U.S. patent application number 14/580356 was filed with the patent office on 2015-04-23 for model building for pressure diagnostics simulation.
The applicant listed for this patent is EnergyWright, Inc.. Invention is credited to Dale Sherman, Kim Sherman, Matthew Wellman.
Application Number | 20150107352 14/580356 |
Document ID | / |
Family ID | 45698329 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150107352 |
Kind Code |
A1 |
Sherman; Kim ; et
al. |
April 23, 2015 |
Model Building for Pressure Diagnostics Simulation
Abstract
A scale model pressure building for teaching pressure
diagnostics and weatherization strategies for residential and
commercial building structures. The model building is designed for
ease of fabrication and ease of assembly. The design allows the
instructor to simulate numerous construction errors, airflow
problems, air sealing strategies, and testing procedures while in a
classroom setting.
Inventors: |
Sherman; Kim; (Spencerport,
NY) ; Sherman; Dale; (Manlius, NY) ; Wellman;
Matthew; (Rochester, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EnergyWright, Inc. |
Manlius |
NY |
US |
|
|
Family ID: |
45698329 |
Appl. No.: |
14/580356 |
Filed: |
December 23, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13222861 |
Aug 31, 2011 |
8954296 |
|
|
14580356 |
|
|
|
|
61378535 |
Aug 31, 2010 |
|
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Current U.S.
Class: |
73/204.25 |
Current CPC
Class: |
G01F 1/69 20130101; G09B
23/12 20130101 |
Class at
Publication: |
73/204.25 |
International
Class: |
G01F 1/69 20060101
G01F001/69 |
Claims
1-55. (canceled)
56. An airflow indicator, comprising: a) an airflow sensor
comprising a Wheatstone bridge, comprising: a first leg and a
second leg, each leg comprising a series arrangement of a
thermistor having a resistance value and a resistor having a
resistance value, the resistance values of the resistors being the
same, and the resistance values of the thermistors being the same
when the thermistors are not exposed to air flow; a first end of
each thermistor being connected to a power source, a first end of
each resistor being connected to ground, a second end of each
thermistor being connected at a junction point to a second end of
one of the resistors, such that a voltage between the junction
point of the first leg and the junction point of the second leg
indicates an out of balance condition between the legs in the
Wheatstone bridge; the thermistors being arranged such that when
the thermistors of the airflow sensor are located in a stream of
air moving in a first direction, the thermistor of the first leg is
at least partially shielded from airflow by the thermistor of the
second leg, and when the stream of air is moving in a second
direction opposite to the first direction, the thermistor of the
second leg is at least partially shielded from airflow by the
thermistor of the first leg, such that when the thermistors are
exposed to air flow, the resistance value of the thermistor which
is partially shielded from air flow is different from the
thermistor which is not shielded from air flow, causing an
imbalance between the legs of the Wheatstone bridge; b) an
amplifier having a differential input coupled to the junction
points of the Wheatstone bridge, and an output having a signal
proportional to a voltage difference between the junction points;
c) a microcontroller having an input coupled to the output of the
amplifier and a plurality of outputs; and d) a plurality of lights
coupled to plurality of outputs of the microcontroller; such that
the microcontroller illuminates the plurality of lights in a
sequence simulating a moving light, the direction and speed of the
moving light being proportional to the signal at the output of the
amplifier; the direction and speed of the moving light indicates a
direction and speed of airflow of the stream of moving air.
57-58. (canceled)
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims one or more inventions which were
disclosed in Provisional Application No. 61/378,535, filed Aug. 31,
2010, entitled "MODEL BUILDING FOR PRESSURE DIAGNOSTICS
SIMULATION". The benefit under 35 USC .sctn.119(e) of the United
States provisional application is hereby claimed, and the
aforementioned application is hereby incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention pertains to the field of model buildings. More
particularly, the invention pertains to model buildings adapted for
zonal pressure diagnostics simulation.
[0004] 2. Description of Related Art
[0005] As a result of the current movement toward making building
structures more energy efficient, there is an increasing need to
train building weatherization technicians for residential and
commercial buildings. Model buildings are often used in the
training classes as a way of demonstrating some of the many
possible construction errors, air pressure imbalances, and
resulting airflow problems, as well as the testing procedures used
to identify those errors and problems and energy inefficiencies.
The models may also be used to teach strategies for correcting
those problems.
[0006] One of the primary testing procedures performed on buildings
is zonal pressure diagnostics (ZPD). ZPD involves the use of a
"blower door test" in which a blower door is temporarily installed
in place of an exterior door of the building being tested. The
blower door seals off the doorway and has a powerful exhaust fan
that depressurizes the structure. By using a manometer to compare
the air pressures between various interior spaces (rooms, wall
cavities, attic, basement, crawl spaces, knee walls, etc.), as well
as between interior spaces and the exterior environment, and the
flow rate through the blower door fan, it is possible to determine
the airtightness of the building and the location of leaks.
[0007] There are also other testing procedures frequently used in
pressure diagnostics. One of these procedures is duct diagnostics,
which includes duct airflow balancing, checking for blocked ducts,
leaky ducts, and the use of a blower door, duct diagnostic fan (a
fan used to pressurize or depressurize air ducts), and air handler
(furnace and/or central air conditioner) to determine leakiness of
ducts to outside (also known as delta Q). Another procedure is
"add-a-hole, subtract-a-hole". This procedure quantifies the amount
of leakage in a particular zone. Combustion Appliance Zone (CAZ)
testing is a procedure for determining if combustion appliances
(furnace, water heater, etc.) will operate safely in all conditions
of weather and worst-case depressurization. Worst-case
configuration is a process for determining the configuration of
doors and air handlers that causes the greatest depressurization in
the CAZ, which in turn can cause chimneys to back draft. Targeted
air sealing uses zonal pressure diagnostic techniques to determine
where to focus air-sealing measures.
[0008] Currently, the model buildings used in training classes are
typically one of two types: compact human-scale models or
scaled-down tabletop models.
[0009] Compact Human-Scale Models
[0010] One example of a human-scale model is the Telltale House,
which is no longer in production, shown in FIG. 1. Another example
of a human-scale model, shown in FIG. 2, is the Pressure House by
Elliot Management Consulting (Bozeman, Mont.). FIGS. 3A and 3B show
an outside and cutaway view, respectively, of another example, the
NYSWDA (New York State Weatherization Directors Association)
Pressure Diagnostics Training House.
[0011] By using full-scale components in its construction (e.g.
doors, furnace, water heater. etc.), the human-scale model provides
a more real-world look and feel. To some degree, this allows the
instructor and students to interact with the model and perform
specific tests as they might with a real building. However, to
maintain a reasonable cost for fabrication, it is necessary to
limit the scope and complexity of the building structure and air
handling system. The result is a compact model that demonstrates
some specific training concepts well, but lacks the complexity of
an actual building with multiple rooms, windows, doorways, air
ducts, exhaust fans, and interstitial cavities (i.e. the space
inside walls, floors, ceilings, etc.). With the human-scale model,
it is also difficult for the viewer to see all of the elements at
play in the diagnostic process because many of the features are
hidden from view.
[0012] Scaled-Down Tabletop Models
[0013] The tabletop models, in addition to being lower-cost and
more easily transported than the human-scale models (many which are
not transportable at all), have the potential to illustrate, in a
classroom setting, many of the issues found in the field. The small
size of these models also provides a comprehensive view of the
building at a glance. The challenge is to create a model that can
provide an effective simulation of airflow problems among multiple
rooms and interstitial cavities while maintaining a relatively low
production cost, as well as a more reasonable size and weight for
transport.
[0014] One example of a tabletop model is the House of Pressure
(New River Center for Energy Research and Training, Christianburg,
Va.), shown in FIG. 4. Another tabletop model, shown in FIG. 5, is
the Mad Air house (no longer in production).
[0015] In an effort to reduce fabrication time and control
production costs in both the human-scale and tabletop models, the
building structure and air handling are simplified compared to
actual building structures. There are fewer air ducts, doors, and
interstitial cavities (wall and ceiling cavities). While some
simplification is desirable to clarify the concepts being taught,
the existing prior art models are oversimplified making it
difficult to convey the complex interaction among the various
pressure zones in an actual building structure and to correlate
model simulations with real building characteristics.
SUMMARY OF THE INVENTION
[0016] A model pressure building simulates conditions that are
helpful in teaching pressure diagnostics and weatherization
strategies for residential and commercial building structures. The
model building is designed for ease of fabrication and ease of
assembly.
[0017] The design allows the instructor to simulate numerous
construction errors, airflow problems, air sealing strategies, and
testing procedures while in a classroom setting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a prior art compact human-scale model
building.
[0019] FIG. 2 shows another prior art compact human-scale model
building.
[0020] FIG. 3A shows another prior art compact human-scale model
building.
[0021] FIG. 3B shows a cutaway of the model building shown in FIG.
3A.
[0022] FIG. 4 shows a prior art tabletop model building.
[0023] FIG. 5 shows another prior art tabletop model building.
[0024] FIG. 6 shows a model building in an embodiment of the
present invention.
[0025] FIG. 7A shows a front exploded view of the layered
construction of a model building in an embodiment of the present
invention.
[0026] FIG. 7B shows a back exploded view of the layered
construction of a model building in an embodiment of the present
invention.
[0027] FIG. 8A shows an exploded view of a bypass valve and
portions of wall panels in an embodiment of the present
invention.
[0028] FIG. 8B shows a view of an assembled and installed bypass
valve in an open position an embodiment of the present
invention.
[0029] FIG. 8C shows a view of an assembled and installed bypass
valve in a closed position in an embodiment of the present
invention.
[0030] FIG. 9 shows an exploded view of the back of the back wall
and shutoff slides of a model building in an embodiment of the
present invention.
[0031] FIG. 10A shows the back wall with the shutoff slides
installed in an embodiment of the present invention.
[0032] FIG. 10B shows the air handler in an embodiment of the
present invention.
[0033] FIG. 11 shows a hinged door and control rod.
[0034] FIG. 12 shows a sliding door, control rod and rails.
[0035] FIG. 13A shows a cutaway view of an exhaust fan check valve
with the check valve locked open.
[0036] FIG. 13B shows a cutaway view of an exhaust fan check valve
with the check valve locked closed.
[0037] FIG. 13C shows cutaway view of an exhaust fan check valve
with the check valve in a normal operating position.
[0038] FIG. 14 shows another embodiment of an exhaust fan check
valve.
[0039] FIG. 15A shows an exploded front view of a blower door in an
embodiment of the present invention.
[0040] FIG. 15B shows a back view of the blower door in a closed
position.
[0041] FIG. 15C shows a back view of the blower door in an open
position.
[0042] FIG. 15D shows a back view of the blower door in an A-ring
position.
[0043] FIG. 16 shows a cut-away view of an installed leaf spring
with a shut-off slide in an embodiment of the present
invention.
[0044] FIG. 17A shows a single panel that can be used to make a
room in an embodiment of the present invention.
[0045] FIG. 17B shows the foldable single panel of FIG. 17A with a
first fold.
[0046] FIG. 17C shows the foldable single panel of FIG. 17B with a
second fold.
[0047] FIG. 17D shows the foldable single panel of FIG. 17C with a
third fold, creating a four sided-room.
[0048] FIG. 17E shows a blown up view of one of the folds of the
foldable single panel of FIG. 17A.
[0049] FIG. 18A shows a blower door having a sliding plate with
holes.
[0050] FIG. 18B shows a blower door having a sliding plate with a
variable-size slot.
[0051] FIG. 19 shows a schematic of an airflow indicator.
[0052] FIG. 20 shows a circuit block diagram of the airflow
indicator in use in a model house.
[0053] FIG. 21 shows a partial cut-away view of the airflow
indicator.
DETAILED DESCRIPTION OF THE INVENTION
[0054] The current invention is a model pressure house that employs
a number of cost-effective fabrication methods, and design features
that are improvements over current human-scale and tabletop model
buildings used in weatherization training These innovations make it
financially and physically feasible to produce a model that more
accurately replicates the complex problems a technician is likely
to face in the field. The model can be easily reconfigured to
produce scenarios that imitate various airflow and air pressure
problems, as well as leaks, obstructions, testing procedures, and
remediation techniques.
[0055] While the model is designed to replicate the complexity and
pressure readings found in real-world building structures, the
design also facilitates experimentation, exploration and easy
viewing of all features. The accurate modeling of real-world
scenarios, coupled with ease of use, make this design a more
effective teaching tool than products currently available.
[0056] The model building disclosed herein includes a number of
improved production methods. The primary components are preferably
assembled in a layered format. For example, the front-to-back room
panels are captured or sandwiched between the front and back walls.
The panels that run from the front wall to the back wall are
captured by the front and back walls by the grooves cut in them. In
one embodiment, the air ducts are cut only in the back wall and the
back panel is used to cover and seal the air ducts from each other
and external air. In one example of this embodiment, the back wall
is preferably approximately 0.5'' thick and the back panel is
approximately 0.25'' thick.
[0057] In addition, the front and back walls preferably have
recesses, such as grooves and/or holes, to capture the panels and
other components running from front to back. This speeds the
assembly of the model building for use. This also makes the
assembly self-fixturing, requiring less time to assemble.
Self-fixturing or self-aligning are common terms used in
manufacturing meaning that the components nest together in such a
way that they are properly aligned before bolting or gluing without
the need for fixtures, clamps, straps, etc. The panel-in-groove
joints also create better air sealing.
[0058] The box-type (substantially square or rectangular, with the
exception of the room(s) on the top floor, which follows the
contour of the roof) inherently creates interstitial cavities in
various areas of the house, including, but not limited to, the
ceiling, the interior walls, the exterior walls, the roof, and the
knee wall. This more closely simulates actual building construction
and airflow scenarios without requiring complex manufacturing
methods to produce the model.
[0059] Bypass valves, which are preferably butterfly valves, are
preferably used to simulate leaking (open position) and sealed
(closed position) interstices. A flexible sealing component of the
valves preferably has a football shaped cross-section. The sealing
component, which is preferably a flexible sealing and floating
component, fits over the rotatable positioning shaft. The shaft has
ribs running lengthwise on opposite sides which force the sealing
component to rotate with the shaft, yet move slightly freely as
needed to provide maximum seal against panels of the interstitial
cavity. Flexible and floating sealing components are low-cost and
effective. In some preferred embodiments, these components are made
of a low-cost plastic extrusion.
[0060] Folded structural panels are preferably used where possible
rather than assembling multiple panels. Cutting a v-groove where a
fold is desired creates a living hinge. This fabrication method
allows the use of a thicker, more rigid material for wall
construction while still having the benefits of folded corners. As
a result, there are no air leaks at corners where the panels meet
and no sealing is required. In addition, there are fewer parts to
handle during assembly. The living hinge precisely positions the
fold, making folding easier. The hinge also creates a tighter
corner and allows for better air sealing.
[0061] In preferred embodiments, a plastic material is chosen for
the panels because plastic can have a v-groove cut in it and be
folded without cracking. In other preferred embodiments, a 70%
recycled plastic is used, which is an environmentally responsible
material that creates an energy efficient product, an important
consideration for the intended market.
[0062] Some of the features of the model building are preferably
machined into fabrication materials rather than being fabricated as
discrete components. These features are preferably designed to be
machined by CNC (computer numerically controlled) machining (or
manual router with templates). As a result, there are fewer parts
to make, stock, and assemble. This reduces costs. It increases the
number of possible features without significantly increasing costs.
Some features that could be machined in embodiments of the model
building include, but are not limited to, supply and return air
ducts, shut-off slides (for air ducts, windows, and interstitial
bypasses) with stop-block notch, channels for shut-off slides with
stop-block, windows, window channels, and slides, and front to back
panels fit into grooves cut in front and back walls. Machining the
components in this manner results in better air sealing, and
self-fixturing during assembly.
[0063] In preferred embodiments, corrugated plastic sheets are used
for sliding and hinged doors. Corrugated sheets are made from two
outer layers with a corrugated layer between the two outer layers.
Corrugated cardboard, for example, is made of fluted paper glued
between two sheets of paper. Flutes are the parallel hollow
channels within the corrugated layer. The term "flute" typically
means an exposed groove or channel on a surface, but "flute" was
carried over to the corrugated plastic industry to include the
channels enclosed within the corrugated layer.
[0064] The hinged door is formed from a panel of corrugated
material, which is split into a door section and a mounting
section, separated by cutting through only one of the outer layers
along a flute of the corrugated layer, so that the remaining outer
layer and the material of the corrugated layer form a "living
hinge" for the door. Flutes allow easy attachment to an external
control rod, easy addition of vents to the door if needed, and easy
addition of guide rails on sliding doors. The lightweight
construction of the doors helps keep the overall weight down and
facilitates transport of the model building. The use of a living
hinge provides a low-cost hinge with precise movement.
[0065] Air handler return ducts are preferably cut in the back wall
and lead to the center of the return plenum. The supply ducts are
positioned at the perimeter of the supply plenum. Because of this
arrangement, there is typically no need for supply and return air
ducts to cross because they can normally run parallel to each other
which allows them to be machined in the back wall as part of the
CNC process. This generally radial layout of supply and return
ducts around the supply and return plenum obviate the need for
crossover between the supply and return ducts. The radial layout is
in turn made possible with an air handler that moves air in a
direction that is generally perpendicular to the panel containing
the supply and return ducts. In other embodiments, the design would
be reversed. In these embodiments, the supply ducts would be
located in the center and return ducts would be located around the
perimeter.
[0066] The model building disclosed herein also includes many
improved training features compared to the prior art. Reduced cost
per feature allows additional features with little or no increase
in production cost beyond the cost of additional CNC cuts. Features
such as additional rooms, interstices, air ducts, and exhaust fans
allow for greater complexity and interaction of various elements,
resulting in a more realistic representation of real-world
scenarios.
[0067] The model building is also preferably a thin model, which is
one room deep, and thin in depth compared to the width. A model
building that is one room deep and with a thin depth gives better
visibility of the all elements of the model in a classroom setting.
A thin model is also easier to transport. In one preferred
embodiment, the model building includes at least two capture layers
(the front wall and the back wall) and a middle layer (the rooms
layer) between the capture layers, where a ratio of a width of the
model building to a depth of the model building is greater than
5:1. In a further preferred embodiment, the width of the model
building to the depth of the model building is greater than
8:1.
[0068] Butterfly valves are preferably used to simulate partial or
full leaking (open position) and sealed (closed position)
interstices. Using butterfly valves permits the simulation of
complex airflow scenarios, which more closely simulates actual
building construction and airflow scenarios. The selected placement
of bypass valves in specific locations in the interstices allows
the user to simulate either balloon-frame construction with open
cavities from basement to attic, typical of older homes, or
platform construction in which floors built on exterior walls for
each floor seal wall cavities between floors, typical of more
contemporary homes. The valves also allow the user to simulate
targeted air sealing to correct various airflow or air leakage
problems.
[0069] In preferred embodiments, exhaust fans preferably have a
cover flap that can be locked open, locked closed, or allowed to
move freely to serve as a check valve to replicate any of three
possible scenarios in a real-world setting. In other preferred
embodiments, placement of a Venturi port on the blower door
measures air speed and allows the calculation of a volume of air
that moves in a given period of time. This can simulate measurement
of cubic feet per minute (CFM).
[0070] In other preferred embodiments, an Electronic Air Flow
Indicator (AFI) gives a visual representation of air speed and
direction preferably with the use of a sequence of "chasing"
lights. The lights are preferably light emitting diodes (LEDs). The
illusion of flowing smoke is created by the gradual brightening and
dimming of LEDs in the sequence. This provides a visual indication
of correct or incorrect chimney draft or other airflow issues. The
AFI can give a visual representation of air pressure in various
portions of the model, since airflow results from a pressure
differential. This permits the user to instantly see and compare
pressures in various parts of the model.
[0071] In other preferred embodiments, feet are attached to the
model to prevent it from tipping since it is so thin. The feet
preferably fold out of the way but remain attached. This creates a
more stable model building and increases ease of storage and
transport. Since the feet are attached, they can not be left behind
when the model building is transported to another location.
[0072] FIGS. 6, 7A and 7B show a model building 1 in an embodiment
of the present invention. The overall structure of the tabletop
model building 1 shown in FIGS. 6, 7A and 7B is only one room in
depth 36 from front to back. The combined innovations in the design
of elements such as the building structure, doors 5 or 82, bypass
valves 11, air ducts 31 (supply), 32 (return), shut off slides 2
and air handler 93 in the model building 1 described herein, allow
for a thinner model (measured from front to back, depth 36 compared
to width 38) compared to existing prior art model buildings, which
improves visibility. The air handler 93 includes the supply plenum
64, the return plenum 29, and the fan 25, which are shown in FIGS.
7A, 7B and 10B. FIG. 10B also shows an air handler supply port 46.
The ratio of the model's width 38 to depth 36 is preferably greater
than 5:1. This allows all of the instructional elements (rooms 37,
doors 5, interstitial cavities, etc.) to be easily visible from the
front of the model 1. This is ideal for multiple viewing angles in
a classroom setting.
[0073] The assembly process and structure described herein is
unique among the models used in the weatherization training field.
The model building 1 includes a back wall 13 and a clear front wall
12 that are drawn toward each other with fasteners 10 (such as
bolts), adhesives (such as glue), or an interference fit (such as a
snap-fit). Captured between the back 13 and front 12 walls are all
of the interior wall panels 35, exterior wall panels 40, floor 41,
ceilings 42, roof structures 43, and other model components that
run from front to back in the model.
[0074] Each room element 37 is preferably essentially a box
structure that is open in the front and back prior to assembly. The
interstice of an actual house is represented by the space 44
between a room structure and adjacent model structures such as
exterior wall panels 40, roof 43, and other rooms 37.
[0075] FIGS. 7A and 7B show the layered configuration of the model
building 1. The basic structural configuration in the preferred
embodiment has four layers 50, 51, 52, and 53. The four layers,
from front to back, are: a front wall layer 50, a room layer 51, a
back wall layer 52, and a back panel layer 53. Other numbers of
layers are also possible, but there are preferably at least three
layers. In one alternative embodiment, there are three layers: a
middle layer (the "room" layer 51) and two "capture" layers 50, 52.
In this alternative embodiment, the middle layer includes all
structures running from the first to the second capture layer. The
structural elements and other design features of the middle layer
are secured between the two capture layers in this alternative
embodiment.
[0076] In another alternative embodiment, instead of a single layer
51 of rooms 37, the model could have multiple layers of rooms 37
with an added dividing wall for each new layer to more accurately
replicate the multiple rooms in actual building configurations. In
another alternative embodiment, instead of stacking layers
horizontally, layers can be stacked vertically. This configuration
would allow a more accurate replication of actual building
construction with multiple floors and a unique floor plan for each
floor.
[0077] The "rooms" layer 51 preferably includes all of the panel
structures and other design elements that run between the front 12
and back 13 walls of the model. This includes, but is not limited
to, such structures as interior wall panels 35, exterior wall
panels 40, floors 41, ceilings 42, roof 43, and bypass valves 11
(in interstitial cavities 44). A standard "room" is preferably
formed by four panels (two interior wall panels 35, a floor panel
41 and a ceiling panel 42) creating a box that is open in the front
and back. A "room" 37 can be created by any number of panels, three
or greater. Two or more rooms 37 can be captured between the front
12 and back 13 walls creating multiple enclosures. Exterior wall
panels 40 and roof panels 43 are also preferably captured between
the front 12 and back 13 walls.
[0078] Stairs 34 attach to the back wall 13, and preferably do not
run all the way to the front wall 12. The stairs 34 preferably
extend approximately 1/2 the distance between the front wall 12 and
the back wall 13 of the model building 1. The stairs 34 are
enclosed in a stairwell 33 (see FIG. 7A). The stairwell 33 allows
air to flow between floors, similar to airflow in an actual house.
Doors on the stairway 33 allow airflow to be restricted or
shut-off.
[0079] For the purposes of this application, a distinction is made
between a "wall" and a "wall panel". A "wall panel" is defined as a
panel that separates an interior or exterior space from the
interstitial cavity of the wall. A "wall" is defined by two
adjacent "wall panels" and the interstitial cavity 44 contained
between them. Similarly, a "roof" section is typically defined by
"roof panel", "ceiling panel", and an interstitial cavity; a
"floor" section is defined by a "floor panel", "ceiling panel", and
an interstitial cavity. Exceptions to this definition are the front
12 and back 13 walls and the basement floor 45, which are
predominantly solid with no interstitial cavity.
[0080] In addition to the room panels, components such as exterior
wall panels 40, roofs 43, interstitial bypass valves 11, etc. that
extend from the front wall 12 to the back wall 13 are captured
between the front 12 and back 13 walls. In preferred embodiments,
the front 12 and back 13 walls are drawn toward each other by
fasteners 10. This reduces or eliminates the need for additional
fasteners or bonding agents beyond the fasteners that join the
front 12 and back 13 walls. Bolts are preferred and shown in the
figures, but the walls could be held by other types of fasteners
including, but not limited to, screws, connecting rods, and zip
ties. Components could also be held together with some type of
adhesive.
[0081] In alternative embodiments, rather than using fasteners to
draw the front and back walls toward each other, each wall may be
mechanically fastened, chemically bonded or fused to structural
elements of the middle layer. In embodiments using chemical
bonding, adhesives may be used. In embodiments using fusing,
plastic or other material may be directly fused together using a
method such as sonic welding. In other embodiments, an interference
fit (including, but not limited to, a press fit, a friction fit, or
a snap fit) may be used. An interference fit is a fastening between
two parts achieved by friction after the parts are pushed together,
rather than by any other means of fastening. A snap fit maintains a
connection between two parts by causing an undercut on one part to
engage with an undercut in another such that the two parts cannot
be separated without forcibly moving the undercuts past each
other.
[0082] Front 12 and back 13 walls preferably have grooves 54 and
holes 55 to receive and secure panel components (e.g. floors 41,
wall panels 35, 40, ceilings 42, and roofs 43) and other design
elements (e.g. interstitial valves 11). This method of attachment
provides self-fixturing assembly ensuring proper component
alignment without the need for fixtures or clamps. This method also
provides a better air seal than simply abutting components against
the front and rear wall surfaces. Proper air sealing is critical
for producing valid and consistent air pressure readings.
[0083] The model building preferably has a thin cross-section with
a width 38 to depth 36 ratio of greater than 5:1. In a preferred
embodiment, the ratio is greater than 8:1. The thin cross-section
allows better visibility in a classroom setting from multiple
viewing angles. The thin profile also results in lighter weight and
easier transport in the back seat or trunk of a car. The model 1 is
scalable to a larger classroom wall size with minimal projection
into the classroom.
[0084] The model building 1 includes interstitial cavities 44,
which simulate actual structures. The space 44 created between a
first room panel and an adjacent room panel, exterior wall panel,
roof panel, or floor panel replicates the interstitial cavities of
an actual building structure (for example, the cavities between
roof rafters, floor joists, wall studs, etc.). The model building 1
includes interstitial cavities 44 in the walls, floors, roof, and
knee wall, and allows user controlled airflow among them. The
nature of real-world construction automatically creates these
interstices 44 and it is simply a matter of the designer/builder
deciding where to allow the air to flow, and where to seal off
airflow. The ability to demonstrate airflow through leaks in
interstitial cavities 44 in the model, and the ability to seal off
this airflow as desired, is critical to teaching the complex
airflow scenarios in an actual house and how to address
problems.
[0085] The model building also preferably includes interstitial
bypass valves 11, which are shown in FIGS. 7A, 7B and 8A-8C. Bypass
valves 11 located at key points in the interstitial cavities 44 of
the model 1 are preferably butterfly valves that allow the
instructor and students to simulate air-sealing techniques used to
block unwanted airflow in a building structure. The bypass valves
11 may have any cross-section longer than it is wide, including,
but not limited to, elliptical, or diamond-shaped cross-sections.
The valves 11 preferably include an expanding flexible
football-shaped valve cross-section, which can be seen in FIGS.
8A-8C. A football-shaped extrusion valve seal can flex as needed
when turned to the closed position to create a more effective seal
against panels of an interstitial cavity 44. A flexible sealing
component 56 preferably has the football shaped cross-section. In
some preferred embodiments, the sealing component 56 is a flexible
and floating sealing component 56. The sealing component 56 fits
over a rotatable positioning shaft 57. The shaft 57 has ribs 58
running lengthwise on opposite sides which force the sealing
component 56 to rotate with the shaft 57, yet move slightly freely
as needed to provide maximum seal against panels of the
interstitial cavity 44. Flexible and floating sealing components 56
are low-cost and effective. In some preferred embodiments, these
components are made of a low-cost plastic extrusion. The valve
preferably extends the full depth of the interstitial cavity such
that, when closed, it completely seals off the interstitial cavity.
When the valve is open, the full depth of the cavity allows
airflow.
[0086] To the Applicant's knowledge, a butterfly valve has never
been used in the interstitial cavities of a human-scale or tabletop
model pressure house to seal off sections of the interstitial
space. The valves 11 also allow the user to simulate targeted air
sealing to correct airflow problems in interstices 44. Bypass
valves 11 also allow the model to simulate either balloon-frame or
platform construction.
[0087] Using a butterfly valve allows the full depth of the
interstitial cavity to be sealed or opened as needed. Valves that
seal off or open an entire cross-section of an interstitial cavity
would be a benefit in both the tabletop and human-scale model
pressure houses. Alternate embodiments may include valves that open
some portions of the depth of the interstice. In one preferred
embodiment, the valves open approximately 50% or more of the depth
of the interstice. In another preferred embodiment, the valves open
approximately 50% or less of the depth of the interstice. In
another alternate embodiment, a half-butterfly or flap valve may be
used to control airflow in the interstice. In this embodiment, the
valve is a rectangular valve and the valve's rotational control
shaft pivots against one panel of the interstice rather than in the
center of the interstice (as with the butterfly valve). In this
embodiment the valve can lay flat against a room panel thereby
moving the valve completely out of the airstream.
[0088] In other embodiments, the bypass valves could be any valve
that can open or close off an interstitial cavity, including
flexible flaps or rigid flaps that close against seals, or other
designs that create the same effect by opening or closing off an
interstitial cavity.
[0089] In preferred embodiments of the model building 1, folded
panels in the rooms layer 51 reduce fabrication cost. Rather than
being formed of discrete panels, layer structures are made of
single panels that are folded to create interconnected panels. As
one example, a four-sided room is made of a single panel that is
folded at three corners. A single foldable panel 96 that creates a
four sided room 100 is shown in FIGS. 17A through 17E. A v-groove
is preferably cut where each corner fold 97, 98, 99 is to be
located, creating a living hinge. This accurately positions the
fold without fixturing and decreases assembly time. The number of
components and time required for assembly is reduced. An airtight
seal is achieved at three of the four corners.
[0090] In other embodiments of the model building, supply 31 and
return air ducts 32 are cut into the back of the back wall 13, as
shown in FIG. 10A, rather than fabricated as discrete components
such as a system of tubes and connecting joints. This results in
reduced production costs because of reduced fabrication and
assembly time. Alternatively, to get more airflow, the depth of the
back panel 14 is increased. In one preferred embodiment, the depth
of the back panel 14 is increased to approximately one inch. This
allows adding to the depth of the air ducts by cutting channels
into the back panel 14 that are aligned with the air ducts of the
back wall. This more than doubles the depth of the air ducts 31,
32, allowing better air flow. Adding additional depth to the duct
in a thicker back panel 14 provides better airflow without adding
complexity or material to the back wall 13. Doubling the volume of
the air ducts by simply making them wider would require making the
model approximately twice the size. This added thickness of the
back panel 14 and air duct expansion is visible in FIGS. 7A and 7B.
Supply 8 and return 24 vents are openings that preferably are cut
into the back wall 13 to allow the exchange of air between the room
and the air ducts 31 and 32, respectively. In some embodiments, the
supply 8 and return 24 ducts are also cut into the back panel 14.
FIG. 10A shows the supply and return slides 26 in an open position
to reveal the supply 8 and return 24 vents. FIG. 10 also shows a
window slide open 27, revealing a window 6. The window slide opens
27 the room to exterior air through openings in the back wall and
back panel.
[0091] The unique design of the air handler allows effective and
cost effective integration of the air handler with the structure of
the pressure house, the supply and return ducts, and the
supply/return shut-off slides.
[0092] FIG. 10B shows the construction of the air handler 93.
Return ducts 24 are preferably cut or machined in the back wall and
lead to the center of the return plenum 29. The air handler fan
mounted to the back wall moves air from the return plenum to the
supply plenum.
[0093] The supply plenum is formed by an enclosure 64 fastened with
an airtight seal to the front of the back wall. Supply ports 46
located at the perimeter of the supply plenum connect the supply
plenum to end of the supply ducts which are cut into the back of
the back wall. This arrangement allows supply and return ducts to
be located adjacent to each other on the back of the back wall in
an alternating and somewhat radial configuration. Supply and return
ducts can run to each room typically with no need to cross one
another or other pairs of room air ducts. This configuration also
allows the air ducts, return plenum, and supply ports all to be
machined in the back wall as part of a CNC machining process. In
other embodiments, the airflow could be reversed, meaning that with
the same physical configuration, the fan could be reversed and the
air could flow in the opposite direction in the air handler,
effectively reversing the role of supply and return ducts.
[0094] The return plenum of the air handler is also cut into the
back of the back wall 13 allowing the return ducts to connect
directly with the return plenum without the need of additional
components.
[0095] The grooves cut in the back wall to form the supply and
return ducts extend past their destination supply and return vents
to the perimeter of the back wall. This additional groove provides
a channel for the shut-off slides that control airflow at the
respective vents from outside of the model.
[0096] The fastening of the back panel, preferably with gasketing
material, to the back wall, seals the air handler, air ducts, and
slide channels from the outside air and from each other.
[0097] A back panel 14 is fastened or bonded to the back of the
back wall 13 to seal the air ducts 31, 32 from each other and the
exterior air. This is done in a single operation rather than
multiple operations for each duct. This reduces assembly time. A
gasket sheet 21 is preferably installed between the back wall 13
and the back panel 14 to ensure a proper seal. Vents 8 and 24 are
installed in the various rooms by simply cutting holes from the air
ducts 31, 32 to the front of the back wall 13. Vents 8 and 24 are
cut slightly narrower than the air duct to create a better seal
against the shut-off slide 2.
[0098] There is a single leaf spring 17 behind each slide 2, as
shown in FIGS. 7A and 16. In one preferred embodiment, the leaf
spring 17 is located near the end of the slide 2 closest to the
window 6 or air duct opening into the room 37, to ensure a good
seal. The spring 17 is preferably made of a thin, flexible spring
material such as metal or plastic. One preferred example is 0.020''
polycarbonate sheet. Each end of the spring 17 fits securely into a
groove 60 cut into the back panel 14. The spring spans the two
grooves 60 such that it forms a compressible arch pressing against
the slide 2. Each end of the spring 17 is bent back toward itself
forming a kind of barb to more fully secure the end of the spring
17 in the slot 60. The design is low cost and very effective.
[0099] This spring 17 serves several purposes. It presses the slide
2 against the front of the groove 61, ensuring a tight fit between
the slide 2 and the groove 61 whether the slide 2 is in the open or
closed position. The spring 17 pushes each slide 2 forward to
ensure a proper seal against the vents 8 and 24 in the back wall
13. The leaf spring 17 is wide enough that, as it presses against
the slide 2, it prevents excessive airflow between the slide 2 and
the back panel 14. The spring 17 also applies consistent pressure
holding the slide 2 securely in any position while still allowing
easy movement. In other embodiments, other types of spring material
can be used instead of a leaf spring. Some examples include, but
are not limited to, a coil spring or a soft elastomeric block
mounted in a recess in the back panel 14 such that it presses
against the slide 2.
[0100] In preferred embodiments, the shut-off slides 2 allow vents
and windows to be opened and closed from outside the model 1.
Slides 2 are commonly used in the prior art, but they are normally
made up of a number of components for each slide: a slide, two
rails, fasteners to hold the rails, and possibly some means of
stopping the slide from coming out such as a bolt or pin. In
contrast, in embodiments of the present invention, the shut-off
slides 2 are contained by grooves 61 cut in the back wall, as shown
in FIGS. 9 and 10. Rather than adding two guide rails to hold each
slide 2, the back panel 14 attached to the back wall 13 holds and
seals all of the slides 2. The slides 2 extend past the edge of the
back wall 13 for easy access. A stop block 23 is preferably located
in each slide groove 61. A corresponding notch 22 that is longer
than the stop block 23 is cut in the facing surface of the slide 2.
These two elements serve to limit the range of motion of the slide
2. The stop block 23 may be installed as a separate component, but
it is preferred that it be machined to reduce costs. The back panel
14 that seals air ducts also captures the slides 2. Conversely, the
stop block could be part of the slide 2 and the notch 22 could be
located in the groove 61.
[0101] One preferred method of fabrication for the model building
is a CNC mill or router. The model building is preferably designed
to facilitate fabrication using one of these methods. Compared to a
more conventional fabrication process that uses discrete components
for air ducts and air handler, this model building has a reduced
number of components, which results in reduced fabrication and
assembly time. Additional features or components can be added with
little or no additional cost. In alternative embodiments, the model
building may be fabricated using a traditional hand-held router and
templates.
[0102] Some features that facilitate CNC machining include using
materials that are primarily flat sheet stock, room layer 51 being
made of a foldable panel 96 having a v-groove cut to create a
living hinge for corner folds to become a room with a ceiling,
floor, and two walls, grooves 54 that are cut in the front and back
walls to accept and position the room layer panels, air ducts 31
and 32 that are cut in the back wall 13, grooves 61 for air duct
shut-off slides 2 that are cut in the back wall 13, stop blocks 23
that are machined into slide grooves 61, and slides 2 with notches
22 for stop blocks 23 that are machined from sheet material (see
FIGS. 9 and 10).
[0103] FIGS. 11 and 12 show different embodiments for doors 69, 82
that can be used in the model building 1. In preferred embodiments,
corrugated plastic sheets 80 are used for fabricating hinged doors
69 or sliding doors 82 in the model building 1. In one preferred
embodiment, Coroplast.RTM. corrugated plastic sheet (Coroplast,
Inc., Dallas, Tex.) may be used. Corrugated plastic sheets
facilitate a number of desirable design features including, but not
limited to, a living hinge, simple and secure attachment of the
rotational or rotatable door control rod 3 and precise door
venting. Corrugated plastic sheets are a relatively rigid material,
however, slicing through one surface along the length of one of the
flutes allows easy flexing along the opposite surface, thereby
creating a living hinge. The flutes 72 of the door preferably run
vertically. As far as the Applicant knows, corrugated plastic
sheets have not been used in doors of model pressure houses.
[0104] Each door control rod 3 in the preferred embodiments is made
of wire, and gripped by a friction clutch 4, which allows the user
to position the door in various positions, including open, closed,
or ajar. The friction clutch 4 preferably includes two rubber
washers on a bolt. The bolt is fastened to the back wall 13 next to
one of the door control rods 3. The rod passes between the two
washers such that, as the bolt is tightened, the friction on the
door control rod 3 is increased. The rod 3 comes down through the
roof 43 and any ceiling 42 or floor 41 panels necessary to reach
the door 5, 69. The friction clutch 4 and the rods 3 are preferably
fastened onto clamp blocks 39 on the back wall 13, as shown in FIG.
6. The clamp blocks 39 serve several purposes. They move the
friction clutch 4 forward of the back wall 13 so the control rod 3
can better align with the door hinge. They also provide an
additional surface, separate from the back wall 13, to fasten the
friction clutches 4 to, thereby avoiding interference between the
friction clutch 4 fasteners and the slides 2 in the back wall
13.
[0105] The rotational control rod 3 shown in FIG. 11 should be
substantially in line with the hinge 70 of the hinged door 69 to be
controlled to avoid unwanted forces on the door components. The rod
3 is preferably formed into a square "J" shape at the bottom with a
width that is slightly less than the width of the door 5. The short
leg 71 of the J extends up into a flute 72 along the edge of the
door 69 furthest from the hinge 70 such that as the control rod 3
is rotated by the user, the door 69 moves. The long leg 73 of the J
is collinear with the door hinge 70 and extends above the roof 43
to allow the position of the door 69 to be controlled by the user.
The door 69 also includes mounting holes 74 and a door vent
102.
[0106] FIG. 12 shows an alternative sliding door structure. Similar
to FIG. 11, corrugated plastic sheets 80 with flutes 72 are
preferably used as the sliding door 82. The flutes 72 easily accept
the sliding control rod 123 and guide rails 81 into the door 123 so
that it can slide to reveal a doorway 16. The guide rails 81 are
preferably fixed so that the door 82 slides along the guide rails
81 when moved by the control rod 123.
[0107] The door 82 to the attic crawl space 83 is also preferably
made of corrugated plastic 80 and is an example of the sliding door
structure shown in FIG. 12. Two parallel rods 81 mounted to the
attic floor serve as guide rails 81. A third rod 123 serves as a
sliding control rod projecting through the front wall to allow the
user to position the door as needed. In one preferred embodiment,
the rods are made of metal. The use of corrugated plastic reduces
the need for machining and reduces fabrication costs.
[0108] It may be desirable to allow a precise amount of air to flow
past a door 69 that seals one room 37 from another. A door vent 102
is shown in door 69 in FIG. 11. Precise venting of the corrugated
door 69 can be achieved by cutting a groove or vent 102 of a given
width and length through one surface of the material. The side of
the door 69 that seals against the doorway 9 when closed is the
side the vent 102 is preferably cut on. The air can then flow from
one room, into the vent and out the top and bottom of the door
flutes 72 (or back in the opposite direction). The number of flutes
72 cut during fabrication and the width of the cut determines the
amount of venting allowed.
[0109] FIGS. 13A through 13C show an exhaust fan 65 with an exhaust
fan flap 66. Each exhaust fan valve flap 66 may be locked open
(FIG. 13A), locked closed (FIG. 13B), or allowed to move freely to
serve as a check valve (FIG. 13C). This represents three possible
scenarios in a building structure respectively. The first scenario
simulates an exhaust fan 65 with no check valve flap 66 (flap 66
locked open). The second scenario simulates no exhaust fan 65 (flap
66 locked closed). The third scenario simulates a properly working
check valve. The valve 66 in the model building is preferably a
thin flat rigid material that is attached at the top by some type
of hinge that allows it to swing freely. The hinge may include a
flexible material 68 such as fabric or plastic membrane. A pivoting
latch 103 located near the bottom of the flap 66 can be rotated to
hold the flap open, hold the flap closed, or allow the flap to move
freely as a check valve. A rotatable control shaft 75 that is
securely attached to the latch is also shown. Exhaust fan ports 28
are shown in FIG. 10A.
[0110] In another embodiment a thin flat rigid material hangs
freely from the top two mounting screws of the exhaust fan screws
67, as shown in FIG. 14. Each of the two top screws preferably has
a short standoff (preferably less than 0.05'' longer than the
thickness of the valve flap) between the head of the screw and the
fan body. Each standoff has a smaller diameter than the screw head.
A hole is preferably located in each of the two upper corners of
the valve flap. The holes are slightly larger than the standoffs to
allow free movement of the flap 66, but smaller than screw heads to
ensure it is held in place. A pivoting latch 103 located near the
bottom of the flap 66 can be rotated by means of control shaft 75
to hold the flap open, hold the flap closed, or allow the flap to
move freely as a check valve.
[0111] Air handler 93 airflow from the center of the return plenum
29 to the perimeter of the supply plenum 64 allows return 32 and
supply air ducts 31 to be laid out in a planar configuration in the
back wall 13 without the need for crossovers. In a preferred
embodiment, air is pulled from the center of the return air plenum
29, located behind the back wall 13, forward through the fan 25 and
into the supply air plenum 64, located in front of the back wall
13. An air handler fan port 30 is shown in FIG. 10B. The supply air
flows back into the supply ducts 31 in the back wall 13 as shown by
the arrows 76 in FIG. 10B. The return air flows from the return
ducts 32 back into the fan 25. In nearly all circumstances, this
configuration allows the supply 31 and return 32 air ducts for each
room to run parallel to each other without crossover.
[0112] If the model 1 is configured so the air handler fan 25 is
rotated 90 such that the air in the air handler moved laterally,
from left to right for example, within an enclosing cover that
serves as a return plenum on the left and a supply cover on the
right, supply ducts 31 would run from supply ports on the right
side of the air handler 93 and return ducts 32 would run to supply
ports on the left. Numerous crossovers with additional components
would be required in routing supply 31 and return 32 ducts to each
room 37, adding significantly to the cost for design and
manufacture.
[0113] The blower door 15 in the model building 1 simulates an
actual blower door. Similar to actual blower doors, this model
preferably uses a Venturi type pressure measurement system on the
intake side of the blower door 15 to calculate air velocity and
subsequently determine volume of airflow. Volume of airflow in turn
allows calculations to determine the airtightness of the building.
However, a relatively airtight building will restrict airspeed to
the point that it is difficult to get an accurate pressure reading
at the Venturi. Actual blower doors typically have some means of
restricting airflow to compensate for this. While the volume of
airflow remains relatively constant when restricted, the resulting
increase in airspeed near the Venturi allows for more accurate
pressure readings. Manometers typically used in performing zonal
pressure diagnostics on actual buildings compensate for the
restricted airflow and increased airspeed when calculating the
volume of airflow (measured in cubic feet per minute). The
manometers work the same on the model blower door of this invention
as they do in the real-world setting.
[0114] In a preferred embodiment, as shown in FIGS. 15A through
15D, the model configuration simulates three flow settings of an
actual blower door 15: open (FIG. 15C), A-ring (FIG. 15D), and
closed (FIG. 15B). Three settings allow the model to more closely
replicate circumstances of real-world scenarios. The blower door 15
includes a fan 91 mounted in an open area of the door for blowing
air through an air port 87 through the door 15. Fasteners 84 hold
the blower door 15 components together.
[0115] The three settings of the blower door are accomplished by
moving an airflow control plate 85 movably mounted adjacent to the
air port of the fan. In one preferred example the plate 85 is an
obround control plate having a hole 86 at one end which is of
smaller area than the air port 87, restricting air flow. The
control plate 85 is movable between an "A-ring" position where the
hole 86 is aligned with the air port 87, allowing limited air flow
through the port 87, a "closed" position in which the opposite end
of the plate 85, with no hole, seals off the air port 87, blocking
air flow through the port, and an "Open" setting, when the control
plate 85 is moved completely out of the way of the air port 87.
This could be accomplished by pivoting the control plate 85 as
shown in the FIGS. 15A-15D, or by slideably moving the plate 85
across the port 87, or in other ways known to the art.
[0116] External control of the airflow control plate 85 is provided
by a knob 88 (at the front of the blower door 15) that is securely
attached to rotatable shaft 92 that is securely attached to airflow
control plate 85, thereby allowing rotation of the airflow control
plate 85 to one of three positions. The blower door 15 settings can
be changed quickly as required by various airflow scenarios.
[0117] In other embodiments, additional settings may be added to
the airflow control plate 85, or additional plates may be added to
better simulate actual blower doors, which may have an "Open"
setting as well as airflow restrictor rings "A" through "E".
Alternatively, the hole in the airflow control plate could be made
of variable size.
[0118] FIG. 18A shows a restrictor hole slide plate 77 as another
embodiment of control plate 85. This embodiment shows restrictor
rings "A" through "C". Handle 104 protrudes through the sidewall of
the model allowing the user to position any one of the restrictor
holes 106 in the airflow of the fan 91, or moved completely out of
the way to expose the Open Ring 87.
[0119] FIG. 18B shows restrictor slot slide plate 78 in yet another
embodiment of control plate 85. Unlike the restrictor hole slide
plate, the restrictor slot slide plate does not need to move
discrete increments for each setting. This allows more precise
adjustment of restrictor settings and reduces the distance the
slide plate needs to travel for a given range of settings. The
reduced distance allows for a more compact design.
[0120] A relatively small rigid tube 89 is preferably positioned
radially in the opening 87 of the "Open ring". The open end of the
tube is in the center of the blower door and serves as the Venturi
port. The other end is attached to a manometer 20 by a flexible
tube 90 to provide pressure readings (see FIG. 6). Airspeed is
greatest at the center of a restricted section of airflow. By
placing the end of the Venturi tube 89 at the center of the blower
door opening, laminar airflow across the Venturi 89 is ensured
regardless of any restriction of airflow by restrictor rings.
[0121] The model building 1 also preferably includes an airflow
indicator (AFI) 7. Back-to-back thermistors in a Wheatstone bridge
are preferably used to sense airflow in the model building 1. While
this is a well-known method of accurately measuring speed and
direction of airflow, to the Applicant's knowledge, this is the
first time such a device has been used on a pressure house used for
teaching zonal pressure diagnostics. Light bulb filaments may be
used in place of the back-to-back thermistors to detect airflow
with greater sensitivity. The back-to-back thermistors in the
Wheatstone Bridge are preferably coupled with an LED sequencer to
display rate and direction of airflow in chimneys, ducts,
interstitial cavities or rooms in the form of sequential
illumination of a plurality of lights (preferably
light-emitting-diodes (LEDs)), such that air flow speed and
direction are indicated by the motion of a "chasing" light
display.
[0122] The Air Flow Indicator (AFI) circuit is designed to display
the rate and direction of airflow between two areas of different
pressures. For example, the AFI could be mounted in the chimney
such that it provides a visual representation of the speed and
direction of the airflow in the chimney This is useful in a
training environment for identifying conditions that can cause a
dangerous chimney back draft.
[0123] FIG. 19 shows a typical Wheatstone bridge coupled with an
LED array. FIG. 20 shows a block diagram of the circuit and the LED
array's relation ship to the path of the airflow across the
thermistors, and FIG. 21 shows a partially cut-away view of an AFI
corresponding to the block diagram in FIG. 20. FIG. 20 shows the
chasing light display simulating the upward moving airflow in the
air channel, while the air flow in FIG. 21 is the opposite
direction.
[0124] The AFI circuit works by utilizing a circuit comprised of
two thermistors R11 and R12 combined with two fixed resistors R10
and R13 in an arrangement known as a Wheatstone bridge. A first leg
of the bridge is formed by a series arrangement of resistor R10
coupled to thermistor R11 at a junction point, and a second leg is
formed by a series arrangement of resistor R13 coupled to
thermistor R12 at another junction point. One end of each leg of
the bridge is attached to a voltage source V.sub.cc, and the other
end of each leg of the bridge is grounded. The resistance values of
resistors R10 and R13 are the same, and the values of thermistors
R11 and R12 are the same when the thermistors are not affected my
moving air. Thus, the voltage at the R11-R10 junction of the first
leg is normally equal to the voltage at the R12-R13 junction of the
second leg, and the relative voltage between the junctions is thus
balanced at zero volts. Any change in the resistance of thermistor
R11 relative to thermistor R12 will result in an imbalance between
the legs of the bridge, causing a voltage difference between the
junction points.
[0125] The thermistors are preferably physically oriented between
two areas such that when the air pressure within a first area is
lower than the air pressure in a second area, air flowing from the
second area into the first area is cooling the first thermistor R11
in the bridge more than the second thermistor R12, which is
shielded by the first thermistor R11, thus leading to a voltage
imbalance in the bridge, which, as explained above, is registered
as a measurable positive voltage difference between the junction
points of each leg of the Wheatstone bridge circuit. For air that
is moving faster across the thermistors there is a greater
potential difference across the midpoints of the bridge, and if the
air is flowing in the opposite direction, the polarity of the
voltage difference is reversed.
[0126] The junctions are coupled to differential inputs to
amplifier U3, which amplifies the difference and feeds it into a
microcontroller U1. Microcontroller U1 interprets the magnitude of
the voltage level and then pulses an array of lights LED1-LED6 in a
chasing sequence that gives the illusion of downward movement in
the direction of the air flow. As the magnitude of the voltage
difference increases, the microcontroller U1 pulses the array of
lights LED1-LED6, causing the sequence to appear to move faster,
giving a visual indication of air speed.
[0127] When the air pressure in the first area is greater than the
pressure in the second area, air flowing from the first area to the
second area initiates the same process but in reverse order,
cooling the second thermistor R12 and shielding the first R11
resulting in a negative voltage being sent to the amplifier U3. The
microprocessor U1 reads the voltage from the amplifier U3 and
reverses the light sequencing of the array LED1-LED6 creating an
apparent upward movement of the chasing LED to indicate the
airflow.
[0128] If, for example, an AFI 13 as shown in FIG. 21 is mounted in
a chimney 111 in a model building, air flow as shown by the arrows
represents a chimney back draft situation in which smoke in the
chimney 111 can be drawn down into the living quarters of a house.
In this situation, the air flows first past first thermistor 109,
then past thermistor 110, which is arranged to be partially
shielded by the first thermistor 109. As explained above, this
means that thermistor 109 is cooled more by the airflow than
thermistor 110, causing an imbalance between the two legs of the
Wheatstone bridge. The circuitry mounted on the printed circuit
board 107 will then, through the process described above, cause the
lights in the LED array 108 to flash in a sequence showing downward
movement of the air in the channel 111. If the airflow reverses,
the direction of the chasing light display reverses as well.
[0129] As mentioned earlier, the AFI in one embodiment is used to
indicate the speed and direction of air in a chimney, but a
pressure house can be designed with an AFI built between any two
zones in the model to indicate pressure differences and the
resulting airflow between them.
[0130] It will be understood that as used herein, the term
"thermistor" is meant to encompass resistive elements in which a
resistance value of the resistive element changes as a temperature
of the element changes. For example, a light bulb filament or other
resistive wire element could be used as a thermistor in the
Wheatstone bridge of the AFI within the meaning of the term.
[0131] In preferred embodiments, feet 19 are attached to the model
building to prevent it from tipping since it is so thin. The feet
19 are shown in FIGS. 6, 7A and 7B. In one embodiment, a pair of
feet 19 are attached to a structural component 18, such as a
gusset, that in turn is fastened by a hinge 63 to the back of the
model. Although two feet 19 are shown in the figures, additional
feet could be used to increase stability. Alternatively, a single
foot could be used. The feet 19 preferably fold out of the way
under the model building 1 for transport. They preferably pivot to
provide a stable base. In one preferred embodiment, the feet 19
pivot roughly 90.degree. to create a stable base. They remain
attached during use and transport. Because the feet 19 fold under
the model, the model may be hung on a wall without removing the
feet. This is desirable in some classroom situations.
[0132] It will be understood that the term "model building" used in
this description is intended to encompass both reduced-scale models
and human-scale models.
[0133] Accordingly, it is to be understood that the embodiments of
the invention herein described are merely illustrative of the
application of the principles of the invention. Reference herein to
details of the illustrated embodiments is not intended to limit the
scope of the claims, which themselves recite those features
regarded as essential to the invention.
* * * * *