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CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2015/055311, filed on Mar. 13, 2015, and claims benefit to European Patent Application No.14160171.6, filed on Mar. 17, 2014. The International Application was published in German on Sep. 24, 2015 as WO 2015/140068 A1 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The invention relates to a sliding door assembly, in particular a lift and slide door assembly, including a fixed frame, a horizontally displaceable door leaf and a drive device for displacing the door leaf which includes a drive motor, arranged on the leaf, having a gear wheel which cooperates with a toothed belt arranged on the frame. 
       BACKGROUND 
       [0003]    A sliding door assembly for a stackable sliding wall is known from EP 0 953 706 B2. With sliding door assemblies or with lift and slide door assemblies which are used as part of the glazing of a building, there is the problem that in particular door leaves having multiple glazing can be very heavy, and may weigh for example 200 kilograms or more. If such a door leaf is to be displaceable not manually, but driven by a motor, the drive motor has to provide a correspondingly high motive force. At the same time, however, for visual reasons the drive motor should only take up as little installation space as possible. 
       SUMMARY 
       [0004]    Proceeding therefrom, it is the object of the present invention to improve a sliding door assembly of the type referred to at the outset such that the drive device is also suitable for heavy door leaves and can be integrated in the door leaf as visually unobtrusively as possible. 
         [0005]    This object is achieved according to the invention in that the toothed belt wraps around the gear wheel over a partial circumference of the gear wheel, and in that at least two teeth of the gear wheel are simultaneously fully engaged with at least two teeth of the toothed belt. 
         [0006]    According to the invention, a motive force of the drive motor is transmitted to a toothed belt by way of a gear wheel, at least two teeth of the gear wheel and at least two teeth of the toothed belt simultaneously being fully engaged with one other. The drive device according to the invention makes it possible to even out the transmission of force from the drive motor to the toothed belt. This evening-out thus involves the possibility of avoiding torque peaks of the drive motor. This allows the use of drive motors which are not designed for a high peak power and which therefore can be of comparatively small and slim construction. In this manner, it is possible to integrate the drive motor in the door leaf in a visually appealing manner, yet in which it is simultaneously able to displace even very heavy door leaves if required. 
         [0007]    It is preferable if the partial circumference is at least 45°, preferably at least 90°, in particular at least 120°. In this manner, not only at least two pairs of teeth, but preferably at least three pairs of teeth, in particular at least four pairs of teeth, can be fully engaged with each other simultaneously if required. 
         [0008]    Preferably at least a first deflecting element is provided which cooperates with a rear side of the toothed belt. Such a deflecting element enlarges the partial circumference over which the toothed belt wraps around the gear wheel. 
         [0009]    It is particularly preferable if a second deflecting element is provided that cooperates with the rear side of the toothed belt. This makes possible further enlargement of the partial circumference with which the toothed belt wraps around the gear wheel. 
         [0010]    When using two deflecting elements, it is preferable, viewed in the running direction of the toothed belt, if a first deflecting element is arranged on the input side of the gear wheel and the second deflecting element on the output side of the gear wheel. 
         [0011]    It is possible for the deflecting element or the deflecting elements to have sliding faces along which the rear side of the toothed belt slides. However, it is preferable for the deflecting element to be formed as a deflecting roll, or for the deflecting elements to be formed as deflecting rolls. This allows particularly low-friction rolling contact between the rear side of the toothed belt and a deflecting face of the deflecting rolls. 
         [0012]    It is preferable if the deflecting rolls and the gear wheel have axes of rotation which are parallel to one other, so that the toothed belt is not twisted, viewed in the running direction of the toothed belt. 
         [0013]    In a preferred embodiment, the axes of rotation of the deflecting rolls and of the gear wheel are arranged within one plane. This makes a particularly compact arrangement of deflecting rolls and gear wheel possible. 
         [0014]    It is possible to use a continuous toothed belt. However, it is preferable if a toothed belt which is open at the end and the ends of which are fixed to the frame is used. This facilitates particularly unobtrusive and space-saving integration of the toothed belt on the fixed frame. 
         [0015]    The integration of the toothed belt is further facilitated if it is arranged on a horizontal frame part, at the top when in the installation position, of the fixed frame. 
         [0016]    A drive motor of particularly small construction can be used if the drive device includes a reduction gear for reducing a drive speed of the drive motor. In this case, this is preferably a planetary gear which is of particularly compact construction, in particular a two- stage planetary gear. Using a two-stage planetary gear has the advantage that the self-locking of the reduction gear is not so great that manual displacement of the door leaf would no longer be possible. 
         [0017]    However, it is also possible to use a direct drive (i.e. without a reduction gear), or an only single-stage reduction gear, in order to further reduce the self-locking of the drive. 
         [0018]    It is further preferable if a drive axis of the drive motor is oriented in the vertical direction. In this manner, when using a toothed belt running in the horizontal direction it is possible to dispense with a deflection gear, for example an angular gear. 
         [0019]    In order to integrate the drive motor in the door leaf, it is proposed that the drive motor be arranged in a vertical profile section of the door leaf, in particular in a vertical profile section remote from a handle side of the door leaf. This has the advantage that when the door leaf is upright, the drive motor can be mounted in a simple manner and can be accessed rapidly if required. 
         [0020]    It is particularly preferable if at least one battery arranged on the leaf is provided to supply power to the drive motor. Such a battery has the advantage that it is, in principle, not necessary to also have suitable, but space-consuming, power supply equipment, for example trailing cables or conductor bars with sliding contacts. 
         [0021]    The at least one battery is preferably likewise arranged in a vertical profile section of the door leaf, in particular in a vertical profile section remote from a handle side of the door leaf. This makes simple mounting of the at least one battery on an upright door leaf possible. In addition, the replacement of a battery which may possibly be necessary after a relatively long period of use is thus possible without problems. 
         [0022]    Finally, it is preferable if a controller for controlling the drive motor is provided which is preferably arranged in a vertical profile section of the door leaf, in particular in a vertical profile section remote from a handle side of the door leaf. Not only does this result in a particularly visually appealing design but also in particularly good accessibility of all the components of the drive device which are arranged on the leaf, in particular in combination with integration of the drive motor and at least one battery in the same vertical profile section of the door leaf. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
           [0024]      FIG. 1  is a schematic view of an embodiment of a sliding door assembly having a drive device configured to displace a door leaf; 
           [0025]      FIG. 2  is an exploded view of part of the drive device according to  FIG. 1 ; 
           [0026]      FIG. 3  is a perspective view of the part of the drive device according to  FIG. 2 ; and 
           [0027]      FIG. 4  is an exploded view of a further embodiment of a part of a drive device. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    An embodiment of a sliding door assembly is schematically illustrated in  FIG. 1  and is denoted by the reference numeral  10 . The assembly  10  includes a frame, represented by broken lines, which is fixed and is attached to the building. The frame  12  preferably has an in particular glazed fixed panel  14  which is marked with a diagonal cross in the drawing. 
         [0029]    The frame  12  also serves for arranging a door leaf  16 , which can be displaced between a closed position illustrated in  FIG. 1  and an opened position in which the door leaf  16  overlaps the fixed panel  14  at least in portions. 
         [0030]    The door leaf  16  is in particular a lift and slide door, which is therefore not only horizontally displaceable, but can also be raised and lowered. In a lowered state of the door leaf, effective sealing of the door leaf  16  on the frame  12  is facilitated. In a raised state of the door leaf  16 , it can be displaced horizontally. 
         [0031]    The door leaf  16  has a sash frame  18  which delimits a sash panel  20 . The sash panel  20  may be formed for example by glazing. The sash frame  18  has an upper profile section  22 , a lower profile section  24  and also vertical profile sections  26  and  28 . 
         [0032]    When the door leaf  16  is closed, the vertical profile section  26  is in contact with a vertical frame part  30  of the frame  12 . In the context of the present invention, this vertical profile section is understood to be the “handle-side” profile section. When the door leaf  16  is closed, it is possible for the vertical profile section  26  and the vertical frame part  30  of the frame  12  to be bolted together. 
         [0033]    In the event that the door leaf  16  is to be raised by manual force, the first vertical profile section  26  serves for arranging a lift and turn handle (not shown). 
         [0034]    The first vertical profile section  26  and the vertical frame part  30  also serve for arranging electrical contacts  32  and  34 , which, when the door leaf  16  is closed, are in contact with each other in order to supply power from the building. The electrical contacts  32  and  34  may touch each other, or alternatively may be designed inductively in order to achieve a contactless power supply. 
         [0035]    In a preferred embodiment, the first vertical profile section  26  serves for arranging an operating unit  36 , which is built into the door leaf  16  in particular instead of a handle. 
         [0036]    In a preferred embodiment, the door leaf  16  can be raised by way of a motor-driven lifting device  38 . When the door leaf  16  is raised, rollers  40  arranged in the leaf are in contact with a runner rail  42  arranged on the frame. When the door leaf  16  is lowered, the door leaf  16  lies with an underside  44  on the runner rail  42 . 
         [0037]    The second vertical profile section  28  serves for arranging components of a drive device  46 , described below, for displacing the door leaf  16  in the horizontal direction. 
         [0038]    A drive motor  48 , the drive axis  50  of which is oriented in the vertical direction, is arranged in an upper region of the second vertical profile section  28 . The drive motor  48  cooperates with an output stage  52  which is preferably arranged beneath the drive motor  48  in the second vertical profile section  28 . 
         [0039]    An output stage  54  which cooperates with the motor-driven lifting device  38  is preferably arranged on a lower end of the second vertical profile section  28 . 
         [0040]    Furthermore, the second vertical profile section  28  serves for arranging a controller  56  and also at least one battery  58 ,  60 . 
         [0041]    In the schematic view of  FIG. 1 , lines between the described components of the sliding door assembly  10  are illustrated with unbroken or dotted lines. In this case, the unbroken lines represent current-conducting lines, while the dotted lines represent data lines. The lines mentioned likewise run within the profile sections  22 ,  24 ,  26 , and  28  of the door leaf  16 ; however, in order to improve clarity, in  FIG. 1  the lines are illustrated as if they run through the panel  20 . 
         [0042]    The drive motor  48  has an output shaft  62  which cooperates in positive manner with a shaft  64  illustrated in  FIG. 2 . The shaft  64  is connected for conjoint rotation with a gear wheel  66 . The gear wheel  66  meshes with a toothed belt  68  which is arranged within an upper, horizontal frame part  70  of the frame  12 . 
         [0043]    The toothed belt  68  is open at the end and is fastened by its ends  72  and  74  to the frame part  70  of the frame  12 . 
         [0044]    Upon displacement of the door leaf  16 , the door leaf  16 , together with the above-described components of the drive device  46  and together with the components illustrated in  FIGS. 2 and 3 , moves along the fixed toothed belt  68 . In this case, the components illustrated in  FIGS. 2 and 3  slide within a sliding guide, which is open at the bottom and is formed on the frame part  70 . 
         [0045]    The unit of  FIGS. 2 and 3  includes a support  76  on which two deflecting elements in the form of deflecting rolls  78 ,  80  are mounted. Bearing pins  82 ,  84  which are fixed to the support are provided for mounting the deflecting rolls  78 ,  80 , which bearing pins define axes of rotation  86 ,  88  of the deflecting rolls  78 ,  80 . 
         [0046]    The support  76  preferably also serves for guiding a side of the gear wheel  66  which is remote from the drive motor  48 . For example, an annular guide face  90  can be provided for this. 
         [0047]    The support  76  also serves for arranging a curved guide face  92  which is in the form of part of a circle and cooperates with a rear side  94  of the toothed belt  68 . The rear side  94  of the toothed belt  68  furthermore cooperates with the running faces  96 ,  98  of the deflecting rolls  78 ,  80  which point radially outwards. 
         [0048]    The axes of rotation  86 ,  88  of the deflecting rolls  78 ,  80  extend in parallel with one another and are arranged within one plane. An axis of rotation  100  of the gear wheel  66  extends preferably likewise within the plane or is spaced apart only slightly, for example by at most 20 mm, from the plane. 
         [0049]    A minimum spacing provided between the deflecting faces  96 ,  98  is only slightly greater (for example by at most 20 mm) than a diameter of the gear wheel  66  measured on the outside of the teeth. In this manner, the toothed belt  68  can be guided such that it wraps around the gear wheel  66  over a partial circumference of at least approximately 120°. In this manner, at least two, in particular at least four, teeth  102  of the gear wheel  66  are simultaneously fully engaged with respective teeth  104  of the toothed belt  68 . 
         [0050]    It is preferable for the deflecting rolls  78  and  80  and of the gear wheel  66  to be secured on the support  76 , in particular using a plate  106 , illustrated merely in  FIG. 2 , which can be screwed to the support  76  by way of a screw  108 . 
         [0051]    For particularly low-friction running of the door of the door leaf  16 , it is preferable to use deflecting rolls  78 ,  80 . In a simplified and particularly inexpensive embodiment, provision is made for the deflecting elements  110 ,  112  to have immobile deflecting faces  114 ,  116 . The rear side  94  of the toothed belt  78  slides on these deflecting faces. Moreover, the functions of the components illustrated in  FIGS. 2 and 3  and also in the figure correspond to each other. 
         [0052]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
         [0053]    The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

Summary:
The invention relates to a sliding-door assembly, including a stationary frame, a horizontally movable door leaf, and a drive device for moving the door leaf, which drive device includes a drive motor, which is arranged on the leaf and has a toothed wheel, which interacts with a toothed belt arranged on the frame, wherein the toothed belt is wrapped around the toothed wheel over a partial periphery of the toothed wheel and wherein at least two teeth of the toothed wheel are simultaneously fully engaged with at least two teeth of the toothed belt.