FR2589068A1 - TENNIS BALL - Google Patents

Abstract

THE INVENTION RELATES TO A TENNIS BALL INCLUDING A SPHERICAL CORE COVERED WITH A PLURALITY OF DISCREET, SENSITIVELY IDENTICAL, AND POLYGON-SHAPED OVERLAP ELEMENTS. ADJACENT EDGES OF ADJACENT COVER ELEMENTS 20, 21, 25; 21, 22, 25; 22, 23, 25; 23, 24, 25; 24, 20, 25 ARE PLACED IN A PARALLEL AND SPACED RELATIONSHIP TO DEFINE A CONTINUOUS CHANNEL 30 EXTENDING, GEOMETRICALLY SYMMETRICALLY, OVER THE SPHERICAL SURFACE OF THE CORE; NO LIAISON AGENT IS PRESENT IN THE CHANNEL; THE DEGREE OF HYSTERESIS LOSS IN THE BALL, ACCOUNTABLE TO THE NEEDLE-PERFORATED CANVAS USED FOR THE COATING ELEMENTS, IS REDUCED BY COMPARISON TO A TENNIS BALL INCLUDING A BINDING AGENT PRESENT IN THE CALCULATION. APPLICATION TO THE FIELD OF TENNIS.

Description

The present invention relates to a tennis ball, and in particular

  a tennis ball in which a plurality of discrete, substantially identical, polygon-shaped overlapping members are glued to the surface of a spherical core. UK Patent No. 2,124,504 of the Applicant, corresponding to the French patent application No. 83 12 462, describes a method of manufacturing a tennis ball according to which twelve pentagon-shaped covering elements are glued to the surface of the a spherical core, adjacent edges of adjacent overlapping elements defining a junction channel which is filled with a bonding agent before said adjacent edges are pushed into abutment

One against the other.

  It has now been found that an improved tennis ball can be achieved by omitting the connecting agent filling the junction channel described in FIG.

U.K. patent mentioned above.

  Surprisingly, it has also been found that

  tennis ball made in accordance with the present invention

  tion has a lower hysteresis loss (ie

  say less elasticity) than a bullet made

  according to the aforementioned U.K. patent.

  Accordingly, the present invention relates to a tennis ball comprising a spherical core and a plurality of substantially identical, polygon-shaped, discrete overlays in which the cover elements are glued to the surface of the core such that adjacent edges of adjacent overlapping members are placed in a parallel and spaced relation, a continuous channel being defined between said adjacent edges

  and no linker being present in said channel.

  Preferably the channel extends in a manner

  geometrically symmetrical on the spherical surface of the nucleus.

  In a particularly preferred embodiment of the present invention, the bale is provided with twelve cover members, each cover member having the shape

of a regular pentagon.

  Advantageously, each covering element

  is formed of a needle punched cloth.

  It has been found, in accordance with the present invention, that the use of a needle punched web for the cover members provides for deep penetration of the web by an adhesive and thereby improves adhesion.

  covering elements on the spherical core. As a result

  that the covering elements have little or no tendency to "lift" on the edges or corners and the obligation to seal adjacent edges by means of a

liaison officer.

  It has also been found that the absence of a bonding agent in the channel allows the cover elements to react individually when the ball is deformed during the game of tennis. Although it is not intended that the present invention be established with reference to a particular theory, it is believed that the continuous and geometrically symmetric channel may act as a "gate".

  elasticity extending over the entire surface of the ball.

  In other words, each cover element can be considered as a zone of reduced elasticity on the flexible surface of the core, the channel acting as a part

improved elasticity.

  Other features and advantages of the invention

  will be highlighted in the following description, given

  as a non-limiting example, with reference to the single drawing

  attached o the single figure is a schematic perspective view

  a portion of a tennis ball according to the present invention. In the drawing, a tennis ball consists of a spherical core 10 of elastomeric material, having twelve cover elements (six are represented; 20, 21, 22, 23, 24 and 25) which are substantially identical, which have a form of pentagon and which are glued on the nucleus. Adjacent edges of adjacent overlapping elements are placed in a parallel and spaced relation so as to define a channel which extends, in a geometrically symmetrical manner, on

  the entire spherical surface of the ball.

  A comparison of the properties of a bullet according to the present invention with a similar bullet in which the channel is filled with a bonding agent (such that adjacent overlays are sealed together on adjacent edges) gave the results

indicated in the following.

  To establish the properties of a bullet made in accordance with the present invention, it is necessary to describe the manner in which tennis balls are tested, and

  the interpretation of the results of these tests.

  It is desirable to make tennis balls

  with improved performance and this is done in accordance

  to the present invention in attempting to reduce the loss

  hysteresis in the ball. A loss of hysteresis is traditional

  tionally measured by applying a static force

  7.17 kg to the bale and measuring the corresponding deformation

  the ball (called "direct deformation"), in con-

  nuance to apply a force until the ball is deformed by 25 mm, gradually reducing this force until again a force of 7.17 kg is applied and measuring the deformation + (called "deformation" in return "). The difference between the values of the direct deformation and the deformation in return is a measure of the hysteresis loss of the ball - the more the difference is

  large, the greater the loss of hysteresis is large. For an elasticity

  In this case, the values of the direct deformation and the back deformation should be identical, but this can never be achieved in practice. However, it is possible to get closer to this ideal by focusing in a particular way on

  the design of a tennis ball.

  The application of a textile covering the core of the ball greatly increases the loss of hysteresis and it is desirable to reduce this as much as possible. A textile covering is necessary to give a ball

  desirable aerodynamic and wear qualities.

  The present invention reduces the degree of hysteresis loss attributable to the fabric and this is demonstrated by the following test results. The loss of hysteresis is measured first of all for the core of the tennis ball and then for the actual tennis ball when covered with canvas in the manner described herein, and further in the manner described in the patent. UK No. 2,124,504. LOSS OF HYSTERESIS (0025 mm) Augmentat-coated bullet: Only keroidal canvas hysteresis ion loss

___________

  1. Ball manufactured in accordance with 124 the present invention 112

117

  Average 119.0 2. Ball manufactured 128 as above 119 but with 110 seal connection 113 112 patented

U.K.2 124 504 -----

  Mean 116.4 We see that the least important degree by omissi joint. , 0 ------ e 21.4

148.2 31.8

  hysteresis is increased to an ion of the binding material of

  _____________________________________________________________

  + See Tennis Rules: Official Lawm Tennis Handbook

Association ".

--------------- 1 --------------- i

Claims (4)

  A tennis ball comprising a spherical core covered with a plurality of substantially identical, polygon-shaped discrete overlays, characterized in that the cover elements (20, 21, 22, 23, 24,) are stuck to the core surface such that adjacent edges of adjacent cover members   (20, 21, 25; 21, 22, 25; 22, 23, 25; 23, 24, 25, 24, 20,   ) are placed in a parallel and spaced relation, a continuous channel (30) being defined between said adjacent edges and no linker being present in said channel (30).   2. Tennis ball according to claim 1, characterized in that the channel (30) extends geometrically   symmetrical on the spherical surface of the nucleus.   Tennis ball according to one of claims 1 or 2,   characterized in that each covering element (20, 21, 22, 23, 24, 25) is in the form of a regular pentagon and in that twelve covering elements are provided which are glued together on the spherical surface of the nucleus.   4. Tennis ball according to any one of the claims   1, 2 or 3, characterized in that each covering element (20, 21, 22, 23, 24, 25) is formed of a perforated canvas by needles.