Abstract:
A door-latching system for a sectional door with multiple door panels helps hold the door at its fully open position in case the door&#39;s counterweight torsion spring fails to do so. The door-latching system includes a latch assembly that moves between a maintained release position and a door-blocking position. In the door-blocking position, the latch assembly helps hold the door open by providing an obstruction to the door panels. In the maintained release position, the latch assembly allows the door to move freely between open and closed positions without the door-latching system clacking as the door panels or their guide rollers travel past the latch assembly. Movement of the door panels automatically shifts the latch assembly from its release position to its door-blocking position, and manual actuation returns the latch assembly back to its release position. The latch assembly is especially suited for mounting to a track that guides the movement of the door panels.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention generally pertains to sectional doors and more specifically to a latch assembly for such a door. 
   2. Description of Related Art 
   A sectional door typically includes a series of panels whose adjacent horizontal edges are connected by hinges. As the door opens or closes, the door panels travel along two lateral tracks that, for some door styles, curve between horizontal and vertical. To close the door, the tracks guide the panels to a vertical position across the doorway. When the door opens, the hinges allow the panels to curve around onto horizontal sections of the tracks, where the door panels store horizontally overhead. For other door styles, the sectional door maintains a generally vertical, planar configuration and is stored more directly above the doorway. Such doors, regardless of their configuration, are often open and closed manually. To ease the operation of the door, a torsion spring is often used to counteract the weight of the door panels. Sectional doors are commonly used as residential garage doors; however, they are also often used in warehouses and other industrial buildings. 
   When used in high-traffic industrial applications, overhead-storing doors are very susceptible to being struck by large trucks, trailers, forklifts and other vehicles passing through the doorway. Collisions are often caused by a door&#39;s torsion spring becoming weak with age or not being properly preloaded, which can allow a door to droop or not stay in its fully open position. Consequently, an upper edge of a vehicle may catch the lower edge of the door, and thus break or damage the door. 
   Holding a sectional door fully open without relying solely on the door&#39;s torsion spring can be accomplished by a safety catch disclosed in U.S. Pat. No. 3,426,829. Such a catch includes a spring that urges the catch to an extended position. In this position, the catch is able to engage the underside of a roller or its shaft to prevent the door from accidentally falling down to its closed position. To release the door, a solenoid pulls on the catch. This rotates the catch out from underneath the roller, which allows the door to close. Such a device, however, has a few drawbacks. 
   For example, as the door opens, several rollers or their shafts repeatedly snap the catch between its extended position and a release position, as the rollers or their shafts travel past the catch. The wasted snapping movement of the catch can create noise, as well as create wear on various parts of the door and wear on the catch itself. Moreover, to release the door out from underneath the catch, the catch rotates in such a way as to first raise the door panels slightly before allowing them to descend. Thus, the weight of the door could add significantly to the force needed in moving the catch to its release position. 
   SUMMARY OF THE INVENTION 
   In order to help hold the door panels of a sectional door at their fully open position, a latch assembly is mounted adjacent to the door. In response to movement of the door panels, the latch assembly moves from a maintained release position to a maintained door-blocking position. In the door-blocking position, the latch assembly helps hold the door open by providing an obstruction to movement of the door panels toward the closed position. In the release position, the latch assembly allows the door panels to move freely between the door panels&#39; open and closed positions. 
   In some embodiments, the position of the door is sensed, and the latch assembly moves from the maintained release position to the maintained door-blocking position when it is sensed that the door is at or approaching the open position. 
   In some embodiments, the sensing of the door position is achieved, at least in part, by a traveling member coupled to the door for movement therewith. 
   In some embodiments, the traveling member is a protrusion mounted to the door or a panel thereof. 
   In some embodiments, the movement of the latch assembly from a release position to a door-blocking position is triggered by the traveling member. 
   In some embodiments, the motive force for movement of the latch assembly from a release position to a door-blocking position is provided by the movement of the protrusion with the door. 
   In some embodiments, the protrusion is mounted so as to be movable relative to the door panels so that the protrusion does not interfere with the latch assembly as the door closes. 
   In some embodiments, a latch assembly is added to help hold the door closed, wherein the second latch assembly also moves to a door-blocking position in response to movement of the door panels. 
   In some embodiments, a latch member of the latch assembly moves linearly from its door-blocking position to its release position to minimize the force needed to move the latch member. The linear movement allows the latch member to retract without having to forcibly raise the door slightly in the process. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of a sectional door with one embodiment of a door latch and with the door in a closed position. 
       FIG. 2  is similar to  FIG. 1 , but with the door in an open position. 
       FIG. 3  is a top view of the latch assembly of  FIGS. 1 and 2  with the door partially open. 
       FIG. 4  is a front view of  FIG. 3 . 
       FIG. 5  is similar to  FIG. 4 , but with the door slightly above its fully open position. 
       FIG. 6  is a cross-sectional top view taken along line  6 — 6  of  FIG. 2 . 
       FIG. 7  is a front view of  FIG. 6 . 
       FIG. 8  is similar to  FIG. 7 , but with the door having descended slightly after the catch having moved to its release position. 
       FIG. 9  is similar to  FIGS. 3 and 6 , but with the door approaching its closed position. 
       FIG. 10  is a front view of  FIG. 9 . 
       FIG. 11  is an end view of  FIG. 10 . 
       FIG. 12  is similar to  FIG. 11 , but with the door in its fully closed position and the a lower latch in its door-blocking position. 
       FIG. 13  is similar to  FIG. 12 , but with the lower latch in its release position and the door just starting to open. 
       FIG. 14  is a front view of another exemplary door latching system in a release position. 
       FIG. 15  is similar to  FIG. 14 , but with the door latching system in the door blocking position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A sectional door  10 , shown closed in  FIG. 1  and open in  FIG. 2 , includes a series of door panels  12 ,  14 ,  16  and  18  that are interconnected along their adjacent horizontal edges by hinges  19 . As door  10  opens or closes relative to a doorway  11 , guide members, such as rollers  13 , guide the movement of the panels along two lateral tracks  15  and  17 . In this example, tracks  15  and  17  curve between horizontal and vertical; however, it is well within the scope of the invention to have tracks  15  and  17  run generally linearly or only curve slightly, so that when the door opens, the door panels move above doorway  11 , but remain in a generally vertical or slightly angled orientation. To close door  10 , the vertical sections of tracks  15  and  17  guide the panels to a vertical position across doorway  11 . When door  10  opens, hinges  19  allow the panels to curve around onto the horizontal sections of tracks  15  and  17 , where the door panels store horizontally overhead. 
   Typically, a torsion spring or other form of counterbalance is used to help counteract the weight of the door panels and help hold door  10  open. Other times, however, a torsion spring is not used, or the spring may be broken, weak or out of adjustment. Thus, to help ensure that door  10  can be held at its fully open position, door  10  is provided with a door-latching system, which fundamentally includes a latch member, an actuating member, and a sensing member that detects when door  10  is generally open. In response to the sensing member determining that door  10  is open, the actuating member moves the latch member to a position that inhibits door  10  from closing or drooping below the door&#39;s fully open position. Such a door-latching system can assume a variety of structural configurations. 
   For example, in the embodiment of  FIGS. 1–13 , a door-latching system  20  comprises a latch assembly  22  that includes a latch member  24 , an actuating member  34 , and a sensing member  30 . Latch assembly  22  has a release position, as shown in  FIGS. 1 ,  3 ,  4  and  8 , and a door-blocking position, as shown in  FIGS. 2 ,  5 ,  6  and  7 . In the door-blocking position, latch member  24  of assembly  22  creates an obstruction that blocks the downward movement of the door panels. In the release position, latch member  24  retracts to allow the door panels substantially free up and down movement. 
   Sensing member  30  is a T-shaped plate attached to a frame  32  of latch assembly  22 . A pin  28  allows sensing member  30  to pivot relative to frame  32 , while frame  32  is generally fixed with respect to track  17 . To sense when door  10  is open, sensing member  30  extends out over an area where door  10  or some part on door  10  can strike and thus lift sensing member  30  as door  10  approaches its open position. In this case, a traveling member  26  attached to the right-hand side of door panel  12  is used to trip sensing member  30 . Sensing member  30  being T-shaped allows latch assembly  22  to be mounted alongside track  15  or  17  for either a right-hand or left-hand installation. 
   Actuating member  34 , in this case, is an integral extension of sensing member  30 , whereby members  30  and  34  both pivot about pin  28 . Alternatively, one could consider actuating member  34  and sensing member  30  to be coextensive—i.e. the generally l-shaped member pivotal about pin  28 . However, in other embodiments, actuating member  34  and sensing member  30  are separate and distinct. Actuating member  34  is positioned to engage one end of latch member  24 . Latch member  24 , in turn, slides linearly within a sleeve  36 , with sleeve  36  being attached to frame  32 . 
   As door  10  approaches its fully open position, traveling member  26  strikes the underside of sensing member  30 , which pivots sensing member  30  and actuating member  34  clockwise about pin  28 . This causes actuating member  34  to push latch member  24  through an opening in the side of track  17 . In the extended, door-blocking position, shown in  FIG. 5 , latch member  24  creates an obstruction underneath roller  13  that limits the downward movement of door  10 . 
   To prevent door-latching system  20  from clacking as the panels of door  10  travel past upper latch assembly  22 , the release position of latch assembly  22  is preferably a maintained position. In other words, as door  10  opens, latch member  24  remains retracted to avoid hitting the door panels or their rollers until door  10  is fully open. That is, the latch assembly does not assume its operative position until it is needed—until the door is in the open position. It is only when it is sensed that the door is generally open that the latch assembly assumes this position. In this embodiment, this can be accomplished by mounting a traveling member  26  to panel  12 , such that traveling member  26  first triggers latch assembly  22  to extend latch member  24  when door  10  is at or near its open position. 
   Often, the panels of door  10  tend to travel above and beyond their fully open position, usually due to the momentum of the door panels as door  10  opens. To allow for this overshoot, in some embodiments, door-latching system  20  avoids the use of a solid stop that could abruptly force the door panels to an immediate, forceful stop at their fully open position. For example, if the door panels travel above their position of  FIG. 5 , sensing member  30  simply slips off the edge of traveling member  26  and falls back down to the position of  FIG. 7 , while roller  13  of door panel  12  descends a short distance to rest upon latch member  24 . 
   In order to close door  10 , latch member  24  is retracted to the release position of  FIG. 8 . This removes the obstruction to roller  13 , which allows the door to close. Retracting latch member  24  can be accomplished by a variety of powered or manually-operated mechanisms, such as, for example, a releasing member comprising a cord  40  or some other pliable elongated member attached to eyelet  42  on latch member  24 . Cord  40  threads through a hole in an endplate  44  of frame  32 , so that upon pulling downward on a lower end  46  of cord  40 , the other end of cord  40  pulls latch member  24  out from underneath roller  13 . To minimize the force needed to retract latch member  24 , in some embodiments, the movement of latch member  24  is linear so that it does not lift roller  13  in the process of retracting. 
   Once latch member  24  is retracted to the release position of  FIG. 8 , roller  13  and the door panels are free to descend. So that traveling member  26  does not impede the downward movement of the door panels, traveling member  26  can be provided with a protruding pivotal arm  48  that can swing back as traveling member  26  descends past sensing member  30 . For example, a pin  50  can pivotally attach arm  48  to a bracket  52  of traveling member  26 . A second pin  54  attached to bracket  52  limits the downward pivotal movement of arm  48 , so arm  48  can still trip sensing member  30  when door  10  opens. To prevent arm  48  from ever hanging pendant, arm  48  can be constrained to move between its horizontal position of  FIG. 7  and an upwardly pointing vertical orientation by adding another pin or some other arm-engaging stop to bracket  52 . 
   Referring to  FIGS. 9–13 , traveling member  26  can also be used in conjunction with a second latch assembly  56  for holding door  10  at its closed position. Latch assembly  56  includes a frame  58  attached to track  17  by way of fasteners  60 . A sleeve  62  attached to frame  58  slidingly holds a bar  64 . To selectively hold and release door  10 , bar  64  slides within sleeve  62  between a door-blocking position ( FIGS. 1 and 12 ) and a release position ( FIG. 13 ). A spring, such as a short section of flexible tube  66 , biases bar  64  to the door-blocking position, where bar  64  extends over an upper edge  68  of bracket  52  when door  10  is closed. To release door  10 , a pivotal lever  70  acting against the side of a screw  72  attached to bar  64  can be manually operated to push bar  64  back to its release position of  FIG. 13 . A threaded fastener  74 , such as a shoulder screw or stripper bolt, attaches lever  70  pivotally to an internally threaded boss  76 , which is welded to frame  58 . An arm  78  extending from frame  58  prevents lever  70  from simply falling down against the floor. 
   In closing door  10 , the descending door panels lower bracket  52  toward lower latch assembly  56 . When traveling member  26  reaches bar  64 , a lower edge  80  of bracket  52  pushes against a tapered face  82  of bar  64 . This forces bar  64  to retract against the urging of spring  66  as door  10  continues closing. Upon door  10  reaching its fully closed position, spring  66  is able to push bar  64  out over edge  68  of bracket  52 , thereby holding door  10  closed. 
   To open door  10 , lever  70  is manually pushed against screw  72 , which moves bar  64  back to its release position of  FIG. 13 . This allows door  10  to be lifted toward its open position. As the door panels ascend from their position of  FIG. 4  to that of  FIG. 5 , arm  48  trips sensing member  30 , which moves latch member  24  from its release position to its door-blocking position. After rising above sensing member  30 , the door panels settle back down with roller  13  of panel  12  resting atop latch member  24 , as shown in  FIG. 7 . It should be noted that spring  66  serves as a spring-return for returning bar  64  to its position of  FIG. 11 . It should also be noted that while second latch assembly  56  has been described in conjunction with use of traveling member  26 , its use is not so limited. Rather, latch assembly  56  could be used with a variety of other traveling members or posts, etc. carried on the door—irrespective of whether such traveling member is associated with the latch assembly  22 , above. Indeed, second latch assembly  56  need not even be disposed at the bottom of the door, and is advantageously placed waist-high. 
   To close door  10 , pulling end  46  of cord  40  downward draws latch member  24  back out from underneath roller  13 , which releases door  10 . 
   In another embodiment, shown in  FIGS. 14 and 15 , a door latching system includes a latch assembly  22 ′ in the form of a latch member  24 ′, an actuating member  34 ′, and a sensing member  30 ′. Here, latch member  24 ′ is preferably a moving core of a solenoid (or a mechanical extension thereof), but is schematically illustrated to represent any device for obstructing downward movement of a door  10 ′. 
   Actuating member  34 ′ is preferably a coil of a solenoid, but is schematically illustrated to represent any device for moving latch member  24 ′ between a release position ( FIG. 14 ) and a door-blocking position ( FIG. 15 ). 
   Sensing member  30 ′ is schematically illustrated to represent any device for detecting when door  10 ′ is at a predetermined open position. Examples of sensing member  10 ′ include, but are not limited to, a mechanically actuated electric switch, a proximity switch and a photoelectric eye. Sensing member  30 ′ can determine that door  10 ′ is open by detecting that a certain feature of door  10 ′ is at particular location. For example, a photoelectric eye or a mechanically actuated limit switch could detect when a lower edge  88  of door  10 ′ or some other part on door  10 ′ is adjacent sensing member  30 ′, or a proximity switch could detect when a particularly unique door roller  13 ′ (i.e., distinguishable from the others) or some other part on door  10 ′ is adjacent sensing member  30 ′. In this sense, roller  13 ′ equates with the traveling member  26  in the previous embodiments. The term, “photoelectric eye” refers to any device that provides an electric signal in response to a change in light. The term, “proximity switch” refers to any device that provides an electric signal in response to a change in an electric or magnetic field. 
   A control circuit  90  provides electrical communication between sensing member  30 ′ and actuating member  34 ′. Control circuit  90  is schematically illustrated to represent any electrical link connecting sensing member  30 ′ and actuating member  34 ′. Examples of control  90  include, but are not limited to, conventional hardwiring, radio transmission, a power source, electromechanical relays, circuits of integrated and/or discrete components, and various combinations thereof. 
   In operation, actuating member  34 ′ places latch member  24 ′ at its release position of  FIG. 14 . This allows door  10 ′ to move up and down without any appreciable impedance from latch member  24 ′. When sensing member  30 ′ detects that door  10 ′ has reached a predetermined open position, sensing member  30 ′ provides control  90  with an electrical signal  92 . In response to signal  92 , control  90  provides an output signal  94  that causes actuating member  34 ′ to move latch member  24 ′ (or allow it to move, e.g., powered extension and spring-return or vice versa) to its door-blocking position of  FIG. 15 . 
   To release door  10 ′, control  90  can be given an input signal  96  that control  90  responds to by changing output signal  94 . This causes latch member  24 ′ to retract to its release position, which allows door  10 ′ to close. Input signal  96  can be inputted to control  90  manually (e.g., a push button switch) or can be inputted in some other conventional manner. 
   While the embodiment of  FIGS. 14 and 15  is depicted as using electrical components, it is additionally intended to generically represent the functions performed by the assembled components according to either this embodiment, or that of  FIGS. 1–13 , regardless of whether they are mechanical or electrical components. That is, latch members  24  and  24 ′ can both be considered as means for retaining the door in the open position. A variety of other specific structures in addition to the post-like structures depicted herein can also perform this function —such as flat plates, hooks and the like—which can be moved between release and door-blocking positions. Similarly, both actuating members  34  and  34 ′ can be considered as means for actuating the latch members (or means for retaining) to the door-blocking position. Other structures could perform this function (motors, springs, pistons, etc.) by providing or transmitting the necessary motive force to move the latch member to the door-blocking position. In the same vein, sensing members  30  and  30 ′ can be considered as means for sensing the position of the door, or more specifically, a means for sensing that the door is in the generally open position. A variety of structures could perform this function, including those disclosed according to both embodiments herein. Accordingly, the door latching system depicted herein can alternatively be represented as a combination of structural components (latch member, actuating member, sensing member), or as a combination of functional blocks (means for retaining, means for actuating, means for sensing). In addition, the door latching system can also be identified by the method steps by which the advantageous latching function is performed. 
   Although the invention is described with reference to preferred embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. For example, although latch member  24  obstructs roller  13 , latch member  24  could be modified or relocated to create an obstruction to other parts associated with door  10 , such as traveling member  26 , a roller shaft, or a bottom edge of one of the door panels. Moreover, the upper and lower latch assemblies  22  and  56  can be used on the same door or used alone without the other. Therefore, the scope of the invention is to be determined by reference to the claims that follow.