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. A ramp on the circumference of one end of a pullback sleeve works in conjunction with a post on a grip end fitting to more tightly couple the club head end to a shaft.

Description:
[0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 14/142,739, filed Dec. 27, 2013 (pending), which claims the benefit of U.S. Provisional Application No. 61/747,180, filed Dec. 28, 2012 (expired), and this application claims the benefit of U.S. Provisional Application No. 62/031,145, filed, Jul. 30, 2014 (pending). 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    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. 
         [0004]    2. Background of the Invention 
         [0005]    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. Due to costs associated with renting gold club sets at remote destinations, it is fairly common for golfer to bring their own clubs. Cost is not the only detractor to renting golf clubs at destination locations. Another factor is the quality of rental clubs often varies. In addition, golfers often develop a personal feel for, and comfort level with, their own golf clubs. Therefore, even a high quality rental or demo golf club sets may be unsuitable depending on a specific golfer&#39;s needs and/or desires. For example, experienced golfers may prefer to give themselves an advantage by using their own clubs. 
         [0006]    A compact set of golf clubs may appeal to a wide and varied range of golfers. For example, those with cars may have inadequate trunk space for gold clubs. Some common sports cars, such as, for example the Corvette, have trunks that will not accommodate even one full-sized set of golf clubs. As used herein, a full-sized set of golf clubs refers to a set of golf clubs whereby each club comprises a club head fixedly attached to its own full-sized shaft. Many smaller vehicle trunks also have trouble accommodating more than a single set. Those with homes may have inadequate storage space for golf clubs. Cars are not the only place where sets of full size golf clubs can be difficult to manage. Golfers with homes may have inadequate storage space for golf clubs. Thus, there are many uses for sets of golf clubs that can be conveniently stored and transported. 
         [0007]    Full-sized golf club sets are also heavy. As a result, more senior players may have trouble lifting and/or carrying a full-sized set of golf clubs. Full-sized sets of golf clubs may also be bulky, noisy when moved, and awkward to move, among other negative characteristics. When such full-sized golf club sets are placed in a hard-shell flight case the situation is generally exacerbated. Due to the weight of a flight case, flight cases can double the weight of a full-size set of clubs. Flight cases also add considerable bulk. Soft-shell flight cases are generally lighter and less bulky than hard-shell cases. However, soft-shell flight cases do not protect the clubs from the rigors of travel and expose the clubs to the vagaries of baggage handlers. 
         [0008]    Thus, what is needed is a way to reduce the bulk and weight of a golf club set while preserving the playing physics and other desirable characteristics of the clubs. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Embodiments of the present invention are directed to golf club sets that preserve playing physics while at the same time reduce the weight, bulk, and other undesirable characteristics of a full-sized set of golf clubs. As a result, embodiments allow golfers to enjoy these and other attendant advantages in a compact, easy to use set of golf clubs. Beyond the benefit of increased portability, it is also possible to choose among several shafts for any one club head. The ability to select different shafts for a particular club head expand the game of golf to include a new dimension of performance tuning because shafts vary considerably in stiffness or spring. Thus, embodiments of the present invention can allow all club heads to be matched to the best shaft for the playing situation at hand. 
         [0010]    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 is tightness of fit. That is, the club heads and their male coupling pins needed to be held in contact with the coupler in the shaft without discernable wobble. 
         [0011]    One 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 dulling can be particularly problematic when many cuts are required such as, for example, in mass producing sets. 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. 
         [0012]    Another difficulty of this early design was the need for strong springs to force the wedges in place. While strong springs helped the wedges snap into place, the strong springs 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. 
         [0013]    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. 
         [0014]    A potential issue with the final design is 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. 
         [0015]    Finally, the components of a compact golf system according to embodiments 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. 
         [0016]    According to one exemplary aspect, an embodiment of 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. 
         [0017]    According to another exemplary aspect, an embodiment of 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. 
         [0018]    According to a further aspect, the coupler according to an embodiment 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. 
         [0019]    In another embodiment, a golf club according to an embodiment comprises a grip end having a shaft; and a coupler coupled to the shaft. The coupler comprises a grip end fitting coupled to the shaft, the grip end fitting having a hole into which a post is inserted and a notch; and a pullback sleeve with two ends, the pullback sleeve having a ramp on one end going around the circumference of the pullback sleeve, the ramp extending to a wall, wherein when the pullback sleeve is twisted in one direction, the post rides up the ramp until it becomes too difficult for twisting to continue, and when the pullback sleeve is twisted in the other direction, the post rides down the ramp until it is stopped by the wall such that it is aligned with the notch. 
         [0020]    In another exemplary embodiment, a golf club comprises a grip end having a shaft, a golf club head that is coupled to the shaft, a coupler attached to the shaft to couple the golf club head to the shaft, wherein the coupler comprises a grip end fitting coupled to the shaft, the grip end fitting having a hole, a post (or pin) inserted into the hole in the grip end fitting, and a pullback sleeve with two ends and a slot, the pullback sleeve having a ramp on one end extending a portion of the way around the circumference of the pullback sleeve to a wall, wherein when the pullback sleeve is twisted in one direction, the post rides up the ramp until it becomes too difficult for twisting to continue, and when the pullback sleeve is twisted in the other direction, the post rides down the ramp until it is stopped by the wall such that it is aligned with the slot. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a shaft with grip and head fitted with the coupler components ready to be connected; 
           [0022]      FIG. 2  shows the pull-back sleeve according to an exemplary embodiment of the present invention in isolation; 
           [0023]      FIG. 3  is a cross sectional view through line  3 - 3  of the coupler of  FIG. 2 ; 
           [0024]      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; 
           [0025]      FIGS. 5A-5C  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; 
           [0026]      FIG. 6  shows a spring for use inside the coupler; 
           [0027]      FIG. 7  shows another exemplary embodiment of a coupler having a second set of ball bearing for locking the couple and pin during operation. 
           [0028]      FIGS. 8A-8D  are schematic illustrations of a pullback sleeve  800  according to an embodiment. 
           [0029]      FIGS. 9A-9J  are schematic illustrations of a coupler body according to an embodiment. 
           [0030]      FIGS. 10A-10F  are schematic illustrations of a grip end fitting according to an embodiment. 
           [0031]      FIG. 11A  illustrates a coupler assembly in a loose condition according to an embodiment. 
           [0032]      FIG. 11B  illustrates a coupler assembly in a tightly coupled condition according to an embodiment. 
           [0033]      FIG. 12  illustrates a fully assembled golf club using two couplers according to an embodiment. 
           [0034]      FIG. 13  illustrates a collar that can be used with a coupler that couples an upper shaft segment to a lower shaft segment. 
           [0035]      FIG. 14  illustrates a tool that can be used to assist in tightening a coupler using a collar as shown in  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIG. 1  illustrates an exemplary golf club  10  according to an embodiment. 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 ). 
         [0037]    The length of shaft section  100  is fixed, while the length of shaft section  102  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. 
         [0038]    The diameter of pin  108  is selected optimally to fit the inner diameter of shaft  100  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. 
         [0039]    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. 
         [0040]    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 . 
         [0041]    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 . 
         [0042]    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. 
         [0043]    Housing  200  also includes a press-fit pin  210  to hold a twist to a spring  400  (see  FIG. 6 ). As shown in  FIGS. 5A-5C , pin  210  and hole  214  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  212   a  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. 
         [0044]    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. 
         [0045]    Coupler  200  also includes a pullback sleeve  202 . In an embodiment, pullback sleeve  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. Sleeve  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 . 
         [0046]    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  116 . 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 . 
         [0047]    As sleeve  202  moves in the direction away from club head  500 , locking pin  110  becomes clear of notch  212 . As this occurs, the twisting force of spring  400  causes sleeve  202  to rotate until pin  110  slides into channel  212   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 . 
         [0048]    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. 
         [0049]    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. 
         [0050]    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. 
         [0051]      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  1106  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. 
         [0052]    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. 
         [0053]    While the foregoing embodiments are acceptable in the vast majority of cases, the above-described issues with machine tolerances can result in slight movements between components of the coupler.  FIGS. 8A-8D ,  9 A- 9 J,  10 A- 10 F, and  11 A- 11 B are schematic diagrams illustrating a coupler that addresses such movements by modifying a grip end fitting and pullback sleeve of the coupler. 
         [0054]      FIGS. 8A-8D  are schematic illustrations of a pullback sleeve  800  according to an embodiment.  FIG. 8C  is a cross-sectional view of pullback sleeve  800  taken at line A-A in  FIG. 8B .  FIG. 8D  is a view looking down into pullback sleeve  800 . In an embodiment, pullback sleeve  800  having a top end  808  and a bottom end  812 . In an embodiment, top end  808  is closer to the handle end of the golf club than bottom end  812 . Pullback sleeve  800  includes a notch or slot  802 , a wall  804 , and a ramp  806 . In an embodiment, ramp  806  extends around a top end  808  of pullback sleeve  800  and ends at wall  804 . As illustrated in  FIGS. 8A and 8B , ridges  810   a ,  810   b ,  810   c , etc. are present in an outer surface of pullback sleeve  800 . Any desired number of ridges can be used in an embodiment. 
         [0055]      FIGS. 9A-9J  are schematic illustrations of a coupler body  900  according to an embodiment.  FIG. 9C  is a view looking down into coupler body  900 .  FIG. 9D  is a view looking up into the coupler body  900 .  FIG. 9F  is a cross-sectional view of coupler body  900  taken at line F-F in  FIG. 9B .  FIG. 9G  is a cross-sectional view of coupler body  900  taken at line G-G in  FIG. 9B .  FIG. 9H  is a cross-sectional view of coupler body  900  taken at line H-H in  FIG. 9B .  FIG. 9I  is expanded detail of “I” in  FIG. 9F .  FIG. 9J  is expanded detail of “J” in  FIG. 9F . A first set of ball bearings  904   a ,  904   b , and  904   c  is seated in holes  906 . A second set of ball bearings  902   a ,  902   b , and  902   c  is seated in holes  908 . For example, in an embodiment, ball bearing  902   a ,  902   b , and  902   c  correspond to ball bearings  1350  in  FIG. 7 , and ball bearing  904   a ,  904   b , and  904   c  correspond to ball bearings  1300  in  FIG. 7 . In an embodiment, coupler body  900  corresponds to coupler body  1202  in  FIG. 7 . 
         [0056]      FIGS. 10A-10F  are schematic illustrations of a grip end fitting  1000  according to an embodiment. Grip end fitting  1000  fits into the grip end or shaft  100  as a base for the coupler housing, such as the coupler of  FIG. 7 . Grip end fitting  1000  includes a hole  1002 . A post or pin  1004  (see  FIGS. 11A and 11B ) is inserted into hole  1002 . In an embodiment, such insertion is by press fitting pin or post  1004  into hole  1002 .  FIG. 10C  is a cross-sectional view of grip end fitting  1000  taken at line C-C in  FIG. 10B .  FIG. 10D  is a view looking down into grip end fitting  1000 .  FIG. 10E  is a cross-sectional view of grip end fitting  1000  taken at line E-E in  FIG. 10B .  FIG. 10F  is a cross-sectional view of grip end fitting  1000  taken at line F-F in  FIG. 10D . As shown in  FIGS. 10A ,  10 B, and  10 C, grip end fitting has a top end  1006  and a bottom end  1008 . In an embodiment, top end  1006  is positioned closer to the handle of a golf club. 
         [0057]      FIG. 11A  illustrates a coupler assembly  1100  in the loose condition according to an embodiment. In the loose condition, slot  802  allows for the pullback sleeve to be pulled back to insert an interchangeable club head.  FIG. 11B  illustrates a coupler assembly  1100  in a tightly coupled condition according to an embodiment. In an embodiment, section  1102  of coupler assembly  1100  is inserted in a lower shaft segment  1902  of the golf club described in  FIG. 12 . In an embodiment, coupler assembly  1100  is coupler  200  as described above with respect to  FIG. 3  or coupler  1200  as described above with respect to  FIG. 7 . 
         [0058]    No interchangeable club head is shown in  FIG. 11A  or  11 B. However, in operation, pullback sleeve  800  is pulled back (toward the right in  FIG. 11A ), post or pin  1004  moves into notch  802 , and an interchangeable club head is inserted as described above. Once inserted, the user releases pullback sleeve  800 , which moves pin  1004  out of slot  802 . To more tightly couple the coupler components, that is to transition from the configuration in  FIG. 11A  to  FIG. 11B , the user twists pullback sleeve  800  (counterclockwise in the illustration of  FIGS. 11A and 11B ), which causes pin or post  1004  to ride up ramp  806 . Eventually, the user will no longer be able to twist pullback sleeve  800  the due to the slope of the ramp and the coupler components being very tightly coupled. 
         [0059]    To uncouple a club head, the user twists pullback sleeve  800  (in the clockwise direction as shown in  FIGS. 11A and 11B ) such that the post travels down ramp  806 . Wall  804  stops the travel of post  1004  such that post  1004  is aligned with slot  802 . At this point, the user can pull back pullback sleeve  800  with post or pin  1004  moving into slot  802 , and removes the club head. 
         [0060]    The ramp angle of ramp  806  must be steep enough such that pin or post  1004  will ultimately make twisting pullback sleeve  800  difficult, that is, essentially stopping twisting, but not so steep that twisting pullback sleeve  800  is initially difficult. The ramp also should also prevent twisting prior to the twisting going all the way round to notch  802 . For example, a ramp angle can be chosen that will cause twisting of the pull back sleeve to become too difficult within 270 degrees of rotation. A ramp angle of 6 degrees has been found to be acceptable, and generally results in twisting becoming too difficult within a fairly short distance. Ramp angles may be different for different club head due to the length of shaft segment  102 . 
         [0061]      FIG. 12  illustrates a fully assembled golf club  1900  using two couplers. A first coupler  200  (or coupler  1200 ) couples interchangeable golf club heads to a golf shaft such as described above, and a second coupler  1900  an upper shaft segment  1904  having a grip  1926  to a lower shaft segment  1902 . Such a second coupler is described in U.S. patent application Ser. No. 14/142,739, filed Dec. 27, 2013, published Jul. 3, 2014 as U.S. Pub. No. 2014/0187342, entitled “Golf Club System with Golf Club Bag”, to Brady, which is hereby incorporated by reference in its entirety. In embodiment, coupler  1900  has a collar  1908  that is used to tighten the coupler  1900  to tightly couple the upper shaft segment  1904  and to lower shaft segment  1902 . In an embodiment, coupler  1900  is a screw-type coupler, and collar  1908  facilitates screwing one portion of coupler  1900  to the other. Such a collar  1908  is shown in  FIG. 13 . As shown in  FIG. 13 , collar  1908  has an aperture  1910 . 
         [0062]    Because some people may not have the strength to twist collar  1908  sufficiently to tightly couple the upper and lower shaft segments, a tightening tool can be employed to assist in tightening the coupler. An exemplary tightening tool  2002  is illustrated in  FIG. 14 . Tightening tool  2002  comprises a handle  2004  and a pin  2006 . In operation, pin  2004  fits into an aperture  1910  in collar  1908  as shown in  FIG. 13 . Handle  2004  provides leverage to allow coupler collar  1908  to be held in place while the upper shaft segment  1904  or lower shaft segment  1902  is rotated to tightly couple the upper and lower shaft segments. 
         [0063]    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. 
         [0064]    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.