U.S. patent application number 10/992522 was filed with the patent office on 2006-05-18 for football with a modified surface conferring altered aerodynamic properties.
Invention is credited to Hansan Ma.
Application Number | 20060105866 10/992522 |
Document ID | / |
Family ID | 36387127 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060105866 |
Kind Code |
A1 |
Ma; Hansan |
May 18, 2006 |
Football with a modified surface conferring altered aerodynamic
properties
Abstract
A generally prolate-spheroidal, inflatable game ball with a
plurality of air-turbulence-producing depressions distributed over
a majority of the outer surface of the skin. The depressions
produce a preferably circular surface shape, with a breadth of less
than about one-quarter inch and preferably having a breadth to
depth ratio of about 2 to about 6. The game ball of the present
invention is preferably an American-style football, wherein the
depressions are distributed substantially uniformly over the
majority of the outer surface. A method for providing the game ball
with altered aerodynamic performance may include forming
depressions by embossing the skin or molding depressions
therein.
Inventors: |
Ma; Hansan; (Hong Kong,
CN) |
Correspondence
Address: |
William A. Birdwell;BIRDWELL & JANKE, LLP
Suite 1400
1100 SW Sixth Avenue
Portland
OR
97214
US
|
Family ID: |
36387127 |
Appl. No.: |
10/992522 |
Filed: |
November 17, 2004 |
Current U.S.
Class: |
473/603 |
Current CPC
Class: |
A63B 2243/007 20130101;
A63B 41/08 20130101 |
Class at
Publication: |
473/603 |
International
Class: |
A63B 41/00 20060101
A63B041/00 |
Claims
1. A game ball, comprising: a flexible, inflatable skin having a
generally prolate-spheroidal shape when inflated; and a plurality
of depressions formed in the skin, the depressions being
distributed over the majority of the outer surface of the skin and
having sufficient depth and breadth to cause turbulence when the
ball is thrown through the air.
2. The game ball of claim 1, wherein the depressions are
distributed substantially uniformly over the outer surface of the
skin.
3. The game ball of claim 1, wherein the depressions are
distributed in a substantially hexagonal array over the outer
surface of the skin.
4. The game ball of claim 1, wherein the depressions form
substantially circular shapes in the outer surface of the skin.
5. The game ball of claim 4, wherein the depressions have a
diameter of less than about one-half inch.
6. The game ball of claim 4, wherein the depressions have a
diameter of less than about one-quarter inch.
7. The game ball of claim 4, wherein the depressions have a surface
diameter to depth ratio of about 2 to about 6.
8. The game ball of claim 4, wherein the depressions comprise a
substantially hemispherical surface.
9. The game ball of claim 8, wherein the depressions have a surface
diameter to depth ratio of about 2 to about 6.
10. The game ball of claim 1, wherein the ratio of the maximum
surface breadth to depth of a majority of the depressions is about
2 to about 6.
11. The game ball of claim 1, wherein the surface density of the
depressions is about 23 to about 27 depressions per square inch
inclusive.
12. The game ball of claim 1, wherein the depressions have a
diameter of less than about one-quarter inch.
13. The game ball of claim 1, wherein the skin comprises a material
selected from among leather, rubber, or plastic.
14. The game ball of claim 1, wherein the skin forms a hollow
inflatable interior.
15. The game ball of claim 1, wherein the skin is inflated by an
air bladder.
16. The game ball of claim 1, wherein the skin is inflated by an
elastic foam material.
17. A method for providing a generally prolate-spheroidal game ball
with altered aerodynamic performance, comprising providing a
flexible, inflatable skin having a generally prolate-spheroidal
shape when inflated; and forming a plurality of depressions in the
skin, the depressions being distributed over the majority of the
outer surface of the skin and having sufficient depth and breadth
to cause turbulence when the ball is thrown through the air.
18. The method of claim 17, further comprising distributing the
depressions substantially uniformly over the outer surface of the
skin.
19. The method of claim 17, wherein the skin provided is comprised
of one of rubber or leather, and the depressions are formed in the
skin by embossing the skin with a die.
120. The method of claim 19, wherein the skin is first formed as
one or more substantially flat sections, all or a portion of the
sections are embossed with the depressions, and the one or more
sections are thereafter stitched into the hollow, inflatable
form.
21. The method of claim 17, wherein the skin provided is comprised
of plastic, and the depressions are formed by molding them into the
plastic.
Description
FIELD OF THE INVENTION
[0001] This invention relates to game balls having a generally
prolate-spheroidal shape, particularly American-style footballs,
and to altering the aerodynamic behavior of the balls by providing
air-turbulence-generating depressions in the surface thereof.
BACKGROUND OF THE INVENTION
[0002] In sports involving throwing, hitting, kicking or otherwise
impelling a game ball, the performance characteristics of the ball
can greatly affect the play of the game. Properties of the ball
such as the inflation pressure, rigidity, and surface
characteristics all influence the speed with which the ball can be
projected and the attributes of its flight. Although the size,
shape and weight of a particular kind of ball are typically
governed by the traditions and rules of the given game, it is
possible to modify or improve the performance properties of a ball
through altering its surface properties. For instance, tennis balls
with differing surface properties of their felt coverings and
different rigidities or inflation pressures are well known to be
used under different circumstances.
[0003] Golf balls, which are of solid construction having an
enameled surface covering and a relatively dense resilient core
formed of rubber or synthetic plastics, ordinarily are covered by
dimples. In the history of development of the golf ball, the
surface was originally smooth, but it was discovered from the
experience of golfers that a dented ball whose surface had been
more or less covered with minute depressions caused by impacts on
the ball of hard objects flew further. Golf balls were then
deliberately covered with dents or dimples, small depressions in
the surface, substantially over their entire surface. This surface
texturing provided such a distinct advantage that today all golf
balls are covered with such dimpling. The depressions on a typical
golf ball are about 1-3 mm in diameter and about 0.5-1.5 mm in
depth, and are distributed over the surface uniformly. The physical
basis underlying the improved flight characteristics of the dimpled
golf ball has been explained as resulting from turbulent flow of
the air around a dimpled ball which in turn causes less "flow
separation" and a reduced aerodynamic resistance to the ball's
travel. Lift may also be generated by a traveling golf ball which
has been hit to impart a backspin.
[0004] Few other examples of surface texturing designed to affect
the aerodynamic performance, as opposed to the grip, of game balls
appear to be known. Another solid and not inflatable ball, the
baseball, has been modified by covering the surface with
depressions of a size similar those found on golf balls. Thus, U.S.
Pat. No. 4,256,304 discloses a baseball suitable for use in an
automated pitching machine that is substantially covered with a
multiplicity of cup-like or hemispherical depressions. This
modification is disclosed to enable the ball to travel greater
distances with enhanced accuracy.
[0005] Depressions on an inflatable spherical game ball have also
been disclosed in U.S. Pat. No. 5,518,234, although the depressions
are much larger than those used on golf balls. The depressions are
stated to be for the purpose of improving the player's grip on the
ball. Each depression is of an approximate size to a fingertip to
allow the player to grip a ball having a larger convex surface than
is otherwise possible. No disclosure is provided regarding any
alteration of aerodynamic properties of this ball.
[0006] The type of ball used in the game of American-style football
possesses an almost unique shape among the various types of game
balls; perhaps only the ball used in the game of rugby resembles
the elongate American-style football. The term "generally
prolate-spheroidal shape" is used herein as a convenient
characterization of a ball having, in essence, the shape of an
American-style football, and not in the strict mathematical sense
of an ellipse rotated about an axis. When the term "football" is
used herein, it is understood to refer to an American-style
football, rather than to the spherically shaped "football" or
"soccer ball" that much of the world outside the United States
usually understands the word to mean.
[0007] The unusual shape of the American-style football produces
some unique properties of flight when it is thrown, as rotation
imparted to the ball such that it rotates about its longitudinal
axis produces quite a different resulting flight than does rotation
imparted to the ball about any other axis. The football being
circular in transverse section but oval shape in longitudinal
section, the first kind of rotation produces a "spiraling" flight
in which the ball translates along a path defined by the
longitudinal axis of the ball while spinning about that axis,
whereas the second kind of rotation results in the ball tumbling
end over end. In a spiraling flight, rotation or "spin" of the
football about its longitudinal axis provides for lessened
aerodynamic resistance to forward travel as the ball is
gyroscopically stabilized to translate point first through the air,
a configuration that is more streamlined than a tumbling flight
produces. The rotation of the ball also provides for a more stable
trajectory, similar to the stability of flight imparted to a bullet
fired from a rifled barrel. Minor imperfections in the surface
which would otherwise result in deviation from the planned flight
path or unpredictability of position after the ball has traveled
some distance, are averaged out by the spinning action, so the
flight is more true.
[0008] The surface of the football is typically smooth but may be
slightly convexly textured to aid in gripping the ball. A common
form of surface texturing to aid in gripping the ball on a football
is a knobbly texture consisting of small bumps projecting outwardly
from a base, covering the exterior of the ball. While regulation
footballs also have a laced seam whereby an air bladder is placed
inside the outer skin of the ball, which may also be gripped by the
player and where the fingertips of someone endeavoring to throw the
football are placed in common practice, many footballs such as
those molded from plastic do not have a separate air bladder which
must be inserted into the shell, but are inflated with a needle and
thus do not have laces, or have only simulated laces. Otherwise,
apart from the surface texturing, the football typically has a
featureless surface.
[0009] A number of examples of texturing of the surface of a
football can be found. U.S. Pat. No. 2,866,644 discloses a football
with a "non-slip" surface for improving the grip of the ball by the
player. The surface is covered with ribbing whose main axis is at
an angle of about 30 degrees to the longitudinal axis of the
football. U.S. Pat. No. 4,772,020 discloses a football with helical
groove that provides for improved handling. U.S. Pat. Nos.
5,851,161 and 5,984,812 disclose a gripable surface for throwable
objects including footballs which comprise a mesh panel that fits
over the surface of the ball. U.S. Pat. Nos. D488,524 and D491,240
show a football with pyramidal pebble texturing of the surface.
However, these various texturing features address the handling of
the football, rather than the aerodynamic properties of the
football.
SUMMARY OF THE INVENTION
[0010] The present invention provides a generally
prolate-spheroidal game ball with a plurality of
air-turbulence-producing depressions distributed over a majority of
the outer surface of the skin. The depressions are preferably
circular in shape, with a breadth of less than about one-quarter
inch and preferably having a breadth to depth ratio equaling about
2 to about 6, and a surface density of about 23 to about 27
depressions per square inch. The game ball of the present invention
is preferably an American-style football, substantially covered by
a regular array of the depressions. When the football translates
through the air, particularly when the football is thrown in a
spiral pass wherein it rotates only around its longitudinal axis
while translating through the air, air turbulence induced by the
depressions alters the aerodynamic properties of the football. The
depressions reduce separation of the flow of air by the translating
ball and thus reduce air resistance, resulting in a longer flight
for a given initial impetus. The depressions also reduce air
resistance to the spinning motion, thus allowing for a more
prolonged spin and a decreased rate of loss of rotational velocity
for a given initial rotational impetus, which results in improved,
longer-lasting gyroscopic stabilization of the flight.
DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows side view of an inflatable, prolate-spheroidal
game ball according to the present invention.
[0012] FIG. 2 shows a cross-sectional view of a section of the skin
of a game ball according to the present invention.
[0013] FIG. 3 shows a detailed view of a preferred embodiment of
the depressions in a game ball skin according to the present
invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0014] Referring to FIG. 1, a preferred embodiment of a
prolate-spheroidal game ball according to the present invention
comprises an American-style football 10. As viewed from the side,
the football is substantially oval-shaped, although the ends 12 are
typically blunt rather than smoothly curving as in a perfect
ellipse. However, the ends may be smoothly curving as in a rugby
ball, rather than blunt, without departing from the principles of
the present invention. Elsewhere the outer surface 14 of the
football forms a smooth monotonic curve. In the preferred
embodiment, the football has a length of about 111/2 inches, a
diameter of about 61/2 inches, and a measurement from end to end
over the surface of the football of about 131/2 inches. The
football 10 is circular in any cross-section taken perpendicular to
the longitudinal axis of the ball. The cross section taken along
the mid-point line of FIG. 1 in the plane of longitudinal symmetry
of the ball has the greatest diameter.
[0015] Thus, a football according to the present invention has a
generally prolate spheroidal shape, that is, the solid figure
obtained by rotating an ellipse about its major axis. It may
however deviate somewhat from the ideal form by not being prolate
spheroidal in the strict mathematical sense, for instance not being
truly elliptical in longitudinal cross-section, or as indicated
above, in having the two blunt ends typical of the American-style
football.
[0016] The football 10, which is hollow and formed of an at least
moderately flexible skin 16, sometimes enclosing an air bladder 18
as is shown in FIG. 2, preferably assumes substantially the
dimensions stated upon inflation with air or another suitable gas.
The skin is preferably formed of leather, rubber, plastic, or
similar suitable material that is both at least moderately flexible
and is resistant to tearing or puncturing. The preferred air
bladder, which may be constructed of any suitable material,
pressurizes the skin upon inflation.
[0017] Alternatively, the skin of the football may be supported by
a foam material in which the air pressure in the foam cells is
introduced at the time of formation of the foam. In this
alternative embodiment, the game ball is not hollow in the strict
sense of the word, but is filled with an elastic foam which
contains many minute individually hollow cells. Regardless, the
skin 16 is preferably tough enough to withstand damaging abrasion
during handling and play and to protect the air bladder, if any,
from puncture and the resulting loss of air pressure.
[0018] Typically, the football is inflated to a pressure within a
range suitable to confer sufficient elasticity and rigidity to
allow it to be firmly grasped, to maintain its shape when subject
to acceleration upon being thrown or kicked, but also permitting
elastic deformation allowing the football to bounce, or to be
kicked substantial distances. Normally the football is filled with
air via a port (not shown) in the skin and bladder that allows for
insertion of a hollow needle attached to a source of compressed
air, the port then closing to seal the air in the bladder when the
needle is removed. Alternatively, the ball may be filled with an
elastic foamed material, preferably a plastic, wherein the gas that
induces the foaming in the resin used to form the foam is trapped
within the cells of the foam, providing resiliency. When the term
"inflated" or "inflatable" is used herein, it is defined as
covering both means of providing internal air pressure to keep the
ball elastic.
[0019] If the skin is formed of leather, it typically comprises
several segments of elongated shape that are stitched together at
their edges and at the ends to form the covering. If the skin is
formed of rubber or plastic, it may be molded into shape. During
construction of the football, the air bladder is inserted into the
interior prior to the final closing of the skin by stitches,
adhesives or the like.
[0020] Turning to FIGS. 2 and 3, the game ball according to the
present invention is provided with depressions 22 on the surface of
the ball; the skin is preferably substantially covered by the small
depressions. The depressions serve to create air turbulence when
the ball is moving relative to the air. The amount of turbulence
created is dependent upon a number of factors including the size,
breadth and depth of the depressions 22, as well as their shape,
their density and distribution over the surface, the total
proportion of the surface that is covered by the depressions, and
the relative velocity of the skin of the ball to the air.
Preferably, about 23 to about 27 depressions per square inch cover
the surface of the football 10.
[0021] Preferably the depressions 22 on the preferred football 10
are circular in shape, about 3/16 inches in diameter, and about
1/16 inch deep with a hemispherical profile as shown in FIG. 3.
They preferably substantially uniformly cover a majority of or
substantially the entire surface of the ball, such as in a
close-packed hexagonal array, but other arrangements may be
employed without departing from the principles of the present
invention. The preferred size, shape and distribution of the
depressions 22 results in a game ball the size and shape of the
preferred football 10 shown in FIG. 1, a total number of about 3300
depressions being disposed on the football.
[0022] Turning to FIG. 2, a cross-sectional detail of a section of
the football's covering shows the skin 16 and an air bladder 18
respectively on the outer and inner surfaces thereof. The
depressions 22 are preferably hemispherical in contour in the depth
dimension. The unmodified skin areas 24 between the depressions 22
form a substantially continuous surface or network over the surface
of the football. Depending on the size and spacing and thus the
density of the depressions, the unmodified skin areas may
constitute a greater or lesser proportion of the total surface area
of the football. In the preferred embodiment wherein there are
about 23 to about 27 depressions per square inch, each depression
being a circle of diameter 3/16 inches, the skin areas 24 comprise
about 30% and the depressions 22 comprise about 70% of the total
surface area of the football 10.
[0023] However, the depressions may be of other shapes, sizes and
distributions over the outer skin of the ball without departing
from the principles of the present invention. For example, the
depressions may be polygonal, or even irregularly shaped. For
example, the depressions could be hexagonal in form. The
depressions may be close packed, or may be substantially separated
from each other over the outer skin of the game ball.
[0024] The depressions serve to alter the aerodynamic properties of
the game ball when it is traveling through the air after being
thrown or kicked. The aerodynamic properties of a game ball
according to the invention are altered to a greater or lesser
degree depending upon the variables as outlined above. Analogously
to the operation of depressions on a golf ball as described above,
the depressions on the game ball according to the present invention
serve to create air turbulence as the ball flies, which lessens
aerodynamic resistance by diminishing "separation of the flow."
However, due to the relative asymmetry of a football, compared to
the spherical symmetry of a golf ball, the football according to
the present invention displays some unique aerodynamic
properties.
[0025] Particularly when a football is thrown in a "spiral" pass,
as discussed above, the depressions on the surface of the football
10 according to the invention alter the aerodynamic properties of
the ball and thus the trajectory of the flight. While a football
that is kicked generally tumbles end over end in flight, a
spiraling pass will cause the football to rotate only on its
longitudinal axis as it translates through the air. The special
two-fold motion of the spiraling pass, that is, the forward
translational motion and the rotational motion on the longitudinal
axis, results in the depressions on the ball's skin bringing about
desirable aerodynamic effects. In this type of motion especially,
the presence of depressions 22 have an effect compared to when the
ball is not spinning or is tumbling more slowly than the spiraling
rotation. The reduced air resistance to translational motion of a
ball covered with depressions, due to diminished separation of the
flow of the surrounding air, allows a pass thrown with a given
force to travel further due to the reduction in air resistance of
the ball in flight. In addition, the reduced air resistance to
rotation induced by the depressions allows a ball thrown with an
initial rotational impetus to continue to rotate longer and at a
higher rate, providing for enhanced stability of flight due to
gyroscopic stabilization of the ball's flight.
[0026] Thus, both an increased distance that can be achieved by a
throw of a given force, and an increased accuracy over the enhanced
distance obtained from the throw of a given force, are desirable
aerodynamic results. Contrary to the result that is obtained with a
baseball, where spin put on the ball results in a "curve" or
deviation from the theoretical flight path due to the spin of a
baseball about an axis other than the axis defined by the
baseball's direction of flight, the spin of the football along its
longitudinal axis in a football according to the principles of the
present invention enhances the gyroscopic stabilization of the
flight of the football.
[0027] The depressions 22 may be introduced onto the surface of the
football 10 using a variety of suitable methods. If the skin 16 is
formed of leather, the depressions may be impressed into the
surface through the use of a die under pressure. The leather
surface may then optionally be coated, hardened or fixed as is
known in the art. Alternatively, a flat leather surface may be
ablated by suitable means, such as by drilling or grinding out the
recesses, particularly in the case of circular depressions. The
leather so-treated is then assembled into the intact ball. If the
skin is to be formed of rubber the depressions may either be molded
in place prior to vulcanization of the rubber, or may be embossed
with a die or ground out as in the case of the leather. If the skin
is to be formed of plastic, the depressions may similarly be formed
in place during the molding operation when the plastic monomer is
polymerized in a mold, or may be embossed or ground subsequent to
the polymerization operation. In the case of a plastic ball which
may be cast or molded in final three-dimensional form in a single
operation rather than as a flat structure or set of structures that
are assembled by stitching or gluing as in the case of a leather
skin, the depressions may be emplaced at the time of formation of
the intact football.
[0028] The terms and expressions which have been employed in the
foregoing specification are used therein as terms of description
and not of limitation, and there is no intention, in the use of
such terms and expressions, of excluding equivalents of the
features shown and described or portions thereof, it being
recognized that the scope of the invention is defined and limited
only by the claims which follow.
* * * * *