Note: Descriptions are shown in the official language in which they were submitted.
1
APPARATUS AND METHOD FOR CONTROLLING AIR FLOW OF AN
EXTRACTION FAN
This invention relates to a fan construction which includes a damper
that closes firmly to prevent air backdraft 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
results.
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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.
According to one aspect of the invention there is provided a damper
flap assembly for use with a fan housing and a fan mounted in the housing
where
the fan is operable at a high speed and at a low speed lower than the high
speed;
the damper flap assembly comprising:
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a mounting member having an opening through which the air passes
and an engagement surface surrounding the opening, the mounting member being
arranged for mounting the housing in a location where the opening is exposed
to
exterior wind forces;
a damper flap pivotally mounted on a hinge arranged to extend in a
fully closed position across the opening, when the fan is halted, with an
outer
peripheral portion of the damper flap engaging the engagement surface around
the
opening;
the damper flap being movable from the fully closed position to an
open position in response to forward air flow from the fan, when said fan is
operating
at said high speed, by pivoting on the hinge away from the engagement surface;
biasing means biasing the damper flap into the fully closed position
during at least part of movement from said open position to the fully closed
position;
and a member movable to an abutting position to hold the damper flap
in a partially open position less open than said fully open position, when
said fan is
operating at said low speed;
said member being arranged such that, in the partially open position,
the damper flap extends across the opening to resist wind forces in a
direction
opposite to said forward air flow;
said member being arranged to hold the damper flap in said partially
open position against said closing biasing force from said biasing means and
against
wind forces biasing the damper flap to the fully closed position when the wind
forces
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overcome the low speed forward air flow from the fan operating at said low
speed
with a net effect biasing the damper flap to the closed position;
the member being operable when the fan is not running to move from
the abutting position to release the damper flap to move into the closed
position.
Preferably the damper flap assembly comprises:
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 having a front surface facing forwardly away from the
fan and a rear surface facing toward the fan;
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;
the damper flap being suspended by a hinge member adjacent an
upper edge of the damper flap and pivotal about a hinge axis of the hinge
member;
the hinge member including a transverse support at the hinge axis and
at least one support arm extending from the transverse support adjacent the
upper
edge in a direction forwardly of the damper flap to a position in front of the
damper
flap, said at least one support arm being connected by a connection member to
the
damper flap at a position below a top edge of the damper flap.
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Preferably said connection member is arranged at a position adjacent
or below a transverse center line of the damper flap. However the connection
member can be placed above the transverse center line of the damper flap in
some
cases.
Preferably said at least one arm is connected to the damper flap only
at said connection member allowing top and bottom edges of the damper flap to
flex
relative to said connection member.
Preferably said at least one support arm includes a depending portion
extending along the front face of the flap member and spaced therefrom.
Preferably there is provided at least one bracket fastened to the front
face of the flap member and said depending portion of said at least one
support arm
is engaged with the bracket.
Preferably the depending portion comprises a rod and the rod is
engaged through a hole of the bracket.
Preferably the transverse support is located at a position in a vertical
plane rearward of the rear face of the flap member.
Preferably the transverse support is located at a height above the top
edge of the flap member.
When used, the spring biasing arrangement includes two springs
which are independently adjustable.
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That is the two springs are arranged to provide different forces to the
damper flap such that independent adjustment provides different changes in the
biasing forces.
Preferably one of the two springs is arranged on one side of the hinge
member and the other on the other side of the hinge member.
Preferably said at least one arm comprises two arms spaced
transversely so that each is located on a respective side of a vertical
centerline of
the flap member.
Preferably the two arms are mounted on two separate components of
the transverse support such that the arms can pivot independently.
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.
One key point of this new automatic mechanism described hereinafter
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 described
hereinafter increases by more than 15% the efficiency of the fan running at
full
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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 even more decreased 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
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,
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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
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
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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
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
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.
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It has been determined that the conventional louver arrangement used
with agricultural fans is not sealed enough to prevent back-draft and virus
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
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
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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
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
backdraft
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.
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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.
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.
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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
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
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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
backdraft 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
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
Simple mechanism requiring no electricity
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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
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
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
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).
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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
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.
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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.
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
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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 wintertime, 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;
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.
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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.
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
spring force to the damper flap to bias it both into the fully open and fully
closed
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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
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
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
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
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.
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Figure 18 is a side elevational view of the housing and flap member
only showing a further alternative mechanism for mounting and control of the
flap
member.
Figure 19 is a front elevational view of the housing and flap member of
Figure 18.
Figure 20 is an isometric view of the housing and flap member of
Figure 18 showing an alternative arrangement of the spring biasing system.
Figure 21 is a side elevational view of the housing and flap member
only showing a further alternative mechanism for mounting and control of the
flap
member.
Figure 22 is a side elevational view of the housing and flap member
only showing a further alternative mechanism for control of the flap member.
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
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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
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,
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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
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
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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
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)
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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.
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
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
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
upstream from the fan. So that, in that case, the only objective is to block
the
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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
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
assembly thereof is mounted directly at the outside surface of the wall. In
this
arrangement there is provided a wire mesh 18D 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.
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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
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
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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
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
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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
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.
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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.
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.
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
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 7B.
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
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
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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
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.
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
536 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
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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.
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.
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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.
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 outside 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.
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Turning now to Figures 18, 19 and 20 there is shown an alternative
arrangement of a cylindrical housing 70 for mounting on the fan housing and a
circular disk shaped flap member 71 for pivotal movement between an open
position
and a closed position as shown butting against the rim 72 of the housing 70.
The damper flap assembly therefore comprises a mounting plate
defined by the housing having an opening through which the air passes and a
flange
72 surrounding the opening. In this Figure the mounting plate is not shown,
only the
flange is shown that is about 4 inches deep. The depth of the flange will
change
depending on the fan housing on which it is mounted. For example, if the
outside
perimeter of the fan housing is very tilted, there is a need to have a bigger
flange in
order to cover this. This flange is then mounted on the mounting plate (not
shown for
convenience of illustration). The pivotally mounted circular damper flap 71 is
arranged to extend in the closed position across the opening when the fan is
not
running, with the outer peripheral edge portion 73 of the damper flap 71
engaging
the flange 72 around the opening. The damper flap 71 is formed as a flat
circular
disk and has a front surface 74 facing forwardly away from the fan and a rear
surface 75 facing toward the fan. The damper flap 71 is formed as a flat
circular disk
but could be designed with other shapes and arrangements as required.
The damper flap is suspended by a hinge member 76 adjacent an
upper edge 77 of the damper flap 71 and pivotal about a hinge axis 78 of the
hinge
member. The hinge member 76 includes a transverse support 79 at the hinge axis
and two support arms extending 80 and 81 from the transverse support 79
adjacent
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the upper edge 77. The arms are arranged symmetrically at spaced positions on
respective sides of a vertical center line CL2. The arms include a first
horizontal
portion 80A and 81A in a direction forwardly of the damper flap to a position
in front
of the damper flap. The arms further include vertically depending portions 80A
and
806 each of which is connected by a connection member 80C and 81C to the front
face 74 of the damper flap 71 at a position below the top edge 77 of the
damper flap
71.
The connection members 80C and 81C are arranged at a position
adjacent or below a transverse center line CL1 of the damper flap and are
connected to the damper flap 71 only at said connection members allowing top
77
and bottom edges 77A of the damper flap to flex relative to the connection
members
and therefore relative to the arms.
Thus the depending portions 80B and 816 extend along the front face
74 of the flap member 71 and spaced therefrom so as to move independently of
the
front face when flexing action of the flap member occurs.
The connection member 80C and 81C are formed by brackets
fastened to the front face 74 of the flap member 71 and the depending portions
80B
and 81B each comprises a rod and the rod is engaged through a hole 80D, 81D in
a
horizontal flange of the bracket.
The transverse support 79, as shown in Figures 18 and 19, is located
at a position in a vertical plane VP (Figure 18) rearward of the rear face 75
of the
flap member 71 and is located at a height above the top edge 77 of the flap
member.
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The two arms 80 and 81 are mounted on two separate components
79A and 79B of the transverse support 79 such that the arms can pivot
independently. That is the component 79A is supported between an outer support
wall 76A and an intermediate support wall 76B and the component 79B is
supported
between an outer support wall 760 and an intermediate support wall 76E. All of
the
support walls depend from a top plate 76C and form a rigid frame structure
from
which the transverse member 79 pivots. As the frame 76 holds the transverse
member 79 at a fixed position on the line 78 but the space between the walls
76B
and 76E allows the components 79A and 79B to pivot or rotate relative to one
another to allow flexing of the flap member.
The flap member can be used with no spring bias so that the flap
member closes under gravity. However in some arrangements, there is provided a
spring biasing arrangement 90 applying biasing forces from two springs 93 and
94
though levers 91 and 92 to the arms 80 and 81 in directions both toward the
open
position and toward the closed position. The springs are arranged in similar
manner
to that previously described so as to provide the lever 91, 92 with an over
center
action. The springs 93 and 94 which are independently adjustable to provide
different forces to the damper flap such that independent adjustment provides
different changes in the biasing forces. The spring 93 is arranged on one side
of the
hinge member and the spring 94 is arranged on the other side of the hinge
member.
In Figure 21 is shown the same flap member and housing but using a
modified spring arrangement 176 which includes two springs in a cam and cam
CA 2927369 2018-06-15
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follower 177 in the arrangement previously described.
In Figure 22 is shown the same flap member and housing but using a
modified spring arrangement 180 which includes a single spring and two levers.
Thus the flap 71 is pivotal on the previously described arms on a transverse
shaft
181. Control of the rotation of the shaft 181 is obtained by a gear 184 which
meshes
with a second gear 185. Rotation of the gears about their respective axes is
controlled by a pair of levers 182 and 183 and a spring 186 connecting the
levers.
Thus, in the open position shown, the levers are biased by the spring 186 to
rotate
the lever 182 and the flap 71 carried on the shaft 181 in a direction toward
the open
position. As the flap closes due to drop in air flow, this causes rotation of
the levers
182 and 183 in a direction apart to stretch the spring up to the position of
maximum
length when the lever 182 is at the 12.00 position and the lever 183 is at the
6.00
position. After this position, the levers move over center and the spring
pulls them
together with the lever 182 rotating in clock-wise direction thus biasing the
flap 71
into the closed position butting the flange 72.
Thus the spring biasing arrangement includes the first lever 182
connected to the shaft 181 and the spring 186 acting on the lever 182 to pivot
the
shaft 181. The meshing gears 184, 185 connect the first and second levers for
common movement in opposite directions as the shaft pivots. The spring 186 is
connected between the two levers 182 and 183 and passes an over-center
position
OC as the levers rotate so as to bias the first lever 182 in a first direction
D1 on one
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side of the over-center position and in a second direction D2 on the other
side of the
over-center position.
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