Brake pipe pressure modulating valve device

A modulation valve device for governing pressure in a brake pipe has coaxial accelerating and releasing valves provided wherein accelerated application and release pistons are dovetailed together to reduce the size and the weight of the modulating device.

BACKGROUND 
This invention relates to brake pipe pressure modulating valve devices and 
more particularly relates to an improved modulation valve device that is 
simplified by combining application and release propagation signal 
generating valves coaxially in coaxial stepped bores of a housing. 
To minimize time requirement for air brake application and release of a 
train, it is required that modulating valves be provided, particularly on 
long railway cars for sensing brake control pressure changes in a brake 
pipe and locally enhancing the signals for faster propagation of the 
control signals in a brake pipe of a railway train. This is accomplished 
at present, for example, by A-1 relay devices having respective 
accelerating and releasing application valves secured by a pipe bracket at 
an intermediate point between brake control valve devices. Another such 
device is disclosed in the U.S. Pat. No. 4,653,812, to Engle granted Mar. 
31, 1987, in which several separate valves are required. This patent 
discloses separate accelerating application and accelerating release 
valves, but is still much too large and heavy for use on a railway car. 
An object of the present invention is to provide improved brake pipe 
pressure modulating apparatus that substantially obviates one or more of 
the limitations and disadvantages of the described prior systems. Another 
object of the present invention is to provide an improved modulating valve 
device that is much lighter and more compact than the prior art systems. 
Another object of the present invention is to provide and improved brake 
pipe pressure modulating valve device that is simplified and less 
expensive to manufacture than the above described prior art devices. 
SUMMARY 
A modulated valve device has a housing with first and second end-to-end 
coaxial stepped bores. The first of the stepped bores contain telescoped 
accelerated application and accelerated release pistons, together with 
brake pipe and quick action chamber pressure chambers at opposite ends of 
the pistons, the same fluid pressure chambers being common to both 
pistons. The brake pipe chamber is connected to the quick action chamber 
through a breather choke. 
A vent valve piston in the second stepped bore in provided for emergency 
application signal venting of the brake pipe and is operably connected by 
a pushrod to the accelerated application piston. 
Valves are operably connected to the three pistons respectively for 
providing continuous quick service in response to a service brake 
application signal, accelerated release after a brake release signal, and 
the venting of the brake pipe upon sensing an emergency application 
signal. 
For a better understanding of the present invention, together with other 
and further objects thereof, reference is had to the following 
description, taken in connection with the accompanying drawing, while its 
scope will be pointed out in the attending claims.

With reference to FIGS. 1A and 1B, a modulation valve device is illustrated 
as having a housing 100, having first and second coaxial stepped bores 101 
and 102 respectively formed therein. An accelerated application piston 103 
is provided in the first of the stepped bores 101, and a vent valve piston 
104 is disposed in the second stepped bore 102. A pushrod 105 is coaxial 
with the pistons 103 and 104 and operably connects these pistons. A 
cup-shaped piston 106 is dovetailed over the accelerated application 
piston 103, and has an opening in the bottom thereof forming a part of 
quick action chamber 107 at the left hand end of pistons 106 and 103, the 
right hand ends of the pistons 103 and 106 being exposed to brake pipe 
pressure in a brake pipe chamber 108. Various springs are provided for 
graduating operation of the pistons 103, 104 and 106 as will be more 
readily apparent as the description progresses relative to consideration 
of the mode of operation of the modulation valve device. 
A spool valve 109 is coaxial with the accelerated application piston 103 
and is operable thereby to provide a continuous quick service release of 
brake pipe fluid to atmosphere for service brake application as will be 
hereinafter considered. The accelerated release piston 106 has an annular 
valve 110 at its right hand end for accelerating release of a brake 
application by venting fluid to the brake pipe chamber 108 and from there 
to the brake pipe 1. The vent valve piston 104 is operably connected to 
annular vent valve 45 for releasing fluid from the brake pipe at a rapid 
rate upon sensing an emergency application signal in the brake pipe 1. 
Having thus considered the general organization of a modulation valve 
device of FIGS. 1A and 1B, further detail will now be considered relative 
to the normal mode of operation of the system. 
OPERATION 
DRY CHARGE 
As air pressue in a train line brake pipe is increased from a locomotive it 
flows via the modulating valve branch pipe 1 to annular port 2 where it is 
distributed to filter 3 and passage 4. After passing through the filter 3, 
brake pipe air is directed via annular port 5 to brake pipe fluid pressure 
chamber 108 at the right hand end of pistons 103 and 106, causing the 
accelerated application piston 103 to move to the left where it contacts 
accelerated release piston 106. A further increase of pressure in the 
chamber 108 increases the force across accelerated application piston 7 
causing it to move further to the left against the combined force of 
spring bank 9 until contact is made with combined end cap and piston stop 
10. Although this action moves accelerated released piston 8 away from the 
valve seat 23, air is not allowed to flow in either direction between 
brake pipe or the accelerated release volume 29 as brake pipe pressure is 
higher than pressure in the volume 29 holding a back flow check valve 35 
(see FIG. 1C) closed cutting off this communication. Fluid from the brake 
pipe 1 also flows through passage 4 to annular chamber 11 on the outer 
face of vent valve 45 where it is stopped by seal 12. 
At the same time, brake pipe fluid passes through quick action breather 
choke 13 from brake pipe chamber 108 to chamber 107 on the left hand side 
of accelerated application piston 103 and through annular port 15, passage 
16, annular port 17 to chamber 18 and to the face of vent valve pilot 
piston 104 where it is stopped by a seal 20. Brake pipe fluid also 
continues from annular port 17 by way of passage 21 to quick action 
chamber 22 (see FIG. 1C). As quick action chamber pressure approaches the 
pressure of the brake pipe 1, spring bank 9 forces accelerated release 
piston 106 and accelerated application piston 103 to the right, closing 
the accelerated release valve 110 against seat 23. 
During charging, brake pipe fluid also flows from chamber 108 through 
passage 24, chamber 25 and passage 26 through reservoir charging choke 27 
to the underside of accelerated release volume charging check valve 28, 
creating a pressure differential which opens check valve 28 allowing the 
accelerated release volume to be charged to brake pipe pressure. 
CONTINUOUS QUICK SERVICE AND SERVICE BRAKE APPLICATION 
As brake pipe pressure is reduced by means of a locomotive brake valve, or 
similar device, fluid flows from the modulating valve branch pipe 1 causes 
a reduced pressure on the face of accelerated application piston 103 in 
chamber 108, causing a pressure differential across the quick action 
breather choke 13 causing fluid from the quick action chamber to flow to 
the brake pipe. If the brake pipe pressure is being reduced at a rate 
exceeding the rate of drop of quick action chamber pressure, the pressure 
differential across the accelerated application piston 103 increases until 
the the force of a biasing spring 36 is overcome, at which time the 
accelerated application piston 103 moves to the right, taking with it 
accelerated application spool valve 109. This movement continues until 
accelerated application piston 103 contacts pushrod 105 which is held 
stationary by vent valve spring 38. 
When open, the accelerated application spool valve 109 allows brake pipe 
fluid to exhaust to atmosphere at a controlled rate via open check valve 
seat 31, passage 32, chamber 33 and exhaust choke 34. Because of an area 
differential across accelerated application piston 103, and bias of spring 
36, a differential of nominally one-half psi. is required between brake 
pipe and quick action chambers 108 and 107 respectively before the 
accelerated application valve can move to a service position. Once in the 
service position, accelerated application piston 103 and accelerated 
application spool valve 30 will not move again until the reduction of 
brake pipe at a locomotive has been terminated, at which time brake pipe 
pressure and quick action chamber pressure are equal by way of quick 
action breather choke 13 returning the accelerated application piston by 
means of bias spring 36 and the aforementioned area differential to the 
release positoin, cutting off the flow of brake pipe air to atmosphere. 
This action at the accelerated application valve assists the reduction of 
brake pipe pressure by venting pressure continuously at a rate of 
approximately 1/4 psi. per second as long as the brake pipe pressure is 
being reduced by the locomotive. 
ACCELERATED EMERGENCY BRAKE APPLICATION 
At the onset of an emergency brake application the accelerated application 
valve responds as described for service application until a rate of brake 
pipe pressure drop of nominally 1 psi. per second is exceeded, at which 
time quick action exhaust check valve 39 opens, due to a pressure 
differential between brake pipe and quick action chamber pressure, 
allowing quick action fluid to flow to the brake pipe 1 via quick action 
exhaust check valve 39 and exhaust breather choke 40. This operation 
reduces the sensitivity of the emergency vent valve 45 which prevents the 
vent valve 45 from opening until an predetermined rate of brake pipe drop 
of nominally 18 psi. per second is exceeded. Once the proper rate of brake 
pipe pressue drop is reached, there is sufficient pressure differential 
across accelerated application piston 103 to start to compress emergency 
sensitivity spring 38 by means of pushrod 105 and emergency pilot piston 
104. As the emergency pilot piston 104 moves to the right, seal 20 becomes 
out of contact with combined filter housing retainer and seat 41, allowing 
quick action blow down choke 43. As chamber 42 is charged by quick action 
fluid it cannot escape rapidly enough through choke 43, resulting in the 
development of a back pressure in chamber 42 which moves the emergency 
pilot piston 104 to the right further compressing emergency sensitivity 
spring 38. Once a small dead band has been crossed, the emergency pilot 
piston contacts actuating pin 44, which allows vent valve 45 to be moved 
against vent valve return spring 46. Moving vent valve 45 away from seal 
12 allows brake pipe fluid to flow through exhaust via large capacity 
exhaust valve passage 47 and vent protector 48. This operation results in 
brake pipe pressure being reduced to zero locally at a very rapid rate. 
ACCELERATED RELEASE 
During a release of a brake application from either a service or emergency 
application, brake pipe pressure is restored from the locomotive brake 
valve and is transmitted via the modulating valve branch pipe 1, filter 3, 
annular port 5 and chamber 6 to the face of accelerated application piston 
103. As brake pipe pressure increases above quick action fluid chamber 
pressure, which following a service application is at brake pipe pressure 
and following an emergency application is at zero pressure, a pressure 
differential is developed across accelerated application piston 103 as 
quick action breather choke 13 limits the amount of air being admitted to 
chamber 107 at the left hand end of piston 103. Thus piston 103 contacts 
the bottom end of accelerated release piston 106, moving it to the left 
and opening accelerated release valve 110 to vent fluid from accelerated 
release chamber 29 through passage 50 annular chamber 51, brake pipe 
chamber 108 and filter 3 to brake pipe 1. 
As fluid in injected into the brake pipe 1 from the accelerated release 
volume 29, the local pressure in the brake pipe increases and a pressure 
wave is transmitted along the brake pipe for signally the release of the 
brake application. Following a service brake application control valves 
adjacent to the modulating valves are moved to a release position by the 
local increase in brake pipe pressure. The pressure wave travels along the 
brake pipe in order to initiate operation of the next modulating valve and 
the next service valve along the brake pipe. This operation creates a 
rapid serial release of the brakes throughout the train. Following an 
emergency brake application, operation of the modulating valve accelerated 
release valve 106 assists the locomotive with the recharge of the brake 
pipe to reduce the time required to release the application. 
FIG. 2 MODIFICATION 
With reference to FIG. 2, a modified form of the present invention is 
illustrated wherein an emergency vent valve 130, an accelerated release 
valve 131 and an accelerated application valve 132 are coaxial with each 
other and operably connected by pushrods 133 as in the form of the 
invention illustrated in FIGS. 1A and 1B. In this form, the accelerated 
application valve 132, rather than having its continuous quick service 
vented directly to atmosphere, has the quick service signal applied over 
passage 139 to control a pulsing device 132 for venting the brake pipe to 
atmosphere as a series of pulses, rather than a steady flow of fluid at a 
pressure comparable to the rate of flow of fluid from the brake pipe in 
generating a signal at the locomotive. 
The device 132 can be, for example, as is used in the well-known ABDW 
control vavle in that it has a Brake Pipe Volume and Intermittent Charge 
Control 135 and an Accelerated Exhaust Pulse Timer 136 that are controlled 
by an accelerated application signal on passage 139. The application of 
this signal to the accelerated exhaust pulse timer 136 starts the pulsing, 
wherein fluid is delivered from brake pipe volume 135, through choke 137 
over passage 138 and through Accelerated Exhaust Pulse Timer 136, over 
passage 140 and through choke 141 to atmosphere. When initiated, the 
Accelerated Exhaust Pulse Timer 136 delivers an output over passage 142 
and through choke 143 to atmosphere that reduces fluid pressure under a 
piston of the Accelerated Exhaust Pulse Timer to reset the Accelerated 
Exhaust Pulse Timer to start a new cycle for delivery of another pulse of 
brake pipe fluid to atmosphere. 
Having thus described a brake pipe pressure modulating valve device as a 
preferred embodiment of the present invention, it is to be understood that 
various modifications and alterations may be made to the specific 
embodiment shown without departing from the spirit or scope of the present 
invention.