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CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Patent Cooperation Treaty National Stage of International Application No. PCT/DE2014/000056, filed Feb. 12, 2014, which takes priority from German Patent Application No. DE 20 2013 001 433.4, filed Feb. 14, 2013. The contents of both of Applications PCT/DE2014/000056 and 20 2013 001 433.4 are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Existing electromagnetic door openers are, for example, known from German Document DE 10 2004 056 567 A1. The remotely operable electric door opener described also comprises locking members, which during a first stage are form-locked with each other. In a second stage however, the resistance to open the door by force is produced by a rather weak formlock between the locking members, i.e. by a leaf spring hook which is in engagement with the door opener strike bolt. The second stage is thus not very effective as a safeguard against twisting. 
       SUMMARY 
       [0003]    The present invention relates to an electromagnetic door opener with a housing for fitting into a doorframe, with a hinged flap rotatable between an open position and a closed position, and having a safety device to resist forcibly twisting the flap from the closed position into the open position, the safety device having a primary safety stage and a secondary safety stage. 
         [0004]    It is therefore an objective of the invention to develop an electromagnetic door opener in such a way that the resistance against forcibly opening the door is equally strong both in the first stage and in the second stage. 
         [0005]    This requirement is met in that the locking members, in a closed position, form a formlock and are supported against the floor of the housing. 
         [0006]    With the aid of the electromagnetic door opener the resistance against opening the door by force is achieved by the formlock both in the first stage and in the second stage, and also by supporting the form-locked locking members against the floor of the housing. 
         [0007]    An advantage of the invention is that it allows the door opener to be held in the closed position against a force of 10,000 Newtons acting upon the door opener strike bolt. 
         [0008]    A further advantage of the present invention is that the locking members of the first stage comprise a first lever and a second lever and the housing floor and in that the formlock is produced by an oblique surface between the two. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will now be described in detail with reference to the drawings, in which: 
           [0010]      FIG. 1  shows a schematic side view of a door lock with an electromagnetic door opener attached to a stale plate in the closed position; 
           [0011]      FIG. 2  shows a schematic side view of the electromagnetic door opener in a closed position; 
           [0012]      FIG. 3  shows a schematically drawn detail from  FIG. 2 ; 
           [0013]      FIG. 4  shows a schematic view in cross-section of the electromagnetic door opener according to  FIG. 2 ; 
           [0014]      FIG. 5  shows a schematic side view of the electromagnetic door opener of  FIG. 2  in an open position; 
           [0015]      FIG. 6  shows a schematically drawn detail from  FIG. 5 ; and 
           [0016]      FIG. 7  shows a schematic view in cross-section of the electromagnetic door opener according to  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  is a schematic side view of a door lock  1  that cooperates with an electromagnetic door opener  100  attached to a strike plate  3 . In the present embodiment the door lock  1  is a box lock adapted to being actuated by an electromagnetic door opener  100 . Cooperation with the electromagnetic door opener  100  involves a door opener strike bolt  5  and locking member  7  connected with the door opener strike bolt  5 . The door lock  1  comprises a housing  9 , with which the door lock is attached to a fore-end track  11 . In addition the door lock  1  may further comprise a lock bolt  13 , which can engage in a bolt opening  15  of the strike plate  3 . 
         [0018]    The electromagnetic door opener  100  is attached to the strike plate  3  such that, when in a closed position, it can receive the door opener strike bolt  5  and hold it in the closed position, and when it is in an open position, releases the door opener strike bolt  5  so that it can move back, pre-tensioned, into the housing  9  of the door lock  1 . 
         [0019]    The electromagnetic door opener  100  comprises a door opener housing  101 , which in the sectional view depicted in  FIG. 1  is shaped into an approximate U-shape. 
         [0020]    In  FIG. 2  the electromagnetic door opener  100  is schematically shown in greater detail. The U-shaped door opener housing  101  has a lifting magnet  103  arranged in it, with which a plunger core pin  105  is connected in a back and forth moving manner. The lifting magnet  103  is supported against the housing floor  107  of the door opener housing  101 . In  FIG. 2  a situation is shown, in which the door opener strike bolt  5  and the locking member  7  are in a closed position. 
         [0021]    In the closed position the plunger core pin  105  is in a retracted position. Several levers, i.e. lever  111 , lever  113 , lever  115  and lever  117  are arranged between the plunger core pin  105  and a hinged flap  109 , in conjunction with a stop  110 . 
         [0022]    The kinematic chain is shown in detail in  FIG. 3 . The plunger core pin  105  with its free end  119  abuts against a straight side  121  of the lever  115 . Lever  115  comprises a pivot axis  123 . The lever  117  comprises a pivot axis  125  and a stop pin  127 , which is aligned parallel to the pivot axis  125 . The stop pin  127  runs on a circular-arc-shaped outer edge  129  of the lever  115  so that a movement of the lever  115  about the pivot axis  125  is in counterclockwise direction. This results in an unlocking position. 
         [0023]    The lever  117 , in the view shown in  FIG. 2  and  FIG. 3 , is configured into approximately an L-shape. A long arm extends between the pivot axis  125  and the stop pin  105  and a shorter arm extends approximately perpendicularly to the longer arm between the pivot axis  125  and a free end configured as a blocking element  131 . The blocking element  131  blocks the lever  113  in the closed position. The lever  113  comprises a pivot axis  133 . The pivot axis  133 , the pivot axis  125 , and the pivot axis  123  extend parallel to each other and perpendicularly to the planes shown in  FIG. 2  or  FIG. 3 , 
         [0024]    Pivoting the lever  117  results in the blocking element  131  releasing the lever  113  to allow counterclockwise rotation about the pivot axis  133 . 
         [0025]    When applying a force to open the door, the lever  111 , as the block is released, is rotated downwards in a clockwise direction (see  FIG. 2 ), causing the lever  113  to deflect and twist in counterclockwise direction. 
         [0026]    As a force is applied to open the door, the hinged flap  109 , in conjunction with the stop  110 , rotates in a counterclockwise direction about the pivot axis  137 . 
         [0027]    The aforementioned kinematic chain is a means for providing the electromagnetic door opener  100  with a safety device, which provides resistance twisting the door opener strike bolt with force from the closed position into the open position and represents both a primary safety stage and a secondary safety stage. The primary safety stage comprises the lever  111 , the lever  113 , and the housing floor  107 . In the primary safety stage the lever  111  is supported in a formlock against the housing floor  10  via the lever  113 . Contact between the lever  111  and the lever  113  is via a first lever gliding surface  139  on the lever  111  and a second lever gliding surface  141  on the lever  113 , preferably at an angle of 25° to the housing floor  107 . Due to a movement of the lever  113 , a gliding contact is obtained at the first lever gliding surface  139  and at the second lever gliding surface  141 , which leads to movement of the lever  111 . Supporting the lever  111  via the two gliding surfaces  139  and  141  and the lever  113  against the housing floor  107  creates a stable lock of the electromagnetic door opener  100  in the closed position. 
         [0028]    Should an external force be applied that is sufficient to overcome the primary safety stage, the depicted arrangement according to the invention provides a secondary safety stage. This secondary safety stage involves the lever  115 , which is also supported in a formlock against the housing floor  107 . Due to the lever  115  being directly supported against the housing floor  107 , following the primary safety stage a second safety stage is created, which provides high resistance. The primary safety stage and the secondary safety stage in the depicted embodiment of the invention show a stability against twisting the hinged flap  109  and releasing the door opener strike bolt, which is in the region of approx. 10,000 N. 
         [0029]    The pivot axis  135  of lever  111  extends perpendicularly to the pivot axes  123 ,  125  and  133  as well as parallel to the pivot axis  137  of the hinged flap  109 . The hinged flap  109  is best understood with reference to  FIG. 4 . A recess  145  is formed in a flap part  143  on the inside, which extends beyond the strike plate  3 . The recess  145  comprises an undercut  147  on the side of the lock. In the closed position shown in  FIG. 4  the door opener strike bolt  5  is shown as having advanced into the electrical door opener and engaging the recess  145  with the locking member  7 . To this end the locking member  7  comprises a locking tab  7 . 1 , which comprises a stop surface  7 . 2  extending parallel to the undercut  147 . 
         [0030]      FIG. 5  shows the electromagnetic door opener  100  depicted in  FIG. 2  in an open position. The components shown in  FIG. 5  of the electromagnetic door opener  100  are identical to those in  FIG. 2 , though the components are depicted in  FIG. 5  in changed relative positions to the extent where the door opener strike bolt  5 /the locking member  7  is released from the engagement in the hinged flap  109  in conjunction with the stop  110 , and, due to being pre-tensioned in opening direction, is pulled out of the strike plate and into the door lock  1 . 
         [0031]    The changed alignment of the above mentioned components in relation to each other is triggered by the plunger core pin  105 . The resulting rotary movement of the components within a kinematic chain is described above.  FIG. 6  shows in detail, how the stop pin  127 , due to the rotary movement of the lever  115 , has migrated along the circular-arc-shaped outer edge  129  thereof. Due to the pivotal movement of the lever  117  about the pivot axis  125  the second lever  113  is depicted out of a locking engagement with the blocking element  131 . The blocking element  131  comprises an indentation  131 . 1 , into which a free end  113 . 1  of the second lever  113  engages in a formlock in the closed position. In the opening position the lever  113  swiveled counterclockwise about the pivot axis  133  is actuated by the lever  111 , which is depicted turned in a clockwise direction (see  FIG. 7 ).  FIG. 7  shows, how the hinged flap  109 , compared to  FIG. 4 , has twisted counterclockwise about the pivot axis  137  of the flap. The locking tab  7 . 1  is shown having released itself out of the recess  145  so that the door opener strike bolt  5 , together with the locking member  7 , could retract in the direction of the door lock  1 . 
         [0032]    The described and shown movements of the above-mentioned components, which trigger one another, are only possible due to the individual components being elastically pre-tensioned. Numerous springs are mounted in the electromagnetic door opener  100  and in the door lock  1 . Pre-tensioning is in all cases in the direction of the open position. Actuation of the lever  115  by the plunger core pin  105  therefore permits a sequence of movements, leading to a complete opening of the door lock  1 . 
         [0033]    The construction of this depicted embodiment according to the invention allows the first safety stage to fail without significant adverse effect on the second safety stage such that twisting of the flap  109  and stop  110  is not possible even in the event of such first stage failure. The lever  115  can only be actuated via the plunger core pin  105  which creates the added measure of safety. 
         [0034]    Those skilled in the art will realize that this invention is capable of embodiments different from those shown and described. It will be appreciated that the detail of the structure of the disclosed apparatuses and methodologies can be changed in various ways without departing from the invention itself. Accordingly, the drawings and detailed description of the preferred embodiments are to be regarded as including such equivalents as do not depart from the spirit and scope of the invention.

Summary:
The invention relates to an electromagnetic door opener comprising a housing for installing in a door frame, a pivotable cover which can be rotated between an open position and a closed position, and a security device operating counter to a forced rotation of the cover from the closed position into the open position, which comprises a primary security step and a secondary security step. Said door opener is characterized in that the secondary security step comprises a locking element which is supported in a form fit on the base of the housing of the door opener housing.