JPS58216077A - Racket - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes several discoveries arrived at through experience, experimentation, and support analysis in order to significantly improve the tension surface of tennis rackets, racquets, toyball racquets, and other sports racquets. It includes.

Their efforts are generally more effective, more efficient, and
It is directed to determining the optimal tensioning parameters and configuration of the tensioning surface to create a tensioning surface that responds well and imparts a force on the ball. , the present invention not only recognizes that longer threads have significant advantages, but also explains why longer threads work better and how to improve the long thread tension surface for improved results. I am aware of what can be configured. The present invention includes several proposals for extending the warp threads up to the throat or shank surface of the racquet to have a sufficiently long threading length, and for fanning, guiding and fixing the longer warp threads. This paper proposes several types of configurations.

The present invention recognizes that longer warp threads should be tensioned at a higher tension than shorter weft threads, and in order to achieve a much better working relationship within the thread tensioning plane, the longer threads have a higher tension. The reason and its higher tension range is to be determined.

A mechanical study of yarn mechanics carried out using experiments, mathematical analysis and real competition experience.
Considerable evidence has been obtained as to the true effective lengths and tensions for warp and weft threads to work effectively together. With this information, the necessarily burning but equally tensioned 1/~
It has been shown that the thread is subjected to a load that is much more than half the load when striking the ball. This not only wastes the excellent performance of the warp threads, which support the load of the ball, but also causes twisting torque and shock to be applied to the player's arm due to the ball hitting various places in the center of the thread tension surface. are doing.

The present invention not only recognizes the advantages of a surface tensioned with longer warp threads having higher tension than short weft threads, but also combines the greater tension and length of the warp threads with the smaller tension and length of the weft threads. It approximately quantifies the functional relationship that allocates a larger portion of the IJ heavy load to the warp threads in a balanced manner. Due to the ribbing, the threaded surface has a higher repulsion coefficient that gives a higher velocity to the bouncing ball, and the higher repulsion coefficient is spread over a wide range of the threaded surface, This reduces losses caused by string elongation, friction, and ball deformation, and reduces the impact of torque on the player's arm. A tennis racket strung in accordance with the present invention has been tested and verified with measurable data for competitive use, and the present invention has been tested and verified with measurable data for use in competition. This is subjectively established by confirming the analytical results that it provides a good momentum and a non-impact feel.

The inventor's discovery of functionally interrelating thread length and tension in order to adjust the thread tension surface and improve ball-striking performance is useful for tennis racquets and other sports racquets. Applies to. These rackets have a grip connected to a frame supporting a threading surface extending across the ball hit surface separated from the grip, the frame extending from the grip, widening outwardly at the throat, and extending from the weft thread. It has a shank surface that extends around a generally oblong ball-striking surface that is tensioned by warp threads.

The inventors have found that at least the central warp yarns, and preferably all warp yarns, should have a tension length that is at least 30% longer than the weft yarns. The preferred method of doing this H is to extend the warp threads to the throat or shank face of the frame, preferably into the grip area. These long warp threads can fan out outwardly across the ball striking face, or they can run approximately parallel to the ball striking face and slope toward the shank face into the throat area.

The inventors have also discovered that the long warp threads should be tensioned at least 30 inches higher than the weft threads. This not only adjusts the long and short threads so that they work in harmony, but also converts more hitting force into the initial tension of the thread, causing ball deformation, thread elongation, and This reduces losses caused by friction between the threads.

Applicants have also discovered an important functional relationship between long warp taut lengths and high tensions, short weft taut lengths and low tensions. The length and tension of the yarn selected according to this relationship will effectively apply a force much thicker than #1 #Y half to half of the force of the yarn on long warp threads to slow down the ball as it sinks into the threaded surface when the ball is struck. It is assigned to

In other words, in contrast to conventional racquets that apply a load on the weft thread that is significantly greater than half of the ball striking load, the longer length of the warp thread is used to apply a load that is significantly greater than half the PI or half of the ball striking load on the warp thread; Higher tensions are selected for shorter lengths of weft threads and lower tensions.

This relationship significantly improves traditional thread tensioning surfaces in several ways. Longer warp threads receive more load when hitting the ball, which has a greater impact on the shot. That alone is a significant improvement, since the longer warp yarns have a better ability to store energy and return energy to the ball than the shorter weft yarns. Long threads elongate less than short threads due to the deformation of the thread tension surface that occurs when the ball sinks into the thread tension surface, so long threads lose less energy due to thread elongation and friction between the threads. Long threads create greater ball resistance due to higher tension tension, eliminating the need to stretch the thread. Longer, more tightly taut strings stop the ball with less force and deform more, resulting in less ball deformation and less energy loss as the ball deforms. Furthermore, the warp threads, which are identified closer to the racket's longitudinal traps, carry the batted ball load more than the weft threads, which are fixed to the sides of the frame and transmit a greater torsional impact to the player when hit somewhere other than the center. Geometrically more suitable for support. Their associated benefits include a responsive and maneuverable spot area, a higher coefficient of rebound on the tension surface, easier shot adjustment and higher shot velocity, and less vibration. It will be done.

#1 Most of the recent improvements to tennis rackets have been to the frame and racket construction rather than the tensioning aspect. The sweet spot, more properly speaking, the center of impact where the impact of the ball is felt by the player to be the smallest,
Considerable research has been conducted on the size and location of C. This is influenced by the shape, dimensions, stiffness and weight distribution of the frame, including the throat and handle, and to a lesser extent by the tension and length of the thread.

The thread tension plane has not changed except for a few changes in its size, the material of the threads, and the spacing between the threads.The current state of racket making is that the same tension is applied to the weft and warp threads, Since the average length of the warp threads is longer than the weft threads, the racket frame as a whole forms an oval ball hitting surface.

Understanding the present invention requires an overall understanding of rackets and ball mechanics. When the ball and thread tension surface collide,
By the ball due to the speed of the ball relative to the racket
The retained kinetic energy is divided into three parts. The first part is spent bending the frame, the second
The second part is spent flattening the ball, and the third part is spent sinking the ball into the threaded surface, increasing the tension in the thread and causing the net to dent. Among those three parts, the energy expended to bend the frame is almost the total loss. Since the ball is in contact with the tension surface for only 2 to 3 thousandths of a second, the frame is bent even when the ball bounces off the tension surface. Therefore, the energy stored in the bent frame is not returned fast enough to be added to the bounce of the ball. The energy expended in deforming the ball due to the final impact force between the tensioned surface and the ball will cause the ball to deform even when it rebounds from the tensioned surface, since it is still partially deformed. Some of the energy expended in the deformation of is not recovered during the rebound, and at least some of it is lost.

Energy lost due to frame bending and ball deformation, clearly visible in high-speed photographs, is generally recognized as an undesirable part of racket mechanics. Modifications to tennis balls to retain higher internal pressures and the use of high-strength materials such as composites, metals, and boron-reinforced synthetic materials to make racquets lighter yet stronger have improved their dynamic A third part, which is an effort to reduce energy loss, involves the ball sinking into the tensioned surface upon impact, storing energy, and the rebound of the tensioning surface returning kinetic energy to the bouncing ball. is known to be important. And various thread materials and tensions were investigated for this purpose. However, apart from some proposals that were never adopted in the past, the threading surface is limited to an oblong ball striking surface, with weft and warp threads made of the same material and stretched at right angles to each other with the same tension. was used.

(Mechanics of thread) The tension generated in the thread due to the impact of the ball is the initial tension To and the additional tension A caused by stretching the thread.
E (X/Ll)'', where A is the cross-sectional area of the yarn, E is the Young's modulus of the yarn, X is the depth of the ball, and L is the length of the yarn. It's half.

These two components combine to form a retraction force that resists the forward movement of the ball while storing the ball's decreasing kinetic energy. Timoshenko
o) [Vibration Problems in Engineering (Vibrati
on Problems in Engineering
ng) J, D, VanNostrand Co.
The differential equation describing this dynamic equilibrium, obtained from NewYnrk, P., 116, is. Here, F is the force acting from the thread to the hole, and the negative sign on the right side indicates that the force is a deceleration force.

It is important to recognize that the initial tension term To is much larger than the tension term due to elongation and is proportional to the ball penetration depth X. Therefore, the initial tension of the thread is
It behaves very similar to a linear spring in that it receives the kinetic energy of the ball and stores it. When the ball's penetration depth X is small, X/L becomes a very small value 1
Since it is proportional to the cube of , the elongation term AE is small. but,
When the relative velocity of the ball is high and the biting depth X is deep, this elongation term AE gradually becomes thicker.

In the present invention, a long yarn with a large Ll reduces the influence of the elongation term AE, and indirectly increases the contribution of the initial tension To. Both of these are beneficial to the performance of the threading surface. When the yarn is repeatedly stretched and contracted, hysteresis loss occurs from molecular friction inside the yarn, and when the yarn stretches, friction, wear, and friction loss occur due to the relative movement of the yarns.This is because the elongation term AE is kept as small as possible. long threads are the best way to achieve this.

As the yarn becomes longer, the initial tension To of the yarn should also increase so that T o /L I does not become smaller. This results in a long, taut yarn with high tension resistance to ball bite and a much smaller portion of pole resistance derived from yarn elongation. Also, from a vibrational point of view, the thread tension must be increased in proportion to the increase in thread length so that both threads vibrate with the same number of vibrations.

Since the length of the weft thread is limited by the length of the racquet frame, only the warp thread can be lengthened to take advantage of higher tension resistance. The long warp yarns can be extended to the throat, shank and handle areas to obtain a sufficiently long tension length for the weft yarns.

Previous applications filed by the applicant indicate several fixing and guiding structures for extending the warp threads up to the shank or grip area of the thread, and many other possibilities are probably also viable. be,.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Two embodiments with suitable widths are shown in FIGS. 1 and 2.

The preferred ratchet 0 warp threads 15 shown in FIG. 1 fan out outwardly from the tether 16 in the shank 11 across the ball striking face. The tethers 16 can be located anywhere from the sight 12 to the grip 13 depending on the length and tension desired for the warp threads 5.

Another preferred racket 20 shown in FIG. 2 has warp threads 5 extending from the throat piece guide 22 parallel to the axis or slightly flared outwardly across the ball striking face. The throat piece guide part 22Fi has a guide element 24 that makes the warp oblique between the warp anchoring part 26 in the shank 21 and the course in which the warp crosses the ball hitting surface. Also, the tether 26 can be located along the shank 21 or in the grip path.

The embodiment shown in Figure 2 closely resembles a conventional racket;
Although it may be generally accepted, the throat guide 22 introduces some frictional losses. The embodiment shown in FIG. 1 is preferable because not only the friction is small, but also the torsional torque generated when the ball is hit at a portion other than the center portion is small. It is also possible to anchor the warp threads extending somewhat deeper into the throat guide portion 22#i than in a normal racket. The desired performance of warp yarns of varying lengths and tensions is discussed in more detail below.

In the embodiment shown in FIGS. 1 and 2, the warp threads 15 or 25 are arranged so as to receive a larger batted ball load than the weft threads 17 or Fi 27, thereby reducing the torsional torque that occurs when the ball hits a part other than the central part. . However, in the fan-out arrangement shown in Figure 1, the warp threads are closer to each other in the center area where most balls strike, placing the warp threads 15 within a smaller average distance from the axis of the racquet to minimize twisting torque. It is something to suppress. The player's vagina bulges from the impact of the ball - the so-called tennis elbow caused by twisting - can be reduced (mathematical analysis). The practical possibility of tensioning results from the optimal relationship between long and short threads. This is done in order to determine for different yarns the effect that varying parameters of the yarn have on the load distribution.
It requires mathematical analysis that derives more realistic dynamic equations and uses more realistic mathematical models.

Figures 3 to 5 show the center warp threads 30 and weft threads 31 supported elastically by the other thread in a tension plane perpendicular to each other and deformed as shown when the ball is struck. It shows a mathematical model that easily approximates the operation.

The width of the thread adjacent to the ball is 2bVi, which simulates the part of the thread that matches the flattened surface of the ball when the ball is embedded in the threaded surface. Total length of thread Lo FiL+ +
It is divided into L2 + L3 parts. Their portions, ~L3, correspond to respective lengths of yarn that are to be folded by different depths. Break #j! 32 and 33 are simulations of elastic support from other threads that support the two threads shown by solid lines, and the impact on the thread tension surface in the area where the ball contacts the thread tension surface. Bite depth d
Accordingly, the elastic supporting threads 32 and 33 are also compressed to a depth of d/2.

The dynamic equations described below, based on the models of FIGS. 3-5, more closely approximate the complex reality of the interaction between the warp and weft threads. These equations assist in determining the appropriate values of thread length and tension on the thread to achieve optimal tension surface response.

The tension surfaces of the two elastically supported threads shown in Figures 3 to 5 resist the force represented by the mass m of the ball moving at an initial relative velocity The threads share the load. If r represents the 100% ratio of the load shared by the warp threads, and subscripts c and L represent the weft threads 31 and warp threads 30, respectively, a more complex analysis can be performed by calculating the movement of the two threads under various lengths and tensions. The following equation describing the equilibrium is obtained.

rmVr+'-(pTo)L"-(Y"f,)1.
” = 0- (2'a)P=(3/2) (1/(
L+ -b)+1/(L2b)l-(3
a) The maximum penetration depth d is obtained from the following formula in the case of warp threads.

This gives the percentage r of the batting load *, and for the weft this gives the percentage 1-r of the batting load.

As the pole sinks into the threaded surface, the force of the thread against the movement of the pole increases, reaching its maximum when the pole stops. At that time, the deceleration is at its maximum and the force F0 is also at its maximum. This maximum force determines the maximum strain in the pole, while the maximum force rF in the case of the warp
6 and the maximum force (1-r)Fo in the case of weft threads are given by the following equations, respectively.

rF o = (pTo)1. d + (AEt)
Ld" - (5a) (1r) Fo" (p
To) (d + (AEt) (” ・= (5b) where the force equal to the product of mass and deceleration FOi is the combined force exerted on the pole by the two-strand thread, r it
The 100% ratio of the load supported by the warp threads 30, 1-r is the weft thread 3
1 is the 100th ratio of the load supported by c1, which is the maximum depth at which the ball is embedded under tension.

When the biting depth is the same, it is preferable that the force FO is small because the deformation of the pole is small.

It is very clear from the mechanics of the tension surface that the consistent practice of the prior art of tensioning the warp and weft threads at the same tension allows the short weft threads to carry a much larger portion of the batting load. Equation 1i described above approximates the disparity of the load between two threads, and shows the tendency for overload to be applied to the weft thread in the existing racket.

For example, an oversized head Prince 7 rack cut with a weft of approximately 27.9 cm (11 inches) and a warp of approximately 33.0 cm (13 inches) would have a 9 (72 bond)
When both threads are stretched at a tension of , the weft threads share 57% of the load, while the warp threads share only 43% of the load. Dunlop Volley
The corresponding load sharing for TI is 56% weft and 44% warp.
%. The proportion of the ball hitting load on the weft is much more than half of all rackets currently on the market.

Calculate using the above equation to approximate a real example,
A comparison of conventional thread tension and long, taut warp yarns with balanced weft yarns in accordance with the present invention helps to clarify the significance of the improvements of the present invention. The warp forces in a conventional racket strung in the conventional manner with equal tension in the weft and warp threads as shown in FIG. compared to a racquet of the present invention having long, taut warp threads. This comparison assumes that the tennis ball travels at 50 miles per hour and hits a stationary racket and tension surface. Also, the four weft threads and four warp threads touch the pole,
It is assumed that it provides the force required to stop the pole.

Using those assumptions, the previous equation shows that the mass of the pole impinging on the string being in contact with the thread tension is The surface is 20.5mm deep and 0. .

It shows that you are giving a compliment. This makes the duration of pole contact and shot adjustment equal for both racquets. In a conventional racket, the tension applied to the weft and warp threads is approximately 2
2.5 to 9 (50 bonds), and in the racket of the present invention, the tension on the weft is approximately 22.5 kg (50 pounds) 1
．． The tension on the warp yarns is approximately 42.2 ni (93 bonds).

The graphs in Figures 6 and 7 show the curve of the impact force when the pole is biting into the thread tension surface, in a part where the resistance force of the pole is based on the initial tension To of the thread, and in a part where it is based on the elongation AE of the thread. This is an easy-to-understand graph. This result is a big 7! It clearly shows that for long warp threads under tension, only a much smaller portion of the ball stopping force contributes to the elongation of the thread. This graph,
It also shows that the maximum impact force at the end of the ball bite is greater for the conventional racket than for the racket strung according to the invention. Therefore, the shot adjustment is also the same. In addition, the fact that the maximum force on the thread tensioning surface of the present invention is small means that the rebound is performed more efficiently. These two differences represent a significant qualitative advantage of the threading aspect of the present invention.

Reducing the force that stretches the thread reduces the loss caused by internal friction of the thread as it stretches, and the loss caused by friction between the threads. This also reduces yarn wear and fatigue while increasing the life of the yarn tension surface.

The smaller the maximum force required to stop the ball means less energy is lost due to the deformation of the ball, making it more efficient and responsive to return energy to the bouncing ball. This means that it is a threaded surface.

Of course, actual racquets have a much more complex threading surface than those assumed in their calculations, and include a large number of vertical tip threads of varying lengths and actual tensions.

However, the trends shown by comparing the calculated results have been found to be true when applied to the tension surface of an actual racket.

(Confirmation through Tests) In the tests conducted, the tensioned surfaces of two of the best tennis rackets currently on the market were compared between the tensioned surfaces according to the present invention and the conventional tensioned surfaces. . The present invention includes improved performance from an optimally tensioned tension surface, and does not improve the shape or construction of the racquet or the Fi7 frame, making it the best two racquet frames available. was selected for comparison of thread tensioning efficiency. One racquet used in the test was the Volley II, made by Dunlop Cotnpany as a medium size head racquet. Industry magazine 1 Tennis World (Tenn1s World) J's 19
The April 1980 issue includes a special report praising this Volley 2 racket as the best.

One other racket used in the test was manufactured by the famous Pr1nce Manufacturing C.
The famous Prince Classic is an oversized head racket made in accordance with U.S. Patent No. 3,999,765 by
sic) J.

Since the relevant comparison includes differences in tension surfaces and does not include differences in frame structure or weight distribution that would affect the overall performance of the racquet, the tension surface of the racket should be horizontally free and the racket Fix the periphery of the frame and
2! The test was conducted by dropping a tennis ball from a constant height of Mm (49.2 inches) and accurately measuring the bounce height of the ball from the threaded surface. The bounce height was measured with an Instar J television camera.

This television camera records the bounce of the ball on magnetic tape, which is then played back on a television monitor to show the frame showing the maximum height as a still image. This test was conducted by William Parsina of Xerox Corporation.
ygnat) conducted by Dr.

The tension recommended by the manufacturer for the Dunlip Volley 2 racket and the Prince Classic racket (approximately 28.2 to 9 (62 bond) for the Volley 2, and approximately 32.7 kg (72 bond) for the Prince Classic). The new nylon threaded surface was first tested under tension.

A ball drop test is performed at various points on the hitting surface of each racket to accurately record the bounce height of the ball, which is then measured to determine the recovery factor (bounce height divided by drop height). Established. The test results are shown on the right side of Figures 8 and 9 on the same scale.Next, a long warp thread was stretched on the same racket frame with the thread length and tension selected according to the calculations described above. was configured. The threaded surface tensioned according to the invention is
As shown in FIG. 1, warp yarns were used that were anchored to the shank near the grip and extended outwardly across the ball striking surface. In calculations to determine the length and tension of the string in those rackets, the relative ball speed was approximately 80 m.p.h.
50 miles), and the ball was assumed to contact four weft threads and four warp threads, as described above.

The weight of the ball is approximately 46.7f (0,103 bond), and the weight borne by one weft and one warp is approximately 0.0
012Kg -see,'/m (0,0008/b
-5ec2/ft).

Use nylon thread with an AE of approximately 1026 to 9 (2260 bond), and set the tension on both threads to approximately 28 as recommended by the manufacturer.
．． For a regular volley 2 racket set to 2 Kf (62 bond), the ball penetration depth was found to be approximately 1.76 cm (0.69 inches) by calculation using equation <43>: (4b). The racquet frame, strung according to the invention in order to equalize their formula, ball penetration depth, impact duration and shot execution adjustment, is made of approximately 9 inch (22.9 cm) long nylon Approximately 19. A length of 1 Kevlar thread with a tension of IK9 (42 lbs) and a warp of 1-tAE of approximately 5902 Kg (13000 bond) to approximately 45.7 (7) (18 inches) weighs approximately 45.4 Kg. (100 pounds) of tension. For this purpose, the length of the long warp threads is twice the length of the weft threads, the tension in the warp threads is made to be more than twice the tension in the weft threads, and the load sharing ratio between the weft threads and the warp threads is significantly changed.

In the commercially available Volley 2 racket, the distribution ratio of the batted ball load is -56% for the weft and 44% for the warp, whereas in the Volley 2 frame having a threaded surface tensioned according to the present invention, the distribution ratio of the batted ball load is -56% for the weft and 44% for the warp. The weft is -41% and the warp is 59%.

Next, a ball drop test was conducted on two volleyball rackets strung with string according to the present invention, and the bounce height and recovery coefficient of the ball were measured at various points on the stringed surface. The measurement results are shown on the left side of FIG. This measurement shows a significant improvement.

The maximum recovery coefficient of the thread tension surface of the present invention is 1. tO, 76 was obtained, which is greater than any return coefficient obtained with conventional tensioning using the same racket frame. Maximum return coefficient 0.74 to 0.75 with conventional thread tension
The area where this is obtained is slightly around the center of the thread tension surface, about 5
Although it is only 8.1 crfl (9.0 square inches) (
In the case of the thread tension of the present invention, the area where the same value of the return coefficient can be obtained is expanded to about 221.9 m (34.4 square inches), and the magnification is 3.82 (Fig. 8 right). (left side of figure). The area where a return coefficient of 0.72 to σ, 73, which is smaller than the above, can be obtained with a conventional string tension racket is approximately 150.9.
m (23.4 square inches), whereas the range in which the same recovery coefficient can be obtained on the thread tension surface of the present invention is approximately 332.
．． It is enlarged to 2crI (51,5 square inches) and has a magnification of 2.2. In those tests, by making the threading surface so that it bounces with high 1/) efficiency when holding the ball, and by greatly expanding the most efficient area of the threading surface,
This clearly shows that the racquet of the present invention is a significant improvement over conventional racquets.

In a test comparison for a Prince racquet, shown in Figure 9, an 11 inch nylon weft and a 1.3 inch warp were tested using the recommended 32 Instead of using a tension of about 20.4 K9 (4 K9) on the weft threads, instead of using 72 lbs.
5 lbs.) tension, and the warp threads are stretched approximately 45.7 cm (18 lbs.).
2.54σ from the hand grip
(1 inch) apart, the warp threads are moored at mooring locations approximately 45
．． Kevlar yarn is used in the warp to withstand a large tension of 4 to 9 (100 bonds), so the load sharing ratio is 57 in the weft in the original Prince Rakey).
It can be seen that the load was 43L% in the warp, but in the case of the present invention, 42L% of the load was applied to the weft and 58L% of the load was applied to the warp, indicating a significant change in the ratio of load sharing.

Measuring the bounce height of the ball on the threaded surface of the present invention,
Ball drop tests were repeated to determine the return coefficient. The results are shown on the left side of FIG. From this result, according to the present invention, the range in which the maximum return coefficient of 0.76 can be obtained is approximately 289.7 m (44.3 square inches) from the original (right side of Figure 9) of approximately 45.8 m (7.1 square inches). ) is extended to (9th same left (+lI), the magnification is t1-cho 6.3
It is. The range with a return factor of 0.74 to 0.75 has been expanded from the original approximately 249.6 Cffl (38,7 square inches) to approximately 424.4 m (65,8 square inches), with a magnification of 1.7. be. This improvement represents a very large increase in the area of maximum rebound response and clearly demonstrates the superiority of the tensioning aspect of the present invention.

The return coefficient obtained in those tests only represents the comparative coefficient a of the tension surface during ball rebound, since the racket frame is restrained and not allowed to interact during the test. .

As disclosed in U.S. Patent No. 3,999,765, the results of a test in which a ball was hit against the threaded surface of a Prince racket holding a handle showed that the recovery coefficient was around 0.3 to 0.4. there were.

The performance of a racket not only depends on the thread tension, but also on the frame shape, material, and M amount distribution. Therefore, the threading surface improvements made by the present invention may not improve the overall performance of the racquet in direct proportion to the improvements. On the other hand, the improvements made to the threading surface of the present invention can be applied to existing rackets without any additional cost. And the pole drop test confirmed that the present invention creates a more efficient tensioning surface with higher ball bounce performance that undeniably improves the overall performance of the racquet. Racquets strung according to the invention have been used extensively by experienced athletes.

Those competitors have compared this racquet with conventional racquets and reported their subjective impressions confirming the test results. According to the report, the racket of the present invention bounced the ball easily, gave a clear feeling that it could be used well, and was able to hit well-aimed and strong shots.

According to the calculation results and the comparison results between the conventional threading surface and the threading surface of the present invention, it was found why the threading surface of the present invention makes the racket superior.

The long, taut string can absorb the ball's energy by applying a small force to the ball, thus reducing the ball's deformation. As a result, less energy is lost due to pole deformation, and more energy stored in the string is returned to the ball as kinetic energy, resulting in a higher bounce speed of the ball.

As an example, considering a volley 2 racket, calculations using equations (5a) and (5b) show that the conventional thread tension surface is 2
The main thread is shown to stop the ball with a final load or maximum force of approximately 28.2 Kq (62 Bonds). This apparently large force is only sustained for a short time. The reason is that the total contact time between the ball and the threading surface is only 1000 minutes and 2 to 3 seconds.

On the other hand, in the thread tension aspect of the present invention, approximately 19.1 K
A weft thread under tension of F (42 pounds) contributes approximately 10.4 Kf (23 bonds) to stopping the ball, and a long warp thread under tension of approximately 45.4 Kf (100 bonds) contributes approximately 10.4 Kf (23 bonds) to stopping the ball. Approximately 15.3 to stop
Kg (33.8 bonds), so the load sharing ratio is 4:6. The maximum force of the thread applied to the ball is approximately 25,8 K9 (56,8 Bond). This is approximately 92 inches of the maximum force from the conventional threading surface. This reduction in maximum impact force reduces the deformation of the ball and increases the rebound velocity.

Test results also confirm that impact can be reduced with rackets strung according to the invention.

Comparative tests conducted by several professionals and experienced amateurs, again using the Volley 2 racket strung according to the invention, have shown that this racket has significantly less impact than oversized rackets and graphite frames. It has been confirmed that the vibration suppression performance is better than all other rackets known to date, including the racket of This is especially beneficial for tennis players who want to avoid tennis elbow and want a racquet with very low vibration.

(Practical Limitations) The warp threads can be extended to the very edge of the grip, but if they are made that long, the tension that must be applied to the warp threads will be extremely large, exceeding the capabilities of current thread materials and racket frames. Is it F? This is known by calculation. Nylon thread cannot withstand tensions of about 40.9 Kf (90 bonds), and the upper tension limit for 17 gauge Kevlar systems is about 45 kf (about 100 bonds). If yarn materials that can withstand greater tension are developed and stronger frame threads are developed, the warp threads can be extended to the handle to take full advantage of the invention.

Within the current constraints of thread and frame materials, threaded surfaces can be created to increase control or power. Increasing the tension and medium length of the thread will emphasize the power and shorten the contact time between the ball and the thread tension surface. In this case, control is reduced. Conversely, a very long length and moderate tension will increase the contact time between the ball and the tension surface, providing better control and reducing impact, but at the cost of less power. The present invention improves the performance of the threading surface so that increased control, increased power and reduced impact can all be achieved. Then, a method of emphasizing one of these characteristics can be selected in advance through calculation.

The present invention improves the thread tension surface, since in conventional rackets such as the Volley 2 racket or Prince racket, the tension applied to all warp threads is uniformly increased in direct proportion to slightly lengthening the warp threads. The sides become very hard and the sweet spot becomes small. Therefore, to take advantage of the improvements of the present invention, the conventional warp threads must be made at least slightly longer than the weft threads. Calculations and experience have shown that the warp threads must be at least 30% longer than the weft threads to achieve any significant improvement. In addition, the tension on the warp threads should be at least 5
0% greater tension must be applied and the functional relationship between the warp and weft threads must be predetermined to apply approximately half or more of the force to the warp threads than the force that strikes the ball. Compare the warp length and tension '5C minimum 30
% increase, the warp of a conventional racquet like the Pudding 7 or Volley 2 racquet should be at least 2.54
(7) or 5.1 cm (1 or 2 inches) longer. This can be done by changing the oblong frame into an egg-shaped frame, with the ends of greater curvature facing outward and the ends of less curvature towards the grip, or This can be done by changing the throat so that it approaches

For example, in a Prince racket where the weft threads are stretched at a tension of about 31.8 Kf (70 bond), the warp threads are fanned out from the throat part, which is about 2.54 crn (1 inch) below the current throat part, and nylon threads are added to the warp threads. The limit of about 40
．． By applying a tension of 9 Kf (90 bond), the percentage of the batted ball load applied to the warp threads was increased from 43 to 47.
It can be increased rapidly. According to the results of actually using this racket, by increasing the tension on the warp threads by 30% compared to the tension on the weft threads, it is easier to play, responsive, smooth, and when hit from the center. It has been found that the same control results in more power and much less vibration when hitting off-center.

No significant improvement can be expected in the warp yarns, which are tensioned at an increase rate of 30%v lower than the weft yarns. Also, at least 5
A warp yarn with a thicker tension of 0 or more is clearly desirable, but
It is then generally necessary to extend the warp threads well into the throat or shank area of the racquet. In order to take full advantage of the potential of the invention for improvement, it is necessary to lengthen and tension the #1 warp threads enough to share at least 50 inches and up to 65% of the batted ball load. is the best. Increase power or increase control
It is also possible to change the thread tension surface to suit the athlete's playing style, either by reducing the impact.

(Regarding Thread Length Regulations) After the patent was registered, the International Tennis Council (ITC) adopted new rules in June 1981 limiting the string length of tennis rackets. The new rules, taken from the 1982 edition of the Pritanica Encyclopedia, state that the ball-striking surface of a racket has a length of not more than 81 crn (32 inches), and has a patterned frame as its starting point, and a V-shape formed by alternately woven threads.
Must consist of threaded surface 1.39.4 x 29.9
The size is crn (157 squares and 11 inches).
, , -1.

In applying this invention, this rule sets the warp length to 39
．． Since it is restricted to 4cIrL, it is not possible to fix the mooring part to the handle part and tension the thread with a length that violates this rule. Therefore, the anchoring part of the warp is located far from the nigiri part, and the longest warp in the shank area is 39.
It's a shame if it's not in a position where it doesn't exceed 4crn.

Another effect that cascades from this rule is that if the warp threads fan out across the threading surface as described above, and assuming that the racquet has the maximum allowable IJ, At least 2 stretched towards the sides
The warp of a book cannot be longer than the longest weft by 30 inches. For example, 26.9 cPn (10,7
The longest warp, which has a width of 5 inches and spreads out like a fan, is 39
．． In a Prep Classic racquet with a length of 4 cIn, the two warp threads running toward the sides of the racquet are only 24% longer than the longest weft thread, which is 14 cm.

Warp threads running parallel to each other instead of fanning across the threading plane also create shorter threads in the periphery than desired.

In order to properly handle warp threads stretched to the side of the threading plane, the length of which does not exceed the length of the longest weft thread by at least 30%, it is necessary to vary the tension. Warp yarns in peripheral areas that are not of adequate length and have excessive tension are too stiff and have the effect of narrowing the high efficiency ball striking surface.

Applying different tensions to threads of different lengths and applying tension to threads 3
It is possible to use twice the tension. This gives the warp yarns in the side sections of intermediate length a tension intermediate in strength between the low tension applied to the weft yarns and the high tension applied to the warp yarns in the center. This means that there are two or more medium length warp threads in the armpits.
It is particularly preferred if the center warp threads are tensioned with an excess tension of 50 inches or more of the weft threads, and several intermediate length threads tensioned at some intermediate tension are used in the center warp threads. It fills the relatively wide tension gap between the threads and weft threads.

If one or two warp yarns in the periphery are a little shorter than the desired length, which is at least 30% more than the longest weft yarn, one reasonable solution is to reduce the warp yarns in the side area to a tension that is 30% greater than the tension in the weft yarns. It is to be stretched with the same tension as the other warp yarns, which is ~40% more. Many of the warp yarns in the side areas have not reached the desired length of 30% increase, and the maximum and minimum tensions applied to the warp yarns and weft yarns in the center have a difference of 30% or more, which is the minimum target value. In this case, the intermediate tension is preferably used so as to vary smoothly between the two extreme values.

Although this rule change disables the use of some of the accessories for keeping warp lengths shorter than the geometric limits allowed by the rule, the general purpose remains the same. The idea is to make the warp threads as long as possible and keep the tension at a suitably high tension to support half or more of the batting load. The armpit warp threads require higher or lower tension depending on their length. That is, intermediate tensions are used for the side threads, but this situation does not change the overall purpose.

[Brief explanation of the drawing]

1 and 2 are plan views of different embodiments of rackets strung according to the present invention, FIG. 3 is a plan view of a racket model for analyzing the string tension surface according to the present invention, and FIG. 4 is a plan view of the racket according to the present invention. FIG. 5 is a side view of the model; FIG. 5 is an end view of the racket model; FIGS. 6 and 7 respectively show the force exerted on the string when hitting a ball with a conventional racket and a stringed racket according to the present invention. The graphs, FIGS. 8 and 9, show "
2 is a schematic diagram comparing the "return coefficient" with experimentally determined areas. 10, 20... racket L, 11, 21... shank, 12, 22 throat, 13, 23-
Grip, 15, 25, 30 Warp, 16,
26 Mooring part, 17 , 27 , 31 - Weft. Figure 5 Figure 3 1

Claims (1)

[Claims] (Li. It is connected at a distance to a frame that supports a threaded surface on which weft and warp threads that cover the ball-hitting surface are stretched.) In the racket, the tension length of at least a plurality of long warp threads in the center portion of the warp threads is at least 30% longer than the longest weft thread in the thread tension plane, and the plurality of warp threads in the center a racquet comprising at least one-third of all warp threads of the racquet, said long warp threads being tensioned at least 30 cm greater than said weft threads. (2) The racket according to claim 1, wherein the long warp extends at least into the region. (3) The racket according to claim (2), wherein the long warp threads are arranged so as to spread outward across the ball hitting surface. (4) The racket according to claim (2), wherein the racket includes a guide element in the shank region and the guide element for slanting the long warp between the shank region and the ball-striking surface. (5) The racket according to claim (1), wherein the long warp threads are tensioned with a tension greater than that of the weft threads by at least 50 inches. (6) The racket according to claim 1, wherein the warp threads shorter than the long warp threads are stretched with an intermediate strength greater than the tension of the weft threads. (7) The racket according to claim (1), wherein the long warp threads share more than half of the force of the thread that decelerates a ball that attempts to pass through the center of the thread tension surface that controls the warp threads. (8) The long warp extends at least into the throat area. (9) The long warp extends at least 5 times the tension of the weft.
The racket according to claim (8), which is stretched with a tension of 0.0 or more. (10) The racket according to claim (9), wherein the long warp threads are arranged so as to spread outward across the ball hitting surface.