U.S. patent application number 09/778813 was filed with the patent office on 2001-09-06 for golf ball with improved directional stability in putting stroke.
This patent application is currently assigned to SUNRISE ENTERPRISE. Invention is credited to Hanada, Hideto, Suzuki, Yutaka, Yoshida, Kimiyo.
Application Number | 20010019974 09/778813 |
Document ID | / |
Family ID | 26586853 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019974 |
Kind Code |
A1 |
Hanada, Hideto ; et
al. |
September 6, 2001 |
Golf ball with improved directional stability in putting stroke
Abstract
A golf ball having a predetermined radius, and a spherical outer
surface with a multiplicity of dimples formed therein, wherein said
spherical outer surface has at least one hit portion which has a
diameter of 5-15 mm. The hit portion may be an undimpled portion in
which the dimples are absent; a single-dimple portion in which the
dimples are absent except a single one of the dimples that is
located at a central part thereof; a groove portion in which a
plurality of grooves are formed; or an increased contact-area
portion in which a protrusion is formed in each dimple.
Inventors: |
Hanada, Hideto; (Nukata-gun,
JP) ; Suzuki, Yutaka; (Toyokawa-shi, JP) ;
Yoshida, Kimiyo; (Ichinomiya-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
277 S. WASHINGTON STREET, SUITE 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
SUNRISE ENTERPRISE
|
Family ID: |
26586853 |
Appl. No.: |
09/778813 |
Filed: |
February 8, 2001 |
Current U.S.
Class: |
473/378 |
Current CPC
Class: |
A63B 37/0004 20130101;
A63B 37/001 20130101; A63B 37/0011 20130101; A63B 37/002 20130101;
A63B 37/0006 20130101; A63B 37/0005 20130101; A63B 37/0009
20130101 |
Class at
Publication: |
473/378 |
International
Class: |
A63B 037/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2000 |
JP |
2000-060667 |
May 18, 2000 |
JP |
2000-146010 |
Claims
What is claimed is:
1. A golf ball having a predetermined radius, and a spherical outer
surface with a multiplicity of dimples formed therein, wherein said
spherical outer surface has at least one hit portion which has a
diameter of 5-15 mm and within which said dimples are absent.
2. A golf ball according to claim 1, wherein said at least one hit
portion consists of a plurality of hit portions which are
positioned relative to each other such that a center of balance of
said plurality of hit portions coincides with the center of the
golf ball.
3. A golf ball according to claim 1, wherein said diameter of said
at least one hit portion is 8-12 mm.
4. A golf ball having a predetermined radius, and a spherical outer
surface with a multiplicity of dimples formed therein, wherein said
spherical outer surface has at least one hit portion which has a
diameter of 5-15 mm and within which said dimples are absent except
a single one of said dimples that is located at a central part of
said hit portion.
5. A golf ball according to claim 4, wherein said at least one hit
portion consists of a plurality of hit portions which are
positioned relative to each other such that a center of balance of
said plurality of hit portions coincides with the center of the
golf ball.
6. A golf ball according to claim 4, wherein said diameter of said
at least one hit portion is 8-12 mm.
7. A golf ball having a predetermined radius, and a spherical outer
surface with a multiplicity of dimples formed therein, wherein said
spherical outer surface has at least one hit portion which has a
diameter of 5-15 mm and within which said dimples are absent, and
wherein a plurality of grooves are formed within said hit portion
and are distributed evenly in the entirety of said hit portion,
each of said grooves having a predetermined shape and a width which
is smaller, than a diameter of each of said dimples.
8. A golf ball according to claim 7, wherein said at least one hit
portion consists of a plurality of hit portions which are
positioned relative to each other such that a center of balance of
said plurality of hit portions coincides with the center of the
golf ball.
9. A golf ball according to claim 7, wherein said diameter of said
at least one hit portion is 8-12 mm.
10. A golf ball according to claim 7, wherein said grooves are
arranged in a lattice and intersect each other.
11. A golf ball according to claim 7, wherein said grooves are
annular grooves having respective diameters different from each
other and respective centers lying at a center of said hit
portion.
12. A golf ball according to claim 7, wherein said grooves are
arranged to be parallel to each other.
13. A golf ball having a predetermined radius, and a spherical
outer surface with a multiplicity of dimples formed therein,
wherein said spherical outer surface has at least one hit portion
which has a diameter of 5-15 mm and within which a protrusion is
formed in each of said dimples, said protrusion having a distal end
whose radial distance from the center of the golf ball is equal to
said predetermined radius of the golf ball.
14. A golf ball according to claim 13, wherein said at least one
hit portion consists of a plurality of hit portions which are
positioned relative to each other such that a center of balance of
said plurality of hit portions coincides with the center of the
golf ball.
15. A golf ball according to claim 13, wherein said diameter of
said at least one hit portion is 8-12 mm.
16. A golf ball according to claim 13, wherein said protrusion is
positioned relative to said each of said dimples such that said
protrusion has a concentric relation with said each of said
dimples.
17. A golf ball according to claim 13, wherein said protrusion has
a partition wall which divides a space in each of said dimples into
a plurality of segmental spaces.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates in general to improvements in
a golf ball.
[0003] 2. Discussion of the Related Art
[0004] There is known a golf ball consisting principally of, for
example, a spherical body having a certain degree of elasticity,
and a rubber-made cover covering an outer surface of the spherical
body. The spherical body includes a rubber-made, spherical core
which is wound with a rubber thread or other fiber. In an outer
surface of the rubber-made cover, there are formed a multiplicity
of shallow recesses or dimples each having, in general, a
substantially circular shape whose diameter is about 1-3 mm, such
that the dimples are distributed substantially evenly over the
entire outer surface of the cover. The dimples assist the ball,
when hit by a club, to fly high and straight in a golf course. That
is, the dimples serve to increase the flight distance and the
directional stability of the ball.
[0005] In the following description, the term "golf course" is
interpreted to mean a golf course area excluding a green, unless
otherwise specified.
[0006] In general, a putter is used as a club for putting in a
green of the golf course. It is considered important, in a putting
play, to set a hitting surface of the putter to be perpendicular to
a desired direction in which the ball is intended to run, namely,
to be perpendicular to a line to a target hole which line is
determined on the basis of various factors such as influences of
grass grain upon the ball, and to then swing the putter to stroke
the ball parallel to the determined line. However, even if the
putter is swung or stroked straight and parallel to the determined
line, the ball does not necessarily run along the line, resulting
in difficulty of making the ball run in the desired direction with
a sufficient stability. Such a difficulty of controlling the
direction of the ball tends to be increased, particularly, in a
putting stroke with what is called a "soft touch", in which the
ball is hit with a comparatively small hitting force.
[0007] Various experiments conducted by the present inventors for
studying about the above-described problem revealed that dimples
formed in the outer surface of the ball make it difficult to putt
the ball in the desired direction with a sufficient stability. A
pressed area of the outer surface of the ball, which is pressed by
a face of a club as the ball is hit by the club, is elastically
deformed to become substantially flat, and a reaction force is then
generated as a result of the elastic deformation in the pressed
area. This reaction force which restores the pressed area to its
original shape, i.e., a part-spherical face serves as a thrust
force for thrusting or moving the ball. In this instance, strictly
speaking, the pressed area does not become entirely flat due to the
presence of the dimples, and some protrusions and recesses remain
in the pressed area. The thrust force is generated by a
comparatively protruding area of the pressed area which is located
between the dimples, namely, by a contact area of the pressed area
which is actually brought in contact with the club face. The thrust
force is not generated by the other area of the pressed area which
is not actually brought in contact with the club face.
[0008] In a putting stroke, in which the ball is generally hit with
a comparatively small hitting force, the above-described pressed
area generally has a diameter so small as about 5-15 mm, for
example, about 10 mm, so that the dimples each having a diameter of
about 1-3 mm are not necessarily distributed evenly within Such a
small pressed area, unless the dimples and the pressed area are
intentionally positioned relative to each other. The uneven
distribution of the dimples within the pressed area means that the
center of balance of the contact area of the pressed area which is
actually brought into contact with the club face, i.e., the center
of distribution of the reaction force applied to the club face from
the ball deviates from the center of the circular-shaped pressed
area, whereby the reaction force does not act in a direction
parallel to a direction in which the club is swung or stroked,
resulting in difficulty of making the ball run in the desired
direction with a sufficient stability.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of the present invention to
provide a golf ball which is capable of minimizing the deviation of
the center of balance of the contact area from the center of the
pressed area, so that the ball is made to run in a desired
direction with an improved stability.
[0010] The above object may be achieved according to a first
preferred form of the present invention, which provides a golf ball
having a predetermined radius, and a spherical outer surface with a
multiplicity of dimples formed therein, wherein the spherical outer
surface has at least one hit portion which has a diameter of 5-15
mm and within which the dimples are absent.
[0011] When the golf ball constructed according to the first
preferred form of the invention is pressed at any one of the
above-described at least one hit portion by a face of a club, the
hit portion becomes substantially flat with substantially no
protrusions and recesses therein, owing to the absence of the
dimples within the hit portion, and is brought into contact in its
entirety with the club face, so that the center of distribution of
the reaction force of the ball substantially coincides with the
center of the pressed area. In other words, the hit portion, i.e.,
the undimpled portion having the diameter of at least 5 mm provides
a flat portion having a diameter of at least 5 mm, within the
pressed area which has a diameter of about 5-15 mm in a putting
stroke, whereby a sufficiently increased part of the pressed area
is brought in contact with the club face. That is, a sufficiently
increased contact area actually brought in contact with the club
face is provided within the pressed area so that the center of
balance of the contact area substantially coincides with the center
of the pressed area.
[0012] Such a substantial coincidence of the center of distribution
of the reaction force and the center of the pressed area is
obtained even where the diameter of the pressed area is made larger
than the diameter of the hit portion, namely where some part of the
pressed area is not brought in contact with the club face.
Therefore, the reaction force acts in a direction substantially
parallel to a direction in which the club is swung or stroked,
irrespective of the amount of the hitting force. It is noted that
the diameter of the hit portion may be interpreted to mean a
diameter as seen in projection by parallel rays emitted in a
direction parallel to a straight line connecting the center of the
hit portion and the center of the ball.
[0013] As described above, the dimples serve to advantageously
increase the flight distance of the ball and improve the
directional stability of the ball. These advantageous effects
provided by the dimples are not so influenced by the undimpled hit
portion. That is, the influences of the undimpled hit portion upon
the flight distance and the directional stability of the ball are
negligibly small, since the maximum diameter of the undimpled hit
portion is as small as about 15 mm.
[0014] It is not possible to control the ball, which has been hit,
to be stopped such that the undimpled hit portion of the ball is
positioned in a desired position relative to a target hole.
However, it is possible to adjust the position of the undimpled hit
portion of the ball relative to the target hole when the ball is
replaced at a stopped position on a green, on which the ball is
allowed to be picked up after the stopped position is marked. Thus,
the ball can be put on the green such that the center of the hit
portion is positioned on a predetermined line to the target line
and such that the center of the hit portion is remoter from the
target hole than the center of the ball, so that the undimpled hit
portion serves as the pressed area to be pressed by the club face
in a putting stroke.
[0015] It might be possible to putt a conventional ball (which does
not have a particular portion equivalent to the hit portion) in a
desired direction, by pressing a suitable point of the outer
surface of the conventional ball by a putter face such that the
dimples are distributed evenly in the entirety of the pressed area,
namely, such that the center of balance of the contact area
substantially coincides with the center of the pressed area.
However, the diameter of the pressed area in a putting stroke is so
small that the distribution of the dimples or the center of balance
of the contact area is easily changed or displaced even with a
small amount of deviation of an actually pressed point from the
above-described suitable point. Thus, for making the conventional
ball run in a desired direction, it is necessary to accurately
locate the suitable point and then press the ball precisely at the
suitable point, which are extremely difficult to be done by a golf
player during his putting play.
[0016] According to one advantageous arrangement of the first
preferred form of the invention, the above-described at least one
hit portion consists of a plurality of hit portions which are
positioned relative to each other such that a center of balance of
the plurality of hit portions coincides with the center of the golf
ball. This balanced arrangement of the hit portions permits the
golf ball to enjoy an aerodynamic uniformity, during its flight in
a golf course, as a conventional ball which does not have the
undimpled hit portions, thereby minimizing a negative aerodynamic
effect and preventing a reduction of the flight distance.
[0017] The above object may be also achieved according to a second
preferred form of the present invention, which provides a golf ball
having a predetermined radius, and a spherical outer surface with a
multiplicity of dimples formed therein, wherein the spherical outer
surface has at least one hit portion which has a diameter of 5-15
mm and within which the dimples are absent except a single one of
the dimples that is located at a central part of the hit
portion.
[0018] In the hit portion of the golf ball of the second preferred
form of the invention, the single dimple is located at the central
part of the hit portion, and an annular part of the hit portion
surrounding the central part constitutes a part of the spherical
outer surface. When the golf ball of the second preferred form of
the invention is pressed at the hit portion by a club face, the
annular part of the hit portion becomes substantially flat with
substantially no protrusions and recesses therein, and is brought
into contact with the club face, so that the center of distribution
of the reaction force of the ball substantially coincides with the
center of the pressed area. In other words, the hit portion, i.e.,
the single-dimple portion having the diameter of at least 5 mm
provides an annular-shaped flat portion having a diameter of at
least 5 mm, in the pressed area which has a diameter of about 5-15
mm in a putting stroke, whereby a sufficiently increased contact
area actually brought in contact with the club face is provided in
the pressed area so that the center of balance of the contact area
substantially coincides with the center of the pressed area.
[0019] Such a substantial coincidence of the center of distribution
of the reaction force and the center of the pressed area is
obtained, even where the center of the pressed area does not
exactly coincide with the center of the hit portion, or even where
the diameter of the pressed area is made larger than the diameter
of the hit portion, namely where some part of the pressed area is
not brought in contact with the club face. Therefore, the reaction
force acts in a direction substantially parallel to a direction in
which the club is swung or stroked, so that the ball is made to run
in a desired direction substantially equal to the direction in
which the club is stroked.
[0020] The hit portion of the golf ball of the second preferred
form of the invention has the single dimple located at the center
part, while the hit portion of the golf ball of the first preferred
form does not have any one of the dimples. This means that the golf
ball of the second preferred form has a smaller area in which the
dimples are absent, than that of the golf ball of the first
preferred form, thereby further minimizing a negative aerodynamic
effect. Further, the golf ball of the second preferred form is
advantageous over the golf ball of the first preferred form, for
minimizing a negative sensuous effect. For example, the smaller
undimpled area provides a better appearance of the ball. The
provision of the single dimple in the hit portion provides a better
hit sound in a putting stroke, since the ball is hit at the central
part of the hit portion at which the single dimple is located.
[0021] The above object may be also achieved according to a third
preferred form of the present invention, which provides a golf ball
having a predetermined radius, and a spherical outer surface with a
multiplicity of dimples formed therein, wherein the spherical outer
surface has at least one hit portion which has a diameter of 5-15
mm and within which the dimples are absent and a plurality of
grooves are formed to be distributed evenly in the entirety of the
hit portion, each of the grooves having a predetermined shape and a
width which is smaller than a diameter of each of the dimples.
[0022] In the hit portion of the golf ball of the third preferred
form of the invention, the dimples are absent while the grooves
each having the width smaller than the diameter of each dimple are
formed to be distributed evenly in the entirety of the hit portion.
Where the golf ball is pressed at this hit portion by a club face,
the deviation of the center of balance of the contact area from the
center of the pressed area tends to be reduced more than where the
golf ball is pressed at the other portion of the spherical outer
surface in which the dimples each having the diameter larger than
the width of each groove are formed. Thus, by hitting the ball at
the hit portion in a putting stroke, it is possible to make the
center of the pressed area substantially coincide with the center
of distribution of the reaction force, so that the reaction force
acts in a direction substantially parallel to a direction in which
the club is swung or stroked, whereby the ball is made to run in a
desired direction substantially equal to the direction in which the
club is stroked.
[0023] In the golf ball of the third preferred form of the
invention, a negative aerodynamic effect is more reduced, owing to
the provision of the grooves or recesses in the hit portion, than
in the golf ball of the first preferred form having the undimpled
hit portion in which any one of the dimples or recesses is not
formed.
[0024] According to a first advantageous arrangement of the third
preferred form of the invention, the grooves are arranged in a
lattice and intersect each other, so that the grooves formed in the
hit portion are symmetrical with each other. The lattice or
symmetrical arrangement of the grooves further reduces the
deviation of the center of distribution of the reaction force from
the center of the pressed area, where the center of the pressed
area is deviated from the center of the hit portion, i.e., where
the golf ball is not hit at the center of the hit portion. Thus,
the arrangement of this first advantageous arrangement is effective
to further improve the directional stability of the ball in a
putting stroke.
[0025] According to a second advantageous arrangement of the third
preferred form of the invention, the grooves are annular grooves
having respective diameters different from each other and
respective centers lying at a center of the hit portion, so that
the grooves are held in a concentric relationship with each other.
This concentric arrangement of the grooves also further reduces the
deviation of the center of distribution of the reaction force from
the center of the pressed area, where the center of the pressed
area is deviated from the center of the hit portion. Thus, the
arrangement of this second advantageous arrangement is also
effective to further improve the directional stability of the ball
in a putting stroke.
[0026] According to a third advantageous arrangement of the third
preferred form of the invention, the grooves are arranged to be
parallel to each other. This parallel arrangement of the grooves
also further reduces the deviation of the center of distribution of
the reaction force from the center of the pressed area, where the
center of the pressed area is deviated from the center of the hit
portion. Thus, the arrangement of this third advantageous
arrangement is also effective to further improve the directional
stability of the ball in a putting stroke. Further, the arrangement
of this third advantageous arrangement provides another advantage
of minimizing undesirable displacement of the center of balance of
the contact area relative to the center of the pressed area, by
setting the ball on a green such that the parallel grooves are
brought in parallel to the vertical or horizontal direction in a
preparation for a putting stoke, even if the center of the pressed
area is deviated from the center of the hit portion in the putting
stroke.
[0027] The above object may be also achieved according to a fourth
preferred form of the present invention, which provides a golf ball
having a predetermined radius, and a spherical outer surface with a
multiplicity of dimples formed therein, wherein the spherical outer
surface has at least one hit portion which has a diameter of 5-15
mm and within which a protrusion is formed in each of the dimples,
the protrusion having a distal end whose radial distance from the
center of the golf ball is equal to the predetermined radius of the
golf ball.
[0028] In the hit portion of the golf ball of the fourth preferred
form of the invention, the protrusions, each having the distal end
whose radial distance from the center of the golf ball is equal to
the predetermined radius of the golf ball, are formed in the
respective dimples. Where the golf ball is pressed at this hit
portion by a club face, the protrusion constituting a part of area
inside each dimple, as well as an area surrounding each dimple, is
brought in contact with the club face, thereby providing a
sufficiently increased contact area within the pressed area and
accordingly minimizing the deviation of the center of balance of
the contact area from the center of the pressed area, so that the
center of balance of the contact area substantially coincides with
the center of the pressed area. Thus, by hitting the ball at the
hit portion in a putting stroke, it is possible to make the center
of the pressed area substantially coincide with the center of
distribution of the reaction force, so that the reaction force acts
in a direction substantially parallel to a direction in which the
club is swung or stroked, whereby the ball is made to run in a
desired direction substantially equal to the direction in which the
club is stroked.
[0029] In the golf ball of the fourth preferred form of the
invention, a negative aerodynamic effect and a negative sensuous
effect such as deterioration of the appearance are more reduced,
owing to the provision of the dimples in the hit portion as well as
in the other portions of the spherical outer surface of the golf
ball, than in the golf ball of the first preferred form having the
undimpled hit portion in which any one of the dimples is not
provided.
[0030] According to a first advantageous arrangement of the fourth
preferred form of the invention, the protrusion is positioned
relative to each of the dimples such that the protrusion has a
concentric relation with each of the dimples.
[0031] According to a second advantageous arrangement of the fourth
preferred form of the invention, the protrusion has a partition
wall which divides a space in each of the dimples into a plurality
of segmental spaces.
[0032] In either of the first and second arrangements of the fourth
preferred form, a sufficiently increased contact area actually
brought in contact with a club face is provided in the pressed
area, and the directional stability of the ball in a putting stroke
is accordingly improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above object, features and advantages of the present
invention will be better understood by reading the following
detailed description of presently preferred embodiments of the
invention, when considered in connection with the accompanying
drawings, in which:
[0034] FIG. 1(a) is a view showing a golf ball according to a first
embodiment of this invention;
[0035] FIG. 1(b) is a view for explaining the arrangement of
undimpled portions provided on the surface of the golf ball of FIG.
1(a);
[0036] FIG. 2(a) is an upper plan view showing the golf ball of
FIG. 1(a) at an impact moment when the golf ball is hit by a
putter;
[0037] FIG. 2(b) is a view taken in a direction of arrow b of FIG.
2(a);
[0038] FIGS. 3(a) and (b) are views illustrating examples of a
contact area at which a conventional golf ball is brought in
contact with a putter face;
[0039] FIG. 4 is a view for explaining an experiment conducted for
confirming influences of dimples of a conventional ball upon a
rebounding direction of the conventional ball;
[0040] FIG. 5 is a view illustrating a contact area of the
conventional ball which was actually brought in contact with a flat
horizontal surface when the ball was dropped from each of various
height levels in the experiment of FIG. 4;
[0041] FIG. 6 is a view showing a golf ball according to a second
embodiment of this invention;
[0042] FIG. 7 is a view corresponding to that of FIG. 2(b) and
taken from the side of a pressed area, for showing the ball of FIG.
6 at an impact moment when the ball is hit at the pressed area;
[0043] FIG. 8 is a view showing a golf ball according to a third
embodiment of this invention;
[0044] FIG. 9 is a view showing a golf ball according to a fourth
embodiment of this invention;
[0045] FIG. 10 is a view showing a golf ball according to a fifth
embodiment of this invention;
[0046] FIG. 11 is a view showing a golf ball according to a sixth
embodiment of this invention;
[0047] FIG. 12(a) is a view showing a golf ball according to a
seventh embodiment of this invention;
[0048] FIG. 12(b) is an enlarged view showing a part of the surface
of the ball of FIG. 12(a);
[0049] FIG. 12(c) is a view showing a cross section of the
above-described part of the surface of the ball of FIG. 12(a);
[0050] FIG. 13(a) is a view showing a golf ball according to an
eighth embodiment of this invention; and
[0051] FIG. 13(b) is an enlarged view showing a part of the surface
of the ball of FIG. 13(a).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0052] Referring first to FIGS. 1(a) and (b), there is shown a golf
ball 10 of a first embodiment of this invention which is
constructed in accordance with golf international standards. The
golf ball 10 has a predetermined radius, and is made of a rubber
material similar to that used in conventional golf balls to have a
certain degree of elasticity. The golf ball 10 has, in its
spherical outer surface 12, a multiplicity of shallow depressions
or dimples 14 formed to be arranged according to a predetermined
pattern. Each of the dimples 14 has a substantially circular shape
whose diameter is about 1-3 mm.
[0053] In the major portion of the spherical outer surface 12 of
the ball 10, the spacing interval between adjacent ones of the
dimples 14 is not larger than, for example, about 1 mm. However, in
local portions of the spherical outer surface 12, the spacing
interval between the adjacent dimples 14 is increased to, for
example, about 10 mm. That is, the spherical outer surface 12 has,
in its local portions, substantially circular-shaped undimpled
portions 16 in each of which the dimples 14 are not formed. Each
undimpled portion 16 is dimensioned such that a circle having a
diameter of about 10 mm is inscribed in the undimpled portion 16.
In the golf ball 10 of the present embodiment, the spherical outer
surface 12 has six undimpled portions 16 which are symmetrically
arranged as shown in FIG. 1(b). Specifically described, the
undimpled portions 16a, 16b are arranged so as to lie on X-axis,
which is one of three axes perpendicular to each other and meet at
the center of the ball 10, so as to be symmetrical with each other
with respect to the center of the ball 10. The undimpled portions
16c, 16d are arranged to lie on Y-axis to be symmetrical with each
other with respect to the center of the ball 10. The undimpled
portions 16e, 16f are arranged to lie on Z-axis to be symmetrical
with each other with respect to the center of the ball 10.
[0054] It is noted that each of the undimpled portions 16, which is
represented by a circle in FIG. 1(b), is defined by profiles of
ones of the dimples 14 surrounding the undimpled portion 16. Thus,
each undimpled portion 16 has a profile consisting of a succession
of recesses and protrusions arranged alternately in the
circumferential direction of the undimpled portion 16, wherein the
recesses and protrusions are provided by the profiles of those ones
of the dimples 14 surrounding the undimpled portion 16. It is also
noted that each undimpled portion 16 has a part-spherical outer
surface which constitutes a part of the spherical outer surface
having a radius R. Namely, the undimpled portions 16 cooperate with
the above-described major portion to constitute the spherical outer
surface of the ball 10.
[0055] FIG. 2(a) is an upper plan view showing the ball 10 at an
impact moment when the ball 10 is hit at a pressed area 22 of the
spherical outer surface 12, by a putter face 20 of a putter head 18
for putting the ball 10 on a green. At the impact moment, the
pressed area 22 is deformed to become a substantially flat face
conforming to the putter face 20, due to a friction force acting
between the ball 10 and a grass of the green on which the ball 10
lies, and also a pressing force applied to the ball 10 from the
putter face 20. The pressed area 22 has a substantially circular
shape (whose diameter A is about 5-15 mm), as shown in FIG. 2(b)
which is a view taken in a direction of arrow b of FIG. 2(a). The
diameter of the circular-shaped pressed area 22 varies depending
upon amount of a hitting force with which the ball 10 is hit, and
tends to be reduced with a reduction of the amount of the hitting
force. The diameter of the pressed area 22 is about 5-15 mm in a
putting stroke in which the ball is generally hit with a
comparatively small hitting force. It is appreciated that the
entirety of the pressed area 22 is located within one of the
undimpled portions 16 in FIG. 2(b). That is, in a preparation for
putting the ball 10, the ball 10 is put on the green while taking
account of a direction of stroke of the putter head 18, such that
one of the undimpled portions 16 serves as the pressed area 22. In
the present embodiment, the undimpled portions 16 correspond to lit
portions.
[0056] Since the ball 10 is brought into contact in almost the
entirety of the circular-shaped pressed area 22 with the putter
face 20 at the above-described impact moment, the center of balance
of a contact area actually brought in contact with the putter face
20 substantially coincides with the center of the pressed area 22.
Described specifically, when the ball 10 is pressed at the
undimpled portion 16, which has the diameter of about 10 mm and
within which the dimples 14 are not formed, by the putter face 20,
the pressed area 22 becomes substantially flat with substantially
no protrusions and recesses therein, so that the center of
distribution of the reaction force applied to the putter face 20
from the ball 10 substantially coincides with the center of the
circular-shaped pressed area 22 which is brought in contact with
the putter face 20 so as to become substantially flat. Accordingly,
a reaction force, which serves as a thrust force for thrusting or
moving the ball 10, is generated based on a restoring force of the
ball 10 for restoring the pressed area 22 to its original shape,
i.e., a part-spherical shape, and acts in a direction which is
substantially parallel to a direction P in which the putter head 18
is swung or stroked, on the assumption that the putter face 20 is
kept in perpendicular to the direction P during the stroke of the
putter head 18. The ball 10 runs based on the thrust force in a
direction B which is substantially parallel to the direction P of
the stroke of the putter head 18, thereby making it possible to
putt the ball 10 in a desired direction with an improved
stability.
[0057] On the other hand, when a conventional golf ball, in which
the dimples are formed to be arranged evenly in its entire
spherical outer surface, is hit by the putter face 20, the
conventional ball is brought in contact with the putter face 20, as
illustrated in FIG. 3(a) or (b). In FIGS. 3(a) and (b), a circle 24
defined by one-dot chain line represents a pressed area at which
the conventional ball is hit by the putter face 20, an area 26
indicated by oblique lines represents a contact area of the pressed
area 24 which area is actually brought in contact with the putter
face 20, and areas 28 indicated by voids or blanks represent the
dimples formed in the spherical outer surface. There is a case
where the center of the pressed area 24 does not coincide with the
center of balance of the contact area 26, as shown in FIG. 3(a) or
(b). In such a case, the center of the pressed area 24 does not
coincide with the center of distribution of the reaction force
applied to the putter face 20, so that the running direction of the
ball does not coincide with the stroke direction of the putter head
18. The running direction is undesirably variable depending upon
how the ball is brought in contact with the putter face 20, thereby
making it difficult to putt the ball in a desired direction with a
high stability.
[0058] As described above, the undimpled portions 16 are arranged
to be symmetrical with each other with respect to the center of the
golf ball 10, so that a center of balance of the undimpled portions
16 coincides with the center of the ball 10. This arrangement of
the undimpled portions 16 permits the ball 10 to enjoy an
aerodynamic uniformity, during its flight in a golf course, as the
conventional ball which does not have the undimpled portions 16. In
other words, the symmetrical or balanced arrangement of the
undimpled portions 16 is effective to minimize a negative
aerodynamic effect due to the absence of the dimples 14 in each
undimpled portion 16, thereby avoiding a reduction of the flight
distance.
[0059] FIG. 4 shows the result of an experiment conducted by using
a conventional golf ball 32 in which the dimples 28 are formed
evenly in the entire spherical outer surface, for confirming
influences of the dimples 28 over a direction in which the ball 32
advances, runs or flies. In the experiment, the conventional ball
32 was made to freely fall from various height levels towards a
flat horizontal surface 30 having a hardness and other material
characteristics similar to those of the putter face 20, and
variations in an inclination of a rebounding direction j of the
ball 32 with respect to a falling locus g of the ball 32 are
measured. The j4, j3, j2, j1 and j0.5 represent the respective
maximum inclinations of the rebounding direction j with respect to
the falling locus g (which are described to be symmetrical with
respect to the falling locus g), when the ball 32 was made to fall
from the respective heights of 4 m, 3 m, 2 m, 1 m and 0.5 m. In
other words, the j4, j3, j2, j1 and j0.5 represent the respective
variations in the inclination of the rebounding direction j with
respect to the falling locus g when the ball 32 was made to fall
from the respective heights. It is appreciated from FIG. 4 that the
maximum inclination, i.e., the variation in the inclination was
increased with a reduction in the height from which the ball 32 was
made to fall.
[0060] FIG. 5 illustrates a contact area of the spherical outer
surface of the ball 32 which area was actually brought in contact
with the flat horizontal surface 30 when the ball 32 was made to
fall from each of the various height levels in the above-described
experiment. Each illustration of FIG. 5 was obtained by applying an
ink to the entire outer surface of the ball 32 except the dimples
28 before the ball 32 was made to fall. It is considered that the
actual contact area of the spherical outer surface of the ball 32
is not necessarily exactly represented by the corresponding
illustration, since the ink was not necessarily applied evenly to
the entire spherical outer surface of the ball 32.
[0061] In FIG. 5, a circle 34 defined by one-dot chain line
represents a pressed area of the spherical outer surface of the
ball 32 which portion was pressed by the flat horizontal surface 30
to become flat, while an inked area within the circular-shaped
pressed area 34 represents a contact area which was actually
brought in contact with the flat horizontal surface 30. As is
apparent from FIG. 5, the dimples 28 were not necessarily
distributed evenly in the entirety of the pressed area 34. This
means that the center of balance of the contact area was likely to
be deviated from the center of the pressed area 34. When the ball
32 was made to fall from the comparatively small height, e.g., from
a height not larger than 3 m, the circular-shaped pressed area 34
was so small that the amount of the deviation of the center of
balance of the contact area from the center of the pressed area 34
tended to be increased. However, the deviation amount tended to be
reduced with an increase in the height from which the ball 32 was
made to fall, namely, with an increase in the number of the dimples
28 included in the pressed area 34. The deviation amount was
reduced to almost zero, when the ball 32 was made to fall from the
height of 4 m.
[0062] The above-described inclination of the rebounding direction
j with respect to the falling locus g relates to this "deviation"
which is caused by the presence of the dimples 28 in the spherical
outer surface of the ball 32. The maximum inclination was increased
with the increase in the deviation as a result of the reduction of
the pressed area 34 when the ball 32 was made to fall from the
comparatively small height. The maximum inclination was reduced
with the reduction in the deviation as a result of the increase of
the pressed area 34 when the ball 32 was made to fall from the
comparatively large height.
[0063] This means that the influences of the dimples 28 upon the
direction in which the ball 32 advances are reduced with an
increase in the hitting force so that the advance direction of the
ball 32 is somewhat stabilized. However, the advance direction of
the ball 32 is considerably influenced by the dimples 28 when the
ball 32 is hit with a small hitting force, e.g., in a "soft touch"
putting stroke so that the advance direction of the ball 32 is not
stabilized. In this view, it is possible to improve the directional
stability even in a soft touch putting stroke, by providing the
undimpled portions 16 in the spherical outer surface of the ball
and thereby eliminating or minimizing the influences of the
dimples, as in the golf ball 10 of the present embodiment.
[0064] Referring next to FIGS. 6-13, there will be described some
other golf balls constructed according to second, third, fourth,
fifth, sixth, seventh and eighth embodiments of this invention. In
these embodiments, the same reference numerals as used in the first
embodiment of FIGS. 1(a) and (b) will be used to identify the
elements which are the same as or similar to those in the first
embodiment. No redundant description of these elements will be
provided, in the interest of simplification of the description.
[0065] FIGS. 6 and 7 show a golf ball 40 of the second embodiment
which has single-dimple portions 42 in place of the undimpled
portions 16. That is, the spherical outer surface 12 of the ball 40
has six single-dimple portions 42 which are arranged to be
symmetrical with each other with respect to the center of the golf
ball 40, in addition to the major portion in which the spacing
interval between adjacent ones of the dimples 14 is not larger than
about 1 mm. In each of the six single-dimple portion 42 (three of
which are invisible in FIG. 6), the dimples 14 are absent except a
single one 14a of the dimples 14 which is located at a central part
of each of the single-dimple portions 42. Each single-dimple
portion 42 is dimensioned such that a circle having a diameter of
about 10 mm is inscribed in the single-dimple portion 42. The
dimple 14a located at the central part of the single-dimple portion
42 has a diameter of about 1-3 mm and the same shape as the other
dimples 14, and has a concentric relationship with the inscribed
circle. Thus, the dimple 14a has a size sufficiently smaller than
that of each single-dimple portion 42. An annular part of each
single-dimple portion 42 which surrounds the dimple 14a and which
is located between the dimple 14a and those ones of the dimples 14
surrounding the single-dimple portion 42 has a part-spherical outer
surface which constitutes a part of the spherical outer surface 12
having a radius R. Namely, the annular parts of the respective
single-dimple portions 42 cooperate with the major portion to
constitute the spherical outer surface 12 of the ball 40.
Therefore, the single-dimple portion 42 is substantially identical
with the undimpled portion 16 except for the provision of the
single dimple 14a at the central part of portion.
[0066] FIG. 7 is a view corresponding to that of FIG. 2(b) and
taken from the side of the pressed area 22, for showing the ball 40
at an impact moment in a putting stroke. At the impact moment, the
pressed area 22 is deformed to become a flat face conforming to the
putter face 20 and having a substantially circular shape whose
diameter A is about 5-15 mm, as in the case of the ball 10 of the
first embodiment. FIG. 7 shows a case where the pressed area 22 is
brought in a concentric relationship with the substantially
circular-shaped single-dimple portion 42, namely, with the single
dimple 14a located at the central part of the single-dimple portion
42, and where the entirety of the pressed area 22 is located within
the single-dimple portion 42. In the present embodiment, the
single-dimple portions 42 correspond to hit portions. In a
preparation for putting the ball 40, the ball 40 is put on the
green such that one of the single-dimple portions 42 serves as the
pressed area 22.
[0067] Since the ball 40 is brought into contact in almost the
entirety of the circular-shaped pressed area 22 with the putter
face 20 at the above-described impact moment, the center of balance
of a contact area actually brought in contact with the putter face
20 substantially coincides with the center of the pressed area 22.
Described specifically, when the ball 40 is pressed at the
single-dimple portion 42, which has the diameter of about 10 mm and
within which the single dimple 14a is located at the central part,
by the putter face 20, the annular part of the single-dimple
portion 42 having an inside diameter of 1-3 mm becomes
substantially flat, and is brought into contact with the putter
face 20, so that the center of distribution of the reaction force
applied to the putter face 20 from the ball 40 substantially
coincides with the center of the circular-shaped pressed area 22.
Accordingly, a reaction force, which serves as a thrust force for
thrusting or moving the ball 40, is generated based on a restoring
force of the ball 40 for restoring the pressed area 22 to its
original shape, i.e., a part-spherical shape, and acts in a
direction which is substantially parallel to the direction P in
which the putter head 18 is swung or stroked, on the assumption
that the putter face 20 is kept in perpendicular to the direction P
during the stroke of the putter head 18. The ball 40 runs based on
the thrust force in a direction B which is substantially parallel
to the direction P of the stroke of the putter head 18, thereby
making it possible to putt the ball 40 in a desired direction with
an improved stability.
[0068] The single-dimple portion 42 serving as the hit portion in
the golf ball 40 of the present second embodiment has the single
dimple 14a at the central part, while the undimpled portion 16
serving as the hit portion in the golf ball 10 of the
above-described first embodiment does not have any one of the
dimples 14. This means that the golf ball 40 has a smaller area in
which the dimples are absent, than that of the golf ball 10,
thereby further minimizing a negative aerodynamic effect. Further,
the golf ball 40 is advantageous over the golf ball 10, for
minimizing a negative sensuous effect. For example, the smaller
undimpled area provides a better appearance of the ball. The
provision of the single dimple 14a in the single-dimple portion 42
provides a better hit sound in a putting stroke, since the ball 40
is hit at the central part of the single-dimple portion 42 at which
the single dimple 14a is located.
[0069] As described above, the size of each single-dimple portion
42 is sufficiently larger than that of the dimple 14a which is
located within the single-dimple portion 42. In other words, the
size of the dimple 14a, which does not constitute a part of the
spherical outer surface 12, is sufficiently smaller than that of
the single-dimple portion 42. Therefore, the above-described
substantial coincidence of the center of distribution of the
reaction force and the center of the pressed area 22 is made, even
where the center of the pressed area 22 does not exactly coincide
with the center of the single-dimple portion 42, namely where the
ball 40 is not hit at the center of the single-dimple portion 42.
This is because the size of the dimple 14a located within the
single-dimple portion 42 is so small that the direction of the
reaction force is kept substantially unchanged even if the center
of the pressed area 22 is somewhat deviated from the center of the
single-dimple portion 42. Further, as in the golf ball 10 of the
first embodiment with the undimpled portions 16, the
above-described substantial coincidence is obtained, even where the
diameter A of the pressed area 22 is made larger than the diameter
of the single-dimple portion 42, namely where some part of the
pressed area 22 is not brought in contact with the club face
20.
[0070] FIG. 8 shows a golf ball 50 of the third embodiment of the
present invention. The golf ball 50 has lattice-arranged groove
portions 54 in place of the undimpled portions 16. That is, the
spherical outer surface 12 of the golf ball 50 has six
lattice-arranged groove portions 54 which are arranged to be
symmetrical with each other with respect to the center of the golf
ball 50, in addition to the major portion in which the dimples 14
are provided with the spacing interval between adjacent ones of the
dimples 14 being not larger than about 1 mm. In each of the six
lattice-arranged groove portions 54 (three of which are invisible
in FIG. 8), the dimples 14 are absent while a plurality of grooves
52 are formed. Each of the grooves 52 has a width of, for example,
about 0.5-1.0 mm which is sufficiently smaller than the diameter of
each dimple 14. The grooves 52 are arranged generally in a lattice,
in which some of the grooves 52 are parallel to a predetermined
direction and spaced apart from each other at a pitch of 2-3 mm
between the centers of the adjacent ones, and in which the others
of the grooves 52 are parallel to a direction perpendicular to the
predetermined direction and spaced apart from each other at a pitch
of 2-3 mm between the centers of the adjacent ones. Each
lattice-arranged groove portion 54 is dimensioned such that a
circle having a diameter of about 10 mm is inscribed in the
lattice-arranged groove portion 54. In the present third
embodiment, the lattice-arranged groove portions 54 correspond to
the hit portions. The ball 50 is put on the green in a preparation
for putting the ball 50, such that one of the lattice-arranged
groove portions 54 serves as the pressed area 22.
[0071] The lattice-arranged groove portion 54 of the ball 50 has
the diameter of about 10 mm and the grooves 54 arranged in a
lattice. Where the ball 50 is pressed at the lattice-arranged
groove portion 54 by the putter face 20, the deviation of the
center of balance of the contact area from the center of the
pressed area 22 tends to be reduced more than where the ball 50 is
pressed at the other portion of the spherical outer surface in
which the dimples 14 each having the diameter larger than the width
of each groove 52 are formed. Thus, by hitting the ball 50 at the
lattice-arranged groove portion 54 in a putting stroke, it is
possible to make the center of the pressed area 22 substantially
coincide with the center of balance of the contact area, i.e., the
center of distribution of the reaction force applied from the ball
50 to the putter face 20. Accordingly, the reaction force, which
serves as a thrust force for thrusting or moving the ball 50, is
generated based on a restoring force of the ball 50 for restoring
the pressed area 22 to its original shape, i.e., a part-spherical
shape, and acts in a direction which is substantially parallel to
the direction in which the putter head 18 is swung or stroked, so
that the ball 50 runs based on the thrust force in a direction
which is substantially parallel to the direction of the stroke of
the putter head 18, thereby making it possible to putt the ball 50
in a desired direction with an improved stability.
[0072] In the golf ball 50 of the present third embodiment, a
negative aerodynamic effect is more reduced, owing to the provision
of recesses in the form of the grooves 52 in the lattice-arranged
groove portion 54, than in the golf ball 50 of the above-described
first embodiment having the undimpled portions 16 each constituting
a part of the spherical outer surface 12.
[0073] In the golf ball 50 of the present third embodiment, the
grooves 52 of the lattice-arranged groove portion 54 are arranged
in a lattice so as to be symmetrical with each other. The
symmetrical arrangement of the grooves 52 further reduces the
deviation of the center of distribution of the reaction force from
the center of the pressed area 22, where the center of the pressed
area 22 is deviated from the center of the lattice-arranged groove
portion 54, i.e., where the golf ball 50 is not hit at the center
of the lattice-arranged groove portion 54. Thus, the symmetrical
arrangement of the grooves 52 is effective to further improve the
directional stability of the ball 50 in a putting stroke.
[0074] FIG. 9 shows a golf ball 60 of the fourth embodiment of the
present invention. The golf ball 60 has annular groove portions 58
in place of the lattice-arranged groove portions 54. That is, the
spherical outer surface 12 of the golf ball 60 has six annular
groove portions 58 (three of which are invisible in FIG. 9) in each
of which a plurality of annular grooves 56 are formed. The annular
grooves 56 have respective diameters different from each other, and
are positioned relative to each other to be held in a substantially
concentric relationship with each other. Each of the annular
grooves 56 has a width of, for example, about 0.5-1.0 mm which is
sufficiently smaller than the diameter of the dimples 14. The
concentric annular grooves 56 are radially spaced apart from each
other at a pitch of, for example, about 1-2 mm between the centers
of the radially adjacent ones. The six annular groove portions 58
have a diameter of, for example, about 10 mm, and arranged to be
symmetrical with each other with respect to the center of the golf
ball 60. In the present fourth embodiment, the annular groove
portions 58 correspond to the hit portions. The ball 60 is put on
the green in a preparation for putting the ball 60, such that one
of the annular groove portions 58 serves as the pressed area
22.
[0075] Where the ball 60 is pressed at the selected one of the
annular groove portions 58 by the putter face 20, the deviation of
the center of balance of the contact area from the center of the
pressed area 22 tends to be reduced, as the ball 50 of the
above-described third embodiment having the lattice-arranged groove
portions 54. Thus, by hitting the ball 60 at the annular groove
portion 58 in a putting stroke, it is possible to make the center
of the pressed area 22 substantially coincide with the center of
balance of the contact area, i.e., the center of distribution of
the reaction force applied from the ball 60 to the putter face 20,
thereby making it possible to putt the ball 60 in a desired
direction with an improved stability.
[0076] FIG. 10 shows a golf ball 66 of the fifth embodiment of the
present invention. The golf ball 66 has parallel groove portions 64
in place of the lattice-arranged groove portions 54. That is, the
spherical outer surface 12 of the golf ball 66 has six parallel
groove portions 64 (three of which are invisible in FIG. 10) in
each of which a plurality of grooves 62 arranged to be parallel to
each other are formed. Each of the grooves 62 has a width of, for
example, about 0.5-1.0 mm which is sufficiently smaller than the
diameter of the dimples 14. The grooves 62 are spaced apart from
each other at a pitch of, for example, about 2-3 mm between the
centers of the adjacent ones. The six parallel groove portions 64
are dimensioned such that a circle having a diameter of about 10 mm
is inscribed in each of the parallel groove portions 64. It is
noted that a direction in which the grooves 62 of each parallel
groove portion 64 extend is not particularly limited, but is
preferably determined such that the directions of the grooves 62 of
all of the parallel groove portions 64 are symmetrical with each
other with respect to the center of the ball 66.
[0077] In the present fifth embodiment, the parallel groove
portions 64 correspond to the hit portions. The ball 66 is put on
the green in a preparation for putting the ball 66, such that one
of the parallel groove portions 64 serves as the pressed area 22.
Where the ball 66 is pressed at the selected one of the parallel
groove portions 64 by the putter face 20, the deviation of the
center of balance of the contact area from the center of the
pressed area 22 tends to be reduced, as the ball 50 of the
above-described third embodiment having the lattice-arranged groove
portions 54. Thus, by hitting the ball 66 at the parallel groove
portion 64 in a putting stroke, it is possible to make the center
of the pressed area 22 substantially coincide with the center of
balance of the contact area, i.e., the center of distribution of
the reaction force applied from the ball 66 to the putter face 20,
thereby making it possible to putt the ball 66 in a desired
direction with an improved stability.
[0078] In the golf ball 66 of the present fifth embodiment, the
grooves 62 are arranged to be parallel to each other in each of the
parallel groove portion 64. This parallel arrangement provides
another advantage of preventing displacement of the center of
balance of the contact area, by setting the ball 66 on a green such
that the grooves 62 are brought in parallel to the vertical or
horizontal direction in a preparation for a putting stoke, even if
the center of the pressed area 22 is deviated from the center of
the parallel groove portion 64 in the putting stroke.
[0079] FIG. 11 shows a golf ball 74 of the sixth embodiment of the
present invention. The golf ball 74 has groove portions 72 in place
of the lattice-arranged groove portions 54. That is, the spherical
outer surface 12 of the golf ball 74 has six groove portions 72
(three of which are invisible in FIG. 11) in each of which a
W-shaped groove 68 and a M-shaped groove 72 are formed. The
W-shaped groove 68 and the M-shaped groove 72 are positioned
relative to each other so as to be symmetrical with each other, as
shown in FIG. 11. The groove portions 72 provide substantially the
same advantages as the lattice-arranged groove portions 54, the
annular groove portions 58 and the parallel groove portions 64 of
the third, fourth and fifth embodiments. The grooves 68, 70 have
the same width as the grooves 52, 56, 62 of these embodiments. The
groove portions 72 have the same size as the groove portions 54,
58, 64 of these embodiments.
[0080] FIG. 12(a) shows a golf ball 76 of the seventh embodiment of
the present invention. In the golf ball 76, the dimples 14 are
formed to be distributed evenly in the entirety of the spherical
outer surface 12 as in the conventional golf ball 32. However, the
spherical outer surface 12 of the golf ball 76 has six increased
contact-area portions 78 (three of which are invisible in FIG.
12(a)) which are arranged to be symmetrical with each other with
respect to the center of the golf ball 76, and each of which is
dimensioned such that a circle having a diameter of about 10 mm is
inscribed in the increased contact-area portion 78. In each of the
six increased contact-area portions 78, a columnar protrusion 80
having a circular cylindrical shape is formed in each of the
dimples 14 and extends from a bottom of the dimple 14 in a radial
direction of the ball 76, as shown in FIG. 12(b). The columnar
protrusion 80 has, at a distal end thereof, a diameter of about 1-2
mm which is equal to about 1/4-1/2 of the diameter of the dimple
14, and has a concentric relationship with the dimple 14. The
distal end of the columnar protrusion 80 has a radial distance from
the center of the ball 76, which distance is equal to the radius of
the ball 76. Thus, the distal end of the columnar protrusion 80
lies on the same surface as the spherical outer surface 12, as best
shown in FIG. 12(c) (in which only one of the dimples 14 is shown
while the other simples 14 actually located in the vicinity of the
shown one are not described in the interest of simplification of
the drawing). In the present seventh embodiment, the increased
contact-area portions 78 correspond to the hit portions. The ball
76 is put on the green in a preparation for putting the ball 76,
such that one of the increased contact-area portions 78 serves as
the pressed area 22.
[0081] In the increased contact-area portions 78 having the
diameter of about 10 mm, the columnar protrusions 80 are formed in
the respective dimples 14. Where the golf ball 76 is pressed at the
selected one of the increased contact-area portions 78 by the
putter face 20, the columnar protrusion 80 constituting a part of
area inside each dimple 14, as well as an area surrounding each
dimple 14, is brought in contact with the putter face 20, thereby
leading to a larger contact area provided in the pressed area 22,
than where the ball 76 is pressed at the other portion of the
spherical outer surface 12 in which the columnar protrusions 80 are
not provided, so that the deviation of the center of balance of the
contact area from the center of the pressed area 22 tends to be
reduced. Thus, by hitting the ball 76 at the increased contact-area
portion 78 in a putting stroke, it is possible to make the center
of the pressed area 22 substantially coincide with the center of
balance of the contact area, i.e., the center of distribution of
the reaction force applied from the ball 76 to the putter face 20.
Accordingly, the reaction force, which serves as a thrust force for
thrusting or moving the ball 76, is generated based on a restoring
force of the ball 76 for restoring the pressed area 22 to its
original shape, i.e., a part-spherical shape, and acts in a
direction which is substantially parallel to the direction in which
the putter head 18 is swung or stroked, thereby making it possible
to putt the ball 76 in a desired direction with an improved
stability.
[0082] In the golf ball 76 of the present seventh embodiment of the
invention, a negative aerodynamic effect and a negative sensuous
effect such as deterioration of the appearance are more reduced,
owing to the provision of the dimples 14 in the increased
contact-area portions 78 as well as in the other portions of the
spherical outer surface 12, than in the golf ball 10 of the
above-described first embodiment having the undimpled portions 16
in which any one of the dimples 14 is not provided.
[0083] FIG. 13(a) shows a golf ball 82 of the eighth embodiment of
the present invention. In the golf ball 82, the dimples 14 are
formed to be distributed evenly in the entirety of the spherical
outer surface 12 as in the conventional golf ball 32. However, the
golf ball 82 has six increased contact-area portions 84 (three of
which are invisible in FIG. 13(a)) which are arranged to be
symmetrical with each other with respect to the center of the golf
ball 82, and each of which is dimensioned such that a circle having
a diameter of about 10 mm is inscribed in the increased
contact-area portion 84. In each of the six increased contact-area
portions 84, a cross-shaped partition protrusion 86 is formed in
each of the dimples 14 and extends from a bottom of the dimple 14
in a radial direction of the ball 82, as shown in FIG. 13(b). The
cross-shaped partition protrusion 86 consists of two partition
walls which are perpendicular to each other and intersect at right
angles for dividing a space in the dimple 14 into four segmental
spaces. Each of the two partition walls has a thickness of, for
example, about 0.5-1.5 mm. The cross-shaped partition protrusion 86
has a distal end whose radial distance from the center of the ball
82 is equal to the radius of the ball 82. Thus, the distal end of
the cross-shaped partition protrusion 86 lies on the same surface
as the spherical outer surface 12. In the present eighth
embodiment, the increased contact-area portions 84 correspond to
the hit portions. The ball 82 is put on the green in a preparation
for putting the ball 82, such that one of the increased
contact-area portions 84 serves as the pressed area 22.
[0084] Where the golf ball 82 is pressed at the selected one of the
increased contact-area portions 84 by the putter face 20, the
cross-shaped partition protrusion 86 constituting a part of an area
inside each dimple 14, as well as an area surrounding each dimple
14, is brought in contact with the putter face 20, thereby leading
to a larger contact area provided in the pressed area 22, than
where the ball 82 is pressed at the other portion of the spherical
outer surface 12 in which the cross-shaped partition protrusions 86
are not provided, so that the deviation of the center of balance of
the contact area from the center of the pressed area 22 tends to be
reduced. Thus, by hitting the ball 82 at the increased contact-area
portion 84 in a putting stroke, it is possible to make the center
of the pressed area 22 substantially coincide with the center of
balance of the contact area, i.e., the center of distribution of
the reaction force applied from the ball 82 to the putter face 20.
Accordingly, the reaction force, which serves as a thrust force for
thrusting or moving the ball 82, is generated based on a restoring
force of the ball 82 for restoring the pressed area 22 to its
original shape, i.e., a part-spherical shape, and acts in a
direction which is substantially parallel to the direction in which
the putter head 18 is swung or stroked, thereby making it possible
to putt the ball 82 in a desired direction with an improved
stability.
[0085] In the golf ball 82 of the present eighth embodiment of the
invention, a negative aerodynamic effect and a negative sensuous
effect such as deterioration of the appearance are more reduced,
owing to the provision of the dimples 14 in the increased
contact-area portions 84 as well as in the other portions of the
spherical outer surface 12, than in the golf ball 10 of the
above-described first embodiment having the undimpled portions 16
in which any one of the dimples 14 is not provided.
[0086] While the presently preferred embodiments of this invention
have been described in detail, for illustrative purpose only, it is
to be understood that the present invention is not limited to the
details of the illustrated embodiments, but may be otherwise
embodied.
[0087] While the number of the hit portions (such as the undimpled
portions 16, the single-dimple portions 42, the groove portions 54,
58, 64, 72 and the increased contact-area portions 78, 84) is six
in the above-illustrated embodiments, the number of the hit
portions may be suitably changed while taking account of, for
example, a desired degree of directional stability of the ball and
a desired amount of lift or upward force acting on the ball during
its flight in a golf course. That is, the object of the present
invention can be achieved by providing the ball with at least one
hit portion which serves as the pressed area 22 in a putting
stroke. However, it is preferable to provide the ball with a
plurality of hit portions, so that any one of the hit portions can
be selected for serving as the pressed area 22, thereby
facilitating a preparation for a putting stroke. Where the number
of the hit portions is two, the two hit portions preferably may be
provided in respective two portions which are diametrically
opposite to each other, so as to be symmetrical with each other
with respect to the center of the ball, so that a center of balance
of the hit portions coincides with the center of the ball. Where
the number of the hit portions is three, four or five, too, the hit
portions preferably may be arranged such that a center of balance
of the hit portions coincides with the center of the ball. It is
possible to increase the number of the hit portions as long as
deterioration of performance of the ball in a golf course due to
the increased number is tolerable.
[0088] While the hit portions have the diameter of about 10 mm in
the above-illustrated embodiments, the diameter or size of the hit
portions may range from about 5 mm to 15 mm, preferably from about
8 mm to 12 mm, depending upon, for example, a degree of elasticity
of the ball.
[0089] The hit portions of the spherical outer surface 12 of the
golf ball of each of the above-illustrated embodiments are
identical in form to each other. That is, the each of the hit
portions take the form of one of the undimpled portion 16, the
single-dimple portion 42, the groove portions 54, 58, 64, 72 and
the increased contact-area portions 78, 84. However, the hit
portions of the spherical outer surface 12 of the golf ball may be
different in form from each other.
[0090] The width of the grooves 52 of the lattice-arranged groove
portions 54, the annular grooves 56 of the annular groove portions
58, the grooves 62 of the parallel groove portions 64 or the
grooves 68, 70 of the groove portions 72 may range, for example,
from 0.1 mm to 1.5 mm, depending upon various factors such as a
desired degree of directional stability and a desired amount of
flight distance during its flight in a golf course. Similarly, the
distance between the centers of the adjacent ones of these grooves
may range from 0.5 mm to 4 mm, depending upon the various factors.
Further, the grooves may have the respective widths different from
each other. The distance between the centers of the adjacent
grooves does not necessarily have to be constant.
[0091] The diameter of the columnar protrusions 80 provided in the
increased contact-area portions 78 may be suitably changed as long
as the diameter of the columnar protrusions 80 is sufficiently
smaller than the diameter of the dimples 14. While the columnar
protrusions 80 have the circular cylindrical shape in the
above-illustrated embodiment, the columnar protrusions 80 may have
a polygonal shape or other shape.
[0092] The thickness of the partition walls of the partition
protrusions 86 of the increased contact-area portions 84 may be
suitably changed as long as the thickness is sufficiently smaller
than the diameter of the dimples 14. While the partition
protrusions 86 have the cross shape in the above-illustrated
embodiment, the partition protrusions 86 may have other shape which
is suitable for dividing the space in each dimple 14 into at least
two segmental spaces.
[0093] The distal ends of the columnar-shaped protrusions 80 or the
cross-shaped partition protrusions 86 do not have to lie on the
same surface as the spherical outer surface 12, but may be slightly
protruded or recessed from the spherical outer surface 12.
[0094] It is to be understood that the present invention may be
embodied with various other changes, modifications and
improvements, which may occur to those skilled in the art, without
departing from the spirit and scope of the invention defined by the
following claims:
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