INSERT FOR A GOLF CLUB HEAD
United States Patent 3836153
A golf club having a head portion including a face adapted to strike a ball and an insert mounted on the face. The insert consists essentially of a molded piece prepared by curing a suspension polymerized polymethyl methacrylate powder, including from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylate as crosslinking monomers at a temperature at least about 170° F.
US Patent References:
Golf club head with transparent insert
Boznos - May 1964 - 3134596
Golf club head having a plastic striking face insert bonded to the club head material and method for making same
Baker et al. - March 1965 - 3172667
Golf club striking surface of polycarbonate
Flom - February 1966 - 3233905
COMPOSITION OF MATTER AND GOLF BALL MADE THEREFROM
Chmiel et al. - January 1969 - 3421766
METHOD OF MOLDING A GOLF CLUB HEAD
Hardesty - March 1971 - 3571900
Golf club head with transparent insert
Boznos - May 1964 - 3134596
Golf club head having a plastic striking face insert bonded to the club head material and method for making same
Baker et al. - March 1965 - 3172667
Golf club striking surface of polycarbonate
Flom - February 1966 - 3233905
COMPOSITION OF MATTER AND GOLF BALL MADE THEREFROM
Chmiel et al. - January 1969 - 3421766
METHOD OF MOLDING A GOLF CLUB HEAD
Hardesty - March 1971 - 3571900
Application Number:
05/345242
Publication Date:
09/17/1974
Filing Date:
03/26/1973
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
273/DIG.016
International Classes:
A63B53/04; A63B53/04
Field of Search:
273/167-175,DIG.1,DIG.16 32/17
Other References:
"Orthodontic Resin," Rocky Mountain Dental Products Co., P.O. Box 1887, Denver, Col. 80201; 1964; pp. 1-14. .
"Modern Plastics"-"Polycarbonate Resin," April 1958; pp. 131-139 and 218..
Primary Examiner:
Apley, Richard J.
Attorney, Agent or Firm:
Fitch, Even, Tabin & Luedeka
Claims:
What is claimed is
1. In combination, a golf club having a head portion including a face adapted to strike a ball and an insert mounted on said face, said insert consisting essentially of a molded piece prepared by curing a suspension polymerized polymethyl methacrylate powder, including at least from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylates as cross-linking monomers at a temperature at least about 170° F.
2. The insert of claim 1 wherein said insert has a modified Izod impact strength of at least about 5 foot pounds per inch, water sorption of less than about 0.7 milligrams per square centimeter, a Knoop surface hardness of 14, a flexural strength of about 10,000 pounds per square inch, a tensile strength of about 10,600 pounds per square inch, and a flexural modulus of between about 320,000 and 400,000 pounds per square inch.
1. In combination, a golf club having a head portion including a face adapted to strike a ball and an insert mounted on said face, said insert consisting essentially of a molded piece prepared by curing a suspension polymerized polymethyl methacrylate powder, including at least from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylates as cross-linking monomers at a temperature at least about 170° F.
2. The insert of claim 1 wherein said insert has a modified Izod impact strength of at least about 5 foot pounds per inch, water sorption of less than about 0.7 milligrams per square centimeter, a Knoop surface hardness of 14, a flexural strength of about 10,000 pounds per square inch, a tensile strength of about 10,600 pounds per square inch, and a flexural modulus of between about 320,000 and 400,000 pounds per square inch.
Description:
This invention relates to accessories for golf clubs and particularly to an insert for the striking face of a "wood" type golf club.
Wood-type golf clubs commonly have an insert provided on the ball-striking face of the club, frequently for enhancing the "click" and/or "feel" of the club when it strikes a golf ball. These terms refer to the contact of the club with the ball and are well recognized in the game of golf. Inserts which provide good "click" and "feel" appear to help the golfer drive the ball longer distances.
Various materials have been suggested heretofore for use as an insert in the striking face of wood-type golf clubs. These materials have been suggested heretofore for use as an insert in the striking face of wood-type golf clubs. These materials have included ivory, metal, and various plastic materials. Such materials as ivory are expensive and difficult to obtain. Hard materials are desirable but metal inserts have been found to cut golf balls, hence are not desirable. Partly because of their low cost and ready availability, plastic materials have been used as inserts for golf club faces. However, the plastic inserts used heretofore have been "dead" in that they provided a poor "click" and "feel" when the club struck a golf ball.
It is an object of the present invention to provide an insert for the face of a wood-type golf club. It is another object to provide an insert of the type described which provides good "click" and "feel" when the club strikes a golf ball. Other objects and advantages of the invention will be recognized from the following description including the drawings in which:
FIG. 1 is a representation of a wood-type golf club including an insert and depicting various features of the invention; and
FIG. 2 is a representation, partly cut-away and in section, of an insert for a wood-type golf club and depicting various features of the invention.
The present inventor has discovered a novel plastic insert having specified properties which provides good "click" and "feel" and which appears to increase the distance which a golfer can drive a golf ball. Stated generally, the present insert comprises a moldable plastic composition including a polymer and an elastomer. More specifically, the material employed by the inventor as the insert comprises a suspension polymerized polymethyl methacrylate powder, including from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylate as cross linking monomers. The preferred insert has an impact strength of at least about five pounds per inch (measured by a modified Izod test), water absorption of less than about 0.7 milligrams per square centimeter (per American Dental Association [ADA] Specification No. 12), a Knoop hardness (surface) of about 14 (after wet storage for 7 days at 37°C), a flexural strength of about 10,000 pounds per square inch (by ADA 12), a tensile strength of about 10,6000 pounds per square inch (measured while dry), a tensile strength of about 10,300 pounds per square inch (measured wet after storage in water for 7 days at 37°C), and a flexural modulus between about 320,000 and 400,000 pounds per inch. This insert preferably is secured to the face of the golf club employing an adhesive.
As shown in FIG. 1, the present insert 10 is mounted on the ball-striking face 12 of a wood-type golf club 14. Normally, the insert 10 is embedded in a depression 15 in the face of the club so that the face 16 of the insert becomes a continuation of the face 12 of the club. As desired, grooves 18 frequently are provided across the face of the club and insert to enhance the degree of control over the flight of the ball exerted by the club.
The thickness and size of the disclosed insert is chosen such as provides assurance that there is sufficient mass of the insert for its properties to be effective in propelling the golf ball and that the force of impact of the club striking a golf ball will not destroy the insert. In the present insert, a thickness about one-fourth inch has been found suitable. Thicker inserts require more plastic hence are more expensive, while substantially thinner inserts appear to not provide the more desirable "click" and "feel" characteristics. Suitably, such inserts have a volume of about three-fourth cubic inch of plastic composition.
One insert 10 as disclosed herein is depicted in FIG. 2 and comprises a quantity of plastic composition molded into a generally trapezoidal shape having a face 16 and rear portion 20 adapted to be received in a mating depression in the face of the golf club 14. The face 16 of the insert normally is contoured in accordance with specifications set by the Professional Golfers Association for various kinds of clubs. As depicted in FIG. 2, the insert includes a plurality of relatively short fibers 22 dispersed throughout the insert, preferably in a uniform manner.
As noted, the present inventor employs a moldable plastic in making his insert. To obtain the desired "click" and "feel" when the club provided with the present insert strikes a golf ball, the insert is fabricated of a plastic material having specific properties. One particularly suitable plastic material is a polymer and elastomer based composition. More specifically, a proprietary material known as Lucitone 199 sold by L. D. Caulk, P. O. Box 359, Milford, Del., has been found particularly desirable for use in the manufacture of the present insert. This material is supplied as a two-component system including a particulate or powdered polymer and elastomer component and a liquid component. These components are mixed to provide a moldable composition. Lucitone 199 is an impact resistant dental molding composition comprising a suspension polymerized polymethyl methacrylate powder, including from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylate as cross linking monomers.
In manufacturing an insert employing Lucitone 199, approximately 28 cubic centimeters of polymer and elastomer powder component are admixed with approximately 8 milligrams of the liquid component to provide a moldable composition. This composition is placed in a two-piece mold having a cavity dimensioned to the outside dimensions of the desired insert shape and size. The quantity of composition added to the mold is at least sufficient to fill the mold. The mold is closed and sealed as by clamping the two pieces of the mold together using a closing force sufficient to seal against escape of composition or entry into the mold of foreign materials during subsequent curing of the plastic composition.
The composition, in the closed mold, is heated to cure it. One suitable curing cycle comprises heating the mold insert for approximately 9 hours at a temperature of about 170°F. The temperature of the insert is then caused to rise to about 212°F over a 1-hour period and held at about 212°F for approximately 1 additional hour. This relatively long curing period has been found preferable to insure that the resultant insert has those physical properties which are desirable and which are referred to hereinafter. Alternatively, the molded insert may be cured by heating it for 2 hours at about 170°F, heating it to about 212°F over a 1-hour period and holding it at about 212°F for an additional hour. During the curing cycle the insert is contained within a closed mold. The mold is maintained in its closed position by means of applied pressure of a magnitude sufficient to prevent opening of the mold as the plastic cures. In one embodiment, the curing is accomplished by placing the sealed mold in a water bath and heating the water bath as per the described heating cycle.
The cured insert, after removal from the mold, may be attached to the face of the golf club by any of several well-known means for attaching such inserts. For example, screws may be passed through the thickness of the insert and anchored in the wood golf club head. Preferably, however, the insert is secured to the face of the golf club by means of an adhesive such as an epoxy resin. Other adhesives will be apparent to one skilled in the art.
An insert prepared in accordance with the procedure outlined above has been found to have an impact strength of at least about 5 foot pounds per inch as measured by a modified Izod test. In this test, specimens were prepared in accordance with American Dental Association (ADA Specification No. 12). Each of the specifications were broken as desribed in ADA Specification No. 12. The halves of the specimens were then mounted in a standard impact tester as described in ASTM D-256 for evaluations of impact strength by the unnotched Izod test. The specimens were 0.1 inch wide, as mounted, so that the value read from the Izod tester was multiplied by 10 to provide the dimensions: foot pounds per inch. The specimens were mounted so that they stood 17 millimeters above the top of the device. This test was conducted dry but the specimen itself was wet, having been stored in water at 37°C, as described in ADA No. 12, until the impact test was conducted. This physical characteristic is of importance in that it denotes the ability of the present insert to resist breakage when the ball is struck. Plastic materials having impact strengths of about 3 foot pounds per inch have been noted to break under such impacts. It is believed also that the elastomer contained in the plastic composition contributes to the ability of the insert to absorb the energy of impact without breaking.
Sorption of water by an insert, such as when playing on a wet course, can change the performance of the club over its performance when dry. The water sorption of the present insert is less than 0.7 milligrams per square centimeter (per ADA No. 12) which shows the resistance of the insert to the sorption of water which could change its performance.
The hardness measured at the surface of the disclosed insert is about 14 when measured using a conventional Knoop hardness tester and after the sample had been stored wet at 37°C for 7 days. The tensile strength of this same material was about 10,300 pounds per square inch (measured per ADA 12). The tensile strength of a dry sample is about 10,600 pounds per square inch (measured per ADA 12). The flexural strength of the insert is about 10,000 pounds per square inch (measured per ADA 12). These strength properties of the insert appear to combine with its impact strength to prevent breakage during use. The hardness of the insert appears to provide a non-yielding characteristic to the insert when a ball is struck such that the ball is better propelled forwardly. In tests, wood type golf clubs fitted with the present inserts were found to drive a golf ball further than did golf clubs fitted with conventional plastic inserts. Moreover, the present insert produced a better "click" and "feel" when the ball was struck.
The disclosed insert exhibited a flexural modulus of between about 320,000 and 400,000 pounds per inch. It is believed that this resiliency of the insert is in large part established by the elastomer in the insert and that the degree of resiliency displayed accounts in part for the observed increase in driving distance obtained when using a golf club fitted with the present insert.
While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.
Wood-type golf clubs commonly have an insert provided on the ball-striking face of the club, frequently for enhancing the "click" and/or "feel" of the club when it strikes a golf ball. These terms refer to the contact of the club with the ball and are well recognized in the game of golf. Inserts which provide good "click" and "feel" appear to help the golfer drive the ball longer distances.
Various materials have been suggested heretofore for use as an insert in the striking face of wood-type golf clubs. These materials have been suggested heretofore for use as an insert in the striking face of wood-type golf clubs. These materials have included ivory, metal, and various plastic materials. Such materials as ivory are expensive and difficult to obtain. Hard materials are desirable but metal inserts have been found to cut golf balls, hence are not desirable. Partly because of their low cost and ready availability, plastic materials have been used as inserts for golf club faces. However, the plastic inserts used heretofore have been "dead" in that they provided a poor "click" and "feel" when the club struck a golf ball.
It is an object of the present invention to provide an insert for the face of a wood-type golf club. It is another object to provide an insert of the type described which provides good "click" and "feel" when the club strikes a golf ball. Other objects and advantages of the invention will be recognized from the following description including the drawings in which:
FIG. 1 is a representation of a wood-type golf club including an insert and depicting various features of the invention; and
FIG. 2 is a representation, partly cut-away and in section, of an insert for a wood-type golf club and depicting various features of the invention.
The present inventor has discovered a novel plastic insert having specified properties which provides good "click" and "feel" and which appears to increase the distance which a golfer can drive a golf ball. Stated generally, the present insert comprises a moldable plastic composition including a polymer and an elastomer. More specifically, the material employed by the inventor as the insert comprises a suspension polymerized polymethyl methacrylate powder, including from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylate as cross linking monomers. The preferred insert has an impact strength of at least about five pounds per inch (measured by a modified Izod test), water absorption of less than about 0.7 milligrams per square centimeter (per American Dental Association [ADA] Specification No. 12), a Knoop hardness (surface) of about 14 (after wet storage for 7 days at 37°C), a flexural strength of about 10,000 pounds per square inch (by ADA 12), a tensile strength of about 10,6000 pounds per square inch (measured while dry), a tensile strength of about 10,300 pounds per square inch (measured wet after storage in water for 7 days at 37°C), and a flexural modulus between about 320,000 and 400,000 pounds per inch. This insert preferably is secured to the face of the golf club employing an adhesive.
As shown in FIG. 1, the present insert 10 is mounted on the ball-striking face 12 of a wood-type golf club 14. Normally, the insert 10 is embedded in a depression 15 in the face of the club so that the face 16 of the insert becomes a continuation of the face 12 of the club. As desired, grooves 18 frequently are provided across the face of the club and insert to enhance the degree of control over the flight of the ball exerted by the club.
The thickness and size of the disclosed insert is chosen such as provides assurance that there is sufficient mass of the insert for its properties to be effective in propelling the golf ball and that the force of impact of the club striking a golf ball will not destroy the insert. In the present insert, a thickness about one-fourth inch has been found suitable. Thicker inserts require more plastic hence are more expensive, while substantially thinner inserts appear to not provide the more desirable "click" and "feel" characteristics. Suitably, such inserts have a volume of about three-fourth cubic inch of plastic composition.
One insert 10 as disclosed herein is depicted in FIG. 2 and comprises a quantity of plastic composition molded into a generally trapezoidal shape having a face 16 and rear portion 20 adapted to be received in a mating depression in the face of the golf club 14. The face 16 of the insert normally is contoured in accordance with specifications set by the Professional Golfers Association for various kinds of clubs. As depicted in FIG. 2, the insert includes a plurality of relatively short fibers 22 dispersed throughout the insert, preferably in a uniform manner.
As noted, the present inventor employs a moldable plastic in making his insert. To obtain the desired "click" and "feel" when the club provided with the present insert strikes a golf ball, the insert is fabricated of a plastic material having specific properties. One particularly suitable plastic material is a polymer and elastomer based composition. More specifically, a proprietary material known as Lucitone 199 sold by L. D. Caulk, P. O. Box 359, Milford, Del., has been found particularly desirable for use in the manufacture of the present insert. This material is supplied as a two-component system including a particulate or powdered polymer and elastomer component and a liquid component. These components are mixed to provide a moldable composition. Lucitone 199 is an impact resistant dental molding composition comprising a suspension polymerized polymethyl methacrylate powder, including from 2 to 5 percent of a butadiene styrene copolymer containing at least 65 percent butadiene grafted thereto, and a liquid consisting essentially of methyl methacrylate and glycol methacrylate as cross linking monomers.
In manufacturing an insert employing Lucitone 199, approximately 28 cubic centimeters of polymer and elastomer powder component are admixed with approximately 8 milligrams of the liquid component to provide a moldable composition. This composition is placed in a two-piece mold having a cavity dimensioned to the outside dimensions of the desired insert shape and size. The quantity of composition added to the mold is at least sufficient to fill the mold. The mold is closed and sealed as by clamping the two pieces of the mold together using a closing force sufficient to seal against escape of composition or entry into the mold of foreign materials during subsequent curing of the plastic composition.
The composition, in the closed mold, is heated to cure it. One suitable curing cycle comprises heating the mold insert for approximately 9 hours at a temperature of about 170°F. The temperature of the insert is then caused to rise to about 212°F over a 1-hour period and held at about 212°F for approximately 1 additional hour. This relatively long curing period has been found preferable to insure that the resultant insert has those physical properties which are desirable and which are referred to hereinafter. Alternatively, the molded insert may be cured by heating it for 2 hours at about 170°F, heating it to about 212°F over a 1-hour period and holding it at about 212°F for an additional hour. During the curing cycle the insert is contained within a closed mold. The mold is maintained in its closed position by means of applied pressure of a magnitude sufficient to prevent opening of the mold as the plastic cures. In one embodiment, the curing is accomplished by placing the sealed mold in a water bath and heating the water bath as per the described heating cycle.
The cured insert, after removal from the mold, may be attached to the face of the golf club by any of several well-known means for attaching such inserts. For example, screws may be passed through the thickness of the insert and anchored in the wood golf club head. Preferably, however, the insert is secured to the face of the golf club by means of an adhesive such as an epoxy resin. Other adhesives will be apparent to one skilled in the art.
An insert prepared in accordance with the procedure outlined above has been found to have an impact strength of at least about 5 foot pounds per inch as measured by a modified Izod test. In this test, specimens were prepared in accordance with American Dental Association (ADA Specification No. 12). Each of the specifications were broken as desribed in ADA Specification No. 12. The halves of the specimens were then mounted in a standard impact tester as described in ASTM D-256 for evaluations of impact strength by the unnotched Izod test. The specimens were 0.1 inch wide, as mounted, so that the value read from the Izod tester was multiplied by 10 to provide the dimensions: foot pounds per inch. The specimens were mounted so that they stood 17 millimeters above the top of the device. This test was conducted dry but the specimen itself was wet, having been stored in water at 37°C, as described in ADA No. 12, until the impact test was conducted. This physical characteristic is of importance in that it denotes the ability of the present insert to resist breakage when the ball is struck. Plastic materials having impact strengths of about 3 foot pounds per inch have been noted to break under such impacts. It is believed also that the elastomer contained in the plastic composition contributes to the ability of the insert to absorb the energy of impact without breaking.
Sorption of water by an insert, such as when playing on a wet course, can change the performance of the club over its performance when dry. The water sorption of the present insert is less than 0.7 milligrams per square centimeter (per ADA No. 12) which shows the resistance of the insert to the sorption of water which could change its performance.
The hardness measured at the surface of the disclosed insert is about 14 when measured using a conventional Knoop hardness tester and after the sample had been stored wet at 37°C for 7 days. The tensile strength of this same material was about 10,300 pounds per square inch (measured per ADA 12). The tensile strength of a dry sample is about 10,600 pounds per square inch (measured per ADA 12). The flexural strength of the insert is about 10,000 pounds per square inch (measured per ADA 12). These strength properties of the insert appear to combine with its impact strength to prevent breakage during use. The hardness of the insert appears to provide a non-yielding characteristic to the insert when a ball is struck such that the ball is better propelled forwardly. In tests, wood type golf clubs fitted with the present inserts were found to drive a golf ball further than did golf clubs fitted with conventional plastic inserts. Moreover, the present insert produced a better "click" and "feel" when the ball was struck.
The disclosed insert exhibited a flexural modulus of between about 320,000 and 400,000 pounds per inch. It is believed that this resiliency of the insert is in large part established by the elastomer in the insert and that the degree of resiliency displayed accounts in part for the observed increase in driving distance obtained when using a golf club fitted with the present insert.
While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.