Note: Descriptions are shown in the official language in which they were submitted.
CA 02965468 2017-04-21
WO 2016/064422
PCT/US2014/062217
TITLE
BRAKE CYLINDER MAINTAINING VALVE WITH IMPROVED
PRESSURE REGULATION
1. FIELD OF THE INVENTION
[0001] The present invention relates to brake cylinder maintaining
systems and, more
particularly, to a combined brake cylinder maintaining check valve and quick
service limiting
valve.
2. DESCRIPTION OF THE RELATED ART
[0002] Control valves are used in freight car braking systems to supply
air pressure to
the brake cylinders of a freight car. If the plumbing between the control
valve and the freight
car has a leak or there is a leak in the brake cylinder itself, however, then
the brake cylinder
will not maintain the original set pressure. One approach for addressing this
problem is to
have a valve that maintains the brake cylinder pressure. When the pressure in
the brake
cylinder drops below its original set pressure, a brake cylinder maintaining
valve may feed
brake pipe pressure through a choke to replenish and maintain the brake
cylinder pressure up
to a designed point. For example, one conventional brake cylinder maintaining
(BCM)
system for the service portion of a AAR-type control valve includes a BCM
charging check
valve to reduce brake cylinder pressure by an amount equal to the quick
service limiting
valve (8-12 psi) plus an amount equal to the sum of the hysteresis, part to
part variations, and
environmental variations, so that the resulting brake cylinder reference
pressure acting on the
BCM control side of the diaphragm of the quick service limiting valve plus the
quick service
limiting valve spring setting (8-12 psi) will always be less than the
target/actual brake
cylinder pressure.
[0003] Because of the aforementioned sources of variation, it is
necessary to set the
BCM charging check valve cracking value at 16 to 18 psi. This results in an
undesired loss
of efficiency of BCM pressure regulation, as the actual brake cylinder
pressure would have to
leak an amount equal to or greater than the 4-10 psi offset of the BCM
charging check before
the BCM valve will open to replenish brake cylinder pressure. As a result, a
more precise
BCM regulation pressure is needed, with a smaller pressure offset, for more
accurate and
improved brake cylinder maintaining.
BRIEF SUMMARY OF THE INVENTION
[0004] The present invention comprises a brake cylinder maintaining (BCM)
system
having low hysteresis, thereby providing for more precise BCM regulation
pressure and
smaller pressure offset. The system includes a BCM charging check valve that
is integrated
1
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
into a quick service limiting valve (QSLV) valve. By combining these
functions, significant
sources of part to part and environmental variations are eliminated and more
precise control
of the BCM valve is possible. The combined quick service check valve and brake
cylinder
maintaining valve has a first seat for selectively allowing communication
between a brake
cylinder pressure chamber and a brake cylinder maintaining pressure chamber
and a second
seat for selecting allowing communication between the brake cylinder pressure
chamber and
a quick service pressure chamber. The first seat is normally closed and opens
in response to a
first predetermined amount of pressurization of the brake cylinder pressure
chamber and the
second seat is normally open and closes in response to a second predetermined
amount of
pressurization of the brake cylinder pressure chamber. A diaphragm separates
the brake
cylinder maintaining pressure chamber and the brake cylinder pressure chamber
so that
compression of the diaphragm toward the brake cylinder maintaining pressure
chamber
closes the second seat to prevent communication between the brake cylinder
pressure
chamber and the quick service pressure chamber. If there is additional
compression of the
diaphragm toward the brake cylinder maintaining pressure chamber opens the
first seat to
allow communication between the brake cylinder pressure chamber and the brake
cylinder
maintaining pressure chamber. The diaphragm is biased from the brake cylinder
maintaining
pressure chamber toward the brake cylinder pressure chamber so that the first
seat is closed
and the second seat is open when the pressure in the brake cylinder pressure
chamber is less
than the first predetermined amount. Preferably, the first predetermined
amount is about 10
psi.
[0005] A first embodiment of the invention comprises a valve having a a
needle
passing through the diaphragm and having a channel therethrough that is in
communication
with the brake cylinder maintaining pressure chamber at one end and is open on
the opposing
end. The valve further includes a check positioned in the quick service
pressure chamber that
is biased toward the needle to close the open end of the channel of the
needle. Movement of
the diaphragm and needle toward the brake cylinder maintaining pressure
chamber allows the
check to move and close the second seat, thereby preventing communication
between the
brake cylinder pressure chamber and the quick service pressure chamber.
Further movement
of the diaphragm toward the brake cylinder maintaining pressure chamber will
separate the
open end of the channel of the needle from the check and bring the open end of
the channel
into communication with the brake cylinder pressure chamber, thereby opening
the first seat
and allowing communication between the brake cylinder pressure chamber and the
brake
cylinder maintaining pressure chamber.
2
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
[0006] In another embodiment of the invention, the valve includes a first
stem passing
through the diaphragm and defining a passageway between the brake cylinder
maintaining
pressure chamber and the brake cylinder pressure chamber and a valve head
positioned on an
end of the valve stem for movement into and out of engagement with the
diaphragm, thereby
closing or opening the passageway, respectively. A second stem having a post
associated
with the first stem that extends through the brake cylinder pressure chamber
into the quick
service pressure chamber. A check is positioned in the quick service pressure
chamber and
biased toward the post of the second stem so that the check may close the
second seat,
thereby closing communication between the brake cylinder pressure chamber and
the quick
service pressure chamber, when the post moves a predetermined distance toward
the brake
cylinder maintaining pressure chamber. If the diaphragm moves further, the
valve head
separates from the diaphragm, thereby opening the first seat and allowing
communication
between the brake cylinder pressure chamber and the brake cylinder maintaining
pressure
chamber.
[0007] In yet another embodiment of the invention, the valve includes a
guide
positioned in the diaphragm and a stem having a taper passing through the
guide to define a
passageway between the brake cylinder maintaining pressure chamber and the
brake cylinder
pressure chamber. An 0-ring engages the taper of the valve step and closing
the passageway
when the first seat is closed.
[0008] In a further embodiment of the invention, the valve includes a
diaphragm
having a hole formed therethrough that is sealingly engaged by an end of a
valve stem
positioned in the brake cylinder pressure chamber for selective opening and
closing of the
hole in the diaphragm. The opposing end of the valve stem engages a check
positioned in the
quick service pressure chamber and biased toward the valve stem so that the
check may close
the second seat when the stem moves a predetermined distance toward the brake
cylinder
maintaining pressure chamber. The valve stem is biased toward the diaphragm by
a spring
positioned in the brake cylinder pressure chamber.
[0009] In an additional embodiment of the invention, the valve includes a
first stem
engaged with one side of the diaphragm and extending through the brake
cylinder
maintaining pressure chamber into a portion of the brake cylinder pressure
chamber to define
a passageway therebetween, wherein the first stem engages a check that is
biased to close the
passageway if the stem is moved out of the portion of the brake cylinder
pressure chamber.
The valve also includes a second stem engaged with the opposing side of the
diaphragm and
extending through a second portion of the brake cylinder pressure into the
quick service
3
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
pressure chamber to define a second passageway extending between the brake
cylinder
pressure chamber and the quick service pressure chamber, wherein the second
stem engages a
second check that is biased to close the second passageway if the second stem
is moved out
of the quick service pressure chamber.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0010] The present invention will be more fully understood and
appreciated by
reading the following Detailed Description in conjunction with the
accompanying drawings,
in which:
[0011] Fig. 1 is a cross-sectional view of a first embodiment of a
combined BCM
reference pressure charging check valve and quick service limiting valve
according to the
present invention;
[0012] Fig. 2 is a cross-sectional view of a second embodiment of a
combined BCM
reference pressure charging check valve and quick service limiting valve
according to the
present invention;
[0013] Fig. 3 is a cross-sectional view of a third embodiment of a
combined BCM
reference pressure charging check valve and quick service limiting valve
according to the
present invention;
[0014] Fig. 4 is a cross-sectional view of a fourth embodiment of a
combined BCM
reference pressure charging check valve and quick service limiting valve
according to the
present invention;
[0015] Fig. 5 is a cross-sectional view of a fifth embodiment of a
combined BCM
reference pressure charging check valve and quick service limiting valve
according to the
present invention;.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring now to the drawings, wherein like reference numerals
refer to like
parts throughout, there is seen in Fig. 1 a first embodiment of a brake
cylinder maintaining
valve 10 that integrates a quick service limiting valve and a BCM reference
pressure charging
check valve into a single unitary structure that cooperates to provide all of
the relevant
functions with more precise control that otherwise possible. Valve 10
comprises a check
valve assembly 12 having a nozzle 14 with a channel 16 formed therethrough
that is attached
to and extends through a quick service limiting valve (QSLV) diaphragm 18.
Nozzle 14
extends along a longitudinal axis through a brake cylinder pressure chamber 20
in an upper
portion of a bushing 22 and through a narrow passageway 24 that separates
brake cylinder
pressure chamber 20 from a quick service pressure chamber 26 defined in a
lower portion of
4
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
bushing 22. It should be recognized that the various chambers are in
communication with the
corresponding elements of a conventional braking system such that the pressure
in a
particular chamber reflects the pressure in the corresponding element of the
braking system.
For example, brake cylinder pressure chamber 20 is in open communication with
a brake
cylinder (not shown) so that the pressure in chamber 20 reflects the pressure
in the brake
cylinder.
[0017] Nozzle 14 extends through brake cylinder pressure chamber 20 and
into quick
service pressure chamber 26 to define a first seat A, which selectively
controls
communication between a BCM reference pressure chamber 28 positioned above
QSLV
diaphragm 18 and brake cylinder pressure chamber 20, as well as a second seat
B, which
selectively controls communication between quick service pressure chamber 26
and brake
cylinder pressure chamber 20. Seat A is formed between the end of nozzle 14
and a check 30
positioned in quick service pressure chamber 26 so that check 30 is in contact
with the end of
nozzle 14, seat A will be closed to seal off channel 16. A second seat B is
formed by a
clearance gap 32 between the outer surface of nozzle 14 and the interior of
passageway 24.
[0018] A QSLV spring 34 is positioned in a spring guide 36 and configured
to bias
QSLV diaphragm 18 and nozzle 14 downwardly so check valve 12 is closed at seat
A and
open at seat B when the pressure in brake cylinder pressure chamber 20 is less
than a nominal
amount, such as 10 psi. By contrast, check 30 in quick service pressure
chamber 26 is biased
longitudinally upward by a spring 38 to maintain engagement with the end of
nozzle 14 until
nozzle 14 withdraws from quick service pressure chamber 26 and check 30 is
biased
upwardly into engagement with a bead seat 40 surrounding the lower end of
passageway 24,
thereby closing seat B. As nozzle 14 continues to withdraw into brake cylinder
pressure
chamber 20, and thus away from bead seat 40 and the stationary check 30, seat
A is opened to
allow communication between brake cylinder pressure chamber 20 and BCM
reference
pressure chamber 28 via channel 16 in nozzle 14.
[0019] In a brake application, after preliminary quick service, quick
service pressure
chamber 26 will be pressurized by brake pipe pressure as in a conventional
braking system.
In valve 10, however, the brake pipe pressure in quick service pressure
chamber 26 will flow
through open seat B, thereby pressurizing brake cylinder pressure chamber 20
on the
underside of QSLV diaphragm 18 and thus pressurizing the brake cylinder which
is in open
communication with brake cylinder pressure chamber 20. When brake cylinder
pressure
chamber 20 under QSLV diaphragm 18 reaches a predetermined amount, such as
approximately 10 psi, diaphragm 18 and nozzle 14 move upward. Check 30 will
then be
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
biased upwardly by spring 38 and will close against bead seat 40 while nozzle
14 continues to
move upward, thereby severing the communication between brake pipe pressure in
quick
service pressure chamber 26 and brake cylinder pressure chamber 20 (and thus
the brake
cylinder). As brake cylinder pressure increases further, diaphragm 18 and
nozzle 14 will
continue to move upward so that nozzle 14 enters brake cylinder pressure
chamber 28, while
seat B remains closed and check 30 is stopped in the closed position by bead
seat 40, thereby
allowing nozzle 14 to disengage from check 30 and move into brake cylinder
pressure
chamber 20 while seat A opens. When seat A opens, brake cylinder pressure in
brake
cylinder pressure chamber 20 can then flow through nozzle 14 to the top side
of QSLV
diaphragm 18. Seat A closes when the sum of the pressure in BCM reference
pressure
chamber 28 acting over the upper area of diaphragm 18 plus the force provided
by QSLV
spring 34 is equal to or greater than the pressure in brake cylinder pressure
chamber 20 acting
on the underside of diaphragm 18. As a result, BCM reference pressure 28 is
almost
precisely the amount required for a zero-loss BCM function.
[0020] In a brakes applied position, QSLV diaphragm 18 goes to a lap
state, where
both seat A and seat B are closed. If there is a leak leading to the loss of
pressure in the brake
cylinder, the pressure in brake cylinder pressure chamber 20 on the underside
of QSLV
diaphragm 18 will be reduced and diaphragm 18 will move nozzle 14 downward,
thereby
pushing check 30 against the bias of spring 38 and opening seat B. As a
result, brake pipe
pressure may flow from quick service pressure chamber 26 through open seat B
to the brake
cylinder via brake cylinder pressure chamber 20 until a pressure balance is
restored across
QSLV diaphragm 18.
[0021] Additional embodiments, such as the second, third, fourth and
fifth
embodiments discussed below, may be structured to add a predefined amount of
hysteresis or
pressure offset to the BCM reference pressure to provide added valve
stability. For example,
in a second embodiment of a combined quick service check valve and brake
cylinder
maintaining valve 50, a normally closed check valve 52 is integrated into a
QSLV diaphragm
54 under a valve cover 56. Check valve 52 includes a first valve stem 58 that
passes through
a valve guide 60 positioned in an opening 62 in QSLV diaphragm 54. A valve
head 64
positioned on the lower side of QSLV diaphragm 54 defines a first seat A
between the edge
of valve head 64 and the lower side of QSLV diaphragm 54. Seat A allows for
selective
communication between a brake cylinder pressure chamber 66 positioned below
QSLV
diaphragm 54 and a BCM reference pressure chamber 68 positioned above QSLV
diaphragm
52 via a clearance gap 70 between valve guide 60 and valve stem 58. QSLV
diaphragm 52 is
6
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
biased downwardly by a QSLV spring 72 positioned in a spring guide 74 so that
seat A is
normally closed. First valve stem 58 is also biased by a spring 76 that
engages a retaining
ring 78 positioned at the upper end of valve stem 58 to hold valve head 64
into engagement
with QSLV diaphragm 52. As explained below, however, valve head 64 will
separate from
QSLV diaphragm 52 if first valve stem 58 moves upwardly distance D into
contact with
valve cover 56.
[0022] As further seen in Fig. 2, first valve stem 58 cooperates with a
second valve
stem 80 that is positioned in brake cylinder pressure chamber 60 and that
includes a post 82
extending through an passageway 84 into a quick service pressure chamber 86.
Post 82 is
moveable into engagement with a check 88 to define a second seat B. Check 88
is biased
upwardly against post 82 by a spring 90 and can move through a distance C
before engaging
a bead seat 92 and closing off passageway 84. Post 92 does not completely
occupy
passageway 84, thereby allowing for communication between quick service
pressure chamber
86 and brake cylinder pressure chamber 66 when check 88 has not closed
passageway 84.
Second seat B therefore allows for selective opening of communication between
quick
service pressure chamber 86 and brake cylinder pressure chamber 66 when post
92 has
opened seat B against the bias of spring 90 and for closing of communication
when post 92 is
withdrawn by the movement of second valve stem 80 to allow check 88 to be
biased into the
closed position by spring 90.
[0023] When a brake application is made, brake pipe pressure initially
flows from
quick service pressure chamber 86 through open valve seat B to the underside
of QSLV
diaphragm 54 and brake cylinder pressure chamber 66 (and thus the brake
cylinder). When
the brake cylinder pressure in brake cylinder pressure chamber 66 reaches a
threshold, e.g.,
nominally 10 psi, QSLV diaphragm 54 moves upward through distance C until
valve seat B
closes, thereby severing the communication between the brake pipe and the
brake cylinder.
As the brake cylinder pressure increases further, QSLV diaphragm 54 will
continue to move
axially upward against QSLV spring 72, closing gap D until valve stem 58 moves
into
contact with valve cover 56. Any further pressure increase in brake cylinder
pressure
chamber 66 will continue to move QSLV diaphragm 54 upward against the bias of
spring 72
as valve stem 58 is held stationary by valve cover 56, thereby opening seat A.
When seat A
is open, brake cylinder air can flow through the cylindrical clearance between
stem 58 of
valve 52 and a check valve bushing 94. Check valve seat A closes when the sum
of the BCM
reference pressure in BCM reference pressure chamber 68 acting over the upper
area of
QSLV diaphragm 54 plus the force of QSLV spring 72 is equal to or greater than
the brake
7
CA 02965468 2017-04-21
WO 2016/064422
PCT/US2014/062217
cylinder pressure in brake cylinder pressure chamber 66 acting on the
underside of diaphragm
54. In this arrangement, the reference pressure is equal to the brake cylinder
pressure minus
the QSLV setting (e.g., nominally 10 psi) minus the amount of the check valve
opening times
the QSLV spring rate K. This results in a definable pressure offset equal to:
Pressure Offset = [(height D- height C) * K]/(wetted area of the diaphragm)
[0024]
Referring to Fig. 3, another embodiment of a combined quick service check
valve and brake cylinder maintaining valve 100 has many of the same components
as valve
50, but instead of check valve 52, valve 100 includes a check valve seat A
that is defined by a
check valve 102 having a tapered cylindrical check valve stem 104 that passes
through a
check valve stem guide 106 in QSLV diaphragm 108 to define a cylindrical
clearance
therebetween. The cylindrical clearance is selectively opened and closed when
check valve
102 is moved upwardly so that an 0-ring is brought into sealing engagement
with the
cylindrical clearance. When check valve seat A is open, brake cylinder air
flows from a
brake cylinder pressure chamber 112 through the cylindrical clearance
positioned between
check valve stem 104 and check valve stem guide 106 and into a BCM reference
pressure
chamber 114 positioned on the top of QSLV diaphragm 108. Check valve 102
closes when
the reference pressure is sufficient to restore force balance as detailed
above. A second seat
B operates as discussed above with respect to system 50.
[0025]
Referring to Fig. 4, a further embodiment of a combined quick service check
valve and brake cylinder maintaining valve 120 comprises a check valve
assembly 122
housed in a brake cylinder pressure chamber 124 of a bushing 126 and sealed
against a
resilient QSLV diaphragm 128 positioned in a valve cover 130 above brake
cylinder pressure
chamber 124 to define a first seat A. QSLV diaphragm 128 is biased downwardly
by a
QSLV spring 132 positioned in a spring guide 134 within valve cover 130. Check
valve 122
is held in sealing engagement witht QSLV diaphragm 128 by a check valve spring
136 that is
also positioned in brake cylinder pressure chamber 124 of bushing 126. Check
valve 122 is
moveable upwardly through a distance D as QSLV diaphragm 128 until a shoulder
138 of
check valve stem 122 engages a retaining ring 140 positioned in the bore of
bushing 126.
When check valve stem 122 engages retaining ring 140 positioned in the bore of
bushing 126,
valve stem 122 and diaphragm 128 separate, thereby opening seat A. A passage
142 formed
through diaphragm 128 allows for communication between brake cylinder pressure
chamber
124 positioned below diaphragm 128 and a BCM reference pressure chamber 144
positioned
above diaphragm 128 when seat A is opened. Seat A is preferably formed by a
profiled
8
CA 02965468 2017-04-21
WO 2016/064422 PCT/US2014/062217
cylindrical seat surface 146 formed on the upper end of check valve 122 to
securely seal
against resilient QSLV diaphragm 128.
[0026] The opposing end of check valve 122 includes a post 148 extending
through
an internal passageway 150 and a bead seat 152 in the bore of bushing 126.
Post 148 further
extends into a quick service pressure chamber 154 in a lower portion of the
bore of bushing
126. Post 148, as in prior embodiments, provides for a clearance gap 156 with
passageway
150 and extends into quick service pressure chamber 154 to engage a check 158
that is biased
upwardly as in prior embodiments to define a second seat B. Check 158 can move
upwardly
a distance C before closing against bead seat 152, and thus closing clearance
gap 156 of
passageway 150. Seat B thus allows for communication between quick service
pressure
chamber 154 and brake cylinder pressure chamber 124 when post 148 has opened
seat B, and
closes communication between chambers 124 and 148 when post 148 is withdrawn
and check
158 closes against bead seat 152.
[0027] As brake cylinder pressure increases in system 120, QSLV diaphragm
128 is
biased against QSLV spring 132 by air pressure in brake pressure chamber 124.
As QSLV
diaphragm 128 is compressed upwardly, check valve 122 will move through
distance D until
shoulder 138 engages retaining ring 140. Any additional brake cylinder
pressure increases
will further compress QSLV diaphragm 128 against QSLV spring 132, thereby
opening seat
A as valve 122 can no longer move and will separate from diaphragm 128,
thereby opening
passage 142 at seat A. When check valve seat A is open, brake cylinder air may
flow from
brake pressure chamber 124 through open seat A, and then through passage 142
formed in
diaphragm 128, to reach BCM reference pressure chamber 144 positioned above
QSLV
diaphragm 128. Check valve 122 closes when the reference pressure is
sufficient to restore
force balance as detailed in the second embodiment above. Seat B operates as
explained
above with respect to prior embodiments.
[0028] In yet another embodiment of the present invention, a combined
quick service
check valve and brake cylinder maintaining valve 160 comprises a check valve
assembly 162
positioned in an upper portion 1 of a QSLV cap 166 and having a first seat A
formed from a
check 168 that is biased downwardly by a check valve spring 170 for selective
engagement
with a bead seat 172. Bead seat 172 encloses an annular passage 174 formed
through a
shoulder 176 in QSLV cap 166. Passage 174 permits communication between a
brake
cylinder pressure chamber 178 associated with upper portion 164 of cap 166 and
a BCM
reference pressure chamber associated with the lower portion 182 of cap 166.
Spring 170 is
biased so that seat A is normally in a closed position.
9
CA 02965468 2017-04-21
WO 2016/064422
PCT/US2014/062217
[0029] BCM reference pressure chamber 180 in lower portion 186 of cap 166
contains a QSLV spring 184 positioned in a spring guide 186 that engages a
QSLV
diaphragm 188 positioned in the lower side of BCM reference pressure chamber
180. A stem
190 associated with diaphragm 188 extends upwardly through BCM reference
pressure
chamber 180 and into passageway 174 so that movement of diaphragm 188 upwardly
against
the bias of spring 184 will cause post 190 to move through a distance D to
engage check 168
and open seat A. Distance D defines the amount of BCM pressure offset and is
controlled by
the length of check valve stem 190 and the distance to check valve 162.
[0030] A bushing 192 is positioned below diaphragm 188 and includes an
upper
portion defining a brake cylinder chamber 194 that is separated from a lower
portion defining
a quick service pressure chamber 196 by a narrow passageway 198. A stem 200
having a
lower post 202 is positioned in brake cylinder chamber 194 so that it engages
diaphragm 188
at its upper end and post 202 extends through passageway 198 into quick
service pressure
chamber 196. Quick service pressure chamber 196 includes a check 204 that is
moveable
through distance C to close of a second seat B, and thus passageway 198, so
that
communication between brake cylinder pressure chamber 194 and quick service
pressure
chamber 196 is also closed as discussed in prior embodiments.
[0031] As the brake cylinder pressure increases, QSLV spring 184
compresses until
distance D is zero. Additional increase of brake cylinder pressure will
further compresses
QSLV diaphragm 188 and spring 184, thereby opening check valve 162 at seat A.
When
check valve seat A is open, brake cylinder air flows through open seat A into
BCM reference
pressure chamber 180 on the top of QSLV diaphragm 188. Check valve 162 closes
when the
reference pressure is sufficient to restore force balance, as explained in the
other
embodiments above.
