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BACKGROUND OF THE INVENTION 
     The present invention concerns a locking mechanism for a door driven by a motorized transmission, especially an overhead door, a tilting, swinging, or sectional door for instance, whereby the locking mechanism operates in conjunction with a coupling mechanism that couples the door&#39;s panel to a carrier, the transmission moves the carrier back and forth, preventing the closed door from opening when not subjected to force by the carrier, the locking mechanism includes a lever and a connector, the lever is mounted directly or indirectly on the carrier and pivots around a first axis in two opposite directions, the lever is provided with an engagement mechanism that engages a stationary counterbearing, the counterbearing operates in conjunction with a track that guides the carrier, locking the door, the engagement mechanism engages the counterbearing as the lever pivots in one direction and disengages it as the lever pivots in the opposite direction, the connector is rigid and is preferably in the form of a connecting rod, the connecting rod has an attachment mechanism at one end that attaches it to the door panel and is pivoted at the other end to the lever around another axis that is some distance from the first axis, whereby the lever accordingly pivots around the firstaxis in the first direction when the connector is pushed while in alignment with the door and in the opposite direction when the connector is pulled while in alignment with the door. The present invention also concerns a door-drive mechanism provided with such a locking mechanism. A locking mechanism and door-drive mechanism of this genus is known from European Patent 0 743 416 A1, which will be discussed in detail hereinafter. 
     Motorized drive mechanisms that open and close overhead doors have long been known. 
     A mechanism of this genus is known from DE 2 741 539 A1 for example. They usually include a carrier, preferably a carriage, that can be moved along the track positioned horizontal above the route traveled by the door. The carrier is usually attached to the door by connecting rods. Detaching the carrier from the door or from a traction mechanism between the carrier and the drive mechanism in the event of an emergency, when the mechanism malfunctions, has also long been known. 
     Problems can be encountered with such drive mechanisms. The closed door can be forced up from outside by muscle power, the carrier moving in the door-opening direction without or even against the force exerted by the transmission. 
     Additionally preventing the carriage and/or the closed door from unauthorized opening has accordingly often been proposed. Examples of such locking mechanisms are known from German Patent 1 961 916, U.S. Pat. No. 3,704,548, German 8 802 127 U1, French A 2 349 014, U.S. Pat No. 3,909,980, and the aforesaid European Patent 0 743 416 A1. 
     In German Patent 1 961 916, a carrier in the form of a carriage travels back and forth along a track between two stops. The closure stop is provided with a stationary pawl. The carriage is secured in its locking position when it engages the pawl. The engaged pawl is subject to tension. To disengage the carriage, it is attached by way of a two-armed lever to a traction mechanism between it and the motorized transmission. The lever&#39;s arms act as stops, limiting its pivoting motion. The free end of one arm engages below the pawl when the lever is in its locking position. When the traction mechanism is actuated, the lever pivots before the carrier begins moving. The pawl is accordingly lifted and disengaged, releasing the carrier. This drive mechanism is indeed provided with a coupling mechanism that couples a carrier in the form of a carriage to the door, but the coupling mechanism pivots around the same axis as the lever, although independently thereof. 
     In the mechanism disclosed in U.S. Pat. No. 3,704,548, it is the upper end of the door and not the carrier in the form of a carriage that is locked. Releasing the tensioned locking device again in order to open the door requires a highly complicated system of levers and slides. 
     German 8 802 127 U1 discloses a locking mechanism wherein a connecting rod attached to the door lifts a carrier when force is applied to the door from outside and accordingly engages the carrier with a cogged rack or with a chain above it. This locking mechanism is not completely reliable. The carrier can move at a right angle to its intended direction, resulting in unpleasant rattling and imprecise movement. The carrier can even tilt out of alignment and impinge on the rack or chain in ordinary operation. 
     French A 2 349 014 discloses a locking mechanism wherein the connecting rod that comprises the coupling mechanism travels back and forth in a slot in the carrier. A pawl on the connecting rod pivots around a pin accommodated in the slot and engages a counterbearing on the track. As the carrier leaves its locking position, the connecting rod is pulled along the slot, disengaging the pawl by way of a sloping plane. The mechanism known from U.S. Pat. No. 3,909,980 also employs means of displacement comprising a pawl in conjunction with a slot and a sloping plane to lever the pawl out of its engagement against a counterbearing. Generally, devices of this genus, which exploit displacement of a rod in relation to a carrier, are problematic with respect to wear and are complicated to manufacture and to install and adjust on site. 
     The locking mechanism of the aforesaid genus known from European Patent 0 743 416 A1 on the other hand has proven very reliable and easy to manufacture and install. The connecting rod employed therein between the carrier and the door is not directly attached to the carrier but to a lever that pivots around an axis on the carrier. A coupling mechanism constituting a toggle composed of the rigid connector, which is in the form of a connecting rod, and the lever, couples the carrier to the door. The lever has only one arm and is provided with a hooked pawl in the vicinity of another pivoting axis and engaging a notch in the vicinity of the track. This mechanism has few moving parts, and they only pivot among themselves and are not relatively displaced. The mechanism is accordingly very simple and operates reliably in that, with the exception of the pawl, none of the components slide along any of the others, which would subject them to wear. The mechanism is also very easy to install and adjust. 
     Even this known mechanism, however, needs improvement with respect to its adaptability to various installation situations. The toggle for instance allows the connecting rod to rotate only to a limited extent without detriment to the function of the pawling system. This is of disadvantage in particular when the track is to be mounted high above the doorway. The site might also provide insufficient vertical space, in the opening and closing direction, that is, in which event a shorter connecting rod would be desirable. The limits dictated by the operation of the toggle will still be too narrow in some situations. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is an improved locking mechanism and associated drive mechanism of the genus disclosed in European Patent 0 743 416 A1 that will operate just as reliably and that can be manufactured, installed, and adjusted just as easily while adapting readily to a wider range of situations on site. 
     This object is attained in accordance with the present invention in a locking mechanism of the aforesaid genus in that the lever comprises two arms, the connector being attached to the arm, and in that the mechanism that engages the counterbearing while or after the lever and hence the second arm pivots in the first direction, pushing the connector attached to the door, and that disengages the counterbearing while or after the lever and hence the second arm pivots in the opposite direction, pulling the connector attached to the door, is mounted on the second lever arm. 
     These amazingly simple measures allow the connector or connecting rod to be farther uncoupled from the lever. The connector, specifically the connecting rod, that is, can be attached to the door at a wider range of angles, while the lever is rotated in the first direction only when subjected to force in the opening direction. 
     A door-drive mechanism with a locking mechanism of this species can accordingly be installed considerably above the doorway and be provided with shorter connecting rods. 
     Advantageous embodiments of the present invention are addressed by the subsidiary claims. 
     Various types of engagement mechanism can be employed. The mechanism can for example be a pin that engages a barbed structure from a depression therein. In a simpler and preferred embodiment, however, the end of the second lever arm pointing along the first pivoting direction is provided with an engagement mechanism in the form of a hook or nose that hooks onto or engages behind the counterbearing while or after the lever pivots in the first direction and releases it while or after the lever pivots in the second direction. 
     To facilitate directly transmitting the pushing and pulling forces from the carrier to the door by way of the coupling mechanism, the lever and connecting rod, that is, during normal operation, one advantageous embodiment of the locking mechanism in accordance with the present invention features two stops, the first stop limiting the motion of the lever as it pivots in the first direction once engagement has been achieved and the second stop limiting the motion of the lever&#39;s first and/or second arm as it pivots in the second direction once engagement has been achieved. The lever can accordingly pivot only to a limited extent, just far enough to engage or disengage. 
     The regulations that govern the safe operation of doors driven by motorized drive mechanisms prescribe that the doors can be opened in emergencies and when their drive mechanisms malfunction. This demand is of particular importance when the door is the only form of access to the other side. For such events, one particularly advantageous embodiment of the drive mechanism in accordance with the present invention features an emergency unbarring mechanism that disengages the lever, allowing the door to be opened by muscle power. The locking mechanism can accordingly be released when the drive mechanism malfunctions, in the event of a power failure for example, and the drive mechanism will not stand in the way of opening the door by muscle power. Since many door-drive mechanisms are self-inhibiting, however, it is not only the locking mechanism itself that must be overcome when opening the door by muscle power, but the motorized transmission itself. It will accordingly be of advantage for the emergency unbarring mechanism that unlocks the locking mechanism and uncouples the door to be constituted by the motorized transmission itself. It will be of further advantage in this case for the emergency unbarring mechanism to be provided for this purpose with a separating mechanism that separates the carrier from the motorized transmission. The separating mechanism in one preferred embodiment can be provided with an unlocking-lever component that manually shifts the carrier out of a normal position, wherein the carrier is coupled to the motorized transmission, and into a detachment position, wherein the carrier is detached from the motorized transmission, especially by traction means. The separating mechanism can for example be actuated by way of manually actuated traction means. The traction means can for example comprise a traction cord accessible from inside the door and/or a Bowden cord accessible from outside. Other means—levers, rods, etc. for example—of actuating the emergency unbarring mechanism are of course also conceivable. Although manual actuation is preferred, automatic actuation by way of an emergency mechanism of some sort is also possible. 
     To ensure that the locking mechanism can be unlocked to allow the door to be opened by muscle power, the emergency unbarring mechanism in one embodiment of the present invention can include means of applying tension, especially in the form of a spring that maintains the lever in its release position. The engaging component in all known locking mechanisms is maintained in its engaged position subject to tension. Although this feature does ensure that the engagement mechanism will engage and remain engaged as long as the door remains closed, it is not absolutely necessary in that the engagement mechanism must only remain engaged while the door is actually subjected to force from outside. If, for example, as provided in this particular embodiment of the present invention, the lever is maintained in its release position by tension, the advantage will be that the door can easily be opened by muscle power with the carrier coupled by way of the traction mechanism without having to first shift the engaging mechanism out of its engaged position. All that would be necessary to disengage the system in an emergency in such an embodiment would be to uncouple the carrier from the motorized transmission. 
     Practice has demonstrated, however, that this theoretically simplest approach is not sufficient in all cases to ensure absolutely reliable emergency unbarring. The emergency unbarring mechanism in one preferred embodiment of the present invention can accordingly include an unlocking mechanism that will when actuated shift and in particular force the lever out of its engaged position or locking position, whereupon the door panel can be pulled or pushed up, allowing the door to be opened subject to muscle power in an emergency. 
     The unlocking mechanism is also preferably designed such that, when the emergency unlatching mechanism is actuated, by tugging on the traction means for example, it will not pivot the second lever arm out of its engagement position and into its release position until the separating mechanism has separated the carrier. The emergency unbarring mechanism can accordingly be operated in two phases. In the first, the carrier is uncoupled from the motorized transmission. In the next phase, as the emergency unbarring mechanism continues to be actuated, by continuous tugging on the traction means for example, the locking mechanism will be unlocked. The unlocking mechanism that unlocks the locking mechanism in one concrete and advantageous embodiment is mounted on, located on, or associated with the unlocking-lever component that unlocks the carrier from the motorized transmission such that it will not, as the unlocking-lever component pivots out of its normal position and beyond its unlocking position, seize a vicinity of the lever that pivots along with the second lever arm such that the second lever arm will pivot in the second direction, until the unlocking-lever component has traveled beyond its unlocking position. In the simplest version of this embodiment, both the unlocking mechanism and the unlocking-lever component comprise a single component, that will, as it pivots out of its normal position around an acute angle, uncouple the carrier from the motorized transmission and, as it continues beyond that angle, seize the locking mechanism&#39;s lever and force it out of its engagement position. In the simplest version, the unlocking mechanism is constituted by the unlocking-lever component itself, whereby once it has traveled beyond its unlocking position, the unlocking-lever component will directly seize the lever and push or pull it out of its engagement position. The unlocking-lever component in one preferred embodiment can be pivoted manually, especially by way of the traction means. The unlocking-lever component is connected to a coupling pin. The pin is in particular tensioned in the coupling position and couples the carrier to the traction mechanism. As it pivots into the unlocking position, the unlocking-lever component releases the pin. The unlocking-lever component is preferably provided with a contact vicinity that contacts a matching contact area on the lever, pivoting the second lever arm out of its engagement position and into its release position. 
     The contact area of the lever that constitutes the locking lever in another preferred embodiment is provided with a third lever arm that is connected to and pivots along with the second lever arm around the first axis. The third lever arm extends into the vicinity wherein the unlocking-lever component pivots such that, when the lever is in its engagement position and the unlocking-lever component in its normal position, the third arm will be far enough from one arm of the unlocking-lever component to allow emergency unbolting to take place in two phases. It is in this event preferable for the distance to be long enough to prevent the unlocking-lever component and the third lever arm from seizing each other until the unlocking-lever component has pivoted out of its normal position and beyond its unlocking position such that the second arm of the lever can be released as the unlocking-lever component continues pivoting. 
     One concrete embodiment of the present invention features a bearing that accommodates the lever, whereby the bearing extends downward from the carrier when the mechanism is employed as intended, the carrier travels back and forth along a track, the track extends horizontally above the route traveled by the door panel as the door opens, the first axis is provided against the bearing extending downward as viewed from a specified angle and at a distance from the horizontal track when the mechanism is employed as intended, and the first and/or the second axis are preferably provided on the bearing. This situation can be attained for example if the bearing is provided with a housing in the form of a sleeve or is sleeve-like or cylindrical, with the lever coming to rest against the interior wall surface of the housing upstream and/or downstream and above and/or below the axis during the pivoting motion. 
     Instead of the bearing that establishes a position below the carrier track. The first axis can be accommodated inside the carrier itself. In this case, the lever will be accommodated inside the carrier. The interior wall surfaces of the housing that face the first lever arm will preferably act as the first and/or second stop. The second axis will, however, preferably be below the carrier track when the mechanism is employed as intended. 
     The first lever arm in one especially advantageous embodiment can extend for this purpose downward, essentially downward, that is, from the first axis in when the mechanism is employed as intended such that, as it pivots in the first direction, its free end will move in the opening direction traveled by the carrier. The lever arm need not point precisely downward but only essentially downward, extending across the direction traveled by the door panel and/or the carrier and accordingly transmitting the maximum of torque. Due to the force exerted on the connecting rod during the first attempt to open the door from outside, the first lever arm will pivot into the premisses being closed off. 
     The second lever arm can extend upward, essentially upward, that is, from the first axis for example when the mechanism is employed as intended such that, as the arm pivots in the first direction, its free end will move along with the engagement mechanism opposite the direction traveled by the carrier until it arrives in its engagement position. The first and second lever arm in one embodiment of the present invention can thereby extend essentially perpendicular to each other, more or less at 180°, at least in the vicinity of the first axis. This approach will simplify manufacture of the lever, which will act like a motion-reversing lever. 
     The lever arms in one advantageous embodiment either constitute a simple single component or are otherwise fastened together, pivoting as a whole in both directions. 
     The first and second lever arms in one alternative embodiment, however, can be separate components coupled together. They will then preferably be coupled together by way of a carrier mechanism such that the second lever arm will move along with the first lever arm only when pivoting in one particular direction. It is accordingly preferably subjected to tension such that both lever arms will engage each other by way of the carrier mechanism. When force is exerted against the second lever arm in opposition to the engagement provided by the carrier mechanism, however, the latter will pivot out of engagement with the first lever arm. It will in this case be preferable for both the first and second lever arm to pivot simultaneously as the carrier travels in the opening direction and to uncouple from each other, especially by pivoting relative to each other, as the carrier travels in the closing direction. The advantage here is that the second lever arm can slip beyond the counterbearing and snap into place without having to carry the first lever arm and the connector coupled thereto along with it. Furthermore, the second lever arm, once uncoupled from the first lever arm by the emergency release mechanism comprising the unlocking mechanism, can easily be shifted out of its engagement position without having to move the first lever arm and hence the coupling mechanism. With such an embodiment it is also conceivable in principle to eliminate two-phase actuation of the emergency unbolting mechanism or to unlock the locking mechanism first and then [un] couple the carrier from the motorized transmission. To ensure that the locking mechanism will remain locked in any case once the lever arms have been uncoupled, it will be preferable for the second lever arm to be tensioned, preferably by a spring, in its engagement position. 
     The free end of the second lever arm in another embodiment of the present invention is bent or curved along the first pivoting direction, creating the engagement mechanism, especially the hook, whereby the face of the bent or curved free end that faces the first direction is provided with a hook nose with an engagement area that seizes the counterbearing and locks it. The lever can accordingly as a whole comprise a straight, curved or, depending on the situation, bent, at an essentially right angle for example, strip of sheet metal that terminates in a hook. If the end is straight, it can act as a first lever arm for example, with a point of engagement, a bore for example, for the first axis located therein. In this case, the other end, which can be bent for example, will act as a hook that hooks onto the counterbearing as the lever pivots in the first direction. It is on the other hand also conceivable for the first and second lever arm to bend toward each other, with a bore or similar bearing for the first axis located in the vicinity of the bend. The entire second lever arm will in this case comprise a hook with a nose at the end. A third lever arm can be provided in the form of a straight extension of the second lever arm, representing a point of contact for the unlocking component. 
     To allow the hook to hook onto or the nose to travel beyond the counterbearing that it is to engage behind even while it is being advanced during normal operation, it will also be preferable to provide the engagement mechanism with a snap-in nose and in particular for the hook nose or nose to be in the form of a snap-in nose. The side of the snap-in nose that faces the engagement area can be provided with an on-ramp shoulder. If the engagement mechanism is also provided with an obliquely angled capture area for seizing the counterbearing, the second lever arm will not be able to hook over the counterbearing subject to powerful force as might happen if a pointed capture area were to bore into the counterbearing. Tests have indicated that reliable locking can be attained even with an obliquely angled capture area. 
     It will be preferable to be able to fasten the counterbearing at various points along the track. The track can for example be a rail in the form of a length of C section, the counterbearing tensioned across it from one mutually facing edge to the other. An embodiment of the present invention is preferable wherein the counterbearing simultaneously constitutes or comprises a limiting mechanism that limits the closing motion of the carrier and accordingly prescribes its closing position. It will also be preferable for /27. the counterbearing to be constituted by one edge of the limiting mechanism and especially by an edge that extends into the C section. 
     The locking mechanism can be adapted to various sites even more easily if /28. the connecting rod is provided with several means of attaching it to any desired point on the door panel and of articulating it to any desired point on the first lever arm. This feature will be even more advantageous if it allows various distances between the door panel and the carrier to be spanned. T /29. he connecting rod in one concrete version is preferably flat and elongated and in particular a perforated strip of metal, whereby the means of attaching it to any desired point on the door panel and of articulating it to any desired point on the first lever arm are in the form of several preferably round holes distributed along it. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various embodiments of the present invention will now be specified by way of example with reference to the accompanying drawing, wherein 
     FIG. 1 is a partly sectional lateral view of part of one embodiment of a door-drive mechanism and locking mechanism adjacent to a doorway during an attempt to open the door from outside subject to muscle power, 
     FIG. 2 is a cross-section along the line A A in FIG. 1, 
     FIG. 3 is a lateral view similar to FIG. 1 of the door drive mechanism&#39;s carrier with the door closed and subject to no force, 
     FIG. 4 is a partly sectional lateral view similar to FIG. 1 of part of another embodiment of a door-drive mechanism and locking mechanism, 
     FIG. 5 is a view of the second embodiment from below along the direction indicated arrow A in FIG. 4, 
     FIG. 6 is a view similar to FIGS. 3 and 4 of a third embodiment of a door-drive mechanism and locking mechanism, 
     FIG. 7 is a view from below of the part of the third embodiment of a door-drive mechanism and locking mechanism illustrated in FIG. 6, and 
     FIG. 8 is a cross-section along the line B—B in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures illustrate various embodiments of a drive mechanism  3  for an overhead door  2  in the vicinity of its attachment to the door&#39;s panel  1 . More specifically, only the end of drive mechanism  3  that is to be fastened to the doorway&#39;s lintel  4  is represented. At the other end, the drive mechanism  3  is provided with an unillustrated motorized transmission that shifts a carrier in the form of a carriage  6 ,  106 , or  206  back and forth between two limits, specifically a door-opening position and an illustrated door closing position subject to a traction mechanism, the cogged belt  5  in the illustrated embodiment for example. Carriage  6 ,  106 , or  206  travels along a track in the form of a rail  7  comprising a length of C section like that described in WO 98/12407, which can be referred to for details. Rail  7  is fastened horizontal to lintel  4  above panel  1  and along the direction the panel opens in. A pulley  8  guides and reflects belt  5  inside rail  7 . The door opening-and-closing motions of carriage  6 ,  106 , or  206  are limited by structures in the form of stops  9  like those described in WO 98/12405, which can be referred to for details. FIGS. 1 and 3 through  7  show only the stop  9  that limits the closing motion of carriage  6 ,  106 , or  206 . Stop  9  can be clamped onto rail  7  at any desired location along it, allowing adaptation to various sites of installation and limits. 
     The door  2  in the illustrated embodiment is a tilting door with a single flat panel  1 . The carriage  6 ,  106 , or  206  that acts as a carrier in drive mechanism  3  is coupled to panel  1  by a coupling mechanism  10 ,  110 , or  210 . A locking mechanism  11 ,  111 , or  211  that prevents panel  1  from being opened from outside by unauthorized persons acts in conjunction with coupling mechanism  10 ,  110 , or  210 . Coupling mechanism  10 ,  110 , or  210  comprises a connecting rod  12  or  112  attached to carriage  6 ,  106 , or  206  by way of a lever  13 ,  113 , or  213  and to panel  1  by way of an L-shaped structure  14 . Such an L shaped structure  14  is described in European Patent 0 768 444 A1, which can be referred to for details. Drive mechanism  3  can be adapted to various motorized door panels  1  by way of structure  14 . Locking mechanism  11 ,  111 , or  211  essentially comprises connecting rod  12  or  112  and lever  13 ,  113 , or  213 , attached to carriage  6 ,  106 , or  206 , in conjunction with stop  9 . The illustrated embodiments of drive mechanism  3  differ in the design of locking mechanism  11 ,  111 , or  211  and in the design of an emergency unlatching mechanism  40 ,  140 , and  240  that allows the door to be opened subject to muscle power in the event of an emergency, when, for example, there is a power failure or when drive mechanism  3  malfunctions for some other reason. 
     One embodiment of the present invention will now be specified with reference to FIGS. 1 through 3. 
     The lever  13  in this embodiment is secured in a bearing  15  on carriage  6 . Otherwise, the carriage is similar to the one described in WO 98/13569. It is accordingly provided with a groove-and-spring device  17  that includes a groove  16  and attaches it to bearing  15 . The bearing is provided with a more or less sleeve-like housing  18  that extends downward from carriage  6  and wherein lever  13  pivots to a limited extent around an axis  19  that extends perpendicular to the direction traveled by the carriage. Lever  13  has two arms. One arm  20  is positioned below axis  19 , and the other arm  21  above it. 
     Connecting rod  12  pivots around another axis  22  at the free end  23  of first lever arm  20 . Specifically, free end  23  is forked, and connecting rod  12 , a flat strip, is articulated between its two prongs at second axis  22 . Second lever arm  21  extends initially straight out of first axis  19  but bends at an angle paralleling first pivoting direction  30 , pointing upstream in the direction traveled by carriage  6  as the door opens. The free end  24  of second lever arm  21  terminates in a downward-pointing hook  25 . Hook  25  is provided with an on ramp shoulder  26  facing down and along the closing-motion direction and with a capture area  27  that can engage behind a limiting edge  28  of stop  9 . 
     The free end  24  of second lever arm  21 , with its hook  25 , shoulder  26 , capture area  27 , in conjunction with stop  9  or limiting edge  28 , accordingly constitute a barbed structure that engages a component  29 . By way of this engagement, locking mechanism maintains carriage  6  and panel  1  in the state represented in FIG.  1 . 
     Whereas FIG. 1 represents engagement component  29  engaged, FIG. 3 shows it disengaged, with lever  13  subject to the tension exerted by a spring  41 . The front and back walls of housing  18  are designed to allow lever  13  to pivot in first direction  30  around first axis  19  out of the disengaged position represented in FIG.  3  and into the engaged position represented in FIG.  1 . As it pivots, lever  13  in second direction  31 , in the opposite direction, that is, moves out of the engaged position represented in FIG.  1  and into the disengaged position represented in FIG.  3 . As the lever pivots in first direction  30 , the wall  32  of housing  18  near panel  1  acts as a stop, limiting the motion of second lever arm  21 , and the opposite wall  33  as a stop limiting the motion of first lever arm  20 . The lever&#39;s motion in second direction  31  is limited by the wall  33  farther from panel  1  on second lever arm  21  and by the wall  32  near panel  1  on first lever arm  20 . 
     The emergency unlatching mechanism  40  in this embodiment accordingly essentially comprises the spring  41  that maintains lever  13  in its release position and a mechanism  34  that separates the carriage  6  from belt  5 . Separating mechanism  34  comprises a traction cord  35  that pulls an unillustrated engagement pin (cf. FIG.  8  and hereinafter) out of its engagement with a cogged-band coupling  36  (FIG. 2) inside carriage  6 . Such a cogged-band coupling is described in WO 98/13625, which can be referred to for details. 
     To allow its attachment to any desired points on door panel  1  and lever  13 , connecting rod  12  is provided with several fastenings in the form of openings  37   a . The connecting rod itself is a strip of sheet metal with openings  37   a  distributed equally along it. In other words it is perforated. 
     How this embodiment of the door-drive mechanism and its associated locking mechanism work will now be specified. 
     How drive mechanism  3  shifts the open door  2  into the closed state represented in the figures will be specified first. Lever  13  is initially in the position relative to bearing  15  and hence to carriage  6  represented in FIG.  1 . When the free end  24  of second lever arm  21  contacts stop  9 , the shoulder  26  of hook  25  slides over limiting edge  28  until capture area  27  engages behind limiting edge  28 . Carriage  6  can now continue traveling until it contacts stop  9 , coming to rest in the position represented in FIG.  1 . Door  2  will now be closed. Drive mechanism  3  will now turn off, and lever  13  will be maintained subject to tension in the position illustrated in FIG. 3, in the release position, that is. 
     FIG. 1 represents what happens when an external force is applied to panel  1  in this state. When an attempt is made to lift the door from outside, a force or push  37  is applied to connecting rod  12  along its length. Due to the articulation of connecting rod  12  to first lever arm  20  accordingly, lever  13  will pivot around first axis  19  in first direction  30  until engagement component  29  arrives in its engagement position. Second lever arm  21  will now come to rest against the stop constituted by wall  32 , and carriage  6  will be subjected to force in the opening direction. This force, however, will remain in action only until seizing area  27  comes to rest against limiting edge  28 . Panel  1  will be prevented from moving any farther in its opening direction no matter how much force is applied to the door. 
     It will, however, still be possible when drive mechanism  3  malfunctions due to a power failure for instance, to open door  2  by means of emergency unlatching mechanism  40  by just uncoupling carriage  6  from belt  5  with a tug on traction cord  35  and a pull on the carrier, carriage  6 , that is, in the present example, in the opening direction. As drive mechanism  3  shifts the carriage  6  in the present embodiment into the closing position against the force of spring  41 , lever  13  will preferably enter its engagement position. Spring  41 , which acts as an unbolting spring on lever  13 , is tensioned to ensure that door  2  can be lifted and opened by muscle power immediately once carriage  6  has been unbolted. This is particularly important in the event of emergency unbolting when there is no other access to the garage. A second embodiment of door-drive mechanism  3  and a second embodiment of door-locking mechanism  111  will now be specified with reference to FIGS. 4 and 5. Identical parts will be provided with the same reference numbers, and the specification of the first embodiment can be referred to for the overall design. 
     Here again locking mechanism  111  is associated with a coupling mechanism  110  that couples panel  1  to a carrier in the form of a carriage  106 . The carriage&#39;s motion is transferred to panel  1  by way of a lever  113  mounted therein and by way of a connector in the form of a connecting rod  112 . 
     Lever  113  comprises two lever arms  120  and  121  that pivot in two directions  30  and  31  around an axis  119  inside rail  7 . 
     Axis  119  is embodied by a pin  151  mounted in the carriage&#39;s housing  150  (FIG.  5 ). Pin  151  extends through lever arms  120  and  121 . First lever arm  120  is constituted by two cheeks  162  and  163 , in the form of strips of metal in the present embodiment, one on each side of second lever arm  121  and connecting rod  112 . Connecting rod  112  pivots between and at the free ends  123  of cheeks  162  and  163  around another axis  122  below rail  7 . 
     The free end  124  of second lever arm  121  is provided with a hook  125  similar to the hook  25  in the first embodiment, with that is, an on-ramp shoulder  126  and an edge  127  that engages a limiting stop  9 . Second lever arm  121  is in the form of a length of structural section mounted on pin  151  that could as a whole be called a locking hook or locking-hook component and that extends along second lever arm  121  and beyond first axis  119 , accordingly constituting a third arm  152  for lever  133 . Third lever arm  152  bends down at its free end  153 . Between first lever arm  120  and the bent-down free end  153  of third lever arm  152  is a resilient structure, in the form of a compression spring  144  in the present example. Compression spring  144  tensions second lever arm  121  and third lever arm  152  with its locking hook in first direction  30  and accordingly maintaining second lever arm  121  in the engagement position represented in FIG.  4 . 
     The end of third lever arm  152  pointing away from first axis  119  is provided with an emergency unlatching mechanism  140  in the form of a contact area  154  that engages an unlocking lever component  143 . 
     Carriage housing  150  is provided with inner surfaces  132  and  133  that act as stops, limiting the pivoting motion of first lever arm  120 , cheeks  162  and  163 , that is. First lever arm  120  is also provided with a carrier  155  with a pin mounted between the cheeks. Carrier  155  is mounted on first lever arm  120  where it engages second lever arm  121  in the position represented in FIG.  4 . FIG. 4 shows lever  113  in its engagement position, with lever arms  120  and  121  pivoted in first direction  30 , wherein a push  37  is being exerted on connecting rod  112 . As first lever arm  120  pivots in second direction  31 , carrier  155  will move second lever arm  121 , which accordingly shifts out of its engagement position and into an unillustrated release position. 
     Emergency unlatching mechanism  140  permits the door  2  to be opened by muscle power. The mechanism essentially comprises, first, a mechanism  141  that unlocks the locking lever along with its second lever arm  121  and, second, a mechanism  134  that separates a coupling between carriage  106  and means  5  of applying tension. 
     The unlocking mechanism includes unlocking-lever component  143 , which can by way of contact area  154  pivot third lever arm  152  and hence second lever arm  121  in second direction  31  and accordingly into its release position. Separating mechanism  134  also includes unlocking-lever component  143 , which can, before locking mechanism  111  has been unlocked by releasing second lever arm  121 , extract the spring-loaded engagement pin out of its engagement with cogged-band coupling  36 . 
     As will be most evident from FIG. 5, unlocking-lever component  143  pivots around a third axis  145  perpendicular to direction traveled by carriage  106 . The free end of the first lever arm  146  of unlocking-lever component  143  is engaged by one component of a traction means in the form of a cable bell  147  that can be actuated from inside the premisses being closed off. Another lever arm  148  is engaged by another component of the traction means in the form of a Bowden cord  142  that can be actuated from outside the premisses. Applying tension to Bowden cord  142  or cable bell  147  will pivot unlocking-lever component  143  around third axis  145 . As unlocking-lever component  143  pivots, a pin  149  that travels back and forth in a curved slot will extract the engagement pin out of engagement with the cogged-band coupling, whereupon, once a detachment position has been attained, carriage  106  will be uncoupled from cogged belt  5 . As unlocking-lever component  143  pivots out of the normal position represented in FIG. 5, a contact vicinity  156  on the second lever arm  148  of unlocking-lever component  143  will also engage the contact area  154  located in that normal position at some distance from contact vicinity  156 , unlocking second lever arm  121 . How this second embodiment of locking mechanism  111 , illustrated in FIGS. 4 and 5, operates will now be specified. 
     FIG. 4 shows the state of the locking mechanism while door  2  is closed. Carriage  106  is resting against limiting stop  9 , lever arms  120  and  121  have pivoted in first direction  30 , and lever  113  is in its engagement position. When an exterior force  37  is applied to panel  1 , carriage  106  will be shifted in the opening direction until the engagement component  129  constituted by second lever arm  121  with its hook  125  and engagement section  127  engages the limiting edge  28  of stop  9 . Further motion of carriage  106  and hence further opening of panel  1  subject to exterior force will be impossible. 
     When door-drive mechanism  3  is actuated, cogged belt  5  will drag carriage  106  in opening direction  170 . The resulting traction on connecting rod  112  will pivot first lever arm  120  in second direction  31 . Carrier  155  will engage, and lever arms  120  and  121  will pivot in second direction  31 , shifting the mechanism out of the engagement position represented in FIG.  4  and into the release position. With locking mechanism  111  unlocked, accordingly, carriage  106  can now travel in opening direction  170  until door  2  is all the way open. As the door closes, carriage  106  will move in the direction opposite opening direction  170 . First lever arm  120  will pivot in first direction  30  into the position represented in FIG. 4, coming to rest against interior wall surface  132 . Panel  1  can now be closed by way of carriage  106 . Second lever arm  121  will, subject to the force exerted by compression spring  144 , pivot into the engagement position represented in FIG.  4 . Once on-ramp shoulder  126  reaches limiting edge  28 , second lever arm  121  will be forced to pivot in second direction  31  against the force exerted by spring  144  but without being accompanied by connecting rod  112  until engagement section  127  travels beyond limiting edge  28 . Carriage  106  will continue moving until it comes to rest against limiting stop  9 . 
     When emergency unbolting is necessary, a tug on cable bell  147  from inside or on Bowden cord  142  from outside will actuate them manually. Bowden cord  142  terminates in a space not accessible to unauthorized persons outside the premisses being closed off. This is of particular importance when access to the premisses is only by way of the doorway. 
     The tug causes unlocking-lever component  143  to pivot, detaching carriage  106  from cogged-band coupling  36 . Contact vicinity  156  engages the contact area  154  of the bent-down free end  153  of third lever arm  152 , forcing second lever arm  121  out of its engagement position. Since lever arms  120  and  121  are separated, they will both be uncoupled, and engagement component  129  can be shifted out of its engagement position without first lever arm  120  having to move. Door  2  can now be lifted by muscle power. 
     Due to the uncoupling of lever arms  120  and  121 , it is unnecessary to adjust locking mechanism  111  to various situations as precisely as in the prior art. The second embodiment of locking mechanism  111  is particularly outstanding in that the lever comprising second lever arm  121  and third lever arm  152  is maintained in its engagement position or in its bolting position by a compression spring for example. This lever, which can be considered a locking hook, pivots around first axis  119 . A mechanism, in the form of cheeks  162  and  163  in this case, that attaches panel  1  to the closing rod, or connecting rod  112 , pivots around first axis  119  to a limited extent. Locking-hook lever  121  and  152  and cheeks  162  and  163  or a similar pivoting mechanism for attaching connecting rod  112  can be pivoted mutually to a certain extent around first axis  119 . This pivoting motion is limited by carrier  155 , a carrier pin, that forces locking hook lever  121  and  152  out of the bolting position or engagement position when connecting rod  112  and carriage  106  apply traction to each other and as cheeks  162  and  163  pivot. 
     A lever system  134 ,  143 , and  140  is available for emergency unbolting. This system can be employed to force locking-hook lever  121  and  152  out of its engagement position against the force of spring  144 , subsequent to which door  2  can be lifted by muscle power. 
     The illustrated embodiment of locking mechanism  111 , which prevents break-ins and keeps the door closed, includes locking-hook lever  121  and  152  and two cheeks  162  and  163  connected together by a pin  155  that constitutes the carrier. 
     Locking-hook lever  121  and  152  is maintained in its closing position by compression spring  144 . This lever pivots along with cheeks  162  and  163  and carrier pin  155  around first axis  119 . First axis  119  is accommodated and prevented from axial displacement by pin  151 . FIG. 4 represents the door-closing state. 
     As they travel during the door-closing state, the cheek surfaces extending along the carriage&#39;s opening and closing directions rest against matching carriage-guidance surfaces- interior wall surfaces  132  and  133 . Locking-hook lever  121  and  152  is in its closing or engagement position. Just prior to the door-closing state, the locking nose or hook  125  in locking-hook lever  121  and  152  will arrive at the elevated edge  28  of stationary limiting stop  9  and will accordingly rise. Once hook  125  has traveled beyond this edge, compression spring  144  will force it back into its closing or engagement position. 
     As they travel in door-opening direction  170 , cheeks  162  and  163  will pivot around first axis  119 , carrier pin  155  carrying locking-hook lever  121  and  152  along with it. Locking-hook lever  121  and  152  will accordingly pivot around first axis  119 , and hook  125  will rise. The door-opening motion will be unimpeded. Emergency unbolting, in the event of malfunction on the part of drive mechanism  3  for instance, can be initiated from outside by way of Bowden cord  142  or from inside by way of cable bell  147  or of a similar traction cord. Both cable bell  147  and Bowden cord  142  engage unlocking-lever component  143 , which pivots around the essentially vertical axis  145 . When tension is applied to either of these traction means, unlocking-lever component  143  will pivot around axis  145 . When unlocking-lever component  143  is actuated, its contact vicinity  156  will apply force to the oppositely directed contact area  154  of locking-hook lever  121  and  152 . The locking-hook lever will thereupon be shifted out of its closing or engagement position. Another mechanism could also be employed to maintain the unlocking-lever component unlocked following emergency unbolting, although this embodiment is not illustrated. Door  2  can be opened by muscle power once locking-hook lever  121  and  152  has been unlocked. 
     FIGS. 6 through 8 illustrate a third embodiment of a door drive mechanism and locking mechanism  211 . Identical parts will be provided with the same reference numbers. 
     The locking mechanism  211  illustrated in FIGS. 6 through 8 includes a coupling mechanism  210  for coupling panel  1  to a carriage  206  and a connecting rod  12  that is coupled to the carriage by way of a lever  213  that pivots to a limited extent around a first axis  219 . Lever  213  has three arms  220 ,  221 , and  252 . Connecting rod  12  pivots around another axis  222  at the free end of first arm  220 . The free end of second arm  221  is provided with an engagement component  229  with a nose  225 . Third arm  252  is similar to third arm  252  [sic] and is provided with a bent down end  253  with an edge that engages an unlocking-lever component  243 . 
     As will be evident from FIG. 7, lever  213  comprises two flat components united by rivets  270 . The areas of the components that constitute first arm  220  are offset, creating two cheeks  262  and  263  that enclose the lever&#39;s point of attachment to connecting rod  12 . 
     Nose  225  is provided with an engagement section  227 . Unlike engagement sections  27  and  127 , however, section  227  is bent down obliquely rather than acutely. Nose  225  is also provided with an on-ramp shoulder  226 . 
     Emergency unlatching mechanism  240  comprises a component  241  for unlocking a locking mechanism  211  and a mechanism  134  for separating carriage  206  from cogged belt  5 . Separating mechanism  234  and emergency unlatching mechanism  240  are essentially constituted by an unlocking-lever component  243  similar to unlocking-lever component  143 . 
     Unlocking-lever component  243  can be pivoted around a third axis  245  by way of traction means  235  that comprises a cable bell  247 . 
     Comparing FIGS. 5 and 7 will reveal the differences between the emergency unlatching mechanism  240  or, more specifically, unlocking mechanism  241  employed in the second embodiment and the emergency unlatching mechanism  140  and unlocking mechanism  141  employed in the third embodiment. It will be evident that the curved slot that pin  149  or  249  travels in as it uncouples carriage  106  or carriage  206  from cogged-band coupling  36  is longer in the third embodiment and that the distance between the contact vicinity  256  on unlocking-lever component  243  and the contact area  254  on the third lever arm is longer than the distance between the contact vicinity  156  and the contact area  154  in the second embodiment. 
     Separating mechanism  234  will now be specified with reference to FIG. 8, which shows a coupling-or-engagement pin  275  similar to the ones discussed in relation to the two aforesaid embodiments and employed to couple carriage  206  to cogged-band coupling  36 . The pin  249  in unlocking-lever component  243  extends through pin  275 . 
     How the third embodiment of the locking mechanism operates will now be specified. 
     FIG. 6 represents locking mechanism  211  in the door-closing state. When drive mechanism  3  is actuated, cogged belt  5  will move carriage  206  in the opening direction  170 . The resulting traction on connecting rod  12  will pivot lever  213  around first axis  219  in second direction  31 . The pivoting motion is limited by a stop in the form of an inner wall surface  233  of carriage housing  250 . As carriage  206  continues to move in the opening direction  170 , the door will open. With lever  213  resting against the inner wall surface  233  of housing  250 , second arm  221  will be unlocked, and engagement component  229  will be in its release position. The door can be opened unimpeded. 
     If the motion of drive mechanism  3  is reversed, lever  213  will, due to the pushing force applied to connecting rod  12 , pivot in first direction  30  into the position illustrated in FIG. 6, with first arm  220  resting against a first stop in the form of one interior wall surface  232  of carriage housing  250 . The door will then close due to the accordingly established interlocking connection between connecting rod  12  and carrier  206 . Once on-ramp shoulder  226  has arrived at the stop&#39;s limiting edge  28 , lever  213  will pivot until nose  225  can slip over edge  28  and into the engagement position represented in FIG.  8 . The closing motion will continue until carriage  206  arrives at limiting stop  9 . The door is closed. If force is applied to the door from outside, it will act as a push  37  against connecting rod  12 . Carriage  206  will accordingly also be pushed in opening direction  170  until engagement section  227  arrives at limiting edge  28 . Even though engagement section  227  is not pointed, limiting edge  28  cannot be conquered because push  37  will be forcing lever  213  into its engagement position. The oblique slope toward limiting edge  28 , however, has the advantage that nose  225  cannot hook over edge  28  even subject to powerful closure forces. The obliquity also decreases wear. 
     Although the arms  220  and  221  in the third embodiment are in one piece in contrast to the arms in the second embodiment, emergency unbolting will still be simple and reliable. This is ensured in the third embodiment in that carriage  206  is initially uncoupled from cogged belt  5  and in that, due to the longer distance between contact vicinity  256  and contact area  254 , lever  213  cannot be forced out of engagement until uncoupling is complete. Since carriage  206  has been entirely uncoupled by this time, lever  213  having already pivoted in second direction  31 , allowing emergency unbolting, the displacement between carriage  206  and connecting rod  12  needed for the pivoting motion can be initiated without further measures by the travel of carriage  206  along rail  7 . 
     Locking mechanism  211  can accordingly be very easily unlocked by way of emergency unlatching mechanism  240 , and the door can be opened by muscle power. 
     The locking mechanism. 211  in the third embodiment is accordingly provided with a locking hook in the form of lever  213  that pivots around first axis  219 . Axis is accommodated in the carriage  206  attached to door panel  1  and prevented from axial displacement by an unillustrated cam. FIG. 6 shows the mechanism in the door-closed state. 
     As the locking hook constituted by lever  213  travels in the door-closing direction, the surfaces of its cheeks  262  and  263  that face along opening direction  170  will come to rest against a surface constituted by the interior wall surface  232  of carriage  206 . The locking hook, lever  213 , is now in its closing or engagement position. Just before arriving at the door-closed position, the nose  225  of the locking hook or lever  213  will encounter the elevated limiting edge  28  of stop  9  and will accordingly be lifted. Once nose  225  has traveled past limiting edge  28 , the closing force exerted by door  2  will return the edge to its engagement position. 
     As it travels in the door-opening direction, the lever  213  that constitutes the locking hook will pivot around first axis  219 , lifting nose  225 . The cheeks  262  and  263  of lever  213  will simultaneously come to rest against inner wall surface  233 . 
     Emergency unbolting is accomplished from outside by means of Bowden cord  242  or from inside by means of cable bell  247 . Unlocking-lever component  243  can pivot around third axis  245 . Actuation of unlocking-lever component  243  will initially cause the pin  249  to shift the spring-loaded slide or the coupling-or-engagement pin  275  in direction  280 , disengaging carriage  206  from the cogged-band coupling  36  with cogged belt  5 . Further actuation of unlocking-lever component  243  will close the distance between the contact vicinity  256  of unlocking-lever component  243  and the contact area  254  of lever  213 , and contact vicinity  256  will apply force to contact area  254 . The locking hook constituted by lever  213  will pivot in the second direction around first axis  219 , and nose  225  will be lifted. The system is now unlocked and the door can be opened by muscle power. 
     The third embodiment is particularly outstanding in that it operates in two phases, with unbolting, i.e. the separation of the carriage from the motorized transmission, independent of unlocking, i.e. separation of the carriage from the stationary limiting stop. 
     The nose  225  on the lever  213  that constitutes the locking hook is not pointed. This prevents carriage  206  from hooking up as it travels in the door-opening direction in doors with powerful closing forces. 
     The particular characteristics of the individual embodiments specified herein can, unless obviously inapplicable, be combined in various ways to create additional embodiments.

Summary:
The invention relates to a locking device and a door-drive device comprising a locking device for a door which can be secured against opening by unauthorized persons using force from the exterior. The locking device has a lever element consisting of two lever arms which pivot about a first pivoting shaft. A connecting element is hinged to the first lever arm for connecting the door and the second lever arm which has an engaging device.