Vent valve device having disabling means

A railway car vent valve device having a bleed valve that is selectively operable to disable the vent valve device during a single car test procedure in which the service stability of the car control valve is checked. The bleed valve is automatically reset when the car brake pipe pressure drops below a predetermined value, such as occurs when the single car test apparatus is disconnected from the car brake pipe following completion of the single car test procedure.

BACKGROUND OF THE INVENTION 
This invention relates to vent valve devices and particularly to a means 
for temporarily disabling a vent valve device when conducting a single car 
test in accordance with the new single car test procedure specified by the 
A.A.R. (Association of American Railroads) for checking the general 
condition of the brake system of "in date" railway freight cars and cars 
having undergone "periodic repairs". A single car test device enables this 
test procedure to be accomplished without removal of any of the air brake 
components from the car. 
In one phase of this test procedure, referred to as the service stability 
test, the car control valve is checked to assure that it does not go to 
emergency during a service rate of reduction of brake pipe pressure. 
Typically, this test was performed satisfactorily without having to 
isolate the car vent valve device, when equipped with such. Recently, a 
revised single car test procedure was instituted, however, for carrying 
out the service stability test for control valves on long cars having over 
75 feet of brake pipe. Essentially this revision of the test procedure 
requires a faster rate of brake pipe pressure reduction, which causes the 
car vent valve device to fire. In order to prevent the vent valve from 
influencing the rate of brake pipe pressure reduction, when inadvertently 
actuated during the new single car test, the vent protector was removed 
and reinstalled in the vent valve exhaust port in its closed position to 
block the exhaust of brake pipe pressure. In the industry standard #8 and 
KM-2 vent valves, this proved to be an effective means of preventing an 
actuated vent valve from dumping brake pipe pressure and thereby adversely 
affecting the service stability test. 
In attempting to employ this same procedure with the recently developed VX 
Vent Valve disclosed in U.S. Pat. No. 4,974,911, it was found that even 
with the vent valve exhaust port plugged, a sudden 1 psi drop in brake 
pipe pressure still occurs, due to the particular design of the exhaust 
valve diaphragm causing relatively high volumetric displacement when the 
vent valve is fired. While this brake pipe pressure drop is beneficial in 
terms of transmitting an emergency application in actual operation, it 
adversely affects the control valve stability during the new service 
stability test. 
SUMMARY OF THE INVENTION 
In accordance with the foregoing, it is the object of the present invention 
to provide a means of selectively disabling a vent valve device that is 
low in cost, reliable in operation, and requires no tools to activate. 
Another object of the invention is to provide a vent valve disabling 
mechanism that is automatically reset when brake pipe pressure is reduced 
below a predetermined value. 
Briefly, these objectives are achieved in a vent valve device for locally 
venting a railway car brake pipe when an emergency rate of reduction of 
the fluid pressure carried in the brake pipe is initiated comprising a 
housing having an inlet port to which the brake pipe is connected, a vent 
port, a first chamber connected to the inlet port, and a second chamber, 
flow restrictor means between the first and second chambers for 
controlling the rate at which fluid pressure is released from said second 
chamber in response to a reduction of said brake pipe pressure to thereby 
establish a predetermined pressure differential between said first and 
second chambers when said brake pipe pressure is reduced at an emergency 
rate, piston valve means for establishing fluid pressure communication 
between the inlet port and vent port in accordance with a predetermined 
pressure differential being established between the first and second 
chambers and selectively operable disabling means for releasing fluid 
under pressure from said second chamber in parallel with said flow 
restrictor means to prevent such predetermined pressure differential 
between the first and second chambers from being established during the 
single car test procedure.

DESCRIPTION AND OPERATION 
Vent valve device 1 comprises preferably a die cast housing including a 
body portion 2 and a cover portion 3 that closes an opening at one end of 
body portion 2 through which the majority of the valve components may be 
installed. Cover portion 3 is held in place by bolts 5 and, in turn, 
retains a pair of diaphragm clamping plates 6, 7 in place against a 
shoulder 8 of body portion 2. A control piston 9 in the form of an 
elastomeric diaphragm member is clamped at its outer periphery between 
clamping plates 6, 7 and a vent valve piston 10 in the form of a similar 
elastomeric diaphragm member is clamped at its outer periphery between 
clamping plate 7 and cover portion 3. 
Formed between piston members 9 and 10 is a pilot chamber 11, the bounds of 
which are delineated by clamping plate 7. On the upper side of diaphragm 
member 10 opposite pilot chamber 11 is a control chamber 12 delineated by 
clamping plate 6 and body portion 2. On the under side of diaphragm member 
10 opposite pilot chamber 11 is an actuating chamber 13 delineated by 
cover portion 3 and the outer periphery of an annular sealing bead 14 of 
diaphragm member 10 that, in conjunction with a seat 15 formed on cover 
portion 3, constitutes an exhaust valve 16. A vent port 17 is formed in 
cover portion 3 at a location within the bounds of annular sealing bead 14 
and is fit with a vent protector 18. 
Control piston 9 is fixed at its midpoint to a guide stem 19 that is 
disposed in a bore 20 formed in a projection 21 of body portion 2. One end 
22 of stem 19 projects through bore 20 for operating a pilot valve 23 
comprising a movable valve cartridge 24 that is disposed in a counterbore 
25 of bore 20. Carried by valve cartridge 24 is a valve element 26 having 
an annular sealing bead 27 that is engageable with a valve seat 28 
provided by the projecting end 22 of stem 19. Compressed in counterbore 25 
between valve member 24 and a threaded plug 29 that closes counterbore 25 
is a spring 30. 
An outturned flange 31 of stem 19 is adapted to engage a stop 32 provided 
by projection 21 to establish the upwardmost position of diaphragm member 
9. A spring 33 is positioned between diaphragm members 9 and 10 in order 
to bias diaphragm member 9 toward its upwardmost position, while biasing 
diaphragm member 10 in the opposite direction to a position in which 
sealing bead 14 of exhaust valve 16 is engaged with its seat 15. 
The length of stem 19 is such that when flange 31 of stem 19 is engaged 
with stop 32, end 22 of stem 19 hold valve member 24 of pilot valve 23 a 
predetermined distance X away from a stop 34 formed at the base of 
counterbore 25. In this position, spring 30 is effective to provide a 
force sufficient to assure positive engagement of sealing bead 27 with 
seat 28, while concurrently stop 32 limits the potentially high fluid 
pressure forces acting on diaphragm member 9 to a value corresponding to 
the load of spring 30, to thereby prevent undue wear and/or damage to 
sealing bead 27. 
An inturned flange 35 of clamping plate 7 provides a seat 36 with which an 
annular sealing bead 37 on the under side of diaphragm member 9 is 
engageable, seat 36 and sealing bead 37 constituting a cut-off valve 38. 
When diaphragm member 9 is in its upwardmost position, sealing bead 37 is 
displaced from seat 36 a distance Y that is greater than the distance X 
that valve member 24 is displaced from its stop 34. 
Adapted to be connected to a branch pipe of the train brake pipe by a pipe 
flange (not shown) is a port 40 that is communicated with pilot chamber 11 
via a passage 41 and with actuating chamber 13 via a passage 42. 
Extending through guide stem 19 is a central passage 43 that communicates 
pilot chamber 11 with an exhaust passage 44 via pilot valve 23. A 
"breather" choke 45 is preferably provided in piston member 9, as shown, 
but may be alternatively located in clamping plate 6 in order to provide a 
restricted flow communication between control chamber 12 and brake pipe 
port 40. The restriction provided by choke 45 prevents the air in control 
chamber 12 from being reduced at the same rate as brake pipe pressure is 
reduced in pilot chamber 11. The size of this choke restriction is chosen 
so that the "breathing" of control chamber air via this choke will prevent 
a pressure differential across pilot piston 38 sufficient to open pilot 
valve 23, except in response to an emergency rate of reduction of brake 
pipe pressure. 
Affixed to the vent valve body portion 2 is a bleed valve device 60 having 
a square-shaped plug member 61 in which is formed a blind bore 62. A 
mounting hole 63 is drilled or otherwise formed in the vent valve body 
portion in the area of control chamber 12 to receive plug member 61. A 
threaded end 64 of plug member 61 is inserted through hole 63 from the 
chamber 12. A clamp nut 65 is threaded onto the threaded end 64 to draw a 
shoulder 66 of plug member 61 up tight against the inside surface of body 
portion 2, as the clamp nut is tightened against the outer surface of body 
portion 2. A seal ring 67 is provided between the clamp nut 65 and outer 
housing surface, which preferably is spot faced to provide a flat on the 
generally cylindrical surface of body portion 2, against which seal ring 
67 is compressed to prevent the escape of air from chamber 12 via the 
bleed valve mounting hole. 
Operably disposed within blind bore 62 is a piston valve 68 having an 
actuating stem 69 that projects through an opening 70 in clamp nut 65. 
Fitted on the projecting end of actuating stem 69 is an O-ring 71 and 
washer 72. A hole 73 in stem 69 receives a pull ring 74 that retains 
washer 72 on stem 69, while at the same time providing the means by which 
bleed valve device 60 may be manually actuated. Retaining washer 72 
provides a bearing surface by means of which O-ring 71 is clamped against 
a recess 75 surrounding opening 70 in clamp nut 65 to seal bore 62 from 
the elements of the environment in the de-actuated condition of bleed 
valve device 60. 
A spring 76 is disposed in bore 62 between clamp nut 65 and the head 77 of 
piston valve 68 to normally maintain piston valve 68 in a cutoff position 
in which a pair of O-rings 78, 79 on head 77 are located on opposite sides 
of a radial inlet passage 80 in body portion 61. A central passage 81 in 
actuating stem 69 opens at one end into an actuating chamber 82 formed 
between head 77 and the end of blind bore 62, while the other end of 
central passage 81 is connected by an orifice restriction 83 to the 
surface of stem 69 on the side of O-ring 71 opposite washer 72. A shoulder 
84 on stem 69 provides a stop that engages clamp nut 65 at opening 70 in 
the actuated position of piston valve 68. 
It will be understood that prior to charging, i.e., in the absence of any 
air pressure at port 40 of vent valve device 1, spring 33 establishes 
closure of vent valve 16 by reason of its biasing action on vent valve 
piston 10, while at the same time urging control piston 9 in an upward 
direction. The opposing force of spring 30, however, being greater than 
that of spring 33, forces pilot valve member 24 to move distance X into 
engagement with stop 34. This, in turn, forces flange 31 of stem 19 away 
from stop 32. Once valve member 24 engages stop 34, spring 30 becomes 
caged and, in effect, supports the upward-acting force of spring 33 on 
piston member 9. Consequently, piston member 9 is positioned so that 
flange 31 is spaced from stop 32 a distance X. Since distance Y is greater 
than distance X, as previously explained, sealing bead 37 of cut-off valve 
38 will be disengaged from its seat 36 to assure that cut-off valve 38 
remains open to accommodate subsequent charging of the vent valve device 
1, as now explained. 
During charging in normal service operation of the train, compressed air 
from the train brake pipe is registered at vent valve port 40, from where 
this air is directed via passage 42 to actuating chamber 13, via passage 
41 to pilot chamber 11, and via choke 45 to control chamber 12. With 
cut-off valve 38 open, exhaust valve 16 and pilot valve 23 closed, as 
above explained, pressure develops in actuating chamber 13 and pilot 
chamber 11 in accordance with the pressure carried in the train brake 
pipe. The resultant differential force on vent valve piston 10 due to its 
differential effective area reinforces spring 33 to maintain exhaust valve 
16 closed. With bleed valve 60 in its cutoff position, the air in pilot 
chamber 11, in turn, charges control chamber 12 at a restricted rate via 
choke 45 to thereby establish an upward-acting pressure differential 
across control piston 9 which, in conjunction with the force of spring 33, 
moves control piston 9 upwardly through distance X until flange 31 engages 
stop 32. As this movement takes place, stem 19 forces valve member 24 off 
of its stop 34, further compressing spring 30. With the charging pressure 
forces on piston member 9 thus supported by stop 32, spring 30 is 
effective to establish a limited sealing force on sealing bead 28. It will 
be appreciated, therefore, that the potentially high forces capable of 
being developed on control piston 9 during charging are isolated from 
valve element 26 and particularly from sealing bead 27, thus protecting 
sealing bead 27 from premature wear and/or damage. 
When charging is complete, the pressures effective in pilot chamber 11 and 
control chamber 12 equalize, it being understood that bleed valve 60 is 
normally in its de-actuated position in which venting of control chamber 
12 is cut off. Control piston 9 continues to be supported by stop 34, 
since the force of spring 30 is insufficient to overcome the combined 
force of spring 33 and the pressure force on control piston 9 due to its 
differential pressure area. 
During a service brake application, brake pipe pressure is reduced at a 
service rate, in a well-known manner, such reduction being registered at 
port 40 and consequently in pilot chamber 11. The pressure in control 
chamber 12 is reduced with the brake pipe pressure reduction in pilot 
chamber 11, but at a slower rate due to the restriction of choke 45, 
thereby creating a downward-acting pressure differential across control 
piston 9. While this pressure differential will vary with the actual 
service rate of reduction of brake pipe pressure, a maximum pressure 
differential will develop in response to a full service brake application. 
The resultant maximum differential pressure force acting downward on 
control piston 9 combined with the force of spring 30 will only be 
sufficient to deflect control piston 9 in a downward direction a distance 
X, since at this point valve member 24 picks up stop 34, thereby caging 
spring 30. With spring 30 caged and thus ineffective to exert a force on 
control piston 9, the control piston is stabilized against further 
downward deflection. Accordingly, closure of pilot valve 23 is maintained 
by continued engagement of sealing bead 27 of valve element 26 with seat 
28. The differential area of vent valve piston 10 subject to brake pipe 
pressure in chambers 11 and 13 is such a to maintain closure of vent valve 
16 by reason of sealing bead 14 having engagement with seat 15, so long as 
closure of pilot valve 26 is maintained, as above explained. 
During an emergency brake application, brake pipe pressure is reduced at an 
emergency rate that is greater than the aforementioned service rate, so as 
to produce a pressure differential across piston member 9 that is greater 
than the pressure differential resulting from a service rate of reduction 
of brake pipe pressure. The resultant downward-acting force on piston 
member 9 is sufficiently greater than the force created during a service 
brake application, as to overcome the loss of force resulting from the 
caging of spring 30 when control piston 9 has been deflected distance X. 
Consequently, control piston 9 continues to be deflected in a downward 
direction beyond distance X, thereby pulling seat 28 formed at the end of 
guide stem 19 away from sealing bead 27 of valve element 26, to thereby 
open pilot valve 23. As the pilot valve opens, air is vented directly from 
chamber 11 at an unrestricted rate to encourage continued downward 
deflection of control piston 9. As this downward deflection of control 
piston 9 continues through distance Y, control piston 9 assumes its 
emergency position in which sealing bead 37 engages seat 36 to close 
cut-off valve 38 and thereby isolate pilot chamber 11 from port 40 and the 
train brake pipe. By isolating pilot chamber 11 from the brake pipe, the 
air in the relatively small volume of pilot chamber 11 is vented quickly 
to accelerate the reduction of pressure in pilot chamber 11 acting on vent 
valve piston 10. This establishes a high pressure differential between 
pilot chamber air effective above vent valve piston 10 and actuating 
chamber air acting on the underside of vent valve piston 10, to overcome 
the bias force of spring 33 and deflect vent valve piston 10 in an upward 
direction. 
Immediately upon such upward deflection of vent valve piston 10, exhaust 
valve 16 is opened by disengagement of sealing bead 14 from seat 15, 
thereby exposing the entire area of the underside of vent valve piston 10 
to brake pipe pressure to positively establish and maintain exhaust valve 
16 fully open. Accordingly, a local venting of brake pipe pressure is 
provided from port 40 to atmosphere via passage 42, actuating chamber 13, 
exhaust valve 16, vent port 17 and vent protector 18 to supplement the 
brake pipe pressure reduction initiated via the train brake pipe in order 
to hasten the emergency application through the train. 
Following closure of cut-off valve 38, the pressure effective in control 
chamber 12 will continue to maintain control piston 9 in its downwardmost 
position in which pilot valve 23 is held open, while the control chamber 
pressure blows down via choke 45. Since the size of choke 45 is chosen to 
establish a predetermined pressure differential across control piston 9 
during an emergency brake application sufficient to force the control 
piston to its emergency position, it will be apparent that the volume of 
control chamber 12 is selected in accordance with the chosen size of choke 
45, such that the time required to blow down control chamber 12 
corresponds to the time required to assure that the train comes to a 
complete halt. 
Whenever the brake pipe pressure has been exhausted, spring 33 becomes 
effective to reset vent valve piston 10 and close exhaust valve 16. 
However, until the "blowdown" period has expired, the open pilot valve 
will maintain pilot chamber 11 vented, so that any attempt to recharge 
brake pipe pressure prematurely will result in the air under vent valve 
piston 10 causing exhaust valve 16 to open. Thus, any air supplied to the 
brake pipe is simply bypassed to atmosphere via vent protector 18. When 
the control chamber pressure has blown down to approximately 3 psi, 
control piston 9 is forced in an upward direction to open cut-off valve 
38, but not sufficiently far to effect closure of pilot valve 23. During 
this final "blowdown" period, any air supplied to the brake pipe is vented 
via port 40, passage 41, the open cut-off valve, pilot chamber 11, central 
passage 43 in stem 19, the open pilot valve 23, and exhaust passage 44. 
Following expiration of the "blowdown" period required to exhaust control 
chamber 12 via choke 45, spring 33 will be effective to move piston member 
9 in an upward direction sufficiently to not only open cut-off valve 38, 
but to also close pilot valve 23 by engagement of seat 28 with sealing 
bead 27 of valve element 26. Vent valve device 1 is thus reset to 
accommodate charging of the brake pipe, as previously explained, with 
flange 31 being spaced from stop 32 a distance X. 
Having explained the basic operation of vent valve device 1, the manner in 
which this vent valve device 1 may be selectively disabled, in accordance 
with the present invention, will now be explained. As hereinbefore 
mentioned, disabling vent valve device 1 when performing the single car 
test procedure is essential to prevent the vent valve from operating 
during the service stability test, due to the more stringent standards 
imposed by the newly mandated A.A.R. test code. In particular, a higher 
rate of reduction of brake pipe pressure is required by this new test 
code, at which rate the car control valve must remain stable as an 
indication of its ability to distinguish between service and emergency 
rates in actual service, particularly when employed in the longer modern 
railway cars being placed in service today. 
In performing the single car test, the test apparatus is connected by an 
outlet hose and hose coupling to the railway car brake pipe hose in the 
usual, well-known manner. The regulating valve of the single car test 
apparatus is then placed in handle position #1 to fully charge the car 
brake pipe to the desired test operating pressure. As the car brake pipe 
becomes charged, air is directed from vent valve port 40 to actuating 
chamber 13 via passage 42, to pilot chamber 11 via passage 41, and to 
control chamber 12 via choke 45, as previously explained relative to 
charging the train brake pipe during normal service operation. Bleed valve 
60 is assumed to be in its normal de-actuated position, as shown in FIG. 
2a. With cut-off valve 38 open, exhaust valve 16 and pilot valve 23 
closed, as previously explained, pressure develops in actuating chamber 13 
and pilot chamber 11, in accordance with the pressure to which the car 
brake pipe is charged by the single car test apparatus. The resultant 
differential force on vent valve piston 10 due to its differential 
effective area reinforces spring 33 to maintain exhaust valve 16 closed. 
The air in pilot chamber 11, in turn, charges control chamber 12 at a 
restricted rate via choke 45 to thereby establish an upward-acting 
pressure differential across control piston 9 which, in conjunction with 
the force of spring 33, moves control piston 9 upwardly through distance X 
until flange 31 engages stop 32. As this movement takes place, the end 22 
of stem 19 engages valve member 24 to isolate the pilot chamber pressure 
from atmosphere. 
Following completion of this charging and prior to initiating the service 
stability test, pull ring 74 should be manually pulled to open bleed valve 
60. In pulling ring 74, actuating stem 69 is shifted axially until stop 
shoulder 84 engages clamp nut 65. In this open or actuated position, as 
shown in FIG. 2b, O-ring 78 carried on piston head 77 is shifted across 
radial passage 80 in body 62 to allow the air in control chamber 12 to 
flow into bleed valve actuating chamber 82 and thence to atmosphere via 
passage 81 and bleed orifice 83, which is open to atmosphere in this 
actuated position of stem 69. 
Due to the restricted flow capacity of bleed orifice 83, pressure builds up 
in actuating chamber 82 and acts on the face of piston head 77 to maintain 
stem 69 in this actuated position against the closure force of spring 76, 
which is compressed between piston head 77 and clamp nut 65. Thus, the 
manual force on pull ring 70 may be released after only a momentary pull 
and the bleed valve will remain in its actuated position, as shown in FIG. 
2b, until the pressure in chamber 12 and consequently in chamber 82 blows 
down to a predetermined level. 
In this manner, the air in control chamber 12 is released at a controlled 
rate via bleed orifice 83. Until the service stability test is initiated, 
however, the air supplied via choke 45 at the appropriate test pressure 
will be sufficient to maintain control chamber 12 charged against the 
bleed of control chamber pressure via orifice 83. When the service 
stability test is initiated by moving the single car test apparatus 
regulating valve handle to a position in which a reduction of brake pipe 
pressure occurs at the brake pipe reduction rate specified in the new, 
A.A.R. mandated single car test, this bleed of control chamber pressure 
via orifice 83 will supplement the internal "breathing" of control chamber 
pressure with brake pipe pressure via choke 45. Accordingly, the brake 
pipe pressure reduction effective in pilot chamber 11 will be incapable of 
creating a pressure differential across pilot piston 9 sufficient to cause 
the pilot piston to open pilot valve 23. In this manner, the vent valve 
device 1 is disabled to prevent its inadvertent and undesirable operation 
during this service stability test. 
Following completion of the service stability test, and re-charge of the 
car brake pipe preparatory to conducting further tests in accordance with 
the single car test procedure, bleed valve 60 should be reset. This is 
accomplished by pushing actuating stem 69 back to its normal closed 
position, as shown in FIG. 2a, in which O-rings 78 and 79 isolate radial 
passage 80 from bleed valve actuating chamber 82. From the time O-ring 78 
crosses radial passage 80 until seal ring 71 engages recess 75 in clamp 
nut 65, bleed orifice 83 remains open to atmosphere to maintain actuating 
chamber 82 vented. This allows any residual pressure in chamber 82 to be 
dissipated, thereby preventing any dashpot effect from occurring, which 
would otherwise prevent positive reset of piston valve 68 to its cutt-off 
position. In thus terminating the supplemental "breathing" of control 
chamber pressure via bleed orifice 83, vent valve device 1 is conditioned 
for normal service, as hereinbefore explained. 
In the event a tester performing the single car test fails, for whatever 
reason, to manually reset bleed valve 60 in accordance with the prescribed 
practice, the bleed valve will be automatically reset any time brake pipe 
pressure is reduced blow a predetermined value of approximately 55 psi. 
Normally this would occur in the course of conducting subsequent tests, 
but even in failing to perform such subsequent tests, would nevertheless 
occur when the brake pipe pressure is dumped at the time of removing the 
single car test device from its coupling with the car brake pipe. In 
either case, spring 76 is effective when the brake pipe pressure falls 
below this predetermined value of approximately 55 psi to force piston 
valve 68 to its normal closed position, as shown in FIG. 2a. In this 
manner, the bleed valve is assured of being closed when the car is put 
back into service following completion of the single car test. 
It should be noted that spring 76, in resetting bleed valve 60 when brake 
pipe pressure drops below approximately 55 psi, also prevents accidental 
actuation of the bleed valve, in that a positive manual force of 
approximately six pounds is required to actuate piston valve 68. 
It should also be noted that the opening of bleed valve 60 will have no 
affect on the brake pipe pressure reduction rate during the control valve 
stability test, since the brake pipe pressure is lower than the vent valve 
control chamber pressure during the test and therefore does not feed back 
into the control chamber 12 to support the exhaust at the bleed choke. 
In accordance with the foregoing, it will be appreciated that the vent 
valve bleed valve 60 effectively prevents the vent valve device 1 from 
being inadvertently actuated during the control valve service stability 
test; does not influence the brake pipe reduction rate required for 
carrying out the stability test; is automatically re-settable; and is not 
susceptible to accidental operation during normal service.