Abstract:
This invention embodies golf clubs and heads providing visual, auditory, and/or tactile aids useful to a golfer in determining whether a golf ball has been accurately struck. The head of the golf club is designed to produce a fundamental musical tone upon impact with a golf ball at the sweet spot of the club face. When a golf ball is struck at areas outside of the sweet spot, the head produces audible harmonic overtones that resonate above the fundamental pitch. Furthermore, the shaft of the golf club is preferably made from a resonant material that is attached to the head at a vibratory node of the head such that when a golf ball has been accurately struck using the sweet spot of the club face, no harmonic vibrations are transferred along the shaft to the grip.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. provisional application serial No. 60/434,309, filed Dec. 17, 2002. 
     
    
     
       BACKGROUND  
         [0002]    Golf putters, and other short-range golf clubs such as chippers, come in a wide variety of designs and styles, each designed with the intention of either improving control or acting as a teaching aid, for the novice and experienced golfers alike. Design attributes include club head shape, the method of attaching the shaft to the putter head, the parameters chosen for the shaft, the overall club head weight, the distribution of the weight from toe to heel or the face relative to the back, and the use of different sound- and/or vibration-producing mechanisms to indicate proper technique.  
           [0003]    Numerous golf club heads incorporate sound chambers or other types of sound-producing features into their design such that a discernible sound and/or other vibration is produced when a ball is struck with the club face.  
           [0004]    For example, U.S. Pat. Nos. 5,160,144; 5,551,694; and 4,123,056 are all directed to sound-producing putters that are based, in part, on the principles of tuning forks in which the vibration of tines produces a tone. U.S. Pat. Nos. 5,346,219; 5,803,825; 4,113,249; 5,322,285; and U.S. patent application Publication No. 2002/0055394 all describe golf clubs for producing sound that utilize various sound chambers formed within the main body of a golf club head. Other golf clubs with sound-producing heads are also known, including those described in U.S. Pat. Nos. 4,383,690; 5,718,641; 6,406,378; and 5,830,084.  
           [0005]    It is desirable in the design of a golf club to provide auditory, visual, and tactile aids to help a golfer correct an inaccurate golf swing and/or to indicate to a golfer when a golf ball has been hit properly using the “sweet spot” (an area on the face that, when striking a golf ball, provides optimum control to the golfer).  
           [0006]    A club is also desirable that compensates for an inaccurate swing by mitigating the swing&#39;s negative impact on the speed and direction of the hit ball. It is further desirable that the structure of a golf club allows greater control over the speed and direction of a golf ball when it is hit properly, and that a golfer is easily able to choose a golf club, or a head for a given shaft based on course conditions (e.g., turf having high or low moisture content).  
           [0007]    All references cited herein are incorporated in their entirety to the extent not inconsistent herewith.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides golf club heads and golf clubs, incorporating auditory, tactile, and visual aids useful to a golfer to indicate when a golf ball has been struck properly and/or to correct for an inaccurate golf swing. Specifically, the golf club of this invention comprises a head that produces a dominant fundamental tone when used to strike a golf ball. A shaft made of resonant material is joined to the head at one of two vibratory nodes within the head. The resonant material is matched to the club head such that when a golf ball is struck correctly, each vibrate to their fundamental frequency and are not felt by the golfer within the grip. When a golf ball impacts the face of the club outside of the sweet spot, vibrations are felt by the golfer at the grip due in part to the overtones generated in the shaft and club head.  
           [0009]    In one embodiment of this invention, the golf club head is shaped such that when a golf ball is hit incorrectly, the overtones (notes having frequencies that are whole-number multiples of the fundamental tone) produced by the vibrating head become more audible or detectable and indicate to a golfer that he has not properly hit the ball. The vibrations associated with these overtones are maximized at the vibratory nodes. Optionally the vibrations are transferred to the shaft.  
           [0010]    It is an object of the present invention to provide a golf club that produces a ringing tone when used to strike a golf ball. It is further an object of this invention to provide a ‘window’ in the head of the golf club such that the line of the club&#39;s swing may be seen by the golfer. It is further an object of this invention to provide a golf club putter that minimizes jumping, skipping, or sliding of a golf ball upon contact with the putter face, and that minimizes the negative effects of an inaccurate swing on a golf ball&#39;s distance or direction.  
           [0011]    This invention provides a golf club comprising: a head made of a first material capable of producing a tone, preferably a selected musical note, when struck by a golf ball, and having at least one vibratory node; and a shaft made of a resonant material attached to said head at said vibratory node wherein the first material is selected from the group consisting of metals, including metal alloys, ceramics, wood, polymers, and glass. Preferably, the first material is aluminum or bronze and the head has a weight between about 250 g and about 500 g.  
           [0012]    In one embodiment of this invention, the golf club head is made of a single piece of metal having two free ends which face but do not touch each other at the back of said head to form a space between said two ends wherein the pitch of the tone capable of being produced can be tuned by changing the size of the space. In an embodiment of this invention, the free ends are on the back of the head, opposite the face, and they face each other. Optionally, the tone may be dampened by placing a baffle in the space, such that the baffle touches both sides forming the space. The baffle can be made of any material that dampens the sound, including rubber and foam. In an embodiment of this invention, a head is designed to have the tone dampened by including a damping hole through the free ends to allow for a baffle to be inserted, optionally requiring a tool. In embodiments of the invention, the damping hole extends from the top to the bottom or from the back to the hole.  
           [0013]    In embodiments of this invention, the head has a thickness from top to bottom that is thinner than, about the same as, or thicker than that the diameter of a standard golf ball, and at least about one inch. The head further comprises a cylindrical hole (also called a “window”) formed therethrough from top to bottom, the size and/or shape of which may be changed to alter the pitch produced by the club. The distance between the face of the club head and the edge of the cylindrical hole is between about three sixteenths of an inch and one inch, about one fourth and about three quarters of an inch, or about three-eighths and about five-eighths of an inch. The top and bottom of the head may be substantially planar, but may also be curved or rounded.  
           [0014]    In another embodiment of this invention, the head of the golf club of this invention is a solid bar that optionally has a portion of its material cut away at the rear of the club centered behind the sweet spot.  
           [0015]    In other embodiments of this invention, the plane of the face of said head is angled toward the back of the head at about 1 to about 65 degrees from the bottom to the top of said face. Alternatively, the bottom of said club head is angled upward from about 1 to about 65 degrees from the face to the back such that when the bottom sits flush with the ground the face of the club is angled back.  
           [0016]    The face optionally further comprises mill lines, such as are formed by a milling process, that are linear or nonlinear. Golf club heads embodying by this invention may also optionally comprise a marking or markings on the top of said head indicating that the “sweet spot” is located at a corresponding lateral location relative to the toe and heel on the face of the head, e.g., a straight line having a constant distance from the toe and heel sides of the head to the face may mark the center of the “sweet spot.” 
           [0017]    In one embodiment of this invention, the shaft is made of hardwood selected from a group of woods known for their acoustical properties and widely used in the building of fine musical instruments. These “tone-woods” include pernambuco, rosewood, vermillion, granadillo, ebony and osage orange. Alternatively, the shaft is made from steel, graphite, carbon fiber, plastic, or Keylon™ (a plastic formulated, for example, for use in the manufacture of synthetic xylophone bars). Materials useful in the practice of this invention include materials not yet utilized in the construction of golf clubs and golf club components, including materials useful for construction of musical instruments.  
           [0018]    In one embodiment of this invention, the shaft of the golf club of this invention is attached to the head at the vibratory node of the head via a hole in the head adapted to receive the shaft. In one embodiment, a tapered hole is utilized for fitting a tapered end of shaft. A tapered connector (a “hosel”) may be used having one end adapted to receive an end of said shaft. The tapered connector may further comprise a hexagonally shaped nut above the section inserted into the head to assist in securing or removing the shaft from the head. Alternatively, the head can be formed to have an impression on the bottom, such as a hemispheric indentation, in line with the nodal axis, for attaching a shaft using a drive pin and a hammer. In one embodiment of this invention, the shaft and head can only be attached, adjusted, or separated using a tool.  
           [0019]    In one embodiment of a golf club of this invention, the shaft comprises a rounded top designed to fit against the navel of a golfer. This rounded top is preferably substantially ball-shaped and is optionally formed on a segment that is removable from the shaft, wherein the removable segment comprises a tapered bottom. The shaft may further comprise a cap having a tapered hole to receive the tapered bottom of the removable segment. Preferably the rounded top is not removable from the shaft. Preferably the rounded top is constructed from a material having similar vibrational qualities as the shaft. Preferably the shaft and rounded top are made from the same material. Preferably the shaft and rounded top are constructed from the same piece of material.  
           [0020]    Preferably, the golf club of this invention is a putter, chipper, or other short-range club.  
           [0021]    This invention further provides for a set of golf clubs constructed and adapted to produce separate or detectably distinct selected musical notes when each strikes or hits a golf ball. In an embodiment of this invention, each of the club heads is assigned a marking, e.g., color, texture, or pitch symbol, indicative of the note each produces when it strikes a golf ball.  
           [0022]    This invention further provides a method for hitting a golf ball comprising positioning a golf club of this invention adjacent to the golf ball; and striking or hitting the golf ball with the head of the golf club to produce a musical note or tone. As used herein, “hit” refers to contact resulting in production of a musical tone or note. Optionally a hit is preceded by a swing.  
           [0023]    This invention also provides a method for hitting a golf ball on a course having particular conditions affecting golf ball speed. With a golf club of this invention, said method comprising determining the condition of the golf course and choosing a head from said set of heads in accordance with said conditions.  
           [0024]    A method is also provided for determining when a golf club has hit a golf ball at the golf club head&#39;s sweet spot, said method comprising: hitting the golf ball with a club of this invention; and determining that the golf ball has been hit at the golf club&#39;s sweet spot by detecting when the head produces a fundamental musical tone indicative of having hit the ball with the sweet spot. This method further comprises determining that the golf ball has been hit by the golf club&#39;s sweet spot by feeling or otherwise detecting minimum or no vibration at the grip of the shaft. Detecting a fundamental tone can occur by any means known in the art including by a human ear or a computer. Detecting minimum or no vibration can occur by any means known in the art including by human hands or navel.  
           [0025]    As used herein, the term ‘substantially planar’ refers to a surface that, when placed against a planar surface, at least two points of the surface are in contact with the planar surface. Substantially planar surfaces include for example, surfaces which are planar, planar surfaces with rounded edges and flat surfaces in which a part of the surface material is removed, and/or in which a planar portion of a surface is in contact with one or more curved portions of a surface.  
           [0026]    As used herein, the term ‘vibratory node’ indicates a point, line, or area on the golf club head surface, which extends through a cross section of the head, at which, when the rest of the head vibrates to produce a fundamental tone, there are no or minimum vibrations in this area arising from the fundamental tone.  
           [0027]    The term ‘resonant material’ as used herein indicates a material that can be used as a shaft for the golf club of this invention that is joined to the head at the head&#39;s vibratory node such that when the face of the head is struck at its sweet spot, although vibrations are produced resulting in a fundamental tone or note by the head, minimal energy and/or vibrations are transferred to the shaft with minimum or no vibration felt by the golfer at the grip. Preferably a resonant material is selected that does not interfere with transfer of vibrational energy.  
           [0028]    The term ‘solid’ refers to a material that is not hollow, or does not have any completely contained cavities within. Solid materials include materials with partially contained cavities.  
           [0029]    The terms “toe and heel” as used herein refer to the sides of the golf club head that are farthest from and closest to, respectively, the golfer&#39;s feet when the golf club is in use.  
           [0030]    As used herein, the term ‘fundamental tone’ refers to the primary tone produced by the golf club of this invention when struck at its sweet spot. An ‘overtone’ is an integral multiple of the frequency of the fundamental tone, e.g. the ‘first overtone’ is two times the frequency of the fundamental tone. The term ‘harmonic’ is also used to reference integral multiples of the fundamental tone (the first harmonic).  
           [0031]    The term ‘to tune’ is used herein to refer to changing the fundamental tone produced by the golf club head.  
           [0032]    “Cylindrical” is used as in the art and is intended to include generalized cylinders, cylinders that have parallel sides that are perpendicular to the bottom, cylinders having one radius wherein the cross-section is a circle, cylinders having a textured face, and cylinders wherein on average the axes of one or more sides are parallel, but in a small section the sides are not parallel, e.g., the sides are rippled. A head having a hole having one or more small sections which are not parallel, can be designed to produce a selected number of fundamental tones.  
           [0033]    A standard golf ball is one that is recognized as legal for play by the PGA, the LPGA, and/or other international bodies governing golf. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]    [0034]FIGS. 1A and 1B are angled top view illustrations of two golf club heads of this invention, each comprising a solid bar.  
         [0035]    FIGS.  2 A- 2 C are illustrations of a golf club head of this invention. FIG. 2A is a top view. FIG. 2B is a side view of the back. FIG. 2C is a side view.  
         [0036]    [0036]FIG. 3 is an angled top view illustration of a golf club of this invention.  
         [0037]    FIGS.  4 A- 4 C are illustrations of the golf club head of the club shown in FIG. 3. FIG. 4A is a top view. FIG. 4B is a side view. FIG. 4C is a side view.  
         [0038]    [0038]FIGS. 5A and 5B are illustrations of a golf club head of this invention. FIG. 5A is a top view. FIG. 5B is a side view.  
         [0039]    FIGS.  6 A- 6 D are top view illustrations of golf club heads of this invention.  
         [0040]    [0040]FIGS. 7A and 7B are illustrations of golf club heads of this invention. FIG. 7A is a top view. FIG. 7B is a side view.  
         [0041]    [0041]FIGS. 8A and 8B are illustrations of golf club heads of this invention. FIG. 8A is a top view. FIG. 8B is a side view.  
         [0042]    [0042]FIGS. 9A and 9B are illustrations of golf club heads of this invention. FIG. 9A is a top view. FIG. 9B is a side view.  
         [0043]    [0043]FIG. 10 illustrates the top of a shaft of a golf club of this invention, having a rounded navel knob.  
         [0044]    FIGS.  11 A- 11 C are illustrations of a golf club head of this invention not having an open sight line. FIG. 11A is a top view. FIGS. 11B and 11C are cross sections as marked. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]    The golf club of this invention comprises a head made of a material capable of producing a fundamental tone when struck on its face. The face comprises a zone known as the ‘sweet spot’ that when struck, maximizes the fundamental tone and minimizes the overtone series. To minimize damping of the vibrations associated with the fundamental tone, the shaft of the golf club attaches to the head at the vibratory node. By attaching the shaft to a vibratory node, the transfer of vibrations arising from the fundamental tone from the head to the shaft is negligible, and the predominant vibrations in the shaft arise from the bending of the shaft when the golf ball is struck.  
         [0046]    As the face is struck outside of but closer to the ‘sweet spot’, the harmonics become more predominant, and are maximized at the vibratory nodes. The overtones are minimized at the nodes.  
         [0047]    The club head is frequency-matched to the shaft as to allow the head, when struck, to maintain a sustained fundamental tone without being dampened or diminished by a shaft producing frequencies dissonant to the club head&#39;s fundamental tone and/or harmonic series. One of ordinary skill in the art will be able to select a suitable shaft for the club heads of this invention, without undue experimentation.  
         [0048]    The tones produced by the clubs of this invention can encompass any audible or otherwise detectable range. Preferably, the tones range from 300 Hz to 1200 Hz and depend on the shape and size of the head, as well as the material from which the head is made. The tone that is produced is the result of resonant vibration of the head. When a golf ball strikes the sweet spot on the face of a golf club of this invention, energy is transferred both to the club head, resulting in vibrations producing a sound, and to the golf ball, resulting in the ball&#39;s traveling away from the club face. Efficiency of the transfer of energy of impact is reflected in the production of a clear, ringing tone when using the golf club of this invention. The efficient transfer of the energy of impact is also reflected in the smooth transfer of energy to the ball, resulting in less jumping, skidding, or skipping of the ball as it leaves the club face.  
         [0049]    The pitch of the fundamental tone produced by a head of the golf club of this invention in part corresponds to the amount of energy transferred between the club head and the ball, and thus plays a role in how far a ball hit with the club will travel under identical conditions (e.g. weight and club head proportions, force with which the ball is hit, surface conditions and the like). Golf clubs having heads that produce different fundamental tones will transmit different amounts of energy to a golf ball than those producing other fundamental tones, resulting in different distances traveled by the ball. This effect can be useful to a golfer in choosing a club head that is best suited to course conditions, e.g. wet and slow, or dry and fast.  
         [0050]    In its simplest embodiment, golf club head of this invention is a solid bar capable of producing a fundamental tone when struck at a particular spot. The bar may be made of any material capable of producing such a fundamental tone, including metals, ceramics, polymers, and glass. Preferred materials include aluminum, bronze, brass, and glass because of their strength, weight, and ability to produce a clear, ringing tone of pleasing pitch. Preferred materials include materials having sound qualities similar to aluminum. To lower the tone produced by a solid bar head, the back (the side opposite the striking face) can have a portion carved out. The carving can form any shape, including an arch, triangle, diamond, or a square among others. The apex of the carved-out shape can correspond to the sweet spot on the face of the club. Preferably, the carved-out portion is an arch to most closely mirror the shape of the golf ball.  
         [0051]    In another embodiment of this invention, the head of the golf club is made of a single piece of solid material having two free ends that face, but do not touch each other at the back of the head to form a space between each other. The edges of the two free ends may be parallel, or may be slanted relative to one another. In addition, the two free ends form part of a cylindrical hole in the head that passes through the entire head from the top of the head to the bottom. The cross-section of the hole may be any shape, including but not limited to circular, triangular, rectangular, square, or hexagonal. In an embodiment of this invention, the cylindrical hole is a circle. In an embodiment of this invention, the hole is an arc or a “T” (see FIGS. 9A and 9B). The overall shape of the head, as seen from above, can also be any shape, symmetrical or not. Preferably, the two free ends and the cylindrical hole form a c-shape in which the ‘c’ may be multifaceted. (e.g. triangular, square, rectangular, pentagonal, hexagonal, octagonal and the like) or round, as long as the face of the head is planar along the length of the sweet spot. In this embodiment, the tone that is produced by the golf club head may be changed (tuned) in several ways; by choice of head material, by removing material from the back portion of the head or the face, by changing the size of the space between the facing free ends, and by changing the size of the cylindrical hole. In all embodiments of this invention, the hole is large enough to allow the head to vibrate and produce a detectable tone or note. In an embodiment of this invention, the hole is about as long, from head to toe, as the distance between the nodes, and is optionally adjacent to one or both nodes. The size of the area that functions more similarly as the sweet spot correlates with the length of the hole. Preferably the length of the hole is large.  
         [0052]    As the size of the hole increases, the tone produced by the head decreases in pitch. As the space between the free ends increases, the tone produced by the head increases in pitch. As the distance between the face of the club head and the edge of the hole decreases, the tone produced by the head decreases in pitch. In an embodiment of this invention, in one or more heads, the distance between the face of the club head and the edge of the hole and the size of the space are selected wherein the clubs with different distances and space sizes produce about the same tone. In one embodiment, two or more clubs producing the same tone comprise a set. The hole dimension and placement are selected to not interfere with shaft attachment.  
         [0053]    In an embodiment of this invention, the free ends on the sides of the space are not perpendicular to the bottom of the head or not parallel to each other. Preferably the toe and heel portions of the head, as divided at the location of the center of the space, are about equal in weight. In an embodiment of this invention, the hole and/or space is designed to prevent creating a sight line through the head, such as in a step pattern.  
         [0054]    In an embodiment of this invention, a head and/or a club complies with United States Golf Association regulations (The Official Rules of Golf/by the United States Golf Association and the Royal and Ancient Golf Club of St. Andrews, Scotland (1993)).  
         [0055]    The vibrational properties of a given shaft can be altered by changing its length, thickness, or material. In addition, a shaft may be a constant-diameter rod, or it may be tapered. Preferably, the shaft is tapered (from thick to thin from its free end (top) to its attached end (bottom), to confer added stability to the club head. The degree of taper can vary widely. Resonant materials useful for the shafts described herein are hardwoods, including but not limited to pernambuco, rosewood, vermillion, granadillo, ebony and osage orange, as well as steel, graphite, glass fiber, carbon fiber, plastic, fiber-reinforced plastic, or Keylon™.  
         [0056]    The shaft of this invention may optionally comprise a rounded knob at its top end that is adapted to fit against the golfer&#39;s naval while the golf club is in use. This rounded knob imparts additional stability to the club during use. The knob may be permanently affixed to the top of the shaft, or it may be removable. In one embodiment, the rounded knob is attached to a tapered removable segment, the narrow end of which is inserted into a tapered recess in the top of the shaft that is designed to accept the tapered removable segment.  
         [0057]    The shaft may be directly connected to the head using any connection method known in the art. Means utilized to secure the shaft to the head are selected to not interfere with the hole. In a club of this invention, the shaft may be attached directly to the head, or via a tapered connector piece known as a hosel. In an embodiment of this invention, a hosel is permanently attached to the head, or the head comprises a hosel. In an embodiment, the hosel is milled or machined from the same piece of material as the head.  
         [0058]    Connection methods can be selected to allow maximal vibration or to dampen vibration transferring to the shaft. For example, the shaft may be glued to the top of the head, or threaded, pinned, or frictionally held within a hole in the head at the vibratory node. Such a hole into which the shaft is inserted may be formed perpendicular to the top surface of the head, or may angle towards the toe of the head. Preferably the shaft and securing mechanism protrude into the head by less than about half the thickness of the head. In an embodiment of this invention, the shaft and securing mechanism are inserted at location and angle such that half of the shaft and securing mechanism embedded in the head is on the toe side of the node and half is on the heel side of the node. In an embodiment of this invention, the shaft is inserted far enough back from the face to not interfere with sound and/or golfing qualities.  
         [0059]    Preferably, the head has a shaft hole formed at the vibratory node nearest the heel portion and is tapered from wide to narrow from the top to the bottom. The shaft, which is similarly tapered, slides into the shaft hole. In one embodiment of the club of this invention, the shaft is frictionally engaged in the shaft hole such that it is secure under normal use, but removable with the application of sufficient pulling force in combination with the counter-clockwise rotation of the shaft. The shaft may also be tightened or loosened from the head using a slight turning motion that can be facilitated by using a wrench on an optionally hexagonally shaped (or other shape) nut built into the shaft or the hosel, when present. In another embodiment, the shaft and the head both have pinholes that are aligned when the shaft is inserted into the shaft hole. A set pin is then passed through both the shaft pinhole and the head pinhole to permanently secure the shaft to the head.  
         [0060]    Alternatively, the bottom of the head comprises a bottom recess that is approximately the diameter and depth of a bolt (screw) head and is in alignment with the shaft hole. A narrower through-hole passes through the center of the bottom recess such that the threaded end of a bolt, when inserted through the bottom recess from the bottom side of the head, passes through the through-hole. If the bottom end of the shaft has a threaded hole to match the bolt threads, the bolt is used to secure the shaft to the head. Again, an optional nut can be incorporated into the shaft or hosel above the section that is inserted into the shaft hole and used with or without a wrench to aid in securing the shaft to the head, or loosening the shaft from the head.  
         [0061]    One of ordinary skill in the art will recognize that any of the securing means described herein can be used alone or in combination to secure the shaft to the head. Numerous other attachment means exist in the art, and may be used with the golf club of this invention. In addition, these methods may be used in embodiments in which a hosel is used as an intermediate piece between the shaft and the head. In practice, a particular shaft is fitted with a hosel and the shaft-hosel pair is then matched with a head such that the pair and the head are matched and no, or minimal vibrations are felt in the grip of the shaft when a golf ball is stuck at the sweet spot on the club head face. The use of a hosel to secure the shaft to the head imparts additional stability to the golf club to prevent ‘wobble’ (rotation) of the head when a ball is hit at a spot other than the sweet spot.  
         [0062]    The weight and balance of a golf club head between its face and its back and/or between its toe and heel can affect the smoothness and consistency of a golf swing. Ways to affect this balance include changing the distribution of weight between the face and the back, and the toe and the heel of the head. Heads of the golf club of this invention weight approximately 250 g to about 500 g. Preferably, the head of the golf club of this invention weights about 280 g to about 440 g. In an embodiment of this invention, the head weight is between about 330 g and about 340 g, or between about 290 g and about 310 g. Additional control is imparted to the head by ‘back weighting’ the club, i.e. by positioning the shaft such that more head weight is behind (towards the back of) the shaft than in front of it (towards the face). FIGS.  2 - 4  and  8 - 9  illustrate back-weighted heads. Furthermore, additional weight can be added to the back of the club head by adding weighted plugs behind the through-hole and adjacent to the two free ends that face, but do not touch each other at the back of the club head. In one embodiment of this invention, a golf club head is made of a two or more materials. In the practice of this invention, the second material is more dense than the first material and is inserted inside the head to increase the weight of the head. In one embodiment, a second material is a brass insert. Materials in addition to a first material preferably do not interfere substantially with production of tones and/or vibrations.  
         [0063]    It may also be desirable to impart spin to a golf ball when it is struck. Top spin, for example, helps to minimize skipping, jumping, or sliding of the ball as it moves away from the face of the head. Imparting spin is possible by changing the angle (loft) of the face of the head from 90 degrees (relative to the plane of the ground) to less than 90 degrees (towards the back of the head) by about 1 degree to about 65 degrees. For putters, the optimal angle is approximately 1-4 degrees. For chippers, angles of 1-30 degrees are preferable.  
         [0064]    This invention provides golf club heads that are not solid. This invention also provides a golf club head which does not have an open sight line. This invention provides golf club heads having a zigzag or step-type hole and/or space.  
         [0065]    Golf club heads of this invention have two nodes. One node is utilized to attach a shaft to construct a right-handed club, and the other to construct a left-handed club.  
         [0066]    This invention provides a method for making a golf club head comprising shaping the head from a resonant material wherein the head has at least one vibratory node and a hole adapted for attaching a shaft at the vibratory node, wherein the head produces a tone when struck by a golf ball. This invention also provides a method for making a golf club comprising: shaping a golf club head from a resonant material wherein the head has at least one vibratory node whereby the head produces a tone when struck by a golf ball; shaping a hole adapted for attaching a shaft at the vibratory node; and attaching a shaft made of a resonant material to the head in said hole.  
         [0067]    This invention provides a golf club head having an open sight line comprising: a head capable of producing a tone when struck by a golf ball, wherein the head has an open sight line, at least one vibratory node, and a hole adapted for attaching a shaft at the vibratory node. This invention provides a method for evaluating a golf club swing comprising: providing a golf club comprising a head having an open sight line, attached to a resonant material shaft, and a hole in the head, wherein the open sight line has an open sight distance a measured from head to toe; applying a stripe on a floor or ground surface whereby the width of the stripe is about equal to or less than the open sight distance of said open sight line; swinging said club over said stripe; and detecting and analyzing the amount and pattern of said stripe visible through said open sight line of said head. Preferably, the stripe is visible to the human eye and straight. In an embodiment of this invention, the sweet spot is centered at the axis about perpendicular to the face and parallel with the bottom of the head, at the center of the open sight line, the hole, and/or the space. Marking methods include using paint and/or tape. In an embodiment of this invention, the width of the stripe is about equal to the width of the hole or the space, in the direction from head to toe, of the head used for practicing swinging. In an embodiment of this invention, the straightness of said swing is evaluated.  
         [0068]    In an embodiment of this invention, the method for evaluating a swing also comprises: placing a golf ball on the floor or ground surface near or adjacent to an end of the stripe, before the swinging step; hitting the golf ball with the club resulting from the swinging step; and detecting and analyzing a tone produced by the club head and/or detecting vibration of said shaft. The ball is placed near or adjacent to an end of the stripe whereby swinging the head over the stripe whereby about the entire width of the stripe is visible through the open sight line during the swing, leads to the ball hitting the club in the sweet spot. In an embodiment of this invention, the swing is evaluated for accuracy at hitting said ball with the sweet spot of the club.  
         [0069]    The particular dimensions of a head of this invention, can optionally be calculated, as is known in the art, after selecting a material, using the density of the material. Heads can also optionally be designed to meet regulations of the PGA, and then the material selected after calculating what density is required to construct the designed club at a selected weight.  
         [0070]    The following figures and examples are exemplary only and are not meant to limit the invention to any particular configuration.  
         [0071]    [0071]FIG. 1A is a top angled view of one embodiment of a head of a golf club of this invention. Head  105  comprises a solid bar having four sides: face  115 , toe  112 , heel  110 , and back  130 , top  101 , and bottom  102 . Cutout  134  is positioned on the center of back  130  and is aligned with sweet spot  116  on face  115 . Shaft hole  150  is located along the nodal line  160  close to heel  110 . FIG. 1B is the top view of one embodiment of a head of a golf club of this invention. Head  105  comprises a solid bar having four sides: face  115 , toe  112 , heel  110 , and back  130 , top  101 , and bottom  102 . Cutout  134  is positioned on the center of back  130  and is aligned with sweet spot  116  on face  115 . Shaft hole  150  is located along the nodal line  160  close to heel  110 .  
         [0072]    FIGS.  2 A- 2 C are illustrations of a golf club head of this invention. FIG. 2A is the top view. Head  105  comprises a solid bar having four sides: face  115 , toe  112 , heel  110 , and back  130 , top  101 , and bottom (not shown). Cutout  134  is positioned on the center of back  130  and is aligned with sweet spot (not shown) on face  115 . Shaft hole  150  is located at the node close to heel  110 . FIG. 2B is a side view from the back. Head  105  comprises a solid bar having four sides (face (not shown), toe (not shown), heel  110 , back  130 ), top  101 , and bottom  102 . Cutout  134  is positioned on the center of back  130  and is aligned with the sweet spot (not shown) on the face (not shown). The cutout  134  has an additional inside cutout  255 . FIG. 2C is a side view from the face  115  of the golf club head. Head  105  comprises a solid bar having four sides: face  115 , toe  112 , heel  110 , and back (not shown)), top  101 , and bottom  102 . Sweet spot  116  is shown on the face  115 .  
         [0073]    [0073]FIG. 3 illustrates a perspective view of one embodiment of a golf club of this invention. The golf club comprises a head  105  and a shaft  140  having grip  131  attached to head  105 . Head  105  comprises a single piece of solid material having two free ends  132  that face, but do not touch each other at the back  130  of the head to form space  125 . The general shape of head  105  is a “C”, although other shapes are within the scope of this invention. Cylindrical hole  120  passes through the head from top to bottom and is aligned with sweet spot  116  on face  115 . The area capable of responding similarly to the sweet spot  116  is bound by sweet spot area lines  224 . Nodal line  160  is a line along which there are no to minimal vibrations when face  115  is struck at sweet spot  116 , e.g., with a golf ball. Shaft hole  150  is disposed along the nodal line  160  close to the heel edge  110  of the head and is adapted to receive shaft  140 , optionally via hosel  145 . The toe  112 , heel  110 , and back  130  surfaces may have optional contours  135 . Head  105  further comprises alignment-marking  155  which is located on top surface  101  near face  115  and in alignment with the center of sweet spot  116 . In this embodiment, the hosel further comprises an optional hosel nut  147  in the shape of a hexagon, which is used to assist in tightening and/or loosening the shaft and head. The angle of the face  115  to the ground is changed from 90 degrees by 2 degrees, i.e., it is 88 degrees.  
         [0074]    FIGS.  4 A- 4 C show the club head of FIG. 3 from other angles. FIG. 4A shows the bottom surface  102  of the head depicted in FIG. 3. Optional bottom recess  152  and through-hole  154  are used for securing the shaft to the head. FIG. 4B is a front view of the head depicted in FIG. 3, showing optional contours  135 . Bottom surface  102  is substantially planar, although the transitions to toe  110  and the heel  112  are rounded. FIG. 4C shows a side view of the head depicted in FIG. 3. The heel  110  is rounded. Face  115  is substantially planar and is angled toward the back  130  from bottom  102  to top  101  by about 2 degrees.  
         [0075]    [0075]FIGS. 5A and 5B illustrate a golf club head of this invention. FIG. 5A is a top view. The golf club head  105  comprises a single piece of solid material having two free ends  132  that face, but do not touch each other at the back  130  of the head to form space  125 . The general shape of head  105  is a “C”, although other shapes are within the scope of this invention. Cylindrical hole  120  passes through the head from top to bottom and is aligned with the sweet spot (not shown) on face  115 . Shaft hole  150  is at the node close to the heel edge  110  of the head  105 . The toe  112 , heel  110 , and back  130  surfaces may have optional contours  135 . Head  105  further comprises alignment-marking  155  which is located on top surface  101  near face  115  and in alignment with the sweet spot (not shown). FIG. 5B shows a side view of the head  105  having top  101 , contours  135 , face  115 , sweet spot  116 , and bottom  102 .  
         [0076]    FIGS.  6 A- 6 D show other “C”-shaped golf club head embodiments of this invention. FIG. 6A depicts a golf club head  105  in which all of the sides: face  115 , toe  112 , heel  110  and back  130 , are planar. FIG. 6B depicts a golf club head, in which face  115  is planar, but toe  112 , heel  110 , and back  130  are rounded. FIG. 6C depicts a golf club head  105  in which the face  115 , toe  112 , and heel  110  are planar and the back  130  is angular. FIG. 6D depicts a golf club head  105  in which all of the sides are substantially planar but with rounded transitions between each side. Each of the embodiments pictured in FIGS.  6 A- 6 D show a circular cylindrical hole  120 , although is it readily apparent to one of ordinary skill in the art that other shapes are possible. In FIG. 6D, two examples of open sight distances  200  and  201  are labeled. The sweet spot (on face, not shown) is centered on the sweet spot axis  202  which, on this head, runs through the center of the hole  120  and the space  125 . The alignment marker  155 , which is also in line with the axis, is shown on the top surface  101 . In FIGS.  6 A- 6 D, the heads  105  also show a hole  150  at the node close to the heel  110 , which is useful for attaching a shaft (not shown). Parts are numbered consistently in FIGS.  6 A- 6 D.  
         [0077]    [0077]FIGS. 7A and 7B illustrate a “C”-shaped golf club head of this invention. FIG. 7A is a top view. The golf club head  105  comprises a single piece of solid material having two free ends  132  that face, but do not touch each other at the back  130  of the head to form space  125 . Cylindrical hole  120  passes through the head from top to bottom and is aligned with the sweet spot (not shown) on face  115 . Shaft hole  150  is at the node close to the heel edge  110  of the head  105 . The toe  112 , heel  110 , and back  130  surfaces may have optional contours  135 . The free ends  132  can also have optional contours  230 . FIG. 6B shows a side view of the head  105  having top  101 , contours  135 , face  115 , sweet spot  116 , and bottom  102 .  
         [0078]    [0078]FIGS. 8A and 8B illustrate a “C”-shaped golf club head of this invention. FIG. 8A is a top view. The golf club head  105  comprises a single piece of solid material having two free ends  132  that face, but do not touch each other at the back  130  of the head to form space  125 . Five-sided pentagonal hole  120  passes through the head from top to bottom and is aligned with the sweet spot (not shown) on face  115 . Shaft hole  150  is at the node close to the heel edge  110  of the head  105 . The toe  112 , heel  110 , and back  130  surfaces may have optional contours  135 . FIG. 8B shows a side view of the head  105  having top  101 , contours  135 , face  115 , sweet spot  116 , and bottom  102 .  
         [0079]    FIGS.  9 A- 9 C illustrate another “C”-shaped golf club head of this invention. FIG. 9A is a top view. The golf club head  105  comprises a single piece of solid material having two free ends  132  that face, but do not touch each other at the back  130  of the head to form space  125 . Arc-shaped hole  120  passes through the head from top to bottom and is aligned with sweet spot (not shown) on face  115 . Shaft hole  150  is at the node close to the heel edge  110  of the head  105 . The toe  112 , heel  110 , and back  130  surfaces may have optional contours  135 . FIG. 9A also shows an optional damping hole  255  extending from the top  101  to the bottom (not shown). FIG. 9B shows a side view of the head  105  having top  101 , contours  135 , face  115 , sweet spot  116 , and bottom  102 . The edges from the top  101  to both the toe  112  and heel  110  all the way to the bottom  102  are contoured  135  and rounded. FIG. 9C shows a side view from the back  130 . An optional damping hole  256  is shown through the back  130  to the hole (not shown).  
         [0080]    [0080]FIG. 10 illustrates the optional rounded knob attached to the top of the shaft of the golf clubs of this invention. Rounded knob  175  is designed to fit into the golfer&#39;s navel during use. Knob  175  is attached to tapered fitting  170 , which is inserted into tapered shaft opening  180 . Optional metal cap  165  covers the top end of shaft  140 , covering the tapered end  212 , which is fitted into the shaft grip  211 .  
         [0081]    [0081]FIG. 11A- 11 C illustrate a head  105  having the hole  320  and  420  and space  325  and  425  designed in a step pattern to prevent creating an open sight line from the top  101  to the bottom  102  of the head  105 . The lower hole section  420  and the lower space section  425  are not visible from the top and are shown with dashed lines. FIG. 11A is a top view and FIGS. 11B and 11C are cross sections as marked B-B and C-C, respectively, in  11 A. In FIG. 11B a hole opening  300  connects the upper hole section  320  and the lower hole section  420  while preventing the free ends  132  from contacting and preventing the formation of an open sight line. In FIG. 11C a space opening  301  connects the upper space opening  325  with the lower space opening  425  while preventing the free ends  132  from contacting and preventing the formation of an open sight line.  
       EXAMPLE 1  
       [0082]    Seven heads of the design shown in FIG. 6A were constructed with holes of varying diameter, from one and three eighths inches to one and five eighths inches by forty thousandth increments. The nodes were in the same locations for all heads. The pitch of each head was different.  
       EXAMPLE 2  
       [0083]    A head of the design shown in FIGS.  5 A-B was constructed of aluminum T60-61. The locations of the vibratory nodes was determined by suspending the head, top up, sprinkling sawdust on the top, and striking the face, on the sweet spot, with an item capable of causing the head to vibrate, e.g., a golf ball. The sawdust pieces moved as a result of the vibrations, such that the sawdust collected over the nodes, where no or minimum vibrations occurred. The head was anodized. A shaft was turned from pernambuco and constructed to be attached to the head using a turning motion.  
       EXAMPLE 3  
       [0084]    A head of the design shown in FIGS.  2 A-C was constructed of bronze.  
       EXAMPLE 4  
       [0085]    A head of the design shown in FIGS.  7 A-B was constructed of brass.  
       EXAMPLE 5  
       [0086]    A head of the design shown in FIGS.  8 A-B was constructed of aluminum.  
       EXAMPLE 6  
       [0087]    A head of the design shown in FIGS.  9 A-B, without the damping holes, was constructed of aluminum.  
         [0088]    Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. Golf club shaft and head designs, attachment mechanism, and materials useful for making golf clubs and heads are intended to be within the scope of this invention. Further, while a number of statements appear throughout this application regarding possible mechanisms by which, for example tones are produced or dampened, or vibrations are produced transferred or dampened, the inventors do not wish to be held to any particular theory regarding the operation of the device of this invention.