U.S. patent application number 15/356611 was filed with the patent office on 2018-05-24 for polycarbonate-siloxane copolymer use in baseball and softball bats.
This patent application is currently assigned to Hoon/Forsythe Technologies, LLC. The applicant listed for this patent is Paul D. Forsythe, Douglas M. Hoon. Invention is credited to Paul D. Forsythe, Douglas M. Hoon.
Application Number | 20180140915 15/356611 |
Document ID | / |
Family ID | 62144187 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180140915 |
Kind Code |
A1 |
Hoon; Douglas M. ; et
al. |
May 24, 2018 |
Polycarbonate-Siloxane Copolymer Use in Baseball and Softball
Bats
Abstract
This invention describes the use of a polycarbonate-siloxane
block copolymer in the fabrication of various components,
especially those subject to repeated impact, for devices such as
baseball and softball bats. This material has been shown to possess
excellent impact fatigue resistance, a benign mode of failure, and
an ability to maintain its shape following impact that was not
observed in any other tested polymers.
Inventors: |
Hoon; Douglas M.; (Guilford,
CT) ; Forsythe; Paul D.; (Phoenix, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hoon; Douglas M.
Forsythe; Paul D. |
Guilford
Phoenix |
CT
AZ |
US
US |
|
|
Assignee: |
Hoon/Forsythe Technologies,
LLC
Guilford
CT
|
Family ID: |
62144187 |
Appl. No.: |
15/356611 |
Filed: |
November 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 59/54 20151001;
C08L 83/10 20130101; A63B 59/56 20151001; A63B 2209/02 20130101;
C08G 77/448 20130101 |
International
Class: |
A63B 59/54 20060101
A63B059/54; A63B 59/56 20060101 A63B059/56 |
Claims
1. A device comprising: a first barrel section comprising a
generally cylindrical hollow body 8-14'' in length and 2-3''
diameter with walls of 0.08-0.25'' thickness developed about a
central axis of revolution, a proximal first cylinder end and a
distal second cylinder end, wherein the two ends are separated by a
mid-section, a handle section comprising a straight cylindrical
body 0.625-1'' diameter, a proximal first end and a distal second
end, and a central axis that is collinear with the central axis of
the first barrel section, a transition section comprising a
generally conical body revolved about a central axis collinear with
the central axes of revolution of the first barrel section and the
handle section, the body having a proximal first end sized to be
equal in diameter and coplanar to the distal end of the handle and
a distal second end sized to be equal in diameter and coplanar to
the proximal first cylinder end of the first barrel section, a knob
comprising a short cylindrical body revolved about a central axis
collinear with the central axis of the handle with a proximal first
end defining the proximal end of the device and a distal second end
coplanar with the proximal first end of the handle, and an endcap
comprising a short cylindrical body revolved about a central axis
collinear with the central axis of the first barrel section, the
body having a proximal first end coplanar with the distal end of
the first barrel section and a distal second end defining a distal
end of the device wherein at least one of these sections is
manufactured using a polycarbonate-siloxane block copolymer.
2. The device of claim 1 further comprising a second hollow barrel
section comprising a generally cylindrical body disposed concentric
to and inside of the first barrel section and having a proximal
first end and a distal second end, wherein the two ends are
separated by a mid-section, and wherein the outside diameter of the
second barrel section is smaller than the inside diameter of the
hollow first barrel section and the inside diameter of the second
barrel section is larger than the outside diameter of the handle
section.
3. The device of claim 2 wherein the second barrel section is
manufactured using one of a fiberglass composite, a carbon fiber
composite, a metal, or a polycarbonate-siloxane block
copolymer.
4. The device of claim 2 wherein only at least one of the first
barrel section and the second barrel section are manufactured using
a polycarbonate-siloxane copolymer.
5. The device of claim 1 wherein the handle extends beyond the
proximal first end of the transition section, through and
concentric to one or more of the transition section and the first
barrel section.
6. The device of claim 1 wherein the siloxane component of the
polycarbonate-siloxane block copolymer comprises a molecule within
the family of polydimethylsiloxane chemistry.
7. The device of claim 1 wherein the polycarbonate component of the
polycarbonate-siloxane block copolymer comprises a molecule within
the families of bisphenol A polycarbonate or poly-(4,4
isopropyliden diphenyl carbonate).
8. The device of claim 1 wherein the molecular weight of the
polycarbonate-siloxane block copolymer is in the range of 10,000 to
32,000 Daltons.
9. The device of claim 1 wherein the molecular weight of the
polycarbonate-siloxane block copolymer is in the range of 24,000 to
32,000 Daltons.
10. The device of claim 1 wherein the Melt Flow Index of the
polycarbonate-siloxane block copolymer is in the range of 2 to 12
grams per 10 minutes as measured in accordance with ASTM D1238 at a
temperature of 300.degree. C. and a load of 2.65 pounds.
11. The device of claim 1 wherein the Melt Flow Index of the
polycarbonate-siloxane block copolymer is in the range of 2 to 6
grams per 10 minutes as measured in accordance with ASTM D1238 at a
temperature of 300.degree. C. and a load of 2.65 pounds.
12. The device of claim 1 wherein the tensile modulus of the
polycarbonate-siloxane block copolymer is about 320,000 psi as
measured in accordance with ASTM D638 at a loading rate of 50
mm/min.
13. The device of claim 1 wherein the tensile yield of the
polycarbonate-siloxane block copolymer is about 8700 psi as
measured in accordance with ASTM D638, Type I, at a loading rate of
50 mm/min.
14. The device of claim 1 wherein a 0.1'' thick section of the
molded polycarbonate-siloxane block copolymer has a visible light
transmission rate of at least 80% in accordance with ASTM
D1003.
15. The device of claim 14 wherein product graphics are disposed on
the inside surface of the first barrel section.
16. The device of claim 14 wherein the device further comprising a
second hollow barrel section comprising a generally cylindrical
body disposed concentric to and inside of the first barrel section
and having a proximal first end and a distal second end, wherein
the two ends are separated by a mid-section, and wherein the
outside diameter of the second barrel section is smaller than the
inside diameter of the hollow first barrel section and the inside
diameter of the second barrel section is larger than the outside
diameter of the handle section and wherein product graphics are
disposed on the outside surface of the second barrel section.
17. The device of claim 1 wherein a 0.1'' thick section of the
molded polycarbonate-siloxane block copolymer has a visible light
transmission rate of less than 20% in accordance with ASTM
D1003.
18. The device of claim 1 wherein a 0.1'' thick section of the
molded polycarbonate-siloxane block copolymer has a haze value for
visible light transmission rate of less than 5% in accordance with
ASTM D1003.
19. The device of claim 1 wherein the mid-section of the first
barrel section is larger in diameter than the proximal first
cylinder end or the distal second cylinder end.
Description
RELATED APPLICATIONS
[0001] This application relates to and claims priority under 35
U.S.C. .sctn. 119(e) to U.S. Provisional Patent Application No.
62/259250, titled "Polycarbonate-Siloxane Copolymer Use in Baseball
and Softball Bats," which was filed on Nov. 24, 2015 and is hereby
incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The technical field relates generally to the use of a
thermoplastic material with superior impact fatigue properties and
a benign failure mechanism for use in the manufacture of baseball
and softball bats as well as other devices where impact fatigue
resistance would be a benefit.
BACKGROUND
[0003] Historically, baseball and softball bats were first made
from wood, a material readily available and easily formed using
technology available in the 19th century. (For purposes of clarity
and simplification, the terms "baseball bat" or "bat," whether
singular or plural, as used herein shall apply to both baseball and
softball bats, regardless of the size or type.) Subsequently, once
the advantages of hollow bats were recognized, both for weight and
performance reasons (the trampoline effect), the material of choice
transitioned first to metals such as high performance aluminum
alloys and titanium and later to composites such as graphite
fiber/epoxy compounds or mixtures of graphite, glass and aramid
fibers in some suitable matrix material. The use of thermoplastics,
other than for toy bats (e.g., for whiffle ball), and for portions
of the bat such as end caps and the handle (knob), was unknown
until the invention of a replaceable barrel bat was disclosed in
U.S. Pat. No. 6,875,137. This patent specifically claimed the use
of polycarbonate and urethane thermoplastics for these other
components such as the barrel section of the bat.
[0004] There are several compelling reasons for using a
thermoplastic compound in the fabrication of a softball or baseball
bat barrel section or other components susceptible to regular
impact during play [0005] These materials are easily and
cost-effectively extruded or injection molded using techniques that
are well known, yielding repeatable, dimensionally accurate
components. [0006] These materials are easily welded together using
commonly available ultrasonic or inertial welding processes. [0007]
Thermoplastics are lower in density than metals or composites, so
for certain product types, e.g., youth bats or girls' fast pitch
softball, exceptionally light weight bats are possible.
[0008] Since the publication of U.S. Pat. No. 6,875,137, it is
known that neither unalloyed polycarbonates nor unalloyed urethane
performs well under conditions of repeated impact against hollow
tubular structures. (In this context, the term "unalloyed" means
that the base polymer family has not been combined with another
major polymer type. For example, an alloy in this context could be
achieved by combining a urethane and a nylon, or a PET molecule
with an ABS molecule. The term, as used herein, is not meant to
include addition of specific agents for enhancing certain
properties of the base polymer, e.g., UV protection, flow
characteristics, etc.) Both alloys have excellent Izod and Charpy
impact resistance as measured by ASTM D256 and ISO 179/1eu
respectively. What these tests results do not reveal, however, is
what might be termed "impact fatigue" performance. The window of an
armored car, for example, typically needs to protect its occupants
from one or even dozens of bullet impacts distributed over a broad
area. For this application, polycarbonate has proven to be very
effective. A baseball bat, however, needs to withstand hundreds of
impacts at essentially the same place. Experience has shown that
for these baseball bat applications, polycarbonate usually will
fail somewhere between 10 to 100 impacts, depending on the swing
speed, barrel wall thickness, etc. There are no published figures
in the literature for "impact fatigue" for different materials.
[0009] Another problem that has been observed with these unalloyed
polymers is that when failure does occur following repeated
impacts, the failure can be catastrophic, with shards of material
flying away from the test article at high speed. While failure
itself can probably be tolerated (it's more an issue of economics
than performance), the safety aspects of this type of failure in a
sporting venue is totally unacceptable. Nothing in the published
literature for these or other thermoplastics addresses the
long-term failure mechanism.
[0010] What is needed is a material with sufficient impact fatigue
resistance to withstand several hundred ball/bat impacts and one,
that when failure does occur, presents less danger from flying
debris.
SUMMARY
[0011] The design criteria and material discovery described herein
improve the overall durability and safety for baseball and softball
bats utilizing thermoplastic polymers for sections of the bat
routinely exposed to impact.
[0012] The disclosed subject matter includes specific polymer
chemistry and a rationale for choosing the best grades or alloys of
that chemistry. It also addresses the portions of the bat assembly
best suited for conversion to thermoplastics.
[0013] The disclosed subject matter further describes a range of
attributes for the selected polymer chemistry that promote bat
designs that take full advantage of the color, transparency, and
opportunities for novel graphics presentation afforded by different
material choices.
[0014] While the technical field of this application primarily
applies to baseball and softball bats, it can more generally be
applied to any device which comprises a hollow body whose walls are
stressed during impact and repeated impacts in the same general
location are to be expected.
[0015] In some embodiments, the device comprises a first barrel
section comprising a generally cylindrical hollow body 8-14'' in
length and 2-3'' diameter with walls of 0.08-0.25'' thickness
developed about a central axis of revolution, a proximal first
cylinder end and a distal second cylinder end, wherein the two ends
are separated by a mid-section.
[0016] In some embodiments, the device further comprises a handle
section comprising a straight cylindrical body 0.625-1'' diameter,
a proximal first end and a distal second end, and a central axis
that is collinear with the central axis of the first barrel
section.
[0017] In some embodiments, the device further comprises a
transition section comprising a generally conical body revolved
about a central axis collinear with the central axes of revolution
of the first barrel section and the handle section, the body having
a proximal first end sized to be equal in diameter and coplanar to
the distal end of the handle and a distal second end sized to be
equal in diameter and coplanar to the proximal first cylinder end
of the first barrel section.
[0018] In some embodiments, the device further comprises a knob
comprising a short cylindrical body revolved about a central axis
collinear with the central axis of the handle with a proximal first
end defining the proximal end of the device and a distal second end
coplanar with the proximal first end of the handle.
[0019] In some embodiments, the device further comprises an endcap
comprising a short cylindrical body revolved about a central axis
collinear with the central axis of the first barrel section, the
body having a proximal first end coplanar with the distal end of
the first barrel section and a distal second end defining a distal
end of the device.
[0020] In some embodiments, at least one of these sections is
manufactured using a polycarbonate-siloxane block copolymer.
[0021] In some embodiments, the device further comprises a second
hollow barrel section comprising a generally cylindrical body
disposed concentric to and inside of the first barrel section and
having a proximal first end and a distal second end, wherein the
two ends are separated by a mid-section, and wherein the outside
diameter of the second barrel section is smaller than the inside
diameter of the hollow first barrel section and the inside diameter
of the second barrel section is larger than the outside diameter of
the handle section.
[0022] In some embodiments, the second barrel section is
manufactured using one of a fiberglass composite, a carbon fiber
composite, a metal, or a polycarbonate-siloxane block
copolymer.
[0023] In some embodiments, only at least one of the first barrel
section and the second barrel section are manufactured using a
polycarbonate-siloxane copolymer.
[0024] In some embodiments, the handle extends beyond the proximal
first end of the transition section, through and concentric to one
or more of the transition section and the first barrel section.
[0025] In some embodiments, the siloxane component of the
polycarbonate-siloxane block copolymer comprises a molecule within
the family of polydimethylsiloxane chemistry.
[0026] In some embodiments, the polycarbonate component of the
polycarbonate-siloxane block copolymer comprises a molecule within
the families of bisphenol A polycarbonate or poly-(4,4
isopropyliden diphenyl carbonate).
[0027] In some embodiments, the molecular weight of the
polycarbonate-siloxane block copolymer is in the range of 10,000 to
32,000 Daltons.
[0028] In some embodiments, the molecular weight of the
polycarbonate-siloxane block copolymer is in the range of 24,000 to
32,000 Daltons.
[0029] In some embodiments, the Melt Flow Index of the
polycarbonate-siloxane block copolymer is in the range of 2 to 12
grams per 10 minutes as measured in accordance with ASTM D1238 at a
temperature of 300.degree. C. and a load of 2.65 pounds.
[0030] In some embodiments, the Melt Flow Index of the
polycarbonate-siloxane block copolymer is in the range of 2 to 6
grams per 10 minutes as measured in accordance with ASTM D1238 at a
temperature of 300.degree. C. and a load of 2.65 pounds.
[0031] In some embodiments, the tensile modulus of the
polycarbonate-siloxane block copolymer is about 320,000 psi as
measured in accordance with ASTM D638 at a loading rate of 50
mm/min.
[0032] In some embodiments, the tensile yield of the
polycarbonate-siloxane block copolymer is about 8700 psi as
measured in accordance with ASTM D638, Type I, at a loading rate of
50 mm/min.
[0033] In some embodiments, a 0.1'' thick section of the molded
polycarbonate-siloxane block copolymer has a visible light
transmission rate of at least 80% in accordance with ASTM
D1003.
[0034] In some embodiments, a 0.1'' thick section of the molded
polycarbonate-siloxane block copolymer has a visible light
transmission rate of less than 20% in accordance with ASTM
D1003.
[0035] In some embodiments, a 0.1'' thick section of the molded
polycarbonate-siloxane block copolymer has a haze value for visible
light transmission rate of less than 5% in accordance with ASTM
D1003.
[0036] In some embodiments, the product graphics are disposed on
the inside surface of the first barrel section and can be viewed
through a sufficiently transparent first barrel section wall.
[0037] In some embodiments, the product graphics are disposed on
the outside surface of the second barrel section and can be viewed
through a sufficiently transparent first barrel section.
[0038] In some embodiments, the mid-section of the first barrel
section is larger in diameter than the proximal first cylinder end
or the distal second cylinder end.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Various objects, features, and advantages of the disclosed
subject matter can be more fully appreciated with respect to the
following detailed description of the disclosed subject matter when
considered in conjunction with the following drawings, in which
like reference numerals identify like elements.
[0040] FIG. 1 illustrates an exploded view of a replaceable barrel
bat of the described in U.S. Pat. No. 6,875,137. A first barrel
subassembly is located on the left, a second barrel section
(referred to as a "ballast tube" within the referenced patent) is
in the center, and a handle subassembly is located on the
right.
[0041] FIG. 2 illustrates an exploded view of a first barrel
subassembly showing an end cap, a first barrel section, a proximal
support section and the transition. These components are all
subject to impact with a baseball or softball and readily made from
thermoplastic.
[0042] FIG. 3 illustrates an exploded view of a first barrel
subassembly and a shortened handle section designed to be joined to
the transition section of the barrel subassembly.
[0043] FIG. 4 illustrates a one-piece bat wherein the handle,
transition and barrel are fabricated as a continuous unit and knob,
endcap and a second barrel section can be added separately.
[0044] FIGS. 5A and 5B are photographs of the cracks that occurred
in the thermoplastic barrel section of a bat during testing.
[0045] FIG. 6 illustrates an exploded view of a bat similar to the
bat of FIG. 1 except that the handle section and the transition
section have been co-molded as one piece and the end cap and aft
support are made of an energy absorbing compound.
DETAILED DESCRIPTION
[0046] In the following description, numerous specific details are
set forth regarding the systems and methods of the disclosed
subject matter and the environment in which such systems and
methods may operate to provide a thorough understanding of the
disclosed subject matter. It will be apparent to one skilled in the
art, however, that the disclosed subject matter may be practiced
without such specific details, and that certain features, which are
well known in the art, are not described in detail to avoid
complication of the disclosed subject matter. In addition, it will
be understood that the embodiments described below are exemplary,
and that it is contemplated that there are other systems and
methods that are within the scope of the disclosed subject
matter.
[0047] For purposes of clarity, the use of the term "siloxane" as
used herein (e.g., polycarbonate-siloxane block copolymer) is
understood to also include "polysiloxane" chemistries. In some
embodiments, the block formed by this polysiloxane molecule can be
hundreds or thousands of units long. Also, whenever used herein,
the term "about" is meant to define a value of plus or minus 10% of
the nominal value listed.
[0048] As noted above, multiple thermoplastic polymers are
advertised in the marketplace with excellent impact performance as
defined by Izod and Charpy test methods. These test methods do not,
however, adequately characterize the impact fatigue properties of
these materials when tested as hollow tubular structures typical of
a baseball bat's barrel section or other hollow components of a bat
subject to impact with a baseball or softball. These methods also
do not adequately characterize the failure mechanism. Failures
which occur catastrophically, with shards violently ejected from
the bat test section clearly are inappropriate for use in any
sporting venue, especially those used by children. Failures which
result in permanent deformation of the product are less serious.
For market acceptance, a bat should be able to withstand hundreds
of impacts, preferably greater than 500 impacts by the intended
player segment. For safety, the bat should fail benignly, with slow
growth of any failure mechanism and the complete absence of
shattering or the ejection of shards.
[0049] A wide variety of materials were selected for testing, all
with strong recommendations from manufacturers sales
representatives and technical specialists for the materials. These
included:
TABLE-US-00001 Polymer Trade Name Source Composition Comments
Polycarbonate Manufacturer PC Advertised in catalog unknown; as
"impact resistant" purchased from and comparable to catalog
retailer Lexan, Hyzod, Tuffak and Makrolon Noryl Sabic PPE Xenoy
1403B Sabic PET/PC or PBT/PC Texin 4210 Bayer PU/PC Crastin ST820
DuPont PBT NC010 Isoplast EZ202 Lubrizol TPU Nylon 6/6 Manufacturer
PA Advertised as "Good" unknown; impact resistance purchased from
catalog retailer Lexan EXL Sabic PC/Siloxane 1433T Block Copolymer
Lexan EXL Sabic PC/Siloxane 1033C Block Copolymer HFD 1034 Sabic PC
with a soft HFD is an block copolymer abbreviation for derived from
"High Flow Ductile." castor oil It is a specialty grade of Sabic's
Lexan PC. ERXL 2054 Sabic PC/Siloxane Block Copolymer Tarflan
Idemitsu PC/Siloxane Neo/AG2530 Block Copolymer Tarflan Neo/PC-
Idemitsu/PTS PC/Siloxane 10XE1-CL01(V) Block Copolymer Tarflan
Neo/PC-XM- Idemitsu/PTS PC/Siloxane CL01/NPD207R1 Block Copolymer
Tarflan Neo/PC- Idemitsu/PTS PC/Siloxane 10XE2-CL01(V) Block
Copolymer Key (meaning of abbreviations as used herein): PC
Polycarbonate PET Polyethylene Terephthalate PPE Polyphenylene
Ether PU Polyurethane TPU Thermoplastic Polyurethane PBT
Polybutylene Terephthalate Siloxane Polysiloxane
[0050] Testing occurred over a period of approximately five years
and involved over 150 bats of various types, both sample bats using
various thermoplastic polymers and wall thicknesses in the barrel
section and "controls"--purchased, commercially available bats made
from traditional composite or aluminum alloys to help rank relative
performance for each batter. Testing included a combination of
field testing, lab testing using air cannons, lab testing using
robotic batting machines, and high speed photography. Field testing
occurred both outdoors in a typical softball diamond setting and
indoors using batting cages. In both situations batters chosen to
participate were primarily adult males playing in softball leagues
at "A" or "B" levels of competition (most competitive) and capable
of hitting a regulation softball (as defined by the Amateur
Softball Association or the United States Specialty Sports
Association) between 350 and 450 feet. (The objective was to
subject the bats to as high a level of impact as could be expected
in the most competitive settings and to rate durability as the
number of hits to failure under this worst-case scenario.) Lab
testing with air cannons involved the use of balls accelerated to
speeds as high as 110 miles per hour and directed at specific
locations on a stationary bat. Lab testing with robotic batting
machines involved using a machine to rotate a bat up to speeds that
would yield a ball/bat impact equivalent to that from the combined
speed of a pitched ball and a swung bat. High speed photography was
done at shutter speeds up to 10,000 frames per second to capture
the 0.001-0.003 second duration of the ball/bat impact so the
degree of distortion of both ball and bat could be observed. The
bat distortions of interest consisted of both hoop
(circumferential) compression and axial bending.
[0051] Sample bats used in testing generally were fabricated as a
group of injection molded and/or extruded components inertially
welded (also known as friction welding) together to create a barrel
subassembly. This construction is illustrated in FIGS. 1 and 2 and
further described in U.S. Pat. No. 6,875,137. Referring to FIG. 1,
barrel subassembly 20 is designed to be mounted on handle
subassembly 10, which passes through the entire bat section and is
locked in place as described in U.S. Pat. No. 6,875,137. A ballast
tube or second barrel section 30 can optionally be included inside
barrel subassembly 20, but for the testing conducted during this
research program it was not added. Referring to FIG. 2, the
components of barrel subassembly 20 utilized during testing
included a first barrel section 21, a transition section 23, a
proximal support 22, and an end cap 24. In some test samples, all
components were fabricated from the same polymer. In some test
samples, especially during initial testing, only the first barrel
section 21 was fabricated from the target polymer and the other
three components were assembled from available stocks of different
plastics or composites. Impacts were targeted for the first barrel
section. During lab testing the impact location could be precisely
controlled (within an inch or two of the intended location) and was
typically targeted to the "sweet spot" or a point 1-2 inches away,
either offset toward the transition 23 or offset toward the end cap
24. (As used herein, the term "sweet spot" usually means a point
near the middle of the barrel length where the best performance and
least vibration following impact are achieved. It is determined by
the location of vibration nodes which, in turn, are affected by
barrel geometry and end conditions.) During field testing the level
of control was a function of the skill of the batter. In some
instances, impacts occurred toward an extreme end of the first
barrel section 21, even impacting end cap 24 or transition 23.
[0052] The bat design illustrated in FIG. 3 is an alternative
design that was also used during testing. This design utilizes a
similar barrel sub assembly 20 as used in FIG. 1, but in this
design the handle subassembly 40 is shorter than the handle
assembly 10 in FIG. 1 and engages only the transition section 23
(from FIG. 2). It does not pass through the barrel section.
[0053] FIG. 4 illustrates a one-piece bat 50 wherein the handle,
transition and barrel are fabricated as a continuous unit while the
knob, endcap and a second barrel section (not shown) may be added
separately. If added, the second barrel section is held inside and
concentric to the first barrel section using a combination of
adhesives, the natural taper of the transition, and geometric
features molded into the end cap.
[0054] Testing yielded the following observations:
TABLE-US-00002 Trade Name Comments Polycarbonate Shattered after
less than 50 impacts. Noryl Distorted out-of-round after less than
100 impacts. Xenoy 1403B Distorted out-of-round after less than 100
impacts. Texin 4210 Shattered after less than 20 impacts. Crastin
ST820 Distorted out-of-round after less than 10 impacts. NC010
Isoplast EZ202 Shattered after less than 100 impacts. Nylon 6/6
Distorted out-of-round after less than 100 impacts. Lexan EXL
Retained shape throughout testing. Failed benignly via 1433T
progressive crack development in skin after 100-300 impacts. Lexan
EXL Same general performance and failure mode as EXL1433T, 1033C
but durability extended to 500-1000 impacts. Taken off market by
Sabic because of cost of one special ingredient. HFD 1034 Shattered
after less than 50 impacts. ERXL 2054 Same general performance and
failure mode as EXL 1033C. Specially formulated to replicate 1033C
impact fatigue characteristics, but without one high-cost
component. Withdrawn from market for internal reasons. Tarflan
Performance equal to or superior to ERXL 2054 and same Neo/AG2530
failure mode; only available as an opaque product. Tarflan Neo/PC-
Similar performance to AG2530 and same failure mode, with
10XE1-CL01(V) greater transparency - approximately 2% haze. Tarflan
Neo/PC-XM- Reduced impact performance as compared to PC-10XE1-
CL01/NPD207R1 CL01(V), but same failure mode and improved clarity.
Tarflan Neo/PC- Similar impact performance and failure mode as
compared to 10XE2-CL01(V) PC-10XE1-CL01(V), but improved
clarity.
[0055] Analysis of the initial test results (up through testing
with the EXL1433T) identified bats made using the
polycarbonate/siloxane block copolymer chemistry as clearly
superior to bats made from all the other tested polymers in both
impact fatigue and the ability to avoid flattening under impact.
That said, bat barrels incorporating the EXL1433T performance were
still not sufficiently durable to meet the goal of 300-500 impacts
before failure. Further research suggested that impact fatigue
performance might be related to the molecular weight of the
specific polycarbonate-siloxane copolymer selected. While the
specific molecular weight of the polymers being tested was not
available to the research team (not published), data was published
on the relative Melt Flow Index (MFI) of all the EXL products and
the value of the MFI has been observed to have an inverse
correlation with molecular weight, i.e., as molecular weight goes
up, the molecules get longer and become more intertwined, leading
to higher viscosity at melt and lower MFI. (Melt Flow Index is
defined by ASTM D1238 and ISO 1133. It is also sometimes referred
to as Melt Volume Flow. The units of measure are grams/10 minutes
and cubic centimeters/10 minutes, respectively. For this family of
polymers, the test is conducted at 300.degree. C. using a weight of
2.65 pounds.) It is believed that this molecular intertwining was
the reason behind enhanced impact fatigue. As a secondary benefit
of this low MFI, it was found that the ease of manufacturing using
an extrusion press was also improved. Manufacturing trials and
field performance of EXL1033C supported the durability hypothesis
that lower MFI correlated with better impact fatigue life, as the
number of impacts to benign failure climbed into the range of
500-1000 impacts.
[0056] FIGS. 5A and 5B illustrate the benign mode of failure
experienced by all the test samples incorporating the
polycarbonate/siloxane block copolymer chemistry. This benign
failure mode was an unexpected and fortuitous result that could not
have been predicted at the start of the project. Typically, a small
sub-surface crack 60 first appeared, running generally axially,
with no noticeable loss of performance as measured by player "feel"
and ball hit distance. With repeated impact, this crack 60 would
grow in length and come to the surface, both on the ID and the OD
of the tube wall. These cracks were often observed to grow in
length to two inches or more and they would eventually result is a
radial displacement of one side of the crack relative to the other.
Even then, while performance began to degrade, there was never an
incident where a barrel section broke into pieces or created
projectile shards. There was always clear and obvious indication
that failure was occurring and positive motivation (loss of
performance) for the user to take the bat out of service. This
benign failure mode was observed in all temperatures tested,
including those cold enough that damage to aluminum and composite
bats was likely.
[0057] Further analysis of the test results suggested that the
"secret sauce" for the family of materials exhibiting the best
performance was a siloxane molecule that was co-polymerized with
polycarbonate. Several patents have been filed by GE describing
this technology including U.S. Pat. No 4,397,973, 5,194,524 and
5,455,310, which are incorporated herein by reference.
[0058] Toward the end of the test program, samples of various
polycarbonate-siloxane thermoplastics were sourced from Idemitsu
and prepared to our specifications by a US-based distributor. This
Idemitsu product worked marginally better than the Sabic product
and was subsequently identified as being comprised of a
polycarbonate molecule based either on bisphenol A or poly-(4,4
isopropyliden diphenyl carbonate) chemistry combined with a
siloxane component based on polydimethylsiloxane chemistry. The
molecular weight of the best products tested ranged from 10,000 to
32,000 Daltons and, preferentially, from 24,000 to 32,000 Daltons.
The Melt Flow Index for the best products was also identified as
2-12 grams/10 minutes and, preferentially, 2-6 grams/10
minutes.
[0059] While FIG. 1 illustrates one embodiment of a baseball or
softball bat design that consists of various parts which may be
assembled together and replaced as pieces should one or another
break, it is understood that other, more traditional, permanently
assembled embodiments of baseball or softball bats would also
benefit from the use of polycarbonate-siloxane copolymer based
thermoplastics for many of the same or equivalent parts. Barrel
subassembly 20 and the secondary barrel section 30 are the
principle parts of the bat subject to impact. Handle subassembly 10
typically requires more stiffness than can be provided by
unreinforced thermoplastics, but thermoplastic construction for the
handle subassembly 10 is still possible and, since the ball
occasionally impacts the handle (as in a very inside pitch), handle
subassembly 10 will still benefit from good impact tolerance.
[0060] In some embodiments, all the components of the barrel
subassembly 20 and the second barrel section 30 are fabricated
using a polycarbonate-siloxane copolymer thermoplastic. In this
case, it may be advantageous to weld various pieces together to
simplify final assembly of the bat or to permanently position one
component relative to another. In some embodiments, these
components are ultrasonically or inertially welded together using
techniques that are well known in the field. In other embodiments,
the materials of construction for each component may vary. For
example, the first barrel section 21 and the second barrel section
30 may be fabricated from the polycarbonate-siloxane copolymer
while other less impacted components such as the end cap 24 or knob
or transition 23 are manufactured from an alternative, possibly
lower cost thermoplastic. In some embodiments, the first barrel
section 21 might be made from the polycarbonate-siloxane copolymer
while the second barrel section is made from aluminum or a
composite material such as fiberglass/epoxy or carbon fiber/epoxy,
both with a higher modulus of elasticity and therefore stiffer and
capable of reducing the hoop deflection of the first barrel section
21 more or adding more ballast weight than if any thermoplastic
material was used for the second barrel section 30. In yet another
embodiment, the choice of first barrel section 21 and second barrel
section 30 materials might be reversed, with the stiffer material
used for the first barrel section 21 and the polycarbonate-siloxane
copolymer material used for second barrel section 30. Thus, in
addition to helping to manage the weight distribution and center of
mass of the bat, the material chosen for the second barrel section
30 can also help to control the overall barrel subassembly 20 hoop
deflection and thus the overall bat performance level.
[0061] FIG. 6 illustrates an embodiment wherein the long central
handle and the transition section have been co-molded creating
handle assembly 70. The first barrel section 21 and the second
barrel section 30 are similar to those shown in earlier figures.
For some embodiments, end cap 24 and aft support 71, designed to
support at least one of the first barrel section and the second
barrel section, can be manufactured using a resilient material such
as silicone rubber or a polyurethane to act as energy absorbers and
vibration isolators, helping to reduce the level of vibrations
created during the ball/bat contact being transmitted into the
handle assembly 70 and ultimately into the batter's hands.
[0062] Manufacturers who can provide this polycarbonate-siloxane
copolymer generally can add certain other proprietary compounds to
the basic copolymer to enhance color, clarity or cold weather
performance, though sometime at the expense of lower impact fatigue
life. For specific marketing/commercial purposes, this may still be
desirable. For example, in some embodiments it is advantageous to
put the product graphics on the inside of a clear first barrel
section 21 or to dispose them onto the outer surface of the second
barrel section 30. In this condition, the graphics are less likely
to be damaged and it can add a sense of depth visually that is not
possible with graphics mounted on the outside surface of barrel
subassembly 20.
* * * * *