Patent Abstract:
An adjustable-width spring-operated roller shade that maintains proper orthogonal tracking at all available widths within the shade&#39;s range of width adjustment. The adjustable-width roller shade utilizes two overlapping window shades and a telescoping roller to provide a shade that is repeatedly width-adjustable within its original range of width adjustment. To keep the shade sufficiently perpendicular to the roller as the shade winds onto the roller, orthogonal tracking spacers, such as continuous, pliable strips constructed from the same material as the shades, are attached to non-overlapped portions of the shade material to compensate for the extra layers of material existing at the overlapped portion of the shades. Thus, the roller shade maintains proper orthogonal tracking of the shade at all available widths within the shade&#39;s range of width adjustment.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    Roller-type retractable window shades have long been used to provide shade and privacy for the interiors of buildings and automobiles. A multitude of different window widths is a problem that has plagued the designers of these window shades. One approach to solving this problem is to construct a wide range of different fixed-width window shades, such that a different fixed-width window shade is available for every different window width. Of course, this approach to the problem results in a very large inventory of fixed-width shades, and prevents using the same window shade with windows of different width.  
           [0002]    To avoid having to construct a different fixed-width shade for each different window width, attempts have been made to construct adjustable-width window shades. In particular, “cut-to-fit” window shades have been constructed that permit easy width modification at the site of installation. However, once cut to a desired size, these window shades can no longer be expanded to their original maximum width. Thus, these configurations only provide a partial solution to the problem. In particular, these “cut-to-fit” window shades are not truly “adjustable-width” in that they are not repeatedly width-adjustable within their original range of width adjustment. Moreover, adjustable-width roller shades, which are specifically configured for deployment in automobiles, are not commercially available at present.  
           [0003]    It is believed that the present unavailability of truly adjustable-width widow shades results from the inability of roller shade designers to solve the problem of mounting overlapping shade sheets on a roller that telescopes to provide width adjustment. A second unsolved problem is to design a telescoping shade that maintains “proper orthogonal tracking” at all available widths within the shade&#39;s range of width adjustment. Generally, “proper orthogonal tracking” is the ability of the shade to remain sufficiently perpendicular to the roller, as the shade winds onto the roller, to prevent an unacceptable amount of movement of the shade along the roller. In other words, proper orthogonal tracking allows the shade to wind on top of itself as it winds onto the roller, in order to prevent the shade from traveling along the length of the roller, as the shade repetitively wraps around the roller. In general, partial overlapping of the shade material being wound around the roller results in a varying thickness of the shade material along the length of the roller, prevents proper orthogonal tracking and causes the shade to move along the roller with subsequent turns of the shade around the roller. When this occurs, the window shade may form a cone rather than a cylinder as it winds, and thus bind or become damaged during retraction.  
           [0004]    Accordingly, a need exists in the art for an improved adjustable-width window shade that is repeatedly width-adjustable within its original range of width adjustment. There is a further need for an adjustable-width roller shade that is specifically configured for deployment in automobiles. And there is a further need for an adjustable-width roller shade that maintains proper orthogonal tracking within the shade&#39;s range of width adjustment.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention meets the needs described above in an adjustable-width roller shade that maintains proper orthogonal tracking at all available widths within the shade&#39;s range of width adjustment. More particularly, the adjustable-width roller shade utilizes two overlapping window shades and a telescoping roller to provide a shade that is repeatedly width-adjustable within its original range of width adjustment. To keep the shade sufficiently perpendicular to the roller as the shade winds onto the roller, orthogonal tracking spacers, such as strips of pliable material attached to non-overlapped portions of the shade material, compensate for the extra layers existing at the overlapped portion of the shades. Thus, the roller shade maintains proper orthogonal tracking of the shade at all available widths within the shade&#39;s range of width adjustment.  
           [0006]    This configuration of the window shade allows the same shade to be adjusted to fit many different windows without having to cut or otherwise permanently alter the window shade. For this reason, multiple window shades may be adjusted, as desired, and placed side-by-side to fit curving and odd-shaped windows, such as automobile windshields and rear windows. Of course, the same roller shade may be used for side windows as well. Thus, the same window shade may be easily and cost effectively deployed to fit most of the windows of every different automobile make and model on the road, without having to cut or otherwise permanently alter the window shades. It is expected that this advantage will result in a far greater deployment of automobiles window shades than prior window shades have been able to accomplish.  
           [0007]    In addition, the outer facing surfaces of the window shades provide advertising space that is visible to the public when the shades are pulled down inside parked automobiles. Thus, making the window shades more attractive to a substantial portion of automobile owners has the associated benefit of deploying millions of square feet of advertising space. Accordingly, automobiles including these window shades, with and without advertising indicia printed on the outward facing surfaces of the shades, are considered to be within the scope of the present invention.  
           [0008]    Generally described, the present invention is an adjustable-width roller shade including a telescoping roller assembly having an adjustable width. The telescoping roller assembly is characterized by a shade mounting system that allows free telescoping of the roller assembly. The telescoping roller assembly carries a telescoping shade assembly that varies in width in cooperation with changes in the width of the telescoping roller assembly. The telescoping shade assembly is characterized by two shades with inner portions that overlap each other by an amount that varies with the width of the telescoping shade assembly. In addition, each shade defines an outer portion located away from the overlapped inner portion of the corresponding shade. To provide proper orthogonal tracking of the shades onto the roller, the outer portion of each shade carries an orthogonal tracking spacer, such as a strip of pliable material attached along the edge of the sheet with a thickness selected to compensate for the overlapped condition of the inner portion of the corresponding shade as that shade winds around the roller assembly. The shade also includes a spring motor, which is coupled to the roller assembly that operates to store spring energy as the shades are moved from a rolled-in configuration to a rolled-out configuration. This spring motor also uses stored spring energy to move the shades from the rolled-out configuration to the rolled-in configuration.  
           [0009]    The roller shade may also include written indicia carried on at least one of the first and second shades that is available for viewing when the shades are in a substantially rolled-out configuration. In particular, the invention may include an automobile having a front windshield of substantial width and carrying multiple roller shades positioned in side-by-side relation across the width of the front windshield. In addition, the invention may include an automobile having a rear window of substantial width and carrying multiple roller shade positioned in side-by-side relation across the width of the rear window.  
           [0010]    More specifically described, the telescoping roller assembly may include an inner roller having an outer longitudinal surface defining a cylinder with a longitudinal ridge extending radially outward from the cylinder. The telescoping roller assembly may also include an outer roller having an outer longitudinal surface defining a cylinder with a longitudinal channel cut through a substantial portion of the longitudinal extent of the outer surface. In addition, the inner roller is concentrically received within the outer roller, with the ridge positioned within the channel, to form a telescoping roller assembly of adjustable width. Typically, the first shade is attached to the ridge of the inner roller, and the second shade is connected to the outer surface of the outer roller.  
           [0011]    The roller shade may also include a telescoping outer cover housing the roller assembly and constraining the spring motor from unintended release of stored spring energy. In this case, the first and second shades pass through an opening in the cover as the shades move between a fully rolled-in configuration and a substantially rolled-out configuration.  
           [0012]    The roller shade may also include a first rod carried by a free edge of the first shade, a second rod carried by a free edge of the second shade; and a clip for securing the first and second rods together after the roller shade has been adjusted to a desired width. In this case, roller shade may also include a hook coupled to at least one of the first and second shades, typically at the clip, for securing the shades in a substantially rolled-out configuration. 
       
    
    
       [0013]    In view of the foregoing, it will be appreciated that the adjustable-width roller shade avoids the drawbacks of conventional roller shades, including those configured for “cut-to-fit” width adjustment. The specific techniques and structures employed by the invention to improve over the drawbacks of the prior roller shades and accomplish the advantages described above will become apparent from the following detailed description of the embodiments of the invention and the appended drawings and claims.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is an exploded, perspective view of an adjustable-width window shade made in accordance with the present invention.  
         [0015]    [0015]FIG. 2 is a perspective view of the adjustable-width window shade.  
         [0016]    [0016]FIG. 3 is a perspective view of an automobile with its windshield protected by two adjustable-width window shades positioned side by side.  
         [0017]    [0017]FIG. 4 is a perspective view of the receiving end of the second roller tube.  
         [0018]    [0018]FIG. 5 is a perspective view of the inner end of the first roller tube.  
         [0019]    [0019]FIG. 6 is an exploded, perspective view of an attached clip assembly.  
         [0020]    [0020]FIG. 7 is a perspective view of the cap end of the second roller tube.  
         [0021]    [0021]FIG. 8 is a perspective view of the cap end of the first roller tube with the short collar in place.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    The invention may be deployed as a retractable, spring-operated, horizontally-mounted, adjustable-width window shade that can be adjusted and readjusted in width without tools, training or trimming, to provide an adjustable width window shade that maintains accurate orthogonal tracking at any allowable width. This window shade typically includes a structurally integrated cover tube that protects the shade material when not in use, provides mounting points for attachment to a window, and prevents the spring motor from unwinding prior to installation. The window shade can be advantageously shipped and stored in its relatively small fully-retracted size and, once received by the customer, it may be quickly and easily adjusted to a desired width and installed by automobile technician or end user.  
         [0023]    It should be appreciated that, although the preferred embodiment of the invention is described as a retractable, spring-operated, horizontally mounted window shade, many other window shade configurations may be constructed using the principles of the present invention. For example, roller-to-roller shades, rather than a telescoping single-roller retractable shade, may be constructed. Similarly, hand-crank or motorized shades, rather than a spring-operated shade, may be constructed. Further, vertically or angularly mounted shades, rather than a horizontally mounted shade, may be constructed. Many other modifications and variations of the invention described herein, which will become obvious to those skilled in the art, are within the spirit and scope of the present invention.  
         [0024]    The invention may also be used for shades or covers other than window shades. For example, the invention may be deployed in an adjustable-width projector screen, an adjustable-width fish tank screen or cover, or an adjustable-width cover for an interior room opening, such as those commonly located between a kitchen and a living room. Many other applications for the invention described herein, which will become obvious to those skilled in the art, are within the spirit and scope of the present invention.  
         [0025]    In a preferred embodiment, the retractable, spring-operated, horizontally-mounted, adjustable-width window shade comprises a first assembly, a second assembly, a telescoping housing or cover tube, and a retaining hook. The first and second assemblies may each be based on one half of a hollow two piece roller tube designed to telescope.  
         [0026]    The first assembly begins with that half of the telescoping roller tube with the smaller outside diameter. Attached to one side of this first roller tube, along its entire length, is a narrow, rectangular shaped ridge. This first roller tube ridge is of sufficient height, or thickness, so as to match the wall thickness of the second, larger diameter, section of the telescoping roller tube. This first assembly roller tube also has a short collar mounted on the outer tube end. This collar is slotted along its length to matingly engage the rectangular first roller tube ridge. This short collar has an outer circumference that matches the outer circumference of the larger diameter second roller tube. A pliable first sheet of shade material is attached by its leading or top horizontal edge to the top of the first roller tube ridge. This first shade sheet is as wide as the first roller tube is long. A first orthogonal tracking spacer, such as a strip of pliable material, is attached on the inner surface adjacent to the outer vertical edge of the first shade sheet. This spacer is attached a predetermined distance from the top horizontal or mounting edge and runs to the bottom horizontal edge. This first orthogonal tracking strip is as wide as the first roller tube short collar and as thick as the second shade sheet. A square stiffening rod is attached along the entire length of the bottom or trailing horizontal edge on the inner surface of the first shade sheet. This stiffener rod extends a predetermined length beyond the inner vertical edge of the first shade sheet.  
         [0027]    The second assembly begins with that half of the telescoping roller tube with the larger outside diameter. This second roller tube has an inner circumference sufficient to matingly engage the outer diameter of the first roller tube. This second roller tube is longer than the first roller tube by a predetermined amount and has a narrow channel along one side to matingly engage the first roller tube ridge. This channel is long enough to accept that length of the first roller tube ridge not covered by the first roller tube collar. The outer circumference of the second roller tube is sufficient so that when the first roller tube is fully inserted into the second roller tube the outer surfaces of the first roller tube ridge and the first roller tube short collar are approximately flush with the outer circumference of the second roller tube. A pliable second sheet of shade material is attached by its leading edge to the second roller tube at a point in advance of the second roller tube channel. The width of this second shade sheet is equal to the second roller tube length. Another orthogonal tracking spacer is attached to the inside face of the second shade sheet along the entire outer vertical edge. This second orthogonal tracking spacer, again a pliable strip of material, is as thick as the first shade sheet and as wide as the first shade sheet orthogonal tracking strip. A second square stiffening rod is attached to the outer face of the second shade sheet along the entire length of the bottom or trailing horizontal edge.  
         [0028]    The orthogonal tracking spacer may be a strip constructed from a relatively thin, continuous strip of the same material from which the sheet is constructed. However, it should be appreciated that the orthogonal tracking strip may be constructed from any other type of pliable material having the desired flexibility. In addition, structures other than a thin, continuous strip of pliable material may be used as the orthogonal tracking spacer. For example, one or more strips of thin, flat wire could be attached to the sheet material. Rather than being continuous, the tracking spacer may be intermittent, such as a series of patches or plastic tabs spaced along the edge of the sheet. That is, any type of structure configured to maintain acceptable orthogonal tracking by offsetting the overlapped thickness of the sheets at the center of the roller will function properly as an orthogonal tracking spacer. Nevertheless, a continuous orthogonal tracking strip attached along the outer edge of each sheet, which is constructed from a relatively thin, continuous strip of the same material from which the sheet is constructed, has been found to be the most convenient, effective and technically successful structure for implementing the orthogonal tracking spacer.  
         [0029]    With the first roller tube inserted into the second roller tube, the second shade sheet overlaps and slidably engages the first shade sheet. During the rolling process the second shade sheet is rolled upon the inner edge of the first shade sheet and the second orthogonal tracking spacer. During winding, the orthogonal tracking spacer attached to the second shade sheet continuously adjusts the circumference of the outer end of the second roller tube to match the change in circumference occurring on the inner end of the second roller tube where the two shade sheets overlap.  
         [0030]    The first shade sheet is rolled upon the inner end of the second roller tube and the first roller tube short collar for the first full revolution. At the beginning of the second revolution the first shade sheet begins to be wound on top of, or overlap, the first layer of the inner edge of the second shade sheet. At this point, the first shade sheet orthogonal tracking spacer begins adjusting the circumference of the first roller tube outer end to match the change in circumference occurring on the inner end of the second spin tube where the two shade sheets overlap. This allows each sheet to maintain proper orthogonal tracking as it winds onto the roller. True telescoping ability is achieved by utilizing the ridge and channel so that the sheet mounted onto the first roller tube does not interfere with the telescoping action. This roller system, in combination with the orthogonal tracking strips, establishes telescoping ability and maintains orthogonal tracking at any available width of the adjustable-width roller.  
         [0031]    The roller and shade assembly is typically housed within a cover tube that includes two sections designed to telescope freely while resisting any rotational movement, allows free extension and retraction of the two shade sheets, prevents stored spring energy in the roller assembly from unwinding, and provides convenient attachment points for attaching the shade to a window.  
         [0032]    Referring now to the drawings, in which like reference numerals designate corresponding parts throughout the several figures, reference is made first to FIG. 1, which shows an exploded and perspective view of an adjustable-width window shade  10 . The shade  10  comprises a first assembly  20 , a second assembly  40 , a housing  60 , and a retaining hook  70 .  
         [0033]    Referring to FIG. 1, the first assembly  20  has an elongated, cylindrically shaped first spin tube  21  having a cap end  22 , a mating end  23 , a first tube longitudinal axis extending between the cap and mating ends  22  and  23 , a first bore  24 , a first surface  25 , and a ridge  26  extending outwardly from the first surface  25  and being substantially parallel to the first tube longitudinal axis. A first sheet  27  having a first upper edge  27   a  and a first lower edge  27   b,  a first inner edge  27   c,  and a first outer edge  27   d,  is mounted to the ridge  26  proximate the first upper edge  27   a.  Attached proximate the first outer edge  27   d  is an orthogonal tracking spacer  13  and proximate the first lower edge  27   b  is a rib  64   a.  Mounted to the first spin tube  21  proximate the cap end  22  is a short collar  29 . The short collar  29  has a collar groove  30 , which matingly engages the ridge  26 , and a collar surface  31 . Preferably, the short collar surface  31  is substantially flush with the outer most portion of the ridge  26 . Disposed within the first bore  24  at the cap end  22  is a bushing  32  and axle  33  that is threaded at one end to facilitate attachment of a first cap  36  and a mounting bracket  37 . A first rod  33  having a first threaded end  34  is inserted into and rotatably engages the first busing  32 . Disposed over the first threaded end  34  is a first washer  35  and a first cap  36 . The first threaded end  34  extends through and beyond the first cap  36 . A mounting bracket  37  is placed onto the first threaded end  34  and secured to the first rod  33  and the first cap  36  by a nut  38 .  
         [0034]    Again referring to FIG. 1, the second assembly  40  has an elongated, cylindrically shaped second spin tube  41  having a cap end  42 , a receiving end  43 , a second tube longitudinal axis extending between the cap and receiving ends  42  and  43 , a second bore  44  extending therethrough, and a channel  45  extending a predetermined distance substantially parallel to the second tube longitudinal axis from the receiving end  43  toward the mount end  42 . The channel  45  has a first side  45   a  and a second side  45   b.  A slot  46  extends from the mount end  42  toward the receiving end  43  within the second bore  44 . A second sheet  47  having an upper edge  47   a,  a lower edge  47   b,  an inner edge  47   c  and an outer edge  47   d,  is mounted proximate the upper edge  47   a  to the second spin tube  41  substantially parallel to the second tube longitudinal axis and adjacent the second side  45   b  of the channel  45 . Attached proximate the outer edge  47   d  is an orthogonal tracking spacer  14  and proximate the lower edge  47   b  is a rib  64   b.  Disposed within the second bore  44  at the mount end  42  is a hollow drive gear  50 . The drive gear  50  has both a reduced portion which forms a spring receiver  51  and a tooth  52  for engaging the slot  46 . Disposed within the drive gear  50  is a hollow second bushing  53 . A second rod  54  having a second threaded end  55  and a spring end  56  is inserted through the second busing and the drive gear  50  and rotatably engages the first busing  32 . A spring  57  is disposed on the second rod  54 . One end of the spring  57  is fixedly mounted to the spring receiver  51  of the drive gear  50 , and the other end of the spring  57  is fixedly mounted to the spring end  56  of the second rod  54 . Disposed over the second threaded end  55  is a second washer  58  and a second cap  59 . The second threaded end  55  extends through and beyond the second cap  59 . Another mounting bracket  37  is placed onto the second threaded end  55  and secured to the second rod  54  and the second cap  59  by another nut  38 .  
         [0035]    To obtain true telescoping ability, the first sheet is mounted utilizing the system of ridge and channel to allow the first tube to be inserted into the second tube without interference by the first sheet. To maintain orthogonal tracking, an adjustment may be made for the difference in the circumference of the roller assembly in the area where the sheets overlap, as compared to the non-overlapping areas, as the sheets are wound onto the roller. That is, when fully assembled, the inner edge  47   c  of the second sheet  47  will overlap the inner edge  27   c  of the first sheet  27 . This establishes a concentric relationship between the two sheets being wound. To maintain proper orthogonal tracking, and offset the extra layers accumulating at the overlapping portion of the sheets, the outer edge  47   d  of the second sheet  47  carries an orthogonal tracking strip or spacer  14 . With each revolution of the roller, this orthogonal tracking spacer  14  increases the effective circumference of the cap end  42  of the second roller tube  41  to match that increase occurring where the two sheets overlap. Because the lower edge  47   b  has an attached rib  64   b,  the sheet material is kept flat and is able to bridge the unsupported area occurring in the center of the second roller tube  41 .  
         [0036]    The first sheet  27  is wound upon the short collar  29  and the receiving end  43  of the second roller tube  41  for the first full revolution. At the beginning of the second revolution of the roller tubes  21  and  41 , the overlapping area of the second sheet  47  begins to be wound under the inner edge  27   c  of the first sheet  27 . At this point in the winding process, the orthogonal tracking spacer  13  begins to adjust the circumference of the first roller tube  21  at the cap end  22 . This adjustment increases the circumference of the cap end  22  at the same rate occurring at the mating end  23  where sheets  27  and  47  overlap. This allows the sheets to maintain proper orthogonal tracking as they wind on and off the roller. Because the lower edge  27   b  has an attached rib  64   a,  the sheet material is kept flat and able to bridge the unsupported area occurring at the center of the first roller tube  21 , which results in proper orthogonal tracking.  
         [0037]    With continued reference to FIG. 1 and additionally to FIGS. 2 and 3, the housing  60  has a housing longitudinal axis extending therethrough and comprises a hollow first cover tube  61  and a hollow second cover tube  62 . The first cover tube  61  has an outside diameter no larger than the inside diameter of the second cover tube  62  so that the first cover tube  61  is insertable into the second cover tube  62 . As shown in the drawings, the cover tubes  61  and  62  have a cylindrical shape; however, other shapes such as square, triangular, hexagonal and the like may be utilized with the present invention and are included within the scope of the present invention. Each of the cover tubes  61  and  62  has a slot  63  which extends substantially parallel to the housing longitudinal axis, preferably the entire length thereof. The first assembly  20  is inserted into the first cover tube  61  with the first sheet  26  extending through the slot  63 . The first cap  36  securely engages a respective end of the first cover tube  61 . Likewise, the second assembly  40  is inserted into the second cover tube  62  with the second sheet  47  extending through the slot  63 . The second cap  59  also securely engages a respective end of the second cover tube  62 . The first cover tube  61  and first assembly  20  are inserted into the second cover tube  62  and second assembly  40  with the slots  63  of each being aligned, thereby having a telescoping engagement.  
         [0038]    Additionally, as the first spin tube  21  is inserted into the second spin tube  41 , the ridge  26  slidably engages the channel  45  and a rotational axis is formed between the first and second spin tubes  21  and  41 . Importantly, the second sheet inner edge  47   c  overlaps the first sheet inner edge  27   c  and the outer edge  47   d  is supported by the orthogonal tracking spacer  14 . This defines a plane for the second sheet leading edge  47   a  that is substantially parallel to the rotational axis and extends from the orthogonal tracking spacer  14  to the first sheet inner edge  27   c  at any point in the winding process.  
         [0039]    For the leading edge of the first sheet  27 , a plane substantially parallel to the rotational axis is established between the receiving end  43  of the second roller tube  41  and the short collar surface  31  for the first full revolution of the roller assembly. Because the first and second sheet inner edges  27   c  and  47   c  overlap, this plane changes at the beginning of the second revolution of the winding process. At the start of the second revolution, the circumference of the winding cylinder begins to grow twice as fast where the first and second sheets overlap as it does at the first roller tube cap end  22 . To maintain a plane substantially parallel to the rotational axis for the leading edge of the first sheet  27 , the orthogonal tracking spacer  13  begins to be wound under the first sheet outer edge  27   d  at the start of the second revolution to compensate for the inner edge  47   c  of the second sheet.  
         [0040]    The width of the shade  10  can now be varied by extending or retracting the first cover tube  61  within and with respect to the second cover tube  62 .  
         [0041]    As the first and second sheets  27  and  47  are extracted or pulled from the housing  60 , a standard spring motor is used to exert a biasing force to retract the first and second sheets  27  and  47  into the housing  60 .  
         [0042]    Respectively mounted substantially perpendicular to the first and second sheets  27  and  47  proximate the first and second lower ends  27   b  and  47   b  are ribs  64   a  and  64   b.  As shown in FIGS. 1, 2 and  3 , the first and second sheets  27  and  47  contact one another at the first and second lower ends  27   b  and  47   b.  The ribs  64   a  and  64   b  are mounted to the sheets  27  and  47  so that each respective rib  64   a  and  64   b  projects outwardly and away from one another. Once the first and second sheets  27  and  47  have been withdrawn from the housing  60  so that the ribs  64   a  and  64   b  are a desired distance from the housing  60 , the retaining hook  70  is utilized to secure the sheets  27  and  47  to an object of a vehicle  1 , such as a vent  2 . The retaining hook  70  has a substantially U-shape body  71  and a substantially L-shaped hook  73  extending from the body  71 . Arms  72  project toward one another from the U-shaped body  71 , and the L-shaped hook has a catch  74 . The arms  72  removably engage the ribs  64 , and the catch  74  removably engages the vent  2 , or other object, of the vehicle  1 . Obviously, various types of securing devices such as buttons, locks, latches, hook and loop material, stops, brakes and the like may be utilized to prevent undesired retraction of the first and second sheets  27  and  47 , and are included within the scope of the present invention.  
         [0043]    The first and second sheets  27  and  47  can be made of plastic, vinyl, cloth or any material capable of being rolled. Additionally each sheet  27  and  47  can comprise a light reflective material or have a light reflective coating or color on one or both sides.  
         [0044]    With respect to the above description, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. It should be understood that the foregoing relates only to the exemplary embodiments of the present invention, and that numerous changes may be made therein without departing from the spirit and scope of the invention as defined by the following claims.

Technology Classification (CPC): 4