GB2187779A - Blind - Google Patents

Abstract

A blind comprises a plurality of slat boards 1 each coated on the inner side with selectively absorptive or transmissive film 2, and on the outer side with a heat radiation reflecting film 3. The inner side film 2 has a relatively low long wave emissivity and the outer side film 3 has a high solar radiation reflectivity. <IMAGE>

Description

SPECIFICATION Blind The present invention relates to a blind as installed on a window or the like of a building.

A blind is, like a curtain, a typical solar shield and may comprise a plurality of slat boards adapted to be angularly adjusted by means of cords vertically or horizontally in a manner which is well known. When these slat boards themselves are heated under solar radiation, however, a long wave radiation occurs from their surfaces towards the interior of a room, tending to reduce a desired effect of a solar shield.

As a countermeasure to this problem, it has already been proposed to apply a film or the like having a high reflectivity on to a surface of each slat board.

Japanese Utility Model Application No 5715672 (Unexamined Publication No 58118198) discloses a slat board comprising polyester film vacuum metallized with aluminium, adhesive film uniformly coated with suitable adhesive agent applied on one side of said polyester film and another adhesive film uniformly coated with suitable adhesive agent applied on this assembly.

Furthermore, Japanese Utility Model Application No 47-130005 (Unexamined Publication No 49-84935) discloses slat boards coated on one side with aluminium foil to improve their solar shielding effect.

Nevertheless, these prior proposals merely improve the reflectivity but cannot prevent the temperature of each slat board from rising due to the fact that solar radiation is partially absorbed into the slat board itself and, in consequence, radiation of heat into the room increases.

A principal object of the present invention is to provide an improved blind adapted to improve the solar shielding effect and thereby to eliminate the abovementioned problem encountered by the prior art.

According to the present invention, the foregoing object is achieved by coating each slat board with film adapted for selective radiation of a predetermined wave length. As a result the thermal radiation into the room is controlled.

The invention will now be further described with reference to the accompanying drawings which illustrate, by way of example, several embodiments of the invention. In the drawings: Fig. 1 is a sectional side view illustrating an embodiment of a blind constructed according to the present invention; Fig. 2 is a section illustrating by way of example selectively transmissive film; Fig. 3 is a diagram plotting by way of example light transmissivity of a reflective film in the above-mentioned embodiment; Fig. 4 is a diagram plotting by way of example light transmissivity and reflectivity of the selectively transmissive film in the same embodiment; Fig. 5 illustrates an air conditioner system arranged when a blind according to the present invention is installed on the room side;; Figs. 6(a) and (b) are sectional side views illustrating another embodiment of a blind constructed according to the present invention; Fig. 7 is a diagram plotting by way of example light transmissivity of a reflective coating in the embodiment of Fig. 6; and Figs. 8 and 9 are sectional side views illustrating further embodiments.

Referring to Figs. 1 through 5, reference numeral 1 designates a slat board of the blind, of which the inner side or the room side is coated with selectively absorptive or transmissive film 2 having a relatively low long wave emissivity.

Said film 2 when constructed in the form of selectively transmissive film may be formed on the surface of the slat board in various manners as follows: (1) the slat board is coated by vacuum metallizing or spattering with inductive material such as MgF2 having a relatively low refractive index and serving as anti-reflection film; (2) a surface of glass or like is selectively etched to form a surface layer presenting a relatively low index of refraction; (3) metallic film having a high reflectivity in the infra-red range is sandwiched between inductive layers to improve the transmissivity within a visual range; and (4) "Drude Mirror" method utilizing cut off effect due to plasma oscillation of free carrier in a semiconductor having a band cap sufficient to be transparent within a visual range (3eV or higher).

Fig. 2 illustrates, in section, a selectively transmissive film 2 comprising a protective film layer 3a as made of polypropylene or polyethylene, a transparent heat ray reflecting layer 3b, polyester film 3c, an adhesive layer 3d, and release film 3e.

Although it is not a feature essential to the present invention, the outer surface of the slat board or the surface thereof upon which the solar radiation is incident may be coated with the heat radiation reflecting film 3 having a high solar radiation reflectivity.

Such reflecting film 3 comprises base film as made of polyester having aluminium va cuum metallized thereon and a polyester layer placed thereon to form said reflecting film (e.g. the reflective film as commercially avail able under the trade mark "SUNSHADE") and may be bonded to the surface of the slat board 1 by means of suitable adhesive agent or welding.

Now the operation and function of the blind according to the present invention will be de scribed. Although a major part of the solar radiation incident upon the slat boards 1 of the blind is reflected by the reflective film 3 outwardly, the remainder is absorbed by these slat boards 1, increasing the temperature thereof. In consequence, the surface of each slat board 1 facing the room emits corresponding radiant heat 4 towards the room.

However the coating 2 covering this surface of each slat board 1 has a low emissivity in spite of its high long wave reflectivity, so that an emission of the radiant heat 4 towards the room is effectively suppressed and the solar heat radiation or the outdoor heat is substantially prevented from entering the room particularly in high summer.

In the winter season, on the other hand, the warmth within the room is reflected back by the coating 2 and thus the heated air within the room is prevented from flowing out into the outdoors.

When the sunshine control film having aluminium vacuum metallized thereon is used as the reflecting film 3, an infra-red transmissivity in the order of 10% and a reflectivity of 70 to 80% are achieved, as seen in Fig. 3, in which a broken line represents a curve obtained in the case of glass not coated with film.

When the polyester film, spattered with the transparent heat radiation reflecting layer is utilized as the coating 2, a visual ray transmissivity in the order of 65%, a near infra-red ray reflectivity also in the order of 65%, and a far infra-red ray reflectivity in the order of 85% are observed, as seen in Fig. 4.

It should be noted that a following relationship: transmissivity (T) + reflectivity (R) + absorptivity (A) = 100% is established.

For a wave length of 9.siam, T = O, R = 85, A = 100 - (0 + 85) = 15, s(emissivity) = 0.15 and Radiation = efts4 Where Ts represents an absolute temperature (K) of the slat board and a represents Stefan-Boltzmann's Constant.

The reflecting film 3 and selectively absorptive or selectively transmissive coating 2 may be formed as thin as possible to transmit the visual rays while the desired reflectivity and emissivity are maintained. Thus, the base of the slat board or like may be of transparent material such as polycarbonate, acrylic or glass and such transparent base may be covered with said reflecting film 3 and said coating 2 in order that a person can see the outdoors from the room through the blinds, without any substantial obstruction of vision.

As has previously been mentioned, both the reflecting film 3 and the coating 2 have their transmissivities for visual rays so high that, even in the case of coloured slat boards, this colour is not deteriorated by the reflecting film 3 and coating 2.

When such blind is installed on the room side of the window, the heat partially ab sorbed by the slat boards of the blind is certainly prevented from being emitted towards the room but emitted outwardly, i.e., towards the window glass with a result that a quantity of air within a space defined between the window glass and the blind is correspondingly heated. In view of this phenomenon, it is further preferred to exhaust this quantity of air to the exterior of the room by suitable means such as a fan.

Fig. 5 illustrates an example of such a case.

Reference numeral 5 designates an office room in which a window glass 6 is provided on its inner side with a blind 7 comprising said slat boards 1. An end of a duct connected with an exhaust fan 12 communicates with an upper extension of an exhaust slit 8 provided along the window in said space defined between the window glass 6 and the blind 7.

Reference numeral 11 designates an air conditioner, 9 an air outlet for air conditioning, 13 an exhaust gallery and 10 a changeover damper.

Figs. 6(a) and (b) illustrate another embodiment of the present invention, in which, as a measure to suppress heat radiation directed towards the room, a long wave radiation in a predetermined wave length range is effected to reduce a temperature of the slat boards themselves.

More specifically, the respective slat boards are covered on their outer surfaces or their surfaces upon which the solar radiation is incident with a coating 12 having a selectively radiative characteristic.

This slat board 11 is preferably reflective and this is achieved, for example, by metallic material having a high reflectivity over a range from the visual range to the long wave range such as aluminium, or another slat board 14 or the previously mentioned slat board 1 coated on the outer side with aluminium or said sunshine control film. In the latter case, the slat board may be perforated in a pattern so as to allow a view of the outdoors.

Said coating 12 may be film made of fluoric resin such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl flouride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, chlorotrifluoroethylene-ethylene copolymer and may be bonded to the surface of the slat board 11 by means of adhesive agent or welding.

It is also possible to coat the surface of the slat board 11 with said fluoric resin in liquid form.

Although a major part of solar radiation incident upon the respective slat boards of the blind is reflected by these slat boards 11, the remainder thereof is absorbed by the slat boards, resulting in increasing temperature of the latter.

When tetrafluoroethylene-hexafluoropropylene copolymer (FEP) (commercially available under the trade name of Neoflon) is used as material of the coating 12, a selective long wave radiation 13 outstandingly occurs towards the sky from the surface of said coating 12 particularly in a range from approximately 8 to 13 ,um wave length in which range the atmospheric air has a relatively high transmissivity, as seen in Fig. 7. In consequence, the temperature of the slat boards 11 and the coating 12 themselves is reduced and the long wave radiation directed towards the room is also reduced. It should be understood that a brokenline in Fig. 7 plots the case of non-processed glass.

Such function as mentioned above will now be described more specifically. It is well known that the earth's surface is cooled by so-called radiant heat exchange with cold atmospheric air of the upper air region to a temperature several degrees lower that the atmospheric temperature, causing frost or morning dew. Such phenomenon of radiant cooling has empirically and traditionally been utilized in the cities of Middle and Near East countries as a natural but tactful method of air conditioning the scorching heat of daytime under a coolness holding-over effect of building bodies.

It is notable in connection with the abovementioned fact the the wave length distribution of the atmospheric radiation includes a region commonly referred to as "atmospheric window" at approximately 8 to 13 m, in which range the atmospheric radiation is lower than that of a black body at the same temperature. Thus, a surface adapted to emit radiation selectively at approximately 8 to 13 itm as in the case of said atmospheric window may be utilized to achieve a cooling effect at a considerably low temperature.

It is evident that a further improved effect can be achieved by providing the slat board 11 on its surface facing the room with said coating 2.

In both the first embodiment and the second embodiment, a shielding effect of the slat boards 1, 11 is improved when the slat boards constituting the respective blinds are in contact with one another as closely as possible as the associated blinds are pulled down.

To achieve such effect, it is also possible that a plurality of slat boards 11 carried by ladder cords in the form of vertical steps are formed from synthetic resin by extrusion so that each slat board 11 has a corrugated cross-section of which the thickness progressively increases from one edge to the opposite edge of the cross-section to define a thinner side 1 1a and a thick side 1 it, as shown in Figs. 8 and 9. In this way, the slat board 11 has its centre of gravity offset from the middle point to the thick side 11 b as seen in Fig. 8.Therefore, when the slat board 11 is angularly adjusted with its thick side 11 b directed downwardly, as shown in Fig. 9, the slat board 11 can be easily rotated substantially to its vertical position at which only an extremely small gap is left between each pair of adjacent slat boards 11 and thus a substantially reliable shielding effect is obtained.

Although the description hereinabove is made with respect to slat blinds, the present invention is not limited to such blinds but applicable also to the internal sunshine shields such as curtain and roller blinds, the external sunshine shields such as louvre and pent roof, and various types of window. The term "blind" as used herein is to construed accordingly in a broad sense wherever appropriate, particularly in the clai-ms which follow.

As will be clear from the foregoing description, a blind constructed in accordance with the present invention effectively suppresses thermal radiation towards the room so that the sunshine shielding effect may be sufficiently increased to keep the room cool even in summer, on the one hand, and reflects warm air within the room back towards the room so as to keep the latter warm even in winter.

Furthermore, it suffices to coat the slat board on its opposite surfaces and, therefore, not only can the manufacturing costs be reduced but handling is also facilitated.

Claims (5)

1. A blind comprising a plurality of slat boards each of which is coated with film adapted for selective radiation of a predetermined wave length.

2. A blind according to claim 1, wherein said film comprises selectively absorptive or selectively transmissive film of a low emissivity for long wave lengths and covering the inner surfaces of said slat boards.

3. A blind according to claim 1 or claim 2, wherein said film comprises selectively emissive film made of fluoric resin and covering the outer surface of the slat board.

4. A blind constructed and arranged substantially as herein particularly described with reference to Fig. 1, Fig. 2, Fig. 5, Fig. 6a and 6b, or Figs 8 and 9, of the accompanying drawings.

5. A blind coated with film adapted for selective radiation of a predetermined wave length.