Abstract:
A door closing mechanism for pulling a door tight to a frame to which the door is mounted comprises a latch arm assembly having a latch arm pivotally secured to a panel of the door and pivotable between a first, open position and a second, latched position. An activating mechanism is operably connected to the latch arm assembly by a connecting apparatus and actuates the latch arm between its first and second positions. A latch member is secured to the jamb in which the door is mounted and is arranged and constructed so that when the latch arm is moved into its second, closed position, the latch arm engages the latch member and exerts force upon the latch member in a direction substantially normal to the plane of the door so as to cause the door to contact the door frame over substantially its entire height.

Description:
This application is a continuation of 09/523,752, filed Mar. 13, 2000, now U.S. Pat. No. 6,547,292. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mechanism for sealing a door tight to a door frame in which the door is mounted. More specifically, the present invention is an over-center door latching mechanism for sealing a bifold door tight to the frame in which it is mounted. 
     2. Description of The Related Art 
     A typical overhead bifold door assembly, such as that described in U.S. Pat. No. 4,609,027, issued to Keller on Sep. 2, 1986, includes an upper door panel and a lower door panel, with the upper door panel hingedly connected to the lintel or header of the door frame. When in its first, closed position, the panels of the overhead door are vertically aligned and cooperate to close the doorway, while in its second, open position the panels of the overhead door are in a folded, generally horizontal, parallel relation. Generally, a door of the size contemplated by the present invention is movable by a winch mounted to the lower door panel, with the winch having a cable extending to a fixed location above the doorway for vertically raising and lowering the bottom edge of the lower door panel and bringing the overhead door to its closed position. 
     Various systems have been developed to address the need for a locking mechanism that will securely lock the panels in their closed, vertically aligned position. In the above-mentioned U.S. Pat. No. 4,609,027 issued to Keller, the weight of the motor and winch mounted on the lower door panel were relied on to act as an anchor to provide dead weight to help keep the door closed. However, such an arrangement would not necessarily provide the affirmative latching action desired to maintain securely the overhead door in its closed position. 
     An example of a latching system is disclosed in U.S. Pat. No. 4,903,747 issued to Johnson on Feb. 27, 1990. The system disclosed in this patent, however, is directed to a device usable with a pair of relatively small, vertically disposed left and right bifold door assemblies used as closet doors, window shutters, or the like, and cooperates with the inner panels of the two bifold door assemblies. Further, the system disclosed in this patent does not operate automatically as a part of the door opening and closing operation. 
     Another example of a latching mechanism is disclosed in U.S. Pat. No. 4,637,446 issued to McQueen et al. on Jan. 20, 1987, which shows a spring biased latching system. The system disclosed in this patent shows a latch member that engages a catchplate mounted on the door track. Opening and closing of the door is done manually, however, with a lift cable being used to disengage the latch member from the catchplate. 
     U.S. Pat. No. 5,168,914, also issued to Keller, discloses a latching assembly, which includes a latch arm cooperating with a latch member affixed to an adjacent doorjamb. The latching mechanism of U.S. Pat. No. 5,168,914 includes a latch shaft that is rotatably mounted to a latch bracket which is itself attached to the door. A latch arm is affixed to one end of the latch shaft so as to be able to engage the latch member secured to the door jamb to which the door is mounted. The opposite end of the latch shaft has affixed thereto a first tensioning arm, which is arranged generally parallel to the latch arm secured to the opposite end of the latch shaft. The latch shaft is spring biased so that the latch arm is normally rotated away from the latch member secured to the doorjamb. An actuation assembly is operatively connected to the latching mechanism by a cable secured to the tensioning arm of the latching mechanism. In order to securely latch and latching mechanism, the actuation assembly applies tension to the cable secured to the tensioning arm which in turn transmits a moment to the latch arm, thereby rotating the latch arm downward and into contact with the latch member affixed to the doorjamb. The force exerted upon the latching member secured to the doorjamb by the latch arm acts to pull the door panel into contact with the door jamb thereby latching and sealing the door. 
     A door latching mechanism manufactured and marketed by Schweiss Distributing, Inc. of Fairfax, Minn. comprises a latch arm which is pivotally mounted to a panel of a bifold door. This latch arm contacts a latch member substantially at the distal end of the latch arm. The latch arm of the Schweiss mechanism is urged into contact with the latch member secured to the doorjamb by a cable and pulley arrangement coupled to the latch arm also substantially at the distal end thereof. Because the point of contact between the latch arm and the latch member attached to the doorjamb is at substantially the same location as the point of connection for the cable and pulley system to the latch arm, i.e. at the distal end of the latch arm, the Schweiss door latching mechanism operates by main force alone and does not realize a mechanical advantage. 
     Accordingly, it is an object of this invention to provide a mechanism for securely locking and sealing a door such as a bifold door to the door frame in which the door has been mounted. In addition, it is an object of this invention to provide a door sealing mechanism that may be actuated by a number of distinct actuation mechanisms. Finally, it is an object of this invention to provide a door sealing mechanism which applies a sealing force to a door which is substantially normal to the plane of the door and which utilizes the mechanical advantage of a lever to limit the magnitude of forces which must be applied to the latching mechanism by a chosen actuation mechanism. 
     These and other objectives and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views. 
     SUMMARY OF THE INVENTION 
     The door closing mechanism of the present invention includes a latch arm assembly and an actuation mechanism or assembly. The latch arm assembly includes a latch arm that is pivotally secured to a panel of a bifold door. The latch arm is pivotable between a first, open position and a second, latched position. A latch member is secured to the jamb of the door frame to which the door frame is mounted. The latch member is mounted to the jamb adjacent to where the latch arm assembly is mounted to the door panel so that the latch arm may engage the latch member when the latch arm is in its second, latched position. A spring biasing mechanism is preferably connected between the door panel and the latch arm to bias the latch arm towards its first, open position. 
     A bracket having a pivot pin is used to secure the latch arm to the panel of the bifold door. In a preferred embodiment of the present invention, an offset arm or bar, rather than the latch arm itself, is rotatably mounted on the bracket pivot pin with the latch arm being secured to the distal end of the offset arm. 
     In order to realize the mechanical advantage present in the latch arm assembly, the latch member, which may comprise a rigid bracket or roller bearing affixed to the door jamb in which the door is mounted, is located such that the latch arm contacts the bracket along a first half of the latch arm nearest the pivot point of the latch arm. In some applications of the present invention, it may be preferred to have the latch arm contact the latch member bracket along the first third of the latch arm nearest the pivot point of the latch arm. 
     It is preferred to arrange and construct the latch member so that when the latch arm is moved into its second, closed position, the force exerted upon the latch member by the latch arm is substantially normal to the plane of the door so as to cause the door to contact the door frame over substantially its entire height. In addition, it is preferable that the latch arm be substantially parallel to the panel of the bifold door when in its second, latched position. 
     The connecting means is the operative connection between the actuation mechanism and the latch arm assembly and transmits the motive power that moves the latch arm from the actuation mechanism to the latch arm assembly. The actuation mechanism which is used to move the latch arm between its first and second positions may comprise a hand-operated winch or a lever arm that is pivotally secured to a panel of the bifold door. Another embodiment of the actuation mechanism includes a cylindrical threaded portion having a first end and a second end with the cylindrical threaded portion being co-axial with, and secured to, a power shaft mounted upon the door for raising and lowering the door. The power shaft is operatively connected to a motor for rotating the power shaft. A threaded nut travels along the cylindrical threaded portion and has a connecting arm projecting therefrom. The connecting arm is attached to the connecting means which in turn connects to the latch arm assembly. A stopping segment is located near an end of the cylindrical threaded portion for the purpose of confronting the threaded nut which travels along the cylindrical threaded portion. When the threaded nut confronts the stopping segment, the threaded nut, and hence the connecting arm, rotate with the power shaft to actuate the latch arm assembly. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of the outside of a typical structure having an overhead bifold door in its vertical, closed position; 
         FIG. 2  shows a cutaway view taken along line  2 — 2  of  FIG. 1  showing an end view of the over-center door latching mechanism in the fully latched position; 
         FIG. 3  shows a view similar to that of  FIG. 2  but with the door somewhat opened and the over-center door latching mechanism in the unlatched position; 
         FIG. 4  shows a view similar to that of  FIG. 3  but with the overhead bifold door in its fully open position; 
         FIG. 5  shows a rear view of the overhead bifold door in its closed, vertical position, with an over-center door latching mechanism installed on both ends of the overhead bifold door; 
         FIG. 6  shows a rear perspective view of the over-center door latching mechanism mounted on an overhead bifold door as the door is being opened; 
         FIG. 7  shows a fragmentary, perspective view of one embodiment of the actuation assembly of the over-center door latching mechanism; 
         FIG. 8  shows a close up view of the latch arm assembly of the over-center door latching mechanism in its fully closed position; and, 
         FIGS. 9–12  show perspective views of the over-center door latching mechanism mounted on an overhead bifold door with the door in its vertical, closed position and the latch arm in its latched position, each respective Figure illustrating a different embodiment of the actuation mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     Although this disclosure of the present invention is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     With reference to the drawings the over-center door latch mechanism for an overhead bifold door is generally indicated by reference numeral  10 . Door latch mechanism  10  includes a latch arm assembly  12  and an actuation assembly  14 . In its preferred embodiment, door latch mechanism  10  is mounted on the inside surface of an overhead bifold door  16  covering an opening to a garage or other utility building  18  ( FIG. 1 ). Door latch mechanism  10  is preferably mounted to the first or lower panel  20  of overhead bifold door  16 , although embodiments are envisioned that include a door latch mechanism  10  on both panels of overhead door  16 . Further, door latch mechanism  10  may include latch arm assemblies  12  located on both ends of overhead bifold door ( FIG. 5 ), in which case an actuation assembly  14  is required for each latch arm assembly  12 . Alternatively, a single actuation assembly may be constructed and arranged to actuate each of the latch arm assemblies. ( FIGS. 9 ,  11 – 12 ) Yet a third latch arm assembly  12  may be provided, mounted to the upper panel  28  of overhead bifold door  16 . A third latch arm assembly  12  so described may be actuated by means of an actuation assembly  14  already provided for one of the first two latch arm assemblies  12 . 
     Overhead bifold door  16  may be attached to building  18  by any number of means, including by hinge means  22  that includes first attachment plate  24  and second attachment plate  26 , as shown in  FIGS. 4–6 . First attachment plate  24  is fixedly attached as by screws to the second or upper panel  28  of overhead bifold door  16 , and second attachment plate  26  is fixedly attached as by screws to the lintel or horizontal header  30 . In the embodiment shown, both lower corners of lower panel  20  include projecting therefrom rollers  32  that ride within tracks  34 . One track  34  is mounted to first door jamb  36  and the other track  34  is mounted to second door jamb  38 . 
     As shown in  FIGS. 2–5  and  9 – 12 , an electric motor  40  is mounted to lower panel  20  of overhead bifold door  16 . The preferred embodiment of this device includes motor  40  to raise and lower overhead bifold door  16 , although a manual winch system may be substituted for the motor. Further, motor  40  may be mounted to upper panel  28 , header  30  or an interior wall portion of building  18  above or otherwise adjacent to overhead bifold door  16 . Overhead bifold door  16  is raised when a switch mounted on an interior wall surface of building  18  is turned to start motor  40 . Motor  40  then rotates power shaft  42  in the direction of arrow  44  ( FIG. 6 ), which in turn rotates take-up shaft  46 , which is a coaxial extension of power shaft  42 . Take-up cable  48 , an end of which may be fixedly attached to an upper portion of overhead bifold door  20 , as at hook  50  projecting from first attachment plate  24  ( FIGS. 2 and 4 ), is then wound around take-up shaft  46 , and the lower edge of overhead bifold door  16  is raised in the direction of arrow  52  ( FIG. 6 ), causing panels  20  and  28  to fold about hinges  54 , fastened to upper panel  28  and lower panel  20 . Hinge means  54  may include a pivot extending inward from the panels, mounted to hinge extension brackets  55  ( FIGS. 2–4 ), as taught in U.S. Pat. No. 4,609,027, issued to Keller on Sep. 2, 1986. Such a modification serves to maximize the clearance between overhead bifold door  16  and the surface beneath, such as a garage floor, when overhead bifold door  16  is in its fully open position as shown in  FIG. 4  by permitting lower door panel  20  and upper door panel  28  to approach a generally parallel relationship when open. 
     Referring to  FIGS. 2–12  generally and specifically to  FIG. 8 , latch arm assembly  12  includes a latch arm  100  secured to an offset arm  102  that is rotatively mounted to the lower panel  20  of bifold door  16  by a bracket  104 . In some applications of the present invention offset arm  102  may be omitted in favor of a straight or curved latch arm  100  as needed. The latch arm assembly  12  is preferably secured to the lower panel  20  of bifold door  16  near the first or second door jamb  36 ,  38  so that the latch arm  100  may address and engage a latch member attached to the door jamb  38  that may take the form of a rotatable metal roller  86  or a jamb bracket  87 . Roller  86  is mounted to a roller shaft (not shown) projecting from a plate  88  whereas jamb bracket  87  is secured as by welding directly to plate  88 . While the connection means  101  which connects the actuation assembly to the latch arm assembly  12  may be secured directly to the free end of the latch arm  100 , it is preferred to secure a flange  106  to the free end of the latch arm  100  for attaching the connection means  101  to the latch arm assembly  12 . Flange  106  also provides a point of attachment for a backspring assembly  108 . Backspring assembly  108  comprises a spring  110  connected in line with a chain or cable  112  that is secured at is upper end to the bifold door  16  (preferably the upper panel  28  thereof, though it is envisioned that the backspring assembly  108  may also be secured to the lower panel  20  of the bifold door  16 ) and at its lower end to flange  106 . Backspring assembly  108  acts to bias the latch arm assembly  12  into a first, open position when the bifold door  16  is open as illustrated in  FIG. 4  or is being opened as in  FIG. 3 . The backspring assembly  108  also acts to prevent the latch arm  100  from contacting the lower panel  20  of the bifold door  16  as the door is being opened.  FIGS. 3–4 . The actuation assembly  14 , through the connection means  101 , opposes the backspring assembly  108  and acts to rotate the latch arm assembly  12  into a second, closed position in which bifold door  16  is securely latched as illustrated in FIGS.  2  and  8 – 12 . Connection means  101  may further include a spring. 
     Latch arm  100  of latch arm assembly  12  has a midpoint indicated in  FIG. 8  by center line  116 . In order to utilize the mechanical advantage inherent in the latch arm assembly  12  of the present invention, it is important that the roller bearing  86  or bracket  87  of the latch member engage the latch arm  100  as near tot he pivot point of the latch arm  100  as possible. Preferably, the latch member will contact the latch arm  100  between the center line  116  and offset arm  102 . In this manner, the forces applied to the latch arm assembly  12  by the actuation assembly  14  will be amplified by the leverage afforded by the latch arm and will achieve a satisfactory seal between the bifold door  16  and the door jambs  36 ,  38 . Furthermore, it is important to size the offset arm  102  and locate the roller bearing  86  or bracket  87  of the latch member so that the sealing force (arrow  118  in  FIG. 8 ) applied to the jamb bracket  87  is substantially normal to the plane created by the jambs  36 ,  38  and the header  30 . As seen in  FIG. 8 , the latch arm  100  is preferably parallel to the door panel to which it is mounted when in its second, latched position. When the forces applied to the latch member are substantially normal to the plane of the door frame, the forces acting upon the door panels through the latching mechanism will also be substantially normal the plane of the door frame and will act to evenly seal the door panels  20 ,  28  to the door frame. Constructing and arranging the latch member and offset arm  102  as described results in a more even and complete seal between the bifold door  16  and the door jambs  36 ,  38 . 
     The arrangement of the latch arm assembly  12  of the present invention is such that there exist numerous distinct actuation assemblies  14  that may be suitable for actuating the latch arm assembly  12  in securing a bifold door  16  in its closed position. A number of suitable actuation assemblies  14  are described hereinbelow. 
     A preferred actuation assembly  14  is illustrated in  FIG. 9 . This actuation assembly  14  comprises a hand operated double acting winch  90  that is secured to the lower door panel  20  of the bifold door  16 . A connection means  101 , which is in the case of the embodiment illustrated in  FIG. 9  a metal cable  91 , is connected between the winch  90  and the latch arm  100  for actuation of the latch arm assembly. The cable  91  is wound about the winch  90  and passes over pulleys  92  before being secured to the latch arm assembly  12 . By rotating winch handle  93  in the direction indicated by arrow  94 , cable  91  is wound up on winch  90  and pulls latch arm  100  into sealing contact with roller  86  or bracket  87  of the latch member to securely lock and seal the bifold door  16  in a closed position, as shown in  FIG. 9 . Rotating winch handle  93  in a direction opposite of that indicated by arrow  94  will pay out cable  91 , allowing back spring assembly  108  to rotate the latch arm  100  away from the latch member and thereby unlocking the latch arm assembly  14  as illustrated in  FIG. 3 . Where two or more latch arm assemblies  12  are in use on a bifold door  16 , additional cables  91   a  may be secured to cable  91  as by splicing or by use of an appropriate fitting  95  as illustrated in  FIG. 9 . Pulleys  92   a  allow cable  91   a  to connect winch  90  to any additional latch arm assemblies  12 . 
     In another embodiment of the present invention, the actuation assembly  14  of door latch mechanism  10  uses motor  40  to automatically actuate latch arm assembly  12 . This actuation mechanism  14  is similar to that disclosed in U.S. Pat. No. 5,168,914, issued to Keller and commonly assigned herewith. As best seen in  FIGS. 6–7  and  10 , the actuation assembly  14  may include an arm  56  projecting from a threaded nut  58 . Threaded nut  58  is threadedly engaged with threaded rod  60 , which is a coaxial extension of power shaft  42  and take-up shaft  46 . Thus, as motor  40  rotates power shaft  42  and take-up shaft  46 , it simultaneously rotates threaded rod  60 . Each of these three rod segments—i.e., power shaft  42 , take-up shaft  46  and threaded rod  60 —rotates in the same direction, as, for example, indicated by direction arrow  44  ( FIG. 6 ). To the end of arm  56  is attached connecting means  101 , the other end of which is attached to latch arm assembly  12 . In this embodiment, the connecting means  101  is preferably a wire cable  91  which is passed around pulleys  92  before being secured to the latch arm assembly  12 . Connecting means  101  may further include an adjustment leader or turnbuckle (not shown) permitting the length of connecting means  101  to be easily lengthened or shortened. With overhead bifold door  16  in its open position ( FIG. 4 ), motor  40  rotates power shaft  42  in the direction opposite to that indicated by direction arrow  44  ( FIG. 6 ) to bring overhead bifold door  16  to its closed position ( FIG. 2 ). As threaded rod  60  rotates, threaded nut  58  moves along rod  60  in a direction opposite to that indicated by direction arrow  64  ( FIG. 6 ), moving, for example, from right to left when configured as illustrated in  FIG. 6 . Arm  56  is maintained in its upward extending position as it travels along threaded rod  60 , as shown, for example, in  FIG. 6 , because of the upward tension placed on the latch arm assembly  12  by backspring assembly  108 . Upon reaching the end of threaded rod  60 , threaded nut  58  encounters stop  68 , which is fixedly attached to and rotates with threaded rod  60 . Stop  68 , also coaxial with power shaft  42 , now causes threaded nut  58  to rotate with threaded rod  60  approximately one quarter to one half rotation, which in turn causes arm  56  to rotate downwardly to the position shown in  FIG. 10 . The length of travel of threaded nut  58  along threaded rod  60  is so measured that threaded nut  58  encounters and travels with stop  68  at the very end of the closing cycle of overhead bifold door  16 . The rotation of threaded nut  58  and the resulting travel of arm  56  overcomes the resistance of backspring  110  and tensions connecting means  101 , thereby causing latch arm  100  to rotate from its open position as illustrated in  FIGS. 3–4  to its closed position illustrated in  FIGS. 2 and 10 , and in doing so, securely locks the overhead bifold door  16  in its closed position. 
     In the embodiment illustrated in  FIGS. 6–7  and  10 , upon beginning the cycle that results in moving overhead bifold door  16  to the open position, motor  40  rotates power shaft  42  in the direction indicated by arrow  44 , causing threaded rod  60  also to rotate in the direction indicated by arrow  44 . Threaded nut  58  and arm  56  also rotate with threaded rod  60 , until arm  56  contacts bumper plate  70  ( FIGS. 7 and 10 ). Upon striking bumper plate  70 , arm  56  and threaded nut  58  break contact with stop  68 , and thereafter travel along threaded rod  60  in the direction indicated by arrow  64  ( FIG. 6 ). As threaded nut  58  and arm  56  rotate with stop  68  to the position indicated in  FIG. 6 , latch arm assembly  12  is released, and overhead bifold door  16  is free to move to its open position. (See  FIGS. 2–4 .) 
       FIG. 11  illustrates another alternate embodiment of actuation mechanism  14 . The embodiment of  FIG. 11  includes a lever arm  120  that is rotatively secured to the lower door panel  20  of the overhead bifold door  16  by a bracket  122 . A cable take up shaft  124  is connected coaxially with power shaft  42  intermediate cable take up shaft  46  and motor  40 . A cable  126  is passed around a pulley  128  suspended from a spring  130  that is secured to the lower panel  20  of the overhead bifold door  16 . Both ends of the cable  126  are fastened to cable take up shaft  124  so that when cable take up shaft  124  is rotated in the direction indicated by direction arrow  132 , as when the bifold door  16  is being closed, cable  126  is wound up on cable take up shaft  124 . As the cable  126  is wound up on cable take up shaft  124 , cable  130  causes pulley spring  130  to elongate, thereby moving the pulley  128  to move to a lower position. As the cable  126  is also connected to lever arm  120  by cable fitting  121 , the lever arm  120  is also rotated to a lower position as the cable  126  is wound up on cable take up shaft  124 . In this lower position, the lever arm  120  places the connection means  101  under tension. In this embodiment, the connection means is a cable  134  which is passed over pulleys  136  to connect the actuation assembly  14  to the latch arm assembly  12 . A spring  138  is preferably connected between the lever arm and the connection means  101  to prevent excess forces from being applied to the latch arm assembly  12 . When the lever arm  120  is moved to its lower position by the action of cable take up shaft  124 , the tension placed on the cable  134  overcomes the tension placed on the latch arm assembly by the backspring assembly  108  and moves the latch arm  100  to its closed position in which it bears against the latch member secured to the jamb  36 . When the cable take up shaft  124  is rotated in the direction opposite that indicated by direction arrow  132 , as when the door  16  is being opened, cable  126  is paid out from the cable take up shaft  124 , thereby allowing pulley  128  and lever arm  120  move to their upper positions. When the lever arm  120  is rotated to its upper position, the tension placed on cable  134  is released and backspring assembly  108  biases latch arm  100  to its open position, thereby unlocking the door  16 . Care must be taken to make the cable  126  the appropriate length as the cable take up shaft  124  will rotate continuously with shaft  42  as the door  16  is opened and closed. Springs  130  and  138  act to prevent the cable  128  from becoming too slack and simultaneously act to prevent the imposition of extreme forces on the connection means  101  which might damage the latching assembly  12 . 
     Yet another alternate embodiment of the actuation assembly  14  is illustrated in  FIG. 12 . Actuation assembly  14  of  FIG. 12  includes a cable take up shaft  140  having both ends of cable  142  wound thereabout. The middle portion of cable  142  is passed over a pulley  144  that is suspended from block  148  by spring  146 . Block  148  is in turn suspended from the lower door panel  20  of overhead bifold door  16  by springs  150 . The connection means  101  of the embodiment of  FIG. 12  includes cable  152  which extends from block  150 , around pulleys  154 , to the flange  106  of latch arm assembly  12 . In closing and locking the door  16 , motor  40  rotates shaft  42  in the direction indicated by direction arrow  151 , thereby winding cable  142  up on cable take up shaft  142  while simultaneously paying out cable  48  from cable take up shaft  46 . As cable  142  is wound up on cable take up shaft  140 , pulley  144  is pulled downward. As pulley  144  moves downwards, so does block  148 , and, as block  148  moves downward, tension is applied to cables  152 . As the tension applied to cables  152  exceeds the biasing force placed upon the latch arm assembly  12  by the backspring assembly  108 , the latch arm  100  is rotated downward into contact with the latch member. The length of cable  142  is arranged such that when the shaft  42  stops rotating, as when the door is in its fully down position, the latch arms  100  of the latch arm assembly  12  will have been rotated into their lower, closed positions so that the overhead bifold door is securely latched in its closed position as described more fully above. When the door  16  is to be opened, motor  40  rotates shaft  42  in the direction opposite that indicated by direction arrow  151 . This causes cable  48  to be wound up on cable take up shaft  46  to raise the door panels  20 ,  28  and simultaneously pays out cable  142  from cable take up shaft  140 , thereby releasing the tension on cable  152 . The drop in tension in cable  152  allows the backspring assembly  108  to rotate the latch arm  100  of latch arm assembly  12  to its open position, unlocking the door and allowing the door panels  20 ,  28  to be folded into their open position. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.