 |
Description  |
|
|
BACKGROUND OF THE INVENTION
This invention relates to a thermal energy utilization and conservation
apparatus for use on a conventional window sash where such window sash is
oriented to receive solar radiation.
Fuel economy in heating enclosed spaces, energy conservation and reduction
in heating system installation costs are more desirable today than ever
before when considered in relation to fuel shortages, high fuel costs and
national policy. Prior to construction, buildings can be designed and
located at a site to advantageously use topography, sun positions,
prevailing winds, adjacent buildings, natural shading, material color and
texture, etc., in order to reduce heating requirements. Economics and
availability of fuel supplies can be factored into selection of the
thermal control system.
However, for the majority of heated structures, whether residential,
commercial or industrial, which are already constricted and in use,
significant reduction in consumption of thermal energy is only
accomplished by reduction in usage of the facility or its heat generating
equipment or by relatively significant and costly modification to the
structure to reduce heating requirements.
Venetian blinds have been used in the past to control entrance to an
enclosure of light and thermal energy by using a highly heat-absorptive
coating on one face of the blind slats and a reflective surface on the
other face. Blinds of this type are described in U.S. Pat. Nos. 2,288,465,
2,857,634 and 3,012,294. However, conventional blinds have been
inefficient and ineffective in delivering solar heat to a room because a
blind having its slats in the "closed" position to block direct sunlight
(and prevent fading of curtains, carpets, furniture, etc.) transfers heat
to the room only from the slat surfaces facing into the room. This occurs
by natural convection of room air over the inner surface which,
unfavorably from the standpoint of heat transfer, has a temperature not
insubstantially cooler than the outside surface directly receiving radiant
energy. Little, if any, energy passes directly to the room air from the
hotter outer slat surfaces because present venetian blind construction and
installation traps air and prevents free circulation in the space between
window pane and slat surfaces.
Thus, desirable features in the construction of a blind apparatus using
solar energy to supplement room heating are efficient performance,
simplicity, ease of installation, low initial cost, attractive appearance
and minimal, if any, power consumption in operation.
SUMMARY OF THE INVENTION
Accordingly, it is among the objects of this invention to provide a new and
improved venetian blind apparatus to utilize radiant solar energy to heat
an enclosed space such as a room in a residence.
Other objects are to provide a solar heating and energy conservation
apparatus which has one or more of the following features: effective
performance, economical cost, little, if any, operating expense, simple
installation, and attractive appearance.
In one embodiment of this invention a venetian blind installed at a window
provides room (or other enclosure) heating control by means of improved
head and bottom rails and special purpose coatings applied to both faces
of each slat. The concave face of each blind slat has a highly
heat-absorptive surface thereon and the opposite face has a highly
reflective surface; openings in the head rail and bottom rail permit free
air circulation by natural convection between the room to be controlled
and the air space between the window and blind slats. For room heating,
the slats are oriented in the "closed" position and the highly
heat-absorptive surface is exposed to solar radiation entering the window
glass whereby the temperature of the slats increases. Air contacting or
adjacent the hot surfaces is heated and this heated air otherwise trapped
in the space between slats and window glass rises and passes through the
openings in the head rail to enter the room. Simultaneously, cooler air
from the room moves to replace the outflowing heated air, passing through
openings in the bottom rail and through upwardly oriented passages which
exist between slats (even in a "closed" orientation). Thus, a continuous
circulation current of air is caused to enter the space between slats and
window pane, be heated, rise and exit without expenditure of energy.
Additionally, by similar "chimney" effect, heat is transferred to the room
by air flowing upwardly over the cooler, but nevertheless hot, slat
surfaces facing the room interior.
In hot weather the slats are oriented to expose their highly reflective
surface to the sun's incoming rays thereby turning away the thermal energy
before it enters the room space. Thus, the quantity of heat entering the
room is reduced, comfort is improved and, where an active cooling system
is employed, cooling load, power consumption and equipment requirements
are reduced.
The device is mounted in the window pane in a manner similar to that used
with a conventional venetian blind, requires no modification to the
existing building structure, and presents an attractive appearance when
viewed from inside or outside the building.
BRIEF DESCRIPTION OF THE DRAWING
The foregoing and other objects of this invention as well as various
features thereof, may be more fully understood from the following
description when read together with the accompanying drawing, in which:
FIG. 1 is a front elevational view of the venetian blind of this invention
as seen from within a room;
FIG. 2 is a side view, with parts omitted, of the blind of this invention
taken along the section 2--2 of FIG. 1;
FIG. 3 is a partial side view to an enlarged scale, with parts omitted, of
overlapping venetian blind slats with the concave sides facing a window;
FIG. 4 is a partial side view of an embodiment of this invention similar to
FIG. 2 using a special mounting bracket;
FIG. 5 is an exploded partial view of the special bracket in relation to
the blind of FIG. 2;
FIG. 6 is a partial side view similar to FIG. 3 with the convex sides of
the slats facing a window; and,
FIG. 7 is a front view of a modification.
In the drawing, corresponding parts are referenced by similar numerals
throughout. Figures are not to scale and for clarity of illustration,
scale varies between views.
DESCRIPTION OF A PREFERRED EMBODIMENT
In an embodiment of this invention, FIGS. 1-3, an otherwise conventional
venetian blind 10 installed in window 12 is improved and adapted for
efficient control of solar heating of an enclosure by incorporation of a
plurality of vent holes in the head rail and bottom rail of the blind.
These vent holes enhance heat transfer from the slats of the blind by
allowing air from the enclosure to be heated to circulate freely by
natural convection through the space between the window pane and the
slats. A highly heat-absorptive coating on the slat surface facing the
window pane substantially absorbs incoming solar radiation and further
improves the heat transfer effectiveness of the apparatus.
The venetian blind 10 of this invention in a window 12 is comprised of a
plurality of elongated horizontal slats 14 of arcuate cross-section (FIGS.
2, 3) supported in spaced parallel relationship one to the other on the
rungs 15 of a plurality of vertical ladder-like flexible tapes 16. In the
known manner by means of known mechanisms cooperating with said flexible
tapes 16 including a tilt rod, tape barrels, (not shown) and tilt gear 18
located within the head rail 20 at the top end of the blind 10, the slats
14 are each tiltable in unison about a longitudinal axis through an angle
approximately 180.degree.. See FIGS. 3, 6. A pair of operating cords 24
engaging the tilt mechanism extend downward from the head rail 20 and
depending upon which cord 24 is pulled and the distance pulled the arcuate
slats 14 are tilted to expose either the concave or convex faces to the
window pane 26, generally parallel thereto or at any intermediate angle.
As in conventional venetian blinds of known design, the flexible tapes 16
attach by means of tape clips 28 at their bottom ends to the bottom rail
30. A second pair of operating cords 32 to raise and lower the blind 10
attach one at either side to the bottom rail 30, pass upward through
openings (not shown) in the slats 14, enter the head rail 20, engage
pulleys (not shown) therein, emerge together from the head rail 20 via a
cord lock device (not shown) and extend downward from the head rail 20
into the room 34. By pulling the free-hanging portion of these cords 32
and releasing and engaging the cord lock in the known manner, the bottom
rail 30 is raised or lowered and fixed in any position intermediate the
head rail 20 and the fully-extended condition, FIG. 1, of the flexible
tapes 16 when the bottom rail 30 rests on the sill 36 of the window 12.
The flexible tapes 16 fold and lower slats 14 rest one on another, all in
the known manner, as the bottom rail 30 is raised. Other methods are known
and may be used for tilting of slats and height adjustment of the bottom
rail; however, none of the means and procedures described above are to be
considered as novel parts of this invention.
As seen in FIGS. 1, 2, the venetian blind 10 of this invention is secured
within the recess of the frame of a window 12 comprised of the sash 38,
glass pane 26, the generally horizontal sill 36 at the bottom, vertical
window jambs 40 at opposite sides and a horizontal lintel 42 at the top.
The head rail 20 seats against the side jambs 40 and rests against the
lower horizontal face 44 of the lintel 42 and is fixedly attached thereto
by end brackets 46 attached by suitable means (e.g., nails, screws) to the
jambs 40. In the fully extended condition the bottom rail 30 of the blind
10 rests upon the window sill 36. The assemblage of horizontal slats 14
lying generally in a plane parallel to the transparent glass pane 26 of
the window 12 have an air space 48 between the pane 26 and the slats 14.
The improvements in the venetian blind of this invention result in one
embodiment from modified design of the head rail and bottom rail each of
which has a plurality of holes passing through its exposed surfaces. The
head rail 20 is an elongated, rigid, e.g., sheet metal, generally U-shaped
channel open at the top and ends and having a plurality of vent holes 50
in each face. For the free passage of air the bottom rail 30, which is
hollow has holes 50 in every surface including the bottom surface 52 which
is curved away from the flat surface of the sill 36 or in a tilted
position when the slats 14 are tilted (FIG. 2). Caps 54 at both ends
provide ornamental closures for the bottom rail 30. Vent holes 50 in the
caps 54 and end brackets 46 enhance air circulation.
The slats 14 are finished on the concave face 56 with a highly heat
absorbing coating, e.g., black paint, (not shown), to efficiently absorb
solar radiation 60 entering through the glass window pane 26 and impinging
directly (or by reflection) on the concave surface 56. Slat temperature
increases as energy is absorbed. Generally solar radiation 60 is best
absorbed and room heating is effective when the blind slats 14 are
oriented to the approximately vertical "closed" position (FIG. 3) with
concave faces 56 facing the window glass 26 and with the lower edge 62 of
each slat 14 overlapping and concealed by the upper edge 64 of the next
lower slat 14 as seen through the window pane 26.
As the temperature of the slats 14 increases because of the absorption of
solar radiation 60, air in contact or in close proximity with the slat
faces is heated and rises by natural convection. Air on the room side 34
of the slats 14 moves freely in a natural circulating manner from the
heated slats 14 to the interior of the room 34. Air in the air space 48
between the window glass 26 and the "closed" slats 14 is heated by contact
and proximity to the concave absorptive faces 56, rises and leaves the air
space 48 through the plurality of vent holes 50 in the head rail 20. (Air
outflow is generally represented by arrows 61 in FIG. 2). To replace the
outflowing heated air 61 cooler air from the room 34 enters the air space
48 passing through plurality of holes 50 in the surfaces of the bottom
rail 30 and through the narrow passages 66 which exist between adjacent
slats 14 even in the so-called "closed" position. (Air inflow is generally
represented by arrows 63 in FIG. 2). Air enters each passage 66 between
the lower edge 62 of the hot concave face 56 and the convex room-facing
face 68 of the slat 14 below and rises by natural convection in effective
heat transfer relationship with the hot absorptive face 56. Thus, both
slat faces 56, 68, i.e., facing the room interior 34 and facing the window
glass 26, are active in transferring solar radiation 60 into the room
ambient environment 34 when the radiation absorbent surfaces 56 face the
window 12 and when a complete circuit for convective air flow between
window pane 26 and slats 14 is provided. The air space 48 is of sufficient
width 70 to allow substantially unimpeded natural circulating flow between
the room 34 and the air space 48; approximately four inches between the
slats 14 and the window glass 26 provides effective performance. The
number, shapes and spacing of vent holes 50 in the head 20 and bottom rail
30 is not critical, performance improving generally as flow area
increases. In the head rail 20 and bottom rail 30, a series of staggered
holes 50 approximately 0.625 inch in diameter spaced approximately 0.75
inch apart in parallel rows approximately one inch apart provide effective
performance.
In window frames of shallow depth, FIG. 4, such that sufficient space 48
between the blind slats 14 and the window glass 26 to allow adequate flow
by natural convection is normally lacking, a pair of end brackets 72 one
at each jamb 40 is used in mounting the blind 10 to the window frame. Each
end bracket 72 is a thin, rigid (e.g., sheet metal) generally L-shaped
receptacle having an L-shaped vertical face 74 (FIG. 4). Flanges extend in
one direction perpendicularly from said vertical face 74 forming
horizontal, top 76, 77 and bottom faces 78, and additional flanges 80
extend perpendicularly in the same direction from the vertical leg of the
L-shaped face 74 thereby forming said L-shaped receptacle 72 open at the
end of the horizontal leg and on one side. An angle 82 removably attached
by a suitable fastener 84 (e.g., a sheet metal screw) to the upper
horizontal face 76 and hingedly attached to the lower horizontal face 78
of the bracket 72 provides reversible closure for the open end of said
bracket 72. In order to provide one left-hand and one right-hand bracket
the flanges 76, 77, 78, 80 extend on separate brackets 72 in opposite
directions from the vertical L-shaped faces 74. A thin, rigid, vertical
tab 86 extends perpendicularly from the vertical L-shaped face 74 in the
direction of the flanges 76-78, 80 described above for purposes explained
hereinafter.
In use the brackets 72 are mounted in the recess of the window frame, one
on each side with the vertical L-shaped side 74 generally perpendicular to
the window glass 26 and adjacent and parallel to the side of the jamb 40.
The uppermost horizontal face 77 of the bracket 72 is generally parallel
and adjacent to the horizontal face 44 of the lintel 42 and the bracket 72
is fixedly attached to these surfaces by means of suitable fasteners (not
shown), e.g., screws, nails.
The compartment 88 in the bracket 72 bounded by the tab 86, and upper and
lower flanges 76, 78 has a height and depth approximately equalling the
height and depth, respectively, of the head rail 20. When assembled, blind
10 to bracket 72, the head rail 20 is positioned and nested in the
compartment 88, resting against the tab 86 and upon the lower flange 78.
The hinged end cover 82 of the bracket 72 allows for easy entry and
withdrawal of the head rail 20 from the room side 34 of the bracket for
mounting or removal of the blind 10. When positioned in the bracket 72, as
described above, the blind 10 is spaced from the window glass 26 by an
additional amount approximately equalling the distance 90 between sash 38
and the bracket tab 86 whereby adequate passage 70 for air between the
window pane 26 and the slats 14 is provided. Additionally, the headrail 20
when supported in the end brackets 72 is lowered from the lintel 42 by a
distance 92 approximately equalling the difference between the height of
the vertical leg of the L-shaped bracket 72 and the height of the head
rail 20 thereby providing an unobstructed opening 94 (FIG. 4) to replace
or supplement the vent holes 50 in the head rail 20 for passage of air
into the room 34 from the space 48 between window glass 26 and slats 14.
Application of the highly heat-absorbing coating uniformly to the concave
side 56 of the arcuate slats 14 improves the effectiveness of the blind 10
in collecting the sun's radiant energy 60. As seen in FIG. 3, the slats 14
are in a nearly vertical ("closed") position for heating with the
absorbent coated concave surfaces 56 facing the glass pane 26. Radiant
energy 60 entering the window 12 from an angle generally above the
horizontal impinges on the absorbing surface 56 where it is partially
absorbed and converted into heat and partially reflected. A portion of the
reflected energy is diffused from the slat face 56 and directed back
toward the window pane. Another portion of the reflected energy bounces
from the first concave surface 56 to strike the convex back surface 68 of
the slat 14 directly below where it is partially absorbed and converted
into heat and partially reflected into the room 34. Uniformity and
smoothness of the absorptive coating reduce diffused reflection (and
ensure a greater degree of reflection in accordance with the known
physical principle that reflection angle will equal the angle of
incidence) and thereby provide for increased reception of reflected energy
by the slat 14 directly below the initially receiving slat. Thus, both
heat and a limited amount of light enter the room 34 in the heating mode
of operation; the amount of light entering the room 34 is advantageously
controlled by tilting the slats without allowing direct sunlight to
contact fabrics and wooden surfaces subject to fading.
In the summer or anytime that solar heating is not desirable the slats 14
are tilted to have the concave absorptive surfaces 56 facing into the room
34 and the convex surfaces 68 facing the window 26. In this condition
(FIG. 6) the lower edge portion 64 of the convex face 68 of each slat
overlaps and conceals the upper edge portion 62 of the slat 14 immediately
below as seen from the window 26. With the slats in this position, the
rays 60 of the sun striking the convex surfaces 68 are partially absorbed
and partially reflected; however, the reflective angle is such that
reflected radiation is directed toward the window glass 26 and not into
the room 34. A special highly-reflective surface coating or finish, e.g.,
polished aluminum, may be applied to the convex face 68 to minimize the
amount of solar radiation 60 which is absorbed and converted to heat;
however, many attractive colors, e.g., white, pastels, also provide
substantial reflection of solar radiation. Thus, the outwardly facing
convex surface 68 is more effective in the "closed" position in rejecting
incoming solar heat and light than would be concave surface 56, and,
conversely, the outwardly facing concave surface 56 is more efficient in
the "closed" position accepting incoming solar heat and light than would
be a convex surface 68. The use of the highly heat absorbing surface on
the concave slat face 56, and the highly-reflective surface on the convex
slat face 68 further amplifies the advantage of each condition of
operation.
Additionally, with the slats 14 approximately at the midpoint between the
two opposite "closed" positions, FIG. 1, the concave side 56 of the
conventional blind 10 faces downward. Thus, in the summer with the slats
horizontally tilted for viewing and entry of light through the window 12,
the highly heat-absorbent face 56 is concealed completely from direct
solar radiation 60 and undesirable heat transfer into the room 34 is not
enhanced.
Various modifications of this invention may be made and will be apparent
from the foregoing description which is presented by way of illustration
of and not as a limitation on the scope of this invention. For example,
slat profiles other than arcuate may be used in other embodiments;
nevertheless, head rail and bottom rail vent openings ensure effective
heat transfer even when adjacent slats are in linear contact and
substantially close off the flow passages between slats. Additionally, a
plurality of elongated slots may provide openings through the head and
bottom rail as compared to the vent holes described above. In another
embodiment removal of a slat adjacent the top and bottom rail provides
enlarged passage respectively for air outflow and inflow to the space
between the window pane and the slats.
Further, in an alternative embodiment a pair of enlarged endcaps are used,
one at each end of the bottom rail. These endcaps extend beyond the
profile contours of the bottom rail such that when the blind is fully
lowered the endcaps contact the sill and the bottom rail is located above
the sill. Thus, an unobstructed opening is provided below the bottom rail
which may replace or supplement vent holes in the bottom rail for passage
of air from the room to be heated into the space between window glass and
slats.
Additionally, in a venetian blind of known design having vertically
oriented slats provision at the bottom and top for free air entrance to
and outflow from the space between slats and window glass will enhance the
effectiveness of such a blind as a solar heater. Incorporation of a highly
heat absorbing coating on the concave slat surface and a highly reflective
coating to the convex slat surface will have further advantages as
described above. As noted above, the reflective coating may take various
forms and colors; likewise, the absorbing coating may assume different
dark colors and still be effective absorbers, and it could have the same
hue as the reflective coating.
A modified ventilated bottom rail construction is shown in FIG. 7. The
ventilated bottom rail 94 is a hollow tubular member generally rectangular
and about the same width as the slats 14. End caps 95 enclose the tubular
member and have pivot pins projecting from vertical extensions. These
pivot pins engage in pivot holes provided in the end caps 54' of the
conventional bottom rail 30. Thereby, when the blind is dropped, the
pivoted rail 9 always hangs free due to the pivoted, pendulum-like action.
The conventional bottom rail, when tilted for the solar heating operation
and when touching the window sill, tends to block the movement of air at
the bottom of the blind. This air blockage is prevented and actually air
movement is ensured by reason of the pendulum rail. One set of slots 96
extend through the front and rear walls of the tubular member and pass air
from the room to the window side of the blind. In addition, a set of slots
in the top wall of the tubular member and along the window edge thereof
also pass air from the tubular member onto the concave surface of the
curved slats.
* * * * *
|
|
 |
|
 |
Description |
|
