JP2507397Y2 - racket - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION This invention relates generally to rackets, such as tennis rackets, for playing games with a ball of limited repulsion.

[0002]

BACKGROUND OF THE INVENTION In a conventional tennis racket, the stiffness or rigidity of the frame and shaft portions causes the head frame portion to move in the longitudinal direction of the racket when the ball strikes the string or gutted surface of the racket. It's like being pushed out of the axis. This deflection is
It adversely affects the flight path of a bouncing ball.

A complex vibrational response occurs in any body or body subject to an input load. This complex deformed shape of the fuselage can be deformed into the sum of a myriad of simple vibrational mode shapes with varying amplitudes and frequencies. The particular frequencies, mode shapes, and amplitudes associated with the vibrating body depend on several factors. Among these factors are stiffness or stiffness within the body and distribution of weight, as well as the level of body restraint.

Stiffness and weight distribution can be controlled in two ways. One way is to use special reinforcing materials in the body part, where these materials have a greater strength to weight ratio and stiffness to weight ratio. Another way to control stiffness and weight distribution is to change the shape of the fuselage cross-section, and in particular the area moment of inertia of the cross-section so that the stiffness-to-weight ratio changes.
A constant amount of material is used in the cross section while changing the a-moment-of-inertia). Increasing the stiffness increases the vibration frequency and reduces the dynamic deformation amplitude. Increasing weight reduces vibration frequency and reduces dynamic deformation amplitude.

Two particular suppression states are important in this description. One extreme condition, the "free-free" restraint condition, represents a body that oscillates unrestrained in space. This is done by suspending the fuselage with an elastic band and allowing it to vibrate freely,
It can be approximated in the laboratory. “Free-free” suppression state (“f
The first two vibration mode shapes for a simple beam in bending under ree-free "constraint conditions) are shown in FIG.

At the opposite extreme, "clamped-free" constraint conditio
n), where one end of the body is fixedly clamped to the support fixture and the other end is free to vibrate. The first three vibration mode shapes for a simple beam in bending under "clamp-free" restraint conditions are shown in FIG. It can be seen that modes 1 and 2 in FIG. 10 have substantially the same shapes as modes 2 and 3 in FIG. 11, respectively. The addition of a fixed clamp to the body during bending under "free-free" conditions results in the excitation of additional low frequency mode vibrations.

The frequencies of modes 1 and 2 under "free-free" suppression conditions are not the same as the frequencies for the relevant mode shapes under "clamp-free" conditions (modes 2 and 3, respectively). The frequency of the mode shape under one of the suppressed states can be approximated from the frequency of the mode shape under the other state using the following equation:

[0008]

[Equation 1] Freq cf = Freq ff × (Lff / Lcf) ² (Equation 1) (with Lcf = Lff − Lcc) where Freq cf = frequency of mode shape under “clamp-free” state Freq ff = Frequency of mode shape under "free-free" condition Lff = length of beam under "free-free" condition Lcc = length of beam held under clamp fixture Lcf = under "clamp-free" condition Equivalent length of beam at

Tennis rackets exhibit similar vibration characteristics to those described above for simple beams due to ball / racket collisions that occur during play. Laboratory tests were conducted on various rackets. The results of the tests showed that for a conventional tennis racket under "free-free" restraint conditions, the first mode of bending was in the range 100 Hz to 170 Hz.
A normal racket under "clamp-free" suppression
25 for each of the first and second modes of bending
Frequency ranges between Hz and 50 Hz and 125 and 210 Hz were exhibited. U.S. Pat. No. 4,664,380 (DE-OS 3434898) states that the resonance frequency of the racket described here under "clamp-free" suppression is 70 Hz to 200 Hz.

Tennis that vibrates under the "freedom-freedom" condition
Studies have shown that the racket more closely approximates the behavior of a tennis racket during play than the racket vibrates in the "clamp-free" state. If a "clamp-free" suppression condition exists during the test,
Equation 1 must be used to modify the value of the frequency so that the second mode of bending under the "clamp-free" state approximates the value of the frequency of the first mode for "free-free" .

Balls /
It has been observed that the racket impact times range between 2 and 7 ms, with an average between 2 and 3 ms. During this period, the head portion of the racket bends backward due to the pressing input from the ball. In a normal racket, at some time between the ball / racket collision point when the racket begins to deform and shortly after the racket reaches its maximum deflection,
The ball leaves the thread. As a result, the flight path of the shot is affected (see Figure 12), and energy is lost because the racket does not return to its undeformed position where the bounce angle is zero and the racket head speed is maximum. Becomes

[0012]

[Outline of the device] While the racket is flexing, if the ball stays on the thread and does not leave the thread until it returns to an undeformed position, the flight path of the ball is not affected and the accuracy of the shot is improved (See FIG. 13). In addition,
Since the racket head speed is maximum at this point, more energy is imparted to the ball, resulting in a more powerful shot. Changing the deformation period of a tennis ball is not considered as a desirable solution to the problem. Therefore, in optimal operation, a tennis racket must be designed such that the frequency of the dominant vibrational modes excited in the racket during play matches the duration of ball / racket contact. In particular, the half duration of the first mode of bending for a tennis racket under "free-free" restraint conditions should be equal to the time the tennis ball is on the thread. This mode is chosen because the first mode of bending under "free-free" restraint is the dominant vibrational mode that is excited during play.

Optimal tennis rackets have a typical ball / racket impact time of 2 to 3 milliseconds, so bending between 180 Hz and 250 Hz under "free-free" restraint conditions It will have a first mode. Using Equation 1, frequency range under "clamp-free" condition, considering a 68.58 cm (27 inch) racket suspended by a solid support at 7.62 cm (3 inches) on the handle. Is 21 for the second mode of bending.
It will be between 5 Hz and 315 Hz. One particular example of a racket is 200 Hz and 210 Hz for the first mode of bending under "free-free" restraint conditions.
Frequency range between, and 230 Hz and 265 for the second mode of bending under "clamp-free" conditions.
It has a frequency between Hz.

The present invention will be described below with reference to the illustrated embodiments shown in the accompanying drawings.

[0015]

EXAMPLE As described above, after a normal tennis ball hits a tennis racket, the tennis racket returns to its original undeformed position before the ball leaves the racket thread or gut material. It is desirable to control the hardness or stiffness of the racket. Under these conditions, the ball's flight path before and after hitting the racket will be unaffected, and shot accuracy will be improved as shown in FIG. In addition, more energy is given to the bouncing ball, resulting in a more powerful shot.

It is desirable to adjust the stiffness of the tennis racket so that the racket has a first mode of bending under free-free restrained conditions between 180 Hz and 250 Hz. Such rackets are 215 Hz and 315
Between Hz, it will have a second mode of bending under clamp-free restraint conditions. 1-9 show one particular embodiment of a tennis racket 15 having such frequencies.

Referring initially to FIGS. 1 and 2, the racket 15 includes a grip or handle portion 18 and a throat portion 19.
And a frame 17 having a head portion 20. The throat portion 19 includes a pair of frame members 21 and 22 that branch from the handle portion 18 and merge with the head portion 20. A yoke piece or frame piece 23 extends between the throat pieces 21 and 22 and forms the bottom of the head portion, which is generally loop-shaped or oval.

The tennis racket also has a head portion 20.
And a plurality of longitudinal threads 24 and transverse threads 25 extending into the normal openings in the frame 23. A plastic or plastic bumper 26 extends around the top of the head portion to protect the head from rubbing and abrasion. The bumper is held in place by the thread and also protects the thread from scuffing against the holes in the racket frame. A plastic insert 27 extends between the end of the bumper 26 and the throat portion 19 and protects the thread in the lower portion of the head.

The racket also includes a conventional handle coating 28 and end cap 29 on the handle portion 18. The handle coating may be formed from a spirally wound leather strip.

3 and 4 show a racket frame 17 without threads and handle coating.

Referring to FIGS. 5-8, the frame portion 1
Each of 8-23 is formed from a tubular frame member having a wall thickness of from about 0.1143 cm (0.045 inch) to about 0.127 cm (0.050 inch). The tubular frame member is formed from a layer of resin impregnated graphite fiber wrapped around an inflatable bladder or bag. As is well known in the art, when the racket frame is placed in a mold or mold, the bag is inflated to press a layer of graphite fiber onto the mold until the resin hardens.

FIG. 9 illustrates a resin impregnated graphite material used to form the preferred embodiment tubular fiber member.
The layers 31-42 of fibers are shown. Each of layers 31-42 comprises unidirectional graphite fibers oriented in the direction shown by the diagonal lines. Layers 31, 32, and 35-42 are approximately 2275288.4 × 10 ⁶ N / m
² (33,000,000 pounds per square inch or p
It includes a graphite fiber having a modulus of elasticity of si). Layers 33 and 34 are approximately 310266 × 10 ^6.
It includes a graphite fiber having a modulus of elasticity of N / m ² (45,000,000 pounds per square inch or psi). About 10% to 20% of the graphite fiber used in the racket frame has a high elastic modulus, and about 80% that of the graphite fiber.
% To 90% has a low elastic modulus. The use of high modulus graphite fibers increases the racket stiffness or stiffness without increasing the racket weight. The outer layer 43 of the racket frame shown in FIG. 9 is a layer of paint.

Returning to FIGS. 3-6, the outer surface of the head is provided with grooves 45 in which thread holes 46 are located.
The groove 45 also serves to position the bumper 26 and the insert 27 (FIG. 2).

The racket frame height is determined with respect to FIG. 4 and measures the racket's dimensions at right angles to the midplane MP extending through the longitudinal centerline CL of the handle portion 18. The longitudinal centerline CL also forms the longitudinal axis of the racket of FIG. The yarn of the racket lies in the central plane MP, and the bending of the racket shown in FIGS. 10 and 11 occurs in the plane extending at right angles to the central plane.

The height of the racket frame of FIG. 4 continuously increases from dimension A at the top of the head portion of the frame to dimension B at the throat portion of the frame. The racket height decreases continuously from dimension B to dimension C at the top of the handle portion 18. The height of the handle portion increases from dimension C to dimension D and remains continuously up to the bottom of the handle portion.

The maximum height B of the racket frame occurs in the area where the throat members 21 and 22 merge with the head portion 20. Comparing FIGS. 3 and 4, the largest dimension B is that the frame 2 is crossed by a longitudinal centerline CL.
Generally aligned with the center of 3. Comparing FIGS. 6 and 7, the height of the frame piece 23 is substantially less than the height of the frame members 21 and 22 and the height of the head portion 20 in the region of the maximum height B.

In one particular embodiment of a large head racket, the inner longitudinal dimension E of the head portion is 3
It is 4.9623 cm (13.7647 inches), and the lateral dimension F inside the head portion is 25.7970 cm (1.
0.1563 inch), and the total length L is 68.4.
It was 784 cm (26.960 inches). The height A at the top of the head is 2.7686 cm (1.090 cm).
Inch) and the maximum height B is 3.81 cm (1.500 cm).
Inches), the height C is 2.54 cm (1,000 inches), and the height D varies depending on the size of the handle in accordance with the normal handle size. Referring to FIG. 5, the entire width G of the head portion at the top of the head portion
Was 0.935 cm (0.380 inches). Figure 7
Referring to, the height H of the frame piece 23 is 2.743 cm.
(1.080 inches) and the width I is 1.016.
cm (0.400 inches). The ratio of the maximum height B to the minimum height A of the head portion was 1.5 / 1.09 or 1.376.

The area moment of inertia of the racket at a point on the frame of maximum cross-sectional height
inertia) is 13.73 cm ⁴ (0.333 inch ⁴ ). The frequency of the first mode of bending under the free-free restrained state was 204 Hz and the frequency of the second mode of bending under the clamp-free state was 230 Hz.

In one particular embodiment of an intermediate size racket, the inner longitudinal dimension E of the head portion is 3
It was 1.801 cm (12.520 inches), the inner lateral dimension F was 23.698 cm (9.330 inches), and the length L was 68.423 cm (26.938 inches). Height A at the top of the head is 2.337 cm
(0.920 inch) and the maximum height B is 3.175.
cm (1.250 inches) and height C is 2.54 cm
(1,000 inches), and the height D varied depending on the size of the handle. The width G of the head portion at the top of the head was 1.029 cm (0.405 inch). The height H of the frame piece 23 is 2.299 cm (0.90).
5 inches) and the width I is 1.1422 cm (0.1 inch).
4497 inches). The ratio or ratio of the maximum height B to the minimum height A of the head part is 1.25 / 0.9.
2, or 1.3587.

The frequency of the first mode of bending under the free-free state was 208 Hz and the frequency of the second mode of bending under the clamp-free state was 230 Hz.

The shape and dimensions of the racket frame shown in FIGS. 3-9 are such that the racket is stiffer or stiffer than a conventional racket, and the first of the bends under free-free restraint. 180 Hz to 250 Hz for modes or 215 Hz to 315 H for the second mode of bending under clamp-free restraint
It provides a moment of inertia for the midplane MP to have the desired frequency up to z. The ratio of the maximum height B to the minimum height A is preferably about 1.35 to about 1.38.

The use of relatively high modulus graphite fibers in layers 33 and 34 reduces the weight of the frame while maintaining the total weight of the racket within normal limits.
Allow sufficient reduction to accommodate bumper 26.
The frame uses about 270 grams of graphite fiber and resin, which can be a regular resin.

Large head rackets and midsize rackets having particular shapes and dimensions have been described herein to achieve the desired stiffness and frequency. However, it is understood that other shapes and dimensions may be used, so long as the resulting stiffness or robustness provides the desired frequency. The important purpose is 180 Hz and 25
To achieve a frequency of the first mode of bending under free-free suppression between 0 Hz or a frequency of the second mode of bending under clamp-free suppression between 215 Hz and 315 Hz.

While particular embodiments of the present invention have been described above in detail for purposes of illustration, many of the details provided herein do not depart from the spirit and scope of the invention. It is understood that it can be changed considerably by the vendor.

[Brief description of drawings]

FIG. 1 is a top view showing a tennis racket formed according to an embodiment of the present invention.

2 is a side view of the racket of FIG. 1. FIG.

FIG. 3 is a top view showing the frame of the racket of FIG. 1 without threads and handle coating.

FIG. 4 is a side view of the racket frame of FIG.

5 is a cross-sectional view taken along line 5-5 of FIG.

6 is a cross-sectional view taken along line 6-6 of FIG.

7 is a cross-sectional view taken along line 7-7 of FIG.

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG.

FIG. 9 is a perspective view of a portion of a racket frame showing a multi-layer flavite fiber.

FIG. 10 is a view showing first and second bending modes of a tennis racket in a free-freedom restrained state.

FIG. 11 is a view showing first, second, and third modes of bending a tennis racket under a clamp-free restrained state.

FIG. 12 is a diagram showing a modification of a conventional racket when a normal tennis ball bounces from the racket after a collision.

FIG. 13 is a view showing a modification of the tennis racket according to the present invention when a normal tennis ball bounces from the racket after collision.

[Explanation of symbols]

 15 Tennis racket 17 Frame 18 Handle part 19 Throat part 20 Head part 21, 22 Frame member 23 Frame piece 24 Longitudinal thread 25 Horizontal thread 26 Bumper 27 Insert 31-42 Resin impregnated graphite fiber layer 43 Paint Layer 45 Groove 46 Thread hole

Claims (14)

(57) [Scope of utility model registration request] 1. A handle having a handle portion (18), a loop-shaped head portion (20), and a throat portion (19) connected to the handle portion (18) and the head portion (20), and A racket (15) having a longitudinal axis (22) aligned with the centerline of the, and a central plane (MP) extending through the longitudinal axis parallel to the plane of the loop-shaped head portion (20), A racket (15) having a frequency of a first mode of bending under free-free restrained conditions in a plane extending perpendicularly to the central plane (MP) within a range of 180 Hz to 250 Hz. 2. The frequency ranges from 200 Hz to 210H.
The racket of claim 1 in the range of z. 3. The racket of claim 1 having a second mode of bending frequency under clamp-free restraint in a plane extending perpendicularly to said central plane (MP) in the range of 227 Hz to 315 Hz. 4. The frequency of the second mode of bending under clamp-free restraint conditions is from 230 Hz to 265 Hz.
The racket of claim 3 in the range of. 5. The racket is formed from a tube of multilayer (31-42) resin impregnated graphite fibers, some fibers of which are approximately 227528.4 × 10 ⁶ N / m ² (33,
The other layer of fiber has a modulus of elasticity of, 000,000 pounds per square inch or psi, and is about 310266 x 10 ⁶
A racket according to any of claims 1 to 4 having a modulus of elasticity of N / m ² (45,000,000 pounds per square inch or psi). 6. The racket is formed from a tube of 12 layers (31-42) of resin impregnated graphite fiber,
The two layers of the layer are approximately 310266 × 10 ⁶ N / m ² (45,
The other layer of fiber has a modulus of elasticity of about, 000,000 pounds per square inch or psi, and is about 227528.4 x 10 ⁶
A racket according to any of claims 1 to 5 having a modulus of elasticity of N / m ² (33,000,000 pounds per square inch or psi). 7. About 10% to 20% of said fiber is about
It has a modulus of elasticity of 310266 × 10 ⁶ N / m ² (45,000,000 pounds per square inch or psi), with about 80% to 90% of the fiber having about 227528.4 × 10 ⁶ N / m ² (33, 0
6. An elastic modulus of 0,000 psi)
Or 6 rackets. 8. The two inner layers (31, 32) and the eight outer layers are about 227528.4 × 10 ⁶ N / m ² (33,000,000 pounds / third).
8. The racket of claim 6 or 7 comprising graphite fiber having a modulus of elasticity of square inches or psi. 9. The tube is approximately 1.143 mm to 1.27 mm (0.0
45-0.05 inch Wall Hücknen (a wal
racket according to any one of claims 5 to 8 having a l Hucknen). 10. The throat portion has a pair of frame members (21, 22) branching from the grip portion (18) and united with the head portion (20), and the racket (15) is Including a frame piece (23) extending between the diverging frame members (21, 22) and forming the bottom of the loop-shaped head portion (20),
Height (B) of the racket (15) perpendicular to the central plane (MP)
The racket according to any one of claims 1 to 9, wherein is the largest in a region where the frame piece (23, 22) and the branched frame member (21, 22) are combined in the branched frame member (21, 22). 11. Height (A) of the top of the head portion (20)
The racket of claim 10, wherein the ratio of the maximum height (B) of the racket (15) to the is about 1.35 to 1.38. 12. The moment of inertia of the area at a point on the frame (17) having the maximum sectional height (B) is about 13.73 cm ⁴
The racket according to claim 10 or 11, which is (0.33 inch ⁴ ). 13. The height of the racket is the maximum height.
Racket according to claim 10 or 11, which continuously decreases from (B) to the top of the head portion (20) and from the maximum height (B) to the top of the handle portion (18). 14. The racket of claim 1, having a length of about 685.8 mm (27 inches).