JP5397581B2 - Baseball or softball bat - Google Patents

Description

  The present invention relates to a baseball or softball bat (hereinafter also simply referred to as “bat”), and more particularly to a bat in which an elastic body is attached to a hit ball portion.

In order to provide a bat that exhibits excellent durability and can extend the flight distance of a hit ball, a bat in which an elastic body is integrally coated on a concave portion of a hit ball portion is described in, for example, Japanese Patent Application Laid-Open No. 2003-19236 Has been.
JP 2003-19236 A

  Since the bat described in the above document is mainly intended to reduce the deformation of the ball at the time of hitting, according to the technical idea described in the above document, the hardness of the elastic body attached to the hitting ball portion is reduced. It is better to do it.

  However, simply lowering the hardness of the elastic body causes problems in terms of durability and the like. Therefore, it can be said that the bat described in the above document has a limit in improving the resilience characteristics.

  In view of the above, an object of the present invention is to provide a bat in which an elastic body is attached to a hit ball portion, which can improve the resilience characteristics while ensuring durability.

The baseball or softball bat according to the present invention includes a core member having a recess in a portion to be a hitting ball portion, and an elastic body that is attached to the recess and forms the hitting ball portion. on the order 55 to 0.60, a degree JIS C hardness of 6-9 or 82 or less of the surface layer, and the elastic modulus at elongation 100% of the order or 2.03MPa or less 1.93MPa, urethane elastomer Consists of foam. That is, the elastic body is composed of a urethane elastomer foam having a relatively high hardness and elastic modulus.

  The elastic body has a surface layer and an interior. It is preferable that the hardness of the surface layer is higher than the internal hardness, and the difference in hardness between the surface layer and the internal JIS C hardness is about 7 or more and 15 or less. Further, a lubricating layer may be provided between the elastic body and the core material.

The above-mentioned elastic body is obtained by applying a compressive load at the same speed from the integrated value of the product of the load and the displacement when a compressive load of 800 N is applied to a part of the elastic body removed from the core material at a speed of 10 mm / min. The hysteresis value, which is a value obtained by subtracting the integral value of the product of the load and displacement at the time of removal, is 0.15 J or more and 0.00. You may further provide the 1st characteristic which is 31 J or less, and the 2nd characteristic that the bounce height of the weight based on ASTM-D2632 becomes 121.2 mm or more and 133.6 mm or less.

  Moreover, you may comprise the said elastic body with the fine cell urethane elastomer foam whose cell magnitude | size is 75 micrometers or more and 115 micrometers or less.

  The bat has a tip portion and a grip portion. The bottom surface of the recess has a tip-side tapered portion located on the tip side, a grip-side tapered portion located on the grip portion side, and a center located between the tip-side tapered portion and the grip-side tapered portion. It may have a part. In this case, it is preferable that the outer diameter of the core material constituting the central portion is not more than the minimum value of the outer diameters of the core materials constituting the tip side tapered portion and the grip side tapered portion.

Baseball or softball bat of the present invention, the elastic body is attached to the portion serving as the hitting portion, a degree JIS C hardness of 6-9 or 82 or less of the surface layer, and the elastic modulus at elongation 100% Since it is composed of a urethane elastomer foam having a relatively high hardness and elastic modulus of about 1.93 MPa or more and 2.03 MPa or less, the resilience characteristics can be improved while ensuring the durability.

  Hereinafter, a baseball or softball bat 1 according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the bat 1 in the present embodiment mainly includes a core (base material) 2 having a recess 2b1 in a portion that becomes the hitting ball portion 2b and an elastic body 3.

  In the example of FIG. 1, the core member 2 includes a tip portion, a recess 2b1 at a portion corresponding to the hit ball portion, a grip portion, and a tapered portion positioned between the recess 2b1 and the grip portion. The tip portion of the core material 2 becomes the tip portion 2 a of the bat 1, the portion where the elastic body 3 is attached to the concave portion 2 b 1 of the core material 2 becomes the hitting ball portion 2 b of the bat 1, and the taper portion of the core material 1 is the taper of the bat 1. The grip portion of the core material 2 becomes the grip portion 2 d of the bat 1. The core material 2 may have a hollow structure or a solid structure.

  The front end portion 2a of the bat 1 is a front end (one end) of the bat 1 on the hitting ball portion 2b side and a portion in the vicinity thereof, for example, a portion in a range of about 50 mm from the end portion on the hitting ball portion 2b side of the bat 1 It corresponds to 2a. For example, a cap member may be attached to the distal end portion 2a.

  The hitting portion 2b of the bat 1 is a portion where the ball is actually expected to be hit. For example, a range of about 200 mm to 350 mm from the end portion on the grip portion 2d side of the tip portion 2a to the grip portion 2d side. This corresponds to the hit ball portion 2b.

  FIG. 5 shows an example of the shape of the recess 2 b 1 of the core material 2. As shown in FIG. 5, the bottom surface of the recess 2b1 (the outer peripheral surface of the core member 2 in the recess 2b1) is positioned on the tip side taper portion 20 located on the tip portion (2a) side and on the grip portion (2d) side. A grip-side tapered portion 22 and a central portion 21 located between the tip-side tapered portion 20 and the grip-side tapered portion 22.

  In the example of FIG. 5, the tip-side tapered portion 20 has a maximum outer diameter on the tip portion (2 a) side, and the outer diameter of the tip-side tapered portion 20 becomes smaller toward the center portion 21. The outer diameter of the central portion 21 is constant. The grip side tapered portion 22 has a maximum outer diameter on the grip portion (2d) side, and the outer diameter of the grip side tapered portion 22 becomes smaller toward the center portion 21. Therefore, the outer diameter of the core material 2 constituting the central portion 21 is equal to or smaller than the outer diameter of the core material 2 constituting the tip side tapered portion 20 and the grip side tapered portion 22.

  As described above, the distal end side tapered portion 20 and the grip side tapered portion 22 are provided, and the outer diameter of the core material 2 constituting the central portion 21 is configured to constitute the distal end side tapered portion 20 and the grip side tapered portion 22. By setting it to the minimum value or less of the outer diameter of the core material 2, the thickness of the elastic body 3 in the hit ball portion 2b can be ensured. This can also contribute to the improvement of the resilience characteristics of the bat 1 described later.

  Moreover, the thick region of the elastic body 3 can be increased in the hit ball portion 2b. Thereby, it is possible to reduce the degree of flight distance reduction when the ball is hit at a place other than the sweet spot. In particular, it is possible to reduce the degree of flight distance reduction when a ball is hit at a position closer to the grip portion 2d than the sweet spot of the bat 1.

  The length L1 of the tip-side tapered portion 20, the length L2 of the central portion 21, and the length L3 of the grip-side tapered portion 22 can be appropriately set. For example, the length L1 is about 100 to 110 mm. It is conceivable that L2 is about 30 to 40 mm and about 100 to 110 mm. In this way, it is conceivable that the length L1 of the tip side tapered portion 20 and the length L3 of the grip side tapered portion 22 are made larger than the length L2 of the central portion 21.

  The taper portion 2c of the bat 1 is a portion that is located between the hit ball portion 2b and the grip portion 2d, and whose outer diameter gradually decreases from the hit ball portion 2b toward the grip portion 2d. For example, a portion in the range of about 150 mm to 450 mm from the end of the hitting ball portion 2b on the grip portion 2d side to the grip portion 2d side corresponds to the tapered portion 2c.

  The grip portion 2d of the bat 1 is a portion that the batter is scheduled to hold by hand, and the portion from the end portion of the tapered portion 2c on the grip portion 2d side to the other end (grip end) of the bat 1 is the grip portion. It corresponds to 2d. The grip end is typically composed of an enlarged diameter portion. The grip end may be formed integrally with the core material 2, but may be formed separately from the core material 2 and attached separately to the core material 2.

  As the material of the core material 2, for example, a material that can be used for the bat such as wood, metal, or fiber reinforced plastic can be used. In the present embodiment, the material is made of fiber reinforced plastic.

  As shown in FIGS. 1 and 2, the elastic body 3 is attached to the concave portion 2 b 1 provided in the portion that becomes the hitting ball portion 2 b in the core material 2. The elastic body 3 can be attached to the concave portion 2b1 of the hitting ball portion 2b via an adhesive tape, an adhesive, or the like. The elastic body 3 typically has a cylindrical shape, but any other shape can be adopted. The elastic body 3 is preferably made of a single material, but the elastic body 3 may be made of a plurality of materials. Furthermore, you may comprise the elastic body 3 combining several parts. Preferably, the inner diameter of the elastic body 3 is made smaller than the outer diameter of the recess 2b1 of the core material 2. Thereby, tension can be applied to the elastic body 3 when the elastic body 3 is attached to the concave portion 2b1 of the core material 2, and the wrinkles on the surface of the elastic body 3 can be suppressed while suppressing displacement and slipping of the elastic body 3. It is also effective in suppressing the occurrence of

  In the present embodiment, the elastic body 3 attached to the recess 2b1 of the core material 2 has a “JIS C hardness” of about 54 to 82 and an “elastic modulus at 300% elongation” of 3. It is composed of a urethane elastomer foam that is about 85 MPa to 5.6 MPa (in terms of elastic modulus at 100% elongation, about 1.84 MPa to 2.03 MPa). That is, by maintaining both “JIS C hardness” and “elastic modulus at 300% elongation” at relatively high values, both rebound characteristics and durability are made favorable. The elongation of the elastic body 3 is preferably about 290 to 400.

  Here, “elastic modulus at 300% elongation” means the elastic modulus (tensile stress) when the elastic body 3 is elongated by 300%. Further, “elastic modulus at 100% elongation” means an elastic modulus (tensile stress) when the elastic body 3 is elongated by 100%. “JIS C hardness” refers to the hardness measured according to the spring hardness test type C test method of Annex 2 of JIS K 7312.

  The elastic body 3 preferably has the following characteristics. That is, the product of a load and a displacement (a deformation amount of the elastic body 3 at the time of compression) when a compressive load of 800 N is applied to a part of the elastic body 3 removed from the core material 2 at a speed of 10 mm / min. The hysteresis value, which is a value obtained by subtracting the integral value of the product of the load and the displacement (the amount of deformation of the elastic body 3 at the time of unloading) when the compressive load is removed at the same speed, is 0.15 J or more. It is preferable that it is 42 J or less.

  Here, the “hysteresis” refers to the difference between the work given to the test piece during loading on the stress-strain curve and the work returned from the test piece during load reduction. Therefore, the “hysteresis value” can be calculated by the energy value (E1) in the load increase range−the energy value (E2) in the load decrease range. The energy value is a value obtained by integrating the value of load × displacement (deformation amount) during the test.

  Next, a method for measuring the hysteresis value will be described. The size of the test piece for measuring the hysteresis value is 25 mm (width) × 90 mm (length) × 20 mm (thickness). This test piece can be manufactured as follows.

  First, the elastic body 3 is removed from the core member 2, and a part thereof is cut out from the cylindrical elastic body 3 by a circumferential length L4 as shown in FIG. Thereby, a part of the curved rectangular elastic body 3 is obtained. At this time, the circumferential length L4 is about 30 mm, for example. A part of the cut out elastic body 3 is cut into a size of 90 mm × 25 mm. Thereafter, the thickness of the elastic body 3 is adjusted by rolling the elastic body 3 or the like. Thereby, a test piece of 25 mm (width) × 90 mm (length) × 20 mm (thickness) can be prepared. In addition, you may produce the test piece of the said size by superimposing the some elastic body 3. FIG.

  After preparing a test piece as described above, a compression test is performed using Autograph AG-5000G (trade name: manufactured by Shimadzu Corporation). The compression speed is 10 mm / s and a load is applied up to 800N. Then return at the same speed to remove the load on the specimen. Based on the load / displacement curve at this time, the hysteresis value is obtained by the above formula.

  The inventors of the present invention have a specific gravity of 0.45, JIS C hardness of the surface layer: 69, elastic modulus at 300% elongation: 3.85 MPa (elastic modulus at 100% elongation: 1.84 MPa), The hysteresis value of the size test piece was determined to be 0.412 J. Similarly, the specific gravity is 0.55, the JIS C hardness of the surface layer is 78, the elastic modulus at 300% elongation is 4.1 MPa (elastic modulus at 100% elongation: 1.93 MPa), and the above size test. The hysteresis value of the piece was determined to be 0.307 J. Moreover, the specific gravity: 0.6, the JIS C hardness of the surface layer: 82, the elastic modulus at 300% elongation: 5.6 MPa (elastic modulus at 100% elongation: 2.03 MPa), and a test piece of the above size The hysteresis value was determined to be 0.151J.

  In addition, it is a conventional product, specific gravity: 0.35, JIS C hardness of the surface layer: 43, elastic modulus at 300% elongation: 1.23 MPa (elastic modulus at 100% elongation: 0.54 MPa), The hysteresis value of the test piece of the above size is 1.067. From this, it is considered that the energy loss before and after the hit ball can be reduced by using the elastic body 3 having the characteristics of each test piece as compared with the conventional product.

  Further, the elastic body 3 has a bouncing height of a weight based on ASTM-D2632 (for example, a height of a bouncing of 27.9 g of weight on a part of an elastic body having a thickness of 20 mm removed from the core material 2) It is preferable to provide such a characteristic that the thickness is 121.2 mm or more and 133.6 mm or less.

  The rebound height can be measured by performing the following drop test (simple rebound test). The size of the test piece is 25 mm (width) × 90 mm (length) × 20 mm (thickness), and is prepared by the method described above.

  As a testing machine, “Vertical Rebound Reliance Tester” (manufacturer: Gotech, product number: GT-7042-V) is used, and ASTM-D2632 (Standard Test Method for Rubber Property-Resilience Test) is conducted. Thereby, the above-mentioned bounce height can be measured.

  The inventors of the present invention have a specific gravity of 0.45, JIS C hardness of the surface layer: 69, elastic modulus at 300% elongation: 3.85 MPa (elastic modulus at 100% elongation: 1.84 MPa), It was 30.3 mm when the bounce height of the test piece of size was measured. Similarly, the specific gravity is 0.55, the JIS C hardness of the surface layer is 78, the elastic modulus at 300% elongation is 4.1 MPa (elastic modulus at 100% elongation: 1.93 MPa), and the above size test. It was 31.7 mm when the bounce height of the piece was measured. Moreover, the specific gravity: 0.6, the JIS C hardness of the surface layer: 82, the elastic modulus at 300% elongation: 5.6 MPa (elastic modulus at 100% elongation: 2.03 MPa), and a test piece of the above size It was 33.4 mm when the bounce height of was measured.

  In addition, it is a conventional product, specific gravity: 0.35, JIS C hardness of the surface layer: 43, elastic modulus at 300% elongation: 1.23 MPa (elastic modulus at 100% elongation: 0.54 MPa), The rebound height of the test piece of the above size is 11.3. From this, it is considered that the resilience characteristics can be improved as compared with the conventional product by using the elastic body 3 having the characteristics of each test piece. Moreover, the value of the said JIS C hardness is an average value of 5 times (point) measurement.

  The specific gravity of the elastic body 3 is 0.45 or more and 0.60 or less. The reason is that when the specific gravity is less than 0.45, a lot of voids are generated and molding becomes difficult, and when the specific gravity is greater than 0.6, it becomes overpack and is generated from the material. This is because the air to be discharged does not pass well and the surface of the elastic body 3 is struck. Further, if the TPU sheet is placed on the overpacked elastic body 3, peeling easily occurs.

  In the case of the elastic body 3 used in the present embodiment, the JIS C hardness and elastic modulus of the elastic body 3 are proportional to the specific gravity of the elastic body 3. In this case, by setting the specific gravity of the elastic body 3 in the range of 0.45 or more and 0.60 or less, the JIS C hardness of the elastic body 3 becomes 54 or more and 82 or less, and the elastic modulus at 300% elongation is 3 It is 0.85 MPa or more and 5.6 MPa or less (in the elastic modulus at 100% elongation, 1.84 MPa or more and 2.03 MPa or less).

  Until the invention of the present application was made, as described in Japanese Patent Application Laid-Open No. 2003-19236, in a bat in which an elastic body is mounted on a hit ball portion, various research and development have been made with a focus on reducing the hardness of the elastic body. It was. However, if the hardness of the elastic body is lowered, not only the durability of the elastic body is lowered, but also the production of the elastic body becomes difficult, so it has been thought that further improvement of the resilience characteristics may be difficult.

  However, while the inventors of the present application have made various studies to improve the durability of the elastic body, when the hardness of the elastic body is considered to be a relatively high range, not only can the durability be improved, As a result, it has been found that the resilience characteristics may be improved. That is, instead of simply reducing the hardness of the elastic body to reduce the deformation of the ball at the time of hitting, the hardness of the elastic body is set to a relatively high range and the elasticity of the elastic body itself is effectively exhibited. It has been found that the resilience characteristics can be improved by controlling the elastic modulus of the elastic body in a relatively high range while suppressing deformation of the ball at the time of hitting. In particular, by using a fine cell urethane elastomer foam having a cell size of 75 μm or more and 115 μm or less as the elastic body 3, the above-described effect becomes remarkable.

  The inventors of the present application conducted the following test to support the above effect, and the result will be described.

  First, the specific gravity is 0.45, the JIS C hardness of the front and back surface layers is 70 to 74, the internal JIS C hardness is 54 to 60, and the elastic modulus at 300% elongation is 3.85 MPa (100% elongation). 5 types of urethane elastomer foams (samples A to E: elastic body 3) with different thicknesses are prepared, and the coefficient of restitution after the ball collides with them is measured. The results are shown in Table 1.

  Here, the test apparatus and test method used in this test will be described with reference to FIG. As shown in FIG. 3, the test apparatus includes a pitching machine 8, a high-speed video camera 6, and an image analysis device (not shown). As the hitting ball model 9 that is a collision target for colliding the ball 5, only an iron plate and a material in which the urethane elastomer foam is attached to the iron plate were prepared. Then, the ball 5 launched from the pitching machine 8 is caused to collide with a fixed hitting ball model 9 and this collision is photographed from the side by a high-speed video camera 6, and the coefficient of restitution is calculated from the velocity of the ball 5 before and after the collision. did.

  Samples A to E used for the hit ball model 9 have a square with a side of 15 cm and a thickness of 10 mm, 12.5 mm, 15 mm, 20 mm, and 30 mm, respectively. In this test, a soft baseball was used, and a repulsion test was performed by causing the soft baseball to collide with each hitting ball model 9 at an incident speed of 147 km / h.

  Next, a method for calculating the restitution coefficient e will be described. The restitution coefficient e is calculated using Equation 1 below. In addition, description of the code | symbol in numerical formula is written together under the following numerical formula 1.

  The center-of-gravity velocity of the ball in the above calculation formula can be obtained by analyzing an image taken by a high-speed video camera using an image analysis device.

  As can be seen from the test results in Table 1, it can be seen that the coefficient of restitution of Samples A to E is very excellent compared to the steel plate. It can also be seen that the coefficient of restitution improves as the thickness increases from 10 mm to 30 mm.

  Next, since the same coefficient of restitution was measured for samples F, G, and H having different specific gravities (0.45 to 0.60), the results are shown in Table 2 below.

  As shown in Table 2, when the resilience coefficient of each sample (elastic body) is compared, it can be seen that those having a small specific gravity exhibit excellent resilience characteristics. From the results of Tables 1 and 2, the elastic body 3 having excellent resilience characteristics can be obtained by setting the specific gravity of the elastic body 3 to about 0.45 or more and 0.60 or less, but the specific gravity value is low (for example, It is estimated that the resilience characteristics can be improved more effectively by using the elastic body 3 (about 0.45 to 0.55).

  The JIS C hardness of the front and back surface layers of Sample F having a specific gravity of 0.45 is 69, the internal JIS C hardness located between the surface layers is 54, and the elastic modulus at 300% elongation is 3.85 MPa (100% The elastic layer has an elastic modulus of 1.84 MPa when stretched, and the surface layer of sample G having a specific gravity of 0.55 has a JIS C hardness of 78, an internal JIS C hardness of 65, and an elastic modulus of 300% when stretched is 4 .1 MPa (elastic modulus at 100% elongation is 1.93 MPa), and the surface layer of sample H with a specific gravity of 0.60 has a JIS C hardness of 82, an internal JIS C hardness of 75, and a 300% elongation. The elastic modulus of 5.6 MPa (elastic modulus at 100% elongation is 2.03 MPa).

  From the above test results, the JIS C hardness is about 54 or more and 82 or less, and the elastic modulus at 300% elongation is about 3.85 MPa or more and 5.6 MPa or less (the elastic modulus at 100% elongation is 1. It is considered that a bat having excellent resilience characteristics can be obtained by configuring the elastic body 3 with a urethane elastomer foam that is about 84 MPa or more and 2.03 MPa or less. In addition, since any of the above samples has a relatively high hardness of about 50 or more in JIS C hardness, durability can also be improved.

  Regarding the JIS C hardness of the outer peripheral portion and the inner peripheral portion of the elastic body 3, the JIS C hardness of the inner and outer peripheral surface layers (skin layers) is about 69 to 82, and the internal JIS C hardness located between the surface layers is It is preferably about 54 or more and 75 or less.

  Focusing on the durability, the JIS C hardness is about 65 or more and 82 or less, and the elastic modulus at 300% elongation is about 4.10 MPa or more and 5.6 MPa or less (in the elastic modulus at 100% elongation, 1. It is conceivable that the elastic body 3 is composed of a urethane elastomer foam that is about 93 MPa to 2.03 MPa.

  As shown in FIG. 2, the elastic body 3 has a surface layer (skin layer) 3a on the inner and outer peripheries and an interior 3b between the surface layers 3a. Here, it is preferable that the hardness of the surface layer 3a (the hardness on the outer peripheral surface) is higher than the hardness of the internal 3b, and the difference in hardness in the JIS C hardness between the surface layer 3a and the internal 3b is about 7 to 15. . More preferably, it is about 13 or more and 15 or less. By increasing the hardness difference in this manner, both the resilience characteristics and the durability can be improved.

  In FIG. 2, for convenience of explanation, a boundary line is illustrated by a dotted line between the inner and outer surface layers 3 a and the inner part 3 b, but actually there is no clear boundary line between the two.

  Since the hardness of the elastic body 3 is relatively high as described above, the thickness of the elastic body 3 can be reduced to about 5 mm to 6 mm. Moreover, since the flat strength of the elastic body 3 is high, the thickness of the core material 2 can be reduced. Thereby, the weight of the bat can be reduced.

  Further, it is possible to provide the lubricating layer 10 between the elastic body 3 and the core material 2 by making the hardness of the elastic body 3 relatively high. Thereby, the elastic body 3 can be easily attached and detached, and the replacement work of the elastic body 3 can be easily performed. As the lubricating layer 10, for example, a silicon release agent layer can be employed. However, any layer other than the silicon release agent layer can be adopted as long as it has a lubricating function. In the present embodiment, the lubricating layer 10 may be locally formed, but the lubricating layer 10 may be formed on the entire surface of the recess 2 b 1 in the core material 2.

  Next, Examples 1 and 2 of the bat 1 of the present invention will be described using Table 3 below. Table 3 below shows the specifications of the bats of Examples 1 and 2 and the specifications of the bats of Comparative Examples 1 and 2. Table 3 also shows the coefficient of restitution obtained by the rebound test performed on each bat.

  In addition, as the core material 2 of the bat of Examples 1 and 2 shown in Table 3 above, fiber reinforced plastic (FRP: Fiber Reinforced Plastics) is used. Further, the elastic body 3 attached to the bat of Example 1 has a thickness of 10 mm, a specific gravity of 0.45, a JIS C hardness of 69 on the outer peripheral surface layer, and an internal JIS C hardness located between the inner and outer surface layers. 54, an elastic body that is composed of a urethane elastomer foam having an elastic modulus at an elongation of 300% of 3.85 MPa (an elastic modulus at an elongation of 100% is 1.84 MPa) and is attached to the bat of Example 2 3 is a modulus of elasticity when the thickness is 12.5 mm, the specific gravity is 0.45, the outer surface layer has a JIS C hardness of 69, and the inner JIS C hardness located between the inner and outer surface layers is 54, 300% elongation. Is made of a urethane elastomer foam of 3.85 MPa (elastic modulus at 100% elongation is 1.84 MPa). The elastic body 3 attached to the bat of Comparative Example 1 is an elastic body used in the current product, has a thickness of 12.5 mm, a specific gravity of 0.35, a surface layer having a JIS C hardness of 43, and located between the surface layers. The internal JIS C hardness is 38, and the elastic modulus at 100% elongation is 0.54. The bat of Comparative Example 2 is a metal bat made of aluminum alloy (7046 series).

  Here, the repulsion test method performed with respect to each bat shown in Table 3 is demonstrated using FIG.

  As shown in FIG. 4, the experimental apparatus includes a pitching machine 8, a high-speed video camera 6, an image analysis device (not shown), and a bat table 7.

  In this test, a ball (soft baseball ball) 5 launched from the pitching machine 8 is caused to collide at 130 km / h with the hitting portion of the bat 1 placed on the bat stand 7. Then, this collision is photographed from directly above by the high-speed video camera 6, and the restitution coefficient is calculated from the speed of the ball 5 before the collision, the speed of the ball 5 after the collision, and the speed of the bat 1. The restitution coefficient e is calculated by the following formula 2.

  As shown in Table 3, it can be seen that the resilience characteristics of the bats of Examples 1 and 2 are superior to the resilience characteristics of the bats of Comparative Examples 1 and 2. That is, by using the bat based on the present embodiment, the resilience characteristics can be improved as compared with the conventional product including the current product.

  Next, Examples 3 and 4 of the bat 1 of the present invention will be described using Table 4 below. Table 4 below shows the specs of the bats of Examples 3 and 4 and the specs of the bat of Comparative Example 3. Table 4 also shows the coefficient of restitution obtained by the rebound test performed on each bat.

  As the core material 2 of the bat of Examples 3 and 4 shown in Table 4 above, fiber reinforced plastic is used. The elastic body 3 attached to the bat of Example 3 is the same type as that of Example 1. The elastic body 3 attached to the bat of Example 4 has a thickness of 15 mm, a specific gravity of 0.45, and an outer peripheral side. The surface layer is composed of a urethane elastomer foam having a JIS C hardness of 69 and an elastic modulus at 300% elongation of 3.85 MPa (elastic modulus at 100% elongation of 1.84 MPa). The bat of Comparative Example 3 is a bat made of an aluminum alloy (7050 series) and having a hit ball thickness of 1.7 mm.

  As shown in Table 4, it can be seen that the resilience characteristics of the bats of Examples 3 and 4 are superior to the resilience characteristics of the bat of Comparative Example 3.

  Table 5 below shows the physical property test results of three types of elastic bodies 3 (elastic bodies I, II, III) having a thickness of 20 mm. Table 5 also shows the coefficient of restitution when the elastic body 3 is attached to an iron plate and the test shown in FIG. 3 is performed. Furthermore, also about Comparative Examples 4-9, a physical-property test result and a restitution coefficient are shown. Comparative Example 4 is made of the current soft polyurethane material, Comparative Example 5 is made of Urethane A, Comparative Example 6 is made of Urethane B, Comparative Example 7 is made of Urethane C, Comparative Example 8 is made of NR (natural rubber), Comparative Example 9 Is made by NBR (Nitrile Butadiene Rubber).

  As shown in Table 5, it can be seen that the elastic bodies I to III have a higher coefficient of restitution than the elastic body of the comparative example.

  The inventors of the present application also conducted an actual hitting durability test on the bat of the embodiment of the present invention and the current bat using a polyurethane material as an elastic body. As a test, a soft ball having a speed of 100 to 110 km / h was hit at a swing speed of 100 to 120 km / h, and the number of balls until the hitting portion was broken was measured. As a result, it was confirmed that the bat of this example had 1.7 times the durability of the current bat.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. is there. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

1 is a partial cross-sectional plan view of a baseball or softball bat in one embodiment of the present invention. It is the II-II sectional view taken on the line of the baseball or softball bat shown in FIG. It is a schematic diagram of the test apparatus used for the rebound test of the hit ball model. It is a schematic diagram of the test apparatus used for the rebound test of a bat. It is a figure which shows the example of a shape of a core material. It is a schematic diagram for demonstrating the preparation methods of a test piece.

Explanation of symbols

  1 Bat (baseball or softball bat), 2 core material, 2a tip, 2b hitting ball, 2b1 recess, 2c taper, 2d grip, 3 elastic body, 3a surface layer, 3b inside, 5 ball, 6 high Speed video camera, 7 butt stand, 8 pitching machine, 9 hitting ball model, 10 lubrication layer, 20 tip side taper part, 21 center part, 22 grip side taper part.

Claims (6)

A core material (2) having a recess (2b1) in a portion to be a hitting ball portion (2b);
An elastic body (3) mounted on the recess (2b1) and forming the hitting ball part (2b);
It said elastic body (3), specific gravity of 0.55 to 0.60, JIS C hardness of the surface layer (3a) is at 6 9 or 82 or less, 1 elastic modulus at elongation 100%. A baseball or softball bat made of a urethane elastomer foam having a pressure of 93 MPa to 2.03 MPa. The elastic body (3) has the surface layer (3a) and the internal (3b),
The hardness of the surface layer (3a) is higher than the hardness of the internal (3b), and the hardness difference between the surface layer (3a) and the internal (3b) is 7 to 15 in terms of JIS C hardness. Item 2. The baseball or softball bat according to item 1.   The baseball or softball bat according to claim 1 or 2, wherein a lubricating layer is provided between the elastic body (3) and the core material (2). The elastic body (3)
From the integral value of the product of the load and the displacement when a compressive load of 800 N is applied to a part of the elastic body (3) in a state removed from the core material (2) at a speed of 10 mm / min, at the same speed. A first characteristic in which a hysteresis value, which is a value obtained by subtracting an integral value of a product of a load and a displacement when the compressive load is removed, is 0.15 J or more and 0.31 J or less;
The baseball or softball bat according to any one of claims 1 to 3, further comprising a second characteristic such that a rebound height of the weight based on ASTM-D2632 is 121.2 mm or more and 133.6 mm or less. .   The baseball or softball bat according to any one of claims 1 to 4, wherein the elastic body (3) is made of a fine cell urethane elastomer foam having a cell size of 75 µm to 115 µm. A tip portion (2a) and a grip portion (2d);
The bottom surface of the recess (2b1) includes a tip-side tapered portion (20) located on the tip portion (2a) side, a grip-side tapered portion (22) located on the grip portion (2d) side, A center portion (21) located between the tip-side tapered portion (20) and the grip-side tapered portion (22);
The outer diameter of the core material (2) constituting the central portion (21) is set to be equal to the outer diameter of the core material (2) constituting the tip side taper portion (20) and the grip side taper portion (22). The baseball or softball bat according to any one of claims 1 to 5, wherein the baseball or softball bat is not more than a minimum diameter.

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