U.S. patent application number 16/123344 was filed with the patent office on 2019-01-10 for gas turgine engine with transmission.
The applicant listed for this patent is PRATT & WHITNEY CANADA CORP.. Invention is credited to Kevin A. DOOLEY, Jean DUBREUIL, Stephen KENNY, Ilya MEDVEDEV, Lazar MILTROVIC, Keith MORGAN, Richard ULLYOTT, Johnny VINSKI.
Application Number | 20190010875 16/123344 |
Document ID | / |
Family ID | 51257920 |
Filed Date | 2019-01-10 |
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United States Patent
Application |
20190010875 |
Kind Code |
A1 |
ULLYOTT; Richard ; et
al. |
January 10, 2019 |
GAS TURGINE ENGINE WITH TRANSMISSION
Abstract
A multi spool gas turbine engine with a differential having a
selectively rotatable member which rotational speed determines a
variable ratio between rotational speeds of driven and driving
members of the differential. The driven member is engaged to the
first spool and a rotatable shaft independent of the other spools
(e.g. connected to a compressor rotor) is engaged to the driving
member. First and second power transfer devices are engaged to the
first spool and the selectively rotatable member, respectively. A
circuit interconnects the power transfer devices and allows a power
transfer therebetween, and a control unit controls the power being
transferred between the power transfer devices. Power can thus be
transferred between the first spool and the selectively rotatable
member to change the speed ratio between the first spool and the
rotatable shaft.
Inventors: |
ULLYOTT; Richard; (St.
Bruno, CA) ; MORGAN; Keith; (Westmount, CA) ;
DUBREUIL; Jean; (Boucherville, CA) ; MILTROVIC;
Lazar; (Longueuil, CA) ; DOOLEY; Kevin A.;
(Toronto, CA) ; KENNY; Stephen; (Caledon Village,
CA) ; MEDVEDEV; Ilya; (St. Petersburg, RU) ;
VINSKI; Johnny; (Chateauguay, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PRATT & WHITNEY CANADA CORP. |
Longueuil |
|
CA |
|
|
Family ID: |
51257920 |
Appl. No.: |
16/123344 |
Filed: |
September 6, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13754304 |
Jan 30, 2013 |
10094295 |
|
|
16123344 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05D 2220/327 20130101;
F05D 2220/324 20130101; F02C 3/113 20130101; F02C 7/36
20130101 |
International
Class: |
F02C 7/36 20060101
F02C007/36; F02C 3/113 20060101 F02C003/113 |
Claims
1. A method of adjusting a speed of a rotatable shaft of a gas
turbine engine having a high pressure section including
interconnected compressor and turbine rotors, the method
comprising: rotating at least one rotor of a low pressure turbine
with a flow of exhaust gases from the high pressure section;
driving a rotation of the rotatable shaft with a power shaft
through a variable transmission, the power shaft being driven by
the at least one rotor of the low pressure turbine; and
transferring power between the power shaft and a rotational member
of the transmission to change a ratio of rotational speeds between
the rotatable shaft and the power shaft.
2. The method as defined in claim 1, wherein transferring power
includes transferring power from the power shaft to the
transmission to increase the rotational speed of the rotatable
shaft and transferring power from the transmission to the power
shaft to decrease the rotational speed of the rotatable shaft.
3. The method as defined in claim 1, wherein driving a rotation of
the rotatable shaft includes driving a rotation of at least one
rotor of a low pressure compressor located upstream of the high
pressure section and coupled to the rotatable shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. application
Ser. No. 13/754,304 filed Jan. 30, 2013 the content of this
application being incorporated herein by reference.
TECHNICAL FIELD
[0002] The application relates generally to gas turbine engines
and, more particularly, to a gas turbine engine having a
transmission.
BACKGROUND OF THE ART
[0003] In a turbofan engine, rotor(s) of the low pressure turbine
driven by the exhaust flow of the core section are generally
drivingly connected to rotor(s) of a low pressure compressor,
including the fan, through the low pressure shaft. In turboprop and
turboshaft engines, a low pressure compressor rotor may also be
connected to the low pressure or power shaft, and the propeller or
output shaft is driven by the low pressure shaft either directly or
through a fixed ratio gearbox.
[0004] Because power demands on the engine vary, for example
between take-off and cruise conditions, the turbine and compressor
rotors of the core section typically have to rotate at a relatively
large range of rotational speeds in order for the low pressure
turbine rotor(s), and thus the low pressure compressor rotor(s)
and/or propeller or output shaft, to have the required rotational
speed. Low power requirement conditions may require the rotors of
the core section to rotate relatively far below their optimal
rotational speed, which may limit the engine's efficiency in such
conditions.
SUMMARY
[0005] In one aspect, there is provided a gas turbine engine
comprising: at least two independently rotatable engine spools; at
least one turbine rotor drivingly engaged to a first one of the
engine spools; a differential having coupled members including a
driven member, a driving member, and a selectively rotatable member
with a rotational speed of the selectively rotatable member
determining a variable ratio between rotational speeds of the
driven and driving members, the driven member being drivingly
engaged to the first spool; a rotatable shaft drivingly engaged to
the driving member and rotatable independently from all but the
first of the engine spools; a first power transfer device drivingly
engaged to the first spool; a second power transfer device
drivingly engaged to the selectively rotatable member; a circuit
interconnecting the power transfer devices and allowing a power
transfer therebetween; and a control unit controlling the power
being transferred between the power transfer devices through the
circuit.
[0006] In another aspect, there is provided a gas turbine engine
comprising: a low pressure turbine located downstream of and in
fluid communication with an exhaust of a high pressure section of
the engine, the low pressure turbine having at least one turbine
rotor; a differential having coupled members including a driven
member, a driving member, and a selectively rotatable member with a
rotational speed of the selectively rotatable member determining a
variable ratio between rotational speeds of the driven and driving
members; a low pressure shaft drivingly interconnecting each
turbine rotor to the driven member; a low pressure compressor
located upstream of and having an exhaust in fluid communication
with the high pressure section of the engine, the low pressure
compressor having at least one compressor rotor drivingly
interconnected to the driving member; first means for transferring
power at least one of to and from the low pressure shaft; second
means for transferring power at least the other of to and from the
selectively rotatable member; and a control unit connecting the
first and second power transfer means and controlling power being
transferred therebetween.
[0007] In a further aspect, there is provided a method of adjusting
a speed of a rotatable shaft of a gas turbine engine having a high
pressure section including interconnected compressor and turbine
rotors, the method comprising: rotating at least one rotor of a low
pressure turbine with a flow of exhaust gases from the high
pressure section; driving a rotation of the rotatable shaft with a
power shaft through a variable transmission, the power shaft being
driven by the at least one rotor of the low pressure turbine; and
transferring power between the power shaft and a rotational member
of the transmission to change a ratio of rotational speeds between
the rotatable shaft and the power shaft.
DESCRIPTION OF THE DRAWINGS
[0008] Reference is now made to the accompanying figures in
which:
[0009] FIG. 1 is a schematic cross-sectional view of a gas turbine
engine having a transmission in accordance with a particular
embodiment;
[0010] FIG. 2 is a schematic cross sectional view of an exemplary
gas turbine engine such as that shown in FIG. 1;
[0011] FIG. 3 is a schematic cross sectional view of a transmission
of the gas turbine engine of FIG. 2;
[0012] FIG. 4 is a schematic cross sectional view of an alternate
transmission of the gas turbine engine of FIG. 2;
[0013] FIG. 5 is a tridimensional view of a differential of the
transmissions of FIGS. 3-4;
[0014] FIG. 6 is a schematic cross sectional view of an alternate
transmission of the gas turbine engine of FIG. 2;
[0015] FIG. 7 is a schematic cross sectional view of another
exemplary gas turbine engine such as that shown in FIG. 1; and
[0016] FIG. 8 is a schematic cross sectional view of a further
exemplary gas turbine engine such as that shown in FIG. 1.
DETAILED DESCRIPTION
[0017] FIG. 1 schematically illustrates a gas turbine engine 10,
generally comprising in serial flow communication a low pressure
compressor section 12 and a high pressure compressor section 14 for
pressurizing the air, a combustor 16 in which the compressed air is
mixed with fuel and ignited for generating an annular stream of hot
combustion gases, a high pressure turbine section 18 for extracting
energy from the combustion gases and driving the high pressure
compressor section 14, and a low pressure turbine section 20 for
further extracting energy from the combustion gases and driving at
least the low pressure compressor section 12.
[0018] The engine 10 includes a high pressure shaft or spool 22
interconnecting the rotors of the high pressure turbine and
compressor sections 18, 14, and a low pressure or power shaft or
spool 24 allowing the rotor(s) of the low pressure turbine section
20 to drive the rotor(s) of the compressor sections 12, as will be
further detailed below. In a particular embodiment, the high
pressure shaft 22 is hollow and the low pressure shaft 24 extends
therethrough. The two shafts 22, 24 are free to rotate
independently from one another. The engine 10 further includes a
variable transmission 30, 130 driven by the low pressure shaft 24
and driving a rotatable transmission shaft 32. The transmission 30,
130 is controlled to vary a ratio between the rotational speeds of
the low pressure shaft 24 and the transmission shaft 32.
[0019] The engine 10 schematically illustrated in FIG. 1 can be any
type of gas turbine engine. In a particular embodiment shown in
FIG. 2, the gas turbine engine 10 is a turboshaft engine. The high
pressure compressor section 14 includes at least one high pressure
compressor rotor 114 drivingly engaged to the high pressure shaft
22. The high pressure turbine section 18 includes at least one
turbine rotor 118 also drivingly engaged to the high pressure shaft
22. The high pressure compressor and turbine rotors 114, 118 are
directly engaged to the high pressure shaft 22, so that they rotate
at a same speed.
[0020] The low pressure turbine 20 includes at least one low
pressure turbine rotor 120 directly drivingly engaged to the low
pressure shaft 24 so as to rotate at the same speed. The engine 10
further includes an output shaft 26, which in a particular
embodiment is an extension of the low pressure shaft 24 extending
through the transmission 30, such that the transmission shaft 32 is
hollow (see FIG. 3) and extends around the low pressure shaft and
output shaft 26. In other words, in this particular embodiment, the
output shaft 26 of the engine 10 is an integral section of the low
pressure shaft 24 and not affected by the transmission 30.
[0021] The low pressure compressor 12 includes at least one low
pressure compressor rotor 112 connected to the transmission shaft
32 to be drivingly engaged to the low pressure shaft 24 through the
variable transmission 30. The variable transmission 30 allows for a
variation of the rotational speed of the low pressure compressor
rotor(s) 112 independently of the speed of the turbine sections 18,
20, e.g. while keeping the rotational speed of the turbine sections
18, 20 substantially constant or constant. For example, the ratio
of the variable transmission 30 may be adjusted such as to have a
lower low pressure ratio and flow at lower power demands (e.g.
cruise) and an increased low pressure ratio and flow at higher
power demands (e.g. take-off).
[0022] Referring to FIGS. 3-5, in a particular embodiment, the
variable transmission 30 generally includes a differential 34, two
means for transferring power which in the particular embodiment
shown are electric power transfer devices 36, 38 usable as electric
motor/generators, and a control unit 40. The two power transfer
devices 36, 38 are interconnected through an electrical circuit 68
to allow transfer of power therebetween. In the embodiment shown,
the control unit 40 is part of the circuit 68.
[0023] The first power transfer device 36 is coupled to the low
pressure shaft 24, either directly (FIG. 3) or through one or more
intermediate members such as for example an offset gear arrangement
42 (FIGS. 4-5); the coupling is preferably selected to match the
machine's optimal rotational speed with that of the low pressure
shaft 24.
[0024] The differential 34 has coupled members which include a
driven member 44 connected to the low pressure shaft 24, a driving
member 46 connected to the transmission shaft 32, and a selectively
rotatable member 48 which is coupled to the driven and driving
members 44, 46 such that its rotational speed determines the ratio
between the rotational speeds of the driven and driving members 44,
46. The second power transfer device 38 is coupled to the
selectively rotatable member 48, either directly or through an
offset gear arrangement 50 (as shown) such as to vary the ratio of
the transmission 30 in a continuous manner.
[0025] In the embodiment shown, the differential 34 includes two
coupled planetary gear systems 52, 54 (see FIG. 3). The sun gear of
the first system is the driven member 44 and as such is drivingly
engaged to the low pressure shaft 24, for example by being formed
integrally therewith. The first system 52 includes a plurality of
planet gears 56 (only one of which is shown) meshed with the sun
gear 44 and retained by a carrier 58, and an annular ring gear 60
(only partially shown in FIG. 3) surrounding the planet gears 56
and meshed therewith. The ring gear 60 of the first system 52 is
fixed.
[0026] The sun gear of the second system 54 is the driving member
46 and as such is drivingly engaged to the transmission shaft 32,
for example by being formed integrally therewith. The second system
54 includes a plurality of planet gears 62 (only one of which is
shown) meshed with the sun gear 46 and retained by a carrier 64,
and an annular ring gear surrounding the planet gears and meshed
therewith. The two carriers 58, 64 are interconnected such as to
couple the two planetary systems 52, 54. The ring gear of the
second system is the selectively rotatable member 48 and as such is
drivingly engaged to the second power transfer device 38. The
second power transfer device 38 maintains a torque on the second
ring gear 48 to prevent its free rotation.
[0027] Alternate transmission configurations are also possible. For
example, the configuration described above could be used with the
first power transfer device 36 being indirectly coupled to the low
pressure shaft 24 through engagement with the connected carriers
58, 64. The configuration described above could also be modified by
inverting the roles of the two ring gears, i.e. having the second
power transfer device 38 coupled to the ring gear of the first
system 52 with the ring gear of the second system 54 being fixed. A
differential with a single planetary system may alternately be
used, for example with the first power transfer device 36 engaged
to the low pressure shaft 24, the ring gear engaged to the second
power transfer device 38, the carrier engaged to the transmission
shaft 32 and the sun gear engaged to the low pressure shaft 24,
provided the speed ratios and maximum rotational speeds are adapted
for a single planetary system. Other alternate configurations are
also possible, including a differential having a different
configuration than a planetary system.
[0028] In use, the speed of the transmission shaft 32 may be
adjusted independently of the rotational speed of the high pressure
compressor and turbine rotors, e.g. while keeping the rotational
speed of the high pressure compressor and turbine rotors 114, 118
at a constant or substantially constant value, by transferring
power between the low pressure shaft 24 and the transmission 30
through the power transfer devices 36, 38, to change the rotational
speed ratio between the transmission shaft 32 and the low pressure
shaft 24.
[0029] In a particular embodiment, the power transfer devices 36,
38 form a bidirectional system, i.e. both power transfer devices
36, 38 may alternately be used as a motor and as a generator.
Accordingly, the differential 34 is sized such that when the second
ring gear 48 is maintained in a fixed position, the transmission
shaft 32, and as such the low pressure compressor rotor 112,
rotates at an intermediate speed, for example 50% of its maximum
speed. To increase the speed of the transmission shaft 32, the
second power transfer device 38 is used as a motor to rotate the
second ring gear 48 in a direction opposite that of the carriers
58, 64, which causes the sun gear 46 of the second system 54 to
rotate faster. A faster rotation of the second ring gear 48 in a
direction opposite of that of the carriers 58, 64 causes the second
sun gear 46 together with the transmission shaft 32 and the low
pressure compressor rotor 112 to rotate faster. The first power
transfer device 36 is used as a generator to produce electricity
from the rotation of the low pressure shaft 24, which is converted
to the appropriate frequency by the control unit 40 and transferred
to the second power transfer device 38 through the circuit 68 to
power its rotation.
[0030] To reduce the speed of the transmission shaft 32, the second
ring gear 48 is allowed to rotate in the same direction as the
carriers 58, 64, and the second power transfer device 38 is used as
a generator to brake the rotation of the second ring gear 48. A
slower rotation of the second ring gear 48 causes the second sun
gear 46 together with the transmission shaft 32 and the low
pressure compressor rotor 112 to rotate slower. The electricity
produced by the second power transfer device 38 is converted to the
appropriate frequency by the control unit 40 and transferred to the
first power transfer device 36 through the circuit 68 to return
power to the low pressure shaft 24 in the form of increased
torque.
[0031] In another embodiment, the power transfer devices 36, 38
form a unidirectional system. For example, the second power
transfer device 38 coupled to the second ring gear 48 is used only
as a generator and the first power transfer device 36 coupled to
the low pressure shaft 24 is used only as a motor. Accordingly, the
differential 34 is sized such that when the second ring gear 48 is
maintained in a fixed position, the transmission shaft 32 rotates
at a maximum desired speed. The speed of the transmission shaft 32
is decreased from that point as detailed above, and the power
generated is returned to the low pressure shaft 24 in the form of
increased torque. Alternately, the second power transfer device 38
coupled to the second ring gear 48 may be used only as a motor with
the first power transfer device 36 coupled to the low pressure
shaft 24 used only as a generator. The differential 34 is sized
such that when the second ring gear 48 is maintained in a fixed
position, the transmission shaft 32 rotates at a minimum desired
speed. The speed of the transmission shaft 32 is increased from
that point as detailed above, using power generated from the low
pressure shaft 24 by the first power transfer device 36 to drive
the second power transfer device 38. The unidirectional systems
however typically necessitate larger power transfer devices 36, 38
since the necessary torque range will generally be larger to obtain
a same speed variation as an equivalent bidirectional system.
[0032] Referring to FIG. 6, a variable transmission 130 in
accordance with another embodiment includes the differential 34
described above and means for transferring power in the form of two
hydraulic power transfer devices 136, 138. The power transfer
devices 136, 138 are interconnected by a closed hydraulic circuit
168 and connected to a control unit 140, and hydraulic power is
transferred between the devices 136, 138 through a flow of
hydraulic fluid in the circuit 168.
[0033] In one embodiment, the first power transfer device 136 is a
pump including an auxiliary pump (not shown) to pump hydraulic
fluid from a reservoir 166 as required. In the embodiment shown,
the first power transfer device 136 has a smaller optimal
rotational speed than the rotational speed of a low pressure shaft
24 and as such is coupled thereto through an offset gear
arrangement 142. Alternately, for power transfer devices having
optimal rotational speeds corresponding to that of the low pressure
shaft, a direct connection may be provided.
[0034] The second ring gear 48 is drivingly engaged to the second
power transfer device 138, for example through an offset gear
arrangement 50. The second power transfer device 138 maintains a
torque on the second ring gear 48 to prevent its free rotation.
[0035] In a particular embodiment, the power transfer devices 136,
138 may both be alternately operated as a pump and as a motor,
providing for a bidirectional system. The power transfer device
136, 138 acting as a pump supplies a flow of hydraulic fluid to the
power transfer device 136, 138 acting as a motor through a closed
hydraulic circuit 168. In a particular embodiment, at least one of
the power transfer devices 136, 138 has a variable displacement
such as to be able to vary the rotational speed of the second power
transfer device 138 through variation of the displacement. In one
embodiment, both power transfer devices 136, 138 have a variable
displacement for increased controlled speed range. The control unit
140 changes the displacement of the variable unit(s) as required.
Alternately, the rotational speed of the second power transfer
device 138 may be varied by changing the hydraulic pressure in the
circuit 168, for example by having the control unit 140 actuating a
pressure valve.
[0036] Accordingly, as above, the differential 34 is sized such
that when the second ring gear 48 is maintained in a fixed
position, the transmission shaft 32 rotates at an intermediate
speed, for example 50% of its maximum speed. To increase the speed
of the transmission shaft 32, the second power transfer device 138
is used as a motor to rotate the second ring gear 48 in a direction
opposite that of the carriers 58, 64. The first power transfer
device 136 is used as a pump, driven by the low pressure shaft 24
to circulate the hydraulic fluid within the circuit 168 to power
the rotational motion of the second power transfer device 138. To
reduce the speed of the transmission shaft 32, the second ring gear
48 is allowed to rotate in the same direction as the carriers 58,
64, and the second power transfer device 138 is used as a pump,
braking the rotation of the second ring gear 48. The hydraulic flow
produced by the second power transfer device 138 powers the first
power transfer device 136 which is used as a motor to return power
to the low pressure shaft 24 in the form of increased torque.
[0037] In another embodiment, the power transfer devices 136, 138
form a unidirectional system. For example, the second power
transfer device 138 coupled to the second ring gear 48 is used only
as a pump, with the fixed position of the second ring gear 48
corresponding to the maximum desired speed of the transmission
output shaft 32. The speed of the transmission shaft 32 is
decreased from that point as detailed above, and the power
generated is returned to the low pressure shaft 24 in the form of
increased torque by the first power transfer device 136 working
only as a motor and powered by the hydraulic flow produced by the
second power transfer device 138. Alternately, the second power
transfer device 138 coupled to the second ring gear 48 may be used
only as a motor, with the fixed position of the second ring gear 48
corresponding to the minimum desired speed of the transmission
output shaft 32. The speed of the transmission shaft 32 is
increased from that point as detailed above, by powering the second
power transfer device 138 with the hydraulic flow generated by the
first power transfer device 136 driven by the low pressure shaft
24.
[0038] The means for transferring power may alternately be other
types of power transfer devices, for example pneumatic
motors/compressors. Pneumatic power is transferred between the
power transfer devices through a flow of compressed air in a
pneumatic circuit between the devices. As above, bidirectional or
unidirectional systems can be used.
[0039] Advantageously, the variable transmission 30, 130 driving
the low pressure compressor rotor(s) 112 may help optimize the
performances and surge margin of the low pressure compressor 12, by
scheduling the speed of the low pressure compressor rotor(s) 112 as
a function of the aerodynamic speed of the high pressure compressor
rotor(s) 114. This can be done for example by using the engine
electronic control (EEC), which typically receives data on the
rotational speed of the rotors 112, 114 of both compressors 12, 14.
The EEC governs the low pressure turbine 120 to a set rotational
speed and from the other data received from the various engine
sensors (e.g. temperatures at the inlet of the low and high
pressure compressors 12, 14, rotational speed of the low and high
pressure compressor rotors 112, 114, fuel flow, rotational speed of
low pressure turbine rotor(s) 120) determines a desired rotational
speed for the low pressure compressor rotor(s) 112 and commands it
from the control unit 40, 140, which accordingly actuates the power
transfer between the power transfer devices 36, 38, 136, 138.
[0040] The use of the transmission 30, 130 may also allow for the
power output of the engine 10 to be varied while maintaining core
temperature and rotational speeds where the turbine sections 18, 20
are most efficient. The variable transmission 30, 130 may allow for
the low pressure compressor 12 to operate at a more optimum speed
relative to the power demand, thus increasing its efficiency even
when keeping the turbine sections 18, 20 at constant or relatively
constant speeds. Accordingly, it may also allow for the high
pressure section to be maintained at a more constant speed
throughout the range of power demands. In a particular embodiment,
the variable transmission 30, 130 allows for the rotational speed
of the high pressure turbine section 18 to be kept within a range
of approximately from 80 to 100% of its optimal speed, by contrast
with an equivalent engine having the low pressure compressor
directly driven by the low pressure shaft which typically has the
high pressure turbine section rotating within a range of 50 to 100%
of its optimal speed.
[0041] Although the transmission 30, 130 has been described here as
being applied to driving the low pressure compressor rotor(s) 112
in a turboshaft engine, other applications are also possible. The
transmission 30, 130 can be used to drive the rotor(s) of low
pressure compressors 12 in other types of gas turbine engines, for
example turbofans (FIG. 7) and turboprops. Also, the engine output
shaft 26 of FIGS. 1-2 may be an integral part of or connected to
the transmission shaft 32 such that the transmission 30, 130
affects the rotational speed of the engine output shaft 26. Such a
configuration can be used in replacement of or in addition to
having the low pressure compressor rotor(s) 112 driven through the
transmission 30, 130. Similarly, for a turbofan, the transmission
shaft 32 may be keyed to the fan such that the transmission 30, 130
affects the rotational speed of the fan, in addition or in
replacement to having other rotor(s) of the low pressure compressor
12 driven through the transmission 30, 130. The transmission 30,
130 may also be used to drive a propeller 15 in a turboprop engine
in replacement to having a low pressure compressor driven through
the transmission, as shown in FIG. 8, or in addition thereto. The
transmission 30, 130 may also be used in any type of gas turbine
engine, including industrial power plants and auxiliary power
units, for example to drive low pressure compressor rotor(s).
[0042] Accordingly, the above description is meant to be exemplary
only, and one skilled in the art will recognize that changes may be
made to the embodiments described without departing from the scope
of the invention disclosed. Still other modifications which fall
within the scope of the present invention will be apparent to those
skilled in the art, in light of a review of this disclosure, and
such modifications are intended to fall within the appended
claims.
* * * * *