Patent Publication Number: US-2022212497-A1

Title: Wheel holder

Description:
The invention relates to a wheel holder or wheel clamp, in particular a wheel holder for vehicle wheel alignment measurement. The invention also relates to a method of mounting and to a method of unmounting such a wheel holder to and from a wheel of a vehicle, in particular a motor vehicle. 
     For vehicle wheel alignment measurement, there are often mounted wheel holders, which are adapted to support sensors and/or measurement marks (“targets”), on the wheels of the vehicle to be measured for wheel alignment. The handling of such wheel holders, in particular the attaching and detaching thereof to and from the wheels of the vehicle, is as a rule complex and difficult. In particular, there are several working steps required that have to be carried out using two hands. There is a risk that the measurement results of the wheel alignment measurement will be falsified by incorrect and/or inaccurate attachment of the wheel holders. 
     It is an object of the invention to simplify mounting and unmounting of a wheel holder to and from the wheels of a vehicle and to reduce the risk of incorrect and/or inaccurate mounting. 
     This object is met by the wheel holder of independent claim  1  and by methods of mounting and removing a wheel holder according to claims  14  and  15 . Advantageous developments are indicated in the dependent claims. 
     The invention relates to a wheel holder that is provided for fastening to a wheel, in particular to a wheel of a motor vehicle, and comprises at least two arms which extend outward from a center of the wheel holder in a radial direction. Each arm comprises a stationary element and at least one movable element, e.g. a carriage, that is movable with respect to the stationary element. The movable element is movable in the radial direction in relation to the stationary element, so that the length of each arm can be varied by moving the movable element in the radial direction. 
     The wheel holder comprises a synchronization system having a central rotation element which is arranged in the center of the wheel holder such that it can rotate, and at least two coupling elements each extending between one of the movable elements and the central rotation element such that the movable elements are movable in the radial direction by rotation of the rotation element and, vice versa, the rotation element is rotatable by movement of at least one of the movable elements. 
     The length of the arms of a wheel holder according to the invention can be varied simply by moving the movable elements in the radial direction in order to fix the wheel holder to a wheel and release the same from the wheel, respectively. The synchronization system synchronizes the movements of the movable elements so that all movable elements at all times move synchronously, i.e. all inward or all outward, and across the same movement distance. 
     The rotation element is mounted on the base plate of the wheel holder with a freewheeling system. The freewheeling system has at least one operating state in which the rotation element can be rotated in a freewheeling direction and rotation of the rotation element is blocked in a blocking direction opposite to the freewheeling direction. 
     In particular, the freewheeling system has a first and a second operating state, with the freewheeling direction and the blocking direction being mutually reversed in the first and second operating states. 
     The invention also comprises a method of mounting a wheel holder according to the invention to a wheel, in particular a wheel of a motor vehicle. The method comprises the steps of bringing the freewheeling system into a mounting state in which the movable elements can be moved outward in the radial direction into a mounting position and inward movement of the movable elements is blocked. The method comprises furthermore the step of moving the movable elements outward in the radial direction so as to increase the lengths of the arms; applying the wheel holder with the extended arms to a wheel, in particular a wheel of a motor vehicle; bringing the freewheeling system into a fixing state in which the movable elements can be moved inward in the radial direction and outward movement of the movable elements is blocked; and moving the movable elements inward in the radial direction into a fixing position in which they fix the wheel holder to the wheel. The method may comprise furthermore the step of exerting, by a clamping device, additional forces directed towards the center on the movable elements in order to fix the wheel holder to the wheel in particularly secure manner. 
     The invention also comprises a method of removing a wheel holder according to the invention from a wheel, in particular from a wheel of a motor vehicle. The method comprises the steps of bringing the freewheeling system into the mounting state in which the movable elements can be moved outward in the radial direction and inward movement of the movable elements is blocked; moving the movable elements outward in the radial direction into a mounting position so as to increase the lengths of the arms; and removing the wheel holder from the wheel. If the wheel holder is provided with a clamping device, the method comprises in addition the step of releasing the damping device so as to be able to move the movable elements outward in the radial direction. 
     A wheel holder according to the invention can be easily and securely mounted to a wheel and unmounted from the wheel. Due to the blocking effect of the freewheeling mechanism in the mounting state, the movable elements need not be held in the mounting position by muscle power when the wheel holder is applied to the wheel. In particular, there is no risk that the movable elements move inwardly in uncontrolled manner. The risk of injury during mounting of the wheel holder is thus reduced considerably. A wheel holder according to the invention is equally suitable for right and left-handers. 
     In one embodiment, the freewheeling system is in the form of a ratchet mechanism having a toothed rotor and at least one movable locking member engaging with teeth of the rotor. A ratchet mechanism, as it is used e.g. also in tools, makes available a reliable and proven freewheeling system. Instead of a ratchet mechanism, it is however also possible to make use of other kinds of freewheeling mechanisms. For example, also freewheeling mechanisms as they are used on the rear wheels of bicycles. 
     In one embodiment, the freewheeling system can be switched between a first operating state, in which the rotation element can be rotated in clockwise direction with respect to the arms and anticlockwise rotation of the rotation element is blocked, and a second operating state, in which the rotation element can be rotated in anticlockwise direction with respect to the arms and clockwise rotation of the rotation element is blocked. In this manner, the freewheeling system can be switched between the mounting state and the fixing state. 
     In one embodiment, the freewheeling system can be switched into a third operating state in which the rotation element can be rotated freely in both directions. The blocking function of the freewheeling mechanism is deactivated in this operating state, and the movable elements are freely movable in both directions, i.e. inward and outward. 
     In this third operating state, the wheel holder or adapter behaves like a conventional wheel adapter without a freewheeling system. The third operating state allows a user familiar with the use of a conventional wheel adapter to make use of a wheel adapter according to the invention without having to adapt. The range of the application of the wheel adapter is thus increased. 
     In one embodiment, the wheel holder comprises a clamping device which is designed to apply a force to the freewheeling system in a tensioned state in order to apply additional forces (“tensioning forces”) which are directed towards the center of the wheel holder, to the movable elements by rotation of the freewheeling system. By applying additional forces to the movable elements, which are directed towards the center of the wheel holder, the wheel holder can be fixed to the wheel in particularly secure manner. 
     In one embodiment, the clamping device comprises a clamping handle and a clamping force transmitting element. The clamping force transmitting element is adapted to transfer a clamping force exerted on the clamping handle to the ratchet system or the rotation element. The clamping force transmitting element may comprise a rod, a chain, a wire or cable pull, a belt and/or a hydraulic system. 
     In one embodiment, the clamping device comprises a locking mechanism permitting locking of the clamping device in a tensioned state, so that the clamping force generated by the clamping device is applied to the movable elements without further action of a user, in particular without manual holding of the clamping handle. The locking mechanism may comprise in particular a releasable ratchet mechanism, e.g. with a serrated tooth geometry which automatically locks the clamping device in a tensioned state and which can be released so as to permit removal of the wheel holder from the wheel. 
     In one embodiment, the freewheeling system has a main body which is rotatably mounted on the base plate, and a rotation body connected to the rotation element. The force transmitting element is connected to the main body of the freewheeling system in order to permit, by applying a tensioning force to the main body of the freewheeling system, tensioning of the rotation element in such a manner that it exerts an additional force on the movable elements. 
     In one embodiment, the wheel holder comprises at least one drive device which is connected to one of the movable elements via a force transmitting element and is designed to apply to said one movable element a force directed towards the center of the wheel holder via the force transmitting element. 
     In one embodiment, the at least one force transmitting element extends substantially parallel to one of the arms, in particular along one of the arms of the wheel holder. In this manner, the force may be transferred from the drive device to the movable elements of the wheel holder in particularly efficient manner. 
     In one embodiment, the at least one force transmitting element comprises a rod, a chain, a wire, a cable pull, in particular a steel cable pull as it is used in a Bowden cable, or a belt. Such a force transmitting element is flexible so that it can be routed easily between the drive device and the respective movable element. A flexible force transmitting element, for example, can be passed around rollers. A flexible force transmitting element can also be wound onto a rotary element, for example a wheel, a roller or a drum, of the drive device so as to apply a tensile force or traction to the movable element, 
     In one embodiment, the at least one drive device comprises a wheel, a roller or a drum, and the at least one force transmitting element can be wound onto the wheel, the roller or the drum in order to apply a tensile force to the movable element. In one embodiment, the wheel, roller or drum is rotatable about an axle that is aligned orthogonal to a common plane of the arms. In this manner, the tensile force can be transferred efficiently from the drive device to one of the movable elements. 
     In one embodiment, the at least one drive device comprises an elastic element that is designed to drive the force transmitting element. The elastic element may be a spiral spring, for example. A spiral spring allows the provision of an inexpensive and reliable drive device. 
     In one embodiment, the at least one drive device is arranged outside of the center of the wheel holder, in particular spaced apart from a central axis about which the rotation element rotates (“rotation element axis”). In one embodiment, the at least one drive device is arranged in particular in a region/angle between two adjacent arms of the wheel holder. In particular, the at least one drive device may be arranged near the base plate and/or adjacent the base plate between two adjacent arms of the wheel holder. 
     Such a configuration permits a particularly space-saving and compact construction of the wheel holder. In particular, the dimension (thickness) of the wheel holder in a direction orthogonal to the plane spanned by the arms of the wheel holder can be kept small. Furthermore, such a configuration permits an efficient transfer of the force generated by the at least one drive device to one of the movable elements. 
     In another embodiment, the at least one drive device is arranged in the center of the wheel holder, in particular on the rotation element axis. 
     In one embodiment, the wheel holder comprises at least two drive devices and at least two force transmitting elements. By making use of two or more drive devices, the elastic force acting in total on the movable elements (“overall force”) can be increased. By applying a high overall force, the wheel holder can be fixed to the wheel in particularly secure and tight manner. 
     In one embodiment, the drive devices are arranged between different arms of the wheel holder and act on different movable elements of the wheel holder. By distributing the forces exerted by the drive devices to several movable elements, it is possible to reduce the forces acting on the coupling elements and the rotation element. The coupling elements and the rotation elements can then be formed less massive, i.e. lighter and of less material, and thus can be formed at lower costs. 
     In one embodiment, the rotation element is rotatable about a rotation element axis that is aligned orthogonal to a common plane of the arms, and/or the coupling elements extend substantially parallel to a virtual plane spanned by the arms. In this manner, the movements of the movable elements can be synchronized with each other in particularly efficient manner. 
     In one embodiment, the rotation element is designed as a star-shaped rotation element comprising a central portion and at least two rotation element arms, and each of the coupling elements is connected to one of the rotation element arms. By way of a star-shaped rotation element formed with the rotation element arms, it is possible to realize, with little material usage, a mechanical transmission in order to increase the movement distances over which the coupling elements move when the rotation element is rotated by a predetermined angle. 
     In one embodiment, the coupling elements are each pivotably connected to the rotation element and the movable elements in order to enable an efficient transmission of force from the rotation element to the movable elements. 
     In one embodiment, the wheel holder has three arms that allow the wheel holder to be securely attached to a wheel. In particular, the three arms can be aligned in a symmetric configuration with equal angular distances of 120°, with other angular distances, however, being possible as well. 
     In other possible embodiments the wheel holder has more than three arms. 
     An exemplary embodiment of a wheel holder according to the invention will be described in more detail in the following with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic representation of a wheel with a wheel holder attached to the wheel. 
         FIG. 2  shows a perspective view of a wheel holder according to an embodiment the invention. 
         FIG. 3  shows a plan view of the wheel holder shown in  FIG. 2 . 
         FIG. 4  shows an exploded view of the wheel holder shown in  FIGS. 2 and 3 . 
         FIG. 5  shows an exploded view of a drive device as it is used with the wheel holder shown in  FIGS. 2 to 4 . 
         FIG. 6  shows a perspective view of a freewheeling system as it is used with the wheel holder shown in  FIGS. 2 to 4 . 
     
    
    
     DESCRIPTION OF THE FIGURES 
       FIG. 1  shows a simplified schematic representation of a wheel  1  together with a wheel holder or wheel clamp  2  which is mounted on the wheel  1  and has a target  3  attached thereto. 
       FIG. 2  shows a perspective view of a wheel holder  2  according to an exemplary embodiment of the invention.  FIG. 3  shows a plan view of the wheel holder shown in  FIG. 2 , and  FIG. 4  shows an exploded view of the wheel holder  2  shown in  FIG. 2 . 
     The wheel holder  2  comprises a base plate  10  and three arms  22 ,  23 ,  24  extending radially outward from a central portion (“center”)  28  of the wheel holder  2 . The arms  22 ,  23 ,  24  extend substantially parallel to the plane of the base plate  10 . The arms  22 ,  23 ,  24  may be, but do not have to be, aligned at equal angular distances of 120° relative to one another. 
     One of the arms  22 ,  23 ,  24  has a handle  15  formed thereon for facilitating transport and handling of the wheel holder  2 . 
     A central axis (“rotation element axis”)  30  extends orthogonal to the base plate  10  through the center  28  of the wheel holder  2 . 
     The arms  22 ,  23 ,  24  each comprise a stationary inner element  32   b,    33   b,    34   b  and a movable outer element  32   a,    33   a,    34   a  which is movable with respect to the stationary elements  32   b,    33   b ,  34   b  and is movable, in particular slidable, along the respective inner element  32   b,    33   b,    34   b  in the radial direction. The length of the arms  22 ,  23 ,  24  in the radial direction can thus be varied by moving, in particular sliding, the outer elements  32   a,    33   a,    34   a  along the inner elements  32   b,    33   b,    34   b.    
     At outer ends of the outer elements  32   a,    33   a,    34   a  facing away from the center  28 , claws  12 ,  13 ,  14  are mounted which extend substantially at right angles to the arms  22 ,  23 ,  24 . The claws  12 ,  13 ,  14  are designed to rest on the tread surface  7  of a wheel  1  (not shown in  FIGS. 2 to 4 ) when the wheel holder  2  is attached to the wheel  1 , as shown in  FIG. 1 , in order to fix the wheel holder  2  to the wheel  1 . 
     By moving/sliding the outer elements  32   a,    33   a,    34   a  outward in the radial direction, the length of the arms  22 ,  23 ,  24  is extended so that the wheel holder  2  can be easily attached to the wheel  1  in the axial direction of the wheel  1 . By moving the outer elements  32   a,    33   a,    34   a  inward, i.e. in the direction towards the center  28 , the length of the arms  22 ,  23 ,  24  is decreased, so that the claws  12 ,  13 ,  14  rest on the tread surface  7  of the wheel  1  and fix the wheel holder  2  to the wheel  1 , as shown in  FIG. 1 , 
     A wheel holder  2  according to an exemplary embodiment of the invention comprises furthermore a central rotation element  40 , for example a rotation plate  40 . The rotation element  40  is mounted on the central axis  30  in the center  28  of the base plate  10  such that it can be rotated about the central axis  30 . The rotation element  40  extends substantially parallel to the virtual plane spanned by the base plate  10  and the arms  22 ,  23 ,  24 . 
     Each of the movable elements  32   a,    33   a,    34   a  is connected to the rotation element  40  by a respective coupling element  52 ,  53 ,  54 . 
     An inner end  52   b,    53   b,    54   b  of each coupling element  52 ,  53 ,  54 , which is directed towards the center  28 , is movably, in particular pivotably, connected to the rotation element  40 . An outer end  52   a,    53   a,    54   a  of each coupling element  52 ,  53 ,  54 , which is directed away from the center  28 , is movably, in particular pivotably, connected to one of the movable elements  32   a,    33   a,    34   a.  The coupling elements  52 ,  53 ,  54  are thus pivotable with respect to the rotation element  40  and the movable elements  32   a,    33   a,    34   a  in a plane extending substantially parallel to the plane of the base plate  10 . 
     The coupling elements  52 ,  53 ,  54  transform any rotational movement of the rotation element  40  about the central axis  30  into translational movements of the movable elements  32   a,    33   a,    34   a  in the radial direction along the stationary inner elements  32   b,    33   b,    34   b,  and vice versa. Thus, by rotating the rotation element  40  about the central axis  30 , the movable elements  32   a,    33   a,    34   a  can be moved synchronously in the radial direction along the inner elements  32   b,    33   b,    34   b  in order to thus vary the length of the arms  22 ,  23 ,  24 . Likewise, the rotation element  40  rotates about the central axis  30  when the movable elements  32   a.    33   a,    34   a  are moved in the radial direction along the inner elements  32   b,    33   b,    34   b.    
     By way of the rotation element  40  and the coupling elements  52 ,  53 ,  54 , the movable elements  32   a,    33   a,    34   a  of the arms  22 ,  23 ,  24  are coupled to one another such that all movable elements  32   a,    33   a,    34   a,  and thus also the claws  12 ,  13 ,  14 , move synchronously, i.e. in the same direction (“inward” or “outward”) and at the same speed, when one of the movable elements  32   a,    33   a,    34   a  is moved. The rotation element  40  and the coupling elements  52 ,  53 ,  54  thus constitute a synchronization system. 
     The distance between the claws  11 ,  12 ,  13  of a wheel adapter  2  according to the invention can thus be easily adjusted by moving one of the movable elements  32   a,    33   a,    34   a,  such that the wheel holder  2  can be easily, in particular with just one hand, applied to the wheel  1 . 
     In the exemplary embodiment shown in  FIGS. 2 to 4 , the coupling elements  52 ,  53 ,  54  are designed as coupling rods  52 ,  53 ,  54 , The coupling rods  52 ,  53 ,  54  may be formed of e.g. stamped sheet metal parts. 
     The coupling elements  52 ,  53 ,  54  may also have a different shape, as long as they fulfill the previously described function of coupling the rotation element  40  with the movable elements  32   a,    33   a,    34   a  such that rotational movement of the rotation element  40  causes translational movements of the movable elements  32   a,    33   a,    34   a,  and vice versa. 
     In the exemplary embodiment shown in  FIGS. 2 to 4 , the rotation element  40  is in the form of a star-shaped rotation element  40  with three rotation element arms (“rotation element projections”) which extend radially outward from a central portion of the rotation element  40 . The inner ends  52   b,    53   b,    54   b  of the coupling elements  52 ,  53 ,  54  are each pivotably connected to an outer portion of one of the rotation element arms  42 ,  43 ,  44 . 
     By way of a star-shaped design of the rotation element  40 , it is possible with little expenditure and little material usage to implement a mechanical transmission which increases the distance over which the movable elements  32   a,    33   a,    34   a  move in the radial direction when the rotation element  40  is rotated about the central axis  30  by a predetermined angle. 
     However, the rotation element arms  42 ,  43 ,  44  of the rotation element  40  shown in the figures are not a necessary feature of the invention. The rotation element  40  may also be in the form of e.g. a round, in particular a circular or elliptical, disk or an angular, e.g. triangular, square or polygonal, disk. 
     A wheel holder  2  formed in accordance with an exemplary embodiment of the invention comprises, furthermore, at least one drive device  64  designed for driving or drivingly moving at least one of the movable elements  32 ,  33 ,  34 . 
     The wheel holder  2  shown in  FIGS. 2 to 4  comprises one single drive devices  64  which is designed to drive the movable element  34   a  of an arm  24 . However, a wheel holder  2  according to an exemplary embodiment of the invention may also comprise a plurality of drive devices  64 , in particular a separate drive device  64  for each one of the arms  22 ,  23 ,  24 . 
     The drive device  64  is arranged between two adjacent arms  23 ,  24  of the wheel holder  2 . In particular, the drive device  64  is arranged in the angle that is formed by two adjacent arms  23 ,  24  at the base plate  10 . 
     In an alternative embodiment, not shown in the figures, the drive device  64  is arranged in the center  28  of the wheel holder  2 , in particular on the central axis (“rotation element axis”)  30 . 
     The drive device  64  is connected to an inner end of an associated force transmitting element  74 . An outer end of the force transmitting element  74  is connected to the movable element  34   a , 
     Together with the force transmitting element  74 , the drive device  64  forms a drive system  64 ,  74  which drives or drivingly moves the movable element  34   a  connected to the force transmitting element  74 . In particular, the drive device  64  is designed to apply an elastic force to the force transmitting element  74  which elastically pulls the force transmitting element  74 , and thus also the movable element  34   a  connected to the force transmitting element  74 , in the direction towards the center  28  of the wheel holder  2 . 
     Although the wheel holder  2  shown in  FIGS. 2 to 4  has only one drive device  64  which drives only one of the movable elements  32   a,    33   a,    34   a,  the coupling/synchronization of the movable elements  32   a,    33   a,    34   a  by way of the synchronization system  40 ,  52 ,  53 ,  53  has the effect that the movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  of the wheel holder  2  move synchronously in the radial direction along the stationary elements  32   b,    33   b,    34   b  of the arms  22 ,  23 ,  24 , when at least one of the movable elements  32   a,    33   a,    34   a  and/or one of the claws  12 ,  13 ,  14  is moved. 
     In particular, the movable elements  32   a,    33   a,    34   a  and/or claws  12 ,  13 ,  14  can be moved outward against the elastic force generated by the drive device  64 , which acts in the direction towards the center  28  of the wheel holder  2 , e.g. by muscle power in order to extend the arms  22 ,  23 ,  24  such that the wheel holder  2  can be conveniently attached to a wheel  1  or removed from the same. 
     Due to the elastic force generated by the drive device  64 , which is directed towards the center  28  of the wheel holder  2 , the wheel holder  2  automatically adapts to different sizes (diameters D) of the wheel  1  in the radial direction within the scope of movement, i.e. the maximum path length, of the outer elements  32   a,    33   a,    34   a.  A wheel holder  2  according to the invention thus can be very easily attached to wheels  1  of different sizes and removed from such wheels  1 . 
       FIG. 5  shows an enlarged exploded view of a drive device  64  as it may be used in a wheel holder  2  formed in accordance with an exemplary embodiment of the invention. 
     The drive device  64  shown in  FIG. 5  has a substantially rotationally symmetrical housing  104  extending about a central axle  114 . Mounted on the axle  114  is a drum  94 . The drum  94  is rotatable about the axle  114  and designed to wind up a flexible force transmitting element  74 , e.g. a flexible steel rope, on the drum  94 . 
     The axle  114  is aligned substantially orthogonal to the plane spanned by the arms  22 ,  23 ,  24  of the wheel holder  2 . 
     The flexible force transmitting element  74  may also be in the form of a chain, belt, wire or the like, as long as it can be wound onto a drum  94  or a wheel or similar rotating element not shown in the figures, and is capable of transferring a sufficiently large force from the drive device  64  to the movable element  34   a.    
     Between the drum  94  and the axle  114 , there is disposed an elastic element  84 , for example a spiral spring. The elastic element  84  is connected to the drum  94  and the axle  114  such that it drivingly moves the drum  94  so that the drum  94  endeavors to rotate about the axle  114  and, in doing so, to wind up and thus shorten the flexible force transmitting element  74 . 
     By winding-up the flexible force transmitting element  74  on the drum  94 , the force transmitting element  74  exerts an elastic (tensile) force on the movable element  34   a  connected to the second end of the force transmitting element  74  (not shown in  FIG. 5 ), with the elastic force trying to pull the movable element  34   a  in the direction towards the center  28  of the wheel holder  2 . 
     When the claws  12 ,  13 ,  14  of the wheel holder  2  are pulled apart, the force transmitting element  74  is unwound from the drum  94 . 
     The rotation of the drum  94  about the axle  114  which is caused by unwinding the force transmitting element  74  from the drum  94 , effects additional tension in the elastic element  84  connected to the drum  94 . The movable element  34   a  of the wheel holder  2  is thus pulled again in the direction towards the center  28  of the wheel holder  2  by the force transmitting element  74 , as soon as the force applied by a user for pulling apart the movable elements  32   a,    33   a,    34   a  or claws  12 ,  13 ,  14  is removed, e.g. because the claws  12 ,  13 ,  14  are released. 
     The rotation element  40  is attached to the base plate  10  of the wheel holder via a freewheeling system  100 . A perspective external view of the freewheeling system  100  is shown in  FIG. 6 . 
     The freewheeling system  100  comprises a main body  108  attached to the base plate  10 , and a rotation body  103  which is rotatable with respect to the main body  108 . The rotation element  40 , which is not shown in  FIG. 6 , is mounted on the rotation body  103 . 
     The freewheeling system  100  comprises furthermore a switching lever  106  which permits switching of the freewheeling system  100  between at least two different operating states. 
     In a first operating state, the rotation body  103  together with the rotation element  40  is rotatable with respect to the main body  108  in clockwise direction (“freewheeling direction”), as shown in the illustration in  FIGS. 2 and 3 , whereas rotation of the rotation body  103  in the opposite direction (“blocking direction”), i.e. anti-clockwise, is blocked. 
     In the first operating state, the movable elements  32   a,    33   a,    34   a  along with the claws  12 ,  13 ,  14  can be moved, by muscle power and/or by the force generated by the drive device  64 , in the direction towards the center  28  of the wheel holder  2  in order to press the claws  12 ,  13 ,  14  against the tread surface  7  of a wheel  1  and to thus securely fix the wheel holder  2  to the wheel  1 , The first operating state thus is a fixing state. 
     Due to the fact that the rotation element  40  and the rotation body  103 , in the first operating state/fixing state cannot be rotated in anticlockwise direction with respect to the main body  108 , the respective movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  cannot be moved outwardly in the first operating state/fixing state for extending the arms  22 ,  23 ,  24  to permit removal of the wheel holder  2  from the wheel. 
     For being able to remove the wheel holder  2  from the wheel  1 , the freewheeling system  100  is brought into a second operating state by shifting the switching lever  106 . In the second operating state, the rotation body  103  together with the rotation element  40 , in the illustration shown in  FIGS. 2 and 3 , is rotatable in anticlockwise direction with respect to the main body  108 , whereas rotation of the rotation body  103  in the opposite direction, i.e. in clockwise direction, is blocked. 
     Thus, in the second operating state, the freewheeling direction and the blocking direction are mutually reversed with respect to the first operating state. 
     In the second operating state, the movable elements  32   a,    33   a,    34   a  together with the claws  12 ,  13 ,  14  can be moved outwardly from the center  28  of the wheel holder  2   y,  e.g. by muscle power, in order to be thus able to remove the claws  12 ,  13 ,  14  and the wheel holder  2  from the wheel  1 . Also, the movable elements  32   a,    33   a,    34   a  together with the claws  12 ,  13 ,  14  can be moved outwardly in the second operating state, before the wheel holder  2  is applied to the wheel  1 , in order to thus match the distance between the claws  12 ,  13 ,  14  to the size of the wheel  1 , so that the wheel holder  2  can be applied conveniently to the wheel. The second operating state thus is a mounting state. 
     In the second operating state/mounting state, the blocking effect of the freewheeling system  100  prevents the movable elements  32   a,    33   a,    34   a  along with the claws  12 ,  13 ,  14  to be pulled by the drive device  64  in the direction towards the center  28 . Thus, in the second operating state/mounting state, the movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  remain in their outwardly pulled positions until the freewheeling system  100  is brought into the first operating state/fixing state. 
     Due to the fact that the movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  in the second operating state/mounting state do not have to be retained in their outer positions by muscle power, handling of the wheel holder  2  is simplified. Moreover, operational safety is enhanced, since uncontrolled “snapping back” of the movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  in the direction towards the center  28  of the wheel holder  2  is prevented by the blocking effect of the freewheeling system  100 . 
     Optionally, the freewheeling system  100  may have a third operating state in which the blocking function is deactivated in both directions, so that the rotation body  103  is rotatable with respect to the main body  108  in both directions. 
     Switchable freewheeling systems  100  that are suitable for use in a wheel holder  2  according to the invention are known to the skilled person. 
     A freewheeling system  100 , for example, may be formed with an externally toothed rotor which is connected to the rotation body  103 , and with a locking member which is connected to the main body  108  and engages with the external teeth of the rotor such that the rotor can be rotated in one direction only (“freewheeling direction”), while the locking member blocks rotation of the rotor in the opposite direction (“blocking direction”). 
     In a wheel holder  2  according to the invention, there may also be used other known, in particular switchable, freewheeling mechanisms, in particular freewheeling mechanisms with low friction in the freewheeling direction and/or with a sufficiently high holding force in the blocking direction. 
     In a wheel holder  2  according to the invention, the main body  108  of the freewheeling system  100  is rotatably attached to the base plate  10 . The main body  108  is provided with a clamping lever  102  extending from a central portion of the main body  108  outward in the radial direction. 
     A clamping force transmitting element  120  (see  FIGS. 2 to 4 ) connects the clamping lever  102  to clamping handle  122  provided at the handle  15  of the wheel holder  2 . The clamping handle  102  and the clamping force transmitting element are constituent parts of a clamping device  120 ,  122 . By operating the clamping handle  122 , the clamping device  120 ,  122  allows an additional force to be applied to the freewheeling system  100 , which pushes the claws  12 ,  13 ,  14  still tighter against the tread surface  7  of the wheel  1  in order to fix the wheel holder  2  still more securely to the wheel  1 . 
     In/at the handle  15  of the wheel holder  2 , there is formed a locking mechanism  124 . The locking mechanism  124  permits fixing of the clamping handle  122  and/or the clamping force transmitting element  102  in a tensioned position, in which the additional force is applied to the claws  12 ,  13 ,  14 , without requiring a user of the wheel holder  2  to constantly exert muscle power for retaining the clamping handle  122  in a tensioned position. 
     The locking mechanism  124  is releasable to permit release of the clamping device  120 ,  122 , so that the wheel holder  2  can easily be unmounted from the wheel  1 . 
     The clamping force transmitting element  120  may be provided in the form of a cable wire (e.g. a “Bowden cable”), in particular with a steel rope as shown in  FIGS. 2 to 4 . As an alternative, the clamping force transmitting element  120  may comprise a rod, a chain, a belt and/or a hydraulic system for transferring the force exerted on the clamping handle  122  to the clamping lever  102  of the freewheeling system  100 . 
     For mounting a wheel holder  2  formed according to an exemplary embodiment of the invention to a wheel  1 , the freewheeling system  100  is brought first into the mounting state, in which it is possible to pull the movable elements  32   a,    33   a,    34   a  with the claws  12 ,  13 ,  14  outwardly against the force of the drive device  64 , and to increase the distance between the claws  12 ,  13 ,  14  (i.e. the “diameter” of the wheel holder  2 ) such that the wheel holder  2  can easily be applied to the wheel  1 . The blocking effect of the freewheeling system  100  in the mounting state prevents undesired “snapping back” of the claws  12 ,  13 ,  14  in this state. Thus, the claws  12 ,  13 ,  14  need not be held in a pulled apart state by muscle power when the wheel adapter  2  is applied to the wheel  1 . 
     The wheel holder  2  is applied to the wheel in the expanded state such that the claws  12 ,  13 ,  14  extend across the tread surface  7  of the wheel  1 . 
     By shifting the switching lever  106 , the freewheeling system  100  is then switched from the mounting state to the fixing state. In the fixing state, the freewheeling system  100  sets free rotation of the rotation element  40  such that the movable elements  32   a,    33   a,    34   a  with the claws  12 ,  13 ,  14  are pulled “inward” by the force of the drive device  64  in the direction towards the center  28  of the wheel holder  2 . The claws  12 ,  13 ,  14  are thereby pressed against the tread surface  7  of the wheel  1  and thereby fix the wheel holder  2  to the wheel  1 . 
     The blocking effect of the freewheeling system  100  in the fixing state prevents the movable elements  32   a,    33   a,    34   a  from moving outward again so as to release the claws  12 ,  13 ,  14  from the tread surface  7  of the wheel  1 . 
     When the claws  12 ,  13 ,  14  rest on the tread surface  7  of the wheel  1 , it is possible by actuation of the clamping handle  122  to exert an additional force, via the clamping force transmitting element  120 , the freewheeling system  100  and the synchronization system  40 ,  52 ,  53 ,  54 , to the movable elements  32   a,    33   a,    34   a  and the claws  12 ,  13 ,  14  in order to fix the wheel holder  2  still more tightly to the wheel  1 . 
     The clamping handle  122  can be fixed in the tensioned position by the locking mechanism  124  so that it is not necessary to permanently grip or hold the clamping handle  122 . 
     For unmounting the wheel holder  2 , the locking mechanism  124  is released first, In addition, the freewheeling system  100  is returned to the mounting state by shifting the switching lever  106 , in which it is possible to move the movable elements  32   a,    33   a,    34   a  with the claws  12 ,  13 ,  14  outwardly so as to permit simple removal of the wheel holder  2  from the wheel  1 . In doing so, the blocking effect of the freewheeling system  100  in the mounting state prevents the movable elements  32   a,    33   a,    34   a  with the claws  12 ,  13 ,  14  from moving inward due to the force exerted by the drive device  64 . The wheel holder  2  can thus be removed easily from the wheel  1  without the claws  12 ,  13 ,  14  having to be retained against the force of the drive device  64 . In particular, there is no risk of injury by claws  12 ,  13 ,  14  snapping back in uncontrolled manner. 
     A wheel holder  2  formed in accordance with an exemplary embodiment of the invention can thus be easily and securely mounted on a wheel  1  and unmounted from the wheel  1 .