Note: Descriptions are shown in the official language in which they were submitted.
CA 02819735 2013-07-03
DUAL DISK CHECK VALVE WITH SLOTTED STOP BAR
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to a dual disk check valve
and, more particularly, to a dual disk check valve with a slotted stop bar.
[0002] Dual disk check valves are employed in various types of ductwork and
piping and utilize pivoting disks that are commonly referred to as flappers.
The
flappers swing open and close depending on the corresponding direction of
fluid flow
through the ductwork. When the valve opens during normal conditions, it is
imperative that the disks do not swing near or over the center position due to
the
typical configuration of dual disk check valves. If such a condition occurs,
net forces
on the upstream side of the disks could hold the check valve open during
reverse flow
conditions. This would prevent the check valve from performing its primary
function
of preventing reverse flows by closing.
[0003] In a common method of preventing the disks from opening too much, a
"stop pin" is employed. The disks hit the pin at a predetermined angle, which
is
usually no more than 80 degrees, and stop swinging open. However, because the
disks
are typically swinging open at maximum velocity when they hit the pin, the pin
needs
to be relatively stiff. Thus, an impact load occurs when the disk(s) hits the
pin. Over
many cycles, these high loads can fatigue the disks or the pin and cause
either to
fracture. Fracture would be considered a catastrophic failure since loose
metal parts
could be released into a fluid stream.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention, a dual disk check valve is
provided and includes a mechanical stop. The mechanical stop has a central
portion
and includes bars disposed in the central portion. The bars have substantially
rectangular cross-sectional shapes and are disposed substantially in parallel
with one
another to define a slot in the central portion.
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[0005] According to another aspect of the invention, a mechanical stop of a
dual disk check valve is provided and includes an elongate member having
distal
sections at opposite ends thereof, intermediate sections coupled to the distal
sections
and a central portion between the intermediate sections. The mechanical stop
further
includes bars respectively coupled to the intermediate sections. The bars have
substantially rectangular cross-sectional shapes and are disposed
substantially in
parallel with one another to define a slot in the central portion.
[0006] According to yet another aspect of the invention, a mechanical stop of
a dual disk check valve is provided and includes an elongate member having
distal
sections formed as anti-rotation features at opposite ends thereof,
substantially
rectangular intermediate sections coupled to the distal sections and a central
portion
between the intermediate sections, and bars respectively coupled to respective
interior
portions of the intermediate sections for disposition thereof in the central
portion. The
bars have substantially rectangular cross-sectional shapes and are disposed
substantially in parallel with one another to define a slot in the central
portion.
[0007] These and other advantages and features will become more apparent
from the following description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The subject matter, which is regarded as the invention, is particularly
pointed out and distinctly claimed in the claims at the conclusion of the
specification.
The foregoing and other features, and advantages of the invention are apparent
from
the following detailed description taken in conjunction with the accompanying
drawings in which:
[0009] FIG. I is a schematic view of a check valve in accordance with
embodiments;
[0010] FIG. 2 is a schematic view of a check valve in accordance with further
embodiments;
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[0011] FIG. 3 is a perspective view of a dual disk check valve with a slotted
stop bar;
[0012] FIG. 4 is a top-down view of a slot of the dual disk check valve of
FIG.
3 in accordance with embodiments;
[0013] FIG. 5 is a perspective view of a closed dual disk check valve in
accordance with embodiments;
[0014] FIG. 6 is a perspective view of the dual disk check valve of FIG. 5 in
a
partially open condition; and
[0015] FIG. 7 is a perspective view of the dual disk check valve of FIGS. 5
and 6 in a fully open condition.
[0016] The detailed description explains embodiments of the invention,
together with advantages and features, by way of example with reference to the
drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0017] A dual disk check valve typically includes a check valve body and
disks. The check valve body includes a seat, a hinge and a housing. The seat
may be
annularly shaped and formed to define an aperture. The hinge may be provided
as a
pin-hinge with a central pivot axis defined along a pin and is disposed to
bifurcate the
aperture defined by the seat to thereby further define an opening on one side
of the
hinge and another opening on the other side of the hinge. The housing is
coupled to
opposite ends of the hinge and normally includes a mechanical stop, such as a
stop
pin.
[0018] The disks are pivotably coupled to the hinge to pivot or swing about
the central pivot axis in response to a fluid pressure differential between
fluid
disposed upstream and fluid disposed downstream from the dual disk check
valve. In
particular, the disks are configured to pivot from respective closed positions
at which
the disks prevent fluid flow through the openings to respective open positions
at
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which fluid flow through the openings is permitted. When the disks swing
toward the
respective open positions, they independently impact the mechanical stop and
are
prevented from swinging beyond a given opening angle.
[0019] In accordance with aspects of the invention, problems associated with
the use of stop pins in dual disk check valves are addressed. These problems
include
the need for the stop pins to be relatively rigid as required to meet internal
stresses
caused during impacts. This in turn increases impact loading imparted by the
disks
and limits an effective gain of increasing a size of the stop pins. Also, the
round cross-
section of a stop pin inherently makes the stop pin a relatively poor
geometric
candidate from strength to weight standpoint. Since check valve pins are
usually
formed of solid stainless steel or similar metals, this problem leads to a
substantial
increase in the weight of the check valve as a whole. Moreover, increasing the
diameter of the stop pin to handle increased impact loading will decrease the
possible
open angle of the disks and increase a pressure drop across the check valve.
This
increased pressure drop can lead to a need for increasing a size of the check
valve,
which will compound the effects of increased weight, size and cost. Finally,
the
roundness of a stop pin means that there is essentially line contact between
disks and
the stop pin when contact is made. This creates high bearing stresses that are
superimposed with the bending stresses.
[0020] With reference to FIG. 1, a dual disk check valve ("check valve") 10 is
provided. The check valve 10 is interposed between upstream ductwork 11 and
downstream ductwork 12. As shown in FIG. 1, the upstream ductwork 11 is formed
of
a single duct 111 and the downstream ductwork 12 is similarly formed of a
single
duct 121. This configuration is, of course, exemplary, and it is to be
understood that
alternate configurations are possible.
[0021] One such alternate configuration is illustrated with reference to FIG.
2
in which at least one of the upstream ductwork 11 and the downstream ductwork
12 is
illustrated as possibly including multiple ducts 110. For example, as shown in
FIG. 2,
both the upstream and the downstream ductwork 11 and 12 may include two ducts
110 each whereby corresponding ducts 110 in the upstream and downstream
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ductwork 11 and 12 communicate with one another by way of the check valve 10.
In
such cases, the disks may open and close independently. Although illustrated
as
having a 1:1 ratio, it is to be understood that the upstream ductwork 11 and
the
downstream ductwork 12 need not have the same number of multiple ducts 110.
That
is, the two ducts 110 of the upstream ductwork 11 could lead to a single duct
110 in
the downstream ductwork 12, for example.
[0022] With reference to FIG. 3, a mechanical stop 20 is provided for use with
a valve, such as the check valve 10 described above, to prevent the disks of
the check
valve from swinging open beyond a given angle. The mechanical stop 20 would
normally be supported by the check valve 10 housing in a location defined
along the
opening tracks of each of the disks. As shown in FIG. 3, the mechanical stop
20 is an
elongate member 200 and includes first and second distal sections 21, 22 at
opposite
ends thereof. Proceeding inwardly from the first and second distal sections
21, 22 the
mechanical stop 20 further includes intermediate sections 23, 24 coupled to
respective
interior portions of the distal sections 21, 22. A central section 25 is
defined between
the intermediate sections 23, 24.
[0023] The first and second distal sections 21, 22 are anti-rotation features
and
may be formed as polygonal (i.e., six-sided) volumetric bodies 211, 221 that
may be
slightly elongated in a dimension that is defined transversely with respect to
an
elongation dimension of the mechanical stop 20 as a whole. The first and
second
distal sections 21, 22 are configured to be inserted into through-holes
defined through
posts disposed on the check valve 10 housing. The six-sided shaped of the
first and
second distal sections 21, 22 insures that an angular orientation of the
mechanical stop
20 is correct and prevents rotation of the mechanical stop 20 in use. In
accordance
with embodiments, the first and second distal sections 21, 22 may be formed
from
rectangular bodies with chamfered or, in some cases, rounded edges.
[0024] The intermediate sections 23, 24 are generally rectangular in shape.
Thus, each of the intermediate sections 23, 24 includes opposing faces 231,
232 and
241, 242 that face in opposite directions. When the disks of the check valve
10
respectively impact the mechanical stop 20, the interior surface of one of the
disks
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contacts the corresponding faces 231, 241 and the interior surface of the
other disk
contacts the corresponding faces 232, 242. This contact is spread over the
surface area
of the faces 231, 232 and 241, 242 and is therefore non-linear with bearing
areas that
are orders of magnitude larger than those of corresponding stop-pin designs.
Thus,
bearing stresses on the disks and the mechanical stop 20 are substantially
lower than
those generated with a typical stop pin.
[0025] The intermediate sections 23, 24 are further formed to define
grounding holes 30 proximate to the central section 25. The grounding holes 30
extend through the intermediate sections 23, 24 and serve to support tension
springs
that may be installed in the check valve 10 to bias the disks toward the
respective
closed positions.
[0026] The central section 25 is defined between the intermediate sections 23,
24 and is formed to define a thin slot 40 that extends along the elongate
dimension of
the mechanical stop 20. This slot 40 is formed between two separate thin bars
41, 42
that are coupled to respective interior portions of the intermediate sections
23, 24 and
are disposed substantially in parallel with one another. The thin bar 41 has a
main
portion 411 with a substantially rectangular cross-sectional shape and flared
ends 412
that are coupled to the respective interior portions of the intermediate
sections 23, 24.
The thin bar 42 is similarly constructed and has a main portion 421 with a
substantially rectangular cross-sectional shape and flared ends 422 that are
coupled to
the respective interior portions of the intermediate sections 23, 24. A
shortest
dimension of the thin bar 41 and the thin bar 42 is oriented transversely with
respect
to the elongation dimension of the elongate member 200.
[0027] Relative sizes and shapes of each of the thin bars 41 and 42 may be
independently tunable for various applications of the check valve 10. That is,
the thin
bar 41 may be configured substantially similarly to thin bar 42 in some
embodiments
and substantially dissimilarly in other embodiments. The latter case may be
particularly suitable where the check valve 10 is disposed in ductwork with
multiple
independent ducts upstream and downstream from the check valve 10.
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[0028] Due to the thin bars 41 and 42 having the main portions 411 and 421
with substantially rectangular cross-sectional shapes, the thin bars 41 and 42
effectively transform the single mechanical stop 20 into two separately acting
mechanical stops for each of the disks of the check valve 10. This
accomplishes
several benefits. First, the two thin bars 41, 42 create a lower spring
constant stop
thereby enabling larger deflections with lower stresses. Second, the
mechanical stop
20 is made into effective mechanical stops for each disk that are independent
of one
another. Thus, when both disks hit the mechanical stop 20 at virtually the
same time,
relatively large impacts are avoided due to deflection of the mechanical stop
20. That
is, the slot 40 permits a bending of the mechanical stop 20 that would not be
otherwise possible.
[0029] The rectangular cross-sectional shapes of the thin bars 41, 42 have
advantages over round cross-sectional shapes especially as utilized in check
valves.
Rectangular cross-sectional shaped sections are relatively efficient for
carrying
bending loads with respect to their size. So, for any given diameter stop pin,
the
strength of the equivalent rectangular section is about 1.7 times greater. In
addition, a
rectangular cross-sectional shaped section can be employed without decreasing
the
opening angle of the disks by lengthening only one leg of the rectangle. So, a
rectangular section with a 2:1 aspect ratio, for example, would have about 3.4
times
the strength of the equivalent pin with a diameter of the shorter side of the
rectangle.
Rectangular cross-sectional shaped sections are also more efficient for
carrying
bending loads with respect to weight than stop pins. As the rectangular
section gets
thinner and wider, it begins to function as mechanical spring, allowing larger
deflections upon contact with the corresponding disk. As the deflections get
larger,
the nature of the loading changes from impact loading to pure dynamic bending
loading. A mechanical stop that performs like a spring converts kinetic energy
from
the disk to potential energy stored in the spring as well as some energy that
is
dissipated in the form of heat.
[0030] In accordance with embodiments and, with reference to FIG. 4, the slot
40 may be filled a non-elastic energy absorbing material 400. For expected
fluid
temperatures lower than approximately 500 degrees F, non-metallic materials
such as
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plastics, elastomers or trapped viscous fluids may be considered for the
filling. Where
appropriate for expected conditions, metallic energy dissipating materials can
also be
considered for the filing. These may include wire meshes or friction plates.
[0031] With reference to FIGS. 5-7, a check valve 10 is illustrated in
closed,
partially open and fully open conditions, respectively. As shown, the check
valve 10
may include a check valve body 100 and disks 101. The check valve body 100
includes a seat 102, a hinge 103 and a housing 104. The seat 102 may be
annularly
shaped and formed to define an aperture 105 (see FIG. 7). The hinge 103 may be
provided as a pin-hinge with a central pivot axis defined along a pin and may
be
disposed to bifurcate the aperture 105 defined by the seat 102 to thereby
further define
openings on either side of the hinge 103. The housing 104 is coupled to
opposite ends
of the hinge 103 and normally includes the mechanical stop 20 as described
above.
[0032] The disks 101 are pivotably coupled to the hinge 103 to pivot or
swing
about the central pivot axis in response to a fluid pressure differential
between fluid
disposed upstream and fluid disposed downstream from the check valve 10. In
particular, the disks 101 are biased by elastic elements 106 to remain in
respective
closed positions (see FIG. 5) at which the disks 101 prevent fluid flow
through the
openings. However, when the fluid pressure differential is sufficiently large
to
overcome the bias applied by the elastic elements 106, the disks 101 begin to
open
(see FIG. 6) and eventually swing into respective open positions (see FIG. 7)
whereby
fluid flow through the openings is permitted. When the disks 101 swing toward
the
respective open positions, they independently impact the mechanical stop 20
and are
thereby prevented from swinging beyond a given opening angle.
[0033] The scope of the claims should not be limited by the preferred
embodiments set forth in the examples, but should be give the broadest
interpretation
consistent with the description as a whole.
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