WO2003099387A2

WO2003099387A2 - Tennis racket, plastic string for carrying out the racket stringing and process for carrying out the racket stringing

Info

Publication number: WO2003099387A2
Application number: PCT/RO2003/000007
Authority: WO
Inventors: Gheorghe Stoenescu
Original assignee: Gheorghe Stoenescu
Priority date: 2002-05-27
Filing date: 2003-05-27
Publication date: 2003-12-04
Also published as: WO2003099387A3; RO119687B1; AU2003248576A1; AU2003248576A8

Abstract

The invention relates to a tennis racket provided with a plastic stringing, destined to execute both flat and sliced or lifted strokes, to the string used for carrying out the stringing, to a handle ensuring a better grip as well as to the process for carrying out the stringing. The tennis racket comprises a continuous profiled frame element (1) for making the frame (A) proper, on which the stringing (7) is carried out, and its handle (B). A protective and connecting strip (8) destined for carrying out the stringing and placed outside the frame element (1) is provided lengthwise with some small nozzles (c, d) of different diameters, namely some smaller nozzles (c) for passing a single stringing thread therethrough and other bigger ones (d) diametrically split at the end for passing two stringing threads therethrough. On the racket handle (B) a layer of putty or a resin is applied in two steps of different thicknesses and lengths.

Description

TENNIS RACKET, PLASTIC STRING FOR CARRYING OUT THE RACKET STRINGING AND PROCESS FOR CARRYING OUT THE RACKET STRINGING

The invention relates to a tennis racket provided with plastic stringing, meant for executing both flat and sliced and lifted strokes. The invention further relates to the string used for carrying out the stringing, as well as to a process for carrying out the stringing. Though specially conceived for lawn tennis, the racket may still be used - if subjected to suitable shaping and sizing - to other games involving the use of a racket and ball, such as badminton, squash.

There are known the tennis rackets made of multilaminated wooden material. These have the advantage of satisfactorily damping the vibrations and shocks generated by heavily hitting the ball, but, at the same time, they have the disadvantage of an exigent, consequently, costly manufacturing technology.

Unlike these rackets, the ones made up of special materials, such as plastics, glass or carbon fibres are lighter and much stronger allowing to enlarge the stringing surface. The major consequence of this fact was mainly the increase of the hitting force, and there became prevailing the flat stroke- where the effect imparted to the ball because of the manner of hitting is very reduced. This caused a more intensive use of the plastic string. A major shortcoming of these rackets consists in poorly damping the shocks and vibrations generated by heavily hitting the ball.

The climbing of the heavy strokes, shown above, points out this shortcoming. These rackets are more expensive. Because of the poor damping of the vibrations, there shall be taken measures which many times consist in mounting additional devices which render the racket construction more complicate. Relating to the string material and shape, it must be said that, first, it is necessary to make clear the impact in the tennis game of what is called "Magnus effect" in physics.

It is known that the ball hit by the racket advances towards the net on a parabolic trajectory. Any moment in its displacement the ball spins about one of the axes passing through the centre of gravity, said axis, as a rule, being parallel to the ground. Depending on the direction of this rotation, according to the Magnus effect, an upwards or downwards oriented vertical force is manifested on the ball, the magnitude of this force increasing simultaneously with the increase of the angular speed about the axis passing through the centre of gravity. This force influences the technique of the game much, particularly upon returning the balls having a low position below the net band at the moment of the impact with the racket. The player is obliged to impart an impulse to the ball in order to send it on a trajectory covering the net as well as to impart a rotation motion about the ball axis parallel to the ground, that is in simpler words, to execute a sliced or lifted stroke. That will be possible only if there is sufficient adherence between the ball and stringing, condition which depends mainly on the material and string shape, as well as on the technical characteristics of the racket stringing. The string made of animal gut processed and twisted correspondingly, having a round cross-section, offers a good but not optimum adherence of the ball to the stringing. In order to increase the adherence, some players use a string tensioning at a slacker stringing. From a technical point of view, the disadvantage of this type of string consists in its rapid wearing, more particularly in case of slacker tensioning, due to repeatedly displacing some strings from their initial stringing position. On the other hand the gut string is expensive.

The plastic strings are usually made of one or more plastic threads twisted and processed in a more special manner and having a round cross-section. Obviously, the string made up of a round cross-section thread has the lowest price but also the most disadvantages. One of the major disadvantages of the string made up of a single thread consists in that it is not possible to execute a sliced or lifted stroke due to the low adherence of the ball to the racket stringing.

The strings made of more threads twisted together allow a better adherence of the ball to the stringing during executing the stroke. However, this adherence does not offer the certainty of an efficient sliced or lifted stroke to the player.

A major disadvantage of both types of round-section strings consists in their rapidly wearing in the place or places undergoing the most strokes, the strings being slackly tensioned from the desire of thereby increasing the adherence of the ball to the stringing.

The fact is normal since the pointwise contact of two superimposed crossed threads is punctiform and consequently, the specific pressure in said point during the execution of the stroke is very high and results in the premature wearing of the strings in their contact points.

There shall still be mentioned that, from this point of view, the strings made up of more threads twisted together wear more rapidly in comparison with a one-thread string.

Finally, a last disadvantage of this type of rackets is due to the manner of carrying out the stringing - a web of threads interwoven on two directions perpendicular to each another- one of them being parallel to the longitudinal axis of the racket. Since during the game the number of strokes executed with the racket having its axis positioned parallel or almost parallel to the ground is much greater than the number of strokes executed with the racket inclined at an angle, let us say of about 45°, a relative topical sliding takes place between the threads, thereby determining a wearing thereof on a larger surface.

The technical problem solved by the invention consists in making a racket provided with a stringing which, irrespective of the thread material, allows a sufficient adherence of the ball, or in other words, allows to execute the sliced or lifted strokes more easily, even if the string is very well tensioned. At the same time there is the problem of making a racket which allows an increased damping of the shocks and vibrations caused by heavily hitting the ball, as well as of making a handle capable of ensuring a more efficient grip during the game.

The racket claimed by the invention eliminates the above-mentioned disadvantages and it solves the proposed technical problem by the fact that, within an embodiment preferred by the author, it comprises a continuous frame element from which both the racket frame proper, on which the stringing is carried out, and the racket handle are made.

In the region immediately neighbouring the handle, the frame element is additionally stiffened by means of a reinforcing ridge, and in the handle region, the frame element is reinforced in the known manner by means of a median spacing and reinforcing element.

At the same time, a layer of putty or resin is applied around said element in two steps of distinct thicknesses and lengths, the step so formed helping as a rest for the forefinger of the hand holding the tennis racket handle. The handle assembly is additionally stiffened by means of a leather wrapping, in a known manner, being fastened at the upper side, namely towards the frame, by a ribbon and at the lower side by a flaring cover.

Also, according to the invention, the string for carrying out the stringing shall have two flat opposing surfaces, namely the ones on which the interweaving takes place. The other two faces may also be flat but they may also be rounded to the string flat surfaces. With regard to the process of carrying out the stringing, this differs from the classical one by the fact that the web of interwoven strings is no longer parallel to and perpendicular, respectively, to the handle longitudinal axis, but it is by 45° rotated as against this axis, fact which reduces the relative slipping between the threads.

The tennis racket claimed by the invention exhibits the following main advantages:

- allows to execute the sliced or lifted strokes by using a plastic stringing;

- allows to obtain a much greater stringing durability, the premature string wearing being eliminated by increasing the contact surface of two superimposed strings;

- the making of the stringing is facilitated since this is no longer necessary in the handle region, the holes not being necessary in this portion of the frame;

- allows a more secure and more comfortable grip.

There is given hereinafter an embodiment of the invention in conjunction with Figures 1 to 12 which represent:

- Figure 1 , a general view of a tennis racket as claimed by the invention;

- Figure 2, a detail of carrying out the racket stringing as claimed by the invention;

- Figure 3, a detail of attaching the stringing to the racket frame in the regions where stringing is simple;

Figure 4, a detail of attaching the stringing to the racket frame in the regions where two strings come into a single hole;

- Figure 5, a detail of making the stringing in the lateral sides of the racket;

- Figure 6, a detail of carrying out the simple stringing in the frame regions positioned at about 45°;

- Figure 7, a detail of carrying out the crossed alternative stringing;

- Figure 8, a detail of carrying out the stringing thread with rectangular cross-section and rounded corners;

- Figure 9, a schematic detail of carrying out the racket handle in its reinforced region provided with a grasping shoulder;

- Figure 10, a schematic detail of carrying out the racket handle in its reinforced region, but not provided with a grasping shoulder;

- Figure 11 , a general view concerning the manner of gripping, by the hand, a racket provided with a grasping shoulder (step) as claimed by the invention;

- Figure 12, idem, but viewing the opposed face of the hand.

Within an embodiment preferred by the author, the tennis racket claimed by the invention consists of a continuous profiled frame element 1 , which is bent to form both the racket frame A proper, on which the stringing is carried out, and its handle B mainly formed by the two frame element ends. In the region immediately neighbouring the handle B, the frame element is additionally stiffened by providing a ridge 2 between the two arms thereof. The handle B proper is reinforced in a known manner, such as by means of a median reinforcing and spacing element 3 placed between the two terminal ends of the frame element. Obviously, the two elements 2 and 3 may be made together, from a single piece, in order to constitute a more resistant assembly. The upper part of ridge 2 starts immediately after the last hole in the frame. The handle assembly B made from the two ends of the frame element, the median reinforcing and spacing element 3 and a filler to be described later on, may be additionally wound in the known manner, with a leather wrapping 4 being fastened at the lower side with the flaring cover 5 and at the upper side, namely towards the frame, with a ribbon 6, or in any other way. According to the invention, the stringing is carried out with a stringing thread - string 7- which may be even from a usual plastic material, such as nylon. In addition, in order to carry out the stringing, at least two opposing surfaces of the string 7, namely the ones on which the interweaving is made, shall be flat. The other two surfaces may also be flat, as shown in detail C presented in Fig. 4, but they may also be slightly rounded to the other two flat surfaces of the string.

With regard to the handle B, after it has adequately been stiffened, such as through a median element 3, a layer of putty or resin 9 will be applied around it in two distinct length steps, namely, a thicker layer applied only on the two spaced and opposing side faces of the frame element 1 and a thinner layer for the remainder. At the same time, the thicker layer will be applied only on a length a of the whole handle length, this depending on the player's hand size, following a reduction in this layer thickness by a step "b" up to the thinner layer thickness. Said step is meant to help as a rest for the forefinger of the hand holding the racket, with a view to improving the grip, and the use thereof is presented in Figures 11 and 12. The size of that step, in fact the difference in thickness between the two layers shall be sufficient to provide a secure and comfortable rest for the forefinger.

Regarding the process of carrying out the stringing, this differs from the classical one by that the web of interwoven strings is no longer parallel to and perpendicular, respectively, to the longitudinal racket axis, but it is 45° rotated relative to that axis. Thereby, the effect of the interwoven threads being spaced apart due to the hitting force component acting on the racket plane is diminished. The stringing proper is carried out after applying a protective and connecting strip 8, usually made of plastic material, onto the outline of the racket frame. This strip is provided lengthwise with equally spaced small nozzles of different diameters, namely smaller nozzles c and bigger nozzles d, corresponding to some similar holes cut on the frame outline. The smaller diameter nozzles c are meant for passing a single thread therethrough, while the bigger diameter nozzles d for passing two threads therethrough.

All the bigger diameter nozzles d will still have in their end side a diametrical cutting e. As the whole frame plane shall be provided with a complete hitting grid- or in other words, with a complete web of interwoven strings - the ellipse-shaped racket frame determines the frame portions located at 45° and denoted by f to be provided with a simple web of interwoven parallel strings. On these portions, the protective and connecting strip 8 will be provided only with small diameter nozzles c arranged on one row. On the side portions of the frame, in its median zone denoted by g , the protective and connecting strip 8 will be provided with small diameter nozzles c, arranged on two rows, as shown in Figure 5. This is because in that place two threads should be passed through some nozzles in order to achieve a complete and quality grid in the immediately neighbouring portion, fact ascertained after carrying out and experimenting more embodiments of the stringing. In particular, the problem is to avoid the crossing of two threads coming out from the same hole. It is recommended that the rackets with large hitting surface should be provided on the tip portion h with three big diameter nozzles d, the first being a central nozzle located on the longitudinal axis of the racket, followed by one small diameter nozzle c to the left and right and then again a big diameter nozzle on each side. It is also recommended, according to Fig.2, to start the stringing from the two axially symmetrical holes located close to ridge 2. Both branches are continued simultaneously crossed and symmetrical to the racket axis, ending with the branches entering together in the axial hole opposing to the handle. Then they go to the left and right, respectively, reaching to the closest big hole, then they are turned back, being interwoven on the already formed stringing up to the frame edge where the knot is made in the known manner.

Obviously, there may be adopted other embodiments of the racket having solutions which are more convenient for various reasons, such as from a technological point of view. The main thing is to use a plastic stringing having square cross-section or with flat and parallel opposing sides, namely the sides effecting the interweaving, the grid being inclined at 45° to the longitudinal racket axis, and to have the racket handle provided with the step b for resting the forefinger.

Claims

TENNIS RACKET, PLASTIC STRING FOR CARRYING OUT THE RACKET STRINGING AND PROCESS FOR CARRYING OUT THE RACKET STRINGINGCLAIMS

1. Tennis racket characterized in that it comprises a continuous profiled frame element (1) from which there are carried out both the racket frame (A) proper on which the stringing (7) is carried out and the racket handle (B), said frame element being additionally stiffened, in the region immediately neighbouring the handle, by means of a ridge (2), said handle being reinforced by means of a median spacing and reinforcing element (3); a protective and connecting strip (8) destined to carry out the stringing and placed on the outer side of the frame element (1) is provided lengthwise with some small nozzles (c, d) of different diameters, namely some smaller nozzles (c) for passing a single stringing thread therethrough and other bigger ones (d) diametrically split at the end for passing two stringing threads therethrough, said nozzles being placed in correspondence with similar holes made on the frame outline, starting with a bigger diameter hole (d) located in the tip of the racket and on the longitudinal axis thereof, alternately and symmetrically followed by one or more smaller or bigger diameter holes; on the racket handle (B) there is applied a putty or resin layer in two steps of different thicknesses and lengths, so that the transition step from the thicker to the thinner layer constitutes a resting and grasping surface for the forefinger of the hand gripping the handle, the thicker layer being applied only on the symmetrically axially opposing end surfaces of the frame element (1).

2. Tennis racket according to claim 1 , characterized in that the frame portion confined towards the handle by the stiffening ridge (2) is free of holes, the side portions located at about 45° to the median racket plane are provided only with smaller diameter holes (c) for passing a single stringing thread therethrough and the median portions are provided with alternating smaller diameter holes (c) arranged on two parallel rows.

3. Plastic string for carrying out a racket stringing according to claim 1 and 2, characterized in that it has a rectangular cross-section, at least two of the opposing surfaces thereof, namely the ones on which the interweaving is carried out, being flat, the other two faces being also possibly flat and slightly rounded to the flat ones.

4. Process for carrying out the stringing of a racket according to claims 1 to 3, characterized in that the web of interwoven strings is located in a position rotated by 45°, the two axially symmetrical holes proximate to the stiffening ridge continuing simultaneously with the two branches, being crossed to 45° and symmetrical about the racket axis up to the axial hole opposite to the handle, in which both branches enter, and from which they start to the left and to the right, respectively, up to the big hole which is closest to the central hole and then they are turned back, being interwoven on the already carried out stringing up to the frame edge where the knot is made in the known manner.