Note: Descriptions are shown in the official language in which they were submitted.
117S738
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FOLDING SCREEN FOR LIGHT-PERMEABLE SKYLIGHTS AND THE LIKE
BACKGROUND OF THE INVENTION
This invention relates to a folding screen useful in conjunction with
transparent and translucent skylights, and roof panels of various types, all of
5 which are designed to control the light and heat generated by the sun's rays,
and are referred to generally as skylights. In particular, skylights transmit
light in the range from about the near-infrared to about the near-ultraviolet
regions, not all of which light is desirable all the time. The folding screen ofV.S. Pstent No. 3,924,671,
10is designed to control sunlight transmitted by a
skylight. It was essential, for proper functioning of the screen, that adjacent
hinges, each formed by interdigitation of longitudinal edges of the panels, be
vertically displaced relative to one another, a principle of operation which is
common to both the patented screen and our novel screen.
15To maintain the relatively vertically displaced relationship of
adjacent hinges, the patent provides a bi-level track on each side of the
screen. In a first embodiment the bi-level track comprises a lower track and
a vertical guiding lip; in a second embodiment the bi-level track comprises a
lower tracl~ and an upper track. Roller means travel in the lower track; and
20 on the upper track, washer or spacer means (in the first embodiment), and
roller means (in the second embodiment), maintain the relative vertical
displacement of the adjacent hinges. In relatively wide folding screens,
particularly those having a width greater than about 6 feet, the patented
screen required interdigitation of panels having a length corresponding to the
25 width of the screen, and contiguous panels of such length have a tendency to
bind when interdigitated, due to their weight which is supported only at the
tracks at the ends of the panels. Also, notching a panel is not only
technically difficult, but weakens the panel making it less rigid and thus
increasing its tendency to bind. As a consequence, patented folding screens
30 were made with arcuate panels which, because of their geometry, had the
dual disadvantages of coverlng less area than planar panels for a given mass
of extruded resin, and of occupying far too much spa¢e when the panels are
stacked, (the screen's collapsed position). Moreover, rollers on the lower
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.. . .. . .. .. . . . . ..
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track are expensive to install, require too much maintenance to be attractive,
and adherence to the principle of preventing the screen to assume a planar
position necessitated a bi-level track, irrespective of the particular embodi-
ment chosen, all of which further increased the expense of manufacturing the
5 screen. It was the necessity of solving these problems economically which
- spurred the invention of the novel folding screen which now permits the use
of planar panels, obviates the use of bi-level tracks, rollers and spacer means,and the necessity of interdigitating contiguous panels; and at the same time,
simplifies its operation.
10Various folding panel structures have been designed for diverse
purposes such as garage doors, hatch covers, awnings, cabinet closures, and
the like. Of necessity, each particular folding panel structure is directed to
the specific purpose for which it is designed, is essentially complete taken
alone, and neither requires nor suggests that any other reference's structure
15 be utilized to supply additional features to help execute the function of that
particular folding panel structure. This is to be expected since folding p~nel
structures are used in a host of diverse industries wholly unrelated to one and
another. A light-permeable radiation screen in particular, must be designed
subject to myriad considerations so that it is as functional as it is compatible20 with a specific roof structure.
The folding screens of the prior art, as might be expected, disclose
numerous ways to cope with the particular problems posed by: (a) the type
and geometrical disposition of the opening to be screened~ for example, a
garage, swimming pool, shower stall, window, furniture cabinet, etc.; (b) $he
25 size and shape of the screen; (c) the guide means for the screen and how and
where these guide means may be iocated; (d) the drive means to be employed
to open and close the screen, whether manual or not; (e) the exposure of the
screen to the elements; and, not less important than any of the foregoing
among still other considerations, (f) the cost of manufacturing the folding
3 0 screen.
A Venetian blind has been used as a skylight screen as disclosed in
U.S. Patent No. 3,2~5,117, to Lorentzen et al, with a ladder assembly or
tapes, and strut-like members which act as mechanical ties. A retractable or
foldable roof for covering a swimming pool is designed in U.S. Patent No.
~5~3i~
3,333,621 to Elder, to function as a load bearing structure which seals out
wind, snow and rain. Though Elder does not define the problem, he has
circumvented a problem similar to the one faced by applicants, namely,
binding of the panels when the screen is to be collapsed after it is opened.
5 Elder uses grooved wheels mounted coaxially with the hinge axis of an upper
hinge, and grooved wheels rnounted coaxially with the hinge axis of a lower
hingeS which wheels are translatable along widely separate paths. The result
is that the screen never assumes an undulating near-planar position.
A folding cover for a cabinet is disclosed in U.S. Patent No.
10 3,570,579 to Matsushima. The cover is pendently supported and includes
plural panels hingedly connected with a hinge of special design, which hinge
permits adjacent panels to rotate through an angle of 120. This rotation
permits the panels to be folded in a stacked relationship, either vertically or
horizontally, by virtue of the weight of the panels which commence to fold
15 only after their weight is unsupported. The fitting slots in the specially
designed hinge limits the rotation of a panel in only one direction, and this
design is essential for the folding cover to assume a planar configuration
when it is opened, this planar configuration being so essential that even the
visible portions of the hinges are designed to preserve the planar appearance
20 of the cover. However, the arcuate fitting slots cause binding of relatively
long panels, that is, panels which are at least 3 feet long, such as are used for
a folding screen for a skylight.
SUMMARY OF THE INVENTION
The present radiation screen is directed for use in conjunction with
parallel, horizontal overhead mono-level tracks disposed beneath a bubble of
a skylight or other transparent or translucent portion of a roof structure. A
folding screen is formed with a pluralit~ of hingedly connected, elongated,
rigid, light-controlling panels having thickened longitudinal edges supported
30 for to-and-fro translation in hinges in the overhead tracks~ The screen may
be stacked in a generally vertical configuration, or extended into an
undulating, planar configuration beneath the bubble to control the amount of
radiation which passes from the bubble to an area below the screen by virtue
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of the hinge members which are speciaI~y designed. One end panel adjacent
one end of the tracks is fixedly disposed for pivotal movement about a
longitudinal edge of the end panel, and the lead panel is connected to a
flexible cable or similar drive means, preferably in a closed loop, which lead
5 panel is subjected to sufficient force either to pull the screen into an
- extended position beween one end of the tracks and the other, or to pull the
screen into a stacked position. Where the skylight is inclined from the
horizontal, the radiation screen may be supported in overhead tracks similarly
inclinedly disposed beneath the bubble.
10In a specific embodiment the radiation screen is supported for
translation at an angle less than about 75 from the horizontal, on a linear
rail provided in each overhead track integral with a support beam of the curb.
Plural elongated rigid upper and lower hinge members are each provided with
back-to-back tubular twin channels, symmetrically disposed about a vertical
15 plane, with a longitudinal slot in each channel. In one embodiment, either the
upper or lower hinges, and preferably both, have the slot cut to a precise
width, so that it has a camming action limiting movement of the panels when
the screen is extended. The width of a camming slot is such that extended
panels lie at an angle of from about 5 to about 30 to the horizontal, and
20 preferably from about 10 to about 20.
In another embodiment, the longitudinal slot is cut too wide to
provide the necessary camming action, but not so wide that a thickened
longitudinal edge of a panel can drop out of the slot. At least the upper hinge
members are provided with a vertical web integral with the hinge, about
25 which web the twin channels are symmetrically disposed. The height of the
web is chosen so that, with the web resting vertically on the mono-level
track, the screen, when extended, assumes an undulating planar configuration.
Irrespective of which embodiment of hinge mémber is used, the
extended panels lie at the above-specified angle, and the screen is supported
30 in successive hinge members, and at least alternate ones are always in turn
always supported on a rail in each overhead track.
A novel curb assembly for a skylight, which skylight includes a dome
(or "bubble"~ and folding screen below the bubble, is provided with an access
panel for the folding screen which is housed in the curb assembly. The access
35 panel is adjacent the skylight's "bubble" which is mounted on the walls of the
curb assembly. This construction of the curb assembly permits maintenance
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of the folding screen without disturbing the seal of the bubble on the walls.
BRIEF DESCRIPTION OF THE DR~WINGS
Figure 1 is a front elevational view with Q portion broken away, of a
rectangular bubble in a skylight in which a coUapsed radiation screen is
5 housed;
Figure 2 is a plan view of the bubble and sl~ylight shown in Fig 1.
Figure 3 is a side elevation cross-sectional view along the line 3-3,
witll the central portion broken away, diagrammatically illustrating the
radiation screen showing details of the side walls of the curb assembly on
10 which the rectangular bubble is disposed, the screen being shown partially
collapsed, and partially extended in an ~mdulating planar configuration;
Figure 4 is a detail view in cross section, of upper and lower hinges
without a web member, the hinges connecting adjacent panels, and camming
slots in the hinges limiting movement of the panels.
Figure 5 is a detail view in cross section of upper and lower hinges
including a web member, the hinges connecting adjacent panels, when the
camming slots in the hinges are too wide to priovide a camming function, but
where the height of the web of the hinge prevents the screen from assuming a
planar configuration.
Figure 6 is an enlarged detail view of the skylight and the central
support member shown in Fig. 3, and of the end wall also shown in Fig. 3, with
portions of the skylight broken away to show details of construction.
DETAILED DESCRIPTION OF THE INVENT~ON
The skylight of this invention is an all-seasons skylight with a motor
driven light-permeable shade to control sunlight and solar heat gain. Each
unit is double-glazed, the side walls are insulated, and the curb assembly is
designed with thermo-barriers to minimize through-metal conduction of heat.
The skylight allows one to design a room for the level of outdoor light desired
30 for esthetic and environmental reasons while permitting energy conservation
through the control of solar heat gain. The system operates on available
current whether 115 or 220 volts; controls for the system operate on 2~ volts
circuitry.
~ eferring to the drawings, and particularly to Figs 1 - 3, and 6,
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there is shown in Fig 1 a front elevational view with a portion broken away,
- of a skylight, indicated generally by reference numeral 10, which includes a
curb assembly indicated generally by reference numeral 11, mounted on a
curb 12 provided in a roof. Roof material 13 is "flashed" up against the wall
5 of the curb 12, usually a wood framework, and nailed to it in a conventional
- manner. The skylight 10 also includes a rectangular bubble 14, preferably one
with a twin-wall for better insulation, which bubble is typically transparent ortranslucent to sunlight. The bubble 14 is mounted on one side of the curb
assembly, on three walls, namely, on one end wall 15 (of two end walls
10 indicated generally by reference numerals 15 and 15'), and side walls
indicated generally by reference numerals 16 and 16'. An access panel 17 is
mounted adjacent the bubble 14, on the other end wall 15', and side walls 16
and 16', with bolts 18. The access panel 17 is preferably insulated with a
foam insulation 19 and provided with a flange 21 which fits snugly over end
15 wall 15', and side walls 16 and 16', as shown in Figs 1 and 3, to ensure a
weather-tight seal against leakage of air and water. A gasket means 22 helps
provide the desired seal.
Each end wall and side wall of the curb assembly 11 is similarly
constructed. Each wall includes a right angle member 23 which is sealingly
20 fitted to a wall of the curb 12 so that vertical portion 23' of the angle
member tightly holds roof material 13 against the wall of the curb.
Horizontal portion 23" (shown in Fig 6) of the right angle member 23 is
gasketed with a gasket 24 which forms a thermo-barrier when bolted to a
support beam, indicated generally by reference numeral 30. Each end wall
25 and side wall of the curb assembly 11 includes a support beam 30.
The support beam 30 comprises a base having an internal planar
portion 31 and an external portion 32, both in the same horizontal plane. The
internal portion 31 functions as a mono-level track upon which a folding
screen, indicated generally by reference numeral 50, is translatably disposed
30 so that it can be extended from its position under access panel 17 to opposite
end wall lS, and then retracted or collapsed under the access panel. The
folding screen S0 is made up of a plurality of planar panels, indicated
generally by reference numeral 60, hinged together with hinge members,
indicated generally by reference numeral 70. To decrease friction, it is
35 preferred to provide a rail 40 on the internal portion 31, and the lower hinge
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members 70' are supported on the rail. Alternatively, the lower hinge
members may be provided with rollers which provide low-friction movement
- though the rollers rest directly upon the mono-level track. It will be evident
that the lower hinges are always supported on the track. Upper hinges 70"
5 may or may not be supported on the track when the panels are extended,
depending upon which embodiment of hinge member is chosen. The drive
means for opening and closing the screen includes an electric motor M. The
manner in which the screen operates, and details of the construction of the
pnnels and the hinges, will be described further hereinafter.
lOI`hc suppor~ beurn 30 also incllides an upper stepped flangc por~ion
33 which extends horizontally and outwardly from a vertical web 34 which
connects the portion 33 to the base portions 31 and 32 (see Eig 6). A gutter
35 is provided on the web 34, interiorly thereof, to collect condensate which
is drained out of the walls through a condensate passage 36 provided therein.
15 Flange portion 33 is grooved to accept gaskets 37 and 38, and includes a
pendent vertical ~lange 39, and several fasteners 42 are self-threaded in the
channel 41. Each self-threaded fastener 42 secures a right angle upper cap 43
fitted with a gasket 44 against an elongated spacer 45, and also against
gasket 38, so as to form a weather tight seal. The vertical flange 39 serves
20 to anchor a side cap 46 with screws 47 which secure a thermo-barrier gasket
48 between the flange and side cap. Machine screws 49 are used to secure
the side cap 46 to the horizontal flange portion 23" of the right angle member
23. The right angle member 23, the support beam 30, the upper cap 43, and
the side cap 46 are all preferably formed from aluminum extrudates. Foam
25 insulation 19' fills the space enclosed within each end wall and side wall.
Referring now to the folding screen 50, and particularly to Figs 4
and 5, it is made up of a plurality of rigid, light-controlling planar panels 60.
By "rigid" I refer to a lack of noticeable deflection of a panel under its own
weight, when the panel is supported along its thickened longitudinal edges 61
30 and 62 which extend continuously along each side of a strip 63. Each
thickened edge is preferably provided with a longitudinal flxial bore 64 to savematerial. Each panel strip is from about 8 cm to about 20 cm wide and from
about 2 mm to about 5 mm thick. As will be evident, wider strips will
normally require greater thickness for rigidity, but the strips may be provided
35 with stiffening ribs (not shown) if desired. The thickened edgcs 61 and 62 are
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preferably cylindrical in cross section having an outside diameter in the range
from about 5 mm to about 1 cm depending on the width and length of the
panels. The panels are preferably cut to a preselected length about the width
of the bubble, from an extrudate of synthetic resinous material such as
5 poly(methyl-methacrylate), polytvinyl chloride), or the like, preferably stabil-
ized with ultraviolet light stabilizers. Alternatively, a strip may be extruded,and then transverse stiffening ribs (which cannot be extruded on the strip),
and longitudinal edges solvent-welded thereon.
The length of the panels, and therefore the width of the folding
10 screen, is limited only by the practical considerations of forming a
sufficiently rigid panel within the framework of the dimensional requirements
of the skylight and its folding screen. Also, the materials from which the
panels are formed are not limited to extruded plastic materials. The panels
may also be made of translucent glass fiber reinforced plastic, or from tinted
15 glass. However, the ease with which glass may be extruded, and tinted, is
offset by the difficulty of handling it. The choice of material depends upon
its ability to maintain a predetermined radiation permeability, and the cost of
forming a panel of desired dimensions. By predetermined radiation
permeability is meant a preselected desirable characteristic of the material
20 from which the panel is formed, both with respect to the intensity and the
range of wavelengths of heat and light radiation to which the panel is
permeable.
As indicated hereinabove, bubble 14 and access panel 17 are
mounted adjacent one and another on the curb assembly 11, bubble 14 being
25 sealed and supported on end wall 15 and side walls 16 and 16', and, the access
panel being sealed and supported on end wall 15' and side walls 16 and 16'.
Adjacent edges of the bubble and the access panel are supported on a cross-
member 80 which in turn is supported at each end by the condensate gutters
35 of the side walls 16 and 16'. It will now be seen that the gutters 35 of the
side walls are so located as to support the bubble and access panel coplanarly
with the upper surfaces of the end walls 15 and 15' and side walls 16 and 16'.
The cross-member 80 includes a central vertical support member 81 having an
upper channel member 8~ having a longitudinal channel 83 in which there is
provided several self-threaded fasteners 8~, a right which fasteners secure a
right angle cap 85, preferably having the same cross section as uppcr cap 43.
~ ~.7573~3
Central support member 81 is provided with a groove 86 in which a neoprene
gasket 87 is held, and, with a base 87 having portions 87' and 87"
. .
symmetrically disposed about the support member 81. Each portion includes
a condensate gutter 88 and a vertical support member 89, one of which
5 vertical support members is fitted with Q neoprene gasket 91. A similar
gasket 92 is directly oppositely disposed in a groove 93 provided in the right
angle cap 85, so that bubble 14 is tightly held between gaskets 91 and 92.
Flange 21' of the access panel preferably fits over and exteriorly of, the
gasl~et 92. Thus, bubble 14 is sealed aguinst the weather on the cross-member
10 80. Condensate from the gutters 88 of the cross-member 80 drains into the
gutters 35 of the side walls, and is disposed of outside the skylight.
Referring further to Figs 1 and 3, the folding screen 50 includes a
pivot panel 65 pivotable about a fixed lower edge, and a lead panel 66
connected by a series of intermediate panels 67, all shown in a generally
15 vertical stacked configuration when the screen is collapsed. The panels are
hingedly connected successively, for side-by-side coaction with hinge mem~
ers 70, along opposite longitudinal edges of the panels. The lower edge of
lead panel 66 is also inserted in a hinge 70, for better to-and-fro translation
of the screen.
Though all hinge members 70 are conveniently cut from the same
extruded stock, and are essentially identical, for the sake of clarity, lower
hinge members are referred to by reference numeral 70' and upper hinge
members are referred to by reference numeral 70". The screen rests at all
times on the lower hinges 70' which in turn rest on the rail 40. In the stacked
25 essentially vertical configuration, upper hinges 70" are vertically spaced
apart from lower hinges 70' by substantially the width of a panel, and in the
extended configuration, alternate hinges are vertically spaced apart by at
least the height of the web 73, if the camming slots are cut too wide to
provide a camming function. If the camming slots are cut to provide a
30 camming function, that is, to maintain a predetermined angle of repose for
the panels when the screen is extended, the vertically spaced apart
relationship of the upper and lower hinges is determined by the predetermined
angle. The predetermined angle may be chosen such that the vertically
spaced apart relationship of the upper and lower hinges is greater than the
35 height of the web 73, and in such a case the web 73 may be used simply to
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provide additional rigidity to the hinge members.
The lead panel 66 is connected by a lug (not shown) on its hinge 70'
to a cable which is trained over an idler pulley mounted on the side wall
towards which the screen is extended, and returned so as to form a closed
s loop to open and close the folding screen, as is conventional, and which is
more specifically described in U.S. Patent No. 3,924,671. Though the folding
screen of our invention may be manually operated, it is preferred to use a
motor means to open and close the screen. This is accomplished by at least
one, and preferably two closed loop chains drivingly trained on a pair of
10 sprockets 94, one at each end of a shaft which extends the width of the
screen, which sprockets are reversibly rotatable with an electric motor means
indicated by reference symbol M. Idler sprockets (not shown) are positioned
opposite each drive sprocket, on the opposite side wall of the curb assembly.
It is further preferred to use any conventional chain tensioning means, either
15 on the idler sprocket which may be spring biased, or directly as part of the
chain itself, to prevent the chain from dragging on the internal portion 31
when the screen is opened and closed. Limit switches 95 and 96 are provided,
one at each end of the screen, to stop rotation of electric motor M and drive
sprockets 94 when the screen is either fully extended, or fully collapsed. The
20 means for opening and closing the screen are well-known to those skilled in
the art, and therefore are not described in greater detail. It is important
however, to note that the drive for the screen is simplified, requiring no
spring biasing means on the panels, because the construction of the hinges
permits the screen to be opened to an undulating, near-planar configuration,
25 but never allows the screen to become planar. If the screen were permitted
to be opened into a planar configuration, it could not thereafter be closed
with the drive mechanism described, because it would jam.
A panel 60 is inserted in a hinge 70 by inserting an end of a
thickened longitudinal edge 61 or 62 in the end of the channel, and sliding the
30 edge longitudinally into the channel. The panels cannot be pulled out of the
slots by pulling the panels directly outward, but only by sliding the panel out
of the channels, in a reverse manner from that required for insertion of the
panels. It is preferred that the camming slots are also symmetrical about the
vertical axis, for practical purposes. Two specific embodiments of the hinge
35 member 70 are illustrated in enlarged cross-sectional views in Figs 4 and 5.
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In Fig 4, hinge member 70 is indicated for clarity, by reference numeral 76,
and in Fig 5 by reference numeral 77; also, reference numerals for channels
and slots in Fig 5 are primed to indicate they may be dimensionally different
from those illustrated in Fig 4.
Referring first to Fig 4, hinge 76 comprises back-to-back twin
tubular channels 71 and 72 symmetrically disposed about a vertical axis.
Each channel has an internal diameter large enough to slidably accomodate a
thickened edge 61 or 62 of the panels. Camming slots 74 and 75, each
narrowcr than th~ outside diameter of a panel edge, are cut longitudinally
along the entire length of channels 71 and 72 respectively. Each slot, cut in
each channel provides a camming function because it limits the movement of
the hingedly connected panels, when the screen is extended, so that a panel is
never less than 5 from the horizontal, and more preferably, is not less than
about 10 from the horizontal3 though it may be as much as 30. Thus, the
upper edges of camming slots 74 and 75 abut against the upper surface of
strip 63 of each panel and limit the panels' further movement. When the
panels are stacked, the slots permit the panels to assume an upstanding,
essentially vertical position.
It will nov~\be evident that when the slots do provide a camming
function, it is not essential that both the upper and lower hinges have
camming slots. It is sufficient if either the upper hinges or the lower hinges
have slots which provide a camming function, since the camming action of a
single slot, whether it is on the upp~ or lower ,hinge, will limit the movement
of the panel. Of course, from a practical polnt of view, all hinges would be
extruded with the same cross-section, and the width of the slots would be the
same in both the upper and lower hinges. However, referring to Fig 3, it will
be seen that if the upper edges of the camming slots of the upper hinges 70"
cam against the upper surface of strip 63, then the slots of lower hinge 70'
may be wider, so that the lower edges~of the slots do not cam against the
30 lower surface of the strip 63. In other wbrds, if the slots of the upper hinges
70" provide a camming function, the slots of the lower hinges 70' serve simply
as slots to provide free movement of the panel from an essentially vertical
position when the panels are stacked, to a horizontal position when the screen
is extended, provided of course that the panels do not come out of the slots.
Referring now to ~ig 5, hinge 77 comprises back-to-back twin
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tubular channels 71' and 72' symmetrically disposed about a vertical web 73.
As before, each channel slidably accomodates edges 61 and 62 of the panels,
and camming slots 74' and 75' are cut longitudinally along the entire length of
each channel. The width of the camming slots is not critical because the web
5 73 acts as a spacer and does not require that the slots provide a camming
function. However, if the slots are cut too wide, that is, wider than the
maximum diameter of a thickened edge of a panel, the panel will drop out.
The height of the web mernber 73 is chosen to prevent the screen from being
opened into a planar configuration, and to limit the extension of the screen to
10 an undulating planar configuration. As before, a panel is neYer less than 5
from the horizontal, and is preferably less than 30 from the horizontal. It
will be evident that the more nearly planar the extended form of the screen,
the less material is used, and it is preferred to maintain the extended panels
at about 10 from the horizontal. Also as before, when the panels are
15 stacked, the slots permit the panels to assume an upstanding, near-vertical
position.
As illustrated in Figs 4 and S, the channels are back-to-back, that is,
there is substantially less stock (preferably aluminum) displacing the outside
surfaces of each channel from one and another than the outside diameter of a
20 channel, otherwise the opening and closing action of the screen will be
impaired. Each hinge 76 and 77 is preferably made from metal so that it is
substantially rigid, that is, the hinges do not permit sufficient deflection of
the panels, due to their weight, to interfere with the action of the screen.
Since it is convenient to manufacture the hinges by extruding aluminum, it is
25 preferred to enhance the rigidity of each hinge with the vertical web 73,
which web would be unnecessary if the back-to-back channels were
sufficiently rigid without it. Since it is difficult to maintain tolerances whencutting camming slots of precise width to provide the desired camming
function, it is preferred to provide the web 73 on hinges to serve as a spacer
30 which provides the precise necessary vertical displacement of alternate
hinges, when the screen is extended, to give it the required undulating planar
configuration. ~t has earlier been stated that the screen is made up of light-
controlling panels. It will now be evident that the panels will typically be
tinted so as to control direct sunlight transmitted through the bubble.
35 However, the panels may a~so be provided with reflectorized upper surfaces
which may reflect some or all of the transmitted light. If no light is to be
transmitted into the room, the panels may be made from opaquc material
such as aluminum.
