US3390881A - Golf club woods with coresurrounding shell - Google Patents

Description

July 2, 1968 o. SENNE 3,390,881

GOLF CLUB WOODS WITH CORE-SURROUNDING SHELL Filed March 22, 1965 4 Sheets-Sheet 1 POLYCARBONATE RESIN OR VULCANIZED FIBER EPOXY RESIN AND POLYAMINE HARDENER 25 I-IIIJIIIIII4 IIIIII'IIIIIIIIIIII.

July 2, 1968 D. L. SENNE Filed March 22, 1965 GOLF CLUB WOODS WITH CORE-SURROUNDING SHELL 4 Sheets-Sheet D- L. SENNE July 2, 1968 GOLF CLUB woons WITH CORE-SURROUNDING SHELL V 4 Sheets-Sheet 3 Filed Marc GOLF CLUB woobs WITH CORE-SURROUNDING SHELL Filed March 22, 1965 D. L. SENNE July 2, 1968 4 Sheets-Sheet 4 VULCANIZED FIBER THERMOPLASTIC RESIN Unite Stat s Pat-info 6,390,881 GOLF CLUB WOODS-WITH CORE- :SURROUNDINGSHE'LL I David L. Senne,,La-'Habra, Calif, assignor tow. J. Voit I Rubber Corp.,acorporation of California Filed Mar. 22, 1965,'Ser. No. 441,519

Clainis. (Cl. 273%173) ABSTRACT OF THE DISCLOSURE 'This invention relates to a golf club comprising a head havinga front face,said head including a core having two cheeks constituting a portion of said front face-and a synthetic resin shell"surrounding-said core except said cheeks. The shellforms a neck portion for attaching ashaft to the head in anintegral arrangement. The golf club also includes a front face insert bonded to the shell and left and right shell portions interconnecting the edges of the cheeks with the adjoining side edges of the insert and a sole plate bonded to the lowerportion of the shell.

This invention resides in an improved golf club and in the method of making the same, and particularly relates to the class of clubs commonly referred to as the woods or drivers. w

The club head of a conventional --wood =or -driver comprises a suitably shaped laminated or solid wood block having one or more special fiber-face inserts and a metal sole plate fastened'directly thereto, land a wood, glass fiber or metal shaft secured in a bore therein. Per simmon wood has been found to possess particularly good density, strength and grain for this purpose, and is generally used in the better grades of golfclubs. The finishing of a club head after sanding thereof typically entailsthe application of a-variety of sealing agents, paints, lacquers; varnishes and waxes to produce a bril liant, smooth and attractive surface. Further light sanding maybe involved between these finishing steps. Re-

cently there has been a trend-toward painting the club head in various decorative colors, including the pastelshades. Following painting (depending on the' techniques of a-particular shop) it may be necessary to-re-' move paint from the club face and sole plate. The final steps in the conventional club manufacturing. process are the application of a wound thread or one-piece ferrule at the neck of the head, the provision of'a suitable grip at the upper shaft end, and the application of various trademarks and identification marks." 1

From the above description of a typical golf club manufacturing operation it is evident that it has suffered a lack of technical progress in several respects: First, too many operations-and handling steps are involved, particularly in the surface finishing. Second, every operation requires exacting standards of tolerance and workmanship. Third, almost every step is performed by highly skilled labor, and thetypical professional grade wood has remained essentially .ahand-made product. As examples, the rough wood block is manually shaped and sanded to exactly the shape of a 'finished club, and

other steps performed manually are the fitting ofthe' face inserts and sole plate, securing the shaft in place,

p g way'excess paint, winding the ferrule, and em bossing identification marks.

From the standpoint ofthe finished club itself, factors of appearance, feel, durability and dynamic elfectiveness are involved. The sound, or click, of a club making impact with a ball can mean almost as much to the golfer as the distance the ball travels. The resistance of the club finish to scratching, cracking, peeling and 3,390,881 Patented July 2, 1968 fading under rough usage also is of importance to the golfer. The presence of moisture is a factor affecting .not only; the longevity of the exterior club finish but also the internal structure of the wood core and the fit of the sole plate and face inserts. The penetration of moisture behind the sole plate and ,face' inserts, -beneath the surface finish layer, and into the wood grain inevitably will diminish the beauty and/or effectiveness of the club. The advent of laminated woods (bonded with synthetic adhesives such as phenol formaldehydes, epoxies, .etc.) solved this, problem to some extent, but-this has not materially changed the basic club manufacturing process. Solid clubs molded from synthetic resins. have been produced commercially, but by preferred standards ,of golf club performance ,theyhave flno tabeen satisfactory. Examples of these plastics are nylon, acrylonitrile-butadiene-styrene copolymers and polycarbonates. Because the density of these plastics is greater (by over 100%) than that of wood, it has been necessary to incorporate a central cavity in the solid plastic head. Major disadvantages of this construction are that they do not produce the desired sound on impact, and itsdynamic characteristics, particularlyin terms of distance, are not sogood as those of a conventional wood club.

In the prior art it has been proposed to encase a wooden core in a metallic shell, as in the Drevitson U.S. Patent No. 1,673,973 (1928) and Butchart US. Patent No. 1,638,916 (1927). Also, it was proposed to cast synthetic resins around a synthetic or lead core, as in Bright US. Patent No. 2,534,947 (1950). In all of these approaches, the club head was unsatisfactory be cause of problems in maintaining an integral, bonded and unitary structure, and in the lack of proper dynamic characteristics.

It is a further principal object of this invention to produce a superior club; in terms of durability against aging, moisture and rough usage; attractive appearance, pleasing sound at impact, and other characteristics.

' A further principal object is to produce a golf club which looks and feels as good as, if not better than, the best professional grade golf clubs available, and which resembles them in external design.

A still further object is to produce a golf club having a surface which is outstanding in resistance to scratching, denting, fadin and cracking; further, it is an object to reduce the deleterious effects of moisture.

In accordance with this invention, a wood core, which need not .be hand-finished exactly to the final club shape, is encased in a hard, durable molded synthetic resin shell. The surface of this shell, as it comes from the molding process, is basically in finished condition,

whereby the ordinary steps of painting and finishing are eliminated.

Instead of hand-fitting a sole plate, face inserts and shaft, these parts can be directly integrated and keyed into the club head structure in the course of molding the synthetic resin shell. The sole plate, for example, is spaced from the bottom of the wood core and the synthetic resin shell material fills the space beneath the plate and surrounds its edges.

In the preferred embodiment disclosed herein, the Wooden core has two projecting frontal portions separated by a cutaway channel and defining exposed face areas in the finished clubs. In the molding of the shell a hard fiber or synthetic resin faceinsert occupiesthis channel with a space between it andthe wood core, and the synthetic resin molding material fills this space to integrate the core, shell and face insert as a unitary structure. A-further desirable feature of this construction is that the 'club shaft can also be secured in the' neck of the head during the molding operation, thus eliminating an additional fittin operation.

In a modified embodiment discussed herein, it will be seen that a composite core can be employed. That is, a core can be made up of different materials having certain dynamically advantageous properties in combination.

Further objects, advantages and details of this invention will become evident from the following description when read with reference to the accompanying drawings in which:

FIGURE 1 is a perspective exploded view of the core, face insert, sole plate and mandrel, and the screws and spacers for fastening the insert and the sole plate in spaced relationship with respect to the core.

FIGURES 1A and 7B are perspective views of two modifications of a sole plate.

FIGURE 2 is a plan view of the upper half of the mold with the mandrel and club head, partly in section, resting in the cavity of the mold and a ferrule mounted over the shaft.

FIGURE 3 is a cross-sectional view of the mold and of the club head taken in a plane 33 indicated in FIGURE 2.

FIGURE 4 is a perspective view of the partially finished club head, with the upper part of the neck out off, and with the two core cheeks projecting beyond the insert.

FIGURE 4A is a perspective view of that half of the mold which receives the face portion of the core.

FIGURE 5 is a perspective view of the finished club head, with the lower portion of the shaft projecting slightly from the neck and the remaining portion of the shaft cut-off.

FIGURE 6 is a cross-sectional view of the golf club head taken in a plane 6-6 indicated in FIGURE 5. FIGURE 7 is a plan view of the lower part of the head including a sole plate attached to the head.

FIGURE 8 is a plan view of a modified version of one-half of the mold and a sectional view of the club head within the mold used for making the club head, identical to the mold illustrated in FIGURE 2, except that the neck portion of the mold in FIGURE 8 has been enlarged to include a ferrule so that the ferrule now becomes an integral part of the molded shell and its neck.

FIGURE 9 is a perspective view of a cut-off piece of hardwood known in the industry as dimension stock used for making the wooden portion of the clubs core.

FIGURE 10 is a perspective view of a cut-off piece of the reshaped dimension stock shown in FIGURE 9.

FIGURE 11 is aperspective view of two members used for making up a composite core.

FIGURE 12 is a perspective view of the core made of two members bonded to each other.

FIGURE 13 is a transverse section of the mold. suitable for casting a liquid res-in around the core for making the outer shell.

FIGURE 14 is a transverse section of the mold suitable for injection molding a thermoplastic resin shell around the core.

FIGURES 15 and 16 are the perspective views of two heads and of their insets, with the inset in FIG- URE 16 also including plastic sidebars.

The invention will be described first assuming that the shell is made of a thermoplastic resin injected at high pressure (20,00030,000 p.s.i.) and a temperature of 350-525 F., depending on the particular thermoplastic resin used, and also with prior impregnation of the wooden core with liquid thermosetting resin. It will also be assumed that the wooden core is made of either solid or laminated wood suchas birch, maple, or persimmon.

As described hereafter, impregnated wood cores may be used, and due to their resin content such cores withstand high injection molding pressures without addicores with self-curing adhesive resins, such as an epoxy resin for example, will enable them to withstand high injection pressures used with some thermoplastic resins used for making the shell.

Referring to the drawings, acore 10 has a rearward portion 11 approximating a semi-ellipsoidal form, and a truncated frontal portion having two forwardly projecting face portions 12 and" 13 and a keystone-shaped slot 14, with the wide portion off-theslot being at the bottom portion of the cor'e'. The core 10 preferably is made of such wood as persimmon, birch or maple, the preference being in the order mentioned, with the grain of the wood preferably being oriented in the direction indicated in the drawing. a i

Core 10 also can be made of laminated wood or molded wood shavings or flour bound with such adhesive resins as phenol-formaldehyde, epoxies, polystyrenes, or acrylonitrile-butadienestyrene copolyrners, melamines, ureaformaldehyde, or otherresins commonly used for bonding wood. A suitable formula for the molded wood core is as follows:

Example Approximate percentage by weight Phenol-formaldehyde resin 14.6 Pine wood shavings 85.0 Hexamethylenetetramine .4

After mixing the wood shavings and the phenol-formal dehyde resin, the mixture is compressed in a mold and then cured for example for ten minutes at 325 to 350 F.

A semi-circular'seat 17 in the core accommodates the lower end of the shaft 16. Although the shaft can be satisfactorily held in proper relationship with respect to the core and seat 17 by the two halves of the mold; and it can be attached in a preliminary manner to the core 10 by means of a staple, or adhesive screw, to obtain a .positive bond between the shaft and the resin shell 26, the lower end of the shaft preferably is roughened by a coarse abrasive belt or the like.

Rather than molding the shell, the neck and the ferrule directly onto the shaft it is possible to use a tapered metallic mandrel covered with a moldreleasingagent such as silicone greases or polyvinyl alcohol. (When using a thermoplastic resin, the releasing agent may optionally be dispensed with.) The mandrel is withdrawn from the tapered hole formed in the molding operation. If polyvinyl alcohol is used as a releasing agent, for example, the tapered hole is rinsed clean before the shaft is bonded to the head. Positive removal of traces of mold releasing agent can also be accomplished by reaming out the hole after the molding operation. However, if a highly polished and hard chrome-plated mandrel is employed, the use of a mold-releasing agent may not be required for either thermosetting or thermoplastic resins, and this is the preferred procedure according to this invention.

Also fastened to core 10 is a sole plate 18 provided with four holes 19, 20, 21 and 22 through which four screws 24 are inserted to fasten the plate to the core. It is im portant to note that spacers 23 hold the plate in spaced relationship with respect to the bottom of the core. Spacing can be effected by projecting integral bosses 23 as illustrated in FIGURE 1B. Bent-over lugs 61 and 62, FIGURE 1A, can be used for holding the plate in a fixed position within the mold and in spaced relationship with respect to the core. (The lugs are placed at the mold parting line 300 to permit opening of the mold.) The screws 24 can be eliminated altogether, or used for decorative purposes only, when cast thermosetting resins are used as the shell,

the sole plate then being bonded to the core.

A face insert 25 is similarly fastened to core 10 by means of four screws 24, with spacers 23 holding it in spaced relationship with respect to the keystone-shaped recess in core 10.

After thesole plate 18, face insert 25 and shaft 16 (or mandrel) are fastened to core 10, this assembled core is placed in the lower, orbase, half 200 of a two-piece, mold. The second, or bottornhalf201 .of the mold is illustrated inFIGURES. A portion of the upper half .200 of the mold is also illustrated in a perspective view in FIGURE 4A; a raised central -bqss 400 is shown which is also shown in. partial cross-sectionalview in.FIGURE 3..I n FIGURE 3,,boss 400 abuts directly against thefront partof; the face insert25 and against the two side edges. of the cheeks 12 13. Boss 400 thereby prevents casting resin from covering the frontofface portion 'and between the projecting cheeks 12 and 13. The wedge-shaped boss 400 is clearly seen in FIGURE 3.,

The mold half 200 15 provided with a cone shaped sprue opening 302 and i a plate 303 that has a seat 304 adapted to receivean injection nozzle 305, v

.FIGU E 14 illustrates a mold structure which is identieal to that shownin FIGURE 3 except that itis shaped for casting of a club withoutthe face insert in place. Note that the lower half 1400 has a-ditferent shape at 1401 since, inthis case, the insert is not present at the time core 1 402 issurrounded with the resin shell 1404. Therefore,=the.metal boss 1401 is raised-higher in FIGURE 14 by the amount of the thickness ofthe inserts 1500 and 1600 illustrated in FIGURES 15 and 16, respectively, and described hereafter. Thecore is aligned in the mold with the aid of the sole plate. 1405. The sole plate 1405 and the two projecting portions of the two cheeks, one of these) being illustrated by dotted lines at 1406 in FIGURE 14, are attached to core 1402 prior to molding by means of screws'as previouslydescribed. v

The mold shown in FIGURE 14 is preferablefor use with thermoplastic resins inthat'the shrinkageof such resins maygtendto produce separation between the side edges of the cheeks and the adjacent resin at regions 500 and SOL-(FIGURE these tiny cracks appearing along the junction lines 502 and 503'. To avoid suchv cracks, inserts 1500 and 1600 are bonded or. otherwise fastened to the head after molding shell 1404 over core 1402. The resulting heads produced in these molds are illustrated in FIGURES l5 and l6.'The thermoplastic resin shellincludes the neck 1501, the main semi-elliptical portion 1502 and recess portion 1503 joined to the main portion 1502. The inserts 1500 an 16 00 are then bonded to the head byusing screws and/ or a synthetic glue, such as epoxy. The insert 1500 is a single-piece vulcanized fiber, while insert'1600 has two contrasting resin bars 1601 and 1602 bonded to it for decorative effect.

Among thermosplastic resins which are suitable for ;-making a shell are resins which have high impact i resistance, resistance to abrasion and chipping. Polyvinyl chloride, polyvinyl'acetates, copolymers of polyvinyl chloride; and polyvinyl acetate, polypropylene, polycarbonates, and acryl'onitrile-butadiene-styrene are such resins.

Reverting again to the description of the upper mold half 200, it is provided. with a semi-circular groove 202 which surrounds the entire cavity. A round rubber stringlike gasket. 204, having a circular cross-section, is .laid in the groove 202. Gasket 204 seals the two halves 200 and 201 of the mold with respect to each other.

An additionalseal is provided in the form of'aring 205 whichis slipped over shaft or mandrel in the mariner indicated in FIGURE 2, to semi-circular grooves being provided in the two halves 200 and 201 ft} accommodate thegasket 204, s o' that the mold becomessealed around the. shaft. ormandrel between the two halves 200 and 201,.(Seals of this type are'req'uired mainly when liquid thermosetting resins are used.) a u 7 The.transyerse cross:section of a modifiedmold which is particularly suitable for casting a shell of thermosettingresin is. illustrated in FIGURE 13. The lower half is identical to,thatv illustrated in FIGURE 2 at200. The upper half 1300 is provided with a straight cylindrical hole 1301 through which the resin is poured into the mold. To pressurize the resin thereafter, a piston 1302 is inserted into hole 1301 and then the mold is placed in a press to exert pressure on head 1304. When thermosetting resins are pressurized in this manner before polymerization begins, the shrinkage of the resin is reduced. Thermosetting resins form a very positive bond between the core, insert or metal sole plate, so that screws can be eliminated altogether unless desired for decorative. effect. Suitable thermosetting resins for casting a shell for purposes of this invention are epoxy, polyurethane, caprolactam nylon, polyesters and methyl methacrylate. Epoxy, polyurethane and caprolaetam nylon produce a shell having particularly good impact strength, proper degree of resilience and rebound characteristics, tensile, compression and shear strengths, and resistance to scratching. h

Examination of the drawings indicates that shell 26 completely surrounds core 10 except for the front of cheeks 12 and 13. In'this manner, thecore 10 isv substantially completely waterproofed. These frontal portions 12 and 13 are waterproofed after appropriate cutting off and sanding of those portions 43 (FIGURES 6 and 1) which extend beyond the desired loft angle 63 as illustrated in FIGURES 3 and 6. The core 10 is provided with the two excess projections 43, extending beyond the dotted loft angle lines 44 in FIGURE 1 and line 45 in FIGURE 6 in order to provide positive means for mounting, seating and aligning the core assembly in the mold. Angles 46 and 47 both are 90 with respect to the flat sole plate 18. Also, by providing core 10 with two projections 43, the face of the club is provided with an extra amount of wood which is cut off after completion of the molding operation. In this manner, the actual faces 48 and '49 in the finished club head have two clean wood surfaces to be sandedand polished with convex surfaces having a radius of from 8 to 10 inches along an X-axis (FIGURE 6) and the same radius along a Y-axis (FIGURE 7).

After the face of the head is given the desired convexity, the frontal face portions 48 and 49 are covered with several layers of waterproofing transparent lacquer so that the wood striations of the core 10 are visible on the club face. The sole plate 18 is then also covered in like manner with several layers of lacquer. The shell portion of the head is buffed before applying lacquer to the face and the sole plate. v u I Before shaft 16 is bonded to core 10,. synthetic resin ferrule 210, and colored rings 212, 213 and 214 are slipped over the shaft in the manner indicated in FIG- URE 2. These sleeves and rings canbe niade of such materials as phenol-formaldehyde. After the casting operation, sleeve 210 is moved over the neck portion 216 (FIGURE 5) and is fastened to the outer surface of the neck 216 by shrinking-the sleeves and the rings at a temperature which may be of the order of 212 F. Shrinking of the sleeves and rings constitutes the lastmanufacturing step of the head portion of the club. The remaining additional step is the application of a hand grip to the upper end of shaft 16, this step not being illustrated in the'drawings since it is known to the prior art and does not constitute a part of this invention. l FIGURES 8 through 12 illustrate an optional method of making the golf club head. A long rectangular piece of hardwood known in the trade as a dimension wood, is commercially available in such dimensions as 1%" x 3" cross-section and several feet in length. This rectangular piece of wood is passed through a machine known as a sticker, which reshapes the rectangular form of this wood into a long piece having 'a transverse section as illustrated at 91 and resembling a distorted ellipse. This piece of wood 90 is then cut transversely at right angles to its longitudinal axis in the manner illustrated by a dotted line 92, after which the sawed-off piece 93 is passed through a milling machine to cut out a key-shaped recess 94. This produces a piece of hardwood 7 100 as illustrated in FIGURE 11. A separate rear portion 101 (preferably having a specific gravity in the order of from 0.5 to 0.8) is molded in a properly shaped mold by using either a sponged plastic material, such as acrylonitrile resin or polyurethane, or by molding this piece from wood shavings bonded with phenol-formaldehyde or epoxy resin, for example. Another material suitable for making the rear piece 101 which forms a positive bond with the shell when the shell is made of epoxy is hard rubber. Suitable glue for attaching the piece of hardwood 100 to the rear portion 101 is an epoxy resin.

The composite piece is then used as a core in the manner identical to that illustrated in FIGURES 1 through 4A or in a mold illustrated in FIGURE 8. The one-half of the mold 120 illustrated in FIGURE 8 is, for all practical purposes, identical to that illustrated in FIGURE 2, except that it is shaped so as to produce an integral neck 121 and ferrule 122.

The preferred version of the epoxy resin suitable for making shells is selected from the diglycidyl ethers of bisphenol.

The preferred hardeners for the epoxy resin are polya-mine hardeners in which the amine groups are separated by between 6 and 30 carbon atoms and preferably between about 8 and 20 atoms, on the average, along the back-bone of the molecular chain of the polyamine hardener. Polya-mine hardeners as contemplated herein include diamines, triamines, tetramines, as well as higher polyamines. In most instances, best properties are obtained with hardeners of this kind when the backbone chain on the average contains between 11 and 16 carbon atoms.

If the reactive amine groups are too close together in the amine hardener molecule, and are used alone, the resultant cured epoxy resin has an impact resistance which is too low for use in golf club heads. However, if the epoxy resin is cured using a long chain diamine such as the polyether diamine where n equals about 2 on the average, or if diethylene triamine is in combination with a long chain diamine, then the cured product has 'very good impact strength. n=2 on the average means only that the polyamine may consist of a molecule in which n may be zero or a whole number, but on the average It equals about 2. It appears that this relatively long chain hardener, having about 13 carbon atoms between the reactive amine groups, produces a less tightly crosslinked product and, therefore, one having improved impact resistance. On the other hand, with amine hardeners having an excessively large number of atoms separating the reactive amine groups, i.e., more than about 30 atoms, the resulting reaction product, the cross-linked epoxy resin, is too rubber-like or elastomeric and does not have sufficient surface hardness or toughness for use in golf club shells.

It is, however, also possible to produce these high impact resistant cured epoxy resins by using blends of amine hardeners where the weighted average distance between reactive amine groups on all the hardener portion is essentially between about 6 and 30 atoms between amine units.

The cured epoxy resin club shell as taught herein has a very good color stability and excellent impact strength and abrasion resistance. An additional advantage of the polyether diamine hardener-epoxy resin system is that this combination has a relatively low viscosity which permits beneficial processing. For example, when a liquid epoxy resin is thoroughly mixed with a stoichiometric amount of a polyether diamine where the primary amine groups are separated by -15 alkyl ether groups on the average, the mix has a low viscosity without the need to add inert solvent. An important feature of the absence of inert solvent is that the mix may be readily degassed and the rapid filling of molds is possible. In conventional systems when it becomes necessary to process the material in'a practical manner, it is possible to reduce the viscosity of the resin/hardener mix by the addition of inert solvents. Complete degassing of the resin/hardener mix becomes diflicult in these cases, and bubbles usually result from volatilization of the low boiling inert solvents during the curing'step. It is of very substantial benefit to have a system of workable viscosity wherein it is unnecessary to add such solvents. The viscosities of epoxy resin/ amine hardener systems have also beenreduced by the addition of reactive diluents such as phenyl, butyl or allyl glycidyl ethers. However, the excessive use of these reactive diluents generally may impair physical properties such as impact and tensile strength. a

The advantages of the club, and especially of the head made in accordance with the disclosed method, reside in the fact that a wooden core 10, a sole plate 18, and an insert 25 are integrated into a unitary structure in a very positive manner by means of a hard resinous shell, having a Rockwell hardness reading in the order of 60 to on Scale L which completely surrounds the core, the

three sides of the insert 25, the three sides of sole plate' 18, and the lower part of the shaft, the shell also including the neck which thus connects shaft 16 in a very positive rigid manner to the head.

Because of the use of the wooden core, with the end grain being substantially perpendicular to the face, the dynamic impact characteristic of the club at least is equal to, if not better than, the dynamic impact characteristic of the very best persimmon clubs, and yet it has the advantage of having a very hard shell waterproofing the core and also positively "integrating all of the parts of the head into a unitary structure.

The epoxy resin and the amine and the polyether diamine produce the following desirable end product. It has high impact resistance, sufficient hardness to resist scratching of the highly polished surface, adequate clarity for producing any type of desired aesthetic effect, such as pearlescence, coloring, etc.

Example Example Caprolactam mixed with a suitable catalyst such as a base metal, a hydride or oxide of a base metal. The mixture may be cast in a mold around a wood core.

A suitable formulation is:

Parts byweight Epsilon-caprolactam 100 Sodium hydride l N-acetyl caprolactam 3.5

The materials are mixed at 160 C. and under a dry nitrogen atmosphere and transferred to a suitable mold holding a core. Reaction of the caprolactam is complete in 10-12 hours at 160' C.

What is claimed is:

1. A golf club comprising a head having a front face, said head including a core'having two cheeks constituting a part of said front face, a synthetic resin shell surrounding said core except said cheeks, a shaft, said shell also forming a neck attaching said shaft to said head, a front face inset attached to said shell, said shell including left and right portions interconnecting the inner edges of said cheeks with adjoining side edges of said inset, said front facealso including said portions and said inset, and a sole plate bonded to said shell.

2. The golf club as defined in claim 1 in which said shell also includes a ferrule, said ferrule being an integral part of said neck.

3. The golf club as defined in claim 1 in which said core is a wood block and said sole plate includes means projecting outwardly therefrom to facilitate positioning said plate with respect to the core, the projecting means spacing the plate in a predetermined relation with respect to the core.

4. The golf club as defined in claim 1 in which said core includes a front wood block including said cheeks, and a rear plastic member bonded to said front wood block.

5. The golf club as defined in claim 4 in which said rear member is an expanded resin block having a specific gravity in the order of from 0.5 to 0.8.

6. The golf club as defined in claim 4 in which said rear molded block is an expanded hard rubber block having a specific gravity in the order of from 0.5 to 0.8.

7. A golf club having a face, a shaft, a wood core having left and right cheeks forming left and right portions, respectively, of said face, a synthetic resinous shell surrounding said core with the exception of said cheeks, said shell also surrounding the lower portion of said shaft, said shell. also forming a neck interconnecting said core and said shaft, and a face inset and a sole plate bonded to said shell, said inset being mounted in spaced relationship with respect to said core and said cheeks, said shell surrounding at least three sides of said inset, said face including said left and right cheeks, said inset and that portion of said shell which is between said cheeks and said inset.

8. The golf club as defined in claim 7 in which said face inset comprises a vulcanized fiber.

9. The golf club as defined in claim 7 in which said inset comprises a polycarbonate resin.

10. The golf club as defined in claim 1 in which said shell also includes a ferrule and at least one heat-shrinkable ring, said ferrule being mounted about the neck portion of the shell which surrounds the shaft and the ring being shrunk thereabout to secure the ferrule in position.

References Cited UNITED STATES PATENTS 2,301,369 11/1942 Carvill 273-172 3,172,667 3/1965 Baker et a1 273-78 FOREIGN PATENTS 9,847 1912 Great Britain.

ANTON O. OECHSLE, Primary Examiner.

R. I. APLEY, Assistant Examiner.

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