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CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 11/079,700 filed on Mar. 14, 2005, now abandoned. 

   FIELD OF THE INVENTION 
   This invention relates to retainers for rolling doors and in particular to rolling doors for aircraft hangars in which relatively wide openings are closed by multiple doors arranged at opposite sides of the door opening to be stacked in a door open position at one side of the opening and to slightly overlap each other in a door closed position. 
   BACKGROUND OF THE INVENTION 
   Sliding or rolling doors and windows are commonly used in household and commercial buildings usually with a pair of doors closing an enclosure. Such doors typically have their own upper and lower guide tracks and are removable by vertical movement upwardly a small amount into the upper guide track to dislodge the lower portion of the door and permit its removal. Various devices have been developed to prevent such movement but their installation and use require the sides of guiding tracks or doors to be exposed. Also, such devices often prevent all movement of the doors which prevents their normal use. With aircraft hangar doors the door opening is very wide and multiple doors are used at each side of the door opening which obstruct the access to the upper track and upper door portions that are required to mace the prior art installation. 
   Aircraft doors of the rolling type typically are of light structure with a perimeter formed of channel members on the skin of light metal on one or both sides. The lower perimeter of the door typically supports track-engaging rollers which support the weight of the door during rolling and sliding movement between open and closed positions. The upper perimeter member of the door also supports rollers on vertical axis which engage the inside surfaces of flange members of a channel shaped guide member and hold the door in vertical position. Such doors are moveable vertically upwardly into the upper guide channel to permit placement of the lower track engaging rollers on the guide track. It is this characteristic of sliding doors to which the invention is directed. 
   SUMMARY OF THE INVENTION 
   Hurricanes and high winds are known to cause such doors to be lifted off of the tracks and to fall against expensive aircraft causing much damage. Violent earth motion during earthquakes can cause the same phenomenon. 
   Examination of aircraft hangars damaged following hurricanes that impacted Florida in 2004 found that a principal damage to aircraft in hangars was caused by the doors of the hangars which high winds caused to be displaced from their intended position and crash against the airplane housed in the hangar. 
   It would be very desirable to provide a means for preventing door displacement from their guiding tracks unless needed for door replacement and repair. Therefore, it is an object of the invention to provide a door retainer which prevents vertical displacement of the door and its rollers from its supporting track and at the same time permits the doors to be used without interference. 
   It is another object of the invention to provide such a door retainer which is easily installed on existing doors when they are in position on their tracks. 
   It is an object of the invention to provide a door retainer which prevents vertical displacement of the door and its rollers from the supporting track. 
   These and other objects of the invention are attained by a door retainer for aircraft hangar doors in which vertical movement of the door rollers to raise them off of their supporting tracks is prevented by a vertical retainer bolt adjustable to project above the upper top edge of the doors to engage the top guiding channel of the doors to limit upward door movement that might otherwise occur in strong or high wind conditions or during earthquakes. Such adjustment does not hinder normal opening and closing of the doors. The door retaining bolts are adjustable to a retracted position to permit door removal or replacement when required. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevation of an airplane hangar with multiple doors of the type to which the present invention is directed shown with the doors in their closed position; 
       FIG. 2  is an elevation similar to  FIG. 1  in which the doors are in an open position; 
       FIG. 3  is a diagrammatic sectional view generally on line  3 - 3  in  FIG. 1  showing the doors in their closed position; 
       FIG. 4  is an elevation of one door separated from the upper guiding tracks; 
       FIG. 5  is a cross-sectional view of three doors in their stacked condition as shown along line  5 - 5  in  FIG. 2 ; 
       FIG. 6  is a cross sectional view of one of the door rollers taken on line  6 - 6  in  FIG. 5 ; 
       FIG. 7  is a view of an alternative form of roller used with doors of the type related to this invention; 
       FIG. 8  is a cross sectional view of the upper end of one of the doors on line  8 - 8  in  FIG. 5 ; and 
       FIG. 9  is an enlarged view of the retainer of the invention shown in cross section. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The rolling doors to which the retainer of the present invention are related are shown in  FIGS. 1 through 3 . There are a wide variety of rolling and sliding doors and windows in use but those used for aircraft hangars such as designated at  10  must cover wide openings  12  to accommodate large wing spans of airplanes  14 . Consequently, they are used in larger numbers of four, six, eight or more to cover the hangar wide door opening. The present description will make reference to three doors at each side of an opening for a total of six doors. 
   Such doors are designated generally at  16  and typically are fabricated of light metal channel members defining the perimeter of the door and which can best be seen in  FIG. 5  with at least one side of the doorframe being covered with a light metal panel  18  often of a corrugated configuration. Each door typically has an upper channel member  20 , a lower horizontal frame member  22  and opposed vertically disposed door edge members  24  as seen diagrammatically in  FIG. 4 . 
   As best seen in  FIGS. 1-3  and  5 , with a six door arrangement having three doors disposed at each side of the door opening  12  a pair of central doors  16   a  are disposed to roll on a track  26   a . A pair of intermediate doors  16   b  are disposed adjacent each of the central doors  16   a  and are disposed to roll on tracks  26   b . Similarly a pair of end doors  16   c  are disposed to roll on tracks  26   c  and are adjacent to the intermediate door  16   b.    
   The tracks  26   a ,  26   b  and  26   c  are parallel to each other and each support a pair of doors  16   a ,  16   b  and  16   c , respectively, for movement at opposite sides of the door opening  12 . Such tracks extend beyond the sides of the door opening  12  to provide storage space for the doors in their open position as indicated at  FIG. 2 . 
   In  FIGS. 1 and 2  the doors  16  are disposed on the outside of the hangar  10  with storage of the stacked open doors extending beyond the sides of the building. Alternatively, however, where space permits, such doors are often mounted on the inside of the building so the stacked open doors  16  are within the interior of the hangar. 
   As best seen in  FIGS. 5-6 , the bottom frame member  22  of each of the doors  16   a ,  16   b  and  16   c  are provided with rollers or wheels  34  which roll on tracks  26   a ,  26   b  and  26   c . The rollers  34  seen in  FIG. 5  are formed with a V groove  36  which are complementary to the tracks  26   a ,  26   b  and  26   c . Such tracks typically are fabricated of ninety-degree angle iron which is readily available. The rollers  34  as seen in  FIG. 5  have a central track engaging portion  38  and opposed cheeks  40 . The cheeks  40  are larger radius than the central portion  38  to maintain the doors on their track. Because of the shape of the tracks, the V shaped wheels have a tendency to be cammed off the tracks when lateral pressure such as that due to high winds or earthquakes is applied to the doors. As an alternative to the V shaped rollers those of the type seen in  FIGS. 6 and 7  are used. Such rollers  42  are intended to engage conventional rail type tracks  44 . The rollers  42  have a central track engaging portion  46  and a larger diameter opposed cheeks  48  to maintain the rollers on the track  44 . 
   Whether the rollers  34  or  42  or employed both are supported on axles  50  which are held in position on the doors  16   a ,  16   b  and  16   c  by a U shaped bracket member  52  which can be bolted or otherwise fastened to the bottom channel member  22  of each of the doors. Preferably, a roller is attached adjacent to each of the opposite edges of each of the doors. 
   As best seen in  FIGS. 8 and 9 , the doors  16   a ,  16   b  and  16   c  are maintained in a vertical position by means of guide rollers  58  arranged at the upper edge of each of the doors for engagement with a guide track  60 . The guide track  60  is an inverted channel member having a central web  62  with opposed depending flanges  64 . A separate guide track  60  is used for each of the pairs of doors and each of the tracks  26   a ,  26   b  and  26   c . The upper tracks  60  extend continuously across the opening  12  in the hangar  10  and often extend beyond the opposite edges of the building as seen in  FIGS. 1 and 2 . 
   The guide rollers  58  are adapted to roll about vertical axis for engagement with the inner walls of opposed flanges  64 . For that purpose a pair of rollers  58  is disposed adjacent the opposite edges of the door so that one of the pair engages one of the flanges and the other of the pair engages the other flange  64  of the guide tracks  16 . 
   The guide rollers  58  are spaced from the central web  62  of the guide tracks  16  a sufficient amount so that the doors  16   a ,  16   b  and  16   c  can be placed on their respective tracks  26   a ,  26   b , and  26   c  or  44  by moving a door upwardly in the space between the flanges  64  until they engage the rollers  58  with the central web  62 . This allows sufficient space of the rollers  34  or  42  to clear their respective tracks  26   a ,  26   b , and  26   c  or  44  by moving the bottom of the door laterally to align the rollers with the tracks. It is this vertical movement which causes aircraft hangar doors to be displaced by high winds during hurricanes and tornadoes or earthquakes. It is to this characteristic of rolling doors for aircraft hangars to which the invention is addressed. 
   The door retainer to which the invention is directed is designated generally at  70 . The retainer  70  is disposed vertically in the upper door channel  20  of each of the doors and is in the form of a threaded bolt  72  passing through an opening  74  in a horizontal web portion  76  of the top door channel  20  of each of the doors,  16   a ,  16   b  and  16   c . Because hangar doors typically are made of light materials, the web  76  is often best reinforced with washers  78  disposed at the underside and topside of the web  76 . Similarly nuts  80  are threaded on the bolt  72  and tightened against each other to clamp the washers  78  and web  76  together and to firmly hold the bolt  72  in a vertical position. Adjustment of the retainer bolt  72  vertically to place its upper end  82  in closely spaced relation to the web  62  of the guide marks  60 . Proper adjustment requires that the space designated at  86  in  FIG. 9  be less than the depth of the guide rollers  34  or  42  at the bottom of the doors. The depth is the difference between the radius of the central portion  38  and checks  40  in the case of the roller  34  in  FIG. 5  and the central portion  46  and checks or flanges  48  of the rollers  42  in  FIG. 7 . 
   The difference in the radius of the central track engaging portions  38  or  46  and the associated checks  40  or  48  represents the amount of vertical movement of the associated door required to remove the door from its track and also the amount of required movement of the upper guide rollers  58  in the channel shaped guide track  60 . By adjusting the bolt  72  in close relation to web  62  thus vertical movement is limited to prevent removal manually or due to high winds or earthquakes. To remove the doors under normal conditions the retainer bolt  72  must be retracted a sufficient amount. 
   Installation of the retainer  70  preferably is at least two to each door closely adjacent to the opposite side edges of each door. If a single retainer is installed on each door, it should be disposed centrally between the side edges of the door. 
   Such installation of retainers  70  can be made easily with the doors in their usual vertical position on the tracks  16   a ,  16   b  and  16   c  by drilling a hole  74  to receive bolt  72  with the backing washers  78  and nuts  80  at opposite sides of the web as seen in  FIG. 5 . Tightening of the nuts toward each other grips the threaded bolt  72  and holds it firmly in position. 
   The installation of the retainer  70  and adjustment to their position to prevent displacement of the rollers from the associated tracks does not interfere with normal opening and closing of the doors  16   a ,  16   b  and  16   c.    
   It should be noted that with stackable rolling doors such as those used with aircraft hangars, various prior art retainers cannot be used because they require the sides of the doors or the guide tracks to be accessible for installation. 
   A retainer for aircraft hangar rolling doors has been provided in which multiple doors at either side of a door opening are each provided with retainers that are adjustable between positions permitting movement of door rollers from being displaced laterally of their supporting tracks  26   a ,  26   b  and  26   c  a position preventing such movement to maintain the doors on their tracks. In the latter position the doors can operate manually between open and closed positions. The retainers are easily installed in new construction or on existing doors.

Summary:
A retainer for aircraft hangar doors in which vertical movement of doors is adjustably limited to allow sufficient movement to permit door removal from their supporting tracks or to prevent such undesirable displacement during high wind conditions as experienced during hurricanes and tornadoes or violent earth motions during earthquakes. The retainer in its retaining position does not obstruct normal opening and closing of the doors and is economical to manufacture and install.