AIR REGULATOR OUTLET FILTER
STATEMENT REGARDING FEDERALLY SPONSORED
RESEARCH OR DEVELOPMENT
[0001] This invention was made with Government support under DE-EE0005447
awarded by DOE. The Government has certain rights in this invention.
BACKGROUND
[0002] Air Maintenance Technology (AMT) is a system to use a pump that is built
into a tire to automatically maintain a vehicle's tire pressure at a target pressure. A
regulator senses when the tire is at the target pressure. If the pressure drops below
the target level, an inlet filter in the regulator allows some outside air into the pumping
tube which runs circumferentially around the inside of the tire. Deformations of the
tube as the tire rolls compress air inside the tube. The air may be discharged through
the regulator into the tire cavity to inflate the tire.
SUMMARY
[0003] An air pressure regulator outlet filter for an Air Maintenance Technology
(AMT) tire includes a filter body to be attached to a housing of an air regulator of the
AMT tire. The housing has a cavity to be in fluid communication with an air outlet of
the regulator. The cavity is also in fluid communication with a tire cavity of the AMT
tire. A filtration media is to block contaminants from entering the cavity while allowing
pressurized air to be exhausted through the filtration media into the tire cavity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Features and advantages of examples of the present disclosure will become
apparent by reference to the following detailed description and drawings, in which like
reference numerals correspond to the same or similar, though perhaps not identical,
components. For the sake of brevity, reference numerals or features having a

previously described function may or may not be described in connection with other
drawings in which they appear.
[0005] Fig. 1 is a perspective view of an example of an AMT regulator with an outlet
filter of the present disclosure;
[0006] Fig. 2 is a cross-sectional view of a wheel and tire depicting an example of a
regulator mounted on the tire according to the present disclosure.
[0007] Fig. 3 is a semi-schematic rear view of the example of the AMT regulator
with outlet filter depicted in Fig. 1;
[0008] Fig. 4 is a semi-schematic, right side view of the example of the AMT
regulator with outlet filter depicted in Fig. 1 with a cross-section taken through A-A as
shown in Fig. 3;
[0009] Fig. 5 is a semi-schematic, partial rear side view of the example of the AMT
regulator with outlet filter depicted in Fig. 1 with a cross-section taken through B-B as
shown in Fig.4; and
[0010] Fig. 6 is a side, partially exploded view an outlet filter module of the present
disclosure.
DETAILED DESCRIPTION
[0011] The present disclosure relates generally to an air pressure regulator outlet
filter. Such a filter may be used, for example, with an AMT system used with the tires
of a commercial truck. It is to be understood that outlet filters according to the present
disclosure may be used with various sizes of tires for various types of vehicles.
[0012] Debris may be found inside a tire cavity. For example, dust, water, insects,
rubber particles, mounting lubricants, and air compressor oil may be present in the tire
cavity. The regulator includes valves to regulate a discharge of air through a
discharge port into the tire cavity. In examples of the present disclosure, an outlet filter
blocks entry of debris from the tire cavity into the regulator while allowing air to flow
from the discharge port into the tire cavity.
[0013] Fig. 1 is a perspective view of an example of a regulator 10 according to the
present disclosure. A docking station 20 is depicted mounted on the regulator 10. Air
from the pump (not shown) is ultimately discharged through the outlet filter 14. The

outlet filter 14 substantially prevents foreign matter that may be in the pressurizable
tire cavity 52 (see Fig. 2) from fouling the regulator 10.
[0014] It is to be understood that the mass of air pumped into the tire cavity 52 by
the AMT pump (and therefore through the outlet filter 14) according to the present
disclosure in a single revolution may be relatively small compared to the mass of air in
a fully inflated tire 50. In an example, an AMT system may pump enough air to make
up for normal losses in a tire. For example, an AMT system may pump about 1 psi
into a 100 psi tire over a month. A range of airflow from about 250 SCCM (Standard
Cubic Centimeters per Minute) to about 1000 SCCM may flow through the outlet filter
14. In terms of mass airflow the same example would range from about 0.3 g (gram)
to about 1.3 g of dry air at STP. In an example, a commercial truck tire may contain
150 liters of air at about 100 psi (689 kilopascals) under normal operating conditions.
[0015] It is to be understood that although the air flowing from the regulator 10 into
the tire cavity 52 passes through the filter, the air passing through the filter will
normally be clean, having passed through an inlet air filter (not shown). The outlet
filter 14 of the present disclosure prevents contamination of the regulator 10 by debris
that would otherwise enter the regulator 10 from the tire cavity 52 during times when
air is not flowing through the outlet filter 14. For example, debris may move in the tire
cavity 52 when the tire 50 drops off a curb at low vehicle speed.
[0016] Fig. 3 is a semi-schematic rear view of the example of the AMT regulator 10
with outlet filter 14 depicted in Fig. 1. Fig. 4 is a semi-schematic, right side view of the
example of the AMT regulator 10 with outlet filter 14 depicted in Fig. 1 with a cross-
section taken through A-A as shown in Fig. 3. Fig. 5 is is a semi-schematic, partial
rear side view of the example of the AMT regulator 10 with outlet filter 14 depicted in
Fig. 1 with a cross-section taken through B-B as shown in Fig.4. Referring to Figs. 3,
4 and 5 together, the filtration media 16 may be disposed in contact with the filter
cover 19 to filter air flowing through the filtration media 16 into a cavity 26 of the outlet
filter 14. The cavity 26 is in fluid communication with at least one port 23 receiving air
from the pump via the regulator 10. The filtration media 16 may block contaminants
from entering the cavity 26 while allowing atmospheric air to be discharged through the

filtration media 16 from the cavity 26 into the tire cavity 52. In an example, the filtration
media 16 may substantially block contaminants from entering the cavity 26 while
allowing a small amount of contaminants to pass through the filtration media 16. As
used herein, substantially block means contaminants in the form of particulate matter
will be blocked if the particulate matter is larger than a predetermined size. For
example, the efficiency of the filtration media 16 may be at least about 90 percent
when exposed to exposed to 150 grams of dust at a maximum flow rate using SAE
J726 JUN2002, Air Cleaner Test Code, Section 5.4. After exposure to the dust, the
pressure drop across the outlet filter 14 is within about 70% of the pressure drop at
clean outlet filter 14 conditions. Pressure drop is measured at maximum flow rate.
The pressure drop across a clean outlet filter 14 may be less than about 1 psi when
measured at maximum flow rate. The cover 19 and cavity 26 may be sized to
accommodate the airflow requirements of the outlet filter 14.
[0017] In an example, the outlet filter 14 may omit the filter cover 19. The clean
side 68 of the filtration media 16 is opposite the dirty side 70 of the filtration media 16.
The dirty side 70 of the filtration media 16 is the side of the filtration media 16 exposed
to the tire cavity 52. The clean side 68 of the filtration media 16 is exposed to the
cavity 26.
[0018] A membrane may be used as a filtration media 16 to block water or other
contaminants. As used herein, membrane means a layer of material which serves as
a selective barrier between two phases (i.e. liquid water and vapor) and remains
impermeable to specific particles, molecules, or substances when exposed to the
action of a driving force. The membrane, in examples, may be about 0.5 mm thick and
may be fixed to the filter cover 19 with an adhesive.
[0019] Contaminants may be introduced to the tire cavity in many ways. For
example, before the tire is mounted, insects and rodents may occupy the tire 50 and
build nests that may not be removed before the tire 50 is mounted. Lubricants used
during mounting may remain in the tire cavity 52. Water and compressor lubricant
may be carried in the airstream during an initial fill of the tire 50. Ice crystals may form
in the tire cavity 52. Rust particles may become detached from wheels and be carried

by currents in the tire. The contaminants listed herein are nonlimitative examples of
contaminants that may be encountered by the outlet filter 14 of the present disclosure.
[0020] The filtration media 16 may include a membrane layer; woven fiber layer; a
non-woven fiber layer; a reticulated foam layer; an activated carbon layer; a porous
solid layer; or combinations thereof. Examples of fiber layers may include a
Polytetrafluoroethylene (PTFE) fiber (e.g., Teflon® fiber, available from E. I. du Pont
de Nemours and Company, Wilmington, Delaware and may include Gore-Tex® brand
materials, available from W. L. Gore & Associates, Inc., Elkton, Maryland. Examples
of the porous solid layer may include compressed carbon charcoal. In an example,
the filtration media 16 may include a layer of activated carbon disposed between two
woven fiber layers. An example of a membrane layer may include a non-woven nylon,
e.g. Versapor® 450R from Pall.
[0021] In examples of the present disclosure, the outlet filter 14 may be modular,
thereby allowing simple replacement of the filtration media 16 when the tire 50 is
dismounted from the wheel 98. In an example, the filtration media 16 is replaceable
without permanently disabling a portion of the regulator 10 other than the filtration
media 16 to be replaced. For example, the housing 12 may be permanently fixed in
the regulator 10, e.g., by welding, whereas the cover 19 may be removable to provide
access to the filtration media 16 for replacement.
[0022] As shown Figs. 3, 4 and 5 together, slots 62 engage retention feature 64 of
housing 12. The retention feature 64 may be a resilient tab, interoperable with slot 62
to deform and enter the space created by slot 62 to form a snap lock between the
cover 19 and the housing 12. Alternatively, the retention feature 64 may be stiffer than
the housing 12 and therefore the housing 12 may deform around retention feature 64
during assembly. The snap retention of the cover 19 onto the housing 12 allows
retention without separate fasteners, eases assembly, and facilitates serviceability of
the outlet filter 14. The outlet filter 14 allows the filtration media 16 to be replaced
without destroying the outlet filter 14.
[0023] Fig. 6 is a side, partially exploded view an outlet filter module 27 of the
present disclosure. The filtration media 16 is shown outside of the outlet filter module

27 to indicate that the filtration media 16 is replaceable in the outlet filter module 27.
In the example depicted in Fig. 6, the retention features 64 are deformable tabs that
may be bent under a rim to retain the filter cover 19 on the filter body 28. A groove 55
is defined in the stem 56 to operably receive a seal, e.g. an o-ring (not shown) for
sealing the outlet filter module 27 against the port 23.
[0024] It is to be understood that the terms "connect/connected/connection" and/or
the like are broadly defined herein to encompass a variety of divergent connected
arrangements and assembly techniques. These arrangements and techniques
include, but are not limited to (1) the direct communication between one component
and another component with no intervening components therebetween; and (2) the
communication of one component and another component with one or more
components therebetween, provided that the one component being "connected to" the
other component is somehow in operative communication with the other component
(notwithstanding the presence of one or more additional components therebetween).
[0025] In describing and claiming the examples disclosed herein, the singular forms
"a", "an", and "the" include plural referents unless the context clearly dictates
otherwise.
[0026] It is to be understood that the ranges provided herein include the stated
range and any value or sub-range within the stated range. For example, a range from
about 250 SCCM to about 1000 SCCM should be interpreted to include not only the
explicitly recited limits of about 250 SCCM and about 1000 SCCM, but also to include
individual values, such as 250 SCCM, 375 SCCM, 750 SCCM, etc., and sub-ranges,
such as from about 270 SCCM to about 500 SCCM, etc. Furthermore, when "about" is
utilized to describe a value, this is meant to encompass minor variations (up to +/-
10%) from the stated value.
[0027] Furthermore, reference throughout the specification to "one example",
"another example", "an example", and so forth, means that a particular element (e.g.,
feature, structure, and/or characteristic) described in connection with the example is
included in at least one example described herein, and may or may not be present in
other examples. In addition, it is to be understood that the described elements for any

example may be combined in any suitable manner in the various examples unless the
context clearly dictates otherwise.
[0028] While several examples have been described in detail, it will be apparent to
those skilled in the art that the disclosed examples may be modified. Therefore, the
foregoing description is to be considered non-limiting.

We Claim:
1. An air regulator outlet filter for an Air Maintenance Technology (AMT) tire,
comprising:
a filter body to be attached to a housing of an air regulator of an AMT tire, the
housing having a cavity to be in fluid communication with an air outlet in fluid
communication with a tire cavity of the AMT tire; and
a filtration media to block contaminants from entering the cavity while allowing
pressurized air to be exhausted through the filtration media into the tire cavity.
2. The outlet filter as defined in claim 1 wherein the filtration media
includes:
a membrane layer;
a woven fiber layer;
a non-woven fiber layer;
a reticulated foam layer;
an activated carbon layer;
a porous solid layer; or
combinations thereof.
3. The outlet filter as defined in claim 1 wherein the filtration media is
replaceable without permanently disabling a portion of the outlet filter other than the
filtration media to be replaced.

ABSTRACT

An air pressure regulator outlet filter for an Air Maintenance Technology (AMT) tire
includes a filter body to be attached to a housing of an air regulator of the AMT tire.
The housing has a cavity to be in fluid communication with an air outlet of the
regulator. The cavity is also in fluid communication with a tire cavity of the AMT tire. A
filtration media is to block contaminants from entering the cavity while allowing
pressurized air to be exhausted through the filtration media into the tire cavity.