Abstract:
An overhead door, which is adapted to have its primary tracking members temporarily disengaged from their primary track when impacted by a substantial force when in the closed or partially closed position, is adapted to smoothly transition from its vertical, closed position to a non-vertical, open position by the use of second tracking members and track which come into use as the door panels transition from a vertical orientation to a non-vertical orientation. The impact caused disengagement feature is therefore effective without interference from the second tracking members, but progressively gives way to the second tracking members and track as the door is raised toward an open position.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to overhead doors and, more particularly, to a door with two separate track systems which allow for an effective transition from a breakaway mode when in the down position to the stored mode when in the raised position. 
         [0002]    Overhead doors are used to occlude openings in structures such as warehouses, factories, and other commercial establishments. Typically such a door is comprised of a series of panels hinged together and moveable between a doorway blocking position to an overhead storing position. In the stored position, the door may be disposed in a vertical, horizontal, or oblique angle position. For either of the horizontal or oblique angle dispositions there is generally provided a curved track to transition from the vertical closed position to the non-vertical stored disposition. 
         [0003]    Overhead doors used at loading docks are often subject to impacts from forklifts, other loading devices, and freight. Such impacts often cause damage to an overhead door and sometimes to the building structure supporting the door. Accordingly, various types of “breakaway” devices have been designed to allow for the door to be temporarily disengaged from its vertical track when impacted by a substantial force. One such assembly, described in U.S. Pat. No. 6,988,528, having common inventorship with the present invention, provides for the use of brushes on the side edges of the door, with the brushes being slideably disposed in a track and disengageable therefrom upon impact. Another apparatus, shown in U.S. Pat. No. 5,927,368, assigned to HPD International, Inc., provides a plurality of plungers extending outwardly from the door&#39;s edges to engage a groove of a track, with the spring biased plungers being disengaged from the track when the door&#39;s impacted. Another, U.S. Pat. No. 6,321,822, assigned to Rite-Elite Holding Corporation, includes a roller and track combination that is moveable relative to each other upon application of a breakaway force to the door. 
         [0004]    In each of the above systems, a problem arises when the door is raised and the breakaway apparatus is caused to move along a curved portion of the track to move the door to the stored position. That is, because the mounting structure is designed to provide the breakaway feature, it is not so flexible as to be easily made to move through the curved portion of the track without complications such as frictional loading or leaving the track. 
       SUMMARY OF THE INVENTION 
       [0005]    Briefly, in accordance with one aspect of the invention, a secondary track is provided above the doorway opening to accommodate a secondary tracking mechanism mounted on the door, such that when the door is in the down position, only the primary, disengageable, tracking mechanism is engaged in its primary track, but as the door is raised, the secondary tracking mechanism is fed into the secondary track, while at the same time the primary tracking mechanism is exiting its track. In this way, a smooth transition is made between the primary and secondary tracking mechanisms as the door is moved from the closed to the open position. 
         [0006]    In accordance with another aspect of the invention, the secondary tracking mechanism comprises a plurality of rollers that are mounted on the outer side of the door and in a location which is inboard from the outer edge of the primary tracking member such that they do not interfere with the movement of the door during a disengagement process as caused by an impact. 
         [0007]    In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the spirit and scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of an overhead door with the present invention incorporated therein. 
           [0009]      FIG. 2  is a top partial view of one side of the door as seen along lines  2 - 2  of  FIG. 1 . 
           [0010]      FIG. 3  is a perspective top view thereof of the other side of the door. 
           [0011]      FIG. 4   a - 4   c  are illustrative of various types of door mounting arrangements for which the present invention is applicable. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]    Referring now to  FIG. 1 , the invention is shown generally at  10  as applied to an overhead door  11  which is mounted in a vertically orientated, closed position to close an opening  12  in a building side wall  13 . The door  11  is comprised of a plurality of panels  14  that are hingedly connected at their edges, such that the door  11  is flexible to permit its movement around a curved track as it is moved to an open position. The door  11  has upper and lower edges  16  and  17  and side edges  18  and  19 . 
         [0013]    Mounted to the wall  13 , on either side of the door  11  are vertical support members  21  and  22 . The door  11  is supportably mounted within the vertical support members  21  and  22  in a manner which permits the door  11  to be temporarily disengaged from its mounting position when impacted by a substantial force as shown and described in U.S. Pat. No. 6,988,528, having common inventorship herewith, and incorporated herein by reference. 
         [0014]    As shown in  FIG. 2 , a primary track member  23  is mounted to the vertical support member  22  and includes a U-shaped track opening  24 . Attached to the door side edge  19  is a laterally extending brush  26 , which extends the vertical length of the door and projects into the U-shaped track opening  24  at its end  25 . The brush  26  is properly sized with respect to the track opening  24  such that the brush  26  can freely move upwardly and downwardly within the track opening  24  while, at the same time, providing a sealing relationship between the brush  26  and the track opening  24 . Further, as described in the above referenced patent, the brush  26  is sufficiently flexible such that when the door  11  is impacted on either side thereof by a sufficient force, the brush  26  can be caused to be dislodged from its position within the track opening  24  so as to permit the doors outward or inward movement to prevent significant damage to the door. 
         [0015]    Considering now the manner and structure for moving the door  11  to an open position, a lift bracket  27  is attached to the door side edge  19  at a point near the bottom of the door  11 , and a cable  28  is secured to the lift bracket  27 . The cable  28  passes upwardly to be wound around a pulley  29  mounted on a shaft  31  (see  FIG. 1 ). A torsion spring  32  mounted to the shaft  31  biases the rotation of the shaft  31  such that the door  11  is biased to move in the upward position. 
         [0016]    It should be recognized that other mechanisms for opening and closing the door  11  can be used while remaining within the scope of the invention. For example, rather than the pulley  29  and spring  32 , the cable  28  may be secured to a counterweight to provide the biasing effect. 
         [0017]    Having discussed the position of the door in the closed position, it is necessary to consider its position when moved to an open condition. As shown in  FIG. 1 , a pair of horizontally disposed rails or tracks  33  and  34  are provided to guide the movement of the door  11  to an open/storage position. Also, in order to bridge the movement of the door  11  between the vertical primary track members  23  and the tracks  33  and  34 , arcuate track members  36  and  37  are provided as shown. 
         [0018]    The applicants have found that when a door with side brushes mounted in vertical track openings is caused to move along an arcuate path, such as the arcuate track members  36  and  37 , the brushes are likely to come out of the track such that the door is no longer properly supported. The same problem is seen as occurring with other, non-brush, mounted arrangements such as those discussed hereinabove with respect to the prior art. Accordingly, the need was seen for a disengageable type of overhead door which, when moved to the open/stored position, will ensure that the door remains in a properly supported condition. The present invention accomplishes this in a simple and effective manner with the structure which will now be described. 
         [0019]    As will be seen in  FIG. 3 , rather than providing a continuous track which allows movement along the track from a closed door to an open door condition, a secondary track  38  (the portion shown being a vertical and linear portion of the arcuate track member  36 ) is provided in a position which is separate from and not aligned with the U-shaped track opening  24 . As will be seen in  FIG. 2 , the secondary track member  38  is mounted to the vertical support member  22  by a bracket  39 . 
         [0020]    Attached to the door outer side  41  is a plurality of secondary tracking mechanisms  42  (that shown being one mounted near the top of the door) which include a mounting bracket  43 , a shaft  44  and a roller or a wheel  46 . Preferably, such a secondary tracking mechanism  42  is attached to each side of each of the panels  14 . As will be seen in  FIGS. 2 and 3 , when the door  11  is in the closed position, the secondary tracking mechanism  42  which is nearest the top of the door, is engaged within the secondary track member  38 . As the door  11  is moved upwardly from the closed position, the secondary tracking mechanisms  42  progressively move into the secondary track member  38 , while at the same time, the brush  26  progressively exits from the U-shaped track opening  24  such that when the door is in the fully opened position, the brush is entirely outside of the U-shaped track opening  24  and free of engagement with any other structure, while the secondary tracking mechanisms  42  are all within the secondary track member  38 . The secondary track member  38  therefore comprises the vertical, linear portion of the arcuate member  36 , the arcuate portion of the arcuate track member  36  and the horizontal track  33 . When the door  11  is in the fully opened position, the secondary tracking mechanisms  32  should all be located within the tracks  33  and  34 . 
         [0021]    It should be recognized that, in order for the disengageable feature of the door (i.e. the tracking mechanism that is effective during periods in which the door is fully closed or in the partially closed position), to properly function, it is necessary that the secondary tracking mechanism be so placed so as to not interfere with the disengaging function. This is accomplished with the present invention by locating the secondary tracking mechanism  42  on the outer side of the door and in a position where its wheel is disposed transversely inwardly (i.e. toward the center of the door) from the outer edge of the brush  26 , as shown in  FIG. 2 . Thus, when the door is in the fully closed position, only the secondary tracking mechanism  42 , with its wheel  46 , is engaged with the secondary track member, and all of the other wheels  46  of the other secondary tracking mechanism are disengaged and free to move. Accordingly, almost the entire length of the door is free to be disengaged from the primary track  23 , and only at the very top of the door  11  will the secondary tracking mechanism  42  be prevented from being disengaged because of its having a wheel  46  engaged in the secondary track member  38 . 
         [0022]    Referring now to  FIGS. 4   a - 4   c,  there are shown various arrangements for storage of an overhead door. The arrangement shown in  FIG. 4   a  is that which is described hereinabove and is known as a high-lift arrangement.  FIG. 4   b  is a variation thereof wherein the support tracks are disposed at an oblique angle to the vertical. Although the oblique members are shown as disposed at a sharp angle with the vertical members, they may also include an arcuate section between the oblique and vertical members. In either case, the problem of the tracking members moving from the vertical to the oblique members as discussed hereinabove, remains. Accordingly, the present invention is very suitable for this arrangement as well. 
         [0023]    The  FIG. 4   c  arrangement, which is known as a true vertical arrangement, does not have the problem of the tracking member transitioning between members as discussed hereinabove since the tracking member can remain in the same track for both the closed door and open door position. However, the present invention may be used, if desired.