EP0093210B1 - Raquette à cordage à différentes tensions - Google Patents
Raquette à cordage à différentes tensions Download PDFInfo
- Publication number
- EP0093210B1 EP0093210B1 EP82302234A EP82302234A EP0093210B1 EP 0093210 B1 EP0093210 B1 EP 0093210B1 EP 82302234 A EP82302234 A EP 82302234A EP 82302234 A EP82302234 A EP 82302234A EP 0093210 B1 EP0093210 B1 EP 0093210B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- strings
- ball
- string
- racket
- longitudinal
- 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
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Classifications
-
- 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
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B49/028—Means for achieving greater mobility of the string bed
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B49/03—Frames characterised by throat sections, i.e. sections or elements between the head and the shaft
-
- 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
- A63B51/004—Stringing tennis, badminton or like rackets; Strings therefor; Maintenance of racket strings using strings with different tension on the same frame
-
- 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
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
- A63B60/54—Details or accessories of golf clubs, bats, rackets or the like with means for damping vibrations
Definitions
- This invention relates to an improved string network of tennis rackets, racquetball rackets, and other sport rackets that is more effective, efficient, and responsive in applying hitting force to a ball.
- the invention not only recognizes that longer strings have important advantages, but it recognizes why longer strings work better and how they can be arranged to produce improved results.
- In includes several suggestions for extending longitudinal strings into the throat or shank region of a racket to have a substantially longer strung length; and it proposes several different arrangements for fanning out, guiding, and anchoring longer longitudinal strings.
- the invention also recognizes that longer longitudinal strings should be strung with a higher tension than shorter transverse strings, and the invention determines both the reasons for and the extent of the higher tension for the longer strings to achieve a significantly better working relationship within the string network.
- the invention not only recognizes the advantages of longer longitudinal strings strung at higher tension than the shorter transverse strings, but also quantifies an approximate functioning relationship that balances the greater tension and length of the longitudinal strings with the lesser tension and length of the transverse strings effectively to apportion more of the ball-hitting load to the longitudinal strings.
- This gives a string network a higher coefficient of restitution imparting a higher velocity to a rebounding ball, spreads the higher coefficient of restitution throughout a wider network area, reduces losses from stretching and rubbing strings and deforming the ball, and lessens torque shock to the arm of the player.
- Tennis rackets strung according to the invention have been made, tested, and used in play to verify measureable data, confirm analysis, and establish subjectively that the invention produces better control, higher velocity returns, and a lively and shock-free feel in shot making.
- a racket including transfer strings and significantly longer longitudinal strings.
- all the longitudinal strings extend through a throat region to an anchorage or anchorages within the grip of the racket.
- the longitudinal strings are divided into a central plurality and side groups, the side groups in one embodiment being anchored to the racket frame around the ball-hitting region as in a conventional racket.
- This type of racket can be generally described as a racket having a hand grip joined to a frame supporting a string network having transverse and longitudinal strings extending throughout a ball-hitting region spaced from said grip, said frame having a shank region extending from said grip and flaring outward in a throat region and a generally oval region extending around said ball-hitting region, at least a central plurality of said longitudinal strings having a strung length at least 30% longer than the transverse strings; said central plurality of longer longitudinal strings including at least one-third of all the longitudinal strings; and said plurality of longer longitudinal strings being strung with at least 30% more tension than said transverse strings; and said central plurality of longer longitudinal strings extending into said throat region.
- said central plurality of longer longitudinal strings stops short of said grip at a single anchorage.
- the greater length and tension of the longitudinal strings is selected relative to the lesser length and tension of the transverse strings to place nearly half or considerably more than half of the ball-hitting load on the longitudinal strings in contrast to prior art rackets that place substantially more than half of the ball-hitting load on the transverse strings.
- longitudinal strings anchored nearer the longitudinal axis of the racket are geometrically more suited to bearing the ball-hitting load than the transverse strings anchored at the sides of the frame and transmitting more twisting shock to the player from off center axis.
- Advantages related to these include a more responsive sweet spot area, a higher coefficient of restitution of the string network, more control and velocity for shots, and less vibration.
- GB-A-2 056 288 proposed to increase the length of all the longitudinal strings and extend them very close to and even into the handle, and made their tension substantially greater than that of the cross strings.
- the longitudinal strings near the side of the frame have to be channelled into the throat, they have to mesh with the cross strings at a sharp angle, quite different from the conventional orthogonal direction, which made the contact very unstable, sliding against each other during play, so that the strings move out at an unacceptable rate of deterioration.
- the present invention intends to correct the problems described above.
- the tension that develops in a string on impact with the ball consists of two components-an initial strung tension To and an additional tension AE(x/L,) ⁇ from stretching or elongating the string, where A is the string's cross sectional area and E is its Young's modulus, x is the ball penetration, and L, is the half length of the string.
- the initial tension To term is much larger than the stretching term and is linearly proportional to the ball penetration distance x.
- Initial string tension thus acts much like a linear spring in receiving and storing the kinetic enery of the ball.
- the stretching term AE is small since it is proportional to the cube of x/L) which is very small when ball penetration x is small.
- the stretching term AE becomes increasingly significant.
- My invention recognizes the fact that a longer string with a large L 1 reduces the influence of the stretching term AE and indirectly increases the contribution of initial tension To, both of which benefit the performance of the network. Repeated stretching and unstretching of a string cause hysteresis loss from molecular friction within the string, and string stretching also causes rubbing, wear, and friction loss as strings move against one another. This suggests that the stretching term AB should be kept as small as possible, and that long strings are the best way to achieve this.
- transverse or cross strings Since the length of the transverse or cross strings is limited by the width of the racket frame, only the longitudinal strings can be made longer to take advantage of higher tension resistance. Longer longitudinal strings can be extended into the throat, shank, and even into the handle to provide a substantially longer strung length than the transverse strings.
- GB-A-2 056 288 suggests several anchorage and guidance arrangements for extending longitudinal strings into the shank or grip region of a racket, and many other possibilities are probably workable. The two most preferred arrangements are schematically shown in Figs. 1 and 2.
- Anchorage 16 can be positioned anywhere from throat 12 to grip 13, depending on the length and tension desired for strings 15.
- the other preferred racket 20 of Fig. 2 has longitudinal strings 25 that either extend axially parallel or diverge slightly across the ball-hitting region from a throat piece guide 22 having guide elements 24 that angle the strings between their anchorage 26 in shank 21 and their course across the ball-hitting region.
- anchorage 26 can be positioned along shank 21 or within grip 23.
- Fig. 2 looks more conventional and might be better received, but its throat guide 22 produces some friction loss.
- the embodiment of Fig. 1 is preferred not only for reducing friction, but for the additional advantage of reducing twisting torque from off center shots.
- Throat guide 12, 22 can also provide an anchorage for some of the shorter longitudinal strings extending less far than the central plurality of longer strings. The tendency of different string lengths and tensions to produce a desired performance is explained more fully below.
- Both the embodiments of Figs. 1 and 2 arrange the longer longitudinal strings 15 or 25 to bear more of the ball-hitting load than the transverse strings 17 or 27, and thus reduce the twisting torque from off center hits. But the fan out arrangement of Fig. 1 spaces the longitudinal strings closer together in the central region where most balls are hit and disposes strings 15 within a closer average distance from the racket axis to keep twisting torque to a minimum. This relieves the so-called tennis elbow caused by repeated twisting movement of the player's arm from ball-hitting shock.
- Figs. 3-5 show a mathematical model simplifying and approximating the action of a central longitudinal string 30 and a central transverse string 31 perpendicular to each other and elastically supported by other strings in the network to be deformed as shown when hitting a ball.
- the string width 2b adjacent the ball simulates the string portion that conforms with the flattened surface of the ball when the ball penetrates into the string network.
- the overall string lengths L a are divided into subscript portions to account for different lengths of string depressed by different amounts.
- the broken lines 32 and 33 simulate the elastic support from other strings supporting the two string system shown in solid lines, and the penetration d of the ball into the string network in the area of contact also dents the elastic supporting strings 32 and 33 by d/2.
- the string force resisting the advance of the ball increases with penetration of the ball into the string network and reaches its maximum value when the ball is stopped. At that instant, the deceleration is maximum, and the force F o is greatest.
- This maximum force, rF o on the long string and (I-r)F o on the transverse string, which determines the final deformation of the ball is given respectively by: where F e , which is equal to the mass times the deceleration, is the combined force on the ball from the two string system, r is the load percentage borne by the long string 30, I-r is the load percentage borne by the cross string 31, and d is the maximum penetration by the ball. For the same penetration, a smaller F e will deform the ball less and hence is preferable.
- the graphs of Figs. 6 and 7 plot the impact force against the penetration of the ball into the string networks and divide the ball-resisting force into the portion attributable to initial string tension To and the portion attributable to stretching of the string AE as previously explained.
- the results clearly show that longer strings at higher tensions allocate a much smaller portion of the ball- stopping force to string stretching.
- the results also show that the maximum impact force at the end of the ball penetration is higher for the prior art racket than for a racket strung according to the invention. Since the ball penetration is the same for both string networks, shot control is the same; and the lesser maximum force for the inventive network means a more efficient rebound. Both of these differences represent significant qualitative advantages for the inventive network.
- Reducing the force involved in stretching strings reduces losses that necessarily occur from internal friction as a string stretches and from interstring friction as strings rub together. It also reduces string wear and fatigue so that the network lasts longer. Reducing the maximum force required to stop the ball wastes less energy in ball deformation and means a springier, more responsive string network that is more effective in returning energy to the rebounding ball.
- Test measurements have compared string networks strung according to the invention with conventionally strung string networks for two of the best tennis rackets in the current market. Because the invention involved improved performance from an optimally strung network and not an improved shape or configuration of racket or frame, the frames of the two best rackets available were chosen for comparison of stringing efficiency.
- One is the "Volley II” made by the Dunlop Company as a medium size head racket.
- the trade magazine “Tennis World” has a special feature report in the April 1980 issue praising this racket as excellent.
- the other racket is the famed "Prince Classic", an over size head racket made by Prince Manufacturing Company according to U.S. Patent No. 3,999,765.
- the tests were made by clamping the periphery of the racket frame in a horizontal position leaving the string network free, dropping a tennis ball down from a fixed height of 1.25 m (49.2 inches), and accurately measuring the height of the rebound of the ball from the string network.
- the rebound height was measured by an "Instar" video camera that recorded on magnetic tape and allowed playback on a television to stop the frame showing maximum rebound height.
- the tests were conducted by Dr. William Parzygnat, who has a PhD in Mechanical Engineering from Cornell University and works for the Xerox Corporation.
- equations 4a and 4b indicate a ball penetration of 0.69 inches or 1.76 centimeters.
- equations 4a and 4b suggest that the same racket frame strung according to the invention to achieve the same ball penetration and thereby the same impact duration and shot- making control, should tension the 0.23 m (9 inch) transverse nylon strings at 19 kg (42 pounds) and use 0.46 m (18 inch) longitudinal strings strung at (100 pounds) 45.4 kg tension on a "Kevlar" string having an AE of 5897 kg (13,000 pounds).
- the inventive string network achieves a 0.76 maximum coefficient of restitution that is higher than any coefficient of restitution attained with conventional stringing for the same racket.
- the region of the highest coefficient at restitution from 0.74 to 0.75 for conventional stringing is only 58 cm 2 (9.0 square inches) in the center of the network and is enlarged to 222 cm 2 (34.4 square inches) in the inventive network, an increase by a factor of 3.82.
- Racket performance depends not only on the string network, but also on frame configuration, material, and weight distribution. So the improvement the invention achieves in the string network may not result in a directly proportional improvement in overall racket performance.
- the inventive improvement in the network stringing can be applied to existing rackets without additional cost, and the drop tests establish that the invention makes a more efficient string network with better ball- rebounding ability that undoubtedly improves a racket's overall performance.
- Rackets strung according to the invention have been used extensively by experienced players who have compared them with conventionally strung rackets and reported a subjective impression confirming the test results. Rackets strung according to the invention are lively and responsive, feel definitely "playable", and make well controlled and powerful shots.
- Test results have also confirmed the shock reduction capability of rackets strung according to the invention.
- rackets strung according to the invention using as an example the Dunlop Volley II strung according to the invention as explained above, comparative test play by several professionals and experienced amateurs verifies that this racket is remarkedly shock free and suppresses vibration better than all other known rackets, including oversized rackets and graphite frame rackets. This can particularly benefit players who wish to avoid tennis elbow and want a racket that vibrates the least.
- a string network can be structured to emphasize either control or power.
- High string tension and moderate string length emphasize power and make the ball and network contact brief, which reduces control.
- exceptionally long strings with moderately high tension increase the duration of ball and network contact to improve control and reduce shock at the expense of hitting power.
- the invention improves the network performance so that control, power, and shock reduction can all be enhanced; and the calculations aid in preselecting ways of emphasizing one of these characteristics.
- a Prince racket with transverse strings strung at 31.7 kg (70 pounds) can have longitudinal strings fanning out from a throat piece one inch behind the present throat piece, and the greater length of these strings can be tensioned to the 40.8 kg (90 pounds) limit of nylon to increase the ball hitting load on the longitudinal strings from 43% to 47%. Field tests have shown that this 30% increase in the tension of the longitudinal strings over the cross strings makes a superior racket that is more playable, more responsive, and smooth; maintains the same control with added power to the center hits; and vibrates much less from of center hits.
- the angle is about ninety degrees.
- the angle might be 70 degrees or less, depending on the number of longitudinal strings.
- the large tension force in the slanted longitudinal string will make the contact point unstable and will make it slide during play.
- the wear of string due to this sliding is quite severe and it could be impractical.
- the merits of the prior art with long string and high tension for the mainstring become evident.
- Such shorter longitudinal strings are terminated along the side of the frame.
- the central plurality of the longer longitudinal strings will then be anchored at a distance far enough from the throat position to make them long enough.
- the essence of the invention is the fact that some of the longitudinal strings have to be terminated along the side and the central plurality of longer longitudinal strings have to be very long, high tensioned, and terminated at a distance far enough behind the throat position to allow them to be that long.
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Physical Education & Sports Medicine (AREA)
- Pulmonology (AREA)
- Golf Clubs (AREA)
Claims (5)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8282302234T DE3279456D1 (en) | 1982-04-29 | 1982-04-29 | String load apportioned racket |
EP82302234A EP0093210B1 (fr) | 1982-04-29 | 1982-04-29 | Raquette à cordage à différentes tensions |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP82302234A EP0093210B1 (fr) | 1982-04-29 | 1982-04-29 | Raquette à cordage à différentes tensions |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0093210A1 EP0093210A1 (fr) | 1983-11-09 |
EP0093210B1 true EP0093210B1 (fr) | 1989-02-22 |
Family
ID=8189655
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP82302234A Expired EP0093210B1 (fr) | 1982-04-29 | 1982-04-29 | Raquette à cordage à différentes tensions |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0093210B1 (fr) |
DE (1) | DE3279456D1 (fr) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0515586A1 (fr) * | 1990-10-16 | 1992-12-02 | KUHNEL, Ulrich | Procede de cordage de raquettes |
DE4201144A1 (de) * | 1992-01-17 | 1993-07-22 | Ulrich Kuehnel | Verfahren und vorrichtung zur bestimmung der zugkraefte zum besaiten von schlaegern |
GB2265316A (en) * | 1992-03-19 | 1993-09-29 | Lo Kun Nan | Method for stringing a game racket. |
JPH06315547A (ja) * | 1993-03-09 | 1994-11-15 | Yamaha Corp | テニス用ラケットフレーム |
US6027419A (en) * | 1994-05-25 | 2000-02-22 | Cogito Holdings Limited | Method of tensioning the strings in a racquet |
EP1108447A1 (fr) | 1999-12-15 | 2001-06-20 | Tsai Chen Soong | Raquette de sport |
EP3241591A1 (fr) * | 2016-05-06 | 2017-11-08 | Head Technology GmbH | Pont de raquette de jeu de balle |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB291141A (en) * | 1927-02-23 | 1928-05-23 | Archibald Milne Hamilton | Improvements in racquets used in tennis, badminton and such-like games |
US4196901B1 (en) * | 1977-03-07 | 1998-05-26 | Enoch J Durbin | Tennis racquet |
DE2752624A1 (de) * | 1977-11-25 | 1979-05-31 | Kuebler & Co | Tennisschlaeger |
GB2056288B (en) * | 1979-08-22 | 1983-02-02 | Soong Tsai C | Long string racket |
DE3015960A1 (de) * | 1980-04-25 | 1981-11-05 | Kuebler & Co, 7700 Singen | Tennisschlaeger |
-
1982
- 1982-04-29 DE DE8282302234T patent/DE3279456D1/de not_active Expired
- 1982-04-29 EP EP82302234A patent/EP0093210B1/fr not_active Expired
Also Published As
Publication number | Publication date |
---|---|
DE3279456D1 (en) | 1989-03-30 |
EP0093210A1 (fr) | 1983-11-09 |
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