Abstract:
The various embodiments of the invention are directed to a golf club head having an adjustable loft, wherein the loft angle is hydrodynamically locked during impact of the club head with the ball.

Description:
FIELD OF THE INVENTION 
     The present invention relates to golf clubs, and more particularly relates to a golf club head having an adjustable loft. 
     BACKGROUND OF THE INVENTION 
     In golf, clubs are used having varying loft angles to impart greater or lesser distance or height to the ball. Drivers having a slight angle from the vertical are used to drive the ball a great distance horizontally with a relatively flat trajectory. A putter with virtually no loft angle is used on the green itself. At intermediate distances, irons having varying loft angles measured from the vertical are used. Typically, larger loft angles are used for shorter distances. Most golfers use up to 14 clubs (limited by rule) with varying lofts at approximately four-degree increments. The need for multiple clubs creates a number of disadvantages, such as the high cost of a complete or partial set, and the need for transportation of a bulky and heavy set of clubs, both to and on the course. 
     A number of adjustable golf clubs have been developed with the object of reducing the number of clubs required. Many designs have used one or more sets of teeth or splines to key-in the various desired loft angles. Adjustable club heads using splined shafts are exemplified by U.S. Pat. Nos. 1,219,417 to Vories; 2,305,270 to Nilson; 1,429,569 to Craig; 2,571,970 to Verderber; 3,601,399 to Agens et al; and 4,878,666 to Hosoda. Clubs employing multiple toothed rings for vernier adjustment are exemplified by U.S. Pat. Nos. 2,882,053 to Lorthiois; and 3,840,231 and 5,538,245, both to Moore. A ratcheting vernier adjustment is taught in U.S. Pat. No. 5,133,553 to Divnick. Sealed containers having permeable elastomeric sheets sealed together and inflated with a gas having low permeability therethrough is taught in U.S. Pat. No. 4,287,250, to Rudy. The teachings of the patents cited above are entirely incorporated herein by reference. 
     As the impact of the club head with the ball generates large forces and torques acting in unpredictable directions, various auxiliary fastening devices such as nuts, screws and levers have been used to lock-up the head so that the loft angle does not accidentally change during use. These auxiliary devices are undesirable, as they detract from the enjoyment of the game. They are also prone to failure with repeated use, due to over or under tightening, and to contamination or corrosion. 
     It would be desirable for a club to be self-locking, so that no auxiliary devices would be needed. It would also be desirable that the concentration of the golfer not be broken by the need to make complicated adjustments to the club. And it would be most desirable that the loft angle be changeable in one continuous and smooth motion by the golfer. 
     SUMMARY OF THE INVENTION 
     The present invention provides a uniquely simple solution to the problems associated with adjustable golf clubs, and does so without requiring that the golfer remember arcane and complicated adjustment procedures. Rather, the instant invention provides a perfectly natural and aesthetically desirable look and feel for both the club and the adjustment thereof, while also enhancing the technical performance of the club. 
     An important feature of an adjustable club is that the loft angle, once set, does not change during use. First of all, if the equipment is not reliable, the player&#39;s lack of confidence can negatively effect his game, and secondly, a club head that moves under impact conditions can damage the adjustment mechanism, and ruin the club. In the present invention, the head, once set at the desired loft angle, is hydrodynamicly locked-up, and cannot move into an unlocked position due to the collision of the club with a ball. This lock-up is achieved automatically during impact conditions. 
     As golf is an aesthetic game, it is important that the head adjusts smoothly, substantially without noise or snap-back, and without requiring tools. It is also important that the adjustment is easily achieved without the need for calculation on the part of the golfer. 
     The present invention accomplishes the above and other objectives by dividing the working volume within the adjustable club head into at least three chambers: first and second chambers filled with an incompressible fluid, and a third chamber filled with a compressible fluid. 
     The working volume within the club head comprises a splined (toothed) pivot shaft which mates with a splined inner cylinder surface fixed within the adjustable club head. It is desirable that both the exterior splined surface of the pivot shaft and the interior splined surface of the cylinder are segmented, with gaps therebetween, so as to reduce the total axial motion required to de-couple the splines while providing sufficient tooth area to resist rotation. When not being adjusted, the splines are aligned so as to prevent relative rotation, and the pressure of the gaseous fluid within the third chamber maintains this coupled axial alignment. The third chamber pressurizes the second liquid filled chambers by means of a flexible diaphragm or floating piston therebetween. The first chamber is pressurized by means of a fluid conduit between the first and second chambers, so that, at rest, the pressures in all three chambers are equal (and above atmospheric). Most typically, all chambers are coaxial with the pivot shaft, with the second chamber between the first and third chambers. 
     The conduit between the first and second chambers restricts the rate of fluid flow between them. This results in a small pressure build-up within the first chamber relative to the second, resulting in a resistance and a smooth axial motion of the club head on the pivot shaft as the two are pressed together by the golfer during adjustment. During a stroke, while under impact conditions, the pressure build-up is much greater than it is during adjustment, and tends to resist axial motion and the resultant de-coupling of the splines. By way of example only, and not limitation, if one pound of force applied for one second is necessary to de-couple the splines during adjustment (this is the hydrodynamic force generated by fluid flow in the conduit only, and neglects the gas pressure in the third chamber, which must also be overcome), then, during an impact of the golf head with a ball lasting only one millisecond, a million pounds of force would be required to move the fluid through the conduit and thereby de-couple the splines. The force required is so much greater because the hydraulic force generated varies inversely with the square of the time period involved. If the impact period is three orders of magnitude smaller than the adjustment period, then the de-coupling force required will be six orders of magnitude greater. This force resisting de-coupling is so large that the head remains effectively locked-up during the brief period of impact. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above as well as other objects of the invention will become more apparent from the following detailed description of the preferred embodiments of the invention, when taken together with the accompanying drawings in which: 
     FIG. 1 is a cross-sectional exploded view of a pivot cartridge showing the various elements of one embodiment of the invention. 
     FIG. 2A is a cross-sectional view of an assembled pivot cartridge according to an embodiment of the invention, with the cartridge in the distal or engaged position. 
     FIG. 2B is a cross-sectional view of an assembled pivot cartridge as in FIG. 2A, with the cartridge in the proximal or disengaged position. 
     FIG. 3 is a cross-sectional view of an assembled adjustable head comprising a pivot cartridge according to a preferred embodiment of the invention, with the head in the distal position. 
     FIG. 4A is a partial cross-sectional view of an assembled adjustable head according to an alternative embodiment of the invention, wherein a fluid cell is substituted for the piston of FIG.  3 . 
     FIG. 4B is a partial cross-sectional view of an assembled adjustable head according to an alternative embodiment of the invention, wherein a diaphragm is substituted for the fluid cell of FIG.  4 A. 
     FIG. 4C is a partial cross-sectional view of an assembled adjustable head according to an alternative embodiment of the invention, wherein a spring is substituted for or supplements the compressed fluid of FIG.  3 . 
     FIG. 5 is a cross-sectional view of an assembled adjustable head according to an embodiment of the invention. 
     FIG. 6A is a partial cross-sectional view of an assembled adjustable head according to another embodiment of the invention, shown in the distal orientation, and wherein the hosel is integrated into the pivot shaft. 
     FIG. 6B is a partial cross-sectional view of the assembled adjustable head of FIG. 6A, shown in the proximal orientation. 
     FIG. 7 is a cross-sectional view of an assembled adjustable head according to another embodiment of the invention, with the head in the distal position. 
     FIG. 8 is a right side view of the adjustable head shown in FIG.  7 . 
    
    
     DESCRIPTION OF THE INVENTION 
     An exploded view of a pivot cartridge for insertion into an adjustable club head according to a preferred embodiment of the instant invention is shown generally as numeral  3  in FIG. 1, and the assembled pivot cartridge is shown in the engaged (distal) position generally as numeral  1  in FIG.  2 A and in the disengaged (proximal) position generally as numeral  1 ′ in FIG.  2 B. Referring now to FIGS. 1,  2 A,  2 B, the pivot shaft  11 , comprises a bearing surface  10  and a shaft extension  16 . A plurality of exterior spline (toothed) segments  12  are spaced apart by exterior gap segments  14 . A splined shaft  8  and threaded shaft extension  6  are provided for attachment with a hosel (not shown). The pivot shaft  11  mates with cylinder  30 , comprising a bearing surface  22 , having a diameter slightly larger than the diameter of the bearing surface  10  of the pivot shaft  11 . Interior spline segments  24  engage exterior spline segments  12  when in the engaged position illustrated in FIG. 2A. A bushing  31  has a bushing ID  33  for press fitting or otherwise attaching to shaft extension  16 , and a bushing OD  32 , slightly smaller than the diameter of the bearing surface  28  of the cylinder  30 , so that it may freely rotate and slide therein. A seal  18  fits into groove  20  of cylinder  30 , and prevents fluid leakage from between the mating bearing surfaces  22 ,  10 . Piston  60  having seal  64  fitting into groove  62  floats in bearing surface  28 . Tapered hole  66  is plugged by tapered pin  68 . Seal  17  fits in the groove  27  of the exterior surface of the cylinder  30 . 
     In FIG. 2A, chamber  100  constitutes the first chamber, which is filled with a substantially incompressible fluid. This incompressible fluid may be any liquid or gel; but oil or grease are preferred, due to the lubricating action and prevention of corrosion of the internal components of the cartridge. In FIG. 2A, the pivot cartridge  1  is in the engaged (distal) position, while the pivot cartridge  1 ′, shown in FIG. 2B, is in the disengaged (proximal) position. (“Distal” and “proximal” refer to the relative position of the club head with inserted pivot cartridge, to the hosel.) In FIG. 2B, fluid has been driven from the chamber  100  of FIG.  2 A through the engaged interior and exterior spline segments  24 ,  12 , which together constitute a restricted conduit, to chamber  102 . If the bushing OD  32  is larger or equal to the diameter of the bearing surface  10 , chamber  102  constitutes the second chamber. If the bushing OD  32  is smaller than the diameter of the bearing surface  10 , then fluid is also forced between the mating surfaces of the bushing OD  32  and the bearing surface  28  (a restricted conduit in series with the engaged interior and exterior spline segments) into chamber  106 , which then constitutes the second chamber. In moving between the distal to the proximal positions, the fluid pressure in the first chamber increases by an amount which is generally proportional to the square of the rate of movement, and this increased pressure acts to resist the motion of the pivot shaft  11  relative to the cylinder  30 . The primary purpose of chamber  106  is to provide volumetric compliance for the changing volume of the first chamber during motion. The first and second chambers and restricted conduit(s), i.e., the volume bounded by seals  18 ,  64 , may be filled with an incompressible fluid by immersing the assembled cartridge  1  (sans piston  60 ) in the fluid and drawing and releasing a vacuum. The piston  60  may then be inserted so that air escapes through tapered hole  66 , which is then sealed with tapered pin  68 . Other means such as screws may be used to seal the hole  66 , and the piston  60  may be also be installed under vacuum so that no hole is necessary. 
     Turning now to FIG. 3, the club head, generally indicated by numeral  200 , comprises the pivot cartridge  1 , shown inserted in the engaged or distal position into the club support  13 , which supports club face  7 . The pivot cartridge  1  is shown mounted to hosel  4  by means of nut  2 . Hosel  4  is the interface to handle shaft  5 , by which the club is gripped and swung. Chamber  104 , formed by the piston  60 , the bearing surface  28  and the blind hole  108 , is filled with a compressible fluid, preferably a gas or gas and liquid and/or gel mixture. This compressible fluid may be compressed and trapped during the installation of the pivot cartridge  1 , as it is preferably press-fit into the blind hole  108 . The compression of this fluid may be regulated by the position of the seal  17  along the cylinder  30 , with excess fluid vented by means of groove  109  until the seal  17  makes contact with the open end of the blind hole  108 , at which point further leakage is prevented. Knurled surface  23  is provided on the exterior of cylinder  30  to prevent rotation of the cylinder  30  within the blind hole  108 . A heavy press fit, adhesives, pins, keys or brazing may also be used to prevent rotation. Insertion is facilitated by the prior assembly of the pivot cartridge  1 . 
     Turning now to FIG. 4A, wherein the club head is generally indicated by numeral  201 , an alternative configuration of the third chamber containing the compressible fluid is shown as fluid cell  35 , which comprises a hollow flexible. Fluid cell  35  may comprise polymeric, elastomeric, rubber or other flexible materials resistant to the incompressible fluid and substantially impermeable to the compressible fluid. The fluid in the fluid cell  35  may be compressed during insertion of the pivot cartridge  1  in the same way as described above with reference to FIG.  3 . While the compressible fluid may consist entirely of air, or of gases such as nitrogen, oxygen, argon, methane, ethane, propane, butane, fluoroform, neo-pentane, and others, there are advantages that accrue from using gases having intrinsically low diffusion rates due to large size and symmetrical molecular shape. Use of such gases would be especially valuable when used within a fluid cell comprised of rubber, elastomer, or polymer. Such gases would include perfluoropentane, perfluorohexane, perfluoroheptane, octafluorocyclobutane, perfluorocyclobutane, hexafluoropropylene, tetrafluoromethane, monochloropentafluoroethane, 1,2-dichlorotetrafluoroethane; 1,1,2-trichloro-1,2,2 trifluoroethane, chlorotrifluorethylene, bromotrifluoromethane, and monochlorotrifluoromethane, hexafluoroethane, sulfur hexafluoride, perfluoropropane, perfluorobutane and mixtures thereof. If the fluid cell is filled with one of this group, and with a less than atmospheric partial pressure of nitrogen and oxygen (and preferably no nitrogen or oxygen), then any air that might leak into the club head and mix with the incompressible fluid would, over time, tend come into contact with the surface of the fluid cell  35  and would diffuse into the fluid cell, as the fluid cell composition may be altered to allow a slow rate of permeability for the atmospheric gases, while still preventing leakage of the inflatant gas. The fluid cell would thus act as a scavenger to rid the incompressible fluid of undesired compressible fluid, as the compressible fluid would undesirably tend to reduce the bias pressures generated during axial motion. For scavenging of air, the fluid cell inflatant gas should preferably have a permeability relative to the fluid cell of less than 0.1 times that of air, and preferably less than 0.01 times that of air. 
     In FIG. 4B, wherein the club head is generally indicated by numeral  202 , the fluid cell is replaced with a diaphragm  37  held in place with clamp  39 , forming the flexible side of chamber  104 . In practice, the diaphragm  37  operates in the same manner as the fluid cell  35 . Alternatively, a sealed metal bellows may be used, and the chamber would then be completely impermeable. 
     In FIG. 4C, wherein the club head is generally indicated by numeral  203 , the pressure supplied by the compressible fluid in the third chamber is partially or completely replaced by a spring  34 , operating on piston  60 . 
     Turning now to FIG. 5, the pivot shaft  11  is attached to hosel  4  by means of a press fit with smooth shaft  9 , which may also be welded to the hosel. The pivot shaft  11  is inserted into a through hole  110 , into which external spine segments  24  are directly formed. A piston  74  serves with end cap  72  to trap a compressible fluid. Extrusion of the end cap  72  is prevented by snap ring  70 . The club head is generally indicated by the number  205 . 
     In FIG. 6A, an alternative construction is shown wherein the hosel  4  is integrated with the pivot shaft. The club head  204  is shown in the distal or engaged position. In FIG. 6B, the club head  204  is shown in the proximal or disengaged position. This proximal position also facilitates the reading the loft angle by way of the indicia  90 . 
     Turing now to FIG. 7, yet another embodiment is shown wherein the chamber  111  acts as the first chamber, and is filled with an incompressible fluid. The motion of the plunger  76  into cup  78  as the club head  206  is moved from the distal to the proximal position drives fluid into the second chamber formed by the gap between piston  61  and cup  78 . In this case, the third chamber constitutes the volume between seal  64  and seal  18 , and is filled with a compressible fluid, which may comprise a gas, or gas and liquid and/or gel mixture. Hole  80  facilitates the insertion of the pivot cartridge by venting air during insertion. In FIG. 8, the right end view of the embodiment shown in FIG. 7 is illustrated, showing strike surface  40 . 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.