GB2267512A

GB2267512A - Racket strings

Info

Publication number: GB2267512A
Application number: GB9212084A
Authority: GB
Inventors: Peter Vongehr
Original assignee: VONTEC
Current assignee: VONTEC
Priority date: 1992-05-21
Filing date: 1992-06-08
Publication date: 1993-12-08
Also published as: AU1819692A; JPH05345054A; SE9201795A0; IT1255454B; GB9212084D0; FR2691368A1; ITMI921610A1; SE9201795D0; ITMI921610A0; DE4216739A1; ES2049170B1; ES2049170A1

Abstract

A string for the stringing of e.g. tennis rackets comprises a fine rope consisting exclusively of metallic strands, particularly of a plurality of round stranded wires, as shown. Overall rope diameter is 0.8mm to 1.5mm. The metal may be Cr Ni-steel plus Mo. Cover 8 may be of plastics, e.g. polyamide or P.T.F.E. The high number of metallic strands improves tensile strength, oscillation behaviour, handling, control, and service life. <IMAGE>

Description

22-6-7512 A STRING FOR THE STRINGING OF GAME RACKETS The present invention

refers to a string for the stringing of game rackets for tennis or similar games, e.g. badminton and squash.

The stringing of a game racket of the kind mentioned above has to meet a variety of requirements. Besides the price of the string itself and for the stringing, good playing characteristics and a prolonged useful life of the stringing cre the two most important criteria by which the stringing of a game racket is judged. As far as the playing characteristica are concerned, a sufficiently high elasticity of the string has to be aimed at. A high elasticity is favourable not only for the control and the acceleration of the ball, but also as far as the reduction of the impact feedback to the player is concerned. Also the oscillation behaviour of the stringing in the moment the ball has left the stringing has an important influence on the impact feedback to the player. In order to reduce this influence, the oscillations of the stringing in the moment the ball has left the racket should be dampened as efficiently as possible. Such dampening should be effected by the presence of a high self-dampening behaviour of the string in order to avoid the provision of additional dampening means. Finally, the weight of the stringing is of some importance, i.e the weight should not exceed a certain limit in order to ensure that the balance between racket head and racket handle is not impaired when the kind of stringing is replaced by another one.

Decisive for the service life or durability of a stringing are the tensile strength, the abrasion resistance as well as the sensitivity towards the influences of temperature and humidity. Furthermore, certain creep effects have to be considered which origin from structure alterations of the string under varying 2 conditions of load. All these influences have the result that the tension and the elasticity of the string decrease quite rapidly. Thus, the playing characteristics of the racket are rapidly gone for the worse and the stringing has to be replaced in quite short intervals.

Known in the art are game rackets having a stringing consisting of strings made of plastic material or consisting of catgut strings. As experience has shown, such strings are quite sensitive towards external influences, particularly change of temperature and humidity, with the result that the tension of the stringing is reduced, i.e. the stringing becomes soft. A stringing made of plastic material or a catgut stringing usually have only a short useful life, particularly under heavy-duty conditions e.g. when the racket is used by a professional tennis player. The reason therefore is that the tensile strength of the stringing known in the art is quite low and is even decreased due to the above mentioned external influences. Finally, it is possible that an atmosphere with a. certain composition, e.g. salt containing air in sea regions, may have an adverse effect on the material characteristics of the stringing known in the art.

Tests have been performed in the prior art also with metallic strings, particularly with stranded wire strings in which the metallic center wire has been replaced with a plastic material center wire in order to improve the elasticity of the string. For instance, such a string, known in the prior art, is constituted by six metallic wires each having a diameter of 0.28 mm and wounded around a center wire made of a plastic material having a diameter of 0.7 mm. However, practical experience has shown that metallic strings of the kind described above cannot meet all the requirements expected from a perfect string for the stringing of a game racket because its quality decreases quite rapidly, particularly under the influence of temperature variations, due to the fact that an important part, i.e. the center wire, still had to be made of plastic material. Moreover, also the oscillation behaviour of such a string fell short of the expectations.

It is an object of the present invention to provide a string for the stringing of game rackets for tennis or similar games which does not have the disadvantages of the strings known in the prior art.

Particularly, it is an object of the present invention to provide a string for the stringing of game rackets for tennis or similar games which provides improved game control and which has a prolonged usable life.

It is a still further object of the present invention to provide a string for the stringing of game rackets for tennis or similar games which keeps its good characteristics over a long period of time even under the influence of temperature variations and humidity.

It is a still further object of the present invention to provide a string for the stringing of game rackets for tennis or similar games which has a very high tensile strength and by use of which a stringing can be realized having a high elasticity and tension over a prolonged period of time whereby the oscillation behaviour is simultaneously superior.

To meet these and other objects, the invention provides a string for the stringing of game rackets for tennis or similar games. According to the invention, the string is constituted by a fine rope comprising a plurality of strands which are exclusively made of metallic material.

A pure metallic stringing, per se, is much less sensitive to 4 influences caused by atmospheric conditions like variation in temperature or humidity than a stringing comprising plastic material strings or catgut strings. Besides these facts, it comprises usually a higher tensile strength and, consequently, is more durable. Even under heavy- duty conditions, a metallic stringing keeps its elasticity and tension over a prolonged period of time. With the wire materials available today, furthermore, a sufficiently high elasticity of the stringing may be realized.

By avoiding the use of plastic material as the supporting central part of the string, the favourable characteristics of the metallic string of the invention fully show off to advantage without impairment due to the presence of plastic material with its disadvantageous characteristics. Thereby. the fact that the tensile strength of a metallic string is the higher the smaller the diameter of the individual strands is, the overall crosssectional area of the string being constant, is of particular importance. Thus, in using a high number of small diameter strands, a very high tensile strength and, consequently, a prolonged life of the stringing can be realized, particularly if the strands are made of stainless high-grade steel.

A particular advantage of the string according to the invention is the fact that due to the provision of a high number of metallic strands by which the fine rope is constituted as conpared to the known common stranded wires a corresponding high number of friction areas is effective. Thus, under dynamic load during the kick-off of a ball, a pronounced inner friction of the string occurs and, thereby, the oscillations of the stringing are effectively dampened.

Preferably, the fine rope is constituted by a plurality of stranded wires. Particularly well performed a fine rope which is constituted by a twolayer round stranded wire rope which comprises a central stranded wire. It is possible to design the fine rope by using flat stranded wire. However, ropes constituted of flat stranded wires are much more expensive to manufacture and are, thus, less suitable for the purpose of the invention.

Particularly good results can be achieved with fine ropes having an overall diameter of between 0.8 mm and 1.5 mm and whose metallic strands are made of stainless high-grade steel with an at least nearly uniform diameter of between 0.02 mm and 0.05 mm.

The useful life of the string of the invention can be further prolonged by providing the fine rope with a protective cover layer protecting the surface of the fine rope from mechanical and chemical aggressions, particularly at the points of intersection of the individual strings of the stringing and further at the points where the string is bent or knotted; these points are particularly endangered. Preferably, the protective cover layer is made of plastic material, e.g. of polyamide or Teflon (M). As the protective cover layer is not an operatively effective part of the fine rope, it does not have a disadvantageous influence on the characteristics of the string per se.

In the accompanying drawing, an embodiment of a string for the stringing of a game racket, e.g. a tennis racket, is schematically shown in a greatly enlarged cross sectional view. Thereby, the particular design of the fine rope constituting the essential part of the string can be clearly seen.

The fine rope is designated with reference numeral 1 and is designed as a two-layer round stranded wire rope having a central stranded wire 4. In all, the fine rope is constituted by (8 x 19) and (7 x 7) = 201 metallic strands 7. Particularly, the two-layer round stranded wire rope comprises a first layer 2 and a second layer 5 as well as the central stranded wire 4.

The central stranded wire 4 is composed of seven metallic strands 7 and is sourrounded by the first layer 2 being constituted by six stranded wires each comprising seven metallic strands. The second, outer layer 5 is composed of eight round stranded wires 6 each comprising nineteen metallic strands 7.

Each of the metallic strands 7 used to form the stranded wires 3, 4 and 6 are mad of high-grade steel 1.4401 (designation according to DIN), i.e. a CrNi-steel with an addition of molybdenum. The diameter of the metallic strands 7 is between 0.02 mm and 0.05 mm, preferably between 0.03 mm and 0.05 mm.

The second outer layer 5 of the fine rope 1 is covered by a protective layer 8 consisting e.g. of polyamide or tetrafluor ethylene (TEFLON). The overall diameter of the fine rope 1, including the cover layer 8, amounts to between 0.8 mm and 1.5 mm, preferably to between 0.95 mm to 1.5 mm.

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Claims

PATENT CLAIMS

1. A string for the stringing of game rackets for tennis or similar games, said string being constituted by a fine rope comprising a plurality of strands which are exclusively made of metallic material.

2. A string according to claim 1, characterized in that said fine rope is constituted by a plurality of stranded wires having essentially circular cross section.

3. A string according to claims 1 and 2, characterized in that said fine rope is constituted by a two-layer round stranded wire rope comprising a central stranded wire.

4. A string according to claim 1, characterized in that said plurality of strands are made of high-grade steel.

5. A string according to claim 1, characterized in that the overall diameter of the fine rope is between 0.8mm and 1.5 mm.

6. A string according to claim 1, characterized in_ that said strands constituting said fine rope all have essentially the same diameter.

7. A string according to claim 6, characterized in that said strands constituting said fine rope have a diameter of between 0.02 mm and 0.05 mm.

8. A string according to claim 1, characterized in that said fine rope is provided with a protective cover layer.

9. A string according to claim 8, characterized in that said protective cover layer is made of plastic material.

10. A string according to claim 9, characterized in that said protective cover layer is made of polyamide or Teflon (M).

11. A string according to claims 3-8, characterized in that said fine rope comprises (8x19) + (7x7) metallic strands which are made of CrNi- steel with an addition of Mo, whereby the individual metallic strands have a diameter of-between 0.03 mm and 0.05 mm and whereby the overall diameter of the fine rope is between 0.95 and 1.5 mm.