Racket frame, racket comprising such a frame and method of manufacturing such a frame or racket.

Abstract

The invention relates to a racket frame, comprising a handle and a racket head, made at least in part of a composite material, the upper part of said head comprising at least one ductility-enhancing layer, comprising aramid, covered with a sliding layer, improving abrasion resistance, comprising a fluoropolymer. The invention also relates to a racket comprising such a frame. The invention further relates to a method of manufacturing such a racket frame or such a racket. FIGURE 3

Description

Title of the invention: Racket frame, racket comprising such a frame and method of manufacturing such a frame or such a racket. Field of invention

[0001] The present invention belongs to the field of rackets used in racket sports on courts surrounded by walls or partitions, such as squash or padel.

[0002] More particularly, the invention relates to the improvement of the frames of such rackets, in particular with respect to the shocks and friction that they may undergo against these walls or partitions. Technological background

[0003] In racket sports played on a court defined by walls, practiced both for leisure and professional purposes, racket frames are subject to two types of significant stresses, friction and shocks. Friction along the ground, walls or partitions, for example glass or mesh, as well as shocks, also with the ground or walls (hereinafter, the term "wall" is used to define these different vertical and horizontal surfaces (ground) defining the court) or the frame of a partner's racket, not only harm the effectiveness of the shot struck but, above all, can cause damage to the racket, for example in the form of deformations or breakage.

[0004] Racket frames are now mostly manufactured with a composite material, such as glass and carbon fibers pre-impregnated with epoxy resin, using a molding process suitable for shaping thermosetting materials. Composites, and particularly carbon, have an excellent stiffness / mass ratio. However, although this well-known molding process makes it possible to manufacture a rigid and lightweight racket structure, the commonly used composite material has insufficient impact resistance, due to its lack of ductility, i.e. its insufficient capacity to deform upon impact. This makes the racket frame fragile upon impact and shock.

[0005] This problem having been identified, it has been proposed, to protect racket frames from the effects of shock, and also from abrasion, to use a bumper strip, generally called a "bumper". This is a plastic part which is injected and attached to the racket frame, at the level of the upper part of the head of the frame. The bumper is generally made of polyamide or polycarbonate.

[0006] This protective element is relatively effective. However, it is not without some drawbacks. Indeed, although the bumper is intended to prevent damage the racket frame, it does not provide any mechanical performance and in particular does not contribute to its rigidity. To obtain sufficient rigidity, it is generally necessary to use high modulus composites in the manufacture of the racket, i.e. with a high stiffness / mass ratio, which leads to an increase in the total weight of the racket. In addition, the bumper often has a tendency to break itself. Replacing a damaged bumper then requires not only the purchase of a new part, but also the adjustment of the racket, a long and tedious exercise.

[0007] Another disadvantage of the bumper is that it makes the racket heavier, while players generally look for lightweight rackets: the total mass of the racket can be a significant issue for squash players, particularly because of its impact on maneuverability.

[0008] As a result, it is common for players, especially professional players, to remove the bumper from the frame of their racket themselves, to gain comfort and / or efficiency. While this approach is conceivable for professional players, whose mastery reduces the risk of damaging their racket, this is generally not the case for recreational players.

[0009] Furthermore, in certain cases, imperfect docking of the plastic bumper on the composite frame can introduce vibrations.

[0010] Finally, some players may consider that the bumper detracts from the aesthetic appearance of their racket.

[0011] Thus, there is a need for a solution to overcome these and other drawbacks of the prior art.

[0012] One objective of the invention is thus to propose a solution making it possible to dispense with the presence of a bumper (or in certain embodiments to at least reduce its weight and / or size) on racket frames, while ensuring good resistance to shocks and friction against the walls, and presenting good vibration damping performance.

[0013] In particular, one objective of the invention is to reduce the weight of the racket, by removing the bumper, or to exploit the corresponding weight saving to improve the efficiency of the racket. Statement of the invention

[0014] For this purpose, the invention provides a racket frame, comprising a handle and a racket head, made at least partly of a composite material. According to the invention, at least the upper part of said head comprises at least one ductility-enhancing layer, comprising aramid, covered with a sliding layer, improving abrasion resistance, comprising a fluoropolymer.

[0015] The invention thus makes it possible to eliminate the bumper of the rackets of the prior art, while ensuring good shock resistance. This is made possible by the combination of two aspects. On the one hand, the improvement of ductility, using aramid. The ductility of aramid is in fact much higher than that of carbon, which has a good stiffness / mass ratio, but very low ductility, i.e. a very low capacity to deform on impact. On the other hand, the improvement of abrasion resistance, using a material facilitating sliding against a wall.

[0016] These two aspects combined make it possible to obtain a more efficient, less heavy racket (or one in which the weight of the bumper is partly transferred to the new layers), also having aesthetic advantages, such as the absence of a bumper, decoration, in the form of paint or varnish for example, protected by the sliding layer. The invention is based on a completely new and original approach to giving a racket frame good impact resistance, in particular with regard to the walls or glass walls of a squash hall, the floor of a squash or padel court, or even the racket of a pair, while improving the sliding and abrasion resistance of such a frame. Thus, it is possible to do away with the unnecessary mass represented by the bumper, and therefore to reduce the mass of the racket, without sacrificing the strength of said frame when it undergoes strong impacts during play.Such an improved frame also helps to eliminate vibrations initially caused by bumper / frame contact.

[0017] The ductility-enhancing layer according to the invention, comprising aramid, can also cover any part of the racket frame likely to receive impacts during practice.

[0018] It should be noted that it is known to apply a decorative varnish to racket frames. This should not, however, be confused with the application of a fluoropolymer, the main function of which is to facilitate sliding against a surface, and therefore to improve the abrasion resistance of the frame. This compound is particularly effective due to its very low coefficient of friction, making it possible to improve the sliding of racket frames covered with it, in the event of contact with walls. It has a lubricating effect. It is also chemically inert, which makes it interesting from the point of view of its use in a racket manufacturing process.

[0019] According to one embodiment, the ductility improvement and sliding layers are located at the level of said upper part of the head of the frame, on a peripheral portion of 25 to 35 cm.

[0020] This portion corresponds to the upper part of the head, in an area between, for example, 8:20 and 10:10, by analogy with a watch dial (the upper point of the racket therefore corresponding to 12 o'clock). When the racket is considered in its length, this portion can thus extend over a height (L3) of between approximately 8 and 14 cm.

[0021] This portion of the head of the racket frame may in particular correspond to the section on which a bumper is usually arranged. The racket according to the invention is therefore reinforced at the level of its part most exposed to shocks and friction, in particular in the case of racket sports which are played in a hall, and / or between players sharing the same playing surface.

[0022] According to another embodiment, the racket frame comprises a series of plies comprising said composite material and a last ply comprising aramid.

[0023] The frame of the racket according to the invention is therefore mainly composed of a composite material found in conventional rackets, within reach of all racket manufacturers. The fact that the aramid ply is positioned last in the manufacturing process makes it possible to adequately ensure the function of improving ductility according to the invention. The aramid is in direct contact with the walls of the playing room or the pair's racket, in order to improve the impact resistance of the racket frame.

[0024] According to yet another embodiment, the composite material, respectively the aramid, of the plies is pre-impregnated with epoxy resin.

[0025] Epoxy resin is a thermosetting material that irreversibly hardens under the effect of heat. Combined with aramid, it allows the last ply to be adequately maintained, ensuring improved ductility in the racket frame.

[0026] According to yet another embodiment, the aramid is in the form of a fabric.

[0027] Such an aramid fabric can therefore be arranged at the frame of the racket in a simple and secure manner.

[0028] According to yet another embodiment, the aramid is or comprises poly(p-phenyleneterephthalamide), or a similar material. The materials and their weights can be adapted according to the needs and the rackets.

[0029] This compound is particularly well suited to the invention. It has both good rigidity and low density, which makes its use particularly suitable as a matrix reinforcement in composite materials that make up racket frames. It also has good shock resistance and allows it to absorb vibrations that pass through the racket during play.

[0030] According to one embodiment, the fluoropolymer is chosen from polytetrafluoroethylene and / or perfluoroalkoxy.

[0031] These different compounds, applied to a racket frame, allow for the improvement of its sliding during play. Friction against the different walls and the pair's racket is limited, preventing the racket from blocking in the event of contact with these elements. These fluorinated chemical compounds also help improve abrasion resistance, particularly at the head of the racket frame.

[0032] A second object according to the invention relates to a racket comprising a frame as defined previously.

[0033] According to one embodiment, this racket is a squash racket.

[0034] According to another embodiment, this racket is a padel racket.

[0035] Thus, a racket according to the invention is particularly suitable for racket games played in an enclosed space, with walls or partitions, in which the players share the same playing surface.

[0036] A third object according to the invention relates to a method of manufacturing a racket frame comprising the following steps:

[0037] - draping at least one ply of composite material over a bladder; - draping on the at least one ply of composite material a ply comprising an aramid fabric, on at least a portion corresponding to the upper part of the head of the frame; - molding of the assembly formed by the bladder and all the folds in a mold to the final dimensions of the frame; - injection of air into the bladder and cooking; - demolding of the whole thing after cooking; - addition of a layer of fluoropolymer on at least the upper section of the racket frame.

[0038] Such a method makes it possible to conventionally manufacture an improved racket frame according to the invention, which has good resistance to impact and abrasion. This method involves racket manufacturing steps which are well known and perfectly mastered today. The innovation based on the combination of aramid fibers and varnish at the head of the frame therefore does not require more specific equipment than that already used in the usual squash or padel racket manufacturing processes.

[0039] The aramid ply is notably placed in the upper part of the racket frame in a simple manner. This step of draping the aramid fiber composite does not slow down the racket manufacturing process.

[0040] According to one embodiment, in the step of adding a layer of fluoropolymer, the layer is deposited by spraying droplets onto at least the upper section of said racket frame.

[0041] Adding the varnish in the form of a spray or aerosol allows this material to be spread evenly and homogeneously over the head of the racket frame. This step is therefore easy to implement and quick. List of figures

[0042] Other aims, characteristics and advantages of the invention will appear more clearly on reading the following description, given as a simple illustrative, and non-limiting, example, in relation to the figures, among which:

[0043] [Fig-1]: [Fig.l] shows an overall view of a squash racket according to the invention;

[0044] [Fig.2]: [Fig.2] illustrates an enlarged view of the head of the frame of a racket of squash according to [Fig.l];

[0045] [Fig.3]: [Fig.3] shows a sectional view of the frame head of a racket of squash according to [Fig.2], showing the different materials that such a frame head comprises, as well as their location in the structure of the frame;

[0046] [Fig.4]: [Fig.4] schematically illustrates a diagram of the fa process construction of a racket frame according to the invention.

[0047] Detailed description of an embodiment of the invention

[0048] A racket, particularly for squash or padel, is particularly exposed during play at the head of the frame, due to the risk of friction or impacts against the walls defining the playing space. It is for this reason that a protective "bumper" is now almost systematically provided at the upper part of the frame extending, by analogy with a time dial, over a section more or less between 10 and 2 o'clock.

[0049] As mentioned previously, one objective of the invention is to do away with such a bumper, while improving the aspects of impact resistance, comfort and efficiency. For this purpose, the invention is based on a combination of two elements, namely a ductility-enhancing layer, comprising aramid, and a sliding layer, improving abrasion resistance, comprising a fluoropolymer. Thus, a racket according to the invention effectively meets the constraints of resistance to both impact and abrasion. In particular, by facilitating sliding, a new solution is provided, which is very effective in combination with the reinforcement provided by the aramid.

[0050] The total mass of the racket impacts its handling, this parameter is therefore a major issue for players. Removing the bumper, which is a generally useless mass, allows the mass to be reduced and / or all or part of the mass thus "saved" to be used to improve the mechanical performance of the racket. Removing the bumper also helps limit vibrations that can be induced by imperfect docking of the plastic bumper on the composite frame.

[0051] Carbon, the main and usual component of the frame of a racket, traditionally provides a rigid and light structure, but does not on its own provide sufficient resistance to the sometimes violent impacts suffered by the frame of a racket. racket during a match, particularly at the head of the frame. According to the invention, the shock resistance function, despite the absence of a bumper, is provided by a ply of aramid, a composite fiber that absorbs shocks, at the head of the frame. This fiber is, for example, added during a draping step of the racket manufacturing process, braided with carbon fibers and impregnated with an epoxy resin.

[0052] It is noted that the use of aramid has already been considered in certain racket frames. On the other hand, its combination with a sliding layer is new and not obvious. Indeed, according to the invention, a sliding layer provides an abrasion resistance function at the upper part of the racket frame, over the aramid fibers. This sliding layer comprises in particular at least one fluoropolymer. Fluoropolymers suitable for the invention are polytetrafluoroethylene and perfluoroalkoxy. This fluorinated compound is preferably added after a demolding step of the racket manufacturing process, in order to protect the frame from abrasion. This fluoropolymer can be spread on the racket frame in the form of a spray. This method is rapid and allows the fluoropolymer to be spread evenly over the entire upper part of the frame.

[0053] Furthermore, when it was considered to use aramid to reinforce a racket, it was embedded between layers of carbon. Preferably, however, according to the invention, the carbon layers are first assembled, and the aramid layer constitutes a final (external) layer, only covered by the sliding layer.

[0054] Furthermore, the object of the invention being essentially to protect the racket against impacts against the walls, these layers are preferably only applied to the upper part of the racket head, on a portion corresponding substantially to that usually covered by a bumper.

[0055] The invention thus allows the production of a racket frame which is light, while having an improved structural quality, which makes it possible to ensure both shock and abrasion resistance functions, while eliminating the presence of a bumper.

[0056] In [Fig. 1] is presented, as an example of implementation, a general view of a squash racket 11 according to the invention, comprising a frame having a head 12 (intended to receive the stringing) and a handle 13. The head conventionally has a length L1 of between 35 and 42 cm, for example between 38.5 cm and 39.5 cm, and a handle of length L2 of between 25 and 35 cm, for example between 29.5 cm and 30.5 cm. The aramid ply is located, according to the invention, at the level of an upper portion of the head of the frame, corresponding to a height L3 of between 80 and 140 mm, preferably between 90 and 110 mm.

[0057] A racket frame according to [Fig.l], that is to say without the strings, weighs between 125 and 145 g, for example between 130 and 140 g. For comparison, a conventional squash racket according to the prior art and equipped with a bumper conventionally weighs between 130 and 160 g.

[0058] [Fig.2] provides an enlargement of the head 12 of the frame of the racket 11. It can still be seen that the aramid ply according to the invention is located on an upper section of the head 12 of the frame, such a section running from point 21 to point 22. This section 21-22 extends over the height L3, thus covering substantially the same peripheral portion P3 of the frame as a bumper (for example between 8:20 and 10:10, making the analogy between the head of the frame and a watch dial).

[0059] [Fig. 3] illustrates a sectional view of the head 12 of the frame of the racket 11. This section shows the different materials constituting the head 12 of the frame of the racket 11 presented in Figures 1 and 2. Three types of main layers of materials constituting the head 12 of the frame of a racket 11 according to the invention are thus distinguished. The basic material of the head 12 of the frame is a composite material 31 which corresponds to a semi-finished product comprising a thermosetting resin. This composite 31 is composed of carbon impregnated with an epoxy resin, like known tennis, squash or padel rackets. This composite 31 is also called pre-impregnated. Several layers, for example between 8 and 12 layers, of the composite 31 are generally provided.

[0060] Surrounding the base prepreg 31, a layer of a second material 32 is placed according to the invention, at least on the upper part of the head 12. This material 32 is also a prepreg, composed of aramid and carbon fibers impregnated with an epoxy resin. The aramid and carbon fibers of this prepreg 32 are advantageously interlaced in the manner of a checkerboard. [Fig. 3] shows the aramid fibers 321 in the checkerboard, braided with the carbon fibers 322. This composite 32 of aramid fibers provides improved impact resistance to the frame of the racket 11 at the former location of the bumper according to the prior art, without significantly increasing its weight.

[0061] The head 12 of the racket frame 11 also comprises a sliding layer 33 deposited over the pre-preg 32. This third material allows the head 12 of the racket frame 11 not to catch (or to catch less) along the walls or the floor of the playing surface, by allowing sliding against these walls while not being abraded.

[0062] The diagram in [Fig.4] shows the main steps of a method 41 for manufacturing the frame of a racket 11 according to the invention.

[0063] The first step 42 is based on an approach known in the field of racket manufacturing. Sheets of a first pre-impregnated material 31, consisting of carbon combined with epoxy resin, are cut upstream into specific shapes adapted to the manufacture of the frame of a racket 11. They are then draped by hand onto a plastic bladder, at a rate of 5 to 30 sheets. Such a bladder is a part known to those skilled in the art and commonly used for molding articles made of composite materials. This first draping step 42 is carried out according to a draping plan, which makes it possible to define the arrangement of the different layers of materials on the racket.

[0064] According to the invention, the method 41 comprises a second step 43 of draping at least one sheet of the second prepreg comprising aramid 32, previously cut according to the desired predetermined shape (to cover the upper part of the frame). The prepreg 32 composed of aramid fibers is placed last on the bladder, so that it is correctly located on the upper periphery of the head 12 of the racket 11.

[0065] According to a following molding step 44, the plastic bladder thus surrounded by the layers, or folds, of the two composite materials 31 and 32 is placed in a metal mold, for example steel. This mold corresponds to the final dimensions of the racket 11 to be manufactured.

[0066] The next step 45 consists of baking these pre-impregnated materials around the bladder. This baking consists of raising the temperature to between 130 and 160 degrees, preferably between 135 and 150 degrees, for a period of 5 to 15 minutes, preferably between 7 and 12 minutes. During this step 45, air can be injected to inflate the bladder, thus making it possible to press the composites 31 and 32 against the walls of the racket mold. Once baking 45 is complete, a step 46 of the method consists of deflating the bladder and opening the mold to be able to remove the bladder. The racket thus formed is removed from the mold. The excess resin is removed with a knife and / or by sandblasting. A finishing step by sanding / puttying makes it possible to fill the porosities of the frame.

[0067] This provides a clean and smooth frame, capable of receiving the sliding layer. The last step 47 according to the invention thus consists of applying this layer comprising a fluoropolymer, for example polytetrafluoroethylene, for example in spray form, to cover at least the upper part of the head 12 of the racket 11 in a homogeneous and uniform manner and thus protect it from abrasion. Where appropriate, this sliding layer also protects a decoration of the frame previously made on the layer 32.

Claims

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9. Claims Racket frame, comprising a handle and a racket head, made at least in part from a composite material, characterized in that at least the upper part of said head comprises at least: - a ductility enhancing layer (32), comprising aramid, and - a sliding layer (33) covering said ductility-enhancing layer(s) (32), improving abrasion resistance, comprising a fluoropolymer, said ductility and sliding improvement layers being located on a portion of said frame capable of coming into contact with a wall, at the level of said upper part of the head, on a peripheral portion of 25 to 35 cm, said sliding layer (33) being able to come into contact with a wall so as to facilitate the sliding of said frame against said wall. Racket frame according to claim 1, characterized in that said frame comprises a series of plies comprising said composite material and a last ply comprising aramid. Racket frame according to claim 2, characterized in that said composite material, respectively aramid, of said plies is pre-impregnated with epoxy resin. Racket frame according to claim 2 or 3, characterized in that said aramid is in the form of a fabric. A racket frame according to claim 4, characterized in that said aramid is or comprises poly(p-phenyleneterephthalamide). Racket frame according to claim 1, characterized in that said fluoropolymer is chosen from polytetrafluoroethylene and / or per-fluoroalkoxy. Racket comprising a frame according to any one of claims 1 to 6. Racket according to claim 7, characterized in that it is a squash racket. Racket according to claim 7, characterized in that it is a padel racket.

10. A method of manufacturing a racket frame according to any one of claims 1 to 6, characterized in that it comprises the following steps: - draping at least one ply of composite material over a bladder; - draping on said at least one ply of composite material a ply comprising an aramid fabric, forming a ductility-improving layer, on at least a portion corresponding to the upper part of the head of said frame; - molding the assembly formed by said bladder and all of said folds in a mold to the final dimensions of said frame; - injection of air into said bladder and cooking; - demolding of said assembly after cooking; - adding a layer of fluoropolymer on at least the upper section of said frame of said racket, forming a sliding layer, said ductility-improving and sliding layers being located on a portion of said frame capable of coming into contact with a wall, at the level of said upper part of the head, on a peripheral portion of 25 to 35 cm.

11. A method according to claim 10, characterized in that, in said step of adding a layer of fluoropolymer, said layer is deposited by spraying droplets onto at least said upper section of said frame of said racket.

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