The invention relates to the field of golf. It is aimed more specifically at a novel structure of the head of a golf club of the “wood” or “iron” type. The invention makes it possible to optimize the trampolining effects of the striking face.
In general, golf clubs the heads of which are initially made of solid wood before they were made even of hollow metal or of composite are known as “woods”.
The invention protects the type of clubs known as woods the interior of which is hollow. The striking face of these woods is relatively weakly inclined with respect to the vertical, which means that such clubs are dedicated to the taking of long shots.
More specifically, the head of a “wood” has an internal cavity delimited by various walls. One of these walls forms the striking face. Among the walls adjacent the one forming the striking face are the wall forming the sole and the side walls and a crown wall. The rear of the cavity is closed off either by a rear wall, which may be of various shapes, or by the prolongation of the various adjacent faces.
The invention is also of benefit to clubs known as “irons”. The head of an “iron” comprises a striking wall the front face of which forms the actual striking surface and the rear face of which may possibly be situated at the end of a cavity in the case of irons said to have “peripheral weighting”.
As is known, and this is true of woods and irons, the striking face is the face which makes impact with the ball. This impact preferably occurs at the center of the striking face, also known as the sweet spot, so as to minimize the vibration transmitted up the shaft and so as to optimize the trajectory of the ball.
Given the forces exerted at the time of impact, the striking face has a tendency to deform, and the lesser its thickness, the more it will do so. This deformation toward the inside of the cavity of the head generates a trampolining effect which contributes to accelerating the ball. It is known that the official regulations laid down by golfing federations are seeking to limit this trampolining effect, so as to prevent performance from being excessively influenced by the mechanical properties of the hardware, for example by mounting the striking face with a certain latitude for movement relative to the head, by inserting elastic elements, as described in document U.S. Pat. No. 5,505,453.
Various constructional steps have already been proposed in order to make progress in this direction. Thus, a certain number of solutions consist in equipping the inside of the cavity with an element able to block the deformation of the striking face, after a predetermined deformation travel. Such solutions are described in particular in documents U.S. Pat. No. 6,165,081, JP 81 502 30, JP 2001-238988, U.S. Pat. No. 6,299,547 and U.S. Pat. No. 5,499,814.
These solutions make it possible only to limit the deformation of the striking surface but have no influence on the trampolining effect. In addition, the disadvantages associated with these solutions lie in the fact that the deformation of the striking face is altered abruptly when the back of the striking face comes into contact with the element placed for that purpose in the cavity. This discontinuity in the deformation of the striking face may cause certain vibrations to arise.
It has also been proposed for the back of the striking face to be equipped with elements in the form of bridges forming springs, so as to modify the intrinsic stiffness of the striking face. Such a solution is described in particular in document JP-110 42 302. Such a construction is relatively complicated because it combines the bending effect with the warping effects of a leaf constrained at its ends. The deformation and therefore the elastic effect of such an embodiment are very random.
Other devices have also been proposed to influence the deformation of the striking face. Thus, it is possible for the head to be equipped with a free mass, which is kept in contact with the back face of the striking face by a resilient device. Upon impact with the ball, this additional mass detaches from the striking face and moves toward the back of the head. This “beater” effect transfers some of the energy of the impact to the additional mass. These devices have the disadvantage of generating significant vibration and have no real influence on the trampolining effect, because the latter is determined solely by the inherent characteristics of the striking face, once the additional mass detaches therefrom. Such devices are described for example in documents U.S. Pat. No. 5,911,637, JP 05269224, JP 02-131788.
One of the objectives of the invention is to give the striking place an ability to deform which is relatively controlled in spite of the fact that the thickness of the striking face is relatively small.
Another objective of the invention is to give the club head a structure that allows the deformation of the striking face to be adjusted, while at the same time being easy to manufacture.
SUMMARY OF THE INVENTION
The invention therefore relates to a head of a golf club of the “wood” or “iron” type. In a known way, such a head has a wall which forms the striking face, fixed to the rest of the head, and at least one wall adjacent the wall forming the striking face. Among these adjacent walls are, in particular, the sole wall and the lateral and crown walls, and a rear wall in the case of woods.
According to the invention, the head is one which also comprises an elastic leaf one end of which is fixed to one of the walls adjacent the wall forming striking face, and the free other end of which bears with preload against the back face of the wall of the striking face.
In other words, the head according to the invention includes a spring-forming leaf which is firmly fixed, for example by screwing or welding, to the sole or alternatively the lateral walls or the crown wall in the case of a wood. The other end of this leaf exerts load on the internal face of the wall of the striking face without being fixed to this wall. In that way, during the deformation movements of the striking face, the end of the spring leaf remains in contact with the back of the striking face, and therefore produces a continuous and progressive effect. The region of contact between the leaf and the striking face can move slightly without generating excessive stresses in the actual wall of the striking face. As the spring leaf is fixed only at one of its ends, its stiffness is practically constant regardless of its deformation.
In addition, such a device, by limiting the vibrations of the striking face, makes it possible to correct the sound resulting from impact of the ball on the club.
To improve the properties of this contact, it is possible to make provision for the free end of the elastic leaf to be curved, so that contact between the leaf and the striking face is tangential.
In practice, it will be preferable for the free end of the elastic leaf to bear in close proximity to the optimum point of impact on the striking face. To put it another way, the metal leaf exerts a force behind the sweet spot.
For an iron with peripheral weighting which therefore has an open cavity, the constrained end of the leaf may be fixed to the bottom part forming the sole or to the upper or lateral flange contributing to the peripheral weighting. In the case of a wood, this end may be fixed to any one of the walls delimiting the closed cavity. The elastic leaf may be made of metal or of glass composite or alternatively still of carbon.
The club head according to the invention may be produced using various methods. Thus, a first method of manufacture may consist:
first of all, before fitting the plate that forms the wall of the striking face on the head, in fixing one end of the metal leaf to a wall adjacent the wall of the striking face,
then secondly, in fitting the wall of the striking face, elastically deforming the metal leaf,
then finally in fixing the plate that forms the wall of the striking face to the head.
In other words, it is by fixing the plate that forms the wall of the striking face to the head that the metal leaf is placed under tension.
In an alternative form of embodiment designed specifically for woods, the method may consist in:
first of all, in producing a hollow head comprising the crown, lateral, rear walls and the wall comprising the striking face,
then secondly, in fitting the sole to which one end of the elastic leaf has already been fixed, in such a way that the other end of the elastic leaf comes into contact with the wall of the striking face, experiencing a preload,
then finally in fixing the wall of the sole to the head.
In other words, in this alternative form, it is while the sole is being fitted that the elastic leaf is deformed to exert the characteristic force on the back of the striking face.