FR2673115A1 - Tennis racket - Google Patents

Abstract

The invention relates to tennis rackets. <??>A racket (10) comprises an oval frame (20) and a shaft (11) integral with the frame (20). The frame (20) has a staged inner periphery (20b) forming a shoulder (23) and a series of holes (21) for the passage of the strings adjacent to the shoulder (23) and which form spaced notches (26) on the shoulder (23). The network of strings (30) is stiffer when the strings (30) bear against the shoulder (23) when a face (20) of the network which is opposite the shoulder (23) receives an impact. The shoulder (23) also limits the amplitude and the duration of the vibration of the strings (30) when the network receives an impact. <??>Principal application: racket with differentiated effect.

Description

Tennis racket

The invention relates to a tennis racket

nis, more particularly to a perfected racket frame.

ted with reduced vibratory effects and improved rigidity when one face of the sieve made up of crisscrossed strings held by the racket frame

suffers an impact.

Snowshoes usually include a ta-

put composed of crossed ropes which are stretched

in an open frame, of substantially oval shape at the-

what is attached a handle When the sieve is hit by

a bullet, the resulting impact is transmitted by the cor-

to the racket frame and handle This can affect the

evoke an injury if the force of the impact is relative-

ment great.

To reduce the vibrations that occur

when the strings are struck, we fix an ab-

additional shock absorber to the frame of the racket so as to absorb a certain part of the force which,

otherwise, could be transmitted to the handle.

Another disadvantage of classic snowshoes

consists in that, for the same value of force of im-

pact, the bouncing force of a ball hitting the strings is always the same regardless of the face

of the sieve of ropes which is struck by the ball.

The aim of the invention is therefore to achieve a

racket frame with re-

tendrils and greater stiffness when it is one face of the string screen held by the racket frame

who receives the impact only when it is the other.

Another object of the present invention is to provide a racket having a greater rebound force when it is hit on a paddle.

face and lower rebound force when

that it is struck on the other side.

The preferred embodiment of the racket

according to the invention therefore comprises a frame of sensi-

oval frame and a handle integral with the oval frame The oval frame has an outer periphery, a peri-

inner pheria stepped so as to form a shoulder-

ment extending the entire length of the periphery

interior, and a plurality of cor-

which extend from the outer periphery to the peri-

inner pheria in a region adjacent to the shoulder-

ment and which form spaced notches on the shoulder-

ment The holes for the passage of strings are provided for

view and hold a sieve made of crossed ropes.

The sieve exhibits greater stiffness when the strings bear against the shoulder at the time when the face

of the sieve which is opposite the shoulder undergoes the

pact The shoulder therefore limits the amplitude and duration of the string vibration that occurs when the

sieve receives an impact.

Other features and advantages of the

present invention will become apparent from the description

detailed description of a preferred embodiment which is given below with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a ra-

quette according to the invention; FIG. 2 is a perspective view of a section of a racket frame according to the invention;

Figure 3 is an illustration of the ra-

quette, when a sieve of intersecting ropes is

from one edge to the other of this frame; figure 4 shows the deflection of a string stretched from one edge to the other of a racket frame

of the preferred embodiment of the invention when

that it is struck in a first sense; Figure 5 shows the deflection, in the opposite direction, of the string shown in Figure 4, under the effect of vibrations; Figure 6A shows how a shoulder of a racket frame of the preferred embodiment resists string movement; Figure 6B illustrates the string of Figure 6A as it flexes in the opposite direction under the effect of vibrations;

Figure 7 is a graph which compares the

brations of a rope stretched from one side of the frame to the other

racket of the preferred embodiment with

brations of a rope stretched from one side to the other of a

classic racket dre; Figure 8 is an illustration of a string stretched side-to-side of a racket frame of the preferred embodiment; Figure 9 shows the deflection of the string shown in Figure 8 when struck on one side of the racket frame; and figure 10 shows the deflection of the

rope shown in Figure 8 when struck

sword on the other side of the racket frame.

In Figure 1, a preferred embodiment

tion of a racket 10 according to the present invention is

shown in a form which comprises a handle 11 re-

linked to a first end of a frame 20 of sensory shape

sibly oval.

In Figures 1 and 2, the frame 20 of form

oval is a hollow tubular element, curved into a bou-

key, which has an outer periphery 20 a and a pe-

inner riphérie 20 b which is wider than the peri-

outer ring 20 a The inner periphery 20 b is stepped so as to form a shoulder 23 which extends

over the entire length of the inner periphery 20 b.

A series of 21 string passage holes, aligned and

spaced apart, start from the outer periphery 20 a, and through

pour the peripheral edge of the shoulder 23, to form a series of notches 26 aligned and spaced along the peripheral edge of the shoulder 23 As can be seen by referring to Figures 2 and 3, the through holes 21 of strings receive and retain without play a sieve formed of crisscross strings 30 (The attachment of the crisscross strings 30 to the frame 20 of the racket is known to those skilled in the art and will not be

described in detail below) One side of the strings between

30 butts normally against the shoulder 23, at the

notches level 26.

When a bullet hits the string sieve 30

intersecting, as shown in Figure 4, the cor-

of the 30s flex due to their own properties

elastic The ropes 30 flex in the opposite direction.

when the ball bounces off the sieve 30, as re-

shown in Figure 5 Since the two ends

moths of each rope 30 are held without play by the

dre 20 of the racket, the strings 30 vibrate in a damped sinusoid until they have returned to

state of equilibrium.

As can be seen by referring to the figures

res 2 and 6 A, strings 30 can be struck on a

first face 24, in which case the strings 30 bear con-

be the shoulder 23 to the right of the notches 26 The shoulder-

ment 23 resists sagging of the strings 30, reducing

thus knowing the amplitude of the resulting vibrations (The transparent lines represent the sag of the strings 30 in the absence of the shoulder 23, as in the case of conventional racket frames) In Figure 6B, the strings 30 therefore flex less strongly in the opposite direction, when the ball bounces off the strings 30 When the strings 30 flex once

more towards the shoulder 23, the shoulder 23 also cushions

re the amplitude of the vibration Figure 7 is a graph

phic which illustrates the amplitude of the vibrations of the

30s and strings of a classic racket (the vibra-

the strings of the classic racket are drawn by dashed lines) it will be noted that the amplitude and the effective period of the vibration of the

30 strings are much smaller than those of cor-

of the classic racket The 30 strings are stabilized

therefore smells faster.

As can be seen by referring to the figures

gures 2 and 8, strings 30 can also be struck

on the second face 25, which is opposite the first

re face 24 The bending length H (measured from the point

B or at point B ') of the strings 30 when they are struck.

swords on the first face 24 is shorter than the long

bending strength L (measured from point A to point A ')

strings 30 when struck on the opposite side

posed 25, this because of the presence of the shoulder 23 which resists the movement of the strings 30 The strings 30 therefore have greater stiffness when they are

stamped on the first side 24.

Figures 9 and 10 are illustrations of the string 30 as it is struck on the first face 24 and on the second face 25 respectively Assuming that the string screen 30 is struck at point P, as shown in Fig. figure 3, and that the voltage of

the rope 30 is the same in Figures 9 and 10, the rope

of 30 bends at an angle (el) in figure 9, and of

angle (e 2) in figure 10 Since the length

length L / 2 in Figure 10 is greater than the length

length H / 2 of figure 9, the angle (e 1) is greater than the angle (82) Since the tension Fl of the string 30 of figure 9 is equal to the tension F 2 of the string 30 of figure 10, with reference to diagram

corresponding forces, we see that the rebound force

Ql strain of the chord 30 of Figure 9 is greater

that the rebound force Q 2 in figure 10.

Since the length L is greater than the length H, the strings 30 are more flexible when struck on the second side 25 This is ideal if it is desired that the ball describes a greater length when the strings 30 are hit on the first face 24, the rebound force is greater This is ideal when hitting the ball with a

reverse In this way, the second side 25 will be used.

used to hit a backhand ball to obtain greater rebound force and the first face 24 is instead used to hit a backhand ball.

forehand, to get a longer distance.

Claims (1)

R E V E N D I C A T I O N Racket (10) comprising a shaped frame (20) substantially oval and a handle (11) integral with said casing oval dre (20), characterized in that said oval frame (20) has an outer periphery (20 a), an inner periphery (20 b) stepped so to form a shoulder (23) which extends over the entire length of said inner periphery (20 b) and a series holes (21) for the passage of ropes which extend from the said outer periphery (20 a) to said inner periphery (20b) in a region adjacent to said shoulder. ment (23), in this way forming spaced notches. cées (26) on said shoulder (23), said string passage holes (21) being provided to receive and hold a sieve of intersecting ropes (30), said sieve having with greater stiffness when said cords (30) bear against said shoulder (23), at the time o a first face (24) of said screen which is opposite to the said shoulder (23) receives an impact, said shoulder (23) limiting the amplitude and duration of the vibration said cords (30) when said screen receives an im- pact.