U.S. patent number RE33,735 [Application Number 07/365,951] was granted by the patent office on 1991-11-05 for golf club shaft.
This patent grant is currently assigned to Brunswick Corporation. Invention is credited to Joseph W. Rumble, William G. Sprague.
United States Patent |
RE33,735 |
Rumble , et al. |
November 5, 1991 |
Golf club shaft
Abstract
A shaft for a golf club includes a first series of step
portions, with the step portions increasing in diameter along the
shaft from a tip or hosel end of the shaft toward a grip end. The
step portions are separated from adjacent step portions by
transitional portions which consist of a relatively gentle taper
which smoothly link the surfaces of one step portion with another.
A second series of step portions is disposed between the first
series of step portions and the grip end of the shaft, with the
diameter of the step portions increasing by a predetermined amount
from the first series of step portions toward the grip end. The
second series of step portions are separated from adjacent step
portions and from the grip end further transitional portions which
are similar to the transitional portions discussed above. The golf
shaft of the present invention has reduced stress concentration
points along the circumferential axis of the shaft, a smoother line
of dynamic deflection and a unique finished product appearance.
Inventors: |
Rumble; Joseph W. (Hartford,
CT), Sprague; William G. (Litchfield, CT) |
Assignee: |
Brunswick Corporation (Skokie,
IL)
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Family
ID: |
27003171 |
Appl.
No.: |
07/365,951 |
Filed: |
June 13, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
391988 |
Jun 25, 1982 |
04431187 |
Feb 14, 1984 |
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Current U.S.
Class: |
473/323 |
Current CPC
Class: |
A63B
53/10 (20130101); A63B 60/00 (20151001); A63B
60/10 (20151001); A63B 60/08 (20151001); A63B
60/06 (20151001); A63B 60/0081 (20200801) |
Current International
Class: |
A63B
53/10 (20060101); A63B 053/12 () |
Field of
Search: |
;273/8R,77R,77A,8B |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO/8100520 |
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Mar 1981 |
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EP |
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WO/8100521 |
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Mar 1981 |
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EP |
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389353 |
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Mar 1933 |
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GB |
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482164 |
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Jan 1938 |
|
GB |
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1262896 |
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Feb 1972 |
|
GB |
|
2071504 |
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Sep 1981 |
|
GB |
|
Primary Examiner: Coven; Edward M.
Assistant Examiner: Passaniti; Sebastiano
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Claims
We claim:
1. A golf club shaft having a grip end, a hosel end and a main
shaft portion intermediate the grip and hosel ends, the main shaft
portion having a plurality of .[.stop.]. .Iadd.step
.Iaddend.portions with each adjacent pair of step portions having a
transitional portion therebetween, the main shaft portion
comprising:
a first step portion extending partly along a length of the main
shaft portion and having a first diameter;
a second step portion extending partly along the length of the main
shaft portion and spaced from the first step portion and having a
second diameter different than the first diameter; and
a transitional portion disposed between the first and second step
portions having a tapered outer surface of changing diameter
smoothly linking the first and second step portions, .Iadd.the
tapered outer surface being characterized by a taper angle of
approximately 1.5.degree., .Iaddend.the length of the transitional
portion being substantially greater than the difference between the
first and second diameters wherein the pattern of the step portions
and transitional portions of the main shaft portion is
substantially as shown in FIG. 1.
2. A golf club shaft having a grip end, a hosel end and a main
shaft portion intermediate the grip and hosel ends, .Iadd.the main
shaft portion .Iaddend.comprising:
a first series of equally spaced step portions disposed adjacent
the hosel end .[.on the main shaft portion.]., each step portion of
the first series having a first length;
a second series of equally spaced step portions disposed .[.on the
main shaft portion.]. between the first series and the grip end and
spaced therefrom, each step portion of the second series having a
second length different than the first length, the diameters of the
first and second series of step portions decreasing by a constant
amount from the grip end to the hosel end; and
a plurality of tapered transitional portions wherein a transitional
portion is disposed between adjacent step portions for smoothly
linking the surfaces of the adjacent step portions, .Iadd.the
tapered transitional portions being characterized by a taper angle
of approximately 1.5.degree., .Iaddend.the length of each
transitional portion being substantially greater than the
difference between the diameters of the respective adjacent step
portions, wherein the pattern of the step portions and the
transitional portions is substantially as shown in FIG. 1.
3. The golf club shaft of claim 2, wherein the transitional
portions are tapered to provide a frustoconical surface joined
between adjacent step portions.
4. The golf club shaft of claim 2, wherein the step portions are
each cylindrical in shape.
5. The golf club shaft of claim 2, wherein further transitional
portions are disposed between the second series of step portions
and the grip end and between the first series of step portions and
the hosel end.
6. The golf club shaft of claim 2, wherein each transitional
portion includes a frustoconical surface, all of the frustoconical
surfaces having an equal length.
7. The golf club shaft of claim 6, wherein all of the frustoconical
surfaces form equal angles with respect to the adjacent step
portions.
8. The golf club shaft of claim 6, wherein the length of each
frustoconical surface is on the order of 1/4 inch.
9. The golf club shaft of claim 2, wherein the diameter of each of
the step portions from the grip end toward the hosel end is less
than the diameter of the adjacent step portion toward the grip end
of the order of 0.012 inch.
10. The golf club shaft of claim 2, wherein there are nineteen step
portions in the first series of step portions and each such step
portion is 3/4 inch long.
11. The golf club shaft of claim 2, wherein there are two step
portions in the second series of step portions and each such step
portion is on the order of 23/4 inch long.
12. A golf club shaft having a grip end, a hosel end and a main
shaft portion intermediate the grip and hosel ends, .Iadd.the main
shaft portion .Iaddend.comprising:
a first series of equally spaced cylindrical step portions disposed
adjacent the hosel end on the main shaft portion, each step portion
of the first series having a first length and having a diameter
which differs from the diameter of adjacent step portions by a
predetermined amount;
a second series of equally spaced cylindrical step portions
disposed on the main shaft portion between the first series and the
grip end and spaced therefrom, each step portion of the second
series having a second length greater than the first length and
having a diameter which differs from the diameter of adjacent step
portions by the predetermined amount; and
a plurality of transitional portions wherein each transitional
portion includes a frustoconical surface disposed between and
smoothly linking adjacent step portions, all of the frustoconical
surfaces .Iadd.in said first and second series .Iaddend.being of
equal length and forming equal angles .Iadd.of approximately
1.5.degree..Iaddend. with respect to adjacent step portions, the
length of each transitional portion being substantially greater
than the predetermined amount.
13. The golf club shaft of claim 12, wherein the length of each
frustoconical surface is on the order of 1/4 inch.
14. The golf club shaft of claim 13, wherein the predetermined
amount is on the order of 0.012 inch.
15. The golf club shaft of claim 14, wherein the length of each
step portion of the first series of on the order of 3/4".
16. The golf club shaft of claim 15, wherein the length of each
step portion of the second series is on the order of 23/4".
.Iadd.17. The golf club shaft of claim 12, wherein further
transitional portions are disposed between the second series of
step portions and the grip end and between the first series of step
portions and the hosel end. .Iaddend.
Description
DESCRIPTION
BACKGROUND OF THE INVENTION
This invention relates generally to golf club apparatus, and more
particularly to a shaft for a golf club which is lightweight but
can provide the necessary stiffness characteristics demanded by
golfers.
Ideally, a golf shaft should be designed such that the outer
diameter thereof is smoothly tapered by reducing the diameter from
a grip end to a tip or hosel end by means of a swaging operation.
This swaging would achieve the reduced diametrical dimensions along
the circumferential axis of the shaft without introducing abrupt
diameter reductions while at the same time maintaining a gradual
wall thickness increase from the grip end to the tip. It has been
found, however, that the manufacturing expense of such a golf shaft
processed by the above noted swaging method is prohibitive and that
the final appearance of the golf shaft is less pleasing than other
types of configurations.
Moreover, it is generally known that an ideal golf shaft should be
of negligible weight while at the same time providing sufficient
stiffness characteristics to allow effectively all of the kinetic
energy developed by the golfer to be transmitted to the golf ball
with a high degree of control over the resulting shot. However, in
practice, it is not possible to manufacture an effective club shaft
having negligible weight; therefore, the design of conventional
club shafts varies substantially from the ideal.
Conventional present day golf shafts typically achieve the
reduction in diameter from the grip end to the tip by means of a
series of step portions disposed along the length of the shaft,
with the diameters of the step portions becoming progressively
smaller toward the tip end. Adjacent step portions are separated by
narrow transitional portions which comprise an abrupt reduction of
diameter from one step to an adjacent step. It has been found,
however, that the use of these abrupt transitional portions results
in undesirable characteristics for the golf shaft. These
undesirable characteristics include: (a) the establishment of
stress concentration points along the circumferential axis of the
shaft at the abrupt transitional portions; (b) the assumption of a
relatively disjointed line of dynamic deflection of the shaft
during swinging of the club; and (c) the club shaft must be of
relatively heavy weight to overcome the disadvantages (a)-(b) noted
above.
One successful attempt at reducing the weight of a golf shaft is
shown and described in Kaugars U.S. Pat. No. 4,169,595, assigned to
the assignee of the instant application. The club shaft disclosed
in that patent utilizes a series of steps of varying lengths
disposed along the length of the shaft wherein the particular
configuration of steps results in a stronger shaft. This increase
in strength permits the average wall thickness of the shaft to be
reduced, in turn leading to a reduction of weight with the
attendant advantages noted above.
SUMMARY OF THE INVENTION
In accordance with the present invention a golf club shaft is
configured so as to include a plurality of constant diameter steps
separated by transitional portions which are designed so as to
result in a club shaft which is light in weight yet has the
desirable characteristic deemed necessary by golfers.
The golf club shaft includes a first series of alternating steps
and frustoconical transitional portions, with each of the
transitional portions having a first length and each of the steps
having a second length. Disposed adjacent to this first series is a
second series of alternating steps and frustoconical transitional
portions, with each of the steps having a third length and each of
the transitional portions having a length equal to the first
length. Each of the transitional portions forms a relatively gentle
taper which smoothly links adjacent step portions, thereby avoiding
the abrupt transitions found in the prior art. It has been found
that this configuration results in a reduction of stress
concentration points along the circumferential axis of the shaft,
as well as smoothing out the line of dynamic deflection. The above
noted configuration also results in a unique finished product
appearance which is pleasing to the eye.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a golf club shaft according to the
present invention;
FIGS. 2A and 2B are elevational view showing the distinction
between the golf club shaft of the present invention and a
conventional shaft, respectively;
FIGS. 3A and 3B are enlarged partial elevational views of the
shafts shown in FIGS. 2A and 2B, respectively, showing the
transitional portions thereof;
FIGS. 4A and 4B are schematic elevational views of the shafts shown
in FIGS. 2A and 2B, respectively, showing the deflection of the
shafts in response to an applied weight; and
FIG. 5 is a graph showing the difference in the degree of
deflection of the typical shaft step shown in FIGS. 4A and 4B in
response to the application of varying weights thereto.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, there is illustrated a golf shaft 10
according to the present invention. The shaft 10 includes a grip
end 12 which is received within a hand grip (not shown), and a tip
or hosel end 14 to which a club head (not shown) is secured. A main
shaft portion 13 is disposed between the grip end 12 and the hosel
end 14. It should be noted that the hosel end 14 may be tapered or
may have a parallel tip such as that shown in the figures to
accommodate different types of club heads, as required. The club
shaft shown in FIG. 1 is intended for use as a shaft for the woods
of a golf club set, but it is understood that the shaft can be used
on irons, putters and other types of shafts.
The main shaft portion 13 includes a first series or set of equally
spaced step portions 16, some of which are shown as 16a,16b,16c,
disposed along the length of the shaft adjacent the tip end 14,
with adjacent step portions being separated by frustoconical
transitional portions 18.
In the preferred embodiment, each step portion is cylindrical in
shape, i.e., has a constant diameter along its length, and the
diameter of each step portion 16 varies by a predetermined amount
from the diameter of adjacent step portions. In the preferred
embodiment, the diameter of the step portion 16a is less than the
diameter of the step portion 16b by 0.012" and the diameter of the
step portion 16c is greater than the diameter of the step portion
16b by this same amount. It should be noted that this predetermined
amount may be varied to suit.
Moreover, in the preferred embodiment the lengths of the step
portion 16 are equal and are on the order of 3/4". However, the
step portions 16 may have different lengths, if desired.
Each of the transitional portions 18 comprises a taper which
smoothly links the varying diameters of adjacent step portions 16.
In the preferred embodiment, the length of each transitional
portion 18 parallel to the axis of the shaft is on the order of
1/2". Moreover, the length of each transitional portion is
substantially greater than the difference between the diameters of
the adjacent step portions.
In one preferred embodiment, there are 19 step portions 16 and
transitional portions 18, with the combined length of a step
portion and an adjacent transitional portion being on the order of
1". The step portion 16a adjacent the hosel end 14 has a diameter
of 0.348" while the diameter of the step portion 16d, i.e. the last
step portion in the first series, has a diameter of 0.564", with
the diameter of intermediate step portions differing from the
diameter of adjacent step portions by 0.012" as previously
noted.
Disposed adjacent to the first series of step portions 16 is a
second series of equally spaced step portions 20 consisting of a
step portion 20a and a step portion 20b. In one preferred
embodiment, the diameter of the step portion 20a is larger than the
diameter of the adjacent step portion 16d by 0.012". Similarly, the
diameter of the step portion 20b is larger than the diameter of
step portion 20a by this same amount.
The lengths of the step portions 20a, 20b are equal and in the one
preferred embodiment are on the order of 23/4".
The second series of step portions 20 are separated by
frustoconical transitional portions 22, which in the preferred
embodiment comprise tapered portions 22a, 22b. The transitional
portions 22a, 22b in the one preferred embodiment have the same
length parallel to the axis of the shaft as the transitional
portions 18 noted above, i.e., on the order of 1/4".
There are two further frustoconical transitional portions 24a, 24b
between the series of step portions 16, 18 and the hosel end 14 and
the grip end 12, respectively. The transitional portion 24B is
disposed between the step portion 20B and the grip end 12 and
comprises a tapered portion 1/4" in length which smoothly joins the
0.012" diametrical transition between the two portions 20b, 12.
Similarly, the transitional portion 24a comprises a tapered portion
which is 1/4" in length and provides a smooth transition between
the 0.348" diameter of the step portion 16a and the 0.335" diameter
of the hosel end 14.
In the one preferred embodiment, the shaft is manufactured of
S.A.E. 5046 modified alloy steel and has the dimensions noted
below:
______________________________________ Dimensions
______________________________________ Length of grip end 12 + 8"
transitional portion 24b Length of first series of step portions 16
+ 19" transitional portions 18 + transitional portion 24a Length of
second series 6" of step portions 20 + transitional portions 22
Length of hosel end 14 14" Overall length of shaft 47"
______________________________________
Referring also to FIG. 3A, since each of the transitional portions,
18, 22 and 24b are of the same length and link adjacent step
portions having diameters which differ by a constant amount, it
follows that all of the transitional portions form equal taper
angles, designated A in FIG. 3, with respect to the adjacent step
portions. In the preferred embodiment, the taper angle A is equal
to: ##EQU1## In the conventional shaft 100 shown in FIGS. 2B and
3B, non-tapered step portions 116 are separated by abrupt
transitional portions 118 which in some cases can lie perpendicular
to the step portions 116 and in other cases have a length of very
limited extent.
It should be noted that the angle A of each transitional portion
primarily determines the increase of strength of the shaft 10 over
conventional shafts regardless of the lengths or diametrical
difference of adjacent step portions. In fact, it would be
desirable to manufacture a shaft having a taper angle less than
approximately 1.5.degree. and having shorter and/or fewer step
portions so as to more closely approximate the ideal; however, it
is presently not economically feasible to manufacture shafts having
a taper angle less than the angle A.
In any event, regardless of the difference between the diameters of
adjacent step portions and the lengths thereof, it is desirable to
maintain the taper angle A as close to approximately 1.5.degree. as
possible, if not less than this amount to achieve the best
results.
The shaft 10 shown in FIG. 1 has a weight of 4.20 ounces before
trimming for assembly. The shaft 10 may be trimmed for assembly by
removing 2" from the grip end 12 for a gear flex shaft, or by
removing 2" from the tip end 14 for a stiff flex shaft. The
resulting weight of the shaft after trimming is 4.00 ounces.
As seen in FIGS. 2A, 2B, 3A and 3B, the alternating series of step
and tapered portions results in a unique appearance of the shaft 10
of the present invention as opposed to conventional shafts, such as
shown in FIG. 2B. Moreover, the use of the transitional portions
18, 22 results in improved characteristics for the shaft, as
opposed to the use of abrupt transitions between adjacent step
portions of a conventional shaft, such as shown in FIG. 3B.
For example, as shown in FIGS. 4A and 4B, there is illustrated a
graphical representation of a test for determining the relative
stiffness of a shaft 10 according to the present invention, shown
in FIG. 4A, and a conventional shaft shown in FIG. 4B. In the test
illustrated in FIGS. 4A and 4B, the shafts were constructed from
identical shaft blanks having an outer diameter of 0.600", a weight
of 4.00 ounces and identical step patterns. In each case, the
shafts shown in FIGS. 4A and 4B were supported at their grip end
and weights were applied at equal distances from the tip of the
hosel end so as to determine the stiffness of the shafts. As shown
in FIG. 4A, a weight of 2.90 kilograms caused the tip of the hosel
end 14 to deflect by a distance X. On the other hand, a weight of
2.84 kilograms attached to the hosel end of the standard shaft
shown in FIG. 4B caused an equal deflection by an amount X. In
fact, securing a weight of 2.90 kilograms to the hosel end of the
conventional shaft shown in FIG. 4B caused the shaft tip to deflect
by an amount equal to X+.DELTA.X. Clearly then, the shaft 10 of the
present invention as shown in FIG. 4A is stiffer than the
conventional shaft shown in FIG. 4B even though the shafts are of
the same diameter and are of equal weights.
Moreover, tests have been performed comparing the deflection
characteristics of the golf shaft of the present invention with a
heavier conventional or standard shaft.
The results of the test were as follows:
__________________________________________________________________________
Deflection at Average Grip End Tip End X in. from grip end Shaft
Weight Diameter Diameter X = 151/2" X = 281/4" X = 401/2"
__________________________________________________________________________
Improved 4.00 oz. 0.600 0.335 121/2 mm 59 mm 143 mm Shaft Std.
Shaft 4.30 oz. 0.600 0.335 121/2 mm 601/4 mm 141 mm
__________________________________________________________________________
As seen by the results of this test, the deflection characteristics
are approximately the same for the golf shaft of the present
invention and a standard shaft of heavier weight. One might expect
that, due to the lighter weight of the shaft of the present
invention, the shaft would deflect significantly more in response
to an applied weight than the regular shaft of heavier weight to
which this same deflective force is applied. However, the stiffer
sectional deflection characteristics of the shaft of the present
invention results in the shaft having the same approximate
deflection characteristics as standard shafts, even though the
shaft of the present invention weighs approximately 0.30 ounces
less.
Another test was made comparing the deflection characteristics of
the shaft of the present invention with a light weight shaft, such
as that shown in U.S. Pat. No. 4,169,595. In this test, the
lightweight shaft and the present shaft have the same weight,
however, the diameter at the grip end of the lightweight shaft was
greater than that of the shaft of the present invention. The
results of the test are as follows:
__________________________________________________________________________
Deflection at X ins. Average Grip End Tip End From Grip End Shaft
Weight Diameter Diameter X = 151/2" X = 281/4" X = 401/2"
__________________________________________________________________________
Improved 4.00 oz. 0.600 0.335 121/2 mm 59 mm 143 mm Shaft Light-
4.00 oz 0.620 0.335 13 mm 64 mm 152 mm weight Shaft
__________________________________________________________________________
One might expect the larger diameter lightweight shaft to deflect
less than the shaft of the present invention due to the stiffness
introduced by the increase in grip end diameter, however, the
stiffer sectional deflection of the shaft of the present invention
results in less deflection thereof.
Further tests have been performed comparing the characteristics of
the shaft of the present invention with conventional shafts. In a
first test, the two types of shafts were tested on an Instron
testing machine to test the bending strength and deflection
resistance of the two types of shafts. In each case, the test
location was selected to be the first portion from the hosel end
with a lever arm of 2". The shafts were subjected to bending forces
in the vicinity of the test location until failure of the material
resulted. In each case, the outer diameter of the test location was
equal to 0.348" with a wall thickness of 0.017 inches. Also, in
both cases, section modulus were equal to 0.0013948. It was found
that the yield strength and the ultimate strength were equal as
follows:
Improved Shaft Yield Strength=180 lb =360 in-lb=258,000 PSI
Conventional Shaft Yield Strength=180 lb=360 in-lb=258,000 PSI
Even though the bending strength of the two samples were identical,
the deflection resistance of the shaft of the present invention was
found to be higher than the deflection resistance of the
conventional shaft. As seen in FIG. 5, the difference in deflection
resistance between the two types of shafts increased with
increasing loading of the shafts, with the difference in deflection
at 110 lbs of applied load being approximately equal to 0.003 and
the difference at 170 lbs of applied load being equal to
0.010".
Two samples each of the shaft of the present invention and of a
conventional shaft were tested to determine the breakage resistance
thereof. In this case, the shafts were assembled into identical
club heads and were swung in an arc, similar to a golfer's swing,
against a simulated ball mounted on a track which moves with the
impact of the club head. These strokes were repeated until shaft
breakage occurred. The speed of the stroke and the impact forces of
the shaft hitting the ball were held equal through the testing of
all shifts. The results of the tests were as follows:
______________________________________ Strokes Before Shaft
Breakage Improved Shaft Conventional Shaft
______________________________________ Sample #1 2,855 976 Sample
#2 4,818 703 ______________________________________
It can be seen that the shaft of the present invention experienced
approximately three times of number of strokes before breaking than
did the conventional shaft. The test performed on the second
samples of shafts shows that the shaft of the present invention
withstood nearly seven times of the number of strokes before
breaking than did the conventional shaft. It is felt that this
increased resistance to breakage is a result of the reduction in
stress concentration points along the length of the shaft due to
all absence of abrupt diametrical changes between step
portions.
Finally, a test was performed on two samples of each type of club,
i.e., the shaft of the present invention and a conventional shaft,
to determine the fatigue resistance thereof. This test was
performed by rotating the shafts at a constant speed while at the
same time applying a severe bending force along the shaft axis.
This cycle was repeated until failure of the material and shaft
breakage occurred. In this type of test all breakage occurs at the
transition between steps. The result of this test were as
follows:
______________________________________ Cycles Before Breakage
Improved Shaft Conventional Shaft
______________________________________ Sample #1 46 14 Sample #2 40
8 ______________________________________
Again, it can be seen that fatigue resistance is improved in the
shaft of the present invention, it being capable of being cycled
approximately 3-5 times the number to which the conventional shaft
can be subjected. This improvement in fatigue resistance is felt to
be a direct result of the elimination of the abrupt transitional
changes in diameter between step portions.
* * * * *