Abstract:
A covering for an architectural opening comprising: a rail; a covering material, attached to said rail; at least two cords for guiding, supporting and/or lifting the covering material, the cords extending through the rail; and at least one weight disposed within the rail; characterised in that the rail comprises a longitudinally extending front portion, a longitudinally extending rear portion and a longitudinally extending central portion disposed between the front portion and the rear portion, and wherein said at least one weight is positioned at a location remote from the central portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the national stage application of International Patent Application No. PCT/NL2013/000014, filed Feb. 28, 2013, entitled “A Covering For an Architectural Covering”, which claims priority to Netherlands Patent Application No. 2008371, filed Feb. 28, 2012, entitled “A Covering For an Architectural Opening,” which are hereby incorporated by reference herein in their entireties. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a covering for an architectural opening, and in particular a covering which requires extra weight to be incorporated into at least one of the rails of the covering. 
     It is known to add extra weight to a rail of a covering. This may for instance be done to provide extra stability for the rail, so as to prevent it from wobbling during raising and lowering. 
     Applying extra weight to a rail of a covering can also be advantageous in the case of, for example, pleated and/or honeycomb blinds to facilitate lowering of the blind. The extra weight helps to overcome the friction of the cords that run through the pleated and/or honeycomb material. At every hole in the fabric through which these cords pass, some friction is exerted on the cords by the edges of the holes. This friction increases as the material is extended. In a collapsed condition, the pleat/honeycomb material extends substantially perpendicular to the cords. Therefore, in this condition, the cords may not even contact the edges of the holes and the friction will be low. However, as the fabric extends, the angle between the pleat material and the horizontal may go from 0° to for instance 45° or 60° or more and in such cases, the edges of the holes will contact the cords and exert a frictional force thereon. The total friction will of course also increase with the height of the blind, as there will be more holes for the cords to pass through. Inserting extra weight into the lower rail of the blind will help to overcome this friction. 
     Typically, most rails have in essence two longitudinally extending side walls connected together by a central wall. The side walls and the central wall are usually an integral unit formed by extrusion. The edge of the fabric is disposed on one side of the central wall, and the cords (for lifting, guiding and/or supporting the covering material) may extend through the central wall to a cord chamber on the other side. After assembly, the cord chamber, which is bounded by the central wall and the side walls of the rail, may be closed with a cover which can be slid into grooves provided at the end of the side wall. 
     In known coverings, the weight is normally shaped as a metal bar. This bar is attached to the inner surface of the central wall, i.e. the surface that forms part of the boundary of the cord chamber. Known means of attaching the bar to the central wall include glue and other adhesives, double-sided tape, Velcro, for example. 
     This conventional way of applying extra weight, however, has several disadvantages. For example, during transport the weight may become dislodged and may start to slide in the rail. This may cause damage to end caps of the rail that will usually be mounted on either end of the rail. Furthermore, in conventional rails, the location of the weights may not be optimum. This is because the weights have to be positioned such that they do not interfere with the cords which enter the rail via holes in the central wall of the rail. Thus care has to be taken when mounting the weights so as to ensure that the weights do not obstruct the holes and/or the routing of the cords. Accordingly, the positioning freedom of the weights is limited. In some instances, the weights may even have to be cut to fit between adjacent holes. A further consequence is that the weights must be mounted at an early stage of assembly, in any case prior to assembling the cords, because if the weights are mounted afterwards, the cords may become trapped between the weight and the central wall of the rail. However, mounting the weights at such an early stage may be disadvantageous. For instance, an installer may only find out during installation of the blinds that the number of weights is insufficient, or the position of the weights is wrong. In conventional rails, it is difficult to add extra weights at a later stage and it is also difficult to adjust the position of the weights later if required. 
     SUMMARY 
     The present invention aims to alleviate the above problems. 
     According to the present invention there is provided a covering for an architectural opening comprising: a rail;
         a covering material, attached to said rail;   at least two cords for guiding, supporting and/or lifting the covering material, the cords extending through the rail; and   at least one weight disposed within the rail;   characterised in that the rail comprises a longitudinally extending front portion, a longitudinally extending rear portion and a longitudinally extending central portion disposed between the front portion and the rear portion, and wherein said at least one weight is positioned at a location remote from the central portion.       

     Preferably the rail comprises a plurality of chambers. Advantageously a first cord chamber for receiving the lift cords is provided within the rail, the cord chamber being at least partially bounded by the central portion of the rail. 
     The rail is preferably constructed such that it permits an edge of the fabric to be disposed on one side of the central portion, and the cord chamber is located on the other side of the central portion. The central portion has holes provided through it for receiving the cords which extend from the fabric through the holes in the central portion and into the cord chamber, where they may be routed towards and fixed to an adjuster, for example, such as the one disclosed in EP 0 892 144. 
     Advantageously, the weight is located in the second chamber, and the first cord chamber and the second chamber are constructed in a manner which acts to prevent the weight from entering the first cord chamber. 
     This advantageously prevents the weight from touching the cords and thereby hindering their function. Furthermore, by providing a second chamber for receiving the weight remote from the cord chamber, the location of the weight is no longer dependent on the position of the holes in the central portion and the position of the cords. This allows one or more weights to be optimally positioned. The length of the weight will also no longer be limited by the spacing between the holes. 
     In one embodiment of the invention, the front portion and the rear portion of the rail both comprise a rib which extends laterally from said longitudinally extending front and rear portions and which is located remote from the central portion. Ideally the weight is located between the rib of the front portion and the rib of the rear portion of the—rail. This permits the weight to be located along the longitudinal axis of the covering, to help to maintain stability of the rail when the covering is raised or lowered. 
     In another embodiment of the present invention, the weight is positioned adjacent one of said front portion and said rear portion. This results in the rail being imbalanced, in that the weight distribution between the front portion and the rear portion of the rail is no longer equal. This imbalance is advantageously used to correct an imbalance caused, for example, by adding a handle to the rail. If the handle is added to the front portion of the rail, a weight may be added to the rear portion to maintain stability of the rail. 
     The weight may be attached to the rail by means of an adhesive. Alternatively, the weight may be manufactured to a tolerance which permits an interference fit between the weight and the rail. Alternatively, the weight may be clamped in a desired position in the rail. The weight may comprise a bent rod which is inserted into the second chamber. Alternatively, the weight may comprise a spring rod which is bent prior to insertion into the second chamber and which, once inserted, acts to maintain the weight in position in the chamber by exerting pressure on the walls of the chamber. Alternatively, the weight may be provided with two projections, the first projection being for engaging the rib of the front portion of the rail and the second projection being for engaging the rib of the rear portion of the rail. 
     It is desirable, but not essential, that the weight is attached to the rail in a manner that readily allows it to be removed or readjusted. 
     The rail may be provided with a plurality of weights. Advantageously, a weight may be provided at each of the longitudinal ends of the rail. 
     The covering may be of a top down/bottom up type. Such coverings comprise a head rail and two moveable rails, a first rail (known as a top rail) being located in use above the second rail (known as a bottom rail). Advantageously, one or more weights may be disposed in either or both of these rails. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the drawings, of which 
         FIG. 1  shows an isometric external view of an architectural covering incorporating the invention. 
         FIG. 2  shows a cross-section through a rail of a covering for an architectural opening in accordance with a first embodiment of the present invention. 
         FIG. 3  shows a plan view looking in the direction of the arrow A of the rail of  FIG. 2 . 
         FIG. 4  shows a close-up view of part of the weight used in the rail of  FIGS. 2 and 3 . 
         FIG. 5  shows a cross-section through a rail for a covering for an architectural opening in accordance with a second embodiment of the present invention. 
         FIGS. 6 a  and 6 b    show a weight in the form of a rod suitable for use in the second embodiment of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an architectural covering  50  having a bottom rail  52 , a top rail  54  and a covering material, also referred to as covering member  56  extending between these rails  52 , 54  is illustrated. The covering material  56  may for instance be pleated material or honeycomb material. The top edge of the covering member  56  is secured to the top rail  54 . The top rail  54  can be raised or lowered relative to a head rail (not shown). As the top rail  54  is raised, the covering member  56  is extended to cover more of the window. As the top rail  54  is lowered, the covering member  56  is retracted to uncover more of the window. Similarly, the bottom edge of the covering member  56  is secured to the bottom rail  52 , and the bottom rail  52  can be raised or lowered to extend or retract the covering member  56 . Accordingly, the covering member  56  can be extended or retracted to any desired degree between the two rails  52 ,  54 . The top and bottom rail can be independently positioned at any desired location relative to each other. To facilitate manual movement of the top rail and the bottom rail, an optional handle  58  is provided on each rail. A weight is disposed within one or both of the rails, as described with reference to  FIGS. 2-6   b.    
     A rail  1  (which may be a top rail  54  or a bottom rail  52 ) of a covering in accordance with the first embodiment of the present invention is shown in  FIG. 2 . The rail  1  comprises a rear portion  4 , a front portion  2  and a central portion  6  which extends between the rear portion  4  and the front portion  2 . All three portions extend longitudinally along the length of the rail and are formed integrally by extrusion. The top of the rail  1  has a groove  14  for receiving an edge of the covering material. On the other side of the central portion  6 , a cord chamber  12  is provided. The covering may comprises at least two cords, e.g. for lifting and/or supporting the covering material. For each of the cords (not shown) a hole (not shown) is provided in the central portion  6  of the rail  1 . This permits each cord to extend through the fabric down through the central portion  6  and into the cord chamber  12 . Once in the cord chamber  12 , the cords may be routed along some length of the rail, or be connected to some length adjustment means or tensioning means (not shown). Members  18 ,  20  extend perpendicular to the central portion  6  and also define the cord chamber  12 . The lower edges of the rear portion  4  and the front portion  2  are provided with lateral ribs  8 ,  10  respectively. Thanks to such cantilevered arrangement the ribs may exhibit some resilience. A weight  24  is disposed between the ribs  8 ,  10  and is held in position by the ribs  8 ,  10 . Preferably, the weight  24  is held in position through the resilient arrangement of the ribs  8 ,  10 . Members  18  and  20  further act to prevent the weight  24 , should it become loose, from entering the cord chamber  12 . By preventing the weight  24  from entering the cord chamber  12 , the weight  24  will not interfere with the cords. A groove  22  is provided on the lower edges of the rear portion  4  and the front portion  2 . The groove  22  may serve to receive a cover (not shown). 
     During assembly, the cords are first directed through the holes in the central portion  6 . The weight  24  is then inserted into the second chamber  16  and is held firmly in position by the ribs  8 ,  10 . Once the weight has been located in the desired position, a cover (not shown) may be slid into grooves  22  to cover the bottom of the rail  1  along its longitudinal length, and to shield the weight  24  and the interior of the rail  1  from view. 
       FIG. 3  shows a plan view of the weight  24  located in the rail  1  of  FIG. 2 . This is the view that a user would see looking up at the underside of the rail  1 , and is a portion of the rail near to one end of its longitudinal length. Ribs  8 ,  10  are holding weight  24  in position within the second chamber  16  of the rail  1 . Projections  30 ,  32  are provided on the weight  24  for enabling the weight  24  to be tightly held in position by the ribs  8 ,  10 .  FIG. 4  shows the projections  30 ,  32  on the weight  24  in more detail. The projections may for instance be made by coining the surface of the weight  24  adjacent its edges  34 ,  36  so as to locally deform the material. Coining is a form of precision stamping in which the weight  24  is subjected to a sufficiently high stress to induce a deformation on the surface of the weight. A press is used to exert pressure at two locations  26 ,  28  located adjacent the edges  34 ,  36  on the surface of the weight  24 . As a result of the pressure applied, tiny projections  30 ,  32  are formed and extend laterally, to give the surface of the bar a slightly greater width at the location where the projections are formed. The tiny projections  30 ,  32  permit a tight interference fit between the weights  24  and the ribs  8 ,  10  of the rail  1 . Thus, the weight  24  is effectively clamped in position on the rail  1 . If re-positioning of the weight is desired, this can be achieved by simply exerting a downward force on the weight sufficient to overcome the friction between the tiny projections  30 ,  32  and the ribs  8 ,  10  of the rail  1 . In this manner the weight can be easily removed and re-positioned at another location along the length of the rail, if needed. 
     Generally, it is advantageous to provide two weights, one at either end of the rail. This improves the stability of the rail. Of course additional weights may be added to either end of the rail, or to the middle of the rail, or at any position along the rail, as may be required to achieve stability and to facilitate lowering of the blind. 
       FIG. 5  shows a rail which, in structure, is identical to the rail  1  shown in  FIGS. 2 and 3 . The rail  1  of  FIG. 5  has a front portion  2 , a rear portion  4  and a central portion  6  which connects the front portion  2  and rear portion  4 . Central portion  6  has two members  18 ,  20  which extend downwardly and substantially perpendicular to the central portion  6 . Central portion  6  and members  18 ,  20  define a cord chamber  12 . As explained with reference to  FIG. 2 , central portion  6  includes holes (not shown) for receiving the cords (not shown). The rail  1  comprises a groove  14  for receiving an edge of the fabric (not shown). Once the covering is assembled, the fabric will be retained by groove  14  and the cords which extend through the fabric will pass through the holes located in the central portion  6  into the cord chamber  12 . The cords will then extend longitudinally through the cord chamber and might be connected, for example, to an adjuster. In this embodiment, it is not desired that a weight be located along the longitudinal axis of rail  1  for maintaining stability. Rather, a weight  11  is provided in side chamber  7  as a counter-balance to handle  3  which is located in groove  5  of the front portion  2  of the rail  1 . In some blinds and shades, it is desirable to provide a handle for allowing a user to manually adjust the position of the blind or shade. Where very lightweight handles are used, it may not be necessary to provide a counter-balance. However, for aesthetic reasons, it may sometimes be desirable to provide a heavier handle made for example of metal. Such a handle is heavy and may cause the rail to tilt around its longitudinal axis. This is clearly undesirable from an aesthetic point of view. Providing weight  11  at the opposite side of the rail from the handle, i.e. adjacent the rear portion  4 , acts to counter-balance the weight of the handle and thereby prevent the rail from tilting around its longitudinal axis. To accommodate the weight  11 , a side chamber  7  is provided, and is bounded by the rear portion  4  and the member  18  of the central portion  6 . Similarly, another side chamber  9  may be provided on the front portion  2 . In this case the side chamber  9  is bounded by the front portion  2  and the member  20  of central portion  6 . The members  18 ,  20  and the lateral ribs  8 ,  10  act to prevent a weight  11  from falling out of the side chamber  7 ,  9  should it become dislodged. This ensures that the weight  11  is not able to enter the cord chamber  12  and interfere with the cords. As in  FIG. 2 , a groove  22  is provided on the lower end of rear portion  4  and on the lower end of front portion  2  for receiving a cover (not shown). The cover is adapted to be readily slid into the groove  22  and acts to shield the interior of the rail  1  from view. 
     The provision of a weight  11  in either of the side chambers  7 ,  9  may also be desirable when fabrics having an asymmetric cross-section are used in the covering. Some honeycomb-like fabrics have an asymmetric cross-section in that one side of the fabric is more or less straight when in an extended condition while the other side features half a honeycomb profile. This results in an asymmetric force on the rail, which tends to tilt the rail about its longitudinal axis. Again, this is clearly undesirable for aesthetic reasons. To counter-balance this effect, an additional weight may be applied to the opposite side of the rail. 
       FIGS. 6 a  and 6 b    show a rod-shaped counter-balancing weight  11 , suitable for use in the embodiment described in  FIG. 5 . The rods  11  are slightly bent, as can be seen from  FIG. 6   a,  where the dotted lines represent the longitudinal axis of the rod, if it were straight. In use, the rod  11  may be urged into one of the side chambers  7 ,  9  on the side where the counter-balance is required. The rod can be inserted into the side chamber at either of the longitudinal ends of the rail, at whichever location the counter-balance is desired. 
     It will be recognised by persons skilled in the art that it would be perfectly possible to combine both of these embodiments, i.e. to provide a rail  1  which has a counter-balance weight  11  located in the side chamber  7  and furthermore has a separate weight  24  extending between the ribs  8 ,  10  as shown in  FIG. 2 . Such an arrangement can advantageously be used where a counter-balance is required and in addition extra weight is required to allow easy raising and lowering of the blind whilst maintaining stability. 
     Although the weights shown in these examples are of a substantially rectangular or square cross-section, it will be appreciated that weights having a different cross-section may equally be used in this invention. Also, the weights may be fixed in the rail  1  by adhesive means, rather than the clamping means described with respect to  FIGS. 2 and 5 . Similarly, other ways of clamping the weight in position in the rail, such as by providing sprung legs on one end of the weight, may be used instead. Clamping the weight in position has the advantage that the weight can be easily removed and remounted at another location along the length of the rail if required. 
     The chambers can be formed by providing ribs within the inner part of the rail, such as ribs  8 ,  10  or members  18 ,  20 . Of course it will be appreciated that many other geometries are possible in addition to the one shown. 
     It will be recognised that the present invention may be incorporated in blinds having one moveable rail, or instead in blinds of the top down/bottom up variety. Such blinds comprise three rails, namely a head rail, a top rail and a bottom rail. It is envisaged that weights may be provided in either or both of the bottom and the top rail of a top down/bottom up blind. 
     It can be seen that the present invention advantageously allows weights to be positioned in one or more of the lower rails of a blind, without the risk of the weights interfering with the cords. Furthermore, freedom of assembly of the blind is enhanced. The weights can easily be mounted after assembly of the cords and may even be mounted after transport, at the installation site. Also if the number of weights is insufficient, adding extra weights is easy, as is the re-positioning of weights already installed.