EP0260671B1 - Racket, especially for tennis, and a device for stringing it - Google Patents

Abstract

PCT No. PCT/DE87/00418 Sec. 371 Date May 17, 1988 Sec. 102(e) Date May 17, 1988 PCT Filed Sep. 16, 1987 PCT Pub. No. WO88/01889 PCT Pub. Date Mar. 24, 1988.A racket for ball games, in particular tennis, comprises a stringing system in the form of individual strings. The individual strings are each held in the racket frame by means of rivet sleeves, with the rivet heads bearing against the outer edges of the holes in the racket frame. In the event of a string breaking, there is no reaction on the adjoining strings, and only the broken string has to be changed. The individual strings which are provided for the first stringing or for replacement stringing have a fixedly disposed rivet sleeve at one end. In addition there is a loose rivet sleeve which is intended for being pushed on and connected after the string has been inserted into oppositely disposed holes. In addition described is a stringing device of simple design, by means of which individual strings can be easily replaced even by technically unskilled persons.

Description

The invention relates to a racket for ball games, in particular tennis games, with a covering of the racket surface, the covering being led through holes in the frame and the covering between opposite holes each having individual strings, and the individual strings in the racket frame being attached to the strings by squeezing pressure a pair of pliers or the like. Locked sleeves are held which rest with a part projecting over their outer circumference against hole edges and whose locking areas lie within the racket frame, together with individual strings and stringing processes therefor.

The covering of rackets for ball games, in particular tennis rackets, is carried out in such a way that a string is guided through holes in the edge of the racket, for example from the inside to the outside, deflected and then guided in the subsequent hole from the outside in again, so that there is an overall meandering string arrangement results. If a string breaks, this of course also affects the neighboring strings, so that in this case the entire string must be replaced. Another disadvantage of rackets with this known type of stringing is that due to the deflection of the strings, each of the areas of adjacent holes facing one another are loaded with large forces (so-called hole reveal forces), which can sometimes lead to breakage, particularly after prolonged use of the racket. Another disadvantage is that the covering of rackets by means of quite complex, usually only stringing devices to be used by specialists.

From DE-OS 29 28 728 a racket for ball games, in particular tennis games is known, in which the covering between opposite holes each has individual strings, and the individual strings in the racket frame by means of sleeves attached to the strings and locked by pinching pressure of a pair of pliers or the like are held, which rest with a part projecting over their outer circumference against hole edges. The sleeves are of such a length that, when they are inserted into the holes in the frame, they have inwardly projecting areas in the covering surface of the frame. To attach the individual strings, these are each passed through the sleeve, pretensioned, and then the area of the sleeve projecting inward beyond the racket frame is subjected to a pinch pressure of a pair of pliers or the like, so that the respective individual string is locked in this way. Thus, the locking takes place in areas of the rivet sleeves that lie within the stringing area, as a result of which the stringing area effectively available to the player is considerably reduced. If the regions of the rivet sleeves projecting into the stringing surface over the racket frame cross this leads to a deformation of the stringing. Furthermore, it is necessary in the known racket that the bores in the racket frame lie in the longitudinal direction of the respective string, since otherwise the rivet sleeve between the part which is inside the racket frame and the part which is outside the racket frame and forms the locking area, would kink, which could endanger the string. Another disadvantage of the known racket is that in the conventional oval or round racket shapes the length of holes or bores in the longitudinal direction in the racket frame is of different sizes, so that rivet sleeves of different lengths are required for the covering. Depending on the desired string spacing it cannot be ruled out that the corresponding holes intersect with oval or round clubs.

From FR-A-855 446 a racket for ball games of the type mentioned is known. Here, the sleeve has an external thread on its outside and a cylindrical region without an external thread. The external thread extends to almost half the total length of the sleeve. The part intended to be placed against the edge of the hole is designed as a nut with an internal thread, which can be screwed onto the external thread.

The area without external thread is designed to absorb the pinching pressure of a pair of pliers or the like for the purpose of locking a string inserted into the sleeve. The squeezing pressure is applied in the area of the stringing surface of the racket frame. The sleeve is then inserted into the respective hole from the inside of the holes in the racket frame so that the external thread is directed forward. A nut is then screwed onto the external thread from the outside of the hole and the desired tension is thereby applied. If the end piece of the sleeve protrudes beyond the nut and the outer edge of the racket after the required tension has been applied, this is cut off separately.

The invention has for its object to improve a racket of the type mentioned in such a way that the disadvantages of the rackets described do not occur, so that a racket which is useful in practice for ball games with single strings is of extremely simple construction and has a high utility value, which has the advantages of a racket with single strings. These consist, inter alia, that if a string breaks, there is no effect on the adjacent strings, so that only the broken string has to be replaced and that the replacement is as simple as possible Way can be done without expensive stringing device.

According to the invention it is provided that the sleeves are designed as rivet sleeves and the part projecting over the outer circumference is designed as a rivet head which is fixedly connected to the respective rivet sleeve, and that the entire outer side of the rivet sleeve is cylindrical and thus the entire outer side is designed as a region for receiving the squeezing pressure .

It is advantageous here that the entire shaft of the rivet sleeve is available for absorbing the squeezing pressure and thus the rivet sleeve can be made shorter in comparison with the sleeve in the known racket. This then has the further advantage that it is not necessary to cut off a protruding sleeve end after the attachment. The tension on the string of the racket is not applied by screwing relative to the sleeve. The rivet head, which is firmly connected to the rivet sleeve, rather leans against the hole edge as a result of a pretension applied from the outside to the projecting end of the string.

In a further embodiment of the invention it can be provided that a base made of elastic material, preferably plastic, is arranged between the rivet heads and the outer hole edges.

In a further embodiment of the invention it can be provided that the rivet sleeves are surrounded by a protective tube. The protective tube can advantageously serve to facilitate the sliding of the rivet sleeve into the hole.

The individual strings that can be used for the first stringing or also for the replacement stringing are characterized in that a rivet sleeve is firmly attached to one end of the respective single string, and that one for sliding on and connecting after certain loose rivet sleeve is provided the insertion of the string into opposite holes.

In contrast, it is known from FR-A-855 446 to provide both ends of a single string to be fitted with a sleeve which has an external thread in one area and to lock it by pinching pressure of a pair of pliers or the like. This requires that the user must predict the distance that the sleeves are to be placed fairly accurately before the squeeze pressure is applied.

The method for stringing rackets for ball games, in particular tennis games, with individual strings is carried out according to DE-OS 29 28 748 so that first the sleeve is inserted into the respective hole, then the string is seen through the sleeve from the stringing side of the racket frame , then - if a locking has already taken place on the opposite side - a pretension is applied to the projecting end of the string and then pinching pressure is applied to the part of the respective sleeve projecting inward in the stringing area by means of pliers or the like. Then the free end of the string protruding outwards is cut off.

From FR-A-855 446 it is also known to apply the pinch pressure to the sleeve in the stringing area of the racket. While in the subject of DE-OS 29 28 748 the squeezed locking area of the sleeve remains within the stringing area, in the item of FR-A-855 446 the squeezed locking area of the sleeve is subsequently turned by turning the nut screwed on from the outside into one within the racket frame area.

In contrast, an advantage of the method according to the invention is that the application of the squeezing pressure to the rivet sleeve from the outside of the racket frame by means of a suitable device String done. As a result of the applied preload, the rivet sleeve slips into the hole of the racket frame when the clamping device is relieved after the sleeve has been locked in such a way that the rivet head comes to rest against the hole edge provided for this purpose. Since the pretension initially applied to the string decreases as the rivet sleeve slides into the hole, it goes without saying that this fact must be taken into account when dimensioning the pretension to be applied.

Conventional racket frames can easily be used to implement the invention by replacing the previously customary covering with the covering according to the invention.

Fig. 1

eine Draufsicht auf einen Abschnitt eines Schlägers gemäß der Erfindung;

Fig. 2

eine Ansicht einer Einzelsaite;

Fig. 3

eine schematische Ansicht einer auf den Rahmen eines Schlägers aufgesetzten Bespannvorrichtung;

Fig. 4

eine Teilansicht der Vorrichtung gemäß Fig. 3, gesehen in Pfeilrichtung IV in Fig. 3;

Fig. 5

eine Detaildarstellung der unter Spannung durch die Besaitungsvorrichtung und in Fig. 3 dargestellten Saite, zusätzlich mit einer Seitenansicht einer als Zange ausgebildeten Stauchvorrichtung;

Fig. 6

eine Schnittdarstellung entsprechend der Linie VI-VI in Fig. 5;

Fig. 7

eine schematische Darstellung der unter Vorspannung in das Loch hereingerutschten Saite mit Niethülse, wobei das vorstehende Ende noch nicht abgeschnitten ist.

The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the drawings. Show it:

Fig. 1

a plan view of a portion of a racket according to the invention;

Fig. 2

a view of a single string;

Fig. 3

a schematic view of a stringing device placed on the frame of a racket;

Fig. 4

a partial view of the device of FIG 3, seen in the direction of arrow IV in Fig. 3.

Fig. 5

a detailed view of the tension under tension by the stringing device and shown in Figure 3, additionally with a side view of a compression device designed as pliers;

Fig. 6

a sectional view taken along the line VI-VI in Fig. 5;

Fig. 7

is a schematic representation of the string slid into the hole under tension with rivet sleeve, the protruding end is not yet cut off.

A racket head, generally designated 1, of a racket for ball games, in particular tennis games, has a covering, generally designated 2. The covering 2 is individual strings 3 arranged in the transverse direction and individual strings 4 arranged in the longitudinal direction. The frame of the racket head 1, designated 5, has holes 6 for receiving the cross strings 3 in a known manner and holes (not shown) in a corresponding manner Recording the main strings 4. The ends of the individual strings 3 and 4 are each firmly enclosed by rivet sleeves 7. The outer diameter of the rivet sleeves 7 is smaller than the inner diameter of the holes 6. The rivet sleeves 7 each have a rivet head 8, the outer diameter of which is larger than the inner diameter of the holes 6. In the exemplary embodiment shown, the outer hole edges 9 of the holes 6 are recessed, and in such a way that the rivet heads 8 do not protrude beyond the outer surface of the edge of the frame 5 when the racket is in use. The strings 3 and 4 are held under tension in the frame 5 in that the rivet heads 8 rest against the outer edges 9 of the holes 6. In the exemplary embodiment shown, a base 10 made of elastic material, for example plastic, is arranged between the hole edges 9 and the rivet heads 8. Furthermore, the rivet sleeves 7 are surrounded by a protective tube 11. The protective tube 11, which is preferably made of elastic material, in particular facilitates the sliding of the rivet sleeves 7 into the holes 6.

In Fig. 2 one of the individual strings 3, 4 is shown before clamping. The length of these individual strings suitably corresponds to at least the maximum length of the longest string of the racket. A rivet sleeve 7 with the rivet head 8 is firmly attached to the left end of the single string as shown in the drawing. The firm connection can preferably be achieved in that the rivet sleeve 7 pushed onto the string has been compressed by means of a suitable device such that the rivet sleeve 7 tightly encloses the string. Furthermore, a loose rivet sleeve is provided, which is denoted by 7ʹ in FIG. 2 and which can be pushed onto the free (right according to the drawing) end of the string.

The individual strings are then tensioned so that each of the individual strings 3, 4 with the "free" end, which therefore does not have a fixed rivet sleeve, is passed through one of the bores 6 from the outside, so that - if already present - transverse strings are crossed, and that the free end is then guided from the inside through the hole 6 opposite the first hole 6. Since the fixed rivet sleeve 7 is located at the rear end, this rivet sleeve 7 is pulled into the hole 6, and the rivet head 8 rests against the hole edge 9. The free end of the single string then protrudes from the opposite hole 6. One of the rivet sleeves 7 'is then pushed onto the free end from the outside. Then a pretension in the direction of arrow A (FIG. 1) is applied to the projecting end 12 of the string 3, and then the rivet sleeve 7 'is firmly connected to the single string 3 by upsetting. If you now let go of the end 12 of the string 3, the string 3 contracts as a result of the preload previously applied, as a result of which the rivet sleeve 7 'is then pulled into the corresponding hole 6.

As a result, the rivet head 8 of the rivet sleeve 7ʹ comes into contact with the corresponding hole edge 9 of the hole 6. The free end 12 protruding above the head 8 of the rivet sleeve 7 'is cut off.

It is understood that in this state, the pretension that each individual string has when the racket is in use is less than the pretension that was applied in the direction of arrow A during the tensioning process. However, this fact can easily be taken into account.

A device for covering the racket has a tensioning device, generally designated 13, and an upsetting device, generally designated 14. The tensioning device 13 operates in the manner of a torque wrench and has a contact part 15 which can be placed on the racket edge 5 and a holding part 16 which is provided for contact with the racket inner edge and is movable and thus adjustable to different frame thicknesses. The holding part 16 is plate-shaped and is adjustably attached to the contact part 15 via a wing screw 17. For this purpose, the system part 15 has a plurality of holes 18, 19 and 20. On the opposite side, a contact pin 21 is provided on the contact part. Furthermore, a lever 22 is pivotally mounted at 23 in the clamping device 13. If the lever 22 is pivoted in the contact position shown in FIG. 3 against the racket frame 5 in the direction of arrow B, the lever part 24 lying opposite to the pivot axis 23 is pivoted in the direction of arrow C. A clamping device 25 for clamping the end region 12 of a string 3 is provided on the lever part 24. Furthermore, the tensioning device 13 has a measuring device designed as a scale 26 for indicating the preload reached and a ratchet 26 with a spring-loaded, detachable pawl 27 which engages in notches 28 in the system part 15.

The clamping device 25 has a clamping surface 29 fixedly attached to the contact part 15 and an eccentrically mounted clamping disc 31 which is biased by a spring 32 against the tension direction A (or C) of the string 3. The operation of the tensioning device 13 is as follows:
3 is placed on the racket frame 5, and the free end 12 is inserted into the clamping device 25 after the rivet sleeve 7 'has been pushed on. The lever 22 is then actuated in the direction of arrow B. As a result of the eccentrically designed clamping disk 31 and the tension spring 32, the free end 12 of the string 3 is held in place in the event of a pivoting movement in the direction of the arrows B or C. Through the action of the ratchet 26, the prestress applied in each case is retained, the size of which can be read off the scale 26.

The upsetting device 14 shown schematically in FIGS. 5 and 6 is designed as a pliers-like structure 32 and has semicircular regions 33 on the pliers head, the length of which corresponds approximately to the length of the rivet sleeves 7, so that the rivet sleeves 7 are each enclosed by the regions 33 and then can be compressed by operating the pliers levers 35, 36. The upsetting device 14 can furthermore have a cutting device for cutting off the projecting end 12. Such a cutting device is shown schematically and designated 37.

The pretensioning device can, for example, also be designed to be adjustable via thread, so that the pretensioning force is adjusted by a rotary movement. The prestressing force can be measured via a pressure load cell, and the achievement of the desired prestressing force can be indicated by a signal, for example a light signal. The desired preload can be set on the pressure cell.

Claims (6)

1. A racket for ball games, in particular tennis, with stringing of the racket face, wherein the stringing is passed through holes in the frame and the stringing comprises respective individual strings between oppositely disposed holes and the individual strings are held in the racket frame by means of sleeves which are fitted on to the strings and fixed in position by squeezing pressure of tongs or the like, the sleeves bearing with a portion projecting beyond their outside periphery against edges of the holes while the fixing regions thereof lie within the racket frame, characterised in that the sleeves are in the form of rivet sleeves (7) and the portion projecting beyond the outside periphery is in the form of a rivet head (8) fixedly connected to the respective rivet sleeve (7), and that the entire outside of the rivet sleeve (7) is cylindrical and thus the entire outside is formed as a region for receiving the squeezing pressure.
2. A racket according to claim 1 characterised in that a respective support (10) of resilient material is disposed between each of the rivet heads (8) and the outer edges (9) of the holes.
3. A racket according to claim 1 or claim 2 characterised in that the rivet sleeves (7) are enclosed by a protective tube (11).
4. An individual string for rackets for ball games, in particular according to one of claims 1 to 3, wherein the individual strings are held in the racket frame by emans of sleeves which are fitted on to the strings and which are fixed in position by squeezing pressure of tongs or the like and which bear against edges of the holes with a rivet head projecting beyond the outside periphery and wherein the entire outside of the rivet sleeve is cylindrical and thus the entire outside is formed as a region for receiving the squeezing pressure, characterised in that a rivet sleeve (7) is fixedly disposed at one end of the individual string (3, 4) and that there is provided a loose rivet sleeve (7') which is intended to be pushed on and connected after insertion of the string into oppositely disposed bores.
5. An individual string according to claim 4 characterised in that the rivet sleeves (7, 7') have an internal knurling.
6. A method of stringing rackets for ball games, in particular tennis, with individual strings, characterised in that a respective individual string (3) which has a fixedly disposed rivet sleeve at an end is passed with its free end through one of the bores (6) in the racket frame, that then, if already present, transversely extending strings are crossed, and that then the free end is passed from the inside through the hole in the frame which is opposite the first hole (6) and thus the rivet sleeve (7) is pulled into the hole (6) and the rivet head (8) bears against the edge (9) of the hole, and that a rivet sleeve (7') is pushed on to the free end from the outside and a prestressing force which exceeds the magnitude of the desired tension in the string is applied to the projecting end (12) of the string (3), then the rivet sleeve (7') is fixedly connected to the individual string (3) by upsetting and then the prestressing force is released, whereby the rivet sleeve (7') is pulled into the corresponding hole (6) and the rivet head (8) of the rivet sleeve (7') comes to bear against the corresponding edge (9) of the hole (6) and that the free end (12) which projects beyond the head (8) of the rivet sleeve (7') is cut off.

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