Bat for baseball or softball

A bat for baseball or softball of the present invention includes a first tube formed from FRP or synthetic resin having a part to be hit and a stopper part, a cylindrical second tube having two ends which are open and including at least two or more layers, a first fixing component including a body part, an interior periphery surface of the body part is fixed to the first tube, a second fixing component including an insertion part, and a gap located between the first tube and the second tube and being formed by the second tube being attached to an exterior periphery of the first tube, one end of the second tube being fixed to an exterior periphery surface of the body part, and the other end of the second tube being fixed to the insertion part which is inserted between the first tube and the second tube.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-293791, filed on Nov. 17, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improving the rebound characteristics of a bat for baseball or softball.

2. Description of the Related Art

Conventionally, the flying distance of a ball is thought to be extended when hit by a high strength bat. This is because it was considered that a bat with a high degree of strength has excellent rebound characteristics and the flying distance of a ball depended solely on these rebound characteristics of the bat. However, in recent years, it is understood that the flight distance of a ball which does not rely on the strength of the bat but on a bat which can reduce the consumption of impact energy as ball transformation energy when a ball and bat collide and can extend the flying distance of a ball. In addition, it is understood that the higher the rebound force of the bat itself, the further the flying distance of a ball is extended.

Thus, in order to extend the flying distance of a ball, a variety of bat structures were tried. As a first structure, as shown in Japanese Laid Open Patent 2005-305146, a method was attempted in which a number of urethane layers were arranged on the exterior of a part to be hit of a metal bat and the urethane layers reduced the consumption of impact energy as ball transformation energy. As a second structure, as is shown in 2008-29620, a method was attempted in which a double layered metal bat was formed and the consumption of impact energy as ball transformation energy was reduced by bending of the metal thin tube.

However, in the method in which urethane layers are arranged on the exterior of the part to be hit of a metal bat, because a urethane layer deteriorates by secular distortion, the durability of the bat is inferior compared to a metal manufactured bat. In addition, the bat also suffered from an increase in miss hits.

However, while a metal bat with a double layered structure has no durability problems and the flight distance of a ball is extended, it is difficult to make a light metal bat. Particularly, in the case of a child's or girl's bat, it is impossible to swing the bat unless it is light since they are weak. Generally, swing speed is largely proportional to the weight of a bat and the lighter the bat the faster the swing speed. Therefore, in the case of a child's or girl's bat, lightness is particularly demanded and further improvements in a double layered bat are also demanded. In particular, requests for lightness are predominant for female softball bats.

The present invention can reduce the consumption of impact energy as ball transformation energy and in particular aims to provide a light bat for baseball or softball. Furthermore, the present invention is easy to manufacture and aims to provide a low cost bat for baseball or softball.

BRIEF SUMMARY OF THE INVENTION

A bat for baseball or softball related to one embodiment of the present invention includes, a first tube formed from FRP or synthetic resin having a grip part, a taper part, a part to be hit, a tip part, and a stopper part formed by gradually opening the first tube from the part to be hit side towards the tip part side, and a hollow for latching having a groove shape formed by reducing the diameter of the first tube, a cylindrical second tube having two ends which are open, and having an interior diameter which is larger than an exterior diameter of the part to be hit and smaller than an exterior diameter of the stopper part, the second tube including at least two or more layers, a first fixing component having a donut shape and including a body part and a flange part, the flange part having a larger exterior diameter than an exterior diameter of the body part, and the first fixing component having an opening larger than an exterior diameter of the part to be hit, and an interior periphery surface of the body part being fixed to the first tube and one surface of the flange part being fixed to the stopper part, a second fixing component having a donut shape and including a base part and an insertion part, the insertion part having a smaller exterior diameter than the largest exterior diameter of the base part, and also including a protrusion part which protrudes inwards and an opening which is larger than an exterior diameter of the part to be hit, the protrusion part being fixed by interlocking with the hollow for latching, and a gap located between the first tube and the second tube and being formed by the second tube being attached to an exterior periphery of the first tube, one end of the second tube being fixed to an exterior periphery surface of the body part, and the other end of the second tube being fixed to the insertion part which is inserted between the first tube and the second tube.

A bat for baseball or softball related to another embodiment of the present invention includes, a first tube formed from FRP or synthetic resin having a grip part, a taper part, a part to be hit, a tip part, and a stopper part formed by gradually opening the first tube from the part to be hit side towards the tip part side, and a hollow for latching having a groove shape formed by reducing the diameter of the first tube, a cylindrical second tube having two ends which are open, and having an interior diameter which is larger than an exterior diameter of the part to be hit and smaller than an exterior diameter of the stopper part, the second tube including at least two or more layers, a cylindrical third tube having two ends which are open and having a larger exterior diameter than an exterior diameter of the first tube and a smaller exterior diameter than an exterior diameter of the second tube, a first fixing component having a donut shape and including a body part and a flange part, the flange part having a larger exterior diameter than an exterior diameter of the body part, and the first fixing component having an second body part which has a smaller exterior diameter than an exterior diameter of the body part and being formed so that it protrudes in an opposite direction of the flange part from the body part, and an opening larger than an exterior diameter of the part to be hit, a second fixing component having a donut shape and including a base part and a first insertion part, the first insertion part having a smaller exterior diameter than the largest exterior diameter of the base part, and also including a protrusion part which protrudes inwards, and a second insertion part having a smaller exterior diameter than the exterior diameter of the first insertion part and being formed so that it protrudes in an opposite direction of the base part from the first insertion part, and an opening which is larger than an exterior diameter of the part to be hit, the protrusion part being fixed by interlocking with the hollow for latching, a first gap located between the first tube and the third tube and being formed by the third tube being attached to an exterior periphery of the first tube, one end of the third tube being fixed to an exterior periphery surface of the second body part, and the other end of the third tube is being fixed to the second insertion part which is inserted between the first tube and the third tube, and a second gap located between the third tube and the second tube and being formed by the second tube being attached to an exterior periphery of the third tube, one end of the second tube being fixed to an exterior periphery surface of the body part, and the other end of the second tube being fixed to the first insertion part which is inserted between the third tube and the second tube.

The bat for baseball or softball according to this invention, wherein the second tube may be formed as one body from an inner layer formed from metal or FRP, and at least one or more outer layers formed from either of metal, FRP or wood and may be attached to an exterior periphery of the inner layer.

The bat for baseball or softball according to this invention, wherein the outer layer of the second tube may be formed from a combination of a first part formed from metal and one or more second parts formed from either of metal which is different the metal, FRP or wood, and at least one of the first part and the one or more second parts may be formed from a different material to the other part.

The bat for baseball or softball according to this invention, may further include a cap, the cap including a cap tip part, a cap recessed part and a cap fixing part, the tip part including a curled part in which a tip of the tip part curves inwards, and an exterior diameter of the cap fixing part being smaller than an interior diameter of the first tube from the curled part as far as the stopper part, and an exterior diameter of the cap recessed part being smaller than an interior diameter of the curled part, and the cap recessed part being latched by the curled part.

The bat for baseball or softball according to this invention, wherein a tip of the tip part may curve inwards and may be closed.

The bat for baseball or softball according to this invention, wherein the first tube may further include a step part having an exterior diameter which is smaller than an exterior diameter of the stopper part and larger than an exterior diameter of the part to be hit, and a gap located between the first tube and the second tube and being formed by the second tube being attached to an exterior periphery of the first tube, one end of the second tube being fixed to the step part and the other end of the second tube being fixed to the insertion part which is inserted between the first tube and the second tube.

The bat for baseball or softball according to this invention, wherein the first tube may include a grip part, a taper part, a part to be bit, a tip part and a stopper part formed by opening of the first tube towards the tip part side from the part to be hit side, and the second fixing component may include a base part and an insertion part which has a smaller exterior diameter than a largest diameter of the base part, the second fixing component being fixed to an exterior periphery of the first tube via an adhesive, and a gap located between the first tube and the second tube and being formed by the second tube being attached to an exterior periphery of the first tube, one end of the second tube being fixed to an exterior periphery surface of the body part, and the other end of the second tube being fixed to the insertion part which is inserted between the first tube and the second tube.

The bat for baseball or softball according to this invention, wherein the first tube may be formed from either C-FRP, B-FRP, K-FRP or synthetic resin and an inner layer of the second tube may be formed from either aluminum, an aluminum alloy, titanium, a titanium alloy, a magnesium alloy, an aluminum-scandium alloy, a scandium alloy, a steel alloy or FRP, and an outer layer of the second tube may be formed from either aluminum, an aluminum alloy, titanium, an titanium alloy, a magnesium alloy, an aluminum-scandium alloy, a scandium alloy, a steel alloy, FRP or wood.

The bat for baseball or softball according to this invention, wherein the stopper part may be formed in a position of the part to be hit side at least 100 mm or more from a tip of the tip part, and the second tube may be arranged in the best position for an impact.

The bat for baseball or softball according to this invention, may further comprise a grip end, the grip end being either fixed to the first tube by a screw or an adhesive, or being formed as one body with the first tube.

The bat for baseball or softball according to this invention, wherein the second fixing component may include a first screw part in which an interior of the opening undergoes a thread process, and the first tube may include a second screw part in which a predetermined place on an exterior periphery of the first tube undergoes a thread process, and the second fixing component may be attached to an exterior periphery of the first tube, the first screw part and the second screw part may be fixed by a screw and adhesive.

DETAILED DESCRIPTION OF THE INVENTION

[Structure of a Double Layered Bat]

The bat for baseball or softball related to embodiment one of the present invention will be explained below based on the diagrams. Furthermore, the same structural components have the same symbols and thus an explanation of these components which overlap between embodiments will be omitted. In addition, due to the diagrams, with regards to the material of one part, for example, the overall length of the second fixing component40is sometimes displayed longer than in actuality. The proportions related to length for example in a longitudinal direction of each element is not limited to the diagrams.

FIG. 1Ais a longitudinal direction notch sectional view of a bat1for baseball or softball related to embodiment one of the present invention.FIG. 1Bis a cross sectional view of the line α-α′ in a width direction of a bat1for baseball or softball related to embodiment one of the present invention. In addition,FIG. 2is an enlarged cross sectional view in a longitudinal direction of a bat tip part11and a part to be hit12of a bat1for baseball or softball related to embodiment one of the present invention. In addition,FIG. 3is an enlarged cross sectional view in a longitudinal direction of a part to be hit12and a taper part13of a bat1for baseball or softball related to embodiment one of the present invention. Furthermore, one example of a bat for baseball or softball of the present invention is shown in the embodiments below. However, the bat1for baseball or softball of the present invention is not limited to these embodiments.

InFIG. 1A, the bat1for baseball or softball related to embodiment one of the present invention is roughly comprised of a first tube10including a tip part11, a part to be hit12, a taper part13and a grip part14, a second tube20which is fixed to the exterior of the part to be hit12of the first tube10, a first fixing component30, a second fixing component40, a cap50and a grip end80. Furthermore, in embodiment one of the present invention, the second tube20is sometimes called an exterior tube20. In addition, in the bat1for baseball or softball related to embodiment one of the present invention, the part to be hit which hits a ball is formed as one part comprising the part to be hit12of the first tube10and one part of the second tube20located on the exterior of the part to be hit12, however, for the purposes of explanation, only this part of the first tube10is called the part to be hit12below.

InFIG. 1A, the first tube10is the part which forms the center when a ball is hit by a batter. The batter holds the grip part14, swings the bat1and hits a ball which is thrown. As stated above, the first tube10is comprised of roughly four component parts, and the bat1for baseball or softball related to embodiment one of the present invention is formed as one body from Fiber Reinforced Plastics (herein referred to as FRP) or a synthetic resin in order to secure lightness and strength in particular. Preferably, as a material of the first tube10, Carbon Fiber Reinforced Plastics (herein referred to as C-FRP), Boron Fiber Reinforced Plastics (herein referred to as B-FRP), and Kevlar (registered trademark) Fiber Reinforced Plastics (herein referred to as K-FRP) may be used. Furthermore, there is foam molding or non-foam molding as a method of forming the first tube10with a synthetic resin, and the first tube10of the bat1for baseball or softball related to embodiment one of the present invention may be formed by either method.

In embodiment one of the present invention, in order to achieve lightness across an entire bat having a double layered structure, the first tube10is formed with a thickness of 1 mm-6 mm for example. Furthermore, the above stated thickness is only an example and not limited to this. Then, a screw is cut into interior of the grip part14of the first tube10and the grip end80which is mainly formed from metal is attached by screwing. The grip end80is fixed by either screwing, an adhesive or by screwing and adhesive. However, it is not limited to this, the bat grip part14and the grip end80may be formed as one body. In addition, the material of the grip end80is not limited to metal.

Characteristically, the exterior diameter of the bat tip part11of the first tube10of the bat1for baseball or softball related to the first embodiment of this invention, is set larger than the exterior diameter of the bat part to be hit12. In other words, the first tube10is formed so that its diameter increases from the part to be hit12to the bat tip part11. Then, the exterior diameter of this part in which the diameter increases is set larger than the interior diameter of the second tube20and preferably is set the same as the exterior diameter of the second tube20. This increased diameter part is called stopper part16and prevents the second tube20falling off from the bad tip part11. Furthermore, the exterior diameter of the stopper part16is set the same as the exterior diameter of the second tube20so that the exterior surface of the stopper part16and the exterior surface of the second tube20are formed as one surface.

Furthermore, the bat1for baseball or softball related to embodiment one of the present invention is formed so that the tip of the bat tip part11curves inwards at a certain length. In other words, the tip of the tip part11is almost bent in a perpendicular direction towards the interior of the bat. Below, this part is called curled part19and this bending process is called a curl process. The curled part19plays the role of latching a cap50. Therefore, the certain length should be a length sufficient to latch the cap50which is processed by press fit processing, and generally is 3 mm-10 mm or more preferably about 5 mm.

In addition, the bat1for baseball or softball related to embodiment one of this invention includes a groove which is formed so that it depresses inwards at a place near the border between the part to be hit12and the taper part13. In other words, the bat related to the present invention is processed by reducing the diameter in a certain place on the taper part13side of the bat part to be hit12. This part is called the hollow for latching15below. Furthermore, the location where the hollow for latching15is formed is not limited to this certain place. The hollow for latching15is a part in which a protrusion part43of the second fixing component40interlocks and plays the role of fixing the second fixing component40to the first tube10. The hollow for latching15is formed in a circular shape on the periphery of the first tube10, however it is not limited to this, it may also be formed only in a specific circular place.

The first tube10is formed by FRP or a synthetic resin as stated above. Because the method of forming the first tube10by a synthetic resin is a general forming method an explanation is omitted here. However, in a manufacturing method of a bat by FRP, there is a Filament Winding method, a Sheet Winding method and a press manufacturing method, however, the bat1for baseball or softball related to embodiment one of the present invention is preferably formed by an internal pressure manufacturing method in which a FRP cylinder formed by a Braiding method (a method which weaves fiber of a fiber reinforced plastic according to a braiding technology) is used. This is for including places in which for example, the diameter of the grip part14is small or in places where the diameter of the taper part13which gradually increases is not uniform. That is, in the case of forming a bat using FRP by a Sheet Winding method, the bat is formed by winding an FRP sheet on a mandrel which is formed in the shape of a bat and has the above stated places in which the diameter is not uniform. However, even if a sheet which is cut into small pieces is used, it is not easy to evenly wind an FRP sheet on the places in which the diameter is not uniform.

However, while an explanation of the details of the formation method of an FRP cylinder by a Braiding method is omitted, the FRP cylinder (below, this is called an FRP prepreg) which is formed has a triaxial structure in which the FRP which is formed in a filament shape, is formed into cylinder having a woven net shape in three directions. That is, while one FRP fiber continues in a longitudinal direction from the tip to the butt, the other two FRP fibers are woven so that they each intersect at certain fiber orientation angles (this is called in-plane weaving angle). Therefore, an FRP prepreg with uniform strength in a circumference direction can be formed and it is possible to easily design a rigidity distribution by an adjustment of the in-plane weaving angle. Then, because the FRP prepreg which is formed is retractable in the direction of three dimensions, it is possible to easily wind the FRP prepreg on places where the diameter of the mandrel formed in the shape of the bat is not uniform. For the above reasons, when manufacturing the bat1for baseball or softball related to embodiment one of the present invention, an FRP prepreg formed by a braiding method can be used preferably.

Next, a manufacturing method of a bat which uses an FRP prepreg formed by the above stated braiding method will be explained. The bat1for baseball or softball related to embodiment one of the present invention as stated above, is manufactured by an internal pressure method. However, it is not limited to this. The bat1may be also be manufactured by other formation methods.

Specifically, first, an FRP prepreg formed by a braiding method is cut to predetermined dimensions to match the dimensions of a first tube10.

Next, the FRP which is cut is attached so that it covers a mandrel which is formed almost equal to the interior diameter of the first tube10,

The mandrel is removed and in order to apply internal pressure a nylon tube is passed through the FRP prepreg. In the case where the tip part of the first tube10is formed as one body, the tip part is created by an FRP prepreg as a cap according to necessity.

The FRP prepreg with the nylon tube running through it is set in a metal mold. In the case where a grip end80is formed on one body, a rounded FRP prepreg is packed into the metal mold in places equivalent to the grip end, however, it is not limited to this. A protrusion part or recession part formed at predetermined places to match the shape of the stopper part16which has an enlarged diameter or hollow for latching15which has a reduced diameter may be formed in the metal mold.

The prepreg set with the nylon tube running through it is put into a press and it heated while applying internal pressure. Next, the prepreg is removed, the internal pressure tube is taken out and after-cure is performed if necessary. Here, after-cure means a process which hastens the progress of heating and hardening in the post process in the case where hardening at the time of formation is not sufficiently complete.

In order to make the interior solid with foam, foam beads are filled from a hole in the grip end and further heated. The above manufacturing process is the manufacturing process of the first tube10of the bat1for baseball or softball related to embodiment one of the present invention which uses an FRP prepreg formed by a braiding method.

A second tube20of the bat1for baseball or softball related to embodiment one of the present invention is a cylindrical tube in which both ends are open and have a uniform exterior diameter. The interior diameter of the second tube20is larger than the exterior diameter of the bat part to be hit12and preferably is a diameter about twice the height of a gap60formed between the first tube10and second tube20larger than the exterior diameter of the first tube10.

Characteristically, the second tube20uses multi-layer structure which includes an inner layer and an outer layer. In the present embodiment, a tube having a composite two layer structure is used as the second tube20, however, it is not limited to this, for example, a tube having a composite three layer structure may also be used. For the purposes of explanation, in the embodiments and examples below, an example will be explained which uses the second tube20having a composite two layer structure

Here a composite two layer structure is a tube having a two layer structure including an inner layer and an outer layer (a surface layer in the case of a two layer structure) attached to the periphery of the inner layer and formed from a different material to the inner layer. Details regarding the materials the inner layer and outer layer are shown inFIG. 4. As is shown inFIG. 4, aluminum, aluminum alloy, titanium, titanium alloy, magnesium alloy, aluminum-scandium alloy, scandium alloy, steel alloy or any FRP may be used as a material for the inner layer. However, as shown inFIG. 4, aluminum, aluminum alloy, titanium, titanium alloy, magnesium alloy, aluminum-scandium alloy, scandium alloy, steel alloy, FRP or any wood material may be used. Here, wood material in the present specification refers to a wood material formed in the shape of a thin sheet and attached by winding at a predetermined diameter to form a cylinder shape, or a wood material formed in the shape of a cylinder in which the interior is hollowed out. However, it is not limited to this. A tube formed using a wood material is generically named. In the bat related to the present embodiment, aluminum, aluminum alloy, aluminum-scandium alloy, scandium alloy and FRP may be preferably used as the material of the inner layer. In addition, titanium, titanium alloy, magnesium alloy and FRP which are light and have excellent rebound characteristics can be preferably used as the material of the outer layer, and a wood material from which a batter receives a good feeling when hitting a ball, can be preferably used. In the present embodiment, aluminum or aluminum alloy is used as the material of the inner layer and titanium or titanium alloy having excellent rebound characteristics is used as the material of the outer layer. The inner layer and outer layer are formed separately and normally the inner layer is pressed into place in the outer layer, however, the exterior surface of the inner layer may be applied with an adhesive or resin and attached by inserting within the outer layer. In addition, the layers may be formed by other methods. In the case where a metal is used as the material of the inner layer and outer layer, the metal is used once the inner layer and outer layer have been heat treated. In a general double layered metal bat, particularly when the material of the exterior tube and interior tube are different, due to the difference in the rate of thermal expansion of each tube, a heat process for releasing stress is extremely difficult. However, the materials of the inner layer and outer layer of the bat related to the present embodiment are different, and because each layer is formed separately and formed as one body by press fit processing for example, a heat process of a metal tube is easier compared with a general double layered metal bat.

Furthermore, because an inner layer and outer layer are used in as a composite, even if each tube is formed thinly it is possible to secure strength. Therefore, in the present embodiment, the thickness of each tube is formed about half as thick as the thickness of the second tube of the bat shown in Japanese Laid Open Patent 2008-29620 and in the case where the tubes are attached together using press fit processing so that no gap remains between the tubes, the total thickness is almost the same as this second tube However, it is not limited to this. The thickness of each tube may be determined according to the demanded strength and the thickness of the inner layer and outer layer may be different. In whichever case, it is possible to achieve lightness while securing strength across the entire second tube20by this composite multi-layer structure.

Although not shown in the diagrams, a make-up sheet can be applied to the exterior of the above stated second tube20for the purpose of protecting the second tube20from damage and for design effect. This make-up sheet can be formed from, for example, a resin film such as a polyethylene film, an elastomer film and a plastic film or an FRP sheet.

As is shown inFIG. 2, a first fixing component30has a donut shape in the form of an opening and is a component for fixing one end of the second tube20to the tip end part12of the first tube10. The first fixing component30includes first fixing component body part31and a first fixing component flange part32. The diameter of the opening is set slightly larger than the exterior diameter of the bat part to be hit12of the first tube10.

The body part31of the first fixing component30has a certain height. This height is the height when the gap60having a certain height is formed between the first tube10and the second tube20in the case where the first fixing component30is attached to the first tube10via an adhesive70and the second tube20is fixed to the periphery of the body part31by the adhesive70. In other words, this height is set at a height after the height of the intervening hardened adhesive70is subtracted from the certain height of the formed gap60. Furthermore, this body part31plays a role equivalent to the fulcrum of a spring when the second tube20bends when a ball is hit.

However, the flange part32of the first fixing component30plays the role of preventing damage by contact of the end part of the second tube20contacting the stopper part16of first tube10or for preventing the generation of a metal sound. The exterior diameter of the flange part32is set the same as the exterior diameter of the stopper part16and the second tube20. The exterior surface of each of the stopper part16, the flange part32and the second tube20is for making the same flat surface.

As is shown inFIG. 3, the second fixing component40has an opening and has a roughly conic shape where the upper part was severed. The second fixing component40is a component for fixing the other end of the second tube20to the taper part13side of the bat part to be hit12of the first tube10. The second fixing component40includes a second fixing component based part41, a second fixing component insertion part42and a second fixing component protrusion part43. The diameter of the opening of the second fixing component40is the same as the diameter of the opening of the first fixing component30and is set slightly larger than the exterior diameter of the bat part to be hit12of the first tube10.

The exterior diameter of the base part41of the second fixing component40is set so that it steps down in one direction and in the case where the second fixing component40is fixed to the first tube10, the periphery of the base part41connects smoothly with the exterior periphery of the taper part13of the first tube10and forms one exterior surface. In addition, the largest exterior diameter of the base part41is set the same as the exterior diameter as the second tube20and the exterior surface of the second tube20and the exterior surface of the base part41are formed as one exterior surface.

The insertion part42of the second fixing component40is inserted between the first tube10and the second tube20and has a certain height. This height is generally the same height as the height of the body part31of the first fixing component30. Therefore, in the case where the first tube10and the second tube20are fixed via the adhesive70and insertion part42, a gap60with a certain height is formed between the tubes. However, the height of the insertion part42is not limited to this and may be different to the height of the body part31.

Characteristically, the second fixing component40includes a protrusion part43having a ring shape and arranged so that it protrudes toward the interior of the opening. The cross sectional form of the protrusion part43is the same as cross sectional form of the hollow for latching15which is formed on the first tube10and is a shape which interlocks with the hollow for latching15. Therefore, in the case where the second fixing component40is attached to the first tube10, by interlocking the protrusion part43to the hollow for latching15the second fixing component40is rigidly fixed to the first tube10. However, the shape of the protrusion part43is not limited to this and may be a shape in which a part of the ring is cut in a plurality of places and may also be any other shape.

In addition, the second fixing component40may also include a first screw part (not shown in the diagram) which has undergone a thread cutting process and is arranged within the opening, and in this case, a second screw part (not shown in the diagram) which has undergone a thread cutting process is arranged in certain places on the periphery of the first tube10. Then, the second fixing component40is attached to the exterior periphery of the first tube10and the first screw part and second screw part are fixed by a screw stop and adhesive.

The first fixing component30and the second fixing component40explained above formed from a plastic or synthetic rubber such as polyurethane, polyamide or polyethylene or a different elastomer material. However, the material of the first fixing component30and the second fixing component40is not limited to this. A synthetic resin, metal or ceramic may also be used for the material of the first fixing component30and the second fixing component40.

In the present embodiment a cap50is attached to the tip part11of the first tube10shown inFIG. 1by press fit processing. When the bat is being used, it is usually thrown after a ball has been hit. In addition, depending on the user, there are times when the tip of bat hits a spike or is dropped in dirt or mud and also hits the ground. The cap50acts to protect the bat in these cases. That is, the cap50also acts to protect the bat from damage caused by actions other than hitting a ball.

The cap50which fulfills this function is formed by a resin in the present embodiment and is inserted into the tip of the first tube10by press fit processing as stated above. However, the material of the cap50is not limited to this. The cap50will be explained in detail while referring toFIG. 2. As is shown inFIG. 2, the cap50is comprised of a cap tip part51, a cap recessed part52, a cap fixing part53and a cap second fixing part54. The cap tip part51protects the tip part11of the first tube10after the bat is formed.

The cap recessed part52plays the role of fixing the cap50to the tip part11of the first tube10in the case where the cap50is inserted into the tip part11of the first tube10by press fit processing. Here, the exterior diameter of the cap recessed part52is smaller than the interior diameter of a curled part19of the tip part11. Therefore, when the cap50is press fitted, because the curled part19cuts into the recessed part52of the cap50, the cap50fits onto the tip part11of the first tube10.

The cap fixed part53has a larger exterior diameter than the interior diameter of the curled part19. Therefore, when the cap50is once inserted into the tip part11of the first tube10by press fit processing, this cap fixed part53is hooked by the curled part19and the cap50is prevented from jumping out. Furthermore, at the time of press fit processing, the interior of the tip part11of the first tube10is applied with the adhesive70, the adhesive hardens between the exterior of the cap fixed part53and the interior of the tip part11of the first tube10and the cap50is more rigidly fixed. In the same way the cap second fixed part54plays the role of fixing the cap50to the tip part11of the first tube10by the adhesive70.

Next, the manufacturing process of the bat1for baseball or softball related to embodiment one of the present invention using the components stated above will be explained. First, adhesive70is applied to the inside of the opening of the first fixing component30and one surface of the flange part32. Next, the first fixing component30which is applied with the adhesive70is attached to the first tube10from the grip end14side and is fixed to the tip part11side of the part to be hit12of the first tube10by the adhesive70. At this time, one surface of the flange part32is fixed to the stopper part16by the adhesive70and the first fixing component is more rigidly fixed.

After the first fixing component30is fixed to the first tube10, the adhesive70is applied to the outside of the body part31of the first fixing component30and the other surface of the flange part32. By attaching the second tube20to the exterior periphery of the first tube10from the grip part14side so that one end of the second tube20is in contact with the flange part32, the exterior of the body part31and the other surface of the flange part32are fixed with one end of the second tube20by the adhesive70.

Next, the adhesive70is applied to the interior of the opening of the second fixing component40and the exterior of the insertion part42. This second fixing component40is attached to the first tube10from the grip14side and the insertion part42is inserted between the first tube10and the second tube20. By inserting the insertion part42while applying pressure the protrusion part43of the second fixing component40is interlocked with the hollow for latching15of the first tube10and the second fixing component40is fixed to the first tube10by the adhesive70. However, the fixing of the second fixing component40is not limited to this. A screw may be threaded in advance on the inside of the opening of the second fixing component40and the second fixing component40is attached to the first tube10by screwing. The adhesive and screwing may be used together.

Lastly, a thread is cut into the inside of the grip part14of the first tube10and the grip end80formed separately by metal in advance is attached by screwing. The grip end80may be attached by screwing and an adhesive, or another method may also be used.

The bat1for baseball or softball related to embodiment one of the present invention is manufactured by the above process. Here, because one end of the second tube20is fixed to the body part31of the first fixing component30and the other end of the second tube20is fixed to the insertion part42of the second fixing component40, a gap60having a certain height is formed between the first tube10and the second tube20. The second tube20bends inwards when a ball is hit, and the gap60is a space which plays the role of reducing the consumption of impact energy as ball transformation energy. The height of this gap60can be adjusted by a certain height of the body part31and the insertion part42(in other words, a certain diameter). In the present embodiment, the interval of the gap60is set for example between 0.1 mm and 3.0 mm or more preferably between 0.3 mm and 0.5 mm according to the material of the first tube10and second tube20.

(Effects of a Double Layered Bat)

It is possible to reduce the consumption of impact energy as ball transformation energy by the present invention and in particular a light bat for baseball or softball is proposed. In addition, a bat for baseball or softball which is easy to manufacture and low cost is proposed.

The bat1for baseball or softball related to embodiment one of the present invention is arranged with a gap60having a certain height between the first tube10and the second tube20. Then, the second tube20has a composite multi-layer structure and the surface layer of the multi-layers is mainly formed from a metal having superior rebound characteristics than the first tube10. Therefore, when a ball is hit, mainly the second tube20bends inwards, consumption of the impact energy as ball transformation energy is reduced and because the second tube20itself has superior rebound characteristics, the flight distance of the ball can be extended. Furthermore, because the second tube20has a composite multi-layer structure, it is possible to design the bat1related to the present embodiment with low flat bending rigidity and improve rebound characteristics.

Secondly, as stated above, because the first tube10of the bat1for baseball or softball related to embodiment one of the present invention is formed by FRP or synthetic resin each of which has excellent rigidity and lightness, it is possible to make the entire bat lighter. Therefore, in the case of a child's or girl's bat it is possible to improve a batter's swing speed. Because the bat related to the present embodiment is light, the rebound characteristics of the bat itself due to a double structure having a gap and the flight distance of a ball can be significantly extended. It is possible to finely adjust the weight of the entire bat1for baseball or softball related to the present embodiment by appropriately selecting the material of the outer layer and inner layer of the composite multi-layer structured second tube20. Therefore, even in the case of an adult men's bat it is possible to finely adjust the bat according to the needs of the user and also manufacture an order made bat.

Thirdly, because the bat related to embodiment one is a double layered bat with a first tube10comprised from the above stated FRP or synthetic resin, and a second tube20having an outer layer and inner layer composite multi-layer structure, vibration effects can be improved and the feeling when a ball is hit can be significantly improved compared to a bat with a single layer structure. The pain felt by a batter when a ball is miss-hit for example, can be reduced by the bat of the present invention. Because the second tube20which directly contacts with a ball is externally interlocked with the first tube10and because the second tube20itself is a composite multi-layer structure in which a plurality of layers are press fitted or stuck together, the effects of vibration control are demonstrated by a shear phenomenon and the vibration of the grip end14can be reduced. In addition, the feeling when a ball is hit can be particularly improved in the case where the outer layer of the second tube20is formed from a wood material.

Fourthly, the bat for baseball or softball related to the present invention is formed as one body from FRP or synthetic resin up to the bat tip end11which gives high rigidity to the bat tip part. For example, the rigidity of the bat is higher than that of the bat cited in Japanese Laid Open Patent 2008-29620. Therefore, even if the ball is hit with the tip end side of this bat, the flight distance of the ball can be extended. Furthermore, as stated above, because the bat is formed from up to the tip end part from FRP or synthetic resin, fifthly, durability of the bat can be improved.

As stated above, because the cap50is inserted into the tip part11of the first tube10by press fit processing, processing becomes easy. Therefore, the sixth effect is that it is possible to reduce the operational processes of the bat1for baseball or softball related to embodiment one of this invention. In addition, there is no need to use complex processes in order to interlock the parts and strict processing accuracy of the tip part11of the first tube10is not demanded. Therefore, it is both possible to reduce the cost of the various parts and therefore the overall manufacturing costs of the bat.

Seventh, safety is improved in the bat1for baseball or softball related to embodiment one of this invention. In the bat related to the present invention as stated above, the second tube20is latched by the stopper part16of the first tube10. Therefore, the first tube10and second tube20can be securely latched by adjusting the interior diameter of the second tube20and exterior diameter of the first tube10. As a result, even if the resin cap50is damaged, as long as the first tube10itself is not damaged the second tube20will not come loose and jump out and thus safety is improved.

Eighth, the life cycle of the bat1for baseball or softball related to embodiment one of this invention is much longer. The bat for baseball or softball related to embodiment one of this invention has a double layered structure, however, the second tube20is attached and fixed via the first fixing component30and the second fixing component40with the adhesive70or because the second fixing component40is fixed to the first tube10by adhesive70or screw and adhesive70, it is possible to easily replace the second tube20alone which can cause damage when a ball is hit. In a conventional bat with a metal, double layered structure, because the exterior tube (or the interior tube) is latched to the body by a swaging process, even when the exterior tube (or the interior tube) is damaged, it could not be replaced. The life cycle of the bat related to the present embodiment can be made much longer by replacing the exterior tube20. Furthermore, because the second tube20of the bat related to the present embodiment has an inner layer and outer layer composite multi-layer structure, the effects of secular distortion are few and durability is excellent compared to a double layer bat having urethane layer.

Example One

Another example of the bat1for baseball or softball related to embodiment one of the present invention will be explained. As stated above, the bat1for baseball or softball related to embodiment one of the present invention includes a cap50. However, if the bat tip end can be formed by the entire first tube10then rigidity of the tip part11can be further increased. The present example is an example where the bat tip is formed by the first tube10.

An explanation will be made based on the diagrams.FIG. 5is an enlarged cross sectional view in a longitudinal direction of a bat tip part11of the bat1for baseball or softball related to example one of embodiment one of the present invention. As is shown inFIG. 5, in the present example, the first tube10includes the stopper part16and the gap60is formed between the first tube10and the second tube20. This is the same as the bat1for baseball or softball related to embodiment one of the present invention stated above.

In the bat1of the present example, the bat1is formed with the first tube10up to the tip of the first tube (that is, bat tip)15from the stopper part16. The formation method of the bat for baseball or softball of the present example, is basically the same as the manufacturing method of the bat for baseball or softball related to the above described embodiment one. The only difference is that in the case where the mandrel is removed and a nylon tube is passed through in order to apply internal pressure, a cap which is created separately by a prepreg is set on the bat tip end. The process of heating while applying internal pressure is the same.

Because the bat1for baseball or softball related to the present example having the above described structure is formed as one body from FRP or synthetic resin up to the bat tip part11, the rigidity of the bat tip part11is significantly increased. In addition, because the bat1is one body of FRP or synthetic resin formed up to the bat tip part11, durability is further improved. Furthermore, because a process of pressing the cap into place is omitted, it is possible to reduce operation time. The points including being able to increase the flight distance of a ball by a double layered structure having a gap60, being able to lighten the entire bat, improve vibration damping effects, reduce hand pain, improve safety, extend the life cycle of the bat and improve durability compared with a hybrid type bat are all the same as in embodiment one.

Second Example

Another example of the bat1for baseball or softball related to embodiment one of the present invention will be explained. In the bat for baseball or softball related to embodiment one of the present invention, latching of the second tube20near the taper part13of the first tube10takes place by using the second fixing component40via the adhesive70, or via a screw and adhesive70. The second example of the bat for baseball or softball related to embodiment one of the present invention is an example in which fixing this second fixing component to the first tube10is made easier. An explanation is made based on the diagrams.FIG. 6is an enlarged cross sectional view in a longitudinal direction of a part to be hit12and a taper part13of the bat1for baseball or softball related to example two of embodiment one of the present invention.

As is shown inFIG. 6, the second fixing component40related to example two only includes a base part41and an insertion part42. However, the hollow for latching15is not formed on the first tube10. In addition, in the case where the second fixing component40is fixed by a screw, a first screw part is arranged within the opening of the second fixing component40and a second screw part is arranged on the periphery of the first tube10the same as in embodiment one explained above.

Fixing of the second tube20of the bat1for baseball or softball related to the second example is performed only via the adhesive70. Generally, because centrifugal force operates when a ball is hit, the force which tries to move the second tube20of the double layered bat which formed towards the bat tip part11also operates. Therefore, latching in the bat tip part11side of the second tube20is extremely important. However, there is not centrifugal force in operation on the grip part14side. As a result, latching in the grip part14side does not demand as much strength compared to latching in the bat tip end part11side. Therefore, latching via the adhesive70or latching via a screw and adhesive70sufficiently fulfills the demands for latching strength.

In the bat related to the second example, because it is not necessary to form the hollow for latching of the first tube10and the protrusion part of the second fixing component40, it is not necessary to design in detail the positioning for interlocking. In addition, in the case where the second tube20is damaged for example, because it is possible to easily remove and exchange the second tube20by simply removing the adhesive70or by simply removing the second fixing component40which is stopped with a screw, maintenance is easy. The points including being able to increase the flight distance of a ball by a double layered structure having a gap60, being able to lighten the entire bat, improve vibration damping effects, reduce hand pain, improve safety, extend the life cycle of the bat and improve durability compared with a hybrid type bat are all the same as in embodiment one and thus an explanation is omitted.

Furthermore, the second example can be applied to the bat shown in example one. The effects in this case were the same as the effects described above.

Example Three

Another example of the bat1for baseball or softball related to embodiment one of the present invention will be explained. As stated above, in the bat1for baseball or softball related to embodiment one of the present invention, in order to form the gap60between the first tube10and the second tube20, the first fixing component30and the second fixing component40are used. Here, if the diameter of the bat tip end part11side of the part to be hit12of the first tube10is increased by a certain diameter, even if the first fixing component30is omitted and only fixed by the adhesive70, it is possible to form the gap60with a certain height. The bat related to example three is an example in which the first fixing component is omitted. An explanation will be made based on the diagrams.FIG. 7andFIG. 8, are enlarged cross sectional views in a longitudinal direction of the end tip part11of the bat1for baseball or softball related to example three of embodiment one of the present invention.FIG. 7shows a bat with the cap50andFIG. 8shows a bat without the cap.

As is shown inFIG. 7, the first tube10of the bat of example three to is formed so that the exterior diameter gradually increases towards the tip part11from a certain position on the bat tip part11side of the part to be hit12and extends at a certain diameter which is increased up to the stopper part16from a first place which the exterior diameter is increased to a certain diameter. This part which is extended at a certain diameter is called a step part17. In addition, a place where the exterior diameter between the step part17and the part to be hit12gradually increases is called a connecting part18. Furthermore, although a stopper part16and a curled part19are formed this is the same as example one and example two of embodiment one described above.

Here, the exterior diameter of the step part17is set so that the gap60is formed to a desired height between the first tube10and the second tube20in the case where the second tube20is fixed to the step part17by the adhesive70. That is, the exterior diameter of the second tube20is enlarged so that it is equivalent to the height of the body part31of the first fixing component30of example one and example two of embodiment one described above. Therefore, the first fixing component30which is used in order to form the gap60with a desired height is no longer required.

The bat1for baseball or softball related to example three having this structure is completed simply by attaching the second tube20to the exterior periphery of the first tube10after the adhesive70is applied to this step part17and stopper part16in the case where the second tube20is fixed to the first tube10. Therefore, the operation for attaching the first fixing component30to the first tube10in advance can be omitted and operation time can be reduced. Therefore, manufacturing costs can also be further reduced. In addition, the points including being able to increase the flight distance of a ball by a double layered structure having a gap60, being able to lighten the entire bat, improve vibration damping effects, reduce hand pain, improve safety, extend the life cycle of the bat and improve durability compared with a hybrid type bat are all the same as in embodiment one and thus an explanation is omitted.

Furthermore, example three can be applied to the bat shown in example one and an example of this is shown inFIG. 8. Because the manufacturing process is the same as that process described above, an explanation is omitted here. In addition, the effects are also the same.

Furthermore, it is possible for the second fixing component40of the bat of example three shown inFIG. 7andFIG. 8to not have the protrusion part43shown in example two and be fixed only by the adhesive70. The manufacturing method and effects in this case are the same as in example two and thus an explanation will be omitted here.

Second Embodiment

The bat1for baseball or softball related to embodiment two of the present invention will be explained. As stated above, the bat1for baseball or softball related to embodiment one of the present invention is a double layered bat which has a gap60. By forming the bat by fixing two thin tubes so that the gap60is formed, and when the thin tubes bend inwards when a ball is hit it is possible to reduce consumption of impact energy as ball transformation energy and increase the flight distance of the ball. By forming a three layered structure by inserting a third tube25between the first tube10and second tube20, it is possible to further reduce the thickness of each tube (10,20,25) respectively. In addition, by a synergistic effect of the bending of each tube (10,20,25) it is possible to further increase the flight distance of a ball. The bat1for baseball or softball related to embodiment two of the present invention is a three layered bat.FIG. 9Ais a longitudinal direction notch sectional view and a partial enlarged view of a second tube of the bat1for baseball or softball related to embodiment two of the present invention.FIG. 9Bis a cross sectional view of the line β-β′ in a width direction and a partial enlarged view of a second tube of a bat for baseball or softball related to embodiment two of the present invention. Furthermore, inFIG. 9A,9B, for the purposes of display, because the entire second tube20can not be displayed as a composite multi-layered structure, it is displayed as one layer in the overall diagram and as a composite multi-layered structure (a composite two layered structure inFIG. 9A,98) in the partially expanded view.

As is shown inFIG. 9A, the bat1for baseball or softball related to embodiment two of the present invention is comprised of a first tube10, a second tube20, a third tube25, a first fixing component30, a second fixing component40, cap50and a grip end80The third tube25is added to the bat1for baseball or softball related to embodiment one of the present invention and thus there is no large difference between the structure which is explained in the preferred embodiment. However, because the structure of the first fixing component30and second fixing component40has been changed to correspond with the three layered bat, this point will be explained in detail. Furthermore, because the same parts as those of the bat1for baseball or softball related to embodiment one of the present invention have the same symbols, an explanation will be omitted here.

The first fixing component30of the bat1for baseball or softball related to embodiment two includes a second body part33in addition to a body part31and a flange part32in order to latch the two exterior tubes (second tube20and third tube25) of the three layered bat. In addition, the second fixing component40of this part also includes a second insertion part44in addition to a base part41, an insertion part42and a protrusion part43. The body part31and the insertion part42have a certain first height and the second body part33and second insertion part44have a certain second height.

Here, the second height is equal to the height of a second gap62which is formed between the first tube10and the third tube25. In addition, the first height is equal to a height in which the height from the exterior of the first tube10up to the exterior of the third tube25is added to the height of a first gap61which is formed between the third tube25and the second tube20. Furthermore, these equivalent heights are a result of considering the height in the case where the adhesive70which hardens between each tube (10,20,25) and the first fixing component30or the second fixing component40. Furthermore, the height of the first gap61and the second gap62is appropriately set according to the material of the first tube10, the second tube20and the third tube25. In the embodiment two, the second height is set between, for example, 0.1 mm and 3.0 mm or more preferably between 0.3 mm and 0.5 mm. The first height is larger than the exterior diameter of the third tube25and is set within 6.0 mm or more preferably between 0.6 mm and 1.0 mm.

The first tube10of the three layered bat related to the second embodiment is formed from the same FRP or synthetic resin as that of embodiment one described above. C-FRP, B-FRP and K-FRP can be appropriately used as FRP, however, C-FRP is preferable. Because the formation method of the first tube10is the same as in embodiment one of the present invention described above an explanation will be omitted here.

The second tube20is cylindrical tube with both ends open and which has a composite multi-layer structure comprised of an inner layer and an outer layer the same as in embodiment one described above. Because the material of the inner layer and the outer layer is the same as in embodiment one described above an explanation is omitted here. The inner layer and outer layer are formed separately and are joined together by a press fit processing or the adhesive70which forms a composite multi-layer structure. Furthermore, in the case where the inner layer and outer layer are formed from metal, stress is released by performing a heat process after formation. Because the bat has a three layered structure which includes the third tube25, the thickness of the inner layer and outer layer is set thinner than the second tube20of the bat related to embodiment one of the present invention and is set according to the material used and the range within which a required strength and rigidity can be secured in the first tube10, second tube20and third tube25.

The third tube25is a cylindrical tube in which both ends are open bends inwards together with the second tube20when a ball is hit and plays the role of reducing consumption of impact energy as ball transformation energy. The third tube25may be formed from FRP and may also be formed from metal. As an FRP, C-FRP, B-FRP or K-FRP may be used. As a metal, aluminum, aluminum alloy, aluminum-scandium alloy, scandium alloy, titanium, titanium alloy, magnesium alloy or steel alloy may be used. In the case where a bat which must be light such as a child's bat or girl's bat is requested, C-FRP may be preferably used in order to achieve lightness over the entire bat.

Because the bat has a three layered structure, it is sufficient if a certain strength and rigidity is secured across the entire bat, and the thickness of the three tubes are each set thinner than the thickness of each of the double layered bat. In addition, weight can be reduced across the entire bat.

By making the bat1for baseball or softball related to embodiment two a three layered structure it is possible to further reduce the thickness of each exterior tube and it is also possible to further improve the flight distance of a ball by a synergistic effect of the bending of each of the tubes. In addition, the effects of improving safety, increasing the length of the life cycle of the bat compared to a hybrid type bat, improving rigidity of the bat tip part and increasing durability, are the same as the above stated embodiment one.

Furthermore, the bat1for baseball or softball related to embodiment two can also be transformed into example one, example two and example three of the bat for baseball or softball related to embodiment one stated above. That is, the tip part11is formed by the first tube10and the cap50may be omitted, the protrusion part43is omitted and the second fixing component40may be easily fixed. Furthermore, it is possible to omit the first fixing component30by forming a first step part17a, a second step part17b, a first connecting part18aand a second connecting part18b. While these two step parts (17aand17b) and connecting parts (18aand18b) are formed, because their formation is achieved by a change of metal mold there is no effect on the manufacturing process such as an increase in processes. In addition, the effects of each are the same as the transformation example of the bat for baseball or softball related to embodiment one.

Embodiment Three

The bat1for baseball or softball related to embodiment three of the present invention will be explained. By using a material which has excellent rebound characteristics for the material of the outer layer of the second tube20which has a composite multi-layered structure, for example, titanium or a titanium alloy, the bat is further formed to improve the flight distance of a ball. However, this titanium or titanium alloy is expensive and if the entire second tube20is formed form titanium or a titanium alloy, manufacturing costs increase significantly. Therefore, if the outer layer of the second tube20is formed from a plurality of tubes and titanium or a titanium alloy is used only on a sweet-spot which is the center of an impact with a ball, then an increase in costs can be controlled. The bat1for baseball or softball related to embodiment three is a bat which has a double layered structure in which an outer layer of the second tube20has a composite multi-layered structure.FIG. 10Ais a longitudinal direction surface view of a bat1for baseball or softball related to embodiment three of the present invention.FIG. 10Bis a longitudinal direction notch cross sectional view of a bat for baseball or softball related to embodiment three of the present invention.

As is shown inFIG. 10B, the bat1for baseball or softball related to embodiment three is comprised of a first tube10, a second tube20, a first fixing component30, a second fixing component40, a cap50and a grip end80. The, outer layer of the second tube20is comprised of several parts (InFIG. 10B, the case where it is comprised of three parts is shown as an example). The inner layer of the second tube20is one tube formed from metal or FRP the same as in the above described embodiment one. A plurality of outer layers are each attached and fixed via the adhesive70to the exterior periphery of the inner layer which is one tube and forms the second tube20as one tube. Alternatively, the second tube20is formed by press fitting the inner layer to the plurality of outer layers which are alternately attached in a longitudinal direction. InFIG. 10Beach part of the second tube20which is formed as one body are called a second tube first part20a, a second tube second part20band a second tube third part20ceach of which correspond to a different outer layer. Because the first tube10, the first fixing component30, the second fixing component40, the cap50and the grip end80are the same as in the bat1for baseball or softball related to embodiment one explained above, the same symbols are attached to the same parts and thus an explanation is omitted here.

In the present embodiment, each outer layer of the second tube first part20aand the second tube third part20cis formed from aluminum, aluminum alloy, aluminum-scandium alloy, scandium alloy, steel alloy, FRP or a wood material. From the viewpoint of ease of processing and cost, an A7000 aluminum alloy such as aluminum alloy AA7050, AA7046 regulated under the American Aluminum Association Regulation, aluminum-scandium alloy or scandium alloy is preferable. However, because the outer layer of the second tube second part20bis the part which is equivalent to what is called the sweet-spot where the ball travels furthest when hit, it is formed from high cost titanium or a titanium alloy which has excellent rebound characteristics. The second tube second part20bmay also be formed from a magnesium alloy. The plurality of outer layers of the second tube20are cylindrical and each tube is formed with both ends open and each heat treated separately and used once stress is released. Furthermore, either the outer layer of the second tube second part20aor the outer layer of the second tube third part20cmay be formed from the same material as the outer layer of the second tube second part20b. As a result, at least the outer layer of one of the three second tube second parts (20a,20b,20c) is formed from a different material to the other two outer layers. In addition, the thickness of each part of the three second tube second parts (20a,20b,20c) is formed to the same thickness.

In this way, the outer layer of the second tube20which has a composite multi-layer structure is formed from parts which have different materials and by interlocking one inner layer the second tube20is formed as one tube in which the exterior is comprised of a plurality of different materials. Therefore, in the case of a double layered bat, by fixing both ends of the second tube20by the first fixing component30and the second fixing component40it becomes possible to easily form a gap with a desired height between the first tube10and the second tube20. In the Japanese Laid Open Patent 2008-29620, the structure of a similar double layered bat having a plurality of second tubes is disclosed, however, the bat shown in Japanese Laid Open Patent 2008-29620 requires another fixing component for fixing one end or both ends of the plurality of second tubes. Because the bat related to embodiment three does not require another fixing component it can be easily manufactured compared to the bat shown in Japanese Laid Open Patent 2008-29620.

In the bat1for baseball or softball related to embodiment three of the present invention which has the structure explained above, by arranging the second tube second part20bwhich is formed from titanium or a titanium alloy having excellent rebound characteristics only in a sweet-spot position which when hit can increase the flight distance of a ball, it is possible to reduce an increase in manufacturing costs even if expensive titanium or a titanium alloy is used. In addition, it is possible to form the other parts of the second tube (20a,20c) with a cheaper metal such as a steel alloy and thus it is possible to propose a double layered bat in which manufacturing costs can be easily reduced

Furthermore, the second tube second part20bwhich has excellent rebound characteristics is arranged only on the sweet-spot part and the other parts of the second tube (20a,20c) for example, can be formed with a metal which has poorer rebound characteristics than an aluminum alloy or a steel alloy. In this case, the bat becomes a bat in which a ball does not travel as far if hit in a place other than this sweet-spot, however, this bat can be preferably used as a practice bat for batting skill acquisition.

In addition, the effects of increasing the flight distance of a ball by a double layered structure, reducing operational processes, improving safety, increasing the length of the life cycle of the bat compared to a hybrid type bat, making the entire bat lighter, improving vibration damping effects and reducing hand pain, increasing durability and improving rigidity of the bat tip part, are the same as in the above stated embodiment one and embodiment two of the present invention. Furthermore, a transformed example is possible as in embodiment one and embodiment two of the present invention stated above wherein the cap50can be omitted by forming the tip part11with the first tube10, omitting the protrusion part43of the second fixing component40and easily latching the second fixing component40, and omitting the first fixing component30by forming the step part17on the first tube10. In addition, each of these effects is the same as in the transformed examples of the bat for baseball or softball related to embodiment one stated above.

Embodiment Four

Next, the bat1for baseball or softball related to embodiment four of the present invention will be explained. As stated above, the outer layer of the second tube20in the double layered bat related to embodiment three of the present invention is comprised of a plurality of tubes and the second tube20bwhich is formed from titanium or a titanium alloy having excellent rebound characteristics, is arranged in the sweet-spot position. In the bat1for baseball or softball related to embodiment four of the present invention, the arrangement of the second tube20which is formed from titanium or a titanium alloy having excellent rebound characteristics in the sweet-spot position is the same as in embodiment three, however, in embodiment four this second tube20is comprised from one inner layer and one outer layer. That is, the structure of the second tube20is the same as the bat related to embodiment one.FIG. 11Ais a longitudinal direction surface view of the bat1for baseball or softball related to embodiment four of the present invention.FIG. 11Bis a longitudinal direction cross sectional view of a bat for baseball or softball related to embodiment four of the present invention.

As is shown inFIG. 11, the bat1for baseball or softball related to embodiment four of the present invention is comprised of a first tube10, a second tube20, a first fixing component20, a second fixing component40, a cap50and a grip end80. Characteristically, the length of the second tube20is short, while the tip part11of the first tube10is formed so that it extends as far as a position of the sweet-spot. In this way, it is possible to make the length of the second tube20shorter and arrange the second tube20only in the position of the sweet-spot. Furthermore, the cap50does not have the cap second fixed part54shown inFIG. 1. Because the other parts are the same as in embodiment one described above, the same parts have the same symbols and therefore an explanation is omitted here.

Because the formation method of the first tube10of the bat related to embodiment four is the same as the bat1for baseball or softball related to embodiment one of the present invention, a detailed explanation is omitted. However, because the formation of the mandrel is different it will be explained. In the mandrel which is used when forming the bat1for baseball or softball related to embodiment four, the distance from a place equivalent to the curled part19to a place equivalent to the stopper part16is set at least the same or more than a predetermined distance. This predetermined distance can be appropriately adjusted according to the position of the sweet-spot of the bat which is manufactured and is set at least 100 mm or more from the end tip side of the tip part. Therefore, the first tube10which is formed by winding an FRP prepreg using this mandrel is a shape which extends at the same diameter from the curled part19to the stopper part16. As a result, as shown inFIG. 11, the bat tip part11can be formed longer compared to the bat related to embodiment one. The method of fixing the second tube20using the first fixing component30and the second fixing component40is the same as in embodiment one.

The bat related to embodiment four having the above described structure has a structure in which the second tube20is only attached to the position of the sweet-spot as can be judged from the notch cross section inFIG. 11(b). Therefore, because a tube which is formed from titanium or a titanium alloy as a material of the outer layer of the second tube20having excellent rebound characteristics is used only on the part which makes a ball travel far when hit, an increase in manufacturing costs can be reduced.

In addition, the effects of increasing the flight distance of a ball by a double layered structure having a desired gap60, improving rigidity of the bat tip part, improving safety, improving vibration damping effects and reducing hand pain, increasing the length of the life cycle of the bat compared to a hybrid type bat and increasing durability are the same as in the bat in the above stated embodiment one, embodiment two and embodiment three of the present invention

Furthermore, the bat related to the present embodiment can be transformed as an example the same as in the above stated example one and example three of embodiment one of the present invention. The effects in this case are also the same. In addition, as explained in embodiment three, the first tube10can be formed from a metal which has poorer rebound characteristics than an aluminum alloy or a steel alloy and can be used as a practice bat for batting skill acquisition. The effects in this case are also the same.