Softball bat

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US005415398A

United States Patent [19] [n] Patent Number: 5,415,398

Eggjman [45] Date of Patent: May 16, 1995

5,415,398

1 2

In light of the shortcomings of the prior art, it is an

SOFTBALL BAT objective of the present invention to provide an improved bat.

This application is a continuation of application Ser. It is another objective of this invention to provide a

No. 08/062,307, abandoned, filed on May 14, 1993. 5 bat that increases the power transferred from the bat to

a batted ball.

FIELD OF THE INVENTION It is yet anotner objective of this invention to provide The present invention relates to Softball and baseball a simple construction for a tubular bat with an insert, bats and more particularly relates to the use of struc- In accordance with a preferred embodiment of the tural members inside such bats to improve their impact 10 present invention, a tubular aluminum bat frame is proresponse, vided with a large-diameter impact portion, an intermediate tapering portion, and a small-diameter handle BACKGROUND AND SUMMARY OF THE portion. A tubular insert is suspended within the impact INVENTION portion by interference fits at each insert end. A first Tubular metallic Softball (and baseball) bats are well 15 interference fit is achieved by forcing the first end of the known in the art. A familiar example is a tubular alumi- insert mt0 the tapering portion of the bat frame. The num bat. Such bats have the advantage of a generally second interference-fit is then formed by curling the end good impact response, meaning that the bat effectively of the impact portion over upon the second end of the transfers power to a batted ball. This effective power msert A SaP exists alom? the leaS& of the suspended transfer results in ball players achieving good "slug- 20 msert separating the insert from the interior of the imging" distances with batted balls. An additional advan- Pact portion. The gap is filled with grease to facilitate tage of such aluminum bats is the improved durability TMve movement between the msert and the tubular over crack-prone wooden bats. frame when a ball ,s batted.

Even though today's aluminum bats perform well, 11?e foregomg and additional features and advantages there is an ever-continuing quest for bats with a better 25 °f the mventI°n will be more readily apparent "slugging" capacity. Accordingly, one important need from ^following detailed description, which prois to optimize the impact response of a bat. Generally ceeds wlth reference t0 the accompanying drawings, speaking, impact response is best when a bat undergoes BRIEF DESCRIPTION OF THE DRAWINGS

a greatest elastic deflection, before rebounding with a , , , . ^, , it_ .

^ *r ■ I. 1 ^?*4 - 30 FIG. 1 shows a sectional view through the center of

greatest force m the shortest amount of time. Optimiza- „ , . . , ... & ^ . . .

• tli f ^ • vu « • » t a Softball bat in accordance with one aspect of this

tion of these three factors increases the spring" of a . m .- y

, „ _. , . ,,. , ., . f e> mvention.

ball off a bat, yielding a bat with a superior power trans- FIQ 2 ig a ified cut yigw of the bat f FIG

fer and faculty for slugging. j

Constraining the design of aluminum bats is the re- 35 'FIQ 3 is a ... view ^ ^ ^ 3_3 Qf quirement that the elastic deflection not be accompa- -p\Q 2 nied by any plastic deformation. Plastic deflection lessens the power transfer to a ball and leaves the bat per- DETAILED DESCRIPTION manently dented. Thus, aluminum bat design is driven Referring to FIG. 1, a Softball bat 10, according to by the elastic and plastic deformation characteristics of 40 one embodiment of the present invention, has a tubular aluminum. For example, when the tubular wall is too aluminum frame 11 with a relatively large-diameter thin, a desirable large amount of elastic deflection is impact portion 12, an intermediate tapering portion 14, achieved, but with unwanted permanent plastic defor- and a relatively small-diameter handle portion 16. mation. On the other hand, when the aluminum tubular To provi(}e for an improved impact response yielding wall is too thick, the bat may be too stiff to elastically 45 a better transfer of power from the bat to a batted ball, deflect appreciably. In this case, the bat responds with a tubular insert 18 is suspended within the impact porrelatively little spring, resulting in lower power trans- tion 12 of the tubular frame. The tubular insert is a fer- hollow tube of an outer diameter slightly less than the

To provide for greater "spring," tubular bats using inner diameter of the tubular frame impact portion 12. other materials, such as titanium, have been developed. 50 A first end 20 of the tubular insert 18 is inserted through

Titanium is a high-strength material permitting thin bat the impact portion 12 to be forcefully lodged in abut

frame walls which provide a substantial elastic deflec- ment with the diametrically narrowing interior wall of

tion without plastic deformation. Such bats provide the tapering portion 14, thus forming a first interference

excellent spring-like response and power transfer to a fit. A second end 22 of the tubular insert 18 is spaced batted ball. However, the material cost and difficulty of 55 inwardly from the top end of the impact portion 12

working titanium result in a high consumer cost. when the tubular insert 18 is secured in the first interfer

The prior art also includes tubular bats using inserts. ence fit. A second interference fit is created at the insert

While most often inserts are used for vibration deaden- second end 22 by curling the topmost portion of the

ing purposes, U.S. Pat. No. 3,963,239 of Fujii discloses impact portion over upon the insert second end 22. The a metallic bat frame with a large-diameter impact por- 60 curled-over portion forms a reduced-diameter head

tion receiving an insert to adjust the weight and im- portion 24 of the tubular frame 11.

prove the "repelling action" of the bat. Fujii teaches an Because the outer diameter of the insert 18 is slightly

insert in tight abutment within the tubular frame, so that less than the inner diameter of the tubular frame impact

the insert is fixed relative to the frame. The engagement portion 12, the suspended insert 18 contacts the tubular is improved by forcing the insert into the tapered inter- 65 frame only at the interference fits of the first and second

mediate portion of the bat and/or by gluing the insert insert ends 20, 22. A narrow, uniform gap 26 exists

within the frame. The tightly-fitted Fujii insert simply between the insert 18 and the inner wall of the impact

acts to thicken the wall of the impact portion of the bat. portion 12. The gap extends uniformly around the insert 3 4

(see FIG. 3) and along the length of the insert between from a constant-diameter aluminum tube to yield an the first and second ends 20, 22 thereof. integral, weld-free frame. Such swaging results in a

As best seen in FIG. 2, the gap 26 is filled with a tubular frame with thinner walls at the impact portion lubricant, such as grease. The grease is brought within 10 and thicker walls at the handle portion 16. While the gap 26 by coating the insert 18 with grease before 5 swaging is used to produce the tubular frame 11 of the the insert is inserted into the tubular frame 11. Once the illustrated embodiment, it shall be understood that other insert 18 is secured between the first and second inter- methods of manufacturing the tubular frame may work ference fits, the lubricant-filled gap 26 is effectively equally as well.

sealed by the first and second interference fits. Using aluminum of 80,000 pounds/inch2 yield

The operation of the softball bat of the illustrated 10 strength, an excellent batting response is achieved when embodiment is designed for an improved transfer of the impact portion 12 is about 13 inches long with a wall power to a batted ball. Specifically, the bat 10 responds thickness of 0.058 inch. An insert 18 slightly shorter to the impact with a ball by providing a large elastic than the impact portion 12 and having a wall thickness deflection, which rebounds with a large force in a short of 0.048 inch is inserted into the impact portion 12. The amount of time. 15 outer diameter of the insert is chosen so that the gap

The tubular frame 11 with the suspended insert 18 between the outer surface of the insert 18 and the inner attached at both ends to the tubular frame 11 yields a surface of the impact portion 12 is about 0.007 inch, mechanical system with characteristics similar to a leaf While such dimensions yield excellent results, it is to spring. When the bat 10 strikes a ball on the impact be understood that they are exemplary only, and that portion 12, the impact portion 12 wall deflects inwardly 20 many permutations of bat frame, insert, and gap dimenthrough the grease-filled gap 26 to load and inwardly sions will work equally as well. All permutations of deflect the underlying insert wall. The deflection of the component dimensions and configurations fall within impact portion 12 can be considered as generally arcu- the scope of the present invention, ate. Accordingly, the insert 18 deflects arcuately to Further describing a preferred construction, the incradle the arcuate deflection of the impact portion 12. 25 sert 18 is coated with the lubricant before being inserted

Because the insert 18 arcuate cradles the impact por- into the tubular frame 11. The first end 20 of the insert tion 12 arcuate, the insert 18 arcuate has a radius of 18 is forcefully inserted into the tapering portion to curvature greater than the impact portion 12 arcuate. achieve a tight interference fit. Plastic deformation of Because the insert 18 is fixed within the tubular frame at the aluminum insert at the interference fit increases the the insert ends 20,22, the greater radius of curvature of 30 tightness of the attachment and the seal. The second the insert deflection causes the insert 18 to be stretched, interference fit is then obtained within a frame head as well as bent, around the deflection of the impact portion 24, which is formed by curling the topmost end portion 12. Therefore, the insert 18 undergoes substan- of the impact portion 12 over upon the insert second tial tensile, as well as bending stress when a ball is bat- end 22. It has been found that a tight fit is achieved by ted. 35 curling in a one-half-inch radius forcefully enough to

The leaf-spring-like attachment of the insert 18 within cause some plastic deformation in the insert second end the impact portion 12 provides a rebound to yield im- 22. The curling may be facilitated by locally heating the proved power transmission to the ball. The bending end of the impact portion.

stresses are released as the walls of the impact portion It should be understood that the foregoing is exem12 and the insert 18 rebound into the unloaded state. 40 plary only, and that equally good results can be The tensile loading of the underlying insert wall is re- achieved without heating, curling, or plastic deformaleased simultaneously, adding "snap" which increases tion of the insert ends. For instance, the head portion 24 the force and velocity of the rebound. Accordingly, the of the frame could be pre-formed and threaded into the extra snap owing to the leaf-spring-like suspension of top of the impact portion 12. In this case, the head the insert 18 within the tubular frame yields an im- 45 portion 24 may be threaded to impinge tightly upon the proved transfer of power to the batted ball, and a insert second end 22, to create the interference fit. heightened "slugging" capacity for the bat. The interference fits of the illustrated embodiment

The grease permits relative movement between the offer excellent performance and are advantageous in the impact portion 12 and the insert 18, so that the insert simplicity of design and manufacture (notably in the can independently stretch around the deflection of the 50 absence of any required welding). However, it is to be impact portion 12. The sealed condition of the grease understood that welding or other fasteners may also be within the gap offers another advantage. The impact used. For instance, additional friction-improving dewith a ball may occur so rapidly that the grease cannot vices may be used at the interference fits of the inserts appreciably flow. Rather, the grease hydrostatically and the tubular frame 11. Alternatively, adhesives or supports the wall of the impact portion away from the 55 mechanical fasteners for joining the insert ends to the insert. In this case, a substantial layer of grease is main- tubular frame may be used. Any fastener may also serve tained between the impact portion and the insert, facili- the purpose of sealing the lubricant within the gap 26. tating the movement of the insert relative to the impact Any attachment mechanism or fastener maintaining the portion. In another aspect, any flow of the grease that leaf-spring-like suspension falls within the scope of the does occur during impact serves to distribute the force 60 present invention.

of impact over an expanded area of the impact portion While the present embodiment utilizes aluminum for 12. The distribution of the impact stress permits a thin- the frame and the insert, it should be understood that ner-walled impact portion because high stress concen- many other materials will perform equally well with the trations causing plastic deformation are not likely to present invention. For instance, at a slightly higher cost, occur. 65 titanium could be used as insert material with excellent

In a preferred embodiment, both the tubular frame results. A titanium insert is advantageous owing to its and the insert are made of aluminum. An exemplary excellent impact response characteristics. In addition, construction of the bat has the tubular frame 11 swaged because the insert is a hollow tube, the machining and