Abstract:
The present invention relates to a drive arrangement, comprising a motor drive shaft, which makes the drive force of a motor available, an output shaft, via which the drive arrangement outputs and accumulates a rotational force, a coupling, which is designed to transmit a rotational force from the motor drive shaft to the output shaft and from the output shaft to the motor drive shaft, and a braking arrangement, which counteracts a rotational movement of the output shaft with a braking force.

Description:
BACKGROUND 
       [0001]    The present invention relates to a drive arrangement, comprising a motor drive shaft, which provides driving force of a motor, a working shaft, via which the drive arrangement delivers and receives operating torque, a coupling, which is set up to transmit torque from the motor drive shaft to the working shaft and from the working shaft to the motor drive shaft, and a brake arrangement which counters a rotational movement of the working shaft with a braking force. Furthermore, the invention relates to a flap control system that has a flap pivotally mounted about a pivot axis, a motor and a drive arrangement of the aforementioned kind. 
         [0002]    In prior art, drive arrangements, in particular for the electromechanical driving of doors or flaps, are known, for example apparatuses for the electromechanical opening and closing of vehicle flaps. In the process, the force of the electric motor is transmitted by a coupling onto a working shaft bearing the flap. Depending on the field of application, situations also inevitably occur when using known apparatuses, in which a rotational movement is introduced into the drive arrangement by the working shaft. In particular, in the case of vertically moving flaps, operating torque is introduced into the drive shaft by the gravity of the flap. Furthermore, when using the drive arrangement by manual movement of the flap by the user, rotational movement can be introduced into the drive shaft. 
         [0003]    In order to avoid an excessive load on the motor during torque transmission from the working shaft to the motor drive shaft or to prevent an unintentional adjustment of the flap (for example as a result of gravitational force) when the motor is switched off, known drive arrangements occasionally have brake arrangements, which counter the rotation of the shafts of the drive arrangement with a predetermined resistance. In the case of flaps moving in a vertical direction, the braking force of the brake arrangement is to be rated such that when the motor is idle, an autonomous downward movement of the flap is prevented such that the set pivot position of the flap is retained. In addition, brake arrangements are known, which fix a certain turning position between working shaft and motor drive shaft when the motor is idle in order to prevent a manual rotation of the motor by the user and therefore a potential overload of the motor. 
         [0004]    In the case of drive arrangements with brake arrangements of the kind referred to above, the disadvantage emerges that the braking effect of the brake arrangement must be overcome by the motor when operating the drive arrangement in order to start the working shaft rotating. The use of a brake arrangement described above therefore works at the cost of energy efficiency when operating the drive arrangement. 
         [0005]    Against the background of his problem, the object of the present invention is to provide a drive arrangement and a flap control system which have a high functional range and at the same time work with high energy efficiency. 
       BRIEF DESCRIPTION 
       [0006]    According to a first aspect, the above object of the invention is achieved by a drive arrangement comprising a motor drive shaft, which provides driving force of a motor, a working shaft, via which the drive arrangement delivers and receives operating torque, a coupling, which is set up to transmit torque from the motor drive shaft to the working shaft and from the working shaft to the motor drive shaft, and a brake arrangement which counters a rotational movement of the working shaft with a braking force, the brake arrangement countering the rotational movement during the transmission of torque from the working shaft to the motor drive shaft with a first braking force and the brake arrangement countering the rotational movement during transmission of torque from the motor drive shaft to the working shaft with a second braking force which is smaller than the first braking force or substantially countering it with no braking force. 
         [0007]    According to an important feature of the first aspect of the present invention, the braking force generated by a brake arrangement in the case of a transmission of torque from the working shaft to the motor drive shaft is greater than in the case of a transmission of torque from the motor drive shaft to the working shaft, the brake arrangement preferably not substantially releasing any braking force at all in the latter case. Depending on the direction of the torque transmission (from the working shaft to the motor drive shaft or in the opposite direction), the brake arrangement therefore changes its braking force and its braking effect. As a result, the brake arrangement acts with the required force when torque is introduced at the working shaft, for example due to the gravitational force of a flap attached to the working shaft or due to the introduction of a rotational movement by a user, while in the case of power transmission emanating from the motor, the brake arrangement is switched into a reduced braking mode or a mode with released brake such that the motor only has to overcome a reduced braking force or preferably substantially no braking force at all when driving the working shaft. Consequently, the motor power can be used more efficiently and the energy efficiency of the drive arrangement can be increased. 
         [0008]    In a preferred embodiment of the invention, the coupling is set up to transmit operating torque in both directions of rotation, i.e. when transmitting operating torque from the motor drive shaft to the working shaft, the working shaft can be rotated in both directions by motor force and/or the drive arrangement is set up to receive a rotational movement from the working shaft in both directions of rotation and either slow it down or allow it. In this manner, the functional scope of the drive arrangement is increased. In the case of transmission of operating torque from the working shaft to the motor drive shaft, in one variant of the invention, the brake arrangement can generate a first braking force in a second direction of rotation which counters the rotational movement, the brake arrangement generating a third braking force countering the rotational movement, which braking force is smaller than the first braking force or substantially countering with no braking force, during transmission of the operating torque from the working shaft to the motor drive shaft in a first direction of rotation opposing the second direction of rotation. During transmission of operating torque from the working shaft to the motor drive shaft, the brake arrangement can therefore work depending on the direction of rotation such that it generates the first braking force in one direction of rotation and a smaller, third braking force or no braking force at all in the other direction of rotation. This variant of a drive arrangement is, for example, of particular advantage if the working shaft is connected to a flap that is movable in a vertical direction and the brake arrangement applies the first (higher) braking force during a downwards movement of the flap in order to hold the flap in the adjusted position even if the motor is idle, and simultaneously to allow a manual upwards movement of the flap by the user. 
         [0009]    In a further preferred embodiment of the invention, it is provided for the coupling to have a first coupling component, which is arranged or constructed on one element out of the working shaft and motor drive shaft and that the coupling has a second coupling component, which is arranged or constructed on the other element out of the working shaft and motor drive shaft, both coupling components being coupled together or it being possible to couple both coupling components together to transmit operating torque. In the process, the first coupling component can have a first stop which hits against a second stop of the second coupling component in the circumferential direction in relation to the axis of rotation in order to carry the second stop along in rotation in a first direction of rotation and to transmit operating torque onto the second coupling component in the first direction of rotation. Such rotation stops allow an interlocking coupling between coupling components and therefore the rotational movement is reliably carried along in a relatively simple mechanical arrangement. 
         [0010]    Furthermore, when using a coupling having rotation stops of the kind referred to above, it is preferable for the first coupling component to have a third stop, which hits against a fourth stop of the second coupling component in the circumferential direction in relation to the axis of rotation in order to carry the fourth stop along in rotation in a second direction of rotation opposite to the first direction of rotation and to transmit operating torque onto the second coupling component in the second direction of rotation, the first stop being arranged at a distance from the second stop when the third stop hits against the fourth stop, such that there is a predetermined idling angle between the coupling components. The provision of the idling angle can advantageously be used to detect in which direction the operating torque is being transmitted, i.e. from the working shaft to the motor drive shaft or from the motor drive shaft to the working shaft. To be more precise, by providing the idling angle, an angle range can be created in which the two coupling components can rotate towards one another without carrying one another along immediately such that a changeover device arranged within the idling angle can detect whether the rotary drive is emanating from the first coupling component or from the second coupling component, i.e. whether the operating torque is being introduced from the motor drive shaft or from the working drive. One part of the brake arrangement is therefore preferably active in the form of said changeover device when the two coupling components are rotating relative to one another within the idling angle. 
         [0011]    The brake arrangement preferably comprises a brake block moved together with the working shaft or the motor drive shaft (if applicable, with the respective assigned coupling component), which in the event of braking is pressed against a brake surface fixed relative to the working shaft and to the motor drive shaft. This allows a frictional braking effect and therefore a certain damping of the braking process to protect material and reduce sound. In the process, the brake block can be a rolling element, in order to reduce the wear on the brake arrangement. The brake block can surround the axis of rotation in an annular manner, as a result of which a simple integration of the brake arrangement emerges. 
         [0012]    A reliable and, at the same time, in mechanical terms relatively simple brake arrangement and coupling can be achieved if the brake block rolls or slides on a control surface of the first coupling component along a direction of the control surface, the direction of the control surface being orientated orthogonally to the axis of rotation and at an angle to the radial direction, preferably at least in portions orthogonally to the radial direction, and/or the control surface being formed by a local recess or flattening on a cylindrical outer circumference of the first coupling component. In this and also in other variants using a brake block, it is advantageous to use a plurality of brake blocks, which are advantageously distributed at even angular distances from one another about the axis of rotation. In this manner, a balanced mechanical load of the brake arrangement in the event of braking emerges and a load on the axes of rotation in directions transverse to the axis of rotation is largely avoided. 
         [0013]    A brake block of a brake arrangement can be controlled with directional dependency to achieve the present invention in a particularly simple manner in that when operating torque is transmitted from the working shaft to the motor drive shaft in a predetermined direction of rotation, the brake block is pressed by the first coupling component against the brake surface and when operating torque is transmitted from the motor drive shaft to the working shaft in the predetermined direction of rotation, the brake block is moved by the second coupling component in a direction to release the engagement with the brake surface. Depending on from which component the operating torque is being introduced (from the working shaft or from the motor drive shaft), the respective coupling component assigned to this element then moves the brake block either towards the brake surface or away from the brake surface. Depending on the direction of power flow, the rotation is therefore braked by applying the brake block to the brake surface (when operating torque is introduced into the working shaft) or the brake block is pressed away from the brake surface and the braking effect is cancelled (when the operating torque is introduced via the motor drive shaft). 
         [0014]    According to a second aspect of the present invention, the object of the invention referred to above is achieved by a flap control system comprising a flap pivotally mounted about a pivot axis, a motor and a drive arrangement according to the first aspect of the present invention, the motor axle providing the driving power of the motor and the working axle moving the pivot axle in order to actuate the flap in an opening direction and a closing direction. Using a flap control system of the second aspect of the invention, the advantages and functions described above in connection with the first aspect of the invention can be exploited for controlling the movement of a flap, for example in automotive construction in the case of a tailgate of a vehicle. Alternatively, the flap control system can be used to pivot doors or other components which are to be pivoted electromagnetically about a predetermined angle range. 
         [0015]    In order to allow a compact arrangement, the pivot axis is preferably arranged coaxially to the working axle or is formed by the working axle. The flap control system can then in particular also be integrated into a hinge arrangement of the flap so as to be visually inconspicuous and so as to save installation space and therefore has advantages in particular over a known triangular configuration with a telescopic cylinder between flap and frame. 
         [0016]    The advantages of the present invention, in particular the directionally dependent brake arrangement, come into effect in particular when the flap is lowered in the closing direction and the brake arrangement counters a movement of the flap in the closing direction with a first (higher) braking force. The first braking force can then be used to hold the flap when the motor is idle, while a lower or no braking force acts during a motor-operated upwards movement of the flap such that the motor can apply its power in an effective manner to overcome the gravity of the flap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention is described in more detail below with reference to preferred embodiments and the accompanying drawings, in which 
           [0018]      FIG. 1 : is an overall view of the drive arrangement according to a first embodiment of the present invention as a section along the axis of rotation, 
           [0019]      FIG. 2 : is an enlarged view of a detail from  FIG. 1  in the region of a coupling of the drive arrangement, 
           [0020]      FIG. 3 : is a perspective exploded view of the coupling of the drive arrangement, 
           [0021]      FIG. 4 : is another perspective exploded view of the coupling of the drive arrangement, 
           [0022]      FIG. 5 a   : is a sectional view of the coupling according to a section line A-A in  FIG. 2  while the motor is driving in a first direction of rotation, 
           [0023]      FIG. 5 b   : is a sectional view according to a section line B-B in  FIG. 2  while the motor is driving in the first direction of rotation. 
           [0024]      FIGS. 6 a  and 6 b   : are views according to  FIG. 5 a    and  FIG. 5 b   , but for a motor drive in a second direction of rotation, 
           [0025]      FIGS. 7 a  and 7 b   : are views according to  FIG. 5 a    and  FIG. 5 b   , but for a drive on the flap in the first direction of rotation, and 
           [0026]      FIGS. 8 a  and 8 b   : are views according to  FIG. 5 a    and  FIG. 5 b   , but for a drive on the flap in the second direction of rotation, 
           [0027]      FIG. 9 : is a view like  FIG. 5B , but for a drive unit according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    A drive arrangement according to a first embodiment of the present invention is generally marked as  10  in  FIGS. 1 to 8  and comprises a motor drive shaft  12 , which provides the driving force of a motor that is not shown in the drawings, a working shaft  14 , which delivers operating torque to a working element (likewise not shown) connected thereto or takes operating torque from this working element, and a coupling  16  arranged between the motor drive shaft  12  and the working shaft  14  in order to transmit operating torque from the motor drive shaft  12  to the working shaft  14  or from the working shaft  14  to the motor drive shaft  12 . The motor drive shaft  12  and the working shaft  14  are preferably arranged coaxially to one another. Said components of the drive arrangement are accommodated in a housing  18  and in particular are rotatably mounted in the housing  18  about an axis of rotation R. Accordingly, the housing can in particular have a cylindrical form with the axis of rotation R as the axis of the cylinder. 
         [0029]    As can be seen in particular in  FIG. 2 , the motor drive shaft  12  (or motor output shaft) is connected for conjoint rotation with a rotor  20  of a motor, in particular an electric motor, which is not illustrated in any greater detail, in order to introduce operating torque of the motor into the drive arrangement  10 . The motor is preferably accommodated in the housing  18  and fixed therein. The working shaft  14  is rotatably mounted on a bearing  22  in the housing  18 . Ends of the motor drive shaft  12  and of the working shaft  14  that face one another are connected for conjoint rotation with assigned coupling components of the coupling  16 , as will be described in more detail below. 
         [0030]    With reference to  FIGS. 2 to 4 , the construction of the coupling  16  is described in more detail. The coupling  16  comprises a first coupling component  24  connected for conjoint rotation with the working shaft  14  and a second coupling component  26  connected for conjoint rotation with the motor drive shaft  12 . The coupling components  24 ,  26  can be brought into mutual engagement in an interlocking manner in order to transmit operating torque onto one another. The interlocking can be achieved by at least one protrusion  28 , which protrudes from one of the two coupling components  24 ,  26  and engages in an assigned recess  30  of the other of the two coupling components  24 ,  26 . When the coupling components  24 ,  26  are rotated relative to one another, the protrusion  28  and the recess  30  can then carry one another along in the circumferential direction. In the illustrated embodiment, a plurality of protrusions  28  (for example four protrusions) are provided, distributed in the circumferential direction, and engage in a corresponding number of recesses  30  such that the coupling components  24 ,  26  engage with one another in the manner of a tooth system. 
         [0031]    In  FIGS. 5 a , 6 a , 7 a  and 8 a   , the protrusions  28  and the recesses  30  are shown in section. It can be seen in  FIG. 6 a   , that a protrusion  28  of the first coupling component  24  extends along a circumferential length L 1 , which is preferably smaller than a circumferential length L 2  of an assigned recess  30 , such that between the protrusion  28  and the recess  30  a gap  32  remains in the circumferential direction. The gap  32  corresponds to an idling angle W, within which the two coupling components  24 ,  26  can rotate freely relative to one another. 
         [0032]    The drive arrangement  10  further comprises a brake arrangement  34 , which is preferably arranged in the region of the coupling  16 . In the illustrated embodiment, the brake arrangement  34  comprises a brake cylinder  36  and at least one brake block  38 , which is accommodated between an inner cylindrical brake surface  40  of the brake cylinder  36  and a control surface  42  of the first coupling component  24 . The brake block  38  is constructed as a rolling element, in particular as a cylindrical roller, and rolls in a recess or flattening that forms the control surface  42  on the outer circumference of the first coupling component  24  and on the inner brake surface  40  of the brake cylinder  36  respectively. A pair of brake block stop surfaces  44 ,  46  limit the movement of the brake block  38  in the circumferential direction in both directions. 
         [0033]    The brake arrangement  34  can be integrated into the coupling  16  in a particularly space-saving manner without significant enlargement of the installation space of said coupling. For this purpose, as achieved in the illustrated embodiment, the control surface  42  can be provided on a cylindrical protrusion  48  of the first coupling component  24 , which is inserted into the second coupling component  26  in the axial direction of the axis of rotation R. In a circumferential portion of the second coupling component  26  assigned to the control surface  42 , a through opening  50  is formed, in which the brake block  38  is arranged and the inner edges of which form the stops  44 ,  46  for the brake block  38 . A wall thickness of a cylindrical wall  52  of the second coupling component  26  in the region that accommodates the cylindrical protrusion  48  of the first coupling component  24  is smaller than a diameter of the brake block  38  such that the brake block  38  resting on the control surface  42  of the first coupling component  24  passes through the through opening  50  and extends as far as to an outer surface of the cylindrical wall  52  or beyond. Therefore, the brake block  38  can come into contact with the inner brake surface  40  of the brake cylinder  36 , which is pushed over the wall  52  of the second coupling component so as to fit. 
         [0034]    As can be seen in particular in  FIGS. 5 b , 6 d , 7 b  and 8 b   , the control surface  42  is preferably of a form such that it has a greater radial distance from the axis of rotation R at least one first end  54  in the circumferential direction (i.e. in the rolling direction of the brake block  38 ) than in a central portion  56 . In the central portion  56 , the radial distance between the control surface  42  and the inner brake surface  40  of the brake cylinder  36  is equal to or greater than the diameter of the brake block  38 , such that the brake block  38  is accommodated in a movable manner or even with play between the control surface  42  and the brake surface  40  of the brake cylinder  36 . In the region of the first end  54  of the control surface  42 , i.e. away from the central portion  56 , the radial distance between the control surface  42  and the brake cylinder  36  is smaller than the diameter of the brake body  38 . As a result, the brake block  38  is clamped in the gap between the control surface  42  and the brake cylinder  36  when it moves from the central portion  56  towards the end  54  of the control surface  42  such that a relative movement between the first coupling component  24  and the brake cylinder  36  is blocked and the brake arrangement  34  is in the braked state. If, on the other hand, the brake block  38  is arranged in the central portion  56  of the control surface  42 , then the first coupling component  24  and the brake cylinder  36  can be rotated relative to one another. 
         [0035]    The brake cylinder  36  can generally be rigidly connected directly to the housing  18  or even formed by the inner wall of the housing  18 . Preferably however, the brake cylinder  36  is coupled to the housing  18  by a resilient device such that a sudden blocking of the rotation of the working shaft  14  and therefore possible damage to the drive arrangement  10  or components connected thereto does not occur when the brake is applied. In the embodiment, the resilient device is achieved by a wrap spring which acts as a torsion spring and is connected at one end  60  to the brake cylinder  36  and at the other end  62  is fixed to the housing, in particular is connected to a retaining element  64  attached to the housing  18 . 
         [0036]    The functionality of the drive arrangement  10  of the first embodiment of the invention is described in more detail below with reference to  FIGS. 5 a    to  8   b.    
         [0037]    In a first motor operation shown in  FIGS. 5 a  and 5 b   , the motor, which is not shown, drives the motor drive shaft  12  and thus the second coupling component  26  in a first direction of rotation indicated by an arrow M 1  (anticlockwise in the drawings). As a result, a first stop  64  of the recess  30  of the second coupling component  26  hits against a first stop  66  of the protrusion  28  of the first coupling component (if applicable, having traversed part of the idling angle W) in the circumferential direction and then when it rotates, carries the second coupling component  24  along in the direction M 1  ( FIG. 5 a   ). As can be seen in  FIG. 5 b   , in this rotational position of the two coupling components  24 ,  26 , the brake block  38  is retained by the stop  44  on the inner edge of the opening  50  in the region of the central portion  56  of the control surface  42 , such that it is released from the clamping engagement with the brake cylinder  36 . The rotation of the motor is thus converted into rotation of the second coupling component  24  and thus the working shaft  14  in the direction of rotation M 1 . 
         [0038]    If the rotational movement of the motor is reversed, such that the second coupling component  26 , as shown in  FIG. 6 a   , rotates in a second direction of rotation M 2  (clockwise in the drawings) opposite to the first direction of rotation M 1  then a second stop  68  of the recess  30  located opposite the first stop  64  of the recess  30  hits against a second stop  70  of the protrusion  28  located opposite the first stop  66  of the protrusion  28  (if applicable, having traversed at least part of the idling angle W) such that the second coupling component  26  carries the first coupling component  24  along in the second direction of rotation M 2 . As can be seen in  FIG. 6 b   , in this rotational position, the second stop  46  rests against the inner edge of the opening  50  of the second coupling component  26  on the brake block  38  and retains the brake block in the central portion  56  of the control surface  42  such that the brake block  38  is not engaged in a clamped manner with the brake cylinder  36  even during rotation in the second direction of rotation and does not impede the common rotation of the coupling components  24 ,  26  relative to the brake cylinder  36 . As a result, the operating torque of the motor drive shaft  12  is not transmitted onto the working shaft  14  in the second direction of rotation M 2 . 
         [0039]      FIGS. 7 a  and 7 b    show the case in which operating torque is introduced into the working shaft  14  in the first direction of rotation M 1  and accordingly the first coupling component  24  is rotated in the first direction of rotation M 1 . The second stop  70  of the protrusion  28  of the first coupling component  24  then comes to rest against the second stop  68  of the recess  30  and thus carries the second coupling component  26  along in the first direction of rotation M 1 . As shown in  FIG. 7 b   , the control surface  42  of the first coupling component  24  has such a contour that the brake block  38  also continues to be released from engagement with the brake cylinder  36  even if it is slightly distanced away from the central portion  56  and has moved towards a second end  55  of the control surface  42  opposite the first end  54 . It can be seen by comparing  FIGS. 6 b  and 7 b    that in the first embodiment, the control surface  42  is formed such that when the second stop  68  of the second coupling component  26  hits against the second stop  70  of the first coupling component  24 , the brake block  38  can move freely between the opposite edges  44 ,  46  of the through opening  50  without generating the brake effect with the brake cylinder  36 . When operating torque is introduced into the working shaft  14  in the first direction of rotation M 1 , the rotational movement is thus substantially transmitted to the motor drive shaft  12  without the effect of a braking force. 
         [0040]    If operating torque acts on the working shaft  14  in the second direction of rotation M 2  ( FIGS. 8 a  and 8 b   ), then the first stop  66  of the protrusion  28  in turn comes to rest against the first stop  64  of the recess  30  such that operating torque is transmitted from the first coupling component  24  onto the second coupling component  26  in the second direction of rotation M 2 . As shown in  FIG. 8 b   , however, when the first coupling component  24  rotates in the second direction of rotation M 2 , the brake block  38  rolls on the control surface  42  starting from the central portion  56  towards the end  54  of the control surface  42 . Since at the end  54  of the second control surface  42 , the radial gap between the control surface  42  and the brake surface  40  of the brake cylinder  36  becomes smaller, the second control surface  42  presses the brake block  38  increasingly towards the brake cylinder  36  in the process until the brake block  38  is ultimately clamped between the brake cylinder  36  and the control surface  42 . The operating torque of the first coupling component  24  is thus introduced into the brake cylinder  36  which is connected to the housing  18  rigidly or via the spring arrangement  58 . The rotation of the first coupling component  24  is thus braked or completely blocked and thus is only converted into a rotational movement of the motor drive shaft  12  in a braked manner or not at all. 
         [0041]    The drive arrangement described above according to the first embodiment of the invention can advantageously be used as part of a flap control system, in which a flap, for example a door of a motor vehicle, a building door or similar is mounted on the working shaft  14  such that the flap can be opened and closed electromagnetically by a motor coupled to the motor drive shaft  12 . For example, the direction of rotation M 1  can then be a direction for opening the flap and the direction of rotation M 2 , which is opposite to the first direction of rotation M 1 , can be a direction for closing the flap. According to the operation of the motor in  FIG. 5 a , 5 b , 6 a , 6 b    described above, the motor can then be operated for opening and closing the flap while, during exertion of a force onto the flap by a user or due to gravity or due to other external influences, operating torque can be introduced into the working shaft  14  in the opening direction ( FIGS. 7 a  and 7 b   ) or in the closing direction ( FIGS. 8 a  and 8 b   ). In the illustrated first embodiment, an opening movement of the flap is then allowed, for example as a result of manual activation by a user, while a closing movement of the flap is braked or blocked. Such a flap control system is, for example, advantageous in the case of a flap that is pivotable in the vertical direction (for example the tailgate of a vehicle), where the closing movement of the flap due to gravity should be prevented when the motor is not being driven, i.e. the flap is to be retained or held in the adjusted position that has been reached. 
         [0042]    In  FIG. 9 , a second embodiment of the present invention is shown. Only the differences to the first embodiment are described hereinafter and, apart from this, reference is made fully to the above description and the drawings of the first embodiment. 
         [0043]    The second embodiment differs from the first embodiment by the shape of the control surface  142 . A central portion  156  of the control surface  142  has a distance away from the inside of the brake cylinder  136  that is equal to or greater than the diameter of a brake block  138  arranged therebetween, such that the brake block  138  can move in a rolling manner or freely or with play in the central section  156 . The distance of the control surface  142  from the brake cylinder  136  reduces with increasing distance from the central portion  156 , and, in the case of the second embodiment, in both directions towards a first end  154  and towards a second end  155 . When it moves either in the direction of the first direction of rotation M 1  or in the direction of the second direction of rotation M 2  away from the central portion  156 , the brake block  138  is thus caught in between the control surface  142  and the brake cylinder  136  and blocks a rotational movement between the coupling components and the brake cylinder  138  and thus rotation of the motor drive shaft and the working shaft relative to the housing. 
         [0044]    In this way, the drive arrangement of the second embodiment allows a transmission of operating torque from the motor drive shaft to the working shaft in both directions of rotation M 1  and M 2  and brakes or blocks a rotational movement, which is attributable to the introduction of a rotational movement from the working shaft  14 , in both directions of rotation M 1  and M 2 . When using such a drive arrangement in a flap control system of the kind described above, the flap would then be secured in both directions in any position adjusted by the motor, i.e. cannot then be pivoted further either by gravity or by manual use.