Abstract:
A drive with an electric motor, a housing and a direction-dependent brake, which includes a driver splined to a motor shaft, a drive output coupled freely pivotable around a small angle and shape-mated with the driver, several clamping devices and a clamping ring, in which the clamping devices cooperate with the clamping ring so that the brake conveys a torque from the electric motor to the driver output and brakes a back-driving torque of the drive output. The task of the invention is to present a brake in which no static redundancy occurs, which is simple to construct and in which no abrupt blocking is possible. This task is solved according to the invention in that the clamping ring is connected radially movable to the housing, a gearbox or a part attached to the housing so that the clamping ring after overcoming a defined force can be moved at least slightly radially by a clamping device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (1) Field of the Invention 
         [0002]    The invention concerns a drive that includes an electric motor, a housing and a direction-dependent brake. 
         [0003]    (2) Description of Related Art 
         [0004]    The invention concerns a drive that includes an electric motor, a housing, and a direction-dependent brake. A problem exists in the prior art related to the reliability of braking when the motor changes direction. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    The object of the invention is to provide a brake in which no static redundancy is present, is simply constructed, and in which no abrupt blocking is possible. 
         [0006]    In a first embodiment the clamping ring is elastically connected to the motor housing, the gearbox or a part attached to the housing. Through this expedient no reverse rotation of the drive can occur even at high torque. 
         [0007]    Since elastic systems have a tendency toward vibrations, it is proposed as an alternative solution to connect the clamping ring frictionally to the motor housing, the gearbox or a part that is attached to the housing. Rotatability is produced on this account beyond pivotability. 
         [0008]    In order to produce a desired frictional force, the clamping ring should be spring-loaded against a part that is attached to the housing. 
         [0009]    A particularly simple structure can be achieved by forcing the clamping ring axially against a part that is attached to the housing through the spring force of a spring washer. The same applies if the clamping ring lies against an intermediate housing cover or on an end plate. 
         [0010]    It has proven expedient to arrange the clamping ring and clamping devices in a brake housing in which the clamping ring is slightly movable radially within the brake housing. 
         [0011]    In order to obtain an even simpler design, when three clamping devices are present, two clamping devices should be rigid support devices and one clamping a movable clamping device. The number of parts is also reduced because of this structure. In order to improve functionally reliable clamping and self-inhibition it is proposed to design one clamping device as a roll body and two clamping devices as rigid support devices. By designing the rigid support devices in one piece with the driver output, the number of parts can be reduced. 
         [0012]    It is advantageous to distribute the forces on the three clamping devices differently so that the moving clamping device experiences a smaller force than the two rigid support devices. This is achieved in that the angular distance of the rigid support devices relative to each other is greater than the angular distance between a support device and the moving clamping device. The angular distance of the rigid support device should lie in the range between 120 and 175°. 
         [0013]    In a modification of the brake, the drive output should have a recess with a control surface in which the moving clamping device is accommodated in the recess. The control surface determines the properties of the brake. The flatter the control surface, the higher the attainable clamping force. In order to improve the functional reliability in each angle position the moving clamping device is formed by two roll bodies that are spaced from each other with a spring. 
         [0014]    In another embodiment of the invention, three wedge-like clamping devices are provided. These are arranged at uniform angular distance around the drive output. The clamping devices also have an outer friction surface in the form of a circular ring segment with which they are frictionally connected tangentially to the clamping ring in the radially loaded state. Because of the large friction surfaces the surface pressure and friction are reduced so that the components are less loaded. 
         [0015]    In order for sufficient braking effect to be attainable, the clamping devices on the side facing the motor shaft have two surfaces sloped toward a tangent, which cooperates with complimentary mating surfaces of the drive output, in which a maximum of one slope surface per clamping device is engaged with the corresponding mating surface. 
         [0016]    It is also proposed that the drive output have a crown-like design and have three coupling protrusions extending axially from an annular region on which the corresponding mating surfaces are informed, that the drive output have two coupling surfaces per coupling protrusion, which cooperate with mating coupling surfaces of the driver, that the driver have two or three radial protrusions on which the mating coupling surfaces are formed and that the driver have at least one drive surface that cooperates tangentially with a mating drive surface of a clamping device. 
         [0017]    In order to guarantee the best possible efficiency during motor operation, at least one drive surface of the driver should lie against a mating drive surface of a clamping device and against a coupling surface of the drive output. The sloped surfaces of a clamping device and the complimentary mating surfaces of the drive output are arranged relative to each other so that no radial force components are exerted on the clamping device. 
         [0018]    In order to guarantee reliable braking during operation through an external torque acting on the output of the drive, after free pivoting of the drive output relative to the clamping devices around a small angle, at least a sloped surface of a clamping device lies against a complementary mating surface of the driver output, so that during further pivoting, a radial force component is exerted on the clamping device. The outer surface of the coupling device, which represents a braking surface, rubs against a mating braking surface of the clamping ring or frictionally connects the corresponding surfaces so that the rotational movement of the drive output is braked and, if necessary, stopped. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which: 
           [0020]      FIG. 1   a  shows a sectional view of a first embodiment of the invention with direction-dependent brakes and reduction gearing, 
           [0021]      FIG. 1   b  shows an enlarged cutout of the brake of  FIG. 1   a,    
           [0022]      FIG. 2   a  shows the first embodiment of the brake in a first phase of operation, 
           [0023]      FIG. 2   b  shows the first embodiment of the brake in a second phase, 
           [0024]      FIG. 2   c  shows the first embodiment of the brake in a third phase, 
           [0025]      FIG. 2   d  shows the first embodiment of the brake in a fourth phase, 
           [0026]      FIG. 3  shows a further version of the first embodiment of the brake, 
           [0027]      FIG. 4  shows a three-dimensional view of a second embodiment of the brake, 
           [0028]      FIG. 5   a  shows the second embodiment in a first phase, 
           [0029]      FIG. 5   b  shows the second embodiment in a second phase, 
           [0030]      FIG. 5   c  shows the second embodiment in a third phase, 
           [0031]      FIG. 5   d  shows the second embodiment in a fourth phase, 
           [0032]      FIG. 6  shows an exploded view of the second embodiment of the brake, 
           [0033]      FIG. 7   a  shows the second embodiment of the brake in three dimensions, 
           [0034]      FIG. 7   b  shows the second embodiment of the brake from  FIG. 7   a  with a section through a drive output, 
           [0035]      FIG. 8   a  shows a further version of the second embodiment in a first phase and 
           [0036]      FIG. 8   b  shows the version of the second embodiment in a second phase. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    In describing preferred embodiments and variations of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0038]      FIG. 1   a  shows a sectional view of drive  1  with an electric motor  10 , consisting of a stator  14 , with a housing  11 , permanent magnet  141  and end plate  13 , a rotor  15 , with a motor shaft  151 , a Commutator  152 , a bearing  142 , a bearing  143 , a direction-dependent brake  2  and reduction gearing  3 . The brake  2  consists of a driver  21 , which is pulled firmly onto shaft  151 , clamping devices  22 , a clamping ring  24 , which is movable in a limiting clamping ring free space  206  after overcoming a forced threshold radially or in any direction, spring  25  and a drive output  23 . 
         [0039]      FIG. 1   b  shows an enlarged cutout from the brake according to  FIG. 1   a.  The spring  25  is an annular spring which is supported on one side on the end plate and on the other side on clamping ring  24  and forces the clamping ring  24  against a cover  26 . The cover is fastened to end plate  13 . The clamping ring free space  206  is bounded by an annular protrusion  131  of end plate  13 , this protrusion determining the installation position of spring  25 . The drive force of electric motor  1  is transferred by driver  21  to the drive output  23 , the driver  21  cooperating with the drive output  23 , like a positive clutch with a free pivot space. The brake  2  becomes active when a retroactive torque occurs from the drive output  23 . The clamping devices  22  and clamping ring  24  serve as braking surfaces. The clamping ring  24  is frictionally connected to the end plate  13 . During blocking of brake  2  a jerky behavior of the brake is prevented by frictional connection of the clamping ring  24  to end plate  13 . 
         [0040]      FIGS. 2   a  to  2   d  show a first embodiment of the brake  2  in different phases of operation. In the interest of simplicity, the housing parts, the end plate  13  and the spring  25  are left out. A driver  21  is pressed onto shaft  151 . The driver  21  engages in shape-mated fashion into intermediate spaces between support devices  232  and a coupling protrusion  236  of a drive output  23 , in which a drive free space  201  remains, which must initially be overcome from the initial position in order to drive the drive output, especially during a reversal in direction of rotation. No additional function is present during drive by the electric motor  10 . During reversal of a torque from the drive output, the drive free space  201  is generally initially overcome. A moving clamping device, here designed as a roll body  222 , is then moved, which is held in shape-mated fashion between a recess  231  of the coupling protrusion  236  and the clamping ring  24 . 
         [0041]    By the special geometric shaping of recess  231 , whose inside surface is a control surface  238 , in which the intermediate space between the coupling protrusion  236  and the inside surface of clamping ring  24  tapers, a pivot movement of the drive output leads to clamping of the moving clamping device  222 . During clamping, radial forces occur through which rigid support devices  232  are forced against the inside surface of clamping ring  24 . In the present embodiment, the rigid support devices  232  are arranged around the periphery of the drive output so that their spacing from each other is much greater than their spacing to the moving clamping device  222 . Because of the resulting force distribution, large forces occur on the support devices  232  and a small force on the moving clamping device  222 . The control surface  238  can be designed concave to convex. In convex control surfaces their radius must be larger than the radius of clamping ring  24  and its inside surface. In order to be able to loosen the clamped brake mechanically, the driver  21  is provided with radial protrusions  216  that serve to drive the drive output and tangential catches  217  are connected to the protrusions  216  which reduce the spacing to the moving clamping device  222 . The length of catches  217  is dependent on the shape and radius of control surface  238 . In a flatter control surface the moving clamping device can move in a large clamping device free space  205  until a clamping effect occurs, for which reason the catches  217  in this case are designed shorter or omitted entirely. 
         [0042]    In the position depicted in  FIG. 2   a,  the shaft  151  and driver  21  are moved clockwise and carry along the drive output in shape-mated fashion. At the same time the moving clamping device is continuously pushed out by catch  217  from a position that would be suitable for clamping. 
         [0043]    In the position depicted in  FIG. 2   b,  a pivot movement counterclockwise is executed by the driver output  23 , in which the moving clamping device  222  is forced into a position in which clamping occurs. 
         [0044]    The phase in which the motor has rotated the driver  21  counterclockwise until one of the catches  217  touches the moving clamping device  222  and then moves it from the clamped position is shown in  FIG. 2   c.    
         [0045]    The moving clamping device  222  is already pushed out of the clamped position in  FIG. 2   d  and the electric motor can rotate the drive output  23  freely counterclockwise. During reversal of the direction of rotation of the electric motor the driver  21  would initially pivot back around the free pivot angle defined by the drive free space  201  with the drive output  23  stopped, in which the moving clamping device  222  is not actively moved. 
         [0046]      FIG. 3  shows a version of the first embodiment of brake  2  in which the moving clamping device consists of two roller bodies  222  that lie in contact with the inside surface of the clamping ring  24  on one side through a pressure spring  223  and with the control surface  238  of a drive output, on the other side. Through this expedient, the brake becomes more reliable and reacts more quickly to back-torques. Because of the space requirement of the two roller bodies  222  and the compression spring  223 , the control surface  238 , the width of the coupling protrusion  236  and the length of the catches  217  are correspondingly adjusted. 
         [0047]    A second embodiment of the brake is show in  FIGS. 4 to 8 .  FIG. 4  shows a three-dimensional view of the brake with a motor shaft  151 , a driver  21  with radial protrusions  216 , which together with coupling protrusion  236  of a coupling output  23  form a positive clutch in which a drive free space  201  remains between the coupling protrusions  236  and the protrusions  216 , which permits limited free pivoting during a change of rotation direction. The difference relative to the first embodiment is that three coupling protrusions  216  are distributed uniformly around the periphery of a driver  21  and the same applies to coupling protrusions  236 , coupling devices  22  are designed rigid without exception and the clamping effect is achieved by wedging of oblique surfaces  225 ,  235 . The three clamping devices  22  are shaped identically and form annular segments in their base shape, in which limited intermediate spaces remain between their ends on the periphery in order to guarantee limited radial mobility. The clamping devices  22  during the action of a back-driving torque are nestled against the brake output  23  on the inside surface of clamping ring  24 , which serves as a friction surface. A radial force component required for this is achieved through the oblique surfaces  225  of the clamping device  22  and the oblique surfaces  235  of the coupling protrusion  236 . In the present example the oblique surfaces  225  of the clamping device  22  are formed on protrusions and the oblique surfaces  235  on indentations. A reversed arrangement would have had essentially the same effect with the difference that the cooperating surfaces  225 ,  235  would be radially farther removed from the axis of rotation. 
         [0048]      FIGS. 5   a  to  5   d  show the second embodiment of the brake in different phases of operation. The phase in which the electric motor  10  rotates the shaft  151  and with it the driver  21  clockwise is shown in  FIG. 5   a,  in which the radial protrusions  216  lie on the inside with their drive surfaces  211  against coupling surfaces  234  of the coupling protrusions  236  on the outside against mating drive surfaces  221  of clamping device  22 . Because of this the clamping devices  22  are held in a neutral position in which no clamping effect occurs. The mating drive surfaces  221  border recesses on the edges of clamping devices  22 . 
         [0049]    The phase in which a back-driving torque comes from drive output  23  and acts on brake  2  is shown in  FIG. 5   b,  in which case the coupling protrusions  236  of the coupling output lie with their coupling surfaces  234  against the drive surfaces  211 , whereas an additional pivoting through the oblique coupling surfaces  225  of clamping devices  22  may lie against the complementary mating surfaces  235  of coupling protrusion  236  so that a radial force component is produced that forces the clamping devices  22  against the inside surface of the clamping ring and therefore causes friction until clamping occurs. 
         [0050]    The phase in which motor movement has just started until drive surfaces  211  lie against the mating drive surfaces  221  is shown in  FIG. 5   c.  In this state, in which clamping is still present, a drive free space  201  remains between the drive protrusions  216  of driver  21  and the coupling protrusions  236  of the brake output  23 . This angle, which is defined by the drive free space  201  is further covered during further movement of the driver  21  until the coupling surface  234  of coupling protrusions  236  is reached (see  FIG. 5   d ). During this pivot movement the clamping devices  22  are carried along over the mating drive surface  221  of the drive surfaces  211  of driver  21  and brought from the clamped position into a neutral position and on further pivoting or rotational movement in the same direction are held in this position. 
         [0051]      FIG. 6  shows an exploded view of the second embodiment of the brake with a end plate  13 , spring  25 , clamping ring  24 , motor shaft  151 , the three clamping devices  22 , the driver  21  pressed onto the motor shaft  151 , the driver output  23 , which is made in one piece with a pinion  233 , cover  26  and a screw  261  for fastening of cover  26  to end plate  13 . Clamping ring  24  is clamped by the spring force of spring  25  between the end plate  13  and the cover. Clamping ring is slightly movable radially on this account and after overcoming a torque defined by the spring force and friction parameters is also pivotable or rotatable. This arrangement permits relative jerk-free braking and during the action of back-driving torque on the drive output. 
         [0052]      FIG. 7   a  shows the second embodiment of the brake in three dimensions with the cover removed. It is readily apparent that there is a clamping free space  206  that permits slight radial deflection of a clamping ring  24  after overcoming the aforementioned friction. This radial reflection capability prevents status redundancy and compensates for manufacturing inaccuracies. This leads to a more reliable operation of the brake. 
         [0053]      FIG. 7   b  shows the second embodiment of the brake in  FIG. 7   a  with a section through a drive output. 
         [0054]    A version of the second embodiment is shown in a first phase in  FIG. 8   a  and in a second phase in  FIG. 8   b.  The first phase shows the brake in a clamped position and the second phase shows the brake in an unclamped position (motor operation). The clamping devices  220  are divided and the two halves are forced from each other by a compression spring  223  so that in each phase there is freedom of play of the clamping devices  220 . Because of this more reliable and more fast-acting operation is guaranteed. 
         [0055]    It is to be understood that the present invention is not limited to the illustrated embodiments described herein. Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           1  Drive 
           10  Electric motor 
           11  Housing 
           13  End plate 
           131  Protrusion 
           14  Stator 
           141  Permanent magnet 
           142  Bearing 
           143  Bearing 
           15  Rotor 
           151  Shaft 
           152  Commutator 
           2  Coupling 
           201  Drive free space 
           202  Coupling free space 
           205  Clamping device free space 
           206  Clamping ring free space 
           21  Drive 
           211  Drive surface 
           214  Mating coupling surface 
           216  Radial protrusion 
           217  Catch 
           22  Clamping device 
           220  Clamping device half 
           221  Mating drive surface 
           222  Roll body 
           223  Compression spring 
           227  Braking surface 
           225  Sloped surface 
           23  Drive output 
           231  Recess 
           232  Support device 
           233  Pinion 
           234  Coupling surface 
           235  Complementary mating surface 
           236  Coupling protrusion 
           238  Control surface 
           24  Clamping ring 
           247  Mating braking surface 
           25  Spring 
           26  Cover 
           261  Screw 
           3  Reduction gearing 
           31  Gearbox 
           32  Brakes