Patent Publication Number: US-9901795-B2

Title: Club length adjustment device

Description:
RELATED APPLICATIONS 
     The current application is a continuation-in-part of U.S. patent application Ser. No. 14/069,665, Club Length Adjustment Device, to Knutson, filed on Nov. 1, 2013, currently pending, the disclosure of which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present technology generally relates to systems, devices, and methods related to golf clubs, and more specifically to adjustable length golf clubs. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     One of the more important factors in golf club equipment is the club shaft. The shaft transfers the golfer&#39;s power to the club head. Golf club shafts are available in various types of materials and structures. Steel shafts can be stronger, last longer, more durable and generally less expensive than graphite or carbon fiber shafts, and are usually made from carbon steel, although stainless steel is sometimes used. The steel shafts are available in stepped or rifle designs. The graphite shafts can be more expensive and less durable; however, the lighter weight creates greater swing speed for more power. Also available are multi-material and titanium shafts. 
     When installing a shaft, the proper length must be accurately determined. The length can be as important to a golf shaft as is the flex or torque. Most measurements of the correct shaft length for the player involve a determination of a particular player&#39;s height and distance of his hands to the floor. Shaft length will impact whereon the clubface the ball will be consistently struck, and often, an incorrect shaft length is the main cause of a golfer to alter his natural swing arc in order to make optimum impact. According to most research, if ball impact is but one inch off-center this can equate to a 14% loss of carry distance, so it is vitally important that the length of the club be accurately fitted for each particular player. 
     If it is seen in the fitting process that a player needs to adjust his club length, such as adding or removing a half inch, inch or two inches to the length of the club, it would be highly desirable to lengthen his present club(s) rather buy and install new shafts. Typical driver shaft lengths are from 43 to 47 inches. 
     Prior art shafts having adjustable lengths have been used for many years for a wide variety of applications. Each of these applications has its own functional and aesthetic requirements for the shaft construction which is employed. As a consequence, a number of different mechanisms and devices have been developed to satisfy the particular application requirements. A majority of golf club shaft extension patents are directed to use mainly as putters, or to extending shafts of an existing set of clubs to accommodate growing children. 
     SUMMARY 
     The systems, methods, and devices described herein have innovative aspects, no single one of which is indispensable or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features will now be summarized. 
     One aspect of the present technology is the realization that existing golf club designs do not provide a convenient and hidden shaft length adjustment system. Thus, there exists a need for a rigid, secure, and easily adjustable club length adjustment system, which is hidden from view and does not require a custom grip. The present technology is directed to a golf club length adjustment device. The club length adjustment device provides the ability for a golfer to adjust the length of a golf club to suit their preference. 
     One non-limiting embodiment of the present technology includes a golf club length adjustment device for use in a golf club, comprising a first member affixed to a main shaft, said main shaft configured to couple to a golf club head; a second member slideably coupled to said first member, said second member adapted to couple to a golf club grip, said golf club grip including an internal cavity configured to receive a golf club shaft; wherein said first member is configured to slide relative to said second member to change the length of said golf club; wherein said first member and said second member are configured to limit rotation of said first member relative to said second member; a locking system configured to selectively limit said first member from sliding relative to said second member; wherein said locking system comprises a locked position and an unlocked position; wherein said locking system is configured to selectively lock said first member relative to said second member at each of a plurality of discrete golf club lengths; wherein said locking system comprises at least one locking member and a plurality of detents, wherein said locking member is configured to selectively engage at least one of said plurality of detents; wherein said locking system is hidden from view inside said golf club. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein at least a portion of said at least one locking member is deflectable and, wherein said at least one locking member, when in said unlocked position, is configured to partially engage at least one of said plurality of detents at each of said discrete golf club lengths creating a click. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said at least one locking member, when in said locked position, is configured to fully engage at least one of said plurality of detents and limit said first member from sliding relative to said second member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said at least one locking member comprises a protrusion configured to engage at least one of said plurality of detents, wherein said protrusion comprises a partial sphere shape. 
     Another non-limiting embodiment includes a golf club length adjustment device comprising an actuating member configured to force said at least one locking member into said locked position, wherein said actuating member comprises a tool receiving portion such that a user can adjust said actuating member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein rotation of said actuating member forces said at least one locking member into said locked position. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said plurality of detents are formed in said second member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said at least one locking member is formed integrally in said first member, wherein said first member comprises an actuating bore comprising an internal thread, wherein said actuating bore is configured to receive said actuating member, wherein said actuating member comprises a complimentary external thread, wherein said actuating member is configured to translate through said actuating bore via rotation of said actuating member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said actuating member comprises at least one tapered portion configured to engage said at least one locking member and force said locking member into said locked position. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said tool receiving portion of said actuating member is configured to receive a tool inserted through an access hole formed in a proximal portion of said golf club grip, wherein said golf club grip comprises a standard commercially available golf club grip. 
     Another non-limiting embodiment includes a golf club length adjustment device comprising a length indication system comprising a plurality of marking indicia on said main shaft configured to indicate said length of said golf club. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said first member comprises a first spline and said second member comprises a complimentary second spline, said first spline and said second spline configured to limit rotation of said first member relative to said second member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said first spline and said second spline comprise complementary clocking features configured to prevent said first member and said second member from being assembled at an incorrect relative angular orientation. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said clocking features comprise at least one enlarged spline recess and at least one enlarged spline protrusion. 
     Another non-limiting embodiment includes a golf club length adjustment device comprising a backout prevention member configured to limit said first member from uncoupling from said second member after said golf club length adjustment device has been assembled. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said second member comprises a receiving bore, wherein said second member is configured to receive at least a portion of said first member within said receiving bore of said second member. 
     Another non-limiting embodiment includes a golf club length adjustment device, wherein said club length adjustment device further comprises a hollow receiving shaft having an interior and an exterior, wherein said second member is affixed to said interior of said receiving shaft, wherein said exterior of said receiving shaft is configured to couple to said golf club grip, wherein said interior of said receiving shaft is configured to slideably receive a portion of said main shaft. 
     Another non-limiting embodiment includes a golf club length adjustment device for use in a golf club, comprising a first member affixed to a main shaft, said main shaft configured to couple to a golf club head; a second member slideably coupled to said first member, said second member adapted to couple to a golf club grip, said golf club grip including an internal cavity configured to receive a golf club shaft; wherein said first member is configured to slide relative to said second member to change the length of said golf club; wherein said first member and said second member are configured to limit rotation of said first member relative to said second member; a locking system configured to selectively limit said first member from sliding relative to said second member; wherein said locking system comprises a locked position and an unlocked position; wherein said locking system is configured to selectively lock said first member relative to said second member at each of a plurality of discrete golf club lengths; wherein said locking system is hidden from view inside said golf club; wherein said locking system is configured receive a tool inserted through an access hole formed in a proximal portion of said golf club grip, wherein rotation of said tool selectively locks and unlocks said locking system, wherein said golf club grip comprises a standard commercially available golf club grip. 
     Another non-limiting embodiment includes a method for adjusting the length of a golf club, comprising inserting a tool through an access hole formed in a proximal portion of a golf club grip; rotating said tool in a first direction to unlock a golf club length adjustment device hidden from view; sliding a main shaft of said golf club relative to said golf club grip towards one of a plurality of discrete golf club lengths, wherein said main shaft is configured to couple to a golf club head, wherein sliding of said main shaft relative to said golf club grip is at least partially inhibited when said golf club reaches each of said plurality of discrete golf club lengths; rotating said tool in a second direction, opposite said first direction, to lock said golf club length adjustment device once said golf club has reached said one of a plurality of discrete golf club lengths. 
     Another non-limiting embodiment of a method for adjusting the length of a golf club includes sliding a main shaft of said golf club relative to said golf club grip further comprises utilizing marking indicia on said main shaft of said golf club to reach a desired golf club length. 
     Another non-limiting embodiment includes a golf club length adjustment device for use in a golf club, comprising: a first member affixed to a main shaft, said main shaft configured to couple to a golf club head; a second member slideably coupled to said first member, said second member adapted to couple to a golf club grip, said golf club grip including an internal cavity configured to receive a golf club shaft; wherein said first member is configured to slide relative to said second member to change the length of said golf club; wherein said first member and said second member are configured to limit rotation of said first member relative to said second member; a locking system configured to selectively limit said first member from sliding relative to said second member; wherein said locking system comprises a locked position and an unlocked position; wherein said locking system is configured to selectively lock said first member relative to said second member at each of a plurality of discrete golf club lengths; wherein said locking system comprises at least one locking member and a plurality of detents, wherein said locking member is configured to selectively engage at least one of said plurality of detents; wherein said first member is formed of a first material having a first density; wherein said locking member is formed of a second material having a second density; wherein said locking system is hidden from view inside said golf club. 
     In another non-limiting embodiment, at least a portion of said at least one locking member is deflectable and, wherein said at least one locking member, when in said unlocked position, is configured to partially engage at least one of said plurality of detents at each of said discrete golf club lengths creating a click. 
     In another non-limiting embodiment, said at least one locking member, when in said locked position, is configured to fully engage at least one of said plurality of detents and limit said first member from sliding relative to said second member. 
     In another non-limiting embodiment, said at least one locking member comprises a protrusion configured to engage at least one of said plurality of detents, wherein said protrusion comprises a partial sphere shape. 
     Another non-limiting embodiment includes an actuating member configured to force said at least one locking member into said locked position, wherein said actuating member comprises a tool receiving portion such that a user can adjust said actuating member. 
     In another non-limiting embodiment, rotation of said actuating member forces said at least one locking member into said locked position. 
     In another non-limiting embodiment, said plurality of detents are formed in said second member. 
     In another non-limiting embodiment, said second member is formed from said first material. 
     In another non-limiting embodiment, said locking member is formed separately from said first member. 
     Another non-limiting embodiment includes a length indication system comprising a plurality of marking indicia on said main shaft configured to indicate said length of said golf club. 
     In another non-limiting embodiment, said first member comprises a first spline and said second member comprises a complimentary second spline, said first spline and said second spline configured to limit rotation of said first member relative to said second member. 
     In another non-limiting embodiment, said first spline and said second spline comprise complementary clocking features configured to prevent said first member and said second member from being assembled at an incorrect relative angular orientation. 
     In another non-limiting embodiment, said clocking features comprise at least one enlarged spline recess and at least one enlarged spline protrusion. 
     Another non-limiting embodiment includes a backout prevention member configured to limit said first member from uncoupling from said second member after said golf club length adjustment device has been assembled. 
     In another non-limiting embodiment, said backout prevention member is formed from said second material. 
     In another non-limiting embodiment, said second member comprises a receiving bore, wherein said second member is configured to receive at least a portion of said first member within said receiving bore of said second member, wherein said club length adjustment device further comprises a hollow receiving shaft having an interior and an exterior, wherein said second member is affixed to said interior of said receiving shaft, wherein said exterior of said receiving shaft is configured to couple to said golf club grip, wherein said interior of said receiving shaft is configured to slideably receive a portion of said main shaft. 
     In another non-limiting embodiment, said second density is greater than said first density. 
     Another non-limiting embodiment includes a golf club length adjustment device for use in a golf club, comprising: a first member affixed to a main shaft, said main shaft configured to couple to a golf club head; a second member slideably coupled to said first member, said second member adapted to couple to a golf club grip, said golf club grip including an internal cavity configured to receive a golf club shaft; wherein said first member is configured to slide relative to said second member to change the length of said golf club; wherein said first member and said second member are configured to limit rotation of said first member relative to said second member; a locking system configured to selectively limit said first member from sliding relative to said second member; wherein said locking system comprises a locked position and an unlocked position; wherein said locking system is configured to selectively lock said first member relative to said second member at each of a plurality of discrete golf club lengths; wherein said locking system comprises at least one locking member and a plurality of detents, wherein said locking member is configured to selectively engage at least one of said plurality of detents; wherein said first member is formed of a first material having a first density; wherein said locking member is formed of a second material having a second density; wherein said second density is greater than said first density. 
     Another non-limiting embodiment includes a second locking member, said second locking member formed integrally with said first locking member. 
     In another non-limiting embodiment, at least a portion of said locking member is deflectable, wherein at least a portion of said second locking member is deflectable, wherein said locking member is configured to deflect in a first direction, wherein said second locking member is configured to deflect in a second direction, wherein said first direction is substantially opposite said second direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings form a part of the specification and are to be read in conjunction therewith. The illustrated embodiments, however, are merely examples and are not intended to be limiting. Like reference numbers and designations in the various drawings indicate like elements. 
         FIG. 1  illustrates a perspective view of one embodiment of a club length adjustment device coupled to a grip. 
         FIG. 2A  illustrates a cross section view of the club length adjustment device of  FIG. 1  coupled to a grip. 
         FIG. 2B  illustrates a cross section view of a portion of the club length adjustment device of  FIG. 1  coupled to a grip. 
         FIG. 3  illustrates a cross section view of the club length adjustment device of  FIG. 1 . 
         FIG. 4A  illustrates a perspective view of one embodiment of a first member of the club length adjustment device. 
         FIG. 4B  illustrates a side view of the first member of  FIG. 4A . 
         FIG. 4C  illustrates an additional side view, rotated 90 degrees relative to  FIG. 4B , of the first member of  FIG. 4A . 
         FIG. 5  illustrates a perspective view of one embodiment of a second member of the club length adjustment device. 
         FIG. 6  illustrates a perspective view of an additional embodiment of a club length adjustment device. 
         FIG. 7  illustrates an additional perspective view of the club length adjustment device of  FIG. 6 . 
         FIG. 8  illustrates an exploded perspective view of the club length adjustment device of  FIG. 6 . 
         FIG. 9A  illustrates an exploded cross sectional view of the club length adjustment device of  FIG. 6 . 
         FIG. 9B  illustrates an additional exploded cross sectional view of the club length adjustment device of  FIG. 6 . 
         FIG. 10A  illustrates a cross sectional view of the club length adjustment device of  FIG. 6 . 
         FIG. 10B  illustrates an additional cross sectional view of the club length adjustment device of  FIG. 6 . 
         FIG. 11A  illustrates an end view of an embodiment of the second member of the club length adjustment device of  FIG. 6 . 
         FIG. 11B  illustrates a perspective view of the second member of  FIG. 11A . 
         FIG. 12A  illustrates a perspective view of an embodiment of the first member of the club length adjustment device of  FIG. 6 . 
         FIG. 12B  illustrates an additional perspective view of the first member of  FIG. 12A . 
         FIG. 13A  illustrates a side view of the first member of  FIG. 12A . 
         FIG. 13B  illustrates an additional side view of the first member of  FIG. 12A . 
         FIG. 14A  illustrates a cross sectional view of an additional embodiment of a club length adjustment device. 
         FIG. 14B  illustrates an additional cross sectional view of the club length adjustment device of  FIG. 14A . 
         FIG. 15A  illustrates a side view of the first member  100  of the club length adjustment device of  FIG. 14A . 
         FIG. 15B  illustrates an additional side view of the first member  100  of the club length adjustment device of  FIG. 14A . 
         FIG. 16A  illustrates a side view of an embodiment of the backout prevention unit of the club length adjustment device of  FIG. 14A . 
         FIG. 16B  illustrates a side view of an embodiment of the locking unit of the club length adjustment device of  FIG. 14A . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part of the present disclosure. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and form part of this disclosure. For example, a system or device may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, such a system or device may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. Alterations and further and further modifications of inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. 
     Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, moments of inertias, center of gravity locations, loft and draft angles, and others in the following portion of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used. 
     In describing the present technology, the following terminology may have been used: The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an item includes reference to one or more items. The term “plurality” refers to two or more of an item. The term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. A plurality of items may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same lists solely based on their presentation in a common group without indications to the contrary. Furthermore, where the terms “and” and “or” are used in conjunction with a list of items, they are to be interpreted broadly, in that any one or more of the listed items may be used alone or in combination with other listed items. The term “alternatively” refers to a selection of one of two or more alternatives, and is not intended to limit the selection of only those listed alternative or to only one of the listed alternatives at a time, unless the context clearly indicated otherwise. 
     Features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the illustrated features serve to explain certain principles of the present disclosure. 
     Embodiments described herein generally relate to systems, devices, and methods related to golf clubs. More specifically, some embodiments relate to a golf club length adjustment device  10 . 
       FIG. 1  illustrates a perspective view of one embodiment of a club length adjustment device  10  coupled to a grip  20 . In some embodiments, a golf club can include a club length adjustment device  10 . The club length adjustment device  10  can be at least partially hidden from view once the club has been assembled, advantageously allowing the golf club to appear just like a standard non-adjustable golf club. In some embodiments, the device can be completely hidden from view. As illustrated in  FIGS. 1 and 2 , the club length adjustment device  10  can be located at a proximal  30  portion of the golf club. “Proximal,” when used herein, is used to describe a portion of the golf club closer to the golfer when in use and “distal” is used to describe a portion of the golf club further from the golfer. The head of the golf club utilized to strike the ball, which is not illustrated, is located at the distal  40  end of the golf club, and more specifically at the distal  40  end of the main shaft  50  which has been abbreviated for clarity in  FIGS. 1 and 2 . The golf club head can be coupled to the distal  40  end of the main shaft  50  through a variety of techniques. 
     The length of the golf club, which is measured along the club axis  90  (illustrated in  FIG. 1 ), can be adjusted by sliding the main shaft  50  either towards or away from the grip  20 . In some embodiments, the club length adjustment device  10  can include a ferrule  60  located at the distal  40  end of the grip  20 . The ferrule  60  can serve a variety of purposes. The ferrule  60  can add to the strength of the club length adjustment device  10 , increasing rigidity and providing a solid feel for the golfer. The ferrule  60  can also aid in hiding portions of the club length adjustment device  10  from view. In some embodiments, the club length adjustment device  10  can include a club length indication system, indicating to the user the present length of the club. The main shaft  50  can include marking indicia  70 , as illustrated in  FIG. 1 , which when referenced against another part of the golf club, which may include the ferrule  60  for example, can help the user achieve the desired club length when adjusting the club length adjustment device  10 . In other embodiments, a different portion of the club such as the receiving shaft  80  or grip  20  can be used as a reference point. In some embodiments, the marking indicia  70  can include relative lengths which may include, for example, +2″, +1.5″, +1″, +0.5″, STD, −0.5″, −1″, −1.5″, −2″. Smaller or larger increments and/or smaller or larger ranges of adjustment can be included as well. Marking indicia  70  can be produced with paint, etching, laser marking, stickers, etc. 
     While the club length adjustment device  10  can be adjusted and manipulated by a golfer, it is also within the scope of this disclosure that the device can be manipulated by a technician assembling the club or a fitting expert modifying the club for the golfer. For purposes of this disclosure, golfers, technicians, fitting experts, etc., are referred to herein as users. 
       FIG. 2A  illustrates a cross section view of the club length adjustment device  10  of  FIG. 1  coupled to a grip  20 .  FIG. 2B  illustrates a cross section view of a portion of the club length adjustment device of  FIG. 1  coupled to a grip. In some embodiments, the club length adjustment device  10  can include a first member  100  and a second member  200 . The first member  100  can be affixed to a proximal  30  portion of a main shaft  50 . In some embodiments, the main shaft  50 , which is hollow, can receive at least a portion of the first member  100  within its interior. The exterior surface of the first member  100  can be affixed to the interior surface of the main shaft  50 . Affixing the first member  100  to the main shaft  50  can include, for example, bonding, welding, interference fitting, etc. A distal  40  portion of the main shaft  50 , the end opposite the first member  100 , can be coupled to a golf club head. 
     The second member  200  can be coupled to the grip  20 . In some embodiments, the club length adjustment device  10  can couple to a standard commercially available golf club grip  20 , minimizing costs. The club length adjustment device  10  can comprises a hollow receiving shaft  80  having an interior and an exterior. The second member  200  can be affixed within the interior of the receiving shaft  80  and the exterior of the receiving shaft  80  can be dimensioned to receive the grip  20 . In some embodiments, the second member  200  can be affixed to a proximal  30  portion of the receiving shaft  80 . The exterior of the receiving shaft  80  can be configured to receive tape on an exterior surface, just like a standard shaft, before the grip  20  is installed, aiding in coupling the grip  20  to the club length adjustment device  10  and allowing the diameter of the grip  20  to be customized to a golfer&#39;s preference. 
     In some embodiments, the receiving shaft  80  can be dimensioned to be substantially the same length as a standard golf grip  20 . In other embodiments, and as illustrated in  FIG. 2A , the receiving shaft  80  can extend distally beyond the distal  40  end of the grip  20  once installed in the grip  20 . In such embodiments, as illustrated in  FIG. 1 , a ferrule  60  can be affixed to the exterior of the distal  40  end of the receiving shaft  80 . In some embodiments, in order to further strengthen the distal  40  end of the receiving shaft  80 , the receiving shaft  80  can include a reinforcing ring bonded to the end of the receiving shaft  80 . The reinforcing ring can increase the hoop strength at the end of the receiving shaft  80 , helping to reduce the chances of failure due to the bending moment caused by each swing of the club. The reinforcing ring can comprise a contrasting color to the main shaft  50 , aiding in reading the marking indicia  70 . In some embodiments, the reinforcing ring can be composed of titanium. 
     In some embodiments, the first member  100  can be slideably coupled to the second member  200  such that the first member  100  can slide relative to the second member  200  to change the length of the golf club and thus change the distance between the grip  20  and the golf club head. The receiving shaft  80  can be dimensioned to slideably receive a proximal  30  portion of the main shaft  50  and the first member  100 . In some embodiments, the main shaft  50  can slide within a distal  40  portion of the receiving shaft  80 . The second member  200  can include a receiving bore  210  dimensioned to receive at least a portion of the first member  100 . 
     In some embodiments, the club length adjustment system can include a locking system  300 . The locking system  300  can selectively limit the first member  100  from sliding relative to the second member  200 , and thus the main shaft  50  relative to the grip  20 . The locking system  300  can include a locked position and an unlocked position. The club length adjustment system can include an actuating member  400 . The actuating member  400  can force the locking system  300  from an unlocked position to a locked position. The actuating member  400  can include a tool receiving portion. The tool receiving portion can be located at the proximal  30  end of the actuating member  400 . The grip  20 , as is the case with most standard grips, can include an access hole  22  at the proximal  30  end. As illustrated in  FIG. 2B , a tool  500  can be inserted through the access hole  22  to engage the tool receiving portion of the actuating member  400  to manipulate the actuating member  400  and to lock or unlock the locking system  300 . In some embodiments, the actuating member  400  can be hidden from view once the club length adjustment device  10  is assembled. In some embodiments, the length of a golf club including the club length adjustment device can be adjusted without the addition or removal of any spacers or additional materials. In some embodiments, the only elements, in addition to the club itself, necessary to adjust the length of the club is a tool and the hands of the user. 
       FIG. 3  illustrates a cross section view of the club length adjustment device  10  of  FIG. 1 .  FIG. 3  does not illustrate the main shaft  50 , grip  20 , or receiving shaft  80 .  FIG. 4A  illustrates a perspective view of one embodiment of a first member  100  of the club length adjustment device  10 .  FIG. 4B  illustrates a side view of the first member  100  of  FIG. 4A .  FIG. 4C  illustrates an additional side view, rotated 90 degrees relative to  FIG. 4B , of the first member  100  of  FIG. 4A .  FIG. 5  illustrates a perspective view of one embodiment of a second member  200  of the club length adjustment device  10 . 
     In some embodiments, the locking system  300  can selectively lock the first member  100  relative to the second member  200  at each of a plurality of discrete golf club lengths. Discrete golf club lengths can be advantageous, allowing a user to replicate or choose a desired golf club length quickly and easily. In some embodiments, as illustrated in  FIGS. 3 and 5 , the locking system  300  can include a plurality of detents  330  formed in the second member  200 . The detents  330  can comprise apertures formed through the sidewall of the second member  200 . In other embodiments, the detents  330  can comprise indentations or cavities formed in the second member  200 . The detents  330  can be dimensioned to receive the locking member  310  and limit the first member  100  from sliding relative to the second member  200 . The plurality of detents  330  can be spaced down the length of the second member  200 , providing a plurality of discrete points at which to lock the locking system  300  and thus set the length of the golf club. In some embodiments, as illustrated in  FIG. 3 , the second member  200  can include a plurality of detents  330  at each discrete club length, allowing for multiple locking members  310  to engage multiple detents  330  at each discrete club length. 
     In some embodiments, the locking system  300  can include at least one locking member  310  moveably attached to the first member  100 . The locking member  310  can be adapted to engage the detents  330  of the second member  200  and limit movement between the first member  100  and second member  200 . In some embodiments, as illustrated in  FIGS. 3, 4A, and 4B , the at least one locking member  310  can be formed integrally in the first member  100 . The locking member  310  can include a protrusion  320  dimensioned to engage at least one of the plurality of detents  330  in the second member  200 . In some embodiments, the protrusion  320  can be partial sphere shaped. In other embodiments, the protrusion  320  may include other shapes. In some embodiments, at least a portion of the locking member  310  can be deflectable. The locking member  310  can deflect from an unlocked position to a locked position. In some embodiments, the default position of the locking member  310  is an unlocked position. The locking member  310  can be dimensioned such that in an unlocked position, the locking member  310  will partially engage at least one of the plurality of detents  330  at each of the discrete golf club lengths. When the locking member  310  partially engages a detent  330 , the protrusion  320  extends partially into the detent  330 , offering some resistance to moving the first member  100  relative to the second member  200 , but not locking the first member  100  relative to the second member  200 . In addition, when the locking member  310  reaches a detent  330  at each of the discrete golf club lengths, the locking member  310  partially engaging the detent  330  can produce a click. In some embodiments, the click can be audible to the user, indicating that they have reached a discrete golf club length. In some embodiments, the click can produce resistance to movement, offering a tactile feel for the user indicating that they have reached a discrete golf club length. In some embodiments, the click can be both audible and tactile. Once the user has reached a discrete golf club length and confirmed that the particular length is the preferred length, they can lock the locking system  300 , moving the locking member  310  into a locked position, wherein the locking member  310  fully engages the detent  330 , and the protrusion  320  is fully seated within the detent  330 , limiting movement between the first member  100  and second member  200 , and locking the club at the desired club length. In some embodiments, the locking member  310  can be hidden from view once the club length adjustment device  10  is assembled. 
     As illustrated in  FIG. 3 , the first member  100  can include an actuating bore  410  dimensioned to receive an actuating member  400 . The actuating bore  410  can include an internal thread. The actuating member  400 , illustrated in  FIGS. 2A and 2B , can include a complementary external thread, such that rotation of the actuating member  400  within the actuating bore  410  causes the actuating member  400  to translate along the club axis  90 . The actuating member  400 , along with the first and second member  200 , can be hidden from view underneath the grip  20 , yet still be manipulated by the user via a tool  500  as illustrated in  FIG. 2B . As described above the tool  500  can be inserted through the access hole  22  in the proximal  30  end of the grip  20 . Rotating of the actuation member via the tool  500  in a first direction can cause the actuating member  400  to translate proximally. Rotating the actuation member in a second direction, opposite the first direction, can cause the actuating member  400  to translate distally. The actuating member  400  can include a tapered surface adapted to engage the at least one locking member  310 . When the actuating member  400  is rotated in a second direction and translates distally, the tapered surface can engage the at least one locking member  310  and lock the locking system  300  by forcing the at least one locking member  310  outwards in a direction substantially perpendicular to the club axis  90 , forcing the locking member  310  to deflect and engage at least one of the plurality of detents  330  formed in the second member  200 . In some embodiments, the club length adjustment system can include a torque limiting tool configured to provide the optimal amount of torque in the second direction when locking the locking system  300 . 
     In an alternative embodiment, which is not illustrated, the actuating member  400  can comprise a cam which displaces the locking member  310  through rotation of the actuating member  400  and without translation of the actuation member. The actuating member cam can rotate over center, maintaining the actuating member cam in a locked position until the user rotates the cam back into the unlocked position. 
     In some embodiments, as illustrated in  FIG. 4C , the locking member  310  can be formed integrally to the first member  100  through a machining process. Material can be removed from the first member  100  to produce a beam like structure. In some embodiments, material may be removed from the first member  100  forming a “U” shaped cavity surrounding the locking member  310 . In addition, material can be removed from the portion of the locking member  310  furthest from the club axis  90  to provide the desired locking characteristics as well as the desired click discussed above. The protrusion  320  of the locking member  310  can be machined or can be added later via fastening, welding, bonding, etc. In other embodiments, the locking member  310 , rather than being constructed integrally with the first member  100 , can comprise a moveable member configured to travel substantially perpendicular to the club axis  90  relative to the first member  100  to engage the second member  200  when the user rotates the tool and locks the locking mechanism (not illustrated). 
     In some embodiments, the club length adjustment device  10  can limit the rotation of the first member  100  relative to the second member  200 , and thus rotation of the main shaft  50  and club head relative to the grip  20 . The club length adjustment device  10  can incorporate splines to prevent rotation about the club axis  90  but allow for sliding along the club axis  90  between the first member  100  and second member  200 . In some embodiments, the first member  100  can include a first spline and the second member  200  can incorporate a complimentary second spline. The first member  100  can be dimensioned to slide within the second member  200  and thus incorporate a male spline  130 . The second member  200  can be dimensioned to receive the first member  100  and thus incorporate a female spline  230 . Each spline includes complementary spline protrusions and recesses which can slide within one another, but the splines prevent angular rotation between the first member  100  and second member  200 . 
     Most splines allow for a plurality of rotational positions between two members during assembly. In order for the locking system  300  to operate correctly, it can be necessary for the first member  100  and second member  200  to be slideably coupled at a particular angular orientation. In the example of the of the embodiment illustrated in  FIG. 3 , the first member  100  incorporate two locking members  310  and thus there are two angular orientations at which the first member  100  and second member  200  can be assembled and still function properly, each separated 180 degrees from one another. In order to ensure the first member  100  and second member  200  are assembled at the correct orientation, the first member  100  and second member  200  can each include complementary clocking features. In one embodiment, as illustrated in the figures, the male spline  130  can include at least one enlarged spline protrusion  132  and the female spline  230  can incorporate at least one complementary enlarged spline recess  232  to receive the at least one enlarged spline protrusion  132 . 
     It can be preferable to prevent the first member  100  from being uncoupled from the second member  200  once the club length adjustment device  10  has been assembled. Thus, in some embodiments, the club length adjustment device  10  can include at least one backout prevention member  110 . The backout prevention member  110  can limit the first member  100  from sliding out of the second member  200 , even when the locking system  300  is unlocked. In some embodiments, the backout prevention member  110  can be formed integrally with the first member  100 . The backout prevention member  110  can allow the first member  100  to pass a certain point during assembly, but prevent the first member  100  from travelling back past that point in the opposite direction. In some embodiments, including those illustrated in the figures, the backout prevention member  110  can include a backout protrusion  120 . The backout protrusion  120  can include a proximal surface  122  which is ramped and a distal surface  124  which is substantially vertical. At least a portion of the backout prevention member  110  can be deflectable such that when the first member  100  is assembled into the second member  200  the ramped proximal surface  122  engages an enlarged portion of the second member  200 , which may include for example, at least one protrusion of the female spline  230 , the backout prevention member  110  deflects to allow the first member  100  to slide within the receiving bore  210  of the second member  200  until the backout protrusion  120  clears the enlarged portion and the backout prevention member  110  returns towards its original position. If the first member  100  is pulled distally away from the second member  200 , the substantially vertical distal surface  124  will interfere with the enlarged portion of the second member  200 , preventing the first member  100  from sliding any further distally. In some embodiments, the proximal surface  122  can be curved to complement the curved inner surface of the second member  200 . The second member  200  illustrated in  FIGS. 3 and 5  include an access port  220  to allow for the insertion of a tool to deflect the backout prevention member  110  and disassembly of the club length adjustment device  10 . The access port  220  is not necessarily required for the club length adjustment device  10  to operate. 
     In some embodiments, as illustrated in  FIG. 4C , the backout prevention member  110  can be formed integrally to the first member  100  through a machining process. Material can be removed from the first member  100  to produce a beam like structure. In some embodiments, material may be removed from the first member  100  forming a “U” shaped cavity surrounding the backout prevention member  110 . In addition, material can be removed from the backout prevention member  110  to form the backout protrusion  120 . In other embodiments, the backout protrusion  120  can be affixed to the backout prevention member  110  via fastening, welding, bonding, etc. In other embodiments, the backout prevention member  110  can be formed separately from the first member  100  and include a resilient member configured to force the backout protrusion  120  in a direction substantially perpendicular to and away from the club axis  90 . In some embodiments, the clocking feature on the first member  100  can extend further proximally along the first member  100  than at least a portion of the backout protrusion  120  such that the first member  100  can be clocked at the correct angular orientation relative to the second member  200  prior to the backout protrusion  120  from engaging the second member  200 . In other embodiments, the backout protrusion  120  can engage the second member  200  prior to the clocking feature of the first member  100 . In other embodiments, the backout prevention member  110  and locking member  310  can be combined, wherein a single member performs the function of both the backout prevention member  110  and locking member  310  described above. 
     Various portions of the club length adjustment device  10  can be manufactured from a variety of materials which may include for example, titanium, aluminum, steel, plastic, graphite, composites, etc. Various portions of the club length adjustment device  10  can be manufactured using a variety of methods which may include for example, casting, machining, rapid prototyping, laser sintering, laser cutting, etc. 
     In order to maintain the weight of a more conventional golf club it can be preferable to make the club length adjustment device as light as possible.  FIG. 6  illustrates a perspective view of an additional embodiment of a club length adjustment device  10 .  FIG. 7  illustrates an additional perspective view of the club length adjustment device  10  of  FIG. 6 .  FIG. 8  illustrates an exploded perspective view of the club length adjustment device  10  of  FIG. 6 .  FIG. 9A  illustrates an exploded cross sectional view of the club length adjustment device  10  of  FIG. 6 .  FIG. 9B  illustrates an additional exploded cross sectional view of the club length adjustment device  10  of  FIG. 6 .  FIG. 10A  illustrates a cross sectional view of the club length adjustment device  10  of  FIG. 6 .  FIG. 10B  illustrates an additional cross sectional view of the club length adjustment device  10  of  FIG. 6 .  FIG. 11A  illustrates an end view of an embodiment of the second member  200  of the club length adjustment device of  FIG. 6 .  FIG. 11B  illustrates a perspective view of the second member  200  of  FIG. 11A .  FIG. 12A  illustrates a perspective view of an embodiment of the first member  100  of the club length adjustment device of  FIG. 6 .  FIG. 12B  illustrates an additional perspective view of the first member  100  of  FIG. 12A .  FIG. 13A  illustrates a side view of the first member  100  of  FIG. 12A .  FIG. 13B  illustrates an additional side view of the first member  100  of  FIG. 12A . 
     The embodiment of the club length adjustment device  10  and components illustrated in  FIGS. 6-13  are configured to weigh as little as possible. As illustrated, the club length adjustment device  10  and components illustrated in  FIGS. 6-13  are similar to those illustrated in  FIGS. 1-5  and operate similarly, but weigh less through the new and innovative configuration illustrated. Key differences included in the embodiments illustrated in  FIGS. 7-13  include the locking members  310  and backout prevention members  210  located adjacent one another in the first member  100 . This shortens the necessary length of the first member  100 , reducing the weight of the first member  100 . Additionally, the plurality of detents  330  formed in the second member  200  are directly adjacent one another such that when the locking system  300  is adjusted to a locked position, the protrusion  320  of the locking member is forced into one of said plurality of detents  330 , rather than having the ability to press against the inside of said second member without locking into one of said plurality of detents  330 . This ensures a positive locking experience for the user and no chance of the club changing length after the locking system  300  is adjusted to a locked position. 
     An additional requirement for a golf club length adjustment device is durability.  FIG. 14A  illustrates a cross sectional view of an additional embodiment of a club length adjustment device  10 .  FIG. 14B  illustrates an additional cross sectional view of the club length adjustment device  10  of  FIG. 14A .  FIG. 15A  illustrates a side view of the first member  100  of the club length adjustment device  10  of  FIG. 14A .  FIG. 15B  illustrates an additional side view of the first member  100  of the club length adjustment device  10  of  FIG. 14A .  FIG. 16A  illustrates a side view of an embodiment of the backout prevention unit  710  of the club length adjustment device  10  of  FIG. 14A .  FIG. 16B  illustrates a side view of an embodiment of the locking unit  810  of the club length adjustment device  10  of  FIG. 14A . 
     The embodiment of the club length adjustment device  10  and components illustrated in  FIGS. 7-13  are configured to weigh as little as possible while maintaining a high level of durability over time. This means the club length adjustment device  10  operates consistently and successfully, even after being locked and unlocked multiple times and after striking golf balls multiple times. Materials that are strong and durable generally have a relatively high density, and thus contribute to a higher weight component. Additionally, materials that are strong yet have a low density are generally cost prohibitive. 
     The club length adjustment device  10  of  FIGS. 14-16  utilizes multiple materials to ensure a lightweight and durable construction. The first member  100  includes at least one backout prevention window  500 . Additionally, the first member  100  includes at least one locking window  600 . The club length adjustment device  10  includes a backout prevention unit  700  formed separately from said first member  100 . The club length adjustment device  10  also includes a locking unit  800  formed separately from said first member  100 . The backout prevention unit  700  includes a first backout prevention member  110  having a backout protrusion  120  and a second backout prevention member  111  having a second backout protrusion  121  connected by a backout prevention bridge member  710 . The locking unit  800  includes a first locking member  310  having a first protrusion  320  and a second locking member  311  having a second protrusion  321  connected by a locking bridge member  810 . The backout prevention window  500  is configured to receive the backout prevention unit  700  as illustrated in  FIG. 14A . Additionally, the locking window  600  is configured to receive the locking unit  800  as illustrated in  FIG. 14B . 
     This construction allows the backout prevention members  110 ,  111  and locking member  310 ,  311  to be made of different materials than the rest of the club length adjustment device  10  as the backout prevention members  110 ,  111  and locking members  310 ,  311  are generally required to have a higher strength than the first member  100  or second member  200 , for example, due to these portions of the device having to deflect during the life of the club. Once the backout prevention unit  700  and locking unit  800  are installed in the first member  100  and the first member  100  installed in the second member  200 , the backout prevention unit  700  and locking unit  800  are restricted from exiting their locations in the club length adjustment device  10  by the second member  200 , and in some embodiments, the actuating member  400 . 
     In some embodiments, the first member  100  can be formed from a first material and the locking members  310 ,  311  can be formed from a second material. The second material can have a higher density than the first material. The second material can have a higher strength than the first material. The second material can have a higher surface hardness than the first material. The second material can have a higher stiffness than the first material. The first material could include, for example, aluminum, plastic, etc. The second material could include, for example, titanium, steel, etc. In some embodiments, the second member  200  could be formed from the first material. In some embodiments, the backout prevention members  110 ,  111  could be formed from the second material. 
     In some embodiments, a golf club incorporating the club length adjustment device  10  described herein could weigh the same as a conventional, non-length adjustable golf club. One way to achieve this goal is by having a lightweight grip. A traditional grip can weight approximately 50 to 52 grams and a lightweight grip can weight approximately 27-32 grams. Therefore, in order for the adjustable club with a light weight grip to weigh the same as a traditional club with a traditional grip, the club length adjustment device  10  and related components can only add approximately 18 to 25 grams to the golf club construction. That is why the lightweight embodiments of the club length adjustment device  10  described herein are so crucial to bringing a length adjustable golf club to market. 
     In describing the present technology herein, certain features that are described in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable sub combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub combination or variation of a sub combination. 
     Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure as well as the principle and novel features disclosed herein.