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BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of window coverings, and more specifically, to a multi-positional rolling window screen apparatus for selectively covering an open window. 
     It is well known that many windows may be opened in order to allow air to pass the outside environment into a dwelling. However, an open window also enables small animals and insects to enter a dwelling. Consequently, in order to allow the passage of air without allowing the passage of animals and insects, building owners commonly cover some or all of a window with a window screen. 
     A common window screen assembly utilizes mesh contained within an aluminum housing sized to fit a window. This screen assembly is affixed to the outside of a window within the window frame and generally stays in place covering the entire window until removed for storage. Installation must be done either through the use of a ladder or by maneuvering each screen through the interior of the building and through the open window. The difficulties involved in the process usually dictate that the screens are installed and removed seasonally at most, or, alternatively, left in place permanently. These screens are bulky and cumbersome and require careful storage preventing the mesh from being damaged. 
     Additionally, these screen assemblies, when deployed in a window frame, commonly collect dirt or insect matter or deteriorate in harsh weather conditions. The aesthetic appearance of the screens is thus diminished over time. Once installed, framed screens remain deployed at all times whether or not the window is open. 
     Furthermore, some attempts have been made which employ rolled up screens which are unrolled to cover a window opening. While such screens are useful for their intended purpose, limitations exist which prevent the screens from being used in a more advantageous manner. For instance, some screens are intended to only partially cover a window area or are designed to fully cover the entire window area. However, a need arises to provide a user with the option of positioning the window screens in a manner determined at the time of operation versus the limitations of the screen itself in determining the positioning of the screen. 
     There is a need, therefore, in the industry for a window screen apparatus for selectively covering an open window for these and other related, and unrelated, purposes. 
     SUMMARY OF THE INVENTION 
     Briefly described, the present invention, includes a preferred rolling window screen apparatus for selectively covering a window. The rolling window screen may be deployed in two extended states preventing animals and insects from entering the building through the window when the window sash is open. Since windows generally consist of a top window sash and a bottom window sash, the rolling window screen is designed to cover the area left open by either the top or bottom sash. When the top sash is lowered opening the upper portion of the window, the rolling window screen may be partially deployed in a first extended state covering the upper window portion. When the lower sash is lifted opening the lower portion of the window, the rolling window screen may be fully deployed covering the lower window portion. Alternatively, the rolling window screen may be left in a third, retracted undeployed state. In this state, no obstruction exists for blocking light from entering the building or obstruct the view through the window. Additionally, when in the retracted, undeployed state, the rolling window screen improves the aesthetic appearance of the window in which it is installed by not being seen when not needed. 
     In one preferred embodiment, the rolling window screen apparatus comprises a take-up roller rotatably attachable between sides of a window frame and adjacent the outer sides of an upper window sash slideably mounted between the sides of the window frame. A flexible screen wraps and unwraps, as required, around the take-up roller during the deployment and retraction of the screen. Preferably, the flexible screen is manufactured from plastic-coated fiberglass filaments woven together to form a mesh. The rolling window screen apparatus also includes a resilient pull-down bar which receives and securely grips a lower edge of the flexible screen. Opposing ends of the pull-down bar ride within vertical slots defined by side channels, which are affixed to opposing sides of the window frame and extend for substantially the height of the window frame. The side channels guide the pull-down bar and the flexible screen during deployment and retraction, thereby limiting movement of the flexible screen to a substantially vertical direction and promoting smooth operation. 
     The rolling window screen apparatus also comprises a pull-cord apparatus for effecting movement of the flexible screen. The pull-cord apparatus includes the pull-down bar and a pair of cords. A first, non-elastic pull-cord depends from a location on the pull-down bar which is centrally-located between the ends of the pull-down bar. A second, elastic take-up cord has a first end secured to one end of the pull-down bar. The remainder of the elastic take-up cord is guided from the first end of the pull-down bar to the second, opposite end of the pull-down bar. An interface interfaces the non-elastic pull-cord with the elastic take-up cord. The elastic property of the elastic take-up cord causes the second end of the elastic take-up cord to be normally pulled toward the second end of the pull-down bar, and, hence, guides the pull-cord in a direction parallel to the axial direction of the take-up roller and allows the pull-cord cord to depend, in an aesthetically-pleasing manner, adjacent a side of the window frame. When a user exerts a generally downward force on the pull-cord for the purpose of manually deploying the flexible screen, the elastic property of the elastic take-up cord allows the pull-cord to become repositioned centrally beneath the pull-down bar, thereby enabling the downward force of the user to be applied centrally beneath the ends of the pull-down bar. Upon the removal of the downward force, the interface, positioned adjacent the second end of the pull-down bar, allows the pull-cord to depend adjacent a side of the window frame. 
     The rolling window apparatus further comprises a first automatic deployment interface which is suitable for engaging a retention deployment interface mountable on the uppermost segment of the upper window sash. When engaged, should a user slide down the upper sash of the window, the retention deployment interface engages the first automatic deployment interface and exerts a generally downward force on the pull-down bar, thereby causing the flexible screen to automatically deploy from the take-up roller as the upper sash is slideably moved downward by the user and retains the flexible screen in a deployed position covering the window area left open by the lowering of the upper sash. 
     The rolling window apparatus further comprises a pair of retention members which are mountable to the lowermost segment of the window frame. The retention members engage the first automatic deployment interface retaining the flexible screen in a fully deployed position covering the entire window. 
     In operation, the flexible screen may be deployed in at least three deployment states. The three deployment states include the following: (i) a first engagement state wherein the flexible screen is releasably engaged to the window frame to enable the flexible screen to be deployed statically to cover at least a portion of the opening; (ii) a second engagement state wherein the flexible screen is releasably engaged to the sash to enable the flexible screen to be deployed dynamically according to the position of the sash; and (iii) a third engagement state wherein the flexible screen is disengaged from the window assembly to enable the retraction of the flexible screen onto the roller to expose substantially all of the opening. 
     It is therefore an object of the present invention to provide a retractable window screen. 
     Another object of the present invention is to provide an apparatus for quickly and easily deploying and removing a window screen. 
     Another object of the present invention is to provide a rolling window screen apparatus which automatically deploys when a window is opened. 
     Another object of the present invention is to provide a rolling window screen apparatus which may be deployed in at least three engagement states. 
     Another object of the present invention is to provide a rolling window screen apparatus which is aesthetically pleasing. 
     Yet another object of the present invention is to provide a rolling window screen apparatus which is easily mountable to a window. 
     Still another object of the present invention is to provide a rolling window screen apparatus having a pull-cord which is aesthetically pleasing. 
     Still another object of the present invention is to provide a rolling window screen apparatus having a convenient pull-cord apparatus for easily deploying the screen. 
     Still another object of the present invention is to provide a pull-cord assembly which may be utilized with other window coverings. 
     These and other objects, features and advantages of the present invention will become apparent upon reading and understanding this specification, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a rolling window screen apparatus, in a typical window environment, in accordance with the preferred embodiments of the present invention. 
     FIG. 2 is a front view of the rolling window screen apparatus of FIG. 1 with the front wall member removed, in which the screen is in a fully deployed position. 
     FIG. 3 is a front view of a rolling window screen apparatus of FIG. 2 in which the screen is in a partial deployment facilitated by the positioning of the upper sash 
     FIG. 4 is a front view of the rolling window screen apparatus of FIG. 1 with the front wall member removed, in which the lower window sash is raised. 
     FIG. 5 is a detailed cross-sectional view of the roller, screen and housing of the rolling window screen apparatus of FIG.  4 . 
     FIG. 6A is a perspective view of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 6B is a front view of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 6C is a side view of one end of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 6D is a side view of the opposite end of the front wall member of the rolling window screen apparatus of FIG.  6 C. 
     FIG. 6E is a back view of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 6F is a top view of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 6G is a bottom view of a front wall member of the rolling window screen apparatus of FIG.  1 . 
     FIG. 7 is a detailed perspective view of a pull-down bar of the rolling window screen apparatus in accordance with the preferred embodiments of the present invention. 
     FIG. 8 is a cross-sectional view of the first automatic deployment interface and the retention deployment interface of the rolling window screen apparatus of FIG.  3 . 
     FIG. 9 is a cross-sectional view of the first automatic deployment interface and retention members of the rolling window screen apparatus of FIG.  2 . 
     FIG. 10 is a cross-sectional view of the rolling window screen apparatus and window of FIG. 1 as viewed from a side. 
     FIG. 10A is a detailed cross-sectional view of a side channel of the rolling window screen apparatus of FIG. 1 as viewed from above. 
     FIG. 11 is a front view of the rolling window screen apparatus of FIG. 4 in which the pull-cord apparatus is partially tensioned. 
     FIG. 12 is a front view of the rolling window screen apparatus of FIG. 4 in which the pull-cord apparatus is fully tensioned and the screen is partially deployed 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, in which like numerals represent like components throughout the several views, a rolling window screen assembly  5 , in accordance with the first preferred embodiment of the present invention, is shown in FIG.  1 . The window screen assembly  5  is positioned within a window assembly  10  for deployment within the window area. The window assembly  10  is shown including a window frame  15 , an upper window sash  20  and a lower window sash  25 . The window frame  15  includes a pair of sides  30 ,  35  and a sill  17 . The sill  17  is located substantially at the lower ends of the sides  30 ,  35  and connects the pair of sides  30 ,  35  together. The upper window sash  20  and the lower window sash  25  are slideably mounted between the window frame sides  30 ,  35 . The upper window sash  20  and the lower window sash  25  are conventionally operable to be lowered and raised, respectively, in order to open the window. 
     As shown in FIG. 2, the rolling window screen assembly includes a flexible screen  45  which may be deployed from the top of the window frame to the bottom of the window frame to fully cover the window area. In this position, should the lower window sash  25  be opened, flexible screen  45  will cover the window opening. 
     As shown in FIG. 3, flexible screen  45  may be partially deployed to cover a window opening created by the lowering of the upper sash. In this manner, flexible screen  45  is releasably attached to the upper sash and automatically lowered covering the window opening when the upper sash is lowered. 
     As shown in FIG. 4, flexible screen  45  may be maintained in an undeployed state leaving a window opening open and unrestricted. 
     As best shown in FIGS. 2 and 5, the rolling window screen assembly  5  comprises a take-up roller  40  rotatably attached between the window frame sides  30 ,  35  substantially near the top of the window frame  15 . A flexible screen  45  having a first end and a second end is connected at the first end to the roller  40 . Preferably, the flexible screen is a window screen manufactured from plastic-coated fiberglass filaments woven together to form a mesh. The flexible screen  45  may be unwound and wound, as desired, about the roller  40 . The roller  40  includes a conventional roller retractor which comprises a bias which preferably is an internal, spring-tensioned retractor mechanism  215 . The bias is capable of applying continuous tension to the flexible screen  45  while also permitting the flexible screen  45  to be withdrawn against the spring force and wrapped again. The retractor mechanism  215  also provides sufficient spring force to keep the flexible screen  45  taut when unwound. 
     Preferably, the roller  40  is mounted within a housing  185  by means of pins  190 ,  195 . The housing  185  comprises a first end cap member  200 , a second end cap member  205  and a front wall member  210 . The pins  190 ,  195  are held in place in recesses in first and second end cap members  200 ,  205 , respectively. Each end cap member  200 ,  205  further comprises a mounting hole  220  in which a bushing  225  is inserted. The housing  185  may be securely mounted to the window frame sides  30 ,  35  by inserting a wood screw  230  through the bushing  225  in each end cap member  200 ,  205  and into the respective window frame side  30 ,  35 . 
     As best shown in FIGS.  1  and  6 A- 6 G, the front wall member  210  covers take up roller  40  and housing  185 . Front wall member  210  includes a series of horizontal slats which are positioned at various angles to provide shadowing to create an appearance which suggests that window screen assembly  5  is absent from the window assembly. A front wall top member  210   a  is located substantially adjacent the lower surface of the top of the window frame  15 . First slat member  210   b  depends downward from front wall top member  210   a  generally at an angle of one hundred and seventeen degrees. Second slat member  210   c  depends downward from first slat member  210   b  at an angle generally equal to one hundred and sixty-three degrees. Third slat member  210   d  depends downward from second slat member  210   c  at a general angle of one hundred and forty-eight degrees. Fourth slat member  210   e  depends downward from fourth slat member  210   d  and a general angle of one hundred and fifty-five degrees. Fifth slat member  210   f  depends downward from fourth slat member  210   e  at a general angle of two hundred and nine degrees. Sixth slat member  210   g  depends downward from fifth slat member  210   f  at a general angle of one hundred and forty-eight degrees. The overall construction of front wall member  210  creates shadowing on the respective horizontal slats in a manner replicating the shadowing of the top of window frame  15  and upper window sash  20  which would exist in the absence of window screen assembly  5 . Hence, this aids in creating the optical illusion that window screen assembly  5  is not present. 
     As shown in FIGS. 4 and 7, a resilient pull-down bar  50  is connected to the second end of the flexible screen  45 . Preferably, as shown in FIGS. 5 and 7, the pull-down bar  50  comprises a pair of elongated planar members  55 ,  60  and a first automatic deployment interface  65 . The elongated planar members  55 ,  60  are secured on either side of an edge of the flexible screen  45 . The first automatic deployment interface  65  is affixed to a first elongated planar member  55  which protrudes from the first elongated planar member  55  substantially between the ends of the elongated planar members  55 ,  60 . The first automatic deployment interface  65  is comprised of a first portion  70 , a second portion  75 , and a third portion  77 . The first portion  70  of the first automatic deployment interface  65  extends from the first elongated planar member  55  in a generally rearward direction toward the upper window sash  20  to connect to the second portion  75  at a vertex. The second portion  75  extends from the vertex in a generally downward direction toward the sill  17 . The third portion  77  extends from the first elongated planar member  55  in a generally upward direction toward the roller  40 . 
     As shown in FIGS. 3 and 8, the rolling window screen assembly  5  also comprises a retention deployment interface  80  mounted, generally, across and protruding from the uppermost segment of the upper window sash  20  at a location which enables it to cooperate with the first automatic deployment interface  65 . The retention deployment interface  80  comprises an elongated mounting flange  85 , a first interface portion  87 , a second interface portion  90  and a third interface portion  92 . The elongated mounting flange  85  may be secured to the upper window sash  20  using a plurality of wood screws  94 . The first interface portion  87  extends from the elongated mounting flange  85  in a generally forward direction away from the upper window sash  20 . The second interface portion  90  extends from the elongated mounting flange  85  in a, generally, downward direction. Preferably, the third interface portion extends generally vertically from an outer edge of the first interface portion  87  to an outer edge of the second interface portion  90 . The third portion  77  of the first automatic deployment interface  65  and the second and third interface portions  90 ,  92  of the retention deployment interface  80  are sized so that the second and third interface portions  90 ,  92  of the retention deployment interface  80  may be manually placed in a position between the third portion  77  of the first automatic deployment interface  65  and the remainder of the pull-down bar  50 . Once the first automatic deployment interface  65  is thus engaged by the retention deployment interface  80 , upward movement of the pull-down bar  50  is thus prevented by the force of the retention deployment interface  80 . 
     As shown in FIG. 2, the rolling window screen assembly  5  further comprises a pair of retention members  170  which are mountable to the sill  17  of the window frame  15 . As best shown in FIG. 9, each retention member includes a screw  175  rotatably inserted through a retention bracket  180  and secured into the sill  17 . The retention brackets  180  may be rotated to a position suitable for engaging an upper surface of the third portion  77  of the first automatic deployment interface  65 . When engaged, the retention members  170  prevent the flexible screen  45  from being retracted. 
     Referring again to FIG. 9, an additional feature of the effect of the retention members  170  on the first automatic deployment interface  65  is next shown and described. The force of the retention brackets  180  on the upper surface of the third portion  77  of the first automatic deployment interface  65  axially biases the upper portions of the pull-down bar  50  toward the retention members  170 . Similarly, the lower surface of the second portion  75  of the first automatic deployment interface  65  is axially biased downward, thus bringing the second portion  75  into contact with the sill  17 . The contact between the second portion  75  and the sill  17 , and between the bottom of the elongated planar members  55 ,  60  and the sill  17 , prevents insects and the like from going around the flexible screen  45  to gain entry into a building. 
     As shown in FIGS. 10,  10 A and  12 , the ends of the pull-down bar  50  and the side edges of the flexible screen  45  arc slideably inserted into vertical slots  95  defined by side channels  100 ,  105 . The side channels  100 ,  105  are affixed to the window frame sides  30 ,  35  and extend for substantially the height of the window frame. Preferably, the side channels  100 ,  105  may be mounted to the window frame sides  30 ,  35  using a fastener  107 , which preferably may be a wood screw. Each side channel comprises a front channel member  235 , a rear channel member  240 , and a channel mounting member  245 . 
     As best shown in FIG. 10A, each front channel member  235  includes a series of generally vertical slats which are positioned at various angles to provide shadowing to create an appearance which suggests that window screen assembly  5  is absent from the window assembly. First front channel slat member  235   a  is located substantially parallel to the upper and lower window sashes  20 ,  25 . Second front channel slat member  235   b  depends from first front channel slat member  235   a  toward the window sashes generally at an angle of one hundred and fifty degrees. The overall construction of front channel member  235  creates shadowing on the respective vertical slats in a manner replicating the shadowing of the side of window frame  15  and upper and lower window sashes  20 ,  25  which would exist in the absence of window screen assembly  5 . Hence, the overall construction of the front channel member  235 , along with that of the front wall member  210 , creates the optical illusion that window screen assembly  5  is not present. 
     Referring again to FIGS. 5 and 8, an additional feature of the first automatic deployment interface  65  relative to the retention deployment interface  80  is next shown and described. 
     As shown in FIG. 7, the rolling window screen assembly  5  also comprises a pull-cord apparatus  110  for effecting movement of the flexible screen. The pull-cord apparatus  110  includes the pull-down bar  50  and a pair of cords  115 ,  120 . A first, non-elastic pull-cord  115  depends from the pull-down bar  50  through an aperture  125  in its bottom surface. The aperture  125  is centrally located between the ends of the pull-down bar  50 . A first end of the pull-cord  115  is secured to a short length of tubing  135  for a purpose to be explained below. The short length of tubing  135  is located generally inside the pull-down bar  50 . As shown in FIGS. 4 and 7, the remainder of the pull-cord  115 , including a force transmitting portion  145  of the pull-cord  115  and a second end of pull-cord  115 , resides substantially adjacent the outer side of the window sashes  20 ,  25 . 
     A second, elastic take-up cord  120  has a first end secured internally to one end of the pull-down bar  50 . The first end of the elastic take-up cord  120  may be easily retained by inserting the first end through a slit  155  in the end of the pull-down bar and tying a knot  160  near the first end of the elastic take-up cord  120 . The knot  160  and the slit  155  are preferably sized so that the knot  160  cannot travel through the slit  155 . The remainder of the elastic take-up cord  120  is guided from within the pull-down bar  50  through the short length of tubing to the second, opposite end of the pull-down bar  50  and through an opening  140  to depend from the second end of the pull-down bar  50 . Preferably, the opening  140  is comprised of a first eyelet. The second end of the elastic take-up cord  120  connects to a second eyelet  130  outside the pull-down bar  50 . The opening  140  and the eyelet  130  are preferably sized so that the second eyelet  130  cannot travel through the opening  140 . The pull-cord  115  extends through the second eyelet  130  such that the force transmitting portion  145  of the pull-cord  115  depends from the second eyelet  130 . 
     As shown in FIG. 4, the elastic property of the elastic take-up cord  120  causes the second end of the elastic take-up cord  120  to be normally pulled toward the first eyelet  140 , and, hence, causes the second eyelet  130  to be normally positioned adjacent the first eyelet  140 , thereby guiding the pull-cord  115  first in a direction parallel to the axial direction of the take-up roller  40  and then allowing the pull-cord  115  to depend, in an aesthetically-pleasing manner, adjacent a side  30  of the window frame  15 . However, when a generally downward force is exerted on the pull-cord  115 , a corresponding force is exerted on the eyelet  130  connected to the elastic take-up cord  120 . As shown in FIGS. 11 and 12, the elastic property of the elastic take-up cord  120  allows the elastic take-up cord  120  to stretch when the corresponding force is exerted upon the eyelet  130 . As the elastic take-up cord  120  is stretched, it moves through the short length of tubing  135  and through the first eyelet  140 . Preferably, the first eyelet  140  is comprised of a material creating a relatively low amount of friction on the elastic take-up cord  120  as the elastic take-up cord  120  is moved through it. Similarly, the short length of tubing  135  protects the elastic take-up cord  120  from additional friction created by contact with the pull-cord  115  near the centrally located aperture  125  in the pull-down bar  50 . The elastic take-up cord  120  is stretched until the eyelet  130  becomes repositioned beneath the pull-down bar as shown in FIG. 12 in a location generally central to the pull-down bar  50 , thereby enabling the downward force to be applied centrally to the pull-down bar  50 . Upon the removal of the downward force, the elastic nature of the elastic take-up cord  120  causes the elastic take-up cord  120  to contract until the second eyelet  130  becomes, once again, positioned adjacent the first eyelet  140 . This allows the pull-cord  115  to depend, once again, adjacent a side  30  of the window frame  15 , as shown in FIG.  4 . 
     As shown in FIG. 11, preferably, the second end of the first cord  115  is connected to a third eyelet  150  which may be secured to the window frame side  30  using a wood screw. The third eyelet  150  is attached at a location on the window frame side  30  generally midway between the top and bottom of the side  30 . The location at which the third eyelet  150  is attached is chosen to be substantially adjacent the location of the second end of the pull-cord  115  when no downward force is being exerted on the pull-cord  115  so that the second eyelet  130  is free to maintain its position adjacent the first eyelet  140 . In addition, the pull-cord apparatus  110  preferably further comprises a handle  155  slideably connected to the force transmitting portion  145  of the pull-cord  115 . The handle  155  preferably comprises a plastic tube of such a size that it may be grasped easily. Together, the attachment of the second end of the first cord  115  and the handle  155  provide a means for more conveniently exerting the generally downward force previously described. When a force is exerted on the handle  155  which has a component which is generally downward and a component which is generally lateral from the attachment side  30  of the window frame  15  toward the opposite side  35 , the handle  155  begins to slide from the second end of the pull-cord  115  toward the first end of the pull-cord  115  as shown in FIG.  11 . As the handle moves away from the window frame side  30  and becomes repositioned underneath a central location of the pull-down bar  50 , the generally downward component of the force allows the elastic take-up cord  120  to stretch and move as described previously and as shown in FIG.  12 . 
     In operation, the flexible screen  45  may be selectively deployed and retracted to cover all or part of a window in order to prevent objects from passing through an open window. The general operation of the flexible screen  45  is as follows. As shown in FIGS. 2,  3  and  4 , the spring force exerted by the retractor mechanism  215  on the roller  40  continuously urges the flexible screen  45  into a substantially retracted position in which the flexible screen  45  is substantially fully wound around the roller  40  and statically held in place. As described previously, in the substantially fully retracted position, the second eyelet  130  of the elastic take-up cord  120  is thus pulled toward the second end of the pull-down bar. In the substantially fully retracted position, the second end of the pull-down bar  50  is substantially adjacent an upper corner of the window frame  15 . Thus, the first cord is guided from a location generally central to the pull-down bar toward the upper corner and then to depend adjacent the window frame side  30 . However, when a generally downward force is exerted on the force transmitting portion  145  of the first cord  115  or, preferably, on the handle slideably connected to the force transmitting portion  145  of the first cord  115 , a corresponding force is exerted on the eyelet  130  connected to the elastic take-up cord  120 . The elastic property of the elastic take-up cord  120  allows the elastic take-up cord  120  to stretch, as shown in FIG. 11, until the second eyelet  130  becomes repositioned beneath a location generally central to the pull-down bar  50 , thereby enabling the downward force to be applied centrally to the pull-down bar  50 . The continued application of the generally downward force causes the flexible screen  45  to begin to unwind from the roller  40 , as shown in FIG.  12 . As the flexible screen  45  is moved downward, the side channels  100 ,  105  guide the pull-down bar  50  and the flexible screen  45  in the vertical slots  95 , thereby limiting movement of the screen  45  to a substantially vertical direction and promoting smooth operation. The positioning of the pull-cord apparatus enables a user located within a dwelling to deploy the flexible screen from inside the dwelling. 
     Once the generally downward force on the pull-down bar is removed, the operation of the flexible screen  45  is reversed and the flexible screen  45  is retracted. The flexible screen  45  is wound onto the roller  40 . The side channels  100 ,  105  guide the smooth upward movement of the pull-down bar  50  and the edges of the flexible screen  45  within the vertical slots  95  until the screen returns to the substantially fully retracted position once more. 
     At any given time the flexible screen  45  may be engaged, under the above generally described method of operation, in one of at least three engagement states. In a first engagement state, shown in FIG. 2, the flexible screen  45  is statically deployed using the operation generally described previously. The generally downward force is applied to the pull down bar  50  until the pull down bar  50  is substantially adjacent to the sill  17 . The retention members  170  may then be adjusted to engage the pull-down bar by abutting the upper surface of the third portion  77  of the first automatic deployment interface  65 , as shown in FIG.  9 . The tension imposed on the flexible screen  45  by the retractor mechanism  215  is resisted by the downward force imposed by the retention members  170  to statically deploy the flexible screen  45  to cover the entire window. It should be clear that although, as described, the flexible screen is deployed to cover substantially the entire window, retention members  170  may alternatively be placed in other locations in the vertical direction to enable alternative static deployments of the screen  45 . Thus, the user located within the dwelling may deploy the flexible screen from inside the dwelling. 
     In a second engagement state, shown in FIG. 3, the flexible screen  45  is dynamically deployed using the operation generally described previously. However, the generally downward force is applied to the pull down bar  50  by engaging the pull down bar  50  to the retention deployment interface  80  as shown in FIG.  8  and applying the generally downward force to the upper window sash  20 . As the upper window sash  20  is slid downward between the window frame sides  30 ,  35 , the retention deployment interface  80  secured to the upper window sash  20  is moved as well. The second and third portions  75 ,  77  of the retention deployment interface  80  engage the first portion  70  of the first automatic deployment interface  65  and retained against the remainder of the pull down bar  50 . This engagement thus exerts a generally downward force on the pull down bar  50  and the flexible screen  45  is thus deployed as described previously. The tension imposed on the flexible screen  45  by the retractor mechanism  215  is resisted by the downward force imposed by the retention deployment interface  80 . In the second engagement state, however, the extent to which the flexible screen  45  is deployed depends on the position in which the upper window sash  20  is placed by a user. Thus, in the second engagement state, the flexible screen  45  is deployed dynamically according to the position of the upper window sash  20 . Once again, the user may deploy the flexible screen from inside the dwelling by merely positioning the upper sash. 
     In a third engagement state, shown in FIG. 4, the retention deployment interface  80  is disengaged from the first automatic deployment interface  65  and no generally downward force is applied to the pull down bar  50 , thus allowing the flexible screen to substantially fully retract onto the roller. In this engagement state, the movement of the upper window sash  20  does not affect the deployment of the flexible screen  45 , as best shown in cross-section in FIG. 12, and the substantially full retraction of the flexible screen  45  enables substantially all of the window to be exposed. 
     In an additional feature of the present invention, the pull-down bar  60  and the flexible screen  45  may be easily adjusted from one engagement state to another. To adjust the flexible screen  45  from the first engagement state to the second engagement state, the retention members  170  are first manipulated to achieve the release of the first automatic deployment interface  65  from the retention brackets  180 . As previously described, the tension imposed by the retractor mechanism  215  causes the flexible screen  45  to be gradually wound onto the roller  40  The side channels  100 ,  105  guide the smooth upward movement of the pull-down bar  50  and the edges of the flexible screen  45  within the vertical slots  95  until the third portion  77  of the first automatic deployment interface  65  is engaged by the retention deployment interface  80  in the second engagement state. The steps just described may be reversed to adjust the flexible screen  45  from the second engagement state to the first engagement state. 
     To adjust the flexible screen from the second engagement state to the third engagement state, the first automatic deployment interface  65  is first disengaged from the retention deployment interface  80  by moving the pull-down bar downward until the pull-down bar  50  is generally no longer adjacent to the retention deployment interface  80 . The pull-down bar  50  may then be manipulated to laterally displace the first automatic deployment interface  65 , in a direction generally away from the window sashes  20 ,  25 . The lateral displacement must be of a sufficient distance to allow the first automatic deployment interface  65  to be successfully moved upward without significant interference from the retention deployment interface  80 . It is a feature of the present invention that sufficient lateral displacement may be achieved by removing the pull-down bar  50  and flexible screen  45  from the vertical slots  95  or by flexing the resilient pull-down bar  50  without removing the bar from the slots. Similarly, the flexible screen may be adjusted from the first engagement state to the third engagement state by first manipulating the retention members  170  to achieve the release of the first automatic deployment interface  65  from the retention brackets  180  and then following the procedure just described. 
     To adjust the flexible screen from the third engagement state to the second engagement state or to the first engagement state, a centrally-located generally downward force is exerted upon the pull-down bar  50  to move the pull-down bar  50  downwardly until the lower surface of the second portion  75  of the first automatic deployment interface  65  is makes contact with the first interface portion  87  of the retention deployment interface  80 . It is an additional feature of the present invention that the slope of the lower surface of the second portion  75  of the first automatic deployment interface  65  effectuates the outward movement of the first automatic deployment interface  65  when sufficient downward force is exerted upon the pull-down bar  50 . The lateral displacement created by this action, in combination with the flex created in the resilient pull-down bar, is sufficient to allow the first automatic deployment interface  65  to be moved downard past the retention deployment interface  80  while the pull-down bar is still being retained within the vertical slots  95  by the side channels  100 ,  105 . The pull-down bar  50  may then be manipulated to engage the first automatic deployment interface within the retention deployment interface  80  to achieve the second engagement state, or the pull-down bar  50  may then be lowered to enable the retention members  170  to be manipulated to engage the first automatic deployment interface  65  to achieve the first engagement state. 
     Although the pull-down bar  50  and pull-cord apparatus  110  are depicted only as being operable with the flexible window screen  45  described previously, it should be clear that they may similarly be used with shades and other window treatments, and that such use is within the scope of the present invention. 
     While the embodiments of the present invention which have been disclosed herein are the preferred forms, other embodiments of the method and apparatus of the present invention will suggest themselves to persons skilled in the art in view of this disclosure. Therefore, it will be understood that variations and modifications can be effected within the spirit and scope of the invention and that the scope of the present invention should only be limited by the claims below.

Summary:
A rolling window screen assembly for use with a window assembly. The screen assembly is deployable in at least three positions. The first engagement position exists wherein the flexible screen may be extended over the entire window. The second engagement position exists wherein the flexible screen is releasably engaged to a sash to enable the flexible screen o be deployed dynamically according to the position of the sash. Finally, the flexible screen may be disengaged from the window assembly and retracted to expose substantially all of the window opening. A pull-cord apparatus having a pull-down non-elastic cord interfacing with an elastic take-up cord may be utilized for manipulating the flexible screen.