EP0239985B1 - Strings for sports rackets - Google Patents
Strings for sports rackets Download PDFInfo
- Publication number
- EP0239985B1 EP0239985B1 EP87104727A EP87104727A EP0239985B1 EP 0239985 B1 EP0239985 B1 EP 0239985B1 EP 87104727 A EP87104727 A EP 87104727A EP 87104727 A EP87104727 A EP 87104727A EP 0239985 B1 EP0239985 B1 EP 0239985B1
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- EP
- European Patent Office
- Prior art keywords
- strings
- string system
- string
- stretching
- rackets
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B51/00—Stringing tennis, badminton or like rackets; Strings therefor; Maintenance of racket strings
- A63B51/02—Strings; String substitutes; Products applied on strings, e.g. for protection against humidity or wear
Definitions
- the invention relates to a covering of sports rackets consisting of stretched plastic cords including profiled cords made of polyurethane or a braid made of such cords.
- Plastic racquets made of polyamides are used for sports rackets such as tennis, squash or badminton rackets, if no natural products such as ground casings are used.
- sheathed strings the properties of which depend primarily on the core material, whereby the sheath has a protective function, for example against moisture and to improve the slip resistance and knot strength. The result is an elongation at break of approx. 125% with a tensile strength of approx. 50 dN; string thicknesses of approx. 1.32 to 1.36 mm are common. Extreme dimensions are 1.45 and 1.25 mm (Kleine Saitenischen, Vollmer tennis strings, 1981).
- the strings formed in this way are relatively hard, in any case, each stroke is accompanied by a clearly perceptible noise development, which results from the swinging of the string and the racket frame.
- the higher the player's abilities the higher the hardness and thus the resilience when the string is wound on a racket.
- the high tension strings occasionally break during a tournament.
- the invention proposes that the cords are made of a thermoplastic PUR elastomer with a tensile strength of 30 to 60 MPa and an elongation at break of 550 to 660% based on the initial state, and that the stretching consumes part of the elongation at break he follows.
- the part of the elongation at break consumed during stretching is 35 to 50 parts if the elongation at break is set at 100 parts.
- Polyester types or polyether types or polycaprolactone types are preferred as thermoplastic PUR elastomers.
- the cords are preferably formed by extrusion of the thermoplastic PUR elastomer.
- the materials mentioned are currently used for purposes in which the high elongation at break is not used directly, but only indirectly, for example in the case of hoses and jackets to avoid breakage in the event of severe deformations.
- the material is used for the first time in an expansion range just below the elongation at break and thus the excellent elastic properties are used.
- the good rebound resilience and optimal acceleration and spring properties there is sufficient tear resistance, so that fractures are practically no longer to be feared. This is partly due to the fact that extreme tension forces are no longer required to form a playable covering.
- Tennis racquets with a stringing according to the invention for example, have a tension force of 14 dN in the playable state, while for squash racquets the value is approximately 7 dN.
- the relatively low tension of the cords of a covering according to the invention also has an effect advantageous to the breaking strength of the fabric compared to conventional cords.
- the relatively high pressure under which the strings lie on one another at the points of intersection of the covering causes corresponding notches, which are initially less pronounced, but increase in use as a result of the beats.
- the strings literally snap into the notches at the crossing points.
- the strings tear at these notched points, even if the tension has decreased over time.
- the covering according to the invention inter alia, due to the lower tensioning force, there is no longer any notch effect at the crossing points. This is partly due to the lower tension and secondly due to the higher elasticity.
- the cord below gives way and dodges, so that the cord above it can hardly be pressed in.
- the extraordinarily high coefficients of friction of the material used according to the invention also ensure that the necessary slip resistance of the cords against one another is present even without notches, so that the braid once specified is retained.
- the tensile strength of 30 to 60 MPa claimed by the invention for the new cords used appears extremely low at first glance. However, it should be taken into account that this value relates to the initial cross-section of a cord, for example, for a tennis string to an initial diameter of 4 mm. which has a cross-sectional area of 12.566 mm 2 . Assuming an average tensile strength of 45 MPa, the tensile strength is at least about 56 dN. The cord has shrunk to a diameter of 1.6 mm. This tensile strength value is in the range of conventional polyamide strings, which, however, have somewhat smaller values in diameter. The material in the pre-stretched state has a diameter of 2.6 mm.
- the high resilience which is over 50%, but at least 20%. This value is a measure of the decrease in the material as the tension decreases. With conventional cords, the resilience is about 3 to 5%. Thus, if the string of a string breaks with a free span length of 20 cm, the break point in a conventional racket gapes 0.6 to 1 cm apart, while in the same case there would be a gap of at least 4 cm with the string according to the invention.
- the covering according to the invention is extremely gentle on the joints because of its good elasticity, so that the appearance of the so-called tennis arm cannot be observed.
- the great elasticity of the covering can be recognized by the particularly muted tone that is emitted when a ball hits the racket.
- the strings and frame vibrate very low frequency without dangerous harmonics.
- there is a substantial enlargement of the so-called sweet spot i.e. the area within a racket in which the ball control is best.
- a side effect of the high elasticity is also the small amount of force that must be applied to a ball that is to leave the racket at high speed.
- the previously developed special strokes such as slice and top spin can also be carried out, the desired effects of ball rotation occur around its own axis.
- the sensitivity of the cords according to the invention to moisture is low. In damp weather and even in rain, the covering can be played. Only a certain amount of care must be taken with regard to elevated temperatures, so that high temperature effects do not result in a temperature-like effect over a long period of time. Such a situation can arise, for example, in a black racket bag that is exposed to the blazing midsummer sun.
- a profile can be created which consists, for example, of grooves or edges or projections running in the direction of the fibers.
- the round cord cross section can not only be circular, but also, depending on the selected nozzle cross section, oval or of another shape.
- the starting material is ESTANE 54353, a polycaprolactone polyurethane, from BF Goodrich Chemical (Deutschland) GmbH with the following mechanical properties:
- the polyurethane is extruded so that fibers are formed in the form of round cords in a diameter range of 2-5 mm, depending on the intended use.
- the extruded cords are stretched in the usual way, whereby the cross-sectional area decreases by about 30-50% depending on the degree of stretching.
- Cords are preferred for covering squash rackets, the diameter of which in the undrawn state is approximately 2 mm.
- a string is formed on the racket with the cords or fibers by the cords or fibers crossing each other and being intertwined with one another. Deviating from the usual way of covering, only one cord should be passed through each frame bore, because the cords do not slide well together due to the rough surface structure. Moreover, the cords do not need to be drawn up with the otherwise usual high tension in order to achieve a comparable high rebound resilience as with fabrics made of conventional material.
- the cords or fibers of the covering are made from a polyester polyurethane of type ESTANE 58271 from BF Goodrich Chemical (Deutschland) GmbH with the following properties:
- This covering is characterized by greater flexibility compared to the first embodiment.
- the covering becomes softer and is therefore particularly suitable for beginners and advanced users.
- the cords or fibers of the covering are made from an ESTANE 58311 polyether polyurethane from Firmal BF Goodrich Chemical (Germany) GmbH with the following properties:
- the processing is also carried out according to the first example.
- the playability and the game characteristics are similar to the second example.
- the material is completely insensitive to moisture.
Abstract
Description
Die Erfindung betrifft eine Bespannung von Sportschlägern bestehend aus gereckten Kunststoffschnüren einschließlich profilierter Schnüre aus Polyurethan oder aus einem Geflecht aus solchen Schnüren.The invention relates to a covering of sports rackets consisting of stretched plastic cords including profiled cords made of polyurethane or a braid made of such cords.
Für Sportschläger wie Tennis-, Squash- oder Badmintonschläger werden Kunststoffschnüre aus Polyamiden eingesetzt, wenn keine Naturprodukte wie geschliffene Därme eingesetzt werden. Darüber hinaus gibt es ummantelte Saiten, deren Eigenschaften sich jedoch in erster Linie nach dem Seelenmaterial richten, wobei der Mantel eher eine Schutzfunktion beispielsweise gegen Feuchtigkeit und zur Verbesserung der Rutschfestigkeit und Knotenfestigkeit mit sich bringt. Im Ergebnis wird eine Bruchdehnung von ca. 125% angestrebt bei einer Reißkraft von ca. 50 dN; dabei sind Saitenstärken von ca. 1,32 bis 1,36 mm üblich. Extreme Maße sind 1,45 bzw. 1,25 mm (Kleine Saitenkunde, Vollmer Tennissaiten, 1981).Plastic racquets made of polyamides are used for sports rackets such as tennis, squash or badminton rackets, if no natural products such as ground casings are used. In addition, there are sheathed strings, the properties of which depend primarily on the core material, whereby the sheath has a protective function, for example against moisture and to improve the slip resistance and knot strength. The result is an elongation at break of approx. 125% with a tensile strength of approx. 50 dN; string thicknesses of approx. 1.32 to 1.36 mm are common. Extreme dimensions are 1.45 and 1.25 mm (Kleine Saitenkunde, Vollmer tennis strings, 1981).
Es hat früher schon Versuche gegeben, die Elastizität zum Beispiel einer Tennissaite zu erhöhen, und zwar durch die Verdrillung von gereckten, einfädigen Gebilden wie Fäden oder Drähten aus Polyamiden oder Polyurethanen und durch Fixieren des entstandenen Dralles (Deutsche Patentschrift 900 373). Aufgrund der angegebenen Materialien, die Polyamide einschließen, kann vermutet werden, daß mit dieser Maßnahme aus der damaligen Zeit gerade die Elastizität von guten Darmsaiten erreicht wurde, also im Bereich der bereits angegebenen Bruchdehnung von 125% lag. Selbst bei einer erheblichen Überschreitung dieser vermuteten Werte bleibt die Größenordnung der Bruchdehnung der Schnüre von unter 150% für Sportschläger im Rahmen dessen, was zur Zeit als optimale Bespannung gilt. Dabei werden Spannkräfte von 20 bis 30 dN für Tennisschläger und ca. 12 dN für Squashschläger aufgebracht, wodurch etwa die Hälfte der bis zum Bruch zur Verfügung stehenden Dehnung aufgezehrt wird.Attempts have previously been made to increase the elasticity of, for example, a tennis string, namely by twisting stretched, monofilament structures such as threads or wires made of polyamides or polyurethanes and by fixing the twist formed (German patent specification 900 373). On the basis of the materials specified, which include polyamides, it can be assumed that this measure from the time was used to achieve the elasticity of good intestinal strings, that is to say in the range of the break elongation of 125% already specified. Even if these presumed values are exceeded considerably, the magnitude of the elongation at break of the cords of less than 150% for sports racquets remains within the scope of what is currently considered to be optimal covering. Tension forces of 20 to 30 dN are applied for tennis rackets and approx. 12 dN for squash rackets, which means that about half of the stretch available until the break is consumed.
Die so gebildeten Bespannungen sind relativ hart, jedenfalls ist jeder Schlag von einer deutlich wahrnehmbaren Geräuschentwicklung begleitet, die aus dem Schwingen der Saite und des Schlägerrahmens herrührt. Als Faustregel gilt dabei, daß die Härte und damit die Spannkraft beim Aufziehen einer Saite auf einen Schläger umso höher gewählt wird, je besser die Fähigkeiten des Spielers sind. Als Folge dieses Trends kommt es bei den mit hoher Spannkraft aufgezogenen Saiten gelegentlich zu Brüchen während eines Turnieres.The strings formed in this way are relatively hard, in any case, each stroke is accompanied by a clearly perceptible noise development, which results from the swinging of the string and the racket frame. As a rule of thumb, the higher the player's abilities, the higher the hardness and thus the resilience when the string is wound on a racket. As a result of this trend, the high tension strings occasionally break during a tournament.
Es ist Aufgabe der Erfindung, eine Bespannung der eingangs genannten Art so zu verbessern, daß sie sich durch ein hohes Maß an Reißfestigkeit in Verbindung mit guten Feder- und Rückpralleigenschaften auszeichnet; schwierige Konstruktionen und hoher Aufwand sollen dabei vermieden werden.It is an object of the invention to improve a covering of the type mentioned at the outset in such a way that it is distinguished by a high degree of tear resistance in conjunction with good spring and rebound properties; difficult constructions and high expenditure should be avoided.
Zur Lösung dieser Aufgabe schlägt die Erfindung vor, daß die Schnüre aus einem thermoplastischen PUR-Elastomer bestehen mit einer Zugfestigkeit von 30 bis 60 MPa und einer Bruchdehnung von 550 bis 660% bezogen auf den Ausgangszustand, und daß die Reckung unter Aufzehrung eines Teiles der Bruchdehnung erfolgt. Der beim Recken aufgezehrte Teil der Bruchdehnung beträgt 35 bis 50 Teile, wenn die Bruchdehnung zu 100 Teilen festgesetzt wird. Bevorzugt werden Polyestertypen oder Poly- äthertypen oder Polycaprolactontpyen als thermoplastische PUR-Elastomere. Besondere Eignung weisen als Polycaprolactontypen ESTANE 54353, als Polyestertypen ESTANE 58271 und als Polyäthertypen ESTANE 58311 jeweils von der Firma BF Goodrich Chemical (Deutschland) GmbH auf. Die Schnüre werden vorzugsweise durch Extrusion des thermoplastischen PUR-Elastomers gebildet.To achieve this object, the invention proposes that the cords are made of a thermoplastic PUR elastomer with a tensile strength of 30 to 60 MPa and an elongation at break of 550 to 660% based on the initial state, and that the stretching consumes part of the elongation at break he follows. The part of the elongation at break consumed during stretching is 35 to 50 parts if the elongation at break is set at 100 parts. Polyester types or polyether types or polycaprolactone types are preferred as thermoplastic PUR elastomers. Particularly suitable as ESTANE 54353 polycaprolactone types, ESTANE 58271 polyester types and ESTANE 58311 polyether types from BF Goodrich Chemical (Deutschland) GmbH. The cords are preferably formed by extrusion of the thermoplastic PUR elastomer.
Die genannten Werkstoffe werden zur Zeit für Zwecke verwandt, bei denen die hohe Bruchdehnung nicht unmittelbar ausgenutzt wird, sondern nur mittelbar, beispielsweise bei Schläuchen und Ummantelungen zur Vermeidung eines Bruches bei starken Deformationen. Im Zusammenhang mit der Erfindung wird das Material erstmals in einem Dehnungsbereich knapp unterhalb der Bruchdehnung eingestzt und damit die hervorragenden elastischen Eigenschaften ausgenutzt. In Verbindung mit der guten Rückprallelastizität und optimalen Beschleunigungs- und Federeigenschaften ist eine ausreichende Reißfestigkeit vorhanden, so daß Brüche so gut wie nicht mehr zu befürchten sind. Das liegt unter anderem daran, daß es zur Bildung einer gut spielbaren Bespannung keiner extremen Spannkräfte mehr bedarf. Tennisschläger mit einer Bespannung gemäß der Erfindung weisen zum Beispiel im spielfähigen Zustand eine Spannkraft von 14 dN auf, während für Squashschläger der Wert bei ca. 7 dN liegt.The materials mentioned are currently used for purposes in which the high elongation at break is not used directly, but only indirectly, for example in the case of hoses and jackets to avoid breakage in the event of severe deformations. In connection with the invention, the material is used for the first time in an expansion range just below the elongation at break and thus the excellent elastic properties are used. In conjunction with the good rebound resilience and optimal acceleration and spring properties, there is sufficient tear resistance, so that fractures are practically no longer to be feared. This is partly due to the fact that extreme tension forces are no longer required to form a playable covering. Tennis racquets with a stringing according to the invention, for example, have a tension force of 14 dN in the playable state, while for squash racquets the value is approximately 7 dN.
Gegenüber herkömmlichen Bespannungen ist das ein deutlich geringerer Wert; bei herkömmlichen Bespannungen liegen die Werte beispielsweise für Tennisschläger bei 25 dN und für Squashschläger bei 12 dN.This is a significantly lower value than conventional fabrics; With conventional clothing, the values are, for example, 25 dN for tennis rackets and 12 dN for squash rackets.
Diese Werte besagen noch nicht, daß mit dieser Spannkraft auch die Schnüre zur Bespannung in den Rahmen eingebracht werden. Vielmehr können, die Werte beim Aufziehen wesentlich höher liegen, wenn im Anschluß an das Aufziehen noch eine Temperung vorgenommen wird. Diese Wärmebehandlung bei erhöhter Temperatur über einen vorgegebenen Zeitraum läßt die ursprünglich aufgebrachte Spannkraft sinken, so daß die oben genannten Werte erreicht werden. Mit der Temperung wird einmal eine Ungleichmäßigkeit der Bespannung beseitigt, die möglicherweise durch das Aufziehen in die Bespannung eingebracht worden ist, und zum anderen wird das Nachlassen der Spannkraft über einen langen Zeitraum, das ohne Tempern zu beobachten ist, quasi vorweggenommen,so daß ein Schläger im Ergebnis über einen langen Zeitraum gleichbleibende Eigenschaften aufweist. Eine Bespielbarkeit ist bis zu einer Spannkraft von 4 dN möglich. Eine weitere Unterschreitung führt dann zu einem Verrutschen der Saite, so daß die Gestalt eines optimalen Geflechtes nicht mehr gewährleistet ist.These values do not yet indicate that the cords for covering are also inserted into the frame with this tensioning force. Rather, the values during winding can be significantly higher if tempering is carried out after the winding. This heat treatment at an elevated temperature for a predetermined period of time causes the clamping force originally applied to drop, so that the above-mentioned values are achieved. With the tempering, an unevenness in the covering, which may have been introduced into the covering by pulling it up, is eliminated on the one hand, and, on the other hand, the release of the tensioning force is virtually anticipated over a long period of time, which can be observed without tempering, so that a racket has consistent properties over a long period of time. Playability is possible up to a clamping force of 4 dN. A further shortfall then leads to the string slipping, so that the shape of an optimal braid is no longer guaranteed.
Die relativ niedrige Spannkraft der Schnüre einer Bespannung gemäß der Erfindung wirkt sich auch vorteilhaft auf die Bruchfestigkeit der Bespannung gegenüber herkömmlichen Schnüren aus. Bei den bekannten Polyamidsaiten verursacht der relativ hohe Druck, unter dem die Saiten an Kreuzungspunkten der Bespannung aufeinander liegen, entsprechende Kerben, die zunächst weniger ausgeprägt sind, jedoch im Gebrauch durch die Schläge immer mehr zunehmen. Die Saiten rasten an den Kreuzungspunkten in den Kerben regelrecht ein. Infolge der Querschnittsschwächung und der Kerbwirkung reißen die Saiten an diesen eingekerbten Stellen ein, selbst wenn die Spannkraft im Laufe der Zeit nachgelassen hat.The relatively low tension of the cords of a covering according to the invention also has an effect advantageous to the breaking strength of the fabric compared to conventional cords. In the known polyamide strings, the relatively high pressure under which the strings lie on one another at the points of intersection of the covering causes corresponding notches, which are initially less pronounced, but increase in use as a result of the beats. The strings literally snap into the notches at the crossing points. As a result of the cross-sectional weakening and the notch effect, the strings tear at these notched points, even if the tension has decreased over time.
Bei der erfindungsgemäßen Bespannung kommt es unter anderem infolge der geringeren Spannkraft zu keiner Kerbwirkung an den Kreuzungspunkten mehr. Das liegt einmal an der geringeren Spannkraft und zum anderen an der höheren Elastizität Beim Auftreffen eines Balles gibt die unten liegende Schnur nach und weicht aus, so daß die darüberliegende Schnur sich so gut wie nicht eindrücken kann. Die außerordentlich hohen Reibwerte des erfindungsgemäß verwandten Materials sorgen im übrigen dafür, daß auch ohne Kerben die notwendige Rutschfestigkeit der Schnüre gegeneinander vorhanden ist, so daß das einmal vorgegebene Geflecht erhalten bleibt.In the covering according to the invention, inter alia, due to the lower tensioning force, there is no longer any notch effect at the crossing points. This is partly due to the lower tension and secondly due to the higher elasticity. When a ball hits it, the cord below gives way and dodges, so that the cord above it can hardly be pressed in. The extraordinarily high coefficients of friction of the material used according to the invention also ensure that the necessary slip resistance of the cords against one another is present even without notches, so that the braid once specified is retained.
Die von der Erfindung beanspruchte Zugfestigkeit für die verwendeten neuen Schnüre von 30 bis 60 MPa erscheint auf den ersten Blick äußerst gering. Dabei ist jedoch zu berücksichtigen, daß sich dieser Wert auf den Ausgangsquerschnitt eine Schnur bezieht, beispielsweise also bei einer Tennissaite auf einen Ausgangsdurchmesser von 4 mm. der einer Querschnittsfläche von 12,566 mm2 aufweist. Geht man von einer mittleren Zugfestigkeit von 45 MPa aus, so beträgt die Reißkraft immerhin ca. 56 dN. Die Schnur ist dabei auf einen Durchmesser von 1,6 mm geschrumpft. Dieser Reißkraftwert liegt im Bereich üblicher Polyamidsaiten, die allerdings im Durchmesser etwas geringere Werte aufweisen. Das Material im vorgereckten Zustand hat dabei einen Durchmesserwert von 2,6 mm.The tensile strength of 30 to 60 MPa claimed by the invention for the new cords used appears extremely low at first glance. However, it should be taken into account that this value relates to the initial cross-section of a cord, for example, for a tennis string to an initial diameter of 4 mm. which has a cross-sectional area of 12.566 mm 2 . Assuming an average tensile strength of 45 MPa, the tensile strength is at least about 56 dN. The cord has shrunk to a diameter of 1.6 mm. This tensile strength value is in the range of conventional polyamide strings, which, however, have somewhat smaller values in diameter. The material in the pre-stretched state has a diameter of 2.6 mm.
Eng verbunden mit der guten Elastizität der von der Erfindung vorgeschlagenen Schnüre ist das hohe Rückstellvermögen, das über 50%, mindestens jedoch 20% beträgt. Dieser Wert ist ein Maß für das Zurückgehen des Materials bei nachlassender Spannung. Bei herkömmlichen Schnüren beträgt das Rückstellvermögen etwa 3 bis 5%. Wenn also bei einer freien Spannlänge von 20 cm der Schnur einer Bespannung ein Bruch erfolgt, klafft bei einem herkömmlichen Schläger die Bruchstelle 0,6 bis 1 cm auseinander, während im gleichen Fall bei der erfindungsgemäßen Bespannung eine Lücke von mindestens 4 cm klaffen würde.Closely associated with the good elasticity of the cords proposed by the invention is the high resilience, which is over 50%, but at least 20%. This value is a measure of the decrease in the material as the tension decreases. With conventional cords, the resilience is about 3 to 5%. Thus, if the string of a string breaks with a free span length of 20 cm, the break point in a conventional racket gapes 0.6 to 1 cm apart, while in the same case there would be a gap of at least 4 cm with the string according to the invention.
Die erfindungsgemäße Bespannung ist wegen ihrer guten Elastizität außerordentlich gelenkschonend, so daß die Erscheinung des sogenannten Tennisarms nicht zu beobachten ist. Rein äußerlich ist die große Elastizität der Bespannung an dem besonders gedämpften Ton zu erkennen, der beim Auftreffen eines Balles auf den Schläger abgegeben wird. Saiten und Rahmen schwingen also nur sehr niederfrequent ohne gefährliche Oberschwingungen. Darüber hinaus ergibt sich eine wesentliche Vergrößerung des sogenannten Sweet Spots, also derjenigen Fläche innerhalb eines Schlägers, in der die Ballkontrolle am besten ist. Eine Begleiterscheinung der hohen Elastizität ist außerdem der geringe Kraftaufwand, der für einen Ball aufgewendet werden muß, der mit hoher Geschwindigkeit den Schläger verlassen soll. Die bisher entwickelten Spezialschläge wie Slice und Top Spin können ebenfalls durchgeführt werden, es treten die gewünschten Effekte der Ballrotation um eine eigene Achse ein.The covering according to the invention is extremely gentle on the joints because of its good elasticity, so that the appearance of the so-called tennis arm cannot be observed. On the outside, the great elasticity of the covering can be recognized by the particularly muted tone that is emitted when a ball hits the racket. The strings and frame vibrate very low frequency without dangerous harmonics. In addition, there is a substantial enlargement of the so-called sweet spot, i.e. the area within a racket in which the ball control is best. A side effect of the high elasticity is also the small amount of force that must be applied to a ball that is to leave the racket at high speed. The previously developed special strokes such as slice and top spin can also be carried out, the desired effects of ball rotation occur around its own axis.
Die Empfindlichkeit der erfindungsgemäßen Schnüre gegen Feuchtigkeit ist gering. Bei feuchter Witterung und sogar bei Regen kann also die Bespannung gespielt werden. Lediglich ist eine gewisse Sorgfalt gegenüber erhöhten Temperaturen aufzubringen, damit durch hohe Temperaturwirkungen über eine lange Zeit kein temperähnlicher Effekt entsteht. Eine solche Situation kann zum Beispiel in einer schwarzen Schlägertasche entstehen, die der prallen Hochsommersonne ausgesetzt ist.The sensitivity of the cords according to the invention to moisture is low. In damp weather and even in rain, the covering can be played. Only a certain amount of care must be taken with regard to elevated temperatures, so that high temperature effects do not result in a temperature-like effect over a long period of time. Such a situation can arise, for example, in a black racket bag that is exposed to the blazing midsummer sun.
Bei der Herstellung der Schnüre durch Extrusion kann ein Profil erzeugt werden, das beispielsweise aus in Faserrichtung verlaufenden Riefen bzw. Kanten oder Vorsprüngen besteht. Ferner kann der Rundschnurquerschnitt nicht nur kreisrund sondern auch, je nach gewähltem Düsenquerschnitt, oval oder von anderer Form gestaltet sein.In the manufacture of the cords by extrusion, a profile can be created which consists, for example, of grooves or edges or projections running in the direction of the fibers. Furthermore, the round cord cross section can not only be circular, but also, depending on the selected nozzle cross section, oval or of another shape.
Nachlfolgend werden Ausführungsbeispiele der Erfindung erläutert:Exemplary embodiments of the invention are explained below:
Ausgangsmaterial ist ESTANE 54353, ein Polycaprolacton Polyurethan, von Firma BF Goodrich Chemical (Deutschland) GmbH mit folgenden mechanischen Eigenschaften:
Tempern würde die Werte noch verbessern.Annealing would improve the values even more.
Das Polyurethan wird so extrudiert, daß Fasern in der Form von Rundschnüren in einem Durchmesserbereich von 2-5 mm, je nach Verwendungszweck gebildet werden.The polyurethane is extruded so that fibers are formed in the form of round cords in a diameter range of 2-5 mm, depending on the intended use.
Die extrudierten Schnüre werden in üblicher Weise verstreckt, wodurch die Querschnittsfläche je nach Verstreckungsgrad um ca. 30-50% abnimmt.The extruded cords are stretched in the usual way, whereby the cross-sectional area decreases by about 30-50% depending on the degree of stretching.
Für eine Bespannung von Squashschlägern werden Schnüre bevorzugt, deren Durchmesser im unverstreckten Zustand ca. 2 mm beträgt.Cords are preferred for covering squash rackets, the diameter of which in the undrawn state is approximately 2 mm.
Mit den Schnüren bzw. Fasern wird am Schläger eine Bespannung gebildet, indem die Schnüre bzw. Fasern einander kreuzen und miteinander verflochten sind. Abweichend von der üblichen Bespannungsweise soll durch jede Rahmenbohrung möglichst nur eine Schnur hindurchgeführt werden, weil die Schnüre infolge der rauhen Oberflächenstruktur nicht gut aufeinander gleiten. Im übrigen brauchen die Schnüre nicht mit der sonst üblichen hohen Spannung aufgezogen zu werden, um eine vergleichbare hohe Rückprallelastizität wie bei Bespannungen aus herkömmlichem Material zu erzielen.A string is formed on the racket with the cords or fibers by the cords or fibers crossing each other and being intertwined with one another. Deviating from the usual way of covering, only one cord should be passed through each frame bore, because the cords do not slide well together due to the rough surface structure. Moreover, the cords do not need to be drawn up with the otherwise usual high tension in order to achieve a comparable high rebound resilience as with fabrics made of conventional material.
Die Schnüre bzw. Fasern der Bespannung werden aus einem Polyester Polyurethan vom Typ ESTANE 58271 der Firma BF Goodrich Chemical (Deutschland) GmbH hergestellt mit folgenden Eigenschaften:
Diese Bespannung zeichnet sich durch eine höhere Flexibilität gegenüber dem ersten Ausführungsbeispiel aus. Die Bespannung wird weicher und eignet sich daher vor allem für Anfänger bzw. Fortgeschrittene.This covering is characterized by greater flexibility compared to the first embodiment. The covering becomes softer and is therefore particularly suitable for beginners and advanced users.
Die Schnüre bzw. Fasern der Bespannung werden aus einem Polyäther Polyurethan vom Typ ESTANE 58311 der Firmal BF Goodrich Chemical (Deutschland) GmbH hergestellt mit folgenden Eigenschaften:
Die Verarbeitung erfolgt ebenfalls gemäß dem ersten Beispiel. Die Bespielbarkeit bzw. die Spieleigenschaften sind ähnlich wie im 2. Beispiel. Das Material ist völlig feuchtigkeitsunempfindlich.The processing is also carried out according to the first example. The playability and the game characteristics are similar to the second example. The material is completely insensitive to moisture.
Claims (10)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT87104727T ATE53504T1 (en) | 1986-04-01 | 1987-03-31 | STRINGING OF SPORTS RACKETS. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3610816 | 1986-04-01 | ||
| DE19863610816 DE3610816A1 (en) | 1986-04-01 | 1986-04-01 | COVERING OF RACKETS |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0239985A1 EP0239985A1 (en) | 1987-10-07 |
| EP0239985B1 true EP0239985B1 (en) | 1990-06-13 |
Family
ID=6297628
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87104727A Expired - Lifetime EP0239985B1 (en) | 1986-04-01 | 1987-03-31 | Strings for sports rackets |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0239985B1 (en) |
| AT (1) | ATE53504T1 (en) |
| DE (2) | DE3610816A1 (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE900373C (en) * | 1950-01-24 | 1953-12-28 | Basf Ag | Process to increase the elasticity of single-strand structures, such as threads or wires, made of polyamides or polyurethanes |
| DE1669423C3 (en) * | 1967-03-10 | 1974-07-18 | Bayer Ag, 5090 Leverkusen | Process for the production of elastic polyurethane threads |
| DE2737751A1 (en) * | 1977-08-22 | 1979-03-08 | Johann Heiss Kg Maschinen Und | Tennis racquet stringing - has polygonal cross=section with sharp edges to increase friction with ball |
| US4183200A (en) * | 1977-10-03 | 1980-01-15 | Pepsico, Inc. | Tennis racket string |
| DE2804446C3 (en) * | 1978-02-02 | 1980-12-18 | B. Braun Melsungen Ag, 3508 Melsungen | String for rackets |
| US4320129A (en) * | 1979-02-05 | 1982-03-16 | Merck & Co., Inc. | Pyromellitic diimide complexes |
-
1986
- 1986-04-01 DE DE19863610816 patent/DE3610816A1/en not_active Withdrawn
-
1987
- 1987-03-31 DE DE8787104727T patent/DE3763143D1/en not_active Expired - Lifetime
- 1987-03-31 EP EP87104727A patent/EP0239985B1/en not_active Expired - Lifetime
- 1987-03-31 AT AT87104727T patent/ATE53504T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0239985A1 (en) | 1987-10-07 |
| ATE53504T1 (en) | 1990-06-15 |
| DE3763143D1 (en) | 1990-07-19 |
| DE3610816A1 (en) | 1987-10-08 |
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