Abstract:
A bearing arrangement for the support of tensile forces, in particular for the suspended mounting of a mass, in order to simulate the weightlessness of the latter in a gravitational field, has a first bearing element comprising at least one magnet and a second, metallic bearing element, to which the first bearing element is attracted magnetically. At least one of the bearing elements has, in its bearing surface, gas outflow nozzles which are loaded by a compressed gas, so that a gas stream flowing out of the gas outflow nozzles forms a gas cushion between the bearing elements attracting one another due to the magnetic force, said gas cushion keeping the bearing elements at a distance from one another. The magnetic attraction force between the bearing elements is, in this case, equal to the sum of the tensile force exerted by the mass and the first bearing element and of the repulsion force of the gas cushion. A bearing arrangement of this type may be used for the gravity-compensating suspension of a foldable solar panel arrangement for a satellite in a test apparatus for testing the deployment operation in a gravitational field so as to simulate weightlessness or may serve, in general terms, as a low-friction conveying system.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a bearing arrangement for the support of tensile forces, in particular for the suspended mounting of a mass, in order to simulate the weightlessness of the latter in a gravitational field, the bearing arrangement having a first bearing element comprising at least one magnet and a second, metallic bearing element which is attracted magnetically by a first bearing element. 
     A bearing arrangement of this type is known, for example, from DE 195 01 571 A1. 
     The invention relates, furthermore, to a bearing head for the bearing arrangement, with a bearing body into which a magnet is integrated. 
     Satellites are usually equipped, for the supply of power, with foldable solar panels which, during transport from Earth into orbit, are folded together and rest against the outer casing of the satellite. In orbit, after the satellite has been released, these solar panels are then deployed in a zigzag-like manner by means of a deploying mechanism. 
     This deployment of the solar panels is critical to the system, since the supply of power to the satellite is not ensured without sufficiently and completely unfolded solar panels, and the satellite then cannot be used at all or can be used only to a restricted extent. The deployment operation therefore has to be simulated on Earth and the corresponding mechanism tested. 
     For this simulation and for this testing operation, the joints of a solar panel arrangement have hitherto been suspended on a rolling bearing track mounted on the ceiling, the corresponding suspension devices being capable of moving about the vertical axis within the rolling bearing track in the longitudinal and transverse directions and at their suspension point. A fundamentally free movement of the unfolding solar panel arrangement was thereby achieved during the deployment operation. However, frictional forces arise in the rolling bearings both in the longitudinal direction and in the transverse direction and also in the rotary bearing of the suspension and do not allow a completely free movement of the unfolding solar panel arrangement, as is the case under conditions of weightlessness in space. Furthermore, the suspension of the solar panels gives rise, in the region of their joints, to a gravity-induced axial force in the joints which in the joints causes frictional resistances which do not occur under conditions of weightlessness. The suspension of the solar panels of this test apparatus, which is generally known and cannot be vouched for by prior art, is therefore suitable only to a limited degree for ensuring an actual free moveability of the deploying solar panels. 
     It is not only the above-described operation of deploying solar panels which requires a load suspension system capable of being moved without friction. In many other sectors of manufacturing, assembly or conveying technology it is necessary to move suspended loads virtually without friction in a horizontal plane. This is necessary particularly when highly accurate positioning of the load is to be carried out. Such highly accurate positioning is not possible in transport systems where friction occurs, since, because of the friction, there is always an, albeit only slightly detectable, jolt-like movement of the conveying system. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a generic bearing arrangement which, on the one hand, reliably supports tensile forces and, on the other hand, allows virtually frictionless movement in one plane and about a vertical axis. 
     This object is achieved, according to the invention, in that at least one of the bearing elements has, in its bearing surface, gas outflow nozzles which are loaded by a compressed gas, so that a gas stream flowing out of the gas outflow nozzles forms a gas cushion between the bearing elements attracting one another due to the magnetic force, said gas cushion keeping the bearing elements at a distance from one another. The magnetic attraction force between the bearing elements is, in this case, equal to the sum of the tensile force exerted by the mass and the first bearing element and the repulsion force of the gas cushion. 
     The combination of magnetic retention and compressed gas bearing makes it possible in a reliable way to build up a holding force between the two bearing elements which reliably supports the tensile forces, without a mechanical connection between the two bearing elements being made at the same time. 
     U.S. Pat. No. 4,860,600 discloses a microgravity simulator, in which air bearings are used to support a mass to be tested. However, in this known arrangement, the air bearings act counter to gravity so that here a standing arrangement, that is to say a compressive force, is supported by the air bearings. However, where very narrow and high masses to be tested are concerned, as is the case, for example, with solar panels, even the least possible lateral deflections can cause tilting forces which may nullify a conventional standing air mounting according to U.S. Pat. No. 4,860,600 due to tilting moments. A standing gas pressure bearing arrangement having the same disadvantages is also known from U.S. Pat. No. 5,501,114. 
     It is advantageous, in the bearing arrangement according to the invention, that the suspended arrangement of the mass, and therefore the design of the bearing arrangement as a suspended bearing and not as a standing bearing, is relatively immune to deflections even of a thin high mass, since a stable equilibrium always prevails in a suspended mounting, whereas an unstable equilibrium always prevails in a standing mounting. 
     In an advantageous development, the first, magnet-equipped bearing element also has the gas outflow nozzles for generating the gas cushion. This bearing arrangement is advantageous in manufacturing terms and from a sales point of view, since only one bearing element has to be of a technologically high-quality design, whereas the other bearing element can be designed relatively simply. 
     It is also advantageous if the first, magnet-equipped bearing element has a plurality of bearing means, and if the second bearing element is formed by an essentially planar metal plate. The provision of a planar metal plate as the second bearing element makes it possible to concentrate the entire functionality of the bearing arrangement according to the invention onto the first, magnet-equipped bearing element. 
     Preferably, at the same time, the metal plate forming the second bearing element is arranged fixedly, and the first, magnet-equipped bearing means is connected effectively to the mass to be mounted, the bearing means in each case being designed as a bearing head provided with at least one magnet and with gas outflow nozzles. 
     It is also advantageous if the bearing heads of the first bearing element are pivotably mounted individually on a carrying structure connected effectively to the mass to be mounted. By virtue of this arrangement, any unevennesses in the metal plate and also slight exogenic disturbances exerting a tilting moment on the respective bearing heads can be compensated for, since the individual bearing heads in each case come to bear optimally against the sheet-like bearing element, without an increase in the distance between the two bearing surfaces and consequently a lifting-off of the bearing head from the second bearing element occurring at the same time. 
     It is particularly advantageous if the bearing heads of the first bearing element are arranged in a row, at least two bearing heads being provided, which in each case are articulated laterally moveably on one end of a balance-beam-like carrying beam, and the carrying beam being pivotably mounted indirectly or directly in the manner of a balance beam on a suspension structure for the mass to be mounted. This design makes it possible to have an ideally uniform distribution of the tensile force to the individual bearing heads and consequently a homogeneous and reliably effective distribution of tensile force over the entire bearing arrangement. 
     At the same time, it is particularly advantageous if the carrying structure has, in a first plane, an even number of first balance-beam-like carrying beams, at the respective ends of which two bearing heads adjacent to one another are pivotably mounted. It is further advantageous if the carrying structure has, in a second plane, a number of two balance-beam-like carrying beams, at the respective ends of which two first carrying beams adjacent to one another are pivotably mounted in the manner of a balance beam. It is desirable if the carrying structure has, preferably in one or more further planes, balance-beam-like carrying beams, at the respective ends of which two carrying beams, adjacent to one another, of the upper plane are pivotably mounted in the manner of a balance beam, and if the lowest plane has a single last carrying beam which is pivotably mounted in the manner of a balance beam on the suspension structure for the mass to be mounted. This design makes it possible to provide a multiplicity of bearing heads and, at the same time, ensure that each bearing head absorbs the same tensile force. Preferably, the magnets provided are permanent magnets. The advantage of this is that, in the event of a system failure, the mass suspended on the bearing arrangement does not fall down, but instead, due to the attraction force of the permanent magnet, acts on the second bearing element, so that the mass to be held does not fall down during a system failure. 
     It is also advantageous if at least one magnet is formed by a solenoid. It is thereby possible, for example, to provide a controllable braking device for a moving mass suspended on the bearing arrangement, and, by the solenoid being activated until the compressed gas cushion is overcome and there is physical contact with the second bearing arrangement, a braking action can be achieved by means of a bearing head provided with a solenoid. It is advantageous, in particular, if the attraction force of the solenoid and/or the repulsion force of the gas cushion are capable of being controlled or regulated. As a result, even a dynamic load can be controlled to a limited extent, and, by increasing the force of the solenoid and reducing the repulsion force of the gas cushion, a greater attraction of the bearing arrangement onto the second bearing element can be achieved. 
     A further object of the invention is to specify a bearing head for a generic mounting, into which bearing head a magnet is integrated. 
     This object is achieved in that a gas outflow structure is provided around the magnet in the bearing surface of the bearing head. 
     It is advantageous in this case if the gas outflow structure consists of a multiplicity of gas outflow nozzles arranged around the magnet, and, in particular, micronozzles may be provided, which ensure that a highly effective gas cushion is built up. 
     Alternatively, however, the gas outflow structure may also have at least one gas outflow nozzle which is fluidly connected to an air distributor structure arranged in a groove-like manner around the magnet. 
     In a particularly preferred embodiment of the bearing head, the housing is designed to be essentially axially symmetrical, preferably cylindrical, the bearing surface extending orthogonally, preferably all-round orthogonally, to the axis of symmetry of the bearing head, the magnet being arranged coaxially to the axis of symmetry of the bearing head, the inner flux lines of the magnet extending essentially parallel to the axis of symmetry, and the gas outflow nozzles being arranged around the magnet circularly on at least one ring which is likewise placed coaxially to the axis of symmetry. This special rotationally symmetrical design of the entire bearing head is distinguished in that, in the event of a movement, the bearing head does not have any directional priority, so that a movement of the bearing head in any translational direction is possible without obstructions and without preferences. 
     Alternatively to this, the bearing head may be designed in such a way that the bearing body has, in horizontal projection, a rectangular or trapezoidal form and that the magnet has, likewise in horizontal projection, a rectangular or trapezoidal form. An unequivocal directional preference of the bearing body is thereby afforded, and this may be advantageous if a predetermined direction of the movement of the bearing body is to be defined in a controlled manner, as may be advantageous, for example, in a transport system which uses the bearing arrangement according to the invention. 
     It is particularly advantageous if the gas outflow nozzles in the bearing surface are formed by microholes which are drilled by means of a high-energy beam and which are of conical form, their narrowest cross-section being located at the issue into the bearing surface. This form of the gas outflow nozzles, which is already known per se from DE 44 36 156 C1, has the advantage that the air consumption of the individual nozzles is extremely low and that a large number of nozzles for a high static carrying force can be introduced into the bearing body, without thereby causing the overall air consumption to rise into uneconomic ranges. In the bearing head according to the invention, this embodiment of the gas outflow nozzles, in conjunction with the magnet provided in the bearing head, provides extremely homogeneous attraction and repulsion of the cooperating bearing elements, so that these have a high reliable carrying capacity. 
     The bearing arrangement according to the invention, particularly when it is equipped with the bearing heads according to the invention, serves in a preferred use for the gravity-compensating suspension of a foldable solar panel arrangement for a satellite in a test apparatus for testing the deployment operation in a gravitational field so as to simulate weightlessness, at least one bearing arrangement being provided in order to suspend the solar panel arrangement so that it is freely moveable horizontally. 
     At the same time, it is particularly advantageous if a plurality of bearing arrangements are provided, a bearing arrangement of which in each case mounts one solar panel of the solar panel arrangement consisting of a plurality of solar panels, so as to be freely moveable horizontally in suspension and so as to be freely rotatable about the vertical axis running through the center of gravity of the respective solar panel. In particular, this embodiment makes it possible to ensure a moveability of the individual solar panels which is already frictionless in the suspension and, moreover, to prevent the occurrence of axial forces in the joints connecting the solar panels to one another, so that even in these joints no gravity-induced frictional forces take effect. 
     In principle, the bearing arrangement according to the invention and, in particular, the bearing heads according to the invention are also suitable for carrying out any other support of a suspended load, so that they can also be used, for example, for a conveying system which moves essentially without friction. 
     The invention is explained in more detail below by means of an example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an almost completely deployed solar panel arrangement having a plurality of bearing arrangements according to the invention for suspended mounting; 
     FIG. 2 shows a detail drawing of a bearing arrangement according to the invention, according to the detail II in FIG. 1; 
     FIG. 3 shows a perspective view of a bearing head of a bearing arrangement according to the invention; 
     FIG. 4 shows a vertical section through a bearing head according to the invention; and 
     FIG. 5 shows an assembly means capable of being positioned with high accuracy by means of the bearing arrangements according to the invention, in a perspective view obliquely from below. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a solar panel arrangement  2  which is mounted in suspension and so as to be freely moveable horizontally by means of a bearing arrangement  4 . 
     The solar panel arrangement  2  comprises a plurality of solar panels  6  which in each case are connected to one another via hinge-like joints  8  on two vertical sides facing away from one another, so that the solar panel arrangement  2  can be folded together and unfolded in a zigzag-like manner. The first solar panel  6  is connected in an articulated manner, on its vertical side facing away from the joint  8 , via a hinge-like joint  8 ′ to a trapezoidal fastening structure  10  which, at its free end, possesses a fastening plate  12  capable of being attached to a satellite (not shown). In a test apparatus, the fastening plate  12  is secured fixedly. 
     The bearing arrangement  4  comprises a plurality of first bearing elements  14  and a second bearing element  16  cooperating with the first bearing elements  14 . 
     The second bearing element  16  has a planar metal plate extending essentially horizontally. 
     The first bearing elements  14  each have at least one magnet  18  which, by means of the magnetic force, supports in suspension the associated bearing element  14 , the solar panel  6  connected effectively to it and the fastening structure  10  connected effectively to the first bearing element  14 , so as to be suspended below the second bearing element  16  having the metal plate. Furthermore, each first bearing element  14  has, in its bearing surface  20 , gas outflow nozzles  22  (FIG. 4) which are loaded by a compressed gas, a gas stream which flows out of the gas outflow nozzles  22  forming a gas cushion between the respective first bearing element  14  and the second bearing element  16 , said gas cushion keeping the bearing elements  14 ,  16  at a distance from one another. The gas pressure of the outflowing gas stream is, in this case, set in such a way that the sum of the gas cushion repulsion force caused by said gas pressure and of the tensile force exerted by the mass of the solar panel arrangement  2  and of the first bearing elements  14  is equal to the magnetic attraction force between the bearing elements  14 ,  16 . In this way, the first bearing elements  14 , together with the solar panel arrangement  2  attached to them, are held in suspension below the second bearing element  16 , without the two bearing elements  14 ,  16  touching one another. This suspended mounting allows a free moveability of the solar panels  6  of the solar panel arrangement  2  along the second bearing element  16  (that is to say, in this example, in the horizontal direction) and a free moveability about the vertical axis of each first bearing element  14 , so that the system described has three degrees of freedom. 
     Both the magnets  18  and the gas outflow nozzles  22  do not necessarily have to be arranged in the suspended first bearing element, although this is a particularly advantageous refinement of the invention; the gas outflow nozzles and/or the magnets  18  may also be arranged in the plate-like second bearing element  16 , in which case an activating means is expediently provided for the gas outflow nozzles  22 , said activating means activating only those gas outflow nozzles in the region of which a suspended first bearing element  14  is located. 
     It can also be seen in FIG. 1 that the first bearing elements  14  are in each case fastened via a vertical tension rod  24  to a horizontal bearer  26  attached to the upper edge of each solar panel  6 , the tension rod being mounted vertically above the mass center of gravity S of each solar panel  6 . This avoids vertical forces occurring in the hingelike joints  8  connecting the solar panels  6  to one another. A similar design with the same effect for the hinge-like joint  8 ′ is also provided for the suspended mounting of the fastening structure  10 . 
     The design of each bearing element  14  is explained with reference to FIG.  2 . 
     FIG. 2 shows an enlarged view of a first bearing element  14  suspended below the second bearing element  16 . The first bearing element  14  comprises, in addition to the tension rod  24  and the horizontal bearer  26  holding the solar panel  6  or, in the example of FIG. 2, the fastening structure  10 , a plurality of bearing means  28  and also a carrying structure  30 . Each bearing means  28  comprises a bearing head  32  with an upper bearing surface  34  directed toward the second bearing element  16 , and also a tension strut  36  attached on the underside facing away from the bearing surface  34 . The design of the bearing means  28  is described later with reference to FIGS. 3 and 4. 
     The carrying structure  30  comprises a multiplicity of carrying beams  38 ,  38 ′,  38 ″,  38 ′″;  40 ,  40 ′;  42 ,  42 ′;  44  arranged in a plurality of planes E 1 , E 2 , E 3  and E 4  located one above the other. The lowest plane E 4  of the carrying structure  30  consists of a balance-beam-like carrying beam  44  which has the contour of an isosceles triangle and which is articulated pivotably on the upper end of the tension rod  24  in the region of the triangle vertex which is formed by the two equal sides. A further carrying beam  42 ,  42 ′, which is likewise designed in the form of an isosceles triangle, is in each case pivotably mounted, in the region of its vertex formed by the equal sides, on the other two vertices of the carrying beam  44 . The two carrying beams  42 ,  42 ′ form the next higher plane E 3  of the carrying structure  30 . The arrangement located above the carrying beams  42 ,  42 ′ is in each case designed identically, so that only the structure located above the carrying beam  42  is described below. 
     A carrying beam  40 ,  40 ′ of an upper plane E 2  of the carrying structure  30  is in each case pivotably mounted on the two further vertices of the carrying beam  52  in the same way as the carrying beams  42 ,  42 ′ are mounted on the carrying beam  44 . These carrying beams  40 ,  40 ′ also in each case again mount, at their free vertices, a carrying beam  38 ,  38 ′ and  38 ″,  38 ′″ of an upper plane E 1  pivotably and in the manner of a balance beam in the same way. The carrying beams  38 ,  38 ′,  38 ″,  38 ′″ also have a design similar to that of the lower balance-beam-like carrying beams, the respective points of articulation being located at the vertices of an imaginary isosceles triangle. The two upper points of articulation of the uppermost carrying beams  38 ,  38 ′,  38 ″,  38 ′″ in each case pivotably mount the lower end of the tension strut  36  of an associated bearing means  28 . The above-described pivoting work of the individual elements, but at least that of the tension struts  36  on the uppermost carrying beams  38 ,  38 ′,  38 ″,  38 ′″, is not restricted to the direction of the plane formed by the carrying beams, but is also possible transversely to this plane. 
     This design of the carrying structure  30  ensures that the tensile force introduced into the carrying structure  30  via the tension rod  24  is introduced into the respective bearing means  28  independently of lateral components of the tensile force which possibly act on the tension rod  24 , solely in the vertical direction of force, that is to say in the direction of the respective longitudinal axis X of the bearing means  28 . For this reason, no tilting forces arise on the bearing surface  34  of each bearing means  28 , so that the distance between the bearing surface  34  of the respective bearing means  28  and the downwardly pointing bearing surface of the second bearing element  16  is constant. This ensures that a uniformly thick gas cushion is formed between the respective bearing means  28  and the second, upper bearing element  16 , so that the displacement of a bearing surface  34  out of its ideal position and consequently a weakening of the magnetic holding force, and also a collapse of the gas cushion, are reliably avoided. Moreover, this avoids the situation where, if the bearing surface  34  is tilted, an obliquely directed force component of the gas stream flowing out of the gas outflow nozzles causes a lateral movement of the first bearing element  14 , so that, as a result of this too, free moveability of the solar panel arrangement  2  suspended on the first bearing element  14  is ensured in the horizontal direction. 
     FIG. 3 shows a perspective view of an individual cylindrical bearing means  28  obliquely from above. On the top side of the bearing means  28 , the bearing surface  34  can be seen, at the center of which is located the end face of the likewise cylindrically designed permanent magnet  18 . A multiplicity of micronozzles  22 , as a gas outflow structure  47  for the outflow of the gas stream, are provided, illustrated diagrammatically as a ring  46  in FIG. 3, around the permanent magnet  18 . 
     The design of the bearing means  28  is described below with reference to the vertical section illustrated in FIG.  4 . 
     The bearing means  28  consists of a bearing head  32  and of the tension strut  36 . The cylindrical bearing head  32  has a housing  48  which receives the magnet  18  and in which is formed the gas distributor structure for the gas outflow nozzles  22 . The housing  48  consists of an upper outer annular casing  50 , a lower outer annular casing  52 , an upper inner core  54  and a lower inner core  56 . 
     The gas outflow nozzles  22  are formed in the upper outer annular casing  50  in the bearing surface  34  located at the top in FIG.  4 . An annular duct  58 , which is open toward the lower outer annular casing  52 , is provided inside the upper outer annular casing  50  behind the gas outflow nozzles  22 . 
     The lower outer annular casing  52  is provided, on its surface pointing upward to the upper outer annular casing  50 , with a groove-like annular duct  60  which, after the two annular casings  50 ,  52  have been assembled, is fluidly connected to the annular duct  58 . Radially inwardly directed radial ducts  62 ,  62 ′ run from the annular duct  60  of the lower outer annular casing and are fluidly connected to radial ducts  64 ,  64 ′ in the lower inner core  56  when the latter is inserted into the assembled annular casings  50 ,  52 . The annular casings  50 ,  52  are joined sealingly to one another in a way known to a person skilled in the art, for example by welding, adhesive bonding, screwing or the like. 
     The lower inner core  56  is screwed by means of an external thread into an internal thread provided in the inner wall of the unit composed of the upper outer annular casing  50  and of the lower outer annular casing  52 , an O-ring seal  66  being inserted between the lower end face of the lower outer annular casing  52  and an upper annular surface of the flange-like lower portion of the lower inner core  56  and ensuring sealing off of the lower inner core  56  and the unit composed of the two annular casings  50 ,  52 . 
     The lower inner core  56  possesses a central threaded bore  68  which is fluidly connected to the radial ducts  64 ,  64 ′ in the wall of the lower inner core  56 . Screwed into the central threaded bore  68  is a fluid connection piece  70  which is formed at the upper end of the tension strut  36  and which has a supply duct  72  for the compressed gas. The supply duct  72  is provided in a way known per se with a hose connection for a gas supply hose (not shown) which is connected to a compressed gas source (not shown). 
     The upper inner core  54  is likewise screwed into the threaded interior of the upper outer annular casing  50 , at least one sealing plate  74  being provided between the upper inner core  54  and the lower inner core  56 . The upper inner core  54  is provided, in the region of its upper end face forming the bearing surface  34 , with a central blind-hole bore  76 , into which the magnet  18  is inserted and is secured, for example, by means of a grouting compound  78  surrounding the magnet  18 . The upper outer annular casing  50 , the upper inner core  54 , the magnet  18  and the grouting compound  78  together form the planar bearing surface  34  on their top side. 
     The gas outflow nozzles  22  are designed as micronozzles which are formed by means of a high-energy beam, for example a laser beam, in the thin wall portion  50 ′ between the bearing surface  34  and the bottom surface  58 ′ of the annular duct  58 . In this case, as can be seen in FIG. 4, the gas outflow nozzles  22  taper conically from the annular duct  58  toward the bearing surface  34 . 
     The compressed gas introduced into the supply duct  72  enters the central threaded bore  68  of the lower inner core  56  and flows from there through the radial ducts  64 ,  64 ′ and  62 ,  62 ′ into the annular duct  60  in the lower outer annular casing  52  and further on into the annular duct  58  in the upper outer annular casing  50 , said compressed gas flowing out of the annular duct  58  through the gas outflow nozzles  22 . 
     FIG. 5 shows an example in which the bearing arrangement according to the invention is provided in a load conveying system, by means of which a suspended load can be positioned with high accuracy. 
     A first bearing element  114  having four bearing heads  132  is suspended in a way already described, as in the first example, by means of magnetic force on a ceiling structure serving as a second bearing element  116 . The first bearing element  114  has two carrying beams  138 ,  138 ′ which are connected at their respective ends, via tension struts  136 , to a respectively associated bearing head  132 . In the middle, the carrying beams  138 ,  138 ′ are in each case connected in a pivotably articulated way to the ends of a lower common carrying beam  140  in the manner of a balance beam, and this common carrying beam  140  is pivotably connected at its center in an articulated way to a tension rod  124 , at the lower end of which the load  102  is held likewise pivotably via an auxiliary tension rod  125 . In the present example, the load  102  consists of a shaft which is to be inserted into a bearing bush  101  illustrated as being free in space in FIG. 5, but in reality secured to an assembly plate. 
     The first bearing element  114 , together with the load  102  suspended on it, is freely moveable, without friction, in the horizontal direction in the plane spanned by the axes Y and Z and formed by the ceiling structure, as has already been described with regard to the first example. A translational drive, not shown in any more detail, for the first bearing element  14  ensures the desired translational movement in the plane spanned by the axes Y and Z. 
     When the shaft forming the load  102  is placed exactly above the receiving bore  101 ′ of the bearing bush  101  secured on the assembly table, the shaft is lowered into the receiving bore  101 ′ of the bearing bush  101 . In order to make this lowering possible, either the tension rod  124  or the auxiliary tension rod  125  is extendable downward telescopically. 
     For the better positioning of the load at the unloading point reached, the gas stream flowing out of the gas outflow nozzles of the bearing heads  132  can be reduced, so that the magnetic force predominates and an undesirable lateral movement of the first bearing element  114 , together with the load suspended on it, is thus avoided. 
     The invention is not restricted to the above exemplary embodiment, which serves merely for a general explanation of the essential idea of the invention. On the contrary, within the scope of protection, the apparatus according to the invention may also assume embodiments other than those described above. 
     Reference symbols in the claims, description and drawings serve merely for a better understanding of the invention and are not intended to restrict the scope of protection.