Note: Descriptions are shown in the official language in which they were submitted.
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DUCKBILL VALVE
The invention concerns a new duckbill valve of improved performance,
and lower manufacture cost than traditional ones.
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Duckbill valves are utilized to regulate pressure in a host of devices
spanning many industries. Applications for these devices are found in
automotive brakes, small home appliances, kidney dialysis, hypodermic
syringes,
sporting goods, toys, non-aerosol pumps and a variety of industrial equipment.
Their popularity stems from their simple construction. No moving parts are
present, other than the rubber housing itself.
Despite their simplicity, antiquated manufacturing processes have
rendered the traditional duckbill valve relatively expensive. Standard
manufacture employs compression molding of a rubber, followed by a second
separate step of cutting a slit into the molded rubber valve. This two step
procedure slows production and adds cost.
U.S. Patent 5;010,925 (Atkinson et al.), assigned to Vernay Laboratories, Inc.
discloses a more sophisticated version of a duckbill valve assembly. In one
embodiment (Fig. 6), an outer wall of the valve body is formed in an oval
shape. Insertion of the oval body into a circular recess of a valve fitting
biases
tapered lips 38, 40 together to close the valve assembly. Unfortunately, the V-
shaped tapered walls intersect only at a relatively narrow contact point. This
results in a less than robust seal.
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It is an object of the present invention to provide a duckbill valve having a
stronger seal.
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Another object of the present invention is to provide an improved duckbill
valve manufacturable in a single process step.
Yet another object of the present invention is to provide a duckbill valve
of less expensive construction.
Still a further object of the present invention is to provide a duckbill valve
having improved longevity and performance.
In a first aspect a duckbill valve is provided which includes a hollow
cylindrical elastomeric body with first and second ends, the first end having
parabolic outer wails tapering to an elongate slit, the second end having an
outer and inner wall terminating in an open mouth, with at least one of the
outer
and inner wails of the second end being non-uniformly round.
Preferably the non-uniformly round outer and/or inner walls are oval in
shape.
The elastomeric body preferably includes a cylindrical mid-section
between the first and second ends. Preferably, a collar surrounds the mouth,
and projects radially outwardly from outer walls of the second end.
In another aspect of the invention, the elongate slit in the open position
/as originally molded) is ovaloid in shape, somewhat resembling an American
football. Conveniently, an upper and lower lip surround the ovaloid slit, with
each lip having a surface orthogonal to a longitudinal axis traversing the
duckbill from the first to second ends. Preferobly, upper and lower lips in
the
open position converge to pointed elongate left and right lip ends.
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Advantageously, the lips extend substantially across the full diameter of the
first
end. By the term "substantially" is meant at least 70%, preferably at least
85%,
but optimally at least 95% across the diameter of the first end. Preferably,
the
parabolic curvature of the slit and lip arrangement allow the lips when biased
together to engage a relatively large mutual contact surface. A tighter sea!
may thereby be achieved.
Materials of construction for the elastomeric body may comprise, or even
consist of an elastomer prepared from the polymerization of a monomer
selected from the group consisting essentially of ethylene, propylene,
styrene,
butadiene, acrylonitrile, and mixtures of these (providing copolymers).
Silicones
may also be used as a material of construction. Most preferred is the use of
Kraton0 rubber. The elastomeric body may conveniently be transparent.
Duckbill valves of the present invention are conveniently formed in a
method which includes injecting an elastomer in fluid state into a mold. The
mold should contain surface structures that allow formation of an open slit
within
the elastomeric body. Subsequent to injection, the molded body is ejected
from the mold of the injection molding machine.
A key advantage of the present invention is that through injection
molding, duckbill valve bodies can be manufactured with a slit concurrently
constructed with other parts of the device. It is no longer necessary to have
a
second step of slit cutting. It is also an advantage that typically less
material is
needed to form the valve body. The new valve permits thinner walls, and
indeed even requires less wail material to function. By contrast, prior art
duckbill
valves must use relatively thick or poorly pliable rubber walls to obtain
rigidity.
Without rigidity, the old duckbills cannot maintain a closed slit. Rigid
rubber
cannot be injection molded; it is shaped by compression molding.
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Duckbill valves of the present invention according to a first embodiment,
wherein the outer wall is non-uniformly round (e.g. oval), are intended to be
inserted into a fitting having a round interior wall against which is
positioned the
outer walls of the elastomeric body mid-section. Interaction between the round
fitting and non-round wall forces the latter into a round shape, thereby
compressing together the lips of the slit. Under this arrangement, the slit
remains
shut so long as atmospheric pressure within the valve and outside the slit are
essentially identical. Any significant pressure increase within the hollow
cylindrical elastomeric body will cause the slit to part its lips and open,
allowing
for equalization of pressure between inner and outer parts of the valve.
A further embodiment of this invention is a duckbill valve having a round
outer wall, but a non-uniformly round (e.g. oval) inner wall. Accordingly, a
duckbill valve assembly is achieved by inserting a rounded outer wall fitting
into
the non-uniformly round (e.g. oval) inner walled hollow cylindrical
elastomeric
body. Interaction between the round fitting and non-uniformly round inner wall
of the duckbill valve forces the latter into a round shape, thereby
compressing
together the lips of the slit. As in the earlier embodiment, the slit remains
shut so
long as atmospheric pressure within the valve and outside the slit are
essentially
identical. Any significant pressure increase within the hollow cylindrical
elastomeric body will cause the slit to part its lips and open, allowing for
equalization of pressure between inner and outer parts of the valve.
The various objects, features and advantages of the present invention will
more fully be explained by way of example only, with reference to the
accompanying drawings, in which:
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Fig. 1 is a perspective view of a duckbill valve in the open position
according to a first embodiment of the present invention;
Fig. 2 fS a front elevational view of the duckbill valve according to Fig. l ;
Fig. 3 is a cross-sectional view taken along line 3-3 of Fig. 1;
Fig. 4 is a front elevational view of the duckbill valve shown in Fig. 1
inserted within a fitting (seen in partial view), wherein the slit is in a
closed
position;
Fig. 5 is a cross-sectional view of a shortened version of Fig. 1 with the
slit in
an open position;
Fig. b is a cross-sectional view of the shortened version according to Fig. 5
wherein the duckbill valve has been inserted within a fitting, the slit being
in the
closed position;
Fig. 7 is a side elevational view of a second embodiment of the duckbill
valve according to the present invention;
Fig. 8 is a cross-sectional view taken along line 8-8 of Fig. 7;
Fig. 9 is a cross-sectional view of Fig. 7 in the longitudinal direction
wherein
a fitting is inserted within the duckbill valve, the slit being in the closed
position;
and
Fig. 10 is a cross-sectional view taken along 10-10 of Fig. 9.
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Fig. 1 illustrates a first embodiment of the duckbill valve of the present
invention. The valve includes a hollow cylindrical elastomeric body 2 with a
first
end 4 and a second end 6. Parabolically tapered walls 8 are located near the
first end converging toward an elongated slit 10 defined by lips 7 2. The
second
end of the elastomeric body has an oval shaped outer wall 16 terminating in an
open mouth 14, defined by a non-circular inner wall 15. A cylindrical mid-
section 18 connects the first and second ends. A collar 22 is positioned near
the
second end, and projects radially outwardly from outer walls 20 of the mid-
section.
Fig. 2 best illustrates the lips 12, which are formed with an upper lip 13 and
a lower lip 17. Upper and lower lips in the open (originally molded) position
are
ovaioid shaped, intersecting at left and right slit ends 21 I, 21 r.
Fig. 3 best illustrates the outer walls of the mid-section as being non-
circular in circumference. In cross-section, walls of the mid-section have a
pair
of thicker segments 24, spaced apart by thinner segments 26. Both inner and
outer walls of the mid-section therefore define an oval shape. Major axis O, I
of
respective outer and inner walls defining oval shapes are orthogonal to one
another. In other words, the oval shapes in their long axis are perpendicular.
For
purposes of this invention, it is optional to have both the inner and outer
wails
being non-uniformly round.
Fig. 4 illustrates the duckbill valve having slit 10 compressed into a closed
position which results from the elastomeric body being pressed within a
tubular
fitting 28 to form a valve assembly. The oval geometry of the elastomeric bodv
is forced into a round configuration by the round inner walls 30 of the
tubular
fitting 28.
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Fig. 5 illustrates a shortened version of the embodiment of Fig. 1. In this
embodiment, tapered wails 8 at an end distant from the slit include a securing
ridge 32. Mid-section 18 separates ridge 32 from collar 22, and provides a
recess for lodging tubular fitting 28.
Fig. 6 illustrates the elastomeric body of the duckbill valve inserted within
a
perfectly round opening of the tubular fitting, the latter bowing the oval
walls of
the elastomeric body to obtain a seal. As a consequence, slit 10 is forced
into a
closed position. Opening of the slit occurs only when pressure within the
duckbill
valve becomes greater than air pressure outside the slit.
Fig. 7 illustrates a second embodiment of the present invention. !n this
embodiment, as best illustrated in Fig. 8, the outer walls of the mid-section
are
round in circumference, while the inner walls are non-circular. In cross-
section,
walls of the mid-section have a pair of thicker segments 124 spaced apart by
thinner segments 126. Thus, the inner wall of the mid-section defines an oval
shape. Similar to the first embodiment, the duckbill valve of Fig. 7 and 8
includes
an elongated slit 110 surrounded by lips 112, the latter being formed with an
upper and lower lip 1 13 and 1 17.
Fig. 9 illustrates the hollow cylindrical elastomeric body 102 of the duckbill
valve, with non-circular inner wall 115 being seated over a perfectly round
tubular fitting 128, the fatter bowing the oval inner walls of the elastomeric
body
102. As a consequence, slit 1 10 is forced into a closed position. Fig. 10
illustrates
the closed position resulting. from the valve assembly combination of the
duckbill valve and tubular fitting. Opening of the slit occurs only when
pressure
within the duckbill valve becomes greater than air pressure outside the slit.
The
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tubular fitting 128 may be a rigid plastic tube such as a diptube in a liquid
dispensing container.
Although only two embodiments have been described, those skilled in the
S art will be able to supply further modifications and adaptations all of
which are
considered within the purview and scope of the present invention.
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