GB1586801A

GB1586801A - Apparatus for insulating against conductive convective and radiant heat transmission

Info

Publication number: GB1586801A
Application number: GB32279/77A
Authority: GB
Original assignee: INSULATING SHADE LP
Current assignee: INSULATING SHADE LP
Priority date: 1977-07-19
Filing date: 1977-08-01
Publication date: 1981-03-25
Also published as: CH615977A5; FR2398170A1; CA1120784A; IL52616A; NL7708483A; DE2735654A1; SE7708571L; JPS5421656A; IL52616A0; NO772707L; SE419257B

Abstract

An apparatus for insulating against conductive, convective, and radiant heat transmission comprises a plurality of substantially non-transparent and generally parallel sheets. The sheets may be attached to a retracting device from which they can be drawn to extend and cover a building opening such as a window or onto which they can be retracted to uncover the opening. A number of spacers which may be in the form of collapsible or nestable devices are mounted within the apparatus to separate each pair of adjacent sheets and, thus, define a dead air space therebetween. At least one of the sheets has a surface, facing on the dead air space, that exhibits a low surface emittance. This surface emittance is sufficiently low to yield a total effective emissivity of the surface and dead air space of no greater than 0.60. Importantly, the spacer devices are designed so as not to abrade or otherwise harm the reflective surface. The combination of these dead air spaces with the low emittance surface synergistically results in an apparatus having low total effective emissivity that effectively impedes radiant heat transfer. The dead air spaces also effectively impede conductive and convective heat transfer.

Description

(54) APPARATUS FOR INSULATING AGAINST CONDUCTIVE, CONVECTIVE, AND RADIANT HEAT TRANSMISSION (71) We, INSULATING SHADE (limited partnership), an unincorporated partnership of the State of Connecticut, United State of America, formerly of Blue Hills Road, Durham, and now of P.O. Box 282, Branford, Connecticut, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be employed, to be particularly described in and by the following statement:- The present invention relates to an apparatus for providing insulation against radiant, conductive, and convective heat transmission in areas in which only relatively thin insulators may be installed. This apparatus may take the form of a shade and may be used to insulate, areas such as windows and doors in residential, commercial, and industrial buildings that ordinarily are relatively good heat transmitters.

It has become increasingly apparent in recent years that presently known sources of energy derived from the earth are finite and are, in fact, being rapidly depleted. Therefore, energy conservation has become a subject of great national concern.

The heating and cooling systems of residential, industrial and commercial buildings use approximately 25% of all energy consumed in the United States of America. It is important to note, therefore that transparent pane or double insulated pane windows in these buildings are very poor heat insulators and consequently represent a significant cause of inefficient energy consumption. For example, in winter the heat loss per unit area through windows is typically three to ten times as great as that through adjacent walls depending on the type of wall insulation. Similarly, in summer the total heat entering through a sunlit window may be more than ten times that through the adjacent wall. (See, ASHRAM Handbook of Fundamentals (1972); R. C. Dix and Z. Lavan; "Window Shades and Energy Conservation"; Mechanics, Mechanical and Aerospace Engineering Department, Illinois Institute of Technology, 1974). Therefore, substantial amounts of energy can be saved if window areas are effectively insulated. However, it is desirable to do so without permanently blocking windows and thus preventing their use for ventilation as well as for visual acces to the outside world.

It may may also be advantageous to insulate other areas where the permissible thickness of insulation is limited.

Various attempts have been made to provide insulation against heat transmission through building areas such as windows where only thin apparatus can be installed. For example, research conducted at the Illinois Institute of Technology by R. C. Dix and Z. Lavan and published under the title "Window Shades and Energy Conservation" shows that a simple, single-sheet window shade is superior to either draperies or venetian blinds in preventing unwanted heat loss through windows. Further, the insulating effect is improved if the shade is sealed at its edges with tape and provided with a white or silver reflective surface (Id. at 23).

U.S. Patent No. 2,305,085 (Smith) discloses a thermally insulating window shade construction that is retractibly mounted at the top of a window frame and includes two shades sheets separated by a spacer in the form of a wooden rod fixed with the window frame. However, this device has certain practical disadvantages.

The spacer rod has a tendency to abrade the sheets when drawn past it causing them to wear. Further, no provision is made for sealing the shades to the window frame or for otherwise preventing convection air currents from developing in the space between the shade sheets when drawn over the window. This is a major source of breakdown of insulating effectiveness provided by the Smith construction.

ASH RAE, Handbook of Fundamentals (1972) considers the total emissivity of two surfaces having various average emissivities which enclose a single air space.

However, no mechanical structure is disclosed.

Other shade constructions are disclosed in U.S. Patents, Nos. 2,140,049 (Grauel); 2,328,257 (Butts); and 2,865,446 (Cole). Each of these constructions is designed to control the admission of light and air through a window in the manner of a conventional shade and is not well suited for use as an insulator against heat loss. For example, the shade apparatus disclosed in the Grauel and Butts Patents include perforated sheets which induce convection air current about the shade sheets and windows on which the sheets are installed. Similarly, the shade sheets used by the Cole device are made of an open mesh fabric which would not prevent development of such convection air currents.

A pneumatically-actuated roll-up closure is disclosed in U.S. Patent No.

3,231,006 (Fisher et al.) and includes multiple layers which define inflatable, fluid containing pockets. However, the Fisher device is not intended to be an insulator and nowhere in the patent does the inventor consider the desirability of providing surfaces of its multiple layer construction with low emissivity characteristics. In particular, the limits of emissivity which provide an acceptable structure are nowhere mentioned.

Other window closing apparatus are disclosed in the U.S. Patents No.

2247634 (Houston); 2,234,432 (Pidgeon); and 2,361,762 (Glenn et al.). However, both apparatus are as poor insulators as are conventional windows.

The present invention provides apparatus for insulating an area such as a window, door, or wall against conductive, convective, and radiant heat transmission, comprising a plurality of substantially non-transparent imperforate shade sheets; retracting means for mounting the sheets for simultaneous movement between a drawn position covering the area and a retracted position not covering the area; and spacer means for spacing the sheets apart in the drawn position in order to provide a dead space between the or each pair of adjacent sheets, the spacer means including at least one elongate spacer device extending transversely between a pair of adjacent sheets, intermediate the ends of the sheets, the or each spacer device being attaced to only one of the sheets in the said pair and permitting the sheets to collapse together when in the retracted position.

In use, the apparatus of the present invention will be mounted to temporarily or permanently cover an area to be insulated against heat transmission. The area may be a wall or an opening, such as a window, in a building. When embodied in its preferred form, used to insulate a window, the apparatus functions as a shade which may be either completely drawn or opened or set in any position in between and, consequently, need not inhibit normal operation of the window to admit air for ventilation or to admit light. However, when the shade apparatus is drawn at night during the winter months, significant energy savings are realized by preventing substantial loss of heat, generated by the heating system of the building, through the window. Similarly, when this shade apparatus is drawn during the day in the summer months, significant energy savings are realized by limiting admission of heat and thus reducing the need for cooling ordinarily provided by the air conditioning system of the building.

The shade apparatus of this preferred embodiment is designed for use with conventional windows, for example, those of the double hung type slidably mounted in a frame. The apparatus includes a plurality of opaque or translucent, that is, essentially non-transparent, imperforate shade sheets, which are attached to a retracting roller that is mounted to horizontally span the window frame at its upper end. The sheets may be drawn downwardly from the roller to cover the window or may.be retracted back onto the roller to uncover the window. Of course, the shade apparatus may be mounted to be drawn sidewardly across the window.

A number of spacers are mounted with one sheet of each pair of adjacent shade sheets to separate those sheets, when they are drawn to cover the window, to define dead spaces therebetween. These spacers may be collapsible or nestable so that when retracted onto the roller, the layers of sheets may be tightly compacted thereon. Further, since the spacers are mounted with individual shade sheets and travel with them during drawing and retracting operations, minimal abrasion which would tend to wear the sheet or scratch the surface occurs. Other non-abrading space embodiments which are not mounted with the shade sheets are also disclosed.

A low emittance surface is associated with at least one of the sheets and faces on a dead air space. The surface emittance of the surface is sufficiently low to yield an effective emittance of the surfaces bounding the said dead air space of no greater than 0.60. The surface emittance of the surface is, in particular, no greater than 0.60. Effective eittance is the combined effect of the surface emittance of bounding surfaces of an air space where the boundaries are assumed to be parallel and of large dimensions compared with the distance between them (see ASH RAE, Handbook of Fundamental (1972)).

Thus, dead air spaces defined between adjacent shade sheets form an effective thermal insulator against conductive and convective heat transmission. Moreover, the low surface emittance of the dea air space sufaces, in cooperation with these multiple dead air spaces, provide an apparatus having low total emissivity, highly effective to impede radiant heat transfer.

The shade apparatus of the present invention also provides certain practical advantages. In particular, it can be installed as easily as a conventional shade using similar hardware. Since the low emittance surfaces incorporated in the apparatus are not abraded or scratched by the spacers which either travel with the sheets or are fixed, a long useful life of the shade apparatus to effectively insulate a window against heat transmission may be realized. since the apparatus is simple it may be economically manufactured and, therefore, place in wide use.

The apparatus of the invention may be used to insulate other building areas such as floor-to-ceiling length windows, sliding glass or non-glass doors and conventional doors. Further, the apparatus may be embodied in forms other than a shade. For example, it may be mounted in extended, non-retractable fashion to insulate a wall our other area and may be mounted to extend horizontally, vertically or obliquely.

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view illustrating a shade apparatus of the present invention in its drawn position from the inside of a conventional window in which it is mounted.

FIGURE 2 is a front elevational view of this shade apparatus, also from the inside of the window in which it is mounted, illustrating it in a partially drawn position.

FIGURE 3 is a vertical cross-sectional view of this shade apparatus and window taken through plane 3-3 in FIGURE 1 looking toward the left.

FIGURE 4 is a further enlarged partial cross-sectional view similar to that shown in FIGURE 3 illustrating preferred devices for spacing adjacent shade sheets apart to define a dead air space therebetween.

FIGURE 5 is a second enlarged cross-sectional view of these spacer devices showing the manner in which they collapse or nest when retracted onto the roller.

FIGURE 6 is a vertical cross-sectional view of an arrangement for sealing the top of the shade apparatus, alternative to that shown in FIGURE 3, to prevent convection currents from developing between the apparatus and the window.

FIGURE 7 is a horizontal cross-sectional view taken through plane 7-7 in FIGURE 1 looking downward showing a suitable arrangement for sealing the sides of the shade apparatus to prevent development of such convection currents.

FIGURES 8, 9 and 10 are enlarged partial vertical cross-sectional views similar to that shown in FIGURE 3 illustrating alternative devices for spacing adjacent shade sheets apart to define a series of dead air spaces.

FIGURE 11 is a fragmentary vertical cross-sectional view similar to FIGURE 3 of another embodiment of the invention showing additional spacer devices and showing the apparatus mounted to extend at an oblique angle.

FIGURE 12 is a perspective view, partly broken away to show detail of the embodiment shown in FIGURE 11.

FIGURES 13, 14, 15, and 16 are vertical cross-sectional views of spacer devices which are particularly useful as an alternative to the spacer devices shown in FIGURES 11 and 12.

FIGURE 17 is a vertical cross-sectional view of an automatically and/or remotely operable embodiment of the invention.

FIGURE 18 is a perspective view showing the location of a photovoltaic cell for operating embodiment of the invention shown in FIGURE 17.

FIGURE 19 is a vertical cross-sectional view of another automatic embodiment of the invention.

As shown in FIGURES 1 and 2, the apparatus of the present invention, embodied in the form of a shade and generally indicated at 10, is mounted to be drawn over a conventional window, generally indicated at 12, to insulate the window against convective, conductive and radiant heat transmission. However, this shade apparatus may be used with equal advantage to insulate any other opening, such as a sliding glass door, in a commercial, institutional, industrial or residential building against heat transmission. Similarly, it may be embodied as a permanent non-retractible insulator for, as an illustration, a wall. Nevertheless, by way of example, the window 12 may be of the double hung type which comprises a frame 14 that extends about the sides and top and a sill 16 that projects horizontally outwardly from the bottom. A closure in the form of upper and lower multiple glass panes, 18 and 20 respectively, is mounted in a well-known manner with each pane slidably carried in vertically extending tracks (not shown) for upward and downward movement. Further, these glass panes are recessed in the frame 14.

As shown in FIGURE 3, the shade apparatus 10 includes a number of essentially non-transparent, imperforate shade sheets 22 which are attached to a retracting roller 24 that is mounted to horizontally span frame 14 at its upper end.

(Note that the thickness of shade sheets 22 is exaggerated in the interest of clarity.) Readily available or slightly modified hardware may be used to mount the roller which may advantageously include a conventional, spring-loaded retracting mechanism (not shown) like that commonly used in ordinary window shades. This retracting mechanism provides a means for moving the shade sheets between a drawn position (FIGURES I and 3) and a tightly compacted, retracted position.

One sheet of each pair of adjacent shade sheets 22 is provided with a number of devices 26 for spacing the adjacent sheets apart when in the drawn position as shown in FIGURE 3. Moreover, these spacer devices may be mounted more closely together at the top of each sheet to effectively separate adjacent sheets in the region where they tangentially leave roller 24 and thus have a tendency to lie together.

In the preferred embodiment as shown in detail in FIGURE 4, each spacer device 26 is formed of an elongated elastic tape-like strip to assume a partially cylindrical or arcuate shape having an axis parallel to the major axis of the tape-like strip, and is attached, for example by heat welding or sewing, at its upper edge 27 to the sheet surface to extend horizontally or transversely thereacross. (Note that the thickness of space devices 26 is also exaggerated in the interest of clarity.) However, the lower edge 29 of each device is free. Further, each device 26 is made from a material having a high "elastic memory", that is, the material when formed to its desired arcuate shape, naturally reverts to that shape after deformation.

Additionally the devices should be heat set to avoid loss of the "elastic memory" in summer heat. Accordingly, devices 26 separate adjacent sheets along the entire extended sheet length in order to define a dead air space 38 therebetween.

Therefore, these dead air spaces operate as insulators against conductive and convective heat transmission.

As shown in FIGURE 5, the spacer devices 26 tightly compact on roller 24 when the shade sheets 22 are retracted thereon by virtue of their design.

Specifically, the radius of curvature of each spacer device matches the radius of the roller 24 as it rolls thereon and the lower strip edge 29 slides only slightly downwardly on the sheet adjacent that to which it is attached. The free end 29 is preferably rounded to insure that the sliding movement, though slight, is also smooth. However, since the spacer device has high elastic memory, when the apparatus is extended from roller 24, each device tends to maintain or remember the radius of the roller 24 to space adjacent sheets apart in a manner opposite to that when the sheets are retracted.

Referring again to FIGURE 3, the trailing ends 31 of the respective sheets 22 are attached to the curved roller surface in circumferentially staggered fashion.

The spacer devices are also staggered from one sheet to the next in slanted vertical arrays so that only a small portion of one collapses against another on an adjacent sheet when the apparatus is retracted. Accordingly, distribution of the sheet and spacer device material is relatively even when the apparatus is retracted onto the roller. Therefore, though the apparatus may comprise many sheets, they are stored on roller 24 in a relatively compact way to occupy little more space than an ordinary shade. For example, it has been found that an apparatus having three sheets that is eight feet long and has thickness of one and one-half inches when extended, has a retracted diameter of two inches on a roller having a diameter of one inch.

As shown in FIGURE 3, the outermost sheets 22a and 22f are interconnected at location 36 by virtue of being formed of the same sheet of material. Further, each of the single internal sheets 22b through 22e is provided with an elongated weight 37 at its leading end to provide full sheet extension to a point contacting or nearly contacting continuous sheet 22a - 22f at location 36. The respective dead air spaces 38 are, thus, sealed at the bottom by the outer sheets 22a and 22tans their contact with the internal sheets 22b - 22e to prevent the development of convection air currents therein. This is particularly desirable since such convection currents would interfere with effective operation of the dead air spaces to prevent conductive and convective heat transmission.

As the sheets are retracted onto the roll, the radii of the sheets outermost from the roller axis are greater than that of those nearer the roller axis. Therefore, sheet 22f will be retracted onto roller 24 more rapidly than sheet 22a. However, the continuous shade sheet construction permits easy retraction without binding in spite of this occurrence since the sheet 22a22tpivots at location 36. Moreover, the weighted ends of internal sheets 22g-22e retract in staggered fashion because of the difference in radius to the respective sheets on the roller. Suitable discs or large washers may be installed at the ends of roller 24 to insure that the sheets retract evenly thereon.

At least one of the shade sheets is provided with a low emittance surface 39 facing on a dead air space 38. Emittance is defined as the ratio of the total radiant flux emitted by a surface to that emitted by an ideal black body at the same temperature. In the preferred embodiment, at least one and preferably both sides of each of the internal sheets 22b-22e have a low emittance surface and may be, for example, copper, nickel, aluminium, silver or gold foils or foils of alloys of these metals. Material sold under the trademark "Mylar" by the E. I. DuPont de Nemours & Co., when provided with an aluminized coating, is also suitable for use as the shade sheets to provide low emittance surface.

It has been found that each low emittance surface should have a surface emittance sufficiently low to yield an effective emittance of the surfaces bounding the associated dead space of no greater than 0.60. Effective emittance is defined as the combined effect of the boundary surface emittances. Therefore, the maximum acceptable surface emittance of a single surface 39 facing on a single dead space 38 is 0.60; In the preferred embodiments of the invention each low emittance surface has a surface emittance sufficiently low to yield an effective emittance of the surfaces bounding an associated dead space of no greater than 0.06. Thus the maximum preferred surface emittance of a single surface 39 facing on a single dead space 38 is 0.06. The acceptable surface emittance value can be obtained with any of the materials mentioned above.

Further the acceptable and preferred surface emittance and effective emittance values described above should be achieved in the infrared range of the energy spectrum and in the temperature range of 30"C to 1300F.

In light of the description provided above, the term "low surface emittance" is accordingly defined as a surface emittance of no greater than 0.60.

The low emittance surfaces synergistically combine with an associated dead air space to effectively insulate against radiant heat transmission. To illustrate, if thermal conductance U is defined as the time rate of heat flow through a body (frequently per unit area) from one boundary surface to another for unit temperature difference under steady conditions, and thermal resistance R is defined as the reciprocal of thermal conductance, then R is a measure of the effectiveness of a body to prevent heat transmission. The thermal resistance R, of each surface, or the film resistance, of a free standing shade sheet, independent of surface emittance, is 0.68. Thus, the total thermal resistance, which is additivie, of the entire shade sheet is R, =2R,= 1.36. The thermal resistance of two high surface emittance shade sheets spaced apart to form a dead air space is R2 and is equal to the outer film resistance of both sheets, 2R,= 1.36, plus the thermal resistance of the air space, Rasi = 0.96. Therefore, R2= 2Rf + Rasi = 2.32. This, of course, would also be expected resistance of the shade configuration if the sheets had low surface emittance. However, when the sheets are provided with low emittance surfaces, as defined above, facing on the air space, the thermal resistance of the air space is increased to Ras2 = 2.95 so that the total resistance R3= 2Rf + R552 = 4.31. Similar results are achieved as more air spaces are added.

Accordingly, the apparatus comprising a plurality of shade sheets enclosing a plurality of dead air spaces each associated with a low emittance sheet surface, effectively insulates against convective, conductive and radiant heat transmission.

In accordance with the present invention, it is particularly important that the spacer devices do not damage low emittance surfaces when a retracting mechanism is provided. A stationary non-rotatable spacer past which the shade sheets are drawn would abrade these surfaces attached to or forming a part of the sheet face, degrade its low emittance characteristic and thus limit its effectiveness in conjunction with the dead air spaces to insulate against heat transmission.

However, spacer devices of the type described above keep surface abrasion to a minimum and thus preserve and extend the useful life of the apparatus.

The shade apparatus also incorporates certain features which prevent development of convection currents between the apparatus and the window itself As shown in FIGURE 3, a flap 40 is attached to the outermost shade sheet 22a and is weighted by an elongated rod 42 to firmly contact the upper surface of sill 16 when the shade apparatus is in its drawn position. Accordingly, convection air currents are prevented from developing between the bottom of the shade apparatus and the sill. Similarly, a valance in the form of two depending loops 44 is mounted on the undersurface of the horizontal upper portion of frame 14. The loops 44 are sealed at locations 46 to also define dead air spaces 47. Further, each loop may have a low emittance inner surface 49. Therefore, since the loops are positioned to contact the outermost shade sheet 22f as it is- retracted onto roller 24, they effectively prevent convection currents from developing between the frame and the top of the apparatus and also prevent conductive and radiant heat transmission.

As shown in FIGURES I and 7, a resilient seal arrangement, similar to the valance shown in FIGURE 3, may be provided for the side of the shade apparatus.

This arrangement 48, mounted on the side portions of frame 14, includes a pair of opposing loops 50, sealed at locations 51, and made, for example, from a plastic material having high elastic memory, which are formed to tightly contact the edges of the shade apparatus and prevent convection currents from developing thereby.

These loops 50 also enclose dead air spaces 53 and may have low emittance inner surface 55.

As shown in FIGURE 6, an alternative loop arrangement 57 may be used for either the top or side seal arrangements shown in FIGURES 3 and 7. This arrangement includes two loops 54 made of a resilient material, formed to press about the shade apparatus as it is retracted onto a roller 24 regardless of its diameter during various stages of shade sheet retraction.

Alternative forms of spacer devices shown in FIGURES 8 through 10, may be used to separatethe shade sheets in the manner described above. Each alternative spacer embodiment is shown arranged to be retracted in a clockwise direction onto a roller rather than in a counterclockwise direction as shown in FIGURE 3.

FIGURE 8 shows a spacer device which is integrally formed with its associated shade sheet to extend laterally thereacross. Specifically, each sheet 22 is formed at several vertically spaced locations with a first fold 58 that exceeds the elastic limit of the material from which the sheet is made and, therefore, is permanent. The fold may, for example, be bent in the counterclockwise direction. The sheet is then bent backwardly in the clockwise direction at 60 onto itself to form a loop 62. The face of the sheet 22 adjacent the first permanent fold 58 is bonded, for example, with adhesive or by heat sealing to the contacting face at a location 64. The sheet is then bent in a second permanent fold 66, again in the counterclockwise direction, at a location beyond the bond location 64. Thus, a portion of the sheet extends beyond the bond to form a moment arm 68. When a tension force, such as the weight of the sheet itself, indicated by arrow F, is applied to opposite ends of a shade sheet 22, loop 62 tends to rotate outwardly away from the plane of the sheet about fold 58 as indicated by arrow R. In this manner, loop 62 acts as a lateral spacer between adjacent sheets in order to define a dead air space 38 therebetween. The respective dead air spaces operate as thermal insulators in the same manner described above.

The loop 62 is also formed to roll tightly onto a retractor such as roller 24. A second alternative spacer is shown in FIGURE 9 and comprises a loop 70 formed of an elongated strip, attached at its upper edge 72 to the shade sheet 22. The lower strip end is curved back and ultimately to be adhered to itself at 75. The loop material has low elastic memory. Therefore, when the shade apparatus is drawn the loops acts to equalize radial forces within it to accordingly assume a nearly circular cylindrical shape and space adjacent sheets apart. However, when retracted onto a roller 24, the loop 70 collapses to permit the shade sheets to be compacted in closely adjacent relation. A third alternative spacer device is shown in FIGURE 10 and comprises a tear-shaped loop 80 formed of an elongated strip attached at its common free edges to shade sheet 22 at 82. This material from which loop 80 is formed also has low elastic memory and assumes a bulbous configuration when the apparatus is drawn in an attempt to equalize radial forces therein.

FIGURES Il and 12 illustrate a modified embodiment of the present invention which may be used to insulate any area insulated by embodiment illustrated in FIGURE 3. However, this modified embodiment has particular utility for insulating areas such as skylights, roofs of greenhouses or any other area that extends at an oblique or horizontal attitude. As shown in FIGURE 11, the shade apparatus comprises a plurality of shade sheets 102 which are attached to a roller retracting mechanism 104 in a fashion similar to that described with reference to FIGURE 3. The retracting mechanism is mounted between two the roller. Since the spacers 140 are rigid, when the apparatus is moved to its drawn position, the sheets are effectively separated as shown in FIGURE 13.

FIGURE 14 illustrates an alternative spacer which operates by a principle similar to that of the embodiment illustrated in FIGURE 8. This spacer device comprises a rigid strip which has a partially cylindrical or arcuate cross section having an axis parallel to the major axis of the strip. At one edge 146 of the strip, on one face thereof, the spacer is attached to the shade sheet 102b. On its opposite face and opposite edge 148, the spacer is attached also to its central shade sheet 102b. Accordingly, as shown in FIGURE 14, when tension is placed on this shade sheet the spacer device 144 tends to rotate to a position not parallel to the shade sheet. In other words, the spacer tends to rotate outwardly away from the plane of the sheet as indicated by arrow S. In this manner, the spacer acts as a lateral divider between adjacent sheets in order to define dead spaces therebetween. When the apparatus is retracted, the spacer may fold against the shade sheets to tightly compact against the roller 104.

FIGURE 15 illustrates a fixed spacer that comprises a drum 150 which is concentric with and encircles the retracting roller 104. The drum is provided with several slots 152 which extend in the direction of its axis A. Each shade sheet 102 is threaded through one of the slots 152. The drum 150 is mounted with roller 104 to dispose slots 152 is spaced relation transversely to the plane of the extended shade sheets when the sheets are in their fully drawn position as shown in FIGURE 15.

FIGURE 16 illustrates perhaps one of the least expensive spacer embodiments in the form of a solid elongated foam cam member 154 which is attached to one of a pair of the shade sheets 102 (only two of which are shown), in the region of the attachment of the pair of sheets to the roller 104. The cam member extends transversely across the sheets. This spacer configuration has particular utility in situations where cost is an important factor.

FIGURE 17 through 19 illustrate automatically and remctely operable embodiments of the apparatus of the present invention. In FIGURE 17, the shade maybe moved to its drawn and retracted positions by a motor 160 which powers a worm gear 162 and a worm wheel 164 that moves the roller 104 on which the multilayer shade apparatus is mounted. The motor 160 may be automatically driven by a photovoltaic cell as described in greater detail below or may be selectively actuated by a manual switch. Further, the motor shaft 166 may be rotated through a pulley 168 about which is reeved a pull cord 170. This alternative arrangement permits manual operation of the shade apparatus.

It may be desirable to enclose the apparatus between two panes of transparent material 220 such as glass. The panes serve to minimize convection air current which might arise between the parallel sheets of the apparatus. A slight vacuum may be maintained in the space defined between the panes to further suppress convection losses.

FIGURES 18 and 19 illustrate a self-contained motor drive arrangement for the apparatus of the invention. This embodiment includes a power system, mounted inside the roller tube 104, that includes a flat blade 180 which may be engaged in a conventional mounting bracket 182 fixed to a window frame 184. The blade 180 includes separate portions 186 and 188 respectively which are separated by a solid insulating shaft 190. Each of the separate portions of the blade 180 are contacted by suitable spring contacts 192 and 194 mounted inside the bracket 182.

Further, the electrically separate portions are connected through the shaft 190 to a commutator 196 which is adapted to make electrical connection with two brushes 198 and 200. The brushes are, in turn, connected to a motor 202 and a microcomputer 204. The motor has a shaft 206 equipped with a pinion 208 that drives a gear 210 that in turn drives a gear reduction assembly mounted in a gear box 215. Gear 212 engages gear 214 that is non-rotatably mounted with the fixed shaft 190. Accordingly, when the motor is actuated, the shade is rotated through an interaction with the fixed shaft 190. Antifriction bearings 216 are provided to facilitate free rotation of the shade apparatus.

The exterior contacts 192 and 194 are coupled to a photovoltaic cell 218 which is mounted on the window 220 in which the apparatus of the invention is installed as shown in FIGURE 18. The photovoltaic cell is actuated by incident light from the exterior environment. The microcomputer 204 is desirably programmed to move the apparatus to its drawn position during the daylight hours in the air conditioning season. Similarly, in the air conditioning season, the apparatus is moved to its retracted position at night. During the heating season, the converse is true. In particular, the microcomputer is programmed to actuate the motor to move the apparatus to its drawn position at night during the heating season and to its retracted position during the day during the heating season.

It will be appreciated from the above description, that many forms of the present invention may be conceived. It is adaptable to various environments to serve specific insulating requirements.

It has been found that use of the apparatus of the present invention throughout the year can result in substantial conservation of energy. When used during the winter, this apparatus prevents substantial heat loss from the interior to the exterior of a building opening in which it is installed. The apparatus can be most effectively used during the winter months at night. Similarly, during the summer months, the apparatus of the present invention prevents substantial unwanted heat from entering the building from its exterior through the building opening. By way of example, it has been found that the preferred embodiment of the present invention having six shade sheets and enclosing five dead air spaces yields the following results for thermal resistance, R, and conductance, U, as defined above: TABLE 1 Results without Results with Shade Apparatus Shade Apparatus Single Glass Pane Window R 0.96 16.67 U 1.04 0.060 Insulated Glass Pane Window R 1.54 17.25 U 0.65 0.058 These results were obtained when both sides of each interior shade sheet are provided with a low surface emittance surface facing on a dead air space and the effective emittance of the surfaces bounding each dead air space is equal to 0.03. It is apparent that this apparatus represents a sixteen-fold improvement over an uncovered window in preventing heat transmission when all other variables are maintained at constant values.

Note that the present invention may be practised with more or less than six shade sheets. However, it has been found that the minimum number of sheets which provide acceptable results is three, thus enclosing two dead air spaces. Such a shade apparatus yields the following results: TABLE 2 Results without Results with Shade Apparatus Shade Apparatus Single Glass Pane Window R 0.96 7.82 U 1.94 0.128 Insulated Glass Pane Window R 1.54 8.40 U 0.65 0.119 This apparatus then yields an eight-fold improvement over the single pane window in preventing convective, conductive, and radiant heat transmission again when all other variables are maintained at constant values.

Therefore, in its preferred embodiments, the apparatus of the present invention is extremely effective in preventing thermal heat losses to provide substantial conservation of energy.

Claims

WHAT WE CLAIM IS:

I. Apparatus for insulating an area such as a window, door, or wall against conductive, convective, and radiant heat transmission, comprising a plurality of substantially non-transparent imperforate shade sheets; retracting means for mounting the sheets for simultaneous movement between a drawn position covering the area and a retracted position not covering the area; and spacer means for spacing the sheets apart in the drawn position in order to provide a dead space between the or each pair of adjacent sheets, the spacer means including at least one elongate spacer device extending transversely between a pair of adjacent sheets, intermediate the ends of the sheets, the or each spacer device being attached to only one of the sheets in the said pair and permitting the sheets to collapse when in the retracted position.
2. Apparatus as claimed in claim 1, wherein the or each spacer device comprises a strip having an arcuate cross-section, one edge of the strip being attached to one of the sheets in the said pair.
3. Apparatus as claimed in claim 2, wherein the retracting means comprises a roller and wherein the strip curves in the same direction as the roller when the sheet is retracted thereon.
4. Apparatus as claimed in claim 1, wherein the or each spacer device comprises a strip attached at one edge to one of the sheets in the said pair and curling back into the region of the attached edge to form a closed loop, the other edge of the strip being free.
5. Apparatus as claimed in claim 4, wherein the retracting means comprises a roller and wherein the strip curves in the same direction as the roller when the sheet is retracted thereon.
6. Apparatus as claimed in claim 1, wherein the or each spacer device comprises a strip formed into a tear-drop shaped section, one edge of the strip overlying the other and both edges being attached to one sheet in the said pair.
7. Apparatus as claimed in claim I, wherein the or each spacer device comprises a loop formed from one of the sheets in the said pair by folding the sheet back upon itself at a position intermediate its ends and attaching a portion of the folded facing sheet surfaces together so that the loop rotates outwardly away from the general plane of the sheet when tension is applied to the sheet and collapses against the sheet when the tension is removed.
8. Apparatus as claimed in claim 7, wherein the said sheet has two permanent parallel folds and the loop has been formed by attaching the face of the sheet adjacent one of the folds to the face of the sheet at a location intermediate the two folds so that a portion of the sheet extends beyond the location of attachment to form a moment arm for rotating the loop outwardly when tension is applied to the sheet.
9. Apparatus as claimed in claim I, wherein the or each spacer device comprises an elongate strip formed of rigid sheet material having a cross-sectional shape which is arcuate about an axis extending in the direction of the major dimension of the strip, a first part of one sheet of the pair being attached to one face of the strip adjacent one edge of the strip which extends in the direction of the said axis, a second part of the said sheet being attached to the other face of the strip adjacent the opposite edge of the strip, whereby tension applied to the sheet causes the strip to rotate toward a position substantially perpendicular to the surface of the said sheet.
10. Apparatus as claimed in claim 1, wherein the or each spacer device comprises a member mounted on one sheet of the said pair in the region of the attachment of the sheets to the retracting roller.
I I. Apparatus as claimed in any of claims I to 9, wherein there are a plurality of said spacer devices distributed along a sheet.
12. Apparatus as claimed in claim 11, wherein, in two adjacent dead spaces, the spacer devices in one dead space are staggered with respect to those in the other.
13. Apparatus as claimed in any of claims I to 12, wherein the retracting means comprises a single retracting roller to which all the sheets are attached to be rolled thereon.
14. Apparatus as claimed in any of claims I to 13, further comprising means for automatically actuating the retracting means in response to environmental conditions on the exterior of the area.
15. Apparatus as claimed in claim 14, wherein the actuating means comprises motor means for driving the retracting means to move the sheets between the drawn and retracted positions, and sensor means for detecting the environmental condition.
16. Apparatus as claimed in claim 15, wherein the sensor means comprises a photosensor.
17. Apparatus as claimed in claim 16, further comprising a microcomputer, connected to the photosensor and the motor means, programmed to actuate the motor means to move the sheets to the drawn position during the daylight hours and retracted position at night in the air conditioning season and to move the sheets to the drawn position at night and retracted position during the daylight hours in the heating season.
18. Apparatus as claimed in any of claims 1 to 17, including a low emittance surface associated with at least one of the shade sheets, facing on a said dead space, the said surface having a surface emittance which is sufficiently low to yield an effective emittance of the surfaces bounding the said dead space of no greater than 0.60.
19. Apparatus as claimed in claim 18, wherein the said effective emittance is no greater than 0.06.
20. Apparatus as claimed in claim 18, wherein the surface emittance of the said surface is not greater than 0.60.
21. Apparatus as claimed in claim 18, wherein the surface emittance of the said surface is not greater than 0.06.
22. Apparatus as claimed in any of claims 18 to 21, wherein the said effective emittance is achieved in the infra-red range of the radiant energy spectrum.
23. Apparatus as claimed in any of claims 18 to 22, wherein the said effective emittance is achieved in the temperature range of 30"F to 1300F.
24. Apparatus as claimed in any of claims I to 23, wherein the two outer shade sheets of the plurality are interconnected at at least one end, to seal the dead spaces defined between adjacent sheets and thereby prevent convection air currents from developing in the dead spaces.
25. Apparatus as claimed in claim 24, wherein the two outer shade sheets are continuously formed of the same sheet of material.
26. Apparatus as claimed in any of claims 1 to 25, further comprising seal means for preventing convection air currents from developing between the apparatus and the area to be insulated.
27. Apparatus as claimed in claim 26, mounted on an upper portion of the area to be drawn over it from the retracting means, the area having a bottom sill surface, wherein the seal means comprises a flexible flap mounted with the outermost sheet opposite the area to rest on the still surface and prevent air currents from flowing under the apparatus.
28. Apparatus as claimed in claim 26, wherein the seal means comprises a flexible seal mounted within the area to engage the sides of the shade sheets when in the drawn position to prevent convection air currents from flowing thereby.
29. Apparatus as claimed in claim 26, mounted at an upper portion of the area to be drawn down over it from the retracting means, wherein the seal means comprises a flexible valance mounted at the top of the area to contact the shade sheets mounted with the retracting means when in both the drawn and retracted positions and to prevent convection air currents from flowing past the top of the apparatus.
30. Apparatus as claimed in any of claims 1 to 23, further comprising a pair of mutually parallel transparent panes mounted in the area, the sheets being mounted to be moved to their drawn position between the panes.
31. Apparatus as claimed in any of claims I to 29, wherein the shade sheets extend at an angle to the vertical when in the drawn position.
32. Apparatus as claimed in claim 31, wherein the retracting means is arranged to urge the shade sheets toward their retracting position and wherein the apparatus further comprises tensioning means for urging the shade sheets toward their drawn position to hold them at an angle to the vertical.
33. Apparatus for insulating an area against head transmission, as claimed in claim 1, substantially as described herein with reference to, and as shown in, the accompanying drawings.