U.S. patent number RE31,811 [Application Number 06/291,563] was granted by the patent office on 1985-01-22 for baseball bat with modified internal air pressure.
Invention is credited to Ronald Foreman.
United States Patent |
RE31,811 |
Foreman |
January 22, 1985 |
Baseball bat with modified internal air pressure
Abstract
An aluminum baseball bat with plug of solid rubber or similar
material at one end thereof and a knob at the other end is
disclosed. The rubber end plug is sealed in place in a leak-proof
junction to define a hollow interior space. By inserting a needle
through the end plug, fluid communication between a source of air
or other gas which is pressurized either above or below atmospheric
pressure and the interior of the bat space can be provided to
achieve a desired pressure therewithin. Once the desired interior
pressure has been achieved, the needle is withdrawn and the natural
resiliency of the rubber acts to immediately seal the puncture to
thereby permanently maintain the desired interior pressure
conditions.
Inventors: |
Foreman; Ronald (Narberth,
PA) |
Family
ID: |
26966858 |
Appl.
No.: |
06/291,563 |
Filed: |
August 10, 1981 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
973039 |
Dec 26, 1978 |
04241919 |
Dec 30, 1980 |
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Current U.S.
Class: |
473/566 |
Current CPC
Class: |
A63B
59/50 (20151001); A63B 59/56 (20151001); A63B
59/51 (20151001); A63B 2102/18 (20151001) |
Current International
Class: |
A63B
59/06 (20060101); A63B 59/00 (20060101); A63B
059/06 () |
Field of
Search: |
;273/67R,72A,73R,73C,73H,76,77R,78,82R,82A,162R,167R,167H,61D |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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19675 |
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1902 |
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GB |
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834280 |
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May 1960 |
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GB |
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Primary Examiner: Oechsle; Anton O.
Attorney, Agent or Firm: Spivak; Karl L.
Claims
What is claimed is:
1. A metallic bat comprising sidewalls which terminate at one end
in a closed end and at the other end in an open end, the open end
being closed with a resilient end plug secured to the interior
surface of the sidewalls to define an interior space capable of
maintaining a quantity of confined gas therewithin, the confined
gas being characterized by a pressure other than atmospheric, the
resilient end plug having a passage therethrough in communication
with the interior space, the passage being open when a pressure
introducing needle is inserted through the plug to introduce gas
into the interior space and the passage being closed when the
needle is withdrawn to seal the said interior space,
the said pressure being appropriate to produce a natural frequency
of free vibration of such frequency and amplitude in the bat that
when coupled with the excitation frequency caused by the impact of
the bat striking a ball, resonance results.
2. The bat of claim 1 wherein the said pressure is approximately 6
psi greater than atmospheric.
3. The bat of claim 1 wherein the pressure is less than
atmospheric.
4. The method of modifying the initial pressure of a gas entrapped
within the interior of a metallic baseball bat of the type having
an interior space defined by the bat sidewalls and having one
closed end and one open end, the open end being closed by a
resilient plug, comprising the steps of
forming an opening through the resilient plug part of the bat
construction in communication with the interior space by forcing a
hollow conduit therethrough until its inner end reaches the
interior space and its outer end extends outwardly of the plug;
determining the critical structural frequency of the bat;
introducing a gas at a pressure other than the initial pressure to
the outer end of the conduit and forcing the gas through the
conduit to establish the final pressure of the gas in the interior
space;
pressurizing the gas to a final pressure necessary to achieve
critical structural frequency in the bat; and
removing the conduit and automatically closing the opening through
the resilient plug and maintaining the final pressure of the gas in
the interior space.
5. The method of claim 4 including the step of pressurizing the gas
to a final pressure of approximately 6 psi .Iadd.greater than
atmospheric pressure..Iaddend..Iadd.
6. In a metallic bat construction of the type comprising sidewalls
and closed first and second ends defining an interior space and
capable of maintaining a quantity of confined gas therewithin, the
improvement comprising
gas passage means in the bat construction in fluid communication
with the interior space to pass gas therethrough,
the confined gas being characterized by a pressure that is other
than atmospheric, and
the said pressure being appropriate to produce a natural frequency
of free vibration of such frequency and amplitude in the bat that
when coupled with the excitation frequency caused by the impact of
the bat striking a ball, resonance results. .Iaddend. .Iadd.7. The
bat of claim 6 wherein the said pressure is approximately 6 psi
greater than atmospheric..Iaddend. .Iadd.8. The bat of claim 6
wherein the pressure is less than atmospheric. .Iaddend. .Iadd.9.
The method of modifying the initial pressure of a gas entrapped
within the interior of a metallic baseball bat of the type having
an interior space defined by the bat sidewalls and having a first
closed end, a second closed end and gas passage means in fluid
communication with the interior space, comprising the steps of
determining the critical structural frequency of the bat;
introducing a gas at a pressure other than atmospheric pressure to
the gas passage means and forcing the gas through the gas passage
means to establish the final pressure of the gas in the interior
space;
pressurizing the gas to a final pressure necessary to achieve
critical structural frequency in the bat; and maintaining the final
pressure of the gas in the interior space. .Iaddend. .Iadd.10. The
method of claim 9 including the step of pressurizing the gas to a
final pressure of
approximately 6 psi greater than atmospheric..Iaddend. .Iadd.11.
The bat of claim 6 wherein the pressure is greater than
atmospheric..Iaddend. .Iadd.12. The method of claim 9 including the
step of pressurizing the gas to a final pressure that is greater
than atmospheric..Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to a novel hollow metallic
baseball bat, and more particularly, is directed to the method and
apparatus resulting therefrom for modifying the interior air
pressure of the bat.
It is presently common practice to fabricate baseball bats of solid
wood or hollow or filled aluminum construction. The hollow aluminum
bats are conventionally formed and shaped of aluminum tubing of
suitable wall thickness with the handle end enclosed by a formed
aluminum end cap or knob which is secured to the handle
construction. The large end or ball striking end of the bat is
closed by metal spinning or by a solid rubber plug which is
cemented in place. The end plug acts to provide necessary balance
weight and closure to produce an entirely satisfactory device. One
such bat construction is disclosed in U.S. Pat. No. 3,479,030 to
Merola.
In accordance with the present invention, it has been found that
the efficiency and capability of a hollow aluminum bat of
conventional design can be greatly improved by varying the internal
air pressure to achieve optimum results. The improved ball driving
characteristics of the modified internal pressure bat have as their
basis certain fundamental results which can be explained by some of
the concepts of theory of mechanical vibrations.
In accordance with fundamental principles of mechanical vibrations,
when a body is set into motion, if the motion is periodic, that is,
if it repeats itself with time, this motion is termed vibration.
The number of independent variables used to completely specify the
configuration of the vibrating system is referred to as the number
of degrees of freedom of the system. The response of a body to a
disturbance may be analyzed into a number of periodic motions, one
periodic motion for each degree of freedom of the body. These
periodic motions are called the normal modes of free vibration and
each of these normal modes has an associated natural frequency of
free vibration.
In order to study the vibratory properties of a body, a knowledge
of the free vibration characteristics of the body is important. In
particular, in order to predict the response of a body to any
external excitation, the natural frequencies of free vibration
together with their associated normal modes of vibration must be
known. This is due to the fact that the vibratory response of a
body due to some disturbing force is composed of a linear
combination, or a weighted sum, of all of the individual normal
modes of vibration.
In addition, it is important to know the free vibration
characteristics of a body in order to know or to calculate the
excitation frequencies which would give rise to the phenonmenum
called resonance. A system is considered to be in resonance when
the exciting force oscillates with a frequency that is the same or
nearly the same as one of the natural frequencies of the system,
whereby the addition of the frequencies results in a response of
the system that becomes very large. The critical structural
frequency of a bat as used herein is defined as the resonance
condition produced when natural frequencies are modified by
modifying the internal air pressure to produce maximum ball
striking force.
It should be noted that it is this phenonmenum of resonance that
provides the basis of the improved performance of the modified
internal pressure bat of the present invention.
With particular reference to the improved bat of the present
invention, a hollow aluminum bat consists of an infinite number of
particles all coupled together elastically. The bat therefore has
an infinite number of degrees of freedom and correspondingly, an
infinite number of natural frequencies and modes of vibration. In
the context of the present invention, only the lowest frequencies,
at most about twenty of these frequencies, are of any practical
importance in predicting the response due to an excitation.
In order that the vibration theory above set forth be put to use in
describing the highly improved performance of a modified internal
pressure bat, the actual mechanics of a bat striking ball and the
nature of the response resulting from this motion must first be
considered.
In the process of striking a ball with a bat, the batter produces
within the bat a vibratory motion. These vibrations are due to an
excitation produced by the motion of the bat during the batter's
swing and the short duration force or impulse on the bat resulting
from the ball making contact with the bat. Along with the energy
produced by the batter's swing, this vibratory motion in the bat
imparts a force to the ball while the ball is in contact with the
bat. The obvious result of this contact is the placement of the
ball in flight.
When the bat being used is of the conventional hollow aluminum type
with a sealed in place end rubber plug, the vibratory motion
produced within the bat is of a frequency much different in
magnitude than any of the important natural frequencies of the bat.
Because of this difference, resonance is not approached and the
force imparted to the ball due to the vibration of the bat is of a
nearly negligible amount.
When as in the present invention, the pressure maintained within
the hollow aluminum bat is modified, an important effect takes
place, namely, significant changes in the natural frequencies and
normal modes of vibration of the bat can be noted. The changes in
the natural frequencies and the normal modes of vibration of the
bat are due to the displaced configuration and the resulting change
in the bat's stiffness characteristics which occur due to the
modification of the pressure within the hollow chamber or interior
of the bat.
SUMMARY OF THE INVENTION
The present invention relates generally to baseball bats, and more
particularly is directed to a metallic bat including means to vary
the internal pressure maintained within the interior space defined
within the bat construction.
In accordance with the teachings of the present invention, a hollow
aluminum or other metal bat of conventional manufacture and
configuration is produced with a sealed in place end plug affixed
at one end thereof in an airtight connection with an air sealed
knob at the other end, all of which is well known to those skilled
in the art. Preferably, the end plug is constructed of rubber or
other similar resilient, dense material.
The present invention starts with the usual hollow, metallic bat
construction and then provides means to vary the internal air
pressure, either by the introduction of pressurized gas or
alternately by removing some of the air already contained within
the hollow interior which was entrapped by the affixation of the
rubber plug to enclose the end of the bat. In practice, it is
contemplated that a hollow needle will be forced through the entire
thickness of the rubber plug to communicate the hollow interior
channel of the needle with the interior air chamber defined within
the bat construction. Then, by attaching a source of pressurized
gas or vacuum to the needle, a predetermined pressure, either above
or below atmospheric, can be created within the interior of the
bat. By quickly withdrawing the needle from the rubber plug, the
natural resiliency of the plug body will close the passageway
forged by insertion of the needle to thereby quickly seal the
impressed pressure or vacuum within the interior space of the
bat.
When the hollow aluminum bat is pressurized or is maintained under
vacuum conditions, significant changes in the natural frequencies
and normal modes of vibration of the bat will occur due to the
displaced configuration and the resulting changes in the stiffness
characteristics of the bat created by the interior pressure
changes.
Predictably, the changes in the natural frequencies and normal
modes of vibration due to the pressure or vacuum conditions created
within the hollow interior of the bat can have, as most important
results, a much improved hitting power of the bat when the bat
strikes the ball. This improvement is due to the fact that with the
change in the natural frequencies and the normal modes of
vibrations, the vibratory motion within the bat can result in an
excitation of a frequency very close to one of the important
natural frequencies of the pressurized or vacuumized bat. In other
words, the vibratory motion of the bat, after being subject to the
pressure or vacuum changes, can be designed to approach the
resonance condition. Accordingly, the response amplitude of the
bat's vibration becomes much more significant. Hence, the force
transmitted to the ball due to the vibration of the bat when the
bat strikes the ball has a much greater effect on the motion of the
ball than an unpressurized bat of the same material.
The addition of an internal pressure or vacuum of a specific
amount, depending upon the geometric properties of the hollow
aluminum bat, results in significant changes taking place in the
magnitudes of the natural frequencies and correspondingly in the
nature of the normal modes of vibration of the bat. Because of the
fact that the excitation frequency resulting from a batter's
attempt to hit the ball is close to one of the important new
natural frequencies of vibration, the condition of resonance is
approached and the response amplitude of vibration of the bat
becomes correspondingly larger. The larger the response amplitude,
the larger the resulting force directly upon the ball due to the
vibration. Therefore, when utilizing the same effort or swing, the
batter is able to impress upon the ball a much larger driving force
with the modified bat then he would be able to impress with a
conventional, hollow metallic, unpressurized bat. As a result, when
using the same swinging force for both a conventional bat and a bat
modified in accordance with the teachings of the present invention,
a batter is capable of driving a ball a much greater distance upon
making proper contact therewith.
It is therefore an object of the present invention to provide a
novel, metallic baseball bat with modified interior air
pressure.
It is another object of the present invention to provide a novel
aluminum baseball bat with a predetermined increased pressure
maintained therewithin.
It is another object of the present invention to provide a novel
aluminum baseball bat with a predetermined pressure, either above
or below atmospheric pressure, maintained therewithin.
It is another object of the present invention to provide a novel
aluminum baseball bat with rubber end plug and means to modify the
air pressure maintained within the interior space defined with the
bat construction.
It is another object of the present invention to provide a method
and apparatus for modifying the internal pressure or vacuum
maintained within the interior space defined within a hollow
aluminum baseball bat.
It is another object of the present invention to provide a novel
aluminum baseball bat with means to increase the hitting power of
the bat when utilizing the same ball driving force.
It is another object of the present invention to provide a novel
aluminum baseball bat with modified interior air pressure of
predetermined magnitude to vibrate the bat at critical structural
frequency upon striking a ball with the bat.
It is another object of the present invention to provide an
aluminum baseball bat that is inexpensive in construction, that is
capable of improved ball driving efficiency and which is trouble
free when in use.
Other objects and a fuller understanding of the invention will be
had by referring to the following description and claims of a
preferred embodiment thereof taken in conjunction with the
accompanying drawings wherein like reference numbers refer to
similar parts throughout the several views and in which: dr
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a baseball bat constructed in
accordance with the teachings of the present invention, partially
broken away to expose interior construction details.
FIG. 2 is an enlarged, partial, cross-sectional view taken along
line 2--2 of FIG. 1, looking in the direction of the arrows.
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2,
looking in the direction of the arrows.
FIG. 4 is a cross-sectional view similar to FIG. 3 showing the
needle hole resealed upon removal of the needle.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Although specific terms are used in the following description for
the sake of clarity, these terms are intended only to refer to the
particular structure of the invention selected for illustration in
the drawings and are not intended to define or limit the scope of
the invention.
Referring now to the drawings, there is illustrated in FIG. 1 a
metallic baseball bat 10 of known type, for example, a hollow
aluminum bat similar to that disclosed in U.S. Pat. No. 3,479,030.
Such a bat is characterized by an aluminum sidewall construction 12
which terminates at one end in a closed handle 14 with sealed knob
and at the other end in an open ball striking end 16. The open ball
striking end 16 is closed with a rubber or other resilient end plug
18 which is securely cemented to the interior surfaces 20 of the
bat at the open end 16 in a manner to prevent separation when in
use.
As illustrated in FIGS. 1 and 2, the interior surface 22 of the
rubber end plug 18 and the enclosing sidewalls 12 of the bat 10
define therewithin an interior space 24, which air space 24
formerly was maintained at atmospheric pressure or slightly over
atmospheric pressure due to compression of the retained air as the
plug 18 was forced into the hollow interior of the bat when
assembling the plug in the manner indicated. It is the essence of
the present invention to modify the pressure of the air retained
within the air space 24 to attain the optimum pressure, either
above or below atmospheric pressure, inside of the bat 10 to enable
the bat to vibrate at critical structural frequency to thereby
impart resonance conditions upon the ball (not illustrated) when
the ball is struck by the bat.
In order to achieve such change in internal air pressure, a
suitable, sturdy, metallic needle 26 of known design can be pushed,
punched or otherwise powered to press the needle 26 through the
resilient plug 18 until the needle end 28 communicates with the
interior air space 24 which is defined within the bat 10. Then, by
connecting the needle 26 to a known source of pressure, such as an
air pump (not illustrated) or to a known source of vacuum, such as
a vacuum pump (not illustrated), the application of pressure or
vacuum forces to the air space 24 can be readily accomplished
through the hollow needle 26. In the case of the type of metallic
bat in which the end is enclosed by metal (not illustrated) a
suitable valve or fitting of known design would have to be employed
for use with a suitable gas introduction source.
When the internal air space 24 has been adjusted to the desired
pressure conditions which presently are above atmospheric pressure,
but which conceivably could also be below atmospheric pressure, the
needle 26 is then withdrawn from its association with the rubber
plug 18. The natural resiliency of the material comprising the plug
18 acts to close the passageway punched by the entrance of the
needle 26 to automatically, permanently seal the opening
immediately upon withdrawal of the needle 26 from the plug 18. As
illustrated in FIG. 4, upon removal of the needle 26, there will
remain no passage or opening through the plug 18 which will permit
the escape of pressure or vacuum forces from the air space 24.
Further, the cement or other adhesive (not illustrated) which is
utilized in known manner to affix the plug 18 to the interior
periphery 20 of the bat sidewall 12 will also serve as a seal to
prevent air leakage thereabout. Accordingly, once a predetermined
internal condition has been impressed within the air space 24, such
as employing a needle 26, and the needle has been removed, the
pressure or vacuum condition thus created will remain permanently
part of the bat construction to provide enhanced performance
capability of the novel baseball bat 10.
While it will be appreciated that exhaustive tests have not been
completed by the applicant due in part to time considerations and
in part to the somewhat inexact nature of test data achievable by
striking a ball with a bat and in part to the numerous various
hollow bat constructions, the following results are illustrative of
applicant's invention.
EXAMPLE 1
A conventional, hollow, aluminum baseball bat with substantially
atmospheric internal air pressure and with a rubber end cap
cemented in place, such as the aluminum bat manufactured and sold
by Ten Pro Corporation, King of Prussia, Pa. was utilized in
conventional manner to drive a baseball by swinging the bat against
the ball in manner well known to those skilled in the game of
baseball. The distance that the ball was driven and the general
"feel" of the bat while striking the ball was noted.
EXAMPLE 2
A bat similar in all respects to the bat utilized in Example 1 was
pressurized by pushing, punching or otherwise inserting a hollow
metallic needle through the end plug until the one end of the
needle was in fluid communication with the interior air space
defined within the hollow bat. The other end of the needle was then
connected in usual manner to a source of pressure, for example, an
air pump and a pressure of 6 psi above atmospheric pressure was
introduced into the hollow interior of the bat and maintained. The
needle was then withdrawn from its association with the plug and
the natural resiliency of the plug material acted to immediately
and automatically close the channel or path which was created by
the insertion of the needle through the plug whereby the
introduced, increased air pressure was permanently sealed within
the hollow bat interior space.
The bat was then utilized to strike a baseball in the same manner
employed in Example 1. Greatly increased efficiency and ball
driving force was noted. Utilizing substantially the same effort
and the same swing characteristics as in Example 1, it was noted
that the bat had much greater effect on the motion of the ball and
the ball was driven considerably further when utilizing
approximately the same swinging force.
EXAMPLE 3
Employing the same type of bat as in Example 1, and utilizing the
same needle and pressure source as in Example 2, an internal air
pressure within the hollow interior of the bat of 20 psi was
impressed and the needle was quickly withdrawn without air leakage
or pressure drop. The bat was again employed to strike a ball by
utilizing substantially the same swing and the same effort as
employed in Example 1. Under these conditions, it was found that
the feel of the bat striking the ball was "dead" and that the
operator was unable to drive the ball even as far as in Example 1
when utilizing an unmodified internal pressure bat.
EXAMPLE 4
A bat similar to that of Example 1 was pressurized using a needle
and pressure source similar to Example 2 to achieve an internal air
pressure of 14 psi. The needle was then quickly withdrawn without
air leakage and the bat was again employed by the operator to drive
a baseball as in Examples 1 and 2. Under these conditions, the feel
of the bat striking the ball was "dead" and again the operator was
unable to drive the ball even as far as Example 1 when utilizing an
unmodified internal pressure bat.
From the foregoing examples, it can be concluded that the amount of
internal air pressure maintained interiorly of a bat greatly
affects its resonance frequency. When a hollow aluminum bat of the
type described is pressurized to 6 psi and is utilized to propel a
baseball, the vibrations generated by the bat striking the ball
approach the critical structural frequency of this particular bat.
The resonance frequency produces an improved performance whereby
the force transmitted from the bat to the ball due to the
vibrations set up in the bat has a much greater and improved effect
on the motion of the ball that when utilizing an unpressurized bat
of the same construction.
The test results further show that internal pressures of 20 psi and
14 psi fail to produce critical structural frequency when the
vibrations caused by bat striking ball are set up. At these
pressures, it can be observed that the amplitude of vibration due
to excitation and the natural frequencies of free vibration of the
bat are not additive and the bat is not in resonance.
It is anticipated that other conditions of internal pressure or
internal vacuum may be found when testing hollow metallic bats
which also will result in enhanced bat performance. Also,
additional testing will be required when utilizing the hollow
aluminum bats of various manufacturers to determine the critical
structural frequency of each such bat. Such variables as the
natural frequency of each bat construction when coupled with the
excitation frequencies of such bats must be considered to achieve
resonance, that is the critical structural frequency necessary to
achieve maximum driving force applied to the ball at the moment the
ball is struck by the bat.
Although the invention has been described with reference to the
particular embodiments herein set forth, it is understood that the
present disclosure has been made only by way of example and that
numerous changes in the details of construction may be resorted to
without departing from the spirit and scope of the invention. Thus,
the scope of the invention should not be limited to the foregoing
specification but rather only by the scope of the claims appended
hereto.
* * * * *