Plural service rate sensitivity control valve

A control valve having, in a series with a first inlet valve of a quick brake volume, two different rates of flow restrictions operable as a function of the position of the piston. The first flow rate of one first restriction is insufficient to cause the piston to a braking position for applying a minimum service application for first range of piston positions which would generally be produced by the mechanical vibration. The second restriction has a greater flow and will accelerate the piston to a braking position for a second range of piston positions which will be produced by the reduction of the brake pipe pressure on one face of the piston. By providing two flow rates, the valve becomes insensitive to mechanically produced forces while maintaining the reaction time of the valve to fluidically produced reduction of brake pipe pressure.

SUMMARY OF THE INVENTION 
The present invention relates generally to brake control valve systems for 
operating a vehicle's air brakes, in response to brake pipe pressure in a 
brake pipe, and more specifically to a brake control valve system which is 
insensitive to increased mechanical vibrations. 
Brake control valve systems for a vehicle having air brakes generally 
include a brake control valve responsive to the brake pipe pressure in a 
brake pipe to operate the brakes of a vehicle. For a reduction of brake 
pipe pressure, the brakes are proportionally applied. For an increase in 
brake pipe pressure, the brakes may be released totally or gradually. In 
the AAR system, the brake control valves include a service section and an 
emergency section which are responsive respectfully to a service rate of 
reduction and emergency rate of reduction to apply the brakes 
appropriately. Each section includes a separate diaphragm responsive to 
the brake pipe pressure on one side and a reference pressure on the other. 
Not only must the brake control valve differentiate between a service and 
an emergency application, but also must react in a specific amount of time 
to apply the brakes and propagate the signal throughout the brake system. 
Historically the control valves have been designed to be substantially 
insensitive to pneumatic noise signals in the brake pipe which could cause 
undesired emergency (UDE) braking and undesired release (UDR). Various 
mechanisms have been used, for example, chokes or restrictions 
interconnecting the brake pipe and the reference chamber of the 
diaphragms, to accommodate pneumatic noise. The pneumatic noise or shock 
is produced by the mechanical vibration of the vehicle. A major 
identifiable source of this mechanical vibration is in the longitudinal 
motion or slack action between the different cars of the vehicle or train. 
The insensitivity or the stability built into the brake control valves to 
accommodate the pneumatic noise or shock have, unbeknownst to the 
designers, accommodated and therefor masked, mechanically produced 
vibration on the brake control valve which can produce undesired minimum 
(UDM) service braking. 
With the introduction of aluminum and other building materials as well as 
the modification of other portions of a car of a train, the empty car 
gross weight has been reduced from the range of 55,000 to 65,000 lbs. to 
40,000 to 45,000 lbs. For these lighter cars, it has been noticed that the 
control brake valves have been experiencing an undesired minimum service 
application. Initially, only longitudinal forces were investigated as the 
source of vibration. Upon further investigation by the applicant, it has 
been determined that the lighter cars have a greater natural frequency of 
vibration than the previous cars and this increase in vibration has placed 
the control valve under greater G-forces for these same longitudinal 
G-forces. For the previously constructed cars in the empty load condition, 
the natural frequency was in the range of 40 to 50 Hertz while the new 
lighter cars have a natural frequency in the range of 80 to 100 Hertz. 
With a car's natural frequency of approximately 85 Hertz and a service 
piston's natural frequency of approximately 170 Hertz, the piston's 
natural frequency is the second harmonic of the car's natural frequency. 
Thus both shock and frequency of the shock must be taken into account. 
Experimentation has shown that the undesired minimum service application is 
a function of the horizontal G-forces and its duration. For a low 
horizontal G-force in the range of 5 to 7 Gs, typical duration of 2.6 to 
2.7 milliseconds generally does not produce an undesired minimum service 
application. For larger residual durations, larger vertical G-forces 
result during the residual 4.6 milliseconds of 5.2 milliseconds producing 
undesirable minimum service brake application. The applicants have 
observed vertical acceleration produced by horizontal impact in the range 
of approximately plus and minus .+-.15 Gs. 
The applicant has observed for this increased vertical force, that the 
differential motion between the service piston and the housing will cause 
the service piston to operate the quick service chamber check valve in the 
downward motion of the oscillating valve. This opening, even though for 
short periods of time, has been sufficient to trigger a minimum service 
application. Thus in addition to the previously recognized horizontal buff 
and draft forces, the control valve is also subjected to significant 
vibration and vertical shock components during slack action. 
Thus as an object of the present invention is to provide a service valve 
which is insensitive to mechanically produced vibrations. 
Another object of the present invention is to provide a brake control valve 
having a service section which is insensitive to mechanically produced 
vibration while not detrimentally affecting the operation time of the 
brake control valve. 
A still even further object of the present invention is to provide a brake 
control valve which is insensitive to mechanically induced forces with a 
minimum modification to the existing designs. 
These and other objects are achieved by providing, in a series with a first 
inlet valve of quick brake volume, two different rates of flow 
restrictions operable as a function of the position of the piston. The 
first flow rate of one first restriction is insufficient to cause the 
piston to apply a minimum service application for first range of piston 
positions which would generally be produced by the mechanical vibration. 
The second restriction has a greater flow and will accelerate the piston 
to a braking position for a second range of piston positions which will be 
produced by the reduction of the brake pipe pressure on one face of the 
piston. By providing two flow rates, the valve becomes insensitive to 
mechanically produced forces while maintaining the reaction time of the 
valve to fluidically produced reduction of brake pipe pressure. The 
control of the restriction, as a function of the displacement of the 
piston, accommodates for mechanical displacement instead of for 
differential pressure as in the other stability and sensitivity devices in 
the brake control valve. 
A bore adjacent to and connected to the first valve receives an actuator 
which connects the piston and the first valve. In a first embodiment, the 
first and second restrictions are defined by the space between the bore 
and first and second portions respectively of the actuator. During some or 
all of when the first portion is in the bore, the second portion may also 
be in the bore, therefore the first and second restrictions are considered 
in series fluidically. In the second embodiment, the first restriction may 
also be produced by the space between the bore and an actuator and the 
second restriction by a passage in the actuator connecting the brake pipe 
pressure to a first port on the actuator to a second port of the actuator 
in the first portion of the actuator, such that the passage defines a 
second flow rate operating in parallel to the first restriction for the 
second range of piston positions. In either embodiment, the first and 
second restrictions connect the brake pipe side of the piston to the first 
valve. The actuator is connected to the piston by a mechanism which allows 
the actuator to freely align to the bore. The first valve preferably is a 
poppet valve. A third restriction may be provided having a greater rate of 
flow than the second restriction such that the second rate of flow may be 
a transition rate of flow. 
The brake control valve in the service section includes a second valve, 
interconnected to the first valve or the quick service inlet valve of the 
quick service chamber, for providing air pressure to the brakes when open. 
The second valve is opened subsequent to the first range of piston 
positions and subsequent to at least a second range of piston positions 
wherein the first and second restrictions respectively are operative. A 
biasing mechanism is also provided to bias the piston toward the braking 
position. The biasing structure applies a first force insufficient to 
cause the piston to assume the braking position for the first range of 
piston positions and has a second force greater than the first force to 
accelerate the piston to its braking position for a range of piston 
positions subsequent to the first range and prior to range of positions 
which opens the second or braking valve.

DETAILED DESCRIPTION OF THE DRAWINGS 
The present invention is being described with respect to an improvement on 
a DB-60 control valve available from New York Air Brake a unit of Knorr 
Brake Holding Corporation of Watertown, N.Y. A detailed description of the 
complete DB-60 control valve is found in instruction manual MU-21 
available from New York Air Brake. Although the improvement has been 
incorporated into the service section of the DB-60, the present 
improvement may be provided to any brake control valve portion which 
includes a piston responsive to brake pipe pressure on one side thereof. 
Thus, the invention may be used in other ARR styled brake control valves 
or non-ARR brake control valves. Only those portions of the service 
section of the DB-60 which explain the operation of the present invention 
have been included in the schematics and others have been intentionally 
deleted for sake of clarity. 
The brake control valve includes a housing 10 having a service piston 12 
with brake pipe pressure in the top chamber 14 connected to the brake pipe 
BP by passage 16. The bottom chamber 18 on the other side of the piston 12 
is connected to the auxiliary reservoir AR through passage 20. An 
auxiliary reservoir charging valve 22 is controlled by the piston 12 
through operator 24 and includes spring 21. The auxiliary reservoir 
charging valve 22 is connected to the brake pipe BP by sensitivity choke 
26 in passage 28. A stability choke 30 connects the brake pipe chamber 14 
on the top of diaphragm 12 to the auxiliary reservoir AR by passage 32. 
Where as the sensitivity choke 26 interconnects the two chambers 14 and 18 
of the piston 12 as long as the auxiliary reservoir charging valve 22 is 
open, the stability choke 30 interconnects the two chambers 14, 18 for all 
service positions of the service piston 12 and is closed off in the 
emergency position of the service position 12. The restrictions 26 and 30 
define the sensitivity of the service position 12 against pneumatic noises 
in the brake pipe. 
A quick service inlet valve 40 includes a seat 42 and connects the top or 
brake pipe chamber 14 of piston 12 to the quick service chamber 44. 
Operator 46, extending from the service piston 12, includes a guide 
portion 48 moving within bore 50 of the housing. A passage 52 in the guide 
48 connects the brake pipe chamber 14 of the piston 12 to the bore 50. A 
smaller bore 58 connects bore 50 to the valve seat 42. The operator 46 
includes an actuator having a first portion 54 of a first cross-sectional 
area and a second contiguous portion 56 of a second cross-sectional area 
smaller than the first cross-sectional area 54. The first portion 54 
engages the quick service inlet valve 40. Portion 54 and 56 define 
restrictions between themselves and the bore 58. As will be explained more 
fully below, the restriction formed by 54 is sufficiently small so as to 
minimize the flow to the quick service chamber 44 whereas the restriction 
formed between bore 58 and portion 56 permits a flow rate to provide 
normal operation of the quick service inlet valve 40. 
The cross-section of the portion 54 and 56 of the actuator have been 
exaggerated in the drawings to illustrate the present invention. For 
example, the bore 58 would have a diameter of approximately 5.02 
millimeters, the first portion 54 would have a diameter of 4.92 
millimeters and the portion 56 would have a diameter of 4.69 millimeters. 
The effective length of the first section 54 would be approximately 1.5 
millimeters (2.0 millimeters less 0.5 millimeters of the valve seat 42). 
Thus, for the first 1.5 millimeters of travel of the piston 12 during the 
opening of the quick service inlet valve 40, the flow through the open 
valve 40 is defined by the restriction between the first portion 54 and 
the bore 58 and, for the remainder of the travel of the piston 12, the 
flow is defined by the restriction between the second portion 56 and the 
bore 58. This design provides 75 percent less annular area during the 
initial 1.5 millimeters of travel and 140 percent more annular area during 
subsequent travel than the standard design. As will be explained below, 
the restriction between portion 54 and portion 58 is selected to be 
insufficient to reduce the brake pipe pressure in chamber 14 to cause the 
piston 12 to become unstable and assume a braking position. 
An enlarged view of the operator 46 is illustrated in FIG. 8. Shoulder 41 
of operator 46 receives the plates of the diaphragm 12 which are secured 
thereto by a nut, not shown, which is received on the threaded portion 43 
of operator 46. A bore 45 in operator 46 receives the actuator having the 
portions 54 and 56. The diameter of the bore 45 is greater than the 
diameter of the portion 56 such that the actuator and the first portion 54 
freely align within the bore 58 which defines the restrictions. A cross 
bore 47 in the actuator 46 and bore 51 in the actuator receive a pin 49. 
This maintains the actuator within the operator 46 during assembly. The 
end of actuator portion 56 rests at the bottom of the bore 45. Therefore, 
there is no longitudinal motion therebetween during operation. In prior 
art devices, the actuator and the operator are one continuous piece. With 
the reduced dimension between the first portion 54 and the bore 58, the 
free connection allows appropriate alignment so as to maintain the 
required restrictions. The actuator having portions 54 and 56 is 
permanently lubricated with an electroless nickel, impregnated with 
teflon. 
A spring cage 60 connects a spring 62 to the quick service inlet valve 40 
and biases it closed. A slide 64 is operatively connected to the quick 
service inlet valve 40, and includes a passage 66, which in FIG. 1 
connects exhaust EXH through passage 68 in the housing to the brake 
cylinder by passage 70 in the housing. O ring 72 and K ring 74 on the 
slide 64 seals the slide in the bore 73 of the housing. A brake cylinder 
inlet valve 76 including spring 78 connects the brake cylinder passage BC 
70 to the auxiliary reservoir via passage 80. The slide 64 operates the 
brake cylinder valve 76 in response to the quick service inlet valve 40. 
A balancing valve 82 with spring 84 includes an operator 86 which is 
controlled by the service piston 12. A passage 88 in the operator 86 
connects the auxiliary reservoir chamber 18 at the bottom of service 
piston 12 to a balancing piston 92 via passage 90, when the balancing 
valve 82 is closed and passage 88 is opened. The balancing piston 92 has 
chamber 94 on its top side connected to exhaust EXH. A spring 96 resting 
on spring cage 98 biases the service system 12 towards its braking 
position. The spring cage 98 rests on shoulder 100 of an element 102 
connected to the service piston 12. An extension 104 of the balancing 
piston 102 will engage the spring cage 98 to change the biasing of the 
spring 96 to be explained below. 
Except for the modification of the first portion 54 of the operator 46 to 
form a restriction smaller than the restriction formed by portion 56, the 
control valve portions described are that of the prior art described of 
the DB-60 control valve. In the charging lap position of FIG. 1, the 
auxiliary reservoir charging valve 24 is open and the balancing valve 82 
is open with the passage 88 blocked. The first portion 54 lies in bore 58 
and the quick service inlet valve 40 and the brake cylinder inlet valve 76 
are closed. Passage 66 is open connecting the brake cylinder passage 70 to 
the exhaust passage 68. Both the sensitivity choke 26 and the stability 
choke 30 are operative. 
For a first portion of the quick service, as illustrated in FIG. 2, the 
piston 12 has moved a first range of positions equal to the length of the 
first portion 54 such that the portion 54 is emerging out of the bore 58. 
During this first range of the service piston position 12, the quick 
service inlet valve 40 has opened but the flow has been determined by the 
first restriction defined by portion 54. As the portion 54 emerges or 
leaves the bore 58, the auxiliary reservoir charging valve 22 begins to 
close. If the motion or amount of travel of the service piston 12 is 
produced only by the mechanical vibration, the amount of reduction of the 
brake pipe pressure in chamber 14 above the piston 12 is insufficient to 
cause the piston 12 to become unstable and reversably move toward a 
braking position which would open the brake cylinder inlet valve 76. 
Balancing valve 82 has not closed and therefore the balancing piston 92 
has not moved up to change the biasing of the spring 96 on the piston 12. 
It is this additional biasing which causes the piston 12 to move into an 
unstable condition, moving irreversibly towards its braking position. 
Up to this point, the stability choke 30 and the sensitivity choke 26 have 
been operative to balance the pressure in chambers 14 and 18 on opposite 
sides of the service piston 12. As auxiliary reservoir charging valve 22 
closes, the sensitivity choke 24 becomes inoperative and only the 
stability choke 30 is operative. Thus, a drop in the brake pipe pressure 
at a rate greater than that defined by the stability choke 30 will cause 
the piston 12 to continue moving upward in response to the drop in brake 
pipe pressure from the brake pipe and not from any fluid flowing through 
the first restriction 54/58 of the open quick service inlet valve 40. 
A second quick service stage, as illustrated in FIG. 3, is produced by the 
drop in the brake pipe pressure in chamber 14 at a greater rate than 
sensitivity choke 30. This causes the brake pipe pressure in chamber 14 to 
flow into the quick service chamber 44 through the restriction defined by 
portion 56 and the bore 58 through the open quick service inlet valve 40. 
The auxiliary reservoir charging valve 22 is completely closed and 
balancing valve 82 is closed and passage 88 has been opened. This allows 
auxiliary reservoir in chamber 18 to flow through passages 88 and 90 to 
the bottom of the balancing piston 92 causing it to move up and engage the 
spring cage 98 and increase the biasing of spring 96 to accelerate the 
response of the service piston 12 towards its braking position. This 
causes the service position 12 to become unstable and irreversibly move 
towards its braking position. The reduction of the brake pipe pressure in 
chamber 14 into the quick service chamber 44 and the increase of the 
tension on spring 96 are two feedback signals which cause the instability 
of the service position 12 to cause it to irreversibly move towards its 
braking position. 
Also in the second stage of the quick service of FIG. 3, slide 64, under 
the influence of brake pipe pressure, moves off spring cage 60 and comes 
into contact with the brake cylinder inlet valve 76 closing off passage 
74, and thereby disconnecting the brake cylinder passage 70 from the 
exhaust passage 68 without opening the valve 76. With continued upward 
movement of the service piston 12, the quick service inlet valve 40 
continues to move up forcing slide 64 to open brake cylinder valve 76 
connecting the auxiliary reservoir passage 80 to the brake cylinder 
passage 70 as illustrated in FIG. 4. 
A valve constructed according to the embodiments of FIGS. 1-4 has been 
tested and has shown an insensitivity or resistance to vertical shocks up 
to 15 Gs for residual pulse durations of 4-6 milliseconds. Tests on a 75 
car test rack indicates no loss of transmission time at pressures from 70 
to 90 psi of brake pipe. Thus, the use of a smaller restriction of 54 
during a first small portion of the travel during the opening of the quick 
service inlet valve 40 does not affect the transmission time or the 
response of the control valve to a brake pipe pressure while providing 
insensitivity and stability to vibration induced motion of the service 
piston 12. The increased cross-section 54 may be produced on existing 
equipment by adding a cap to the operator 46. Although two different 
cross-sections or restrictions have been shown for operator 46 as portion 
54 and 56, three different cross-sections may be used such that there 
would be a transition stage between 54 and 56. In that 54 and 56 are both 
in the bore 58 during some portion of their travel simultaneously, these 
restrictions are in series fluidically. The flow through the bore 58 is 
defined by the smallest flow rate of the two restrictions. 
The connections of the two restrictions in parallel fluidically is 
illustrated in a second embodiment of FIGS. 5-7. Only those portions of 
the operator 46 to be modified to provide the two restrictions are shown. 
The actuator 46 includes the first portion 54 having the same dimension as 
the first portion in FIGS. 1-4 to define the first restriction having a 
rate of flow sufficient to reduce the brake pipe pressure in chamber 14 
alone to cause the piston 14 to assume a braking position. The second 
restriction at the second rate of flow is defined by a passage 105 in the 
operator 46 which connects a port 110 adjacent to the top of the operator 
46 with a lower port 108 opening into bore 58. The brake pipe pressure in 
chamber 14 is connected to the bore 58 by port 106 below the guide 48. As 
distinguished from FIG. 1, the guide 48 is solid and does not include the 
passage 52. The range of positions of the piston 12 that the first 
restriction is operative is defined by the distance that the port 110 is 
from the end of the operator 46. If a passage 52 is provided in the guide 
48 in the second embodiment, the port 106 would be eliminated and the port 
108 and 110 would be the only ports connected to the internal passage 105. 
In the charging lap position of FIG. 5, the quick service inlet valve 42 is 
closed and port 110 is blocked. During a first quick service range of 
travel of the piston 12 as illustrated in FIG. 6, the quick service inlet 
valve 40 is opened and the port 110 is closed. Thus the flow from the 
brake pipe chamber 14 to the quick service chamber 44 is defined by the 
first restriction defined by the first portion 54 and bore 58. In the 
second stage of quick service, as illustrated in FIG. 7, the service 
piston 12 is in its second range of positions wherein the port 110 is out 
of the bore 58 and completely opened. This allows flow of the brake pipe 
from chamber 14 to the quick service chamber 44 at a rate defined by 
passage 105 and ports 106, 108 and 110. Since port 110 is in effect a 
spool valve, it offers a third range or transition as it slowly becomes 
unblocked as it leaves the bore 58. This would increase the reaction of 
the service piston 12 to a service reduction of the brake pipe pressure 
without adversely affecting the stability or insensitivity to vibration 
induced motions of the service piston 12. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, and is not to be taken by way of 
limitation. The spirit and scope of the present invention are to be 
limited only by the terms of the appended claims.