EP0589906B1 - Tennis, squash or other racquet - Google Patents

Abstract

The present invention relates to a system of tensioning for strung sports equipment like tennis racquets with adjustable string tension in which some of the strings are connected to the tensioning mechanism as 'primary string sections' while the rest, as 'secondary string sections', are only indirectly connected to the tensioning mechanism via the primary string sections. The arrangement of the primary and secondary string sections means that a ball striking any part of the surface contacts the same number of primary and secondary string sections.

Description

The invention relates to a tennis, squash, racquetball or other racket with an essentially elliptical frame, a handle connected to this and a string arranged within the frame head, consisting of strings crossing one another, which several deflected on the frame with low friction and stretched over the frame Include strings with substantially parallel string sections, the stringing being connected to a tensioning device which exerts an adjustable tensile force on the strings, a part of the string sections guided through the frame head being directly connected to the tensioning device as primary string sections.

The tensioning device integrated in a ball racket should make it possible to change the string tension and adapt it to individual needs. Such rackets are known for example from US-A-2 089 118, US-A-2 206 548, US-A-2 165 701 and EP 0 108 150 A.

The strings, or part of the strings, should be extended beyond the striking surface and guided up to the handle or at another suitable point in such a way that the tensioning device arranged there exerts a tensile force on the strings and enables adjustment of the string tension. The rackets according to the aforementioned publications show different stringing patterns.

The basic problem of tensionable ball rackets, especially tennis rackets, is that when the tensile force is introduced into the two ends of the string, the tension due to the friction and the elasticity of the string is not distributed sufficiently evenly over the entire face. The attempt, To remedy this by means of friction-reducing components such as rollers or sliding elements (cf. EP 0 108 850 A), fails because a large part of the friction losses result from the crosslinking points when the string is woven in the face and is practically unavoidable there, since according to the Rules of the tennis federation a weaving of the strings is mandatory.

In the case of rackets known according to the prior art, in which tensile force is introduced only at the string ends of one or two strings which form the stringing, in practice there have not yet been satisfactory adjustment options.

The obvious alternative, to connect all string sections with a tensioning mechanism after only one crossing through the face, is possible in principle, but leads to a very voluminous string tree, which has to be guided along the frame and also leads to very high pressure loads in the frame, which in turn require a very complex frame structure. It is currently not possible to manufacture a satisfactory, marketable product within the existing material specifications with regard to strength, rigidity and weight.

On the other hand, in the case where not all of the string sections are directly connected to the tensioning mechanism, a tension gradient occurs, i.e. the tension decreases asymptotically with increasing distance from the tensioning mechanism. Strings that are then only indirectly connected to the tensioning mechanism must therefore have a lower tension than those strings that are connected to the tensioning mechanism over short lengths.

If you define string sections that are directly connected to the tensioning mechanism as primary strings and string sections, which only lead indirectly to the tensioning mechanism via the primary strings as secondary strings, it follows from the above explanations that the tension of primary strings will generally not be identical to the tension of the secondary strings. However, since the tension has a significant influence on the return behavior of the ball, this return behavior will depend very much on whether the ball strikes primarily primary or predominantly secondary strings, depending on the location of the striking surface of the ball. The distribution of the primary and secondary strings on the playing surface is an essential parameter influencing the playing behavior of rackets that can be tensioned.

According to EP 0 106 850 A, the stringing pattern is selected such that at least part of the stringing means that the immediately adjacent string sections belong to different strings and that the distance between the parallel string sections belonging to the same string is at least about a ball radius. The consequence of this is that when the ball strikes the string centrally, it primarily hits primary strings, which naturally have a higher tension, and that secondary hits are struck predominantly, which are generally relatively softer. In addition, each string is guided outside the target area along the frame over a relatively large distance, which brings about a great elasticity of the entire string bed, but the resulting softer feel is not pleasant for all players.

A racket of the type mentioned is known, for example, from US-A 21 65 701, but all primary strings are guided there in the direction of the longitudinal axis of the handle or parallel thereto, while the secondary strings are, without exception, stretched perpendicularly to this. This stringing pattern results in string sections of different lengths, each with a different string tension, with the result that neither a stabilized head shape nor even an approximately uniform tension can be achieved.

It is an object of the present invention to improve the above-mentioned ball racket in such a way that offensive players are given a desired “direct”, less elastic feel, and yet the racket has the functional adjustment of the string tension.

This object is achieved with the tennis, squash, racquetball or other racket specified in claim 1. This is characterized in that essentially all strings, consisting of primary string sections and respective sections connected beyond the striking surface with additionally fixed diagonally or orthogonally stretched strings between the frame points or of a primary and a secondary, namely only indirectly via the primary string sections with the The string section connected to the tensioning device and the respective sections, which are extended beyond the striking surface and connect the primary and secondary sections to one another or to the tensioning device, are of essentially the same length, so that the tension when the tensioning device is actuated is approximately the same and in the same amount is changed. In other words, the different strings representing the strings are each of the same length. However, the strings of the string sections that are guided along the frame are each as short as possible, i.e. the string is led from a first hole into the hole next to it. This keeps the elasticity of the string guide on the frame small. Furthermore, this string guide has the effect that when the ball hits the strings which are adjacent to one another and which are connected to one another, so that a tension exchange with further additional elasticity (via other strings) does not take place.

Furthermore, the primary and secondary string sections or the primary string sections and fixed strings are arranged that an impacting ball touches essentially the same number of primary and secondary strings at all points on the face of the frame head. Here, a string guide is selected, which leads to a tensioning mechanism along the frame along the handle in the handle, but the jump of the connected strings by at least one ball radius is dispensed with and, on the contrary, the string guide is designed so that the ball strikes touches as many primary and secondary strings as possible in all areas of the face.

According to an advantageous development of the invention, at least some of the primary and secondary string sections are arranged next to one another in an alternating sequence. As an alternative to this, however, at least some of the primary string sections can also be arranged in such a way that two primary string sections lie alternately with two secondary string sections.

The racket preferably has a diagonal or orthogonal stringing pattern. According to a further embodiment, in the case of a diagonal stringing pattern, the string guide of the right side of the frame head is displaced to the left-hand side in such a way that crosslinking points result on the longitudinal axis of the racket, which are formed from a primary and a secondary string section.

In at least part of the stringing, the distance between two strings lying next to one another in parallel is preferably about 1/4 of the ball diameter. The fact that in a stringing pattern according to the invention essentially the same number of primary and secondary string sections are touched by the ball - in the aforementioned case 2 x 4 cross-arranged string sections - enables a very uniform distribution of elasticity over the entire face and thus a very controlled bounce behavior of the ball. Because usually one there is a certain difference in the string tension between the primary and secondary string sections, the primary string sections exhibiting a harder tension will force the adjacent secondary string sections to a greater vertical change in course, so that a vertical structure in the string bed, the stringing, is created. This vertical structure significantly improves the possibility of introducing a spin or spin into the balls by appropriate racket guidance.

Preferably, the angle of the string guide in the racket head in relation to the head shape is selected so that in the racket head area of the frame, with essentially all set tensions, the force curves at essentially all deflection points in the frame have no resultants which change the head geometry of the racket, i.e. the head shape is longer , wider or otherwise deformed. In other words, bending stresses, which can cause the frame head to be deformed, are avoided.

According to a preferred embodiment, the tensioning device is arranged in the handle so as to be longitudinally displaceable. In particular, as is known in principle from EP 0 106 850 A, a string guide is selected in which the string sections extending beyond the frame surface are guided into the handle along the outer surface of the frame, where they are fastened to the tensioning device mentioned.

The number of string sections which are guided in the handle and connected to the tensioning device is preferably greater than 10, preferably at least 14 and less than 36, preferably at most 28. By the number of string sections which are connected directly to the tensioning device and in Frame head each form primary string sections, an optimal string density of the stringing is achieved, which ensures that an impacting ball is seen in each stringing direction, hits multiple primary strings to allow for controlled ball control. On the other hand, the number of string sections to be handled as a string tree is limited to a maximum.

According to the present invention, the string density in the playing surface can also be increased independently of the number of (primary and secondary) strings being handled by additionally tensioning string sections in the playing surface that are not connected to the tensioning device. These additional fixed strings which are stretched diagonally or orthogonally between two frame points are drawn in and stretched in the conventional manner using known aids. The fixed strings will preferably be arranged in the outer edge zone, so that a ball hitting the racket hits the centrally arranged tensionable primary and secondary string sections in the majority of the strikes.

According to a further embodiment, the number of fixed strings can be increased to such an extent that only primary string sections are required. In this case, the arrangement of the fixed and the tensionable strings is also chosen such that the tensionable strings preferably run through the center of the face and the fixed strings lie in the edge zone.

A further limitation of the elasticity of the stringing can be achieved according to a further development of the invention in that a viscoelastic material is arranged between the string sections guided on or over the frame and / or in the handle. A polymer plastic, preferably polyurethane, is particularly suitable for this purpose.

In the present case, a viscoelastic material refers to substances whose elasticity behavior is different in the case of brief abrupt movement sequences than in the case of longer influences. Thus, the viscoelasticity of the intermediate layers, which can also be designed as sleeves for string sections, means that a tennis ball occurring during a stroke does not result in a relative movement of the string section or sections in question with the intermediate layer, and on the other hand, the string slips easily when tensioned thereon is possible, so that overall the impact behavior of the racket according to the invention is even "harder, more direct".

Fig. 1 und 2

jeweils schematische Draufsichten auf eine Ausführungsform eines erfindungsgemäßen Tennisschlägers.

Embodiments of the invention are shown in the drawings. Show it

1 and 2

each schematic top views of an embodiment of a tennis racket according to the invention.

The tennis racket shown in the figures has a handle 10 and a frame 11. The handle is hollow and has a tensioning device, not shown. The basic structure of a tennis racket with a tensioning device is known from the prior art, so that reference is made to EP 0 106 850 A, for example. Both tennis rackets shown in Fig. 1 and 2 have a diagonal stringing pattern, which is formed by 2 x 4 strings.

1, the ends of the strings 12 to 19 are each firmly connected to the tensioning device. The connection points of the string 12 are denoted by a and b. The string 12 guided by the clamping end a on the tensioning device in the handle 10 along the frame is passed through a bore in the frame 11 and forms a primary string section 121, since it is directly connected to the tensioning device. The string section 121 ends at an opposite bore in the frame 11, where the string 12 is guided along the frame as a short string section piece 122 to pass into the adjacent bore to run and form the secondary string section 123. As the string 12 continues, the string is again guided through a bore in the frame 11, where it is guided along the frame to form a short string section 124, again projecting through a bore, whereupon the string 12 continues as a further secondary string section 125 to the opposite end. Forming a further short string section 126, the string section 127 finally runs back to the clamping end b on the tensioning device. The strings 127 and 121 thus form primary string sections, the string sections 123 and 125 secondary. The string sections 122, 124 and 126 are chosen as short as possible in order to obtain a minimum of elasticity from the relevant sections.

Correspondingly, the string 13 is guided starting from the clamping point c to the other clamping point d; The same applies to the strings 14 to 19. In the course of the string 19, the primary string sections are designated 191 and 194, whereas the string sections 192 and 193 represent secondary string sections. If a ball now strikes in the area in which the strings 19 and 12 intersect several times over their string sections, the ball touches two primary string sections 191 and 194 as well as 121 and 127, which essentially determine the restoring force and thus the ball trajectory. The same applies accordingly when the ball strikes at other locations, where it touches two pairs of primary strings arranged in a crossed manner. The striking behavior is essentially constant over the entire stringing, ie regardless of the impact of the ball. The guidance of the strings 12 to 19 is selected so that there is an asymmetrical stringing pattern with respect to the racket longitudinal axis 20 on the right and left. On this axis 20 there are respective crossing points of primary and secondary strings, but no crossing points of primary strings. On the transverse axis 21 perpendicular to this, respective crossing points of primary strings and secondary strings alternate. String sections running parallel to each other alternately represent secondary and primary string sections.

In the embodiment according to FIG. 2, in which only the strings 22 to 25 relating to a diagonal direction are entered, which are connected at the clamping locations r to y to the clamping device arranged in the handle 10, on the other hand, pairs of primary string sections and secondary string sections lie in alternating sequence next to each other, which is clear from the example of the primary string sections 251 and 252 and the secondary string sections 253 and 254. In this case too, an arrangement of the primary and secondary strings which is symmetrical to the longitudinal axis 20 or - analogously to FIG. 1 - can be selected.

Between the frame 11 and the handle 10 and the string sections 122, 124 and 126 or adjacent string sections adjacent to each other, a PUR intermediate layer is arranged, which allows the string sections to slide against each other and relative to the intermediate layer and relative to the frame or handle when tensioned, but in the event of brief force influence, such as a blow, the relative movement in question is blocked.

As can be seen in FIG. 2, fixed strings 30 tensioned according to conventional methods can also be provided in the edge zone between two frame points 31 and 32.

Claims (9)

1. Tennis- Squash-, Racquetball- or other racquet, comprising a generally elliptical frame, a handle (10) fixed thereto and a stringing (13 to 19, 2 to 25) located in the frame head comprising strings in a woven pattern and said strings being pull through holes in the frame (11) over round support points with a low degree of friction and said strings being arranged in generally parallel sections ( 121, 123, 125, 127; 191 to 194; 251 to 245) on their way through the frame head and said strings being connected to a tightening means, which allow to stretch the strings to different degrees of tension, and a part of said strings being so called primary string sections (121, 127; 191, 194; 251, 252) with direct connection to said tightening means (a to y), characterized in that generally all string trains comprising primary string sectionsand string sections (12 to 19), which are pull along the frame beyond the hitting area and with the stringing being completed by fixed string sections (30) passing through the hitting area in diagonal or rectangular directions or comprising primary string sections (121) and secondary strings sections (123, 125), which are only indirectly connected to the tightening means through the primary string sections and the sections (122, 124, 126), which are pull along the frame beyond the hitting area and which connect the primary strings with the secondary strings resp. with the tightening means, have generally the same lengthes and that the primary and secondary strings are arranged in the hitting area in such a way, that the ball in all locations of the hitting area will touch an equal amount of primary and secondary or resp. fixed strings.
2. Racquet according claim 1, characterized in that at least a part of the primary and secondary strings (121, 127; 123,125) is located in alternate positions to each other or that at least a part of the primary strings (251,252) is located in such a way that each two primary strings (251, 252) will be in adjacent positions to each two secondary strings ( 253, 254).
3. Racquet according claim 1 or 2, characterized in that the racquet will be strung diagonally or rectangularly and in case of diagonal stringing pattern the secondary and primary strings being dislocated relatively to each other such that on the longitudinal axis (20) the weaving points of crossing strings will consist out of a set of one primary and one secondary string.
4. Racquet according to one of the claims 1 to 5, characterized in that the tension in all string sections will be changed for in general equal amounts in case the tightening means is operated.
5. Racquet according to one of the claims 1 to 4, characterized in that at least a part of the strings is located in the hitting area in such a way, that the distance between two parallel adjacent strings (121, 123, ...; 191 to 194; 251 to 254) is about a quarter of a ball diameter and/or that the angle (a) of the strings crossing the frame head in relation to the shape of the frame head is such, that in the frame head area (11) under all conditions of various tensions the resulting forces between the strings and the frame will generally not have directions or reactions, which will change the shape the frame, which means change of tension will not make the frame head wider or narrower or change or modify it in any other way.
6. Racquet according to one of the claims 1 to 8, characterized in that the tightening means is located in the handle (10) and can be moved upwards and downwards and/or that the string sections, which exceed the length, which is necessary to cross the hitting area are pull along the frame and into the handle (10) and connected to the tensioning equipment with the number of such string sections being higher than 10, preferably at least 14 and lower than 36, preferably not more than 28.
7. Racquet according to one of the claims 1 to 6, characterized in that on the surface of or between the frame and those strings, which are pull along the frame (11) and/or into the handle (10) a material is applied, which shows viscoelastic friction characteristics, preferably the visoelastic material being a polymer, particularly polyurethane.
8. Racquet according to one of the claims 1 to 7 characterized in that the fixed strings are in the outer zone of the hitting area, which is located close to the frame and in the center only primary and secondary strings are located.
9. Racquet according to one of the claims 1 to 8, characterized in that in the outer zone being only fixed strings and in the center of the hitting area being only primary strings located.

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