FR2841477A1 - Tennis racket frame has portion that accelerates shape restitution comprising two hollow frame members with intermediate element for string - Google Patents

Abstract

The racket frame incorporates a portion (16) that is designed to accelerate shape restitution; it comprises an intermediate element (19) with a hole for a string, fitted between two hollow tubular frame members (17, 18). The thickness (T1) of the tubular frame members and the thickness (T2) of the intermediate element are in a ratio where T2/T1 is below 1. The minimal distance (W1) between the tubular frame members and the distance (W2) between the outer edges of the intermediate element are in a ratio where W1/W2 is less than 1. The intermediate element can be made from a resin, optionally fibre-reinforced, metal or composition material, and has viscoelastic elements (20) between it and the frame members.

Description

The present invention relates to a racket frame and, in particular, a

  snowshoe frame having excellent

  properties of rendering performance and rigidity.

  In recent years, a racket frame has been asked to be lightweight and to have excellent stiffness, strength and durability properties, among others. Fiber reinforced resin is the

  the most successful material for the racket frame.

  Normally, the frame is formed by molding a thermosetting resin reinforced with fibers, for example carbon whose mechanical strength and modulus of elasticity are high. The fiber-reinforced resin containing the thermosetting resin as the resin of the continuous phase is excellent because of its high rigidity, but the fiber-reinforced resin can vibrate when subjected to shock, so that the tennis player can frequently present an epicondylitis. In recent years, it has been proposed a racket frame made of a thermoplastic resin reinforced with continuous fibers. The racket frame formed of such a resin has a high toughness due to the thermoplastic resin and therefore shock resistance characteristics and vibration damping performance better than those of the classic racket frame of

thermosetting resin.

  However, the thermoplastic resin has a greater variation of the elastic modulus and the resistance

  mechanical with the medium as the thermosetting resin.

  So, depending on the medium in which the

  racket frame, the characteristics of the thermoplastic resin, such as rigidity, may change.

  The tennis racket must have significant possibilities of implementation so that they allow a style of play in which a tennis ball can turn on itself. As a result, there is increasing demand for the development of a light racket frame (reduction of the moment of inertia). A player gives the tennis ball a spinning effect by rolling it over the broad part of the racket's ball striking face. Thus, the player wishes to have a racket having a wide

soft beach.

  A competitor's tennis racket must have a stable ball striking face. It was recently realized that rigidity in the direction of the plan was important. As previously described, the racket frame is asked to be lightweight, of high rigidity, of high mechanical strength, to have good performance of restitution, to have a good stability to the face of strike of ball and to have of good damping performance

vibrations.

  From the above point of view, tennis rackets with frames made of two

hollow materials in section.

  As shown in FIG. 13, the tennis racket disclosed in Japanese Patent Laid-open Application No. 63-309284 is composed of two separate hollow members 1 and an intermediate member 2 placed between them so that the maneuverability is better and the cost of manufacture is reduced. The opening 2a of the rope is formed on the intermediate member 2. The two sides of the intermediate member 2 are connected to the

  lateral surface of the hollow separate member 1.

  However, the end 2b of the intermediate member 2 on the side of the face of the rope protrudes from the end of the member 1 on the side of the surface of the rope or is at least at its level. Thus, the range of mobility of the rope is not important. It is therefore impossible to increase the

  performance of restitution of the tennis racket.

  In the tennis racket of Japanese Patent Laid-open Application No. 8-206,256 shown in FIG. 14, the racket frame is composed of two tubes mutually connected to the rope suspension portion so that the length of the rope opening 3a is reduced to a minimum and that the rope's mobility range and the restitution performance of the rope

racket tennis are increased.

  This configuration is such that the connecting part of the two tubes has a small section. Thus, when the racket frame has a twist as a result of a collision between the tennis racket and the tennis ball, it easily deteriorates. We then proposed a tennis racket with a

  rib placed inside the frame.

  In the tennis racket disclosed in Japanese Patent Laid-open Application No. 11-290485, as shown in FIG. 15, the rib 5a is placed in the frame 5, the rib 5a being parallel and adjacent to the face of the rope so that the resistance of the lateral side

racket frame is increased.

  This configuration has the effect of increasing the mechanical strength of the racket frame, but the range of mobility of the string is similar to that of ordinary tennis rackets. This configuration therefore does not allow an increase in performance of restitution of the racket

of tennis in a considerable way.

  Japanese Patent Laid-open Application No. 2002-35170 discloses a tennis racket similar to that disclosed in Japanese Patent Laid-open Application No. 11-290485. however, a considerable increase in performance

of restitution.

  It has also been proposed a third racket having a sleeve opening that is shifted or an opening of

rope that is shifted.

  In the tennis racket described in Japanese Patent Laid-open Application No. 11-9,723 and shown in FIG. 16, the opening 6a of the large frame 6 for the passage of a rope on the side of the rope side is realized so that it widens the

  range of rope mobility. The performance of restitu35 tion of the tennis racket can therefore be increased.

  This configuration gives the interior of the frame 6 a large hollow portion so that its mechanical strength is low. In the racket described in Patent Document No. 2,534,963, as shown in FIG. 17, for the rendering performance to be increased, the range of movement of the rope is widened by forming the opening 9a of rope of the sleeve 9 in the frame 8 in flared form. However, the frame 8 has a large hollow portion and does not have a high mechanical strength. In addition, the range of mobility of the rope is set within the thickness range of the rope.

  sleeve 9. It is thus impossible to increase the return performance of the racket significantly.

  In addition to the devices described in the aforementioned publications, it is possible to consider using the following means to increase the performance of restitution: (1) increase the weight of the racket to increase the moment of inertia, (2) increase the surface of the face to increase the range of mobility of the rope, (3) increase the rigidity of the frame in the direction of the plane, and (4) allow the frame to have a high elasticity. However, the means (1) reduces the workability or workability. The means (2) increases the weight and the moment of inertia and thus reduces the maneuverability. The means (3) gives poor moldability due to the modification of the sectional configuration due to the arrangement of a layered structure or part of a frame. The means (4) reduces

mechanical resistance.

  The invention has been realized in view of the problems that arise. It thus has the object of providing a racket having a high rigidity, a high rendering performance increased considerably, and

  excellent vibration damping performance.

  This object is achieved according to the invention with a racket frame which has a restitution acceleration portion formed on at least a portion of the portion on which is stretched the rope. The restitution acceleration portion has an intermediate member having a rope opening formed along an axis of the intermediate member, and a pair of separate hollow members disposed on both sides of the intermediate member and symmetrically with respect to a surface of rope. These hollow separate members protrude more than the intermediate member to an inner surface of the racket frame to form a space on both sides of the string extending inwardly through

rope opening.

  In this construction, the end surface of the intermediate member on the side of the string face is disposed outside the end surface of the two

  separate bodies hollow on the side of the rope surface.

  Thus, a rope extending from the opening of the intermediate member may move in the space between the hollow separate members. The effective length of the rope can therefore be important. The performance of restitution of the racket can therefore be increased and the region of flexibility of the surface can be enlarged without increasing the

surface of the racket.

  It is advantageous to expand the space between the two separate hollow members in which the rope from the intermediate member can move. If we call T1 the thickness between the outer surface of the frame and its inner surface and T2 the thickness of the intermediate member, the value of the T2 / T1 ratio is less than 1. It is advantageous that this value of T2 / T1 ratio is paid

between 0.3 and 0.7.

  It is assumed that the minimum distance between the two hollow separate members surrounding the intermediate member is equal to W1 and that the distance between the ends of the two separate hollow members at the internal surface of the racket frame is equal to W2, and the value the ratio W1 / W2 is less than 1. It is advantageous that this ratio W1 / W2

between 0.3 and 0.7.

  The body of the racket frame is composed of two separate hollow bodies. The opposed surfaces of the hollow separate members are thus used in the form of two ribs placed towards the inside of the racket frame and

  increase rigidity in the direction of the plane.

  The increased rigidity of the racket frame reduces deformation and reduces energy loss as the racket strikes a ball, thereby contributing to increased restitution performance and surface stability. When the racket frame has a construction allowing the intermediate member having the rope opening to rotate between the two hollow separate members, the end surface of the intermediate member on the side of the rope surface must not necessarily be placed outside the end surface of both

  separate bodies hollow on the side of the rope surface.

  In other words, the effective length of rope mobility can be increased by forming a space whose volume increases towards the rope surface in the region surrounded by the intermediate member and the hollow separate members. Accordingly, according to the invention, a racket frame has a restitution acceleration portion formed in at least a portion of the roped portion, having an intermediate member that has a rope passage opening formed along the axis. of this body, and two

  separate recesses placed on both sides of the intermediate member symmetrically with respect to a rope surface.

  In this construction, if it is assumed that the minimum distance between the two separate hollow members surrounding the intermediate member is equal to W1 and that the distance between the ends of the two separate hollow members to the inner surface of the racket frame is

  W2, the value of the ratio W1 / W2 is less than 1.

  The two ends of each of the two hollow members in the roped portion may be integrally molded by shunting the separate hollow members of a head body made of hollow material of large diameter. More specifically, during the production of a preform by stacking layers of material previously impregnated around two tubes or by winding fibers impregnated with resin around two tubes, for the formation of the head body consisting of a hollow material of large diameter, the previously impregnated elements or the fibers are wound on the peripheral surface of the two connected tubes, whereas, for the formation of the restitution acceleration part having the hollow separate member, the pre-impregnated elements or the fibers are wound on the surface

  peripheral of each of the two separate tubes.

  When the stack is inserted into a cavity of a mold, the intermediate member is compressed in the space between the hollow separate members. The framework

racket is formed.

  The restitution acceleration portion having the hollow separate members and the intermediate member disposed between them may be formed over the entire corded portion. It is possible to form the rendering acceleration part separately beforehand and to connect it to the body of the

  head made of hollow material of large diameter.

  The intermediate member is formed of resin reinforced with fibers, a resin, a metal or a corresponding composite material. The two separate hollow bodies are formed

  a resin or a resin reinforced with fibers.

  As the fiber-reinforced resin, a thermosetting resin and a thermoplastic resin, or the like, containing continuous or short fibers may be used. It is also possible to use as resin a thermosetting sand resin or a thermoplastic resin which is not reinforced with fibers. More specifically, the thermosetting resin comprises an epoxy resin, an unsaturated polyester resin, a phenolic resin, a melamine resin, a urea resin, a diallylphthalate resin, a polyurethane resin, a polyimide resin, and a silicone resin and the like. The thermoplastic resin comprises a polyamide resin, a saturated polyester resin, a polycarbonate resin, an ABS resin, a polyvinyl chloride resin, a polyacetal resin, a polystyrene resin, a polyethylene resin, an acetate resin, polyvinyl, an acrylonitrile-styrene resin, a methacrylate resin, a polypropylene resin and

a fluorinated resin.

  Reinforcing fibers of a fiber-reinforced resin may be fibers which are used as high performance reinforcing fibers. For example, it is possible to use carbon fibers, graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, glass fibers, fibers aromatic polyamide, aromatic polyester fibers, very high molecular weight polyethylene fibers, and the like. Fibers

  Metals can be used as reinforcing fibers.

  Carbon fibers are preferable because they are lightweight and have a high mechanical strength. These reinforcing fibers can be used in the form of long or short fibers. A mixture of at least two types of these reinforcing fibers may also be used. The configuration and arrangement of the reinforcing fibers are not limited to particular provisions. For example, they can be placed in one direction or at random. The reinforcing fibers may have the shape of a

  sheet, felt, fabric, braids and the like.

  It is possible to use metals such as aluminum, titanium and magnesium, or alloys containing one of these metals, as metal of the intermediate member.

less as the main ingredient.

  The intermediate member has a convex or core shape in section on the outside of the racket frame, and an opposite surface of each of the two separate hollow members has

  a configuration that corresponds to the intermediate organ.

  The intermediate organ and the two divided organs

  hollow are connected by an adhesive agent and / or a mechanical connection device.

  Thus, the intermediate member and the two hollow separate members are interconnected by an adhesive agent applied to a joining surface, by a mechanical connection device, that is to say by blocking the intermediate member on the organs separated hollow, the intermediate member being placed between the two hollow separate members,

  or using the adhesive agent and the mechanical connection device in combination.

  Flexible adhesive agents are preferable. Thus, an epoxy adhesive agent, a urethane adhesive agent and an instant adhesive agent, for example cyanoacrylate,

  can be advantageously used.

  The mechanical connection device connects the objects mutually and not via an adhesive material or a chemical bonding force, but according to a difference in configuration of the objects and a combination of variants. The mechanical connection device may comprise an adjustment of concave and convex parts obtained by pressure application of the intermediate member against the body of the racket frame by tension of the rope, by tightening screws, by setting to forms of cooperation,

  by interlocking, by locking, by use of bolts-nuts, using springs and the like.

  It is advantageous for a viscoelastic member to be placed between a connecting surface of the intermediate member

  and that of the hollow separate organ.

  The complex elastic modulus E * of the viscoelastic member, whose thickness is neither less than 0.5 mm nor greater than 4 mm, measured at a frequency of 10 Hz and a temperature of between 0 and 10 C, is lower than

  2.0.10-7 dyn / cm and not greater than 1.0.1010 dyn / cm2.

  The viscoelastic member is placed between the intermediate member and the two hollow separate members. Thus, when a force applied to the rope as a result of a collision between the rope surface and the bale is transmitted to the intermediate member into which the rope has been inserted, the restitution force of the rope is increased because the viscoelastic member is used as a spring. The return performance of a hit ball is therefore increased. A shock force transmitted to the intermediate member when the ball hits the rope surface is absorbed by the elasticity of the viscoelastic member. The

  vibration can be removed.

  The viscoelastic member is thus used as a dynamic damper.

  For the elasticity of the viscoelastic organ, we consider the complex modulus of elasticity E * of the viscoelastic organ measured at a frequency of 10 Hz and a temperature of between 0 and 10 C. It has been confirmed that when this complex elastic modulus E * of the organ

  Viscoelastic is not less than 2.0.107 dyn / cm2 nor greater than 1, 0.1010 dyn / cm2, the racket has excellent performance of restitution and vibration damping.

  It is advantageous for the intermediate member to have a convex sectional shape, a side portion to be placed at an outer surface of the racket frame, and a step concavity that fits on the lateral portion of the member intermediate is formed on an opposite surface of each

  two separate hollow members so that the intermediate member is surrounded by the two hollow separate members.

  It is advantageous for the viscoelastic member to be placed between the lateral part of the intermediate member and

  stepped concavity of separate hollow bodies.

  In this construction, the intermediate member is placed between the hollow separate members, the intermediate member adjusting in the step concavity. This construction therefore has the advantage of connecting the intermediate member and the separate member hollow to one another with

  advantageous mechanical strength.

  The viscoelastic member is placed in the space between the lateral part of the intermediate member and the step concavity of the hollow separate members, a high force being applied in this space. It is therefore possible to increase the effect given by the viscoelastic organ. It is advantageous to place the viscoelastic member between connecting surfaces perpendicular to the rope surface. This is because the viscoelastic member has an effective tension-restoring force in the plane applied to the rope when the ball hits the surface of the rope so that the return force of a struck ball is increased and the transmission from the shock to the body of the

  racket frame is effectively absorbed.

  The length of the restitution acceleration portion composed of the two hollow separate members and the intermediate member in the longitudinal direction of the racket frame is advantageously not less than 2 cm and not more than 15 cm, and preferably n ' is not inferior to

3 cm nor more than 7 cm.

  Thus, if the part consisting of the hollow separate members and the intermediate member placed between them exceeds 15 cm, the racket frame may have a twist when it hits a ball and has a low mechanical strength and therefore high losses. 'energy. The performance of restitution of the racket can not therefore be increased. If the part formed of the hollow separate members and the intermediate member placed between them is less than 2 cm, the effect on the rendering performance due to the formation of the rendering acceleration part

is only slightly increased.

  Consequently, a large part consisting of the two hollow separate members and the intermediate member placed between them is advantageously formed and it is advantageous to realize them at several positions of the frame of

snowshoe at certain intervals.

  Specifically, the rendering acceleration portion is formed over the entire periphery of a rope portion or, if it is assumed that the roped surface represents a clock face and the upper position of the rope surface corresponds at the 12 o'clock position, the rendering acceleration portion is formed in a portion between 3 o'clock and 9 o'clock or at a 12 o'clock position at certain intervals. As previously described, the length of the rendering acceleration portion has an upper limit for reasons of torsional rigidity. In the case where several restitution acceleration parts are formed in the corded part, it is advantageous to make a connection part of the separate members

  hollow between the parts of acceleration of restitution.

  In the case where several restitution acceleration parts are formed locally, it is advantageous to adjust a minimum length of the connecting portion of the separate hollow members between 5 and 20 mm. If the minimum length of this connecting portion is less than mm, the racket frame has a low mechanical strength. On the other hand, if the minimum length of the connecting portion exceeds 20 mm, it is difficult to locally form several restitution acceleration parts at the desired positions. The degree of freedom of design is

then reduced.

  Other features and advantages of the invention

  will be better understood by reading the description that will

  follow of embodiments, with reference to the accompanying drawings in which: Figure 1 is a front elevational view of a racket frame in a first embodiment of the invention; Figure 2 is a section along the line A-A of Figure 1; Fig. 3A is a perspective view showing main parts of a stack of layers; Figure 3B is a section along the line B-B of Figure 3A; Figure 3C is a section along line C-C of Figure 3A; Fig. 3D is a plan view showing the state in which a stack is housed in a mold, Fig. 3E showing an enlarged portion of Fig. 3D; Figure 4 is a front elevational view of a racket frame in a second embodiment; Figure 5 is a front elevational view of a racket frame in a third embodiment; Fig. 6 shows a section in a fourth embodiment; FIGS. 7A and 7B respectively show in section a restitution acceleration part of a racket frame and in section an intermediate member in the case of a fifth embodiment; Figure 8 is a section corresponding to Comparative Example 1; Figure 9 schematically illustrates a method of measuring stiffness of the ball striking surface; Figure 10 schematically illustrates a method of measuring rigidity when applying a lateral pressure; Figs. 11A and 11B illustrate a method of measuring the rendering coefficient; FIGS. 12A-12C illustrate in schematic form a method of measuring the vibration damping factor of the racket frame, FIG. 12A corresponding to a primary vibration and FIG. 12C showing a secondary vibration perpendicular to the plane; Figure 13 is a section illustrating a first prior art; Figure 14 is a section illustrating a second prior art; Fig. 15 is a section illustrating a third prior art; Fig. 16 is a section illustrating a fourth prior art; and FIG. 17 is a section illustrating a fifth

prior art.

  Figure 1 shows a racket frame 100 in one embodiment of the invention. This frame 10 has a roped portion 11, a neck portion 12, a handle portion 13 and a handle portion 14. These various portions are formed continuously. A stirrup 15 is placed between the upper ends of the two regions of the

collar part 12.

  A head body of the rope portion 11 is composed of a large diameter hollow material formed of a fiber-reinforced thermosetting resin containing reinforcing carbon fibers. A restitution acceleration portion 16 having the sectional construction shown in FIG. 2 is realized at the 3 o'clock and 9 o'clock positions of the part

rope 11.

  The length of the rendering acceleration portion 16 in the longitudinal direction of the racket frame is not less than 2 cm and not more than 15 cm. In the first embodiment, the length of the rendering acceleration portion 16 is set to 3 cm. As indicated in FIG. 1, three restitution acceleration portions 16 are formed at each of the 3 o'clock and 9 o'clock positions of the rope portion 11, with the interposition of a portion of

  connection (hollow material in section).

  The restitution acceleration part 16 comprises an intermediate member 19 placed between the separate hollow parts 17 and 18 placed asymmetrically with respect to a rope surface, a viscoelastic member 20 being disposed between the intermediate member 19 and the separate members.

hollow 17, 18.

  More specifically, the intermediate member 19 is convex, an opening 19b in which is inserted a rope 21 is formed in the center of the member 19, and the member 19 is placed between the two hollow separate members 17 and 18, these parts lateral projections 19c and 19d protruding from both sides being accommodated in concave portions 17b and 18b with a stepped sectional L-shaped section formed on the separate members 17 and 18. The viscoelastic member 20 is disposed between a vertical joining surface of the intermediate member 19 and a vertical junction surface (perpendicular to the rope surface) of the concavity 17b, and on a vertical junction surface (perpendicular to the surface of the

rope) of the concavity 18b.

  It is assumed that the width of an end surface 19a of the intermediate member 19 on the side of the rope surface in a direction perpendicular to the plane is equal to W1 and that the distance between the end 17a of the member 17 on the side of the rope surface and the end 18a of the member 18 on the side of the rope surface is equal to W2, and the value of the ratio W1 / W2 is adjusted to

it is less than 1.

  The end surface 19a of the member 19 on the side of the rope surface is outside the end 17a of the member 17 on the same side and the end 18a of the member 18 of the same. side. If Tl is the thickness of each of the hollow separate members 17, 18 in the direction of the rope surface and T2 the thickness of the intermediate member 19 in the direction of the rope surface,

  the value of the T2 / T1 ratio is set to a value less than 1.

  The value of the ratio T2 / T1 is equal to 0.5 in the

first embodiment.

  It is assumed that the width of the intermediate member 19 in the direction perpendicular to the plane is equal to L1 and the thickness of each of the side portions 19c and 19d is equal to L2, the value L1 is adjusted so that it is not less than at 5 mm and not more than 12 mm, and the L2 value is

  adjusted so that it is not less than 2 mm nor more than 5 mm.

  If L3 denotes the thickness of the viscoelastic member, the value L3 is set so that it is not less than 0.5 mm and not more than 4 mm. The L3 value is

  set at 2 mm in the first embodiment.

  The material of the viscoelastic member 20 is SBR butadiene rubber. It is advantageous that the complex modulus of elasticity E * of the member 20 measured at a frequency of 10 Hz and at a temperature of 0 to 10 C is set to a value which is not less than 2.0 × 10 7 dyn / cm 2 nor greater than 1.01010 dyn / cm2. In the first embodiment, the complex modulus of elasticity

  E * of the organ 20 is set at 5.07.107 dyn / cm 2.

  The intermediate member 19 and the hollow separate members 17, 18 are connected by a combination of an adhesive agent, a clamping force of the separate members 17, 18 and a force created by the stretching of the rope 21, causing pressure application of the intermediate member 19 against the step concavity 17b of the member 17 and the

  step concavity 18b of the organ 18.

  A flexible adhesive agent is advantageous. Thus, an epoxy, urethane, instant adhesive adhesive agent or the like may

be advantageously used.

  The intermediate member 19 is formed of a resin reinforced with fibers, a resin, a metal or a corresponding composite material. In the first embodiment, the intermediate member 19 is formed of "nylon 66" armed with

22% by weight of carbon fibers.

  The hollow separate members 17 and 18 are formed of an epoxy resin reinforced with carbon fibers in the first

embodiment.

  Reference is now made to FIGS. 3A to 3E for

  description of the method of making the racket frame.

  A fiber-reinforced resinous material is wound around each of separate tubes 23 and 24 subjected to internal pressure, at a location at which the restitution acceleration portion 16 is formed. On the other hand, at a location where The restoring acceleration portion 16 is not formed, a fiber reinforced resinous material 25 is wound to a peripheral surface of the tubes 23 and 24 subjected to the internal pressure and which are connected. Of this

  way, a stack 27 is made.

  Then, as shown in FIG. 3D, the stack 27 is loaded into a cavity 26a of a mold 26, the intermediate member 19 being placed between the stacking portions 27 to which the fiber-reinforced resinous material 25 has been wound on the separate tubes 23 and 24 as shown in Figure 3E. The mold 26 is closed and heated at 150 C for min. At the same time, an air or nitrogen pressure of 6 to 9 bar (kg / cm 2) is applied to the tubes 23 and 24. When the molding is finished, it is advantageous to remove the tubes

23 and 24.

  Figure 4 shows a second embodiment.

  The second embodiment differs from the first embodiment in that the restoring acceleration portion 16 of a tennis racquet 30 of the second embodiment is made at three locations in the upper part of the strung portion 31 and a molding in one. only piece is

made in a mold.

  The restitution acceleration portion 16 has a length of 3 cm in the longitudinal direction of the racket frame. The construction of the restitution acceleration part 16, its material, the construction of the other parts and their materials are analogous to the first mode of

  production. Their description is therefore omitted.

  Fig. 5 shows a third embodiment.

  In a tennis racket 40 of this embodiment, fifteen restitution acceleration parts 16 are formed at regular intervals throughout the game.

roped 41.

  Each of the restitution acceleration portions 16 has a length of 5 cm in the longitudinal direction of the racket frame. The restitution acceleration portions 16 are separated by 1 cm intervals equal to the gap between the adjacent rope openings. The construction of the restitution acceleration part 16, its material, the construction of the other parts and their materials are analogous to the first mode of

  production. Their description is therefore omitted.

  Figure 6 shows a fourth embodiment.

  The fourth embodiment differs from the first in that the viscoelastic member is not placed between the intermediate member 19 and the two hollow separate members

  17, 18 of a restitution accelerating portion 16 '.

  The construction of the other parts and their materials

  are similar to the first embodiment. Their description is therefore omitted.

  Figs. 7A and 7B show a fifth embodiment. In the fifth embodiment, a rope opening 19a 'is formed in the center of an intermediate member 19' having a cut-away heart shape. Arcuate concavities 17b 'and 18b' are formed on the opposite surfaces of the hollow separate members 17 'and 18' respectively so that opposite surfaces of these members 17 'and 18'

  are in intimate contact with the intermediate member 19 '.

  The separate members 17 ', 18' and the intermediate member 19 'are fixed by an adhesive agent. A viscoelastic member may be placed between the intermediate member 19 'and the

separate members 17 ', 18'.

  If we call P the maximum thickness of the intermediate member having a core shape in section (corresponding to the thickness T2 of the first embodiment), its maximum width (corresponding to L1 in the first embodiment ) and its curvature y, D is between 3 and 8 mm, has between 5 and 10 mm and has a radius of between 2 and

  mm. The ratio of ax to P is set between 0.6 and 3.0.

  The ratio of the thickness P of the intermediate member 19 'to the thickness T1 of the separate hollow members 17', 18 'is similar to the ratio of the thicknesses T2 to T1 of the first mode

of realization.

  It is advantageous to use the following values: a = 8 mm, P = 5 mm, y with R = 4 mm, w1 = 5 mm, W2 = 10 mm,

T1 = 12 mm and T2 = 5 mm.

  The intermediate member in the form of a core in section prevents the local concentration of the stresses and allows the

realization of a light frame.

  The intermediate member 19 'convex section enlarges the region in which can be placed the vibration damping material formed of the viscoelastic member or the like, between the intermediate member and the two hollow separate members. It is therefore possible to increase the damping effect of the vibrations and the effect of the viscoelastic member used as a spring and thus the performance of restitution. For the evaluation of the physical properties of the tennis racket of the first to fourth embodiments, snowshoes according to Example 1 to Example 9 and Comparative Example 1 were prepared. The rigidity of the side face of the strung part and that of the ball striking surface, the coefficient of restitution and the vibration damping factor (primary vibration damping factor perpendicular to the plane, damping factor of vibration secondary perpendicular to the plane) of each racket were measured. A typing test of

ball was also executed.

  The tennis rackets of Examples 1 to 9 and those of Comparative Example 1 had almost the same configuration and the same length of 698.5 mm. The surface of

  bullet strike was equal to 710 cm2.

Example 1

  Example 1 corresponds to the first embodiment.

  Thus, the restitution acceleration part 16 was made at the 3 o'clock and 9 o'clock positions of the rope part 11. The length of the restitution acceleration part 16 was set at 3 cm in the longitudinal direction of the frame

racket.

  The width W1 of the end surface 19a of the intermediate member 19 on the rope side in the direction perpendicular to the plane is 5 mm. The distance W2 between the end 17a of the member 17 on the side of the rope and the end 18a of

  the member 18 on the rope side is 10 mm (W1 / W2 = 0.5).

  The thickness T1 of each of the separate members 17, 18 in the direction of the rope surface is 12 mm. The thickness T2 of the intermediate member 19 in the direction of the rope surface is 6 mm (T2 / T1 = 0.5). The thickness of the racket frame in the direction perpendicular to the plane was

set at 24 mm.

  The intermediate member 19 was formed of "nylon 66"

  armed with 22% by weight of carbon fibers.

  SBR butadiene-styrene rubber has been used as the material of the viscoelastic member 20. The thickness L3 of this member 20 is equal to 2 mm. The complex modulus of elasticity E * of the viscoelastic member 20 measured at a frequency of 10 Hz and a temperature of 0 to 10 C is 0.77. 107 dyn / cm 2. The weight of the tennis racket is 253 g. The balance point BP (center of gravity) of the tennis racket is 361 mm from the handle end when the

  Total length of the racket is 698.5 mm.

Exemption 2

  Example 2 corresponds to the second embodiment.

  The restitution acceleration portion 16 has been formed at three locations at the upper portion of the roped portion 31. The length of the rendering acceleration portion 16 in the longitudinal direction of the frame is 3 cm.

  The other constructions of Example 2 were similar to those of Example 1.

Example 3

  Example 3 corresponds to the third embodiment. The restitution acceleration portion 16 was formed at fifteen positions at regular intervals throughout the periphery of the roped portion 41. Each of the fifteen rendering acceleration portions 16 had a length of 5 cm in the longitudinal direction of the frame. racket. The restitution acceleration portions 16 were separated by 1 cm intervals. The other constructions of Example 3 were similar to those of

Example 1

Example 4

  Example 4 corresponds to the fourth embodiment. A restitution accelerating portion 16 'not having the viscoelastic member 20 was formed at the 3 o'clock and 9 o'clock positions of the corded portion. Each of the parts 16 'of acceleration of restitution had a length of 3 cm

  in the longitudinal direction of the racket frame.

  The width W1 of the end surface 19a of the intermediate member 19 on the side of the string face in the direction perpendicular to the plane is 5 mm. The distance W2 between the end 17a of the separate member 17 on the side of the rope surface and the end 18a of the separate member 18

  the side of the rope surface is 10 mm (W1 / W2 = 0.5).

  The thickness T1 of each of the separate members 17, 18 in the direction of the rope surface is 12 mm. The thickness T2 of the intermediate member 19 in the direction of the

  rope area is 6 mm (T2 / T1 = 0.5).

  The intermediate member 19 is formed of "nylon 66" armed

  22% by weight of carbon fibers.

EXAMPLE 5

  Example 5 corresponds to the first embodiment.

  The width W1 of the end surface 19a of the intermediate member 19 on the side of the rope surface in a direction perpendicular to the plane is 5 mm. The distance W2 between the end 17a of the separate member 17 on the side of the rope surface and the end 18a of the separate member 18 on the side of the rope surface is equal to 15 mm

(W1 / W2 = 0.33).

  The rest of the construction of Example 5 is analogous

in example 1.

Example 6

  Example 6 corresponds to the first embodiment.

  The width w1 of the end surface 19a of the intermediate member 19 on the side of the rope surface in a direction perpendicular to the plane is 5 mm. The distance W2 between the ends 17a of the member 17 and 18a of the member 18 on the side of the rope surface is equal to

6 mm (W1 / W2 = 0.83).

  The rest of the construction of Example 6 is analogous

in example 1.

Example 7

  Example 7 corresponds to the first embodiment.

  The width W1 of the end surface 19a of the intermediate member 19 on the side of the rope surface in a direction perpendicular to the plane is 3 mm. The distance W2 between the ends 17a of the member 17 and 18a of the member 18 on the side of the rope surface is 10 mm

(W1 / W2 = 0.33).

  The rest of the construction of Example 7 is analogous to Example 1. EXAMPLE 8

  Example 8 corresponds to the first embodiment.

  The thickness L3 of the viscoelastic member 20 is set to 1 mm. The rest of the construction of Example 8 is analogous

in example 1.

Example 9

  Example 9 corresponds to the first embodiment.

  The thickness L3 of the viscoelastic member 20 is set to

4 mm.

  The rest of the construction of Example 9 is analogous

in example 1.

  Comparative Example 1 In the tennis racket of Comparative Example 1, the entire periphery of the roped portion is formed of a separate hollow member 50 shown in Figure 8. The tennis racket has no acceleration portion of restitution. The width W1 of the end of the rope opening 50a on the side of the rope face and the distance W2 of the end of a hollow separate member 50 on the side of the rope surface is equal to 5 mm. The thickness T1 of the hollow separate member 50 in the direction of the rope face is

12 mm (T2 / T1 = 1).

  The rest of the construction of Comparative Example 1

is analogous to Example 1.

* The table shows the results of the examples and of

the comparative example.

Board

  El E2 E3 Arrangement of part 3 h part all of acceleration of restitution and 9 h greater periphery Wl (mm) 5 5 5 W2 (mm) 10 10 10 T2 / Tl 0.5 0.5 0.5 Material of the intermediate member NY66 + CF22% NY66 + CF22% NY66 + CF22% Length of the restitution acceleration part 3 3 5 Number of acceleration parts 6 3 15 of restitution Minimum length of parts of 8 8 8 connection Body Nature SBR SBR SBR viscoThickness L3 (mm) 2 2 2 elastic Complex modulus of elasticity d5,07E + 07 5,07E + 07 5,07E + 07 elasticity (dyn / cmu) WT (g) / BP (mm) 253 / 361 252/363 358/363 Stiffness Beating face (N / cm) Bale / Pressure 1 680/903 1 620/893 1 815/991 Lateral Restitution 0.436 0, 432 0.438 Vibration Primary vibration damping factor 0.8 0.8 0.9 perpendicular to the plane Secondary perpendicular vibration damping factor 0.9 0.9 0.9 to the plane Flight Strike 4.5 4.2 4.5 Ball Vibration 4.2 4.1 4, 2 Table (continued)

E4 E5 E6

  Part 3 hrs 3 hrs 3 hr acceleration and 9 hrs and 9 hrs and 9 hrs Wl (mm) 5 5 5 W2 (mm) 10 15 6

T2 / T1 0.5 0.5 0.5

  Material of intermediate member NY66 + CF229 NY66 + CF22% NY66 + CF22% Length of restitution acceleration part 3 Number of acceleration parts 6 of restitution Minimum length of parts 8 8 connection Body Nature SBR SBR visco - Thickness L3 (mm) nil2 2 elastic Complex module

elasticity (dyn / cm2).

  WT (g) / BP (mm) 250/360 253/360 252/359 Stiffness Impact face of (N / cm) ball / pressure 1 690/961 1 670/893 1 720/922 lateral Restitution 0.426 0, 438 0.431 Vibration Primary vibration damping factor 0.7 0.8 0.8 perpendicular to the plane Perpendicular vibration damping factor 0.7 0.9 0.9 to the plane Flight Strike 3.8 4.6 4 , 3 Ball Vibration 3.6 4.1 4

Table (end)

E7 E8 E9 CE |

  Part 3: 3: 3 pm 3 hours acceleration and 9: 00 and 9: 00 am and 9 am Wl (mm) 3 5 5 5 W2 (mm) 10 10 10 5

T2 / T1 0.5 0.5 0.5 1

  NY66 NY66 NY66 Intermediate Body Material

+ CF22% + CF22% + CF22%

  Length of restitution acceleration part 3 3 3 nil Number of acceleration parts 6 6 6 of restitution Minimum length of parts of 8 8 8 connection Body Type SBR SBR SBR visco- Thickness L3 (mm) 2 1 4 Elastic void Complex module 5.07E + 07 5.07E + 07 5.07E + 07 elasticity (dyn / cm2) WT (g) / BP (mmn) 253/361 252/360 254/362 245/360 Rigidity Face of striking of 1710 / 1,680 / 1,670 / 1,470 / (N> cm) ball / pressure 848 893 893 785 Lateral Restitution 0.436 0.434 0.439 0, 401 Vibration Primary vibration damping factor 0.8 0.7 0.9 0 , 4 perpendicular to the plane perpendicular vibration damping factor perpendicular 0.9 0.7 1 0.5 to plane Flying Stroke 4.4 4.3 4.5 2.8 Ball Vibration 4.2 4.2 4 , 4 2.9 E designates an example and CE a comparative example Measurement of rigidity of the beating striker face For measuring the rigidity of the beating striker face (stiffness in a perpendicular direction) as shown in FIG. 9, the racket d The tennis of each of the examples and the comparative example has been placed horizontally. An upper part reads of a roped part 11 a

  was supported by a mounting device 51 (R = 15 mm).

  A location 340 mm apart from the upper bed, disposed in the range between the two sides of the neck portion 12 and the stirrup 15, was supported by a mounting device 52 (R = 15 mm). In this state, a charge of 784 N was applied at a location separated by mm from the position of the mounting device 51 to the mounting device 52 by means of a pressure application instrument 53 (R = 10 mm), for the calculation of a stiffness from the amplitude of displacement of the face of

strike ball.

  Stiffness measurement of the lateral surface For the measurement of the rigidity of the lateral surface of the racket frame as indicated in FIG. 10, the racket of each of the examples and of the comparative example was held on the wafer while the surface F ball striking was arranged vertically. In this state, a load of 784 N was applied to the upper face 11 of the rope part 11 by a flat plate P for the calculation of a stiffness according to the displacement amplitude of the side of the rope.

racket frame.

  Measurement of the coefficient of restitution As shown in FIG. 11, a rope was fitted to the tennis racket of each of the examples and of the comparative example with a tensile force of 267 N in the vertical direction and 245 N in the horizontal direction. . The handle portion of each racket was fixed in the vertical direction so that each racket was free. A tennis ball was thrown by a bullet throwing apparatus at a constant velocity Vi (30 m / s) and struck the ball striking face of the racket frame for

  the measurement of the V2 rebound speed of the tennis ball.

  The coefficient of restitution is equal to the ratio of

  bounce speed V2 at launch speed V1 (V2 / V1).

  The higher the coefficient of restitution, the higher the

  speed of the ball is high. The coefficient of restitution was measured in this way.

  Measurement of the Trimaire Vibration Damping Factor Perpendicular to the Plane As shown in FIG. 12A, when the upper end of the roped portion 11 of the tennis racket of each of the examples and the comparative example was suspended by a link 61, an acceleration measuring sensor 63 has been placed on a connecting portion of the rope portion 11 and the neck portion 12, the acceleration sensor 63 being perpendicular to the face of the racket frame. As shown in FIG. 12B, in this state, the other connecting portion between the roped portion 11 and the neck portion 12 has been struck by a hammer 65 for vibrating the racket frame. An input vibration F measured by a force sensor placed on the hammer 65 and a response vibration ax measured by the acceleration sensor 63 were introduced into a frequency analyzer 67 (HP3560A single dynamic analyzer manufactured by Hewlett-Packard Company). via amplifiers 66A and 66B. A transmission function in the frequency region obtained by analysis was calculated to obtain the frequency of the racket frame. The vibration damping ratio of the racket frame, i.e., the primary vibration damping factor perpendicular to the plane, was calculated by the following equation. The measurement was made for a tennis racket of each of the examples and of the comparative example: = (1,2). (Ao / wn) To = Tnvi Measurement of the secondary vibration damping factor perpendicular to the vlan As the 12C, when the upper end of the roped portion 11 of the racket of each of the examples and the comparative example was suspended at the link 61, the acceleration sensor member 63 was placed on a connecting portion of the neck portion 12 and the handle portion 13, the acceleration sensor 63 being perpendicular to the face of the racket frame. In this state, the rear face of the racket frame in the portion facing the sensor installation position was struck by the hammer 65 for vibrating the racket frame. The damping factor, that is the damping factor of the secondary vibration perpendicular to the plane, for each racket, was calculated by a method equivalent to the method of calculating the vibration damping factor. primary perpendicular to the plane. The measurement was made for the snowshoe

  tennis of each of the examples and the comparative example.

  Method for the Ball Strike Test The ball strike test was performed with the tennis racket of each of the examples and the comparative example. 50 players hit balls and gave a score of 1 to 5 for the following items. The average of

  50 player ratings were calculated.

  Vibration: present 1-2-3-4-5 absent Flight performance: poor 1-23-4-5 good As indicated by the results in Table 1, the tennis racket of each of Examples 1 to 9 having the parts 16 and 16 'formed feedback acceleration had excellent rigidity of the ball striking surface and lateral pressure with respect to the racket frame of Comparative Example 1 not having the restitution acceleration portion. The racket of each of Examples 1 to 9 was more advantageous than that of the example

  comparative 1 from the point of view of the coefficient of restitution.

  The damping factors of the primary vibration and the secondary vibration perpendicular to the snowshoe plane of each of Examples 1 to 9 were greater than those of the racket of Comparative Example 1. The racket of each of Examples 1 to 9 was therefore better than the racket of Comparative Example 1 from the point of view

  vibration damping performance.

  It was also confirmed that the tennis racket of each of Examples 1 to 9 was superior to that of Comparative Example 1 with respect to flight performance and vibration damping performance examined during the test. ball striking. For performance of restitution and vibration damping, the racket of Examples 1 to 3 and 5 to 9 having the viscoelastic member 20 is greater than the

  racket of Example 4 which did not have the viscoelastic organ 20.

  The damping performance of the racket vibrations of the examples other than Example 8 were greater than those of Example 8, the thickness L3 of the viscoelastic member 20 was 1 mm. The racket of Example 9, the thickness L3 of the member 20 was 4 mm was the most advantageous in terms of performance

vibration damping.

  In the comparison of the snowshoes of Examples 1 to 3, of which the restitution acceleration part 16 has different positions, the racket of Example 3, the part 16 of which is formed over the entire periphery, is a bit higher than the snowshoes of the others. examples for all items examined. The racket of Example 5 was considered better than those of the other examples with regard to the flight performance examined during the ball striking test. Thus, the higher the ratio Wi / W2 is small and

  better are the rendering performance.

  As the above description indicates, according to

  the invention, the restitution acceleration part is formed on at least part of the rope portion, and the ratio W1 / W2 is set to a value less than 1 so that the rope can not come into contact with the separate members hollow when the rope vibrates in a direction perpendicular to its plane. The rope therefore has a wide range of mobility and performance of restitution of the frame of

racket are increased.

  The value of the ratio T2 / T1 is set to a value less than 1. It is thus possible to obtain a long mobile length of rope and to increase the performance of restitution without increasing the surface. It is also possible to expand the flexible region. Since the racket frame consists of two separate hollow members, the opposite surfaces of these members constitute two ribs placed inside the frame of

  racket so that the rigidity of it is increased.

  The increase in rigidity of the racket frame reduces its deformation and also reduces the energy losses when the racket strikes a ball, and thus contributes to the improvement of the performance of restitution and the surface stability. The viscoelastic member is placed between the intermediate member and the two hollow separate members. The restitution force of the rope is thus increased by the viscoelastic member which acts as a spring. The return performance of a hit ball is therefore increased. A shock force transmitted to the intermediate member is thus absorbed by the elasticity of the viscoelastic member. The

  vibrations can be reduced.

  Of course, various modifications can be made by those skilled in the art racket frames that have just been described as an example not

  limiting without departing from the scope of the invention.

Claims (11)

  Racket frame, characterized in that it comprises a restitution acceleration part (16) formed on at least a portion of a roped part and having: an intermediate member (19) having a rope opening formed according to an axis of the intermediate member (19), and two hollow separate members (17, 18; 17 ', 18') placed on both sides of the intermediate member (19) and symmetrically relative to a rope surface, the hollow separate members (17, 18; 17 ', 18') protruding more than the intermediate member (19) from the side of the rope surface so that they form on both sides of the rope a space extending towards the interior since the opening of rope.   2. Racket frame according to claim 1, characterized in that, if T1 designates the thickness of each of the two hollow separate members (17, 18; 17 ', 18') between an outer surface and an inner surface thereof. ci and T2 denotes the thickness of the intermediate member (19) between an external surface and an internal surface thereof, the   T2 / T1 ratio is less than 1.   Snowshoe frame according to one of claims 1   and 2, characterized in that, if Wl is the minimum distance between the two hollow separate members (17, 18; 17 ', 18') surrounding the intermediate member (19) and W2, the distance between ends of the hollow separate members (17, 18, 17 ', 18') at the inner surface of the frame   racket, the ratio W1 / W2 has a value less than 1.   Racket frame, characterized in that it comprises a restitution acceleration part (16) formed on at least part of the roped part and comprising: an intermediate member (19) having a rope opening formed according to a axis of the intermediate member (19), and two hollow separate members (17, 18; 17 ', 18') placed on both sides of the intermediate member (19) symmetrically with respect to a rope side, in which, if we call Wl the minimum distance between the two hollow separate members (17, 18; 17 ', 18') surrounding the intermediate member (19) and W2 the distance between the ends of the two hollow separate members (17, 18; 17 ', 18') on the inner surface of the frame   racket, the ratio W1 / W2 has a value less than 1.   Racket frame according to one of claims 1 to 4, characterized in that both ends   of each of the two hollow members (17, 18; 17 ', 18') in the cord portion are integrally molded bypassing the hollow separate members (17, 18; 17 ', 18') from 'a head body made of a material hollow of large diameter.   6. Racket frame according to any one of claims 1 to 5, characterized in that the intermediate member (19) is formed of a material selected from a resin reinforced with fibers, a resin, a metal, a material resin composite, and a composite material of metal, and has a cross-sectional shape selected from a convex shape and a core shape that protrudes from the outer side of the racket frame, and the two hollow separate members (17, 18; 17 ', 18') are formed of a material selected from a resin and a fiber-reinforced resin, an opposing surface of each of the hollow separate members (17, 18; 17 ', 18') having a configuration   which corresponds to that of the intermediate member (19).   7. Racket frame according to any one of claims 1 to 6, characterized in that the intermediate member (19) and the two hollow separate members (17, 18; 17 ',   18 ') are connected by means selected from at least one   adhesive agent and a mechanical connection device.   8. Racket frame according to any one of claims 1 to 7, characterized in that a viscoelastic member (20) is disposed between a connecting surface   of the intermediate member (19) and a surface of the hollow separate member, and the complex modulus of elasticity E * of the viscoelastic member (20) having a thickness of not less than 0.5 mm not more than 4 mm, measured at a frequency of Hz and a temperature of 0 to 10 C, is not less than   2.0.107 dyn / cm2, nor greater than 1.01010 dyn / cm2.   Racquet frame according to claim 8, characterized in that the intermediate member (19) has a convex section, a lateral portion of this member is placed at an outer side of the racket frame, and a step concavity which fits on the side portion of the intermediate member (19) is formed at an opposite surface of each of the two hollow separate members (17, 18; 17 ', 18') so that the intermediate member (19) is disposed between the two hollow separate members (17, 18; 17 ', 18'), and the viscoelastic member (20) is disposed between the lateral portion of the intermediate member (19) and the concavity stepped.   Racket frame according to one of claims 1 to 9, characterized in that the length of the   part (16) of restitution acceleration composed of the two hollow separate members (17, 18; 17 ', 18') and the intermediate member (19) in the longitudinal direction of the frame   is not less than 2 cm and not more than 15 cm.   11. Snowshoe frame according to any one of   Claims 1 to 10, characterized in that the part (16)   of restitution acceleration is formed at its entire periphery of the corded part or at least at the 3 o'clock and 9 o'clock positions or at the 12 o'clock position, assuming that the face   corded represents a clock face.