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[0001]    This application claims priority from U.S. Provisional Application Ser. No. 60/252,610, filed Nov. 22, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a bottom rail for a covering for an architectural opening such as Venetian blinds, pleated shades, and other blinds and shades. Typically, a blind transport system will have a top head rail which both supports the blind and hides the mechanisms used to raise and lower or open and close the blind. The raising and lowering is done by lift cords which support the bottom rail (or bottom slat). This bottom rail is normally heavier and larger in cross-section, or more rigid, than any of the slats that are intermediate between it and the head rail. The blind may be tilted in the forward direction and in the rear direction. The tilting is typically accomplished with ladder tapes (and/or tilt cables) which run along the front and back of the blind and are also attached to the bottom rail. By shortening one of the tilt cables relative to the other, the corresponding edge of the blind is lifted up, causing the blind to tilt upwardly in the direction of the shortened tilt cable and downwardly in the direction of the extended tilt cable. The lift cords (in contrast to the tilt cables) may run along the front and back of the stack of slats or through slits in the middle of the slats, and are connected to the bottom rail.  
           [0003]    In these constructions, the closure of the blinds (tilting closed) tends to become less effective toward the bottom of the blind. When the blind is fully lowered, all the weight has been lifted off of the lift cords and transferred to the ladder tapes containing the tilt cables. This enables the ladder tapes to have the maximum influence on tilting the bottom rail, which tends to maximize the closure at the bottom of the opening. However, even then, while the shortened cable adjacent to the edge of the blind which is tilted upwardly is under tension, the edge of the blind which is tilting downwardly is under no tension except what little tension gravity can afford, since the tilt cables can only function under tension, but not under compression (you cannot push on a rope). This gravitational influence on the downwardly tilting edge of the blind is partially offset by the ladder tapes, which take some of the weight of each slat away from the extended tilt cable and transfer it to the shortened tilt cable. Thus, the shortened tilt cables support more of the weight and, as a result, tend to stretch more, while the extended cables support less of the weight and thus tend to stretch less. This often results in incomplete closure of the blind.  
           [0004]    This situation is aggravated for a product in which the lift cords run along the front and back of the stack of slats. In this instance, when the blind is fully lowered, once again all the weight has been lifted off of the lift cords and transferred to the ladder tapes. However, as soon as the tilting action is started, the edge of the blind which is tilted upwardly is free to rise, but the opposite edge is not free to go downwardly, because, as soon as it starts to do so, it encounters interference from the lift cable. This stops the downward movement of that tilting edge, and the bottom rail stops pivoting around its center and instead begins to pivot about its now fixed, downwardly tilting edge, therefore lifting the center of gravity of this bottom rail and causing poor closure. Thus, in this type of product, the poor closure is due both to a lack of tension on the ladder tapes on the downwardly tilting edge of the bottom rail, and to the interference by the lift cords with the downward motion of the downwardly tilting edge.  
           [0005]    The Swedish Patent application SE 15427/64 (filed on Dec. 19, 1964) attempts to address this incomplete closure problem by installing a free rolling weight in the bottom rail. As the bottom rail is tilted, the free rolling weight shifts to one edge of the bottom rail, thus putting the extended tilt cable under increased tension caused by the shifting weight. However, this solution does nothing to alleviate the problem caused by the interference by the lift cords with the downward motion of the downwardly tilting edge in the situation where the lift cords run along the front and back of the stack of slats.  
         SUMMARY OF THE INVENTION  
         [0006]    One example of an embodiment of the present invention provides a bottom rail with a shifting weight and lift cords which support the bottom rail while being free to move in the forward-to-rear direction relative to the bottom rail. In this arrangement, the shifting weight in the bottom rail moves to whatever edge is the downwardly tilting edge of the bottom rail and thus, by increasing the weight at that edge, aids in putting the extended tilt cables under tension, enhancing the closure of the blind. Furthermore, because the bottom rail is free to move in the front-to-back direction relative to the lift cords, the lift cords do not interfere with the tilting of the blind. Thus, the blind closes properly, even at the bottom. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a partially broken away perspective view of a blind made in accordance with the present invention;  
         [0008]    [0008]FIG. 2 is a schematic broken away side view of a conventional prior art bottom rail when in the untilted position;  
         [0009]    [0009]FIG. 3 is a schematic broken away side view of the conventional prior art bottom rail of FIG. 2 but tilted closed in one direction;  
         [0010]    [0010]FIG. 4 is a schematic broken away side view of the conventional prior art bottom rail of FIG. 3 but tilted closed in the other direction;  
         [0011]    [0011]FIG. 5 is a schematic broken away side view of the shifting weight bottom rail of FIG. 1 when in the untilted position;  
         [0012]    [0012]FIG. 6 is a schematic broken away side view of the shifting weight bottom rail of FIG. 5 but tilted closed in one direction;  
         [0013]    [0013]FIG. 7 is a schematic broken away side view of the shifting weight bottom rail of FIG. 6 but tilted closed in the other direction;  
         [0014]    [0014]FIG. 8 is a perspective view of a tie off ring used to secure a lift cord to the rod of FIG. 1;  
         [0015]    [0015]FIG. 9 is a partially broken away perspective view of the bottom rail of FIG. 1 before the tie off ring is inserted through a slot at one edge;  
         [0016]    [0016]FIG. 10 is a schematic broken-away front view of the bottom rail of FIG. 1 showing the slot used to feed the tie off ring of FIG. 8 into the bottom rail;  
         [0017]    [0017]FIG. 11 is the same view as FIG. 9, except the tie off ring has been inserted through the slot of FIG. 10;  
         [0018]    [0018]FIG. 12 is the same view as FIG. 11, except the tie off ring has been rotated 90 degrees to align the hole in the ring in readiness to receive the rod;  
         [0019]    [0019]FIG. 13 is the same view as FIG. 12, except it shows the rod being inserted at one end of the bottom rail;  
         [0020]    [0020]FIG. 14 is the same view as FIG. 13, except it shows the rod threaded through the hole in the tie off ring inside the bottom rail;  
         [0021]    [0021]FIG. 15 is the same view as FIG. 14, except it shows the rod totally inserted within the bottom rail, and the ring insertion tab broken off from the tie off ring;  
         [0022]    [0022]FIG. 16 is the same view as FIG. 5, showing a schematic broken away side view of the shifting weight bottom rail of FIG. 1 when in the untilted position;  
         [0023]    [0023]FIG. 17 is similar to FIG. 16, but a plurality of individual balls is used as the shifting weight instead of using a rod;  
         [0024]    [0024]FIG. 18 is similar to FIG. 16, showing a schematic broken away side view of a shifting weight bottom rail when in the untilted position, but the bottom rail is a U-shaped open top bottom rail;  
         [0025]    [0025]FIG. 19 is similar to FIG. 18, showing a schematic broken away side view of the shifting weight bottom rail but using individual balls as a weight instead of a rod;  
         [0026]    [0026]FIG. 20 is similar to FIG. 16, showing a schematic broken away side view of a shifting weight bottom rail when in the untilted position, where the bottom rail is a U-shaped (open bottom) bottom rail with an optional cover;  
         [0027]    [0027]FIG. 21 is similar to FIG. 20, showing a schematic broken away side view of the shifting weight bottom rail but using individual balls as a weight instead of a rod;  
         [0028]    [0028]FIG. 22 is a view similar to the view of FIG. 5, but showing an embodiment in which the lift cord extends around the bottom of the bottom rail and is not fastened to the weight; and  
         [0029]    [0029]FIG. 23 is a view similar to the view of FIG. 5, but showing an embodiment in which the lift cord extends through an eyelet opening in the bottom rail and is not fastened to the weight. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    Referring now to FIG. 1, the blind  10  includes a head rail  12 , and a plurality of slats  14  suspended from the head rail  12  by means of tilt cables  18  and the associated cross cords  19  which together comprise the ladder tapes  21 . (The cross cords  19  are shown in FIGS.  5 - 7 .) Lift cords  16  extend through the head rail and along the front and back of the stack of slats, and are fastened at the bottom slat (or bottom rail)  20 , which is heavier and larger in cross-section, or more rigid, than the other slats  14 . Inside the head rail  12  there are one or more drives or mechanisms to raise and lower the lift cords  16 , in order to raise and lower the blind, and mechanisms to raise and lower the tilt cables  18  to tilt the blind open or closed, as is known in the art.  
         [0031]    [0031]FIG. 2 shows a typical prior art bottom rail  20 A. In this instance, both the lift cords  16  and the tilt cables  18  are fastened to the front and rear edges of the bottom rail  20 A. Since the lift cords  16  do not pass through holes in the slats  14 , there are no holes through which light can pass when the blind is closed, which is an advantage. However, as can be appreciated in FIGS. 3 and 4, as the blind is tilted closed, the downwardly tilting edge  22 A of the bottom rail  20 A is held up by the lift cord  16 , which has a fixed length from the head rail  12  to the edge of the bottom rail  20 A. Since this edge of the bottom rail  20 A is not allowed to drop, but the opposite edge of the bottom rail  20 A is being pulled up, the bottom rail  20 A begins to pivot around its downwardly tilting edge  22 A instead of pivoting around its center. This action tends to raise the center of gravity of the bottom rail  20 A, resulting in poor closure of the blind and an arcing of the bottom of the blind.  
         [0032]    [0032]FIGS. 5, 6, and  7  show one embodiment of a shifting weight bottom rail  20  made in accordance with the present invention. An elongated rod  24 , which acts as the shifting weight, is inserted lengthwise along the central portion of the hollow bottom rail  20 . The lift cords  16  pass through small slotted openings  26  (See FIGS. 10 and 11), which are present at both the front and rear edges of the bottom rail  20 , as will be explained in more detail later, and are attached to the rod  24 . The front and rear lift cords  16  may be directly opposite each other, essentially forming a continuous cord, or they may be longitudinally-spaced from each other. By extending through the slots  26 , the lift cords  16  extend below at least a portion of the bottom rail  20 , in order to support the weight of the bottom rail  20 . As the blind is tilted closed (See FIGS. 6 and 7), the lift cords  16  are brought closer together to each other. The lift cords  16  which are on the upwardly tilting edge of the bottom rail  20  are free to slide through the slotted openings  26 , allowing the rod  24  to fall toward the downwardly tilting edge  22  of the bottom rail  20 . As the rod  24  falls to the downwardly tilting edge  22  of the bottom rail  20 , it allows more lift cord  16  to feed out through the slotted openings  26  at the downwardly tilting edge  22  of the bottom rail  20 , effectively lengthening the lift cords  16  on the side of the bottom rail  20  adjacent to this downwardly tilting edge  22  of the bottom rail  20 . Thus, the bottom rail  20  is allowed to pivot around its center of gravity without being held up by the lift cords  16 , and the rod  24  provides an added weight to put increased tension on the ladder tapes  18  on the downwardly tilting edge  22  of the bottom rail  20  to result in a complete closure of the blind.  
         [0033]    [0033]FIG. 8 shows a tie off ring  28  when it is outside the bottom rail  20 . The tie off ring  28  may be used to secure the lift cord  16  to the weight  24 . The tie off ring  28  includes a head  29  having a substantially annular opening  30  with an inside surface that has a diameter and profile closely matching the outside of the rod  24 , so that the rod  24  can be fed through the annular opening  30 . A small slotted recess  32  extends from the annular opening  30  and is used to secure the lift cord  16  to the tie off ring  28 . In order to secure the lift cord  16  to the tie off ring  28  an enlargement (not shown) such as a knot is secured to the lift cord  16 , and then the lift cord  16  is slid through the slot  32 , with the enlargement trapped behind the slot  32 . Once the rod  24  is fed through the opening  30  of the tie off ring  28 , the lift cord  16  will be secured to the tie off ring  28 , since the enlargement on the cord  16  will not allow the lift cord  16  to be pulled out. The tie off ring  28  also has a handle  34  which has a narrow neck  36  at the point where the handle  34  joins with the head  29 . The neck  36  is a weak link, designed to break away in order to readily separate the head  29  from the handle  34 .  
         [0034]    [0034]FIG. 9 shows the tie off ring  28  with the lift cord  16  attached to it just as it is readied to be inserted into the bottom rail  20  via one of the slotted openings  26  on the front edge of the rail  20 . The thickness of the head  29  of the tie off ring  28  is relatively small in relation to its diameter, so that it may be inserted into the bottom rail  20  using a slender slotted opening  26  (See FIG. 10) in the edge of the bottom rail  20 . The dimensions of the slender slotted opening  26  are such that it is just slightly wider than the thickness of the head  29  and it is just lightly longer than the diameter of the head  29 . The slotted openings  26  are oriented with the long direction in line with the longitudinal axis of the bottom rail  20  and centered vertically in the edge of the bottom rail  20  because this minimizes the adverse effect on the strength of the bottom rail  20  by making such slotted openings  26 . When the bottom rail  20  is in a vertical position, it has a very strong beam strength, but when it is in a horizontal position the beam strength is minimized. The slotted openings  26  preferably are located in its neutral web in order to minimize the impact on the beam strength.  
         [0035]    [0035]FIG. 11 shows the tie off ring  28  inserted into the bottom rail  20 , with the head  29  having passed through the slotted opening  26 , but the handle  34  still extending out of the slotted opening  26  at the front edge of the bottom rail  20 . The lift cord  16 , which is secured to the head  29  of the tie off ring  28 , is also extending out of the front edge of the bottom rail  20  through the slotted opening  26 .  
         [0036]    [0036]FIG. 12 shows the tie off ring  28  rotated  90  degrees, by rotating the handle  34  about its longitudinal axis. This is done to line up the annular opening  30  with the rod  24  which is inserted from one end of the bottom rail  20  as shown in FIG. 13. FIG. 14 shows the rod  24  after it has been inserted through the annular opening  30  of the tie off ring  28 .  
         [0037]    Once the tie off ring  28  is secure around the rod  24 , the handle  34  is twisted until it snaps off at the weakened point  36 . The handle  34  then is removed through the slotted opening  26 . The head  29  remains attached to the rod  24 , and the lift cord  16  remains attached to the head  29  (and thus now also attached to the rod  24 ). The lift cord  16  then extends out of the bottom rail  20  via the slotted opening  26 . This same process is repeated for as many lift cords  16  as are deemed necessary for a particular blind, and these lift cords may be attached from either edge of the bottom rail  20 , either the front edge facing the room or the rear edge facing the wall. End caps (not shown) may be installed at the ends of the bottom rail to hide and confine the rod  24  within the bottom rail  20 . After the ladder tapes  18  are connected to the edges of the bottom rail  20 , the assembly is ready to operate in the manner which was described earlier. As the blind is tilted closed, the bottom rail  20  pivots around its center of gravity. The bottom rail  20  is not impeded by the lift cords  16 , since the lift cords  16  are freely movable in the front-to-rear direction relative to the bottom rail and move with the weight  24 . The rod  24  provides an added weight to put increased tension on the ladder tapes  18  on the downwardly tilting edge  22  of the bottom rail  20  to result in a complete closure of the blind as shown in FIGS. 6 and 7. When the blind is tilted open, the action is reversed. The bottom rail  20  once again pivots around its center of gravity, and the rod  24  moves to a position midway between the two edges of the bottom rail  20  as shown in FIG. 5.  
       ALTERNATE EMBODIMENTS  
       [0038]    [0038]FIG. 16 depicts the first embodiment of the present invention, with a rod  24  inserted longitudinally inside the bottom rail  20 , and the lift cords  16  attached to the rod  24  by means of the tie-off ring  28 , as already described above. FIG. 17 depicts the same bottom rail  20  but, in this instance, the shifting bottom weight is made up of a plurality of discrete short rods or spheres  24 A. Thus, at each location where lift cords  16  enter the bottom rail  20 , a single short rod or sphere  24 A may be placed, and the lift cords  16  are secured to these short rods or spheres  24 A. These short rods or spheres  24 A will likely be of larger diameter than the single rod  24  of the preferred embodiment in order to have sufficient weight to aid in the proper closing of the blind  10 .  
         [0039]    Since the previously described means for tying off the lift cords  16  to the rod  24  using the tie-off ring  28  will not work for individual spheres  24 A, an alternate method for tying the lift cords  16  is employed. If the bottom rail  20  is a “one-piece”, enclosed design, as in FIG. 17 (this one-piece design does not count the optional end caps at the ends of the bottom rail  20  as additional pieces), then the lift cords  16  may be “fished” through to the end caps of the bottom rail  20 , where they are secured to the spheres  24 A before being inserted back into the bottom rail  20 . Alternately, the spheres  24 A may be modified so that a tie-off hook (instead of the tie-off ring  28 ) may be latched onto the sphere  24 A through an opening in the bottom rail  20 .  
         [0040]    Other solutions to the problem of tying off the lift cords  16  to the rod  24  or to the spheres  24 A are offered in FIGS.  18 - 21 . FIG. 18 depicts a “one-piece” hollow bottom rail  20 A which is a U-shaped “open top” bottom rail. Using this open top bottom rail  20 A eliminates the need for using the tie-off ring  28 , since the bottom rail  20 A is now open, and thus the rod  24  or spheres  24 A (See FIG. 19) are readily accessible for securing the lift cords  16  to them. FIG. 20 depicts a “one-piece” hollow bottom rail  20 B which is U-shaped and is open on the bottom (instead of on the top as was the case in FIGS. 18 and 19 with bottom rail  20 A). This new “open bottom” bottom rail  20 B offers the same accessibility for securing the single rod  24  or plurality of individual weight elements  24 A to the lift cords  16  without the need for the tie-off ring  28 . An optional cover  20 C (See FIGS. 20 and 21) may be snapped onto the rail  20 B in order to enclose the bottom rail so that it resembles the one-piece, enclosed design bottom rail  20  of the first embodiment while still allowing easy accessibility to its interior space. FIG. 21 shows the same arrangement as FIG. 20 but using a plurality of individual weight elements  24 A instead of the rod  24 .  
         [0041]    [0041]FIG. 22 shows an alternate embodiment, in which the lift cords  16  extend around the bottom of the bottom rail  20  in order to support the bottom rail  20  while permitting freedom of movement of the lift cords  16  relative to the bottom rail  20 . In this embodiment, the rod  24  moves freely in the bottom rail  20  as the tilt cables  18  tilt the blind. The lift cords  16  in this embodiment are not secured to the weight  24 .  
         [0042]    [0042]FIG. 23 shows another alternate embodiment, in which the lift cords  16  extend through respective openings in eyelets  25 , which project upwardly from the top surface of the hollow bottom rail  20 D. The lift cords  16  thus extend below a portion of the bottom rail  20 D in order to support the weight of the bottom rail  20 D, while being freely movable relative to the bottom rail in the front-to-rear direction. The weight  24  is freely movable within the rail  20 D and is not secured to the lift cords  16 .  
         [0043]    The embodiments described above are intended for illustration purposes only. They are not intended to show every possible embodiment of the present invention but rather are intended to show some illustrative examples of the present invention. It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention.

Summary:
A covering for an architectural opening is made for better closure, especially adjacent to the bottom rail. A movable weight is mounted on the bottom rail, so that the weight shifts to the lower side of the bottom rail when the bottom rail is tilted. A lift cord is mounted to support the bottom rail while being freely movable relative to the bottom rail at least in the front-to-back direction. The weight helps shift the bottom rail into the desired position, and, by being freely movable in the front-to-back direction, the lift cord does not interfere with the motion of the bottom rail.