Patent Application
20090270197
This invention is an extension for a putter shaft which uses spacers to provide different extension lengths and a system of pins to prevent unwanted loosening. The pins, spacers, and threaded attachment method are designed to make incorrect assembly virtually impossible. The extension is especially suitable for extending a conventional putter shaft so the putter can be used as a mid-length “belly” putter.
1. Description of Prior Art
Putting can be a frustrating part of a golfer's game and consequently golfers often try putters with different shaft lengths to improve this part of their game. Conventional length putters typically have overall lengths of 84 cm (33 inches) to 91 cm (36 inches) and are held only in the golfer's two hands. A putter with a longer overall length, typically 104 cm (41 inches) to 114 cm (45 inches), is commonly called a mid-length, or belly putter. The belly putter has a longer shaft than a conventional putter which enables the golfer to place the end of the shaft into his navel, thereby helping to stabilize the putter. Putters with even longer shafts are sometimes used in which the shaft end is placed in the golfer's sternum or even his chin, and these putters are commonly called long putters.
If a golfer has a conventional length putter but would like to try a longer putter, a belly putter for instance, this can be difficult and expensive. Belly putters are not commonly found in golf pro shops and smaller golf retailers, and therefore it is not easy to “demo” one to see if it is a fit for the golfer. Usually the golfer must purchase a belly putter, from an on-line retailer for instance, and they are typically more expensive than conventional putters. Also, there is no good way, apart from trying several putters, to determine a shaft length that is most suitable. If the golfer randomly chooses a length and orders that length, he may face purchasing one or more additional putters to obtain a suitable shaft length. In many cases, this expense and difficulty prevents golfers from trying belly putters. A putter shaft extension which could easily and inexpensively convert an existing putter into a belly putter or long putter and which could provide different extension lengths, would aid golfers in their effort to try these longer putters.
A consideration in any putter shaft extension, especially one that is adjustable, is acceptance by the United States Golf Association (USGA) as conforming to the rules of golf. One applicable USGA rule is that all adjustable parts must be firmly fixed and that there is no reasonable likelihood of them coming loose during play. Friction fit methods of adjustment are generally not permitted because they are not considered firmly fixed. Another important rule is that the adjustment cannot be readily made but must require the use of a special tool such as a screwdriver or Allen key. Another consideration which appears to be desirable to the USGA is that an assembly which can be installed or removed from a golf club has design features which make it virtually impossible for the user to install incorrectly. Several prior art patents appear to fall short of one or more of these rules.
2. Objects and Advantages
It is an object of this invention to provide an extension for a putter shaft which uses spacers to provide different extension lengths and pins to prevent accidental loosening.
It is a further object of this invention to provide an extension for a putter shaft which is virtually impossible to assemble incorrectly, helping insure its conformance with the rules of golf.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
The procedure for installing and using extension assembly 1 with a putter is as follows. First, hole 14 must be provided in putter grip 12. This can be done either with grip 12 installed on putter shaft 10, or it may be provided before grip 12 is installed on shaft 10. Then insert 16 is secured in shaft 10, preferably using a suitable adhesive such as epoxy, but other mechanical methods are possible such as a press fit. The product is preferably supplied to the user with dowel pin 22 already pressed and secured in hole 24 in extension handle 26. The projecting end of dowel pin 22 is inserted in clearance hole 20 of insert 16 and short screw 51 is started in threaded hole 18 and tightened, securing extension handle 26 to insert 16 and thus to putter shaft 10. If a longer extension is desired, such as that provided by assembly 2 or 3, screw 51 is removed, short spacer 41 or long spacer 42 is inserted between extension handle 26 and insert 16, dowel pins 22 are inserted into their respective clearance holes 20, and intermediate screw 52 is used to secure if short spacer 41 is used or long screw 53 is used if long spacer 43 is used.
Conformance with the rules of golf and acceptance by the USGA is an important consideration in this invention. As discussed above, it is desirable, therefore, to have a putter extension which not only can be assembled and used to conform to the rules of golf, but additionally has features which make it virtually impossible to assemble and use in a manner which is not conforming. Two aspects of this invention provide this explicit conformance while covering two important USGA rules.
As discussed in the prior art section, one rule is that any club with adjustable parts must have its parts firmly fixed with no reasonable likelihood of them working loose during a round of golf. Inventor has found that extension handle 26 with grip 28 can act like a “screwdriver handle” to inadvertently loosen screw 51, 52, or 53. Pin(s) 22, positioned off-axis, working with screws 51, 52, or 53, positioned axially, severely limit rotation of extension handle 26 relative to insert 16, thereby preventing this undesirable loosening of screw 51, 52, or 53.
Another rule is that when extension shaft assembly 1, 2, or 3 is installed, it must be straight with putter shaft 10; the axis of shaft 10 must be essentially collinear with the axis of assembly 1, 2, or 3. If any pin 22 of assemblies 1, 2, or 3 is not properly placed in its clearance hole 20, it would be a “bump” which would cause a misalignment when assembly 1, 2, or 3 was installed on shaft 10. Two features are incorporated in this invention to prevent assembly unless all pins of assemblies 1, 2, and 3 are properly engaged in their clearance holes 20, thereby preventing misalignment.
The first feature is the fact that hole 18 in insert 16 is shown as being only partially threaded; it is not completely threaded through insert 16 but has a limited full thread length. Screws 51, 52, and 53 used for this product typically come completely threaded, and therefore if hole 18 were totally threaded, long length screw 53 could tighten not only assembly 3, but also assemblies 1 and 2. But since hole 18 is only partially threaded, long screw 53 can only enter hole 18 a limited distance which is approximately the full thread length of hole 18. It can readily be seen that by choosing a full thread length for hole 18 which is only slightly longer than the thread engagement distance of screws 51, 52, and 53 when tightened in hole 18 in assemblies 1, 2, and 3 respectively, it is impossible to use the wrong screw in any of these assemblies. For instance, with the above limitations, if an attempt was made to use intermediate length screw 52 in short assembly 1, screw 52 would bottom in hole 18 before any tension existed in screw 52. Extension handle 26 would be noticeably loose and wobbly, rendering extension assembly 1 useless. Conversely, if an attempt was made to use short screw 51 in intermediate assembly 2, screw 51 would not be long enough to engage the threads in hole 18 and extension handle 26 could not be secured to insert 16. Therefore, by limiting the full thread length of hole 18, by partial threading for instance, it is possible to design assemblies 1, 2, and 3 so that the proper screw 51, 52, and 53 must be used with each assembly 1, 2, and 3 respectively. If short spacer 41 has a length of 2.5 mm (1 inch) and long spacer 43 has a length of 5 mm (2 inches), then intermediate screw 52 should be 2.5 mm (1 inch) longer than short length screw 51 and long length screw 53 should be 2.5 mm (1 inch) longer than intermediate length screw 52. If hole 18 has a full thread length of about 9 mm (0.35 inches) and screws 51, 52, and 53 in assemblies 1, 2 and 3 respectively have thread engagement distances of about 6 mm (0.25 inches), then the proper screw 51, 52, or 53 must be used in each assembly 1, 2, and 3.
Since the proper screw 51, 52, or 53 must be used in each assembly 1, 2, and 3, to insure that all pins used in assemblies 1, 2, and 3 engage their clearance holes 20 it is only necessary to make the insertion distance of all pins 22 into their respective clearance holes 20 greater than the thread engagement length of screws 51, 52, and 53 when tightened in hole 18. Then, if any pin 22 is not properly engaged in its clearance hole 20, screws 51, 52, and 53 cannot engage the threads of hole 18 and extension handle 26 cannot be fastened to insert 16. This therefore insures that an incorrectly positioned pin 22 cannot cause a misalignment of extension assembly 1, 2, or 3 with shaft 10.
Inventor believes a preferred way to transfer torque between adjacent members of these extension assemblies is by using dowel pin(s) 22 having one end secured in a press fit hole 24 in one member and having its other end inserted in a clearance hole 20 of its adjacent member. But
In summary, this invention is an extension for a putter shaft which, in its shortest version, is an extension handle attached to an insert secured in the grip end of a putter shaft. In a preferred embodiment, the extension uses an axial screw tightened in a partially threaded hole in the insert to force the extension handle against the insert. An off-axis pin, working cooperatively with the screw, prevents accidental loosening of the screw. Different extension lengths are obtained using appropriately longer screws and spacers placed between the extension handle and insert. Off-axis pins are also used with the spacers to prevent accidental loosening of these longer screws even with the spacers installed. The partially threaded hole in the insert requires the use of the proper screw for each length assembly. This, combined with sufficient pin projections from the members in which they are secured, makes assembly impossible unless all pins are properly engaged in their clearance holes. Therefore, the extension and putter shaft must be assembled correctly and the extension is straight with the putter shaft.
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments. For instance, the attachment screw is shown as being axial with the pins off-axis, but they could reverse positions, or both could be off-axis. An example is shown of a pinning projection which is a semicircular tab integrally machined into a member for engagement into an appropriately shaped clearance hole of its adjacent member, but other shapes are possible. Dowel pins are discussed as being preferably pressed into an appropriately under-sized hole, but a threaded stud secured in a threaded hole would also work. Two spacers could be stacked together to obtain an even longer overall extension length, and by using appropriate pins in both spacers, accidental loosing of the extension could still be prevented. Other modifications could be made which do not affect the essence of the invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
