Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE
VENT SYSTEM
BACKGROUND
[0001] Generally, this disclosure relates to embodiments of systems,
methods, and devices for venting an enclosure. Some embodiments relate more
specifically to venting an enclosure containing synthetic or non-synthetic oil-
based products, such as an enclosure containing machinery and a lubricant, for
example.
[0002] Gas-permeable, liquid-impermeable vents find use in many
applications in the automotive industry, such as electrical component
housings,
gear housings, vehicle bodies, and brake housings, for example, where pressure
equalization between a housing interior and the surrounding environment is
desirable. Machinery enclosures, such as gearbox housings and axles, are often
subject to thermal cycling. As the machinery is operated, temperatures of the
lubricant and internal air begin to rise, causing air pressure to rise in the
enclosure. When the machinery is stopped, temperature and pressure fall within
the enclosure. Vents are often employed with the dual purposes of facilitating
pressure equalization while sealing the interior of the housing from liquid,
dirt,
dust particles, or other unwanted contaminants. Failure to exclude water or
other
contaminants from various automotive housings can result in damage to the
interior of the housing, damage to the components in the housing, or other
undesirable results, such as reduced machinery performance, for example.
[0003] Some machinery vents employ expanded polytetrafluoroethylene
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(ePTFE) membranes, where the vent includes a body having a passageway and
a gas-permeable, water-impermeable ePTFE membrane covering the
passageway, and a fibrous sorbent disposed within the passageway between the
machinery space and the ePTFE membrane for sorption of lubricant aerosol.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a perspective, or isometric view of a vent system in a
disassembled state, according to some embodiments.
[0005] FIG. 2 is an enlarged, sectional view of a portion of the vent
system of FIG. 1 in the disassembled state with the section taken along the
longitudinal axis of the system, according to some embodiments.
[0006] FIG. 3 is an isometric view of a valve of the vent system of FIG. 1,
according to some embodiments.
[0007] FIG. 4 is a sectional view of the valve of FIG. 3 with the section
taken longitudinally along the valve, according to some embodiments.
[0008] FIG. 5 is an end view of the valve of FIG. 3, according to some
embodiments.
[0009] FIG. 6 is a sectional view of a valve configuration similar to that
shown in FIG. 3 with the section taken longitudinally along the valve,
according to
some embodiments.
[0010] FIG. 7 is a schematic view showing valve operation, according to
some embodiments.
[0011] FIG. 8 is a perspective view showing another valve and another
vent module body employed in the system of FIG. 1, according to some
embodiments.
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[0012] FIG. 9 shows another valve, which is a duckbill valve.
[0013] FIG. 10 is a perspective view of an insert for a buckbill valve
according to an exemplary embodiment of an aspect of this disclosure.
[0014] FIG. 11(a) is a perspective view of the insert of FIG. 10 disposed
in a duckbill valve according to an exemplary embodiment of an aspect of this
disclosure.
[0015] FIG. 11(b) is a cross-sectional view of the insert of FIG. 10
disposed in a duckbill valve according to an exemplary embodiment of an aspect
of this disclosure.
DETAILED DESCRIPTION
[0016] Various embodiments described herein provide systems,
methods, and devices for venting a liquid containing enclosure using a flow
control module to enhance service life and overall venting system performance,
for example. Some embodiments relate to a cost effective, easy to integrate,
and
durable vent system for venting an enclosure containing synthetic or non-
synthetic oil-based liquids, such as lubricants, fuel, transmission oil, and
hydraulic fluids, although a variety of liquids are contemplated. Such
enclosures
can include vehicle housings such as gear housings, axle housings, fuel tank
housings, electrical component housings, and brake housings, for example.
[0017] Some embodiments relate to a venting system for an enclosure
that includes a flow control module to help avoid or reduce instances of
liquid
from the enclosure migrating through the venting system and coming into
unwanted contact with sorbent of the venting system where such contact can
otherwise reduce overall sorption capacity of the sorbent, and thus reduce
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service life and overall performance of the venting system. In some
embodiments, the control module includes a valve configured to help reduce or
prevent contact between liquid inside the enclosure and the fibrous sorbent
while
allowing effective pressure equalization between the interior of the enclosure
and
the environment. Although some features and advantages of systems, methods,
and devices are described by way of example, various additional and
alternative
features and advantages are contemplated.
[0018] U.S. Publication No. 2007/0240537, filed April 17, 2006 and
entitled "Axle Vent" discloses various components and features associated with
vent modules for a machinery space.
[0019] FIG. 1 is a perspective, or isometric view of a vent system 10 in a
disassembled state, according to some embodiments. FIG. 2 is an enlarged,
sectional view of a portion of the vent system 10 in the disassembled state
with
the section taken along the longitudinal axis of the system 10, according to
some
embodiments. As shown, the vent system 10 includes a vent module 12 and a
flow control module 14 secured to an enclosure 16, which is indicated
generally
as a box in FIG. 1.
[0020] The vent module 12 includes a cap 18, also described as a cover,
a membrane 20, also described as a filter, a sorbent 22, also described as a
pre-
filter, and a body 24, also described as a housing. In some embodiments, the
vent module 12 is an automotive vent for powertrain components sold by W.L.
Gore & Associates of Newark, Delaware under the trade name, "SERIES: AVS
41."
[0021] In some embodiments, the cap 18 of the vent module 12 is
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configured to form a complementary fit with the body 24 (e.g., a snap fit) or
to
otherwise be secured to the body 24 and allows air or other gas to pass into
and
out of the body 24 during pressure equalization,
[0022] In some embodiments, the body 24 of the vent module 12 has a
first end 26 and a second end 28 and defines a first passageway 30 (FIG. 2),
also described as a flow path, which extends through the body 24 from the
first
end 26 to the second end 28. As shown, the body 24 includes a receptacle
portion 32 toward the first end 26 and an insert portion 34 toward the second
end
28. The receptacle portion 32 optionally defines a seat 36 for receiving the
membrane 20 and a barrel 38 (FIG. 2) for receiving the sorbent 22. The insert
portion 34 of the body 24 is optionally configured to be inserted into and
mate
with a connector, such as relatively flexible or inflexible tubing, for
example. As
shown, the receptacle portion 32 has a larger diameter than the insert portion
34,
where the seat 36 generally defines a larger diameter than the barrel 38 of
the
receptacle portion 32.
[0023] In some embodiments, the membrane 20 is configured to be
received in the seat 36 of the body 24 and to cover the first passageway 30.
The
membrane 20 is hydrophobic, gas-permeable, and liquid-impermeable, according
to some embodiments. In some embodiments, the membrane 20 is oleophobic.
The membrane 20 is optionally formed of ePTFE, such as an ePTFE membrane
sold by W.L. Gore & Associates of Newark, Delaware under the trade name
"AM 6XX,"
[0024] In some embodiments, the sorbent 22 is substantially cylindrical in
shape or is otherwise shaped to be received in the barrel 38 of the body 24.
The
sorbent 22 is optionally formed of a fibrous material, including natural fiber
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material, for example. The sorbent 22 is disposed within the first passageway
30
such that air flowing from the enclosure 16 encounters the sorbent 22 before
the
membrane 20, according to some embodiments.
[0025] In some embodiments, the flow control module 14 includes a
connector 50 and a valve 52, also described as a flow control element. As
shown, the flow control module 14 is a separate component attached to the vent
module 12. In other embodiments, the flow control module 14 is formed as a
part
of the vent module 12. For example, components of the flow control module 14
are optionally formed as a part of the body 24 such as when the connector 50
is
integral with or part of the body 24 and/or when the valve 52 is disposed
inside a
portion of the body 24.
[0026] In some embodiments, the connector 50 of the flow control
module 14 is a hollow, cylindrical tube defining a second passageway 60 (FIG.
2), also described as a second flow pathway. In some embodiments, the vent
module body 24, and thus the first passageway 30 is connected to the connector
50 by inserting the insert portion 34 into the connector 50 and/or the valve
52. In
turn, the connector 50 is connected to the enclosure 16 to create a flow path
through the first and second passageways 30, 60 to the enclosure 16.
[0027] Though shown in a disassembled state in FIGS. 1 and 2, the valve
52 is disposed at least partially within the second passageway 60 when the
flow
control module 14 is in an assembled state. FIG. 3 is an isometric view of the
valve 52, FIG. 4 is a sectional view of the valve 52 with the section taken
longitudinally along the valve 52, and FIG. 5 is an end view of the valve 52,
according to some embodiments.
[0028] As shown in FIGS. 3 to 5, the valve 52 includes a body 64 defining
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a first end 66, a second end 68, and an inner channel 70 extending between the
first and second ends 66, 68. In some embodiments, the body 64 includes a
first
portion 72 toward the first end 66 and a second portion 80 toward the second
end 68. The first portion 72 is optionally adapted to receive the insert
portion 34
of the vent module body 24. As show, the second portion 80 thins, or tapers to
a
reduced overall thickness at the second end 68 and the first portion 72 is
substantially non-tapered or has a relatively constant thickness.
[0029] As shown in FIG. 4, the inner channel 70 at the tapered portion 80
defines a tapered section 82 that narrows, or tapers in width to a slot 84,
that is
open at second end 68. In some embodiments, the tapered section 82 defines a
taper angle Ta from about 5 degrees to about 80 degrees. In some
embodiments, the taper angle Ta is about 10 degrees, although a variety of
angles are contemplated. As shown, the slot 84 is relatively thin (e.g.,
compared
to the origin of the inner channel 70 at the first end 66 of the first section
82 of the
inner channel 70). As shown in FIG. 4, the taper of the tapered section 82
stops
before the second end of the body 64. FIG. 6 shows the valve 52, according to
some other embodiments where the tapered section 82 terminates at the slot 84
at the second end 68 of the body 64.
[0030] The body 64 is optionally formed of an elastomeric material to
help allow the body 64 to selectively prevent fluid (e.g., lubricant) from
flowing up
through the slot 84 and back through the inner channel 70 while permitting gas
(e.g., air) to pass in both directions, from the first end 66 to the second
end 68
and vice versa, during pressure equalization. In other words, the valve 52 is
adapted to allow air or other gases to flow in both directions within the
first and
second passageways 30, 60, for example to facilitate pressure equalization
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between the environment and the enclosure 16, such as a machinery space,
while acting as a barrier to liquid, such as lubricant. For example, the
narrowed
inner channel 70 at the slot 84 remain open to permit air flow in either
direction
through the valve 52 (a cracking pressure of zero), but the body 64 is
sufficiently
flexible and tapered and the inner channel 70 is sufficiently narrow at the
slot 84,
such that that body 64 flexes to close the inner channel 70 when the valve 52
is
under pneumatic pressure to impede fluid flow through the valve 52.
[0031] FIG. 7 is a schematic showing valve operation according to some
embodiments. As shown in the schematic of FIG. 7, when a liquid such as liquid
lubricant approaches the valve 52, pneumatic pressure due to trapped air
outside
of the tapered portion 80 of the valve body 64 applies pressure to the tapered
portion 80 of the body 64, pinching the tapered section 82 of the inner
channel 70
closed, thereby impeding liquid flow.
[0032] In some embodiments, the valve 52 is formed of cross-linked
elastomers or thermoplastic elastomers having adequate chemical, thermal, and/
or mechanical resistance to the fluid in the enclosure 16. For example, in
some
embodiments the valve 52 is formed from a blend of Nitrile rubbers such as NBR
and HNBR, fluoropolymer elastomers such as Viton or Fluorosilicone, or others.
It has been found that soft elastomeric materials (e.g., 25 Shore A or less)
are
particularly suitable for lubricant applications, although other hardness
materials
are employed depending upon implementation desired. The valve 52 is
optionally formed using molding methods such as liquid injection molding (LIM)
or compression molding.
100331 As shown in FIG. 5, the slot 84 defines a slot geometry including a
width W, a slot thickness T, and an end chamfer angle A. In some embodiments,
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the slot thickness T is about 1 mm or less, about 0.250 mm or less, or about
0.125 mm or less, and the slot width W is at least 2 mm, although a variety of
dimensions are contemplated. In some embodiments, the end chamfer angle is
less than 90 degrees or is about 45 degrees, or is non-orthogonal and 45
degrees or greater, for example, although a variety of angles are
contemplated.
[0034] According to various methods of forming the valve 52, slot
geometry is selected based upon hardness of an elastomer used to construct the
valve 52. For example, it has been found that a valve similar to the design of
valve 52 and formed of an elastomeric material having a durometer of about 25
Shore A effectively closes with slot thickness T of about 1mm, while those
made
with elastomers of a higher durometer material of about 80 Shore A required a
slot thickness T of less than about 0.125mm. Although some examples of
effective slot thicknesses and material durometers have been provided, it
should
be understood that additional factors contribute to effective valve closing
action,
including taper angle, slot geometry, fluid type, fluid temperature, fluid
pressure
and the rate at which the fluid pressure is applied to the valve 52, for
example.
[0035] In some embodiments, the enclosure 16 (FIG. 1), also described
as a machinery space, contains a liquid (not shown), such as a synthetic or
non-
synthetic petrochemical lubricant, and components (not shown), such as gears
or
other machinery, that applies a shearing force to the liquid during operation
of the
machinery. In some embodiments, the enclosure 16 is a powertrain gearbox
housing. In other embodiments, the enclosure 16 houses fuel or electrical
components, for example, in need of two way air venting with a liquid barrier.
[0036] FIG. 8 is a perspective view showing another valve 152 and
another vent module body 124 employed in the system 10, according to some
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embodiments. As shown, the valve 152 is positioned inside of the body 124 and
the body 124 is positioned in the connector 150. The valve 152 is optionally
formed of similar materials using similar techniques with similar slot
geometries
to those previously described, according to some embodiments.
[0037] As shown in FIG. 8, the body 124 is optionally substantially similar
to the body 24, where the body 124 has a first end 126 and a second end 128
and defines a first passageway 130, also described as a flow path, which
extends through the body 124 from the first end 126 to the second end 128.
Similarly to the body 24, the body 124 includes a receptacle portion 132
toward
the first end 126 and an insert portion 134 toward the second end 128.
[0038] As shown, the receptacle portion 132 optionally defines a valve
seat 137 for receiving the valve 152. In some embodiments, the valve seat 137
is
an annular recess at the transition from the receptacle portion 132 to the
insert
portion 134. In some embodiments, a flexible or inflexible tubular element,
such
as the connector 150 is utilized to connect the vent module body 124, and thus
the first passageway 130 to the enclosure 16 (e.g., by inserting the insert
portion
132 into the tubular element and connecting the tubular element to the
enclosure
16).
[0039] As shown in FIG. 8, the valve 152 includes a body 164 defining a
first end 166, a second end 168, and an inner channel 170 extending between
the first and second ends 166, 168. In some embodiments, the body 164
includes a first portion 172 toward the first end 166 that defines an widened
flange and a second portion 180 toward the second end 168, where the second
portion 180 thins, or tapers to a reduced overall thickness at the second end
168
and the first portion has a greater cross-section or thickness. The first
portion, or
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widened flange, is optionally received in the seat 137 and secured there
(e.g.,
using an adhesive or other fastening means).
[0040] As shown, the inner channel 170 at the tapered portion 180
defines a first section 182, also described as a tapered section, that
narrows, or .
tapers in width to a slot 184 that is open at second end 168. As shown, the
slot
184 is relatively thin (e.g., compared to an origin of the inner channel 170
at the
first end 166).
[0041] In some embodiments, the body 164 is formed of an elastomeric
material selected to help selectively prevent fluid (e.g., lubricant) from
flowing up
through the slot 184 and back through the inner channel 170 while permitting
gas
(e.g., air) to pass in both directions, from the first end 166 to the second
end 168
and vice versa, during pressure equalization. In other words, similarly to
various
embodiments of the valve 52, the valve 152 is adapted to allow air or other
gases
to flow in both directions through the inner channel 170, for example to
facilitate
pressure equalization between the environment and the machinery space, while
acting as a barrier to liquid, such as a liquid lubricant, from passing
through the
body 164 from the second end 168 to the first end 166.
[0042] FIG. 9 shows another valve 252, which is a duckbill valve.
Although not shown, the valve 252 is optionally modified from the depicted
duckbill valve to form a valve according to various embodiments by molding a
slot (not shown) into the tapered end of the valve 252 to allow airflow
passage in
both directions while helping minimize pressure drop across the valve (e.g.,
to
achieve zero cracking pressure). It should be understood that a traditional
duck
valve configuration (e.g., as shown in FIG. 9) narrows to a slit end that is
normally in a closed state. The valve is a one-way valve that allows airflow
in
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one direction only and only once a predetermined amount of pressure is applied
from inside the valve, commonly referred to as "cracking pressure." According
to
some embodiments, the valve 252 is modified, for example similarly to valves
52,
152 to include a slot that accomplishes a normally open duck bill valve
configuration having a cracking pressure of zero. The slot may be constructed
either during molding or in a secondary operation wherein the slot may be
stamped out of the typical duck bill valve.
[0043] In another aspect, in order to prevent leaks around the corners of
a buckbill valve, this disclosure includes a rigid insert which closely
resembles
the interior surface of the molded duck-bill; however much of the geometry is
slightly undersized to allow airflow between the rigid element and the
elastomer
valve body. When corner geometry of the rigid insert matches the inside of the
duckbill, the interior corners of the elastomer can be pulled in tension, This
tension enables the elastomer to permit airflow between the flat rectangular
surfaces of the valve during ambient conditions; however the flat surfaces
will
contact the matching surfaces of the rigid insert during positive pressure
conditions. In the pressurized, "closed" condition, the insert provides large
sealing surfaces for the elastomer, as well as support for the "pinched"
corners of
the elastomer duckbill. This supporting element is a new way of preventing
leaks
through the corners of the duckbill described above.
[0044] In this regard, FIG. 10 shows an insert 1000 having edges 1001
and a taper 1002. Edges 1001 and taper 1002 are sized such that they fit
snugly
into an inner channel of a duckbill valve while leaving space for airflow but
promoting sealing of the valve against upstream fluid flow.
[0045] FIG. 11(a) shows insert 1000 seated within inner channel 1070 of
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duckbill valve 1152. Edges 1001 engage the corners (chamfer angles A) of inner
channel 1070. Spaces 1005 and 1006 allow air flow around insert 1000 and
through duckbill valve 1152. When tapered portion 1080 duckbill valve 1152 is
sealed or pinched, by application of pressure from the external sides thereof,
spaces 1005 and 1006 are closed to form a seal prevent fluid flow into inner
channel 1070 of duckbill valve 1152. The seal is particularly tight at the
chamfer
angles A because of the secure engagement of edges 1001 of insert 1000
therewith. Using such an insert 1000, leakage of fluid into duckbill valve
1152 at
the chamfer angle A is prevented or greatly reduced.
[0046] Fig. 11(b) shows a cross-sectional view of insert 1000 seated
within inner channel 1070 of duckbill valve 1152. This view further
illustrates
spaces 1005 and 1006 described in connection with Fig 11(a).
[0047] The particular size and shape of the insert can vary, depending on
the specific design of both the duckbill (or other type) of valve, and the
sealing
characteristics thereof. In particular, means for anchoring the insert within
the
valve may vary from a simple friction fit, to integration with a cap or other
supporting member extending out of or beyond the wide end of the valve and
mated with the insert portion of a receptacle or connector or outer tube
themselves.
[0048] The material of construction of the insert can also vary, provided
that such material is capable of sealing against the valve under pressure in
use.
Preferred materials for the insert include polyamides such as nylon,
polyesters,
polyolefins such as polypropylene or polyethylene, and polyetherimides.
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[0049] EXAMPLES
[0050] A valve configured similarly to the valve 52 was constructed using
stereo lithography by injecting a viscous elastomer into a molding tool with
subsequent vulcanization resulting in a cross-linked elastomeric sample. The
valve was formed of an RN elastomer, silicone, having a durometer of about 60
Shore A. The slot geometry included a slot thickness T of about 0.25 mm, a
slot
width W of about 5 mm discounting the end chamfer or a maximum slot width W
of about 5.26 mm including the end chamfers. During testing, air flow of the
valve of this example was measured to permit desirable air flow, indicating
that
the valve has adequate airflow to function as an effective vent for pressure
equalization. No liquid lubricant passage was observed during the liquid
resistance test indicative of the efficacy of the flow control element as a
barrier to
liquid flow.
[0051] COMPARATIVE EXAMPLE
[0052] A traditional duck bill valve without a slot according (e.g., with a
slit as shown in the valve 252 of FIG. 9) was constructed by using stereo
lithography. The air flow of this sample was measured to be zero, indicating
that
the unmodified design was ineffective for pressure venting.
[0053] TEST METHODS
[0054] Effective operation of the valve was tested using the following test
methods.
[0055] AIR FLOW TEST
[0056] The air flow through the valve was measured at a pressure
differential of 0.19 psi across the element. An air flow measurement of at
least
100 ml/min was selected as indicative the valve would have enough air flow to
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function as an effective vent for pressure equalization.
[0057] LIQUID RESISTANCE TEST
[0058] The valve was pressurized with a liquid lubricant (tapered end
facing direct lubricant flow) at a pressure ranging from 0.036 psi up to 5
psi. A
lack of fluid passing through a valve is indicative of the efficacy of the
valve as a
liquid barrier.
[0059] While particular invention embodiments have been illustrated and
described herein, the scope of invention should not be limited to such
illustrations
and descriptions. For example, although some valves are described taking the
form of a modified duckbill valve, valves having any of a variety of forms and
shapes are contemplated according to various embodiments. It should be
apparent that changes and modifications may be incorporated and embodied as
part of the invention within the scope of the following claims.
