Device of rackets

Technical Field:

The present invention relates to a device of rackets, which comprise a frame in which frame a huge number of each other crossing strings are arranged under tension so as to form a surface of impact.

Prior art:

When performing racket sports, especially tennis, many players have problems because of moving strings due to the transversal forces which arise at the moment of impact of the ball. This is especially evident for top spin- and slized-strokes, at which the main plain of the racket is kept in an angle to the planned direction of the ball. An erroneous ^" positioning of the strings can affect the properties of the racket in an unfavou¬ rable manner, which is the reason why the player has to reestablish the positioning of the strings several times. These .transversal movements of especially the longitudinal strings imply, specially for rackets having a highly tensioned stringing, that the wear of the strings considerably increases in the crossing areas, not at least due to the particles gathering in the crossing areas of the strings, which consi¬ derably reduces the life time of the string.

It is prior known to arrange plastic shims in the crossing areas of the strings, but these are separate elements which are made of plastic material which is slippery and relatively hard, which elements reduce the wear to a certain extent but do not prevent the movement of the crossing areas.

It has also been suggested to provide some of the strings with enclosing tubes made of a soft and flexible material. As a consequence thereof the crossing strings will be pressed into the material of the tube and do thereby achieve a fixation.

Technical problem:

A disadvantage, however, with such an arrangement is that the tubes only can be fitted on the strings by threading, accor¬ dingly in conjunction with a restringing of the racket. A certain, wear of the strings is also affected in this case and if the tube is worn to such an extent that a hole is created, a considerable amount of the effect is lost and if these tubes are to be exchanged this has to be done at a restringing.

The solution:

In a racket, provided with the device according to the inven¬ tion, means in the shape of one or several longitudinal units of elastic, extensible material, are arranged to extend along certain strings, preferably so, that they form a frame in the outer edge of said impact surface, said means being wound around the strings, crossing the string, along which said means extend respectively, said means further being arranged to be fixed at the ends of their extension along the string or strings in question.

Advantages:

The device in accordance with the invention enables a good fixation of the ^' strings ^' and a fitting of the device can be performed without the necessity of restringing the racket. By means of this possibility the above mentioned disadvantages of prior solutions are elminated.

Description of the drawings:

In the following the invention will be explained in more detail with reference to some modes of example and referring to the annexed drawings in which. Fig. 1 shows a partly cut- a-way view of a tennis racket which is provided with the device according to the invention in a first mode of example; Fig. 2 shows an enlarged part-view of the mode of example according to Fig. 1; Fig. 3 shows a part-view of a tennis racket which is provided with a device according to the invention in a second mode of example and Fig. 4 is a cut-a¬ way-view of the cut along IV-IV of Fig. 1.

Preferred modes of examples:

The device in accordance with the first mode of example of the invention Fig. 1 and 2 comprises four tube-like units 1, 2, 3, 4 which are intended to extend along certain parts of the

• strings 5, 6 of a racket 7, i.e. a tennis racket, which head is shown but which shaft is broken away due to consideration of space. In a conventional manner the shaft comprises a longish unit which is rigidly attacked to the head and protru¬ des in the main plane of the racket head, i.e. the main plane in which the frame 8 and the strings 5, 6 protrude. The strings are connected to the frame 8 in a conventional manner and are either separate strings for each longitudinal or transversal extension or by continuous strings, which are threaded through holes in the frame.

In the mode of example which is shown i Fig. 1 and 2 do the tube-like units 1-4 comprise four elements, of which two tube¬ like units 1, 2 are arranged along the outermost longitudinal strings 5, whereas the two other tube-like units 3, 4 are arranged along the .outermost, transversal strings 6. The expression longitudinal strings are intended to cover the strings who extend in the longitudinal direction of the racket i.e. along the length of the oval frame, whereas the transver¬ sal strings extend in the transversal direction of the racket i.e. across the frame. Hence, the longitudinal strings 5 extends generally parallel to the shaft.

As is especially evident from Fig. 2 and 3 the tube-like units are not threaded upon any string but follows a string. Hence, in accordance with Fig. 2 do the units 1 and 2 follow the outermost longitudinal strings 5 and the- units 3 and 4 follow the outermost transversal strings, in each case on the outer _ side of the strings. The tube-like units are fixed by means of being wound around those strings which cross the string that said tube-like unit follows. When it concerns the unit 2, does this consequently follow one of the two outermost longitudinal strings 5 and is thereby wound around each of the crossing

transversal strings 6, which cross this string. How the winding can be performed is shown in Fig. 4. According to this figure the tube-like units are wound in such a manner that the extension between strings around which it is wound, is such that if they leave a string on one side therefore does the unit extend to the other string on this string's other side, around the latter and consequently away from this latter on the very same side as it arrived on, but then angled over to the opposite side of the next string and so on in a zig¬ zag pattern.

This is in accordance with a view of a cut. In the view, see Fig. 2 and 3, the tube-like unit in one gap extends close to, preferably in contact with the string which the unit extends along, and after being wound around a crossing string in an helical manner the tube-like unit extends in the following gap distanced from the string along which it extends. This distan¬ ce is dependent on how much space the unit occupies in the transversal directon when it is wound around a string. At the following string it is wound in such a manner that it in the following gap again extends in contact _, with the string along which it extends, etc, etc. The pattern of winding in a transversal view, in relation to the surface of impact, with tube-like element having angled parts is shown in Fig. 4, whereas the pattern comprising parallel but in a zig-zag manner displaced parts, in relation to the surface of impact, is best shown in Fig. 2 and 3.

In the mode of example according to Fig. 2, there are four units. Consequently, there are eight endparts, which are to be secured. In accordance with Fig. 2, this is achieved by making a knot of the end part of the tube-like unit around that string, along which it extends after having been wound around the last crossing string. Due to the fact that the unit is secured to the string along which it extends, the unit cannot slide away from the same. In the mode of example according to Fig. 3, when only one single tube-like unit 10 is used, the winding of the unit around the crossing strings is made in the

same manner as described above. The tube-like element however, may extend from an extension shown in Fig. 3 with the referen¬ ce numeral 11, where it shows a transversal extension along one of the strings 6, after being wound around the last crossing string along the extension, in a diagonally manner to the outermost transversal string, which crosses the outermost longitudinal string at the same side of the racket, whereafter it follows along the latter string in such a manner as descri¬ bed above. This part of the tube-like unit 10 is referred to with reference numeral 12 in Fig. 3. Such a change in direc¬ tion of the extension, from following a transversal string to following a longitudinal string and vice versa does occur at three of the corners of the impact surface of the racket, which has a tube-like unit attached thereto. At the fourth corner do the endparts of the tube-like unit meet and are here secured by means of knots in such a manner as is described in conjunction with the first mode of example. Alternatively, it is possible to have two tube-like units which accordingly has to be secured at two different places of the racket frame.

The tube-like units are produced in a flexible, resilient preferably elastic material. This enables the units to follow the small elastic movement of the strings in a direction perpendicular to the impact surface, which movements occur at the moments of impact. Accordingly, a certain small amount of prolongation of the tubes occur at these moments in the longitudinal direction and as a consequence of the elastic properties they return to their original positions and do therefore reestablish each strings correct position in the main plane of the racket, which considerably reduces the possibility of permanent transversal displacement of the strings and therefore also of the crossing areas.

A certain small amount of the crossing areas is of course allowed in order to provide for good playing properties of the racket, which properties will be even improved since the transversal movability of the strings has been limited. As a consequence the power of a stroke will be more efficiently

transformed to the ball when using top spin and slized strokes since the movability of the strings is reduced, which provides for an improved spin effect and an increased power of the ball.

Further it has been confirmed that the tube-like units have a vibration damping effect which accordingly implies the solu¬ tion of a huge problem of modern tennis rackets made of metal and composite materials where otherwise there is an especially big need for special vibration damping elements. Due to the damping, injuries of the arm of the player are preverted for to a major extent. Suitable material for the tube-like units would be, as a matter of example, a relatively hard rubber material or a plastic material. It has proved to be especially preferable to use tubes made of polyurethane. This material has an inner friction which is relatively high and by the time of prolongation, due to the transversal forces agianst the crossing strings, the material will reestablish its original position, after the prolongation, so that the strings will be returned to their correct position, however, not in a jerk¬ like manner but by means ^" of the inert friction in a somewhat timeextended action. Hereby the vibrations of the strings are cushioned and as a consequence also in the racket, which is of major importance of physiological aspects.

It has been made clear above that tube-like units are not used to contain anything. That suc units are chosen instead depends on the fact that they transform into a flattened form when they are wound around the crossing strings. Hereby a good connection to these are achieved, so that they can support the adjacent string, along which said unit (or in accordance with a mode of example showed in Fig. 3, a part of the unit) extends along. Threads are characterised by being easily moved in a transverse direction by means of rolling and thereby the problem would arise that such a unit would move away from string, along which it should extend, and consequently the aimed effect of securing and vibration damping would therefore be hazardous. A ribbon on the other hand is more difficult to

work with during the fitting, since the ribbon is easily unintentionally twisted, which can be unfavourable. The tube¬ like unit, on the other hand, does not comprise any sepcific side and adopts its form to a ribbon once it is wound around a crossing string. Furthermore, it has turned out that the tube¬ like unit, once it is flattened receives a certain skin friction, which also is effected for damping of vibrations in conjunction with said inert friction of the material.

It is important that the tube-like units are tightly wound around the string and that they are stretched during the fitting with an adapted force. This can be achieved by produ¬ cing the units with a length which is adapated to the racket, so that if the unit is not sufficiently stretched it will not fit. In order to have sufficient length at the ends of the units, the units can be made with oversized comprising some kind of marking to mark the correct stretch, i.e. the markings should be leveled with the outermost crosing strings.

The invention is not limited to what has been described above and to those of examples shown in the drawings, but can be varied with in the scope defined by the following claims. As a matter of example it is possible that the strings are secured against the tube-like units by means of friction locking, where the surfaces of the tube-like units have been treated in order to achieve this. Form locking however, is judged to provide for lower wear in case the friction is not so high that the crossing areas adjacent to the tube-like units is not moved. The movement of the crossing areas adjacent the tube¬ like units, which occur is allowed due to the deformation of the tube-like units and the flexibility of their length, i.e. so that these follow the movements of the strings in question, extension and elastic contraction respectively, which implies that the distance between the crossing areas varies to some extent at the moment of impact. Permanent movement however, is el inated since the crossing areas are secured, and therefore an irregular spacing concerning the distance between the string is prevented for. The major problems with the movement

of the strings are the longitudinal strings which are the longest and are most subjected to transversal forces at the moment of impact.

Moreover it is possible that the device is applied to other rackets than tennis rackets, i.e. squash rackets.