U.S. patent number RE37,974 [Application Number 09/442,082] was granted by the patent office on 2003-02-04 for uni-directional fluid valve.
This patent grant is currently assigned to 3M Innovative Properties Company. Invention is credited to John Lawrence Bowers.
United States Patent |
RE37,974 |
Bowers |
February 4, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Uni-directional fluid valve
Abstract
A uni-directional fluid valve particularly for use as an
exhalation valve for a filter mask comprises a flexible flap
attached at one end to a concave portion of a seat. The mounting of
the flap imparts to it a transverse curvature, stiffening the flap
sufficiently for it to remain seated in the absence of a pressure
differential across it even when orientated with the seat above the
flap.
Inventors: |
Bowers; John Lawrence (High
Wycombe, GB) |
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
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Family
ID: |
10778752 |
Appl.
No.: |
09/442,082 |
Filed: |
November 15, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
686839 |
Jul 26, 1996 |
05687767 |
Nov 18, 1997 |
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Foreign Application Priority Data
Current U.S.
Class: |
137/855;
128/205.24; 128/206.15 |
Current CPC
Class: |
A62B
18/10 (20130101); F16K 15/144 (20130101); F16K
15/16 (20130101); Y10T 137/7891 (20150401) |
Current International
Class: |
A62B
18/00 (20060101); A62B 18/10 (20060101); F16K
15/14 (20060101); F16K 015/16 () |
Field of
Search: |
;137/855,856,857,858
;128/205.24,206.15,205.25,203.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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40 29 939 |
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Mar 1992 |
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DE |
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2072516 |
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Oct 1981 |
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GB |
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2 072 516 |
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Oct 1981 |
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GB |
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Primary Examiner: Rivell; John
Attorney, Agent or Firm: Jacobson Holman, PLLC
Claims
I claim:
1. A uni-directional fluid valve comprising a cantilevered flexible
flap and a cooperating valve seat surrounding a valve orifice; the
cantilevered flexible flap having a planform defining a root end
and free end at opposite ends of a longitudinal axis of the flap,
and two peripheral side edges respectively extending between the
root end and the free end; the valve seat having sealing surfaces
that contact the flap along said root end, free end and peripheral
side edges when the fluid valve is closed; the cantilevered
flexible flap is .[.attached to.]. .Iadd.mounted in contact with
.Iaddend.the respective sealing surface of the valve seat at said
root end and is freely movable to flex away from the respective
sealing surfaces of the valve seat at said free end and along at
least portions of said peripheral side edges when fluid flows
through the fluid valve and the fluid valve is open; and said root
end of the cantilevered flexible flap and the respective sealing
surface that contacts the cantilevered flexible flap at said root
end have a fixed curvature in a direction transverse to said
longitudinal axis, said transverse curvature biases the flap and
maintains it substantially in contact with all said sealing
surfaces of the valve seat in the absence of an opening pressure
differential across the flap, in any orientation of the valve.
2. A valve according to claim 1 wherein the cantilevered flexible
flap exhibits said curvature in its natural state.
3. A valve according to claim 1 wherein said curvature is imparted
to the cantilevered flexible flap by virtue of its mounting on the
valve seat.
4. A valve according to claim 3 wherein the cantilevered flexible
flap is trapped at said root end between confronting respectively
concave and convex surfaces of first and second structural members,
said concave surface comprising a said sealing surface of said
valve seat.
5. A valve according to claim 4 wherein said second structural
member presents a further surface in contact with a central portion
of the cantilevered flexible flap adjacent to said root end to
accentuate the curvature thereof.
6. A valve according to claim 1 wherein the respective said sealing
surface of the valve seat which the free end of the cantilevered
flexible flap contacts is substantially flat.
7. A valve according to claim 1 wherein the respective said sealing
surface of the valve seat which the free end of the cantilevered
flexible flap contacts is of concave curvature.
8. A valve according to claim 1 wherein the respective said sealing
surfaces of the valve seat which the peripheral side edges of the
cantilevered flexible flap contact are substantially flat.
9. A valve according to claim 1 wherein the mounting of the
cantilevered flexible flap in the valve seat imparts a longitudinal
curvature to the central section of the cantilevered flexible
flap.
10. A filter mask having an exhalation valve comprising a
cantilevered flexible flap and a cooperating valve seat surrounding
a valve orifice; the cantilevered flexible flap having a planform
defining a root end and a free end at opposite ends of a
longitudinal axis of the cantilevered flexible flap, and two
peripheral side edges respectively extending between the root end
and the free end; the valve seat having sealing surfaces that
contact the cantilevered flexible flap along said root end, free
end and peripheral side edges when the exhalation valve is closed;
the cantilevered flexible flap is .[.attached to.]. .Iadd.mounted
in contact with .Iaddend.the respective sealing surface of the
valve seat at said root end and is freely movable to flex away from
the respective sealing surfaces of the valve seat at said free end
and along at least portions of said peripheral side edges when a
user of the filter mask exhales and causes the exhalation valve to
open: and said root end of the cantilevered flexible flap and the
respective sealing surface that contacts the cantilevered flexible
flap at said root end have a fixed curvature in a direction
transverse to said longitudinal axis, said transverse curvature
biases the flap and maintains it substantially in contact with all
said sealing surfaces of the valve seat in the absence of an
exhalatory pressure differential across the flap, in any
orientation of the valve.
11. A filter mask according to claim 10 wherein the exhalation
valve is so located that during normal head movements of a wearer
the cantilevered flexible flap will lie below the valve
seat..Iadd.
12. A uni-directional fluid valve comprising: a cantilevered
flexible flap and a cooperating valve seat surrounding a valve
orifice; the cantilevered flexible flap having a planform defining
a root end and a free end at opposite ends of a longitudinal axis
of the flap; the valve seat having sealing surfaces that contact
the flap at said root end and the free end when the fluid valve is
closed; the cantilevered flexible flap being mounted in contact
with the respective sealing surface of the valve seat at said root
end and being freely movable to flex away from the respective
sealing surface of the valve seat at said free end when fluid flows
through the fluid valve and the fluid valve is open; and said root
end of the cantilevered flexible flap and the respective sealing
surface that contacts the cantilevered flexible flap at said root
end having a transverse configuration extending in a direction
transverse to said longitudinal axis, said transverse configuration
resulting in maintaining the flap substantially in contact with
said sealing surfaces of the valve seat in the absence of an
opening pressure differential across the flap, in any orientation
of the valve..Iaddend..Iadd.
13. A uni-directional fluid valve comprising: a cantilevered
flexible flap and a cooperating valve seat surrounding a valve
orifice; the cantilevered flexible flap having a planform defining
a root end and a free end at opposite ends of a longitudinal axis
of the flap, and two peripheral side edges respectively extending
between the root end and the free end; the valve seat having
sealing surfaces that contact the flap at said root end, said free
end, and said peripheral side edges when the fluid valve is closed;
the cantilevered flexible flap being mounted in contact with the
respective sealing surface of the valve seat at said root end and
being freely movable to flex away from the respective sealing
surface of the valve seat at said free end and along at least
portions of said peripheral side edges when fluid flows through the
fluid valve and the fluid valve is open; and said root end of the
cantilevered flexible flap and the respective sealing surface that
contacts the cantilevered flexible flap at said root end having a
transverse configuration extending in a direction transverse to
said longitudinal axis, said transverse configuration resulting in
maintaining the flap substantially in contact with said sealing
surfaces of the valve seat in the absence of an opening pressure
differential across the flap, in any orientation of the
valve..Iaddend..Iadd.
14. A filter mask having an exhalation valve comprising: a
cantilevered flexible flap and a cooperating valve seat surrounding
a valve orifice; the cantilevered flexible flap having a planform
defining a root end and a free end at opposite ends of a
longitudinal axis of the cantilevered flexible flap; the valve seat
having sealing surfaces that contact the cantilevered flexible flap
along said root end and said free end when the exhalation valve is
closed; the cantilevered flexible flap being mounted in contact
with the respective sealing surface of the valve seat at said root
end and being freely movable to flex away from the respective
sealing surface of the valve seat at said free end when a user of
the filter mask exhales and causes the exhalation valve to open and
wherein said root end of the cantilevered flexible flap and the
respective sealing surface that contacts the cantilevered flexible
flap at said root end have a transverse configuration extending in
a direction transverse to said longitudinal axis so that the flap
is substantially maintained in contact with all of said sealing
surfaces of the valve seat in the absence of an exhalatory pressure
differential across the flap, in any orientation of the
valve..Iaddend..Iadd.
15. A filter mask having an exhalation valve comprising: a
cantilevered flexible flap and a cooperating valve seat surrounding
a valve orifice; the cantilevered flexible flap having a planform
defining a root end and a free end at opposite ends of a
longitudinal axis of the cantilevered flexible flap, and two
peripheral side edges respectively extending between the root end
and the free end; the valve seat having sealing surfaces that
contact the cantilevered flexible flap along said root end, free
end and peripheral side edges when the exhalation valve is closed;
the cantilevered flexible flap being mounted in contact with the
respective sealing surface of the valve seat at said root end and
being freely movable to flex away from the respective sealing
surfaces of the valve seat at said free end and along at least
portions of said peripheral side edges when a user of the filter
mask exhales and causes the exhalation valve to open and wherein
said root end of the cantilevered flexible flap and the respective
sealing surface that contacts the cantilevered flexible flap at
said root end have a transverse configuration extending in a
direction transverse to said longitudinal axis so that the flap is
substantially maintained in contact with all of said sealing
surfaces of the valve seat in the absence of an exhalatory pressure
differential across the flap, in any orientation of the
valve..Iaddend.
Description
.Iadd.Notice: More than one reissue application has been filed for
the reissue of U.S. Pat. No. 5,687,767. The reissue applications
are application Ser. No. 09/442,082, the present application and
Ser. No. 09/986,346, a continuation reissue of U.S. Pat. No.
5,687,767..Iaddend.
BACKGROUND OF THE INVENTION
The present invention relates to a uni-directional fluid valve
which may in particular be used as an exhalation valve for a filter
mask. By a "filter mask" we mean a device adapted to be worn over
the nose and mouth of a user and made from or incorporating a
filter material to remove one or more unwanted components from the
inspired air. To improve the comfort and efficiency of such devices
it is common to provide a uni-directional exhalation valve on the
mask which opens under the pressure differential consequent upon
exhalation of the user to allow for a relatively unrestricted flow
of exhalate out of the mask, but which closes under other
conditions. Examples of valved filter masks are shown in
GB-2072516, DE-4029939, U.S. Pat. No. 4,414,973, U.S. Pat. No.
4,838,262, U.S. Pat. No. 4,873,972, U.S. Pat. No. 4,934,362, U.S.
Pat. No. 4,958,633, U.S. Pat. No. 4,974,586, U.S. Pat. No.
4,981,134 and U.S. Pat. No. 5,325,892.
A common type of exhalation valve comprises a circular diaphragm of
e.g. silicone rubber and a cooperating circular valve seat
surrounding the orifice which passes the user's exhalate. The
diaphragm is clamped at its centre and marginal portions flex away
from the seat when the user exhales. In another known type the
diaphragm is in the form of a flexible flap which is attached to a
cooperating seat structure at one end, that is to say in cantilever
fashion, and flexes away from the rest of the seat when the user
exhales. In the design of an exhalation valve it is important to
maximise the cross-sectional area of the open orifice to allow free
flow of exhalate through the valve, and also to minimise the
differential air pressure required to open the valve (i.e. the
valve "cracking" pressure). Centrally clamped diaphragm valves
require a grater force to open them than cantilevered flap type
valves of equivalent size because their available "lever arm" is
less. Furthermore, the structure of a cantilevered flap type valve,
when open, generally presents less of an obstruction to flow than
the centrally clamped circular diaphragm type valve, or in other
words imposes a smaller pressure drop for a given orifice size. A
potential problem which must be addressed in the design of a
cantilevered flap valve, however, lies in ensuring that the flap
will remain closed in all orientations of the structure while it is
not subject to an exhalatory pressure differential. That is to say,
while in order to minimise the opening pressure differential of the
valve it is desirable to employ a highly flexible flap of minimal
thickness, the very flexibility of the flap may mean that if the
valve is inverted in use (i.e. orientated with the seat lying above
the flap), the flap may droop down from the seat when the user is
not exhaling. This is clearly undesirable as it may open a leakage
path into the mask for the contaminants which it is intended to
exclude.
U.S. Pat. No. 5,325,892 discloses an exhalation valve with a
cantilevered flap in which the valve seat has a seal ridge which is
curved in the longitudinal direction of the flap, the curvature
corresponding to a deformation curve exhibited by the flap when it
bends under its own weight (with no pressure differential). In
other words the design of that valve recognises that the flap is
unable to stay flat when the structure is inverted and matches the
configuration of the seat to the curvature of the flap under that
condition.
SUMMARY OF THE INVENTION
In accordance with the present invention a uni-directional fluid
valve comprises a flexible flap and a cooperating valve seat
surrounding an orifice adapted to pass a fluid; the flap being
attached to the seat at one end, in cantilever fashion, and being
adapted to flex away from other portions of the seat when fluid
flows in the permitted direction; and wherein there is a transverse
curvature to at least the said one end of the flap whereby to
maintain the flap substantially seated in the absence of a pressure
differential across it, in any orientation of the valve.
The effect of the transverse curvature of the flap in a valve
according to the invention is therefore stiffen the flap
sufficiently to resist any drooping away from the seat when there
is no applied pressure differential, even in the inverted
orientation of the structure. As soon as the flap is "cracked" by
an appropriate pressure differential, however, the free end of the
flap will rapidly flex away from the seat and this flexure will
progress along the length of the flap to a position determined by
the instantaneous rate of fluid flow. At least the root end of the
flap, at its position of attachment to the seat, will retain its
transverse curvature however, and this will apply a restorative
force to the flexed flap, assisting to reseat the flap when the
permitted flow of fluid ceases. The stiffening effect of this
transverse curvature is therefore to be distinguished from the
longitudinal curvature of the flap in U.S. Pat. No. 5,325,892.
The flap for a valve according to the invention may be manufactured
to exhibit the requisite transverse curvature in its natural state,
e.g. by means of injection moulding or thermoforming. In the
preferred embodiment to be described hereinafter, however, the flap
as manufactured is flat and its curvature is imparted in use by
means of the shaping of the valve structure in which it is
mounted
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be more particularly described, by way of
example, with reference to the accompanying schematic drawings, in
which:
FIG. 1 is a perspective view of a filter mask incorporating a
uni-directional valve in accordance with the invention as an
exhalation valve;
FIG. 2 is an "exploded" isometric view of the components of a
preferred embodiment of the exhalation valve for the mask of FIG.
1;
FIG. 3 is an isometric view showing the interior of the upper
housing member of FIG. 2;
FIG. 4 is a longitudinal section through the valve assembled from
the components of FIG. 2, on the line IV--IV of FIG. 5, in the
closed condition; and
FIG. 5 is a section on the line V--V of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the illustrated mask 1 is made from one or
more layers of flexible sheet filter material cut from a blank,
folded and welded to form a cup-shaped structure to be worn over
the nose and mouth of the user. It is in particular shaped in
accordance with the invention in GB-2046102, to which reference is
directed for a fuller description of the method of forming the mask
from a flat blank. In use the peripheral edge of the mask forms a
seal against the wearer's face and it is held in place by elastic
headbands 2 and a deformable wire nose clip 3 as well known in the
art.
At a suitable location in the side wall of the mask 1 an aperture
is formed in which an exhalation valve 4 is fitted, the structure
of which is more clearly illustrated in FIGS. 2 to 5.
The illustrated valve 4 comprises two interfitting moulded plastics
housing members 5 and 6, and an elastomeric flap 7 which in the
assembled valve is trapped at one end between the housing members.
The upper housing member 5 as viewed in FIG. 2 is also seen from
its opposite face in FIG. 3. It has inlet ports 8 passing through
it which on the downstream side are surrounded by a seal ridge
9A/9B/9C of generally trapezial planform. The lower housing member
6 as viewed in FIG. 2 is of dished form with a series of outlet
ports 10, and snaps onto the member 5 by means of a pair of
integral lateral lugs 11 engaging in slots 12 formed in member 5.
The flap 7 is of generally trapezial planform sized to fit over the
seal ridge and is formed from a thin and highly flexible piece of
elastomer, e.g. 0.5 mm thick latex natural rubber having a Shore
micro hardness of about 30.
The flap 7 is positioned in the valve by a notch 13 at one end
embracing a block 14 on housing member 5, and when the housing
members are snapped together that end of the flap becomes trapped
between the adjacent portion 9A of the seal ridge and a profiled
block 15 upstanding from housing member 6. That is to say it is
mounted in the valve in cantilever fashion. In its natural state,
if the flap 7 is held horizontally at one end it will tend to bow
longitudinally under the force of gravity, i.e. so that its
opposite end droops down considerably from the plane of its fixed
end. Both the block 15 and the facing portion 9A of seal ridge are,
however, curved so as to impart to the flap a transversely arched
configuration in the assembled valve, as seen particularly in FIGS.
4 and 5. In the illustrated embodiment this arching is accentuated
for the central part of the flap by means of a second profiled
block 16 upstanding from the housing member 6 in front of and to a
slightly greater height than the block 15, although this is not
essential in all embodiments of the invention. The arching of the
flap stiffens it sufficiently to prevent it drooping away from any
part of the seal ridge under zero pressure differential conditions,
whatever the orientation of the valve. The preferred orientation of
the valve is in fact with the outlet ports 10 directed with a
downward component, as indicated in FIG. 1, so that the user's
exhalate will not mist any associated eyewear, and if the user
lowers his head the valve may become oriented with the flap 7 lying
wholly below the housing member 5.
In use, therefore, the flap 7 seats upon the seal ridge to prevent
the passage of any air into the mask through the valve 4 while the
user is not exhaling. At the commencement of exhalation, as soon as
a minimum "cracking" pressure differential is applied to the flap 7
from the interior of the mask the free end of the flap will lift
away from the seal ridge in the sense of the arrow X in FIG. 4, and
flexure of the flap will progress rapidly along its length towards
the fixed (root) end, to a position determined by the instantaneous
rate of flow of exhalate out through ports 8 and 10. When
exhalation ceases, the restorative effect of the arched mounting of
the flap will cause the flap as a whole rapidly to reseat upon the
seal ridge, to minimise the risk of any inward leakage of
contaminant through the valve in the period between the end of
exhalation and the commencement of inhalation. In particular, the
flap 7 does not depend for its closure upon the subsequent
application of an inhalatory pressure differential.
From FIG. 3 it will be seen that while the portion 9A of the seal
ridge at the root end of the flap has a concave curvature the
remainder 9B/9C of the ridge has a flat surface. From FIGS. 3 and 4
it will also be seen that the portion 9C of the seal ridge at the
free end of the flap rises further from the plane of the member 5
than does the root end portion 9A, and the two side portions 9B are
straight but inclined as viewed in elevation. The combined effect
of this configuration is that the transverse curvature of the flap
7 decreases towards its free end, which lies flat against seal
ridge portion 9C, while a degree of longitudinal curvature is also
imparted to the central section of the flap (but not to its side
edges which lie flat against the ridge portions 9B). This has been
found to enhance the stability of the flap in its closed condition
while minimising the opening pressure differential for the
particular embodiment illustrated. In other embodiments, however,
there may be no longitudinal curvature of the flap and/or its
transverse curvature may extend throughout its whole length, in the
latter case the seal ridge portion 9C being modified to a concave
form as indicated in broken line in FIG. 3.
* * * * *