Patent Publication Number: US-6698490-B2

Title: Release mechanism for industrial doors

Description:
This is a Continuation-In-Part of U.S. application Ser. No. 09/541,830, filed Apr. 3, 2000, which will issue as U.S. Pat. No. 6,321,822 on Nov. 27, 2001, which is, a Continuation of U.S. application Ser. No. 09/280,343, filed Mar. 29, 1999, now U.S. Pat. No. 6,148,887 which is a continuation of U.S. application Ser. No. 08/654,500, filed May 28, 1996, now U.S. Pat. No. 5,887,385. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed generally to industrial doors, and more specifically to a release mechanism for allowing an industrial door to break away from its associated guide track upon an applied force above a certain magnitude. 
     BACKGROUND OF THE INVENTION 
     A wide variety of doors are used in industrial settings. Such industrial doors include conventional sectional doors, comprising a series of panels hinged together to form the door. Typically, such a sectional door is movable between doorway-blocking positions and overhead-storing positions. For this purpose, a curved guide track is disposed on either side of the doorway, with one leg (adjacent to the doorway opening) extending vertically along the doorway, and the second leg (projecting back from the doorway opening) disposed above and behind the doorway. A curved track section joins the two legs. Sectional doors may also be vertically stored, that is they may have straight tracks and be movable in a continuous plane between doorway-blocking and doorway-opening positions. Typically, the panels comprising such a sectional door are formed of either metal or wood. 
     In other types of industrial doors, the door itself may be formed of fabric. One such type of fabric industrial door is a roll-up door, in which the door is a curtain of fabric rolled on a roller tube typically disposed above the doorway opening. To close the door, the curtain is drawn off of the roller, and the roller is reversed to roll the curtain up on the roller for the purpose of opening the door. Another type of fabric industrial door is a so-called “concertina” door. In a concertina door, the door typically also comprises a fabric curtain and a roller is disposed above the doorway opening. Straps are wound onto and off of the roller, and are connected typically to a leading edge of the curtain for the purpose of drawing the curtain up out of the way of the door opening, and allowing the curtain to fall and unfold to cover the door opening. The curtain itself does not wind on the tube, however, and rather is gathered in folds at the top of the door. A still further type of fabric industrial door is a sheet of fabric that is maintained in a flat orientation, and is moved between a doorway-blocking and a doorway-opening position. The doorway opening position may either be above the doorway or overhead, similar to an overhead-style sectional door. Further, while all of these doors have been described as moving vertically, they may also be modified such that their movement between door opening and door closing positions is in a horizontal or other direction, as opposed to a vertical direction. Roll-up doors comprising metal or chain sections are also known. 
     All of the industrial doors just described typically share a common feature of having a member extending across the doorway opening when the doorway is either in the closed or any of a variety of doorway-blocking positions. Such structure will be referred to herein as an “extension member.” In sectional doors, the extension members are the door panels themselves. Fabric doors typically include either a relatively rigid bottom bar extending across the leading edge of the door, and/or other relatively rigid bars extending across the width of the door at locations other than at the leading edge (these are often referred to as “wind bars” as they assist in adding stability to the door and preventing it from billowing under wind load conditions). 
     A common problem associated with such doors as a result of the presence of these extension members extending across the doorway is unintentional impact. In an industrial or warehouse setting, such impact may occur by virtue of a fork lift or other material handling equipment (or a load carried thereon) being driven into the door and the impact is thus directly or indirectly transmitted to the extension members. In situations where such doors are used in automated factories, conveyors or other devices may cause objects being conveyed to accidentally impact the doors. Given the fact that such impacts are bound to occur, certain types of industrial doors can be designed to withstand such impacts. For example, the panels comprising a sectional door, and the associated track and hardware can be reinforced to withstand such impacts. Of course, this adds significant expense to the door. Further, fabric-type industrial doors typically do not have this option as the door itself is formed of fabric which is more easily damaged than the metal or wood typically comprising sectional doors. 
     Accordingly, another solution to allowing industrial doors to withstand impact is to allow them to have a controlled breakaway under such an impact. That is, the door is designed for certain components to separate upon an unintentional impact, thus protecting the remainder of the door. One example of such a structure is shown in U.S. Pat. No. 4,676,293, assigned to the assignee of the present invention. In that patent, a sectional door is disclosed that includes a bottom panel having significant flexibility, thus allowing it to absorb impact. However, if the impact is above a predetermined magnitude, the door is designed to allow the roller associated with the bottom-most panel to disengage from the panel, thus allowing the panel to swing free relative to the rest of the door. This action protects the bottom panel from damage. 
     The various breakaway mechanisms disclosed in the prior art may adequately perform the desired function, but may be limited in use to certain environments or types of doors. In other circumstances, the disclosed breakaway mechanisms may not adequately function. Even when they do function properly, however, reassembly or repair of such doors following breakaway may be a cumbersome or time-consuming process. Spare parts may need to be maintained on hand, and trained technicians may need to be called to reassemble the door following breakaway. Complex breakaway mechanisms may also significantly increase the costs associated with a given door. 
     Another common problem associated with industrial door applications is unintentional impact on the tracks guiding the doors. Such track impacts occur from vehicles being driven into the tracks directly or vehicles hitting the tracks as they accidentally impact on doors or objects near the tracks. The tracks are typically mounted on the inside wall of the doorway and, thus, mostly impacted by vehicles traveling in one direction through the doorway. These impacts may damage the track and its alignment and prevent the door from smooth guided movement. As such, these unintentional impacts often necessitate the replacement of the tracks, which is time consuming and costly. 
     It would be advantageous to have a guard or shield for a track to protect it from unintentional impacts. Some shields which protect tracks from impact are commercially available, for example, the Warden™ TR Sectional Door Guard available from Rite-Hite Aftermarket Corporation of Milwaukee, Wis. Such guards are mounted to an external wall and/or an adjacent floor to allow easy installation. It is desirable in some applications, however, to have a guard that can mount directly with the door track, to add further protection from impacts. Furthermore, it is desirable to provide guards that facilitate breakaway and that protect the track from damage during the impact. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is the primary aim of the present invention to provide an improved releasing mechanism for industrial door as compared to those previously provided. 
     In accordance with that aim, it is an object of the invention to provide an industrial door release mechanism that provides simple construction and operation. 
     It is the further object of the invention to provide an industrial door release mechanism that allows for easy reassembly of the door following a breakaway condition. 
     A still further object is to provide an inexpensive and reliable release mechanism that may be used on a variety of industrial doors. 
     In accordance with other embodiments, there is provided a guiding mechanism for use with an industrial door. The industrial door includes an extension member extending across a doorway opening. The track is mounted to a guard bracket extending along the doorway. The guard bracket protects the track during a track impact condition. The guard bracket has a mounting segment upon which the track is mounted and a guard segment that protects the track during a track impact condition. 
     The guard bracket may be mounted to a wall defining the doorway, either directly or indirectly. In some embodiments the guard segment includes a overhang member that extends at least partially along a direction parallel to an inner face of the mounting segment offering further protection of the track. 
     In an embodiment, the track is movable relative to the wall upon application of a track impact force to the guard bracket. The relative movement in response to the track impact force further protects the track from damage during the track impact. In another embodiment, the track is movable relative to the wall upon application of a breakaway force to the extension member of the door, which might happen with the door in the blocking or partially blocking position. The relative movement here allows a roller or just the end of the extension member traveling within the track to escape from the track upon either a breakaway condition or a track impact condition. To achieve relative movement, the guard bracket is preferably mounted to the wall through a resilient member. Relative movement may also be achieved by mounting the track to the guard bracket through a resilient member. In both, the preferred resilient member is deformed or compressed to allow the track to move relative to the wall. Furthermore, the resilient member preferably returns to its original shape after the condition is removed. 
     The invention also encompasses a novel method for protecting a track during a track impact condition, where the track guides movement of an industrial door having an extension member and being moveable between blocking and unblocking positions relative to a doorway. The method comprises the step of mounting a guard bracket along the doorway, the guard bracket having a guard segment extending at least partially parallel to the doorway. A further step includes affixedly mounting a track to the guard bracket such that the guard segment protects the track form impact from a track impact force applied to the guard segment. 
     In some embodiments, the method further comprises the steps of mounting the guard bracket to a first resilient member and mounting the first resilient member to a wall defining the doorway, the first resilient member being mounted to the guard bracket such that the first resilient member deforms in response to the track impact force applied to the guard segment to allow the track to move relative to the wall. 
     In some embodiments, the method further comprises the step of disposing a second resilient member between the track and the guard bracket such that the second resilient member deforms in response to the track impact force applied to the guard segment to allow the roller to escape from the track. 
     The embodiments of the invention will be described herein in reference to the appended drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an industrial door embodying one aspect of the invention, and showing the door in a closed position; 
     FIG. 2 is a perspective view of the industrial door of FIG. 1, and showing the door in an open position; 
     FIG. 3 is a perspective view of the door of FIGS. 1 and 2, showing the door releasing or breaking away for an applied force, according to an aspect of the invention; 
     FIGS. 4-6 are a series of top section views showing the door of FIG. 1 in response to an applied breakaway force; 
     FIG. 7 is a side sectional view of a portion of the door of FIG. 1; 
     FIG. 8 is an inside elevation of a portion of the door of FIG. 1; 
     FIG. 9 is a rear elevation of a portion of the door of FIG. 1; 
     FIGS. 10-12 are a series of top section views showing the door of FIG. 1 responding to an impact on the tracks by an object; 
     FIGS. 13-15 are a series of perspective views of a refeed mechanism for an industrial door according to an aspect of the invention; 
     FIG. 16 is a side section view of the refeed mechanism illustrated in FIGS. 13-15; 
     FIG. 17 is a front elevational view of an alternative embodiment of the refeed mechanism according to the invention; 
     FIG. 18 is a side elevational view of the refeed mechanism of FIG. 17; 
     FIGS. 19-24 are a series of operational side elevations, showing the operation of the refeed mechanism of FIG. 17; and 
     FIG. 25 is a door including a breakaway or release mechanism according to an alternative embodiment of the invention. 
     FIG. 26 is a door including a breakaway or release mechanism according to an alternative embodiment of the invention. 
     FIG. 27 is a view of the door in FIG. 26 showing the door releasing or breaking away for an applied force. 
     FIG. 28 is a view of a guard bracket mounted to a track according to an embodiment of the disclosure. 
     FIG. 29 is a view of the guard bracket and track of FIG. 28 alternatively mounted to a resilient member that facilitates relative movement of the track during a track impact condition. 
     FIG. 30 is a view of the apparatus of FIG. 29 showing the guard bracket, track, and resilient member during a track impact condition. 
     FIG. 31 is a view of an alternative track mounted to the guard bracket of FIG.  30 . 
     FIG. 32 is an illustration of an exemplary bracket mounting a guard bracket to a resilient member in accordance with an embodiment of the disclosure. 
     FIG. 33 is a view of the guard bracket alternatively including a resilient member between the track and the mounting member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as are included within the scope and spirit of the invention as defined by the appended claims. 
     An industrial door  10  according to the invention is shown in FIG.  1 . The particular industrial door used for the illustrative embodiments of this invention is an overhead-type sectional door. This type of door typically includes a plurality of extension members in the form of panels  12  which extend across a doorway opening and are connected together by hinges (not shown). The door is movable between the door blocking position shown in FIG. 1, and a door open position (FIG. 2) in which the door  10  is not disposed over the doorway designated D in FIG.  2 . It will be appreciated that the door  10  may still block at least a portion of doorway D at positions other than the fully closed position of FIG.  1 . Accordingly, door  10  will be described as having a range of “doorway blocking” positions. In this embodiment of the invention, the door  10  is stored overhead in the doorway-open position of FIG.  2 . Toward that end, the door includes a pair of tracks  20 , each disposed on opposed sides of the doorway D. Each of the tracks  20  according to this embodiment includes two legs. The first leg of the track  22 , extends along the doorway D. In this embodiment that means that first leg  22  extends vertically along the lateral edge of the doorway opening D. The second leg  24  of this track extends horizontally in an overhead position with respect to the doorway D. For a vertically storing door, both sections of track  20  would extend vertically. Coupling door  10  to the tracks  20  is a plurality of rollers  26 , which cannot be seen in FIGS. 1 and 2 but which are shown in the section views of FIGS. 4-6. In this embodiment, a pair of rollers  26  are associated with each panel  12  of the door  10 , a roller extending from each lateral edge of the panels  12  (FIG.  3 ). These rollers are received within guideways  28  forming a portion of the tracks  20 . The guideways  28  may be integral with the track  20 , as in the present embodiment, or may be separate members fixed to track  20 . The guideways  28  can be seen in more detail in the cross section of FIGS. 4-6. In this embodiment, the guideway  28  is generally U-shaped, with the arms of the U being separated by slightly more than the diameter of the rollers  26 . Door  10  is driven between the doorway blocking and doorway open positions by a conventional section door driving mechanism illustrated in FIGS. 1-3. 
     According to a significant aspect of the invention, the rollers  26  and the tracks  20  are designed to move relative to each other to provide for breakaway of the rollers from the tracks upon a breakaway force being exerted on the door. A typical impact exerting a breakaway force is illustrated in FIG. 3, showing a fork truck F with load L accidentally impacting door  10 . Any of a wide variety of specific forces will cause the door  10  according to the invention to breakaway. However, since the driving mechanism that moves the door up and down necessarily causes relative vertical movement between the rollers  26  and the tracks  20 , the door does not provide for breakaway in this direction. Rather, the door  10 , according to the invention, is designed to breakaway for a force having a component perpendicular to the plane of the doorway (which is typically parallel to the plane of the door in the closed configuration). Clearly, then direct perpendicular blows to the door (assuming the force is above of predetermined magnitude) will cause breakaway. In addition, however, forces beside those being only in a direction perpendicular to the door can also cause breakaway. This may include, for example, glancing blows or blows exerted on the door at some angle. So long as the force has a component in the direction perpendicular to the plane of the door, and assuming that force is above a predetermined magnitude, breakaway will occur. Accordingly, such forces will be referred to herein as “breakaway forces”—if they have a component in the perpendicular direction above the predetermined magnitude. The door is designed to breakaway only above a certain predetermined magnitude of breakaway force to prevent the door from breaking away for only incidental contact. As will be described in greater detail below, various components of the door according to the invention can be selectively designed to provide a desired breakaway force. 
     A first embodiment of this aspect of the invention, and showing structure providing for relative movement between the rollers  26  and the tracks  20  so as to allow the rollers  26  to escape from the tracks  20  upon a breakaway force, is detailed in the sectional view of FIGS. 4-6. According to this embodiment of the invention, the track  20  is coupled to a fixed member in the form of angle bracket  46  which is fixed to the wall W on one side of the doorway D. The coupling between the track  20  and the bracket member  46  will be discussed in greater detail below. To allow the track  20  to move relative to the roller  26  and thus to provide for escape of the roller  26  from the track  20  upon a breakaway force, a resilient member  48  is disposed between track  20  and bracket member  46 . 
     The resilient member  48  is preferably formed of neoprene rubber, illustratively having a durometer of 55-65 on the Shore 00 scale. This material has the property of allowing the resilient member to be compressed and distorted by external forces, and yet retain its original shape once the force is removed. The presence of the resilient member  48  between the track  20  and the bracket member  46  allows the track  20  to move relative to the rollers  26  for a breakaway force. That is, the breakaway force is typically exerted on the panel  12 , which forms an extension member which extends across the doorway. The breakaway force is then translated along the extension member  12  to the roller  26 , and to the track  20  and its guideway  28 . This force, as seen best in FIG. 5, is then translated to the resilient member  48  which, in response to this force, responsively deforms to allow the track  20  to move to a position where it does not impede movement of the roller  26  in a direction perpendicular to the plane of the door. Once the track  20  moves to this position, and assuming that the breakaway force is still being exerted on the extension member or panel  12 , the panel  12  and attached roller  26  are now unimpeded (or less impeded) from moving in the direction perpendicular to the door plane, and the roller  26 , and panel  12  to which it is attached, will now escape from the guideway  28  and move out of the plane of the doorway. By virtue of this breakaway, damage to either the panel, the roller, or the track is avoided or minimized. 
     The roller  26  and attached panel  12  are shown in the fully broken-away position in the section view of FIG.  6 . Once the roller  26  and attached panel  12  have broken away, and the breakaway force is thus removed from the track  20  and resilient member  48 , the resilient member  48  resumes its original shape, and track  20  is returned to its normal position. Thus, once the rollers  26  are reinserted into the tracks  20 , normal door operation can occur. A structure, according to the invention, for automatically achieving such reinsertion of the rollers is detailed below. In the absence of an automatic refeed mechanism, however, the present embodiment provides for simple reassembly of the broken-away door. Since the resilient member  48  is compressible and deformable, the track  20  can be moved manually (or with an appropriate tool) to a position where the roller  26  can be reinserted into track  20  by moving the panel or extension member  12  toward the track  20 . FIG. 5 is an example of an orientation of track  20  that would allow for reassembly following breakaway. 
     According to an aspect of the invention, track  20  is coupled to bracket member  46  by a “floating” coupling. This coupling maintains the track  20  in the proper vertical orientation, while also providing for limited horizontal motion of that leg  22 . In this embodiment, the floating coupling is in the form of a series of U bolts connected between the track  20  and the bracket member  46 . One such U bolt is shown in the side section view of FIG.  7 . The U bolt  50  passes through a pair of spaced holes  52  in the track  20 . The spaced holes  52  are seen most clearly in the elevational view of FIG.  8 . The bail section  56  of the U bolt  50  is disposed between the spaced holes  52 . Additionally, track  20  may include a grooved recess between the spaced holes  52  to allow the bail  56  of the U bolt  50  to be recessed into the face of the guideway  28 . The opposite ends of the U bolt  50  pass through a pair of oversized holes  54  (relative to the diameter of the U bolt) on the bracket member  46 , seen most clearly in the elevational view of FIG.  9 . Accordingly, and as can be seen in the successive views of FIGS. 4-6, the track  20 , while being coupled to the bracket member  46 , is capable of limited horizontal movement, provided both by the free play of the U bolt  50  within the oversized holes  54  of the bracket member  46  and by the translation provided by deformation of the resilient member  48 . This floating coupling between track  20  and the bracket member  46  enhances the relative motion between track and roller  26  provided for by the presence of the resilient member  48  between the bracket member  46  and the track  20 . However, the door according to the invention does not require this combination, and would work adequately with a different type of coupling between the bracket member  46  and the track  20 , provided that such coupling allowed for the relative movement between the track  20  and the roller  26  as provided by the deforming resilient member  48 , as described above. 
     The door according to this embodiment of the invention will only provide the relative movement between the track  20  and rollers  26  so as to provide breakaway for a breakaway force defined as a force having a component perpendicular to the plane of the door, and above a certain magnitude. The predetermined magnitude of that perpendicular component can be modified in a variety of ways. For example, the durometer of the resilient member  48  can be changed to make the resilient member  48  either more or less stiff depending on the magnitude breakaway force desired. In the alternative, or additionally, the position of nuts  58  on the U bolt  50  can either reduce or increase the separation between the bracket member  46  and the track  20 . Increasing the distance would lessen the compressive force on the resilient member  48 , and thus provide a lower breakaway force, while reducing this distance would pre-compress the resilient member  48 , thus limiting the range of motion of the resilient member  48  and increasing the force required to provide for relative movement between the roller and the track  20 , and thus to provide escape of the roller from the guideway  28 . Further, although a single resilient member  48  has been shown, two or more individual resilient members, such as foam pads or springs, could also be used. 
     The presence of the resilient member  48  between the bracket member and track  20  also provides an additional advantageous feature. Since the roller  26 , in this embodiment of the invention, is rigidly connected to the panel  12 , the total width of the panel and attached roller or rollers  26  must be less than the width of the doorway D. Otherwise, upon breakaway, the rollers  26  and/or the panel  12  would strike the wall W in which the doorway D is formed. Since the width of the panel  12  and rollers  26  is thus less than the width of the doorway D, this also means that the tracks  20  must be disposed within the width of the doorway D. This is potentially problematic with the door  10  raised, since material handling vehicles passing through the doorway D could strike the tracks  20 , potentially damaging them or limiting their lifetime. Fortunately, however, the resilient member  48 , since it is deformable, will allow the track  20  to move out of the way of such a passing vehicle, or the load carried thereby, thus reducing or eliminating any damage to the track. A schematic example of this action is shown in FIGS. 10-12. In FIG. 10, the corner of a load L, shown as having the same width as the doorway D (since the outer edge of load L, is shown engaging the edge of the doorway D) is shown when it first makes contact with track  20 . For a rigidly-disposed track  20 , this contact would damage either the load or the track. However, by virtue of the compressible and deformable nature of the resilient member  48 , illustratively in combination with the floating coupling provided by U bolt  50  and holes  54  in the bracket member  46 , the track can be moved to a nonblocking position relative to the load L as shown in FIG.  11 . FIG. 12 shows the load L further advanced, and a different compression state for the resilient member  48 , as well as a different orientation for the U bolt  50  forming the floating coupling between track  20  and the bracket member  46 . Importantly, FIG. 11 also shows that the floating coupling between the track  20  and the bracket member  46  allows not only horizontal motion of the track  20  perpendicular to the plane of the doorway in the sense of FIG. 12, but also allows the track  20  to float in a horizontal direction toward and away from the bracket member  46 . This advantageous motion of the track  20  relative to the bracket member  46 , as provided by the resilient member  48  and the floating coupling, reduces or eliminates damage to the track  20  by a wide load such as L in FIGS. 10-12. 
     While this embodiment of the invention has been described in conjunction with an overhead-storing sectional door, it is equally applicable to other types of doors. For example, a sectional door which stores above the opening would be nearly identical to the overhead-type storing door with the exception that the second leg of the track  20  would simply be disposed directly above the first section of the track  20 . The invention could also be used in combination with fabric doors. As discussed above, such doors typically include either a bottom bar or wind bars which would form the extension members extending across the width of the door. In these doors, the bars form the extension members, rather than the individual panel as in a sectional-type door. Like panels in a sectional door, wind bars and bottom bars are relatively rigid members which extend across a doorway with the door in doorway-blocking positions. The rollers of the embodiment would then be disposed in the ends of either the wind bar or the bottom bar, and a track would extend along the doorway in a similar fashion to the track  20  in the disclosed embodiment. For a breakaway force on one or several of the bars, breakaway would be provided by that section of track being movable relative to the rollers by virtue of a resilient member such as resilient member  48  disposed between the track  20  and a bracket member  46 . Other similar modifications of the invention for use in combination with other types of industrial doors will be apparent to one of skill in the art. In addition, while this embodiment has been described in conjunction with doors that roll up and down vertically, the invention could be equally applicable to horizontally disposed and moving doors. Further, it should be appreciated that a breakaway force exerted on an extension member (panels  12  or bottom bars/wind bars on roll-up doors) need not be exerted directly on the member itself Depending on the structure of the door, an impact or other force on a different part of the door could be translated to a given extension member by the structure of the door itself. Thus, a “breakaway force” on an extension member may be either directly or indirectly applied. Further still, it should also be appreciated that the breakaway or release mechanism provides for breakaway in both directions perpendicular to the plane of the doorway (into and out of the doorway). 
     Nor is this aspect of the invention limited to the specific breakaway embodiment shown in FIGS. 1-12. On the contrary, alternative embodiments, providing relative movement between rollers  26  and track  20  for a breakaway force, also fall within the scope of the invention. For example, the relative movement between the roller and the track, which provides for escape of the roller from the track upon application of a breakaway force to the extension member extending across the door, could be provided by the roller being pivotally attached to the extension member about an axis disposed in the plane of the door in the closed position (i.e., a vertical axis for the door of FIGS.  1 - 12 ). Such an arrangement is shown in the drawings at FIGS. 26-27, with the door shown in normal operation and broken-away, respectively. Roller  26  is pivotally mounted to panel  12  about a vertical axis VA and is disposed within track  20  (FIG. 26) for normal door operation. For a breakaway force, roller  26  can rotate about axis VA to allow the roller  26  to escape from the guideway  28  of the track  20  as in FIG.  27 . In such an embodiment, the track could preferably be designed to be immobile, as is shown in FIG. 26 with the track  20  coupled directly to the bracket  46 ″. Further, since the rollers would fold out of the plane of the doorway on impact, the tracks could be placed at a width greater than the width of the doorway. Such placement would reduce the possibility of the track being impacted by a vehicle or its load. Further alternative means for providing relative movement between rollers disposed at the ends of extension members, and associated tracks, and which thus fall within the scope of this invention, will occur to those of skill in the art. 
     A further aspect of the present invention is an automatic refeeding mechanism, for returning the rollers to the track following breakaway. An embodiment of the automatic refeed mechanism according to this aspect of the invention can be seen with reference to FIGS. 13-16. The refeed mechanism takes advantage of the movement of the door between doorway-blocking and doorway-unblocking positions to guide the broken away rollers  26  back into the track  20  through a notch or break in the track  20 . As can be seen in the top section view of FIG. 4, the track  20 , and its integral guideway are u-shaped in cross-section. The notch in the track  20 , that provides for refeed according to this embodiment of the invention is formed in at least one leg of the u-shaped track, and can be seen in the perspective view of FIG. 13 bearing reference numeral  80 . To ensure that a broken away roller  26  re-enters the track  20  as the roller moves toward the doorway-unblocking position, the refeed mechanism, according to the invention, also includes a guide member  84  disposed adjacent the track notch  80 . In the present embodiment, the guide member is attached to the track  20 . The guide member  84  is disposed to be in the path of travel of the broken away roller  26  as it approaches the notch  80 . The engagement of the roller  26  with the guide member  84  guides the roller to the notch  80 , causing the roller to re-enter the guideway  28  of the track  20  for continued movement of the door to a doorway unblocking position. In the present embodiment, the guide member  84  includes an angled camming surface  86  which guides and translates the roller  26  to the notch  80  for upward movement of the door upon engagement of the roller with the surface  86 . FIGS. 13-15 sequentially show a broken-away roller approaching the guide member  84 , engaging the member  84  (causing the roller  26  to be guided toward the notch  80 ), and entering the notch  80 , thus refeeding roller  26  into the guideway of the track  20 . FIG. 16, shows a similar action from a side section view, but with subsequent positions of the roller being shown in phantom. Of course, an automatic refeed mechanism according to the invention will preferably be disposed on both lateral sides of the door  10 , as can be seen in FIG.  1 . 
     While the automatic refeed mechanism according to the invention has been shown in a representative embodiment in the Figures, the invention is not so limited. For example, guide member  84  has been shown attached to the track  20  in FIG. 13-15, but other mountings of the member  84  adjacent to the notch  80  are possible, including attachment of the member  84  to the wall W. Further, the refeed mechanism has only been shown on the side of the door closest to the doorway D for an overhead-storing sectional door. For the case of a vertically-stored sectional door, such a refeed mechanism could be disposed on both sides of the door. Various other alternatives for roll-up and other types of industrial doors are also possible. 
     An alternative embodiment of the automatic refeed mechanism is shown in FIGS. 17 through 24. According to this embodiment, the guide member  84  from the previous embodiment is in the form of two separate guide members  84   a  and  84   b . The first guide member ( 84   a ) is to translate a refeeding roller  26  that has become misaligned in a lateral direction to ensure that it will re-enter the notch  80 . The other portion of the guide member ( 84   b ) is designed to direct and translate the roller  26  through the notch  80 . To prevent a roller properly engaged within the track  20  from accidentally exiting the track  20  through the notch  80 , this embodiment also includes a notch cover  85 , which normally covers the notch  80  in the track  20 , but which is pushed open by a properly refeeding roller  26 . 
     The two portions  84   a  and  84   b  comprising the guide member according to this embodiment of the invention can be seen most clearly in the elevational views of FIGS. 17 and 18. Lateral guide member  84   a  includes an angled surface  86   a  which would guide a broken-away roller  26  that had become misaligned in a lateral direction (indicated by the arrow  87  in FIG.  17 ). Thus, surface  86   a  ensures that the roller  26  is properly aligned with the notch  80  during refeed. The second guide member  84   b , according to this embodiment of the invention, and is seen most clearly in FIG. 18, is an angled member attached to the face of guide track  20  at a position slightly above that of the notch  80 . In the present embodiment, the angled member  84   b  is a piece of spring steel. Member  84   b  includes an angled surface  86   b  which guides a broken-away and properly aligned (by means of first guide member  84   a ) roller back into the track  20  through notch  80 . 
     According to a further aspect of the invention, notch door  85  is associated with the notch  80 . The purpose of the notch door is to prevent a roller that is properly within the track  20  from accidentally escaping from the track  20  through the notch  80 . Accordingly, the notch door  85  covers the notch  80  in all situations except the situation when a refeeding roller is guided into the notch  80  by the guide member  86   b . To provide for this function, the notch door, according to this aspect of the invention, is simply a piece of spring steel  85  attached to the inside edge of the side wall of the track  20  associated with the notch  80 . Of course, if both side walls of the track  20  include a refeed mechanism according to the invention, a notch door  85  would be associated with each notch  80 . The spring steel of the notch door  85  is biased to normally cover notch  80 . However, upon an applied force by a refeeding roller  26 , notch door  85  will move away from a covering position with respect to the notch  80 , and allow the roller  26  to re-enter the guide track  20 . 
     A sequence of operation for the refeed mechanism according to this aspect of the invention is shown in FIGS. 19-24. FIG. 19 shows a refeeding roller  26  approaching the notch  80 . In FIG. 19, roller  26  is shown engaging angled surface  86   a  of the first guide member  84   a . If the roller is misaligned in a lateral direction, guide surface  86   a  will realign it with notch  80 . FIG. 20 shows the roller further advanced and engaging angled surface  86   b  of the second guide member  84   b . Similarly, FIG. 21 shows the roller slightly further advanced, it having pushed the spring steel member  84   b  such that the angled surface  86   b  is slightly raised. The leading edge of the roller  26  is also shown entering notch  80  in FIG.  21 . FIG. 22 shows the roller continuing upward and inward as it is refed into the track  20 , and showing roller  26  pushing against an opening notch door  85 . Thus, the force of the refeeding roller was sufficient to overcome the bias force on notch door  85  which normally holds notch door  85  in position over the notch  80  in the guide track  20 . FIG. 23 simply shows further progression of the roller  26  such as it is now fully engaged within the guide track  20 , the notch door  85  being displaced its greatest amount. Finally, FIG. 24 shows the roller  26  continuing upward within the guide track. Since roller  26  is no longer in engagement with notch door  85 , the spring bias of the spring steel forming notch door  85  has returned it to its normal closed position with respect to the notch  80 . 
     According to this aspect of the invention, the guide member for guiding a broken-away roller  26  back into the guide track  20  comprises both a lateral guide member  84   a  and a horizontal guide member  84   b  for guiding the roller back into the notch  80 . Also included is a notch door  85  which is disposed to normally cover the notch  80 , but which may be engaged by the roller  26  to expose the notch and allow the roller  26  to re-enter guide track  20 . 
     A further aspect of the invention, which provides for breakaway of an industrial door upon application of a breakaway force to the door, is illustrated in the embodiment of FIG.  25 . Similar reference numerals to the previous embodiments will be indicated in reference to FIG. 25 with a prime (′). FIG. 25 shows a sectional door in which the extension member or panel  12 ′ extends into the track  20 ′. That is, a lateral end portion  13 ′ of the panel  12 ′ is received within and guided by the guideway  28 ′ of the track  20 ′ as the door moves between doorway blocking and doorway unblocking positions. To reduce friction, rollers  26 ′ may also be included in the lateral end portions, although they are not required. Rollers  26 ′, if used, are oriented about horizontal axes perpendicular to the plane of the doorway, as opposed to axes parallel to the plane of the doorway as in the embodiment of FIGS. 1-12. 
     The present embodiment provides for breakaway by virtue of the track  20 ′ moving relative to the lateral end portions  13 ′ for application of a breakaway force to the extension member or panel  12 ′. As in the previous embodiment, the track  20 ′ is preferably coupled to a fixed member in the form of a bracket member  46 ′, and a resilient member  48 ′ is preferably disposed between the track  20 ′ and the bracket member  46 ′. The deformability of the resilient member  48 ′ for a breakaway force applied to the extension member  12 ′ and transmitted to member  48 ′ allows the track  20 ′ to move to a position where it does not impede movement of the panel  12 ′ in a direction perpendicular to the plane of the doorway. The lateral end portions  13 ′ of the panel  12 ′ thus escape from the guideway  28 ′ of the track  20 ′ allowing the panel  12 ′ to breakaway. It should be noted that the embodiment shown in FIGS. 1-12 also achieves breakaway in the same manner if the rollers  26  are associated with the lateral end portions  13 ′ of the present embodiment. 
     In the above embodiments, the track  20  is exposed, meaning that a vehicle or object passing through a doorway could strike the track  20  directly. The breakaway mechanism shown, like the breakaway mechanisms of FIGS. 1-12, protects the track  20  from damage. However, damage to the track  20  could still occur from a vehicle approaching the doorway from the inside, for example, a vehicle traveling through the doorway when the door is in rolled-up or open position. FIG. 28 shows track  20  in another embodiment in which the track  20  is shielded from such track impacts by a guard bracket  102 . The guard bracket  102  has a linear mounting segment  104  having an inner face  106 . The track  20  is mounted to the inner face  106 , in the preferred embodiment. The track  20  is preferably mounted through a screw, bolt, other mount that allows for the track  20  to be readily removed and replaced. The track  20  may also be mounted to the inner face  106  through a resilient member like the embodiment shown in FIGS. 1-12 although it could also simply receive one end of the extension member. Mounting the track  20  on a resilient member would provide the further benefit of door breakaway movement. 
     The track  20  is shown receiving roller  26  of door panel, or extension member,  12  like that of FIGS. 1-12. The door panel  12  moves between a doorway blocking position and a doorway unblocking position. The track  20  is only exemplary shown. Various tracks for guiding door movement may be used. The roller  26  and panel  12  of FIGS. 26 and 27 are another useful alternative that offer the advantage of panel breakaway, by having the roller rotatably coupled to the panel. A C-channel track that may be used, for example, with non breakaway doors, is shown in FIG.  31 . In fact, numerous track and guided door combination may be used, and doors may be breakaway doors and non-breakaway doors. Door breakaway is not important in most instances of track damage, as the doors would typically be in the unblocking positions before vehicles would attempt to pass through the doorway. 
     The guard bracket  102  has a guard segment  108  extending substantially transversely from the mounting segment  104 . The guard segment  108  preferably extends at least as far from the inner face  106  as the track  20  extends from the inner face  106 , though this need not be the case. The guard segment  108  prevents a vehicle or object from impacting the track  20  during a track impact condition, thereby increasing the lifetime of the track  20  and reducing the number of time-consuming track replacements. The term “track impact” herein refers to an impact that would cause damage to an unprotected track from direct impact or indirect impact as may occur through impact on a door, a frame, or other object adjacent to the track. 
     To protect the track  20  from objects approaching at an acute angle to the doorway, and thus at an acute angle to the guard segment  108 , the guard segment  108  includes an overhang segment  109 . The overhang segment  109  may extend partially or entirely parallel to the mounting segment  104 . In the preferred embodiment, the overhang segment  109  extends in a direction at least partially parallel to the inner face  106 . In any event, the guard segment  108  is only exemplarily shown; other profiles and shapes of the guard segment  108  are contemplated and considered within the scope of the present disclosure. The guard bracket  102  is shown affixedly mounted to wall W through arm  110 , though a resilient mounting to the wall W may alternatively be used, as now explained. 
     In FIG. 29, the mounting segment  104  is mounted to a resilient member  112  through the arm  110 . The resilient member  112  may be formed of any of the materials described above with respect to resilient member  48 . The resilient member  112  deforms during a breakaway condition, as shown in FIG. 30, but is otherwise resilient and biased to the shape shown in FIG.  29 . The resilient member  112  is shown mounted to a mounting plate  114  that is mounted to wall W, but it may be mounted directly to or flush with the wall W. 
     FIG. 30 shows an exemplary track impact condition for the structure of FIG.  29 . An impinging track impact force, depicted by arrow  116 , impacts the guard segment  108  creating a track impact condition. The affixed mounting of segment  108  to resilient member  112  and the affixed mounting of the plate  114  to the wall W results in the force  116  deforming the resilient member  112 , as shown. Therefore, the track  20  and the guard bracket  102 , both affixedly mounted to one another, move relative to the wall W during the track impact condition, thereby dampening and deflecting the force of the impact. The guard segment  108  simultaneously protects the track  20  from damage during the entire impact condition. In the preferred embodiment, the guard segment  108  is shaped to bias the track movement during the track impact condition toward the doorway opening, as shown. Preferably, this biasing occurs whether the force  116  is normal to the guard segment  108  or impinging at an angle thereto. As a result, during track movement the guard segment  108  continues to shield the track  20  from the vehicle or other obstacle. 
     The depicted embodiment exemplarily relates to tracks with a breakaway door. If the door were in the doorway blocking position during the track impact, the roller  26  would release from track  20  during the track impact condition due to the relative movement of the track  20  created by the resilient member  112 . The amount of force  116  needed to facilitate breakaway may be adjusted by adjusting the resiliency of the resilient member  112  or by using an additional resilient member mounted between the track  20  and the inner face  106 , like the structures described above. Further adjustment may be made by using a rotatably mounted roller, with or without a biasing force or detent affecting relative movement of the roller and the panel  12 . Persons of ordinary skill in the art will recognize other structural and geometrical alternatives that may be used to achieve a desired door breakaway condition. These are considered within the scope of the present invention. Of course, under typical operation the track impact condition would occur when a door is in the unblocking condition. Thus, embodiments which do not achieve door breakaway are also considered within the scope of the present invention. 
     FIG. 31 exemplarily shows an embodiment in which a track  120 , in the shape of a C-channel, is used in lieu of the track  20 . The track  120  guides door rollers to move the door between doorway blocking and unblocking positions. The track  120  has retaining ends  122  and  124  which prevent door rollers from escaping from the track  120  during normal door operation. The retaining ends  122  and  124  may also prevent door rollers from escaping the track  120  during a door breakaway condition, i.e., an impact to the door. With the structure of FIG. 31, the track  120  is protected during a track impact condition by the guard bracket  102  and is moveable relative to the wall W due to the resilient member  112 , similar to the structure of FIGS. 29 and 30. Other types of tracks are within the scope of the invention. 
     FIG. 32 shows an alternative embodiment to those shown in FIGS. 29-31. The embodiment allows for a guard bracket and track to be adjustably positioned with respect to a wall and a doorway. The structure shown may be used in various doorway applications with tracks of varying shape and dimensions. Specifically, a guard bracket  200  is shown having a guard segment  202  and mounting segment  204 . The guard segment  202  further has an overhang member  206 . The track  20  is mounted to an inner face  208  of the mounting segment  204 , and the mounting segment  204  is mounted to the resilient member  212  through a bracket  210 . The bracket  210  has an elongated receiving hole  213  for a bolt mounting of the bracket  210  to the segment  104 . The elongated receiving hole  213  allows the guard bracket  200  to be mounted at a variety of distances from the wall W. This adjustability is particularly useful in reusing the guard bracket  200  with tracks of different size and different optimum positions from a wall or doorway. The bolt mount of the guard bracket  200  to the bracket  210  also allows for the easy replacement of the guard bracket  200  with another guard bracket without the need to replace or remove the resilient member  212  from being affixed to the wall W. The resilient member  212  is mounted to the wall W through a mounting plate  214 , which also has a pair of elongated receiving holes  216  for a bolt mount. The holes  216  allow adjustment of the position of the plate  214  relative to the doorway. The embodiment depicted allows the track  20  to move relative to the wall W during a track impact condition upon the guard segment  202 . The guard segment  202  also protects the track from damage during the impact condition. 
     FIG. 33 depicts a guard bracket  102 ′ that is similar to the above described guard brackets  102 , however it also includes a resilient member  48 ″ in between a track  20 ″ and a mounting segment  104 ′. The guard bracket  102 ′ further includes a corresponding guard segment  108 ′. The use of the resilient member  48 ″ in between the track  20 ″ and the mounting segment  104 ′ is similar to embodiments previously described in FIGS. 4-6 and  10 - 12 . 
     The different embodiments of a release mechanism for an industrial door, as just described, provide a unique method for allowing the breakaway of a door from its associated track. According to that method, a track is provided along a doorway, and a door is provided which includes extension members having lateral edges received within and guided by the track as the door moves between doorway blocking and doorway unblocking positions. In response to a breakaway force applied to an extension member, the track is moved to a position where it does not impede movement of the extension member in a direction perpendicular to the plane of the doorway. According to the method of the invention, the extension member may either be provided with a lateral end portion forming a continuation of the extension member itself, or it may be provided with a lateral end portion in the form of a roller. In either event, the relative movement of the track for a breakaway force allows the breakaway action. In the preferred embodiment of this invention, the movement of the track to a position that allows the lateral edge to escape is provided by transmitting the breakaway force to a resilient member disposed between the track and a fixed member, and by compressing and deforming the resilient member, thus allowing the track to move. 
     There has thus been provided a novel breakaway or release mechanism for an industrial door, as well as an automatic refeed mechanism and a method for providing such breakaway. In a door using breakaway according to the invention, damage to the door as well as the associated track or sideframe is minimized for an impact on the door. The source of that impact, such as a forktruck will also exhibit minimized damage as compared to prior art breakaway systems. 
     There has also been provided a novel guard bracket for protecting the track from damage during a track impact condition, which typically occurs when the door is in an unblocking position and a vehicle or other object impinges upon the track location. The track is mounted to the guard bracket adding further protection to the track. Mounting the track in this way makes track and guard replacement easier. The guard bracket preferably has a guard segment that extends a sufficient distance to protect the track during the track impact condition. In an embodiment, the track allows breakaway of a door during the track impact condition. In another embodiment, the mounting of the track promotes door breakaway during either a track impact condition or a door breakaway condition. For example, the track may be mounted to the guard bracket through a resilient member, and/or the guard bracket may be mounted to a wall through a resilient member. In either, the track moves relative to the wall to facilitate door breakaway. In another embodiment, the track prevents door breakaway. 
     While the foregoing illustrative embodiments of the invention represent the best mode presently contemplated for carrying out the invention, these embodiments are in no way restrictive of the scope of the invention. Rather, the invention is intended to cover all modifications and equivalents of these and other embodiments as fall within the spirit and scope of the appended claims.