Improved roman shades

Abstract: An improved expandable and contractible window covering comprising an assembly of elongated cells (2) is disclosed. Each cell (2) is formed by folding a strip of material and joining the opposed edges to the next adjacent cell. The rear wall (13) of the cell is less wide than the front wall (11) of the cell (2), and the material of the cell is chosen to be relatively soft and flexible, so that the front wall (11) of each cell droops downwardly and outwardly away from the rear wall (13).

Description: This invention relates to an improved window covering. Several publications show cellular shades, wherein a fabric material is formed to define parallel tubular cells extending horizontally across the width of the shade. Air within each of the cells only circulates minimally, such that when expanded the shade provides good thermal insulation. It is of course desirable to make the physical appearance of the shade as attractive as possible. Similarly, it is desirable to make such shades as economically as possible, which requires both that a minimal amount of material be used to form each cell and that the manufacturing process be as expeditious as possible. FR-A-1568745 discloses a screen wherein a plurality of strips of a fabric material are folded about fold lines extending longitudinally and bonded together, the two edges of each strip being bonded to the centre of the successive strip, to form a shade consisting of a plurality of tubular cells. This screen is intended to be used such that the cells extend vertically, and discloses symmetrical cell shapes only. US-A-4347887 shows a "thermal shutter". A wide band of material is folded transversely to form a double row column of adjacent cells, which may have rounded visible contours and is symmetrical, so that both sides of the shade thus formed have essentially the same appearance. The cells are adhesively bonded to one another. US-A-4450027 shows a method and apparatus for fabricating a multiple cell shade wherein a continuous relatively narrow strip of fabric is sharply creased longitudinally in order to define pleats in the shade material to facilitate the formation of the cells. A U-shaped cell structure is thus formed and successive cells are assembled by applying an adhesive to opposed edges of the folded strips, and adhering each formed strip to the strip making up the next preceding cell. US-A-4631217, 4676855 and 4677013 show in Figure 3 a shade of asymmetrical construction. A rear wall section of each cell is essentially straight or linear when the shade is in its expanded position. The width of these rear wall sections thus defines the spacing of the adjacent cells, while the front of each cell, containing more material, maintains a non linear shape. The shade is formed by assembling horizontal parallel cells, in which the cell structure is formed from a material folded into a Z-shape rather than from a U-shaped material. US-A-4846243 shows a foldable window covering formed of a wide relatively soft material folded transversely, as in US-A-4347887, to yield a collapsible shade. The front surface of the shade consists of a number of drooping loops formed by doubling the material back on itself. The successive cells are spaced in the expanded position of the shade by a relatively vertical rear wall section of each cell. This construction is relatively complex and requires a large amount of material per cell. Furthermore, since the shade is formed of a wide strip of material folded transversely, this limits the width of the shade which can thus be formed to the width of the stock material available. It is an object of the invention to provide an improved window covering which is inexpensive and of pleasing appearance. According to the invention there is provided an expandible and contractible window covering comprising an assembly of an integral single row of parallel generally tubular cells, with the longitudinal cell axis generally perpendicular to the direction of expansion and contraction, each cell being formed of at least one individual elongate strip of flexible material, the length of each strip being at least equal to the width of the assembly, a top portion of each cell being attached along its length to the bottom portion of the adjacent cell thereabove, where present, characterised in that a front wall portion of each cell defines, together with the bottom wall portion, a smoothly curved loop drooping downwardly at least to the level of the juncture of each cell with the adjacent cell therebelow, where present, when said window covering is in the expanded state. Each cell may be formed of a single narrow strip of relatively soft flexible material. The strip of material is folded into a cell structure and bonded to one or more adjacent and similar cell structures to make up the assembly of cells. Each cell may include a rear wall portion, which is substantially vertical or linear when the shade is in its expanded state, a bottom portion extending forwardly from the back wall, and a front wall portion defining a generally drooping curved surface extending in a curve from the front top portion of the cell downwardly and away from the rear wall portion. The cell front surface provides an extremely attractive appearance. The shade may be manufactured generally using the known techniques and apparatus, from a relatively narrow strip of material, such that a shade of any desired width can be manufactured. In order that the present invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings in which:- Figure 1 shows a first embodiment of the shade of the invention in its nearly collapsed state; Figure 2 shows the shade of Figure 1 in its expanded state; Figure 3 shows a cross-sectional view through a portion of the shade of Figure 1 in the expanded state showing the individual cell structure of the shade; Figure 4 shows a cross-sectional view of the embodiment of Figure 1 in the nearly collapsed state; Figure 5 shows a cross-sectional view of further embodiments of the invention; Figure 6 shows schematically a modification to the manufacturing technique which is used in fabrication of the shade of the invention; Figure 7 shows a cross-sectional view of another embodiment of the invention; Figure 8 is a plan view of a suitable apparatus for fabricating the shade structure according to the method of the present invention; Figure 9 is a cross-sectional view, taken along lines 9-9 of Figure 8, of the strip material used to form the cell structure of Figure 3, after an initial folding step; and Figure 10 is a cross-sectional view, similar to Figure 9, of the strip material used to form the cell structure of Figure 7, after an initial folding step. As seen in Figures 1 and 2, the shade comprises an assembly 1 made of a plurality of parallel cells 2 extending horizontally. The assembly of cells 2 is fitted with a bottom rail 3 and a head rail 4 (omitted from Figure 2 for clarity). The assembly is adapted to be fitted into a window opening, for example, with the longitudinal cell axis at an angle of 90° with respect to the direction of expansion and contraction of the assembly. The motion of the shade between the collapsed state of Figure 1 and the expanded state of Figure 2 is controlled by two or more control cords 5 extending from the bottom rail 3 upwardly through the cells 2, and into the head rail 4. The cords are directed by generally conventional control pulleys, guides and the like, and are engaged by a conventional locking dog engaging mechanism (not shown). As can be seen from Figures 3 and 10, each cell 2 is formed of a strip of material 6 folded longitudinally and bonded at its longitudinal edges to a bottom portion of the next upper cell. In this way, each strip of material is formed into a tubular cell with open ends. As typically used, these shades are disposed between opposed surfaces of the casing of a window. The width of the shade is preferably chosen so that the ends of the cells approach the casing closely, such that little air flow takes place through the cells. In this way the air mass in each cell is essentially static, whereby the cells of air form a very effective thermal insulation. According to this embodiment of the present invention, each strip of material is formed into a cell 2 having a top rear edge portion 7 which is bonded by a bead 8 of adhesive to the directly adjacent upper cell 2 (or to the head rail 4). A rear wall portion 9 extends downwardly from the top rear portion 7, and a bottom portion 10 extends forwardly from the rear wall portion 9 to a front wall portion 11. The front wall portion 11 extends forwardly from the bottom portion and then upwardly to a top front edge portion 12. The top front edge portion is adhesively bonded by a second bead 8 of adhesive to the cell bottom portion 10 of the directly adjacent upper cell 2 (or to the headrail 4). The formed cell in cross-section effectively defines a continuous closed loop of strip material. The basic method of forming the assembled cell structures of the embodiment of Figure 3 includes an initial step of folding the strip of material 6 into a tubular form as shown in Figure 10. The method is fully disclosed, most particularly at column 4, line 4 to column 9, line 55, of US-A-4450027, the disclosure of which is incorporated herein by reference. According to the invention, it is desirable that the cell be asymmetrical in that the front wall portion 11 be substantially wider (as measured in the vertical direction of the final window covering, i.e., at 90° to the longitudinal axis of the cell) than the rear wall portion 9. Also, it is preferred that the entire strip be formed of a relatively soft and flexible fabric material so that in the expanded position shown in Figure 3, the front wall portion 11 droops downwardly and outwardly away from the rear wall 9, forming a smoothly rounded curve. Typically, the lowest part of the front wall portion is level or beneath the juncture of the cell with the directly adjacent lower cell. This provides an extremely attractive appearance. Typically, the plane in which the two adhesive bonds 8 lie is inclined downwardly from back to front of the cell so that the rear bond is higher than the front bond (see Figure 6). It is further preferred that the front wall portion not be creased perceptibly when the shade is in use, principally for aesthetic reasons. However, as discussed below it may be desirable in some embodiments to form a temporary crease in the front wall portion 11 to assist in fabrication of the shade. As also indicated in Figure 3, the rear wall portion 9 may include a longitudinal crease 13 extending generally along its centre. Such a crease can be formed by pressure and heat applied during the formation of the strip into a cell, see US-A-4450027. The crease 13 serves to provide a reference surface by which the strip of material can be guided during the fabrication process and also guides the collapse of the cell, such that the cells collapse uniformly and evenly. In the expanded state of the shade of the invention shown in Figure 3, the width of the rear wall 9 effectively defines the extent of expansion of the cells 2. In this way the cells 2 are of uniform width from the top to the bottom of the shade, and the curvature of the front wall portion of the cell is thus determined and gives a uniformity of appearance. Figure 4 shows the shade of Figure 3 in the nearly collapsed state. If used, the creases 13 at the rear of each cell serve to ensure uniform collapsing of the cells. The drooping front wall portions 11 of each cell extend substantially over the next lower cells. In some embodiments, the rear crease 13 may not be desirable. As shown in Figure 5, creases 14 an 15 are provided at both of the junctures of the rear wall portion 9 with the top and bottom portions of the cell. These creases serve as a guide during the manufacturing process. In the finished shade, these creases 14 and 15 will not be as evident as the single crease 13. In other respects, the structure of Figure 5 is the same as that of Figure 3. Preferably, the cells each comprise smooth and uncreased curved front wall portions 11, and in which permanent creases are avoided during assembly. In the conventional process of US-A-4450027, each strip of material can be typically creased longitudinally to create front and rear edge portions which essentially meet each other. Next, beads of adhesive are applied along the edges of the creased strips of material, and they are stacked, one on top of the other, on a stacking arm. Pressure is applied to ensure that the adhesive bond is properly formed. According to the present invention, it is desired to avoid flattening of the cells which would prevent the front wall portion 11 from remaining smooth and uncreased. Figures 6 and 8 of the present application show the apparatus of US-A-4450027 as used in accordance with the present invention. As shown in Figure 9, a supply of foldable material is provided by the roll 17, and a length 6 of material is directed around the guide roller 18 and through an alignment block 19, which block functions to keep the length of material in proper alignment for the initial creasing of the material. creasing, to the extent desired as discussed above, is initiated by the creaser assembly 20, which includes a backing roller 21 disposed on one side of the length of material 6 and a crease wheel 22, which has a sharp peripheral surface. As the length of material 6 passes through the creaser assembly, a crease 13 is formed in the material on one side thereof. After leaving the creaser assembly 20, the length of material 6 is fed through a folding mechanism 23, which folds the length of material longitudinally along the crease line 13 and to fold the longitudinal edge 7 over one side of the length of material. The longitudinal edge 12 is at the same time folded over the one side of the material with or without a permanent or temporary crease, as desired. This folding of the edges is done progressively as the length of material is fed through the folding mechanism 23. The folded condition of the length of material as it exits from the folding mechanism 23 is shown in Figure 9 to be generally in a U pattern and the folded edges generally meet but do not overlap. After folding of the material, it is directed through a crimper assembly 24 which comprises aligned facing crimp rollers 25 and 26, which overlie the desired fold lines tightly to press and squeeze the material so as to form a permanent fold along these lines. Depending on the nature of the material, this crimper may or may not be necessary. Where the material has the characteristics of the polyester film material disclosed in US-A-4450027, the crimper assembly 24 would be utilized. Also with such material, the fold can be assured of being permanently set by further passing the folded material around the peripheral surface of the roller 22 which is heated. This roller and the cooperating press rollers 28 and 29 apply rolling pressure across the entire width of the material to set the desired crimps permanently at a sharp angle. Again, the roller structure 28 and 29 need not be included where the material does not require its use. Further, other structures may be used, provided that the fold lines are properly set to maintain the angular configuration shown in Figures 3 and 5. Also in the situations where it is not desirable to have permanent folded lines in both or either of the faces of the final structure, the various crimp and press rollers will be eliminated in the appropriate areas. An adhesive applicator 30 applies progressively in two continuous lengths, to provide the two beads 8. With the asymmetrical structure, the lateral width of the two lengths of adhesive will, in effect, be offset from the centre plane on the structure. This is produced by folding the longitudinal edges of the length of material over onto the centre portion of the length by different width distances. With reference to Figure 9, the longitudinal edge of 7 of the length of material is folded along a fold line 13 and over a width less than the folding of the longitudinal edge 12. After the adhesive beads 8 are applied, the material is directed around suitable guide rollers 31, 32, 33 as in US-A-4450027. From the last guide roller 33, the material is led to a stacking area where it is wound about a stacking arm 34 and into a continuous loop with successive portions of the length overlying preceding portions. This forms a plurality of adjacent stacked layers of folded length of material on the stacking arm. During this stacking operation, the lengths of adhesive beads 8 on the folded material are pressed into engagement with the facing side of the folded material to connect them together and form adjacent connected layers. Figure 6 shows schematically, in part, the construction of the stacking arm 34 which allows the front wall portion of the cell to be smooth and uncreased. A spacer member 35 is located on the arm 34 so as to support the strips of material only in the vicinity of the adhesive bonds as they are being formed. A presser member 36 is provided to ensure good bonding. As shown, the lower surface of the stack of strips is spaced away from the stacking arm 34 by the spacer 35, providing room for the looped surfaces of the front wall portions 11, such that they are not creased. A guide 37 is incorporated against which the creases 13 (if used) engage during the assembly process, to ensure that the stack is formed neatly and the shade is properly assembled. The embodiments of the invention shown in detail in Figures 3-5 all relate to modification of the basic process of US-A-4450027, wherein the strip of material is formed into a generally tubular form prior to formation of the final shade structure. Figure 7 shows a modification of the process shown in US-A-4631217 referred to above, wherein instead of forming a tubular configuration, the strip of material is formed into a Z-shape. More particularly, in the Figure 7 embodiment, each individual cell includes a rear portion 38 and a front portion 39 similar to the rear and front portions of the embodiment of Figure 1. However, the rear portion 38 is creased at 40 and extends to the top rear edge portion 41 similar to the top rear edge portion 7 of the embodiment of Figure 1. The material forming front top portion of the cell does not terminate at the top of each cell, but instead extends into and forms the back wall portion 38 of the directly adjacent upper cell. Similarly, the bottom portion of each individual cell is defined by the material of the front portion as it extends to the adjacent upper cell and by the edge portion 42 of the strip of material. In this embodiment of the invention, the folding and connection of the strip material is such that each individual final cell construction is formed of two separate pieces of material. More particularly, the front wall 39 of each cell, as viewed in cross section in Figure 7, is formed of one piece of material while the back wall 38 of that cell is formed from a separate piece of material. To join the adjacent cells together, the two edge portions of each piece of material are joined to the overlapping parts of the other piece of material by beads of adhesive 8. The process of folding and stacking begins with an initial step of folding the strip material 6 into the Z-shaped configuration shown in Figure 10. The method of US-A-4450027 is employed to produce the cell structures shown in Figure 7, with an additional backing roller 21' and creasing wheel 22', as shown in dotted lines in Figure 9, when desired. Finally, in the embodiment of Figure 7, the front wall portion 39 is formed to be relatively smoothly curved so that it droops downwardly and outwardly away from the rear wall and preferably down over at least a portion of the front of the adjacent lower cell. The rear wall 38 is again essentially straight when the structure is fully expanded, defining the spacing of the cells. As an alternative to forming the cells by folding up a plain flat sheet of material as above, the cells can be formed of an extrudable plastic material. The flattened tubular cell can then be formed directly by extrusion, rather than by folding a continuous strip of material. Such techniques are shown generally in US Reissue patents 31129 and 30254. Such techniques are referred to in the appended claim as formation of the cells from a "shaped" strip of material. In some cases it might also be desirable to use both of these and/or other methods of forming the cells in manufacture of a single shade according to the invention, while maintaining a uniform appearance and satisfactory operational characteristics. In all of the embodiments shown herein, the width of the strip of material is essentially equal to the cross-sectional circumference of the cell, less any gap between its opposed edges. However, it is possible that in some embodiments the edges of the strip may be overlapped and that the width of the strip may be up to two times the actual final circumference of the cell. These techniques may be useful in embodiments of the invention where each strip of material forms portions of two or more cells.

Claims: An expandable and contractible window covering (1) comprising an assembly of an integral single row of parallel generally tubular cells, with the longitudinal cell axis generally perpendicular to the direction of expansion and contraction, each cell being formed of at least one individual elongate strip (6) of flexible material, the length of each strip being at least equal to the width of the assembly, a top portion of each cell being attached along its length to the bottom portion of the adjacent cell thereabove, where present, characterised in that a front wall portion (11, 39) of each cell (2) defines together with the bottom wall portion (10) a smoothly curved loop drooping downwardly at least to the level of the juncture (8, 12) of each cell with the adjacent cell (2) therebelow, where present, when said window covering (1) is in the expanded state. A window covering according to claim 1, characterised in that a rear wall portion (9) of said at least one cell (2) defines a substantially flat surface when said window covering is expanded. A window covering according to claim 1 or 2, characterised in that a permanent longitudinal crease (13) is formed in a or the rear wall portion of said at least one cell to guide and control its expansion and contraction. A window covering according to any preceding claim, characterised in that the front wall portion of said at least one cell include one or more temporary and removable longitudinal crease to shape the front wall portions of the cells during the assembly of said cells. A window covering according to any preceding claim, characterised in that a permanent or temporary longitudinal pleat (16) is formed at least at one of the junctures of the rear wall portion of said at least one cell with top and bottom portions thereof. A window covering according to any preceding claim, characterised in that at least one cell of the assembly is defined by two strips of material (38, 39). A window covering according to claim 6, characterised in that each of said two strips form portions of two adjacent cells. A window covering according to any one of claims 1 to 5, characterised in that at least one cell of the assembly is formed of a strip of material that cross sectionally forms a continuous closed loop. A window covering assembly comprising a window covering according to any preceding claim, characterised in that a head rail to which the cell top portion of the uppermost cell (2) is connected; a bottom rail to which the cell bottom portion of the lowermost cell is connected; and two or more guide cords (5) extending from the bottom rail upwardly through each of the cells and into the head rail. A method of manufacture of an expandable and collapsible window covering according to any one of claims 1-8 from elongate flexible strip material, said method being characterised in that it comprises the steps of: a) stacking successive lengths of said material one on top of another and joining each of said lengths to the next successive length over its length and over part or parts of its width to form adjacent overlying cell members; b) providing temporary longitudinal pleats defining the shape of the cell for convenience in stacking and joining of successive cells; and c) removing the temporary pleats after formation of said assembly. A method of manufacture of an expandable and collapsible window covering, according to any one of claims 1-8, from at least one elongated strip of flat flexible material having longitudinal side edge portions, said method being characterised in that it comprises the steps of: a) folding over the edge portions of said strip material; b) stacking successive lengths of said material one on top of another and joining of said length of material to the next adjacent length of material over its length and over part or parts of its width to form the cell members; and c) supporting only a part of the cell bottom portion of each cell during stacking, said part underlying the location of said joining of the edge portions and spaced from the loop shaped surface of the front wall portion of each cell.

Inventors: ABREW JEANNE MARGARET, SEVCIK THOMAS, ABREW, JEANNE MARGARET, SEVCIK, THOMAS
Applicants: HUNTER DOUGLAS INTERNATIONAL, HUNTER DOUGLAS INTERNATIONAL NV
Application year: 1990
Main classification: E06B9
IPC codes: E06B9, B31D3