Abstract:
A system of interchangeable club heads sharing one or more shafts and golf bag for carrying the club heads and one or more shafts. The club heads contain a shaft segment to set club length and a coupler to interconnect to the shaft and grip. The shaft contains an opposite gender coupler. The system is very lightweight and much more portable than a conventional set of golf clubs. It also creates the opportunity for players to match club heads with shafts with differing performance characteristics. Additionally, it solves a problem for golfers using long shafts on putters. These long shafts can now be disassembled for storage and transport.

Description:
This application is a continuation of U.S. patent application Ser. No. 12/619,491, filed Nov. 16, 2009 now U.S. Pat. No. 8,083,606, which is a continuation of U.S. patent application Ser. No. 11/237,980, filed Sep. 29, 2005 (now U.S. Pat. No. 7,618,329), which claims the benefit of U.S. Provisional Appln. No. 60/703,452 filed Jul. 29, 2005 and U.S. Provisional Appln. No. 60/613,726, filed Sep. 29, 2004, each of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to golf club and related equipment. More specifically, the present invention relates to a golf club system having interchangeable heads that each can fit onto a single shared shaft. The present invention also relates to carrying cases for such a club system. 
     2. Background of the Invention 
     A common problem for golfers is transportation of a full set of golf clubs. Heavy and bulky sets of clubs are made heavier and bulkier by flight cases or travel bags. It is fairly common for a golfer to bring his/her own clubs because of costs of renting club sets at remote destinations. In addition to cost, among other detracting factors, the quality of such rental clubs often varies. Golfers also often develop a personal feel for, and comfort level with, their own sets of clubs, so even a high quality set of rental or demo clubs may be unsuitable depending on a specific golfer&#39;s needs and/or desires. Experienced golfers may prefer to give themselves an advantage by using their own clubs in such circumstances. 
     A compact club set may appeal to a wide and varied range of player groups. Even the average player may have difficulty finding adequate trunk or storage space for clubs. Some common sports cars, such as, for example the Corvette, have trunks that will not accommodate even one full-sized golf club set. As used herein, a full-sized set refers to a set of golf clubs whereby each club head is fixedly attached to its own shaft. Many smaller vehicle trunks also have trouble accommodating more than a single set. 
     Additionally, more senior players may have trouble lifting and/or carrying a full-sized set. Full-sized sets may also be bulky, noisy, awkward or heavy, among other negative characteristics. When such full-sized sets are placed in a hard-shell flight case the situation can become even worse. Flight cases can double the weight of a full-size set of clubs and add considerable bulk. Soft-shell cases, while they may be lighter and less bulky, still can expose the clubs to the vagaries of baggage handlers. 
     What is needed is a way to reduce the bulk and weight of the set while preserving the playing physics and other desirable characteristics of the clubs. The present invention allows golfers to enjoy these and other attendant advantages in a compact, easy to use set of clubs. Beyond the benefit of increased portability, it is also possible to choose among several shafts for anyone club. This may expand the game of golf to include a new dimension of performance tuning because shafts vary considerably in stiffness or spring. The present invention can allow all club heads to be matched to the best shaft for the playing situation at hand. 
     BRIEF SUMMARY OF THE INVENTION 
     A number of design alternatives were explored before arriving at the current club and head system. One area of particular concern and experimentation is the coupler for connecting the shaft to the head. Several prototypes were built in an attempt to create a coupler that would satisfy the performance requirements of the high end golfer. While many requirements exist, one overarching requirement was tightness of fit. The club heads and their male coupling pins needed to be held in contact with the coupler in the shaft without discernable wobble. 
     An early design utilized two floating wedges that could slide out of the way for insertion of the coupling pin and back into position to wedge the pin in place. The wedge design relied on a long cylindrical opening in the coupler and a straight cylindrical coupling pin. The fit of the device depended, in part, on the tolerance of the machining of these two components. Machining long cylindrical sections has inherent difficulties. Machine tools for cutting these components tend to dull as the cut is achieved. Such tools may dull over many cuts such as, for example, in mass producing sets. This tool wear can be an issue for both drilled or lathed parts or any other machined parts involving a cutting tool that may wear over time. In the end, tolerances must be selected that are realistic for production. Even in prototype production quantities, parts machined to a tolerance of ±0.001 inches resulted in discernable “play” in the club with this design. 
     Another difficulty of this early design was the need for strong springs to force the wedges in place. Strong springs helped the wedges snap into place but made the sleeve hard to pull back with thumb and finger. The wedges also were created by multiple machining cuts which made them more expensive than desired. 
     The final design involved ball bearings set in a coupler body and squeezed between tracks in the coupler body and tracks in a coupler pull-back sleeve. Released tension and lateral motion of the pull-back sleeve can allow the coupling pin to be inserted. Once inserted, the release of tension on the pull-back sleeve brings force to bear on flat surfaces of the coupler pin. Finally, this force pulls a conical surface on the coupler pin into contact with a mated conical sheath surface in the coupler. These two conical surfaces can be manufactured relatively easily and inexpensively and do not suffer from the many of the machining tolerance issues of the straight cylinder design. 
     A deficiency of this design may be loss of friction and fit from vibration during ball and head impact. Despite a tight fit, the spring and ball/race combination may be subject to release during high vibration. A twist lock would be desirable to minimize unintentional separation. There are also a number of alternate methods of locking the coupler. The method described herein is preferred, but other locking methods would be known to those skilled in the art based upon the present disclosure. 
     Finally, the components of the golf system are stored in a unique bag. The small size and shape of this bag are a direct result of the design of the club system and provides an advantage to users in itself. This unique club head system makes many new bag designs possible. 
     According to one exemplary aspect, the present invention includes a coupler for mating a golf shaft handle to a club head comprising a first pin adapted to fit into a handle end of a golf shaft, a second pin adapted to fit into a club head end of a golf shaft, and a coupling sleeve fixedly attached to one of the first pin and the second pin, the coupling sleeve further being reversibly attachable to the other of the first pin and the second pin to allow for mating of the golf shaft handle to the club head when the coupler is in use on a golf club. 
     According to another exemplary aspect, the present invention includes A golf club having a detachable head comprising a first shaft segment and a second shaft segment, the first shaft segment having a grip or handle attached thereto and the second shaft segment being fixedly attached to a golf club head, and a coupler affixed to either the first shaft segment or the second shaft segment for reversibly mating the handle to the club head. 
     According to a further aspect, the coupler comprises an inner housing and a pull-back sleeve, whereby the pull-back is sleeve movable with respect to the inner housing to allow for movement of one or more first ball bearings within the coupler such that in a first pull-back sleeve position, the ball bearings allow insertion of an insertion pin during mating of the first and second shaft segments, and in a second pull-back sleeve position, the ball bearings hold the insertion pin axially in place to reversibly secure the first shaft segment to the second shaft segment. 
     According to another exemplary aspect, the present invention includes a golf bag for carrying a set of golf clubs comprising one or more shafts and a plurality of club heads that for attachment to the one or more shafts via a coupler. The golf bag comprises a compartment for holding the one or more shafts and a compartment having a plurality of fitted compartments for housing each of the plurality of club heads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a shaft with grip and head fitted with the coupler components ready to be connected; 
         FIG. 2  shows the pull-back sleeve according to an exemplary embodiment of the present invention in isolation; 
         FIG. 3  is a cross sectional view through line III-III of the coupler of  FIG. 2 ; 
         FIG. 4  is a cross-sectional schematic view of a coupler according to an exemplary embodiment of the present invention showing a locking mechanism to limit rotational motion of the club head with respect to the shaft when the head is assembled to the shaft; 
         FIGS. 5   a - 5   c  show three views of the shaft coupler insert with pressed in spring pin retainer for the locking mechanism according to a preferred embodiment of the present invention; 
         FIG. 6  shows a spring for use inside the coupler; 
         FIG. 7  shows another exemplary embodiment of a coupler having a second set of ball bearing for locking the couple and pin during operation; 
         FIG. 8  shows a partial prospective view of a carrying bag according to an exemplary embodiment of the present invention; 
         FIGS. 9   a - 9   c  shows front and side elevation views of the bag of  FIG. 8 ; 
         FIG. 10  shows the top of the bag of  FIG. 8 ; and 
         FIG. 11  shows an open view of the bag of  FIG. 8  having cut foam for insertion of club heads. 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIG. 1 , a golf club  10  includes a large shaft segment  100  with a detachable head  500 . Shaft  100  is cut from a standard full-sized shaft to accommodate the shortest club length—usually the putter. Alternatively, shaft segment  100  may be originally manufactured to the desired length, rather than cut from a longer shaft length. Club head  500 , intended for mating with shaft segment  100 , includes a shorter shaft section  102  between a club shaft insert sheath  504  and a head shaft segment coupler pin  106  (see  FIG. 3 ). 
     The length of shaft section  100  can vary from club to club and may be used to set the club length optimally for that club. For example, longer clubs such as woods or long irons usually have longer overall shafts than short irons, wedges, and or putters (although some golfers prefer putters having long shaft length). By fixing the length of shaft segment  100 , shaft section  102  can be varied to allow for varying shaft lengths desired for the various clubs in a golfers bag. Large shaft segment  100  is fitted to a coupler mechanism  200  via an insert pin  108  (see  FIG. 3 ). Insert pin  108  is pressed and glued into the shaft, but may be affixed by any suitable manner known in the art. 
     The diameter of pin  108  is selected optimally to fit the internal diameter of the shaft at the shaft length used for the average person, but may also be custom fit to various players&#39; specifications. Modern club shafts are often tapered such that their inner diameter varies along the length of the shaft. Club lengths for players usually vary less than six inches and are typically based on arm length and height of the player, but shaft lengths may be suited to any player&#39;s specifications. Because the difference in diameter for a shaft over a six inch section typically is not significant, the diameter of insert pin  108  is set to fit the smallest diameter of shaft  100  in an embodiment of the present invention. This corresponds, for example, to the longest club for the tallest player. 
     Pin  108  includes a threaded end  108   a  to accept fixed coupler housing  202 . This thread is preferably counter-clockwise for right handed players and clockwise for left handed players. The desire for different threading direction based on handedness is due, in part, to the opposing torque/twists generated by left- and right-handed golfers about the shaft. Coupler housing  202  has internal threads to appropriately match the threaded end  108   a  of pin  108 . Coupler housing  202  may also be affixed to shaft  100  in other ways known in the art, for example, using expoxy. 
     As seen in  FIG. 3 , coupler housing  202  has several features. It has a conical portion  204  to mate with matching conical surface  106   a  of the coupler pin  106  affixed to club head  500 . It has multiple ball bearing guide holes  206  to hold ball bearings  300  in place. As seen in  FIG. 3 , only one such guide hole  206  is shown in the cross section, but others may be located about the perimeter. In a preferred embodiment, there are three equally spaced guide holes  206  located about a perimeter of coupler housing  202 . 
     As seen in  FIGS. 2 and 4 , there is a notch  208  to provide a clocking fit to alignment pin  120  in the coupler pin  106 . Pin  120  and notch  208  assure the shaft handle always lines up the same way with all club heads. Another pin  110  is press fit into the side of coupler housing  200  to provide clocking into the “L” shaped guide of the pull back sleeve  202 . 
     Head coupling pin  106  is inserted and glued, or otherwise affixed, into the head shaft segments  102  as previously described. These shaft segments  102  vary in length significantly and thus the inside diameter of these shaft segments varies significantly also. In this case, the variation is enough to affect the need for head coupling pins  106  of various diameters. This may or may not be a need in other embodiments since manufacturers may make all parts for a design and simply standardize on an inner diameter of this part. The design described here relies on modification of readily available club components which have variations. 
     Housing  200  also includes a press-fit pin  210  to hold a twist to a spring  400  (see  FIG. 6 ). As shown in  FIGS. 5   a - 5   c , pin  210  and hole  212  work together to hold spring  400  in a position of tension to provide a twisting force for the operation of the locking mechanism. Pin  210  wedges the base of the spring  400  and hole  214  receives a short vertical section  402  at the end of spring  400 . Spring  400  is twisted to latch during assembly. The twist maintains coupler  200  in locked position at all times. The pull back sleeve  202  must be twisted and pulled back by the golfer in order to pull out the head. When the coupler pin is extracted, pin  110  slides into retaining area  112  to hold it in place until another coupler pin  106  for another head is inserted. This simplifies the hand motions necessary to insert and extract a club while allowing an automatic locking of the coupler. 
     The head coupling pin  106  has a pressed in pin  120  for locking fit as previously described. Although other kinds of pins can be used, the use of a press fit pin here, and other places in the invention, is preferred as it reduces cost and complexity of manufacture. 
     The pull back sleeve  202  is the last major component of the coupler  200 . Part  202  has a knurled surface  230  which facilitates gripping for hand operation. Although this is shown as a knurled surface, it may be of any surface texture, including being smooth, so long as the sleeve is movable by a user gripping coupler  200  by hand. The sleeve  202  must be pulled and rotated at various times during operation. Part  202  has several surfaces which help make the coupler hold without “play”. The conical, or rounded, surface of the end of coupler pin  106  is slowly sloping to allow easy insertion. This rounded end surface presses on the ball bearings  300  during insertion. The ball bearings  300  alternately push on the surface  216  of the pull back sleeve  202 . The force of insertion is translated by the angles and rotation of the ball bearings into a motion of the pull back sleeve  202  against spring  400 . 
     During insertion, the operator pulls sleeve  202  toward the shaft using thumb and index finger. This positions the ball bearings  300  free from surface  216  so they can allow passage of the nose of pin  106 . When the ball bearings  300  pass over the crest of the nose surface on pin  106  they “fall” into contact with surface  118 . When this occurs sleeve  202  can be released coming to rest close to the coupler pin hilt ring  114 . In this position the clocking pin  120  is at rest in the notch  208  and the ball bearing  300  is in contact with surfaces  116  and  216 . 
     As sleeve  202  moves in the direction away from club head  500 , locking pin  110  becomes clear of notch  112 . As this occurs, the twisting force of spring  400  causes sleeve  202  to rotate until pin  110  slides into channel  112   a . As pin  106  presses further into the coupler  200 , sleeve  202  continues to move further away from club head  500 . This can be seen as an increasing gap between sleeve  202  and the “hilt” region  114  of coupler pin  106 . When the ball bearings  300  pass over the crest of the surface  116  they “fall” into contact with surface  216 . As this occurs, sleeve  202  changes direction and comes to rest close to the coupler pin hilt ring  114 . In this position, the locking pin  120  is at rest in the notch  208  and the ball bearing  300  is in contact with surfaces  116  and  216 . 
     The angle of surface  116  is steep enough to make a force large enough to enable the ball bearing  300  to “climb” up and thus uncouple. Under static conditions, the force necessary to make this uncoupling occur are well beyond those found in golf club operation. The angle of surface  216  should not be so steep, however, that it cannot be uncoupled by hand when the pull-back sleeve  202  is manipulated by the user. For example, in one embodiment of the present invention angle of surface  216  is approximately 12 degrees. 
     Testing showed that there is, however, a possibility of vibration assisting this “climb”. To account for this possibility, the locking mechanism described above can be employed. However, the locking mechanism is not necessary for the operation or manufacture of a golf club with interchangeable heads according to embodiments of the present invention. 
     Moreover, other locking mechanisms, for example, the use of a ball bearing for locking pin  110  can be used in embodiments of the present invention to assure adequate locking during operation. The mechanism described here was selected to simplify the manual operation of the coupler. 
       FIG. 7  shows coupler  1200  with pin  1106  inserted and held in place by ball bearings  1300  and locked by bearings  1350 . Bearings  1350  are held in coupler  1202  by holes  1226 . There are three bearings  1350  oriented 120 degrees apart (similar bearings  1300 ). When these bearings are between surfaces  1140  of pin  106  and surfaces  1240  of the pull back sleeve  1202 , the coupler  1200  will be locked and can only be released by manual operation. To visualize this, one can imagine ball bearings  1300  climbing surface  1206  and thus causing pull back sleeve  1202  to move towards the shaft  100  (not shown in  FIG. 7 ). This would allow pin  1106  to begin to uncouple. Ball bearings  1350  will then wedge against surface  1142 , which is perpendicular to this direction of motion. The combination of surfaces  1140 ,  1142 , and  1240  form a sort of box, which is filled by ball bearing  1350 , thus preventing uncoupling. 
     Manual uncoupling is possible because the operator moves the pull back sleeve  1202  against spring  1400 , positioning surface  1250  at ball bearing  1350 . In this position, the ball bearings  1350  can move out of the way of the coupling pin  1106  and extraction can occur. Insertion is done in an analogous, but reverse manner. 
     Such a golf club system would not necessarily be suitable for use with present golf bags, which are designed to carry multiple clubs, each with its own shaft. Accordingly, a new bag design would be desirable for carrying the various heads and shaft(s). Such a bag according to an embodiment of the present invention is shown in  FIGS. 8 through 11 . The size and weight of the bag are considerably less than standard golf bags. 
     While bag design may vary considerably, any bag carrying such a system preferably has components and shape roughly as shown in bag  600 . The height of the bag can be less than a conventional golf bag because the length of the shaft  100  sets the height. In a conventional golf bag the longest club (the driver, or one wood, for instance) will set the overall height of the bag. In an embodiment of the invention the height of bag  600  was 36 inches in height—a full 14 inches less than what a bag using standard clubs would be. The width and depth of the bag are also considerably less than a conventional bag since the heads can be stacked for a close fit in the bag. 
       FIG. 11  shows an example of how these heads  602  may be stored in such a bag. In this example, the bag  600  is filled with foam  601 . Recessed areas  603  are cut in foam  601  for club heads and holes  604  are drilled for shaft segments  102  attached to coupling pins  106 . Other materials may be used to contain the clubs as well as other physical orientations selected to optimize space reduction or ease of club access. Another orientation of clubs in the bag could leave the club heads in the foam with the coupling pin end  106  exposed. This orientation would allow the user to press the shaft coupler  202  onto the coupler pin  106  to perform the coupling while the head is held by the bag. The assembled club would then be extracted by the user. 
     The foregoing disclosure of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.