FR2687324A1 - Racket equipped with stringing, such as a tennis racket - Google Patents

Abstract

The present invention relates to a strung racket for a ball game, such as a tennis or squash racket. According to the invention, a racket (1) including longitudinal strings (2) and transverse strings (3) located substantially in one and the same plane includes first strings, at least one mechanical characteristic of which is substantially equal to a first value (V1), and includes second strings, the said mechanical characteristics of which has a second value (V2) which is different from the said first value (V1). The technical field of the invention is that of the manufacture of tennis and squash rackets and of stringing for such rackets.

Description

 Racket with a string such as a tennis racket.

DESCRIPTION
The present invention relates to a strung racket for ball games, such as a tennis or squash racket.

 The technical field of the invention is that of the manufacture of tennis and squash rackets, and strings for such rackets.

 Snowshoes are commonly used and in very many countries, the general design of which is relatively old, and the performance of which is adjusted to the level of qualification of the player by various physical parameters of design and construction of the racket which in particular influence its precision, its handling and aerodynamic behavior.

 We also know that the effect that can be given to the ball upon its impact with the stringing of the racket plays a major role in the tactics of tennis.

 Many documents relate to improvements in the structure of rackets, particularly tennis, intended to improve performance.

 Among these documents, a large number relate to complex ropes, in particular double ropes; US Patent 4,804,183 (Doran et al.) describes a racket provided with two strings extending in parallel planes, each of the strings being stretched to a different value; the invention described in this document also relates to a tactile indicator by which the player can differentiate the face and therefore the rope that he uses, at all times.

Patent application FR 2 360 325 (Fischer) relates to another type of tennis racket comprising three layers of strings in which the pitch of the transverse strings arranged on one layer and of the longitudinal strings arranged on two layers is different, and the racket includes sheathing means at the point of contact between the strings of the different layers
Other attempts have been made, which are for example described in US Pat. No. 4,462,591 (Kenworthy) which describes a racket string having particular sections, in particular strings having sections whose opposite external faces are respectively concave and convex .

 However, the various improvements and improvements to tennis rackets known to date, are all very complex, therefore expensive to manufacture and therefore very little, if not used.

 The objective of the invention is to improve the performance of a racket (of tennis in particular) of the most common type and easy to manufacture, which comprises a string contained in a single plane, which string comprises longitudinal and transverse strings crossed, usually at right angles, and intertwined.

 The solution to the problem posed consists in providing a racket such as a tennis racket comprising crossed longitudinal strings, substantially at right angles, and intertwined with transverse strings, which longitudinal and transverse strings are each held by their two ends at a frame. by means of retaining means, which longitudinal and transverse cords are situated substantially in the same plane (P), in which, among said longitudinal cords and transverse cords, first cords, also called main or "overactive" cords, have at least a mechanical characteristic substantially equal to a first value V1, which mechanical characteristic of second strings (or secondary strings) is substantially equal to a second value V2 different from said first value V1.

It should be noted that the present invention applies particularly to strung rackets, the strings of which extend substantially in the same plane, that is to say rackets comprising a single string, in contrast to rackets provided with double strings or complex ropes as described in particular in the
U.S. Patent 4,804,183 above.

 It should also be noted that the terms "mechanical characteristics" applied to said first and second strings according to the invention must be understood as being related either to at least one intrinsic mechanical characteristic of said first or second strings such as for example the elongation at breaking, breaking load, modulus of elasticity, or to a mechanical characteristic of assembly of said first and second rope, that is to say the force or tension of assembly.

 Thus, according to a particular characteristic of the invention, said first ropes are prestressed, that is to say stretched or mounted or stretched with a first prestressing force, for example of the order of 25 kg, which is substantially very different from a second mounting force or prestressing of said second ropes which can for example be of the order of 1 to 5 kg.

According to a particular characteristic of the invention, said intrinsic mechanical characteristic is the elongation at break of said strings, for example expressed as a percentage, and the ratio
V1 / V2 between said first and second values is less than 0.5, preferably less than 0.3, for example close to 0.2 to 0.1.

 According to a particular characteristic of the invention, said intrinsic mechanical characteristic is the breaking load and the ratio V1 / V2 between said first and second values is greater than 2, preferably greater than 5, for example close to 10 to 20.

 According to a particular characteristic of the invention, said intrinsic mechanical characteristic is the modulus of elasticity (longitudinal, in tension) and the ratio V1 / V2 between said first and second values is greater than 2, preferably greater than 5, for example neighboring from 10 to 20.

 Advantageously, the racket according to the invention comprises said longitudinal strings which form part of said first strings and it comprises main transverse strings which form part of said first strings and which are arranged alternately with secondary transverse strings which constitute said second strings.

 According to another embodiment, the racket according to the invention comprises said transverse strings which form part of said first strings and it comprises main longitudinal strings which form part of said first strings and which are arranged alternately with secondary longitudinal strings which constitute said second strings.

 According to a preferred embodiment of a racket according to the invention, said racket comprises, arranged longitudinally or transversely, a set of strings parallel to each other which successively comprises: one of said first strings of high mechanical characteristics, then an odd number of said second strings with weak mechanical characteristics, then a first string with high mechanical characteristics, an odd number of said second strings with weak mechanical characteristics ...

 Advantageously, said first cords are of substantially rectangular section, preferably of substantially square section, for example with rounded angles.

Advantageously, said first cords are made of synthetic material (for example nylon or elastomer);
Advantageously, said second cords are fixed by their ends to said frame by means of very flexible elastic means.

 Advantageously, said second strings comprise a central part which is not very elastic (whose elasticity modulus is of the order of magnitude of the elasticity modulus of said first strings) and two very elastic end parts (very flexible).

 Advantageously, said first cords have a section whose surface is greater than or equal to 1.8 10 -6 m2, for example a section whose surface is close to, 2.25 10 -6 m2; in the case of cords of circular section, said first cords have a diameter greater than 1.5 10-3m, for example close to 1.7 10-3m.

 According to a particular embodiment, said strings have a low mutual (surface) coefficient of friction.

 Said low mutual friction coefficient can in particular be achieved by coating at least partially the external surface of at least part of said strings with a material facilitating the sliding of said crossed and interlaced strings with respect to the others, such as for example polytetrafluoroethylene (for example distributed under the brand name "TEFLON").

 Alternatively, said low mutual friction coefficient can be obtained by means of intermediate parts provided with a low friction coefficient which are arranged at points of contact between said transverse cords and said longitudinal cords, between them.

 Said second cords can be made of flexible extruded (or overmolded) elastomer on a core essentially constituted by a wire, for example a metallic or nylon wire, of smaller diameter.

 Thanks to the specific characteristics of a tennis racket according to the invention, rackets having increased performance can be obtained at low cost.

 In fact, thanks to the characteristics of the invention, the relative movement possible is favored between at least part of said transverse cords and at least part of said longitudinal cords and / or between said longitudinal cords between themselves and / or between said transverse cords between them, and it modifies and thus improves the performance of the rackets, in particular promoting the "effect" that can be given to the ball upon impact with the racket.

 The numerous advantages provided by the invention will be better understood through the following description which refers to the appended drawings which illustrate without any limiting character particular embodiments according to the invention.

 Figure 1 is a plan view of a tennis racket according to the invention. invention.

 Figure 2 is a partial perspective view of a particular embodiment of a racket according to the invention.

 Figure 3 is a view along III / III of Figure 1.

 Figure 4 is a cross section of a rope entering into the development of a particular embodiment of a racket according to the invention.

 As it clearly appears in FIGS. 1, 2 and 3, the present invention relates to snowshoes of known types which include a string comprising longitudinal strings 2 which are crossed and intertwined with transverse strings 3; it can be seen more precisely in FIG. 2 that the transverse cords 3 which are substantially parallel to each other, and held in the frame 4 by retaining means 10, which pass through said frame by channels 4a provided in said frame, pass successively above and below the longitudinal cords 2 which they meet; in the same way and, conversely, each of the longitudinal strings 2 passes successively above and below the transverse strings 3a / 3b that they meet; said longitudinal strings 2 being fixed in substantially the same manner as said transverse strings, and being parallel to each other and perpendicular to said transverse strings.

 According to the invention, the racket strings are made with two different types of strings, namely first strings or main strings which have "high" mechanical characteristics and second strings or secondary strings which have different mechanical characteristics, know much more "weak".

 By way of example, it can in particular be envisaged that said main cords or first cords, for example of circular section and made of a material usually used, for example nylon, have a diameter of the order of 1.7 mm, a load at break of the order of 60 to 70 kg, an elongation at break of 20 to 25% said second strings or secondary cords are for example of the same diameter as said main strings but are provided with a load characteristic at breaking which is less than 10 kgs, for example less than or equal to 5 kgs, and have a characteristic of elongation at break, for example at least equal to 50% or in another example of the order of 100 to 500 %.

 As illustrated in FIG. 1, it can be seen that said tennis racket comprises, in a known manner, a frame 4 of oval shape extended by uprights 6 terminated by a handle 5 allowing the handling of the racket; said racket may also include a part 7 completing said frame.

 In the embodiment shown in Figure 1 and in accordance with the invention, the part of the racket stringing formed by the longitudinal strings 2 is formed by an alternating succession of main strings or first strings 2a, and secondary or second strings strings 2b, all of said longitudinal strings being parallel to each other and parallel to the longitudinal axis of the racket, which longitudinal strings are all located substantially in the plane of FIG. 1; in the same way, it can be seen that said transverse cords 3 are alternately and successively constituted by first transverse main cords or cords 3a and second transverse secondary cords or cords 3b which are also substantially situated in the plane of FIG. 1.

 With reference to FIG. 2, it can be seen that, in a preferred embodiment, said longitudinal cords 2 which are parallel to each other, are spaced apart by a substantially constant pitch d1 which can for example be of the order of 7 or 11 mm, said transverse cords 3a and 3b which are also parallel to one another, are separated by a transverse pitch d2 which is substantially constant and which can for example be equal to said pitch d1 separating said longitudinal cords 2.

 With reference to FIG. 3, it can be seen that said longitudinal 2 and transverse 3, in particular 3b, strings are substantially located in the plane P of the string which corresponds substantially to the median plane of symmetry of said racket and said frame 4.

 In the particular embodiment shown in FIG. 3, said secondary transverse cord 3b is made up of a central part 8 which is not very elastic, which can for example be made up as illustrated in FIG. 4, of a metallic or nylon core 13, coated or coated with an elastomeric material, which is extended by end portions of said rope, which end portions 9a and 9b of said secondary transverse rope 3b being very elastic and being provided with said means for holding the ends of said rope relative to said frame.

 In a particular embodiment, said transverse 3 and longitudinal 2 cords can be connected by connecting means 14, such as knotting means; alternatively, in another mode also shown in FIG. 3, the external surfaces of said transverse and longitudinal cords, respectively 12 and 11, can be such that their relative coefficient of friction is low.

 With reference to FIG. 4, it can be seen that in a particular embodiment of cordage provided with secondary or second strings according to the invention, said cord 2 which comprises a core which can be constituted by a wire 13, has a general section of square shape, limited by substantially equal side faces 21, which faces forming the sides of said section are separated by rounded angles 22 of said square.

Claims (10)

 1. Racket (1) comprising longitudinal strings (2) crossed and intertwined with transverse strings (3), which longitudinal and transverse strings are located substantially in the same plane (P), characterized in that among said longitudinal strings and strings transverse, first strings have at least one mechanical characteristic substantially equal to a first value (V1), which mechanical characteristic of second strings is substantially equal to a second value (V2) different from said first value (V1).  2. Racket according to claim 1, characterized in that said mechanical characteristic is the elongation at break of said strings, and in that the ratio (V1 / V2) between said first and second values is less than 0.5.  3. Racket according to any one of claims 1 to 2, characterized in that said mechanical characteristic is the load at break and in that the ratio (V1 / V2) between said first and second values is greater than 2.  4. Snowshoe according to any one of claims 1 to 3, characterized in that said mechanical characteristic is the elastic modulus and in that the ratio (V1 / V2) between said first and second values is greater than 2.  5. Racket according to any one of claims 1 to 4, characterized in that it comprises said longitudinal strings which form part of said first strings and it comprises main transverse strings (3a) which form part of said first strings and which are arranged alternately with secondary transverse strings (3b) which constitute said second strings.  6. Racket according to any one of claims 1 to 4, characterized in that it comprises said transverse strings which are part of said first strings and it comprises main longitudinal strings (2a) which are part of said first strings and which are arranged alternately with secondary longitudinal cords (2b) which constitute said second cords.  7. Racket according to any one of claims 1 to 6, characterized in that said first strings are of substantially square section.  8. Racket according to any one of claims 1 to 7, characterized in that said second strings are fixed by their end to said frame by means of very flexible elastic means  9. Racket according to any one of claims 1 to 8, characterized in that said second strings comprise a central part (8) not very elastic and two end parts (9a / 9b) very elastic.  10. Racket according to any one of claims 1 to 9, characterized in that said first strings have a section whose surface is greater than or equal to 1.8 10-6m2, that is to say in the case of strings circular section, said first cords have a diameter greater than 1.5 10-3m.