JP7524936B2 - racket - Google Patents

Description

The present invention relates to a racket used in tennis and other sports.

A tennis racket has a frame and strings. In the past, the strings were threaded directly through holes formed in the frame. In recent tennis rackets, the strings are threaded through holes via grommets. A proposal regarding the shape of the grommet is disclosed in JP-A-5-345052. This grommet can contribute to the hitting feel of the tennis racket.

Japanese Patent Application Publication No. 5-345052

As tennis rackets have become more powerful, drive shots have become more common in tennis in recent years. Drive shots impart overspin to the tennis ball. Players want tennis rackets that make it easier to apply spin.

The objective of the present invention is to provide a racket with excellent spin performance.

The racket according to the present invention comprises:
(1) frame,
(2) a grommet attached to the frame and having a plurality of tubular portions;
and (3) a string forming a face. Each of the tubular portions has a through hole through which the string passes. These tubular portions include a parallel movement tubular portion that allows the string to move mainly in a direction parallel to the face, and a vertical movement tubular portion that allows the string to move mainly in a direction perpendicular to the face.

Preferably, each translational tube is adjacent to at least one vertically moving tube. Preferably, each vertically moving tube is adjacent to at least one translational tube.

Preferably, the translation cylinder has a through hole whose inside dimension in a direction parallel to the face is larger than the inside dimension in a direction perpendicular to the face. Preferably, the cross-sectional shape of the through hole of the translation cylinder is an ellipse or an oval. Preferably, the ratio (L1/L2) of the inside dimension L1 in a direction parallel to the face to the inside dimension L2 in a direction perpendicular to the face of the through hole of the translation cylinder is 1.3 or more. Preferably, the ratio (L1/D) of the inside dimension L1 in a direction parallel to the face to the string diameter D of the through hole of the translation cylinder is 1.5 or more.

The through hole of the translation cylinder may have a base opening, a side wall, and a tip opening. Preferably, in this translation cylinder, the string abuts against the side wall from the base opening to the tip opening. Preferably, in the translation cylinder, the string abuts against a widthwise inner wall surface of the side wall.

Preferably, the translation cylinder has a through hole with a congruent cross-sectional shape from the base opening to the tip opening.

Preferably, a vertical string is passed through the parallel movement tube and another vertical string is passed through the vertical movement tube.

Preferably, the parallel movement tube and the vertical movement tube are positioned near the top of the frame.

When the racket of the present invention impacts the ball, the string threaded through the translation tube undergoes a large deformation in a direction parallel to the face. The string then returns to its original shape. This deformation and restoration imparts high-speed spin to the ball.

When the racket of the present invention impacts the ball, the string passed through the vertical movement tube portion is greatly deformed in a direction perpendicular to the face. On the other hand, the string passed through the parallel movement tube portion is only slightly deformed in a direction perpendicular to the face. Therefore, a large pressure is applied to the ball from the string passed through the parallel movement tube portion. This pressure imparts high-speed spin to the ball.

The racket of the present invention has excellent spin performance.

FIG. 1 is a front view showing a racket according to an embodiment of the present invention. FIG. 2 is an enlarged view of a portion of the racket shown in FIG. FIG. 3 is a partially exploded view of the racket of FIG. FIG. 4 is an enlarged view of a portion of the grommet of the tennis racket of FIG. 5(a) is a front view showing a portion of the grommet in FIG. 4, FIG. 5(b) is a cross-sectional view taken along line B-B in FIG. 5(a), and FIG. 5(c) is a cross-sectional view taken along line CC in FIG. 5(a). 6(a) is a front view showing a portion of the grommet in FIG. 4, FIG. 6(b) is a cross-sectional view taken along line B-B in FIG. 5(a), and FIG. 6(c) is a cross-sectional view taken along line CC in FIG. 5(a). 7(a) is a front view showing the grommet of FIG. 5 together with a string, and FIG. 7(b) is a cross-sectional view taken along line BB of FIG. 7(a). 8(a) is a front view showing the grommet of FIG. 6 together with a string, and FIG. 8(b) is a cross-sectional view taken along line BB of FIG. 8(a). FIG. 9 is an enlarged view showing the top portion and vicinity of the racket shown in FIG. FIG. 10 is a front view of the racket of FIG. 1 shown together with a tennis ball. FIG. 11 is a front view showing the top vicinity of FIG. 12 is a cross-sectional view showing the first cylindrical portion of the racket of FIG. 1. FIG. FIG. 13 is a bottom view of the translation tube of FIG. 5 with a string. FIG. 14 is a bottom view of the vertical movement tube of FIG. 6 together with the string. FIG. 15 is a bottom view of a translation tube of a tennis racket according to another embodiment of the present invention, together with a string. FIG. 16 is a bottom view of a translation tube of a tennis racket according to still another embodiment of the present invention, shown together with a string. FIG. 17(a) is a front view showing a parallel movement tube portion of a tennis racket according to yet another embodiment of the present invention, FIG. 17(b) is a cross-sectional view taken along line B-B in FIG. 17(a), and FIG. 17(c) is a cross-sectional view taken along line CC in FIG. 17(a).

The present invention will now be described in detail based on a preferred embodiment, with reference to the drawings as appropriate.

First Embodiment
1-3 show a tennis racket 2. This tennis racket 2 has a frame 4, a grip 6, grommets 8, and strings 10. This tennis racket 2 can be used for hard tennis. In Figures 1 and 2, an arrow X indicates the width direction of the tennis racket 2, and an arrow Y indicates the axial direction of the tennis racket 2.

The frame 4 has a head 12, two throats 14, and a shaft 16. The head 12 forms the outline of the face 17 (described in detail later). The front shape of the head 12 is approximately elliptical. The long axis direction of the ellipse coincides with the axial direction Y of the tennis racket 2. The short axis direction of the ellipse coincides with the width direction X of the tennis racket 2. One end of each throat 14 is continuous with the head 12. This throat 14 merges with the other throat 14 near the other end. The throat 14 extends from the head 12 to the shaft 16. The shaft 16 extends from the point where the two throats 14 merge. The shaft 16 is formed continuously and integrally with the throat 14. The portion of the head 12 sandwiched between the two throats 14 is the yoke 18.

The frame 4 is made of a pipe. In other words, the frame 4 is hollow. The material of the pipe is fiber-reinforced resin. The matrix resin of the fiber-reinforced resin is a thermosetting resin. A typical thermosetting resin is an epoxy resin. A typical fiber of the fiber-reinforced resin is a carbon fiber. The fiber is a long fiber.

The grip 6 is formed by a tape wrapped around the shaft 16. The grip 6 prevents slippage between the player's hand and the tennis racket 2 when the tennis racket 2 is swung.

As shown in FIG. 3, the tennis racket 2 has a first grommet 8a, two second grommets 8b, and a third grommet 8c. Each grommet 8 has a base 20 and a number of tubular portions 100. Each tubular portion 100 is integrally formed with the base 20. The grommet 8 is typically made of a synthetic resin that is softer than the frame 4.

As shown by arrow A1 in FIG. 3, the first grommet 8a is attached near the top of the head 12. With this attachment, each tubular portion 100 of the first grommet 8a passes through a hole (not shown) provided in the head 12. As shown by arrow A2 in FIG. 3, each second grommet 8b is attached to the side of the head 12. With this attachment, each tubular portion 100 of the second grommet 8b passes through a hole (not shown) provided in the head 12. As shown by arrow A3 in FIG. 3, the third grommet 8c is attached to the yoke 18. With this attachment, each tubular portion 100 of the third grommet 8c passes through a hole (not shown) provided in the head 12.

The strings 10 are strung around the head 12. The strings 10 are strung along the width direction X and the axial direction Y. The portions of the strings 10 that extend along the width direction X are called cross strings 10a. The portions of the strings 10 that extend along the axial direction Y are called longitudinal strings 10b. The multiple cross strings 10a and the multiple longitudinal strings 10b form a face 17 (see FIG. 1). The face 17 generally lies along the X-Y plane.

Figure 4 is an enlarged view showing a portion of the grommet 8 of the tennis racket 2 of Figure 3. As described above, the grommet 8 has a base 20 and a plurality of tubular portions 100. These tubular portions 100 include a parallel movement tubular portion 100a and a vertical movement tubular portion 100b. These tubular portions 100 may also include tubular portions 100 other than the parallel movement tubular portion 100a and the vertical movement tubular portion 100b.

Figure 5 (a) is a front view showing a part of the grommet 8 in Figure 4, Figure 5 (b) is a cross-sectional view taken along line B-B in Figure 5 (a), and Figure 5 (c) is a cross-sectional view taken along line C-C in Figure 5 (a). Figure 5 shows the parallel movement tube 100a. The parallel movement tube 100a has a through hole 24a. The through hole 24a has a base side opening 26a, a side wall 28a, and a tip side opening 30a. The cross-sectional shape of the through hole 24a is an ellipse. The through hole 24a has a congruent cross-sectional shape from the base side opening 26a to the tip side opening 30a. In this through hole 24a, the inner dimension in the direction parallel to the face 17 (the left-right direction in Figure 5 (a)) is larger than the inner dimension in the direction perpendicular to the face 17 (the up-down direction in Figure 5 (a)).

Figure 6(a) is a front view showing a part of the grommet 8 in Figure 4, Figure 6(b) is a cross-sectional view taken along line B-B in Figure 6(a), and Figure 6(c) is a cross-sectional view taken along line C-C in Figure 6(a). Figure 6 shows the vertical movement tube 100b. The vertical movement tube 100b has a through hole 24b. The through hole 24b has a base side opening 26b, a side wall 28b, and a tip side opening 30b. In this through hole 24b, the inner dimension in a direction parallel to the face 17 (left-right direction in Figure 6(a)) is constant from the base side opening 26b to the tip side opening 30b. The inner dimension in a direction perpendicular to the face 17 (up-down direction in Figure 6(a)) gradually increases from the base side opening 26b to the tip side opening 30b. The shape of the base side opening 26b is approximately circular. The tip opening 30b has an elliptical shape. The inside dimension of this tip opening 30b in a direction perpendicular to the face 17 is larger than the inside dimension in a direction parallel to the face 17.

7(a) is a front view of the grommet 8 of FIG. 5 together with the string 10, and FIG. 7(b) is a cross-sectional view taken along line B-B of FIG. 7(a). The string 10 is passed through the through hole 24a. The string 10 abuts against the side wall 28a from the base side opening 26a to the tip side opening 30a. The string 10 abuts against the left wall surface of the side wall 28a. Since the left-right inner dimension of the base side opening 26a is the same as the left-right inner dimension of the tip side opening 30a, the string 10 can abut against the side wall 28a from the base side opening 26a to the tip side opening 30a. As is clear from FIG. 7(a), the left-right inner dimension of the through hole 24 is sufficiently larger than the diameter of the string 10. Therefore, the string 10 can move to the right in the translation tube 100a. The string 10 can hardly move up and down in the translation tube 100a. In other words, the parallel movement tube portion 100a allows the string 10 to move primarily in a direction parallel to the face 17.

8(a) is a front view of the grommet 8 of FIG. 6 together with the string 10, and FIG. 8(b) is a cross-sectional view taken along line B-B of FIG. 8(a). The string 10 is passed through the through-hole 24b. The string 10 extends in a direction substantially coinciding with the axis of the through-hole 24b. As is clear from FIG. 8(a), the inner vertical dimension of the tip-side opening 30b is sufficiently larger than the diameter of the string 10. Therefore, the string 10 can move vertically in the vertical movement tube 100b. The string 10 can hardly move left and right in the vertical movement tube 100b. In other words, the vertical movement tube 100b allows the string 10 to move mainly in a direction perpendicular to the face 17.

In FIG. 2, the symbol CL indicates a center line. The tennis racket 2 has a shape symmetrical with respect to the center line CL. As shown in FIG. 2, the tennis racket 2 includes a first cylindrical portion 101, a second cylindrical portion 102, a third cylindrical portion 103, a fourth cylindrical portion 104, a fifth cylindrical portion 105, a sixth cylindrical portion 106, a seventh cylindrical portion 107, an eighth cylindrical portion 108, a ninth cylindrical portion 109, a tenth cylindrical portion 110, an eleventh cylindrical portion 111, a twelfth cylindrical portion 112, a thirteenth cylindrical portion 113, a fourteenth cylindrical portion 114, a fifteenth cylindrical portion 115, a sixteenth cylindrical portion 116, a seventeenth cylindrical portion 117, an eighteenth cylindrical portion 118, The tennis racket 2 has a nineteenth tube portion 119, a twentieth tube portion 120, a twenty-first tube portion 121, a twenty-second tube portion 122, a twenty-third tube portion 123, a twenty-fourth tube portion 124, a twenty-fifth tube portion 125, a twenty-sixth tube portion 126, a twenty-seventh tube portion 127, a twenty-eighth tube portion 128, a twenty-ninth tube portion 129, a thirty-tenth tube portion 130, a thirty-first tube portion 131, a thirty-second tube portion 132, a thirty-third tube portion 133, a thirty-fourth tube portion 134, and a thirty-fifth tube portion 135. Thirty-five tube portions 100 are shown in FIG. 2. As described above, the tennis racket 2 has a symmetrical shape with respect to the center line CL, so the number of tube portions 100 in this tennis racket 2 is 70.

As shown in FIG. 2, the vertical string 10b is passed through the first tube portion 101, the second tube portion 102, the third tube portion 103, the fourth tube portion 104, the fifth tube portion 105, the sixth tube portion 106, the seventh tube portion 107, the ninth tube portion 109, the twenty-seventh tube portion 127, the twenty-ninth tube portion 129, the thirty-tenth tube portion 130, the thirty-first tube portion 131, the thirty-second tube portion 132, the thirty-third tube portion 133, the thirty-fourth tube portion 134 and the thirty-fifth tube portion 135. The cross string 10a is passed through the eighth tube portion 108, the tenth tube portion 110, the eleventh tube portion 111, the twelfth tube portion 112, the thirteenth tube portion 113, the fourteenth tube portion 114, the fifteenth tube portion 115, the sixteenth tube portion 116, the seventeenth tube portion 117, the eighteenth tube portion 118, the nineteenth tube portion 119, the twentieth tube portion 120, the twenty-first tube portion 121, the twenty-second tube portion 122, the twenty-third tube portion 123, the twenty-fourth tube portion 124, the twenty-fifth tube portion 125, the twenty-sixth tube portion 126, and the twenty-eighth tube portion 128.

9 is an enlarged view showing the vicinity of the top of the tennis racket 2 in FIG. 1. In FIG. 9, the frame 4 and the cross string 10a are omitted. In FIG. 9, the base 20, the first tube portion 101, the second tube portion 102, the third tube portion 103, the fourth tube portion 104, and the fifth tube portion 105 are shown. In this embodiment, the first tube portion 101, the third tube portion 103, and the fifth tube portion 105 are vertical movement tube portions 100b. In each vertical movement tube portion 100b, the tip side opening 30b has a vertically long oval shape (see FIG. 6). The second tube portion 102 and the fourth tube portion 104 are parallel movement tube portions 100a. In each parallel movement tube portion 100a, the tip side opening 30a has a horizontally long oval shape (see FIG. 5). In this tennis racket 2, multiple parallel movement cylinders 100a and multiple vertical movement cylinders 100b are arranged alternately. Each parallel movement cylinder 100a is adjacent to at least one vertical movement cylinder 100b. Each vertical movement cylinder 100b is adjacent to at least one parallel movement cylinder 100a.

As shown in FIG. 9, in the second tubular section 102, the vertical string 10b abuts against the left (widthwise inner) wall surface of the side wall 28a of the through hole 24a. In the fourth tubular section 104, the vertical string 10b abuts against the left (widthwise inner) wall surface of the side wall 28a of the through hole 24a.

Fig. 10 shows a tennis ball 32 together with the tennis racket 2. Fig. 10 shows the moment of impact between the tennis racket 2 and the tennis ball 32. In Fig. 10, the tennis ball 32 collides with the face 17 below the center line CL (on the ground G side). In this state, the player swings the tennis racket 2 forward and upward. This swing is a drive swing.

This swing applies a force outward in the width direction to the vertical string 10b that is passed through the second tube portion 102. The inner width dimension of the through hole 24a of the second tube portion 102 is sufficiently large. Therefore, the vertical string 10b deforms without being hindered by the second tube portion 102 and moves outward in the width direction. Figure 11 shows the vertical string 10b after it has moved. The vertical string 10b then returns to its original shape. The vertical string 10b that is passed through the fourth tube portion 104 also deforms and returns to its original shape in the same way. The deformation and restoration of the vertical strings 10b achieves a long contact time between the tennis racket 2 and the tennis ball 32. The tennis ball 32 is hit with a high spin rate.

Figure 12 is a cross-sectional view showing the first tube portion 101 of the racket in Figure 1. In Figure 12, the arrow Z indicates the thickness direction of the tennis racket 2. As described above, in the first tube portion 101, the shape of the tip end opening 30b is a vertically long oval. Therefore, under pressure from the tennis ball 32, the vertical string 10b passed through the first tube portion 101 is deformed in the Z direction. The first tube portion 101 does not hinder this deformation. Therefore, the vertical string 10b can be sufficiently deformed in the Z direction. Figure 12 shows the vertical string 10b after deformation. After this, the vertical string 10b returns to its original shape. The vertical string 10b passed through the third tube portion 103 and the vertical string 10b passed through the fifth tube portion 105 can also be sufficiently deformed in the Z direction.

As described above, in the parallel movement tube portion 100a (the second tube portion 102 or the fourth tube portion 104), the shape of the tip end opening 30b is a horizontally long oval. Therefore, this parallel movement tube portion 100a inhibits the movement of the vertical string 10b in the Z direction. The vertical string 10b that is passed through the parallel movement tube portion 100a does not deform sufficiently in the Z direction.

When the tennis racket 2 and the tennis ball 32 impact, the vertical string 10b passed through the parallel movement tube 100a deforms little in the Z direction, while the vertical string 10b passed through the vertical movement tube 100b deforms little in the Z direction. In other words, only the vertical string 10b passed through the vertical movement tube 100b moves back significantly upon impact. The vertical string 10b passed through the parallel movement tube 100a does not move back significantly. The vertical string 10b passed through the parallel movement tube 100a fully bites into the tennis ball 32 at the time of impact. This bite causes the tennis ball 32 to spin at a high speed.

In FIG. 9, the arrow W2 indicates the width of the zone near the top. It is preferable that the parallel movement tube 100a and the vertical movement tube 100b are disposed in this zone near the top. This width W2 is preferably 15% to 60% of the half width W1 (see FIG. 1) of the tennis racket 2, and more preferably 20% to 50%.

In order to provide the tennis racket 2 with the performance intended by the designer, the tubular portion 100 may be formed so that the strings 10 abut against the outer wall surface in the width direction.

This tennis racket 2 has a parallel movement cylinder 100a and a vertical movement cylinder 100b near the top. The tennis racket 2 may have a parallel movement cylinder 100a and a vertical movement cylinder 100b on the yoke 18. The tennis racket 2 may have a parallel movement cylinder 100a and a vertical movement cylinder 100b on the side.

In this tennis racket 2, as described above, the second cylinder portion 102 and the fourth cylinder portion 104 are the parallel movement cylinder portions 100a. Since this tennis racket 2 has a shape symmetrical with respect to the center line CL, it has two second cylinder portions 102 and two fourth cylinder portions 104. Therefore, the total number N1 of the parallel movement cylinder portions 100a is four. The total number N1 is preferably 2 to 16, and more preferably 4 to 12.

As described above, in this tennis racket 2, the first tube portion 101, the third tube portion 103, and the fifth tube portion 105 are vertical movement tube portions 100b. This tennis racket 2 has a shape that is symmetrical with respect to the center line CL, and therefore has two first tube portions 101, two third tube portions 103, and two fifth tube portions 105. Therefore, the total number N2 of vertical movement tube portions 100b is six. The total number N2 is preferably 2 to 16, and more preferably 4 to 12.

Figure 13 is a bottom view of the parallel movement tube 100a of Figure 5 together with the string 10. Figure 13 shows the tip of the parallel movement tube 100a. The direction perpendicular to the paper surface in Figure 13 is the direction of the axis of the parallel movement tube 100a. The parallel movement tube 100a has a tip opening 30a. As mentioned above, the shape of the tip opening 30a is an oval.

In FIG. 13, arrow L1 indicates the inner dimension of the tip opening 30a in a direction parallel to the face 17. The inner dimension L1 is also the major axis of the ellipse. In FIG. 13, arrow L2 indicates the inner dimension of the tip opening 30a in a direction perpendicular to the face 17. The inner dimension L2 is also the minor axis of the ellipse. From the viewpoint that the string 10 is easily deformed in a direction parallel to the face 17 and is difficult to deform in a direction perpendicular to the face 17, the ratio (L1/L2) is preferably 1.3 or more, and particularly preferably 1.5 or more. The ratio (L1/L2) is preferably 4.0 or less.

In FIG. 13, the arrow D indicates the diameter of the string 10. From the viewpoint of allowing the string 10 to easily deform in a direction parallel to the face 17, the ratio (L1/D) is preferably 1.5 or more, and more preferably 1.8 or more. The ratio (L1/D) is preferably 4.5 or less.

Figure 14 is a bottom view of the vertical movement tube 100b of Figure 6 together with the string 10. Figure 14 shows the tip of the vertical movement tube 100b. The direction perpendicular to the paper surface in Figure 14 is the direction of the axis of the vertical movement tube 100b. The vertical movement tube 100b has a tip opening 30b. As mentioned above, the shape of the tip opening 30b is an oval.

In FIG. 14, arrow L3 indicates the inner dimension of the tip opening 30b in a direction parallel to the face 17. The inner dimension L3 is also the minor axis of the ellipse. In FIG. 14, arrow L4 indicates the inner dimension of the tip opening 30b in a direction perpendicular to the face 17. The inner dimension L4 is also the major axis of the ellipse. From the viewpoint of easily deforming the string 10 in a direction perpendicular to the face 17, the ratio (L4/L3) is preferably 1.3 or more, and particularly preferably 1.5 or more. The ratio (L4/L3) is preferably 4.0 or less.

In FIG. 14, the arrow D indicates the diameter of the string 10. From the viewpoint of allowing the string 10 to easily deform in a direction perpendicular to the face 17, the ratio (L4/D) is preferably 1.5 or more, and more preferably 1.8 or more. The ratio (L4/D) is preferably 4.5 or less.

Second Embodiment
15 is a bottom view showing the translation cylinder 34 of a tennis racket according to another embodiment of the present invention together with the string 10. The structure of this tennis racket other than the translation cylinder 34 is the same as that of the tennis racket 2 shown in FIG.

The translation cylinder 34 has a through hole. This through hole has a base side opening, a side wall, and a tip side opening 36. The cross-sectional shape of the through hole is constant from the base side opening to the tip side opening 36. As shown in FIG. 15, the shape of the tip side opening 36 is an ellipse. In FIG. 15, the arrow L1 indicates the inner dimension of the tip side opening 36 in a direction parallel to the face. The inner dimension L1 is also the major axis of the ellipse. In FIG. 15, the arrow L2 indicates the inner dimension of the tip side opening 36 in a direction perpendicular to the face. The inner dimension L2 is also the minor axis of the ellipse. From the viewpoint that the string 10 is easily deformed in a direction parallel to the face and is difficult to deform in a direction perpendicular to the face, the ratio (L1/L2) is preferably 1.3 or more, and particularly preferably 1.5 or more. The ratio (L1/L2) is preferably 4.0 or less.

In FIG. 15, the arrow D indicates the diameter of the string 10. From the viewpoint of allowing the string 10 to easily deform in a direction parallel to the face, the ratio (L1/D) is preferably 1.5 or more, and more preferably 1.8 or more. The ratio (L1/D) is preferably 4.5 or less.

Third Embodiment
16 is a bottom view showing a translation tube 38 of a tennis racket according to still another embodiment of the present invention together with a string 10. The structure of this tennis racket other than the translation tube 38 is the same as that of the tennis racket 2 shown in FIG.

The translation cylinder 38 has a through hole. This through hole has a base side opening, a side wall, and a tip side opening 40. The cross-sectional shape of the through hole is constant from the base side opening to the tip side opening 40. As shown in FIG. 16, the shape of the tip side opening 40 is an ellipse. The major axis of this ellipse is inclined with respect to the direction parallel to the face. In FIG. 16, the arrow L1 indicates the inner dimension of the tip side opening 40 in the direction parallel to the face. In FIG. 16, the arrow L2 indicates the inner dimension of the tip side opening 40 in the direction perpendicular to the face. From the viewpoint that the string 10 is easily deformed in the direction parallel to the face and is difficult to deform in the direction perpendicular to the face, the ratio (L1/L2) is preferably 1.3 or more, and particularly preferably 1.5 or more. The ratio (L1/L2) is preferably 4.0 or less.

In FIG. 16, the arrow D indicates the diameter of the string 10. From the viewpoint of allowing the string 10 to easily deform in a direction parallel to the face, the ratio (L1/D) is preferably 1.5 or more, and more preferably 1.8 or more. The ratio (L1/D) is preferably 4.5 or less.

(Fourth embodiment)
Fig. 17(a) is a front view showing a translation cylinder 42 of a tennis racket according to still another embodiment of the present invention, Fig. 17(b) is a cross-sectional view taken along line B-B in Fig. 17(a), and Fig. 17(c) is a cross-sectional view taken along line CC in Fig. 17(a). The structure of this tennis racket other than the translation cylinder 42 is the same as that of the tennis racket 2 shown in Fig. 1-14.

The parallel movement tube 42 has a through hole 44. The through hole 44 has a base side opening 46, a side wall 48, and a tip side opening 50. The base side opening 46 is circular in shape. The tip side opening 50 is oval in shape. The inner dimension of the through hole 44 in a direction parallel to the face gradually increases from the base side opening 46 toward the tip side opening 50. In this tennis racket, the vertical strings passed through the parallel movement tube 42 can easily deform in a direction parallel to the face.

(Still another embodiment)
The translation tube portion has a string guide that allows the string to move primarily in a direction parallel to the face.
Through holes of various shapes can be used. In each through hole, the ratio (L1/L2) of the inner dimension L1 in the direction parallel to the face to the inner dimension L2 in the direction perpendicular to the face of the tip side opening is preferably 1.3 or more, and more preferably 1.5 or more. The ratio (L1/L2) is preferably 4.0 or less.

The vertical movement tube may have through holes of various shapes that allow the string to move primarily in a direction perpendicular to the face. For each through hole, the ratio (L4/L3) of the inner dimension L4 of the tip opening in the direction perpendicular to the face to the inner dimension L3 in the direction parallel to the face is preferably 1.3 or more, and more preferably 1.5 or more. The ratio (L4/L3) is preferably 4.0 or less.

The racket of the present invention can be used in a variety of sports, including soft tennis, squash, and badminton.

2: Tennis racket 4: Frame 6: Grip 8: Grommet 8a: First grommet 8b: Second grommet 8c: Third grommet 10: String 10a: Horizontal string 10b: Vertical string 12: Head 20: Base 24a, 24b, 44: Through hole 26a, 26b, 46: Base side opening 28a, 28b, 48: Side wall 30a, 30b, 50: Tip side opening 34, 38, 42: Cylindrical portion 100, 101-135, 100a, 100b: Cylindrical portion

Claims (13)

The golf club includes a frame, a grommet attached to the frame and having a plurality of tubular portions, and a string forming a face,
Each of the cylindrical portions has a through hole through which the string is passed,
the tube portions include a parallel movement tube portion that allows movement of the string in a direction parallel to the face, and a vertical movement tube portion that allows movement of the string in a direction perpendicular to the face,
the through hole of the translation cylinder portion has a base side opening, a side wall, and a tip side opening,
In the parallel movement cylinder portion, the string abuts against an inner wall surface of the side wall in the width direction of the racket from the base side opening to the tip side opening,
the arrangement of the parallel movement cylinder portion and the vertical movement cylinder portion on one side in the width direction of the racket with respect to the center line is symmetrical with the arrangement of the parallel movement cylinder portion and the vertical movement cylinder portion on the other side in the width direction of the racket with respect to the center line ;
A longitudinal string is threaded through the parallel movement tube and another longitudinal string is threaded through the vertical movement tube . The racket of claim 1, in which each parallel movement tube is adjacent to at least one vertical movement tube. The racket according to claim 1 or 2, in which each vertical movement tube is adjacent to at least one parallel movement tube. A racket according to any one of claims 1 to 3, wherein the translation tube has a through hole whose inner dimension in a direction parallel to the face is greater than its inner dimension in a direction perpendicular to the face. The racket according to claim 4, wherein the cross-sectional shape of the through hole of the parallel movement cylinder is an ellipse or an oval. The racket according to claim 4 or 5, wherein the ratio (L1/L2) of the inner dimension L1 in the direction parallel to the face to the inner dimension L2 in the direction perpendicular to the face of the through hole of the parallel movement cylinder is 1.3 or more. The racket according to any one of claims 1 to 6, wherein the parallel movement tube has a through hole having a congruent cross-sectional shape from the base opening to the tip opening. A racket according to any one of claims 1 to 7, in which the ratio (L1/D) of the inner dimension L1 of the through hole of the parallel movement cylinder in a direction parallel to the face to the diameter D of the string is 1.5 or more. The racket according to any one of claims 1 to 8, wherein the vertical movement tube has a through hole including a tip opening whose inner dimension in a direction perpendicular to the face is larger than the inner dimension in a direction parallel to the face. The racket according to claim 9, wherein the cross-sectional shape of the tip end opening of the vertical movement tube is an ellipse. The racket according to claim 9 or 10, wherein the ratio (L4/L3) of the inner dimension L4 in the direction perpendicular to the face to the inner dimension L3 in the direction parallel to the face at the tip end opening of the vertical movement tube is 1.3 or more. A racket according to any one of claims 9 to 11, in which the ratio (L4/D) of the inner dimension L4 of the tip end opening of the vertical movement tube in the direction perpendicular to the face to the string diameter D is 1.5 or more. 13. The racket of claim 1, wherein the translational and vertical movement tubes are disposed near the top of the frame.

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