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RELATED APPLICATIONS 
     This application is a continuation-in-part of and claims priority from U.S. patent application Ser. No. 09/044,594, abandoned, filed Mar. 19, 1998, incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to window coverings, and more particularly to powered and manual shades. 
     BACKGROUND 
     Roll-up shades are popular window coverings in which a flexible fabric or other material is suspended from a roller tube. In many instances, the roller tube is enclosed in a head rail that is mounted above the window to be covered. The roller tube can be rotated to raise and lower the shade. Thus, in conventional shades, the shade must be raised or lower to change the amount of light passing through the window, and the amount of light passing through the shade itself (per unit area) cannot be altered. 
     Because it is sometimes desirable to alter the amount of light per unit area passing through a window covering, i.e., to alter the opacity of a window covering in addition to raising and lowering the window covering, devices have been introduced which permit altering both the opacity of the window covering and which also permit raising and lowering the covering. Representative of these devices are horizontal mini-blinds, in which louvered slats of a blind can be moved between raised and lowered positions and also can be rotated in concert with each other between open and closed configurations. Rotating the slats alters the amount of light passing through the blind. 
     Similarly, Hunter-Douglas has introduced a roll-up shade device marketed under the name “Silhouette”, in which horizontal strips of fabric are suspended between two sheets of fabric. The strips can be rotated only when the shade is in the fully lowered position to alter the opacity of the shade. Specifically, a mechanism can be operated to lower the shade completely, and then continued operation of the mechanism causes the strips to turn to the closed configuration. To open the strips, the mechanism is operated to raise the shade, which initially causes the strips to rotate to the open configuration. Continued operation of the mechanism raises the roll-up shade. 
     As recognized by the present invention, both mini-blinds and roll-up shades have certain drawbacks. With respect to mini-blinds, two mechanisms are necessary, one for raising/lowering the shade and one for opening/closing the slats. This increases the relative cost and complexity of mini-blinds. Moreover, the amount of light passing through the slats cannot easily be altered as the blind is being raised or lowered, because the slats can become fouled. Furthermore, the slats stack up against the bottom rail as they are raised, further complicating the ability to rotate the louvered slats between open and closed configurations when the blind is between the fully raised and fully lowered positions. 
     With respect to Silhouette™-type roll-up shades, on the other hand, the strips cannot be rotated at all unless the shade is fully lowered. In shade positions above fully lowered, the amount of light passing through the shade per unit area simply cannot be altered. Thus, as a Silhouette™-type roll-up shade is raised or lowered, and when the shade is in any position above the lowered position, the amount of light per unit area passing through the shade itself (i.e., its opacity) cannot be altered. Moreover, because the opacity of the Silhouette™-type roll-up shade cannot be altered unless the shade is fully lowered, the length of the shade must be precisely measured to fit more or less exactly within the structure of the window sought to be covered, and if the length is even slightly longer or shorter than required for the particular window, the shade will not operate. Consequently, Silhouette™-type roll-up shades are frequently mis-sized for the windows sought to be covered, and as a result have a relatively high return rate to the vendor. 
     As recognized by the present invention, however, it is desirable and possible that a window covering alter its opacity as the window covering is being raised or lowered, for pleasing, aesthetic effects. The present invention also recognizes that it is desirable and possible to facilitate altering the opacity of a shade-type window covering when the covering is in any position between fully raised and fully lowered, as might be desired by a user. 
     Accordingly, it is an object of the present invention to provide a window covering that alters its opacity when being raised and lowered. Another object of the present invention is to provide a shade-type window covering in which the opacity can be altered when the shade-type window covering is between the fully raised position and the fully lowered position. Still another object of the present invention is to provide a window covering which presents an aesthetically pleasing appearance when being raised or lowered. Yet another object of the present invention is to provide a window covering that is easy to use and cost effective to manufacture. 
     SUMMARY OF THE INVENTION 
     A window covering includes a roller tube, a stationary holder next to the roller tube, and a shade having opposed first and second ends. The first end is engaged with the roller tube and the second end is engaged with the stationary holder such that the shade forms a looped bight between its ends, the bight essentially establishing the bottom of the shade. A lift mechanism is coupled to the roller tube to selectively rotate the roller tube and thereby move the shade between a raised position, wherein the bight is closely juxtaposed with the stationary holder, and a lowered position, wherein the bight is distanced from the stationary holder. 
     Preferably, the shade defines a pattern, and because of the cooperation of the pattern on the juxtaposed sheets of the shade, as the shade is raised and lowered, the shade moves between low and high opacity configurations. In a particularly preferred embodiment, the shade is established by alternating first and second strips, with the first strips being characterized by relatively high opacity and the second strips being characterized by relatively low opacity. Or, the first strips can be characterized by a first pattern and the second strips can be characterized by a second pattern. The first pattern is different from the second pattern, and this difference can be attributable to the pattern of the first strips being staggered from the pattern of the second strips. 
     As disclosed in further detail below, a rod is disposed in the bight. Also, the lift mechanism can be manually operated, or the lift mechanism can include a motor and at least one battery. 
     In another aspect, a window covering includes a suspension assembly that in turn includes first and second holders. A shade defines a first sheet and the first sheet is suspended from the first holder. In accordance with the present invention, the first sheet terminates at a bight. The shade also defines a second sheet and the second sheet is suspended from the second holder. Like the first sheet, the second sheet terminates at the bight. At least the first holder is operable to raise the first sheet while the second sheet remains stationary. 
     In still another aspect, a window covering includes a double sheet shade suspended from first and second holders, and at least the first holder is operable to raise and lower the shade such that the sheets of the shade move relative to each other. 
     An alternate window covering includes a roller tube, a holder, and a shade having opposed first and second ends. The first end is engaged with the roller tube and the second end is engaged with the holder such that the shade forms a bight between its ends. A rod is disposed in the bight and a shade guide surrounds the rod and shade to guide the shade around the bight. A lift mechanism is coupled to the roller tube to selectively rotate the roller tube and thereby move the shade between a raised position, wherein the bight is closely juxtaposed with the holder, and a lowered position, wherein the bight is distanced from the holder. 
    
    
     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the present window covering in the fully lowered position and low opacity configuration, with portions of the head rail shown in phantom; 
     FIG. 2 is an exploded perspective view of the present window covering between the fully lowered and fully raised positions, in a high opacity configuration, with portions of the head rail shown in phantom and with the spacing bars or rollers removed for clarity; 
     FIG. 3 is a plan view of a shade showing an alternate pattern; 
     FIG. 4 is a cross-sectional view of an alternate embodiment showing the guide tube, as would be seen along the line  4 — 4  in FIG. 1; and 
     FIG. 5 is an end view of an end cap that can be used with the embodiment of the window covering shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, a window covering is shown, generally designated  10 , which includes a suspension assembly, generally designated  12 , from which is suspended a flexible shade, generally designated  14 . As shown in FIG. 1, the shade  14  defines first and second coparallel planar sheets  16 ,  18  that face each other, with a U-shaped bight  19  being established between the sheets  16 ,  18 . The bight  19  is the lower-most part of the shade  14 . As intended by the present invention, the sheets  16 ,  18  are contiguous to each other, with the boundary between the sheet  16 ,  18  essentially being established by the bight  19 . 
     Also, each sheet  16 ,  18  defines a respective top end  20 ,  22  that is engaged with the suspension assembly  12 . As described in detail below, the suspension assembly  12  is operable to raise and lower the shade  14 , and when the shade is being raised or lowered, the sheets  16 ,  18  of the shade  14  move relative to each other. More particularly, the first sheet  16  is translationally moved upwardly while the second sheet  18  (i.e., the portion of the shade  14  between the top end  22  and the bight  19 ) remains translationally stationary, as the shade  14  is raised. Likewise, the first sheet  16  is translationally moved downwardly while the second sheet  18  (i.e., the portion of the shade  14  between the top end  22  and the bight  19 ) remains translationally stationary, as the shade  14  is lowered. As the present invention recognizes, however, as the shade  14  is raised and lowered, the bight  19  is correspondingly raised and lowered and, consequently, the area of the first sheet  16  correspondingly grows smaller and larger. 
     The above-described relative motion between the sheets  16 ,  18  results in altering the opacity of the shade  14  in a pleasing and useful manner. Specifically, the shade  14  defines a pattern as shown in FIG. 1, and owing to the pattern, as the shade  14  is raised and lowered the shade moves between a low opacity configuration, shown in FIG. 1, in which a relatively large amount of light per unit area can pass through the shade  14 , and a high opacity configuration, shown in FIG. 2, in which a relatively small amount of light per unit area can pass through the shade  14 . 
     More specifically, in the preferred embodiment the shade  14  is established by alternating first and second strips  24 ,  26 , each having a width “W”. In the embodiment shown, the first strips  24  are of the same width “W” as the second strips  26 , although it is to be understood that in other embodiments the first strips can have widths “W” that are different from the widths of the second strips and indeed that are different from each other. Advantageously, the shade  14  can be a single piece of fabric that is commercially available in the patterns disclosed herein. 
     In one intended embodiment, dark, opaque diagonal lines  28  are printed, deposited, or otherwise formed on the first strips  24 , such that the first strips  24  are characterized by relatively high opacity. In contrast, the second strips  26  are characterized by relatively low opacity, and in one intended embodiment the second strips are made of colored translucent material or indeed clear transparent material. To increase the opacity of the shade when it is in the high opacity configuration, the first (i.e., relatively opaque) strips  24  have widths “W” that are greater than the widths “W” of the second (i.e., less opaque) strips  26 . 
     With the above disclosure in mind and in cross-reference to FIGS. 1 and 2, it may now be appreciated that as the shade  14  is raised and lowered, the strips  24 ,  26  of the second sheet  18  are respectively moved upwardly and downwardly, whereas the strips  24 ,  26  of the first sheet  16  are substantially stationary. Thus, the strips  24 ,  26  of the second sheet  18  move past the strips  24 ,  26  of the first sheet  16 . 
     When the second strips  26  of the first sheet  16  are juxtaposed with the second strips  26  of the second sheet  18  (FIG.  1 ), the shade  14  is in the low opacity configuration, because light can easily pass through the juxtaposed second strips  26 . On the other hand, when the first strips  24  of one of the sheets  16 ,  18  are juxtaposed with the second strips  26  of the other sheet  18 ,  16  (FIG.  2 ), it can readily be appreciated that the first strips  24  interfere with the passage of light substantially throughout the shade  14 , thereby configuring the shade  14  to have relatively high opacity. 
     Accordingly, the shade  14  can be easily and rapidly moved between the low and high opacity configurations simply by raising or lowering the shade  14  by an amount equal to the width “W” of each strip  24 ,  26 , regardless of the height of the shade  14 . Moreover, the opacity of the shade  14  constantly waxes and wanes in an interesting and aesthetically pleasing way as the shade  14  is moved between a raised position, wherein the bight  19  is closely juxtaposed with the suspension assembly  12  and the shade  14  is substantially rolled up, and a lowered position shown in FIG. 1, wherein the bight  19  is distanced from the assembly  12  and the shade  14  is substantially unrolled. 
     In understanding how the suspension assembly  12  moves the shade  14  as described above, reference is made to FIG.  1 . The preferred suspension assembly includes left and right end caps  30 ,  32  that are attached to, e.g., a window frame at or near the top of the window. Preferably, a hollow head rail  33  extends between the end caps  30 ,  32  and encloses part or all of the suspension assembly  12 . 
     A movable holder, preferably a roller tube  34 , is rotatably engaged with at least one of the end caps  30 ,  32  at one end of the roller tube  34  and, at the other end of the roller tube  34 , the tube  34  is engaged with a lift mechanism. As shown in FIG. 1, the end  20  of the first sheet  16  is attached to the roller tube  34  by adhesive bonding or by mechanical fasteners such as staples. It is to be understood that in the raised position, the shade  14  is substantially rolled up onto the roller tube  34 . 
     The lift mechanism of the present invention can be a manually operated device such as a conventional clutch mechanism  36  that is engaged in accordance with conventional principles with the roller tube  34  to rotate the tube  34  and thereby lift or lower the first sheet  16  and bight  19 . Or, the lift mechanism can be an electrically powered mechanism that rotates the roller tube  34  to thereby lift or lower the first sheet  16  and bight  19 . 
     In one embodiment, the lift mechanism includes a dc motor  38  that is selectively energized by one or more dc alkaline or lithium primary batteries  40 . The motor  38  is gearedly coupled to a collar  42 , and the collar  42  fits snugly within a complementarily configured channel of the roller tube  34  in stationary engagement therewith, such that when the motor is energized the roller tube is rotated. In the preferred embodiment, the structure and cooperation of the motor  38 , batteries  40 , and collar  42  are fully set forth in co-pending U.S. patent application Ser. No. 08/923,812, filed Sep.  4 , 1997 for an invention entitled “Head Rail Mounted Actuator for Window Coverings”, which claims priority from U.S. Pat. No. 5,698,958, both of which are fully incorporated herein by reference. 
     As seen in FIG. 1, the end  22  of the second sheet  18  is fastened to a stationary holder, such as a wall surface or part of the head rail. Part of the second sheet  18  can indeed be used as a valance. Preferably, however, the second holder is a mounting tube  44  that is received on respective left and right support pins  46  (only the left pin  46  shown in FIG. 1) on the respective end caps  30 ,  32 . The mounting tube  44  can be received on the pins  46  in an interference fit that is sufficiently tight to prevent the tube  48  from rotating during normal operation, while allowing a person to manually rotate the tube  48  to establish the length of the shade  10  in the fully lowered position as appropriate for the particular window sought to be covered. Thus, by “stationary” holder is meant a holder that does not move during normal operation of the shade  10 . In any case, it can readily be appreciated that with the end  20  of the first sheet  16  engaged with the roller tube  34 , and the end  22  of the second sheet  18  engaged with the mounting tube  44  or other stationary holder, the shade  14  hangs downwardly from the head rail  33  to form the bight  19  between the ends  20 ,  22  of the shade  14 . 
     To weight the shade, a solid or hollow cylindrical metal or plastic rod  48  is disposed in the bight  19 . As the shade  14  is moved between the raised and lowered positions, the rod  48  rolls on the shade  14  within the bight  19 . 
     To retain the rod  48  in the bight  19 , left and right rod ends caps  50 ,  52  are positioned in the ends of the rod  48  and/or guide  49 . Alternatively, the rod  48  can be suspended from the head rail  33  by suspension lines (not shown), the length of which is about equal to the distance from the head rail  33  to the bight  19  when the shade  14  is in the lowered position. Moreover, if desired the ends of the rod  48  can be slidably engaged with channels (not shown) that are established by structure in the sill of the window, to hold the shade  10  relatively stationary when, e.g., wind blows the against the shade  10 . 
     If desired, to hold the sheets  16 ,  18  close together when the shade is lower than about midway between the raised and lowered positions, and thereby augment the above-noted effects as the shade  10  is raised and lowered, two parallel spacing bars or rollers  54 ,  56  can be affixed to the rod  48  at the respective ends of the bars or rollers  54  and rod  48 . As shown, the sheets  16 ,  18  extend between the bars or rollers  54 ,  56 . The distance between the spacing bars or rollers  54 ,  56  is established to in turn establish the distance  67  between the sheets  16 ,  18 . It will readily be appreciated that the bars or rollers  54 ,  56  hold the shades  16 ,  18  close together, while allowing for the rod  48  to pass between the bars or rollers  54 ,  56 . 
     In accordance with present principles, the shade of the present invention can have patterns other than the one shown in FIGS. 1 and 2. For example, FIG. 3 shows but one such alternative shade, generally designated  60 , which includes alternating first and second strips  62 ,  64 , The first strips  62  have a row of diamonds thereon, and the second strips  64  likewise have a row of diamonds thereon, with the top vertices  66  of the diamonds in the second strips  64  being vertically aligned with the junctions  68  of the left and right vertices of adjacent diamonds in the first strips  62 . Thus, the first strips  62  are characterized by a first pattern and the second strips  64  are characterized by a second pattern that is staggered relative to the first pattern. As yet another alternative, to provide for almost complete opacity when the shade of the present invention is in the opaque configuration, the present shade can be characterized by a checkerboard pattern. 
     While the above discussion discloses a movable holder that is a roller tube which functions by rolling the shade, it is to be understood that the holder alternatively can function by, e.g., raising the shade to configure the shade in accordion-type pleats. Also, while the above discussion focusses on a stationary holder, it is to be understood that both holders can be rotatable or otherwise movable relative to each other, as long as relative motion between the sheets  16 ,  18  of the shade  14  is effected. 
     FIG. 4 shows an alternate window covering  100  that is in all essential respects identical to the covering  10  shown in FIGS. 1-3, with the following added feature. To guide a patterned shade  102  of the window covering  100  around a lower rod  104  in a bight  106  formed by sheets  108 ,  110  of the shade  102 , and to keep the sheets  108 ,  110  closely juxtaposed as the shade is raised and lowered, thereby enhancing the effect of the moving shade pattern, a hollow shade guide  112  surrounds the rod  104  and the portion of the shade  102  that is engaged therewith. As shown, the shade guide  112  is generally tubular in shape and preferably extends the length of the rod  104 . The preferred shade guide  112  forms an almost complete circle in transverse cross-section, with the almost complete circle being interrupted only by an open slit  114  extending the length of the shade guide  112 . The slit  114  terminates along its long edges in opposed gently curved guide arms  116 ,  118 , between which the sheets  108 ,  110  extend. 
     It is to be understood that the width “w” of the slit  114  is marginally larger than the combined thickness of the sheets  108 ,  110 . Looked at another way, the arms  116 ,  118  extend upwardly from respective locations on the tubular portion of the guide  112  the distance between which is less than the diameter of the guide  112 . 
     In one preferred embodiment, the shade guide  112  is made of a unitary piece of extruded acrylic, although other plastics can be used. The shade guide  112  is slid onto the rod  104  to dispose the guide  112  in the configuration shown. End caps  120  (only a single end cap  120  shown in FIG. 5) can be closely engaged with the ends of the guide  112  to retain the rod  104  and sheet  102 , with the end caps  120  being in all essential respects identical to the end caps  50 ,  52  described above with the exception that the end caps  120  have teardrop shapes, to match the shape of the guide  112 . 
     While the particular ROLL UP SHADE WITH DOUBLED FABRIC HAVING PATTERNS THEREON as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the arts and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”.

Summary:
A roll-up shade is doubled and its ends suspended from a head rail that is mounted above a window. One end is attached to a roller tube and the other end is attached to a stationary tube, with a bight being formed between the tubes. A first sheet is defined from the bight to the roller tube and a second sheet is defined from the bight to the stationary tube. A weighty rod is positioned in the bight to cause the bight to sag away from the head rail, and a shade guide surrounds the rod to guide the shade. With this structure, the roller tube can be rotated to pull up the first sheet and raise the bight or to lower the first sheet with bight, with the second sheet (i.e., the sheet that is directly attached to the stationary tube) remaining unmoving above the bight. The shade is patterned such that when the shade is raised and lowered, the relative motion between the two sheets causes the shade to alternatingly assume high and low opacity configurations. The roller tube can be motorized if desired.