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CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit under 35 U.S.C. § 119(e) to U.S. provisional patent application No. 60/747,957 (“the &#39;957 application”), which was filed on May 23, 2006 and entitled “Skew Adjustment Device For Coverings For Architectural Openings.” The &#39;957 application is incorporated by reference into the present application in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to coverings for architectural openings and more particularly to a skew adjustment device positioned within the head rail of the covering to maintain a uniform rollup of covering fabric onto a roller disposed within the head rail. 
   2. Description of the Relevant Art 
   Coverings for architectural openings have assumed different forms over many years. Early forms of coverings simply consisted of fabric draped across all or some portion of an architectural opening such as a door, archway, window or the like. 
   Retractable coverings have also been a popular product wherein the covering is either suspended vertically and retracted to one or both sides of the architectural opening or rolled up or down about a roller at the top or bottom of the opening. The latter category of retractable coverings include a flexible fabric or fabric like material that is connected to a roller and can be retracted about the roller in a retracted condition of the covering or extended from the roller across the architectural opening in an extended condition. 
   One problem with retractable coverings that include a flexible material that is wound onto or unwound from a roller resides in the material skewing as it is wound onto the roller or unwound from the roller. When the material skews, it translates horizontally along the longitudinal axis of the roller as it is raised and wraps around the roller in a spiral fashion sometimes referred to as barber poling. As a result, the bottom rail along the bottom edge of the material is not desirably horizontally disposed during operation of the covering. Skewing of the material can be caused by various features of the covering including the roller not being horizontally mounted, the fabric not being fixed to the roller horizontally, or the fabric being asymmetrically configured, but regardless of the cause of the skew, it is aesthetically undesirable and can cause the fabric to engage the housing for the roller where it can fray. Accordingly, attempts have been made to correct skew. 
   Typically, the skew is corrected with a ballast bar or bars slidably positioned in the bottom rail of the covering so that the ballast bar or bars can be releasably fixed at any desired location along the horizontal length of the bottom rail. This of course shifts the center of gravity of the bottom rail which counters the bias in the covering material so that the bottom rail remains horizontal as desired for operation and aesthetics. 
   While ballast bars in the bottom rail are typically concealed within the bottom of the bottom rail, under certain circumstances, they can become visible and accordingly alternative anti-skew systems are continually being investigated. 
   It is to provide an alternative skew adjustment system that the present invention has been developed. 
   SUMMARY OF THE INVENTION 
   The skew adjustment system of the present invention is incorporated into the head rail of a rollup covering for architectural openings wherein the covering includes a flexible fabric or fabric-like material adapted to be wound about a roller in the head rail when retracting the covering or unwound from the roller when extending the covering. It has been found that by creating a point of increased tension on the flexible material at a predetermined fixed position along the horizontal length of the roller the tendency of the fabric to skew as it is being rolled on or unrolled from the roller can be offset. 
   In accordance with the present invention, an engagement arm is slidably positionable at releasably fixed positions along the horizontal length of the head rail, with the arm being resilient and adapted to slidably engage the fabric material when it is at least partially wound about the roller. The engagement arm creates a frictional drag on the material which inhibits the wrapping of the material at the location of the engagement arm while allowing other locations along the length of the roller to accept the fabric with a looser wrap so as to counter the skew bias. Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of a preferred embodiment, taken in conjunction with the drawings and from the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a retractable covering for an architectural opening shown in an extended position with a portion of the head rail removed to show the skew adjustment device of the present invention. 
       FIG. 2  is a front elevation of the covering of  FIG. 1  with the skew adjustment device shown in dash lines. 
       FIG. 3  is a front elevation similar to  FIG. 2  showing the covering partially retracted and with the bottom rail inclined relative to horizontal illustrating a skew in the fabric of the covering. 
       FIG. 4  is a front elevation similar to  FIG. 3  with the covering fully retracted and with the bottom rail still forming an incline with horizontal. 
       FIG. 5  is a front elevation similar to  FIG. 2  with the covering in a fully extended position but with the skew adjustment device having been shifted to the right. 
       FIG. 5A  is an enlarged fragmentary section taken along line  5 A- 5 A of  FIG. 5 . 
       FIG. 6  is a front elevation similar to  FIG. 5  showing the covering in a partially retracted position. 
       FIG. 7  is a front elevation similar to  FIG. 6  with the covering fully retracted. 
       FIG. 8  is an enlarged vertical section taken along line  8 - 8  of  FIG. 7 . 
       FIG. 9  is an isometric showing the skew adjustment device of the present invention. 
       FIG. 10  is a view of the skew adjustment device taken along line  10 - 10  of  FIG. 9 . 
       FIG. 11  is a left-side elevation of the skew adjustment device of  FIG. 9 . 
       FIG. 12  is a front elevation of the skew adjustment device. 
       FIG. 13  is a section taken along line  13 - 13  of  FIG. 12 . 
       FIG. 14  is an enlarged vertical section taken through a portion of the head rail of the covering of  FIG. 1  with the skew adjustment device positioned in the head rail. 
       FIG. 15  is a fragmentary isometric showing the skew adjustment device being inserted into the head rail. 
       FIG. 16  is an isometric of a second embodiment of the skew adjustment device. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 1 , a covering  20  for an architectural opening such as a door, window, archway or the like is illustrated in a fully extended position. The covering can be seen to include a head rail  22  that rotatably supports a roller  24  ( FIG. 5A ) that is reversibly driven by a control cord  26  in a conventional manner. The roller supports a flexible fabric material  28  which for illustrative purposes is shown as being comprised of a pair of face sheets  30  of material such as sheer interconnected at vertically spaced locations by horizontally disposed translucent flexible vanes  32 . Other fabric or fabric-like materials could be used in lieu of the material illustrated as will be appreciated with the description that follows. The bottom edge of the fabric material supports a rigid bottom rail  34 . A fabric covering of the type illustrated is described in detail in applicant&#39;s U.S. Pat. No. 5,313,999, the disclosure of which is hereby incorporated by reference. As can also be seen in  FIG. 1 , at the location where the head rail is broken away, a skew adjustment device  36  in accordance with the present invention is incorporated into the head rail and the device and its operation will be described hereafter. 
   The covering  20  shown in  FIG. 1  is shown in a front elevation in  FIG. 2 . As will be appreciated, the bottom rail  34  is disposed horizontally and in a parallel relationship with the head rail  22  as is desired for aesthetics. In  FIG. 3 , however, the covering is shown partially retracted and it can be seen the bottom rail forms an acute angle with horizontal with this position of the covering being referred to in the industry as skewed. In other words, as the fabric material is being wrapped around the roller  24 , the right edge is wrapping more rapidly or more tightly than the left edge causing the bottom rail to skew or tilt as illustrated. Of course, such a skew is undesirable from an aesthetic standpoint, and in fact, when the covering is fully retracted as shown in  FIG. 4 , the bottom rail is clearly no longer parallel with the head rail as it was when the covering was fully extended in  FIG. 2 . It should also be noted in  FIGS. 2-4  that the skew adjustment device  36  which is shown in dashed lines, as it is hidden within the head rail, is longitudinally centered within the horizontal head rail. 
   As will be more clearly appreciated with the description that follows, the skew adjustment device  36  is slidably disposed within the head rail  22  and can be releasably fixed at any position along the horizontal length of the head rail. The skew adjustment device is a frictional device that slidably engages and compresses the fabric material  28  as it is being wrapped onto the roller or unwrapped from the roller  24 . The frictional engagement with the fabric material provides drag and compression at a preselected position along the horizontal length of the roller so that the rate at which the fabric wraps about the roller at the location of engagement and the tightness of the wrap can be controlled thereby controlling skew. 
   With reference to  FIGS. 5-7 ,  FIG. 5  shows the covering  20  fully extended and of course the bottom rail  34  is horizontal and parallel with the head rail  22 . The skew adjustment device  36  is positioned to the right of center so as to correct the skew illustrated in  FIGS. 2-4 . In  FIG. 6 , the covering has been partially retracted and due to the affect of the skew adjustment device on the fabric material  28  being wrapped about the roller, the bottom rail remains horizontal and parallel with the head rail as desired.  FIG. 7  shows the covering fully retracted and as will be appreciated, the bottom rail is flush and parallel with the head rail as desired. 
   With reference to  FIGS. 9-13 , the skew adjustment device  36  can be seen to be a punched or molded member that is made of a semi-rigid but resilient material such as plastic, aluminum, spring steel or the like and includes an arched plate-like back  38  with an integral forwardly and upwardly inclined engagement arm  40 . The bottom edge  42  of the engagement arm is integral with the bottom edge of an opening  44  through the plate-like back of the device and due to the integral connection of the engagement arm with the back along an edge of the engagement arm and the resilient semi-rigid characteristics of the material from which the device is made, the engagement arm is spring biased so that if deflected up or down, it will be encouraged or biased to return to the neutral position shown in  FIG. 9 . A second opening  46  is provided through the back plate  38  adjacent to the bottom edge thereof thereby defining a somewhat flexible arched segment  47 . As is possibly best appreciated by reference to  FIGS. 11 and 13 , the plate-like back of the device is generally arcuate and concave in a forward direction having an optional horizontally wavy or serpentine segment  48  immediately above the location of attachment of the engagement arm  40  with the back  38 . An illustration of the skew adjustment device without the serpentine segment  48  is shown in  FIG. 16 . A flat horizontal tab  50  is provided in the device above the serpentine segment for a purpose to be described hereafter. 
   It should also be noted that the free or distal edge  52  of the engagement arm is hook shaped so as to provide a smooth curved forwardly convex edge portion which as will become more clear hereafter, slidably engages the fabric material  28  in the covering to correct any skew that may be inherent therein. 
   The head rail  22  for the covering as possibly best seen in  FIG. 8 , includes an arcuate front wall  54  connected to a rear component  56  and a top wall  58 . The space between the front wall and an open rear of the head rail along the bottom of the head rail is also open so the fabric for the covering can be rolled onto or unrolled from the roller  24  through the open bottom of the head rail. End caps  62  are also provided at opposite ends of the head rail for aesthetics. 
   The front wall  54  of the head rail  22 , again as probably best seen in  FIG. 8 , has an arcuate main body  64  continuous upwardly with an inclined flat segment  66  that is in turn continuous with a generally flat upper ledge  68  that interconnects with the top wall  58  of the rear component  56  of the head rail in a conventional manner. Adjacent to the uppermost edge of the inclined flat segment  66  of the front wall, a generally inverted T-shaped rib  70  extends inwardly perpendicularly to the inclined flat segment and defines a downwardly opening pocket or groove  72  for receipt of the horizontal tab  50  along the upper edge of the skew adjustment device  36  as will be more clear hereafter. Adjacent to the lower edge of the arcuate main body  64  of the front wall of the head rail is another generally T-shaped inward projection  74  which defines an upperwardly opening seat or groove  76  for the lower edge of the skew adjustment device. 
   The front wall  54  of the head rail  22  is preferably an extruded member that can be made from aluminum, plastic or other suitable material so that the features described above are formed continuously along the horizontal length of the front wall. Accordingly, the pocket  72  and the seat  76  are confronting along the inner surface of the front wall for slidable receipt of the top and bottom edges of the skew adjustment device. 
   With reference to  FIG. 15 , the skew adjustment device  36  can be seen being inserted into the space on the front wall  54  between the pocket  72  and the seat  76  by positioning the flat horizontal tab  50  along the top edge of the skew adjustment device into the pocket at the top of the front wall of the head rail and then sliding the skew adjustment device along the inner surface of the front wall of the head rail until the bottom edge of the skew adjustment device is received in the upwardly opening seat  76 . The skew adjustment device, as mentioned, is made of a semi-rigid but resilient material and is sized so that it is compressed into the space between the upperwardly opening seat and the downwardly opening pocket with some spring bias being provided by the serpentine segment  48  of the skew adjustment device along with the inherent resilient characteristics of the material from which the skew adjustment device is made. Due to the flexibility of the device, it can also be inserted into the head rail laterally and snapped into place at a desired location. 
   When the skew adjustment device  36  is fully and slidably mounted on the front wall  54  of the head rail  22 , it is positioned as seen best in  FIG. 14  so as to apply pressure along the top and bottom edges against the pocket  72  and the seat  76  so that it can be releasably frictionally fixed at any position along the length of the head rail. As will be appreciated in  FIGS. 5A and 8 , when the skew adjustment device is desirably and slidably mounted on the head rail, the engagement arm  40  projects inwardly toward the roller  24 . 
   The hook shaped distal edge  52  of the engagement arm  40  as mentioned above provides a smooth curved convex surface for engagement with the material or fabric  28  of the covering and due to the arcuate nature of the distal edge of the engagement arm, the arm engages the material of the covering tangentially so as not to snag the material. As will be appreciated in  FIGS. 5A and 8 , when the material is substantially unwrapped from the roller  24 , the engagement arm remains in frictional engagement with the material as it obviously does when the material is fully wrapped about the roller as shown in  FIG. 8 . 
   The engagement of the arm  40  with the material  28  is designed to establish a frictional drag on the material and compresses the material on the roller as it is being wrapped or unwrapped from the roller. As will be appreciated by providing frictional drag and compression at a predetermined location along the length of the roller  24  the fabric is encouraged to wrap or unwrap in an unnatural way. This of course is designed to counter or offset the natural bias that may be in the fabric causing it to skew if not corrected. In other word, at the location on the fabric where the skew adjustment device  36  is engaged, the fabric is compressed toward the roller causing the material beneath the engagement arm to wrap more slowly and more tightly about the roller or unwrap more slowly and more tightly from the roller. Due to the fact that the skew adjustment device can be releasably fixed through friction at any position along the length of the head rail  22 , any degree of skew or inherent bias in the covering can be corrected. 
   By way of example, if the skew in the covering is as illustrated in  FIG. 3  with the right edge of the fabric  28  being wrapped more rapidly and more loosely than the left edge, the skew adjustment device  36  can be shifted to the right as shown in  FIGS. 5-7  to provide a frictional drag and increased tension toward the right side of the fabric allowing the left side to catch up so that the covering can be extended and retracted without skew. 
   An alternative embodiment of the skew adjustment device is shown in  FIG. 16  where again the device is made of a semi-rigid but resilient material wherein an arched plate-like back  78  of the device is smooth and does not include the serpentine segment  48  of the first-described embodiment. The device again includes an integral forwardly and upwardly inclined engagement arm  40  with the bottom edge  42  of the engagement arm being integral with the bottom edge of an opening  44  through the plate-like back  78  of the device and due to the integral connection of the engagement arm with the back along an edge of the engagement arm and the resilient semi-rigid characteristics of the material from which the device is made, the engagement arm is spring biased so if deflected up or down, it will be encouraged or biased to return to the neutral position shown in  FIG. 16 . Again, an opening  46  is provided through the back plate adjacent to the bottom edge thereof which defines a somewhat flexible arched segment  47  as in the first-described embodiment. The resiliency of the material and the relatively thin arched segment  47  in comparison to the remainder of the back plate enables the device to be laterally inserted and snapped into place within the head rail. It will be appreciated the serpentine segment  48  of the first-described embodiment is an optional feature of the device and is not mandatory. 
   Although the present invention has been described with a certain degree of particularity, it is understood the disclosure has been made by way of example and changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.

Summary:
A device for correcting skew in roll-up retractable coverings for architectural openings includes a friction device positioned within the head rail for movement between releasably fixed positions and disposed for engagement with the fabric of the covering to regulate the rate at which the fabric is wrapped about a roller in the covering at selected locations along the length of the roller to correct for any inherent skew in the covering.