An industrial sliding door has one or more panel assemblies, each panel assembly having a track panel secured to a header and a swinging panel hinged at the inner edge of the track panel to pivot in either direction about a vertical axis if the swinging panel is impacted by a vehicle such as a fork lift. Both panels can also pivot in at least one direction about a horizontal axis. A rail mounted stationary relative to the doorway at the lower edge of the door holds the lower edge of the door in proximity to the doorway and is disengagable if the door is hit from the opposite side, to permit the door panel assembly to swing about the horizontal axis away from the doorway. The swinging panel is held by a detent in the plane of the track panel in a normal position.

CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/463,749 filed Apr. 17, 2003. 
     
    
     STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       FIELD OF THE INVENTION  
       [0003]     This invention relates to industrial doors, and in particular to a sliding industrial door that has features built into it to make it capable of enduring an accidental impact.  
       BACKGROUND OF THE INVENTION  
       [0004]     Sliding doors for industrial applications are well known. For example, for a large scale industrial freezer, in which forklift trucks are continually coming in and out of the freezer, insulated sliding doors have been used. The sliding doors are typically suspended by trolleys that have wheels engaged on tracks which are mounted to the wall over the doorway. There may also be tracks on the walls at the bottom of the door to hold the bottom of the door close to the doorway. Two panels are typically provided which meet in the middle of the doorway and are operated by a belt which is power driven at the top of the doorway and has a lower run of the belt attached to one of the panels and an upper run of the belt attached to the other panel, so that when the belt is driven, the panels move away from one another to open the doorway. When the belt is driven in the other direction, the panels move together toward one another to close the doorway. The opening of the door is typically actuated by a motion detector, a pull cord connected to a switch or an induction loop in the floor that senses the presence of a vehicle. Although the sliding doors open and close with considerable speed, the forklifts also travel with considerable speed. Sometimes, when a door is opening or closing, the forklift may impact the door, usually adjacent to a leading edge of one of the door panels. When this happens, severe damage can occur to the door.  
         [0005]     Prior art doors made to endure impacts such as this have typically been made of fabric covered foam or other soft materials, which can absorb impact without significant damage to the door. However, the materials of these doors have other disadvantages, including that they wear out, the severity of the impact that can be endured is quite limited, they are not easily cleaned, they absorb moisture, they can contribute to mold growth which is important in a food storage facility, and they can become torn, and do not present a structural or aesthetic appearance.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides an impactable sliding door that addresses these issues. In a door of the invention, there is at least one door panel assembly having a track panel that is suspended from the track and slidable relative to the track so as to open and close the doorway and a swinging panel that is hingedly connected to the track panel so as to pivot about a generally vertical axis relative to the track panel so that it can pivot in either direction out of the plane of the track panel. Thereby, the swinging panel can move out of the way regardless of which side it is struck from.  
         [0007]     The swinging panel is preferably held in the plane of the track panel, in a normal position, by a detent mechanism. The detent can be at the top of the swinging panel with one part of the detent on the swinging panel and the other part of the detent on a header that extends from the first panel inwardly over the second panel. The detent permits release of the door in either direction and the hinge connection of the swinging door panel to the track door panel permits the swinging door panel to pivot in either direction out of the plane of the track door panel, when it is impacted from one side or the other.  
         [0008]     It is also preferred that the swinging door panel have a leading edge, that is the edge that contacts the leading edge of the other sliding door panel in a two door panel assembly where the two door panels meet in the middle of the doorway, or the edge that contacts the threshold of the doorway in a single door panel assembly door closing system. The leading edge is preferably provided by a foam or otherwise highly compressible and impact-absorptive material, which may be covered with a reinforced fabric like nylon or canvas. Each of the track and swinging door panel sections may primarily be made, however, of a structurally rigid material. Preferably, if the door is to be used in a freezer or refrigerated room application, the material is an insulating material and should be of light weight to reduce its inertia and therefore the accelerating force necessary to swing it open when it is impacted. The leading edge may also be provided with a pressure responsive sensor that detects if the leading edge has been compressed or impacted, and a sensor may also be provided that senses whether the swinging panel has been swung out of the plane of the track panel.  
         [0009]     In addition, it is preferred that an impact resistant sheet be added to the outside, on both sides of the second panel, in the area of the second panel which is most likely to be hit by a fork lift, that is in the area of about the lower half of the door and over substantially the entire surface area of the structurally rigid part of the second door panel. For example, a ⅛ inch thick sheet of ultra high molecular weight polyethylene is such a material.  
         [0010]     A soft leading edge of each door panel also contributes to sealing of the door when it is closed, either against the threshold of the doorway if it is a side closing door (having one door closing assembly), or against the leading edge of the other door panel assembly if it is a center closing door (having two door panel assemblies). The leading edges of the door panels may be provided with tubular or other structures that overlap when the doors are closed for better sealing.  
         [0011]     In another aspect of the invention, the entire door panel assembly, including both the first and second panels, is able to be swung about a horizontal axis in at least one direction. In the preferred embodiment, the horizontal axis is provided by the connection between the trolley wheels and the track, which is a conventional connection for sliding industrial doors, each trolley wheel having an outer circumference that is concave so that the wheel can engage a similarly shaped convex rail of the track and be guided by the rail and pivot about the horizontal rail. The mating concave and convex shapes permit rotation of the trolley wheels about the rail so that the door panel assembly can be swung about a horizontal axis in the direction away from the adjacent wall to which the track is mounted.  
         [0012]     Another feature of the present invention is that the bottom of the door is connected in a releasable fashion to a track that is fastened to the wall so that if the door is impacted and swung away from the wall, the connection can release. When the door is pivoted back into its normal operating position, which is generally in a vertical plane adjacent to the wall, the connection will automatically reengage to hold the bottom of the door adjacent to the wall as the door slides parallel to the wall and parallel to the doorway opening in the wall that the door closes. A feature can also be included that will automatically pivot the door back into a vertical plane, such as a re-engagement member that re-engages the door with the track when the door is fully opened.  
         [0013]     These and other features and advantages of the invention will be apparent from the detailed description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1A  is a front plan view of a two door panel assembly center closing door of the invention suspended from a track;  
         [0015]      FIG. 1B  is a perspective view of the door of  FIG. 1A ;  
         [0016]      FIG. 1C  is like  FIG. 1B , but with the swing panels of both door panel assemblies swung inwardly;  
         [0017]      FIG. 1D  is like  FIG. 1B , but with the swing panels of both door panel assemblies swung outwardly;  
         [0018]      FIG. 2  is a detail view of the top portion of  FIG. 1B ;  
         [0019]      FIG. 3  is view like  FIG. 2 , but showing the track, trolleys and door panels with the door headers removed;  
         [0020]      FIG. 4  is a perspective view of the left-hand lead trolley for suspending a door assembly;  
         [0021]      FIG. 5  is a perspective view of the right-hand lead trolley for suspending the right-hand door assembly;  
         [0022]      FIG. 6  is a perspective view of a standard trolley which is used to suspend both door assemblies from the track;  
         [0023]      FIG. 7A  is an end view of the left-hand lead trolley shown in  FIG. 4 ;  
         [0024]      FIG. 7B  is an end view of the track and drive components of the door;  
         [0025]      FIG. 8  is a perspective view of the left-hand door assembly of  FIG. 1  with the swinging panel in the normal position, and without the track or trolleys;  
         [0026]      FIG. 9  is a detail view of a top portion of the assembly of  FIG. 8 ;  
         [0027]      FIG. 10A  is a view like  FIG. 9 , but with the header and sealing elements removed;  
         [0028]      FIG. 10B  is a detail view of  FIG. 10A  in the top hinge area;  
         [0029]      FIG. 11  is a perspective view of a hinge for the door assembly, each door panel assembly having two such hinges, one at the top and one at the bottom between the two panels;  
         [0030]      FIG. 12A  is a top schematic view illustrating the door with the swinging panel swung open and illustrating the gas spring;  
         [0031]      FIG. 12B  is a view like  FIG. 12A , but with the swinging panel in the normal, closed position;  
         [0032]      FIG. 12C  is a top plan detail view of the detent for holding the swinging panel in the normal position, not showing the header so that the detent spring is visible;  
         [0033]      FIG. 12D  is a side view of the detent, showing the detent spring bolted to the header;  
         [0034]      FIG. 12E  is a partial perspective view illustrating the detent spring fixed to the header; and  
         [0035]      FIG. 13  is a left end view of the left door panel assembly shown in  FIG. 1  illustrating a track secured to the adjacent wall near the bottom of the door panel assembly and a releasable spring lever secured to the bottom of the door which engages the track. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0036]     FIGS.  1 A-D illustrate a door  10  including a left door panel assembly  12  and a right door panel assembly  14 . The two door panel assemblies  12  and  14  are identical mirror images of one another. The door panel assemblies  12  and  14  are suspended from a track  16  in well-known manner by standard trolleys  18  at the outward top sides of each door panel assembly  12  and  14  and by a left-hand trolley  20  at the inward top side of the assembly  12  and by a right-hand trolley  22  at the inward top side of the assembly  14 . The track  16  is bolted or otherwise affixed to a wall  30  (see  FIG. 13 ) and, preferably, a lower rail  33  ( FIG. 13 ) is also affixed to the wall  30  at the sides of the doorway opening, the lower rail  33  engaging a leaf spring extension of the door panel assembly to hold the lower end of the door panel assembly adjacent to the wall  30 , as further described below. In well known fashion, the track  16  on each side of center angles down slightly toward center (in a bi-part door; down toward the closed side in a single part door) so that the bottom of the door is closer to the floor when it is closed, to compress elastomeric seal strips  141  ( FIG. 13 ) at the bottom of the door against the floor.  
         [0037]     Referring to  FIGS. 2-7B , the trolleys illustrated in  FIGS. 4-7  are affixed to a header  50  which is attached to the top of the track panel  52  of the door panel assembly  12  or  14  as described below. Each trolley  18 ,  20 , and  22  includes a pair of rollers  32 , each of which has a concave groove which defines its circumference. Each roller  32  receives a convex rail  34  ( FIGS. 2 and 3 ) of the track  16 . The shape of the rail  34  matches the convex shape of the circumference of each roller  32  such that the door panel assemblies  14  can swing in a direction away from the wall  30 . The wall  30  being adjacent to the inside surfaces of the door  10  obviously keeps the door panels  12  and  14  from swinging in the direction toward the wall  30 . When swinging about the axis defined by the concave surfaces of the rollers  32  and convex surface of rail  34 , the door panel assemblies  12  and  14  swing about a horizontal axis, since the rail  34  and rollers  32  define an axis which has its orientation horizontal. As illustrated in  FIG. 7A , the trolleys  18 ,  20 , and  22  may also be provided with spacers  36  which keep the rollers  32  on the rail  34  in case an impact should ever tend to lift or dislodge the rollers  32  from the rail  34 .  
         [0038]     The door panel assemblies  12  and  14  are driven toward one another to close the doorway or away from one another to open the doorway (since they close in the middle of the doorway) by a power operated belt  37  in conventional fashion. The left-hand lead trolley  20  and the right-hand lead trolley  22  have respective drive attachments  40  and  42 , with the attachment  40  being attached to the upper run of the drive belt  37  and the attachment  42  being attached to the lower run of the drive belt  37 . When the drive belt  37  is driven by an electric motor  39  ( FIG. 7B ) in conventional fashion, for example to open the door, the upper run of the belt  37  moves to the right and the lower run moves to the left, driving the respective door panel assemblies  12  and  14  in the same respective directions. The opposite occurs when the door is closed, and the belt is driven in the opposite direction. The drive mechanisms, sensors (e.g., the motion detector that actuates the opening of the door), and related circuitry and hardware for opening and closing the door are well known and conventional. Any type of drive, sensors and circuitry could be used. Also illustrated in  FIGS. 2 and 3  is an e-chain  46  which is a cable carrier that permits routing wires to the movable door assemblies  12  and  14  in a movable fashion, also well known in the art, and any suitable means of supplying power to the moving components of the door that require power could be used.  
         [0039]     Referring also to  FIGS. 8 and 9 , which show only the door panel assembly  12 . The door panel assembly  14 , which is the mirror image of assembly  12 , is the same and this description applies to it also except as otherwise noted. Each door panel assembly includes a header  50  at its top, to which the trolleys are bolted or otherwise affixed. The header  50  is bolted or otherwise affixed to the track panel  52  of the assembly  12 . The header  50  has a beam section  54  which extends for substantially the entire width of the door panel assembly  12  and, in the area over the track panel  52  has flanges  56 , preferably on both sides of the panel  52  which are bolted to the panel  52 , or otherwise suitably affixed. Flanges  56  are provided on both sides of the panel  52  and the top of the panel  52  is inserted between the flanges  56 , and the bolts may either extend all the way from one flange  56  to the other, or the bolts may extend into the panel  52  through holes in each flange  56  if separate bolts are used. Separate bolts may be preferable in a refrigeration application so that heat is not conducted from one end of the bolt on one side of the door to the other.  
         [0040]     The entire door panel assembly including the track panel  52  and the swinging panel  58  is supported from the track  16  by the header  50 . Thus, the swinging panel  58  is essentially cantilevered from the track panel  52 . Suitable weather stripping or other sealing means (not shown for clarity) is preferably provided between the top of the door panel assembly and the extending portion of the header  50 , the extending portion being the portion that is inward from the flanges  56 , over the panel  58 , to seal off the area between the extending portion of the header  50  and the portion of the door panel assembly which is not directly affixed to the header  50 .  
         [0041]     Referring to  FIG. 10A , it is preferable that if the door panel assembly is to be used for a refrigerated application, that it be an insulating door. To that end, each door panel  52  and  58  has a core  62  (e.g., 4 inches thick) of an insulating material such as expanded polystyrene (eps). For strength and appearance, the core  62  is laminated on each of its two opposite side faces with a fiberglass skin  64 . Steel or other high strength material reinforcing strips  66  are laminated to the tops and to the bottoms of the fiberglass skins  64  of each panel  52  and  58 , as it is in these areas that the hinges are attached to the door panels  52  and  58 . The metal reinforcing strips  66  help prevent tear out of the hinges in the case of a severe impact. In addition, end caps  68  and  70 , which may be made of steel, another metal, or plastic, are preferably provided on the outward end of panel  52  and over the inward end of panel  58 . This construction also helps provide a door of low weight and therefore low inertia that requires a relatively low accelerating force to get out of the way when it is struck. Other constructions could also be used, and the panels could be hard sided or soft-sided.  
         [0042]     The end cap  70  over the inward end of panel  58  mounts at its inward side, a fabric covered foam pad  72  which serves as the leading edge of the assembly  12 . The end caps  68  and  70  are channels into which the outward end of the eps/fiberglass lamination of panel  52  and the inward end of the eps/fiberglass lamination of panel  58  are respectively inserted and adhered or otherwise fixedly attached. As shown in  FIGS. 1C, 1D  and  1 A, the inward or exposed end of each foam pad  72  may be radiused with a convexity, and tubes  73  and  75  may be provided in sleeves secured to the leading edges, one on one side and the other on the other side of the respective leading edges, on the respective assemblies  12  and  14 , so that they overlap when the panels are closed to provide a better seal when closed. Also, since both leading edges are made of foam, they may be precompressed with each closing of the door, to create a better seal. Also, as is known in the art, each leading edge may be provided with a pressure tube  77  ( FIGS. 8 and 10 A) having a sensor that detects pressure changes in the tube  77  to detect if the leading edge has been compressed, for example by bumping into a vehicle, to trigger opening of the door.  
         [0043]     The panel  58  also has a gas spring attachment  74  and a center detent block  76  attached to its top. Any suitable means of attachment may be used, and as illustrated, the gas spring attachment  74  is attached by being mounted on a sheet metal yoke that is adhered to the plates  66  or otherwise affixed thereto, and the detent block  76  is also mounted on the bent-up flange of a yoke that is adhered or otherwise fixedly attached to the strips  66 . The yokes  78  and  80  may have legs which extend on both sides of the panel  58  for a very secure connection with adhesive, bolts, or other suitable means, or may be attached to the flanges  98  of the hinge  96  for a secure connection with the door panel  58 .  
         [0044]      FIGS. 12A and 12B  illustrate the gas spring  82 . The gas spring  82  is a constant force compression spring, and other types of compression springs or other centering mechanisms may be used to bias the panel  58  back into the plane of the panel  52  if it is swung one way or the other out of the plane of panel  52 . One end of the gas spring  82  is attached to the gas spring attachment  74 , and the other end is attached to the header  50  so that the hinge axis of the panel  58  relative to the panel  52  is on a line between the two ends of the gas spring when the panel  58  is aligned in the plane of the panel  52 , as shown in  FIG. 12B . It is also noted in  FIG. 12A  that the inward edge of panel  52  has a seal  86  that presents an inward facing convex surface, and the outward end of panel  58  has a seal  88  with an outward facing concave surface that mates with the convex surface of the seal  86 , the radii of the concave and convex surfaces being centered on the hinge axis of the panel  58  relative to the panel  52 . This helps seal the space between the outward end of the panel  58  and the inward end of the panel  52  when the door is closed with the panel  58  in the plane of the panel  52  as shown in  FIG. 12B . The gas spring  82  biases the panel  58  into the plane of the panel  52  regardless of whether the panel  58  is swung clockwise or counter-clockwise relative to the panel  52 .  
         [0045]     In addition, heat tape  97 , preferably of the self-regulating type, may be provided at areas of the door where frost or ice may otherwise form. This may include, for example, on the cold side at the outside comer of the panel  52 , running vertically down the comer for substantially the height of the panel  52  (illustrated in  FIG. 12A ), inside the seal  86  running vertically for substantially the height of the seal  86  (illustrated in  FIG. 12A ), and in the bottom of each of the panels  52  and  58  running horizontally along the bottom surfaces, inside the door preferably (not shown). A bulb seal  99  ( FIG. 12A ) may also be provided at the comer of each panel  52  that extends toward the wall  30  of the opening in which the door is installed, so as to seal against the wall when the door is shut. The door may be installed in the opening so that is moves slightly away from the wall and from the floor so that the door seals only contact the adjacent walls and floor in the closed position of the door.  
         [0046]     The centered detent block  76  is also illustrated in  FIGS. 12A and 12B  and is further illustrated in FIGS.  12 C-E. The block itself is preferably made out of a hard and lubricious plastic material (e.g., UHMW polyethylene) so that it can slide easily on the lead-in ramps of the spring detent  90  and snap positively into engagement with the spring  90  in the center position. The spring  90  is bolted or otherwise suitably fastened to the header  50  by a bracket  92 . The block  76  (shown by itself in  FIG. 12E  relative to spring  90 ) is attached to the top of the swinging panel  58  and rides up on the ramped sides of the spring  90  when it is returning to the centered position, and when it reaches the center of the spring  90 , it snaps into the centered position shown in  FIGS. 12C and 12D . The spring  90  flexes to release it from the centered position upon impact or other force sufficient to overcome the detent, in either direction. In addition, a magnet  101  can be embedded or fastened to the block  76  or elsewhere on the panel  72  and a magnetically actuated reed switch installed on the header  50  that is actuated by the magnet, so as to provide an electrical signal indicative of whether the panel  58  is in the plane of the panel  52  or is swung out of that plane.  
         [0047]     Referring to  FIGS. 10A, 10B , and  11 , the hinges  96  are as illustrated in  FIG. 11 . To fit these to the door panels, the two (upper and lower) outward comers are cut out of the panel  52  to form a recess so as to substantially close the gap between the inward end of panel  52  and the outward end of swinging panel  58 . Any remaining gap is substantially closed by the seals  86  and  88  as described above. The hinge  96  has opposed yokes that receive the thickness of the panels  52  and  58 , over the reinforcing panels  66 , and the yoke flanges  98  of the hinge are bolted or otherwise suitably affixed to the respective panels  52  and  58 . On each side of the assembly  12 , both the upper hinge  96  at the upper comer of the panel  52  and the lower hinge  96  at the lower comer of the panel  52  may be covered, for example by a rubber or other material cover, on both sides of the hinge so as to weatherstrip the hinge area to prevent heat transfer or any significant open spaces at those locations. The axis of hinge pin  102  defines the vertical axis about which panel  58  hinges in or out relative to the panel  52 . The hinge pin  102  at the upper hinge  96  is coaxial with the hinge pin  102  at the lower hinge  96 .  
         [0048]     Referring to  FIG. 13 , at the bottom of each door panel assembly  12  and  14 , there is preferably provided a rail  33  which is bolted or otherwise suitably affixed to the wall  30 . The rail  33  runs lengthwise for at least the length of travel of each door assembly  12  or  14  on the respective side of the doorway and serves to hold the respective door assembly  12  or  14  adjacent to the wall  30  for its entire back and forth travel, in a generally vertical orientation. Rail  33  defines a downwardly facing shoulder  110  which faces toward the wall  30  and behind which a keeper  114  is received from the bottom of the shoulder  110 . The keeper  114  is made of a hard and lubricious plastic material, for example UHMW polyethylene, and is fixed to the free end of a cantilever spring  116 . The cantilever spring  116  is secured to the bottom of the door panel  52  at the bottom outward comer with bolts or other suitable means, by means of plate  118 . A wear block  120  is also mounted on the inward side of the bottom outward comer of the panel  52 , which is also made of a hard and lubricious plastic material like UHMW polyethylene, which rubs on the outer surface  122  of the rail  33  as the door assembly  12  travels back and forth. The UHMW wear piece  120  may extend all the way across the thickness of the panel  52  as illustrated in  FIG. 13 , with the plate  118  fitting in a groove of the wear piece  120 .  
         [0049]     In any event, the door assemblies  12  and  14 , being fitted with the releasable connection provided by the rail  33  and spring  116  arrangement, can be easily dislodged from the rail  33  if it is hit on its inward side, i.e. its side facing the wall  30 . If so, the slightly angled surface  124  on the keeper  114  cams against the inwardly facing surface of the shoulder  110  to flex spring  116  downwardly as door assembly  12  pivots away from the wall  30 , about the horizontal axis provided by the wheels  32  and rail  34 . The door assemblies  12 ,  14  are thereby released from being held adjacent to the wall  30 . When the obstruction is removed, the door assemblies  12 ,  14  are free to rotate back to their position adjacent to the wall  30 , and when they do, the keeper  114  cams on the angled surface  126  of the rail  33 , which flexes the spring  116  downwardly and permits keeper  114  to reengage behind the inwardly facing surface of the shoulder  110 , back into the position shown in  FIG. 13 . As shown in  FIG. 1B , re-engagement members  111  may be provided near the ends of the rail  33  that cam on the wear pieces  120  when the door is near fully opened to move the door panel assemblies  12  and  14  back toward the wall  30  and the keeper  114  back into re-engagement with the rail  33 .  
         [0050]     The leading edge may be approximately six inches, and the entire width of the second panel may be approximately 30 inches, for example, with the first panel that is supported by the trolleys from the track, also being about 30 inches wide or so, but any dimensions may be applied to a door of the invention. In addition, an impact plate  133  as shown in  FIG. 1A  may be provided covering at least the lower portion of each swinging panel  58  over the fiberglass skins, to absorb impacts and preserve the surface finish. The impact plates are preferably made of a tough material, such as ⅛ inch thick UHMW polyethylene.  
         [0051]     Many modifications and variations to the preferred embodiment described will be apparent to those skilled in the art. Therefore, the invention should not be limited to the embodiment described, but should be defined by the claims which follow.