JP4252538B2 - Ball bat with barrel section optimized for strain energy - Google Patents

Description

  The present invention relates to a ball bat having a barrel portion with optimized strain energy.

  Baseball and softball bat manufacturers are constantly striving to develop ball bats that exhibit high durability and good performance characteristics. The ball bat typically includes a grip portion, a barrel portion, and a tapered portion that connects the grip portion to the barrel portion. The outer shells of these bats are typically formed of aluminum or other suitable metal and / or one or more composite materials.

  In the design specifications of modern bats, the structure of the barrel is particularly important. A barrel section with a single wall structure has been developed, and recently a barrel section with a multiple wall structure has been developed. Modern ball bats typically have a hollow internal structure, which makes the bat relatively light and allows ball players to fully play "bat speed" or "swing speed". ) ”.

  Single-walled bats generally include a single tubular spring in the barrel. A multi-walled barrel section typically includes two or more tubular springs or similar structures within the barrel section, which may be of the same or different material composition. Also good. These multi-walled bat tubular springs are typically in contact with each other so that they form a frictional connection, bonded together by welding or adhesive, or separated from each other and are frictionless One of the forms. When the tubular spring is bonded using a structural adhesive or other structural adhesive material, the barrel portion is basically a single wall structure.

  While the bat generally has a durable barrel, it is desirable to exhibit optimal performance characteristics. Hollow bats typically exhibit a phenomenon known as the “trampoline effect”. This basically involves the rebound speed of the ball leaving the barrel portion of the bat as a result of the bending of the wall of the barrel portion. Thus, it is desirable to build a ball bat with a high “trampoline effect”, which allows the bat to produce a high rebound rate against the thrown ball when contacted.

  The “trampoline effect” is a direct result of compression and a result of barrel distortion recovery. In the process of barrel compression and decompression, energy is transferred to the ball resulting in a barrel effective coefficient of restitution (COR). This is the ratio of the velocity of the ball after the collision to the velocity of the ball before the collision (COR = Vpost impact / Vincident). In other words, the “trampoline effect” of the bat becomes better as the COR of the barrel portion of the bat increases.

  Multi-wall bats were developed with an effort to increase the amount of barrel deflection within an acceptable range beyond that possible with typical single-wall bats. These multiple wall structures generally produce high barrel deflection without increasing the stress beyond the material limit of the barrel material. Thus, the multi-wall barrel is typically more effective at returning energy to the ball. The bending characteristics of the multi-wall barrel section reduce the undesirable deflection and deformation of balls that are typically made of very inefficient materials.

  In addition, multi-wall bats differ from single walls in that no shear energy transfer occurs through an interfacial displacement control zone ("ISCZ"), i.e., a region between barrel walls. As a result of the balance of strain energy, this shear energy causes shear deformation in the single-wall barrel and is converted to bending energy in the multi-wall barrel. And since the bending deformation is more effective for energy transfer compared to the shear deformation, the walls of the multi-walled bat typically exhibit a lower strain energy loss than the single-walled bat. Thus, a multi-wall barrel is generally preferred over a single-wall to produce effective bat-to-ball collision mechanics or a better “trampoline effect”.

  In a single-walled bat, there is a single neutral axis, defined as the centroid axis around which all deformation occurs, for radial and axial deformation. Along the neutral axis, the shear stress at the wall portion of the barrel portion becomes maximum, and the bending stress becomes zero. In multi-walled bats, an additional independent neutral axis results from each ISCZ present. That is, each wall of the multiple wall barrel includes an independent neutral shaft. When the ball collides with the barrel of the bat, the wall of each barrel produces the highest radial compressive stress on the neutral axis (ie, on the impact side), while under the neutral axis (ie, the non-impact side) In order to produce the highest tensile stress in the radial direction.

  In general, the COR decreases as the wall thickness or barrel stiffness increases within the barrel of the bat. However, the durability of a ball bat typically decreases if the wall is too thin, so it is important to maintain a sufficient wall thickness. If the barrel wall is too thin, denting will occur in the barrel in the case of a metal bat, and progressive material failure will occur in the case of a composite bat. As a result, if the barrel wall is not thick enough, the performance and life of the bat will be reduced.

  In modern barrel design specifications, the use of composite materials is increasing rapidly. The behavior of composites in impact and failure is very complex. In structural composites, plastic deformation like metal does not occur, but a series of local failures occur, resulting in very complex stress redistribution. The final failure of the structure occurs when the resulting stress exceeds a predefined limit. It is very difficult, if not impossible, to accurately predict the onset and progression of functional degradation in these composites based on the behavior of uniformly oriented laminates within the structure. However, there are methods to predict the amount of elastic energy per unit mass that can be stored for a particular mode of stress generation. This is defined as the specific energy storage, which is the amount of energy that can be stored in the material before it degrades.

The specific energy storage capacity of a material for a tensile load or a compressive load is defined by the following equation.

ξ = σ _lt ² / E _lt ρ

ξ = accumulated specific energy
σ _lt = longitudinal tensile (compressive) strength at the elastic limit
E _lt = Young's longitudinal tensile (compression) modulus
ρ = specific gravity

Thus, materials with high tensile / compressive strength, low modulus and low specific gravity will have good energy storage properties.

  An elastic material deforms (ie, spring-like behavior) when affected by the application of force. Under conditions such as a load caused by a collision, kinetic energy is converted into potential energy in the form of deformation at the interface of the elastic material when a large force is applied in a short time. As a result of entropy, there is some irreversible loss of noise and heat form during this energy transfer process.

  When the kinetic energy of the impact is converted into energy due to deformation of the elastic material, the elastic material, if in contact, returns this stored energy to the form of kinetic energy and transfers it to the colliding object (ie, the ball) To do. If the impacted object is not in contact with the elastic material, the stored energy is dissipated in the elastic material. As a result of irreversible energy loss, the elastic material eventually returns to its original state without stress.

The overall energy conservation equation for bat-ball collisions is:

_{U K1b + U K2b = U K1a} + U K2a + U ll + U BM + U MS

U _K1b = Kinematic energy of the ball before impact
U _K2b = Kinetic energy of bat before collision
U _K1a = Ball kinetic energy after impact
U _K2a = Kinetic energy of bat after collision
U _ll = Local bat and ball strain energy loss
U _BM = Energy loss associated with beam mode of bat
U _MS = energy loss related to heat and noise (Maston, Timothy J., Sherwood, James, "Use of LS-DYNA to improve baseball bat performance and design tools", 6th International LS- DYNA Users Conference, Detroit, MI, April 9-10, 2000 (Mustone, Timothy J., Sherwood, James, "Using LS-DYNA to Develop a Baseball Bat Performance and Design Tool", 6th International LS-DYNA Users Conference , Detroit, MI, April 9-10, 2000))

  Controlling and optimizing these losses is important in designing high performance and durable ball bats, especially in designing losses related to local bat and ball strain energy. . Other losses, such as those associated with heat and noise, are important components of the overall balance equation, but are less important than strain energy losses. Thus, to design a high performance and durable bat, it is desirable to minimize strain energy loss within the ball bat barrel.

  The present invention provides a neutral shaft within the barrel wall by providing one or more integral interface shear control zones within the barrel of the bat and / or. It is an object to provide a ball bat that exhibits minimal strain energy loss associated with the bat-ball collision by selection and placement of a particular composite material for the (neutral axis).

  In the first aspect, the barrel portion of the bat has a first material arranged radially outside the outer wall neutral axis and a second material arranged radially inside the outer wall neutral axis as seen in the radial direction. And a substantially cylindrical outer wall including material. The barrel portion further includes a substantially cylindrical inner wall portion that is separated from the outer wall portion by an interface shear control zone, the inner wall portion being radially spaced from the inner wall neutral axis. A third material disposed on the outer side and a fourth material disposed on the inner side of the inner wall neutral axis in the radial direction are included. The first and third materials each have a specific energy storage value of compression of at least 2000 psi, while the second and fourth materials each have a tensile modulus of at least 18000000 psi.

  In another aspect, the first and third materials each include a structural glass-reinforced epoxy resin.

  In another aspect, the second and fourth materials each comprise a graphite-reinforced epoxy resin.

  In another aspect, at least one of the first, second, third, and fourth materials includes a boron-reinforced epoxy resin.

  In another embodiment, a layer of bond inhibiting material separates the outer wall from the inner wall. In a related embodiment, the outer wall, the inner wall, and the layer of anti-adhesion material are all terminated or blended together at at least one end of the barrel.

  In another aspect, the barrel portion of the bat includes a substantially cylindrical outer wall portion and a substantially cylindrical inner wall portion disposed within the outer wall portion. The outer wall and the inner wall are blended together at at least one end of the barrel.

  In another aspect, the barrel portion of the bat includes a first material disposed radially outward from the wall neutral axis and a second material disposed radially inward of the wall neutral axis. And a substantially cylindrical wall containing material. The first material has a specific energy storage value of compression of at least 2000 psi. And the second material has a tensile modulus of at least 18000000 psi.

  Further embodiments will be apparent, including modifications, variations and improvements of the present invention. The invention resides in the sub-combinations of features described or illustrated herein.

  In the accompanying drawings, like reference numerals designate like elements throughout the several views.

  Hereinafter, detailed description will be given with reference to the drawings. As shown in FIGS. 1 and 2, a baseball or softball bat 10 (hereinafter collectively referred to as “ball bat” or “bat”) includes a grip portion 12, a barrel portion 14, and a grip portion 12. And a taper portion 16 for connecting to the barrel portion 14. The free end of the grip 12 is provided with a knob 18 or a similar structure. The barrel portion 14 is preferably closed by a suitable cap 20 or stopper. The interior 19 of the bat 10 is preferably hollow. This allows the bat 10 to be relatively light, so that a ball player can generate sufficient bat speed when swinging the bat 10.

  The ball bat 10 preferably has a total length of 20 to 40 inches, more preferably 26 to 34 inches. The overall barrel diameter is preferably 2.0 to 3.0 inches, more preferably 2.25 to 2.75 inches. Typical bat diameters are 2.25 inches, 2.69 inches or 2.75 inches. Here, bats having various combinations of such overall lengths and barrel diameters are envisioned. The particular preferred combination of bat dimensions is generally determined by the user of the bat 10 and will vary greatly from user to user.

  The present invention relates primarily to the ball striking area of the bat 10, which typically extends over the entire length of the barrel portion 14, but extends partially to the taper portion 16 of the bat 10. Also good. For the sake of simplicity, in the following part of this specification, this striking area is generally referred to as the “barrel”.

  As shown in FIG. 2, the barrel portion 14 is formed of one or more substantially cylindrical layers. The actual shape of each layer of the barrel portion will vary depending on the desired shape of the overall structure of the barrel portion. Therefore, “substantially cylindrical” is used herein to mean a cylindrical barrel portion layer as well as a similar barrel shape. The barrel portion 14 preferably includes an outer barrel wall 22 and an inner barrel wall 24 disposed within the outer barrel wall 22, each preferably formed of one or more layers of composite material 38. Yes. Alternatively, the barrel portion 14 may only include a single wall portion and may include three or more wall portions. The wall of the barrel portion may additionally or alternatively be formed of one or more metallic materials such as aluminum or titanium.

  An anti-adhesion layer 30 or a non-adhesive layer preferably separates the outer barrel wall 22 from the inner barrel wall 24. The adhesion prevention layer 30 functions as an interlayer shear control zone (“ISCZ”) between the outer wall portion 22 and the inner wall portion 24. Therefore, the adhesion preventing layer 30 prevents the shear stress from being transmitted between the outer wall portion 22 and the inner wall portion 24, and the outer wall portion 22 is applied to the inner wall portion 24 when the bat 10 is cured and within the usage period of the bat 10. Prevents adhesion. As described above, since the anti-adhesion layer 30 functions as an ISCZ, the outer barrel wall 22 has a first neutral shaft 32 and the inner barrel wall 24 has a second neutral shaft 34.

  The radial thickness of the anti-adhesion layer 30 is preferably approximately 0.001 to 0.004 inches, more preferably 0.002 to 0.003 inches. The anti-adhesion layer 30 is preferably FEP (fluorinated ethylene propylene), ETFE (Ethylene Tetrafluoroethylene), PCTFE (PolyChloro TriFluoroEthylene) or PTFE (Polyethylene). Teflon (trademark) material such as tetrafluoroethylene (Polytetrafluoloethylene) and / or PMP (Polymethylpentene), PVF (Polyvinyl Fluoride), Nylon (polyamideimide) or cellophane It is made of other materials such as. Other ISCZs such as friction joints, sliding joints or elastic joints may be used as an alternative to the anti-adhesion layer 30. The anti-adhesion layer 30 or other ISCZ may be located at the radial midpoint of the barrel portion 14 such that each barrel wall 22, 24 has approximately the same radial thickness, or You may arrange | position in the other position of the barrel part 14. FIG. That is, the adhesion preventing layer 30 is shown at a substantially central position in the radial direction of the barrel portion 14 by way of example only.

  If the barrel portion 14 includes three or more walls, an anti-adhesion layer 30 or other ISCZ is preferably placed between each barrel wall to increase barrel deflection. Thus, the barrel portion with three walls preferably includes two anti-adhesion layers 30 or other ISCZ, and the barrel portion with four walls preferably includes three anti-adhesion layers 30 or other ISCZ. Including, and more than this is the case. Alternatively, the anti-adhesion layer 30 or ISCZ may be disposed only between selected barrel walls. In order to simplify the description, the barrel portion 14 having two walls will be described here, but any other number of barrel walls may be provided in the ball bat 10.

  In the embodiment shown in FIGS. 2 and 3, the outer and inner barrel walls 22 and 24 each include a plurality of composite plies. The composite material used is preferably fiber-reinforced, glass, graphite, boron, carbon, aramid, ceramic, kevlar, and / or any other, preferably in the form of an epoxy resin. Any suitable reinforcing material may be used. The thickness of each composite layer is preferably approximately 0.003 to 0.008 inches, more preferably 0.005 to 0.006 inches. The total radial thickness of each barrel wall 22, 24 (including the barrel portions on either side of the central axis of the bat) is preferably approximately 0.060 inches to 0.100 inches, more preferably 0.075 to 0.090 inch. Hereinafter, the optimal selection and arrangement of a specific composite material used for the ball bat 10 will be described in detail.

  The radial position of the neutral axis in each wall depends on the distribution of the composite layer and the stiffness of the particular layer. Here, only the stress component in the radial direction is considered because it is relatively larger than the stress in the axial direction. If the barrel wall is formed of a homogeneous and isotropic layer, the neutral axis will be in the middle position of the wall. If more than one composite material is used for the wall and / or if the material is not homogeneously distributed, the neutral axis will be at different radial positions. Thus, the first and second neutral shafts 32, 34 are shown at approximately the center position in the radial direction of each wall 22, 24, by way of example only.

  As shown in FIG. 4, the barrel structure with two walls is divided into four zones numbered 1, 2, 3 and 4. Since the zones 1 and 3 are arranged on the outer side (that is, the collision side) or the upper side of the neutral axis in the radial direction, they are compressive stress regions of the outer barrel wall and the inner barrel wall. Since zone 2 and zone 4 are arranged on the inner side (that is, the non-collision side) or the lower side of the neutral axis in the radial direction, they are the tensile stress regions of the outer barrel wall and the inner barrel wall.

  The materials of the compression zone 1 and the compression zone 3 are mainly used for enhancing the durability of the barrel portion 14. The tension zone 2 and tension zone 4 materials primarily increase the rigidity of the barrel section 14 and substantially match the fundamental frequency of the outer and inner barrel walls 22, 24. It is used to minimize energy loss in the interior. The fundamental frequency of each barrel wall 22, 24 is preferably within a constructive coupling range between the barrel walls 22, 24, and thus during energy transfer from the outer barrel wall 22 to the inner barrel wall 24. The loss of is minimal. In a preferred embodiment, the fundamental hoop frequency of the outer barrel 22 (ie vibration measured around the diameter of the barrel wall) is within 20% of the fundamental hoop frequency of the inner barrel 24; More preferably, it is within 10%. The fundamental hoop frequency of each of the outer and inner barrel walls 22, 24 is preferably in the range of 900 to 2000 Hz, more preferably 1000 to 1200 Hz.

  Table 1 in FIG. 5 lists various physical properties of some common structural composite materials. Materials with high compression specific energy storage values are best suited for Zone 1 and Zone 3, while materials with high stiffness (ie, high tensile modulus) are best suited for Zone 2 and Zone 4. The composite material used for Zone 1 and Zone 3 consequently determines the durability of the structure. On the other hand, the composite material used for Zone 2 and Zone 4 adjusts the rigidity of the barrel portion to maximize the energy coupling between the outer barrel wall 22 and the inner barrel wall 24. Thus, by placing a specific material in a specific zone, the performance and durability of the structure can be adjusted independently of each other.

  In a preferred embodiment, structural (S) glass reinforced epoxy resin or S-glass epoxy is predominantly in Zone 1 and Zone 3 due to its extremely high specific energy storage value of its compression (approximately 2230 psi). Used. Boron reinforced epoxy resins or boron epoxies have a specific energy storage value of approximately 2220 psi compression, but can be used additionally or alternatively in Zone 1 and Zone 3. Other materials with high compression specific energy storage values can be used additionally or alternatively in Zone 1 and Zone 3. The specific energy storage value of the compression of the materials used in Zone 1 and Zone 3 is preferably at least 2000 psi, more preferably 2200 to 2400 psi. The material used in zone 1 may be the same as or different from the material used in zone 3.

  S-glass epoxy can also be utilized for Zone 2 and Zone 4 due to its high tensile specific energy storage value (approximately 4790 psi). Actually, from the viewpoint of durability, it is advantageous that the entire barrel portion has a 100% S-glass multiple wall structure. However, S-glass epoxy has a relatively low stiffness or tensile modulus (approximately 6910000 psi). Thus, if S-glass epoxy is overwhelmingly used in Zone 2 and Zone 4, due to the weak energy coupling between the barrel walls 22, 24 and the lack of barrel stiffness, the barrel performance is It will get worse. Therefore, a graphite reinforced epoxy resin or graphite epoxy having a tensile modulus or stiffness of approximately 20000000 psi is preferably used in Zone 2 and Zone 4 to adjust the barrel stiffness. However, a limited amount of S-glass epoxy may be used in Zone 2 and Zone 4.

  Boron epoxies with a tensile modulus or stiffness of approximately 296,000 psi can be used additionally or alternatively in Zone 2 and Zone 4. However, graphite epoxy is preferred over boron epoxy because the specific energy storage value of graphite epoxy (approximately 1380 psi) is much larger than the specific energy storage value of boron epoxy (approximately 565 psi).

  Other materials with high stiffness or tensile modulus can be used additionally or alternatively in Zone 2 and Zone 4, preferably coupled with a relatively high tensile specific energy storage value. The stiffness or tensile modulus of the material used in Zone 2 and Zone 4 is preferably 18000000 psi, more preferably 20000000 to 30000000 psi. The stiffness of the material that determines the performance of the bat is a more important variable, but the tensile specific energy storage value of the materials used in Zone 2 and Zone 4 is preferably 1000 psi. The material used in Zone 2 may be the same as or different from the material used in Zone 4.

  The selected layers of composite material can be oriented at various angles relative to the respective neutral axes 32, 34, further modifying or enhancing the performance and durability of the barrel portion, and Better match the fundamental frequency of the barrel walls 22,24. In the preferred embodiment, each of the composite layers 38 in Zone 1 and Zone 3 is oriented approximately 50-70 ° relative to the respective neutral axis 32,34. Each of the composite layers 38 in zone 2 and zone 4 is preferably oriented approximately 20 to 50 ° relative to the respective neutral axis 32, 34. Each layer in the zone can be oriented at the same or different angle as the other layers in this zone. Thus, the position and angle of a particular structural layer with respect to the neutral axis makes it possible to enhance the durability of the barrel portion while minimizing strain energy loss at the barrel portion.

  The idea of placing graphite epoxy in the tension zones (zone 2 and zone 4) was not initially understood. Durability tests were performed on barrel portions according to conventional design specifications using graphite epoxy that is overwhelmingly arranged in zone 1 and zone 3. When this test was completed, no functional deterioration of the graphite epoxy fiber was observed in the compression zone (zone 1 and zone 3) of the barrel portion. Therefore, since the graphite epoxy fiber did not have a reduced compression function, there was no motivation to move the graphite fiber to the tensile zone.

  In the bat sample according to the design specification according to one embodiment of the present invention, the graphite epoxy was not transferred to the tension zone. And S-glass epoxy was overwhelmingly used in the compression zone. Thereafter, a durability test was performed on the bat. Surprisingly, it was found that the durability increased by a factor of 3 compared to that of the conventional design specification (for example, when the ball was hit with about 150 balls, the function was degraded. The function does not deteriorate until almost 450 balls are hit).

  Thus, in the first analysis, the bat according to the conventional design specification did not show a decrease in the compression function of the graphite epoxy fiber, but an invisible deterioration of the graphite fiber actually occurred in the compression zone. It is possible that In other words, the discovery of the dramatic increase in bat durability resulting from using graphite epoxy fibers in the bat barrel tension zone and using S-glass epoxy in the bat barrel compression zone is It was unexpected. This is because the analysis did not show that the samples according to the conventional design specifications that follow are experiencing a reduction in compression fiber function.

  The bat 10 is generally constructed by wrapping various layers of the bat 10 around a mandrel or similar structure having the desired bat shape. The ends of the layers are preferably “clocked” or offset from each other. For this reason, they do not all end in the same position before curing. Thus, when heat and pressure are applied to cure the bat 10, the various barrel layers together integrate into a unique “one-piece” multi-wall structure. In other words, all layers of the bat are “cured together” in a single step and terminate or integrate together at at least one end. The result is a single-piece multi-wall structure with no gaps (at least at one end). For this reason, the barrel portion 14 is not a series of tubular objects with wall thicknesses that each terminate at the end of the tubular object. As a result, all layers act in unison under load conditions such as hitting a ball.

  Integrating the layers into a unitary multi-wall structure is very durable, especially when collisions occur at both ends of the layer separation zone, as are the ends of the leaf springs joined together. Is generated. By integrating multiple layers together, the barrel portion 14 functions as a unitized structure, in which case no single layer functions independently of the other layers. One end or both ends of the barrel portion 14 may be terminated together so as to form an integral barrel portion.

  In the preferred embodiment, the bat 10 is constructed as follows. First, the various layers of the bat 10 are pre-cut and pre-shaped with conventional machines. A composite layer 38, such as made of graphite epoxy and / or other suitable material, used to form an inner wall tension zone is rolled onto a bat-shaped mandrel. Thereafter, a composite layer 38, such as made of S-glass epoxy and / or other suitable material, used to form an inner wall compression zone is wrapped around the inner wall tension zone layer 38.

  After this, an anti-adhesion layer 30 or other ISCZ layer or material (if such a layer is desired) is wrapped around the compression zone layer 38 of the inner wall. Next, a composite layer 38, such as made of graphite epoxy and / or other suitable material, used to form an outer wall tensile zone is wrapped around the anti-adhesion layer 30. When the adhesion preventing layer 30 is not used, it is wound around the layer 38 of the compression portion of the inner wall portion. Thereafter, a composite layer 38, such as made of S-glass epoxy and / or other suitable material, used to form the outer wall compression zone is wrapped around the outer wall tension zone layer 38.

  As noted above, the composite layers 38 are preferably wrapped around the mandrel with their ends offset from the others so that they do not all end in the same position before curing . After all the layers are in place, heat and pressure are applied to these layers to cure the bat 10 into a unitary multi-wall barrel structure. Here, all the ends of the layers are terminated together such that no gap is created between the barrel wall and the ISCZ. These layers may be arranged to terminate with such specifications at one or both ends of the barrel portion 14.

  The bat structure and the manufacturing method thereof provide a bat having excellent “trampoline effect” and durability. These results are primarily due to the selection and placement of specific materials relative to the neutral axes in the outer and inner barrel walls 22,24. In particular, placing a material with a high compression specific energy storage value on the neutral shaft and placing a material with high stiffness or tensile modulus under the neutral shaft is durable and has high performance. A provided ball bat is provided. Furthermore, the integration of the barrel layer by a single curing process results in high durability, especially during collisions at both ends of the barrel layer.

  While several embodiments have been shown and described herein, it will be appreciated that various modifications and alternatives may be made without departing from the spirit and scope of the invention. Therefore, the invention should not be limited in any way except the appended claims and their equivalents.

It is a perspective view of a ball bat. It is a partial cross section perspective view of the ball bat shown in FIG. It is an expanded sectional view of the part shown by A of FIG. It is the schematic of the cross section of the outer cylinder shown in FIG. It is a table | surface which shows the various physical-property value of a general composite structure material.

Explanation of symbols

  10 baseball or softball bat (ball bat), 12 gripping part, 14 barrel part, 16 taper part, 18 knob, 20 cap, 22 outer barrel wall, 24 inner barrel wall, 30 anti-adhesion layer, 32 1st Neutral axis, 34 Second neutral axis, 38 Composite layer.

Claims (17)

A ball bat including a barrel portion, a grip portion, and a tapered portion connecting the barrel portion to the grip portion,
The barrel part is
A substantially cylindrical outer wall including a first material disposed radially outward of the outer wall neutral axis and a second material disposed radially of the outer wall neutral axis; ,
A third material disposed radially outward of the inner wall neutral axis and a fourth material disposed radially inner of the inner wall neutral axis as viewed in the radial direction and through a region between the walls; A substantially cylindrical inner wall separated from the outer wall by an interface zone in which shear energy transfer does not occur ;
A ball bat in which the first and third materials each have a specific energy accumulation value of compression of at least 2000 psi, while the second and fourth materials each have a tensile modulus of at least 18000000 psi. The ball bat of claim 1, wherein the first and third materials each have a specific energy accumulation value of compression of 2200 to 2400 psi.   The ball bat of claim 1, wherein the second and fourth materials each have a tensile modulus of 20000000 to 30000000 psi. The ball bat of claim 1, wherein the second and fourth materials each have a tensile specific energy accumulation value of at least 1000 psi.   The ball bat of claim 1, wherein at least one of the first, second, third and fourth materials comprises a fiber reinforced resin composite material.   6. The ball bat of claim 5, wherein the composite material includes at least one material selected from the group of materials consisting of glass, graphite, boron, carbon, aramid, and ceramic.   The ball bat of claim 1, wherein the first and third materials each comprise a structural glass reinforced epoxy resin.   The ball bat of claim 1, wherein the second and fourth materials each comprise a graphite reinforced epoxy resin.   The ball bat of claim 1, wherein at least one of the first, second, third, and fourth materials comprises a boron reinforced epoxy resin. The ball bat of claim 1, wherein the interface zone includes an anti-adhesive material layer that separates the outer wall portion from the inner wall portion.   The adhesion prevention material layer contains at least one material selected from the material group consisting of Teflon (registered trademark), polymethylpentene, vinyl fluoride resin, nylon, and cellophane. Ball bat.   The ball bat according to claim 10, wherein the outer wall portion, the inner wall portion, and the adhesion preventing material layer all terminate at at least one end of the barrel portion. The ball bat of claim 1, wherein the interface zone includes at least one of a friction connection, a slip connection, and an elastic connection.   The ball bat according to claim 1, wherein the basic hoop frequency of the outer wall portion is within 20% of the basic hoop frequency of the inner wall portion.   The ball bat according to claim 14, wherein the basic hoop frequencies of the outer wall portion and the inner wall portion are each in a range of 1000 to 1200 Hz. A ball bat including a barrel portion, a grip portion, and a tapered portion connecting the barrel portion to the grip portion,
The barrel portion includes a substantially cylindrical outer wall portion and a substantially cylindrical inner wall portion disposed inside the outer wall portion, and the outer wall portion and the inner wall portion are at least one end of the barrel portion. Together,
The barrel portion includes an interface zone that separates the outer wall portion from the inner wall portion and does not cause energy transfer through a region between the wall portions , and the outer wall portion is a first neutral shaft by a first neutral shaft. The inner wall portion is divided into a second outer portion and a second inner portion by a second neutral shaft while being divided into an outer portion and a first inner portion,
The first and second outer portions each comprise a material having a specific energy accumulation value of compression of at least 2000 psi, while the first and second inner portions each comprise a material having a stiffness of at least 18000000 psi. Ball bat. A ball bat including a barrel portion, a grip portion, and a tapered portion connecting the barrel portion to the grip portion,
The barrel portion includes a first material disposed outside the first wall neutral axis in the radial direction and a second material disposed inside the first wall neutral axis in the radial direction. Including a substantially cylindrical first wall, wherein the first material has a compression specific energy storage value of at least 2000 psi, while the second material has a tensile modulus of at least 18000000 psi;
The barrel portion is disposed between the first wall portion and the substantially cylindrical second wall portion, and the region between the wall portions separating the first wall portion from the second wall portion. a first field Menzo over down movement of the displacement energy does not occur, separating the substantially cylindrical third wall disposed inside of the second wall portion, the second wall portion from the third wall portion the second field Menzo over emissions and the ball bat includes that to the energy shift through the region between the wall portions are moved not occur.

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