Computer golf club

A golf ball distance computer built entirely into a golf club utilizing a molecularly polarized piezoelectric plastic film composite as a ball impact transducer.

BACKGROUND OF THE PRESENT INVENTION 
There have been a plurality of attempts over the last several decades to 
incorporate electronic swing analyzing devices directly into golf clubs, 
particularly into "wood" clubs, bearing in mind that today's "wooden 
clubs" are constructed of metal and other materials such as compression 
molded graphite, besides natural wood. 
Such swing analyzing devices include swing angle sensing devices that use 
orthogonally related accelerometers located within the club head to 
provide club head deceleration signals occurring during impact to 
analyzing circuitry located externally of the club head, and a ball 
distance computer driven by a single accelerometer mounted within the club 
head providing club head deceleration signals to an analyzing circuitry 
mounted within the club head grip. 
While there appears to be a demand for such self-contained club swing 
analyzing devices, none has achieved any degree of commercial success thus 
far for a plurality of reasons. Firstly, there has been a general 
misunderstanding in the prior art with respect to the physics involved in 
club-ball collision, and there has also been a failure to provide accurate 
conditioning signal production and proper signal modification to achieve a 
proportional representation of the sensed condition. For example, in a 
known distance computer, an accelerometer is employed to sense club head 
deceleration during and after ball impact. While club head deceleration is 
one parameter that determines ball exit velocity from the club face, it 
cannot by itself provide an accurate determination of ball exit velocity 
without knowing the time of impact between the ball and the club or 
initial club head velocity. The correct collision theory formula for 
determining ball exit velocity V.sub.b2 is m.sub.1 V.sub.b1 
+.intg.Fdt=m.sub.2 V.sub.b2, where the V.sub.b1 =initial ball velocity, 
m.sub.1 =initial mass of ball, F=impact force between the ball and the 
club, and t=the time of impact between the ball and the club, m.sub.2 
=final ball mass, and V.sub.b2 =the exit velocity of ball from the club. A 
similar equation may be derived with respect to the club head as opposed 
to the ball during collision. 
Since initial ball velocity is zero and mass m is constant, it can readily 
be seen that final ball velocity V.sub.b2 is proportional to the integral 
.intg.Fdt or more simply expressed, exit ball velocity is proportional to 
the average impact force between the ball and the club head multiplied by 
the time duration of impact. Thus one problem in prior art devices for 
measuring ball distance is that they do not take into account the duration 
of impact between the ball and the club. 
This time duration of impact can be expressed in laymen's terms as the 
follow-through of the club impacting on the ball, and the longer the time 
period of impact the greater the exiting ball velocity and the greater the 
distance the ball travels. 
Another deficiency in built-in swing analyzing devices and particularly 
ball distance computers is that known sensing or transducing devices 
cannot be readily built into the club head either because they are not 
sufficiently durable or because they alter the weight, swing-weight or 
torquing characteristics of the club. Even a small additional weight added 
to the club head alters swing-weight significantly, for example 1.0+ grams 
added to the club head increases the swing-weight of the club one full 
swing-weight, e.g. from D-1 to D-2, in addition to increasing the overall 
weight of the club head. While this weight addition can be compensated in 
terms of swing weight by adding weight to the butt end of the shaft, such 
a compensating maneuver is not desirable because it further increases the 
overall weight of the club. Thus, these prior built-in sensing and 
computing devices have not been acceptable because they either varied the 
club's swing weight or the overall weight of the club, or both. 
Built-in swing sensing and computing devices have also not demonstrated an 
acceptable level of durability to withstand the high force impact, 
frequently over 50 lbs., generated in the few milliseconds or less of 
impact time. 
Furthermore, in all of the prior literature on built-in swing analyzing 
devices there is a notable lack of technology with respect to specific 
transducer constructions and the exact method of attaching the transducer 
to the club head. 
Another problem in these prior systems is that they do not take into 
account the non-linear relation between ball-club impact and ball travel 
distance. 
A ball distance computing device manufactured by Mitsubishi Corp. has 
achieved some degree of commercial success even though the sensing device, 
computer circuitry and visual display are external to the club head. This 
system utilizes a Hall effect transducer in a floor mat driven by magnetic 
tape attached to the club head, and while this system has been found 
satisfactory for many purposes, it produces inaccuracies in the ball 
distance computing function because of the failure to measure ball impact 
time, because of misapplication of the magnetic tape to the club head and 
failure to account for club head mass, and because exact club head loft 
angle is not considered, all of which control ball travel distance. 
An example of a built-in ball distance computer is shown and described in 
the Farmer U.S. Pat. No. 4,088,324 and it utilizes an accelerometer in the 
club head in an attempt to compute ball distance. Accelerometers built 
into the club head are also shown in the Evans U.S. Pat. Nos. 3,788,647; 
3,806,131 and 3,270,564 as well as the Hammond U.S. Pat. No. 3,945,646, 
for generating information relating to ball striking direction as well as 
club velocity and acceleration. 
It is a primary object of the present invention to ameliorate the problems 
noted above in club built-in swing analyzing devices and particularly to 
club self-contained distance computers. 
SUMMARY OF THE PRESENT INVENTION 
In accordance with the present invention a golf ball distance computer is 
provided incorporated entirely within a conventionally styled club without 
significantly altering the swing-weight, total weight, feel or durability 
of the club. 
Toward this end the present computer club is provided with a transducer 
built into the forward face of a metal club head that produces signals 
representing the impact force and duration of impact between the ball and 
the club, and signal processing circuitry built inside a conventional 
"Tru-Temper".sup.* shaft that drives an LCD display built into a grip cap 
at the butt end of the shaft. The transducer is a polarized piezoelectric 
polyvinyladin fluoride bimorph that has a shape corresponding to the front 
face of the club head. It provides accurate impact readings almost 
entirely across the club face. 
FNT *Reg. TM of Tru-Temper Corp. 
The club head itself is preferably investment cast stainless steel having a 
wall thickness of approximately 0.125 inches throughout except for the 
forward wall, ordinarily the ball striking wall of the club, which is 
0.080 inches. This latter wall thickness has been found necessary to 
provide club face structural integrity and to achieve reduced club head 
subassembly weight. For a men's driver, an exemplary overall club head 
weight is 205 grams and this weight can be achieved with a conventional 
0.125 inch walled stainless steel club filled with a suitable foam 
material. 
The forward wall a reduced thickness compensates for the additional weight 
of the remaining transducer components. This forward wall has a uniform 
thickness and has roll and bulge identical to the desired roll and bulge 
for the club face, i.e. vertical plane radius and horizontal plane radius. 
The transducer bimorph is mounted on the forward surface of this forward 
wall and in one embodiment has an L-shaped copper conductor sandwiched 
between the films that extends through a diagonal slot in the wall into 
the hollow interior of the club head adjacent the club head hosel. 
The transducer and forward wall of the club head are covered by a face 
plate that defines the ball striking surface. This face plate is 
constructed of a die cast high-impact magnesium alloy and is fastened to 
the club head forward wall by four threaded screws that impale the 
transducer. The face plate has score lines or grooves molded in so that no 
machining is required of this piece and is approximately on the order of 
0.080 inches thick so that the total effective forward wall is 0.160 
inches, significantly thicker but lesser in weight than the conventionally 
employed 0.125 inch stainless steel forward wall. The face plate has a 
uniform thickness with the same roll and bulge as the forward wall of the 
club head. The face plate with the forward stainless steel wall provide an 
effective forward wall strength greater than presently known stainless 
steel club head constructions while at the same time provide a somewhat 
lesser overall club head weight that compensates for the 5-10 gram weight 
of the transducer, connectors, cable, and associated supporting posts. 
The transducer itself is extremely thin, on the order of 102 um. so that 
its contribution to the increase in effective thickness of the forward 
wall and is insignificant. An important advantage of the present 
transducer is its capability of conforming to the roll and bulge radii on 
the forward wall, which it can do because of the flexibility of the 
polymer film from which the transducer is constructed. During manufacture 
the transducer is applied to the forward wall of the club head and then 
coated with an epoxy film along with the surrounding portions of the 
forward wall and plate. The face plate is then placed over the forward 
wall and threaded down tightly with the fasteners. This pots the 
transducer between the face plate and the forward wall without any voids 
and reduces face plate vibration that would otherwise provide unwanted 
transducer signals, and at the same time improves impact "feel" of the 
entire club. 
In assembling the transducer subassembly, the positive or+sides of the two 
polyvinyladin fluoride films are placed toward one another so that the 
negative sides of the films face outwardly and engage the club head 
forward wall and the face plate. In this way the club head face plate, and 
shaft themselves form an effective ground and excellent electrical shield 
for the transducer and its circuit without any additional components. In 
one embodiment of the present invention both the club head and the club 
shaft are electrically conductive and connected together so that they 
shield both the transducer and a conductor connecting the transducer to 
the shaft mounted circuitry eliminating the need for a coax type cable 
with its cost and extra weight. 
The circuit components are mounted on an elongated circuit board carried 
within the butt end of a conventional 0.620 inch butt diameter club shaft. 
The PC board is mounted in the shaft parallel to the shaft axis with 
several "O" rings in a very inexpensive fashion while at the same time 
providing a shock mount for the board. 
The transducer provides a somewhat sinusoidally shaped pulse at impact 
representing the force of impact with a time base equalling the time 
duration of impact. The circuitry integrates this signal, thereby deriving 
a signal proportional to the impulse delivered to the ball, i.e. the 
parameter .intg.Fdt defined above, proportional to the ball exit velocity 
V.sub.b2. The circuitry utilizes this signal to drive an LCD driving 
circuit that in turn drives the LCD indicator mounted in the end cap. 
While the circuitry and LCD add several grams to the overall weight of the 
club, this additional weight can be utilized to offset any small increase 
in weight in the club head, if that be necessary, without affecting 
swing-weight and these several grams have negligible effect on the overall 
club weight feel since the overall club weighs on the order of 340 grams.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings and particularly to FIGS. 1 to 8, a computer 
driver golf club 10 is illustrated consisting generally of a club head 
assembly 11, a shaft 12, a grip 13 and a grip end cap assembly 14. The 
club head assembly 11 includes a tranducer assembly 16 that derives 
signals responsive to impacting the club head 11 against a golf ball, that 
are conducted through a coaxial cable 17 (FIG. 5 and 8) extending through 
the club head 11 and the hollow shaft 12 to a circuit assembly 19 mounted 
within hollow shaft 12 adjacent its butt end (see FIG. 12) that drives a 
visual display LCD assembly 21 contained within the end cap assembly 14 in 
a manner to display directly total yardage traveled by the impacted ball. 
The club head assembly 11 also includes an investment cast stainless steel 
club head 24 and a magnesium alloy face plate 26. Club head subassembly 24 
is by itself similar in design to many stainless steel "wooden" club heads 
manufactured today. That is, it is an investment casting constructed of a 
fairly low chromium content stainless steel with a substantially uniform 
wall thickness of approximately 0.125 inches, except that its forward wall 
27 has a somewhat lesser thickness than the remaining portions of the club 
head and preferably has a thickness on the order of 0.080 inches. Club 
head subassembly 24 is heat-treated to a hardness on the Rockwell-D scale 
of approximately 30 and is seen to generally include a spheroidal top wall 
28, spheroidal forward wall 27, spheroidal side wall 30, sole plate 31 and 
hosel 33. The geometry of the top wall 28, side wall 30, sole plate 31 and 
hostle 33 is conventional. 
The forward wall 27 is smooth without any score lines and is of uniform 
thickness having a roll and bulge identical to that desired on the face 
plate 26. For example, the forward wall 27 may have a bulge radius, i.e. 
radius in a horizontal plane, of 10 inches, and a roll radius, i.e. radius 
in a vertical plane passing through the center line of the club head, of 
10 inches. 
The reduced thickness of the forward wall 27 compensates and offsets the 
added club head weight of the transducer 16 (almost negligible) and the 
lightweight magnesium face plate 26. There is however no loss in forward 
wall strength because of the supporting and strengthening function 
provided by the face plate 26. The magnesium face plate 26 also has 
excellent vibration dampening characteristics which not only improve club 
"feel" but also improve the shape of the transducer signal. 
The magnesium face plate 26 has an outer configuration complementary to the 
forward face 27 of club head subassembly 24 and is fastened to the club 
head forward face 27 by four threaded fasteners 34, 35, 36 and 37 that 
threadedly engage threaded bores 39, 40, 41 and 42 in the club head 
forward face 27. Face plate 26 is preferably constructed of a high impact 
magnesium alloy such as AZ91B which contains 99% Al., 0.13 Mn. and 0.7 Zn. 
as alloys. Since face plate 26 has a uniform thickness of 0.080 inches, 
the effective composite forward wall thickness is approximately 0.160 
inches, some 0.035 inches thicker than the conventional 0.125 inch walls 
found in today's stainless steel club heads. This additional thickness 
compensates for the somewhat lesser strength of the magnesium alloy plate. 
Because magnesium is five times lighter than stainless steel the combined 
forward wall assembly has a somewhat lesser weight than a standard club 
head with a 0.125 inch forward wall. The added weight of the transducer, 
connectors, cable and circuit board results in overall club weight equal 
to a conventional club with about the same swing weight because the 
circuit board weight at the butt end balances the transducer, connectors 
and effective cable at the head end in the 2 to 1 swing weight ratio. 
The face plate 26 has a roll and bulge on both sides thereof equal to the 
roll and bulge on the forward club head wall 27, and it has horizontal 
grooves 45 and two converging generally vertical grooves 46 and 47 
therein. 
The transducer assembly 16 is complementary in shape to the face 27 but 
0.030 inches smaller and is a bimorph of two polyvinyladin fluoride films 
50 and 51 that sandwich an "L" shaped copper plate conductor 53 having leg 
portions 54 and 55. Each of the films 50 and 51 is molecularly polarized 
with a high-energy electrical field by known polarization techniques to 
provide the desired piezoelectric effect. One such piezoelectric film that 
has been found satisfactory is manufactured under the trademark "Kynar" by 
Pennwalt Corp. 
The films 50 and 51 each have a thickness of approximately 52 um. and are 
sufficiently flexible to conform to both the roll and bulge of the forward 
wall 27 and face plate 26 as seen clearly in FIGS. 10 and 11. Both 
surfaces of the polarized films 50 and 51 have conductive aluminum alloy 
coatings (electrodes) 56, 57, 58 and 59 with electrodes 57 and 58 being 
positive and electrodes 56 and 59 being negative. The films are bonded 
together with a uniformly applied contact adhesive. This arrangement 
grounds the transducer to both the club head 24 and face plate 26. In this 
way the club head 24 and the face plate 26 serve to electrically shield 
the transducer 16 from undesirable transients. 
The "L" shaped plate conductor 53 is in electrical contact with both 
positive electrodes 57 and 58. The conductor or terminal 53 has a width of 
approximately 0.25 inches and a thickness of approximately 0.010 inches 
except that leg 54 as seen in FIGS. 4 and 10 may be thinned down to 0.006 
inches to minimize the space between the forward wall 27 and the rear of 
face plate 26. The terminal leg 55 extends through a diagonal slot 52 in 
film 50 and complementary aligned slot 52a in club head forward wall 27 
into the hollow interior of the club head. Slot 52a is positioned near the 
hosel end of the club head 33 approximately on a line between fasteners 36 
and 37. 
In assembly, the transducer assembly 16 is temporarily attached to forward 
wall 27 and face plate 26 with a uniformly applied high-strength contact 
adhesive. This assures that there will be no relative movement between the 
face plate 26, the forward wall 27 and the transducer assembly 16, and in 
this manner unwanted vibration of the elements are eliminated or minized 
so that they are not seen by the transducer 16 thereby providing improved 
signal generation. 
As seen in FIG. 8, cable 17 is a small gauge coax-type cable such as 174 U 
and is seen to include central conductor 60 surrounded by insulation, an 
annular conductive mesh sheath 61 and an outer layer of insulation 62. A 
conductive support post 64 is fastened to the rear of forward wall 27 by a 
threaded fastener 65 and has an upper portion 67 that surrounds and clamps 
against the ground sheath 61. In this way the cable 17 is grounded to the 
club head 24 and face plate 26 though screws 34, 35, 36 and 37 and 
transducer 16. The central conductor 60 is connected to terminal 53 by 
soldering at 70 and is conveniently held in position during soldering by 
the support post 64. 
Alternatively and as seen in FIG. 9 an unshielded conductor 68 may be 
provided utilizing the club head 24 and the club shaft 12 to shield the 
conductor 68. In this case the shaft 12 is conductive and connected to 
club head 12 by a conductive epoxy. Circuit 19 is then grounded to shaft 
12 as well. This eliminates the need for the somewhat more costly and 
heavier coaxial cable 17 in the FIG. 8 embodiment. 
As an alternative to the "L" shaped terminal 53, and the bimorph lamination 
of transducer 16, a single film transducer can also be employed with an 
integral coplanar tab that extends through the slot 52a into the club head 
interior. The tab has laterally spaced positive and negative terminals, 
that are continuation of the electrode coatings on the film, to minimize 
unwanted signal generation. The positive terminal is connected directly to 
conductor 60 with a conductive epoxy and the negative terminal connected 
to the coax sheath 67 by a small conductor also with conductive epoxy. A 
non-conductive film covers the positive side of the film isolating it from 
the face plate 26. This eliminates the terminal 53 from between the face 
plate 26 and design wall 27, providing a more uniform thickness transducer 
and improved signal uniformity across the club face. 
It is also possible to construct the face plate of stainless steel and in 
this case its thickness is 0.060 to 0.080 inches depending upon the 
thickness of forward wall 27. The thickness of both should be equal with a 
total thickness in the range of 0.140 to 0.170. 
The transducer 16 with the construction of face plate 26 "sees" only forces 
normal to the surface of the transducer 16. This is important because the 
polarized films 50 and 51 have piezoelectric effects in three directions 
and since it is not possible to electrically isolate these three effects, 
it is important that the transducer see only the forces desired to be 
measured and in this case the force desired to be measured is the normal 
force to the transducer compressing the films 50 and 51. In this way the 
transducer 16 provides a signal upon ball impact with the face plate 26 
proportional to the normal compression of the films 50 and 51 with a time 
duration equal to the time of contact of the ball with the face plate 26. 
These signals are illustrated in FIGS. 16 and 17 for low-force and 
high-force impacts respectively and as shown are actual signals, without 
any signal processing and prior to receipt by the computing circuitry 19 
illustrated in FIGS. 12, 14 and 15. 
The club shaft 12 is a standard stepped tapered tempered steel club shaft 
having a constant diameter portion 75 in club head hosel 33 and an 
enlarged constant diameter portion 76 within grip 13 having an outer 
diameter of 0.620 inches and an inner diameter of approximately 0.580 
inches. Tru-Temper Corp. manufactures a club shaft of this configuration 
that performs adequately. 
The circuit assembly 19 receives the transducer compression signal from 
cable 17 as seen in FIG. 12 and includes an elongated narrow circuit board 
78 having a first pair of opposed slots 79 in the sides thereof axially 
spaced from a second pair of opposed slots 80. Slots 79 and 80 receive 
torroidal rubber rings 81 and 82 that support and shock mount the circuit 
board 78 within the butt end portion 76 of the shaft 12. Circuit board 78 
carries a low-voltage cylindrical battery 82, power supply components 83 
and IC components 85 and 87 that provide integrator, memory and LCD driver 
circuitry functions described in more detail with respect to FIGS. 14 and 
15. The LCD driver is connected through conductors 84 to a PC board 89 in 
the LCD display assembly 21. 
As seen in FIG. 12, end cap 14 is generally annular in configuration and 
includes an enlarged flange portion 88 having an outer diameter equal to 
the outer diameter of the grip 13 at the butt end thereof, and a reduced 
annular portion 90 having an outer diameter equal to the inner diameter of 
the shaft portion 76. Annular portion 90 receives one end of the circuit 
board 19 and a roll pin 91 pressed through diametrally opposed bores 92 
and a hole 93 in circuit board 78 to attach the circuit 19 to the end cap 
14 so that upon removal of the end cap 14 the entire circuit 19 is 
removed. 
The outer end of the cap 14 has a circular recess 96 therein having a 
bottom wall 97 with an aperture 98 therein communicating with the interior 
of annular cap portion 90. A membrane switch 149 is mounted in the bottom 
of the recess for turning the circuit 19 on and off when the display 21 is 
pressed by the user's thumb. 
The LCD assembly 21 is entirely contained within circular recess 96 and is 
seen to include an annular bezel 100 having a rim 101 that holds together 
a transparent lens 102, a plastic generally circular plastic frame 104 
with a recess 105 that receives an LCD element 108, a rubber conductor 110 
and a printed conductor board 85 to which conductors 84 are attached. LCD 
driving signals are conducted from conductor board 85 to the LCD display 
108 through the rubber conductor 110 in a fashion similar to the displays 
in miniaturized LCD watches commonly found in today's marketplace. 
As seen in FIG. 14, the circuit 19 includes an optional signal processor 
116 for shaping compression signal to remove unwanted frequencies and 
improve its form, and inverter and attenuator 117 and an integrator 118. 
Integrator 118 provides a signal proportional to the integral .intg.Fdt 
representing the impulse applied to the ball by the club head described 
above and this signal is applied to digital voltmeter-converter 120 which 
corrects and converts the DC level output of integrator 118 to a value 
proportional to total distance traveled in yards. The DC level signal at 
the input of A/D converter 120 is held by holding stage 122 for eight 
seconds while displayed on LCD display 21. A/D converter 120 provides DC 
level signals to LCD driver 124 that provides the necessary logic to drive 
the three seven bar code digits in LCD element 108. 
FIG. 15 is a schematic diagram of the present computing circuit including 
signal gating, an integrator, a digital voltmeter and LCD display drive, 
according to the present invention corresponding substantially to the 
block diagram illustrated in FIG. 14. As seen, the schematic generally 
includes a 9-volt power supply 82, power switch 149, transducer 16, an 
inverting stage 117, a "window" stage 132, a peak and hold stage 122, a 
curve matching stage 135, and an analog-to-digital converter and LCD 
display drive 136 that drives LCD display 21. A/D converter decoder 136 
corresponds to blocks 120 and 124 in FIG. 14. The amplifiers in stages 
117, 132, 122 and 135 can be on a single integrated circuit chip such as a 
TL 084 CN. 
Resistors 142 and 143 attenuate the negative input from transducer 16 and 
the associated amplifier inverts the input providing an output at 8 having 
rise and fall times and a duty cycle equal to the transduced signal, which 
is on the order of 0.6 to 1.8 milliseconds (ms). The output of stage 117 
is utilized in the timing or gating stage 132 to develop a gating pulse at 
7 having a pulse width equal to the transduced signal, and this signal is 
applied to the base of gating transistor 147, which gates the output of 
stage 117 to input pin 31 of the analog-to-digital converter and display 
drive 136. 
The analog-to-digital converter 136 is by itself conventional and may take 
the form of a single chip A/D converter, such as ICL 7106 manufactured by 
Intersil, Inc. It is a low-power three or three and one-half digit A/D 
converter that contains all necessary active devices on a single CMOS 
integrated circuit and it includes seven segment decoders, display 
drivers, reference and a clock and it is designed to interface with the 
liquid crystal display. Capacitor 148 integrates the gated transducer 
signal at input 31. The holding stage 122 provides an eight-second holding 
pulse for integrating capacitor 148, so that the numerical distance 
dislayed by display 21 appears for eight seconds and then is reset as 
capacitor 148 is discharged by stage 122. 
The curve matching stage 135 provides an input at reference pin 36 equal to 
-ke.sub.i wherein k is a constant and e.sub.i is the input signal at pin 
31. This provides the necessary non-linear output at pins 2 through 25 to 
the input at pin 31 to compensate for the non-linear relation between ball 
velocity V.sub.b and ball distance S.sub.x. Initial ball velocity V.sub.b 
exiting from the clubhead at an effective angle .theta. is related to 
total distance traveled S.sub.x by the equations: 
S.sub.x =V.sub.x tk.sub.1 =k.sub.2 S.sub.x1, where V.sub.x the horizontal 
ball exit velocity=Cos .theta. V.sub.b, t equals elapsed time of ball 
travel, k.sub.1 and k.sub.2 are constants, S.sub.x1 =V.sub.x k.sub.1 and 
the radical k.sub.2 S.sub.x1 compensates for ball roll after impact with 
the ground. Thus total ball distance traveled is a function of 
V.sub.b.sup.2 and thus the V.sub.b input at pin 31 is multipled by the 
variable reference at pin 36 to achieve the desired S.sub.x. 
Potentiometer 152 varies the constant k.sub.2 at pin 36 to effect small 
changes in the ball velocity vs. distance curve. 
Pins 2 through 25 drive the three-digit LCD display 21.