Note: Descriptions are shown in the official language in which they were submitted.
s CA 02302903 2000-03-24
PNEUMATICALLY DRIVEN TRAIN BRAKE
PIPE PRESSURE EXHAUST VALVE
This application is a divisional application of Canadian
Patent Application No. 2,209,401 filed on July 2, 1997.
FIELD OF THE INVENTION
The present invention relates, in general, to a pneumatic
type brake pipe pressure regulating valve disposed at a location
remote from a railroad locomotive for exhausting the air
pressure present in the brake pipe of a railroad train
substantially concurrently with a locomotive brake valve service
reduction of brake pipe air pressure at the train locomotive
and, more particularly, this invention relates to a regulating
valve that utilizes a single pneumatic drive system for both a
service brake application and an emergency brake application.
BACKGROUND OF THE INVENTION
There is currently an ongoing engineering effort, by
suppliers of railway braking equipment, to develop an electro-
pneumatic type brake system for railroad freight trains. It is
generally acknowledged in the railroad industry that the
development of such an electro-pneumatic brake control will
substantially enhance the operation of a train by achieving a
faster brake response, more equalized car retardation and a
generally more uniform braking effort throughout a long train
of cars.
These enhanced results are based on the assumption that all
of the cars, or at least a majority of the cars, making up a
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CA 02302903 2000-03-24
train will be appropriately equipped for utilizing such improved
electro-pneumatic braking system, in which case direct control
of the brake cylinder air pressure is envisioned. With the
possible exception of certain unit trains, however, it currently
cannot be reasonably expected that any such majority of cars
will be immediately implemented with the required electro-
pneumatic brake equipment.
Accordingly, for the present, indirect brake cylinder air
pressure control is contemplated, in which the train brake pipe
air pressure is controlled not only at the locomotive, but also
at one or several remote cars located throughout the train to
accelerate the reduction of brake pipe air pressure in order to
achieve a faster and more uniform brake response.
When the brake pipe pressure is reduced at any given point
along the brake pipe, however, a transient low pressure is
created in the vicinity of that point. Consequently, if the
exhaust creating the transient low pressure is closed too
quickly, i.e., before the entire length of the brake pipe
pressure is stabilized, air will flow towards the low pressure
point thereby causing a localized increase in pressure at that
point which can cause control valves in that vicinity to
inadvertently release.
On the other hand, if the exhaust is closed too slowly, the
pressure will be reduced to a level below the desired target
pressure. Therefore, anytime the air pressure is reduced at any
one or more remote locations along the brake pipe, it is vitally
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CA 02302903 2000-03-24
necessary that a flow equilibrium be established and maintained
thereat following reduction of the brake pipe pressure to a
commanded target value. This then requires that an exhaust flow
be carefully controlled to continuously match the changing flow
of air from the rest of the brake pipe to the exhaust location.
At the present time, most railway freight trains are
required to utilize an end-of-train unit disposed on the last
car in the train. Such an end-of-train unit, among other highly
critical functions, may be equipped to independently and
remotely initiate a reduction of the brake pipe air pressure
from the rear of the train in response to the train operator's
activation of a special triggering device located in the cab of
the locomotive. This may be accomplished, for example, by the
operator transmitting a brake application command signal from
the locomotive to the end-of-train unit via radio communication .
One approach to effecting such an air pressure reduction
in the brake pipe has been to utilize a control valve which
includes a variable type orifice through which the brake pipe
air pressure is discharged. Normally, in these self-regulating
type valves, either a spring setting against a pressurized area
or a reference control pressure is utilized to effectively
control the variable orifice.
In contrast thereto, nonself-regulating type valves require
the use of a microprocessor to constantly monitor the brake pipe
pressure to obtain pressure feedback information in order to
establish an appropriate valve orifice size in response to a
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changing difference between the commanded target pressure and
the feedback pressure.
SUMMARY OF THE INVENTION
This invention, according to a first aspect thereof, is
predicated on the development of a new, unique and simplified
valve body incorporating a variable orifice type valve through
which the brake pipe pressure is discharged for service brake
applications, whereby the variable orifice, and accordingly the
discharge rate, can be regulated by electronic control of supply
and exhaust solenoids based on brake pipe pressure feedback
information received by a microprocessor. The invention further
includes a separate and distinct dump valve arrangement which
opens concurrently with the variable orifice type valve for
emergency brake applications. In essence, the improved valve
of this invention is intended to be incorporated into a more or
less conventional radio control system for exhausting the brake
pipe air pressure at the last car of the train in accordance
with service, as well as emergency, brake application signals
transmitted from the locomotive. In its broadest sense, the
valve apparatus comprises a regulating valve device having two
distinct valves controlled by a single pneumatic control system
for reducing the brake pipe air pressure in the last car, or any
selected car. The first valve is an adjustable orifice type
valve adapted to controllably vent air pressure from the brake
pipe when the valve is at least in a partially open position,
with the rate of discharge being in proportion to the extent the
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CA 02302903 2000-09-14
valve is open for the purpose of making a service brake
application to a conunanded target pressure and thereafter
regulating the exhaust flow to maintain the target pressure as the
brake pipe pressure gradient settles out. The second valve is a
dump valve, i.e., a va7_ve capable of opening to provide a large
orifice to quickly vent air pressure from the brake pipe at a more
rapid rate consistent with the requirements for making an
emergency brake a~~plication.
In a more specific aspect of the present invention, the
regulating valve device comprises a valve body having at least one
supply passage to which the brake pipe is connected, an exhaust
passage open to atmosphere and a bore with which the supply
passage and the exhaust. passage are in fluid communication. A
dual function valve stem is reciprocally disposed within the bore
:L5 in which two separate valves are incorporated. A first valve of
such dual function valve establishes an exhaust opening under
control of a pneumatic drive means to effect a controlled brake
pipe air pressure reduction for making service brake applications.
A second valve of such dual function valve is a dump valve which
~'.0 can be opened by the same pneumatic drive means to provide a
relatively large orifice to exhaust brake pipe air pressure at a
more rapid rate for the purpose of making an emergency type brake
application.
In an even more specific aspect of this invention, the
~:5 regulating valve device comprises a valve means having two
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CA 02302903 2000-09-14
supply passages t:o whic:h the brake pipe is connected. Both of
these two supply ~~assages are in fluid communication with the bore
on either spde oj= the exhaust passage. A reciprocal valve stem
includes two valves. A first adjustable orifice valve lies
between the first one of the supply passages and the exhaust
passage. A second dump valve lies between the second one of the
supply passages and the exhaust passage. A pneumatic drive means
is responsiv~s to <~ microprocessor controlled actuating pressure in
order to controllably open the first valve for controlled brake
pipe air pressure reductions for making a service brake
application. The same pneumatic drive means will open the second
valve in re~~ponse to an emergency actuating pressure for a more
rapid brake pipe ,air pressure reduction for purposes of making an
emergency brake application.
L5 According to another aspect, this invention provides a
microprocessor controlled regulating valve device for use in an
end-of-train unit disposed on a railway car at a location in a
train remote from a 1_ocomotive. Such microprocessor controlled
regulating valve c.evice includes a microprocessor unit disposed in
the end-of-train unit and is equipped to receive a brake command
signal transmitted from such locomotive. A first pressure
transducer is connected t:o a brake pipe disposed on such railway
car for determining bra~:e pipe air pressure and is connected for
transmitting an electrical signal to such microprocessor unit
~:5 representative of such brake pipe air pressure. There is a
regulating valve disposed in such end-of
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CA 02302903 2000-03-24
train unit that is connected to receive air pressure from such
brake pipe and to exhaust air pressure therefrom at a first
service rate and at a second emergency rate. Additionally, an
electro-pneumatic control means is connected to receive air
pressure from such brake pipe and electrical signals from the
microprocessor unit for communicating control air pressure to
such regulating valve in response to electrical signals received
from such microprocessor unit.
OBJECTS OF THE INVENTION
It is, therefore, one of the primary objects of the present
invention to incorporate in the end-of-train unit an
electrically controlled pneumatic regulating valve device for
venting the train brake pipe air pressure at a location remote
from the locomotive in accordance with service, as well as
emergency, brake application signals transmitted from the
locomotive.
Another object of the present invention is to provide a
valve device for exhausting the brake pipe air pressure at a
location remote from the locomotive at a variable service rate
as determined by the continually changing difference between
brake pipe pressure and a commanded target pressure until the
brake pipe pressure gradient stabilizes.
A further object of the present invention is to provide a
valve device for reducing the brake pipe air pressure at a
location remote from the locomotive which is capable of venting
brake pipe air pressure for service brake applications at a
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first rate and for venting brake pipe air pressure at a second
faster rate for emergency brake applications.
Still another object of the present invention is to provide
a valve device for reducing the brake pipe air pressure at a
location remote from the locomotive, as in the foregoing, that
does not require the use of a relatively large air reservoir and
can be suitably sized for installation in presently used end-of-
train units.
An even further object of the present invention is to
provide a valve device for reducing the brake pipe air pressure
at a location remote from the locomotive, as in the foregoing,
that has increased reliability and enhanced ruggedness.
In addition to the specific objects and advantages of the
present invention described in some detail above, various other
objects and advantages of the pneumatically driven train brake
pipe pressure exhaust valve will become more readily apparent
to those persons who are skilled in the relevant railway braking
art from the following much more detailed description of the
invention, particularly, when such detailed description is taken
in conjunction with the attached drawing Figures and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic illustration of a railroad train
having a plurality of freight cars headed by a locomotive which
is in radio communication with an end-of-train unit disposed on
the last car of the train;
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Figure 2 is a block diagram of a microprocessor based
indirect brake cylinder air pressure control system adapted for
end-of-train service as can be utilized in conjunction with the
presently preferred embodiment of the pneumatic controlled valve
device of the invention; and
Figure 3 is a diagrammatic, cross-sectional view showing
a presently preferred embodiment of the pneumatic controlled
valve device of this invention for carrying out service and
emergency reduction of brake pipe air pressure in accordance
with the indirect brake cylinder pressure control system
illustrated in Figure 2.
BRIEF DESCRIPTION OF A PRESENTLY PREFERRED
AND VARIOUS ALTERNATIVE EMBODIMENTS
OF THE PRESENT INVENTION
Prior to proceeding to the more detailed description of the
present invention, it should be noted that, for the sake of
clarity and a fuller understanding of such invention, identical
components which have identical functions have been identified
with identical reference numerals and/or symbols throughout the
several views illustrated in the attached drawings.
As best shown in Figure 1, railroad cars CN which make up
a train are physically coupled to a locomotive L by typical
prior art type car couplers (not shown) and are further coupled
pneumatically by a brake pipe BP that extends continuously from
the locomotive L to the last car CNL in the train. Associated
with the last car is an end-of-train unit EOT that is coupled
to the locomotive L via radio communication.
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CA 02302903 2000-03-24
The last car Cue, of the train is further provided with a
brake control valve device CV, as are all of the other cars CN.
These brake control valve devices CV are, preferably, an A.A.R.
standard AB type control valve, such as an ABD, ABDW or ABDX
control valve. Each of these standard AB type control valves
is presently being manufactured by Westinghouse Air Brake Co.
As is well known, these car control valve devices CV operate to
control the car brakes in response to variations of the train
brake pipe air pressure at the respective cars.
Reference is now made to Figure 2. Illustrated therein is
an end-of-train unit EST which includes a microprocessor unit
MPU. This microprocessor unit MPU, at relatively frequent
intervals, monitors the existing brake pipe pressure in brake
pipe BP. Such monitoring of the brake pipe pressure is achieved
by a first pressure transducer T1 which will transmit a signal
to such microprocessor unit MPU that is representative of the
brake pipe pressure in brake pipe BP.
The microprocessor unit MPU is programmed to compare the
existing brake pipe pressure as represented by the signal from
the pressure transducer T1 to a given target pressure. This
given target pressure is supplied to the microprocessor unit MPU
as an input signal 9 transmitted via radio transmission from the
locomotive for either a controlled brake pipe air pressure
reduction for making a service brake application or a quick and
substantial brake pipe air pressure reduction for making an
emergency brake application.
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CA 02302903 2000-03-24
In addition, a second pressure transducer T2 monitors the
air pressure in the stability reservoir SR and transmits a
signal to the microprocessor unit MPU that is representative of
this pressure. In response to these signals, the microprocessor
unit MPU in turn selectively operates an exhaust solenoid valve
EV and/or a supply solenoid valve SV, to which the brake pipe
BP is connected by a branch pipe 1 Q and accordingly operates
brake pipe air pressure regulating valve device RV.
Exhaust solenoid valve EV and supply solenoid valve SV are
normally closed, solenoid operated, spring returned valves, as
are common in such equipment. Pursuant to such operation, the
microprocessor unit MPU either opens supply solenoid valve SV
to admit pressurized air to a stability reservoir SR, or opens
exhaust solenoid valve EV to vent pressurized air from stability
reservoir SR. The controlled pressure within stability
reservoir SR is responsible for operation of pneumatic drive 15
on pressure regulating valve device RV, and accordingly the
essential operation of regulating valve device RV, as necessary
to either controllably open a service valve 20 or an emergency
valve 22, as described below.
Each car CN, including the last car CNL, has its control
valve CV connected to such brake pipe BP via branch pipe 12.
Control valve CV on each car is associated with an auxiliary
reservoir AR and an emergency reservoir ER that are charged via
such brake pipe BP and provide a source of compressed air for
operating the car's brake cylinder device BC in response to
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service and emergency rates of reduction in the brake pipe air
pressure.
Control valve device CV, connected to brake pipe BP via
branch pipe 12, operates in response to increasing brake pipe
air pressure to charge the auxiliary reservoir AR and the
emergency reservoir ER to the operating pressure of brake pipe
BP, while concurrently venting the car's brake cylinder device
BC. Such operation is well-known to those skilled in the art,
being known as "release and charging", and thus requires no
further explanation.
In accordance with the embodiment illustrated in Figure 3,
the valve device RV of this invention comprises a valve housing
30 with an elongated valve stem 32. Such elongated valve stem
32 is reciprocally disposed within an elongated bore 34 that is
centrally disposed within valve housing 30.
A primary supply passage 36 extends from an upper portion
of such elongated bore 34, namely receiving chamber 40, to which
the brake pipe BP is connected via primary supply pipe 38.
Accordingly, the receiving chamber 40 is normally charged with
compressed air at brake pipe pressure. Branch supply passage
42 extends from the primary supply passage 36 to similarly
maintain the emergency chamber 44 charged with compressed air
at brake pipe pressure.
In normal operation, i.e., with control volume 66 vented
consistent with the absence of either a service or an emergency
brake application, such service valve 20 and the emergency valve
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CA 02302903 2000-03-24
22 are each in a closed position, thereby allowing the pressure
within chambers 40 and 44 to be maintained in accordance with
the operating pressure in the brake pipe BP.
With further regard to elongated valve stem 32, a small
cylindrical upper end 50 thereof extends upwardly from the
service valve 20 within the receiving chamber 40. Chamber 40
forms a part of the elongated bore 34 and serves as the terminus
of such primary supply passage 36. Service valve 20 is disposed
immediately below receiving chamber 40 and is adapted to vent
brake pipe air pressure from such receiving chamber 40 for the
purpose of making a service brake application.
As can be seen, the service valve 20 comprises a male
conical valve head portion 70 circumferentially disposed on such
elongated valve stem 32 and is adapted to seat within a female
conical valve seat 72 which forms a part of the bore 34. There
is an 0-ring type seal 74 provided on the conical valve head
portion 70 to prevent escape of brake pressure from the
receiving chamber 40 when the service valve 20 is intended to
be closed. An exit chamber 76 is provided below service valve
20 into which conical valve head 70 recedes when such service
valve 20 is opened and which is in fluid communication with
exhaust passage 78.
Accordingly, when service valve 20 is even partially
opened, air pressure within such receiving chamber 40 will pass
into the exit chamber 76 and further pass to the atmosphere via
such exhaust passage 78.
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With regard to service valve 20, it can be seen that a
cylindrical portion 46 of the valve stem 32 is disposed at the
apex of the male conical valve head 70, which is reciprocally
disposed within a cylindrical port 48. The clearance between such
cylindrical portion 46 and the cylindrical port 48 is restricted
so that the venting of brake pipe air pressure therethrough is
also restricted and s:Lowed. This permits a rather exacting
control of brake pipe air pressure venting through such service
valve 20, as is normally necessary for making a service brake
application.
A reciprocal piston element 80, forming a part of elongated
valve stem 32 is provided below the exhaust passage 78. Such
piston element 80 is adapted for reciprocal motion within cylinder
port 82 which forms a part of bore 34. Here again, there is an O-
ring seal 89, preferably, provided on such piston element 80 to
prevent escape o:E brake pipe air pressure from the emergency
exhaust chamber ~~4 which is disposed below cylinder port 82.
There is a compression spring 86 compressively disposed between
the under-side of such piston element 80 and the base of bore 34.
a?0 Spring 86 serves to bias the valve stem 32 upward.
The combination of the piston element 80, the cylindrical
port 82 and the emergency exhaust chamber 44 all serve to form a
second valve, namely the emergency valve 22. This valve is opened
when such piston element. 80 moves downwardly sufficient to clear
the lower edge oj= suc:h cylinder port 82 to thereby expose the
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CA 02302903 2000-09-14
exhaust chamber 9~~ to both the chamber 76 and the exhaust passage
78.
The pneumatic drive 15 is incorporated into the upper portion
of such valve housing 30 and comprises a diaphragm operated piston
member 60 that is operatively disposed for reciprocal motion
within a guide bore 62. The diaphragm 64 separates the control
chamber 66 on the upper side from the atmospheric chamber 52 on
the lower side. This control chamber 66 is connected to a control
passage 68 to admit coni~rol pressure from the stability reservoir
:LO SR via control supply pipe 56 while the atmospheric chamber 52 is
vented to atmosphere via outlet 54.
The base of piston member 60 is disposed to directly engage
the cylindrical push stem 50 at the upper end of valve stem 32.
Consequently, any downward motion of such piston member 60,
:_5 resulting from an increase in control pressure within control
chamber 66, will cause the valve stem 32 to be moved downward
within such bore 34. Compression spring 58 is disposed between
the head portion cm the piston member 60 and a horizontal portion
of housing ~~0 to bias such piston member 60 upwardly when the
20 pressures in such control chamber 66 and such atmospheric chamber
52 are equal, thereby assuring that valves 20 and 22 are closed.
CA 02302903 2000-09-14
As should be readily apparent, just a small minor downward
movement of such valve :>t:em 32 will normally be sufficient to open
the valve 20, but a significant major downward movement would be
required to open the valve 22.
Pursuant to normal operation, the brake pipe BP will be
charged to the train operating air pressure by movement of the
locomotive brake valve handle (not shown) to a release position in
a manner well-knocm in i:he railroad industry. The branch pipe 12
conducts compressed ai.r from such brake pipe BP to each control
LO device CV disposed on e;~ch car CN thereby charging each auxiliary
reservoir AR and each emergency reservoir ER and exhausting any
compressed air in each brake cylinder BC.
Concurrently with t:he charging of the brake pipe BP, a
corresponding radio signal is transmitted to the EOT unit at the
:LS last car CxL. M:LCroprocessor MPU operates in response to this
radio signal to close t=he supply solenoid valve SV and to open
solenoid exhaust valve EV in order to maintain atmospheric
pressure within such stability reservoir SR. With atmospheric
pressure within stability reservoir SR, such pressure will also be
20 maintained within such control chamber 66 which will equalize the
pressures in control chamber 66 and atmospheric chamber 52. This
renders springs 5f3 and 86 effective to urge piston member 60 to
its uppermost position in which both valves 20 and 22 are closed.
When it is desired to make a service brake application
c:5 following charging of t:he brake pipe BP, the locomotive brake
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CA 02302903 2000-03-24
valve (not shown) is set in a position to achieve a brake pipe
air pressure reduction to the degree of brake pipe pressure
reduction corresponding to the degree of brake application
desired. This reduction of brake pipe air pressure constitutes
a pneumatic signal that propagates through the train from front
to rear via such brake pipe BP.
Concurrently, a service brake command signal is transmitted
via radio from the locomotive to the end-of-train unit EOT
corresponding to the reduced locomotive brake pipe air pressure.
Microprocessor unit MPU operates in response to that service
brake command signal to selectively open the supply solenoid
valve SV to effect a controlled increase of control pressure
within the stability reservoir SR. This increased control
pressure within such stability reservoir SR, as determined by
the second pressure transducer T2, is matched within control
chamber 66, to the extent that such piston member 60 is
controllably forced downward and accordingly opens valve 20
against the combined force exerted by springs 58, 86. When the
control pressure within the stability reservoir SR is equal to
the pressure within control chamber 66, the supply solenoid
valve SV and the exhaust solenoid valve EV are closed. In other
words, the system is now operated in a lap condition.
For further control of routine service brake applications,
the microprocessor MPU will selectively open and close either
the supply solenoid valve SV or the exhaust solenoid valve EV
to regulate the control pressure within such stability reservoir
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CA 02302903 2000-03-24
SR in response to appropriate signals received by the EOT unit
to accordingly cause application and release of such service
brake as signaled.
When an emergency brake application is desired,
microprocessor MPU receives the appropriate radio signal from
the locomotive and, in this case, the microprocessor MPU will
quickly and fully open the supply solenoid valve SV causing such
supply reservoir SR to be charged with compressed air at full
brake pipe pressure, which in response thereto will comparably
charge the control chamber 66 which will cause the piston member
60 to be forced downward to the maximum extent possible thereby
fully opening valve 22.
Specifically, by moving the valve stem 32 downward to the
maximum extent, such piston element 80 is caused to move below
the cylindrical port 82 thereby permitting the pressurized air
in the emergency chamber 44 to be quickly vented via the chamber
76 and exit passage 78. At the same time, the valve 20 is also
opened to its maximum extent in order to vent the brake pipe air
pressure from such chamber 40. Obviously, the size of piston
element 80 and its displacement from cylindrical port 82 when
valve 20 is fully open must be such that the rate of brake pipe
pressure reduction via valve 20 will be sufficiently fast enough
to cause emergency brake application.
With both valves 20 and 22 fully opened, the brake pipe air
pressure in chambers 40 and 44 is quickly vented via exhaust
passage 78 and the air pressure within such brake pipe BP is
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CA 02302903 2000-03-24
quickly vented via supply passages 42, 36 and line 38, which
will accordingly cause application of the emergency brake via
control valve CV in a well-known manner.
As should be apparent from the above detailed description,
a number of modifications and other embodiments could be
incorporated without departing from the spirit of the invention .
Therefore, while the detailed description above represents the
preferred valve and valve control arrangement, it should be
apparent that a great number of changes could be incorporated
and varied embodiments could be devised without departing from
either the spirit of the invention or the scope of the appended
claims.
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