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CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/814,674, filed on Apr. 22, 2013, entitled “DRIVE ASSISTED ROLLER ASSEMBLY FOR ROLLING DOOR”, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The disclosed embodiments relate to the field of drive systems for opening and closing rolling doors. 
     BACKGROUND OF THE INVENTION 
     Existing drive systems for rolling curtains/doors employ rollers on the door edges which engage surfaces of a track in a door guide positioned on a pair of opposite sides of a door opening. The door (curtain) may be a vertical door, which is deployed from top to bottom across a door opening; a side-coiling curtain, which is deployed sideways from left-to-right (or right-to-left) across the door opening; or a horizontal curtain, which is deployed across a horizontal opening such as, for example, a floor opening containing an escalator. 
     In such doors, the rollers provide a rolling engagement along the guide tracks. The door (curtain) itself is typically comprised of interlocking, loosely-fitted slats, which are locked together at their ends to maintain the slats in alignment with each other. 
     A problem can arise with any door traversing a significant space in that, in a high wind or other load condition, such as during a storm, a wind force against the door can create a bowed condition at an unsupported portion of the door slats, which bowing has the effect of creating an unwanted locking condition between the rollers and a surface of the tracks. Such condition can have the effect of prohibiting or restricting rolling movement of the door, depending on the wind load. 
     Even during regular load conditions, some movement or “play” exists between the rollers and the guide track such that the front faces of the rollers will contact the edges of the guide tracks and cause friction there-between. This condition limits the closing and opening speeds of the door. 
     Typically, for horizontal and side-coiling curtains, (and in instances where vertical curtains require constant operating speed), a pusher, in particular, a cog, is used to move the curtain between the opened and closed positions. In conventional systems, this is typically accomplished by positioning the cog for engagement with surfaces of the door slats to deploy and retract the curtain with respect to a coil that holds the undeployed portion of the curtain. In systems that use direct engagement of the pusher cog with the slats, wear on the slat surfaces is created and unwanted noise generated due to the striking of the cog with the slats as the curtain is moved between its opened and closed positions. To account for the wear to the slats, the metal gauge used to manufacture the slats need to be of a sufficient thickness. This adds to the cost and weight of the curtain. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved roller assembly that overcomes the deficiencies of the prior art and that, even under heavy load conditions on the door/curtain, provides for rolling contact of the rollers in the guide track. 
     In accordance with one aspect of the present invention, a door assembly for covering an opening defined by at least one structural element of a building, the door assembly includes: a shutter roller rotatable about an axis of rotation; a drive mechanism configured to rotate the shutter roller about the axis of rotation; a flexible door/curtain windable on and off the shutter roller such that the flexible door/curtain is movable into retracted and extended positions by operation of the drive mechanism, the flexible door having a plurality of connected slats, each having two ends; at least one guide rail assembly positioned on at least one side of the opening and coupled to the at least one side of the opening, the at least one guide rail assembly having: (a) an outer track, coupled to the at least structural element of the building and having at least a first portion extending parallel to the flexible door/curtain, (b) an inner track, coupled to the at least structural element of the building and having at least a first portion extending parallel to the outer track and parallel to the flexible door/curtain, (c) a roller support guide, arranged fixedly between the outer track and the inner track, and (d) first and second roller guides disposed opposite one another between the inner track and the outer track, with a space maintained between the first and second roller guides; and a plurality of coupling mechanisms, each of the plurality of coupling mechanisms being affixed to ends of one or more of the plurality of slats of the door/curtain, each of the plurality of coupling mechanisms comprising: (a) at least two door/curtain mounting brackets, each door/curtain mounting bracket having: (i) a mounting surface configured to connect to a slat of the door/curtain, and (ii) an extending surface oriented at approximately 90 degrees with respect to the substantially rectangular portion, the extending surface having at least one endlock configured to maintain alignment of the slats of the door/curtain; (b) a roller mounting bracket having: (i) a first roller arranged at an upper portion of the roller mounting bracket, the first roller being rotatable around an axis perpendicular to the lengthwise direction of the slats, and (ii) an extending portion, oriented at approximately 90 degrees with respect to the upper portion of the roller mounting bracket and connected to the at least one endlock; and (c) at least one second roller, each at least one second roller being rotatable around an axis perpendicular to the axis of rotation of the first roller and connected to the at least one endlock. The first roller and the at least one second roller are arranged so as to cooperate with the outer track, inner track, roller support guide and first and second roller guides to ensure that the door/curtain moves rollingly within the guide rail assembly even when the door/curtain is subjected to a deflecting force. 
     In another aspect, the at least one guide rail assembly further has a mounting support configured to secure the at least one guide rail assembly to the at least one structural element of the building, at least a first end of the mounting support being configured to be affixed to the at least one structural element of the building. 
     In another aspect, the coupling mechanisms are linked to one another by a link coupled to posts of adjacent coupling mechanisms. 
     In another aspect in an assembled state of the door assembly, the at least one second roller of each of the plurality of coupling mechanisms is maintained between the first and second roller guides even when the door/curtain is subjected to a deflecting force. 
     In another aspect, in an assembled state of the door assembly, the door assembly is configured such that each first roller is maintained in the at least one guide rail assembly between the roller support guide and at least one of the inner track and outer track, to ensure rolling contact between the first roller and the guide rail assembly even when the door/curtain is subjected to a deflecting force. 
     In another aspect, the coupling mechanisms each further include a spacing mechanism arranged between the at least one second roller and one or both of the extending surface of door/curtain mounting bracket and the extending portion of the roller mounting bracket. 
     In another aspect, the at least one second roller includes two second rollers. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller via an intermediate pusher cog. 
     In another aspect, the pusher cog has a plurality of cog teeth, and the pusher cog assists in moving the door/shutter between a closed position and an open position by engagement of the cog teeth with spaces formed in the plurality of coupling mechanisms between the second rollers. 
     In another aspect, the drive mechanism is contained within a drive housing. 
     In another aspect, the door assembly is a side coiling door assembly in which: the at least one guide rail assembly is coupled to a top side of the opening; the slats and shutter roller are arranged perpendicular to the ground; and the coupling mechanisms are arranged at top ends of the slats, proximal to the top side of the opening. 
     In another aspect, the drive mechanism is contained within a drive housing. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller via an intermediate pusher cog. 
     In another aspect, the pusher cog has a plurality of cog teeth, and the pusher cog assists in moving the door/shutter between a closed position and an open position by engagement of the cog teeth with spaces formed in the plurality of coupling mechanisms between the second rollers. 
     In another aspect, the door assembly is a horizontal coiling door assembly in which: the opening comprises a hole formed in a floor of the building; the at least one guide rail assembly comprises two guide rail assemblies, one coupled to the floor at one side of the hole formed in the floor, and the other coupled to the floor at the other side of the hole formed in the floor; the slats and shutter roller are arranged parallel to the ground and perpendicular to the direction of closing and opening the door/curtain; and the coupling mechanisms are arranged at both ends of the slats, respectively proximal to the one side of the hole in the floor and to the other side of the hole in the floor. 
     In another aspect, the drive mechanism is contained within a drive housing. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller via an intermediate pusher cog. 
     In another aspect, the pusher cog has a plurality of cog teeth, and the pusher cog assists in moving the door/shutter between a closed position and an open position by engagement of the cog teeth with spaces formed in the plurality of coupling mechanisms between the second rollers. 
     In another aspect, the door assembly is a vertical coiling door assembly in which: the opening is a hole formed in a wall of the building; the at least one guide rail assembly comprises two guide rail assemblies, one coupled to one side of the hole formed in the wall, and the other coupled to the other side of the hole formed in the wall; the slats and shutter roller are arranged perpendicular to the ground and perpendicular to the direction of closing and opening the door/curtain; and the coupling mechanisms are arranged at both ends of the slats, respectively proximal to the one side of the hole in the wall and to the other side of the hole in the wall. 
     In another aspect, the drive mechanism is contained within a drive housing. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller. 
     In another aspect, the drive mechanism includes a motor coupled to the shutter roller via an intermediate pusher cog. 
     In another aspect, the pusher cog has a plurality of cog teeth, and the pusher cog assists in moving the door/shutter between a closed position and an open position by engagement of the cog teeth with spaces formed in the plurality of coupling mechanisms between the second rollers. 
     In another aspect, the motor is coupled directly to the shutter roller by a belt or chain drive configuration. 
     In accordance with a second aspect of the present invention, a coupling is provided for a door assembly for covering an opening defined by at least one structural element of a building, the door assembly having: a shutter roller rotatable about an axis of rotation; a drive mechanism configured to rotate the shutter roller about the axis of rotation; a flexible door/curtain windable on and off the shutter roller such that the flexible door/curtain is movable into retracted and extended positions by operation of the drive mechanism, the flexible door having a plurality of connected slats, each having two ends; at least one guide rail assembly positioned on at least one side of the opening and coupled to the at least one side of the opening, the at least one guide rail assembly having: (a) an outer track, coupled to the at least structural element of the building and having at least a first portion extending parallel to the flexible door/curtain, (b) an inner track, coupled to the at least structural element of the building and having at least a first portion extending parallel to the outer track and parallel to the flexible door/curtain, (c) a roller support guide, arranged fixedly between the outer track and the inner track, and (d) first and second roller guides disposed opposite one another between the inner track and the outer track, with a space maintained between the first and second roller guides. The coupling includes: a plurality of coupling mechanisms, each of the plurality of coupling mechanisms being affixed to ends of one or more of the plurality of slats of the door/curtain. Each of the plurality of coupling mechanisms includes: (a) at least two door/curtain mounting brackets, each door/curtain mounting bracket having: (i) a mounting surface configured to connect to a slat of the door/curtain, and (ii) an extending surface oriented at approximately 90 degrees with respect to the substantially rectangular portion, the extending surface having at least one endlock configured to maintain alignment of the slats of the door/curtain; (b) a roller mounting bracket having: (i) a first roller arranged at an upper portion of the roller mounting bracket, the first roller being rotatable around an axis perpendicular to the lengthwise direction of the slats, and (ii) an extending portion, oriented at approximately 90 degrees with respect to the upper portion of the roller mounting bracket and connected to the at least one endlock; and (c) at least one second roller, each at least one second roller being rotatable around an axis perpendicular to the axis of rotation of the first roller and connected to the at least one endlock. The first roller and the at least one second roller are arranged so as to cooperate with the outer track, inner track, roller support guide and first and second roller guides to ensure that the door/curtain moves rollingly within the guide rail assembly even when the door/curtain is subjected to a deflecting force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects and advantages will become more apparent and more readily appreciated from the following detailed description of the disclosed embodiments taken in conjunction with the accompanying drawings in which: 
         FIGS. 1A and 1B  are front elevational and side views, respectively, illustrating a coupling attached to a section of a door/curtain, in accordance with an embodiment of the present invention; 
         FIG. 1C  is a perspective view of the coupling separate from the door/curtain to which it is shown attached in  FIGS. 1A and 1B ; 
         FIGS. 2A and 2B  are front elevational and side views, respectively, illustrating a plurality of couplings attached to an extended section of a door/curtain, in accordance with an embodiment of the present invention; 
         FIG. 3  is a diagram showing the couplings and door/curtain shown in  FIGS. 1A to 2B  in a guide track, in accordance with an embodiment of the present invention; 
         FIG. 4  is a side view illustrating the coupling and door/curtain being driven by a pusher cog, in accordance with an embodiment of the present invention; 
         FIG. 5  is a perspective view illustrating the coupling and door/curtain being driven by a pusher cog, in accordance with an exemplary embodiment of the present invention as used in a horizontal coiling door; 
         FIGS. 6A to 6D  are diagrams illustrating the use of the coupling and door/curtain shown in  FIGS. 1A to 2B  in the context of a side coiling door; 
         FIGS. 7A to 7C  are diagrams illustrating the use of the coupling and door/curtain shown in  FIGS. 1A to 2B  in the context of a vertical coiling door; 
         FIGS. 7D and 7E  are diagrams illustrating the use of the coupling and door/curtain shown in  FIGS. 1A to 2B  in the context of a vertical coiling door using a pusher cog; and 
         FIGS. 8A to 8D  are diagrams illustrating the use of the coupling and door/curtain shown in  FIGS. 1A to 2B  in the context of a horizontal coiling door. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed exemplary embodiments relate to rolling steel door/curtains provided with an inventive roller coupling configured to movably secure the door/curtain to a guide track. The door/curtain according to a preferred embodiment is made of a plurality of interlocking slats which are pivotally connected to each other to provide for a rolling of the curtain about a take-up roll. Exemplary configurations of rolling steel door/curtains employing the inventive modified roller coupling will be described below in detail with regard to  FIGS. 1A to 8D . 
     According to an exemplary embodiment, discussed herein in connection with  FIGS. 1A-2B , a steel door/curtain  10 , having slats  100 , is affixed at at least one side to a coupling mechanism comprising a plurality of couplings  200 . 
       FIGS. 1A and 1B  depict front and side views of a single instance of the modified coupling  200 , connected to two slats  100 .  FIG. 1C  is a perspective view of a single instance of the coupling  200 , not shown as being attached to slats  100  of the door/curtain  10 .  FIGS. 2A and 2B  depict front and side views of a plurality of such couplings  200  connected to plural slats  100  making up a door/curtain  10 . 
     As can be seen in  FIGS. 1A-2B , the slats  100  are connected to the couplings  200  at at least one end of the slat  100 , by a portion of the coupling  200  that will be referred to as a curtain mounting bracket  201 , having a rectangular member  202 . The connection is effected preferably via a plurality of rivets or screws  204 . In the views of  FIGS. 1A and 2A , the curtain mounting brackets  201  are shown in phantom, to indicate that they are behind the door slats  100  in those views. 
     One end of the mounting bracket  201  has an extending surface  206  oriented at approximately 90° with respect to the rectangular member  202 . This extending surface forms an endlock  208  to maintain alignment of adjacent slats of the curtain. Formed at each endlock  208  is a post  210  about which a traveling roller  212  is disposed and sandwiched between two spacers. In the illustrated embodiment, the spacer  213 , for example an annular brass spacer, is used to maintain the spacing between the top of each travelling roller  212  and transversely extending portion of the locking roller mounting bracket  216 . 
     The spacing between the bottom of the travelling roller  212  and the endlock  208  is preferably maintained by an annular ridge, formed in the inner wall of the travelling roller  212 , abutting a ledge formed on the post  210 , neither of which is visible in the figures. However, the bottom spacing is not limited to this configuration and can also be achieved, for example, by providing another annular spacer  213  in the gap between the endlock  208  and the travelling roller  212 . 
     The locking roller mounting bracket  216  has a transversely extending portion  217  that has a hole at each end. In the assembled combination of the door/curtain  10  and the coupling  200 , the posts  210  each extend through the inner opening of the travelling roller  212 , the spacer  213 , a hole in the transversely extending portion of the locking roller mounting bracket  216 , and a receiving hole formed in a connecting link  214 , as shown in  FIGS. 1A and 1B , and are secured to those respective components by fasteners such as nuts  218 , preferably using a washer  219  between the nut  218  and the connecting link  214 . 
     When coupled with the door slats  100 , the connecting links  214  and locking roller mounting brackets  216  are alternated such that, except for an endmost curtain locking roller mounting bracket  216 , each post  210  will be fastened to adjacent connecting links  214  and locking roller mounting brackets  216 , as shown, for example, in  FIGS. 2A and 2B . An endmost curtain mounting bracket would not include a connecting link on the side of the locking roller mounting bracket  216  towards the end of the door/curtain  10 . 
     The posts  210  provide a location for the traveling rollers  212  but also a spacing between the endlock  208  of each curtain mounting bracket  201  and either an end of a locking roller mounting bracket  216  or a connecting link  214 . 
     As shown in the side view of  FIG. 1B , the locking roller mounting bracket  216  has a longitudinal L-shaped cross section with one end corresponding to the transversely extending portion  217 , in this cross sectional view, fastened to the post  210 , and another end supporting a locking roller  220 , which is rotatably mounted on the locking roller mounting bracket  216 . As can be seen in  FIG. 1A , each instance of the locking roller mounting bracket  216  is associated with one locking roller  220  and two traveling rollers  212 . For each locking roller mounting bracket  216 , the locking roller  220  and two travelling rollers  212  are oriented at 90° with respect to each other such that they engage different surfaces of a door mounting guide track  300 , to be described next. 
     With reference to  FIG. 3 , the guide track  300  for one side of a door/curtain  10  is shown. In certain known door configurations, such as a side coiling door, the guide track  300  would only be used at one side of the door, namely the top side. In other configurations, such as a horizontal coiling door and a vertical coiling door, each side of the door/curtain  10  cooperates with a guide track  300 . In cases in which a second instance of the guide track  300  and second set of couplings  200  are utilized at the other side of the door/curtain  10 , the structure on the other side would be a mirror image of the structure shown in  FIG. 3 . 
     In the illustrated embodiment of  FIG. 3 , the guide track  300  includes a mounting/support angle  302 , an outer track angle  304 , an inner track angle  306 , and a locking roller retaining guide  308 . A pair of traveling roller guides  310  are positioned in opposing relation to each other on the outer track angle  304  and inner track angle  306  on either side of the traveling rollers  212  to provide a guide surface along which the traveling rollers  212  may roll during deployment and retraction of the door/curtain  10 . 
     In a preferred embodiment, the travelling roller guides  310  are preferably of different heights. For example, as in the exemplary embodiment illustrated in  FIG. 3 , the height of the roller guide  310  on the outer track angle  304  can be made larger than the height of the roller guide  310  on the inner track angle  306 . Such a configuration advantageously provides clearance for a smoke seal  312 , which, in the exemplary embodiment, is also attached to the inner track angle  306  and extends toward the door/curtain  10 . The smoke seal  312  functions to prevent the escape of smoke from one side of the door/curtain  10  to the other side of the door/curtain  10 , which would otherwise occur through the track  300  in the absence of the smoke seal. 
     In the mounting configuration illustrated in  FIG. 3 , the locking roller  220  is positioned between the outer track angle  304  and the locking roller retaining guide  308 . The locking roller  220  maintains positioning of the edges of the door/curtain  10  in the track  300  and also facilitates opening and closing of the door/curtain  10 , especially during a wind load condition, which can cause a deformation of the door/curtain  10 , such as a bowing of the door/curtain  10 . 
     In such a bowed condition, for example, the locking roller  220  will contact either the locking roller retaining guide  308  or the outer track angle  304 . In either event, rotational movement of the locking roller  220 , and therefore the door/curtain  10  to which it is attached, along either surface is accommodated, thereby allowing the door/curtain  10  to be opened or closed, even in a high wind load condition. 
     In the exemplary illustrated embodiment, the mounting/support angle  302  has a L-shaped configuration and is affixed at one end to the outer track angle  304  and the inner track angle  306  by a nut and bolt combination  314   b . The other end is preferably affixed to, e.g., a masonry wall  500 , by a nut and bolt combination  314   a.    
       FIGS. 4 and 5  illustrate how the door/curtain  10 , coupling  200  and guide track  300  cooperate to allow for movement, by operation of a pusher cog  400 , of the door in either a deployment direction or a retracting direction. As can be seen in  FIGS. 4 and 5 , the positioning of the connection links  214  provides a space, between the travelling rollers  212 , into which teeth  402  of the pusher cog  400  can be received to facilitate deployment and retraction of the roller curtain without requiring contact between the cog and the slats of the curtain. While not shown in  FIGS. 4 and 5 , the pusher cog  400  can be driven, for example, in any known manner, e.g., either directly or indirectly, by an electronic or manual door operator via, for example, a sash chain, timing belt, or the like. 
     The arrangement illustrated in  FIGS. 4 and 5  advantageously allows the pusher cog  400  to be positioned proximate the tracks, to engage the travelling rollers  212  in the space to drive the door/curtain  10  between the opened and closed positions. Also, as described above, the locking rollers  220  are oriented with respect to the locking roller retaining guide  308  and the outer track angle  304  so that, even during high wind conditions, which can deform the door/curtain  10  into, for example, a bowed condition, no sliding motion will occur between the door/curtain  10  and surfaces in the guide track  300 . Instead, due to the advantageous configuration of the rollers, coupling, door/curtain and guide track illustrated in  FIGS. 1A to 5 , all engagement between the door/curtain  10  and guide track  300  are with rollers. This arrangement provides for rolling curtains to no longer be restricted in movement during a load condition. 
     Unlike some conventional horizontal and side-coiling curtain systems, the configuration described above with respect to  FIGS. 1A to 5  does not require the pusher cog to directly engage the door slats themselves. Thus, no wear or damage is caused to the door slats. This reduces operational noise and also allows for a smaller gauge metal to be used for the door slats, thereby reducing weight. The reduced weight, in turn, allows for less stored spring energy to be used to open and close the door. 
     Moreover, because no pusher surface is needed on the door slats, an insulated, two-sided curtain can be used because the driving cog engages the openings but not the slats. In other words, because a slat surface is not needed to provide for engagement with the teeth of the pusher cog, a two-sided curtain having a flat surface on either curtain side can be used, with insulation sandwiched between the two sides. In addition, because there is no direct contact between the pusher cog and the slats, the door opening cycle is increased. Further, a lighter gauge metal stock can be used for the curtain slats because a less rugged curtain can now be employed as a result of the elimination of direct contact between the pusher cog and the curtain slats. 
     For vertical coiling curtains, an increased operational speed with a higher cycle can be achieved. Moreover, the curtain will be capable of regular opening and closing operation in high load conditions because of reduced friction between the door rollers and the track. A pusher cog can also be added to increase or regulate the opening and closing speed of the curtain. 
       FIGS. 6A to 6D  illustrate an exemplary utilization of the inventive coupling mechanism comprising couplings  200  in the context of a side coiling door. When referring to components already described above, the same reference numeral is used as in the prior description. 
     As is known to those skilled in the art, side coiling doors extend and retract horizontally, with the door/curtain  10  remaining perpendicular to the ground. In such a configuration, the bottom end of the door/curtain  10  typically runs in a track formed in the floor (not shown in the drawings), using, e.g., rollers or a sliding configuration. 
     In the side coiling door configuration illustrated in  FIGS. 6A to 6D , the top of the door/curtain  10  is fitted with couplings  200  which ride in guide track  300  in a manner substantially as shown in  FIGS. 3-5 . Also, while the engagement of the pusher cog  400  and the couplings  200  are shown schematically in  FIGS. 6A and 6C , the engagement between the pusher cog  400  and the couplings is effected in the same manner as shown in detail in  FIGS. 4 and 5 . 
     As shown in  FIGS. 6A to 6D , in the side coiling door configuration, the door/curtain  10  is opened and closed by operation of a drive unit  403 , preferably enclosed in a drive unit housing  406 , which, in the illustrated embodiment, extends from the floor to the top of the side coiling door. The drive unit  403  includes the pusher cog  400 , having cog teeth  402 , which cooperate with and engage the couplings  200  attached to the top of the door/curtain  10 , to move the door/curtain  10  in the manner discussed above with respect to  FIGS. 4 and 5 . The pusher cog  400  is configured to rotate in one direction to un-coil the door/curtain  10  from a coil pipe  408 , when closing the door/curtain  10 , and in the opposite direction when retracting the door/curtain  10  to an open position. The coil pipe  408  extends in the housing  406  the entire height of the door/curtain  10 . In the closed (i.e., retracted) position, the door/curtain  10  is substantially completely wrapped around the coil pipe  408  for secure storage. 
     The drive unit  403  also includes a motor  410  configured to set the pusher cog  400  in motion in either a clockwise or counter-clockwise direction. The motor  410  can be any standard motor that can be controlled, e.g., by a switch or other control, to drive a pusher cog  400  in the required directions, e.g., the clockwise and counter-clockwise directions. 
       FIG. 6A  is a front elevational view of the side coiling door configuration that utilizes the inventive couplings  200 , and  FIG. 6B  is a view taken along section  6 B- 6 B′. In the side coiling door configuration, the guide track  300  is disposed along the top of the door/curtain  10  and is affixed, in the manner shown in  FIG. 6B , to a structural support  700 . The structural support  700  is, for example, a laterally extending portion of the structure of the building in which the side coiling door is installed, for example a steel cross beam or a concrete member. 
     As can be seen in  FIG. 6B , in the exemplary embodiment of the side coiling door, the rails of the guide track  300  are affixed to the door/curtain  10  and coupling  200  in substantially the same manner as shown in  FIGS. 1-3 . In the illustrated embodiment, the rails of the guide track  300  are affixed to the structural support  700  by a transverse structural support member  704 , coupled to, and suspended from, the structural support  700  using, e.g., nut and bolt combinations  702 . In particular, each of the outer track angle  304  and the inner track angle  306  are affixed by nuts and bolts to the transverse structural support member  704 . 
     The door/curtain  10  is attached, along its top edge, to the couplings  200 , in the manner discussed above in relation to  FIGS. 1-3 , that is, by the curtain mounting brackets  201 , preferably via rivets or screws  204 . As can been in  FIG. 6B , the locking roller  220  rollingly contacts the locking roller retaining guide  308 , which, in the case of a side coiling door, supports at least a portion of the weight of the door/curtain  10 , since gravity tends to urge contact between the locking roller  220  and the locking roller retaining guide  308 . 
     The travelling roller guides  310  are disposed at each side of the travelling rollers  212  and function to maintain the door/curtain  10  moving along the guide track  300 , even in the case of a force being applied to the door/curtain  10 . In a typical configuration, a finish ceiling  706  can be provided at the top of the coiling door, at a position that hides guide track  300  and the portion of the door/curtain  10  at which the door/curtain  10  attaches to the couplings  200 , although the finish ceiling does not form any part of the present invention. Although not shown in  FIG. 6B , the door also preferably includes a smoke seal  312 , in the same manner as shown in  FIG. 3 , situated between the door/curtain and one rail. 
       FIGS. 6C and 6D  are a plan view and magnified partial view, respectively, of the side coiling door configuration. In  FIG. 6C , the door/curtain  10  itself, and the rails of the guide track  300 , are illustrated schematically to show the workings of the coil pipe  408 , the pusher pipe  404  and the pusher cog  400  in the drive unit housing  406 , which has already been described above. 
     At the right side of  FIG. 6C , the furthest extending portion of the door/curtain  10  in the closed position is shown in relation to a side wall reception unit  750  that receives the leading edge of the door/curtain. A detailed view of this portion of  FIG. 6C  is shown in the magnified view of  FIG. 6D . 
     In particular, in a preferred embodiment, in order to provide a secure connection of the leading edge of the door/curtain  10  with the wall, the door/curtain  10  has, at its leading edge, a leading edge unit  250  configured to lockingly engage in the side wall reception unit  750 . The side wall reception unit  750  has side members  752  at right angles to a wall  754 . A receiving channel  756  provides a break in the wall  754  into which the leading edge unit  250  can engage. As seen in  FIG. 6D , the leading edge unit  250  is configured to lockingly engage with a support  758  that is surrounded by side wall reception unit  750 . 
     Next, operation of a vertical coiling door will be described utilizing the inventive couplings  200 . As before, elements having the same configuration as those described previously will be denoted with the same reference numerals as in the previous figures. Two variations of the vertical coiling door are described below. In the first variation, the coil of the vertical coiling door is directly driven by a motor, without the use of a pusher cog. This variation is described with reference to  FIGS. 7A to 7C . 
     In a second variation, which is described with reference to  FIGS. 7D and 7E , the motor drives a pusher cog, which cooperates with the couplings  200  to wind and unwind the door/curtain  10  onto and off of the coil pipe. 
     With regard to the first variation, as shown in  FIGS. 7A to 7C , a vertical coiling door configuration comprises a door/curtain  10  that is wrapped around a horizontally oriented coil pipe  408  located along the top of the vertical coiling door. Guide tracks  300  extend vertically along each edge of the door/curtain  10  to form channels that permit the door/curtain  10 , attached at each edge to couplings  200 , to move easily up and down, from a closed to an open position, or vice versa. When the door is in the open position, the door/curtain  10  may be maintained, rolled up on the coil pipe  408 , entirely within the housing  606  that surrounds the coil pipe  408 . To close the door/curtain  10 , rotational force is applied from the motor  410  to the coil pipe  408 , for example by belt/chain  409 , to unspool the wound door/curtain  10  from the coil pipe  408 . 
     As shown in  FIGS. 7A to 7C , in the vertical coiling door configuration, the door/curtain  10  is opened and closed by operation of a drive unit  604 , preferably enclosed in a drive unit housing  606 , which, in the illustrated embodiment, extends across the top portion of the vertical coiling door. The drive unit  604  includes a motor  410  configured to set the coil pipe  408  in motion in either a clockwise or counter-clockwise direction. The motor drives the coil pipe using a belt or chain  409 . The motor  410  can be any standard motor that can be controlled, e.g., by a switch or other control, to drive the coil pipe in the required directions, e.g., the clockwise and counter-clockwise directions. The coil pipe  404  is configured to rotate in one direction to un-coil the door/curtain  10 , when closing the door/curtain  10 , and in the opposite direction when retracting the door/curtain  10  to an open position. The coil pipe  408  extends the entire width, from one lateral side of the door/curtain  10  to the other lateral side, along the top of the vertical coiling door. In the closed (i.e., retracted) position, the door/curtain  10  is substantially completely wrapped around the coil pipe  408  for secure storage. 
       FIG. 7A  is a plan view of the vertical coiling door configuration that utilizes the inventive couplings  200 , and  FIG. 7B  is a view taken along section  7 B- 7 B′. In the vertical coiling door configuration, two guide tracks  300  are provided, one proximal to each lateral edge of door/curtain  10 . Each guide track  300  is affixed, in the manner shown in  FIG. 7C , to a structural support  900 . The structural support  900  is, for example, a portion of the wall structure of the building in which the vertical coiling door is installed, for example a masonry wall. 
     The plan sectional view of  FIG. 7C , shows the one side of the door/curtain  10  attached to the roller assembly of the couplings  200  in the guide track  300 . A mirror image identical structure is employed at the other side of the door/curtain  10 . As discussed above with respect to  FIG. 3 , the door/shutter  10  is attached to the couplings  200  by curtain mounting brackets  201 . As in  FIG. 3 , the guide track  300  includes a mounting/support angle  302 , an outer track angle  304 , an inner track angle  306 , and a locking roller retaining guide  308 . A pair of traveling roller guides  310  are positioned in opposing relation to each other on the outer track angle  304  and inner track angle  306  on either side of the traveling rollers  212  to provide a guide surface along which the traveling rollers  212  may roll during deployment and retraction of the door/curtain  10 . The locking roller  220  is positioned between the outer track angle  304  and the locking roller retaining guide  308 . The locking roller  220  maintains positioning of the edges of the door/curtain  10  in the track  300  and also facilitates opening and closing of the door/curtain  10 , especially during a wind load condition, which can cause a deformation of the door/curtain  10 , such as a bowing of the door/curtain  10 . 
     The second variation is exactly the same as the first variation except that door/curtain  10  is moved from the closed to the open position, and vice versa, using pusher cogs  400  at either end of the housing, which engage the couplings  200  in the same manner shown in  FIGS. 4 and 5 . As can be seen from  FIG. 7D , the housing  606  extends across the top of the vertical coiling door, but in the second variation, the housing has within it both a pusher pipe  404  and a coil pipe  408 , upon which the door/curtain  10  is stored in the retracted, i.e., open door position. 
     In this variation, the drive unit  604  includes two pusher cogs  400 , each having cog teeth  402 , which cogs  400  cooperate with and engage the couplings  200  attached to both lateral sides of the door/curtain  10 , to move the door/curtain  10 , at each side, in the manner discussed above with respect to  FIGS. 4 and 5 . Preferably, in the second variation of the vertical coiling door configuration, one pusher cog  400  is disposed at each end of a pusher pipe  404 . The pusher cogs  400 , and the pusher pipe  404 , are configured to rotate in one direction to un-coil the door/curtain  10  from a coil pipe  408 , when closing the door/curtain  10 , and in the opposite direction when retracting the door/curtain  10  to an open position. In all other ways, the structure of the second variation of the vertical coiling door is identical to that of the first variation and those identical elements will not be described again here. 
       FIGS. 8A to 8D  illustrate an exemplary utilization the inventive coupling mechanism comprising couplings  200  in the context of a horizontal coiling door. When referring to components already described above, the same reference numeral is used as in the prior description. 
     A horizontal coiling door configuration is used, for example, for covering a gap in a floor, for example, one formed by an escalator. In such configuration the door/curtain  10  is oriented horizontally in a plane substantially parallel with the plane of the floor. The door/curtain  10  can, in this configuration, be opened by winding the door/curtain onto a coil pipe. 
     As is known to those skilled in the art, horizontal coiling doors extend and retract substantially horizontally, with all or the majority of the door/curtain  10  remaining parallel to the ground, i.e., the floor. 
     In the horizontal coiling door configuration illustrated in  FIGS. 8A to 8D , both lateral sides of door/curtain  10  are fitted with couplings  200  that ride in respective guide tracks  300  arranged, at each lateral side of the horizontal coiling door, in a manner substantially as shown in  FIGS. 3-5 . Also, while the engagement of the pusher cog  400  and the couplings  200  are shown schematically in  FIGS. 8A and 8C , for one side of the horizontal coiling door, the actual engagement between the pusher cog  400  and the couplings  200  is effected in the horizontal coiling door, in the same manner as shown in detail in  FIGS. 4 and 5 . 
     As shown in  FIGS. 8A to 8D , in the horizontal coiling door configuration, the door/curtain  10  is opened and closed by operation of a drive unit  503 , preferably enclosed in a drive unit housing  506 , which, in the illustrated embodiment, extends across the floor from one side to the other side of the horizontal coiling door. The drive unit  503  includes two pusher cogs  400 , each having cog teeth  402 , which cogs  400  cooperate with and engage the couplings  200  attached to both lateral sides of the door/curtain  10 , to move the door/curtain  10 , at each side, in the manner discussed above with respect to  FIGS. 4 and 5 . Preferably, in the horizontal coiling door configuration, one pusher cog  400  is disposed at each end of a pusher pipe  404 . The pusher cogs  400 , and the pusher pipe  404 , are configured to rotate in one direction to un-coil the door/curtain  10  from a coil pipe  408 , when closing the door/curtain  10 , and in the opposite direction when retracting the door/curtain  10  to an open position. The coil pipe  408  extends the entire width, from one lateral side of the door/curtain  10  to the other lateral side. In the closed (i.e., retracted) position, the door/curtain  10  is substantially completely wrapped around the coil pipe  408  for secure storage. 
     The drive unit  503  also includes a motor  410  configured to set the two pusher cogs  400  in motion in either a clockwise or counter-clockwise direction. The motor  410  can be any standard motor that can be controlled, e.g., by a switch or other control, to drive the pusher cogs  400  in the required directions, e.g., the clockwise and counter-clockwise directions. 
       FIG. 8A  is a plan view of the horizontal coiling door configuration that utilizes the inventive couplings  200 , and  FIG. 8B  is a view taken along section  8 B- 8 B′. In the horizontal coiling door configuration, two guide tracks  300  are provided, one proximal to each lateral edge of door/curtain  10 . Each guide track  300  is affixed, in the manner shown in  FIG. 8B , to a structural support  800 . The structural support  800  is, for example, a downwardly extending portion of the floor structure of the building in which the horizontal coiling door is installed, for example a steel cross beam or a concrete member. 
     As can be seen in  FIG. 8B , in the exemplary embodiment of the horizontal coiling door, the rails of the guide track  300  are affixed to the door/curtain  10  in substantially the same manner as shown in  FIGS. 1-3 . In the illustrated embodiment, the rails of the guide track  300  are affixed to the structural support  800  by the mounting/support angle  302 , coupled to the structural support  800  using, e.g., nut and bolt combinations  314   a . As in  FIG. 3 , each of the outer track angle  304  and the inner track angle  306  are affixed by nut and bolt combination  314   b  to the mounting/support angle  302 . This configuration is repeated, in a mirror image, at the other lateral edge of the door/curtain  10 . 
     The door/curtain  10  is attached, along each lateral edge, to the couplings  200 , in the manner discussed above in relation to  FIGS. 1-3 , that is, by the curtain mounting brackets  201 , preferably via rivets or screws  204 . As can been in  FIG. 8B  the locking roller  220  is maintained between the locking roller retaining guide  308  and the outer track angle  304 . 
     The travelling roller guides  310  are disposed at each side of the travelling rollers  212  and function to maintain the door/curtain  10  moving along the guide track  300 , even in the case of a force being applied to the door/curtain  10 . It is noted that in the case of a horizontal coiling door, the travelling rollers  212  will rollingly contact the lower one of the roller guides  310  under normal conditions, since the travelling rollers  212  are being urged to contact the lower roller guide by the force of gravity. Although not shown in  FIG. 8B , the door also preferably includes a smoke seal  312 , in the same manner as shown in  FIG. 3 , situated between the door/curtain and one rail. 
       FIGS. 8C and 8D  are a sectional view and magnified partial view, respectively, of the horizontal coiling door configuration. In  FIG. 8C , the door/curtain  10  itself, and the rails of the guide track  300 , are illustrated schematically to show the workings of the coil pipe  408 , the pusher pipe  404  and the pusher cog  400  in the drive unit housing  506 , which has already been described above. 
     At the right side of  FIG. 8C , the furthest extending portion of the door/curtain  10  is shown in relation to a side wall reception unit  850  that receives the leading edge of the door/curtain  10 . A detailed view of this portion of  FIG. 8C  is shown in the magnified view of  FIG. 8D . 
     In particular, in a preferred embodiment, in order to provide a secure connection of the leading edge of the door/curtain  10  with the wall, the door/curtain  10  has, at its leading edge, a leading edge unit  260  configured to allow the end of the door/curtain  10  to lockingly engage in the reception unit  850 . The reception unit  850 , in the illustrated example, has a J-shaped member  802  that is coupled to the rails of the guide track  300  and to a support  804 , which is affixed to the floor of the building. The J-shaped member  802  forms a receiving channel  806  into which the leading edge unit  260  can lockingly engage with the reception unit  850  by dropping into the receiving channel  804  when the door/curtain  10  is at a point of full extraction. 
     Although example embodiments have been shown and described in this specification and figures, it would be appreciated by those skilled in the art that changes may be made to the illustrated and/or described example embodiments without departing from their principles and spirit.

Summary:
A coupling for a door/curtain includes a plurality of coupling mechanisms affixed to ends of slats of the door/curtain. Each coupling mechanism includes a roller mounting bracket having a first roller arranged at an upper portion of the roller mounting bracket, and an extending portion, oriented at approximately 90 degrees with respect to the upper portion of the roller mounting bracket; and at least one second roller. Each second roller is rotatable around an axis perpendicular to the axis of rotation of the first roller. The first roller and the at least one second roller are arranged so as to cooperate with an outer track, inner track, roller support guide and first and second roller guides of a guide rail assembly to ensure that the door/curtain moves rollingly within the guide rail assembly even when the door/curtain is subjected to a deflecting force.