Abstract:
The invention relates to an interchangeable part of a golf putter, as well as the golf putter head comprising the interchangeable part. The interchangeable part including the putter striking surface being constituted by a band shaped material being mounted on a tension bar providing a chosen and prefixed tension to the band material at the striking surface. 
     The band-shaped material constitutes a loop and the tension bar is provided at least partially inside the band shaped material thus being adapted to apply a tension to the band, the tension bar also includes protrusions on each side of the striking surface thus defining a recess behind the band at the striking surface, and the putter head comprises holding means for receiving the stretched band and tension bar and locking them into position in the putter head.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a golf putter head comprising an interchangeable part such as a cassette including the putter striking surface being constituted by a band shaped material being mounted on a tension bar providing a chosen tension to the band material at the striking surface. 
     2. Description of the Related Art 
     When using a putter (to put a golf ball) on a putting green, the golfer strikes the ball applying a roll-spin to the ball as soon as possible after stroke of putter in order to move the golf ball along a desired (and a more predictable) path and length. When a golf ball is to be putted into the intended hole it is important that the ball follow an expected-desired path and length. The conformity between expected and actual length and path of a put is vital. In this connection, the aim is normally to give the ball an even rolling movement over the surface, i.e. with rolling contact with the grass on the green, and preferably without causing the ball to jump unintentionally in initial phase after impact of the putter on the grass. 
     According to this invention, the aim is to give the golf ball an intentional roll as soon as the stroke is played. It is also important to transfer as much as possible of the kinetic energy from putter to the ball to obtain a more predictable length of ball roll. 
     In other words, it is desirable—at least with certain putting strokes—to transfer a large part of the kinetic energy from the golf club to the golf ball thereby causing the ball to take on a rolling movement, i.e. instead of applying a non-rolling stroke to the ball, a stroke is played which gives the ball a combined thrust and rolling movement. Using conventional golf clubs the golf ball is given an intentional roll of this kind by, for example, by holding the strike area of the putter at an appropriately oblique angle. 
     Alternatively, the putter can “top” the golf ball by striking it at a level above its the horizontal mid-plane. The strike area of the putter normally has a vertical position when the putter is in a normal vertical position in connection with a putting stroke. But by having the strike area at an oblique angle in relation to the vertical plane one may deliberately seek to create great friction between the golf ball and the grass of the green already in the very first phase of the ball&#39;s rolling movement as a result of the obliquely angled stroke played against the golf ball. The better less energy loss in energy transition from putter to movement of the ball, will give a more and better prediction both in length and path of the ball in relation to aim/hole. 
     Consequently, the aim is to apply as controlled a roll as possible to the golf ball at an early stage in the movement of the golf ball. In practice, however, in many cases the point at which the roll starts after the stroke has been played is a matter of chance, and also the degree of roll, since after being struck by the golf club the golf ball, in certain cases, may be given a rapid upward lifting movement from the underlying surface and may therefore make a subsequent soaring movement in relation to the underlying surface. Thus, the golf ball is given a limited or more or less uncontrollable roll. Until now, the position of the strike area of the putter in relation to the golf ball has been very decisive for the movement of the golf ball in relation to the underlying surface. However, local conditions (humidity/dampness, unevenness etc.) on the green affect, to a varying degree, the friction of the golf ball and thereby its speed of movement and pattern of movement, including the roll movement and the speed of the roll. When the player&#39;s putter stroke meets the golf ball in an area above the horizontal mid-plane of the ball, the golf ball may experience an element of downward force in the direction of the grass on the green, with the result that one achieves intentionally greater friction and an intentional roll on the golf ball at an early stage of the stroke, thereby allowing the ball to roll in an intentional spinning plane and obtaining the gyro effect. 
     Further, when the player places the strike area of the putter at an oblique angle upwards and forward, it is possible, by applying this intentional initial friction against the grass, to ensure that a controlled pattern of movement of the golf ball is achieved in more or less continuous contact with the grass during the rolling movement. 
     On the other hand, if, for example, the player places the strike area of the putter at an oblique angle upwards and backward, it is possible to give the golf ball an intentional soaring or jumping movement, in cases where this is desired. Using this invention, the aim is to arrive at a solution whereby the putter can give the golf ball a relatively soft and sensitive stroke whereby the gyro effect is obtained as soon as possible after impact and more of the force from the putter is transmitted to the ball at an early stage after the stroke. This give a more predictable length of roll and direction of the the balls movement. The level of power transferred is adjustable and where the putter, in this connection, can easily give the golf ball the exactly desired movement by giving it the intended roll and the desired gyro effect. The aim is to ensure that the intended roll movement of the golf ball can be effected directly from the strike area of the putter, i.e. at an early stage in the  1 . stroke of the putter against the actual golf ball and with easy and sensitive control of the stroke and to overcome the inertia force of the ball. 
     International patent application No. PCT/NO99/00314 describes a golf club in which this problem is solved by arranging the strike area of the putter in such a way that an interchangeable/replaceable longitudinal, lengthwise extended tension bar is attached to two fastening points at each end of the putter head through the two opposite ends of the tension bar, and with the lengthwise tension bar, attached through the two opposite ends, stretching freely over a hollow in the putter head. Using the lengthwise extended tension bar, which extends freely over a hollow in the putter head, it is possible to achieve some softening of the putter stroke against the golf ball and at the same time have the possibility of giving an initial roll to the golf ball immediately on striking the ball. 
     This solution is, however, complicated and is not easily adjusted to specified tensions in the band. If the band is stretched it may lose its tension, depending on the material used, and it is impossible to apply further tension later. Also, in the above mentioned application the size and shape of the striking area is fixed, as the hollow behind the band at the striking area is defined by the opposite ends of the tension bar. Also, it is not possible to have the putter accepted for use in competitions as the striking surface will be too flexible. 
     U.S. Pat. No. 5,643,109 describes a putter head having a striking surface being constituted by a band loop and being adjustable in the back using a screw mechanism. The band material is not mentioned but it is said to be flexible and is probably a fibre material or similar. The putter head also comprises a recess behind the band and the putter head. 
     The solution according to U.S. Pat. No. 5,643,109 in which the striking surface is flexible and not hard and rigid, as demanded by the golf rules according to R&amp;A and USGA. Also, the solution does not conform with the rules of golf in being adjustable during use. 
     It is therefore an object of this invention to provide a golf putter head which may be allowable according to the rules of golf having an improved replaceable striking surface as a cassette prefixed tensile tension in the band, varies from cassette to cassette, consituted by a tension band, the tension of said band being within a wide range, depending on the whishes of the player. 
     It is an additional object of this invention to provide a golf putter head in which the shape and size of the flexible part of the striking surface may be chosen with a wide range of shapes and tension in the band. 
     It is also an object of this invention to provide an interchangeable part, or cassette, comprising a replaceable part adapted to the abovementioned golf club. 
     It is another object of this invention to provide an interchangeable part being inexpesive to produce. 
     An interchangeable part for use in golf clubs is described in U.S. Pat. No. 5,190,290. This, however, represents a completely different solution being related to golf clubs, and not putters and being based on different types of synthetic materials being positioned in the back of the cassette to provide a softer and more flexible feel. 
     U.S. Pat. No. 4,422,638 and GB 2,281,041 describe interchangeable parts in a golf putter in which the interchangeable striking surfaces are made from a rubber material. This solution results in larger friction between the ball and the striking surface and loss of energy in the strike thus providing a non-optimal solution. 
     SUMMARY OF THE INVENTION 
     The objects of this invention are obtained by providing a golf putter and an interchangeable cassette for a golf putter as described above, and being characterized in that the band-shaped material constitutes a loop and the tension bar is provided at least partially inside the band shaped material thus being adapted to apply a tension to the band, the tension bar also being including protrusions on each side of the striking surface thus defining a hollow or recess behind the band at the striking surface, and that the putter head comprises holding means for receiving the stretched band and tension bar and locking them into position in the putter head. 
     According to the invention, by ensuring that the said tension bar is locally pliable it is possible to achieve a relatively extensive, i.e. a relatively wide strike area between the putter head and the golf ball. By giving the said tension bar a relatively smooth and low-friction strike surface it is possible to ensure that there is low friction between the putter head and the golf ball in order to deliberately cause the golf ball to have the intended rolling movement. This can also be further controlled, for example by raising or lowering the putter head in relation to the centre of gravity of the ball. A delayed transfer of the force (kinetic energy) from the putter head to the ball will give a smoother and softer stroke. This greatly affects the ball and causes the ball to roll soon after the stroke. The roll is desirable immediately after the stroke in order to obtain the gyro effect, which in turn gives better stability both in direction and length. 
     Also according to the invention is an interchangeable cassette in which the parts may be produced using extruding profiles which are cut in chosen sizes, and the band may similarly be mass produced as thin tubes which also may be cut into the chosen dimension, thus providing a cost efficient production method. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Other features of this invention are shown in the following description with reference to the accompanying drawings, as follows: 
     FIG. 1 is a drawing of a golf club of the putter type, as  10  seen facing the strike area of the club head. 
     FIG. 2A is a partially exploded drawing showing the different parts of a putter head according to the invention. 
     FIG. 2B is an exploded drawing showing the different parts of a putter head according to the invention. 
     FIG. 3 is a view of the embodiment shown in FIG. 2A and 2B being assembled. 
     FIGS. 4A-G illustrates different embodiments of the interchangeable cassette of the invention. 
     FIGS. 5A-B illustrates two alternative embodiments of the golf putter head according to the invention. 
     FIG. 6 illustrates another embodiment of the gulf putter head according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a golf club  10  of the putter type, consisting of a club head  11 , connected to a shaft section  12 . The shaft section  12  is shown with a traditional hand grip  14  to be included: long shaft, lefthand. This particular case relates to a putter with a putter head which can be adjusted in different ways relatively simply. In accordance with the adjustment requirements laid down by the “Royal and Ancient Golf Club of St. Andrews” and the “United States Golf Association”, the weight of other golf clubs than putters may be adjusted. However, as regards putters, other adjustments may be made in accordance with the following: 
     (I) It must not be possible to make the adjustment easily. 
     (II) All adjustable parts shall be fixed firmly in place during use so that there is no reasonable possibility of parts loosening or of them actually being re-adjusted during use/play. 
     (III) All results of adjustments made must be in accordance with stipulated rules. 
     (IV) Striking area shall be hard and rigid. No visible movement to be observed in the striking area, when pressing at striking area by manual force. 
     The conclusion is that the functional properties of a golf club (in this connection also including a putter) cannot be changed during play and that any change during play will entail the disqualification of the player from the game in play. 
     According to the invention, the golf club (the putter) is described and shown taking account of the permitted adjustments, as mentioned above. In other words, according to the invention, the different versions and the different alternative parts provide the possibility of making a number of different adjustments, including the interchange/replacement of different parts and some adjustment of the parts in relation to each other. It is envisaged that adjustments of this kind will be made in a workshop, or using special tools, thereby—as intended—making it difficult to adjust the putter during use/play. The actual club head  11 , in accordance with the version shown, can be made of light metal, such as an aluminium alloy, while the interchangeable/replaceable part in the club head which is the actual strike area may be made of another material. 
     The club head  11  in the version shown in FIGS. 2A and 2B has a stiff and stable part made of steel or light metal and with a curved or relatively flat bottom part  37 . The putter bead defines milled or cast space  36  for the interchangeable part, or cassette,  33 . 
     The interchangeable part  33  comprises a tension bar  34 , 35  in the drawing including a flat locking plate  35  and two end pieces  34 , both of which are positioned inside the loop shaped band material  32  constituting the striking surface. 
     The tension bar  34 , 35  comprises protrusions extending toward the striking surface thus providing a recess  30  behind the band in the striking area  19 . Thus a slightly flexible striking area is obtained. The tension bar is fitted into the milled space  36  being adapted to keep it firmly in place during use. Connection between the front band with striking surfaces and the back band may be effected by pins  39  or similar protrusions through the tension bar  35 , as shown in FIGS. 4F and 4G. 
     The physical dimensions of the end pieces  34  and the locking plate  35  are adapted to provide a prefixed tensile tension on the band when being positioned within the loop. The tension may be adjusted by exchanging the cassette-interchangeable part, the locking plate  35  or the end pieces  34 , or as an alternative embodiment, the length of the tension bar may be adjustable in a per se known way not being essential to this invention. 
     The end/bottom plate  37  of the putter head locks the interchangeable part  33  into place using locking screws  38 . Thus the band tension is not easily adjusted or the interchangeable part exchanged during use. 
     According to the invention, with the version shown, the aim is to devise an especially simple, barely concealed, and relatively uncomplicated club head construction and a relatively simple interchangeable/replaceable part cassette which is firmly attached to the club head construction. The cassette is attached to the club head  11  preferably with an exactly measured, permanent band loop tensile force. The tensile strength may be determined using a tension device, details of which are not essential to the invention and thus not described here. 
     The band material may itself consist preferably of metal, e.g. steel, but may also consist of a fibre material with a high tensile strength in the form of a band. In the latter case a certain elasticity may be achieved in the weaving, for example locally in the weaving, and more specifically, locally in the actual strike area  19  of the tension bar  34 , 35 . Typically the thickness of the band material may be in the range of 0.5-1.0 mm, depending on the material. It is, however, important that the combined thickness and tension should provide a band which is not noticably moved when subject to an applied manual force. To provide a differentiated flexibility over the striking surface the band may have a varying thickness. 
     An important aspect of the invention is that the band material should have low friction relative to the golf ball. This may be obtained using a coating, e.g. teflon®- or grafite-coatings. 
     Alternatively, the band  32  may be made of metal or other suitable material with a high tensile strength, such as a composite material with certain tension-absorbing components and other more elastic components. Using a metal band it is possible to achieve the desired low degree of friction by polishing or coating the band/striking area with low friction material-coating, and thereby the desired effective friction effect between the surface of strike area  19  and the golf ball to obtain an earlier roll of ball after impact/stroke of putter. 
     The remaining parts of the putter head are preferably made from metal, the putter head  11 , the bottom plate  37  and the end pieces  34  from steel or titanium and the locking plate  35  from titanium or other metals or materials. 
     FIGS. 4A-4G illustrates different embodiments of the interchangeable part according to the invention. 
     In FIG. 4A the outer ends  40  of the end pieces  34  are wedge shaped in the vertical direction, thus forcing a larger tension on the lower end of the striking surface  19  then the upper end, an uneven tensile tension in section of the band  31  providing a possibility to adjust the tension of the striking surface hitting the ball by adjusting the height of the golf putter relative to the ball. 
     FIG. 4B provides a simple, rectangular striking surface  19  with an even tensile tension distribution in the band  32 . 
     FIG. 4C provides a small flexible striking area  19  and a larger solid area in which the golf ball hits the end pieces  34  directly through the band  32 . 
     FIG. 4D shows an embodiment providing an alternative shape of the striking area by altering the shape of the parts of the end pieces  34  extending toward the middle of the locking plate  35 . As the tension of the band  32  is evenly distributed, but the length of the flexing area changes the flexibility of the band is largest in the middle of the striking area  19 . 
     FIG. 4E illustrates a similar situation as FIG. 4D, providing an oval recess  30  behind the striking area  19 . 
     In FIG. 4F the tension bar includes an additional protrusion  39  shaped as a pin extending toward the band  32  in the striking area. This solution provides a possibility for altering the flexibility of the striking area locally, providing special features when striking the golf ball. The pins  39  may be made from metal or another suitable material depending on the wishes of the user. The same relates to the positions and shapes of the additional protrusions  39 , as well as the length with which they extend toward the band. 
     In a preferred embodiment the pin  39  extends through the tension bar or locking plate  35 , toward the band back, thus also providing a possibility for a controlled movement using the flexibility of the band at the back as a counterforce when exceeding a chosen force. The gap between the pin and the band, at both sides of the interchangeable cassette, may be chosen according to the force with which the band should be subject to before the pin and the back part of band goes into action. Typically thee size of the gap may be less than one mm preferably in the range from 1/500 mm to 7/10 mm. 
     The drawing shows one pin, but in some cases a number of pins distributed over the surface may be provided. 
     Any combinations of the shown embodiments are also within the scope of this invention, as defined by the accompanying claims. FIGS. 5A and 5B illustrate two alternative embodiments of the club head according to the invention in which the interchangeable cassette may be inserted. Preferably the dimensions should be chosen so as to accept interchangeable part having varying dimensions, e.g. by clamping the cassette position when locked together. 
     FIG. 6 shows another alternative in which the cassette  33  is positioned in through the front of the putter head  11  and is held in position using clamps  40  fastened to the putter head by screws  41  from the back of the putter. 
     As indicated above the end pieces  34  and locking plate  35  may, according one embodiment of the invention, be made in one piece constituting the tension bar. This will, however, limit the flexibility of the invention, as both the applied tension and the shape of the hollow or recess  30  may be chosen in a great variety of ways with the preferred solution. 
     The physical size of the interchangeable cassette may vary within the practical limits of a putter head, and the band length. A typical circumference of the band may be in the range of 150-160 mm, the thickness and length of the cassette thus for example being in the range of 12-16 mm and 65-110 mm, respectively.