Games using tangible projectile – Player held and powered – nonmechanical projector – per se,... – Bat
Reexamination Certificate
1999-12-15
2002-07-30
Graham, Mark S. (Department: 3711)
Games using tangible projectile
Player held and powered, nonmechanical projector, per se,...
Bat
C473S566000
Reexamination Certificate
active
06425836
ABSTRACT:
TECHNICAL FIELD
The present invention relates to baseball or softball bats. More particularly, the present invention relates to a baseball or softball bat capable of increasing the hit distance of a ball and reducing the manufacturing cost.
BACKGROUND ART
Conventionally, the baseball or softball bat (hereinafter, referred to as a bat) market deals with bats of various materials. For example, there are wooden bats, metal bats made of titanium alloys or aluminum alloys, and fiber reinforced plastic (hereinafter, referred to as FRP) bats which are manufactured by impregnating a matrix resin, represented by an epoxy resin and other synthetic resins, into yarns, cloths, Sleeves or the like, which are formed of carbon fibers, glass fibers or the like, and curing the impregnated yarns, doths, sleeves or the like.
In order to improve the rebound characteristics of a bat when it hits a ball, Japanese Patent Publication No. 50-7976, for example, previously proposed a metal bat with a double pipe structured hitting surface which is formed by bonding a metal pipe of a suitable length inside the hitting surface of the bat body.
Japanese Utility Model Publication No. 51-13165 also proposed a metal bat with a triple structured hitting surface which is formed by bonding a metal pipe of a suitable length inside the hitting surface of the bat body, and then inserting and adhering a lubber or synthetic resin plate or pipe in the interlayer of double pipes, which are formed of the bat body and the bonded metal pipe, (in the layer between the bat body and the bonded metal pipe).
U.S. Pat. No. 5,415,398 also proposed a bat which has a tubular insert placed and bonded inside the hitting portion of the bat body so as to leave a gap between the insert and the bat body, or a bat which contains grease sealed in the gap.
However, the conventionally proposed bats as described above have the following problems.
As described above, the bat disclosed in Japanese Patent Publication No. 50-7976 has a metal pipe of a suitable length bonded inside the hitting surface of the bat body. In manufacturing such a bat, a metal pipe is inserted and bonded in the hitting surface of the bat body while the pipe is under heavy load or pressure. In the process of inserting and bonding the metal pipe, the inner wall of the hitting surface of the bat body may be damaged. If the inner wall of the hitting surface is thus damaged, the bat may crack from the damaged portion or may be broken in use.
The bat disclosed in Japanese Utility Model Publication No. 51-1316 has a rubber or synthetic resin plate placed in the interlayer of double pipes as described above. That causes a dull sound and reduces the rebound characteristics of the bat when the bat hits a ball.
A bat body deforms more as the bat hitting portion is thinner. The bat can hit a ball farther by utilizing the force of restoring the bat body from the deformed shape to the original shape. When the bat body hitting portion is too thin, however, the strength of the bat body is insufficient. Therefore, the bat body may dent or crack when hitting a ball.
In order to solve such problems, the bat disclosed in U.S. Pat. No. 5,415,398 has the above described structure to prevent the outer shell wall of the thin bat body from being plastically deformed by impact stress caused when the bat hits a ball. Therefore, the bat body can deform in a range which allows elastic deformation without causing plastic deformation. Then, the force of restoring the outer shell wall of the bat body from its elastically deformed state (force by spring reaction) can improve the rebound force against a ball. In other words, the bat disclosed in U.S. Pat. No. 5,415,398 satisfies the both demands of improving the rebound characteristics for hitting a ball farther and securing a sufficient strength of a bat by combining the thin outer shell wall of the bat body and the insert placed to leave a gap between the insert and the outer shell.
Further, grease which is sealed in the gap enables smooth transfer of impact force, which is caused when the bat hits a ball, from the outer shell wall of the bat body to the tubular insert. As a result, the rebound characteristics of the bat can be improved further.
As described above, the bat disclosed in U.S. Pat. No. 5,415,398 has superior rebound characteristics and can increase the hit distance of a ball.
However, the bat disclosed in U.S. Pat. No. 5,415,398 requires formation of a minute gap between the bat body and the tubular insert at a high dimensional accuracy in order to realize the above described superior rebound characteristics. To implement good rebound characteristics at the entire circumference of the bat, it is also necessary to strictly control and set the height of the gap between the bat body and the tubular insert so as to be uniform at the entire circumference of the bat. Accurate formation of such a minute gap in the bat manufacturing process takes a lot of trouble and time, which results in the increased bat manufacturing cost.
Although above described U.S. Pat. No. 5,415,398 discloses a bat which contains grease sealed in the gap, the grease in this case has to be relatively high in viscosity because a failure such as leakage of the grease from the gap to the outside of the bat in use should be prevented. Since the process of sealing such viscous grease inside the gap also takes a lot of trouble and time, the bat manufacturing cost is further increased.
DISCLOSURE OF THE INVENTION
One object of the present invention is to provide a baseball or softball bat capable of increasing the hit distance of a ball and reducing the manufacturing cost.
Another object of the present invention is to provide a method of manufacturing a baseball or softball bat capable of increasing the hit distance of a ball and reducing the manufacturing cost.
According to one aspect of the present invention, a baseball or softball bat including a hitting portion, a taper portion, and a grip portion includes a tubular member and a metal tubular member. The tubular member includes an outer circumference plane extending from the hitting portion to the grip portion, and an inner circumference plane located inside the outer circumference plane and extending from the hitting portion to the grip portion. The metal tubular member is placed between the outer circumference plane and the inner circumference plane at least in the hitting portion The metal tubular member has a weak boundary layer formed on its surface.
Since the metal tubular member is placed between the outer circumference plane and the inner circumference plane of the tubular member is described above, the metal tubular member can improve the strength and durability of the bat. That is, the tubular member can be made thinner while the bat strength is maintained as compared with a case where the metal tubular member is not placed. Further, by forming the weak boundary layer, the tubular member and the metal tubular member can deform independently from each other when the bat hits a ball. Therefore, as compared with a case where the tubular member and the metal tubular member are bonded at nearly the entire contact plane, a portion of the tubular member which is located on the outer circumference side of the metal tubular member can elastically deform easily when the bat hits a ball. The force of restoring the portion of the tubular member from the elastically deformed state can increase further the hit distance of a ball. It is noted that the weak boundary layer is a layer which exists on the surface of a body to be bonded (the surface of the metal tubular member) and does not have the mechanical strength higher than a targeted bond strength. The weak boundary layers are, for example, grease which covers a metal surface and a lubricant for a molded plastic surface. In a region where the weak boundary layer is formed, the metal tubular member and the tubular member contact with each other without being bonded.
If the weak boundary layer is formed on the surface of the metal tubular member in this manner, the effects as
Ishida Kazuya
Kida Toshiaki
Misono Kazunori
Okuyama Masaaki
Boss Gerald R.
Graham Mark S.
Mizuno Corporation
Troutman Sanders LLP
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