US 3556532 A
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United States Patent  lnventor James E. Ballmer Cincinnati, Ohio ] Appl. No. 749,682  Filed Aug. 2, 1968  Patented Jan. 19, 1971  Assignee Brunswick Corporation a corporation of Delaware  PLASTIC GOLF CLUB HEAD WITH CAVITIES THEREIN TO SOUND LIKE A WOODEN CLUB HEAD 7 Claims, 5 Drawing Figs.
 US. Cl 273/167, 273/169  Int. Cl A63b 53/04  Field of Search 273/ l 67-  References Cited UNITED STATES PATENTS 1,592,463 7/1926 Marker 273/173 Primary ExaminerGeorge J. Marlo Assistant Examiner-Richard J. Apley Attorney-Hofgren, Wegner, Allen, Stellman and McCord ABSTRACT: An impacting element characterized in that a plurality of cavities in a body are formed therein to give to the element a desired acoustical quality upon striking a solid object. The impacting element will have many uses but one important one will be in plastic golf club heads wherein it is desired to produce a head which will produce a desired sound upon impacting a golf ball.
PATEINTIEBJANIQIBYI mm 3556532 INVENTOE ./dh1eS E. Ba/lmer' 50%, 2% m, M M1 PLASTIC GOLF CLUB HEAD WITH CAVITIES THEREIN TO SOUND LIKE A WOODEN CLUB HEAD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to controlled acoustics and more particularly to an improvement in controlling the acoustics of nonmetallic elements.
2. Description of the Prior Art For years golf club heads of the typeutilized to drive long distances and commonly referred to as woods" have been so named because they have been made out of wood material. Recently there have been efforts to make such golf club heads out of other materials in order to reduce the expense of manufacture. While golf club heads made of plastic materials have been produced which have desirable. appearance qualities as well as the capabilities of propelling golf balls substantially the same distance as the conventional wood club heads, these plastic golf club heads have produced a different sound upon striking a golf ball than is produced when a wood golf club head strikes a golf ball. This is undesirable in that golfers are accustomed to hearing the rather sharp solid high frequency sound when a conventional woodengolf club head strikes a golf ball and find the' rather dull hollow low frequency sound of the plastic head striking a golf ball disconcerting and generally undesirable. Thus, a need has arisen to provide a golf club head which has acoustical properties similar to that of the presently utilized wooden golf club head so that the sound of the golf club head made of any material striking a golf ball will simulate that of a conventional wooden golf club head striking a golf ball.
SUMMARY OF THE INVENTION This invention is directed, in brief, to the provision of an impacting element, such as a golf club head having acoustical properties which tend to simulate the acoustical properties of a conventional element, such as a conventional wooden golf club head, upon engagement with an object such as a golf ball. The best mode presently contemplated for carrying out the invention is to provide, in the impacting element, a plurality of cavities, cores, openings or holes. Preferably, though not necessarily, the holes may be of different diameters, different orientations and of different depths. Also, preferably, but not necessarily, the holes are to be formed inwardly from the bottom surface of the element and open outwardly thereto so that a plate will completely cover the openings when attached to the impacting element's bottom surface.
When impacting elements, such as golf club heads, were made of molded plastic material they were'much too heavy to meet the exacting requirements of specifications established as standards. Accordingly, the elements were cored with one large core opening which when used to strike an object, such as a golf ball, an undesirable sound resulted.
By forming an impacting element such as a golf club head with a cored body in accordance with the presently disclosed best mode forcarrying out the invention, the weight of the elemeat is reduced so that it more closely approximates the weight of a conventional element, such as a wooden golf club head. Likewise, the element can be attuned to a desired sound by adjusting the orientation and/or the depths and/or diameters of the cores in the body of the element.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top I plan view of an impacting element such as a club head of the wood" type made in accordance with this invention; v
FIG. 2 is a side elevational view of the impacting element shown in FIG. 1;
FIG. 3 is a bottom plan view of the impacting element shown in FIG. I l;
FIG. 4 is a sectional view of the impacting element taken generally along the line 4-4 of FIG. 3; and
FIG. 5 is a rear elevational view of the impacting element shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT An impacting element such as a golf club head 10 of this invention is of the usual configuration for the type known as a golf "wood" and has a large impacting surface or club head striking surface I2, a bottom or sole portion l4, and an angularly upwardly extending hosel 16. As shown in FIG. I, hosel 16 has a bore 18 for receiving a club shaft to connect the impacting element or head 10 to the shaft.
Impacting element or club head I0 may be of any material. The presently preferred embodiment is produced by.introducing thermoplastic material into a mold which conforms to the exterior configuration of the impacting element or club head 10 and allowing the thermoplastic material to harden or set". Preferably the material of the club head is that known by the trade name Cycolac." It has been found that this plastic material has very suitable qualities for simulating the performance of playing conditions of an impact element or a wood club head except for its weight and acoustical qualities. The Cycolac impact element or club head tends to be somewhat heavier than a wood club head of the same size and shape.
It has been found that the acoustical properties of the impacting element or club head can be improved to the extent that the engagement of the element or club head with the golf ball provides a solid high frequency sound, indistinguishable from that of the engagement of a conventional wooden club head with a golf ball, by providing two or more cavities, cores or holes in the element or club head such as is illustrated for example by the cavities 21 through 35 in FIG. 3. A sole plate can be secured over. the bottom of the club head if desired. It is believed that the provision of the cavities in the club head produces the improved acoustical characteristics in that the airspaces in thedifferent cavities will resonate at different frequencies while the webs or walls between the cavities being of different thicknesses and lengths will not resonate in sympathy with the soundresonance in the cavities to thereby prevent acoustical resonance of the element of or golf club head and an objectionable sound. Put another way, the webs or walls between the cavities are of different dimensions and resonate at lower frequencies while the sound waves in the cavities are held at a low level thereby minimizing sound propagation. The varying frequencies in the different cavities and in the webs and walls between the cavities will tend to damp each other to render the element or club head vibrationally dead.
In addition, the provision of the holes in the club head reduces the mass thereof so as to reduce the weight of the club head, thereby enabling the club head to more closely approximate a conventional wooden club head in weight so that clubs made therefrom will be able to meet specification standards set by the associations. Another advantage of providing cavities in an impacting element or club head molded of plastic material is that there is no large concentrated mass of thermoplastic material so that the molten plastic material cools and sets very fast, thereby increasing speed of production and resulting in lower production cost.
The present impacting element is designed to make use of the basic principles of sound to produce a device which will be capable of generating almost any desired sound upon striking (or being struck) by a separate member such as, for instance,
a golf ball. It is well-known, for instance, that sound travels in coming'waves to resonate at a particular frequency. Different diameter cavities will resonate at different frequencies and at different intensities (power). The material of the impacting element will have a predetermined elastic modulus which will determine'to' some extent the sound vibrations which will be propagated within the body formed from said material. Hereinabove it was mentioned that part of the sound waves traversing the cavities are reflected back into the cavity, the remaining sound waves setup resonance in the webs or walls between thehcavities which resonance will have an intensity and frequency dependent'upon the wall thickness and wall length. The webs or walls are varied so that they will not resonate in sympathy with each other or with the sound waves in the cavities. The diameters and spacing of the cavities will be such as to prevent acoustical resonance of the impacting element in such a way as to produce an objectionable sound upon impact with another device. The varying frequencies generatedwithiri the cavities and walls of the impacting element will tend to damp each other and thereby render the head vibrationally dead.
An impacting element has been made up and successfully" tested which had l5 cavities varying in diameter from .250 inches to .312 inches, having depths varying from 0.969 inches to L250 inches and being spaced from a reference point to a cavity center at distances from 0.] l0 inches to L872 inches on one axis to 0.227 inches to L314 inches on an axis transverse thereto. The resulting sound was at a solid high pitched frequency simulating almost exactly the sound v produced in hitting the same member with a solid laminated wood impacting element.
It has been found that the sound created by the impacting element canbe modified in the direction of higher frequency sounds by as few as two cavities of two different sizes. The size difference preferably goes to a difference in diameters, but it could be different depths. The sound resulting from the impacting element striking an object with two or more cavities of two or more different sizes is to create a higher frequency sound which is more desirable in many uses such as in the golf club art where a solid higher frequency sound is desired.
It has been found that different cavity sizes and with a different distributional array of the cavities will produce desirable acoustical characteristics, reduce the amount of time necessary for club heads of molten material to cool, and provide a lighter club head, the precise weight of which may be controlled by using weighted pins inserted into a few of the holes. Generally speaking, all of these desirable characteristics are obtained by providing a plurality of cavities of different sizes and of different depths in the club head.
This invention provides a means for producing a club head in a wide range of materials which will have acoustical properties of that of inventions presently utilized with golf club heads. The desired acoustical properties are imparted by forming two or more cores in the club head in two or more different sizes and in two or more different depths. As a result, club heads may be made from much less expensive material. such as thermoplastic compounds. S uch club heads may also be made in less time than that previously required for club heads made of wood laminations and the combination of reduced material expense and reducedproduction time results in a club head which may be offeredto the public at a reduced cost.
The foregoing detailed description hasbeentgiven for clearness of understanding only, and'no unnecessary limitations should be understood therefrom, as some modifications may be obvious to those skilled in the art.
l. A golf club head of plastic material molded into a configuration of a wood club head having a-hosel portion with a hollow bore and a sole portion 'atthe' bottom thereof;said head having a plurality of cavities of different depths therein; each of said cavities resonating at a different frequencyupon impact with a golf baliand beingsep'aratedby substantially vertical walls; said walls differing in thickness and len th, so that the frequencies generated within said cavities an walls will not amplify one another but will'dampen each other rendering the club head substantially vibrationally dead.
2. A club head ofclaim lwhereinthe plurality of cavities therein differ in diameters.
3. The club head of claim 2 wherein a plurality of the cavities therein are elongated along an axis substantially perpendicular to the bottom face of the 'club'head.
4. The club head of claim 3 further including a sole plate, and wherein the cavities therein open through the sole portion of the club head and are closed by said sole plate.
5. The club head of claim I wherein the 'cavities therein range in diameter from .250 inches to .3 lSiinches and range in depth from .969 inches to l .250i'nches'. vi
6. The club head of claim 5 wherein the centers of the cavities thereinare spaced upon transverse axes at distances from the intersection of said axes varying frornll 10 inches to l.872 inches on one and from .227-inclies to 1.3'14-inches on the other of said axes. v
7. Agolf club head of plastic material, molded into a configuration of a wood-type club head; said club head having a bottom face and a plurality of bores therein of differing depth and diameter communicating with said bottom face; said bores being substantially perpendicular to said bottom face and so positioned upon' thc bottom face that the walls therebetween differ in length and thickness; and a sole plate covering the opening openings ofthe bores in the bottom face of said head, whereby when hit; said club head produces a sound substantially identical to a club head made of wood.