Note: Descriptions are shown in the official language in which they were submitted.
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
BRAKE MAINTENANCE INDICATOR
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
[0001] The present invention relates to rail car braking systems and,
more
particularly, to a warning indicator reflecting low brake cylinder pressure
and brake system
leakage into the brake cylinder.
2. DESCRIPTION OF THE RELATED ART
[0002] Control valves used in freight car brake systems, such as the DB-
60 control
valve manufactured by New York Air Brake Corporation of Watertown, New York,
or the
AB-type control valves manufactured by Wabtec Corporation of Wilmerding,
Pennsylvania,
typically supply air pressure to the brake cylinder of a freight car. If the
brake cylinder or the
plumbing between the control valve and the car has a leak, however, the brake
cylinder will
not maintain the original set pressure. In addition to brake cylinder leakage,
resulting in low
brake cylinder pressure, the brake system can leak into the brake cylinder,
resulting in high
brake cylinder pressure.
[0003] Recent improvements to AAR brake systems include the addition of
brake
cylinder maintaining valves, which compensate for brake cylinder leakage.
Another
improvement includes the addition of a brake cylinder limiting valve, which
exhausts brake
cylinder over-pressure resulting from leakage into the brake cylinder. While
these
improvements may improve the overall safety of the brake system, they may
obscure the
presence of brake defect, making detection more difficult and thereby delaying
corrective
action. As a result, there is a need for a system that can provide a clear
indication when the
braking system low brake cylinder pressure or brake system leakage into the
brake cylinder
BRIEF SUMMARY OF THE INVENTION
[0004] The present invention comprises a brake maintenance indication
system
having a first portion in communication with a source of brake cylinder
pressure that is
configured to determine the brake cylinder pressure and a second portion in
communication
with a source of brake pipe pressure and a source of emergency reservoir
pressure that is
configured to determine the intended brake cylinder pressure based on the
difference between
the brake pipe pressure and the emergency reservoir pressure. A first
indicator provides a
signal when the brake cylinder pressure is less than the intended brake
cylinder pressure and
a second indicator provides a signal when the brake cylinder pressure exceeds
the intended
brake cylinder pressure. Preferably, the intended brake cylinder pressure is
determined to be
1
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
2.5 times the difference between the brake pipe pressure and the emergency
reservoir
pressure.
[0005] In one embodiment, the first indicator is an indicator button that
is moveable
between a retracted position when the brake cylinder pressure is the same as
the intended
brake cylinder pressure and an extended position when the brake cylinder
pressure is less
than the intended brake cylinder pressure. The second indicator is an
indicator button that is
moveable between a retracted position when the brake cylinder pressure is the
same as the
intended brake cylinder pressure and an extended position when the brake
cylinder pressure
exceeds the intended brake cylinder pressure. The indicators may retract after
providing the
signal, or may be held in the extended position until manually reset.
[0006] The first portion of the system determines actual brake cylinder
pressure and
may be provided using pressure chambers and a diaphragm to have a first
chamber in
communication with the source of brake cylinder pressure, a second chamber in
communication with atmospheric pressure, and a first diaphragm separating the
first and
second chambers and having a first wetted area, where the diaphragm configured
to move the
first indicator between the retracted and extended positions. A spring may be
used to provide
a force biasing the indicators into the retracted position and thus produce a
small level of
tolerance. The second portion of the system determines the intended brake
cylinder pressure
and has a third chamber in communication with a source of brake pressure, a
fourth chamber
in communication with a source of emergency reservoir pressure, and a second
diaphragm
separating the third and fourth chambers that has a second wetted area that is
greater than the
first wetted area by a ratio of 2.5:1, with the diaphragm being configured to
move the second
indicator between the retracted and extended positions.
[0007] In another embodiment of the invention, the system may be provided
using
digital or analog circuitry. In this embodiment, the first portion comprises a
first pressure
transducer, the second portion comprises second and third pressure transducers
as well as a
circuit for calculating the intended brake cylinder pressure as 2.5 times the
difference
between the brake pipe pressure and the emergency reservoir pressure. The
first and second
indicators preferably comprise light emitting diodes. The circuit for
calculating the intended
brake cylinder pressure may be an analog circuit, a digital circuit, or some
combination
thereof.
[0008] The various embodiments of the present invention may be interfaced
to a
braking system by providing the indictor in a housing that encloses the first
and second
portions and the retracted first and second indicators, and additionally has a
series of conduits
2
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
configured to operatively interconnect said first and second portions to a 4-
port testing
interface that can provide the source of brake cylinder pressure, the source
of brake pipe
pressure, and the source of emergency reservoir pressure. The housing may
include a series
of ports configured to operatively connect the conduits of the housing to a 4-
port test adaptor
affixed thereon so that conventional testing operations can be conducted with
the invention
installed in place on the 4-port testing interface. Alternatively, the first
and second portions
and the first and second indicators may coupled to a control valve in any of
at least various
locations that can provide the source of brake cylinder pressure, the source
of brake pipe
pressure, and the source of emergency reservoir pressure.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0009] The present invention will be more fully understood and
appreciated by
reading the following Detailed Description in conjunction with the
accompanying drawings,
in which:
[0010] Fig. 1 is a schematic of a first embodiment of a brake maintenance
indication
system according to the present invention;
[0011] Fig. 2 is a schematic of a second embodiment of a brake
maintenance
indication system according to the present invention in a first position;
[0012] Fig. 3 is a schematic of a second embodiment of a brake
maintenance
indication system according to the present invention in a second position;
[0013] Fig. 4 is a schematic of a third embodiment of a brake maintenance
indication
system according to the present invention;
[0014] Fig. 5 is a schematic of a first embodiment of an attachment
location for a
brake maintenance indication system according to the present invention;
[0015] Fig. 6 is a schematic of a second embodiment of an attachment
location for a
brake maintenance indication system according to the present invention;
[0016] Fig. 7 is a schematic of a brake control valve having various
positions for
attachment of a brake maintenance indication system according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring now to the drawings, wherein like reference numerals
refer to like
parts throughout, there is seen in Fig. 1 a brake maintenance indication
system 10 for
indicating over-pressurization of a brake cylinder or a brake cylinder leak
that leads to under-
pressurization. As seen in Fig. 1, indication system 10 comprises a first port
12 in fluid
communication with a source of brake cylinder pressure BC, a second port 14 in
fluid
communication with an exhaust EX (atmospheric pressure), a third port 16 in
fluid
3
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
communication with a source of brake pipe pressure BP, and a fourth port 18 in
communication with a source of emergency reservoir pressure ER.
[0018] Indication system 10 further comprises a first diaphragm 20
separating a first
chamber 22 that is in communication with first port 12 from a second chamber
24 that is in
communication with second port 14. Diaphragm 20 is operatively engaged to a
visual
indicator 26 that is moveable between a retracted position, where indicator 26
is housed
substantially within first chamber 22, and an extended position, where
indicator 26 extends
outwardly from first chamber 22. Indicator 26 is biased into the retracted
position by a spring
28. Spring 28 preferably has a preload that provides a force of about 10 psi
biasing indicator
26 toward the retracted position, providing a defined hysteresis between the
actual brake
cylinder BC pressure and the target brake cylinder BC pressure, to prevent
erroneous fault
indication. Other values of pressure bias may be provided by selecting the
corresponding
spring 28 preload. A transparent or translucent indicator cover 30 may be
positioned in
covering relation to indicator 26, thereby maintaining the pressure envelope,
protecting
indicator 26 and preventing the ingress of any environmental contaminants into
indication
system 10, while allowing indicator 26 to move into an extended position that
is visible from
outside system 10.
[0019] A second diaphragm 32 is positioned in indication system 10 to
separate a
third chamber 34 that is in communication with third port 16 and thus brake
pipe pressure BP
from a fourth chamber 36 that is in communication with fourth port 18 and thus
emergency
reservoir pressure ER. Diaphragm 32 is operatively engaged to a second visual
indicator 38
that is moveable between a retracted position, where indicator 38 is housed
substantially
within fourth chamber 36, and an extended position, where indicator 38 extends
outwardly
from fourth chamber 36. Indicator 38 is biased into the retracted position by
a second spring
40. Spring 40 preferably has a preload that provides a bias force of about 10
psi moving
indicator 38 into the retracted position. A second transparent or translucent
indicator cover
42 may be positioned in covering relation to indicator 38, thereby maintaining
the pressure
envelope, protecting indicator 38 and preventing the ingress of any
environmental
contaminants into indication system 10, while allowing indicator 38 to be
visible from the
outside when in the extended position. Forces associated with the movement of
second
diaphragm 32 are communicated to first diaphragm 20 via a floating pin 44.
[0020] The wetted area of second diaphragm 32 is selected to be about 2.5
times the
wetted area of first diaphragm 20. The 2.5:1 differential pressure is selected
to account for
the ratio of brake pipe pressure BP reduction to brake cylinder pressure BC
required in an
4
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
AAR compliant system. More specifically, because of the volumetric
relationship between
the auxiliary reservoir and the brake cylinder in an AAR braking system, a
reduction in the
brake pipe pressure BP will cause an increase in brake cylinder pressure BC
which is 2.5
times the brake pipe pressure BP reduction. For example, when an operator
makes a 10 psi
brake pipe pressure BP reduction to actuate the brakes, the brake cylinder
pressure BC is
increased by 25 psi. The present invention may be configured for a different
differential
pressure as desired or as required by a non-AAR compliant system or a braking
system
having different requirements.
[0021] Indication system 10 thus has one portion that determines the
difference
between the emergency reservoir pressure ER and the brake pipe pressure BP to
determine
any brake pipe reduction, and thus the intended brake cylinder pressure BC
increase,
according to the 2.5:1 pressure ratio. System 10 also includes another portion
that compares
the intended brake cylinder pressure to the actual brake cylinder pressure BC
to determine
whether the appropriate brake cylinder pressure BC has actually resulted and,
if not, system
will indicate any under-pressurization or over- pressurization that exceeds
the small force
bias of springs 28 and 40, respectively.
[0022] More specifically, indication system 10 will indicate a brake
cylinder leak if
the brake cylinder pressure in first chamber 22 leaks to 10 psi or more below
the brake
cylinder pressure BC target pressure, as determined by a reduction in brake
pipe pressure BP.
Second diaphragm 32 acts as an intended brake cylinder pressure BC as it will
move in
response to the force differential acting across diaphragm 32 due to emergency
reservoir
pressure acting in chamber 36 and the brake pipe BP pressure acting in chamber
34, where
the brake pipe BP pressure has been reduced from equilibrium with the
emergency reservoir
pressure by the amount of the brake pipe BP reduction , thereby exerting a
force via floating
pin 44 onto first diaphragm 20. Because of the 2.5 to 1 differential in the
wetted area of
second diaphragm 32 relative to the wetted area of first diaphragm 20, brake
cylinder
pressure BC in first chamber 22 must increase by a corresponding 2.5 times of
the pressure
difference action across diaphragm 32 in third chambers 34 and 36, otherwise
the force
supplied by second diaphragm 32 will move first diaphragm 20 against bias
spring 28. When
the force supplied by second diaphragm 32 offset by the force of the brake
cylinder BC
pressure acting in chamber 22 across diaphragm 20, exceeds the preload of
spring 28, e.g.,
about 10 psi, indicator 26 will be moved into the extended position, thereby
providing a
visual indication that the actual brake cylinder pressure BC is lower than
what it should be at
any given time. As a result, the movement of indicator 26 provides a signal
that there has
5
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
been leakage of brake cylinder pressure BC such that the brake cylinder
pressure BC is less
than the intended brake cylinder pressure BC by an amount equal to the preload
of spring 28..
[0023] Indication system 10 will also indicate undesired leakage into the
brake
cylinder such that the brake cylinder pressure BC is higher than it should be
at any given
time. During a normal service brake application, brake cylinder pressure BC is
nominally 2.5
times the reduction in brake pipe pressure BP. In a full release and recharge
state, the brake
pipe BP pressure, auxiliary reservoir pressure and emergency reservoir
pressure are all
charged to nominally the same amount, typically 90 psi, and the brake cylinder
pressure is
released to 0 psig. For a service brake application, brake pipe pressure BP is
reduced the
desired amount by the train driver. A control valve in the braking system
includes a service
piston which is pressurized on one side by the brake pipe and on the other
side by the
auxiliary reservoir. When brake pipe pressure BP is reduced to make a brake
application, the
service piston moves to a brake apply position as a result of the reduction of
the brake pipe
pressure BP. In the brake apply position, air from the auxiliary reservoir is
allowed to flow to
the brake cylinder until the auxiliary reservoir pressure substantively equals
brake pipe
pressure BP, at which time the main service piston moves to the service lap
position, where
communication between the auxiliary reservoir and brake cylinder is severed,
and the brake
cylinder pressure BC is bottled.
[0024] Because of the 2.5:1 ratio of the wetted areas of second diaphragm
32 to first
diaphragm 20, indication system 10 will be in force balance with neither
indicator in the
extended or flagged position if the brake cylinder pressure BC is in the
appropriate ratio to
brake pipe pressure BP reduction during a service brake application. If the
brake cylinder
pressure BC in chamber 22 increases in an amount that is equal to or greater
than 2.5 times
the brake pipe pressure BP reduction as determined by the force differential
acting across
diaphragm 32 due to emergency reservoir pressure acting in chamber 36 and the
brake pipe
pressure acting in chamber 34 and the preload of bias spring 40 (such as when
there is
undesired leakage from the brake pipe, the auxiliary or emergency reservoirs
into the brake
cylinder), diaphragms 22 and 32 will be moved downward and indicator 38 will
be moved
into the extended position, thereby visually indicating a brake cylinder
overcharge. As
undesired leakage into the brake cylinder that produces overpressure is
normally due to a
defective control valve, indication system 10 can provide an immediate
notification of a
defective control valve.
[0025] Indictor 10 may also be used to indicate when a braking system
retainer valve
is inadvertently left in the high pressure position. AAR brake systems include
a retainer
6
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
valve that, when manually activated, will bottle up the brake cylinder
pressure BC by sealing
the brake cylinder exhaust. This allows the train driver to bottle up the
brakes on the cars,
and then make a release and recharge of the brake pipe and all of the control
valves on the
train while the retainer bottles the brake cylinder pressure. Retainers are
typically used while
descending long grades and, according to AAR standards, will bottle about 20
psi in the high
pressure setting. Prior to leaving a yard, trains are subjected to a number of
required tests,
which includes releasing the brakes on and inspecting each car to verify that
the brakes have
released. Indication system 10 will provide a visual flag if the car has had
brakes released,
but the retainer was inadvertently set, because the 20 psi overpressure is
enough to overcome
the preload in spring 40 and move indicator button 38 into the extended
position.
[0026] While the embodiments of the present invention are illustrated
using flexible
diaphragms and a floating pin to provide force communication, indication
system 10 could be
implemented by any combination of pistons and sealing means that provide the
requisite 2.5
to 1 ratio and resulting indications.
[0027] In another embodiment of the present invention, a brake
maintenance
indication system 50 may include indicator buttons 52 and 54 configured to
remain in the
extended position once moved by diaphragms 20 and 32, respectively. As seen in
Fig. 2 and
3, indicator buttons 52 and 54 merely rest upon diaphragms 20 and 32,
respectively, and are
thus free to remain in the extended position when diaphragms 20 and 32 return
from the
extended position to the retracted position. As seen in Fig. 3, indicator
buttons 52 and 54
may be retained in the extended position by the use of 0-rings 56 and 58 that
frictionally
engage indicator buttons 52 and 54 to retain them in the extended position
while maintaining
the integrity of indication system 10 and to preserve the signal of a brake
system error.
Indicator buttons 52 and 54 may be manually returned to the retracted
position, i.e., they may
be pushed back into the retracted position by maintenance personnel after the
error signal has
been observed or logged.
[0028] In another embodiment of the present invention, a brake
maintenance indicator
60 may be implemented electronically using a brake pipe pressure transducer
62, an
emergency reservoir pressure transducer 64, and a brake cylinder pressure
transducer 66,
along with accompanying analog or digital logic circuitry to evaluate the
intended brake
cylinder pressure PBc based on the emergency reservoir pressure PER and the
brake pipe
pressure PBp using the following equation:
2.5 X (PER-PBP) = PBC=
7
CA 02958226 2017-02-15
WO 2016/028285 PCT/US2014/051802
[0029] In this embodiment, the electronics could include light emitting
diodes (LEDs)
in combination with LED driver circuits 68 and 70, or other conventional
visual indicators
drive by the circuitry, for each of fault modes discussed above. Indication
system 60
preferably uses a low power electronic circuit and a battery 72 for power, and
may include a
sleep mode function to conserve power when the brake pipe pressure is detected
to be at zero
or a nominal pressure. For example, Fig. 4 illustrates a simple analog circuit
embodiment of
indication system 60 that uses strain gauge type pressure transducers 62, 64,
and 66, LED
circuits 68 and 70 for indicating fault modes, and a battery 72 as a power
source. The circuits
are arranged so that all of the signals are ratio-metric with the voltage of
battery 72 so that the
circuit function is independent of the state of charge of battery 72. In the
case of an analog
embodiment, resetting can occur via a switch or comparable electronic circuit.
A digital
embodiment may be programmed to additionally provide a memory function that
would
"latch" a failure indication until manually reset or until cleared by internal
diagnostic logic.
It should be recognized that the analog circuit of Fig. 4 could easily be
provided as an
integrated digital circuit, as firmware running on a microprocessor or
microcontroller, or as a
combination of analog and digital circuitry.
[0030] The various embodiments of a brake maintenance indicator according
to the
present invention may be positioned on a standard AAR pipe bracket, as further
seen in Figs.
and 6. For example, as seen in Fig. 5, indication system 10 may be provided in
a module
80 that is adapted for interconnection to a single-sided pipe bracket 82 via
the existing 4-port
interface 84 on the pipe bracket 82 that is normally used for periodic
connection to a single
car testing device. 4-port interface 84 includes conduits that provide for
fluid communication
to brake pipe pressure BP, auxiliary reservoir pressure AR, emergency
reservoir pressure ER,
and brake cylinder pressure BC and can thus provide all of the needed inputs
for the present
invention. In Fig. 5, module 80 is connected directly to 4-port interface 84
of pipe bracket
82. As a result, module 80 would have to be removed so that a single car
testing device could
be connected to 4-port interface 84 for periodic testing of the braking
system.
[0031] As seen in Fig. 6, the present invention may be incorporated into
a module 90
that is attached directly along one side of module 90 to 4-port interface 84.
Module 90
includes a series of conduits formed therein that provide fluid communication
to the present
invention as well as to a corresponding set of ports located on the second
side of module 90
that replicate 4-port interface 84 so that a test adaptor 92 may be bolted
over module 90 to
allow for periodic connection to a single car testing device.
8
CA 02958226 2017-02-15
WO 2016/028285
PCT/US2014/051802
[0032] It
should be recognized by those of skill in the art that the indication system
of the present invention may be configured into any portion of a braking
system control
valve, such as by redesigning the packaging of the control valve, to include
interface to the
release valve interface, or be fitted between either the service portion and
the pipe bracket or
the emergency portion and the pipe bracket (or by including the present
invention in any
other location that has pneumatic access to brake pipe pressure BP, emergency
reservoir
pressure ER, and brake cylinder pressure BC). As seen in Fig. 7, indication
system 10 may
be integrated into any one of at least three different locations, Alt 1, Alt
2, and Alt 3,
respectively, in a control valve 94.
9
