It is known to provide blinds constructed from interconnected slats which, in their closed position, are lowered along tracks positioned at the sides of an opening such as a window or door and, in their open position, are rolled around a spindle located in a cavity above the opening. For domestic applications, the slats are commonly made from polymer materials while partly or wholly metallic constructions may be preferred for larger or higher-security applications. Raising and lowering of the blind is typically performed either manually or electrically. All such blinds will be referred to herein generically as"roller blinds".

A typical slat configuration for a roller blind of this type is shown in Figure 1. The blind is made up of a number of similar slats 10, each having a bottom slot 12 and an upper ridge 14. The upper ridge 14 is formed with lateral projections 16 configured to lock within the bottom slot 12 of the adjacent slat 10.

Optionally, upper ridge 14 may feature a row of small holes 18 which allow a very small amount of light transmission and air flow through the blind

when it is not fully closed. However, the area of these holes is very small, typically corresponding to well under 5% of the total area of the blind.

There is therefore a need for a roller blind structure employing connecting slats which are exposed in an open state and concealed in a closed state, thereby facilitating the provision of a significant but controllable amount of light transmission and/or ventilation through the blind.

SUMMARY OF THE INVENTION The present invention is a roller blind structure employing connecting slats which are exposed in an open state and concealed in a closed state.

According to the teachings of the present invention there is provided, a roller blind comprising: (a) a plurality of elongated slats having a length and a height, each of the elongated slats having a front surface and a rear surface interconnected by at least one intermediate rib, the front surface and the rear surface forming therebetween an upper cavity extending downwards from an upper edge of the slat for at least about a quarter of the height along substantially the entirety of the length, the front surface and the rear surface additionally forming therebetween a lower cavity extending upwards from a lower edge of the slat for at least about a quarter of the height along substantially the entirety of the length; and (b) a plurality of connecting slats, each of the connecting slats having an upper portion configured to be slidingly engaged within a lower cavity of a first of the elongated slats, a lower portion configured to be slidingly engaged within an upper cavity of a second of the

elongated slats, and an intermediate portion attached to the upper and lower portions, a distance between the upper portion and the lower portion being at least about a third of the height, such that the roller blind assumes an open state in which a major part of the intermediate portion is exposed between adjacent ones of the elongated slats, and such that the roller blind further assumes a closed state in which the connecting slats are accommodated within the upper and the lower cavities so that the intermediate portion is substantially concealed.

According to a further feature of the present invention, the intermediate portion of each of the connecting slats features at least one ventilation opening configured so as to permit air flow through the roller blind when the roller blind is in the open state.

According to a further feature of the present invention, the intermediate portion of each of the connecting slats features at least one window configured so as to permit transmission of light through the roller blind when the roller blind is in the open state. The window may be implemented as an open aperture, a region of mesh, or using transparent or translucent material.

Preferably, the at least one window extends over a total area corresponding to at least about half of the major part of the intermediate portion which is exposed in the open state. Adjacent elongated slats are preferably separated by at least about half of the height in the open state.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. 1 is a schematic representation of a conventional slatted roller blind; FIG. 2 is a schematic representation of a roller blind, constructed and operative according to the teachings of the present invention, in an open state; and FIG. 3 is a schematic representation of the roller blind of Figure 2 in a closed state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a roller blind structure employing connecting slats which are exposed in an open state and concealed in a closed state The principles and operation of roller blinds according to the present invention may be better understood with reference to the drawings and the accompanying description.

Referring now to the drawings, Figures 2-3 show a roller blind, generally designated 20, constructed and operative according to the teachings of the present invention.

Generally speaking, roller blind 20 includes a plurality of elongated slats 22 having a length I and a height h. Each slat 22 has a front surface 24 and a rear surface 26 interconnected by at least one intermediate rib 28. Front surface

24 and rear surface 26 form between them an upper cavity 30 extending downwards from an upper edge of the slat for at least about a quarter of the height along substantially the entirety of the length, and a lower cavity 32 extending upwards from a lower edge of the slat for at least about a quarter of the height along substantially the entirety of the length.

Slats 22 are interconnected by a plurality of connecting slats 34, each having an upper portion 36 configured to be slidingly engaged within lower cavity 32 of one slat 22, and a lower portion 38 configured to be slidingly engaged within upper cavity 30 of another slat 22. An intermediate portion 40 attaches upper and lower portions 36 and 38 which are separated by a distance of at least about a third of the height h.

The structure is thus configured such that roller blind 20 assumes an open state (Figure 2) in which a major part of intermediate portion 40 is exposed between adjacent elongated slats 22, and a closed state (Figure 3) in which connecting slats 34 are accommodated within upper and lower cavities 30 and 32 so that intermediate portion 40 is substantially concealed.

At this point, it will be readily apparent that the present invention provides connecting slats which may be selectively revealed and concealed, depending upon the state of opening of the blind. By providing these connecting slats with openings or windows, the structure of the present invention may be used to provide highly controllable lighting and/or ventilation properties.

Turning now to the features of the present invention in more detail, it is a particular feature of certain most preferred embodiments of the present invention that intermediate portion 40 of each connecting slat 34 features at least one window 42 which is revealed in the open state of the blind. The window may be configured primarily as a ventilation opening configured so as to permit air flow through the roller blind, or may be primarily for illumination configured so as to permit transmission of light through the roller blind when the roller blind is in the open state. In either case, the window is substantially obscured when the blind assumes its closed state.

Structurally, window 42 may be implemented most simply as an open aperture. Where it is preferred to provide ventilation without allowing insects to enter through the windows, a region of mesh (also known as"screen"or "netting") may be provided. In the latter case, depending upon choice of materials, in may be possible to form the mesh integrally with connecting slats 34. Alternatively, a separate mesh, most commonly of aluminum or polymer material, may be attached by known techniques to cover the windows 42.

In cases in which illumination is required without ventilation, window 42 is typically implemented using transparent material. Examples of suitable transparent materials include, but are not limited to, glass and various transparent plastics. The materials may be tinted as desired. Where illumination is required without compromising privacy, translucent light scattering materials may be used.

In order to maximize the range of illumination and/or ventilation conditions which can be obtained, the at least one window 42 preferably extends over a total area corresponding to at least about half of the part of intermediate portion 40 which is exposed in the open state. Similarly, the intermediate portion 40 itself preferably corresponds to a relatively large proportion of the area of the open blind, preferably in excess of about 30% of the total area. To this end, adjacent elongated slats 22 are preferably separated by at least about half of height h in the open state, corresponding to a height of connecting slats 34 greater than hl2. In a most preferred case, the height of connecting slats 34 is in excess of about 0.7h, or even 0.8h. This requires dimensions of upper and lower cavities 30 and 32 which together define a storage space for connecting slats 34 which extends over in excess of two thirds of height h.

It should be noted in this context that upper and lower cavities 30 and 32 need not necessarily, or even typically, be symmetrical. Thus, upper cavity 30 may be larger than, or smaller than, lower cavity 32, so long as the combined dimensions of the cavities are sufficient to accommodate connecting slats 34.

As mentioned earlier, the roller blinds of the present invention may be made from any suitable materials. Typical non-limiting examples include plastics, aluminum, steel and combinations thereof. Particular significance is noted for high security applications of the present invention where metals or metal alloys are used either as the main structural materials or as reinforcing elements. In this case, both in the open and in the closed states, the blinds of

the present invention provide higher security than offered by sliding or retractable security bars while still allowing an adjustable degree of illumination and/or ventilation.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention.