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The present application is a 371 of International application PCT/DE2011/075265, filed Nov. 10, 2011, which claims priority of DE 10 2010 051 003.3, filed Nov. 10, 2010, the priority of these applications is hereby claimed and these applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention pertains to a double-floor construction with floor plates and a support structure to be built on a subfloor, on which structure the floor plates can be laid with their edges abutting each other a certain distance from the subfloor. 
     Flooring which can be laid with little effort is known from EP 162 733 A2; it comprises floor plates with a stiff lower backing layer and an upper decorative layer in the form of tiling, for example. An intermediate layer is foamed or sprayed onto the backing layer and the decorative layer. The intermediate layer merges integrally with an edging element and with contrivances for connecting the edges of the floor plates to each other, wherein the edging and the contrivances are produced simultaneously with the intermediate layer. 
     SUMMARY OF THE INVENTION 
     The invention is based on the goal of creating a new double-floor construction of the type indicated above which can be manufactured with little effort, which comprises a high degree of impermeability to liquid and air, and the floor plates of which can be quickly replaced. 
     The inventive double-floor construction achieving this goal is characterized in that the support structure comprises support rails, which extend underneath and along the butt joints between the floor plates, and in that the floor plates and support rails comprise contrivances which allow the floor plates to be set down vertically onto the support rails under horizontal compression of the edges forming the butt joints of the floor plates. 
     It is advantageous that the floor plates need to be moved only vertically when they are to be connected to each other and when they are to be removed; no cumbersome horizontal movements to connect the plates to each other are required. If desired, an individual floor plate can be easily removed from the flooring assembly and replaced by, for example, a floor plate with an integrated electrical outlet. The horizontal pressure which the floor plates exert against each other ensures that the floor covering will be leak-proof. 
     In a preferred embodiment of the invention, each of the support rails comprises a longitudinal channel extending under the associated butt joint; hooking sidepieces formed on the edges of the floor plates can be inserted into these channels. The transverse forces which arise during insertion press the floor plates together along their edges; this is associated advantageously with a stabilizing effect and improves the sealing function of the flooring. 
     The floor plates can preferably be set down onto the support rails in such a way that they latch themselves into the rails. 
     In a further elaboration of the invention, each of the support rails comprises a U-shaped section, which forms the longitudinal channel, the material of this U-section being different from that of the rest of the support rail. This U-section can be produced with a high degree of precision from, for example, aluminum or plastic, whereas the remainder of the support rail can be made out of a steel section, especially a steel U-section, with wider manufacturing tolerances. 
     It is advantageous for the first U-section, which can have a latching projection on the outward-facing surface to latch with the other part of the support rail, to comprise a projection, especially a latching projection, on each of the inward-facing surfaces of the U-section, to which the previously mentioned hooking sidepiece can latch. 
     In a further elaboration of the invention, contrivances to allow the vertical placement of the floor plates onto the support rails are formed on an intermediate layer of the floor plate, which is foamed or sprayed onto the backing layer and the decorative layer. This intermediate layer can consist of, for example, polyurethane foam. 
     After the floor plates, which have been installed with their edges abutting each other under a certain horizontal pressure and which are also connected by tongue-and-groove joints produced via the intermediate layer, and after the tongue-and-groove joints between the floor plates and the U-section produced via the intermediate layer, the U-section forming the longitudinal channel, because it is closed off at the bottom, represents, as it were, a third sealing plane. 
     In one embodiment of the invention, the support structure comprises uprights, which are preferably arranged underneath the corners of the floor plates and which are designed to hold the support rails. 
     These uprights can comprise seatings, preferably edge slots, to accept the support rails, which are laid continuously across several uprights. It is advantageous for the support structure also to comprise support rails which extend between and perpendicular to the support rails laid continuously over several uprights. 
     These support rails extending between the continuously laid support rails are advisably designed so that they can be suspended from the uprights. 
     In a further elaboration of the invention, the uprights comprise an adjustable three-point or four-point base by which they rest on the subfloor. Adjustments can be made by changing the height and angle of the upright, e.g., by manipulating it from above by inserting a tool from above into a sleeve, into which a foot of the upright is screwed from underneath, this foot having an engagement slot for the tool at its upper end. 
     In another embodiment, the three-point or four-point base can be adjusted remotely through the laid floor plates by, for example, the use of magnetism. For example, a set of gears actuated externally by a magnetic coupler can be used to adjust the height. This makes it possible to readjust the flooring after it has been laid. Preferably, however, the support structure is adjusted precisely before the floor plates are laid. 
     It is also possible to make adjustments by means of, for example, a single screw located at each of the intersections of the joints between the floor plates. A removable cap can cover an insertion opening for a screwdriver and be removed when it is desired to make an adjustment. It is possible in this way to readjust the flooring without removing any of the floor plates. 
     The uprights are preferably designed as rectangular boxes open at one end or at both ends, wherein the walls of the box which face each other comprise openings at the edges, especially slots, to form the previously mentioned seating or to form contrivances for the suspension of the support rails. 
     The vertical uprights can be easily set up by themselves first. Then the support rails, which are to be oriented horizontally, are then installed on the uprights in such a way that they extend continuously over several of them. Stops, especially slots therein, can hold the uprights precisely in position. Alternatively, the support rails can comprise markings for the position of the uprights. Between two longitudinal beams created in this way, it is then possible to suspend the perpendicular connecting beams from the uprights between the support rails forming the two longitudinal rails. Thus square receptacles of precise dimensions are formed, which accept the floor plates provided with latching elements and brace them against each other. 
     This bracing function can also be served by the self-adjustment of the floor plates themselves, especially when there is a certain amount of play in the latching connections. Because the floor plates fit precisely, they cause the support structure to shift where necessary all the way around and thus bring the support elements into their exact positions. 
     The shorter connecting support rails extending between the continuously laid support rails can comprise slots at their ends so that they can be suspended from the uprights. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention is explained in greater detail below on the basis of exemplary embodiments and the attached drawings, which pertain to one of these examples: 
         FIG. 1  shows a top view of a double-floor construction according to the invention; 
         FIG. 2  shows a perspective view of an upright for a support structure for the double-floor construction of  FIG. 1 ; 
         FIG. 3  shows a top view of part of the support structure of the double-floor construction of  FIG. 1 ; 
         FIG. 4  shows a side view of part of the support structure of the double-floor construction of  FIG. 1 ; 
         FIG. 5  shows a side view of an upright of the support structure of  FIG. 1 ; 
         FIGS. 6 and 7  show diagrams which explain the butt joint between two floor plates of the double-floor construction of  FIG. 1 ; 
         FIG. 8  shows a butt joint between two floor plates corresponding to another exemplary embodiment of the invention; 
         FIGS. 9 and 10  show another upright, which can be adjusted by means of a magnetic coupler; 
         FIGS. 11-13  show cross sections of additional exemplary embodiments of support rails of the double-floor construction; 
         FIG. 14  shows a transverse stiffener between elongated uprights of an inventive stage floor; and 
         FIG. 15  shows a quick-connect clamp for attaching the transverse stiffener of  FIG. 14  to the uprights of the stage floor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the exemplary embodiment shown here, a double-floor construction comprises square floor plates  1 , which are laid with their edges abutting each other on a support structure. Rectangular floor plates can also be used, however, and it is also possible to omit the suspended connecting beam. The support structure mounted on the subfloor also comprises uprights, arranged under the corners of the abutting floor plates  1 . 
     Support rails  3  and  4  are arranged on the uprights  2 ; each of the support rails  3  extends continuously over several uprights  2 , and each of the support rails  4  extends only between two such support rails  3  and two uprights  2 . 
     As can be seen in  FIGS. 6 and 7 , the floor plates  1  consist of several layers, namely, a stiff backing layer  5 , a decorative layer  6 , and an intermediate layer  7  foamed or sprayed onto the backing layer  5  and the decorative layer  6 . The stiff backing layer  5 , which gives the floor plate stability, is preferably made out of recycled material or some other incombustible material (e.g., fiber-reinforced plasterboard or the like). The decorative layer can comprise, for example, tiles or some other material with a decorative surface. The foamed-on or sprayed-on intermediate layer preferably consists of polyurethane foam. 
     The intermediate layer  7  merges integrally with the edging  8 , which extends around the floor plate  1 ; this edging forms a butt joint  9  with the edging of the adjacent floor plate. Also connected integrally to the intermediate layer  7  is a hooking sidepiece  10 . Both the hooking sidepiece  10  and the edging  8  are produced simultaneously with the intermediate layer  7  by foaming or spraying. It is also possible as an alternative, however, to embed ready-made connecting elements (e.g., extruded parts) in the foam. In contrast to the peripheral edging  8 , the hooking sidepieces  10  do not extend all the way around but are interrupted at the corners of the plate. 
     The uprights  2  are designed essentially as hollow rectangular boxes, the opposite ends of which are open. The horizontal cross section of the box is square and has four side walls  11 . Each of the side walls  11  merges at the corners with an internally threaded vertical sleeve  12 . The feet  13  of the uprights are screwed into these sleeves  12 . At the top end, the threaded bolts of the feet  13  advisably comprise an opening for the insertion of a screwdriver, which can be introduced from above into the sleeve  12 . If the base body of the upright is produced as an extruded part, the inside thread mentioned above will be provided in the form of a pressed-in sleeve. 
     Each of the side walls  11  comprises two edge slots at the upper edge. 
     In the example shown, both the continuous support rails  3  and the shorter support rails  4  each consist of a U-shaped section  15  of steel and a U-shaped section  16  made, for example, of aluminum or plastic. An indentation  17  in the base of the U-shaped steel section  15  accepts the section  16 , the base of which comprises a projection  18  on the outside surface. Additional projections  19  are formed on the inside of the section  16 , one at the end of each of the sides of the U. These are latching projections, which are designed to engage in a recess  20  in the hooking sidepiece  10 . The latching projections form a second sealing plane. 
     The sections  15 ,  16  do not necessarily have to have the shape of a “U”, and materials others than those mentioned can also be considered. 
     Both the support rails  3  and the support rails  4  comprise edge slots  21  in both sides of the U-section  15 . 
     For the production of a double-floor construction from the components described above, the uprights  1  are first arranged on the subfloor in the positions corresponding to the abutting corners of the floor plates  1 . Then the continuous support rails  3  are laid in place, the sides of the U of the steel sections  15  engaging in the associated edge slots  14  in the side walls  11  of the support elements  2 . The slots  21  in the sides of the U automatically ensure the precise positioning of the support rails  3 ,  4 . Instead of the slots  21  in the support rails  3  and/or  4 , it would also be possible to provide suitable markings to facilitate the installation of the support structure with precision through the longitudinal displacement of the support rails  3  and/or  4 , while still making it possible to compensate for manufacturing tolerances. In the absence of slots  21  customized to the dimensions of specific floor plates or other stops to determine the horizontal positioning of the support rails  3 ,  4  on the support elements  2 , the support structure can be easily adapted to accommodate floor plates of different dimensions. In certain cases, only the support rails  4  need to be adapted. 
     After the support rails  3 ,  4  have been installed in their proper horizontal positions, the support structure can now be adjusted by using a screwdriver or wrench to raise or lower the adjustable feet  13  of the uprights  2  from above by screwing the feet into or out of the sleeves  12  to a greater or lesser extent until each upright  2  is resting solidly on the subfloor without the danger of tipping. 
     Then the floor plates  1  can be installed. Their hooking sidepieces  10  are inserted into the channel formed by, for example, the aluminum section  16 , wherein the edges of the floor plates  2  are thus pressed against each other to form the butt joint  9 . 
     Finally, vertical pressure is applied to the floor plates. The slots sized to fit the dimensions of the floor plates can comprise enough play that the support rails can shift their positions slightly all the way around the plate to conform to the positions of the hooking sidepieces of the floor plates, which are highly precise. In a corresponding manner, the main flooring formed by the floor plates ensures the precise horizontal adjustment of the overall system. 
     The uprights can also be tall enough that the flooring could be used to produce a stage floor. For this purpose, stronger connections would be provided between the support rails and the uprights; they could, for example, be screwed together. 
     Alternatively, transverse stiffeners, diagonal bracings, or the like could be provided, especially in cases where the uprights are quite tall. 
     Reference will now be made to  FIG. 8 , which shows part of another exemplary embodiment of a double-floor construction. The same parts and parts with the same function as those of the preceding exemplary embodiment have been given the same reference numbers, to which the letter “a” has been added. 
     The exemplary embodiment of  FIG. 8  differs from the preceding one primarily in that an additional latching projection  22  and a latching recess  23  are provided on opposite edgings  8   a  of the floor plates  1   a.    
     The edgings  8   a  which butt up against each other when pressure is exerted form a first sealing plane. The latching projection  22  engaging in the latching recess  23  provides the double-floor construction with an additional sealing effect. Finally, projecting sidepieces  10   a  of the edgings  8   a  engage in the U-section  16   a , the closed part of which faces downward and thus serves as a sealing barrier, which allows no liquid whatever to pass through. 
       FIGS. 9 and 10  show an upright  2   b , which comprises a lower part  25 , which is the same as the upright  2  shown in  FIG. 2  with respect to its basic outline. The feet corresponding to the feet  13  are not shown in  FIG. 9  or  FIG. 10 . 
     A threaded bushing  26  is installed nonrotatably in the upper end of each of the four vertical sleeves  12   b.    
     On top of the lower part  25 , the upright  2   b  comprises an upper part  27 , which has the same horizontal cross section as the lower part  25 ; slots for the suspension of the support rails are formed in its upper edge (not shown). 
     On an intermediate plate  28 , which can be placed on the lower part  25 , a gear wheel  29  is supported with freedom to rotate. A magnetic coupling device  30  projects axially from it. 
     The gear wheel  29  engages with four gear wheels  31  rotatably supported on the intermediate plate  28 ; a threaded bolt  32  passes through each of these four gear wheels but is not free to rotate in them. Each threaded bolt  32  engages in one of the threaded bushings  26 . 
     With the help of the magnetic wrench  33  shown in  FIG. 10 , the upper part  27  of the upright  2   b  can be adjusted after the floor plates  1   b  have been laid. When the magnetic coupling device  30  is turned by the magnetic wrench  33 , the gear wheel  29  drives the four gear wheels  31 , so that the four threaded bolts  32  rotate along with them and move up in the threaded bushings  26 , thus lifting the upper part  27 . By the use of right-handed/left-handed threads, action in both directions is possible. 
     In a departure from the exemplary embodiment shown, it would also be possible to provide threaded bushings only in the upper part  27  or to connect them nonrotatably to the intermediate plate  28 . It should be obvious that this requires corresponding combinations of right-handed and left-handed threads. 
     In a departure from the exemplary embodiment described above, the support rails  3 ,  4  can be manufactured as one-piece units; that is, they can be bent out of a single piece of sheet steel.  FIGS. 11-13  show cross sections of various exemplary embodiments of such support rails. Each support rail forms a longitudinal channel  40 , into which the hooking sidepieces formed on the edges of the floor plates can be inserted. 
     The section  16  of the two-part support rails  3 ,  4  described further above could be extruded from copper, for example, instead of from aluminum, copper being more highly conductive. In conjunction with conductive floor plates, such sections offer in particular the advantage that they can carry electricity away from the surface flooring. The hooking sidepieces which engage in the longitudinal channel of the section  16  and which are connected integrally to the joint material can be made of, for example, conductive polyurethane. It is then possible for defined leakage currents to flow away via the sections  16 . 
     As shown in  FIG. 14 , transverse stiffeners  41 , extending between the tall uprights  2   a  and  2   a ′ of a stage floor (not otherwise shown), can be attached at points  42  by means of the quick-connect clamps shown in  FIG. 15 . 
     The quick-connect clamp comprises an outside tube  43  and an inside tube  44 , guided through the outside tube  43 . The inside tube is connected at one end to a clamping head  45 . A knee lever  48  rotatably supported in an opening  46  in the outside tube at  47  has an eccentric head  49 , which engages in an opening  50  in the inside tube  44 . By pivoting the knee lever  48  in the direction of the arrow  51 , the clamping head  45 , which passes through an opening  53  in a wall  52  of the upright  2   a  or  2   a ′ and which grips the wall  52  from behind, can be moved in the direction of the arrow  54 . The wall  52  will thus be clamped between the end surface of the outside tube  43  and the clamping head  45 . 
     Designs which make use of a screwing action to shift the stiffener longitudinally and thus to perform the clamping function would also be possible.

Summary:
A double-floor design with flooring panels and a support structure to be placed on a sub-floor on which the flooring panels can be laid abutting one another edge to edge and spaced from the sub-floor. The support structure includes support rails which extend below the joints between the flooring panels along the joints. The flooring panels and support rails include devices for vertically fitting the flooring panels onto the support rails, wherein the edge faces of the flooring panels forming the joints are pressed together horizontally.