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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a concealed hinge mechanism mounted on a door frame and a door and more particularly to the concealed hinge mechanism concealed from outside view when the door is closed. 
         [0003]    2. Description of Related Art 
         [0004]    Conventional hinges are known in the art providing rotational opening to a door relative to the door frame. A typical hinge consists of two plates in which the first plate is mounted to the vertical edge of the door and the second one mounted to the vertical edge of the door frame. The plates ending with a vertical knuckle are connected with a hinge pin inserted into the knuckles. The benefits of that simple mechanism are easy manufacturing, easy installation and low cost. But the hinge elements—knuckles and the hinge pin—are exposed and accessible from the outside when the hinge is installed in a way to provide outward opening which causes security and aesthetic problems. Exposed elements can be tampered even-though the door is locked. 
         [0005]    To eliminate those issues the conventional hinge can be installed internally. But this installation method provides inward opening only. 
         [0006]    Also, concealed hinges are known in the art to eliminate exposing the hinge parts to provide security and aesthetic benefits. The problem with the existing concealed hinges is that some parts of the mechanism have to be placed into the cavities of the door and/or door frame. The alteration of the door and/or door frame requires additional tools and skill set. Fixing or replacing the incorrectly altered material can be time consuming and costly. Also the existing concealed hinge mechanisms comprise many parts require complex and costly manufacturing techniques. 
       SUMMARY OF THE INVENTION 
       [0007]    The object of the present invention is to provide a concealed hinge mechanism that can be installed similar to a conventional hinge which requires no cavities or alterations on the door and/or door frame. That brings the benefits of easy manufacturing, easy installation and low cost. 
         [0008]    A further object of the present invention is to conceal the hinge elements from outside view, preventing tampering when the door is closed. 
         [0009]    A further object of the present invention is to eliminate the unaesthetic look of the hinges those are visible from outside. 
         [0010]    A further object of the present invention is to allow the door to be opened up to 225 degree angle relative to door frame. 
         [0011]    A further object of the present invention is to allow the door to be placed inside the door frame or outside of the door frame. 
         [0012]    To achieve the above and other objects the present invention introduces a mechanism that provides guided swinging movement to allow the door to rotate about the vertical axis and at the same time move the door away from the door frame slightly to create a clear path for the rotation. 
         [0013]    According to present invention the concealed hinge mechanism consists of two fixed plates, each having a vertical knuckle at one end, an upper and a lower track horizontally extending end to end. The plates are fastened on the door and door frame to support connecting elements and the weight of the door. 
         [0014]    According to another aspect of the present invention, the concealed hinge mechanism further comprises two connecting elements to connect fixed plates and provide the said guided swinging movement. The connecting elements designed in L shape with a short plate and a long plate, having a knuckle at the end of the short plate end to be connected to the fixed plate, a hole at the apex to connect connecting elements to each other and laterally extending pins for engaging the upper track and the lower track of the fixed plates. 
         [0015]    According to the present invention, in the closed position the connecting elements are at 45 degree angle relative to the door and door frame; and the door is at 90 degree angle relative to door frame. When a force is applied to open the door the connection elements&#39; apexes moves away from the door and door frame until the angle reaches 90 degree which moves the door away from door frame to create a clear path while rotating. 
         [0016]    Over 90 degree angle the door starts moving towards the door frame on the horizontal axis to complete the opening movement. The mechanism of the present invention is described in greater clarity by the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a perspective view of the concealed hinge mechanism fixed to the door and the door frame in closed position; 
           [0018]      FIG. 2  is a perspective view of the concealed hinge mechanism fixed to the door and the door frame in closed position in accordance; 
           [0019]      FIG. 3  is an exploded perspective view of the concealed hinge mechanism of  FIG. 1  and  FIG. 2 ; 
           [0020]      FIG. 4  is a top view of the concealed hinge mechanism of  FIG. 1  in closed position; 
           [0021]      FIG. 5  is a top view of the concealed hinge mechanism of  FIG. 1  in 45 degree opened position; 
           [0022]      FIG. 6  is a top view of the concealed hinge mechanism of  FIG. 1  in 90 degree opened position; 
           [0023]      FIG. 7  is a top view of the concealed hinge mechanism of  FIG. 1  in 110 degree opened position; 
           [0024]      FIG. 8  is a top view of the concealed hinge mechanism of  FIG. 2  in closed position; 
           [0025]      FIG. 9  is a top view of the concealed hinge mechanism of  FIG. 2  in 45 degree opened position; 
           [0026]      FIG. 10  is a top view of the concealed hinge mechanism of  FIG. 2  in 90 degree opened position; 
           [0027]      FIG. 11  is a top view of the concealed hinge mechanism of  FIG. 2  in 110 degree opened position; 
           [0028]      FIG. 12  is a perspective view of the fixed plate, isolated from the surrounding elements; 
           [0029]      FIG. 13  is a perspective view of the first L-shaped connecting element, isolated from the surrounding elements; 
           [0030]      FIG. 14  is a perspective view of the second L-shaped connecting element, isolated from the surrounding elements; 
           [0031]      FIG. 15  is an assembled view of the first L-shaped connecting element and the second fixed plate connected by the first hinge pin, isolated from the surrounding elements; 
           [0032]      FIG. 16  is an assembled view of the second L-shaped connecting element and the first fixed plate connected by the first hinge pin, isolated from the surrounding elements; 
           [0033]      FIG. 17  is a perspective view of the laterally extending pins of the first connecting element, engaging the upper track and the lower track of the first fixed plate; 
           [0034]      FIG. 18  is a perspective view of the laterally extending pins of the second connecting element, engaging the upper track and the lower track of the second fixed plate; and 
           [0035]      FIG. 19  is assembled view of the first connecting element and second connecting element, connected the interlocking knuckles at the apexes by the second pin. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    In accordance with the principles of the present invention, referring to  FIG. 1 , there is depicted the door  12  and the door frame  14  connected by the concealed hinge mechanism  10  in closed position. The door  12  is depicted as placed outside of the door frame  14 . The concealed hinge mechanism  10  comprises the first fixed plate  20  fastened to the door frame  14  and the second fixed plate  20  fastened to the door  12 . The first fixed plate  20  and the second fixed plate  20  are connected to each other with two connecting elements: the first L-shaped connecting element  50  and the second L-shaped connecting element  51 . 
         [0037]    Referring to  FIG. 2 , there is depicted the door  12  placed inside of the door frame  14  in closed position and connected by the concealed hinge mechanism  10 . 
         [0038]    Referring to  FIG. 3 , the concealed hinge mechanism  10  depicted in an exploded perspective, further showing the details of the present invention. As shown in  FIG. 3 , there may be fasteners  34 , such as screws, which go through the apertures  32 , to affix the fixed plates  20  to the door  12  or door frame  14 . The concealed hinge mechanism  10  allows the door  12  to be placed outside of the door frame  14  and opened up to a 225 degree angle DA relative to door frame  14 , starting at a 90 degree angle DA closed position. Several angles of the rotational and outward movement depicted in figures  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 7  as examples. 
         [0039]    Referring to  FIG. 4 , the door  12  and the door frame  14  depicted in 90 degree angle DA closed position connected by the concealed hinge mechanism  10 . The short plates  54  of the connecting elements  50  and  51  are at 45 degree angle relative to the door  12  and the door frame  14 . 
         [0040]    Referring to  FIG. 5 , the door  12  is shown in open position, at the angle DA of 135 degree relative to the door frame. Now the shorter second plate  54  of the second L-shaped connecting element  51  is at 90 degree angle relative to the door frame  14 , moving the apex  56  of the second L-shaped connecting element  51  away from the door frame  14  and moving the door  12  away from the door frame  14  on the z axis. The shorter second plate  54  of the first L-shaped connecting element  50  is at 90 degree angle with the door  12 , moving the apex  56  of the first L-shaped connecting  50  element away from the door  12  and moving the door  12  outward on the x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid inward, forcing the door  12  to rotate outward. 
         [0041]    Referring to  FIG. 6 , the door  12  is shown in open position, at the angle DA of 180 degree relative to the door frame. The shorter second plate  54  of the second L-shaped connecting element  51  is at 135 degree angle relative to the door frame  14 , pulling the apex  56  of the second L-shaped connecting element  51  toward the door frame  14  and pulling the door  12  toward the door frame  14  on z axis. The shorter second plate  54 , of the first L-shaped connecting element  50  is at 135 degree angle with the door  12 , pulling the apex  56  of the first L-shaped connecting  50  element toward the door  12  and moving the door  12  further outward on the x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid further inward, forcing the door  12  to rotate further outward. 
         [0042]    Referring to  FIG. 7 , the door  12  is shown in open position, at the angle DA of 200 degree relative to the door frame. The shorter second plate  54 , of the second L-shaped connecting element  51  is at 155 degree angle relative to the door frame  14 , pulling the apex  56  of the second L-shaped connecting element  51  toward the door frame  14  and moving the door  12  away from the door frame  14  on z axis. The shorter second plate  54 , of the first L-shaped connecting element  50  is at 155 degree angle with the door  12 , pulling the apex  56  of the first L-shaped connecting  50  elements toward the door  12  and moving the door  12  inward on x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid further inward, forcing the door  12  to rotate further outward. 
         [0043]    The concealed hinge mechanism  10  allows the door  12  to be placed inside of the door frame  14  and opened up to 225 degree angle relative to door frame  14 , starting at 90 degree angle closed position. Several angles of the rotational and outward movement depicted in figures  FIG. 8 ,  FIG. 9 ,  FIG. 10  and  FIG. 11  as examples. 
         [0044]    Referring to  FIG. 8 , the door  12  and the door frame  14  depicted in 90 degree angle DA closed position connected by the concealed hinge mechanism  10 . The short plates  54  of the connecting elements  50  and  51  are at 45 degree angle relative to the door  12  and the door frame  14 . 
         [0045]    Referring to  FIG. 9 , the door  12  is shown in open position, at the angle DA of 135 degree relative to the door frame. Now the shorter second plate  54  of the second L-shaped connecting element  51  is at 90 degree angle relative to the door frame  14 , moving the apex  56  of the second L-shaped connecting element  51  away from the door frame  14  and moving the door  12  away from the door frame  14  on the z axis. The shorter second plate  54  of the first L-shaped connecting element  50  is at 90 degree angle with the door  12 , moving the apex  56  of the first L-shaped connecting  50  element away from the door  12  and moving the door  12  outward on the x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid inward, forcing the door  12  to rotate outward. 
         [0046]    Referring to  FIG. 10 , the door  12  is shown in open position, at the angle DA of 180 degree relative to the door frame. The shorter second plate  54  of the second L-shaped connecting element  51  is at 135 degree angle relative to the door frame  14 , pulling the apex  56  of the second L-shaped connecting element  51  toward the door frame  14  and pulling the door  12  toward the door frame  14  on the z axis. The shorter second plate  54 , of the first L-shaped connecting element  50  is at 135 degree angle with the door  12 , pulling the apex  56  of the first L-shaped connecting  50  element toward the door  12  and moving the door  12  further outward on the x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid further inward, forcing the door  12  to rotate further outward. 
         [0047]    Referring to  FIG. 11 , the door  12  is shown in open position, at the angle DA of 200 degree relative to the door frame. The shorter second plate  54 , of the second L-shaped connecting element  51  is at 155 degree angle relative to the door frame  14 , pulling the apex  56  of the second L-shaped connecting element  51  toward the door frame  14  and moving the door  12  away from the door frame  14  on the z axis. The shorter second plate  54 , of the first L-shaped connecting element  50  is at 155 degree angle with the door  12 , pulling the apex  56  of the first L-shaped connecting  50  elements toward the door  12  and moving the door  12  inward on the x axis. The longer first plate  52  of the L-shaped connecting elements  50  and  51  slid further inward, forcing the door  12  to rotate further outward. 
         [0048]    Referring to  FIG. 12 , the fixed plates  20  are made of a sturdy metal, having apertures  32  to be fastened on the door  12  and the door frame  14 . The fixed plates  20  have vertical first knuckle  30  at one end. The upper edge  22  and the lower edge  24  are folded inwardly to form the upper track  26  and the lower track  28  extending horizontally end to end and opposing each other. According to the present invention the two fixed plates  20  are identically constructed. 
         [0049]    Referring now to  FIG. 13 , the first connecting element  50  constructed in L shape and made of a sturdy metal, consists of a longer first plate  52  and a shorter second plate  54  connected at the apex  56  at 110 degree angle A. The first end  60  of the first plate  52  having laterally extending pins  70  and a notch  72  shaped to pass over the apertures  32  without interference. The second end  62  of the second plate  54  having a second knuckle  64 . The first connecting element  50  has the interlocking knuckle  58  at the apex  56  shaped to engage one or more interlocking knuckles  58  at the apex of the second connecting element  51 . 
         [0050]    Referring to  FIG. 14 , the second connecting element  51  constructed in L shape and made of a sturdy metal, consists of a longer first plate  52  and a shorter second plate  54  connected at the apex  56  at 110 degree angle A. The first end  60  of the first plate  52  having laterally extending pins  70  and a notch  72  shaped to pass over the apertures  32  without interference. The second end  62  of the second plate  54  having a second knuckle  64 . The second connecting element  50  has the interlocking knuckle  58  at the apex  56  shaped to engage one or more interlocking knuckles  58  at the apex of the first connecting element  50   
         [0051]    Referring to  FIG. 15 , the first L-shaped connecting element  50  is shown pivotally connected to the fixed plate  20  by inserting the first pin  36  in the knuckle  64  of the first connecting element  50  and the first knuckle  30  of the fixed plate  20 . 
         [0052]    Referring to  FIG. 16 , the second L-shaped connecting element  51  is shown pivotally connected to the fixed plate  20  by inserting the first pin  36  in the knuckle  64  of the second connecting element  51  and the first knuckle  30  of the fixed plate  20 . 
         [0053]    Referring to  FIG. 17 , to provide horizontal sliding back and forth, the laterally extending pins  70  of the first L-shaped connecting element  50  are placed in the upper track  26  and lower track  28  of the fixed plate  20 . The notch  72  passes over the apertures  32  without interference. 
         [0054]    Referring to  FIG. 18 , to provide horizontal sliding back and forth, the laterally extending pins  70  of the second L-shaped connecting element  51  are placed in the upper track  26  and lower track  28  of the fixed plate  20 . The notch  72  passes over the apertures  32  without interference. 
         [0055]    Referring to  FIG. 19 , the first L-shaped connecting element  50  is operably connected to the second L-shaped connecting element  51  at their apexes  56  by the second hinge pin  68 . The second pin  68  holds the interlocking knuckles  58  together and allow the apexes  56  to rotate relative to each other. This forms a pivotal connecting hinge connecting the apexes  56  of the pair of connecting elements  50 ,  51 . 
         [0056]    As defined in the present application, the term ‘about’ is defined to have an uncertainty of +/−5%, according to expected variations in manufacturing and constructions. For example, “about 100 degrees” indicates a range from 95-105 degrees.

Summary:
A concealed hinge mechanism for connecting a door and a door frame has two fixed plates mounted on the door and the door frame, and two L-shaped connecting elements to connect the fixed plates while providing a rotational and outward movement for opening.