CA2004916C - Multi-piece golf balls and methods of manufacture - Google Patents

Abstract

An improved golf ball comprising a hollow, spherical shell of a polymeric material having a thickness of between about 0.060 and 0.410 inches and a unitary, non-cellular core of a material which, at the time of introduction into the shell, is a liquid.

Description

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MULTI-RIECE GOLF BALLS AND ~ETHODS OF ~ANUFACTVRE

TECHNICAL FIELD
This invention relates to multi-piece golf balls and their method of manufacture and, more particularly, to golf balls comprising a hollow, spherical shell of a polymeric material and a unitary, non-cellular core of a material which, at the time of introduction into the shell, is a l~quid.

BACKGROUND OF THE lNv~hllON
Golf balls are of two types, solid balls and multi-piece balls. Solid balls consist of a polymeric sphere into which is molded a plurality of dimples to aid the flight characteristic. Multi-piece balls consist of either a wound or solid core which is covered with a separate and distinct cover. The present invention is concerned with the latter-mentioned multi-piece-type golf balls and their methods of - manufacture at a reduced cost while maint~lnfne or enhancing their performance.
Over sixty years ago, balata, a natural resin, came into widespread usage as a golf ball cover composition.
Balata is a natural resln. When balata is used as a golf ball cover it becomes necessary to incorporate into the golf ball a complex core. Often the core of the golf ball has been its most complex component. In accordance with the present invention, known golf ball cores are replaced with simplified, unitary cores of inexpensive materials which, in their fluid state, are in~ected into a hollow shell. This invention thus relates to a new golf ball comprising a hollow polymeric shell into which is inJected the core material.

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During the last tweDty years, synthetic polymeric materials and mixtures thereof have come into widespread use as golf ball covers. In order to maintain the per~ormance o~
golf balls, whether with co~ers of nntural or synthetic materials, it has been necessary to utilize expensive, preformed core systems with ~he cover material molded therearound which complicates the manufacturing process and thus ralse the cost of manufacturing.
Uith the prèsent invention9 it is possible to eliminate the complicated, costly core system snd yet produce golf balls with surprisingly good Coefficient of Restitution which can be manufactured for reduced costs. Further, it is possible to ad~ust the radius of gyra~ion of the balls of this invention. These bene~its are attained while still allowing for the utilization of op~ic~l bri~hteners in the polymeric shells. This invention is thus concerned with golf balls including their shell compositions as well as their core cnmpos~tions.
The literature d~scloses various game balls and their methods of manufacture. Note in p~rticular United Kingdom Patent Number 6566 to Hodgson and U.S. Patent Nu~ber 4,653,752 to Miller. Hodgson d;scloses ~ golf ball w~th an Internal core having an india rubber bladder which is filled with a pressurized gas, and this whole structure i9 encased in a thick external shell of gutta percha. Resilience is allegedly attained from the compress~ble inner core acting upon the resilient shell. The golf ball of the present invention derives all or a substantial portion of lts t~6111ence ~ro= it- she11. Accordlng to the Ml11er p6ten~, a .

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softball or baseball is fabricated of a plastic shell formed ~rom hemispheres with an in~ected cellular core. The resulting produc~ i5 a softball wherein the resilience ~
characteristics are completely different than that of the golf ball of the present invention. Lastly, U.S. Patent Number 4,798,386 to Berard discloses a golf ball which employs a preformed core to which is subsequently applied a thick shell.
For approximately the last 40-50 years golf balls have been made by bonding a cover about a core. The cover can be applied to the preformed core by compression molding of two half shells, or a core can be positioned in an injec~ion mold and the cover directly molded onto the prepositioned core.
For at least 50 years, golf balls have been formed using various liquid components. In the most common manner, a pre-formed bladder was ~ormed and filled with a suitable liquid. These preformed bladders in the pas~ were filled with liquids such as water, mineral oil, honey, aqueous solutions of organic and inorganic materials. Likewise, the applicant believes that liquids were further in~ected into the above-descrlbed partially filled bladders subsequent to the complets formation of the balls. Further, the Applicant believes that liquids were injected into the spaces between the various strands of rubber~wound cores subsequent to the formation of a finished ball.
Additional patents of interest are listed in applicant's statement of the background art.
From the abo~e descriptions, it is obvious golf balls have been r-mtf~ctured with centers compr~sing both rubber and liquid components such as a liquid in a bladder , ~
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;~:0~ 16 center and liquid in the rubber windlng centers. However, no golf ball has been manufactured with a shell whose center was solely inltially Eilled with a liquid.
No prior disclosure or golf ball or method of manufacture teaches or suggests the pr~sent inventive combination of a golf ball comprising n hollow, 6phericnl shell of a polymeric material and a unitary, non-cellular core of a material which is, at the time of introduction into the shell, a liquid, wherein such a golf ball can be made more efficien~ly and economically from known materials with conventional ~nllf~rturing processes.
Therefore, it is an ob~ect of the present invention to provide golf balls and methods of manufacturing which overcome the inadequacies of the prior art and which represent a sign~ficant contribution to the golf ball art.
Another ob~ect of this invention is to reduoe the cost of multi-piece golf balls by in~ecting a non-cellular liquid core material into a preformed shell.
It is yet a further ob~ect of the in~ention to improve golf ball shel Vcore constructions for cost reduction.
Lastly, it ~s an ob~ect of ~he present invention to ro~ntnin or improve the performanee of golf balls by a design which allows for a reduction in the oost of ~aterials and simplification of manufacturing steps by utilizing a preformed shell, rather than a preformed core, as the starting point for fabrication.
The foregoing has outlined some ~f the more pertinent ob~ects of the invention. These ob~ects should be construed to be merely illustrative of some of the more pr. ~nPnt features and applications of the intended ': , ' ' . ' , .;~;..... . .

9~6 invention. Many other beneficial resul~s can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure.
Accordingly, other ob~ects and a fuller underst~n~ng of the invention may be had by referring to the ~ummary of the invention snd the detailed description of the preferred embodiment in addition to the scope of the inventlon deflned by ~he claims taken in con~unction with the accompanying drawings.
The invention is defined by the appended cl~ms with the specific embodiments shown in the attached drawings. For the purpose of summarizing the invention, the invention may be incorporated into an improved golf ball having a unitary core and a shell, the shell being formed as a hollow, spherical shell of polymeric material and a non- cellular core injected into the ~hell, the core being formed of a material, at the time of introduction into the shell, is a liquid.
The invention may also comprise an improved ~ethod of fabricating a golf ball having the steps of: (1) molding a pair of hollow, generally hemispherically shaped halves from a polymer; ~2) coupling together the halves to form a hollow, spherical shell; (3) introducing a liquid through a hole in the shell to form a non-cellular core and (4) sealing the hole.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention thst fcllows may be better understood so that the present contribution to the art can be more fully appreciated.
Additional features of the lnvention will be described -: --- : : : :

~:0~ L6 hereinafter which form the subject of the claims of the inventio~. It should be appreciated by those skilled in th~
art that the conceptlon and the disclosed specific embodiments may be readily utilized as a bnsis for modifying or designing other methods and constructions for csrrying out the same purposes of the present invention. It should also be realized by those skilled in the art thAt such equivalent methods and constructions do not depart from the spirit and scope of the inven~ion as set forth in the appended claims.

DESCRIPTION OF THE DRAUINGS
For a fuller underst~n~ne of the nature and ob~ects of the invention, reference should be had to the following detailed description taken in con~unction with the ~cc ,anying drawings in whioh:
F~gure 1 is an elevational view, partly in section, showing a golf ball constructed in accordance with the principles of a primary embodiment of the present invsntion.
Figure 2 is an elevational view ~imilar to that of Figure 1 but illustrating an alternate core construction.
Figure 3 is an elevational view similar to Figure 1 but showing an alternate, thin wall, shell construction.
Figure 4 is an elevational vlew similar to that of Figure 3 but illustrating an alternate core construction.
Figures 5 and 6 are sectional ~iews of mold halves for forming the two mating halves of a golf ball shell.
Figure 7 is a sectional view of two hemispherical shell halves loaded in opposed fixtures of a spin welding ~hln~ prior to being coupled for forming a shell.
Figures 8, 9, and 10 are fragmentary ~ews of alternate embodiments of the area of ~o~ning the shell halves - , -2(~

and also showing parts of the fixtures.
Figures 11 and 12 are sectional views of shell halves of a further alternative em~odiment prior to being ~oined.
Figures 13, 14 and 15 are sectional ~iews o~ a golf ball shell after ths shell halves have been coupled together and sequenti~lly illustrating the in~ection of cor0 material to fill the shell and constitute its core.
Figures 16, 17, 18 and 19 illustrate, in fragmentary sectional view, additional embodiments of shell construction wherein the shells are ~ailored to yield intended physical characteristics.
Similar referenced characters refer to cimilar parts throughout the several Fl~ures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
An Overview Figure 1 illustrates 8 golf ball 10 constructed in aecordance with the principles of the present invention.
Fi~ure 1 is partly in section with parts br~ken away to show certaln internal constructions The golf ball of the present invention maintains or improves the performance of presently known and utilized golf balls. It is constructed of two major components, an internal portion or core 12 and an external portion or shell 14. The core is o~ a spherical configuration while the shell is formed of a hollow spherical cDnfi~uration w1th the exterior surface of the core in contact with the interior surface of the shell. The exterior surface of the shell is formed with dimples 16 to proYide lmproved flight characteristics and to create an appearance essentially identical with commercially available ~olf ; t ~ ''t:.'' . ' ~' : :,~ ' . , ~0g~3~6 balls. The selection of the proper dimple pattern is within the purview of one skilled in the golf ball art.
Describing the components of the sub~ect golf ball, the term spherical is used in con~unction with both the core and the shell. It is understood by one skilled in the ar~
that when referring to ~olf balls and their c~ ,_ne.,ts , th~
term spherial includes surfaces which may have minor deviations from the perfect ideal geometric shapes, ss for example, dimplas on the exterior sur~nce of the bsll to effect its aerodynamlc properties. Further the internal surface of the shell as well as the core may likewise incorporate intentionally designed pstterns.
In the Figure 2 embodiment, the core 18 is of a solid material rather than the liquid materiAl of Figure 1.
Figures 3 and 4 illustrate an alternate embodiment of the invention with a thin wall shell 20 with a liquid core 22 in the Figure 3 embodiment and with a solid core 24 in the Figure 4 embodiment.

The Shell Thermoplastic materials are generally preferred for use as shell materials in accordance with this invention.
Typical, but not limitive of the properties desirable for the resin, are good flowability, moderate stiffness, high abrasion resistance, high tear strength, high resilience, and good mold release, among others. Preferred polymeric materials for use in accordance with this invention are ionic copoly~ers of ethylene and an unsaturated monocarboxylic acid which are available under the trademark "SURLYN" of E.I.
DuPont De Nemours & Company of Wilmington, Del. which are copolymers of ethylene and methacrylic acid partially .

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neutralized with zinc, or sodium or lithium and under the trademark ESCOR by Exxon Chemical Company, Houston, TX, which ara copolymers o~ ethylene and acrylic acid psrtially neutralized with zinc or sodium.
In nccordance with the various embodiments of the present invention, the shells are of a thickness from about 0.060 inches to about 0.410 inchss. Standard golf ball covers in use today are generally about 0.090 inches in thickness.
In accordance wi~h a preferred embodiment of this lnvention, the shell in question is formed from mixtures or blends of zinc and sodium ionic copolymers sold by E.I.
DuPont De Nemours Company, Inc., under the trademarks "SURLYN". A more preferred embodiment comprises mixtures or blends of Surlyn and ~SURLYN" 1706/9910 and 1605/8940.
Singular ionic copolymers can be used as shell materials in the sub~ect invention. These singular materials are described in V.S. Patent Number 3,454,280 issued July 8, 1969. The use of mixed Surlyn resins in accordance with the above described preferred embodiment is described ~n U.S.
Patent Number 3,81~,789 issued June 25,1974. Ionic copolymers of the type suitable for use in this invention are further described in detail in U.S. Patent Number 3,264,272 issued August 2, 1966 and U.S. Patent Number 4,679,795 issued July 14, 1987.
Surlyn resins are ionic copolymers which are the sodium or zinc salts of the reaction product of an olefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from 3 to 8 carbon atoms. The carboxylic acid groups of the copolymer may be totally or part~ally neutrali~ed.

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This invention can likewise be used in con~unction with cellular polymeric golf ball shells as are described in U.S. Patent Number 4,274,637 issued June 23, 1981.
Synthetic polymeric materials, other than those described above, which can be used in accordance with thi~
invention as shell materials include homopolymeric and copolymer materials which may be adapted for use in this ~nvention are as follows:

(1) Vinyl resins formed by the polymerization of vinyl chloride, or by the copolymerization of vinyl chloride with ~inyl acetate, acrylic esters or vinylidene chloride;

(2) Polyolefins such as polyethylene, polypropylene, polybutylene and copolymers such as polyethylene methylacrylate, polyethylene ethylacrylate, polyethylene vinyl acetate, polyethylene methacrylic or polyethylene acrylic acid or polypropylene acrylic acid or terpolymers made from these and acrylate esters and their metal ionomers, polypropylene/EPDM grafted with acrylic acid as sold under the trademark "Polybond" by Reichhold Chemicals, Inc., Hackettsto~n, New Jersey 07840, or anhydride modified polyolefins as sold under the trademark "Plexar" by Northern Petrochemical Company, Rolling Meadows, IL 60008.

(3) Polyurethanes, such as are prepared from polyols and diisocyanates or polyisocyanates;

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(4) Polyamides such as poly (hexamethylene adipamide) and others prepared from ~m~n~s and dibasic acids, 8S well as thos~ from amino acids such as poly (caprolactam), and ~lends of polyamldes with Surlyn, polyethylene, ethylene copolymers, EDPM, etc.

(5) Acrylic resins and blends of these resins with poly vinyl chloride, elastomers, etc.

(6) Thermoplastic rubbers such as thc urethanes, olefinic thermoplastic rubbers such as blends of polyolefins with EPDM, block copolymers of styrene and butadiene, or isoprene or ethylene-b~tylene rubber, polyether blocX amides, an example of such a product is sold under the trademark "Peba~" by Rilsan Industrial, Inc., Birdsboro, PA 19508; ~

(7) Polyphenylene oxide resins, or blends of polyphenylene oxide with high impact polystyrene as sold under the trademark "Noryln by General Electric company, Pittsfield, MA.
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(8) Thermopla~tic polyesters, such as P~T, PBT, PETG and elastomers sold under the trademarks "Hytrel" by E.I. DuPont De N UlS & Company of Wilmington, Del. and "Lomod" by General Electric company of Pittsfield, MA.

(9) Blends and alloys includ~ng polycarbonate with ABS, PBT, P~T, SMA, PE, elastomers, etc. and ; ' '' ; , '' ' ~

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PVC with ABS or EVA or other elastomers. Blends of thermoplastic rubbers with polyethylene, polypropylene, polyacetal, nylon, polyesters, cellulose esters, etc.

In the above description shorth~nd symbols are used to describe certain polymers. The symbols used nnd their description are as follows:

ABS Acrylonitrlle butadiene styrene PBT Polybutylene terephthalate PET PolyethyleDe tereph~halate SNA Styrene malei~c snhydride PE Polyethylene PETG Polyethylene terephthalate/glycol modified EPDN Ethyl-propylene-non-con~ugated d~ene terpolymer PVC Polyvinyl chloride EVA Ethylene vinyl aceta~e The above list is not meant to be limiting or exhaustlve, but merely illustrates the wide range of polymeric materials which may be used to form the shell in the present invention. Mixtures of the above-described materials may also be used. Further the polymers used to form the outer shell, in accordance with the presen~
invention, may be stress oriented subsequent to the formation of the shell. Likewise, ln accordance with the present ~nvention, reinforced ~oly~eric ma~erials ma~ be utilized in the shell.

21~916 It is within the purview of this lnvention to add to the shell compositions o~ this invention materials which do not affect the basic novel characteristics of the composition of this invention. Among such materials are antiox$dants, antistatic figents, snd stabilizers.
As can be seen from the discussion above, the sub~ect in~ention can be used in con~unction wi~h a wide varie~y of polymeric materials which are sultable for ~he formation of shells.
The white basic color of the golf ball shell is formed by ~he pigmentation of one of the above-mentione~
polymeric materiAls. Suita'ole pigments for use in accordance with this invention include the following: titanium dioxide, zinc oxide, zinc sulfide and 'oarium sulfate.
The amount of pigment used in con~unction with the polymerlc shell composition naturally depend on the particular polymeric material utilized and the particular plgment uti~7ed. The concentration of the pigment in the polymeric shell composition can be from about 1 percent to about 25 percent as based on the weight o~ the polymeric material. A more preferred ran~e is from ~bout 1 percent to about 5 percen~ as based on the weight of the polymerlc material. The most preferred range is from about 1 percent to abou~ 3 percent as baQed on the weight of the polymeric material. The percent pigment utilized is in large part determined by the weight needed to provide ~ golf ball with the prei'erred physical characteristic. It is understood by ona skilled ln the art that the percent of pi~ment added must be balanced with the weight of the core materi~l in order to attain the desired density of the resultin~ golf ball.
Preferr~d sheIl compo~itions for use in accordance .

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2~9~6 with this invention are the ionomers described above including Surlyn and ESCOR resins and they may be used in con~unction with fillers, pigments and other add~tives. The most preferred pigment for use in accordance with this invention, if one is to be used, ls titanium dioxide. When this combination of components is utilized, it is preferred that the concentration of tltanium dioxide in the shell composition be from about 1 percent to about 10 percent as based on the weight of Surlyn resin utilized. A more preferred range for the concentratlon of titanium dioxide i9 from about 1 percent to about 5 percent as based on the Surlyn resin utilized. A most preferred concentration for the titanium dioxide is about 2 percent as basç.d on the weight of the Surlyn resin utilized.
As has been amply discussed above, the sub~ect ~nvention can utilize a wide variety of polymers. When pigmented, many of the polymers in question and ~n particular Surlyn resins, are not glossy after in~ection molding.
Experience has demvnstrated that the a~erage golfer prefers a glossy golf ball. In order to produce glossy golf balls, the balls of this invention may be coated with a clear epoxy-urethane coating system subsequent to molding. The system in question consists of a clear epoxy primer and/or water borne primer, followed by a clear urethane coat. Use of this clear coat system is not mandatory in order to achieve the desirable results of this inVent~Qn; however, it ~s highly desirable. In addition to high initlal gloss, the above-mentioned system produces a golf ball which i9 durable and maintains its gloss during play. It is understood by one skilled in the art that other clear coat systems can llkewise be utilized.

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Further, it is understood by one skilled in the art that the golf balls of the invention can be painted with a pig~ented paint in a conventional manner.
The radius of gyration of a ~olf ball is an important attribute o~ a golf ball. Tha radlus o~ gyration of a golf ball is generally deflned as the way it handlcs rotative forces when the ball is spinning. In the sub~ect ~olf ball, the radius of gyration can be easily varied by either increasing or decreasing the density of the outer shell snd/or by increasing or decreasing the density of the inner core. For example, if one wanted to create at golf ball wherein the radius of gyration was located near the outer periphery of the ball, the outer shell of the ~olf ball of thls invention can incorporate heavy material which would not effect the play characteristics of the ball in question but which would create mass in the outer shell. For example, the outer shells could incorporate small smounts of heavy metal salts such as a tungsen salt or a lead salt. Like wise, the outer shell could contain powdered metals. To put it in other words, the distribution of the mass along the radius of the ball can be varied by varying the density of either the core material or the outer shell material.

The Core The specific gravity of the shell as described above is between about 0.75 and about 1.25, preferably about 0.97.
Standard golf balls have an average specific gravity of 1.13, a diameter of st least 1.68 inches and a weight of less than 1.62 ounces. In this preferred embodiment, in order to provlde a golf ball which has similar physical properties and functional characteristics to standard golf balls, it is - .
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9~i preferred to form the core of a material having 8 specific gravi~y greater than that of the ball and the shell. In this invention, the core may have a diameter of between about 0.860 inehes and about 1.43 inches, preferably 1.30 inches.
The core filled with core material may have a speciflc gravity of between about 0.8 and about 3.9, preferably at abou~ 1.32.
It is understood by one skilled in the art that the specific gravi~y of the core must be varied depe~in~ on th0 physical dimensions and density of ~he outer shell and the diameter of the f~n~Qh~d golf ball.
It should be appreciated tha~ a wide variety of materials could be utilized including gels, hot-maltR and liquid materials. Hot-melts are materials which at or abou~
normal room temperatures are solid but at elevated temperatures become liquid. This property allows its easy in~ection into the shell to form the core. Examples of suitable gels include water gela~in gels, hydrogels, and water/methyl cellulose gels. Ball embodiments with a gel or other solid core are shown ln Figures 2 and 4. Ex~mples of suitable melts include waxes and hot melts. ~xamples of suitable liquids, as shown in Figures l and 3, include either solutions such as glycol/water, salt in water or oils or coloidal suspensions, such as clay, barytes, carbon black in water or other liquid, or salt in water/glycol mixtures. The preferred material ~s the liquid solution as described above. An example of a suitable core material is a solution of inorganic salt in a mixture of water and glycol. The inorganic salt is preferably calcium chloride and the glycol is glycerine.
In the thicker (about 0.410 inches down to about , - .: :: . . -:.

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~:0~3~9:~6 0.160 inches) walled embodiments, the shell material provide~
most or 811 of the resilience necessary for the proper performance of the golf ball of the present invention. In the thinner (about 0.060 inches up to about 0.160 lnches) walled embodiments, the ball functions and performs in the standard malmer, deri~ing resilience from the core material as well as the shell. The shell may thus vary ~rom about 0.060 to 0.410 ~nches in thickness, pref~rably ~bout 0.075 to 0.300 inches or, most preferably sbout 0.090 to 0.190 inches. It will be understood by one skilled in the art that the properties of ~he shell material and the thickness of the shell are inter-related. These two ~ariables must be tuned to optimi~e performance.
The liquid material which is inserted in the shell in accordance with this invention to form the core can be reactive l~quid systems which combine to form a solid.
Examples of suitable reactive liquids are silicate gels, agar gels, peroxide cured polyester reslns, two part epoxy resin systems and peroxide cured liquid polybutadiene rubber compoqitions. It ls understood by one skilled in ~he art that other reactive liquid systems can likewise be utili~ed depending on the physical properties of the shell and the phys~cal properties desired in the resulting f~n~.~hed golf balls.
The core of all embodiments, whether liquid or solid, is unitary, of a com~on material throughout its entire extent, with its exterior surface in contact with the interior surface of its shell. All cores sre also essentially homogenous throughout their mass.

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Methods of Manufacture In the preferred method of manufacture of the golf balls as described above, ~wo hemispherically-shaped shell halves 28 and 30 arc formed, preferably through inJectlon molding prior to being coupled to form the completed ~hell.
Figures 5 and 6 illustrate mold halves 34 and 36 with holes 38 and 40 for the introducing of the materiAl, in fluid form, of which the shell is to be formed. They are identlc~l ln shape except at their equa~or where they are ~oined. Such halves may be fully identical with flat, planar surfaces 42 and 44 at the equator of the ball at the areas o~ coupling.
Note Figure 8. It is preferred, however, that male and female tongue 46 and groove 48 surface configurations are provided to assist in the proper placing of the halves wlth respect to each other. Note Figures l and 2 as well as Figures 5, 6 and 7 as well as 13, 14, and 15. Other configurations at the equator could be utilized, such as a mating undulations 50 and 52 of male an~ female segments across the shell thickness as shown in Figure 9. In the embodiment of the thin walled shell of Figures 3, 4 and lO, the parting line 54 and 56 may take the form of a cyl~nder around the periphery of the ball with the parting line in an orientation a~ an angle to the equator of the ball. This forms a triangular pro~ection in the lower shell half and a mating triangular recess in the upper shell half. Additional surface area is thus provlded for bonding purposes. Further, during spin welding, centrifugal forces acting with the shell edges and tooling wall urge together the matlng halves ~or superior coupling.
Figures ll and 12 illustrate a preferred tongue and groove arrangement with the tongue of a length H-l slightly less than the length H-2 of the interior wall of the groove , S

.; ' but slightly greater than the l~ngth H-3 of the exterior wall of the groove.
Other techniques for forming the shall include conventîonal blow ~olding, in~ection blow molding and rotational casting.
The dimples 16 on the exterlor sur~ace of the shell halves are shown as being formed during the in~ection molding of the halves. It should be appreciated, however, that, in certain embodiment~, the ball may be molded with a smooth exterior surface and the dimples molded in af~er tha ~oining of the halves later durin~ the fabrication process, sither before or after the in~ection of the core and plugging of the hole. The temperature for dimple molding must be sufficiently low as not to be detrimental to the core.
The halves are Joined together by any one of a wide variety of manufacturing methods. The preferred method is the spin welding of the halves as effected by fixedly supporting one of the halves 30 in a f$xed fixture 60, shown as the lower half in Figure 7, and supporting the other half 28, shown as the upper half, ln a flxture 58 which is rapidly rotated about a vertical axis while moved axially toward the fixed half. Note the arrows of Figure 7. The frictional energy generated by the v~ Ert of one half with respect to the other, while being brought together into mutual contact, will generate sufficient heat to create a final cohesive bond between the melting and coalescing thermoplsstic materials o~
the halves. The resulting structure is then a total, unitary hollow sphere for constituting the shell of the ball. The spin weld~ng is of the conventional type as dascribed, for example, in U.S. Patent 2,956,611 to Jendrisak. A
commercially available spin welding ~qehln~ acceptable for ..
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, performing this Method is Model No. SPW-l-EC ~f~tured by Olsen Manufacturing Company of Royal Oak, Michigan. Other coupling techniques may be readlly utilized for ~oining the halves. Such other techniques include known methods such as ultrasonic welding, vibrational welding, laser welding, solvent welding, compression molding or e~en adhesive bondlng with a suitable adhesIve having properties matched to the properties of the shell halves.
Next subsequsnt in the manufacturing process for the preferred embodiment is the forming of a hole 64 in t~e shell 14 as through drilling. The hole could also be formed during molding. The hole is preferably tapered radially i~wardly toward the center of the sphere to facllitate its subsequent closure. It is understood by one skilled ~n the art that two or more holes of the same or different sizes may be drilled or molded for the purposes associsted with in~ecting the liquid core material into the outer shell. Thereafter the material of the core 12 is in~ected through the hole lnto the center of the shell, as through a hypodermic needle 66 or the like, to totally fill the center of the shell for constituting the core. The plugging of the hole with a conical plug 68 and trimming its cylindrical extension completes the fabrication process unless, of course, the dimples are to be applied following the prior manufacturing steps. The material of the plug is preferably that the same as the re~n~er of the shell 14. The plug is secured in the hole to seal the shell through any of the above described fabrication techniques, spin welding being presently preferred. In certain embodiments, the core material may be relied upon to seal the hole.

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Alternate Embodiments In an alternate embodiment of the invention, the shell and core are fabricated by any o~ the techniques as described above. The shell 72 of Figure 16, however, ls formed of a flrst or inner layer 74 of a thickness sllghtly less than the final ball, 8uch shell constituting an internal layer of the final composite shell or laminate formed of plural shell layers. The final exterior shell layer 76 Is applled to the exterior surface of the internal shell layer 74, preferably through conventional in~ection or rotational molding technlques. After the exterior layer 76 of the shell is fabricated, the dimples 16 are then formed in the exterior surface of the ball. The dimples could also be formed during moldin~ through the use of properly configured mold segments.
By fabrication the shell as a multi-layer lp~n~te~
its materials can be selected for tailoring the performance of the ball to a particular use or application. For example, the properties such as color, frictlonal bite, durability, and resistant to scuffs and cuts could be built lnto the outer layer. The inner layer could simply provide the desired resilience. Furthert the interior layer could be of a relatively high modulus of elasticity for increased life and sesilience while the external layer could be formed of a lower modulus of elasticity for gre~ter frictional contact with the ball striking surface of the golf club for greater bite and playability. Brightness could be added to the exterior layer only up to ~ loading for ~n~zing the utilization of such brightening agents This embodiment of the shell which is formed of a plurality of bonded layers could be manufactured in a conventional shuttle mode. In this me~hod, the interior ' " " , ' ~ '.' ~ ~ , , .:~ '' ''.: ' ' . , , ' : , : . ':

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molded layer is first in~ected into the mold to form the interior layer. Thereafter, or ~isa versa, the exterior l~yer, of 8 different material than the interior layer, ~8 in~ected over the first layer. Such is effectsd through consecuti~e shootings into a common mold over a mold component in the fabricutlon of layered shell halves. This molding technique is common in the molding of typewriter kéys wherein the different in~ect~d materials form the visible lettering.
Figures 17, 18 and 19 represent three additional embodiments of the ~ub~ect invention for tailoring the shell properties to a particular application or use. While these three distinct embodiments are illustrated on a part~cular core, it is understood that the embodiments as illustra~ed in Figures 17, 18, 19 as well as 1~, csn likewise be used in fabricat~ng a hollow shell or on a hemispherical mold half.
Figure 17 represents a further embodiment of this in~ention. In this embodiment the shell 78 incorporates a central cellular stratum 90 which is sandwiched between two non-cellular skins 92 and 94. Non-cellulsr skins 92 and 94 are formed in situ by varying the process para~e~ers wherein the shell 88 is molded.
Skins 92 and 94 can be altered and formed by a plurality of techniques, fGr example, the s~ins can be formed by varying the temperature of the mold during the initial stages of the in~ection molding process and by varying other parameters, such as melt temperatures, in~ection time, in~ection speed, i:n~ection pressura, nozzle type, gating, venting, holding pressure, holding time, shot weight, blowlng agent concentration, nucleator concentration, polymeric composition, mold ~urface treatment and mold lubricant. See :, ' , ' ~ . ' ,' ~ .: ' ' ' ~ ':' ' .: : ':

0~31~.

U.S, Patent Number 4,274,637 to Molitor for greater details.
Figure 18 illustrates yet another embodiment of this invention wherein the shell 98 incorporates an essentially uniform cellular structure. In this embodiment the shell 98 is molded over a hemispherical mold half.
Figure 19 represents still another embodiment o~
this inventlon. The shell 102 incorporates A central stratum 104 which is sandwiched between a pair of strata 106 and 108. The central stratum 104 has an apparent denslty which is less than that of the strata. To put it in other words, the strata have a greater apparent density than ~hat of the central stratum. Naturally, it is obv~ous to one skilled in the art that in ~he region of the interfaces between the stratum, the spp~rent density of the cover will vary. The respect~ve apparent densities of the strata can be varied by one skilled in the art by alterin~ the process parameters as discussed above.

Terms Utilized:
For purposes of this application, when denslties and specific gravities are referred to, they are referred to in "apparent densities~ and "apparent specific ~ra~ities. n These terms take into consideration the fact ehat some of the csver stocks of this i~vention are non-uniform in that they may incorporate skins and variable cell structures. These terms take into conslderation these variables and give the actual density and specific gravity of the aYerage structure.
The terms "apparent densities" and "apparent specific ~ravities" also apply to the density and speclfic gravity of the liquid materials injected into the shell to form the core.

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~:0~ 16 The golf ball shell and/or core materials of the sub~ect invention can be used as a means of alterlng or regulating the coefficien~ of restitution. The coefficient of restitution of a golf ball is generally indicstive of the resiliency of the ball in question, hence indicative of the distance the ball will travel when struck wlth a gol~ club.
The coefficient of restitution is generally maasured by propelling a finished golf ball against a hard surfa~e at a fixed velocity. After the ball has rebounded from the surfa~e its velocity is again measured. The ratio of the rebound velocity over the spproach velocity is the coefficient of restitution, The coefficient of restitution is directly related to the resiliency of a golf ball and how far it will travel when struck by a golf club, all other varisbles being constan~.
The resiliency of a golf ball is regulated by the United States Golf Association Vi8 a test which is generally referred to as the Initlal Velocity test. In this tes~, a golf ball is struck by a rotating mass. The rotating mass is traveling at a speed of approximstely 143 feet per second Once struck by this club face, the velocity of the ball is measured as it passes through two light screens which are posiSioned forward of the club face. The l~ prescribed lim~t for a golf ball which is tested in this manner is 255 feet per second at 75 degrees Fahrenheit. This upper limit standard o~ 255 feet per second corresponds to an avera~e coefficient of restitution of approximately 0.815 measured with an approach velocity of 125 feet per second.
The coefficient of restitutlon data as specified below was arrived at by firing balls from a pneumatic cannon at muzzle velocity of 125 feet per second against a steel ,:, ' ~' ..

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plate which i9 positioned ten feet from the muzzle of ~aid cannon and measuring both the inltlal velocity and return velocity of the re'oounding ball. Th~ ratlo of ~aid return velocity to the initial velocity is the speci~ied coefficient of restitution.

Using the procedures described above, golf balls wers prepared as follows:
Formulation 514-92-1 was in~ection molded into half shells, app'roximately 1.68 inches in diameter and 0.190 inches thick. Formulation 514-92-1 is AS follows:
Parts by ~eight Surlyn 1605/8940 50 (SURLY~ is a Trademark of E.I. DuPont De Nemours & Company of Wilmin~ton, Delaware) Surlyn 1706/9910 50 Unitana 0-110 Titanium Dioxide 2.35 (Unitane 0-110 is a Trademark of Kemira, Inc. of Sa~annah, Oeorgia) Vvitex OB 0.10 (Uni~ex OB is a Trade~ark of Ciba-Oei~y of Hawthorne, New York) Ultramarine Blue 0.024 (Ultramarine Blue is ~omlfRotured by ~hittaker~Clark and Daniels of South Plainfield, New Jersey) Total ' 102.474 The pole he~ght was greater than the equator radius by 0.007 inches to allow for material flow durin~ spin weldin~ of the two half shçlls to form the hollow sphere. The two shells , .

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20~

had a tongue and groove configuration. The two half shells were spin bonded t~gether to produce a hollow sphere at 4100 revolutions per minute (rpm) and l5 second dwell. The ' grooved half shell had a molded tapered hole 0.125 inches in diameter at the exterior ball surface and 0.0625 incheR in diameter at the interior ball surface.
Specific gravity of the cover material can range from .95 to 1.25. The preferred range is .97 to 1Ø
The flex modulus expressed ln p9i at 73 degrees Fahrenheit has a range of 30,000 to 60,000. The preferred range ~s 45M to 60M. Flex modulus are measured in accordance with A.S.T.M. Test D 790.
Samples to date using ionomer compounds as listed below have the follo~ing average data:

Specific gravity: .97 Actual flex modulus: 50,000 Cover weight: 21 grams Estlmated volume of cover is 0.979 cubic inches, or 13.04 cubic centimeters.
Liquid core ma~er~al, For~ulat~on A, was introduced using a hypodermic syringe to completely fill the interior void. Formulation A is:

Formulation A Parts by Weight Calcium Chloride 45 ~ater 45 Glycerine 10 Total 100 .
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, A molded plug in the shape as shown in Figures 12 aDd 15 of the same materi~l as ths shell was spin bonded into the hole to seal the contents. Spin bonding conditions were 3150 rp~ and 15 seconds dwell.
The resulting product after defl~h~n~ had the following average properties:

Average Diameter: 1.694 inches Average ~eight: 45.9 gram~
Average PGA Gompression: 104 Average Coeff~cient of Restitution: 0.747 These results are the average of the three highest coefficient balls from six (6) balls produced.
The test as described abov~ was repeated. Qnly 12 balls were manufactured.

Average Diameter: 1.685 inches Average We~ght: 45.4 grams Average PGA Compression: 99 Average Coefficient of Restitution: 0.725 The procedure of ~x mple 1 was followed, except that the fill~ng material was ~lycerine.
The resulting product after defl~hl~g had the following properties:

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~:0~9~ 1 Average Diameter: 1.693 inches Average Weight: 44.4 grams Average PGA Compression: 107 Average Coefficient of Restitution: 0.758 These results are the average of the three highest çoeff~cient balls,oE four balls produced.
As is described in Example 1, above, 12 addltional balls were manufactured, Average Diameter: 1.Ç86 inches A~erage ~eight: 43.8 grams Average PGA Compression: 99 Average Coefficient of Restitution: 0.732 The procedure of Example 1 ~as followed, except that the filling material was hydraulic oil, Mobil Etna 26 wh~h is a Trademark of Nobil Oil Corp. of New York City, New York.
The resulting product after deflA~hing had the following properties:

Average Di~meter: 1.693 inches Aver~ge Weight: 37.5 grams Average PGA Compression: 108 Average Coefficient of Restitution: 0.749 These results are the a~erage of the three highest coefflcient balls of four balls produced.
As ~s described in Exa~ple 1, above, the tests of Example 3 were,repeated and 12 balls manufactured. The :: ~ :: - :, : : , 2~ 6 ~

.
resulting prod~cts after defl~ch~n~ had the following properties:

Average diameter: 1.683 inches A~erage w~ight: 37.1 grams Average PGA Compression 99 Average Coefficient of Restitution: 0.745 The procedure of E~ample 1 was followed, except that the fllling material was gelatln/sugar/water solution, Formulation B. Formulation B is as follows:

Formulation B Parts by Weight Gelatin 45 Royal Gelatin Desert, manufactured by Nabisco Brands, Inc. of East Hanover N.J. 07936 Sugar 80 ~ater . 240 : Total 3~5 ~ntroduced at one hundred fi~ty (150) degrees Fahrenheit. On cooling, a solid gel is produced.
The resulting product after deflashing had the following properties:

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- -Average Di&meter: 1.687 inches A~erage Weight: 42.7 grams Average PGA Compression: 106 Average Coefficient of Restitution: 0.749 These results are the average of the three highest coefficient balls of four balls produced.
As is descrlbed above relative to Exampl~ 1, the tests were repeated and 12 balls were manufactured. The resulting products after flR~h~n~ had ~he following properties:

Average diameter: 1.684 inches Average weight: 42 grams ~ Average PGA Compression 98 ~verage Coefficient of Restitution: 0.733 ~XAMPLE 5 The procedure of Example 1 was followed, except that the shell material was 514-93-3, as follows:

Parts bY Wei~ht Escor 900 50 (Escor is a Trade~ark of Exxon Chemical of Houston, Texas) Escor 4000 50 Uritane 0~110 Titanium Dioxide 2.35 Uvitex OB 0.10 Ultramarine Blue 0.024 Total 102.474 -3~-.

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The resulting product after defl~h~n~ had the following properties:

Average Diameter: 1.693 inche~
Aver~ge Weight: 45.9 grams Average PGA Compression: 104 Average Coefficient of Restitution: 0.747 These results are the avera~e of the three highest coef~icient balls of four balls produced.
As is described above in Example 1, the tests of Example l were repeated and 12 golf balls formed: The resulting products after defl~e~ne had the followi~g physical properties.

Average diameter: 1.687 inches Average weight: 45.4 grams Average PGA Compression 104 Average Coefficient of Restitution: 0.738 The present disclosure includes that contained ln the appended claims as well as that of the foregoing description. Although this invention has been described in its preferred forms with a certain degree of particularity, it is understood that -the present disclosure of the preferred form has been made only by way of example and numerous chan~es in the details of construction and combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.
Now that the invention has been described, ., . -- ~ , ~''' '' ~ ' ,. ..
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Claims (5)

1. A method of making a golf ball, which is suitable for use in regulation play and which conforms to the initial velocity requirements of the U.S.G.A., comprising the steps of:
(1) forming a hollow shell in the configuration of a sphere from a deformable polymeric material; and (2) introducing into said shell a liquid material which forms a homogeneous core filling said shell, the structural characteristics of said shell and core being such that said golf ball has a high coefficient of restitution.

2. The method of claim 1 wherein the shell is formed of two essentially hemispherically shaped molded halves and further including the step of coupling together the halves from a process selected from a member of the group consisting of spin welding, sonic welding, solvent welding, compression molding and adhesive bonding.

3. The method of claim 2 wherein the liquid material is introduced into the shell by injecting said liquid material into the shell through a hole in the shell and further including the steps of drilling or forming one or more holes through the shell prior to injecting and plugging the hole or holes after injecting.

4. The method of claim 1, 2, or 3 wherein said coefficient of restitution is at least 0.700.

5. A golf ball made by the method of claim 1, 2, 3, or 40