Electro-pneumatic brake system with valve actuating checking circuit

A fluid pressure brake system includes electrically actuated application and release valves. Upon brake application, brake control pipe pressure is vented electrically to accelerate application. Upon brake release, supply reservoir pressure is admitted electrically to the brake control pipe to accelerate release. In emergency situations, auxiliary equipment may be operated from the main reservoir pipe, the supply reservoir or the brake pipe, as desired. A novel solenoid-actuated valve is disclosed, which cooperates with unique indicator circuitry to provide a positive, continuous indication of a preceding electrically assisted application or release.

CROSS REFERENCE TO RELATED APPLICATION 
This application is related to an application filed concurrently herewith 
by W. W. Banker under the title Fluid Pressure Brake System With 
Electronically Assisted Application and Release, assigned Ser. No. 
716,057. 
BACKGROUND OF THE INVENTION 
Prior art rail vehicles sometimes have been provided with fluid pressure 
operated friction brake systems including some sort of an electrical 
assist feature. In a typical prior art system, a conduit known as a brake 
pipe extends from the operator's station aft through both the locomotive 
and any trailing cars. Also extending from the locomotive through the 
trailing cars is a main reservoir equalizing pipe which is pressurized to 
a predetermined level from a compressor located in the locomotive. Each 
individual rail car includes a control valve which responds, for example, 
to reductions in the brake pipe pressure by admitting pressurized fluid 
from a reservoir located in the rail car to the fluid pressure operated 
friction brake apparatus of the vehicle. 
Where there are a large number of rail cars and a correspondingly long 
brake pipe running from car to car, significant delays in response can be 
experienced as a pressure signal initiated at the locomotive moves aft 
along the train through the brake pipe. Various efforts have been made to 
improve the speed with which the pneumatic signal moves through the train, 
such as the provision of mechanically and electronically actuated venting 
valves in the cars which modify brake pipe pressure locally in some manner 
to accelerate movement of the brake application signal through the train. 
To release the brakes in such prior art systems, it is necessary to 
repressurize or recharge the brake pipe so that the control valve will 
vent the pressure applying the friction brakes. As in the case of brake 
application, repressurization of the long brake pipe requires considerable 
time which may lead to an unacceptable delay in obtaining a full release 
of the friction brakes. Some prior art systems which deal with the problem 
of accelerating brake application and release by the use of electrically 
operated valving systems are shown in Instruction Pamphlet #78 of the New 
York Air Brake Company, published in 1970 for the PS-68 Brake Equipment. 
Also, U.S. Pat. Nos. 3,709,564 and 3,716,274 of the Westinghouse Air Brake 
Company deal with a related problem. 
In the prior art brake systems of the type just mentioned and other brake 
systems not having electrical assist features, it is known to provide the 
individual rail cars with fluid pressure operated auxiliary equipment such 
as load levelling springs, pneumatically operated entrance and exit doors, 
fresh water supply systems and the like. Typically, such auxiliary devices 
are connected alternatively to the main reservoir pipe or the brake pipe 
of the vehicle. Thus, the auxiliaries will operate properly as long as 
pressure is maintained in the brake pipe and/or main reservoir pipe. 
However, in the event of a separation of one rail car from the train due 
to an accident such as a derailment, a situation may arise in which the 
auxiliary equipment, particularly the exit doors, is not able to function 
properly due to a shortage of pressurized fluid. 
While the prior art does teach the use of electrically assisted fluid 
pressure operated brake systems, it has generally been the practice to 
design such systems with a large factor of safety so that the fluid 
pressure actuated brakes will function adequately even if the electrical 
assist feature is rendered inoperative. In recent years, however, more and 
more sophisticated brake systems have been developed which rely to a 
greater extent upon the accelerated brake application and release achieved 
due to the presence of electrical assist features. In order to assure 
proper train operation with the electrical assist features, it is 
mandatory that the electrical assist valves function properly on every 
trailer car. To ensure that these solenoid actuated valves are operative, 
the Federal Railway Association has required that a terminal test be 
performed on each train before it goes into service. To determine whether 
the valves in each car of a train have responded to an electric 
application and release, it is necessary to apply the brakes and then have 
an inspector walk the length of the train to determine whether the brakes 
on each car have been applied properly; and then to release the brakes and 
have the inspector again walk the length of the train to determine whether 
the brakes on each car have released properly. 
In such a situation, several problems have found to be prevalent. For 
example, the solenoid actuated valves are only energized for a short 
period of time, even with a full service application. Thus, the inspector 
does not have sufficient time to walk the length of the train before the 
solenoids have become deenergized. Also, the electrical and pneumatic 
systems function in parallel, so that the presence of a brake cylinder 
pressure is not necessarily an indication that the electrical assist 
valves have functioned properly. It has been suggested that the electrical 
continuity checks could be made to establish that a circuit has been 
completed through the train; however, this does not provide a foolproof 
indication that the valve elements have actually moved in response to the 
electrical signal directed to the valve's solenoid. One prior art approach 
to monitoring such valve actuation is shown in U.S. Pat. No. 3,937,074. 
OBJECTS OF THE INVENTION 
An oject of the invention is to provide a fluid pressure operated brake 
system for a rail vehicle having an electrical assist feature which 
provides for an accelerated depressurization of the vehicle brake pipe 
during brake application. 
Another object of the invention is to provide such an electrically 
assisted, fluid pressure actuated brake system in which an accelerated 
repressurization of the brake pipe is achieved via an electrically 
operated valve which connects the brake pipe to the supply reservoir of 
each individual car. 
Yet another object of the invention is to provide a fluid pressure operated 
brake system in which the rail car auxiliary devices are pressurized via a 
governor portion and separate reservoir isolated from the main reservoir 
pipe by a check valve. 
Still another object of the invention is to provide such a brake system 
having a monitoring circuit for indicating continuously that a brake 
application or release has recently occurred by actuating an alarm such as 
a light at an exterior location on each car, in response to physical 
movement of the valve elements. 
The above objects of the invention are given only by way of example; thus, 
other desirable objects or advantages inherently achieved by the invention 
may occur to those skilled in the art. Nonetheless, the invention embodies 
certain advantageous features as will be apparent from the following 
description. 
SUMMARY OF THE INVENTION 
The above objects and other advantages are provided in the 
Electro-Pneumatic Brake System according to the present invention which 
includes a brake pipe for conveying pressure signals for brake application 
and release through a rail vehicle, an electrically operable release valve 
which interconnects the brake pipe with a source of pressure for 
repressurizing the brake pipe during brake release and an electrically 
operable application valve which interconnects the brake pipe with 
atmosphere for depressurizing the brake pipe during brake application. 
Signal apparatus is provided which responds to the opening of the 
application valve to give a continuous signal until the release valve is 
opened and which also responds to the opening of the release valve to give 
a continuous signal until the application valve is opened again.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
There follows a detailed description of the preferred embodiments of the 
invention, reference being had to the drawings in which like reference 
numerals identify like elements of structure in each of the several 
figures. 
FIGS. 1A and 1B show a schematic diagram of a brake system according to the 
present invention as configured for application to a single rail car. A 
conventional main reservoir equalizing pipe 10 runs along the length of 
the car and conveys pressurized air from a compressor and reservoir 
located in the lead car or locomotive (not shown). Also extending along 
the car is a conventional brake pipe 12 which leads aft through the train 
from a brake control valve (not shown) located in the lead car or 
locomotive. A partial pressure reduction in brake pipe 12 signals the need 
for a corresponding brake application and is known as service braking; 
whereas, a repressurization of brake pipe 12 signals the need for a brake 
release. Connected to brake pipe 12 is a conventional reduction relay 
valve 14 which serves in the well-known manner to release a measured 
volume of pressurized fluid from brake pipe 12 in response to a preset 
drop in brake pipe pressure, thereby accelerating service brake 
application signals through brake pipe 12. A vent valve 16 is attached to 
reduction relay valve 14 and also serves to accelerate the pressure 
reduction signal through the brake pipe 12 for emergency braking or 
completely venting the brake pipe. At either end of the rail car, local 
brake valves 18 and 20 are provided which may be actuated by the train 
conductor to effect an emergency brake application via brake application 
valves 22 and 24 in the known manner. A manifold block or pipe bracket 26 
is mounted to the underbody of the car to receive inward flow of 
pressurized fluid from main reservoir pipe 10 and to control both the 
inward and outward flow from and to brake pipe 12. A brake cylinder pipe 
28 leads from manifold 26 to the fluid pressure actuated friction brakes 
of the vehicle (not shown). 
Charging the system according to the invention is usually accomplished 
through the main reservoir line but may be done through the brake pipe 12 
which is pressurized from a compressor located in the locomotive or lead 
car when the main reservoir line is not in use. Pressurized fluid, 
normally air, flows through a combined dirt collector and cut out valve 30 
which strains the air flowing to the control valve 32 and also may be used 
to remove control valve 32 from the system when desired. 
Control valve 32 is an automatic control valve of generally known design 
which responds to pressure reductions in brake pipe 12 to develop braking 
pressures in brake cylinder pipe 28 as a function of the pressure levels 
existing in brake pipe 12 and a control reservoir 34. Control valve 32 
includes a service spool valve 36 which comprises two diaphragms 38 and 40 
selected for proper reference of brake cylinder pressure development in 
volume 42, guided by reductions in brake pipe pressure in volume 44 with 
additional reference to control reservoir pressure in volume 46. An 
application and release valve element 48 controls the movement of air from 
a supply reservoir 50 to a relay valve control pipe 52 during application 
and from pipe 52 to atmosphere via port 54 during release. Whenever a 
brake pipe pressure reduction occurs, service spool valve 36 moves 
upwardly to close the release valve and to open the application valve 
portions of valve element 48. Service valve spool 36 exhausts control 
pressure from relay valve 56 whenever brake pipe pressure is increased 
after an automatic brake application. The diaphragm area ratio of 
diaphragms 38 and 40, together with springs 58 and 60, permits stable 
operation of the automatic brake together with proper development of the 
brake cylinder pressure to operate satisfactorily with other systems of 
automatic brake control. Control valve 32 includes a charging valve 62 
which cuts off the flow of air from the quick service volume 64 to 
atmosphere and from control reservoir 34 to brake pipe 12 during graduated 
release operation of the control valve. 
Also included in control valve 32 are a number of check valves for 
controlling flow of pressurized air through the device. Supply reservoir 
charging check valve 66 controls charging of supply reservoir 50 from 
brake pipe 12. Charging check valve 68 controls charging of control 
reservoir 34. Control reservoir dissipation check valve 70 controls 
dissipation of control reservoir air into brake pipe 12 during direct 
release operation of control valve 32. Finally, backflow check valve 72 
controls dissipation of brake pipe air from spring chamber 74 of selector 
valve 76 back to the quick service volume 64, during the initial stages of 
a brake application. Selector valve 76 is a diaphragm operated spool valve 
which functions similarly to a triple valve. With air pressure from 
selector volume 80 on the outer face of the diaphragm 82 opposed by brake 
pipe pressure in spring chamber 74, it functions at the start of a brake 
pipe pressure reduction to produce a quick service function. The valve 
also provides a graduated release function with graduated release cap 78 
in the graduated release position shown in FIG. 1A. With graduated release 
cap 78 in the direct release position shown in FIG. 1C, the valve provides 
a direct and prompt release. Selector valve 76 controls the release of an 
emergency brake application by locking up selector volume pressure on the 
outer face of the selector valve diaphragm during the application, making 
it necessary to first increase brake pipe pressure to the value of 
selector volume pressure before the release of the emergency brake 
application can be accomplished. 
Two brake cylinder pressure limiting valves 84 and 86 are provided. Valve 
84 limits the maximum brake cylinder pressure obtained during service 
brake applications and valve 86 limits the maximum brake cylinder pressure 
obtained during emergency brake applications. The two valves are arranged 
in parallel so that emergency brake cylinder pressure limiting valve 86 is 
held closed by a predetermined brake pipe pressure which permits maximum 
brake cylinder pressure valve 84 to remain open during service brake 
applications. Valve 86 is opened to limit the brake cylinder pressure only 
after te brake pipe pressure has been reduced to a value of approximately 
10 to 15 psi, as occurs when venting the brake pipe during emergency brake 
applications. 
When the brake system according to the invention is to be charged, 
pressurized air is introduced through cut out cock and strainer 30 to 
passage or port 88 of the pipe bracket. Air flows to spring chamber 74 of 
selector valve 76 and to chamber 44 located between the diaphragms 38 and 
40 in service valve 36. In emergency brake cylinder pressure limiting 
valve 86, brake pipe pressure opposes spring pressure to keep the spool of 
the limiting valve in its downward or closed position, as illustrated. The 
chamber above control reservoir dissipation check valve 70 is pressurized; 
and at the same time, air flows through charging choke 90 into passage 92, 
through the spool of charging valve 62, to passage 94, and through the 
spool of selector valve 76 and into passage 96 through which control 
reservoir 34 is pressurized. With the graduated release cap 78 in its 
direct release position as shown in FIG. 1C, passage 92 is connected 
directly to passage 94 through the cap, thus bypassing charging valve 62. 
Finally, flow is introduced through choke 98 to supply reservoir charging 
check valve 66 through which supply reservoir 50 is charged. Control 
reservoir air flowing through the selector valve spool from passage 94 
flows through port 100 to the spool valve end chamber from which it flows 
through choke 101 to both the selector valve reservoir 80 and the chamber 
102 on the outer face of selector valve diaphragm 82. 
With the brake system fully charged, the control reservoir and brake pipe 
pressures acting on the opposite faces of large diaphragm 40 of service 
valve 36 are identical. The service valve piston and diaphragm assembly 
are therefore held in their lower-most position by the tension of the 
release spring acting on the diaphragm assembly. The end of the service 
valve diaphragm stem is drawn away from seating contact with the 
application and release check valve 84, as shown, to allow brake cylinder 
pipe 28 to be exhausted to atmosphere through passage 104. 
When it is desired to make a service application of the brakes, the 
operator vents brake pipe 12 at the lead car or locomotive which results 
in a drop in brake pipe pressure. This drop in brake pipe pressure is 
sensed by reduction relay valve 14 which releases a predetermined volume 
of air from brake pipe 12 to accelerate the pressure signal through the 
brake pipe. During normal operation with the brakes released, brake pipe 
pressure is directed into a reservoir volume 106 located below diaphragm 
108 of vent valve 16. When the brake pipe pressure drops during a service 
application, the pressure in volume 110 located above diaphragm 108 drops 
much more quickly than the pressure in reservoir 106, causing diaphragm 
108 to move upwardly but without adequate force to open valve 114. 
During emergency braking the brake pipe pressure drops rapidly to zero 
causing the pressure in volume 110 located above diaphragm 108 and 
therefore the downward force on the diaphragm 108 to reduce at a rate such 
that the pressure in reservoir 106 results in an upward force of such 
magnitude to pivot arm 112 and open valve 114 venting brake pipe to 
atmosphere. 
The accelerated pressure reduction in brake pipe 12 during service braking 
is further augmented by solenoid actuated application valve 116 which is 
opened in response to an electrical signal received from the locomotive or 
lead car to vent brake pipe 12 to atmosphere via an open choke 118. When 
the operator has signalled for a service brake application by moving his 
brake valve handle, the brake pipe pressure will drop to a predetermined 
level at a rate which is governed primarily by reduction relay valve 14, 
and application valve 116 in the manner just discussed. The gradual 
reduction in brake pipe pressure will be felt in chamber 44 above large 
service valve diaphragm 40. The pressure differential caused by the higher 
control reservoir pressure acting against the outer face of diaphragm 40 
will initiate upward movement of the service valve diaphragm assembly and 
piston stem, thus closing the release valve and opening the application 
valve. Opening of the application valve admits pressurized fluid from 
supply reservoir 50 to control pipe 52 of relay valve 56. 
The reduction of brake pipe pressure also occurs in spring chamber 74 of 
selector valve 76. The resulting pressure differential set up across 
selector valve diaphragm 82 then moves the diaphragm assembly and spool 
valve to permit flow through a number of passages. Port 100 is closed, 
isolating the selector reservoir from the control reservoir. Passage 94 is 
disconnected from port 100 at the selector valve spool, thus isolating 
control reservoir air from brake pipe air. Quick service action occurs 
when the brake pipe air in spring chamber 74 is allowed to flow through 
port 120, choke 122, backflow check valve 72 and port 124 to quick service 
volume 64. The air collected in volume 64 is then dissipated through choke 
126 and port 128 to atmosphere past the end of the spool of charging valve 
62. The selector reservoir pressure acting through choke 101 and against 
the outer face of selector valve diaphragm 82 is vented at a controlled 
rate through the spool of valve 76 past check valve 130 to atmosphere. The 
service spring in the selector valve is engaged and its force, coupled 
with the brake pipe pressure, opposes the force of the selector volume air 
pressure. Whenever the point of equalization of forces across diaphragm 82 
is reached, the selector valve 76 will assume a lapped position, at which 
time the selector volume is cut off from exhaust at the selector valve 
spool to terminate further reduction of selector volume pressure. 
When the application valve is open as described above, supply reservoir air 
flows through port 132 past the unseated application valve and through the 
service brake cylinder limiting valve 84 into a number of passages and 
chambers. Air moves via passage 134 to the outer face of the diaphragm of 
charging valve 62, where the initial build up of pressure will move the 
charging valve spool to first cut off the flow of brake pipe air from 
quick service volume 64 through port 128 to atmosphere. The charging valve 
spool will also cut off charging connection between passages 92 and 94. 
Air also flows to port 136 in the pipe bracket and from there to relay 
valve 56. Air moving into the large spring chamber above diaphragm 38 will 
cause pressure at that location to build up until the combined forces of 
spring 60, the air pressure in the spring chamber and the brake pipe 
pressure balance the force of the control reservoir pressure acting 
upwardly on large diaphragm 40. As this balance point is approached, 
service valve diaphragm assembly and piston stem will be moved downward to 
assume a lapped position where the application valve has been seated by 
spring tension and the release valve remains seated. Also, air pressure 
builds up on the underside 138 of the service brake cylinder limiting 
valve 84 until its pressure increases to a point in excess of the force 
applied by the limiting valve spring. When this occurs, the spool valve is 
moved upwardly to a position in which further flow of air from the 
application valve to port 136 is terminated. The spring force of the 
limiting valve spring thus limits the maximum pressure that can be 
delivered to relay valve 56 during a service brake application. 
When the pressure in brake pipe 12 is reduced at a rate indicative of an 
emergency application, control valve 32 functions essentially as 
previously described for a service application; however, some additional 
features now come into play. The increased pressure differential across 
diaphragm 82 in the selector valve, resulting from the venting of brake 
pipe pressure, positions the diaphragm assembly and spool valve to enable 
the valve to provide not only those features obtained during service brake 
applications, but also to close off the selector volume. That is, the vent 
path through check valve 130 is closed. The supply reservoir air flowing 
past the application valve 48 flows to the brake cylinder limiting valve 
84 through port 136 and on to relay valve 56. A chamber 140 is provided 
for brake pipe air in the emergency brake cylinder limiting valve 86. It 
is the pressure in chamber 140 that normally holds down the spool of 
emergency brake cylinder limiting valve 86. During the initial stages of 
an emergency brake application, emergency brake cylinder limiting valve 86 
remains closed. As the brake pipe pressure continues to drop, and is 
reduced to a value between 10-15 psi, the force of the spring within the 
emergency brake cylinder limiting valve overcomes the force of the brake 
pipe pressure acting in chamber 140. The spool valve will then be moved 
upwardly, unseating the check valve 142 and providing an alternate passage 
for supply reservoir air to port 136 and relay valve 56. During emergency 
brake applications, the brake pipe pressure drop is so fast that at the 
time the emergency brake cylinder limiting valve 86 opens its check valve 
142, service brake cylinder limiting valve 84 is still open. Check valve 
142 will remain open to permit a continued flow of air to relay valve 56. 
The pressure of the air admitted to relay valve 56 increases and the 
service brake cylinder limiting valve 84 eventually closes when its 
pressure setting is reached. The continued increase of pressure also 
affects a downward force on the spool of the emergency brake cylinder 
limiting valve 86. When this pressure reaches a point slightly in excess 
of the force of the spring within the spool, the spool will be forced 
downwardly, permitting the check valve 142 to be seated to terminate 
further flow of supply reservoir air to relay valve 56. 
The operation of relay valve 56 is familiar to those in the art. During a 
brake application, air pressure is developed by control valve 32 in the 
line connecting port 136 to relay valve 56. This air pressure is also 
developed in the chamber 144 below the large relay valve diaphragm and 
piston, causing the diaphragm assembly and piston to be moved upwardly. 
During this upward movement, the end of the piston stem, which includes an 
exhaust valve seat, first contacts and seals against the underside of the 
rubber check valve 146 to close the exhaust connection through the piston 
stem from the brake cylinder port 148. Further upward movement causes the 
rubber check valve 146 to be moved off its supply valve seat so that 
supply reservoir air is then free to flow past rubber check valve 146 to 
port 148 and the brake cylinders (not shown). Port 148 is also connected 
through a stabilizer choke 150 to the spring chamber on the inner face of 
the relay valve diaphragm so that as pressure is being developed in the 
brake cylinders, an equal pressure is being developed in the spring 
chamber. As the diaphragm becomes balanced, it is moved downwardly to a 
lap position where the rubber check valve 146 is seated against its supply 
valve seat to terminate further flow of air to the brake cylinders. 
To release the brakes, the operator moves the brake valve handle to cause 
repressurization of brake pipe 12. The increase in brake pipe pressure 
causes a similar pressure increase in brake pipe chamber 44 above large 
service valve diaphragem 40 in the control valve 32. The combined forces 
of the brake cylinder pressure in volume 42, brake pipe pressure in volume 
44 and release spring 66 act against control reservoir pressure in volume 
46 to move the service diaphragm assembly and piston stem downwardly, 
thereby drawing the release valve seat out of contact with check valve 48. 
This permits a backflow of pressurized air through port 136 to atmosphere. 
The pressurized air acting on the outer face of the diaphragm of charging 
valve 62 is also vented so that spring force will return the charging 
valve spool and diaphragm assembly to its normal or charging position, 
wherein brake pipe to control reservoir charging is reestablished. 
Continued drop of brake cylinder pressure in the brake cylinder limiting 
valves 84 and 86 permits the spring within the service brake cylinder 
limiting valve 84 to move the valve downward. As the brake pipe pressure 
continues to build up, the emergency brake cylinder limiting valve 86 is 
also closed. With both valves 84 and 86 in their downward position, the 
remaining pressure acting through port 136 is rapidly vented. Increase of 
brake pipe pressure in the selector valve spring chamber 74 eventually 
causes the selector valve spool to return to its normal position, thereby 
reestablishing charging of the control reservoir and selector volume 
reservoir to brake pipe pressure. 
During brake release, relay valve 56 experiences a reduction in the control 
air pressure acting on the outer face of the relay valve diaphragm. Due to 
the higher brake cylinder pressure remaining on the other side of the 
diaphragm, the diaphragm assembly and piston will move downward so that 
the exhaust valve seat will be drawn out of contact with rubber check 
valve 146. Brake cylinder air is then free to flow past the exhaust check 
valve seat and through the piston stem to exhaust port 152 and atmosphere. 
A graduated release of brake cylinder air may also be obtained whenever 
the controlled air pressure from control valve 32 is intermittently 
released. When this occurs, the higher brake cylinder pressure causes the 
diaphragm assembly to operate to open the exhaust valve until the 
diaphragm again becomes balanced after which it will again assume its 
lapped position and close the exhaust valve. 
Repressurization of brake pipe 12 to achieve an accelerated brake release 
is caused by opening magnet valve 154 in response to the operator's brake 
release signal. Opening valve 154 connects brake pipe 12 to supply 
reservoir 50 for repressurization. This unique feature of the invention 
also permits the brakes of a single rail car to be released locally 
provided there remains sufficient pressure in supply reservoir 50 and a 
source of power to release valve 154. 
Although charging can be accomplished from the brake pipe in the brake 
system according to the present invention, charging is normally via the 
main reservoir pipe and a check valve 156, as mentioned previously. The 
downstream side of check valve 156 is connected to supply reservoir 50 and 
to port 132 of control valve 32 so that charging from either the brake 
pipe or the main reservoir pipe may be easily achieved. Also connected to 
the downstream side of the check valve 156 via passage 158 is a governor 
valve 160 which controls flow of air to the rail car auxiliary devices 
schematically indicated at 162. Governor valve 160 comprises an inlet 
strainer or filter portion 164 through which all air to the auxiliaries 
passes. Pressurized air then reaches the underside of a diaphragm 166 
which is held against a valve seat 168 by a heavy spring 170. When the 
pressure in the volume below diaphragm 166 has reached a preselected 
level, diaphragm 166 is forced upward against the force of spring 170 
thereby permitting flow past check valve 172 to passage 174. From passage 
174, the air flows to an auxiliary storage reservoir 176 which is sized to 
maintain a sufficient reserve capacity to operate the auxiliary devices in 
the event of a loss of brake pipe or main reservoir pressure, or both. 
Passage 178 leads to auxiliary devices 162. The use of governor valve 160 
ensures that the pressure existing in brake pipe 12 and main reservoir 
pipe 10 will not be depleted for the operation of auxiliary devices; 
moreover, the inclusion of auxiliary reservoir 176 ensures that sufficient 
air pressure will be available to operate critical auxiliary devices such 
as car doors and the like, as may be necessary during an emergency period. 
Magnet valves 116 and 154 are identical in structure as shown in FIG. 2. 
Each valve comprises a base 180 of magnetic material such as steel which 
includes a radially extending coil support flange 182. A central bore 184 
is provided in base 180. Central bore 184 extends upwardly to a smaller 
diameter plunger bore 186 which is located in a central boss 188 extending 
upwardly from coil support flange 182. Flange 182 includes a plurality of 
blind holes 190 located radially therein for cooperation with a 
conventional spanner during valve installation via threads 192. 
A valve guide cylinder 194 of non-magnetic materials such as bronze is 
press-fitted within central bore 184. Guide cylinder 184 includes a 
central spool bore 196 at its upper end and a wider diameter inlet bore 
198 at its lower end. A valve carrier 200 is slideably located within 
spool bore 196 and comprises a piston and O-ring assembly 202. Extending 
upwardly from piston and O-ring assembly 202 is a piston extension shaft 
204 which terminates in a thin, cylindrical valve carrier guide 206. Guide 
206 is sized to have a close fit within spool bore 196 so that the valve 
carrier 200 will be constrained to essentially axial movement with bore 
196. Without guide 206, there would be some tendency for carrier 200 to 
rock about the center of piston and O-ring assembly 202. 
Just below piston and O-ring assembly 202, a plurality of outlet ports 208 
pierce guide cylinder 194. A valve seat 210 is provided between outlet 
port 208 and inlet port 212 located at the lower end of guide cylinder 
194. Extending downwardly from piston and O-ring assembly 202 is a shaft 
214 on which a valve washer 216 is secured by a nut 218. Nut 218 includes 
a radial bore 220 in communication with an axial bore 222 (in phantom) 
which passes upwardly through shaft 214, piston and O-ring assembly 202 
and piston extension 204. At the upper end of axial bore 222, a radial 
bore 224 communicates with the volume between piston and O-ring assembly 
202 and valve carrier guide 206. A passage 226 through guide 206 provides 
communication between the bottom of valve carrier 200 and the top of 
carrier guide 206 so that pressure equalization across the valve carrier 
is achieved. 
A plunger rod 228 of aluminum or other non-magnetic material is slidably 
located in plunger bore 186 in position to contact the upper surface of 
carrier guide 206. A plunger 230 of suitable magnetic material is 
threadingly mounted on the upper end of plunger rod 228 and slideably 
located within a plunger guide tube 232 which is threaded onto boss 188 as 
indicated. Surrounding plunger guide tube 232 is a solenoid coil 234 of 
conventional construction which rests on coil support flange 182. Coil 234 
is held in place by a retainer 236 which is secured to plunger guide tube 
232 by means such as a snap ring 238. A two-position application or 
release switch 240, 242 is mounted in the inlet plenum to the valve just 
below nut 218. Switch 240, 242 includes an upwardly extending plunger 244 
which is positioned to be contacted by nut 218 when the valve is opened in 
response to energization of coil 234. Upon de-energization of coil 234, 
valve carrier 200 is returned to its illustrated, closed position by a 
return spring 246 located in inlet bore 198 of valve guide cylinder 194, 
as illustrated. 
As previously mentioned, the invention provides a signalling means for 
indicating exteriorly of the rail vehicle that application and release 
magnet valves 116 and 154 have actually been operated to accelerate brake 
pipe depressurization or repressurization. The circuitry shown in FIG. 3 
accomplishes this purpose. In general, the electric brake checking circuit 
shown in FIG. 3 consists of two silicon controlled rectifiers 248 and 250. 
These rectifiers, when triggered by pulses resulting from the closure of a 
switch, provide a visual signal in the form of an application or release 
indicator light, indicating that either a brake application or release has 
been made on that specific car. This visual indication remains in effect 
until the opposite operation (application or release) has been performed, 
at which time the circuit switches to provide a correct application or 
release indication. 
The electric brake checking circuit is designed to operate with an input 
voltage of 50 to 90 volts direct current. When a voltage in this range is 
applied to input terminals 252 and 254, a path is established through the 
normally closed contacts of the two-position apply magnet switch 240 and 
release indicator light 256 to the anode 258 of the release rectifier 248. 
The light is not illuminated, however, because rectifier 248 is in its 
blocking or non-conducting state. Similarly, a path is set up through the 
normally closed contact of the two-position release magnet switch 242 and 
application indicator light 260 to the anode 262 of the application 
rectifier 250. A capacitor 253 and a voltage dependent, symmetrical 
resistor 255 are connected across terminals 252 and 254 for transient 
suppression. 
When the application magnet 116 is energized, it mechanically actuates the 
apply magnet switch 240. This opens the path to the release indicator 
light 256 and rectifier 248 and closes the path through resistors 264 and 
266 to the gate of rectifier 250, causing it to conduct and illuminate the 
application indicator light 260 to provide a continuous indication of 
brake application. This light remains illuminated until a release is made 
at which time the release magnet 154 actuates the release magnet switch 
242. Actuating this switch opens the path to the application indicator 
light 260 causing it to be extinguished and, at the same time, closes the 
path through resistors 268 and 270 to the gate of rectifier 248 causing it 
to conduct and illuminate release indicator light 256 to provide a 
continuous indication of brake release. Release indicator light 256 will 
remain illuminated until another application is made, at which time the 
circuit will operate as previously described to illuminate application 
indicator light 260. With this type of checking curcuitry, it is a 
relatively simple matter for a trainman to walk the length of the train to 
see whether the electrical assist features are responding properly to 
application and release signals from the operator. Of course, if the 
magnet valves 116 and 154 are not functioning properly, the proper 
indicator lights will not be illuminated on that particular car. 
In some applications, the circuitry of FIG. 3 may be simplified by deleting 
those portions of the circuit connected to the right of connectors 272, 
274 and 276, leaving only rectifier 250, application indicator light 260 
and their associated circuitry. Thus, when application magnet valve 116 is 
energized, it mechanically actuates apply magnet switch 240. This closes 
the path through resistors 264 and 266 to the gate of rectifier 250, 
causing it to conduct and illuminate application indicator light 260 to 
provide a continuous indication of brake application. Light 260 remains 
illuminated until a release is made, at which time release magnet 154 
actuates release magnet switch 242. Actuating this switch opens the path 
to application indicator light 260, causing it to be extinguished to 
provide a continuous indication of brake release. Light 260 remains 
extinguished until another application is made, at which time the 
simplified circuit will operate as previously described to illuminate 
light 260.