CA2248844A1

CA2248844A1 - Ball racket

Info

Publication number: CA2248844A1
Application number: CA002248844A
Authority: CA
Inventors: Helmut Umlauft; Herfried Lammer
Original assignee: Head Sport GmbH
Current assignee: Head Sport GmbH
Priority date: 1997-10-03
Filing date: 1998-10-02
Publication date: 1999-04-03
Also published as: DE59808144D1; EP0909572B1; ATE238827T1; EP0909572A1

Abstract

There is disclosed a ball racket and, in particular, a tennis racket including a racket head and a handle portion. The frame members extend from the handle portion over the strung region of the head portion. The open area defined between the frame members running into the handle portion at acute angles as a whole constitutes the string plane and the longest central string extending in the longitudinal axis of the racket is tightened between the head and the point of origin adjacent the handle, of the acute angles (.alpha.) of the frame members running into the handle portion. The racket has a strung weight of less than 260 g and a free-free vibration frequency of more than 200 Hz. The ratio of the width of the string area to the length of the longest string of the string area is smaller than 0.6.

Description

' CA 02248844 1998-10-02 This invention relates to a ball racket and, in particular, a tennis racket comprising a racket head and a handle portion with the frame members extending from the handle portion over the strung region of the head portion, wherein the open area defined between the frame members running into the handle portion at acute angles as a whole constitutes the string plane and the longest central string extending in the longitudinal axis of the racket is tightened between the head and the point of origin adjacent the handle, of the acute angles of the frame members running into the handle portion.
A racket of the initially mentioned type may be taken, for instance, from Re. U.S. Pat. No. 33,372. In addition to a number of further developments of ball rackets aimed at keeping away from the player's wrist hard impacts and vibrations, modern tennis rackets with a view to obtaining this effect stand out for their ever decreasing overall weights, what has become feasible without considerable deterioration of the sti~ness values not least due to modern materials.
The playing properties of a racket and hence the handling of a racket and, in particular, the impartation of the precise direction on the ball, the translation of the player's reaction speed on the ball via the racket and a high acceleration of the ball have each been enhanced with the hitherto known rackets by varying the weight and stiffness distribution, it having been recognized that all of these playing properties are decisively influenced not only by the weight of a racket, but also by the center of gravity of the racket and the center of gravity of impact or dynamic center of gravity, measured from the grip end. A further criterion with a view to reducing the vibration acting on the wrist is the free-free vibration ~requency (eigenfrequency), which could be raised to accordingly higher values at a reduced weight and a suitable material choice.
While the initially mentioned racket described in Re.
U.S. Pat. No. 33,372 had free-~ree vibration frequencies _ 1 _ ranging ~rom about 1 0 to 150 Hz, subsequent developments such as, for instance, the racket described in U.S. Pat. No.
5,36~,295 aimed at free-free vibration frequencies of 190 Hz at reduced weights and elevated stiffness values. The weight of such a racket is to be less than 270 g.
Further increase in the free-free vibration frequency and further reduction of the weight without loss of stiffness have yet resulted in the substantial loss of criteria essential to the playability of a ball racket. Further reduction of the weight, in fact, caused the socalled sweet spot to become smaller and smaller and the racket to become more and more sensitive to off-center impacts. So far, with particularly light rackets good ball control, therefore, has been feasible only with an extremely precise play, the ball having had to impinge on an extremely small region of the string area in order to be controllable.
The invention aims at designing a ball racket of the initially defined kind particularly light and wrist-saving and, at the same time, guaranteeing a better ball control even to less good players by an enlarged sweet spot. To solve this object, the ball racket according to the invention of the initially defined kind essentially consists in that the racket has a strung weight of less than 260 g and a free-free vibration frequency of more than 200 Hz and the ratio of the width of the string area to the length of the longest string of the string area is smaller than 0.6. While tennis rackets with frame members extending from the handle portion over the string area of the head portion and running into the handle portion at acute angles so far, as a rule, have been made to include a throat portion, also conventional so-called mono-shaft rackets usually have been relatively wide in relation to the length of the string area. Surprisingly, it has now been found that, if the length of the longest string is increased accordingly overproportionally relative to the width of the string area so as to obtain a ratio of the width of the string area to the length of the longest string of the string area of less than 0.6, the playability of the ball racket will be ' CA 02248844 1998-10-02 substantially improved despite the extremely low weight and the high vibration ~requency desired. This is said to be due to the ~act that, on account o~ the relatively narrow racket in relation to the length of the longest string, an over-proportional enlargement o~ the sweet spot is obtained. Thelength o~ the longest string in rackets with throat portions or in conventional monosha~t rackets might, however, be altogether extended only by an overproportional extension o~
the racket, which, in turn, would result in a weight increase and in other undesired playing properties as caused ~rom shifts o~ the dynamic center o~ gravity and the static center o~ gravity.
The combination according to the invention, o~ an extremely low weight and a high ~ree-~ree vibration ~requency o~ the ~irst mode with the measure to overproportionally extend the stringing of a ball racket having substantially the usual length o~ a racket, thus, results in a light-weight, arm- and wrist-saving ball racket easy to play with also by less trained tennis players and allowing for an enhanced translation o~ the player's reaction speed and a high acceleration o~ the ball.
In a pre~erred manner, the geometry o~ the racket is chosen such that the ratio of the longest string o~ the stringing to the overall length o~ the racket is greater than 0.6 and, pre~erably, greater than 0.65 By such a configuration, it is ~easible to realize the geometry required ~or a better playing behavior also with rackets having conventional overall lengths.
Further improvement in the translation o~ the reaction speed o~ a player and ~urther reduction o~ vibrations that might be transmitted into the wrist may be obtained in that the racket has a strung weight o~ less than 250 g and a ~ree-free vibration ~requency o~ more than 210 ~z.
While conventional rackets and, in particular, also known monosha~t rackets on grounds o~ their structures and geometries, as a rule, are characterized in that the vibration ~requencies measured perpendicular to the string plane di~er ' CA 02248844 1998-10-02 only slightly, and usually by less than 5 %, from the vibration frequences measured in the string plane, the ball racket according to the invention advantageously is characterized in that the vibration frequencies measured perpendicular to the string plane di~er ~rom the vibration ~requencies measured in the string plane by at least 20 % and, pre~erably, 25 ~. The vibration frequency measured per-pendicular to the string plane corresponds to the free-~ree vibration frequency, which, according to the invention, is to amount to at least 200 Hz. Due to the structure provided by the invention and the obviation of a throat portion, a higher sti~fness is achieved such that the obtainment o~ accordingly increased values in the range of 300 Hz will be feasible in the string plane, the ball control thus bei~g enhanced even further.
In order to ~urther reduce the strung weight of the ball racket, a preferred string pattern is provided. While a denser stringing in the central region, and a stringing with accordingly larger string intervals in the peripheral region, of the string area was chosen in Re. U.S. Pat. No. 33,372, the weight o~ the strung racket according to a pre~erred ~urther development may be reduced in that the strings extending in the longitudinal direction of the ball racket extend so as to diverge towards the head on both sides, starting ~rom the central string located in the longitudinal axis of the racket.
In this manner, the socalled sweet spot will be increased not only in terms o~ length but also in terms of width, thereby further improving the playing properties at a simultaneously reduced weight. In this respect, the configuration advantageously may be such that the divergence of neighboring strings in the lateral regions increases by increments towards the edge o~ the racket.
In tennis racket construction, carbon fibers have become established as the preferred material with a view to obtaining the high stiffness values required at simultaneously reduced weights. In an advantageous manner, the ball racket according to the invention with the required values in terms of weight, ' CA 02248844 1998-10-02 vibration ~requency and elevated sti~~ness ~or the stringing may be manufactured in that the ~rame members are comprised o~
carbon ~ibers and/or metals such as, e.g., aluminum or titanium.
The racket according to the invention as well as the racket geometry according to the invention are explained in more detail schematically by way o~ the exemplary embodiment illustrated in the drawing. From the drawing, the frame member 1 of a tennis racket 2 is apparent, which, starting ~rom a handle portion 3, is bent through the stringing oval and returned to the handle portion while enclosing an acute angle ~. There is no throat portion at all adjacent the handle portion 3 such that a particularly long longest string 4 may be realized there, which, starting ~rom the bottom o~ the groove defined by the acute angle ~, extends as far as to the racket head 5. The ratio o~ the string area width _ to the string area length a, which corresponds to the ratio o~ the respectively longest strings in the direction o~ the string area width and in the direction of the string area length, is chosen to be smaller than 0.6 so as to obtain a slim racket having a string area extended relative to the unchanged overall length. In order to be able to increase the longest length a o~ the longest string 4 without changing the overall length c o~ the ball racket 2, the ratio o~ the longest string a o~ the stringing to the overall length c o~ the racket in a pre~erred manner is greater than 0.6 and, pre~erably greater than 0.65.
The ~rame members are made o~ synthetic ~ibers and/or metals such as, e.g., aluminum or titanium.
From the geometry illustrated, considerable deviations between the vibration ~requencies perpendicular to the string plane and the vibration ~requencies measured in the string plane result, thereby obtaining an altogether extremely sti~
as well as readily playable and highly arm-saving racket.

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A ball racket and, in particular, a tennis racket including a racket head and a handle portion with the frame members extending from the handle portion over the strung region of the head portion, wherein the open area defined between the frame members running into the handle portion at acute angles as a whole constitutes the string plane and the longest central string extending in the longitudinal axis of the racket is tightened between the head and the point of origin adjacent the handle, of the acute angles of the frame members running into the handle portion, characterized in that the racket has a strung weight of less than 260 g and a free-free vibration frequency of more than 200 Hz and the ratio of the width of the string area to the length of the longest string of the string area is smaller than 0.6.

2. A ball racket according to claim 1, wherein the ratio of the longest string of the stringing to the overall length of the racket is greater than 0.6 and, preferably, greater than 0.65.

3. A ball racket according to claim 1, wherein the racket has a strung weight of less than 250 g and a free-free vibration frequency of more than 210 Hz.

4. A ball racket according to claim 1, wherein the vibration frequencies measured perpendicular to the string plane differ from the vibration frequencies measured in the string plane by at least 20 % and, preferably, 25 %.

5. A ball racket as set forth in claim 1, wherein the strings extending in the longitudinal direction of the ball racket extend so as to diverge towards the head on both sides, starting from the central string located in the longitudinal axis of the racket.

_6_

6. A ball racket as set forth in claim 5, wherein the divergence of neighboring strings in the lateral regions increases by increments towards the edge of the racket.

7. A ball racket as set forth in claim 1, wherein the frame members are comprised of carbon fibers and/or metals such as, e.g., aluminum or titanium.