EP0611316B1 - Balanced golf club - Google Patents

Abstract

A golf club, preferably a driver, comprising a shaft (1) at the lower end (10) of which is mounted a head (2) and at the upper end (11) of which is mounted a grip (3). This lightweight club has a mass of under 340 grammes and the ratio of the equivalent pendulum length to the club length is less than 0.87, preferably 0.87-0.85.

Description

The present invention relates to an improved golf club more particularly of the "wood" type, as well as a set comprising such a club and having the same advantages as said club.

A golf club essentially comprises a handle commonly called a "shaft", at the lower end of which is secured a head, or striking member, and at the upper end, a handle also called a "grip".

The current trend is to make light golf clubs; on the one hand, to obtain a performance gain in terms of length and accuracy of the stroke, and on the other hand, to improve the playing comfort of the player; whether beginner or professional player.

A lightening of the head of the club directly influences the length of the stroke and therefore causes the opposite effect to that desired. Also the mass gain is obtained on the handle thanks to the use of composite materials technology. Clubs equipped with such sleeves make it possible to play strokes with a length increased by about 10% compared to that of clubs equipped with traditional sleeves.

Despite these advantages, most players dislike this kind of lighter clubs, because of the unpleasant sensations experienced when performing the strike movement, commonly called "swing" due to poor dynamic balance of the club. In particular, the applicant has noticed that poor dynamic balancing directly influences the trajectory of the ball, leading to "slice", that is to say an outgoing trajectory to the right for a right-handed player (conversely outgoing to the left for a left-handed player), or "hook", that is to say a re-entrant trajectory to the left for the same player (reciprocally re-entering to the right for a left-handed player).

It is for these various reasons that professional circuit players continue to use certain traditional so-called "heavy" clubs whose sleeves are generally metallic or graphite, and which they find correctly balanced but whose performance is inferior to clubs whose handle light is made of carbon fibers for example.

The prior art has proposed, for example by document US-A-4,674,324, a method of balancing a set of golf clubs. This method requires the player to select a club that suits him. This reference club makes it possible to define the moment of inertia for a given equivalent pendulum length, then to determine a corresponding static moment value and the equivalent pendulum length of each club, in order to locate the center of percussion. The method then requires adding counterweights to each club to position the center of percussion, then to balance each club to have the same static moment as the reference club, and finally to adjust the radius of gyration.

This complex method makes it possible to obtain clubs which are pleasant to use, but which remain heavy and limited in terms of performance.

The aim of the present invention is therefore to overcome the above-mentioned drawbacks, particularly by proposing a lean club, therefore efficient and whose dynamic balancing is identical or very close to that of the clubs preferred by most players.

The aim is also to offer a club set having the same advantages as the club thus created.

For this, the club of the invention consists of a handle at the upper end of which is secured a grip and at the lower end, a head; the total mass of said club being less than 340 grams and is characterized in that the ratio of the length of the equivalent hanged to the length of the club is less than 0.87 preferably between 0.85 and 0.87.

An additional feature of the invention is that the mass distribution on the club is such that the mass of the grip and the handle represents 30 to 40% of the total mass of the club.

Another characteristic of the invention is that the grip is light and its mass is less than or equal to 35 grams.

• la figure 1 représente une vue simplifiée du club selon l'invention,
• la figure 2 représente un graphique montrant le positionnement d'un exemple du club de l'invention selon ses caractéristiques par rapport aux clubs traditionnels connus,
• la figure 3 représente une vue simplifiée d'un club de golf de l'art antérieur,
• la figure 3a représente un détail agrandi de la figure 3, notamment de la partie supérieure du club,
• la figure 3b représente le manche du club de la figure 3,
• la figure 4 représente une vue simplifiée d'un club de golf selon l'invention,
• la figure 4a représente un détail agrandi de la figure 4,
• la figure 4b représente le manche du club de la figure 4,
• la figure 5 représente une variante de la figure 4,
• la figure 5a représente un détail de la figure 5,
• la figure 5b représente le manche du club de la figure 5,
• la figure 5c représente un perfectionnement du club de la figure 5,
• la figure 6 représente un club de golf de l'invention selon un autre mode de réalisation,
• la figure 7 représente un graphique montrant la variation du rapport LPE/Lc en fonction de la position d'une masselotte sur le manche du club de la figure 6.

Other characteristics and advantages of the invention will emerge from the description which will follow with reference, without limitation, to the appended drawings and of which,

• FIG. 1 represents a simplified view of the club according to the invention,
• FIG. 2 represents a graph showing the positioning of an example of the club of the invention according to its characteristics compared to known traditional clubs,
• FIG. 3 represents a simplified view of a golf club of the prior art,
• FIG. 3a represents an enlarged detail of FIG. 3, in particular of the upper part of the club,
• FIG. 3b represents the handle of the club of FIG. 3,
• FIG. 4 represents a simplified view of a golf club according to the invention,
• FIG. 4a represents an enlarged detail of FIG. 4,
• FIG. 4b represents the handle of the club of FIG. 4,
• FIG. 5 represents a variant of FIG. 4,
• FIG. 5a represents a detail of FIG. 5,
• FIG. 5b represents the handle of the club of FIG. 5,
• FIG. 5c represents an improvement of the club of FIG. 5,
• FIG. 6 represents a golf club of the invention according to another embodiment,
• FIG. 7 represents a graph showing the variation of the LPE / Lc ratio as a function of the position of a counterweight on the handle of the club of FIG. 6.

The golf club of FIG. 1 comprises a handle (1) of length ls and mass ms at the lower end (10) to which a head (2) of mass mt is secured. From the upper end (11) of the handle (1) is secured a handle (3) of mass mg and length lg and extending over part of the length of the handle.

By convention, the length of the club (Lc) is considered to be the length measured between a point O 'on the longitudinal axis (I, I') of the handle located 5 mm from the upper end or point O of the handle (3), and a point O '' corresponding to the perpendicular projection on the axis (I, I ') of the center of gravity (20) of the head (2) of the club.

The club of the invention mainly concerns a "driver", that is to say the club having the greatest length (Lc) among the clubs of the same set. But as will be explained later the invention extends in the same way to any club of said set which have the same advantages as the "driver" as they have been defined before.

According to the manufacturers, the "driver" is a club whose length (Lc) can vary from 1041.4 mm (or 41 inches) for the shortest to 1143 mm (or 45 inches) approximately. Typically, the average length is around 1092.2 mm (43 inches).

For these club lengths, the applicant has established a graph illustrated in FIG. 2 on which measurements made on 26 drivers on the market appear to be compared with a driver of the invention. On this graph, the total mass (MT) expressed in grams of the driver is shown on the abscissa and the ratio of the equivalent pendulum length (LPE) to the length (Lc) of the club is shown on the ordinate.

The LPE is given in mm and corresponds to a length equivalent to that of a simple pendulum whose oscillation period (T) is equal to that of the club if it is mounted pivoting around a point O1 corresponding to the point of rotation of the club in the hands of the player. In our example, it is located on the axis (I, I ') 101.6 mm (4 inches) from point O.

   (g étant la constante gravitionnelle exprimée en mm/s²).The measurement of LPE can be carried out by various means such as those set out in US patent 4,674,324. As an example, we can cite the simplest method which consists in rotating the club around the point O1 and measuring its period (T) of oscillation. The LPE is then obtained by the following formula: $${\text{LPE = (T}}^{\text{2}}{\text{g) / 4 π}}^{\text{2}}$$

(g being the gravitational constant expressed in mm / s²).

The characteristic of the invention is illustrated in FIG. 2. Among the 26 clubs on the market represented, the applicant has noticed that among the so-called "heavy" drivers numbered from 1 to 11 having a mass greater than approximately 340 grams, only clubs 1 to 4 with an LPE / Lc ratio of less than 0.87 have satisfactory dynamic balancing during the "swing". The clubs numbered from 5 to 11 have proved to be generally unsatisfactory, as have the so-called "light" clubs, that is to say those whose mass is less than 340 grams and numbered from 12 to 26.

On the other hand, clubs 12 to 26 have shown themselves to be more efficient in terms of speed of departure of the ball and therefore distance of the stroke played. This observation enabled the applicant to determine the characteristics of the driver of the invention whose total mass (MT) is less than 340 grams, preferably between 280 and 340 grams and the LPE / Lc ratio is less than 0.87, preferably between 0.87 and 0.85.

An additional advantageous characteristic of the invention consists in distributing the mass over the club in such a way that the sum of the mass of the handle (mg) and the mass of the handle (ms) is between 30 and 40% of the mass total of the club (MT), which allows to keep a traditional head mass greater than at least 190 grams.

Point 27 in Figure 2 illustrates the position on the graph of an example club according to the invention having a total mass equal to 322 grams and an LPE / Lc ratio equal to 0.866. As an example, the characteristics of such a club are presented in the following table: (for a static moment d2 of the lorythmic scale of "swing-weight" measured at 14 inches, ie 355.6 mm O) Table 1 CLUB HEAD HANDLE HANDLE Mass (in g) 322 205 82 35 Cdg position (in mm) 840 (compared to O) 1095 (compared to O ') 499 (compared to O ') 100 (relative to O) Inertia (in kg.m²) 4,983.10⁻² 2.2.10⁻⁴ 7.1.10⁻² 2,3.10⁻⁴ Length (in mm) 1095 (Lc) 1057.3 260

• MT étant la masse totale du club est égale à $\text{mg + ms + mt}$
  
  exprimée en kg
• G étant la position du centre de gravité du club à partir du point O exprimé en m
• Ic étant le moment d'inerte du club exprimé en kg.m² et calculé par le théorème de Huygens selon la formule : $${\text{Ic = Is + Ig + It + (mg (G-Gg)}}^{\text{2}}{\text{) + (ms (G-Gs-0,005)}}^{\text{2}}{\text{) + mt (Lc-G)}}^{\text{2}}\text{)}$$
  

   Dans cette formule,

• G, Gs, Gg sont exprimés en m
• mg, ms, mt sont exprimés en kg
• où Gg est la position du centre de gravité du grip par rapport à O ; et Gs est la position du centre de gravité du shaft par rapport à O,
• Is étant le moment d'inerte du manche par rapport à Gs,
• Ig étant le moment d'inertie de la poignée par rapport à Gg,
• It étant le moment d'inertie de la tête par rapport au centre de gravité (20) de la tête.

In general, the distribution of mass, inertias, centers of gravity, of the club and of the various elements constituting it can be determined by the following formulas: $$\text{LPE (at 0.1016 mm or 4 inches) = Ic / (MT (Gc - 0.1016)) + (Gc - 0.1016)}$$

• MT being the total mass of the club is equal to $\text{mg + ms + mt}$
  
  expressed in kg
• G being the position of the center of gravity of the club from the point O expressed in m
• Ic being the moment of inertia of the club expressed in kg.m² and calculated by Huygens' theorem according to the formula: $${\text{Ic = Is + Ig + It + (mg (G-Gg)}}^{\text{2}}{\text{) + (ms (G-Gs-0.005)}}^{\text{2}}{\text{) + mt (Lc-G)}}^{\text{2}}\text{)}$$
  

In this formula,

• G, Gs, Gg are expressed in m
• mg, ms, mt are expressed in kg
• where Gg is the position of the center of gravity of the grip with respect to O; and Gs is the position of the center of gravity of the shaft with respect to O,
• Is being the moment of inertia of the handle with respect to Gs,
• Ig being the moment of inertia of the handle with respect to Gg,
• It being the moment of inertia of the head with respect to the center of gravity (20) of the head.

The various constructions which will follow are given by way of example and are therefore in no way limiting.

In a preferred embodiment of the invention, the lightening of the club can be obtained by choosing a handle whose mass (mg) is less than 35 grams, preferably between 25 and 35 grams. For this, provision can be made for the handle generally made of elastomeric material to have a thin and substantially constant thickness of the order of 1 to 2.5 mm.

In this particular case, and by the formulas previously described, the characteristics of mass (ms), position of the center of gravity (Gs) and inert (Is) of the handle can be optimized by calculation.

Thus, one can define a mass of the handle (ms) between 70 and 100 grams, preferably between 80 and 90 grams.

The results appearing in the following table are given as a specific example for a fixed mass of the handle of 35 grams and under the same conditions as in the example in Table 1. Table 2 ms (in g) Gs (mm) Is (kg.m²) mt (in g) 82 500.2 7.08 10-3 205.5 83 507.4 7.43 10-3 204.5 84 514.4 7.77 10-3 203.5 85 521.2 8.10 10-3 202.5

Advantageous characteristics of the invention and particularly of the preferred mode previously described, are illustrated in Figures 4, 4a, 4b, 5, 5a, 5b in comparison with the prior art illustrated in Figures 3, 3a, 3b.

Figure 3 shows a prior art golf club with a handle (1), a head (2) and a handle (3). The handle (1) has a regular frustoconical shape, the weakest section of which is located at its lower end (1), which is embedded in the head (2), and the strongest section is located at its upper end (11 ) from which extends the handle (3). By regular tapered shape, it is meant that the generatrix G of the truncated cone formed by the handle (1) is substantially rectilinear and forms an angle θ with the median longitudinal axis (I, I ') as shown in Figure 3b. For ergonomic reasons of play, the thickness (e) of the handle is variable along the handle and increases towards the end (11) of the handle so that the section is sufficient in the grip zone of the hands.

In a complementary characteristic of the invention illustrated in FIG. 4, 4a and 4b, the handle (1) comprises a first portion (13a) in the form of a truncated cone of length ls1 partially or completely covered by the handle (3) of thin, substantially constant length lg. The handle comprises a second remaining portion (13b) in the form of a truncated cone of length ls2 also connecting to the first portion (13a). The generator G1 of the first portion (13a) has an average angle θ1 relative to the axis (I, I ') and greater than the average angle θ2 formed between the generator G2 of the second portion (13b) and the axis (I, I '). In the example described, the generators G1 and G2 are rectilinear but it is accepted that they can have a slight curvature in particular for the generator G1 of the first portion (13a).

The particular advantage of the mode of FIGS. 4 to 4b and which is added to those targeted by the invention and described above is mainly that the handle retains its ergonomic qualities in the hand tightening region due to its particular configuration.

Figures 5 to 5c show another example of possible configuration of the handle (1) leading to the same advantages. The handle (1) comprises a first upper frustoconical portion (14a) of length ls1 completely or partially covered only by the handle (3) of length lg. A second frustoconical portion (14b) not covered by the handle extends to the lower end (10) of the handle. The lower end (140a) of diameter d1 of the first portion (14a) is linked to the upper end of diameter d2 (140b) of the second portion (14b) via a third connection portion (14c ) of length ls3; the diameter d1 of the first portion being less than the diameter d2 of the second portion. The generator G3 of the handle (3) can advantageously be confused with the generator G'3 of the second portion (14b). In this way, the handle is integrated flush with the handle (1). In addition in this case, the diameter d2 of the second portion being at any point greater than the diameter of a handle of the prior art like that of FIG. 3; the handle is more rigid in flexion and torsion than a conventional handle without being heavier.

Figure 5c shows an improvement made to the club of Figure 5 on which is added a connecting ring (16) covering the third connection portion (14c). This ring can advantageously be made of viscoelastic material having damping properties for example.

The sleeves (1) of the examples in FIGS. 4b and 5b are preferably produced in a composite structure based on carbon fibers and organic resin of the epoxy type for example. The manufacturing process for such sleeves is described in French patent applications No. 90 15387 and No. 90 15388 belonging to the applicant and which are added to the present description.

Of course, provision can be made for these handles by other more conventional methods well known to those skilled in the art.

FIG. 6 illustrates another embodiment of the invention. In this case, the handle (3) is conventional and has a mass (mg) of between 45 and 55 grams, preferably 50 grams. The handle (1) is very light and has a mass of less than 80 grams and includes a flyweight (4) located in an area (15) located at a distance d from O 'equal to about 0.5 Lc and of length equal to about 0.15 Lc.

The flyweight has a mass between 1 and 40 grams. The area (15) defined in the context of the invention corresponds to the area for which dynamic balancing is carried out by adding the minimum mass by the counterweight. This characteristic is illustrated as an example in the graph in FIG. 7 which shows the variation of the LPE / Lc ratio as a function of the position of the counterweight (4) relative to the point O '.

On the abscissa is the length of the club Lc expressed in mm.

On the ordinate is the LPE / Lc ratio.

Curve C1 illustrates an example of a non-jogged handle and whose balancing is not satisfactory.

Curves C2 and C3 illustrate two examples with a weight of 12 and 16 grams respectively.

The other parameters in C1, C2 and C3 are given in the following table by way of example (for a static moment d2 or "swing weight" of the club at 14 inches): C1 C2 C3 - Club Lc (mm) 1095 1095 1095 MT (in g) 329.5 337 339.9 Gc (in mm) 829.9 819 815 Ic (kg.m²) 0.05637 0.05645 0.05662 - Sleeve ls 1057 1057 1057 ms 65 65 65 Gs 495 495 495 Is 0.0065 0.0065 0.0065 - Handle lp 260 260 260 mp 50 50 50 Gp 100 100 100 Ip 0,00029 0,00029 0,00029

The handle (1) of Figure 6 is made of composite material based on carbon fibers and resin.

The counterweight (4) can be arranged inside the handle (1) as shown in FIG. 6a. In this case, the counterweight can consist of an elastomer plug or other deformable material. It is also possible to envisage having a flyweight (4) in the form of a ring on the external surface of the handle (1) as in the case of FIG. 6b. It can also fill a housing (17) provided for this purpose so as to come flush with the external surface of the handle as illustrated in FIG. 6c. Finally, the counterweight (4) can be integrated into the internal structure of the handle as shown in FIG. 6d.

The use of a counterweight in the defined zone (15) can also be envisaged in the first embodiment of the invention, illustrated in FIGS. 4 to 5b if a readjustment of the dynamic balancing proves to be necessary after the manufacturing process of the club due to the dispersion of the different elements composing it. In this case, the addition of the mass is very low and of the order of only 1 to 10 g.

The present invention also extends to a golf club set comprising at least one club of the invention and in which each club which composes it has an LPE / Lc ratio of less than 0.87, preferably between 0.87 and 0.85.

In the normal declination of a set, the other clubs in the set have a total mass greater than that of the club of the invention, if this one is the driver, due to the mass of the head which increases as Lc decreases in the set. Also the head mass can vary from a minimum mass of 190 grams for a driver to a maximum mass of 350 grams for a putter.

   avec

• SW exprimé en kg m
• MT exprimé en kg avec $\text{MT = mg + ms + mt}$
  
• Gc exprimé en m

   Bien entendu, l'invention telle que definie dans les revendications n'est pas limitée aux modes de réalisation décrits et représentés à titre d'exemples, mais elle comprend aussi tous les équivalents techniques ainsi que leurs combinaisons.An additional characteristic of the set of the invention is that each club can be balanced according to the traditional technique of static balancing known as "swing-weighting" without substantially modifying the LPE / Lc ratio for each club. The swing-weighting technique consists in balancing each club in the set by modifying the head mass so as to have the same static moment measured at 355.6 mm (either 14 inches or 355.6 mm O). As an example, the formula of the static moment as a function of the mass of the club is: $$\text{SW = MT (Gc - 0.3556)}$$

with

• SW expressed in kg m
• MT expressed in kg with $\text{MT = mg + ms + mt}$
  
• Gc expressed in m

Of course, the invention as defined in the claims is not limited to the embodiments described and shown by way of examples, but it also includes all the technical equivalents as well as their combinations.

Claims (20)

1. Golf club, preferably a driver, comprising a shaft (1) at whose bottom end (10) there is mounted a head (2) and at whose top end (11) there is mounted a grip (3); the said club having a total weight of less than 340 grammes, characterised in that the ratio of equivalent pendulum length to length of club is less than 0.87, preferably between 0.87 and 0.85.
2. Golf club according to Claim 1, characterised in that the sum of the weight of the grip (3) and shaft (1) is between 30 and 40% of the total weight of the said club.
3. Golf club according to Claim 1 or 2, characterised in that the grip (3) is light and weighs less than 35 grammes, preferably between 25 and 35 grammes.
4. Golf club according to Claim 3, characterised in that the shaft (1) weighs between 70 and 100 grammes, preferably between 80 and 90 grammes.
5. Golf club according to Claim 1 or 2, characterised in that the grip (3) weighs between 45 and 55 grammes.
6. Golf club according to Claim 5, characterised in that the shaft (1) weighs less than 80 grammes.
7. Golf club according to Claim 6, characterised in that the shaft (1) comprises a weight (4) located in an area situated at a distance d from the point O' equal to approximately 0.5 Lc and extends over a length equal to approximately 0.15 Lc.
8. Golf club according to Claim 7, characterised in that the weight (4) weighs between 1 and 40 grammes.
9. Golf club according to Claim 6 or 7, characterised in that the weight consists of a plug disposed inside the shaft.
10. Golf club according to Claim 9, characterised in that the plug is made of elastomer or another deformable material.
11. Golf club according to Claim 6 or 7, characterised in that the weight (4) is a ring disposed on the external surface of the shaft (1).
12. Golf club according to Claim 11, characterised in that the ring (4) is disposed, flush with the external surface of the shaft, in a housing (16).
13. Golf club according to Claim 6 or 7, characterised in that the weight (4) is integrated into the internal structure of the shaft.
14. Golf club according to Claim 2 or 3, characterised in that the grip (3) has a fine thickness (e) substantially constant over its entire length (lg).
15. Golf club according to Claim 14, characterised in that the grip (3) has a thickness of between 1 and 2.5 mm.
16. Golf club according to Claim 14 or 15, characterised in that the shaft comprises a first portion (13a) in the shape of a truncated cone of length ls1, covered at least partially by the grip (3) of length lg and connected to a second portion (13b), the said first portion in the shape of a truncated cone (13a) having a generator G1 whose mean angle θ1 with respect to the longitudinal axis (I, I') is greater than the mean angle θ2 of the generator G2 of the remaining second portion in the form of a truncated cone (13b) of length ls2 of the shaft.
17. Golf club according to Claim 14 or 15, characterised in that the shaft comprises a first, top tapered portion (14a) of length ls1 covered at least in part by the grip (3) of length lg, a second, bottom tapered section (14b) not covered by the grip and extending as far as the bottom end of the shaft; the diameter d1 of the bottom end (140a) of the said first top tapered portion (14a) being less than the diameter d2 of the top end (140b) of the said bottom tapered portion (14b) and the said first and second tapered portions (14a, 14b) being connected by a third, connecting portion (14c) of length ls3.
18. Set of golf clubs comprising several clubs of different lengths (Lc), characterised in that it comprises at least one club according to Claims 1 to 17 and in that each club in the said set has a ratio EPL/Lc of less than 0.87, and preferably between 0.87 and 0.85.
19. Set of golf clubs according to Claim 18, characterised in that each club has the same statical moment measured at 355.6 mm (or 14 inches).
20. Set of golf clubs according to Claim 18 or 19, characterised in that the weight of the head can vary between a minimum value of 190 grammes and a maximum value of 350 grammes.

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