Electropneumatic master controller for an air brake system

An electropneumatic master controller for an electromagnetic straight air brake system for railway vehicles has a brake valve, brake solenoid valve, a release solenoid valve, and an electrical interface circuit. The electrical interface circuit includes a first and a second sensor and a first and a second comparator which are responsive to the pressure of the control line and straight air line to open and close the brake and release solenoid valves for applying and releasing the brake cylinder.

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. 
BACKGROUND OF THE INVENTION 
In previous air brake system, it was common practice to employ apparatus as 
illustrated and described in FIG. 1 of Japanese Patent (Tokuko) No. 
45-6082 and in FIG. 1 of Japanese Patent (Tokukai) No. 59-50850. A example 
of such 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 exhausted to 
atmospheric pressure. In addition, since the braking contact 104 is 
opened, the brake command line BS is disconnected from the power source 
line, and the 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 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 exhaust 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 energized 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 upward to unseat and open the air supply valve. 
Thus, the compressed air pressure in the air reservoir AR is fed into the 
brake cylinder 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 soleoid valve BMV is deenergized and its valve is 
reseated. Thus, the straight air line SAP is no longer pressurized 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 selected 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 right and the release contact 103 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 there 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 effects 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 controllers of the prior art are almost entirely 
composed of 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 troubleless 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. 
Another 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 controller 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 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 the 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 that 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 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 receives 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 of the signals between 
straight air line of the delay circuit signal and the control line signal 
produced by the first senseor 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 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 atmospheric pressure so that the electrical output signal 
of the first sensor, namely, the control line signal at a zero (0) level. 
The difference from which the straight air signal is substracted 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 atmospheric 
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 
pressurized. 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 CO1 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 CO2 opens the solenoid brake valve BMV. Thus, the 
straight air line SAP is pressurized and causes the brake cylinder BC to 
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 CO2 closes 
the soleniod 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 that the first set point. Thus, the 
first comparator opens the solenoid release valve RMV, and the straight 
air line SAP will 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 2, namely, the straight air line 
signal E2 will decrease. The differential signal from the above will 
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 converts it to an 
electrical signal. 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 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 CO1, and a second comparator circuit CO2. The first sensor S1 
takes the form of a brake network which includes at least one pressure 
sensing strain gauge element, not specifically characterized 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 E1. 
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 NO which changes the sign of the incoming 
signal and produces an output signal E2. The first comparator CO1 compares 
the sum of the straight air line output signal E2 and a first set point A1 
with the control line signal E1. In other words, the comparator CO1 
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 A1. It will be appreciated that the first set point A1 is controlled 
by the variable resistor VR1. This first set point A1 is functionally 
equivalent to the added force of the return spring 101 which is 
illustrated in FIG. 3. 
A series circuit including the diode D1 and the variable resistor VR3 
stabilizes the operation by producing a small amount of hysteresis B1, 
where B1&lt;&lt;A1. Under certain conditions, the induced hysteresis may be 
unnecessary. The output of the comparator circuit CO1 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 CO1 collector electrode is connected to the winding of relay 
R1. 
The second comparator CO2 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 (E1-E2) with the second set 
point, A2 which is set to be larger than the first set point A1 by 
adjusting the variable resistor VR2. This difference between the two set 
points (A2-A1) 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 A1. In addition, the series circuit of the diode D2, and the 
variable resistor VR4 produces a small hysteresis B2 where B2&gt;&gt;A2 to 
stabilize the operation. In some cases, B2 can be equal 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 CO2. 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 TR1 which is switched ON and OFF by the closing and the opening 
of the normally-opened contact R1a of the first output relay R1. 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 power 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 amplifiers, and relays are 
powered by a +15 v voltage source while the brake and release valve are 
powered by a DC 100v 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 E1 is at a 0 level. 
The differential signal (E1-E2) where the straight air line signal E2 is 
subtracted from this control line signal E1, is less than the first set 
point A1. Therefore, the first comparator CO1 turns the output transistor 
TR3 to an ON condition, and the first output relay R1 is energized. This 
causes the normally-open contact R1a to be closed. Thus, the first power 
transistor TR1 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 
second comparator CO2 is deenergized so 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 0 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 E1 increases. 
Thus, the differential 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 R1a becomes open and the 
first power transistor TR1 is turned OFF. Accordingly, the release 
solenoid valve RMV is deenergized and its pneumatic valve is closed so 
that straight air line SAP is cut off from the atmosphere. At this time, 
the brake solenoid valve BMV is still closed. When the above-mentioned 
differential signal (E1-E2) increases further and reaches the second point 
A2, the second comparator CO2 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 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 E1, 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 CO2 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 SAP is 
interrupted. At this time, the release solenoid valve RMV is also still 
closed and it assures 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 E1 decreases and 
the differential signal (E1-E2) from the straight air line signal E2 
decreases. When it becomes less than the difference between (A1-B1), the 
first comparator CO1 switches the output transistor TR# to an ON 
condition. Thus, the first output relay R1 is energized and its electrical 
contact R1a is closed so that the first power transistor TR1 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 E1 increases. Now when the differential signal (E1-E2) reaches 
the first set point A1, the first comparator CO1 turns the output 
transistor TR3 OFF. Thus, the first output relay R1 is deenergized and its 
normally-open contact R1a becomes opened so that the first power 
transistor TR1 is turned OFF. The turning OFF of transistor TR1 causes the 
release solenoid valve RMV 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. 
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 transistion 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 valve 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 of 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 
CO1--first comparator 
CO2--second comparator 
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.