Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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(Case ~o. 8440)
ELECTROPNEUMATIC MASTER CONTROLLER FOR AN
AIR BRAKE SYSTEM
FIELD OF THE INVENTION
This invention relates to an electropneumatic master
controller for an electromagnetic straight air brake system
for railway vehicles in which a failure will not result in
motor burn-out or in unnecessary compressor operation.
DESCRIPTION OF T~IE DRAWINGS
The above objects and other attendant features and
advantages will be more readily appreciated as the present
invention becomes better understood by reference to the
following detailed description when considered in
conjunction with the accompanying drawings, wherein:
Fig. 1 is a schematic circuit diagram of an embodiment
of the e].ectronic type of straight air master controller
for an electropneumatic air brake system for the vehicles
of a railway train;
Fig. 2 is a ~raphical illus~ration of the operation of
the embodiment shown in Fig. 1; and
Fig. 3 is a mechanical version of an electropneumatic
straight air controller of the prior art.
BACKGROUND OF THE INVENTION
In previous air brake systems, it was common practice
to employ apparatus as illustrated and described in Fig. 1
25 of Japanese Patent (Tokuko) No. 45-6082 and in Fig. 1 of
Japanese Patent (Tokukai) No. 59-50850. An example of such
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prior art systems is illustrated in Fig. 3 of the present
application in which the following is a detailed
description of the components and operation thereof. It
will be seen that Fig. 3 shows a system in which the brake
valve BV is in the release position and the brake cylinder
BC is exhausted. In the release position, the control line
CP is exhausted by the brake valve BV so that the pressure
is at atmosphere. Under such a condition, the
electropneumatic master controller 100 moves the rod 102 to
the left due to the added force of the return spring 101.
Thus, the release contact 103 switches to a closed position
while at the same time the contact 104 switches to an open
position. When the release contact 103 is closed, the
release command line RS is connected to the power source
line and the release solenoid valve RMV is energized and is
opened so that the straight air line SAP is e~hausted to
atmospheric pressure. In addition, since the braking
contact 10~ is opene~, the brake command line BS is
disconnected Prom the power source line, and th~ brake
solenoid valve BMV is deenergized and is closed. Thus, the
straight air line SAP is not connected to the main air
reservoir line MRP. Therefore, the relay valve RV closes
the air supply, and at the same time the intermediate
exhaust valve rod moves downward so that the brake cylinder
BC is exhausted to atmosphere. In viewing Fig. 3, it will
be seen that the check valve CV1 is arranged in such a
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manner that the blocking direction is from the straight air
line SAP. It will be noted that the throttle valve NV is
connected in parallel to the check valve CV1. The air
reservoir AR which supplies the air to the brake cylinder
BC through the relay valve RV and the check valve CV2 in
which the free flow direction is toward the air reservoir
AR. The output or the ezhaust outlet EX relay valve RV is
connected to atmosphere.
Let us assume that the brake system is in the released
state, as is illustrated in Fig. 3, and that it is desired
to move the handle of the brake valve BV into an
appropriate braking position. Thus, the control line CP
will be pressurized a given amount which is dictated by the
selected brake position so that the rod 102 is urged toward
the right against the force of the return spring 101, as
viewed in Fig. 3. This causes the release contact 103 to
open so that the releasing solenoid valve RMV is
deenergized and the exhaust port EX is closed.
Accordingly, the straight air line SAP is disconnected from
the atmosphere. Now as the rod 102 moves further to the
right, it causes the compression of the buffer spring 105,
and in turn causes the closing of the braking contact 104.
Therefore, the brake solenoid valve BMV is energiæed so
that it becomes open and the compressed air pressure in the
main air reservoir line MRP is conveyed to the straight air
line SAP. The exhaust valve rod of relay valve RV moves
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upward to unseat and open the air supply valve. Thus, the
compressed air pressure in the air reservoir AR is f~d into
the brake cvlinder BC so that a brake force is applied to
the wheel of the railway car. In addition, when the rod
102 of controller 110 is pushed back slightly to the left
due to the pressure in the straight air line SAP and the
pushing forces of the two sides, an equilibrium is reached
on the right and left sides of the rod 102. Thus, the
braking contact 104 will be opened so that the brake
solenoid valve BMV is deenergized and its valve is
reseated. Thus, the straight air line SAP is no longer
pressuri.zed by the main pressure reservoir line MRP. At
this time, the release contact 103 also remains opened.
Therefore, the straight air pipe or line SAP is neither
pressurized nor exhausted so that the system is in a lapped
condition.
In this lapped condition, if the brake valve BV is
moved to a lesser or lower notch, or position of braking,
the control line CP will be exhausted to a certain degree
depending on the particular selacted brake position. Thus,
the rod 102 will move to the left and the release contact
103 will close. This causes the release solenoid valve RMV
to be energized which results in the unseating and opening
of the air portion of the valve. Since the straight air
line SAP is exhausted, the rod 102 will again move to the
rîght and the release contact ~03 will open. Thus, the
opening of release contact 103 causes the deenergization
and closing of release solenoid valve RMV. Thus, the
exhausting of the straight air line SAP is stopped and the
system assumes the same lapped condition as described
above. At the same time, as a result of the movement of
the relay valve RV, the brake cylinder BC is also exhausted
to a certain degree, depending on the above~mentioned brake
position. After this, when the brake valve BV is moved
into the release position, each of the structural parts are
again returned to the release position, as shown in Fig. 3.
It will be appreciated that ther~ are various types of
electropneumatic master controllers in operations of the
prior art besides the system shown and disclosed in the
present application. However, they are all basically the
same
The electropneumatic master controllers are generally
designed so that the pressure to the straight air line SAP
is introduced via the throttle valve NV to protect it from
transient efects during the pressurization. Thus, any
water vapor contained in the compressed air condenses due
to adiabatic expansion at the throttle valve NV during its
introduction. Therefore, the inside of the diaphragm plate
chamber can sometimes become frozen in winter, thereby
causing defective operation and/or complete failure.
Although Fig. 3 is drawn simply for purposes of
explanation, a great many electropneumatic master
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controllers of the prior art are almost entirely composed
o~ mechanical components which results in a highly
complicated mechanical design so that it is necessary to
make great many checks and adjustments in order to achieve
troublPless operation.
OBJECTS OF THE INVENTION
Therefore, it is an object of this invention to provide
an improved electropneumatic master controller which is
mainly composed of electrical components.
A further object of this invention is to provide a new
and improved electropneumatic master controller which is
not susceptible to freeze-up during cold weather.
~ nother object of this invention is to provide a unique
electropneumatic master controller employing electronic
circuitry for controlling brake solenoid and release
solenoid valves in a straight air brake system for railway
vehicles.
Yet a further object of this invention is to provide an
electropneumatic master controllar comprising, a first
sensor for converting the air pressure in a control line
which is pressurized during a braking operation of the
brake valve and which is discharged during a releasing
operation of the brake valve into an electric signal
equivalent to the value of the pressure, a second sensor
for converting the air pressure in the straight air line
which is pressurized by closing a solenoid valve for
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releasing and by opening the solenoid valve for braking and
which is discharged by closing the solenoid valve for
braking and by opening the solenoid valve for releasing,
and th~ brake cylinder is operated by this increased or
decreased pressure, into an electric signal equivalent to
its pressure, a delay circuit which provides an output
signal to the second sensor and which provides the output
signal to the straight air line. A first comparator
compares the variation straight air of a signal from the
control line signal based on the output signal of the first
sensor with a first set point which opens the releasing
solenoid valve when the variation is less than the first
set point and which closes the releasing solenoid valve
when the variation is larger than the first set point, and
the second comparator which compares the variation with a
second set point which is larger than the first set point
and which closes the braking solenoid valve when the
variation is less than the second set point and which opens
the braking solenoid valve when the variation is larger
than the second set point.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is
provided an electropneumatic master controller having
electrical circuitry including a first sensor which may
take the form of a pressure-sensitive strain gauge. The
first strain gauge senses the air pressure in the control
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line which is pressurized by the brake application
operation of the brake valve and which is exhausted by the
brake release operation of the brake valve and converts the
pressure into a proportional electric signal. A second
sensor which also may take the form of a pressure-sensitive
strain gauge senses the air pressure in the straight air
line. The straight air line is pressurized by closing the
solenoid release valve and by opening the solenoid brake
valve. The straight air line is exhausted by closing the
solenoid brake valve and by opening the solenoid release
valve. The brake cylinder is operated by increasing or
decreasing the air in the control line pressure, and the
pressure is converted into a proportional electric signal.
A delay circuit rece.ives an input signal from the second
sensor and provides an output signal proportional to the
straight air line signal. A first comparator compares the
difference o~ the signals between straight air line of the
delay circuit signal and the control line signal produced
by the first sensor with a first set point. The solenoid
release valve is opened when the difference is less than
the first set point, and the solenoid release valve is
closed when the difference is larger than the first set
point. A second comparator compares the difference with
the second set point which is larger than the first set
point. The solenoid brake valve is closed when the
difference is less than the second set point, and the
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solenoid brake valve is open when the difference is larger
than the second set point.
Now when the brake valve BV is in the release position,
the control line CP is exhausted to atmosheric pressure so
that the electrical output slgnal of the first sensor,
namely, the control line signal at a zero (0) level. The
difference from which the straight air signal is subtracted
from this control line signal is less than the first set
point, the first comparator opens the solenoid release
valve RMV and at the same time the second comparator closes
the solenoid brake valve BMV. When the straight air line
SAP is in the state in which the pressure is reduced to the
atmospharic level, the straight air signal is at a zero (0)
level. Now when the brake valve BV is operated into the
brake position, the control line CP is presæurized. Thus,
the output signal of the first sensor S1 will rise
according to the control line signal, and since the output
signal of the second sensor S2, namely, the straight air
line signal is at a zero (0) level at this time, the
difference increases and eventually reaches the first set
point. Thus, the first comparator C01 closes the solenoid
release valve RMV so that the straight air line SAP is
disconnected from the atmosphere. When the difference
reaches the second set point, the second comparator C02
opens the solenoid brake valve BMV. Thus, the straight air
line SAP is pressurized and causes the brake cylinder BC to
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initiate a braking condition. When the straight air line
SAP is pressurized, the output of the second sensor,
namely, the straight air line signal will increase from the
zero (0) signal level. Thus, the differential signal from
the control line signal which is dependent upon the
selected brake position decreases. Now when the
differential signal becomes less than the second set point,
the second comparator C02 closes the solenoid brake valve
BMV so that further pressurization of the straight air line
SAP is prevented. At this time, the solenoid release valve
RMV is still closed so that the braking system assumes an
overlapped condition for maintaining the selected braking.
In this overlapped condition, if the brake valve BV is
moved to a lower or reduced brake position, the control
line or pipe CP will be exhausted to a pressure level
corresponding to the newly selected brake position. Thus,
the output signal of the first sensor, namely, the control
line signal will also decrease. The differential signal
eventually correspondingly decreases and eventually becomes
less than the first set point. Thus, the first comparator
opens the solenoid release valve RMV, and the straight air
line SAP wi11 begin to exhaust. At this time, the solenoid
brake valve BMV is still closed. Due to the exhausting of
the straight air line SAP, the output signal of the second
sensor S2, namely, the straight air line signal E2 will
decrease. The differential signal from the above will
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increase. Now when the differential signal becomes larger
than the first set point, the first comparator closes the
solenoid release valve RMV so that the exhausting of the
straight air line SAP ceases. Since the brake solenoid
valve BMV is closed at this time, the system again assumes
an overlapped condition. In the overlapped condition, the
given amount of braking continues until the brake valve BV
is moved to a lower position or to the full release
position. In the present invention, the function of the
delayed circuit is substantially equivalent to the throttle
valve NV as illustrated in Fig. 3. Accordingly,
transitional effects occurring during the pressure change
in the straight air line SAP are readily handled and
quickly eliminated electrically. Thus, the second sensor
S2 which receives the pressure from the straight line SAP
conv~r~s it to an electrical si~nal. Thus, the throttle
valve NV is eliminated in the area which introduces the
pressure from the straight air line SAP. Therefore, there
is no adiabatic expansion of the compressed air in the
introduction area, so that the formation of drainage of the
water vapor in the compressed air is prevented.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and in particular to
Fig. 1, there is shown a preferred embodiment of an
electronic version of an electropneumatic straight air
controller for use in an air brake system for railway
vehicles. In viewing Fig. 1, it will be seen that the
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electropneumatic master controller primarily includes a
first strain gauge sensor S1, a second strain gauge
sensor S2, a time delay circuit DL, a first comparator
circuit C01, and a second comparator circuit C02. The
first sensor S1 takes the form of a brake network which
includes at least one pressure sensing strain gauge
element, not specifically characteriz~d in Fig. 1, for
sensing the pressure in the pressure control line of the
brake valve. The first sensor converts the air pressure
in a corresponding output voltage or first electrical
signal. This output voltage signal is amplified by
amplifying circuit AM1 to produce a control line signal
El. The second sensor S2 also takes the form of a bridge
network which includes at least one pressure sensing
strain gauge,element, not specifically characterized in
Fig. 1, for sensing the pressure in the straight air line
SAP. The second sensor converts the air pressure into a
corresponding output voltage or second electrical signal.
This output signal is amplified by a second differential
amplifier AM2 to the control level of the later step.
This amplified output is fed to the time delay circuit DL
which has a function similar to the throttle valve NV and
the check valve CV1 of Fig. 3. After a certain time
delay, the delay circuit DL passes an output signal which
is proportional to the pressure in the straight air line
to an inverter N0 which changes the sign of the incoming
signal and produces an output signal E2. The first
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comparator C01 compares the sum of the straight air line
output signal E2 and a first set point Al with the
control line signal E1. In other words, the comparator
C01 subtracts the straight air line signal E2 from the
control line signal E1 and then compares this
differential signal (E1 - E2) with the first set point
Al. It will be appreciated that the first set point A1
is controlled by the variable resistor VRl. This first
set point Al is ~unctionally equivalent to the added
force of the return spring 101 which is illustrated in
Fig. 3.
A series circuit including the diode Dl and the
variable resistor VR3 stabilizes the operation by
producing a small amount of hysteresis Bl, where B1 <<
A1. Under certain conditions, the induced hysteresis may
be unnecessary. The output of the comparator circuit C01
is connected to the input of output transistor TR3. The
NPN transistor TR3 controls the conductive condition of a
first output relay R1. That is, the base electrode of
transistor TR3 is connected to the output while the first
comparator C01 collector electrode is connected to the
winding of relay Rl.
The second comparator C02 compares the sum of the
straight air line signal E2 and the second set point A2
with the control line signal E1. In other words, it
compares the differential signal (El - E2) with the
second set point, ~2 which is set to be larger than the
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first set point Al by adjusting the variable resistor
VR2. This difference between the two set points (A2 -
Al) is substantially equivalent to the added biasing
force of the buffer spring 105 as illustrated in Fig. 3.
The interchangeability of the two set points A2 and
A1 was considered to be an important factor over the
controller 100 of the prior art. Therefore, if it is
desired, the second set point A2 can be the same as the
first set point Al. .In addition, the series circuit of
the diode D2, and the variable resistor VR4 produces a
small hysteresis B2 where B2 <~ A2 to stabilize the
operation. In some cases, B2 can be e~ual to B1, and in
some instances, the hysteresis can be eliminated
altogether. It will be noted that there is a second
output relay R2 connected to the output of the second
comparator C02. It will be understood that the release
solenoid valve RMV and/or the brake solenoid valve BMV
may be opened and closed in response to the release
command and the brake command signal produced by the
electropneumatic master controller of Fig. 1.
The release solenoid valve, RMV is connected in
series with the first power transistor TRl which is
switched ON and OFF by the closing and the opening of the
normally-opened contact Rla of the first output relay Rl.
This NPN transistor TR1 is functionally equivalent to the
release contact 103 illustrated in Fig. 3. The brake
solenoid valve BMV is connected in series to the second
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po~er transistor TR2 which is switched ON and OFF by the
closing and the opening of the normally-opened contact
R2a of the second output relay R2. This NPN transistor
TR2 is functionally equivalent to the brake contact 104
illustrated in Fig. 3. As shown, the sensors,
amplifiers, inverter, comparators, output amplifier, and
relays are powered by a +15v voltage source while the
brake and release valves are powered by a DC lOOv voltage
source.
The functional operation of the preferred embodiment
of the subject invention which is illustrated in Fig. 1
will be explained in conjunction with reference to
Fig. 2.
When the brake valve BV is in the release position,
the control line CP is at atmospheric pressure, and the
control line signal El is at a O level. The differential
signal tE1 - E2) where the straight air line siynal E2 is
subtracted from this control line signal El, is less than
the first set point Al. Therefore, the first comparator
COl turns the output transistor TR3 to an ON condition,
and the first output relay Rl is energized. This causes
the normally~open contact Rla to be closed. Thus, the
first power transistor TRl turns ON and causes the
release solenoid valve RMV to be energized. Thus, the
valve RMV is opened to the exhaust port EX and the
straight air line SAP is connected to the atmosphere. At
this time, the sQcond comparator C02 is deenergized so
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that the second output relay R2 and the second power
transistor TR2 are turned OFF. Thus, the normally-open
contact R2a remains open, and the brake solenoid valve
BMV remains deenergized. Thus, the valve BMV is
pneumatically closed, and the straight air line SAP is
cut off from the original air reservoir line MRP.
Therefore, the straight air line signal E2 is at a O
pressure level. Now when the brake valve BV is moved to
the brake position, the control line CP will become
pressurized so that the control line signal El increases.
Thus, the differantial signal (E1 - E2) from the straight
line signal E2 increases. When it reaches the first set
point A1, the first comparator CO1 turns the output
transistor TR3 OFF so that the first output relay R1 is
deenergized. Thus, its normally-open contact Rla becomes
open and the first power transistor TR1 is turned OFF.
Accordingly, the releas~ solenoid valve BMV is
deenergized and itæ pneumatic va]ve is closed so that
straight air line SAP is cut off from the atmosphere. At
this time, the ~rake solenoid valve BMV is still closed.
When the above-mentioned differential signal (El-E2)
increases further and reaches the second point A2, the
second comparator C02 energizes the second output relay
R2. Thus, the relay R2 closes its normally-open contact
R2a so that the second power transistor TR2 turns ON.
Thus, the brake solenoid valve BMV is energized and the
pneumatic valve is opened. Accordingly, air pressure is
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supplied from the main air reservoir line MRP into the
straight air line SAP so that a brake application is
initiated. In response to this pressurization of the
straight air line SAP, the straight air control signal E2
increases and the differential signal (E1 - E2) from the
control line signal El, which corresponds to the brake
position, decreases. Now when the differential signal
(E1 - E2) becomes less than the difference between (A2 -
B2), the second comparator C02 deenergizes the second
output relay R2. In response to the opening of its
normally-opened contact R2a, the second power transistor
TR2 is turned OFF and the brake solenoid valve BMV is
deenergized. Thus, the biasing spring returns the valve
BMV to its closed position and the pressurization of the
straight air line S~P is interrupted. At this time, the
release solenoid valve RMV is also still closed and it
assumes the overlapped state which is a brake maintaining
state. In this overlapped state, when the brake valve BV
is released or operated to the lower braking position,
the control line CP is exhausted until the pressure
reaches a level which is equivalent to the newly operated
brake position so that the control line signal El
decreases and the differential signal (E1 - E2) from the
straight air line signal E2 decreases. When it becomes
less than the difference between (A1 - Bl), the first
comparator CO1 switches the output transistor TR3 to an
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ON condition. Thus, the first output relay Rl is
energized and its electrical contact Rla is closed so
that the first power transistor TRl is turned ON and the
release solenoid valve RMV is energized and opens exhaust
port to atmosphere. Thus, the straight air line SAP is
exhausted to atmosphere, and at this time the brake
solenoid valve BMV remains closed.
In response to this exhaustion of the straight air
line SAP, the straight air line control signal E2
decreases while, at the same time, the control line
signal El increases. Now when the differential signal
(El - E2) reache.s the first set point Al, the first
comparator COl turns the output transistor TR3 OFF.
Thus, the first Outpllt relay Rl is deenergized and its
normally-open contact Rla becomes opened so that the
first power transistor TRl is turned OFF. The turning
OFF of transistor TR1 causes the release solenoid valve
R~V to be deenergized. Thus, the exhaust port is closed,
and the exhaustion of the straight air line SAP is
interrupted. At this time, the brake solenoid valve BMV
remains closed so that an overlapped condition results.
In this overlapped condition, if the brake valve BV is
moved to the release position, it will return to the
release position. In addition, each movement of each
structural part in the embodiment described above, in
other words, ON, OFF, open and/or close, can be reversed
as desired.
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The operation of the invention of the embodiment
described above is equal and/or superior to that of the
mechanical type electropneumatic master controller of the
prior art. Diagnostic testing and adjustments are simple
to perform, since the equipment is mainly electrical in
nature, and the function of the delay circuit is
equivalent to the throttle valve of the prior art. Thus,
the transition effects which occur during the change in
pressure of the straight air line can be easily processed
and overcome by the electrical circuit. Thus, the
throttle va].ve is not required in the second sensor which
measures the air pressure of the straight air line.
Therefore, the adiabatic expansion of the compressed air
does not occur in the introductory portion of the
pressurization of the straight air line. Therefore, the
formation o~ drainage from the water vapor in the
compressed air is prevented and operational failure due
to freezing in winter is avoided.
The following is a nomenclature list of components
or elements shown and disclosed in the drawings and
specification of the subject invention:
S1 - first sensor
S2 - second sensor
E1 - control line signal
E2 - direct connecting line signal
C01 - first comparator
C02 - second comparator
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A1 - first set point
A2 - second set point
DL - delay circuit
BV - brake valve
CP - control line
SAP ~ straight air line
RMV - solenoid release valve
BMV - solenoid brake valve
Thus, the present invention has been described in
such full, clear, concise and exact terms as to enable
any person skilled in the art to which it pertains to
make and use the same, and having set forth the best mode
contemplated of carrying out this invention. We state
that the subject matter, which we regard as being our
invention, is particularly pointed out and distinctly
asserted in what is claimed. It will be understood that
variations, modifications, equivalents and substitutions
for components of the above specifically-described
embodiment of the invention may be made by those skilled
in the art without departing from the spirit and scope of
the invention as set forth in the appended claims.
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