Note: Descriptions are shown in the official language in which they were submitted.
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FLUID BRAKE CONTROL SYSTEM
1. Background of Invention
This invention relates to fluid brake control systems,
and while the invention is su~ject to a wide range of appli-
cations, a preferred embodiment of the invention will be
particularly described as applied to a fluid brake control system
having an improved quick service and accelerated release control
device.
The present invention is an improvement over currently
used quick service and accelerated release control devices such
10. as the quick service and accelerated release control devices of
the well-known ABD control valve generally used for governing
the brakes of freight cars. In the ABD valve, a form of quick
service function is provided by the service slide valve but to
provide repeated quick service cycles as long as the brake pipe
pressure continues to be reduced from an extraneous source, the
ABD valve must be supplemented by a special q~ick service ontrol
device such as the well-known Bl quick service valve.
` The accelerated release function as provided in the
ABD valve requires separate control devices for service and
20. emergency release functions respectively. The AB~ device for ;
accelerated service release senses relative brake pipe and
auxiliary reservoir pressures, while the accelerated release
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for an emergency brake application is provided by the actuation
of a spool valve associated with an emergency release slide
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valve.
.
These valves as provided in the ABD valve are costly
to manufacture and are somewhat slow to respond because of
sliding friction. Smooth and quick application and release of
brakes~ of a train is dependent upon the speed at which a change
30~ in control is sensed by each car and passed along from car to
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1. car, beginning at the front end of the train. It is therefore
very important that there be as little delay as possible in the
successive operation of the quick service and accelerated re-
lease valves on the respective cars of a train. It is therefore
highly desirable to increase the speed and integrity of pro-
pagation of a brake control signal through a train over the
rate of operation currently possible with ABD slide and spool
valves.
An object of the present invention is to provide a
10. fluid brake control system having improved quick service and
accelerated release valves which substantially obviate one or
more of the limitations and disadvantages of the described prior
system.
Another object of the present invention is to reduce
the numbe~ of control devices required to provide the functions
of quick service and accelerated release controls.
Another object of the present invention is to reduce
manufacturing and maintenance cost of brake application and
release control devices.
20. Other objects, purposes and characteristic features
of the present invention will be in part obvious from the
accompanying drawings, and in part pointed out as the descrip-
tion of the invention progresses.
Summary of Invention
A fluid brake control system is provided ~or a train
of cars including a car having a brake control pipe, a quick
action chamber s~ubject to charge periodically from the brake
pipe and an improved quick service control device comprising
a~housing containing a fluid pressure differential operated
30. abutment subject to actuation from a normal position by diff-
~erences in pressure between respective brake pipe and reference
fluid pressure chambers acting on opposite sides of the abutment.
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1. Two poppet type valves are provided on the brake pipe pressure
chamber side of th~ abutment for selectively venting the
pressure chambers, each of the valves being spring biased in
a direction of the abutment -to a normally closed position and
the valves having respective operatiny push rods longitudinally
disposed between the associcated val~es and the abutment. The
poppet valves are opened by movement of the abutment in one
direction from its normal position and fluid circuits are provid-
ed, including the poppet valves, for permitting flow from the
10. brake pipe pressure chamber and from the reference pressure
chamber respectively for cyclically locally reducing pressure in
the brake pipe repeatedly as long as the brake pipe continues to
be reduced in pressure independent of the action of the poppet
valves~
-The above described control device also provides
accelerated release control by providing a poppet type valve on
the reference chamber side of the abutment that is spring biased~
in the direction of the abutment to a normally closed position,
this valve having an operating push rod longitudinally disposed
20. between the poppe~ type valve and the abutment for opening the
valve in accordance with movement of the abutment in the direc-
tion of the reference pressure chamber to permit fluid to flow
from the emergency reservoir to the brake pipe. Additional
spring biasing means including a piston having an axial bore
for free pa~sage of the vaLve operating push rod is provided
for applying additional spring bias against movement of the
- abutment in the direction of the reference pressure chamber to
~pen the accelerated release valve only when fluid pressure is
materially reduced in the reference chamber~ such as after an
30. emergency brake application. Thus this spring is e~fective for
a~cslerated release control after an emergency brake application
but not after a service brake application.
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1. Although the functions of quick service and accelerated
release are combined in a single control device as compared to
prior use of several devices for each oE these functions, it is
to be understood that the accelerated release control function
and the quick service control function can be used separately,
independent of the other function if such is the requirements
of practice.
The poppet valves used are preferably of the ball
type, spring biased to a closed position against a seat for
10. requiring a minimum travel of the abutment to actuate the valves
with a minimum amount of friction involved. It has been found
that satisfactory operation is obtained in an operating range
of the abutment from its normal position of approximately fifty
thousandths of an inch.
For a better understandiny of the present invention,
` together with other and further objects thereof, referance is
had to the following description ta]cen in connection with the
accompanying drawing, while its scope will be pointed out in
the appending claims.
20. The drawing,is-a sectional axial view of a ~uick ser-
vice and accelerated release control device together with a
schematic diagram of a fluid brake control system in which it can
be used as a preferred embodiment of the present invention.
With reference to FIG. 1, a fluid brake control system
is illustrated for a typical car in a train including a brake
control'pipe 10, a reference fluid reservoir in the form of
quick action chamber ll that is subject to charge from the
brake pipe 10 and an improved quick service control device 13.
~he device 13 has a housing 14 containing a fluid pressure diff-
30. erential operated abutment 15 subject to actuation ~rom a normal
position in which it is illustrated by differences in pre~sure
between respective brake pipe and'reference fluid pressure ,'
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1. chambers 16 and 17 respectively acting on opposite sides of
the abutment 15 within the housing 14.
Two poppet type valves 18 on the brake pipe pressure
chamber side of the abutment 15 are provided for selectively
venting the chambers 16 and 17, each of these valves 18 being
biased by a spring 19 in the direcl:io.n of the abutment 15 to
a normally closed position and the valves 18 having respective
. operating push rods 20 longitudinally d.isposed between the
associated valve 18 and the abutment 15. The poppet valves 18
10. are op~ned by movement of the abutment 15 downwardly and fluid
circuits are controlled by the valves 18 for permitting fluid
.. flow from the brake pipe pressure chamber and from the reference
~, pressure chamber respectively for cyclically locally reducing
,: . pressure in the brake pipe 10 as long as the brake pipe 10
continues to be reduced in pressure extraneous of the valves
` 18 as by brake pipe pressure reduction in an adjoining car or
., in the locomotive.
~ Improved accelerated release control is provided by
, another poppet type valve 18 on the upper side of the abutment
'~, 20. lS that is biased by a spring 19 in the direction of the abut-
-', ment 15 to a normally closed positionO This valve has an
., . operating push rod 20 longitudinally disposed between the
associated poppet type valve 18 and the abutment lS for opening
the accelerated release valve 18 ,in accordance with the movement
., ~
, ~ ~ upwardly of the abutment 15 from its normal position. When this
q valve~is opened, fluid is supplied from emergency reservoir 12
: through the accelerated release valve 18 to the brake pipe 10.
Additiona} spring biasing means is used for accelerat-
ed release after~an emerg.ency brake application, including a
30. piston 21 having an axial bore 33 for free passage of the push : ,',
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.',~` ~ rod 20 associated with the accelerated release valve 18~ The
~ ; pLston 21 is biased downwardly by a spring 22, and is biased
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1. upwardly by fluid pressure in the reference chamber 17. It is
this upward bias by fluid pressure ln chamber 17 that makes the
spring 22 selectively effective against the abutment during
accelerated release after an emergency application but not after
a service brake application. The piston 21 is operable in a
bore 23 to an extent limited by a stop 24 which is illustrated
as a snap ring in the bore 23. This ring limits downward move-
ment of the piston 21 so that it will have no influence on
movement of the abutment 15 downwardly from its normal position
10. in which it is illustrated.
The laterally spaced push rods 20 associated with the
valves 18 beneath the abutment 15 are connected at their upper
ends by a bridge 25 that is pivotally connected to the right-
hand push rod 20 by a pin 26. At a mid-point in the bridge 25,
the bridge 25 is recessed downwardly at 25a to receive a detent
27 in abutment 15.
The abutment 15 comprises an annular diaphragm 28
secured between upper and lower housing portions 14a and 14b
respectively, and annular diaphragm follower plates 29 and 30
20. are secuxed axially on upper and lower sides respectively of
the diaphragm 28. The plate 29 has a bearing surface 29a for
the lower end of push rod 22 above the abutment 15. Similarly
the lower plate 30 has a detent 27 integral therewith for
engagement with bridge 25 as has been described to operate the
push rods 20 below the abutment 15 for actuation of the valves
18 below the abutment 15, and permit sequential operation of .
these valves 18, dependent upon relative forces of their
springs 19. ~ .
A light stabilizing spring 31 is preferably disposed
~ 30. axially between plate 29 and the upper housing portion 14a as ~.
: provided by the two springs 19 of the valves 18 on the lower
.
~ side of the abutment 150 Thus the val~es can be adjusted, if
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1. desired, so that substantially the same dif~erence in pressure
in one direction is required -to open the valves above the abut-
ment 15 that is required in the opposite direction to open the
valves below the abutment lS.
The valves 18 are similar in that they are ball poppet
valves urged by springs 19 against ends of tubular resilient
seats 32. The push rods 20 for ope:rating their associated
valves 19 are operable with minimum friction within bores 33,
and O-rings 34 are used to prevent leakage from the pressure
10. chambers 16 and 17. The push rods 20 are of reduced diameter
at their ends adjoining the valves 18 to permit free passage
of fluid through the associated valves 18 when these valves are
opened. The valve biasing springs 19 are contained in suitable
bores 35 in the housing 14. The lower right-hand push rod 20
is larger in diameter than the other push rods 20 to include
an internal passage 36 as an inlet port for the lower right-hand
valve 18. Also the push rod 20 for valve 18 on the upper side
of the abutment 15 is longer than the other push rods to extend
through a bore 33 in piston 21 as has been described,
20~ An accelerated release check valve 3~ is provided for
connecting the accelerated release valve 18 to the brake pipe
10. The quick action chamher 11 is charged from the brake pipe
10 through a choke 38, and quick action chamber 11 is connected
: to emergency reservoir 12 through a spill-over check valve 39.
In practice, the quick service and accelerated release
control device 13 that has been d~scribed can be used in place
: ~ of sev~ral valves providing coxresponding functions in the ABD
valve, thus simplifying and improving the ABD valve control
apparatus~ It should be.considered that the simplified~dis~
30. alosure of a railway car braking system in the present em~odi-
: ment is done to simplify the disclosure of the present invention :.
rather than to limit the environment in which the invention can
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1. be applied. For example, additional controls can be provided
as in the ABD valve for charging the emergency reservoir 12
and the quick action chamber 11 and in connection with venting
the pressure chamber to atmosphere in accordance with the
requirements of practice.
Upon initially charging the brake pipe 10, fluid enters
chamber 16 via passage 40 and choke 41. The quick action chamber
11 also charges at this time through choke 38, and the emergency
reservoir 12 can be charged from the brake pipe through a
10. suitable choke (not shown) as is done in the ABD valve. The
reference chamber 17 is charged through port 42 from the quick
action chamber 11. Thus, under normal conditions, chambers 16
and 17 are charged to substantially the same pressures, and the
abutment 15 assumes its normal position as is illustrated permit-
ting the closure of all valves 18 by their associated biasing
springs 19.
- To illustrate the quick service operation of the
control device 13, it will be assumed that the brake pipe 10
has been fully charged, and that a service brake application
20. is initiated by causing a continuous reduction in the pressure
in brake pipe 10 at a service rate. This reduces the pressure
in chamber 16 of oontrol device 13 relative to the reference
pressure in chamber 17, causing the abutment 15 to be actuated
downwardly to successively open the valves 18 below the abut-
ment 15, the right-hand valve 18 being opened first because o
having a weaker spring 19 than the left-hand valve so as to
; initlally vent fluid from the brake pipe through passage 40,
choke 41,~ch~amber 16, passage 36, valve 18 and vent passage 44;
to atmosphere. Thus a cycle of local quick service reduction
30. of brake pipe pressure is initiated, and as the right-hand ~-
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valve 18 draws the pressure down further in chamber 1~ relative
to chamher 17, tha abutment~lS becomes deflected downwardly
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1. further so as to open the left-hand valve 18 for venting the
quick action chamber 11 to atmosphere. The sequential opening
of these valves is permitted by the rocking of the bridge 25
about its pivot point 25a on the detent 27 of ab~ltment 15.
Openin~ of the lower left-hand valve 18 causes quick action
chamber air to be vented to vent passage 44 from the quick action
chamber 11 through passage 45, inlet port 46, lower left-hand
valve 18, outlet port 47, passage 48 and choke 49. When the
lower left-hand valve 18 becomes fully opened, it ve~ts reference
10. chamber 17 at a faster rate than the venting of brake pipe
chamber 16, and thus pressure difference between chambers 16 and
17 becomes reduced to a point of causing the abutment 15 to be
restored substantially to its normal position, shutting off both
lower valves 18 and completing a first cycle of operation for
quick service reduction.
If the brake pipe 10 continues to be reduced in
pressure from an extraneous source such as from the locomotive
or from an adjoining car, brake pipe chamber 16 continues to
reduce in pressure relative to the reference chamber 17, and
20. another cycle of operation like that which has just been des-
cribed iq operable to again cyclically reduce the pressure in
the brake pipe locally to provide more local quick service
brake pipe reduction. These ~ycles of operation are e~fective
continuously as long as there is a continuous extraneou~
reduction in pressure in brake pipe 10.
Typical choke sizes that have been found to provide
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satisfactory cycling operation as described are .02, .125, .05
and .081 inches for chokes 38, 41, 43 and 49 respectively. It
should be understood, however, that the sizes of these chokes
30. can be varied in accordance with the requirements of practice.
These sizes have been chosen to be used in connection with a
well-known quick aation cbamber volume of 145 cubic inches that
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is built into a standard pipe bracket to which the control
device 13 would be sec~red.
The frequency of cycling of the quick service valves
is determined by the size of the choke 41 and varies inversely
with the size of this choke. It has been found that sa-tisfactory
operation is obtained with the size of choke 41 varying at least
in a range from .097 to .125 inches.
Also the frequency of cycling of the quick service
valves is dependent upon the relative volumes of the quick
action chamber 11 and the brake pipe 10. The quick action
volume is the same on all lengths of cars, while the brake pipe
volume varies in accordance with the lengths of tlle cars.
It will be readily apparent from the mode of opera-
tion as it has been described that where an entire train is
equipped with this type of quick service control as a part of
the control valve, the longer cars will have more air vented
from their brake pipes than the smaller cars, thus reducing the
necessity to provide auxiliary quick service valves for long
cars as is the current practice. The present quick service
valve that can be included as a part of an ABD type control
valve, ~or example, therefore provides the dual function of
increasing the rate of brake signal propagation for standard
length cars and reducing the necessity of providing quick service
valves separate from the ABD valve for longer cars.
i, .
For consideration of the mode of operation to provide
~accelerated release, it will be assumed that the charging of
the~brake pipe lO is initiated to cause release of a service
application.~ Under these~conditions, the pressure in brake
pipe~;~chamber 16 bullds;up more~rapidly than in reference
30. chamber~l7, causing abutment 15 to move upward]y and open the
upper valve 18~to permit fluid from emergenc~ reservoir 12 to
be~applied~ to the~ brake pipe 10. Under these conditions,
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1. emergency reservoir 12 is connected -to brake pipe 10 through
passage 50, input port 51 of accelerated release valve 18, output
port 52, passage 53, choke 54 in the input to check valve 37,
outlet port 55 of choke 37 and passage 56. It will be noted
that in this mode of operation, the push rod 20 slides within
the piston 21, as the piston 21 is maintained in its normal
position as shown by fluid pressure in the reference chamber 17.
Thus the spring 22 does not ac-tuate piston 21 to a contacting
position with the abutment 15 during accelerated release follow-
10. ing a service brake application. As the pressure builds up inthe train brake pipe 10, the quick action chamber 11 becomes
charged through its choke 38, and thus pressure builds up in
chamber 17 of the control device 13 to terminate the local
accelerated release by restoring the abutment 15 to its normal
position.
To consider another condition of accelerated release,
it will be assumed that brakes are to be released after an
emergency application. During emergency braking conditions, the
pressures in brake pipe chamber 16 and reference cha~ber 17 are
20. substantially depl~ted, and thus the piston 21 is actuated by
its spring 22 to a position limited by the snap ring 24 in
contact with the abutment 15 in its normal position. The pur- ~
pose of this additional spring applied to the abutment 15 is ~i
to stabilize the abutment 15 to insure that it will not actuate
the accelerated release valve to an open position in response
to a small build-up of pressure in the train brake pipe 10 that
is not intended as a signal for brake release.
When a brake release signal is applied to the train
brake pipe 10 after an emergency application~ pressure builds
30. up in brake pipe chamber 16 faster than in reference chamber
17, and when the pressure difference is sufficient to overcome
the additional biasing spring 22 as well as the pressure of the
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1. stabilizing spring 31 and of the valve spring 19, the piston 21
and push rod 20 above abutment 15 are both actuated upwardly to
open the accelerated rele.ise valve 18 and permit the application
of fluid from the emergency reservoir 12 to the brake pipe for
accelerated release as has been described when considering the
mode of operation for release of a service brake application.
PLS was considered for a service brake release, the pressures
in the brake pipe chamber 16 and the reference charnber 17 sub-
stantially equalize, thus restoring the abutment 15 to its
lO. normal position as is illustrated in FIG. 1 and restoring the
accelerated release valve 18 and piston 21 to their normal
positions.
I~aving thus described a fluid brake control system
for a vehicle having an improved quick service and accelerated
release control 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 department from the spirit or scope of the invention.
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