U.S. patent application number 10/537369 was filed with the patent office on 2006-06-15 for golf simulator or measurement apparatus.
Invention is credited to James Hourihan, Brian Francis Mooney.
Application Number | 20060128489 10/537369 |
Document ID | / |
Family ID | 32375345 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060128489 |
Kind Code |
A1 |
Mooney; Brian Francis ; et
al. |
June 15, 2006 |
Golf simulator or measurement apparatus
Abstract
The invention provides a simulator or measurement apparatus for
use in a bail game where a ball is hit from a stationary position.
The apparatus includes a bail (2), a connecting means (1), a base
(48) and a measurement means. The ball (2) is connected by the
connecting means (1) to the base (48). The connecting means (1)
operates to provide a number of degrees of freedom to the movement
of the ball (2), and is in a unique arrangement for each position
of the bail. It operates to allow the bail (2), when struck by an
object, to substantially replicate some or ail of the motion
characteristics of an unconnected ball, over a distance sufficient
to measure such motion characteristics. The measurement means
measures motion characteristics of the connected ball (2) over the
distance when such motion characteristics are substantially
replicated.
Inventors: |
Mooney; Brian Francis;
(Dublin, IE) ; Hourihan; James; (County Tipperary,
IE) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
32375345 |
Appl. No.: |
10/537369 |
Filed: |
December 3, 2003 |
PCT Filed: |
December 3, 2003 |
PCT NO: |
PCT/IE03/00160 |
371 Date: |
November 25, 2005 |
Current U.S.
Class: |
473/139 ;
473/146 |
Current CPC
Class: |
A63B 69/3658 20130101;
A63B 69/3655 20130101; A63B 2210/50 20130101; A63B 2024/0031
20130101; A63B 24/0021 20130101; A63B 69/0091 20130101 |
Class at
Publication: |
473/139 ;
473/146 |
International
Class: |
A63B 69/36 20060101
A63B069/36 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2002 |
IE |
S2002/0934 |
Claims
1-116. (canceled)
117. A simulator or measurement apparatus for use in a ball game
where a ball is hit from a stationary position, the apparatus
including a ball, a connecting means, a base and a measurement
means, wherein the ball is connected by the connecting means to the
base, characterised in that the connecting means is operable to
provide a plurality of degrees of freedom to the movement of the
ball; the connecting means is substantially in a unique arrangement
for each position of the ball; and the connecting means is operable
to allow the connected ball, when struck by an object, to
substantially replicate some or all of the motion characteristics
of an unconnected ball, over a distance sufficient to measure such
motion characteristics, and where the measurement means is operable
to measure motion characteristics of the connected ball over the
distance when such motion characteristics are substantially
replicated, wherein the connecting means comprises members of rigid
construction and wherein the connecting means is operable to
provide at least three degrees of freedom and a replicated motion
characteristic is substantially straight line movement.
118. A simulator or measurement apparatus according to claim 117,
wherein the connecting means comprises a plurality of joints; the
joints are interconnected in series, with interconnecting members
between each joint; and an interconnecting member connects the ball
to a first of the joints and an interconnecting member connects a
last of the joints to the base.
119. A simulator or measurement apparatus according to claim 118,
wherein one or more of the joints are pivot joints; and each pivot
joint is operable to rotate in one plane.
120. A simulator or measurement apparatus according to claim 119,
wherein the ball is free to move in three-dimensional space over
the limited region where each pivot joint has its interconnected
members at a relative angle which is less than 180.degree. and
where the pivot joints remain capable of further rotation; and
motion characteristics are measured while the ball remains in this
region.
121. A simulator or measurement apparatus according to claim 119,
wherein the distance between the centre of the ball and the axis of
the first pivot is in the range 130 mm to 200 mm; the distance
between the axis of the first pivot and the axis of the second
pivot is in the range 10 mm to 40 mm; and the distance between the
axis of the second pivot and the axis of the third pivot is in the
range 20 mm to 70 mm.
122. A simulator or measurement apparatus according to claim 121,
wherein the distance between the centre of the ball and the axis of
the first pivot is 165 mm; the distance between the axis of the
first pivot and the axis of the second pivot is 20 mm; and the
distance between the axis of the second pivot and the axis of the
third pivot is 50 mm.
123. A simulator or measurement apparatus according to claim 121,
wherein prior to the shot, the principal axis of the
interconnecting member between the ball and the first pivot joint
is oriented in a substantially horizontal plane and the angle,
between the principal axis and the intended direction of motion of
the ball, is less than 90.degree. on the side adjacent where the
ball is struck, wherein the angle is around 78.degree. or in a
range between 73.degree. and 83.degree..
124. An apparatus according to claim 119, which includes a spring
supporting means, and wherein the spring supporting means is
operable to support the interconnecting member between the ball and
the first pivot joint such that its principal axis is horizontal or
at a small angle to horizontal, as required, prior to the shot; the
spring supporting means is operable to permit the ball and the
interconnecting member between the ball and the first pivot joint
to freely move vertically upwards; the spring supporting means is
operable to prevent the ball and the interconnecting member between
the ball and the first pivot joint from moving vertically downwards
due to the force of gravity, but is operable to allow it to move
vertically downwards where a significantly greater force is
applied; and where the spring supporting means is operable to
return the ball and the interconnecting member between the ball and
the first pivot joint to their original positions when the
significantly greater force is removed.
125. A simulator or measurement apparatus according to claim 118,
wherein the movement of a joint on the connecting means is limited
by a buffer means where the limits of the buffer means are outside
the range of movements which are measured by the measurement
means.
126. A simulator or measurement apparatus according to claim 118,
which includes a docking means, wherein prior to the shot, the
docking means is operable to dispose the ball in a starting
position relative to other parts of the apparatus; the docking
means comprises an engagement member fixed relative to the
interconnecting member between the ball and the first joint and a
corresponding engagement member fixed relative to the base; the
engagement members being operable, when engaged with each other, to
dispose the ball in the desired starting position prior to the shot
and being operable to freely disengage when a shot is taken.
127. A simulator or measurement apparatus according to claim 126,
wherein one or both of the engagement members comprises a tapering
or guiding surface; and the progressive engagement of the
engagement members urges the ball to the starting position.
128. A simulator or measurement apparatus according to claim 117,
wherein the ball game is golf in which the ball is hit in a range
of golf shots, including a drive and a putting shot.
129. A simulator or measurement apparatus, for use in a ball game
where a ball is hit from a stationary position, the apparatus
including a ball, a connecting means and a base, wherein the ball
is connected by the connecting means to the base and wherein the
connecting means comprises an elongated rigid member between the
ball and a joint connected to the base, or to other parts connected
to the base, and about which the arm principally moves when the
ball is struck characterised in that the elongated rigid member is
manufactured from high strength-to-weight material; all or part of
its external surface is tapered with its minimum dimensions closer
to the ball; and the inertia of the connecting means about the
joint is significantly less than the inertia of the ball about the
joint, wherein the ball game is golf and the ball is a real or
simulated golf ball.
130. A simulator or measurement apparatus according to claim 129,
wherein the length of the elongated rigid member, measured from the
centre of the ball to the centre of the joint about which the arm
principally moves when the ball is struck, is between 150 mm and
200 mm.
131. A simulator or measurement apparatus according to claim 129,
wherein the elongated rigid member is of circular cross section;
its outer diameter in the region adjacent the ball is in the range
8-14 mm; and its outer diameter in the region away from the ball is
in the range 14-20 mm.
132. A simulator or measurement apparatus according to claim 129,
wherein the elongated rigid member is hollow, wherein the elongated
rigid member has an internal bore, substantially of circular cross
section; and its internal diameter is in the range 5-9 mm.
133. A simulator or measurement apparatus according to claim 129,
wherein the elongated rigid member is manufactured from hardened
aluminium alloy or hardened steel.
134. A simulator or measurement apparatus according to claim 129,
wherein the elongated rigid member and components attached to the
elongated rigid member are arranged such as to minimise mass and to
position it as close as possible to the joint about which the
elongated rigid member principally moves when the ball is
struck.
135. A simulator or measurement apparatus, for use in a ball game
where a ball is hit from a stationary position, the apparatus
including a ball, a connecting means, a base and a measurement
means, where the ball is connected by the connecting means to the
base, characterised in that the connecting means comprises an
elongate member which is connected to the ball; the elongate member
and the ball are operable to rotate collectively about an axis
which is the elongate axis of the elongate member; the apparatus
includes a sensing means which is operable to measure rotation of
the shaft; and the sensing means communicates with the measurement
means, wherein the elongate member is a rigid member such as a
rigid shaft and wherein the sensing means is associated with the
distal end of the elongate member.
136. A simulator or measurement apparatus according to claim 135,
wherein the sensing means comprises a vane with irregularities; the
vane is connected to the elongate member; the sensing means further
comprises a detecting means which is operable to detect the passage
of irregularities on the vane; the sensing means communicates with
the measurement means; and the measurement means is operable to
measure the rotation speed of the ball.
137. A simulator or measurement apparatus according to claim 135,
wherein the measurement means is operable to measure the linear
speed of the ball and is operable to estimate the loft of the ball
from measurement of the rotation speed and linear speed of the
ball.
138. A simulator or measurement apparatus, for use in a ball game
where a ball is hit from a stationary position, the apparatus
including a ball, a connecting means, a base and a measurement
means, wherein the ball is connected by the connecting means to the
base, characterised in that the connecting means is operable to
allow the ball to spin about two different set axes; the
measurement means is operable to measure the rates of rotation
about these two set axes; the measurement means is operable to
determine the rotation characteristics which the ball would have
had about its natural spin axis if it had not been restrained by
the set axes, wherein the rotation characteristics include or
relate to the back spin and side spin of the ball.
139. A simulator or measurement apparatus according to claim 138,
which is operable to repeatedly alter the axis between the
different set axes positions; and the measurement means is operable
to ascertain average values to more accurately determine the
rotation characteristics which the ball would have had about its
natural spin axis if it had not been restrained by the set
axes.
140. A simulator or measurement apparatus according to claim 138,
which is operable to alter the axis between the two different set
axes positions without substantially altering the height or
position of the ball.
141. A simulator or measurement apparatus, for use in a ball game
where a ball is hit from a stationary position, the apparatus
including a ball, a connecting means, a base and a measurement
means, wherein the ball is connected by the connecting means to the
base, characterised in that the apparatus includes sensor means
which produce input signals when the ball is hit; and the
measurement means is operable to determine the motion
characteristics of an unconnected ball by comparison of these input
signals to input signals corresponding to previous shots with known
motion characteristics.
142. A simulator or measurement apparatus according to claim 141,
wherein the measurement means includes an artificial neural-type
intelligence means.
143. A simulator or measurement apparatus according to claim 141,
wherein the artificial neural-type intelligence means has been
trained using a ball striking means, wherein training inputs to the
artificial neural-type intelligence means are determined by
striking the connected ball with the ball striking means, and
training outputs to the artificial neural-type intelligence means
are determined by striking an unconnected ball with the ball
striking means in like manner and measuring its motion
characteristics.
Description
[0001] The present invention relates to a method and apparatus for
simulating or measuring the movement characteristics of a ball
which has been struck from a stationary position by a moving
object. The invention relates more specifically, but not
exclusively, to a method and apparatus for simulating or measuring
the movement characteristics of a golf ball, which has been struck
by a golf club in a shot which may comprise a drive shot.
[0002] The game of golf is one of the most popular universal
sports. As is well known, it comprises sets of shots, each set
typically involving an initial long drive shot from a starting tee,
followed by a series of progressively shorter shots towards a hole
on a green.
[0003] Most golf players, from beginners to professionals, reserve
their greatest interest for the initial drive shot. It is this
shot, which provides the greatest level of satisfaction when well
hit and which has the most deleterious effect when badly hit. It
receives far more attention and practice off the course than its
relative frequency would otherwise warrant. The drive shot retains
an element of intrigue for most players because its dynamic
characteristics are beyond the normal range of human perception.
The transfer of energy to the ball is so rapid that the ball has
departed far from the tee before the player can register the impact
either by feel or sight. For example, in a well hit golf drive shot
the ball and club face are typically in contact for only about 0.45
ms, during which time the ball moves about 15 mm to 20 mm, and the
average force between the ball and club face is around 12,000 N to
13,000 N. The ball departs from the club face at a speed of about
65 m/s. The ball also acquires significant spin motion from the
driving shot, typically acquiring a back spin about a horizontal
axis of around 3,500 rpm but no significant spin in the direction
of travel of the ball. The ball may also acquire a side spin
component about a vertical axis, which when combined with its back
spin, causes a resultant spin about an axis tilted in a plane which
is perpendicular to the direction of travel of the ball. The side
spin component is not always present and its magnitude is typically
less than a few percent of that of the back spin component on well
hit drive shots. During impact, typically about 39% of the club
head energy is transferred to the ball, about 8% is lost and about
53% is retained in the club head. Usually, over 99% of the ball's
energy is acquired as linear kinetic energy, with spin energy
accounting for less than 1%.
[0004] The prior art has produced various means whereby the initial
drive shot can be carried out away from the golf course to allow
player practice or to permit measurement of the characteristics of
the drive shot.
[0005] The most common means for player practice is the dedicated
driving range. In a typical arrangement, players are positioned in
a row, are each supplied with a quantity of balls and drive the
balls from a tee piece out across the practice range. The range is
usually several hundred meters long and may be supplied with
markers which indicate the distance from the driving position.
Typically, the range is outdoors and the player position is under
cover.
[0006] Although the dedicated driving practice range is of great
benefit to the player, it suffers from several disadvantages. There
is usually far more noise and distraction that would occur during
normal golfing play. It may be very difficult for the player to see
or judge the shot or to discriminate his or her ball, since other
players are simultaneously hitting balls, the balls can be very far
distant and there can be many stationary balls lying on the range.
Furthermore, the location of the range may be inconveniently
distant from the player and there may be uncertainty as to whether
space will be available when the player arrives. In addition, the
range may not be playable in poor light or inclement weather. The
driving practice range also has several inherent disadvantages. One
inherent disadvantage is that there is no automatic method for
statistically measuring performance. Another is that the player
cannot maintain his or her stance between shots because of the
necessity to look up and follow the progress of the ball.
[0007] In another type of driving range, which occurs where space
is limited, rows of players are arranged in tiers, with large
numbers hitting at the same time into a large enclosure. In this
instance, the player has little opportunity to distinguish his or
her ball from those of the others players and there is very little
feedback of information to the player other than the sound and feel
of the shot.
[0008] The prior art has attempted to overcome some of the
disadvantages of the dedicated driving range. The most successful
of these alternatives to the practice driving range appear to be
those which allow the player to hit a ball into a large net or
screen and which measure the speed and direction of the ball in
flight using remote sensors such as electromagnetic wave emitters
and receivers. Although they have overcome some of the
disadvantages of the driving range, they have achieved very limited
success due to several drawbacks. They are very expensive and
require a large amount of space to set up. They are not readily
portable and many are not suitable for outdoor use. They usually
require a substantial electrical power source. They typically do
not measure certain important characteristics of ball flight, such
as back spin and side spin and in consequence cannot accurately
predict the free flight trajectory of the ball. They usually are
not compatible with ground shots such as the putting shot.
[0009] The prior art has also proposed various alternatives to the
practice driving range where the ball is connected or tethered to
an apparatus. However, none of these alternatives appears to
provide a satisfactory solution. Some simply do not adequately
simulate a real practice shot. Those which have attempted to
provide adequate or accurate details of the characteristics of the
movement of the ball appear to be impractical and to display a
failure to appreciate the mechanics of the ranges of golf
shots.
[0010] Rutherford et al., WO 89/00065, discloses a golf practice
apparatus, which comprises a golf ball connected to a shaft. The
ball is operable to rotate in a continuous fixed circular orbit in
a horizontal plane about a pivot. The practice apparatus roughly
estimates the single parameter of shot distance by counting the
revolutions of the ball about the pivot. No explanation is given as
to how the apparatus will withstand the forces from lofted or badly
hit shots. Although the shaft appears to be of rigid construction,
no details are given of its construction or of the ball attachment
method.
[0011] Barry et al., EP 0278150, discloses a golf practice
apparatus, which comprises a golf ball connected to a shaft which
is operable to rotate in a continuous fixed circular orbit in a
slightly inclined horizontal plane about a pivot. When a shot is
taken, the club is caused to pass across light detectors located in
the base of the machine. These detectors directly sense the
movement of the shadow of the club and an analysis of the movement
is made to estimate shot distance and angle. No explanation is
given as to how the apparatus will withstand the forces from lofted
or badly hit shots and details of shaft construction and ball
attachment appear to be impractical.
[0012] Onozuka et al., U.S. Pat. No. 4,958,836, discloses a golf
practice apparatus, which comprises a golf ball connected to a
shaft comprised of an elastic material, which is operable to rotate
in a continuous circular orbit about a pivot. The orbit can be
selectively set in different fixed planes, all of which are close
to a horizontal plane. When a shot is taken, the club is caused to
pass across light emitters and detectors located in the base of the
machine. These detectors directly sense the movement of the
reflection of light from the club and an analysis of the movement
is made to estimate shot distance and angle. As with the previous
cited specification, no explanation is given as to how the
apparatus will withstand the forces from lofted or badly hit shots
and details of shaft construction and ball attachment again appear
to be impractical.
[0013] Russell et al., U.S. Pat. No. 5,997,405, discloses a golf
practice apparatus which comprises a golf ball connected to a
flexible tether which is operable to rotate in a continuous
approximately circular horizontal orbit about a vertical pivot. The
practice apparatus roughly estimates the single parameter of shot
distance by determining the rate of rotation about the vertical
pivot.
[0014] Dennesen, U.S. Pat. No. 5,178,393, and Tortola, U.S. Pat.
No. 6,257,989, both disclose a golf practice apparatus which
comprises a golf ball connected to a flexible tether which is
operable to rotate in a continuous approximately circular vertical
orbit about a horizontal pivot. The apparatus roughly estimates the
shot distance by determining the number of rotations or rate of
rotation about the vertical pivot by using an electronic optical
sensor, directly wired to the electronic circuitry of the
apparatus. The sensor detects the interruption of a light beam
passing through a slotted element on a vane attached to the pivot.
The Tortola practice apparatus additionally attempts to roughly
estimate the direction of the shot by determining the lateral pull
at the top of the flexible tether. This estimate is made using
either a pair of strain gauges or a pair of axial optical
electronic sensors electrically wired to the circuitry of the
apparatus. The strain gauges or axial optical sensors are arranged
out of phase to each other to allow determination of the direction
of axial movement.
[0015] The present invention is more particularly defined in the
appended claims 1 to 116 which are incorporated into this
description by reference.
[0016] The present invention provides a simulator or measurement
apparatus, for use in a ball game where a ball is hit from a
stationary position, which includes a ball, a connecting means, a
base and a measurement means, where the ball is connected by the
connecting means to the base.
[0017] The invention relates particularly, but not exclusively, to
a simulator or measurement apparatus suited to the game of golf
where a golf ball receives an impact from a golf club and the
motion characteristics of the ball relate to the initial movement
characteristics of the ball. The invention relates more
particularly to a simulator or measurement apparatus suited to the
game of golf, embracing all golf shots, including the drive shot
and the putting shot.
[0018] Throughout the specification, where the method or apparatus
refers to the game of golf, an apparatus is described which is
suited to players who strike the ball to the left, as would
normally be the case for right handed golfers. A mirror image
arrangement, similar in other respects, can be used for players who
strike the ball to the right.
[0019] The invention will now be described more particularly with
reference to the accompanying drawings which show, by way of
example only, an embodiment of the invention which is suitable as
an apparatus to measure the movement characteristics of a golf ball
which has been struck by a golf club across a range of shots
including the drive shot and the putting shot.
[0020] In the drawings:
[0021] FIG. 1 shows an oblique view of the ball and connecting
means of a apparatus which simulates and measures the movement
characteristics of a golf ball which has been struck by a golf
club, the view includes a ball spin rotation pivot, a vertical
pivot, a horizontal pivot and a supplemental pivot;
[0022] FIG. 2 shows an oblique view of the ball and connecting
means shown in FIG. 1, but with parts, other than shafts and vanes,
shown sectioned along a vertical plane through the centre of the
ball and ball shaft--the view omits the supplemental pivot;
[0023] FIG. 3 also shows an oblique view of the ball and connecting
means shown in FIG. 1, but with parts, other than shafts and vanes,
shown sectioned along a horizontal plane through the centre of the
ball and ball shaft with upper parts of the horizontal pivot vane
casing, and supplemental pivot and vane casing omitted to show the
horizontal pivot vane and supplemental pivot vane;
[0024] FIG. 4 shows an oblique view of the apparatus with the ball
in the home position; the view omits a protective housing, display
screen, ball retardation means and playing surface;
[0025] FIG. 5 shows a plan view of the apparatus as shown in FIG.
4;
[0026] FIG. 6 is similar to FIG. 5, except that the ball and
connecting means have moved away from the home position;
[0027] FIG. 7 is a sectional end view of the apparatus, taken on
X-X as shown in FIG. 5; and shows the apparatus with the connecting
means orientated in a horizontal plane; the view omits the pinions
shown in FIG. 5, but includes a representation of the playing
surface;
[0028] FIG. 8 is similar to FIG. 7, but shows the connecting
apparatus oriented at an angle tilted down from the ball;
[0029] FIG. 9 shows a diagrammatic plan view of the connecting
means and theoretical movement path of the ball where the ball is
hit straight along its intended line of direction;
[0030] FIG. 10 shows a similar view to FIG. 9, but where the ball
is hit to the right of its intended line of direction;
[0031] FIG. 11 again shows a similar view to FIG. 9, but where the
ball is hit to the left of its intended line of direction;
[0032] FIG. 12 is a diagram showing the relationship between the
perpendicular to the free spin axis of a ball and the
perpendiculars to two fixed axes set at angles .beta. to the
horizontal, where the free spin axis is at a smaller angle to the
horizontal than the angle of either of the fixed axes;
[0033] FIG. 13 is a diagram similar to FIG. 12, but where the free
spin axis is at a greater angle to the horizontal than the angle of
either of the fixed axes;
[0034] The following is an index of the reference numerals used in
the drawings: [0035] 1. Connecting means [0036] 2. Ball [0037] 3.
Ball cavity plug [0038] 4. Ball shaft insert [0039] 5. Ball shaft
flange [0040] 6. Ball shaft [0041] 7. Ball shaft receiver [0042] 8.
Outer ball shaft casing [0043] 9. Outer ball shaft casing retaining
screws [0044] 10. Inner ball shaft casing [0045] 11. Ball
spin-rotation joint [0046] 12. Ball spin-rotation vane [0047] 13.
Docking engagement member [0048] 14. Vertical-pivot. [0049] 15.
Vertical-pivot shaft. [0050] 16. Vertical-pivot clevis cheek.
[0051] 17. Horizontal-pivot. [0052] 18. Horizontal-pivot block
[0053] 19. Horizontal-pivot shaft. [0054] 20. Horizontal-pivot
clevis cheek [0055] 21. Horizontal-pivot vane [0056] 22.
Horizontal-pivot vane casing [0057] 23. Connecting arm [0058] 24.
Supplemental-pivot [0059] 25. Supplemental-pivot shaft [0060] 26.
Supplemental-pivot connecting arm bush [0061] 27.
Supplemental-pivot vane [0062] 28. Supplemental-pivot vane casing
[0063] 29. Support bush [0064] 30. Playing surface [0065] 31. Axis
tilt means [0066] 32. Axis tilt means crank member [0067] 33. Upper
pivot connected to the support bushes [0068] 34. Upper pivot
connected to the base [0069] 35. Lower pivot connected to the
support bushes [0070] 36. Lower pivot connected to the base [0071]
37. Upper pivot connecting member [0072] 38. Lower pivot connecting
member [0073] 39. Electrical actuator [0074] 40. Threaded bush and
lead screw [0075] 41. Height setting means [0076] 42. Hand wheel
[0077] 43. Pinion [0078] 44. Rack [0079] 45. Vertical lifting block
[0080] 46. Pillar [0081] 47. Ratchet and pawl [0082] 48. Base
[0083] In overview, the ball 2 is connected to the body of the
apparatus by a connecting means 1, comprising a ball shaft 6, which
is connected in series to a ball spin rotation joint 11, a vertical
pivot joint 14, a horizontal pivot joint 17 and a supplemental
pivot joint 24. These joints are referred to as the ball
spin-rotation joint 11, the vertical-pivot 14, the horizontal-pivot
17 and the supplemental-pivot 24, respectively. The ball
spin-rotation joint allows the ball and ball shaft to spin or
rotate freely about the shaft axis. The vertical-pivot allows
movement in a vertical plane and the horizontal-pivot and
supplemental-pivot allow movement in a horizontal plane. The three
pivots allow substantially straight line movement of the ball for a
short distance when hit from the starting or home position. The
spin rotation position of the ball and the positions of the
horizontal-pivot and supplemental-pivot are monitored by sensors
operating in conjunction with a controller. The apparatus is
operable to automatically change the tilt angle of the ball spin
rotation axis over successive shots without changing the tee height
of the ball. The apparatus is also operable to allow the tee height
of the ball to be changed by the player. The part of the apparatus
which rests on the ground and generally supports the apparatus is
referred to as the base 48 in the description.
[0084] The ball 2 comprises a real or simulated golf ball attached
to a ball shaft 6. The ball 2 is of the solid type with an exterior
which is resistant to wear or cutting. It may comprise one material
throughout or may comprise a cover and concentric layers of
different materials. Preferably it is of the type which produces
high spin rates. For example, it may comprise a relatively hard
centre and relatively soft outer layer. The combination of a hard
centre and soft outer layer is known to promote high spin rates.
The use of a hard centre also facilitates the use of a relatively
inflexible shaft connection near the ball centre because there is a
reduced tendency for relative movement where the shaft is connected
to the ball material. Also, the relatively inflexible shaft
connection interferes less with the natural flexing of the ball 2.
Preferably any materials used in the construction of the golf ball
do not comprise fillers of the type which are frequently used to
increase the density of the ball but which are not otherwise
necessary.
[0085] Particular care is required in the connection between the
ball 2 and ball shaft 6, due to the very high transmitted forces
and the difference in flexibility between the ball shaft and ball.
The ball shaft is securely connected to the ball and comprises a
rigid hollow component. Axial forces in a direction along the axis
of the ball shaft, away from the body of the apparatus, are
resisted by a rigid external rim or flange 5 on the ball end of the
shaft, which bears directly or indirectly against the material of
the ball. Where the tapered ball shaft is machined from thick
walled tube material, this rim or flange can be conveniently
produced in the machining process. Rotational forces between the
ball and ball shaft are resisted by a ball shaft insert 4, one side
of which is rigidly fixed to the ball shaft and the other side of
which comprises projections, such as projecting blades which engage
with the material of the ball 2. The ball shaft insert is provided
with a short spigot which is positioned in hole in the end of the
hollow ball shaft and which is fixed by means such as adhesive
bonding or by one or more cross rivets through the spigot and ball
shaft. The spigot and hole may also be formed in matching
non-circular shapes, to assist the prevention of relative rotation
between the parts. The ball shaft insert comprises a relatively
strong and rigid material, such as a reinforced polymer moulding or
a metal die casting. In an alternative arrangement, the ball shaft
insert additionally comprises the retaining rim or flange.
[0086] The ball shaft 6 and ball shaft insert 4 are held captive
within a cavity in the ball 2. The ball shaft and ball shaft insert
are not bonded to the internal surface of this cavity and relative
movement can freely occur between the contacting surfaces when the
ball 2 is deformed when struck by the club. This avoids failure of
the connection by fracture of bonds between rigid and flexible
materials when the flexible material is deformed.
[0087] The cavity in the ball 2 is created by forming a hole in the
ball 2 and then filling it with a ball cavity plug 3 which
corresponds to the shape of the hole. The ball cavity plug is
assembled on the ball shaft and ball shaft insert, prior to being
inserted in the ball 2.
[0088] The ball cavity plug 3 comprises a resilient polymer
material with a modulus which is similar to or compatible with that
of the material in the ball 2, thereby avoiding significant stress
concentration occurring at the mating surfaces when the ball is
deformed. The material is also chosen such that it can be strongly
bonded to the ball material. For example, it may comprise a polymer
which is the same or similar to that used in the ball. Bonding may
be achieved, for example, by joining the surfaces with a high
strength flexible adhesive or by appropriate polymer welding
methods.
[0089] The cavity plug 3 may be moulded in two halves and assembled
on the ball shaft 6 and ball shaft insert 4. Where bonding is by
adhesive methods, the outer surface of the cavity plug is in the
form of a frustum of a cone with a very shallow taper. The narrow
end of this surface terminates in a coaxial cone with a very steep
angle or taper corresponding to the shape suitable for the leading
face of a milling cutter. A hole is machined in the ball 2 using a
rotary milling tool which produces a tapered hole which matches the
external shape of the cavity. The cavity plug and corresponding
hole are arranged without sharp boundary edges to minimise stress
concentration points when the parts are deformed during play.
Adhesive is added to the mating surfaces, the two parts are
assembled and bonded together. The tapered frustum shape allows the
adhesive to remain on the surfaces as the parts are being assembled
and allows pressure to be evenly applied to the joint when the
parts are brought together. The steeply angled end facilitates
machining of the hole. Depending on the materials to be bonded and
the adhesive used, the surfaces may require surface preparation.
Chemically treating or machining the surface of the anchor and
using it with a newly machined hole will usually satisfy any such
requirements. Where bonding is achieved by welding methods, the
surfaces may be tapered or parallel, depending on the chosen
materials and welding methods.
[0090] Connecting the ball 2 from the shaft side, has the advantage
that it avoids disturbance of the ball cover and underlying
material in the region where the ball is struck by the club and
where the ball is subject to maximum trauma and distortion.
[0091] A reinforcing member, such as a flat ring comprising the
same or similar material as the ball cover, may optionally be
bonded to the ball 2 where the shaft exits the hole. The cover of
the ball 2 surrounding the hole may be lightly machined to a flat
surface to receive it, during the hole drilling operation. A
reinforcing member is not shown in the figures.
[0092] In an alternative embodiment, the core and outer layer of
the ball 2 is directly moulded over the ball shaft and ball shaft
insert. Similar to the previous embodiment, the arrangement is not
dependent on adhesion between the relatively flexible ball material
and the rigid material of the ball shaft and ball shaft insert. The
contacting surfaces of these parts can move relative to each other
when the ball 2 is deformed without detriment to the mechanical
connection between them.
[0093] In a further alternative arrangement, not shown in the
figures, the ball 2 or ball core is comprised of a hollow metal
sphere. A ball of this type may, for example, be constructed from
stainless steel and comprise dimples to simulate a conventional
golf ball. The ball shaft 6 passes though the ball 2 and connects
at both sides for added strength. The weight of the hollow ball 2
and the connecting ball shaft are ideally arranged such that their
combined inertia is substantially the same as a conventional free
golf ball. The wall thickness and wall thickness distribution of
the ball 2 may be varied to provide a resilience which presents
playing characteristics similar to a conventional golf ball. The
weight of the ball shaft and connection may be varied to provide an
overall required weight.
[0094] Returning to the preferred embodiment, the ball shaft 6 is
securely connected to the ball 2 and is arranged such that it does
not unduly influence the performance of the ball when struck. The
ball shaft is made from a material with a very high strength to
weight ratio. Hardened aluminium alloy, grade 7075 T6, has been
found suitable. The ball shaft is also shaped such as to provide
high strength to weight performance. It is substantially formed
with a tapered exterior and hollow centre. The tapered exterior
allows its strength to be varied along its length, providing
increasing strength with increasing distance from the ball 2. The
hollow centre provides increased rigidity for a given quantity of
material.
[0095] The dimensions of the ball shaft 6 are arranged sufficiently
large to enable it to withstand the considerable stresses which
arise when the ball 2 is struck by the club head. The type of
stress most likely to cause failure of the ball shaft is bending
moment stress caused by the inertia of the ball shaft largely
resisting rotational movement about the horizontal-pivot when the
ball is struck in a drive shot. The magnitude of this stress is
greatest in regions furthest from the ball. It is important to
provide a balance which minimises the inertia, yet still provides a
ball shaft of sufficient strength. Minimising the inertia within
this design constraint has further advantages. It minimises the
difference in momentum transfer between the shot and an equivalent
free shot taken without a connecting means, thereby making the
apparatus operable to provide a shot with a more realistic `feel`.
It also minimises the forces between the ball and ball shaft when a
shot is taken, thereby prolonging the life of the ball and its
connection to the ball shaft.
[0096] The ball shaft 6 terminates in a male threaded section which
connects to a corresponding female threaded section on a ball shaft
receiver 7. The thread form is arranged such that the normal
tendency of the ball 2 to back-spin causes the threaded joint to
tighten. A right hand thread is used on apparatus suitable for
right handed players. A left hand thread is used on apparatus
suitable for left handed players, where the geometric arrangement
shown in the figures is reversed.
[0097] The ball shaft 6 is arranged such that it and the connected
ball 2 are free to rotate about their common axis in a ball
spin-rotation joint 11. The ball shaft is supported by a ball shaft
casing which comprises an outer ball shaft casing 8 and an inner
ball shaft casing 10. Preferably the ball shaft casing is produced
from a light weight high strength material such as a reinforced
polymer. This lessens its weight and inertia and allows it to be
economically moulded to the required shape. Carbon fibre filled
nylon provides a high strength solution with permissible abrasion
and friction characteristics. A small clearance is provided between
the ball shaft casing and the ball shaft to allow free rotation.
Preferably this clearance is such that the ball shaft casing can
act as an effective bearing surface for the rotating ball shaft.
Although the primary purpose for providing free rotation of the
ball is to allow the ball to simulate the spin rotation which
occurs with an unconnected ball, the freedom to rotate also reduces
stresses which might otherwise damage the structure of the ball and
its connection to the ball shaft. It also provides a varying
surface on which the ball is struck, thereby spreading wear and
increasing the longevity of the ball. The inner ball shaft casing
10 is also provided with thrust bearings which resist axial forces
on the ball shaft while the ball shaft is rotating. These thrust
bearings comprises passive annular members, concentric with the
ball shaft, which bear against projecting shoulders and surfaces on
the ball shaft receiver 7. The thrust bearings comprise a low
friction material, such as reinforced PTE, and are fixed in
concentric internal recesses or pockets within the inner ball shaft
casing 10.
[0098] The ball shaft casing comprises two separate parts to
facilitate ready replacement of the outer ball shaft casing 8 by
the player should this be inadvertently damaged by contact with the
club head. The outer ball shaft casing 8 is connected to the inner
ball shaft casing 10 by four screw fasteners 9, arrayed
symmetrically around the ball shaft and with their axes parallel to
the ball shaft axis.
[0099] The ball shaft receiver 7 is provided with holding means
which is operable to manually prevent its rotation, thereby
allowing the ball shaft 6 to be screwed on or off by manually
turning the connected ball 2. The holding means comprises a radial
hole through the ball shaft receiver which can be aligned with
corresponding radial holes in the inner ball shaft casing.
Insertion of a pin, through the aligned holes, prevents rotation of
the ball shaft receiver relative to the inner ball shaft casing 10.
This allows a player to readily replace the ball and ball shaft
where an existing one is damaged or worn or where a ball with
different play characteristics is required. The holding means is
not shown in the figures.
[0100] Measurement of the various motion characteristics presents
potential difficulties when related to the severe conditions which
arise, for example, when the golf ball is struck by the golf club
in a drive shot. One of these relates to the shock conditions
created by the impact between the ball and club face, where the
forces and rates of acceleration are very high. Any parts directly
influenced by the motion of the ball may also be subjected to these
shock conditions. If appropriate precautions are not taken, these
may result in interference with the accurate measurement of the
motion characteristics or damage to the measurement means. Further
potential difficulties relate to the very fast response which is
required due to the high speed of the ball following the impact and
to the small distances or angles to be measured.
[0101] In the preferred embodiment, measurement is carried out by
one or more sensing means which operate in cooperation with a
controller means.
[0102] The sensing means comprises a target means comprising a
target with irregularities. The sensing means also comprises a
bridging means comprising an electromagnetic wave circuit, such as
an optic light circuit and henceforth referred to as a light, light
beam or optic circuit, and an emitter and receiver means which are
operable to bridge an opening in the circuit by emitting and
receiving light across the irregularities. The target means is
located on the portion of the apparatus which endures the greater
degree of shock or acceleration and the bridging means is located
on the portion which endures the lesser degree of shock or
acceleration. The target means is arranged as a relatively simple
passive component which is operable to withstand high levels of
shock or inertia forces. The bridging means is operable to detect
the presence or absence of the irregularities, which may comprise
slots or holes, by interruption of the light beam, and thereby
detect motion of the target means relative to the bridging means.
The light beam is generated from and reconverted to an electronic
signal, by suitable electronic apparatus such as a light emitting
diode and a photo diode, respectively, and these in turn
communicate with a controller, such as a programmed electronic
processor, where the electronic signals are processed as
required.
[0103] The bridging means comprises a light emitter and a light
receiver which are held in a spaced apart relationship and are
operable to pass a light beam across a gap between them. The target
irregularities are passed through the gap and interrupt the light
beam. Shock forces are advantageously reduced at the bridging means
because direct physical contact is not made with the target
means.
[0104] A reduced level of shock will usually still occur at the
bridging means, due to it being transmitted through the joint of
the connecting means 1 or through other interconnected parts. Where
the bridging means lies between the ball 2 and one of the other
joints of the connecting means, it will still be subject to some
degree of rapid acceleration. This shock and acceleration is
isolated from the electronic components of the apparatus by
arranging the light signals to be communicated from the light
emitter and receiver to the electronic components by means of
flexible optical fibres. The electronic components may be mounted
in a stationary position away from all significant shock
forces.
[0105] The use of light beam apparatus, directly connected to the
region where the electronic controller and apparatus are located,
is also advantageous in producing a very rapid response. The signal
reaches the electronic components at the speed of light and is then
processed by very high speed electronics. The direct communication
avoids the need for local electronic apparatus, such as remote
amplifiers, which could cause significant response delays.
[0106] In the preferred embodiment, the optic fibres comprise
single flexible polymer fibres, of circular cross section, with a
diameter ranging from about 0.5 to 1.0 mm. The fibres are provided
with a protective polymer sheath, which has an external diameter
which is approximately twice that of the fibre. The sheath may be
omitted in the region of the bridging means and the region where
fibres are routed through the pivoted joints to reduce space and
routing cavity dimensions. Where unsheathed fibres are used, care
is taken to avoid contact between parts where optical leakage may
take place, such as where fibres are severely curved.
[0107] The bridging means comprises spaced apart opposing fibre
ends without additional focusing lens. These fibre ends are those
of the emitter fibre and the detector fibre. The fibre ends are
polished or otherwise formed flat to improve light transmission
efficiency and signal quality. The fibre ends are spaced apart by a
distance which is as small as can be practically achieved and
approximately equal to twice the diameter of the fibres. The reason
for using a small distance is to minimise the diffusion which
occurs as light is emitted from the end of the emitter fibre.
[0108] The light beam is also passed or received though a
collimating slot on the bridging means. The collimating slot has
substantially parallel sides and is positioned between the target
means and the end of the fibre. The parallel sides of the
collimating slot are substantially orthogonal to the direction of
motion of the irregularities or slots on the target means and are
spaced apart less than the width of the fibre. In the preferred
embodiment the width is approximately half the diameter of the
fibre. The purpose of the collimating slot is twofold. One purpose
is to improve the quality or sharpness of the light signals,
meeting or departing the slots in the target means, by providing
them with a flat leading and trailing edge. The other purpose is to
provide a narrower light beam which increases the resolution of the
sensor means by permitting a greater number of vane slots to be
used. In some instances, it may be advantageous to use a
collimating slot which is much narrower that half the diameter of
the fibre, to increase resolution, where there are reasons to
maintain greater fibre diameters than would otherwise be required
by the bridging means.
[0109] The body of the bridging means, including the collimating
slots, comprises a polymer moulding which includes the collimating
slots and appropriate grooves and supports for the fibres. The
fibres may be formed into tight bends as required by the
application of moderate heat in the production process. The fibres
are fixed in position, by methods such as bonding or clamping. The
bridging means is of robust and economical construction.
[0110] In the preferred embodiment, the target means comprises a
rotary vane with irregularities in the form of open or closed
radial slots and teeth around its periphery. The vane may be
capable of limited rotation or of continuous rotation, depending on
the type of motion characteristics which are being measured. As the
vane rotates, the light beam from the emitter fibre traverses a
circular locus on one side of the vane and crosses the slots and
interstitial regions to provide a series of on and off signals to
the detector fibre on the other side of the bridging means.
[0111] It is important that the vane slot spacing is minimised
within the design constraints of the apparatus, because in the
measurement of certain motion characteristics, the locus of the
vane may travel a very small distance through the bridging means.
In the preferred embodiment, the width of the slots and the teeth
are approximately equal and each is approximately equal to the
width of the collimating slot. This will ensure that the beam of
light is not spread over more than one slot on the vane. The radial
depth of the slots is approximately equal to 1.5-2.0 fibre
diameters.
[0112] The vane should be constructed with high dimensional
accuracy and consistency in the spacing of the slots along the
locus of the optic path, since this accuracy and consistency will
be directly reflected in the accuracy and consistency of
measurements produced by the apparatus. For example, the vane may
be constructed from thin stainless steel material produced with a
high dimensional accuracy by photo etching. This process produces
dimensional accuracies ranging from.+-.10% to.+-.15% of material
thickness. This corresponds to dimensional accuracies ranging
from.+-.0.02 mm to.+-.0.03 mm where a material thickness of 0.2 mm
is used. The vane material may advantageously be supported by
material which is set back from the edges of the vane slot.
[0113] The vanes are enclosed within sealed vane casings to prevent
contamination of the optical surfaces or optical path by dust or
moisture. Elastomeric seals are used to seal the vane casings where
they are penetrated by the rotating pivot shafts.
[0114] The circuit carrying the light beam may be routed across the
pivoted joints on the connecting means 1, with a portion of the
circuit aligned along the axis of the pivoted joint. This is
achieved by providing a central passage along part of its axis of
the shaft of the pivoted joint and routing a relatively loose,
slightly twisted arrangement of fibres through the passage, with
the opposing portions of the polymer fibres in the central passage
connected to the portions of the circuit on each side of the
pivoted joint. One end of the fibre arrangement in the passage
rotates in fixed relationship with one side of the pivoted joint
and the other end of the fibre arrangement in the passage rotates
in fixed relationship with the other side of the pivoted joint. The
relatively loose and slightly twisted centre region of the fibre
region twists or untwists a little further with the movement of the
joint, but causing only minimal and acceptable strain on the fibre
arrangement. In the preferred embodiment, the fibres comprising the
ball spin-rotation sensor are routed though cavities in the
vertical-pivot and horizontal-pivot shafts 15 and 19 using this
method. Similarly, the fibres comprising the horizontal-pivot
sensor are routed though the cavity in the horizontal-pivot shaft
using the same method. The method has several advantages. The
fibres are better protected because relatively loose external loops
of fibre are avoided. The fibres are also subjected to less strain
than would occur with relatively loose external loops. The
connecting means 1 presents a neater and more compact appearance,
particularly where parts are exposed to view outside its protective
housing.
[0115] In the preferred embodiment, each sensing means comprises
two bridging means, one of which is asymmetrically set out of phase
with the other with respect to the irregularities, such that the on
and off signals occur at different times as the vane rotates. This
has several advantages. It makes it possible for the controller to
detect false signals from the receiver circuits, because a set
pattern of signals is expected from the two bridging means as the
vane rotates. If one of the receiver circuits provides more or less
signals than would be expected in this pattern, the controller
detects the error and is programmed to respond in an appropriate
manner. For example, where a single bridging means is used, a vane
may stop with the light beam just at an edge corresponding to the
transition between an on and off signal. Vibration of the system
may cause it to repeatedly move between the two signal states, thus
giving a false reading. Where a second out-of-phase bridging means
is used, one would record no signal change when the other gave such
a false signal, thus enabling the controller to distinguish between
valid and invalid signals. An additional advantage arises in that
the resolution of the sensor is increased because the number of
signals is doubled. A further advantage arises in that the sensor
is operable to determine the direction of motion of the vane,
because clockwise motion will result in a different pattern to
counterclockwise motion due to the bridging means being
asymmetrically set out of phase to each other. The two bridging
means are located such that one is an even number plus one half
slot away from the other. Ideally, one is just one half slot away
from the other. Where the two bridging means are adjacent each
other, it may be possible to share one emitter fibre between them.
In this instance, the collimating slots may conveniently be
positioned between the vane and the detector fibres. The emitter
fibre may also be of larger diameter than the detector fibres.
[0116] The controller or measurement means is also provided with
timing means which is operable to measure the time duration between
events which are directly or indirectly related to the signals
received from the sensing means. This allows fine resolution by
interpolation of the measurement of motion of the target
irregularities relative to the bridging means. The controller is
operable to subdivide a count into smaller divisions to improve the
resolution. The measurement of motion is accordingly not limited to
the relatively coarse measurement of the number of irregularities
passing the sensor between two identified events, but rather the
fine measurement of the length of time elapsed between identified
events, where these identified events relate to the detection of
individual irregularities.
[0117] The signal from the pair of bridging means gives four signal
events per slot, two positive edges and two negative edges. This
gives a measurement resolution of four times the slot spacing.
Interpolation of the signals, as described above, increases this
resolution by about ten times, or about forty times the slot
spacing.
[0118] Returning now to FIGS. 2 and 3, the ball shaft receiver 7 is
provided with a ball spin-rotation sensing means to detect the
relative rotation of the ball shaft 6 within the inner ball shaft
casing 10. The target means comprises a ball spin-rotation vane 12
mounted on the ball shaft receiver and two bridging means mounted
in a moulded pocket within the inner ball shaft casing. The
location of the sensor means on the ball shaft receiver, at a
position which is distant from the ball end, has the advantage that
the sensor is subject to far lower inertia forces resulting from
the rotation of the ball shaft about the horizontal-pivot or
vertical-pivot than it would have if it were located nearer to the
ball 2. The controller monitors the resulting light signals
following the impact between the ball 2 and club head and
determines certain of the relevant motion characteristics.
[0119] The inner ball shaft casing 10 is connected to the apparatus
by the vertical-pivot 14, which allows relative rotational movement
in a vertical plane. The vertical-pivot has several functions. It
allows the ball to assume a natural movement when struck from the
start or home position, by providing a vertical component of
movement. This provides one of the degrees of freedom necessary to
allow the ball to follow its natural movement when struck. It
additionally prevents damage to the apparatus by allowing freedom
for the ball to move up or down, particularly in the event of a
badly hit ball which is hit too high or too low.
[0120] Referring to FIGS. 1, 2 and 3, the vertical-pivot 14
comprises a clevis type pivot joint with a vertical-pivot shaft 15,
the axis of which is orientated in a horizontal direction. The
inner ball shaft casing is connected to the vertical-pivot by a
plurality of clevis cheeks 16 which comprise horizontal holes which
engage the vertical-pivot shaft. The vertical-pivot is connected to
an adjoining component of the apparatus which is referred to as the
horizontal-pivot block 18. A plurality of clevis cheeks on the
horizontal-pivot block comprise a horizontal hole and engage the
vertical-pivot shaft 15. Washers may be positioned on the
vertical-pivot shaft between the adjacent clevis cheeks.
[0121] The vertical-pivot 14 is provided with a spring stop means,
which is not shown in the figures. The spring stop means is
operable to support the arm at a required rest angle, but which
allows the ball shaft to rotate downwards if the ball shaft is
subjected to a force which might otherwise damage it or another
part of the apparatus. For example, it protects the apparatus from
damage which might otherwise result from the ball being struck too
high by the club head. The spring stop means does not restrict
upward rotation of the arm above the rest angle.
[0122] In one embodiment, the spring stop means comprises one or
two sets of helical springs in moulded pockets in the
horizontal-pivot block 18. The spring drives a moulded pin to a
stop on the pocket. The extended position holds the inner ball
shaft casing 10 at the correct angle relative to the
horizontal-pivot block. The ball shaft 6 and casing can freely
rotate upwards and away from the pin. In the event of a shot being
inadvertently downwards, the ball shaft and casing can rotate
downwards, depressing the pin into the pocket. Where two sets of
springs are used, they are positioned on each side of the lower
region of the horizontal-pivot block. In an alternative embodiment,
the spring stop means comprises a torsion spring with coils mounted
coaxially on the vertical-pivot shaft. The end arms of the torsion
spring are pre-energised in a position corresponding to the home
rest position, with the arms of the torsion spring bearing against
stops on the horizontal-pivot block. An extension of one of the
torsion spring arms supports the shaft and ball by bearing against
the outer arm casing. This extension is operable to deflect and
allow the shaft and ball to rotate downwards when subjected to a
force significantly greater than that resulting from the weight of
the shaft and ball. In another alternative embodiment, the spring
stop means comprises a substantially flat spring, one end of which
is fixed to the underside of the horizontal-pivot block and the
other end of which supports the ball shaft casing by bearing
against a bearing surface provided on its underside. The flat
spring may be provided with a slightly profiled shape, such as a
slightly convex shape elongated along the length of the spring as
seen in plan view, which allows the spring to decrease its
resistance to deformation when the deforming force exceeds a
planned threshold. The threshold force causes the spring to
temporarily buckle and allow the arm to rotate downwards. The
spring retains sufficient force to subsequently return the arm to
the unbuckled state against the resisting force of gravity.
[0123] Referring again to FIGS. 1 to 3, the set of components from
the ball 2 to the vertical-pivot 14 are connected to the apparatus
through the horizontal-pivot 17, which allows relative rotational
movement in a horizontal plane. The horizontal-pivot allows the
ball to move away from the club face by providing a horizontal
component of movement. This provides another of the degrees of
freedom necessary to allow the ball to follow its natural movement
when struck. The horizontal-pivot 17 comprises a horizontal-pivot
block 18 with a plurality of clevis cheeks, a horizontal-pivot
shaft and a connecting arm with a plurality of clevis cheeks which
engage with those of the horizontal-pivot block. The
horizontal-pivot block and connecting arm comprise a reinforced
polymer similar to the ball shaft casing. The horizontal-pivot
shaft comprises an inner part of reinforced polymer and an outer
thin walled metal shell. The shaft is fixed to the horizontal-pivot
block clevis cheeks and is free to rotate in the connecting arm
clevis cheeks.
[0124] The horizontal-pivot is provided with a sensing means which
is similar in construction and operation to that described for the
ball spin-rotation sensing means. The target means comprises a
horizontal-pivot vane 21 fixed to the lower region of the
horizontal-pivot shaft 19. A horizontal-pivot vane casing 22 is
moulded integrally with the connecting arm and two bridging means
for the sensing means are mounted in a pocket within the vane
casing. The horizontal-pivot sensing means communicates with the
controller and is operable to detect changes in the relative angle
between the ball shaft axis and the connecting arm axis.
[0125] The connecting arm 27 is connected to the apparatus by the
supplemental-pivot 24, which allows a further degree of relative
rotational movement in a horizontal plane. It allows the
horizontal-pivot to move in a horizontal plane by rotation about a
second vertical axis. This provides the third degree of freedom
necessary to allow the ball to follow a substantially straight line
movement, both when struck by the club and for a short period
afterwards, when certain of the critical launch conditions are to
be measured. The supplemental-pivot 24 comprises a
supplemental-pivot shaft 25, a central bush 26 connected to the
connecting arm and a set of support bushes, above and below the
central bush, which are connected to the apparatus. The shaft is
fixed to the bush of the connecting arm and is free to rotate
within the two support bushes. The arrangement ensures that the
horizontal-pivot shaft and supplemental-pivot shaft remain parallel
to each other. The supplemental-pivot central bush and support
bushes comprise a reinforced polymer similar to the ball shaft
casing.
[0126] The supplemental-pivot is provided with a sensing means
which is again similar in construction and operation to that
described for the ball spin-rotation sensing means. The target
means comprises a supplemental-pivot vane fixed to the lower region
of the supplemental-pivot shaft. A supplemental-pivot vane casing
is moulded integrally with the support bushes and a bridging means
for the sensing means is mounted within a pocket in the vane
casing. The supplemental-pivot sensing means is operable to detect
changes in the relative angle between the connecting arm axis and
the support bushes connected to the apparatus. However, in the
preferred embodiment, the vane and vane casing do not form a
complete disk, but rather a vane comprising a segment of a disk
rotates within a vane casing comprising a larger segment of a disk.
The region close to the axis of the supplemental-pivot, where the
vane and vane casing are absent, is used to accommodate a
strengthening pillar between the upper and lower support
bushes.
[0127] The supplemental-pivot is also provided with a buffer means
which includes a contact member comprising a rotation limiting arm,
which is not shown in the figures. This arm is fixed to the
supplemental-pivot shaft and extends in the direction of the
support body of the apparatus. It is free to move within limits
described by the range of shots which is measured by the apparatus.
For example, where the range of shots which measured by the
apparatus is within.+-.15.degree. of the intended direction of the
shot, the rotation limiting arm will have freedom to move in all
positions which correspond to the ball being hit
within.+-.15.degree. of the intended direction of the shot, over
the region where the ball travels in substantially straight line
movement. Contact members are also provided on the base which
prevent the rotation limiting arm from moving any appreciable
distance outside of this range. The contact members on the base
comprise robust buffer stops, made from a resilient elastomeric
material, which are progressively deformed by the movement of the
arm outside the free limits, providing a cushioned stop on the
movement, with minimal generation of noise. The buffer stops revert
to their original shape when the arm returns to the normal region
corresponding to the.+-.15.degree. limits.
[0128] The apparatus is additionally provided with a docking means,
which is operable to dispose the ball 2 and connecting means 1 in a
starting or home position, relative to other parts of the
apparatus. The docking means comprises male and female engagement
members. The male engagement member is positioned on the exterior
of the inner ball shaft casing and is shown in an exaggerated
format in FIG. 1 and FIGS. 3-6. The female engagement member is
positioned on the base of the connecting means 1 and is shown in an
exaggerated format in FIGS. 4-6. FIG. 4 shows the ball in the home
position with the docking means fully engaged. FIG. 5 shows the
ball away from the home position with the docking means fully
disengaged.
[0129] The male and female engagement members comprise vee shapes.
The female vee shape is at a somewhat shallower angle than that
shown in the figures, and its apex is closer to the edge of the
apparatus. The components are arranged such that the ball 2 is in
the starting home position when the male engagement member is fully
entered into the female engagement member. The engagement members
are arranged such that they can freely withdraw from each other
when the ball moves in the direction of a shot. The shape of the
female engagement member is determined by the range of movements
which allow the ball to freely move within limits described by the
range of shots which is measured by the apparatus, similar to the
rotation limiting arm described earlier. For example, where the
apparatus measures shots which fall within.+-.15.degree. of the
intended direction of the shot, the shape of the female engagement
member will be such as to allow the male engagement member to
freely disengage without bearing against the female engagement
member.
[0130] The shapes and material of the engagement members are
arranged such that the male engagement member, when pressed against
the female engagement member, is automatically guided into the
central home position. The docking means may also comprise springs
which are operable to ensure that the supplemental-pivot is at an
angle sufficiently close to the angle corresponding to the home
position such that the male engagement member will always engage
the entry to the female engagement member when the ball is pushed
backwards towards the starting position. These springs, which are
not shown in the figures, comprise low force torsion springs which
engage the movement of the supplemental pivot when its angle
exceeds a value which is arranged to be less than that which
corresponds to the entry of the male into the female engagement
member, but which do not engage it when the angle does not exceed
the normal angle range of shots.
[0131] The engagement members are also provided with means which
allow one or both of them to deflect if a shot is taken, which is
outside the limits where measurement is taken. The engagement
members return to their normal position when the members have
disengaged. This is achieved by providing the female engagement
member with spring loaded or resilient supports.
[0132] The docking means is also provided with a docking sensor
means, which is operable to detect the presence of the male
engagement member in the home position in the female engagement
member. The docking sensor means, which is not shown in the
figures, comprises a proximity sensor, such as a Hall Effect type
sensor mounted in the interior of the female engagement member and
a sensor target, comprising a permanent magnet, mounted in the
interior of the male engagement member. The proximity sensor is
operable to detect the close proximity of the permanent magnet and
to communicate a corresponding signal to the controller, indicating
that the docking means and ball are in the home position. The
player receives a visible and audible signal that the ball is
correctly docked. The visible signal may be given on the screen
display. The controller ignores any shots taken from an incorrectly
docked starting position.
[0133] The docking means is positioned in a region which lies just
within the protection of the housing. The connecting means 1 and
docking means are arranged such that the axis of the ball shaft 6,
at the starting or home position, is in a substantially horizontal
plane, and the angle between it and the intended direction of
movement of the ball, is less than 90.degree. on the side on which
the ball is struck, as can be seen in FIGS. 4. An angle between
73.degree. and 83.degree., such as 78.degree., has been found
suitable. This angular set-back has important advantages in the
measurement of the motion characteristics of the ball. It has the
advantage that the region where the ball is connected to the arm is
kept away from the region where the club makes contact with the
ball. In addition to keeping this weakened region of the ball away
from the contact area, it also reduces the possibility of the club
striking the arm where the shot is very badly directed. The angular
set-back also advantageously causes the axis of the ball to be
approximately perpendicular to the direction of movement during the
period after the ball and club face lose contact with each other,
in the period immediately following the impact. This assists in
promoting realistic ball movement during the period when its
characteristics are being measured.
[0134] The connecting means 1 is arranged in a manner which
minimises the rotational inertia of the moving components of the
apparatus about the horizontal-pivot. This is done for several
reasons including the provision of a shot that feels and behaves
similar to that of a free or unconnected ball. It is also done to
minimise the forces on the connecting means 1 and ball 2 when the
shot is taken. Subject to a first overriding consideration of
keeping the ball sufficiently distant from the stationary body of
the apparatus, such that its proximity does not disturb or
influence the player's shot, and a second overriding consideration
of maintaining the various operating characteristics of the
apparatus, the following guidelines should be followed. The
distance between the ball and the horizontal-pivot should be
minimised. The centre of gravity of the various components should
be away from the ball and as close as possible to the pivot point.
The weight of the components should be minimised. For similar
reasons, the connecting means 1 is similarly arranged to minimise
the rotational inertia of the moving components of the apparatus
about the supplemental-pivot.
[0135] The connecting means 1 is also arranged in a manner such
that the club cannot contact and damage the connecting means in the
interval when the ball has ended contact with the club. Although
the ball will be travelling faster than the club, parts of the
connecting means 1 closer to the horizontal-pivot may be travelling
at speeds which are less that that of the club. To prevent the
possibility of club contact with the connecting means 1, the
horizontal-pivot must be set back a sufficient distance from the
outside edge of the housing and the ball shaft must be sufficiently
less than 90.degree. from the direction of the intended movement of
the ball, as mentioned earlier. In addition, the ball must have a
sufficiently high coefficient of restitution to ensure that ball
speed is always much higher than club speed following the impact
between the ball and club. In practice, a medium golf ball
coefficient of restitution has been found adequate. The restitution
characteristic is commonly referred to in terms of ball
`compression` and should be about 90. Care should be taken not to
use balls with unnecessarily high restitution characteristics,
because these will increase the forces on the connecting means 1
and ball when a shot is taken.
[0136] The connecting means 1 is also arranged such that its
components, where possible, are subjected to tension rather than
bending stresses when the ball is struck. Bending stresses on the
connecting means 1 are potentially much higher that tensile or
compressive stresses and more liable to cause failure or
distortion.
[0137] The connecting means 1, as described in the preferred
embodiment, provides three principal degrees of freedom to the
connected ball over a distance sufficient to replicate the motion
of an unconnected ball, such that within the limits of this
movement, the connecting means 1 is in a unique geometric
arrangement for each possible position of the ball. The term
`degree of freedom` refers to each type of two-dimensional means of
movement made available to the connecting means 1, including the
ability to rotate at a fixed radius about a remote axis, the
ability to rotate about an axis passing part of the connecting
means 1 and the ability to move in a linear direction without
rotation. The invention is not limited in the number of degrees of
freedom provided, and as will be discussed later, additional
degrees of freedom can sometimes be advantageously provided.
[0138] In the preferred arrangement shown in the figures, the
connecting means 1 comprises three pivot joints, each capable of
partial rotation in one plane, with each joint connected in series
between the ball and the body of the apparatus and with an
interconnected member between each of the components in series. Two
of the pivot joints allow partial rotation in a substantially
horizontal plane and the other pivot joint allows partial rotation
in a substantially vertical plane. The ball is operable to move
freely in three-dimensional space over the limited region where
each pivot joint has its interconnected members at an angle which
is less than 180.degree. and where the pivot joints remain capable
of further rotation. All of the characteristics of motion, other
than spin characteristics, are measured while the ball remains in
this region. Since, within the limits of such movement, each of the
pivot joints and interconnecting members is in a unique position
for each possible position of the ball, the movement
characteristics of the ball can be determined by timing and
measuring the relative positions or angles of the pivot joints or
interconnecting members. The spin characteristics may be measured
both in this and subsequent regions.
[0139] The pivot joint which allows partial rotation in a
substantially vertical plane is the first of the three pivot joints
on the connecting means 1, closest to the ball. This relative
position has the advantage that it allows vertical movement of the
ball throughout the shot as the interconnecting member closest to
the ball rotates about the pivots which allows rotation in the
horizontal plane. If it was not the first joint, it is likely that
two degrees of freedom would be required for vertical movement,
most probably requiring an additional pivot joint.
[0140] The three principal degrees of freedom may also be provided
by alternative arrangements. For example, they may be provided by a
connecting means 1 comprising two pivot joints, each capable of
partial rotation in one plane, and one linear sliding joint. Each
joint, along with interconnected members as appropriate, is
connected in series between the ball and the body of the apparatus.
The sliding joint allows partial extension or retraction of the
distance between the ball and the pivot joint nearest the ball. The
pivot joint nearest the ball allows partial rotation in a
substantially vertical plane and the other pivot joint allows
partial rotation in a substantially horizontal plane. The ball is
free to move freely in three-dimensional space provided the sliding
joint remains capable of further movement and each pivot joint has
its interconnected members at an angle which is less than
180.degree. and where the pivot joints remain capable of further
rotation. The principal characteristics of motion are measured
while the ball remains in this region where it is free to move in
three-dimensional space.
[0141] As will be discussed later, for a ball of known
characteristics, the loft angle of the ball in a lofted shot can be
estimated from knowledge of the ball's linear speed and back spin.
In the preferred embodiment, it is therefore possible to determine
the unique position of the ball with knowledge only of the
positions of the two pivots which allow rotation in a horizontal
plane, if the back spin can be separately determined. Accordingly,
where the back spin is separately determined, the motion
characteristics of the shot, including the speed and angle of
direction of the shot, can be determined by measuring the angles of
these two pivots when the ball is in substantially free
movement.
[0142] Reference is now made to FIG. 9, FIG. 10 and FIG. 11, which
show an application of the preferred embodiment projected onto the
horizontal plane. In each of the figures, the solid lines represent
interconnecting members between pivot joints at different positions
of the ball. The broad dashed line CLM represent the movement path
of the ball, with straight line movement along CL and orbital
movement along LM. Point C represents the starting position of the
centre of the ball. In the starting position, point A represents a
pivot joint which allows movement in a substantially horizontal
plane between interconnecting member AB and the base of the
apparatus, and point B represents a pivot joint which allows
movement in a substantially horizontal plane between
interconnecting members AB and BC. Line CE represents the direction
of travel of a ball which is hit straight. Line CF represents a
selected maximum allowable deviation in the direction of travel of
a ball hit to the right and line CD represents a selected maximum
allowable deviation in the direction of travel of a ball hit to the
left. The apparatus is also provided with a pivot joint which
allows movement in a vertical plane, but which is not shown in the
figures.
[0143] Although the movement path of the ball is shown as a
straight line in the figures, in practice the movement is partly
curved to the right due to forces arising from the interconnected
members and pivot. These side forces are relatively small at the
beginning of the shot when the connecting shaft is close to being
perpendicular to the direction of travel of the ball, but increase
as the ball comes closer to the point where it is pulled into
circular orbit. In practice, the transition from straight to
circular orbit does not occur at a sharp point as shown in the
figures. The degree of curvature of the pre-orbit movement also
depends on the velocity of the shot. To simplify the figures and to
aid description, this curvature is not shown in the figures and the
movement which would otherwise be straight line movement is
sometimes referred to as substantially straight line movement.
[0144] FIG. 9 shows the arrangement where the ball is hit straight
along its intended line of direction. The starting position is
arranged such that the angle of pivot joint B, <ABC, is less
than 90.degree., and the straight shot direction is taken as the
direction parallel to AB. Accordingly, the ball will travel along
path CE if a straight shot is taken, where CE is parallel to
AB.
[0145] The apparatus is operable to accurately measure the
direction of shots over the angle range <DCE, where shots are to
the left of centre and over the angle <FCE where shots are to
the right of centre.
[0146] The apparatus is operable to measure the angle of each of
the two pivots joints which allow rotation in a horizontal plane.
The apparatus monitors these angles as the shot progresses, where
the ball is moving in substantially straight line movement, and
determines the angle of direction.
[0147] FIG. 10 shows the same arrangement but where the ball
travels to the right of center along direction CF. The
interconnecting member rotates from its starting position at AB, to
a maximum clockwise position at AP, where PQ is perpendicular to
the line of ball movement CL, and then moves counter-clockwise to
the position AK. Simultaneous measurement of the angles at both
pivot joints, while the ball is travelling along the straight line
path CL, will be sufficient to determine the angle of direction of
movement <FCE.
[0148] FIG. 11 again shows the same arrangement but where the ball
travels to the left of center along direction CD. The
interconnecting member rotates counter-clockwise from its starting
position at AB to the position AK. Simultaneous measurement of the
angles at both pivot joints, while the ball is travelling along the
straight line path CL, will be sufficient to determine the angle of
direction of movement <DCE.
[0149] The motion characteristics measured by the method of the
invention also include the spin of the ball about an axis through
the ball. This aspect of the invention provides a method for
calculation of the spin of the ball about its natural spin axis,
such as would occur if the ball was unconnected, by measurement of
the spin of the ball about different set axes passing through the
ball. The method includes connecting the ball such that it is free
to spin about these different set axes, and arranging the
connecting means 1 to provide these different set axes at
successive strikes of the ball. In a preferred embodiment, the
apparatus comprises a spin-rotation joint which is operable to
allow the ball rotate about a set axis while connected to the
apparatus. The apparatus is operable to measure the speed of
rotation and to vary the angle of inclination of the axis about
which the ball rotates. The apparatus is also operable to compute
the relative components of back spin and side spin by analysis of
the speeds of spin or rotation at different set angles of
inclination of the axis.
[0150] When a free ball is struck unevenly by a flat surface, such
as when a golf ball is struck by a golf club, a rotational motion
may be transmitted to the ball. In the case of a golf ball being
perfectly struck by a club such as a driver, the lofted club face
imparts a significant back spin to the ball, causing it to rotate
about a horizontal axis. If the ball is unevenly struck, as
frequently occurs, an additional component of side spin is imparted
and the ball rotates about a resultant axis which is inclined to
the horizontal and which is frequently understood by technical golf
players in relation to its back spin and side spin components. In
practice, over the common ranges of golf ball shots struck with
driver or low wood clubs, the axis of rotation is usually within an
angle of about.+-.10.degree. to the horizontal, the direction of
slope depending on the rotational direction of the component of
side spin. Side spin is important in the game of golf because it
can cause significant lateral movement during the flight of the
ball. If the resultant axis is tilted down to the right, the ball
will drift to the right during flight displaying what is commonly
called `slice` or `fade` for right handed players, depending on
whether the motion is unintentional or intentional, respectively.
Tilting down to the left will result in the ball drifting to the
left during flight, displaying what is commonly called `hook` or
`draw` for right handed players, again depending on whether the
motion is unintentional or intentional, respectively. The
directions are reversed for left handed players.
[0151] The method of the invention relates to an insight that when
spin is limited to rotation about a specific set axis, a golf ball
will spin about this set axis with a spin value which is
substantially equal to that which the component of its free or
unconnected spin would have, if appropriately projected onto the
specific set axis. According to the invention, the appropriate
projection is the projection of a spin vector, perpendicular to the
axis of free spin, onto a perpendicular to the specific set axis of
spin. Since the spin axis is known to lie in a plane which is
perpendicular to the direction of movement of the ball, the
projection will lie in this plane.
[0152] This is illustrated by the example of a ball which is free
to rotate about any axis and which when struck assumes a spin with
a magnitude of S about its axis of free spin, which is at an angle
of .alpha. to a fixed reference axis, such as the horizontal. If
this same ball is struck in the same manner, but its axis of
rotation is fixed at an angle .theta. to the fixed reference axis,
then the magnitude of its spin will be S.theta.=S.cos .theta.. If
the ball is similarly struck at two different set angles, .theta.1
and .theta.2, the values of which are known, two values of spin
magnitude S.theta.1 and S.theta.2 will result, which if measured
will be sufficient to determine values for S and .alpha..
[0153] In one embodiment, two set axes are used, which are tilted
at angles of equal magnitude in opposite directions relative to the
horizontal.
[0154] Reference is now made to FIG. 12 and FIG. 13, which refer to
an embodiment with two set axes tilted at angles .beta., to the
horizontal, one clockwise and the other counterclockwise to it.
Lines AF, AE and AG represent perpendiculars to the horizontal, to
the set axis tilted to the left and the set axis tilted to the
right, respectively. Line AB represents the spin vector and is of
length proportional to the magnitude of rotation of free spin, S.
It is perpendicular to the axis of free spin and is at an angle of
.phi. to the perpendicular to the horizontal, AF, and an angle of
.theta. to the perpendicular to the set axis which is tilted to the
right, AG.
[0155] FIG. 12 relates to the situation where the axis of free spin
is at a smaller angle to the horizontal than the angle of the set
axis. This results in the spin vector AB being between lines AF and
AG. A shot which would result in spin vector AB, when allowed free
spin, will result in the projected vector AD where spin is limited
to the set axis perpendicular to AD. Line BD is perpendicular to
line AG. Similarly, it will result in vector AC where spin is
limited to the set axis perpendicular to AC. Line BC is
perpendicular to line AE. Since .theta.=(.beta.-.phi.) and AB=S,
simple trigonometry yields AD=S.cos(.beta.-.phi.) and
AC=S.cos(.beta.+.phi.), where AD and AC are the measured magnitudes
of spin about the two set axes.
[0156] FIG. 13 is similar to FIG. 12, but shows a shot where the
angle of the spin axis is at a greater tilt angle than either of
the set axes. In this instance, .theta.=(.phi.-.beta.),
<CAB=(.beta.+.phi.) and again AB=S. Simple trigonometry yields,
AD=S.cos(.phi.-.beta.) and AC=S.cos(.beta.+.phi.). If absolute
values of magnitude are used and due account is taken of whether
values are positive or negative, cos(.beta.-.phi.) may be
substituted for cos(.phi.-.beta.), whereupon the relationships are
the same as those relating to FIG. 12.
[0157] When the values of the free spin vector S and .phi. are
determined, the magnitude of its components can be determined,
since back spin=S.cos.phi. and side spin=S.sin.phi..
[0158] If the two measured values, AD and AC, are found equal, this
indicates that side spin is absent. If the value of AC is found to
be greater than AD, this indicates that the spin axis is tilted
down to the left and the result is a hooked or draw shot. If the
value of AC is found to be less than AD, this indicates that the
spin axis is tilted down to the right and the result is a sliced or
fade shot. The values of measured spin about the two set axes may
be processed by a controller in various ways. For example, they may
be processed by comparing the relative magnitudes of the two
values, since there is a unique relationship between the tilt angle
of the axis of spin .phi. and the ratio of the spin values about
the two set spin axes for any given value of .beta..
[0159] In an alternative preferred embodiment, two set axes are
again used, but in this instance one axis is horizontal and the
other is tilted relative to the horizontal. Values measured when
the axis is set at the horizontal position give a direct reading of
the back spin component and completely filter out the side spin
component. If the second axis is tilted down by an angle .phi. to
the right, then where equal spin values are obtained at both axes,
this indicates that the free spin axis is tilted down to the right
by half the angle .phi., corresponding to a sliced or fade shot. If
the spin value at the tilted inclination is greater than that
obtained at the horizontal inclination, this indicates a greater
degree of slice or fade. If it is less than that obtained at the
horizontal inclination, the free spin axis may be tilted to the
left, to the right, or not tilted at all, depending on the relative
magnitudes of the two values. The relationship can be readily
determined by trigonometric analysis similar to that described in
relation to FIG. 12 and FIG. 13.
[0160] The preferred embodiment is advantageous where the apparatus
is required to additionally simulate and measure the putting shot,
because the horizontal axis setting can be used to more
realistically simulate the putting stroke. The low energy involved
in the putting stroke is also better accommodated because there are
no significant gravity effects present when the connecting means 1
operates in a horizontal plane. This embodiment also advantageously
reduces the necessary height of the apparatus relative to the
height of the ball and thereby minimises player distraction and
provides more realistic play simulation.
[0161] Various fixed axes angles .beta. or .phi. may be
successfully used in the apparatus. Increases in the tilt angle
.beta. will cause the apparatus to become proportionately more
sensitive to the measurement of the side spin component and less
sensitive to the measurement of back spin component. Increases in
the angle are advantageous because the former component is
invariably much smaller in magnitude than the latter and is more
difficult to measure. It also has the advantage that it will reduce
the proportional masking influence of any variations in the back
spin component over successive shots. The proportional influence of
the set axes angle .beta. can be seen from consideration of its two
extreme values. Where .beta. has the extreme value 0.degree., the
apparatus will directly measure the back spin component and will
not measure the side spin component at all. Similarly, where .beta.
has the extreme value 90.degree., the apparatus will directly
measure the side spin component and will not measure the back spin
component at all.
[0162] When a golf ball is struck in a drive shot, its rate of back
spin is very close to being directly related to its speed and its
loft angle. For a given speed and set of conditions, back spin and
loft angle substantially follow a unique relationship. Accordingly,
it is possible to make a close estimate of loft angle from a
knowledge of ball speed and back spin under the known conditions
which apply on the apparatus of the invention, and it is usually
unnecessary to make a separate measurement. Alternatively, the loft
angle may be determined by providing means to measure the angle of
the pivot which allows rotation in a vertical plane. The
measurement should be taken when the ball is describing
substantially straight line movement because the loft angle will be
altered by the restraining force of the arm when the ball is pulled
into orbit about the pivots.
[0163] The measurements of angle of direction and ball speed may be
influenced by loft angle because the effective length of the member
connecting the ball to the vertical-pivot, when projected onto the
horizontal plane, will change as the ball gains elevation, and this
gain in elevation is influenced by the loft angle. The projected
length will be the product of the actual length multiplied by the
cosine of the angle of the vertical pivot relative to the
horizontal. In a drive shot, the vertical-pivot angle, relative to
the horizontal, is very small, ranging up to about 4.degree., where
the apparatus has dimensions similar to those described in the
preferred embodiment. Since the cosine of 4.degree. is
approximately 0.9976, the effect of loft angle is not significant
and may be disregarded. If measurements are taken where the
elevation of the ball is much more significant, due allowance may
be made for the effective change in the projected length of the
members in the horizontal plane. When substantially straight line
movement changes to orbital movement, the orbital path is
substantially an inclined curved arc which reaches its highest
point after about 90.degree. of rotation and then gradually
descends.
[0164] In the preferred embodiment, the apparatus comprises an axis
tilt means 31 which is operable to set the axis of rotation of the
ball and ball shaft at different angles prior to the shot. As
previously mentioned, this provides a means for determining the
relative components of horizontal and vertical spin, as would have
occurred if the ball had been free or unconnected, by comparing the
rotation speeds of successive shots with the axis of rotation at
different angles. The axis tilt means is also operable to retain
the ball at the same vertical height above the playing surface 30
when the angle of the axis is changed. The purpose of this is to
avoid any noticeable change in the starting position of the ball
and to retain the same playing height or tee height between
shots.
[0165] The axis tilt means is operable to either retain the axis at
a horizontal angle or to alternate it between two angles, one with
the axis tilted downwards from the ball, and the other with the
axis horizontal.
[0166] Referring now to FIGS. 4-8, the axis tilt means comprises a
quadrilateral pivoting arm arrangement. The arrangement causes back
or forth linear movement by an electrical actuator 39 to alter the
angle of the ball 2 and ball shaft axis between an orientation
which is horizontal and one which is 10.degree. down from the
ball.
[0167] The quadrilateral arrangement has four pivots 33, 34, two
upper pivots and two lower pivots 35, 36. One upper pivot 34 and
one lower pivot 36 are pivotally connected to the base of the
apparatus. The other upper pivot 33 and lower pivot 35 are
pivotally connected to the support bushes 29 which support the
supplemental-pivot of the connecting means 1. The two upper pivots
are connected by an upper pivot connecting member 37 and the two
lower pivots are connected by a lower pivot connecting member
38.
[0168] Movement by the actuator 39 is provided by a threaded bush
40 connected to a crank member 52 connected to the lower pivot
connecting member 38. The threaded bush is linearly driven by
relative rotation of a lead screw which is powered by a small DC
motor, mounted on a trunnion support. The motor is controlled by
the controller and electrical power is taken from a rechargeable
battery. The arrangement is provided with mechanical stops at each
end of the required linear movement. The controller is provided
with an electronic circuit which is operable to readily detect and
react to changes in the back EMF of the motor drive circuit when
the motor commences stalling against the mechanical stops. The
controller is operable to stop the motor when such changes are
detected.
[0169] By careful selection of the relative positions and distances
between the four pivot centres, it is possible to cause the linear
movement to alter the ball shaft axis between the two desired
angles and to retain the ball at a constant height. In particular,
the distance between the pivots connected to the fixed base is made
greater than the distance between the pivots connected to the
support bushes on the supplemental-pivot. The upper pivot connected
to the fixed base is set back further than the lower pivot
connected to the fixed base.
[0170] FIGS. 7 and 8 show the ball shaft at angles which are
horizontal and tilted down 10.degree. from the ball, respectively.
The ball remains suspended at the same height above the playing
surface at both angle settings of the ball shaft.
[0171] Various sets of dimensions can be used with the
quadrilateral pivoting arm arrangement to achieve the required axis
tilt angles and maintain the ball at the same height. The following
dimensions have been found suitable in the preferred embodiment.
The lengths of the upper pivot connecting member and lower pivot
connecting member are 39.96 mm and 41.82 mm, respectively, measured
between pivot axes. The distance between axes of the two pivots
connected to the base is 51.77 mm. The distance between axes of the
two pivots connected to the support bushes is 42 mm. The upper
pivot connected to the support bushes has its axis 10 mm vertically
higher than the centre of the ball, and is directly above the axis
of the lower pivot connected to the support bushes, when the ball
shaft is in the horizontal position. The upper pivot on the base
side is 5.09 mm has its axis vertically lower than the centre of
the ball and 18 mm behind the horizontal-pivot axis, in a direction
which is orthogonal to the intended direction of movement of the
ball, when the ball shaft is horizontal.
[0172] Referring to FIGS. 4, 5 and 6, the pivots and pivot
connecting members are of elongated shape, the axial lengths of the
pivots being much longer than the distance between the pivots. The
elongated pivots comprise a large number of clevis joints. The
pivot axes are also aligned with the intended direction of movement
of the ball and are therefore also approximately aligned with the
direction of travel of the club, as projected in the horizontal
plane. The arrangement provides a structure which has high strength
and rigidity which is appropriately aligned to that which is
required when a drive shot is taken. It also provides an
arrangement which is clear of the normal path of the club and has a
generally low height which is unobtrusive and minimises player
distraction.
[0173] In an alternative embodiment, the axis tilt means retains
the quadrilateral pivoting arm arrangement, but comprises much
shorter pivots and pivot connecting members. The axis tilt means
additionally comprises an anchor means which securely anchors the
axis tilt means to the body of the apparatus but does not impede
the required relative movement between the axis tilt means and the
body of the apparatus. The anchor means may, for example, comprise
one or more retaining members running in one or more curved slots,
with the slots orientated in a plane which is substantially
orthogonal to the intended direction of motion of the ball.
[0174] In a further alternative embodiment, the axis tilt means may
comprise a curved sliding or rolling means which corresponds to a
portion of an arc of a circle where the centre of the circle
corresponds to the position of the centre of the ball and the ball
shaft lies along a radius from the ball to the circumference of the
circle. The arc is retained in a fixed position, and the radius,
along which the ball shaft lies, is rotated between one tilt angle
and the other. The ball remains at a fixed height at the centre of
the arc. The curved sliding or rolling means may comprise a curved
sliding track, a wheeled carriage running on a curved track or a
curved track running between fixed wheels.
[0175] Referring again to FIGS. 5-7, the apparatus includes a ball
height setting means, which is operable to vary the tee height of
the ball above the playing surface in small incremental steps. The
ball height setting means 41 comprises a manually operated hand
wheel which is directly connected to a small toothed pinion 43a
which engages a larger toothed pinion 43b. The larger pinion is
connected by a common horizontal shaft to three further similar
pinions. The four connected pinions engage with vertical toothed
racks which are positioned on the sides of two vertically lifting
blocks 45. Each block is mounted around a telescoping pillar 46
which is fixed to the base frame of the apparatus. Each pillar 46
comprises a set of concentric captive tubes, provided with low
friction bushes, with the outermost tube fixed to the block and the
innermost tube fixed to the base. The pillars are operable to
telescope upwards, providing strong support for the blocks over the
required range of tee height adjustment. When the hand wheel 42 is
rotated, the set of four pinions rotate and simultaneously lift the
racks 44 and blocks. Relatively large lift pinions are used in
order to apply the lift force close to the centre of the pillars,
thereby reducing side load forces and consequent friction and
wear.
[0176] The blocks are directly connected to the base which supports
the quadrilateral pivoting arrangement, which in turn is connected
to the connecting means 1 and ball. Thus operation of the hand
wheel results in direct vertical lifting of the ball. The operator
rotates the wheel until the required tee height is achieved.
[0177] The lifted components are maintained at the required tee
height by a ratchet and pawl 47 arrangement. The ratchet comprises
a vertical set of ratcheted teeth positioned on the rear surface of
the base which supports the quadrilateral pivoting arrangement, in
the region between the two blocks. The ratchet engages a pivoted
spring loaded toothed pawl which freely allows upward movement of
the ratchet, but prevents downward movement unless the pawl is
disengaged by a player operated disengagement means. The
disengagement means comprises a simple lever arrangement which
pulls the spring loaded toothed pawl away from the ratchet,
allowing the lifted components to descend under the force of
gravity. The telescoping pillars are provided with enclosed
pockets, which compress entrapped air when the pillars descend. The
enclosed pockets are provided with small apertures through which
the entrapped air gradually escapes and this provides advantageous
damping of the downward movement of the lifted components.
[0178] The ratchet and pawl 47 provides an advantageous rapid
method for resetting a tee-ed up ball to ground level for
subsequent fairway and putting shots. The ratchet tooth pitch also
provides an advantageous incremental range of tee height settings
allowing consistent tee heights to be rapidly achieved. A simple
scale and pointer are provided which indicates the tee height
setting level.
[0179] The ratchet and pawl 47 are shown in FIGS. 5 and 6. The
disengagement means and tee height scale are not shown in the
figures.
[0180] In an alternative embodiment, the ball height setting means
comprises a parallel motion linkage which connects the axis tilt
means to the base. The parallel motion linkage may comprise four
parallel arms of equal length, with each connected to a pivot on
the axis tilt means and pivot on a bracket connected to the base.
The axes of the pivots are orientated in a direction which is
orthogonal to the plane of the intended movement of the ball. The
linkage may be lifted to the required tee height by various means,
such as a cam or a rack and pinion arrangement and may be held in
the tee-ed position by means such as a cam or a ratchet and pawl
arrangement.
[0181] Although not shown in the figures, the apparatus also
includes a retardation means which is operable to bring the ball to
rest after a shot is taken.
[0182] In the preferred embodiment, the retardation means comprises
a deflector means against which the ball makes contact when it has
described an orbit of just less than 180.degree. about the
horizontal-pivot. Allowing the ball to move through approximately
180.degree. ensures that a lofted ball will have descended from its
orbit to a level similar to the home position level, as the jointed
movement is constrained within an approximate spherical orbit.
[0183] The retardation means also includes a buffer means which
comprises a substantially horizontal energy absorbing surface, the
top of which is at a level similar to the lower surface of the ball
in the home position. The buffer means comprises a flat flexible
receptacle of energy absorbing material, such as gel or sand, with
a tough resilient flexible cover. The buffer means is located under
the path of the ball in the region to the rear of an extended line
running along the front of the apparatus, such that it does not
obstruct the swing of the club.
[0184] The deflector means comprises a deflector plate which has a
soft but durable rubber contact surface facing the direction of the
incoming ball and inclined at about 30.degree. to the vertical.
Care should be taken to provide a contact surface which emits
minimal sound when struck. The ball is deflected downwards by the
deflector plate and its energy is substantially absorbed by the
buffer means. The deflector plate is operable to recoil from the
impact in two recoil modes. One recoil mode comprises the deflector
plate pivoting about a pivot at its base, with the pivot axis in
the plane of the contact surface. The second recoil mode comprises
the entire deflector plate and its supports pivoting away from the
impact about a horizontally orientated pivot. Each recoil movement
is ultimately retarded by soft but durable rubber stops. The
deflector plate comprises a heavy mass relative to the ball.
[0185] The recoil of the deflector plate and the vertical ground
resistance of the buffer means, both advantageously contribute to
minimising retardation forces which might otherwise cause the
apparatus to move relative to the ground when the ball is brought
to rest.
[0186] The deflector plate is also operable to fold flat onto the
buffer for storage and transportation. A safety apparatus, which
ensures that it is erect before a shot is taken, operates in the
following manner. The deflector plate is arranged such that it can
only be folded flat against the action of a spring and the ball
connecting means 1 forms part of the arrangement to hold the
deflector plate flat for storage or transportation. The deflector
plate must be unfolded to the erect position before the connecting
means 1 can be released to allow operation of the apparatus.
[0187] The retardation means also includes a spring which is
operable to return the retarded ball and ball shaft back to the
playing area when the shot is complete. The spring movement is
limited such that it does not influence the motion of the ball when
it is above the play area.
[0188] The inner parts of the connecting means 1, the axis tilt
means and the ball height setting means are enclosed within a
protective housing. The housing has a front and side aperture
through which the ball, ball shaft and outer ball shaft casing
protrude and which allows movement of the ball and ball shaft. The
electronic components, including the controller and display screen,
are mounted within the housing or above the housing in a sealed
controller enclosure. The housing is also provided with a
protective club buffer to prevent damage to the apparatus or the
club, or injury to the player, in the event of the club
inadvertently striking the housing. The club buffer comprises a
resilient rubber moulding fixed to the side of the housing or
mounted from the base. The moulding has a sloping surface to
deflect rather than abruptly stop movement of the club.
[0189] A playing surface, comprising a durable mat and simulated
grass surface, is provided under the region of the ball. The
playing surface is provided with one or more lines or patterns to
indicate the direction of a straight shot to the player. The
playing surface is also provided with a tee position marker to
assist the player in returning the ball to the home or starting
position. The player stands on a platform to elevate his or her
ground height to that of the playing surface. The playing surface,
housing, ball shaft and outer ball shaft casing are arranged to be
as visually unobtrusive as is practically possible. Ideally, they
are provided in a dark contrasting colour to the ball, such as dark
green, dark grey or black. They may also be provided with
camouflage type irregular textures or markings.
[0190] It is important that the apparatus provides the required
functions with minimal height at the top of the housing, both
relative to the ball and to the ground. In the preferred
embodiment, the top of the housing nearest the player is similar to
or slightly below the height of the top of the ball. This part of
the housing is about 90 nm above ground level.
[0191] The controller is connected to a display screen, a player
selector means and an external signal output port.
[0192] The display screen is directed towards the player to allow
it to be readily viewed without the need for the player to vary his
or her stance between successive practice shots. This is
advantageous for the player in isolating and correcting faults or
improving specific aspects of play. The apparatus is operable,
following each shot, to display values on the screen to indicate
the distance the shot would have travelled, if it had been a free
or unconnected ball on an open course, and the deviation to the
right or left of centre which it would have taken. In addition, it
is operable to indicate the proportion of the deviation which is
due to incorrect direction and the proportion which is due to hook
or slice. Further trajectory details, such as roll-on, may be
included, if required. The controller and screen are operable to
display these values in various ways. For example, they may be
displayed as simple values for the last shot played or they may be
displayed in a statistical manner related to previous shots,
details of which are memorised by the controller. The player
selector means may comprise a keypad which operates in conjunction
with instructions and choices displayed on the screen. The player
selector means is used by the player to select various options
including the required type of display or settings which simulate
different types of playing conditions.
[0193] Over the course of a shot, the controller monitors the
status of the ball-spin-rotation sensor, horizontal-pivot sensor
and supplemental-pivot sensor, recording the characteristics of the
detected signals. The angle of direction of movement and the speed
of movement are computed over the period when the ball has departed
from the clubface and substantially straight line movement takes
place. This has several advantages. The measurements are little
affected by the elevation of the arm. The measurements are carried
out before possible distortion arises from the shock or strain when
the ball is pulled into circular orbit. The computations are more
acceptable to the player because the measurements are known to be
taken with the ball is in realistic straight line movement.
[0194] The direction of movement of the ball can be determined by
measurement of the angles at the horizontal-pivot and
supplemental-pivot because the connecting means 1 is in a unique
arrangement for each possible position of the ball, within the
limits of such movement.
[0195] For a given ball and set of playing conditions, hitting a
ball in a specific manner will always result in the same movement
characteristics. A mathematical model can be derived which
theoretically links the inputs from the various sensor means on the
apparatus to the movement characteristics of the connected ball.
The mathematical model can be extended to theoretically link the
movement characteristics of the connected ball to the movement
characteristics of an unconnected ball. When a mathematical model
is constructed, the calculations can be executed by conventional
sequential electronic processing methods. However, a completely
different method and means to determine the movement
characteristics of the unconnected ball is used in the preferred
embodiment of the invention. This method and means is described
below.
[0196] The apparatus is provided with a measurement means, which is
operable to pre-process or convert the primary signals from the
sensor means into data which can be more readily processed in a
subsequent stage. For example, the light pulses from the
horizontal-pivot and supplemental-pivot sensor means may be
pre-processed or converted to a single vector from the starting
position of the centre of the ball to the moving position of the
centre of the ball, as the shot progresses, and the light pulses
from the ball spin-rotation sensor means may be pre-processed or
converted to a changing angle of spin-rotation, as the shot
progresses. This pre-processing stage is carried out by
conventional electronic processing methods and apparatus. The
mathematical models are readily derived by methods including
trigonometry and interpolation.
[0197] The measurement means is also operable to interpret the
pre-processed results in terms of the motion characteristics of an
unconnected ball, by using an artificial neural-type intelligence
means which has been previously trained with information relating a
wide range of pre-processed results to resulting motion
characteristics of an unconnected ball. By artificial neural-type
intelligence means is meant, determination or problem solving
means, which operate in a manner which has similarities to human
determination or problem solving. In particular, this type of
determination of problem solving relates to previously learned
experience from which a solution can be determined or interpolated
when a new problem or situation arises. A typical characteristic of
this type of determination or problem solving is the use of
multiple parallel determination or calculation paths, leading to a
solution, rather than a single sequential calculation path as
occurs with conventional electronic determination or calculation.
Proprietary software and hardware means are available to effect
artificial neural-type intelligence, and the preferred embodiment
comprises a type commonly referred to as an artificial neural
network. An appropriate version uses a trained feed forward system,
which produces relevant outputs when relevant information is fed to
a set of inputs. A typical example of a simple neural net function
is given by y=f tan h(dx+b)+g tan h(ex+c)+a where y is the output,
x is the input and a to g are training weights. The hyperbolic tan
function tan h is a non linear function that can be used with the
weights to model the desired process. The network comprises a vast
number of functions of this type where weights are automatically
adjusted as training progresses. The training and learning process
is carried out on a training unit and the results are replicated on
production units of the same characteristics by appropriate
electronic programming of their measurement means.
[0198] Training of the artificial neural-type intelligence means is
carried out using an artificial ball striking means, which is
operable to strike the ball in a consistent and repeatable manner
and which is operable to be set with variable repeatable settings
relevant to the game. In the present instance, the striking means
will be referred to as a mechanical golfer. Arrangements are made
such that the mechanical golfer can carry out pairs of shots, with
equal settings, where one shot strikes the connected ball and the
other shot strikes an unconnected ball which is positioned in the
same spatial relationship to the mechanical golfer. The mechanical
golfer is operable to be set with various ranges of club face
settings, including velocity, direction, loft and oblique angle.
When each pair of shots is taken, the pre-processed signals from
the sensor means provide the inputs and the measured results from
the unconnected shot provides the corresponding output. Each set of
inputs and outputs is fed into the artificial neural-type
intelligence means in an appropriate format to provide a training
element. When the artificial neural-type intelligence means has
received sufficient of these training elements, spanning examples
of the range of possible shots which the apparatus is expected to
measure, the artificial neural-type intelligence means will then be
operable to predict the outputs corresponding to any shot within
the range of the training.
[0199] In the preferred embodiment, training is carried out for
different categories of shots, and different or partly different
networks or programs developed for each category. Taking two
extreme examples, different training routines and resulting
programs are appropriate for drive shots and putting shots. The
motion characteristics of these categories of shot have little in
common in relation to learned experience and the artificial
neural-type intelligence means is more readily trained and performs
better where they are treated as separate categories. The
categories of shot which are intermediate between drive and putting
shots may also be treated as separate categories, although the
proportion of shared motion characteristics increases. Training
categories may also be advantageously devised for different playing
conditions. For example, training may be carried out on a apparatus
with a standard connected ball, matched against shots with
different types of unconnected balls. Inclusion of these programs
on the apparatus will allow selection from a range of ball types,
with the motion characteristics of the selected ball type
accurately represented without the need to change the connected
ball on the apparatus.
[0200] The measurement means determines the appropriate category of
shot in various ways. Distinguishing between drive shots, putting
shots and intermediate categories, can be achieved by analysis of
the approximate magnitudes of the forward speed and backspin of the
connected ball. This determination may be carried out during the
primary signal pre-processing stage. Where a setting selection is
carried out, as in the example of selected ball type mentioned
above, the determination may be made by player manual selection or
automatic selection by a remote apparatus, such as computer running
a simulated golf game.
[0201] Interpretation and presentation of the result outputs from
the artificial neural-type intelligence means may be carried out by
conventional electronic processing methods.
[0202] The use of an artificial neural-type intelligence means, in
the manner described above, has several important advantages
compared to conventional methods and means. It is capable of more
accurately replicating real play. It is capable of replicating play
without the need to understand the underlying mechanics of the
movement characteristics. It remains open to increased refinement
by further training. It is more acceptable to the player because it
is based on actual golf play measurement rather than theoretical
calculation.
[0203] The measurement means is also arranged to be selectably
adjusted by the player or by other inputs, such as a game
simulation program, to show the motion characteristics which would
result with different playing conditions or different playing
circumstances. The example of different ball types has already been
discussed. The measurement means can also be appropriately
adjusted, for example, to allow for different ground or wind
conditions. Ground conditions include ground hardness and
roughness, which affect how far a ball will bounce or roll. Ground
conditions also include the slope of the ground.
[0204] The measurement means is additionally arranged to permit
calibration of the apparatus. This allows the apparatus to be
checked and reset without the need to make mechanical adjustments.
In the preferred embodiment, the measurement means is provided with
a calibration mode which can be selected using the player keypad.
One or more test shots are taken, ideally with a test apparatus
such as a mechanical golfer with known characteristics, and the
results entered using the player keypad. The measurement means is
automatically adjusted to correspond to the test results.
[0205] Visual feedback plays no real part in the high speed golf
shots, such as the drive shot, because the typical human reaction
time for this sense is much longer than the period over which the
shot is taken and a ball will have travelled far from its starting
position before any visual feedback is registered. The player's
actual perception comprises a mixture of the feel of the twist or
momentum change in the club head experienced at the top of the club
shaft, the sound of the shot and varying psychological
preconceptions. The feel of a normal shot experienced through the
wrists is far less important than is commonly believed. Although a
player will feel the effect of a very bad shot transmitted through
the golf club shaft, there is little or no perceptible difference
in the feel of a good and a very good shot, with respect to the
sense of touch. Similarly, where inertia effects are correctly
minimised in the apparatus, there will be little or no perceptible
difference between it and the feel of an unconnected shot. The
sound of the shot is far more important than is commonly recognised
and includes the sound of the impact between the ball and club and
the aerodynamic sound of the ball travelling through the air. The
aerodynamic component does not naturally occur with the apparatus
because the ball is held captive by the connecting means 1. To
increase the realistic feel of the shot, the apparatus is provided
with a sound synthesiser means which is operable to replicate or
exaggerate the sound of an unconnected ball when a shot is taken.
Exaggeration of aspects of the sound can be advantageous in
screening any sounds which the apparatus may make which differ from
the natural shot. The controller is operable to rapidly interpret
the type of shot and trigger the sound synthesiser means to deliver
the appropriate sound through a sound emitting means such as a
speaker. In the preferred embodiment, the sound synthesiser means
comprises a conventional electronic apparatus, which is programmed
with the appropriate range of sounds.
[0206] If not otherwise restrained, the rotation and retardation of
the moving parts of the apparatus could cause it to move relative
to its ground position. As previously mentioned, this tendency to
movement is reduced by the use of recoil elements in the
retardation means. The movement is also prevented by the employment
of restraining means. In the preferred embodiment, the apparatus is
connected to the platform upon which the player stands and the
weight of the player and platform prevent movement of the
apparatus.
[0207] The apparatus is provided with a small free standing safety
net to protect against the unlikely event of the ball or other
parts breaking away from the apparatus during a shot. The safety
net is of much lighter construction than a typical golf practice
net because it is permissible for the safety net to travel a small
distance when restraining moving parts and also because it does not
require to be operable for frequent use. The safety net is also
much smaller than a practice net because it can be positioned
closer to the apparatus than a practice net, which requires the
player to observe the movement of the ball into the net.
[0208] An external signal output, such as an output port, is
provided to allow the apparatus to be optionally connected to
peripheral processing and display equipment, such as computers,
computer screens and digital projectors, or to external
communications systems, such as telephone or internet connections.
The external signal output communicates the relevant signals from
the apparatus and is provided at little additional cost. When
appropriately programmed, the peripheral equipment may, for
example, project a simulated three dimensional representation of
the shot on a relatively large screen or display it on a computer
monitor. The external output may also used to communicate details
of the shot to equipment programmed to assist player instruction,
either as an aid to an instructor working with a player or as an
interactive aid used by the player without the need for the
presence of an instructor. The external output may additionally be
used to assist fitting and selection of golfing equipment or to
provide an input to golf simulation gaming equipment. By connection
to a remote communication apparatus, it also allows two or more
players, in remote locations to each other, to play a simulated
game of golf.
[0209] The following dimensions have been found suitable for use
with the preferred embodiment of the invention. The ball has a
diameter of 42 mm and a compression of 90. Its centre is 185 mm
distant from the centre of the horizontal-pivot axis. The ball is
set back in a horizontal plane in the home position, at an angle of
78.degree., measured relative to the intended direction of travel.
The ball shaft comprises hardened aluminium alloy 7075 in T6
temper. It is of hollow circular cross section and has a constant
internal diameter of 6.8 mm along its length. It has an external
diameter of 11 mm along the region within the ball and has a
continuous external diameter of 16 mm in the region within the
outer ball shaft casing. The external diameter tapers between 11 mm
and 16 mm in the region between the ball and the outer ball shaft
casing. The centre of the horizontal-pivot axis is 20 mm distant
from the centre of the vertical-pivot axis and 50 mm distant from
the centre of the supplemental-pivot axis. The outermost section of
the inner ball shaft casing and ball shaft receiver is 44.5 mm from
the centre of the horizontal-pivot axis. The outermost section of
the outer ball shaft casing extends 30 mm beyond the outermost
section of the inner ball shaft casing and ball shaft receiver. The
centre of the horizontal-pivot axis lies 40 mm within the perimeter
of the protective housing.
[0210] The ball spin-rotation vane, horizontal-pivot vane and
supplemental pivot vane have external radii of 14 mm, 18 mm and 35
mm, respectively. The vanes are produced in stainless steel with a
thickness of around 0.2 mm in the region of the vane slots and with
a slot dimensional accuracy of.+-.0.02 mm. In an embodiment with
optical fibres of 1 mm diameter, the slot and tooth width on the
vanes is approximately 0.5 mm and the radial slot depth is around
1.75 mm. The width of the collimating slots on the bridging means
is 0.5 mm and the distance between the emitting and detector fibres
is 2 mm. The slot spacing on the ball spin-rotation vane,
horizontal-pivot vane and supplemental pivot vane is approximately
4.5.degree., 3.5.degree. and 1.75.degree., respectively. All of
these values are proportionately reduced where optical fibres of
smaller diameter are used. Optical fibres of 0.5 mm diameter are
used where the production process is capable of controlling tight
dimensional tolerances.
[0211] It is to be understood that the invention is not limited to
the specific details which are described herein by way of example
only and that various modifications and alterations are possible
without departing from the scope of the invention as defined in the
appended claims.
[0212] In particular the applicant retains the right to redefine
the invention by amending the claims to different combinations of
features recited in and between the different groups of claims.
* * * * *