FR2675698A1 - RACKET. - Google Patents

Abstract

The racket is made from a synthetic resin with a density of 0.9 to 1.4 gm/cm<3> having a handle of a length (A') and an oval head of a thickness (D), of a major diameter (A) and of a minor diameter (B), and the total length of the racket is (L), where (L = A + A'). The oval head is included between two striking surfaces (S1) and (S2) having holes serving to lighten it and also to minimise its air resistance. The racket is characterised in that: - the thickness (D) is chosen such that: (A/D) = 11 to 19, and (B/D) = 9 to 16, and, - the holes have a diameter 0.8 to 1.2 cm, and their number (n) is chosen such that the apparent density (d) of the said head is between 0.21 and 0.36 gm/cm<3>.

Description

The present invention relates to a racket of the type of

  those having a handle and a full oval blade.

  It concerns, more precisely, a racket of a ball game

known as "PADDLE".

  A racket of "PADDLE" is manufactured, at present, in specific plywood whose density is close to

0.5 gm / cm 3 (origin: Argentina).

  The racket blade is about 1.2 cm thick and has 80 circular holes with a diameter of about 1 cm. The hazards of manufacture often lead to products of a

variable quality.

  The key parameters for having a good quality classic racket are divided into three stages: a stage concerning obtaining even the plywood, for example, the choice, the drying and the gluing of the wood, a stadium of plywood machining to obtain a racket and finally a stage of storage of the machined rackets Indeed, the reactions of rackets made vis-a-vis atmospheric changes also determine, at any

moment, the quality of the racket.

  The use of a stable material against atmospheric changes such as, for example, common synthetic resins (such as polyolefins, polyamides, polyvinyl chlorides (PVC), acrylonitriles butadiene styrene (ABS) and polycarbonates whose density varies from 0.9 to 1.4 g / cm 3 poses two problems: 1 a problem of density and, consequently, of the final mass of the racket and 2 a problem of mechanical properties because the mechanical properties of these resins are very different from those

plywood.

  Indeed, the manufacture of a racket whose thickness and number of holes are identical to those of the traditional racket "PADDLE" leads to a racket whose final mass and flexibility are greater than those of the

said traditional racket.

  Increase the number of holes to lighten the racket leads to

an even more flexible racket.

  Increasing the number of holes while increasing the thickness can lead to a brittle racket (brittle) especially in the case

  an accidental hit on the racket's song.

  For these reasons, the purpose of the present invention is to provide a racket made from synthetic resins, as previously designated, while maintaining the final mass and the mechanical properties of the said racket identical to those of a racket traditional of good quality. Another object of the present invention is to propose a racket whose mechanical characteristics are previously

  known and do not depend on the hazards of manufacture.

  Yet another object of the present invention is to provide a racket of good quality and whose manufacturing cost is

  inexpensive compared to that of a traditional racket.

  Yet another object of the present invention is to provide a racket whose mechanical qualities are stable with respect to

  atmospheric conditions, including humidity.

  For this purpose, the racket, subject of the present invention, is manufactured in one piece from a resin

  synthetic material with a density of 0.9 to 1.4 gm / cm 3.

  The racket has a handle of a length (A ') and an oval blade of a thickness (D), a large diameter (A) and a small diameter (B), the total length of the racket being (L) o (L = A + A '), the oval blade being between two striking surfaces (Si) and (52) and having holes for lightening and

minimize its resistance to air.

  The racket is essentially characterized in that the thickness (D) is chosen such that: (A / D) = 11 to 19 and, (B / D) = 9 to 16 and, the holes have a diameter of 0 , 8 to 1.2 cm, their number (n) is chosen so that the apparent density d of the said

blade is 0.21 to 0.36 gm / cm 3.

  According to another characteristic, the apparent density (d) and the thickness (D) are chosen so that the density of the surface (ds = D X d) has a value of between 0.48 and

0.58 gm / cm 2.

  According to another characteristic, the two striking surfaces (Si) and (52) are two parallel flat surfaces and the dimensions of the blade are: (A) = 26 to 29 cm, (B) = 23 to 26 cm, and

(D) = 1.5 to 2.5 cm.

  The present invention will be better understood on reading the

  detailed description given below, and accompanied by

  drawings in which: Figure 1 is a front view of the racket according to the invention, the holes of the blade being square, Figures 1A and 1B are sectional views along A / A and B / B of the FIG. 1 is a partial front view of the blade, the holes being circular, FIG. 3 is a partial front view of the blade, FIGS.

holes being hexagonal.

  The synthetic resins used for making the racket, subject of the present invention, may be

  common resins such as: polyolefins, acrylonitriles

  Butadian styrene triles (ABS), polyamides, chlorides

  polyvinyl (PVC) and polycarbonates.

  The characteristics of these resins are:

  I | IPOLY | POLYAMIDE JACRYLO ICHLORIDE IPOLYCARI

  I | IPROPYLENE I INITRILE IDE POLY | BONATE |

IBUTADIENE IVINYL I I

I I ISTYRENE i (PVC) I I

I I I | (ABS) I I I

IàààààE

IDENSITY I I I I I I I

  ICHOISIE I 0.9 I 1.12 I 1.06 I 1.40 o 1.20 | jgm / cm 3 I I I I I I I

| EXTENSION I I I I I I

  I AT I 250 I 100 1 20 1 40 I 100 |

IRUPTURE * I I I I I I I

IDURETE I I I I I I I

  IROCKWELL I 75 I 100 1 110 I 90 I 120 j

II I I III

IMODULE I I I I I I I

ID'ELASTI I I I I I

  CITE EN | 1,200 d 1,800 I 2,200 I 1,700 12,400

| FLEXION I I I I I I I

IMN / m 2 I I I I I I I

IRESISTANCE I I I I I

A IMPACTI I I I I

  ITEST IZORDI 120 j 130 j 120 100 900 j J / MIIIIII It is quite obvious that the density for a given resin can change according to its length of chain, which entails changes of its mechanical properties: when the density of a given resin increases the hardness and modulus of elasticity in flexion increase while the elongation at the

rupture decreases.

  As noted above, the manufacture of a racket from these resins, to replace the traditional racket made of plywood poses two problems:

  a problem of density and a problem of flexibility.

  Indeed, these resins are, in general, more dense and more flexible than the plywood used for the manufacture of a

traditional racket.

  Flexibility refers to the elastic deformation in relation to the applied force. It is therefore inversely proportional to the

modulus of elasticity in flexion.

  According to the invention, the density, for a given resin, is adjustable by making a number (n) more or less important holes in said racket blade, this leads to a variable density (d) variable: increasing the number of holes of a given diameter leads to a lower apparent density

and vice versa.

  The flexibility is adjustable by increasing more or less the thickness (D) of the blade: increasing the so-called thickness makes

the less flexible blade.

  To adjust the flexibility, the modulus of elasticity in bending of the resin and the number of holes to be made in the blade are both taken into consideration; a relatively inflexible resin (modulus of elasticity in high bending) and a small number of holes lead to a little blade

flexible and vice versa.

  By way of example, a resin such as polyolefins having a density of 0.9 gm / cm 3 and whose flexural modulus of elasticity is 1200 MN / m 2 requires: making a number of holes (n) in the blade making its apparent density 0.22 gm / cm 3, make the thickness (D) equal to 2.5 cm for an oval blade whose diameters (A) and (B) are respectively 27.5 cm and

24.5 cm.

  For a resin such as polycarbonates with a density of 1.2 gm / cm 3 and whose flexural modulus of elasticity is 2400 MN / m 2, the bulk density (d) to be obtained is 0.35 gm / cm. 3 and the thickness (D) to be respected is 1.5 cm; this for a blade having the same shape and the same extent, that is to say, a shape

  oval of which (A) = 27.5 cm and (B) = 24.5 cm.

  For other resins with a density between 0.9 and 1.4 gm / cm 3 and a flexural modulus of elasticity between 1200 and 2400 MN / m 2, the apparent density (d) to be obtained should be be siute between 0.22 and 0.35 gm / cm 3 and the thickness (D) between 1.5 and 2.5 cm, this obviously for the same oval blade whose large diameter (A) = 27.5 cm and the small diameter (B) = 24.5 cm. In all cases, the ratio (A / D) always has a value

  between 11 and 19 and the ratio (B / D) between 9 and 16.

  Our experiments have shown that the respect of these two conditions, namely, the ratios between on the one hand the diameters of the blade (A) and (B) and on the other hand its thickness (D) and also the limits of the apparent density (d), this respect makes it possible to manufacture from standard synthetic resins, a racket whose mechanical characteristics

  look like a traditional racket of good quality.

  These mechanical characteristics translate into sensations

identical by the user.

  It should be noted that for a given resin, the density can be increased, as has been pointed out above, by increasing the length of the chain, this leads to increase in parallel the

modulus of elasticity in flexion.

  This density can also be increased, or generally adjusted, by incorporating into the resin a filler such as, for example, glass fibers, mineral fibers,

  mineral powders, or expanded spheres.

  The density variation will be accompanied by a variation

  parallel of the modulus of elasticity.

  In FIG. 1 the racket 1 has an oval shaped blade 2 having a large diameter (A) and a small diameter (B), a handle 3 whose length is (A '). The total length of the racket is (L)

o (L = A + A ').

  The thickness of the blade is (D) and that of the handle is (D '),

(Figures 1A and 1B).

  The handle 3 and the blade 2 are made in one piece by

molding, for example.

  In Figure 1, the handle 3 is provided with holes as the blade 2; the blade and the handle have the same ribbed structure,

  this is a preferred but non-critical embodiment.

  Indeed, the handle can be, for example, made hollow.

  In all cases the handle and the blade form a single piece.

  The handle will be dressed, as well as for a racket of tennis racket, by a dressing (not presented) suitable This

dressing is known per se.

  The thickness of the handle (D ') is, in general, greater than that

of the blade (D).

  The blade has two striking surfaces (Si) and (52) These two

  surfaces are preferably parallel.

  The holes made on the blade may have a square shape (generally rectangular), a circular shape or a hexagonal shape, in any case, the hole diameter (circular, rectangular or hexagonal) preferably has a value between

0.8 and 1.2 cm.

  This value is chosen such that its lower limit 0.8 cm, allows easy manufacture and its upper limit 1.2 cm, does not change the bouncing of the ball on the

striking surface (Si) or (52).

  It is therefore possible that the hole diameter has a value less than 0.8 cm without this modifying the rebound of

the ball.

  The hole shapes presented are purely indicative, because the holes may have other shapes

  like, for example, a triangular shape.

  The holes are arranged, preferably, staggered and their shape

is preferably repetitive.

  The repetitive form, here, is to be understood as a form that can be repeated in continuity, on a surface, without revealing other forms on this surface: the repetitive forms are therefore the square form (or in a general way

  rectangular) the triangular shape and the hexagonal shape.

  This makes it possible to have a surface whose mechanical characteristics are identical whatever the direction

of observation on this surface.

he

Claims (5)

  1 One-piece synthetic resin racket with a density of 0.9 to 1.4 gm / cm 3 having a handle of a length (A ') and an oval blade of a thickness (D) of a large diameter (A) and a small diameter (B), the total length of the racket being (L) o (L = A + A '), the oval blade being between two striking surfaces (Sl) and (52) and having holes for lightening it and also for minimizing its resistance to air, racket being characterized in that: the thickness (D) is chosen so that: (A / D) = 11 to 19 and , (B / D) = 9 to 16 and, the holes have a diameter of 0.8 to 1.2 cm, their number (n) is chosen so that the apparent density (d) of the said   blade is between 0.21 and 0.36 gm / cm 3.   2 racket according to claim 1 characterized in that the apparent density (d) and the thickness (D) are chosen, so that the surface density (ds = D Xd) has a value   between 0.48 and 0.58 gm / cm 2.   Racket according to claim 1 and / or claim 2 characterized in that: (A) = 26 to 29 cm, (B) = 23 to 26 cm, (D) 1.5 to 2.5 cm.   Racket according to claim 3, characterized in that   the two surfaces (Si) and (52) are parallel.   Racket according to claim 1 characterized in that   the holes are of a repetitive form.   Racket according to claim 1, characterized in that   the holes are staggered.