Note: Descriptions are shown in the official language in which they were submitted.
CA 02558723 2001-06-28
TITLE
APPARATUS AND METHOD FOR PNEUMATICALLY CONTROLLED
GRADUATED BRAKE PRESSURE RELEASE
FOR FREIGHT TRAIN BRAKE SYSTEM
This application is a division of copending commonly owned Canadian Patent
Application No.
2,351,915 filed June 28, 2001.
BACKGROUND
This invention relates generally to freight train brake control systems, and
more particularly, to
an apparatus and method for a pneumatically controlled graduated release of
brake cylinder pressure in a
freight train brake control system.
In conventional freight train braking systems controlled by a pneumatic
control valve,
pressurized fluid is utilized to control braking functions on each car of the
train. One or more
locomotives and each car are interconnected by a brake pipe which supplies
pressurized fluid from a
main reservoir on the locomotive to reservoirs on each car. Each car in a
standard pneumatically
operated freight braking system has onboard a reservoir, typically divided
into emergency and auxiliary
compartments which are charged via the brake pipe, a pneumatic control valve
(PCV) and a fluid
pressure activated brake cylinder device. The PCV selectively communicates
between the brake pipe,
each reservoir compartment, the brake cylinder device and the atmosphere. The
PCV controls the
operation of the brakes on the car by controlling the access of pressurized
fluid between the brake
cylinder and the reservoirs or the atmosphere. The operation of the PCV is
controlled by the engineer
from the locomotive by adjusting the pressure in the brake pipe. Basically, a
reduction in brake pipe
pressure signals the PCV to admit pressurized fluid from a reservoir into the
brake cylinder device to
apply the brakes. Conversely, an increase in brake pipe pressure signals the
PCV to vent the brake
cylinder to the atmosphere thereby releasing the brakes.
Overall, the conventional pneumatic braking system utilizing the PCV has
proven to be a very
safe and reliable system. However, a couple of disadvantages of the PCV
controlled system are that it
takes time for the pressure change initiated at the locomotive to propagate
throughout what may be
hundreds of cars. As a result, the PCV on each car senses the pressure change
sequentially such that the
brakes on each car are applied in sequence rather than simultaneously. The PCV
on cars near the
locomotive will sense the pressure change sooner and thus the brakes on that
car will be applied in
advance of the brakes on cars down the line.
CA 02558723 2001-06-28
Another disadvantage is that once the brakes are applied, the only way to
release them is to vent
the brake cylinder to atmosphere, thus completely exhausting all pressure from
the brake cylinder. In
other words, the brake cylinder pressure cannot be partially reduced. Either
all of the pressure must be
kept or it all must be dumped. Furthermore, once the brake cylinder pressure
is vented it can take time to
recharge the brake pipe and reservoirs sufficiently to make further brake
applications.
Prior art devices include the use of retainer valves with ABDW, ABDX type
equipment to
"retain" a portion of the brake cylinder pressure upon a direct release.
A relatively recent development in freight train braking controls is the
Electrically Controlled
Pneumatic (ECP) brake control system. In a conventional ECP system, an
electronic controller (EC) is
provided on each car along with solenoid operated valves which control the
exchange of pressure
between the brake cylinder device and the reservoirs or the atmosphere,
basically taking over the
functions of the PCV. Thus, the EC directly controls the brake cylinder and
may be referred to as a brake
cylinder control (BCC) type ECP system.
Initially, this BCC type ECP system has been tested as an overlay system on
the conventional
pneumatic system, with the PCV functioning as a back-up brake control device.
However, all electronic
BCC type ECP brake control systems are being prepared and the American
Association of Railroads
(AAR) is in the process of promulgating certain requirements regarding minimum
equipment and
operating conditions for such ECP systems.
One of the advantages of the BCC type system is that the EC is electrically
signaled from the
locomotive to operate the brake cylinder device. Thus, the brake signal is
propagated essentially
instantaneously and the brakes on every car can be actuated at virtually the
same time. Another
advantage is that the level of brake cylinder pressure is adjustable because
the solenoid valves can
partially vent brake cylinder pressure without completely exhausting all of
the pressure to the
atmosphere. As a result, the engineer can signal the EC to increase or
decrease the braking force by any
amount desired.
However, one disadvantage is the cost of implementing such an ECP system. For
example, the
AAR minimum requirements include, among other things, the requirement of a
2500 W power source on
the locomotive, a 230 VDC tramline cable and a communications device one every
car each with having
a battery as a back-up power source. These requirements impose a significant
cost factor.
Accordingly, there is a need for a device which provides a pneumatically
controllable graduated
release of brake cylinder pressure to obtain the graduated release advantages
of the ECP system without
the need for all of the associated electrical equipment and costs.
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CA 02558723 2001-06-28
SUMMARY
A release graduating valve (RGV) according to the invention is preferably
integrated into a
pneumatic control valve, such as an otherwise standard ABDX, or ABDX-L, for
use in either
conventional pneumatically braked freight trains, or in unit trains of
similarly equipped cars.
In normal freight train service, the RGV must provide direct release in
concert with all other cars
in the train, many or most of which typically would not be equipped with an
RGV. Consequently, the
RGV preferably includes a changeover valve portion for selectively switching
between a graduated
release mode and a direct release mode.
In the conventional direct release mode, the changeover valve isolates the
graduated release
portion of the RGV to permit the PCV to exhaust brake cylinder pressure in a
conventional manner. In
the graduated release mode, the changeover valve interposes a metering valve
portion which exhausts
brake cylinder pressure generally proportional to a reduction in pressure in
the brake pipe.
The changeover valve can be selectively actuated responsive to the pressure in
a secondary
trainlined air pipe, for example a main reservoir pipe, which is supplied with
pressurized fluid from a
remote source. Alternatively, the changeover valve can be responsive to brake
pipe pressure such that a
secondary trainlined air pipe is not necessary. In this case, a brake pipe
sensor valve portion can
additionally be provided for controlling the activation of the RGV.
As an alternative to the selectively operable configuration, the RGV could
also be provided in a
"permanent" version. A permanent RGV is one in which there is no changeover
valve portion to permit
an optional direct release. Thus, brake cylinder pressure can routinely be
exhausted in a graduated
manner.
In any event, the selectively actuable RGV is the presently preferred type.
Any car equipped
with a selectively operable RGV would be capable of operation in a train of
standard (non-equipped) cars
for switching, positioning of equipment, and simply allows the fullest, most
economical use of the car in
any service for which it was otherwise suitable, without special handling
procedures.
In a unit train of similarly equipped cars, graduated release operation of the
individual car brakes
can provide several benefits, and this may be one application for the
"permanent" version. For example,
the partial release of brakes may permit reduction of friction braking as a
train slows to the desired speed
on a downgrade, in order to use a higher percentage of dynamic braking to
retard the train, with the
benefit of reducing wear of the friction brake shoes. Additionally, the
gradual release of brakes provides
smoother control of slack, reducing inter-train forces and the damage it can
cause. This is especially true
when pulling a train out of a "sag." Moreover, a saving of air and locomotive
fuel will be realized. This
savings resulting from being able to reduce braking in undulating territory
and avoid either slowing the
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CA 02558723 2001-06-28
train unnecessarily or applying wasteful power braking in order to avoid
releasing the brakes. This
situation occurs when the train is slowing below the desired speed, but the
engineer realizes that heavier
braking will be required on a downgrade ahead. The availability of graduated
release avoids the
necessity to completely release brakes, thereby saving the air and time that
would be necessary to re-
apply them to a higher degree when needed on the increased downgrade. A unit
train of cars equipped
with the release graduating valves described herein can use the graduated
release feature to provide
improved brake performance.
The invention of the parent application provides a solution to the problems of
the prior art by
providing a graduated release valve for a rail vehicle having a pneumatic
control valve, a brake pipe, at
least one reservoir charged from the brake pipe, and a brake cylinder, with
the release valve comprising:
a metering valve controlling the exhaust of pressure from the brake cylinder
generally responsive to
changes in brake pipe pressure; a changeover valve selectively switchable
between a direct release
position and a graduated release position; wherein the metering valve is
interposed for controlling the
exhaust of pressure from the brake cylinder device in a graduated manner in
the graduated release
position; wherein the metering valve in the direct release position is
isolated from the brake cylinders
such that the pneumatic control valve controls the exhaust of pressure from
the brake cylinder; and a
brake pipe sensor valve communicating with the changeover valve and the brake
pipe, the sensor valve
controlling the selectively switchable changeover valve between the direct
release position and the
graduated release position.
On the other hand, the present invention provides a graduated release valve
for a rail
vehicle having a pneumatic control valve, a brake pipe, at least one reservoir
charged from the
brake pipe, and a brake cylinder device, the graduated release valve
comprising: a metering valve
communicating with the brake cylinder device and controlling the exhaust of
pressure therefrom
responsive generally to increases in brake pipe pressure. The metering valve
communicates with
a relatively small volume charged from the at least one reservoir, the volume
being communicated with
the brake pipe when the pneumatic control valve triggers a service accelerated
release.
Further details, objects, and advantages of the invention will become apparent
from the following
detailed description and the accompanying drawings figures of certain
embodiments thereof.
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:
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CA 02558723 2001-06-28
Figure 1 is a diagrammatic representation which illustrates a prior art type
pneumatic freight
train braking system;
Figure 2 is a diagrammatic representation which illustrates an combined ECP
and pneumatic
freight train braking system where the ECP is an overlay system for the
conventional pneumatic braking
system shown in Figure 1;
Figure 3 is a diagrammatic representation which illustrates a prior art direct
brake cylinder
control fully ECP freight train braking system;
Figure 4 is a diagrammatic representation which illustrates the pneumatic
braking system of
Figure 1 further having a release graduating valve;
Figure 5 shows an embodiment of a selectively actuable release graduating
valve;
Figure 6 shows the embodiment of Figure 5 in a graduating release position;
Figure 7 shows another embodiment of a selectively actuable release graduating
valve;
Figure 8 shows the embodiment of Figure 5 in a direct release position and
further having a brake
pipe sensor valve;
Figure 9 shows the embodiment of Figure 8 wherein the sensor valve is at the
critical position;
Figure 10 shows the embodiment of Figure 9 wherein the sensor valve has moved
the changeover
valve to the graduated release position;
Figure 11 shows an embodiment of a "permanent" release graduating valve;
Figure 12 is a brake cylinder pressure versus time graph which illustrates the
type of braking
control enabled by a release graduating valve;
Figure 13 is a brake cylinder pressure versus time graph which illustrates
braking control using
conventional braking systems; and
Figure 14 illustrates an embodiment of an adapter plate for operatively
connecting a release
graduating valve to a type ABD pneumatic valve.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
To aid in understanding the present preferred embodiments it will be helpful
to first describe
certain prior art freight train brake control systems illustrated in Figures 1
and 2.
A conventional pneumatically operated freight train braking system on a
railcar is shown in
Figure 1 wherein a pneumatic control valve ("PCV") 10 such as an ABDX, ABDW or
DB-60 is
connected to a brake pipe ("BP") 13 and auxiliary ("AUX") 15 and emergency
("EMER") 17 reservoir.
Each reservoir is normally charged with pressurized fluid supplied by the BP
13 through auxiliary and
emergency ports 11, 12 in the PCV 10. The PCV 10 is also connected to a fluid
pressure activated brake
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CA 02558723 2001-06-28
cylinder device ("BC") 19 which applies friction brake shoes to the wheels of
the car to control its speed.
The PCV 10 also has an exhaust port 21 for venting the BC 19 to the
atmosphere. Alternatively, the PCV
can be connected to a retainer ("RET") 23 through which brake cylinder
pressure can be exhausted to
the atmosphere at a restricted rate.
5 In operation, the PCV 10 senses changes in brake pipe pressure and, based
upon such changes in
pressure, can either apply the brakes by pressurizing the brake cylinder I9
with fluid from one or both of
the reservoirs 15, 17 or, can release the brakes venting the brake cylinder
19. Conventionally, a
reduction in brake pipe pressure signals the PCV 10 to apply the brakes in an
amount proportional to the
brake pipe reduction whereas an increase in brake pipe pressure of any amount
above a small
IO predetermined minimum is a signal to release the brakes completely, venting
the BC.
A prior art combined ECP/pneumatic freight train brake control system is shown
in Figure 2
having an electronic controller ("EC") 25 which is operatively connected to
the AUX 15 and EMER
reservoirs 17 along with a pair of solenoid actuated application valves
("APPS," "APPe") 27, 29 for
controlling the supply of pressurized fluid from the reservoirs to the brake
cylinder 19 in order to apply
I S the brakes on the railcar. The EC 25 is also connected to a solenoid
actuated release valve ("SOL REL")
27 which can vent the brake cylinder 19 to the atmosphere. As in Figure 1, a
the RET 23 can also be
provided.
In this system, the PCV 10 is used as a back-up brake control device while the
EC 25 normally
directly controls the brake cylinder pressure. Since the AUX 15 and EMER 17
reservoirs are charged
with pressurized fluid directly from the brake pipe 13, backflow check valves
33 can be provided
between each reservoir and the BP 13. Alternative ways known to those skilled
in the art for preventing
backflow from the reservoirs into the brake pipe can also be provided.
The EC 25 can monitor the brake cylinder pressure via a pressure transducer
("P") 35. In
operation, the EC 25 can typically receive an electrical command signal ("CS")
26 from a locomotive
which can instruct it to either apply or release the brakes. The level of
increased or decreased braking
can be communicated by both the CS 26 and/or the BP 13. The BP 13 can in some
installations (not
shown) communicate the brake command to the PCV 10 so that in event of any
problems with the ECP
system the PCV 10 can operate the brakes. Under normal conditions, to apply
the brakes the EC 25 can
actuate either or both of the application valves 27, 29 to supply pressurized
fluid to the BC 19 from the
reservoirs. To release the brakes, the EC 25 actuates the SOL REL 31 to vent
the BC 19. The EC 25 can
control the release of BC 19 pressure to provide incremental reductions in
pressure (graduated release)
without completely exhausting the brake cylinder as in the conventional
pneumatic system.
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CA 02558723 2001-06-28
Figure 3 illustrates a fully ECP brake control system, similar to the ECP
system shown in Figure
2 except that no PCV 10 is utilized. In this type of system, a single
compartment reservoir 14 can be
used for a couple of reasons. First of all, the PCV 10 requires separate AUX
15 and EM 17 reservoirs to
operate. Without the PCV 10 the dual compartments are not needed. Also, in the
fully ECP system the
BP 13 pressure is maintained at full charge since all brake commands are sent
to the EC 25 via the CS 26.
Additionally, because a single reservoir is used only a single application
valve "(APPN") 28 is needed.
Like the ECP system of Figure 2, the ECP system is of the BCC type in that the
EC 25 can directly
control the BC 19 pressure. Similarly, graduated release of brake pressure can
also be provided by the
EC 25.
In the pneumatically controlled freight train braking system shown in Figure
1, wherein the
braking functions are performed by the PCV 10, the BC 19 pressure is
completely exhausted whenever a
brake release is signaled (subject to the retainer system). The obvious
disadvantage is that the level of
braking cannot be partially reduced, it can only be fully exhausted. If the
braking force is slowing the
train too much, the engineer only has two choices: release the brakes
completely or use power braking.
Releasing the brakes completely means that there may be a certain period of
time after the release before
the brake pipe and reservoirs are recharged sufficiently, during which
adequate braking force will be
available. In the second case, power braking is inefficient and wasteful.
Power braking is when the
engineer leaves the brakes applied and applies power to increase the train
speed against the brakes. This
is clearly an undesirable procedure, however it may be the only option. For
example, when the train is
slowing too much yet the engineer knows that there is not be enough time for
the brake pipe and
reservoirs to recharge before braking is again required.
Referring now to Figure 4, this advantage of graduated release can be provided
by the use of a
pneumatically functioning release graduating valve (RGV) 40. According to the
invention, the RGV 40
can be operatively incorporated into the freight brake control system shown in
Figure 1 by simply
connecting the RGV 40 to the PCV 10. Thus, whenever a release of brakes is
signaled, the PCV 10
exhausts the brake pressure through the RGV 40 which controls the release of
the brake pressure to the
atmosphere in a graduated manner.
The RGV 40 can be designed to operate either continuously or selectively.
Presently preferred
embodiments of selectively actuable RGVs 41, 43 are shown in Figures 5-10. A
preferred embodiment
of a "permanent," RGV 45, i.e. continuous graduated release mode, is shown in
Figure 11. The different
embodiments will be described more fully below in connection with the
corresponding drawing figures.
A selectively actuable RGV 41, 43 may be enabled in several presently
preferred ways. A first
way is that the cars in the unit train can be equipped with the aforementioned
trainlined AP 37. The
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CA 02558723 2001-06-28
metering valve 42 will thus be interposed by changeover valve 44 which
responds to pressure changes in
the AP 37. Thus, the BPS valves may not be required.
Alternatively, the unit train might be equipped with a second locomotive or
remote air
compressor car located toward the rear of the train for improved brake pipe
pressure control by either
radio or direct wire, as is done with present remote controlled locomotives.
The RGV 41 would include
the BPS valve 90 for actuating the changeover valve 44 to interpose the
metering valve 42. The
additional compressed air source would permit the BP 13 pressure signals to be
propagated more rapidly
and the graduated release provided by the RGV 41, 43 would improve brake
control and dynamic brake
utilization. In this case a trainlined AP 37 would not be necessary.
Another alternative similar to the just described option is that, in the event
that the unit train is
short enough, the additional locomotive or compressor to provide BP 13 control
at locations remote from
the lead locomotive would not be required. The RGV 41 could be operated of the
BP 13 via the BPS
valves as explained above. Although the propagation of the BP 13 signals would
not be as rapid, the
RGV 41 would still provide a smoother release of the brakes and the
possibility of better dynamic brake
utilization.
An additional alternative for enabling the RGV 40 involves the use of a brake
pipe control unit
("BPCU") which is an electrically controlled device connected at multiple
selected locations remote from
the locomotive along the BP 13. The BPCU includes solenoid valves for locally
adjusting brake pipe
pressure in response to a CS 26 in order to speed the propagation of a signal
through the BP 13 to the
PCV's 10 on each car. The BPCU's can be used with either the AP 37 or just the
BP 13 as just
previously described. The advantage being that the BP 19 signal is propagated
significantly faster
resulting in brake operations being carried out by the PCV 10 on each car more
quickly and more in
unison with every other car in the train. Briefly put, each BPCU device has or
controls solenoid valves to
either vent a certain amount of pressure from the BP 13 corresponding to a
brake application command or
put pressure into the BP 13 in response to a release command. In this system,
multiple remote BPCU's
are connected to the BP 13 at spaced apart locations along the unit train.
Each BPCU receives electrical
command signals CS 26 from the locomotive to either reduce or increase BP 13
pressure at that location
along the BP 13. In doing so, the BP 13 signal is propagated through the train
significantly faster than it
could propagate unassisted. This type of system could be referred to as a
brake pipe control ("BPC")
type of ECP system since BP 13 pressure, as opposed to brake cylinder
pressure, is controlled. The BCC
is basically an electrically assisted pneumatic control system and can closely
approximate the rapid and
uniform brake application provided by the BCC type ECP system. Importantly,
the BPC system retains
the use of the proven, reliable, and common PCV 10 which is already provided
on virtually all freight
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CA 02558723 2001-06-28
cars currently in service. Moreover, the use of the RGV 40 further enhances
the BPC system by
providing the additional feature of graduated release of brake pressure.
Consequently, a BCC system,
which is basically a conventional pneumatic system with the added BPCU's, that
also utilizes an RGV 40
can provide virtually braking performance nearly the equal of the BCC type ECP
system. Plus, this
system requires only the limited electronic equipment needed for the BPCU's.
In the embodiment shown in Figures 5-7, the RGV 41, 43 can be selectively
interposed into the
system using the AP 37. Referring back to Figure 4, the AP 37 shown in dashed
lines, because it can be
optional, may be a main reservoir pipe supplied with pressurized fluid from a
locomotive. Pressure
changes, and preferably a pressure in the AP 37 above a predetermined level,
can be used to activate the
interposition of the RGV 41, 43. When the pressure in the AP 37 is below the
predetermined level, the
BC 19 will be exhausted by the PCV 10 in a conventional manner.
Basically, the selectively operable RGV 41, 43 can have two separate valve
portions. The first
portion is a metering valve portion 42 and the second portion is a changeover
valve portion 44. As
shown in Figures 5-7, the changeover valve portion 44 is actuated by AP 37
pressure to switch between a
graduated release position and a direct release position. Although the
changeover valve portion 44
shown in the drawings utilizes a simple spool valve 47, alternate types of
changeover valves could be
satisfactorily employed.
In the graduated release position, the changeover valve 44 interposes the
metering valve 42 to
control the exhaust of the BC 19 during a release application by venting BC 19
pressure responsive to
increases in BP 13 pressure. In the direct release position, the metering
valve 42 is isolated from the BC
19 such that the PCV 10 controls the exhaust of BC 19 pressure in a
conventional manner.
The main components of the metering valve 42 include a graduating piston 60, a
graduating
spring 62 and a graduating check 64. In the conventional direct release mode,
shown in Figure 5, the
graduating piston 60 is subject to EMER 17 reservoir pressure on one side 68
and BP 13 pressure on the
other side 66. In addition to BP 13 pressure, BC 19 pressure be can
communicated on the same side 66
through a brake cylinder exhaust port 72 in the PCV 10 (see Figure 7). In this
particular configuration,
the BC 19 pressure is communicated with the graduating piston 60 only when the
PCV 10 moves to a
release position which causes the BC 19 pressure to be connected through the
port 72 in the PCV 10 to
the metering valve 42.
As shown in Figure 5, the RGV 41 is configured for conventional direct release
operation
because no air is present in the AP 37. This permits the changeover spool 47
to be held down by the
changeover spring 48. Under this condition, the EMER 17 reservoir is charged,
as is normal, from the
service portion's emergency charging port, and air is available from EMER 17
reservoir to flow back
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CA 02558723 2001-06-28
through this port when accelerated service release is called for. Within the
metering valve 42, BP 13 air
is blocked by the upper land 50 of the changeover spool 47, and EMER 17
reservoir air is ported through
the upper annulus 56 of the changeover spool 47 to the left side 66 of the
graduating piston 60. Since
EMER 17 reservoir air is always present on the right side 68 of the graduating
piston 60, the piston 60 is
essentially balanced, and the graduating spring 62 holds the graduating check
64 off its seat as shown,
permitting unrestricted communication between the service portion's exhaust
port 72 and the retainer
pipe, so that when brake release is called for it will be unrestricted except
by the RET 23 in the normal
way.
When main AP 37 air is present, the situation is as shown in Figure 6. As
shown, the pressure in
the AP 37 has forced the changeover spool 47 upward. In this position, the
upper land 50 of the spool 47
uncovers communication with the BP 13, while the middle land 52 cuts off
communication between the
EMER 17 reservoir and the left side 66 of the graduating piston 60.
Consequently, BP 13 now communicates, through the spool's 47 upper annulus 56,
with both the
left side 66 of the piston 60 and, through the internal passages of the valve
44 and a control orifice 70,
with the underside of the emergency reservoir charging check valve 75.
Finally, the lower land 54 of the spool 47 blocks communication from or to the
service portion's
emergency reservoir exhaust port 72, thus nullifying EMER 17 reservoir
dumpback to BP 13 in service
release so as to permit the gradual restoration of BP 13 pressure necessary to
control graduated release
operation.
This blockage would also prevent EMER 17 reservoir charging except for the
provision of the
charging check in the valve 75 which allows charging of the EMER 17 reservoir
any time this reservoir's
pressure is exceeded by that in the BP 13.
Charging of reservoirs and application of brakes is, from the car's
standpoint, no different than
the conventional pneumatic system. When brakes were released after an
application, however, the
pressure on the left side 66 of the graduating diaphragm 65 is 12-30 psi lower
than that on the right side
68, allowing EMER 17 reservoir pressure, acting on the diaphragm's 65 right
side 68 to overcome the
graduating spring 62 , shift the graduating piston 60 to the left and hold the
graduating check 64 on its
seat.
At this point however, as a result of the PCV 10 shifting to release, the full
value of brake
cylinder pressure is ported to the underside of the graduating check 64, where
it acts on the check's 64
seat area and aids the graduating spring 62 in urging the check 64 off its
seat. The seat diameter, spring
force, and diaphragm area have all been so chosen that the forces tending to
unseat the graduating check
64, under this condition will slightly overbalance the diaphragm force, thus
allowing the check 64 to lift,
CA 02558723 2001-06-28
and reducing brake cylinder pressure slightly until the unseating force (which
decreases with decreasing
brake cylinder pressure) is just balanced by the force on the graduating
piston 60, at which point the
graduating check 64 will seat and block further brake cylinder exhaust.
Note that in this balanced condition the graduating piston 60 stem force is
only affected by the
differential of EMER 17 reservoir over BP 13 (or for the condition of steady
state emergency reservoir
which would obtain during brake release, simply by the BP 13 pressure). Thus
an increase in BP 13
pressure will reduce the differential, and upset the balance holding the
graduating check 64 to its seat
until brake cylinder pressure is again reduced, to the point where the check
64 again closes as described
above, but at a lower BC 19 pressure. This action will continue throughout the
brake release, providing
gradual controlled decrease in BC 19 pressure in step with the gradual
increase in BP 19 pressure.
Further, since the initial release lowered the value of brake cylinder
pressure by about 5 psi, this
differential will be maintained, and complete release of brakes will occur at
a BP 13 pressure about 5-8
psi lower than its initial value. This assures that all brakes will be
released when brake pipe pressure is
restored to its initial value on each individual car, permitting operation in
a train having brake pipe taper
without dragging brakes toward the rear.
Since some trains on which the system is intended to work may have augmented
brake pipe
pressure control, this latter feature will be more important in some
operations than others, but will assure
reliable brake release.
In the RGV 43 embodiment shown in Figure 7, the BP 13 can communicate with
both the AUX
15 and EMER 17 reservoirs through a pair of charging check valves 75, 77. This
ensures that the EMER
17 reservoir will always be equal to or more highly pressurized than the BP 13
and also that the AUX 15
reservoir will be charged more quickly after a brake application. The
reservoir charging check valves 75,
77 permit the transfer of pressurized fluid in only one direction-- from the
BP 13 into the reservoirs 15,
17. Each charging check valve 75, 77 includes a check plate 79, 81 which is
biased by a check spring 83,
85 against the port into the BP 13. The check springs 83, 85 create a certain
pressure differential which
the BP 13 pressure must overcome before pressurized fluid is transferred into
the reservoirs 15, 17. In
particular, the check spring 85 for the AUX 15 reservoir check valve 77 can be
provided in varying rates
of stiffness to perform important functions regarding controlling the position
of the PCV 10, with respect
to application and release modes, as will be described more fully below in
connection with the operation
of the RGV 43.
As in the previously described RGVs 41, 43, the changeover valve 44
selectively interposes, or
isolates, the metering valve 42 in response to the pressure in the AP 37 and
exhausts pressure in the
graduated release mode in the same manner described in connection with Figures
5-6.
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CA 02558723 2001-06-28
The areas of each side of the graduating piston 60, along with the spring rate
of the graduating
spring 62, are preferably designed such that the forces on each side of the
graduating piston 60 generally
balance during braking applications so that the graduating check 64 is seated
and no brake cylinder
pressure is exhausted whenever BC 13 pressure is reduced. As explained above
in connection with the
prior art, a reduction in BP 13 pressure signals the PCV 10 to apply the
brakes. Thus, when BP 13
pressure is reduced, the PCV 10 shifts to an application position and supplies
an amount of pressure,
proportional to the reduction in BP 13 pressure, to the BC 19 from the AUX 15
reservoir. Since the BP
13 pressure has decreased, the EMER 17 reservoir continues to hold the
graduating check 64 closed so
that no pressure is exhausted while the brakes are being applied. However, a
subsequent increase in BP
13 pressure signals the PCV 10 to shift to release position which connects the
BC 19 pressure behind the
graduating check 64. The BC 19 pressure thus adds to the increased BP 13
pressure and results in a
greater amount of force on the brake pipe side 68 of the graduating piston 60
than on the emergency
reservoir side 66. This causes the metering valve portion 42 to exhaust a
proportional amount of BC 19
pressure. The BC 19 pressure is exhausted until the forces on each side of the
graduating piston 60
equalize again and the graduating check 64 returns to its closed position. The
RGV 43 exhausts BC 19
pressure generally as a function of the BP 13 pressure since the amount of
increase in BP 13 pressure is
approximately the differential in pressure which overcomes the EMER 17
reservoir to open the
graduating check 64. When a proportional amount of pressure is exhausted from
the BC 19, the
graduating piston 60 resumes its generally balanced state. If, after a
graduated release of BC 19 pressure,
a higher braking force is desired, the BP 13 pressure can be reduced again to
signal the PCV 10 to supply
proportionally more pressure to the BC 19. While the PCV 10 remains in an
application mode,
reductions in BP 13 pressure do not affect the graduating piston 60 because
the EMER 17 reservoir
pressure remains generally constant and holds the graduating check 64 closed
such that no BC 19
pressure is exhausted. Consequently, the pressure in the BC 19 is captured and
conserved which permits
the level of braking to be either reduced or increased in incremental amounts
at any time without the need
to vent all of the pressure from the BC 19 each time.
As mentioned previously, the position of the PCV 10, in regard to application
and release modes,
during graduated release can be controlled by using, for example, the spring
rate of the auxiliary
reservoir check valve 77. This is so because the PCV 10 can typically be
configured to switch between
the release and application modes responsive to the pressure differential
between the AUX 15 reservoir
and the BC 19, and/or BP 13. Generally, the PCV 10, and specifically a service
portion thereof, can be
prevented from going to release by connecting the BP 13 to the AUX 15
reservoir. However, in such a
case the brake cylinder exhaust port 72 would have to be directly connected to
the metering valve portion
12
CA 02558723 2001-06-28
42. The operation of a RGV 40 in such a configuration is described more fully
in connection with an
embodiment of the permanent RGV 45 below. Additionally, a more detailed
description of the how the
position of the PCV 10 can be controlled using the spring rate of the AUX 15
reservoir check valve
spring 85 is also provided in connection with the description of the RGV 45.
In the event that remote locomotives or compressor cars are used as the brake
pipe control
augmentation means, there ~ be no trainlined AP 37 on the cars to operate the
changeover valve
portion 44. In this case changeover will be effected by BP 13 change and, as
shown in Figures 3 and 4,
the BP 13 would be connected to the RGV 40 via line 14. In particular, a BP 13
pressure of some
amount above that carried on freight trains (90 psi max) can be used to signal
the cars that the
changeover valveportions 44 should be set for graduated release operation.
If BP 13 pressure is to be carried at 110 psi the pressure operated changeover
feature shown in
Figures 8-10 can be used to shift the changeover spool 47 to graduated
position when a critical value of,
say 95 to 105 psi is exceeded, and not to return it to direct release
operation until BP 13 pressure drops
below this point by a greater amount than required for a full service brake
application.
Assuming that a fully charged BP 13 pressure of 110 psi was used, full service
equalization
would occur at 78.5 psi and it ought to be allowable for a 15 psi over
reduction to be made. Thus the
spool 47 should move up at a BP 13 pressure of 100 psi as above, and not move
back down until the
pressure had been reduced below 63 psi. The configuration shown in Figures 8-
10 can accomplish this
operation.
Referring to Figure 8, the metering valve portion 42 and changeover valve
portion 44 remain
unchanged from the previous embodiments where their operation was described in
connection with
Figures 5-7. In this case however, the passage formerly used to connect the AP
37 to the underside of the
spool 47 is instead connected with a brake pipe sensor (BPS) valve 90. Figure
8 depicts the situation at
initial charging wherein this passage is initially vented to atmosphere
through the BPS 90 valve's pilot
stem 92, into the sensing spring 94 chamber, thence to atmosphere through that
chamber's permanently
connected vent marked EX in the figure.
Note that BP 13 pressure is ported into the sensing valve 90, where it acts on
the right hand side
of the sensing diaphragm 96, urging the stem 92 to the left against the
preloaded sensing spring 94. At
100 psi, the force from the sensing diaphragm 96 will overcome the spring 94
moving the stem 92 to the
left until its end contacts the face of the pilot check 98, as shown in Figure
9.
Figure 9 shows that the stem 92 has moved to contact the right hand surface of
the pilot check
98, thus blocking communication between the passage to the bottom of the
changeover spool 47 and
atmosphere. Any leakage past the pilot check 98 will thus be trapped and will
tend to fill this passage
13
CA 02558723 2001-06-28
along with the chamber on the right hand side of the lockover diaphragm 100,
with which it is in constant
communication.
A slight further increase in BP 13 pressure will overcome the pilot check
spring 102 and begin to
unseat the pilot check 98 which will result in such a buildup. As this occurs,
the lockover diaphragm 100
will add its force to that of the sensing diaphragm 96, forcing the check 98
further off its seat and
resulting in a prompt movement of the stem 92 to its graduated release pilot
position, as shown in Figure
10.
In this position, BP 13 air flows both to the lockover diaphragm 100 face as
explained above, and
up the passage to the changeover spool 47 face, where it overcomes the
changeover spring 48, and shifts
the changeover valve 44 to the graduated release position.
With the changeover spool 47 in the graduated position, as mentioned
previously, graduated
release is enabled, EMER 17 reservoir charging is via the charging check 75 in
the metering valve
portion 42, and dumpback to BP 13 during service release is nullified.
When BP 13 pressure is reduced after the changeover point has been exceeded,
as outlined
above, which it must be during service brake application for example, the BPS
valve 90 will not return to its original direct release position. Only when BP
13 pressure has been
reduced to the point where the sum of the forces on both the sensing 96 and
lockover 100 diaphragms is
lower than the preloaded value of the sensing spring 94 can the BPS valve 90
reset to the direct release
position.
Since the area of the lockover diaphragm 100 is equal to or greater than that
of the sensing
diaphragm 96, the pressure acting on the pair must be reduced to 50% or less
than that which caused the
shift. Thus if a 100 psi BP 13 charge shifts the BPS valve 90 to graduated
release position, BP 13
pressure will have to be reduced below 50 psi for the BPS valve 90 to reset to
direct release. As this is
well below the 78 psi full service equalization from a 110 psi brake pipe,
unintended shifting of cars back
to direct release operation should not occur. Further, by increasing the size
of the lockover diaphragm
100, the switch point from graduated to direct release may be made as low as
desirable.
The BPS valve 90 described above can be easily mounted on a filling piece
between the service
portion and the pipe bracket face of a PCV 10, as shown in Figure 14.
Referring now to Figure 11, a continuous graduated release RGV 45 is
incorporated into a
pneumatically controlled freight brake system in the same manner as the
selectively operable RGVs 41,
43-- by connecting it to the PCV 10. However, in this configuration, there is
no optional direct release
mode and pressure from the BC 19 is always released in a graduated fashion.
Such a permanent RGV 45
has no changeover valve 46 to selectively interpose the metering valve portion
42. The RGV 45 thus
14
CA 02558723 2001-06-28
always vents the BC in a graduated manner whenever a release application is
signaled. In this
configuration, the AUX 15 reservoir charging check valve 77 can be eliminated.
Additionally, the BC 19
exhaust can be ported directly to metering valve portion 42 along with the
brake cylinder exhaust port 72
from the PCV 10. In other respects, however, the RGV 45 can function in much
the same way as the
selectively operable RGVs as shown in Figures 5-10. For example, the
graduating piston 60 is subject to
the same BP 13 pressure and BC 19 exhaust pressure on the brake pipe side 66
of the piston graduating
piston 60 and to the EMER 17 reservoir pressure on the opposite side 68. One
difference however is that
BC 19 pressure is directly connected on the brake pipe side 66 of the
graduating piston 60. This is in
contrast to the selectable RGVs 41, 43 wherein the graduating check 64 is
normally subject to BC 19
pressure only when the PCV 10 is in a release position and connects the BC 19
pressure to the metering
valve portion 42 via the brake cylinder exhaust port 72 in the PCV 10. This
modification to the RGV 45
can be made so that the RGV 45 can control the exhaust of BC 19 pressure
whether or not the PCV 10 is
in a release position. This can be necessary, since it may be desirable to
prevent the PCV 10 from going
to release when BP 13 pressure is increased in order to permit the RGV 45 to
exhaust the BC 19.
However, as referred to previously, the auxiliary charging check valve 77 in
the selectively operable
RGV 43 could be designed to prevent the PCV 10 from going to a release
position during operation of
the graduated release. In this case, the BC 19 exhaust would have to be routed
directly to the RGV 43 in
Figure 7 similarly to the permanent RGV 45 shown in Figure 1 l, for the same
reason explained above.
If desired, the permanent RGV 45 can also operationally be provided with a
port 108 which
connects a relatively small volume of pressurized fluid, preferably about 90
cubic inches, to an
emergency reservoir port 73 in the service portion of the PCV 10. The PCV 10
could feed portions of
this volume into the BP 13 if a service accelerated release function is
desired, thus increasing the BP 13
pressure by an additional 1 or 2 psi locally and serving as a release ensuring
feature.
Generally, the metering valve portion 42 exhausts BC 19 pressure generally
proportional to the
increase in BP 13 pressure. Particularly, the graduating piston 60 is normally
held by EMER 17 reservoir
pressure in a position where no BC 19 pressure can be exhausted. On the other
side of the graduating
piston 60, the BP 13 pressure and BC 19 exhaust pressure urge the piston 60
against the EMER 17
reservoir pressure. Initially, the forces on each side of the piston 60 are
generally balanced such that the
graduating check 64 is held fast so that the BC 19 is isolated from the
atmosphere. The RGV 40 is
designed such that the graduating check 64 remains seated during brake
applications. When a brake
application is signaled by a reduction in BP 13 pressure, the PCV 10 supplies
a proportional amount of
pressurized fluid into the BC 19 from the AUX 15 reservoir.
CA 02558723 2001-06-28
Unlike the selectively actuable RGVs, in the RGV 45, the BC 19 is directly
connected to the
brake pipe side 68 of the metering valve 42. However, because this BC 19
pressure is generally
proportional to the reduction in BP 13 pressure, the forces on each side of
the graduating piston 60
remain generally balanced. Once the brakes have been applied, if a reduction
in BC 19 pressure is
desired the BP 13 pressure can be increased, thus signaling for a proportional
reduction in BC 19
pressure. The increased in BP 13 pressure disturbs the balance, overcoming the
EMER 17 reservoir
pressure and causing BC 19 pressure to be exhausted. However, the graduating
check 64 will only
remain open until an amount of BC 19 pressure proportional to the increase in
BP 13 pressure has been
exhausted. When this happens the graduating check 64 seat again because the
combined BP 13 pressure
and BC 19 pressure will have once again equalized with the EMER 17 reservoir
pressure. Thus, it can be
seen that the pressure exhausted from the BC 19 is a generally a function of
the increase in BP 13
pressure.
In addition to exhausting only a selectable portion of the BC 19 pressure,
each particular
embodiment the RGV 40 also makes it possible to incrementally increase the BC
19 pressure after a
graduated release. For example, if increased BC 19 pressure is subsequently
desired, a reduction in BP
13 pressure can signal the PCV 10 to supply more pressurized fluid to the BC
19. As explained above, a
reduction in BP 13 pressure does not result in any BC 19 pressure being
exhausted. Thus, BC 19
pressure can also be incrementally increased by the PCV 10. Furthermore, less
additional pressurized
fluid is required to be supplied to the BC 19 for increases in BC 19 pressure
because there is already a
certain amount of pressure captured in the BC 19 by the RGV 40. After such
increase, if less BC 19
pressure is once again deemed desirable, a simple increase in BP 13 pressure
can accomplish the exhaust
of a proportional amount of BC 19 pressure in the manner described above.
Consequently, the RGV 40
allows the BC 19 pressure to be incrementally adjusted, up or down, on demand.
Plus, by conserving the
pressure in the BC 19, less pressurized fluid from the reservoirs will be
required.
The improved braking control provided by an RGV 40 according to the invention
is illustrated in
the "BC Pressure" versus "Time" graphs shown in Figures 12 and 13. Line 110 in
Figure 12 visually
illustrates how the RGV 40 can incrementally reduce the pressure in the BC 19
without entirely venting
the BC 19 to the atmosphere. The graph illustrates only the exhaust of BC 19
pressure by the RGV 40. It
should be remembered that the BC 19 pressure can also be stepped up (using the
PCV 10) and then
stepped down again. In Figure 13, two conventional methods of exhausting the
BC 19 to atmosphere are
represented by curves 112, 114. Curve 112 represents the exhaust of BC 19
pressure directly to the
atmosphere. As can be seen, in a matter of a few seconds all of the pressure
from the BC 19 is
exhausted. In the case of using a RET 23, represented by curve 114, it can be
seen that, although it may
16
CA 02558723 2001-06-28
take longer, for example about sixty seconds, all of the pressure is
nevertheless eventually exhausted
from the BC 19.
Consequently, it can be easily understood how the RGV 40 can greatly improve
the braking
capabilities of a pneumatically controlled freight brake control system.
Moreover, the BPC type ECP
system having a RGV 40 can now include the advantages of the BCC type ECP
system, including the
incremental control over the brake cylinder pressure provided by the RGV 40,
while maintaining the
proven safety and reliability of the pneumatically controlled braking system.
Figure 14 illustrates how a RGV 40 can be operatively connected to a type ABDX
(or ABDX-L)
pneumatic control valve 120. Similarly it can be used with a DB-60 type valve.
The ABDX type control
valve 120 manufactured by Westinghouse Airbrake Company typically includes a
central pipe bracket
portion 123, on one side of which is connected a service portion 126 and the
other side of which is
connected an emergency portion 129. The service portion 126 typically controls
"service" braking
applications, which are those braking applications calling for a BC 19
pressure below a predetermined
level. The pressurized fluid from the AUX 15 reservoir is the normal source of
pressurized fluid for such
service braking applications. The emergency portion 129 and EMER 17 reservoir
are normally reserved
only for emergency situations where the train must be stopped as quickly as
possible. Consequently, the
RGV 40 is designed primarily for use in connection with service braking
applications. Preferably, an
interface plate 132 is provided between the service portion 126 and the pipe
bracket 123. The interface
plate 132 provides all of the requisite interconnecting ports such that the
RGV 40 can simply be
connected to the interface plate. An example of such an interface plate 132 is
described in U.S. Patent
No. 5,451,099, assigned to the assignee herein. The control valve with the
interface plate and RGV
attached can then be operatively incorporated into the freight brake control
system as shown in Figure 3.
System Operation
The operation of, for example, the RGV 43 shown in Figure 7, is described
below in more detail
as it may be operated when connected to an ABDX valve in a unit train having a
trainlined main reservoir
pipe as the AP 37. The following details are provided only as an example so
that the operation of such
an RGV may be better understood and are not intended to be limiting to the
scope of the invention which
is entitled to the full breadth of the claims which follow the description.
With the RGV 45 connected to an ABDX valve and the AP 37 being a main
reservoir pipe, the
train brakes will automatically operate in conventional direct release unless
the AP 37 is charged to main
reservoir pressure. When the AP 37 is charged above 105 psi the changeover
valve 44 automatically
interposes the graduated release valve 43. Therefore, the AP 37 can be charged
to main reservoir
pressure (approximately 135 psi) when it is desired to operate in the
graduated release mode; and it may
17
CA 02558723 2001-06-28
either not be charged or charged to BP 13 pressure (up to a maximum of 100
psi) for operation in direct
release.
Graduated Release
Three things occur when the changeover valve 44 activates graduated the
release: (1) The brake
cylinder exhaust port 52 from the service portion is routed to the RGV valve
43, permitting the RGV 43
to then control exhaust in accordance with any incremental increase in BP 13
pressure; (2) BP 13
pressure is admitted to the EMER 17 reservoir charging check valve 75 to
handle recharging after
emergency and to an AUX 15 reservoir charging check valve 77 to increase the
rate of re-charging AUX
reservoir during a graduated release; and (3) EMER 17 reservoir is cut off
from the ABDX service
10 portion to nullify the release connection of EMER 17 reservoir to BP 13 and
to also nullify service
accelerated release. This allows small changes in train BP 13 pressure to be
controlled from the
locomotive and the ECP BP 13 pressure control units throughout the train
(utilizing AP 37 pressure as a
continuous high pressure air source).
When operating in graduated release, incremental BP 13 pressure reductions may
be made at any
15 time to increase service brake cylinder pressure. Although preliminary
quick service bites will be taken
out of BP 13 pressure each time a reapplication is made, imposing reductions
of at least 1.5 to 2 psi, the
continued presence of BC 19 pressure will nullify any quick service limiting
valve activity.
In this example, there are at least two options for controlling the operating
position of the ABDX
valve during graduated release operation. The auxiliary reservoir check valve
spring 83 may be set at
about 2.5 psi, which would cause the service portion to move to release at the
first increase in BP 13
pressure following an application. In this case the AUX 15 reservoir would be
able to charge faster with
any additional increase in BP 13 pressure, but would charge through the more
restrictive charging choke
at pressure differentials below 2.5 psi after going to release.
Alternatively, the AUX 15 reservoir charging check valve 77 differential may
be set at about 0.5
psi, well below the service portion release differential, thereby allowing the
connection of BP 13 pressure
to AUX 15 reservoir to prevent the PCV 10 from moving to release position. In
this case the actual BC
19 pressure line would be routed to the metering valve portion 42 and the
changeover valve 44 would
need to also cut off communication with the auxiliary reservoir charging check
valve 77 when BC 19
pressure reduced to about 12 psi. This would then force the PCV 10 to release
with any further increase
in BP 13 pressure. It is presently believed that allowing the service portion
to release would be the
simpler and more reliable choice.
Where utilized, the distribution of multiple remote BPCUs 38 throughout the
train would allow
for a reasonably fast complete release of the brakes, even when the PCV's 10
are set to operate in
18
CA 02558723 2001-06-28
graduated release. The BPCUs can be supported by AP 37 pressure. Testing would
be required to
determine the specific full release times, but this would not be a critical
factor because all brakes would
release generally simultaneously, eliminating the concern for creating
undesirable slack action.
Recharging chokes provided between main reservoir and BP 13 and between BP 13
and AUX 15
reservoir would be set to provide a fast response, but without drawing the
main reservoir pressure at the
rear of a long train below the 105 psi graduated release threshold pressure.
The use of 1-1/2 inch pipe for
the AP 37 would maximize the flow capacity and minimize the pressure gradients
during periods of high
flow demand. If it were deemed necessary, the graduated release threshold
could be reduced to 95 psi
rather than 105 psi, limiting the BP 13 pressure to 90 psi when operating in
direct release. Alternately, a
large hysteresis could be designed into the changeover valve portion 44, so
that once the AP 37 pressure
exceeded the changeover pressure, it would need to be reduced substantially
below that pressure to allow
the changeover valve portion 44 to reset to direct release.
Inexhaustibility
Because BP 13 pressure will be reduced to apply the brakes, the full reservoir
charge generally
cannot be maintained, as is done with direct acting ECP brakes, i.e. a BCC
type system. The
inexhaustibility of the system is nevertheless still somewhat enhanced in that
the AUX 15 reservoir is
gradually, and relatively quickly, recharged along with the BP 13 during
graduated release.
GRV Interface for ABDX Pneumatic Control Valve
Referring to Figure 14, the RGV 40, which for this example can be the RGV 43,
is preferably
mounted to an interface plate 132 between the pipe bracket 122 and service
portion 126 of an ABDX
valve 120, intercepting the RET 23 and the EMER 17 reservoir port, and
communicating with the other
requisite ports. The changeover valve portion 44 is actuated by AP 37 pressure
acting on changeover
spool 47. When AP 37 pressure is below about 105 psi, the changeover valve
portion 44 stays in a direct
release mode, keeping all normal pneumatic connections to the service portion
126, including the
connection of BC 19 exhaust to the atmosphere, or a RET 23. When AP 37
pressure exceeds 105 psi,
overcoming the force of the changeover spring 48, the changeover spool 47 is
moved to graduated release
position wherein the metering portion 42 controls the exhaust of BC 19
pressure in a graduated fashion
as a function of the BP 13 pressure.
In graduated release, the several port connections are changed. EMER 17
reservoir is cut off
from the service portion 126 to prevent feedback of EMER reservoir to BP 13
following release. This
also nullifies accelerated service release. Also, BP 13 pressure is admitted
to both the emergency and
auxiliary charging check valves 75, 77. This allows EMER 17 reservoir to be
recharged without going
through the PCV 10, and AUX 15 reservoir can be charged faster than normal
after the service portion
19
CA 02558723 2001-06-28
126 releases. Finally, the brake cylinder exhaust port 72 from the service
portion 126 is routed to the
metering valve portion 42. The metering valve 42 traps and exhausts BC 19
pressure proportional to
incremental increases in BP 13 pressure.
If necessary, it would be possible to link a small volume of about 90 cubic
inches, as shown in
Figure 6, to the EMER 17 reservoir port 73 in the service portion 126 of the
ABDX valve 120. In
particular, this may be desirable where a permanent RGV 45 is employed. This
volume would then feed
into BP 13 if service accelerated release was triggered in the service portion
126, increasing BP 13
pressure by an additional 1 or 2 psi locally and serving as a release ensuring
feature.
Brake Cylinder Pressures
The brake cylinder pressure chart, Table 1, shows some typical brake cylinder
pressures for
various brake pipe pressure reductions, from both 90 psi and 110 psi.
TABLE 1
GRADUATED RELEASE VALVE BALANCE
Differential Pressure Controlled Valve
ER PRESS BP PRESS BCP Viv BCP
Stem Dia. 0.25
90 86.26 0.00 0.00 ER Area: 1.767144
90 80 20.65 20.65 BP Area: 1.718057
90 75 37.15 37.15 BCP Area 0.5205
90 70 53.66 53.65 Spring:10.85
90 66.4 65.54 65.53
(Spring Optimized for 90 psi)
110 106.83 0.00 -1.88
110 100 22.54 20.65
110 95 39.04 37.15
110 90 55.54 53.65
110 85 72.05 70.15
110 81.76 82.72 80.8222
CA 02558723 2001-06-28
Stem Dia. 0.25
D. Diam: 1.5
90 85.70 0.00 1.3 ER Area: 1.767144
90 80 18.81 20.65 BP Area: 1.718057
90 75 35.30 37.15 BCP Area 0.521
90 70 51.78 53.65 Spring:11.8
90 66.2 64.31 66.10
(Spring Optimized for 110 psi)
110 106.27 0.00 -0.06
110 100 20.69 20.65
110 95 37.18 37.15
110 90 53.67 53.65
110 85 70.16 70.15
110 81.55 81.53 81.535
Included for comparison are the graduated release proportioning valve
pressures and the nominal brake
cylinder pressures normally provided by the control valve, for the same brake
pipe pressure reductions.
These pressures closely match, which means the brake cylinder pressure will be
exhausted by the
graduated release valve on the same track as it is applied by the control
valve for any BP 13 pressure
reduction, without significant hysteresis. This allows for indiscriminate
incremental increases and
decreases of brake cylinder pressure, without imposing any disruptively large
steps during turnarounds.
As various other embodiments of the invention are utilized, other valves will
be used depending upon
specific design configurations.
Following a pneumatic emergency application, emergency reservoir will provide
a lower
reference pressure for graduated release, fully exhausting brake cylinder
pressure at a lower BP 13
pressure (with less increase) than normal. The reservoirs will then need to be
fully re-charged to restore
the normal graduated release pattern. This would not be expected to cause any
significant problems,
because the train will definitely be stopped during the release of an
emergency application, and the
system must be re-charged in any case.
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
21
CA 02558723 2001-06-28
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.
22
