Abstract:
A transporting apparatus ( 10 ) comprises a transporting plane ( 11 ) and a transporting platform which can be displaced in different directions in a largely friction-free manner on an air cushion above the transporting plane ( 11 ), the air cushion being generated by air nozzles ( 13 ) which are distributed in the transporting plane ( 11 ) and can be optionally opened and closed individually in each case by means of a valve, and through which compressed air flows out in the upward direction from beneath through the transporting plane ( 11 ), and the valves of the air nozzles ( 13 ) and the transporting platform being designed such that they interact with one another depending on the position of the transporting platform. In the case of such a transporting apparatus, simplified and functionally reliable control is achieved in that the valves of the air nozzles ( 13 ) are designed as solenoid valves ( 12, 21 ) equipped with a magnet coil, and in that the transporting platform has ferromagnetic regions which interact with the magnet coils (b 28) of the solenoid valves ( 12, 21 ) in dependence on the position of the transporting platform.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of transport. It relates to a transporting apparatus according to the preamble of claim  1  and to a method of operating such a transporting apparatus.  
           [0002]    A transporting apparatus of the type mentioned is known, for example, from U.S. Pat, No. 4,896,610.  
         BACKGROUND OF THE INVENTION  
         [0003]    Transporting apparatuses in which a transporting platform can be moved in a largely friction-free manner by means of an air cushion generated between the transporting platform and a transporting plane have been known for some time now. It is possible here for the air cushion to be generated either by the platform itself or by an apparatus arranged beneath the transporting plane. A known example of the first-mentioned alternative is constituted by the sea-going and land-bound vehicles for passenger transport which have become known as hovercrafts.  
           [0004]    The second-mentioned alternative is used, in particular, wherever, on the one hand, there are transporting planes with a comparatively. small lateral extent present and, on the other hand, the transporting platform itself is intended to be constructed as straightforwardly as possible and without any additional installations and energy sources. U.S. Pat. No. 3,610,695 thus describes a (horizontally operating) transporting apparatus for metal plates, in the case of which the metal plate which is to be transported is mounted, and moved in a friction-free manner, on an air cushion. The air cushion is generated by air which flows out continuously into the interspace between the metal plate and transporting surface through nozzles distributed uniformly in the transporting surface. The metal plate is moved by an electromagnetically acting linear motor which is formed by coils arranged in iron cores beneath the transporting surface. The coils are activated in accordance with the current position of the metal plate, this position being determined by (optical) sensors located above the metal plate. The disadvantage with this solution is that air flows out uniformly through all the air nozzles of the transporting apparatus irrespective of where the metal plate is actually located. The disruptive arrangement of the sensors above the metal plate which is to be transported is also disadvantageous. Finally, the linear motor has the disadvantage that it is not only associated with considerable outlay, as far as its construction and operation are concerned, but is also inflexible in terms of transporting direction, because it only allows one movement direction.  
           [0005]    A further transporting apparatus with a combination of linear motor and mounting on an air cushion is described in U.S. Pat. No. 4,077,507.  
           [0006]    U.S. Pat. No. 3,648,852 discloses a transporting apparatus with two parallel sliding rails on which a transporting pallet can be displaced horizontally. Air channels for generating an air cushion open out in a uniformly distributed manner into the planar top surfaces of the sliding rails. The air channels are closed in each case by a ball valve, of which the ball, in the closed state of the valve, projects a little beyond the top surface of the sliding rails. The ball valves are only opened when the transporting pallet, as it slides over the valves, presses the associated balls, counter to the pressure of a spring, into the top surface of the sliding rails. This achieves the situation where only those ball valves and/or air channels which are actually required beneath the transporting pallet for forming the air cushion are activated. The disadvantage here, however, is the mechanical engagement between the transporting pallet and the valve balls, which obstructs the movement, results in wear and renders the functioning of the arrangement susceptible to disruption. It is also the case here that the movement direction is limited by the direction of the sliding rails. Furthermore, an active movement mechanism is not provided in the case of this transporting apparatus.  
           [0007]    U.S. Pat. No. 4,896,610, mentioned in the introduction, proposes a transporting apparatus which acts in two independent directions and in the case of which air nozzles provided with valves are distributed uniformly on the transporting surface. In a manner similar to U.S. Pat. No. 3,648,852, the valves may be designed as ball valves, which are actuated mechanically by the transporting platform. However, it is also proposed (page 2, lines 34-63 of the document) to use electrically switched valves which are opened by different proximity detection systems when the platform approaches the valves. In addition to the transporting platform being mounted on a planar air cushion, a description is also given of possible ways in which the platform can be actively advanced by means of an advancement mechanism. One possibility consists in using a hydraulically actuated repulsion mechanism (FIG. 10) fitted on the platform. Another possibility for an advancement mechanism consists in using two magnetic plates on the platform which are each made to rotate by a battery-operated motor and interact with the metallic transporting surface (FIG. 11). The disadvantage here is that, on account of the advancement mechanism installed, the transporting platform has a comparatively complicated construction and requires a dedicated energy source. The fact that a wire-bound or wireless connection to the platform has to be provided in order to control the movement is also disadvantageous.  
         SUMMARY OF THE INVENTION  
         [0008]    It is thus an object of the invention to provide a transporting apparatus, with air supply through the transporting plane, which avoids the disadvantages of the known transporting apparatuses, is distinguished, in particular, by simplified and functionally reliable control and can be used to realize an active movement mechanism without high outlay. It is also an object of the invention to specify a method of operating such a transporting apparatus.  
           [0009]    The objects are achieved by the features of claims 1 and 10 taken as a whole. The core of the invention consists in designing the valves of the air nozzles as solenoid valves equipped with a magnet coil and in providing the transporting platform with ferromagnetic regions which interact with the magnet coils of the solenoid valves in dependence on the position of the transporting platform. It is thus easily possible, with a (passive) transporting platform, for the various tasks of valve control, localization and active advancement of the transporting platform to be achieved reliably via a single mechanism.  
           [0010]    It is conceivable, in principle, for the transporting platform only to be provided with ferromagnetic regions on the periphery. By the interaction with the solenoid valves, this then establishes, in the transporting plane, the edge of an area which corresponds to the extent of the transporting platform. A control means can then determine which solenoid valves are located inside, and which are located outside, this area and can actuate one or more solenoid valves located within the area. The transporting apparatus is particularly straightforward if, according to a preferred configuration, the transporting platform is designed as a ferromagnetic carrier plate (throughout). This easily achieves interaction with all the solenoid valves located beneath the platform and/or the carrier plate.  
           [0011]    The interaction is particularly intensive if the magnet coils of the solenoid valves are designed as ring coils and are arranged beneath the transporting plane with the coil axis perpendicular to the transporting plane, if a non-magnetic cover plate, preferably made of aluminum, is arranged between the magnet coils and the transporting plane, and the air nozzles are formed by bores in the cover plate, and if the magnet coils are arranged in each case in a yoke which is made of ferromagnetic material and is open in the direction of the transporting plane.  
           [0012]    If the magnet coils are intended to be used, at the same time, for the active advancement of the transporting pallet, it is advantageous for the solenoid valves to be designed such that they are closed in the de-energized state of the magnet coil and open when the magnet coil is supplied with a current of suitable magnitude, it being the case that, in the de-energized state of the magnet coil, the solenoid valves are kept closed in each case by a spring element.  
           [0013]    A maximum level of flexibility can be achieved in the case of the transporting apparatus in that the solenoid valves are connected to a control means such that they can be activated individually. It is expedient, in particular, if the solenoid valves are arranged in a two-dimensional matrix in the transporting plane and are connected to the control means via corresponding control lines which are assigned to the rows and columns of the matrix.  
           [0014]    A preferred configuration of the method according to the invention is characterized in that the extent and/or the position of the transporting platform are/is determined from the measured inductances of the magnet coils. It is thus possible for different transporting platforms to be moved at the same time on the transporting apparatus. Active advancement of the transporting pallet can be achieved easily and without additional auxiliary means, according to one configuration of the invention, in that, utilizing the interaction between the transporting platform and the magnet coils of the solenoid valves, the transporting platform is moved in a predetermined movement direction by selected solenoid valves being switched on and off.  
           [0015]    Further embodiments can be gathered from the dependent claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention will be explained in more detail hereinbelow with reference to exemplary embodiments, in conjunction with the drawing, in which:  
         [0017]    [0017]FIG. 1 shows, in a schematic illustration, the plane view of a transporting apparatus according to a preferred exemplary embodiment of the invention; the transporting platform or carrier plate has been omitted here;  
         [0018]    [0018]FIGS. 2 a - c  show, in a number of steps, the mechanism for active advancement of a transporting plate on the transporting apparatus according to FIG. 1; and  
         [0019]    [0019]FIG. 3 shows the cross section through the transporting apparatus according to FIG. 2 in the region of an individual solenoid valve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    FIG. I represents, in a schematic illustration, the plan view of a transporting apparatus according to a preferred exemplary embodiment of the invention. The transporting apparatus  10  comprises a horizontal transporting plane  11 , the lateral extent of which is adapted to the respective requirements of the transporting problem which is to be solved. Provided in the transporting plane  11 , in a uniformly distributed manner over the surface, are air nozzles  13  which, in the example illustrated, are arranged in rows and columns of a two-dimensional matrix. It is, of course, also possible for the air nozzles  13  to be provided in other arrangements, e.g. (hexagonally) in offset rows, in order to achieve, for example, a higher packing density and thus greater positioning accuracy. The spacing between the air nozzles  13  depends essentially on the size of the transporting platform which is to be moved on the transporting plane  11  and on the necessary positioning accuracy. The air nozzles are supplied with compressed air from an air chamber ( 24  in FIG. 3) located beneath the transporting plane  11 , said compressed air being generated, for example, by an air pump  14  and being fed in via a connecting line  15 . The air nozzles  13  are each provided with solenoid valves  12 , which allow the air nozzles  13  to be opened and closed in a controlled manner.  
         [0021]    The solenoid valves  12 , which, analogously to the air nozzles  13 , form a matrix, are connected to a control means  16  via control lines  17 ,  18 , which are assigned to the rows and columns of the matrix. If two specific control lines are selected from the group of control lines  17  and  18 , that solenoid valve which is located at the crossover point of said control lines is activated. It is just as conceivable, however, for the solenoid valves  12  to be activated individually by two-wire lines or for the activating means to be positioned (in a decentralized manner) directly alongside the individual solenoid valves. The cover plate made of aluminum ( 25  in FIG. 3) provided and a further electrode, which is common to all the valves, may be used as electric supply lines here. It is thus possible to realize a control principle with “distributed intelligence”: it is possible for the activation command for a solenoid valve to depend on the neighboring valves of the latter or to be transmitted from these valves. Direct communication with the transporting platform is also possible.  
         [0022]    The control lines  17 ,  18 , however, do not just serve for activating the solenoid valves  12 ; they also make it possible, on account of the electromagnetic interaction between the solenoid valves and the transporting platform (not shown in FIG. 1), to determine the size and position of the transporting platform. In this way, the control means obtains position-related information, on the basis of which the activation of the solenoid valves  12  can be carried out.  
         [0023]    [0023]FIG. 3 illustrates a cross section of the construction, by way of example, of an arrangement comprising air nozzle  13  and solenoid valve  12  beneath the transporting plane  11 . The solenoid valve  12  is accommodated in a carrying body  26 , which is preferably produced from a suitable polymer. Introduced into the carrying body  26  from the underside onward is a first, annular recess  29 , in which the magnet coil  28  of the solenoid valve is accommodated together with a ferromagnetic (cup-like) yoke  27 . The axis  39  of the magnet coil  28  here is located perpendicularly to the transporting plane  11 . A second, circular recess  30  is introduced into the carrying body  26 , concentrically to the first recess  29 , from the top side. The actual valve body  32 , which has a ferromagnetic actuating element  34  in its interior, is arranged in said recess  29 .  
         [0024]    Provided above the carrying body  26  is a (round) cover plate  25  which is made of a non-magnetic material, preferably aluminum, and of which the top surface is part of the transporting plane  11  and which has, in the center (coaxially with the core axis  39 ), the air nozzle  13 , which is configured as a vertical bore. On the top side, the valve body  32  has an integrally formed hemispherical closure part  33 . Arranged beneath the valve body  32  is a spring element  31 , for example in the form of a foam-rubber disk, which subjects the valve body  32  to prestressing and presses it with sealing action, by way of the closure part  33 , against the bottom opening of the air nozzle  13 . The second recess  30  is connected to the air chamber  24 , which encloses the solenoid valve  12 , via an air channel  38 . If the magnet coil  28  is supplied with an appropriate current by the control means  16 , the valve body  32  is drawn downward counter to the force of the spring element  31  and the compressed air flowing via the air channel  38  can flow out of the air nozzle  13  in the upward direction. If the stream through the magnet coil  28  is switched off, the spring element  31  closes the valve.  
         [0025]    In addition to the abovedescribed actuation of the valve, the magnet coil  28  has a second essential function: if—as is shown in FIG. 3—the transporting platform, which can be displaced on the transporting plane  11 , is designed as a ferromagnetic carrier plate  19 , electromagnetic interaction takes place between the carrier plate  19  and the magnet coil arranged directly beneath the transporting plane  11 . This interaction causes the inductance of the magnet coil  28  to change if the carrier plate  19  is displaced from a position in which it does not cover the magnet coil  28  into a position in which it wholly or partially covers the magnet coil  28 , as is illustrated in FIG. 3. This change in inductance can be measured for all the solenoid valves by the control means  16 . Since the magnet coils (of the solenoid valves  21  in FIG. 2) covered by the carrier plate  19  have a considerably different inductance from those which are not covered, the measurements of all of the magnet coils  28  in their entirety make it possible to determine not just the size, but also the current position, of the carrier plate  19  on the transporting plane  11 . It is thus possible, in particular, for the control means  16  only to open solenoid valves which are located beneath the carrier plate  19 , with the result that compressed air only flows out through the air nozzles which are effectively necessary for building up the air cushion. One open air nozzle is sufficient here, in principle, for generating the necessary air cushion. If further solenoid valves covered by the carrier plate  19  are opened, the attracting forces generated by the magnet coils reduce the carrying force of the carrier plate  19 . For advancement, in contrast, only the magnet coils located at the edges are active.  
         [0026]    If the carrier plate  19  moves in the transporting plane  11 , those valves which are no longer covered by the carrier plate  19  following the movement are closed and the newly covered valves are opened. The consumption of compressed air may further be reduced if a sealing element  36  in the form of a rubber seal is provided at the edges of the carrier plate  19 , in the direction of the transporting plane  11 , in a sealing groove  35  provided for this purpose, said rubber seal sealing the air gap  37  between the carrier plate  19  and transporting plane  11  in the outward direction.  
         [0027]    In addition to the valve-actuating function and the position-sensor function, however, the magnet coils  28  also have a third function: if those magnet coils which are located at the edge, but outside, the carrier plate  19  are supplied with current, the magnetic interaction with the carrier plate  19  in the vicinity causes the carrier plate  19  to be subjected to a force which tries to draw the carrier plate  19  in the direction of the magnet coils. Suitable activation of the magnet coils  28  and/or solenoid valves  12  thus makes it possible for the carrier plate  19  to be moved in any desired predetermined direction. Such a movement is illustrated, by way of example, in parts (a) to (c) of FIG. 2. FIG. 2( a ) shows a transporting plane  11  according to FIG. 1 with a carrier plate  19  floating thereon. Some or all of the solenoid valves  21  covered by the carrier plate  19  have been switched on, while the rest of the solenoid valves have been switched off. If then, the carrier plate  19  is to be moved in the movement direction  20  indicated by the arrow, i.e. in the downward direction to the right, the valve rows  22  and  23  which are in the vicinity of the edges and are located in the movement direction are switched on (illustrated by hatching in FIG. 2( b )). As a result, the carrier plate  19  is moved in the desired direction (FIG. 2( c )). Of course, the switched-on solenoid valves which, during the movement of the carrier plate  19 , are no longer covered by the latter are switched off in order to avoid obstruction of the movement by the magnet coils thereof.  
         [0028]    Overall, the invention describes a universal system for moving extremely small to extremely heavy loads in a transporting plane. The friction is reduced here by a compressed-air cushion which is generated between the transporting plane and a ferromagnetic (soft-iron) carrier plate. The carrier plate is the load carrier. In order to minimize the air losses, the carrier plate is sealed in relation to the transporting plane all the way around by a (rubber) seal. In a manner controlled by solenoid valves, the compressed air is removed from the transporting plane through air nozzles. The solenoid valves are seated in the center of magnet coils which are distributed over the transporting plane. The quantity, size and positioning of the solenoid valves depend on the dimensions and requirements (positioning accuracy) of the loads which are to be moved.  
         [0029]    The magnet coils generate a magnetic field in the region of the air cushion and of the carrier plate, which results in the latter being subjected to forces. Suitable activation of the magnet coils in the region beneath and around the carrier plate makes it possible for the latter to be displaced in any desired direction. Depending on the activation, it is possible to move a plurality of loads one after the other or else simultaneously (individual control). Activation of a magnet coil thus results, simultaneously, in the opening of the air nozzle and the displacement of the load, which simplifies the activation.  
         [0030]    The arrangement thus constitutes a two-dimensional linear motor—with the transporting plane as the stator and the carrier plate as moveable pole. At the same time, use is made of the principle of a hovercraft, although the air is supplied from the “bottom”. With an operating pressure of 1 bar, it is thus possible for a carrier plate of A4 size to displace a load of half a tonne.  
         [0031]    By virtue of suitable additional devices, it is possible for a randomly positioned load to be “located” by the change in inductance of the magnet coils located therebeneath and also measured roughly (covered coils). Other sensors may possibly also be suitable.  
         [0032]    Apart from the valve bodies (and the spring element, e.g. made of open-cell foam rubber, therebeneath), the apparatus does not have any moveable parts. The air nozzles are self-cleaning and the transporting plane may serve as a floor.  
         [0033]    Possible applications are as follows: automation, conveying, sorting; automatic storage; loading and unloading aids for trucks; automatic configuration (conversion) of production lines; studios, stages, etc.  
         [0034]    List of Designations  
         [0035]    [0035] 10  Transporting apparatus  
         [0036]    [0036] 11  Transporting plane  
         [0037]    [0037] 12 ,  21  Solenoid valve  
         [0038]    [0038] 13  Air nozzle  
         [0039]    [0039] 14  Air pump  
         [0040]    [0040] 15  Connecting line  
         [0041]    [0041] 16  Control means  
         [0042]    [0042] 17 ,  18  Control line  
         [0043]    [0043] 19  Carrier plate (ferromagnetic)  
         [0044]    [0044] 20  Movement direction  
         [0045]    [0045] 22 ,  23  Valve row  
         [0046]    [0046] 24  Air chamber  
         [0047]    [0047] 25  Cover plate (e.g. aluminum)  
         [0048]    [0048] 26  Carrying body  
         [0049]    [0049] 27  Yoke (ferromagnetic)  
         [0050]    [0050] 28  Magnet coil  
         [0051]    [0051] 29  Recess (annular)  
         [0052]    [0052] 30  Recess (circular)  
         [0053]    [0053] 31  Spring element (e.g. foam-rubber disk)  
         [0054]    [0054] 32  Valve body  
         [0055]    [0055] 33  Closure part (hemispherical)  
         [0056]    [0056] 34  Actuating element (ferromagnetic)  
         [0057]    [0057] 35  Sealing groove  
         [0058]    [0058] 36  Sealing element  
         [0059]    [0059] 37  Air gap  
         [0060]    [0060] 38  Air channel  
         [0061]    [0061] 39  Coil axis