EP0275805B1 - Tennis racket - Google Patents

Abstract

A tennis racket provided with a vibration damping device. The racket includes at least one pair of viscoelastic dampers, symmetric relative to a longitudinal axis of the racket and working in opposition. Each damper of the pair consists of a plate of viscoelastic material, whose one face is glued against the racket at a selected spot of the racket, and which includes on its other face a stress plate of rigid material. The selected spot corresponds to the antinode of a specific mode of vibration of the racket.

Description

The present invention relates to a ball game racket, more particularly intended for the game of tennis, this racket being provided with a vibration damping device.

• les critères de performance : rendement, nervosité, raideur, etc.
• les critères de confort du joueur : douceur, maniabilité, etc.

The playing qualities of a racket are determined by a fairly large number of criteria which can, in general, be classified into two categories:

• performance criteria: performance, nervousness, stiffness, etc.
• the player's comfort criteria: softness, maneuverability, etc.

Certain criteria, for example tolerance to decentering ball impact, can however fall into both categories.

These two categories of criteria are most often contradictory, so that, most of the time, comfort can only be improved at the expense of performance and vice versa.

It is known that a system subjected to a disturbance vibrates around one or more natural frequencies which are characteristic of its structure and result from its distribution of mass and stiffness. The behavior resulting from this set of vibrations is the sum of the displacements which are generated, in various directions, by the resonant frequencies of this structure. These displacements are minimum at the places commonly called "nodes" of vibration, and maximum at the places commonly called "bellies" of vibration.

This vibratory behavior would be infinite in the absence of any damping property of the structure. In general, any physical system is subjected to one or more types of damping as long as the energy is dispersed there either by friction, or by other dissipative systems, for example viscoelastic, or hysteresis.

• trois se situent dans une direction perpendiculaire au plan de la raquette ; ce sont les modes de flexion simple perpendiculaires au plan longitudinal médian de la raquette ;
• deux se situent dans le plan de la raquette ; ce sont les modes de flexion latérale ;
• deux autres sont des couplages entre des vibrations de flexion perpendiculaire au plan longitudinal médian de la raquette, et de torsion par rapport à son axe longitudinal médian.

It has been shown that, in the case of the tennis player, the vibrations which are transmitted to him via his racket after a ball impact are directly correlated to his perception of the behavior of his machine. In the frequency range from 0 to 1000 Hz, range in which humans are highly receptive to vibrations, tennis rackets vibrate in several directions and frequencies, which correspond to what will later be agreed to be called "clean vibration modes". This is how om was able to highlight seven specific vibrational modes strongly correlated to the behavior in play of the racket:

• three lie in a direction perpendicular to the plane of the racket; these are the simple flexion modes perpendicular to the median longitudinal plane of the racket;
• two are in the plane of the racket; these are the modes of lateral flexion;
• two others are couplings between vibrations of flexion perpendicular to the median longitudinal plane of the racket, and of torsion with respect to its median longitudinal axis.

• en figure 1 le premier mode vibratoire propre d'une raquette 1, vue selon la direction F de la figure 4, dans une direction perpendiculaire au plan 2 de cette raquette : il s'agit d'une flexion simple orthogonale à ce plan 2 ;
• en figure 2 le second mode vibratoire propre de cette raquette 1, en flexion simple perpendiculaire à ce plan 2 ;
• en figure 3 le troisième mode vibratoire propre de cette raquette 1, en flexion simple perpendiculaire a ce plan 2 ;
• en figure 4 le premier mode vibratoire propre de cette raquette 1, vue en plan, en flexion latérale par rapport à son axe longitudinal y'y dans son plan 2 ;
• en figure 5 son second mode vibratoire propre, toujours en flexion latérale par rapport à y'y dans le plan 2.

By way of illustration of some of these vibratory modes, there is shown diagrammatically in the accompanying drawings:

• in Figure 1 the first proper vibration mode of a racket 1, seen in the direction F of Figure 4, in a direction perpendicular to the plane 2 of this racket: it is a simple bending orthogonal to this plane 2;
• in Figure 2 the second proper vibration mode of this racket 1, in simple bending perpendicular to this plane 2;
• in FIG. 3 the third proper vibratory mode of this racket 1, in simple bending perpendicular to this plane 2;
• in FIG. 4, the first proper vibratory mode of this racket 1, seen in plan, in lateral flexion with respect to its longitudinal axis y'y in its plane 2;
• in FIG. 5 its second own vibratory mode, still in lateral bending with respect to y'y in the plane 2.

The natural vibratory modes on which it is most important to act are, of course, the modes of higher energy, that is to say those which generate important deformations of the structure.

Priority should therefore be given to influencing the first three bending modes perpendicular to the plane of the racket, the first two bending modes in the plane of the racket, as well as the first mode of coupling the bending vibrations perpendicular to the racket plane and torsion with respect to its longitudinal axis.

It is already known, to adjust the playing qualities, to provide relatively complex means on a tennis racket to dampen vibrations. Thus it is known to bring damping elements, relatively complex and also bulky, in selected locations on the frame of the racket.

In addition, document FR-A-2 336 299 describes a device intended to damping the dynamic deformations of the oscillations of a wing or of a helicopter blade, comprising at least one overlapping layer and an elastomer damping layer superimposed and placed directly on the wing in the deformation zone dynamic.

The invention aims, by simple and inexpensive means, to settle selectively the damping of a tennis racket by applying to it, in determined locations, a damping element whose damping coefficient is found to be optimal in the temperature range and operating frequency of the racket. It therefore relates to a ball game racket comprising at least one vibration damping system, positioned locally, of the stress plate type associated with a visco-elastic material intended to be stressed in shear and attached integrally to the outside of the structure of the racket, where each damping system consists of a bi-material plate of which one of the materials is a visco-elastic material whose damping coefficient β is at least 0.5 in a temperature range located between 10 and 30 ° C, and for frequencies ranging from 0 to 1000 Hz, bonded by vulcanization on a rigid stress plate whose modulus is very high compared to that of the visco-elastic material, and where each damping system is located in the zone where the visco-elastic material located between the racket and a stress plate is the most stressed in shear deformation, for one of the vibra modes tones of higher energy, that is to say at the level of a belly of vibration of one of the vibratory modes of higher energy.

Each damping system is arranged on a vibration belly of one of the six modes of highest energy, that is to say the first three modes of flexion perpendicular to the plane of the racket, the first two modes of flexion in the plane of the racket, as well as the first mode of coupling of flexural vibrations perpendicular to the plane of the racket and of torsion with respect to its longitudinal axis.

Advantageously, the thickness of the plate of visco-elastic material is between 0.5 and 1.2 mm, the damping coefficient of this visco-elastic material is between 0.8 and 1.2 and the thickness of the stress plate is between 0.5 and 1.2 mm.

For example, each shock absorber has a Zicral stress plate, 0.6 mm thick, which is bonded to a blade of visco-elastic material 0.8 mm thick, and with a damping coefficient generally called β, of the order of 1.2, optimal in a temperature range between 10 and 30 ° C and for vibration frequencies between 10 and 1000 Hz.

This racket can therefore include at least one shock absorber. visco-elastic, working in shear, which is placed in the area where the visco-elastic material located between the racket and the Zicral stress plate is most stressed in shear deformation: it thus absorbs and dissipates a large amount of energy that is not returned to the structure. The effect of the vibration is then modified, reducing the amplitude of movement of the structure.

To make this racket, place the shock absorber (s), optionally combined, on the bridge, on the branches, on the sides of the branches, or on any other part of the racket located in areas capable of supplying great energy to the material. visco-elastic constituting the lower part of the damping element.

Depending on its position on the racket, the shock absorber reduces the amplitude of certain vibration modes, which causes a modification of the player's sensations. Thus, to dampen the amplitude of the first mode of vibration in bending perpendicular to the plane of the racket, the damping system is positioned on the outside and / or inside of the arms of the racket, from the front part of the handle. to the root of the bridge. We then feel the racket as being more flexible, with a longer ball contact.

By positioning the shock absorber system on the deck or on either side of the deck and / or on the head or on either side of the basket head, symmetrically with respect to both the longitudinal axis of the racket and / or at the plane of the racket, the amplitude of both the second and third modes of vibration in flexion perpendicular to the median plane of the racket is damped, as well as the amplitude of the first mode of vibration coupling the flexion perpendicular to the plane racket median and torsion with respect to the median longitudinal axis of the racket. The racket appears both more nervous and with improved performance. For reasons of decoration, these strictly symmetrical shapes can be slightly modified.

By positioning the damping system on the sides of the basket, coupled in pairs, symmetrically both with respect to the median longitudinal plane of the racket and with respect to the nodal line of the first bending mode perpendicular to the plane of the racket, it is preferentially damped the amplitude of the vibration of these modes in the basket area. The racket then appears more stable at the time of impact between the ball and the string.

• Figure 6 est une vue en plan de cette raquette,
• Figure 7 est une vue en plan agrandie du pont de cette raquette,
• Figure 8 est une vue en coupe selon VIII-VIII de la figure 7.

In any case, the invention will be well understood, and its advantages as well as other characteristics will emerge during the following description of a few non-limiting examples of embodiment of this racket, with reference to the appended schematic drawings in which:

• FIG. 6 is a plan view of this racket,
• FIG. 7 is an enlarged plan view of the deck of this racket,
• Figure 8 is a sectional view along VIII-VIII of Figure 7.

Referring to Figure 6, this tennis racket 1 is composed of a handle 12 extended by two branches 6,7 which carry the basket 3, the lower part of which forms the bridge 4. The basket 3 itself carries the sieve 5, composed of longitudinal and transverse ropes and forming the striking surface.

As best seen in Figures 7 and 8, it has been fixed by gluing, on the two sides of the bridge 4 which are parallel to the plane of the racket 1, a pair of identical viscoelastic dampers 8,9. Each of these two shock absorbers, for example the shock absorber 8, is formed of a plate 10 of visco-elastic material on which a stress plate 11 is bonded, in Zicral for example. Each damper, such as 8, is glued flat to the deck 4 by the face of the plate 10 which is opposite to the stress plate 11.

The plates 10 and 11 are of the same shape and dimensions and their periphery matches that of the surface of the bridge 4 on which the plate 10 is glued, while being slightly lower thereto. The thickness of the plate 10 is 0.8 mm and its damping coefficient β is 1.2 in the temperature range between 10 and 30 ° C, which is the most frequent use range of the racket. The stress plate of Zicral 11 has a thickness of 0.6 mm. Each shock absorber, 8 or 9, is completely symmetrical with respect to the longitudinal axis y'y of the racket and can therefore be considered to be composed of a pair of shock absorbers 81, 82 symmetrical with respect to this axis y, y and working in shear and in opposition. In this case there is a pair 8.9 of shock absorbers each placed on either side of the bridge.

With this arrangement, each pair of dampers 81.82 dampens the vibration modes which arise in the plane of the racket, which increases the comfort of the player.

• au moins un élément amortisseur 8 et/ou 9 fixé sur le pont 4 de la raquette 1,
• deux éléments amortisseurs 8 et 9 couplés et fixés de part et d'autre du pont 4,
• au moins un élément amortisseur 18 et/ou 19 et/ou 20 fixé sur le panier 3,
• au moins un élément amortisseur 18 fixé en tête du panier 3,
• deux éléments amortisseurs 18 couplés et fixés en tête du panier 3 de part et d'autre du plan 2 de celui-ci,
• au moins deux éléments amortisseurs 19,20 couplés et fixés sur le panier 3 de part et d'autre de l'axe longitudinal y'y de la raquette,
• quatre amortisseurs 19,20 couplés et fixés sur le panier 3 de part et d'autre de son plan 2 ainsi que de son axe longitudinal y'y,
• au moins un élément amortisseur 14 et/ou 15 et/ou 16 et/ou 17 fixé à l'intérieur ou à l'extérieur d'une branche 6 et/ou 7 de la raquette,
• deux éléments amortisseurs 16 et 17 couplés et fixés à l'intérieur des deux branches 6,7,
• deux éléments amortisseurs 14 et 15 couplés et fixés à l'extérieur des deux branches 6,7,
• quatre éléments amortisseurs 14 à 17 couplés et fixés à l'intérieur et à l'extérieur des deux branches 6,7,

ou une autre combinaison en positions et dimension de ces éléments amortisseurs.The invention is obviously not limited to this embodiment. It is possible to provide, in addition to the dampers 8, 9 or instead of these, similar dampers 14, 15, 16, 17 bonded, preferably symmetrically with respect to the axis y, y, on the external lateral faces. , and / or interior, of the two branches 6,7. These shock absorbers 14 to 17 dampen the vibration modes perpendicular to the plane of the racket, which tends to improve its performance. One can also provide, alone or combined with others in other places, shock absorbers 18 attached to the top of the basket 3, and / or shock absorbers 19,20 attached to the basket 3, for example in the middle of the latter , on either side of the y'y axis. In each case, instead of having pairs of shock absorbers coupled 8.9, one on each side of the racket, it is possible to have only one shock absorber on one side, for example shock absorber 8 only and not the damper 9. The symmetry with respect to the y'y axis is only preferential. This racket can therefore include, as preferred examples:

• at least one damping element 8 and / or 9 fixed on the deck 4 of the racket 1,
• two damping elements 8 and 9 coupled and fixed on either side of the bridge 4,
• at least one damping element 18 and / or 19 and / or 20 fixed on the basket 3,
• at least one damping element 18 fixed at the head of the basket 3,
• two damping elements 18 coupled and fixed at the head of the basket 3 on either side of the plane 2 thereof,
• at least two damping elements 19,20 coupled and fixed to the basket 3 on either side of the longitudinal axis y'y of the racket,
• four shock absorbers 19,20 coupled and fixed to the basket 3 on either side of its plane 2 as well as its longitudinal axis y'y,
• at least one damping element 14 and / or 15 and / or 16 and / or 17 fixed inside or outside of a branch 6 and / or 7 of the racket,
• two damping elements 16 and 17 coupled and fixed inside the two branches 6,7,
• two damping elements 14 and 15 coupled and fixed outside the two branches 6,7,
• four damping elements 14 to 17 coupled and fixed inside and outside the two branches 6,7,

or another combination in positions and dimensions of these damping elements.

A racket 1 with an inverted bridge 4 has been described, but this racket can be of any other kind, for example with a bridge perpendicular to the axis y'y, with a bridge of curvature opposite to that of the head of the basket, with a bridge having two opposite and opposite curvatures, etc.

Claims (21)

1. A racquet for ball games, more particularly intended for the game of tennis, having at least one system, positioned locally for absorbing vibrations, of the type having a restraint plate associated with a visco-elastic material intended to be acted upon in shear and rigidly joined to the exterior of the racquet structure, in which each absorbing system is constituted by a two-material plate (8, 9, 14, 29) of which one of the materials is a visco-elastic material (10) having a coefficient of absorption β of at least 0.5 in a temperature range located between 10 and 30°C, and for frequencies from 0 to 1,000 Hz, adhered by vulcanisation onto a rigid restraint plate (11) of which the modulus is very high compared with that of the visco-elastic material, and on the other hand in that each absorbing system is located in the zone in which the visco-elastic material located between the racquet and the restraint plate is most urged into shear deformation, for one of the highest energy vibratory modes, i.e. in the region of a vibration peak of one of the highest energy vibratory modes.
2. A racquet according to Claim 1, characterised in that at least one absorbing system (14-17) is arranged on a vibration peak corresponding to the first vibratory flexion mode perpendicular to the plane of the racquet.
3. A racquet according to Claim 1, characterised in that at least one absorbing system (8, 9, 18, 19, 20) is located on a vibration peak corresponding to a second vibratory flexion mode perpendicular to the plane of the racquet.
4. A racquet according to Claim 1, characterised in that at least one absorbing system (8, 9, 18, 19, 20) is located on a vibration peak corresponding to the third vibratory flexion mode perpendicular to the plane of the racquet.
5. A racquet according to Claim 1, characterised in that at least one absorbing system (8, 9) is located on a vibration peak corresponding to the first vibratory mode of lateral flexion of the racquet.
6. A racquet according to Claim 1, characterised in that at least one absorbing system (19, 20) is located on a vibration peak corresponding to the second vibratory mode of lateral flexion of the racquet.
7. A racquet according to Claim 1, characterised in that at least one absorbing system (8, 9, 18, 19, 20) is located on a vibration peak corresponding to the first coupling mode of flexion vibrations perpendicular to the plane of the racquet, and of torsion with respect to its longitudinal axis.
8. A racquet according to one of Claims 1 to 7, characterised in that the thickness of the plate (10) of visco-elastic material is between 0.5 and 1.2 mm, in that the coefficient of absorption β of the visco-elastic material is between 0.8 and 1.2, and in that the thickness of the restraint plate is between 0.5 and 1.2 mm.
9. A racquet according to one of Claims 1 to 8, characterised in that the thickness of the plate (10) of visco-elastic material is of the order of 0.8 mm, and in that its coefficient of absorption β is of the order of 1.2.
10. A racquet according to Claim 9, characterised in that the restraint plate (11) is of Zicral and has a thickness of the order of 0.6 mm.
11. A racquet according to one of Claims 1 to 10, characterised in that it has at least one absorbing element (8 and/or 9) fixed to the bridge (4) of the racquet (1).
12. A racquet according to Claim 11, characterised in that it has two coupled absorbing elements (8 and 9) fixed to either side of the bridge (4).
13. A racquet according to one of Claim 1 to 10, characterised in that it has at least one absorbing element (18 and/or 19 and/or 20) fixed to the racquet head (3).
14. A racquet according to Claim 13, characterised in that it has at least one absorbing element (18) fixed to the top of the racquet head (3).
15. A racquet according to Claim 14, characterised in that it has two coupled absorbing elements (18) fixed at the top of the racquet head (3) to either side of the plane (2) thereof.
16. A racquet according to one of Claims 13 to 15, characterised in that it has at least two coupled absorbing elements (19, 20) fixed on the racquet head (3) to either side of the longitudinal axis (y', y) of the racquet.
17. A racquet according to Claim 16, characterised in that it has four coupled absorbers (19, 20) fixed on the head (3) to either side of its plane (2), as well as of its longitudinal axis (y', y).
18. A racquet according to one of Claims 1 to 10, characterised in that it has at least one absorbing element (14 and/or 15 and/or 16 and/or 17) fixed to the interior or to the exterior of one branch (6 and/or 7) of the racquet.
19. A racquet according to Claim 18, characterised in that it has two coupled absorbing elements (16 and 17) fixed to the interior of the two branches (6, 7).
20. A racquet according to Claim 18, characterised in that it has two coupled absorbing elements (14 and 15) fixed to the exterior of the two branches (6, 7).
21. A racquet according to Claim 18, characterised in that it has four coupled absorbing elements (14 to 17) fixed to the interior and to the exterior of the two branches (6, 7).

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