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Bat and method of manufacturing the sameRelated Patent Categories: Games Using Tangible Projectile, Player Held And Powered, Nonmechanical Projector, Per Se, For Projecting Aerial Projectile By Striking; Part Thereof Or Accessory Therefor, Bat (e.g., Baseball Bat, Etc.)Bat and method of manufacturing the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070037639, Bat and method of manufacturing the same. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCES TO RELATED APPLICATION [0001] This application claims priority from Japanese Patent Application Serial No. 2005-233105 filed Aug. 11, 2005, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD [0002] Described herein is a bat used for playing a baseball game or a softball game, and a method for manufacturing the same. BACKGROUND [0003] Generally, a conventional bat for playing an amateur baseball game or a softball game is made from wood, FRP, or metallic material. Such a bat is manufactured by filling resin core material in a hollow bat body in order to enhance mechanical rigidity and impact absorbing characteristics of the bat and to control swinging balance thereof. [0004] For example, Japanese Patent Laid Open Patent No H08-280860, discloses an FRP bat body in which foamed polyvinylidene chloride resin particles, foamed polypropylene resin particles, or foamed polystyrene resin particles are filled so that bat swinging balance can properly be controlled. Japanese Laid Open Patent No. 2001-79132, discloses that in order to secure as much repulsive characteristics as that of the conventional wooden bat, the inner space of an aluminum bat body is filled with a foamed DCPD (dicyclopentadiene) resin etc. [0005] In the FRP bat described in Japanese Laid Open Patent No. H08-280860, the bat swing balance is controlled by adjusting specific gravity and injecting foamed resin material. [0006] However, the foamable resin particles used as the core material of the conventional FRP bat have insufficient foamability and low rigidity. Hence, in the case of the FRP bat, if the foaming power is reduced so as to enhance the rigidity, it will in turn result in the increased weight of the resin core material, so that it is difficult to manufacture a practically usable bat. Further, the FRP bat filled with foamed resin material has a technical problem in that the ball flying distance and effective batting area can be hardly extended, i.e., the sweet-spot area can be hardly enlarged or the impact absorbing characteristics can be hardly enhanced. [0007] In addition, in Japanese Patent No. 2001-79132, a conventional aluminum bat is disclosed, in which the aluminum bat has high repulsive characteristics and impact absorbing characteristics substantially equivalent to those of the wooden bats. In such a conventional aluminum bat, generally, the bat body is manufactured in a swaging molding process in the cold atmosphere. However, this process also involves another technical problem that the thickness of a portion from the tapered portion to the handgrip portion of the bat is increased, thereby increasing the weight of the bat, so that proper balance of the bat itself is deteriorated. Hence, conventional aluminum bat manufacturers have adapted measures to thin off the thickness of the bat by carrying out a swaging molding process after thinning off the thickness of the bat in a preliminary grinding process which is carried out to, for example, an area ranging from the tapered portion to the handgrip portion. [0008] Nevertheless, in the process for manufacturing an aluminum bat, an aluminum tube as a base material is damaged or scratched in the grinding process so that the mechanical strength of the bat is lowered. Further, in order to precisely meet the criterion value, some conventional aluminum bat manufacturers need to perform a grinding process under precise control over the grinding amount, and since the tapered area to be processed is ground stepwise, so that a step-like portion is formed thereon. SUMMARY [0009] Accordingly, the bat according to embodiments set forth below solves at least one of the above technical problems of the conventional bats made from FRP material or aluminum etc. In the bat according to the embodiments, a sweet spot is enlarged and impact absorbing characteristics are enhanced, and the leveled thickness of the bat body is also secured so as to enhance the mechanical strength, and the weight of the bat is decreased so as to secure satisfactory swing balance for a user. A method for producing such a bat is also described. [0010] The embodiments set forth below includes a bat comprising a bat body and a foamed core member formed with foamed resin beads filled up in the inner space thereof. Further, the bat body may be made of metallic material such as aluminum, aluminum alloy, titanium, or titanium alloy, or made from fiber-reinforced plastic (FRP) material, wherein the bat body has a cylindrical body having the closed tip portion and an opening at the grip end so that the entire body having the bottom portion extends along a longitudinal axis. The inner space of the cylindrical bat body may be filled with pre-foamed resin beads fed from the grip-end opening. The inner space of the bat body may be filled with pre-foamed methacryl resin beads which is treated with a predetermined foaming process in advance. By closing the grip-end opening, the inner space of the bat body filled with the pre-foamed methacryl resin beads may be tightly closed, and then, the bat body may be thermally treated to cause the resin beads to be expanded, thereby completing formation of the foamed core member. [0011] The foamed methacryl resin material that forms the foamed core member has greater foaming capability, higher rigidity, and lighter weight than that of conventionally available foamed resin materials such as foamed vinylidene resin material, foamed polypropylene resin material, or foamed polystyrene resin material. For example, the foamed methacryl resin material has the rigidity about 1.8 times as high as that of the vinylidene resin material, and also has the weight about 0.7 times as large as that of the vinylidene resin material, in the same volume. Therefore, since the pre-foamed methacryl resin beads are filled up in the body of the bat so that approximately 100% of the volume of the inner space of the bat body is filled up, after the un-foamed methacryl resin beads are foamed so as to increase the volume thereof, for example twenty times as large as that of un-foamed beads, the amount of the methacryl resin beads to be filled in the bat body can be reduced, so that it is possible to reduce the weight of the foamed methacryl resin beads to be filled up. By the thermal treatment applied at a relatively low temperature within a short time after charging (filling up) the pre-foamed methacryl resin material, it is possible to execute a secondary foaming process, thereby generating substantial inner pressure to the bat body. [0012] Accordingly, by reducing the weight of the foamed core member made of the foamed methacryl resin beads and by applying internally generated predetermined pressure to the bat body, a sweet spot can be enlarged, and the impact absorbing characteristics are enhanced. [0013] Furthermore, the embodiments include steps of filling up pre-foaming methacryl resin beads into the inner space of the bat body from the opening formed in part of a grip end portion so that approximately 100% of the volume of the inner space is filled up with the pre-foamed methacryl resin beads, a step of sealing the inner space of the bat body, and a step of heating the pre-foamed methacryl resin beads to carry out a secondary foaming process inside the inner space by treating the bat body. [0014] Further, in the method for manufacturing the bat, the process for manufacturing the bat body may comprise a step of forming a cylindrical base material, a step of carrying out a spinning rolling process, and a step of carrying out a swaging process before eventually forming a bat body having a predetermined shape provided with an opening at the grip-end portion. In the method, by using selected material, a cylindrical body material having the bottom portion may be formed in the step for manufacturing the bat body. Further, the method may includes a step of inserting a core metal member in the inner hole of the cylindrical material and a step of pressing a plurality of rollers of a rolling mill respectively disposed at different positions on the circumference of the cylindrical material in order to implement a spinning rolling process, and a step of forming the bat body material having an area corresponding to the grip-end portion having a predetermined thickness around the local area corresponding to the handgrip portion of the bat body material. According to the method, by applying a cold swaging process to the bat body material, a bat body having a predetermined shape may be eventually formed, wherein the handgrip portion is linked with the sweet-spot portion via the tapered portion so as to form a continual surface. [0015] As described above, the foamed methacryl resin beads used for the foamed core member has greater foaming capability and higher rigidity than those of the conventionally available foaming resins such as foamed vinylidene resin, foamed polypropylene resin, or foamed polystyrene resin, and further the foamed methacryl resin beads are lighter than that of the others in the weight. For example, in the same volume, the foamed methacryl resin beads have the rigidity about 1.8 times higher than that of the foamed vinylidene resin, and has the weight about 0.7 times lighter than that of the foamed vinylidene resin. Accordingly, in the method for manufacturing a bat, by filling up the inner space of the bat body with pre-foamed methacryl resin beads whose volume is increased by about twenty times as large as the un-foamed methacryl resin beads so that approximately 100 % of the inner space of the bat is filled up with the pre-foamed methacryl resin beads, whereby the bat weight can be reduced. Further, in the method for manufacturing a bat, a plug member may be inserted and fixed to an opening formed on part of a handgrip portion so that the inner space of the bat body is fully closed, and then the foamed methacryl resin beads filled up in the closed inner space of the bat body are thermally treated so that a secondary foaming of the heated resin beads is carried out therein. The secondary foaming process may be carried out by the thermal treatment for a short time at a relatively low temperature. Accordingly, substantial predetermined inner pressure is generated from the inside of the body of the bat by the foamed core material, so that it is possible to manufacture a bat having an enlarged sweet-spot area and the enhanced impact absorbing characteristics. [0016] Further, according to the method for manufacturing a bat, in the spinning rolling process, in a state in which the core metal has been inserted in the inner hole of the cylindrical material, the external circumference of the cylindrical metallic material is simultaneously pressed by rotating pressure rollers from three directions at a speed of, for example, 300.about.600 rpm, so that while bringing the cylindrical material in contact with the core metal member, the cylindrical metal material is rolled in the axial direction so as to carry out a spinning rolling process thereby forming a base material for a bat body. Further, since in the method for manufacturing a bat, the controlling unit properly controls the pressing operation of the pressure rollers on the cylindrical metal material, it is possible to form a bat body material having an ideal thickness along the entire bat body in the axial direction without causing the grip-corresponding area to become thicker. Still further, in the method for manufacturing a bat, by performing a cold swaging process to the bat body material, it is possible to form a bat body having a predetermined shape with a continual surface ranging from the handgrip portion to the sweet spot portion through a taper portion. The cold swaging process is a method of reducing or forming steel or other material while cold, by drawing to a point or reducing the diameter, as may be required. Thus, since the bat body can be formed with the predetermined thickness throughout the entire bat body in the axial directional, it is possible to securely realize lighter weight and proper balance, and further, it is possible to enhance the rigidity as well. [0017] As described above, the amount of foamed methacryl resin beads to be filled up in the inner space of the bat body is reduced by performing a predetermined foaming process for foaming the beads in advance, and the foamed methacryl resin beads are filled up in the inner space of the bat body so as to substantially fill the inner space of the bat body (approximately 100 % of the volume of the inner space), and further a secondary foaming process is carried out to the --pre-foamed methacryl resin beads in the state in which the inner space of the bat body remains closed. Consequently, it is possible to reduce the actual weight of the foamed methacryl resin beads and allow the bat body to be affected by substantial predetermined pressure generated from the inside of the bat body throughout a wide area thereof by the foamed core member, thereby making it possible to secure a wide sweet-spot area and enhance the impact absorbing characteristics. BRIEF DESCRIPTION OF THE DRAWINGS [0018] Other features and advantages of the bat, and the method according to the present invention will be apparent from the ensuing description, taken in conjunction with the accompanying drawings, in which: [0019] FIG. 1 is a cross-sectional view of a bat according to an embodiment; Continue reading about Bat and method of manufacturing the same... Full patent description for Bat and method of manufacturing the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Bat and method of manufacturing the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Bat and method of manufacturing the same or other areas of interest. ### Previous Patent Application: Game apparatus Next Patent Application: Arrowhead assembly Industry Class: Games using tangible projectile ### FreshPatents.com Support Thank you for viewing the Bat and method of manufacturing the same patent info. IP-related news and info Results in 0.2431 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. 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