Note: Descriptions are shown in the official language in which they were submitted.
CA 02737208 2013-07-29
EXTRACTION FAN ASSEMBLY INCLUDING A DAMPER THAT CLOSES FIRMLY
WHEN THE FAN .IS NOT RUNNING AND REDUCES THE PRESSURE DROP
WHEN THE FAN IS RUNNING AT FULL SPEED
This invention relates to a fan construction which includes a damper
that closes firmly to prevent air backd raft when the fan is inoperative, or
when the
fan is running at minimum speed against strong opposing winds. The device also
reduces the pressure drop when the fan is running at full speed.
BACKGROUND OF THE INVENTION
In recent years prevention of disease to animal husbandry barns has
reached the extent where attempts are made to ensure that all air entering the
barn
is filtered of pathogens that can be airborne. For this reason a number of
companies
provide systems for filtering the air at the intakes. Typically the air
intakes
communicate with the roof space with the air entering into the containment
area
through the ceiling and also from the wall. This can be done by providing
filtration
membranes engaging the air as it enters the roof space or it can be done by
providing on each intake duct a separate membrane assembly attached onto the
intake opening within the roof space.
Much work has been done, for example by Noveko of Quebec, on
developing improved membranes which provide an effective and cost efficient
filtration system. However it is known that pathogens can still enter the
containment
area by the fans louvers and disease can still strike, often with very
damaging
CA 02737208 2013-07-29
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results.
However it is known that pathogens can still enter the containment
area through closed fans louvers, due to known negative air pressure (0.05 to
0.2
inch of water) inside the building. It has been experimented that a 24" fan
that is not
running even with the louvers closed, can allow in as much as 400 cfm of viral
contaminated air into the building (with inside static pressure of 0.05 inch
of water),
and that 3 x 24" fans can allow in as much viral contaminated air into a
building as a
12" running fan would do if it were used to push viral contaminated air into a
building, which may cause airborne pathogen to strike, often with very
damaging
results.
The animals concerned are typically pigs and poultry but of course
other animals require the same protection from pathogens that can be airborne.
The arrangement described herein is applicable not
only to the sector of animal confinement barns, .but also to any other
sectors where ventilation applies, such as industry, commercial,
residential applications, or any other, where backdraft must be
controlled for whatever reason.
SUMMARY OF THE INVENTION
It is one object of the invention to provide a fan construction with a
damper flap to prevent reverse flow of air when not required.
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According to one aspect of the invention there is provided a damper flap
assembly for mounting on a fan construction having a fan housing and a fan
mounted in the
housing;
the damper flap assembly comprising:
a mounting member having an opening through which the air passes and a
flange surrounding the opening;
a pivotally mounted damper flap arranged to extend in a closed position
across the opening when the fan is not running, with an outer peripheral
portion of the
damper flap engaging the flange around the opening;
the damper flap being movable from the closed position through an
intermediate position to a fully open position under forward air flow from the
fan by pivoting
on a hinge away from the flange;
and a biasing arrangement for applying force to the damper flap, the wing
biasing arrangement being arranged on one side of the intermediate position
adjacent the
closed position to bias the damper flap into the closed position and on an
opposed side of
the intermediate position adjacent the fully open position to bias the damper
flap into the
fully open position.
Preferably the damper flap is suspended by a hinge at an upper edge
and pivotal about the upper edge to utilize gravity in the closing action but
this is not
essential and the hinge line may be at any location including for example one
side
edge or may be across a center line of the damper flap.
Where required for hermetic sealing, there is preferably provided a
resilient deformable seal between the outer peripheral portion of the damper
flap and
the flange arranged to seal the damper flap to prevent reverse flow of air
through the
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fan housing when the fan is not running. The seal can be preferably on the
flange
but may also be on the flap.
Preferably the two directional biasing arrangement includes a spring
for providing a spring force in both directions.
Preferably when used for preventing infiltration of airborne pathogens,
the closure of the flap can act to provide a hermetic seal using for example a
resiliently deformable fin seal.
Preferably the spring biasing arrangement includes a cam surface
engaging a cam follower with a spring applying spring force between the cam
follower and the cam surface.
Preferably the cam follower is attached to the flap and the cam is
mounted on the housing. However the cam follower can be attached to the
housing.
Preferably the cam follower is mounted on a lever attached to the
damper flap for pivotal movement therewith.
Preferably the cam surface is pivotally mounted and the spring is
arranged to pivot the cam surface in a direction to apply force to the cam
follower
thus applying the required spring force to the damper flap. However other
arrangements for applying the spring forces can be used. The spring force can
be
adjustable.
Preferably there is provided an operable device such as a solenoid for
applying additional force to the spring biasing arrangement to increase the
force to
more effectively hold the damper flap in the required positions. The solenoid
can be
CA 02737208 2013-07-29
dependent, or not, on operation of the fan so that when the fan is off the
device is
operated to hold the flap in the closed position.
Preferably the spring biasing arrangement is arranged to apply force to
the damper flap to tend to hold the damper flap in the partially open
position, such as
5 by a recess in the cam surface.
Preferably the seal is carried on the flange around the outer peripheral
portion of the damper flap and the damper flap includes a flat surface butting
the
seal. However it can be on the flap.
Preferably the mounting plate includes a hood having a top wall
extending over the top of the damper flap and a down-turned front flange
extending
downwardly and forwardly along the damper flap.
Preferably the down-turned front flange extends parallel to the damper
flap in the fully open position thereof.
Preferably the down-turned front flange extends to a bottom edge of
the flange at or beyond a bottom edge of the damper flap.
Preferably the mounting plate includes a hood having a bottom wall
extending forwardly from the mounting plate and a down-turned front flange
extending downwardly and forwardly.
Preferably there is provided an abutment member for holding the
damper flap in a slightly open position against opposing wind forces when the
fan is
operating at a low speed, the abutment member being arranged to allow closing
of
the damper flap. In particular, a solenoid can be installed and can block the
action of
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6
the cam in order to open the flap to a minimum opening when the fan running at
minimum speed. This will block the opposing wind and also reduced the pressure
drop.
According to a second aspect of the invention there is provided a
damper flap assembly for mounting on a fan construction having a fan housing
and a
fan mounted in the housing;
the damper flap assembly comprising:
a mounting plate having an opening through which the air passes and
a flange surrounding the opening;
a pivotally mounted damper flap arranged to extend in a closed
position across the opening when the fan is not running, with an outer
peripheral
portion of the damper flap engaging the flange around the opening;
the damper flap being movable from the closed position between a
partially open position to a fully open position under forward air flow from
the fan by
pivoting on the hinge away from the flange;
wherein the mounting plate includes a hood having a top wall
extending over the top of the damper flap and a down-turned front flange
extending
downwardly and forwardly along the damper flap.
The arrangement described herein is applicable not only to the sector
of animal confinement barns, but also to any other sectors where ventilation
applies,
such as industry, commercial, residential applications, or any other, where
backdraft
must be controlled for whatever reason.
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One key point of this new automatic mechanism described herein is to
control almost 100% of backdraft (when cover is tightly closed), for example
to
prevent any pathogen infiltration in an air-filtered animal confinement
building, when
the fan is not running at all, or running at slow speed against the opposing
force of
strong winds, in the latter case the cover being slightly opened and
automatically
mechanically maintained in this position.
A second key point is that this new automatic mechanism increases by
more than 15% the efficiency of the fan running at full speed in comparison
with
conventional shutters used in the agricultural sector. This can be explained
by the
mechanism applying a force helping the flap to be opened at its maximum
opening
and therefore avoiding or reducing pressure drop. Fan efficiency is increased
when
conventional shutters are dirty. When the fan is running at minimum speed, the
device with the abutment option, increases the efficiency of the fan because
the
design of the exterior outlet permits blocking of any opposing wind coming
from any
direction, allowing the air to be exhausted toward the exterior totally
freely, even in
case of strong opposing winds.
The seal can be carried on the outer peripheral portion of the damper
flap.
Preferably the seal comprises a deformable fin of a type which can
readily deform under the relatively low forces involved from gravity on the
damper
flap and from back pressure of reverse air flow so that a sealing effect is
obtained.
Typically the opening is rectangular although other shapes are also
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possible particularly circular.
Preferably the mounting plate includes a hood extending from the
hinge over the top of the damper flap to maintain protection from falling
contaminants such as snow and preferably the hood has a down-turned flange to
engage the damper flap and prevent pivotal movement of the damper flap beyond
a
predetermined angle.
Preferably there is provided an abutment member, such as a pin
carried on the mounting plate, for holding the damper flap in a slightly open
position,
the abutment member being retractable for example by an electrically operable
remote control device to allow closing of the damper flap. The key point is
the -
provision of the abutment, which acts to hold the flap slightly ajar to allow
the low
airflow to escape with a protection against the wind forces. Other shapes and
arrangement of abutment member can be used and these can be actuated in many
different ways than the electrical solenoid primarily proposed.
Preferably there is provided a latch for providing a closing force for
holding the damper flap in the closed position to provide an increased closing
force
when the flap is closed but allowing release to the open position as soon as
the air
flow generates enough force to overcome the latch. The latch can be a magnetic
strip around the periphery of the damper flap or a magnet located at the
bottom edge
of the damper flap. Other types of latch or system can be used for example a
spring
or counterweight etc, to assist in holding the flap in the closed position
which latch is
released as soon as the air flow operates to move the flap away from the
closed
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9
position.
Preferably the damper flap comprises a flat panel which may be an
insulated panel of a foam material or similar stiff flat member. Other
constructions of
flap can be used which may not necessarily be insulated.
Preferably the damper flap assembly is mounted on outside end of the
fan housing. In this case the fan housing may retain or include an additional
louver
closure at the wall opening.
Alternatively the damper flap assembly can be mounted on the fan
housing at the wall opening inside the building.
There may be provided a heating wire for heating the seal to prevent
freezing.
Preferably the hinge is a flexible strip extending from the damper flap
to the mounting plate and mounted on a spacer strip at the mounting plate.
Other
types of hinge can also be used with the intention that they are resistant to
jamming
or freezing and they are not restricting the airflow.
Preferably the air inlets are arranged at the ceiling of the containment
area communicating with a roof space above the containment area. However other
locations of the filtered air inlets are possible and many different designs
of barn
ventilation can be used. Preferably each air inlet includes a filter assembly
carried in
the roof space. However the air flow into the roof space through the eaves can
be
filtered by exterior mounted filters added on the outside of the building. It
is of
course intended that, apart from the inlets and the extraction fans, the
containment
CA 02737208 2013-07-29
area is sealed against ingress of pathogen containing air.
The arrangement described above can have two different and
independent objectives. Firstly to block the virus contained in air back-
draft, from
infiltrating fan louvers when a fan is not running in an air-filtered barn for
swine and
5 also for a poultry barn. Secondly to block the wind effect against the
fan when a fan
is running at slow or minimum speed to prevent air-back draft pathogen
contamination.
It has been determined that the conventional louver arrangement used
with agricultural fans is not sealed enough to prevent back-draft and virus
10 contamination.
Thus the flap and the pin action control the minimum ventilation rate for
the fan when the fan faces wind forces. This can be used both in air-filtered
barns
and even for barns without air filters.
The addition of the pin at the bottom of the panel is used in order to be
able to keep a continuous minimum opening which can vary from 0.5 to 6 inch
according to the remote adjustment of the pin. Then, even if the slow running
fan
faces a lot of wind, the damper will stay open and the air can be easily blown
out by
the fan, preventing air back-draft pathogen contamination in air-filtered
barns. In the
case of barns that are not air-filtered, the objective is not to prevent virus
transmission but only to control the minimum ventilation rates even with or
without
windy conditions. The purpose is to improve the air quality inside the barn
even if
winds faces the fans. This will allow an easy minimum ventilation rate
adjustment for
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the operators and reduced energy cost for fan operation and building heating.
In order to have a better minimum ventilation rate control, the standard
louvers installed on the fan can be removed.
In a filtered building, this arrangement can allow the number of fans in
the first and second ventilation stage to be reduced by using larger fans,
which
provide both reduced contamination risk by virus from air back-draft and also
reduced energy consumption. With higher flow rates on the first and second
ventilation stage, this will also allow to reduce the number of fans on stage
three and
more. In some cases, this feature will allow to avoid the use of stage three
and
more.
In non-filtered swine and poultry barn, this feature allows a better
minimum ventilation rate control during windy period. When the wind comes in
the
fan direction, this has a restriction effect on the fan's airflow. When a fan
is running
at its minimum speed, a strong wind can almost totally block the airflow and
cause
air quality problem inside the building because the contaminants are still in
the barn.
Then, this flap assembly will help to optimized the air quality control and
the heating
cost in the barns. Also, this concept can allow to reduce the number of fans
on first
and second ventilation stage by using larger fans and reduced energy
consumption.
The basic idea of this improved backdraft damper flap design consists
in the addition of an innovative automatic mechanism that requires no
electricity for
its operation, permitting through mechanical applied pressure on the damper
flap, to
make the damper flap absolutely airtight when the fan is not running. A second
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important aspect is that there is almost no airflow restriction (less than 1%
compared
to 15% for the conventional shutters used in agricultural fans) caused by the
damper
flap when the fan is running, the damper flap mechanism exercising a
significant
outward force on the damper flap to keep it opened. A third aspect of this
backd raft
damper flap design is that it permits to use a reduced number of damper flaps
(but of
larger dimension) on large size fans, which allows for much less air flow
restriction, if
compared to traditional dampers that feature numerous louvers.
This innovative Backdraft Damper flap System as described in more
detailed hereinafter may have one or more of the following features and
advantages.
It may be used with variable speed fans or 1-speed fans, which is
different from competitive products.
Its mechanism permits to apply significant pressure on the damper flap
to prevent any air infiltration when the fan is not running and keeps the
damper flap
partially or fully opened when the fan is running. It is important to note
that the same
mechanism plays both roles, which is to maintain the damper flap closed when
the
fan is not running, and to maintain it partially or fully opened when the fan
is running.
It is a simple, low-cost and maintenance-free mechanical system that
requires no electricity, contrary to costly dampers that are currently sold on
the
market, which louvers are activated by an electrical motor.
This backdraft damper flap also features a rubber strip on its edges,
which optimizes airtightness when the fan is not running, and which by far
favorably
compares to any traditional gravity closed dampers used in the agricultural
sector.
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The light damper flap itself causes almost no air-flow restriction when
the fan is running, which permits to increase the airflow ventilated out of
the building.
This way when many fans are required to ventilate a certain building, the
increase of
airflow exhausted from the building through each fan, permits to reduce the
power of
fans, and/or simply permits to avoid using one or more fans, which saves
energy.
The system saves electricity by improving the cfm ratio per watt. For a
fan that runs at full speed, with the same energy used, the airflow exhausted
from
the building is increased (higher cfm ratio per watt).
The system can be used for any one or more of the following targeted
Markets
Animal producers who currently have or plan to have air-filtered
confinement buildings, and who want to block out non-filtered air backdraft
when
fans are not running.
Producers who have buildings that are not equipped with air filters, but
who wish to increase the efficiency rate of airflow exhausted from their
buildings
through their fans. This can be accomplished by replacing their traditional
dampers
by the backdraft damper flaps, which may be installed on interior or exterior
building
walls. The damper flap also contributes to the reduction of fan energy
consumption
and/or to the improvement of air quality in buildings.
For both types of clienteles, the backdraft damper flap also eliminates
the need to use traditional fan winter damper flaps (winter cover), saving on
annual
installation and removal labor cost, plus eliminating the need of storage
space for
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those winter damper flaps during the summer. Cold air infiltration through non-
running fans during the cold season creates a need for increased heating,
which
means higher energy consumption to heat the building(s).
In the sector of pig, chicken and other types of animal confinement
buildings, air-filtered buildings with negative pressure (pig market is
specially
targeted here), it is particularly important for backdraft damper flaps to be
low-cost,
maintenance-free and most important, to be airtight to avoid infiltration of
non-filtered
air through non-running fans, or fans that need to be run at minimum speed in
presence of strong opposing winds.
The main benefits of the airtight damper flap for animal confinement
buildings are as described hereinafter:
Prevents infiltration of airborne parasites, non-desired air flow, or
backd raft that may transport airborne pathogens (for air-filtered building
application).
Replaces traditional winter cover to prevent cold air infiltration
No negative impact on the airflow that is exhausted by fan(s) when
added to traditional dampers (for air-filtered building application, the
addition of the
airtight damper flap to the traditional damper is highly recommended)
Increases the airflow exhausted from the building when traditional fan
louvers are removed in non-filtered building application
Meets the needs of all animal producers, including those who have air-
filtered buildings
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Works as well with variable speed fans or 1-speed ones (on-off),
contrary to those marketed by the competition, which work only with 1-speed
fans
Works on all fan dimensions
Easy installation
5 Simple mechanism requiring no electricity
Maintenance-free and reduces corrosion of sheet metal exterior walls
of animal confinement buildings
Closes automatically when fan is turned off or stops running for any
reason
10 No dust or dirt build-up
Easy pressure washer cleaning
Specially designed to push exhausted air away from the building,
which otherwise is known to cause corrosion on exterior walls
Prevents air, pathogen, dust or dirt from infiltrating the building when
15 installed on exterior wall, which keeps the fan area clean, and which
allows for easy
access to the fan without having to remove the backdraft damper flap, thus
eliminating potential risks of airborne pathogen infiltration.
The higher the negative pressure in the building, the more airtight the
damper flap is.
What is of particular importance in this arrangement, is that the damper
flap can be and remain airtight closed when the fan is not running in an air-
filtered
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building, and also the fact that the damper flap itself does not create any
restriction
when the fan is operating.
As described herein, this new airtight backdraft damper flap may be
either installed on the interior wall of a building (figure 8), or on the
exterior wall
(figure 3).
This airtight backdraft damper flap can be installed on any type of fans
ranging from 10" to 55".
As described hereinafter, this new airtight backdraft damper flap is
usually installed on the exterior wall of the building (figure 9) but it can
also be
installed on the interior wall.
This airtight backdraft damper flap can be installed on any 10" to 55"
interior fans but it can also be used with larger fan dimensions.
The new featured damper flap mechanism also allows to keep the
backdraft damper flap in minimal opening setting to prevent the wind from
affecting
the outward air flow when the fan is running at a slow speed in presence of
strong
opposing winds. In an air-filtered building, when a fan stops running, the
mechanism
minimal opening function is automatically neutralized by a solenoid
(optional), which
instantly closes the damper flap.
In a traditional non-filtered building the idea is to completely remove
and replace standard fan louvers by the airtight damper flap, though here, the
damper flap does not need to be as airtight as it must be for air-filtered
building
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17
applications, for which the main objective is to prevent airborne virus
infiltration. The
damper flap and its innovative mechanism still offer here several benefits:
The damper flap causes no air-flow restriction whatsoever when the
fan is operating, which increases the exhaust capacity of the fan at a given
power,
which increases energy efficiency by increasing the cfm ratio per watt.
The damper flap mechanism automatically shuts and renders the
backdraft damper flap airtight during the winter, preventing any infiltration
of
undesired cold air through fans that are not running, thus eliminating the
need to
install traditional winter cover on fan outlets.
The damper flap mechanism also allows to lock the backdraft damper
flap in minimal opening setting to prevent the wind from affecting the outward
air flow
when the fan is running at a slow speed. In an air-filtered animal confinement
building, when a fan is not running, the damper flap lock mechanism is
automatically
neutralized by a solenoid, which instantly closes the damper flap.
As described hereinafter, the new airtight backdraft damper flap may
be either installed on the interior wall of a building (see figure 8), or on
the exterior
,
wall (figure 3)
This airtight backdraft damper flap can be installed on any type of fans
ranging from 10" to 55".
As described herein, the new airtight backdraft damper flap is usually
installed on the exterior wall of the building (figure 9) but it can also be
installed on
the interior wall, but in this case, with no impact on wind control.
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This airtight backdraft damper flap can be installed on any 10" to 55"
interior fan but it can also be used for larger fan dimensions.
In the commercial, institutional and industrial market, this airtight
backdraft damper flap can also be used on any type of fan or air duct inlets
or
outlets. In the winter time, the damper flap can be closed to avoid heat loss
and save
energy, or maintained open when the fan is running. It can also be kept in a
minimal
opening setting when a minimum air flow control is required in the presence of
strong opposing winds, in which case, the automatic minimal opening function
of the
mechanism represents an interesting and valuable characteristic.
The backdraft damper flap mechanism permits to close the damper
flap when necessary, or to keep it open when the fan is running, which in both
cases
saves energy.
The arrangement can also be used in the residential market for
example as a clothes dryer damper, stove fan damper, air exchange damper or
furnace inlet and outlet damper. In the winter time, the damper flap can be
closed to
avoid heat loss and save energy, or maintained fully or partially opened when
the
fan is running, causing no air flow restriction, which also saves energy.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a plan view of a barn including a fan construction according
to the present invention;
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Figure 2 is a vertical cross-sectional view of the barn of Figure 1;
Figure 3 is a cross-sectional view along the same lines as Figure 2 on
a much enlarged scale showing one fan construction with the closure flap
thereof in
an open position;
Figure 4 is a front elevational view of the fan construction of Figure 3.
Figure 5 is a cross-sectional view on a further enlarged scale than
Figure 3 showing one part only of the fan construction with the closure flap
thereof in
a closed position with the magnet at the bottom part of the flap;
Figure 6 is a cross-sectional view on a further enlarged scale than
Figure 3 showing one part only of the fan construction with the closure flap
thereof in
a partly open position held opened by a pin;
Figure 7 is a cross-sectional view of a modified embodiment on a
further enlarged scale than Figure 3 showing one part only of the fan
construction
with the closure flap thereof in the closed position with the magnet on the
perimeter
of the flap;
Figure 8 is a cross-sectional view similar to that of Figure 3 showing a
modified fan construction with the closure flap assembly thereof at the inlet
end at
the wall opening inside the building.
Figure 9 is a cross-sectional view similar to that of Figure 3 showing a
modified fan construction which has no exterior duct on the fan housing so
that the
closure flap assembly thereof is mounted on the fan housing directly at the
wall
opening outside the building.
CA 02737208 2013-07-29
Figure 10 is a cross-sectional view similar to that of Figure 3 showing a
modified fan construction which provides more than one row of closure flaps.
Figure 11 is a cross-sectional view of a further embodiment showing a
modified hood and including an additional mechanism (partially shown) for
applying
5 spring force to the damper flap to bias it both into the fully open and
fully closed
positions and showing the damper flap in the fully closed position.
Figure 12 is a side elevational view of the further embodiment of Figure
11 showing in more detail the additional mechanism for applying spring force
to the
damper flap to bias it both into the fully open and fully closed positions and
showing
10 the damper flap in the fully open position.
Figure 13 is an isometric view from the front and one side.
Figure 14 is a side elevational view similar to that of Figure 12 showing
in larger scale the additional mechanism for applying spring force to the
damper flap
showing the damper flap in the fully closed position and showing an optional
15 solenoid for applying an additional force to move the damper flap to the
partially
open position.
Figure 15 is a side elevational view similar to that of Figure 12 showing
in larger scale the additional mechanism for applying spring force to maintain
the
damper flap closed when required, showing the damper flap in the fully closed
20 position and showing an optional solenoid for increasing the spring force
when
required.
Figure 16 is a side elevational view similar to that of Figure 12 showing
CA 02737208 2013-07-29
21
an alternative mechanism for applying the spring force to maintain the damper
flap
closed when required.
Figure 17 is a side elevational view similar to that of Figure 12 showing
a further alternative mechanism for one-speed fans, for applying the spring
force to
maintain the damper flap closed or fully opened when required.
In the drawings like characters of reference indicate corresponding
parts in the different figures.
DETAILED DESCRIPTION
In Figures 1 and 2 is shown an animal husbandry barn 100 including
peripheral walls 101 defining a containment area 102. A roof 103 defines a
roof
space 104 above a ceiling 105.
A plurality of air inlets 106 provide air entry into the containment area
where each air inlet 106 has an air filter system 107 for extraction from
incoming air
of pathogens so as to prevent transmission of disease to the animals.
A plurality of extraction fans 110 are located at spaced positions
around the walls for generating an air stream exiting the containment area so
as to
generate a negative air pressure within the barn so as draw replacement air
into the
containment area through the air inlets 106. Apart from the inlets and the
extraction
fans, the containment area is sealed against ingress of pathogen containing
air.
The extraction fans can be driven at variable rate including at least
high and low speed and can be shut off when not required. Shutting off fans
when
possible of course reduces energy usage. High fan speed is required at the
highest
CA 02737208 2013-07-29
22
temperatures to provide the required level of ventilation and cooling. Lower
fan
speed is required at other times. The system can be computer controlled to
ensure
sufficient ventilation and cooling while minimizing energy usage.
As shown in Figure 3, each fan has a fan housing 17 defining a duct
extending from an end plate 17A which mounts in the wall 101. The plate and
duct
form a circular or rectangular passage for air escaping from the wall opening.
A fan
18 with a motor 18A and fan blades 18B is mounted in the duct of the fan
housing to
drive the air outwardly from the wall opening to an open end 17C of the fan
housing
17. The open end 17C thus forms an opening spaced outwardly from the wall 101.
The fan housing thus defines an inlet opening 17D at the wall and an
outlet duct 17 extending through the wall to an outlet opening 17C outside the
wall.
A damper flap assembly 120 is mounted on the fan housing which
includes a mounting plate or board 12 having an opening 12A through which the
air
passes and a flange 12B surrounding the opening and defining top flange 12C,
bottom flange 12B and side flanges. A flexible rubber seal or silicon 10
allows to seal
the joint between fan housing 17 and the mounting plate 12.
A damper flap 1 in the form of a styrofoam or similar board covered
with a plastic sheet on each surface and covering the edges. The board or flap
1 is
suspended by a hinge 16 at an upper edge engaging the top flange 12C. The
board
1 is pivotal about its upper edge so as to hang from the hinge under gravity.
The
board 1 can therefore extend in a closed position across the opening 12A with
an
CA 02737208 2013-07-29
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outer peripheral portion 1A, 1B, 1C and 1D (Figure 4) of the damper flap
engaging
the flange 12B, 12C around the opening 12A.
The damper flap 1 is movable to an open position as shown in Figure 3
under pressure from forward air flow 18F from the fan 18 by pivoting on the
hinge 16
away from the flange 12B, 12C.
A resilient deformable fin seal 2 is provided on the peripheral portions
1A, 1B, 1C and 1D so as to act between the outer peripheral portion of the
damper
flap and the flange. The seal surrounds the opening 12A and is arranged to
seal the
damper flap to prevent reverse flow 18R of air through the fan housing.
The seal comprises a deformable fin 2A (Figure 6) which can be
readily depressed and provide an effective seal under the low forces of back
pressure from the negative air pressure inside the building.
The mounting plate 12 includes a top cover 13 extending from the
hinge 16 outwardly over the top of the damper flap 1 and includes down-turned
flange 14 with a bottom edge 14A to engage the damper flap 1 and prevent
pivotal
movement of the damper flap 1 beyond a predetermined angle. The cover 13 can
also include side plates 11 which prevent air from engaging the sides of the
flap 1.
In operation, the flap is held open by air flow at a high rate from the fan
18 in the forward direction 18F. In the event that the fan is shut off when
the air flow
is not required, the flap closes under gravity until it engages the plate 12
causing the
seal to engage. In this case the back pressure on the flap will hold it closed
forming
a seal to prevent back flow of any contaminated air into the building. This is
CA 02737208 2013-07-29
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particularly important in times of the year such as Fall or Spring where the
outside
temperature is not sufficiently high that high fan flow is required, and when
the
minimum ventilation causes the air to be humid and slow moving, leading to
high
levels of contaminants.
In order to hold the flap slightly open during times when the fan is
driven at a lower rate for less air movement, an abutment member 7 is provided
for
butting the bottom edge portion 1C holding the damper flap in a slightly open
position. The abutment member 7 (figure 6) includes a pin 7A which is
retractable
on a solenoid 7B mounted on a plate 6 underneath the fan housing 17 on the
rear of
the plate 12 to allow closing of the damper flap. Thus the pin is electrically
operable
by a remote control device for full retraction to allow closing and for
adjustment to
set the required amount of opening depending on required air flow rate.
In order to increase the closing pressure to supplement the back air
pressure, a magnet latch is provided for providing a closing force for holding
the
damper flap in the closed position. This can comprise a magnetic strip 20
(figure 7)
around the periphery of the damper flap cooperating with a metal strip 21 on
the
mounting plate 12.
Alternatively the magnet latch comprises a magnet 3 (figure 7) carried
on a support plate 4 and cooperating with a metal plate 5 on the mounting
plate 12
located at the bottom edge of the damper flap.
A heating wire 8 can be provided for heating the seal to prevent
freezing.
CA 02737208 2013-07-29
The hinge 16 (figure 3) is a flexible strip across the top of the flap 1
and extending from the damper flap 1 to the mounting plate 12 and mounted on a
spacer strip 15 at the mounting plate 12. Other types of hinge can be used.
The typical additional louver closure 19 remains in some cases at the
5 wall opening to provide an interior closure when the fan is shut off.
The arrangement described above includes a fan housing with an
exterior duct, which extends outwardly of the wall where the damper flap
assembly is
mounted on an outer end of the duct.
In Figure 8 is shown a cross-sectional view similar to that of Figure 3
10 showing a modified fan construction with the damper flap assembly
thereof at the
inlet end at the wall opening. In this case the device is located in front of
the louver
arrangement 19, which can be removed or may remain in place. Apart from this
modification, the construction is the same as that described above. In figure
8, the
damper flap will not act to block the wind effect at low speed because it is
installed
15 upstream from the fan. So that, in that case, the only objective is to
block the
contaminated reverse flow of the air in the back-draft. Thus the solenoid
abutment is
not required. A solenoid may be provided to open the flap when the flap is
blocked
by freezing and/or keep minimum opening when the fan running at minimum speed.
A duct 22 which can be rectangular or circular is located between the damper
flap
20 and the fan inlet. This duct is suitably fastened to the wall.
In Figure 9 is shown a cross-sectional view similar to that of Figure 3
showing a yet further modified fan construction with no duct so that the
damper flap
CA 02737208 2013-07-29
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assembly thereof is mounted directly at the outside surface of the wall. In
this
arrangement there is provided a wire mesh 180 on the inside surface at the fan
18B
as a protection guard and a fan venturi 18G. In this arrangement the louvers
23 are
mounted on the outside of the wall with its box insert into the wall. There
may be
provided also a short duct 24 between the wall and the damper flap. Apart from
this
modification, the construction is the same as that described above.
In Figure 10 there is shown an arrangement with two rows of flaps 120.
This arrangement can be used for example with a 36 inches fan. The flap
dampers
can be either installed inside or outside the building as described above. In
some
constructions there may also be more than two rows as well as more than 1
column
of flaps for example for 55 inches fans.
Turning now to Figures 11 to 17, the following additional elements
have been added:
Item 32 which is a circular extension lip where the flap is closed on the
edge.
Item 33 which is a rod or flat bar attached on one end to the hinge and
attached on the other end to the center of the flap which forces the flap to
close
tightly on the edge of the circular extension lip 32. In Figure 13 it will be
noted that
the rod 33 or engagement member acts centrally of the circular damper flap
along a
center line of the flap to equalize forces on the peripheral edge or edges of
the
damper flap.
Item 34 which is an electric heating cable which can be installed either
CA 02737208 2013-07-29
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on the periphery of the flap and/or the periphery of the circular extension
lip to
prevent freezing and is optional.
Item 35 which is a stainless steel rod hinge.
Item 36 which is a hood or cover acting as wind breaker. This piece
protects the damper flap against snow and rain and provides a nozzle or
opening
through which the air escapes while resisting back flow of wind against the
flap. The
hood shown 36 in Figures 11 and 13 has a horizontal top wall 36A extending
forwardly over the top of the damper flap and its hinge, and a down-turned
front
flange 36B extending downwardly and forwardly from the front edge of the wall
36A
along the damper flap to a bottom edge 36C. The hood has a width a little
wider
than the opening from the fan and the flap so as to contain the flap and
define side
. walls 36D and 36E. The down-turned front flange 36B, as shown in Figure 12,
extends parallel to the damper flap in the fully open position thereof with
the bottom
edge 36C of the flange at or beyond a bottom edge 30A of the damper flap 30 so
that the whole of the flap is contained within the hood. The hood also has a
bottom
wall 36F extending forwardly from the mounting plate and a down-turned front
flange
49 extending downwardly and forwardly from a front edge of the wall 36F. The
deflector is provided in order to create a shield against strong opposing
winds, and
to reduce or prevent draft on the wall of the barn, which is known to be an
important
cause of rust on exterior sheet metal siding of animal confinement buildings.
That is
the objective of this part to move the air away from the building as it
exhausts from
the fan. Also the hood side walls, top wall and bottom wall are connected to
form a
CA 02737208 2013-07-29
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nozzle directing the air outwardly and downwardly from a mouth 36G of the
nozzle
which is in an inclined plane facing forwardly and downwardly.
Item 37 shown in Figure 12 and in larger view in Figure 14 is a spring
biasing arrangement helping to control the opening and closing of the flap.
The
spring biasing arrangement is arranged for applying force to the damper flap.
The
spring biasing arrangement 37 includes a cam plate 42 pivotally mounted on a
pin
40 carried on the housing. The cam plate 42 has a cam surface 42A engaging a
cam
follower roller 39. A spring 44 applies a spring force to the cam so as to
cause the
cam to rotate around the pin 40 in an upwards or downwards direction and apply
a
force to the cam follower roller 39 from the cam surface 42A. The cam follower
roller
39 is attached to the flap 30 by a lever 38 to apply a force thereto at the
hinge 35
through the rod 33.
In Figure 14, the cam surface 42A is shaped so as to control the forces
applied to the roller 39 and therefore to the flap. In this embodiment, the
surface
42A includes a peak 42B at a position part way along the surface between a
left
hand end 48 at the fully open position and a right hand end 46 at the fully
closed
position. In this way, on the left side of the peak as viewed, the roller 39
tends to
move toward the left, under the spring pressure from the spring 44 biasing the
surface upwardly toward the roller. Symmetrically on the right side of the
peak, the
roller 39 tends to move toward the right. Thus the spring biasing arrangement
is
arranged on the right side of a partially open position at the peak 42B to
bias the
CA 02737208 2013-07-29
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damper flap into the fully closed position and on an opposed side of the
partially
open position to bias the damper flap into the fully open position.
The spring is attached at one end to a chain 43, which connects to a
hole 41 in the housing. At the other end the spring is attached to a screw 45
or other
connecting item attaching the spring to the damper housing
This mechanism allows inwards pressure to be put on the flap when
the flap is closed so that, when the fan has stopped running, the flap is and
remains
tightly closed. The pressure is adjustable by adjusting the spring pressure.
When the
fan is at the minimum speed, the mechanism will keep the flap at minimum
opening
in order to reduce the inwards pressure drop caused by strong opposing winds
or
the weight of the flap itself. When the fan is running at maximum speed, the
mechanism will help to keep open the flap and reduce the pressure drop to
increase
the fan performance. The spring tension can be adjusted to adjust the flap
pressure
on the edge of the lip edge.
In position 46 of the roller 39, the biasing arrangement puts inwards
force on the flap in order to close it tightly.
In addition to the peak 42B, the surface 42A includes a raised section
42C between a position 47 and the end position 46. In position 47 of the
roller 39,
the biasing arrangement acts by the raised portion 42C to apply a slight
outwards
force on the flap in order to keep it open at minimum opening when the fan is
running at minimum speed in order to reduce pressure drop on the fan caused by
strong opposing wind or the flap weight itself.
CA 02737208 2013-07-29
In position 48 of the roller 39, the biasing arrangement applies
outwards force on the flap in order to keep it fully open when the fan is
running at
maximum speed, in order to reduce the pressure drop on the fan caused by the
flap
weight itself, and maximize the fan performance.
5 Also in
Figure 14 is shown a solenoid 50 (optional), operated in
response to actuation of the fan, which is positioned to apply outwards force
directly
to the lever 38 when the lever is in the position 46. Thus when the fan
starts, the
solenoid 50 applies a push on the lever 38 for maintaining the flap minimum
opening
as desired. When the fan stops, the solenoid is also deactivated to retrieve
its initial
10
position to let the flap close. The solenoid does not apply any force on the
flap to
close it. The solenoid can be also installed in the previous arrangement as
shown in
figure 6 at parts 7, 7A and 76.
Also in Figure 15 is shown a solenoid 51 which operates in the same
manner as solenoid 50. However in this case the solenoid is located at the end
of
15 spring
44 to apply an increased force on the spring 44. This can be used when the
fan stops running to put inwards pressure on the flap to maximize the flap air
tightness. When the fan starts, the solenoid moves outwardly to reduce the
spring
force and to reduce the pressure on the flap when the fan is running at
maximum
speed and avoid the reduced fan performance or fan airflow. The solenoids 50
and
20 51 can
be installed in various ways on the device in order to close the flap firmly,
to
allow a minimum opening and help the mechanism to retain the flap fully open
when
fan is at maximum speed.
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=
31
Thus as described above there is provided an operable device such as
a solenoid 50 or 51 for applying additional force to the spring biasing
arrangement to
increase the force when required. The operable device is dependent on
operation of
the fan so that it operates when the fan is actuated and uses power from the
fan
operation. The cam surface 42A includes a recess at the partially open
position 47
so as to apply spring force to the damper flap to tend to hold the damper flap
in the
partially open position. However additional forces to the right or left will
overcome
this partial restriction and allow the flap to move to the fully open and
fully closed
positions as required.
The solenoid can be installed in various ways and can be replaced by
a simple adjustable pin which can be manually or automatically opened or
closed
with variable adjustment.
Turning now to Figure 16 there is shown an alternative arrangement of
the spring biasing arrangement as shown at 53 where the cam 53A has a surface
53B which is straight so that the peak previously described is omitted.
However this
arrangement also operates by the geometry of the system on one side of the
partially open position to bias the damper flap into the closed position and
on an
opposed side of the partially open position to bias the damper flap into the
fully open
position. This is achieved in that there is a top dead center position of the
cam roller
53C when the cam surface 53B is horizontal and the lever 38 is vertical. On
the left
of this the roller moves to the left. On the right of this the roller moves
toward the
right.
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32
Turning now to Figure 17, there is shown another alternative for
applying spring force to the flap so that on one side of the partially open
position to
bias the damper flap into the tightly closed position and on an opposed side
of the
partially open position to bias the damper flap into the fully open position.
In this
arrangement 60 there are two levers 60A and 60B pivotally connected at a pin
60C
at one end to each other, with the other end of the lever 60B connected to the
housing and the other end of the lever 60A connected to the flap. A spring 60D
applies spring force to the lever arrangement. Again there is a top dead
center
position of the spring and lever configuration by which the spring 60D on one
side of
the position applies outwards force in one direction to the open position and
on the
other side of the position applies inwards force in the other direction to the
tightly
closed position.
The main points of importance herein are as follows:
The device acts both to close the flap tightly and also to put outward
force to maintain the open position in order to reduced or avoid the pressure
drop,
and maintain or improved the fan airflow or performance.
The device acts to put the pressure on the center of the flap in order to
equally put the pressure on the edge perimeter even if any unexpected slight
deformation occur on the edge.
The inward and outward force can be adjustable.
The cam may have different shapes or design in order to adapt the
mechanism for the purpose required.
CA 02737208 2013-07-29
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The device can be used on any types of fans, ducts, inlets and outlets.
The use of the proper seal is important in order to be airtight.
The abutment engaging the flap (retractable or not) (automated or not)
( for air-filtered facilities or not) will allow the flap to main a certain
minimum flap
opening in order to control the minimum ventilation rate event with strong
opposing
wind.
The hood is designed to avoid airflow directly on the building and
throwing the air far away from the building.
This system is either for air filtered and non air filtered facilities
(agricultural, industrial etc sectors).
This system can be installed inside or inside the building.
In comparison with conventional louvers, the device provides
increased fan performance by decreasing pressure drop and at the same time
increasing the flap air-tightness.
The arrangement takes into account the four seasons in order to be
always airtight and to not have freezing problem during the cold season.
