cavity 74 becomes bell-shape~ as it approaches and opens to the -xterior of the ball's rubber shell 12. That is, the cavity smoothly curves fro.n being about normal to the surface of the shell 12 on the inner end to being tangential to the shell's surface at the exterior end. At ~ its inner en~, the nipple ~8 is ~nolde~ with a soli~ close~
en~, which is then lance~ t'nrough with a sharp bla~e, leaving a ~lit 76 that is hel~ close~ by the elasticity of the rubber but which can be spread apart when the air pressure in the cavity 74 is great2r than the pressure inside the ball.
The construction of the cavity 94 in co~bination with the we1ging action makes iny tennis ball virtually leak-proof even in hi~h-shock ~ame play. The cavity 74 is formed by mol~ing it with a male mold piece having knife 3~ e~ges and a mirror-smooth polishe~ surface for the portion forming at least the inner half of cavity 74. As a result, the forme~ cavity 74, for at least the inner half of its length~ is a lat-~raliy-elon~ate~ narrow slit having slightly space~ mirror-s~mooth facing surf ces 78 an~ 80.
The slit tapers to the lateral knife edyes shown in Fiyure 21.

i3~3 ~y amployin~ th polisha~ surfaces and kniEe e~ges the previously unrecognized leakage paths of prior art ga~e ball check i~alves as ~iscussed above ~re eliminated. As a result, when the nipple 63 is collapsed by air pressur2 within the ball, a portion of the cavity 74 is closed an~
sealed airtight. In this collapsed or close~ condition, _oupl-d with the wedgin~ action, the valve 66 is tightly sealed against leakage and no air escapes from the ball even during the inost violent game play.
The relationship o t~e valve 56 to the wedging a~tion just -described in simplified form with reference to Fi~ures 13-15, can best be understoo~ with refer2nc2 to Fl~ure 17 where valve S6 is shown in superimpose~ nor~al and pressurized states. The normal position is shown with the ghosted lines and the pressurized state is shown in the solid lines. As can be seen, the area of nipple 68 containing the lance~ slit 76 comprises the normally closed portion. In like manner, the area of nipple 68 having flat sides 70 an~ 72 separated by internal cavity 74 (with the knife edges and polished surfaces) comprises the normally opened portion. The area of rubber of the shell bounded by the dashe~ lines 82 is the passageway (hole) and is, therefore, labeled 40' for relation to the previous discussion relative to Figures 13-15. V~lve 66 as shown in the ~hoste~ position of Figure 17 corresponds to sinpliEied valve 42 of Figure 13. Thus, in corresponding fashion, when the ball is being inflated from no or very low internal pressure, the lance~ slit 76 serves as an initial seal to prevent air from leaking out before enou~h ~ressure 3 can be built up within the ball to collapse the sidewalls of the nipple o8.
As air pressure buil~s up, the nipple ~ collapses fro;n the lateral pressure forces an~ the polished surfaces 66, 80 close ~gainst one anotiler to for~ the secondary 3 airtight seal which is capable of hol~in~ the relatively high shock load pressure~ ~nat are created when a fully 9635;~

inElated ball is hit har~ by a racquet. Then, as internal pressure (indicated by the arrows 84) continues to increase, the ~alves ~5 is ~eformed increasingly into we~ged contact with the sidewalls of the integral hole 40'.
Since the length of the nipple ~B from the boun~ary line 3~
at any point i3 longer than the radius of the passa~eway 40' at tnat point (in the same manner as described in relation to Fi~ure l~), the internal compressive sealin~
forces in~icate~ by the arrows 5OI are crea-ted in the same fashion as previously ~escribed with relation to Figure 15.
The desi~n of the valve 66 is such that when constructe~ of substantially sii~ilar material to the ball, the total volu,ne of rubber in the nipple ~8 is almost exactly the same as the airspace volume of the cavity 74O
Additionally, as shown in Fi3ure 20, the valve 5~ is distributed along a radius line such that its slightly heavier ~eight (as shown by the arrow 85) acts through the radial ~istance ~2 which is slightly shorter than the 2Q ~istance ~l through which the weight opposite (shown by arrow 88) acts such that the rotational forces on the ball are equal an~ opposite making the ball ~ynamically balanced. ~s a result, the valve 65 has no appreciable effect on the balance of my tennis ball.
Figures l~ and l9 show the dimensions (in inches) of such a valve as actually constructed and teste~ in a playing ball.
In manufacturing my tennis balls, two he.~ispherical core sections are first molde1. One contains the integral valve an~ one is without a valve. The two hemispherical core se~ments are then bonded together un~er heat an~
pressure to Eorm a spherica1 core having an integral valve in its si~ewalls. The fabric covering is then bonde~ to the surface to complete the tennis ball.
Because of the preSsurQs involved and the materials required to achieve the co~plete sealing of the valve, it was Eoun~ that an unexpecte~ problem can occur. That is, ~ ~L9~3~3 in or~er to achieve the desiro~ sealin~ the valve US?~l in my tennis ball is of soEt natural rubber or a material having the ~ualities of soft natural rubber. Also, the mating surface are forme~ in a mirror-smooth mol~ such that the surfaces themselves are mirror-smooth. When subjecte~
to internal pressur2 the valve is forced into a wedging state wherein the mating surfaces are we~ge~ into a firm sealing relationshiQ. Enploying conventional manufacturing techniques causes such a sealing arrangenent to be affecte~
1~ as a result of the molding an~ joining process of the spherical core. The manufacturin~ process itself creates a hollow spherical core containing an internal pressure which can force the soft rubber surEaces into a we~ge~
relationship sufficient to create a virtual diffusion welding or bonding of the ,nating surfaces. ~ater, when the ball is place~ within the pressurized container, the differential pressure between the outsi~e ~esired pressure and the pre-established internal pressure in the ball is insufficient to break the diffusion bond. The ball is merely ~eforme~ and the correct pressurization is not achieved.
I have found that coating the internal, matin~
surfaces of the valve with a light coating of silicone grease or the like prior to the joining of the two hemisp'nerical core segments results in an elimination of this problem. The internal pressure still occurs as part of the manufacturing process, but the sealing of the valve is a nor.nal sealing wit'nout the ~iffusion surface bonding which previously occurre~ so,netimes.
Tt is important when employing this proce~ure that the ~re~se employed by a silicone-based grease, or the like, which does not attack the soft natural rubber as would be the case with normal petroleum-based ~reases. The tern "gr-ase" as employe~ herein inclu~es any material which would provi~e the ~esire~ surface coating action without causin~ ~eterioration thereof.

63~3 ~ urni~n3 now to Fi~ures 23 and 24, havin~ thus pre?are~ the moL~e~ rubber shell 12' with valve 5 in it shell 12' is cover2~ in the usual ,nanner ~ith a pair of generally fi~ure-3-shape~ pieces of Eelt fabric 90 as shown in Figure 24 to form the classic tennis ball cov~ring. Fabric go for .ny tennis ball shoul~ be of an air-permeable inaterial and is place~, as shown in ~igure 24, with th- fabric 90 _overin~ the opening to valve 65.
F~bric 90 is a~h-sively attache~ to rubber shell 12' in the usual .nanner but _are must be taken to prevent the a~hesive from entry into the openin~ of valve 65.
Also, it is preferre~ to further separate the opening to valve ~O from any possible contamination by first covering it with ~ ~isc or patch 9l o gauze material. In teste~ balls without the gauze -material~ the objectives of preventin~ the dirt an~ conta.nination oE -the playing environment were ~et, but, after a time, the balls unexpectedly leaked. It was finally determined that a single fiber ~islo~ged fro-,n the surface of the felt fabric used to cover my tennis ball was sufficient to enter the valve 66 an~ destroy its unique sealing qualities. The ;3auze Eilt2r oatch 91, bein~ free of loose fibers, filters the opening of valve 66 and keeps it in goo~ sealing con~ition. While other materials coul~ be used, the gauze is preferre~ since it is thin and practically weightless in tne size require~ so that the weight an~ balance of the ball is not affecte~ by it.
The tennis ball 92 thus for-.ne~ can be pressurize~ by placing the ball 92 into any of a number of containers 3~ presently available ~or shipping an-~/or storin3 tennis balls und-r pressur~. In this regard, the fabric cov~ring 90 serves two functions. Being perneable, it allows the air to pass therethrouJh an~ through valve 6~ to the interior of ball 92. Moreover, since the sealing qualities oF valve o5 depen~ upon the firm mating of the mirror-smooth si~ewalls to achieve the ~esire~ pressure ~963~3 retention r-sul ta / f~bric 90 s~rves as a filter to pr~vent the entry ~f s~all for~i~n particles into va1ve 56 which woul~ ~ause valve o6 to lose its pressur~-retontion capabilities as ~iscusse~ above.
It is very i.~portant to note that if rather than prepressurizin~ the tennis ball as is the usual custom, .~y tennis ball is prossurized at the play site by placin~ it in one of the available containers which subject it to on-site chan~e of Jolu~e pressurization rather than pressurizing it to a fixe~ ~auge pressure, my tennis ball ~ill be pres3urized in a manner ~hich compensates completely for altitu~e an~ temperature variations. It is therefore pressurized in a manner which imparts the same bounce ch~racteristics re~ar~less of the altitude an~
temperature of the site.
~ ith ~y tennis ball 92 incorporating valve ~6, iE it sho~ld be necessary to reduce the inflation pressure, all that is necessary is to insert a toothpick, paper clip, or the like into the valve opening so as to spread the se31ing lips apart and break the seal. It has been foun~
that the adjuste~ pressure can be set to an accuracy of ~lus or .~inus a fraction of a millimeter of mercury. It has been found that _hanges in the altitude of play or te~perature variations can cause a n~cessity for the release of e~cess pressuro within tll2 ball an~ subsequent repressurization to a ~esired new pressure to ,orovi~e proper oounce. To this en~, in tho preferre~ embo~iment as shown in ~i~ure 24, fabric cover 90 is provi~ed with an in~icia 34 over the location of valve 66 so that a toothpick, paper _lip, or the like can be oass--~ throu~h th- fabric 90 to open valve 66 in the above-~escribe~
~anner to relieve the pressure within ball 92. ~n~icia 9~
is conveniently in the fori~ of a ~ot or circle of ink applie~ to fabri_ 90 at the proper location.
The embodiment of the invention in which an exclusive property or privilege is claimed are defined as follows:

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a tennis ball having a spherical, hollow, rubber shell covered with a pair of generally figure-8-shaped pieces of fabric, the improvement characterized by the fabric being permeable to the passage of air therethrough and by a one-way check valve disposed in the sidewall of the shell beneath the fabric for allowing air to pass therethrough into the ball.

2. A tennis ball comprising:
(a) a spherical, hollow, rubber shell having a bore through the sidewall thereof;
(b) a unitary check valve disposed in the bore for seal-ing the bore to allow pressurized fluid to flow axially through the bore in one direction and prevent pressurized fluid from flowing axially through the bore in the opposite direction, said valve com-prising, (b1) an annular body portion carried coaxially within the bore, said body portion being thick enough in the axial direc-tion adjacent the outer edges of the bore that in combination with the support provided by the material defining the bore said portion is substantially non-deformable in the axial direction, and, (b2) a sealing nipple portion carried within said body portion tapering radially inward and axially in the direction of desired fluid flow from said body portion on one end to meet in sealed contact adjacent the opposite end, the thickness of said sealing nipple portion in the axial direction becoming increasingly thinner and correspondingly increasingly deformable in the axial direction radially inward from said one end whereby the application of fluid under pressure to said valve in the direction opposite desired fluid flow causes said nipple portion to be deformed axially into said body portion in a wedging action increasingly sealing the passageway as increased fluid pressure is applied, said taper being a smooth curve extending from a point on a line sub-stantially normal to the axis of the bore on said one end to a point on a line substantially parallel to the axis of the bore on said other end whereby fluid pressure within the bore tending to move fluid through the bore in a non-desired direction acts normal to the axis on said nipple portion adjacent said other end to initially prevent fluid passage therethrough as it also acts axial-ly on the rest of said nipple portion to deform said nipple portion in said wedging action into said body portion, said nipple portion being of a material having the deformation and sealing qualities of soft natural rubber, the surfaces of said nipple portion that meet during said wedging deformation into said body portion having a finish produced by a mirror-smooth mold; and, (c) a pair of generally figure-8-shaped pieces of fabric bonded to the outer surface of said shell with narrow seams between the abutting edges thereof, said fabric being permeable to the pressurizing fluid and covering the outer opening to said valve.

3. The tennis ball of claim 2 wherein:
the length of said nipple portion from said one end to said other end is sufficiently long in relation to the deformability thereof that said other end remains in sealed contact and said nipple portion still deformably wedges into said body portion when said body portion is deformed radially outward by expansion of the material defining the bore.

4. The tennis ball of claim 2 wherein:
said mirror-smooth inner surfaces that are pressed together in fluid-tight sealing engagement come together in knife edges.

5. The tennis ball of claim 2 and additionally comprising:
filter means disposed over the outer opening of said check valve and under said fabric for filtering out fibers from said fabric which would otherwise, if dislodged, enter said check valve and diminish its sealing qualities.

6. The tennis ball of claim 5 wherein:
said filter means comprises a piece of gauze material.

7. A tennis ball comprising:
(a) a molded, spherical, hollow, rubber shell having a unitary check valve of elastomeric material integrally molded into the sidewall thereof, said valve comprising a substantially flattened tubular nipple portion having external rounded edges and generally flat sides defining an internal cavity with an elongated axis, said cavity smoothly curving from a point on a line normal to said axis of the entrance end of said nipple to a point on a line parallel to said axis as it approaches and opens to the interior end of said nipple, said nipple having an inner end defining an inner extremity of said cavity, said inner end being a solid closed end having a thin slit therethrough which communicates with said cavity, said slit being normally held closed by the elasticity of the elastomeric material, said cavity being configured for at least an inner half of its length in the form of a laterally elongated narrow slit having spaced walls produced from a mirror-smooth mold, said walls tapering down to lateral knife edges, said cavity being further configured at its inner end adjacent said solid end of said nipple by its tapering down to a knife edge adjacent and communicating with said thin-slit opening; and, (b) a pair of generally figure-8-shaped pieces of fabric bonded to the outer surface of said shell with narrow seams between the abutting edges thereof, said fabric being permeable to the pressurizing fluid and covering the outer opening to said valve.

8. The tennis ball of claim 7 and additionally comprising:
filter means disposed over the outer opening of said check valve and under said fabric for filtering out fibers from said fabric which would otherwise, if dislodged, enter said check valve and diminish its sealing qualities.

9. The tennis ball of claim 8 wherein:
said filter means comprises a piece of gauze material.

10. The method of producing a tennis ball having predictable and repeatable bounce characteristics at different altitudes and temperatures comprising the steps of:

(a) producing a spherical, hollow, rubber shell having a bore through the sidewall thereof which bore contains a unitary check valve for sealing the bore to allow pressurized fluid to flow axially through the bore in one direction and prevent pressurized fluid from flowing axially through the bore in the opposite direc-tion, said valve comprising, (a1) an annular body portion carried coaxially within the bore, said body portion being thick enough in the axial direc-tion adjacent the outer edges of the bore that in combination with the support provided by the material defining the bore said portion is substantially non-deformable in the axial direction, and, (a2) a sealing nipple portion carried within said body portion tapering radially inward and axially in the direction of desired fluid flow from said body portion on one end to meet in sealed contact adjacent the opposite end, the thickness of said sealing nipple portion in the axial direction becoming increasingly thinner and correspondingly increasingly deformable in the axial direction radially inward from said one end whereby the application of fluid under pressure to said valve in the direction opposite desired fluid flow causes said nipple portion to be deformed axial-ly into said body portion in a wedging action increasingly sealing the passageway as increased fluid pressure is applied, said taper being a smooth curve extending from a point on a line substantially normal to the axis of the bore on said one end to a point on a line substantially parallel to the axis of the bore on said other end whereby fluid pressure within the bore tending to move fluid through the bore in a non-desired direction acts normal to the axis on said nipple portion adjacent said other end to initially prevent fluid passage therethrough as it also acts axially on the rest of said nipple portion to deform said nipple portion in said wedging action into said body portion, said nipple portion being of a mater-ial having the deformation and sealing qualities of soft natural rubber, the surfaces of said nipple portion that meet during said wedging deformation into said body portion having a finish produced by a mirror-smooth mold;

(b) bonding a pair of generally figure-8-shaped pieces of fabric to the outer surface of said shell with narrow seams between the abutting edges thereof, said fabric being permeable to the pressurizing fluid and covering the outer opening to said valve; and, (c) at the altitude and temperature whereat the tennis ball is to be used for play, placing the tennis ball being of a given volume V1 into a collapsible container having a given inter-nal volume V2, sealing the container and compressing the container to a second given internal volume V3 wherein the change in volume (V3-V2) is sufficient to place the tennis ball under a pressure which will impart the desired bounce characteristics to it.