US20140256480A1 - Racket - Google Patents
Racket Download PDFInfo
- Publication number
- US20140256480A1 US20140256480A1 US14/195,204 US201414195204A US2014256480A1 US 20140256480 A1 US20140256480 A1 US 20140256480A1 US 201414195204 A US201414195204 A US 201414195204A US 2014256480 A1 US2014256480 A1 US 2014256480A1
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- US
- United States
- Prior art keywords
- frame
- groove section
- string
- depth
- racket
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B51/00—Stringing tennis, badminton or like rackets; Strings therefor; Maintenance of racket strings
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B49/022—String guides on frames, e.g. grommets
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
- A63B60/54—Details or accessories of golf clubs, bats, rackets or the like with means for damping vibrations
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B2049/0211—Frames with variable thickness of the head in a direction perpendicular to the string plane
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B2049/0217—Frames with variable thickness of the head in the string plane
-
- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B49/00—Stringed rackets, e.g. for tennis
- A63B49/02—Frames
- A63B49/028—Means for achieving greater mobility of the string bed
Definitions
- the invention relates to a racket used in tennis and the like.
- a racket used in tennis and the like there are known ones including: a handle which a player grips; a frame inside which a string is strung; and a shaft connects the handle and the frame.
- a groove section is provided along the circumferential direction of the frame and in the middle in the thickness direction (a direction perpendicular to a hitting surface).
- the frame has a plurality of through holes through which a string passes. The openings of the through holes are formed in the groove section.
- the string passes from the inside to the outside of the frame through a through hole; the string is folded back along the groove section of the frame; and the string passes through the next through hole. Then, in the frame, the portions of the string (longitudinal strings) along the longitudinal direction of the racket are strung at intervals in the width direction intersecting with the longitudinal direction. Also, the portions of the string (transverse strings) along the width direction are strung at intervals in the longitudinal direction so as to intersect the longitudinal strings.
- the net-like hitting surface is formed in the frame (for example, see Japanese Patent Application Laid-open Publication No. 6-269514).
- the sweet spot which has a high rebound performance of a ball and vibrates less when hitting a ball, can be enlarged by increasing the lengths of longitudinal strings and transverse strings and by reducing the difference between the lengths of longitudinal strings arranged in the width direction and/or the difference between the lengths of transverse strings arranged in the longitudinal direction.
- the frame has an annular shape such as an elliptical shape, the string is folded back along the outer peripheral face (the groove section) of the curved frame. Therefore, longitudinal strings and transverse strings passing the ends of the frame are shorter in length than longitudinal strings and transverse strings passing the center of the frame.
- the invention has been made in view of the above issue, and an advantage thereof is to enlarge the sweet spot of a racket without changing the shape of the frame.
- a racket including: a handle; an annular frame having a plurality of through holes, and a groove section provided on an outer peripheral face of the frame along a circumferential direction of the frame; a shaft connecting the handle and the frame; and a string that passes through the through hole to the outside of the frame, and that is folded back on the groove section, wherein when either one of a longitudinal direction of the racket and a width direction perpendicular to the longitudinal direction on a hitting surface of the racket is defined as a first direction, a depth of a position at which the string is folded back at a second position in the first direction is smaller or less than a depth of a position at which the string is folded back at a first position in the first direction, the first position being located on the outer peripheral face of the frame, the second position being located on the outer peripheral face of the frame and outside of the first position in the first direction.
- FIG. 1 is a plan view and a side view of a tennis racket.
- FIG. 2A is a cross-sectional view of a frame in the thickness direction
- FIG. 2B is a diagram showing how the string is strung in the frame.
- FIG. 3 is a diagram of a groove section provided in the frame of the present embodiment.
- FIG. 4 is a diagram of a groove section provided in the frame of a comparative example.
- FIG. 5 is a diagram of the frame and the groove section of a modified example.
- a racket including:
- the position at which the string is folded back on the outer peripheral face of the frame may become shallower in depth as it goes from a center of the frame to an end in the first direction.
- the frame may have substantially an elliptical shape, and a position in an end in the longitudinal direction on the outer peripheral face of the frame at which the string is folded back at a center in the width direction may be deeper in depth than a position in an end in the width direction on the outer peripheral face of the frame at which the string is folded back at a center in the longitudinal direction.
- the sweet spot can be further enlarged while preventing the strength deterioration of the frame. This also allows the racket to rebound a ball more and to vibrate less.
- FIG. 1 is a plan view and a side view of a tennis racket (hereinafter referred to as a racket 1 ).
- the left one is the plan view and the right one is a side view.
- FIG. 2A is a cross-sectional view of a frame 11 in the thickness direction
- FIG. 2B is a diagram showing how a string 12 is strung in the frame 11 .
- the racket 1 includes: a head 10 which hits a ball; a handle 20 which a player grips to hold the racket 1 ; and a shaft 30 connects the head 10 and the handle 20 in an integrated manner.
- the side of the head 10 is called as a tip-end side
- the side of the handle 20 is called as a handle-end side.
- a direction perpendicular to the longitudinal direction is called as a width direction
- a direction perpendicular to the hitting surface of the racket 1 is called as a thickness direction.
- the head 10 includes: the frame 11 with an elliptical shape extending in the longitudinal direction of the racket 1 ; and the string 12 strung inside the frame 11 .
- the frame 11 is made by shaping into an elliptical shape, for example, a hollow rod which is made of fiber reinforced resin and the like. It should be noted that the frame 11 may not be hollow and the inside of the frame 11 may be filled with foamed material.
- a groove section 111 is provided along the circumferential direction of the frame 11 and the groove section 111 has the middle in the thickness direction which is concave compared to the both side sections 112 .
- the frame 11 has a plurality of string holes 13 (corresponding to through holes) along the circumferential direction of the frame 11 ; the string holes 13 extend through from the inner peripheral face 11 b to the outer peripheral face 11 a and are for inserting the string 12 .
- each string hole 13 is provided on the groove section 111 .
- the string 12 is strung in the frame 11 through a grommet 40 .
- the grommet 40 includes: A plurality of tube sections 41 ; and a strip-shaped base section 42 which connects the plurality of tube sections 41 to each other and has communicating holes 43 which communicate the hollow of each tube section 41 .
- the tip end of each of the tube section 41 is placed into the string hole 13 from the side of the outer peripheral face 11 a of the frame 11 .
- the base section 42 is embedded in the groove section 111 of the frame 11 .
- the grommet 40 is placed in the outer peripheral face 11 a of the frame 11 .
- a groove section 44 extending from one end of the base section 42 to the other end is provided in the middle of the thickness direction; the openings of the communicating holes 43 are provided in the groove section 44 .
- the thickness of the base section 42 (the thickness from the surface on which the tube section 41 is placed to the bottom surface of the groove section 44 ) is uniform.
- the shaft 30 branches into two sections toward the tip end in longitudinal direction as seen from the thickness direction, as shown in the left diagram of FIG. 1 . So, an opening 31 extending in the thickness direction is formed by the branched portions and the handle end of the frame 11 .
- a racket may have an unbranched shaft 30 .
- FIG. 3 is a diagram of the groove section 111 provided in the frame 11 of the present embodiment.
- FIG. 4 is a diagram of the groove section 111 ′ provided in the frame 11 ′ of a comparative example.
- a solid line indicates the shape (the outer peripheral edge) of the top surface 112 a of both side sections in the thickness direction (see FIG. 2A ) as seen from the thickness direction.
- Another solid line indicates the shape (the inner peripheral edge) of the inner peripheral face 11 b of the frame 11 as seen from the thickness direction.
- a dotted line indicates the shape of the bottom surface 111 a of the groove section as seen from the thickness direction.
- the width of the frame 11 of the present embodiment (the thickness from the inner peripheral edge to the outer peripheral edge) is substantially uniform through the entire circumference of the frame 11 .
- the groove section 111 is provided continuously along the circumferential direction of the frame 11 ; the groove section 111 is a section on which the string 12 passing through the string holes 13 to the outside of the frame 11 is folded back. The depth of the groove section 111 differs in place.
- the depth of the groove section 111 means the length from the bottom surface 111 a of the groove section to the outer peripheral edge in the direction perpendicular to the bottom surface 111 a .
- the groove section 111 is substantially symmetric about the line along the longitudinal direction passing the center of the frame 11 in the width direction, and is substantially symmetric about the line along the width direction passing the center of the frame 11 in the longitudinal direction.
- the depth of the groove section 111 will be described concretely below.
- the portion of the groove section 111 of the frame 11 provided on the tip end (hereinafter referred to as “the top”) in the longitudinal direction in other words, the groove section 111 within a range in which longitudinal strings 121 are folded back, gradually becomes shallower in depth as it goes from the center to the outside (left or right) in the width direction.
- the depth d1 of the groove section 111 at the center P 1 in the width direction is deepest.
- the depth d4 of the groove section 111 at the point P 4 outside (to the right of) the center P 1 in the width direction is shallower than the depth d1 at the center P 1 .
- the depth d3 of the groove section 111 at the point P 3 outside the point P 4 in the width direction is further shallower than the depth d4 at the point P 4 (d1>d4>d3).
- the portions of the groove section 111 of the frame 11 provided on the ends (hereinafter referred to as “sides”) in the width direction in other words, the portions of the groove section 111 within a range in which transverse strings 122 are folded back, gradually become shallower in depth as they go from the center to the outside (the tip end or the handle end) in the longitudinal direction.
- the depth d2 of the groove section 111 at the longitudinal center P 2 is deepest.
- the depth d5 of the groove section 111 at the point P 5 outside (to the tip end of) the center P 2 in the longitudinal direction is shallower than the depth d2 at the center P 2 .
- the depth d3 of the groove section 111 at the point P 3 longitudinally outside the point P 5 is further shallower than the depth d5 at the point P 5 (d2>d5>d3). It should be noted that, in the present embodiment, the depth d1 of the groove section 111 of the top of the frame 11 at the center P 1 in the width direction is equal to the depth d2 of the groove section 111 of the sides of the frame 11 at the longitudinal center P 2 .
- the elements except for the depth of the groove section 111 ′ of the frame 11 ′, such as the range in which the groove section 111 ′ is formed and the shape of the outer peripheral edge and the inner peripheral edge, are the same as those of the frame 11 of the present embodiment.
- the sweet spot which has a high rebound performance of a ball and vibrates less when hitting a ball, can be enlarged by increasing the lengths of the longitudinal strings 121 and the transverse strings 122 and by reducing the difference between the lengths of the longitudinal strings 121 arranged in the width direction and/or the difference between the lengths of the transverse strings 122 arranged in the longitudinal direction. As shown in FIG.
- the length (La) of one longitudinal string 121 means the length in the longitudinal direction from the point on the handle-end side at which the longitudinal string 121 is folded back to the point on the tip-end side at which the longitudinal string 121 is folded back (to the bottom surface 111 a of groove section; more precisely, to the bottom surface of the groove section 44 in the base section 42 of the grommet 40 ).
- the length (Lb) of one transverse string 122 means the length in the width direction from the point on the left side at which the transverse string 122 is folded back to the point on the right side at which the transverse string 122 is folded back.
- the outer peripheral edge has an elliptical (annular) shape as seen from the thickness direction as in the frame 11 of the present embodiment and the frame 11 ′ of the comparative example
- the string 12 is folded back along the bottom surface 111 a ′ of the groove section, which is greatly curved in the same manner as the outer peripheral edge of the frame 11 ′.
- the longitudinal strings 121 passing both ends of the frame 11 ′ in the width direction are shorter in length than the longitudinal strings 121 passing the center
- the transverse strings 122 passing both ends of the frame 11 ′ in the longitudinal direction are shorter in length than the transverse strings 122 passing the center. Therefore, in the frame 11 ′ of the comparative example, only the center serves as the sweet spot, whose area is not sufficiently large.
- the portion of the groove section 111 is smaller or less in depth at a position (e.g. P 3 ) outside of the certain position (e.g. P 1 ) in the width direction. Therefore, in the present embodiment, the groove section 111 of the top of the frame 11 extending in the width direction has a lower degree of curving than the outer peripheral edge and the inner peripheral edge of the top of the elliptical frame 11 .
- This groove section 111 also has a lower degree of curving than the groove section 111 ′ of the top of the frame 11 ′ of the comparative example extending in the width direction. That is, the bottom surface 111 a of the groove section provided in the top of the frame 11 of the present embodiment is an arc-shaped surface the shape of which is closer to straight line.
- the string 12 is folded back on the groove section 111 provided on the outer peripheral face 11 a of the frame 11 through the base section 42 of the grommet 40 , and the base section 42 of the grommet is uniform in thickness.
- the depth of the position where the string 12 is folded back is smaller or less at a position (e.g. P 3 ) outside of the certain position (P 1 ) in the width direction.
- the depth at the position where the string 12 is folded back when stringing the string 12 through the grommet 40 means the distance from the bottom surface of the base section 42 of the grommet 40 to the outer peripheral edge in the direction perpendicular to the bottom surface.
- the portion of the groove section 111 is smaller or less in depth at a position (e.g. P 3 ) outside of the certain position (e.g. P 2 ) in the longitudinal direction. Therefore, in the present embodiment, the groove section 111 of the sides of the frame 11 extending in the longitudinal direction has a lower degree of curving than the outer peripheral edge and the inner peripheral edge of the sides of the elliptical frame 11 .
- This groove section 111 also has a lower degree of curving than the groove section 111 ′ of the sides of the frame 11 ′ of the comparative example extending in the longitudinal direction.
- the bottom surface 111 a of the groove section provided in the sides of the frame 11 of the present embodiment is an arc-shaped surface the shape of which is closer to straight line. That is, on the outer peripheral face 11 a of the sides of the frame 11 , compared to the depth of the position where the string 12 is folded back at a certain position (e.g. P 2 , corresponding to the first position) in the longitudinal direction (corresponding to the first direction), the depth of the position where the string 12 is folded back at a position (e.g. P 3 , corresponding to the second position) outside of the certain position (e.g. P 2 ) in the longitudinal direction is smaller or less.
- the portions of the bottom surface 111 a of the groove section which are located on the outer ends in the width direction are located closer to the outer peripheral edge compared to the frame 11 ′ of the comparative example.
- the portions of the bottom surface 111 a of the groove section which are located on the longitudinal outer ends are located closer to the outer peripheral edge compared to the frame 11 ′ of the comparative example.
- the longitudinal strings 121 passing the outer ends of the frame 11 in the width direction can be longer than in the frame 11 ′ of the comparative example. Also, in the frame 11 of the present embodiment, compared to the frame 11 ′ of the comparative example, it is possible to reduce the difference in length between the longitudinal strings 121 passing the outer ends of the frame 11 in the width direction and the longitudinal strings 121 passing the center. Also, the transverse strings 122 passing the outer ends of the frame 11 in the longitudinal direction can be longer. And, it is possible to reduce the difference in length between the transverse strings 122 passing the outer ends of the frame 11 in the longitudinal direction and the transverse strings 122 passing the center.
- the depth of the groove section 111 ′ of the frame 11 ′ in the comparative example is 3 mm (a constant); the depth of the groove section 111 of both sides of the frame 11 in the present embodiment at the longitudinal center (e.g. P 2 in FIG. 3 ) is 6 mm; the depth of the groove section 111 at the longitudinal outer end (e.g. P 3 in FIG. 3 ) is 1 mm; and the depth of the groove section 111 becomes gradually shallower from the center toward the outer end in the longitudinal direction.
- the frame 11 ′ of the comparative example of this case when the length of the transverse string (the 10th transverse string 122 ( 10 ) from the tip end) passing the center of the frame 11 ′ in the longitudinal direction is defined as “100%”, the length of the transverse string (the third transverse string 122 ( 3 ) from the tip end) passing the tip-end portion of the frame 11 ′ in the longitudinal direction becomes “85%”.
- the length of the transverse string 122 ( 10 ) passing the center of the frame 11 in the longitudinal direction when the length of the transverse string 122 ( 10 ) passing the center of the frame 11 in the longitudinal direction is defined as “100%”, the length of the transverse string 122 ( 3 ) passing the tip-end portion of the frame 11 in the longitudinal direction becomes “89%”. From this, it will be seen that, compared to the frame 11 ′ of the comparative example, the frame 11 of the present embodiment makes it possible to reduce the difference between the lengths of the transverse strings 122 arranged in the longitudinal direction.
- the sweet spot can be enlarged without changing the elliptical shape of the frame 11 .
- the frame 11 of the present embodiment has an accurate elliptical shape.
- the frame 11 may be substantially elliptical, may have perfect circular shape, or may have a shape close to rectangle.
- a frame having an elliptical or perfect circular shape obtains more the effect caused by making the lengths of the longitudinal strings 121 close to each other or by making the lengths of the transverse strings 122 close to each other.
- a frame having an elliptical or perfect circular shape can reduce air resistance caused when swinging the racket.
- the difference between the lengths of the longitudinal strings 121 arranged in the width direction and/or the difference between the lengths of the transverse strings 122 arranged in the longitudinal direction are reduced across wide range as the depth of the groove section 111 of the top of the frame 11 at the center in the width direction is increased and/or as the depth of the groove section 111 of the sides of the frame 11 at the center in the longitudinal direction is increased.
- the groove section 111 is considerably deep in depth, the thickness from the inner peripheral face 11 b (inner peripheral edge) of the frame 11 to the bottom surface 111 a of the groove section becomes small, which results in deterioration of the strength of the frame 11 . Therefore, it is preferable that the depth of the groove section 111 is decided in the light of this fact.
- the groove section 111 is provided on the outer peripheral face 11 a of the frame 11 and is not provided on the inner peripheral face 11 b .
- the lengths of the longitudinal strings 121 and the transverse strings 122 which affects enlargement of the sweet spot, are a distance in the longitudinal direction or in the width direction from one-end side point of the folding back of the string 12 to other-end side point of the folding back of the string 12 . So, even if the groove section is provided on the inner peripheral face 11 b of the frame 11 , the groove section does not contribute enlargement of the sweet spot.
- providing the groove section 111 on the outer peripheral face 11 a of the frame 11 makes a manufacturing process of the frame 11 easier than providing a groove section on the inner peripheral face 11 b (for example, a mold for shaping the frame 11 into an ellipse is easy to be manufactured). Furthermore, compared to the case in which the groove section 111 is provided on the inner peripheral face 11 b of the frame 11 , providing the groove section 111 on the outer peripheral face 11 a makes it possible to reduce stress concentration when hitting a ball, and can increase the strength of the frame 11 .
- the portions of the groove section 111 at the outer ends in the width direction are shallower than the portion of the groove section 111 at the center; the thickness and the strength from the inner peripheral edge to the bottom surface 111 a of the groove section increase.
- the portions of the groove section 111 at the outer ends in the longitudinal direction are shallower than the portion of the groove section 111 at the center; the thickness and the strength from the inner peripheral edge to the bottom surface 111 a of the groove section increase.
- the frame 11 has an elliptical (annular) shape
- the longitudinal strings 121 become shorter as they pass through either outer portion of the frame 11 in the width direction
- the transverse strings 122 become shorter as they pass through either outer portion of the frame 11 in the longitudinal direction.
- the portions of the groove section 111 which are located on the outer peripheral face 11 a of the frame 11 that is, the portions where the string 12 is folded back, are shallower in depth as they go outwards from the center in the longitudinal direction or the width direction of the frame 11 .
- the portion of the groove section 111 (the positions at which the string 12 is folded back) becomes shallower in depth as it goes outwards in the width direction. Also, in side of the frame 11 , the portions of the groove section 111 (the positions at which the string 12 is folded back) become shallower in depth as they go outwards in the longitudinal direction.
- the groove section 111 varies gradually in depth without varying in steps in depth of the groove section 111 , in other words, without steps in the bottom surface 111 a of the groove section. This makes it possible to prevent stress when hitting a ball from concentrating into steps provided in the bottom surface 111 a of the groove section and to increase the strength of the frame 11 . This also makes it possible to prevent change of the feel produced only when a ball hits a corresponding portion within the frame 11 to the steps provided in the bottom surface 111 a of the groove section.
- the base section 42 of the grommet 40 is uniform in thickness.
- the invention is not limited thereto.
- the portions of the base section 42 of the grommet 40 provided in the outside in the width direction may be thicker than the portions of the base section 42 of the grommet 40 provided in the center in the width direction.
- the portions of the base section 42 of the grommet 40 provided in the outside in the longitudinal direction may be thicker in thickness than the portions of the base section 42 of the grommet 40 provided in the center in the longitudinal direction.
- a thick portion of the base section 42 of the grommet 40 is located far from the frame 11 which is highly rigid, so that elastic deformation of the grommet 40 easily to occur.
- the thick grommet 40 (the base section 42 ) has a high vibration damping capacity. Therefore, even when a player hits a ball with a region far from the center of the frame 11 , the player can experience the feel nearly as much as when hitting a ball with a region of the center. That is, the sweet spot can be enlarged.
- the groove section 111 of the frame 11 may be uniform in depth.
- adjusting the thickness of the base section 42 of the grommet 40 may achieve the followings: on the outer peripheral face 11 a of the frame 11 , compared to a certain position in the longitudinal direction, the depth of the position where the string 12 is folded back is shallower at a position outside of the certain position in the longitudinal direction; on the outer peripheral face 11 a of the frame 11 , compared to a certain position in the width direction, the depth of the position where the string 12 is folded back is shallower at a position outside of the certain position in the width direction.
- FIG. 5 is a diagram of the frame 11 and the groove section 111 of the modified example.
- the frame 1 of the racket 1 in the abovementioned embodiment has an elliptical shape.
- the invention is not limited thereto.
- the frame 1 may have substantially an elliptical shape in which the tip end and the handle end in the longitudinal direction have a lower degree of curving than those of an ellipse.
- the depth (d1) of the point (P 1 in FIG. 3 ) of the groove section 111 of the top of the frame 11 at the center in the width direction is equal to the depth (d2) of the point (P 2 in FIG. 3 ) of the groove section 111 of the sides of the frame 11 at the center in the longitudinal direction.
- the groove section 111 may vary in depth.
- the difference between the lengths of longitudinal strings 121 arranged in the width direction and/or the difference between the lengths of transverse strings 122 arranged in the longitudinal direction can be reduced as the depth of the groove section 111 of the top of the frame 11 at the center in the width direction is increased and/or as the depth of the groove section 111 of the sides of the frame 11 at the center in the longitudinal direction is increased. This reduces the thickness of the frame 11 from the inner peripheral face 11 a to the bottom surface 111 a of the groove section, which results in deterioration of the strength of the frame 11 .
- the frame 11 is substantially in an elliptical shape (including a perfect elliptical shape), the frame 11 is strong and difficult to deform because the top of the frame 11 is smaller in size than the sides.
- longitudinal strings 121 are longer than transverse strings 122 , reducing the difference between the lengths of longitudinal strings 121 arranged in the width direction is more effective than reducing the difference between the lengths of transverse strings 122 arranged in the longitudinal direction. That is, it is possible to further enlarge the sweet spot; also this allows the racket to rebound a ball more and to vibrate less.
- the depth (D+ ⁇ ) of the point (P 1 in FIG. 5 ) of the groove section 111 of the outer peripheral face 11 a of the top (the end in the longitudinal direction) at the center in the width direction be deeper than the depth (D) of the point (P 2 in FIG. 5 ) of the groove section 111 of the outer peripheral face 11 a of either side (either end in the width direction) at the center in the longitudinal direction.
- the depth at the position where the string 12 is folded back on the outer peripheral face 11 a of the top of the frame 11 at the center in the width direction is deeper than the depth at the position where the string 12 is folded back on the outer peripheral face 11 a of the sides of the frame 11 at the center in the longitudinal direction.
- the sweet spot can be further enlarged while preventing the strength deterioration of the frame 11 . This also allows the racket to rebound a ball more and to vibrate less.
- all portions of the groove section 111 located in the top and both sides of the frame 11 become shallower in depth as they go from the center to the outer ends.
- the invention is not limited thereto.
- at least one portion of the groove section 111 located in the top and both sides of the frame 11 may be different in depth.
- the groove section 111 is not provided in the handle end (the portion facing the opening 30 ) of the frame 11 in the longitudinal direction.
- the groove section 111 may be provided in the handle end and the groove section 111 may be shallower in depth as it goes from the center in the width direction to the outer ends.
- the groove section 111 varies gradually in depth.
- the invention is not limited thereto.
- the groove section 111 may vary in depth by providing steps in the bottom surface 111 a of the groove section.
- a tennis racket is taken as an example of a racket associated with the invention.
- the invention is not limited thereto.
- the invention may be applied to a squash racket, a badminton racket and the like.
- the racket 1 in the frame 11 of which the string 12 is strung is taken as an example of a racket associated with the invention.
- the invention is not limited thereto.
- a racket in which the string 12 is not strung may also be employed.
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Abstract
A racket including: a handle; an annular frame having a plurality of through holes, and a groove section provided on an outer peripheral face of the frame along a circumferential direction of the frame; a shaft connecting the handle and the frame; and a string that passes through the through hole to the outside of the frame, and that is folded back on the groove section, wherein when either one of a longitudinal direction of the racket and a width direction perpendicular to the longitudinal direction on a hitting surface of the racket is defined as a first direction, a depth of a position at which the string is folded back at a second position in the first direction is smaller or less than a depth of a position at which the string is folded back at a first position in the first direction, the first position being located on the outer peripheral face of the frame, the second position being located on the outer peripheral face of the frame and outside of the first position in the first direction.
Description
- The present application claims priority upon Japanese Patent Application No. 2013-44426 filed on Mar. 6, 2013 which is herein incorporated by reference.
- 1. Technical Field
- The invention relates to a racket used in tennis and the like.
- 2. Related Art
- As a racket used in tennis and the like, there are known ones including: a handle which a player grips; a frame inside which a string is strung; and a shaft connects the handle and the frame. Generally, on the outer peripheral face of the frame, a groove section is provided along the circumferential direction of the frame and in the middle in the thickness direction (a direction perpendicular to a hitting surface). In addition, along the circumferential direction of the frame, the frame has a plurality of through holes through which a string passes. The openings of the through holes are formed in the groove section. When stringing the string in the frame, the following processes are repeated: the string passes from the inside to the outside of the frame through a through hole; the string is folded back along the groove section of the frame; and the string passes through the next through hole. Then, in the frame, the portions of the string (longitudinal strings) along the longitudinal direction of the racket are strung at intervals in the width direction intersecting with the longitudinal direction. Also, the portions of the string (transverse strings) along the width direction are strung at intervals in the longitudinal direction so as to intersect the longitudinal strings. Thus, the net-like hitting surface is formed in the frame (for example, see Japanese Patent Application Laid-open Publication No. 6-269514).
- The sweet spot, which has a high rebound performance of a ball and vibrates less when hitting a ball, can be enlarged by increasing the lengths of longitudinal strings and transverse strings and by reducing the difference between the lengths of longitudinal strings arranged in the width direction and/or the difference between the lengths of transverse strings arranged in the longitudinal direction. However, if the frame has an annular shape such as an elliptical shape, the string is folded back along the outer peripheral face (the groove section) of the curved frame. Therefore, longitudinal strings and transverse strings passing the ends of the frame are shorter in length than longitudinal strings and transverse strings passing the center of the frame.
- The invention has been made in view of the above issue, and an advantage thereof is to enlarge the sweet spot of a racket without changing the shape of the frame.
- An aspect of the invention to achieve the above advantage is a racket including: a handle; an annular frame having a plurality of through holes, and a groove section provided on an outer peripheral face of the frame along a circumferential direction of the frame; a shaft connecting the handle and the frame; and a string that passes through the through hole to the outside of the frame, and that is folded back on the groove section, wherein when either one of a longitudinal direction of the racket and a width direction perpendicular to the longitudinal direction on a hitting surface of the racket is defined as a first direction, a depth of a position at which the string is folded back at a second position in the first direction is smaller or less than a depth of a position at which the string is folded back at a first position in the first direction, the first position being located on the outer peripheral face of the frame, the second position being located on the outer peripheral face of the frame and outside of the first position in the first direction.
- Other features of this invention will become apparent from the description in this specification and the attached drawings.
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FIG. 1 is a plan view and a side view of a tennis racket. -
FIG. 2A is a cross-sectional view of a frame in the thickness direction, and -
FIG. 2B is a diagram showing how the string is strung in the frame. -
FIG. 3 is a diagram of a groove section provided in the frame of the present embodiment. -
FIG. 4 is a diagram of a groove section provided in the frame of a comparative example. -
FIG. 5 is a diagram of the frame and the groove section of a modified example. - From the description in the detailed description of the invention and the accompanied drawings, at least the following matters will be apparent.
- A racket including:
- a handle;
- an annular frame having
-
- a plurality of through holes, and
- a groove section provided on an outer peripheral face of the frame along a circumferential direction of the frame;
- a shaft connecting the handle and the frame; and
- a string
-
- that passes through the through hole to the outside of the frame, and
- that is folded back on the groove section,
wherein
- when either one of a longitudinal direction of the racket and a width direction perpendicular to the longitudinal direction on a hitting surface of the racket is defined as a first direction,
-
- a depth of a position at which the string is folded back at a second position in the first direction is smaller or less than a depth of a position at which the string is folded back at a first position in the first direction,
- the first position being located on the outer peripheral face of the frame,
- the second position being located on the outer peripheral face of the frame and outside of the first position in the first direction.
- With such a racket, it is possible that, without changing the shape of the annular frame, the length of the string on any outer end of the frame (the second position) in the first direction becomes more equal to the length of the string at the center of the frame (the first position) in the first direction. As a result, sweet spot can be enlarged.
- In such a racket, the position at which the string is folded back on the outer peripheral face of the frame may become shallower in depth as it goes from a center of the frame to an end in the first direction.
- With such a racket, it is possible to reduce the difference in length between strings arranged in a direction intersecting with the first direction. This makes it possible to reduce the differences caused by different hitting positions in the frame of the rebound performance of a ball and the feel, which results in enlarging the sweet spot.
- In such a racket, the frame may have substantially an elliptical shape, and a position in an end in the longitudinal direction on the outer peripheral face of the frame at which the string is folded back at a center in the width direction may be deeper in depth than a position in an end in the width direction on the outer peripheral face of the frame at which the string is folded back at a center in the longitudinal direction.
- With such a racket, the sweet spot can be further enlarged while preventing the strength deterioration of the frame. This also allows the racket to rebound a ball more and to vibrate less.
- An embodiment of a tennis racket will be described below as an example of a racket according to the invention.
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FIG. 1 is a plan view and a side view of a tennis racket (hereinafter referred to as a racket 1). The left one is the plan view and the right one is a side view.FIG. 2A is a cross-sectional view of aframe 11 in the thickness direction, andFIG. 2B is a diagram showing how astring 12 is strung in theframe 11. The racket 1 includes: ahead 10 which hits a ball; ahandle 20 which a player grips to hold the racket 1; and ashaft 30 connects thehead 10 and thehandle 20 in an integrated manner. For the purpose of illustration, of the longitudinal sides of the racket 1, the side of thehead 10 is called as a tip-end side, and the side of thehandle 20 is called as a handle-end side. On the hitting surface of the racket 1 (that is, on the plane along the hitting surface), a direction perpendicular to the longitudinal direction is called as a width direction. A direction perpendicular to the hitting surface of the racket 1 is called as a thickness direction. - The
head 10 includes: theframe 11 with an elliptical shape extending in the longitudinal direction of the racket 1; and thestring 12 strung inside theframe 11. Theframe 11 is made by shaping into an elliptical shape, for example, a hollow rod which is made of fiber reinforced resin and the like. It should be noted that theframe 11 may not be hollow and the inside of theframe 11 may be filled with foamed material. As shown inFIG. 2A , in the outerperipheral face 11 a of theframe 11, agroove section 111 is provided along the circumferential direction of theframe 11 and thegroove section 111 has the middle in the thickness direction which is concave compared to the bothside sections 112. In addition, theframe 11 has a plurality of string holes 13 (corresponding to through holes) along the circumferential direction of theframe 11; the string holes 13 extend through from the innerperipheral face 11 b to the outerperipheral face 11 a and are for inserting thestring 12. - As shown in
FIG. 2B , the opening of eachstring hole 13 is provided on thegroove section 111. In order to protect thestring 12 and to dampen vibrations caused by hitting a ball, thestring 12 is strung in theframe 11 through agrommet 40. Thegrommet 40 includes: A plurality oftube sections 41; and a strip-shapedbase section 42 which connects the plurality oftube sections 41 to each other and has communicatingholes 43 which communicate the hollow of eachtube section 41. The tip end of each of thetube section 41 is placed into thestring hole 13 from the side of the outerperipheral face 11 a of theframe 11. Then, thebase section 42 is embedded in thegroove section 111 of theframe 11. In this way, thegrommet 40 is placed in the outerperipheral face 11 a of theframe 11. In thebase section 42 of thegrommet 40, agroove section 44 extending from one end of thebase section 42 to the other end is provided in the middle of the thickness direction; the openings of the communicatingholes 43 are provided in thegroove section 44. The thickness of the base section 42 (the thickness from the surface on which thetube section 41 is placed to the bottom surface of the groove section 44) is uniform. - Thus, when stringing the
string 12 in theframe 11, thestring 12 passes from the inside of theframe 11 to the outside through one of the tube sections 41 (the string holes 13) of thegrommet 40, and thestring 12 is folded back on thegroove section 44 of thegrommet 40. In other words, through thegroove section 44 of thebase section 42 of thegrommet 40, thestring 12 is folded back on thegroove section 111 of theframe 11. Thereafter, thestring 12 is inserted into the next tube section 41 (string hole 13). This process is repeated. Thus, a plurality of “longitudinal strings 121”, which are the portions of thestring 12 extending in the longitudinal direction, are strung inside theframe 11 at intervals in the width direction. A plurality of “transverse strings 122”, which are the portions of thestring 12 extending in the width direction, are strung at intervals in the longitudinal direction so as to intersect thelongitudinal strings 121. Thus, a net-like hitting surface is formed. - The
shaft 30 branches into two sections toward the tip end in longitudinal direction as seen from the thickness direction, as shown in the left diagram ofFIG. 1 . So, anopening 31 extending in the thickness direction is formed by the branched portions and the handle end of theframe 11. However, this invention is not limited thereto. A racket may have anunbranched shaft 30. -
FIG. 3 is a diagram of thegroove section 111 provided in theframe 11 of the present embodiment.FIG. 4 is a diagram of thegroove section 111′ provided in theframe 11′ of a comparative example. In each of these diagrams, of the outerperipheral face 11 a of theframe 11, a solid line indicates the shape (the outer peripheral edge) of thetop surface 112 a of both side sections in the thickness direction (seeFIG. 2A ) as seen from the thickness direction. Another solid line indicates the shape (the inner peripheral edge) of the innerperipheral face 11 b of theframe 11 as seen from the thickness direction. A dotted line indicates the shape of thebottom surface 111 a of the groove section as seen from the thickness direction. - The width of the
frame 11 of the present embodiment (the thickness from the inner peripheral edge to the outer peripheral edge) is substantially uniform through the entire circumference of theframe 11. Of the outerperipheral face 11 a of theframe 11, in other portions in the longitudinal direction except the handle end, that is, in other portions except the portions connecting to theshaft 30 and the portion facing theopening 31, thegroove section 111 is provided continuously along the circumferential direction of theframe 11; thegroove section 111 is a section on which thestring 12 passing through the string holes 13 to the outside of theframe 11 is folded back. The depth of thegroove section 111 differs in place. Note that the depth of thegroove section 111 means the length from thebottom surface 111 a of the groove section to the outer peripheral edge in the direction perpendicular to thebottom surface 111 a. Thegroove section 111 is substantially symmetric about the line along the longitudinal direction passing the center of theframe 11 in the width direction, and is substantially symmetric about the line along the width direction passing the center of theframe 11 in the longitudinal direction. - The depth of the
groove section 111 will be described concretely below. The portion of thegroove section 111 of theframe 11 provided on the tip end (hereinafter referred to as “the top”) in the longitudinal direction, in other words, thegroove section 111 within a range in whichlongitudinal strings 121 are folded back, gradually becomes shallower in depth as it goes from the center to the outside (left or right) in the width direction. For example, in the top of theframe 11, the depth d1 of thegroove section 111 at the center P1 in the width direction is deepest. The depth d4 of thegroove section 111 at the point P4 outside (to the right of) the center P1 in the width direction is shallower than the depth d1 at the center P1. The depth d3 of thegroove section 111 at the point P3 outside the point P4 in the width direction is further shallower than the depth d4 at the point P4 (d1>d4>d3). - Similarly, The portions of the
groove section 111 of theframe 11 provided on the ends (hereinafter referred to as “sides”) in the width direction, in other words, the portions of thegroove section 111 within a range in whichtransverse strings 122 are folded back, gradually become shallower in depth as they go from the center to the outside (the tip end or the handle end) in the longitudinal direction. For example, in the right side of theframe 11, the depth d2 of thegroove section 111 at the longitudinal center P2 is deepest. The depth d5 of thegroove section 111 at the point P5 outside (to the tip end of) the center P2 in the longitudinal direction is shallower than the depth d2 at the center P2. The depth d3 of thegroove section 111 at the point P3 longitudinally outside the point P5 is further shallower than the depth d5 at the point P5 (d2>d5>d3). It should be noted that, in the present embodiment, the depth d1 of thegroove section 111 of the top of theframe 11 at the center P1 in the width direction is equal to the depth d2 of thegroove section 111 of the sides of theframe 11 at the longitudinal center P2. - On the other hand, in the
frame 11′ of the comparative example shown inFIG. 4 , unlike theframe 11 of the present embodiment, thegroove section 111′ is uniform in depth. Specifically, in the top of theframe 11, the depth d1 of thegroove section 111 at the center P1 in the width direction is equal to the depth d3 of thegroove section 111 at the outer end P3 in the width direction. Also, in the right side of theframe 11, the depth d2 of thegroove section 111 at the longitudinal center P2 is equal to the depth d3 of thegroove section 111 at the longitudinal outer end P3 (d1=d2=d3). In the comparative example, the elements except for the depth of thegroove section 111′ of theframe 11′, such as the range in which thegroove section 111′ is formed and the shape of the outer peripheral edge and the inner peripheral edge, are the same as those of theframe 11 of the present embodiment. - The sweet spot, which has a high rebound performance of a ball and vibrates less when hitting a ball, can be enlarged by increasing the lengths of the
longitudinal strings 121 and thetransverse strings 122 and by reducing the difference between the lengths of thelongitudinal strings 121 arranged in the width direction and/or the difference between the lengths of thetransverse strings 122 arranged in the longitudinal direction. As shown inFIG. 4 , the length (La) of onelongitudinal string 121 means the length in the longitudinal direction from the point on the handle-end side at which thelongitudinal string 121 is folded back to the point on the tip-end side at which thelongitudinal string 121 is folded back (to thebottom surface 111 a of groove section; more precisely, to the bottom surface of thegroove section 44 in thebase section 42 of the grommet 40). Also, the length (Lb) of onetransverse string 122 means the length in the width direction from the point on the left side at which thetransverse string 122 is folded back to the point on the right side at which thetransverse string 122 is folded back. Therefore, in a case where the outer peripheral edge has an elliptical (annular) shape as seen from the thickness direction as in theframe 11 of the present embodiment and theframe 11′ of the comparative example, if thegroove section 111 has constant depth as in theframe 11′ of the comparative example, thestring 12 is folded back along thebottom surface 111 a′ of the groove section, which is greatly curved in the same manner as the outer peripheral edge of theframe 11′. Thus, thelongitudinal strings 121 passing both ends of theframe 11′ in the width direction are shorter in length than thelongitudinal strings 121 passing the center, and thetransverse strings 122 passing both ends of theframe 11′ in the longitudinal direction are shorter in length than thetransverse strings 122 passing the center. Therefore, in theframe 11′ of the comparative example, only the center serves as the sweet spot, whose area is not sufficiently large. - As opposed thereto, in the
frame 11 of the present embodiment, on the outerperipheral face 11 a of the top of theframe 11, compared to the portion of thegroove section 111 at a certain position (e.g. P1) in the width direction, the portion of thegroove section 111 is smaller or less in depth at a position (e.g. P3) outside of the certain position (e.g. P1) in the width direction. Therefore, in the present embodiment, thegroove section 111 of the top of theframe 11 extending in the width direction has a lower degree of curving than the outer peripheral edge and the inner peripheral edge of the top of theelliptical frame 11. Thisgroove section 111 also has a lower degree of curving than thegroove section 111′ of the top of theframe 11′ of the comparative example extending in the width direction. That is, thebottom surface 111 a of the groove section provided in the top of theframe 11 of the present embodiment is an arc-shaped surface the shape of which is closer to straight line. - The
string 12 is folded back on thegroove section 111 provided on the outerperipheral face 11 a of theframe 11 through thebase section 42 of thegrommet 40, and thebase section 42 of the grommet is uniform in thickness. Thus, on the outerperipheral face 11 a of the top of theframe 11, compared to a certain position (e.g. P1, corresponding to the first position) in the width direction (corresponding to the first direction), the depth of the position where thestring 12 is folded back is smaller or less at a position (e.g. P3) outside of the certain position (P1) in the width direction. Not that “the depth at the position where thestring 12 is folded back” when stringing thestring 12 through thegrommet 40 means the distance from the bottom surface of thebase section 42 of thegrommet 40 to the outer peripheral edge in the direction perpendicular to the bottom surface. - Similarly, on the outer
peripheral face 11 a of the sides of theframe 11, compared to the portion of thegroove section 111 at a certain position (e.g. P2) in the longitudinal direction, the portion of thegroove section 111 is smaller or less in depth at a position (e.g. P3) outside of the certain position (e.g. P2) in the longitudinal direction. Therefore, in the present embodiment, thegroove section 111 of the sides of theframe 11 extending in the longitudinal direction has a lower degree of curving than the outer peripheral edge and the inner peripheral edge of the sides of theelliptical frame 11. Thisgroove section 111 also has a lower degree of curving than thegroove section 111′ of the sides of theframe 11′ of the comparative example extending in the longitudinal direction. Thebottom surface 111 a of the groove section provided in the sides of theframe 11 of the present embodiment is an arc-shaped surface the shape of which is closer to straight line. That is, on the outerperipheral face 11 a of the sides of theframe 11, compared to the depth of the position where thestring 12 is folded back at a certain position (e.g. P2, corresponding to the first position) in the longitudinal direction (corresponding to the first direction), the depth of the position where thestring 12 is folded back at a position (e.g. P3, corresponding to the second position) outside of the certain position (e.g. P2) in the longitudinal direction is smaller or less. - Therefore, in the top of the
frame 11 of the present embodiment, the portions of thebottom surface 111 a of the groove section which are located on the outer ends in the width direction (the positions at which thelongitudinal strings 121 are folded back) are located closer to the outer peripheral edge compared to theframe 11′ of the comparative example. Similarly, in the sides of theframe 11 of the present embodiment, the portions of thebottom surface 111 a of the groove section which are located on the longitudinal outer ends (the positions at which thetransverse strings 122 are folded back) are located closer to the outer peripheral edge compared to theframe 11′ of the comparative example. Therefore, in theframe 11 of the present embodiment, thelongitudinal strings 121 passing the outer ends of theframe 11 in the width direction can be longer than in theframe 11′ of the comparative example. Also, in theframe 11 of the present embodiment, compared to theframe 11′ of the comparative example, it is possible to reduce the difference in length between thelongitudinal strings 121 passing the outer ends of theframe 11 in the width direction and thelongitudinal strings 121 passing the center. Also, thetransverse strings 122 passing the outer ends of theframe 11 in the longitudinal direction can be longer. And, it is possible to reduce the difference in length between thetransverse strings 122 passing the outer ends of theframe 11 in the longitudinal direction and thetransverse strings 122 passing the center. Therefore, even when hitting a ball with a region far from the center of theframe 11, the difference is small from when hitting a ball with the central region. This improves the rebound performance of a ball and allows the racket to vibrate less when hitting a ball (achieves the same feel). That is, sweet spot can be enlarged. - As a concrete example, consider the following case: the depth of the
groove section 111′ of theframe 11′ in the comparative example is 3 mm (a constant); the depth of thegroove section 111 of both sides of theframe 11 in the present embodiment at the longitudinal center (e.g. P2 inFIG. 3 ) is 6 mm; the depth of thegroove section 111 at the longitudinal outer end (e.g. P3 inFIG. 3 ) is 1 mm; and the depth of thegroove section 111 becomes gradually shallower from the center toward the outer end in the longitudinal direction. In theframe 11′ of the comparative example of this case, when the length of the transverse string (the 10th transverse string 122(10) from the tip end) passing the center of theframe 11′ in the longitudinal direction is defined as “100%”, the length of the transverse string (the third transverse string 122(3) from the tip end) passing the tip-end portion of theframe 11′ in the longitudinal direction becomes “85%”. As opposed thereto, in theframe 11 of the present embodiment, when the length of the transverse string 122(10) passing the center of theframe 11 in the longitudinal direction is defined as “100%”, the length of the transverse string 122(3) passing the tip-end portion of theframe 11 in the longitudinal direction becomes “89%”. From this, it will be seen that, compared to theframe 11′ of the comparative example, theframe 11 of the present embodiment makes it possible to reduce the difference between the lengths of thetransverse strings 122 arranged in the longitudinal direction. - Further, with the racket 1 of the present embodiment, the sweet spot can be enlarged without changing the elliptical shape of the
frame 11. Theframe 11 of the present embodiment has an accurate elliptical shape. However, the invention is not limited thereto. For example, theframe 11 may be substantially elliptical, may have perfect circular shape, or may have a shape close to rectangle. However, compared to a frame whose shape is close to rectangle, a frame having an elliptical or perfect circular shape obtains more the effect caused by making the lengths of thelongitudinal strings 121 close to each other or by making the lengths of thetransverse strings 122 close to each other. Also, a frame having an elliptical or perfect circular shape can reduce air resistance caused when swinging the racket. - The difference between the lengths of the
longitudinal strings 121 arranged in the width direction and/or the difference between the lengths of thetransverse strings 122 arranged in the longitudinal direction are reduced across wide range as the depth of thegroove section 111 of the top of theframe 11 at the center in the width direction is increased and/or as the depth of thegroove section 111 of the sides of theframe 11 at the center in the longitudinal direction is increased. However, if thegroove section 111 is considerably deep in depth, the thickness from the innerperipheral face 11 b (inner peripheral edge) of theframe 11 to thebottom surface 111 a of the groove section becomes small, which results in deterioration of the strength of theframe 11. Therefore, it is preferable that the depth of thegroove section 111 is decided in the light of this fact. - In the racket 1 of the present embodiment, the
groove section 111 is provided on the outerperipheral face 11 a of theframe 11 and is not provided on the innerperipheral face 11 b. The lengths of thelongitudinal strings 121 and thetransverse strings 122, which affects enlargement of the sweet spot, are a distance in the longitudinal direction or in the width direction from one-end side point of the folding back of thestring 12 to other-end side point of the folding back of thestring 12. So, even if the groove section is provided on the innerperipheral face 11 b of theframe 11, the groove section does not contribute enlargement of the sweet spot. Further, providing thegroove section 111 on the outerperipheral face 11 a of theframe 11 makes a manufacturing process of theframe 11 easier than providing a groove section on the innerperipheral face 11 b (for example, a mold for shaping theframe 11 into an ellipse is easy to be manufactured). Furthermore, compared to the case in which thegroove section 111 is provided on the innerperipheral face 11 b of theframe 11, providing thegroove section 111 on the outerperipheral face 11 a makes it possible to reduce stress concentration when hitting a ball, and can increase the strength of theframe 11. - In the racket 1 of the present embodiment, in the top of the
frame 11, the portions of thegroove section 111 at the outer ends in the width direction are shallower than the portion of thegroove section 111 at the center; the thickness and the strength from the inner peripheral edge to thebottom surface 111 a of the groove section increase. Similarly, in the sides of theframe 11, the portions of thegroove section 111 at the outer ends in the longitudinal direction are shallower than the portion of thegroove section 111 at the center; the thickness and the strength from the inner peripheral edge to thebottom surface 111 a of the groove section increase. Thus, when hitting a ball, theframe 11 is likely to be curved inwardly in the longitudinal direction and in the width direction (the side which the ball hits is defined as the inside). That is, theframe 11 is likely to deform so as to rap the ball. This makes it possible to increase the contact area between the ball and the hitting surface (string 12), which results in improvement of control and spin. - If the
frame 11 has an elliptical (annular) shape, when thegroove section 111′ is uniform in depth as in theframe 11′ of the comparative example, thelongitudinal strings 121 become shorter as they pass through either outer portion of theframe 11 in the width direction, and thetransverse strings 122 become shorter as they pass through either outer portion of theframe 11 in the longitudinal direction. Thus, in the racket 1 of the present embodiment, the portions of thegroove section 111 which are located on the outerperipheral face 11 a of theframe 11, that is, the portions where thestring 12 is folded back, are shallower in depth as they go outwards from the center in the longitudinal direction or the width direction of theframe 11. That is, in the top of theframe 11, the portion of the groove section 111 (the positions at which thestring 12 is folded back) becomes shallower in depth as it goes outwards in the width direction. Also, in side of theframe 11, the portions of the groove section 111 (the positions at which thestring 12 is folded back) become shallower in depth as they go outwards in the longitudinal direction. This makes it possible to reduce the difference between the lengths oflongitudinal strings 121 arranged in the width direction and/or the difference between the lengths oftransverse strings 122 arranged in the longitudinal direction while increasing the lengths of thelongitudinal strings 121 and thetransverse strings 122. This makes it possible to reduce the differences caused by different hitting positions in theframe 11 of the rebound performance of a ball or the feel, which results in enlarging the sweet spot. - Further, it is preferable that the
groove section 111 varies gradually in depth without varying in steps in depth of thegroove section 111, in other words, without steps in thebottom surface 111 a of the groove section. This makes it possible to prevent stress when hitting a ball from concentrating into steps provided in thebottom surface 111 a of the groove section and to increase the strength of theframe 11. This also makes it possible to prevent change of the feel produced only when a ball hits a corresponding portion within theframe 11 to the steps provided in thebottom surface 111 a of the groove section. - In the abovementioned embodiment, the
base section 42 of thegrommet 40 is uniform in thickness. However, the invention is not limited thereto. For example, on the outerperipheral face 11 a of the top of theframe 11, the portions of thebase section 42 of thegrommet 40 provided in the outside in the width direction may be thicker than the portions of thebase section 42 of thegrommet 40 provided in the center in the width direction. Similarly, on the outerperipheral face 11 a of the sides of theframe 11, the portions of thebase section 42 of thegrommet 40 provided in the outside in the longitudinal direction may be thicker in thickness than the portions of thebase section 42 of thegrommet 40 provided in the center in the longitudinal direction. - Compared to the case in which only the depth of the
groove section 111 of theframe 11 varies, this makes it possible to further reduce the difference between the lengths oflongitudinal strings 121 arranged in the width direction and also to further reduce the difference between the lengths oftransverse strings 122 arranged in the longitudinal direction. Further, a thick portion of thebase section 42 of thegrommet 40 is located far from theframe 11 which is highly rigid, so that elastic deformation of thegrommet 40 easily to occur. Thus, when a ball impacts the hitting surface, if an force toward the inside of theframe 11 is produced at the positions where thestring 12 is folded back, the force can be absorbed by the thick grommet 40 (the base section 42). Thus, though the portions of the string passing in the outer ends in the width direction or in the longitudinal of theframe 11 are slightly shorter than the portions of the string passing in the center, the thick grommet 40 (the base section 42) has a high vibration damping capacity. Therefore, even when a player hits a ball with a region far from the center of theframe 11, the player can experience the feel nearly as much as when hitting a ball with a region of the center. That is, the sweet spot can be enlarged. - It should be noted that, if the
base section 42 of thegrommet 40 varies in thickness, thegroove section 111 of theframe 11 may be uniform in depth. In other words, adjusting the thickness of thebase section 42 of thegrommet 40 may achieve the followings: on the outerperipheral face 11 a of theframe 11, compared to a certain position in the longitudinal direction, the depth of the position where thestring 12 is folded back is shallower at a position outside of the certain position in the longitudinal direction; on the outerperipheral face 11 a of theframe 11, compared to a certain position in the width direction, the depth of the position where thestring 12 is folded back is shallower at a position outside of the certain position in the width direction. -
FIG. 5 is a diagram of theframe 11 and thegroove section 111 of the modified example. The frame 1 of the racket 1 in the abovementioned embodiment has an elliptical shape. However, the invention is not limited thereto. For example, as shown inFIG. 5 , the frame 1 may have substantially an elliptical shape in which the tip end and the handle end in the longitudinal direction have a lower degree of curving than those of an ellipse. - Further, in the racket 1 of the abovementioned embodiment, the depth (d1) of the point (P1 in
FIG. 3 ) of thegroove section 111 of the top of theframe 11 at the center in the width direction is equal to the depth (d2) of the point (P2 inFIG. 3 ) of thegroove section 111 of the sides of theframe 11 at the center in the longitudinal direction. However, the invention is not limited thereto. Thegroove section 111 may vary in depth. As mentioned above, the difference between the lengths oflongitudinal strings 121 arranged in the width direction and/or the difference between the lengths oftransverse strings 122 arranged in the longitudinal direction can be reduced as the depth of thegroove section 111 of the top of theframe 11 at the center in the width direction is increased and/or as the depth of thegroove section 111 of the sides of theframe 11 at the center in the longitudinal direction is increased. This reduces the thickness of theframe 11 from the innerperipheral face 11 a to thebottom surface 111 a of the groove section, which results in deterioration of the strength of theframe 11. However, if theframe 11 is substantially in an elliptical shape (including a perfect elliptical shape), theframe 11 is strong and difficult to deform because the top of theframe 11 is smaller in size than the sides. Further, sincelongitudinal strings 121 are longer thantransverse strings 122, reducing the difference between the lengths oflongitudinal strings 121 arranged in the width direction is more effective than reducing the difference between the lengths oftransverse strings 122 arranged in the longitudinal direction. That is, it is possible to further enlarge the sweet spot; also this allows the racket to rebound a ball more and to vibrate less. - As shown in
FIG. 6 , it is preferable that, in theframe 11 having substantially an elliptical shape, the depth (D+α) of the point (P1 inFIG. 5 ) of thegroove section 111 of the outerperipheral face 11 a of the top (the end in the longitudinal direction) at the center in the width direction be deeper than the depth (D) of the point (P2 inFIG. 5 ) of thegroove section 111 of the outerperipheral face 11 a of either side (either end in the width direction) at the center in the longitudinal direction. That is, it is preferable the depth at the position where thestring 12 is folded back on the outerperipheral face 11 a of the top of theframe 11 at the center in the width direction is deeper than the depth at the position where thestring 12 is folded back on the outerperipheral face 11 a of the sides of theframe 11 at the center in the longitudinal direction. As a result, the sweet spot can be further enlarged while preventing the strength deterioration of theframe 11. This also allows the racket to rebound a ball more and to vibrate less. - In the racket 1 of the abovementioned embodiment, all portions of the
groove section 111 located in the top and both sides of theframe 11 become shallower in depth as they go from the center to the outer ends. However, the invention is not limited thereto. For example, at least one portion of thegroove section 111 located in the top and both sides of theframe 11 may be different in depth. Further, in the racket 1 of the abovementioned embodiment, thegroove section 111 is not provided in the handle end (the portion facing the opening 30) of theframe 11 in the longitudinal direction. However, the invention is not limited thereto. For example, thegroove section 111 may be provided in the handle end and thegroove section 111 may be shallower in depth as it goes from the center in the width direction to the outer ends. Furthermore, in the racket 1 of the abovementioned embodiment, thegroove section 111 varies gradually in depth. However, the invention is not limited thereto. For example, thegroove section 111 may vary in depth by providing steps in thebottom surface 111 a of the groove section. - It should be noted that the aforementioned embodiment is for facilitating understanding of the invention, and are not limiting of the invention, and are not to be interpreted as limiting the invention. The invention can of course be altered and improved without departing from the gist thereof, and equivalents are intended to be embraced therein.
- For example, in the abovementioned embodiment, a tennis racket is taken as an example of a racket associated with the invention. However, the invention is not limited thereto. For example, the invention may be applied to a squash racket, a badminton racket and the like. Also, in the abovementioned embodiment, the racket 1 in the
frame 11 of which thestring 12 is strung is taken as an example of a racket associated with the invention. However, the invention is not limited thereto. A racket in which thestring 12 is not strung may also be employed.
Claims (3)
1. A racket comprising:
a handle;
an annular frame having
a plurality of through holes, and
a groove section provided on an outer peripheral face of the frame along a circumferential direction of the frame;
a shaft connecting the handle and the frame; and
a string
that passes through the through hole to the outside of the frame, and
that is folded back on the groove section,
wherein
when either one of a longitudinal direction of the racket and a width direction perpendicular to the longitudinal direction on a hitting surface of the racket is defined as a first direction,
a depth of a position at which the string is folded back at a second position in the first direction is smaller or less than a depth of a position at which the string is folded back at a first position in the first direction,
the first position being located on the outer peripheral face of the frame,
the second position being located on the outer peripheral face of the frame and outside of the first position in the first direction.
2. A racket according to claim 1 , wherein
the position at which the string is folded back on the outer peripheral face of the frame becomes shallower in depth as it goes from a center of the frame to an end in the first direction.
3. A racket according to claim 1 , wherein
the frame has substantially an elliptical shape, and
a position in an end in the longitudinal direction on the outer peripheral face of the frame at which the string is folded back at a center in the width direction is deeper in depth than a position in an end in the width direction on the outer peripheral face of the frame at which the string is folded back at a center in the longitudinal direction.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2013-044426 | 2013-03-06 | ||
JP2013044426A JP6196786B2 (en) | 2013-03-06 | 2013-03-06 | racket |
Publications (1)
Publication Number | Publication Date |
---|---|
US20140256480A1 true US20140256480A1 (en) | 2014-09-11 |
Family
ID=50272300
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/195,204 Abandoned US20140256480A1 (en) | 2013-03-06 | 2014-03-03 | Racket |
Country Status (4)
Country | Link |
---|---|
US (1) | US20140256480A1 (en) |
EP (1) | EP2774658B1 (en) |
JP (1) | JP6196786B2 (en) |
CN (1) | CN104027956A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170173407A1 (en) * | 2014-05-20 | 2017-06-22 | Yonex Kabushiki Kaisha | Racket and grommet |
US20180178085A1 (en) * | 2016-12-26 | 2018-06-28 | Dunlop Sports Co. Ltd. | Tennis racket frame |
US20180290027A1 (en) * | 2015-06-05 | 2018-10-11 | Yonex Co., Ltd. | Racket |
US20180290026A1 (en) * | 2015-06-05 | 2018-10-11 | Yonex Co., Ltd. | Badminton racket |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110193177A (en) * | 2019-05-29 | 2019-09-03 | 华南理工大学 | A kind of racket threading method |
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US4834383A (en) * | 1986-09-11 | 1989-05-30 | Skis Rossignol S. A. | Tennis racket with equal string lengths |
US4930782A (en) * | 1987-05-26 | 1990-06-05 | Karakal Corp. Of The Americas | String tension transmitting apparatus |
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ZA852092B (en) * | 1984-07-31 | 1985-11-27 | Cons Sporting Goods | Tapered racquet |
JP2690671B2 (en) | 1993-03-16 | 1997-12-10 | 住友ゴム工業株式会社 | tennis racket |
JPH0938241A (en) * | 1995-07-28 | 1997-02-10 | Mitsuru Usui | Racket having four throats |
JPH1033722A (en) * | 1996-07-30 | 1998-02-10 | Bridgestone Sports Co Ltd | Tennis racket |
JP2991129B2 (en) * | 1996-10-02 | 1999-12-20 | ブリヂストンスポーツ株式会社 | tennis racket |
GB9914090D0 (en) * | 1999-06-17 | 1999-08-18 | Dunlop Slazenger Group Ltd | Improved games racket |
JP2001170219A (en) * | 1999-12-20 | 2001-06-26 | Bridgestone Sports Co Ltd | Tennis racket |
DE102006004863B4 (en) * | 2006-02-02 | 2007-12-27 | Head Technology Gmbh | Racket for ball games |
US7806789B2 (en) * | 2007-05-03 | 2010-10-05 | John L Sledge | Sports racket |
CN202315168U (en) * | 2011-11-04 | 2012-07-11 | 陈良山 | Badminton racket |
CN202366404U (en) * | 2011-12-12 | 2012-08-08 | 李宁体育(上海)有限公司 | Badminton racket |
-
2013
- 2013-03-06 JP JP2013044426A patent/JP6196786B2/en active Active
-
2014
- 2014-03-03 US US14/195,204 patent/US20140256480A1/en not_active Abandoned
- 2014-03-05 EP EP14157836.9A patent/EP2774658B1/en active Active
- 2014-03-05 CN CN201410078010.7A patent/CN104027956A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4834383A (en) * | 1986-09-11 | 1989-05-30 | Skis Rossignol S. A. | Tennis racket with equal string lengths |
US4930782A (en) * | 1987-05-26 | 1990-06-05 | Karakal Corp. Of The Americas | String tension transmitting apparatus |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170173407A1 (en) * | 2014-05-20 | 2017-06-22 | Yonex Kabushiki Kaisha | Racket and grommet |
US9750989B2 (en) * | 2014-05-20 | 2017-09-05 | Yonex Kabushiki Kaisha | Racket and grommet |
US20180290027A1 (en) * | 2015-06-05 | 2018-10-11 | Yonex Co., Ltd. | Racket |
US20180290026A1 (en) * | 2015-06-05 | 2018-10-11 | Yonex Co., Ltd. | Badminton racket |
US10369422B2 (en) * | 2015-06-05 | 2019-08-06 | Yonex Co., Ltd. | Badminton racket |
US20180178085A1 (en) * | 2016-12-26 | 2018-06-28 | Dunlop Sports Co. Ltd. | Tennis racket frame |
US10245473B2 (en) * | 2016-12-26 | 2019-04-02 | Dunlop Sports Co. Ltd. | Tennis racket frame |
Also Published As
Publication number | Publication date |
---|---|
EP2774658A1 (en) | 2014-09-10 |
JP2014171526A (en) | 2014-09-22 |
JP6196786B2 (en) | 2017-09-13 |
CN104027956A (en) | 2014-09-10 |
EP2774658B1 (en) | 2017-06-14 |
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