U.S. patent number RE39,493 [Application Number 09/030,394] was granted by the patent office on 2007-02-27 for respirator having snap-fit filter cartridge.
This patent grant is currently assigned to 3M Innovative Properties Company. Invention is credited to Thomas W. Holmquist-Brown, Peter O. Rekow, Gregory Yuschak.
United States Patent |
RE39,493 |
Yuschak , et al. |
February 27, 2007 |
**Please see images for:
( Certificate of Correction ) ** |
Respirator having snap-fit filter cartridge
Abstract
A respirator (10) that includes a face piece (14) and a
cartridge receiving structure (22) located on the face piece (14).
The face piece (14) is sized to fit snugly over the nose and mouth
of a person, and the filter cartridge (12) is capable of being
manually snapped into engagement with the cartridge receiving
structure (22). The snap-fit can be instantaneously obtained
without rotational movement of the filter cartridge (12), simply by
pressing the filter cartridge (12) against the receiving structure
(22).
Inventors: |
Yuschak; Gregory (Hudson,
WI), Rekow; Peter O. (Woodbury, MN), Holmquist-Brown;
Thomas W. (St. Paul, MN) |
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
|
Family
ID: |
23482649 |
Appl.
No.: |
09/030,394 |
Filed: |
February 25, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08375855 |
Jan 20, 1995 |
05579761 |
Dec 3, 1996 |
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Current U.S.
Class: |
128/206.17;
128/202.27; 128/206.28; 128/206.12; 128/201.25 |
Current CPC
Class: |
A62B
23/02 (20130101) |
Current International
Class: |
A62B
18/08 (20060101); A62B 18/00 (20060101) |
Field of
Search: |
;128/205.27,206.16,206.17,201.19,202.27 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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634 224 |
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Aug 1936 |
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DE |
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1 708 026 |
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Apr 1971 |
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DE |
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2 609 034 |
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Sep 1977 |
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DE |
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2 322 617 |
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May 1977 |
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FR |
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2 537 695 |
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Jun 1984 |
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FR |
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530 285 |
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Dec 1940 |
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GB |
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2 128 897 |
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May 1984 |
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GB |
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63-13421 |
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Sep 1938 |
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JP |
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Primary Examiner: Lewis; Aaron J.
Attorney, Agent or Firm: Hanson; Karl G.
Claims
What is claimed is:
1. A respirator that comprises: (a) a face piece .Iadd.that is
.Iaddend.sized to fit at least over the nose and mouth of a person;
(b) a cartridge receiving structure .Iadd.that is .Iaddend.located
on the face piece; and (c) a filter cartridge that has a housing
into which a filter element is contained, the filter cartridge
capable of being manually snapped into engagement with the
cartridge receiving structure to produce an audible noise, the
engagement being instantaneously obtainable by pressing the filter
cartridge against the receiving structure without rotational
movement .Iadd.of the filter cartridge relative to the receiving
structure, the filter cartridge further being capable of being
readily separated from the cartridge receiving structure by pulling
manually thereon without additional manual
manipulation..Iaddend.
2. The respirator of claim 1 being a negative pressure
respirator.
3. The respirator of claim 1, wherein there is an interference fit
between the filter cartridge and the cartridge receiving structure
such that an essentially air-tight seal is provided.
4. The respirator of claim 1, wherein the filter cartridge has a
flange that has a radially outward projecting surface, and the face
piece has a skirt that has a radially inward projecting surface,
the radially outward and radially inward projecting surfaces
forming an essentially air-tight seal between the cartridge and the
face piece during engagement.
5. The respirator of claim 1, including a snap-fit engagement
mechanism that comprises a male member and a female member, wherein
during engagement of the filter cartridge to the cartridge
receiving structure, the female member first expands and then
compresses radially inward.
6. The respirator of claim 1, including a snap-fit engagement
mechanism that comprises a male member and a female member, wherein
during engagement of the filter cartridge to the cartridge
receiving structure, the male member first compresses while the
female member simultaneously first expands and then the male member
expands radially outward while the female member simultaneously
compresses radially inward.
7. The respirator of claim 1, wherein the filter cartridge includes
a cylindrical housing that contains a cylindrical filter element,
the cylindrical filter element being offset axially from the
cartridge receiving structure when the filter cartridge is in
engagement with the cartridge receiving structure.
8. The respirator of claim 7, wherein the cartridge receiving
structure encompasses an aperture having a circumference that is
substantially less than the circumference of the cylindrical filter
element.
9. The respirator of claim 1, wherein the filter cartridge can be
snapped into engagement with the face piece by the steps that
consist essentially of pressing the filter cartridge against the
face piece in a direction normal to the face piece.
10. The respirator of claim 9, wherein the filter cartridge can be
removed from the face piece by the steps consisting essentially of
grasping the filter cartridge and pulling thereon axially in a
direction normal to the face piece.
11. The respirator of claim 1, wherein the filter cartridge mates
with the cartridge receiving structure such that a force of 10 to
60 Newtons is required to remove the filter cartridge from
cartridge receiving structure.
12. The respirator of claim 11, wherein 10 to 15 Newtons of force
is required to remove the filter cartridge from the cartridge
receiving structure.
13. The respirator of claim 1, including a snap-fit engagement
mechanism that comprises a male member and a female member, wherein
during engagement of the filter cartridge to the cartridge
receiving structure the male member first compresses and then
expands radially outward.
14. The respirator of claim 13, further including a second
engagement mechanism that is located laterally from the snap-fit
engagement mechanism.
15. The respirator of claim 13, wherein the snap fit engagement
mechanism is offset laterally from the filter element and includes
an outflow aperture having a circumference substantially smaller
than a circumference of the filter element.
16. The respirator of claim 1, wherein the cartridge receiving
structure is in the form of a projecting flange, and wherein the
filter cartridge includes a skirt that engages the projecting
flange.
17. The respirator of claim 16, wherein the skirt is made from a
polymeric resin that has a flexural modulus of 2.times.10.sup.8 to
30.times.10.sup.8 pascals, and wherein the projecting flange is
made from a more rigid polymeric material that has a flexural
modulus of 6.times.10.sup.8 pascals to 70.times.10.sup.8
pascals.
18. The respirator of claim 16, wherein the projecting flange has a
radially outward projecting surface that engages a radially inward
projecting surface on the skirt.
19. The respirator of claim 18, wherein the skirt expands radially
outward from a rest condition and the projecting flange is pressed
radially inward when the filter cartridge is pressed towards the
face piece.
20. The respirator of claim 19, wherein the skirt exerts pressure
on the projecting flange during engagement to create an essentially
airtight seal between the skin and the flange.
.[.21. A respirator that comprises: a face piece sized to fit at
least over the nose and mouth of a person; a filter cartridge that
includes a housing and a filter element, the filter element being
contained within the housing; and a snap-fit engagement mechanism
that enables the filter cartridge to be instantaneously and audibly
secured to the face piece, the snap-fit engagement mechanism
including a male member and a female member, wherein during the
snap-fit engagement of the filter cartridge to the face piece the
male member initially compresses radially inward while the female
member simultaneously initially expands radially outward followed
by the male member expanding radially outward while the female
member simultaneously compresses radially inward..].
22. A filter cartridge useful for filtering contaminants that are
inhaled through a respirator worn by a person and for permitting
instantaneous attachment and removal from a cartridge receiving
structure on a face piece of the respirator, the filter cartridge
comprising a housing and a filter element, the filter element
residing in the housing and the housing including a means for
allowing the filter cartridge to be manually and audibly snapped
into engagement with a cartridge receiving structure by pressing
the filter cartridge against a cartridge receiving structure on a
face piece without using rotation movement .Iadd.of the cartridge
relative to the receiving structure and for readily separating the
filter cartridge from the cartridge receiving structure by pulling
manually thereon without additional manual
manipulation.Iaddend..
.[.23. A respirator that comprises: a face piece sized to fit at
least over the nose and mouth of a person; a filter cartridge that
includes a housing and a filter element, the filter element being
contained within the housing; and a snap-fit engagement mechanism
that enables the filter cartridge to be instantaneously and audibly
secured to the face piece, the snap-fit engagement mechanism
including a male member and a female member, wherein during the
snap-fit engagement of the filter cartridge to the face piece, the
male member initially compresses radially inward while the female
member remains essentially static followed by the male member
expanding radially outward..].
.[.24. A respirator that comprises: a face piece sized to fit at
least over the nose and mouth of a person; a filter cartridge that
includes a housing and a filter element, the filter element being
contained within the housing; and a snap-fit engagement mechanism
that enables the filter cartridge to be instantaneously and audibly
secured to the face piece, the snap-fit engagement mechanism
including a male member and a female member, wherein during the
snap-fit engagement of the filter cartridge to the face piece, the
male member remains essentially static while the female member
initially expands radially outward followed by compressing radially
inward..].
.Iadd.25. A respirator that comprises: (a) a face piece that is
sized to fit at least over the nose and mouth of a person; (b) a
cartridge receiving structure that is located on the face piece;
(c) a filter cartridge that includes a housing and a filter
element, the filter element being contained in the housing; and (d)
means for manually snapping the filter cartridge into instantaneous
engagement with the cartridge receiving structure to produce an
audible noise by pressing the filter cartridge against the
receiving structure without rotational movement of the cartridge
relative to the receiving structure and for readily separating the
filter cartridge from the cartridge structure by pulling manually
thereon without additional manual manipulation..Iaddend.
.Iadd.26. The respirator of claim 25, wherein the means for
manually snapping includes a male member and a female member so
configured wherein during the snap-fit engagement of the filter
cartridge to the face piece the male member initially compresses
radially inward while the female member simultaneously initially
expands radially outward followed by the male member expanding
radially outward while the female member simultaneously compresses
radially inward..Iaddend.
.Iadd.27. The respirator of claim 25, wherein the means for
manually snapping includes a male member and a female member so
configured wherein during the snap-fit engagement of the filter
cartridge to the face piece, the male member initially compresses
radially inward while the female member remains essentially static
followed by the male member expanding radially
outward..Iaddend.
.Iadd.28. The respirator of claim 25, wherein the means for
manually snapping includes a male member and a female member so
configured wherein during the snap-fit engagement of the filter
cartridge to the face piece, the male member remains essentially
static while the female member initially expands radially outward
followed by compressing radially inward..Iaddend.
Description
TECHNICAL FIELD
This invention pertains to a respirator that has a snap fit filter
cartridge.
BACKGROUND OF THE INVENTION
Many techniques have been used in the respirator art to attach
filter elements to respirators. A common technique has the filter
element disposed in a threaded cartridge that is attached to a
corresponding threaded fitting on the body of the respirator; see,
for example, U.S. Pat. Nos. 5,222,488, 5,063,926, 5,036,844,
5,022,901, 4,548,626, and 4,422,861. Known filter cartridges
typically possess helical or advancing spiral threads that mate
with a tapped collar or socket that receives the threaded portion
of the filter cartridge. Rotating the filter cartridge in an
appropriate direction allows the cartridge to be attached to or
removed from the respirator. A resilient, deformable gasket often
is used to ensure an airtight fit to the respirator body.
In lieu of threads, a bayonet type closure has been used to attach
a filter cartridge to a respirator; see, for example, U.S. Pat.
Nos. 5,062,421, 4,934,361, and 4,850,346. The bayonet type closure
disclosed in the '421 patent has locking tabs and notches to secure
the components together. The locking tabs project from the filter
cartridge and engage the notches in an aperture on the respirator
body. .[.By rotating the filter cartridge in the appropriate
direction, the cartridge snaps into engagement..]. .Iadd.Each notch
receives a locking tab and permits the cartridge to be snapped into
place and prevented from rotating. .Iaddend.In the '361 and '346
patents, an audible device is used to indicate that the filter
cartridge is properly coupled to the respirator face piece. A lug
on the face piece is provided with a detent ramp or cam having an
inclined surface that is positioned to gradually deflect or deform
a rib on the cartridge. As the cartridge and face piece are rotated
relative to each other into a locking position, the cam engages the
rib and causes the rib and lug to deflect until the rib abruptly
drops off the end of the cam. The abrupt action produces the
audible click.
In another technique disclosed in U.S. Pat. No. 5,148,803, a
bellows is used to fasten a filter to the respirator. The bellows,
together with a rigid band, form a rigid cuff which receives the
filter. The cuff is continued in an elastic sleeve that surrounds
the filter in a gas-tight manner. To change the filter, the sleeve
is first folded back to the level of the cuff, the filter element
is inserted into the cuff, and the sleeve is then folded back over
the filter element.
U.S. Pat. Nos. 5,033,465 and 5,078,132 disclose a respirator that
uses edge seals to secure a filter element to the respirator's
elastomeric face piece. The filter element includes bonded
activated carbon granules, and the edge seals are disposed between
the filter element and the elastomeric face piece. The edge seals
are made of a suitable adhesive material such as a hot-melt
adhesive, a hot-melt foam adhesive, or a latex adhesive.
A foam mask shell is disclosed in U.S. Pat. No. 4,856,508 for
receiving a filter cartridge. The foam mask shell possesses a
collar that defines an opening for receiving the filter cartridge.
The filter cartridge has an extension with an outside dimension
approximately equal to the inside dimension of the cylindrical
passage through the collar. To mount the filter cartridge, its
extension is inserted into the opening where it makes a relatively
tight friction fit. The mask shell is made of a flexible foam
material that expands when the extension is inserted in the
opening. To replace a filter element, it is grasped and twisted
back and forth while pulling it away from the mask shell.
In U.S. Pat. No. 4,790,306, a respirator is described that uses
insert molding to permanently secure a bonded absorbent filter
element to a respirator face piece.
A plug-in frame is described in U.S. Pat. No. 4,771,771 to secure a
filter cartridge in a chamber of the respirator. The filter
cartridge is disposed in the chamber by seals that bear tightly
against the cartridge to hold it in place. The filter cartridge can
be fitted to the respirator by sliding it through an opening in the
plug-in frame.
In U.S. Pat. No. 4,630,604, locking tongues are employed on a
filter retainer to hold a replaceable filter member in an abutting
relationship to the respirator frame. The filter member can be
replaced by snapping off the filter retaining member from the
frame.
A further technique is disclosed in U.S. Pat. No. 4,562,837 where
the respirator is provided with a guide ring for engaging a filter
housing. The guide ring is carried by a sleeve portion that defines
an opening through which the glasses pass. The filter housing
slides on the guide ring from a retracted stand-by position to an
extended use position. A bellows, located between the filter
housing and respirator, permits movement of the filter housing
between its retracted stand-by position and its extended use
position.
Sundstrom Safety AB of Lidingo, Sweden markets a respirator in
Europe and Australia under the designation SR-62, which uses an
elastomeric rubber filter retainer for accommodating a filter
cartridge. The filter cartridge comprises a gas and vapor or
particulate filter in a rigid injection molded plastic cartridge.
To insert the filter cartridge into the retainer, the retainer is
stretched over the filter element's periphery. When two different
filters are used in series, they may be snapped together and
inserted into the retainer as a single unit. To separate the
filters, a tool is provided on the harness system to pry them
apart.
Although the above-discussed respirators use various techniques for
securing a filter and filter cartridges to respirators, these
techniques have a number of drawbacks. For example, the filter
cartridges that are threaded to the respirator typically include a
housing or canister into which the filter material is retained. The
cartridge's cylindrical geometry typically requires using the
filter cartridge as an external appendage that can interfere with a
wearer's vision. Further, the threaded cartridges employ many parts
that add to the filter element's total volume and the respirator's
overall weight. In other designs, such as disclosed in U.S. Pat.
Nos. 5,078,132, 5,033,465, and 4,790,306, the filters are not able
to be readily replaced, and thus when the filter element's service
life has met its limit, the whole respirator is discarded as waste.
In the model SR-62 respirator sold by Sundstrom, the filter
cartridge is replaceable; however, the retainer lacks physical
strength relative to the filter element, and thus, like placing a
rubber tire on a wheel, a number of manipulations are needed to
place the filter element in the elastomeric rubber retainer. In
addition, elastomeric materials can be relatively expensive and
more difficult to process. Some of the other respirators discussed
above possess the drawback of using gaskets or O-rings to obtain a
hermetic seal or use fairly complicated systems for mounting filter
elements to respirators.
SUMMARY OF THE INVENTION
The respirator of this invention overcomes many of the drawbacks of
prior art respirators. The respirator does not employ many parts to
secure the filter cartridge to the respirator face piece, and there
is no need for a gasket, O-ring, or permanent adhesive to obtain a
hermetic fit between the cartridge and face piece. Also, the filter
cartridge is relatively lightweight, and it can be mounted to and
removed from the face piece in a single motion without excessive
manipulation. The respirator is relatively easy to manufacture,
allowing production costs to be minimized.
In brief summary, the respirator of the invention comprises: (a) a
face piece sized to fit at least over the nose and mouth of a
person; (b) a cartridge receiving structure located on the face
piece; and (c) a filter cartridge that has a housing into which a
filter element is contained, the filter cartridge capable of being
manually snapped into engagement with the cartridge receiving
structure to produce an audible noise, the engagement being
instantaneously obtainable by pressing the filter cartridge against
the receiving structure without rotational movement.
The present invention also includes a filter cartridge useful for
filtering contaminants that are present in air that is inhaled
through a respirator worn by a person. The filter cartridge permits
instantaneous attachment and removal from a face piece of the
respirator and comprises a housing and a filter element. The filter
element is contained in the housing, and the housing includes a
means for allowing the filter cartridge to be manually snapped into
engagement with a cartridge receiving structure by pressing the
filter cartridge against the cartridge receiving structure without
using rotation movement.
The invention differs from known respirators in that the filter
cartridge can be instantaneously snapped into engagement to the
respirator face piece without rotational movement. This is achieved
simply by pressing the first cartridge against the corresponding
receiving structure on the face piece. The invention thus provides
an extraordinarily easy means for attaching a filter cartridge to
the respirator face piece. An audible noise is provided to indicate
a secure attachment. The invention also can allow the filter
cartridge to be quickly removed from a respirator face piece. This
can be accomplished simply by pulling on the cartridge in a
direction opposite to which it was pressed onto the face piece.
Rotational movement also is not necessary to separate the filter
cartridge from the respirator face piece.
The above and other advantages of the invention are more fully
shown and described in the drawings and detailed description of
this invention, where like reference numerals are used to represent
similar parts. It is to be understood, however, that the drawings
and description are for the purposes of illustration only and
should not be read in a manner that would unduly limit the scope of
this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a respirator 10 in accordance with
the invention;
FIG. 2 is a front view of respirator 10 in accordance with the
invention, without filter element 16 disposed in cartridge 12.
FIG. 3 is a partial cross-sectional view of respirator 10 taken
along lines 3--3 of FIG. 2;
FIG. 4 is an expanded cross-sectional view illustrating the
engagement of filter cartridge 12 to face piece 14 in accordance
with the invention.
FIG. 5 is a cross-section of a filter cartridge 12 in accordance
with the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the practice of this invention, a respirator is provided that
has a filter cartridge that can be manually attached to and
detached from a respirator face piece without risk of leakage. The
seal between the cartridge and face piece is hermetic, and
attachment and detachment can be instantaneous.
FIGS. 1, 2, and 3 illustrate a respirator 10 that comprises a
filter cartridge 12 and a face piece 14. Filter cartridge 12
includes a cylindrical housing 13 that contains a cylindrical
filter element 16. Filter element 16 may comprise, as shown, a
gaseous filter 18 and a particulate filter 20. Filter element 16 is
described in more detail below. The filter cartridge's housing 13
surrounds the peripheral surface of the filter element and covers
its inflow surface at the periphery.
Filter cartridge 12 can be snapped into engagement with face piece
14 by the steps that consist essentially of pressing the filter
cartridge against the face piece in a direction generally normal to
the face piece (or parallel to the filter cartridges axis). The
cartridge can be secured to the face piece without rotational
movement of the cartridge or face piece--although the invention
does not necessarily rule out such movement. The cartridge 12 can
be quickly removed from the face piece by the steps consisting
essentially of grasping the filter cartridge 12 (including an
appendage thereto) and pulling thereon axially in a direction away
from and normal to the face piece 14. Rotational movement also is
not necessary to remove the cartridge from the face piece.
Face piece 14 is sized to fit at least over the nose and mouth of a
person. A face piece conceivably could be provided that fits over
other portions of a person's face (namely, the eyes), such as in a
full face configuration; however, the face piece, as illustrated
here, typically is fashioned in a half-mask configuration--that is,
one that fits only over the nose and mouth. As shown, face piece 14
may comprise a soft, compliant portion 15 molded in sealing
engagement about a rigid central portion 17. The rigid central
portion 17 includes an aperture 19 through which filtered air
travels to enter the respirator's interior. An inhalation valve can
be mounted at 21 as so desired. Respirators having soft, compliant
facial portions and rigid central sections onto which the filter
cartridge(s) are mounted are known in the art as shown in U.S. Pat.
No. 5,062,421.
As shown, the respirator 10 is a "negative pressure" respirator.
That is, the respirator relies on the wearer's lungs as the means
for drawing air through the respirator. Such respirators are termed
"negative pressure" because the pressure inside the respirator is
less than ambient during an inhalation. In contrast, "positive
pressure" respirators rely on forced air (e.g., from a pressure
tank or blower that is carried by the person) to supply oxygen to
the wearer, and the pressure inside the respirator is greater than
atmospheric. The present invention also may be suitable for use
with positive pressure respirators.
When using respirator 10, the negative pressure created by the
expansion of the wearer's lungs causes air to be drawn through the
filter element 16 in cartridge 12, out an outflow aperture (23,
FIGS. 3 and 4) in the filter cartridge 12, and through an inflow
aperture (19, FIGS. 3 and 4) in the respirator face piece 14, to
enter the face piece's interior where the air can be inhaled by the
wearer. Thus, the filter cartridge is disposed in fluid
communication with the interior of the respirator face piece.
FIGS. 3 and 4 illustrate structurally how filter cartridge 12 can
be snap-fitted to face piece 14. Face piece 14 does not include a
filter element but includes a cartridge receiving structure in the
form of a projecting flange 22 for allowing a filter element to be
secured to the face piece 14. As shown, projecting flange 22
engages a skirt 24 on filter cartridge 12. projecting flange 22
preferably has a radially outward projecting surface 26 that
engages a radially inward projecting surface 28 on shirt 24. When
filter cartridge 12 is pressed axially towards face piece 14, skirt
24 expands radially outward from its rest condition, while
projecting flange 22 is pressed radially inward. As filter
cartridge 12 continues to be pressed towards face piece 14,
radially inward projecting surface 28 passes the maximum radially
outward point 29 of radially outward projecting surface 26 allowing
skirt 24 to contract inwards and flange 22 to expand outwards.
Filter cartridge 12 then snaps into direct engagement with face
piece 14. In the attached state, the skirt 24 relaxes to
essentially its pre-engaged position but still exerts some pressure
against the projecting flange 22--that is, it creates an
interference therewith--to provide an essentially air-tight seal
between the components. To obtain such an interference, the
radially inward projecting surface 28 has a circumference, or in
this circular configuration, a diameter that is nominally smaller
than the circumference or diameter of the radially outward
projecting surface 26. The seal may be accomplished without using a
gasket or other suitable sealing mechanism. Thus, when the
respirator is worn by a person, inhaled air enters the interior of
face piece 14 essentially exclusively by passing from outflow
aperture 23 on filter cartridge 12 through inflow aperture 19 on
face piece 14. A duct 25 is located behind the filter element to
facilitate air flow from the filter element through outflow
aperture 23. The outflow and inflow apertures preferably encompass
a substantially smaller area (i.e., have a substantially smaller
circumference) than the filter element's circumference. The
snap-fit hermetic seal may consist essentially of the projecting
flange 22 and the skirt 24. Exhaled air can exit the face piece's
interior 27 through an exhalation port 31.
The radially inward projecting surface 28 on the inside of skirt 24
may take a variety of forms. For example, the radially inward
projecting surface can be, as shown, a surface angled slightly
inward (at less than 90.degree.), or it can be in the form of a
rib, a bevel, cam, or other inwardly facing projection. When skirt
24 is in a circular configuration, its inner diameter preferably
decreases axially in the direction of end 30. The radially outward
projecting surface 26 on projecting flange 22 also may come in a
variety of forms, including those listed above for skirt 24.
Conceivably, projecting flange 22 also can have a groove (not
shown) into which a corresponding rib from skirt 24 engages.
Thus, the respirator of the invention includes a snap-fit
engagement means that comprises a male member or projecting flange
22 and a female member or skirt 24, wherein during engagement of
the filter cartridge 12 to the cartridge receiving structure 22,
the projecting flange 22 first compresses and then expands radially
outward and the skirt 24 first expands and then radially compresses
inward. The compression of the flange 22 and expansion of the skirt
24 preferably occur essentially simultaneously, and the subsequent
expansion of the flange 22 and compression of skirt 24 also occur
simultaneously. A snap fit also could be achieved by having only
one of the flange or skirt expand and contract and by having the
other remain essentially static.
The radially outward and inward projecting surfaces 26 and 28 can
influence the ease, or conversely the difficulty, of attaching and
removing the filter cartridge. Increasing the size of the radially
outward and radially inward projecting surfaces 26 and 28 increases
the degree to which the skirt 24 is stretched radially outward,
which, in turn, can make attachment or removal more difficult.
Also, the geometry of surfaces 26 and 28 can influence how
gradually or suddenly filter cartridge 12 snaps into position. The
material properties of the component parts also is a factor
relevant to ascertaining adequate forces for manually attaching and
manually separating the parts. What is meant by "manually" is that
the filter cartridge can be readily attached and removed from the
face piece by use of a person's hands without assistance from any
mechanical source separate from the respirator. There is no need
for any external tool or instrument or any need to destroy or
dismember the respirator to attach or remove the filter cartridge
from the face piece. The material properties and other parameters
may be adjusted to provide a desirable balance between a snug
secure attachment and easy removability. It has been found that a
force of 10 to 60 Newtons can provide ease of removability and
still provide a secure attachment, and that a removal force of 15
to 25 Newtons is preferred.
Skin 24 preferably is made from a resilient polymeric resin capable
of elastic deformation to permit skin 24 to snap over projecting
flange 22 and to return its approximate former dimension. Materials
with a flexural modulus of 2.times.10.sup.8 to 30.times.10.sup.8
pascals (.about.30,000 to 400,000psi) at 22.degree. C. (73.degree.
F.) may be suitable for this purpose. When the flexural modulus is
less than this range, substantial deformation or stretching may be
needed to ensure that a good seal is made between the cartridge and
the face piece, making it cumbersome to secure the former to the
latter. When the flexural modulus is greater than this range, the
material may be difficult to deform, making the force required for
removal undesirably large and the manufacturing tolerances
undesirably narrow. The skin material preferably also is a
thermoplastic to facilitate fabrication. Some materials useful for
forming a skirt 24 include polyethylene, polypropylene, and
thermoplastic rubbers. Low density polyethylene, such as
Dowlex.TM.2553 polyethylene (Dow Chemical Company, Midland, Mich.)
which has a flexural modulus of 6.6.times.10.sup.8 pascals
(.about.95,000 psi), is a particularly suitable material. High
density polyethylene, such as Dow 8454, which has a flexural
modulus of 9.5.times.10.sup.8 pascals also is particularly
suitable. One embodiment of this invention has an injection molded
filter cartridge made of low density polyethylene, a bonded filter
element which is compression fit into the cartridge housing, and
optionally a particle filter stacked on the bonded filter element.
The bonded filter element may be produced in accordance with the
teachings of U.S. Pat. Nos. 5,033,465 and 5,078,132 to Braun and
Rekow. The particulate filter element can be an
electrically-charged fibrous web; see, for example, U.S. Pat.
Reissue No. 32,171 or U.S. Pat. Reissue. No. 30,782 to Van
Turnhout.
Projecting flange 22 preferably is made from a material that is
somewhat stiffer than the skirt material. Materials having a
flexural modulus greater than 6.times.10.sup.8 pascals
(.about.95,000 psi) at 22.degree. C. (73.degree. F.) preferably are
used to form flange 22. Typically the flange 22 has a flexural
modulus of less than 70.times.10.sup.8 pascals (.about.1,000,000
psi). Examples of suitable materials include
acrylonitrile-butadiene-styrene copolymers (ABS), acetals,
polycarbonates, polyethylene, polypropylene, polystyrene, et
cetera. polypropylene, such as Amoco.TM. 3234 polypropylene (Amoco
Chemical Company, Chicago, Ill.), which is believed to have a
flexural modulus of 17.times.10.sup.8 pascals (245,000 psi), is
particularly suitable material for use in forming projecting flange
22.
As indicated above, when skin 24 is snapped into engagement with
flange 22, there is an audible noise such as a click. An audible
noise alerts the user that the cartridge is in position ready for
use. A click can be provided when the skirt is stretched beyond a
certain limit and then is suddenly relaxed.
In some instances, there may be a need to provide an additional
securing means beyond the snap fit. The additional securing means
may be furnished to assist in preventing accidental dislodgement of
the filter cartridge from the face piece such as from an unexpected
lateral force. The additional securing means could take the form of
a hook 34 shown in FIGS. 3 and 5 disposed laterally from the skin
24 and cartridge receiving structure 22. Hook 34 is insertable into
a corresponding slot 36 in face piece 14. Attachment of the filter
cartridge 12 to face piece 14 involves first engaging hook 34 in
slot 36. Hook 34 then acts as a hinge about which the cartridge 12
pivots as it is pressed generally axially towards or away from face
piece 14. A tab 38 can be provided on cartridge 12 to facilitate
detaching the cartridge from the face piece 14.
When hook 34 and slot 36 are not employed on filter cartridge 12,
the cartridge can be grasped about its periphery to cause its
separation from the face piece 14. Leverage is another factor that
affects ease or difficulty of filter cartridge attachment or
removal. Because the skirt 24 is dimensioned to encompass a smaller
area than filter 16 and is not concentric with or offset axially
from the center of filter cartridge 16, leverage is available for
separating cartridge 12 from face piece 14. As shown, the projected
area of the skirt is not encompassed by the projected area of the
filter element--that is, the radius of the filter element is less
than the sum of the offset plus the radius of the outflow aperture.
If hook 34 is disengaged or is not employed, a person grasping
filter cartridge 12 can simply pull from end 32 opposite skirt 24
to separate cartridge 12 from face piece 14.
Although the present invention has been illustrated with the face
piece 14 having a projecting flange 22 and the filter cartridge 12
having a skirt 24, it may be possible in this invention to do the
reverse. That is, alternatively the filter cartridge could be
provided with a projecting flange and the face piece could possess
the skirt. In lieu of a projecting flange and a skirt, other
suitable mechanisms may be envisioned to provide a snap-fit in
accordance with this invention. Thus, it is to be understood that
the invention is not to be limited to the above-described
embodiments but is to be controlled by the limitations set forth in
the claims and any equivalents thereof. It also is to be understood
that this invention may be practiced in the absence of any
limitation or item not explicitly set forth above.
* * * * *