Note: Descriptions are shown in the official language in which they were submitted.
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EXTRACTION FAN ASSEMBLY FOR AN ANIMAL HUSBANDRY BARN
This invention relates to a fan construction for use in an animal
husbandry barn.
Typically such barns comprise a containment area; a plurality of air
inlets into the containment area and a plurality of extraction fan
constructions for
generating an air stream exiting the containment area so as to draw
replacement air
into the containment area through the air inlets. In many cases each air inlet
has an
air filter system for extraction from incoming air of pathogens so as to
reduce
transmission of disease to the animals
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
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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.
However it is known that pathogens can still enter the containment
area through closed fans louvers, due to known negative air pressure (.05 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, 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.
SUMMARY OF THE INVENTION
It is one object of the invention to provide a fan construction for use in
an animal husbandry barn.
According to one aspect of the invention there is provided a fan
construction for use in an animal husbandry barn where the barn comprises:
a containment area;
a plurality of air inlets into the containment area where each air inlet
has an air filter system for extraction from incoming air of pathogens so as
to prevent
transmission of disease to the animals;
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and a plurality of extraction fan constructions for generating an air
stream exiting the containment area so as to draw replacement air into the
containment area through the air inlets;
each fan construction comprising:
a fan housing arranged to be mounted in a wall;
the fan housing having an inlet opening at the wall and an outlet
duct extending through the wall to an outlet opening outside the wall;
a fan mounted in the housing;
and a damper flap assembly mounted on the fan housing, the
damper flap assembly including:
a mounting plate having an opening through which the air
passes and a flange surrounding the opening;
a damper flap suspended by a hinge at an upper edge and
pivotal about the upper edge so as to extend in a closed position across the
opening
with an outer peripheral portion of the damper flap engaging the flange around
the
opening;
the damper flap being movable to an open position under
forward air flow from the fan by pivoting on the hinge away from the flange;
and 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 fan housing.
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The seal is preferably carried on the outer peripheral portion of the
damper flap but it can also be located on the flange.
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 top cover extending from the
hinge over the top of the damper flap to maintain protection from failing
contaminants such as snow and preferably the top cover 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
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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
5 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 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
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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 louver when a fan is not running in air-filtered barn for
swine and also
for 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
contamination.
According to a second aspect of the invention there is provided a fan
construction comprising:
a fan housing;
a fan mounted in the housing;
the fan being operable at high speed and at low speed;
and a damper flap assembly mounted on the fan housing, the damper
flap assembly including:
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a mounting plate having an opening through which the air passes and
a flange surrounding the opening;
a damper flap suspended by a hinge at an upper edge and pivotal
about the upper edge, so as to extend in a closed position across the opening
with
an outer peripheral portion of the damper flap engaging the flange around the
opening;
the damper flap being movable to an open position under forward air
flow from the fan when the fan is operating at low or high speed, by pivoting
on the
hinge away from the flange;
wherein 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 low speed.
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
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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 rates
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
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 equipment 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.
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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.
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
CA 02725245 2010-12-13
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
5 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.
In the drawings like characters of reference indicate corresponding
10 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.
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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,
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
I is
suspended by a hinge 16 at an upper edge engaging the top flange 12C. The
board
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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, 1 B, 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
1 A, 1 B, 1 C and 1 D 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 I 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
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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 IC holding the damper flap in a slightly open
position. The abutment member 7 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
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 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.
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A heating wire 8 can be provided for heating the seal to prevent
freezing.
The hinge 16 is a flexible strip across the top of the flap I 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
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. 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
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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
5 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
10 can be either installed inside or outside the building as described above.
In some
constructions there also be more than two rows as well as more than 1 column
of
flaps for example for 55 inches fans.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
15 within the spirit and scope of the claims without department from such
spirit and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
