JP2013013550A - Racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a racket which has favorable shot feeling and is light in weight and durable.SOLUTION: In a racket having a frame having a hollow portion, when its face is compared to a clock with its top in the 12 o'clock position, vibration dampeners are arranged in the hollow portion in the 12, 4 and 8 o'clock positions. It is preferable that no vibration dampener is arranged in the hollow portion in the 3 and 9 o'clock positions in the racket. Also, in the racket, vibration dampeners may be further arranged in the hollow portion in the 2 and 10 o'clock positions. The racket may be a tennis racket or a badminton racket.

Description

  The present invention relates to a racket for tennis, badminton, etc. that has a good shot feeling and is lightweight and durable.

  In recent years, as a racket for tennis or badminton, a lightweight racket with good flight performance has been demanded. For this reason, the racket frame is mainly made of fiber reinforced resin such as carbon fiber having high strength and light weight.

  However, for example, if the tennis racket is light, the impact applied to the tennis racket at the time of hitting the ball becomes large, and the player feels unpleasant vibration and the impact is easily transmitted to the elbow, which may cause a tennis elbow. For this reason, a tennis racket that is lightweight and has high vibration absorption is desired, and various ideas have been made.

  The main vibrations that occur when a ball or shuttle collides with a gut racket include out-of-plane primary vibration, out-of-plane secondary vibration, in-plane primary vibration, and in-plane secondary vibration. Here, the out-of-plane means a direction perpendicular to the gut surface with the gut stretched, and the in-plane means vibration in a direction parallel to the gut surface. Paying attention to such vibration, it has been proposed to attach a vibration suppression material to the abdomen (position of large vibration) of these vibrations (for example, Patent Document 1). In addition, a dynamic damper in which a vibration absorbing material is interposed in a part of the frame in order to attenuate the out-of-plane primary vibration, and a vibration absorber and a mass additive are laminated in a part of the frame in order to suppress the out-of-plane secondary vibration. It has been proposed that the primary and secondary vibration damping rates and ratios be in a predetermined range (for example, Patent Document 2).

  On the other hand, it has been proposed to attach or incorporate a mass body into a node portion of in-plane vibration (for example, Patent Document 3), and it has been proposed to fill the entire face portion of the frame with a foam material (for example, Patent Document 4). ).

  Conventionally, however, the relationship between the vibration and the feel at impact is not always clear, and there is a problem that a racket with good vibration absorbability does not necessarily have a good feel at impact. In addition, in the case of a wearable vibration suppression material, there are disadvantages such as an increase in racket weight and an increase in the air resistance of the racket.

JP 2000-157649 A JP 2003-10362 A JP 2001-269424 A JP 2001-145711 A

  In order to solve the above-mentioned conventional problems, the present invention provides a racket with a good shot feeling, light weight and high durability.

  In the racket having a frame having a hollow portion, the vibration absorbing material is disposed in the hollow portion at the 12 o'clock, 4 o'clock and 8 o'clock positions when the top position is set to 12 o'clock when the face surface is viewed as a clock. It is a racket characterized by that.

  The racket of the present invention is a racket for tennis, badminton, etc. that has a good shot feeling and is lightweight and highly durable.

FIG. 1A is a schematic view of an example of the racket of the present invention. FIG. 1B is a diagram illustrating a hollow portion in the tennis racket. FIG. 1C is a diagram illustrating a hollow portion in the badminton racket. FIG. 2 is a diagram for explaining the method of vibration evaluation analysis of a racket according to the present invention. FIG. 3A is a diagram showing a position where a tennis racket is hit with an impact hammer and a position of an accelerometer pickup meter attached to the tennis racket in an out-of-plane vibration evaluation analysis. FIG. 3B is a diagram illustrating a position where the badminton racket is hit with an impact hammer and a position of an accelerometer pickup meter attached to the badminton racket in the out-of-plane vibration evaluation analysis. FIG. 4A is a diagram illustrating a position at which a tennis racket is hit with an impact hammer and a position of an accelerometer pickup meter attached to the tennis racket in in-plane vibration evaluation analysis. FIG. 4B is a diagram illustrating a position where the badminton racket is hit with an impact hammer and a position of an accelerometer pickup meter attached to the badminton racket in the in-plane vibration evaluation analysis. FIG. 5 shows an out-of-plane vibration board diagram of the first comparative example. FIG. 6 shows an out-of-plane vibration board diagram of the first embodiment. 7 shows an in-plane vibration board diagram of Comparative Example 1. FIG. FIG. 8 shows an in-plane vibration board diagram of the first embodiment. FIG. 9 shows an out-of-plane vibration board diagram of Comparative Example 2. FIG. 10 shows an out-of-plane vibration board diagram of the second embodiment. FIG. 11 shows an in-plane vibration board diagram of Comparative Example 2. FIG. 12 shows an in-plane vibration board diagram of the second embodiment. FIG. 13A is a diagram showing the positions of antinodes and nodes of in-plane primary vibration in a tennis racket. FIG. 13B is a diagram illustrating the positions of antinodes and nodes of in-plane secondary vibration in the tennis racket.

  The present inventor clarified that “there is an unpleasant vibration that should be suppressed as a vibration at the time of hitting and a vibration that should not be suppressed. A racket with a good shot feeling can be obtained by selectively removing the unpleasant vibration. As a result of various studies on vibration absorptivity and feel at impact based on the hypothesis of “obtained”, the present inventors have completed the present invention.

  In the present invention, the meaning of “good shot feeling” means that “where the ball hits the racket surface with less vibration that becomes noise when hitting the ball, and how the ball hits the racket surface, ie, the racket surface. It is defined that the speed at which the ball collides, the angle at which the ball collides with the racket surface, and the crushing feeling of the ball on the racket surface are easily felt by vibrations transmitted to the grip. In the following description, the tennis racket will be mainly described, but the badminton racket can be similarly understood by replacing the ball with a shuttle.

  Information obtained from the speed at which the ball collides with the racket surface transmitted to the grip, the angle at which the ball collides with the racket surface, and the vibration for feeling the ball collapsing on the racket surface is referred to as “hit information”.

  A racket with a good shot feel is important for the player to control shots and improve their playing skills.

  The present inventor has found that the feeling of hitting is common among the athletes from the results of the statistics of the racket that the athlete feels good or bad. With respect to this racket having a good shot feeling, the present inventor performed vibration analysis by hitting several places near the center of the face surface. In addition, the vibration mode analysis results of a racket with a good hit feeling and a bad racket were compared. Moreover, the elastomer damper was attached to the racket with a good hit feeling and a bad racket by various methods, and the change in hit feeling and the mode analysis result at that time were compared. From these results, it was found as to which vibration mode is important for transmitting hit ball information and which vibration mode is not important in the racket with “good shot feeling”.

<Out-of-plane primary vibration>
When the ball collides with a relatively large distance from the vicinity of the sweet spot of the racket, a large difference in vibration occurs, so that this vibration is necessary to know the rough collision position of the ball. However, since this vibration is usually large, the hitting information is not lost even if it is suppressed to some extent. Rather, it is easier for the player to feel out-of-plane secondary vibration and the hit feeling is improved. Further, by suppressing this vibration, there is an advantage that the burden on the athlete's body can be reduced.

<Out-of-plane secondary vibration>
Even when the ball collides near the sweet spot on the racket, the magnitude of the vibration generated by the slight difference in the way of collision changes slightly. This is an important vibration because it allows you to know detailed position information on where and at what angle.

<In-plane primary vibration and in-plane secondary vibration>
Since the same vibration occurs regardless of where the ball collides near the sweet spot of the racket, it is a vibration that is not very important for transmitting hit ball information. Further, particularly in the soft tennis racket and the hard tennis racket, these frequencies are close to the frequencies of the out-of-plane primary vibration and the out-of-plane secondary vibration which are important for transmitting hit ball information. The in-plane secondary vibration is felt as these “noise”.

  Based on the above, by “suppressing out-of-plane primary vibration to some extent, suppressing out-of-plane secondary vibration as much as possible, and suppressing in-plane primary vibration and in-plane secondary vibration as much as possible”, The present inventors have found that "good" rackets can be produced.

  Specifically, in order to "suppress out-of-plane primary vibration to some extent, suppress out-of-plane secondary vibration as much as possible, and suppress in-plane primary vibration and in-plane secondary vibration as much as possible", A vibration absorbing material was disposed at a location near the antinodes of the in-plane primary vibration and the in-plane secondary vibration and at a node of the out-of-plane secondary vibration (or as close to the node as possible). Further, it is more preferable if a vibration absorbing material is disposed in a place where out-of-plane primary vibration of the frame can be suppressed to some extent.

  In the hard tennis racket and the soft tennis racket, the places of in-plane and out-of-plane vibrations are the following places when the face position is viewed as a clock and the top position is 12 o'clock (see FIGS. 13A and 13B).

  From the above, in a racket having a frame having a hollow portion, when the top position is set to 12:00 when the face surface is viewed as a clock, the vibration absorbing material is disposed in the hollow portion at the position of 12:00, 4 o'clock and 8 o'clock. The racket of the present invention can suppress out-of-plane primary vibration, and can suppress in-plane primary vibration and in-plane secondary vibration without suppressing out-of-plane secondary vibration. The 4 o'clock and 8 o'clock positions correspond to antinodes of the in-plane primary vibration to be suppressed, and correspond to nodes of the out-of-plane secondary vibration that are not to be suppressed. The 12 o'clock position corresponds to the antinode of the in-plane secondary vibration to be suppressed. As a result, the unpleasant vibration generated at the time of hitting is reduced, and the vibration useful as the hitting ball information is left, so that the feeling of hitting is good. Further, in the racket of the present invention, the vibration absorbing material is partially disposed only at a necessary portion of the frame. Accordingly, the increase in weight is small compared to a racket having a frame having a hollow portion where no vibration absorbing material is disposed. Furthermore, in the racket according to the present invention, the vibration absorbing material is disposed only in the hollow portion of the frame where necessary. Therefore, the racket of the present invention does not increase the air resistance as compared with a racket having a frame having a hollow portion in which no vibration absorbing material is arranged. Therefore, the racket of the present invention is less necessary to reduce the amount of material of the frame itself than the racket in which the vibration absorbing material is disposed on the entire frame, and as a result, the decrease in frame strength can be reduced. Moreover, the racket of this invention reduces the burden resulting from the vibration which a player receives compared with the racket in which the vibration-absorbing material is not inserted at all.

  Furthermore, it is preferable that the vibration absorbing material is not disposed in the hollow portion at the 3 o'clock and 9 o'clock positions when the top position is 12 o'clock when the face surface is viewed as a clock. These 3 o'clock and 9 o'clock positions correspond to antinodes of out-of-plane secondary vibration that you do not want to suppress vibration, and placing a vibration absorber at this position suppresses out-of-plane secondary vibration that becomes important hitting ball information It is because it will do.

  Further, the vibration absorbing material may be further disposed in the hollow portion at the 2 o'clock and 10 o'clock positions. Thus, when arrange | positioning in the said hollow part of the position of 12:00, 4 o'clock, 8 o'clock, 2 o'clock, and 10 o'clock, the in-plane primary vibration can be further suppressed.

  The racket of the present invention may be a tennis racket (hard or soft) or a badminton racket.

In the racket of the present invention, the vibration absorbing material is preferably a foamed resin or a synthetic rubber. This is because the foamed resin is light in weight, and as a result, the weight increase of the racket of the present invention can be suppressed. Moreover, if it is foamed resin, it is because it is easy to arrange | position in the hollow part of a flame | frame. The raw material resin for the foamed resin is preferably one or more resins selected from the group consisting of ethylene-vinyl acetate copolymer resin (EVA), polyurethane, polyvinyl chloride, polyolefin and polyester. The raw material resin for the foamed resin is more preferably an ethylene-vinyl acetate copolymer resin (EVA) and polyurethane because it has good adhesion to the material of the frame and can change the hardness of the resin over a wide range. . These raw material resins can be suitably selected appropriately according to the type of vibration to be suppressed, the type of racket, and the shape of the racket. When the vibration absorbing material is a foamed resin, the specific gravity of the foamed resin disposed in the hollow portion is, for example, 0.1 to 1.0. This specific gravity can be obtained from the following equation.

  In the racket of the present invention, the total length of the portions where the vibration absorbing material is disposed is preferably 5 to 40% of the length having the hollow portion of the frame. This is because the desired vibration suppressing effect can be sufficiently obtained when this ratio is 5% or more. Further, when this ratio is 40% or less, a desired vibration suppressing effect can be obtained without suppressing the out-of-plane secondary vibration that is not desired to be suppressed, and the weight increase of the entire racket is not significant. . Specifically, when the racket of the present invention is a tennis racket, the total length of the portion where the vibration absorbing material is disposed is more preferably 10 to 35% of the length having the hollow portion of the frame. When the racket of the present invention is a badminton racket, the total length of the portion where the vibration absorbing material is disposed is more preferably 15 to 35% of the length having the hollow portion of the frame. In the case of a tennis racket, the length of the frame having the hollow portion is a length obtained by removing the yoke portion from the total of the face portion, the shaft portion, and the grip portion (in FIG. 1B, the hatched portion is the hollow portion). In the case of a badminton racket, it means the length of the entire face part (in FIG. 1C, the hatched part is a hollow part).

  In the racket of the present invention, it is preferable that the vibration absorbing material is disposed at a predetermined position in 50% or more, preferably 100% of the entire cross section of the hollow portion of the frame. This is because if the vibration absorbing material is arranged in 50% or more of the entire cross-sectional area, a vibration suppressing effect can be sufficiently obtained and the peeling from the arranged position is difficult.

  In the racket of the present invention, it is preferable that the amount and position of the vibration absorbing material are equal on the left and right in terms of the balance of the frame. For example, the center of the arrangement position of the vibration absorbing material arranged at the 12 o'clock position is preferably the 12 o'clock point. About the center of the arrangement position of the vibration absorbing material arranged at the 4 o'clock and 8 o'clock positions, it is preferable that the vibration absorbing material is not arranged near the 3 o'clock and 9 o'clock positions. The center may be slightly shifted to the 5 o'clock side at 4 o'clock and to the 8 o'clock side at 9 o'clock, as long as the entire frame is equal to the left and right.

  In the case of a tennis racket, the amount of the vibration absorbing material is preferably 4 to 15 g, more preferably 5 to 10 g. This is because when the amount of the vibration absorbing material is less than 4 g, the effect of improving the hit feeling is low, and when it exceeds 15 g, it is difficult to obtain hit information. The amount of the vibration absorbing material is preferably 1 to 6 g, more preferably 2 to 4 g in the case of a badminton racket. This is because when the amount of the vibration absorbing material is less than 1 g, the effect of improving the hit feeling is low, and when it exceeds 6 g, it is difficult to obtain hit information.

  The frame of the racket of the present invention is made of, for example, a fiber reinforced resin. Specifically, the frame having the hollow portion of the racket of the present invention is preferably formed from a fiber reinforced prepreg laminate made of a hollow pipe. Moreover, what was manufactured by the other well-known method is also used for the flame | frame which has a hollow part in the racket of this invention. Examples of the fibers of the fiber reinforced resin include carbon (carbon) fibers, aramid fibers, silicon carbide fibers, alumina fibers, glass fibers, and polyarylate fibers. Since it is light and has high strength, carbon fiber is preferably used as the fiber of the fiber reinforced resin. Examples of the resin of the fiber reinforced resin include a thermoplastic resin and a thermosetting resin, and a thermosetting epoxy resin is preferable. Moreover, there is no limitation in particular about the shape and arrangement | sequence of fiber reinforced resin.

  FIG. 1A shows a schematic diagram of an example of a racket (tennis racket) of the present invention. In FIG. 1A, 101 indicates a face, 102 indicates a shaft, 103 indicates a yoke, and 104 indicates a grip. In FIG. 1A, assuming that the top portion of the frame is 12 o'clock, the numbers from 1 to 12 indicate positions from 1 o'clock to 12 o'clock. In FIG. 1A, in the racket of the present invention, foamed resins A1, A2 and A3 are arranged in the hollow portions at the 12 o'clock, 4 o'clock and 8 o'clock positions, but other portions are not arranged (hollow Leave). In FIG. 1, the hollow portion of the frame is a portion obtained by removing the yoke 103 from the total of the face 101, the shaft 102 and the grip 104.

The racket of the present invention can be manufactured, for example, as follows.
<Tennis racket>
First, a short nylon tube is prepared, and a foam resin material resin (when the vibration absorbing material is a foam resin) is inserted therein. Thereafter, the end of the nylon tube is closed to obtain a nylon tube in which a raw material resin of foamed resin is enclosed. In the middle of the carbon racquet manufacturing method that is usually used, when the carbon prepreg sheet is laid up, a nylon tube in which the foamed resin raw material resin is sealed on the outside of the pressurized nylon tube is attached to a predetermined position with a double-sided tape. Thereafter, lay-up is performed as usual, fitted into a racket mold, heated and pressurized. At this time, in consideration of the foaming temperature of the raw material resin, the heating temperature and pressure conditions at which foaming proceeds relatively slowly are selected. At a predetermined position of the hollow frame formed by heating and pressurization, the raw material resin is foamed to form a foamed resin (vibration absorber), and the racket of the present invention can be obtained.

  Alternatively, a racket having a frame having a hollow part is prepared by a normal method, and a desired amount of a foamed resin raw material resin is injected into a predetermined position from an opening of the hollow part or a grommet hole, and then heated to be a raw material The resin can be foamed to form a foamed resin (vibration absorber), and the racket of the present invention can also be obtained.

<For badminton>
Prepare multiple sheets of foam resin raw resin. During the carbon racquet manufacturing method that is normally used, when the carbon prepreg sheet is laid up, the raw material resin sheet is stuck to a predetermined position with a double-sided tape on the outside of the pressurized nylon tube. Thereafter, lay-up is performed as usual, fitted into a racket mold, heated and pressurized. At this time, in consideration of the foaming temperature of the raw material resin, the heating temperature and pressure conditions at which foaming proceeds relatively slowly are selected. At a predetermined position of the hollow frame formed by heating and pressurization, the raw material resin is foamed to form a foamed resin (vibration absorber), and the racket of the present invention can be obtained.

  In either case, the raw material resin is foamed in the hollow portion. Foaming in the hollow part tends to be suppressed as compared with foaming in the open place. Therefore, when manufacturing the racket of the present invention, it is preferable to fully study the amount of the raw resin and the specific gravity of the foamed resin.

  Further, in the racket of the present invention, the vibration absorbing material is arranged at the position of 12:00, 4 o'clock and 8 o'clock, but when the vibration absorbing material is a foamed resin, for example, at the position of 12:00, A sheet of foamed resin raw material is pasted on the outside, and at 4 o'clock and 8 o'clock, a different foamed resin is used at each position, such as a nylon tube sealed with a foamed resin raw material resin outside the pressurized nylon tube. Arrangement of raw materials may be performed.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the following examples.

An example in which powdered foam EVA is placed on a tennis racket (face area 97 inch @ ² ) at the 12 o'clock, 4 o'clock and 8 o'clock positions. (When the nylon tube for pressurization is not removed)
First, three nylon tubes having a length of 8 cm were prepared. Inside the nylon tube, powdered EVA was measured by a syringe (2 g) and inserted. The end of the nylon tube was closed to obtain a nylon tube in which a raw material resin of foamed resin was enclosed.

  During the production of a carbon racquet that is usually used, a nylon tube in which the foamed resin raw material resin was sealed on the outside of the pressurizing nylon tube was attached with a thin double-sided tape when the carbon prepreg sheet was laid up. Specifically, the nylon tube in which the raw material resin of the foamed resin is enclosed so that the center of the racket face (12 o'clock) is 35 cm along the face (positions at 4 o'clock and 8 o'clock). Was affixed to a carbon prepreg with double-sided tape. Further, a nylon tube in which the foamed resin material resin was sealed was attached with a thin double-sided tape so that the face top (position at 12 o'clock) was at the center.

Then, lay-up as usual, fit in racket mold, heat and press for 15 minutes or more at 160 ° C and 6 kgf / cm ² , foam resin is placed in the hollow at 12 o'clock, 4 o'clock and 8 o'clock Thus, a tennis racket having a carbon fiber reinforced epoxy resin frame having a hollow portion was obtained. The specific gravity of the foamed resin disposed in the hollow portion was 0.16. The length of the foamed resin placed at the 12 o'clock position of the frame is 8.0 cm, the length of the foamed resin placed at the 4 o'clock position is 8.0 cm, and the length of the foamed resin placed at the 8 o'clock position The total length of the portion where the vibration absorbing material is disposed is the length having the hollow portion of the frame (the length excluding the yoke portion from the total of the face portion, shaft portion and grip portion). Of 15.4%. Also, the foam resin placed at the 12 o'clock position of the frame is 100% of the entire cross section of the hollow part, and the foam resin placed at the 4 o'clock position is 100% of the entire cross section of the hollow part at the 8 o'clock position. The foamed resin placed in the area occupied 100% of the entire cross section of the hollow portion. In addition, the foam resin placed at the 12 o'clock position of the frame is arranged around the point of about 12:00, and the foam resin placed at the 4 o'clock position is arranged around the point of about 4 o'clock, The foamed resin placed at the 8 o'clock position was placed around the 8 o'clock point. Accordingly, the foamed resin as a whole of the frame was arranged substantially equally on the left and right with the 12 o'clock position as the center. Further, no foamed resin was disposed at the 3 o'clock and 9 o'clock positions of the frame. In normal carbon racket production, heating and pressurization gradually increase the temperature and pressure, and finally 160 ° C. and 6 kgf / cm ² continue for 15 minutes or more, but EVA used here is 160 ° C. and 6 kgf. Foaming was completed relatively slowly near / cm ² . By performing such heating and pressurization, the pressure reached the tip of the racket sufficiently, the racket was completely molded, and EVA foaming was fully completed.

<Comparative Example 1>
A tennis racket having a frame having a hollow part in which the foamed resin is not disposed in the hollow part is obtained in the same manner as in Example 1 except that the nylon tube in which the raw material resin of the foamed resin is sealed is not attached. It was. The tennis racket of Comparative Example 1 was adjusted in layup so that the weight and balance point of the tennis racket of Example 1 matched.

An example in which sheet-like EVA is placed on a badminton racket (face area of 56 inch @ ² ) at the 12 o'clock, 4 o'clock and 8 o'clock positions.
First, six EVA sheets having a length of 60 mm, a width of 16 mm, and a thickness of 1 mm were prepared (total:
3.6g).
During the production of the carbon racquet that is usually used, the EVA sheet was attached to a predetermined position outside the nylon tube for pressurization when the carbon prepreg sheet was laid up. From the top of the racket face (12 o'clock), place the EVA sheet on two sheets and attach it to the carbon prepreg with a thin double-sided tape so that it is centered at 25 cm along the face (positions at 4 o'clock and 8 o'clock) I attached. Further, the EVA sheet was overlapped on two sheets so that the face top (12 o'clock) was the center, and was attached to the carbon prepreg with a thin double-sided tape.

Then, lay-up as usual, fit in racket mold, heat and press for 15 minutes or more at 160 ° C and 6 kgf / cm ² , foam resin is placed in the hollow at 12 o'clock, 4 o'clock and 8 o'clock Thus, a badminton racket having a carbon fiber reinforced epoxy resin frame having a hollow portion was obtained. The specific gravity of the foamed resin disposed in the hollow portion was 1.0. The length of the foamed resin placed at the 12 o'clock position of the frame is 6.0 cm, the length of the foamed resin placed at the 4 o'clock position is 6.0 cm, and the length of the foamed resin placed at the 8 o'clock position The total length of the portion where the vibration absorbing material is disposed was 26.0% of the length having the hollow portion of the frame (the entire length of the face portion). Also, the foam resin placed at the 12 o'clock position of the frame is 100% of the entire cross section of the hollow part, and the foam resin placed at the 4 o'clock position is 100% of the entire cross section of the hollow part at the 8 o'clock position. The foamed resin placed in the area occupied 100% of the entire cross section of the hollow portion. In addition, the foam resin placed at the 12 o'clock position of the frame is arranged around the point of about 12:00, and the foam resin placed at the 4 o'clock position is arranged around the point of about 4 o'clock, The foamed resin placed at the 8 o'clock position was placed around the 8 o'clock point. Accordingly, the foamed resin as a whole of the frame was arranged substantially equally on the left and right with the 12 o'clock position as the center. Further, no foamed resin was disposed at the 3 o'clock and 9 o'clock positions of the frame. In normal carbon racquet manufacturing, heating and pressurization eventually continue at 160 ° C. and 6 kgf / cm ² for 15 minutes or more, but EVA used here foams relatively slowly at 160 ° C. and 6 kgf / cm ^2. It was to be completed. By performing such heating and pressurization, the pressure reached the tip of the racket sufficiently, the racket was completely molded, and EVA foaming was fully completed.

<Comparative example 2>
A badminton racket having a frame having a hollow part in which the foamed resin is not disposed in the hollow part was obtained in the same manner as in Example 2 except that the EVA sheet was not attached. In addition, the layup of the tennis racket of Comparative Example 2 was adjusted so that the weight and the balance point coincided with the tennis racket of Example 2.

  The vibration evaluation of the rackets obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was analyzed. The vibration analysis evaluation was performed as follows.

<Vibration evaluation analysis>
A gut was pulled up on the racket of each example and comparative example, and the grip portion of the racket was suspended with a string (see FIG. 2). In FIG. 2, 1 is a racket, 2 is an impact hammer, 3 is an amplifier, and 4 is an FFT (Fast Fourier Transform) analyzer.

(Measurement of Bode diagram of out-of-plane vibration)
In the case of a tennis racket, an acceleration pickup is attached to the acceleration sensor mounting position 1 shown in FIG. 3A, and in the case of a badminton racket at the acceleration sensor mounting position 1 shown in FIG. 3B. ). The response function measured with the force pickup meter attached to the impact hammer and the response function measured with the accelerometer pickup meter were input to the FFT analyzer 4 via the amplifier 3 and analyzed. In the rackets of the respective examples and comparative examples, the results obtained by shaking and averaging five times each were analyzed, and a Bode diagram was created. The obtained out-of-plane vibration board diagram of Comparative Example 1 is shown in FIG. 5, the out-of-plane vibration board diagram of Example 1 is shown in FIG. 6, the out-of-plane vibration board diagram of Comparative Example 2 is shown in FIG. The out-of-plane vibration board diagram of 2 is shown in FIG. In each figure, the vertical axis represents compliance [m / N], and the horizontal axis represents frequency [Hz].

(Measurement of Bode diagram of in-plane vibration)
In the tennis racket, the accelerometer is attached in parallel to the racket surface at the acceleration sensor attachment position 2 shown in FIG. 4A, and in the badminton racket in the acceleration sensor attachment position 2 shown in FIG. 4B. Shake (blow point 2). The response function measured with the force pickup meter attached to the impact hammer and the response function measured with the accelerometer pickup meter were input to the FFT (Fast Fourier Transform) analyzer 4 via the amplifier 3 and analyzed. In the rackets of the respective examples and comparative examples, the results obtained by shaking and averaging five times each were analyzed, and a Bode diagram was created. The obtained in-plane vibration board diagram of Comparative Example 1 is shown in FIG. 7, the in-plane vibration board diagram of Example 1 is shown in FIG. 8, the in-plane vibration board diagram of Comparative Example 2 is shown in FIG. The in-plane vibration board diagram of 2 is shown in FIG. In each figure, the vertical axis represents compliance [m / N], and the horizontal axis represents frequency [Hz].

  Comparing Example 1 (FIG. 6) and Comparative Example 1 (FIG. 5) for out-of-plane primary vibrations, it can be seen that although the amplitude is almost unchanged, the slope of the mountain is slightly gentler and the attenuation rate is increased. Comparing Example 1 (FIG. 6) and Comparative Example 1 (FIG. 5) for out-of-plane secondary vibration, it can be seen that the amplitude is slightly reduced, and the attenuation rate is hardly changed.

  Comparing the in-plane primary vibration between Example 1 (FIG. 8) and Comparative Example 1 (FIG. 7), it can be seen that the amplitude decreases, the slope of the mountain becomes gentle, and the attenuation rate increases. Comparing Example 1 (FIG. 8) and Comparative Example 1 (FIG. 7) for in-plane secondary vibration, it can be seen that the amplitude is reduced and the attenuation factor is increased.

  From the above results, it can be seen that the in-plane vibration is strongly suppressed without excessively suppressing out-of-plane vibration in the racket of the present invention as compared with the racket of the comparative example.

  Comparing Example 2 (FIG. 10) and Comparative Example 2 (FIG. 9) for out-of-plane primary vibration, it can be seen that there is almost no change in both amplitude and attenuation rate. Comparing Example 2 (FIG. 10) and Comparative Example 2 (FIG. 9) for out-of-plane secondary vibration, it can be seen that there is almost no change in both amplitude and attenuation rate.

  Comparing Example 2 (FIG. 12) and Comparative Example 2 (FIG. 11) for in-plane primary vibrations, it can be seen that the amplitude is very small, the slope of the mountain is gentle, and the damping rate is large. That is, the in-plane primary vibration is very strongly suppressed. Comparing Example 2 (FIG. 12) and Comparative Example 2 (FIG. 11) for in-plane secondary vibration, it can be seen that the amplitude is reduced and the attenuation factor is increased.

  From the above results, it can be seen that the in-plane vibration is strongly suppressed without excessively suppressing out-of-plane vibration in the racket of the present invention as compared with the racket of the comparative example.

  Table 2 shows the vibration evaluation and basic specifications of the rackets of Examples 1 and 2 and Comparative Examples 1 and 2 obtained as described above.

  The racket test hit evaluations obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed. The test hit evaluation was performed as follows.

<Trial evaluation analysis>
(Tennis racket trial evaluation)
The tennis string obtained in Example 1 and Comparative Example 1 was stretched with a polyester string (trade name “Polybreak 17”, manufactured by Gossen Co., Ltd.) at 45 lbs (20.512 kg). This tennis racket was painted black, and five people tried it out without mentioning the differences in the racket structure. Specifically, in the trial hit, the tennis racket of Example 1 and the tennis racket of Comparative Example 1 were alternately changed over and the difference in the shot feeling was confirmed while continuing the rally. The test hit evaluation is an evaluation of the shot feeling, that is, “which racket is easy to feel the ball hitting feel”. Note that another racket in which a polyurethane resin is disposed in the hollow portion of the entire frame was also evaluated for trial hitting. The obtained results are shown in Table 3.

<Trial evaluation analysis>
(Badminton racket trial evaluation)
Nylon strings (trade name “R4X TSUYOSHI”, manufactured by Gohsen Co., Ltd.) were stretched on the badminton racket obtained in Example 2 and Comparative Example 2 at 27 lbs (12.247 kg). The badminton racket was painted black, and 38 people tried it without mentioning the differences in the racket structure. Specifically, in the trial hit, the badminton racket of Example 2 and the badminton racket of Comparative Example 2 were alternately changed, and the difference in the shot feeling was confirmed while continuing the basic practice and the game format such as clear, smash, and drive. I got it. The test hit evaluation is an evaluation of the hit feeling, that is, “which racket is easy to feel the feel of the shuttle hit”.

  Of the 38 test hitters, 34 felt that the racket of Example 2 had a better feel at impact than the racket of Comparative Example 2. The remaining four did not feel any difference in either racket. Moreover, about the racket of Example 2, there were also opinions that it was easier to feel the feel of the shuttle hitting than the racket of Comparative Example 2, the weight of the shuttle was easier to feel, and the shuttle feels sinking than expected when smashing.

  The racket of the present invention is also useful for a high-level player. Further, by using the racket of the present invention, it is easy to obtain hitting information necessary for improving the playing technique, and the vibration burden on the player is small, so it is useful for beginners such as children and women.

101 face 102 shaft 103 yoke 104 grip 1 racket 2 impact hammer 3 amplifier 4 FFT analyzer

Claims (8)

  In a racket having a frame having a hollow part, the vibration absorbing material is arranged in the hollow part at the 12 o'clock, 4 o'clock and 8 o'clock positions when the top position is 12 o'clock when the face surface is viewed as a clock. And racket.   The racket according to claim 1, wherein the vibration absorbing material is a foamed resin.   The racket according to claim 1 or 2, wherein the vibration absorbing material is not disposed in the hollow portion at the 3 o'clock and 9 o'clock positions.   The racket according to any one of claims 1 to 3, wherein the vibration absorber is further disposed in the hollow portion at the 2 o'clock and 10 o'clock positions.   The racket according to any one of claims 1 to 4, wherein a total length of a portion where the vibration absorbing material is disposed is 5 to 40% of a length having a hollow portion of the frame.   The resin component of the foamed resin is one or more resins selected from the group consisting of ethylene-vinyl acetate copolymer resin, polyurethane, polyvinyl chloride, polyolefin, and polyester. racket.   The racket according to any one of claims 1 to 6, wherein the racket is a tennis racket, and a weight of the vibration absorber disposed in the hollow portion of the frame is 4g to 15g.   The racket according to any one of claims 1 to 6, wherein the racket is a badminton racket, and a weight of the vibration absorbing material disposed in the hollow portion of the frame is 1g to 6g.

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