Note: Descriptions are shown in the official language in which they were submitted.
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AIR DRYER FOR A BRAKE SYSTEM
This is a divisional of Application No. 2,636,637, filed July 7, 2008.
BACKGROUND AND SUMMARY OF THE DISCLOSURE
[0001] The
present invention relates generally to air dryers, and more specifically, to
an
air dryer for a brake system for vehicles.
[0002] Air
dryers employing membranes consisting of a permeable membrane capable of
blocking the passage of nitrogen and oxygen molecules, but allowing water
vapor
molecules to pass through, as described in U.S. Patents 6,719,825 and
5,525,143 amongst
many others. In one variation of the technology, the air to be dried passes
through the
center of the membrane element. The membrane permits the passage of the water
vapor to
the outside of the membrane, but prevents the passage of the air to the
outside of the
membrane, thereby drying the air. To work effectively, the outside of the
membrane must
be kept dry and at a lower pressure than the inside, creating the partial
pressure differential
to drive the water vapor out. This is done by providing some fraction of the
dry output air
as a counter flow sweep air across the outside of the membrane. The sweep air
can be
provided by sweep air orifice(s) connecting the dry air in the membrane air
dryer outlet to
the sweep air chamber surrounding the outside of the membrane. The orifices
control the
volume of sweep air, typically 10-20% of the dryer capacity and create a
pressure drop in
the sweep air volume. The sweep air and entrapped moisture are expelled to
atmosphere.
U.S. Patent 5,375,620 shows a self-adjusting flow metering device for the
sweep air.
[0003] The present disclosure is directed to an air dryer, for example,
for locomotives,
packaged to fit inside a reservoir. The air dryer is generally cylindrical
with a circular
mounting flange on one end, which bolts to a similar mounting flange welded to
the end of
the reservoir. This arrangement solves the problem of finding room for the air
dryer
between main reservoir #1 and #2 on a locomotive, protects the air dryer and
especially
the vulnerable membrane element from the very high ambient temperatures (as
high as
300 degrees F) during operation of the locomotive in tunnels; protects the air
dryer from
environmental hazards, like flying stone ballast; eliminates installation
piping, and
minimizes weight.
[0004] Such a
membrane air dryer includes a housing with an 'air inlet, an air outlet, a
liquid drain outlet; and a membrane separator having surfaces extending
between a first
and second ends of the membrane. A first passage in the housing is connected
to the air
inlet and air outlet at its respective ends and extends between the first and
second ends of
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the membrane along surfaces of the membrane. A second passage in the housing
is
connected to the drain outlet and air outlet at its respective ends and
extends between the
first and second ends of the membrane along surfaces of the membrane. A valve
is
connected between the second passage and the drain outlet for controlling the
draining of
the liquid and sweep air flow through the second passage.
[0005] Another air dryer includes a housing with an air inlet, an air
outlet and first and
second liquid drain outlets. A membrane dryer is mounted to the housing and
includes a
first passage connected to the air inlet and the air outlet at its respective
ends and a second
passage connected to the first drain outlet and the air outlet at its
respective ends. A
coalescing filter, with or without a particulate filter, maybe connected in a
series in the
housing, connects the air inlet to the first passage of the membrane dryer,
and the
coalescing filter is connected to the second drain outlet.
[0006] The valves may be an electro-pneumatic valve. A cover is
removable mounted to
the housing adjacent the membrane to allow removal of the membrane and the
filters from
the housing. The air inlet and the drain outlet are offset from the axis of
the membrane
and the cap. The housing may be mounted in the inlet of a reservoir and
extends from the
reservoir inlet into the interior of the reservoir so that the housing inlet
is the inlet of the
reservoir, the housing outlet is interior the reservoir and the drain outlet
of the housing is
exterior the reservoir.
[0007] In a vehicle brake system including a brake controller and the
reservoir with the air
dryer, the brake controller controls the valve. The controller opens the valve
when the
brake system uses air from the reservoir and closes the valve after the brake
system
terminates using air from the reservoir. The controller delays closing the
valve after the
brake system terminates using air from the reservoir until the reservoir is
recharged, and
further delays closing for a predetermined time after the reservoir is
recharged to fully
purge the sweep volume in the membrane air dryer of all moisture.
:00081 In a combination of a reservoir having an air port and an
air/liquid separator having
a housing with a separator member between an inlet and an outlet, the housing
extends
from the reservoir port into the interior of the reservoir so that one of the
housing's inlet
and outlet is the port of the reservoir, the other of the housing's inlet and
outlet is interior
the reservoir and the drain outlet of the housing is exterior the reservoir.
The housing may
have a drain interior or exterior the reservoir. A cover removable mounted to
the housing
adjacent the membrane to allow removal of the membrane from the housing; and
the one
of the housing's inlet and outlet and the drain outlet are offset from the
axis of the
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membrane and the cap. The separator member is one of or both a membrane
separator and
a coalescing filter.
[0009] A reservoir includes an air port and a housing at the air port
having a bore into the
interior of the reservoir, an air inlet/outlet and a drain outlet. The bore is
adapted to
removable receive a filter element. The inlet/outlet is exterior the reservoir
and connected
to the bore. The drain outlet connects the bore to the exterior of the
reservoir adjacent the
air port to drain water from the filter element.
[00010] These and other aspects of the present method will become
apparent from the
following detailed description of the method, when considered in conjunction
with
accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[00011] Figure 1 is a schematic of a locomotive air supply and brake
controller according
to the present disclosure.
[00012] Figure 2 is an embodiment of a membrane air dryer according to
the present
disclosure.
[00013] Figure 3 is an embodiment of the membrane air dryer with a test
device according
to the present disclosure.
[00014] Figure 4 is an embodiment of coalescing filter according to the
present disclosure.
[00015] Figure 5 is an embodiment of a membrane air dryer with a
removable membrane
air dryer module according to the present disclosure.
[00016] Figure 6 is an embodiment of an air dryer with a removable
membrane air dryer
module, coalescing filter and particulate filter with two liquid drains
according to the
present disclosure.
[00017] Figure 7 is an embodiment of an air dryer with a removable
membrane air dryer
module, coalescing filter and particulate filter with three liquid drains
according to the
present disclosure.
[00018] Figure 8 is an embodiment of a membrane air dryer with integral
particulate and
coalescing filters arranged for inside-out flow of air through the coalescer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00019] A locomotive brake supply and brake controller is shown in
Figure 1. A
compressor 10 driven by the engines of the locomotive provides a source of
compressed
air through line 12 to inlet 14 of the first main reservoir MR. 16. The outlet
18 of the
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reservoir 16 is connected to other non-brake air consuming devices at line 20.
The outlet
18 is also connected to the inlet 24 of the second main reservoir 26 via one-
way check
valve 22. The outlet 28 of the second main reservoir MR 26 is connected to a
brake
controller illustrated as a CCB computer controlled brake system 32. The
outlet 34 of the
computer controlled brake system 32 provides an appropriate pneumatic control
signals
for the locomotive and train brakes. As will be discussed below, the computer
controlled
brake system 32 provides, via line 36, control of the drain 54 of membrane air
filter 40
within the main reservoir 26. As also will be discussed, control may also be
provided to
the drain valve 19 of the first main reservoir MR 16 either from the computer
brake
control system 32 or other control systems on the locomotive. The main
reservoir 16
includes a coalescing pre-filter 60 therein. Coalescing pre-filter 60,
although shown
schematically in the outlet 18 of MR 16, can alternately be provided in the
inlet 14 of MR
16.
[00020] A membrane air dryer 40 is shown in Figure 2 as including a
housing 44 with an
air inlet 46, an air outlet 48 and a liquid drain outlet 54. A membrane
separator 42 is
shown schematically with an inner surface and an outer surface extending
between a first
and second ends of the membrane 42.= Typical construction of a membrane module
is a
bundle of small diameter hollow fibers (membrane), each with an inner surface
and an
outer surface extending between a first and second ends of the membrane. A
first passage
50, made up of the inner diameters of each of the hollow fiber membranes in
the housing
44 is connected to the air inlet 46 and air outlet 48 at it respective ends
and extends
between the first and second ends of the membrane 42 along one of the interior
and the
exterior of the membrane. A second passage 52 comprising the outer diameters
of each of
the hollow fiber membranes in the housing 44 is connected to the drain outlet
54 and the
sweep air inlet 51 adjacent the housing air outlet 48 at it respective ends.
The second
passage extends between the first and second ends of the membrane 42 along the
other of
the interior and the exterior of the membrane. A valve 56, 58 is connected
between the
second passage 52 and the drain outlet 54 for controlling the draining of the
liquid and
sweep air flow through the second passage 52.
[00021] The valve may be an electro-pneumatic valve or a solenoid
controlled diaphragm-
type (or conventional-type) drain valve 56, 58. A cover plate 47 is removable
mounted to
the housing 44 adjacent the membrane 42 to allow removal of the membrane 42
from the
housing 44. The air inlet 46 and the drain outlet 54 are offset from the axis
of the
membrane 42 and the cover plate 47. This allows servicing the membrane element
42 by
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removal of a cover or cover plate 47, without disturbing piping or removal of
the complete
unit from the reservoir 26.
[00022] The housing 44 may be mounted in the inlet 24 of a reservoir by
a collar 45 which
may be welded to the reservoir 26 or bolted to a flange on the inlet 24. The
housing
extends from the reservoir inlet 24 into the interior of the reservoir 26 so
that the housing's
inlet 46 is the inlet 24 of the reservoir 26. The housing's outlet 48 is
interior the reservoir
26 and the drain outlet 54 of the housing 44 is exterior the reservoir 26.
[00023] Most membrane dryers for industrial use have a constant sweep
flow. This is
undesirable on a locomotive as it wastes air and may deplete the air in the
reservoir if the
locomotive is idled with power shut off. Further, unlike many industrial uses,
the air is
consumed from the reservoirs 16 and 26 only intermittently by the pneumatic
brake
system. Main Reservoir 26 is generally protected by the check valve 22 and is
used
exclusively by the brakes. The membrane air dyer 40 for a locomotive solves
this problem
of wasted air due to a constant sweep flow by adding a solenoid controlled
diaphragm-
type (or conventional-type) drain valve 56,58 to the output of the sweep air
chamber 52
shown in Figure 2. Although the sweep air or drain valve 56, 58 is shown
schematically at
the exhaust of the sweep air chamber, it could also be arranged to control the
flow of
sweep air into the inlet of the sweep air chamber while still venting the
sweep air to the
outside of the MR 2 as shown in Figure 2.
[00024] When closed, the valve 56 closes the communication of the sweep
volume through
passage 52 to atmosphere, thereby preventing the venting of the sweep air. The
drain
valve 56 is controlled by a solenoid valve 58 which is controlled by the CCB
computer
controlled brake system 32 on the locomotive. The CCB 32, because it is a
computer
controlled brake system with transducers and other controls necessary for
brake operation,
can determine when the brakes are consuming air from the MR 26. In operation,
the CCB
32 will open the dryer drain valve 56 whenever the brake system is consuming
air from
MR 26, which allows the resumption of flow of sweep air around the outside of
the
membrane element 42 in passage 52 at the same time that moisture laden air is
flowing
into the inlet 46 of the air dryer 40 to replenish the air used by the brakes.
Thus, the air
dryer 40 only consumes sweep air when sweep air is needed to dry air flowing
through the
air dryer.
[00025] Further, the CCB can maintain sweep flow for a period of time
after the brake
system is no longer consuming air from MR 27 before closing the drain valve 56
to assure
that the MR 26 is fully replenished with dry air, further it can maintain
sweep flow for an
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additional predetermined time to assure that the sweep air volume is free of
moisture. The
lag time, during which the sweep flow is maintained after air consumption by
the brakes,
can be calculated based on the air flow measured by the CCB 32 and the
duration of the
flow, knowledge of compressor 10 on-off pressure switch points, and knowledge
of the
compressor output capacity. The lag time can alternatively or concurrently be
determined
by monitoring the pressure increase in MR 26 as it is replenished by the air
supply system.
When the rate of pressure increase in MR 26 decreases to some pre-determined
level
and/or the pressure in MR 26 reaches the compressor control upper limit
pressure, the
sweep air is terminated. Optionally the lag time calculation could be
optimized by CCB
32 reading a digital signal from the compressor control indicating whether the
compressor
is pumping or not.
[00026] Sweep flow would be enabled whenever 1) the brake system
consumes air, 2) the
compressor 10 is turned on and the pressure in MR 26 is less than the
compressor pressure
upper limit control, typically 145 psi, and 3) for some lag time after
cessation of air
consumption by the brakes, until the MR 26 is substantively recharged and the
sweep air
volume is substantively purged of moist air.
[00027] The membrane air dryer assembly 40 may also includes a test
fitting or pipe plug
which allows the insertion of a test fitting to measure the amount of sweep
air, where
increased amount of sweep air is an indicator of failure or rupture of the
membrane
element. To perform the test, the drain valve 56 is closed, and the test
fitting inserted into
the threaded fitting in the body of the membrane dryer assembly. The test
fitting includes
a fixed test orifice of predetermined size connecting the sweep air volume to
atmosphere,
sized to result in a predetermined pressure drop across the orifice for
expected sweep flow.
The membrane air dryer body 44 or the test fitting also includes a connection
for a
pressure gage or other suitable pressure measuring device to measure the
pressure in the
sweep volume when the drain valve 56 is closed and the test orifice is
installed.
Membrane leakage is thus characterized by an increase in the pressure in the
sweep
volume. The membrane requires replacement when the test pressure exceeds some
predetermined value.
[00028] Alternatively as shown in Figure 3, the test orifice and
pressure measurement
device could be inserted in the drain port of the drain valve, and the test
performed with
the drain valve 56 is open. The test fitting 70 is mounted in the drain port
54 and includes
the restricted test orifice 72 and a pressure gauge 74.
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[00029]
Figures 2 and 3 show the housing 44 as defining the appropriate passage for
the
filter element 42 to be removed from the housing 44. A variation is
illustrated in Figure 5
and shows the membrane filter element 42 and its housing 44A removable as a
module
from the housing 44. The housing 44 is joined to flange 45 of the MR 26 and
includes air
inlet 46. The membrane housing 44A includes the membrane member 42 and has an
air
inlet 46A and the outlet 48. A collar 41 of the housing 44A is received in the
housing 44.
It is sealed thereto by sealing means 43, shown as o-rings. The pair of o-
rings 43 on each
side of the drain port 54 which is aligned with passage 54B with housing 44
and connects
it to the drain the drain outlet 54. Valve 56, 58 are provided at the drain
outlet 54. For
maintenance, the cover plate 47 is removed and the membrane filter 40
including housing
44A, collar 41 and membrane 42 are removed. A new membrane air dryer or filter
40 may
then be installed.
[00030]
The air dryer system for a locomotive may optionally include a coalescing pre-
filter 60 to remove liquid water and oil vapor from the air stream prior to
passing through
the membrane 42, as well as the back-flow check valve 22 typically installed
between MR
16 and 26. The coalescing pre-filter 60 can likewise be packaged in a
cylindrical form
with a circular mounting flange for mounting in the inlet 14 or discharge 18
end of MR 16,
which feeds MR 26. As illustrated in Figure 4, the coalescing filter 60
includes a filter
element 62 in a housing 64 having an inlet 66 and an outlet 68.
[00031]
The coalescing pre-filter 60 is thus mounted inside main reservoir 16, where
it is
protected from the environment, where installation space is available, and
with significant
weight, cost, and complexity reduction. The coalescing pre-filter 60 mounted
inside the
MR 16, can be designed to discharge the condensed oil, water and other liquids
directly
into MR 16, where they are expelled by the pre-existing automatic drain valves
19 on the
bottom of the MR 16. Thus the pre-filter installed inside the MR 16 does not
require a
pressure proof housing around the filter 60, does not require a volume to
capture the
coalesced liquids, does not require separate drain valves or drain valve
heaters, and does
not require separate controls to periodically purge the accumulated liquid.
All of those
functions are provided by the reservoir itself and/or the pre-existing and
necessary
automatic drain valves 19 on the reservoirs. Thus it can be seen that this
mounting
arrangement of the pre-filter installed inside the MR 16 offers significant
advantage.
[00032] The pre-filter 60 can be provided with a by-pass check valve 70
to allow air flow
in the event of plugging of the filter 60 by ice or lack of maintenance.
Pressure
monitoring means 72 can be provided, either a mechanical indicator or an
electrical
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pressure switch or transducer, to measure the pressure drop across the filter
element 62 for
indication of required maintenance. Preferentially that pressure is measured
by a
transducer 72 which is monitored by the on-board locomotive diagnostic system
or by
CCB 32, which in turn can update the maintenance screens on the locomotive.
[00033] The coalescing pre-filter assembly 60 is designed in such a way
that the filter
element 62 can be serviced without disrupting the piping or requiring the
removal of the
complete assembly from the reservoir where it is installed. A cap 67 is
removable to
provide access to the filter element 62.
[00034] Alternatively, the coalescing pre-filter 60 may be installed in
the manner described
above, but in the inlet 14 of MR 16, instead of (or in addition to) the outlet
18 of MR 16.
The backflow check valve 22 may be deleted or could be included as part of the
membrane air dryer assembly. Coalescing filters generally work optimally when
the air
flow is directed from inside to outside the filter element and the coalesced
liquid is
allowed to drain from the outside of the element. Positioning the coalescing
pre-filter in
the inlet 14 to the MR 16 has the advantage of inside to outside air flow
while eliminating
a need for circuitous air routing in the filter housing, and eliminating the
need for a
pressure tight filter housing. In this arrangement, the coalesced liquid can
drip to the
bottom of the MR 16 where it is discharged by pre-existing automatic drain
valves 19.
[00035] As a further alternative, the coalescing pre-filter 60 may be
installed exterior and
between both reservoirs 16 and 26. A drain valve would be provided and
controlled by the
computer control brake system 32 or other locomotive computer. The coalescing
pre-filter
60 may be an integral unit with the membrane filter 40 or mounted to the inlet
of the
membrane filter 40 exterior the reservoir 26.
[00036] Filter 60 may also be provided in the MR 26 in combination with
the membrane air
dryer 40 as illustrated in Figures 6, 7 and 8. The housing 44 is enlarged to
include a
chamber 49 for receiving the coalescing element 62 by itself or in combination
with a
particulate filter 80. They are mounted between the housing 44 and the cover
plate 47.
Appropriate recesses or ledges are provided on the housing 44 and the cover
plate 47 to
align and secure the filters 62 and 80 in the housing 44. As shown in Figure
6, housing 44
is modified to provide a sump 45 to which a drain valves 82, 84 are connected.
These
valves are identical to that of 56, 58 and may also be controlled by the CCB
such that they
are opened at the appropriate time in the operation of the locomotive and/or
flow of the air
from the air supply.
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[00037] In Figures 6 and 7, the filter 62 and 80 are concentric with
each other and coaxial
to the membrane air dryer 40. The air through inlet 46 passes through the
filter 62 and 80
prior to being received in the air inlet 46A of the membrane dryer 40. As is
well-known,
the coalescing filter element 62 precipitates air-born water and oil vapor
from the air
stream. The particulate filter 80 filters out very fine air-born dust and
solid material such
as carbon particles from diesel combustion or other contaminants or other
particulates
which contaminate the membrane dryer module 40.
[00038] The present design differentiates from the prior art in that
the coalescing filter 62,
the particulate filter 80 and the air dryer 40 of the prior art are all
connected in series
external to the tank 26. The present design is an improvement over the prior
art in that
merely removing the cover plate 47 allows replacement and maintenance of the
filter 62
and 80 and the dryer 40. No major disassembly is required. While the
coalescing filter
element 62 and the particulate filter 80 require annual maintenance, the
membrane dryer
40 would be replaced every six to eight years depending on actual service
conditions.
[00039] A variation of the combined module of Figure 6 is illustrated
in Figure 7. Instead
of a common drain valve in 82,84 for the coalescing filter element 62 and the
particular
filter 80, each filter has its own set of valves. The bottom of chamber 49
adjacent the
coalescing filter includes a two-series valve 84A and 84C separated by sump
84B. A
separate port as provided at the inner surface of the particular filter 80. A
series set of
valves 86A and 86C are separated by a sump 86B. The valves 84A and C and 86A
and C
are controlled by the CCB as described for the valves 58 and 84 of Figure 6.
The valves
84A, 86A are operated to remove the water, oil, etc., from the housing chamber
49 and
empty into respective sumps 84B, 86B. The valves 84C, 86C, which empty the
sumps
84B, 86B, may be operated at a different time than valve 84A, 86A.
[00040] As a further modification, perforated tube 84 is provided
between the cover plate
47 and the inlet 46A of the membrane dryer 40. This secures the membrane dryer
within
the housing 44.
[00041] Figure 8 shows yet further modification whereby the particulate
filter 80 and
coalescing filter elements 62 are arranged axially, which provides for
simplified inside-
outside air flow through the coalescer. The chamber 49 of the housing 44 is
divided into
three chambers 49A, 49B and 49C by walls 100 and 102. The air as shown by
arrow 104
flows from inlet 46 and passes through particulate filter 80 and a portion of
perforated tube
88 in chamber 49A to chamber 49B. The air then flows through portion of the
perforated
tube 88 and the coalescing filter element 62 in chamber 49B. Next, the air
flows into
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chamber 49C and through perforated pipe 106 in chamber 49C to the inlet 49A of
the
membrane dryer 40.
[000421 Although the Figure 8 shows separate drain valves for the
particulate filter
chamber 49A and coalescing chamber 49B, a single drain valve could be used to
drain
both chambers as described for Figure 6.
[00943] The interior of the reservoir 26 may include a support bracket
90 welded or
otherwise suitably attached thereto. A seat 92 receives endcap 41A of the
membrane dryer
40. 0-rings may be provided on endcap 41A to secure the endcap 41A in the seat
92 and
to minimize harmful vibration between the two. A cam surface 94 is provided to
guide
and align the endcap 41A into the seat 92. The bracket 90 may be provided in
all the
shown embodiments.
[00044] Although not shown, the area of the air inlet 46 into the
chamber 49 is shaped or
includes a baffle to distribute the air around the filters 62 and 80.
[00045] Although the present method has been described and illustrated
in detail, it is to be
clearly understood that this is done by way of illustration and example only
and is not to
be taken by way of limitation. Although the dryer has been shown in a train
air supply
system, it can also be used in a truck brake system. The particular filter
structure may be
used even if it is not mounted interior the reservoir.. The scope of the
present method is to
be limited only by the terms of the appended claims.
