U.S. patent application number 11/974809 was filed with the patent office on 2008-03-06 for multi-layered film window system.
Invention is credited to Donald Anderson, Clifford Taylor.
Application Number | 20080053628 11/974809 |
Document ID | / |
Family ID | 46329490 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080053628 |
Kind Code |
A1 |
Anderson; Donald ; et
al. |
March 6, 2008 |
Multi-layered film window system
Abstract
A high R-rating window assembly storing multiple, reciprocating
reflective flexible film layers defined by one or more parallel,
displaced films or looped films define the layers. The layers are
contained in a sealed housing between rigid transparent (e.g.
glazed) layers. The glazed layers are separated on the order of 3
to 5-inches and are secured to low thermal conductivity framework
pieces. The framework is capped with a motorized roller and film
housing and the assembly is evacuated and filled with a desiccated,
inert dry gas. Several plastic, reflective coated films are
supported under tension in planar parallel relation between the
glazing layers from the motorized roller and several guide rollers
and guide tracks. Location sensors responsive to indicia on the
films identify film position. Temperature sensors monitor ambient,
internal and user set thermal conditions to control film exposure.
The films are operable via a room control system and window
controllers to define open, closed and partial exposure conditions.
Alternative control functions may control film exposure in relation
to room occupancy.
Inventors: |
Anderson; Donald;
(Northfield, MN) ; Taylor; Clifford; (Northfield,
MN) |
Correspondence
Address: |
LAW OFFICES DOUGLAS L. TSCHIDA
Suite B
633 Larpenteur Avenue West
St. Paul
MN
55113-6544
US
|
Family ID: |
46329490 |
Appl. No.: |
11/974809 |
Filed: |
October 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10862671 |
Jun 7, 2004 |
7281561 |
|
|
11974809 |
Oct 16, 2007 |
|
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Current U.S.
Class: |
160/238 |
Current CPC
Class: |
E06B 9/264 20130101;
E06B 2009/2643 20130101; E06B 9/32 20130101 |
Class at
Publication: |
160/238 |
International
Class: |
A47G 5/02 20060101
A47G005/02 |
Claims
1. A window comprising: a) a sash framework comprising a plurality
of sash pieces mounted to define an endless perimeter and wherein
first and second glazing pieces are mounted to cover said framework
to define an airtight interior primary space; b) a roller mounted
within said primary space and including a plurality of guide
members mounted to said framework to span between opposed first and
second sash pieces; and c) a first film member mounted to said
roller and abutting said guide members to define a plurality of
loops and overlapping film layers, wherein said first film member
is mounted for reciprocating movement and said guide members
displace said plurality of film layers apart from one another and
from said first and second glazing pieces to define a plurality of
non-convective dead airspaces between adjacent ones of said
plurality of films and said first and second glazing pieces.
2. A window as set forth in claim 1 including motorized means
coupled to said roller for extending and retracting said film.
3. A window as set forth in claim 1 wherein said roller includes a
hollow primary roller and wherein said first film member is mounted
to said primary roller and a motor is coupled to the interior of
said primary roller to rotate said roller to extend and retract
said film.
4. A window as set forth in claim 1 wherein said opposed first and
second sash pieces include a plurality of channels and wherein said
plurality of guide members train peripheral edges of each of said
plurality of film loops in said channels.
5. A window as set forth in claim 1 wherein said plurality of guide
members comprise a plurality of rollers mounted to said framework
to support said film layers.
6. A window as set forth in claim 5 wherein said opposed first and
second sash pieces include a plurality of channels and wherein said
plurality of rollers train peripheral edges of each of said
plurality of film loops in said channels.
7. A window as set forth in claim 1 including means for monitoring
changing solar radiation conditions external to an enclosed
building space containing said window and wherein a motorized means
coupled to said roller responsively controls the movement of said
plurality of film loops between retracted and extended
conditions.
8. A window as set forth in claim 7 including means for monitoring
movement of said first film member and limiting the movement of
said layers to a plurality of predetermined stop points that define
selected exposures.
9. A window as set forth in claim 1 wherein a plurality of supports
abut said roller.
10. A window as set forth in claim 1 wherein said plurality of
guide members each exhibit an elongated arcuate surface that
engages said first film member, wherein said first and second sash
pieces are mounted substantially parallel to each other and include
a plurality of channels, and wherein peripheral edges of each of
said plurality of film loops are respectively contained in said
channels.
11. A window as set forth in claim 1 wherein a sash piece mounted
transverse to said first and second sash pieces includes a
plurality of channels and wherein each of said plurality of film
loops respectively mounts in a channel of the transverse sash piece
when said plurality of films are in a fully extended condition.
12. A window as set forth in claim 1 including an expansible member
mounted in said primary space to said framework to define a
secondary interior space and wherein said expansible member is
mounted to flex with pressure changes within the primary space.
13. A window as set forth in claim 1 including means for applying
tension to each of said plurality of film loops to maintain each of
said film loops in a taught, substantially unwrinkled
condition.
14. A window as set forth in claim 1 including a second film
defining at least one layer mounted between said plurality of film
loops and said first and second glazing pieces in parallel relation
to said plurality of loops and said first and second glazing
pieces.
15. A window as set forth in claim 1 including a second film
defining at least one loop and mounted between two of said
plurality of loops of said first film member and said first and
second glazing pieces in parallel relation to said plurality of
loops and said first and second glazing pieces.
16. A window as set forth in claim 1 wherein each of said plurality
of film layers is coated with a material to provide a
low-emissivity and high solar reflectance.
17. A window as set forth in claim 1 wherein said first film member
is mounted to said roller at one end and to said framework at an
opposite distal end.
18. A window as set forth in claim 1 wherein first and second ends
of said first film member are mounted to said roller to define an
endless circumference and said plurality of intermediate loops.
19. A window comprising: a) a sash framework comprising a plurality
of sash pieces mounted to define an endless perimeter and wherein
first and second glazing pieces are mounted to cover said framework
to define an airtight interior primary space; b) a roller mounted
within said primary space and including a plurality of guide
members mounted to said framework to span between opposed first and
second sash pieces; and c) a film member mounted to said roller to
define an endless circumference and abutting said guide members to
define a plurality of intermediate loops and overlapping film
layers, wherein each of said plurality of film layers is coated
with a material to provide a low-emissivity and high solar
reflectance, and wherein said film member is mounted for
reciprocating movement and said guide members displace said
plurality of film layers apart from one another and from said first
and second glazing pieces in planar parallel relation to define a
plurality of non-convective dead airspaces between adjacent ones of
said plurality of films and said first and second glazing
pieces.
20. A window as set forth in claim 19 including motorized means
coupled to said roller for extending and retracting said film
member and further including means for monitoring changing solar
radiation conditions external to an enclosed building space
containing said window and wherein a motorized means coupled to
said roller responsively controls the movement of said plurality of
film loops between retracted and extended conditions.
21. A window as set forth in claim 20 including sensor means for
monitoring a thermal condition in a building space containing said
window and a solar condition representative of solar energy
incident on said film member and responsively coupled to direct
said motorized means.
22. A window comprising: a) a sash framework comprising a plurality
of sash pieces mounted to define an endless perimeter and wherein
first and second glazing pieces are mounted to cover said framework
to define an airtight interior primary space; b) a roller mounted
within said primary space and including a plurality of guide
members mounted to said framework to span between opposed first and
second sash pieces; and c) a film member mounted to said roller at
one end and to an anchor at an opposite distal end and abutting
said guide members to define a plurality of intermediate loops and
overlapping film layers, wherein each of said plurality of film
layers is coated with a material to provide a low-emissivity and
high solar reflectance, and wherein said film member is mounted for
reciprocating movement and said guide members displace said
plurality of film layers apart from one another and from said first
and second glazing pieces in planar parallel relation to define a
plurality of non-convective dead airspaces between adjacent ones of
said plurality of films and said first and second glazing
pieces.
23. A window as set forth in claim 22 including motorized means
coupled to said roller for extending and retracting said film
member and further including means for monitoring changing solar
radiation conditions external to an enclosed building space
containing said window and wherein a motorized means coupled to
said roller responsively controls the movement of said plurality of
film loops between retracted and extended conditions.
24. A window as set forth in claim 23 including sensor means
comprised of a plurality of thermistors coupled to sense a
temperature within the building space and solar radiation incident
on said film member and responsively coupled to direct said
motorized means.
25. A window as set forth in claim 23 wherein said guide means is
selected from a class containing rollers, coated or uncoated wires,
rods, tubes, formed channels or formed flanged webs or combinations
thereof.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to energy efficient windows
and, in particular, to a sealed window having a plurality of
suspended films or film surfaces and controls to extend and retract
the film(s) to control thermal efficiency.
[0002] Energy loss through glazed surfaces comprises a significant
part of a building's total energy loss, and can typically
approximate 50% of the total loss. These losses occur during the
heating season as a consequence of a low insulating rating and
outward heat flow, mitigated by the solar gain of any windows and
walls exposed to the sun. During the cooling season, inward solar
heat flow detracts from the insulating characteristic of the
building walls and windows, unless shading is employed.
[0003] Attempts to improve the thermal transfer properties of
glazed surfaces and particularly to decrease heat loss through
glazed surfaces have in the past primarily consisted of shutters
over the outer surface, for example, wooden "doors" from colonial
times to modern motor-driven roll-up "slats". External covers
suffer from an intrinsic R-value limitation on the order of 5
hrft.sup.2F/BTU per inch of thickness. The consequent rather bulky
cover further precludes the application of such covers to
curtain-wall structures, such as large buildings. It is also
difficult to construct such covers to be weather tight, movable,
and reliable.
[0004] Alternatively, curtains, shades, Venetian blinds, Roman
shades, drapes and other interior window covers have been used to
control thermal transmissions through windows. The effectiveness of
internal covers is limited by a combination of factors including
high infrared emissivity, air convection within the room spaces and
leakage of air around and through window and wall surfaces.
[0005] A number of patents have issued that teach attempts to
decrease air convection via improved sealing around the periphery
of the frame of the window. All of these methods attempt to control
heat and light flow by converting a "window" into a "wall". None of
them, however, have produced structures yielding R-values
approaching that of a frame wall. Some of these patents propose the
use of metallized films or fabrics to decrease infrared emissivity
to perhaps 0.3, but the structures suffer from problems of dust
build-up and the necessity to frequently clean the surfaces and
consequent vulnerability to damage.
[0006] A third approach to reducing energy losses through windows
has been to use multiple glazing layers and/or to increase the
spacing between the layers to perhaps 3 to 4-inches. In one such
arrangement, reference U.S. Pat. No. 3,903,665, dry, insulation
particles (e.g. foam beads or particles of other insulation
materials) are moved through provided air passages via a vacuum or
gravity between a storage space and the glazing air space. While
this "beadwall" approach has provided windows having reported
R-values of the order of 20, several limitations exist. That is,
the ducts or passages to and from these windows must be
incorporated in the adjoining building structure or window framing.
The beads occupy significant storage space when the windows are
emptied. The glazing surfaces in contact with the beads tend to
become covered with dust and statically suspended particles over
time. The static electric charges can also rise to the point where
high voltage discharges can result.
[0007] Yet another approach to attaining energy efficiency has been
to use multiple layers of shading. For example, U.S. Pat. No.
4,187,896 shows a semitransparent curtain layer having a lowered
infrared emissivity on an outer surface. The layer is suspended
within the room space in the fashion of a shade and is mounted to a
roller assembly. U.S. Pat. No. 4,039,019 describes the use of three
or more mutually parallel, opaque shades. The shades can be
attached to a retracting device and cover an internal building
opening, such as a window. A number of resilient spacers separate
the adjacent sheets and create several dead air spaces.
[0008] A variety of motor drives for shades are also found at U.S.
Pat. No. 6,201,34, which discloses a digital microprocessor control
with Hall Effect sensors used to sense limits. U.S. Pat. No.
6,082,443 uses a PLC to "learn" position limits for a motor
equipped with a revolution counter. And U.S. Pat. No. 6,060,852
discloses a DC motor and battery mounted in a hollow tube.
[0009] The present invention improves upon the known art by
providing alternative window assemblies that provide a framework
with two glazing layers and several intermediate film layers. The
film layers can comprise several discrete film pieces and/or
multiple surfaces of a single film that are positioned in displaced
relation to one another. The framework and films are arranged to
obtain windows having R-values approaching that of framed walls.
The films can be raised and lowered via associated
electro-mechanical assemblies to control relative ambient thermal
conditions.
SUMMARY OF THE INVENTION
[0010] It is a primary object of the invention to provide an
airtight, double-glazed window unit having multiple moveable film
surfaces mounted in planar relation to each other and displaced
glazing panels.
[0011] It is further object of the invention to provide a window
unit filled with a desiccated air or a noble gas (e.g. Argon or
Krypton).
[0012] It is further object of the invention to provide a window
unit having a motorized roller assembly that manipulates multiple
film layers mounted within the sealed enclosure.
[0013] It is further object of the invention to provide a motorized
film drive assembly that can be fitted in a double glazed enclosure
and which enclosure can be evacuated and backfilled with a desired
gas.
[0014] It is further object of the invention to provide a film
drive assembly that includes a primary film support roller and a
number of secondary guides (e.g. rollers, wires, rods, channels,
webs and/or frame guide channels) to support several film layers in
stationary or reciprocating parallel alignment.
[0015] It is further object of the invention to provide a film
drive assembly that includes a primary retractable film support
roller and several lateral guides (e.g. rollers, wires, rods or
formed webs and/or frame guide channels) to support several loops
of film in parallel reciprocating alignment to each other.
[0016] It is further object of the invention to provide a film
drive assembly that includes several parallel film surfaces defined
by several films and/or several layers of a single film displaced
from one another by lateral guides (e.g. rollers, wires, rods,
channels, formed webs and/or frame guide channels) in stationary or
reciprocating, parallel alignment to each other.
[0017] It is further object of the invention to provide a primary
film support roller wherein a drive motor linkage is contained in
the hollow bore of the roller.
[0018] It is further object of the invention to provide optical
control circuitry (e.g. infrared LED/phototransistor) to control
the motorized roller drive in relation to sensed environmental
parameters.
[0019] It is a further object of the invention to provide a
plurality of metalized, coated or clear film layers, which layers
can include indicia defining the travel limits of the films.
[0020] It is a further object of the invention to enable automatic
control of the position of the films with the sensing of exterior
and interior temperatures.
[0021] The foregoing objects, advantages and distinctions of the
invention are obtained in a presently preferred, sealed window
assembly. The window assembly incorporates several improvements
over existing window wall systems that can also be incorporated
into curtain-wall systems.
[0022] The present windows provide two high or variable
transmission glazing layers that are separated by a spacing of the
order of 3.5-inches. The glazing layers are sealed to grooved,
frame pieces constructed from low thermal conductivity materials.
The frame is capped with a motorized roller and film housing to
define an airtight assembly. The assembly is purged and filled with
a desiccated, inert dry gas, preferably an inert high molecular
weight noble gas (e.g. Argon or Krypton).
[0023] Several partially or fully reflective, coated films or
multiple loops of an endless or open-ended film are supported in
planar parallel relation between the glazing layers from a
motorized roller via several guides (e.g. rollers, wires, rods,
channels, formed webs and/or frame guide channels). The film layers
are operable to move up and down in response to changing
environmental conditions. The film layers define several
non-convective dead air spaces, each on the order of 1/2-inch. A
single motorized roller assembly collects the several film layers
at the top of the housing in an "open" condition and lowers the
film layers to completely block the glazed space in a "closed" or
"wall" condition, wherein the window exhibits an R rating
comparable to the imperforate framed wall.
[0024] In several constructions the film layers are attached to the
motorized roller and suspended between guide rollers and several
guide tracks with weighted rods or slats fitted to each film layer
to maintain each film layer under tension. A variety of other
devices can also be used to tension the film layers, which can be
used for vertical or non-vertical applications and may comprise
springs, cables, and electromechanical or electromagnetic devices.
Airflow is restricted to limit convection between any two films
with only a small temperature difference per space. The several
dead air spaces provide a low thermal conductivity of still air
with a low infrared coupling, assured by the reflective coatings,
and collectively define a window capable of a R rating on the order
of 18 to 20 hrft.sup.2F/BTU. Some or all of the film(s) and/or film
layers can be mounted for reciprocating motion. Stationary film(s)
or film layers can be fitted between the reciprocating layers. Film
layers of individual films and/or loops of a single film directed
from support assemblies mounted to the opposite walls of an
enclosure can also be interdigitated or interlaced with each other
in parallel, displaced, interlocking alignment over portions of
their respective travel paths.
[0025] The film layers are each preferably comprised of a
mechanically strong and smooth plastic substrate of the order of
0.001-inch to 0.005-inch in thickness. A plastic such as
polyethylene terepthelate (e.g. MYLAR.RTM.) is one type of
acceptable material. Both surfaces of each film substrate are
coated with a suitable material to provide a low-emissivity surface
that is also high in solar reflectance. For example, a
1000-Angstrom "mirror" film of aluminum exhibits an emissivity
below 0.035 and a solar reflectance above 0.85. Other materials
such as gold or copper, etc. might be coated on each film. The
surfaces may also be coated with non-metallic materials or mixtures
of metallic and non-metallic materials. The opaque reflective
coatings reduce visible light transmission and protect the carrier
substrate from ultraviolet degradation. The coating materials may
be applied over a variety of surface preparations, for example a
matte finish will limit specular reflectance. The prepared films
can also be imprinted or embossed to provide decorative
effects.
[0026] The roller assembly should incorporate controls, e.g. limit
switches, to predetermine the stop points for the motor, such as
fully extended, fully retracted and intermediate film positions.
Indicia at the film can define the control points for roller
movement. The roller assembly presently is packaged in a
top-mounted enclosure containing the motor, electronics, films, and
limit switch sensors.
[0027] A control system for one or more windows along a single wall
or specified walls of a defined space can be as simple as a
wall-mounted switch calling for "window" or "wall" conditions. A
control system might also permit manual control of desired roller
assemblies to desired film travel positions, depending upon sensed
thermal and solar conditions.
[0028] Another control system option is to provide occupancy
sensors to control film movement to desired positions, depending
upon room occupancy. Another option is to provide a control system
that promotes solar heating during the heating season and reduces
solar gain during the cooling season. Such a control system
monitors differential between indoor room air temperature and
instantaneous solar heating potential. Solar heating potential is
measured by a temperature sensor mounted to a suitably constructed
and oriented solar absorber.
[0029] Still other objects, advantages, distinctions and
constructions of the invention will become more apparent from the
following description with respect to the appended drawings.
Similar components and assemblies are referred to in the various
drawings with similar alphanumeric reference characters. The
description should not be literally construed in limitation of the
invention to the presently preferred construction or any suggested
improvements or modifications. Rather, the invention should be
interpreted within the broad scope of the further appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a perspective drawing of a window that includes
the improvements of the invention and shows the films in a 40% open
position.
[0031] FIG. 2 is a perspective drawing of a window showing the
roller assembly exposed and wherein the displaced parallel films
are shown in cut section.
[0032] FIG. 3 is a foreshortened vertical cross section view taken
along section lines 3-3 of FIG. 2.
[0033] FIG. 4 is an enlarged view of detail 4 on FIG. 2
[0034] FIG. 5 is a foreshortened horizontal cross section view
taken along section lines 5-5 and through the motorized end of the
drive roller of FIG. 1. The dashed line indicates the relative
orientation between FIGS. 5 and 6.
[0035] FIG. 6 is a foreshortened horizontal cross section view
taken along section lines 5-5 and through the idler roller of FIG.
1. The dashed line indicates the relative orientation between FIGS.
5 and 6.
[0036] FIG. 7 is a foreshortened vertical cross section view taken
along section lines 7-7 of FIG. 2.
[0037] FIG. 8 is a perspective view of the film subassembly.
[0038] FIG. 9 is an enlarged view of detail 9 on FIG. 8.
[0039] FIG. 10 is a foreshortened front view of the film
subassembly.
[0040] FIG. 11 is an enlarged view of detail 11 on FIG. 10.
[0041] FIG. 12 is an enlarged view of detail 12 on FIG. 10.
[0042] FIG. 13 is a front view of a window showing the films in a
fully closed condition.
[0043] FIG. 14 is a foreshortened vertical cross section view taken
along section lines 14-14 of FIG. 13.
[0044] FIG. 15 is a front cutaway view of a window showing the
films in the closed condition.
[0045] FIG. 16 is an enlarged view of detail 16 on FIG. 15.
[0046] FIG. 17 is a top view of an alternate pressure relief
bellows.
[0047] FIG. 18 is a perspective vertical cross section view taken
along section lines 18-18 through FIG. 17.
[0048] FIG. 19 is a foreshortened front view of an alternate
pressure relief membrane assembly.
[0049] FIG. 20 is a perspective vertical cross section view taken
along section lines 20-20 through FIG. 19.
[0050] FIG. 21 is a block diagram of a typical single room/wall
control system.
[0051] FIG. 22 is a schematic diagram of a single room
controller.
[0052] FIG. 23 is a schematic diagram of the window control
circuitry.
[0053] FIG. 24 is a schematic diagram of switch circuitry for
controlling partial exposure of the window films.
[0054] FIG. 25 is a perspective view of an external solar gain
sensor assembly.
[0055] FIG. 26 is a horizontal cross section view taken along
section lines 26-26 through FIG. 25.
[0056] FIG. 27 is a foreshortened vertical cross section view of a
window incorporating a film support assembly that provides a
serpentine directed film mounted open-ended between a retractable
roller and an anchor and several intermediate, moveable and/or
stationary lateral guides (e.g. rollers) to define a desired number
of parallel film surfaces (e.g. six film layers).
[0057] FIG. 28 is a foreshortened vertical cross section view of a
window incorporating a film support assembly that provides a
serpentine directed film mounted in an endless loop to a
retractable roller or mounted open-ended between a retractable
roller and an anchor and several intermediate, moveable and/or
stationary lateral guides (e.g. passive wires, rods, or formed
channel and web pieces) to define a desired number of parallel film
surfaces.
[0058] FIG. 29 is a foreshortened vertical cross section view of a
window incorporating a film support assembly that provides a
serpentine directed film mounted in an endless loop to a
retractable roller or mounted open-ended between a retractable
roller and an anchor and one intermediate, moveable roller to
define two parallel film surfaces.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0059] As generally noted above, the invention seeks to provide a
sealed, glazed window assembly 32 having two layers of glass 52 and
54 or other suitably transparent material separated by several
intermediate film layers 36-46. The assembly 32 is designed to
demonstrate an insulation R-value on the order of a frame wall
(e.g. R18 to R20). In contrast, a typical frame wall R-value of 19
is achieved with fiberglass bats fitted in a 6'' solid, opaque
framed wall.
[0060] The significance of the capabilities of the assembly 32 can
be appreciated upon consideration of the applicable physics
relating to multi-layered glazed assemblies and available
multi-layered windows. The physics of the assembly 32 derives from
basic considerations that glass is transparent in the visible
spectrum and a layer of glazing transmits approximately 95% of
incident sunlight. A single layer of glass, which has a
through-glass resistance of about 0.02 hrft.sup.2F/BTU has a
measured R-value of about 1.0 hrft.sup.2F/BTU. This is the sum of
the coupling of the room air to the interior glazing surface plus
the outside air to the outer glazing surface, depending on wind and
draft-induced reductions.
[0061] Two layers of glass might thus be expected to exhibit an
R-value of approximately 2.0, plus the additional R-value of the
intervening air. Still air is a relatively good thermal insulator
and is used in some windows to separate glazing layers. The thermal
conductance of still air is tabulated as being about 0.177
BTU/hrft.sup.2F/in, which might be expected to increase the R-value
by more than 5 per inch of spacing. Convection, however, usually
limits this insulative value.
[0062] Glass, however, is quite absorptive of long wavelength or
infrared energy and exhibits an emissivity and absorptivity of
about 0.84. This characteristic further limits the effectiveness of
any air spacing provided between adjacent glazing layers to enhance
R-value. This is due to the infrared coupling that occurs between
the glazing layers.
[0063] The thermal resistance, R, of several layers in series must
include the parallel terms for conductance or U-value, where R=1/U.
The radiative heat transfer between two surfaces is given by
Boltzmann's equation. For two surfaces have differing emissivities
and differing temperatures, the U-value depends on the difference
in temperatures of the two surfaces in a non-linear fashion. For an
exemplary surface i having an infrared emissivity .epsilon..sub.i
facing a second surface i having an infrared emissivity
.epsilon..sub.j at two absolute temperatures T.sub.i and T.sub.j
(i.e. in degrees Rankine or in degrees Fahrenheit+459), the net
radiative heat transfer between the two surfaces is:
Q.sub.ij=.sigma..times..epsilon..sub.ij.times.[T.sub.i.sup.4-T.sub.j-
.sup.4], where
.epsilon..sub.ij=1/[1/.epsilon..sub.i+1/.epsilon..sub.i-1/] and
.sigma.=1.712.times.10.sup.-9 BTU/hrft.sup.2F.sup.4.
[0064] Stated differently, assuming a mean annual temperature
gradient of 75.degree. F. across a one square foot window (i.e.
approximately equal summer and winter temperature extremes) and
selecting 1) a temperature T.sub.i of 110.degree. F. (i.e.
569.degree. R) and a temperature T.sub.j of 40.degree. F. (i.e.
499.degree. R) and 2) using the emissivity for glass as 0.84,
provides a U-value of 0.758 and a commensurate R-value for the
exemplary thermal radiation path of only 1.32. Thus, it is clear
that the total R-value of a double glazed window must be less than
2.32, which is the sum of the 1.0 of the external surfaces plus
1.32. This value is further reduced by the heat flow by convection
and conduction between the two glass surfaces.
[0065] The R-value of a double-glazed, air-filled window has been
physically shown to reach a maximum value of approximately 2.0
hrft.sup.2F/BTU at a spacing of about 1/2'' to 5/8'' as
demonstrated by measurements reported by K. R. Solvason and A. G.
Wilson of the National Research Council of Canada, in CBD-46,
Factory-Sealed Double-Glazing, where two different outer air
temperatures and two different outer air velocities were used. This
is a consequence of the convective heat transfer of the air mass
between the glazing layers increasing with increasing separation,
thus limiting the attainable R-value for a larger spacing.
[0066] Even ignoring the losses of the window framing, the best
multi-layered windows promise about 6.0 hrft.sup.2F/BTU. These
"best" windows are triple-glazed and provide an air spacing on the
order of 1/2'', with semitransparent coatings at the glazing to
decrease the infrared emissivity to about 0.35. They also replace
the dry air with argon, which decreases the thermal conductance by
about 15% since this noble gas has a higher molecular weight than
air.
[0067] In lieu of using multiple glazing layers, the invention uses
several layers of metallized plastic film between the two glazing
panels. Those two glazing panels may be tinted and/or colored to
retain a clear view without glare when "open". To "close" the view
and create a "wall", these internal films will typically be opaque
in the visible spectrum. For example, films of polyethylene
terepthelate (such as Dupont Mylar) can be coated on both surfaces
with vacuum-deposited aluminum to exhibit an infrared emissivity
below 0.035. The layer-to-layer conductance of radiation or U-value
between two such films will be approximately 0.019 BTU/hrft.sup.2F,
which is a decrease of 40:1 to that between displaced glass panels.
An offsetting, debilitating characteristic of such films, however,
is that their properties degrade when exposed in air to dust and
humidity. The invention seals these film layers within the glazed
enclosure thus insuring stable performance.
[0068] The invention in several constructions significantly reduces
conductive thermal transfer by using several such films and/or
loops of individual film(s) to subdivide the total space between
the two outer glazing panels. Air has a high R-value and provides
good insulation, as long as it remains still. An insulated glazing
unit (IGU) with one side warmer than the other develops an internal
convective circulation. This circulation transfers heat from the
warm side to the cold side. Larger warm side/cold side temperature
differences (.DELTA.T), result in greater heat transfer. The net
result is significant heat loss in winter and heat gain in
summer.
[0069] This invention's use of multiple film layers to subdivide
the space between the two glazing layers greatly reduces the
convective circulation and heat transfer. For example, a six-film,
seven-space window system operating with an indoor/outdoor .DELTA.T
of 70.degree. F. yields a space-to-space .DELTA.T of 10.degree. F.
This reduced .DELTA.T reduces the convection current's circulation
speed resulting in reduced heat transfer. For example, a standard,
dual-glazed, single-space, IGU operating with an indoor/outdoor
.DELTA.T of 70.degree. F. transfers heat a rate of 31.15
BTU/ft2/hour. The aforementioned six-film, seven-space window
system reduces this heat transfer to 3.5 BTU/ft2/hour, a reduction
of 27.65 BTU/ft2/hour or 89%.
[0070] The efficacy of the foregoing film-based window system
window with R-values approaching framed walls was assessed
theoretically and experimentally. Detailed calculations were
performed to predict the expected R-value if two glass panels were
separated by 3.5'' with six films of aluminized Mylar.RTM. at 1/2''
spacings. The two glazing panels were presumed to be coupled, via
R=0.5 on each face, to air temperatures of 110F and 40F. Tabulated
values were used for the thermal conductivity of still air as a
function of temperature and for 1/8-inch thick glass panels. The
infrared emissivity was taken as 0.84 for glass and as 0.035 for
vacuum-deposited aluminum. This analysis determined that the
maximum temperature difference between any two of the seven 1/2''
airspaces was 10.5.degree. F., and in the complete absence of
convection, provided a highly efficient total R-value of 19.35
ft.sup.2hrF/BTU for the window.
[0071] The calculated R-value was also confirmed with an
experimental apparatus prepared to make direct measurements of heat
transfer through a "test window" having up to six aluminized
Mylar.RTM. films spaced between two glass layers. The glass layers
were 39.75'' square and spaced apart 3.75-inches. The individual
films were selectively supported between the glazing panels on
"frames" of 1/2'' thick Owens-Corning FOAMULAR.RTM. thus leaving an
open area of 36 square inches. A "cold" chamber and a "hot" chamber
were provided on opposite sides of the glazing panels. A "guard"
chamber also separated the hot chamber from the ambient. The guard
chamber could be brought to the same temperature as the hot
chamber. The chambers were segregated with walls of 6''
FOAMULAR.RTM.. Each chamber was provided with a circulating fan.
The "cold room" was filled with ice behind an aluminum plate
painted for high emissivity and thus held around 32F. The "hot
room" was brought to about 110F by use of a measured and controlled
electric heater, again behind a second painted aluminum plate. The
"guard room" had a second electric heater. The "window" being
measured was thus at a mean temperature of 75.degree. F., with both
faces swept by fan-driven air.
[0072] The spacers were covered one by one with layers of
0.002-inch aluminized Mylar.RTM. with all remaining spacers being
used to fill in the total 3.75-inch space opening between the two
"rooms". Measurements were made starting with 0 layers (just one
air space of 1/2'') until a total of six aluminized layers were
added. The measured, experimental results are set forth in TABLE I
below: TABLE-US-00001 TABLE I EXPERIMENTAL MEASUREMENTS Number
Glass-to-Glass R, of Films Spacing, inches ft.sup.2hrF/BTU 0 0.5
1.60 1 1.0 4.29 2 1.5 6.19 3 2.0 8.23 4 2.5 9.49 5 3.0 10.54 6 3.5
17.95
[0073] In a separate measurement intended to validate the
calibration of the measurement apparatus, one measurement was made
with the entire 39.75'' square filled with seven 1/2'' thick layers
of FOAMULAR.RTM.. This "wall" would be expected to have an R-value
of about 18.5, with 3.5'' of R-5 per inch foam plus the air spaces
on the outside of the glazings contributing about the 1.0 of a
single glass. The result of this measurement was R=18.16 ft.sup.2
hrF/BTU.
[0074] The measured value of 17.95 is quite close to the value for
FOAMULAR.RTM., both as measured and as expected from its rating.
Replacing desiccated air with argon is expected to yield R-values
exceeding 20. The agreement between the theoretic prediction and
the measurement in a calibrated system was felt to verify that such
spacers could indeed turn "a window into a wall". The particular
advantage, however, is that the present "wall" can also turn into a
"window", upon rolling the several metallized films onto a "roller"
mounted within the enclosed window space.
Window Assembly Construction
[0075] Referring to FIGS. 1 and 2, perspective drawings are shown
to the construction of a presently preferred window assembly 32.
The window 32 is constructed to exhibit an R-value comparable to a
nominal 6-inch framed wall. The window 32 is particularly capable
of exhibiting an R rating in the range of R18 to R20 with the aid
of several layers of displaced parallel films 36, 38, 40, 42, 44,
46, shown in the various views of FIGS. 1-14. The film layers 36-46
are spaced apart-predetermined distances between interior and
exterior glazing pieces 52 and 54 (e.g. panes of glass or other
relatively rigid transparent or translucent materials).
[0076] The glazing pieces 52 and 54 are typically clear glass, but
other materials can be used and the material may be tinted, coated,
or treated to provide variable light transmission in order to
promote viewing without glare or overheating. The glazing pieces 52
and 54 are attached to a rigid framework 56 in a fashion to provide
an airtight or hermetic seal with the framework 56. The glazing
pieces 52 and 54 should be mounted to minimize undesired thermal
transfer and can be secured using appropriate adhesive materials
and/or routings in the frame 56. The numbers, mounting and types of
film layers 36-46 and/or combinations of film and glazing layers
can be varied as desired and as described in greater detail below.
The particular advantage of the improved window assembly 32 is that
the assembly 32 provides solar illumination with minimal thermal
energy transfer losses throughout the year.
[0077] The framework 56 of the window 32 is constructed of left and
right vertical or longitudinal sash pieces 58 and 60, a horizontal
or transverse, bottom sash piece 62 and a horizontal or transverse,
top sash piece 70. The sash pieces 58, 60, 62 and 70 should be
assembled to minimize the thermal flow around the interior
periphery. The sash pieces 58, 60, 62 and 70 can be constructed
from wood, plastic, foam (e.g. urethane foam), metal or a variety
of composite or covered materials that have a relatively low
thermal conductivity. The materials should exhibit a long-term
stability to ultraviolet light etc., maintain impermeability to gas
and water transmission, and generally be compatible with the
anticipated application and environment. Structural foams extruded
to have nonporous skins on exposed surfaces are well suited for
this application.
[0078] A separately formed and assembled multi-film roller housing
64 is fit to notched recesses 66 and 68 let into the upper ends of
the sash pieces 58 and 60. The housing 64 can however be mounted at
any desired sash location, including adjacent the bottom sash piece
62. The housing 64 is secured to the sash pieces 58 and 60 with
suitable fasteners and/or adhesives. The transverse cap piece 70
encases the framework 56 and housing 64. Front and rear walls 184
and 186 of the housing 64 span between and interlock with the
longitudinal sash pieces 58 and 60. The width of the transverse
sash pieces 62 and 70 defines the space between the glazing pieces
52 and 54, which is a nominal 31/2-inches for the presently
preferred assembly 32.
[0079] Appreciating that the framework 56, glazing pieces 52 and 54
and roller housing 64 are constructed and fitted to be hermetically
sealed, the window assembly 32 must be constructed to withstand the
pressure differences that develop with changing temperatures and
altitudes. For example, a window unit of the same height and width
as the window assembly 32, but with an airspace of only 1/2'', and
sealed with the internal gas temperature at 70.degree. F., would
develop an internal pressure on the order of 0.7 psi or 100 pounds
per square foot when exposed to an exterior temperature of
120.degree. F. and an interior temperature of 70.degree. F. If this
pressure difference were maintained, the glass would flex outward
approximately 1/4 inch. However, an average increase in separation
of 0.024'' would remove the excess pressure. The window 32, in
contrast provides a nominal airspace of 31/2'' between the glazing
pieces 52 and 54. When exposed to the same temperature conditions,
the assembly 32 can experience a significantly greater flexing of
the glazing surfaces.
[0080] The use of flexible seals and adhesives to secure the
glazing pieces 52 and 54 to the frame 56 can accommodate some
pressure equalization. Thicker glass can also provide greater
resistance to flexing. Alternatively, an expandable membrane or
other device that produces an expandable volume can be fitted to
the window assembly 32 to provide pressure relief without releasing
the inert fill gas or allowing the ingress of moisture. Such an
expansible device will also provide pressure relief during high
altitude shipping.
[0081] An example of one type of volume expansion or pressure
equalization device is shown in FIGS. 2, 3, 4, and 7 and comprises
an elastomeric membrane 72. A variety of flexible plastic and film
materials can be used to construct the membrane 72. The membrane is
directly secured to ledges 188 formed in the front and rear walls
184 and 186 of the housing 64 and the lateral sash pieces 58 and
60. Alternatively, the membrane 72 can be mounted to a rigid planar
support piece and over one or more apertures that extend through
the support piece. The support piece can then be sealed to the
ledges 188 and/or channels in the front and rear panels 184 and 186
and sash pieces 58 and 60. The membrane 72 is hermetically sealed
to the walls 184 and 186 and sash pieces 58 and 60 and provides a
primary seal for a lower lying film roller assembly 76 and films
36-46.
[0082] The membrane 72 forms the upper surface of the hermetically
enclosed space 190 that contains the films 36-46. Pressure changes
inside the interior space 190 causes the elastomeric membrane 72 to
passively deflect inward or outward to compensate and reduce the
pressure exerted on the glazing pieces 52 and 54. A vent port 30
through the top sash piece 70 allows air to migrate between the
ambient environment and the interior space above the membrane
72.
[0083] After first being purged of all air, a desiccated, inert dry
gas, preferably an inert high molecular weight noble gas (e.g.
Argon or Krypton), is inserted into the airspace 190 via a
suitable, hermetically sealable, purge-and-fill port 74 to enhance
the thermal efficiency of the window 32. Multiple ports 74 might be
provided through the frame pieces 58-60, 70 and seal 72 to assure a
suitably airtight assembly 64 and permit the routing of necessary
control wiring.
[0084] Examples of two other possible pressure relief devices are
shown in FIGS. 14, 15, and 16. FIG. 14 shows a sectional view of a
U-shaped membrane 154 constructed to create a hermetic seal in
cooperation with the top sash piece 70. Flanges 196 at the edges of
the membrane 154 overlap flanges 198 in the panels 184 and 186 and
sash pieces 58 and 60. Conventional IGU assembly techniques include
application of sealant 158 to the perimeter of the top sash piece
70 that defines the space between the glazing panels 52 and 54. The
shape of the membrane flanges 196 allows perimeter sealant 158 to
encapsulate the edges 198 and provide a positive hermetic seal.
[0085] FIG. 16 shows a flexible accordion-shaped bellows 160 that
can be used in lieu of the membranes 72 or 154. The bellows 160 is
constructed of a suitable long-lived flexible material (e.g.
plastic or polymer or coated material, rubber etc.). A vent tube
162 is attached and hermetically sealed to the bellows 160. The
bellows 160 is mounted inside the housing 64. The vent tube 162
penetrates sash piece 58 at a hole 164. Application of conventional
IGU sealant 158 around tube 162 at the hole 164 completes the
hermetic seal. Pressure increases inside the sealed widow system
exert pressure on the outside of bellows 160 causing it to
compress, forcing air out of vent tube 162. Pressure decreases
inside the interior space 190 causes the bellows 160 to expand,
allowing air to flow into bellows 160 through tube 162.
[0086] In many cases, particularly when multiple windows are
arrayed around an entire floor of a curtain-wall building, it may
be preferred to connect all windows via interconnected runs of
tubing or conduit to a centralized pressure-equalization source.
This source could consist of a bi-directional pump/compressor unit
capable of transferring fill gas to-and-from a pressure vessel.
This function would be under the control of appropriate pressure
sensors. The sensors would control the pump/compressor unit in
order to maintain a slightly positive pressure inside the windows
by adding or removing fill gas. The sensor could also provide
appropriate alerts, for example, fill gas leakage and/or notify a
security system of rapid loss of gas pressure as from a broken
window.
[0087] With additional attention to FIG. 3, the films 36-46 are
mounted to the roller assembly 76 and are operable to extend and
retract in displaced parallel alignment to one another. FIG. 3
shows a detailed sectional view through the active motorized end of
the roller assembly 76 adjacent the sash piece 60 and a detailed
sectional view through the bottom of the window assembly 32.
[0088] The films 36-46 are supported to a hollow, primary roller 78
and are individually directed over secondary guides rollers 80. The
secondary rollers 80 are supported from axles 81 at the sash pieces
58 and 60. Alternatively, coated or uncoated wires, rods, tubes,
formed channels or formed flanged webs or combinations thereof
might be substituted for the rollers 80 and used as guides to
separate the films 36-46 anywhere along the travel path of the
films 36-46. The guides 80 ideally separate the films in a defined
spatial interrelationship (e.g. parallel) as the films are
supported within the assembly 32.
[0089] The lateral edges of the films 36-46 are confined to
vertical channels 82 let into the interior surfaces of the sash
pieces 58 and 60. The films 36-46 are held taut with weights 84
slid into pockets 192 at the bottom edge of each of the films
36-46. This method of mounting the weights 84 prevents wrinkling of
the film surfaces from differential thermal expansion between
weights 84 and the films 36-46. The weights 84 can also be bonded
to the films 36-46 and/or can be attached at any desired location
on the films 36-46. Other film tensioning means may also be used,
for example, spring-assisted assemblies or flexible stays mounted
to the films 36-46.
[0090] The weights 84 nest within grooves 86 let into the bottom
sash piece 62. The nominal spacing between the films 36-46 is 1/2
inch as defined by the centerline spacing of the channels 82 and
grooves 86; other spacings can be provided and might typically be
constructed in a range from 3/8 to 1 inch. Various other guides as
discussed above can also be interspersed along the length of the
films 36-46 to maintain the spacing. When fully extended, the films
36-46 create a number of dead air spaces 88 between the adjacent
film and glazing layers 52 and 54.
[0091] The films 36-46 are preferably constructed of a mechanically
strong and smooth plastic layer on the order of 0.001'' to 0.005''
in thickness. A plastic such as polyethylene terepthelate (e.g.
MYLAR.RTM.) is one type of acceptable material. Both surfaces of
each film 36-46 are metalized to provide a low-emissivity surface
that is also high in solar reflectance. For example, a
1000-Angstrom "mirror" film of aluminum exhibits an emissivity
below 0.035 and a solar reflectance above 0.85. Such a "mirror"
film is opaque and also protects the plastic substrate or carrier
film from ultraviolet degradation. The exterior facing surfaces may
be metalized over a matte finish to limit specular reflectance. The
films 36-46 can also be imprinted or embossed to provide decorative
effects.
[0092] It is recommended that the roller assembly 76 for a given
window be packaged within a generally rectangular insulated housing
64 that is sized to span the top several inches of a desired
double-glazed window unit 32. The housing 64 can include standard
configurations of packaged electronics describe below, including
gearing, motor and limit sensors at one driving end of the roller
assembly 76. Upon tailoring the length of the roller assembly 76
and attaching an appropriate number of metalized films of
appropriate width and length, windows of various width and height
dimensions can be readily assembled.
[0093] With yet further attention to FIGS. 8-12, the films 36-46
can be secured to the roller 78 in various fashions. Of particular
concern is to compensate for any mismatch in the thermal expansion
rates of the roller and/or film materials, which can induce
wrinkling or puckering of the films 36-46 during temperature
extremes. This type of distortion would effect the thermal
efficiency of the assembly 32, be visually objectionable, and could
interfere with the raising and lowering of the films 36-46.
Described below are two possible methods to prevent this from
occurring.
[0094] The first method is shown in FIGS. 8, 9, 10, 11, and 12. In
this method, the films 36-46 are fastened together using
mechanical, adhesive, or thermal methods. As shown in FIG. 11, the
films 36-46 can be bonded to a separate attachment piece 150 that
extends beyond the top edge of the films 36-46. Alternatively, one
film can extend beyond the top edge of the remaining films.
[0095] The extended film or separate attachment piece 150 is
secured to the roller 78 at tabs 134 with mechanical fasteners,
adhesive, or a thermal bonding. The tabs 134 and intermediate
notches 136 between the tabs 134 provide relief from thermally
induced, differential movement along the line of the several
attachment points of the tabs 134 to the roller 78, thereby
preventing localized wrinkling.
[0096] The forming of closely spaced slots 132 into the extended
film or separate piece 150 also creates expansion joints in the
attachment film to take up movement resulting from thermal
expansion or contraction of the roller 78. The slots 132
particularly create multiple strips that are each able to flex
laterally. The slots 132 and notches 136 thus prevent forces
resulting from thermal expansion or contraction of the roller 78
and/or films 36-46 from being transferred into the body of the
films 36-46 to cause distortion.
[0097] A second method of controlling distortion of the films is by
matching the properties of the films and roller. For example, if
the films are made from aluminized Mylar.RTM. the roller could be
constructed from a tube made with Mylar.RTM., or another material
with similar properties. Matching the thermal expansion properties
of the roller 78 and films 36-46 will eliminate the possibility of
thermally induced distortion.
[0098] The roller 78 is constructed of a hollow tubular material
having a circular cross section. The roller 78 can be constructed
of a variety of materials (e.g. aluminum, stainless steel, or a
reinforced composite material) suitable to the film type,
mechanical strength, and anticipated thermal and UV conditions. The
cross-sectional shape can also be varied so long as the roller 78
is able to collect and dispense the films 36-46 without inducing
kinking, stretching or other deformities. The roller 78 might also
be coated with a deformable material that accommodates thermal
expansion.
[0099] With attention to FIGS. 4, 5, and 6, the roller 78 is
supported to the housing 64 with an active end cap assembly 90 and
a passive end cap assembly 92. The assemblies 90 and 92 each
provide a base or inner race piece 94 and 96 that are secured to
opposite ends of the sash pieces 60 and 58. The base piece 94 is
secured through an aperture 98 in a printed circuit board 100 that
supports associated control circuitry of the roller assembly 78.
Annular grooves 102 and 104 are formed into the inner race pieces
94 and 96 and receive bearings 102. The bearings 102 are captured
between outer race pieces 106 and 108 and the inner race pieces 94
and 96 of the respective active end cap 90 and passive end cap 92.
The outer race piece 106 is secured (e.g. press fit) into the end
of the roller 78. The outer race piece 108 of the passive end cap
92 is loosely fit into the roller 78. The roller 78 is thus
radially supported at both ends on two bearing surfaces and is free
to rotate relative to the housing 64 via the active end cap
assembly 90. The roller 78 is also able to expand or contract
lengthwise relative to the housing 64 via the passive end cap
assembly 92.
[0100] Mounted to the base piece 68 is a DC motor 110 that extends
longitudinally into the hollow bore of the roller 78. The motor 110
is suitably selected and/or geared to accommodate the loading of
the films 36-46. Depending upon the applications, a variety of
different motor types 110 might be used with the roller assembly 76
(e.g. rheostat controlled motors, pulse modulated motors, or pulse
width controlled motors) and/or the motor 110 may be mounted in an
exposed condition.
[0101] It should be recognized that the torque requirements of the
gearhead motor must provide sufficient lifting power to raise the
total weight of the several films 36-46 and of their bottom weights
84. Further, a holding torque must be provided when the motor 110
stops, to lock the films 36-46 in place when the motor is "off".
Such gearmotors with attached electrically operated brakes can be
fitted into the end of the drive roller 78.
[0102] Alternatively and/or in combination, the passive end cap
assembly 92 may incorporate a torsion spring of the type normally
used to retract roller blinds, but without any ratchet assembly.
This torsion spring can be pre-wound to balance the torque load of
the weights 84 when the films 36-46 are wound up. As the films
36-46 move down to their fully lowered position, increasing in
torque load, the torsion spring will increase in restoring torque.
The torque constant per turn of the spring, and the number of turns
of pre-wind, can permit an exact cancellation or counter-balance at
both extremes of the film movement. The "hold" requirement with the
motor turned "off" will be near zero with this counter-balance at
any position of the films, and probably will eliminate the need for
a brake assembled with the gearmotor.
[0103] A flexible drive coupling 112 of suitable construction
connects the motor 110 to roller 78 as depicted in FIGS. 4 and 5.
The drive coupling 112 is shown in detail in FIG. 5. The rotational
output of an output shaft 114 of motor 110 is particularly
transmitted via a drive hub 116, flexible member 118 and driven hub
assembly 112. The connection of the hub assembly 112 to the roller
78 occurs at the interface with a number of compressed O-rings 120.
The O-rings 120 are retained between an end clamp plate 124 that is
secured with a screw 128 to the hub 130. A sleeve 112 is fit
between the O-rings 120 and the clamp plate 124 such that drawing
the plate 124 tight to the hub 130 compresses the O-rings 120. The
expansion of the O-rings 120 produces a flexible gripping of the
inside of the roller 78.
[0104] Although the window assembly 32 of FIGS. 1-16 depicts an
assembled window of a specific square dimension (e.g. 40 inches)
with six films 36-46 and having a 31/2 inch airspace between the
glazing layers 52 and 54, other window assemblies ranging from full
ceiling height to widths of several feet can also be constructed
using configurations comparable to the foregoing. Such windows may
include more or less film layers, one or more endless or open-ended
films, interlaced film layers directed from opposite walls of an
enclosure and may also include intermediate immovable coated film
or glazing layers to increase the R-value of the "open" widow. In
the latter instance multiple roller assemblies 76 might be mounted
in the housing 64 between the additional immovable film/glazing
surfaces. In all cases however and even with the use of double or
triple thickness glass, it is contemplated that the thickness of
the window assembly 32 need not be more than about 4 inches, since
an R19 rating is believed most practical and/or cost effective for
most applications.
[0105] The multi-layered film window assembly 32 finds application
in windows of all sizes. The smallest window applications are
principally limited by the minimum physical size of the internal
components. The largest window applications are similarly limited
by the maximum available glass size and structural considerations
of the framework 56 and roller assembly 76.
[0106] To insure uniform performance for large width, multi-layered
film window assemblies 32, several design features that can be
selectively incorporated into any window assembly 32 are shown at
FIG. 7. The primary concern is that as width increases so too does
the potential for sagging of the primary roller 78 and secondary
rollers 80. Any wrinkling of the outer visible films will be
apparent to room occupants and/or passersby and will be
particularly apparent if the outer films are specularly
reflective.
[0107] One method to de-emphasize any such wrinkling is to provide
the exterior film layers 36 and 46 with matte finishes. This will
visually obscure the presence of sag-induced wrinkles.
[0108] Sagging at any of the rollers 78 and/or 80, and particularly
at the primary roller 78, will cause wrinkling to occur in the
films 36-46. Deflection of the primary roller 78 can be overcome
increasing the roller's ability to resist deflection by increasing
its stiffness, for example, by increasing its diameter to prevent
the formation of wrinkles.
[0109] An alternative and preferred method that is suitable for any
width of window 32 is shown in FIG. 7. This method utilizes a
series of laterally displaced rollers 146 that turn on axles 144.
Flanges 142 that extend from the front and rear walls 184 and 186
of the housing 64, in turn, support the axles 144. The rollers 146
exert an upward force on the primary roller 78. The width of the
rollers 146 and the number and spacing between the rollers 146 can
be determined empirically. The total upward force should compensate
for the combined weights of the roller 78 and films 36-46 and the
compensating forces should be applied to maintain uniformity over
the entire length of the roller 78 in relation to other support
considerations such as described above. In lieu of rollers 146,
flexible, resilient, non-marring webs or flanges (possibly similar
to the flanges 142) might be used alone to support the roller 78
without scratching the film(s) 36-46.
[0110] Another significant benefit of the support rollers 146 is
that they form a barrier to circulating air currents from the
exterior side of the outer film layers 36-46 to the interior
layers. If left unimpeded, this air circulation could decrease the
insulative properties of the assembly 32.
[0111] Another significant concern for wide window assemblies 32 is
to prevent sagging in the film spreading rollers 80. The rollers 80
spread the films 36-46 as they unwind from the primary roller 78
and create the insulative dead air spaces 88 between the layers
36-46. Sagging in the rollers 80 can also lead to decreased system
performance and visual distortions at the films. The rollers 80 are
constructed from a lightweight material, such as extruded plastic.
The bending resistance, or stiffness of such rollers is very low.
If such a roller were supported only on its ends, significant
sagging would occur even on relatively narrow windows. This sagging
is prevented by using tensioned wires, strings, cables, or other
similar tensioned strands strung between the sash pieces 58 and 60
as the axles 81 for the rollers 80. Such a tensioned axle 81 is
able to resist the combined weight of the roller 80 and the
overlying film. The use of tensioned axles 81 also allows the
rollers 80 to be constructed as multiple short segments that are
spaced apart and distributed over the width of each film layer
36-46.
[0112] Full-length or segmented coated or uncoated wires, rods,
tubes, formed channels or formed flanged webs or combinations
thereof and trained to span the width of the films 36-46 might be
substituted for the rollers 80 and used as guides to separate the
films 36-46 anywhere along the travel path of the films 36-46. The
guides 80 ideally separate the films in a defined spatial
interrelationship (e.g. parallel) as the films are supported within
the assembly 32.
[0113] Sagging at the roller 78 might also be prevented by using
multiple rollers 78 with the number of films divided between the
rollers 78. One or more rigid or immobile films might depend from
the housing 64 and be mounted between adjacent rollers 78 or 80 or
other lateral guides to span and segregate the interior space into
multiple sections.
System Configuration(s)
[0114] Turning attention to FIGS. 21-24, details are shown to a
block diagram of a typical single room/wall control system (FIG.
21). A schematic diagram detailing the room/wall controller 202 is
shown at FIG. 22. A schematic detailing an up/down, two-stop window
control circuit 200 is shown at FIG. 23; and a schematic detailing
a partial opening, multiple-stop window control circuit 201 is
shown at FIG. 24. FIGS. 25 and 26 disclose details to a solar gain
sensor ES1 used in association with the control system of FIG.
21.
[0115] The room/wall controller 202 of FIGS. 21-23 can be used to
direct the control circuits 200 of one or several window assemblies
32. Additional window assemblies 32 and their controllers 200' can
be added as desired in parallel to each other such as indicated in
dashed line at FIG. 21. Low voltage DC wiring connects each of the
desired windows 32 to the room/wall system controller 202.
[0116] In a typical system, the room/wall system controller 202 may
be connected to operate the films 36-46 in unison to a desired
lighting and thermal transfer condition for the windows along one
wall or for an entire room. The exposure of the films 36-46 may be
directed via provided switches in a range from fully extended to
fully retracted or several intermediate conditions (e.g. 20%, 40%,
60%, 80%). An automatic mode as shown in FIG. 22 may also be
selected and during which thermistors monitor internal and external
solar-influenced temperatures (e.g. T.sub.i and T.sub.e) to
automatically direct film movement in relation to predetermined
threshold conditions and external conditions to minimize heating or
cooling requirements.
[0117] FIG. 22 depicts the circuitry of the controller 202, which
is powered by a rechargeable DC power source B1, and which may
typically be a battery of appropriate voltage (e.g. nominally 12.6
volts). An AC to DC power supply may also be used to power the
circuitry. Multi-position switches S1, S2, and S3 control
associated relays R1, R2, and R3. Switch S1 determines "manual" or
"automatic" modes for film operating conditions. With switch S1 set
to "Manual", switch S2 directs extension and retraction of the
films. With S1 set to "Auto", switch S3 determines the system's
response to monitored temperatures T.sub.i and T.sub.e described
more fully below.
[0118] With the selection of the "Auto" condition, switch S3 is
used to designate whether a winter "Heat" or a summer "Cool" mode
of operation is desired. If the "Heat" mode is enabled, the in-room
temperature T.sub.i is compared to an upper limit T.sub.M. The
output of operational amplifier OA2 will be near 12.6 volts if and
only if "Auto" is selected, the "Heat" (winter) operating mode is
selected and the in-room temperature T.sub.i is less than a maximum
limit temperature T.sub.M. The output of operational amplifier OA3
will be near 12.6 volts if and only if "Auto" is selected, the
"Cool" (summer) operating mode is selected and the in-room
temperature T.sub.i is greater than a lower limit T.sub.m. For
example, T.sub.i may be 70.degree. F., T.sub.M may be 80.degree. F.
and T.sub.m may be 60.degree. F.
[0119] While a variety of thermostatic means may be used to monitor
temperatures and logically direct the operation of relays RL1 and
RL2, the approach shown in FIG. 22 uses bead thermistors BT2, BT3,
and BT4 to sense in-room temperature T.sub.i and, in following
discussions, the exterior temperature T.sub.e by using BT1.
Typically and for example, the resistance of such a sensor will
vary as R(T)=R(To)-.alpha.(T-To)=Ro-.alpha.(T-To). Where Ro in our
example may be 12K at 70.degree. F. and a may be 0.02/.degree. F.
Thus, a resistance of value R.sub.M=10K will be reached at
T.sub.M=80.degree. F. and a resistor of value R.sub.m=14K will be
reached at T.sub.m=60.degree. F. The circuit shown in FIG. 22 uses
resistors in a Wheatstone Bridge arrangement to determine when
operational amplifiers OA2 and OA3 will have a high saturated
output voltage or whether their output will be near zero.
[0120] This bridge arrangement uses operational amplifiers with
high gain and without feedback to compare input voltages to
inverting and non-inverting inputs. If the battery voltage is VB1
and two resistors R14 and R15 are used, the inverting input will be
v.sup.-=VB1.times.R15/(R14+R15) Typically, VB1=12.6 and
R14=R15=10K. The inverting input will then be held at 6.3 volts for
OA1, OA2, and OA3. These amplifiers will switch to high saturation,
typically above 11 volts, if v+exceed 6.3 volts.
[0121] The output of either OA2 or OA3 may thus be at high
saturation if S3 is in either "Heat" or "Cool" mode and if the
interior temperature is in the range where more heat is desired,
with T.sub.i<T.sub.M, or room cooling is desired, with
T.sub.i>T.sub.m. Resistors R18 and R16 are set to equal the
expected resistances of BT3 and BT4 when the limit temperatures
T.sub.M and T.sub.m are reached. Thus, for the case where
T.sub.0=70.degree. F., T.sub.M=80.degree. F., and
T.sub.m=60.degree. F., R18 may be set at 10K and R19 may be set at
14K.
[0122] If either OA2 or OA3 thus provides an output of near VB1,
the other will be near zero. Then, with appropriate logic inversion
dependent on whether "Heat" or "Cool" is selected by S3, the
resistance values of two thermistors BT1 and BT2 will enable
operational amplifier OA1 to control widow operation. Thermistor
BT2 again measures interior room temperature; BT1 is mounted
exterior to the room wall and sensed an available exterior
temperature T.sub.e.
[0123] A separate external sensor ES1, depicted in FIGS. 25 and 26,
contains bead thermistor BT1. This sensor responds to sunlight and
exterior ambient conditions (e.g. intensity and angle of sunlight
incidence, exterior ambient temperature and wind condition) to
define a temperature T.sub.e. The ES1 sensor is designed to model
the expected potential heat flow through each window 32 of a common
wall or room in the "open" position (i.e. films 36-46 retracted).
The T.sub.e and T.sub.i temperatures are appropriately compared to
direct the operation of the relay RL3 and control the up/down
position of the films 36-46. Ideally, the sensing of T.sub.e
provides a response time sufficient to avoid intermittent (i.e.
short duration) responses to passing clouds, shadows and the
like.
[0124] The sensor ES1 is shown in FIGS. 25 and 26 and from which
two leads are fed back to the room controller 202. The sensor ES1
provides a hermetically sealed enclosure constructed to contain
bead thermistor BT1, absorber plate 168, insulated housing 170,
glass 176, spacer 172, glass 178, and retainer 174. The glass
layers 176 and 178 are placed above the absorber plate 168 and
sealed by retainer 174. The absorber plate 168 is placed on
insulated housing 170 and responds to external conditions to define
the T.sub.e temperature via the bead thermistor BT1, which is
attached to the absorber plate 168. The thickness of the absorber
plate 168 can be adjusted to provide a suitable time constant to
accommodate sporadic changes in solar incidence (e.g. approximately
10 minutes).
[0125] The temperatures T.sub.i and T.sub.e are reflected in the
resistance values of the respective bead thermistors BT2 and BT1,
where BT2 is contained in the room/wall controller 202. The bead
thermistors BT1 and BT2 are coupled into a voltage divider
arrangement as resistors R.sub.i and R.sub.e and the output of
which is the non-inverting input to operational amplifier OA1. The
output of the operational amplifier OA1, in turn, is used to
control the voltage across the relay RL3 to direct the motion of
window shades to a closed (down) or open (up) position.
[0126] The foregoing bridge configuration provides a logic
inversion between summer and winter conditions since either OA2 or
OA3 may be driven positive. The output of OA1 in turn determines
whether a higher solar equivalent temperature T.sub.e compared to
room temperature T.sub.i should open or close the films 36-46.
[0127] The operational amplifier OA1 will have an output usually
near 12 volts when an "UP" state is desired or near 0 volts when a
"DOWN" state is desired. The output of the amplifier OA1 is first
compared to a mid-point voltage around 5.2 volts using Zener Diode
ZD1. It is then directed through base resistor R23 and amplified
using transistor Q3 and relay RL3. A diode D8 is incorporated in
the path through relay RL3 to block voltage from returning to the
"Auto" circuit during "Manual" operation of relays RL1 and RL2.
[0128] An "UP" state is designated whenever 1) "Auto" and "Heat"
are selected, T.sub.i is less than T.sub.M, and T.sub.i is less
than T.sub.e; or 2) "Auto" and "Cool" are selected, T.sub.i is
greater than T.sub.m, and T.sub.i is greater than T.sub.e.
Typically, the conditions for (1) are satisfied when sunlight is
shining on ES1 in the winter. During the heating season, walls not
exposed to sunlight will usually have their films 36-46 lowered to
present a darkened or mirror-like wall rather than a window. At
night and in Auto mode, all films 36-46 will typically be lowered.
The conditions for (2) are satisfied during the summer and only
during cool nighttime hours in the hot part of the air-conditioning
season.
[0129] While not explicitly shown in the control circuitry of FIG.
22, it is to be appreciated that an occupancy sensor (shown in
dashed line) can be coupled to enable the Auto mode at any time the
room is empty for any extended period. This option is coupled to
override the UP and DOWN settings and enable AUTO setting whenever
the room is unoccupied. Once occupancy is sensed, the controller
202 reverts to the previous setting.
[0130] The output of the room/wall controller 202 provides two
logic states, either 0 volts (ground) or 12.6 volts (VB1). Relays
RL1 and RL2 are configured as SPDT devices and induce a "shade UP"
condition via conductor 180 and a "shade DOWN" condition via
conductor 182. Both conductors 180 and 182 may be at 0 volts, but
both will never simultaneously be at 12.6 volts. The output(s) of
the room/wall controller 202 are thus fed to all window units 32
via the low voltage conductors 180 and 182.
[0131] The control circuit 200 for each window is shown at FIG. 23.
The control circuit operates to direct the motor 110, which in the
present assembly 32 is a geared, permanent magnet DC motor. As
mentioned, the motor 110 is preferably housed in the hollow bore of
the primary roller 78. Photo sensors PS1 and PS2 are mounted near
the roller 78, see FIGS. 3 and 4, and biased via resistor-diode
combinations R1-D1 and R3-D2 to monitor film movement and provide
upper and lower movement limits. The photo sensors PS1 and PS2
include infrared, LED photodiodes LED 1 and LED2. The photodiodes
LED 1 and LED2 are aligned to indicia or voids at the edges of one
or more of the films 36-46 and phototransistors PT1 and PT2. The
indicia can comprise suitably coated materials or abraded portions
of the low-emissivity metal coatings at the films 36-46. The
indicia and phototransistors PT1 and PT2 can be located as desired
at one or multiple films. The inner films 38 and 44 were presently
selected over the outermost films 36 and 46 to prevent viewing the
abraded areas.
[0132] Activation of either of the phototransistors PT1 and PT2,
the outputs of which are amplified with transistors Q1 and Q2,
engages (i.e. opens) an associated relay RL4 or RL5 to
appropriately control the motor 110. The relay RL5 is coupled to
provide an upper motion stop and the relay RL4 is coupled to
provide a lower motion stop.
[0133] The diodes D1 and D2 are provided to block a potential
breakdown when a reverse bias is applied to either phototransistor
PT1 or PT2. The phototransistors PT1 and PT2 typically have reverse
voltage ratings of only several volts. Resistors R1 and R3 limit
the forward current through LED 1 and LED2 respectively and
resistors R2 and R4 limit the base current of transistors Q1 and
Q2.
[0134] Returning attention to FIGS. 21 and 22 and with additional
attention to FIG. 24, for certain situations it may be preferred
that the films 36-46 be controlled to one or more intermediate
positions to permit the passage of some outside light. The switch
S4 is provided to this end and wherein one of several additional
phototransistors PT3-PT6 and biasing resistors (e.g. R5-R8) and
diodes (e.g. D3-D7) are associated with each of the films 36, 40,
42 and 46. Appropriate sensing indicia are provided at the films
36, 40, 42 and 46 to permit controlling the films in 20%
increments.
[0135] The switch S4 is configured to require that the films 36-46
must have been commanded "Down" using switch S2 before the switch
S4 can enable partial exposure conditions. If a given one of the
intermediate positions is selected by the optional switch S4 of
FIG. 24 when the shades are already above that point, the operation
of gear motor 110 will still cease when the upper limit is sensed
by PS1. Random, intermediate film exposure conditions can be
provided with the inclusion of additional control circuitry.
[0136] It should be emphasized that the details of the circuitry
and operating points shown in FIGS. 21 through 26 are exemplary and
alternative control schemes could be adapted for use with the
improved window assembly 32. For example, some modifications may
include some or all of the following:
[0137] 1. A torsion spring may be mounted in the free hollow end of
roller assembly 78, replacing passive end cap 92, to
counter-balance the torque tending to pull down the weighted films.
For a given window height and width, the values of the downward
torque of the weighted films at the two end positions (fully "up"
and fully "down") are determined. The torque constant per turn of
the spring and the number of pre-load spring turns can be designed
to match the end positions. The gearhead motor will then have very
low torque requirements to move "up" or "down" over the entire
opening range. With the gearhead motor turned off, no net torque
will lead to motion at either end position.
[0138] 2. The use of magnetizable steel rods for weights 84 at the
bottom of the several films would facilitate the use of small
permanent magnets mounted in the side frame pieces 58 and 60 to
"hold" the films at all of the desired stop points set by switch
S4.
[0139] 3. Thermocouples may be used to sense the temperature
difference between one blackened surface just inside the outer
glazing of one window and another just outside the inner glazing of
the same window. As an example, a copper path might lead from one
blackened copper sensor and back from the second with a different
metal, such as constantan, leading between the two sensors.
Operational amplification of that (much smaller) differential
thermocouple voltage could replace the bead thermistors BT1 and
BT2, and the separate packaging of the outside sensor shown in FIG.
26.
[0140] 4. The sensing of the position of the film layers could be
done using mechanical micro switch sensing, or magnetic reed switch
sensing of affixed magnetized tabs on the films for end of travel
and even for intermediate positions, rather than the use of photo
sensors looking for openings in the opaque films on individual
shades.
[0141] 5. Microprocessor controllers and stepper, servo, or encoder
motors could provide for the precise positioning of the film layers
and ranging from fully open to fully closed conditions.
[0142] 6. Set points with different limit temperatures T.sub.M set
for winter and T.sub.m set for summer could be established by
factory-set, or field-set, input temperature values which could be
used with clock and calendar-generated commands replacing selection
of "winter" or "summer". This would be of particular use with
microprocessor control; one bead thermistor could sense interior
temperature and select appropriate operating mode without any
operator intervention. Alternatively, a logic-based control system
could replace manual or calendar-generated commands and
automatically determine the appropriate system responses in order
to maintain maximum effectiveness.
[0143] 7. Hard-wire control of window units, and even the feed of
power to the units, could be replaced by optical paths. That is,
solar cells mounted inside the exterior window glazing could
provide sufficient storable energy to operate motors (e.g. gear or
direct drive; AC or DC; servo, stepper, or encoder); wireless
remote controls could command window shade operations so that no
external paths would be required to a given window.
[0144] 8. Many commercial and industrial buildings use occupancy
sensors to turn off lights in any room not occupied for a set time,
thus saving the cost of lighting. It would be quite easy to
incorporate one path to sense such lighting voltage in the
room/wall controller 202. A "lights out" command could then set the
master control to the "Auto" position.
[0145] 9. Master control of entire walls and/or entire buildings
could be incorporated enabling authorized personnel the ability to
remotely raise or lower any or all shades fully or partially, set
control parameters such as auto/manual/off, or test the operation
of specific units for maintenance purposes.
Single Film, Multi-Layer Assemblies
[0146] Turning attention to FIGS. 27-29 and as mentioned above, it
may be advantageous to deploy a single film to define multiple
displaced film layers such as by forming several parallel loops.
The loops can be supported either in an endless arrangement or an
open-ended, anchored arrangement. Such a multi-layered film can be
used alone or in combination with other film(s), either stationary
or trained from an appropriate support such as a primary
roller.
[0147] For the depicted assemblies, a single film is mounted to
form several loops that define several parallel, displaced layers
that align over the reciprocating travel path of the film. The
film, when lowered, thus divides the space between two glazing
pieces into several divisions. The divisions provide for the same
decrease and control in optical and solar transmission, radiative
heat transfer and convective heat transfer as provided by the
plurality of films deployed in parallel fashion from a primary
roller as discussed above in relation to FIGS. 1-26.
[0148] One assembly 300 of the foregoing type is shown in
foreshortened cross-section at FIG. 27 depicts an open-ended
mechanism for providing a serpentine path that defines several
loops for a single film 179. The film 179 is anchored at one of its
ends to a horizontal or top sash piece 70 at an attachment point or
anchor 180. The opposite end of the film 179 is secured to a roller
302 that is fitted with an appropriate mechanism to control
rotation and the extension and retraction of the film 179.
[0149] The window assembly 300 is enclosed by interior and exterior
glazing pieces 52 and 54 and by sash pieces 58, 60, 62 and 70 in
fashions as discussed above. Secondary lateral guides 304 (e.g.
rollers, coated or uncoated wires, rods, tubes, formed channels or
formed flanged webs or combinations thereof) are attached to left
and right sash pieces 58 and 60 (not shown) to laterally span
several layers 306 defined by the looped film 179. The numbers of
loops 308 can be varied as desired. The guides 304, if constructed
as rollers, are provided with end bearings at the sash pieces 58
and 60 to permit the film 179 to move freely without marring upon
rotation of the roller 302 as the roller guides 304 remain fixed in
proximity to the roller 302. Additional guides 304, such as shown
in dashed line, can be supported between the layers 304 as
necessary to properly support the film 179 relative to the
particular framework 56.
[0150] Weights or other guides 310 are supported within each loop
308 and extend between the sash pieces 58 and 60. The guides 310
tension the film loops 308 and are mounted to permit reciprocating
movement of the loops 308 up and down. The loops 308 can be mounted
to move in synchrony or asynchronously to raise and lower the
layers 304 between the depicted fully extended condition or a
storage condition wherein the film 179 and guides 306 are elevated
into proximity with the guides 304 and/or roller 302. The guides
310 can be mounted in slots or grooves 312 formed at the lateral
sash pieces 58 and 60 and/or at the bottom sash piece 62. Such a
mounting provides an effective edge and bottom seal for the film
layers 304 to block convective heat transfer.
[0151] The assembly 300 thus performs substantially the same
functions and achieves substantially the same results as the films
36-46 for the assemblies shown at FIGS. 1-14. The film layers 306
are supported in reciprocating relation, under tension and in
constant parallel displaced relation as the raise and lower
relative to the surrounding framework 56. If required, additional
tension can be added to the layers 306 such as by providing
clutched friction at the guides 310 or with resilient linkages
(e.g. spring) coupled to the guides 310.
[0152] FIG. 28 depicts an alternative assembly 320 that provides a
serpentine path for another single film 179 that is trained to form
several loops 308 relative to low friction guide members 322 and
324 that span between sash members 58 and 60 to define and engage
the film layers 304. Channel stock of an appropriate weight,
resilience and surface smoothness and hardness is formed with webs
that define U-shaped guides 322 and 324. The guides 322 and 324 can
be mounted to vertical and horizontal slots 312 in the sash pieces
58, 60 and 62 to rise and fall with the film 179 and maintain
tension on the loops 308 and at the film layers 306. The guides 322
and 324 can also be mounted without the benefit of slots 312.
Additional guides 324, such as shown in dashed line, can be
supported between the layers 306 as necessary to properly support
the film 179 relative to the particular framework 56.
[0153] The assembly 320 divides the space between the glazing
pieces 52 and 54 into four spaces or divisions. Like the assembly
300, the film 179 is trained in an open-ended configuration between
a roller 302 and anchor 180. Alternatively and as shown in dashed
line, the film 179 can be supported in an endless fashion by
attaching the distal, otherwise anchored end of the film 179 back
to the roller 302. An additional low-friction guide 326 can be used
to facilitate the transition of the film 179 back onto the roller
302. As before, both the open-ended and endless mountings of the
assembly 320 permit reciprocating movement of the film 179 up and
down with virtually no friction on the guides 322, 324 and/or 326
which do not rotate.
[0154] A further improvement shown in dashed line that can be added
to the assembly 320 is to mount a film layer 328 between the guide
322 and the lower sash 62 at fasteners 330 and 332. Such a mounting
configuration provides an additional film layer, yet still permits
reciprocating motion of the loops 308 as the film 179 is raised and
lowered within the framework 52.
[0155] FIG. 29 depicts yet another assembly 340 that directs a
single film 179 in alternative open-ended and endless
configurations relative to an anchor 180 and roller 302 to provide
two film layers 306 and a single loop 308. A single, low friction
guide 342 (e.g. a roller or other low friction guide type-coated or
uncoated wires, rods, tubes, formed channels or formed flanged webs
or combinations thereof) suspends the loop 308 with an appropriate
tension. Additional guides 342 can be mounted to the framework 56
to support the film 179 in proper layered displacement. Lateral and
bottom slots 312 can also be provided to cooperate with the film
179.
[0156] Although not depicted, it is to be appreciated that
multi-layer window assemblies can be configured such that the
multiple layers and/or looped layers of film provided by multiple
rollers 302 can be configured within a framework to interlace or
interdigitate with one another. That is, the distal ends of the
films and/or looped layers of two assemblies can be interlaced in
parallel relation to each other. With the extension and overlapping
of the travel paths of the films/layers the interior framework
space can be segmented into appropriate divisions with desirable
thermal insulating effects. Such assemblies may be constructed for
assemblies that are required to span large surface areas. In such
constructions, the films might also move laterally instead of
vertically. Provisions in either case would be required to assure
the maintenance of a proper tension on the overlapping distal or
depending film(s) or loop ends.
[0157] While the invention has been described with respect to a
number of preferred assemblies and considered improvements,
modifications and/or alternatives thereto, still other assemblies
and may be suggested to those skilled in the art. It is also to be
appreciated that selected ones of the foregoing assemblies and/or
features can be used singularly or can be arranged in different
combinations. The foregoing description should therefore be
construed to include all those embodiments within the spirit and
scope of the following claims.
* * * * *