Patent Application
20090297653
Not Applicable
1. Field of the Invention
The present invention relates to manufacturing a golf ball. More specifically, the present invention relates to a manufacturing a golf ball cover layer through use of reaction injection molding.
2. Description of the Related Art
Golf balls are typically made by molding a core of elastomeric or polymeric material into a spheroid shape. Alternatively, wound cores comprising a solid, liquid or gel center encapsulated by elastomeric windings or thread also can be produced. A cover is then molded around the core. Sometimes, before the cover is molded about the core, an intermediate layer is molded about the core and the cover is then molded around the intermediate layer. The molding processes used for the cover and the intermediate layer are similar and usually involve either compression molding or injection molding techniques.
In compression molding, the golf ball core is inserted into a central area of a two piece die and pre-sized sections of cover material are placed in each half of the die, which then clamps shut. The application of heat and pressure molds the cover material about the core.
Polymeric materials, or blends thereof, have been used for modem golf ball covers because different grades and combinations have offered certain levels of hardness, damage resistance when the ball is struck with a club, and elasticity, thereby providing responsiveness when hit. Some of these materials facilitate processing by compression molding, yet disadvantages have arisen. These disadvantages include the presence of seams in the cover, which occur where the pre-sized sections of cover material were joined, and high process cycle times which are required to heat the cover material and complete the molding process.
Injection molding of golf ball covers arose as a processing technique to overcome some of the disadvantages of compression molding. The process involves inserting a golf ball core into a die, closing the die and forcing a heated, viscous polymeric material into the die. The material is then cooled and the golf ball is removed from the die. Injection molding is well-suited for thermoplastic materials, but has generally limited applications with some thermosetting polymers. However, several types of these thermosetting polymers often exhibit the hardness and elasticity desired in golf ball cover construction.
Furthermore, some of the most promising thermosetting materials are reactive, requiring two or more components to be mixed and rapidly transferred into a die before a polymerization reaction is complete. As a result, traditional injection molding techniques do not provide proper processing when applied to these materials.
Reaction injection molding (“RIM”) is a processing technique used specifically for certain reactive thermosetting plastics. By “reactive” it is meant that the polymer is formed from two or more components which react. Generally, the components, prior to reacting, exhibit relatively low viscosities. The low viscosities of the components allow the use of lower temperatures and pressures than those utilized in traditional injection molding. In reaction injection molding, the two or more components are combined and react to produce the final polymerized material. Mixing of these separate components is critical, a distinct difference from traditional injection molding.
The process of reaction injection molding a golf ball cover or other component or layer, involves placing a golf ball core into a die, closing the die, injecting the reactive components into a mixing chamber where they combine, and transferring the combined material into the die. The mixing begins the polymerization reaction which is typically completed upon cooling of the cover material. Although satisfactory in many respects, there remains a need for an improved reaction injection molding process for forming golf balls.
Furthermore, there is a need for a new mold or die configuration and a new method of processing for reaction injection molding a golf ball cover or inner layer which promotes increased mixing of constituent materials, resulting in enhanced properties and the ability to explore the use of materials new to the golf ball art.
Additionally, during traditional molding operations in forming a cover or other layer on a golf ball core, a collection of locating pins are used within the mold cavity to retain the core in a fixed, central location within the mold cavity. Covers or other layers formed about such pins typically have voids resulting from the pins which then need to be filled or otherwise addressed. This additional step leads to increased processing and expense. Thus, it would also be desirable in certain circumstances to eliminate the use of locating pins when molding golf balls.
Moreover, after molding a cover or other layer on a golf ball core or intermediate golf ball assembly, the resulting molded assembly must be removed from the mold. Although mold release agents are known, disadvantages can arise from the use of such agents. Mechanical means are also known for removing the molded balls or assemblies from the mold. While sometimes satisfactory, a further need remains for new processes and techniques for removing a golf ball from a mold.
The present disclosure is directed, in various exemplary embodiments, to a two-stage reaction method for forming at least one layer on a golf ball core or intermediate golf ball assembly. The embodiments utilize a collection of molds, including shuttle molds and/or molding assist members, that enable the formation of golf ball components by reaction injection molding.
In one embodiment, the method comprises providing a first mold defining a recessed molding surface. The method also comprises providing a second mold defining a recessed retaining surface. The method further comprises positioning a golf ball core or intermediate golf ball assembly within at least one of the recessed molding surface of the first mold and the recessed retaining surface defined by the second mold. The method also comprises closing or joining the first mold and the second mold whereby a first molding cavity is defined along a first region of the golf ball core or intermediate golf ball assembly. The method also comprises introducing an initially flowable material into the first molding cavity to thereby form a first molded layer portion on the first region. The method further comprises opening the first mold and the second mold to thereby at least partially expose the golf ball core or intermediate golf ball assembly. The method also comprises providing a third mold defining a recessed molding surface. The method further comprises positioning the golf ball core or intermediate golf ball assembly containing the first molded layer portion within at least one of the recessed molding surface of the first mold and the recessed molding surface of the third mold. The method also comprises closing the first mold and the third mold whereby a second molding cavity is defined along a second region of the golf ball core or intermediate golf ball assembly. The method further comprises introducing an initially flowable material into the second molding cavity to thereby form a second molded layer portion on the second region. The method also comprises opening the first mold and the third mold. And, the method comprises removing the golf ball core or the intermediate golf ball assembly containing the first and second molded layer portions, from at least one of the first mold and the third mold.
In another aspect, the exemplary embodiments provide a molding assembly adapted for two-stage reaction injection molding. The molding assembly comprises a first mold defining a recessed molding surface. The molding assembly also comprises a second mold defining a recessed retaining surface. The first mold and the second mold are adapted to engage each other to form a first molding cavity. The molding assembly also comprises a third mold defining a recessed molding surface. The first mold and the third mold are also adapted to engage each other to form a second molding cavity.
In yet another aspect according to the exemplary embodiments, a method of molding a layer formed of at least one flowable reactive material about a golf ball product is provided. The method comprises holding a first portion of the golf ball product in a retaining cavity of a retaining member to expose a second portion of the golf ball product. The method also comprises positioning the exposed second portion of the golf ball product in a first mold cavity of a first mold portion. The method further comprises injecting the reactive material at a mating surface between the retaining member and the first mold portion into the first mold cavity to mold a first portion of the layer over the second portion of the golf ball product. The method also comprises disengaging the retaining member from the golf ball product to expose the first portion thereof while holding the molded first portion of the layer by the first mold portion. The method further comprises positioning the exposed first portion of the golf ball product in a second mold cavity of a second mold portion. The method also comprises injecting the reactive material at a mating surface between the first and second mold portions into the second mold cavity to mold a second portion of the layer over the first portion of the golf ball product. Additionally, the method comprises removing the golf ball product with the molded layer from the first and second molded portions.
In yet another aspect, the exemplary embodiments provide a method of molding a layer formed of at least one reaction injection molding material about each golf ball product in a multi-array of golf ball products. The method comprises holding a first portion of each golf ball product in a retaining cavity of a multi-array of a retaining member to expose a second portion of each golf ball product. The method comprises positioning the exposed second portion of each golf ball product in a first mold portion which contains provisions for one or more cavities. The method also comprises molding a first portion of the layer from a reaction injection molding material over the second portion of each golf ball product. The method further comprises disengaging the retaining member array from the golf ball product array to expose the first portion of each golf ball product while holding the molded first portions of the layers by the first mold portion array. The method also comprises positioning the exposed first portion of each golf ball product in a second mold cavity of a multi-array of second mold portions. The method further comprises molding a second portion of the layer from the reaction injection molding material over the first portion of each golf ball product. Moreover, the method also comprises removing the golf ball product with the molded layer from the first and second molded portions.
In yet another aspect according to the exemplary embodiments, a method is provided for molding a layer formed of at least one reaction injection molding material about a golf ball product. The method comprises holding a bottom or side portion of the golf ball product horizontally, vertically or in any attitude or angle that facilitates molding in a retaining cavity of a retaining member to expose a top or side portion of the golf ball product. The method also comprises positioning the exposed top or side portion of the golf ball product in a top mold cavity of a top mold portion or in another vertical mold. The method further comprises injecting the reaction injection molding material at a mating surface between the retaining member and the mold portion into the mold cavity to mold a top or side portion of the layer over the top or side portion of the golf ball product. The method further comprises disengaging the retaining member from the golf ball product to expose the bottom or another side portion thereof while holding the molded top or side portion of the layer by the top or other vertical mold portion. The method further comprises positioning the exposed bottom or side portion of the golf ball product in a bottom or side mold cavity of a bottom or side mold portion. The method also comprises injecting the reaction injection molding material at a mating surface between the top and bottom or side mold portions into the bottom or side mold cavity to mold a bottom or side portion of the layer over the bottom or side portion of the golf ball product. And, the method comprises removing the golf ball product with the molded layer from the first and second molded portions.
One advantage of the exemplary embodiments is that the constituent materials are mixed thoroughly, thereby providing a more consistent intermediate and/or cover layer, resulting in better golf ball performance characteristics.
Another advantage of the exemplary embodiments is that the use of new, lower viscosity materials may be explored, resulting in enhanced golf ball properties and performance.
Yet another advantage of the exemplary embodiments is that increased mixing of lower viscosity materials allows the intermediate layer or cover to be thinner, resulting in increased ball performance.
Still another advantage of the exemplary embodiments is that enhanced core centering can be produced during the molding process. This results in a golf ball that is more dependably concentric and uniform in construction, thereby improving ball performance.
A further advantage of the exemplary embodiments results from the elimination of locating or support pins used in certain previous processes that can otherwise detrimentally affect cosmetics and resulting durability of the golf ball.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.
Disclosed herein, in various exemplary embodiments, are golf balls in which at least one cover layer, intermediate mantle layer, or core layer comprises a fast-chemical-reaction-produced component. This component comprises particular polyurethane, polyurethane/polyurea, and polyurea compositions, and preferably comprises thermosetting polyurethanes, polyurethanes/polyureas, and polyureas. The phrase “polyurethane/polyurea” will be used herein to mean a polyurethane, a polyurea, or combination thereof.
The exemplary embodiments also include methods of producing golf balls, such as by RIM, which contain a fast-chemical-reaction-produced component. The exemplary embodiments additionally include methods for performing two stage molding operations for forming layers or covers on golf ball cores or intermediate golf ball assemblies. Particularly preferred forms of the exemplary embodiments also provide for a golf ball with a thin, fast-chemical-reaction-produced cover having good scuff and cut resistance. And, the exemplary embodiments provide unique molds, mold configurations, and combinations of molds that enable the exemplary embodiments' methods to be performed.
More specifically, one of the preferred methods of forming a fast-chemical-reaction-produced component for a golf ball according to the disclosure is by a modified RIM process. In a RIM process, highly reactive liquids are injected into a closed mold, mixed usually by impingement and/or mechanical mixing and secondarily mixed in an in-line device such as a peanut mixer, where they polymerize primarily in the mold to form a coherent, molded article. The RIM processes usually involve a rapid reaction between one or more reactive components such as polyether—or polyester—polyol, polyamine, or other material with an active hydrogen, and one or more isocyanate—containing constituents, often in the presence of a catalyst. The constituents are stored in separate tanks prior to molding and may be first mixed in a mix head upstream of a mold and then injected into the mold. The liquid streams are metered in the desired weight to weight ratio, such that the ratio of the —NCO groups to the active hydrogen groups is within a desired ratio, and fed into an impingement mix head, with mixing occurring under high pressure, e.g., 1500 to 3000 psi. The liquid streams impinge upon each other in the mixing chamber of the mix head and the mixture is injected into the mold. One of the liquid streams typically contains a catalyst for the reaction. The constituents react rapidly after mixing to gel and form polyurethane/polyurea polymers. Epoxies and various unsaturated polyesters also can be molded by RIM.
RIM differs from non-reaction injection molding in a number of ways. The main distinction is that in RIM a chemical reaction takes place in the mold to transform a monomer or adducts to polymers and the components are in liquid form. Thus, a RIM mold need not be made to withstand the pressures which occur in a conventional injection molding. In contrast, injection molding is conducted at high molding pressures in the mold cavity by melting a solid resin and conveying it into a mold, with the molten resin often being at about 150 to about 350° C. At this elevated temperature, the viscosity of the molten resin usually is in the range of 50,000 to about 1,000,000 centipoise, and is typically around 200,000 centipoise. In an injection molding process, the solidification of the resins occurs after about 10 to 90 seconds, depending upon the size of the molded product, the temperature and heat transfer conditions, and the hardness or crystalline content of the injection molded material. Subsequently, the molded product is removed from the mold. There is no significant chemical reaction taking place in an injection molding process when the thermoplastic resin is introduced into the mold. In contrast, in a RIM process, the chemical reaction typically takes place in less than about 2 minutes, preferably in under one minute, and in many cases in about 30 seconds or less.
The fast-chemical-reaction-produced component has a flex modulus of from about 1 to about 310 kpsi, more preferably from about 1 to about 100 kpsi, and most preferably from about 2 to about 50 kpsi. The subject component can be a cover with a flex modulus which is higher than that of the centermost component of the cores, as in a liquid center core and some solid center cores. Furthermore, the fast-chemical-reaction-produced component can be a cover with a flex modulus that is higher than that of the immediately underlying layer, as in the case of a wound core. The core can be one piece or multi-layer, filled or unfilled, wound or non-wound, and each layer can be either foamed or unfoamed. Furthermore, density adjusting fillers, including metals, can also be used. The cover of the ball can be harder or softer than any particular core layer.
The fast-chemical-reaction-produced component can incorporate suitable additives and/or fillers. When the component is an outer cover layer, pigments or dyes, accelerators and UV stabilizers can be added. Examples of suitable optical brighteners which probably can be used include Uvitex™ and Eastobrite™ OB-1. An example of a suitable white pigment is titanium dioxide. Examples of suitable and UV light stabilizers are provided in commonly assigned U.S. Pat. No. 5,494,291. Fillers which can be incorporated into the fast-chemical-reaction-produced cover or core component include those listed below in the definitions section. Furthermore, compatible polymeric materials can be added. For example, when the component comprises polyurethane and/or polyurea, such polymeric materials include polyurethane ionomers, polyamides, etc.
Catalysts can be added to the RIM polyurethane system starting materials as long as the catalysts generally do not react with the constituent with which they are combined. Suitable catalysts include those which are known to be useful with polyurethanes and polyureas. These catalyst include dibutyl tin dilaurate or triethylenediamine .
The reaction mixture viscosity should be sufficiently low to ensure that the empty space in the mold is completely filled. The reactant materials generally are preheated to about 80° F. to about 200° F. and preferably to 100° F. to about 180° F. before they are mixed. In most cases it is necessary to preheat the mold to, e.g., from about 80° F. to about 200° F., to provide for proper injection viscosity and system reactivity.
Molding at lower temperatures is beneficial when, for example, the cover is molded over a core. Normally, at higher temperature molding processes, the core may expand during molding. Such core expansion is not of such a concern when molding at lower temperatures and lower cycle times utilizing RIM.
As indicated above, one or more layers of a golf ball can be formed from a fast-chemical-reaction-produced material according to the present disclosure. These layers are preferably formed from polyurethane/polyurea materials.
Polyurethanes/polyureas are polymers which are used to form a broad range of products. Polyurethane and/or polyurea polymers are typically made from three reactants: alcohols, amines, and isocyanate-containing compounds. They react with the isocyanate-containing compound, which is generally referred to as an “isocyanate.” The constituent containing the alcohols, amines or other reactive hydrogen groups is sometimes referred to collectively as the polyol constituent of the RIM formulation. The constituent containing the isocyanate or isocyanate prepolymer is usually referred to as the isocyanate constituent of the RIM formulation.
Several chemical reactions may occur during polymerization of isocyanate and polyol. Isocyanate groups (—N═C═O) that react with alcohols form a polyurethane, whereas isocyanate groups that react with an amine group form a polyurea. A polyurethane itself may react with an isocyanate to form an allophanate and a polyurea can react with an isocyanate to form a biuret. Because the biuret and allophanate reactions occur on an already-substituted nitrogen atom of the polyurethane or polyurea, these reactions increase cross-linking within the polymer.
The polyol component typically contains additives, such as stabilizers, flow modifiers, catalysts, combustion modifiers, blowing agents, fillers, pigments, optical brighteners, surfactants and release agents to modify physical characteristics of the cover. Polyurethane/polyurea constituent molecules that were derived from recycled polyurethane can be added in the polyol component. Cross linking occurs between the isocyanate groups (—NCO) and the polyol's hydroxyl end-groups (—OH) and/or the active hydrogens (—H) of the amines or polyamines. Additionally, the end-use characteristics of polyurethanes can also be controlled by different types of reactive chemicals and processing parameters. For example, catalysts are utilized to control polymerization rates. Depending upon the processing method, reaction rates can be very quick (as in the case for some reaction injection molding systems (i.e., “RIM”).
A wide range of combinations of polyisocyanates and polyols, as well as other ingredients, are available. Furthermore, the end-use properties of polyurethanes can be controlled by the type of polyurethane utilized, i.e., whether the material is thermoset (cross linked molecular structure) or thermoplastic (linear molecular structure). In the present RIM process, thermosetting polyurethanes/polyureas are utilized.
In this regard, polyurethanes are typically classified as thermosetting or thermoplastic. A polyurethane becomes irreversibly “set” when a polyurethane prepolymer is cross linked with a polyfunctional curing agent, such as a polyamine or a polyol. The prepolymer typically is made from polyether or polyester. Diisocyanate polyethers are sometimes preferred because of their water resistance.
The physical properties of thermoset polyurethanes are controlled substantially by the degree of cross linking. Tightly cross linked polyurethanes/polyureas are fairly rigid and strong. A lower amount of cross linking results in materials that are flexible and resilient. Thermoplastic polyurethanes have some cross linking, but primarily by physical means. The crosslinkings bonds can be reversibly broken by increasing temperature, as occurs during molding or extrusion. Polyurethane materials suitable for the exemplary embodiments are formed by the reaction of a polyisocyanate, a polyol, an amine and optionally one or more chain extenders. The polyol component includes any suitable polyether- or polyester polyol. Additionally, in an alternative embodiment, the polyol component may contain polybutadiene diol as a chain extender. The chain extenders include, but are not limited, to diols, triols and amine extenders. Any suitable polyisocyanate may be used to form a polyurethane according to the exemplary embodiment. The polyisocyanate is preferably selected from the group of diisocyanates including, but not limited, to 4,4N-diphenylmethane diisocyanate (“MDI”); 2,4-toluene diisocyanate (“TDI”); m-xylylene diisocyanate (“XDI”); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamethylene diisocyanate (HDI); naphthalene-1,5,-diisocyanate (“NDI”); 3,3N-dimethyl-4,4N-biphenyl diisocyanate (“TODI”); 1,4-diisocyanate benzene (“PPDI”); phenylene-1,4-diisocyanate; and 2,2,4- or 2,4,4-trimethyl hexamethylene diisocyanate (“TMDI”).
Other less preferred diisocyanates include, but are not limited to, isophorone diisocyanate (“IPDI”); 1,4-cyclohexyl diisocyanate (“CHDI”); diphenylether-4,4N-diisocyanate; p,pN-diphenyl diisocyanate; lysine diisocyanate (“LDI”); 1,3-bis(isocyanato methyl)cyclohexane; and polymethylene polyphenyl isocyanate (“PMDI”).
One polyurethane component which can be used in the exemplary embodiment incorporates TMXDI (META) aliphatic isocyanate (Cytec Industries, West Paterson, N.J.). Polyurethanes based on meta-tetramethylxylyliene diisocyanate can provide improved gloss retention, UV light stability, thermal stability and hydrolytic stability. Additionally, TMXDI (META) aliphatic isocyanate has demonstrated favorable toxicological properties. Furthermore, because it has a low viscosity, it is usable with a wider range of diols (to polyurethane) and diamines (to polyureas). If TMXDI is used, it typically, but not necessarily, is added as a direct replacement for some or all of the other aliphatic isocyanates in accordance with the suggestions of the supplier. Because of slow reactivity of TMXDI, it may be useful or necessary to use catalysts to have practical demolding times. Hardness, tensile strength and elongation can be adjusted by adding further materials in accordance with the supplier's instructions.
Suitable glycol chain extenders include, but are not limited to ethylene glycol; propane glycol; butane glycol; pentane glycol; hexane glycol; benzene glycol; xylenene glycol; 1,4-butane diol; 1,3-butane diol; 2,3-dimethyl-2,3-butane diol; and dipropylene glycol. Suitable amine extenders include, but are not limited to, tetramethyl-ethylenediamine; dimethylbenzylamine; diethylbenzylamine; pentamethyldiethylenetriamine; dimethyl cyclohexylamine; tetramethyl-1,3-butanediamine; 1,2-dimethylimidazole; 2-methylimidazole; pentamethyldipropylenetriamine; diethyl toluene diamine (DETDA) and bis-(dismethylaminoethylether).
Polyurethane/polyurea compositions of the exemplary embodiment are especially desirable as materials in forming golf balls. Polyurethanes according to the exemplary embodiment, are suitable materials for any of a core layer, a mantle layer, and a cover layer. Most preferably, the polyurethane materials are used to form a cover layer. Accordingly, golf balls according to the exemplary embodiment, may be formed as two-piece, or multi-layer balls having a wound core a solid, non-wound core, a liquid core, or a thermoplastic non-wound core. In a preferred form, golf balls utilizing a polyurethane composition described herein are solid, i.e., non-wound, multi-layer golf balls comprising a solid non-wound core, a cover formed from the exemplary embodiment polyurethane, and one or more intermediate layers disposed between the cover and the core. Specifically, multi-layer golf balls can be produced by injection molding or compression molding a mantle layer about wound or solid molded cores to produce an intermediate golf ball core or insert having a diameter of about 1.50 to 1.67 inches, preferably about 1.620 inches. The cover layer is subsequently molded over the mantle layer to produce a golf ball having a diameter of 1.680 inches or more. Although either solid, wound, liquid, foamed or thermoplastic non-wound cores can be used in the exemplary embodiment, as a result of their lower cost and superior performance, solid molded cores are preferred over wound cores.
A preferred form of the exemplary embodiments is a golf ball in which at least one cover, intermediate or core layer comprises a fast-chemical-reaction-produced component. This component includes at least one material selected from the group consisting of polyurethane/polyurea, polyurethane ionomer, epoxy, and unsaturated polyesters, and preferably comprises polyurethane. The exemplary embodiment also includes a method of producing a golf ball which contains a fast-chemical-reaction-produced component. A golf ball formed according to the exemplary embodiment preferably has a flex modulus in the range of from about 1 to about 310 kpsi, a Shore D hardness in the range of from about 10 to about 95, and good durability. The Shore B readings, when measured on the ball, are 50 to 100. Particularly preferred forms of the exemplary embodiment also provide for a golf ball with a fast-chemical-reaction-produced cover having good scuff resistance and cut resistance.
As indicated above, the fast-chemical-reaction-produced component can be one or more cover and/or core layers of the ball. When a polyurethane/polyurea cover is formed according to the exemplary embodiment, and is then covered with a polyurethane top coat, excellent adhesion can be obtained. The adhesion in this case is better than adhesion of a polyurethane coating to an ionomeric cover. This improved adhesion can result in the use of a thinner top coat, the elimination of a primer coat, and the use of a greater variety of golf ball printing inks beneath or on top of the top coat. These include but are not limited to typical inks such as one component polyurethane inks and two component polyurethane inks.
A more complete understanding of the processes, products, components and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the present development, and are, therefore, not intended to indicate relative size and dimensions of the golf balls or components thereof.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.
Referring now to the drawings, and first to
Referring to
Inside the mix head 1116, injector nozzles impinge the isocyanate and polyol at ultra-high velocity to provide excellent mixing. Additional mixing preferably is conducted using an aftermixer 1130, which typically is constructed inside the mold between the mix head and the mold cavity. The molding assembly is positionable between an open state in which the interior or contents of the mold are accessible, and a closed state in which the molding cavity or molding chamber is enclosed and defines a sealed interior or void, such as when receiving flowable molding material in a molding operation. The molding assembly can be closed or otherwise positioned to a closed state by moving the molding members in nearly any direction or along nearly any axis. For example, the molding members can be positioned along a vertical axis, a horizontal axis, or any axis therebetween.
As is shown in
The mold cavity may contain retractable pins and is generally constructed in the same manner as a mold cavity used to injection mold a thermoplastic, e.g., ionomeric golf ball cover. However, two differences when RIM is used are that tighter pin tolerances generally are required, and a lower injection pressure is used. Also, the molds can be produced from lower strength material such as aluminum.
In
Turning now to
Each upper and lower half 22A and 22B of the preferred embodiment molding assembly 20 defines an adapter portion 26A and 26B to enable the body 20 to connect to other process equipment as mentioned above and leads to a material inlet channel 28A and 28B as illustrated in
With continuing reference to
Turning now to
At each first planar wall 40A and 40B, the material can no longer continue to flow within the plane of the closed mold, i.e., the halves 22A and 22B being aligned with one another. To aid the present description it will be understood that in closing the mold, the upper half 22A is oriented downward (referring to
Specifically, at the first planar wall 40A the material flows from a point α1 in one half 22A to a corresponding point α1 in the other half 22B. Point α1 in half 22B lies at the commencement of a first convergent portion 42B. Likewise, at the first planar wall 40B the material flows from a point β1 in one half 22B to a corresponding point β1 in the other half 22A. The point β1 in half 22A lies at the commencement of a first convergent portion 42A. The first convergent portion 42A and 42B brings the material to a first common area 44A and 44B. In the shown embodiment, each first convergent portion is parallel to each first diverging branching intersection to promote a smooth material transfer. For example, the portion 42A is parallel to the portion 38A, and the portion 42B is parallel to the portion 38B.
With continuing reference to
In the shown embodiment, each second convergent portion 50A and 50B, is parallel to each second diverging branching intersection 46A and 46B. For example, the portion 50A is parallel to the portion 46A and the portion 50B is parallel to the portion 46B. The second convergent portion 50A and 50B forces the material into a second common area 52A and 52B to once again rejoin the separated material. As with the first common area 44A and 44B, the second common area 52A and 52B has a full circular cross section.
After the common area 52A and 52B, a third branching intersection 54A and 54B again diverges, separating the material and conveying it in different directions. Upon reaching each respective third planar wall, i.e., the planar wall 56A in the portion 54A and the planar wall 56B in the portion 54B, the material is forced to again flow in a transverse, z-direction from the planar x-y direction. From a point α3 at the third planar wall 56A in one half 22A, the material flows to a corresponding point α3 in the other half 22B, which lies in a third convergent portion 58B. Correspondingly, from a point β3 at third planar wall 56B in one half 22B, the material flows to a corresponding point β3 in the other half 22A, which is in a third convergent portion 58A.
The turbulence-promoting peanut mixer structure 30A and 30B ends with a third convergent portion 58A and 58B returning the separated material to the connecting flow channel 32A and 32B. The connecting channel 32A and 32B is a common, uniform circular channel having a curvature of 360<. Once the material enters the connecting channel portion 32A and 32B, typical straight or curved smooth linear flow recommences.
By separating and recombining materials repeatedly as they flow, the exemplary embodiment provides for increased mixing of constituent materials. Through the incorporation of split channels and transverse flow, mixing is encouraged and controlled while the flow remains uniform, reducing back flow or hanging-up of material, thereby reducing the degradation often involved in non-linear flow. Particular note is made of the angles of divergence and convergence of the peanut mixer portions 38A and 38B, 42A and 42B, 46A and 46B, 50A and 50B, 54A and 54B and 58A and 58B, as each extends at the angle of about 30 E to 60 E from the centerline of the linear inlet flow channel 28A, 28B. This range of angles allows for rapid separation and re-convergence while minimizing back flow. In addition, each divergent branching portion and converging portion 38A and 38B, 42A and 42B, 46A and 46B, 50A and 50B, 54A and 54B and 58A and 58B extends from the centerline of the linear inlet flow channel 28A, 28B for a distance of one to three times the diameter of the channel 28A, 28B before reaching its respective planar wall 40A and 40B, 48A and 48B and 56A and 56B. Further note is made of the common areas 44A and 44B and 52A and 52B. These areas are directly centered about a same linear centerline which extends from the inlet flow channel portion 28A, 28B to the commencement of the connecting flow channel portion 32A, 32B. As a result, the common areas 44A and 44B and 52A and 52B are aligned linearly with the channel portions 28A, 28B and 32A, 32B, providing for more consistent, uniform flow. While several divergent, convergent, and common portions are illustrated, it is anticipated that as few as one divergent and convergent portion or as many as ten to twenty divergent and convergent portions may be used, depending upon the application and materials involved.
In a particularly preferred embodiment, the peanut mixer includes a plurality of bends or arcuate portions that cause liquid flowing through the peanut mixer to not only be directed in the same plane in which the flow channel lies, but also in a second plane that is perpendicular to the first plane. It is most preferable to utilize a peanut mixer with bends such that liquid flowing therethrough travels in a plane that is perpendicular to both the previously noted first and second planes. This configuration results in relatively thorough and efficient mixing due to the rapid and changing course of direction of liquid flowing therethrough.
The configuration of the mold channels may take various forms. One such variation is shown in
In the above-referenced figures, the channels 30A and 30B are depicted as each comprising a plurality of angled bends or turns. Turning now to
As shown in
A preferred method of making a golf ball in accordance with the exemplary embodiment is illustrated in
The exemplary embodiments also provide for a two-stage method for molding one or more cover or other layers on a golf ball core or center. This unique molding strategy eliminates the need for locating pins to be used to retain the golf ball core or intermediate ball assembly in a fixed location within the mold during the molding operation.
Removal of the golf ball core 500 and the layers formed thereon from the second final mold 300 can be facilitated by use of an ejection means such as a pin 400 as shown in
Although in the foregoing description and referenced figures, only the intermediate mold assisting member, i.e. mold 200, is described as including a channel for providing pressure communication between the retaining surface and a source of air or inert gas, it is to be understood that the exemplary embodiment includes either or both of the first final mold and the second final mold to also include such provisions.
Regarding the relationship between the first final mold 100, the intermediate mold assisting member 200, and the second final mold 300, it is preferred that the intermediate mold is independent of the second mold. However, the intermediate mold can be stationary or mobile. Preferably, in certain molding assemblies, the first and second final molds and the intermediate mold can each be detachably secured to mold platens. Also, the exemplary embodiment includes embodiments in which the first and second final molds, and optionally the intermediate mold, define a plurality or an array of molding regions such that upon operation, multiple golf balls can be processed.
The assembly 700 also comprises a first molding member 720 disposed along the underside 714 of the first positionable member 710. Upon moving or otherwise displacing the member 710, the first molding member 720 is also displaced.
The assembly 700 further comprises a second positionable member 750 on which is disposed a second molding member 770. The second positionable member 750 can be selectively moved or otherwise positioned to any desired position along the lengths of members 756. A wide variety of strategies can be used to displace the second positionable member 750. The exemplary embodiment includes the use of hydraulic rams and the like, and also linear actuator assemblies using one or more electric motors. The second molding member 770 contains or rather defines various molding features which are described in greater detail herein.
Although the preferred embodiment assembly 700 depicted in
Specifically, the first positionable member 710 defines a first face 712 and a second oppositely directed second face 714. As previously noted, the second face 714 is generally defined along the underside of the member 710. The second positionable member 750 defines a first face 752 and an oppositely directed second face 754. The first face 752 is preferably directed to the second face 714 of the first positionable member 710. Likewise, the stationary member 740 also defines a first face 742 and a second oppositely directed face 744. The second face 744 is preferably directed towards and facing the base 760.
Disposed along the underside 714 of the first positionable member 710, is the first molding member 720. It will be appreciated that the first molding member 720 is preferably releasably secured or otherwise affixed to the underside 714 of the first positionable member 710. Thus, depending upon the particular application, a variety of different molding members can be selectively used in conjunction with the movable member 710.
The second molding member 770 defines a face 772 which includes a first region within which is defined a plurality of molding cavities 780. And, the second molding member 770 defines a second region defining a collection of golf ball retaining recesses 790. Although the particular molding member 770 illustrated in
Next, as illustrated in
After proper alignment as shown in
The remaining portion of the exposed half of each golf ball 797 then receives a corresponding cover layer formed thereon.
Upon engagement between the first molding member 720 and the second molding member 770 such as shown in
After completion of the molding process to thereby form golf balls 799, the first molding member 720 is disengaged from the second molding member 770 such as shown in
In accordance with conventional molding techniques, the preferred embodiment molding processes described herein may utilize one or more mold release agents to facilitate removal of the molded layer or component from the mold. However, it is contemplated that typically, such agents will not be required.
A golf ball manufactured according the preferred methods described herein exhibits unique characteristics. Golf ball covers made through compression molding and traditional injection molding include balata, ionomer resins, polyesters resins and polyurethanes. The selection of polyurethanes which can be processed by these methods is limited. Polyurethanes are often a desirable material for golf ball covers because balls made with these covers are more resistant to scuffing and resistant to deformation than balls made with covers of other materials. The exemplary embodiment allows processing of a wide array of grades of polyurethane/polyurea through RIM which was not previously possible or commercially practical utilizing either compression molding or traditional injection molding. For example, utilizing the exemplary embodiment method and Uniroyal® VibraRIM of Uniroyal, a division of Crompton Corp., materials, a golf ball with the properties described herein has been provided.
Some of the unique characteristics exhibited by a golf ball according to the exemplary embodiment include a thinner cover or intermediate layer without the accompanying disadvantages otherwise associated with relatively thin covers, layers, etc. such as weakened regions at which inconsistent compositional differences exist. A traditional golf ball cover typically has a thickness in the range of about 0.030 inches to 0.080 inches. A golf ball of the exemplary embodiment may utilize a cover having a thickness of about 0.001 inches to about 0.200 inches. This reduced cover thickness is often a desirable characteristic. It is contemplated that thinner layer thicknesses are possible using the exemplary embodiment.
Because of the reduced pressure involved in RIM as compared to traditional injection molding, a cover or any other layer of the exemplary embodiment golf ball is more dependably concentric and uniform with the core of the ball, thereby improving ball performance. That is, a more uniform and reproducible geometry is attainable by employing the exemplary embodiment. Furthermore, utilizing the preferred aspects described herein, cosmetics and durability of the resulting golf balls can be significantly improved since locating pins for the core or the intermediate assembly can be eliminated. Such pins are generally otherwise required during molding operations. Along with cosmetic and durability benefits, the preferred embodiment golf balls are not damaged during ejection such as otherwise might occur using a single pin. The preferred embodiment ejection pin utilizes a tip having a relatively large surface area so that the impact force used to displace the ball from the molding cavity is distributed over a relatively large surface area on the ball thereby reducing the stress required for part ejection and minimizing cover damage.
Preferably, the dimple pattern defined on the molding surfaces of the molds is such that no dimple extends between molds. Thus, the resulting flash on the molded ball is confined to the land area between dimples.
The golf balls formed according to the exemplary embodiments can be coated using a conventional two-component spray coating or can be coated during the RIM process, i.e., using an in-mold coating process.
One of the significant advantages of the RIM process according to the exemplary embodiment is that polyurethane/polyurea or other cover materials can be recycled and used in golf ball cores or covers. Recycling can be conducted by, e.g., glycolysis. Typically, 10 to 90% of the material which is injection molded actually becomes part of the cover. The remaining 10 to 90% is recycled.
Recycling of polyurethanes by glycolysis is known from, for example, RIM Part and Mold Design—Polyurethanes, 1995, Bayer Corp., Pittsburgh, Pa. Another significant advantage of the exemplary embodiment is that because reaction injection molding occurs at low temperatures and pressures, i.e., 90 to 180° F. and 50 to 200 psi, this process is particularly beneficial when a cover is to be molded over a very soft core. When higher pressures are used for molding over soft cores, the cores “shut off” i.e., deform and impede the flow of material causing uneven distribution of cover material.
Golf ball cores also can be made using the materials and processes of the exemplary embodiment. To make a golf ball core using RIM polyurethane/polyurea, the same processing conditions are used as are described above with respect to covers. Furthermore, an undimpled, smaller mold is used. If, however, a one piece ball is desired, a dimpled mold would be used. Polyurethanes/polyureas also can be used for cores.
Golf balls typically have indicia and/or logos stamped or formed thereon. Such indicia can be applied by printing using a material or a source of energetic particles after the ball core and/or cover have been reaction-injection-molded according to the exemplary embodiment. Printed indicia can be formed from a material such as ink, foil (for use in foil transfer), etc. Indicia printed using a source of energetic particles or radiation can be applied by burning with a laser, burning with heat, directed electrons, or light, phototransformations of, e.g., UV ink, impingement by particles, impingement by electromagnetic radiation, etc. Furthermore, the indicia can be applied in the same manner as an in-mold coating, i.e., by applying to the indicia to the surface of the mold prior to molding of the cover.
The polyurethane/polyurea which is selected for use as a golf ball cover preferably has a Shore D hardness of 10 to 95, more preferably 30 to 75, and most preferably 30 to 50 for a soft cover layer and 50 to 75 for a hard cover layer. Alternatively, Shore B can be utilized to characterize the cover hardness. Comparatively, Shore B values are then about 50 to about 100, including from about 60 to about 90. The polyurethane which is to be used for a cover layer preferably has a flexural modulus of 1 to 310 kpsi, more preferably 5 to 100 kpsi, and most preferably 5 to 20 kpsi for a soft cover layer and 30 to 70 kpsi for a hard cover layer.
Non-limiting examples of polyurethanes/polyureas suitable for use in the layer(s) include the following.
Several systems available from Bayer include Bayflex 110-50 and Bayflex MP-10,000.
1Milled glass fiber, OCF 737, 1/16 inch.
2RRIMGLOS 10013 (RRIMGLOS is a trademark of NYCO Minerals, Inc.).
All directional properties are listed parallel to flow.
YFLEX MP-10,000 is a two component system, consisting of Component A and Component B. Component A comprises the diisocyanate and Component B comprises the polyether polyol plus additional curatives, extenders, etc. The following information is provided by the BAYFLEX MP-10,000 MSDS sheet, regarding the constituent components.
Component A
Additionally, Bayer reports the following further information:
Component A
Component B
According to Bayer, the following general properties are produced by this RIM system:
Another suitable system for forming a RIM cover or golf ball component is Spectrum™ available from Dow Plastics. Dow SPECTRIM RM 907 is an isocyanate, which when used in conjunction with a particular polyol available from Dow under the designation DRG 235.01, produces a preferred polyurethane.
(1) Stored in the original sealed drums in a dry place at the recommended temperature.
(2)Indicated metering ratio is for the components cited, prior to addition of any required additives.
(3)Demolding time depends upon the maximum part thickness, the formulation in use, and the process conditions.
(4) Additives and mineral filler pre-blended into polyol component
(5) 24 hours at 100 deg. C.
Another suitable polyurethane/polyurea RIM system suitable for use with the exemplary embodiment is the VibraRIM system:
VibraRIM 813A (Iso) and 81313 (Polyol) are available from Crompton Chemical, now Chemtura of Middlebury, Conn.
A sample plaque formed from the VibraRIM 813A and 813B components exhibited the following representative properties:
Plaque material Shore D (peak)=39
Specific gravity 1.098 g/cc
Other soft, relatively low modulus thermoset polyurethanes may also be utilized to produce the inner and/or outer cover layers. These include, but are not limited to non-ionomeric thermoset polyurethanes including but not limited to those disclosed in U.S. Pat. No. 5,334,673.
Other non-limiting examples of suitable RIM systems for use in the exemplary embodiment are Bayflex7 elastomeric polyurethane RIM systems, Baydur7 GS solid polyurethane RIM systems, Prism7 solid polyurethane RIM systems, all from Bayer Corp. (Pittsburgh, Pa.), SPECTRIM reaction moldable polyurethane and polyurea systems from Dow Chemical USA (Midland, Mich.), including SPECTRIM MM 373-A (isocyanate) and 373-B (polyol), and Elastolit SR systems from BASF (Parsippany, N.J.).
In a particularly preferred form of the exemplary embodiments, at least one layer of the golf ball contains at least one part by weight of a filler. Fillers preferably are used to adjust the density, flex modulus, mold release, and/or melt flow index of a layer. More preferably, at least when the filler is for adjustment of density or flex modulus of a layer, it is present in an amount of at least 5 parts by weight based upon 100 parts by weight of the layer composition. With some fillers, up to about 200 parts by weight probably can be used.
A density adjusting filler according to the exemplary embodiment preferably is a filler which has a specific gravity which is at least 0.05 and more preferably at least 0.1 higher or lower than the specific gravity of the layer composition. Particularly preferred density adjusting fillers have specific gravities which are higher than the specific gravity of the resin composition by 0.2 or more, and even more preferably by 2.0 or more.
A flex modulus adjusting filler according to the exemplary embodiment is a filler which, e.g. when used in an amount of 1 to 100 parts by weight based upon 100 parts by weight of resin composition, will raise or lower the flex modulus (ASTM D-790) of the resin composition by at least 1% and preferably at least 5% as compared to the flex modulus of the resin composition without the inclusion of the flex modulus adjusting filler.
A mold release adjusting filler is a filler which allows for the easier removal of a part from a mold, and eliminates or reduces the need for external release agents which otherwise could be applied to the mold. A mold release adjusting filler typically is used in an amount of up to about 2 weight percent based upon the total weight of the layer.
A melt flow index adjusting filler is a filler which increases or decreases the melt flow, or ease of processing of the composition.
The layers may contain coupling agents that increase adhesion of materials within a particular layer, e.g. to couple a filler to a resin composition, or between adjacent layers. Non-limiting examples of coupling agents include titanates, zirconates and silanes. Coupling agents typically are used in amounts of 0.1 to 2 weight percent based upon the total weight of the composition in which the coupling agent is included.
A density adjusting filler is used to control the moment of inertia, and thus the initial spin rate of the ball and spin decay. The addition in one or more layers, and particularly in the outer cover layer of a filler with a lower specific gravity than the resin composition results in a decrease in moment of inertia and a higher initial spin rate than would result if no filler were used. The addition in one or more of the cover layers, and particularly in the outer cover layer of a filler with a higher specific gravity than the resin composition, results in an increase in moment of inertia and a lower initial spin rate. High specific gravity fillers are preferred as less volume is used to achieve the desired inner cover total weight. Nonreinforcing fillers are also preferred as they have minimal effect on COR. Preferably, the filler does not chemically react with the resin composition to a substantial degree, although some reaction may occur when, for example, zinc oxide is used in a shell layer which contains some ionomer.
The density-increasing fillers for use in the exemplary embodiment preferably have a specific gravity in the range of 1.0 to 20. The density-reducing fillers for use in the exemplary embodiment preferably have a specific gravity of 0.06 to 1.4, and more preferably 0.06 to 0.90. The flex modulus increasing fillers have a reinforcing or stiffening effect due to their morphology, their interaction with the resin, or their inherent physical properties. The flex modulus reducing fillers have an opposite effect due to their relatively flexible properties compared to the matrix resin. The melt flow index increasing fillers have a flow enhancing effect due to their relatively high melt flow versus the matrix. The melt flow index decreasing fillers have an opposite effect due to their relatively low melt flow index versus the matrix.
Fillers which may be employed in layers other than the outer cover layer may be or are typically in a finely divided form, for example, in a size generally less than about 20 mesh, preferably less than about 100 mesh U.S. standard size, except for fibers and flock, which are generally elongated. Flock and fiber sizes should be small enough to facilitate processing. Filler particle size will depend upon desired effect, cost, ease of addition, and dusting considerations. The filler preferably is selected from the group consisting of precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide, metal oxides, metal stearates, particulate carbonaceous materials, micro balloons, and combinations thereof.
A wide array of materials may be used for the cores and mantle layer(s) of the exemplary embodiment golf balls. For instance, the core and mantle or interior layer materials disclosed in U.S. Pat. Nos. 5,833,553; 5,830,087; 5,820,489; and 5,820,488, maybe employed. In particular, it is preferred to utilize the cores described in U.S. patent application Ser. No. 09/226,340 filed Jan. 6, 1999; and 09/226,727 filed Jan. 7, 1999.
Unless stated differently, the following parameters are defined and utilized herein as stated below:
As used herein, “Shore D hardness” of a cover, intermediate layer or core is measured generally in accordance with ASTM D-2240, except the measurements are made on the curved surface of a molded ball component, rather than on a plaque. Furthermore, the Shore D hardness of the cover or intermediate layer is measured while the cover remains over the core. When a hardness measurement is made on a dimpled cover, Shore D hardness is measured at a land area of the dimpled cover.
As used herein, “Shore B hardness” of a cover, intermediate layer or core is measured generally in accordance with the Shore D hardness determination set forth above with the exception that a more rounded stylus is utilized, except the measurements are made on the curved surface of a molded ball component, rather than on a plaque. Furthermore, the Shore B hardness of the cover or intermediate layer is measured while the cover remains over the core. When a hardness measurement is made on a dimpled cover, Shore D hardness is measured at a land area of the dimpled cover.
The resilience or coefficient of restitution (COR) of a golf ball is the constant “e,” which is the ratio of the relative velocity of an elastic sphere after direct impact to that before impact. As a result, the COR (“e”) can vary from 0 to 1, with 1 being equivalent to a perfectly or completely elastic collision and 0 being equivalent to a perfectly or completely inelastic collision. COR, along with additional factors such as club head speed, club head mass, ball weight, ball size and density, spin rate, angle of trajectory and surface configuration (i.e., dimple pattern and area of dimple coverage) as well as environmental conditions (e.g., temperature, moisture, atmospheric pressure, wind, etc.) generally determine the distance a ball will travel when hit. Along this line, the distance a golf ball will travel under controlled environmental conditions is a function of the speed and mass of the club and size, density and resilience (COR) of the ball and other factors. The initial velocity of the club, the mass of the club and the angle of the ball's departure are essentially provided by the golfer upon striking. Since club head, club head mass, the angle of trajectory and environmental conditions are not determinants controllable by golf ball producers and the ball size and weight are set by the U.S.G.A., these are not factors of concern among golf ball manufacturers. The factors or determinants of interest with respect to improved distance are generally the coefficient of restitution (COR) and the surface configuration (dimple pattern, ratio of land area to dimple area, etc.) of the ball.
The COR in solid core balls is a function of the composition of the molded core and of the cover. The molded core and/or cover may be comprised of one or more layers such as in multi-layered balls. In balls containing a wound core (i.e., balls comprising a liquid or solid center, elastic windings, and a cover), the coefficient of restitution is a function of not only the composition of the center and cover, but also the composition and tension of the elastomeric windings. As in the solid core balls, the center and cover of a wound core ball may also consist of one or more layers. The coefficient of restitution is the ratio of the outgoing velocity to the incoming velocity. In the examples of this application, the coefficient of restitution of a golf ball was measured by propelling a ball horizontally at a speed of 125±5 feet per second (fps) and corrected to 125 fps against a generally vertical, hard, flat steel plate and measuring the ball's incoming and outgoing velocity electronically. Speeds were measured with a pair of Oehler Mark 55 ballistic screens available from Oehler Research, Inc., P.O. Box 9135, Austin, Tex. 78766, which provide a timing pulse when an object passes through them. The screens were separated by 36″ and are located 25.25″ and 61.25″ from the rebound wall. The ball speed was measured by timing the pulses from screen 1 to screen 2 on the way into the rebound wall (as the average speed of the ball over 36″), and then the exit speed was timed from screen 2 to screen 1 over the same distance. The rebound wall was tilted 2 degrees from a vertical plane to allow the ball to rebound slightly downward in order to miss the edge of the cannon that fired it. The rebound wall is solid steel 2.0 inches thick.
As indicated above, the incoming speed should be 12515 fps but corrected to 125 fps. The correlation between COR and forward or incoming speed has been studied and a correction has been made over the ±5 fps range so that the COR is reported as if the ball had an incoming speed of exactly 125.0 fps.
The coefficient of restitution must be carefully controlled in all commercial golf balls if the ball is to be within the specifications regulated by the United States Golf Association (U.S.G.A.). As mentioned to some degree above, the U.S.G.A. standards indicate that a “regulation” ball cannot have an initial velocity exceeding 255 feet per second in an atmosphere of 75° F., when tested on a U.S.G.A. machine. Since the coefficient of restitution of a ball is related to the ball's initial velocity, it is highly desirable to produce a ball having sufficiently high coefficient of restitution to closely approach the U.S.G.A. limit on initial velocity, while having an ample degree of softness (i.e., hardness) to produce enhanced playability (i.e., spin, etc.).
Compression is another important property involved in the performance of a golf ball. The compression of the ball can affect the playability of the ball on striking and the sound or “click” produced. Similarly, compression can affect the “feel” of the ball (i.e., hard or soft responsive feel), particularly in chipping and putting.
Moreover, while compression itself has little bearing on the distance performance of a ball, compression can affect the playability of the ball on striking. The degree of compression of a ball against the club face and the softness of the cover strongly influences the resultant spin rate. Typically, a softer cover will produce a higher spin rate than a harder cover. Additionally, a harder core will produce a higher spin rate than a softer core. This is because at impact a hard core serves to compress the cover of the ball against the face of the club to a much greater degree than a soft core thereby resulting in more “grab” of the ball on the clubface and subsequent higher spin rates. In effect the cover is squeezed between the relatively incompressible core and clubhead. When a softer core is used, the cover is under much less compressive stress than when a harder core is used and therefore does not contact the clubface as intimately. This results in lower spin rates.
The term “compression” utilized in the golf ball trade generally defines the overall deflection that a golf ball undergoes when subjected to a compressive load. For example, PGA compression indicates the amount of change in golf ball's shape upon striking. The development of solid core technology in two-piece balls has allowed for much more precise control of compression in comparison to thread wound three-piece balls. This is because in the manufacture of solid core balls, the amount of deflection or deformation is precisely controlled by the chemical formula used in making the cores. This differs from wound three-piece balls wherein compression is controlled in part by the winding process of the elastic thread. Thus, two-piece and multi-layer solid core balls exhibit much more consistent compression readings than balls having wound cores such as the thread wound three-piece balls.
In the past, PGA compression related to a scale of from 0 to 200 given to a golf ball. The lower the PGA compression value, the softer the feel of the ball upon striking. In practice, tournament quality balls have compression ratings around 70 to 110, preferably around 80 to 100. In determining PGA compression using the 0 to 200 scale, a standard force is applied to the external surface of the ball. A ball which exhibits no deflection (0.0 inches in deflection) is rated 200 and a ball which deflects 2/10th of an inch (0.2 inches) is rated 0. Every change of 0.001 of an inch in deflection represents a 1 point drop in compression. Consequently, a ball which deflects 0.1 inches (100×0.001 inches) has a PGA compression value of 100 (i.e., 200 to 100) and a ball which deflects 0.110 inches (110×0.001 inches) has a PGA compression of 90 (i.e., 200 to 110).
In order to assist in the determination of compression, several devices have been employed by the industry. For example, PGA compression is determined by an apparatus fashioned in the form of a small press with an upper and lower anvil. The upper anvil is at rest against a 200-pound die spring, and the lower anvil is movable through 0.300 inches by means of a crank mechanism. In its open position the gap between the anvils is 1.780 inches allowing a clearance of 0.100 inches for insertion of the ball. As the lower anvil is raised by the crank, it compresses the ball against the upper anvil, such compression occurring during the last 0.200 inches of stroke of the lower anvil, the ball then loading the upper anvil which in turn loads the spring. The equilibrium point of the upper anvil is measured by a dial micrometer if the anvil is deflected by the ball more than 0.100 inches (less deflection is simply regarded as zero compression) and the reading on the micrometer dial is referred to as the compression of the ball. In practice, tournament quality balls have compression ratings around 80 to 100 which means that the upper anvil was deflected a total of 0.120 to 0.100 inches.
An example to determine PGA compression can be shown by utilizing a golf ball compression tester produced by Atti Engineering Corporation of Newark, N.J. The value obtained by this tester relates to an arbitrary value expressed by a number which may range from 0 to 100, although a value of 200 can be measured as indicated by two revolutions of the dial indicator on the apparatus. The value obtained defines the deflection that a golf ball undergoes when subjected to compressive loading. The Atti test apparatus consists of a lower movable platform and an upper movable spring-loaded anvil. The dial indicator is mounted such that it measures the upward movement of the spring loaded anvil. The golf ball to be tested is placed in the lower platform, which is then raised a fixed distance. The upper portion of the golf ball comes in contact with and exerts a pressure on the spring loaded anvil. Depending upon the distance of the golf ball to be compressed, the upper anvil is forced upward against the spring.
Furthermore, additional compression devices may also be utilized to monitor golf ball compression so long as the correlation to PGA compression is known. These devices have been designed, such as a Whitney Tester, Instron Device, etc., to correlate or correspond to PGA compression through a set relationship or formula.
Herein, compression was measured using an Instron™ Device (model 5544), Instron Corporation, canton, MA. Compression of a golf ball, core, or golf ball component is measured to be the deflection (in inches) caused by a 200 lb. load applied in a Load Control Mode at the rate of 15 kips, an approach speed of 20 inches per minute, with a preload of 0.2 lbf plus the system compliance of the device.
Cut is a ranking from 1 to 6 of the resistance to the ball cover of a cut, 1 being the best. Cut is measured by dropping a 5.91b weight from a height of 41″ onto a golf ball in a guillotine fashion, i.e., using a tester set up with a guillotine design. The ball is loosely held in a spherical cavity and the guillotine face strikes the approximate middle of the ball surface. The face of the guillotine is approximately 0.125 inches wide by 1.52 inches long and all edges are radiused in a bullnose fashion. The ball is struck in three different locations and is then assigned a ranking based on the degree of damage.
Scuff is also a ranking from 1 to 6, 1 being the best, using a Titlist Vokey Sand Wedge to determine the susceptibility of the ball cover to scuffing from the club. A grooved Vokey Sand Wedge is mounted on the arm of a mechanical swing machine. The sand wedge is swung at 60 miles per hour and hits the ball into a capture net. The ball is hit three times, each time in a different location, and then assigned a ranking based on the degree of damage. The club face of the Vokey Sand Wedge has a groove width of 0.031 inches, cut with a mill cutter with no sandblasting or post finishing. Each groove is 0.018 inches deep and the space from one groove edge to the nearest adjacent groove edge is 0.138 inches. The total number of grooves is sixteen.
The exemplary embodiment is further illustrated by the following examples. It is to be understood that the exemplary embodiment is not limited to the examples, and various changes and modifications may be made in the exemplary embodiment without departing from the spirit and scope thereof.
A series of golf balls produced in accordance with the exemplary embodiment and using the exemplary embodiment molding assembly, exhibited the following dimensions, weight, compression, and coefficient of restitution (COR).
The dimensional data, i.e. the “Off/Equa.” and “Equator” diameters indicate the consistent golf ball diameters achievable by use of the exemplary embodiment. It is significant to note the extremely low values of standard deviation for both of these measurements. Furthermore, variations in weight, compression, and COR were well within acceptable limits. This data reveals the highly consistent and uniform golf balls produced in accordance with the exemplary embodiment. All patents and patent applications cited in the foregoing text are expressly incorporated herein by reference in their entirety.
From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.
The Present application is a divisional application of U.S. patent application Ser. No. 11/202,125, filed on Aug. 10, 2005.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11202125 | Aug 2005 | US |
| Child | 12536976 | US |
