Note: Descriptions are shown in the official language in which they were submitted.
CA 02392197 2002-06-27
TITLE
UNITIZED RAILCAR BRAKE EQUIPMENT
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon copending United States Provisional
Patent Application Serial No. 60/302,319, filed June 29, 2001.
BACKGROUND OF THE INVENTION
The present invention relates generally to controlling brakes on a train
of xailcars, and more particularly to highly efficient, unitized railcar brake
equipment
that is based on electronic control of a pneumatically operated, stand-alone
brake
cylinder that can have a small, integrated air supply volume.
Historically, braking on railcars can has been implemented using
pneumatic brake equipment provided on each railcar. Such prior art equipment
typically can include a control valve which is connected to a brake pipe that
interconnects the locomotive and each railcar in the train. The brake
equipment on
each car further can include a two compartment reservoir of pressurized air
which the
control valve can utilize to pressurize the brake cylinder on the car.
U.S. Pat. No. Re. 30;408, reissued Sept. 30, 1981, to the assignee of the
present application; discloses railway brake apparatus including a brake
cylinder device
and a control valve device. The usual air reservoirs associated with
conventional
pneumatic brake equipment can be minimized or eliminated in the disclosed
apparatus
in favor of storing the compressed air within, the brake cylinder device
itself. The
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brake cylinder device disclosed embodies a pair of tandem-connected pistons of
unequal diameter, the larger piston cooperating with the brake cylinder body
to form
on the respective opposite sides of this piston two chambers that are charged
with
compressed air via the train brake pipe, and in which chambers the air
required for use
by the brake apparatus, including the brake cylinder device, is stored. The
aforementioned control valve device operates in response to variations in the
train
brake pipe pressure to control the transfer of air stored in the brake
cylinder device, so
as to develop differential forces across the respective pistons thereof, and
thereby effect
a brake.application and brake release. In addition to the typical packing cup
type
pressure seals associated with the respective pistons of this brake
cylinderdevice, there
are several additional areas in which dynamic sealing is required, all of
which are
critical in the sense that leakage thereat affects the desired operation of
the brake
cylinder device. Further, passageways are required in the body of the brake
cylinder
device to conduct pressure between the control valve device and brake cylinder
operating components. It is well known that the expense in the manufacture of
a
casting increases with the complexity in the configuration of these passages,
as well as
in the shape of the casting itself.
U.S. Patent No. 4,418,799; issued December 6, 1983 to the assignee of the
present application, discloses a pneumatic brake cylinder device which
improves upon
the brake cylinder device disclosed in Re 30,408: This brake cylinder device
employs
a pair of different sized fluid motors the pressure chambers of which serve as
air
storage reservoirs. The cylinder of the larger fluid motor is forrded by the
main casting
anti contains a larger piston, while the cylinder of the smaller fluid motor
is mounted to
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the main casting in coaxial relationship with the larger cylinder and contains
a smaller
piston having an elongated hollow body that is connected at its open end to
one side of
the larger piston to form a pressure chamber therebetween. The smaller,
positioning
piston fits within the smaller cylinder in spaced-apart relationship therewith
to form a
pressure chamber delimited by a seal fixed on the main casting for engagement
with
the piston periphery at any point along its longitudinal axis. The larger,
power piston
cooperates with the larger cylinder to form pressure chambers on opposite
sides
thereof. As compared to the device disclosed in Re 30;408, the arrangement
in 4,418,799 provides for a design employing fewer seals and a simplified main
casting
in which all the passages to the respective pressure chambers are contained. A
similarity between the two devices is that a pair of pistons are employed,
wherein the
smaller piston displaces the larger piston in order to provide a brake
application. As
the smaller, positioning piston drives the larger, power piston air is
transferred from an
air chamber behind the power piston into a chamber on top of the positioning
piston.
In an emergency application, air in the chamber behind the power piston can be
vented
while air from a third chamber is coupled to the chamber on top of the
positioning
piston. To release the brakes, the chamber on top of the positioning piston is
vented
and the chamber behind the power piston is recharged.
Railcar brake equipment, including the two brake equipment devices
described above, historically initiate brake application and release
operations on the
railcar based upon pneumatic brake commands from a brake control valve on a
locomotive. These pneumatic commands are typically communicated to each
railcar
by pausing pressure changes in a brake pipe connecting each railcar to the
locomotive
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brake control valve. In the past, and particularly on freight ears operating
in North
America, the railcar brake equipment, including the specific brake equipment
described
above, can only implement a "direct" release of brakes on the railcar. Direct
release
means that the pressure in the brake cylinder on the railcar can only be fully
released,
as opposed to gradually releasing the pressure to gradually reduce the braking
force.
However, some pneumatically operated brake equipment has been disclosed which
can
provided graduated release capability. Additionally;:graduated release of
railcar brakes
has recently been the target of brake system development in the American
railway
system and can be implemented using what is commonly referred to today as
electrically controlled pneumatic (ECP) braking systems. ECP braking systems
use
specialized equipment on locomotives and railcars whereby brake command
signals are
generally instantaneously communicated, via a hardwired tramline or RF
communications, between the locomotive and each railcar. The ECP brake
equipment
on each railcar typically utilizes solenoid type valves to control the air
pressure in the
brake cylinders; and are thus easily controllable to gradually increase or
decrease the
level of braking on each railcar. However; use of ECP braking systems can
require a
trainline wire or RF communication equipment and electronic control valves on
each
railcar, as well as electronic control ystems on the locomotive.
SUMMARY
An efficient, unitized' railcar brake equipment can be provided wherein a
pneumatically operated, stand-alone brake cylinder can have a relatively
small,
integrated air supply volume which can be selectively coupled to opposite
sides of a
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singlepiston for gradually applying or releasing the brakes on the railcar.
The unitized
brake equipment can be operated without; or independently of, a conventional
pneumatic control valve, and can be controlled from a locomotive in an ECP
manner
using, for example, a trainIine or an RF communication system. Furthermore,
the
unitized brake equipment could automatically initiate a full pneumatic brake
application responsive to a loss of brake pipe pressure, without electronic
intervention
or control. The unitized brake equipment can include a brake cylinder and a
piston
member housed therein with a first air chamber in communication with the face
of the
piston and a second air chamber in communication with the opposite side of the
piston.
An air reservoir can also be provided, and can be formed as an integral part
of the
brake cylinder. The first and second air chambers and the air reservoir can be
interconnected by air passages and controlled by valves, so that they may be
selectively
coupled and uncoupled to control pressure in the brake cylinder. Some of the
valves
can be electrically operated remotely, for example, by a train engineer, to
control air
pressure in the brake cylinder to operate the brakes on the railcar.
Additionally; same
valves can be co~gured to operate:automatically in response to fluid pressure
conditions prevailing in the air passages in the unitized brake equipment, or
pressure
conditions in the brake pipe, to which the unitized brake equipment can be
connected:
The unitized brake equipment can be supplied with pressurized air from, for
example,
the brake pipe for charging the reservoir andlor the first and second air
chambers.
Additionally, the unitized brake equipment can be selectively vented to the
atmosphere,
for example, by appropriate valves, for reducing the pressure in the brake
cylinder.
The valves for controlling the air pressure in the various chambers and
reservoir can be
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provided as components of an electronic control valve portion, which can be
mounted
on the front or rear of the brake cylinder, via a pipe-bracket type of
interface. The
interface can be a separate component or can be formed as an integral part of
the brake
cylinder.
The unitized brake equipment can employ a "self: actuating" brake
cylinder, wherein air pressure is admissible to both sides of the piston, but
acts on
unequal effective areas provided on the opposing sides. For example, the face
of the
piston can be provided with a larger effective area such that it has an
effective
advantage over the opposite side of the piston: The unitized brake equipment
can be
designed such that, in release position, the internal volume of the first
chamber, acting
on the face of the piston, is relatively small, whereas the largest portion of
the internal
volume of the brake cylinder can be provided as the second chamber, which acts
on the
opposite side of the piston. The second chamber can thus also be utilized as
an
integrated air reservoir. To apply the brakes, the piston is forced to the
applied position
simply by connecting the air chambers on either side of the piston, and
allowing the
pressure on the face of the piston to approach the pressure on the opposite
side, due to
the area advantage. To thereafter reduce pressure in the brake cylinder, the
smaller
first air chamber acting on the face of the piston can be controllably
exhausted to the
atmosphere: Because much of the volume of air stored on the opposite side of
the
piston is simply transferred to the face of the piston in moving the piston to
apply the
brakes, only a relatively small volume of air is left on the opposite side of
the piston
when piston travel is completed and the brakes are fully applied. Thereafter,
the
pressure of this small volume can easily be incrementally increased or
reduced, to
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gradually apply or release braking force by any degree desired, while using
relatively
little compressed air.
Other advantages of the unitized brake equipment over conventional
ECP (all electric)' controlled brake equipment can; in some instances, result
in reduced
cost, size and weight. Further advantages can include simplif ed piping and
installation, higher braking force capability from a given initial pressure,
reduced
consumption of pressurized air, and faster train charging and recharging. With
the
unitized brake equipment, the separate air storage or supply reservoirs and
associated
piping used with conventional railcar brake equipment can be eliminated, as
can be the
separate pipe bracket.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
A more complete understanding of the invention can be obtained by
considering the following detailed description in conjunction with the
accompanying
drawings, in which:
Figure l a is a diagrammatic drawing of prior art type pneumatic railcar
braking equipment.
Figure I b is a diagrammatic drawing of prior art type ECP railcar
braking equipment.
Figure 2 is a diagram bowing a presently preferred embodiment:
Figure 3 is a diagrammatic drawing of the unitized brake equipment
with the piston shown in a release position.
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Figure 4 is a diagrammatic drawing of the unitized brake equipment of
Figure 3, except shown with the piston in an applied position.
Figure 5 is a largerdiagrammatic drawing of the electronic control valve
portion of the unitized brake equipment shown in Figure 3.
Figures 6a and 6b illustrate the concept of "offset area."
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
An example of a prior art type all-pneumatic railcar braking system is
illustrated in Figure la, whereas an example of a prior art type ECP railcar
braking
system is illustrated in Figure 1 b: These two drawing figures are provided
for purposes
of a general comparison of the prior art type braking equipment with the
unitized
railcar brake equipment according to he present invention. Such a comparison
will
likely enable greater understanding and appreciation of the invention, certain
preferred
embodiments of which are described in more detail hereinafter in connection
with
Figures 2 through 6.
As shown in Figure Ia, the prior art type fully pneumatic railcar brake
equipment 6 typically can include a standard pneumatic control valve 8, such
as an
ABD, ABDX or ABDW, manufactured by Westinghouse Airbrake Technologies
Corporation ("WABTECTM"). The brake pipe ("BP") 10 connects to the central
portion 13, i.e. the "pipe bracket," of the pneumatic control valve 8: Service
14 and
emergency 17 portions of the pneumatic control valve 8 are mounted on either
side of
the pipe-bracket 12. The pipe-bracket 13 also communicates with auxiliary 20
and
emergency 23 reservoir compartments of a dual compartment reservoir 24, the
brake
8.
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cylinder 26 and the atmosphere 29, usually through a retainer device 32. The
total
volume of the conventional dual compartment reservoir is typically about 6000
cubic
inches.. Each reservoir compartment 20, 23 is pressurized from the brake pipe
10 via
internal passages in the pipe-bracket 13. Similarly, pressurized air is
selectively
communicated by the pneumatic control valve 8 via internal passages in the
pipe-
bracket 13, between the reservoir compartments 20, 23 , the service 14 and
emergency 17 portions, the brake cylinder 26, and the atmosphere 29, in order
to
control the air pressure in the brake cylinder 26 and thus the braking and
release
functions on the railcar.
Referring now to Figure 1 b, a prior art type ECP railcar brake
equipment is illustrated typically including a local brake control device,
such as an
electronic car control device ("GCD") 38, which can control a pair of
application
valves 40, 42 to supply pressurized air from the dual compartment reservoir 24
to the
brake cylinder 26. The CCD 38 also normally controls a release valve 45 to
reduce
pressure in the brake cylinder 26. As with the fully pneumatic brake control
equipment
shown in Figure la, the brake pipe 1;0 is utilized to supply pressurized air
to each
compartment 20, 23 of the dual compartment reservoir 24. In this case however,
each
compartment 20, 23, of the reservoir 24 can be individually connected to the
brake
pipe 10 for maintaining pressurization thereof. Back-flow check valves 35, 36
are also
typically provided between each compartment 20, 23 so that pressure cannot
escape
back into the BP 10 if the pressure therein reduces below the prevailing
pressure in
either reservoir compartment 20, 23: . As shown; the separate application
valves 40, 42
can be connected between each reservoir compartment 20, 23, respectively, and
the
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brake cylinder 26, with the auxiliary reservoir 20 connected to the auxiliary
application
valve 40 and the emergency reservoir 23 connected to the emergency application
valve 42. As mentioned above, the service and emergency brake application
valves 40, 42 can be controlled by the CCD 38 to selectively communicate one
or both
of the reservoir compartments 20, 23 with the brake cylinder 2b to increase
braking
force on the railcar. Although not Shown; the brake cylinder 26 is
conventionally
connected to a linkage, commonly referred to as brake "rigging," for actuating
the
rigging to apply brake shoes to the wheels of the railcar. The CCD 38 can
control the
release valve 45 for venting the brake cylinder 26 to reduce the pressure
therein and
reduce braking force on the railcar: The CCD 38 can be controlled by a remote
brake
controller. In particular, the CCD 38 can receive command signals 48 from a
train
engineer using a brake controller 49, which can be remotely located on a
locomotive
and can control the CCD 38 via a wireline 11 or wireless communications, such
as an
RF communication system 12. The CCD 38 can also receive feedback 50 from a
pressure sensor 52 which monitors the pressure in the brake cylinder 26.
Additional
pressure sensors, although not shown, could be provided at other locations,
such as the
reservoir compartments 20, 23 and along the brake pipe 10, to monitor the
pressure at
those locations for added feedback.
A train brake system employing an embodiment of a unitized railcar
brake equipment 60 according fo the invention is illustrated diagrammatically
in
Figure 2. As shown, the unitized brake equipment 60 can generally comprise a
brake
cylinder portion 63 and an electronic control valve portion 66, and can be
controlled by
a local brake control. device, such as the CCD 38, to regulate braking on the
railcar.
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However, in contrast to the brake system in Figure 1a, a brake system having
the
unitized brake equipment 60 need not have a reservoir 24, or application 40,
42 and
release 45 valves,, since these functions can all be combined into the
unitized brake
equipment 60. This can result in a simpler, lighter braking system which can
still have
the advantages of an ECP type system; for example one such as shown in Figure
1 a.
The unitized brake equipment can supplied with pressurized air via a pneumatic
connection with the BP 10 and cambe electrically connected to the CCD 38 for
control
thereby. More specific details of the brake cylinder portion 63 and the
electronic
control valve portion 66 are provided below. As with the ECP type system
illustrated
in Figure la, the CCD 38 can receive commands from a remote brake control
device,
such as controller 49, by signals transmitted via wireline l l or wirelessly,
such as by an
RF communications system 12.
Referring to more detailed views in Figures 3 and 4, the electronic
control valve portion 66 can be mounted directly to the pneumatic brake
cylinder
portion 63. The brake cylinder 63 portion can be comprised of several members,
namely-- a brake cylinder 69; a piston 72 operably disposed in the brake
cylinder 69,
and an air reservoir'75 generally circumscribing the brake cylinder 69. The
piston 72
can include a piston head 78 and a push rod 81 connected to the back side 80
of the
piston head 78. Although not shown; it should be understood that the opposite
end of
the push rod 8 l can be connected to rigging for applying brake shoes to the
wheels of
the railcar.
In addition to the air reservoir 75, the volume within the brake
cylinder 63 itselfcar! serve as an additional reservoit of pressurized air.
Moreover, the
1 T.
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brake cylinder 6f can have a pipe bracket interface member 84; to which the
electronic
control valve 66 can be mounted, as shown in the drawing figures. A first bi-
directional seal 87, as opposed to a single direction packing cup which may
typically
be used, can be provided between the piston head 78 and the brake cylinder 69.
Also, a
mechanical return spring 90 can be provided acting on the back side 80 of the
piston
head 78. The push rod 81 can be hollow, and the end opposite the end connected
to the
piston head 78:can extend through an opening provided in a front cover member
64 of
the pneumatic brake cylinder portion 63 for connection to brake rigging for
applying
brake shoes to the .wheels of the railcar. A second; sliding air seal 96 can
be provided
between the push rod 81 and the front cover 64. The brake cylinder portion 69
can
comprise two chambers: an application chamber 97, or "chamber A,"
communicating
on the face 79 of the piston head 78;; and a release chamber 98, or "chamber
R,"
communicating on.the back side 80 of the piston head 78. The reservoir 75 can
be an
annular volume provided encircling, the brake cylinder 69. In one embodiment,
the
combined stored air volume of chambers A 97, chamber R 98, and the reservoir
75 can
be about 2000 cubic inches, wherein the reservoir 75 can be about 11 SO cubic
inches,
and chamber R 98 can be about 850 cubic inches in release position. In the
release
position, the volume of chamber A 97 is generally negligible. In comparison,
conventional freight railcar brake equipment typically can have a total air
reservoir
volume of 6000 cubic inches. The overall: size of the unitized brake equipment
60 can
be very compact; for example-- only about 18 inches in diameter,and about 14
inches
in length. Moreover, with the unitizEd brake equipment 60, the separate air
storage or
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supply reservoirs and associated piiping used with conventional brake
equipment can be
eliminated, as can the separate pipe bracket.
The electronic control valve portion 66 can preferably be mounted to the
front of the brake cylinder 63, as depicted in the drawing figures.
Alternatively; the
electronic control valve 66 could be mounted to the back of the brake cylinder
portion 63, which,would provide similar direct access to the internal brake
cylinder 69
chambers A 97, R 98 and the reservoir 75, but would not need to avoid the
piston push
rod 81. However, such a rear mounting may not be as readily accessible on bulk
commodity freight cars as a front mounted embodiment. The requisite internal
passages can be provided in the pipe bracket interface member 84 , for example
passages 99 and 102. These internal passages can mate with corresponding
internal
passages provided in the electronic control valve portion 66, for example
passages 105, 108. The mating internal passages can provide for controlled
access by
employing appropriate valves; for example valves V 1-V4, in the electronic
control
valve portion 66 between the reservoir 75, chambers A 97 and R 98, brake pipe
10,
and the atmosphere, via passage I09. The various internal passages and
associated
valves far controlling pressures in the different air volumes will be
described in more
detail below, primarily in connection with the enlarged view of the control
valve
portion 66 shown in Figure 5.
Figure 3 portrays the unitized brake equipment 60 with the piston 72 in
a release position, whereas Figure 4 shows the piston-72 in the applied
position: As
displayed in both figures, chamber A 97 communicates with the face; e.g., the
application side, of the piston head 78 and chamber R 98 communicates on the
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opposite side, e.g., the release side, of the piston head 78. The reservoir 75
can be
formed integral with the brake cylinder 63, and in one presently preferred
embodiment,
can be provided in the form of an annular volume which encircles the brake
cylinder b3.
The unitized brake equipment 60 can be "self actuating;" such that air
pressure can be applied to both sides of the piston head 78, but acts on
unequal surface
areas provided on the opposing sides. For example, the face of the piston head
78 can
be provided with a larger surface area such that it can have an effective
advantage over
the opposite side of the piston head 78. The unitized brake equipment 60 can
be
designed such that, in release position, the application chamber A 97 is
relatively small,
whereas the largest portion of the internal volume, i.e., the release chamber
R 98, can
be provided on the opposite side of the piston head 78: The release chamber R
98 can
be charged to the brake pipe pressure, for example, from the brake pipe 10,
and can be
used as an additional air supply along with the air reservoir 75. The piston
72 can be
forced to the applied position merely by coupling the application chamber A 97
with
the release chamber R 98, thereby permitting the pressure in each chamber to
approach
equalization. In one embodiment, a return spring 90 can be provided on the
release
side of the piston head 78; in opposition to pressure acting on the face of
the piston
head 78. The force required to overcome the return spring 90 and move the
piston 72
can be derived from providing an effective surface area advantage provided on
the
application side of the piston head 7$, with respect to the surface area
provided on the
opposite, release side of the piston head 78. Advantageously, as the piston 72
is
moved, much of the tored volume of air in chamber R 98 is simply transferred
to
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chamber A 97, thus leaving a relatively small "operable volume," of, for
example, only
about 200 cubic inches, or less, in chamber R 98 when the brakes are fully
applied. In
contrast, the operable volume of a conventional brake cylinder can typically
be more
than 600 cubic inches. After the piston 72 has been moved to apply the brakes,
the
pressure of the relatively small remaining volume in chamber R 98 can be
incrementally increased, ar reduced; to gradually adjust braking force by
essentially
any degree desired. Moreover, this can all be accomplished using relatively
little
compressed air.
In one embodiment; shown best in Figure 5, the electronic control valve
portion 66 can include four small, electrically operated valves, for example
miniature
solenoid valves V 1-V4. Each valve V 1-V4 can be paired with, and can also
serve as a
pilot to, separate pneumatic booster valves B1-B4 having higher air flow
capacities
than the mailer solenoid valves V 1-V4: The electronic control valve portion
66 also
can include a charging check-valve I l 1,. a pneumatic interlock valve I 14
(which can be
configured for automatic actuation in response to movement of the piston 72);
and a
cut-off valve 116 that can serve to cut off the exhaust of application chamber
A 97
pressure in the event of a substantial loss of brake pipe 10 pressure. In one;
illustrated
in Figure 4, a full stroke of the piston 72 can automatically actuate the
pneumatic
interlock valve 114:
Solenoid valve Vl and its diaphragm booster valve BI can control air
communication between the reservoir 75 and chamber R 98. The reservoir
pressure 75
can serve as a source for pilot air pressure, which normally holds booster
diaphragm
valve B1 closed. When solenoid valve V1 is;energized, it opens to quickly
exhaust the
I 5.
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pilot pressure against a very small feed choke 117, allowing pressure in the
reservoir 75 and chamber R 98 to 'force the diaphragm of booster valve B 1 off
its seat,
against a light spring 120, and connect chamber R 98 with the reservoir 75.
Solenoid valve V2 audits diaphragm booster valve B2 can control the
flow of air under pressure from chamber A 97 to atmosphere via passage 109.
When
energized, valve V2 isolates chamber A 97 from the atmosphere, and when de-
energized connects it. Reservoir 7~ air is used as the pilot pressure, which
is admitted
by solenoid valve V2, when energized, to close the diaphragm booster valve B2.
The
pilot pressure is open fo a small bleed hole I23, which introduces a very
small amount
of leakage flow against an essentially overwhelming supply when valve V2 is
activated, but exhausts the small pilot volume quickly once the valve V2 is
closed.
Solenoid valve V3, in conjunction with its: diaphragm booster valve B3,
can control air communication between the reservoir 75 and chamber A 97. Brake
pipe 10 pressure can be used as the source for pilot air pressure for valve
V3, which
normally holds the diaphragm booster valve B3: closed, disconnecting chamber A
97
from the reservoir 75. When valve V3 is energized, it exhausts the pilot
pressure
against a small feed choke 124; allowing booster valve V3 to open and connect
chamber A 97 to the reservoir 75: It is also noteworthy that the loss of brake
pipe 10
pressure, even without energization of valve V3, will cause the pilot pressure
to be lost
and allow booster valve B3 to open.
Solenoid valve V4 and its diaphragm booster valve B4 can control the
flow of air under pressure from chamber R 98 to the atmosphere via passage
109.
When de-energized, valve V4 isolates chamber R 98 from the atmosphere, and
when
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energized connects it. Similarly to valve V3; pressure in the brake pipe 10
can be used
as the source of pilot air pressure to normally hold booster valve B4 closed,
and thus
the depletion of brake pipe pressure will allow booster valve B4 to open even
without
energization of valve V4.
A piston-travel interlock valve 114 can be designed to work in concert
with booster valves B3 and B4 of solenoid valves V3 and V4 to bring about an
automatic full application of the brakes responsive to a loss of pressure in
the brake
pipe 10. Such an application requires no electronic valve actuation.
The,piston-travel
interlock valve 114 acts in parallel with valve V 1 to connect the reservoir
75 with
chamber R 98 in release position, and in series with valve V4 to control the
exhaust of
chamber R 98 fo atmosphere in the applied position. Reservoir 75 pressure can
communicate with the top of the interlock valve 114 and a beveled stem 126 can
actuate the interlock valve 114. The beveled stem l26 can be positioned
laterally
perpendicular to and abutting the end of the interlock operating valve stem
129. The
beveled stem 126 protrudes into the:release chamber R 98 of the brake cylinder
63 and
is contacted and driven forward by the piston 72 when full piston travel is
approached;
as shown in Figure 4. When the piston 72 is in its noanal release position; a
spring 132
forces the beveled stem 126 outward, causing a ramp profile 13S on the beveled
stem 126 to laterally displace the interlock valve stem 129. As it moves, the
interlock
valve stem 129 first seats on the interlock check valve member 137, cutting
off the
connection of chamber R 98 from atmosphere, and then forces open the check
valve
member 137 from its stationary eat, :connecting chamber R 98 to the reservoir
75.
When brakes on the railcar are applied and the piston ?2 approaches its full
travel, it
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contacts and forces the protruding beveled stem 126 to retract: The beveled
stem 126
then allows the interlock valve stem 129 to be displaced downward by the
interlock
check valve spring 138, permitting the interlock check valve member 137 to re-
seat,
cutting off the reservoir 75 from chamber R 98. The interlock valve stern 129
is also
free to then be forced away from the interlock check valve member137 under the
influence of the check valve spring 138, thus connecting chamber R 98 to
booster valve
B4, and to atmosphere if B4 is also open. Because the interlock valve 114 is
arranged
in series with booster valve B4; no-; air :pressure can be exhausted from
chamber R 98
unless both the interlock valve I 14:. and booster valve B4 are open. The
interlock
valve 114 is only open when the piston 72 is in applied position. Booster
valve B4 can
be opened either as a result of V4 being energized under electronic control or
by the
eternal depletion of brake pipe pressure from the pilot chamber of valve B4.
Solenoid valve V l, which controls communication between chamber R
and the reservoir 75, can also be used in combination with the piston-travel
interlock
valve 114 to perform electronic graduated release. Additionally, a simple
brake
cylinder release :valve (not shown) could also be employed to allow manual
brake
cylinder release by venting chamber A 97 to drain off air pressure without
electrical
control.
Because valve V2 must be energized in order to isolate chamber A 97
from exhaust and retain pressure'dur~ng an application; a pneumatic cut-off
valve 116
can be provided in series with booster valve B2. Brake pipe 10 pressure
communicates
on one side of the pneumatic cut-off valve I 16 and holds the valve open to
connect
chamber A to atmosphere. , with V2;controlling the connection of chamber A to
cut-
18.
CA 02392197 2002-06-27
off valve 116. In the event of a power failure, V2 ,would connect chamber A to
exhaust. i-Iowever, in such case cut-off valve 116 can block the exhaust of
chamber
A 97 when brake pipe 10 pressure is depleted, thereby permitting retention of
chamber
A 97 pressure during the pneumatic application. If a power failure should
occur during
a brake application, and brake pipe pressure were not depleted, V 2 would
exhaust
chamber A. All of this can be best understood from Figure 4. Releasing the
brakes on
an individual railcar experiencing a.power failure can be the desired fault
condition.
However, if this condition were to occur on the whole train of railcars, or a
certain
number of railcars'in the train, an emergency application could be commanded.
A loss
of brake pipe pressure would automatically close the cut-off valve 116,
cutting off
chamber A from atmosphere, and: would also automatically open booster valve
B3,
thereby eonnecting: chamber A to the reservoir.
As a general principle of operation; the unitized brake equipment 64
relies on he control of pressures that act on unequal effective areas across
the piston 72
to apply and release the brakes on the railcar. Referring back to Figure 2, in
release
position chamber A 97 is vented to atmosphere, which allows the return spring
90 and
the pressure in chamber R 98 to force the piston 72 to its fully retracted
position.
When the brakes are to be applied, first the reservoir 75 pressure is admitted
to
chamber A 97 via valve V3. Because the reservoir 75 is also connected to
chamber
R 98 at this time via valve V 1, all three chambers 75, 97, 98 will tend to
equalize in
pressure. Based on selected design volumes for the three chambers 75, 97, 98
and the
specific area unbalance, full equalization would generally cause a reduction
of pressure
in the reservoir 75 and chamber It 98.on the order of about 5 psi. Therefore,
if the
19.
CA 02392197 2002-06-27
initial operating pressure were 90psi, for example; the pressure in all three
chambers 75, 97; 98 would equalize at about 85 psi; if allowed to do so.
Because the .hollow piston rod 81 is sealed where it passes through the
front cover 64 of the brake cylinder b3; chamber A 97 pressure acts on the
piston
head 78 with a larger effective area than the opposing chamber R 98 pressure.
The
difference in the area acted on by pressure on the face 79 of the piston head
78 and the
area acted on by the pressure on the back side 80 of the piston head 78 is
commonly
referred to ws the "area offset." Referring to Figures 6a and 6b; dl could
represent the
diameter of the face 79 of the piston head 78 and d2 could represent the
diameter of
sliding air seal 96., The area of d2 would be the "offset area," since this is
the area not
acted upon by pressure in the release chamber R. Depending upon the actual
areas
selected, some minimum pressure, such as, for example, l0 to 20 psi, will be
required
on the effective: offset area to produce sufficient force to overcome the
resistance of the
return spring 90 and sliding friction; causing full travel or extension of the
piston 72.
At the equalized pressure, such as, for example, 85 psi, the total output
force of the
piston 72 will be generally about equivalent to that of a heavy minimum
service
reduction with a conventional brake arrangement; again, depending on the
specific area
offset.
It should be noted that; during piston 72 movement, chambers A 97and
R 98 remain connected, by way of the reservoir 75, via valves V 1 and V3, and
most of
the volume of air originally residing in chamber R 98 is effectively
transferred across
the piston to expanded chamberA 97; vriith only a modest increase in total
volume and
therefore minimal loss of initial pressure. The increase in pressurized volume
in going
20.
CA 02392197 2002-06-27
from release to applied position consists of the clearance volume of chamberA
97 (in
release) plus the area offset multiplied by the piston. stroke. The relatively
small
volume made up of the area offset multiplied by the piston stroke represents
the
displacement volume (theoretically pressurized: from a complete vacuum created
by
piston displacement). In this case, the area offset is equal to the area of
the front
seal 96 on the push rod 81, because that is the area not acted upon by the
pressure in
chamber R 98 in opposition to chamber A 97. Also, the relatively large brake
cylinder 63 can reduce the overall rigging lever ratio required to achieve the
desired
braking ratio, in turn minimizing the piston stroke necessary to take up a
given brake
shae-to-wheel clearance.
Once the piston travel has been completed and the minimum braking
force established, valve V 1 can be operated to isolate chamber R 98 from the
reservoir 75; and thus chamberA 97. In this applied position, the volume
remaining in
chamber R 98 can be minimal as a result of the piston 72 travel. In order to
exert
increasing braking force, the pressure in this small volume of chamber R 98
can be
exhausted via valve V4 to atmosphere, to whatever extent is needed or desired.
It
should be noted that at this degree of piston travel the piston-travel
interlock valve 114
is open, connecting chamber R fo valve V4. If chamber R 98 pressure is
completely
exhausted, as it could be during an emergency application, the maximum
effective
pressure acting across the full area of the face of the piston head 78 will be
the original
equalization pressure, or about 85 psi. This is comparable to the maximum
emergency
brake cylinder pressure of about 78 psi produced with a conventional reservoir
and
brake cylinder.
21.
CA 02392197 2002-06-27
For any application heavier than a minimum application, chamber R 98
pressure can be supplied or exhausted to maintain a target pressure, which can
be a
function of chamber A 97 pressure and the degree of application commanded.
During
a brake application, the pressure in the reservoir 75 can be continuously
charged from
the brake pipe 10 via charging check valve 111 to raise it back to about 90
psi and
generally maintain it at that pressure. Valve V3 can be used to either
maintain chamber
A 97 at 85 psi,.or to gradually increase it back to 90 psi during a sustained
brake
application by connecting chamber A 97 to fhe reservoir 75 via valve V3. If
such
recharge is desired in system design; chamber:R 98 pressure could also be
recharged to
a controlled degree; by connecting chamber R 98 to the reservoir 75 via valve
V 1, in
order to maintain the desired cylinder output force while recharging chamber A
97.
This may be different during an emergency application.
In order to graduate brake pressure off, to reduce the effective braking
force, it can be necessary only to re-charge chamber R 98 to whatever degree
is
desired, which can be accomplished using valve V 1. The system can be very
efficient
in terms of minimiaang compressed air usage due to the relatively small volume
of
chamber R 98 when the piston 72 is in the applied position: The effective
braking
force may be reduced from any point, up to and including a maximum
application, all
the way down to essentially zero braking force, simply by restoring chamber R
98
pressure to the extent needed to obtain the particular level of braking
desired. Unless
chamber R 98 pressure is increased somewhat above that of chamber A 97, the
piston
will remain in the applied position due to the effective area advantage of
chamber A 97
over chamber R 98. Braking force may, in fact, be repeatedly graduated on and
off to
22.
CA 02392197 2002-06-27
any desired degree simply by exhausting and recharging the small chamber R 98
volume.
When a complete release to a fully retracted running position is desired,
chamber R 98 can be recoupled with the reservoir 75, and chamber A 97 pressure
can
be isolated and reduced by connecting it to exhaust. This step can result in
amore
significant air loss than any other, because the substantial volume of applied
chamber
A 97 must be exhausted to below 40 psi in order to fully retract the piston 72
under the
influence of the return spring 90. Consequently, a full release would be made
only
when it is anticipated that there will be no need for subsequent brake
applications for
some time. As long as a very minimal application is maintained, so that the
piston 72
does not retract, higher braking forces can be reapplied with only minimal air
usage
from the system.
According to one embodiment, four valve operating positions are
provided: release, transition; application and application lap. Transition
occurs both
during piston movement from release to applied position when an application is
initiated, and during graduated release. In transition, the positions of all
valves V I -V4
are intermittently the same regardless of which transition condition is
occurring, but the
effect differs due to the prevailing pressures. The following chartindicates
the
individual valve positions for each of these conditions.
23.
CA 02392197 2002-06-27
Reservvoir ZS Chamber A 97 Atmosphere
Chamber R 98
r ~~
V2 Open
Full
Release ( )
V 1 Open
Transition V3 Qpen
V 1 Open
Application [ 1 [ )
V3 Open V4 Open
Application [ )
Lap V3 Open
In release position chamber9 97 is opened to atmosphere,
allowing the return spring 90 to: move the piston 72 to its fully
retracted position. The reservoir 75 is connected to chamber R
98 and both are fully charged to the operating brake. pipe 10
pressure.
Transition position applies to both initial piston 72 movement
and o graduated relcsase: Piston 72 movement is initiated when
an application is made, by connecting the reservoir 75 to
chamberA 97 while still connected to chamber R 98. The
pressure in chamber A 97 is increased sufficiently to fully
displace the piston 72 and drive the brake shoes against the
wheels: Because of the effective area advantage of chamber A
97 over chamber R 98, full piston 72 movement can occur
before chamber A 97 pressure is increased to that of chamber R
98. Depending on the prevailing pressures; the charging of
chamber A 97 can be controlled to produce he exact amount of
desired cylinder output force; even for light minimum
applications. At higher prevailing pressures; minimum
application forces will be reached priorto equalizing chamberA
97 with chamber R 98, whereas at lower pressures or for heavier
applications, it may be necessaryto equalize the pressures and
possibly reduce chamber It 98 pressure o meet force
requirements. During graduated release, transition position
charges chamber R 9& instead of chamber A 97.
~ Application position connects chamberA 97 to the reservoir 75
to .increase the pressure in chamber A 9? to the desired
24.
CA 02392197 2002-06-27
application force. Additionally, chamber R 98 is isolated from
the reservoir 75 and opened to exhaust; as needed, to reduce
chamber R 98 pressure to derive the desired application force.
'The pneumatic interlock valve 114 is arranged in series with
solenoid V4; so that chamber R 98 pressure cannot be exhausted
until the piston 72 movement has been essentially completed.
~ In application lap; the chamber R 98 exhaust is closed and target
pressures are maintained.
The unitized brake equipment 60 can also be more efficient in the
application of air pressure to produce braking force. From any given pressure,
the
unitized brake equipment 60 with a selfaetuating brake cylinder 63 can be
capable of
generating approximately 9% higher maximum (emergency) effective brake
cylinder
pressure, in substantially larger brake cylinders, with only about one-third
as much
stored air volume as conventional reservoirs. Furthermore; using a 12-inch
diameter
brake cylinder 63 with a 5- to 6-inch piston stroke; the 2000 cubic inch
volume of
stored air in the unitized brake equipment 60 can produce more than
SO°1o higher
maximum cylinder output force than the conventional brake equipment produces
with
a 10-inch brake cylinder. Using a reduced-rigging lever ratio ('tn conjunction
with the
shorter piston stroke); the maximum net brake shoe force on the railcar would
still be
approximately 35% higher using the unitized brake equipment 60. This would
enable
higher loaded car braking ratios, which would not cause excessive in-train
forces with
electronic signal transmission.
A train of railcars equipped with the unitized brake equipment 60 can
provide the capability for fully graduable brake applications and releases,
while
utilizing far less compressed air than a conventionally equipped train.
Because much
less cumulative air volume would need to be delivered through the train brake
pipe 10
25:
CA 02392197 2002-06-27
using the unitized brake equipment 60, train charging times could also be
dramatically
reduced.
In'a certain embodiment, pressures in the reservoir 75 and both
chambers A 97 and R 98 can be controlled electronically by the four solenoid
valves
V2-V4, for example, under the direction of a CGD 38 which receives command
signals 48 from a controller 49 via the wire line 11 or RF. communication
system 12, as
described previously in connection with Figure lb: The CGD 38, and/or the
controller,
can be a computer or other processing equipment. Valve leads L1-L4 can be
electrically connected in a known manner to the CCD 38 actuating the
corresponding
solenoid valves Vl-V4. Alternatively; the valve leads L1-L4 could be simply be
hardwired to an interface provided onboard the railcar, and the interface
could be
connected to the controller 49 via the wireline 11 or 1tF communication system
I 2. In
any case, it is to be understood that: various ways of communicating with and
controlling the solenoid valves V1-V4 on the railcars; whether using both a
CCD 38
and controller 49, or simply hardwiring the electrically operated valves V 1-
V4 for
direct control by the controller 48; can be accomplished employing
conventional
methods such as currently being used in prior art ECP braking systems like
that
described above in connection with Figure 1b. Moreover, feedback from one or
more
sensors 150, 153, 156, for example pressure transducers, can also be provided
to either
or both the CCD 38 and the controller 49. Like the electrical leads L1-L4 of
the
solenoid valves V l-V4; leads 160, 163 and 166 of the pressure sensors 15U,
153, 156,
can be similarly connected to the CCD 38 or controller 49 to provide feedback
regarding the prevailing pressure in each of the air volumes 75, 97, 98, or
other
26.
CA 02392197 2002-06-27
pressures, such as in the brake pipe 10, in order to implement what is
commonly
referred to as "closed-loop" control over the braking functions on the
railcars.
In accord with AAR practice, brake commands to each car can call for
(1) a brake release, (2) a percentage of fuel service; ar (3) an emergency
application, the
maximum brake available. These commands can be interpreted and translated into
a
net shoe force requirement on each car. The proper pressures in chambers A 97
and
R 98 can then be determined based upon appropriate equations. Whatever type of
controller or control devices are utilized; it could be programmed with the
appropriate
equations for calculating the desired shoe force, and for controlling the
electronic
control valve portion to provide the proper pressure in the various chambers
and
reservoir. Various equations for making-such calculations are provided below;
near the
end of the description.
The following tables are spreadsheet calculations of chambers A 97 and
R 98 pressures and' corresponding output forces for the a preferred 12-inch
brake
cylinder b9. Table I shows the brake cylinder output forces for pressure
equalization
of chambersA 97 and R 98, as well.as the maximum cylinder output force, for
various
piston offset areas, from 5 to l3 square inches. These calculations are based
on 90 psi
initial pressure. The equivalent pressure required in a standard I O-inch
brake cylinder
with a conventional brake equipment is also shown for both the light
applications
derived from equal pressures in A 97 and R 98 and for maximum applications.
Additionally, Table 1 shows the theoretical equalization pressure required to
yield 300
pounds cylinder output force with the various unbalanced piston areas.
27.
CA 02392197 2002-06-27
When equaftzationof chamber R 98 with the reservoir 75 and chamber
A 97 is used as a minimum or light service application, the equivalent lU-inch
cylinder
pressure varies from 3.63 to 11.3 psi, as the piston offset area is increased
from S to 13
square inches,; respectively. This suggests that; if it is desired to use a
simple pressure
equalization for minimum applications; the offset area should be approximately
10
square inches, yielding a braking force equal to that which would be obtained
with
about 8:5 psi in a conventional 10-cylinder. This equalization force output
would vary
some, however, if initial pressures other than 90 psi were used.
Table 2 fixes the piston offset area at 12.566 square inches, representing
a 4-inch diameter seal on the push rod 81. This piston offset area was found
to be an
optimum balance for minimizing air usage on one hand; and both for providing
application capability at the lowest charge pressure and providing a rapid
piston
movement in emergency on the other hand. Preferably, the pressure in chamber R
98
should not be reduced to provide high emergency braking force until full
piston travel
has been completed. This is because that exhat,sting chamber R 98 to produce
high
braking forces, prior to full piston travel, would waste much air, and thus
reduce the
available chamber A 97 pressures that could otherwise be provided. Therefore,
the
only force available to actually move the piston 72 is the offset piston area
times the
equalized pressure in both chambers A 97 and R 98: It is also desirable to
move the
piston 72 as fast as possible during an emergency application. Table 2 also
shows the
brake cylinder output force for light applications, where chamber A 97
pressure is
charged to a range of pressures from 80 psi up to 85.2 psi, rwhich is the
equalization
prESSUre from 90 psi. The net cylinder force varies from 218 pounds up to
1070.8
28.
CA 02392197 2002-06-27
pounds, respectively. Equivalent pressures for a conventional 10-inch cylinder
are also
shown for each case. Using this cylinder arrangement, the ideal chamber A 97
pressure
for a light minimum application would be 83:5 to 84 psi, which is below the
full
equalization pressure of 85.2 psi.
Table 3 shows the chamber A 97 pressure required o produce
approximately 7U~ pounds cyti~der output force for initial pressures ranging
from SQ
to 110 psi. Table 4 is a worksheet, and Table 5 shows the chamber A 97
pressures
which will produce nominally 600 pounds cylinder output force. It is believed
that 600
pounds net cylinder output force is about ideal far a true minimum application
with
electronic brakes.
Table 6 is a worksheet used to derive an equation to closely
approxirn:ate the ideally desired chamber A 97 pressure with this cylinder
arrangement
( 12-inch main piston 72 with 4-inch push rod 81 ) for any initial pressure.
The equation
is intended to matchthe chamber A 97 pressures indicated on the previous third
chart,
and it is:
Pp = Pe * (2000'-P;)/1950
Where: PA = Chamber A pressure
Pe = equalization pressure
P; = initial pressure at time of application
The equalization pressure, Pe; is easily calculated from the initial
pressure and the pressure-volume relationships That exist: The equation is
only applied
for initial pressures above 70 psi; where equalization would produce excessive
cylinder
output force. Below this pressure; chamber A 97 is allowed to equalize with
the
reservoir 75 and chamber R 98. Chamber R 98 pressure can be exhausted as
needed to
29.
CA 02392197 2002-06-27
produce the target force output of 600 pounds. As indicated, at initial
pressures of 70
and 80 psi the equation derived yields values lightly lower than the exact
theoretically
desired PA pressure, which produces cylinder::forces of 562 and 587.5 pounds;
respectively. These forces are within 10% of the target and are considered
acceptable
for minimum applications, since they can be increased as desired by the
operator
simply by commanding a slightly heavier service application.
Table 7 illustrates equalization pressures and chamber R 98 pressures
for full service and emergency applications, for initial pressures ranging
from SU to 110
psi. In emergency, chamber R 98 is exhausted to zero (gauge) or atmospheric
pressure,
producing the maximum available cylinder output force. For the maximum service
application, chamber R 98 pressure is exhausted to a pressure required to
produce 19%
lower cylinder output force than the corresponding emergency application.
Tahle 8 compares the target pressure in chamber R 98 to the pressure
computed by the derived equation, and Table 9 simply shows the equalization
pressure
for various initial pressures and' the corresponding chamber A 97 pressure
required to
derive just sufficient force to bring abut full piston travel. This is
significant, because
chamber R 98 should not be exhausted to produce high braking forces until full
piston
travel has been completed. Otherwise, much air would be wasted and available
chamber A 97 pressures reduced. The chart shows that with the selected area
offset,
the full piston travel can be obtained with an initial pressure as low as l2
psi, providing
an equalization pressure of 10'.9 psi. Finally; Table l0 duplicates the
information in
Table 7, except that the simplified equation Pi/4:4 is used for P~.
30.
CA 02392197 2002-06-27
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CA 02392197 2002-06-27
- Equations-
Cylinder equalization pressure:
(l.) Pe;= (2000*(P~+14:7)+V~* 14:7)/(2000+PT*a+V~)-14.7
Where: Pe = equalization pressure for the reservoir and chamber A with R
V~ = total clearance-volume (ctlamber A in release)
PT -- piston travel (typically 6 inches)
a = area of push rod seal (offset piston area - 12:566 sq. in.)
Chamber A pressure for minimum applications:
(2.) PA =Pe*(200fl-P;)/1950
Where: PA = chamber A pressure
Pe = equalization pressure (from equation ( 1:))
P; = initial pressure
Chamber A pressure for all other app~tcateons, including emergency:
~3,) pA = p~
Where: PA = chamber A pressure
Pe _ equalization pressure
Chamber R Pressure for minimum applications:
(4.) pR = (2000*(P~+14.7)+Ve*14.7-(A'*PT+s)*(pA+14.7)/(2004-PT*(A-a)-14.7
Where: PR = chamber R pressure
P; = initial pressure
V~ = clearance volume (24 cubic inches)
PA = chamber A pressure
PT = piston travel (typically 6 inches)
A = main' piston area ( 113.09 sq. in; far 12" cylinder)
a = area of push rod seal (offset area -12.566 sq. in.)
Note: This pressure can be calculated, but need not be for brake applications.
It is the
pressure in chamber R that will result from feeding reservoir and chamber R
into
chamber A to charge chamber A to less than egualization:
Chamber R pressure for all service-applications heavier than minimum and
lighter
than full service:
(5.) pR = (pA*A-F)/(A-a)
Where: PR = chamber R pressure
. PA = chamber A pressure
A = main piston area (113.097 sq. in.)
32.
CA 02392197 2002-06-27
a = push .rod seal area (12:566 sq. in.)
F = cylinder output' force
Chamber R pressure for full service apgtications:
(6.) PR = P;/4:4
Where: PR = chamber R pressure
P; = initial pressure
Net cylinder output force:
(7:) F = pA*A_PR*(A_a)_FS
Where: F = cylinder output force..in pounds
PA = chamber A pressure
PR = chamber R pressure
A = main piston area (113.097 sq. in.)
a = push rod seal area (12.566 sg. in:~
FS = return spring force (nominally 120 lbs.)
Although certain embodiments of the invention have been described in detail;
it
will be appreciated by those skilled in the art that various modifications to
those details
could be developed in light of the overall teaching of the disclosure.
Accordingly, the
particular embodiments disclosed herein are intended to be illustrative only
and not
limiting to the scope of the invention which should be awarded the full
breadth of the
following claims and any and all embodiments thereof.
33:
