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 desirablexe2x80x94at least with certain putting strokesxe2x80x94to 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 xe2x80x9ctopxe2x80x9d 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""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""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 RandA 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.
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.