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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE DISCLOSURE 
       [0001]    The subject disclosure relates generally to a horizontal side-moving door and more specifically to a breakaway element for such a door. 
       BACKGROUND 
       [0002]    Typical horizontal side-moving doors include either a rigid or semi-rigid planar door panel that translates horizontally in front of a doorway or a flexible door panel that coils about a roller as a leading edge of the flexible panel translates horizontally in front of the doorway. Horizontal side-moving doors with a flexible panel and a roller can be referred to as horizontal side-rolling doors. 
         [0003]    Horizontal side-rolling doors, such as the one disclosed in U.S. Pat. No. 4,096,902; include one or two vertical rollers at either one or both lateral edges of the doorway. Some horizontal side-rolling doors have a single roller at one side of the doorway with a single curtain that extends and retracts across the full width of the doorway. 
         [0004]    In some cases, the “single curtain” is actually comprised of two layers, each having its own vertical take-up roller. In such cases, the two rollers are right next to each other at one lateral edge of the doorway. As the door opens, the two layers of the curtain separate at the edge of the doorway and wrap upon their respective rollers. 
         [0005]    Other horizontal side-rolling doors include two individual curtains, each supported by its own roller at opposite lateral edges of the doorway. For such doors, the leading edges of the two separate curtains meet at the center of the doorway as the door closes. To open the door, the two curtains move apart from each other and wrap upon their own roller (or set of rollers if each curtain has two layers). 
         [0006]    The leading edges of roll-up curtains and planar door panels are often reinforced by a relatively rigid vertically elongate member that can be susceptible to being accidentally struck by a forklift passing through the doorway. The collision can damage the door, particularly the elongate member. To prevent such damage, some horizontal side-moving doors have an adjustable telescopic, spring-return arm mechanism with an internal detent or stop that helps establish a normal operating length. The arm mechanism extends diagonally between the elongate member and its supporting track follower. In the event of a collision, the arm mechanism yields resiliently to protect the door. Although somewhat effective, such a mechanism is bulky, heavy and expensive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a front view a horizontal side-moving door shown in a closed position. 
           [0008]      FIG. 2  is a front view of the door of  FIG. 1  but showing the door partially open. 
           [0009]      FIG. 3  is a front view of the door of  FIG. 1  but showing the door fully open. 
           [0010]      FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 2 . 
           [0011]      FIG. 5  is a view taken along line  5 - 5  of  FIG. 4 . 
           [0012]      FIG. 6  is a cross-sectional view similar to  FIG. 4  but showing a breakaway condition. 
           [0013]      FIG. 7  is a cross-sectional view similar to  FIG. 4  but showing another breakaway condition. 
           [0014]      FIG. 8  is similar to  FIG. 4  but showing an alternate example. 
           [0015]      FIG. 9  is similar to  FIG. 5  but showing the example of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness. Additionally, several examples have been described throughout this specification. Any features from any example may be included with, a replacement for, or otherwise combined with other features from other examples. 
         [0017]      FIGS. 1-3  show a horizontal side-moving door  10  with at least one flexible curtain  12  that moves horizontally across a doorway  14  to open and close the door. In this particular example, door  10  includes two curtains  12  and  16  supported by spring-loaded rollers  18  installed in proximity with lateral edges  20  of doorway  14 . A preloaded torsion spring  22  urges each roller  18  to rotate in a direction that tends to draw in and wrap the respective curtain  12  or  16  onto itself. 
         [0018]    In order to open and close door  10 , the leading edges of curtains  12  and  16  are attached to relatively rigid elongate members  24  that are coupled to a drive unit  26 . Members  24  can be made of rectangular steel tubing or any other suitable material and having any suitable shape. For the illustrated example, drive unit  26  comprises two track followers  28  and  30  that are mounted for horizontal translation along an overhead track  32  that is installed in proximity with an upper edge  34  of doorway  14 . Elongate member  24  extends downward from track follower  30 , and the other elongate member  24  extends downward from track follower  28 . A chain  36  and/or cogged belt powered by a motor-driven wheel  38  and an idler wheel  40  is coupled to track followers  28  and  30 . Track follower  28  connects to an upper section  36   a  of chain  36 , and track follower  30  connects to a lower section  36   b  of chain  36  so that depending on the rotational direction of driven wheel  38 , drive unit  26  either moves elongate members  24  apart or together to respectively open or close the door  10 .  FIG. 1  shows door  10  closed with the curtains&#39; leading edges abutting each other near the center of doorway  14 ,  FIG. 3  shows door  10  open with most of the curtains wrapped around rollers  18 , and  FIG. 2  shows door  10  partially open. Numerous other ways of driving elongate members  24  apart and together are well within the scope of the disclosure. 
         [0019]    To hold elongate members  24  substantially vertical to facilitate operation and proper-closed alignment of members  24  yet still make the door  10  able to survive an accidental impact with a forklift or some other collision, elongate members  24  are each supported by a brace  40  that includes a readily replaceable, inexpensive breakable member  42 , as shown in  FIGS. 4-7 .  FIGS. 4 and 5  show brace  40  in a usual configuration with elongate member  24  being in a vertical operative position.  FIG. 6  shows a force of impact  44  forcing elongate member  24  to one dislodged position, and  FIG. 7  shows another impact force  46  in an opposite direction forcing member  24  to another dislodged position. 
         [0020]    In the operative position of  FIGS. 4 and 5 , a conventional fastener  48  pivotally connects an upper end  50  of brace  40  to a lug  52  on track follower  30 , and breakable member  42  connects a lower end  54  of brace  40  to two lugs  56  extending from elongate member  24 . In this example, breakable member  42  is in the form of a steel shear pin extending through end  54  and lugs  56 ; however, breakable member  42  could be of various other designs and could be installed as any breakable link between track follower  30  and elongate member  24 . The location of breakable member  42  and fastener  48 , for instance, could be interchanged. 
         [0021]    If force  44  or  46  is excessive, breakable member  42  shears or breaks from being in an intact shape ( FIG. 5 ) into multiple pieces ( FIG. 6  or  7 ), thereby protectively releasing elongate member  24  from brace  40 . Sufficient clearance  58  ( FIG. 4 ) between lower end  54  and elongate member  24  preferably exists to prevent an otherwise lack of clearance from resisting the breakaway movement of brace  40  relative to elongate member  24 , particularly when the breakaway action is as shown in  FIG. 7 . 
         [0022]    Upon breakage, to prevent any broken pieces of member  42  from falling to the floor or striking someone or something, a setscrew  60  screwed into lower end  54  and holds a central section  42   a  (first piece) of breakable member  42  to end  54 , and other setscrews  62  screwed into lugs  56  hold broken end pieces (second piece)  42   b  to lugs  56 . 
         [0023]    After a breakaway incident, setscrews  60  and  62  can be partially unscrewed, and the broken pieces of member  42  can be replaced by an unbroken member  42  of intact shape. Until such a repair can be done, a pivotal coupling  64  between elongate member  24  and track follower  30  allows member  24  to hang generally vertical so that door  10  can still be open and closed while brace  40  is disconnected. 
         [0024]    Pivotal coupling  64  can be a sleeve  66  journalled to a generally horizontal shaft  68 , wherein shaft  68  is attached to track follower  30 , and sleeve  66  is attached to the upper end of elongate member  24 . Such a coupling permits pivotal motion in the same general direction that forklifts pass through doorway  14 , thus elongate member  24  can “break away” or swing in a direction that member  24  is mostly likely to be struck. 
         [0025]    To ensure that the leading edges of curtains  12  and  16  can come together in sealingly tight engagement when door  10  closes, elongate members  24  preferably hang generally parallel and vertical as viewed face-on in  FIG. 1 . To accomplish this, an adjustment screw  70  between one end of shaft  68  and a lug  72  extending from track follower  30  can be tightened or loosened to level shaft  68 . 
         [0026]    To ensure that the leading edges of curtains  12  and  16  are substantially coplanar, the length of brace  40  can be made adjustable. In a preferred example, a threaded shank  74  of brace  40  can be screwed farther in or out of ends  50  and/or  54  to adjust the brace&#39;s  40  overall length. 
         [0027]    In an alternate example, shown in  FIGS. 8 and 9 , a shear pin block  84  replaces lugs  56 . Shear pin block  84  includes certain beveled surfaces to avoid binding between block  84  and lower end  54  as member  42  breaks away. In some cases, shear block  84  comprises two lugs  86  extending from a base  88  attached to a mounting surface  90  of elongate member  24 . At breakaway, to avoid binding between base  88  and lower end  54 , base  88  includes a beveled surface  92  that generally faces brace  40 , as shown in  FIG. 8 . Surface  92  is angularly displaced out of coplanar alignment with mounting surface  90  to create a ramp along which lower end  54  could readily slide rather than bind. Binding can be further avoided by having lugs  86  include two beveled surfaces  94  that are displaced out of coplanar alignment with each other, as shown in  FIG. 9 . 
         [0028]    It should be noted that the actual structure of track  32  and track followers  28  and  30  could vary widely and still be within the scope of the disclosure. In the illustrated example, track follower  30  includes several rollers  76  for weight support and for limiting the tipping of track follower  30 . An extension arm  78  can enhance the track follower&#39;s  30  ability to resist tipping. Additional rollers  80  can further resist tipping and help guide the track follower  30  along the length of track  32 . In some cases, extension arm  78  on track follower  30  and a similar extension arm  82  on track follower  28  can pass by each other in an overlapping relationship, as shown in  FIG. 1 . Although chain  36  is shown coupled to extension arms  78  and  82 , this was illustrated in this manner to clearly show the functional relationship between chain  36  and track followers  28  and  30 . Chain  36  can be connected to any other suitable point(s) on track followers  28  and  30 . 
         [0029]    At least some of the aforementioned examples include one or more features and/or benefits including, but not limited to, the following: 
         [0030]    In some examples, a horizontal side-moving door includes a breakaway feature that protects the door from permanent damage in the event of a collision with the door. 
         [0031]    In some examples, the breakaway feature is incorporated in a brace that is used for holding a leading edge of the door&#39;s curtain substantially vertical. 
         [0032]    In some examples, the horizontal side-moving door is still functional even after a breakaway incident occurs. 
         [0033]    In some examples, the breakaway feature includes a shear pin that does not fall to the floor after it shears into multiple pieces. 
         [0034]    In some examples, a breakable member is incorporated in a brace that is used for holding a leading edge of the door&#39;s curtain substantially vertical. Other than the breakable member breaking, the brace basically has no moving parts once the brace is installed. 
         [0035]    In some examples, after the breakable member breaks, a pivotal connection between a track follower and a reinforced leading edge of the door&#39;s curtain allows the relatively rigid leading edge to swing away from the general direction of impact. 
         [0036]    The foregoing examples provide a better way of protecting a horizontal side moving door from impact. Furthermore, although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.

Summary:
A horizontal side-moving door with a side-winding curtain or horizontally translating panel includes a breakaway brace that helps hold a relatively rigid leading edge of the curtain or panel in a substantially vertical orientation. Should a forklift accidentally strike the leading edge of the curtain or panel, a replaceable shear pin incorporated in the brace breaks away to release the leading edge, thus protecting the edge from damage. Although the shear pin can break into two or more pieces, the brace includes means for holding the pieces in place and preventing them from falling and hitting anything underneath the pin. Although with some limitations, the door is still operational even while the pin is broken.