Abstract:
The invention relates to a popular amusement device with a personal transportation device, moving along a guide track arrangement ( 14 ), and eddy-current braking device ( 10, 70 ), comprising a magnet arrangement ( 10 ) and an induction body ( 70 ), for the selective braking of the personal transportation device, with one of the pieces of either the magnet arrangement ( 10 ) or the induction body ( 70 ) being provided on a guide track arrangement ( 14 ) and the other piece ( 10  or  70 ) being connected to the personal transportation device. The magnet arrangement ( 10 ) comprises at least two partial magnet arrangements ( 18, 20 ) each with at least one permanent magnet ( 74, 76, 78, 82, 84, 86 ), said partial magnet arrangements ( 18, 20 ) are, at least in the operating position thereof, arranged essentially orthogonal to the braking area guide track direction (B), at a separation (a) from each other, with the induction body ( 70 ) being arranged between the partial magnet arrangements ( 18, 20 ) during the braking. According to the invention, the partial magnet arrangements ( 18, 20 ) may be displaced relative to each other.

Description:
This application is a 35 U.S.C. § 371 National Phase Entry Application from PCT/EP02/13135, filed Nov. 22, 2002, and designating the United States. 
   FIELD OF THE INVENTION 
   The present invention relates to a popular amusement device having a personal transportation device moving along a guide track arrangement and an eddy-current braking device comprising a magnet arrangement and an induction body for selective braking of the personal transportation device. 
   BACKGROUND OF THE INVENTION 
   To form a braking zone on the guide track arrangement, one of the parts, i.e., either the magnet arrangement or the induction body, is provided on the guide track arrangement while the other part is connected to the personal transportation device, and the magnet arrangement has at least two partial magnet arrangements, each having at least one permanent magnet, said partial magnet arrangements being arranged at a distance from one another and essentially perpendicular to the direction of the braking zone guide track in at least one of their operating positions, with the induction body being arranged between the partial magnet arrangements during braking. 
   Such a popular amusement device is disclosed in European Patent 0 820 333 B1. Use of permanent magnets in the magnet arrangement is desirable for safety reasons because in contrast with electromagnets, the magnetic field emanating from permanent magnets does not depend on a power supply and thus the eddy-current braking device continues to supply the desired braking force even in the event of a power failure. However, the variability, i.e., controllability, of the braking force of an eddy-current brake with permanent magnets is still a problem. 
   In the publication cited above, it is proposed that the entire magnet arrangement and the induction body be moved away from and toward one another in order to diminish or interrupt the braking force acting between the magnet arrangement and the induction body in the case of an eddy-current brake on a popular amusement device. To do so, the entire magnet arrangement and/or the induction body is situated movably on the device supporting it and is provided with an actuator drive. 
   One disadvantage of this method of varying a braking force of an eddy-current braking device is that the braking force acting between the magnet arrangement and the induction body can be adjusted only approximately and it can be used practically only between a predetermined braking position with a relatively high braking force and a zero braking force position with and without a negligible braking force. 
   Furthermore, when the magnet arrangement is moved away from the induction body to reduce the coverage between these two parts, relatively large masses are moved, which results in relatively long switching times, and shortening these times in turn requires efficient and expensive actuator drives. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is thus to make available a popular amusement device of the type defined in the preamble in which the braking force acting between the magnet arrangement and the induction body is adjustable as rapidly and accurately as possible and with the lowest possible effort. This object is achieved by a popular amusement device of the generic type in which the partial magnet arrangements are movable in relation to one another. 
   The term “popular amusement device” refers here to transportation businesses in the broadest sense such as those associated with amusement parks, seasonal fairs and popular festivals. These include, for example, drop towers, the tunnel of horrors, roller coasters, etc. 
   The braking zone is an area of the guide track arrangement, preferably a continuous area, in which an eddy-current-based braking force can act between the magnet arrangement and the induction body. The braking zone includes at least the longitudinal section of the guide track in which one of the parts of the magnet arrangement or the induction body is arranged on it. The direction of the braking zone guide track is accordingly the direction of the path of the guide track arrangement in the braking zone. 
   Due to the mobility of the partial magnet arrangements in relation to one another with the resulting change in orientation of the magnetic field vectors, penetration of the induction body by the magnetic field emanating from the partial magnet arrangements and thus the extent of eddy-currents induced in the induction body, said eddy currents being proportional to the effective braking force, can be adjusted rapidly and accurately. In contrast with the state of the art, the total mass of the magnet arrangement is no longer moved to change the braking force but instead only a portion of it is moved. 
   A concrete possibility for influencing the creation of eddy currents in the induction body consists of varying the orthogonal distance from the direction of the braking zone guide track between the partial magnet arrangements through their movement in relation to one another. This may be accomplished, for example, by the fact that the partial magnet arrangements are pivotable in relation to one another about an axis that is essentially parallel to the direction of the braking zone guide track and/or they are linearly displaceable in relation to one another essentially orthogonally to the direction of the braking zone guide track. However, depending on the embodiment, a residual braking force may remain, although it is unwanted under some circumstances due to stray magnetic fields, and it may still be in effect between the magnet arrangement and the induction body. 
   To avoid this residual braking force and to increase the range of variability of the braking force, the popular amusement device is preferably designed so that the partial magnet arrangements can be displaced linearly in relation to one another with a displacement component that points essentially in the direction of the braking zone guide track. The distance between the partial magnet arrangements remains essentially unchanged as a result, with the only thing that changes being the relative position of the poles of the at least one permanent magnet of each of two partial magnet arrangements situated essentially opposite one another. This type of change in braking force requires only a short contact travel to change the braking force. 
   “Essentially in opposition” means that the at least two partial magnet arrangements at least partially overlap in a projection of the magnet arrangement in the distance direction of the parallel planes when the magnet arrangements are each in one of two parallel planes. 
   It is fundamentally conceivable for each partial magnet arrangement to have only one permanent magnet. In one case, starting from an opposition of one pole of the permanent magnet of one partial magnet arrangement and a pole of a different polarity of the permanent magnet arrangement of the other partial magnet arrangement, the braking force could be reduced starting from a maximum braking force by means of a linear displacement of the partial magnet arrangements in relation to one another. In another case, starting from an opposition of poles of the same polarity, the resulting braking force could be increased from a minimal braking force by a linear displacement of the partial magnet arrangements in relation to one another. 
   The resultant braking force may be increased by each partial magnet arrangement having a plurality of permanent magnets. Protection against power outages as mentioned previously can be achieved in the best possible way here by the fact that the magnet arrangement has exclusively permanent magnets as the magnets. In this case, even if there is a sudden total power outage, the personal transportation device can always be decelerated with maximum braking force. 
   In a particularly advantageous embodiment of an inventive popular amusement device, each partial magnet arrangement has a plurality of permanent magnets following one another in the direction of the braking zone guide track. This allows implementation of even longer braking zones in which a relatively high braking force may be in effect, which in turn permits a high allowed velocity of the personal transportation device prior to the respective braking zone, which thus increases the attractiveness of the popular amusement device. The braking force acting in the braking zone may be further increased by arranging a plurality of permanent magnets of each partial magnet arrangement with alternating polarities. This means that poles of different polarities follow one another in the direction of the braking zone guide track on an area of a partial magnet arrangement pointing to the other partial magnet arrangement. 
   An increased number of pole changes means that a higher maximum braking force can be achieved and also improves the variability of a desired braking force acting between the magnet arrangement and the induction body. By displacement of the partial magnet arrangements in relation to one another with a displacement component pointing essentially in the direction of the braking zone guide track, any braking force can be established between a maximum braking force and a virtually negligible minimal braking force. In the preferred embodiment discussed here, the direction of the braking zone guide track is the same as the direction of extent of the partial magnet arrangement. The required maximum displacement distance (contact travel) amounts to one pole pitch length. 
   The maximum braking force is achieved when as many permanent magnet poles as possible of the one partial magnet arrangement of permanent magnet poles of different polarities are arranged opposite another partial magnet arrangement. Magnetic field penetration of the induction body is at a maximum in this position during braking. The minimum braking force is obtained by analogy when as many permanent magnet poles as possible of the one partial magnet arrangement are arranged opposite permanent magnet poles of the same polarity of another partial magnet arrangement, which leads to minimum magnetic field penetration of the induction body during braking. 
   The phrase “as many as possible” takes into account the fact that even with an optimum design of the partial magnet arrangements in one of the two positions, namely maximum braking force position or minimum braking force position, at least one permanent magnet pole lying at one longitudinal end of a partial magnet arrangement in a direction of the braking zone guide track is not opposite any permanent magnet pole of another partial magnet arrangement. 
   A flexible variability of the braking force generated by the eddy-current braking device can be achieved by designing the popular amusement device so that the partial magnet arrangements are displaceable between two end positions in relation to one another, one end position of which is closer at a maximum braking force position and possibly coincides with it, and the other end position of which is closer at the minimum braking force position and optionally coincides with it. 
   Depending on the application, magnet arrangements and induction bodies may be distributed in any desired manner on a guide track arrangement and personal transportation device, As a rule, however, the magnet arrangement will have a greater mass than the induction body, and with many popular amusement devices, there is an emphasis on achieving the greatest possible acceleration of the passengers, so it is advantageous if the magnet arrangement is provided on the guide track arrangement and the induction body is provided on the personal transportation device. This distribution of the parts of the eddy-current braking device also has the advantage that a linear motor may be used to drive the personal transportation device, and the induction body may form part of the linear motor. Thus at least parts of the drive and the brake may be used jointly, which thus reduces the total number of parts required. 
   The safety of passengers using the particular device understandably plays a major role in public entertainment devices. The fact that the inventive eddy-current braking device is not sensitive to power failures has already been emphasized repeatedly. Although the magnetic field of the permanent magnets used cannot fail unforeseeably in the case of the public amusement device according to the present invention, it is, however, possible for an actuator drive that is used to generate the relative motion between the partial magnet arrangements to fail. Such an actuator drive may be, for example, a hydraulically or pneumatically operated piston-cylinder unit or an electric motor. However, in the event of failure of the actuator drive, if the magnet arrangement is not in the maximum braking force position, a restoring force of the partial magnet arrangement acting in the direction of a position of higher braking force, said restoring force caused by the magnetic field of the magnet arrangement, can be utilized. This is due to the fact that the minimum braking force position described above is a position of labile equilibrium, whereas the maximum braking force position described above is a position of stable equilibrium of the partial magnet arrangements in relation to one another. 
   This safety feature of the inventive popular amusement devices can be further improved by the fact that of the at least two partial magnet arrangements, a first is rigidly connected to the device supporting it and a second is connected to the device supporting it and is essentially orthogonally to the direction of the braking zone guide track at a distance from the first arrangement, so that it is linearly displaceable with a displacement component pointing essentially in the direction of the braking zone guide track, with a displacement limiting device cooperating with the second partial magnet arrangement, preventing displacement of the second partial magnet arrangement in a relative direction of movement of the induction body in relation to the magnet arrangement beyond the end position closer to the maximum braking force position and from this end position outward against the direction of relative movement. In this case, not only is there a restoring force induced by the magnet arrangement itself acting in the direction of positions of greater braking force between the partial magnet arrangements but also there is a braking response force acting on the partial magnet arrangements in braking as an additional restoring force component. 
   The relative direction of motion provided is the direction in which the induction body passes through the braking zone of the guide track arrangement in relation to the magnet arrangement. The displacement limiting device defines a position having a relatively high braking force, if desired having the maximum braking force, into which the restoring force restores the second partial magnet arrangement and in which it then remains. This displacement limiting device may be formed by a mechanical stop in a simple manner. 
   It is essentially possible for the at least two partial magnet arrangements to be arranged so that they are linearly displaceable in relation to one another with a displacement component essentially in the direction of the braking zone guide track; this is done by providing linear guides on one or both partial magnet arrangements. An especially simple and inexpensive design option for implementing said linear displaceability of the at least two partial magnet arrangements in relation to one another is to connect at least one of the at least two partial magnet arrangements to another of the at least two partial magnet arrangements or to a framework via a parallelogram crank mechanism. With this type of structural design of the magnet arrangement having its own inventive value, the partial magnet arrangement coupled to the parallelogram crank mechanism has a displacement component directed orthogonally to the displacement component pointing in the direction of the braking zone guide track in the case of a relative movement with respect to the other partial magnet arrangement. Only rotary bearings such as friction bearing bushes or roller bearings are needed on the displaceable partial magnet arrangement. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described in greater detail below on the basis of the accompanying drawing, which shows: 
       FIG. 1  a magnet arrangement of an eddy-current braking device of a popular amusement device according to this invention in a maximum braking force position (solid line) and in a minimum braking force position (dashed line), 
       FIG. 2  a view in the direction of the arrow II in  FIG. 1  of the magnet arrangement shown in  FIG. 1  in the maximum braking force position with the induction body, 
       FIG. 3  a sectional view of the magnet arrangement shown in  FIG. 1  with an induction body in the maximum braking force position along line III-III in  FIG. 1  and 
       FIG. 4  a view of the magnet arrangement shown in  FIG. 1 , where this view corresponds to that in  FIG. 2 , showing the induction body in the minimum braking force position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a side view of a magnet arrangement  10  provided on a roller coaster track. The magnet arrangement  10  is connected to a frame  12  which also carries the guide track arrangement of the roller coaster track. The guide track arrangement is formed by a rail system  14 , which is indicated only schematically in  FIG. 1 . Cars of roller coaster trains (not shown) travel along this rail system  14  in the direction of arrow V. 
   Due to the magnet arrangement  10 , a braking zone  16  is formed on the rail system  14 , extending slightly beyond both longitudinal ends of the magnet arrangement  10 , because of the scattering field that emanates from the magnet arrangement  10 . The effective range of the braking zone  16  is indicated by the dotted lines in  FIG. 1 . Accordingly, the direction of the braking zone guide track is the direction of extent of the rail system  14  within the braking zone  16 . This is indicated with the double arrow B in  FIG. 1 . 
   The magnet arrangement  10  includes two partial magnet arrangements designed as magnetic strips  18  and  20 .  FIG. 1  shows only the magnetic strip  18 , but the magnetic strip  20  is covered by it. Although the magnetic strip  20  is rigidly connected by the magnetic strip holder  22  to the frame  12  of the guide track arrangement, the magnetic strip  18  is displaceable in relation to the magnetic strip  20  by a parallelogram crank mechanism  20  with at least one displacement component pointing essentially in the direction B of the braking zone guide track. More precisely, the magnetic strip  18  is displaceable with respect to the magnetic strip  20  in a plane orthogonal to the distance direction between the magnetic strips  18  and  20 . The term “distance direction” is understood to refer to the distance between two parallel planes in which the magnetic strips  18  and  20 , respectively, are situated. The displacement plane of the magnetic strip  18  as well as the planes in which the magnetic strips  18  and  20  are situated are parallel to the plane of the drawing in  FIG. 1 . 
   The parallelogram crank mechanism is formed by control arms  26  and  28 , and on each of the longitudinal ends of said control arms, a ring bushing  30  is formed on the frame end and a ring bushing  32  is formed on the magnetic strip end. The ring bushing  30  on the frame end surrounds a friction bearing (not shown in  FIG. 1 ) which in turn surrounds a bolt  34  situated on the magnetic strip holder  22  (see also  FIG. 3 ). Control arms  26  and  28  can rotate about this bolt  34 . 
   By analogy, the ring bushings  32  on the magnetic strip end of the control arms  26  and  28  surround friction bearings (not shown in  FIG. 1 ) which in turn surround bolts  36  on the magnetic strips  18  and  20 . The ring bushings  30  and  32  are secured on the bolts  34  and  36  by washers  38  and nuts  40 , which are screwed onto the thread  42  formed on the bolts. 
   By means of the parallelogram crank mechanism  24 , the magnetic strip  18  can be displaced in parallel in the displacement plane described above in a range defined by the length of the control arms  26  and  28  without any change in its orientation in the direction B of the braking zone guide track.  FIG. 1  shows the maximum braking force position of the magnetic strip with a solid line and the minimum braking force position of the magnetic strip  18  with a dotted line. The dotted line in  FIG. 1  is labeled with the same reference notation with an added prime (′). 
   A projection  44  pointing in the direction of movement V of the roller coaster train is designed on the ring bushing  32  on the magnetic strip end of the control arm  36 , said projection being surrounded by a fork-like end part  36  of a hydraulically or preferably pneumatically actuated piston-cylinder unit. The end part  46  is attached to the projection  44  by a screw  48  and a nut  50  so that it has one swiveling degree of freedom in the direction of the double arrow S with respect to the projection  44 . By displacement of the piston rod of the piston cylinder unit, the magnet strip  18  can be moved starting from the maximum braking force position shown with a solid line in  FIG. 1  and moved against the direction of travel V of the roller coaster train into any desired position of a lower braking force. The magnetic strip  18  may of course be moved out of any position of a lower braking force into a position of a higher braking force by tightening the piston rod and/or to the position of maximum braking force. 
   A stop surface  52  is formed on the control arm  26  on its end which points in the direction of travel V; in the case depicted here this stop surface comes to rest against a stop  54  that is fixedly attached to the frame in the maximum braking force position. The stop fixedly mounted on the frame is formed by a damping element holder  56  that is fixedly connected to the frame  12  of the guide track arrangement via a framework  58  and screws  60 . To absorb the impact momentum of the control arm  26  on the stop  54  that is fixedly mounted on the frame, a damping element  62  is situated on the damping element holder  56  pointing toward the control arm  26 . 
   From the maximum braking force position according to  FIGS. 1 and 2 , the magnetic strip  18  may thus be displaced selectively into the minimum braking force position according to  FIG. 4  (shown with a dotted line in  FIG. 1 ) by putting the pneumatic piston cylinder unit under pressure or optionally it may also be displaced into the desired intermediate positions for precision metering of the braking force. A reverse movement into the maximum braking force position is achieved by a corresponding reduction in the pneumatic pressure in the piston-cylinder unit, optionally by opening a corresponding vent valve. The magnetic forces acting between the two magnetic strips  18  and  20  acts as the restoring force; these magnetic forces act in the direction of travel V until the north and south poles of the individual magnets of the two magnetic strips  18  and  20  are each opposite poles of the opposite polarity of the other strip (=maximum braking force position according to  FIGS. 1 and 2 ). 
   As an additional safety measure, two parallel-connected vent valves may also be connected to the piston-cylinder unit in a manner not shown here, so that in the event of failure of one of the two valves, the other valve will in any case ensure restoration back to the maximum braking force position. It is thus sufficient for the piston-cylinder unit to be designed to be only single acting. In cases where it is necessary not only to switch between zero braking force and maximum braking force, but where precision braking force control and/or braking force regulation is also important, a double-acting piston-cylinder unit may also be used, preferably with hydraulic triggering. 
   As shown in  FIG. 1 , the magnetic strip  18  can be moved between the two positions, i.e., the maximum braking force position and the minimum braking force position, as indicated by a double arrow A between the corresponding angular positions  27   a  and  27   b  and  29   a  and  29   b  of a longitudinal axis  27  of the control arm  26  and/or a longitudinal axis  29  of the control arm  28 . In the angular positions  27   a  and  29   a , the longitudinal axis is essentially orthogonal to the direction of travel V (and to the direction B of the braking zone guide track). 
   In deviation from this, however, another possible arrangement is one where the maximum braking force position is in mirror symmetry (with respect to a plane perpendicular to the direction of travel V) to the minimum braking force position. The corresponding angle positions  27   c  and  29   c  of the longitudinal axis  27  and  29 , respectively, in the maximum braking force position are indicated with a dash-dot-dot line in  FIG. 1 . The resulting swivel angle range, which is twice as large, is represented by a double arrow A′. Similarly, the stationary magnetic strip  20  is shifted to the left in  FIGS. 1 ,  2  and  4  so that in the maximum braking force position the desired precise opposition of magnetic poles of different polarities is obtained. 
   The structural design of the magnet arrangement  10  in combination with the stop  54  which is fixedly mounted on the frame and the adjustment of the magnetic strip  18  opposite the direction of travel V of the roller coaster train toward diminishing effective braking forces constitutes an important safety feature of this preferred embodiment. Braking response forces acting on the magnetic strip  18  are introduced directly into the stop  54  which is mounted fixedly on the frame in the maximum braking force position. If the magnetic strip  18  is still in its maximum braking force position in the braking operation, regardless of the reason, then the braking response force supports the magnetic restoration to the stable end position, said restoration acting between the magnetic strips  18  and  20 . In other words, if the induction body  70  travels between the two magnetic strips  18  and  20  in the direction of travel V, then a braking force which acts against the direction of travel V acts on the induction body. Accordingly, a braking reaction force which acts in the direction of travel V, i.e., opposite the braking force which acts on the induction body, is acting on each of the magnetic strips. Under some circumstances, this may reset the magnetic strips until striking the stop  54  which is fixedly mounted on the frame, where it reaches the maximum braking force position and remains in this position for the duration of the braking period. 
     FIG. 2  shows a view of the magnet arrangement shown in  FIG. 1  from the standpoint of the arrow II in  FIG. 1 . In contrast to  FIG. 1 , this shows an induction body  70  between the magnetic strips  18  and  20 , fixedly connected to the car (not shown) that is traveling on the rail system  14 . The stop  54  mounted fixedly on the frame is not shown in  FIG. 2  for the sake of simplicity.  FIG. 2  shows the maximum braking force position of the magnet arrangement  10 . 
   As  FIG. 2  shows, the magnetic strips  18  and  20  are arranged essentially parallel to one another with a distance a, which is essentially orthogonal to the direction B of the braking zone guide track. In the example shown here, the magnetic strip  18  is in the plane  19  and the magnetic strip  20  is in the plane  21  which is parallel to the plane  19 . The two planes  19  and  21  are orthogonal to the plane of the drawing in  FIG. 2 . The distance a is greater than the width of the induction body  70  in the distance direction to leave an air gap between the magnetic strips  18  and  20  and the induction body  70  in braking. This air gap is necessary for preventing material friction between the induction body and a magnetic strip  18  or  20 , among other things. In addition, transverse movements of the induction body  70  may occur in the braking of the roller coaster train. Therefore, the air gap should be large enough so that this transverse movement is possible without contacting a magnetic strip. 
   The magnetic strips  18  and  20  are essentially identical in design. In the following discussion, only the magnetic strip will be described, but this description likewise applies to the magnetic strip  20 . 
   The magnetic strip  18  consists of a magnet holder  72  which is preferably made of a ferromagnetic material to produce a magnetic return. For example, three permanent magnets  74 ,  76  and  78  are attached to the surface  72   a  which faces toward the other magnetic strip, namely magnetic strip  20  in this case. If higher braking forces are desired, a greater number of permanent magnets may also be used. 
   In the case of a braking device for a roller coaster train, in general five to ten magnets are used per magnetic strip. The permanent magnets are attached to the respective magnet holder by casting them with synthetic resin. The permanent magnets are secured in place before casting by using securing pins  81  which are inserted into corresponding boreholes in the respective magnet holder  72  and are in contact with the outside circumference of the permanent magnets. 
   The permanent magnets  74 ,  76  and  78  are attached to the magnet holder  72  in such a way that one pole of each permanent magnet points toward the magnet holder  72  and the other pole points away from the magnet holder  72  toward the other magnetic strip. To increase the braking force that can be achieved by the magnet arrangement  10  and the induction body  70 , the permanent magnets  74 ,  76  and  78  of the magnetic strip  18  are arranged with alternating polarities in the direction B of the braking zone guide track, i.e., any permanent magnet of the magnetic strip  18  is arranged so that it is rotated by 180° about an axis oriented in the direction B of the braking zone guide track with respect to a permanent magnet adjacent thereto in the direction of the braking zone guide track. 
   The permanent magnets  82 ,  84  and  86  of the magnet holder  72  of the magnetic strip  20  are arranged essentially in the same way as the permanent magnets  74 ,  76  and  78  but with the opposite polarity on the magnet holder  72  of the magnetic strip  20 . In the maximum braking force position of the magnet arrangement  10  shown in  FIG. 2 , a north pole of the permanent magnet  82  of the magnetic strip  20  is opposite a south pole of the permanent magnet  74  of the magnetic strip  18 . A corresponding arrangement also applies to the permanent magnet  76  to  84  and  78  to  86 . 
   It should be pointed out here that the magnetic strips  18  and  20  in this exemplary embodiment are shown with their length shortened. The magnetic strips may in reality be designed to be longer and may have more than three permanent magnets. Likewise more than two control arms may also be provided. 
     FIG. 3  shows a sectional view along line III-III in  FIG. 1 . This shows mainly the design of the control arm  28 . 
   Between the inside circumferential wall of the ring bushing  30  on the frame end and the bolt  34 , a sliding bushing  90  is situated as the sliding bearing, surrounding the bolt  34 . The sliding bushing  90  is made of a material which forms a favorable friction pairing with the bolt  34 . For example, the sliding bushing  90  may be made of bronze when the bolt  34  is a steel bolt. The bolt  34  may be welded to the magnetic strip holder  22 . 
   The rotary mounting on the bolt  36  with the ring bushing  32  on the magnetic strip end is designed in the same way as the rotary bearing on the bolt  34 . The sliding bushing  92 , which is also used there, should be selected from the standpoint of a good friction pairing with the bolt  36 . The bolt  36  is attached to the magnet holder  72  by a flange section  36   a , e.g., by screwing and/or gluing. 
   For the sake of thoroughness,  FIG. 4  shows a view of the magnet arrangement  10  in the direction of arrow II from  FIG. 1  (this view corresponding to that in  FIG. 2 ) in its minimum braking force position. 
   In the position illustrated in  FIG. 4 , the permanent magnet  80  of the magnetic strip  20  is opposite the permanent magnet  74  of the magnetic strip  18  and another permanent magnet pairing is formed from magnets  76  and  78 . Poles of the same polarity are now opposite one another so that the induction body that moves between the magnetic strips  18  and  20  in the direction of travel V in braking is hardly penetrated by a magnetic field emanating from the magnetic strips  18  and  20 . A stray field may emanate from the magnets  78  and  82  on one longitudinal end of the magnetic strips  18  and  20 , penetrating through the induction body  70  and thus ensuring a slight braking. This residual braking force occurs because no pole of the same polarity of another magnet is opposite said magnet.