Note: Descriptions are shown in the official language in which they were submitted.
CA 02489869 2004-12-16
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SPIN-ON DESICCANT CARTRIDGE WITH
INTEGRAL OIL REMOVAL FILTER
BACKGROUND OF THE INVENTION
[0001] This invention relates to a compressed air system, and specifically an
air' dryer
assembly for the compressed air system that removes moisture and oil. The
invention finds
particular application in a compressor system for vehicles that use
pressurized air to selectively
control application of vehicle brakes and for other air operated systems
associated with the
vehicle.
[0002] Compressed air systems are used in conventional brake systems, for
example, to
provide and maintain air under pressure to operate vehicle brakes and
auxiliary air systems.
Water, particulates, and oil in the compressed air system can lead to
component degradation and
interfere with optimal operation of the system. Accordingly, an air dryer is
usually incorporated
into the system to remove water from the compressed air. The air dryer
collects and removes air
system contaminants in solid, liquid, and vapor form before the contaminants
enter the system.
The air dryer delivers clean, dry air for braking system components, thereby
increasing system
life and reducing maintenance costs.
[0003] An air brake compressor is typically supplied with oil from the vehicle
engine in
order to lubricate bearings and other components of the compressor. As will be
appreciated, it is
difficult to contain the oil in the compressor and oil occasionally becomes
entrained in the
pressurized air stream exiting the compressor. Modem air dryers use a
desiccant material to
adsorb water vapor as it passes through an air line from the compressor toward
a reservoir or
downstream components. The operation and efficiency of the desiccant is
adversely affected by
oil and thus it is important to minimize contamination of the desiccant with
oil by employing a
filtering element or oil filter that effectively removes the oil.
[0004] In addition, commercially available desiccant-type air dryers provide a
structure
that allows for replacement of the desiccant material. Periodic replacement of
the desiccant
material is desirable since, in use, the desiccant material becomes coated
with contaminants such
as oil, which ultimately reduces its water vapor retention characteristics.
Since other components
of air dryers have a longer service life, a convenient system for selectively
replacing the
desiccant material is desired. For example, a spin-on type desiccant air dryer
cartridge reseriibles
a conventional motor vehicle spin-on oil filter in the form of a canister .,A
load plate, has a
centrally threaded bore such that the entire replaceable air cartridge unit"
:1s..threaded onto` an.
upstanding boss extending from a mounting surface of the vehicle.
[0005] An oil coalescing element removes a majority of aerosols and-liquid oil
entering a
spin-on desiccant cartridge. Unfortunately, known designs have not adequately
addressed
CA 02489869 2010-12-07
removal of coalesced oil from the cartridge. For example, purge flow systems
direct air flow in
a reverse direction or back through the oil coalescing element in an effort to
remove entrained oil
from the desiccant. However, a poor design can lead to desiccant leakage, to a
reduction in the
removal of oil from the cartridge, thus leading to a decrease in desiccant
life, and ultimately to a
negative impact on the performance of the compressed air system.
[0006] Thus, a continued need exists in the art to effectively eliminate
desiccant
contaminant in an air dryer assembly of a compressed air system, to remove the
contaminant from
the dryer assembly, and to contain the desiccant.
BRIEF SUMMARY OF THE INVENTION
[0007] An improved air dryer assembly for removing moisture and oil from a
compressed
air system is provided that meets the above needs and others in a simple and
economical manner.
[0008] More particularly, an exemplary embodiment of the invention includes a
desiccant
material received in a shell for removing moisture as compressed air passes
therethrough. An inlet
is disposed upstream of the desiccant material, and an outlet disposed
downstream thereof. A
coalescing element is disposed in the inlet and has a coalescing material for
removing at least oil
aerosols from the compressed air. A check valve is located in parallel with
the coalescing element
inlet. The check valve forces compressed air to pass through the coalescing
element as air flows
from the inlet to the outlet, and allows compressed air to bypass the
coalescing element as purge
air flows from the outlet to the inlet. An oil collection region is located
proximate to the check
valve, wherein the purge air flow sweeps oil in the region to the outlet
bypassing the coalescing
element.
[0009] In one embodiment of the present invention, a support member
advantageously
retains the coalescing element and check valve in the shell.
[0010] In another embodiment, a biasing assembly exerts a compacting force on
the
desiccant material in the shell.
[0011] Another aspect of the present invention is a method of removing oil
aerosols and
liquid oil from the cartridge is also provided. The method includes the steps
of directing incoming
air through the coalescing element and bypassing the coalescing element during
a reverse purge
flow.
[0012] Further advantages and benefits of the invention will become apparent
to those
skilled in the art after considering the following description and appended
claims in conjunction
with the accompanying drawings.
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CA 02489869 2010-12-07
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention may take physical form in certain parts and arrangements
of parts,
a preferred embodiment of which will be described in detail in the following
specification.
[0014] FIGURE 1 is a longitudinal cross-sectional view of a spin-on desiccant
cartridge
in accordance with the present invention.
[0015] FIGURE 2 is a longitudinal cross-sectional view of another preferred
embodiment
of a spin-on desiccant cartridge.
DETAILED DESCRIPTION OF THE INVENTION
[0016] An air dryer formed in accordance with the present invention is shown
in
FIGURE 1 and is generally designated by reference numeral 10. It will be
appreciated that other
components of the air dryer assembly are generally well known in the art, for
example as, shown
and described in U.S. Patent No. 5,622,544, so that further discussion herein
is deemed
unnecessary. The spin-on cartridge of the present invention includes a first
or outer shell 12 that
is preferably cup-shaped. That is, a first or closed end 14 forms a dome while
a second or open
end 16 is sealingly secured to a load plate 20. The load plate includes an
inlet 22 that allows
pressurized air from a compressor (not shown) to pass through the cartridge
where contaminants
and moisture are removed from the air stream. A second passage or outlet 24 is
also formed in
the load plate 20 and in one embodiment is located at a central location. The
outlet 24
communicates with downstream components, such as a storage reservoir (not
shown) where clean
dry pressurized air is maintained until required by the compressed air system.
[0017] A second or inner shell 30 encloses a desiccant material represented by
beads 34.
The inner shell includes a central wall or cylindrical member portion 32 that
extends outwardly
from one face of a support wall portion 36. The support wall has a series of
openings 38 that are
dimensioned to allow air to flow into the desiccant bed. Extending from an
opposite face of the
support wall portion is a support annulus portion 39. In addition to a
downturned flange 40 along
the periphery of the support wall portion 36, the annulus portion 39 locates
the inner shell 30
within the outer shell 12 of the cartridge assembly 10.
[0018] The desiccant material 34 preferably fills the cavity or space between
the inner
shell 30 and outer shell 12. That is, the desiccant material 34 is received
within the inner shell 30
and fills the annular gap between the cylindrical wall portion 32 and the
outer shell 12. A
perforated material or cloth 50 is air permeable and serves to retain the
desiccant material above
the support wall portion 36 in a manner that is generally conventional so that
further discussion
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regarding the structure and operation of the cloth 50 and perforated support
wall is deemed
unnecessary.
[0019] A biasing member, such as spring 52, exerts a compacting force on the
desiccant
bed. In this embodiment, the spring 52 engages the annular wall portion 39 and
urges the inner
shell 30 toward the closed end 14 of the outer shell 12. An opposite end of
the spring 52 engages
an inner support member portion 60 along an inner ledge portion 62 that
sealingly engages the
load plate 20 around the outlet 24. The inner support member portion 60
extends from the load
plate 20 and includes a radial wall portion 64 that terminates along its
periphery in an axially
extending groove 66. The groove 66 retains a first or upper end of a
coalescing layer or element
70. The coalescing layer 70 is preferably a micro-glass fiber or spun glass
material that has the
consistency of matting or felt. The coalescing layer 70 entraps or coalesces
oil or oil aerosols as
air passes therethrough from the inlet 22 before entering the desiccant bed.
In one embodiment,
the upper end 72 of the coalescing element 70 is received in the inner support
member 60, while
a second or low end 74 is spaced from the load plate 20. This forms a radial
passage 80 that is
selectively open to airflow as will become more apparent below.
[0020] A wicking material 82, such as an open-pored polyester material,
envelops or
surrounds the coalescing element 70 and passage 80. As shown in FIGURE 1, the
wicking
element 82 extends across the entire gap defined between the annular groove 66
and the inner
support member 60 and the load plate 20. The wicking material 82 has a porous
construction
which allows air to flow through the wicking element 82 and serves to draw oil
that coalesces in
coalescing element 70 for deposition in a recessed region 84 disposed radially
between the
wicking element 82 and the outer shell 12.
[0021] A one-way flow control device or check valve 90 is associated with the
purge
outlet passage 80. The check valve precludes airflow from the inlet 22 into
the purge outlet. In
this manner, all incoming flow must pass through coalescing element 70 before
reaching the
desiccant bed. On the other hand, the check valve 90 freely opens when a
reverse or purge flow
is provided. As is known in the art, the reverse or purge flow is periodically
passed through the
desiccant bed to regenerate the desiccant material and carry adsorbed moisture
out of the system,
i.e., purge the collected contaminants and moisture. By locating the check
valve 90 in parallel
arrangement with the coalescing element 70, airflow will travel from the inlet
22 to the outlet 24
through the coalescing element 70, while the purge flow allows airflow to pass
through the check
valve 90 as it migrates from the outlet 24 to the inlet 22. This flowpath
allows the purged air to
bypass the coalescing element 70 in its purge path, while picking up coalesced
oil that is
temporarily collected in the region 84. This oil can migrate through the
wicking element 82 and
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out through the check valve 90, where it communicates with the external
environment,
atmosphere, or other desired location. In this manner, oil laden air passes
through the coalescing
element 70 for removal of oil and oil vapor, yet allows purge airflow to
remove the coalesced oil
without flowing back through the element.
[0022] FIGURE 2 is another embodiment of the invention illustrating various
changes
that can be adopted while incorporating the inventive concepts of the present
invention. For
purposes of brevity, and, ease of understanding, like reference numerals with
a primed (') suffix
refer to like elements and new numerals refer to new components. Particularly,
outer shell 12'
receives an inner shell 30' which is slightly modified to incorporate an
outer, generally
cylindrical wall 92 that is closed at a first or upper end by a compression
plate 94. The
compression plate 94 allows the biasing spring 52' to be positioned between
the closed end 14' of
the outer housing and the desiccant bed 34' held within the inner shell 32'.
[0023] In addition, the lower wall portion 36' of the inner shell has a
conical central
portion 96 that maximizes the volume of desiccant material received in the
inner shell 32'. It will
also be appreciated that the perforated cloth material 50' retains the
desiccant beads within the
inner shell 32' and prevents the beads from passing through openings 38' in
the support wall
portion 36'. Here, the support wall portion 36' is defined by two portions, an
outer annular
portion disposed between walls 32' and 92 and an inner portion dimensioned for
receipt at the
base of the truncated conical wall 96.
[0024] As will be appreciated, the coalescing element 70' is still disposed in
parallel relation with the purge outlet 80' and check valve 90' so that air
flowing from the inlet
22' to the outlet 24' must proceed through the coalescing element 70'. On the
other hand, the
reverse, purge flow from the outlet 24' to the inlet 22' is able to bypass the
coalescing element
70' and remove oil collected in the region 84' through the check valve 90'
from the cartridge.
[0025] The invention has been described with reference to illustrative
embodiments.
Obviously, modifications and alterations will occur to others upon a reading
and understanding
of the preceding detailed description. For example, the cartridge may not be a
spin-on type of
cartridge, or may adopt a wide variety of other structural configurations,
materials of
construction, flow paths therethrough without departing from the spirit and
scope of the invention
described herein. The invention is to be construed as including all such
alterations and
modifications insofar as they come within the scope of the appended claims or
the equivalents
thereof.
